JPH087868B2 - Optical signal readout device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disc player or the like that collects and irradiates a recording medium with a light flux on a disc and records or reproduces a signal by reflected light or transmitted light. The present invention relates to a dynamic signal reading device.

2. Description of the Related Art An example of a conventional optical signal reading device is shown in FIGS.
Shown in the figure. Inside the housing 1, a semiconductor laser 15, photodetection elements 19 and 20, and various optical element groups forming an optical path are incorporated. The objective lens driving device 3 is attached to this housing, and the optical signal reading device is configured by combining the two.

The objective lens driving device is generally screwed to the housing with three or four screws.

Problems to be Solved by the Invention However, when the objective lens driving device is attached to the housing with three or four screws as in the conventional optical signal reading device described above, the following problems occur. Occurs.

Among the components that make up the objective lens driving device, the components that are fixed to the housing and that include fastening elements for fixing (hereinafter referred to as the actuator base) generally depend on the type of the objective lens driving device. An iron-based metal material is used. On the other hand, as a material for the housing, a metal material such as aluminum or a reinforced plastic material is generally used.

However, since the coefficient of linear expansion differs between iron and aluminum, for example, stress is generated at the joint between the actuator base and the housing due to changes in environmental temperature. This stress brings about the same effect as that of a so-called bimetal and causes strain in the housing itself.

As a result, the optical axis of the optical element group built in the housing is displaced, and the beam position on the photodetector is displaced. Therefore, the offset component is superimposed on the electric signal from the photodetector, and the servo signal fed back to the objective lens driving device is displaced, so that the objective lens driving device performs accurate focus position control and tracking control. It causes the problem of being unable to.

In view of the above problems, the present invention can minimize the stress generated at the joint between the objective lens driving device and the housing pair due to the change in the environmental temperature, and reduce the distortion of the housing caused by the stress. Therefore, it is an object of the present invention to provide an optical signal reading device capable of reducing the influence of the distortion of the housing on the optical axis and, as a result, reducing the deviation generated in the focus position control and the tracking control.

Means for Solving the Problems In order to solve the above problems, the optical signal reading device of the present invention uses a single screw and an objective lens driving device as a fixing mechanism for a housing and an objective lens driving device. A fixing mechanism composed of a rotation stopping mechanism and a spring or a fixing mechanism composed of two screws and one or more springs is used.

According to the present invention, when the actuator base is first fixed to the housing with one screw, the rotation stopping mechanism of the actuator base and the spring, the fixing point of the actuator base is 1 screw. It is only a point, and the other part has a structure of a free end and is not fixed to the housing. However, as a position regulation, a rotation stopping mechanism that prevents the actuator base from rotating around a fixed point and a spring that prevents the actuator base from floating from the housing at a point other than the fixed point are provided.

Therefore, when the environmental temperature changes, the difference in the amount of expansion and contraction between the actuator base and the housing due to the difference in the linear expansion coefficient between the materials is a slight misalignment between the actuator base and the housing starting from the fixing point by the screw. Appears.
That is, no stress is generated due to temperature change at the joint between the actuator base and the housing. Therefore, no distortion of the housing caused by stress occurs.

As a result, the optical axis of the optical element group built in the housing does not shift, and the beam position on the photodetector does not shift. As a result, the offset component is not superimposed on the electric signal from the photodetector, so that the servo signal fed back to the objective lens driving device is not displaced, and accurate focus position control and tracking control are executed. .

Next, when fixing with two screws and a spring, stress is generated between the two fixing points, so the influence of strain due to temperature change appears in the focus position control and tracking control.
The effect can be minimized by choosing the positions of the two fixed points. That is, the superiority or inferiority with respect to the temperature change is slightly inferior to the case of fixing by the above-mentioned one point, but the action can be made substantially the same as that of the above.

EXAMPLES Examples of the present invention will be described below with reference to the drawings. FIG. 1 shows an optical signal reading device according to a first embodiment of the present invention. In this embodiment, the same components as those in the conventional example shown in FIG. 3 are designated by the same reference numerals. In this embodiment, four conventional base fixing screws 4 are used.
There is only one and two springs 5 are used instead to prevent the actuator base 2 from rising from the housing 1. Further, in order to prevent the actuator base 2 from rotating around the base fixing screw 4, a position regulating means is provided by a guide pin 7 and a guide groove 8 provided in a linear direction connecting the fixing screw 4 and the guide pin 7. ing.

With such a mechanism, the fixing point between the actuator base 2 and the housing 1 is only one point of the base fixing screw 4,
The other joints have a structure with free ends, and are not fixed from the joint surface. Moreover, with respect to external vibrations and impacts, the relative positional relationship between the actuator base 2 and the housing 1 does not shift because the position is regulated by the spring 5 and the guide pin 7.

In addition, the difference in the amount of expansion and contraction between the actuator base 2 and the housing 1 caused by the difference in linear expansion coefficient between the materials when the environmental temperature changes is due to the mechanism described above, and the actuator base 2 and the housing are centered around the fixing screw 4. It appears as a slight misalignment with the body 1. That is, no stress is generated at the joint between the actuator base 2 and the housing 1 due to temperature change. As a result, it is possible to prevent the occurrence of distortion of the housing due to the stress of the joint portion.

As a result, it is possible to prevent the optical axis of the optical element group incorporated in the housing from being deviated, and to prevent the beam position on the photodetector from shifting. As a result, it is possible to prevent the offset signal from being superimposed on the electric signal from the photodetector, so that the servo signal fed back to the objective lens driving device does not deviate. Therefore, accurate focus position control and tracking control are executed.

Next, a second embodiment of the present invention will be described. FIG. 2 shows an optical signal reading device according to the second embodiment of the present invention. Also in this embodiment, the same numbers are given to the parts having the same configurations as those of the conventional example shown in FIG. In the second embodiment, the conventional four base fixing screws 4 are replaced with two springs 5, and springs 5 are used instead.
Are prevented from rising from the housing 1.

In the case of this joint configuration, the position restriction by the two screws 4 and the spring 5 prevents the relative positional relationship between the actuator base 2 and the housing 1 from being displaced due to external vibration or shock. However, since the point on the straight line connecting the fixing points of the two screws 4 is in a fixed state by sandwiching the joint surface, the stress generated by the change in the environmental temperature is completely eliminated as in the first embodiment. It cannot escape and stress is generated between the two fixing points.

However, if the distance between the two fixing points is made as short as possible, it is possible to minimize the difference in the amount of expansion and contraction caused by the difference in linear expansion coefficient between the two types of materials that sandwich the joint surface. . Further, since the joints other than the points on the straight line connecting the two fixing points are held only by the position regulation by the spring 5, the structure has a free end, and the joint surface is not in a fixed state. . Therefore, except for the point on the straight line connecting the two fixed points, the same effect as the first embodiment can be obtained.

That is, in the second embodiment, when the environmental temperature changes, the difference in the amount of expansion and contraction between the actuator base 2 and the housing 1 caused by the difference in linear expansion coefficient between the materials causes stress on the straight line connecting the two fixing points. Although it appears in the form of occurrence, it appears as a slight positional deviation between the actuator base 2 and the housing 1 starting from a straight line at the joint portion beyond that. As a result, distortion of the housing occurs only on the straight line, but the amount thereof can be made extremely small because the distance between the fixed points is minimized.

As a result, the influence of distortion on the optical axis of the optical element group built into the housing can be made small, and there is almost no deviation of the beam position on the photodetector, and it is superimposed on the electrical signal from the photodetector. The offset component is also small, and the deviation of the servo signal fed back to the objective lens driving device hardly occurs. As a result, almost accurate focus position control and tracking control are executed.

As described above, the second embodiment is slightly inferior to the first embodiment, but it is possible to obtain the characteristics with practically no problem, and it is far superior to the conventional example. A physical signal reading device can be realized.

Although the two springs 5 for restricting the position are used in the first and second embodiments, if the supporting points of the spring and the supporting points of the screw are arranged in a well-balanced manner, only one spring is required. Is also possible.

It is also possible to use a coil spring, a torsion spring, a pin-shaped spring, or the like instead of the leaf spring.

Further, in each of the above-described embodiments, the female screw for the fixing screw 5 is provided on the housing side, but conversely, a female screw may be provided on the actuator base side to stop the fixing screw from the back side of the housing.

EFFECTS OF THE INVENTION As described above, according to the optical signal reading device of the present invention, as a fixing mechanism for the housing and the objective lens driving device,
Fixing mechanism configured using two screws, a rotation stopping mechanism of the objective lens driving device, and a spring, or two screws and 1
By using a fixing mechanism composed of more than one spring, it is possible to reduce the distortion of the housing caused by changes in the environmental temperature, significantly reduce the optical axis deviation inside the housing, and The focus position control and the tracking control can be maintained regardless of the temperature change.

[Brief description of drawings]

1 is an exploded perspective view of an optical signal reading device according to a first embodiment of the present invention, FIG. 2 is an exploded perspective view of an optical signal reading device according to a second embodiment of the present invention, and FIG. FIG. 4 is an exploded perspective view showing an example of a conventional optical signal reading device, and FIG. 4 is a schematic sectional view of the device. 9 ... Objective lens, 10 ... Cover of objective lens driving device, 11 ... Coil, 12 ... Wave plate, 13 ... Polarization beam splitter, 14 ... Collimating lens, 16 ... Single lens,
17 …… Half prism, 18 …… Cylindrical lens,
21 …… Case cover.

Claims (3)

[Claims] 1. A light beam generating element, and an optical element group for condensing and irradiating a light beam emitted from the light beam generating element onto a recording medium to guide reproduction light from the recording medium to a light detecting element. A fixing mechanism that holds an objective lens driving device that holds the photodetection element that converts the reproduction light into an electric signal in a housing and mechanically changes the position of the light beam with respect to the recording medium, to the housing. The housing and the constituent members of the contact surface of the objective lens driving device are made of different materials, and the fixing mechanism of the objective lens driving device with respect to the housing has at least one fixing point and the fixing The optical signal reading device is characterized in that the contact surfaces other than the points are rotationally restricted in a circumferential direction with the fixed point as a rotation center and movement is restricted in a normal direction of the contact surface. . 2. The fixing mechanism includes one screw, a rotation stopping mechanism for the objective lens driving device, and a spring for holding a contact state between the housing and the objective lens driving device. The optical signal reading device according to claim 1. 3. A fixing mechanism comprising two screws and a spring, as claimed in claim 1.
An optical signal reading device according to the above item.