JPH0439741B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical signal pickup device, particularly an optical signal pickup device suitable for adjusting the positional relationship between a light spot and a track on a disk to an optimal positional relationship. It is related to the device.

[Prior Art] FIG. 3 is a perspective view showing a conventional optical signal pickup device. In the figure, 1 is a semiconductor laser as a light source, 2 is a diffraction grating, and this diffraction grating 2 is a rotatable cylinder. It is fixed to the shaped holder 3. 4 is a half prism, 5 is an objective lens, 6
is a disk, 7 is a magnifying lens, and 8 is a photodetector.

Next, the operation will be explained. After the light emitted from the semiconductor laser 1 enters the diffraction grating 2, it is split into a plurality of diffracted lights, of which three diffracted lights, a straight light and ±1st order light, are used. The three diffracted lights pass through the half prism 4, are focused on the disk 6 by the objective lens 5, are reflected on the surface of the disk 6, change their direction at the half prism 4, and pass through the magnifying lens 7 to the photodetector. The light is focused on 8.

As shown in Fig. 4, the above three diffracted lights are focused on the disk 6 at an angle with respect to the bit string BL, and the 0th order diffracted light of the reflected light is detected by photodetection as shown in Fig. 5. incident on the light receiving elements B ₁ to _{B 4} of the device 8,
The diffracted ±1st order light enters the light receiving elements A ₁ and A ₂ in the figure.

The 0th _order diffracted light is used as a digital information signal and a focusing error signal, and _the ± _1st order light is used as _a difference signal (I _A1
-I _A2 ) becomes a tracking error signal, and tracking servo control is performed by adjusting the optical system so that this becomes zero.

By setting the angle of the diffracted light with respect to the bit string on the disk 6 to be the optimum angle, the sensitivity of the tracking control can be improved. For this purpose, the diffraction grating 2 is fixed to a rotatable cylindrical holder 3 as shown in the figure, and a groove 10 formed in the cylindrical surface of the cylindrical holder 3 parallel to the optical axis is provided at the tip of the driver 9. The eccentric pin 11 is engaged, and the cylindrical holder 3 is rotated by the rotation of the driver 9 to perform minute angle adjustment, and the sensitivity of the tracking control is brought to the best state.

[Problems to be Solved by the Invention] Since the conventional optical signal pickup device is configured as described above, the groove 1 of the cylindrical holder 3
The insertion direction of the eccentric pin 11 of the driver 9 with respect to 0 is parallel to the surface of the disk 6, which makes it difficult or impossible to adjust the angle of the diffraction grating after the optical signal pickup device is installed in the player chassis. There was a problem.

This invention was made to solve the above-mentioned problems, and provides an optical signal pickup device that can easily adjust the angle of the diffraction grating even after it is incorporated into the player chassis. The purpose is to obtain.

[Means for Solving the Problems] An optical signal pickup device according to the present invention includes a diffraction grating that splits light emitted from a light source into a plurality of light beams, a rotatable cylindrical holder to which the diffraction grating is fixed, and , an optical signal pickup device comprising an objective lens for condensing the light beam onto a disk, wherein a protrusion is formed on the cylindrical surface of the cylindrical holder, and the protrusion is substantially perpendicular to the optical axis passing through the diffraction grating. An engagement uneven portion is formed relative to the surface of the portion facing the driver that contacts the surface, and one of the engagement uneven portions is formed eccentrically by a predetermined distance from the center of rotation of the driver. It is characterized by

[Example] The cylindrical holder for holding the diffraction grating according to the present invention has a protrusion from the cylindrical surface with a concavo-convex portion for engagement with a driver on a surface perpendicular to the optical axis, so that it can be used in an optical signal pickup device. Even after the disc is assembled into the player chassis, the driver can be engaged with and disengaged from the protrusion from below the player perpendicular to the disc surface, making it possible to easily adjust the angle of the diffraction grating.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the same parts as in FIG. 3 are given the same reference numerals. 12 is a protrusion formed on the cylindrical surface of the cylindrical holder 3, and 13 is a groove as a recess formed in the surface of the protrusion perpendicular to the optical axis passing through the diffraction grating in the radial direction centered on the optical axis. .

The method of focusing a light spot on the disk 6 and focusing the reflected light from the disk on the photodetector 8 is the same as in the conventional apparatus shown in FIG.

To adjust the angle of the diffraction grating 2, a driver 9 is inserted from a direction perpendicular to the disk surface, and an eccentric pin 11 as a convex portion provided at the tip of the driver is inserted into a groove 1.
to engage. Then, when the driver 9 is rotated, the cylindrical holder 3 is rotated around the optical axis by the action of the eccentric pin 11, and the fine angle adjustment of the diffraction grating 2 is performed to bring the sensitivity of the tracking control to the best state.

FIG. 2 shows another embodiment of this invention,
A pin 14 is provided protruding from a surface perpendicular to the optical axis of the protrusion 12, and an eccentric groove 15 is provided in the driver 9 to engage with the pin 14. The same effects as in the above embodiment are achieved.

[Effects of the Invention] As described above, according to the present invention, a protrusion is provided on the cylindrical surface of the cylindrical holder that fixes the diffraction grating,
Since a relatively engaging uneven portion is provided on the surface of the protrusion that is perpendicular to the optical axis passing through the diffraction grating and the surface facing the driver that comes into contact with the surface, the driver for adjusting the rotation angle can be moved perpendicularly to the disk surface. It can be inserted into an optical signal pickup device from the optical axis direction, and even after the optical signal pickup device is installed in the player chassis, the angle of the diffraction grating can be easily adjusted from below the player.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an optical signal pickup device according to one embodiment of the present invention, FIG. 2 is a perspective view showing an optical signal pickup device according to another embodiment of the invention, and FIG. 3 is a perspective view showing a conventional optical signal pickup device. Figure 4 is a perspective view of the optical pickup device, and Figure 4 is a principle diagram of the three-beam tracking control system for optical pickup.
The figure is a front view of the photodetector. 1 is a light source (semiconductor laser), 2 is a diffraction grating,
3 is a cylindrical holder, 4 is a half prism, 5 is an objective lens, 6 is a disk, 8 is a photodetector, 9 is a driver, 11 is an eccentric pin, 12 is a protrusion, 13 is a recess (groove), 14 is a pin , 15 is a recess (eccentric groove).
In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A diffraction grating that divides light emitted from a light source into a plurality of light beams, a rotatable cylindrical holder to which this diffraction grating is fixed, and an objective lens that focuses the light beam onto a disk. In the optical signal pickup device, a protrusion is formed on the cylindrical surface of the cylindrical holder, and a surface of the protrusion that is substantially orthogonal to the optical axis passing through the diffraction grating faces a driver that abuts the surface. Engaging uneven portions are formed relative to the surface,
The optical signal pickup device is characterized in that one of the engaging concave and convex portions is formed eccentrically by a predetermined distance from the center of rotation of the driver. 2. Claim 1, characterized in that a concave portion is formed in the surface of the protrusion that is substantially perpendicular to the optical axis passing through the diffraction grating in a radial direction centered on the optical axis, with which the convex portion at the tip of the driver engages. The optical signal pickup device described. 3. The optical signal pickup device according to claim 1, wherein the surface of the protrusion that is substantially orthogonal to the optical axis passing through the diffraction grating is formed with a convex portion that engages with the concave portion at the tip of the driver.