Optics: image projectors – Methods
Reexamination Certificate
1998-04-27
2003-01-28
Dowling, William (Department: 2851)
Optics: image projectors
Methods
C353S122000, C353S119000
Reexamination Certificate
active
06511187
ABSTRACT:
BACKGROUND OF THE INVENTION
Flat-panel displays are being developed which utilize liquid crystals or electroluminescent materials to produce high quality images. These displays are expected to supplant cathode ray tube (CRT) technology and provide a more highly defined television picture. The most promising route to large scale high quality liquid crystal displays (LCDs), for example, is the active-matrix approach in which thin-film transistors (TFTs) are co-located with LCD pixels. The primary advantage of the active matrix approach using TFTs is the elimination of cross-talk between pixels, and the excellent grey scale that can be attained with TFT-compatible LCDs.
Flat panel displays employing LCDs generally include five different layers: a white light source, a first polarizing filter that is mounted on one side of a circuit panel on which the TFTs are arrayed to form pixels, a filter plate containing at least three primary colors arranged into pixels, and finally a second polarizing filter. A volume between the circuit panel and the filter plate is filled with a liquid crystal material. This material will rotate the polarization of light when an electric field is applied across it between the circuit panel and a ground affixed to the filter plate. Thus, when a particular pixel of the display is turned on, the liquid crystal material rotates polarized light being transmitted through the material so that it will pass through the second polarizing filter.
Preferred embodiments of the present invention relates to projection display devices (i.e. monitors and image projectors) including methods of fabricating such devices using thin films of single crystal silicon in which a light valve matrix (or matrices) is formed for controlling images produced by these devices. In accordance with the present invention, projection display devices employing high density single crystal silicon light valve matrices provide high resolution images compatible with 35 mm optics.
In one preferred embodiment, an optically transmissive substrate is positioned to receive light from a back-light source and a light valve matrix is secured to the substrate. In accordance with the present invention, the light valve matrix includes an array of transistors and an array of electrodes which are formed in the thin film of single crystal silicon. The light valve matrix also includes an adjacent light transmitting material, through which light from the back-light source is selectively transmitted. Preferred embodiments are directed to light valves employing a transmissive light transmitting material such as liquid crystal or a ferroelectric material, although other transmissive materials may be used. Each light valve includes a transistor, an electrode and a portion of the adjacent light transmitting material. Each transistor, by application of an electric field or signal, serves to control the optical transmission of light through the adjacent light transmitting material for a single light valve.
A driver circuit is electrically connected to the light valve matrix to selectively actuate the light valves. The drive circuitry may be formed in the same thin-film material in which the transistors and electrodes have been formed. The drive circuitry is capable of being fully interconnected to the matrix using thin-film metallization techniques without the need for wires and wirebonding. An optical system is also provided for projecting light transmitted through the actuated light valves onto a large viewing surface.
The present devices and related methods for fabricating projectors satisfy the requirements of large screen television or monitor displays for producing highly defined color images. To that end, a projection display device can have multiple light valves each adapted to selectively transmit light of a single primary color. Further, a dichroic prism may be provided for combining the single color light transmitted by each light valve producing a multi-color light image which is projected onto a large viewing surface.
Other preferred embodiments of the present invention relate to an active matrix display panel adapted for use in a conventional 35 mm slide projector for providing monochrome or multi-color images. The display panel is fabricated to have equivalent physical dimensions as a standard 35 mm photographic slide having an image which can be projected by a slide projector. In accordance with the present invention, the active matrix display panel, being packaged to be size-equivalent with a standard 35 mm slide, is insertible into a slide projector with modification thereof for generating the projected images. An electronics unit is connected to the display panel and controls image generation by the active matrix. In preferred embodiments, the display panel is capable of generating monochrome or multi-color images.
In one preferred embodiment of the invention, an active matrix display device is adapted for use with a slide projector having a projector body, a light source, an optical system and a chamber in which a 35 mm slide can be placed for projection of its image onto an external viewing surface. The display device includes a housing and an active matrix display panel movably mounted to the housing. As such, the display panel has a storage position and an operating position. The housing is positioned on the slide projector body such that the display panel, being moved into the operating position, can be securely disposed in the projector chamber for selectively transmitting light from the light source to provide images for projection by the slide projector.
The housing preferably contains a shielded electronics assembly which is electrically connected to the display panel for controlling image generation. The electronics assembly receives image data from an image generation device which may be a computer or any video device. Image data provided by the device is processed by the electronics and sent to the active matrix display panel. Responsive to the received data, the individual active matrix light valves are activated such that the illuminating light from the light source is selectively transmitted through the active matrix to form monochrome or multi-color images.
In another preferred embodiment, the active matrix display device includes an active matrix display panel and a remote electronics housing. The display panel is dimensioned to be securely positioned in the chamber of the slide projector and is electrically connected to electronics in the remote housing by a cable.
In yet another preferred embodiment, the active matrix display device includes an active matrix display panel which is not physically connected to the electronics housing. Instead, the active matrix display panel and the electronics in the housing communicate with each other via antenna elements such as RF antennas or infrared transmitter/detector elements.
As with aforementioned embodiments, an active matrix display panel has an array of pixels or light valves which are individually actuated by a drive circuit. The drive circuit components can be positioned adjacent to the array and electrically connected to the light valves. As such, the individual light valves are actuated by the drive circuit so that illuminating light is selectively transmitted through the active matrix to form an image.
In preferred embodiments, the active matrix circuitry is formed in or on a layer of a semiconductor material such as silicon. It is noted that any number of fabrication techniques can be employed to provide preferred thin-films of polysilicon or single crystal silicon. In embodiments in which a thin-film of single crystal silicon is used, extremely high light valve densities can be achieved such that high resolution images are obtained. Other embodiments employ the use of a solid state material or any material whose optical transmission properties can be altered by the application of an electric field to supply the light valves of the present invention.
A preferred embodiment of the fabrication process for a liquid crystal transmissi
Arney Michel
Beck Benjamin
Chastain David
Hunter Gregory
O'Connor Kevin
Dowling William
Hamilton Brook Smith & Reynolds P.C.
Kopin Corporation
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