JPH04308838A - Optical element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element used for separating and combining polarization components and color components of light in an apparatus having an optical system.

0002

[Prior Art] In an apparatus having a conventional optical system, a polarizing beam splitter for separating polarized components of light, blue, green,
A dichroic prism that separates and synthesizes the three primary colors of red is made by forming a dielectric multilayer film on a prism made of multiple optical glasses as a base material, and then bonding it with an adhesive, as shown in Figures 11 and 12. It was meant to be glued together. In the figure, 1 is an optical glass, 2 is a polarizing beam splitter film, 3 is a red-reflecting dichroic mirror film, and 4 is a blue-reflecting dichroic mirror film.

However, these conventional optical elements have the following problems. First, in a prism using optical glass as a material, birefringence occurs inside the material during the manufacturing process, so the entire prism does not have a uniform refractive index. This birefringence becomes more pronounced as the shape of the prism becomes larger, and in the case of a polarizing beam splitter that separates polarized light components of light, a phenomenon occurs in which the polarized light component that should be reflected is transmitted through a portion of the prism.

Second, when this optical element is made of optical glass, the larger the shape of the prism, the lower the yield due to striae and bubbles inside the glass, and the higher the cost. Furthermore, in the process of applying a dielectric multilayer film to the prism, it is difficult to recycle the dielectric film, so the process involves high risks.

Third, when bonding multiple prisms together to form a single optical element, the process involves carefully bonding them one by one, paying close attention to avoid misalignment of the optical path system. There is no other choice but to do so, and it is a tedious and time-consuming process that requires patience.

Fourth, since the dielectric multilayer film utilizes the interference effect of light, the angle of incidence of the incident light beam has a large dependence on the spectral characteristics. In order to obtain the optimal characteristics of a broadband polarizing beam splitter, if the dielectric material laminated with the glass base material of the prism is limited to a certain extent, the angle of the incident ray to the dielectric multilayer film surface is limited due to its refractive index. be done.

[0007]

[Problems to be Solved by the Invention] This invention was made to solve the above problems, and its purpose is to provide a low-cost and simple structure that does not have birefringence. Therefore, it is an object of the present invention to provide an optical element that can correspond to the optimum angle of incidence of an incident light beam with respect to a dielectric multilayer film surface and that simplifies the bonding process.

[0008]

[Means for Solving the Problems] The optical element of the present invention has one or more transparent substrates formed with a dielectric multilayer film arranged in a container having a plurality of entrance windows and exit windows, The container is characterized by being sealed with a transparent filling material that is liquid during injection and solid or gel during use.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. First Embodiment FIG. 1 shows a perspective view of an optical element according to a first embodiment of the present invention. The container 13 is molded by aluminum die-casting,
There is an entrance window 5 and an exit window 6, and a transparent base material coated with an antireflection film is attached to each with an adhesive. A protrusion 10 is provided inside the container 13 so that the transparent base material 7 coated with a dielectric multilayer film can be installed at a certain angle, and is fixed by pasting it using an adhesive. The film applied to the transparent base material 7 is a broadband polarizing beam splitter film, and is made of titanium oxide, zirconium oxide, or yttrium oxide as a high refractive material and a dielectric material such as silicon oxide or magnesium fluoride as a low refractive material by vacuum evaporation. The body was deposited in multiple layers. The installation angle and spectral optical characteristics of the transparent substrate 7 with respect to the incident light beam are determined to be optimal angles and film configurations for efficiently separating polarized light components by combining these dielectrics.

After installing the transparent base material 7, a top lid 11 is attached using adhesive or a packing structure to seal the inside of the container, and a silicone rubber compound (
(refractive index > 1.4) to fill the interior. In order to remove air bubbles from the silicone rubber compound, the pressure is reduced using a pressure reducer, and then curing is performed at room temperature or under heating at 50 to 150°C.

The spectral characteristics of the optical element thus obtained are shown in FIGS. 2 and 3. FIG. 2 shows the spectral transmittance characteristics of the S-polarized light component and the P-polarized light component in this example, and FIG. 3 shows the spectral transmittance characteristics of only the silicone rubber compound without the transparent base material 7 installed. . The incident light beam has an S polarization component and a P polarization component over a wide range of 400 to 700 mm.
Separated into polarized components. Additionally, silicone rubber compounds have translucency that allows them to be used as optical elements.

FIGS. 4 and 5 show the state of birefringence. The black areas are areas where the polarization component is missing due to birefringence, and in the case of the prism using conventional optical glass shown in Figure 4, these black areas are seen at the four corners, indicating that the polarization component is missing. However, in the case according to the present invention shown in FIG. 5, no birefringent portion is observed. The silicone rubber compound used as the filling material is cured by addition polymerization reaction, so there are no by-products and no distortion occurs. Thus, the absence of distortion and uniform refractive index over the entire optical element is extremely efficient in separating polarized light components when used as a polarizing beam splitter.

FIGS. 6 to 8 show the shape of the container when the installation angle of the polarizing beam splitter film with respect to the incident light beam is changed. Although the structure was the simplest when the incident angle was 45°, it was possible to separate the P-polarized light component and the S-polarized light component even at 30° and 60°.

Second Embodiment FIG. 9 shows a perspective view of an optical element according to a second embodiment of the present invention. The container 13 has four windows made of transparent substrates, each of which allows light divided into three colors of blue, green, and red to enter, and a dielectric multilayer film installed in a cross shape inside the container. A transparent base material coated with a dichroic mirror film selectively reflects and transmits light, and the light is emitted as composite light through a single window. Furthermore, when the light source light enters through one window, the remaining windows emit light that is divided into blue, green, and red, respectively. The inside of the container is filled with silicone rubber compound and sealed in the same manner as in the first embodiment.

FIG. 10 is a spectral transmittance characteristic diagram of the S-polarized light component in this example. It reflects the red and blue color components and transmits the green color component. The half-value wavelength can be arbitrarily set by changing the thickness of the dielectric film. The dichroic mirrors installed in a cross shape have a film breakage in the center, and in order to reduce the effect of this, the thickness of the transparent base material is as thin as 0.2 to 1.0 mm. The silicone rubber compound that fills the inside of the container becomes solid or gel-like after it hardens, so the mirrors arranged in a cross shape are fixed, and it is possible to suppress blurring of the emitted light due to vibration.

[0016]

As described above, according to the present invention, an optical element that conventionally relied on a prism made of an optical material can be made from one container and a plurality of plates having dielectric multilayer films. It is possible to significantly reduce costs and risks. In addition, by filling the inside of the container with a translucent silicone rubber compound, problems with conventional prisms such as striae, bubbles, distortion, and birefringence are eliminated, and the shape can be increased. can also be handled. Furthermore, the angular dependence of the dielectric multilayer film can be easily dealt with by changing the installation angle of the transparent substrate coated with the dielectric multilayer film, and high precision can be achieved in optical elements with complex structures. The required bonding process can be simplified.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a first embodiment of the invention.

FIG. 2 is an optical characteristic diagram of the optical element in the first example.

FIG. 3 is an optical characteristic diagram showing the translucency of a silicone rubber compound.

FIG. 4 is an explanatory diagram of the state of birefringence in the case of a prism using conventional optical glass.

FIG. 5 is an explanatory diagram of a birefringence state according to the first embodiment of the present invention.

FIG. 6 is a plan view showing the shape of the container when the installation angle of the polarizing beam splitter is changed in the first embodiment.

FIG. 7 is a plan view showing the shape of the container when the installation angle of the polarizing beam splitter is changed in the first embodiment.

FIG. 8 is a plan view showing the shape of the container when the installation angle of the polarizing beam splitter is changed in the first embodiment.

FIG. 9 is a perspective view of a second embodiment of the invention.

FIG. 10 is an optical characteristic diagram of an optical element in a second example.

FIG. 11 is an explanatory diagram of a conventional optical element.

FIG. 12 is an explanatory diagram of a conventional optical element.

[Explanation of symbols]

5 Entrance window 6 Output window 7 Transparent base material with polarizing beam splitter film 8 Transparent substrate with red reflective dichroic mirror film 9 Transparent substrate with blue reflective dichroic mirror film 10 Transparent base material fixing protrusion 11 Sealing top lid 12 Inlet port 13 Container

Claims (4)

[Claims] Claim 1: One or more transparent substrates formed with a dielectric multilayer film are arranged in a container having a plurality of entrance windows and exit windows, and the inside of the container is liquid when injected. An optical element characterized in that it is sealed with a transparent filling material that is sometimes solid or gel-like. 2. The optical element according to claim 1, wherein the dielectric multilayer film formed on the transparent base material is a broadband polarization beam splitter film. 3. The optical element according to claim 1, wherein the dielectric band multilayer film formed on the transparent base material is a dichroic mirror film. 4. The optical element according to claim 1, wherein the transparent filling material is a silicone rubber compound.