JP4479982B2 - Projection display device using hologram color filter - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection display device using a hologram color filter, and more particularly to a projection display device having a uniform brightness within a projection plane.
[0002]
[Prior art]
The present applicant has proposed a color filter using a hologram in JP-A-6-222361 in order to greatly improve the utilization efficiency of a liquid crystal display backlight or the like.
[0003]
Further, a liquid crystal projection display device that displays a bright color image on a screen by constructing a liquid crystal display device using such a hologram color filter in a projection type has been proposed in Japanese Patent Laid-Open No. 7-98454.
[0004]
Furthermore, many proposals have been made regarding hologram color filters composed of one or three layers.
[0005]
Further, it has been proposed that such a hologram color filter is used for a reflection type liquid crystal display device as a projection display device (for example, Japanese Patent No. 3,011,228, Japanese Patent Laid-Open No. 9-189809). .
[0006]
On the other hand, the telecentric optical system has an advantage that the size of the image does not change even if the distance between the object and the lens changes, and is used in a projector used for parts inspection or the like.
[0007]
However, since the conventional liquid crystal projection display device does not require such a projection lens, a non-telecentric optical system is generally used.
[0008]
[Problems to be solved by the invention]
Regardless of whether the hologram color filter has a single-layer structure or a three-layer structure, the arrangement of hologram interference fringes generally has a single-element repetitive structure in order to facilitate the production of the original. That is, it has the same optical characteristics at the center and the periphery of the screen. For this reason, the light emitted from the hologram, that is, the liquid crystal display element, needs to have the same angle (typically vertical) in the plane. In such an optical system, when a non-telecentric projection lens used in a conventional projector is used, the luminous flux from the periphery of the screen with respect to the vicinity of the optical axis is vignetted by the aperture stop, so that the amount of light is reduced and the surface is reduced. There was a problem that the uniformity of the brightness could not be obtained.
[0009]
The present invention has been made in view of such problems of the prior art, and an object of the present invention is to make it possible to display a bright uniform color image by making the in-plane luminance of a projection display device using a hologram color filter uniform. Is to do.
[0010]
[Means for Solving the Problems]
The projection display device using the hologram color filter of the present invention that achieves the above object includes an illumination light source, a hologram color filter that separates illumination light from the illumination light source for each color, and a spectrum for each color by the hologram color filter. A projection display apparatus comprising: a spatial modulation element arranged so that the different color lights incident on different pixels; and a projection optical system that projects display light modulated by the spatial modulation element. As an optical system, a telecentric optical system in which an aperture stop is disposed at an image side focal position is used.
[0011]
In this case, the spatial modulation element can be applied to either a transmission type or a reflection type.
[0012]
In the present invention, as the projection optical system, a telecentric optical system in which the aperture stop is disposed at the image side focal position is used, so that an image having the same luminance can be projected and displayed at any position within the projection plane. Brightness can be displayed with high uniformity of in-plane brightness.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a projection display device using the hologram color filter of the present invention will be described below. In the following description, the hologram color filter proposed by the present applicant in Japanese Patent Laid-Open No. 6-222361 is premised, but the present invention can be similarly applied to the case of using a hologram color filter of another principle.
[0014]
FIG. 1 is a diagram schematically showing a configuration of an embodiment of a projection display device using a hologram color filter when a hologram color filter is arranged on the incident side of a transmissive liquid crystal display element.
[0015]
This projection display device is composed of an array of transmissive condensing holographic elements on the incident side of the backlight 4 of the liquid crystal display element 2 which comprises a large number of pixels as spatial modulation elements and the transmittance of each pixel can be controlled independently. The hologram color filter 1 is arranged in parallel, and parallel white illumination light 4 from the light source 3 enters the hologram color filter 1 at a predetermined oblique incident angle. Therefore, the illumination light 4 is angularly dispersed into three lights 5 of R (red), G (green), and B (blue) by each hologram element of the hologram color filter 1, and the three lights 5 are emitted from the liquid crystal display element 2. The light enters the corresponding three adjacent pixels and is modulated at each pixel. Accordingly, since the illumination light 5 of a color corresponding to each of the color-separated pixels of the liquid crystal display element 2 is incident, the liquid crystal display element 2 is transmitted through the liquid crystal display element 2 without providing an absorption type color filter or the like. The light 6 becomes display light for displaying a color image.
[0016]
The display light 6 is projected on the screen 11 by the projection optical system 9, and the color image displayed on the liquid crystal display element 2 is enlarged and formed on the screen 11, and the reflection side of the screen 11 (when the screen 11 is a reflection type) ) Or a bright color image on the transmission side (when the screen 11 is a transmission type).
[0017]
Here, the projection optical system 9 uses, for example, a telecentric optical system including an imaging optical element 7 made of a lens and an aperture stop 8 disposed at the image side focal position based on the present invention. Since the hologram color filter 1 has the same optical characteristics at the center and the periphery of the screen regardless of the hologram color filter, the display light 6 from the liquid crystal display element 2 also has the same light distribution at the center and the periphery of the screen. Has characteristics. Therefore, when the display light 6 emitted from any position is condensed by the imaging optical element 7, both the light beam 10 near the optical axis and the light beam 10 ′ near the periphery are on the image side focal plane of the imaging optical element 7. Since it passes through substantially the same region in the vicinity of the optical axis, a telecentric optical system in which an aperture stop 8 is arranged at that position is used as the projection optical system 9 so that an image having the same luminance can be projected and displayed at any position within the projection plane. can do. If the aperture stop 8 is disposed at the position indicated by the broken line, that is, the position deviated from the image-side focal plane of the imaging optical element 7 as in the prior art, the screen is shown with respect to the light beam 10 near the optical axis as shown in the figure. The peripheral light beam 10 'is vignetted by the aperture stop 8, and the amount of light around the screen decreases with respect to the vicinity of the optical axis, and uniformity of in-plane luminance cannot be obtained. There is no problem.
[0018]
In the above embodiment, the liquid crystal display element 2 is assumed to be a transmissive type, but it can also be applied to a reflective type. In that case, the hologram color filter 1 is generally disposed on the projection optical system 9 side of the liquid crystal display element 2. Illumination light 4 is also incident from the projection optical system 9 side of the liquid crystal display element 2 through a prism or the like. As described above, when the liquid crystal display element 2 is a reflection type, another optical element or optical system is disposed between the liquid crystal display element 2 and the projection optical system 9. Since uniformity cannot be obtained, it is very effective to use a telecentric optical system as the projection optical system 9 according to the present invention.
[0019]
In the above embodiments, the hologram color filter 1 is considered to be composed of an array of transmissive condensing hologram elements, but is composed of a combination of a uniform diffraction grating and a microlens, and a wavelength selection for diffraction. Different in angle of incidence in diffused white light by using a volume hologram with three-layered volume and / or angle selectivity, or a volume hologram with one layer and having a high wavelength selectivity of diffraction angle Or the like that perform color spectroscopy by diffracting different color components at different angles.
[0020]
As described above, the projection display device using the hologram color filter of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.
[0021]
【The invention's effect】
As is clear from the above description, according to the projection display device using the hologram color filter of the present invention, the projection optical system uses a telecentric optical system in which the aperture stop is disposed at the image side focal position. An image having the same luminance can be projected and displayed at any position in the plane, and a bright display with high uniformity of luminance in the plane is possible.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing a configuration of a projection display device using a hologram color filter according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Hologram color filter 2 ... Liquid crystal display element 3 ... Light source 4 ... Backlight (illumination light)
5 ... Three separated light beams 6 ... Display light 7 ... Imaging optical element 8 ... Aperture stop 9 ... Projection optical system 10 ... Light beam 10 'from near optical axis ... Light beam 11 from near screen periphery ... Screen

Claims (1)

An illumination light source, a hologram color filter that separates the illumination light from the illumination light source for each color, and a transmission that is arranged so that light of different colors separated for each color by the hologram color filter is incident on different pixels In a projection display device comprising: a type spatial modulation element; and a projection optical system that projects display light modulated by the transmission type spatial modulation element.
A projection display apparatus using a hologram color filter, wherein a telecentric optical system in which an aperture stop is disposed at an image side focal position is used as the projection optical system.

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