JPS62232618A - Adjusting method for position of concave lens - Google Patents

Abstract

PURPOSE:To improve adjustment accuracy and reliability by digitizing a spot image of an astigmatism shape, which is generated from a half mirror, calculating the second moment of area against a short axis and a long axis and deriving their ratio, and executing a position adjustment in the optical axis direction of a concave lens. CONSTITUTION:When a light beam from an adjusting semiconductor laser 19 passes through a concave lens 2 and transmits through a half mirror 4, an astigmatism is generated and the light is reflected by a mirror 8, passes through a microscope 11 and forms an image as a spot image 16 of an astigmatism shape on the image pickup surface of an image pickup part 10. A stage 32 is made to ascend in the direction (c) by the fourth driving part 25 and the tip of an adjusting pin 18 is inserted into a groove part of the outside diameter of the concave lens 2. With respect to a short axis and a long axis of the spot image of an astigmatism shape which is formed by an image processing part 23, the second moment of area is calculated, and a ratio of two kinds of the second moments of area is derived. When its ratio is '1' or not in the vicinity of a prescribed numerical value, a signal is sent to the third driving part 21 through a controller part 33 from the image processing part 23, and the concave lens is moved in the optical axis direction (b) by the adjusting pin 18.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for adjusting the position of a concave lens used in the manufacturing process of optical pickups for compact disc players and the like.

Conventional technology In recent years, the production of optical pickups has grown significantly, and automation is progressing in the manufacturing process, but the position of the concave lens was adjusted by the operator visually while looking at the image shape on the monitor. In addition to requiring skill, the quality was unstable due to variations in adjustment between workers.

An example of the conventional concave lens position adjustment method described above will be described below with reference to the drawings.

FIG. 3 shows an optical system for optical pickup, and FIG. 4 shows a conventional adjustment method. First, the optical system shown in FIG. 3 will be explained. The light from the semiconductor laser 9 is reflected by the half mirror 4 and the 45° mirror, focused by the objective lens 7, reflected by the recording surface of the flat plate 6, reflected by the 45° mirror 8, transmitted through the half mirror 4, and then condensed by the concave lens. is focused on the photodetector 1.

Next, a conventional method will be explained.

It consists of a slide unit 12 that moves the imaging section 10 and the microscope 11 in the vertical direction a, an adjustment pin 18 that moves the concave lens 2 in the optical axis direction, and an adjustment semiconductor laser 19 provided in place of the photodetector 1.

The operation of the concave lens position adjusted as configured above will be described below. When the semiconductor laser 9 emits light, the light is reflected by the -7 mirror 4, reflected by the 45° mirror 8, passes through the microscope 11, and is imaged as a circular spot image 14 on the imaging surface of the imaging section 1o. At this time, the fine adjustment handle 13 of the slide unit 12 is turned to slide the microscope 11 and the imaging section 1o up and down to visually find the position where the circular spot image 14 is at its minimum. Next, the semiconductor laser 9 is turned off and the adjustment semiconductor laser 19 is made to emit light. The light from the adjustment light guide laser 19 passes through the concave lens 2.
- After passing through the -7 mirror 4, the light is focused from the 45° mirror 8 onto the imaging surface of the imaging unit 10 by the microscope 11, but the light is turned into an astigmatic spot image 1 by the no-f mirror 4. The concave lens 2 is moved in the optical axis direction using the adjustment pin 18 so that the spot image 16 has the same shape as the reference spot shape, and when the spot image 16 becomes the same shape, the adjustment is completed. In short, this concave lens position adjustment is performed by moving the concave lens 2 to make the optical path length from the semiconductor laser 9 to the imaging surface of the imaging section 10 and the optical path length from the adjustment semiconductor layer 9 to the imaging surface the same. The light emitting position of the adjusting semiconductor laser 19 is the same as the light receiving surface position of the photodetector 1.

Problems to be Solved by the Invention However, with the above configuration, (1) All images 14 and 16 on the monitor must be visually judged by the operator, so the work requires skill, and (2) Since the concave lens 2 is moved manually using the adjustment pin 18, the adjustment accuracy is about 0.02 mm, which is insufficient in terms of reliability and resolution. It had some problems.

The present invention addresses the above problems and provides a concave lens position adjustment method that uses image recognition instead of visual judgment and automatically adjusts the concave lens to improve adjustment accuracy and reliability.

Means for Solving the Problems In order to solve the above-mentioned problems, the concave lens position adjustment method of the present invention eliminates astigmatism by passing the light from the adjustment semiconductor laser through the concave lens and then through the half mirror. The second moment of inertia of the digital image obtained by capturing a spot image of the shape and the imaging means and digitizing the captured image is calculated with respect to the short axis and long axis of the digital image, and the two types of The position of the concave lens in one direction on the base side is adjusted so that the ratio of the second moments of area becomes closest to a predetermined value.

Function The present invention uses the above-described method to obtain a cross section 2 in which an astigmatism-shaped spot image obtained by passing through a half mirror changes to be vertically long or horizontally long due to the distance between the concave lens and the adjustment semiconductor laser. By determining the next moment using image processing,
This has the unique effect of eliminating the need for visual judgment by the operator and improving adjustment accuracy and resolution.

EXAMPLE Hereinafter, a concave lens position adjusting method according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a front view of a method for adjusting the position of a concave lens according to an embodiment of the present invention. In FIG. 1, 2o is a base for receiving a base 17 on which an optical system is constructed, and 28 is an adjustment semiconductor laser 19 provided in place of the photodetector 1.
27 is a first drive unit that moves the concave lens 2 in the direction e perpendicular to the optical axis; 29 is a table 28;
26 holds the table 28 and the first drive unit 27.
Adjustment semiconductor laser 19 can be adjusted by moving the drive unit.
a second drive unit that moves the concave lens in the optical axis direction d of the concave lens 2;
1 is a stage 30 that holds the adjustment bin 18 with a concave lens 2
A third drive unit 25 moves the stage 3 with respect to the optical axis of the stage 3.
0 and a fourth drive unit that moves the stage 32 that holds the third drive unit in the direction C perpendicular to the optical axis of the concave lens 2;
A fifth drive unit 23 moves the optical axis in the direction a perpendicular to the optical axis emitted from the 45° mirror 8, and a fifth drive unit 23 digitizes the image obtained from the imaging unit 1o to obtain the second moment of area and uses that information to control each drive unit. An image processing section 24 is an operation section that controls the controller section 33 and the image processing section that sends the image to the monitor 16.

The operation of the concave lens position adjustment method configured as described above will be described below with reference to FIGS. 1 and 2.

First, the semiconductor laser 9 assembled on the base 17 is caused to emit light. The light from the semiconductor laser 9 is reflected by the half mirror 4 at 90'.
It is reflected and further vertically reflected at 90° by a 45° mirror 8, and a circular spot image 1 is formed on the imaging surface of the imaging unit 10 by the microscope 11.
It is imaged as 4. Next, while moving the Z stage 31 (5a direction) in the sixth drive unit 22, the image processing unit 23 calculates the area, and the fifth drive unit 2
Send a signal to 2 to stop when the area becomes the minimum. This completes the setting of the optical path length from the semiconductor laser 9 to the imaging surface of the imaging section 1o.

After completion, the emission of the semiconductor laser 9 is turned off.

Next, the adjustment semiconductor laser 19 is caused to emit light, and the light emission origin is at the same position as the light receiving surface of the photodetector 3, and the concave lens 2
The first drive section 27 and the second drive section 26 are placed on the optical axis of the
to move it. The light from the adjustment semiconductor laser 19 passes through the concave lens 2 and then through the half mirror 4. When passing through the half mirror 4, astigmatism occurs and the 45" mirror 8
The reflected light passes through the microscope 11 and is formed as an astigmatic spot image 16 on the imaging surface of the imaging unit 1o. The stage 32 is raised in the C direction by the fourth drive unit 25 and the tip of the adjustment pin 18 is inserted into the groove on the outer diameter of the concave lens 2. Astigmatism-shaped spot image 16 formed by the image processing unit 23
Calculate the moment of inertia of area with respect to the short axis and long axis of , and find the ratio of the above two types of moment of inertia of area. When the ratio is not 1 or around a predetermined value, the image processing unit 23
A signal is sent to the third drive unit 21 through the controller unit 33, and the adjustment bin 18 moves the concave lens in the optical axis direction, and the above operation is performed until the ratio of the second moment of area at that time becomes 1 or closest to a predetermined value. is automatically repeated.

After completing the adjustment, fix the concave lens 2 with screws. After fixing, the ratio of the second moment of area was measured again to confirm that the concave lens 2 had not shifted due to tightening the screws. The relationship between the amount of change in the ratio of the second moment of area and the amount of change in the position of the concave lens is as shown in FIG.

Effects of the Invention As described above, the present invention digitizes the astigmatism-shaped spot image generated by the half mirror, calculates the second moment of area with respect to the short axis and long axis, and calculates the ratio of the second moment of area. By determining the position of the concave lens in the optical axis direction, automation is possible without visual judgment, and adjustment accuracy and reliability can be improved, as well as workability.

[Brief explanation of drawings]

Fig. 1 is a front view of a method for adjusting the position of a concave lens in an embodiment of the present invention, Fig. 2 is a graph showing the relationship between the ratio of the quadratic moment of cross section and the amount of change in the position of the concave lens, and Fig. 3 is an optical pickup. FIG. 4 is a front view of a conventional concave lens position adjustment method. 2...Concave lens, 4...Mountain/half mirror-11
0...Imaging unit, 11...Microscope, 18
...adjustment pin, 19 ... semiconductor laser for adjustment, 23 ... image processing section.

Claims (1)

[Claims] Light emitted from a semiconductor laser is reflected by a half mirror installed at an angle of 45 degrees with respect to the optical axis, and after changing its traveling direction by 90 degrees, it is focused onto a flat plate by an objective lens, It is reflected at a focal point on the flat plate, reverses its traveling direction, passes through the objective lens, reaches the half mirror, is transmitted through the half mirror without being reflected, and is focused on a photodetector by a concave lens. A method for adjusting the position of the concave lens in the optical axis direction of the optical system, wherein an adjustment semiconductor laser is provided at the position of the photodetector to emit light, and this light is transmitted to the concave lens and the half mirror. The second moment of area of the digital image obtained by capturing an image of the astigmatism shape obtained by passing the image with an imaging means and digitizing the image is calculated with respect to the short axis and long axis of the digital image. A concave lens position adjustment method for adjusting the position of the concave lens in the optical axis direction so that the ratio of the two types of second moments of area becomes closest to a predetermined value.