JPS6360449B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording system for optically recording and/or reproducing information on a disk-shaped information carrier such as an optical disk. The present invention relates to a retrieval device for a reproducing device, and more particularly to a track retrieval device for an information carrier having a groove-shaped guide track formed in advance on the information 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 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 a device for writing information on a disc-shaped information carrier and reading information from a disc-shaped information carrier in which guide tracks can be optically identified. An object of the present invention is to provide a search device that performs a high-speed search for information recorded in a track by counting the number of traversed tracks.

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. Therefore, 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 an information carrier is attached to or detached from a device, the number
It is unavoidable that eccentricity on the order of 10 μm occurs. The presence of this eccentricity is due to the track spacing of 1 μm or more.
For optical disks as narrow as 2 .mu.m, false crossing signals occur when the scanning speed becomes slower than the rotational speed of the information carrier, such as at the beginning 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.

The present invention separates the false crossing signal using a sum signal and a difference signal of the outputs of the two photoelectric sections of the photodetector, thereby making it possible to accurately count the number of crossing tracks. , the purpose is to perform a good high-speed track search.

The present invention will be explained in detail below with reference to the drawings. FIG. 1 is a block diagram of a track search device of an optical information recording and reproducing apparatus for recording and reproducing information according to an embodiment of the present invention. A laser beam 2 emitted from a laser light source 1 changes direction with a tracking mirror 3 and is applied to a disc-shaped information carrier 5 with a diameter of 1 μm using an aperture lens 4.
The light is collected as a minute spot light 6 of about 1000 yen. The aperture lens drive device 7 is composed of a voice coil or the like, and controls the focus so that the minute spot light 6 is always in just focus by slightly moving the aperture lens 4 up and down in accordance with the surface deflection of the information carrier 5.

The information carrier 5, on which a guide track 8 has been previously provided, is rotated at high speed by a motor 9 and transported at high speed in the radial direction by a track retrieval and scanning mechanism 10.

This track search scanning mechanism 10 uses a pulse motor, a feed screw, a linear motor, or the like.

Reflected laser beam 11 reflected by the information carrier 5
is a 1/4 wavelength plate 12 and a polarizing beam splitter 13
The optical path is separated and direction-changed, and then enters the top of the double prism 14. The separated reflected laser beam 15 is separated into multiple beams 17a and 17b by a lens 16 and a double prism 14, and projected onto a focus detection photodetector 18 and a tracking detection photodetector 19, respectively. Since the double beam light flux 17a moves left and right on the focus detection photodetector 18 in accordance with the surface deflection of the information carrier 5, if the outputs of the two divided photoelectric sections are subtracted from each other by the differential amplifier 20, a focus error signal is obtained. 21 is obtained.
This focus error signal 21 is applied to an aperture lens drive circuit 22 to move the aperture lens 4 vertically to control focus.

When the minute spot light 6 traverses the guide track 8 due to the eccentricity of the guide track constructed on the information carrier 5, the light quantity distribution of the double beam light beam 17b changes in such a way that it is biased in the transverse direction. This double beam light flux 17b irradiates two photoelectric parts of the tracking detection photodetector 19, and the output thereof is differenced from each other by a differential amplifier 22 and sent to a tracking mirror drive circuit 24 as a tracking error signal 23. The input is received and tracking mirror 3 is shaken. The tracking mirror 3 changes its angle in response to changes in the tracking error signal 23 so that the minute spot light 6 accurately tracks the guide track 8 on the information carrier 5. 25
is a signal processing circuit detailed in FIG. 5, which sends a track crossing pulse and a track crossing direction signal to the track search scanning drive circuit 26 to drive the track search scanning mechanism 10, so that the minute spot light 6 is accurately directed to the target track. Control to move. 27 is a summing amplifier which is connected to the tracking detection photodetector 19;
A sum signal 28 of the two outputs is output and input to the signal processing circuit 25.

FIG. 2 is a partial sectional view of the structure of the information carrier 5 used in the optical disc retrieval device of the present invention. On the surface R side of the information carrier 5, groove-shaped guide tracks 30a to 30e having a width ω, a pitch P, and a depth δ are formed in a circular or spiral shape. 29a to 29e are flat portions between the grooves. A photosensitive recording material is deposited on the surface R side to form a recording surface 31. The minute spot light 6 is emitted from the side of the substrate 32, for example, and is focused on the surface R to record information. The insides (grooves) of the guide tracks 30a to 30e are used as the portions where information is recorded. Guide tracks 30a to 30e
Specific values of width ω, pitch P, and depth δ are, for example, ω=0.6μm, P=1.6μm, δ≒λ/8.n(λ
is the light wavelength of the laser light source, and n is the refractive index of the base material 32).

FIG. 3 is a diagram illustrating the principle of detection of a tracking error signal when the groove-shaped guide track 30 of the information carrier 5 described in FIG. 2 is irradiated with the minute spot light 6. FIG. 3 is a view of the information carrier 5 viewed from the cross-sectional direction. Tracking detection photodetector 19
consists of two photoelectric sections 19a and 19b, which are arranged on both sides with respect to the direction of the guide track 30. Here, the photoelectric part on the outer diameter side of the information carrier 5 is 1
9a, and the inner diameter side is designated 19b. The double beam beam 17b is the reflected laser beam 1 from the information carrier 5.
1a to 11b are tracking detection photodetectors 19
It represents a spot of light incident on it, and the shading shows changes in the light amount distribution. FIG. 3a shows a situation where a minute spot light 6 is present on the flat portion 29 between the guide tracks of the information carrier 5. In this case, the incident minute spot light 6 is uniformly reflected. Since this reflected laser beam 11a is uniformly distributed on the tracking detection photodetector 19, the output of the differential amplifier 22 becomes zero. That is, the tracking error signal 23 is zero.

FIG. 3b shows a state in which a portion of the minute spot light 6 has previously entered the outer diameter side edge 33a of the groove-shaped guide track. If the depth δ of the groove-shaped guide track 30 is approximately π/4 phase, the reflected laser beam 11b is bent toward the outer diameter side, and the photoelectric section 1
The 9a side becomes brighter, and the photoelectric part 19b side becomes darker. The output of the differential amplifier 22 is transmitted to the photoelectric section 19a, 1
If 9b is applied as a positive input and a negative input, respectively, a negative output will be obtained.

FIG. 3c shows how the central part of the groove of the groove-shaped guide track 30 is irradiated with the minute spot light 6. As shown in FIG. Since the minute spot light 6 touches both edges 33a and 33b of the groove, the reflected laser beam 11c is diffracted to the outside of the groove, and a part of the light quantity is lost at the aperture of the aperture lens 4. Therefore, although the photoelectric sections 19a and 19b of the tracking detection photodetector 19 have a uniform light distribution, the total light amount is as shown in FIGS.
It decreases from the case of d. The difference signal 23 becomes zero as in FIG.
The sum signal obtained by adding the outputs of a and 19b is shown in Figure 3 a,
Its amplitude is smaller than that of b and d.

FIG. 3d is the opposite of FIG. 3b, and shows the situation when the minute spot light 6 has previously entered the inner edge 33b of the groove. In this case, contrary to FIG. 3b, the reflected laser beam 11d is diffracted toward the inner diameter side, and the amount of light is biased towards the photoelectric section 19b on the inner diameter side. Therefore, the difference signal 2
3 is negative.

FIG. 4 shows the output 34a of the inner photoelectric part 19a and the outer photoelectric part 19b of the tracking detection photodetector 19 when the minute spot light 6 explained in FIG. 3 moves in the radial direction of the information carrier 5. The signal waveforms of the sum signal 28 and the difference signal 23 of the output 34b are shown. FIG. 4 shows the output 34a of the outer photoelectric section 19a, the output 34b of the inner photoelectric section 19b, and The waveforms of a difference signal 23 and a sum signal 28 are shown. FIG. 4a shows the output waveform when scanning from the outer diameter to the inner diameter, and FIG. 4b shows the output waveform when scanning from the inner diameter to the outer diameter.

In FIG. 4, the peak of the sum signal 28 is the difference signal 2.
It coincides with the point where 3 crosses zero. It is clear from the description of FIG. 3 that this is not related to the scanning direction. Furthermore, comparing the waveform phases of the sum signal 28 and the difference signal 23, when the groove-shaped guide track 30 is crossed in the inner diameter direction as shown in FIG. On the other hand, when the grooved guide track 30 is traversed in the outer diameter direction as shown in FIG. 4b, the sum signal 28
is delayed in phase from the negative polarity waveform portion of the difference signal 23. By comparing the phase difference between the negative waveform portions of the sum signal 28 and the difference signal 23 in this manner, the direction across the groove-shaped guide track 30 can be easily detected. Furthermore, even if the reflectance of the information carrier 5 changes and the light intensity of the reflected laser beam 11 changes, the peak of the sum signal 28 and the phase of the zero crossing point of the difference signal 23 always match, as described above. Since the phase relationship between the signal 28 and the difference signal 23 does not change, stable detection in the transverse direction can be performed.

FIG. 5 is a block diagram of a signal processing circuit for counting the number of tracks crossed by a guide track and performing track search scanning. FIG. 6 is a diagram showing signal waveforms of each block in FIG. 5.

In Fig. 5, tracking detection photodetector 1
9, the output 34a of the two photoelectric sections 19a and 19b,
34b uses a differential amplifier 22 and a summing amplifier 27 to obtain a difference signal 23 and a sum signal 28. These signals are subjected to waveform shaping by waveform shaping circuits 37 and 38 after removing equipment noise and the like through filters 35 and 36 that transmit only required signal components. Shaped difference signal 39 and shaped sum signal 4 which are waveform-shaped of the sum signal and the difference signal
0 is a signal obtained by slicing the negative polarity portion using a predetermined threshold value. The shaped difference signal 39 triggers a monostable multivibrator 41 on a rising edge to produce a difference signal edge pulse 42. The difference signal edge pulse 42 and the shaped sum signal 40 are ANDed by an AND gate 43 to obtain an inner radial direction transverse pulse 44.
On the other hand, the monostable multivibrator 45 is triggered by the rising edge of the shaped sum signal 40 to generate a sum signal edge pulse 46, and the shaped difference signal 39 and AND gate 47 are used to logically AND the outer radial direction transverse pulse 4.
Get 8.

The total number of pulses counted for each of the inner radial direction traversing pulse 44 and the outer radial direction traversing pulse 48 is determined by the eccentricity of the information carrier 1. When traversed, the number of traversal tracks traversed from the outer diameter to the inner radial direction and the number of traversal tracks traversed from the inner diameter to the outer radial direction are expressed.

Therefore, if the inner radial direction transverse pulse 44 is inputted to the up-down counter 49's count-up clock and the outer radial direction transverse pulse 48 is inputted as the count-down clock, the count output 50 of the up-down counter 49 will be This is the net number of tracks traversed in the inner diameter direction.
Therefore, this count output 50 is compared with the target number of moving tracks 52 set in the moving track number setting register 51 by a comparator 53, and when they match, a track search scanning stop signal 54 is sent to the track search scanning drive circuit 26. to end the track search.

FIG. 7 is a diagram showing the influence of eccentricity and counting of traverse tracks when searching and scanning the guide tracks 55 formed on the information carrier 5.

There is an eccentricity of △ between the center O ₁ of the information carrier 5 and the motor rotation center O ₂ . In FIG. 7a, the minute spot light currently stationary on the track 56 crosses the guide track within the range of ±Δ due to the eccentricity of the information carrier 5 when no tracking control is applied. When a search scan is started from the current track 56 to the target track 57 by the track search scanning mechanism 10, the scanning speed is accelerated to a constant speed as shown by the broken line in FIG. It decelerates and stops at the end point of the target track 57. At this time, since the scanning speed is slower than the rotational speed of the information carrier 5 near the start point and end point of scanning, the same track is traversed multiple times due to eccentricity, as shown in the difference signal 23 in FIG. 6a. A phase reversal occurs such that the inner radial transverse pulse 44 and the outer radial transverse pulse 48 occur simultaneously. The difference between the number of transverse pulses 44 and 48 is the net number of transverse tracks. Therefore, the up-down counter 4 counts the number of traverse tracks.
When the count output 50 of 9 matches the number of tracks to be moved to the target track, the desired target track 57 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 tracks of a disc-shaped information carrier, and it is possible to perform a high-speed track search regardless of the magnitude of eccentricity. In addition, the present invention has the advantage that the phase inversion of the difference signal in the cross-track direction, the decrease in the sum signal during on-track, and the phase of the peak of the sum signal and the zero crossing point of the difference signal match regardless of changes in the reflectance of the information carrier. Since stable detection in the transverse direction is possible, 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 the structure of the information carrier, FIG. 3 is a diagram explaining the light intensity distribution of the reflected laser beam reflected by the groove-shaped guide track on the photodetector, and FIG. FIG. 5 is a block diagram of a signal processing circuit for counting track crossings. FIG. 6 is a diagram showing signal waveforms of each part of FIG. 5. The figure shows eccentricity of an information carrier and track search. 1... Laser light source, 2... Laser beam, 3
...Tracking mirror, 4...Aperture lens, 5
... Information carrier, 6 ... Minute spot light, 7 ... Aperture lens drive device, 8 ... Guide track, 9 ...
Motor, 10... Track search scanning mechanism, 1
1, 11a to 11d...Reflected laser beam, 12
...1/4 wavelength plate, 13... Eccentric beam splitter, 14... Biprism, 16... Lens, 17
a to 17b...Double beam light flux, 18...Photodetector for focus detection, 19...Photodetector for tracking detection, 20, 22...Differential amplifier, 25...
Signal processing circuit, 26...Search scanning drive circuit, 27
... Summing amplifier, 30a-30e ... Guide track, 31 ... Recording surface, 32 ... Base material, 33a-3
3b...Track block, 35, 36...Filter, 37, 38...Waveform shaping circuit, 41, 45
...monostable multivibrator, 43,47...
...And gate, 49...Up-down counter, 51...Movement track number setting register, 5
3... Comparator.

Claims (1)

[Claims] 1. A laser light source that irradiates a light beam onto an optical recording disk having a continuous groove-like track with a uniform depth, a condensing means that irradiates the track with the light beam as a single minute spot light, and a a tracking means for causing the spot light to follow a track; a track search means for transporting the light condensing means to a predetermined track; and a two-split light receiving means for receiving ±1st-order diffracted light from the light beam diffracted by the track;
The track crossing direction detecting means includes a track crossing direction detecting means for detecting the track crossing direction of the light beam, and a crossing track counting means for counting the number of tracks crossed by the light beam.
Using the sum signal of the two outputs of the divided light receiving means as a reference, the track crossing direction of the light beam is detected from the phase relationship with the difference signal of the two outputs of the two divided light receiving means, and together with the difference signal, the cross track counting means 1. A track retrieval device for an optical information recording/reproducing device, characterized in that the error in counting the number of traversed tracks due to eccentricity of the track is corrected by applying a current to the track.