JPH0312830A - Tracking error detection method - Google Patents

Abstract

PURPOSE:To attain accurate error detection in which an unstable element is abolished at the time of a recording/eliminating action by using auxiliary beams which are previously separated from main beams as detection means and arranging two auxiliary beams which execute differential detection on the same side as the main beams in a track direction. CONSTITUTION:A diffraction grating 2a is constituted of a first area E and a second area, both of which are divided by a division line which actually coincides with the track center line T of a disk 6. The direction of the grating of a first area E is formed in such a manner that a diffraction direction inclines counterclockwise with respect to the track center line T by an angle theta1. In the first area E, the first and second auxiliary beams E1 and E2 generated by + or -primary diffraction light beams among high-order diffraction light beams project first and second auxiliary spots S2 and S3 on the disk 6, and they are generated in positions displaced from the track center line T in accordance with an inclination theta1 by a distance P1. Then, error detection is executed by the differential detection. Thus, accurate error detection in which the unstable element is abolished is attained even at the time of recording and elimination.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a tracking error detection method used in an optical recording/reproducing device.

<Summary of the Invention> The present invention provides a novel tracking error detection method that can be applied to any recording, playback, or erasing operation, and includes two regions with different grating spacing and diffraction directions. A diffraction grating means is used to generate two sub-beams consisting of first-order diffracted light in respective regions from the main beam on the same side in the track direction, and these are irradiated onto the tracks of the recording medium to detect their reflection or The first purpose is to detect the amount of racking error by fully detecting the difference in light intensity between the detection lights obtained by transmission.

Further, by the ±first-order diffracted light in the region of the husband 4 of the diffraction grating means, first and second sub-beams are generated in the front and rear directions in the track direction from the main beam, and further, third and fourth sub-beams are generated outside of the main beam. , these are irradiated onto the tracks of the recording medium, and among the four detection lights obtained by reflection or transmission, the difference in light intensity between the pair of detection lights in front of the main beam and the difference in the light intensity between the pair of detection lights in the rear of the main beam. The second purpose is to use the sum of
This makes it possible to obtain a more reliable detection signal.

In addition, in the second aspect above, each light amount of the first, second, third, and fourth detection lights obtained from the first, second, third, and fourth sub beams (ex, e2+f1.fz) The third principle is to use the value obtained by (fz ex) + (e2 - t2) as the tracking error amount, and the effect of the offset in the light amount due to the deviation between the main beam center and the area dividing line of the diffraction grating means is It was designed to be resolved.

Furthermore, in the second aspect of the invention, a correction constant corresponding to the detected light amount ratio between the unrecorded portion and the recorded portion;
The fourth feature is that by incorporating a correction constant corresponding to the ratio of the light source's output during reproduction and the output during recording (or erasing), it can be applied to the same device during recording (or erasing) as well. The main idea.

<Prior art> An optical recording/reproducing device has a method of forming recording pits.
Various recording methods are known, such as phase change type and reflectance change type, and are classified into rewritable type and write-once type depending on the reversibility of pit formation. All playback devices use a recording medium in which guide grooves (sometimes convex parts) corresponding to recording tracks are formed in advance, and the beam traces these guide grooves during recording, playback, or erasing operations. Tracking control is then performed.

As the tracking error detection methods generally used for this purpose, two methods are mainly used: a push-pull method using one beam and a three-beam method.

These will be explained with reference to FIGS. 3 and 4.

1. Push-pull method using one beam This method irradiates a track with one beam (generally serves as a recording/reproduction beam), and divides the detection light obtained by reflection or transmission into two areas by a dividing line that coincides with the track direction. The amount of Q + - racking error is detected by dividing the area into two areas and detecting the difference in light amount between each area.

In FIG. 3(a), a beam irradiated onto a recording medium 33 via a beam splinter 31 and an objective lens 32 is reflected by the recording medium 33, split by a beam brick 31, and incident on a two-split photodetector 34. be done. The photodetector 34 consists of two regions 34a and 34b divided by a dividing line 34c that substantially coincides with the track center, and the outputs of each region are connected to the 10-1 and - side number terminals of the subtractor 35. There is.

With such a configuration, when the beam spot deviates from the track center of the recording medium, each area 34a of the photodetector 34,
A difference occurs in the amount of light 34b, and a tracking error signal TES appears at the output end of the subtracter 35, with the level indicating the amount of error and the phase indicating the direction of shift.

2.3 Beam Method This method is applied to the reproduction of recorded data, and as shown in FIG. Irradiate the two shifted sub-beams 42 and 43',
The respective detection lights obtained by the reflection or transmission are detected by separate photodetectors, and the amount of tracking error is detected by detecting the difference in the amount of light in each area.

<Problem that the invention seeks to solve> Each of the conventional methods described above has the following problems.

1. Push-pull method using one beam This method is used when the perpendicular state of the recording body 33 and the beam is damaged due to the recording body 33 being bent or bent, or when the objective lens 32 If the light is shifted in the direction perpendicular to the track, the position of the photodetector 34 and the detection light will be shifted, and the tracking error signal will be multiplied by an offset, which may prevent normal tracking from being performed.

In addition, during recording/erasing operations, there are times when the reflection state becomes transiently unstable during the generation or erasing process of recorded pits, and if this detection method is also used during recording/erasing, also had to be taken into consideration.

2.3 Beam method This method can be used without any particular problems in the case of reproduction, but
During recording (or erasing), the sub beam 42 that precedes the main beam 41 (when erasing, the sub beam 43 that follows)
) irradiates the unrecorded portion, a discontinuous offset occurs between the beams on both sides based on the presence or absence of the recording pit 44, making it impossible to detect a correct error signal.

The present invention provides a novel tracking error detection method that solves the problems of the existing methods described above.

<Means for Solving the Problems> The present invention provides, as a first means, a first area in which the direction of diffraction is inclined at a predetermined angle with respect to the tracks of the recording medium; First-order diffraction in each region of the diffraction grating means is used, and the second region is inclined at a predetermined angle in the opposite direction to the first region, and the grating interval is different from that of the first region. First and second sub-beams are generated by light from the main beam on substantially the same side in the track direction, deviated in opposite directions from the track center, and emitted at different angles, and these sub-beams are directed to the recording medium. The amount of tracking error is detected based on the difference in the amount of light between the first and second detection lights obtained by irradiation and reflection or transmission.

Further, as a second means, a first area whose diffraction direction is inclined at a predetermined angle with respect to the tracks of the recording body, and a first area whose diffraction direction is tilted at a predetermined angle with respect to the tracks of the recording body in a direction opposite to the first area. using a diffraction grating means having a second region which is tilted and whose grating interval is different from that of the first region;
± according to the above first area approximately in the track direction of the main beam
The first, which consists of first-order diffracted light and is offset from the track center,
Consisting of a second sub-beam and ±first-order diffracted light by the second region, the second sub-beam has a different emission angle from the first and second sub-beams, and is directed from the center of the track to the first and second sub-beams. Third and fourth sub-beams are generated which are deflected in the opposite direction to the first sub-beam, and the first, second, third and fourth sub-beams are irradiated onto the recording medium and obtained by reflection or transmission. , a value obtained by adding the light amount differences between the first and third detection lights and the second and fourth detection lights among the second, third, and fourth detection lights is detected as a tracking error amount.

In addition, as a third means, a first area whose diffraction direction is tilted at a predetermined angle with respect to the tracks of the entire recording body, and a first area whose diffraction direction is tilted at a predetermined angle with respect to the tracks of the recording body in a direction opposite to the first area are provided. and a second region having a grating interval different from that of the first region. It consists of first and second sub-beams that are symmetrically deviated from the track center with the optical axis as the axis of symmetry, and ±first-order diffracted light from the second region, and is different from the first and second sub-beams. Third and fourth sub-beams having an emission angle and symmetrically offset from the track center in the opposite direction to the first and second sub-beams with the main beam optical axis as the axis of symmetry are generated; The light quantities (el) of the first, second, third, and fourth detection lights obtained by irradiating the recording medium with the first, second, third, and fourth sub-beams and reflecting or transmitting them.

Based on Q2* f1* f2 ), (fx
The value obtained by j+ , ) + (e2f2) is detected as the amount of tracking error.

Furthermore, as a fourth means, a first area whose diffraction direction is inclined at a predetermined angle with respect to the tracks of the recording body, and a first area whose diffraction direction is tilted at a predetermined angle with respect to the tracks of the recording body in a direction opposite to the first area. Using a diffraction grating means having a second region which is tilted and has a grating interval different from that of the first region, the diffraction grating means is composed of tenth-first order diffracted light by the first region approximately in the track direction of the main beam, The first and second sub-beams deviated from the track center and the ±-first-order diffracted light beam formed by the second region have an emission angle different from that of the first and second sub-beams, and Generate third and fourth sub-beams that are deviated from the center in the opposite direction to the first and second sub-beams, and irradiate the recording medium with these first, second, third and fourth sub-beams. The first, second, and
Of the third and fourth detection lights, when reproducing the value is the sum of the light intensity difference between the first and third detection lights and the light intensity difference between the second and fourth detection lights, and when recording (or erasing) is the value obtained by multiplying the light intensity difference between the first and third detection lights by a correction constant corresponding to the detection light intensity ratio between the unrecorded area and the recorded area, and the light intensity difference between the second and fourth detection lights. Further, a value obtained by multiplying this by a correction constant corresponding to the ratio of the output during reproduction and the output during recording (or erasing) of the light source is detected as the amount of tracking error.

<Operation> In each of the first means, second, third, and fourth means described above, the sub-beam separated from the main beam in advance is used as a total detection beam, and the two sub-beams for differential detection are used. The beams are arranged on the same side in the track direction with respect to the main beam.

As a result, accurate error detection can be performed while completely eliminating unstable factors even during recording and erasing operations.

In the second, third, and fourth means, two pairs of sub-beams for differential detection are arranged in front and behind the entire main beam in the track direction, and the difference signal ' from each pair is 71
Count to 0. This results in a much higher level error signal.

In addition, in the third and fourth means, the signals in each pair are operated to have opposite phases with respect to the sub-beams from the same area of the diffraction grating means. As a result, even if the diffraction grating means is deviated in the direction perpendicular to the optical axis with respect to the main beam and an imbalance occurs in the first and second regions, this is canceled out by adding the difference signals of each pair, and the detection signal no offset occurs.

Furthermore, in the fourth means, based on the second means, an offset of detected values between each pair caused by the presence or absence of pits at the front and rear of the main beam at the time of recording or erasing, that is, at the above two pairs of detection positions. A correction constant corresponding to the output ratio of the beam during reproduction and a correction constant corresponding to the output ratio of the beam during reproduction are incorporated into the calculation formula. This allows the same detection device to be used during recording or erasing operations.

<Example> Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 and 2.

1 and 2 show embodiments of a device to which the tracking error detection method of the present invention is applied.
An explanatory diagram showing the arrangement of spots on a disk that is a ζE recording medium and the arrangement of spots on a photodetector, FIG. 1(b) is a block diagram of a tracking error signal detection circuit, and FIG. 2(a) and ( b) shows an explanatory diagram of beam generation by the optical system of the optical head and the diffraction grating.

First, the optical system will be explained with reference to FIG. In FIG. 2(a), 1 is a semiconductor laser which is a light source, and 2 is a semiconductor laser as a light source;
Detail M is shown in b). An optical atomizer having a diffraction grating 2ai divided into two parts; 3 is a half mirror for beam splitting and non-war aberration generation; 14 is a Collineau 1-lens; 5 is an objective lens; 6
Reference numeral numeral 1 indicates a disk serving as a recording medium, 7 a plano-concave lens, and 8 a photodetector divided into sections shown in detail at f41 in FIG. 1(a). The beam emitted from the semiconductor laser l is separated by a diffraction grating 2 into a main beam and two pairs of sub beams, which will be detailed later.
After the optical path is bent by the half mirror 3, the beams are irradiated onto the disk 6 via the collimating lens 4 and the objective lens 5 as five beams. After this, it is reflected by the disk,
The five returned Q beams obtained are detected by the objective lens 5,
The light passes through the collimating lens 4 , the half mirror 3 , and the plano-concave lens 7 and enters the photodetector 8 .

Next, the generation of five beams by the diffraction grating 2a will be explained with reference to FIG. 2(b). Figure 2(b) shows the diffraction grating 2.
a'r This is a view seen from the optical axis direction, and shows the beams generated thereby and the spots they project onto the disk.
1 Schematic representation. The diffraction grating 2a consists of two regions, a first region E and a second region F, which are divided into multiple regions by dividing lines substantially coinciding with the track center line T of the deynuk 6. The direction of the grating in the first region E is such that the diffraction direction is inclined counterclockwise in the figure at an angle θ1 with respect to the track center line T.
and has a constant first lattice spacing.

The second region F is formed such that its grating direction is inclined at an angle θ2 in the clockwise direction in the figure, which is opposite to the first region E, with respect to the track center line T, and the second region F is different from the first region E. have a different second lattice spacing.

This diffraction grating 2a makes the beam of the semiconductor laser 1 zero.
It is separated into the next instruction light and two types of multiple higher-order diffracted beams from each area E and F. Of these, the O-order instruction light is directed to the main spot on the disk 6 as a raw beam (indicated by optical axis O). )S
re-project.

In the first region E, first and second sub-beams E, E2 are generated by the ±first-order diffracted lights among the higher-order diffracted lights. The first and second sub-beams E+ and E21d are projected onto the E21d disk 6 by a distance P1 from the track center T due to the above-mentioned inclination θ1. It is set so that it occurs in the position.

In the second region F, υ, third and fourth sub-beams F 1 + F 2 are generated by the ±first-order diffracted light. These third and fourth sub-beams F l+ F2 project third and fourth sub-spots S4, Ss''(f'') onto the disk 6,
Due to the above-mentioned error θ2, these are set to occur at a position offset from the track center T by a distance F1 to the opposite side from the first and second sub-spots S2°Ss.

The lattice spacing of each region is set so that the third and fourth sub-beams F+, F21'i have a large diffraction angle with respect to the first and second sub-beams El+F2.
5 are arranged outside of the spots S2 and Ss, respectively, in the direction of the center track. However, according to the present invention, as will be described in detail later, all the first and third sub-beams E for differential signal detection are
1. These first and third sub-beams E1
．． F1 and the second and fourth sub-beams E2. During each interval F2, the deviation distance P+ffi of each spot with respect to the track center T must be made the same at the same time.

In the conventional three-beam method, which uses only a pair of sub-beams consisting of the ±1st-order diffracted lights of one diffraction grating placed before and after the main beam, the track center can be adjusted by rotating the optical axis of the diffraction grating. Although the deflection distance of the sub beam itself changes, the beams on both sides are always under the same conditions in principle, and no misalignment occurs. However, in this invention,
When the area division line of the diffraction grating 2a is tilted with respect to the I-rack center T, the spots on the same side (S2 and S) as described above are separated.

Or, since the deviation distances P1 of Ss and Ss) from the track center T do not match, it is no longer possible to obtain a correct error signal, so it is necessary to rotate the diffraction grating 2a around the optical axis to match the deviation distances P1. is necessary. At this time, the diffraction angles of the sub-beams E11 E 2 , F 1 , F 2 are large, and the sub-spots S2 , Ss , S,.

The farther Ss is from the main spot (Sl), the greater the displacement due to rotation, and the more difficult the adjustment becomes. For this reason, each sub-spot S2 is
+, Ss, S,, Ss is as close as possible to the main spot) St, the more desirable, and the third and third sub spots) S2
and S4 interval P2 (second and fourth sub-spots S3, S
s) is preferably as short as possible.

Each region E, F of the diffraction grating 2a is designed based on the various conditions described above, including the respective grating intervals and relative angles of the gratings.

In addition, in FIG. 2(b), the sub spot S2. Ss.

54sS5 was shown as a circle, but it is actually the diffraction grating 2a.
The shape is determined by the area dividing line and the outline of the beam from the semiconductor laser 1 or the aperture shape of the optical system (the dividing line is a straight line,
If the outer shape of the beam is a circle, it will be semicircular), but the shape will be slightly distorted due to various aberrations. However, each area E,
Since the shape is symmetrical at F, this does not affect the detection of the error signal.

Next, a method for detecting various signals will be explained with reference to FIG.

In FIG. 1(a), the photodetector 8 consists of eight independent photodetecting elements a, b, c, d, e+, e2f1, F2 arranged in alignment with each other in all longitudinal track directions as shown in the figure. Consists of. The detection light consisting of the reflected light corresponding to the spot S+''-55 on the disk 6 enters the photodetector 8 and forms spots S1 to S'5ffi at the positions shown in the figure, respectively. In a), the disk 6 is assumed to rotate in the direction of arrow H.

(Detection of information signal) Although the detailed circuit is not shown, the information signal is detected by photodetecting elements a, b,
Using c and d, obtain by a + c + d.

(Detection of Focus Error Signal) The focus error signal uses a known astigmatism method, and astigmatism is obtained when focused light passes through the half mirror 3, which is an inclined flat plate. ), photodetector elements a, b, c,
(a+c) (b+d) using d.

(Detection of tracking error signal, i) 1, -', ,
; ,', ,T1-Luckinder error signal is detected by photodetector element e1. ez.

It is generated by the detection circuit shown in FIG. 1(b) using f+ and f2'e. In the figure, each output of the photodetecting elements e1 and fl located in front of the main beam is divided into fl-el by a subtracter 9.
The output is supplied to the movable terminal of the switch 10. One fixed terminal of the switch 10 is connected directly to the gain control circuit 11, and the other fixed terminal I is directly connected to the gain control circuit 11.
The respective outputs of the photodetecting elements e2 and f2, which are connected to the adder 12 through It is supplied to the movable terminal of switch 14.

One fixed terminal J of the switch 14 is connected directly to the adder 12, and the other fixed terminal is connected to the adder 12 via a gain control circuit 15, respectively. Gain control circuit 1
1 is a correction constant g that corrects the difference in the amount of detected light between the front of the main spot SL and the rear where pits are present since there are no pits in front of the main spot SL during recording, and to make it equivalent to the case where pits exist.
et, and applies correction to the output of the subtracter 9 as expressed by gl·(fl e+). Ingenious gain control circuit 1
Since there are no pits behind the main spot S1 during erasing, 5 has a correction constant g2 to correct the difference in detected light amount with the front where the pit I- exists and make it equivalent to the case where a pit exists, and subtraction is performed. g2・(ez f2
).

The adder 12 adds the calculation results before and after the main spot 81 and the calculation results after the main spot S2 as described above, and supplies the output to the movable terminal of the switch 16. One fixed terminal 4 of the switch 16 is directly connected, and the other fixed terminal m is connected to an output terminal TES via a gain control circuit 17, where a tracking error signal is obtained. Since the output of the semiconductor laser 1 is increased during recording and erasing compared to during playback, the gain control circuit 17 has a correction constant G' to correct this and obtain the same detection output as during playback. The erasure is sometimes added to the output of the adder 12 and output as a tracking error signal.

Hereinafter, the tracking error signal detection operation of the husband 4 during reproduction, recording, and erasing will be explained in detail.

1. During playback During playback, the switch 10 is set to the terminal side, the switch 14 is set to the terminal j side, and the switch 16 is set to the terminal β side. (Figure 1(b)
In this state, all of the gain control circuits 11, 15, and 17 are passed, and therefore the 1~racking error signal is obtained by the calculation expressed as (fl-e+)+(ez f2). During playback, pits exist before and after the main spot 81, and each differential detection pair (fl
Since the conditions for el) and Ce2 f2) are the same, no special correction is given.

According to the above formula, if the beam and track center are misaligned,
The light intensity on the same side with respect to the track (i.e. fl and ez or e
Since □ and f2) change by the same amount with the same grain, the calculation results of each differential detection pair (f, -H) and (ez f2) are in phase and change by the same amount, and the error signal doubled by their addition is can get.

Note that this calculation method is devised so that the shadow 41 is less likely to be affected by the deviation between the diffraction grating 2a and the beam.

In FIG. 2(b), when the center of the beam and the dividing line of the diffraction grating 2a are shifted in the direction perpendicular to the dividing line (left and right in the figure), each area E and F is occupied. As a result, there is a difference in the amount.
Eventually, an offset will occur between the photodetecting elements represented by e, which relate to region E, and those represented by f, which relate to region F. However, according to the above formula, each differential detection pair (f+ e+) and (ez f2)
Since what is represented by e and what is expressed by f are subtracted in opposite phases, the offset is canceled by these additions and does not affect the error signal. Therefore, this means that the optical member 2 having the diffraction grating 2ak can be incorporated into an optical system relatively easily.

2. During recording During recording, the switch 10 is set to the i side, the switch 14 is set to the j side, and the switch 16 is set to the m side. In this state, a gain control circuit 11 is provided to the output of the subtracter 9 to provide a correction constant g1, and a gain control circuit 17 is provided to the output of the adder 12 to provide a correction constant G1.
is given, and the tracking error signal is obtained by the calculation expressed as G.[g+'(fl ex)+(e2 F2)]. During recording, main spot S1
Since the front differential detection pair (flel) detects a portion where no pit exists, it is corrected to the same detection value as when a pit exists by adding a correction constant g□.

Furthermore, since the beam intensity is different from that during reproduction, it is corrected to the same state as during reproduction by adding a correction constant G. As a result, tracking error signals are detected in the same way as during playback.

3. When erasing When erasing, the switch 10 is on the h side, the switch 14 is on the bani side,
The switch 16 is set to the m side. In this state, the gain control circuit 15 is interposed to the output of the subtracter 13 to give a correction constant g2, and the gain control circuit 17 is interposed to correct the output of the adder 12 as in the case of recording. Given a constant G, the tracking error signal is G ” [(fl ex)+g2・(e2
F2) It is obtained by the operation expressed as When erasing, the differential detection pair (ex h) rearward of the main slot (S+) will detect the part where there are no pits, so by adding the correction constant g2, the detection value will be corrected to the same value as when pits exist. do. Furthermore, since the beam intensity differs from that during reproduction in the same manner as the recording time, by adding a correction constant G, the beam intensity is corrected to be the same as that during reproduction. As a result, tracking error signals are detected in the same way as during playback.

Note that, if a beam intensity different from that during recording is used during erasing, the value of the correction constant G may be changed accordingly.

<Effects> As described above, according to the present invention, a pair of sub-beams for tracking error signal detection are arranged on the same side in the front or rear of the track direction with respect to the main beam, and the error is detected by differential detection between them. - Since the detection is carried out, it is possible to eliminate the unstable elements of various conventional methods and achieve accurate error detection not only during full playback but also during recording and erasing.

1. Since the above-mentioned pair of sub-beams are provided before and after the main beam, and the error detection values for each are added, a much higher level error signal can be obtained.

In addition, in each differential detection pair, the seeds that have opposite phases are calculated for the sub beams from the same area of the diffraction grating means, and the results are added, so that the influence of the deviation of the diffraction grating means is canceled out. , there is no need for high precision in the integration of the diffraction grating means into the optical system.

Furthermore, during recording or erasing, a correction constant is used to correct the off-seratra caused by the presence or absence of pits before and after the main beam, that is, at each of the above differential detection positions, and a correction constant corresponding to the difference in beam intensity during playback is calculated during playback. Therefore, the same detection device can be used for any reproduction, recording, or erasing operation.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention, and FIG. 1 (
(a) is an explanatory diagram of the spot arrangement on the disk and the spot arrangement on the photodetector; FIG. 1 (b)+a) is a block diagram of the racking error signal detection circuit; FIG. 2 (a). (b) is an explanatory diagram of the three-beam method using the optical system of the optical head and the diffraction grating, respectively. 2a - Diffraction grating, E...first region, F...second region, E□+E2...first and second sub beams, F,
, F2...Third and fourth sub beams, el+62+f
,, F2... Photodetection element, 9, 13... Subtractor, 12... Adder, 11, 15.17... Gain control circuit.

Claims (1)

[Claims] 1. A first region whose diffraction direction is inclined at a predetermined angle with respect to the tracks of the recording body, and a diffraction direction of which is inclined at a predetermined angle with respect to the tracks of the recording body in a direction opposite to the first region. Using a diffraction grating means having a second region which is tilted and whose grating interval is different from that of the first region, the first-order diffracted light in each region of the diffraction grating means is used to generate a beam from the main beam approximately in the track direction. First and second sub-beams are generated that are deviated in opposite directions from the track center on the same side and emitted at different angles, and each of these sub-beams is irradiated onto the recording medium to obtain a second beam by reflection or transmission. A tracking error detection method characterized by detecting a tracking error based on a difference in light intensity between first and second detection lights. 2. A first area in which the direction of diffraction is inclined at a predetermined angle with respect to the tracks of the recording medium, and a first area in which the direction of diffraction is inclined at a predetermined angle in the direction opposite to the first area with respect to the tracks of the recording medium, and the grating interval thereof is Using a diffraction grating means having a second region different from the first region, it consists of ±first-order diffracted light by the first region approximately before and after the main beam in the track direction,
It consists of first and second sub-beams deviated from the track center and ±first-order diffracted light from the second region, and has a different emission angle from the first and second sub-beams, and is centered on the track. generates third and fourth sub-beams that are deflected in the opposite direction to the first and second sub-beams, and
Among the first, second, and fourth detection lights obtained by irradiating the recording medium with the third and fourth sub-beams and reflecting or transmitting them, the first and third detection lights and the second and fourth detection lights A tracking error detection method characterized by detecting a value obtained by adding up differences in light amounts of respective lights as a tracking error amount. 3. A first area in which the direction of diffraction is inclined at a predetermined angle with respect to the tracks of the recording medium, and a grating interval thereof in which the direction of diffraction is inclined at a predetermined angle in the opposite direction to the first area with respect to the tracks of the recording medium. using a diffraction grating means having a second region different from the first region, and consisting of ±first-order diffracted light by the first region approximately in the track direction of the main beam,
Consists of first and second sub-beams that are symmetrically deviated from the track center with the main beam optical axis as the axis of symmetry, and ±first-order diffracted light from the second region, and the first and second sub-beams are Third and fourth sub-beams having different emission angles and symmetrically offset from the track center in directions opposite to the first and second sub-beams with the main beam optical axis as the axis of symmetry are generated. , the light quantities of the first, second, third, and fourth detection lights (e_1, e_2, f_1, f
Based on _2), (f_1-e_1)+(e_2-f_
2) A tracking error detection method characterized in that a value obtained by is detected as a tracking error amount. 4. A first area in which the direction of diffraction is inclined at a predetermined angle with respect to the tracks of the recording medium, and a grating interval in which the direction of diffraction is inclined at a predetermined angle in a direction opposite to the first area with respect to the tracks of the recording medium. using a diffraction grating means having a second region different from the first region, and consisting of ±first-order diffracted light by the first region approximately in the track direction of the main beam,
It consists of first and second sub-beams deviated from the track center and ±first-order diffracted light from the second region, and has a different emission angle from the first and second sub-beams, and is centered on the track. generates third and fourth sub-beams that are deflected in the opposite direction to the first and second sub-beams, and
Among the first, second, third, and fourth detection lights obtained by irradiating the recording medium with the third and fourth sub-beams and reflecting or transmitting them, the light intensity of the first and third detection lights during reproduction. The sum of the difference and the light intensity difference between the second and fourth detection beams is calculated, and during recording (or erasing), the unrecorded area and the recorded area are added to the light intensity difference between the first and third detection beams. Add the value obtained by multiplying the correction constant corresponding to the detected light amount ratio by the light amount difference between the second and fourth detected light, and then add the difference between the light source's output during reproduction and the output during recording (or erasing). A tracking error detection method characterized in that a value obtained by multiplying a ratio by a correction constant is detected as a tracking error amount.