JPS62132241A - Optical head - Google Patents

Abstract

PURPOSE:To shorten an access time, to prevent the influence due to the change of temperature, humidity, etc., and to easily adjust a detecting system by providing a rotatable mounting stand to fit, in a single body, a cell for detecting the out-of-focus to information memory media, a cell for detecting the track dislocation and a light source. CONSTITUTION:A laser beam L, after the beam passes through a projection lens-cum-collimator lens 2, a prism 3, a 1/4 wavelength plate 5 and an objective lens 6, is condensed to information memory media 7, and after reflection, returned to a polarizing beam split surface 4. The beam is guided to a light dividing part 8, and this has a light reflecting plane 9 and a light reflecting non-sphere curved surface 10 having the inclination a little to this. By these, the laser beam L is divided into for detecting the out-of-focus to the information memory media 7 and for detecting the track dislocation, and guided respectively through the polarizing beam split surface 4, the projection lens-cum-collimator lens 2 onto cells 12 and 12 for detecting the track dislocation of a light detecting device 11 and cells 13 and 13 for detecting the out-of-focus again. The light detecting device 11 and a semiconductor laser 1 are provided on the same rotatable mounting stand 14.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an information reproducing device, an information recording/reproducing device (optical disk device), etc. that can read at least information from an information storage medium using, for example, focused light. The present invention relates to an optical head applied to.

[Conventional technology]

An optical head applied to an optical disk device generally focuses laser light emitted from a semiconductor laser onto an information storage medium using an objective lens, and detects the laser light reflected from the information storage medium using a photodetector. By this,
It reads information, detects defocus, and detects track deviation.

[Problem that the invention seeks to solve]

In the above-mentioned optical disk device, the semiconductor laser and the photodetector are installed at separate locations, so the laser beam is detected by a collimating lens (condensing lens) for collimating the laser beam emitted from the semiconductor laser. Optical components having similar functions, such as a light projecting lens (condensing lens) for projecting light onto the device, must be provided redundantly, making the optical head large and heavy. Therefore, there is a problem in that the access time of the optical disk device is as long as 100 m5, while the minimum access time of the magnetic disk device is 30 m5.

In addition, since the semiconductor laser and photodetector are separate structures, even if the optical axis shifts in part due to changes in temperature or humidity, it will not only easily affect defocus detection and tracking deviation detection. However, there is a problem in that the adjustment of the detection system is troublesome.

The present invention has been made based on the above circumstances, and its purpose is to achieve reduction in size and weight, thereby shortening access time, and to be less affected by changes in temperature, humidity, etc. Moreover, it is an object of the present invention to provide an optical head whose detection system can be easily adjusted.

[Means for solving problems]

In order to solve the above problems, the present invention provides at least one light source, an objective lens for condensing the light emitted from the at least one light source onto a track information storage medium, and the above-mentioned information storage medium. a defocus detection cell that receives light from a storage medium and detects at least a defocus of the objective lens with respect to the information storage medium; and at least detects a track deviation of the light focused on the information storage medium with respect to the track. The present invention is characterized by comprising a photodetector having a cell for detecting track deviation, and a rotatable mount base on which the photodetector and the light source are integrally installed.

(Function) Since the light guided from the light source to the information storage medium and the light guided from the information storage medium to the photodetector can be made to pass through similar optical paths, it is possible to standardize optical parts and reduce the number of optical parts. In addition, even if optical axis deviation occurs in some areas due to changes in temperature, humidity, etc., the effects of this are canceled out.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, 1 is a semiconductor laser (light source), and the diverging laser beam emitted from this semiconductor laser 1 is converted into a substantially parallel beam by passing through a collimating lens 2 that also serves as a projection lens, and then passes through a prism. 3. The laser beam entrance surface 3a of this prism 3 is inclined with respect to the optical axis, and therefore, when the laser beam is incident, refraction occurs and the spot size of the laser beam is changed in the direction of refraction, thereby correcting the ellipse of the laser beam. will be held.

The laser light incident on the prism 3 is reflected by the polarized beam split surface 4 formed on the other surface of the prism 3,
After passing through the 1774 wavelength plate 5 and the objective lens 6, the light is focused on the information storage medium 7.

This information storage medium 7 has a recording area provided with a recording layer on at least the enlarged surface that can be stored or reproduced using a laser beam or the like. In this recording area, a tracking guide (track) by a pre-group is formed in a spiral shape or a concentric circle shape.

The laser light focused on the information storage medium 7 is reflected by the information storage medium 7, passes through the objective lens 6 again, and the 1/4 wavelength plate 5, and then enters the prism 3, where it is then reflected on the polarized beam split surface 4. will be returned to.

Here, the laser light becomes linearly polarized light whose vibration direction is rotated by 90 degrees compared to when it is reflected by the polarization beam splitter surface 4 by reciprocating through the quarter-wave plate 5. Therefore, the laser light returned to the polarizing beam splitter surface 4 passes through the polarizing beam splitting surface 4 and is guided to a light splitting member 8 provided superimposed on the polarizing beam splitting surface 4.

The light splitting member 8 has a light-reflecting plane 9 and a light-reflecting aspherical curved surface (such as a cylindrical concave lens surface) 10 slightly inclined with respect to the light-reflecting plane 9. The information storage medium 7 of the objective lens 6 is formed by the light reflective plane 9 and the light reflective aspherical curved surface 10.
The laser beam is divided into a defocus detection laser beam for detecting defocus on the information storage medium 7 and a track deviation detection laser beam for detecting the deviation of the light focused on the information storage medium 7 from the track, and is transmitted through the destination beam split surface 4 again. rear,
The light is guided through the collimating lens 2 which also serves as a projection lens, onto the track deviation detection cell 12.12 and the defocus detection cell 13.13 of the photodetector 11 shown in FIG. 2, respectively.

The laser beam reflected by the light reflective plane 9 is reflected by the objective lens 6.
When in focus on the information storage medium 7 (hereinafter, this state is referred to as in-focus time), the defocus detection cell 13.13
The light is focused on the border of the cell 13 depending on the amount of defocus.
．． 13, and thereby defocus detection is performed using the so-called knife etching method (see Japanese Patent Application Laid-open No. 146546/1983, pages 9 to 11). On the other hand, the laser beam reflected by the light-reflecting aspherical curved surface 10 is
The light is focused on the track deviation detection cell 12, 12 in a state where it is stretched in one direction due to the action of , but in this stretched direction, a far field pattern is formed for the information storage medium 7 when focused. Therefore, track deviation detection is performed using the so-called bush-pull method, in which the track deviation is detected using the diffraction pattern of the reflected light from the tracking guide of the laser beam focused using the track deviation detection cell 12.12. Note that the track deviation detection cell 12.12 and the defocus detection cell 13a.

Information detection is also performed using a composite signal of the signal with 13b.

The photodetector 11 and the semiconductor laser 1 are mounted on the same rotatable mount 14.

That is, this mount base 14 consists of a semi-cylindrical part 14a and a rod annular frame part 14b, and a photodetector 11 is mounted on the end surface of this semi-cylindrical part 14a, and a semiconductor laser 1 is mounted on the side plane part.
are provided for each.

When adjusting the detection system, move the mount base 14 and the collimating lens 2 that also serves as a light emitting lens, and move the light splitting member 8
The position of the track deviation detection laser light on the track deviation detection cell 12.12 is changed by changing the relative positional relationship with respect to the track deviation detection cell 12.12.

Further, the light emitting point of the semiconductor laser 1 is located at the center of rotation of the mount 14, so that the optical axis of the laser beam emitted from the semiconductor laser 1 does not shift when the mount 14 rotates. .

Note that the arrangement of each element on the mount table 14 is as follows:
As shown in the figure, a defocus detection cell 13.13 is arranged along the rotational direction or string direction of this mount 14, and the defocus detection system can be adjusted by rotating only this mount 14. It looks like this. Note that in order to make such adjustments possible, the laser beam moves on the defocus detection cell 13 and 13 in accordance with the circumferential direction of the mount 14 and the defocus on the information storage medium 7. The directions are substantially parallel to each other. Also, to prevent the track deviation detection laser beam from moving on the track deviation detection cell 12° 12 during this rotation,
The photodetection cells 12.12 for detecting track deviation are arranged along the radial (radial) direction of the mount base 14.

According to the above configuration, since the photodetector 11 and the semiconductor laser 1 are installed on the same mount 14, the laser light guided from the semiconductor laser 1 to the information storage medium 7 and the photodetector from the information storage medium 7 are The laser light directed to 11 can follow similar optical paths. Therefore, it is possible to share optical parts such as the collimating lens 2 which also serves as a light projecting lens, and to reduce the number of optical parts, thereby making it possible to reduce the size and weight of the device, thereby shortening the access time. In addition, even if some optical axis misalignment occurs due to changes in temperature, humidity, etc., the inclination of the polarized beam splitting surface 4, or changes in the distance between the semiconductor laser 1 and the collimating lens 2 that also serves as a projection lens, the effects of this are canceled out. Therefore, defocus detection and track deviation detection are unlikely to be affected.

In addition, the mount base 14 is made rotatable, and the defocus detection cells 13 and 13 are rotated along the rotation direction of the mount base 14.
Since they are arranged side by side, the defocus detection system can be easily adjusted by simply rotating the mounting table 14.

Furthermore, since the light emitting point of the semiconductor laser 1 is arranged at the rotation center of the mount 14, and the track deviation detection cells 12 and 12 are arranged side by side along the radial direction of the mount 14, the mount 14 can be rotated. When adjusting the defocus detection system, the track deviation detection signal does not change accordingly (shift to one side).

Note that the track deviation detection cells 12a, 12b and the defocus detection cells 13a, 13b may be arranged as shown in FIG. That is, the trough shift detection cell 12
a and 12b may be fan-shaped, and the boundary surface thereof may be provided in a direction along the circumference centered on the light emitting point of the semiconductor laser 1. Even with this configuration, the signals detected by the track deviation detection cells 12a and 12b do not change even if the mount base 14 rotates.

The present invention can also be applied to those having multiple light sources,
In this case, the light emitting point of at least one light source may be placed at the rotation center of the mount base.

〔Effect of the invention〕

As explained above, according to the present invention, there are provided at least one light source, an objective lens for condensing light emitted from the at least one light source onto a track information storage medium, and the information storage medium. A defocus detection cell that receives light from a medium and detects at least a defocus of the objective lens with respect to the information storage medium; and a track that detects at least a track deviation of light condensed onto the information storage medium with respect to the track. Since it is equipped with a photodetector having a cell for detecting displacement and a rotatable mount base on which this photodetector and the light source are installed integrally, it is possible to reduce the size and weight, thereby shortening the access time. Furthermore, it has excellent effects such as being less likely to be affected by changes in humidity and humidity, and also allowing easy adjustment of the detection system.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention,
FIG. 1 is a perspective view, FIG. 2 is a front view of the main part, and FIG. 3 is a front view of another embodiment of the main part. DESCRIPTION OF SYMBOLS 1... Light III (semiconductor laser), 2... Objective lens, 7... Information storage medium, 11... Photodetector, 1
2a. 12b... Track deviation detection cell, 13a, 13b
... Defocus detection cell, 14... Mounting stand. Applicant's agent Patent attorney Takehiko Suzue Figure 3

Claims (4)

[Claims] (1) at least one or more light sources;
an objective lens for condensing light emitted from one or more light sources onto a track information storage medium; and an objective lens for receiving light from the information storage medium, and detecting at least defocus of the objective lens with respect to the information storage medium. a photodetector having a defocus detection cell for detecting defocus and a track deviation detection cell for detecting at least a track deviation of light condensed on the information storage medium with respect to the track; the photodetector and the light source are integrated; An optical head characterized by comprising a rotatable mount base for installation. (2) The optical head according to claim 1, wherein a light emitting point of at least one of the at least one light source is arranged at the center of rotation of the mount. (3) The first claim characterized in that the track deviation detection cells are arranged in parallel along the radial direction of the mount base.
Optical head described in section. (4) The direction of the light moving on the photodetector depending on the defocus situation on the information storage medium and the direction along the circumferential direction centered on the rotation center of the mount base are substantially the same. An optical head according to claim 1, characterized in that: