JPS63263640A - Optical head device - Google Patents

Abstract

PURPOSE:To rotate and adjust the polarizing bearing of a light emitting source, to efficiently concentrate and radiate projected beam into an information recording medium and to reduce stray light to a photodetector by rotating the light emitting source around the optical axis of projected beams. CONSTITUTION:A lens barrel 15 for fixing the light emitting source 1 and a collimeter lens 2 is allowed to rotate in an arrow A direction. Namely, the lens barrel 15 is rotated by a driver 19 in the arrow A direction, the polarizing bearing of the light emitting source 1 is made to coincide with the P polarizing direction of a beam splitter and the lens barrel 15 is fixed with a fixing screw 29. Although the tip of a rotating device 21 is inserted into a longitudinal groove 18 formed on the outer periphery of the lens barrel 15 in said constitution, any structure can be applied if the lens barrel 15 or the light emitting source 1 can be rotated around the optical axis of a projected beam. Since light can be efficiently radiated to the information recording medium and stray light due to the deviation of the polarized bearing can be removed by said constitution, efficient servo characteristics can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an optical head device that optically records and reproduces information, and in particular, to efficiently irradiate an information recording medium with light output from a light emitting source. The present invention relates to an optical head device which is capable of suppressing stray light due to residual reflection from optical components and can obtain good servo characteristics.

[Conventional technology]

FIG. 3 shows a schematic configuration of the first type of conventional optical head device. This optical head device is a magneto-optical information recording medium that uses a magnetic thin film having a magneto-optic effect as an information recording medium. It is a playback device. In the figure, (1) is a light emitting source such as a semiconductor laser that generates a light beam for recording and reproduction, (2) is a collimator lens that converts the diverging light beam emitted from the light source (1) into a parallel light beam, and (3) is a A diffraction grating for generating tracking sub-beams, (4) an information recording medium such as a magneto-optical disk, and (5) a beam splitter for separating reflected light from the information recording medium (4); It has the characteristics of a prism, allowing 50 to 90% of the light to pass through and the rest being emitted. (6) is the above light emitting source (1)
an objective lens (7) for condensing the parallel light beam emitted from the , which is converted into a parallel light beam by the collimating lens (2) and transmitted through the beam splitter (5), onto the information recording medium (4); ) guides the light beam reflected by the information recording medium (4) and bent in the traveling direction by the beam splitter (5) to the information signal reproducing system (20), and also sends a portion to the servo signal analysis system (30). This is a beam splitter to guide the beam. Here, the information signal reproduction system (20)
includes an analyzer (8) for converting polarization plane rotation in the information signal light from the information recording medium (4) into an intensity change, a photodetector (10) for converting the information signal light into an electrical signal, and the above-mentioned It consists of a lens (9) for guiding the information signal light converted into an intensity fluctuation signal by the analyzer (8) K to the signal detection photodetector (10). The servo signal detection system (30) is composed of a converging lens (11), a cylindrical lens (12) for an astigmatic focus sensor, and a 6-segment photodetector (13) for servo. (1
01) is a bias magnetic field generating coil.

FIG. 4 shows the main parts of a conventional second type optical head device, and this device can be used as an information recording medium.
Use a type that uses unevenness or reflectance differences as recording pits. In FIG. 4, the same reference numerals as in FIG. 3 indicate the same or corresponding parts.

In the figure, (22) is a polarizing beam splitter that separates the reflected light from the Mayuki information recording medium (27), which has the characteristics of a P-polarized light transmittance of about 100% and an S-polarized light reflectance of about 100%. Further, (23) is a quarter wavelength plate, and the polarizing beam splitter (22) and quarter wavelength plate (23) also function as an optical isolator (28). (26)
are the information signal reproduction system and servo signal detection system, and the lens (24) and light detection! (25) etc.

Furthermore, FIG. 5 is an exploded perspective view showing the fixing parts of the conventional light emitting source (1) and collimator lens (2) used in the optical head device shown in FIGS. 3 and 4, and in the figure ( 14) is a fixed block, (15) is a lens barrel to which the light emitting source (1) and collimator lens (2) are attached, (16) is a holding plate for the light emitting (lIX (1)), (31) is a holding plate (
16) is the pawl, (17) is the fixing screw, and the light source (
1) and the lens barrel (15) to which the collimator lens (2) is fixed.
into the fixing block (14) and fix the lens barrel (15) with the setscrew (29).

Next, the operation of the conventional device will be explained.

In Fig. 3, the diverging light emitted from the light emitting source (1) becomes a parallel light beam by the collimator lens (2) K, passes through the diffraction grating (3) and the beam splitter (5), and is sent to the information recording medium by the objective lens (6). (4) Light is focused upward. The information recording medium (4) is a perpendicular magnetization film, and in an unrecorded state, the direction of perpendicular magnetization is uniform. In this state, information signals are recorded. Note that when recording information signals,
In advance, in the direction opposite to the direction of perpendicular magnetization in the unrecorded state,
A magnetic field is applied by a bias magnetic field generating coil (101), and strong light is irradiated onto a portion K where recording pits are to be formed. As a result, the width 1 with the direction of magnetization perpendicular to the surroundings reversed
Recording pits of μ size are formed.

Furthermore, during information signal reproduction, the direction of rotation of the plane of polarization of the reflected light from the information recording medium (4) differs depending on the direction of perpendicular magnetization. This reflected light is transmitted to the beam splitter (5)
and beam splitter (7), and is guided to an analyzer (8)K. The rotation of the plane of polarization in the information recording medium (4) is converted into light intensity by the analyzer (8), and converted into an electrical signal by the photodetector (10)K.

In this conventional optical head device pressure, the light emitting source (13
and the collimator lens (2) are fixed as shown in FIG. At this time, the rotational position of the light source (1) with respect to the optical axis is such that the claw portion (31) of the holding plate (16)
This is done by matching the notch in 1).

The basic operation of the conventional device shown in FIG.
27) An optical isolator (22) consisting of polarizing beam splitters (22) and a quarter-wave plate (23) to guide the
28) and the recording pits of the information recording medium (2B) are recorded with unevenness or reflectance changes,
It was the same as the one in Figure 3 except that the analyzer (8) used in Figure 3 was not required, and the means for fixing the light emitting source (1) shown in Figure 5 was used. .

[Problem that the invention seeks to solve]

Since this type of optical head device according to the prior art is constructed as described above, it has the following problems.

This type of optical head device uses an information recording medium (
4) or (27) Since the optical power for irradiating K is required to be, for example, about 5 to 10 times as much as that for reproduction, the light from the light source (1) had to be used efficiently. In the conventional device (Figure 3), the beam splitter (5) has a P polarization transmittance of 50 to 90% and an S polarization reflectance of approximately 100%, so it can efficiently irradiate light onto the information recording medium (4). To accurately adjust the polarization direction of the light emitting source (1), use the beam splitter (5).
It is necessary to match the P polarization direction of . However, in the conventional device, the claw part n (31) of the holding plate (16)
Since it is only fixed by a screw, accurate positioning is not possible.

Furthermore, when the optical head device is configured as shown in FIG. 4, the P-polarized light transmittance of the beam splitter (22) is approximately 1t)0
%, S-polarized light transmittance is 0%, so if the polarization direction of the light source (1) does not match the P-polarized light of the beam splitter (22), the irradiation power onto the information recording medium (27) will decrease. At the same time, there is a problem in that stray light as shown by the solid line (Bl) occurs during the 4th g, and an offset occurs in the surge signal.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to obtain an optical head device that can improve transmission efficiency to an information recording medium and provide good servo characteristics.

[Means for solving n points between]

The optical head device according to the present invention is equipped with a rotation device capable of rotating a light emitting source by a desired amount around the optical axis of light emitted from one light emitting source.

[For production]

In the optical head device of the present invention, the light emitting source can be rotated around the optical axis of the emitted light, so that the polarization direction of the light emitting source can be rotationally adjusted, and the emitted light from the light emitting source can be efficiently transferred to an information recording medium. Focused illumination reduces stray light to the photodetector.

[Examples] Examples of the present invention will be described below with reference to the drawings. 1 and 2 show essential parts of an optical head device according to an embodiment of the present invention, and the same reference numerals as in the above-mentioned conventional device indicate the same parts. The lens barrel (15) that fixes the light emitting source (1) and the collimator lens (2) is rotatable in the direction indicated by the arrow in FIG. (19) is a driver for rotating the lens barrel (15) in the direction of the arrow; (18) is the driver (1);
This is a groove for inserting the tip of 9). In this embodiment, a lens barrel (15) having the groove (1B) and a driver (
19) K constitutes a rotating device (21).

Next, the operation will be explained.

The driver (19)K rotates the lens barrel (15) in the inward direction, making it possible to easily match the polarization direction of the light emitting source (1) with the P polarization direction of the beam splitter (5) or (28). . After the adjustment is completed, the lens barrel (15) may be fixed using the fixing screw (29).

The above-mentioned embodiment can be implemented by simply modifying the conventional device without increasing the number of parts, and the performance can be improved at low cost.

In the above embodiment, the rotating device f(21) is shown in FIG.
Although the structure is as shown in FIG. 2, any structure may be used as long as the lens barrel (15) or the light emitting source (1) can be rotated in the incoming direction around the optical axis of the emitted light. In addition, the lens barrel (15) of the light source (1) portion was fixed with the fixing block (14), but the fixing block (14) may be omitted and is fixed to the main body base (not shown) of the optical head device. It is also possible to have a structure that allows

It goes without saying that various other changes can be made within the spirit of the invention.

〔Effect of the invention〕

As described above, according to this invention, since the light emitting source is configured to be rotationally adjustable with respect to the optical axis, light can be efficiently irradiated onto the information recording medium, and furthermore, stray light due to deviation in the polarization direction of the light emitting source can be avoided. Since it can be removed, it has the effect of improving the performance of the device, such as obtaining good servo characteristics.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the main parts of an optical head device according to an embodiment of the present invention, FIG. 2 is a sectional view of FIG. 1, and FIGS. FIG. 5, a schematic configuration diagram showing an optical head device, is an exploded perspective view showing main parts of a conventional optical head device. (1) is a light emitting source, (21) is a rotating device, (4), (27
) is an information recording medium, (5) and (1) are beam splitters, and (10) and (25) are photodetectors. Note that the same reference numerals in the figures indicate the same or equivalent parts. Figure 2 Figure 4 Procedural Amendment 1986 9□14

Claims (1)

[Claims] A light emitting source that emits recording or reproducing light to an information recording medium, a rotating device that can rotate the light emitting source by a desired amount around the optical axis of the emitted light, and a rotating device that rotates the light reflected from the information recording medium by a desired amount. An optical head device comprising: a beam splitter that separates the information; and a photodetector that detects the intensity of the light that is separated by the beam splitter among the reflected light from the information recording medium.