JPH0750531B2 - Optical information reproducing device - Google Patents

Description

The present invention relates to an optical information reproducing apparatus for reproducing an information signal recorded on an optical information recording carrier (hereinafter abbreviated as an optical disk), and particularly to an adjacent track. To a means for reducing crosstalk from

[Conventional technology]

When the optical disc in the optical information reproducing apparatus is deformed or bent due to its own weight, crosstalk occurs from the adjacent tracks, and the quality of the reproduced information signal deteriorates. Therefore, conventionally, as disclosed in Japanese Utility Model Laid-Open No. 59-168835, the relative inclination between the optical disk and the optical pickup is detected,
There has been proposed a method of tilting the optical disk so that the optical disk and the optical disk are always parallel to each other.

[Problems to be solved by the invention]

In the above-mentioned prior art, a detector for detecting the inclination between the optical disc and the optical pickup, a mechanism for inclining the optical pickup, a control circuit and a motor for controlling the optical disc and the optical pickup so that they are always in parallel are required. , The configuration becomes complicated.

It is an object of the present invention to provide an optical information reproducing apparatus which does not require the above-mentioned mechanism, circuit, etc. and has a small amount of crosstalk generated from an adjacent track even when the optical disk is deformed or warped due to weight or the like. .

[Means for solving problems]

In order to achieve the above-mentioned object, in the present invention, the crosstalk component from the adjacent track is contained in a large amount in the outer peripheral portion of the spot as the reflected light from the optical disc, which corresponds to the adjacent track side in the optical disc. Focusing on the above, the photodetector for detecting reflected light (spot) is divided into a plurality of light receiving regions, and the information signal is detected only from the entire light receiving region of the spot excluding the outer peripheral portion. .

[Action]

Since the outer peripheral part with many crosstalk components is not detected in the reflected light spot from the optical disk, it is possible to reduce the crosstalk included in the information signal even if a relative tilt occurs between the optical disk and the optical pickup. it can.

〔Example〕

Hereinafter, the optical information reproducing apparatus according to the present invention will be described in detail with reference to the embodiments shown in the drawings.

FIG. 1 is a perspective view showing an embodiment of an optical information reproducing apparatus according to the present invention, FIG. 2 is a plan view of a detection optical system for detecting reflected light from an optical disk in FIG. 1, and FIG. Is a plan view of the photodetector in FIG. 1, FIG. 4 is a circuit diagram showing the signal detection circuit in FIG. 1, and FIG. 5 is an explanatory view showing the relationship between the inclination of the optical disc and the spots on the optical disc. FIG. 6 is an explanatory diagram showing a reflected light intensity distribution on the photodetector.

In FIG. 1, laser light emitted from a semiconductor laser 1 which is a laser light source is converted into parallel light flux by a collimator lens 2 and is converted into three light fluxes of 0th order light, + 1st order light and −1st order light by a diffraction grating 3. After being split, it passes through the beam splitter 4 and is focused by the objective lens 5 on the information track 6a of the optical disk 6 rotated by the motor 10. The reflected light from the optical disc 6 is converted into a parallel light flux again by the objective lens 5, reflected by the beam splitter 4, passes through the convex lens 7 and the cylindrical lens 8, and is irradiated onto the photodetector 9. Of the light beams divided into three by the diffraction grating 3, the + 1st-order light and the -1st-order light are applied to the light-receiving regions on both sides of the photodetector 9, and the 0th-order light is the center of the central 8-division region Is irradiated. From the output signal of the photodetector 9, an information signal, a focusing error signal, and a tracking error signal, which are described in the optical disk 6 as will be described later, are obtained.

Here, the tracking error detection method in FIG. 1 is a multi-spot method, but the description is omitted because it is not related to the essence of the present invention. The focusing error detection method is an astigmatism method.

In FIG. 2, the reflected light 11 from the optical disc 6 separated by the beam splitter 4 is focused by the convex lens 7 and the cylindrical lens 8. Here, the light beam 12 in the direction not receiving the focusing action of the cylindrical lens 8 and the light beam 13 in the direction receiving the focusing action of the cylindrical lens 8 intersect at the position indicated by a in FIG. This a
At the position indicated by, the luminous flux is substantially circular and the luminous flux diameter is D.
By disposing the photodetector 9 at the position indicated by a, the focusing error signal can be detected from the change in the shape of the light beam on the photodetector 9.

Next, the spots on the disk 6 and the intensity distribution of the reflected light on the photodetector 9 when the objective lens 5 and the optical disk 6 are tilted will be described.

In FIG. 5, (a) shows the case where the objective lens 5 and the optical disc 6 are parallel to each other, and (b) and (c) show the case where the objective lens 5 and the optical disc are tilted.

Further, FIG. 5 (a) is a diagram showing the inclination of the objective lens 5 and the optical disc 6, (b) is a diagram showing the relationship between the spot 11 on the optical disc 6 and the signal bit 12 of the information signal, (c). Is the intensity distribution of spot 11.

The spots 11 on the information track 6a are between the signal spots 12, the spots 11a shown by the dotted line are cases where the adjacent track has no signal spot 12, and the spots 11b shown by the solid lines are cases where the adjacent track has the signal spot 12. Here, when the objective lens 5 and the optical disc 6 are tilted, coma is generated, and a strong portion is generated in a crescent shape in the tilted direction. The crescent-shaped portion is generated on the adjacent track when the optical disk 6 is deformed into a bowl shape due to its own weight or the like, and the crescent-shaped portion is adjacent when the spot 11 moves in the track direction (Y direction) by the rotation of the optical disk 6. Crosstalk occurs due to diffraction caused by the track signal pit 12. This is the sixth
It will be described with reference to the drawings.

FIG. 6 shows the intensity distribution of the reflected light 11 on the detector 9, and the luminous flux diameter D corresponds to the luminous flux diameter D in FIG. Further, (a), (b), and (c) of FIG. 6 correspond to (a), (b), and (c) of FIG. 5, respectively, and the solid line intensity distribution and the dotted line intensity distribution of FIG. Correspond to the spot 11b shown by the solid line and the spot 11a shown by the dotted line in FIG. 5, respectively.

It can be seen from FIG. 6 that the intensity of the reflected light on the detector 9 is reduced at the periphery when the signal pit 12 exists in the adjacent track. The shaded portion corresponding to the difference between the solid line and the dotted line is the crosstalk component from the adjacent track. (B),
As shown in (c), the crosstalk generated when the optical disc 6 and the objective lens 5 are tilted also increases, but the crosstalk is the outer circumference corresponding to the adjacent track side of the optical disc 6 of the reflected light on the photodetector 9. Many occur in parts. From the above, it can be seen that crosstalk can be reduced even when the optical disk 6 is tilted by detecting the information signal from the entire portion except the outer peripheral portion where the reflected light is applied.

FIG. 3 shows the light receiving area of the photodetector 9. The three circles shown by the dotted lines show the outer diameters of the 0th-order light, the + 1st-order light, and the -1st-order light, and their diameters correspond to D in FIGS. 2 and 6.

FIG. 4 shows a signal detection circuit. Reference numeral 30 is a direct current power source, 31 and 32 are differential amplifiers, 33 is a high frequency amplifier, and 20 to 29 are light receiving regions of the photodetector 9 shown in FIG. In the learning areas 20, 21, 22, and 23, only the central portion of the reflected light spot in the radial direction of the optical disc 6 is incident, and neither side of the optical disc 6 in the radial direction is incident, and the information signal 34 is obtained from the sum of the output signals. To be The focusing error signal 35 is obtained from the difference between the sum of the light receiving areas 21, 23, 25, 27 and the sum of the light receiving areas 20, 22, 24, 26, and
And the difference between 29 and 29 provides the tracking error signal 36. The focusing error signal 35 is supplied to the focusing actuator 14 and the focusing control is performed by driving the objective lens 5 in the optical axis direction (Z direction).
The tracking error signal 36 is the tracking actuator.
Tracking control is performed by driving the objective lens 5 in the radial direction (X direction) of the optical disk 6 supplied to the optical disk 15.

〔The invention's effect〕

As described above, according to the present invention, in the reflected light from the optical disc, the photodetector is provided with a plurality of light receiving regions, focusing on the fact that the crosstalk component from the adjacent track is mostly included in the spot outer peripheral portion. The information signal is detected only from the central portion of the reflected light spot in the radial direction of the optical disc to reduce the crosstalk, and the information signal is detected by excluding only the portion including the spot crosstalk. Therefore, most of the spots are used for detecting the information signal, an information signal having a large amplitude and good S / N is obtained, and the focusing error signal can be detected from the same photodetector. As a result, it becomes unnecessary to control the relative inclinations of the optical disk and the optical pickup, and the configuration of the optical information reproducing apparatus becomes simple.

[Brief description of drawings]

1 is a perspective view of an optical information reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a plan view of the detection optical system of FIG. 1, and FIG. 3 is a plan view of the photodetector of FIG. 4, FIG. 4 is a circuit diagram showing the signal detection circuit used in FIG. 1, FIG. 5 is an explanatory diagram showing the relationship between the inclination of the optical disc and the spots on the optical disc, and FIG. 6 is the reflected light on the photodetector. It is explanatory drawing which shows intensity distribution. 1 ... Semiconductor laser, 5 ... Objective lens 6 ... Optical disk, 9 ... Photodetector

Claims (1)

[Claims] 1. A laser light source, an objective lens for focusing laser light emitted from the laser light source on an optical information recording carrier, and reflected light from the optical information recording carrier from the laser light source. Optical information reproduction comprising at least a separating means for separating the optical path to the objective lens and a photodetector for irradiating and detecting the separated reflected light from the separated optical information recording carrier as a spot. In the device, the photodetector has a first dividing line that extends in a direction corresponding to a longitudinal direction of a track on the optical information recording medium and a first dividing line that passes through the central point. A second dividing line that is orthogonal to the line, and third and fourth dividing lines that are parallel to the first dividing line and are equidistant from the first dividing line on both sides of the first dividing line. 8 divided by lines A light region, the distance between the third and fourth dividing lines is set to be smaller than the diameter of the spot of the reflected light with which the photodetector is irradiated, and the reflection with which the photodetector is irradiated. An information signal in which crosstalk from adjacent tracks on the optical information record carrier is reduced from the portion of the light spot irradiated to the four light receiving regions within the third and fourth division lines. And a focusing error signal is detected from a portion of the spot of the reflected light with which the photodetector is irradiated, which is irradiated with eight light receiving regions of the photodetector. Information reproduction device.