JPH10213800A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the application efficiency of light from a light source and to reduce uneven luminance in a liquid crystal projector. SOLUTION: Plural optical fibers each at which consists of a core material 23 are bundled and gaps among the bundled optical fibers are filled with a filling material 24 of which refractive index is lower than the core material 23 and a beam radiated from a light source part is converged to the fixed optical fiber flux to irradiate a liquid crystal panel with the beam. The refractive index of the filling material 24 is continuously and stepwisely changed in the length direction of the fibers. Both the end parts of the optical fiber flux are made parallel with the optical axis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device for projecting an image using a liquid crystal panel.

[0002]

2. Description of the Related Art In recent years, an optical system using a liquid crystal, such as a liquid crystal projector, has received particular attention as a large-screen display device replacing a conventional CRT. In these optical systems, a light beam emitted from a light source is guided to a liquid crystal panel by a condensing optical system, and after adding image information, an image is projected on a screen by a projection optical system.

FIG. 13 shows an example of a condensing optical system from a light source through a liquid crystal panel to a screen. The light beam emitted from the light source 1 is reflected by the parabolic reflector 2 to be converted into a parallel light beam 3 and then directly irradiates the liquid crystal panel 4. After the image information is added by the liquid crystal panel 4, the image is projected on the screen 9 via the field lens 5 and the projection lens 6. This method is used for a single-panel type liquid crystal projector composed of a single liquid crystal panel.

FIG. 14 shows another example of the condensing optical system. This is an optical system configuration generally called a flyer lens system or an integrator system. A light beam emitted from a light source 1 is reflected by a parabolic reflector 2 to be converted into a parallel light beam 3, and then transmitted to a first fly-eye lens 7a. After entering, and further passing through the second fly-eye lens 7b, the liquid crystal panel 4 is irradiated. If necessary, a condenser lens may be provided between the second fly-eye lens 7b and the liquid crystal panel 4. The first and second fly-eye lenses are:
It is a collection of small lenses. In general, the exit surface of the first fly-eye lens 7a and the liquid crystal panel display unit 4 are in an image forming relationship, and the shape of each minute lens constituting the fly-eye lens 7 is similar to the shape of the liquid crystal panel display unit 4. doing. Then, the distribution of light transmitted through one microlens is expanded to the illuminance distribution of the liquid crystal panel display unit 4. Therefore, the light beams are overlapped in the liquid crystal panel display unit by the number of the minute lenses constituting the fly-eye lens 7, and the effect of suppressing the uneven brightness of the irradiation light of the liquid crystal panel can be obtained.

However, the fly-eye lens system has a problem that the cost is high since two sets of fly-eye lenses composed of an aggregate of minute lenses and, in some cases, three lenses of a condenser lens are required. . Also, due to limitations in optical design, the position of the first fly-eye lens 7a and the position of the second fly-eye lens 7b cannot be brought into close contact with each other. Since a certain interval is required, there is a problem that the configuration of the optical system becomes large.

On the other hand, there has been proposed a light-condensing method for guiding a light beam emitted from a light source to a liquid crystal panel section using an optical fiber. FIG. 19 shows a configuration disclosed in Japanese Patent Application Laid-Open No. 4-204883. The optical fiber bundle is composed of a large number of optical fibers, and both end faces of the optical fiber bundle are arranged so that the arrangement of the optical fibers is uncorrelated. As shown in the figure, the ends a and b on the A side of each optical fiber are displaced from the ends a 'and b' on the B side. Therefore, even when the light beam on the optical fiber bundle incident end face has a specific luminance distribution, the light emitted from the output end face becomes a light flux with a uniform luminance distribution. By disturbing the arrangement of the optical fibers and making them irregular, the light beams are emitted in a mixed form.

However, when the optical fibers regularly arranged on the light incident side are irregularly disturbed before reaching the output side, the following problems occur. In a circular optical fiber bundle in which a large number of optical fibers are bundled, assuming that the diameter of the end portion where the optical fibers are regularly arranged is φA1, the diameter φA2 of the optical fiber bundle in the portion where the optical fibers are rearranged randomly is: , ΦA1, which results in an increase in the size of the condensing optical system.

When the diameter of one optical fiber is large (thick), the optical fiber becomes harder and harder to deform than the optical fiber having a small diameter. Therefore, as described above, it is very difficult to randomly disturb the arrangement of the optical fibers. On the other hand, when the diameter of one optical fiber is small (thin), a much larger number of optical fibers is required to construct an optical fiber bundle of the same diameter than when the diameter is large. It is very difficult to disturb irregularly as above. These problems become particularly remarkable when trying to shorten the optical fiber length.

FIG. 15 shows another configuration disclosed in Japanese Patent Application Laid-Open No. 3-167520. An optical fiber bundle 15 composed of a plurality of optical fibers is disposed between the light source unit parabolic reflector 2 and the liquid crystal panel 4, and the cross-sectional shape of the optical fiber bundle 15 is a circular shape having substantially the same diameter as the reflector on the reflector 2 side. On the other hand, the liquid crystal panel 4 has the same shape 15b as the liquid crystal panel.

Generally, the parabolic reflector emits light in a circular shape, while the liquid crystal panel has a rectangular shape in which the ratio of the length of the long side to the short side is 4: 3 or 16: 9. For this reason, when irradiating a circular light beam to a rectangular liquid crystal panel, it is not possible to uniformly irradiate all the light beams onto the liquid crystal panel due to the difference in shape, and thus a rectangular conversion loss occurs. However, with the above-described configuration, the light beam out of the light emitted from the reflector 2 and taken into the optical fiber bundle 15 can irradiate the liquid crystal panel 4 without incurring the aforementioned rectangular conversion loss. .

The light emitted from the reflector is not uniform and has a specific illuminance distribution. The lamp, which is the light source, has a luminance distribution of the emitted light, and particularly in the arc axis direction, a dark area with almost no luminous flux is generated because it is blocked by the electrodes and the lamp support. Therefore, the light beam emitted from the light source and reflected by the reflector has a ring-shaped luminance distribution whose center portion is dark and whose periphery is bright. When the light emitted from the reflector is taken into the optical fiber, the cross-sectional shape of the optical fiber bundle on the side facing the reflector is substantially the same as the shape of the light emitted from the reflector,
When the cross-sectional shape on the side facing the liquid crystal panel is substantially the same as that of the liquid crystal panel, the fiber density at both ends of the fiber bundle is made uniform. For example, as shown in FIG. In the case of a fine arrangement, the central portion of the optical fiber bundle is the shadow region of the arc, and the central portion of the light beam guided by the optical fiber and illuminating the liquid crystal panel is also a dark region with a small amount of light. For this reason, since the liquid crystal panel has an illuminance distribution such that the center is dark, the liquid crystal panel has the same illuminance distribution that the center is dark even on the screen.

By the way, propagation of a light beam through an optical fiber is based on the following principle. In FIG. 17, an optical fiber 13 has a double structure in which a core material 10 called a core made of a high reflectance material is covered with a thin sheath material 11 called a clad made of a low reflectance material. The light beam 14 having entered the core layer from the substrate travels while being totally reflected at the core / cladding interface in the core, and is emitted from the other end. Here, it is assumed that the optical fiber 13 is straight without being bent. Wherein in order to repeat the total reflection, there is a limit to the incidence angle phi ₀ into the cladding layer, it is necessary satisfy below.

Assuming that the refractive index of the core is n ₀ and the refractive index of the clad is n ₁ , the incident angle φ ₀ must be larger than the critical angle φ _c determined by the core and the clad, that is, the following condition must be satisfied.

Φ₀≧ φ_c= Sin^-1(N₁/ N₀)  Furthermore, to satisfy this condition in an optical fiber, an example
For example, a light beam traveling in the air (n = 1) is an optical fiber
The following conditions are required as conditions for incidence on the surface.

[0015] ^{_{θ f ≦ sin -1 (1 /}} n · The _{^{(n 0 2 -n 1 2)}} 1/2) light beam incident to the optical fiber satisfies the condition of the light beam incident angle is propagated through the core, light Emitted from the fiber. The light beam emitted from the optical fiber enters the liquid crystal panel. At this time, not all light beams that have entered the liquid crystal panel reach the screen and do not project an image. The luminous flux transmitted through the liquid crystal panel is transmitted through the projection optical system such as a field lens and a projection lens.Each optical component has an allowable incident angle in design, and the luminous flux incident at an excessively large angle is not included in these optical components. Parts cannot be transmitted.

Under the conditions of incidence of the above optical fiber, n =
Assuming that 1, n ₀ = 1.5 and n ₁ = 1.414, θ _f
≦ 30 °, and the light beam incident on the optical fiber within ± 30 ° is emitted at the same angle as the incident angle from the other end surface.

Optical lenses such as a field lens and a projection lens which are components of the projection optical system have an F number which is generally well known. The F number is defined as F = f / D, where D is the effective aperture of the lens (diameter of the allowable incident light beam parallel to the optical axis), and f is the focal length. The smaller the F number, the brighter the image. be able to. However, it is desired that the dimensions of the optical system be as small as possible.
The value of the number cannot be reduced as much as possible, and the distance from the liquid crystal panel to the field lens and the projection lens is limited, and thus the focal length f is also limited.
Further, when the effective aperture of the lens is increased, the size of the lens is increased, so that not only the device incorporating the lens is increased, but also the cost of the lens is increased. Therefore, the value of the F-number of the lens is also actually limited.

Assuming now that the F number of the lens of the projection optical system is F = 2, the effective angle θ _L of the light beam that can be captured by this lens is expressed by the following equation.

ΘL ≦ sin ⁻¹ (1 / 2F) = 14.5 ° The above-mentioned emission angle at the time of emission from the optical fiber is θ
Assuming that _f ≦ 30 °, only the luminous flux within ± 14.5 ° of the luminous flux incident on the liquid crystal panel with a divergence within ± 30 ° can be transmitted through the lens system, and the luminous flux can be used sufficiently effectively. Can not. Incorporation light emitted from the optical fiber to the liquid crystal panel, further, in order to project without waste image on a screen through a projection optical system, when the light beam to the optical fiber uptake, reduce how small incident angle theta _f of the light beam Is important.

The above description is for the case where the optical fibers are arranged straight and the incident angle and the exit angle of the light beam to the optical fiber are equal, and as shown in FIG. When the shapes 15a and 15b are different from each other, each optical fiber is bent and arranged. If the optical fiber is bent, a part of the light beam incident perpendicularly to the optical fiber (θ _f = 0) will also be partially reflected in the optical fiber. turn into. Given that parallelism of the light beams is deteriorated in the optical fiber, when the light beam to the optical fiber incorporation, or reduce how small incident angle theta _f of the light beam becomes more important.

FIG. 18 shows a configuration disclosed in Japanese Patent Application Laid-Open No. 64-26808 as a light condensing method for guiding a light beam emitted from a light source to an arbitrary place using an optical fiber. Here, the reflector output light beam 3 is controlled so that the light distribution on the optical fiber bundle incident surface is substantially ring-shaped, and the end surface 15a of the optical fiber bundle 15 on the reflector facing surface side is formed in a ring shape. With such a configuration, it is possible to reduce the angle of incidence of the light beam on the optical fiber.

However, in this configuration, the optical fiber bundle 1
The end 15c of the reflector 5 on the side facing the reflector is inclined with respect to the optical axis X. In particular, the light beam 3a reflected in a region near the optical axis X of the reflector 2 enters the optical fiber at a large angle. For this reason, even if the reflector outgoing light 3a reflected in the region near the optical axis X of the reflector 2 is taken into the optical fiber 15, it cannot pass through the projection lens system after passing through the liquid crystal panel.

Further, when the light beam emitted from the optical fiber bundle is directly incident on the liquid crystal panel by the condensing optical system using the optical fiber described as the conventional example, the following problem occurs. The optical fiber in the conventional example has a two-layer structure of a core material for transmitting light as described above and a clad material of a material having a smaller refractive index than the core material. Since the light beam is reflected and propagated at the core / cladding material interface, there is no light beam propagating inside the cladding material. Therefore, the light beam emitted from the optical fiber bundle is emitted only from the core portion and not emitted from the clad portion.

When a light beam emitted from an optical fiber bundle having such characteristics is made incident on a liquid crystal panel disposed close to the light emitting surface of the optical fiber bundle, the light beam emitted from the core portion has a certain spread. Even so, the surface facing the clad portion of the liquid crystal panel becomes a region where the light flux is small, and is projected on the screen as contour-shaped uneven brightness corresponding to the cross section of each optical fiber.

In order to reduce such uneven brightness of the contour of the optical fiber section, the spread of the light beam from the core portion causes the influence of the clad portion having no emitted light beam to be negligible. In this case, it is necessary to increase the distance between the liquid crystal panel and the incident surface of the liquid crystal panel.

[0026]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to provide a liquid crystal display device in which the use efficiency of light from a light source is high and luminance unevenness is reduced.

[0027]

Means for Solving the Problems In order to solve the above problems,
According to the present invention, a plurality of optical fibers consisting only of a core material are bundled, and the light source is emitted from the light source unit by an optical fiber bundle which is solidified by filling a filling material having a lower refractive index than the core material between the bundled optical fibers. A liquid crystal display device that condenses the light flux and irradiates the liquid crystal panel, wherein the refractive index of the filling material is continuously changed in the length direction of the optical fiber. You.

Preferably, the refractive index of the filling material is substantially the same as the refractive index of the core material at the end of the optical fiber bundle.

Preferably, the outer peripheral surface of the filling material is coated with a material having a lower refractive index than the filling material.

Preferably, a light beam converting means for converting the light beam emitted from the light source unit into a parallel light beam is provided, and outgoing light from a region excluding a shadow portion of the light source unit is output from the light beam converting unit. The light is focused by the optical fiber bundle, and both ends of the optical fiber bundle are made parallel to the optical axis.

Preferably, the end face of the fiber bundle is opposed to the light beam converting means, and a spacer having an outer surface parallel to an optical axis is inserted into a center portion of the fiber bundle, and each optical fiber is connected to the outer surface of the spacer. Along with the optical axis.

Preferably, the spacer has a cross-sectional area such that a shaded portion of the light source unit is accommodated in a cross-section of the spacer facing the light beam converting means.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. In each of the drawings, the same components are denoted by the same reference numerals.

FIG. 7 shows an embodiment in which the present invention is applied to a liquid crystal projector optical system. A light beam emitted from the light source 1 is reflected by a parabolic reflector 2 which is a light beam converting means into a parallel light beam, and becomes a substantially parallel light beam 3. The parallel light beam 3 from the parabolic reflector 2 irradiates the liquid crystal panel 4 after being incident on the optical fiber bundle 22, and after the video information is added by the liquid crystal panel, the field lens 5 and the projection lens 6
An image is projected on the screen 9 by the projection optical system composed of.

FIG. 8A shows a partial cross section of the optical fiber bundle 22. The optical fiber bundle 22 includes a core member 23 that propagates the light beam.
Are arranged in the closest state. Between each core material 23,
The filling material 24 is filled and hardened. The filling material 24 is formed of a material having a high light transmittance like the core material 23 and a material having a refractive index lower than the refractive index of the core material.

FIG. 8B shows a side section of the optical fiber bundle 22 and a filling material 24 corresponding to the position of the optical fiber bundle 22.
Shows the change in the refractive index. As shown in FIG.
The refractive index of the filling material 24 filled in between changes continuously. Here, the refractive index of the filling material 24 is continuously changed, but may be changed stepwise as shown in FIG. 8C.

FIG. 9 shows a case where the refractive index of the filling material 24 is changed in three stages for the sake of explanation. 1 a refractive index n of the air, the refractive index n ₀ of the core material 1.5, the refractive index n ₁ of the filler material 24-1 of the first region 1.414, the filling material of the second region 24-2 refractive index n ₂ of 1.46, it is assumed that the refractive index n ₃ of 1.49 of the filler material 24-3 of the third region.

FIG. 10A shows a state of transmission of a light beam in the first area. The conditions of incidence and propagation of the light beam at the incident portion (first region) on the optical fiber bundle are θ _f1 ≦ 30 ° and ± 3
The light beam incident on the optical fiber within 0 ° is totally reflected at the boundary between the core 23 and the clad 24-1 and propagates through the core 23. At this time, in the case of an incident light beam of θ _f1 = ± 30 °, the incident angle φ ₁ on the core / cladding boundary is 70.5 °.

FIG. 10B shows a state of transmission of a light beam in the second area. The light beam propagating in the first region travels to the second region. Core / cladding critical angle φ _{c2 in} this region
Is φ _c2 = sin ⁻¹ (n ₂ / n ₀ ) = 76.738 °, and this light beam is incident on the optical fiber bundle at an angle θ _f2 = 20 °.
Light flux. Therefore, among the light beams within the incident angle ± 30 ° to the optical fiber bundle, the light beams within the incident angle ± 20 ° continue to be the core 23 / cladding 24-2 in the second region.
It is totally reflected at the boundary and propagates in the core. On the other hand, the light beam having an incident angle of ± 20 ° to ± 30 ° to the optical fiber bundle is not converted from the core material to the clad material 24 without satisfying the core / cladding critical angle condition.
-2, and further enter the adjacent core material.

FIG. 10C shows a state of transmission of a light beam in the third region. In this region, the core / cladding critical angle φ _c3
Is φ _c3 = 83.38 °, and this light beam corresponds to a light beam having an incident angle θ _f3 = 10 ° on the optical fiber bundle. Of the luminous flux (θ _f2 ≦ 20 °) that has traveled inside the core of the second area, the third area has an incident angle of ± 10 ° on the optical fiber bundle.
The light fluxes within are transmitted through the core after being totally reflected at the boundary between the core 23 and the clad 24-3. On the other hand, a light beam having an incident angle of ± 10 ° to ± 20 ° to the optical fiber bundle passes from the core material to the clad material 24-3 without satisfying the core / cladding critical angle φ _c3 = 83.38 °, and is further adjacent thereto. Incident on the core material.

FIG. 11 shows how the light beam at the outermost periphery of the optical fiber bundle advances in the second region. The outermost peripheral surface of the optical fiber bundle is covered with a filling material 24-2, which is a clad material, and further outside is generally an air layer. As described above, the core / cladding critical angle φ ₁ = 7
The light beam propagating at 0.5 ° does not satisfy the critical angle φ ₂ = 76.738 ° in the second region and passes from the core material 23 to the cladding material 24-2. Angle of incidence θ ₂ (= φ ₁ ) = 7 from the core material on the outermost circumference of the optical fiber bundle to the cladding material
The light beam incident at 0.5 ° is refracted at the core / cladding 24-2 boundary, and θ ₃ = sin ⁻¹ (n ₀ / n ₂ x sin 70.5 °) = 75.
At 537 °, the light travels through the clad 24-2 and reaches the clad / air boundary at the outermost periphery of the optical fiber bundle. Clad 24-2 /
The critical angle φ _a2 of the air boundary is φ _a2 = sin ⁻¹ (n / n ₂ )
= 43.23 °, and the luminous flux having an angle of θ ₃ = 75.537 ° sufficiently satisfies the cladding / air critical angle, and does not leak out of the optical fiber bundle.

Similarly, in the third region, the light flux passing from the core material to the clad material is also reflected at the outermost cladding 24-3 / air boundary, and does not leak out of the optical fiber bundle.

As described above, a plurality of optical fibers consisting only of a core material are bundled, a filler material having a lower refractive index than the core material is filled between the optical fibers and solidified, and the refractive index of the filler material is changed continuously or continuously. By gradually changing the optical fiber bundle, the optical fiber propagates through the core or passes through the clad side depending on the difference in the incident angle of the optical fiber bundle. In this case, even when the arrangement of the optical fibers is not irregularly disturbed, the unevenness of the brightness distribution of the light beam incident on the optical fiber bundle can be made uniform at the time of emission.

Further, the refractive index of the filling material as the clad material is made substantially the same as the refractive index of the core material at the end of the optical fiber bundle. In this case, at the end of the optical fiber bundle,
The distinction between the core material and the filling material is lost. Therefore, the light beam is emitted from the optical fiber bundle emission end face without distinction between the core material and the clad material. Even if the exit end face of the optical fiber bundle and the entrance face of the liquid crystal panel are arranged close to each other, the light flux is not propagated in the clad material as in the conventional case, and the surface facing the clad portion of the liquid crystal panel becomes an area where the light flux is small. An image having a uniform luminance distribution can be obtained without being projected on a screen as luminance unevenness having a contour of one optical fiber cross section.

Further, the outside of the filling material is covered with a coating material 25 having a lower refractive index than the filling material. FIG. 12 shows this state. Outside the filler material at the outermost periphery of the fiber optic bundle is typically a layer of air. If dirt adheres to the outermost peripheral filling material, the condition of light flux reflection is broken, and there is a possibility that the light flux in the optical fiber bundle leaks out of the optical fiber bundle from the adhered dirt. Therefore, by coating the outside of the filling material 24 with a coating material 25 having a lower refractive index than the filling material 24 as a cladding material, even if the refractive index of the filling material 24 is close to the refractive index of the core material 23. At the same time that the coating material 25 functions as a cladding material, it is possible to prevent the filling material 24 from being stained or damaged.

The values of the refractive index used for the above description are close to those of the currently commercially available methyl methacrylic resin-based plastic optical fiber, but the present invention is not limited to these values. Instead, it can be set freely according to the angle distribution characteristics of the light beam incident on the optical fiber bundle and the mixing ratio of the light beam within the optical fiber bundle.

As the cladding material, a (transparent) fluororesin can be used, and as a filler, an oil obtained by adding dimethyl phthalate to liquid paraffin (a compounding ratio according to a required refractive index) Or an ultraviolet curable resin type adhesive or the like can be used.

Here, FIG. 3 shows an example of a schematic structure of a metal halide lamp often used as a light source. The metal halide lamp 12 has two main electrodes 12 inside the arc tube.
Although discharge and light emission occur between a and 12b, since the mounting portion 12c and the outer tube 12d are also provided, these portions are shaded and there is almost no light emission in the optical axis X direction of the lamp 12.

FIG. 4 shows that the parabolic reflector 2 has a lamp 1
2 is shown. Lamp attachment end 12e
Is generally located behind the parabolic reflector 2, and since the parabolic reflector 2 has a hole 2a through which the lamp passes, there is no reflection of the luminous flux emitted from the lamp in this portion. Therefore, the light beam emitted from the lamp 12 is reflected by the parabolic reflector 2, but the shaded area P shown in the figure is a dark portion with almost no light beam for the above reason. In recent years, a liquid crystal projector has been particularly required to produce a bright image on a screen, and one of the measures is to increase the power of a lamp. When the power of the lamp is increased, the structure of the lamp itself generally increases in size. Therefore, when a high-power lamp is used, the region P having almost no luminous flux is enlarged.

FIG. 1 shows another embodiment in which the invention is applied to a liquid crystal projector optical system. In this embodiment, as in the case of FIG. 7, the refractive index of the filling material is changed continuously or stepwise in the length direction of the optical fiber.

The light beam emitted from the light source 1 is reflected by a parabolic reflector 2 which is a light beam converting means into a parallel light beam, and becomes a substantially parallel light beam 3. The light beam 3 emitted from the parabolic reflector 2 is incident on the optical fiber bundle 16 and irradiates the liquid crystal panel 4. After image information is added by the liquid crystal panel, the light beam 3 is projected by the projection optical system including the field lens 5 and the projection lens 6. An image is projected on the screen 9.

FIG. 2A shows the structure of the optical fiber bundle 16. The shape of the end face 16a of the optical fiber bundle on the side facing the parabolic reflector 2 is substantially the same as the shape of the parabolic reflector exit surface. As described above, the vicinity of the optical axis X is the shaded area P of the lamp, which is a dark area with little light flux.
No optical fiber is arranged at the position P 'corresponding to this dark area. Each optical fiber is arranged in a ring shape so as to surround the dark area P '. Since the optical fiber is not disposed in a portion where the light flux layer incident on the optical fiber is extremely small, such as the region P ', the amount of light emitted from each optical fiber irradiating the liquid crystal panel 4 is not so different, and is uniform. Since the liquid crystal panel 4 is illuminated with brightness, an image with less luminance unevenness can be obtained even on the screen 9.

Further, both ends of the optical fiber bundle are configured to be parallel to the optical axis X on both the side 16b facing the parabolic reflector and the side 16c facing the liquid crystal panel. Parabolic reflector 2
By arranging the light source (center of the lamp) at the focal position of, the emitted light becomes substantially parallel to the optical axis X. This is the same at any position of the light beam 3 from the parabolic reflector 2. As described above, since the incident end 16b of the optical fiber is configured to be parallel to the optical axis X, the incident angle (θ _f ) of the light beam 3 on the optical fiber can be reduced. Similarly, since the emission end 16c of the optical fiber is also configured to be parallel to the optical axis X, it is possible to suppress the deterioration of the incident angle of the light beam on the liquid crystal panel due to the inclination of the optical fiber. Thus, the angle of incidence on the optical fiber, and
By making the exit angle as small as possible, even if each of the optical fibers constituting the optical fiber bundle 16 has to be bent slightly, even if the light beam spreads in the optical fiber and the parallelism deteriorates, the The parallelism is suppressed within the allowable angle of the projection optical system in the light beam emitted from the fiber bundle 16 and transmitted through the liquid crystal panel 4, so that the ratio of the light beam used effectively can be increased.

On the other hand, as shown in FIG. 2B, the end face 16d of the optical fiber bundle 16 on the side facing the liquid crystal panel has substantially the same shape as the liquid crystal panel display section 4. In this way, the light emitted from the optical fiber can efficiently irradiate the liquid crystal panel 4 without irradiating a useless area. As a result, a bright image can be obtained on the screen 9.

As described above, the light utilization efficiency can be improved by combining the removal of the influence of the lamp shade by devising the shape of the optical fiber bundle facing the reflector and the parallelizing of both ends of the fiber with the optical axis. A liquid crystal display device which is high and has less luminance unevenness can be obtained.

In the liquid crystal projector optical system, when the size S1 of the liquid crystal panel to be used is determined, the cross-sectional area of the optical fiber bundle 16 on the side facing the liquid crystal panel is substantially equal to S1. Since the thickness of each optical fiber is usually the same, the cross-sectional area of the optical fiber bundle 16 on the side facing the parabolic reflector 2 is also substantially equal to S1. On the other hand, when the power consumption is determined depending on the type of lamp used (metal halide lamp, halogen lamp, etc.), the area of the region P behind the lamp in the light beam 3 emitted from the parabolic reflector 2 also has a unique value. . Since the cross-sectional area S1 of the optical fiber bundle 16 and the area of the region P behind the lamp are determined, in order to take the light beam 3 emitted from the parabolic reflector 2 into the optical fiber bundle 16 without waste, the cross-sectional area of the output portion of the parabolic reflector 2 is required. (Parabola diameter) needs to be close to S1 + P. Therefore, in order to correspond to the used liquid crystal panel size S1,
Either a reflector having a parabolic diameter of S1 + P is used, or an optical system for changing the diameter of a light beam emitted from the parabolic reflector is separately required.

FIG. 5 shows an example of an optical system for changing the light beam diameter. In this example, the reflector 17 is an elliptical mirror, and a light source is disposed at the first focal position F1.
The light beam emitted from the light source 1 is reflected by the elliptical mirror 17, condensed at the second focal position F 2, and then enters the collimator lens 18. By optimizing the characteristics of the collimating lens 18, the light beam diameter φA of the light beam emitted from the collimating lens 18 can be freely changed.

In some cases, the characteristics of the parabolic reflector 2 can be slightly changed. By configuring the emitted light beam 3 from the parabolic reflector 2 to be slightly inclined in the direction of the optical axis X (center), it is possible to prevent the emitted light beam 3 from escaping to the outside of the optical fiber bundle 16 and to take it into the optical fiber bundle reliably. To do. In this case, if the output light angle is too large, the parallelism of the light beam at the time of emitting the optical fiber bundle deteriorates, so that a large angle cannot be provided.

In the configuration shown in FIG. 1, as described above, the vicinity of the optical axis X of the light beam 3 emitted from the parabolic reflector is a shaded area P of the lamp and a dark area with a small light flux. No optical fibers are arranged at P ', and each optical fiber is arranged in a ring shape so as to surround the dark area P'. 6a, 6b and 6c show examples of assembling a fiber bundle having such a configuration. First, the optical fiber 13 is inserted into the ring-shaped holder 20. In this state, as shown in FIG.
They are not parallel to the axes, but each point in an arbitrary direction. Here, the spacer 21 shown in FIG. 6B is inserted into the center of the ring-shaped holder 20. Part of the spacer 21 has a region 21a parallel to the central axis Y of the spacer. The cross-sectional area of the ring-shaped holder 20 where the optical fiber is inserted is substantially the same as the sum (S1 + P ') of the liquid crystal panel size S1 and the cross-sectional area P' of the inserted spacer 21. For this reason, by inserting the spacer 21 into the center of the ring-shaped holder 20, each optical fiber 13 is connected to the ring-shaped holder 20 as shown in FIG.
It can be made substantially parallel to the optical axis X along the outer surface parallel to the optical axis X of the spacer 21.

Further, the influence of the shade of the lamp is reduced by setting the inserted spacer 21 in such a size that the area P of the shade of the lamp falls within the area P 'facing the light beam converting means. Can be reliably removed.

As described above, the sectional shape of the fiber bundle facing the light beam converting means is substantially the same as the sectional shape of the light beam emitted from the light beam converting means, and the sectional shape of the fiber bundle facing the liquid crystal panel is changed. The liquid crystal panel can be illuminated efficiently and evenly by arranging the optical fiber bundle and taking in the light beam except for the shaded portion of the lamp in the region of the light emitted from the light beam conversion means, while having the same shape as the shape. . In addition, by making both ends of the optical fiber bundle parallel to the optical axis, the angle of incidence on the optical fiber bundle can be reduced, and the liquid crystal panel can be irradiated with a light beam with good parallelism. After passing through the panel, there is no light flux that cannot pass through the projection optical system, and a bright and less uneven luminance image can be projected on the screen.

[0062]

[0063]

According to the liquid crystal display device of the present invention, an optical fiber is obtained by bundling a plurality of optical fibers consisting only of a core material, and filling between the bundled optical fibers with a filler material having a lower refractive index than the core material. The light bundle emitted from the light source unit is condensed to irradiate the liquid crystal panel, and the refractive index of the filling material is changed in the length direction of the optical fiber. It is possible to irradiate the liquid crystal panel with such a light beam, and it is possible to obtain an image with high effective use efficiency of light, and a bright image with little luminance unevenness.

Further, by making the refractive index of the filling material substantially the same as the refractive index of the core material at the end of the optical fiber bundle, it is possible to distinguish the core material and the filling material from the exit end face of the optical fiber. The light beam can be emitted uniformly without any change.

Further, by covering the outer peripheral surface of the filling material with a material having a lower refractive index than the filling material, it is possible to prevent light propagating through the optical fiber bundle from leaking to the outside.

Further, there is provided a light beam converting means for converting the light beam emitted from the light source unit into a parallel light beam, and outgoing light from an area of the light emitting unit excluding the shaded portion of the light source unit. By condensing the light with the optical fiber bundle and making both ends of the optical fiber bundle parallel to the optical axis, uneven brightness can be reduced, and the angle of incidence of the incident light beam on the optical fiber bundle can be reduced. Usage efficiency can be improved.

Further, the end face of the fiber bundle is opposed to the light beam converting means, and a spacer having an outer surface parallel to the optical axis is inserted into the center of the fiber bundle, and each optical fiber is connected to the outer surface of the spacer. , The respective optical fibers can be easily made parallel to the optical axis.

Further, by setting the cross-sectional area of the spacer to a value such that the shaded portion of the light source unit falls within the cross-section of the spacer facing the light beam converting means, the emission area of the light emitted from the light source is adjusted. The light flux from only the region excluding the shaded portion of the lamp of the light source can be collected.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a liquid crystal display device according to the present invention.

FIG. 2a is a diagram showing a configuration example of an optical fiber bundle of a liquid crystal display device according to the present invention.

FIG. 2b is a diagram showing a configuration example of an optical fiber bundle of the liquid crystal display device according to the present invention.

FIG. 3 is a schematic configuration diagram of a lamp.

FIG. 4 is an explanatory diagram of a relationship between a parabolic reflector and a lamp.

FIG. 5 is a configuration diagram of a light beam conversion unit.

FIG. 6a is an explanatory diagram of a spacer.

FIG. 6B is an explanatory diagram of a spacer.

FIG. 6c is an explanatory diagram of a spacer.

FIG. 7 is a view showing another embodiment of the liquid crystal display device according to the present invention.

FIG. 8a is a partial cross section of an optical fiber bundle.

FIG. 8b shows the change in the refractive index of the filling material.

FIG. 8c shows the change in the refractive index of the filling material.

FIG. 9 is an explanatory diagram of an optical fiber bundle in which a filling material is provided with a three-step refractive index change.

FIG. 10A is an explanatory diagram of a light beam in a first area.

FIG. 10B is an explanatory diagram of a light beam in a second area.

FIG. 10c is an explanatory diagram of a light beam in a third region.

FIG. 11 is an explanatory diagram of a light beam at the outermost peripheral portion of the optical fiber bundle.

FIG. 12 is an explanatory diagram of a coating material on the outermost peripheral portion of the optical fiber bundle.

FIG. 13 is a diagram showing a conventional light-converging optical system.

FIG. 14 is a diagram showing a conventional light collecting optical system.

FIG. 15 is a diagram showing a conventional optical fiber focusing optical system.

FIG. 16 is a diagram showing an arrangement of optical fibers.

FIG. 17 is an explanatory diagram of the principle of light propagation in an optical fiber.

FIG. 18 is a view showing a conventional optical fiber focusing optical system.

FIG. 19 is a diagram showing a conventional optical fiber focusing optical system.

[Explanation of symbols]

 Reference Signs List 1 light source 2 parabolic reflector 3 parabolic reflector emitted light beam 4 liquid crystal panel 5 field lens 6 projection lens 7 fly-eye lens 9 screen 13 optical fiber 15, 16, 22 optical fiber bundle 20 ring-shaped holder 21 spacer 23 core material 24 filling material 25 coating material

Claims (6)

[Claims] 1. An optical fiber bundle comprising a plurality of optical fibers consisting of only a core material bundled and filled with a filler material having a lower refractive index than the core material between the bundled optical fibers and emitted from a light source unit. What is claimed is: 1. A liquid crystal display device for condensing a light beam and irradiating a liquid crystal panel, wherein a refractive index of the filling material is changed in a length direction of the optical fiber. 2. The liquid crystal display device according to claim 1, wherein a refractive index of the filling material is substantially equal to a refractive index of the core material at an end of the optical fiber bundle. 3. The liquid crystal display device according to claim 1, wherein an outer peripheral surface of the filling material is coated with a material having a lower refractive index than the filling material. 4. A light beam converting means for converting a light beam emitted from the light source unit into a parallel light beam, wherein outgoing light from a region excluding a shadow portion of the light source unit in an outgoing region of the light beam converting unit is provided. The liquid crystal display device according to any one of claims 1 to 3, wherein light is condensed by the optical fiber bundle, and both ends of the optical fiber bundle are made parallel to an optical axis. 5. An end face of the optical fiber bundle is opposed to the light beam converting means, and a spacer having an outer surface parallel to an optical axis is inserted into a center portion of the optical fiber bundle. The liquid crystal display device according to claim 4, wherein the liquid crystal display device is parallel to an optical axis along an outer surface of the spacer. 6. The liquid crystal display according to claim 5, wherein the spacer has a cross-sectional area such that a shaded portion of the light source unit fits within a cross section of the spacer facing the light beam converting means. apparatus.