Invited Paper
Perspective of MEMS Based Raster Scanning Display and Its Requirements for Success Yong-Hwa Park*, Jin-Ho Lee, Seong-Ho Shin and John Sunu Display Lab., Samsung Advanced Institute of Technology, Mt. 14-1, Nongseo-dong, Giheung-Gu, Yongin-City, Korea 449-712 *
[email protected]; phone: +82-31-280-9464; fax: +82-31-280-9473 ABSTRACT The customers’ demand for real life-like display with natural colors and high definition is increasing and hence laser display with the best expression of natural color is being proposed as a way to realize this. In particular, the raster scanning display using the high-speed reflective MEMS scanner plus compact laser sources enables realization of ultrasmall optical engine with great optical efficiency. By the way, in recent years the emerging display systems including FPD (Flat Panel Display) and projection systems based on the microdisplay devices show rapid improvements in terms of picture quality, form factor as well as cost. The object of this paper is introducing a technology analysis of success factors of the MEMS based rater scanning display in order to get high-level development roadmap, through a comparison study with the conventional displays. Proper specifications of brightness, color, contrast, resolution, form factor, power consumption and cost-effectiveness are suggested for mobile projector application. The technical challenges toward achievement of the specifications are summarized. Keywords: laser display, mobile projector, raster scanning, MEMS mirror, compact laser
1. INTRODUCTION Different from analog displays, introducing the digital display technology leads changes of the information processing environments of office, home and personal uses. The digital displays are about to be the gateway of the bi-directional information exchanges for applications of entertainment, work, mobile communication, internet, commerce, broadcasting, digital photography and so on. Visual information flows forward and backward in the chain of the following three sub-domains: 1) visual source generation; 2) visual information storage/manipulation/transmission; and, 3) reproduction of visual information. Digital display technology makes all the three sub-domains full of innovative digital devices such as digital camera, camcorder for source generation; set top-boxes, small-size HDD, PVR (Personal Video Recorder), image editing S/W, high-speed wireless transmission of high resolution images for visual information manipulation; and, HD (high-definition) displays for vision reproduction. Digital display technology impacts consumer products to be more interactive, customized, portable, and have high-image quality. The consumers can easily create and distribute their own visual contents so that they become active prosumers who create and control the market, as Alvin Toffler expected in The Third Wave in early nineties. However, the digital display market is just opened nowadays and most of development activities so far have focused on replacing the CRT in home. The target is improving the image quality in order to get CRT-like image in terms of color, brightness, contrast, response time and image artifacts. Though various functionalities of display devices such as form-factor, ease of information manipulation, mobility are required in the next generation digital displays, the recent consumer survey shows that the picture quality is still the most concerning factor when they buy a next display device as shown in Figure 11. Hence, ‘replacing the CRT’ is still a good strategy to win in the display market in coming several years until the progress of image quality is saturated. Along this line, the customers’ demand for real life-like display with natural colors and high definition is increasing and hence the laser display with the best expressions of natural color and high resolution is being proposed as a way to realize this. The applications of laser display are diverse ranging from ultra small, portable to large screen such as the HMD, mobile projector, projection TV and cinema projectors. In particular, the raster scanning display using the high-speed reflective MEMS scanner plus compact laser source enables realization of ultra-small optical engine with great optical efficiency so large screen video can be realized through low power consumption and small form-factor.
MOEMS Display, Imaging, and Miniaturized Microsystems IV, edited by Hakan Ürey, David L. Dickensheets, Bishnu P. Gogoi, Proceedings of SPIE Vol. 6114, 611403, (2006) · 0277-786X/06/$15 · doi: 10.1117/12.659058 Proc. of SPIE Vol. 6114 611403-1
The positioning of the MEMS based raster scanning display in the market should be derived by comparing the several types of emerging display systems in terms of performance, features, and targeting market segments. Although it is quite early to clarify its development target, it is valuable to investigate the technical features, hurdles and requirements of the raster scanning display in order to initiate high-level product roadmap. Outline of this paper is such that a technology analysis of the key success factors of the MEMS based rater scanning display is shown through a comparison study with the conventional displays. Since the raster scanning display is a type of Microdisplays, the Microdisplay is compared to existing devices as a reference. Then, raster scanning display will be particularly investigated using its differentiation points apart from the existing Microdisplays and FPD (Flat Panel Display). As results, proper specifications of brightness, color, contrast, resolution, form factor, power consumption and cost-effectiveness are suggested for mobile projector application. The technical challenges toward achievement of the specifications are summarized.
Design
Brand 10°/a
3%
Function 1°/o
Price, 200/0
Picture Quality 66°/o Figure 1: Consumer survey result: key concerning factor when buy a new TV. The picture quality is the most concerning factor to customers. (Courtesy of Display Bank, Inc.)
2. EXISTING DISPLAY DEVICES TECHNOLOGY ANALYSIS In recent years, the emerging display systems including FPD and projection systems based on the microdisplay devices such as DMD (Digital Micromirror Device), HTPS (High Temperature Polysilicon), and LCOS (Liquid Crystal on Silicon) have shown rapid improvements in terms of picture quality, form factor as well as cost. This leads war-like competition between the emerging display devices for at least coming several years until the market shares are settled. Market perspective and comparison of devices from viewpoint of technology are summarized as follows. 2.1 Market perspectives Due to extensive investments to the manufacturing facilities in Gen 7, the price of LCD will drop very rapidly in coming couple of years. The price of LCD drives fierce cost competition between major display devices such as LCD, Plasma, and Microdisplays. Figure 2 shows an expectation of market windows of existing/emerging display devices in years 2005 and 2010. LCD’s market window will deploy from under 40 inch screen diagonal sizes up to 60 inches in year 2010 by cost reductions. Due to this aggressive LCD cost drive, market windows for Plasma and Microdisplay will move from 30-70 inch to 40-80 inch, and 40-70 inch to 50-80 and more, respectively. Hot zone will be 45-55 inches, in which LCD, Plasma and Microdisplay probably have similar cost levels in year 2010. Full HD resolution (1920 by 1080p) will be common in most of existing devices in year 2010. The new technology such as OLED will emerge in the major TV market taking the market segment of LCD due to its similarity of manufacturing process. However, the material reliability limits its expansion of screen size over 30 inch and its cost competitiveness against existing LCD would not be enough by that time so that OLED’s major market would be mobile display and personal uses. FED would appear in range of 30-40 inches. Though its low power consumption and CRT-like image quality, large screen size of
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FED more than 40 inch would be difficult due to its lower manufacturability than other devices arising from the vacuum packaging and uniformity issues. Figure 3 shows a street price expectation of average (42 inch) existing displays. Price destruction would happen by year 2006-2007, e.g., 42” Microdisplay projection TV will be around $1,000, which is about half of current price. The key point is that the material cost reduction will be one of the key success factors of existing displays including MEMS based Microdisplays, which conventionally have kept its price position at 2/3 of Plasma’s.
PDP
Year 2010
Year 2005
Full HD (1920*1080)
TFT-LCD TV
TFT-LCD TV
(SXGA)
OLED TV
FED TV
HD (WXGA) FLAT CRT TV CRT PJTV
~ 20”
30”
MD PJTV
PDP
MD* PJTV
40”
50”
60”
70” & Up
FLAT CRT TV
SD (VGA)
~ 20”
30”
CRT PJTV
40”
50”
60”
70” & Up
Figure 2: Expectation of market windows of competing display devices from viewpoint of screen size and resolution up to year 2010. (Source: JEITA, SRI, D/Search, JP Morgan, SEC-internal data)
2003 Large Size (>40”) Display Trend
2004
2005
2006
Microdisplay RPTV CRT RPTV
2007 TFT LCD
Plasma
Appearance of major display product over 40” in the market (Market Size :1M set/year) Price Trend
8000 8000 6000 6000 4000
4000
2000 1500
Market Average Price (Unit : US$)
TFT-LCD Plasma
4000
MD RPTV
3000
CRT RPTV
2000 800
2500 1800 1000 600
Figure 3: Expectation of street prices of major display products (average price of 42 inch screen). About 50% cost reduction is expected by year 2007. (Source: JEITA, SRI, D/Search, JP Morgan, SEC-internal data)
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2.2 Definition of high definition display The ultimate display (perfect reproduction of visual information of nature) is one of human’s eventual engineering targets such as time machine. The standard of display quality has been evolved in line with human eyes standard and human need, closer to reality. The ultimate display can be defined with number of items such as: extreme contrast and brightness, acquisition of detail, natural colors, unlimited viewable region, natural motion, and infinite number of focal points (3D display). The display devices have been developed fulfilling the parts of the performances of the ultimate display. These ultimate display performances can be achieved by: 10,000:1 contrast level, bright light reflection by sunlight, expression of even minute particles, neither dragging nor flicker, color gamut covering more than 180% of NTSC standard, and full viewable region with two eyes. The term ‘High Definition’ display in current market, can be defined conventionally as: screen size more than 40 inch, number of horizontal lines 720p and more, peak white level more than 1,000 nits, average white level 350 nits, black level less than 0.3 nits, color expression of NTSC 70% and more. 2.3 Technology comparison between existing devices As mentioned in Introduction, the performance comparison between existing major display devices such as LCD, Plasma, and Microdisplays is valuable since the raster scanning display is a type of Microdisplay. Hence, Pros and Cons of the Microdisplay are investigated to get initial referencing point of the development of the raster scanning display. Table 1 summarizes typical performances of FPD and rear projection Microdisplays. Device characteristics such as power consumption and set depth are added to image quality characteristics. Table 1: Performance comparison between existing major display devices such as LCD, Plasma, and Microdisplays as of
1Q 2005. 1) SONY 3p LCD, 2) Samsung DLP, 3) Philips LCOS
Performances
Plasma
LCD
Brightness
700 cd/m2
450 cd/m2
Ave. contrast
3,000:1 (dark room)
Resolution
Microdisplays (RPTV) DLP 2)
LCOS 3)
400 cd/m2
550 cd/m2
500 cd/m2
900:1
700:1
1,500:1
800:1
1,366 by 768
1,920 by 1,080
1280 by 720
1280 by 720
1280 by 720
Screen size
30’’~80’’
10”~57’’
42”-70”
42”-70”
42”-70”
Weight (kg)
60~70
60~70
~35
~35
~35
Power Consumption
High
High
Low
Low
Low
Burn-in
Yes
No
No
No
No
Set Depth
3”-6’’
2’’
13”~20”
7”~20”
24”~30”
25,000~30,000
50,000~75,000 (backlight)
8,000~10,000 (lamp)
8,000~10,000 (lamp)
8,000~10,000 (lamp)
Longevity (hrs) Viewing Angle
180˚
170˚
HTPS
1)
