JPH01276432A - Information reproducing device - Google Patents

Abstract

PURPOSE:To exactly reproduce the plural information of different characters by outputting plural bias currents switched in each recording information of the different character and executing the amplification and binarization of a photo-electric converting output from an optical system in correspondence to the bias current to be impressed. CONSTITUTION:Information to be recorded to an optical disk 1 are read by an optical head 3, supplied to an image circuit 19 and amplified by an amplifier 42. A current source 43 impresses the bias current of a different current value in correspondence to the difference of the character in a reproducing signal to be reproduced to the amplifier 42. Then, the bias current of the different current value by the current source 43 is generated with being switched in correspondence to a switching signal from a CPU 23. The reproducing output of the amplifier 42 is binarized by a binarizing circuit 44. Thus, the plural information of the different characters can be exactly reproduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an information reproducing device such as an optical disk device that records or reproduces information on, for example, an optical disk.

(Prior Art) As is well known, various information reproducing devices such as optical disk devices have been developed that record information on an optical disk or read information recorded on an optical disk using laser light output from a semiconductor laser, for example. has been done.

In such an optical disk device, when playing back recorded information on an optical disk, the master preformat data recorded at the time of master disk creation and the recorded data recorded on the actual device are recorded with different characteristics, and these data cannot be played back. The signal amplitudes are different.

For this reason, when attempting to binarize master preformat data and recorded data at the same detection level, transient phenomena due to amplitude differences become large, making it impossible to obtain a stable reproduction signal. This has the disadvantage that stable binarization cannot be performed and accurate reproduction of information cannot be performed.

(Problems to be Solved by the Invention) As described above, when attempting to binarize a plurality of pieces of recorded information with different properties at the same detection level, transient phenomena due to amplitude differences become large, resulting in unstable This eliminates the disadvantage that it is not possible to obtain accurate reproduction signals, and as a result, it is not possible to perform stable binarization of multiple pieces of information with different properties, and it is not possible to reproduce accurate information.
When attempting to binarize multiple pieces of recorded information with different properties at the same detection level, transient phenomena due to differences in amplitude are reduced and a stable playback signal can be obtained. An object of the present invention is to provide an information reproducing device that can accurately reproduce information.

[Configuration of the Invention (Means for Solving the Problem) The information reproducing device of the present invention includes an optical system that detects and photoelectrically converts light obtained by irradiating light onto a recording medium having a recording track, and a plurality of Bias current generating means for generating a bias current; switching means for switching the bias current generated by the bias current generating means for each recording information of different nature; and photoelectric conversion of the optical system according to the bias current switched by the switching means. It is comprised of binarization means for amplifying the output and binarizing the signal obtained by the amplification means.

(Function) This invention detects light obtained by irradiating light onto a recording medium having a recording track using an optical system, converts the light into electricity, and outputs a plurality of bias currents by switching them for recording information of different properties. , amplify the photoelectric conversion output of the optical system according to this switched and applied bias current,
This amplified signal is binarized.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 shows a disk device. A spiral or concentric groove (track) is formed on the surface of an optical disk (disc) 1, and the optical disk 1 is rotated by a motor 2 at a constant speed, for example. This motor 2 is controlled by a motor control circuit 18.

As shown in FIG. 3, the optical disc 1 has a donut-shaped metal coating layer, ie, a recording film made of tellurium or bismuth, coated on the surface of a circular substrate made of, for example, glass or plastic. , a notch, that is, a reference position mark 1, is provided near the center of the metal coating layer.

Further, as shown in FIG. 3, the optical disk 1 is divided into 256 sectors from 0 to 255, with the reference position mark 11 being 0. On the optical disk 1, variable length information is recorded over a plurality of blocks, and on the optical disk 1, 30 blocks are recorded on 36,000 tracks.
Ten thousand blocks are now formed.

The number of sectors in one block on the optical disc 1 is, for example, 40 sectors on the inner side and 20 sectors on the outer side. At the start position of the block, a block header A consisting of a block number, track number, etc. is recorded as master preformat data, for example, when the optical disc 1 is manufactured.

Furthermore, if each block on the optical disc 1 does not end at the sector switching position, a block gap is provided so that each block always starts from the sector switching position.

Recording and reproduction of information on the optical disc 1 is performed by an optical head 3, as shown in FIG. This optical head 3 is fixed to a drive coil 13 that constitutes a movable part of a linear motor, and this drive coil 13 is connected to a linear motor control circuit 17.

A linear motor position detector 26 is connected to this linear motor control circuit 17, and this linear motor position detector 26 is connected to an optical scale 2 provided on the optical head 3.
5, a position signal is output.

Further, a permanent magnet (not shown) is provided in the fixed part of the linear motor, and when the drive coil 13 is excited by the linear motor control circuit 17, the optical head 3 is moved in the radial direction of the optical disk 1. It is now possible to do so.

An objective lens 6 is held on the optical head 3 by a wire or a leaf spring (not shown), and the objective lens 6 is moved in the focusing direction (
The driving coil 4 allows movement in the tracking direction (direction perpendicular to the optical axis of the lens).

Further, the laser beam generated by the semiconductor laser 9 driven by the laser control circuit 14 is transmitted to the collimator lens 1.
1a1 half prism 11b1 is irradiated onto the optical disk 1 through the objective lens 6, and the reflected light from the optical disk 1 is transmitted to the photodetector 8 via the objective lens 6, the half prism 11b1, the condensing lens 10a1, and the cylindrical lens 10b. be guided.

This photodetector 8 has four divided photodetection cells 8 a s8
It is composed of b 18 c s 8 d.

Note that the above-mentioned wire-based objective lens driving device is described in Japanese Patent Application No. 61-284591.
The explanation thereof will be omitted here.

The output signal of the photodetection cell 8a of the photodetector 8 is supplied to one end of the adder 30a%30c via the amplifier 12a, and the output signal of the photodetection cell 8b is supplied to one end of the adder 30a%30c via the amplifier 12a.
The output signal of the photodetection cell 8c is supplied to the other end of the adders 30b, 30c via the amplifier 12c, and the output signal of the photodetection cell 8d is supplied to one end of the adder 30b, 30d via the amplifier 12c. Adders 30a, 30d via 12d
is supplied to the other end.

The output signal of the adder 30a is supplied to the inverting input terminal of the differential amplifier OPI, and the output signal of the adder 30b is supplied to the non-inverting input terminal of the differential amplifier OPI. As a result, the differential amplifier OP1 operates as the adder 30a, 30.
A track difference signal is supplied to the tracking control circuit 16 according to the difference in b. This tracking control circuit 16 creates a track drive signal according to the track difference signal supplied from OPl.

A track drive signal output from the tracking control circuit 16 is supplied to the drive coil 4 in the tracking direction. Further, the track difference signal used in the tracking control circuit 16 is supplied to the linear motor control circuit 17.

Further, the output signal of the adder 30c is transmitted to the differential amplifier OP2.
The output signal of the adder 30d is supplied to the non-inverting input terminal of the differential amplifier OP2. As a result, the differential amplifier OP2 is connected to the adder 30c.
, 30d, a signal regarding the focus point is supplied to the focusing control circuit 15.

The output signal of the focusing control circuit 15 is supplied to the focusing drive coil 5, and is controlled so that the laser beam is always in just focus on the optical disk 1.

Each photodetection cell 8a of the photodetector 8 with focusing and tracking performed as described above.

The sum signal of the outputs of 8d to 8d, that is, the output signal from the adder 30a130b, reflects the unevenness of the pits (recorded information) formed on the track.

This signal is supplied to the video circuit 19, and the video circuit 1
At step 9, image information and address information (track number, sector number, etc.) are reproduced.

The tracking control circuit 16 also controls the CPU 2.
The objective lens 6 is moved in response to a track jump signal supplied from the D/A converter 22 from the D/A converter 22, and the beam light is moved by one track.

The laser control circuit 14 and the focusing control circuit 15
, tracking control circuit 16, linear motor control circuit 1
7. The motor control circuit 18, the video circuit 19, etc. are controlled by the CPU 23 via the pass line 20, and the 200PU 23 is configured to perform predetermined operations according to the program stored in the memory 24. being done.

Further, the D/A converter 22 is used to exchange information between the focusing control circuit 15, the tracking control circuit 16, the linear motor control circuit 17, and the CPU 23, respectively.

The video circuit 19 includes an adder circuit 4 as shown in FIG.
1, amplifier 42, resistors R3, R4, current source 43, binarization circuit 44, envelope detection circuit 45, comparator 47, and reference voltage voltage? It is composed of R47.

The addition circuit 41 adds the addition signals from the adders 30a and 30b, and the reproduction signal as shown in FIG. 4(a) as a result of this addition is output to the non-inverting input terminal of the amplifier 42. It is now possible to do so.

The amplifier 42 is constituted by an operational amplifier, and applies the addition result from the addition circuit 41 to the bias current from the current source 43, with an amplification factor r (R3+R4) determined by resistors R3 and R4 )/R3J, and this amplified signal is sent to the binarization circuit 44.
and is output to the envelope detection circuit 45.

Further, the amplifier 42 outputs a signal that is kept approximately constant by changing the level of the information component side of the output signal in accordance with the detection signal from the envelope detection circuit 45. There is.

The current source 43 generates a different current value depending on whether the data to be reproduced by the amplifier 42 is master Britumat data or recorded data recorded on an actual machine, that is, depending on the characteristics of the reproduced signal. It applies a bias current (changes the operating point), and the bias current is output to the non-inverting input terminal of the amplifier 42. Bias currents of different current values from the current source 40 are as follows:
The generation is switched in response to a switching signal (instruction) from the CPU 23. For example, a high-level bias current is output for master pre-to-mat data, and a low-level bias current is output for recorded data recorded on an actual device.

As described above, when the CPU 23 can instruct the switching of the bias current, even if the format of the optical disc 1 is different, the switching timing can be controlled accordingly.

Further, the bias current switching instruction may be switched in synchronization with the end of reproduction of master pre-to-mat data and the end of reproduction of recorded data in one block.

The binarization circuit 44 binarizes the reproduced signal supplied from the amplifier 42 by comparing it with a predetermined reference value, and this binarized signal is output to the CPU 23. ing.

The envelope detection circuit 45 detects the envelope of the information component side of the reproduced signal from the amplifier 42 and outputs this detection signal (see FIG. 4(d)) to the inverting input terminal of the amplifier 42. It is composed of resistors R1, R2, R5, R6, a diode D1, a capacitor C1, and an amplifier 45a.

That is, the amplifier 42 as shown by the solid line in FIG.
Detects the peak value of the information component side, that is, the lower envelope, as shown by the dotted line in the same figure, using an integrating circuit 51 composed of resistors R1, R2, and a capacitor C.
Based on the detected peak value, the signal level of the amplifier 42 is compensated by a level compensation circuit 52 constituted by the resistors R5 and R6 and the amplifier 45a.

The output of the level compensation circuit 52 is supplied to the inverting input terminal of the amplifier 42 via a resistor R3, and the amount of feedback to the amplifier 42 is increased or decreased. This allows the amplifier 42 to work as an envelope servo amplifier.

The amplification factor of the amplifier 45a is r (R5+R6)/R5
”.

Further, the response time constant τ of the non-information component side of the envelope is expressed as follows.

This time constant τ needs to be 30 ms or less when the optical disc 1 rotates at 1800 revolutions per minute, for example. In other words, due to surface runout, eccentricity, etc., Fig. 4(a) and Fig. 5(a)
As shown in FIG.
d) As shown in Fig. 5(c), the envelope line is traced so that the level of the information component can be kept constant as shown in Fig. 4(C) and Fig. 5(b). There is.

Therefore, as shown in FIG. 7(a), the reproduction signal corresponding to the reflected light from the pit P formed on the track T of the optical disc 1 is as shown in FIG. 7(b).
The lower side, that is, the level corresponding to pit p is constant.

In addition, in order to prevent the level of the above information component from becoming too small and close to the frequency component of the reproduced signal, the envelope cannot be detected correctly and the output waveform becomes distorted, the level between the peaks of the reproduced signal must be is 1 μs at its longest, the time constant τ is 1 μs or more (τ>1 μs).

As a result, in the envelope detection circuit 45, the time constant τ that responds to the non-information component side is faster than the rotation period of the optical disc 1 and slower than the lowest frequency of the frequency components of the recorded information.

Further, when the characteristics of the reproduced signals are different, the envelope detection circuit 45 detects a resistor R1 according to an instruction from the CPU 23.
, R2, and by adding a resistor Rx, etc., the response speed of envelope line detection is changed.

Further, the comparator 46 compares the detection output of the envelope detection circuit 45 with the reference voltage from the power supply 47, thereby converting the binary signal to be used as a recorded detection signal into the C
It is output to the PU23. For example, in Figure 4 (d
) for the envelope line detection signal shown in (e) of the same figure.
As shown in
Since it is at the "L" level, if you check this,
It is now possible to detect whether information is recorded or not.

Next, the operation in such a configuration will be explained. For example, now, the laser beam generated from the semiconductor laser 9 is transmitted through the collimator lens 11a1 half prism 11b1.
The light is irradiated onto the optical disk 1 through the objective lens 6, and the reflected light from the optical disk 1 is guided to the photodetector 8 via the objective lens 6, the half prism 11b1, the condenser lens 10a1, and the cylindrical lens 10b.

Therefore, the output signal of the photodetection cell 8a of the photodetector 8 is sent to the adder 30a s 30 via the amplifier 12a.
The output signal of the photodetection cell 8b is supplied to one end of the photodetection cell 8b.
The output signal of the photodetection cell 8c is supplied to the other end of the adders 30b, 30c via the amplifier 12c, and the output signal of the photodetection cell 8d is , adder 3 via amplifier 12d
It is supplied to the other ends of 0a and 30d.

In this state, the reproduction operation will be explained.

That is, the signals from the adders 30a and 30b are supplied to an addition circuit 41. Then, the adder circuit 41 calculates the sum of the detection signals of the photodetection cells 8a to 8d as shown in FIG. 4(a).
A reproduced signal as shown in FIG. 1 is output to the amplifier 42.

As shown in Fig. 4(a), this playback signal shows a signal amount of l when no information is recorded, and shows a signal amount of 1' when information is recorded (a playback signal corresponding to the master preformat data). ), j' (playback signals corresponding to recorded data recorded on an actual device), the signals are arranged downward in the figure according to the form of information. Furthermore, the signal as a whole is greatly undulated due to surface wobbling, eccentricity, etc. of the optical disc 1.

The amplifier 42 receives the addition result from the adder circuit 41 in a state where a bias current with a high current value from the current source 43 is added or a bias current with a low current value is added, and in addition, the resistor R3 , R4, and outputs this amplified signal to the envelope detection circuit 45.

That is, in response to a switching signal from the CPO 23 as shown in FIG. 4(b'), the current source 40 outputs a bias current with a high current value to the master preformat data, and the recording recorded by the actual machine Outputs a bias current with a low current value for data.

As a result, the envelope detection circuit 45 detects the envelope of the information component side of the reproduced signal from the amplifier 42, and outputs this detection signal (see FIG. 4(d)) to the inverting input terminal of the amplifier 42. The signal level of the amplifier 42 is compensated by increasing the power.

That is, the amplifier 42 as shown by the solid line in FIG.
An integrating circuit 51 composed of resistors R1 and R2 and a capacitor C detects the peak value of the information component side, that is, the lower envelope curve, as shown by the dotted line in the same figure.
Based on the detected peak value, the signal level of the amplifier 42 is compensated by a level compensation circuit 52 constituted by the resistors R5 and R6 and the amplifier 45a. The output of the level compensation circuit 52 is supplied to the inverting input terminal of the amplifier 42 via a resistor R3, and the amount of feedback to the amplifier 42 is increased or decreased. This causes the amplifier 42 to work as an envelope servo amplifier.

As a result, the output of the reproduced signal from the amplifier 42 is as shown in FIG.
As shown in c), both the master preformat data and the data recorded by the actual machine become a signal in which the level of the information component side is kept almost constant, and is output to the binarization circuit 44.

Thereby, the binarization circuit 44 compares the reproduced signal supplied from the amplifier 42 with a predetermined reference value, and thereby
binarize and output this binarized signal to the CPU 23,
Perform playback processing.

As described above, the signal output from the amplifier can be made constant by switching the bias current in consideration of the amplitude difference between reproduction signals having different amplitudes for recorded information of different properties. This allows the same reference value (
Stable binarization can be performed using a threshold value). Also,
Since transient phenomena caused by amplitude differences in the output of the amplifier are reduced, a more stable reproduced signal can be obtained.

[Effects of the invention] As detailed above, according to the present invention, when attempting to binarize a plurality of pieces of recorded information with different properties at the same detection level, transient phenomena due to differences in amplitude are reduced, It is possible to obtain a stable reproduction signal, and as a result, it is possible to provide an information reproduction device that can accurately reproduce a plurality of pieces of information having different properties.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention; FIG. 1 is a diagram showing a schematic configuration of a video circuit, FIG. 2 is a diagram showing a configuration of an optical disk device, and FIG. 3 is a diagram showing a configuration of an optical disk. , Fig. 4 and Fig. 5 are signal waveform diagrams showing the signal waveforms of each part in the video circuit, Fig. 6 is a signal waveform diagram for explaining the relationship between the reproduced signal and the envelope, and Fig. 7 is a signal waveform diagram showing the signal waveform of each part in the video circuit. FIG. 3 is a diagram for explaining the relationship between and a reproduced signal. DESCRIPTION OF SYMBOLS 1... Optical disk, 3... Optical head, 8... Photodetector, 19... Video circuit, 23... CPU. 41...Addition circuit, 42.45a...Amplifier, 43
... Current source, 44 ... Binarization circuit, 45 ... Envelope detection circuit, 46 ... Comparator, 47 ... Power supply, R1
, ~R6, Rx...Resistor, C...Capacitor, D.
··diode. Applicant's agent Patent attorney Takehiko Suzue Figure 4

Claims (1)

[Scope of Claims] An optical system that detects and photoelectrically converts light obtained by irradiating light onto a recording medium having recording tracks; Bias current generation means that generates a plurality of bias currents; and Bias current generation means. a switching means for switching the bias current generated by the means for each recording information of different nature; an amplifying means for amplifying the photoelectric conversion output of the optical system according to the bias current switched by the switching means; An information reproducing device comprising: binarization means for binarizing a signal that is transmitted.