JP2748904B2 - Objective lens position detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an objective lens position detecting device for an objective lens actuator in an optical disk device for performing high-speed access.

[0002]

2. Description of the Related Art Recently, research on an external storage device having both the high-speed accessibility of a magnetic disk for a computer and the large-capacity memory of an optical disk has been rapidly progressing.
It is certain that the next-generation disk device will become an optical disk device from the viewpoints of high-speed transfer rate, high-speed random access, large-capacity memory, medium preservability, and non-contact medium durability.

In order to enable high-speed access, it is necessary to accurately measure the moving distance of the optical head. For example, when moving the optical head from the innermost circumference a to the outermost circumference b of the optical disk, the movement of the objective lens actuator in the tracking direction is stopped, and the number of tracks of the optical disk is counted 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 rectangular lens holder 402 supported by four wires 401, and an L-shaped light-shielding arm 403 is provided on a side surface of the objective lens holder 402. I have. In addition, this light shielding arm 4
03, a U-shaped coupler 404 is arranged. 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,
A substantially parallel light is emitted from the light emitting diode 405, and the beam transmitted through the light shielding 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.

[0006] Japanese Patent Application Laid-Open No. Sho 64-32434 discloses an objective lens position detecting apparatus using these light projecting / receiving methods.
JP-A-64-49123, JP-A-4-39610
And Japanese Patent Application Laid-Open No. 5-266504. For example, JP-A-4-3961
No. 0 has a configuration as shown in FIG.

That is, the actuator provided with the 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). With respect to the tracking, by rotating around the axis 501, the objective lens 502 arranged at a position shifted from the axis 501 is moved in the tracking direction by an arc movement. 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 at a portion surrounding the circular arc to apply a magnetic field.

Further, four rectangular 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. Along with this rotational movement, a counterweight 509 is arranged at an axially symmetric position of the objective lens 502 to achieve a dynamic balance.

The objective lens 50 of the lens holder 507
The reflector 510 is provided on the ring 503 on the side where
The light emitting diode 5 is located at a position facing the reflector 510.
11 and a pair of optical sensors 512 on both sides thereof. The light emitted from the light emitting diode 511 is reflected by the reflector 510 of the objective lens actuator, received by the pair of optical sensors 512,
In step 4, the rotation of the lens holder 507 is detected. Therefore, for example, when the objective lens rotates rightward in the figure, the reflected light a in the figure becomes, and the optical sensor 512 and the differential amplifier 51 rotate.
When the detection is made at 4, the output becomes + (plus).

[0010]

However, in the above-described conventional objective lens position detecting device shown in FIGS. 4 and 5, when the light-shielding arm is attached to the natural vibration system of the lens holder itself, the mechanical strength of this portion is reduced. When 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 increases and the drive sensitivity decreases. Further, there is a problem that a space is required in the optical path, and it is difficult to reduce the size.

In the case of the objective lens position detecting device shown in FIG. 6, a spatial distance between the light emitting diode and the two-divided optical sensor is required, and it is difficult to reduce the size.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an objective lens position detecting apparatus capable of detecting the position of an objective lens at high speed and with high accuracy and achieving downsizing. .

[0013]

Means for Solving the Problems] To achieve the above object objective lens position detecting device according to claim 1 of the present invention, the base and, movably provided an objective lens to the base in the focusing and tracking directions holder and a light emitting element provided in the <br/> base, a pair of light receiving elements provided in a state where the position is shifted in the optical axis direction at both sides of the light emitting element, the light emitting element of the objective lens holder And pair
A reflector provided at a position facing each other , and the pair of light receiving elements
From the pair of light receiving elements, and output from the pair of light receiving elements.
How to track the objective lens holder by detecting the force differential
And a differential amplifier for detecting the direction of the current.

[0014] Preferably, the objective lens holder is supported by a spring which also supplies a drive current, and the reflector is a relay printed circuit board for connecting a focus coil and a tracking coil.

According to the objective lens position detecting device of the present invention having the above configuration, the light emitting element irradiates the reflector with a 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 according to the distance from the reflector.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the 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 one 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 an objective lens position used in the objective lens position detecting device, and FIG. FIG. 3 shows output characteristics of a sensor.
(B) is a diagram showing an objective lens position detection signal obtained by the differential amplifier.

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

A pair of cross-shaped printed circuit boards 104 are adhered to the inner peripheral side (the other side in the figure) and the outer peripheral side (the near side in the figure) of the focus coil 102 of the optical disk device. Four (upper and lower two) wires 106 are attached to the upper and lower portions of the printed circuit board 104 via solder patterns 105. The wires 106 have conductivity and spring properties. The end is fixed to support the objective lens holder 101.

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 has a function as a reflector. It has become.

Reference numeral 107 denotes a sensor box in which an optical detection portion for detecting the position of the objective lens is incorporated. The sensor box 107 is located on the opposite side of the optical disk drive motor rotation shaft of the base 108 so that the optical head can enter the inner periphery of the optical disk. It is attached to the side of. This sensor box 1
In FIG. 7, 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 provided substantially in close contact on both sides thereof are provided as shown in FIG. The sensors 202 and 203 are shifted in the optical axis direction, that is, the light receiving sensor 202 is
It is arranged so as to be farther from the printed circuit board (reflector) 104 by a distance d than the reference numeral 03. Also, the light receiving sensor 2
02 and 203 are connected to a differential amplifier (not shown).

Next, the operation of the above-described objective lens position detecting device will be described. First, a light beam b is emitted from the light emitting diode 201 to the printed circuit board (reflector) 104,
The reflected light c from the printed circuit board 104 is used as the light receiving sensor 2
02 and 203 receive and output. This light receiving sensor 20
The output characteristics of 2, 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. Thus, the light receiving sensor 202,
Reference numeral 203 designates an S-shaped objective lens position detection signal as shown in FIG. Get.

When moving the optical head in the radial direction of the optical disk, the tracking servo is removed, and the S
Zero point e (zero cross point) of the character-shaped objective lens position detection signal
Controlling the objective lens holder so as to lock the objective lens in the tracking direction. In this state, the tracking error signal is counted, and the radial position of the optical disk is detected.

[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 accuracy, and the size can be reduced.

[Brief description of 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 partial side view of one embodiment of the objective lens position detecting device of the present invention.

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

FIG. 4 is 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]

 Reference Signs List 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)

(57) [Claims] 1. A base and an objective lens holder movably provided on the base in the focusing and tracking directions, and the light emitting element provided in the base, is located in the optical axis direction at both sides of the light emitting element shape shifted
A pair of light receiving elements provided in the state, the reflector disposed on the light emitting element and a position facing the objective lens holder receives a signal from the pair of light receiving elements, and the pair
The differential of the output from the light receiving element of
And a differential amplifier that detects the position of the
An objective lens position detecting device, comprising: 2. The objective lens position detecting device according to claim 1, wherein the objective lens holder is supported by a spring also serving to supply a drive current, and the reflector is a relay printed circuit board for connecting a focus coil and a tracking coil.