JPH08248231A - Optical converting device - Google Patents

Abstract

PURPOSE: To provide an optical converting device for generating a parallel light beam having a small cone angle. CONSTITUTION: An incident light ray made incident on a light transmission integrated body 2 composed of integrated light transmission bodies 2A-2D such as optical fibers is divisionally made incident on the entrance end parts 2'a-2'd of the light transmission bodies 2A-2D at the input side end part of the body 2, introduced to the output side by means of the light transmission bodies 2A-2D and outputted from the end parts 2a-2d on the output ends of the respective light transmission bodies as point light sources. The end parts 2a-2d on the output ends of the light transmission bodies are located on the focal distances of the individual lenses 1a-1d of a lens group 1, the light rays transmitted from the end parts 2a-2d on the output side of the light transmission body are taken in the individual lenses 1a-1d corresponding to the end parts 2a-2d on the output side of the light transmission body, respectively, converted to parallel light beams and transmitted. The transmitted light beam is preferably converged once and is made to be a parallel beam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light conversion device used in a liquid crystal display device, an image pickup device and the like, and more particularly to a light conversion device suitable for generating parallel light having a small cone angle.

[0002]

2. Description of the Related Art Generally, a conventional liquid crystal display device generally converts light emitted from a light source into parallel light through a lens and irradiates the liquid crystal display element with the parallel light. Then, the transmitted light or the reflected light of the liquid crystal display element, which is optically modulated according to the video signal in the liquid crystal display element, is enlarged and projected by the projection lens.

FIG. 5 is a schematic diagram of a conventional transmissive liquid crystal display device. In FIG. 5A, 4 is a light source such as xenon or metal halide, 8 is a condenser lens,
Reference numeral 9 is a microlens, 5 is a liquid crystal display element, 10 is a projection lens, and 11 is a screen. The light beam emitted from the light source 4 is converted into parallel light by the condenser lens 8 and is incident on the microlens 9. The microlens 9 is a lens group in which a plurality of individual lenses 9 ′ are arranged adjacent to each other as shown in FIG. 5B, and the individual lenses 9 ′ correspond to the pixels 5 ′ of the liquid crystal display element 5. In addition, the pixels 5 ′ are arranged at a distance so that they are located at the focal positions of the individual lenses 9 ′. Therefore, the light rays incident on the individual lenses 9'are condensed on the pixels 5 ', are optically modulated according to the video signal, and are emitted. Then, it is enlarged and projected onto the screen 11 by the projection lens 10.

[0004]

According to this conventional example,
As shown in FIG. 5B, a light beam having a cone angle of 0 ° (solid line in the figure) is condensed by the individual lens 9 ′ of the microlens 9 at a substantially central position of the pixel 5 ′ of the liquid crystal display element 5. Therefore, all the light rays incident on the microlens 9 are light-modulated by each pixel 5 ′ of the liquid crystal display element 5 and are used for image display, which enables bright image display with high light utilization rate. When a xenon lamp is used as the light source, the cone angle can be made small and the liquid crystal display device having a high light utilization rate as described above can be realized.

However, xenon lamps are limited to special industrial applications because of problems such as low luminous efficiency, high driving voltage due to high gas pressure, and risk of explosion. Generally, in many cases, a metal halide lamp is used as a light source of a liquid crystal display device. However, since the metal halide lamp has a long arc length, it is difficult to make a point light source, and in the conventional illumination optical system composed of a single lens combination,
I was not able to create a light beam with a small cone angle.

The broken line in FIG. 5B shows the state of light condensing by the individual lens 9'when a light beam having a large cone angle is incident on the microlens 9. Due to the existence of the cone angle, the light rays are not converged on one point on the pixel 5 ', and a surface having a spread is formed. Therefore,
There was a problem that a light beam that protrudes from the pixel and is blocked from being transmitted by the black matrix 5 "is generated in a part, which reduces the light utilization rate and makes it impossible to realize a bright projected image. There are some movements to try to use short metal halide lamps with short length, but such short arc metal halide lamps have a short lamp life and impair the reliability as a product.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in a light conversion device for converting the direction of light emitted from a light source, a lens having a plurality of lenses arranged adjacent to each other. There is provided a light conversion device comprising: a group; and a light guide unit that divides the emitted light and emits the light as a substantially point light source from each of the focal positions of the plurality of lenses.

[0008]

Embodiments of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a partially enlarged sectional view showing an embodiment of the light conversion device of the present invention. In FIG.
1 is a lens group, 2 is a light guide 2 such as an optical fiber
Reference numeral 3 denotes a plate, and reference numeral 3 denotes a plate, respectively. The lens group 1 includes individual lenses 1a, 1
b, 1c and 1d are arranged adjacent to each other. Also,
Output side end faces 2a, 2b, 2 of the light guides 2A, 2B, 2C, 2D corresponding to the individual lenses 1a, 1b, 1c, 1d and at the focal positions of the individual lenses 1a, 1b, 1c, 1d.
c and 2d are arranged. Light guides 2A, 2B, 2C,
The 2D output side end is fitted into a hole provided at a predetermined position of the plate 3 to ensure the alignment accuracy with the individual lenses 1a, 1b, 1c and 1d. Also, the light guide 2
Input side end portions 2'a, 2'b of A, 2B, 2C and 2D,
2'c and 2'd are bundled to form a light guide integrated body 2 in a state of spreading substantially radially from the input side to the output side.

The light rays incident on the light guide assembly 2 are guided to the light guides 2A, 2B, 2C and 2D at the input end of the light guide assembly 2.
The input side end portions 2'a, 2'b, 2'c, 2'd are divided and incident. Then, the light guides 2A, 2B, 2C, and 2D guide the light to the output side, and the output side end faces 2a and 2 of the respective light guides.
It is emitted from b, 2c and 2d. The output side end faces 2a, 2b, 2c, 2d of the light guide are the individual lenses 1a, 1b, 1
The surface is sufficiently smaller than the diameter of c and 1d and can be considered as a point light source. Output side end faces 2a, 2b of the light guide,
2c and 2d are individual lenses 1a, 1b and 1 of the lens group 1.
Light rays emitted from the output side end faces 2a, 2b, 2c, 2d of the light guides are located at the focal points of c and 1d, and individual lenses corresponding to the output side end faces 2a, 2b, 2c, 2d of the light guides, respectively. It is taken into 1a, 1b, 1c, 1d, converted into parallel light, and emitted.

FIG. 2 is a conceptual diagram for explaining the occurrence of a cone angle. In FIG. 2, φ1 is the diameter of the individual lens (1a in the figure), φ2 is the diameter of the output side end face (2a in the figure) of the light guide, f is the focal length of the individual lens, and θ is the cone angle. Indicates. From FIG. 2, the cone angle θ has a relationship of θ = arc tan (φ2 / 2f) (1). Therefore, if the output end face of the light guide, that is, φ2, has a finite value, θ also has a finite value, and the cone angle θ is generated. On the other hand, if the aperture ratio of the individual lens is N
Since A is f = φ1 / 2NA (2), θ = arc tan (NA · φ2 / φ1) (3) is obtained from the equations (1) and (2). Therefore, in order to make the cone angle θ as small as possible, the individual lenses 1a, 1b, 1c, and 1c should satisfy the relation of φ1 >> NA · φ2 (4).
1d and the output side end faces 2a, 2b, 2c, 2d of the light guide may be designed. For example, diameter is 1mm, NA is 0.4
In order to produce a luminous flux with a cone angle of ± 1 ° or less using the individual lens of, the output side end face of the light guide is 43 μm or less, that is, the light guides 2A to 2D have a diameter of 4 from the formula (3).
It is sufficient to use an optical fiber of 3 μm or less.

A microlens or a holographic lens may be used as the lens group 1. Further, a light condensing member for efficiently taking in the light flux from the light source may be arranged on the input side of the light guide integrated body 2. Furthermore,
The input end face and the output end face of each of the light guides 2 </ b> A to 2 </ b> D may be configured to have a lens effect on both end faces or one of the faces.

FIG. 3 is a schematic diagram showing an example of a liquid crystal display device using the light conversion device of the present invention. The same components as those in FIG. 1 are designated by the same reference numerals. In FIG. 3, the light beam emitted from the light source 4 is focused on the input side end of the photoconductor integrated body 2,
Enter the light guide assembly 2. Inside the light guide integrated body 2, the entering light beam is divided into individual light guides (not shown) constituting the light guide integrated body 2 and is incident. Then, the divided individual light rays are guided substantially radially toward the output side end portion by the light guide, and are emitted from the focal position of the individual lens (not shown) of the lens group 1 toward the individual lens. If the output side end surface of the light guide and the individual lens are designed so as to satisfy the relationship of the expression (4), the light rays incident on the individual lens are converted into perfectly parallel light and illuminate the liquid crystal display element 5. Since the light rays incident on the liquid crystal display element 5 are completely parallel light, if, for example, a microlens is arranged in front of the liquid crystal display element 5, the light rays that have passed through the microlens are the pixels (not shown) of the liquid crystal display element 5. Since the light can be condensed at one point substantially at the center position, the light utilization rate is improved and a bright projected image can be realized.

Further, when the perfectly parallel light is incident on the reflection type liquid crystal display element through the polarization beam splitter, it is possible to avoid the problem that the contrast ratio is lowered due to the incident angle dependency of the polarization beam splitter.

FIG. 4 is a schematic configuration diagram showing another example of a liquid crystal display device using the light conversion device of the present invention. Here, only the differences from the device of FIG. 3 will be described. According to the liquid crystal display device of FIG. 4, the completely parallel light emitted from the lens group 1 is once condensed by the lens 6 and then converted into parallel light again by the lens 7. In the liquid crystal display device shown in FIG. 3, since the light emitted from the lens group 1 is completely parallel light, the ridge line portion of each individual lens forming the lens group 1 may be a dark portion, resulting in variation in brightness. On the other hand, with the lens configuration shown in FIG. 4, it is possible to avoid the above-described problem of brightness variation and display a high-quality image.

The recent trend of liquid crystal display devices tends to reduce the device size. For small device sizes,
If the design is done with an emphasis on the light utilization rate, it becomes critical lighting and the cone angle becomes large. On the other hand, when designing with emphasis on the cone angle, there is a problem in that the light utilization rate is reduced and a bright image cannot be displayed. But,
If the size of the lens 7 on the output side is designed to be small in accordance with the element size in the lens configuration of FIG. 4, a light beam with a small cone angle can be obtained without reducing the light utilization rate, and a liquid crystal display device having a bright and excellent contrast is obtained. Can be realized.

Further, by utilizing the light conversion device of the present invention, it is not necessary to use a short arc metal halide lamp as a light source, and a highly reliable liquid crystal display device having a long lamp life can be provided.

The light conversion device of the present invention is not limited to the above-described embodiment, and is widely used for irradiating light to a liquid crystal display element or a light detection element in a transmission type or reflection type liquid crystal display device or an image pickup device. It can be used, and high-luminance and high-resolution display and imaging can be realized.

[0018]

As described above, according to the light conversion device of the present invention, it is possible to easily convert parallel light with a small cone angle without reducing the light utilization rate. In addition, since parallel light can be generated regardless of the arc shape of the light source, it is not necessary to use a metal halide lamp with a short arc, and a highly reliable device with a long lamp life can be provided. Further, if the light emitted from the lens group is once condensed by the light condensing means and is converted again into parallel light, then the emitted light having no brightness variation can be obtained. Furthermore, when the light conversion device of the present invention is used in a liquid crystal display device, an image pickup device, or the like, it is possible to realize display and image pickup with high light utilization rate and excellent contrast. Further, if the light emitted from the lens group is once condensed by the condensing means and is again converted into parallel light, it is possible to realize high-quality display and image pickup without variations in brightness. Further, if the second condensing means provided on the output side of the light conversion device is designed in accordance with the size of the liquid crystal display element or the image pickup element, the light utilization rate can be improved even for the small size liquid crystal display element or the image pickup element. The cone angle can be reduced without dropping, and bright and excellent display and imaging can be realized.

[Brief description of drawings]

FIG. 1 is a partially enlarged cross-sectional view showing an embodiment of a light conversion device of the present invention.

FIG. 2 is a conceptual diagram for explaining the occurrence of a cone angle.

FIG. 3 is a schematic configuration diagram showing an example of a liquid crystal display device using the light conversion device of the present invention.

FIG. 4 is a schematic configuration diagram showing another example of a liquid crystal display device using the light conversion device of the present invention.

FIG. 5 is a schematic configuration diagram showing a conventional transmissive liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 lens group 1a, 1b, 1c, 1d individual lens 2 light conductor integrated body (light guide means) 2A, 2B, 2C, 2D light guide 4 light source 5 liquid crystal display element 6 lens (first light collecting means) 7 lens (first lens) 2 light collecting means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hirofumi Imaoka 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Japan Victor Company of Japan, Ltd.

Claims (3)

[Claims] 1. A light conversion device for converting the direction of light emitted from a light source, wherein a lens group in which a plurality of lenses are arranged adjacent to each other, and the light emitted is divided, and focus positions of the plurality of lenses are respectively changed. A light conversion device, comprising: a light guide means that emits light as a substantially point light source. 2. The light guide means is an integrated body of a plurality of optical conductors, wherein the output end side of the integrated body of the optical conductors spreads out substantially radially, and each output end face of the optical conductor has a plurality of lenses. The optical conversion device according to claim 1, wherein the optical conversion device is located at each focal position. 3. A first condensing means for converting the substantially parallel light converted from the light emitted from the light guiding means by the lens into a convergent light, and a second condensing light for converting the converged light into a substantially parallel light again. The optical conversion device according to claim 1 or 2, further comprising: