JPH0997437A - Object lens position detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect a position of an object lens with high accuracy and to miniaturize a detecting device. SOLUTION: A focus coil 102 is wound around an object lens holder 101, and moreover, a tracking coil is stuck to the holder 101. A magnetic circuit 103 is provided to be adjacent to the focus coil 102, and one pair of cruciform printed circuit boards 104 are stuck to the focus coil 102. To the printed circuit boards 104, a wire 106 is fitted, the other ends of the printed circuit boards are fixed to a base 109. Each printed circuit board 104 is constituted to be capable of reflecting light by its surface to have a function as a reflecting body as well. A sensor box 107 is for detecting the position of the object lens, and is arranged with a single light emitting diode and one pair of photosensors, which are deviated by a specific distance in the direction of an optical axis. The photosensors are connected with a differential amplifier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an objective lens position detecting device for an objective lens actuator in an optical disc device for high speed access.

[0002]

2. Description of the Related Art Recently, research on an external storage device having both high-speed accessibility of a magnetic disk for a computer and large-capacity memory characteristic of an optical disk has been rapidly progressing,
The next-generation disk device is certainly expected to be an optical disk device from the viewpoints of high transfer rate, high-speed random access, large-capacity memory, storability of medium, durability of medium due to non-contact, and the like.

By the way, in order to enable high-speed access, it is necessary to accurately measure the moving distance of the optical head. For example, when the optical head is moved from the innermost circumference a to the outermost circumference b of the optical disc, the movement of the objective lens actuator in the tracking direction is stopped and the number of tracks of the optical disc is counted along with the movement. By counting the number of tracks, the radial position of the optical disk is detected and the moving distance ab is measured.

In order to lock the movement of the objective lens actuator in the tracking direction under the servo operation, an objective lens position detecting device for detecting the position of the objective lens is used. For example, there is an objective lens position detecting device as shown in FIGS. The objective lens position detecting device shown in FIG. 4 uses a prismatic lens holder 402 supported by four wires 401, and an L-shaped light-shielding arm 403 is provided on the side surface of the objective lens holder 402. There is. In addition, this light-shielding arm 4
A U-shaped coupler 404 is arranged in correspondence with 03. As shown in FIG. 5, the coupler 404 is provided with a light emitting diode 405 with a convex lens for projecting light, and a two-division optical sensor 406 for receiving light.

In such an objective lens position detecting device,
The beam emitted from the light emitting diode 405, which is substantially parallel to the light, and transmitted through the light blocking arm 403 is received by the two-division optical sensor 406. Then, the outputs of the pair of optical sensor elements are subtracted by the differential amplifier 407 to detect the position of the objective lens in the tracking direction.

Japanese Patent Laid-Open No. 32-32434 discloses an objective lens position detecting device based on these light projecting / light receiving systems.
JP-A-64-49123, JP-A-4-39610
JP-A-5-266504 and the like have been proposed. For example, JP-A-4-3961
The publication No. 0 has a structure as shown in FIG.

That is, the actuator provided with this objective lens position detecting device is of a shaft sliding rotation type,
The movement in the focus direction is the axial direction (vertical direction in the figure), and regarding tracking, the objective lens 502 arranged at a position displaced from the axis 501 is rotated by the circular movement about the axis 501 by the circular movement to perform the tracking direction. Move to. Regarding the movement in the focus direction, a focus coil 504 is wound around a circular ring 503, and a magnetic circuit 506 via a yoke 505 is arranged in a portion surrounding this circular arc to apply a magnetic field.

Further, four prismatic tracking coils 508 are attached to a lens holder 507 having a circular ring 503, and a magnetic field from the magnetic circuit 506 is applied to perform a rotational movement for tracking. Further, along with this rotational movement, a counterweight 509 is arranged at an axially symmetrical position of the objective lens 502 to maintain a dynamic balance.

The objective lens 50 of this lens holder 507
The reflector 510 is provided on the ring 503 on the side where 2 exists,
At the position facing the reflector 510, the light emitting diode 5
11 and a pair of optical sensors 512 on both sides thereof are provided. Then, the light emission beam from the light emitting diode 511 is reflected by the reflector 510 of the objective lens actuator and received by the pair of optical sensors 512, and the differential amplifier 51.
At 4, the rotation of the lens holder 507 is detected. Therefore, for example, when the objective lens is rotated to the right in the figure, the reflected light a in the figure is generated, and the optical sensor 512 and the differential amplifier 51 are shown.
When it is detected in 4, the output is + (plus).

[0010]

However, in the conventional objective lens position detecting device shown in FIG. 4 and FIG. 5 described above, when the light shielding arm is attached to the natural vibration system of the lens holder itself, the mechanical strength of this portion is increased. If it is insufficient, there is a problem that a secondary resonance frequency is generated. Further, since the light-shielding arm is attached to the objective lens holder, there is a problem that the weight is increased and the driving sensitivity is lowered. Further, there is a problem that it is difficult to reduce the size because the optical path requires a space.

Further, in the case of the objective lens position detecting device shown in FIG. 6, there is a problem that it is difficult to reduce the size because a spatial distance between the light emitting diode and the two-divided photosensor is required.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an objective lens position detecting device which can detect the position of the objective lens at high speed and with high accuracy and can be downsized. .

[0013]

In order to achieve the above object, an objective lens position detecting device according to claim 1 of the present invention comprises a base, and an objective lens holder provided on the base so as to be movable in a focus direction and a tracking direction. A light emitting element provided on the base, a pair of light receiving elements provided on both sides of the light emitting element with their positions shifted in the optical axis direction, and a reflector provided on the objective lens holder. After the emitted light is reflected by the reflector, it is received by the light receiving element,
The position of the objective lens holder in the tracking direction is detected by differentially detecting the output from the light receiving element.

Further, preferably, the objective lens holder is supported by a spring which also serves to supply a drive current, and the reflector is a relay printed circuit board for connecting the focus coil and the tracking coil.

According to the objective lens position detecting device of the present invention having the above structure, the light emitting element irradiates the reflector with the light beam, and the reflector reflects the light beam from the light emitting element. The light receiving element receives the reflected light from the reflector and outputs different detection signals depending on the distance from the reflector.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an objective lens position detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of an embodiment of an objective lens position detecting device according to the present invention, FIG. 2 is an enlarged plan view of a sensor box portion for detecting the objective lens position used in the objective lens position detecting device, and FIG. Figure showing the output characteristics of the sensor, Figure 3
(B) is a diagram showing an objective lens position detection signal obtained by a differential amplifier.

In FIG. 1, reference numeral 101 denotes a substantially rectangular objective lens holder, and a focus coil 102 is wound around the objective lens holder 101, and a substantially rectangular tracking coil (not shown) is provided in the focus coil 102. It is pasted. Further, a magnetic circuit 103 for applying a magnetic field to both focus driving and tracking driving is provided adjacent to the focus coil 102, and these constitute a biaxial actuator.

A pair of cross-shaped printed circuit boards 104 are attached to the inner circumference side (the far side in the figure) and the outer circumference side (the front side in the figure) of the focus coil 102 of the optical disk device. Four wires (two wires each on the upper and lower parts) of wires 106 are attached to the upper and lower parts of the printed circuit board 104 via a solder pattern 105, and the wires 106 have conductivity and spring properties. The objective lens holder 101 is supported by fixing the ends.

The cross-shaped printed circuit board 104 serves as a relay member for both the focus coil 102 and the tracking coil, and its surface is configured to reflect light so that it also functions as a reflector. It has become.

Reference numeral 107 denotes a sensor box incorporating an optical detection portion for detecting the position of the objective lens. The sensor box 107 is provided on the opposite side of the optical disc drive motor rotation shaft of the base 108 so that the optical head can be submerged to the inner circumference of the optical disc. It is attached to the side of. This sensor box 1
As shown in FIG. 2, a light emitting diode 07 is provided with a single light emitting diode 201 as a light emitting element and a pair of light receiving sensors 202 and 203 as light receiving elements which are provided in close contact with each other on both sides thereof. The sensors 202 and 203 are displaced in the optical axis direction, that is, the light receiving sensor 202 is the light receiving sensor 2
It is arranged so as to be farther from the printed circuit board (reflector) 104 by a distance d than 03. In addition, the light receiving sensor 2
02 and 203 are connected to a differential amplifier (not shown).

Next, the operation of the above-mentioned objective lens position detecting device will be described. First, the light beam b is emitted from the light emitting diode 201 to the printed circuit board (reflector) 104,
The light receiving sensor 2 receives the reflected light c from the printed circuit board 104.
02 and 203 receive and output. This light receiving sensor 20
The output characteristics of Nos. 2 and 203 are shown in FIG. In this figure, a curve A shows the characteristics of the light receiving sensor 202, and a curve B shows the characteristics of the light receiving sensor 203. In this way, the light receiving sensor 202,
In 203, since the distance to the printed circuit board 104 is different, the output peaks are deviated, and the S-shaped objective lens position detection signal as shown in FIG. To get

When the optical head is moved in the radial direction of the optical disk, the tracking servo is removed and the S
Zero point e (zero crossing point) of the V-shaped objective lens position detection signal
The object lens holder is controlled so that the objective lens is locked in the tracking direction. In this state, the tracking error signal is counted to detect the radial position of the optical disc.

[0023]

As described above, according to the objective lens position detecting device of the present invention, the position of the objective lens can be detected at high speed and with high precision, and the size can be reduced.

[Brief description of drawings]

FIG. 1 shows a perspective view of an embodiment of an objective lens position detecting device of the present invention.

FIG. 2 is an enlarged partial side view of an embodiment of the objective lens position detecting device of the present invention.

FIG. 3A is an output characteristic diagram relating to the distance from the printed circuit board (reflector) of the light receiving sensor. (B) is
The objective-lens position detection signal of a differential amplifier is shown.

FIG. 4 shows a perspective view of a conventional objective lens position detecting device.

FIG. 5 is a partially enlarged perspective view of a conventional objective lens position detecting device.

FIG. 6 shows a plan view of a conventional objective lens position detecting device.

[Explanation of symbols]

 101 Objective Lens Holder 102 Focus Coil 103 Magnetic Circuit 104 Printed Circuit Board (Reflector) 107 Sensor Box 201 Light Emitting Diode 202 Light Receiving Sensor 203 Light Receiving Sensor

Claims (2)

[Claims] 1. A base, an objective lens holder provided on the base so as to be movable in a focus direction and a tracking direction, a light emitting element provided on the base, and a position displaced in the optical axis direction on both sides of the light emitting element. Light receiving element and a reflector provided on the objective lens holder. The light emitted from the light emitting element is reflected by the reflector and then received by the light receiving element. An objective lens position detecting device characterized by detecting the position of the objective lens holder in the tracking direction by detection. 2. The objective lens position detecting device according to claim 1, wherein the objective lens holder is supported by a spring which also serves to supply a drive current, and the reflector is a relay printed circuit board for connecting the focus coil and the tracking coil.