JPS61283038A - Lens position detecting device - Google Patents

Abstract

PURPOSE:To permit a simple circuit and to detect easily the position of a condensing lens with respect to an optical head by constituting a detector of two circuits holding positive and negative peak values of a tracking error signal and a circuit outputting the midpoints of their outputs. CONSTITUTION:The track error signal 11 is inputted to the positive and negative peak holding circuits 1 and 2. Their outputs represent the positive and negative envelops 12 and 13 of signal amplitudes, respectively, and show a DC voltage corresponding to a change in the amplitude. When the condensing lens dislocates in the tracking direction with respect to an optical head, the output 14 of the midpoint output circuit 3 outputting midpoints of both signals denotes a position signal in proportion to the dislocation. Accordingly the simple circuit can easily detect the relative dislocation between the optical head and the condensing lens.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an optical information recording/reproducing device that uses optical means to record information on a recording medium or to reproduce information that has already been recorded. In particular, it relates to a tracking control system for the device.

(Prior art and its problems) A laser beam is used as a light source, and this laser beam is modulated with a pulse-like signal from an external information source, and is transmitted to a recording medium on a disk.
In optical information recording and reproducing devices that record numerically or read information that has already been recorded, focus control is used to keep the recording medium surface at the focal point of the condenser lens in order to accurately record or reproduce information. The position of the condensing lens is controlled so that the position Further, in order to control the tracking position of the optical spot of the laser beam with respect to the information track during recording or reproducing information, a guide groove having an optimal depth for the optical spot is provided on the recording medium, and the guide groove is K so that the minute spot is along the line.

Tracking control is being performed.

Furthermore, when moving the light spot between information tracks, that is, moving the light spot over a relatively short distance between tracks in the disk radial direction (number + tracks), the condenser lens is moved one track in the tracking direction (disk radial direction). The optical spot is moved from track to track by track jumping, and when moving between tracks over a long distance, the entire optical head is moved in the tracking direction by a head actuator to move the optical spot over a long distance. is moving. That is, during long-distance inter-track movement, a two-stage control system is used in which the head actuator first performs rough positioning of the light spot, and then the light spot is precisely positioned by moving the condensing lens. However, when moving the entire optical head using a head actuator, in order to achieve high-speed movement, the head actuator must generate large accelerations and decelerations, and the optical head also needs to generate large accelerations and decelerations. Receive the power that comes with it. When the optical head is subjected to forces associated with such large accelerations and decelerations, the position of the condenser lens changes during acceleration and deceleration, as the condenser lens inside the optical head is normally supported by the head base with springs, etc. Large displacement. In particular, the light spot also undergoes damped vibration in the tracking direction due to the damped vibration of the condenser lens in the tracking direction that occurs during deceleration, that is, after the optical head has been roughly positioned. When damped oscillations occur in this manner, precise positioning of the optical spot cannot be performed until the damped oscillations have subsided to some extent, which slows down the positioning of the optical spot onto the target track. Furthermore, if the condensing lens is largely displaced due to this acceleration/deceleration, it may adversely affect the optical system and cause focus control to be lost.

All of these problems occur because the position of the condenser lens relative to the optical head cannot be detected; if a position signal of the condenser lens can be generated, that signal can be used to control the position of the condenser lens. There is no significant shift in the position of the condenser lens.

Regarding this problem, Japanese Patent Application Laid-Open No. 59-193 by the same applicant
Publication No. 553 (Specification of % Application No. 58-68626), Japanese Unexamined Patent Publication No. 193550/1983 (Specification of Patent Application No. 58-6862)
7 specification) and JP-A-59-207439 (
In Japanese Patent Application No. 58-83080), an optical head capable of detecting the position of a condensing lens is proposed. However, these optical heads require a special optical system for detecting the position of the condenser lens, resulting in disadvantages such as increased size of the optical head, high cost, and difficulty in adjustment.

(Object of the Invention) An object of the present invention is to provide a lens position detector that eliminates the above-mentioned drawbacks and can detect the position of the condenser lens with respect to the optical head even in a conventional optical head.

(Structure of the Invention) According to the present invention, the first peak hold circuit holds and outputs the positive peak value of the tracking error signal indicating the position in the tracking direction of the light spot focused on the recording medium; a second peak hold circuit that holds and outputs the negative peak value of the tracking error signal;
and a midpoint output circuit that outputs the midpoint of the two output signals of the first and second peak hold circuits, and when the light spot crosses between tracks, the output of the midpoint output circuit is used as a lens position signal. A lens position detector is obtained which is characterized in that it outputs as follows.

(Example) The present invention will be described in detail below using the drawings. FIG. 1 shows a block diagram of a lens position detector according to the invention. A track error signal detected by a head and an amplifier (not shown) is input to a positive peak hold circuit 1 and a negative peak hold circuit 2, respectively, and the positive peak hold circuit 1 detects the positive peak value of the track error signal. The negative peak hold circuit 2 holds the negative peak value of the track error signal.

At this time, since the positive and negative peak hold circuits usually have some leakage characteristics, the outputs of the positive and negative peak hold circuits represent the positive and negative envelopes of the track error signal amplitude, respectively, and The DC voltage along the width change is shown.

On the other hand, although not shown, a push-pull method is used for the tracking error signal, that is, a method of detecting the diffraction of light by the aforementioned guide groove based on the difference between a two-split optical sensor disposed on the far field.

In this push-pull method, when the condenser lens misaligns with respect to the optical head in the tracking direction, a DC offset occurs in the tracking error signal in proportion to the misalignment. Therefore, receiving the output 12 of the positive peak hold circuit and the output 13 of the negative peak hold circuit,
The output 14 of the midpoint output circuit 3 that outputs the midpoint of both signals is
It represents a lens position signal proportional to the relative positional deviation between the optical head and the condensing lens described above.

FIG. 2 is a diagram showing operation waveforms for easily explaining the operation of the lens position detector of FIG. 1. When the condensing lens is misaligned with respect to the optical head, a negative or positive DC offset is superimposed on the tracking error signal 11 as shown in the figure.

At this time, the output of the positive peak hold circuit 1 shows a positive envelope 12, and the output of the negative peak hold circuit 2 shows a negative envelope 13.

In this way, the center point output circuit 3 outputs the center values of the positive and negative envelopes, and for the reason mentioned above, this center value represents the lens position signal 14 that is proportional to the positional deviation of the collective lens with respect to the optical head. ing.

(Effects of the Invention) As explained above, according to the present invention, it is possible to detect the relative positional deviation between the optical head and the condensing lens without using a special optical system and with a simple circuit. can.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
The figure is a waveform diagram showing the operating waveforms of each part in FIG. 1. In the figure, 1.-Positive peak hold circuit, 2.. Negative peak hold circuit, 3.. Midpoint output circuit, respectively.

Claims (1)

[Claims] Recording information on a recording medium using optical means, or
In an optical information recording/reading device that reads information that has already been recorded, there is a first controller that holds and outputs a positive peak value of a tracking error signal indicating the position in the tracking direction of a light spot focused on a recording medium. a peak hold circuit, a second peak hold circuit that holds and outputs the negative peak value of the tracking error signal, and a midpoint that outputs the midpoint of the two output signals of the first and second peak hold circuits. Consists of an output circuit and
A lens position detector characterized in that when the light spot crosses between tracks, the output of the midpoint output circuit is output as a lens position signal.