JPH07262568A - Optical pickup device - Google Patents

Abstract

PURPOSE:To obtain a stable track signal and focus signal with decreased errors by detecting the spot light quantities at both ends of spots trisected at the condensing point of a condenser lens by using divided photodetectors. CONSTITUTION:A disk 5 is irradiated with the light source light from a light source 1 through an objective lens 4. The reflected light from this disk 5 is split by the condenser lens 11 through a beam splitter 3, by which the slot light quantity of the light at the condensing point of the lens 11 is trisected. The trisected light quantities are received by three pieces of the trisected photodetectors 13. The stable track signal with the decreased errors is obtd. in spite of generation of optical axis misalignment of the lens by a lens actuator and an inclination in the radial direction of the disk if the detected outputs of the elements 12 at both ends are used. The detected luminous fluxes do not include the track patterns by the detected output of the central photodetector 2, by which the stable focus signal free from fluctuation is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup device in an optical disc drive.

[0002]

2. Description of the Related Art As a conventional device for detecting a tracking error in an optical disk drive, there is, for example, a device using a push-pull method. This push-pull method is small and easy to adjust, and is often used especially for data type optical pickups connected to a personal computer. However, with this push-pull method,
Due to the optical axis shift of the objective lens due to the lens actuator, the radial tilt of the disc, etc., the spot position on the light receiving element changes and an offset occurs in the signal.

Further, in the conventional apparatus for detecting the focus signal, the beam in which the track pattern is generated is used for the detection, so that the focus fluctuation (when the track groove is crossed, during the seek operation). Fluctuation of the focus signal) occurs,
There were problems such as miscounting the number of tracks and the lens focus servo coming off.

FIGS. 3 (a) and 3 (b) show a conventional tracking / error detecting device using the push-pull method, in which 1 is a light source, 2 is a collimator lens, and 3 is a beamer. Beam splitter, 4 objective lens, 5 disk, 6 condenser lens, 7 beam splitter, 8 light receiving element, 9
Is a cylinder lens, and 10 is a four-division light receiving element.

As shown in FIG. 3A, the light beam from the light source 1 is collimated by the collimator lens 2 and passes through the beam splitter 3 and then by the objective lens 4. The light is focused on the surface of the disk 5. The reflected light from the disk 5 is reflected by the beam splitter 3 and is condensed by the condenser lens 6. In the push-pull method, the light passing through the condenser lens 6 is incident on the light receiving element 8 before being condensed at the condensing point. Therefore, for example, when the objective lens 4 is shifted leftward,
Since the reflected light travels along the dotted line, it moves upward on the light receiving element 8 as indicated by the dotted line in FIG. 3B, resulting in the track signal having an offset.

As a countermeasure against such a problem,
It has been proposed to provide (1) a two-step tracking servo, (2) detect the inclination of an objective lens or a disc, and (3) provide a track / offset detector on the disc. However, in the case of (1) above, it cannot follow the high speed rotation of the disk, and in the case of (2) above,
A sensor has to be additionally provided, and in the case of (3), a processing circuit has to be additionally provided, which has led to the occurrence of a new defect.

Further, as a countermeasure for improving the problem caused by using a beam having a track pattern for detecting a focus signal, for example, Japanese Patent Application No.
No. 152082 proposes a detecting means for receiving only the light amount inside the track pattern, but such a detecting means has a drawback that it needs to be aligned and deviates from the center depending on the light amount distribution. It had happened.

[0008]

As described above, in the conventional tracking error detecting means, an offset occurs in the track signal, and in the focus signal detecting means, a track signal is generated.
There was a focus fluctuation during the operation. Further, there is a drawback in that the structure of the device becomes complicated in order to prevent the occurrence of such offset and focus fluctuation.

The present invention has been made in view of the above, and an object thereof is to provide an apparatus capable of obtaining a stable track signal with a simple structure.

Still another object of the present invention is to provide an apparatus capable of obtaining a stable focus signal having a small error with a simple structure.

[0011]

In order to achieve the above object, the present invention provides a light source, an objective lens for condensing a light beam from the light source on a disc, and a reflected light from the disc at a condensing point. A condenser lens for forming at least three separate condensing spots, and at least 2 provided at the condensing point
The present invention proposes a configuration having a divided light receiving element and obtaining a track signal by detecting the light amounts of two spots at both ends of the separated converging spot.

In order to achieve the above object, the present invention has a light source, an objective lens for condensing a light beam from the light source on a disc, and a reflected light from the disc at least at three converging points. A light-receiving element provided at the light-collecting point, and a central spot of the light-collecting spots separated by the light-collecting lens is detected by the light-receiving element. Is proposed to obtain a focus signal.

[0013]

According to the present invention, two spots at both ends of the spots separated into at least three spots at the focal point of the condenser lens are provided.
A track signal can be stably obtained by detecting the light amount of one spot using the divided light receiving elements.

Further, according to the present invention, the focus signal can be stably obtained by detecting the specific focused spot not including the track pattern by the light receiving element.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

1 (a) and 1 (b) show an embodiment of the present invention, in which 1 to 5, 7, 9, 1 in FIG. 1 (a) are shown.
Reference numeral 0 is the same as that in FIG. 3, 11 is a converging / separating lens, 12 is a three-divided light receiving element, and FIG. 1B shows a track pattern.

The structure from the light source 1 to the disc 5 is the same as that shown in FIG. The reflected light from the disk 5 is a condenser lens 1
1, a beam splitter 7 divides the beam into two, and one of them passes through a cylinder lens 9 and a four-division light receiving element 10 generates a focus signal of the astigmatism method. The other is incident on the three-division light receiving element 12. The light receiving position of the three-division light receiving element 12 is the light converging point of the light converging / separating lens 11, and its track pattern.
The three spots A, B, and C shown by circles in FIG.
To separate. That is, spots corresponding to the ± first-order light and the zero-order light are formed on the light receiving elements A and C, respectively. Therefore, the track signal is as follows. Track signal: Tr = (A−C) / (A + C)

FIG. 2 shows another embodiment of the present invention, in which 7, 9, 10, 11, and 12 are shown in FIG. 1 (a).
13 is a pinhole, and 14 is a second cylinder lens.

The structure from the light source to the condenser lens 11 is the same as that shown in FIG. The convergent light from the condensing / separating lens 11 is divided into two by the beam splitter 7, and one convergent light is directed to the three-division light receiving element 12, and a track signal is obtained by this element.

At the converging point of the other convergent light, the pinhole 13 that allows only the 0th-order light (B spot in FIG. 1B) to pass through.
The light passing through the pinhole 13 passes through the second condensing lens 14 and the cylinder lens 9, and the four-division light-receiving element 10 generates a focus signal of the astigmatism method. In this case, since the focus signal is obtained from the light beam which does not include the track pattern, the focus fluctuation does not occur. The focus signal detection method is not limited to the astigmatism method.

[0021]

According to the optical pickup device of the first aspect, even if the optical axis of the objective lens is deviated by the lens actuator or the disc is tilted in the radial direction, the track signal can be stably obtained with a small error. Can be done. Further, since the track patterns are separated, it is easy to adjust the position of the light receiving element.

According to the optical pickup device of claim 2,
Since the focus signal detection light flux does not include a track pattern, it is possible to obtain a stable focus signal with no focus fluctuation.

[0023]

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is a diagram showing a conventional optical pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 collimator lens 3 beam splitter 4 objective lens 5 disk 6 condensing lens 7 beam splitter 8 light receiving element 9 cylinder lens 10 4 division light receiving element 11 light converging separation lens 12 3 division light receiving element 13 pinho -Le 14 second condenser lens

Claims (2)

[Claims] 1. A light source, an objective lens for condensing a light beam from the light source on a disc, and a condensing lens for converting reflected light from the disc into at least three converging spots at converging points. At least 2 provided at the condensing point
An optical pickup device having a divided light receiving element, wherein a track signal is obtained by detecting the light amounts of two spots at both ends of the separated focused spots by the light receiving element. 2. A light source, an objective lens for condensing a light flux from the light source on a disc, and a condensing lens for converting reflected light from the disc into at least three converging spots at converging points. A light-receiving element provided at the light-collecting point, and a focus signal is obtained by detecting the central spot of the light-collecting spots separated by the light-collecting lens by the light-receiving element. Optical pickup device.