Optics: image projectors – Kaleidoscopic
Reexamination Certificate
1999-11-12
2002-02-05
Adams, Russell (Department: 2851)
Optics: image projectors
Kaleidoscopic
C359S616000, C353S033000, C353S034000, C353S037000, C353S038000, C353S099000, C349S008000
Reexamination Certificate
active
06343862
ABSTRACT:
RELATED APPLICATIONS
This application is based on applications No. 10-330379 and 10-335581 filed in Japan, the contents of which are hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention pertains to a projecting image display device that displays images by modulating and projecting the light from a light source, and more particularly to a projecting image display device that first causes the light from the light source to form multiple light source images and then causes the light from these light source images to form an image in each pixel of the image display panel by means of a micro-lens array.
BACKGROUND OF THE INVENTION
Projecting image display devices that display images by modulating and projecting light from a light source are used as projecting televisions or data projectors. Generally, the light modulation is performed by means of a liquid crystal panel. A liquid crystal panel has a number of pixels that are aligned in a two-dimensional fashion, and performs light modulation by changing the polarization of the incident light by means of its pixels so that the distribution of polarization intensity changes. The change in polarization for each pixel is individually controlled based on the image signal. The amount of light of converted polarization varies among the pixels because the degree of polarization change is different from one pixel to another. By projecting the polarized light from the pixels, which differs in amount from one pixel to another, images are displayed that have different brightnesses but which taken together comprise a meaningful image.
It is preferred that a projecting image display device display images that are bright and have uniform brightness. However, the light modulated by a liquid crystal panel comprises only the light component having a plane of polarization aligned in a certain direction, and the light component having a plane of polarization perpendicular to this light component is not used for projection. Therefore, where light is directly supplied to the liquid crystal panel from a light source that emits light having various planes of polarization, images having only half the brightness of the capacity of the light source are displayed. In addition, because the light source generally comprises a lamp, which emits light from an essentially dot-like filament, and a reflector, and the light emitted from the lamp is reflected by the reflector to perform convergence, differences in intensity easily occur between the center and the peripheral areas of the light from the light source. Where this light is led to the liquid crystal panel as is, different areas on the liquid crystal panel receive different amounts of light, resulting in uneven brightness of the displayed image.
In order to modulate and project more of the light from the light source, light comprising light rays having random planes of polarization is separated into two light components having planes of polarization perpendicular to each other, and the polarization of one of the light components is changed so that the planes of polarization of both components matches, whereupon the light is led to the liquid crystal panel. In this way, all of the light emitted from the light source is used for modulation, and the brightness of the image doubles. Normally, the separation is carried out using a polarized beam splitter (PBS) that allows one of the two light components having perpendicular planes of polarization to pass through and reflect the other; the change in polarization is performed using a half-wavelength plate that rotates the plane of polarization by 90 degrees.
Additionally, an integrator is sometimes used in order to make the intensity distribution of the light supplied to the liquid crystal panel uniform, so that the light from the light source is formed into multiple light images and the light from the light source images is led to the entire screen of the liquid crystal panel. An integrator comprises two lens arrays. By using the lens cells of the first lens array, the integrator causes the light from the light source to form images on the corresponding lens cells of the second lens array, and leads the light from the multiple light sources to the entire screen of the liquid crystal panel. In this way, the light from the center of the light ray from the light source and the light in the peripheral areas of the light ray are supplied to all areas of the liquid crystal display in a mixed fashion. As a result, the differences in light amount received by different areas of the liquid crystal panel are eliminated, whereupon an image having a uniform brightness is displayed.
A construction is also used wherein a PBS array and a half-wavelength plate are incorporated into the integrator so that harmonization of light intensity and polarization change are carried out at the same time.
In a liquid crystal panel, it is necessary to divide the pixels in order to prevent the light from adjacent pixels from becoming intermixed, and circuit components such as TFT are used in order to drive each pixel. The area where these partitions and circuit components are located is called a ‘black matrix’, and each pixel is surrounded by a black matrix. Light does not enter a black matrix, and if it does enter it, it does not exit, such that the light entering the black matrix cannot be used for projection. This is another obstacle to improving image brightness.
Japanese Laid-Open Patent Application Hei 9-318904 proposes the use of a micro-lens array in front of the liquid crystal panel so that the light from the integrator is caused to strike the pixel openings only, without hitting the black matrix, in order to increase the efficiency of light utilization and improve the displayed image brightness. The device of this patent application is a single-panel projecting color image display device in which pixels to modulate the red (R), green (G) and blue (B) light are alternately located on a single liquid crystal panel, and the integrator is set such that it causes the R, G and B light to form images individually. One micro-lens cell is used for each group of three pixels, i.e., R, G and B pixels.
In one embodiment, the pixels have an essentially square configuration and the micro-lens cells have an essentially hexagonal configuration. Each micro-lens cell causes the light from the integrator to form images on the corresponding group of pixels and the pixels of its surrounding groups of pixels. In another embodiment, the pixels of the liquid crystal panel have a rectangular configuration and the micro-lens cells comprise cylindrical lenses having a length three times longer than the short sides of the pixels. The cylindrical lenses are located such that their widths are parallel to the short sides of the pixels. Each micro-lens cell causes the light from the integrator to form images on the group of pixels that it faces as well as on the groups of pixels located on either side of the first pixel group.
Generally, the pixels of a liquid crystal panel used for projecting image display devices have a size of at most 30 &mgr;m in order to increase image sharpness, and the F-number of the micro-lens cell that corresponds to this size is 20 or more. A micro-lens cell having such a large F-number has a poor image forming capability because of the effect of diffraction, resulting in a large blurred image. If the wavelength of light is &lgr; the amount of blur <due to diffraction is <=&lgr;×F. Therefore, using a micro-lens cell with an F-number of 20, the blur when using light having a wavelength of 400 to 700 nm (&lgr;=400 to 700 nm) is <=8 to 14 &mgr;m. Therefore, where the size of the pixels is 14 &mgr;m or larger, the micro-lens cell can cause almost all of the light to strike the pixels.
However, in a single-panel projection color image display device, the pixels of the liquid crystal panel flat rectangular configuration and the R, G and B pixels are often stacked together such that their short sides are aligned. The length of the shor
Hayashi Kohtaro
Ishihara Jun
Ohzawa Soh
Ori Yuichiro
Sawai Yasumasa
Adams Russell
Cruz Magda
Minolta Co. , Ltd.
Sidley Austin Brown & Wood
LandOfFree
Projecting image display device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Projecting image display device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Projecting image display device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2961016