JPH04238120A - Focus position controller - Google Patents

Abstract

PURPOSE:To allow the accurate setting of the control target position signals to maximize information signal amplitudes with the focus position controller of an optical recorder. CONSTITUTION:This device has a means 12 which measures the information signal amplitudes in the plural different control target positions and stores the results thereof, a means 13 which approximates a quadratic curve from the stored plural information signal amplitudes and a means 1 sets the control target positions from the max. value of the approximated quadratic curve.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an optical recording device for recording and reproducing information signals from a disk-shaped recording medium in which information signals are recorded in concentric or spiral tracks in an optically detectable manner. The present invention relates to a focal position control device used for.

0002

2. Description of the Related Art In recent years, for example, optical recording devices have been used for recording and reproducing video signals and audio signals. below,
An example of a conventional focal position control device used in the above-mentioned optical recording device will be described with reference to the drawings.

FIG. 3 shows the configuration of a conventional focus position control device. In FIG. 3, 20 is a recording medium on which information signals are recorded, 21 is a spindle motor that rotates the recording medium, 22 is a light beam source, 23 is an objective lens that condenses the light beam, 24 is a half mirror, and 25 is a Lens driving means for moving the objective lens 23 to change the focal position; 26 is a light receiving element that receives reflected light from the recording medium 20 via the half mirror 24; 27 is information signal detection means; 28 is focal position signal detection. means, 29 is phase compensation means;
30 is control target position setting means.

The operation of the focal position control mechanism constructed as described above will be explained below. First, a light source 22 is placed on the recording medium 20 rotated by the spindle motor 21.
The light beam emitted from the recording medium 20 is focused by the objective lens 23, and is irradiated onto the recording surface of the recording medium 20 and reflected. The direction of this reflected light is changed by the half mirror 24,
It hits the light receiving element 26. A signal indicating the amount of light detected by the light receiving element 26 is converted into an information signal by the information signal detection means 27, and is also converted into a focus position signal by the focus position signal detection means 28. Focus position signal detection means 28
The difference between the focal position signal detected by the control target position setting means 30 and the target position signal set by the control target position setting means 30 is transmitted to the lens driving means 25 through the phase compensation means 29. The lens driving means 25 moves the objective lens 23 to align the focal position of the light beam on the recording surface of the recording medium 20.

Next, setting of a target position signal in a conventional example will be explained using FIG. (a) of FIG. 4 shows the relationship between the focal position of the light beam with respect to the recording surface of the recording medium 20 and the focal position signal detected by the focal position signal detection means 28, and (b) shows the relationship between the focal position and the information The relationship with the amplitude of the information signal detected by the signal detection means 27 is shown. If control is performed using the magnitude of the focal position signal in FIG. 4(a), which corresponds to the focal position where the information signal amplitude is maximum in FIG. 4(b), as the target position signal, the amplitude of the information signal will be the maximum. Become. Therefore, the amplitude of the information signal is measured while changing the target position signal manually or automatically, and the target position signal is set so that the amplitude is maximized.

[0006] As described above, even in the above-mentioned conventional focus position control device, the amplitude of the information position signal is measured while changing the control target position signal, and the control target signal is set so that the amplitude is maximized, thereby recording. Information signals recorded on the medium can be detected with maximum strength.

[0007]

[Problems to be Solved by the Invention] However, with the above configuration, the information signal amplitude cannot actually be measured accurately due to scratches or defects on the recording medium, misalignment due to vibrations, or noise in the circuit. Therefore, there is a problem in that the control target position signal cannot be accurately set at the position where the information signal amplitude is maximum. Although it is possible to increase the setting accuracy by measuring the information signal amplitude many times and averaging it, the problem is that as the accuracy increases, the information signal amplitude measurement time takes longer, and in reality, sufficient setting accuracy cannot be achieved due to time constraints. was there.

The present invention solves these conventional problems by accurately determining a control target position signal that maximizes the amplitude of the information signal and extracting the information signal with maximum strength. The object of the present invention is to provide a focus position control device for an optical recording device.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the focus position control device of the present invention includes means for measuring the amplitude of an information signal at a plurality of different control target positions and recording the results. 2 from the amplitudes of the multiple information signals
The apparatus includes means for approximating a quadratic curve, and means for setting a control target position from the maximum value of the approximated quadratic curve.

0010

[Operation] According to the above configuration, the present invention stores a plurality of information signal amplitudes at different control target positions by means of storing measurement results of information signal amplitudes, and uses the measurement results to store information signal amplitudes at different control target positions. By approximating the change in a quadratic curve and determining the control target position from its maximum value, it is possible to accurately set the target position signal even if the measured information signal amplitude contains an error.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a focal position control device for an optical recording apparatus in one embodiment of the present invention. In FIG. 1, 1 is a recording medium on which information signals are recorded, 2 is a spindle motor that rotates the recording medium, 3 is a light beam source, 4 is an objective lens that focuses the light beam, 5 is a half mirror, and 6 is a spindle motor that rotates the recording medium. Lens driving means for moving the objective lens 4 to change the focal position; 7 a light receiving element for receiving reflected light from the recording medium 1 via the half mirror 5; 8 information signal detection means; 9 focal position signal detection. 10 is a phase compensation means, 11 is a control target position setting means, 12 is an information signal amplitude measurement and storage means, and 13 is a curve approximation means.

The operation of the focal position control device constructed as described above will be explained with reference to FIGS. 1 and 2. First, a laser beam emitted from a light source 3 is applied to a recording medium 1 rotated by a spindle motor 2 through an objective lens 4.
The light is condensed by the light beam, and is irradiated onto the recording surface of the recording medium 1, where it is reflected. The direction of this reflected light is changed by the half mirror 5 and hits the light receiving element 7. A signal indicating the amount of light detected by the light receiving element 7 is converted into an information signal by the information signal detection means 8, and is also converted into a focus position signal by the focus position signal detection means 9. The difference between the position signal detected by the focus position signal detection means 9 and the target position signal set by the control target setting means 11 is transmitted to the lens driving means 6 through the phase compensation means 10. The lens driving means 6 moves the objective lens 4 to align the focal position of the laser beam on the recording surface of the recording medium 1.

In order to set the control target position signal, the control target position is changed at predetermined position intervals,
The information signal amplitude at each target position is measured and stored in the information signal amplitude measurement storage means 12. Based on the measurement results stored in the measurement storage means 12, the relationship between the control target position and the information signal amplitude is approximated to a quadratic curve by the curve approximation means 13.

FIG. 2 shows that 15 control target positions are set, the information signal amplitude is measured, and the results stored in the storage means 12 are approximated to a quadratic curve by the curve approximation means 13 to determine the control target position and the information signal. This is a graph showing the relationship with amplitude. If the control target position is set at the position where the signal amplitude of the approximate curve is maximum, that is, the position shown by the broken line in Figure 2, even if the measurement result contains an error, the control target where the information signal amplitude is maximum can be achieved with high accuracy. A position signal can be set.

[0015]

As described above, according to the present invention, there is provided a means for measuring information signal amplitudes at a plurality of different control target positions and storing the results, and a quadratic curve obtained from the plurality of stored information signal amplitudes. and means to set the control target position from the maximum value of the approximated quadratic curve, so even if the measured information signal amplitude contains an error, the control target position signal can be accurately determined This has the effect of allowing settings to be made.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a focal position control device in an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the information signal amplitude and control target position obtained by curve approximation in an embodiment of the present invention.

[Fig. 3] Schematic block diagram of a conventional focal position control device

FIG. 4 (a) is a graph showing the relationship between the focal position signal and the focal position in a conventional example; (b) is a graph showing the relationship between the information signal amplitude and the focal position;

[Explanation of symbols]

1 Recording medium 2 Spindle motor 3. Light beam source 4 Objective lens 5 Half mirror 6 Lens driving means 7 Photo receiving element 8 Information signal detection means 9 Focus position signal detection means 10 Phase compensation means 11 Control target position setting means 12 Information signal amplitude measurement storage means 13 Curve approximation means

Claims (1)

[Claims] 1. Means for rotating a disk-shaped recording medium on which information signals are recorded in concentric or spiral tracks in an optically detectable manner; and a light source for irradiating the recording medium with a light beam. an optical system for guiding and condensing a light beam so that the light beam is focused on the signal recording surface of the recording medium; a position control means for causing the position of the focal point to follow the signal recording surface; and reflection on the recording surface. a means for detecting an information signal from a light beam irradiated on a signal recording surface; a means for detecting a focal position signal from a light beam irradiated on a signal recording surface; and a means for measuring the amplitude of the information signal at a plurality of different control target positions and storing the results. an optical recording device comprising: means for approximating a quadratic curve from the amplitudes of a plurality of stored information signals; and means for setting a control target position from the maximum value of the approximated quadratic curve. Focus position control device.