JPS5826332A - Adjusting device for optical path - Google Patents

Abstract

PURPOSE:To simplify and make the size of a device for focus control and tracking control small, by adjusting an optical path through the arrangement of a substance the refractive index of which is changed with an electric or a magnetic signal in the optical path. CONSTITUTION:A vari-focal lens 7 is constituted by sealing liquid crystal in a transparent glass capsule of lens shape and fitting a transparent electrode 7a at the outside of the capsule and an optical path changing plate 8 is constituted by sealing the liquid crystal in the rectangular glass capsule and providing a transparent electrode 8a at the outside of the capsule. A voltage applied to a vari-focal lens 7 is changed with a focus controlling signal from a photodetector 6 to change an optical path through the change of refractive index of the liquid crystal for tracking control. A voltage applied to the plate 8 is changed with the tracking control signal and the optical path is changed with the change in the refractive index of the liquid crystal for the tracking control. Thus, the device is simplified and made small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical path adjusting device in an optical information recording/reproducing device, and particularly aims to provide a device that is small and capable of easily controlling focus and tracking. be.

FIG. 1 is a diagram schematically showing a conventional optical information reproducing device. The light beam emitted from the light source (semiconductor laser) (1) is
The collimator lens (2) converts the light into parallel light, and after passing through the half mirror (3), the light is focused by the objective lens (4) and irradiated onto the rotating disk (5). Information is recorded on the disk (5) using unevenness, and the reflected light beam from the disk (5) is modulated with this information. The reflected light beam is reflected by a half mirror (3) and input to a photodetector (6). An information signal, a tracking control signal, and a focus control signal are read out from this photodetector (6), and the position of the objective lens (4) is driven in the X-axis and Y-axis directions by the tracking control signal and focus control signal. Control and focus control are provided.

However, in such a conventional example, the objective lens (4)
Since the structure for driving the lens is an electromechanical structure using solenoids, linear motors, etc., the objective lens drive section inevitably becomes large, and furthermore, mechanical vibration interference occurs between the drive mechanisms in the two directions. There were other inconveniences.

Therefore, the present invention provides a variable focus lens (7) and an optical path changing plate (8) that utilize a substance whose refractive index is changed by an electrical or magnetic signal without mechanically driving υ1 of the objective lens. Tracking control and focus control are performed by adjusting the optical path. In the embodiment shown in FIG. 2, a liquid crystal is placed in a lens-shaped Hideaki glass capsule, a transparent electrode (7a) is attached to the outer surface of the capsule to form a variable focus lens (7), and a rectangular parallelepiped is used. A liquid crystal is sealed in an IH-shaped glass capsule, and a transparent electrode (8a) is attached to the outer surface of the capsule to constitute an optical path changing plate (8). By varying the voltage applied to the variable focus lens (7) using the focus zr'j control signal output from Optical path change plate at signal (8)
By varying the voltage applied to the liquid crystal, the refractive index of the liquid crystal is changed to change the optical path and perform tracking control.

Since the refractive index of the liquid crystal also changes depending on the magnetic field, a configuration may be adopted in which the f [(flow) flowing through the electromagnetic coil is controlled by a focusing and dragging control signal to control the magnetic field applied to the liquid crystal.

It should be noted that the photodetector (6) for reading out the information signal, the tracking control signal, and the focus control signal has already been proposed in various configurations, and is not the gist of the present invention.
A specific explanation will be omitted. Furthermore, the optical system is not limited to one that uses a half mirror to separate the irradiated beam and the reflected beam, but may also use a polarizing beam splitter, a λ/4 wavelength plate, and an anti-U'' beam. The so-called S COOP (Se1.f
-Cou,p],,edOpi-ca1. Pick
) method may be used.

According to the present invention described above, a substance whose refractive index changes depending on an electrical or magnetic signal is disposed in the optical path.
Since the optical paths 1 and 9 are adjusted in this manner, the devices for focus control and tracking control can be made simple and compact.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional optical information reproducing device, and FIG. 2 is a diagram showing an optical information reproducing device using an optical path adjusting device according to the present invention. (1) is a light source, (3) is a half mirror, (5) is a disk, (6) is a photodetector, (7) is a variable focus lens, (8
) is the optical path changing plate.

Claims (2)

[Claims] (1) In an optical information recording/reproducing device, an optical path adjustment device that adjusts the optical path by disposing a substance whose refractive index changes in response to an electrical or magnetic signal in the optical path. (2) The optical path adjusting device according to claim 1, wherein the substance whose refractive index changes according to an air or magnetic signal is a liquid crystal.