1、Bo Bai Stephanie Dalquist Megan Galbraith 16 May 2002,Design of a Head Mounted Display for Image-Guided Surgery,Introduction,Develop HMD for surgeons Projects diagnostic images on patient Compare digital X-Rays, NMR Overlay text plans High resolution and accuracy Design micro-display for image sourc
2、e,Technology goals,Full color, 4 bits/color grey scale Minimum frame rate of 100 Hz High resolution 1280 x 1024 Pixel pitch at most 24 m High contrast ratio, at least 100:1 Design for hospital environment, 100 Cdm-2 Minimum brightness 60,000 Cdm-2,Display technology,Active Matrix Organic LED Fast re
3、sponse time of 3 s Pixel pitch down to around 12 m Can reach brightness levels up to 106 Cdm-2 Reliable to 106 hours Preferred over other technologies AMEPD: color difficulties AMLCD: less bright AMELD: not very bright (23 Cd/m2 at 60 V),Grey scale method,Sub-framing Allows for 16 shades from black
4、to white Minimizes flicker at high (1600 Hz) Other options Patterning: Too much flicker, too few greys Voltage modulation: Requires high sensitivity to V More complicated drivers,Pixel structure,Stacked OLED True color High contrast Bright, emissive Flexible Makes pitch spec,Pixel structure,Stacked
5、OLED preferred Other options: Side-by-side monochrome Large pitch or lower resolution Many have decreased viewing angles Color filters Absorption loss Need efficient blue dyes,Pixel circuit,Diode equivalent for each color Single line addressing Voltage across rows Data down columns High frequency Si
6、mpler, cheaper drivers,OLED requirements,9V to reach 60,000 Cdm-2 Current Density of 50 mA/cm2 Area = Apixel - Atransistors = 570 m2 Current = 2.87 x 10-4 mA,CMOS specification,Choose n-doped CMOS: Kn Kp Lowers power consumption VGS = 0.6V ID = 0.5Kn(VGS-VTn)2 VG1 = VGS+Vdiode = 0.6+9 = 9.6V VG2 = V
7、G1+VTn = 9.6+0.5 = 10.1V Column voltage = VG1 = 9.6V Row voltage = VG2 = 10.1V,Driver specifications,Generic driver circuit Can be used with OLED, ELD, LCD, etc. Row driver draws 10.1 V Column draws 9.6 V,I/O data rate for drivers,Row data rate Selects a row to update Consider 16 sub-frames for grey
8、 scaling 1.6 MHz or 205 Kbps Column data rate Sends color information 6.29 GHz or 786 Mbps Much more data, much faster data rate needed,Power consumption,Total power consumption of 4 W 2 x 10-6 W per pixel Ppixel = VI = 9V x 2.87x10-4 mA Display requires 4 W Ptotal = PpixelNrowsNcolumns Conservative
9、 estimate assuming all pixels on,Overall efficiency,Display efficiency display = 27% 4 lumens/Watt power efficiency at 9 V Input Power Pin = 4 W Output Power Pout = 60,000 Cd/m2 Area/(4 lm/W 4 Cd/lm) = 0.9 W dipslay = Pout/Pin Optical subsystem optics = 15% Overall display optics = 4%,Conclusions,Meet target specifications at low cost with current technology Not power hungry Safe (low voltage, amperage, etc.) Take it to the lab for prototyping Revolutionize health-care by 2010,questions?,
