P‐188: Single‐Panel Spatial‐Color and Sequential‐Color LCOS Projectors Using LED Lamps

Abstract

We present and compare two single-panel LCOS projectors using LED lamps. The 0.59" sequential-color LCOS microdisplay with integrated frame buffers can deliver 10.5 lm by a 4W red, green and blue LED. The 0.59" spatial-color LCOS microdisplay with white sub-pixels can deliver 14 lm by a 6W white LED. IntroductionLiquid-crystal-on-silicon (LCOS) microdisplay has been developed for more than 10 years [1,2]. There are three kinds of LCOS microdisplays, arranged in different manners for various applications. The first one was a monochrome and highresolution microdisplay developed in early 1990, and arranged in three-panel architectures for rear projection television (RPTV) applications [3,4]. The second one was a color-sequential microdisplay developed in late 1990, and arranged in single-panel architectures for near-to-eye and RPTV applications [5~7]. The third one was a spatial-color microdisplay developed in early 2000, and arranged in single-panel architectures for near-to-eye and mini-projector applications [8]. These three kinds of LCOS microdisplays and projectors were not designed for use with light emitting diodes (LEDs). But as the fast development of power LEDs, the prospect of using LEDs as light sources for these three LCOS projectors has been greatly increased [9~11].A Corner of 3M applied red, green and blue (RGB) LED lamps to a three-panel LCOS projector, which used three 0.61" SVGA panels, and obtained 267 lm [10]. H Zou of Philips Research replaced the scrolling prism in a single-panel sequential-color projector, which used a 1.3" progressive-scan SXGA panel, by sequential RGB LED lamps and obtained 44 lm [9]. It was expected that the output could be improved to 135 lm if the progressive-scan LCOS panel was replaced by a frame-loading one. H S Lo of ITRI proposed optical designs for very compact mini-projectors using 0.38" color-filter LCOS panels [11]. But the output was low due to the light absorption by RGB color filters.In this paper, we present our works on single-panel spatial-color and sequential-color LCOS projectors using LED lamps. We added white sub-pixels to the color-filter LCOS panel to increase the panel reflectivity from typically 20% to 32%. The output of the spatial-color LCOS projector was correspondingly improved. We integrated frame buffers to the sequential-color LCOS panel to eliminate the frame loading time. As a result, the optical efficiency of the sequential-color LCOS projector was greatly improved. Moreover, the sequential-color LCOS projector had enough time budgets for RGB and white (RGBW) color sequence for more optical output. Spatial-Color LCOS ProjectorThe color-filter LCOS microdisplays were designed to be used with low-cost halogen lamps for low-cost video projectors. Figure 1 shows a palm-size spatial-color LCOS projector using a 50W halogen lamp in a MR11 package. The projector could produce 20 lumen output from a 0.47" VGA panel with a color gamut of 35% NTSC level, which was limited by low color temperature of the halogen lamp. (a) (b) Figure 1 (a) Spatial-co...

71.1: Invited Paper: High Resolution Microdisplays for Pico Projectors

“…Since we control the LC light response with a pulse width rather than a voltage as with analog designs [3], we could use LC formulas that while having fast switching may have poor linearity with respect to the brightness versus voltage (BV). The LC we used has a fairly sharp BV characteristic as shown in the figure below for the primary colors.…”

P‐172: A Same 0.38” Liquid‐Crystal‐On‐Silicon Backplane for Color‐Sequential and Color‐Filter Projector Applications

“…In our earlier work, we have developed a 0.59" CS-LCOS microdisplay of 15μm pixel and of SVGA resolution or 800x600 pixels [7]. A frame buffer was integrated onto the silicon backplane to accelerate the data upload time, and a thin mixed twisted nematic (MTN) LC mode was used for fast LC response [8].…”

Test of reflective MTN liquid crystal cell for the LCOS microdisplay by guided wave method

“…The LCOS microdisplay has very high resolution and yet maintains a large aperture ratio or optical efficiency. 1,2 In Shenzhen Yangtze Live Co., Ltd, China, we have made LCOS microdisplay device based upon mixed-mode twisted nematic (MTN) proposed by Shin-Tson Wu et. al.…”