JPH0622066B2 - Laser diode temperature compensator for optical pickup - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a laser diode temperature compensation device in an optical pickup for recording and reproducing information on an optical recording medium.

[Technical Background of the Invention and Problems Thereof] A high-density recording / reproducing apparatus using a laser beam, which has been put into practical use in recent years, generally has a spiral or concentric fine groove on a rotating recording disk with unevenness. Information such as recorded voices and images is read using the diffraction phenomenon of laser light, which is coherent light controlled to focus on this groove, or information to be recorded by the energy of the laser light. Is made on the groove.
A HeNe laser, a GaAlAs-based semiconductor laser, or an Ar laser is generally used as a laser which is a light source of these optical recording / reproducing devices. When the semiconductor laser is used, the member holding the light source inside the laser expands due to the temperature rise and the distance from the collimator lens changes, which adversely affects the performance of the pickup. Therefore, it is necessary to have a structure in which the optical axis, focus, and distance can be adjusted, and the distance to the collimator lens can always be kept constant regardless of changes in ambient temperature or changes in temperature due to heat generation of the laser.

[Object of the Invention] The present invention has been made based on the above circumstances, and temperature compensation is automatically performed so that the distance between the laser diode and the collimator lens can always be kept constant, and the present invention can be adapted to various temperature environments. , A laser diode temperature compensating device in an optical pickup is provided.

SUMMARY OF THE INVENTION In order to achieve the above object, in the present invention, a light source,
A holding member that holds the light source, a holder that holds the holding member in the optical system body, a collimator lens that converts the divergent light from the light source into a parallel light flux, and a collimator lens that is interposed between the holder and the temperature sensor. It is characterized by comprising a spacer extending by a length substantially equal to the extension of the holding member in the change, and a support member for movably supporting the collimator lens with respect to the optical system main body in accordance with the extension of the spacer. Provided is a laser diode temperature compensation device in an optical pickup.

Embodiments of the Invention Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the divergent light flux emitted from the laser diode 2 enters the collimator lens 6 and is then converted into a parallel light flux. Then, it is reflected upward by the beam splitter 13, passes through the quarter-wave plate 14, and is condensed by the objective lens 15 on the recording surface of the disc (not shown). The condensed light flux is reflected by the disk and travels backward, and becomes a parallel light flux by the objective lens 15 and the quarter wavelength plate 1
4 and is separated by the beam splitter 13. The light beam separated by the beam splitter 13 enters the convex lens 16, is separated again by the beam splitter 17, passes through the cylindrical lens 18, and is received by the detector 19. The focusing error signal is obtained by the output of the detector 19.

In FIG. 2, the laser diode 2 is attached to a holder 3 made of a material having a very small coefficient of thermal expansion (a coefficient of thermal expansion of about 1 × 10 ⁻⁶ 1 / ° C., for example, amber), and a pressing plate 1.
The holder 3 is fixed so as to be movable in the optical axis direction with respect to the holder 4 which is also made of a material having a very small coefficient of thermal expansion (for example, amber). On the other hand, the holder 4 has a structure in which it is screwed to the optical system body 8 and the diameter of the mounting hole for the screw is appropriately increased so that the laser diode 2 can be adjusted in the vertical and horizontal directions with respect to the optical axis.

Further, a light source 10 inside the laser diode 2 is held between the holder 4 and the collimator lens 6, for example, from oxygen-free copper (coefficient of thermal expansion 17 × 10 ⁻⁶ 1 / ° C.) or the like. Of the same material as that of the holding member 11 (see FIG. 3) or a material having a thickness such that the expansion due to thermal expansion is equivalent to that of the holding member 11 (for example, the coefficient of thermal expansion 23).
A spacer 5 made of × 10 ^-6 1 / ° C aluminum or the like) is interposed.

The collimator lens 6 is pressed against the spacer 5 by the coil spring 7, and depending on the extension of the spacer 5 due to thermal expansion,
The position of the main surface is designed to move.

Next, the principle of the present invention will be described with reference to FIG.
The light source 10 inside the laser diode 2 generates heat, the ambient temperature rises, and the holding member 11 extends in a direction approaching the collimator lens 6 (direction of arrow A in the figure).

Generally, when the elongation of a substance is δ (mm), δ = αLΔT- (A) α: coefficient of thermal expansion (1 / ° C) L: length of substance (mm) ΔT: temperature change (° C) To establish.

Then, the holding member 11 extends by δ = αLΔT (mm) in the direction toward the collimator lens 6. On the other hand, the spacer 5 of the collimator lens 6 is
Holding member 11 in the direction away from 0 (direction of arrow B in the figure)
It only has to extend for a length equal to. Here, the holding member 11
The distance between the spacer 5 and the spacer 5 is actually very small, and the atmospheric temperature is considered to be almost the same.
It can be considered by removing T from the equation (A). That is,
The thermal expansion coefficient α ₁ and the length L _{1 of the} holding member 11 and the spacer 5
The relationship between the coefficient of thermal expansion α ₂ of α and the length L ₂ is α ₁ L ₁ = α ₂ L
_The material and length may be selected and set so as to be 2. Further, in an environment where the temperature is low, the holding member 11 and the spacer 5
, Respectively, but the above relationship holds.

As described above, the holding member 11 of the light source 10 expands and contracts due to the ambient temperature change, but since the spacer 5 of the collimator lens 6 expands and contracts by the same amount in the same direction, the light source 1
The distance between 0 and the main surface of the collimator lens 6 can always be kept constant.

[Advantages of the Invention] As described in detail above, according to the present invention, the position of the main surface of the collimator lens can be automatically adjusted according to the expansion and contraction of the holding member of the light source inside the laser diode due to the temperature change. In addition, the light source and the collimator lens are always in focus, and an optical pickup that can be adapted to various temperature environments can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view of the entire optical pickup device according to an embodiment of the present invention, FIG. 2 is a sectional view showing a laser diode temperature compensation device in the optical pickup of the present invention, and FIG. It is explanatory drawing explaining the principle of the laser diode temperature compensation apparatus in an optical pickup. 2 ... Laser diode, 3 ... Holder, 4 ... Holder, 5 ... Spacer, 6 ... Collimator lens, 7 ... Coil spring, 10 ... Light source, 11 ... Holding member

Claims (1)

[Claims] 1. A light source, a holding member for holding the light source, a holder for holding the holding member in an optical system body, a collimator lens for converting divergent light from the light source into a parallel light flux, and the collimator lens. A spacer interposed between the holder and extending by a length substantially equal to the extension of the holding member when the temperature changes, and the collimator lens according to the extension of the spacer,
A laser diode temperature compensating device in an optical pickup, comprising: a supporting member movably supporting the optical system body.