JPH0294131A - Optical pickup - Google Patents

Abstract

PURPOSE:To perform tracking control of focusing control without utilizing the mechanical displacement of an object lens, etc., by providing a variable-phase waveguide type optical deflecting element on the optical path of an optical pickup. CONSTITUTION:A laser beam L emitted from a semiconductor laser 2 is transformed to parallel rays by a collimate lens 4 and made incident on a variable-phase waveguide type optical deflecting element 14 by means of a cylindrical lens 12 after passing through a half mirror 6. The laser beam L made incident on the element 14 is subjected to phase changes in accordance with a tracking signal and focusing signal from a detector 10 at each electrode section 24 and 36 of an optical waveguide layer 30. The phase change can be performed by changing currents of constant-current sources A1-A4. Therefore, the deflection and focal point of the laser beam L can be made variable and tracking control and focusing control can be performed by displacing the focusing point of the laser beam L on the surface of an optical disk 22 by means of an object lens 20 through a reflecting prism 18 by utilizing the change in the deflection and focal point of the laser beam L.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to tracking control and focusing control of a laser beam of an optical pickup.

(Prior Art) Conventionally, tracking control and focusing control of a laser beam of an optical pickup is performed by moving an objective lens 20 that focuses a laser beam onto an optical disk surface 22 in a radial direction with respect to a support shaft 48, as shown in FIG. The objective lens support part 5 is configured to be rotatable in the direction and slidable in the axial direction.
a tracking drive coil 44 wound around 0,
and the drive current to the focusing drive coil 42,
This is done by changing the position of the objective lens 20 according to the tracking signal and focusing signal.

(Problems to be Solved by the Invention) In the conventional optical pickup described above, tracking and focusing control is performed using mechanical displacement of the objective lens, etc., so that problems caused by friction of the sliding part of the objective lens mechanism There have been problems such as changes in related members over time or instability of the optical pickup due to external vibrations.

In order to solve the above-mentioned problems, it is an object of the present invention to provide an optical pickup that enables tracking or focusing control without using mechanical displacement of an objective lens or the like.

(Means for solving the problem) In the present invention, incident light is divided equally into a plurality of parts,
Separated light is created by providing independent optical waveguides for each of the split optical waveguides, electrically changing the propagation constant of each optical waveguide individually, and performing independent electrical control of the phase of the split light. An optical deflection element configured to deflect light by independently controlling the phase of the waveguide (hereinafter referred to as a phase variable waveguide type deflection element) is installed on the optical path of the optical pickup, and the incident light of the phase variable waveguide type deflection element is To provide an optical pickup having a focusing function and a tracking function, in which cylindrical lenses are respectively arranged on the side and the output side.

(Function) According to the present invention, a laser beam is divided by a phase variable waveguide type optical deflection element, and by arbitrarily varying the phase of the divided laser beam, its deflection direction and focus can be adjusted. Since the distance can be varied, optical tracking control and focusing control are possible.

(Example) An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a drawing showing an embodiment of the present invention. In the figure, reference numeral 2 is a semiconductor laser, 4 (the reference numerals are omitted below) is a collimating lens, 6 is a half mirror, 18 is a condenser lens, and 10 is a detector. be. Cylindrical lenses 12 and 16 are provided on the incident side and the output side of the phase variable waveguide type optical deflection element 14, respectively. Next, 18 is a reflecting prism, 20 is an objective lens 20, and 22 is an optical disk.

The phase variable waveguide type optical deflection element 14 adopted in the present invention was filed in Japanese Patent Application No. 82-320972 by the same inventor as the present invention.
Disclosed in issue.

The outline of the phase variable waveguide type optical deflection element will be explained below with reference to FIG. 2 of the accompanying drawings.

FIG. 2 is a perspective view of the optical deflection element 14.

A GaAs substrate 26 is disposed on the second side of the lower electrode 24 forming the lowermost surface of the optical deflection element 14, and a GaAs substrate 26 is disposed on the second side of the lower electrode 24 forming the lowermost surface of the optical deflection element 14.
Lower cladding layer 28 made of o6s AJJo35As
and Gao65A disposed under the GaAs layer 34, which will be described later.
The upper cladding layer 32 made of JLo35As is Gao
7A! ; Arranged with an optical waveguide layer 30 made of Lo3As sandwiched therebetween. On top of the upper cladding layer 32 is the aforementioned GaAs.
A layer 34 is provided, and an upper electrode 36 is provided thereon.

Next, a plurality of parallel angular grooves 13 are bored and upper electrodes 36 are formed on the strip-shaped upper electrodes 38a, 3Bb, 3Ete, and 38d.
, 36b, 38c, and 36d, and these electrodes 38a to 38d are connected to power sources AI, A2 .
A3A4. It is connected to the lower electrode 24 via. However, when electricity is applied, the optical waveguide consisting of the two-part cladding layer 32, the optical waveguide layer 3o, and the lower cladding layer 28 is divided into a plurality of optical waveguides.

In this way, the phase variable waveguide type optical deflection element 14 is formed into a plurality of optical waveguides made of semiconductor that are equally divided when energized.

Usually, a lens system consisting of an entrance side lens and an exit side lens is arranged on each side.

The incident light first passes through the incident side lens and enters the waveguide layer 30 of the leading waveguide.
When the light is energized, the light propagates through the leading wave paths divided for each upper electrode, and then is emitted as parallel light by the exit lens.

As already explained, the optical deflection element 14 is divided into a plurality of optical waveguides made of semiconductor when energized, and the number of carriers is electrically changed by changing the injection current ratio of these optical waveguides, that is, the divided portions. The electro-optic effect induced by applying a bias voltage changes the refractive index of the optical waveguide and changes the propagation constant.

As a result, the propagating light within each waveguide that reaches the output end of the divided optical waveguide undergoes a phase change and is emitted from the output end into free space. By electrically controlling the amount of phase change at this time as described above, it is possible to equivalently change the direction of the equal phase plane, so that the light is deflected at a desired angle.

The laser beam L that has just been emitted from the semiconductor laser 2 is turned into parallel light by the collimator lens 4, and enters the phase variable waveguide type optical deflection element 14 via the half mirror 6 and the cylindrical lens 12. The laser beam L incident on the phase variable waveguide type optical deflection element 14 receives a tracking signal from the detector 10 for each electrode portion of the leading wave layer 30,
It undergoes a phase change depending on the focusing signal. The phase change is caused by constant current sources AI, A2. A3. This can be done by changing the current of A4. This allows the deflection and focus of the emitted beam to be varied. Due to the deflection and focus change of the laser beam, the focal point of the laser beam L on the optical disk 22 surface by the objective lens 20 is displaced via the reflection prism 18, and tracking control and focusing control are performed. be able to.

(Effects of the Invention) As described in detail hereinafter, according to the present invention, a phase variable waveguide type optical deflection element is employed for tracking control and focusing control of a laser beam of an optical pickup, and mechanical Eliminates moving parts. As a result, it is possible to overcome the instability of the optical pickup due to changes over time in related members that inevitably accompany mechanically movable parts and vibrations from the outside, contributing to improvements in durability and vibration resistance and long-term reliability.

[Brief explanation of the drawing]

FIG. 1 is a route layout diagram of an embodiment of an optical pickup according to the present invention, FIG. 2 is a perspective view of a phase variable waveguide type optical deflection element, and FIG. 3 is a route layout diagram of a conventional optical pickup. It is.

Claims (1)

[Scope of Claims] 1. An optical pickup having a focusing control function and a tracking control function, characterized in that a phase variable waveguide type optical deflection element is provided on an optical path of the optical pickup. 2. The incident light entering the optical waveguide is divided equally into multiple parts, each of the divided optical waveguides is provided with an independent electrode, and the propagation constant of each optical waveguide is electrically changed individually. 2. The optical pickup according to claim 1, further comprising a phase variable waveguide type optical deflection element that deflects the light by independently controlling the phase of the split light.