JPS6273435A - Tilt extent detecting device for disc - Google Patents

Abstract

PURPOSE:To always detect stably the tilt extent of a disc without a problem such as mis-detection by using only one photodetecting element. CONSTITUTION:One position detection semiconductor element 5C is used for the photodetecting element, a lens, etc., are assembled between a light emitting element and the photodetecting element so as to focus a spot on the position detection semiconductor element. That is, when the disc 1 is deformed and an angle is tilted by DELTAtheta1, the light from the light emitting element 5A is reflected on the disc 1 by the angle of 2DELTAtheta1 to change the irradiated position of the spot on the position detection semiconductor 5C. Since the spot position is changed on the same position detection semiconductor 5C, the tilt extent is easily extracted as an output signal. In this case, since only one photodetecting element is used, there is no problem such as mis-detection due to the difference in the characteristic between two elements which has been a problem in a conventional system and the tilt extent of the disc is always detected stably.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an optical disc playback device such as a video disc player, and more particularly to a disc tilt detection bag RK for detecting the tilt of a disc in the playback device.

[Background of the invention]

2. Description of the Related Art In optical disc playback devices such as video disc players, there are cases where the disc surface and the information reading laser beam have a certain relative tilt angle due to deformation of the disc. If the disc is reproduced in this state, defects such as crosstalk between information tracks on the disc surface will appear, so it is necessary to provide a mechanism for detecting and correcting this disc tilt.

FIG. 8 is a schematic diagram showing the configuration of a player in a conventional optical disc playback device as shown in Japanese Utility Model Application Publication No. 58-183639, and FIG. 9 is an enlarged view of the pickup portion of the player. be.

Here, 1 is a disk, 2 is a pickup base, 3 is an actuator, 4 is an objective lens, 5 is a disk tilt detection system, 5A is a light emitting element, 5B1 and 5B2 are light receiving elements, 6 is a disk motor, and 7 is a turntable. , 8 is a comparator.

Now, in the disk tilt detection system 5, the light emitted from the light emitting element 5A is reflected by the surface of the disk 10 and enters the two divided light receiving elements 5B1.582. If the disk 1 is tilted in this case, the amount of light entering each light-receiving element 5B1.582 will change, resulting in both lights! The output signal from the comparator 8 that is making all the comparisons changes, thereby making it possible to detect the entire amount of disk inclination.

Furthermore, by correcting the amount of inclination of the disk with another correction mechanism (not shown), the surface of the disk l and the objective lens 4
The laser beam emitted from the can be kept at right angles at all times.

As described above, in the conventional device, the disk tilt ff1t
- Although it is easy to detect, since the light-receiving element is divided into two separate parts, if there is a slight difference in characteristics between the elements,
It becomes difficult to accurately detect the amount of inclination.

The disc deformation detection lid is required to be extremely sensitive (on the order of Or), so if the mutual characteristics change due to changes over time (the light receiving element changes over time? It's easy to cause this), Accurate detection becomes difficult and therefore correction is also impossible, making it difficult to maintain normal function.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a disk tilt detection device that can stably detect the amount of disk tilt over a long period of time without being affected by changes in elements over time.

[Summary of the invention]

Therefore, in the present invention, the light-receiving elements are - position-detecting semiconductor elements, and a lens or the like is incorporated between the light-emitting element and the light-receiving element to connect a spot on the position-detecting semiconductor elements. When the disk is tilted, the spot position changes on the same position detection semiconductor element, so the amount of tilt can be easily extracted as an output signal. In this case, since there is only one light-receiving element, there is no problem such as erroneous detection due to the difference in characteristics between the two elements, which has been a problem in the past, and the amount of tilt of the disk can always be detected stably.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the overall structure of a disc player including an embodiment of the present invention. Here, 1 is the disk,
2 is a pickup base, 3 is an actuator, 4 is an objective lens, 5 is a disk tilt detection system, 6 is a disk motor, 7Vi turntable, and 9 is a detection circuit.

Next, FIG. 2 is a top view of the pickup section in FIG. 1, and FIG. 3 is a side view of FIG. 2 as viewed from the direction of arrow XX. Here, 5A is a light emitting element, 5C is a position detection semiconductor element, and 5D is a lens.

The lens 5D is one or a number of 'fM lenses installed as required, and functions to reflect the light emitted from the light emitting element 5A on the disk 1 and connect the spots on the position detection semiconductor element 5C. be.

Next, FIG. 4 is a side view of FIG. 2 viewed from the direction of arrow Y-Y. Here, if the disk 1 is deformed and the angle is tilted by Δθ1, the light emitted from the five light emitting elements will be reflected at an angle of 2Δθl when reflected by the disk 1, and the spot on the position detection semiconductor element 5C will be The irradiation position changes.

Figure 5 shows this state viewed from above, with the spotlight 5
As the disk tilts, E changes to the position detection semiconductor element 5C.
This shows how the upper irradiation position (Xl) changes.

Next, the operating principle of the position detection semiconductor element is shown in Figures 6 and 7.
This will be explained using figures.

The position detection semiconductor element has a structure in which a high resistivity n layer (i/I) has one high resistivity layer on the front surface and an n layer on the back surface, and has a pn junction lateral/brown photo effect. (L
This is a light receiving element for detecting the position of a light spot, and its cross-sectional structure is as shown in FIG.

Here, the carriers generated in the semiconductor due to the incidence of the optical spot Φ are drifted by the electric field in the depletion layer, and the holes are p
layer, electrons reach the n layer. The holes injected into the p-layer are divided into components flowing through resistors 1 and 2, resulting in a current 'A'.
e taken out from electrodes A and B as IB.

The distance between electrodes A and B! , the resistance is p, the photogenerated current at point Q is characterized by
O・・・・・・(1) In=((about 1+”L)/(
Rp+ 2 months x 1. )...-(2) Io-Z.

+IB・・・・・・
(3) Also, resistance "1 + R2 is connected from point Q to electrode A,
It is proportional to the distance to B and is expressed by the following formula: 0 R1 = (rabbit/2) x (1 + (2//) x2)
・・・・・・(4) Rz=(Tokyo/2)X(1-(2)
// ) In order to eliminate this influence, each output current is normalized by the incident energy, and the ratio of the difference and the sum of the output currents is used as a position signal. Formula (6) is obtained from the above formulas (1) to (5).

(IB-IA)/(fB+IA)-(approximately p/(Rp+2
几L)

Figure 7 shows the output t? This is a characteristic diagram showing the 1fJo difference and the irradiation position of the spot light, and by measuring the output current, it is possible to know the irradiation position and the inclination angle of the disk.

Although the positional resolution varies slightly, it is about 1/4000 when the photocurrent is 3 μ. If this is expressed as an angular change, it will be about o, ooi to 0.004°, which has sufficient resolution.

The angle of inclination of the disk can be determined in the above manner, but by correcting the amount of inclination using a separate correction mechanism (not shown), the surface of the disk 10 and the laser beam emitted from the objective lens 4 can always be kept at right angles. I can do it.

A feature of the present invention is that the inclination angle of the disk is detected by the change in the position of the irradiation spot on the - position detection semiconductor elements, which is different from the conventional method of detecting the inclination angle by the change in the amount of light between two light receiving elements. There is no problem such as erroneous detection due to differences in characteristics between the 572 elements, and the amount of tilt of the disk can always be detected stably.

Note that in this example, a lens was used to narrow down the light from the light emitting element 5A and make it into a spot light, but a method using a slit instead of a lens, or a method in which spot light can be obtained only with the light emitting element, is possible by using a lens, Similar effects can be obtained without using slits or the like.

〔Effect of the invention〕

According to the present invention, since there is only one light-receiving element, there is no problem such as false detection due to the difference in characteristics between two elements, which was a problem in the past, and the amount of tilt of the disk can always be detected stably. , there is an effect.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the overall configuration of a disc player including an embodiment of the present invention, FIG. 2 is a top view of the pickup section in FIG. 1, and FIG. Arrow X-X in the diagram
A side view seen from the direction, Fig. 4 is the arrow Y- in Fig. 2.
5 is a top view of the detection system in FIG. 4, FIG. 6 is a sectional view showing the structure of the position detection semiconductor element in FIG. 5, and FIG. 7 is a characteristic diagram of the same, @ FIG. 8 is a schematic diagram showing the configuration of a conventional player, and FIG. 9 is an enlarged side view of the pickup portion of FIG. 8. Explanation of symbols 1...Disk, 2...Pickup base, 3...Actuator, 4...---
Objective lens, 5...Disc tilt detection system, 5A
...... Light emitting element, 5B1.5B2... Light receiving element, 5C... Position detection semiconductor element, 5D.
...Lens, 5g...Spot light, 6.
... Disc motor, 7 ... Turntable, 8 ... Comparator, 9 ... Detection circuit Representative Patent attorney Akio Namiki 12 1 Tomomi Tisfu 2 Fig. 3 Fig. 5C1 El (Suho hand 4 unligated) =

Claims (1)

[Claims] 1) means for irradiating a spot light onto the disc surface;
A single semiconductor element that receives the reflected spot light from the disk surface of the irradiated spot light, and a change in the light receiving position of the reflected spot light on the semiconductor element when the disk surface is tilted from its previous position. a means for detecting;
A disk tilt detection device comprising: a disk tilt detecting device, wherein the disk tilt is detected from the detected change.