JPH11311762A - Lighting device for liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To structure a fly-eye lighting optical system with high efficiency and high quality by adding irreducible components such as a fly-eye lens and an optical correcting means when a lighting angle needs to have telecentricity (state wherein a light beam is parallel to an optical axis). SOLUTION: This lighting device is provided with an elliptic reflector 12 which converges and reflects the light emitted by a light source 11 placed at 1st focus on 2nd focus, a fly-eye lens part 14 which divides the light emitted by the elliptic reflector by an arbitrary number and projects the light beams inputted to division parts so that the whole liquid crystal panel 18 is irradiated, a condenser lens 15, and a projection lens 20, and also provided with an optical correcting means 13 which makes optical corrections so that the effective diameter of the elliptic reflector becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a liquid crystal projector which is effective for a liquid crystal projector using a light source lamp and a liquid crystal panel, a liquid crystal projection television, and the like.

[0002]

2. Description of the Related Art A relatively large illumination divergence angle is allowed.
For an illumination device for a single-panel type liquid crystal panel using a plate type or a color filter, see JP-A-5-346557 and a paper entitled "Illumination optical system for projectors using a modified aperture lens array" (MICRO OPTICS NEWS Vol.14 / No3 1996- 9-26
). In this device, it is possible to efficiently condense the light emitted from the finite light source to the liquid crystal.

However, if it is attempted to further reduce the size of the liquid crystal panel while maintaining the current shape of the light source under heat-resistant conditions, the size of the liquid crystal panel will be further reduced. The smaller the area to be used, the larger the divergence angle of illumination.

On the other hand, under projection conditions, in order to achieve resolution and various performances as the liquid crystal becomes finer (small size and higher definition), the current cost cannot be maintained unless the liquid crystal divergence angle is made smaller.

Accordingly, it is naturally derived that it is necessary to reduce the liquid crystal transmission divergence angle by reducing the illumination divergence angle and to reduce the load on the projection lens. In the conventional illuminating means, there is no specific solution other than the optical path length extension in the means for reducing the illuminating divergence angle while maintaining the light collection efficiency, which is contrary to the main purpose of miniaturization. Become.

The microlens arranged for each liquid crystal pixel shown in FIGS. 1 and 2 and a microlens color separation type illumination optical system using a dichroic mirror for spectrally irradiating and irradiating with an angular deviation are described below.
In principle, the divergence angle of illumination is very severe, so even if a large optical path length can be secured with the increase in the number of pixels, the effective divergence angle range on the light source side of the fly-eye lens is reduced as a result, resulting in high light collection efficiency At present, there is no effective optical system construction means that can be secured.

[0007]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a liquid crystal projector capable of improving the light use efficiency of a fly-eye lens and improving the display performance of the liquid crystal projector while realizing the miniaturization of the entire apparatus. An object is to provide a lighting device.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an elliptical reflector for condensing and reflecting light emitted from a light source placed at a first focal point to a second focal point, the elliptical reflector and a liquid crystal. A fly-eye lens disposed between the panels, splitting light emitted from the elliptical reflector into a plurality of light beams, and emitting light input to each of the split portions so that the entire liquid crystal panel is irradiated; A condensing lens that controls light emitted toward the liquid crystal panel from the virtual multiple light sources of the fly-eye lens as viewed from the lens to the liquid crystal panel into substantially parallel light, and converts light emitted from the condensing lens into a video signal. In the liquid crystal projector, the liquid crystal panel includes a liquid crystal panel that controls a transmission amount and a projection lens that enlarges and projects light passing through the liquid crystal panel onto a screen. Is characterized in that it has placed an optical correction means effective diameter of the reflector as viewed from the fly's eye lens is smaller in the optical path between the reflector and the fly-eye lens. As a result, the fly-eye lens can effectively use the light from the elliptical reflector while keeping the fly-eye small NA.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a microlens color separation type liquid crystal projector in which the present invention is applied to an optical system.

Reference numeral 11 denotes a light source formed by a metal halide lamp or a high-pressure mercury lamp, which has a small fly-eye configuration inevitably based on the principle of the present system. Control reflection is performed so that light is condensed at The light condensed and reflected by the elliptical reflector 12 is incident on a fly-eye lens unit 14 through an optical correction unit 13 constituting a characteristic part of the present invention. The fly-eye lens unit 14 is configured by first and second fly-eye lenses, divides light emitted from the elliptical reflector 12 into a plurality of light beams, and irradiates the light input to each of the divided units to the entire liquid crystal panel 18. To emit light. The fly-eye lens of the fly-eye lens unit 14 is configured such that, for example, four lens arrays face each other in the horizontal and vertical directions.

The light emitted from the fly-eye lens unit 14 is condensed by a condensing lens 15 and is directed to dichroic mirrors 16B, 16R, and 16G, which are inclined with respect to the optical axis and arranged so that three mirrors substantially overlap each other. Incident.

Here, the dichroic mirror 16R reflects the light in the red wavelength band in the direction of 90 degrees, the dichroic mirror 16B reflects the light in the blue wavelength band in the direction at an obtuse angle less than 90 degrees, and the dichroic mirror 16G. Reflects light in the green wavelength band in directions that are sharper than 90 degrees. The light reflected from the dichroic mirrors 16R, 16B, and 16G all passes through the polarizing plate 17 and passes through the liquid crystal panel 18
Is irradiated. The liquid crystal panel 18 controls each of R, G, and R in accordance with a video signal supplied from a liquid crystal drive circuit (not shown).
The light transmission amount of the cell B is controlled.

The spatial light modulation image emitted from the liquid crystal panel 18, that is, the color optical image, enters the projection lens 20 via the analyzer 19. The projection lens 20 enlarges the incident color optical image and projects it on a screen. Either rear projection or front projection may be used.

FIG. 2 is a partially enlarged view of a portion surrounded by a dotted circle in FIG. As shown in FIG. 2, this projector device is of a microlens color separation type, and a liquid crystal panel 18 has a microlens 18b disposed in front of a liquid crystal display element 18a. Each lens portion of the micro lens 18b is provided with a liquid crystal display element 18a.
Corresponding to each signal electrode of the micro lens 18b
Are arranged so as to correspond to three (G, R, B) openings (openings for one color pixel) of the display element.

In FIG. 2, lights 18R, 18G, and 18B incident on the openings R, G, and B are emitted from dichroic mirrors 16R, 16G, and 16B, respectively. Since the light 18R travels straight, it enters the opening (for red) immediately below the microlens portion. However, since the other lights 18G and 18B are incident on the microlens portion at an angle, the light condensing position is shifted from the opening for red, that is, incident on the openings for G and B. I do.

Thus, the optical image emitted from the liquid crystal panel 18 is output as a color optical image. Here, the items required for the above-described lighting device and each unit will be described as follows.

The angle θ between the light 18R and the light 18R 'as shown in FIG. 3 is an effective illumination angle effective as the present light valve, and a small angle with high accuracy is required. As the definition of the liquid crystal increases, the effective illumination angle becomes smaller and the accuracy is required to be higher. If the lighting conditions cannot secure this effective lighting angle or exceed the effective lighting angle due to optical component placement errors, etc., it will not only be effective as illumination light, but it will also illuminate the ineffective area of the liquid crystal and generate heat and stray light. Have a negative effect,
If the angle is further increased, the illumination light leaks into the next opening, causing so-called color mixing, and a problem occurs in which color purity cannot be maintained.

On the other hand, the fly-eye lens unit 14 functions as a relay lens that causes the light radiated from the elliptical reflector 12 to each lens eye of the element A of the fly-eye lens to be imaged by the condenser lens 15 and collects light. Optical lens 1
At 5, superimposition and averaging are performed on the liquid crystal panel 18 while maintaining the imaging state. Here, the size of the effective illumination angle θ is affected by the size of the fly-eye lens 14 as viewed from the liquid crystal position.

This is because the fly-eye lens 14 has a plurality of virtual light sources corresponding to the fly-eye shape in order to split and condense the light collected from the reflector. It is necessary to reduce the distribution range of the light source, that is, to provide a very small fly-eye lens. For this reason, the effective incident divergence angle (NA) to the fly eye must be reduced together with the number of fly eye divisions. Therefore, in order to ensure the light use efficiency, the elliptical reflector 1 required from the fly eye
In the case of 2, the distance from the fly-eye lens 14 to the reflector needs to be increased until it falls within the effective angle range.

On the other hand, on the other hand, there is a limit to miniaturization of the reflector due to thermal problems, and if the distance from the fly-eye lens 14 to the reflector is increased with a real light source having a finite length, the efficiency is reduced due to the reflection directivity due to the finite arc. This is because the light cannot be focused on the small fly-eye lens 14 well.

Accordingly, the present invention provides a fly-eye lens unit 1
In addition to satisfying the design conditions of No. 4 and the design conditions of the elliptical reflector 12, the above-mentioned difficult problem is solved, the miniaturization of the entire device is realized, the light use efficiency of the fly-eye lens is improved, and the liquid crystal projector is improved. The display performance is also improved.

As an example of the specific means, as shown in FIG. 1, there is provided an optical correction means 13 for reducing the effective diameter of the elliptical reflector 12 as viewed from the fly-eye lens unit 14.

FIG. 4 shows another specific example of the shape of the optical correction means 13 described above. In the example of FIG. 4, a conical lens 21 having the optical axis coaxial is provided between the fly-eye lens unit 14 and the opening of the elliptical reflector 12. As shown in the figure, when a light source 11 such as a metal halide lamp or a high-pressure mercury lamp is used, a second focus f
Up to 2, the light does not reach the optical axis and around the optical axis. This is said to be a bunch. This device is
This prevents the light from becoming non-uniform due to the influence of this hollow.

That is, in this embodiment, the conical lens 21 is applied as an optical means for reducing the reflector system viewed from the fly-eye lens unit 14, that is, for reducing the fly-eye incident angle. As can be seen from the figure, the fly-eye lens unit 1
In consideration of the NA of 4 and the arc characteristics of the elliptical reflector 12, it is possible to reduce the fly-eye incident angle by half by applying the most appropriate conical lens apex angle. At the same time, since the light emitted from the conical lens 12 is mixed along the optical axis corresponding to the hollow portion, a high-quality illumination system can be constructed with a small number of fly-eye divisions. In particular, high-pressure mercury lamps, which have recently become mainstream, have poor arc stability and are very effective means.

FIG. 5A shows an example of the specific shape of another optical correction means 13 according to the present invention. FIG.
(B) is a partially enlarged view. In this example, by arranging the conical lens 21 so as to straddle the second focal point f2 of the elliptical reflector 12, the frequency of light mixing is further improved, and the illumination quality is improved. That is, the elliptical reflector 12 is disposed on the second focal point f2.

According to this example, although the frequency of luminous flux mixing is improved, the telecentricity of the fly-eye incident light is slightly deteriorated. Therefore, a condenser lens 22 may be provided. By performing lens processing on the light source side of the first fly-eye lens 14a, telecentricity is restored to the level shown in FIG.

In this example, not only the conical lens 21 but also a condenser lens 22 is added. The condenser lens function is provided on the light source side of the fly-eye lens 14a and the conical lens 21.
It is possible to incorporate the function of the condenser lens 22 by devising the shape of, and in most cases, there is no additional element.

In the example shown in FIG. 6, when the optical axis must be bent between the elliptical reflector 12 and the fly-eye lens unit 14, a convex mirror 24 having the same effect as the concave lens 23 is added. It is an example. If the optical size of the projector is limited and you need to add a mirror,
When it becomes impossible to arrange the concave lens which has the highest efficiency, the same effect can be obtained by using the convex mirror 24 in this manner, and the deformation of the mirror which was originally required as a configuration precondition is achieved. Because of this, the effect of improving efficiency can be obtained without adding the number of parts, and the present invention can be applied at lower cost.

Next, the process of thinking that became the background to the present invention will be described. The fly-eye lens unit 14 for viewing the reflector 12 can be realized with a small size and high efficiency if there is a certain illumination angle margin, but the micro-lens color separation method requires a large number of pixels due to the high definition tendency. In this case, the size of the panel becomes large and the NA of the projection lens cannot be secured, or the liquid crystal aperture ratio becomes very small, and in any case, the effective illumination angle θ always becomes small.

If an example focusing only on the horizontal direction is shown, assuming that the horizontal pixel pitch Wp is 90 μm in order to secure an aperture ratio of 40% or more in the liquid crystal display element, each dot pitch Wd is 30 μm and the aperture width is 2 Wo. Is about 20 μ.

If the liquid crystal size at this time is set to a wide aspect ratio of VGA class resolution in consideration of a normal television, the panel size becomes about 3.5 inches. It is common sense that Fno is considered to be about 2 as a limit if this resolution, size and cost are considered in a consumer-oriented optical system. Therefore, the condensing angle range 硝 of the projection lens in the glass is about 9.47 degrees. In this, the distance L between the liquid crystal cells and the microlens where all the liquid crystal transmitted light shown in FIG. 5 becomes effective light is about 510 μm. The effective illumination angle range θ as viewed from the illumination side is about 1.71 degrees.

Assuming that the distance Lcd from the liquid crystal to the fly-eye lens portion is 300 mm, the allowable maximum horizontal size Wf of the fly-eye lens portion is about 17.9 mm. If the fly-eye lens part is divided into four parts in the horizontal direction,
The horizontal width Wfp per surface is about 4.5 mm.

Next, the NA of the fly-eye lens portion obtained from the above conditions is calculated. The liquid crystal size is 76.8 from the above formula.
mm, the distance d between the first and second fly-eye lenses is about 4.5 mm. Therefore, fly-eye effective focusing angle θfe
Is about 7.3 degrees, that is, NAfe of fly's eye is 0.1
Only about three.

Assuming that the distance Lr from the reflector opening to the first fly-eye lens is 150 mm, the permissible effective aperture diameter φ of the reflector is about 38.4 mm. Of course, the elliptical reflector 12 also has some restrictions. First, from the heat problem, the distance to the shortest reflecting portion of the elliptical reflector 12 according to the lamp power, that is, the first focal length f
1 needs to be greater than or equal to a number. When the lamp is sealed with protective glass or the like to prevent danger at the time of lamp rupture, it is naturally necessary to increase this value. In a specific example, if a 250 W lamp or the like is used for high luminance, the thermal expansion coefficient α is 3
Due to the heat resistance of the conventional glass material or the vapor deposition coat of about 4 to 38, the above f1 is required to be at least 12 mm.

Here, it is necessary to consider the light distribution characteristics of the lamp. Generally, since the light emission range of the lamp is about 130 degrees, unless a considerable solid angle range is covered, the light distribution characteristic loss increases, and the meaning of using a high-efficiency fly eye is lost.

The aperture diameter when covering 70% or more reaches approximately 90 mmφ. Therefore, an elliptical reflector having an aperture of 32 mmφ requires an extremely small light distribution coverage, a reflector with a very low power lamp, or a reflector using an expensive crystallized glass material and many cooling measures.

In order to avoid this problem, the second focal point of the elliptical reflector is set large, and the focusing angle range is set to
Means for matching with NA of 4 can be considered. 90mm
The distance Lf between the fly-eye portion 14 covering the entire surface of φ and the reflector is about 350 mm.

The elliptic mirror parameters satisfying the above conditions are roughly as follows. f1 = 12mm, f2 = 400mm,
f = 194 mm, major axis a = 206 mm, minor axis b 69.3 m
m, effective opening diameter 90 mm, opening Xo = 49.5 mm, distance Lf 350 between the opening of the elliptical reflector and the fly's eye
mm At this time, when the light emission range Larc (arc length) of the light source lamp is 1.5 mm, and when the neck side opening position Xk for fixing the lamp is 2 mm = 2 mm, the neck opening dφ is 19.
About 3mm. The distance Lv from f1 to the position of the shortest reflecting surface V is about 13.9 mm.

If the angle range on the optical axis of the arc as viewed from the shortest reflecting surface RN is represented as θarc, it is 4.4 degrees. Accordingly, the light emitted from the light source is reflected by the reflector reflection surface V, and the radius Rsl of the width range reaching the opening fly-eye position is 15.1.
mm.

On the other hand, since the fly-eye existence range determined previously is 9 mm, it is understood that the light reflected by the reflector surface near the reflector neck Rn is hardly converged within the fly-eye effective range.

As described above, in an illumination optical system having a strict effective illumination angle as shown in FIG. 1 using a microlens and an angle deviation, a fly-eye illumination optical system determined by a liquid crystal and a projection lens causes all light arriving from the entire surface of a reflector to pass through. Efficiency deteriorates because the light cannot be condensed on the liquid crystal surface, or the fly eye can cover the entire surface of the reflector, but not all the light emitted from the arc can be condensed on the fly eye effective surface, and the efficiency deteriorates.

Therefore, in the present invention, an optical correction means for reducing the effective diameter of the elliptical reflector as viewed from the fly-eye lens is arranged in the optical path between the elliptical reflector and the fly-eye lens to improve the quality.

[0043]

As described above, according to the present invention, when a high degree of telecentricity (a state in which light rays are parallel to the optical axis) is required for the illumination angle, the fly-eye lens and the optical correction By adding parts, it is possible to construct a highly efficient and high-quality fly-eye illumination optical system.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is an enlarged view showing a part of FIG. 1;

FIG. 3 is a diagram further showing a part of FIG. 2;

FIG. 4 is a diagram showing still another embodiment of the present invention.

FIG. 5 is a diagram showing still another embodiment of the present invention.

FIG. 6 is a diagram showing still another embodiment of the present invention.

[Explanation of symbols]

11: light source, 12: elliptical reflector, 13: optical correction means, 14: fly-eye lens unit, 15: condenser lens,
16R, 16B, 16G ... dichroic mirror, 17
... a polarizing plate, 18 ... a liquid crystal panel, 19 ... an analyzer, 20 ... a projection lens.

Claims (5)

[Claims] 1. An elliptical reflector for condensing and reflecting light emitted from a light source placed at a first focal point to a second focal point, and disposed between the elliptical reflector and a liquid crystal panel to arbitrarily generate a plurality of lights emitted from the elliptical reflector. And a fly-eye lens unit configured to emit light input to each of the division units so that the entire liquid crystal panel is irradiated, and a virtual plurality of the fly-eye lens units in the division unit. A condenser lens that controls light emitted from the light source into substantially parallel light; a liquid crystal panel that controls the amount of light transmitted from the condenser lens in accordance with a video signal; and a light that passes through the liquid crystal panel on a screen. A projection lens for enlarging and projecting; and an optical correction means for performing optical correction so that an effective diameter of the elliptical reflector as viewed from the fly-eye lens portion is optically small. Lighting apparatus for a liquid crystal projector, characterized in that the. 2. The illumination device according to claim 1, wherein said optical correction means is a conical lens. 3. The illumination device of a liquid crystal projector according to claim 1, wherein said optical correction means is a concave lens. 4. The illumination device of a liquid crystal projector according to claim 1, wherein said optical correction means is a convex mirror. 5. The liquid crystal panel is provided with a microlens array corresponding to each pixel of the liquid crystal display element on a one-to-one basis, and enters the microlens array for each of red, blue, and green by a folded dichroic mirror. An illumination device for a projection-type liquid crystal projector, which is provided in a microlens color separation type liquid crystal projector illumination device that changes an illumination incident angle.