Computer graphics processing and selective visual display system – Plural physical display element control system – Display elements arranged in matrix
Reexamination Certificate
2000-09-05
2003-07-29
Shalwala, Bipin (Department: 2674)
Computer graphics processing and selective visual display system
Plural physical display element control system
Display elements arranged in matrix
C345S077000, C345S084000, C345S085000, C040S582000
Reexamination Certificate
active
06600474
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to visual display systems and in particular to flat-panel displays produced using micro-machining techniques
BACKGROUND OF THE INVENTION
Flat-panel video displays are ubiquitous components of many consumer, industrial and military products and devices. They are found in computer laptops, automobile dashboards, microwave ovens and a myriad of other machines and devices with which man interacts.
Active-matrix liquid-crystal displays dominate the market for high quality high-resolution flat-panel displays. However, these displays are relatively expensive and the amount of power they consume when operating is relatively large in comparison to the amount of power readily available from many battery driven devices.
The need and desire to incorporate visual displays into more and more products, ranging from portable GPS baedekers to toys, has created a strong demand and expanding market for inexpensive flat-panel displays that can provide high quality images and operate with low power consumption.
In response to the demand, new types of flat panel displays have been developed based on the processing of silicon using MEMS technology. MEMS technology enables microstructures having features on the order of a few microns to be formed on appropriate silicon substrates. The technology can therefore be used to produce “pixel” sized devices, on silicon, that process light. Arrays of these devices are useable to form flat-panel displays that are potentially inexpensive, that operate with low energy consumption and provide high-quality images.
Most flat-panel displays produced using silicon technology belong to one of two general types. A flat-panel display of a first type has pixels each of which comprises a liquid crystal cell formed on a silicon substrate. Light, which may be ambient light or light from an appropriate light source, illuminates the pixels. Transmittance of the liquid crystal in each pixel for the light determines how bright the pixel appears. The transmittance of the liquid crystal is controlled by voltage on electrodes in the pixel. A pattern of pixels having varying levels of brightness is formed on the display to produce an image by controlling the voltage on the electrodes in each pixel of the display. Images provided by this type of display generally suffer from low brightness and low contrast.
A flat panel display, hereinafter referred to as a “micro-mechanical display”, of a second type, has pixels each of which comprises at least one movable structure micro-machined on a silicon substrate. The position of the at least one moveable structure in each pixel controls how bright the pixel appears by controlling an amount of light that the pixel reflects or diffracts. Generally, the position of the at least one moveable element is controlled by electrostatic forces between the at least one moveable element and electrodes in the pixel that are generated by applying appropriate voltages to the electrodes. Often the voltages are relatively high and moving the at least one moveable element requires a relatively large expenditure of energy. Usually, in these types of displays, brightness and image contrast are dependent upon viewing angle, as measured with respect to the normal to the plane of the display, and decrease as the viewing angle increases. Some of these displays require an internal light source that consumes relatively large amounts of power when operating.
A micro-mechanical display in which the at least one moveable structure in pixels in the display comprises a plurality of parallel flexible reflecting ribbons is described in U.S. Pat. No. 5,841,579 to D. M. Bloom et al, which is incorporated herein by reference. The flexible ribbons in a pixel of the display are normally located parallel to the plane of the substrate on which the pixel is formed at a small distance above the plane. The ribbons are controllable to be depressed towards the substrate by electrostatic forces that are generated by voltages applied to electrodes in the pixel.
To form an image on the display, the pixels in the display are illuminated with light from a suitable light source so that light is incident on the pixels at a given angle with respect to the plane of the display. When alternate ribbons of the plurality of ribbons in a pixel are depressed, the plurality of ribbons in the pixel form a diffraction grating that diffracts some of the incident light at an angle such that the pixel appears bright to a user of the display. If alternate ribbons are not depressed, the plurality of ribbons in the pixel reflect the incident light at a different angle such that light from the pixel does not reach the eye of the user and the pixel appears dark. An appropriate pattern of bright and dark pixels forms the image on the display. The patent describes methods for using pixels of the type described to produce a flat-panel displays that provide color images.
Another type of micro-mechanical display is described in U.S. Pat. No. 5,636,052 to S. C. Arney et al, which is incorporated herein by reference. In this flat-panel display the at least one moveable element in a pixel is a membrane. The membrane is flexibly supported so that it is parallel to the substrate with a small air gap between the two. Light that is incident on the pixel is reflected by both the substrate and the membrane. The height of the air gap determines whether the reflected light from the membrane and the substrate interfere constructively or destructively and therefore if the pixel appears bright or dark respectively. An addressable electrode in the pixel, when charged attracts the membrane towards the substrate thereby controlling the height of the air gap and therefore whether the pixel is bright or dark. In order to displace the membrane, relatively high voltages, on the order of tens of volts, must be applied to the addressable electrode.
It would be advantageous to have a flat panel display that uses ambient light, without the need for a separate light source, and that can provide high quality high contrast images while operating at low voltages with low power consumption.
SUMMARY OF THE INVENTION
An aspect of some preferred embodiments of the present invention is related to providing a micro-mechanical flat-panel display that uses ambient light and provides high-contrast images at substantially all viewing angles with respect to the plane of the display.
An aspect of some preferred embodiments of the present invention is related to providing a flat-panel display that operates with low power consumption.
An aspect of some preferred embodiments of the present invention is related to providing a flat-panel display that operates using electrical power supplied at low voltages.
An aspect of some preferred embodiments of the present invention relates to providing a flat-panel display that provides black and white and/or gray level images.
An aspect of some preferred embodiments of the present invention relates to providing a flat-panel display that provides color images.
An aspect of some preferred embodiments of the present invention relates to providing a micro-mechanical flat-panel display formed on a substrate and having pixels that comprise a moveable element.
In a preferred embodiment of the invention, the moveable element is formed in the shape of a thin planar panel having first and second relatively large face surfaces and thin edges. The panel, hereinafter referred to as a “flipper”, is hinged to the substrate in such a way that it is rotatable from one to the other of two limiting positions about an axis of rotation that is parallel to the surface of the substrate. The limiting positions are hereinafter referred to as “on” and “off” positions. The flipper is preferably at least partly formed from a conducting material.
In the on position the first face surface faces a user looking at the display and is visible to the user. The second face surface of the flipper faces the substrate, facing away from the user, and is not visible to the user. In the off position the second face s
Heines Amichai
Karty Adiel
Fenster & Company
Flixel Ltd.
Kovalick Vincent E.
Shalwala Bipin
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