JPH0570209B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical recording and reproducing device for optically recording and reproducing information on a disc-shaped information carrier (disk), and particularly relates to an optical recording and reproducing device that optically records and reproduces information on a disc-shaped information carrier (disc), and in particular, it is an optical recording and reproducing device that optically records and reproduces information on a disc-shaped information carrier (disc). The present invention relates to the configuration of an optical recording/reproducing apparatus using an optical disk having a sector structure in which information is recorded and reproduced by dividing the track of the disk into a plurality of information recording areas.

Conventional structure and its problems A disk is formed using a photosensitive recording material,
The disk is rotated, and by irradiating it with light from a laser or the like focused on a minute diameter of 1 μm or less, signals are recorded on the disk at high density as unevenness, hole formation, or changes in density, etc., or being regenerated. In order to perform high-density recording by narrowing the track pitch in such an optical recording/reproducing device, an optically detectable concentric or spiral guide track is provided on the optical disk, and tracking control is applied to the guide track. In this way, signals are recorded and reproduced. Furthermore, since the length of digital information is not fixed like a television image, it is difficult to efficiently record and reproduce variable length digital data on an optical disk using only track addresses. For this reason, each track is divided into a plurality of information areas and managed. This information area is called a sector, and each sector is given a sector address that is serially numbered within the same track.By doing this, the position of each sector can be specified by the track address and sector address. Such sector address information is cut together as a concave and convex phase groove when forming a guide track on the optical disk 2. FIG. 1 is a partial perspective view showing the groove structure of an optical disk 2 provided with guide tracks 1a to 1d. Grooves 1a to 1d having a width W, a pitch P, and a depth S are provided on the surface R side of the optical disk 2, and these grooves serve as guide tracks 1a to 1d. The guide tracks 1a to 1d are formed concentrically or spirally. A photosensitive recording material is deposited on the surface R side to form a recording layer 4. 5 indicates a recorded portion recorded by a laser beam and whose reflectance has changed. FIG. 2 shows a disk format of an optical disk 2 having a sector structure. TA1,
TA2 is the address area where address information is recorded, S
1 to S32 are sector areas for recording information, SP
1 to SP32 are areas in which sector separation information provided for dividing the guide track into sector areas is recorded. Here, both the address area and the sector separation area are formed in the form of phase grooves on the guide track. The sector separation information described above includes (1) a method of encoding a sector number to form a phase groove, and (2) a method of forming a phase groove using a special pattern of signals. Here, the above-mentioned method (2) will be explained for the purpose of forming a sector separation area that is resistant to scratches and defects on the optical disk and has high information recording efficiency. The sector separation area has a frequency range of 1/6 to 1/10 of the frequency range of the information recording data in order to easily distinguish it from the information recording data, and to obtain a signal with good S/N that is stable against scratches and defects on the optical disk. A frequency domain is selected. By the way, in order to search for a necessary track on an optical disk, the amount of movement of the optical head is detected by counting the change in the diffracted light that occurs when a minute spot light crosses the guide track, that is, the groove crossing signal. However, the above-mentioned change in the diffracted light from the sector separation area is mixed into this groove crossing signal, making it impossible to accurately count the groove signals, so the signal from the sector separation area is modulated at an even higher frequency to improve the frequency characteristics of the light. This suppresses the sector isolation region from being mixed into the down-groove signal. Figure 3a shows a section S32 of a part of the guide track in Figure 2.
This is an enlarged illustration of the area between S1 and S1. b is a sectional view in the track direction. The sector separation region SP1 has a structure in which the unevenness of the groove of width g is further modulated by the unevenness of the groove of pitch h.

A configuration as shown in FIG. 4 can be considered as an apparatus for recording and reproducing an optical disk separated into sector areas in this manner. The light beam emitted from the laser light source 6 is collected by a condensing lens 7, and a beam splitter 8,
The light passes through the λ/4 plate 9 and is irradiated onto the optical disk 2 by the aperture lens 10 as a minute spot light. The optical disk 2 is rotated by a disk motor 11. The reflected light from the optical disk is separated by a beam splitter 8 because the plane of polarization is changed. Further, the light is received by a focus detector 14 and a tracking detector 15 by a convex lens 12 and a split mirror 13, respectively. 5A shows the structure of the light receiving element of the focus detector 14, and FIG. 5B shows the configuration of the light receiving element of the tracking detector 15 and the shape of the light receiving spot. Focus detector 14
is a two-split photodetector FA, FB at the focal point of the reflected light.
are placed. The tracking detector receives a far-field image of the reflected light by arranging two split photodetectors T _A and T _B so that the guide track 1 and its dividing plane are parallel. The outputs F _A and F _B of the focus detector 14 are input to a differential amplifier 16 , and a focus control circuit 17 controls an optical pick-up 18 so that the aperture lens 10 follows the surface vibration of the optical disk.
is driving. The outputs T _A and T _B of the tracking detector 15 are also input to the differential amplifier 19,
The tracking control circuit 20 controls the aperture lens 1.
The optical pickup 18 is driven so as to follow the eccentricity of the optical disk. Also, the total reflected light F _A , F _B ,
The sum of T _A and T _B is amplified by a high frequency amplifier 21, and an address signal is reproduced 22, a recorded signal is reproduced 23, and a sector separation area is detected 24.

High frequency amplifier 2 when the address area and sector address area in the section S32 to S1 in FIG.
The output waveform of No. 1 is shown in FIG. 3c. Since this waveform represents the amount of total reflection from the guide track, the groove 25
Since the amount of reflected light is small due to diffraction, the amplitude is small, and since there is no diffraction between the grooves 26, the amount of reflected light is large and therefore the amplitude is also large. The output waveform of the TA1 section clearly represents this situation. However, in the sector separation area SP1, the change in the reflected light between the grooves is small, and the amplitude is significantly smaller than in the address area TA1, and there are dropouts like 27a to 27c due to scratches and defects on the optical disk. and the sector separation area becomes undetectable. FIG. 6 is a diagram explaining the reason why the amplitude of the sector separation area becomes small. a is address area
The figure shows how minute spot lights 28a to 28b are irradiated onto the TA along the guide track 1. In the address area TA, minute spot lights 28a, 2
The width g of the groove unevenness is set larger than that of 8b. Therefore, the changes in the reflected light from the minute spot light irradiated to the address area are
This is sufficiently large to show the change in the amount of reflected light itself. For example, if the spot diameter is φ1 μm and the groove width is 0.5 μm, the amount of reflected light from the grooves/the amount of reflection between the grooves = 0.5,
A signal waveform with a sufficiently good S/N ratio can be obtained. Figure 3c
The amplitude 29 of the address area TA1 represents this difference in the amount of reflected light. By the way, FIG. 6b shows a case where the minute spot light 28c is irradiated onto the sector separation area SP as described above. In this way, in the sector separation area SP, the width g of the groove unevenness in the address area TA is further modulated by the pitch h. For this reason, even if the minute spot light 28c is irradiated onto the pit row region of the pitch h, since grooves are always included in the minute spot, the amount of reflected light does not reach the level between the grooves. For this reason, the difference in reflectance between grooves is not sufficiently large, and the amplitude of the sector isolation region becomes small, as shown at 30 in FIG. 3c. 27a~
If there is a dropout caused by a scratch or defect on the optical disk such as 27c, there is a risk that the sector separation area will be erroneously detected, making it impossible to perform a stable sector search.

Purpose of the Invention The object of the present invention is to eliminate the instability in detecting sector separation areas as described above, provide an optical information recording and reproducing device that detects sector separation signals with a good S/N, and perform stable sector searches. It is said that

Structure of the Invention The present invention has a groove-shaped guide track, and the guide track is divided into a plurality of information recording areas (sectors), and a far-sighted image of reflected light from an optical disk is displayed on a dividing plane in a direction perpendicular to the guide track. The light is received by a split photodetector. The guide track has a track address area encoded by a change in the unevenness of the groove, and a sector separation area consisting of a row of pits made up of a finer change in the unevenness of the groove than the track address area. The address area is reproduced from the sum signal of the photodetector, and the sector separation area is reproduced from the difference signal of the photodetector. With this configuration, in the sector separation area, changes in the amount of reflected light due to diffraction in the direction parallel to the guide track are detected. This makes playback possible.

DESCRIPTION OF EMBODIMENTS FIG. 7 is a diagram showing the configuration of a light detection section in an optical information recording/reproducing apparatus of the present invention. The focus detector 14 has two divided photodetectors F1 and F2 arranged at the position where the reflected light is focused, as in FIG. 5a. The tracking detector 15 has four divided photodetectors T1 to T4 arranged so as to have dividing planes parallel and perpendicular to the guide track 1, as shown in FIG. 7b. Tracking control is performed by the sum amplifier 31a (T ₁ +T ₂ ) and by the sum amplifier 31b (T ₃
+T ₄ ) and tracking differential amplifier 19
(T1 + T2) - (T3 + T4) is obtained from the output.
The sector separation signal is not detected from the output of the high frequency amplifier 21, that is, from the change in the amount of total reflection light from the optical disk, as shown in FIG. 5c. That is, the photodetector is arranged so as to have a dividing plane perpendicular to the guide track 1, and from the output of the differential amplifier 33,
Detecting sector isolation area. Sum amplifier 32a
(T1+T3), the sum amplifier 32b creates (T2+T4) and outputs a differential output (T1+T3)-(T2+T4). The output waveform of this differential amplifier 33 is
Shown in Figure d. As shown in 34, the waveform amplitude of the sector separation area is equal to the amplitude 30 of the high frequency sum amplifier in FIG. 3c.
It is larger and output with good S/N. When the sector separation area SP is irradiated with a minute spot,
As explained in FIG. 6, the change in the amount of total reflection light is small. However, the minute spot light is diffracted in a direction parallel to the guide track 1 by the unevenness of the pitch h groove provided in the sector separation region SP. Since the tracking detector 15 is arranged to receive a far-field image of the reflected light, it can detect a diffraction image in a direction parallel to the aforementioned guide track 1. Therefore, by setting the dividing plane of the photodetector in the direction perpendicular to the guide track 1 and extracting the differential output as shown in FIG. can also be detected with a large amplitude and a good S/N ratio. Furthermore, due to the characteristic of extracting differential output in the direction parallel to the guide track, defects such as dust and scratches on the optical disk that are larger than the size of the minute spot light are canceled, and the effect of noise is smaller than when detecting by the amount of total internal reflection light. Become.

Furthermore, when recording is performed using changes in the reflectance of the recording material, this change is also canceled, making it possible to detect only the sector separation area with a good S/N ratio, regardless of whether or not there is recording. .

Detection of sector separation areas is an important function for determining specific recording and reproduction locations on an optical disk, and stability is required as well as reproduction of address signals. As described above, by detecting the change in the amount of reflected light due to diffraction in the direction parallel to the track using differential output, it becomes possible to identify the sector separation area SP with stable and high output.

Such a change in the amount of reflected light due to diffraction in the direction parallel to the track allows stable detection not only of the sector separation area but also of the address area TA.
35 in FIG. 3d is a signal waveform of the output of the differential amplifier 33 in a direction parallel to the track in the address area. Regarding the address area TA, as described in FIG. 6a, the minute spot lights 28a and 28b are not irradiated to both the groove portion 25 and the groove gap 26 at the same time, so that the differential output appears only by diffraction by the groove edge 36. Therefore, as shown at 35, it is detected as a differential waveform of the output signal waveform of the high frequency amplifier 21 (FIG. 3c).
In this case as well, as with the detection of sector separation areas, scratches, defects, etc. on the optical disk are canceled, so it is possible to perform signal detection with a good S/N ratio.

The configuration for differentially detecting changes in reflectance in the direction parallel to the track can also be applied to signal detection for read-only optical discs.

Effects of the Invention As described above, the present invention has a groove-shaped guide track, and the guide track is divided into a plurality of information recording areas (sectors). The light is received by a split photodetector with split planes in the direction. The guide track has a track address area encoded by a change in the unevenness of the groove, and a sector separation area consisting of a row of pits made up of a finer change in the unevenness of the groove than the track address area. The track address area is reproduced from the sum signal of the photodetector, and the sector separation area is reproduced from the difference signal of the photodetector. In this way, in the sector separation area, since the difference signal from the photodetector is used for reproduction, changes in the amount of reflected light due to diffraction in the direction parallel to the guide track are detected. Therefore, even if the pit row is made up of uneven grooves that are even finer than the track address area, it is possible to reproduce the sector separation area with higher output and a better S/N ratio than by detecting changes in the amount of total reflection light. It is.

[Brief explanation of the drawing]

FIG. 1 is a partial perspective view showing the groove structure of an optical disk, FIG. 2 is a diagram showing the disk format of an optical disk having a sector structure, and FIG. 3 is a diagram showing the groove structure of the address area, sector separation area, and Figure 4 shows the configuration of the optical recording/reproducing device; Figure 5 shows the configuration of a conventional photodetector and signal processing circuit; Figure 6 shows the diffraction of minute spot light. FIG. 7 is a diagram showing the configuration of an embodiment of the photodetector and signal processing circuit of the present invention. 1...Guidance track, 2...Optical disk, TA
...address area, SP...sector separation area, 6...
Light source, T1 to T4...photodetector, 33...differential amplifier.

Claims (1)

[Claims] 1 A light source such as a laser is focused into a minute spot light, and a concentric or spiral guide groove track is formed, and the track is divided into a plurality of information recording areas (sectors).
means for irradiating light onto an optical disk divided into two; means for receiving a far-field image of reflected light or transmitted light from the optical disk with a photodetector having a dividing surface perpendicular to the track; each guide groove track is a groove; It has a track address area encoded by a change in the unevenness of the track address area, and a sector separation area consisting of a row of pits formed by a change in the unevenness of a groove having a length thinner than the track address area. An optical recording/reproducing apparatus comprising: means for reproducing from a sum signal from a detector; and means for reproducing a sector separation area from a difference signal from the photodetector.