CN1323387C - Optical disc device and method for reading out optical disc - Google Patents

Abstract

The invention discloses an optical disc device, comprising: an optical disc with multiple information surfaces, a laser driving device for driving a semiconductor laser, and a focusing device for focusing and irradiating the light beam of the output light of the semiconductor laser driven by the laser driving device on the optical disc surface , a focus control device for controlling the focus position of the focus point of the light beam focused by the focus device on the optical disc surface, a tracking control device for controlling the position of the focus point of the light beam focused by the focus device on the track in the optical disc surface, and a receiving unit The optical detection device of the reflected light of the focused light beam on the surface of the optical disc, the focus state detection device of the focused state detection device of the light beam irradiated on the multiple information surfaces of the optical disc by the RF signal that has completed the writing, according to the detection of the focus state detection device The value controls the laser drive device, and sets the emitted light amount of the light beam at the time of reading for a plurality of information surfaces of each optical disc.

Description

Optical disc device and method for reading out optical disc

technical field

The invention relates to an optical disc and an optical disc device for writing information on the optical disc medium by irradiating laser light.

Background technique

In recent years, optical disk devices have been widely developed as a method of writing and reading large-capacity data, and it is hoped to achieve higher storage density. One of these methods is to use the reversible state change between crystallization and amorphous state. A phase-change optical disc device.

In the phase-change optical disc device, the storage film on the substrate is irradiated with laser light to heat up the temperature, causing a crystallographic phase change in the structure, and writing and erasing information. By using two types of power, peak power to amorphize the crystal part and bias power to crystallize the amorphous part, the semiconductor laser is irradiated on the optical disc medium to form a mark (amorphous part) on the optical disc medium, and to hold the mark. Space (crystal part). The written marks and spaces have different reflectances, and the difference in reflectance between the marks and spaces is detected as a signal by a light spot focused on the optical disk, and information is read.

These marks and spaces are used in a concave-convex memory technique for writing on both tracks of the convex portion and the concave portion of the guide groove on the optical disc.

On the optical disc medium, address information (pre-pit address) indicating the position (address) on the optical disc is formed in advance at the production factory simultaneously with the guide groove and at regular intervals. In the address area, it is represented by the presence or absence of pits and the change in their length.

The configuration of a conventional optical disc device is shown in FIG. 2 .

In Fig. 2, 201 represents an optical disc, 202 represents a semiconductor laser, 203 represents a collimator lens that transforms the light beam emitted by the semiconductor laser into a parallel light beam, 204 represents a beam splitter, and 205 represents a concentrating device that focuses the light beam on the surface of the optical disc 206 represents a condenser lens that collects light beams reflected and diffracted from the optical disc on the light detection device, 207 represents a light detection device that receives the light collected by the condenser lens, and 208 represents a reader that performs four arithmetic operations on the output voltage of the light detection device. The output signal calculation device, 209 represents the focus control device for controlling the focus position of the light spot on the surface of the optical disc, 210 represents the tracking control device for controlling the position of the light spot on the track of the optical disc, and 211 represents the actuator for moving the light spot , 212 denotes a laser drive device for driving a semiconductor laser, and 215 denotes a signal processing unit.

However, in the existing structure, when the optical disc writes and reads information from one side to a plurality of information surfaces, when the address preset in the second layer (inner layer) is to be read, the address of the second layer is reached. The amount of light beam is lost due to absorption and reflection of the first layer (surface layer), so it is proportional to the transmittance of light transmitted through the first layer.

The light that reaches the second layer is reflected and diffracted by the pre-pit addresses of the second layer, passes through the first layer again, and reaches the photodetector. The light quantity of the beam reaching the photodetector is proportional to the square of the transmittance of the first layer and the reflectance of the second layer.

For example, when the transmittance of the first layer is 50%, the light reaching the second layer is the amount of light that passes through the first layer and is diffracted on the second layer, and then passes through the first layer and returns to the light detection device. When the light intensity of the first layer is 1, 1×0.5×0.5×R2=0.25×R2. Where R2 is the reflectivity of the second layer. In an optical disc having the same optical characteristics as the difference in reflectance (ΔR) of the written marks and spaces of the storage layers of the first and second layers, the amount of light diffracted by the pre-pit returning to the light detection device, Depends on the square of the transmittance of the first layer and the reflectance of the second layer, when the transmittance of the first layer is small, or the reflectance of the second layer is small, the predicted A difference occurs in the signal amplitude of the pit address, and it is difficult to correctly read the pre-pit address of the second layer.

Contents of the invention

The present invention solves the above-mentioned problems, and its purpose is to detect the storage layer where the light spot is focused by the focus state judging means, and improve the readout signal quality by the signal quality improving means to obtain the optimum signal quality corresponding to the storage layer where the light spot is focused. , and improve the readout signal characteristics of the pre-pit address of the second layer.

In order to solve the above-mentioned problems, the optical disc of the present invention has a plurality of information planes, with each information plane being formed into a spiral or concentric concave portion and a convex portion between the concave portions as storage tracks. The identification signal of the position on the optical disc, and the optical disc in which the information signal is written by changing the local optical constant or physical shape through the irradiation of the light beam, is characterized in that the identification signal is different from the optical depth or height on a plurality of information planes. Consisting of the same concave and convex pre-pit.

According to one aspect of the present invention, an optical disc device includes: an optical disc having at least an information surface of a first layer and a second layer; a laser drive device for driving a semiconductor laser; focused irradiation on the optical disc surface is driven by the laser The focus device of the light beam of the output light of the semiconductor laser driven by the device; the focus control device for controlling the focus position of the focus point of the beam focused by the focus device on the surface of the optical disc; the focus control device for controlling the focus by the focus device A tracking control device for the position of the focal point of the light beam on the track in the surface of the optical disc; a light detection device for receiving the reflected light from the surface of the optical disc of the focused light beam; detecting the first layer of the optical disc Or the focus state detecting device of the focus state of the light beam irradiated on the information plane of the second layer; for the write signal clipping level voltage from the reproduced waveform of the write track based on the data area, subtract as from the unwritten state The result of the groove level voltage of the signal of the guide groove is positive or negative, and based on the positive or negative calculation result, the calculation device for judging which layer the beam is focused on on the first layer and the second layer, according to the The detection value of the focus state detection means and the calculation result of the calculation means control the laser driving means to set the emitted light amount of the light beam during reproduction or writing for the information planes of the first layer and the second layer of the optical disc.

According to another aspect of the present invention, it provides a method for reading out an optical disc, comprising the steps of: an optical disc with multiple information surfaces, a laser driving step for driving a semiconductor laser, focusing irradiation on the optical disc surface and being driven by the laser step of focusing the light beam of the output light of the semiconductor laser driven by the step, the focus control step of controlling the focus position of the focus point of the light beam focused by the focusing step on the optical disc surface, and the control step of controlling the focus of the light beam focused by the focusing step The tracking control step of the position of the focus point on the track in the surface of the optical disk, the photodetection step of receiving the reflected light of the focused light beam on the surface of the optical disk, and the detection of the position on the optical disk by the RF signal of the completed writing A focus state detection step of the focus state of the light beams irradiated on the plurality of information surfaces, a step of controlling the laser drive based on the detection value of the focus state detection step, and setting the light beam at the time of reading for the plurality of information surfaces of each of the optical discs. The amount of light emitted.

According to still another aspect of the present invention, it provides an optical disc device, including: an optical disc with multiple information surfaces, a laser drive device for driving a semiconductor laser, and a laser drive device driven by the laser drive device to focus and irradiate on the surface of the optical disc. A focusing device for the light beam of the output light of the semiconductor laser, a focus control device for controlling the focus position of the focus point of the light beam focused by the focusing device on the optical disc surface, and a focus control device for controlling the focus point of the light beam focused by the focusing device A tracking control device for the position on the track in the surface of the optical disc, a photodetection device for receiving the reflected light of the focused light beam on the surface of the optical disc, and a device for detecting the focus state of the light beam from the RF signal of the completed writing The focus state detection means controls the laser driving means based on the detection value of the focus state detection means, and sets the emitted light amount of the light beam at the time of reading for the plurality of information surfaces of each of the optical discs.

Description of drawings

FIG. 1 is a configuration diagram of an optical disc device in Embodiment 1 and Embodiment 5 of the present invention.

FIG. 2 is a block diagram of a conventional optical disc device.

FIG. 3 is a configuration diagram for writing and reading an optical disc in the optical disc device according to Embodiment 1 of the present invention.

FIG. 4 is a diagram for explaining the principle of writing and reading from an optical disc in the optical disc device according to Embodiment 1 of the present invention.

FIG. 5 is a diagram for explaining a focus state detection device in the optical disc device according to Embodiment 1 of the present invention.

FIG. 6 is a diagram for explaining a focus state detection device in the optical disc device according to Embodiment 3 of the present invention.

FIG. 7 is a diagram for explaining a focus state detection device in an optical disc device according to Embodiment 4 of the present invention.

8A, 8B, 8C, and 8D are diagrams showing the configuration of an optical disc device according to Embodiment 1 of the present invention.

FIG. 9 is a diagram illustrating waveforms after signal quality improvement in the optical disc device according to Embodiment 4 of the present invention.

Fig. 10 is a diagram for explaining an optical disc in Embodiment 1 of the present invention.

Fig. 11 is a diagram for explaining an optical disc in Embodiment 6 of the present invention.

Fig. 12 is a diagram for explaining an optical disc in Embodiment 7 of the present invention.

Fig. 13 is a diagram for explaining an optical disc in Embodiment 8 of the present invention.

Fig. 14 is a diagram for explaining an optical disc in Embodiment 9 of the present invention.

Fig. 15 is a diagram for explaining an optical disc in Embodiment 10 of the present invention.

16A and 16B are diagrams illustrating equalizer characteristics in Embodiment 7 of the present invention.

FIG. 17 is a diagram for explaining focus positions in Embodiment 8 of the present invention.

FIG. 18 is a diagram illustrating tracking positions in Embodiment 9 of the present invention.

Fig. 19 is a diagram for explaining radial inclination in Embodiment 10 of the present invention.

Fig. 20 is a diagram for explaining a tangentially tilted optical disc in Embodiment 10 of the present invention.

FIG. 21 is a diagram illustrating a focus state detection device in the optical disc device according to Embodiment 2 of the present invention.

FIG. 22 is a diagram illustrating waveforms after signal quality improvement in the optical disc device according to Embodiment 5 of the present invention.

FIG. 23 is a diagram for explaining the principle of writing and reading in a conventional optical disc device.

Fig. 24 is a diagram for explaining the principle of writing and reading in a conventional optical disc device.

Fig. 25 is a diagram showing test results of writing and reading in a conventional optical disc device.

FIG. 26 is a diagram showing test results of writing and reading in the optical disc device according to Embodiment 11 of the present invention.

Fig. 27 is a diagram showing the configuration of an optical disc device according to Embodiment 12 of the present invention.

FIG. 28 is a diagram for explaining the principle of write compensation in Embodiment 12 of the present invention.

FIG. 29 is a diagram for explaining the principle of write compensation in Embodiment 12 of the present invention.

Fig. 30 is a diagram showing the configuration of an optical disc device in Embodiment 11 of the present invention.

Fig. 31 is a diagram illustrating Embodiment 13 of the present invention.

FIG. 32 is a flowchart showing a write and read procedure in Embodiment 13 of the present invention.

FIG. 33 is a flowchart showing a write and read procedure in Embodiment 14 of the present invention.

Fig. 34 is a diagram showing an optical disc to be written and read in the optical disc device according to Embodiment 1 of the present invention.

Fig. 35 is a diagram showing the configuration of an optical disc in Embodiments 15 and 16 of the present invention.

FIG. 36 is a diagram for explaining the principle of write compensation in Embodiment 14 of the present invention.

Detailed ways

(Embodiment 1)

Embodiment 1 of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram showing an optical disc device according to Embodiment 1 of the present invention.

In Fig. 1, 101 denotes an optical disc, 102 denotes a semiconductor laser, 103 denotes a collimating lens, 104 denotes a beam splitter, 105 denotes a focusing device, 106 denotes a condenser lens, 107 denotes a light detecting device, and 108 denotes a readout signal computing device , 109 represents a focus control device, 110 represents a tracking control device, 111 represents an actuator, 112 represents a focus state detection device, 113 represents a laser drive device, and 115 represents a signal processing unit.

The read operation will be described below.

The optical disc 101 is, for example, an optical disc having two information planes, and a light spot is focused on one of the two information planes of the optical disc 101 to read information.

The laser beam emitted from the semiconductor laser 102 is focused on one of the two information planes of the optical disc 101 through a collimator lens 103 , a beam splitter 104 , and a focusing device 105 . The collected light spot is reflected and diffracted on the optical disc 101 , passes through the focusing device 105 , the beam splitter 104 , and the condenser lens 106 , and is collected on the light detecting device 107 . The gathered light outputs a voltage signal according to the light quantity of each receiving element A, B, C, D on the photodetecting device, and four arithmetic operations are performed on the voltage signal in the readout signal operation circuit 108 .

The FE signal read from the output of the signal arithmetic unit is sent to the focus position control unit 109 . The TE signal read out from the output of the signal arithmetic unit is sent to the tracking control unit 110 . The RF signal read out from the output of the signal arithmetic unit is sent to the focus state detection unit 112 .

The focus position control device 109 drives the actuator 111 based on the voltage output corresponding to the FE signal, and controls the focus position of the light spot on either of the two information planes of the optical disc 101 .

The tracking control device 110 drives the actuator 111 based on the voltage output corresponding to the TE signal, and controls the tracking position control of the desired track position of the light spot on either one of the two information planes of the optical disc 101 .

According to the light spot controlled by the focus position control device and the tracking position control device, by reading the concave-convex pre-pit on the optical disc, or the different shade marks and spaces of the reflectivity of the phase-change optical disc, it is possible to write in the The information on the disc is read out.

The focus state detection unit 112 detects whether the light spot is focused on any one of the two information surfaces of the optical disc 101 based on the RF signal. The detection value of the focus state detecting means 112 is transmitted to the laser driving means 113 to control the light output of the semiconductor laser 102 .

The configuration of the optical disc 101 will be described below using FIG. 3 .

FIG. 3 shows an example of optical characteristics of an optical disc having two information planes.

Of the two information planes, the incident side of the light beam is the information plane of the first layer, and only the light beam passing through the first layer can reach the information plane of the second layer.

The configuration of the first layer will be described. In the phase-change optical disc device, a mark on the optical disc medium is formed by irradiating a semiconductor laser on the optical disc medium with two powers: a peak power to amorphize the crystal part and a bias power to crystallize the amorphous part (amorphous part) and the void (crystalline part) that holds the mark.

As for the optical properties of the crystal portion, the emissivity 301 of the first-layer crystal is 9%, the absorptivity 302 of the first-layer crystal is 41%, and the transmittance 303 of the first-layer crystal is 50%. Here, the percentage refers to the case where the intensity of the irradiated light beam is 100%.

As for the optical properties of the amorphous part, the emissivity 304 of the first layer of amorphous is 3%, the absorption rate of the second layer of amorphous 305 is 27%, and the transmittance of the first layer of amorphous 306 is 70%.

The signal detected from the data region of the first layer corresponds to the signal detected in the first layer by the difference (ΔR1) between the first layer crystalline emissivity 301 and the first layer amorphous emissivity 304 . At this time, ΔR1 of the first layer is 6%.

The configuration of the second layer will be described.

As for the optical properties of the crystal part, the second-layer crystal reflectance 307 is 13%, the second-layer crystal absorptivity 308 is 65%, and the second-layer crystal transmittance 309 is 22%.

As for the optical properties of the amorphous portion, the second layer amorphous reflectance 310 is 37%, the second layer amorphous absorption rate 311 is 37%, and the second layer amorphous transmittance 312 is 26%.

In the signal detected from the data area of the second layer, the difference (ΔR2) between the second layer crystalline reflectance 307 and the second layer amorphous reflectance 310 corresponds to the signal detected in the second layer.

However, only light passing through the information plane of the first layer can reach the information plane of the second layer. Also, among the light reflected and diffracted by the second layer, the light returned to the photodetector can only reach the light transmitted through the first layer.

The transmittance of the first layer differs between the crystal part and the amorphous part, and is 50% in the crystal part and 70% in the amorphous part. At this time, considering the state of the optical disc after initialization, it is considered that the entire surface of the first layer is in a crystalline state. When the entire surface of the first layer is in a crystalline state, since the crystal transmittance 303 of the first layer is 50%, the light reaching the second layer is 50%. These lights are reflected and diffracted on the second layer, and then pass through the first layer again, and 50% of the light reflected from the second layer is transmitted. That is, when the light that reaches the second layer after passing through the first layer passes through the first layer again, a light loss of 50%×50%=25% occurs. In this way, the signal amplitude (ΔR2) of the second layer is the difference between the reflectance of the crystalline state of the second layer and the amorphous reflectance of the second layer multiplied by 25% of the loss to and from the first layer, that is, ΔR2=-24%×25 % = -6%. Here, the calculation of the difference between the crystalline reflectance and the amorphous reflectance in the calculation of ΔR1 and ΔR2 is calculated as (crystalline reflectance)−(amorphous reflectance). ΔR2 of the second layer is a negative number because the crystalline reflectance of the second layer<the amorphous reflectance of the second layer.

In an optical disc having two information planes, the signal amplitudes in the data area of the first layer and the data area of the second layer are balanced by making the above-mentioned optical characteristics, and there is no difference between the first layer and the second layer. difference, a stable signal with guaranteed quality can be obtained.

The flow of writing and reading information will be described below using FIG. 4 .

If an optical disc is inserted into the optical disc device, the laser is turned on (laser ON) in the laser driving step (laser driving device 113). The light spot is controlled (focus ON) at an arbitrary radius of the optical disc and a track of an arbitrary layer in the focus control step (focus control means 109). In the tracking control step (tracking control device 110), the light spot is controlled to be at an arbitrary track position on the first layer (tracking ON). In the focus state judging step (focus state detection means 112), it is judged whether or not it is a layer in which the light spot is in focus (determination of a writing layer).

The following describes a case where the result of detecting the focus state of the light spot in the focus state determination step is focused on the first layer.

In the laser driving step (laser power setting), the readout signal is optimized for the first layer. In the laser driving step, the power of the semiconductor laser is optimally controlled, and address information is accurately detected based on the information calculated in the read signal calculation step (read signal calculation means 108) (layer 1 address detection). Then, data writing and reading are started to the designated sector of the first layer.

The following describes a case where the result of detecting the focus state of the light spot in the focus state determination step is focused on the second layer.

In the laser driving step (laser power setting) command to optimize the readout signal in the second layer. In the laser driving step, the power of the semiconductor laser is optimally controlled, and address information is accurately detected based on the information calculated in the readout signal calculation step (layer 2 address detection). Then, data writing and reading are started to the designated sector in the second layer.

The principle of reading out an address area of an optical disc having the optical characteristics shown in FIG. 3 will be described below.

Fig. 8A is a schematic diagram showing a guide groove and an address portion of the first layer of the optical disc. 801 is a groove track as a guide groove, and 802 is a stepped track between the guide grooves. On the optical disc medium, pre-pits 805 are formed at regular intervals as address information indicating positions (addresses) on the optical disc at the same time as the groove track 801 of the guide groove is formed in a production factory. The area formed by the pre-pit in the guide groove of the optical disc is called the address area 806, and the data rewritable area formed by the other guide grooves is called the data area. In the address area, address information is expressed according to the presence or absence of pits and the length of the pits. In the above address information, there is a section in which pits and spaces of the same length are repeatedly formed in advance. The first half of the repeated pits is listed as 803, and the second half of the repeated pits is listed as 804. The first half row of repeated pits and the second half row of repeated pits are arranged in a zigzag shape around the groove track 801 of the guide groove on the inner and outer peripheral sides, respectively. The interval between the center of the groove track and the center of the first-half repeated pit row is Wa, and the interval between the center of the groove track and the center of the second-half repeated pit row is Wb. The interval between adjacent repeated pit columns is the track pitch Tp. There is a relationship of Wa=Wb=Tp/2 among Wa, Wb, and Tp. 807 represents the pit depth of the pre-pit, the pit depth of the pre-pit of the first layer is d1, and the pit depth of the pre-pit of the second layer is d2.

Although FIG. 8A shows the structure of the first layer, the second layer also has the same structure as the first layer. However, the pit depth 807 of the second layer is d2.

A schematic diagram of a readout signal waveform when the light spot passes through the address region shown in FIG. 8A is shown in FIG. 5 .

Next, the case where the light spot scans the address area of the first layer will be described.

In the upper part of FIG. 5, 501 denotes a readout signal waveform of the repeated pit row in the first half of the first layer, and 502 denotes a readout signal waveform of the repeated pit row in the second half of the first layer. 503 represents the voltage between the average value between the center value of the readout signal waveform of the repeated pit row in the first half and the center value of the readout signal waveform in the second half repeated pit row and the ground level 504 . 505 represents the maximum signal amplitude of the address portion of the first layer. In the optical disc with the optical characteristics shown in FIG. 3, the maximum amplitude ΔAR1 of the address portion is 3%.

Next, the case where the light spot scans the address area of the second layer will be described.

In the lower part of FIG. 5, 506 denotes a readout signal waveform of the repeated pit row in the first half of the second layer, and 507 shows a readout signal waveform of the repeated pit row in the second half of the second layer. 508 represents the voltage between the average value between the center value of the readout signal waveform of the repeated pit row in the first half and the center value of the readout signal waveform in the second half repeated pit row and the ground level 509 . 510 represents the maximum signal amplitude of the address portion of the second layer. In the optical disc with the optical characteristics shown in FIG. 3, the maximum amplitude ΔAR2 of the address portion is 1.1%.

However, the diffraction ratio of the pre-pit is set to 66% with respect to the specular portion of the amount of light diffracted by the pits returning to the photodetection device. Assuming that the depths of the pre-pit on the first layer and the second layer are equal, the ratio of the diffraction of the pre-pit on the above-mentioned mirror portion varies with the depth, width, and length of the pre-pit. Here, 66 % is an example, and other values may be used.

Here, there is a signal amplitude difference of about 3 times between the maximum signal amplitude 505 of the address part of the first layer and the maximum signal amplitude 510 of the address part of the second layer. Since the signal quality of the first layer and the second layer are different, Each layer cannot correctly reproduce the pre-pit address.

The above shows that it is necessary for the focus state detection device 112 in FIG. 1 to determine which layer of the first layer or the second layer the light spot is focused on, so as to improve the signal quality of the address area.

In order to align the signal amplitudes of the address portions of the first layer and the second layer, the amplitudes of the pre-pit of the first layer and the second layer are changed.

Fig. 10 is a graph showing the relationship between the depth of the pre-pit and the readout signal amplitude of the pre-pit address. As shown in FIG. 10, if the wavelength of light is λ, the readout signal amplitude of the pre-pit address is maximum when the effective groove depth of the pre-pit is λ/4.

In the optical disc apparatus of the present invention, by adjusting the depth of the first layer pre-pit and the depth of the second layer pre-pit, the amplitude difference between the addresses of the first layer and the second layer pre-pit can be reduced.

A specific example will be described.

As shown in FIG. 8B, in order to increase the address amplitude of the second layer, it has the following configuration.

d1<d2≤λ/4

The above formula shows that the groove depth of the pre-pit in the second layer is below λ/4, and has a groove depth of about λ/4. In order to reduce the address amplitude of the first layer, by making the depth of the pre-pit in the first layer less than The depth of the second layer pre-pit can increase the read signal amplitude of the second layer pre-pit address and reduce the read signal amplitude of the first layer pre-pit address, thereby reducing the first layer and the second layer. The signal amplitude difference of the layer pre-pit address has the effect of improving the signal amplitude of the address area of the second layer.

As another configuration, a configuration as shown in FIG. 8C is also possible.

d1<λ/4≤d2 and d1>(d2-λ/4)

The above formula shows that the groove depth of the pre-pit in the second layer is above λ/4, and has a groove depth of about λ/4. In order to reduce the address amplitude of the first layer, the depth of the pre-pit in the first layer is less than (The depth of the 2nd layer pre-pit)-(λ/4), can increase the readout signal amplitude of the 2nd layer pre-pit address, reduce the readout signal amplitude of the 1st layer pre-pit address, Therefore, the signal amplitude difference between the pre-pit address of the first layer and the second layer is reduced, and the signal amplitude of the address area of the second layer is improved.

As another configuration, a configuration as shown in FIG. 8D is also possible.

λ/4≤d2<d1

The above formula shows that the groove depth of the pre-pit in the second layer is above λ/4, and has a groove depth of about λ/4. In order to reduce the address amplitude of the first layer, the depth of the pre-pit in the first layer is greater than The depth of the second layer pre-pit can increase the read signal amplitude of the second layer pre-pit address and reduce the read signal amplitude of the first layer pre-pit address, thereby reducing the first layer and the second layer. The signal amplitude difference of the layer pre-pit address has the effect of improving the signal amplitude of the address area of the second layer.

Also, the depth of the pre-pit in the optical disc of the present invention means the optical depth or height in consideration of the refractive index of the medium.

(Embodiment 2)

In Embodiment 1, it is described that the first layer and the second layer are identified by using the characteristics of the optical disc with different groove depths of the first layer and the second layer and the optical disc itself. In an optical disc with the same groove depth in the second layer, the first layer and the second layer are recognized on the writing/reading device side.

Embodiments 2 to 4 describe the focus state detecting means 112 for determining whether the light spot is focused on the first layer or the second layer when a signal is generated when the light spot is focused on the optical disc.

First, Embodiment 2 of the present invention will be described with reference to the drawings.

The focus state detecting device 112 for determining the focus state using the reproduced signal of the pre-pit in the address area will be described with reference to FIGS. 5 and 21 .

However, the configuration diagram of the optical disc device is the same as that of Embodiment 1 of the present invention, as shown in FIG. 1 .

In order to determine which of the first layer and the second layer the light spot is focused on, the focus state detector 112 of the optical disc device of the present invention uses the center value and the rearward The slice voltage 2103 of the average value between the center values of the read signal waveform of the pit row 2102 is repeated halfway to identify the first layer and the second layer. When the clipping level is within a certain range (threshold value 1a to threshold value 1b), it is determined as the first layer, and when the clipping level is within a certain range of voltage values (threshold value 2a to threshold value 2b), it is determined as the second layer.

However, the ranges of (threshold 1a-threshold 1b) and (threshold 2a-threshold 2b) do not overlap, as shown in Figure 5, the judgment method is,

Clipping level...(Threshold 1a～Threshold 1b)=7.5%±Δ...1st layer,

Clipping level...(Threshold 2a-Threshold 2b)=2.75%±Δ...2nd layer. This determination is performed by the focus state detection means 112 . Here, Δ denotes 10% of the value given on the left. That is, (threshold value 1a-threshold value 1b) is (7.5%+0.75%)-(7.5%-0.75%). The following are the same.

In the same way, when there are three or more information planes, it is only necessary to additionally set a slice level within a certain range.

Alternatively, in order to determine which of the first layer and the second layer the light spot is focused on, the optical disc device of the present invention identifies the first layer and the second layer based on the voltage of the maximum amplitude 2105 of the address portion during reproduction of the address area. . When the maximum amplitude of the address part is within a certain range (threshold value 1c ~ threshold value 1d) of the voltage value, it is judged as the first layer, when the maximum amplitude of the address part is within a certain range (threshold value 2c ~ threshold value 2d) of the voltage value, it is judged as the second layer layer.

However, the ranges of (threshold 1c-threshold 1d) and (threshold 2c-threshold 2d) do not overlap, as shown in Figure 5, the judgment method is,

Address section maximum amplitude ΔAR1...(threshold value 1c～threshold value 1d)=3%±Δ...1st layer,

Address part maximum amplitude ΔAR2...(threshold value 2c-threshold value 2d)=1.1%±Δ...second layer. This determination is performed by the focus state detection means 112 .

When there are three or more information planes, it is also sufficient to additionally set the maximum amplitude of the address portion within a certain range.

It has been shown above that the information plane on which the light spot is focused among the plurality of information planes can be identified by the signal from the address field.

FIG. 21 shows an example of an X layer in the case of an N layer.

(Embodiment 3)

Hereinafter, Embodiment 3 of the present invention will be described with reference to the drawings.

The focus state detecting device 112 which determines the focus state using the signal of the track whose data area is in the unwritten state will be described with reference to FIGS. 5 and 6 .

However, the configuration diagram of the optical disc device is the same as that of Embodiment 1 of the present invention, as shown in FIG. 1 .

In order to determine which of the first layer and the second layer the light spot is focused on, the focus state detection device of the optical disc device of the present invention stores the groove level of the signal level in the unwritten track of the read data area. 602.

When the tank level is within a certain range (threshold 1e-threshold 1f), it is determined as the first layer, and when the tank level is within a certain range (threshold 2e-threshold 2f), it is determined as the second layer.

When there are three or more information planes, it is also sufficient to additionally set a slot level within a certain range.

However, the ranges of (threshold value 1e～threshold value 1f) and (threshold value 2e～threshold value 2f) do not overlap, as shown in Figure 5, the judgment method is,

Groove level...(threshold value 1e～threshold value 1f)=6%±Δ...the first layer,

Groove level...(threshold value 2e-threshold value 2f)=2.2%±Δ...the second layer. This determination is performed by the focus state detection means 112 .

Alternatively, in order to determine which of the first layer and the second layer the light spot is focused on, the focus state detection means 112 of the optical disc device of the present invention stores the mirror level 601 for reading the signal level of the mirror portion. The mirror portion, as shown in FIG. 8A , refers to the flat portion between the groove track 801 and the first half repeated pit row 803 , or between the first half repeated pit row 803 and the first half repeated pit row 804 .

When the mirror level is within a certain range (threshold 1g~threshold 1h), it is judged as the first layer, and when the mirror level is within a certain range (threshold 2g~threshold 2h), it is judged as the second layer.

Here, the mirror portion refers to a guide groove on the optical disc or a mirror area where no pre-pit is formed.

When there are three or more information planes, it is also sufficient to additionally set a mirror level within a certain range.

However, the ranges of (threshold value 1g～threshold value 1h) and (threshold value 2g～threshold value 2h) do not overlap, as shown in Figure 5, the judgment method is,

Mirror level...(threshold value 1g～threshold value 1h)=9%±Δ...the first layer,

Specular level...(threshold value 2g-threshold value 2h)=3.3%±Δ...the second layer. This determination is performed by the focus state detection means 112 .

The above shows that the information plane on which the light spot is focused among the plurality of information planes can be identified by the signal from the track whose data area is in an unwritten state.

(Embodiment 4)

Hereinafter, Embodiment 4 of the present invention will be described with reference to the drawings.

The focus state detecting device 112 for determining the focus state using the signal of the track in the writing state in the data area will be described using FIG. 7 .

However, the configuration diagram of the optical disc device is the same as that of Embodiment 1 of the present invention, as shown in FIG. 1 .

In FIG. 7 , 701 to 706 represent schematic diagrams of readout signal waveforms when reading out the mirror portion of the first layer and the write signal portion (the portion of the groove track 801 in FIG. 8 ), and 707 to 712 represent readout of the second layer. A schematic diagram of the readout signal waveform when the mirror portion and the write signal portion (the portion of the groove track 801 in FIG. 8 ) of . In the first layer, a write signal envelope exists below the groove level 704 . Figure 3 shows that if a mark is written in the first layer (the phase change film of the optical disc changes from a crystalline state to an amorphous state), the reflectivity decreases from 9% to 3%. In contrast, there is a write signal envelope above the groove level 710 in the second layer. Figure 3 shows that if a mark is written in layer 2, the reflectivity rises from 13% to 37%. This is because the constitutions of the phase change films of the first layer and the second layer are different.

In order to determine which of the first layer and the second layer the light spot is focused on, the focus state detection means 112 of the optical disc device of the present invention will be described. First, when the light spot is focused on the first layer, the process of determining it as the first layer by the focus state detection means will be described.

The writing signal slice level 703 as the center value of the signal amplitude of the writing signal envelope of the writing signal envelope of the reading waveform of the writing track of the reading data area and the flat mirror surface as a guide groove and no pre-pits are formed The voltage difference between the voltages of the mirror level 701 of the signal of the part is stored as the mirror-slicer voltage difference 702 .

Here, when the mirror-slicer voltage difference 702 is a voltage value within a certain range (threshold value 1i to threshold value 1j), it is determined as the first layer.

Next, when the light spot is focused on the second layer, the process of judging it as the second layer by the focus state detection means will be described.

Write signal slice level 709 as the center value of the signal amplitude of the write signal envelope of the read waveform of the write track of the read data area and the flat mirror surface as a guide groove and no preset pit formed The voltage difference between the voltages of the mirror level 707 of the signal of the section is stored as a mirror-slicer voltage difference 708 .

Here, when the mirror-slicer voltage difference 708 is within a voltage value within a certain range (threshold 2i to threshold 2j), it is determined to be the second layer.

However, the ranges of (threshold 1i~threshold 1j) and (threshold 2i~threshold 2j) do not overlap, as shown in Figure 7, the judgment method is,

Mirror surface-limiting voltage difference...(threshold value 1i～threshold value 1j)=4.95%±Δ...the first layer,

Mirror-slicer voltage difference ... (threshold 2i to threshold 2j) = 1% ± Δ ... the second layer. This determination is performed by the focus state detection means 112 .

Here, instead of the write signal slice level, the write signal maximum level which is the maximum value among the write signals may be used.

Here, instead of using the write signal slice level, the write signal minimum level which is the minimum value among the write signals may be used.

When there are three or more information planes, it is also necessary to additionally set a mirror plane-slicer voltage difference within a certain range.

Alternatively, in order to determine which of the first layer and the second layer the light spot is focused on, write the central value of the signal amplitude of the write signal envelope of the read waveform of the write track as the read data area The voltage difference between the signal clip level 703 and the groove level 704 which is a signal of a leading groove in an unwritten state is stored as a groove-slip voltage difference 706 . When the calculation result of (slicer level of write signal)-(groove level) is positive, it is judged as the first layer, and when the calculation result is negative, it is judged as the second layer.

Here, depending on the optical disc, when the calculation result of (write signal slice level)-(groove level) is negative, it may be determined as the first layer, and when the calculation result is positive, it may be determined as the second layer.

It has been shown above that the information plane of the plurality of information planes on which the light spot is focused can be identified by the signal from the track in which the data area is in the written state.

(Embodiment 5)

Hereinafter, Embodiment 5 of the present invention will be described with reference to the drawings. In Embodiments 2 to 4, the focus state detection device 112 for judging whether it is the first layer or the second layer has been described. In Embodiments 5 to 7, how to make the signal output of the second layer the same as the signal output of the first layer when the focus state detection device 112 determines that the light spot is focused on the second layer will be described.

Figure 1 is used for illustration.

According to the detection value of the focus state detection device 112, when it is determined that the light spot is focused on the first layer, or when the focus state of the light point is not determined, the laser driving device 113 is controlled to drive the semiconductor laser 102 to output the most suitable laser light to the first layer .

According to the detection value of the focus state detection device 112, when it is determined that the light spot is focused on the second layer, the focus state detection device controls the laser driving device 113 to drive the semiconductor laser 102 to output the most suitable laser light to the second layer. The laser driving device 113 issues a command to drive the semiconductor laser 102 to output light about 2.7 times larger than that focused on the first layer to the second layer. The reason for choosing 2.7 times will be explained below.

Referring to FIG. 9, the case where the light spot scans the address area will be described.

The case where the light spot scans the address area of the first layer will be described.

901 denotes a readout signal waveform of the repeated pit row in the first half of the first layer, and 902 denotes a readout signal waveform of the repeated pit row in the second half of the first layer. 903 represents the maximum signal amplitude of the address portion of the first layer. In the optical disc with the optical characteristics shown in FIG. 3, the maximum amplitude ΔAR1 of the address portion is 3%. 904 represents the voltage at the tank level. Also, this ΔAR1 can be expressed as ΔAR1 = 3% as the maximum amplitude 505 of the first layer address portion in FIG. 5 .

A case will be described in which the laser driving device 113 scans the address area of the second layer using the same laser power as that of the first layer instead of 2.7 times. At this time, the maximum amplitude ΔAR2 of the address part of the second layer is 1.1%. This ΔAR2 can be expressed as ΔAR2 = 1.1% as the maximum amplitude 510 of the address part of the second layer in FIG. 5 . To go from 1.1% to 3%, simply multiply 1.1% by 2.7. Therefore, in Embodiment 5, if the focus state detecting device 112 of FIG. 1 judges that the light spot is focused on the second layer, the output of the laser drive device 113 is 2.7 times larger than when the light spot is focused on the first layer. The laser power drives the spot.

FIG. 9 shows a state where the second layer is driven with 2.7 times the power. 905 denotes a readout signal waveform of the repeated pit row in the first half of the second layer, and 906 denotes a readout signal waveform of the repeated pit row in the second half of the second layer. 907 indicates the maximum signal amplitude of the address portion of the second layer. When it is determined by the focus state detection device that the light spot is focused on the second layer, since the laser drive device drives the laser with 2.7 times the laser power, the amount of light returning to the light detection device increases by 2.7 times compared to the light output of the first layer. As a result, the maximum amplitude ΔAR2 of the address portion of the second layer is 3%.

In this way, the maximum amplitudes of the address portions of the first layer and the second layer are both 3%, which improves the read signal quality of the address portions of the first layer and the second layer.

Here, although the light output of the semiconductor laser when the light spot is focused on the second layer is 2.7 times that when it is focused on the first layer, this value is determined by the crystal reflectance of the first layer, the crystal reflectance of the second layer, and the absorption of the first layer. The rate is determined.

Also, although the optical output of the semiconductor laser when the light spot is focused on the second layer is 2.7 times that of the first layer, this value is determined by the written track and the unwritten track of the first layer next to the second layer. Status OK.

Also, although the optical output of the semiconductor laser when the light spot is focused on the second layer is 2.7 times that when it is focused on the first layer, the optical output can be increased only when the light spot is focused on the address area of the second layer.

Also, although the optical output of the semiconductor laser when the light spot is focused on the second layer is 2.7 times that of the first layer, different optical outputs may be set for the address area and the data area of the second layer.

(Embodiment 6)

Hereinafter, Embodiment 6 of the present invention will be described with reference to the drawings.

Description will be made using FIG. 11 .

In Fig. 11, 1101 denotes an optical disk, 1102 denotes a semiconductor laser, 1103 denotes a collimating lens, 1104 denotes a beam splitter, 1105 denotes a focusing device, 1106 denotes a condenser lens, 1107 denotes a photodetecting device, and 1108 denotes a readout signal computing device , 1109 represents a focus control device, 1110 represents a tracking control device, 1111 represents an actuator, 1112 represents a focus state detection device, 1113 represents a laser drive device, 1114 represents a gain control device, and 1115 represents a signal processing unit.

The focus state detecting means 1112 controls the gain control means 1114 to set the output voltage of the light detection means with the most suitable gain for the first layer when it is determined that the light spot is focused on the first layer, or when the focus state of the light spot is not determined gain.

According to the detection value of the focus state detection device 1112, when it is determined that the light spot is focused on the second layer, the focus state detection device controls the gain control device 1114 to set the gain of the output voltage of the light detection device at the most suitable gain for the first layer . The gain control unit 1114 issues a command to set the gain of the output voltage of the photodetection unit 1107 at a gain of approximately 2.7 times the gain when focusing on the first layer. The reason for selecting 2.7 times is the same as that described in Embodiment 5.

The case where the light spot scans the address area of the first layer will be described.

901 denotes a readout signal waveform of the repeated pit row in the first half of the first layer, and 902 denotes a readout signal waveform of the repeated pit row in the second half of the first layer. 903 represents the maximum signal amplitude of the address portion of the first layer. In the optical disc with the optical characteristics shown in FIG. 3, the maximum amplitude ΔAR1 of the address portion is 3%. 904 represents the voltage at the tank level.

The case where the light spot scans the address area of the second layer will be described.

FIG. 9 shows a state where the second layer is set to 2.7 times. 905 denotes a readout signal waveform of the repeated pit row in the first half of the second layer, and 906 denotes a readout signal waveform of the repeated pit row in the second half of the second layer. 907 indicates the maximum signal amplitude of the address portion of the second layer. When it is determined by the focus state detecting device that the light spot is focused on the second layer, since the laser driving device sets the gain of the output voltage of the photodetecting device 1107 with a gain of 2.7 times, with respect to the light output of the first layer, the output of the photodetecting device The voltage is increased by 2.7 times. As a result, the maximum amplitude ΔAR2 of the address portion of the second layer is 3%.

In this way, the maximum amplitudes of the address portions of the first layer and the second layer are both 3%, which improves the read signal quality of the address portions of the first layer and the second layer.

Here, although the gain of the output voltage of the photodetector when the light spot is focused on the second layer is set to 2.7 times that of when the light spot is focused on the first layer by the gain control device, this value is determined by the crystal reflectance of the first layer and the crystal reflectance of the second layer. The layer crystal reflectance and the first layer absorptivity are determined.

Also, although the gain of the output voltage of the photodetector when the light spot is focused on the second layer is set to 2.7 times that when the light spot is focused on the first layer by the gain control device, this value is changed from that of the first layer next to the second layer. Status determination of written and unwritten tracks.

Also, although the gain of the output voltage of the photodetector when the light spot is focused on the second layer is set to 2.7 times that of the first layer by the gain control device, it can also be limited to the address where the light spot is focused on the second layer. Increases light output when in an area.

Also, although the gain of the output voltage of the photodetector when the light spot is focused on the second layer is set to 2.7 times that when the light spot is focused on the first layer by the gain control device, it is also possible to set the address area and the data area of the second layer. Set different gains.

(Embodiment 7)

Hereinafter, Embodiment 7 of the present invention will be described with reference to the drawings.

Description will be made using FIG. 12 .

In Fig. 12, 1201 denotes an optical disk, 1202 denotes a semiconductor laser, 1203 denotes a collimator lens, 1204 denotes a beam splitter, 1205 denotes a focusing device, 1206 denotes a condenser lens, 1207 denotes a light detection device, and 1208 denotes a read signal computing device , 1209 represents a focus control device, 1210 represents a tracking control device, 1211 represents an actuator, 1212 represents a focus state detection device, 1213 represents a laser drive device, 1214 represents an equalization control device, and 1215 represents a signal processing unit. Here, the equalization control device means a device that can increase the gain of only a specific frequency component.

The detection value of the focus state detection device 1212 is obtained by the method described in Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

The focus state detecting means 1212, when it is judged that the light spot is focused on the first layer, or when the focus state of the light spot has not been determined, controls the equalization control means 1214, so that the read signal operation means will be read with the most suitable equalization characteristic for the first layer. The output voltage is waveform equalized.

The focus state detection device 1212, when it is determined that the light spot is focused on the second layer, controls the equalization control device 1214, and the focus state detection device performs waveform equalization on the output voltage of the readout signal calculation device 1208 with the most suitable equalization characteristics for the second layer change.

For example, as shown in FIG. 16A, in the balance control device 1214, two balance characteristics are prepared in advance. One of the characteristics is that the condition for obtaining the maximum increase is frequency 1/2T, gain G1, and the other is that the condition for obtaining the maximum increase is frequency 1/2T, gain G2 (G1<G2). When it is determined by the focus state detecting means 1212 that the light spot is focused on the first layer, one of the balance characteristics is selected, and when it is determined that the light spot is focused on the second layer, the other balance characteristic is selected.

Two equalization characteristics can also be shown in Figure 16B. One of the characteristics is that the condition for obtaining the maximum increase is frequency 1/2T, gain G1, and the other characteristic is that the condition for obtaining the maximum increase is frequency 1/3T, gain G1 .

After the equalization characteristic is selected in this way, it is also possible to further fine-tune the selected characteristic. The signal from the equalization control device 1214 is sent to the signal processing unit 1215, and the readout signal is output from the signal processing unit 1215. Jitter may be detected in the readout signal, and equalization characteristics may be finely adjusted based on the detected jitter. Alternatively, instead of using dithering, fine adjustment may be performed according to any one of BER (Byte Error Rate), resolution, and imbalance.

Fine-tuning of the equalization characteristics set for each layer can be performed by comparing indicators indicating the quality of the read signal, such as jitter, BER, resolution, and imbalance, with a specified threshold.

Jitter refers to the time deviation between the read signal and the original signal. If the writing conditions are the same, generally the smaller the jitter, the more accurate the read. Here, the determination of whether the most suitable equalization characteristic has been obtained may be set so that when the jitter is below a certain threshold, it can be considered that the most suitable equalization characteristic has been obtained.

BER (Byte Error Ratio) refers to the error occurrence rate of a read signal, and generally the smaller the BER, the more accurate the read. Here, the determination of whether the most suitable equalization characteristics have been obtained may be set so that when the BER is below a certain threshold, it can be considered that the most suitable equalization characteristics have been obtained.

Resolution refers to the ratio between the amplitude of the signal at the shortest or corresponding time interval in the read signal and the amplitude of the signal at the longest or corresponding time interval. If the writing conditions are the same, the general resolution The larger it is, the more accurate it can be read. Here, the determination of whether the most suitable equalization characteristic has been obtained may be set so that when the resolution is above a certain threshold, it can be considered that the most suitable equalization characteristic has been obtained.

Unbalance refers to the value of the secondary high-frequency component in the read signal. If the write conditions are the same, generally the smaller the unbalance, the more accurate the read. Here, the determination of whether the most suitable equalization characteristic has been obtained may be set so that when the resolution is below a certain threshold, it can be considered that the most suitable equalization characteristic has been obtained.

Here, jitter, BER, resolution, unbalance, etc. have been described as indicators indicating the quality of the read signal, but other indicators indicating the quality of the read signal, such as amplitude, C/N, bit error rate etc.

Here, the setting of the balance characteristic may be set to different values in the data area and the address area of the same information plane.

The above shows that the read signal characteristics of the address area or data area in each layer can be improved, and the signal quality of the address area or data area of the optical disc can be significantly improved.

(Embodiment 8)

Hereinafter, Embodiment 8 of the present invention will be described with reference to the drawings.

Description will be made using FIG. 13 .

In Fig. 13, 1301 denotes an optical disk, 1302 denotes a semiconductor laser, 1303 denotes a collimator lens, 1304 denotes a beam splitter, 1305 denotes a focusing device, 1306 denotes a condenser lens, 1307 denotes a light detection device, and 1308 denotes a read signal computing device , 1309 represents a focus control device, 1310 represents a tracking control device, 1311 represents an actuator, 1312 represents a focus state detection device, 1313 represents a laser drive device, and 1315 represents a signal processing unit.

The detection value of the focus state detection device 1312 is obtained by the method described in Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

The focus state detection means 1312 controls the focus control means 1309 to set the most suitable focus position for the first layer when it is determined that the light spot is focused on the first layer, or when the focus state of the light spot is not determined.

According to the detection value of the focus state detection device 1312, when it is determined that the light spot is focused on the second layer, the focus control device 1309 is controlled, and the focus state detection device sets the most suitable focus position for the second layer.

The set focus position is a position where the cross-section (beam waist) in the beam profile becomes the smallest as shown in FIG. 17, and is a position in a direction perpendicular to the information plane of the optical disc. After the focus position is selected in this way, it is also possible to further fine-tune the selected focus position. The signal from the readout signal computing unit 1308 is sent to the signal processing unit 1315, and the readout signal is output from the signal processing unit 1315, and jitter may be detected in the readout signal, and the focus control unit 1309 may be finely adjusted according to the detected jitter. Alternatively, instead of using dithering, fine adjustment may be performed according to any one of BER (Byte Error Rate), resolution, and imbalance.

Fine adjustment of the focus position set for each layer can be performed by comparing indicators indicating the quality of the read signal, such as jitter, BER, resolution, and imbalance, with a specified threshold.

Jitter refers to the time deviation between the read signal and the original signal. If the writing conditions are the same, generally the smaller the jitter, the more accurate the read. Here, the determination of whether the most suitable focus position has been obtained may be set such that when the jitter is below a certain threshold, it can be considered that the most suitable focus position has been obtained.

BER (Byte Error Ratio) refers to the error occurrence rate of a read signal, and generally the smaller the BER, the more accurate the read. Here, the determination of whether or not the most suitable focus position has been obtained may be set so that when the BER is below a certain threshold, it can be considered that the most suitable focus position has been obtained.

Resolution refers to the ratio between the amplitude of the signal at the shortest or corresponding time interval in the read signal and the amplitude of the signal at the longest or corresponding time interval. If the writing conditions are the same, the general resolution The larger it is, the more accurate it can be read. Here, the determination of whether the most suitable focus position has been obtained may be set so that when the resolution is above a certain threshold, it can be considered that the most suitable focus position has been obtained.

Unbalance refers to the value of the secondary high-frequency component in the read signal. If the write conditions are the same, generally the smaller the unbalance, the more accurate the read. Here, the determination of whether the most suitable focus position has been obtained may be set so that when the resolution is below a certain threshold, it can be considered that the most suitable focus position has been obtained.

Here, jitter, BER, resolution, unbalance, etc. have been described as indicators indicating the quality of the read signal, but other indicators indicating the quality of the read signal, such as amplitude, C/N, bit error rate etc.

Here, the setting of the focus position may be set to different values in the data area and the address area of the same information plane.

The above shows that the read signal characteristics of the address area or data area in each layer can be improved, and the signal quality of the address area or data area of the optical disc can be significantly improved.

(Embodiment 9)

Hereinafter, Embodiment 9 of the present invention will be described with reference to the drawings.

Description will be made using FIG. 14 .

In Fig. 14, 1401 denotes an optical disc, 1402 denotes a semiconductor laser, 1403 denotes a collimator lens, 1404 denotes a beam splitter, 1405 denotes a focusing device, 1406 denotes a condenser lens, 1407 denotes a light detection device, and 1408 denotes a read signal computing device , 1409 represents a focus control device, 1410 represents a tracking control device, 1411 represents an actuator, 1412 represents a focus state detection device, 1413 represents a laser drive device, and 1415 represents a signal processing unit.

The detection value of the focus state detection device 1412 is obtained by the method described in Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

The focus state detection means 1412 controls the tracking control means 1410 to set the most suitable tracking position for the first layer when it is determined that the light spot is focused on the first layer, or when the focus state of the light spot is not determined.

According to the detection value of the focus state detection device 1412, when it is determined that the light spot is focused on the second layer, the tracking control device 1410 is controlled, and the focus state detection device sets the most suitable tracking position for the second layer.

The set tracking position is a position (beam waist) at which the cross-section in the beam profile is minimized as shown in FIG. 18 , and is a position in a direction crossing the track in the information plane of the optical disc. After the tracking position is selected in this way, it is also possible to further fine-tune the selected tracking position. The signal from the readout signal computing unit 1408 is sent to the signal processing unit 1415, and the readout signal is output from the signal processing unit 1415, and jitter may be detected in the readout signal, and the tracking control unit 1410 may be fine-tuned based on the detected jitter. Alternatively, instead of using dithering, fine adjustment may be performed according to any one of BER (Byte Error Rate), resolution, and imbalance.

The fine adjustment of the tracking position set for each layer can be performed by comparing indicators indicating the quality of the read signal, such as jitter, BER, resolution, and imbalance, with a specified threshold.

Jitter refers to the time deviation between the read signal and the original signal. If the writing conditions are the same, generally the smaller the jitter, the more accurate the read. Here, the determination of whether the most suitable tracking position has been obtained may be set such that when the jitter is below a certain threshold, it can be considered that the most suitable tracking position has been obtained.

BER (Byte Error Ratio) refers to the error occurrence rate of a read signal, and generally the smaller the BER, the more accurate the read. Here, the determination of whether the most suitable tracking position has been obtained may be set so that when the BER is below a certain threshold, it can be considered that the most suitable tracking position has been obtained.

Resolution refers to the ratio between the amplitude of the signal at the shortest or corresponding time interval in the read signal and the amplitude of the signal at the longest or corresponding time interval. If the writing conditions are the same, the general resolution The larger it is, the more accurate it can be read. Here, the determination of whether the most suitable tracking position has been obtained may be set such that when the resolution is above a certain threshold, it can be considered that the most suitable tracking position has been obtained.

Unbalance refers to the value of the secondary high-frequency component in the read signal. If the write conditions are the same, generally the smaller the unbalance, the more accurate the read. Here, the determination of whether the most suitable tracking position has been obtained may be set such that when the resolution is below a certain threshold, it can be considered that the most suitable tracking position has been obtained.

Here, jitter, BER, resolution, unbalance, etc. have been described as indicators indicating the quality of the read signal, but other indicators indicating the quality of the read signal, such as amplitude, C/N, bit error rate etc.

Here, the setting of the tracking position may be set to different values in the data area and the address area of the same information plane.

The above shows that the read signal characteristics of the address area or data area in each layer can be improved, and the signal quality of the address area or data area of the optical disc can be significantly improved.

(Embodiment 10)

Hereinafter, Embodiment 10 of the present invention will be described with reference to the drawings.

Description will be made using FIG. 15 .

In Fig. 15, 1501 denotes an optical disk, 1502 denotes a semiconductor laser, 1503 denotes a collimator lens, 1504 denotes a beam splitter, 1505 denotes a focusing device, 1506 denotes a condenser lens, 1507 denotes a light detection device, and 1508 denotes a read signal computing device , 1509 represents a focus control device, 1510 represents a tracking control device, 1511 represents an actuator, 1512 represents a focus state detection device, 1513 represents a laser drive device, 1515 represents a tilt control device, and 1516 represents a signal processing unit.

The detection value of the focus state detection device 1512 is obtained by the method described in Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

The focus state detecting means 1512 controls the inclination control means 1515 to set the most suitable inclination position for the first layer when it is determined that the light spot is focused on the first layer, or when the focus state of the light spot is not determined.

According to the detection value of the focus state detection device 1512, when it is determined that the light spot is focused on the second layer, the tilt control device 1515 is controlled, and the focus state detection device sets the most suitable tilt position for the second layer.

The set tilt position is the angle formed by the information surface of the optical disc and the optical axis of the laser beam. After the inclination position is selected in this way, it is also possible to further fine-tune the selected inclination position. The signal from the read signal arithmetic unit 1508 is sent to the signal processing unit 1516, and the read signal is output from the signal processing unit 1516. It is also possible to detect jitter in the read signal, and finely adjust the tilt control unit 1515 based on the detected jitter. Alternatively, instead of using dithering, fine adjustment may be performed according to any one of BER (Byte Error Rate), resolution, and imbalance.

If the tilt is distinguished in direction, there are tilts in the radial direction perpendicular to the track and tilts in the tangential direction parallel to the track.

The radial inclination (R inclination) will be described using FIG. 19 .

In FIG. 19, 1901 denotes an optical disk, 1902 denotes an optical head, and 1903 denotes a tilt table. In the radial tilt (R tilt), there are disc R tilt 1904 due to disc curvature, surface wobble caused by disc rotation, inclination of the writing surface of the above-mentioned optical disc 1901 with respect to the optical axis of the light beam, mounting of the optical head The error and the tilt of the tilt table result in the drive R tilting 1905. Essentially, no distinction is made between the disc R tilt and the drive R tilt, and both are called R tilt.

Tangential tilt (T tilt) will be described using FIG. 20 .

In FIG. 20, 2001 denotes an optical disk, 2002 denotes an optical head, and 2003 denotes a tilt table. In the tangential tilt (T tilt), there are disc T tilt 2004 due to disc rotational vibration, surface accuracy error of the disc, etc., inclination of the writing surface of the above-mentioned optical disc 2001 with respect to the optical axis of the light beam, mounting of the optical head The error and the tilt of the tilt table are generated by the drive T tilt 2005. Essentially, no distinction is made between the disc T tilt and the drive T tilt, and both are called tilt.

The fine adjustment of the R and T tilt positions set for each layer can be performed by comparing indicators indicating the quality of the read signal, such as jitter, BER, resolution, and imbalance, with specified thresholds.

Jitter refers to the time deviation between the read signal and the original signal. If the writing conditions are the same, generally the smaller the jitter, the more accurate the read. Here, the determination of whether the most suitable R and T inclination positions have been obtained may be set so that when the jitter is below a certain threshold, it can be considered that the most suitable R and T inclination positions have been obtained.

BER (Byte Error Ratio) refers to the error occurrence rate of a read signal, and generally the smaller the BER, the more accurate the read. Here, the determination of whether the most suitable R and T inclination positions have been obtained may be set such that when the BER is below a certain threshold, it can be considered that the most suitable R and T inclination positions have been obtained.

Resolution refers to the ratio between the amplitude of the signal at the shortest or corresponding time interval in the read signal and the amplitude of the signal at the longest or corresponding time interval. If the writing conditions are the same, the general resolution The larger it is, the more accurate it can be read. Here, the determination of whether the most suitable R and T inclination positions have been obtained may be set so that when the resolution is above a certain threshold, it can be considered that the most suitable R and T inclination positions have been obtained.

Unbalance refers to the value of the secondary high-frequency component in the read signal. If the write conditions are the same, generally the smaller the unbalance, the more accurate the read. Here, the determination of whether the most suitable R and T inclination positions have been obtained may be set such that when the resolution is below a certain threshold, it can be considered that the most suitable R and T inclination positions have been obtained.

Here, jitter, BER, resolution, unbalance, etc. have been described as indicators indicating the quality of the read signal, but other indicators indicating the quality of the read signal, such as amplitude, C/N, bit error rate etc.

The above shows that the read signal characteristics of the address area or data area in each layer can be improved, and the signal quality of the address area or data area of the optical disc can be significantly improved.

As described above, according to the optical disc, optical disc device and optical disc readout method of the present invention, in an optical disc having a plurality of information surfaces, whether the data area is in a written state or an unwritten state, it is possible to determine whether the light spot is in focus. On the information plane, improving the read signal quality of the address area and the data area on multiple information planes can significantly improve the signal quality of the read address area or data area of the optical disc.

(Embodiment 11)

Here, the principle of writing to a phase-change optical disc will be described using FIG. 23 . In the phase-change optical disc device, the storage thin film on the substrate is heated and heated by laser irradiation, causing a crystallographic phase change in the structure, and writing and erasing of information are performed. In FIG. 23, the vertical axis 2301 represents the laser power, and the horizontal axis represents the time axis or the position of the rotating optical disc. By irradiating semiconductor laser light into the optical disc medium with two or more types of laser power mainly including peak power 2302 for crystallization of the crystal part and bias power 2303 for crystallization of the amorphous part, the optical disc medium is formed. A mark 2304 (amorphous portion) and a void 2305 (crystal portion) sandwiching the mark are written. The written marks and spaces have different reflectances, and the difference in reflectance between the marks and spaces is detected by a light spot focused on the optical disk and output as a signal to read information.

Also, as the storage density increases, the length of the written mark may deviate from the regular position of the written signal due to thermal interference between the written marks and the written marks. In order to compensate for this offset, an adaptive write compensation technique has been developed. The adaptive writing compensation technique will be described using FIG. 24 .

In FIG. 24 , 2401 indicates a case where the front gap is short, and 2402 indicates a case where the front gap is long. When the front space is short, when writing is performed with a normal write signal 2407, the leading end of the mark is longer than the normal position by a length 2403 of +S3 due to the influence of thermal disturbance. For compensation, by retreating the position of the first pulse of the write pulse by a length 2405 of -S3, a mark 2408 can be written at the normal position formed after write compensation. Also, when the front space is long, similarly, when writing is performed with the normal write signal 2407, the leading end of the mark is shorter than the normal position by -S6 length 2404 due to the influence of thermal disturbance. For compensation, by advancing the position of the first pulse of the write pulse by a length 2406 of +S6, it is possible to write a mark 2408 at a regular position formed after write compensation. Through such an adaptive writing compensation technology, the interference during reading between marks/spaces of different lengths can be suppressed, and the signal quality can be improved.

FIG. 25 is an eye diagram showing a write signal when the write compensation technique described above is employed. By introducing adaptive write compensation technology, a clear eye diagram can be obtained. These marks and spaces are used in a concave-convex writing technique for writing on both tracks of the step portion and the groove portion of the guide groove of the optical disc.

However, the above-mentioned prior art has the following problems. That is, in the case of the existing double-sided optical storage medium, since it is configured to read the written information or write information by irradiating light beams from the upper side and the lower side of the storage medium, it is printed as a label for identifying the storage medium. There are few places and it is difficult to deal with them. In addition, when reading a double-sided optical storage medium, in a device with only one optical head, it is necessary to take out the optical storage medium and reverse its surface, so continuous reading cannot be performed. Want to carry out automatically, it is necessary to arrange 2 bald heads up and down, increased device, and increased cost.

The writing and reading characteristics when a signal is written on an optical disc having the optical characteristics shown in FIG. 3 will be described below. FIG. 26 is a graph showing the measurement results of a trial production of an optical disc having the optical characteristics shown in FIG. 3 . In the laser power, the phase-change memory material is amorphized from the crystalline state, the peak power of writing is taken as the horizontal axis, and the C/N value of the read signal is taken as the vertical axis.

In Fig. 26, a trial production is made of an optical disk in which a phase-change memory film is formed on two substrates with a substrate thickness of 0.58mm and pasted with an adhesive layer of 0.04mm in between. change, a written mark is formed, and the C/N value of the read signal when the formed written mark is read is measured and shown in FIG. 26 .

2601 indicates a C/N value obtained when reading information written on the first information plane. 2602 indicates a C/N value obtained when reading information written on the second information plane.

When writing information on an optical disc, the C/N of the written signal deteriorates due to defocusing and off-tracking due to surface wobble and eccentricity of the optical disc, vibrations and shocks applied to the device from the outside, etc. Also, the inclination of the optical axis between the optical disc and the light beam degrades the C/N of the write signal. The curvature of the disc may also change due to environmental changes such as humidity. In addition, due to errors in the manufacture of the optical head, aging over time also occurs. Therefore, in order to allow the device to reliably and well write the information to be written on the optical disc, if the degradation of C/N caused by the above-mentioned various reasons is considered, the C/N limit of the write signal is about 45dB.

The following can be explained from FIG. 26 . When the peak power is 12mW or higher on the first information plane, a C/N value of 45dB or higher is displayed, and on the second information plane, a C/N value of 45dB or higher is displayed when the peak power is 13mW or higher. This indicates that the write sensitivity between the first information plane and the second information plane is different.

Furthermore, it is expected from the figure that the C/N of the writing signal can be further increased by further increasing the peak power on which information plane.

However, if the peak power of the laser is increased, it will become the main cause of reducing the life of the laser, or increasing the power consumption, or increasing the damage to the storage film accumulated on the storage film during repeated writing, so it is desirable Write power as low as possible.

As mentioned above, in order to ensure good signal quality on various information planes and solve the above-mentioned problems, it is necessary to set the peak laser power for writing on the first information plane and the second information plane for each information plane.

The following describes how to determine the power to be set. The set peak power can be determined from the C/N value of the written signal by writing the repetition signal of the shortest mark and space in the written data.

For example, the peak power at which the C/N value of the write signal is 50 dB is set as the peak power. Such obtained C/N values are learned on the first information plane and the second information plane.

In addition to the C/N value, the peak power can also be determined by measuring the jitter of the writing signal. In this case, the written data can be identified by measuring the jitter of the signal in which randomized marks and spaces are written.

The peak power determined as above is stored in advance. When actually writing data, according to the result of detecting the first information plane and the second information plane by the focus state detection device, the data is written according to the set peak power of each information plane. Good information quality is obtained, and the semiconductor laser can be driven with a sufficiently large laser output.

As mentioned above, it is easy to print the label, and it can automatically write and read by using one optical head, providing an optical storage medium that is easily interchangeable with only one information surface, and can be used on an optical storage medium with two information surfaces. An optical disc device for writing and reading on a storage medium.

Also, when writing and reading on the second information plane, reading is performed through the first information plane.

The amount of light reaching the second layer is different when the state of the first information plane is a written state (a mixture of crystalline and amorphous states) and an unwritten state (only a crystalline state). For example, when writing on the second layer, when the state of the first layer next to the second layer to be written is an unwritten state (only a crystalline state), the transmittance of the first layer is shown in Figure 3 is 50%, when the state of the first layer next to the second layer to be written is partially or completely in the written state, according to the writing state of the first layer in the passing area of the light spot reaching the second layer The track width increases the transmittance.

Embodiment 11 of the present invention will be described below with reference to the drawings. FIG. 30 is a diagram showing the configuration of an optical disc 1701 in this embodiment.

In FIG. 30, 3002 denotes a read-only area provided on the inner periphery of the optical disc 3001, 3004 denotes pre-pits formed in advance in the read-only area, and 3005 denotes the track pitch of the pre-pit. 3003 denotes a rewritable area arranged outside the read-only area. 3005 in the rewritable area indicates a groove track of a groove-shaped track, and 3006 indicates a step track of an inter-groove track. 3007 denotes marks formed in the groove track.

In the read-only area 3002, information obtained by modulating information indicating whether or not the light spot is focused on any one of the plurality of information planes is written in the pre-pit in advance.

Also, the rewritable area and the read-only area are formed on any one of the plurality of information planes.

In this way, the focus state monitoring device can identify the information plane on which the light spot is focused among the plurality of information planes.

(Embodiment 12)

Hereinafter, Embodiment 12 of the present invention will be described with reference to the drawings. Description will be made using FIG. 27 .

In Fig. 27, 2701 denotes an optical disk, 2702 denotes a semiconductor laser, 2703 denotes a collimating lens, 2704 denotes a beam splitter, 2705 denotes a focusing device, 2706 denotes a condenser lens, 2707 denotes a light detecting device, and 2708 denotes a readout signal computing device , 2709 represents a focus control device, 2710 represents a tracking control device, 2711 represents an actuator, 2712 represents a focus state detection device, 2713 represents a laser drive device, 2715 represents a writing control device, and 2717 represents a signal processing unit.

The detection value of the focus state detection device 2712 is obtained by the method described in Embodiment 2, Embodiment 3 and Embodiment 4 of the present invention.

The focus state detection unit 2712 controls the write control unit 2715 to set the most suitable write compensation value for the first layer when it is determined that the light spot is focused on the first layer, or when the focus state of the light spot is not determined. According to the detection value of the focus state detection device 2712, when it is determined that the light spot is focused on the second layer, the write control device 2715 is controlled, and the focus state detection device sets the most suitable write compensation value for the second layer.

A method of setting an optimum write compensation value will be described using FIGS. 28 and 29 . In Fig. 29, 2901 denotes an NRZI signal. 2902 indicates written marks and spaces before writing compensation written based on the above-mentioned NRZI signal 2901 . The writing marks and spaces 2902 are edge-shifted from the reference edge of the NRZI signal due to thermal disturbance or the like.

In order to eliminate this edge shift, the positions of the first pulse and the last pulse of the pulse waveform at the time of writing are changed according to the length of the written mark and the length of the space before or after the above-mentioned written mark.

FIG. 28 shows an example of a combination table. 2801 is a value of Tsfp indicating the position of the first pulse determined by the written mark length and the pre-space length. For example, when the length of the written mark is 3T and the length of the pre-space is 3T, Tsfp is a. 2802 is a value of Telp indicating the final pulse position determined by the written mark length and the post-space length. For example, Telp is q when the length of the written mark is 3T and the length of the back space is 3T.

Each value of a to af written in the compensation table is determined by optimizing the signal quality of the written signal in each layer.

The writing compensation control means stores the setting value of the writing compensation table in advance, and sets the writing compensation value based on the detection value of the focus state detecting means.

The above shows that by setting the optimum writing power and writing compensation table for each layer, the writing and reading signal characteristics of the data area can be improved, and the reliability of the optical disc with multiple information planes can be significantly improved.

Also, when writing and reading on the second information plane, reading is performed through the first information plane.

The amount of light reaching the second layer is different when the state of the first information plane is a written state (a mixture of crystalline and amorphous states) and an unwritten state (only a crystalline state).

For example, when writing on the second layer, when the state of the first layer next to the second layer to be written is an unwritten state (only a crystalline state), the transmittance of the first layer is shown in Figure 3 is 50%, when the state of the first layer next to the second layer to be written is partially or completely in the written state, according to the writing state of the first layer in the passing area of the light spot reaching the second layer The track width increases the transmittance.

As described above, according to the optical disc device of the present invention, in an optical disc having a plurality of information planes, whether the data area is in a written state or in an unwritten state, it is possible to determine the information plane on which the light spot is focused. Improving the writing and reading signal quality of the data area can significantly improve the reliability of the optical disc with multiple information planes.

(Embodiment 13)

Fig. 31 shows calculation results of the written mark density of the first layer and the skid track ratio of the second layer. The calculated wavelength is 660 nm and the NA is 0.6. In FIG. 31, the horizontal axis represents the density of written marks. When the mark density ratio = 0, it corresponds to an unwritten state. If the written mark density in layer 1 is increased, the slip track strength in layer 2 will decrease. Since the intensity of the skid track decreases, when the power emitted from the semiconductor laser is the same, the light intensity of the second layer will decrease by the amount of the above-mentioned skid track ratio, and it is necessary to increase the output power of the semiconductor laser.

Considering this situation, the power (peak power and bias power) written to the second information plane of the optical disc is determined according to the mark density of the first layer, which can improve the read signal quality of the optical disc.

The configuration of the learning area will be described below using FIG. 34 . Fig. 34 shows the configurations of the optical disks of the first layer and the second layer.

3401 denotes the first layer substrate on the incident side of the light spot, and 3402 denotes the second layer substrate on which the light spot transmitted through the first layer substrate is focused. Layer 1 and Layer 2 are configured in parallel up and down.

The learning region is arranged on the inner and outer peripheral portions of the first-layer substrate as in 3403 in the first layer. Similarly, in the second layer, as in 3404, they are disposed on the inner and outer peripheral portions of the second-layer substrate.

A user data writing area for writing user data between the learning areas of the inner peripheral portion and the outer peripheral portion is arranged on the first layer substrate as in 3405 and on the second layer substrate as in 3406 .

Here, the positions of the learning regions of the first layer substrate and the second layer substrate from the center of the optical disc are substantially the same.

The method of obtaining the writing power of the second layer for the three states of the first layer will be described below.

(1) When the learning area of the first layer is an unwritten area

(2) When the learning area on the first floor is partially written

(3) When all the learning areas on the first floor are written

First, the method of obtaining the writing power of the second layer when all the study areas of the first layer in (1) are unwritten areas will be described. Hereinafter, description will be made using the flowchart of FIG. 32 .

In the learning area of the first layer, if the learning area of the first layer is unwritten, or if there is a certain area which is preliminarily determined to be unwritten, the said area is searched.

Let the light head turn on the focus and track on the second layer of the above-mentioned area. Confirm that the first layer is in the unwritten state, and obtain the writing power of the second layer. There are various methods of obtaining writing power, for example, the above-mentioned 3T method. Assume that the peak power on the step track is Ppl0, the bias power on the step track is Pbl0, the peak power on the groove track is Ppg0, and the bias power on the groove track is Pbg0, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

Then turn on focus and turn on tracking for the study area of layer 1. In order to put the first layer in the writing state, dummy data is written in a certain area of the learning area of the first layer. Turn on focus and turn on tracking for the layer 2 where the above dummy data is written. Confirm that the first layer is in the written state, and obtain the writing power of the second layer.

Assume that the peak power on the step track is Ppl1, the bias power on the step track is Pbl1, the peak power on the groove track is Ppg1, and the bias power on the groove track is Pbg1, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

Next, a method for obtaining the writing power of the second layer when part of the learning region of the first layer in (2) is written will be described. Hereinafter, description will be made using the flowchart of FIG. 32 .

In the learning area of the first layer, when the learning area of the first layer is partially written, the above-mentioned learning area is searched. Turn on focus and turn on tracking for layer 1 above. Confirm that there is a writing area in the learning area of the first layer, delete the data in a certain area of the learning area of the first layer, and make a certain area of the learning area unwritten. Turn on focus and turn on tracking for the optical head on the second layer of the above-mentioned unwritten area. Confirm that the first layer is in the unwritten state, and obtain the writing power of the second layer. There are various methods of obtaining writing power, for example, the above-mentioned 3T method.

Assume that the peak power on the step track is Ppl0, the bias power on the step track is Pbl0, the peak power on the groove track is Ppg0, and the bias power on the groove track is Pbg0, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

Then turn on focus and turn on tracking for the study area of layer 1. In order to put the first layer in the writing state, dummy data is written in a certain area of the learning area of the first layer. Turn on focus and turn on tracking for the layer 2 where the above dummy data is written. Confirm that the first layer is in the written state, and obtain the writing power of the second layer.

Assume that the peak power on the step track is Ppl1, the bias power on the step track is Pbl1, the peak power on the groove track is Ppg1, and the bias power on the groove track is Pbg1, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

The method of obtaining the writing power of the second layer when all the learning regions of the first layer in (3) are written will be described below. Hereinafter, description will be made using the flowchart of FIG. 32 .

In the learning area of the first layer, if all the learning areas of the first layer have been written, the above-mentioned learning area is searched. Turn on focus and turn on tracking for layer 1 above.

Confirm that there is a writing area in the learning area of the first layer, delete the data in a certain area of the learning area of the first layer, and make a certain area of the learning area unwritten.

Turn on focus and turn on tracking for the optical head on the second layer of the above-mentioned unwritten area. Confirm that the first layer is in the unwritten state, and obtain the writing power of the second layer. There are various methods of obtaining writing power, for example, the above-mentioned 3T method.

Assume that the peak power on the step track is Ppl0, the bias power on the step track is Pbl0, the peak power on the groove track is Ppg0, and the bias power on the groove track is Pbg0, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

Then turn on focus and turn on tracking for the study area of layer 1. When the written area of layer 1 is known in advance, the above written area is searched. Turn on focus, turn on tracking for layer 2 of the above written area. Confirm that the first layer is in the written state, and obtain the writing power of the second layer.

Assume that the peak power on the step track is Ppl1, the bias power on the step track is Pbl1, the peak power on the groove track is Ppg1, and the bias power on the groove track is Pbg1, and the learning result is stored in the memory. Here, although the write power is limited to two types of power, peak power and bias power, other powers can also be learned and stored in the memory.

Here, although (1), (2), and (3) determine the initial state of the learning region of the first layer, the determination of the initial state may be omitted to simplify the apparatus. In this case, the method for obtaining the writing power of the second layer may be the method of (2) for partial writing.

The following describes the case of writing in the user data area of the second layer. When writing in the user data area of the second layer, when the area through which the light spot of the first layer passes is in an unwritten state, the writing power adopts the peak power Ppl0 on the step track and the bias power Pb0 on the groove track. The peak power is Ppg0, and the bias power is Pb0 for writing.

When writing in the user data area of the second layer, when the area through which the light spot of the first layer passes is in the writing state, the writing power adopts the peak power Ppl1 on the step track, the bias power Pb1, and the peak power Pb1 on the groove track. The peak power is Ppg1, and the bias power is Pbg1 for writing.

When writing in the user data area of the second layer, the area through which the light spot of the first layer passes is mixed with the unwritten state and the written state, or the writing mark density is between the unwritten state and the written state. When the write power is one of the peak power Ppl0 or Ppl1 on the step track, one of the bias power Pbl0 or Pbl1, the peak power on the groove track is Ppg0 or Ppg1, and the bias power is Pbg0 or Ppg1 for writing Just enter.

Or, when writing in the user data area of the second layer, the area through which the light spot of the first layer passes is mixed with an unwritten state and a written state, or the writing mark density is between the unwritten and written states. Between hours, the writing power adopts Ppl2 interpolated between Ppl0 and Ppl1 for the peak power on the step track, Pbl2 interpolated between Pbl0 and Pbl1 for the bias power, and Ppg0 and Ppg1 interpolated for the peak power on the groove track Ppg2, Ppg2 whose bias power is interpolated between Pbg0 and Ppg1 can be written.

The method of the above-mentioned interpolation will be described. For interpolation, the average value of the two set values can be used as the interpolation value as shown in the following formula.

(Ppl0+Ppl1)/2

(Pbl0+Pbl1)/2

(Ppg0+Ppg1)/2

(Pbg0+Pbg1)/2

In addition, instead of an average value, a weighted value may be used.

Ppl0×y1+Ppl1×y2

In the formula, y1 and y2 are positive real numbers such that y1+y2=1.

y1 and y2 are obtained according to the writing mark density of the light spot through the first layer.

Here, although the peak power of the step track is used for illustration, the bias power, or the peak power and bias power of the groove track can also be obtained by the same method.

As mentioned above, when writing in the second layer, the writing power of the second layer is set according to the writing mark density of the light spot penetrating the first layer, which can improve the writing of data areas on multiple information planes. The quality of the read signal can significantly improve the reliability of optical discs with multiple information planes.

Fig. 31 shows calculation results of the written mark density of the first layer and the skid track ratio of the second layer. The calculated wavelength is 660 nm and the NA is 0.6. In FIG. 31, the horizontal axis represents the density of written marks. When the mark density ratio = 0, it corresponds to an unwritten state. If the written mark density in layer 1 is increased, the slip track strength in layer 2 will decrease. Since the intensity of the skid track decreases, when the power emitted from the semiconductor laser is the same, the light intensity of the second layer will decrease by the amount of the above-mentioned skid track ratio, and it is necessary to increase the output power of the semiconductor laser. Due to the different emission powers of semiconductor lasers, the writing compensation table written on the second information plane of the optical disc is determined according to the mark density of the first layer, which can improve the readout signal quality of the optical disc.

The method of obtaining the writing compensation table of the second layer for the three states of the first layer will be described below.

(1) When the learning area of the first layer is an unwritten area

(2) When the learning area on the first floor is partially written

(3) When all the learning areas on the first floor are written

First, the method of obtaining the writing compensation table of the second layer when all the learning areas of the first layer in (1) are unwritten areas will be described. Hereinafter, description will be made using the flowchart of FIG. 33 .

In the learning area of the first layer, if the learning area of the first layer is unwritten, or if there is a certain area which is preliminarily determined to be unwritten, the said area is searched.

Let the light head turn on the focus and track on the second layer of the above-mentioned area. Confirm that layer 1 is in an unwritten state, and obtain the write compensation table for layer 2. There are various methods for obtaining the write compensation table, for example, the above-mentioned method with the smallest jitter.

Assume that the writing compensation table on the step track is Tl0, the writing compensation table on the groove track is Tg0, and the learning result is stored in the memory. Here, the number of write-in compensation tables is each value of a to af in the above-mentioned write-in compensation table, and the combination of the set values of each value written in the compensation table is collectively referred to as Tl0, Tg0.

Here, the case where the number of times of write compensation is 4 will be described as an example, and the same applies to cases where the number of times of write compensation is other than 4.

Then turn on focus and turn on tracking for the study area of layer 1. In order to put the first layer in the writing state, dummy data is written in a certain area of the learning area of the first layer. Turn on focus and turn on tracking for the layer 2 where the above dummy data is written. Confirm that layer 1 is in the written state, and obtain the write compensation table for layer 2. Assume that the writing compensation table on the step track is Tl1, the writing compensation table on the groove track is Tg1, and the learning results are stored in the memory.

Next, the method of obtaining the writing compensation table of the second layer when part of the learning area of the first layer in (2) is written will be described. Hereinafter, description will be made using the flowchart of FIG. 33 .

In the learning area of the first layer, when the learning area of the first layer is partially written, the above-mentioned learning area is searched. Turn on focus and turn on tracking for layer 1 above.

Confirm that there is a writing area in the learning area of the first layer, delete the data in a certain area of the learning area of the first layer, and make a certain area of the learning area unwritten.

Turn on focus and turn on tracking for the optical head on the second layer of the above-mentioned unwritten area. Confirm that layer 1 is in an unwritten state, and obtain the write compensation table for layer 2. There are various methods for obtaining the write compensation table, for example, the above-mentioned method with the smallest jitter.

Assume that the writing compensation table on the step track is Tl0, the writing compensation table on the groove track is Tg0, and the learning result is stored in the memory.

Then turn on focus and turn on tracking for the study area of layer 1. In order to put the first layer in the writing state, dummy data is written in a certain area of the learning area of the first layer. Turn on focus and turn on tracking for the layer 2 where the above dummy data is written. Confirm that layer 1 is in the written state, and obtain the write compensation table for layer 2. Assume that the writing compensation table on the step track is Tl1, the writing compensation table on the groove track is Tg1, and the learning results are stored in the memory.

The method of obtaining the writing compensation table of the second layer when all the learning areas of the first layer in (3) are written will be described below. Hereinafter, description will be made using the flowchart of FIG. 33 .

In the learning area of the first layer, if all the learning areas of the first layer have been written, the above-mentioned learning area is searched. Turn on focus and turn on tracking for layer 1 above. Confirm that there is a writing area in the learning area of the first layer, delete the data in a certain area of the learning area of the first layer, and make a certain area of the learning area unwritten.

Turn on focus and turn on tracking for the optical head on the second layer of the above-mentioned unwritten area. Confirm that layer 1 is in an unwritten state, and obtain the write compensation table for layer 2. There are various methods for obtaining the write compensation table, for example, the above-mentioned method with the smallest jitter. Assume that the writing compensation table on the step track is Tl0, the writing compensation table on the groove track is Tg0, and the learning result is stored in the memory.

Then turn on focus and turn on tracking for the study area of layer 1. When the written area of layer 1 is known in advance, the above written area is searched. Turn on focus, turn on tracking for layer 2 of the above written area. Confirm that layer 1 is in the written state, and obtain the write compensation table for layer 2. Assume that the writing compensation table on the step track is Tl1, the writing compensation table on the groove track is Tg1, and the learning results are stored in the memory.

Here, although (1), (2), and (3) determine the initial state of the learning region of the first layer, the determination of the initial state may be omitted to simplify the apparatus. In this case, the method for obtaining the writing compensation table of the second layer may be the method of (2) for partially writing.

The following describes the case of writing in the user data area of the second layer. When writing in the user data area of the second layer, when the area through which the light spot of the first layer passes is in an unwritten state, the write compensation table uses Tl0 on the step track and Tg1 on the groove track to write. Can.

When writing in the user data area of the second layer, when the area through which the light spot of the first layer passes is roughly written, the write compensation table uses Tl1 on the step track and Tg1 on the groove track to write. Can.

When writing in the user data area of the second layer, the area through which the light spot of the first layer passes is mixed with the unwritten state and the written state, or the writing mark density is between the unwritten state and the written state. When writing the compensation table, one of Tl0 or Tl1 on the step track and Tg0 or Tg1 on the groove track can be used for writing.

Or, when writing in the user data area of the second layer, the area through which the light spot of the first layer passes is mixed with an unwritten state and a written state, or the writing mark density is between the unwritten and written states. When writing in the compensation table, Tl2 interpolated between Tl0 and Tl1 on the step track and Tg2 interpolated between Tg0 and Tg1 on the groove track can be used for writing.

The above interpolation method will be described using FIG.36. In FIG. 36 , 3605 denotes a write compensation table T10 obtained when the first layer is in an unwritten state, and 3606 denotes a write compensation table T11 obtained when the first layer is in a written state.

In each table of the 3605, there are 32 setting values of A1 to Af1 according to combinations of marks or spaces. In each table of 3606, there are 32 setting values of A2 to Af2 according to the combination of marks or spaces.

The set positions of the combination of marks and spaces, for example, A1 and A2 are the set positions when the length of the front space is 3T and the length of the written mark is 3T.

When interpolating, the average value of the two setting values as shown in the following formula can be used as the interpolation between the same positions of the setting positions of these combinations.

(A1+A2)/2

(B1+B2)/2

...................................

(Af1+Af2)/2

In addition, instead of an average value, a weighted value may be used.

A1×z1+A2×z2

B1×z1+B2×z2

...................................

Af1×z1+Af2×z2

In the formula, z1 and z2 are positive real numbers such that z1+z2=1.

z1 and z2 are obtained according to the writing mark density of the light spot through the first layer.

Here, although the writing compensation tables T10 and T11 of the step track are described, the same method can be used for the groove track.

As mentioned above, when writing in the second layer, the writing compensation table of the second layer is set according to the writing mark density of the first layer through which the light spot penetrates, and the writing of the data area can be improved on multiple information planes. The quality of input and output signals can be improved significantly, and the reliability of optical discs with multiple information planes can be significantly improved.

(Embodiment 14)

Hereinafter, Embodiment 14 of the present invention will be described with reference to the drawings. Fig. 35 is a diagram showing the structure of an optical disk.

In FIG. 35, 3501 denotes the first-layer substrate, 3502 denotes the first-layer user data storage area, 3503 denotes the first-layer learning area, 3504 denotes a write-prohibited area set in the first-layer learning area 3503, and 3505 denotes a A read-only area is arranged further inside the first-layer learning area in the inner periphery.

The configuration of the write-prohibited area will be described in detail. When the above-mentioned write-prohibited area is written into the second layer, the optimum write power or write compensation table for the second layer is different depending on the writing mark density of the light spot penetrating through the first layer area.

For this reason, it is necessary to learn the writing power or the writing compensation table in advance according to the writing mark density.

As shown in FIG. 35 , by setting a write-prohibited area in advance, it is possible to quickly learn that the first layer is in an unwritten state when writing to the second layer. When there is no write-prohibited area, as described earlier, it must be determined

(1) When the learning area of the first layer is an unwritten area

(2) When the learning area on the first floor is partially written

(3) When all the learning areas on the first floor are written

When it is known in advance that it is an unwritten area, it corresponds to the case where there is an unwritten area in the flowchart of FIG. 32 .

At this time, since the unwritten state is known, there is no need to delete data in a part of the first layer, and the learning time can be shortened.

(Embodiment 15)

Hereinafter, Embodiment 15 of the present invention will be described with reference to the drawings. Fig. 35 is a diagram showing the structure of an optical disk.

In FIG. 35, 3501 denotes the first-layer substrate, 3502 denotes the first-layer user data storage area, 3503 denotes the first-layer learning area, 3504 denotes a write-prohibited area set in the first-layer learning area 3503, and 3505 denotes a A read-only area is arranged further inside the first-layer learning area in the inner periphery.

In the read-only area, various information of the optical disc is written in the form of pre-pit modulation. Information on the start radial position and the end radial position of the above-mentioned write-prohibited area is stored in the read-only area.

Alternatively, information on the start address and end address of the above-mentioned write-prohibited area is stored in the read-only area.

In this way, the area that cannot be written in the optical disc can be known in advance, and when the learning of the writing power and writing compensation is performed in the learning area of the second layer, when the light spot penetrates the writing prohibited area of the first layer, it can be predicted in advance. Know that layer 1 is in an unwritten state.

In this way, in the learning of the writing power and the learning of the writing compensation, the first layer is kept in an unwritten state, so that it is unnecessary to delete the written data of the first layer, and the learning time can be shortened.

The above shows that by setting the optimal writing power and writing compensation table in each layer, the writing and reading signal quality of the data area can be improved, and the reliability of the optical disc with multiple information surfaces can be significantly improved. .

As described above, according to the optical disc, optical disc device and optical disc readout method of the present invention, in an optical disc having a plurality of information surfaces, whether the data area is in a written state or an unwritten state, it is possible to determine whether the light spot is in focus. On the information plane, improving the writing and reading signal quality of the data area on multiple information planes can significantly improve the reliability of an optical disc with multiple information planes.

Claims (10)

1. optical disc apparatus comprises:

Drive the laser driving apparatus of semiconductor laser; On cd side, focus on the beams focusing device of irradiation by the output light of the semiconductor laser that described laser driving apparatus drove; Control is by the focus control device of the focal position of beams focusing point on described cd side that described focalizer focused on; Control is by the follow-up control apparatus of the position on the track of beams focusing point in described cd side of described focalizer focusing; Receive described focusing light beam from the catoptrical optical detection device on the described cd side; The focus state pick-up unit of the beams focusing state that detection is shone on the information faces of the ground floor of described CD or the second layer; To from write signal clipping lever voltage based on the reproduction waveform that writes track of data area, deduct as from the result of the groove level voltage of the signal of the guiding groove of write state not, be just or negative computing, operation result based on plus or minus, differentiate the arithmetic unit that light beam focuses on which layer of the ground floor and the second layer, according to the operation result control laser drive of the detected value of described focus state pick-up unit and arithmetic unit, set light beam when reproducing or write fashionable emission light quantity at the information faces of the ground floor of described CD and the second layer.

2. optical disc apparatus according to claim 1 is characterized in that:

The detected value that is detected by the focus state pick-up unit is a detected value set by described optical detection device detection many places on 1 week of the continuous track on the CD, preformed concavo-convex pre-pit.

3. optical disc apparatus according to claim 1 is characterized in that:

The detected value that is detected by the focus state pick-up unit is the detected value that is detected preformed guiding groove on CD by described optical detection device.

4. optical disc apparatus according to claim 1 is characterized in that:

The detected value that is detected by the focus state pick-up unit is by detected detected value in the storage signal of described optical detection device from be written to the optical disc data zone.

5. optical disc apparatus according to claim 1 is characterized in that:

The detected value that is detected by described focus state pick-up unit is the detected value that the signal that writes in advance in the reproduction reserved area of CD is detected by described optical detection device.

6. writing/reproducting method of a CD comprises step:

Drive the Laser Driven step of semiconductor laser, on cd side, focus on the beams focusing step of the output light that shines the semiconductor laser that is driven by described Laser Driven step, control is by the focus control step of the focal position of beams focusing point on described cd side that described focus steps focused on, control is by the tracking Control step of the position on the track of beams focusing point in described cd side of described focus steps focusing, the catoptrical light from the described cd side that receives the light beam of described focusing detects step, the focus state of the beams focusing state that detection is shone on a plurality of information faces of described CD detects step, from write signal clipping lever voltage based on the reproduction waveform that writes track of data area, deduct as from the result of the groove level voltage of the signal of the guiding groove of write state not, be just or negative computing, operation result based on plus or minus, differentiate the calculation step which information faces light beam focuses on, detect the detected value of step and the operation result control Laser Driven step of calculation step according to described focus state, set light beam when reproducing or write fashionable emission light quantity at each information faces of each described CD.

7, writing/reproducting method of a kind of CD comprises step:

Drive the Laser Driven step of semiconductor laser; On cd side, focus on the beams focusing step of the output light that shines the semiconductor laser that is driven by described Laser Driven step; Control is by the focus control step of the focal position of beams focusing point on described cd side that described focus steps focused on; Control is by the tracking Control step of the position on the track of beams focusing point in described cd side of described focus steps focusing; The catoptrical light from the described cd side that receives the light beam of described focusing detects step; The focus state of the beams focusing state that detection is shone on the information faces of the ground floor of described CD or the second layer detects step; To deducting from write signal clipping lever voltage as from the result of the groove level voltage of the signal of the guiding groove of write state not based on the reproduction waveform that writes track of data area, be just or negative computing, operation result based on plus or minus, differentiate the calculation step that light beam focuses on which layer of the ground floor and the second layer, detect the detected value of step and the operation result control Laser Driven step of calculation step according to described focus state, set light beam when reproducing or write fashionable emission light quantity at the information faces of the ground floor of each described CD and the second layer.

8. according to the reproducting method of claim 6 or 7 described CDs, it is characterized in that:

Detecting the detected value that step detected by focus state is to detect step by described light to detect many places detected value that be provided with, preformed concavo-convex pre-pit on 1 week of the continuous track on the CD.

9. according to the reproducting method of claim 6 or 7 described CDs, it is characterized in that:

Detecting the detected value that step detected by focus state is to detect the detected value that step detects preformed guiding groove on CD by described light.

10. according to the reproducting method of claim 6 or 7 described CDs, it is characterized in that:

Detecting the detected value that step detected by focus state is to detect detected detected value in the storage signal of step from be written to the optical disc data zone by described light.

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