JPH02158927A - Optical deck objective lens - Google Patents

Abstract

PURPOSE:To detect the extent of inclination of an objective lens to easily discriminate whether it is within an allowable value by providing a specular surface on the upper face of a flange of the objective lens and irradiating the specular surface with test light and measuring the spot position of the reflected light. CONSTITUTION:An objective lens 17 is attached to an actuator 5, and this actuator 5 is set on a head 19 of an inspecting machine. Parallel rays 23 for test are thrown at an angle alpha to a flange 17b of the lens 17 and are reflected on a specular surface 18 on the upper face. When the lens 17 is not inclined, light 23 is reflected at the angle alpha on the specular surface 18 and passes mirrors 20 and 2 and is projected to a point F on a projection face 22. When the lens 17 is inclined, light 23 is reflected at an angle alpha+DELTAalpha and is projected to a point F' DELTAalpha off the point F. Consequently, the spot position of the reflected light is measured to detect the extent of inclination of the objective lens without contacting with the actuator, and it is easily discriminated whether this extent is within the allowable value or not.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical head, which is one of the main components of an optical deck that records and reproduces information on an optical disk as a memory for code data and image data, and particularly relates to an optical head. This invention relates to an optical deck objective lens used in an optical head.

2. Description of the Related Art Conventionally, as shown in FIG. an optical bench 3 attached to a reference plane A-A perpendicular to the axis;
A semiconductor laser 4 as a light emitting source attached to the optical bench 3, an actuator 5 attached to the top surface of the optical bench 3,
It has an objective lens 6 supported and driven by an actuator 5, and a semiconductor laser 4 emits light during recording and reproduction.
A light beam 7 is focused onto the optical disk 1 by an objective lens 6. Also, the actuator 5 moves the objective lens 6 to
It is driven in the -X direction and the Y-X direction to perform tracking and focusing control.

As shown in FIGS. 5 and 6, the actuator 5 is rotatably and vertically held by the actuator base 8, a solid shaft 9 installed perpendicularly thereto, and the solid shaft 9. The objective lens 6 has a movable body 10, a tracking coil 11 that drives the movable body 10 in the rotational direction, a focus coil 12 that drives the movable body 10 in the vertical direction, a power supply wiring 13, etc. It is held by the movable body 10. The objective lens 6 has a lens barrel 6a and a flange 6b, and is movable by fitting the lens barrel 6a into the mounting hole 10a of the movable body 10 and bringing the flange 6b into surface contact with the upper surface 10b of the movable body 10. It is attached at a predetermined position relative to the body 10. Here, the bottom surface B- of the actuator base 8
B is the reference plane, and the objective lens 6 attached to the movable body 10
The optical axis of the light beam from the optical bench 3 is set to be perpendicular to the reference plane B-H, and when the actuator base 8 is attached to the optical bench 3, The optical axis) 15 is set in advance to be perpendicular to the reference plane B-B.

Problem to be Solved by the Invention However, according to this configuration, as shown in FIG.
There is a problem in that the optical head is tilted relative to the optical head, thereby degrading the optical characteristics of the optical head.

The above-mentioned problem arises for the following reasons. That is, the movable body 10 must rotate and slide with respect to the solid shaft 9, so that the shaft hole d2 is normally lO~15 with respect to the shaft diameter d.
As a result of dz>d+, the movable body 10 is tilted by θ1° with respect to the solid shaft 9 as shown in FIG. Furthermore, although not shown, when the objective lens 6 is fixed to the movable body 10, the objective lens 6 is at an angle θ2 with respect to the reference plane of the movable body.
゜Tilt. Similarly, the solid shaft 9 also has an angle of θ with respect to the reference plane of the actuator base 8. Lean. As a result, the optical axis 6C of the objective lens 6 is inclined at an angle θ with respect to the ideal optical axis 15, and the maximum value of the angle θ is (θ,
+0200, ).

If the objective lens 6 is not tilted, the light beam 7 condensed by the objective lens 6 will be imaged at the ideal point O as shown in FIG. 8 (4), but if the objective lens 6 is tilted, As shown in Figure 2, the light beam condensed by the objective lens forms an image at point 07, which is slightly shifted from the ideal point O.

On the other hand, the position control of the objective lens is
Since there are two directions: focusing in the Y direction and tracking in the X-X direction, the inclination θ of the objective lens in the initial state shown in FIG. ' cannot be corrected to the ideal point O, and the optical characteristics of the optical head deteriorate.

The permissible value of the inclination θ of the objective lens 6 is usually about 0.6°. Conventionally, the processing accuracy of each component is managed so that the inclination θ of the objective lens 6 falls within an allowable value. However, even if the machining accuracy of each part is controlled, assembly errors may occur and the tilt angle θ of the objective lens 6 may become larger than a predetermined tolerance, and the tilt angle θ may also become larger due to wear during use. There was a problem in that the optical characteristics became larger than the allowable value and the optical characteristics deteriorated.

Furthermore, conventionally, it has been impossible to inspect the inclination angle θ of the objective lens in the assembled state, and there has been a problem in that it has been impossible to determine whether or not the inclination angle θ is within a permissible value.

The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an optical deck objective lens that can determine whether the inclination of the objective lens in an assembled state is within a predetermined tolerance. .

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is provided with a configuration in which a mirror surface is formed on the upper surface of the flange formed on the outer periphery of the lens barrel of the objective lens.

Function: As described above, the objective lens of the present invention has a mirror surface on the upper surface of the flange, so when this objective lens is assembled into an actuator, the actuator is placed on the bed of an inspection machine, and the collimated parallel light is placed on the bed of the inspection machine. When the beam is applied to the mirror surface on the upper surface of the flange of the objective lens at a predetermined angle of inclination with respect to the bed, the mirror surface reflects the parallel light at a reflection angle corresponding to the angle of inclination of the flange. Therefore, by measuring the spot position of the reflected light, the tilt angle of the objective lens can be detected with respect to the bottom surface of the actuator, that is, the reference plane, and the tilt angle of the objective lens in the assembled state is within the allowable value. It can be determined whether there is a

Embodiment FIG. 1 is a side view of an objective lens according to an embodiment of the present invention.
FIG. 2 is a top view thereof. The objective lens, which is generally designated by the reference numeral 17, has a lens barrel 17a that holds the lens and a flange 17b provided on the outer periphery of the lens barrel 17a.A mirror surface 18 is formed on the upper surface of the flange 17b by vapor deposition or the like. There is. This objective lens 17 is the same as the conventional objective lens 6 except that it has a mirror surface 18, and is attached to the actuator 5 shown in FIGS. 5 and 6 in place of the objective lens 6.

Next, measurement of the inclination of the objective lens when using the objective lens 17 having the above configuration will be described.

With the objective lens 17 attached to the actuator 5,
As shown in FIG. 3, this actuator 5 is set at a predetermined position on the bed 19 of the inspection machine.

This inspection machine has a reflection mirror 21 fixed in a fixed positional relationship with respect to the bed 19, and a beam spot projection surface n, and further includes a light source ( (not shown). In this inspection machine, the parallel test beam n is set at an angle of incidence α (bed 19
The light is irradiated onto the mirror surface 18 on the upper surface of the flange 17b of the objective lens 17 at an angle α) with respect to the perpendicular line, and is reflected at the mirror surface 18. If the objective lens 17 is not tilted, that is, if the axis of the objective lens 17 is
If it is perpendicular to the lower surface (reference plane B-B), parallel light n
is reflected by the mirror surface 18 at a reflection angle α, reflected by a dot E on the mirror 21, and projected onto a point F (reference point) on the projection plane. However, if the objective lens 17 is tilted,
The parallel light is reflected by the mirror surface 18 at a reflection angle α + Δα, reflected by points D' and E' on the mirrors (9) and 21, and landed at a point F' on the projection plane n, which is △d away from the point F. project. here,
The tilt angle θ of the objective lens 17 is Δα/2. Assuming that the inclination angle θ is normally around 0.6°, if the distance from the objective lens reflecting surface to the beam spot projection surface is approximately 5 m, the deviation of the projection point F' from the reference point F will be Δd is
It can be read directly and measured accurately. From this, the inclination when the objective lens is assembled into the actuator is
It becomes possible to perform measurements without making any changes to the actuator.

Effects of the Invention As is clear from the above explanation, in the present invention, a mirror surface is provided on the upper surface of the flange of the objective lens, so with the objective lens incorporated in the actuator, the actuator is placed in an inspection machine and exposed to parallel light for testing. By illuminating the mirror surface of the flange and observing the spot position of the reflected light, the amount of tilt of the objective lens can be detected without touching the actuator, and it is easy to determine whether the tilt is within the allowable value. This has the effect of being able to be distinguished.

[Brief Description of the Drawings] Fig. 1 is a side view of an objective lens according to an embodiment of the present invention, Fig. 2 is a top view thereof, and Fig. 3 is an inspection machine for inspecting an actuator incorporating the objective lens. FIG. 4 is a side view schematically showing the configuration of a recording/reproducing section of a general optical deck; FIG. 5 is a schematic cross-sectional view showing the actuator of the optical head in FIG. 4; FIG. is a top view of the actuator, FIG. 7 is a cross-sectional view of a part of the actuator to explain the inclination of the objective lens incorporated in the actuator, and FIG. FIG. 3 is a side view for explanation. DESCRIPTION OF SYMBOLS 1... Optical disk, 2... Optical head, 3... Optical bench, 4... Light source, 5... Actuator, 6...
・Objective lens, 8 parts Actuator base, 9...
Solid shaft, 10... Movable body, 17... Objective lens, 1
7a... Lens barrel, 17b... Flange, 18... Mirror surface, 19... Inspection machine bed, 20.21... Mirror,
n: Projection surface, oh: Parallel light for inspection.

Claims (1)

[Claims] An optical deck objective lens comprising a lens barrel holding a lens and a flange provided on the outer periphery of the lens barrel, the flange having a mirror surface formed on its upper surface.