JPH11311752A - Lighting device for liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the device small-sized on the whole and to improve the performance by making components in use hard to be affected by circumferential environment, specially, temperature. SOLUTION: This liquid crystal projector is characterized by that the light emitted by a light source 11 is separated and put together by dichroic mirrors 15, 21, and 27 arranged at nearly 45 deg. and passed through liquid crystal panels 18, 23, and 29 for projecting it on a screen. In this case, spectral cut wavelength is varied obliquely by an arbitrary quantity to a certain direction in the single surface of >=1 dichroic mirrors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system of a projector using a light source lamp and a light light valve, in particular, a liquid crystal projector using a liquid crystal panel, an illuminating device for a liquid crystal projection television, a spectral illumination having an angular displacement and a microlens. The present invention relates to a lighting device for a liquid crystal projector suitable for a used micro lens color separation type liquid crystal projector or the like.

[0002]

2. Description of the Related Art A micro-lens color separation type liquid crystal projector using a dichroic mirror arrangement having an angular displacement and a spectral displacement angle setting illumination and a micro lens described in Japanese Patent No. 2622185, and the like.
Three-panel liquid crystal projectors using three liquid crystal panels and dichroic mirrors have been actively developed to be smaller and more efficient with the development of liquid crystal and optical technology in recent years and expanding demand for large screen displays. I have.

In particular, since the high-temperature polysilicon liquid crystal and the ultra-short and high luminous efficiency lamps have been put to practical use, the liquid crystal size has become extremely compact while securing the aperture ratio and the light-collecting efficiency higher than before, and the polarizing plate and other materials have been developed. The light resistance clear by the reduction of the area has reached the first condition.

[0004]

The operating temperature range of a liquid crystal projector is usually 0 to 40 ° C., and this heat greatly affects each component in the optical box. Except for the heat resistance, color unevenness is caused only by adhesion of materials having different thermal expansion coefficients α and only coated products having sharp characteristics such as dichroic mirrors. In particular, as the size of the device is reduced, such adverse effects become remarkable.

Therefore, according to the present invention, the parts to be used
In particular, it is an object of the present invention to provide a lighting device for a liquid crystal projector that has a structure that is not easily affected by temperature, improves a characteristic change problem that is likely to be caused by miniaturization of the device, and further reduces the influence of an inherent temperature environment. I do.

[0006]

In order to achieve the above object, the present invention separates and combines light emitted from a light source with a plurality of dichroic mirrors arranged at approximately 45 degrees to the optical axis. Is projected through a plurality of corresponding liquid crystal panels for projecting the light on a screen, and within a single plane of one or more of the dichroic mirrors, an arbitrary amount of the spectral cut wavelength is inclinedly changed in one direction. Such a structure is adopted.

As a result, even if the dichroic mirror is affected by a temperature change due to heat due to the ambient temperature, its spectral cut characteristics are corrected to normal characteristics, high quality characteristics can be maintained, and the size of the entire device can be reduced. This is advantageous in design.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, in which the present invention is applied to a three-panel type liquid crystal projector, and FIG. 2 shows another embodiment of the present invention, in which a single-panel microlens color separation type liquid crystal is used. 2 shows a projector.

In FIG. 1, reference numeral 100 denotes an optical box, which is formed in a substantially rectangular tube or cylindrical shape with a synthetic resin or the like, and a light source 11 is disposed at one end of an internal cavity. The light source 11 functions as a high-pressure lamp, for example, a small arc capable of high light condensing and having high luminous efficiency, and a metal halide lamp or a mercury lamp is used. A reflector 12 is arranged around the light source 11, and the light source 11
Is converted into parallel light and is controlled and reflected in an arbitrary direction. There is a fly-eye lens unit 14 (the first fly-eye lens A and the second fly-eye lens B) in the light emission direction from here. Fly-eye lens is reflector 1
The reflected light from 2 is divided and superimposed, and the liquid crystal light valve is irradiated. Outgoing light from here is applied to a dichroic mirror 15 arranged at an angle of approximately 45 degrees with respect to the optical axis. The dichroic mirror 15 reflects, for example, a red wavelength, and the light reflected by the dichroic mirror 15 is reflected by the total reflection mirror 16 in the direction of 90 degrees. The light reflected by the total reflection mirror 16 is applied via a condenser lens 17 to a liquid crystal panel 18 for a red image, which is an optical spatial modulation element. The red optical image emitted from the liquid crystal panel 18 is combined with an optical image of another color by the combining prism 19, guided to the projection lens 20, and projected on a screen (not shown).

The transmitted light that has passed through the dichroic mirror 15 is a dichroic mirror 2 that reflects a green wavelength.
Incident on 1. Approximately 90 with this dichroic mirror 21
The light reflected in the degree direction is also applied to the liquid crystal panel 23 for a green image through the correction lens 22. The green optical image emitted from the liquid crystal panel 23 is
, And is guided to the projection lens 20 to be projected on the screen.

The transmitted light passing through the dichroic mirror 21 is applied to a total reflection mirror 25 for direction change via a relay lens 24. Further, the light from the total reflection mirror 25 is applied to a total reflection mirror 27 for direction change through relay lenses 24, 26, and 28, and the light reflected from the total reflection mirror 27 is transmitted through a correction lens 28 to a blue light. The liquid crystal panel 29 for an optical image is irradiated. The blue optical image emitted from the liquid crystal panel 29 is guided to the projection lens 20 via the combining prism 19, and projected on the screen. The above relay lenses 24 and 26
Is for correcting the blue illumination optical path length difference.

Here, for the sake of simplicity, only the red-based spectroscopic system / synthesizing optical system will be described. As an optical path, white light passing through the fly-eye lens unit 14 is projected on the projection side convex surface of the second fly-eye lens 14B. Thereby, the red liquid crystal panel 18 is condensed with the maximum intensity. The illuminance per unit area increases as the position approaches the liquid crystal panel 18. During that time, only the red band wavelength is spectrally reflected by the dichroic mirror 15, reflected again at a 90 ° angle by the red dichroic mirror or the total reflection mirror 16, and reaches the liquid crystal panel 18.

As a result, in the dichroic mirror 15, the [B] side is converged from the [A] side shown in FIG.
In the vicinity, there are optical components related to the green liquid crystal panel 21 and a blocking wall 30 for blocking stray light, so that natural cooling hardly occurs. Due to this effect, dichroic mirror 1
In most cases, the [B] side of Δ5 is larger than the [A] side by Δ
The temperature rises by T.

If the length of the dichroic mirror 15 in the horizontal direction is L and the amount of wavelength shift of the dichroic mirror 15 due to a temperature change of ΔT is Δλ, the dichroic mirror 15 in the [B] direction relative to the [A] side of the dichroic mirror 15 If the wavelength shift is performed with an inclination of Δλ / L as a whole, the horizontal wavelength shift due to the temperature deviation factor in the actual use situation is canceled, and a high-quality image with high color uniformity can be obtained. . Similarly, the dichroic mirror 21 receives a wavelength shift due to the temperature deviation on the lens 22 side. By controlling the wavelength shift amount so as to cancel this, it is possible to obtain high-quality illumination light without color unevenness. Can be.

An embodiment of the liquid crystal projector shown in FIG. 2 will be described. Reference numeral 200 denotes an optical box, and a substantially rectangular tube or a cylinder is configured in a tail shape as an entire appearance,
A light source 51 is formed at one end of the internal cavity formed of a synthetic resin or the like.
Is arranged. The light source 51 functions as a high-pressure lamp and has a high luminous efficiency with a small arc capable of high light collection. For example, a metal halide lamp or a mercury lamp is used. An elliptical reflector 52 having an elliptical opening is arranged around the light source 51, and converts light from the light source 51 into substantially parallel light and emits the light in one direction. In the opening of the parabolic reflector 52, a UV cut filter 53 is provided.
Is attached.

The light emitted therefrom is transmitted to a cold mirror 54.
And passes through the fly-eye lens unit 55 (there is a first fly-eye lens and a second fly-eye lens). Each fly-eye lens divides the parallel light from the elliptical reflector 52, and superimposes and divides the divided light in a liquid crystal panel irradiation state. When viewed from the light-emitting side of the fly-eye lens unit 55, the entire opening of the elliptical reflector 52 is seen through each of the divisions.

The light emitted from the fly-eye lens unit 55 is
The light is reflected by the total reflection mirror 56 in the direction of about 90 degrees and enters the condenser lens 57. The light emitted from the condenser lens 57 is further reflected in the 90-degree direction by the total reflection mirror 58, and is incident on dichroic mirrors 59B, 59R, and 59G that are inclined with respect to the optical axis and arranged so as to substantially overlap each other. You.

Here, the dichroic mirror 59R reflects the light in the red wavelength band in the direction of 90 degrees, and the dichroic mirror 59B reflects the light in the blue wavelength band more than 90 degrees according to the distance relationship between the liquid crystal pitch and the microlens. The dichroic mirror 59G reflects the light in the green wavelength band in an acute angle according to the liquid crystal pitch and the distance between the microlenses than 90 degrees. That is, the dichroic mirrors 59B and 59G are arranged with an angular deviation with respect to the dichroic mirror 59R. The light reflected from the dichroic mirrors 59R, 59B, 59G is applied to the liquid crystal panel 60 through a polarizing plate (not shown).

The liquid crystal panel 60 controls each of R, G, B in accordance with a video signal supplied from a liquid crystal drive circuit (not shown).
Is controlled as a unit. The spatial light modulation image emitted from the liquid crystal panel 60, that is, a color optical image, is incident on a projection lens 62 via an analyzer (not shown) and a relay lens 61. The projection lens 62
The incident color optical image is enlarged and projected on a screen. Either rear projection or front projection may be used.

FIG. 4 is a partially enlarged view of a portion surrounded by a dotted circle in FIG. As shown in FIG. 4, this projector device is of a microlens color separation type, and a liquid crystal panel 60 has a microlens 60b disposed in front of a liquid crystal display element 60a. Each lens part of the micro lens 60b corresponds to each signal electrode of the liquid crystal display element 60a, and one lens part of the micro lens 60b has three (G, R, B) openings (one color) of the display element. (Openings for pixels).

In FIG. 4, lights 60R, 60G, and 60B incident on the openings R, G, and B are emitted from dichroic mirrors 59R, 59G, and 59B, respectively. Since the light 60R travels straight, it enters the opening (for red) immediately below the microlens portion. However, since the other lights 60G and 60B are respectively incident on the microlens portion at an angle, the condensing position is shifted from the opening for red, that is, the light is incident on the opening for each G and B. I do.

As a result, the optical image emitted from the liquid crystal panel 60 is output as a color optical image. From the fly-eye lens unit 55 to the condenser relay lens 57
Until then, the light split by each cell is enlarged to the size of the liquid crystal panel 60 and enters the condenser relay lens 57. By the condensing relay lens 57, each illumination expansion divided and enlarged by each fly-eye cell (division unit) is made constant, and at the same time, the divided illumination range by the fly-eye lens is superimposed on the liquid crystal panel 60.

Therefore, the dichroic mirrors 59B, 59G, 59R provided between the condenser relay lens 57 and the liquid crystal panel 60 having an angular deviation are not as steep as in the embodiment of FIG. Holds, which means that the light is condensed on the projection side [B] of the dichroic mirrors 59B, 59G, 59R than on the light source side [A].

In this configuration, the dichroic mirror 59B,
Each of the BRGs 59G and 59R has a structure in which the BRGs of the dichroic mirrors 59B, 59G and 59R are very close to the front and rear dichroic because the BRGs of the 59G and 59R are denser in the [B] direction than the [A] side because of the deviation angle setting. , And in the light-collecting direction, the phenomenon that the temperature becomes considerably high with respect to [A] is remarkable due to the difficulty of radiant heat and natural convection.

Therefore, in this apparatus, as in the previous example, the dichroic mirrors 59B, 59G, 59R are used depending on the use condition.
If the dichroic mirrors 59B, 59G, 59R are configured to measure the in-plane temperature difference ΔT and the wavelength shift amount Δλ at the same temperature deviation, High quality color images can be provided.

Since the necessity of the present invention is caused by a temperature deviation, a wavelength deviation is provided within the plane of a single dichroic mirror if cooling conditions are satisfied so that a temperature deviation does not occur in consideration of actual use conditions. This eliminates the necessity, and can eliminate the cost increase of the dichroic mirror and the inspection process of right and left mounting.

Therefore, in this apparatus, if a cooling fan 65 is provided in advance on the [B] side where the temperature becomes high and forced cooling is performed so as to reduce the temperature deviation, the problem of color unevenness due to the temperature deviation in actual use can be reduced.

Further, temperature sensors 66A and 66B are provided on both sides of a dichroic mirror, for example, 59R, and a temperature detecting circuit 67 detects an absolute temperature difference between the left and right sides. By controlling the fan drive voltage in the above, the air flow of the cooling fan 65 is controlled, so that a higher level of temperature management can be performed, that is, a higher quality image can be obtained.

Next, the process leading to the present invention will be described. In the present invention, as described above, it has been noted that all the optical elements are used in a very high brightness state, and that a dichroic mirror which is indispensable for splitting / combining light is not an exception.

Since the temperature around the lamp, which is the light source, is very high, the volume and the first focus corresponding to the lamp power are inevitably provided in the reflector due to the heat resistance problem of the reflector and the light distribution characteristics and efficiency of the finite arc. Requires distance (distance from light source). If the explosion-proof structure to avoid the danger of rupture or the cooling amount by the fan
Clearly, the need for this size will be more pronounced. Therefore, a relationship is established in which light is condensed from the large reflector opening toward the small liquid crystal panel.

Next, a high pressure lamp, which is a light source, is a small arc capable of high light condensing and has high luminous efficiency, and a metal halide lamp or a mercury lamp is used. FIG. 4 shows an example of this emission spectrum.

As a problem of the projector using such a lamp, insufficient red light is pointed out. In other words, red and blue do not have a strong spectrum in the red band after 600 nm with respect to green, and the wavelength characteristics of the optical element and the condensing rate itself tend to deteriorate with respect to green and blue. In order to ensure the white balance, it is necessary to control the wavelength limit and the reflectance of the dichroic mirror, and when the deviation from the black body locus is large, it is necessary to largely reduce green and blue in the liquid crystal panel.

From a different point of view, the band of the red dichroic mirror is secured as wide as possible (up to the short wavelength side) as long as the red color purity can be tolerated. This means that high brightness cannot be achieved. As shown in FIG. 4, in the lamp spectrum, it is desired to secure 590n as the red wavelength low band limit.
At 580 nm near m, there is a very strong orange spectrum. Therefore, it is apparent that a slight change in the wavelength characteristic in the vicinity of 590 nm where this spectrum changes sharply affects a large change in red light quantity = change in hue.

In general, the manufacturing variation of the dichroic mirror is about ± 7 nm from the manufacturing conditions, but from the above situation, the wavelength characteristics are more preferable than the preferable wavelength characteristics particularly for consumer products.
Emphasis is placed on avoiding color change by 7 nm. As a result, the design center has to be shifted to a wavelength with less red light, and the optical design has to be more focused on green and blue.

To accelerate this problem, the dichroic mirror itself includes: (a) the dichroic film composition contains about 50% of moisture (refractive index: 1.3), which changes due to changes in temperature and humidity. Since the film is further separated and hollowed out (refractive index: 1.0), the refractive index change = wavelength characteristic changes when viewed as a whole film. (B) Since the thermal expansion coefficient of the dichroic film is different from the thermal expansion coefficient of the substrate glass, expansion and contraction in the plane direction due to the dominant glass expansion changes the film thickness, that is, the wavelength characteristics.

Due to factors such as the above, there is a property that characteristic changes occur depending on temperature and humidity. The amount of these changes is about 1% per Δ25 ° C. when the humidity is substantially constant, and reaches 6 nm if the 50% wavelength of the red dichroic mirror is 600 nm. Therefore, the white balance of a projector using a dichroic mirror changes depending on the environment. Of course, since this range occurs within the normal use range, it is necessary to add this value to the design wavelength as a margin in order to avoid the above-mentioned problems, and the insufficient red light emission becomes more remarkable.

As a further problem, 4
In an optical box environment close to a closed state with the above two optical systems that split light at an angle of 5 degrees and collect light toward the liquid crystal from the reflector, the right and left light condensing differences, that is, temperature differences, in one dichroic mirror It is a point that has occurred. In particular, in the single-panel type, dichroic light is concentrated on the side where light is collected, convection is difficult to occur, and at the same time, the radiation effect of the front and rear dichroic is large, and furthermore, it requires three times the number of pixels as in the three-plate type, so it is inevitable In addition, the area of the dichroic mirror is large, and the right and left temperature changes are more likely to occur more remarkably.

That is, under such an environment, a large left-right temperature difference occurs in the dichroic mirror surface, and as a result, the wavelength characteristics are different between left and right, and the color tends to change.

In view of the above, if a projector that performs spectral synthesis by arranging a dichroic mirror at 45 degrees is to attempt to secure a red spectrum, which is slightly insufficient, 580 nm
An abrupt change in the vicinity of the orange spectrum has caused a problem that an in-plane color change has occurred, and a choice has been made to narrow the red range in addition to a manufacturing variation margin. Of course, even if the specifications are strict at the expense of cost and a low wavelength shift of several nm can be secured, the operating temperature range is usually 0 to 40 ° C.
Therefore, the wavelength characteristic shift due to the dichroic absolute temperature change in the optical box and the temperature difference between the right and left sides can take a larger value, and as a result, an effect as high as the cost cannot be obtained. In particular, in the optical system shown in FIG. 2, since the light reciprocates, the characteristic change is affected by the square, and the problem is more likely to occur.

The permissible color change due to aging is duv
It is said that the value is about 0.02. However, if color non-uniformity occurs simultaneously within the unified surface, the allowable value will not reach the allowable level unless the allowable value is set to 1/3 or less. In other words, if the color change due to aging changes over a wide range, if only the color change within the same plane can be suppressed to an allowable level, a wider red wavelength band can be secured.

Therefore, in the present invention, if the amount of shift in the wavelength characteristic due to the absolute temperature and the lateral temperature deviation can be grasped, the above-mentioned problem can be solved by giving this measure to the illumination optical system in advance.

The countermeasures are roughly classified into two types. One is a method of giving a left-right deviation to the dichroic characteristics itself.
The other is a contrivance for cooling such that a temperature difference generated due to the light condensing / shape condition is eliminated. Both of these are effective in solving the above-mentioned problems, and more advanced wavelength management has become possible by combining both.

By applying the present invention as described above, it is possible to avoid a problem of a change in in-plane hue of red, which is particularly problematic in the current lamp, and thus it is possible to secure the red wavelength band, which is a problem, that is, to expand the red spectrum. This increased energy directly reduces the amount of green and blue light that was required when securing the white balance. As a result, a higher-luminance projector can be constructed with the same light source light amount, and at the same time, the color uniformity on the screen surface In this respect, the quality has been improved.

The applicable range of the present invention is wide ranging from the one based on the temperature detection control to the one simply devising an air passage so that one side is more cooled, and the cost is the same. Defect reduction is possible.

[0045]

As described above, according to the present invention,
The components to be used have a structure that is hardly affected by the surrounding environment, particularly the temperature, so that the size and performance of the entire apparatus can be reduced.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing another embodiment of the present invention.

FIG. 3 is an enlarged view showing a part of FIG. 2;

FIG. 4 is a graph showing an emission spectrum graph of a light source lamp.

[Explanation of symbols]

100, 200: Optical box, 11, 51: Light source, 1
2, 52: reflector, 13, 53: glass substrate, 1
4,55 ... Fly eye lens part, 15, 21, 27, 5
9R, 59G, 59B ... dichroic mirror, 18,
23, 29, 60: liquid crystal panel, 20, 62: projection lens.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 9/31 H04N 9/31 C

Claims (7)

[Claims] 1. Light emitted from a light source is approximately 45 degrees with respect to an optical axis.
In a liquid crystal projector that separates and synthesizes a plurality of dichroic mirrors at a time, and passes the separated dichroic mirrors to a plurality of corresponding liquid crystal panels for projecting each of the dichroic mirrors on a screen, Within a single plane,
An illumination device for a projector, wherein a spectral cut wavelength is inclined by an arbitrary amount in one direction. 2. A wavelength deviation caused by the inclination change of the spectral cut wavelength of the projector in one direction by an arbitrary amount,
2. The illumination device for a projector according to claim 1, wherein the direction of the light valve or the direction in which the temperature is higher in structure is shifted to a longer wavelength. 3. An R (red), G (green), and B (blue) cell is defined as one pixel, and an arbitrary displacement angle is set with respect to a liquid crystal panel provided with a microlens provided for each pixel. One or more dichroic mirrors in a single-plate microlens color separation type liquid crystal projector that separates and condenses illumination light having a spectral deviation near the R, G, and B openings of each cell using a dichroic mirror An illumination device for a liquid crystal projector, wherein a spectral cut wavelength is inclinedly changed in one direction by an arbitrary amount within a single plane. 4. The wavelength deviation due to the arbitrary change of the spectral cut wavelength in one direction is such that the dense side of the dichroic mirror having an angle shift is in the long wavelength direction. 3. The illumination device for a liquid crystal projector according to item 3. 5. An R (red), G (green), and B (blue) cell is defined as one pixel, and an arbitrary displacement angle is set with respect to a liquid crystal panel provided with a microlens provided for each pixel. In a single-plate micro-lens color separation type liquid crystal projector that separates and condenses illumination light having a spectral deviation through the dichroic mirror near the R, G, and B openings of each cell, the in-plane horizontal of a single dichroic mirror An illumination device for a liquid crystal projector, characterized in that a cooling amount changes in inclination in a direction. 6. The illuminating device for a liquid crystal projector according to claim 5, wherein the cooling amount deviation in which the cooling amount is tilt-converted is such that the dense side of the dichroic mirror having an angle shift is strongly cooled. . 7. The cooling deviation according to claim 5, wherein a temperature sensor is arranged at an arbitrary position of the dichroic mirror, and the left and right cooling amounts are changed according to the left and right temperature difference. Lighting device for liquid crystal projector.