JP2607360B2 - Three beam optical pickup device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a three-beam optical pickup device,
In particular, the present invention relates to an optical pickup device in an optical information reproducing apparatus such as a video disk player and a digital audio disk player.

BACKGROUND ART The configuration of this type of apparatus is shown in FIG. In the drawing, two cylindrical holders 2 and 3 are provided in a pickup body 1, and these holders are movable along the central axes of the respective holders and are rotatable about the central axes. A grating 4 is fixed to the end of the holder 2,
The grating 4 divides a single light beam emitted from the laser diode 5 as a light source into three light beams of zero-order light and ± first-order light by its diffraction action. A collimator lens 6 is fitted in the holder 3, and the collimator lens 6 functions to convert each light beam split by the grating 4 into parallel light.

The three light beams that have passed through the collimator lens 6 are guided to an objective lens 10 through a beam splitter 7, a wave plate 8, and a total reflection prism 9, and are irradiated as three spot lights on the recording surface of the disk 11 by the objective lens 10. Is done.
As shown in FIG. 4, these three spot lights are composed of a main spot light 12 for recording information detection and a pair of preceding and succeeding tracking information detections when the main spot light 12 moves relative to the disk 11, respectively. Are irradiated on the same recording track 14 composed of a pit row as sub-spot lights 13a and 13b.

An actuator 15 is provided on the upper part of the pickup body 1. The actuator 15 drives the built-in objective lens 10 to generate spot lights 12, 13 a and
The position of the optical disk 13b is controlled in the optical axis direction and the disk radial direction. Spot light 1 reflected on the recording surface of disk 11
The three light beams based on 2,13a and 13b are
The light enters the beam splitter 7 via the total reflection prism 9 and the wavelength plate 8, the optical path is changed by the beam splitter 7, and the light enters the photodetector 17 via the cylinder lens 16.

As shown in FIG. 5, the photodetector 17 includes a so-called four-segment detector 18 that receives a light beam based on the main spot light 12 for recording information detection and a pair of sub-spot lights 13a and 13b for tracking information detection. And a pair of detectors 19a and 19b for receiving a light beam based on the light beam.
The four outputs of the quadrant detector 18 are added by an adder (not shown) to become a read RF (high frequency) signal. Each output of the pair of detectors 19a and 19b is
0, the differential amplifier comprising resistors R ₁ to R ₄ and the capacitor C _1, C ₂
21 and the differential output becomes a tracking error signal. The pair of sub-spot light 13a for tracking information detection, among 13b, the output of the detector 19a for receiving the light beam based on the sub-spot light 13 preceding the an operational amplifier 22 and voltage dividing resistors R _5, R ₆ Comparator 23
The comparison output is used as detection information for detecting an abnormal portion such as a defect or a scratch on the disk recording surface. In the reproducing system, control such as changing the servo gain of various servo systems is performed based on the detection information.

In the conventional apparatus configured as described above, the main spot light 12 and the sub-spot lights 13a and 13b are irradiated on the same track, so that the disc recording surface is abnormal based on the preceding sub-spot light. Is detected, the sub spot light and the main spot light are too close to each other and there is no time margin, so that there is a drawback that the reproducing system cannot take sufficient measures (such as changing the servo gain).

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has as its object to provide a three-beam optical pickup device capable of sufficiently coping with abnormalities on a disk recording surface on a reproduction system side. Aim.

A three-beam optical pickup device for irradiating a main spot light on a recording surface of an information recording disc and a pair of preceding and succeeding tracking sub-spot lights when the main spot light moves relative to the disc, respectively. Sub-spot light irradiating means for irradiating the sub-spot light preceding the relative movement to a track different from the recording track irradiated with the main spot light, and a light beam based on the preceding sub-spot light prior to the relative movement A detector that receives the light and converts the light into an electric signal, and abnormality detecting means for detecting an abnormality in the recording surface of the information recording disk based on the signal level of the electric signal.

Embodiment Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

The three-beam optical pickup device according to the present invention is structurally the same as the device shown in FIG. 3, but a pair of sub-spot lights 13a, 13b on the disk recording surface.
The irradiation position of the main spot light 12 is characterized. That is, as shown in FIG. 1, the pair of sub-spot lights 13a and 13b are, for example, recording tracks 14b and 14c adjacent to the recording track 14a irradiated with the main spot light 12.
On the other hand, when the main spot light 12 is applied to the center of the track 14a, the inner half of the main spot light 12 is applied to the tracks 14b and 14c. As described with reference to FIG. 5, the detection information based on the pair of sub-spot lights 13a and 13b is used as tracking error detection information, and the detection information based on the preceding sub-spot light 13a is It will be used as abnormality detection information.

By irradiating the pair of sub-spot lights 13a and 13b on tracks other than the recording track on which the main spot light 12 is irradiated, an abnormal portion of the disc recording surface passes through the position of the main spot light 12. Also passes through the position of the preceding sub-spot light 13a one rotation before the disk, and from the time when the abnormality is detected based on the detection information of the sub-spot light 13a to the time when the abnormal part passes through the position of the main spot light 12 Since a time margin equivalent to one rotation of the disk can be obtained, it is possible to sufficiently cope with abnormalities on the disk recording surface on the reproduction system side, for example, measures such as changing various servo gains.

In the above embodiment, the pair of sub-spot lights 13a, 13a
b indicates that when the main spot light 12 is irradiated on the center of the track 14a, the inner half of the main spot light 12 is irradiated on the tracks 14b and 14c.
As shown in the figure, the irradiation may be performed such that the outer half of the main spot light 12 is located on the tracks 14b and 14c. Further, the pair of sub-spot lights 13a and 13b is applied to the track adjacent to the track irradiated with the main spot light 12, but the invention is not limited to the adjacent track, and the irradiation is performed by shifting by a plurality of tracks. It is also possible. That is, the track pitch is P,
Assuming that the pit width is W, the distance D in the disk radial direction between the center of the main spot light 12 and the centers of the sub spot lights 13a and 13b is D = nP ± (W / 2) (n is an integer).

Effect of the Invention As described above, according to the present invention, a pair of tracking sub-spot lights are applied to a track different from the recording track to which the main spot light is applied. After detecting an abnormal portion of the disk recording surface based on the sub spot light, there is enough time before the main spot light reaches this abnormal portion, and when reading such an abnormal portion,
By taking measures such as adjusting the servo gain using the time margin, it is possible to read the information of the abnormal part.

[Brief description of the drawings]

FIG. 1 is a diagram showing a positional relationship of a main spot light and a pair of sub-spot lights obtained by the present invention with respect to a recording track, FIG. 2 is a diagram showing a modification thereof, FIG. FIG. 4 is a diagram showing a positional relationship between a main spot light and a pair of sub spot lights with respect to a recording track in a conventional example, and FIG. 5 is a circuit diagram of a circuit for generating a tracking error signal and an abnormality detection signal. Description of Signs of Main Parts 1 Pickup Body 5 Laser Diode 7 Beam Splitter 10 Objective Lens 11 Information Recording Disk 12 Main Spot Light 13a, 13b Sub Spot Light 14, 14a ~ 14c …… Recording track

Claims (1)

(57) [Claims] 1. A three-beam type light for irradiating a main spot light on a recording surface of an information recording disk and a pair of preceding and succeeding tracking sub-spot lights respectively when the main spot light moves relative to the disk. A pickup device for irradiating a sub-spot light preceding the relative movement to a track different from a recording track irradiated with the main spot light; and a sub-spot preceding the relative movement. A detector for receiving a light beam based on light and converting the light beam into an electric signal; and an abnormality detecting means for detecting an abnormality on a recording surface of the information recording disk based on a signal level of the electric signal. 3 beam optical pickup device.