JPH05203806A - Beam splitter and optical head - Google Patents

Abstract

PURPOSE:To eliminate the moisture absorption and a change refractive index of a dielectric film and to prevent a change in the reflectivity thereof by interrupting the contact of the dielectric film with the atm. air by using a sealing member. CONSTITUTION:The sealing member 22 is so disposed as to enclose the circumference of the dielectric film 20A of the beam splitter 20 constituted by joining the slopes of 1st and 2nd rectangular prisms 8B, 8C via the dielectric film 20A held therebetween so that the contact of the dielectric film 20A and the atm. air is interrupted by the sealing member 22. Namely, the dielectric film 20A is so formed on the slopes of the prisms 8B, 8C as to avert the circumferences. On the other hand, the sealing member 22 consists of ordinary adhesives for joining optical members (an epoxy adhesive in such a case) and is applied around the dielectric film 20A to directly adhere the prisms 8B, 8c, thereby sealing the dielectric film 20A. Then, the contact of the dielectric film 20A with the atm. air is interrupted by using the sealing member 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a beam splitter and an optical head, and can be applied to, for example, an optical disk device for reproducing thermomagnetically recorded information by utilizing the Kerr effect.

[0002]

2. Description of the Related Art Conventionally, there is an optical disk device which is capable of thermomagnetically recording desired information on a magneto-optical disk which is a magnetic recording medium.

That is, as shown in FIG. 2, in the optical disc device 1, the magneto-optical disc 4 is checked by the spindle motor 2, and thereby the magneto-optical disc 4 is rotationally driven at a predetermined rotational speed. In the optical head 3,
A light beam L having a predetermined polarization plane emitted from the semiconductor laser 5.
A1 is condensed by the objective lens 6, and the light beam LA1 is condensed on the information recording surface of the optical disc 4.

In this state, in the optical disc device 1,
A predetermined modulation coil (not shown) is driven to form a modulation magnetic field, and the modulation magnetic field is applied to the focus position of the light beam.
As a result, in the optical disc device 1, the focus position of the light beam is magnetized in the direction determined by the modulation magnetic field, and desired recording information is thermomagnetically recorded.

On the other hand, during reproduction, in the optical disc device 1, the reflected light beam LA obtained from the optical disc 4 is reproduced.
2 is detected by the light receiving element 10, and the recorded information is reproduced based on the detection result. That is, in the optical head 3, the beam splitter 8 is inserted between the objective lens 6 and the semiconductor laser 5, and the beam splitter 8 separates the reflected light beam LA2.

As shown in FIG. 3, in the beam splitter 8, the predetermined dielectric film 8A is sandwiched between the right prisms 8B and 8C so that the inclined surfaces are joined together. The light beam LA2 reflected by the film 8A
Is guided to the light receiving element 10.

In the light receiving element 10, a filter having a predetermined polarization plane is arranged on the light receiving surface, whereby the reflected light beam L
The signal level of the output signal changes in accordance with the change of the polarization plane of A2. As a result, in the optical disc device 1, it is possible to reproduce the recording information thermomagnetically recorded based on the output signal of the light receiving element 10.

[0008]

In the beam splitter 8 of this type, however, the refractive index of the dielectric film 8A may change, which causes a problem of changing the reflectance of the reflected light beam LA2. .

Therefore, when the beam splitter 8 is applied to the optical head 3 of this type, the incident light amount of the light receiving element 10 changes due to the change of the reflectance of the reflected light beam LA2, and the total of the spectral head 3 is changed. There was a problem that the characteristics changed. Particularly, in the optical disc device 1 of this type, the recorded information is correctly reproduced when the refractive index of the dielectric film 8A changes even a little because the plane of polarization of the reflected light beam LA2 changes only in the range of a few degrees. I won't get it.

The present invention has been made in consideration of the above points, and is intended to propose a beam splitter and an optical head capable of preventing a change in reflectance in advance.

[0011]

In order to solve such a problem, in the first invention, the slopes of the first and second right-angle prisms 8A and 8B are joined with a predetermined dielectric film 20A interposed therebetween. In the beam splitter 20, the sealing member 22 is arranged so as to surround the periphery of the dielectric film 20A, and the sealing member 22 interrupts the contact between the dielectric film 20A and the atmosphere.

Further, in the second invention, the light beam L
A laser light source 5 that emits A1, an objective lens 6 that focuses the light beam LA1 on a predetermined information recording medium 4, and a reflected light beam LA of the light beam LA1 obtained from the information recording medium 4.
Beam splitter 2 which separates the beam 2 from the light beam LA1
0 and the reflected light beam L separated by the beam splitter 20
The beam splitter 20 is formed by joining the slopes of the first and second right-angle prisms 8A and 8B with a predetermined dielectric film 20A interposed therebetween. The sealing member 2 surrounds the body membrane 20A.
2 is arranged so that the sealing member 22 breaks the contact between the dielectric film 20A and the atmosphere.

[0013]

[Function] The sealing member 2 surrounds the periphery of the dielectric film 20A.
If 2 is arranged and the sealing member 22 is used to cut off the contact between the dielectric film 20A and the atmosphere, moisture absorption of the dielectric film 20A can be prevented, thereby preventing the change of the refractive index of the dielectric film 20A. can do.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1 in which parts corresponding to those in FIG. 3 are designated by the same reference numerals, 20 denotes a beam splitter as a whole, and a dielectric member 20A is sealed by a sealing member 22. That is, in this embodiment, the dielectric film 20A is the prism 8
The slopes A and 8B are formed so as to avoid the surroundings.

On the other hand, the sealing member 22 is made of an ordinary adhesive for adhering optical members (in this case, made of an epoxy adhesive), and is applied around the dielectric film 20A to form the prism 8B and the prism 8B. The dielectric film 20A is sealed by directly bonding 8C. With this configuration, the sealing member 22 can be used to break the contact between the dielectric film 20A and the atmosphere.

That is, the dielectric film 2 is formed by using the sealing member 22.
If the contact between 0A and the atmosphere is cut off, the dielectric film 20
Moisture absorption of A can be prevented. On the other hand, the refractive index of the dielectric film 20A can be prevented from changing by absorbing the moisture in the atmosphere and changing the refractive index so that the contact between the dielectric film 20A and the atmosphere is cut off. Therefore, it is possible to prevent the reflectance of the beam splitter 20 from changing.

Accordingly, an optical head can be formed by using the beam splitter 20 instead of the beam splitter 8 (FIG. 1) to form an optical head with stable characteristics and to reliably reproduce recorded information. You can

Further, by applying the optical head to an optical disc device, it is possible to reduce the load on equipment such as a dehumidifying device as a whole system and further to use it in a hot and humid environment. The range can be expanded.

In practice, according to the experimental results, if the periphery of the dielectric film 20A is sealed with an adhesive with a width of about 0.5 [mm] in consideration of the moisture resistance of the adhesive, it will be in a practically sufficient range. The moisture resistance of the optical disk device could be improved.

According to the above construction, the adhesive is applied to the periphery of the dielectric film to form the sealing member, and the sealing member cuts off the contact between the dielectric film and the atmosphere. It is possible to prevent the change in the refractive index of the beam splitter by preventing the absorption of moisture, and thus the change in the reflectance of the beam splitter can be prevented. Therefore, when applied to an optical head, an optical head having stable characteristics can be formed, and recorded information can be reliably reproduced.

In the above-described embodiments, the case where the sealing member is formed by using the epoxy adhesive is described, but the present invention is not limited to the epoxy adhesive, and various adhesives can be widely applied. it can.

Further, in the above-mentioned embodiments, the case where the sealing member is formed by using the adhesive has been described, but the present invention is not limited to this, and for example, a method such as spattering is applied to surround the dielectric film. When a protective film such as silicon nitride is formed on and the dielectric film is sealed by using the protective film as a sealing member, or when a wax is applied around the beam splitter to form the sealing member. It can be widely applied to etc.

Further, in the above-mentioned embodiments, the case where the beam splitter according to the present invention is applied to the optical disk device has been described, but the present invention is not limited to this, and it is applied to various optical devices to improve the moisture resistance. can do.

[0025]

As described above, according to the present invention, the contact between the dielectric film and the atmosphere is cut off by using the sealing member to prevent the dielectric film from absorbing moisture and prevent the change in the refractive index. As a result, it is possible to obtain a beam splitter capable of preventing a change in reflectance. Further, the beam splitter can be applied to an optical head to obtain an optical head with improved moisture resistance.

[Brief description of drawings]

FIG. 1 is a perspective view showing a beam splitter according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an optical disk device.

FIG. 3 is a perspective view showing a conventional beam splitter.

[Explanation of symbols]

1 ... Optical disk device, 4 ... Optical disk, 5 ... Semiconductor laser, 6 ... Objective lens, 8, 20 ... Beam splitter, 8A, 20A ... Dielectric film, 10 ... Light receiving element, 22 ...... Sealing member.

Claims (2)

[Claims] 1. A beam splitter in which inclined surfaces of first and second right-angled prisms are joined with a predetermined dielectric film interposed therebetween, and a sealing member is arranged so as to surround the periphery of the dielectric film. A beam splitter characterized in that the sealing member is arranged to break the contact between the dielectric film and the atmosphere. 2. A laser light source for emitting a light beam, an objective lens for focusing the light beam on a predetermined information recording medium, a reflected light beam of the light beam obtained from the information recording medium, And a light receiving element for receiving the reflected light beam separated by the beam splitter. The beam splitter includes a first dielectric film and a second dielectric film sandwiched between the first and second light splitting films. Is formed by joining the inclined surfaces of the right-angled prism, and a sealing member is arranged so as to surround the periphery of the dielectric film, and the dielectric member and the atmosphere are cut off by the sealing member. And the light head.