JPH0877559A - Device for discriminating pit area from groove area and method thereof - Google Patents

Abstract

PURPOSE: To correctly discriminate a pit area from a groove area on the same optical disk without erroneous discrimination regardless of the fluctuation of a moving speed of a laser spot by providing a means irradiating and detecting respective off positions of an inner peripheral side and an outer peripheral side of a main beam with sub-beams. CONSTITUTION: A laser beam LB emitted from a semiconductor laser 1 is divided to the main beam MB and two pieces of sub-beams SBP, SBM by a diffraction grating 3, and it is converged on a magneto-optical disk 7 through a beam splitter 4, a 1/4 wavelength plate 5 and an objective lens 6. At this time, the sub-beams SBM, SBP irradiate the off positions of the inner peripheral side and the outer peripheral side of the main beam MB. Photodetectors 10, 11 detect reflected light quantities of the sub-beams SBM, SBP from the optical disk 7, and filter and envelope circuits 14-17 take out high band components from detected light quantity signals to detect respective envelopes. A comparison circuit 19 and a discrimination signal output circuit 20 discriminate and output whether the pit area or the groove area based on the result that the detected envelopes are compared with a prescribed threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for determining whether the current position of a laser beam spot is a pit area or a groove area.

[0002]

2. Description of the Related Art In a rewritable optical disc (mini disc, CD-MO, WO, etc.), a TOC (Ta
ble of contents), and management information such as table of contents information is recorded in advance as pits. That is, the innermost peripheral portion of the disc is formed as a read-only area, and the rewritable area is provided outside thereof.

The reproduction-only pit area and the rewritable area (eg, magneto-optical recording area) are used for reproducing the recording signal, tracking servo polarity, and CLV control (disc rotation control of constant linear velocity method). Signal is different.
Therefore, it is necessary to accurately determine whether the current position of the laser beam spot irradiating the optical disk is the pit area or the groove area (rewritable area).

Conventionally, the above-mentioned discrimination uses a method of utilizing the reproduction signal (RF signal) itself of the recorded information. This will be described with reference to FIG. In FIG. 5, (a) shows the recording surface of the optical disc, where the left side of the alternate long and short dash line is the pit area (reproduction-only area: inner side of the disk) and the right side is a groove area (magneto-optical area = recording / reproducing area: outer side of the disk) Is. (B) is an RF signal based on the amount of reflected light when the laser spot for reproducing the information signal moves from the pit area to the groove area, (c) is an envelope detected from the RF signal, and (d) is an integral waveform of the envelope. , (E) are discriminating signals obtained by comparing the integrated waveform with the threshold value SH, and are high level when the integrated waveform is larger. When this determination signal is high level, it is determined to be a pit area, and when it is low level, it is determined to be a groove area.

[0005]

In the above discrimination method, the integration time constant of (d) is constant in terms of circuit. However, the speed at which the laser spot moves in the direction orthogonal to the track is not constant and changes variously. Therefore, (c)
Even though the frequency of the envelope of is undefined and the laser spot irradiates the groove area,
In some cases, the discrimination signal of (e) becomes high level, in which case erroneous discrimination occurred. Further, if misjudgment occurs, problems occur such that the recording signal cannot be read and tracking servo and CLV control become impossible.
Further, the above-mentioned discrimination method has a problem that extremely strictness is required for the condition setting of the discrimination circuit.

According to the present invention, the pit area and the groove area are
The purpose is to enable accurate discrimination without misjudgment.

[0007]

According to the present invention, whether the current position of a laser spot irradiated so as to traverse a track of a rotating optical disk is a pit area dedicated to reproduction or a groove area capable of recording and reproducing. And a sub-beam for irradiating a tracking control sub-beam to each of an inner peripheral side position and an outer peripheral side position separated from the information signal main beam. Detecting means for detecting the amount of light reflected from the optical disk, processing means for extracting a high frequency component of a predetermined frequency or higher from each light amount signal detected by the detecting means, and detecting each envelope, and detecting by the processing means. A discriminating means for discriminating between the pit area and the groove area based on the result of comparing the formed envelope with a predetermined threshold value; A determination device of the pit area and the groove area having.

In the above, each sub-beam may be radiated at a position deviating from the main beam on the optical disk by about 1/4 track pitch. Further, the discrimination by the discriminating means may be performed by comparing the sum of two envelopes with a predetermined threshold value, and comparing the two envelopes with a predetermined threshold value respectively, one of them is discriminated as a pit area. In this case, it may be determined that the area is a pit area.

Further, the present invention is a method for determining whether the current position of a laser spot irradiated so as to cross a track of a rotating optical disk is a read-only pit area or a recordable / reproducible groove area. The sub-beam for tracking control is irradiated to each position on the optical disc deviated from the main beam for the information signal to the inner circumference side and the outer circumference side by about 1/4 track pitch, and the reflected light amount of each sub-beam from the optical disc is changed. Each high-frequency component above the specified frequency is detected from each detected light amount signal, each envelope is detected from each extracted high-frequency component, each detected envelope is added, and the added result is the predetermined threshold value. And a method for discriminating between a pit area and a groove area based on the comparison result. A.

In the above, the process of "adding each detected envelope, comparing the added result with a predetermined threshold value, and determining whether it is a pit area or a groove area based on the comparison result" Instead, “Compare each detected envelope with a predetermined threshold value, determine whether it is a pit area or a groove area based on each comparison result, and determine that it is a pit area from at least one comparison result. If it is done, it is determined that it is a pit area ”.

[0011]

The envelopes of the reflected light amount signals of the two sub-beams moved in the direction orthogonal to the track do not have their respective peaks matched with each other, and have a positional relationship of mutually compensating each other. Therefore, 2
It is possible to determine whether it is a pit area or a groove area by comparing the addition result of two envelopes with a predetermined threshold value or by taking the logical sum of the comparison results with the predetermined threshold value of each envelope. Become.

[0012]

Embodiments of the present invention will be described below. FIG. 1 shows the configuration of the discriminating apparatus of the embodiment, and FIG. 2 shows the relationship between the area on the disk surface and the output signal of each block in FIG.

A laser beam LB emitted from the semiconductor laser 1 is collimated by a collimator lens 2 and is collimated by a collimator lens 2 and a main beam MB and two sub-beams SBP,
After being divided into SBMs and transmitted through the beam splitter 4 and the quarter-wave plate 5, the objective lens 6 is used for the magneto-optical disk 7
Is focused on the recording surface of. At this time, the two sub beams S
As shown in FIG. 2A, the BP and SBM are located at positions deviated from the main beam MB in the opposite direction by ¼ track pitch (0.4 μm). That is, the sub-beam SBP and the sub-beam SBM are located at positions separated by 1/2 track pitch,
Therefore, when the laser spot is moved in the direction orthogonal to the track, one of the sub-beams SBP and SBM always irradiates the pit or groove.

The magneto-optical disk 7 is a rewritable CD (compact disk) having an inner peripheral portion as a reproduction-only pit area and an outer peripheral portion as a recording / reproducing groove area. The pit width of the pit area is 0.6 μm and the pitch is 1.6 μm.
Is. The groove width of the groove area is 1.
At 0 μm, the pitch is 1.6 μm. It should be noted that the groove is provided with a small meandering (wobbling) of 44.1 kHz in the track pitch direction, whereby an address is recorded.

A laser spot reflected by the magneto-optical disk 7 (main beam MB and two sub beams SBP, S
BM) is collimated by the objective lens 6, transmitted through the quarter-wave plate 5, further reflected by the beam splitter 4, and then focused on the photodetectors 9, 10, 11 by the lens 8. It Here, the photodetector 9 is for the main beam, and the photodetectors 10 and 11 are for the sub-beam.

The photodetector 9 comprises four light receiving parts a, b, c,
d. When the main beam MB is reproducing the pit area, the outputs of the light receiving portions a, b, c and d are added by the adder 12, and this is the reproduction signal E. Also,
When the main beam MB is recording / reproducing in the groove area, the difference between the outputs of the light receiving portions a and c and the light receiving portions b and d is calculated by the differential amplifier 13, and this is used as the reproduction signal M.

Sub-beam SB detected by photodetector 10
After P has a high-frequency component extracted by the filter 14 having a cutoff frequency of 50 kHz, the envelope detection circuit 16 detects the envelope (b). Similarly, the photodetector 1
The sub-beam SBM detected at 1 has its high-frequency component extracted by the filter 15 having a cutoff frequency of 50 kHz, and then the envelope detection circuit 17 detects the envelope (c).

Envelope (b) and envelope (c)
Are added by the adder circuit 18, and the signal (d) after this addition is input to the comparison circuit 19. The comparison circuit 19 compares the signal (d) with the threshold value SH. As a result, if “signal (d)> threshold value SH”, the discrimination signal output circuit 20 outputs a discrimination signal (= indicative of pit area) to the switch SW, which causes the switch SW to move to the adder 12 side. Can be switched. The switch SW is the differential amplifier 13 when the discrimination signal output circuit 20 does not output the discrimination signal.

The frequency band of the CD to be reproduced is 20
0 kHz to 720 kHz, the wobbling frequency of the groove in the groove area is 44.1 kHz, and the cutoff frequencies of the filters 14 and 15 are 50 kHz.
At 4 and 15, the CD information signal passes and the wobbling signal is cut. Further, since the track pitch is 1.6 μm, 1.6 μm × 50 kHz = 8 cm / sec, and the area can be accurately discriminated by this device up to the moving speed of the laser spot in the track orthogonal direction of 8 cm / sec.

Next, another embodiment will be described with reference to FIGS. In the other embodiments, each envelope is compared with a threshold value, and if any comparison result is a "pit area", it is determined that the laser spot is in the pit area.

The configuration up to the envelope detection circuits 16 and 17 is the same as that of the above-mentioned embodiment, and therefore its explanation is omitted. The envelopes (b) and (c) detected by the envelope detection circuits 16 and 17 are compared with the threshold values SHP and SHM by the comparison circuits 21 and 22, respectively. If the comparison result of the comparison circuit 21 is “envelope (b)> threshold value SHP”, the determination signal output circuit 23 determines the determination signal (= indicative of pit area).
Is output to the switch SW. Similarly, if the comparison result of the comparison circuit 22 is “envelope (c)> threshold value SHM”, the determination signal output circuit 24 determines the determination signal (= pit area).
Is output to the switch SW. The switch SW determines that it is a "pit area" when the determination signal is input from at least one of the determination signal output circuits 23 and 24, and thereby the switch SW is switched to the adder 12 side. It should be noted that when the discrimination signal output circuit 20 is not outputting the discrimination signal, the switch SW is switched as in the above-described embodiment.
Is the differential amplifier 13.

In the above embodiment, only the switching of the reproduction signal is described, but the polarity of the tracking servo control may be reversed depending on whether the current position of the laser spot is the pit area or the groove area. When the current position of the laser spot is in the pit area, the optical disc is controlled to rotate at a constant linear velocity based on the sum of the RF signals, and when the current position of the laser spot is in a groove region, the rotational speed is controlled to be constant at a linear velocity based on the wobble signal. You can also

[0023]

As described above, the present invention utilizes the fact that the peaks of the envelopes of the reflected light amount signals of the two sub-beams which are moved in the direction orthogonal to the tracks do not match each other, and they are in a mutually compensating positional relationship. Since it is determined whether there is a groove area or a groove area, it is possible to prevent an erroneous determination due to a change in the moving speed and perform an accurate determination. Also, the circuit configuration for that is simple.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a discriminating apparatus according to an embodiment.

2 is an explanatory diagram showing a relationship between an area on the disk surface and an output signal of each block in FIG. 1. FIG.

FIG. 3 is a block diagram showing the configuration of a discriminating apparatus according to another embodiment.

4 is an explanatory diagram showing the relationship between the area on the disk surface and the output signal of each block in FIG. 3. FIG.

FIG. 5 is an explanatory diagram showing a conventional area determination method.

[Explanation of symbols]

 9, 10, 11 Photodetector 14, 15 Filter 16, 17 Envelope detection circuit 18 Adder circuit 19, 21, 22 Comparison circuit 20, 23, 24 Discrimination signal output circuit

Claims (6)

[Claims] 1. A device for determining whether a current position of a laser spot irradiated so as to cross a track of a rotating optical disk is a read-only pit area or a recordable / reproducible groove area. The irradiation means for irradiating the position outside the inner side and the position outside the main beam for the information signal with the tracking control sub-beam, and the amount of light reflected from the optical disc for each of the two sub-beams. Detecting means for detecting, processing means for detecting each envelope by extracting a high frequency component of a predetermined frequency or higher from each light amount signal detected by the detecting means, and an envelope detected by the processing means with a predetermined threshold value. And a discrimination means for discriminating whether the region is a pit region or a groove region based on the result of the comparison, and Over Bed area discriminating device. 2. The device for discriminating between a pit area and a groove area according to claim 1, wherein the irradiating means irradiates each of the sub-beams on the optical disc at a position deviating from the main beam by about 1/4 track pitch. . 3. The pit area / groove area discrimination device according to claim 1, wherein the discrimination means compares the sum of two envelopes with a predetermined threshold value. 4. The pit area according to claim 1, wherein the determining means compares the two envelopes with a predetermined threshold value, and if either one of the envelopes is determined to be a pit area. A device for discriminating between pit areas and groove areas. 5. A method for determining whether a current position of a laser spot irradiated so as to cross a track of a rotating optical disk is a read-only pit area or a recordable / reproducible groove area, Approximately 1/4 from the main beam for information signals on the optical disc
A sub-beam for tracking control is applied to each position deviated to the inner and outer circumferences of the track pitch, the amount of reflected light from the optical disc of each sub-beam is detected, and the high-frequency component of a predetermined frequency or higher is detected from each detected light amount signal. To detect each envelope from each of the extracted high frequency components,
A method for discriminating between a pit area and a groove area, in which each detected envelope is added, the added result is compared with a predetermined threshold value, and whether the pit area or the groove area is discriminated based on the comparison result. 6. A method for determining whether the current position of a laser spot irradiated so as to cross a track of a rotating optical disc is a read-only pit area or a recordable / reproducible groove area, Approximately 1/4 from the main beam for information signals on the optical disc
A sub-beam for tracking control is applied to each position deviated to the inner and outer circumferences of the track pitch, the amount of reflected light from the optical disc of each sub-beam is detected, and the high-frequency component of a predetermined frequency or higher is detected from each detected light amount signal. To detect each envelope from each of the extracted high frequency components,
Each of the detected envelopes is compared with a predetermined threshold value, and it is determined whether each is a pit area or a groove area based on each comparison result, and if at least one comparison result is a pit area, A method for distinguishing between a pit area and a groove area, which determines that the area is a pit area.