JPS58185043A - Track retrieving device - Google Patents

Abstract

PURPOSE:To prevent an erroneous measurement due to eccentricity, by detecting the crossing direction of a guide track with a low speed when a light spot corsses the guide track and adding/subtracting the crossing frequency of the guide track. CONSTITUTION:The outputs of photodetectors 13a and 13b in the inner and outer diameters of an optical disk respectively are amplified by peramplifiers 19, 26 and 28 and then pass through an LPF40 to undergo waveform shaping 41. A difference signal (d) is obtained between detectors 13a and 13b, and a signal (g) indicates the center of a guide track. A speed detector 101 detects the speed of a linear motor 25 which drives an optical pickup and then decides whether a reversible counter 46 is counted up or down by the crossing direction of the guide track as long as the spped of the motor 25 is within a prescribed value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a track search device for an information recording and reproducing apparatus that records and/or reproduces information on a disc-shaped information carrier such as an optical disc.

As an information recording/reproducing device, for example, a disc-shaped information carrier coated or vapor-deposited with a light-sensitive extraction resistant material is rotated, and a light beam from a laser light source 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, a video signal is generated in real time as a change in optical properties such as a phase change due to unevenness, a change in refractive index, or a change in reflectance or transmittance on the information medium. A device has been proposed that is capable of recording information such as optical signals, digital signals, etc., and reproducing the recorded information by detecting changes in the optical characteristics. A guide track is prepared in advance in a concentric circle or a spiral shape to guide the track to be recorded due to partial writing or erasing, and information is recorded on the predetermined track while applying tracking control to follow the guide track. An optical information recording and reproducing device that records information and also reproduces information from the track is considered.

An object of the present invention is to provide a search device that performs a high-speed search by counting the number of times a signal conversion element that records or reproduces a signal traverses a guide track when searching for a predetermined track during recording or reproduction.

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

The guide track is identified based on 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 direction. This bias is photoelectrically converted by a photodetector having two light-receiving sections arranged such that the dividing boundary is parallel to the tangential direction of the guide track, and is applied to the tracking control means. Therefore, when the light is focused on the information phase body and scanned across the guide track, there is a difference in the output of the two light receiving parts of the photodetector in the tracking control direction each time the light passes through the guide track. Since a track crossing signal is obtained as a signal, by counting the number of crossing signals, the number of trunks in which the minute spot light has moved on the information carrier can be determined. Therefore, if the track search scan 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 an information carrier is attached to and detached from a device, the distance is several 1°/1m.
Auto: It is unavoidable that - eccentricity occurs.

The existence of this eccentricity is caused by false crossing when the scanning speed becomes slower than the rotational speed of the information phase at the beginning and end of track search scan on an optical disk with a very narrow track spacing of 1 μm to 2 μm. A signal is generated. Therefore, there is a drawback that the greater the amount of eccentricity, the greater the error in counting the number of tracks traversed.

Therefore, an object of the present invention is to accurately count the net number of tracks traversed by a minute spot light even if the optical disc is eccentric. For this purpose, it is necessary to accurately detect the direction in which the tiny spot light crosses the track. The track crossing direction can be detected by comparing the tracking difference signal with the phase of the tracking and knocking sum signal or the recording/reproduction signal, as will be described later. by the way,
In general, optical discs cannot avoid fine scratches and dust adhesion on the disc surface. Changes in the reflectance of the photosensitive material itself, which is deposited on the shattered disk, may also occur. Further guide to optical disc.

Not only groove tracks, but also address information and
When one track is further subdivided and sector recording is performed, information for sector separation is sometimes inked onto the optical disk in advance using the unevenness of the grooves. A minute spot light guides this crab.

When traversing a groove track, not only the groove crossing signal appears at the photodetector output. Dust, scratches, etc. on the disk, as well as address and sector information appear on the photodetector output.
It mixes with the groove crossing signal and becomes a noise component. Such noise components greatly affect the tracking sum signal of the photodetector. This is because the tracking sum signal output represents the change in reflectance on the disk surface itself.

However, the tracking difference signal is not easily affected by noise on the optical disk, which is larger in size than the minute spot light, because the noise component is canceled due to the nature of extracting the differential output. In other words, the trunking difference signal can output a signal with a better S/N ratio than the sum signal with respect to the groove crossing signal. By the way, the section in which it is necessary to detect the track cross direction due to the influence of eccentricity occurs when the speed of the retrieval transfer table becomes smaller than the cross speed of a minute spot caused by the eccentricity of the disk. This is because when the speed of the search transfer table exceeds the speed of the eccentricity, the track-crossing direction of the minute spot light naturally coincides with the moving direction of the search transfer table. As mentioned above, if the track crossing direction is detected using a tracking sum signal with poor S/N, the crossing direction will be detected incorrectly and the track crossing signal will be counted. The numbers no longer match. Therefore, search errors occur,
It may be unstable and take a long time to search. It is sufficient to detect the shunting transverse direction only in sections where the eccentricity is influential and the transverse direction is uncertain, and in sections where the shunting search transfer table is at a speed lower than the speed of the eccentricity of the optical disk. When the search transfer table exceeds the eccentric speed, the detection of the track cross direction is stopped, the cross direction is fixed to the moving direction of the search transfer table, and the tracking difference signal, which is not affected by the noise component on the disk, is fixed in that section. Count only the direction. The section in which the speed of the actual search transport stage or the maximum eccentricity of the optical disk exceeds the speed is much longer than the section which does not exceed the speed. Therefore, transverse direction detection using a tracking sum signal with poor S/N is the minimum necessary. It can be limited to only the section of . As described above, the present invention is capable of counting the net number of transverse trunks even when the optical disk is eccentric and there is a noise component on the disk surface, thereby performing a high-speed and stable track search. be able to.

An embodiment of the present invention will be described below based on the drawings. 1st
The figure is a configuration diagram of a track search device of an optical information recording/reproducing device. A light beam 2 emitted from a light source 1 such as a semiconductor laser passes through a nokuki/gumira 4, which is a stopper for making the light beam follow a track on a disk 3, and is then narrowed down to a stopper 6.
The light is focused on a track on the disk as a light spot 6.

The reflected light 7 from the top of the screen passes through an aperture lens 5 and a tracking mirror 4, and its 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 respectively projected onto two divided photodetectors 12° and 137. disc 3
Since the optical spot ( ) moves in the photodetector 12 according to the plane deviation of the
4, 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 a 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 not accurately match the track. Do not follow and cross the track. When a light spot or toro crosses the track, a change in light distribution occurs on the photodetector 13-L 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 20 is input to a drive circuit 21 and drives the tracking mirror 4. The tracking mirror 4 changes its angle in accordance with the difference signal and performs tracking control so that the light spot 6 accurately follows the trajectory of the distal point. Reference numeral 22 denotes a signal processing circuit shown in FIG. 5, which sends a track crossing pulse and a signal representing the track crossing direction to the IJ near motor drive circuit 23, compares it with the address signal 24 of the target track, and controls the linear motor 2.
The linear motor 26 is controlled so that the light spot moves accurately to the target track.

A speed detector 101 controls the speed of the linear motor 25. Reference numeral 26 denotes a pre-sum amplifier, in which the recording/reproduction signal from the optical disc 3 outputting a sum signal 27 of the signals detected by the two-split photodetector 13 in the tracking direction is detected by the photodetector 13 and sent to the pre-sum amplifier. High frequency amplifier 28
A reproduced signal 29 is output.

Next, the optical disc 3 used in the track search device of the present invention
An example of the structure will be described based on FIG. 2. FIG. 2 is a diagram showing a part of the disk 3. On the surface R side of the disk 3, there is a groove-shaped guide trunk 3 with a width W, a pitch p, and a depth δ.
0a to 30e are moats concentrically or spirally.

31a to 31e indicate 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 shaft F once. Light source 1 when recording
The optical output of the disc is increased, and the optical energy of the optical spot projected onto the groove-shaped guide track on the disk is increased to expose the recording material coated on the guide track and the rack. As a result, the reflectance of the recorded portion on the grooved guide track changes. By detecting this change in reflectance using a light spot with a smaller optical output than during recording, the recorded part and number can be reproduced. 33 shows how the recording material inside 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.

Width W and pitch p of the guide tracks 30a-0.

Specific values of depth δ are, for example, width W x 0.6 μm pitch p = 1.6 lim, depth δ-1oOoA (
The optical path length is selected to be about 110 times the wavelength of the light of the laser light source 3.

FIG. 3 shows the trunking direction when the light spot 6 is projected onto the groove-shaped guide track 30 (unrecorded part) on the optical disk 3 shown in FIG. 2 (the direction normal to the groove-shaped guide track).
It shows the change in the light amount distribution of the photodetector 13 in .

FIG. 3 is a view of the disk 3 viewed from the cross-sectional direction. 13
13b indicates a photodetector in the inner diameter direction of the optical disc 3, and 13b indicates a photodetector in the outer diameter direction of the optical disc 3. 34 represents a light spot where the reflected light 7 from the optical disc 3 is projected onto the photodetector. The shading within the circle of the reflected light spot 34 represents the change in the light amount distribution within the optical spot. Third
Figure a shows a state in which the optical sub-board 6 is projected onto the flat part of the groove 31 where the groove-shaped guide track 30 is not present. In this case, since the incident light beam 2 is uniformly reflected, the reflected light spot 34 on the photodetector is uniformly distributed, so that the photodetector 13a
The difference signal output 20 between and 13b- becomes zero. FIG. 3 shows the state in which the light spot is projected onto the edge 35b on the outer diameter side of the groove-shaped guide track. If the depth δ of the groove-shaped guide track 30 is an optical path length of 1/8 of the laser light wavelength, 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. When the front differential amplifier 260 inputs the outer radial photodetector 13b as a positive input and the inner radial photodetector 13B as a negative input, the difference signal output 2T becomes positive in the example shown in FIG.

FIG. 3C shows the grooved guide track 30 in both directions.
5a and 36b, a light spot 6 is shown projected onto 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 projected onto the photodetector 13 decreases.

Therefore, the sum signal output 2 of the photodetectors in both directions 13a and 13b
7 has a reduced amplitude compared to FIG. 3 a, b, and d.

In the case of FIG. 3C, if the center of the incident light slot 7 t·6 and the grooved guide track 30 coincide, the likelihood of the reflected light spot projected onto the photodetectors 13a, 13b in both directions will be deception
Since the distribution is uniform, the amplitude of the difference signal output 2o is zero. FIG. 3d shows a state in which the light spot and the toro are once projected onto the edge 35a in the inner diameter direction. In this case, contrary to FIG. 3, the reflected light 7d is diffracted in the inner diameter direction, and the light amount distribution toward the photodetector 13a in the inner diameter direction is shifted. Therefore, the difference signal output 2o becomes negative.

FIG. 4 shows time-varying waveforms of the amplitudes of the photodetector output, the sum signal, and the difference signal output when the light spot 6 crosses the groove-shaped guide track 3°, in winter. 36a represents the photodetector output waveform in the inner diameter direction, 36b represents the photodetector output waveform in the outer diameter direction, 37 represents the difference waveform of both outputs, and 38 represents the sum signal output waveform.

FIG. 4a shows the amplitude change when the light spot crosses the grooved guide track 30 from the outer diameter direction to the inner diameter direction (direction A in FIG. 3). As explained in Fig. 3, difference signal waveform 3
The amplitude of 7 is positive when passing the outer edge, zero at the center of the groove, and characteristic of passing the inner edge. - The amplitude of the aromatic signal waveform 38 decreases at the center of the groove. Figure 4 shows when the light spot crosses the grooved guide track 3o from the inner diameter direction to the outer diameter direction (B in Figure 4).
direction). In this case, since it passes from the inner etch in the opposite direction to that shown in FIG. 49a, the polarity is reversed. What is important here is that when comparing Figure 4 a and b,
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. Further, a sum signal waveform 38 and a negative waveform 37b of the difference signal.

Comparing the phases of the sum signal waveform and the negative waveform 37a of the difference signal, when crossing the groove-shaped guide track 30 in the inner diameter direction (direction A) (FIG. 4a), the phase of the sum signal waveform is earlier than that of the negative waveform 37a of the difference signal. On the other hand, when crossing the groove-shaped guide track 3o in the outer diameter direction (direction B) (
In FIG. 4b), the negative phase 37b of the difference signal is earlier in 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 sound in the direction across the groove-shaped guide track. Furthermore, even if the reflectance of the DSF surface -F changes and the amplitudes of the sum signal and the difference signals A and J change, the peak of the sum signal and the phase of the zero crossing of the difference signal always match, as mentioned above. . Therefore, the phase relationship between the sum 1g signal and the difference signal does not change due to changes in the reflectance on the optical disk surface, so stable detection in the transverse direction of the grooved guide track is possible even when the reflectance changes. be.

The explanations in FIGS. 4a and 4b are for the case where the recording material coated on the surface of the optical disk is exposed to light and traverses the groove-shaped guide track in the unrecorded area. Figure 2 33
FIG. 4C9d shows the output waveform of the photodetector, the sum signal, and the subsignal waveform when the light spot crosses the recording-exposed groove-shaped guide drum. 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 smaller. On the other hand, the sum signal is shown in Figure 3a.
.

In 38a and 38b, the amplitude does not decrease at the center of the groove. 38c, 38d This is because the reflectance within the grooved guide track has increased, and the amount of received light has increased even though the reflected light 7c is vignetted as shown in FIG. 3C. If the amplitude of the sum or signal output is small as shown in c + d of FIG. 4, detection in the transverse direction becomes unstable, so the reproduction signal 29 is used in place of the sum signal 27 in the recording section. 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 39 matches the sum signal waveforms 3ge and 3d 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 light spot crosses the groove-shaped guide tracking nog.

ing. Figure 4C shows how the groove-shaped guide track crosses the optical spot from the outer diameter direction to the inner diameter direction of the disk, similar to a, and Figure 4 d shows how the optical spot crosses the optical spot from the inner diameter direction to the outer diameter direction, as in b. It shows.

From the above, 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, it is possible to easily move in the transverse direction of the groove-shaped guide track. In other words, regardless of whether or not there are recorded tracks on the disk F, it is possible to detect the groove-like cutting direction and to count trunks.

FIG. 5 shows a schematic diagram of the signal processing circuit shown in FIG. 122. Further, FIG. 6 is a circular timing chart showing the A waveforms in each part of FIG. 5 on the same time axis. The signal waveforms of each part in Fig. 5 a-q are as shown in Fig. 6 a-o and Fig. 8.
Shown in figures a-q.

The waveform of the difference signal output a of the pre-differential amplifier 19 is shown in FIG. 6a. The section al shows the difference signal waveform when the light spot crosses from the outer radial direction to the inner radial direction, and the section a2 shows the difference signal waveform when the light spot crosses from the inner radial direction to the outer radial direction. In other words, FIG. 6 shows waveforms at various parts when the speed of the linear motor 25 is smaller than the speed of eccentricity of the optical disk 3. This is a case in which the minute light spot crosses the guide groove track while repeatedly reversing its transverse direction.

The waveform of the sum signal output from the presum amplifier 26 is shown in FIG. 38a, 38b are unrecorded portions 38c.

38d is the sum signal output waveform in the recording portion.

FIG. 6C shows the recording/reproduction signal 39, and the number of recording tracks is 3.
9c and 39d. FIG. 5 28 shows a pre-high frequency amplifier for amplifying 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 grooved 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). The resulting sum signal output is similarly input to a low-pass filter 40 and a waveform shaping circuit 41, and is shaped into the pulse waveform shown in FIG. 6e and output. The recording/reproduction signal C is input to the detection circuit 42 and subjected to envelope detection.
Similarly, low pass filter 40. Waveform shaping circuit 41 (
1 (manually input) and outputs a pulse waveform f. The pulsed sum signal e1 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 upper middle 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 short pulses according to the rising edge of the bamboo pulse.

Fig. 6 h, J. The phases of the mono multivibrator output triggered by the rising edge of the pulsed difference signal and the OR pulse output g are compared by the AND circuit 45, and if the high levels of both pulses match, then , outputs a transverse pulse j in the direction from the outer diameter to the inner diameter. On the other hand, the phases of the mono multivibrator output 1 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 to the outer diameter It outputs a transverse direction pulse k in the direction.

As described above, by connecting the traversal pulses j and k to the up and down inputs of the up-down counter, the net number of traversal tracks traversed by the minute light spot can be calculated. However, in reality, the amplitude of the tracking sum signal differs because the reflectance differs depending on the optical disc. Furthermore, the S/N of the tracking sum signal deteriorates due to dust, scratches, or uneven deposition of the recording layer on the optical disk, resulting in a decrease in waveform quality and the waveform-shaped pulse output e.
Missed pulses also occur. Therefore, the transverse direction pulse and the actual number of track crossings do not match, resulting in a counting error. In general, the tracking sum signal indicates the change in reflectance on the disk itself, and is therefore susceptible to noise such as dust and scratches on the optical disk. However, the tracking difference signal is not easily affected by noise because the noise component is canceled due to the nature of extracting the differential output for defects on the optical disk whose size is larger than that of the minute spot light. From the above, the tracking difference signal a can output a signal with a better S/N than the tracking sum signal. Taking advantage of this property, a stable difference signal pulse d is used as the pulse that actually opens the up/down counter, and a transverse direction pulse j is performed only to change the counter's angle down. A feature is that no counting VC is used. A method of up or down switching using transverse pulses j and k will be described. Reference numeral 102 in FIG. 5 is an R-S flip-flop, and the transverse direction pulse j in the inner radial direction is connected to a set input, and the transverse direction pulse in the outer radial direction is connected to a reset input.

The Q output of the flip-flop 102 is the comparator output q of 111.112.

If r is not at H level, it will be at H level only in the inner diameter direction as shown in 2, so stable difference signal pulses are counted only in this section. In this case, in order to prevent the difference signal pulse from being output at the same time as the timing of the direction change of the transverse direction output 2 and being output as both the inner radial direction pulse n and the outer radial direction pulse 0, the difference signal pulse to be counted is As shown in m, the falling edge pulse of the difference signal pulse d is used.

Therefore, if the difference signal pulse n crossing in the inner diameter direction is inputted to the up-down counter 460 count-up clock, and the difference signal pulse 0 crossing in the outer diameter direction is inputted as the count-down clock, the count output of the up-down counter 46 is This is the net number of trunks that cross from the outer diameter to the inner diameter. Even if the disk is eccentric and the light spot crosses the disk while repeatedly reversing its transverse direction, it is possible to accurately count the grooves that have been crossed. The output signal of the up/down counter 46 and the output signal of the moving truck/trick number setting register 47 are connected to the comparator 4.
8, and if they match, the linear motor drive control circuit 49 performs stop control of the near motor 25.

The above explanation using the waveforms shown in FIG. 6 shows that when the speed of the linear motor 26 is smaller than the eccentricity of the disk, the cross-track direction of the minute optical spot does not match the transport direction of the linear motor and the direction is repeatedly reversed. It is an interval. 7th
The figure is a diagram showing the relationship between the moving distance of the linear motor, the number of tracks traversed, and the speed P of the linear motor (output P of the speed detector). As mentioned above, the sections where the speed of the linear motor is less than the eccentric speed of the disk are the section 110 when the linear motor starts and the section 110' when the linear motor stops, as shown in FIG. Here, the eccentricity speed of the optical disc 3 - [disc eccentricity:)/C time for half rotation of the disc]. For example, the eccentricity of an optical disc can be set to a maximum of 10
0. ljmp''-p, when the disk is rotated at 900 rpm, the eccentric speed is 0.3 cm/S.

This eccentric speed is shown in FIG. 7 106.

In sections 11o and 110' where the shunting linear motor speed is less than or equal to the disk eccentric speed 106, the number of traversed tracks increases while reversing its direction, as shown in FIG. Naturally, transverse direction detection is necessary in this section. However, when the linear motor speed exceeds the eccentric speed 106, the section 109 eventually coincides with the transport direction of the linear motor. Therefore, it is sufficient to stop the transverse direction detection using the tracking sum signal, which is susceptible to noise caused by changes in reflectance on the disk surface, and fix the track counting direction to the transport direction of the linear motor. The section 109 in which the actual speed of the linear motor exceeds the eccentric speed 106 is the section 110 where the speed does not exceed the eccentric speed 106.
Since it is much longer than 11Q', the influence of noise on the track crossing signal on the disk surface in this section can be greatly reduced. Therefore, in the 1090 interval, falling pulses m of the tracking difference signal mentioned above, which are less affected by noise, are counted in only one direction.

FIG. 5 101 is a speed detector for a linear motor, which is generally used for speed control during linear motor transport.

In the present invention, a comparator 111 for the output Pi-up direction of the speed detector, and a comparator 112 for the DOWN direction. -y 7haV -pllll, 11
If the threshold level 2 is set to a value equal to or higher than the eccentric speed of the optical disc, the up force direction DOWN
The comparator output qt or r can be set to H level only in the section where the eccentric speed is exceeded in both directions. For example, in FIG. 5, when the linear motor moves in the count up direction (inner diameter direction of the disk) and exceeds the eccentric speed of the disk, the q output becomes H level. From this point on, the section 109 shown in FIGS. 7 and 8 begins. Figure 8 shows section 10 in which the transfer speed of the linear motor exceeds the eccentric speed of the disk.
9 represents the signal waveforms of each part of FIGS. 6a-q in FIG. When the q output becomes H level (Fig. 8q), the U output obtained by ORing with the transverse direction detection pulse becomes H level regardless of the state of the Q output of the Norinob flop 102 (
Figure 8 2). Therefore, only the falling pulse m of the difference 1g is input to the up input n of the up/down counter 46. At this time, down input is prohibited (Figure 8 0)
.

The noise component to the track crossing signal, for example, the noise waveform when a small light spot crosses the address area is:
The tracking sum signal is as shown at 103, and the tracking difference signal is as shown at 104. In this way, although it appears as a large noise component in the sum signal, its influence on the difference signal is small.

105 and 106 indicate the effects of scratches on the disk surface.

In this case as well, there is little influence 106 on the difference signal. As described above, the moving distance in the section 109 that does not require detection in the transverse direction is much longer than the section 110 that requires detection, so the probability of noise occurring in the tracking sum signal 109 is high. In other words, in section 109, a tracking difference signal (FIG. 8a) with a good S/N ratio is used, and only its falling pulse is input to the anop-down counter/controller n.

As described above, the present invention detects the cross-track direction when the retrieval transfer speed is slower than the eccentric speed of the disk, and stops detecting the cross-track direction when it becomes faster than the eccentric speed.
Track crossing signals using a difference signal with good S/H only in the transport direction are counted. According to such a configuration, the eccentricity of the disk.

Accurate, stable, and high-speed track searches can be performed even when there are noise components in the track crossing signal, such as dust, scratches, and track address areas formed by uneven groove structures on the disk surface. 5,

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram of an embodiment of the present invention, Fig. 2 is a perspective view showing a part of an embodiment of the disk structure, and Fig. 3 is a diagram of reflected light reflected by a groove-shaped guide track. Figure 4 is a diagram explaining the light intensity distribution on the photodetector. Figure 4 is a diagram showing the output waveform of the photodetector and the waveforms of the difference signal, sum signal, and reproduced signal. Figure 5 is
FIG. 6 is a block diagram of a signal processing circuit for counting groove-shaped guide tracks, and FIG. 6 shows signal waveforms of each part in FIG.
FIG. 7 is a diagram showing eccentricity of the optical disc and track search, and FIG. 8 is a diagram showing signal waveforms at various parts when the search transport speed exceeds the eccentric speed of the disc. DESCRIPTION OF SYMBOLS 1... Laser light source, 2... Incident light beam, 3... Optical disk, 4... Tracking mirror, 6... Fist/aperture lens, 7 ...e
・Reflected light beam, 8... Semi-transparent mirror, 9...
...Optical sea urchin 1. 12゜13...Photodetector, 14.19...Pre-differential amplifier, 18...0
...Disc motor, 22... Signal processing circuit,
2.6... Linear motor, 26...
Pre-sum amplifier, 2o... Pre-high frequency amplifier, 3
o... Grooved guide track, 40... Low pass filter, 41... Waveform shaping circuit, 4
3...轡・-OR times 144...lIo・mono multivibrator, 46...AND circuit, 46...°・
...Amplifier down counter, 10111...Fist・
speed detector. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 25A Figure 6 tρ---- Figure 7

Claims (1)

[Claims] ``Signal conversion means that has a concentric or spiral guide track and reproduces a signal by irradiating a light spot from a rotationally driven disc-shaped recording medium, and the signal means is moved in a direction across the guide track. a first detection means for detecting that the light spot from the signal conversion means crosses the guide track; and a first detection means for detecting the direction in which the light spot from the signal conversion means crosses the guide track. a counting means for adding or subtracting the detected output of the first detecting means according to the output of the second detecting means according to the transverse direction of the guide track of the signal converting means; and the moving means. When the moving speed of the signal converting means becomes equal to or higher than the speed at which the optical spot crosses the guide trunk due to the eccentricity of the disc-shaped recording medium, the number of traversed tracks is counted regardless of the detection of the transverse direction of the guide track. The counting direction of the counting means is made to match the moving direction of the signal conversion element by the moving means, and
means for controlling the counting direction of the counting means in accordance with the detection of the transverse direction of the trunk when the moving speed of the i-number converting means becomes less than the speed at which the light spot crosses the guide track due to the eccentricity of the disc-shaped recording medium; A track search device characterized in that it searches for a track based on the count value of the counting means.