JPH076375A - Objective lens position detection circuit for optical disk device - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to accurately detect the position of a lens by avoiding the influence of high-power flare light emitted from a semiconductor laser, which is a light source of a pickup, among disturbance lights. In a position detecting circuit of an objective lens having means for optically detecting a displacement of an objective lens in a direction orthogonal to an optical axis direction by a light source and a plurality of light receiving elements, a light source of displacement amount optical detecting means is turned off. And record / playback /
The offset is removed with the light source used for erasing turned on or off. [Effect] Since the offset including the flare of the light source of the pickup can be canceled, the accurate lens position can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvement of an objective lens position detection circuit for an optical disk device, an optical card device, etc.
In particular, an optical disk device that is not affected by the flare light (stray light) of high power emitted from the semiconductor laser, which is the light source of the pickup, of the ambient light, so that an accurate lens position detection signal can be obtained. Of the objective lens position detection circuit.

[0002]

2. Description of the Related Art In an optical disk device for optically recording and reproducing information, an objective lens is used as a component of an optical system, and the position of this objective lens is controlled so that a light spot is formed at a desired position on the optical disk. I am trying to irradiate. Therefore, conventionally, a light emitting element (such as an LED) and a light receiving element are used to detect the amount of displacement in the direction orthogonal to the optical axis direction of the objective lens (for example, Japanese Patent Laid-Open No. 3-1).
No. 87024).

FIG. 4 is a top view showing a schematic structure of a mechanical section of an objective lens section in a conventional optical disk device. In the figure, 1 is an objective lens, 2 is a lens holder, 3 is a support spring, 4 is a support spring fixing member, 5 is a slit plate, 6 is a light emitting diode (LED), 7 and 8 are light receiving elements, and 9 is a lens position sensor. A housing is shown and A shows the moving direction of the objective lens 1.

The objective lens 1 is movable in a direction perpendicular to the paper surface (optical axis direction) and in a direction indicated by an arrow A (direction perpendicular to the optical axis). It is configured to be movable in the optical axis direction in order to condense the light emitted from the objective lens 1 onto a disk (not shown) placed in a direction horizontal to the paper surface, and the arrow A The reason why it is configured to be movable in the direction of is to allow the light focused on the track on the disk to follow.

This objective lens 1 is supported by a lens holder 2, and the lens holder 2 is further supported by a support spring 3.
It is supported by the support spring fixing member 4. A slit plate 5 is fixed to the lens holder 2 so that a part of the light emitted from the light emitting diode 6 is incident on the light receiving elements 7 and 8 at the opposing positions.

Then, in accordance with the movement of the lens holder 2 in the direction of arrow A, the amount of light incident on each of the two light receiving elements 7 and 8 changes, and the amount of movement of the objective lens 1 in the direction of arrow A is detected. It In FIG. 4, the light emitting diode 6 and the two light receiving elements 7 and 8 form a lens position sensor, and each of these parts is fixed in a predetermined positional relationship by a lens position sensor housing 9.

FIG. 5 is a diagram for explaining a state in which the detection outputs of the two light receiving elements change in the objective lens section shown in FIG. 4 depending on the relative positions of the lens position sensor and the slit plate. Is a normal state in which the objective lens 1 is not moved,
(2) is a diagram showing a state where the slit plate is moved to the right, and (3) is a diagram showing a state where the slit plate is moved to the left. The reference numerals in the figure are the same as those in FIG. 4, and B and C indicate the moving directions of the slit plate 5.

As shown in FIG. 5 (1), in a normal state (the state where the objective lens 1 is not moved), the light emitted from the light emitting diode 6 is incident on the two light receiving elements 7 and 8 by an equal amount of light. To be done. On the other hand, when the slit plate 5 moves to the right (the direction of arrow B) as shown in FIG.
Changes the amount of light received.

The same applies when the slit plate 5 is moved to the left (in the direction of arrow C) as shown in FIG. 5 (3). In the lens position sensor, the position of the objective lens is detected by the difference in the amount of light received by the two light receiving elements 7 and 8 as described above.
In this case, if ambient light enters the light receiving elements 7 and 8, there is a disadvantage that the position of the objective lens cannot be accurately detected.

[0010]

SUMMARY OF THE INVENTION The present invention solves such inconvenience in the conventional objective lens position detection circuit and completely cancels the offset including flare light (stray light) to obtain an accurate lens position. It is an object of the present invention to provide an objective lens position detection circuit of an optical disk device that enables detection of

[0011]

According to the present invention, firstly,
An objective that is a position detection circuit for an objective lens in an optical disk device and that includes a displacement amount optical detection unit that optically detects a displacement of the objective lens in a direction orthogonal to the optical axis direction by a light source and a plurality of light receiving elements. In the lens position detection circuit, a first switch means for turning on / off the light source of the displacement amount optical detecting means, a second switch means for turning on / off the light source used for recording / reproducing / erasing of the optical disc device, and the displacement amount. A detection circuit for amplifying and calculating outputs of a plurality of light receiving elements of the optical detection means and detecting the output; and an offset removing means for removing an offset of the detection circuit,
The offset is removed while the light source of the displacement amount optical detecting means is turned off and the light source used for recording / reproducing / erasing of the optical disk device is turned on or off.

Secondly, the position detecting circuit for the first objective lens is provided with a focus detecting means for detecting that the light emitted from the objective lens is condensed on the optical disk, and the objective lens is substantially compatible. When the focus position is set, the offset is removed.

Thirdly, in the position detecting circuit for the first or second objective lens, when the position detecting circuit for the objective lens is operating, the output power on the objective lens and the output power on the objective lens at the time of offset removal are set. The offset amount is changed according to the ratio of

Fourth, in the position detecting circuit for the second or third objective lens, when the position detecting circuit for the objective lens is in operation, the light receiving element output for receiving the reflected light from the disk during operation and the offset removal The offset amount is changed according to the ratio with the output of the light receiving element that receives the reflected light from the disk at the time.

[0015]

In this invention, the light source for detecting the lens position is turned off and the light source of the pickup is turned on,
By canceling the offset, the offset including the flare of the light source of the pickup is reliably canceled, and the lens position is accurately detected (the invention of claim 1). Also, by canceling the offset at the position where the light emitted from the objective lens is focused on the disc, it is possible to cancel the offset in a state close to the actual operation, so that the lens position can be detected more accurately. (The invention of claim 2).

Further, by canceling the offset in accordance with the light emission power of the light source of the pickup, the flare of the light source of the pickup is sufficiently removed, and the lens position can be accurately detected (claim 3). invention).
In addition, when the flare caused by the light emitted to the disc greatly affects the detection error of the lens position, the offset amount is changed according to the amount of the reflected light from the disc to cancel the offset. The offset is sufficiently removed not only when the light emission power of the light source changes but also when the reflectance of the disc changes, thereby enabling more accurate detection of the lens position (the invention of claim 4). ).

[0017]

Embodiment 1 Next, the objective lens position detection circuit of the optical disk device of the present invention will be described in detail with reference to the drawings. This embodiment mainly corresponds to the invention of claim 1, but is also related to the inventions of claims 2 to 4.

FIG. 1 is a functional block diagram showing an embodiment of the main configuration of the objective lens position detection circuit of the optical disk device of the present invention. Reference numerals in the figure are the same as those in FIG. 4, 11 and 12 are first and second preamplifiers, 13 is an addition circuit, 14 is a subtraction circuit, 15 is a control circuit, 16 is a switch unit, and a to c are Each terminal, 17 is a transistor, 18 is an offset removing circuit, 19 is a D / A converter, 20 is a CPU, 21 is a comparator, 22 is a semiconductor laser lighting circuit, and 23 is a semiconductor laser (LD).

The mechanism of the objective lens is as shown in FIG. 4, and in FIG. 1, only the light emitting diode (LED) 6 and the light receiving elements 7 and 8 are shown. Next, the operation of the objective lens position detection circuit of the present invention shown in FIG. 1 will be described.

After the power is turned on, the CPU 20 operates the switch unit 1
6 is connected to connect its terminals bc, and the transistor 1
7 is turned off so that no current flows through the light emitting diode 6. Further, the CPU 20 turns on the semiconductor laser (LD) 23 with the reproducing power via the semiconductor laser lighting circuit 22.

In this state, since no light from the light emitting diode 6 is incident on the light receiving elements 7 and 8, only flare light (stray light) of the semiconductor laser 23 and light from the outside are incident. The outputs of the light receiving elements 7 and 8 at this time are converted into current-voltage by the first and second preamplifiers 11 and 12, and the subtraction circuit 14 detects the difference signal.

The sum of the obtained difference signal and the output of the D / A converter 19 is obtained by the offset removing circuit 18, and the presence or absence of offset is detected by the comparator 21.
In this case, as a method of removing the offset, the CPU 20
To the offset removal circuit 18 an initial value (for example, A0)
And the output of the comparator 21 at this time is (CPU
20) confirm.

When the output of the comparator 21 is, for example, "H", the value given to the offset removing circuit 18 is increased, and when it is "L", it is decreased. When such an operation is sequentially repeated and the output of the comparator 21 becomes a state of repeating "H" and "L" every time the set value to the offset removing circuit 18 is changed,
This operation ends.

By the above operation, the offset of the offset removing circuit 18 is removed. In other words, even if flare light or ambient light of the semiconductor laser 23 enters the light receiving elements 7 and 8, the output of the lens position sensor (which is composed of the light emitting diode 6 and the two light receiving elements 7 and 8) is , No longer affected.

Next, the CPU 20 controls the switch section 16 to connect the terminals ac to the ON state and to make the first state.
And the outputs of the second preamplifiers 11 and 12 are input to the adder circuit 13 and added. This added output is given to the control circuit 15 to control the transistor 17 to turn on the light emitting diode 6 so that the output of the lens position sensor becomes valid.

By such an operation, the output of the lens position sensor is obtained as a signal that accurately corresponds to the position of the objective lens 1. Next, the CP explained above
The operation of U20 is shown by a flow.

FIG. 2 is a flow chart showing the main processing flow at the time of offset removal in the objective lens position detection circuit of the optical disk device of the present invention. In the figure, # 1 to # 12 indicate steps.

In step # 1, the switch section 16 is controlled to connect its terminals bc. In the next step # 2,
The semiconductor laser 23 is turned on by the reproduction power. Step #
3, the initial value A0 is set in the D / A converter 19.

At step # 4, it is checked whether the output of the comparator 21 is "H". If the output of the comparator 21 is "H", the process proceeds to step # 5, the comparison value COM = 1 is set, the process proceeds to the next step # 7, and if the output is not "H", the step is performed. # 6
The comparison value COM = 0 is set, and the process proceeds to step # 7.

At step # 7, it is determined whether the output of the comparator 21 is equal to the comparison value COM. If the output of the comparator 21 and the comparison value COM are not equal to each other, the process proceeds to step # 8, the switch unit 16 is controlled to connect the terminals a to c, and the flow of FIG. 2 ends.

Further, as a result of the judgment made in the previous step # 7,
When the output of the comparator 21 and the comparison value COM are equal, it is checked in step # 9 whether the comparison value COM = 1. If the comparison value COM = 1, step #
At 10, the value An set in the D / A converter 19 is set to An =
If A (n-1) +1 is not set and COM = 1 is not set, the value An is set to An = A (n-1) -1 in step # 11, and the process proceeds to step # 12.

In step # 12, the value An is set in the D / A converter 19, the process returns to the previous step # 7, and the same operation is repeated. When the output of the comparator 21 alternates between "H" and "L" every time the set value An of the D / A converter 19 is changed, the flow of FIG. 2 is ended.

[0033]

Second Embodiment Next, a second embodiment will be described. This embodiment corresponds to the inventions of claims 2 to 4. The second embodiment is characterized in that the objective lens removes the offset at the position where the semiconductor laser light is focused on the disk.

FIG. 3 is a functional block diagram showing a second embodiment of the essential structure of the objective lens position detection circuit of the optical disk device of the present invention. Reference numerals in the figure are the same as those in FIG. 1, and reference numeral 24 represents a register.

In FIG. 3, the register 2 newly added is added.
Reference numeral 4 is a register for latching the output (digital signal) of the comparator 21. The latch timing is determined by a timing signal. The timing signal moves the objective lens 1 in the vertical direction (direction to move away from or approach to the medium), and a signal detection system (not shown) of the pickup. ) Is generated by the detection signal when the output signal becomes higher than a predetermined value.

By constructing as shown in FIG. 3,
The objective lens 1 can remove the offset at the position where the semiconductor laser beam is focused on the disc, and the lens position is accurately detected even when the semiconductor laser beam irradiated on the disc becomes flare. It is possible (the invention of claim 2). Further, when the light emission power of the semiconductor laser 23 is changed like the power-up for erasing (erasing power Pe), the data given to the D / A converter 19 can be changed as follows, for example. Good.

First, the light emitting diode 6 and the semiconductor laser 23 are both turned off to remove the offset of only the circuit system. Here, the data given to the D / A converter 19 is X0.

Second, the light emitting diode 6 is turned off and the semiconductor laser 23 is turned on (reproduction power Pr is set) to remove the offset. At this time, the data given to the D / A converter 19 is X1.

Thirdly, when the semiconductor laser 23 has the reproduction power Pr, the data X1 is given to the D / A converter 19. Fourthly, when the semiconductor laser 23 is caused to emit light with the erasing power Pe, (X1-X0) * (Pe / Pr) + X0 is given as data given to the D / A converter 19.

By performing such control, even if the emitted light from the semiconductor laser 23 out of the disturbance light incident on the two light receiving elements 7 and 8 is changed, its influence is eliminated, and the accurate lens is obtained. The position of can be detected. Further, when the offset of the output of the lens position sensor is removed while the light emitted from the semiconductor laser 23 is focused on the disk surface, the output signal level of the signal detection system of the pickup at the time of canceling this offset is detected. Then, the data supplied to the D / A converter 19 may be changed in proportion to the detection level.

With this control, even when the emitted light of the semiconductor laser 23 applied to the disk surface is dominant among the disturbance light incident on the two light receiving elements 7 and 8, the semiconductor laser 23 emits light. It is possible to detect the lens position in a stable manner even when the power changes or the reflectance of the disk fluctuates (inventions 3 and 4).

In the above first and second embodiments, the case where the offset of the output of the subtraction circuit 14 of FIG. 1 or 3 is removed has been described. However, the offset of the output of the adder circuit 13 can be removed instead of the output of the subtractor circuit 14, and the present invention is not limited to the case described in the embodiment.

[0043]

According to the position detecting circuit of the objective lens of the first aspect, the light source for detecting the lens position is turned off and the light source of the pickup is turned on to cancel the offset. Therefore, it is possible to cancel the offset including the flare of the light source of the pickup, and it is possible to accurately detect the lens position.

In the objective lens position detecting circuit according to the second aspect, in addition to the function of the objective lens position detecting circuit according to the first aspect, the offset at the position where the light emitted from the objective lens is focused on the disk is provided. I have canceled. Therefore, it is possible to cancel the offset in a state close to the actual operation, so that it is possible to detect the lens position more accurately.

In the objective lens position detecting circuit of the third aspect, in addition to the function of the objective lens position detecting circuit of the first or second aspect, the offset is canceled according to the light emission power of the light source of the pickup. There is. Therefore, the flare of the light source of the pickup is sufficiently removed,
The lens position can be accurately detected.

In the objective lens position detecting circuit according to the fourth aspect, in addition to the function of the objective lens position detecting circuit according to the second or third aspect, flare caused by the light emitted to the disc causes a lens position detection error. When there is a large influence, the offset amount is changed according to the amount of reflected light from the disc to cancel the offset. Therefore, the offset is sufficiently removed not only when the light emission power of the light source of the pickup changes but also when the reflectance of the disc changes, so that the lens position can be detected more accurately.

[Brief description of drawings]

FIG. 1 is a functional block diagram showing an embodiment of a main part configuration of an objective lens position detection circuit of an optical disk device of the present invention.

FIG. 2 is a flowchart showing a main processing flow at the time of offset removal in the objective lens position detection circuit of the optical disk device of the present invention.

FIG. 3 is a functional block diagram showing a second embodiment of the configuration of the main part of the objective lens position detection circuit of the optical disk device of the present invention.

FIG. 4 is a top view showing a schematic configuration of a mechanical section of an objective lens section in a conventional optical disc apparatus.

5 is a diagram illustrating a state in which detection outputs of two light receiving elements change in the objective lens section shown in FIG. 4 depending on a relative position between a lens position sensor and a slit plate.

[Explanation of symbols]

 11 First Preamplifier 12 Second Preamplifier 13 Addition Circuit 14 Subtraction Circuit 15 Control Circuit 16 Switch Unit 17 Transistor 18 Offset Removal Circuit 19 D / A Converter 20 CPU 21 Comparator 22 Semiconductor Laser Lighting Circuit 23 Semiconductor Laser 24 Register

Claims (4)

[Claims] 1. A displacement amount optical detection which is a position detection circuit of an objective lens in an optical disk device and optically detects displacement of the objective lens in a direction orthogonal to an optical axis direction by a light source and a plurality of light receiving elements. In a position detection circuit for an objective lens including means, first switch means for turning on / off the light source of the displacement amount optical detection means, and second switch means for turning on / off the light source used for recording / reproducing / erasing of the optical disk device. A displacement amount optical detection means for amplifying and calculating outputs of a plurality of light receiving elements of the displacement amount optical detection means, and an offset removing means for removing an offset of the detection circuit. The offset is removed with the light source of the optical disc device turned off and the light source used for recording / reproducing / erasing of the optical disk device turned on or off. Objective lens position detecting circuit according to claim. 2. The objective lens position detection circuit according to claim 1, further comprising focus detection means for detecting that the light emitted from the objective lens is condensed on the optical disc, wherein the objective lens is substantially in focus. An objective lens position detection circuit characterized by removing an offset when in position. 3. The position detection circuit for an objective lens according to claim 1, wherein the output power on the objective lens when the position detection circuit for the objective lens is operating and the output power on the objective lens when the offset is removed. A position detection circuit for an objective lens, characterized in that the offset amount is changed according to the ratio. 4. The position detection circuit for an objective lens according to claim 2, wherein when the position detection circuit for the objective lens is in operation, a light-receiving element output for receiving reflected light from the disk during operation and when offset is removed. The position detection circuit for the objective lens, wherein the offset amount is changed according to the ratio to the output of the light receiving element that receives the reflected light from the disk.