Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2000-06-28
2001-07-03
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S636000
Reexamination Certificate
active
06256151
ABSTRACT:
BACKGROUND
The present invention relates to image display systems. In particular, the present invention relates to miniature image display system usable for helmet-mounted displays and other wearable applications.
In the field of miniature image display systems there are continuing challenges and drive to design smaller, lighter, and more energy efficient systems. These challenges stem from the fact that a miniature image display system should preferably be small enough and light enough to be wearable mounted on a helmet or on eyeglasses. And, preferably, the miniature image display system should be foldable for easy storage and transport. Such systems may be used for wearable computer systems, gaming systems, distance interactions between people or between people and machines, virtual-reality system, and for many other applications.
Typically, desktop computer systems and workplace computing equipment utilize CRT (cathode ray tube) display screens to display images for a user. The CRT displays are heavy, bulky, and not easily miniaturized. For a laptop, a notebook, or a palm computer, flat-panel display is typically used. The flat-panel display may use LCD (liquid crystal displays) technology implemented as passive matrix or active matrix panel. The passive matrix LCD panel consists of a grid of horizontal and vertical wires. Each intersection of the grid constitutes a single pixel, and is controlled by a LCD element. The LCD element either absorbs or reflects light depending upon orientation of the pixel. In fact, using quarter wave plates, flat-panel displays reflect light that is 90 degrees rotated from the incident light. That is, when light polarized in a first direction hits the flat panel and reflects off its pixels, the reflected light is polarized in a second, orthogonal direction.
The flat-panel display typically requires external lighting to allow human eyes to see the images displayed on the display panel. This is because flat-panel displays do not generate their own light. For laptop, notebook, or palm computers, the external lighting is typically positioned at the back of the flat-panel. The backlighting allows the user to see the images from the front of the flat-panel.
The flat-panels are also used for miniature image display systems because of their compactness and energy efficiency compared to the CRT displays. For miniature image display systems, reflective lighting, rather than the backlighting, is preferred. This is because, using the reflective lighting technique, miniature image display systems can be designed having higher energy efficiency compared to the energy efficiency of image display systems designed using the backlighting techniques. Various configurations of miniature display systems using flat-panels displays and reflective lighting technique can be found in U.S. Pat. No. 5,808,800.
To further increase the energy efficiency, use of polarizing beam splitting cube (“PBS cube”) has been proposed. However, the PBS cube comes at a price in terms of weight and bulk. Installation of the PBS cube within the miniature image display system introduces additional weight and bulk to the system Typically, the PBS cube occupies majority of the space of the miniature image display system. And, because of the PBS cube, the miniature image display system cannot be folded for easy storage or transport. Furthermore, the energy efficiency gain is limited because each time light enters or exits the PBS cube, the light is attenuated, thus losing energy. Configurations of miniature display systems using the PBS cube can be found in U.S. Pat. No. 5,596,451.
Therefore, there still exists continuing need for more compact, lightweight, energy efficient, and foldable miniature display system usable for helmet mounted or otherwise wearable display applications.
SUMMARY
These needs are met by the present invention. According to one aspect of the present invention, a display system has light source, polarized beam reflector film (PBRF), display panel, quarter wave film, and curved reflector. Polarized light from the light (first direction) source reflects off the PBRF toward the display panel. The display panel modulates, rotates, and reflects the light. The modulated light is now rotated (second direction), so it passes through the PBRF toward the quarter wave film and curved reflector. The quarter wave film and curved reflector are situated such that the modulated light rotated back to the first direction and reflected back toward the PBRF. Since the modulated light is not in the first direction, the modulated light is reflected by the PBRF for viewing.
According to a third aspect of the present invention, a display system includes a light source supplies light polarized in a first direction. A display panel produces image on its surface (“display surface”) such that when the light polarized in the first direction reflects on the display surface, modulated light results wherein the modulated light bears the image and is polarized in a second direction, the second direction being orthogonal to the first direction. A polarized beam reflector film (PBRF) passes light polarized in the first direction but reflects light polarized in the second direction The polarized beam reflector film has a first side and a second side opposite the first side and placed between the light source and the display panel. A curved reflector faces the first side of the polarized beam reflector film for reflecting the modulated light. A quarter wave film disposed between the polarized beam reflector film and the curved reflector. The modulated light passing through the polarized beam reflector film passes through the quarter wave film and is rotated by the quarter wave film, first rotation occurring when the modulated light from the display panel passes through the quarter wave film to reach the curved reflector resulting in quarter-rotated modulated light, second rotation occurring when the quarter rotated modulated light reflecting from the curved reflector passes through the quarter wave film to reach the polarized beam reflector film thus resulting in half-rotated modulated light, the half-rotated modulated light is in the first direction and reflects on the polarized beam reflector film for viewing.
According to a third aspect of the present invention, conic mirror may be added to concentrate the light from the light source to the polarized beam reflector.
According to a fourth aspect of the present invention, a display system includes a light source for supplying back lighting for a display panel, the back light polarized in a first direction and modulated by passing through the display panel. A polarized beam reflector film (PBRF) allows the modulated light to pass the PBRF toward a quarter wave plate and a curved reflector. The quarter wave plate and the curved reflector operating to rotate the modulated light to light polarized in a second direction and directing the rotated light toward the PBRF such that the rotated light is reflected off the PBRF toward an imaging area.
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Jusuf Gani
Ma Guolin
Marty Alan
Agilent Technologie,s Inc.
Mack Ricky
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