JP2002267855A - Optical information transmission device and image magnified display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easily manufacturable optical information transmission device in which the resolution of an input image is not deteriorated even when a flat type display such as a liquid crystal display is used for an image before enlarging. SOLUTION: The critical angle θc of total reflection condition of an optical light guide 2 is made larger than a shape angle θa formed by the central axis of the optical light guide 2 and the side surface 2s of the optical light guide 2. The difference (θc-θa) between the critical angle θc and the shape angle θa is made smaller than the optimum prospective angle θb of the optical light guide 2 regulated by the size of a light emitting point of inputted optical information, the size of the end surface of the optical light guide 2 opposed to the light emitting point, and the distance from the light emitting point to the incident plane of the optical light guide 2. By such settings, light made incident vertically on the end surface of the optical light guide 2 can satisfy the total reflection condition of the optical light guide 2, and can be transmitted through the optical light guide 2, and incident light whose transmission is not originally desirable from an oblique direction of light made incident of the end surface of the optical light guide 2 is cut.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information transmitting device for transmitting information in parallel and an enlarged image display device.

[0002]

2. Description of the Related Art There are two main types of display devices for displaying information: flat-panel displays, such as single-size display devices such as liquid crystal monitors for personal computers, and enlarged projection display devices, such as rear-projection liquid crystal televisions. .

The unit-size display device has the advantage that the thickness of the display can be reduced and the space required for installation is small, but when a large screen, for example, a screen of 30 inches or more, is to be obtained. There is a disadvantage that the cost is increased due to the complexity of the manufacturing process and the poor yield.

On the other hand, an enlarged projection display device has the advantage that a large display size of 50 inches or more can be provided at a lower cost than a 1 × display device, but the display is made as thin as the 1 × display. This is difficult in principle, and has the disadvantage of requiring a large installation space.

[0005] In an existing enlarged projection display device such as a liquid crystal television, a technique of an enlarged optical system using a lens or a mirror is used. As a method for solving the above-mentioned problem that the optical system becomes thick, FIG. The optical fiber is aligned with a small image, and the surface where one end of the optical fiber is tightly bundled is used as the image input surface, and the surface where the other end of the optical fiber is discretely arranged is used as the output surface. (Japanese Patent Application Laid-Open No.
No. 88617). That is, the optical fiber 51
An image matching unit 55 composed of a bundle of optical fibers 54 is interposed between an image enlargement unit 52 using a bundle of the optical fibers and an image element 53 such as a liquid crystal or a film, and one end of the bundle of the optical fibers 54 is focused. The other end of the bundle of optical fibers 54 is slightly expanded so as to face the image element 53 so as to face the entire light incident portion 56 of the image magnifying means 52. As a result, the image displayed on the image element 53 is enlarged by the image matching unit 55 to a size corresponding to the light entering unit 56 and projected onto the light entering unit 56.

[0006]

However, in the configuration disclosed in Japanese Patent Laid-Open No. 5-88617, the area of the image before enlargement and the total cross-sectional area of the optical fiber on the image input side are substantially the same. Therefore, the cross-sectional area of the optical fiber itself limits the thickness of the magnifying optical system, and it is difficult to reduce the thickness of the magnifying optical device to less than half the longitudinal length of the image before magnification.

In order to solve such a problem, for example, as shown in FIGS. 5 and 6, a configuration example in which a light guide path 2 having a tapered shape whose diameter becomes larger toward the outside as shown in FIGS. Proposed by the applicant. With this configuration, image information (optical information) can be taken into the optical fiber 1 from the tip of the tapered light guide path 2, and the optical fiber 1 having a small diameter can be used regardless of the size of the image before enlargement. Therefore, the thickness of the magnifying optical device 3 can be reduced.

When an optical fiber group 4 is constructed by integrating a plurality of optical fibers 1 all having the same diameter, the magnifying optical device 3 serving as this optical information transmitting device has the same configuration.
In order to dispose the optical fiber 1 discretely.
A plurality of sheet-like members 5 are interposed as spacing members in the vicinity of the b side to maintain a constant spacing between the optical fibers 1 and a plurality of sheet-like members also in the vicinity of one end surface 1a side of the optical fiber 1. 6 is interposed as an interval maintaining member to maintain a constant interval between the optical fibers 1. By making the sheet-like member 6 thinner, the interval on the one end surface 1a side becomes larger. It is set to be narrow. Therefore, in the optical fiber group 4, one end face 1
When optical information is input from the a side, the information is output from the other end surface 1b side, and the function of transmitting optical information through the optical fiber 1 is achieved.

At this time, assuming that the one end face 1a of the optical fibers 1 having a small gap is an image input face 7a and the other end face 1b having a wide gap is an image output face 7b, the image information input from the image input face 7a is The image is output after being enlarged from the image output surface 7b side. If a flat display such as a liquid crystal display 8 is provided on the image input surface 7a side,
It can function as an image enlargement display device. Further, a light guide path 2 is provided on one end face 1a of each optical fiber 1, and
Since the optical information is captured through the light guide path 2, the efficiency of capturing the light into the optical fiber 1 increases, and the amount of transmitted light increases. Further, as shown in FIG. 6, if the light guide path 9 whose diameter becomes larger toward the outer side with respect to the other end face 1b of each optical fiber 1, the diameter of the light beam emitted from the other end face 1b is increased. Thus, a smooth image can be obtained.

However, when a flat display such as the liquid crystal display 8 is used as an image before enlargement, the light emitting point is located on the input surface of the light guide path 2 because the light emitting position of the image is inside the display substrate. Cannot adhere. Therefore, the light from the light emitting point of the liquid crystal display 8 diverges before reaching the input surface of the light guide path 2, and the resolution of the input image on the incident surface of the magnifying optical device 3 deteriorates. Would.

As a means for solving this, Japanese Patent Publication No.
A method of arranging a microlens on the input surface of each optical fiber as disclosed in Japanese Patent No. 22569, and a method of disposing a microlens on the input surface of an optical fiber as disclosed in Japanese Patent Application Laid-Open No. 8-114716. Method of arranging a corresponding refractive index distribution type micro lens, Japanese Patent Application Laid-Open No. H11-271
It is conceivable to use a method of providing a large lens for forming an image on an optical fiber input surface as disclosed in Japanese Patent No. 539.

However, in the case of the method disclosed in JP-B-63-22569 or JP-A-8-114716, a plurality of optical fibers and a plurality of lenses are aligned in a one-to-one relationship. Must be performed, and the manufacturing process becomes extremely complicated. On the other hand, JP-A-11-27153
In the case of a method of providing a large lens for forming an image on an optical fiber input surface as disclosed in Japanese Patent Application Laid-Open No. 9-205, in order to obtain an image with less distortion, a focal length longer than the long side of the input image is required. This necessitates a problem that the thickness of the device cannot be reduced.

Accordingly, the present invention provides an optical information transmission device and an image enlargement display device in which even when a flat display such as a liquid crystal display is used as an image before enlargement, the resolution of the input image is not deteriorated and the production thereof is easy. The purpose is to provide.

[0014]

According to a first aspect of the present invention, there is provided an optical information transmitting device comprising an optical fiber group in which a plurality of optical fibers are integrated, and an input from one end of the optical fiber in the optical fiber group. Optical information transmission device having a function of transmitting optical information to the other end of the optical fiber,
The other end faces of the respective optical fibers are arranged at a constant interval between adjacent optical fibers, and the one end faces of the respective optical fibers are adjacent to each other at a narrower interval than the fixed interval. It is arranged with an opening,
A light guide path which is disposed on one end surface side of each of the optical fibers and whose cross-sectional area increases as the distance from the optical fiber increases, and the critical angle θc of the total reflection condition of the light guide path is the center of the light guide path. The difference (θc−θa) between the critical angle θc and the shape angle θa that is larger than the shape angle θa between the axis and the side surface of the light guide path is determined by the size of the light emitting point of the incident light information and the light emission. The light guide path is set to be smaller than the optimum expected angle θb of the light guide path defined by the size of the end face of the light guide path facing a point and the distance from the light emitting point to the entrance surface of the light guide path. I do.

In the present invention and the following invention, the “critical angle θc under the condition of total reflection” means an incident angle at the interface when light transmitted in the light guide path enters the core layer / cladding layer interface. In other words, it means the angle between the core layer / cladding layer interface when the light under the critical condition that causes total reflection at the core layer / cladding layer interface enters the input surface of the light guiding path. The angle θb ”means the maximum angle that does not satisfy the condition for total reflection of the light guide path with respect to light from light emission points other than the light emission point at which light information facing the light guide path incident surface is desired to be captured.

Therefore, the light that is perpendicularly incident on the end face of the light guide path satisfies the condition of total reflection of the light guide path, so that it can be transmitted inside the light guide path, and this optical information transmission device is used for magnifying an image. In this case, of the light incident on the end face of the light guide path, incident light from an oblique direction that is not desired to be transmitted can be cut, and the resolution of an image can be improved.

According to a second aspect of the present invention, in the optical information transmitting device according to the first aspect, the light guide path has a critical angle θc, a shape angle θa, and an expected angle θb, wherein θc>
It is characterized in that a core layer and a cladding layer having a refractive index satisfying a relationship of θa and (θc−θa) <θb are formed as constituent elements.

Therefore, light perpendicularly incident on the end face of the light guide path satisfies the condition of total reflection of the light guide path, so that it can be transmitted inside the light guide path, and this optical information transmission device is used for magnifying an image. In this case, of the light incident on the end face of the light guide path, incident light from an oblique direction that is not desired to be transmitted can be cut, and the resolution of an image can be improved.

According to a third aspect of the present invention, in the optical information transmission device according to the first or second aspect, a gap between the light guide path and the optical fiber is filled with a light-shielding substance having a light-shielding property against visible light. It is characterized by having been done.

Accordingly, of the light incident from the end face of the light guide path, even if there is light that does not satisfy the condition of total reflection and leaks out of the light guide path, the light can be absorbed by the light shielding material before entering the optical fiber, and image transmission In this case, stray light which causes a reduction in contrast can be reduced.

According to a fourth aspect of the present invention, there is provided an image magnifying display device according to any one of the first to third aspects, wherein each of the optical information transmitting devices is provided on the light guide path surface of the optical information transmitting device. It is characterized by comprising a light valve in which a light emitting point position of a pixel is matched with each light guide path, and a light source for illuminating the light valve. According to a fifth aspect of the present invention, in the image enlarged display device according to the fourth aspect, the light valve is a liquid crystal display. According to a sixth aspect of the present invention, in the image enlarged display device according to the fourth or fifth aspect, the light source has a high directivity such that an estimated angle of illuminance is 15 degrees or less.

Therefore, even when a flat display such as a liquid crystal display is used as an image before enlargement as a light valve, it is possible to provide an image enlargement display device capable of performing enlargement display without deteriorating the resolution of an input image. it can. In particular, if the directivity of the light source is high as in the invention of claim 6, the directivity of image information after passing through the light valve is also high, and stray light from an oblique direction incident on the end face of the light guide path is reduced. Thus, the contrast of the transmitted image can be further improved.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to FIGS. The same parts as those shown in FIGS. 5 and 6 are denoted by the same reference numerals, and description thereof will be omitted.

The optical information transmission device according to the present embodiment also has an enlarged image by combining a liquid crystal display 8 as a light valve disposed on the image input surface 7a side, as in the case shown in FIG. It is configured as a display device. A backlight 1 as a light source for illuminating the liquid crystal display 8 from the back side with respect to the liquid crystal display 8
0 is provided.

Here, the components of the optical information transmission device itself are the same as those shown in FIGS. 5 and 6, but in the present embodiment, the configuration of the light guide path 2 is optimized.

First, as shown in FIG. 1, the critical angle θc of the light guide 2 under the total reflection condition is set to be larger than the shape angle θa formed between the central axis φ of the light guide 2 and the side surface 2s of the light guide 2. ing. The difference (θc−θa) between the critical angle θc and the shape angle θa is, as shown in FIG.
The size of the light emitting point Lp of the optical information incident from the liquid crystal display 8 and the end face 2 of the light guide path 2 facing this light emitting point Lp
It is set to be smaller than the optimum expected angle θb of the light guide 2 defined by the size of e and the distance from the light emitting point Lp to the incident surface 2 e of the light guide 2. Here, the “critical angle θc under the condition of total reflection” does not mean the angle of incidence at the interface when the light transmitted through the light guide path 2 enters the core layer / cladding layer interface 11, but the core layer / cladding layer. The light P under the critical condition causing total reflection at the layer interface 11 is incident on the incident surface 2 of the light guide path 2.
e means the angle formed by the core layer / cladding layer interface 11 when the light is incident on e. In addition, the "optimum expected angle θ of the light guide path"
“b” is the maximum angle that does not satisfy the condition for total reflection of the light guide path 2 with respect to light from the light emission points Lp ′ other than the light emission point Lp where the light information is desired to be captured while facing the incident surface 2 e of the light guide path 2. Means

With such a configuration, even if the distance between the light emitting point Lp of the image and the incident surface 2e of the light guide path 2 is large, the light incident on the end face of the light guide path 2 at an angle almost perpendicular to the light guide path is not changed. In order to satisfy the total reflection condition of the optical path 2, the light guide path 2
Can be confined inside the light emitting device, and the incident light from the oblique direction of the light emitting point Lp 'of the pixel which is originally not desired to be transmitted can be cut. In other words, the aperture ratio of the incident surface 2e of the light guide path 2 can be kept low, so that the resolution of an image to be transmitted can be improved.

In the present embodiment, as shown in FIG. 3, as a material for filling the gap between the light guide path 2 and the optical fiber 1, a light-shielding substance 12 having a light-shielding property against visible light is used.
Is used. Thereby, even if light incident from the end face of the light guide path 2 does not satisfy the condition of total reflection and leaks to the outside of the light guide path 2, it is absorbed by the light shielding material 12 before entering the optical fiber 2. Therefore, it is possible to reduce stray light which causes a reduction in contrast during image transmission.

In this embodiment, when viewed as an image enlargement display device, the image before enlargement is an image displayed using the liquid crystal display 8 as a light valve, and is illuminated from the back side by the backlight 10. Like that. At this time, it is preferable to use a backlight having high directivity as the backlight 10.

As described above, when a flat display such as the liquid crystal display 8 is used, the light emitting point Lp of the image is located inside the display substrate, so that the light emitting point Lp is set to the input surface 2 e of the light guide path 2. Can not be adhered to. Therefore, light from the light emitting point Lp of the device may diverge before reaching the input surface 2e of the light guide path 2. In this regard, if the directivity of the backlight 10 that illuminates the liquid crystal display 8 as a light valve is increased, the directivity of image information after passing through the liquid crystal display 8 is also increased, and the oblique direction of incidence on the end face of the light guide path 2 Stray light from the image can be reduced, and the contrast of the transmitted image can be further improved.

Incidentally, when the light emitting point of the image and the input surface of the optical fiber cannot be brought into close contact with each other, see Japanese Patent Application Laid-Open No. 5-8 / 1993.
In a magnifying optical system composed of only an optical fiber as disclosed in Japanese Patent No. 8617, the resolution is also increased by reducing the difference in the refractive index between the core layer and the cladding layer and decreasing the numerical aperture of the optical fiber. Is possible. However, if the aperture ratio of the optical fiber itself is reduced, the aperture ratio on the light output side is also reduced. Therefore, when the optical fiber is used as an image transmission device, there is a problem in that the viewing angle on the output side is reduced. In addition, since the critical angle of the optical fiber becomes small, the fiber cannot be bent greatly, causing a problem that the thickness of the device cannot be reduced. In the case of a device using only an optical fiber, as a method for solving the above problem, a fiber having a low aperture ratio is used on the optical input side, and a fiber having a high aperture ratio is used on the optical output side, as shown in Japanese Patent No. 2880637. The configuration used is also conceivable. However, in such a configuration, two types of optical fibers must be individually bundled and then joined, which makes the manufacturing method extremely complicated. In this regard, in the present embodiment, by reducing the aperture ratio of the light guide path 2 instead of the optical fiber 1, there is no problem even if the optical fiber 1 itself has a high aperture ratio. As a result, the optical fiber 1 having a large aperture ratio can be used, and when used as an image information transmission device, the viewing angle on the output side is large,
Further, even if the bending radius of the optical fiber is reduced, the transmission loss of light is small, so that the thickness of the device can be reduced.

The optical fiber 1 used in the present invention includes a glass fiber including a quartz fiber, a plastic fiber and the like, but the material of the fiber is not particularly limited. In addition, examples of the photocurable resin used as the material of the light guide path 2 in the present invention include acrylic and methacrylic resins, but the material of the light guide path 2 is not limited thereto. Further, the light-shielding substance 12 includes a thermosetting resin material such as an epoxy resin containing a black pigment, but the material of the light-shielding substance 12 is not particularly limited. Further, the material used for forming the clad layer of the light guide path 2 includes a fluorinated epoxy resin, but the material of the cladding layer is not particularly limited.

[0033]

EXAMPLE An example of the present invention based on the above embodiment will be described.

Example 1 640 plastic fibers (core / cladding = 90/100 μm) coated with a transparent epoxy-based thermosetting adhesive were separated by a fiber center line spacing.
Stretch to 50 mm length using a fiber guide to 0.3 mm. Next, a polyester plastic sheet having a thickness of 0.2 mm, a width of 5 mm, and a length of 200 mm is placed on one end of the 480 fiber row so that the longitudinal direction of the sheet is orthogonal to the fiber length direction, and heat is applied. Glue. Next, the fiber on the side not bonded to the sheet should be
It is aligned using a fiber guide so that it is 0.15 mm, and a plastic sheet made of polyester with a thickness of 0.05 mm, a width of 5 mm, and a length of 100 mm is placed thereon so that the longitudinal direction is orthogonal to the fiber length direction, and heat is applied. And glue.

The above process is regarded as one process, and by repeating this process, a fiber group is formed by laminating fiber rows so that the fiber end faces are aligned in a plane.

In this embodiment, the above process is repeated 480 times, and finally the other end is discretely arranged at a pitch of 0.3 mm, and one end is discretely arranged at a pitch of 0.15 mm.
80 rows of integrated optical fiber groups were formed.

Next, both the surface on which the fibers are discretely arranged at a pitch of 0.3 mm (the other end surface) and the surface on which the fibers are discretely arranged at a pitch of 0.15 mm (the one end surface) are optically polished. did. The surface on which fibers are discretely arranged at a pitch of 0.3 mm is called a first surface (the other end surface), and the surface on which fibers are discretely arranged at a pitch of 0.15 mm is called a second surface (one end surface).

After performing the above process, the second surface of the fiber integrated at a pitch of 0.15 mm was immersed in an acrylate-based photocurable resin mixture manufactured by Three Bond Co., Ltd., and was separated by 0.25 mm from the second surface of the fiber. A quartz plate having a thickness of 0.1 mm was arranged at the position. When the light from an ultra-high pressure mercury lamp is introduced from the first surface, the curing reaction proceeds by the photopolymerization reaction, and the cross-sectional area between the optical fiber and the quartz plate becomes wider toward the tip as shown in Fig. 1. Was self-formed.

At this time, an ultraviolet absorbing film is attached to the surface of the quartz plate opposite to the surface facing the optical fiber, so that the light guide path does not grow on the surface of the quartz plate opposite to the surface facing the optical fiber. I made it. An ultraviolet irradiation device EX-250 manufactured by HOYA-SCHOTT was used as a light source. The cross-sectional diameter of the surface of the formed tapered optical waveguide in contact with the quartz plate was 0.15 mm, and the optical waveguide was formed in a state where adjacent optical waveguides were in contact with each other.

After removing the ultraviolet absorbing film attached to the quartz plate, the uncured resin was removed with acetone.
A fluorinated epoxy resin having a refractive index of 1.45 was filled in the space of the tapered light guide path, and thermally cured to form a clad layer. Thereafter, the quartz plate was removed by polishing, and the end surface of the light guide path was finished to an optical mirror surface. The sample manufactured in Example 1 is referred to as Sample 1.

Example 2 The same steps as in Example 1 were performed until the tapered light guide path was formed. After removing the uncured portion of the resin with acetone, the surface of the tapered light guide path was refracted to a thickness of 5 μm. A fluorinated epoxy resin at a rate of 1.45 was applied and thermally cured to form a cladding layer. Thereafter, the void around the cladding layer was filled with an epoxy resin containing a black pigment and thermally cured. Thereafter, the quartz plate was removed by polishing, and the end surface of the light guide path was finished to an optical mirror surface. The sample manufactured in Example 2 is referred to as Sample 2.

Comparative Example 1 The refractive index used in Example 1 was 1.45.
Instead of the fluorinated epoxy resin, filling the voids of the tapered light guide path with a fluorinated epoxy resin having a refractive index of 1.49,
Thermal curing was performed to form a clad layer. Others are Example 1.
And the same.

Comparative Example 2 Refractive index 1.45 used in Example 1
In place of the fluorinated epoxy resin, filling the voids of the tapered light guide path with a fluorinated epoxy resin having a refractive index of 1.35,
Thermal curing was performed to form a clad layer. Others are Example 1.
And the same.

[Evaluation Results of Fabricated Samples]
-No. 2 and Comparative Examples 1 and 2
The liquid crystal display with the backlight on which the TE test chart was displayed was used as an image before enlargement, and the resolution and black-and-white contrast of the image after enlargement were compared. The liquid crystal display has a pixel pitch of 0.15 mm and the pixel size is 80
A transmissive monochrome liquid crystal having a size of μm × 80 μm and a distance from the liquid crystal display surface to the light emitting point of 0.1 mm was used.

As a backlight for irradiating the liquid crystal display from the back side, a backlight A having a high directivity and an expected angle of illuminance falling to half of the illuminance when viewed in the vertical direction is 15 degrees or viewed from the vertical direction. The resolution and the contrast were obtained for the case where the backlight B having low directivity and the expected angle of illuminance falling to half of the illuminance at that time was 45 degrees was used.

Table 1 shows the results. "Resolution"
In the case of the white stripe and black stripe patterns having the same width, the resolution was defined as the stripe interval (lines / mm) of the image before the enlargement at which the MTF became 50 or more. The “contrast” was obtained by measuring the output light amount of each of the white pattern and the black pattern after the enlargement of the monochrome stripe of 1 mm width, and dividing the light amount of the white pattern by the light amount of the black pattern as the contrast. In addition, the shape angle θa between the central axis of the light guide path and the side surface of the light guide path in all the measurement samples is 6.
8 degrees. In addition, in all combinations of the sample and the liquid crystal display, the optimum expected angle θb of the light guide path is set.
Is 19.3 degrees.

Table 1 also shows the refractive index of the core layer and the cladding layer of the light guide, and the critical angle θc of the total reflection condition of the light guide determined by the taper angle of the light guide. Also,
The critical angle under the light incident angle total reflection condition and the difference (θc−θa) between the central axis of the light guide path and the side surface of the light guide path are also shown.

[0048]

[Table 1]

Comparing Sample 1 with Comparative Example 1, it can be seen that Sample 1 is superior in both resolution and contrast both when backlight A and backlight B are used. This is because, in Comparative Example 1, since the difference in the refractive index between the core layer and the cladding layer of the light guide was small, the critical angle θc under the total reflection condition of the light guide was 6.5 degrees, and the central axis of the light guide and the side surface of the light guide were different. This is considered to be due to the fact that light emitted from the pixel and vertically incident on the light guide path can be confined in the light guide path, and the effect of providing the light guide path does not occur. Therefore, it has been found from this experiment that the critical angle θc under the total reflection condition of the light guide path needs to be larger than the shape angle θa between the central axis of the light guide path and the side surface of the light guide path.

Comparing Sample 1 with Comparative Example 2, it can be seen that Sample 1 is superior in both resolution and contrast both when backlight A is used and when backlight B is used. This is because, in Comparative Example 2, since the difference in the refractive index between the core layer and the cladding layer of the light guide was large, as can be seen from Table 1, the critical angle θc of the light incident angle total reflection condition, the central axis of the light guide, and the side surface of the light guide were observed. (Θc−θa) is 29.2 degrees, which is larger than the optimal expected angle θb = 19.3 degrees of the light guide path, and light from pixels other than the pixel for which light is desired to be taken in is also taken into the light guide path. Seems to be the result. Therefore, it is necessary that the difference (θc−θa) between the critical angle of the light incident angle total reflection condition and the angle formed between the central axis of the light guide and the side surface of the light guide is smaller than the optimum expected angle θb of the light guide. It was found from this experiment.

Comparison between Sample 1 and Sample 2 shows that
The resolution was good both when backlight A was used and when backlight B was used, but the contrast was better in sample 2 especially when backlight B was used compared to sample 1. Excellent results were obtained. This is presumably because in Sample 2, as a result of filling the gap between the light guide paths with a substance having a light-shielding property, stray light not taken into the light guide paths was removed, resulting in an improvement in contrast.

[0052]

According to the first and second aspects of the present invention, light perpendicularly incident on the end face of the light guide path satisfies the condition of total reflection of the light guide path, so that the light can be transmitted inside the light guide path. When this optical information transmission device is used for enlarging an image, of the light incident on the end face of the light guide path, it is possible to cut the incident light from an oblique direction that is not originally supposed to be transmitted, thereby improving the resolution of the image. Can be.

According to the third aspect of the invention, of the light incident from the end face of the light guide path, the light does not satisfy the condition of total reflection and leaks to the outside of the light guide path. The stray light which can be absorbed and reduces the contrast at the time of image transmission can be reduced.

According to the fourth and fifth aspects of the present invention, even when a flat display such as a liquid crystal display is used as an image before enlargement as a light valve, the resolution of an input image is not degraded and enlarged display is possible. It is possible to provide an enlarged image display device. In particular, if the directivity of the light source is high as in the invention of claim 6, the directivity of image information after passing through the light valve is also high, and stray light from an oblique direction incident on the end face of the light guide path is reduced. Thus, the contrast of the transmitted image can be further improved.

[Brief description of the drawings]

FIG. 1 is a principle configuration diagram mainly showing a relationship between angles θc and θa in an optical information transmission device according to an embodiment of the present invention.

FIG. 2 is a principle configuration diagram mainly showing a relationship of an angle θb with respect to the optical information transmission device according to one embodiment of the present invention;

FIG. 3 is a principle configuration diagram mainly showing a light-shielding substance in the optical information transmission device according to one embodiment of the present invention.

FIG. 4 is a perspective view showing a conventional example.

FIG. 5 is a principle configuration diagram showing an optical information transmission device of a proposed example.

FIG. 6 is a schematic perspective view thereof.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical fiber 2 light guide path 3 optical information transmission device 4 optical fiber group 8 liquid crystal display, light valve 10 light source 11 light shielding material

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H046 AA02 AA09 AA32 AA42 AA45 AD01 AZ08 2H088 EA12 HA21 HA24 HA28 HA30 MA02 2H091 FA14X FA24X FA26X FA41Z LA03 LA17 MA07 5G435 BB12 BB15 CC09 DD02 GG18

Claims (6)

[Claims] 1. An optical fiber group comprising a plurality of optical fibers integrated therein, and having a function of transmitting optical information input from one end of the optical fiber in the optical fiber group to the other end of the optical fiber. An information transmission device, wherein the other end faces of the respective optical fibers are disposed at regular intervals between adjacent optical fibers, and the one end faces of the respective optical fibers are mutually adjacent optical fibers. A light guide path which is disposed at an interval smaller than a predetermined interval, is provided on one end face side of each of the optical fibers, and has a shape in which a cross-sectional area increases with distance from the optical fiber; Is the shape angle θa between the central axis of the light guide and the side surface of the light guide.
The difference between the critical angle θc and the shape angle θa (θc−θa) is larger than the size of the light emitting point of the incident light information and the size of the end face of the light guide path facing the light emitting point. An optical information transmission device, wherein the optical information transmission device is set to be smaller than an optimum expected angle θb of the light guide path defined by a distance from a light emitting point to an incident surface of the light guide path. 2. The light guide path has a critical angle θc, a shape angle θa, and an expected angle θb, θc> θa, and
The optical information transmission device according to claim 1, wherein a core layer and a clad layer having a refractive index satisfying a relationship of (θc-θa) <θb are formed as constituent elements. 3. The optical information transmitting device according to claim 1, wherein a gap between the light guide path and the optical fiber is filled with a light-shielding substance having a light-shielding property against visible light. . 4. An optical information transmitting device according to claim 1, wherein the light emitting point position of each display pixel arranged on the light guiding path surface of the optical information transmitting device coincides with each light guiding path. An enlarged image display device, comprising: a light valve that is turned on; and a light source that illuminates the light valve. 5. The enlarged image display device according to claim 4, wherein the light valve is a liquid crystal display. 6. The enlarged image display device according to claim 4, wherein the light source has a high directivity with an estimated illuminance angle of 15 degrees or less.