JPH0534608A - Color tone correcting mechanism for wavelength selecting device and image composite projecting device - Google Patents

Abstract

PURPOSE:To correct it at the time when there is a variation in a wavelength selection characteristic of a wavelength selecting element by adjusting an angle against an optical path of a correction filter. CONSTITUTION:When a parallel luminous flux emitted from a light source 10 for emitting a white illuminating light is reflected by a cold mirror 11, only wavelength of a visible area is reflected by its wavelength selection coat, its luminous flux passes through a correction cold filter 30 and only a blue light is reflected and separated by a B dichroic mirror 12. The blue light separated by the B dichroic mirror 12 is made incident on a B liquid crystal panel 14 having image information of the blue light through an aluminum mirror 13, and also, made incident on a projection lens 16 through a condenser lens 15. The correction cold filter 30 is placed in an inclined state from a state being vertical to an optical axis 0, and its inclination angle can be adjusted centering around an adjustment axis P being orthogonal to the optical axis 0. Accordingly, by adjusting the inclination angle, a wavelength shift by time aging of the cold mirror can be corrected.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a wavelength selection device for extracting light of a specific wavelength range from light of a light source.

[0002]

2. Description of the Related Art This type of wavelength selection device is used, for example, in a three-panel liquid crystal color projector. This projector disperses a white light flux from a light source into light fluxes of three colors of red, green and blue by a spectroscopic means, and the light fluxes of the three colors are respectively displayed on three liquid crystal displays for displaying image information of red, green and blue. It is made incident on the panel, and this light flux is projected on the screen through the light flux synthesizing means and the projection lens to obtain a color image.

Conventionally, a cold mirror,
Optical elements having a wavelength selective coating such as dichroic mirrors and dichroic prisms have been used. The wavelength selection coat is formed by a plurality of thin films having a specific refractive index and a specific thickness. However, when the wavelength selection coat is heated by the heat rays from the light source, the wavelength selection characteristics change with the lapse of time, and as a result, the color tone of the image shifts. Alternatively, the characteristics also change due to variations in manufacturing, which causes the same problem.

It is known that this change in wavelength selection characteristic has a property of shifting to a shorter wavelength side than the initial wavelength selection characteristic. The cause is that moisture contained in the thin film disappears due to a change with time due to heat rays. However, it is said that the optical path changes as a result. Conventionally, when such a wavelength shift occurs in the wavelength selection element, there is no means for correcting the color tone deviation of the image other than replacing the element.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device which can correct the wavelength selection characteristic of a wavelength selection element even if the wavelength selection characteristic of the wavelength selection element changes, based on the above-mentioned awareness of the problems of the conventional wavelength selection device. And It is another object of the present invention to provide an image synthesizing / projecting apparatus capable of correcting the deviation of the color tone of an image even if the wavelength selection characteristic of the wavelength selection element changes with time.

[0006]

SUMMARY OF THE INVENTION The present invention resides in the fact that a filter having a wavelength-selective coat placed substantially perpendicular to the optical path has the effect of shifting the selected wavelength when its angle is changed, and that the optical path is hardly changed. It was made paying attention.

That is, according to the present invention, in a wavelength selection device for extracting light in a specific wavelength region by making light from a light source incident on a wavelength selection element having a wavelength selection coat, the wavelength selection device is provided in an optical path including the light source and the wavelength selection element. Make it almost perpendicular to the optical path,
It is characterized in that a correction filter having a wavelength selection coat is arranged and an adjusting means for adjusting the angle of the correction filter with respect to the optical path is provided.

This correction filter has the property of shifting the selected wavelength to the short wavelength side when the angle is changed from the state of being arranged at right angles to the optical path. Therefore, when correcting the shift of the selected wavelength of the wavelength selection element to the short wavelength side due to aging, in the initial state, the correction filter is tilted from the state perpendicular to the optical path, and changes over time occur. After that, it may be rotated in a direction at a right angle.
Of course, when the selected wavelength shifts to the long wavelength side due to the change with time of the wavelength selection element, conversely, the correction filter is positioned at a right angle to the optical path in the initial state, and when the change with time occurs, it is inclined from the right angle. It may be rotated in the direction.

Although the present invention does not ask for a specific selection wavelength of the wavelength selection element, for example, a cold mirror having a wavelength selection coat for extracting visible light from a white light source has a selection wavelength on the short wavelength side due to aging. Shift to. The present invention, for example, the selection wavelength range of this cold mirror is set to be wider than the selection wavelength range originally required,
By forming a wavelength selection coat having a selection wavelength range originally required, which is narrower than the selection wavelength range of the cold mirror, in the correction filter, the wavelength shift can be corrected well.

The color tone correcting mechanism of the image synthesizing and projecting apparatus using the wavelength selecting device described above comprises a spectroscopic means for spectroscopically dividing the light of the light source; and the luminous fluxes dispersed by the spectroscopic means respectively correspond to the spectral luminous flux. In an image synthesizing and projecting device including a plurality of light-transmissive image panels having image information; and a light flux synthesizing means for synthesizing light fluxes transmitted through the plurality of image panels, the spectroscopic means specifies light from light from a light source. A wavelength selection element having a wavelength selection coat for extracting light in a wavelength region, and a correction filter having a wavelength selection coat disposed in an optical path including the light source and the wavelength selection element at a right angle to the optical path. And adjusting means for adjusting the angle of the correction filter with respect to the optical path. With this configuration, it is possible to correct the color tone shift due to the shift of the selected wavelength by adjusting the angle of the correction filter.

[0011]

The present invention will be described below with reference to the illustrated embodiments.
1 to 7 show a first embodiment of an image synthesizing / projecting apparatus having a wavelength selection device according to the present invention. A parallel light flux emitted from a light source 10 which emits white illumination light is reflected by a cold mirror 11. After that, only blue light is reflected and separated by the B dichroic mirror 12. The correction cold filter 30, which is a feature of the present invention, is located between the cold mirror 11 and the B dichroic mirror 12 and has an optical axis O.
It is arranged at an angle with respect to the state of forming a right angle with respect to the (optical path). The inclination angle of the correction cold filter 30 can be adjusted around an adjustment axis P orthogonal to the optical axis O by a rotary knob or the like (not shown).

The blue light separated by the B dichroic mirror 12 enters the B liquid crystal panel 14 having blue image information via the aluminum mirror 13, and further enters the projection lens 16 via the condenser lens 15. To do.

On the other hand, the light transmitted through the B dichroic mirror 12 reaches the G dichroic mirror 17, and the G dichroic mirror 17
The green light reflected by the dichroic mirror 17 enters the G liquid crystal panel 19 having image information. The green light transmitted through the G liquid crystal panel 19 passes through the condenser lens 20 and the G dichroic mirror 21 and then the projection lens 16
Incident on.

The red light transmitted through the G dichroic mirror 17 enters the R liquid crystal panel 22 having red light image information, and further passes through the condenser lens 23, the aluminum mirror 24 and the R dichroic mirror 25 to project the lens 1.
It is incident on 6. The light fluxes having image information of the respective colors incident on the projection lens 16 are superimposed on each other to form a color image, which is projected on the screen.

According to the present invention, in the above embodiment, when the wavelength selected by the cold mirror 11 shifts to the short wavelength side due to the change over time, the wavelength shift is corrected by adjusting the turning angle of the correction cold filter 30. The point is characteristic. Specific examples of wavelength shift and its correction by the cold mirror 11 will be described with reference to FIGS.

The white luminous flux emitted from the light source 10 is reflected by the cold mirror 11 by its wavelength selection coat, and the white luminous flux shown in FIG.
As shown by, only wavelengths in the visible region are reflected. The solid line of the spectral distribution curve in FIG. 2 indicates the initial state (design value). The selected wavelength range is slightly wider than the originally required selected wavelength range. The selected wavelength of the cold mirror 11 has a property of shifting to the short wavelength side as shown by a broken line due to a change with time.

The light reflected by the cold mirror 11 is next B
Although separated by the wavelength selection coat of the dichroic mirror 12, when the B dichroic mirror 12 has no wavelength shift, the B dichroic mirror 12 reflects only blue light with the spectral characteristic shown by the solid line in FIG. However, when the B dichroic mirror 12 has a wavelength shift due to a change with time, the spectral characteristic of the blue light reflected by the B dichroic mirror 12 changes to the short wavelength side as shown by the broken line. As a result, the blue light incident on the B liquid crystal panel 14 has the spectral distribution shown by the solid line in FIG. 6 when the cold mirror 11 and the B dichroic mirror 12 have no wavelength shift, whereas the cold mirror 11 and the B dichroic light have a spectral distribution. When the mirror 12 has a wavelength shift, the spectral distribution shown by the broken line in the figure is obtained. That is, B is originally designed so that blue light having the spectral distribution indicated by the solid line is incident.
Blue light having a spectral distribution indicated by a broken line will enter the liquid crystal panel 14.

In this example, the G dichroic mirror 17
Does not cause wavelength shift due to aging.
Then, the green light incident on the G liquid crystal panel 19 is affected by the wavelength shift of the B dichroic mirror 12, and the red light incident on the R liquid crystal panel 22 is affected by the wavelength shift of the cold mirror 11. The solid and broken lines of the spectral distributions of green light and red light in FIG. 6 indicate the case where the cold mirror 11 and the B dichroic mirror 12 have no wavelength shift to the short wavelength side, and the case where they exist, as in the above example. Shows.
As described above, when the spectral distributions of the light incident on the B liquid crystal panel 14, the G liquid crystal panel 19, and the R liquid crystal panel 22 are different from those designed, the color of the image emitted from each of the liquid crystal panels 14, 19, and 22. Changes from the initial color, and as a result, the color tone of the synthetic projected image changes.

According to the present invention, this wavelength shift can be corrected by the correction cold filter 30. The correction cold filter 30 has the originally desired spectral distribution characteristic shown in FIG. 3, and this spectral distribution has a narrower selected wavelength range than the spectral distribution of the cold mirror 11.
In the initial state, the correction cold filter 30 is inserted so as to be inclined from the state perpendicular to the optical axis O. When the correction cold filter 30 is rotated in the direction of arrow A in FIG. 1 and brought close to the direction perpendicular to the optical axis O, as described above, the wavelength of the light passing therethrough is shifted to the long wavelength side. There is. Conversely, when the correction cold filter 30 is set in a state perpendicular to the optical axis O and is tilted, the selected wavelength has a property of shifting to the short wavelength side. Therefore, when the correction cold filter 30 is rotated in the A direction, the spectral characteristic shown by the broken line in FIGS. 2 to 5 is shifted (corrected) to the long wavelength side as shown by the arrow a, and the spectral characteristic shown by the solid line. Return to. That is, the initial spectral characteristics can be corrected. The correction cold filter 30 can correct the wavelength shift of the cold mirror 11 due to the aging, and at the same time, can correct the wavelength shift of the cold mirror 11 due to the aging. Further, since the correction cold filter 30 is located on the light source side of the B dichroic mirror 12, the change over time of the B dichroic mirror 12 can be reduced.

The rotating operation of the correction cold filter 30 can be manually performed while viewing the projected image.
Alternatively, since the phenomenon of wavelength shift has different temperatures, a temperature sensor 31 is provided in the vicinity of the cold mirror 11 or the B dichroic mirror 12 as shown in FIG.
2 may be driven to rotate the correction cold filter 30.

8 to 12 show another embodiment of the present invention, in which the same components as those in the first embodiment are designated by the same reference numerals. In this embodiment, the B liquid crystal panel 14, the G liquid crystal panel 19 and the R liquid crystal panel 22 are arranged at different positions, and the R, B, G dichroic mirrors 25, 12, 21 are arranged at different positions accordingly. There is. Then, as a correction filter, the cold mirror 1
A correction cold filter 35 is arranged between the 1 and B dichroic mirror 12. The arrangement of the correction cold filter 35 is the same as that of the correction cold filter 30 of the first embodiment.

FIGS. 9 to 12 show the first embodiment shown in FIG.
Through to FIG. In each case, the solid line indicates the spectral distribution characteristic when the cold mirror 11 and the correction cold filter 35 have no wavelength shift, and the broken line indicates the spectral characteristic when the wavelength shift occurs on the short wavelength side. When a wavelength shift as indicated by a broken line occurs in the selected wavelength, the correction cold filter 35 is moved to the optical axis O as shown by an arrow C in FIG.
If the rotation is adjusted so as to approach the direction orthogonal to, the spectral characteristic is shifted to the long wavelength side as shown by the arrow c, and returns to the initial design selection wavelength.

[0023]

As described above, according to the wavelength selection device of the present invention, when the selected wavelength is shifted due to the change over time of the wavelength selection coat, it can be corrected by adjusting the angle of the correction filter. Further, according to the color tone correcting mechanism of the image synthesizing and projecting device of the present invention, when the selected wavelength is shifted, it can be corrected and the light in the predetermined wavelength range can be made incident on the image panel. Therefore, it is possible to correct the color tone of the image that is synthetically projected.

[Brief description of drawings]

FIG. 1 is an optical system diagram showing a first embodiment of an image combining / projecting apparatus having a wavelength selection device of the present invention.

FIG. 2 is a graph showing an example of spectral reflection characteristics by a cold mirror of the projection device in FIG.

FIG. 3 is a graph showing an example of spectral reflection characteristics by a correction cold filter of the projection apparatus of FIG.

FIG. 4 is a graph showing an example of spectral reflection characteristics by the blue reflection dichroic mirror of FIG.

5 is a graph showing an example of spectral reflection characteristics by the green reflection dichroic mirror of FIG.

6 is a B liquid crystal panel, a G liquid crystal panel, and an R liquid crystal panel of FIG.
It is a graph which shows the spectral distribution of the light flux which injects into a liquid crystal panel.

FIG. 7 is a block diagram showing an example of an automatic drive device for the correction filter in FIG.

FIG. 8 is an optical system diagram showing a second embodiment of the image combining / projecting apparatus having the wavelength selecting apparatus of the present invention.

9 is a graph showing an example of spectral reflection characteristics by a cold mirror of the projection device in FIG.

10 is a graph showing an example of spectral reflection characteristics by a correction cold filter of the projection apparatus of FIG.

11 is a graph showing an example of spectral reflection characteristics by the red reflection dichroic mirror of FIG.

12 is a graph showing an example of spectral reflection characteristics by the blue reflection dichroic mirror of FIG.

13 is a graph showing the spectral distribution of light fluxes incident on the B liquid crystal panel, the G liquid crystal panel, and the R liquid crystal panel of FIG.

[Explanation of symbols]

10 light sources 11 cold mirror 12 17 21 25 Dichroic mirror 14 19 22 LCD panel 16 Projection lens 30 35 Cold filter for correction

Continued front page    (72) Inventor Takayuki Iizuka             2-36 Maeno-cho, Itabashi-ku, Tokyo Asahikou             Gaku Kogyo Co., Ltd.

Claims (6)

[Claims] 1. A wavelength selection device for extracting light in a specific wavelength range by making light from a light source incident on a wavelength selection element having a wavelength selection coat, wherein the wavelength selection coat is provided in an optical path including the light source and the wavelength selection element. A wavelength selection device, wherein a correction filter having the above is arranged, and adjustment means for adjusting the angle of the correction filter with respect to the optical path is provided. 2. The wavelength selection device according to claim 1, wherein the wavelength selection element is a cold mirror having a wavelength selection coat for extracting visible light from a white light source. 3. The correction filter according to claim 2,
A wavelength selection device which is a cold filter having a wavelength selection coat of a selection wavelength region narrower than that of the cold mirror. 4. The wavelength selection device according to claim 1, wherein the correction filter is tilted from a position perpendicular to the optical path in the initial state. 5. A spectroscopic unit that disperses light from a light source; a plurality of light-transmissive image panels that have image information corresponding to the spectroscopic luminous fluxes, into which the luminous fluxes dispersed by the spectroscopic unit are respectively incident; A light beam synthesizing means for synthesizing light fluxes transmitted through the image panel; and a wavelength selecting element having a wavelength selecting coat for extracting light in a specific wavelength range from light of a light source, A color filter of a correction filter having a wavelength selection coat in an optical path including the light source and the wavelength selection element; and an adjusting means for adjusting an angle of the correction filter with respect to the optical path. Correction mechanism. 6. The correction filter according to claim 5,
In an initial state, a color tone correction mechanism of an image synthesis projection device which is arranged at an angle with respect to a position perpendicular to the optical path.