Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1999-12-30
2002-04-23
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S033000, C353S081000, C353S084000
Reexamination Certificate
active
06375330
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to rear-projection television (RPTV) systems, computer monitor and portable data display systems, and more particularly to electronic image projector engines. More particularly, the present invention relates to projection engines which enable the use of reflective liquid-crystal-on-silicon semiconductor light valve imaging devices, commonly referred to as ‘liquid-crystal-on-silicon imagers.’
BACKGROUND OF THE INVENTION
Until recently, demand for electronic image projectors has been limited to business and professional environments where the high cost and complexity of prior art image projection systems is a lesser limiting factor in their applicability. The large number of optical components, the requirement to maintain accurate positioning in the projector engine assembly during use, and the high cost of prior art electro-optic ‘imager’ devices (e.g., TFT-LCD, DMD, ILA, etc.) limits the marketability of products using such prior art technologies. Moreover, prior art projection engines inefficiently use the optical information provided by the imager.
Recently, image content with dramatically higher resolutions has emerged in the consumer television and computer display environments, bringing higher demand for projected image systems. However, prior art projected image systems cannot display these high-resolution images with a price that consumers are willing to pay. Moreover, prior art projected image systems do even not provide performance levels that justify their high cost. Thus, there is a need to reduce the complexity and cost of projected image system technology while improving manufacturability, reliability, image quality, system lifetime, heat production, color purity, lamp efficiency and contamination resistance.
The need for large, high resolution display devices is becoming more important because the United States and other countries are in the process of shifting from an analog, low resolution television delivery system, to a digital, high resolution delivery system, sometimes referred to as “high-definition television”, or “HDTV”. There is also a need for larger and higher-resolution computer monitors. In terms of resolution, the current television delivery system in North America, known as NTSC (this format was developed by the National Television Standards Committee-hence the format has been named NTSC) has addressable resolution of approximately 425 by 565 pixels. Pixel density is most common method of expressing the resolution of a display device. A ‘pixel’ is the basic ‘picture element’ of an image (sometimes referred to as ‘pels’). The term pixel usually applies to the quantification of electronic images, which are composed of an array of pixels that each define a tiny portion of the image. This array of image picture elements is usually specified by a vertical number and a horizontal number, the product of which is the total number of pixels. Thus, the NTSC picture can provide, at best, approximately 240,125 total pixels.
For bandwidth conservation reasons, the typical cable television signal fed to most U.S. households arrives with even less resolution, approximately 350 by 466 pixels (163,100 total pixels). While there are as many as eighteen different formats proposed for digital television, there are three different resolutions likely to be established as final standards and used by terrestrial broadcast, direct broadcast satellite and cable companies. These formats are base digital television, 480 by 640 pixels (307,200 total pixels), low HDTV, 720×1280 pixels (921,600 total pixels), and high (or full) HDTV, 1080 by 1920 pixels (2,073,600 total pixels). Thus, it is seen that a television capable of displaying full HDTV resolution must have the ability to display nearly nine times as much picture information (i.e., nearly nine times as many pixels) as current NTSC broadcasts require. Moreover, even lower resolution digital television formats greatly exceed the cost-per-pixel capabilities of the projection-CRT.
Prior art projection image technologies are not capable of efficiently displaying full HDTV resolution at low cost. By far the most popular large screen television system is the rear projection television, known as RPTV. A typical RPTV uses three cathode ray tubes that project picture data onto the rear of a transmission screen. The screen then distributes the picture data into an image viewing field, within which the viewer can see it. Demand for inexpensive televisions and computer monitors having large image sizes and high resolution has prompted leading semiconductor manufacturers to develop reflective liquid-crystal-on-silicon semiconductor imaging device components. This electro-optic component, often referred to as an ‘imager,’ is essentially an electronic device constructed to operate as a reflective light valve. The reflective liquid-crystal-on-silicon light valve is comprised of a semiconductor integrated circuit on a single piece of silicon, similar to a DRAM or other such electronic memory device. Its surface contains the electronic image elements, i.e. its pixels, in regular array within its active area. The integrated circuit is transformed into an electro-optic device through established methods by plating its surface with a reflective mirror metal or suitable dielectric thin-film stack such that light incident upon it is reflected at high efficiency amidst the electric fields created at the surface of the device. Using methods well known in the liquid crystal display trade, a twisted-nematic (TN) or other such liquid crystal cell is bonded atop the surface of the silicon die in close proximity. When this combination is illuminated with polarized light, the resulting construction acts in effect as a reflective light polarization modulator wherein each picture element on the surface of the integrated circuit can be separately controlled electronically.
Reflective liquid-crystal-on-silicon light valve component devices are now readily available from a number of manufacturers. Their development has been driven by the simple fact that they are less expensive to manufacture in high volumes than thin-film transistor (TFT) or digital-micro-mirror (DMD) imager components used in the architectures of established solid-state projection engines. They are also capable of much higher market applicability since their manufacture does not require customized equipment, unlike TFT and DMD imagers, which have experienced only narrow demand in business and professional environments. Instead, reflective liquid-crystal-on-silicon imager devices are manufactured on existing ‘memory chip’ process lines.
For reflective liquid-crystal-on-silicon light valve imagers to be useful in televisions and computer monitors having larger viewing area and higher resolution, a projection engine optical architecture having high performance and low cost is necessary. An image ‘projection engine’ is a term used in the trade to denote the essential assembly within a projection system, usually taken to mean all components from the lamp to the projection lens. None of the prior art projection engine optical architectures can provide either high performance or low cost when using liquid-crystal-on-silicon light valve imagers. The various embodiments of the present invention show television or computer monitor using an engine architecture capable of significantly higher resolution than the resolution limits of projection cathode ray tube technology at cost demands of the consumer user.
The transformation of light collected from a bright lamp into image luminance on a screen is a fundamental purpose of image projection engines. The lamp used in an RPTV or monitor is typically an arc lamp, which emits white light in all directions. Geometrically organizing and redirecting this randomly directed white light into uniformly directional and focused light, thereby creating an image, is the purpose of a projector engine.
Light collection in optics is quantified by either f/# or numerical aperture, yet both quant
Adams Russell
Fuller Rodney
Gain Micro-Optics, Inc.
Lyon & Lyon LLP
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