JPH1139689A - Prism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a good laminated film in a polarizing beam splitter having many numbers of layers. SOLUTION: By holding a multilayer thin film alternately laminated by a thin film of low refractive index and a thin film of high refractive index by glass or resin, sticking a first multilayer film 2 composed of (n) multilayer thin films (n>=10) to a second multilayers film 4 composed of (m) multilayer thin films (m>=10) directly or through a thin glass plate 5 and forming the multilayer film composing a beam splitter of the first/second multilayer films, a number of layers of the respective multilayer films is reduced, the accumulation of internal stress is suppressed to be little and the crack and peeling of laminated film are prevented. Since the total optical characteristic of the first/ second multilayer film is obtained and the optical characteristic as same as that of the multilayer film continuously composed of the first/second multilayer films is contained by sticking the first/second multilayer films directly or through the thin glass plate, the prism having a good beam splitter is constituted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism used for an optical pickup.

[0002]

2. Description of the Related Art In recent years, an optical pickup using a prism has been required in an optical pickup.
This prism is used to split an optical path from a light source and an optical path to a detector, and a polarizing beam splitter is formed in the prism.

The polarizing beam splitter has a structure in which low refractive index layers and high refractive index layers are alternately laminated.

The polarization beam splitter has a severe restriction on the incident angle of the light beam, and in many cases, a desired polarization characteristic can be obtained only at a certain single angle or an angle range of about ± 1 ° with respect to the center angle.

[0005] To solve this problem, Japanese Patent Laid-Open Publication No.
A polarization beam splitter described in 146218 is known.

[0006] This conventional polarizing beam splitter is

[0007]

[Table 1]

As shown in FIG. 1, the first stack and the second stack have a total number of 26 layers. In order to obtain a desired polarizing beam splitter at a wide incident angle, the number of layers of the thin film is increased.

[0009]

However, in the above-mentioned conventional polarizing beam splitter, it is difficult to obtain a good laminated film due to the large number of layers.

That is, in film formation by the vapor deposition method,
It is difficult to control the internal stress of the thin film that constitutes each layer.After laminating a multilayer film, this internal stress causes micro cracks in the thin film, and in extreme cases, peels off and a good beam splitter is obtained. Therefore, there is a problem that a prism cannot be formed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to provide a prism having a good beam splitter without cracks or the like.

[0012]

In order to achieve this object, the present invention provides a prism comprising a multi-layer thin film in which a low-refractive-index thin film and a high-refractive-index thin film are alternately laminated, sandwiched between glass or resin. The thin film is characterized in that a first multilayer film composed of n layers (n ≧ 10) and a second multilayer film composed of m layers (m ≧ 10) are bonded with an adhesive.

Thus, a prism having a good beam splitter free from cracks and the like can be obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a prism comprising a multilayer thin film in which a low refractive index thin film and a high refractive index thin film are alternately laminated, sandwiched between glass or resin,
The multilayer thin film is characterized in that a first multilayer film composed of m layers (m ≧ 10) and a second multilayer film composed of n layers (n ≧ 10) are bonded with an adhesive.

Here, since the number of layers of each multilayer film can be reduced by forming the multilayer film constituting the beam splitter as the first multilayer film and the second multilayer film, accumulation of internal stress is reduced. It is possible to prevent cracking and peeling of the laminated film, and to bond the first multilayer film and the second multilayer film directly with an adhesive or through thin glass, thereby optically forming the first multilayer film. And the overall characteristics of the second multilayer film can be obtained, so that the same optical characteristics as those of the multilayer film in which the first multilayer film and the second multilayer film are continuously formed can be obtained. This has the effect that a prism having the same can be formed.

An embodiment of the present invention will be described below with reference to FIG. (Embodiment 1) FIG. 1 is an external view of a prism having a beam splitter according to a first embodiment of the present invention.

In the prism according to the first embodiment, a first multilayer film 2 is formed on a first substrate 1 by a vapor deposition method. The first multilayer film 2

[0018]

[Table 2]

As shown in the figure, a low-refractive-index film and a high-refractive-index film are alternately laminated, and have a 12-layer structure.

On the second substrate 3, a second multilayer film 4 is formed by a vapor deposition method. As shown in (Table 2), the second multilayer film 4 also has a 12-layer structure in which low-refractive-index films and high-refractive-index films are alternately stacked. Then, the first multilayer film 2 and the second multilayer film 4 are bonded via an adhesive layer 5.

Here, the refractive index of the first and second base materials 1 and 3 is 1.51, and the refractive index of the adhesive layer 5 is the same as that of the base material.
51. Since each of the first and second multilayer films has 12 layers, the residual internal stress is small, and the multilayer films 2 and 4 are not cracked or peeled off during the cleaning after the deposition or before the bonding. A good prism was obtained.

Although the first and second substrates 1 and 3 are made of glass, the same applies to the case where they are made of resin. In addition, although the refractive index of the adhesive is the same as that of the base material, it goes without saying that an adhesive having a different refractive index from that of the base material can be used.

In our experiments, when the number of layers of the multilayer film exceeds 25, the number of cases where microcracks are generated increases,
If the number is zero or more, peeling may occur.

Accordingly, when the number of layers is 20 or more, the number of layers of the first and second multilayer films may be at least 10 or more.

[0025]

As described above, according to the prism of the present invention, the number of layers of each multilayer film is reduced by forming the first multilayer film and the second multilayer film constituting the beam splitter. Therefore, the accumulation of internal stress can be reduced, cracks and peeling of the laminated film can be prevented, and the first
By bonding the multilayer film and the second multilayer film directly with an adhesive or through thin glass, the overall characteristics of the first multilayer film and the second multilayer film can be obtained optically. Since the same optical characteristics as those of a multilayer film in which the first multilayer film and the second multilayer film are continuously formed are obtained, there is an effect that a prism having a good beam splitter can be formed.

[Brief description of the drawings]

FIG. 1 is an external view of a prism according to a first embodiment of the present invention.

[Explanation of symbols]

 1,3 base material 2,4 multilayer film 5 adhesive layer

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Nochi Kidai 1006 Kazuma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. Inside

Claims (1)

[Claims] 1. A prism in which a multilayer thin film in which a low refractive index thin film and a high refractive index thin film are alternately laminated is sandwiched between glass or resin, wherein said multilayer thin film is composed of m layers (m ≧ 10).
Characterized in that a second multilayer film composed of the above-mentioned multilayer film and an n-layer (n ≧ 10) is bonded with an adhesive.