JPH06119656A - Method for adjusting optical pickup - Google Patents

Abstract

PURPOSE:To use simple adjusting tools and to attain reduction in workhours and improvement in work efficiency by adjusting an optical position between a light source and a collimator lens through a derived light beam. CONSTITUTION:A semiconductor laser 2 as a light source, collimator lens 3, and a prism 4 are attached to a casing 1. Then, a distance between the laser 2 and the lens 3 is adjusted at this stage. That is, the light beam 8 is derived from a hole 7, an interferometer is used, and the beam 8 is adjusted in a large spot as is. In other words, if the beam 8 that is made incident on the interferometer is a parallel light, interference fringes are not generated; and if the beam is a converged light or a diffused light, the interference fringes are generated. Therefore, when the interference fringes are generated, the distance and the optical axis between the laser 2 and the lens 3 are adjusted. At this time, since a spot with a large area is dealt with, the adjustment of position of a minute light spot is saved, the adjustment is made easy, and the time required for the adjustment is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical pickup used in an optical disk drive device and the like, and more particularly to an optical system adjusting method for facilitating the assembly of the optical pickup.

[0002]

2. Description of the Related Art The structure of a conventional optical pickup will be described. 4 (a) and 4 (b) are a plan view and a side view, respectively, of a conventional optical pickup for an optical disc, and FIGS. 5 (a) and 5 (b) are optical diagrams for a conventional optical disc, respectively. It is the top view and side view inside a pickup. The optical pickup includes a semiconductor laser 2 as a light source, a collimator lens 3 provided on its optical path, a prism 4, a polarization beam splitter 5, a mirror 6, and an objective lens 10.
And have. The objective lens 10 is attached to the casing 1 so that its position can be finely adjusted by the objective lens actuator 9. The polarization beam splitter 5 may be a half mirror if necessary.

The light emitted from the semiconductor laser 2 is collimated into a parallel beam by a collimator lens 3 for increasing its utilization rate, then shaped into a beam by a prism 4, passed through a polarization beam splitter 5 and folded by a mirror 6. It is bent and focused on the disk surface of the optical disk 15 by the objective lens 10. Here, it is desirable that the optical disc unit using such an optical pickup is downsized by suppressing the height in the direction orthogonal to the disc surface. Therefore, as shown in FIGS. 5 (a) and 5 (b), the longitudinal direction of the optical pickup is usually arranged in parallel with the disc surface of the optical disc 15, and the optical path of the light beam is deflected by the mirror 6 so that the optical disc is deflected. It is irradiating to 15.

In the above-mentioned optical pickup, it is necessary to narrow the light spot to the diffraction limit, but the distance between the semiconductor laser 2 and the collimator lens 3 is a set value (the focal length of the collimator lens is usually 5 to 10 mm). If it goes wrong in μm unit, the collimator lens 3
The light beam that has passed through is not a parallel light but becomes a divergent light or a convergent light, an aberration called astigmatism occurs, and the light spot cannot be narrowed down to the diffraction limit by the objective lens 10. Therefore, it is necessary to precisely adjust the distance between the semiconductor laser 2 and the collimator lens 3.

As shown in FIG. 6, this adjustment is usually performed by a light spot focused by the objective lens 10 (about 1 μmφ).
Monitor 13 through microscope 11 and TV camera 12.
While observing, the semiconductor laser 2 and collimator lens 3
Adjust the distance between and so that the light spot is below a certain set value. In this work, the magnification of the microscope 11 is 1000
Since it is about double, it is not allowed to vibrate a little, and it is very difficult to adjust the light spot to its focal point and put it in the field of view of the objective lens of the microscope. There was a problem called it.

[0006]

In view of the problems of the prior art, the main object of the present invention is to simplify the distance between the light source and the collimator lens without using a magnifying system which is difficult to adjust like a microscope. An object is to provide an adjustable optical pickup adjustment method.

[0007]

According to the present invention, the above-described object is achieved by using a light source, a collimator lens for collimating light emitted from the light source, and a light beam passing through the collimator lens as a medium. In an optical pickup having an objective lens for irradiating, a light beam emitted from the collimator lens is led out of the optical pickup without passing through the objective lens, and the derived light beam is used as the light source. This is achieved by providing an adjusting method of an optical pickup, which is characterized by adjusting an optical position between the collimator lens and the collimator lens.

[0008]

By doing so, the light beam can be taken out of the optical pickup with a large spot and the optical positions of the light source and the collimator lens can be adjusted by using a simple adjusting tool.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. 1A and 1B show the structure of an optical pickup to which the present invention is applied, and FIG. 2 is a system diagram showing an adjusting method thereof. In this embodiment, the entire structure of the optical pickup is the same as that of the conventional optical pickup, but the light beam emitted from the polarization beam splitter 5 when the mirror 6 is removed is led out to the outside of the optical pickup. 7 is formed in the wall 1 a of the casing 1.

To assemble such an optical pickup, first, only the semiconductor laser 2 as a light source, the collimator lens 3 and the prism 4 are attached to the casing 1.
Then, at this stage, the distance between the semiconductor laser 2 and the collimator lens 3 is adjusted. That is, the light beam 8 is directed to the casing 1
The light beam 8 is led out from the hole 7 provided in the optical disk 8 and is adjusted using an interferometer 14 such as a Mach-Zehnder interferometer as shown in FIG. That is, if the light beam 8 incident on the interferometer 14 is parallel light, no interference fringes will occur. However, if the light beam 8 is focused light or diffused light, interference fringes will occur. The distance between 2 and the collimator lens 3 and the optical axis may be adjusted. In this case, since a spot (about several mmφ) having a larger area than the focused spot (about 1 μmφ) narrowed down by the objective lens 10 is handled, the optical axis adjustment on the objective lens 10 cannot be omitted, but a small light spot. Since the position adjustment can be omitted, the adjustment becomes easy, and the time for the entire adjustment can be greatly reduced.

Although the Mach-Zehnder interferometer is used in this embodiment, another type of interferometer may be used as long as it can evaluate the light source. There are also adjustment methods other than using an interferometer. For example, as shown in FIG.
Is taken into the TV camera 12 at a position 1 m or more away from the casing 1, and adjustment is performed on the monitor 13. That is,
If there is astigmatism, the image of the light beam 8 on the monitor 13 has an elliptical shape. Therefore, the distance between the semiconductor laser 2 and the collimator lens 3 is set so that the image becomes a circle having a determined radius.
Adjust the optical axis. However, the use of an interferometer has the advantage that the wavefront of light can be evaluated and the quality of the light beam such as astigmatism can be quantitatively evaluated.

Next, the polarization beam splitter 5 and the mirror 6 are attached to the casing 1, the hole 7 is closed, and the structure shown in FIG.
Then, returning to the structure of the conventional optical pickup as shown in FIG. 5 (b), the focused spot after passing through the objective lens 10 is adjusted (only the optical axis is adjusted). Here, an interferometer such as a Mach-Zehnder interferometer is expensive, but if a large number of optical pickups are produced, there is no particular problem.

In the optical pickup shown in FIGS. 1 (a) and 1 (b), the light beam 8 is taken out from the optical disk unit by placing it on the work table in the same direction as the mounting direction of the optical disk unit to perform the adjustment work. Is possible. By the way, though not shown, it is also possible to take out the light beam 8 out of the optical pickup to the Mach-Zehnder interferometer 14 for adjustment through the mirror 6 without passing through the objective lens 10 and as a large spot. is there. In this case, the attitude of the optical pickup is changed, or the adjustment is performed while turning it over.
Adjusting the optical pickup while it is upright or turned upside down is one of the constraints in designing the optical pickup while maintaining high workability, which imposes a heavy burden on the design of the optical pickup. For example, the collimator lens 3 needs a mechanism that can move in the optical path direction and is firmly fixed, and must be designed so that a wrench or a screwdriver for tightening a screw for fixing does not interfere with other parts. The optical pickups shown in FIGS. 1A and 1B are configured so that such a problem does not occur.

[0014]

As is apparent from the above description, according to the adjusting method of the present invention, it is possible to perform adjustment using an interferometer or the like which is easy to handle without using a magnifying system. That is, work efficiency is improved.

[Brief description of drawings]

FIG. 1A is a plan view showing the structure of an optical pickup to which the present invention is applied, and FIG. 1B is a side view of part (a).

FIG. 2 is a system diagram showing an adjusting method according to the present invention.

FIG. 3 is a system diagram showing another adjusting method according to the present invention.

FIG. 4A is a plan view showing an appearance of a conventional optical pickup, and FIG. 4B is a side view of the portion (a).

FIG. 5A is a plan view showing the inside of a conventional optical pickup, and FIG. 5B is a side view of part (a).

FIG. 6 is a block diagram showing an adjustment method in a conventional optical pickup.

[Explanation of symbols]

 1 Casing 1a Wall 2 Semiconductor laser 3 Collimator lens 4 Prism 5 Polarizing beam splitter 6 Mirror 7 Hole 8 Light beam 9 Objective lens actuator 10 Objective lens 11 Microscope 12 TV camera 13 Monitor 14 Mach-Zehnder interferometer 15 Optical disk

Claims (3)

[Claims] 1. An optical pickup comprising a light source, a collimator lens for collimating light emitted from the light source into parallel light, and an objective lens for irradiating a medium with a light beam passing through the collimator lens. The light beam emitted from the collimator lens is led out of the optical pickup without passing through the objective lens,
A method of adjusting an optical pickup, wherein an optical positional relationship between the light source and the collimator lens is adjusted by using the derived light beam. 2. The method of adjusting an optical pickup according to claim 1, wherein an optical path of light passing through the collimator lens is changed. 3. The method of adjusting an optical pickup according to claim 1, wherein an interferometer is used for the adjustment.