JP2001143284A - Tracking error detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tracking error detector which can accurately detect a tracking error regardless of the displacement of an optical system. SOLUTION: A photodetector 12 has a light receiving part to receive the reflected light of the laser beam that is irradiated on an optical disk, and a real light receiving range of the reflected light is detected out of the light receivable range of the photodetector 12. Then the light receivable range is divided into the 1st and 2nd light receiving ranges on the center line of the detected real light receiving range. A detection signal processing part 10 detects a tracking error signal on the basis of the difference between the reflected light signals which are obtained in the 1st and 2nd light receiving ranges respectively. In such a constitution, a tracking error detector is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording / reproducing apparatus for writing information on an optical information recording medium or reproducing information written on the optical information recording medium.
The present invention relates to a tracking error detection device that detects a tracking error.

[0002]

2. Description of the Related Art At present, CD (Compact Disc), DVD
Optical information recording media such as Digital Versatile Disc (Digital Versatile Disc) have become widespread. Such an optical information recording medium is provided with a tracking error detecting device for detecting a shift of a focusing position of the laser beam with respect to the information track in order to accurately focus the laser beam on the information track of the optical information recording medium. . The tracking error detection device outputs a tracking error signal for monitoring the focus position of a laser beam on an information track during recording and reproduction of information on an optical disc as an optical information recording medium.

[0003] The tracking error signal is a control signal for an actuator for driving an optical system provided in the tracking error detecting device. The actuator finely adjusts the optical system according to the tracking error signal and constantly controls the laser beam. Is focused on the center of the information track.

One of the typical tracking error detection methods is a push-pull method. FIG. 15 and FIG. 16 are diagrams for explaining such a push-pull method. In the push-pull method, the optical disk is irradiated with a laser beam focused by the objective lens 193, the reflected light is received, and the laser beam is accurately focused on the information track of the optical disk (ON state). Track). That is, as shown in FIG. 15, the information track including the land 191a and the groove 191b is formed on the optical disc 9. In this information track, P shown in the figure is one track pitch.

[0005] Reflection at the groove 191b of the information track,
The diffracted laser beam spreads at an angle of θ about the broken line shown in the figure, and generates 0th-order diffracted light A, 1st-order diffracted light B and C. The 0th-order diffracted light A and a part of the 1st-order diffracted lights B and C are divided into a two-divided PD (Photo
Detector 193). The solid line f shown in FIG. 15 is the center line of the light receiving range in which the PD 193 has received the 0th-order diffracted light A, and the broken line f ′ is the center line of the light receiving range preset on the PD 193.

[0006] As shown in FIG.
From the areas g and h divided around the broken line f ′, signals corresponding to the amounts of received light in the respective areas are subtracted from the subtractor 195.
To enter. At this time, the solid line f, which is the center line of the actual light receiving range, and the broken line f 'coincide with each other, and the spot of the laser beam and the land 191a or the groove 19
If the center is the same as 1b, the target diffracted light distribution is obtained in the regions g and h. That is, a tracking error or on-track can be detected from the diffracted light distribution in the light receiving range.

For this reason, in the push-pull method, a signal representing the amount of received light in the area g is G, and a signal representing the amount of received light in the area h is H.
This is input to the subtractor 195. The subtracter 195 calculates the difference value TE between G and H by the calculation of TE = GH. The difference value TE is output as a tracking error signal from the subtractor 195 to a control device that controls the actuator of the optical system.

FIG. 17 shows the relationship between the tracking error signal and the center position of the spot of the laser beam. FIG.
According to the graph, when the tracking error signal is 0, it can be determined that the center of one of the groove 191b and the land 191a coincides with the center position of the spot of the laser beam, that is, it can be determined that the track is on track. When the tracking error signal is a value other than 0, it can be determined that the center of one of the groove 191b and the land 191a and the center position of the spot of the laser beam are shifted.

From the above relationship, the control device of the actuator determines whether or not there is a tracking error from the value of the tracking error signal. When it is determined that the value of the tracking error signal is not 0, that is, when it is determined that a tracking error has occurred, the actuator is driven so that the deviation is eliminated, and the center of the spot of the laser beam is focused on the center of the information track. To do.

[0010]

However, the tracking error detecting device that detects a tracking error by the push-pull method has a problem that the optical axis of the objective lens 192 is misaligned or misaligned, and the optical axis of the optical system such as the two-divided PD 193 is misaligned. Can occur. Such an optical axis shift may cause a fluctuation called a DC offset in the tracking error signal.

If only the objective lens 192 is moved in the direction perpendicular to the optical axis of the laser beam for tracking, the problem shown in FIG. 18 occurs due to the optical axis shift of the objective lens 192. That is, as shown in the figure, when the optical axis of the objective lens 192 is shifted by Δx with respect to the center of the two-part PD 193, the amount of light received in the region g on the two-part PD 193 decreases, and the amount of light received in the region h increases. At this time, if the decrease in the area g is represented by -Δa and the increase in the area h is represented by + Δb, as shown in FIG. 19, a DC offset of − (Δa + Δb) occurs in the tracking error signal. Such a DC offset also occurs when a position shift of the two-divided PD 193 occurs due to a shift of the optical axis of the detection optical system.

When a DC offset occurs, the tracking error signal does not become 0 at the groove 191b and the land 191a, even though the spot of the laser beam is on-track. Alternatively, although the spot of the laser beam is focused on a position shifted from the center position of the track, it may be detected as on-track. In the optical information recording / reproducing apparatus, when tracking is performed according to such a tracking error detection signal, there is a possibility that a track shift may occur instead.

The DC offset is determined by the objective lens 19.
It is also possible to solve the problem by adjusting the two-divided PD 193 or the like with high accuracy and completely eliminating the deviation. However, since such high-precision adjustment is difficult and relatively time-consuming, a tracking error detection device capable of detecting a tracking error more simply and accurately has been required.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a tracking error detecting device capable of accurately detecting a tracking error even when there is a deviation in an optical system.

[0015]

The above-mentioned problems can be solved by the following means. That is, according to the first aspect of the present invention, the light irradiating means for irradiating the collected laser light onto the optical information recording medium, and the laser light irradiated by the light irradiating means is reflected by the optical information recording medium. A light receiving unit for receiving the reflected light; a reflected light detecting means for detecting a reflected light signal based on the reflected light received by the light receiving unit; Actual light receiving range detecting means for detecting a range, and the center line of the actual light receiving range detected by the real light receiving area detecting means, the light receiving range is divided into a first light receiving area and a second light receiving area, Tracking error signal output means for outputting a tracking error signal based on a difference between the reflected light signal obtained in the first light receiving range and the reflected light signal obtained in the second light receiving range. Features A.

With this configuration, even when the light receiving range of the reflected light is shifted due to a shift of the optical system, the like.
An accurate light receiving range is detected as an actual light receiving range regardless of this shift. At the center of the actual light receiving range, the light receiving range is divided into a first light receiving range and a second light receiving range, and a difference value between the reflected light signals obtained in each range is taken to generate a tracking error signal. By doing so, it is possible to accurately generate a tracking error signal indicating the tracking state regardless of a shift of the optical system.

Further, according to a second aspect of the present invention, the plurality of light receiving portions have a long stripe shape in a direction parallel to a track of the optical information recording medium and are arranged in a plurality of directions in a direction orthogonal to the tracks of the optical information recording medium. The tracking error signal output means may divide the receivable range into a first light receiving range and a second light receiving range at a center line of the actual light receiving range parallel to a track of the optical information recording medium. It is a feature.

With this configuration, the reflected light can be received by the light receiving surface where a plurality of stripe-shaped light receiving portions long in the track direction are arranged in the radial direction. Therefore, the distribution of the reflected light signal in the radial direction on the light receiving surface can be understood. Then, the actual light receiving range can be detected from the reflected light distribution. Therefore, even when the actual light receiving range shifts in the radial direction due to the shift of the optical system, the actual light receiving range can be detected regardless of the shift.

According to a third aspect of the present invention, the light receiving unit is a two-dimensional array light receiving unit arranged in a plurality of directions in a direction perpendicular to and parallel to a track of the optical information recording medium, and the tracking is performed. The error signal output means divides the light receivable range into a first light receiving range and a second light receiving range at a center line of the actual light receiving range parallel to a track of the optical information recording medium. It is.

With this configuration, if the actual light receiving range is divided into two in the track direction, the reflected light detecting means can be used as a configuration for detecting a focus error by the astigmatism method or the knife edge method.

According to a fourth aspect of the present invention, the tracking error signal output means outputs a difference value between a reflected light signal obtained in the first light receiving range and a reflected light signal obtained in the second light receiving range. Is calculated, only the reflected light signal obtained in the actual light receiving range of the first light receiving range and the second light receiving range is used.

With this configuration, it is possible to detect a tracking error using only the reflected light signal detected within the actual light receiving range. For this reason, flare light generated in a non-light receiving range outside the actual light receiving range out of the light receivable range, and abnormal light due to abnormal shape or scratches or dust of the optical disk do not affect the value of the tracking error signal.

According to a fifth aspect of the present invention, the tracking error signal output means receives the light in a straight line passing through a minimum position of the reflected light signal in the actual light receiving range and parallel to a track of the optical information recording medium. The possible range is divided into a first light receiving range and a second light receiving range.

With this configuration, the actual light receiving range can be determined based on the minimum value of the reflected light signal, that is, the center position of the range in which only the 0th-order diffracted light is received.
For this reason, flare light generated at the end of the actual light receiving range and abnormal light due to abnormal shape or scratches or dust of the optical disk do not affect detection of the actual light receiving range.

According to a sixth aspect of the present invention, the tracking error signal output means outputs a difference value between the reflected light signal obtained in the first light receiving range and the reflected light signal obtained in the second light receiving range. Is calculated, a reflected light signal obtained in a region where the 0th-order diffracted light and the 1st-order diffracted light of the reflected light overlap in the first light receiving range, and a 0th-order diffracted light of the reflected light and 1 in the second light receiving range. It is characterized by using only a reflected light signal obtained in a region where the next-order diffracted light overlaps.

With this configuration, it is possible to calculate the value of the tracking error signal using only the reflected light signal detected in a range where the 0th-order diffracted light and the 1st-order diffracted light overlap and are received. For this reason, flare light generated outside the range in which the 0th-order diffracted light and the 1st-order diffracted light are superimposed and received, and abnormal light due to optical disk shape abnormalities, scratches, and dust do not affect the value of the tracking error signal. Also, since a relatively strong reflected light signal can be obtained in a range where the 0th-order diffracted light and the 1st-order diffracted light are received in an overlapping manner, even if the detection range of the reflected light signal is narrowed, the reflected light is sufficient for detecting a tracking error. A signal can be obtained.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments 1 to 5 of the present invention will be described below.
Will be described. (Embodiment 1) FIG. 1 is a block diagram for explaining a tracking error device according to an embodiment of the present invention, which is common to Embodiments 1 to 5. As illustrated, the tracking error detection device according to the embodiment of the present invention includes an optical system having a laser light source 1, a collimating lens 3, a beam splitter 5, and an objective lens 7. Such an optical system uses a condensed laser beam (spot light L
1) is a light irradiation means for irradiating the light onto the optical disk 9.

Further, the tracking error detecting apparatus according to the embodiment of the present invention has a photodetector 12 for receiving the reflected light L2 of the spot light L1 radiated by the above-mentioned optical system reflected on the optical disk. The photodetector 12 detects a reflected light signal (a signal representing the relationship between the amount of reflected light received and the detection position) based on the received reflected light, and outputs this information to the detection signal processing unit 10 as a signal s. .

The detection signal processing unit 10 detects an actual light receiving range in which the reflected light is received among the light receiving ranges of the photodetector 12 based on the signal s, and determines the light receiving range by the center line of the actual light receiving range. It is divided into a first light receiving range and a second light receiving range. Then, a difference value between the reflected light signal obtained in the first light receiving range and the reflected light signal obtained in the second light receiving range is output as a tracking error signal.

The laser light source 1 of the optical system shown in FIG. 1 is, for example, a light source of a semiconductor laser, and emits a laser beam toward the collimating lens 3. The emitted laser light is collimated by the collimator lens 3, passes through the beam splitter 5, is condensed by the objective lens 7, becomes a spot light L 1, and is condensed on the optical disc 9. The spot light L1 is reflected on the recording surface or reproduction surface of the optical disk 9, passes through the objective lens 7 again, is deflected by the beam splitter 5, travels toward the photodetector 12, and is received as reflected light L2.

FIG. 2 is a diagram for explaining the photodetector 12 in more detail. The photodetector 12 according to the first embodiment is configured such that the reflected light L
2 has a light receiving section 13a for receiving light. Light receiving section 13a
Have a long stripe shape in the direction parallel to the tracks of the optical disc 9 (hereinafter simply referred to as the track direction), and are arranged in a plurality of directions perpendicular to the tracks (hereinafter the radial direction) to form the light receiving surface 13. are doing. The direction parallel to the track or the direction perpendicular to the track is defined with respect to the track of the optical disc 9 where the light receiving surface 13 receives the reflected light L2.

The light receiving surface 13 receiving the reflected light L2 has an actual light receiving area 12a for receiving the zero-order diffracted light (detection beam) of the reflected light and a non-light receiving area 12 for other areas.
d is formed. In this specification, the actual light receiving range 12a and the non-light receiving range 12d are collectively referred to as a light receivable range. The actual light receiving range 12a further includes a first-order diffracted light receiving range 12 that receives the first-order diffracted light overlapping the 0th-order diffracted light.
b, 12c are formed.

The reflected light received by the light receiving surface 13 is converted by the photodetector 12 into a reflected light signal which is an electric signal corresponding to the light amount. Further, in the first embodiment, since the light receiving surface 13 is constituted by the light receiving portions 13a in the form of a stripe, the arrangement position of each light receiving portion 13a and the obtained reflected light signal are associated with each other, so that the radial The distribution of the received light amount in the direction can be understood. The reflected light signal obtained by each light receiving unit 13a and information on the position of the light receiving unit 13a are input to the detection signal processing unit 10 as a signal s.

FIG. 3 shows the signal s by the detection signal processing unit 10.
It is a figure for explaining processing of. As shown in the figure, the detection signal processing unit 10 controls the actual light receiving range 12 based on the signal s.
The center position in the radial direction of “a” (shown by the arrow A) is determined. Then, a center line C passing through the center position and parallel to the track direction is determined, and the light receiving range is divided into a first light receiving range 30 and a second light receiving range 31 at the center line C. Then, a difference value between the total added value of the reflected light signals obtained in the first light receiving range 30 and the total added value of the reflected light signals obtained in the second light receiving range 31 is calculated, and is calculated as a tracking error signal. Output.

The above processing will be described more specifically with reference to FIGS. FIGS. 4A to 4D are graphs showing the reflected light signal on the vertical axis and the light receiving position on the horizontal axis. Note that this light receiving position refers to a radially arranged position on the light receiving surface 13 of each light receiving unit 13a. FIGS. 4A to 4D show a procedure for dividing the receivable range into a first light receiving range 30 and a second light receiving range 31, a first light receiving range 30, and a second light receiving range. FIG. 3 is a diagram for explaining a method of processing a reflected light signal obtained at 31.

The graphs shown in FIGS. 4A to 4D are actually given as histograms, but here, for simplicity, it is assumed that the change in the reflected light signal is represented by a curve. This curve shows the first-order diffracted light receiving range 12b,
A relatively strong reflected light signal peak is shown at a position corresponding to 12c, and a relatively weak reflected light signal is shown near the center where only the 0th-order diffracted light is received.

The detection signal processing section 10 divides the light receivable range.
First, of the receivable range, the actual
The enclosure 12a is detected (FIG. 4A). In Embodiment 1
Is the range of the light receiving position corresponding to the light receiving range.
Enclosure (hereinafter simply referred to as range) R ₁Of which, the reflected light signal is
Obtained range R₂This is done by detecting So
And the detected range R₂From the light receiving position
A center position A, which is a position, is calculated. In addition, this center position
A is the range R₂Equal to R₃, R₄Place to split into
This is calculated as the position (FIG. 4B).

Next, the detection signal processing unit 10 detects the center position.
Range A at A₁Equal to R₅, R ₆(Fig. 4
(C)). At this time, the range R₅, Range R₆Respectively
Radial direction of first light receiving range 30 and second light receiving range 31
Direction length. By such processing, the form of implementation
In state 1, the receivable range is the track direction passing through the center position A.
The first light receiving range 30 and the second light receiving
This means that the area 31 has been divided.

The reflected light signals obtained in the ranges R ₅ and R ₆ are all added by the detection signal processing unit 10 for each range. The value of the reflected light signal (total added value) added for each range is input to a subtractor incorporated in the detection signal processing unit 10, and the difference value is calculated. This difference value is output from the detection signal processing unit 10 to a control device (not shown) of the actuator as a tracking error signal (FIG. 4D). In this control device, if the value of the tracking error signal is 0, it is determined that the tracking error has occurred. On the other hand, if the value of the tracking error signal is other than 0, it is determined that the tracking error has occurred, and the actuator of the optical system is driven to adjust the position of the objective lens 7.

Next, the processing described above will be described with reference to the flowchart shown in FIG. In the tracking error detection device according to the first embodiment, for example, the operator sets an optical disc in the optical information recording / reproducing device and starts when a reflected light signal is input (S1). The detection signal processing unit 10 detects the actual light receiving range 12a based on the input reflected light signal (S2). Subsequently, the center position A and the center line C of the actual light receiving range 12a detected in step S2
Is calculated (S3), and the receivable range is divided radially into a first light receiving range 30 and a second light receiving range 31 at the center line C (S4).

Next, the detection signal processor 10 calculates the total sum of the reflected light signals obtained in the first light receiving range 30 and the total added value of the reflected light signals obtained in the second light receiving range 31. Is calculated (S5). Then, the difference value is output as a tracking error signal (S6). Thereafter, the detection signal processing unit 10 returns to the process of step S1 again to detect a tracking error at the condensing position of the next spot light L1.

According to the first embodiment described above, the reflected light L2 is received by the light receiving surface 13 in which a plurality of stripe-shaped light receiving portions 13a long in the track direction are arranged in the radial direction. Therefore, the distribution of the reflected light signal on the light receiving surface 13 in the radial direction can be understood. Then, the actual light receiving range 12a of the light receiving surface 13 can be detected from the reflected light distribution. Such a tracking error detection device of the first embodiment detects the actual light receiving range 12a regardless of the shift even when the actual light receiving range 12a is shifted in the radial direction on the light receiving surface due to the shift of the optical system. be able to.

Then, the actual light receiving range 12a detected in this way is divided into a first light receiving range 30 and a second light receiving range 31.
And a tracking error signal is generated by taking the difference value of the reflected light signal obtained in each range. With this configuration, in the first embodiment, it is possible to provide a tracking error detection device that can prevent the occurrence of a DC offset regardless of the displacement of the optical system and can accurately detect a tracking error.

Furthermore, in the first embodiment, a plurality of stripe-shaped light receiving portions 13a long in the track direction are arranged in the radial direction to form the light receiving surface 13, so that the reflected light signal received at one light receiving position can be obtained. One light receiving unit 13a
All can be received. For this reason, the tracking error detection device of the first embodiment can detect the radial reflected light signal distribution in the receivable range by a simpler configuration and simpler reflected light signal processing than the later-described embodiment. It can be said.

(Embodiment 2) Next, a tracking error device according to Embodiment 2 of the present invention will be described. The tracking error detection device according to the second embodiment is partially configured similarly to the tracking error detection device according to the first embodiment. For this reason, the description of the tracking error detection device according to the second embodiment that is the same as that of the first embodiment will be partially omitted.

FIG. 6 is a diagram for explaining the light receiving portion 63a of the photodetector 62 provided in the tracking error detection device according to the second embodiment. Light receiving unit 63a according to the second embodiment
Are arranged in the radial direction and the track direction,
The light receiving surface 63 has a two-dimensional array. Also on such a light receiving surface 63, an actual light receiving range 62a and a non-light receiving range 62d, which is another area, are formed. Also in the second embodiment, the actual light receiving range 62a and the non-light receiving range 62d are collectively referred to as a light receivable range.
The actual light receiving range 62a further includes first-order diffracted light receiving ranges 62b and 62 that receive the first-order diffracted light overlapping the zero-order diffracted light.
c is formed.

The reflected light received by the light receiving surface 63 is converted by the photodetector 62 into a reflected light signal. Embodiment 2
Since the light receiving surface 63 is constituted by rectangular light receiving portions 63a arranged in a matrix,
By associating the arrangement position a with the obtained reflected light signal, the distribution of the received light amount in the radial direction on the light receiving surface 63 can be found. Further, it is also possible to know the distribution of the amount of received light in the track direction if necessary. The reflected light signal obtained by each light receiving unit 63a and the information on the position of the light receiving unit 63a are as follows:
It is input to the detection signal processing unit 10 as a signal s.

FIG. 7 shows the signal s by the detection signal processing unit 10.
It is a figure for explaining processing of. As shown in the figure, the detection signal processing unit 10 outputs the actual light receiving range 62 based on the signal s.
The center position in the radial direction of “a” (shown by the arrow A) is determined. Then, a center line C passing through the center position and parallel to the track direction is determined, and the light receiving range is divided into a first light receiving range 70 and a second light receiving range 71 at this center line. Then, a difference value between the total added value of the reflected light signals obtained in the first light receiving range 70 and the total added value of the reflected light signals obtained in the second light receiving range 71 is calculated, and is calculated as a tracking error signal. Output.

The above processing will be described more specifically with reference to FIGS. FIGS. 8A to 8C show graphs showing the reflected light signal on the vertical axis and the light receiving position of the light receiving section 63a on the horizontal axis. In addition, FIG.
The graph shown in (c) is actually given as a histogram similarly to FIG. 4, but here, it is assumed to be simplified and represented by a curve of the reflected light signal.

In the second embodiment, the light receiving portions 63a are arranged in both the track direction and the radial direction. For this reason, regarding the value of the reflected light signal shown on the vertical axis, for example, in the first light receiving range 70 and the second light receiving range 71, all the light receiving portions 63a at the same light receiving position
Alternatively, the reflected light signals received at the steps (1) and (2) may be added, and this value may be plotted as a reflected light signal corresponding to each light receiving position. In addition, in some representative areas of the first light receiving area 70 and the second light receiving area 71, the reflected light signals received by the light receiving sections 63a at the same light receiving position are added up, and this value is added to the respective values. It may be plotted as a reflected light signal corresponding to the light receiving position.

In dividing the light-receivable range, the detection signal processing unit 10 first detects the actual light-reception range 62a in the light-receivable range, and calculates the center position A in the radial direction. The center position A is to divide the range _{R 2} equal to the range _R 3, _{R 4,} is calculated as a position in the middle (Fig. 8 (a)).

Next, the detection signal processing unit 10 determines the center position.
Range A at A₁Equal to R₅, R ₆(Fig. 8
(B)). At this time, the range R₅, Range R₆Respectively
Radial direction of the first light receiving area 70 and the second light receiving area 71
Direction length. By such processing, the form of implementation
In state 2, the light receiving range is the track direction passing through the center position A.
The first light receiving range 70 and the second light receiving
This means that the area 71 has been divided.

The reflected light signals obtained in the ranges R ₅ and R ₆ are all added by the detection signal processing unit 10 for each range. The total added value of the reflected light signals added for each range is input to a subtractor incorporated in the detection signal processing unit 10, and the difference value is calculated. This difference value is output from the detection signal processing unit 10 as a tracking error signal (FIG. 8C). The processing described above is performed by the processing of the flowchart shown in FIG. For this reason, in the second embodiment, the description of the above processing by a flowchart will be omitted.

The tracking error detection device according to the second embodiment is not limited to performing the above processing. That is, in the above-described processing, the actual light receiving range 62a is divided into two in the radial direction of the optical disc 9 as in the first embodiment. However, if this is divided into two in the track direction, the photodetector 62 can also be used as a split photodetector for detecting a focus error by an astigmatism method or a knife edge method. Therefore, Embodiment 2
The tracking error detection device of the above can provide the photodetector 62 with a plurality of functions in addition to the effects obtained in the first embodiment, which contributes to downsizing and cost reduction of the optical information recording / reproducing device. It can be said that it has an effect.

Third Embodiment Next, a tracking error device according to a third embodiment of the present invention will be described. The tracking error detection device according to the third embodiment is partially configured similarly to the tracking error detection devices according to the first and second embodiments described above. For this reason, the description of the tracking error detection device according to the third embodiment that is the same as that of the first and second embodiments will be partially omitted.

FIG. 9 is a diagram for explaining the photodetector 102 provided in the tracking error detection device according to the third embodiment. A plurality of light receiving units (not shown) provided in the photodetector 102 are arranged in the radial direction and the track direction in the same manner as the light receiving unit 63a of the second embodiment, and constitute a light receiving surface in a two-dimensional array. On the light receiving surface of such a two-dimensional array, an actual light receiving area 102a and a non-light receiving area 102d, which is the other area, are formed. Also in the third embodiment, the actual light receiving range 102a and the non-light receiving range 102d are collectively referred to as a light receivable range. A first-order diffracted light receiving range (not shown) is formed in the actual receiving range 102a.

The detection signal processing unit 10 according to the third embodiment determines the center position (indicated by the arrow A) of the actual light receiving range 102a. Then, a center line C passing through the center position and parallel to the track direction is determined, and the light receiving range is divided by the center line C. Further, the detection signal processing unit 10 calculates a difference value of the reflected light signal obtained in each of the divided light receivable ranges, and outputs the difference value as a tracking error signal. However, in the tracking error detection device according to the third embodiment,
In calculating the difference between the reflected light signals, a first actual light receiving range 90 and a second actual light receiving range 91 (in the figure, which are the actual light receiving ranges 102a (shown by diagonal lines) in the divided light receiving ranges). Is used with only the reflected light signal obtained by the hatching.

The above processing will be described more specifically with reference to FIGS. 10 (a) to 10 (c). FIGS. 10 (a) to 10 (c)
The vertical axis is a graph showing the reflected light signal, and the horizontal axis is a graph showing the light receiving position. Although the graphs shown in FIGS. 10A to 10C are actually given as histograms, they are simplified here and represented by curves of reflected light signals.

The detection signal processing unit 10 of the third embodiment
The actual light receiving range 102a is detected from the light possible range (FIG. 1).
0 (a)) to calculate the center position A in the radial direction.
You. This center position A is within the range R₂Equal to R₃, R
₄Is calculated as the position at the center
(FIG. 10B). At this time, the range R₃, Range R
₄Are the first actual light receiving range 90 and the second actual light receiving range, respectively.
This corresponds to the length of the enclosure 91 in the radial direction. Such a process
In the second embodiment, the actual light receiving range 102a is
Divided into two by a center line C parallel to the track direction passing through the center position A
It was done.

The reflected light signals obtained in the ranges R ₃ and R ₄ are all added by the detection signal processing unit 10 for each range. The total added value of the reflected light signals added for each range is input to a subtractor incorporated in the detection signal processing unit 10, and the difference value is calculated. This difference value is output from the detection signal processing unit 10 to a control device (not shown) of the actuator as a tracking error signal (FIG. 10C).

Next, the processing described above will be described with reference to the flowchart shown in FIG. In the tracking error detection device according to the third embodiment, for example, the operator sets the optical disk in the optical information recording / reproducing device and starts when a reflected light signal is input (S11). The detection signal processing unit 10 detects the actual light receiving range 102a based on the input reflected light signal (S12). Subsequently, the center position A and the center line C of the actual light receiving range 102a detected in step S12 are calculated (S13), and the actual light receiving range 102a is radially shifted from the first actual light receiving area 90 by the center line C.
And the second actual light receiving range 91 (S14).

Next, the detection signal processing section 10 calculates the total sum of the reflected light signals obtained in the first actual light receiving range 90 and the second added value.
Then, a difference value from the total added value of the reflected light signals obtained in the actual light receiving range 91 is calculated (S15). Then, the calculated value is output as a tracking error signal (S16). Thereafter, the detection signal processing unit 10 executes the processing of step S11 again to detect a tracking error at the condensing position of the next spot light L1 (S11).

In the third embodiment described above, a tracking error can be detected using only the reflected light signal detected within the actual light receiving range. For this reason, flare light generated in the non-light receiving range, abnormal light due to abnormal shape or scratches of the optical disk, or dust does not affect the value of the tracking error signal. According to such a third embodiment, the first embodiment,
In addition to the effect obtained in the second embodiment, the effect that the tracking error can be detected more accurately can be obtained except for the influence of the reflected light signal detected in the non-light receiving range on the tracking error signal.

(Embodiment 4) Next, a tracking error device according to Embodiment 4 of the present invention will be described. The tracking error detection device according to the fourth embodiment is partially configured similarly to the tracking error detection devices according to the first to third embodiments described above. For this reason, the description of the tracking error detection device according to the fourth embodiment that is the same as that of the first to third embodiments will be partially omitted.

Also in the fourth embodiment, the detection signal processing section 10 determines the center position and the center line of the actual light receiving range in order to divide the light receivable range. Then, the light receiving range or the actual light receiving range is divided by the center line, and the difference value of the reflected light signal obtained in the divided light receiving range is output as a tracking error signal. However, in the tracking error detecting device according to the fourth embodiment, when dividing the actual light receiving range, the center line of the actual light receiving range that passes through the minimum position of the reflected light signal in the actual light receiving range and is parallel to the track direction of the optical disc 9 is used. Is used to divide the light receiving range into a first light receiving range and a second light receiving range.

FIG. 12 is a diagram for specifically explaining such division of the actual light receiving range and determination of the actual light receiving range. In the fourth embodiment, as shown in the figure, a point M at which the curve 1 representing the reflected light signal takes a minimum value in the actual light receiving range is determined, and the light receiving position corresponding to the point M is set as the center position B. Note that the point M, which is the minimum value, is 2 in the actual light receiving range.
The reflected light signal detected at the center position between the first-order diffracted light receiving ranges of the points is shown, and the center position B indicates the center position in the radial direction between the two first-order diffracted light receiving ranges.

Further, in the fourth embodiment, through the point M,
A straight line parallel to the track direction on the light receiving surface is defined as a center line D. Then, the equal ranges R ₃ and R ₄ are respectively taken from the center line D, and the range of R ₃ + R ₄ is defined as the actual light receiving range R ₂
And According to such a process, for example, as shown in FIG. 13, even when the abnormal signal n is detected at the end of the actual light receiving range with a range R ₂ in the radial direction, the actual light-receiving range is a range R ₂ 'Can be prevented from being erroneously determined. The ranges R ₃ and R ₄ are set in advance according to the diameter of the spot light L1.

In the fourth embodiment described above, the actual light receiving range can be determined based on the minimum value of the reflected light signal, that is, the center position between the first order diffracted light receiving ranges. For this reason, flare light generated at the end of the actual light receiving range and abnormal light due to abnormal shape or scratches or dust of the optical disk do not affect the value of the tracking error signal. According to the fourth embodiment, in addition to the effects obtained in the first to third embodiments,
Except for the influence of the abnormal reflected light signal detected at the end of the actual light receiving range on the determination of the actual light receiving range, an effect that the tracking error can be detected more accurately can be obtained.

(Fifth Embodiment) Next, a tracking error device according to a fifth embodiment of the present invention will be described. The tracking error detection device according to the fifth embodiment is partially configured similarly to the tracking error detection devices according to the first to fourth embodiments described above. Therefore, for the tracking error detection device of the fifth embodiment, the description of the same configuration as that of the first to fourth embodiments will be partially omitted.

Also in the fourth embodiment, the detection signal processing unit 10 determines the center position and the center line of the actual light receiving range to divide the light receivable range. Then, the light receiving range or the actual light receiving range is divided by the center line, and the difference value of the reflected light signal obtained in the divided light receiving range is output as a tracking error signal. However, the tracking error detecting apparatus according to the fifth embodiment calculates the difference value of the reflected light signal, where the 0th-order diffracted light and the 1st-order diffracted light of the reflected light overlap in the two divided light receiving ranges;
That is, the difference value between the reflected light signals obtained in the first-order diffracted light receiving range is calculated.

FIG. 14 is a diagram for explaining the calculation of the difference between the reflected light signals, and is a diagram showing the photodetector 152 according to the fifth embodiment. The photodetector 152 has the same configuration as the photodetector 62 according to the second embodiment shown in FIG. 6, and a plurality of light-receiving units (not shown) are arranged in the radial direction and the track direction. Make up.

The light receiving surface of this two-dimensional array has the reflected light
Actual light receiving range 152a that receives the next-order diffracted light (detection beam)
And a non-light receiving range 152d, which is another area. Further, in the actual light receiving range 152a, first-order diffracted light receiving ranges 152b and 152c that receive the first-order diffracted light overlapping the zero-order diffracted light are formed.

The detection signal processing unit 10 according to the fifth embodiment
The total added value of the reflected light signals obtained only in the next-order diffracted light receiving range 152b is calculated. The first-order diffracted light receiving range 152
The total addition value of the reflected light signals obtained only with c is also calculated.
Then, a difference value between the total added value of the reflected light signals obtained in the first-order diffracted light receiving range 152b and the total added value of the reflected light signals obtained in the first-order diffracted light receiving range 152c is calculated and output as a tracking error signal. I do.

In such processing, the following method can be considered as a specific method for determining the first-order diffracted light receiving range 152b and the first-order diffracted light receiving range 152c. For example, first, the above-described Embodiments 2 to 4
The actual light receiving range is detected by any of the methods described above. Then, only the reflected light signals detected by the light receiving portions located at the light receiving positions that can be regarded as the first order diffracted light receiving range in the actual light receiving range may be added to obtain a difference value of the total added value. In addition, a threshold value of a reflected light signal that can be regarded as being detected in the first-order diffracted light receiving range is set in advance,
The reflected light signal below the threshold value may not be used for calculating the tracking error signal.

In the fifth embodiment described above, the value of the tracking error signal can be calculated using only the reflected light signal detected in the first-order diffracted light receiving range. For this reason,
A tracking error signal can be obtained with a reflected light signal in a relatively narrow range, and the influence of a DC offset or extraordinary light on the value of the tracking error signal can be reduced.

Further, even if the detection range of the reflected light signal is narrowed,
Since a strong reflected light signal is obtained in the first-order diffracted light receiving range, a reflected light signal sufficient for generating a tracking error signal can be obtained. According to the fifth embodiment, in addition to the effects obtained in the first to third embodiments, except for the influence of an abnormal reflected light signal generated in a light receiving range other than the first-order diffracted light receiving range on a tracking error signal, Thus, an effect that a tracking error can be detected more accurately can be obtained.

The configuration of the present invention is not limited to the embodiment described above. That is, the photodetector used in the tracking error detection device of the present invention is not limited to the configurations of the first and second embodiments, but may be any configuration that can detect the actual light receiving range. Configuration may be used. Further, the configuration of the optical system of the tracking error detection device of the present invention and the total light receiving volume of the photodetector,
The optimum shape and size of each light receiving unit and the arrangement method can be selected in consideration of the type of the optical disk, the detection accuracy of the tracking error, the device cost, and the like.

[0078]

The present invention described above has the following effects. That is, according to the first aspect of the present invention, a tracking error signal that accurately indicates a tracking state is generated irrespective of a shift of an optical system, so that an optical information recording / reproducing apparatus can accurately generate a tracking error signal regardless of a shift of an optical system. A tracking error detection device capable of detecting a tracking error can be provided.

According to the second aspect of the present invention, even when the actual light receiving range is shifted in the radial direction due to the shift of the optical system, the actual light receiving range can be detected irrespective of the shift. For this reason, in the optical information recording / reproducing apparatus, it is possible to prevent the occurrence of the DC offset regardless of the displacement of the optical system in the radial direction, and to accurately detect the tracking error.

According to the third aspect of the present invention, the reflected light detecting means can have a plurality of functions, and the optical information recording / reproducing apparatus can be reduced in size and cost.

According to the fourth aspect of the present invention, the flare light and the flare light in the non-light receiving range out of the actual light receiving range in the light receiving range.
Abnormal light due to optical disk shape abnormalities, scratches, and dust does not affect the value of the tracking error signal. Therefore, even when an abnormal reflected light signal is detected in the non-light receiving range, the tracking error can be accurately detected except for the influence of the reflected light on the tracking error signal.

According to the fifth aspect of the present invention, flare light generated at the end of the actual light receiving range, abnormal light due to abnormal shape or scratches or dust of the optical disk does not affect the value of the tracking error signal. . Therefore, even when an abnormal reflected light signal is detected at the end of the actual light receiving range, the tracking error can be accurately detected except for the influence of the reflected light signal on the tracking error signal.

According to the sixth aspect of the present invention, the flare light generated outside the light receiving range where the 0th-order diffracted light and the 1st-order diffracted light overlap, abnormal light due to abnormal shape or scratches of the optical disk, or dust is generated by the tracking error signal. Will not be affected. Therefore, even when an abnormal reflected light signal is detected outside the light receiving range where the 0th-order diffracted light and the 1st-order diffracted light overlap, the tracking error can be accurately corrected except for the influence of the reflected light signal on the tracking error signal. Can be detected.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a tracking error device according to an embodiment of the present invention;
5 is a common diagram.

FIG. 2 is a diagram illustrating the photodetector according to the first embodiment of the present invention in more detail.

FIG. 3 is a diagram for explaining signal processing by a detection signal processing unit according to the first embodiment of the present invention;

FIG. 4 is a diagram illustrating a procedure for dividing a receivable range into a first light receiving range and a second light receiving range according to the first embodiment of the present invention;
FIG. 9 is a diagram for explaining a method of processing reflected light signals obtained in the light receiving range and the second light receiving range.

FIG. 5 is a flowchart illustrating a process according to the first embodiment of the present invention.

FIG. 6 is a diagram for explaining a light receiving unit according to the second embodiment of the present invention.

FIG. 7 is a diagram for explaining signal processing by a detection signal processing unit according to the second embodiment of the present invention.

FIG. 8 is a diagram illustrating a procedure for dividing a receivable range into a first light receiving range and a second light receiving range according to the second embodiment of the present invention;
FIG. 9 is a diagram for explaining a method of processing reflected light signals obtained in the light receiving range and the second light receiving range.

FIG. 9 is a diagram for explaining a photodetector according to a third embodiment of the present invention.

FIG. 10 shows a procedure for dividing a receivable range according to a third embodiment of the present invention into a first real light receiving range and a second real light receiving range, and a first real light receiving range and a second real light receiving range. It is a figure for explaining the processing method of the obtained reflected light signal.

FIG. 11 is a flowchart illustrating a process according to a third embodiment of the present invention.

FIG. 12 is a diagram for describing a procedure for determining a center position of an actual light receiving range and an actual light receiving range according to the fourth embodiment of the present invention.

FIG. 13 is a diagram for describing effects obtained in the fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating a photodetector according to a fifth embodiment of the present invention.

FIG. 15 is a diagram for explaining a general push-pull method.

FIG. 16 is another diagram for explaining a general push-pull method.

FIG. 17 is a diagram illustrating a relationship between a tracking error signal by a push-pull method and a center position of a spot of a laser beam.

FIG. 18 is a diagram for describing a problem that occurs when the objective lens is moved in a direction orthogonal to the optical axis of the laser beam and tracking is performed.

FIG. 19 is a diagram for explaining a DC offset of a tracking error signal.

[Explanation of symbols]

Reference Signs List 1 laser light source 3 collimating lens 5 beam splitter 7 objective lens 9 optical disk 10 detection signal processing unit 12, 62, 102, 152 photodetector 12b, 12c, 62b, 62c, 152b, 152c
1st-order diffracted light receiving range 12a, 62a, 102a, 152a Actual receiving range 12d, 62d, 102d, 152d Non-receiving range 13a, 63a Receiving unit 13, 63 Receiving surface 30, 70, first receiving range 31, 71 Second Light receiving range 90 First actual light receiving range 91 Second actual light receiving range

Claims (6)

[Claims] A light irradiating means for irradiating the converged laser light onto the optical information recording medium; and a laser light irradiated by the light irradiating means for receiving reflected light reflected by the optical information recording medium. Equipped with a light receiving section,
Reflected light detecting means for detecting a reflected light signal based on the reflected light received by the light receiving unit; and actual light receiving range detecting means for detecting an actual light receiving range in which the reflected light is received, among the light receiving ranges of the light receiving unit. The light-receiving area is divided into a first light-receiving area and a second light-receiving area according to the center line of the actual light-receiving area detected by the actual light-receiving area detecting means, and is obtained in the first light-receiving area. A tracking error signal output unit that outputs a tracking error signal based on a difference between the reflected light signal and the reflected light signal obtained in the second light receiving range. 2. The tracking error signal output means, wherein the plurality of light receiving sections have a long stripe shape in a direction parallel to a track of the optical information recording medium and are arranged in a plurality of directions in a direction perpendicular to the tracks of the optical information recording medium. 2. The device according to claim 1, wherein the light receiving area is divided into a first light receiving area and a second light receiving area at a center line of the actual light receiving area parallel to a track of the optical information recording medium. Tracking error detection device. 3. The light receiving section is a two-dimensional array light receiving section arranged in a plurality of directions orthogonal to and parallel to a track of the optical information recording medium, and the tracking error signal output means includes 2. The tracking error detection device according to claim 1, wherein the receivable area is divided into a first light receiving area and a second light receiving area at a center line of the actual light receiving area parallel to a track of the information recording medium. . 4. The tracking error signal output means calculates a difference value between a reflected light signal obtained in a first light receiving range and a reflected light signal obtained in a second light receiving range. 4. The tracking error detection device according to claim 3, wherein only the reflected light signal obtained in the actual light receiving range of the light receiving range and the second light receiving range is used. 5. The tracking error signal output means sets a first light receiving range to a light receiving range by a straight line passing through a minimum position of the reflected light signal in the actual light receiving range and parallel to a track of the optical information recording medium. The tracking error detection device according to claim 1, wherein the tracking error detection device is divided into a second light receiving range and a second light receiving range. 6. The tracking error signal output means calculates a difference value between a reflected light signal obtained in a first light receiving range and a reflected light signal obtained in a second light receiving range. A reflected light signal obtained in a region where the 0th-order diffracted light and the 1st-order diffracted light of the reflected light overlap in the light receiving range of
4. The tracking error detection device according to claim 3, wherein only the reflected light signal obtained in a region where the 0th-order diffracted light and the 1st-order diffracted light of the reflected light overlap in the light receiving range is used.