JPH02218025A - Optical pickup - Google Patents

Abstract

PURPOSE:To improve the simplification and the miniaturization of a constitution and the adaptability to the various kinds of movable members by providing the balancer for adjusting the position of the center of gravity of the movable member with a part of a detecting means for the position of an objective lens. CONSTITUTION:A beam from a light source 21 is adjusted so that the shadow of a light shielding part 20 is positioned nearly at the center of a detector 22 in the case where a lens holder 2 is at a standstill. Now, when a driving control signal is impressed on a focusing coil 3 and a tracking coil 4, the lens holder 2 drive-controlled in a focusing direction and a tracking direction, and follows the track of a recording medium while keeping a focusing state, and information is recorded or read out. When an optical pickup is moved to the prescribed track at high speed, the objective lens 1 causes vibration due to inertia force, and the output signal of plus (or minus) is generated in a differential amplifier 23, and the vibration in the tracking direction of the objective lens 1, that is, a lens position is detected. Then, by feeding back this detection signal to the tracking coil 4, the objective lens 1 can be locked so as not to be vibrated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical pickup having a lens position detection device.

[Conventional technology]

In general, optical pickups used to record and reproduce information on optical recording media such as optical discs such as compact discs and video discs, and magneto-optical discs emit light beams for recording and reproduction through an objective lens. In order to irradiate an optical disc, etc. in a focused state, and to follow the track of an optical disc, the objective lens is movable in the focusing direction, which is the direction of its optical axis, and in the tracking direction, which is perpendicular to the focusing direction. supported by the main body. As such an optical pickup, for example, as disclosed in Japanese Patent Laid-Open No. 59-68840, the center of gravity of the movable part is aligned with the center of the support means, or as disclosed in Japanese Patent Laid-Open No. 58'-32237, As disclosed, by aligning the center of gravity of the movable part with the driving point, the objective lens can be moved appropriately.

Such optical pickups have the disadvantage that, during a so-called access operation in which the pickup is moved to a predetermined track at high speed, the objective lens causes unnecessary vibration in the tracking direction due to inertial force or the like. Therefore, in order to suppress this unnecessary vibration and perform the access operation accurately, the optical pickup is provided with a lens position detection device for detecting the position of the objective lens. An example of an optical pickup device having such a lens position detection device is disclosed in Japanese Unexamined Patent Publication No. 57-178101. This method involves fixing a prism to the objective lens barrel, irradiating the refractive edge of the prism with laser light, dividing it into two sub-beams, and reflecting them.The reflected light is then received by two detectors. In configuration j7, the displacement of the lens barrel is detected based on the detection signal of each detector.

[Problem to be solved by the invention]

However, the method disclosed in JP-A-57-17801 provides a prism in the objective lens barrel, and the second
Since it uses divided reflected light, it has a complicated configuration and has the disadvantage of increasing the size of the device. In addition, there is a method of adjusting the center of gravity of the movable member using the lens holder itself, but when mounting objective lenses of different weights, it is necessary to individually change the design of the lens holder, which has a complex shape. There is a problem in that it is difficult to deal with it.

The present invention is proposed to solve these problems, and is a lens position detection device that is configured to be easily compatible with movable members provided with objective lenses that are compatible with each type of optical recording medium by providing a balancer for each type of optical recording medium. The purpose of this is to reduce the surface area and size of the structure of an optical pickup having the following characteristics.

[Means and effects for solving the problems] In order to achieve the above object, the present invention provides a movable member that holds an optical system, and a movable member that is moved in a first direction and a second direction that are perpendicular to each other with respect to a fixed member. In an optical pickup having a supporting means for displaceably supporting the movable member and a driving means for displacing the movable member in each of the directions with respect to the fixed member, a light shielding member is formed on a balancer that is provided integrally with the movable member and adjusts the position of the center of gravity. , the light shielding member is located at the center, and a light source and a photodetector are arranged at required positions to form a lens position detection section.

In this way, since the balancer for adjusting the center of gravity of the movable member has a part of the function of the position detection means, it is possible to reduce the number of parts and downsize the device. Furthermore, since balancers with simple configurations can be selected and used, it is easy to assemble movable members even when objective lenses of different weights are mounted.

〔Example〕

FIG. 1A is an exploded perspective view showing a first embodiment of the present invention. The objective lens 1 is fixed to the center of the upper part of the lens holder 2, a trunking coil 4 is attached to the surface of the lens holder 2 parallel to the tracking direction (X direction), and the outer periphery of the lens holder 2 including the tracking coil 4 is attached. A focus coil 3 is wound and attached 7. A balancer 5 is fixed to the lower surface of the lens holder 2, and has a pair of light shielding parts 20 formed by bending upward at right angles at both ends. This balancer 5 may be made of various materials, but as long as it is made of the same material, it is sufficient to be able to adjust the thickness, size, etc. Also, the balancer 5 may be formed of symmetrical light shielding parts at both ends in the length direction. By forming 20 in advance, both the left and right sides can function as light shielding parts during assembly, and assembly is easy. A pair of inner yokes 15 are provided at the center in the Y direction on the base 7, and outer yokes 14 are provided at both ends to face the inner yokes 15, respectively.
A fixed magnet 6 is provided inside to form a magnetic circuit.

A fixing member 9 and a substrate 1 are provided on the outside of one outer yoke 14.
0 are sequentially attached using screws 16. Four holes 17.1 are provided on the bottom left and right sides of the lens holder 2 in the tracking direction, the fixing member 9, and the substrate 10 at corresponding positions.
8.19, insert and fix the four wires 8 there, and move the lens holder 2 in the focus direction (Z direction) so that the inner yoke 15 is located in the internal space of the lens holder 2.
, is supported and fixed to the base 7 so as to be movable in the tracking direction. Therefore, when a current is passed through the focus coil 3.5 and the tracking coil 4, a driving force is generated due to electromagnetic interaction with the magnet 6, and the entire lens holder 2 moves in the focusing direction and the tracking direction.

A balancer 5, which is appropriately selected according to the objective lens 1, is fixed to the lower surface of the lens holder 2 so as to be able to move therewith, and a light shielding section 20 is provided at both ends of the balancer 5. 20 in a direction orthogonal to the tracking direction, a sensor base 13 is provided integrally with the base 7 or separately, together with a substrate 12 on which a sensor 11 having a built-in light 'tA 21 and a photodetector 22 is provided on top of the sensor 11.
Fixed to. FIG. 1B is an enlarged plan view of the fixed sensor 11 and its vicinity.

FIG. 2 is an explanatory diagram showing the operation of the sensor 11.
If the lens holder 2 is stationary, the beam from
The shadow of the light shielding part 20 is positioned approximately at the center of the detector 22.

To explain the operation of the optical pink-up configured in this way, when a drive control signal is applied to the focus coil 3 and the tracking coil 4, the lens holder 2 is driven and controlled in the focus direction and the tracking direction, and the lens holder 2 is driven and controlled in the focus direction and the tracking direction, and the lens holder 2 is driven in the focus direction and the tracking direction. Information is recorded or read out following the image in focus.

The position of the objective lens I during the partial access operation is detected as follows. First, when the optical pickup is stationary, a part of the light beam emitted from the light source 21 passes through without being blocked by the light shielding part, and irradiates the detector 22 as shown in FIG.

The detector 22 has two divided detection elements 22a□22b,
difference'? It is connected to the JJ amplifier 23. FIG. 3 shows a state in which a light beam is irradiating the detector 22.
A shows a state in which the optical pickup is stationary and the shadow formed by the light shielding part 20 is equally formed on the left and right detection elements 22a and 22b. The output of the differential amplifier 23 then becomes zero.

When the optical pickup is moved to a predetermined track at high speed, the objective lens 1 vibrates due to inertial force. Then, the light shielding part 20 that moves integrally with the lens holder 2 is displaced, and the state of irradiation of the light beam onto the two-split photodetector 22 is displaced from the center as shown in FIG. 3B. In this state, a positive (or negative) output signal is generated in the differential amplifier 23, and the vibration of the objective lens 1 in the tracking direction, that is, the lens position is detected. By feeding back this detection signal to the trunking coil 4, it is possible to lock the objective lens so that it does not vibrate.

FIG. 4 shows a second embodiment of the present invention, which is a modification of the balancer and detector used therein.

In this embodiment, a circular opening 24 is provided in the light shielding part 24 of the balancer.
a, and further divides the detector 25 into four detection elements 25.
a - d are closed.

FIG. 5 shows the arithmetic circuit of the detector 25 of the second embodiment, in which each detection element 25a, 25b, 25c, 2
Detection signals a, b, c, d from 5d are sent to two adder circuits 2
7°28 and the differential amplifier 31, (a+c)-(
By obtaining the output signal b→−d), the lens position in the tracking direction can be detected.

By feeding this output signal to the trunking coil 4, it is possible to lock the objective lens l so that it does not vibrate.

On the other hand, by obtaining the output signal of (a+b)-(c+d) using the two adder circuits 26 and 29 and the differential amplifier 30, it is also possible to detect the vibration position of the objective lens 1 in the focus direction. . By feeding back this output signal to the focus coil, it is possible to lock the objective lens so that it does not vibrate in the focus direction.

In this way, in the present invention, a part of the light shielding part of the balancer, a light source,
Not only is it possible to detect the lens position with a simple configuration including a detector, but even when objective lenses of different weights are mounted, the center of gravity of the movable member can be easily determined by appropriately selecting and providing the balance of the simple configuration. can be adjusted.

The present invention is not limited to the above-described embodiments, and can be modified and modified in many ways. For example, when forming a light shielding part on a balancer, it may be bent at an oblique angle or in a cross shape instead of being bent at a right angle, and when forming an opening, it may be formed into a uniform opening instead of a circle. Furthermore, the number of openings is not limited to one, but may be a plurality of openings. Moreover, although two light shielding parts are formed symmetrically on the balancer, they may have an asymmetrical shape. Furthermore, it goes without saying that the support method for the optical system is not limited to the wire method, but may be any other support method including a so-called rotary actuator.

Further, a relay lens or the like may be used instead of the objective lens.

〔Effect of the invention〕

As described above, according to the present invention, a part of the objective lens position detection means is provided in the balancer for adjusting the center of gravity position of the movable member, and this balancer is a simple component and is suitable for various optical recording media. Since the optical pickup can be selected and attached in accordance with the drive member selected, it is possible to provide an optical pickup that can simplify the optical pickup configuration, downsize it, and improve its compatibility with various movable members.

[Brief explanation of the drawing]

FIG. 1A is an exploded perspective view of an optical pickup showing the first embodiment of the present invention, FIG. 1B is a plan view of the same part, FIG. 2 is an explanatory view showing the operation of the sensor, and FIG. 4 is a partial perspective view of the balancer of the optical pickup according to the second embodiment of the present invention. FIG. 5 is an explanatory diagram showing the state of light beam irradiation to the detector. FIG. This shows the circuit.

Claims (1)

[Claims] 1. A movable member that holds an optical system, support means that supports the movable member so as to be movable in a first direction and a second direction orthogonal to each other with respect to the fixed member, and a movable member that supports the fixed member. In an optical pickup having a drive means for displacing the movable member in each of the directions, a light shielding member is formed on a balancer that is provided integrally with the movable member to adjust the center of gravity position, the light shielding member is positioned at the center, and a light source is placed at a desired position. What is claimed is: 1. An optical pickup characterized in that a lens position detecting section includes a photodetector and a photodetector.