JPS6132732B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a track detection control device for optically detecting information on a high-density recording medium in a non-contact manner and performing track tracking control in reproduction of a high-density recording medium.

In optical high-density recording and reproducing devices such as video disks, micron-order uneven grooves (hereinafter referred to as pits) are sequentially arranged in a spiral or concentric pattern on a high-density recording medium (hereinafter referred to as a disk). It is recorded as a track, and therefore, in order to reproduce it with a light spot on the order of microns, it is necessary to accurately irradiate the light spot onto the track. However, it is quite conceivable that there will be eccentricity or meandering with respect to the center of rotation when the disk is attached, so it is necessary to make the light spot follow the track correctly by some method.

In a pickup device that includes a light source section, a condensing means, and a detection means in one lens barrel and is equipped with a driving section that controls focus and track following at the same time, it is desirable to provide means for detecting deviation of the light spot from the track. This was difficult because the pickup device was miniaturized.

This invention was made in view of these points, and involves bending a part of the lens barrel with a piezoelectric element to vibrate the light spot at high speed in the direction intersecting the track.
A track detection control device is provided which obtains a signal indicating the positional deviation of a spot with respect to a track.

An embodiment of the present invention will be described below.

FIG. 1 shows a general optical system using a semiconductor laser. In the figure, 1 is a semiconductor laser, 2 is a condenser lens, 3 is a detector, 4 is a laser beam, 5 is a disk, and 6 is a pit. That is, in this optical system, the amount of reflected light changes depending on whether the laser light 4 is on the pit 6 or on other parts, and the light is emitted from the rear of the semiconductor laser 1 and received by the detector 3. It attempts to read information from changes in the amount of light.

2 and 3 show the structure of a lens barrel according to the present invention. In this embodiment, the general optical system shown in FIG. 1 is housed in a lens barrel 7, and a piezoelectric element 8 is attached to this lens barrel 7. It is something that

Next, the operation will be explained using FIGS. 4 and 5.
By expanding and contracting the piezoelectric element 8 between the two states of the arrow a-a direction and the arrow b-b direction, a part of the lens barrel 7 is bent in each direction, thereby causing the condenser lens attached thereto to bend. When the lens 2 is displaced, the light spot 9 focused by the focusing lens 2 is moved as indicated by the arrow c.
It will be displaced in the direction of.

At this time, the amount of beam reflection differs between the pit 6 and other parts, and a detection output indicating a deviation from the track as shown in FIG. 4 is obtained. Therefore, if the optical spot 9 is displaced by a small width at high speed, the frequency at the track center position will be twice that of the displacement frequency, and the position shifted from the track center in either direction will have the same displacement frequency, as shown in FIG. The B region and the C region have a phase difference of 180°, and a detection output having an amplitude corresponding to the amount of deviation is obtained.
Therefore, when this detection output and the oscillator output that vibrates the piezoelectric element 8 are phase-detected, the detection characteristics shown in FIG. 5 are obtained. Therefore, track tracking becomes possible by applying this detection output to, for example, an electromagnetic actuator to operate the entire lens barrel to follow the track.

As described above, according to the present invention, a small light source such as a semiconductor laser is used, and a part of the lens barrel housing the entire optical system is bent by a piezoelectric element to displace the light spot in a direction intersecting the track. , the track was tracked using the reflected light at that time, so
It is only necessary to attach a piezoelectric element to an integrally processed lens barrel, and the lens barrel can be easily machined, making it possible to perform track tracking. Furthermore, since attachment of the piezoelectric element does not affect the optical system at all, adjustment and assembly of the device is easy, and complicated adjustment of the optical system is not required.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing a general optical system of a semiconductor laser, Fig. 2 is a diagram showing a pickup structure according to the present invention, Fig. 3 is a sectional view taken along line A-A in Fig. FIG. 5 is a diagram showing changes in detection output due to deviation, and FIG. 5 is a diagram showing phase detection output. In the figure, 1 is a semiconductor laser, 2 is a condenser lens, 3 is a photodetector, 4 is a laser beam, 7 is a lens barrel, and 8
9 is a piezoelectric element, and 9 is a light spot. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A light condensing means that condenses light emitted from a light source to form a light spot; A light detection means that detects a change in reflected light from a record carrier; and Of the light source or the light condensing means. at least 1
a piezoelectric element that is attached to a part of the lens barrel and deflects the lens barrel so that the optical spot intersects the information track on the record carrier; a phase detector that performs phase detection by comparing the output from the detection means with the output of the oscillator that drives the piezoelectric element; What is claimed is: 1. A track detection control device comprising a means for moving the track.