Image Acquisition Photo sensors Photo diodes and photo

Image Acquisition • Photo sensors – Photo diodes and photo diode array – Photo transistor • Video camera 240 -373 Image Processing 1

Primitive camera structure • • • Slotted board, rotating disc Photosensitive device Lens Illumination for object 240 -373 Image Processing 2

Vidicon 240 -373 Image Processing 3

Color Images • involves the capture of 3 images simultaneously, r, g, b • placing filters over the lens of the camera is unsatisfactory • Use color stripes placed between lens and photo sensor 240 -373 Image Processing 4

Video Image Capture • use a device call --frame grabber-r g --> 8 -bit video A/D --> color converter--> mem --> color converter ->video DAC --> g b • ADC = 6 million conversion/sec, 160 ns per conversion 240 -373 Image Processing 5

Real-time capture • 25 frame/second minimum to avoid flickering • Must be done electronically • Example to grab image of 500 x 500 dot with 256 grey levels requires 6. 25 MB per sec. • Require lots of resources 240 -373 Image Processing 6

Image Scanner • • Flat bed Hand-held for still images only mechanical accuracy can be a problem 240 -373 Image Processing 7

Charge-Coupled Device (CCD( 240 -373 Image Processing 8

Image Display • Display monitors – CRT (Cathode-ray Tube) - based on R, G, B colors - Cannot display all colors that human can see - Black is not real black and white is not real white – LCD (Liquid Crystal Display) - Light weight - Low power consumption - Slow 240 -373 Image Processing 9

Image Display • Printers (mention dithering and patterning) – – – Dot matrix printers Laser printers Inkjet printers (use CMYK color model) Thermal wax transfer printers Dye sublimation printers 240 -373 Image Processing 10