JP2008217885A - Method and apparatus for positioning photodetector substrate for optical pickup - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform focus adjustment (positioning of a photodetector substrate in the direction of an optical axis with respect to an objective lens) on the focus condition that the RF signal of an optical pickup is maximized. <P>SOLUTION: This apparatus is provided with a bias voltage application circuit 21 which applies a predetermined focus bias voltage to the focus actuator 12 of the objective lens 11, a disturbance signal generation circuit 22 which generates a sinusoidal disturbance signal and superimposes it on the focus bias voltage, a peak-to-peak value detection circuiit 23 which detects the peak-to-peak value of the RF signal outputted from the photodetector substrate 15, and a disturbance component extraction circuit 24 which performs synchronous detection of the output signal with the disturbance signal to extract a disturbance component. Thus, the photodetector substrate 15 is positioned in the direction of the optical axis with respect to the objective lens 11 so that the added value of respective positive and negative amplitude values of the disturbance component may become almost zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method and apparatus for adjusting the position of a light receiving element substrate in an optical pickup, and more particularly to a technique for adjusting the position of a light receiving element substrate with respect to an objective lens after assembly of the optical pickup.

  The optical pickup drives a laser light source, an objective lens that irradiates the laser light source toward the optical disc through a half mirror, a light receiving element substrate that receives reflected light from the optical disc through the objective lens and the half mirror, and an objective lens. A focus actuator or the like is provided as a basic component, and various adjustments are made after the assembly.

  One of the adjustment items is the position adjustment of the light receiving element substrate in the optical axis direction with respect to the objective lens. Conventionally, for this position adjustment, for example, a jitter characteristic evaluation method described in Patent Document 1 is applied, and an example thereof will be described with reference to FIGS.

  During this position adjustment, the focus servo control system is turned off, a predetermined focus bias voltage Va is output from a bias voltage application circuit (not shown), and a sine wave disturbance signal is superimposed on the focus bias voltage Va from the disturbance signal generation circuit 6. Applied to the focus actuator 1.

  As a result, the reflected light from the optical disk D is reflected in a state where an objective lens (not shown) included in the optical system 2 vibrates in the optical axis direction according to the amplitude of the disturbance signal with reference to the position corresponding to the focus bias voltage Va. It is detected by a light receiving element substrate including a photodiode (not shown) included in the optical system 2 and is output as an information reproduction signal (RF signal).

  This information reproduction signal is input to the jitter meter 3. Since the information reproduction signal varies due to the disturbance signal, the jitter value output from the jitter meter 3 also varies accordingly.

  Therefore, a disturbance component extraction circuit (synchronous detection circuit) 4 at the next stage extracts (detects) a signal including the same frequency component as the disturbance signal from the output signal of the jitter meter 3 and gives it to the focus characteristic detection circuit 5.

  As shown in FIG. 6A, the focus characteristic detection circuit 5 detects the jitter amount a at one peak and the jitter amount b at the other peak of the disturbance signal, as shown in FIG. 6B. In addition, a focus bias voltage Vb that minimizes the jitter amount (a = b) is output as a focus adjustment signal.

  In the light receiving element substrate position adjusting step, the position of the light receiving element substrate in the optical axis direction with respect to the objective lens is adjusted so that the focus adjustment signal becomes zero. Thereby, the focus characteristic of the jitter value with respect to the disturbance becomes the best.

Japanese Patent Laid-Open No. 2003-99960

  However, the focus condition that maximizes the output signal (RF signal) of the optical pickup may be different from the focus condition that yields the best jitter value, so focus adjustment should be performed under the focus condition that maximizes the RF signal. Cannot be handled by the above-mentioned conventional technology.

  Accordingly, an object of the present invention is to enable focus adjustment (position adjustment of the light receiving element substrate in the optical axis direction with respect to the objective lens) under a focus condition that maximizes the RF signal of the optical pickup.

  In order to solve the above-mentioned problems, an invention according to claim 1 includes an objective lens that irradiates light from a light source toward an optical disc, and a light-receiving element substrate that receives reflected light from the optical disc via the objective lens. A bias voltage application circuit for applying a predetermined focus bias voltage to the focus actuator in a method of adjusting the position of a light receiving element substrate in an optical pickup including a focus actuator that drives the objective lens in a direction in which the objective lens approaches and moves away from the optical disk A disturbance signal generation circuit for generating a disturbance signal having a predetermined frequency that swings in the positive and negative directions with the same amplitude around the zero point and superimposing it on the focus bias voltage, and a peak of the information reproduction signal output from the light receiving element substrate A peak-to-peak value detection circuit for detecting a to-peak value, and the above A disturbance component extraction circuit for synchronously detecting the output signal of the peak-to-peak value detection circuit with the disturbance signal and extracting the disturbance component, and each positive and negative amplitude of the disturbance component extracted by the disturbance component extraction circuit The position in the optical axis direction of the light receiving element substrate with respect to the objective lens is adjusted so that an added value of the values becomes substantially zero.

  According to a second aspect of the present invention, there is provided an objective lens that irradiates light from a light source toward the optical disc, a light receiving element substrate that receives reflected light from the optical disc via the objective lens, and the objective lens. An apparatus for adjusting a position of a light receiving element substrate in an optical pickup including a focus actuator driven in a direction approaching and moving away from the optical disc, a bias voltage applying circuit for applying a predetermined focus bias voltage to the focus actuator, and a zero point A disturbance signal generation circuit that generates a disturbance signal having a predetermined frequency swinging with the same amplitude in the positive and negative directions as a center and superimposes it on the focus bias voltage, and a peak-to-peak value of an information reproduction signal output from the light receiving element substrate Detecting peak-to-peak value detection circuit and the above peak-to-peak value A disturbance component extraction circuit that synchronously detects an output signal of the value detection circuit with the disturbance signal and extracts a disturbance component; a substrate position adjustment unit that adjusts the position of the light receiving element substrate with respect to the objective lens in the optical axis direction; Control means for controlling the substrate position adjusting means, wherein the control means is arranged such that the sum of positive and negative amplitude values of the disturbance component extracted by the disturbance component extraction circuit is substantially zero. The position of the light receiving element substrate in the optical axis direction with respect to the objective lens is adjusted via an adjusting means.

  According to the present invention, the peak-to-peak value of the information reproduction signal output from the light-receiving element substrate is detected, the peak-to-peak output is detected by the disturbance signal, and the disturbance component is extracted, and the disturbance is extracted. An information reproduction signal (output signal; RF signal) of the optical pickup is adjusted by adjusting the position of the light receiving element substrate in the optical axis direction with respect to the objective lens so that the added value of the positive and negative amplitude values of the components becomes substantially zero. Focus adjustment can be performed under the maximum focus condition.

  Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the configuration of a position adjusting device for a light receiving element substrate in an optical pickup of the present invention, FIG. 2 is a waveform diagram showing signal waveforms appearing in the parts (a) to (e) of FIG. 3B is a waveform diagram showing signal waveforms appearing in FIGS. 1D and 1E when the focus adjustment is not complete, and FIG. 4 is a chart showing the relationship between the information reproduction signal (RF signal) and the disturbance signal.

  With reference to FIG. 1, first, the configuration of the optical pickup 10 will be schematically described. The optical pickup 10 basically has an objective lens 11 arranged with the optical axis substantially perpendicular to the information recording surface of the optical disk M that is rotationally driven by a spindle motor M, a laser light source 13, and a light receiving element. And a substrate 15.

  The objective lens 11 is driven in the optical axis direction by the focus actuator 12. The tracking actuator is not shown. The light emitted from the laser light source 13 passes through the half mirror 14 and the objective lens 11 and is irradiated onto the information recording surface of the optical disc M as a laser beam.

  The light receiving element substrate 15 is disposed on the optical axis of the objective lens 11 and receives the reflected light from the information recording surface of the optical disc M via the objective lens 11 and the half mirror 14. For the light receiving element substrate 15, for example, a quadrant type photodiode array substrate is used.

  Various adjustments are made after the optical pickup 10 is assembled. The light receiving element substrate 15 is adjusted in the XY direction orthogonal to the optical axis and in the Z axis direction along the optical axis. Applies to direction adjustment.

  The light receiving element substrate position adjusting device 20 of the present invention includes a bias voltage applying circuit 21 and a disturbance signal generating circuit 22 for driving the focus actuator 12. This position adjustment is performed with the focus servo control system turned off.

  Further, the position of the light receiving element substrate 15 in the Z-axis direction is adjusted by the substrate position adjusting means 26. In this example, the substrate position adjusting means 26 includes a jig 261 that supports the light receiving element substrate 15 and a stepping motor 262 having a feed screw shaft that finely moves the jig 261 in the Z-axis direction.

  The bias voltage application circuit 21 outputs a predetermined focus bias voltage (DC voltage). The disturbance signal generation circuit 22 outputs a disturbance signal (sine wave) having a predetermined frequency that swings in the positive and negative directions with the same amplitude around the zero point as shown in FIG. Hereinafter, (a) in FIG. 2 (a) is taken as a disturbance signal (a).

  A drive signal in which the disturbance signal (a) is superimposed on the focus bias voltage Vb is applied to the focus actuator 12, whereby the objective lens 11 outputs the disturbance signal (a) with reference to the position corresponding to the focus bias voltage. It vibrates in the optical axis direction according to the amplitude.

  The light receiving element substrate 15 receives reflected light from the information recording surface of the optical disc M, and outputs an information reproduction signal (RF signal) contained therein. This RF signal fluctuates as shown in FIG. 2B due to the influence of the disturbance signal (a).

  In the present invention, the RF signal output from the light receiving element substrate 15 is input to the peak-to-peak value detection circuit 23. The peak-to-peak value detection circuit 23 detects the peak-to-peak value of the RF signal. This peak-to-peak value signal also varies as shown in FIG. 2C due to the influence of the disturbance signal (a).

  The peak-to-peak value signal detected by the peak-to-peak value detection circuit 23 is input to the disturbance component extraction circuit 24 at the next stage. The disturbance component extraction circuit 24 extracts a disturbance component (variation component) having the same frequency component as the disturbance signal (a) from the peak-to-peak value signal. That is, the disturbance component is extracted by synchronously detecting the peak-to-peak value signal with the disturbance signal (a).

  The disturbance component extracted by the disturbance component extraction circuit 24 is input to the control means 25 at the next stage. For the control means 25, for example, a CPU or a microcomputer may be used.

  As shown in FIG. 2 (d), the disturbance component is a sine wave as with the disturbance signal (a). Therefore, if the focal point of the laser beam exists on the information recording surface of the optical disk, and the focus adjustment is successful, The positive part V (+) and the negative part V (−) of the disturbance component have the same amount of electricity, and the added value is zero output as shown in FIG.

  On the other hand, when the focal point of the laser beam does not exist on the information recording surface of the optical disk, as shown in FIGS. 3a and 3b, V (+) − V (−)> 0 or V (+) −V (−) <0, and the zero output as shown in FIG.

  Therefore, the control unit 25 outputs a focus adjustment signal so that V (+) and V (−) included in the disturbance component are equal. In the present invention, the focus adjustment signal is output to the bias voltage application circuit. Output to the substrate position adjusting means 26 instead of 21 to adjust the position of the light receiving element substrate 15 in the Z-axis direction.

  As a result, as shown in FIG. 4, focus adjustment can be performed under a focus condition that maximizes the RF signal (output signal) of the optical pickup 10. The method using the jitter value described in FIGS. 5 and 6 and the method using the output voltage according to the present invention may be combined and mounted.

The schematic diagram which shows the structure of the position adjustment apparatus of the light receiving element board | substrate in the optical pick-up of this invention. The wave form diagram which shows the signal waveform which appears in the part of (a)-(e) of FIG. The wave form diagram which shows the signal waveform which appears in (d) and (e) of Drawing 1 when focus adjustment is not perfect. The wave form diagram which shows the signal waveform which appears in (d) and (e) of Drawing 1 when focus adjustment is not perfect. The chart which shows the relationship between the information reproduction signal (RF signal) and disturbance signal in embodiment of this invention. The block diagram which shows the prior art example by the jitter characteristic evaluation method. The chart which shows the relationship between the jitter amount in the said prior art example, and a disturbance signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical pick-up 11 Objective lens 12 Focus actuator 13 Laser light source 15 Light receiving element board | substrate 20 Position adjusting apparatus 21 of a light receiving element board | substrate 21 Bias voltage application circuit 22 Disturbance signal generation circuit 23 Peak-to-peak value detection circuit 24 Disturbance component extraction circuit 25 Control Means 26 Substrate position adjusting means

Claims (2)

An objective lens that irradiates light from a light source toward the optical disc, a light receiving element substrate that receives reflected light from the optical disc through the objective lens, and the objective lens is driven in a direction approaching and separating from the optical disc. In a method for adjusting the position of a light receiving element substrate in an optical pickup including a focus actuator
A bias voltage application circuit that applies a predetermined focus bias voltage to the focus actuator, and a disturbance signal generation circuit that generates a disturbance signal having a predetermined frequency that swings in the positive and negative directions with the same amplitude around the zero point and superimposes it on the focus bias voltage A peak-to-peak value detection circuit for detecting a peak-to-peak value of an information reproduction signal output from the light receiving element substrate, and an output signal of the peak-to-peak value detection circuit as the disturbance signal A disturbance component extraction circuit that extracts a disturbance component by synchronous detection, and the sum of positive and negative amplitude values of the disturbance component extracted by the disturbance component extraction circuit is substantially zero. Adjusting the position of the light receiving element substrate in an optical pickup, wherein the position of the light receiving element substrate in the optical axis direction is adjusted . An objective lens that irradiates light from a light source toward the optical disc, a light receiving element substrate that receives reflected light from the optical disc through the objective lens, and the objective lens is driven in a direction approaching and separating from the optical disc. In a position adjustment device for a light receiving element substrate in an optical pickup including a focus actuator
A bias voltage application circuit that applies a predetermined focus bias voltage to the focus actuator, and a disturbance signal generation circuit that generates a disturbance signal having a predetermined frequency that swings in the positive and negative directions with the same amplitude around the zero point and superimposes it on the focus bias voltage A peak-to-peak value detection circuit for detecting a peak-to-peak value of an information reproduction signal output from the light receiving element substrate, and an output signal of the peak-to-peak value detection circuit as the disturbance signal A disturbance component extraction circuit for extracting a disturbance component by synchronous detection, a substrate position adjusting means for adjusting the position of the light receiving element substrate in the optical axis direction relative to the objective lens, and a control means for controlling at least the substrate position adjusting means; With
The control means is configured such that the addition value of the positive and negative amplitude values of the disturbance component extracted by the disturbance component extraction circuit is substantially zero through the substrate position adjustment means to the objective lens with respect to the objective lens. A position adjusting device for a light receiving element substrate in an optical pickup, characterized by adjusting a position in an optical axis direction.

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