JPH0583967B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical reproducing device for optically reading information recorded on a disc, such as in the case of a video disc, or to an optical reproducing device for optically reading information recorded on a disc, as in the case of a video disc. A light beam such as a semiconductor laser is applied to the coated disk.
It relates to an optical information recording and reproducing device that records or reproduces information signals such as video signals and digital signals with high density as variations in unevenness or shading by focusing and irradiating a minute spot light of about 1 μm, and in particular. Regarding signal detection.

Structure of the Conventional Example and its Problems In recent years, optical video disks have become generally well known among the above-mentioned technologies as devices that only reproduce signals that have been recorded in advance at high density.

Recently, optical information recording and reproducing apparatuses have been attracting attention, which record and reproduce information signals such as video signals, audio signals, and digital signals by coating a disk with the above-mentioned photosensitive recording material.

In an optical information recording/reproducing device, a signal is recorded by irradiating the recording thin film of the disk with a laser beam or the like to melt and evaporate the light irradiated portion of the recording thin film, or by changing the reflectance or transmittance. Recording is then performed. That is, it is common practice to thermally utilize the energy of laser light to change the optical properties of a recording material.

The optical information recording/reproducing apparatus as described above will be explained below with reference to the drawings.

FIG. 1 shows a conventional example of an optical information recording/reproducing device.

In FIG. 1, a light beam output from a semiconductor laser 1 is collected by a condenser lens 2 and converted into parallel light.
The concave and convex cylindrical lenses 3 and 4 spread the beam into a parallel beam only in the direction parallel to the cemented surface of the semiconductor laser 1, and the beam diameter is made almost the same width as in the vertical direction, and an isotropic micro spot is formed on the disk 6 by the aperture lens 5. It converges as light. The disk 6 is preliminarily provided with a groove-shaped guide track having a depth optically related to the wavelength λ of the semiconductor laser (for example, λ/8). Further, the disk 6 rotates at a constant rotation speed such as 1200 rpm.

Two control techniques are generally used in such devices. One is focus control and the other is tracking control. Control signals (error signals) for carrying out these controls are obtained from diffraction or changes in reflectance due to groove-shaped guide tracks of the disk.

In FIG. 1, 7 is a polarized beam splitter that transmits or reflects the laser beam depending on the direction of polarization of the laser beam. Reference numeral 8 denotes a λ/4 plate, and the reflected light from the disk 6 passes through the λ/4 plate 8 again, its deflection direction is changed, and the beam is reflected by the polarized beam splitter 7. 9 is a convex lens, and 10 is a splitting mirror, which splits the light beam into two and changes the direction of the light beam.
The light is guided to divided photodetectors 11a and 11b and two divided photodetectors 12a and 12b, respectively. By obtaining the difference between the two divided outputs of the photodetectors 11a and 11b using a differential amplifier 14, a focus error signal for the focus control is obtained and sent from terminal B. Further, by obtaining a difference between the respective outputs of the photodetectors 12a and 12b using a differential amplifier 13, a tracking error signal for the tracking control is obtained and sent from terminal A. On the other hand, a reproduction signal for reading an information signal such as a digital signal recorded on a disk is transmitted to the photodetectors 11a, 11b, 12.
An adder 15 obtains the output sum of a and 12b. In other words, a reproduced signal is obtained by the sum of the outputs of each of the four photodetectors. 16 is an amplifier. In addition, the reproduced signal is generally passed through a bandpass filter 30 after being output from the amplifier 16.
Then, through an equalizer circuit 31 for removing low-frequency and high-frequency noise components outside the reproduced information signal band and correcting the frequency characteristics and phase characteristics of the reproduced signal, the volume VR1 is adjusted at a comparatively high level 32. It is compared with a predetermined voltage set at , and is converted to the original information signal and output from terminal C.

Next, when recording the information signal etc. on the disk 6, the information signal input from the terminal D is applied to the semiconductor laser drive circuit 17, and the output light of the semiconductor laser 1 is changed depending on the intensity of the light depending on the information signal. Recording is carried out by modulating the beam and irradiating it onto the disk 6.

FIG. 2, FIG. 3, and FIG. 4 show configuration diagrams of the disk 6. FIG. 2A shows a top view of the disk 6. FIG. A guide track 20 is preliminarily provided on the disk 6 in a concentric or spiral shape (FIG. 2A shows a concentric guide track as an example). The guide track 20 has an address signal section 22 in which a unique address signal is pre-formed, and an information recording section 21 for recording the information signal.
is organized into sectors. Therefore, among the address signals, an address signal indicating a track and an address signal indicating each sector are formed respectively. Recording is performed along the guide track 20, reading the address signal and recording the information recording section corresponding thereto.

FIG. 2B shows an enlarged view of the recording pit. In FIG. 2B, 20 is a guide track, and black dots a therein indicate examples of recording pits.

FIG. 3 shows a radial cross-section of the disk 6. As shown in FIG. The disk 6 is formed of a base member f forming a groove-shaped guide track and a recording surface g coated with the above-described photosensitive recording material thereon. Further, a protective layer etc. (shown in FIG. 4) are processed on the recording surface g.
20a, 20b, 20c, 20d...20n indicates a guide track, and b indicates a groove. Each guide track 20 has a width W (for example, W=0.8 μm), a pitch P (for example, P=1.6 μm), and a depth σ (for example, σ=
0.7 μm). An example of pits recorded on the guide track is shown in a.

4A is a plan view of the guide track 20, and FIG. 4B is a sectional view of the guide track 20 in the track direction. In FIG. 4A, 22 is an address signal section in which the address signal and the like are recorded, and 21 is an information recording section for recording information signals and the like. As shown in FIG. 4B, the guide track 20 is a groove-like structure having a depth σ, and in the address signal section 22, address signals and the like are recorded in a pit structure accompanied by discrete chemical changes. On the other hand, the information recording section 21 is a continuous groove-like structure having a depth σ, and information signals are recorded in the form of shading. An example of recorded pits is shown by black dot a in FIG. 4A. The recorded pit portion has a higher density than the unrecorded portion, and the reflectance also changes higher. Therefore, the information signal is reproduced by changing the reflectance.

In FIG. 4B, f is the base material part, g is the recording surface coated with the photosensitive recording material, h is the recording surface coated with dust,
A protective layer to protect from scratches.

FIG. 5 shows an example of the recording format of the optical information recording/reproducing apparatus. In Fig. 5, E ₁ ,
E ₂ indicates the address signal section, and F ₁ and F ₂ indicate the information recording section. The address signal sections E ₁ and E ₂ each include a track address signal A and a sector address signal B indicating a track, and the track address signal A and sector address signal B are read and recorded in the corresponding information recording section. Information signals (c) are recorded for each sector. The same procedure is used when reproducing the data.

In the devices described above, if these address signals cannot be read due to drop-outs due to scratches or dust on the disk, or if there is a recording error in the information signal, or if the information signal is no longer needed after being recorded. In order to make the information signal of that sector unreadable, a code signal or delete mark signal (hereinafter referred to as demark signal) of a relatively low frequency (for example, several tens of kilohertz) different from the frequency band of the information signal is recorded and identified. It is commonly done. Furthermore, the demark signal is generally recorded in the address signal sections E ₁ , E ₂ and the information recording sections F 1 , E ₂ shown in FIG.
Although recording is performed during _F2 , it requires space to record the demark signal, which is undesirable because it reduces the recording capacity of the entire device. It is also possible to record the information signals in the information signal sections F ₁ and F ₂ overlappingly with the information signals and detect them together with the information signals, but this is difficult to detect because the frequency band is different from that of the information signals.

FIG. 6 shows an example of a reproduced waveform when a demark signal is recorded in an information signal section.

FIG. 6i shows the reproduced waveform when no recording is performed, and d shows the address signal. FIG. 6j shows an example of a demark signal, and the demark signal consists of a pulse train with a repetition frequency of about several tens of kilohertz. FIG. 6k shows the reproduced waveform when the above demark signal is recorded on the unrecorded track shown in FIG. 6i. The reproduced waveform in FIG. 6k shows the output waveform of the bandpass filter 30 shown in FIG.

Fig. 6 l and m show the case where the information signal and the demark signal are recorded in an overlapping manner, Fig. 6 l shows the information signal (c) before the demark signal is recorded, and Fig. 6 m
shows the reproduced waveform when the demark signal is recorded in an overlapping manner. When the demark signals are recorded overlappingly, the "1" part of the demark signal (part F in Figure 6 j)
Since a strong light is irradiated on the disc, the recorded information signal is destroyed and cannot be reproduced.

As described above, when a demark signal having a frequency band different from that of the information signal is recorded and reproduced, the demark signal has a sag because it passes through the band pass filter 30 shown in FIG. 1 to limit the band of the information signal. occurs. When a sag occurs, the comparator 31
This makes it difficult to set the volume VR1 that determines the comparison voltage of , which deteriorates the detection accuracy of the demark signal and impairs the reliability of the device.

It is also possible to configure the information signal and the reproduction processing path from a low frequency band that also passes the demark signal, but in this case, the S/N of the information signal deteriorates and the information signal cannot be reproduced accurately. This becomes another cause of deterioration of the reliability of the device.

OBJECTS OF THE INVENTION An object of the invention is to provide an optical information recording and reproducing apparatus that detects demark signals stably and reliably as described above.

Structure of the Invention The present invention relates to a semiconductor device that generates a light beam for recording and reproducing information signals, such as address signals, formed in advance by a guide track formed by a groove-like structure and an address signal formed by a discrete pit structure. laser and
an optical means for condensing the light beam as a minute spot light, and a two-split optical detection unit for obtaining a focus control signal and/or a tracking control signal for following and focusing the minute spot light on the guide track of the disk. an adding means for obtaining the sum of each of the two divided photodetecting means; an amplifying means for amplifying the output signal of the adding means from a DC level; and a bandpass filter for passing only the band of the delete mark signal. and comparing means for comparing the output signal of the bandpass filter means with a predetermined voltage.

DESCRIPTION OF EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 7 shows an embodiment of the optical information recording/reproducing apparatus of the present invention. In FIG. 7, the same parts as in FIG. 1 are given the same numbers and detailed explanations will be omitted.

In Fig. 7, 1 is a semiconductor laser, 2 is a condensing lens, 3 and 4 are concave and convex cylindrical lenses, and 5 is a condenser lens.
1 is an aperture lens, 6 is a disk, 7 is a deflection beam splitter, 8 is a λ/A plate, 9 is a convex lens, and 10 is a dividing mirror. The light beam reflected from the disk 6 is sent to a deflecting beam splitter 7 and a convex lens 9.
is divided into two by a splitting mirror 10, one of which is
The other one is guided to two divided photodetectors 11a and 11b for obtaining a focus control signal, and the other is a two-divided photodetector 1 for obtaining a tracking control signal.
It leads to 2a and 12b. 13 is a differential amplifier for obtaining a tracking control signal; 14 is a differential amplifier for obtaining a focus control signal; each control signal is output from terminals A and B. On the other hand disk 6
As described above, the reproduced signal of the information signal recorded on the photodetector 11a, 11b, 12a, 1
The four sums of 2b are obtained by the adder 15, AMP16,
It is led to a comparator 32 via a breadth pass filter 30 and an equalizer circuit 31, and the comparator 32 compares it with a predetermined voltage set by the volume VR1, converts it into a digital signal that is the original information signal, and outputs it from terminal C. Output. When recording on the disk 6, recording is performed by inputting an information signal from the terminal D and modulating the output light of the semiconductor laser in the semiconductor laser drive circuit 17. Therefore, recording of a demark signal is performed in the same manner.

Next, the configuration for detecting the demark signal according to the present invention will be described in detail using the waveform diagram of FIG. Reference numeral 40 in FIG. 7 denotes two divided photodetectors 11a and 11 for obtaining the aforementioned focus control signal.
This is an adder for obtaining the sum of b, and is generally composed of a resistor adder or the like. 41 is a DC amplifier, which is generally composed of an operational amplifier, etc., and is connected to the photodetector 11a,
The change in the amount of reflected light from the disk detected in step 11b is amplified from the DC level. In addition, it is difficult to widen the bandwidth of such DC amplifiers, and generally the frequency range is 100KHz~
A 200KHz low band DC amplifier is used. 42
is composed of a bandpass filter, generally an LC filter, that passes the band of the demark signal. 4
3 is an amplifier, and 44 is a comparator, which compares the input signal with a predetermined voltage set by the volume VR2 to obtain an output signal.

FIG. 8n shows the waveform of the reproduced signal from the disc when no data is recorded, and the waveform is similar to that shown in FIG. 6i. d in FIG. 8 indicates an address signal.

FIG. 8o shows the waveform of the demark signal to be recorded, which is similar to that shown in FIG. 6j, and the demark signal is composed of a pulse signal with a repetition frequency of about several tens of kilohertz. The demark signal as described above is recorded on an unrecorded track, and the photodetector 1 shown in FIG.
The waveforms reproduced by 1a and 11b and outputted via adder 40 and DC amplifier 41 are shown in FIG. 8p. In Fig. 8p, h is an address signal section, and as shown in Figs. 2, 3, and 4, the guide track is composed of a discrete pit structure, so the reflectance changes depending on the presence or absence of pits. The amount of playback light changes. However, the address signal generally uses a relatively high frequency of about 1M〓, so when it passes through the DC amplifier 41 in the stagnation region, the address signal component is attenuated, averaged as a change in the amount of reflected light, and output as a DC signal. . The circled part in FIG. 8p shows the reproduced signal of the guide track when it is not recorded. Next, in FIG. 8, p shows the reproduced waveform of the demark signal, and the dotted part shows the part where the demark signal is recorded as pits and the reflectance is high.

Next, the reproduction of the demark signal when the demark signal is recorded in addition to the information signal will be described. FIG. 8q shows the reproduced waveform of the information signal before recording the demark signal, and is the same waveform as FIG. 6l. D indicates an address signal, and C indicates an information signal. When the demark signal shown in FIG. 8o is recorded on this and reproduced by the photodetectors 11a and 11b shown in FIG. It becomes a waveform. Figure 8 r
In the figure, H indicates an address signal section as described above, R indicates an unrecorded track section, and O indicates an information signal section.
Similar to the address signal, the information signal in the information signal section O is generally in a high band of MHz, so it is not reproduced, but is averaged as a change in the amount of reflected light and output as a DC signal.
In addition, when using a photosensitive recording material as in this device and recording and reproducing as a change in reflectance by irradiating a light beam, the change in reflectance between the unrecorded area and the recorded area is 7 to 9.
%, and as further recording is made on the recording section, the reflectance has a characteristic that it changes even higher. Therefore, if a demark signal is recorded in the information signal record,
The portion where the demark signal is recorded has a high reflectance and is reproduced as shown in waveform w in FIG. 8r.
By using the bandpass filter 42 that passes only the reproduced signal and the band of the demark signal as described above, changes in the DC level caused by the address signal and information signal components are removed, and the demark signal as shown in FIG. Extract only the signal. This signal is input to the comparator 44 via the amplifier 43, and compared with a predetermined voltage set by the volume VR2 (for example, the dotted line shown in the waveform diagram of FIG. The signal is detected and output from terminal G shown in FIG.

In this embodiment, the focus control signal is used to detect the demark signal, but the tracking control signal or both signals may be used.

Effects of the Invention As in the present invention, the delete mark signal is obtained by adding the sum of the photodetectors divided into two in order to obtain the focus control signal, and is further passed through a low-band DC amplifier to change the reflectance. By separating and detecting only the delete mark signal using a bandpass filter, the delete mark signal can be stably detected even when recording is not performed and when recording is performed. Furthermore, since this can be performed separately from the information signal reproduction, the information signal processing circuit can also be constructed by limiting only the band of the information signal.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an example of a conventional optical information recording/reproducing device, FIG. 2 is a top view and a partially enlarged view of a disk, and FIG. 3 is a radial cross-sectional view of the disk shown in FIG. FIG. 4 is a plan view of the guide track and a sectional view of the guide track in the track direction, FIG. 5 is a configuration diagram showing the recording format of the optical information recording/reproducing apparatus shown in FIG. 1, and FIG. 6 is a conventional demark signal. FIG. 7 is a configuration diagram showing an embodiment of the optical information recording/reproducing apparatus of the present invention. FIG. 8 is a reproduction signal waveform diagram of the demark signal in the optical information recording/reproducing apparatus shown in FIG. 7. shows. 1... Semiconductor laser, 2... Condensing lens, 3,
4... Concave and convex cylindrical lens, 5... Aperture lens, 6... Disc, 7... Deflection beam splitter, 8... λ/4 plate, 9... Convex lens, 10...
...split mirror.

Claims (1)

[Claims] 1. A guide track formed by a groove-like structure, and a semiconductor laser that generates a light beam for recording and reproducing information signals such as address signals formed discretely into a pit structure on a disk provided in advance, and the light beam. an optical means for condensing the light into a minute spot light;
comprising two divided light detection means for obtaining a focus control signal and/or a tracking control signal for following and focusing the minute spot light on a guide track of the disk, each of the two divided light detection means; an amplification means for amplifying the output signal of the addition means from the DC level; a bandpass filter means for passing only the band of the delete mark signal; An optical information recording/reproducing device characterized by comprising a comparison means for comparing voltage.