JPH03163985A - Liquid crystal projector - Google Patents

Abstract

PURPOSE:To omit an optical element which spatially synthesizes images by successively switching and arranging filters, through which red, green, and blue light are selectively transmitted, in the optical path between a dot matrix liquid crystal display panel and a white light source synchronously with switching of images. CONSTITUTION:A red transmission dichroic filter 2R, a green transmission dichroic filter 2G, and a blue transmission dichroic filter 2B have 120 deg. angular width and are connected into a disk with respect to a rotating filter 2, and a revolving shaft of a motor 3 is attached to a center O of this filter. A dot matrix liquid crystal display panel 5 modulates the light transmittance of each picture element by each of red, green, and blue picture signals successively inputted from a control part 7 in time division to form an image of transmitted light contrast corresponding to each of red, green, and blue pictures of the light thrown to the rear face. Thus, red, green, and blue images are successively switched and expanded and projected on a screen 9 by a projection lens 6, thereby obtaining a color image where red, green, and blue are synthesized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a liquid crystal projector that enlarges and projects an image formed on a dot matrix liquid crystal display panel onto a screen or the like using a projection lens.

[Technical background of the invention and its problems]

Conventionally, there is a liquid crystal projector as shown in FIG. 5, for example.

In the figure, 10 is a white light source, 20B is a blue-transmitting dichroic filter that selectively transmits blue light, 20G is a green-reflecting dichroic filter that reflects green light and transmits red light, 40, to 403 is mirror, 50R, 50G,
50B is a condenser lens; 60R, 60G, and 60B are dot matrix liquid crystal display panels that form red, green, and blue images, respectively; 70 is an R prism 70R and a G prism 70G.
and B prism 7. , OB to form a guichroic surface, and 80 is a projection lens.

White light from the white light source 10 is separated into red light R, green light G, and blue light B by a blue-transmitting dichroic filter 20B and a green-reflecting dichroic filter 20G, and each separated light is passed through condensing lenses 50R and 50G, respectively. ,50B
The light is irradiated onto the back surfaces of the red, green, and blue dot matrix liquid product display panels 60R, 6QC;, 60B.

Each dot matrix liquid crystal display panel 60R, 60G, 6
0B modulates the light transmittance of the pixel based on each red, green, and blue image signal, and this tot matrix liquid product display panel 6
The light transmitted through 0R, 60G, and 60B passes through the R prism 70.
The light is reflected or transmitted by the guichroic surfaces of the R and G prisms 70G and the B prisms 70B, and is directed toward the projection lens 80, respectively.

At this time, red, green, and blue images are formed at the same optical position from the projection lens 80 side, and a color image in which the three colors of red, green, and blue are combined is transferred to the screen 90 by the projection lens 80. projected on.

However, in the conventional liquid crystal projector as described above, three liquid crystal display panels form red, green, and blue images, and each image is combined using a prism, etc. There is a problem.

That is, the structure becomes complicated because an optical element such as a prism is used for combining three-color images. Furthermore, since the dichroic surface used to capture images is tilted with respect to the optical axis, color shading occurs and color reproducibility deteriorates. Furthermore, by arranging an optical element for combining images, the distance from the projection lens to the liquid crystal display panel surface increases, and a retrofocus type projection lens must be used, which increases costs.

[Purpose of the invention]

An object of the present invention is to provide a liquid crystal projector that has a simple structure, does not cause color shading, and does not require a retrofocus type projection lens.

[Summary of the invention]

The present invention provides one dot matrix liquid crystal display panel with red,
Images corresponding to green and blue are formed by time-divisionally switching, and a filter that selectively transmits red, green, and blue light is placed between the optical path between the dot matrix liquid crystal display panel and the white light source. The switching is arranged sequentially in synchronization with the switching,
By sequentially forming red, green, and blue images on a tot matrix liquid product display panel, the optical element that spatially aligns the images can be omitted.

〔Example〕

FIG. 1 is a diagram showing the main parts of a liquid crystal projector according to a first embodiment of the present invention.

In the figure, ■ is a white light source having a white lamp la and a rotating paraboloid reflector 1b, and 2 is a disc-shaped rotating filter that is a combination of three types of dichroic filters that selectively transmit red, green, and blue light. , 3 is a motor for rotating the rotary filter 2, 4 is a condenser lens, 5 is a dot matrix liquid crystal display panel, 6 is a projection lens, 7 is a control for display on the dot matrix liquid crystal display panel 5 and a rotation speed of the motor 3. The control unit 8 is a frame memory into which red, green, and blue image signals are sequentially written from a circuit (not shown). Note that the control unit 7 reads each red, green, and blue image signal to be output to the dot matrix liquid crystal display panel 5 from the frame memory 8.

The beam of light from the light source lamp 1a is irradiated toward the rotating filter 2 as parallel light by the reflector 1b.

As shown in FIG. 2, the rotating filter 2 includes a red-transmissive gicchroic filter 2R, a green-transmissive gicchroic filter 2G, and a blue-transmissive gicchroic filter 2B, each connected in a disc shape with an angular width of 120°. The rotating shaft of the motor 3 is attached to the center O.

As the motor 3 rotates, the red-transmitting dichroic filter 2R, the green-transmitting dichroic filter 2G, and the blue-transmitting dichroic filter 2B circulate along the optical path L from the white light source 1 toward the dot matrix liquid crystal display panel 5. red, green, and blue light is irradiated cyclically through the condenser lens 4 onto the back surface of the doso matrix liquid product display panel 5.

The dot matrix liquid crystal display panel 5 modulates the light transmittance of each pixel for each red, green, and blue image signal input sequentially in a time-sharing manner from the control unit 7, and modulates the light transmittance of each pixel with respect to the light irradiated on the back surface. An image of transmitted light contrast corresponding to each of the green and blue images is formed.

The control unit 7 causes the red transmission dichroic filter 2R to cross the optical path L when outputting a red image signal to the dot matrix liquid crystal display panel 5, and the green transmission dichroic filter 2G to output a green image signal. Optical path L
Furthermore, when outputting a blue image signal, the blue-transmitting gichroic filter 2B crosses the optical path L, and the switching of each dichroic filter 2R, 2G, 2B and the output switching of the image signal are synchronized. Controls the rotation speed of the motor 4. Note that the frequencies for switching the image signal and switching the dichroic filters 2R, 2G, and 2B are set to such an extent that the image does not flicker by utilizing the afterimage effect of the naked eye.

As a result, red, green, and blue images are sequentially enlarged and projected onto the screen 9 by the projection lens 6, and the image visually recognized on the screen 9 is a color image in which red, green, and blue are combined. becomes.

FIG. 3 is a diagram showing a second embodiment, in which elements similar to those in the first embodiment are denoted by the same reference numerals, and their explanations will be omitted.

In the figure, 2' is a rotating filter in which three types of gicchroic filters that selectively transmit red, green, and blue light are arranged in sequence, and as shown in Fig. 4, the red-transmitting gicchroic filter 2R ', a green transmitting dichroic filter 2G' and a blue transmitting dichroic filter 2B' are successively connected to form a ring shape, and the roller 21. ′～
215 and is arranged so as to surround the white light source l.

The rotary filter 2' is rotated by a motor 3 attached to a roller 2i+, and is rotated by a red transparent gicchroic filter 2R' and a green transparent gicchroic filter 2G'.
and a blue-transmitting dichroic filter 2B' sequentially cross the optical path L, and similarly to the first embodiment, this rotating filter 2B'
By the light from the white light source l that passes through
~Riks The back surface of the liquid crystal display panel 5 is cyclically illuminated with red, green, and blue light through the condenser lens 4.

Note that, as in the first embodiment, the control unit 7 performs time-divisional output switching of red, green, and blue image signals to be output to the dot matrix liquid crystal display panel 5 and each dichroic filter 2R'.
, 2G', 2B' are controlled in such a manner that the rotational speed of the motor 3 is synchronized with the switching in the optical path L, and red, green, and blue images are sequentially switched and enlarged and projected onto the screen 9 by the projection lens 6. The image visually recognized on the screen 9 is a color image in which red, green, and blue are combined.

In each of the above embodiments, one dot matrix liquid crystal display panel 5 substantially forms a color image, and only a projection lens 6 is disposed in front of this dot matrix liquid crystal display panel 5. is configured to do so. Therefore, there is no need to use a conventional retrofocus type projection lens 6, and a brighter, lighter, and cheaper projection lens can be used.

Furthermore, the structure is simple and does not require an optical element for image alignment. Furthermore, since the dichroic ink filter is orthogonal to the optical axis, color shading does not occur and color reproducibility is excellent.

[Effects of the Invention] As explained above, according to the present invention, images corresponding to red, green, and blue can be displayed on one dot matrix liquid crystal display panel by time-divisionally switching, and images corresponding to red, green, and blue can be displayed on one dot matrix liquid crystal display panel. Filters that selectively transmit light are sequentially switched between the optical path between the dot matrix liquid crystal display panel and the white light source in synchronization with the above image switching, and red, green, By sequentially forming the blue images, we omitted the optical element that spatially combines the images, so it has a simple structure, does not cause color shading, and can be used as a retrofocus type projection lens. You can get an LCD projector that doesn't require an LCD projector.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of a liquid crystal projector according to the first embodiment of the present invention, FIG. 2 is a diagram showing a rotating filter in the first embodiment, and FIG. 3 is a diagram showing the main parts of a liquid crystal projector according to the second embodiment of the present invention. FIG. 4 is a diagram showing a rotary filter in the second embodiment, and FIG. 5 is a diagram showing an example of a conventional liquid crystal projector. 1... White light source, 2, 2'... Rotating filter, 5.
... Dot matrix liquid crystal display panel, 6... Projection lens l1 lens, 2R, 2R'... Red transmitting dichroic filter, 2G, 2G'... Green transmitting dichroic filter,
2B, 2B'... Blue transparent gicchroic filter.

Claims (1)

[Claims] A dot matrix liquid crystal display panel that forms an image by modulating the transmittance of each pixel in response to an input image signal, and an enlarged image formed by the dot matrix liquid crystal display panel. A projection lens for projecting, a white light source arranged on the back side of the dot matrix liquid crystal display panel, and a red,
Three types of filters that selectively transmit green and blue light are sequentially arranged in the optical path between the dot matrix liquid crystal display panel and the white light source, and the light from the white light source that passes through the filters is divided into dots. A wavelength selection means for illuminating the rear surface of the matrix liquid crystal display panel is provided, and image signals corresponding to red, green, and blue images are input to the dot matrix liquid crystal display panel in a time-division manner, and switching of the time-division input is performed. A liquid crystal projector characterized in that red, green, and blue images are sequentially enlarged and projected by synchronizing the switching of three types of filters in the wavelength selection means.