JPH06139583A - Optical disk device - Google Patents

Abstract

PURPOSE:To obtain a proper focus offset in an optical disk device. CONSTITUTION:The offset is added to a focus servo by a focus offset adjustment circuit 109 in the state that a focus servo loop is closed. Then, the offset amount of the focus servo is set to the intermediate value between the offset amount where the modulation factor of a regenerative signal becomes a maximum by a modulation factor detection circuit 110 and the offset amount where the peak value of a tracking error signal becomes a maximum by a tracking error detection circuit 107. Thus, focus servo control is performed stably.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus servo offset adjusting device for a recording / reproducing device for a rotary recording medium.

[0002]

2. Description of the Related Art In an optical disc device for recording and reproducing information recording discs having spiral or concentric recording tracks such as video discs and digital audio discs, the optical disc is generally converted into a light beam of laser light by surface vibration of the optical disc. Since it fluctuates in a parallel direction, it is indispensable to have a focus servo device that accurately follows the focal position of the laser light on the optical disk surface.

In the case of adjusting the focus offset in the focus servo control of such an optical disc device, in the conventional optical disc device, Japanese Patent Laid-Open No. 4-85728 is used.
The focus offset value that maximizes the degree of modulation of the reproduced signal is set as the optimum offset value, or the focus offset value is set so that the peak value of the tracking error signal is maximized as in JP-A-3-296924. It was set.

[0004]

In the conventional optical disk device, the focus offset value which maximizes the modulation degree of the reproduction signal or maximizes the peak value of the tracking error signal is used as the set value, so that it is truly optimum. There was a problem that the focus offset value could not be set.

Therefore, it is an object of the present invention to optimize the focus offset value and improve the stability of the servo control system.

[0006]

In order to solve the above problems, the present invention provides a device for detecting the time when the irradiation position of laser light crosses a track, and an irradiation position of the laser light existing on the track. A detection device, a switch for opening and closing the tracking servo loop, and a controller for opening and closing the switch are provided.

[0007]

By changing the focus offset value with the focus servo closed, the offset value that maximizes the modulation of the reproduced signal is obtained. Next, similarly, the focus offset value is changed to obtain an offset value that maximizes the peak value of the tracking error signal. An intermediate value between the two offset values is calculated and used as the focus offset setting value.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment used in the optical disk device of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of the embodiment. The optical disk medium 101 has spiral tracks, and the track interval is 1.5 μm. In addition, the spindle motor 1
It is rotationally driven by 02 at a speed of 3600 rotations per second. Recording and reproduction of information with respect to the optical disc medium 101 is performed by the optical head 103. This optical head 1
Reference numeral 03 denotes a laser light source, an optical system including an objective lens that focuses the laser light on the optical disk medium, a photodetector that detects the amount of light reflected from the optical disk by the laser irradiation light, and the laser light irradiation position to follow the track. A tracking actuator 115 that drives the objective lens in the radial direction of the optical disc medium, a focus actuator 116 that drives the objective lens in the optical axis direction of the laser beam in order to make the focal position of the laser beam follow the surface of the optical disc medium, and the like are built-in. . The optical head 103 is the course actuator 1 in the radial direction of the optical disc medium 101.
It can be moved by 12.

From the optical head 103 to the optical disk medium 101
The laser light is radiated on the optical disk 101, and the amount of the laser light reflected by the optical disk 101 is converted into a voltage change in the sensor amplifier 104 as an electric signal that is a current change in the optical head 103. Next, the reproduced signal is extracted from the output of the sensor amplifier by the reproduced signal detection circuit 105 and digitized by the analog-digital converter 106. The digitized reproduction signal is output to the tracking error detection circuit 107.
A tracking error signal is generated by the phase / gain compensation circuit 108, and phase compensation and gain compensation are performed by the phase / gain compensation circuit 108.
3 is output as a drive signal for driving the objective lens in the radial direction of the optical disc 101 to the tracking actuator 115. The tracking error signal is simultaneously output to the focus offset adjustment circuit 109,
The peak value of the tracking error signal with respect to the focus offset value is detected. The modulation degree of the digitized reproduction signal is measured by the modulation degree detecting circuit 110 and is similarly output to the focus offset adjusting circuit 109 to obtain the modulation degree of the reproduction signal with respect to the focus offset. On the other hand, the focus error detection circuit 116 generates a focus error signal from the output from the sensor amplifier, the phase / gain compensation circuit 117 performs phase compensation and gain compensation, adds the offset value from the focus offset adjustment circuit, and drives the drive amplifier 114. The output signal is output to the focus actuator 116 in the optical head 103 as a drive signal for driving the objective lens in the focus direction of the optical disc 101.

Here, the focus offset adjusting circuit 10
Reference numeral 9 measures the modulation degree of the reproduction signal and the peak value of the tracking error signal while changing the output of the offset value to the focus servo while the focus servo loop is closed. The focus offset value that maximizes the modulation of the reproduction signal is stored, and the focus offset value that maximizes the peak value of the tracking error signal is recorded in the same manner. An intermediate value between the two offset values is used as the focus offset value. By outputting, the optimum focus offset output can be obtained.

FIG. 2 shows the spot shape of the irradiation light near the focal point. At the focal point 201, the spot has a substantially circular shape, but when the spot is displaced, that is, with an offset, the spot becomes an elliptical shape.

3 and 4 show the relationship with the pits on the optical disk medium when an offset is added to the focus servo and the irradiation light spot has an elliptical shape. Each of the figures shows a sample mark on one track of the sample servo format. However, when the major axis direction of the irradiation light spot 301 is perpendicular to the track direction as shown in FIG. 3, the degree of modulation of the reproduction signal is large. Therefore, the peak of the tracking error signal becomes large when the major axis direction of the irradiation light spot 401 is horizontal to the track direction as shown in FIG. FIG. 5 and FIG. 6 are diagrams respectively showing the modulation factor of the reproduction signal and the peak value of the tracking error signal due to the offset added to the focus servo. As shown in FIG. 5, the degree of modulation of the reproduction signal has a maximum value at a point offset from the in-focus point, and the peak value of the tracking error signal has an offset opposite to the degree of modulation of the reproduction signal as shown in FIG. Has a maximum at the point with. Therefore, the value of the offset to be set is between the point where the degree of modulation of the reproduction signal is maximum and the point where the peak value of the tracking error signal is maximum.

[0014]

As described above, according to the present invention, in the offset setting of the focus servo, the offset amount showing the maximum modulation degree of the reproduction signal and the offset amount showing the maximum peak of the tracking error signal are set to be intermediate. As a result, it is possible to achieve stable servo as compared with the conventional focus setting method of focus servo control.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a servo circuit of an optical disc device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an irradiation light spot shape in the vicinity of an in-focus point and a focus servo offset.

FIG. 3 is a diagram showing a case where a major axis direction of an irradiation light spot on a track of an optical disc of a sample servo format is perpendicular to the track direction.

FIG. 4 is a diagram showing a case where a major axis direction of an irradiation light spot on a track of an optical disc of a sample servo format is horizontal to the track direction.

FIG. 5 is a diagram showing a change in modulation degree of a reproduction signal due to changing a focus offset.

FIG. 6 is a diagram showing a change in peak value of a tracking error signal due to changing a focus offset.

[Explanation of symbols]

101 ... Optical disc, 102 ... Spindle motor, 10
3 ... Optical head, 104 ... Sensor amplifier, 105 ... Reproduction signal detection circuit, 106 ... Analog-digital converter, 10
7 ... Tracking error detection circuit, 108 ... Phase / gain compensation circuit, 109 ... Focus offset adjustment circuit,
110 ... Modulation degree detection circuit, 112 ... Coarse actuator, 113 ... Drive amplifier, 114 ... Drive amplifier, 115 ... Tracking actuator, 116 ... Focus actuator, 201 ... Focus point of irradiation light spot, 301 ... Irradiation light spot, 401 ... Irradiation Light spot.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Saburo Yasukawa 4026 Kuji Town, Hitachi City, Ibaraki Prefecture, Hitate Works Ltd., Hitachi Research Laboratory (72) Inventor Nobuyoshi Tsuboi 4026 Kuji Town, Hitachi City, Ibaraki Prefecture, Nitate Works Co., Ltd. Inside Hitachi Research Laboratory (72) Inventor Tatsuya Sugita 4026 Kuji Town, Hitachi City, Hitachi City, Ibaraki Prefecture

Claims (4)

[Claims] 1. An optical information recording medium having concentric or spiral tracks, an objective lens for converging irradiation light on the surface of the optical information recording medium, and reflection of the irradiation light by the optical information recording medium. A reproduction signal detector for obtaining a reproduction signal by detecting the generated light, a modulation degree detector for obtaining the modulation degree of the reproduction signal from the reproduction signal detector, a center of the track and the objective lens A tracking error detector that detects a tracking error that is a relative position deviation from the irradiation position of the irradiation light; a tracking error amplitude detector that obtains the tracking error amplitude from the tracking error detector; Of the optical information recording medium, and a tracking controller for moving the objective lens in the tracking direction to perform tracking servo. And a focus error detector that detects a focus error that is a relative position deviation between the focus of the irradiation light focused by the objective lens and the light of light that passes through the objective lens based on the focus error. In an optical disc device having a focus controller for performing focus servo by moving in a focus direction parallel to an axis, an offset adjustment for varying an offset in the focus control according to values of the modulation degree detector and the tracking error amplitude detector. An optical disk device characterized by being provided with a container. 2. The output value of the offset is an optimum offset value in the focus control according to the value of the modulation degree detector and an optimum offset value in the focus control according to the value of the tracking error amplitude detector. 2. The optical disk device according to claim 1, wherein the intermediate value of the two is set as the set value. 3. The optical disk device according to claim 1, wherein the output value of the offset makes the shape of the irradiation light spot on the optical disk medium approximate to a perfect circle. 4. The optical disk device according to claim 1, wherein the output value of the offset is used as an optimum offset value for use in a finite optical system.