JP2537840B2 - Photodetector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a light receiving surface of a photodetector for converting an optical signal modulated by, for example, an information track of an optical disc into an electric signal.

2. Description of the Related Art In recent years, a photodetection device that converts an optical signal modulated by an information track, such as an optical disc, into an electric signal has become mainstream, and its use in the field of optical information equipment has been particularly advanced. Therefore, the light receiving surface of the photodetector is currently divided into three beams, one beam, etc., depending on the optical servo system, but the light receiving surface is basically divided into four beams. ing.

With reference to the drawings, a configuration of an optical system and an example of a photodetector of a conventional one-beam type optical pickup will be described below.

FIG. 8 shows a principle diagram of a conventional one-beam optical system configuration, and FIG. 9 shows a light receiving surface of a photodetector used in the conventional optical system.
The figure shows an ideal case where a conventional photodetector is irradiated with a light spot, and FIG. 11 is a case where a conventional photodetector is actually irradiated with a light spot due to a defect on the information surface of an optical disk. FIG. 12 shows the ideal track mapping direction on the 4-division light receiving surface, FIG. 13 shows the actual track mapping direction, and FIG. 14 shows the conventional track mapping direction. FIG. 15 shows a configuration of one-beam optical servo control signal processing, and FIG. 15 shows states of an optical information signal, a focus control signal, and a tracking control signal due to a defect of an optical disk.

In FIG. 8, 1 is a semiconductor laser, 2 is a collimator lens integrated focus lens, 3 is a half mirror,
4 is a laser mirror, 5 is a concave lens, 6 is a photodetector,
Reference numeral 7 is an optical disk, and 8 is an information signal recording surface of the optical disk 7.

In FIG. 9, reference numerals 9, 10, 11, 12 denote the light receiving surfaces of the four-divided light receiving surfaces, 13 denotes the dividing line direction of the photodetector, and 14
Represents a light receiving portion for receiving scattered light due to dust, fingerprints, etc. of the optical disk.

In FIG. 10, reference numeral 15 is a light spot which is ideally irradiated on the light receiving surface (the following is the same as FIG. 9).

In FIG. 11, 16 is a light spot which is actually irradiated onto the light receiving surface due to a defect of the optical disk, and 17 represents the scattered light (the same applies to FIG. 9 below).

In FIG. 12, 18 indicates an ideal track mapping direction of the optical system, and 19 indicates a normal direction mapping of the track mapping (9, 10, 11, 12 are four-division light receiving surfaces in FIG. 9).

In FIG. 13, 20 indicates the actual track mapping direction of the optical system, and 21 indicates the normal direction mapping of the track mapping (9, 10, 11, 12 are the four-divided light receiving surfaces in FIG. 9).

In FIG. 14, 22 is the photodetector of FIG.
Is a focus servo control signal detector, 24 is a tracking servo control signal detector, 25 is an optical information signal detector, 26 is a focus error signal output, 27 is a tracking error signal output, and 28 is an optical information signal output (optical In the detection device 22, each light-receiving surface number a, b, c, d, e and pin number, ...
, Correspond. a-similarly below).

In FIG. 15, 29 is an optical information signal at the time of passing a defective portion of the optical disk, 30 is a focus error signal at that time, 31 is a tracking error signal, 32, 33, 34
Shows the reproduction states of the optical information signal, the focus error signal, and the tracking error signal in the defective portion of the optical disc (in FIG. 15, the vertical axis represents the signal amplitude and the horizontal axis represents the signal time axis).

The operation of the optical system configured as described above and the photodetector used in the optical system will be described below.

In FIG. 8, the light emitted from the semiconductor laser 1 is reflected by the half mirror 3 and the laser mirror 4 and enters the collimator lens-integrated focus lens 2, and the optical disc 7
It is condensed on the information signal recording surface 8. Optical disk 7
The reflected light modulated by is converted into convergent light by the collimator lens-integrated focus lens 2, the convergent light is reflected by the laser mirror 4, is incident on the half mirror 3, is converted into astigmatic light, and is converted by the concave lens 5. The light spot is focused on the light-receiving surface of the photodetector 6, and the pattern of the light spot irradiated on the light-receiving surface changes depending on the positional relationship between the optical disc 7 and the collimator lens-integrated focus lens 2 (hereinafter abbreviated as focus lens). However, since the light intensity distribution of the light spot changes, it can be converted into an electric signal by the photodetector 6 and each signal output can be obtained. As shown in FIG. 14, it is the light receiving surface a, b, c,
Using d and e, the focus servo control signal detector 23 outputs a focus error signal to 26 based on the principle of the astigmatism method, and the tracking servo control signal detector 24 outputs 27 to the focus error signal based on the phase difference method. Output a tracking error signal to the optical information signal detector 25
Can be obtained.

As described above, focus and tracking control are performed based on the output signal of the photodetector 6 (22) so that the optical disc 7 and the focus lens 2 are always in the correct positional relationship, and an optical information signal can be obtained. Become.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above configuration, when the optical disc 7 of FIG. 8 has defects such as scratches on the information recording surface 8 and signal loss, the information recording surface 8 is modulated. The reflected light is
As shown in FIG. 11, on the light receiving surface of the photodetector, the light spot is diffracted by a defect of the optical disk 7, scattered light, etc.
The light intensity distribution causes an imbalance, and the light spot shape in the normal servo state is transformed into a light spot shape such as 16 in FIG.

Therefore, in the optical servo control system of FIG. 14, the signal processed by the focus error detector 23 and the tracking error detector 24 of FIG. 14 due to the generation of the light spot 16 of FIG. 11 generates a similar signal. Will be done. FIG. 15 shows an example of the actual signal waveforms of the optical information signal 29, the focus error signal 30, and the tracking error signal 31 due to the defects on the information recording surface 8 of the optical disk 7. As shown in FIG. The optical information signal 29 has a flaw or a missing portion 32 due to a defect, and the focus error signal 30 and the tracking error signal 31 generate similar error signals 33 and 34, respectively, in synchronization with the position, and the optical servo control system. There is a problem in that the signal reproduction capability is deteriorated due to instability.

The above problem is closely related to the mapping of the track, and the ideal mapping of the optical signal modulated on the information recording surface of the optical disc on the light receiving surface of the photodetector is as shown in FIG. , Track map 18 (indicated by dashed lines) and its normal direction map
As shown by 19 (indicated by a broken line), they are mapped in the direction of the cross line.

However, in the optical system shown in FIG. 8, when the concave lens 5 is actually a spherical lens and there is a wavefront aberration, or when there is an aberration of another optical system, etc., the ray tracing method by the optical simulation analysis method is used. Theoretical analysis of the light spot mapping shows the track mapping 2 as shown in Fig. 13.
0, a mapping direction such as the normal direction map 21 is taken, and a direction different from the dividing line (dividing line direction 13 in FIG. 9) of the light receiving surface of the photodetector is actually taken. The mapping direction is greatly different from the ideal mapping direction particularly in the area outside the light spot just focused on the light receiving surface of the photodetector.

In particular, it has been experimentally considered that, among the mappings, the track mapping has a great influence on the signal reproducing ability (hereinafter referred to as playability), and the optical spot 16 at the time of passing the optical disk defective portion in FIG. Figure 13 Track map 20
Contrasting with each other, for example, if the track map 20 is taken as a dividing line of the light receiving surface of the photodetector, it operates in such a direction as to recover the pseudo error signal generated by the light intensity distribution of the unbalanced light spot 16. It can be seen that, since the dividing line direction of the light receiving surface of the conventional photodetector is different from the actual mapping direction, the optical servo control signal becomes unstable, and there is a problem that playability deteriorates. .

In view of the above problems, the present invention provides a photodetector capable of stably obtaining a control signal and an optical information signal of an optical control system by improving the light receiving surface of the photodetector.

Means for Solving the Problems In order to achieve the above-mentioned object, a photodetector of the present invention provides an optical signal focused on an optical recording medium and modulated by an information recording surface recorded on the recording medium. In a photodetector that receives light and converts it into an electrical signal, its light-receiving surface is divided into at least four, and a dividing line that divides the light-receiving surface is a first dividing line formed in a straight line direction of crosses that are orthogonal to each other,
The first parting line is provided with a second parting line which is continuous with both ends of the first parting line and extends in a different direction from the first parting line.

Operation According to the present invention, the dividing lines of the light-receiving surface of the photodetector that receives an optical signal modulated by a normal optical disc having no scratches or omissions on the information recording surface are perpendicular to each other by the above-described configuration. First configured in the straight direction of the cross
The dividing line of the light receiving surface of the photodetector that receives the optical signal modulated by the optical disc having a defect such as scratch or missing on the information recording surface is the first dividing line and the light receiving surface. The defect of the optical disk by using the second dividing line which is different in direction from the first dividing line, which is along or approximate to the actual track mapping direction of the optical system in the area outside the just-focused optical spot. By reproducing the pseudo focus error signal and tracking error signal generated by the optical signal modulated by, stable servo control signals and optical information signals can be obtained, and playability can be improved.

Example A photodetector according to an example of the present invention will be described below with reference to the drawings.

FIG. 1 shows a light receiving surface of a photodetector in an embodiment of the present invention.

In FIG. 1, reference numerals 35, 36, 37 and 38 denote light receiving surfaces of four-divided light receiving surfaces, 39 is a light receiving portion for receiving scattered light generated by a defect of an optical disc, and 40 and 41 are 35, 36, As the dividing line of the light receiving surface of 37.38, it is the first dividing line formed in the straight line direction of the crosses orthogonal to each other, and 42 and 44 are the first dividing lines 40.
Is continuous at both ends of the light receiving surface 35, 36, 37, 38 and is along the actual track mapping direction in the area outside the just-focused light spot, or approximates the actual track mapping of the optical system. , 42-40-44 is a track map dividing line, which is a second dividing line extending in a different direction from the first dividing line. 43 and 45 are second dividing lines which are continuous at both ends of the first dividing line 41, and the dividing lines 43-41-45 connect the track mapping dividing lines 42-40-44 to the light receiving surfaces 35, 36, 37 and 38. It is a dividing line in the direction of the normal, which is formed at a position rotated by 90 ° with respect to the center of.

FIG. 2 shows an ideal state in which the light receiving surface of the photodetector in the embodiment of the present invention is irradiated with a light spot in reproduction when the information recording surface of the optical disc has no defects such as scratches or omissions. Is.

In FIG. 2, reference numeral 46 denotes an optical spot during normal reproduction of an optical disk having no defect on the information recording surface (the same as in FIG. 1 below).

FIG. 3 shows a state where the light receiving surface of the photodetector in the embodiment of the present invention is irradiated with a light spot in reproduction when the information recording surface of the optical disc has a defect such as a scratch or a drop.

In FIG. 3, 47 is a light spot at the time of reproducing an optical disk having a defect on the information recording surface, and 48 is scattered light at that time (hereinafter, the same as in FIG. 1).

FIG. 4 shows an optical information signal, a focus error signal, and a tracking error signal at the time of reproducing an optical disc having a defect such as a scratch or missing on the information recording surface when the photodetector in the embodiment of the present invention is used. .

In FIG. 4, 49, 50 and 51 are optical information signals, focus error signals and tracking error signals at the time of reproducing an optical disc having a defective information recording surface, and 52, 53 and 54 are optical disc defective portions of each signal. Shows the playback state of.

FIG. 5 shows information on the irradiation of an astigmat-shaped light spot when astigmatism is generated on the four-division light receiving surface in the photodetector in the embodiment of the present invention.

In FIG. 5, 56 and 58 are light spots at the time of defocus, and 57 is a light spot at the time of just focus. Reference numeral 55 designates a four-divided light receiving surface of the photodetector of the present invention in FIG.

6 and 7 show another embodiment to which the present invention is applied.
9,60,61,62,63 are track map division lines at that time.

The operation of the photodetector configured as described above will be described below with reference to FIGS. 1 to 7.

For example, when a normal optical disk having no defects such as scratches or missing on the normal information recording surface is reproduced by using the light receiving surface of the photodetector having the structure as shown in FIG. 1, the size of the spot diameter on the light receiving surface is increased. Depends on the characteristics of the optical system, such as the second
As shown in the figure, the optical information signal, the focus error signal, and the tracking error signal are obtained by utilizing the cross-shaped dividing lines 40 and 41 having the same length as the major axis of the light spot 46 and orthogonal to each other.

Next, when an optical disk having a defect such as a scratch or a drop on the information recording surface is reproduced, the light spot on the light receiving surface has a spot shape as shown in 47 of FIG. 3, and the spot shape is as shown in FIG. Raise the illuminated area of the light spot 46 of
This light spot 47 corresponds to the first dividing line 40 and the second dividing line 40 of the present invention.
Of the present invention, as shown in FIG. 1, since it is deformed in a direction substantially along the dividing lines 42, 44 of FIG. 1 and hardly changes in the other direction of the mapping dividing lines 43, 41, 45. By using the photodetector of FIG. 1 in the conventional optical servo control system as shown in FIG. 14, the first dividing line 40 and the second dividing line 40 of the present invention shown in FIG.
The dividing lines 42 and 44 of FIG. 4 can correct the similar error signals of the focus error signal and the tracking error signal generated by the unbalanced light intensity distribution of the light spot 47. Therefore, as shown in FIG. The focus error signal 50 and the tracking error signal 51, which are synchronized with the defective portion 52 of the information signal, respectively, are similar error signals 53 and 54, respectively.
Compared with the case of FIG. 5, the servo control signal can be stably obtained, and playability can be improved.

Further, the first dividing line and the second dividing line of the present invention are, for example, as shown in FIG. 5, light spots 56 and 57 having an stigma shape at the time of focusing and defocusing based on a normal astigmatism method. , 58 are also correctly divided, the signal can be detected satisfactorily without affecting the focus error detection by the astigmatism method.

Further, in the present invention in FIG. 1, regarding the track direction dividing lines 42, 40, 44 normal direction dividing lines 43, 41, 45,
Although the direction is different from the actual normal direction map 21 of the optical system in FIG. 13, the dividing line of the present invention makes the light receiving area of each of the four divided light receiving surfaces 35, 36, 37, 38 equal, and In order to easily adjust the position on the light receiving surface, the dividing lines 42, 40, 44 are rotated by 90 degrees. This is because the second dividing lines 43, 45 of the normal direction dividing lines 43, 41, 45 have little influence on the generation of the pseudo error signal.

As an application example of the present invention, depending on the design conditions of the optical system,
By taking the track division line in the direction of 59 in Fig. 6a, or by taking the actual track map of the optical system in the direction of 60, 61 as in Fig. 6b, c, Similarly, it is possible to provide a photodetector that improves playability. Further, even in the light-receiving surface constituted by, for example, four or more divisions as shown in FIGS. 7A and 7B, (71 + 75), (72 + 76), (73 + 77), (74+) in each of the light-receiving surfaces 71 to 78.
By using the added sum signal as in 78) and using the track mapping division lines 62 and 63, the same effect as the present invention can be obtained.

As described above, in the photodetector of the present invention shown in FIG. 1, when reproducing an ordinary optical disc having no defects, the first dividing lines 40 and 41 of the crosses which are orthogonal to each other are used, and scratches, omissions, etc. When playing a defective optical disc of
By using the first dividing lines 40, 41 and the second dividing lines 42, 43, 44, 45, stable servo control signals and optical information signals of the optical system can be obtained, and playability is improved. In addition, the signal can be detected without affecting the focus error detection using the astigmatism, and the position of the light spot on the light receiving surface can be easily adjusted.

As described above, according to the present invention, in the light-receiving surface of the photodetector, the light-receiving surface is composed of four or more light-receiving surfaces, and the dividing lines of the light-receiving surface are arranged in the direction of the straight line of the crosses orthogonal to each other. By providing the first dividing line configured and the second dividing line which is approximate to the actual track mapping direction of the optical system in the region outside the light spot just focused on the light receiving surface, A stable servo control signal and optical information signal of the optical system can be obtained, playability can be improved, focus error signal detection is not affected, and the position of the light spot on the light receiving surface can be adjusted. It has no effect and can be adjusted easily.

[Brief description of drawings]

FIG. 1 is a plan view showing a structure of a light receiving surface of a photodetector in an embodiment of the present invention, FIGS. 2, 3, and 5 are plan views for explaining the same operation, and FIG. The waveform diagrams, FIGS. 6 and 7 are plan views showing the structure of the light receiving surface of the photodetector in another embodiment of the present invention, and FIG. 8 is a perspective view showing the structure of a general optical pickup, and FIG. FIG. 10 is a plan view of a light receiving surface of a conventional photodetector, FIGS. 10 to 14 are plan views for explaining the operation of the conventional example, and FIG. 15 is a waveform diagram thereof. 35,36,37,38,39 …… Receiving surface of photodetector, 40,41 …… First dividing line, 42,43,44,45 …… Second dividing line, 46,47 ……
Light spot, 48 …… scattered light, 49 …… optical information signal, 50 ……
Focus error signal, 51 ... Tracking error signal, 52 ... Defective portion of optical information signal, 53,54 ... Similarity error signal, 55 ... Four-division light-receiving surface of photodetector of embodiment, 5
6,57,58 …… Light spot 59,60,61,62,63 …… Track map division line.

Front page continuation (72) Inventor Masayuki Ito 1006 Kadoma, Kadoma-shi, Matsushita Electric Industrial Co., Ltd. (56) References: 61-83120 (JP, U)

Claims (1)

(57) [Claims] 1. A photodetector for receiving an optical signal focused on an optical recording medium and modulated by an information recording surface recorded on the recording medium, and converting the received optical signal into an electric signal, at least the light receiving surface of which is received. A dividing line which is divided into four and divides the light receiving surface is a first dividing line which is formed in a straight line direction of a cross that is perpendicular to each other, and the first dividing line which is continuous to both ends of each of the first dividing lines. And a second parting line extending in a different direction from.