JPS6236286B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a retrieval device for an optical information recording and reproducing device that optically records and/or reproduces information on a disc-shaped information carrier such as an optical disk, and particularly relates to a retrieval device for an optical information recording and reproducing device that optically records and/or reproduces information on a disc-shaped information carrier such as an optical disk. The present invention relates to a track retrieval device for an information carrier having a groove-shaped guide track formed on the carrier.

As an optical information recording/reproducing device, for example, a disc-shaped information carrier coated or vapor-deposited with a photosensitive material is rotated, and a light beam from a laser light source or the like is focused onto the disc-shaped information carrier to a diameter of 1 μm or less. By irradiating it as a spot light and modulating its optical output intensity with a recording signal, video can be recorded in real time on the information carrier as changes in optical properties such as phase changes due to unevenness, changes in refractive index, or changes in reflectance and transmittance. 2. Description of the Related Art Apparatuses have been proposed that can record information such as signals and digital signals, and can reproduce the recorded information by detecting changes in the optical characteristics.

In such a device, a guide track is provided in advance in a concentric circle or a spiral shape to guide the track to be recorded due to high density recording, discrete partial writing or erasing, etc. An optical information recording/reproducing apparatus is conceivable that records information on a predetermined track while applying tracking control to the information, and reproduces information from the track.

SUMMARY OF THE INVENTION An object of the present invention is to provide an apparatus for writing information on a disc-shaped information carrier by coating a recording material on a disc-shaped information carrier and exposing it to light, or for reading information from the disc-shaped information carrier. Among other things, it is an object of the present invention to provide a search device that performs a high-speed search for information recorded on each track by counting the number of tracks traversed.

The guide track formed on the information carrier may suitably have, for example, a groove-like structure with uneven surfaces. Information is recorded on a recording medium, such as an amorphous metal deposited on the information carrier provided with this guide track. Information is stored in the form of holes or local blackening due to evaporation of the recording medium.

The guide track is identified by the far-field pattern of the reflected laser beam reflected by the guide track, with the light intensity distribution being biased on both sides of the guide track. This deviation is photoelectrically converted by a photodetector having two light receiving sections arranged so that the dividing boundary is parallel to the tangential direction of the guide track, and is applied to the tracking control means. Therefore, when a minute spot light is focused on an information carrier and scanned so as to cross the guide track, a track crossing signal is generated as a difference signal between the outputs of the two light receiving sections of the photodetector each time it passes through the guide track. By counting the number of crossing signals, the number of tracks traveled by the minute spot light on the information carrier can be determined. Therefore, if the track search scanning is stopped when the count of the number of traversed tracks matches the target number of moving tracks, a high-speed track search can be performed.

Generally, when the information carrier is attached to and detached from the device, the number 10
It is unavoidable that eccentricity on the order of μm occurs.
The presence of this eccentricity is due to the track spacing of 1 μm to 2 μm.
In an optical disk having a very narrow width of m, a crossing signal is generated when the scanning speed becomes slower than the rotational speed of the information carrier, such as at the start and end of a track search scan. Therefore, there is a drawback that the greater the eccentricity, the greater the error in counting the number of traverse tracks.

As described above, the present invention can accurately count the number of traversal tracks even if the information carrier is eccentric, and even if the reflectance changes by recording on the information carrier.
The purpose is to perform track searches stably and at high speed.

An embodiment of the present invention will be described below based on the drawings. FIG. 1 is a block diagram of a track search device of an optical information recording/reproducing apparatus. Light source 1 such as semiconductor laser
A light beam 2 emitted from the disk 3 passes through a tracking mirror 4 for causing the light beam to follow a track on the disk 3, and is focused by an aperture lens 5 onto a track on the disk as a light spot 6. The reflected light 7 from the disk is passed through the aperture lens 5,
After passing through a tracking mirror 4, the optical path is separated and changed by a semi-transparent mirror 8. This reflected light is separated by an optical wedge 9 into light beams in a focusing direction 10 and a tracking direction 11. The separated light beams are projected onto two divided photodetectors 12 and 13, respectively. Since the light spot moves on the photodetector 12 in accordance with the surface wobbling of the disk 3, the light is inputted from the two-split photodetector 12 to the pre-differential amplifier 14 and a focus error signal 15 is obtained. This error signal is applied via a drive circuit 16 to a voice coil 17 that drives the diaphragm lens up and down, and controls to focus a light spot on the disk.

The disk 3 is rotated by the disk motor 18, but if the center of rotation of the disk motor 18 and the center of the track of the disk 3 are misaligned, the light spot 6 on the disk 3 will accurately follow the track. Cross the track instead. light spot 6
When the light crosses the track, a change in the light distribution occurs on the photodetector 13 as will be described later. This change is detected and input to the pre-differential amplifier 19 to obtain a tracking difference signal 20. This difference signal 2
0 is input to the drive circuit 21 and drives the tracking mirror 4. The tracking mirror 4 changes its angle in accordance with the difference signal to perform tracking control so that the optical spot 6 accurately follows the track on the disk 3. 22 is the fifth
The signal processing circuit shown in the figure sends a track crossing pulse and a signal representing the track crossing direction to the linear motor drive circuit 23, compares it with the address signal 24 of the target track, and drives the linear motor 25 to generate the light spot. The linear motor 25 is controlled to move accurately to the target track. A presum amplifier 26 outputs a sum signal 27 of the signals detected by the two-split photodetector 13 in the tracking direction. A recording/reproduction signal from the optical disk 3 is detected by a photodetector 13, inputted to a pre-high frequency amplifier 28, and outputted as a reproduction signal 29.

Next, an embodiment of the structure of the optical disk 3 used in the track search device of the present invention will be described with reference to FIG. FIG. 2 is a diagram showing a part of the disk of the disk 3, and the surface R side of the disk 3 has a width W, a pitch p,
Grooved guide tracks 30a to 30e having a depth δ are cut concentrically or spirally. 31
a to 31e indicate the grooves. A photosensitive recording material is applied from the surface R side to form a recording surface 32. The light spot 6 is focused on the surface R. During recording and reproduction, tracking control is applied so that the light spot is projected onto the groove-shaped guide track. When recording, increase the light output of light source 1,
The optical energy of the light spot projected onto the groove-shaped guide track on the disk is increased to expose the recording material coated on the guide track. As a result, the reflectance of the recorded portion on the groove-like guide track changes. By detecting this change in reflectance using a light spot with a smaller optical output than during recording, the recorded signal can be reproduced. 33 shows how the recording material in the groove-shaped guide track is exposed to light during recording. This case shows an example in which the recording material becomes black and the reflectance increases.

Specific values of the width W, pitch p, and depth δ of the guide tracks 30a to 30e are, for example, width W=
0.6μm, pitch p=1.6μm, depth δ=1000Å
(The optical path length is approximately 1/8 of the light wavelength of the laser light source 3).

FIG. 3 shows an optical spot 6 placed on a groove-shaped guide track 30 (unrecorded area) on the optical disk 3 shown in FIG.
It shows the change in the light intensity distribution of the photodetector 13 in the tracking direction (the normal direction to the groove-shaped guide track) when projected. Figure 3 shows disk 3
FIG. Reference numeral 13a indicates a photodetector in the inner diameter direction of the optical disk 3, and 13b indicates a photodetector in the outer diameter direction of the optical disk 3. 34 represents a light spot where the reflected light 7 from the optical disk 3 is projected onto the photodetector. Reflected light spot 3
The shading within the circle 4 represents the change in the light quantity distribution within the light spot. FIG. 3a shows the grooved guide track 30.
The light spot 6 is shown being projected onto the flat part of the gap 31 where there is no groove. In this case, since the incident light beam 2 is uniformly reflected, the reflected light spot 34 of the photodetector is uniformly distributed, so that the photodetector 13a
The difference signal output 20 between and 13b becomes zero. Figure 3b
2 shows how the light spot was once projected onto the outer diameter edge 35b of the grooved guide track. If the depth δ of the groove-shaped guide track 30 is an optical path length of 1/8 of the wavelength of the laser beam, the incident light beam 2 will be diffracted and the reflected light 7b will be bent to the outside of the groove. Therefore, the light amount distribution is concentrated toward the photodetector 13b in the outer diameter direction. Assuming that the input of the pre-differential amplifier 26 is the outer radial photodetector 13b as a positive input and the inner radial photodetector 13a as a negative input, the difference signal output 27 becomes positive in the case of FIG. 3b.

FIG. 3c shows the two-way edges 35a, 35b of the grooved guide track 30, with the light spot 6 being projected over the entire grooved guide track. In this case, since the incident light beam 2 covers both edges, the reflected light 7c is diffracted to the outside of the groove in both directions. Since the aperture of the aperture lens 5 is finite, the diffracted reflected light is vignetted. Therefore, the total amount of light from the spot projected onto the photodetector 13 is reduced. Therefore, the sum signal output 27 of the photodetectors in both directions 13a, 13b has a reduced amplitude compared to FIGS. 3a, b, d. In the case of FIG. 3c, if the incident light spot 6 and the center of the groove-shaped guide track 30 coincide,
Since the light intensity distribution of the reflected light spots projected onto the photodetectors 13a and 13b in both directions is uniform, the amplitude of the difference signal output 20 is zero. FIG. 3d shows how the light spot 6 is once projected onto the inner radial edge 35a. In this case, contrary to FIG. 3b, the reflected light 7d is diffracted in the inner diameter direction, and the light amount distribution is concentrated toward the photodetector 13a in the inner diameter direction. The difference signal output 20 is therefore negative.

FIG. 4 shows that the light spot 6 is located on the groove-shaped guide track 3.
3 shows temporal change waveforms of the amplitudes of the photodetector output, the sum signal, and the difference signal output when crossing zero. 36a is the photodetector output waveform in the inner diameter direction;
6b represents the photodetector output waveform in the outer radial direction, 37 represents the difference signal waveform between both outputs, and 38 represents the sum signal output waveform. FIG. 4a shows when the light spot crosses the groove-shaped guide track 30 from the outer diameter direction to the inner diameter direction (the third
The amplitude change in direction A in the figure is shown. As explained with reference to FIG. 3, the amplitude of the difference signal waveform 37 is positive when passing the outer edge, zero at the center of the groove, and negative when passing the inner edge. On the other hand, the amplitude of the sum signal waveform 38 decreases at the center of the groove. In Fig. 4b, the light spot is located on the groove-shaped guide track 3.
This shows the amplitude change when crossing 0 from the inner diameter direction to the outer diameter direction (direction B in FIG. 3). In this case, contrary to FIG. 4a, it passes from the inner edge, so the polarity is reversed. The important thing here is that Figure 4a,
A comparison of b shows that in either case, the peak of the sum signal waveform coincides with the point where the difference signal waveform crosses zero.

This is obvious for the reasons explained in FIG. 3c. Furthermore, the sum signal waveform 38 and the negative waveform 3 of the difference signal
Comparing the phase of groove-shaped guide track 30
when crossed in the inner diameter direction (direction A) (Fig. 4a)
The sum signal waveform is earlier in phase than the negative waveform 37a of the difference signal. On the other hand, when crossing the groove-shaped guide track 30 in the outer diameter direction (direction B) (FIG. 4b), the negative waveform 37b of the difference signal has a faster phase than the sum signal.

By comparing the phases of the sum signal waveform 38 and the negative waveform of the difference signal as described above, it is possible to easily detect the direction of crossing the groove-shaped guide track. Furthermore, even if the reflectance on the disk surface changes and the amplitudes of the sum signal and difference signal change, the peak of the sum signal and the phase of the zero crossing of the difference signal always match, as described above. Therefore, the phase relationship between the sum signal and the difference signal does not change due to changes in the reflectance on the optical disk surface, so even if the reflectance changes, the transverse direction of the groove-shaped guide track remains stable. is possible.

The above explanation of FIGS. 4a and 4b is for the case where the recording material coated on the surface of the optical disk is traversed across the groove-shaped guide track in the unrecorded area where it is not exposed to light. FIGS. 4c and 4d show the output waveforms of the photodetector, the sum signal, and the difference signal waveforms when the light spot crosses the recording-exposed groove-shaped guide track as shown in FIG. 2, 33. When the recording material in the groove-shaped guide track is exposed to recording light, the reflectance increases. Therefore, the output amplitude of each photodetector becomes large, and the difference signal amplitudes 37c and 37d also become large. On the other hand, the amplitude of the sum signal does not decrease as much at the center of the groove as 38a and 38b in FIGS. 3a and 3b. 38c, 38d This increases the reflectivity within the groove-shaped guide track, as shown in Fig. 3c.
This is because the amount of light received increased even though the reflectance 7c was vignetted as shown in FIG. Figure 4 c, d
If the amplitude of the sum signal output is small, as in
The reproduced signal 29 is used instead. The reproduced signal waveform is shown at 39 in FIG. Since recording is performed by projecting a light spot onto the center of the groove-shaped guide track, the phase of the reproduced signal waveform 29 coincides with the sum signal waveforms 38c, d in the tracking direction. In this manner, the recording section compares the phases of the reproduced signal waveform 39 and the negative waveform of the difference signal to detect the direction in which the optical spot crosses the groove-shaped guide tracking. Figure 4c shows how the optical spot is crossed by the groove-shaped guide track from the outer diameter direction to the inner diameter direction of the disk, similar to FIG. 4a, and FIG. ing.

From the above, the transverse direction of the groove-shaped guide track can be easily determined by detecting the phase difference between the sum signal and the difference signal in the unrecorded part, and the phase difference between the reproduced signal and the difference signal in the recording part. That is, cross-groove direction and track counting is possible regardless of whether or not there are recorded tracks on the disk.

FIG. 5 shows a block diagram of the signal processing circuit shown in FIG. 122. Further, FIG. 6 is a timing chart showing the signal waveforms at each part in FIG. 5 on the same time axis. The signal waveforms of each part in FIGS. 5a to 5k are shown in FIGS. 6a to 6k.

The waveform of the difference signal output a of the pre-differential amplifier 19 is shown in FIG. 6a. The section a1 shows the difference signal waveform when the light spot crosses from the outer diameter direction to the inner diameter direction, and the section a2 shows the difference signal waveform when the light spot crosses from the inner diameter direction to the outer diameter direction. The waveform of the sum signal output b of the presum amplifier 26 is shown in FIG. 6b. 38a, 38b are the sum signal output waveforms in the unrecorded portions and 38c, 38d are the recorded portions. FIG. 6c shows the recording/reproduction signal 39,
The recording tracks are 39c and 39d. Figure 5 2
8 is a pre-high frequency amplifier that amplifies the reproduced signal.

The difference signal output a is input to a low-pass filter 40 to remove noise components on the optical disk other than the detection signal when crossing the groove-shaped guide track. The output of the low-pass filter 40 is input to a waveform shaping circuit 41, which shapes only the negative component of the difference signal 37 into a pulse waveform and outputs it. (FIG. 6d) Or the sum signal output b is similarly input to the low-pass filter 40 and the waveform shaping circuit 41, and is shaped into the pulse waveform of FIG. 6e and output. Further, the recording/reproduction signal c is inputted to the detection circuit 42 and subjected to envelope detection, and then similarly inputted to the waveform shaping circuit 41 of the low boss filter 41, and outputted as a pulse waveform f. The pulsed sum signal e and the reproduced signal f are input to an OR circuit, and the logical sum of the two inputs is output (FIG. 6g). As a result, a pulse indicating the center of the groove-shaped guide track is output regardless of whether or not there is recording. The pulsed difference signal d and the pulsed logic output signal g trigger the mono multivibrator 44 to output a short pulse at the rising edge of the pulse.

FIG. 6 h, j, the phases of the mono multivibrator output h triggered by the rise of the pulsed difference signal and the OR pulse output g are compared by the AND circuit 45, and the high level of both pulses is determined. If they match, the transverse pulse j in the direction from the outer diameter to the inner diameter
is outputting. On the other hand, the phases of the mono-multivibrator output i triggered by the rising edge of the pulsed OR output signal g and the pulsed difference signal d are compared, and if the high levels of both pulses match, the inner diameter A transverse pulse k in the outer radial direction is output.

Therefore, if the inner radial direction crossing pulse j is inputted to the count-up clock of the up-down counter 46, and the outer radial direction crossing pulse k is inputted as the count-down clock, the count output of the up-down counter 46 will change from the outer diameter to the inner diameter. This is the net number of tracks traversed in the direction. Even if the disk is eccentric and the optical spot traverses while repeatedly reversing its transverse direction, it is possible to accurately count the grooves traversed. A comparator 48 compares the output signal of the up-down counter 46 and the output signal of the moving track number setting register 47, and when the two match, the linear motor drive control circuit 49 performs stop control of the disk motor 25.

FIG. 7 is a diagram showing the influence of eccentricity and counting of transverse tracks when searching and scanning the groove-shaped guide tracks 30 formed on the optical disk 3. optical disk 3
There is an eccentricity of △ between the center O ₁ and the motor rotation center O ₂ . In FIG. 7a, the optical spot currently stationary on the track 50 crosses the groove-shaped guide track within the range of ±Δ due to the eccentricity of the optical disk 3 when no tracking control is applied.
When a search scan is started from the current track 50 to the target track 51 by the linear motor 18, the scanning speed is accelerated to a constant speed as shown by the broken line in FIG. and stops at the end point of the target track 51. At this time, since the scanning speed is slower than the rotational speed of the optical disk 3 near the start point and end point of scanning, the same track will be crossed multiple times due to eccentricity, as shown in the difference signal in FIG. 6a. A phase reversal occurs and inner radial transverse pulses j and outer radial transverse pulses k occur alternately. This transverse pulse j and k
The difference in the number of pulses is the net number of traversal tracks.
Therefore, when the count output 52 of the up-down counter 46 that counts the number of traversed tracks matches the number of tracks to be moved to the target track, the desired target track 51 can be accessed by reducing the search speed to zero and stopping scanning. .

As explained above, according to the configuration of the present invention, it is possible to accurately count the groove-shaped guide tracks of an optical disc, regardless of recorded tracks and unrecorded tracks. In addition, the target track can be searched quickly and accurately regardless of the eccentricity of the optical disk. Furthermore, the peak of the tracking sum signal or the reproduced signal and the phase of the zero crossing of the difference signal always match. Therefore, even if the recording material or base material of the optical disk is not uniform, the reflectance changes depending on the position of the track, or the difference width of the groove-shaped guide track changes, stable track transverse direction and counting can be performed. Good high-speed search is possible.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention, and FIG.
The figure is a perspective view showing a part of an embodiment of the disk structure, FIG. 3 is a diagram illustrating the light intensity distribution on the photodetector of the reflected light reflected by the groove-shaped guide track, and FIG. 4 is a photodetector. Figure 5 is a block diagram of a signal processing circuit for counting groove-shaped guide tracks.
Figure 6 is a diagram showing the signal waveforms of each part in Figure 5;
The figure shows eccentricity of an optical disk and track search. 1... Laser light source, 2... Incident light beam, 3...
...Optical disk, 4...Tracking mirror, 5...
... Aperture lens, 7 ... Reflected light beam, 8 ... Semi-transparent mirror, 9 ... Optical wedge, 12, 13 ... Photodetector, 14, 19 ... Pre-differential amplifier, 18 ...
Disc motor, 22... Signal processing circuit, 25...
...Linear motor, 26...Pre-sum amplifier, 28...
... Pre-mounted high frequency amplifier, 30 ... Groove guide track, 40 ... Low pass filter, 41 ... Waveform shaping circuit, 43 ... OR circuit, 44 ... Mono multivibrator, 45 ... AND circuit, 46 ...
Updown counter.

Claims (1)

[Claims] 1. The reflected light from the groove-shaped guide track of an optical recording disk having concentric or spiral groove-shaped guide tracks is divided into two discs arranged such that the dividing boundary is parallel to the tangential direction of the groove-shaped guide track. In order to accurately count the number of traversed tracks during a track search, the difference signal, the sum signal, and the recording/reproducing signal outputted from the photodetector are waveform-shaped and then The AND output of the edge pulse of the shaped difference signal, the logical sum output of the shaped sum signal and the shaped recording/reproducing signal is connected to one clock input of a two-clock input up-down counter, and the other clock input is connected to the shaped difference signal. Connect the edge pulse of the OR output signal of the sum signal and the shaped recording/reproduction signal and the AND output of the shaped difference signal, and check that the number of output pulses of the up-down counter matches the target number of traversal tracks. A track search device characterized in that the track search means is stopped upon detection.