JPS63144423A - Optical head device - Google Patents

Abstract

PURPOSE:To constitute the titled device so that an optical axis of a driving device can be brought to an angle adjustment against an optical axis of a photodetecting device, by turning an objective lens driving body centering around a supporting point provided on the outside of an optical path between the driving device and the photodetecting device. CONSTITUTION:When both adjusting screws 14, 14' are tightened in the same way, an objective lens driving device 5 turns centering around a contact part of a supporting shaft 10 and a bearing 11, and an optical axis of an objective lens 4 is inclined in the direction as indicated with an arrow A. Also, when both the adjusting screws 14, 14' are loosened in the same way, the driving device 5 turns in the reverse direction centering around the contact part of the supporting shaft 10 and the bearing 11 by an energizing force of compression springs 13, 15, and the optical axis of the lens 4 is inclined in the direction as indicated with an arrow A'. On the other hand, when both adjusting screws 12', 14' are tightened in the same way, and also, both adjusting screws 12, 14 are loosened in the same way, the optical axis of the lens 4 is inclined in the direction as indicated with an arrow B. Also, when both the adjusting screws 12', 14' are loosened in the same way, and also, both the adjusting screws 12, 14 are tightened in the same way, the optical axis of the lens 4 is inclined in the direction as indicated with an arrow B'. In such a way, by combining these operations, the optical axis of the objective lens 4 can be brought to a fine adjustment in any direction.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical head device of an information recording/reproducing apparatus that optically records information on a record carrier such as an optical disk or reproduces recorded information. In particular, the present invention relates to an optical head device equipped with an optical axis adjustment mechanism for an objective lens.

(Prior art) In an optical recording and reproducing device using laser light,
Signals are detected by concentrating Radical light into a minute spot using an objective lens, etc., but in order to detect signals correctly, the focus of the light spot must be adjusted according to the irregularities and vibrations of the information recording carrier. Focusing control to connect the light spot to the carrier and tracking control to always make the light spot follow the correct signal track are required.

Furthermore, if a time axis error occurs due to uneven rotation of the information recording carrier, tangential control is required to correct this error. In order to perform these controls, an error detection device that detects each wakizashi and an actuator that moves the optical system to cancel this error are required.

(Problems to be Solved by the Invention) Conventionally, in order to perform the above-mentioned control, the holder of the objective lens is supported by an elastic body such as a leaf spring, and the direction of the optical axis of the objective lens is adjusted according to an error signal. A configuration in which the shaft is driven in a direction perpendicular to the front shaft is known.

However, in a device configured in this manner, it is extremely difficult to align the optical axis of the driven object including the objective lens with the optical axis of the photodetection system that includes other non-driven optical systems. . For example, in the optical head device of a player that plays back a connoct disc, the inclination of each optical axis is ±0.
Must be set to 1 degree or less. If this inclination is large, the light spot 7) focused by the objective lens will not form a perfect circle on the information recording carrier, and the sensitivity of the photodetection device that uses this reflected light will deteriorate, resulting in accurate detection. It becomes impossible to read the information.

In order to eliminate the above-mentioned drawbacks, for example, an apparatus disclosed in Japanese Unexamined Patent Publication No. 179946/1983 has been proposed. This is designed to allow the angle of the driven body, including the objective lens, mounted relative to the base to be adjusted by adjusting the screw, but in order to adjust the angle, it is necessary to provide play. Therefore, during adjustment, it is necessary to perform the adjustment while observing the focal spot shape, which is usually on the order of micrometers, while the driven body is unstable, making the adjustment work considerably troublesome.

In addition, as a solution to this drawback, Japanese Patent Application Laid-open No. 61-68
There is a device disclosed in Japanese Patent No. 734.

This is done by adjusting the angle of the optical axis of the support body containing the objective lens with respect to the optical axis of other non-driven optical systems by rotating the objective lens around the principal point, for example, by adjusting a screw. Since the objective lens support can adjust the angle while in contact with the driven body, it has the advantage that the focal spot of the objective lens can be adjusted while keeping it at a substantially fixed position. However, in order to perform adjustment while maintaining the fixed position of the focal spot, unless the dimensional accuracy of each part of the angle adjustment mechanism is quite good, there is a risk that axis deviation will always occur. Further, as described above, in order to make the support body including the objective lens rotatable, it is necessary to form the support body and the driven body that holds the support body into an uneven shape. Moreover, high precision curved surface machining is required to form the contact surface. Furthermore, since the light beam passes through the center of the objective lens support and the driven body,
Sixth, unless the holes through which these light beams pass are formed to have a considerably large diameter, there is a risk that the required optical path will not be secured when the objective lens support is rotated.

This is undesirable because it increases the size of the optical head device.

(Means for Solving the Problem) The problem with the prior art as described above is that the device optically records information on an information record carrier and reads the recorded information f'i, an objective lens driving device that drives a driven body including a lens by a corresponding electric signal; a light source for irradiating light onto the information carrier; and detecting the information by receiving reflected light from the information carrier. In an optical head device having a photodetecting device, the driving device and the photodetecting device.

A light source characterized in that the optical axis of the driving device is angularly adjusted with respect to the optical axis of the photodetecting device while rotating the driving device about a fulcrum provided outside the optical path between and. This problem can be solved by using a head device.

(Function) In the optical head device of the present invention configured as described above, the objective lens driver rotates around a fulcrum provided on the outside of the optical path between the driver and the photodetector. It is possible to adjust the angle of the optical axis of the drive device with respect to the optical axis of the photodetector. According to such a mechanism, adjustment work can be easily performed with a relatively simple configuration.

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

FIG. 1 is a front sectional view of the angle adjustment mechanism in the optical head device of this embodiment, FIG. 2 is a top view of the angle adjustment mechanism in the optical head device shown in FIG. 1, and FIG. 3 shows the configuration of the photodetector. 4(a) and (b) are diagrams for explaining the advantages and disadvantages of adjustment by the arrangement of elastic members, and FIG. 5 is a diagram for explaining the light detection method of the photodetector. .

In FIGS. 1 to 3, Rade light emitted from a Rade diode 1 becomes a parallel beam at a collimator lens 2 and enters a bar 7 and a mirror prism 6. This incident light is transmitted to the half mirror 6 &
The light beam is bent upward at the point where it passes through the objective lens 4, and is condensed into a minute spot by the objective lens 4, and is irradiated onto the recording surface of the information recording carrier 3. This irradiated light beam is reflected by the recording surface, passes through the objective lens 4 again, enters the half mirror prism 6, is separated from the light beam from the laser diode 1 by the half mirror 6a, and is separated into the diffraction grating structure 7. The light is incident on the first surface. On the second surface of the diffraction grating structure 7, there is a diffraction grating 20.21 separated into three regions, for example.
．． 22 is provided, and the light beam incident on the first surface of the diffraction grating structure 7 as described above is transmitted to the diffraction grating 20.21.2.
2 and diffracted in different directions. This diffracted light is totally reflected by the first or second surface of the diffraction grating structure 7 and is guided to the photodetector 8 provided on the end face of the diffraction grating structure. The photodetector 8 has a plurality of photodetection surfaces 8a, 8b, 8c, 8 to receive each of the diffracted lights.
d is provided.

In the above configuration, 5 is an objective lens driving device that drives a driven body including the objective lens 4 using a corresponding focus error signal and tracking error signal,
Reference numeral 9 denotes a photodetector that houses the radar diode 1, collimator 2, half mirror prism 6, diffraction grating structure 7, and the like. A convex support shaft 10 is provided on the lower surface of the objective lens driving device 5, and a concave bearing 11 corresponding to the support shaft 10 is provided on the upper surface of the photodetector 9. These support shafts 10 and bearings 11 are provided outside the optical path of the light beam passing between the objective lens 4 and the half mirror prism 6, and these support shafts 10 and bearings 11 are engaged with each other. By this, the objective lens driving device 5
can rotate relative to the photodetector 9 using the contact point between the support shaft 10 and the bearing 11 as a fulcrum.

Further, screw mounting holes 5b are provided on all sides of the objective lens drive device 5.
, 5c are provided. Among these, the holes 5c are provided on three sides of the support shaft 10 side and below the side of the objective lens driving device 5, as shown in FIG. are provided on three sides opposite to the hole 5c and located above the side of the objective lens driving device 5. Then, the objective lens driving device 5 is
With respect to the photodetector 9, in the hole 5c, the hole 5c
It is fixed via a compression spring 13 on the top thereof, and via a compression spring 15 on the hole 5b and the photodetecting device 9 in the hole 5b by adjustment screws 12.12' and 14.14', respectively. In addition, each screw through hole of the hole portions 5c and 5b has an adjustment screw 1.
2, 12', 15.15' are formed to have an inner diameter that allows some loosening when passing through them.

Therefore, with the Hiko configuration as described above, the objective lens driving device 5 is biased in the direction of pressing the photodetecting device 9 by the biasing force of the compression spring 13 on the hole 5c side, and is pushed into the hole 5b side. Then, it acts against the biasing force of the compression spring 15 to fix the objective lens drive device 5 to the photodetector device 9.

A method for adjusting the angle of the optical head device configured as above will be described. 1 and 2, when both adjustment screws 14 and 14' are tightened in the same way, the objective lens drive device 5 rotates around the contact portion between the support shaft 1o and the bearing 11, and the objective lens 4 The axis is tilted in the direction indicated by the arrow in FIG. Furthermore, when both adjustment screws 14.14' are loosened in the same way, the objective lens driving device 5 is moved around the contact area between the support shaft 10 and the bearing 11 due to the biasing force of the compression spring 13.15. Rotates in the opposite direction, and the optical axis of the objective lens 4 is tilted in the direction of arrow A' in FIG. 2. - Force adjustment screw 12
', 14' in the same way, and adjust screw 12.
．． 14 in the same way, the optical axis of the objective lens 4 is tilted in the direction of arrow B in FIG. Also, adjust screw 12'
, 14' in the same way and adjusting screw 12.1.
When both of 4 are tightened in the same way, the optical axis of objective lens 4 will be the second one.
In the figure, it is tilted in the direction of arrow B'. Thus, by combining these operations, the optical axis of the objective lens 4 can be finely adjusted in any direction.

In addition, in this device, during adjustment, there is a risk that the optical axis of the objective lens 4 may shift in a direction perpendicular to the optical axis direction, but the angle adjustment amount in this type of device is 1°.
The deviation is 0.2 m with a standard size device.
If the following is true, and considering variations in other parts,
The above-mentioned misalignment of this device is not a problem.

Next, the advantages and disadvantages of adjustment depending on the position of the elastic member disposed between the objective lens driving device 5 and the photodetecting device 9 will be explained. In addition to the arrangement shown in this embodiment, the arrangement of the compression spring used as the elastic member is shown in FIGS. 4(,) and 4(b).

In the one shown in FIG. 4 (&), the screw through hole 5d
are located on all four sides of the objective lens drive device 5, and all of them are provided above the side of the drive device 5. An adjustment screw 16 is mounted between such a through-hole portion 5d and the upper surface of the photodetector 9 via a compression spring 17. In the apparatus having this configuration, the objective lens driving device 5
Although the fixation between the light detection device 9 and the light detection device 9 is performed with some degree of certainty, when adjusting the angle, if one of the adjustment screws 16 is loosened,
The objective lens drive device 5 is compressed by the compression spring 1 at the loosened point.
There is a risk that the biasing force 7 causes the shaft to float upward, and the support shaft 10 and bearing 11 to separate.

Further, in the one shown in FIG. 4(b), the screw through holes 5e are provided on all four sides of the objective lens driving device 5, and all are provided below the side of the driving device 5. The adjustment screw 18 is attached between the through-hole portion 5e and the head of the adjustment screw 18 via a compression spring 19. Although the above-mentioned problem does not occur in the device having this configuration, when an external impact or the like occurs, the objective lens driving device 5 is moved by the biasing force of the compression spring 19.
0 and the bearing 11, and there is a risk that the optical axis will not be fixed.

However, in the device of this embodiment, the support shaft 10 and the bearing 1
1 as a fulcrum, one side of the objective lens drive device 5 is compressed in the direction of the photodetector 9, and the other side is biased in the direction away from the photodetector 9, so that the angle adjustment is possible. Even if the objective lens driving device 5 is rotated at this time, the displacement is absorbed by the compression spring 13, and the support shaft 10 and the bearing 11 do not separate. Moreover, with the above-described configuration of the present apparatus, even if the objective lens driving device 5 swings due to an external impact, it can immediately return to its original state.

Next, the principle of focus error and tracking error detection in this apparatus configured as described above will be explained using FIG. 4. FIG. 4 is a perspective view of the above-mentioned diffraction grating structure 7.

In the figure, the reflected light from the information recording carrier 3 becomes convergent light due to the imaging action of the objective lens 4, and after passing through the first surface of the diffraction grating structure 7,
The light is incident on a diffraction grating arranged on the surface. This diffraction grating is
Three parts 20 each with a grid direction set in a different direction
, 21.22. The light beam diffracted by the portion indicated by 20 travels while being totally reflected at 20 m between the first surface and the second surface, and reaches the light receiving surfaces 8& and 8 of the photodetector 8.
straddle bK to form spot) 20b. Here, since the light beam incident on the diffraction grating structure 7 is a light beam having convergence, the diffraction grating may be a simple linear grating. Also,
If the diffraction grating is given a curvature so as to exert a diverging effect on the single diffracted light, the movement of the focus error detection light beam 20b can be increased in a so-called telephoto type sensor lens system.

Now, when the information recording carrier 3 has moved away from the in-focus position,
When approaching, the degree of convergence of the reflected light increases or decreases, that is, the curvature of the wavefront becomes larger or smaller than the normal degree of convergence.

As a result, the position of the spora (spora) 20b moves in response to fluctuations in the optical axis direction of the information recording carrier 3. Then, the light receiving surfaces 8a and 8
From b, signals corresponding to the amount of incident light are detected,
These outputs are amplified and then subtracted to produce a focus error signal.

On the other hand, the light beam diffracted at the portions 21 and 22 is
They are detected by the light receiving parts 8c and 8d of the light detecting part 8, respectively. The output signals from these light-receiving surfaces are amplified and then subtracted, resulting in a tracking error signal of the so-called Bushgur method. Tracking errors can also be detected by detecting the phase or time difference of signal intensity changes when diffracted by hits from each amplified signal.

The information signal recorded on the information recording carrier 3 is transmitted to the light receiving element 8
It is detected from the sum of the outputs from m, 8b*8c, and 8d.

Note that this embodiment relates to tilt adjustment of the objective lens drive device, and the methods of the objective lens drive device and the optical system are not limited to this embodiment. Furthermore, although a coil spring is used as the elastic member in this embodiment, any other material that can obtain a biasing force through expansion and contraction may be used, and is not limited to this embodiment. Further, in this embodiment, the support shaft is provided on the objective lens driving device side, and the bearing is provided on the photodetecting device side, but the present invention is not limited to this, and it may be provided in the opposite manner. Although the spindle and the bearing are separate parts, the spindle may be obtained by engraving the base plate, the bearing may be obtained by machining the housing, etc.

(Effects of the Invention) As explained above, the optical head device of the present invention can be manufactured with a relatively simple configuration, and the angle of the optical axis of the objective lens can be adjusted with a simple operation. .

[Brief explanation of the drawing]

FIG. 1 is a front sectional view of the angle adjustment mechanism in the optical head device of this embodiment, FIG. 2 is a top view of the angle adjustment mechanism in the optical head device shown in FIG. 1, and FIG. 3 shows the configuration of the photodetector. 4(a) and (b) are diagrams for explaining the advantages and disadvantages of adjustment by the arrangement of elastic members, and FIG. 5 is a diagram for explaining the light detection method of the photodetector. . 4... Objective lens, 5... Objective lens drive device, 5
b, 5e, 5d, 5s...screw through hole portion, 9...photodetector, 10...support shaft, 11...bearing, 12. L
2'. 14.14', 16.18...adjustment screw, 13,15
゜17.19... Compression spring. Agent Patent Attorney Jo Taira Yamashita Figure 3 Figure 4 (0) Figure 4 (b)

Claims (3)

[Claims] (1) An objective lens driving device that optically records information on an information recording carrier or reads recorded information, and that drives a driven body including an objective lens by a corresponding electric signal; In an optical head device comprising a light source for irradiating light onto a carrier, and a photodetection device for receiving reflected light from the information carrier and detecting the information, an optical head outside the optical path between the drive device and the photodetection device. An optical head device characterized in that the optical axis of the driving device is angularly adjusted with respect to the optical axis of the photodetecting device while rotating the driving device about a fulcrum provided in the optical head device. (2) The optical head according to claim 1, wherein the fulcrum is comprised of a support shaft portion and a bearing portion provided on each opposing surface of the drive device and the photodetector device. Device. (3) The driving device is fixed to the photodetecting device by an adjustment screw including an elastic member that biases opposing surfaces around the fulcrum in a direction in which one side presses them into contact with the other side and a direction in which they separate. An optical head device according to claim 1, characterized in that: