JPS62239428A - Optical disk information reproducing device - Google Patents

Abstract

PURPOSE:To compensate the astigmatism inexpensively without making a device itself large in size by forming a diffraction grating for generation of main and auxiliary means on the face nearer to a semiconductor layer of a parallel plane plate and forming a beam separating film on the opposite face. CONSTITUTION:The laser beam emitted from a semiconductor laser 2 is led to a parallel plane plate 29. A diffraction grating 3 for generation of main and auxiliary beams is formed on the face nearer to the semiconductor laser 2 of the parallel plane plate 29, and a beam separating film 30 is formed on the opposite face. Three beams which pass the parallel plane plate 29 are converted to parallel rays of a luminous flux by a collimator lens 5 and are focused on and projected to an information recording surface 7a of an optical disc 7 by an objective lens 6. The beam reflected on the information recording surface 7a passes the objective lens 6 and the collimator lens 5 again and is led to the parallel plane plate 29 and is led to a focusing optical system 8 by the beam separating film 30 and is focused on the light receiving surface of a photoelectric transducer 9.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides an optical pickup body provided with an optical system including a semiconductor laser having astigmatism.

The present invention relates to an improvement in an information reproducing device for an optical disc that reproduces information by reciprocating the optical disc in the radial direction.

(Prior Art) Conventionally, an information reproducing apparatus for optical discs having the configuration shown in FIG. 4 has been known. In this Figure 4, ■
is the optical pickup body. This optical pickup main body 1 is provided with an optical system including a semiconductor laser 2. The optical system of this optical pickup main body t includes a diffraction grating 3.
and a beam splitter 4 are provided. The laser beam emitted from the semiconductor laser 2 is transmitted to the diffraction grating 3.
The laser beam is divided by this diffraction grating 3, and reproduction is performed using three beams of 0th order and ±1st order. Of these three beams, the 0th order diffracted light is
It is used as a main beam, and the ±1st order diffracted light is used as a sub beam. These three beams are guided to a collimating lens 5 via a beam splitter 4, and an objective lens 6
An image is formed on the pit surface formed on the information recording surface 7a of the optical disc 7, and is reflected. The three beams reflected by the optical disk 7 are again guided to the beam splitter 4 via the imaging lens 6 and the collimating lens 5, reflected by the beam splitter 4, and guided to the focusing optical system 8.

The focusing optical system 8 forms an image on the light receiving surface of the photoelectric conversion element 9 . The photoelectric conversion signal generated by this photoelectric conversion element 9 is also used for tracking servo.

By the way, in order to perform tracking servo, as shown in FIG. 5, a main beam 10 and a sub beam 11 . , 12 are required to be on one truck 13. As shown in FIG. 6, if the main beam 10 and the sub beams 11 and 12 are not on one track 13, normal tracking servo cannot be performed. If the mechanical error of the optical disk information reproducing device is large, the three beams 10, 11, and 12 will not be placed on one track 13. You need to rotate it to make this adjustment.

(Problems to be Solved by the Invention) However, it is difficult to rotationally adjust the diffraction grating 3 in this way because the adjustment range is very delicate. Furthermore, since the semiconductor laser 2 has astigmatism, it is also required to correct the astigmatism. As a means for correcting the astigmatism, Japanese Patent Application Laid-Open No. 143443/1983 discloses that a parallel plane plate is provided in the optical path of the laser beam emitted from the semiconductor laser 1, and the normal vector of the parallel plane plate is It is disclosed that the junction plane of the semiconductor laser 1 is tilted at a predetermined angle with respect to the optical axis Ω. However, in this conventional optical disk information reproducing device, since the diffraction grating 3 and the beam splitter 4 are formed separately,
If a parallel plane plate for astigmatism correction is provided, there is a problem in that the apparatus itself becomes larger.

(Objective of the Invention) Therefore, the object of the present invention is to be able to correct astigmatism at low cost without increasing the size of the device itself, and to place three beams on one track. It is an object of the present invention to provide an information reproducing device for an optical disc, which can easily adjust the optical characteristics of the optical disc, thereby improving its optical characteristics.

(Means for Solving the Problems) A feature of the information reproducing apparatus for an optical disc according to the present invention is that an optical pickup main body having an optical system including a semiconductor laser having astigmatism is supported by a support member, The optical pickup main body is provided with a parallel plane plate for astigmatism correction in the optical path of the laser beam emitted from the semiconductor laser, and the parallel plane plate In the information reproducing device for an optical disk, the astigmatism is corrected by tilting the normal vector of the semiconductor laser at a predetermined angle with respect to the optical axis of the optical path within the junction plane of the semiconductor laser, a beam separation film that forms a diffraction grating for generating a main beam and sub-beams on a surface closer to the laser, and guides the beam reflected by the optical disk to a photoelectric conversion element on a surface farther from the semiconductor laser; On the other hand, the optical pig-up main body is supported by the support member so as to be rotatably adjustable about approximately the optical axis of the objective lens of the optical system.

(Function) According to the information recording and reproducing apparatus for an optical disc according to the present invention, the laser beam emitted from the semiconductor laser is converted into three beams by one diffraction grating. The three beams are imaged on the information recording surface of the optical disk, reflected, and guided by a beam separation film to a photoelectric conversion element via a focusing optical system. If the three beams are not on one track.

The optical pickup body is rotated approximately around the optical axis of the objective lens of the optical system. Then, by changing the arrangement direction of the three beams, these beams are placed on one track.

(Example) Examples of the present invention will be described below with reference to the drawings.

In FIG. 1, the optical pickup main body 1 has a two-dimensional actuator 14 that acts two-dimensionally in the focus and track directions, and the objective lens 6 is provided on this two-dimensional actuator 14. The optical pickup main body 1 is mounted on a plate 15 as a support member, and a bearing 16 is mounted on the plate 15. Long hole 17.1g
, a notch 21 is formed. The notch 21 is provided at a position corresponding to the two-dimensional actuator 14. On the other hand, screw holes 24 and 25 are formed in the optical pickup main body l at positions corresponding to the elongated holes 17 and 18.

This optical pickup main body 1 has screws 26 and 27.
The mounting is supported by the plate 15.

For this attachment, a feed shaft 28 is fitted into the bearing 16 of the plate 15. The optical pickup main body 1 is guided by the feed shaft 28 and reciprocated in the radial direction of the optical disk 7 (in the direction of arrow A) as shown in FIG.

The elongated holes 17 and 18 are formed in an arc shape centered near the optical axis O of the objective lens 6, and are formed in the optical pickup body 1.
can rotate around the optical axis O. Of course, the notch 21 is set to a size that allows the two-dimensional actuator 14 inserted therein to rotate.

As shown in FIG. 3, the optical system of the optical pickup main body 1 includes a semiconductor laser 2 and a parallel plane plate 29 of a predetermined thickness for astigmatism correction. This parallel plane plate 29 is provided in the optical path of the laser beam emitted from the semiconductor laser 2. This parallel plane plate 29 has its normal vector N inclined at a predetermined angle with respect to the optical axis ρ within the junction plane of the semiconductor laser 2 (for details, see Japanese Patent Laid-Open No.
(See Publication No. 143443). A laser beam emitted from the semiconductor laser 2 is guided to this parallel plane plate 29. A diffraction grating 3 for forming a main beam and a sub-beam is formed on the surface of the parallel plane plate 29 close to the semiconductor laser 2, and a beam separation film 30 is formed on the surface far from the semiconductor laser 2. . 3 that passed through the parallel plane plate 29
The book beam is converted into a parallel light beam by a collimating lens 5, and is irradiated and imaged onto an information recording surface 7a of an optical disc 7 by an objective lens 6. The beam reflected on the information recording surface 7a is returned to the objective lens 6,
guided to a parallel plane plate 29 via a collimating lens 5,
The beam is guided to the focusing optical system 8 by the beam separation film 30,
The image is formed on the light receiving surface of the photoelectric conversion element 9.

Here, when the three beams 10 to 12 are not on one track 13 as shown in FIG.

Loosen the screws 26 and 27, rotate the optical pickup body 1 in the direction of arrow B in FIG. 2 around the optical axis O of the objective lens 6, and as shown in FIG.
3, and tighten the screws 26 and 27 to fix the optical pickup main body 1 to the mounting plate 15.

(Effects of the Invention) As explained above, the information reproducing device for an optical disc according to the present invention enables the optical pickup main body, which is reciprocated in the radial direction of the optical disc, to rotate around the optical axis of the objective lens. A parallel plane plate for astigmatism correction provided in the optical path of the laser beam of a semiconductor laser has a diffraction grating for generating a main beam and a sub-beam formed on the surface closer to the semiconductor laser. Since a beam separation film is formed on the surface far from the semiconductor laser to guide the beam reflected by the optical disk to the photoelectric conversion element, astigmatism can be corrected without increasing the size of the device itself and with an inexpensive configuration. Moreover, the adjustment for placing three beams on one track can be easily performed by rotating the entire optical pickup body, thereby improving its optical characteristics. It produces the effect that can be achieved.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the mechanical configuration of an information reproducing device for an optical disc according to the present invention, FIG. 2 is a plan view showing the positional relationship between the optical disc and the optical pickup body according to the present invention, and FIG. FIG. 4 is a diagram showing the optical arrangement of the optical pickup main body according to the invention; FIG. 4 is a diagram showing the optical arrangement of the optical pickup main body of a conventional optical disc information reproducing device; FIG. FIG. 6 is an explanatory diagram showing a state in which three beams are not mounted on one track. 1... Optical pickup body 2... Semiconductor laser 3... Diffraction grating 6...
・Objective lens 7...Optical disk 9...Photoelectric conversion element IO...Main beam 11.12...
・Sub-beam 13...Track 15...Mounting to plate (supporting member) 17, 18...Long hole 28...
・Feed axis 29...parallel plane plate 30...
・Beam separation membrane O...Objective lens optical axis 2 Figure 3 L-1
−−−−−−−−−JFig.
---1-----Figure 5 Figure 6

Claims (1)

[Claims] An optical pickup main body having an optical system including a semiconductor laser having astigmatism is supported by a support member and is disposed so as to be able to reciprocate in the radial direction of the optical disk. The main body is provided with a parallel plane plate for astigmatism correction in the optical path of the laser beam emitted from the semiconductor laser, and the normal vector of the parallel plane plate is aligned with the light on the optical path within the cemented surface of the semiconductor laser. In an information reproducing device for an optical disk, which is tilted at a predetermined angle with respect to an axis to correct the astigmatism, the parallel plane plate has a diffraction beam for generating a main beam and a sub-beam on a surface closer to the semiconductor laser. A beam separation film is formed on the surface of the grating that is far from the semiconductor laser and guides the beam reflected by the optical disk to the photoelectric conversion element, and the beam separation film is centered approximately on the optical axis of the objective lens of the optical system. An information reproducing device for an optical disc, characterized in that the optical disc is supported in a rotationally adjustable manner.