JP3080693B2 - Polarizing beam splitter array - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing beam splitter array for obtaining linearly polarized light from irregularly polarized light.

[0002]

2. Description of the Related Art Some devices and other devices that use polarized light use linearly polarized light. An example of a device using linearly polarized light is a projection type liquid crystal display device that enlarges and projects a display image of a TN (twisted nematic) liquid crystal display element on a screen using a light source and a projection lens.

Conventionally, when a halogen lamp, a xenon lamp, a metal halide lamp, or the like is used as a light source in such an apparatus, light generated from the light source is indefinitely polarized light. A polarizer such as a polarizing plate or a polarizing beam splitter is used.

[0004]

However, when a conventional polarizing plate is used for a projection type liquid crystal display device, the projection screen becomes dark because the transmittance of the polarizing plate is 50% or less.
When a light source with high luminance is used to brighten the projection screen, the light absorbed by the polarizing plate is converted into heat, and the temperature of the polarizing plate becomes extremely high. The polarizing plate has a structure in which a polarizing film is manufactured by orienting and adsorbing iodine or the like on a polyvinyl alcohol film, and a plastic sheet such as triacetate or acrylic is bonded to the screen for protection, so that the heat resistance is weak, and the temperature is low. The performance is degraded by the rise. Therefore, when a light source with high luminance is used, the polarizing plate is deteriorated by heat, and the degree of polarization is reduced. When the degree of polarization of the polarizing plate decreases,
There is a problem that the contrast of the projection screen is reduced and the image quality is significantly impaired.

On the other hand, a polarizing beam splitter has a structure in which a semi-permeable film made of a dielectric multilayer film is coated on one slope of two right-angle prisms, and the slopes are joined to each other. Are separated as two linearly polarized lights whose polarization directions are orthogonal to each other. Such a polarizing beam splitter is made of glass and a dielectric multilayer film, and has excellent heat resistance. In addition, since it hardly absorbs light, performance does not deteriorate even when a high-power light source is used. However, when used in a projection type liquid crystal display device, the diameter of the projection light beam from the light source is large, so that it is necessary to use a polarizing beam splitter of a large size. Accordingly, the size of the optical system is increased and the weight is increased, so that it is difficult to reduce the size and weight of the projection device. In addition, it is costly to obtain a large and uniform glass material, and there is a problem that the cost of the apparatus increases.

SUMMARY OF THE INVENTION An object of the present invention is to provide a polarizing beam splitter array which can be used as a polarizer which does not deteriorate its performance even when irradiated with very intense light, and which is effective in reducing the size, weight and cost of a projection device. Is to provide.

[0007]

Means for Solving the Problems In order to achieve the above object, a polarizing beam splitter array according to the present invention comprises a polarizing beam splitter array for converting an indeterminately polarized light into two linearly polarized lights, p-polarized light and s-polarized light, whose polarization directions are orthogonal to each other. The three or more polarization beam splitters, each of which has a polarization light splitting surface having an incident angle of 45 [deg.] Formed on the joint surface of the prism, are separated from each other by s-polarization so that adjacent polarization splitting surfaces are orthogonal to each other. It is characterized in that it is bonded via an adhesive adjacent to a direction parallel to the light reflection direction.

[0008]

According to the above configuration of the present invention, on the polarization splitting surface formed in the polarization beam splitter, the variable polarization light incident on the polarization beam splitter array transmits the p-polarized component light as it is and the s-polarized component light. The light is reflected and separated into two linearly polarized lights whose polarization directions are orthogonal to each other. The p-polarized light passes through the polarizing beam splitter array and becomes emitted light. On the other hand, the reflected s-polarized light enters the adjacent polarizing beam splitter and is reflected again by the polarization splitting surface formed on the polarizing beam splitter. here,
The polarization separation plane between adjacent polarization beam splitters is
Since they are orthogonal to each other, the s-polarized light eventually exits in the direction opposite to the incident direction of the indefinitely polarized light. Similarly, the indefinitely polarized light incident on all the polarizing beam splitters constituting the polarizing beam splitter array transmits the p-polarized light as it is and reflects the s-polarized light in the direction opposite to the incident direction by the above-described optical path. And the polarizing beam splitter array
Acts as a polarizer.

Such a polarizing beam splitter array is excellent in heat resistance because it is made of glass as compared with a conventional polarizing plate. Therefore, when used in a projection type liquid crystal display device, a high brightness light source can be used. Thus, the projection screen can be made bright. Also, compared to the conventional polarizing beam splitter, for example, when ten polarizing beam splitters are arranged in an array, the thickness and weight are reduced to 1/10, so that the polarizing beam splitter is used for a projection type liquid crystal display device. If
This is effective in reducing the size and weight of the projection device.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a polarizing beam splitter array showing an embodiment of the present invention.

The polarization beam splitter array 1 has a polarization splitting surface 10 for splitting an indefinitely polarized light into two linearly polarized lights, p-polarized light and s-polarized light, whose polarization directions are orthogonal to each other.
To s-polarized beam splitters 2 to 9, each of which is formed adjacent to each other in a direction parallel to the direction in which the s-polarized light 27 is reflected. Also,
Polarization splitting surfaces 10 of adjacent polarizing beam splitters 2 to 9
17 are arranged so as to be orthogonal to each other.

The principle that the polarizing beam splitter array 1 according to the present invention having the structure shown in FIG. 1 operates as a polarizer will be described with reference to FIG. FIG. 2 is a partial cross-sectional view of the polarization beam splitter array 1 of FIG. 1, and the vicinity of the polarization beam splitters 6 and 7 is enlarged. In FIG. 2, the polarization beam splitter 6 and the polarization beam splitter 7 include:
Polarization separating surfaces 14 and 15 for separating the indefinitely polarized light into two linearly polarized light beams whose polarization directions are orthogonal to each other are formed at an angle of 45 ° with respect to the incident lights 20 and 25, respectively.
The incident lights 20, 25, which are indefinitely polarized lights,
When the light enters the light sources 4 and 15, respectively, the p-polarized light beams 21 and 26 are transmitted, and the s-polarized light beams 22 and 27 are reflected. The polarization beam splitter 6 and the polarization beam splitter 7 output the s-polarized light 2
The polarization separation surfaces 14 and 15 are arranged adjacent to each other in a direction parallel to the reflection directions of the light beams 2 and 27, and are orthogonal to each other.

Here, when incident light 20 which is indefinitely polarized light enters the polarization beam splitter 6, the p-polarized light 21 is transmitted, and the s-polarized light 22 is reflected and Into two linearly polarized lights. p-polarized light 21
Is emitted from the polarization beam splitter 6 as it is and becomes the emission light 23. On the other hand, the s-polarized light 22 enters the adjacent polarization beam splitter 7, is reflected again by the polarization splitting surface 15, and exits from the polarization beam splitter 7. Since the polarization splitting surface 14 and the polarization splitting surface 15 are orthogonal to each other, the s-polarized light 22 becomes the outgoing light 24 propagating in the opposite direction to the incident light 20. Similarly, when the incident light 25, which is indefinitely polarized light, enters the polarization beam splitter 7, the polarization splitting surface 1
At 5, the p-polarized light 26 is transmitted and the s-polarized light 27 is reflected and split into two linearly polarized lights. p-polarized light 26
Exits the polarization beam splitter 7 as it is and becomes the exit light 28. On the other hand, the s-polarized light 27 enters the adjacent polarization beam splitter 6, is reflected again by the polarization splitting surface 14, and exits from the polarization beam splitter 6. Since the polarization separation surface 14 and the polarization separation surface 15 are orthogonal to each other, the s-polarized light 27 becomes the outgoing light 29 that propagates in the opposite direction to the incident light 25. Therefore, the polarization beam splitters 6 and 7 that constitute the polarization beam splitter array 1 transmit the p-polarized light 21 and 26 and reflect the s-polarized light 22 and 27 in the direction opposite to the incident direction, so that the polarized beam splitters 6 and 7 are indefinitely polarized light. Some incident light 2
0 and 25 can be separated into linearly polarized lights whose polarization directions are orthogonal to each other, and act as polarizers.

As is clear from the above description, the polarization beam splitters 2 and 3, 4 and 5, 8 and 9 in FIG. 1 transmit p-polarized light and s-polarized light similarly to the polarization beam splitters 6 and 7. By reflecting light, the indefinitely polarized light can be separated into two linearly polarized lights whose polarization directions are orthogonal to each other.
The polarization beam splitter array 1 including the eight polarization beam splitters 2 to 9 functions as a polarizer.

The configuration shown in FIG. 1 shows an example of a mode in which eight polarization beam splitters 2 to 9 are used, which will be described more specifically below. In FIG. 1, each of the polarizing beam splitters 2 to 9 has a structure in which a semi-permeable film made of a dielectric multilayer film is coated on one of the slopes of two right-angle prisms and the slopes are joined. For non-polarized light with a wavelength in the visible light region,
One having a performance capable of sufficiently separating into p-polarized light and s-polarized light was used. The extinction ratio, that is, the intensity ratio of the p-polarized component to the s-polarized component of the transmitted light was 100: 1 or more. Adjacent polarizing beam splitters 2 to 9 are bonded with an adhesive whose refractive index is matched so that reflected light does not occur at each boundary surface. The adhesive portion has no function of separating polarized light and does not transmit light, but has a thickness of 100
μm or less, the proportion of the area of the light incident surface of the polarizing beam splitter array 1 occupying 1% or less, and the loss of the transmitted light amount is very small. Polarizing beam splitter array 1
An anti-reflection film made of a dielectric multilayer film is applied to the light incident surface and the light exit surface. The size of each of the polarizing beam splitters 2 to 9 is 10 × 60 × 10 mm, and therefore, the size of the polarizing beam splitter array 1 is 80 × 60 × 10 mm.

Compared to a conventional polarizing plate made of plastic, such a polarizing beam splitter array is excellent in heat resistance because it is made of glass and a dielectric multilayer film. For example, even when the light emitted from a 500 W xenon lamp was directly applied to the polarizing beam splitter array, the performance such as the transmittance and the degree of polarization did not change over time. Therefore, when the polarizing beam splitter array is used in a projection type liquid crystal display device, a high output light source can be used, and the projection screen can be made bright.

Also, compared to the conventional polarizing beam splitter, the thickness and weight are reduced to 1/8 by arranging the eight polarizing beam splitters in an array. This is effective in reducing the size and weight of the projection device. Further, each polarizing beam splitter can be made of small-sized glass, and it is not necessary to obtain a large and uniform crystal material, so that the cost can be reduced.

As described above, in the description of the present embodiment, the polarization beam splitter array can be configured using a polarization beam splitter separated by a plane perpendicular to the polarization separation plane. When changing the polarization direction of the linearly polarized light emitted from the polarization beam splitter array, by rotating the polarization beam splitter array about the incident direction of the light, linearly polarized light having a desired polarization direction is obtained. Further, in order to improve the degree of polarization of the emitted light, a conventional polarizing plate may be inserted in the optical path of the emitted light. In this case, since the light incident on the polarizing plate is previously linearly polarized, the polarizing beam splitter array also has an effect of reducing the generation of heat due to the absorption of light by the polarizing plate and the accompanying deterioration in performance. . The polarizing beam splitter array of the present invention is effective not only for a projection type liquid crystal display device but also for an apparatus or an apparatus using polarized light.

[0019]

As described above, according to the present invention,
A light and thin polarizing beam splitter array that can be used as a polarizer whose performance does not deteriorate even when irradiated with extremely intense light was obtained. This polarizing beam splitter array enables the use of a high-output light source in a projection-type liquid crystal display device, realizes a high-brightness projection screen, and reduces the size and weight of equipment and devices that use polarized light. It is also effective in reducing costs.

[Brief description of the drawings]

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

FIG. 2 is a partial cross-sectional view of a polarizing beam splitter according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Polarization beam splitter array 2-9 Polarization beam splitter 10-17 Polarization separation surface 20,25 Incident light 21,26 p polarized light 22,27 s polarized light 23,24,28,29 Outgoing light

Claims (1)

(57) [Claims] 1. A polarization splitting surface having an incident angle of 45 ° for splitting an indefinitely polarized light into two linearly polarized lights, p-polarized light and s-polarized light, whose polarization directions are orthogonal to each other, is formed on the joint surface of the prism. A polarized light beam, characterized in that three or more polarized beam splitters are bonded via an adhesive in a direction parallel to the direction of reflection of the s-polarized light so that the adjacent polarized light separating surfaces are orthogonal to each other. Beam splitter array.