JPH0271437A - Optical head - Google Patents

Abstract

PURPOSE:To reduce the error of the focal position detection signal and tracking position detection signal of a photo-detector by fixing mechanically a holder with prisms in which an integrally molded prism is coated with a reflecting film and the other prism is fixed into an enclosure with screws, etc. CONSTITUTION:One prism is made of plastic material and molded integrally with the holder, the reflecting face of the integrally molded prism is coated with an evaporated film, the other prism is pasted on it and the integrally molded holder is fixed to the enclosure with the screws. For example, a prism 5 is integrated with a holder 21, it is fixed to an enclosure 19 with the screws, therefore, when a temperature change is given and the former temperature is obtained, the position of the prism 5 is returned to its former position. That is to say, the one is molded integrally with the holder, therefore, even when it receives the temperature change repeatedly, the position of the prism to the holder is not dislocated.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical head of an optical recording and reproducing device that optically records and reproduces information. [Prior Art] 1 is a configuration diagram of a conventional optical head disclosed in Publication No. 139950/1982. In Figure 3, (1) is a semiconductor laser that emits laser light (2), (3)
is a collimator lens, (4) is a prism, (5) is prism A, (6) is prism B, (7) is a composite beam splitter, (8) is a wavelength plate, (9) is a condenser lens, (1
0) is the medium, (1, (12) is the lens, (13) is the photodetector that detects the track position and reproduces the signal, (1゛4)
is a cylindrical lens, (15) is a knife, and (16) is a photodetector for detecting the focal position.

Next, the operation will be explained. In Figure 3, the laser beam (2) that has exited the semiconductor laser (1) is transmitted through the collimator lens (3).
), the light becomes parallel light, and the intensity distribution is corrected by the prism (4). The prism (4) is composed of two types of prisms (5) and (6) having different wavelength-refractive index characteristics, and corrects changes in the direction of emitted light due to changes in wavelength. The output light of the prism (4) is the compound beam splitter (7),%
The light passes through a wave plate (8) and a condensing lens (9) to reach a medium (10).

The reflected light from the medium (10) passes through a condensing lens (11) and reaches a photodetector (13), where the track position is detected and the signal is reproduced. The other one is a lens (12), a cylindrical lens (1
4), a part of the light is blocked by the knife (15) and reaches the photodetector (16), where the focal position is detected. When a temperature change occurs, the prism (5), prism (
Due to the temperature-refractive index characteristic (6), the direction of the light emitted from the prism (4) tends to change by θ. At this time, the lens (
11) The light exiting the lens (12) is also tilted by θ, giving an error to the tracking position detection signal and the focal position detection signal. Therefore, the prism (4) is assembled into a housing (19) by an arm (17) and an arm (18) having different coefficients of thermal expansion.
Since the prism (4) is attached to the prism (4), when a temperature change occurs, the prism (4) is rotated in a direction that corrects the change in direction θ of the emitted light from the prism (4).

[Problems to be Solved by the Invention] Since the conventional optical head is configured as described above, two types of arms with different coefficients of thermal expansion must be provided in the optical component, resulting in a problem that the number of parts increases. In addition, the optical components and the arm are attached using adhesive, but due to temperature changes, the adhesive between the optical component and the arm moves to remove distortion, causing the prism to rotate in unexpected directions. There was a point.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to obtain an optical head in which the tracking position detection signal and the focus detection signal do not have errors due to temperature changes.

[Means for Solving the Problems] The optical head according to the present invention is manufactured by integrally molding one side of the prism with the holder using a plastic material, and coating the reflection surface of the integrally molded prism with a vapor deposited film for reflection. The other prism is pasted on top, and the integrally molded holder is fixed to the housing with screws.

[Operation 1] In the optical head configured as described above, one of the prisms is integrally molded with the holder, so that the position of the prism relative to the holder will not shift even if the prism is subjected to repeated temperature changes.

[Example] An example of the invention will be described below. In Figure 1, (1) to (3), (8) to (10) (+6), (19
) is the same as before. (21) is a holder placed inside the housing (19).

This holder (21) is integrally molded with the prism (5) from plastic or the like. A reflective surface of a prism (5) that is integral with the holder (21) is coated with a deposited film (24), and a prism (6) is further bonded thereon. The holder (21) has screws (22) and (23
) is fixed within the housing (19). (27) is an actuator equipped with an objective lens (9), which operates to focus the light from the semiconductor laser (1) on a predetermined position on the medium (10). (25) is a concave lens with a holder (
26) to focus the reflected light from the medium (1o) on the photodetector (16).The operation will now be described. In Figure 1, light emitted from a semiconductor laser (1) passes through prisms (5) and (6), is made into parallel light by a collimator lens (3), passes through a wavelength plate (8), and is attached to an actuator (27). The light reaches the objective lens (9), and is focused as a condensed spot on the medium (10) by the objective lens (9). The light focused by the medium (10) is reflected and made into parallel light by the objective lens (9), and then passed through the wavelength plate (8).
) and returns to the collimator lens (3). The light focused by the collimator lens (3) is reflected by the reflective film (24) on the prism (5), passes through the concave lens (25), and is focused at a predetermined position on the photodetector (16). The position of the detector (16) is adjusted and fixed.

The prism (5) is integrated with the holder (21),
Since it is screwed to the housing (19), even if the temperature changes, the prism (5) will return to its original position once the original temperature returns. The reflective film (24) is attached to the prism (5)
is deposited on.

Therefore, the reflected light from the medium (10) is guided to the photodetector (16) by the reflective film (24) of the prism (5), but since the reflective film (24) also returns to its original position when the temperature returns to its original temperature, the light is reflected from the medium (10). The position of the focal spot on the detector (16) does not move.

In other words, if the prism (5) is attached to the holder (21) with adhesive, the position of the prism (5) will shift due to temperature changes, but in the present invention, the holder (21) and the prism (5) Since they are molded in one piece, their position will not shift even after many years.

[Effect of the invention 1 As described above, according to the present invention, one of the prisms is integrally molded with the holder, the integrally molded prism is coated with a reflective film, and the other prism is further bonded thereon. Since the integrally molded holder is screwed to the housing, the prism coated with a reflective film will return to its original position even if the temperature changes, reducing errors in the focal position detection signal and tracking position detection signal of the photodetector. can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical head according to an embodiment of the present invention, FIG. 2 is a sectional view of a holder with a prism taken along line A-A' in FIG. 1, and FIG. 3 is a sectional view of a conventional optical head. FIG. In the figure, (1) is a semiconductor laser, (5) and (6) are prisms, (10) is a medium, (16) is a photodetector, (21) is a
) is a holder, (22) and (23) are screws, and (24) is a reflective film. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent Patent Attorney Masuo Oiwa Figure 3 27: Actor 1 Figure 2 111 15; Knife Tsuji 17 + end arm 1a arm

Claims (1)

[Claims] (1) A light source and a light beam from the light source are focused onto an information medium by an objective lens, and the reflected light beam from the information medium is reflected by a prism through the objective lens, and is received by a photodetector to record and reproduce information. In the optical head that performs this, one of the prisms is manufactured by integrally molding with the holder, and the integrally molded prism is coated with a reflective film, and the other prism is adhered thereon. An optical head characterized by mechanically fixing a holder to a housing with screws or the like.