Existing Technologies Limit Evolution of Image Devices

Most digital color cameras and color displays capture or create the appearance of a color image by spatially separating the individual colors. In a typical color display, each color pixel (i.e., the basic unit of the composition of an image on a television screen, computer monitor, or similar display) is actually a combination of three monochrome pixels, each assigned a different primary color (red, green, or blue; commonly referred to as "RGB"). Although this technique has been effective for the last 30 years, it has become an inhibitor as display devices such as compact personal digital assistant (PDA) devices, web-enabled cellular phones, and compact flat-screen televisions become smaller and users demand higher resolutions.

ColorLink Proposes Color Sequential Imaging

In 1995, Dr. Kristina Johnson and Dr. Gary Sharp incorporated ColorLink with the goal of developing a tunable optical filter technology that would increase capture and projection display color quality. Previous approaches to color sequential imaging used RGB color wheels or inefficient color shutters to achieve color, but neither of these could achieve the desired size and resolution. The problem with color shutter technology at that time was its use of highly absorptive, poor-quality dye color polarizers. The key distinguishing feature of the ColorLink polarizer is that the separation of primary and complementary color is achieved through a loss-less transformation using a stack of optically transparent retarder films, known as a retarder stack.

ColorLink proposed, in its ATP application to introduce a new paradigm in high-resolution display and imaging by developing the underlying technologies for a high-efficiency, solid-state, electro-optic tunable filter for color sequential imaging. In color sequential imaging, which encodes color in time and not space, the complete color image is displayed as a rapidly changing sequence of primary RGB monochrome images. A switchable color filter selects which color is displayed in each image (red, green, or blue). Since every pixel in the display contributes to every primary image, a color sequential imaging display can have at least three times the resolution of an equivalent display that uses spatial separation. ColorLink's approach would employ color sequential imaging to capture or display information with the highest color quality, resolution, and brightness.

ColorLink's Innovation Has Potential Economic Benefits

If ColorLink's technology proved successful, it would advance the state-of-the-art in projection display and image capture from the pixilated, slow-moving color switches to smaller high-resolution displays with increased switching times. This could dramatically improve the quality in the highly competitive miniature display market and lead to a decrease in cost to consumers. Also, ColorLink's project had the potential to significantly impact the electronic display and digital imaging markets, which, according to the Optoelectronics Industry Development Association, were predicted to exceed $20 billion by 2001.

RGB technique has become an inhibitor asdisplay devices become smaller and users demandhigher resolution.

ColorLink Forms Partnerships and Finds Funding

ColorLink partnered with Polaroid Corporation and Kent State University's Liquid Crystal Institute to assist in the development of the color sequential imaging technology; later in the project, the company also added MicroContinuum, Inc., as a subcontractor. ColorLink had also attracted the interest of the industry's largest players.

The company's early-stage funding from "friends and family" disappeared quickly, however, and as a small company, ColorLink did not have the financial resources to support the development of the technology on its own. Moreover, the proposed research was too long term to attract the interest of venture capitalists. In 1997, ColorLink received an award of approximately $1.8 million from ATP to pursue research and development of its color sequential imaging technology. Its proposed tunable color filter was highly innovative, but needed significant improvements before it would become commercially viable. At that time, Japan and other countries dominated flat-panel display technology overseas, with the United States' world market share at less than 5 percent. The proposed technological developments could give the United States a greater share in at least part of this important and growing market.

ColorLink's color switch uses color sequential imaging to capture or display information with the highest color quality, resolution, and brightness.

Goals Defined for Color Sequential Imaging Project

ColorLink pursued three major technical goals in the color sequential imaging project: 1) maximizing the filter optical efficiency, 2) developing a new class of fast-switching nematic liquid crystals with switching times below one millisecond, and 3) fabricating liquid crystal devices on plastic. The purpose of the company's first objective was to produce the very brightest color-filter technology for integration into direct views and displays. At the time, there was not a high-quality method to colorize monochrome display systems. Their second objective focused on developing a new class of fast-switching nematics (relating to a liquid crystal phase in which the molecules are oriented in loose parallel lines) to optimize the duty cycle of the filter. Their third objective was important in producing a lightweight, compact tunable filter technology for application in displays for portable computing and communication devices.

ColorLink Refocuses on Projection Displays

In order to serve the growing projection display market, ColorLink began to shift its focus from developing a core technology to developing components for applications and, eventually, to system development of projection displays and digital imagery.

To serve the growing projection display market,ColorLink began to
shift its focus to systemdevelopment of projection displays and digital imagery.

ColorLink believed that the next generation of consumer televisions, monitors, and business projectors would be based on liquid crystal on silicon (LCOS) technology. These displays are liquid crystal films that are sandwiched between an integrated circuit chip and a transparent window.

At the time, there were inefficiencies in the technology and widespread acceptance had been slow. One challenge with the LCOS technology involved a lack of color management, as poor color brightness and contrast were evident. ColorLink felt that it could modify its filter technology to further the development of LCOS technology and thus began a testbed program.

The goal of the program was to optimize the component technology and the color management architecture until the company was able to achieve the required performance on a system level. The feedback from the testbed produced many changes to the retarder stack designs and architecture, ultimately allowing ColorLink to identify the best use of its technology.

Subcontractors Provide Insight and Expertise

Polaroid and Kent State, the primary subcontractors, offered technical expertise, technological validation, and valuable industry insight. Polaroid was responsible for thinning and decreasing the weight of the color switch by using plastic cells. Early samples were achieved by the end of the second year of the ATP project, but Polaroid dropped out due to internal financial issues that were unrelated to this project. Although the project failed to reduce filter thickness and weight, reductions in thickness proved to be unnecessary because ColorLink focused on more viable opportunities in the projection display market instead of miniature displays.

Kent State worked primarily in liquid crystal development, in particular trying to increase the switching speed of the liquid crystal devices. One solution they developed involved adding a small amount of polymer to stabilize a particular liquid crystal state, which resulted in a faster relaxation rate. Kent State performed a number of experiments in this area, but results were not promising enough to proceed further. Kent State also assisted ColorLink in other relevant areas, including field-of-view compensation, the design of compound-element liquid crystal switches for improved speed, and the development of diagnostic hardware.

Technical Success in Image Capture and Display

By the end of its three-year ATP project, ColorLink had developed several components that support image capture and display applications. These components have enabled the company to achieve good color quality with filter transmission exceeding 90 percent, something that was previously not possible. In addition, ColorLink produced a five-cell color switch that provides average turn-on and turn-off times of under 0.2 milliseconds, times that are significantly faster than previous color-switching technologies.

ColorLink's Target Shifts to HDTVs and Monitors

Over the course of the project, ColorLink realized that the most promising application was in projection displays, rather than digital imaging. Consumer demand for thin, large-area monitors was high, but so was the cost. For example, a 21-inch flat-panel liquid crystal display (LCD) monitor was over $3,000 and a high-definition television (HDTV) plasma display cost $10,000. However, ColorLink's revolutionary color management components enable a new lower cost class of computer monitors and digital televisions. These new monitors and digital TVs offer larger screens in a slimmer profile with resolution, color, contrast, and brightness that are superior to existing products.

LCOS microdisplay-based TVs with ColorLink technology are emerging as the best solution in this potentially exploding market. LCOS microdisplay-based systems with ColorLink technology can provide a high-quality, greater-than-24-inch screen with enhanced resolution in a 6-inch-deep monitor for about $1,000. The future in projection systems includes computer monitors and digital TVs, a multibillion-dollar market with annual growth rates in excess of 15 percent. The demand for computer monitors and projection devices that utilize LCOS is estimated at 10 million units per year by 2004.

Commercialization

Conclusion

Research and data for Status Report 96-01-0263 were collected during October 2001-December 2001.

Return to Table of Contents or go to next section of Status Report No. 3.

Date created: April 4, 2006
Last updated: July 6, 2006

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