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Processing 1

Image Acquisition

• Photo sensors– Photo diodes and photo diode array– Photo transistor

• Video camera

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Processing 2

Primitive camera structure

• Slotted board, • rotating disc• Photosensitive device• Lens• Illumination for object

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Processing 3

Vidicon

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Processing 4

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

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Processing 5

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

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Processing 6

Real-time capture

• 25 frame/second minimum to avoid flickering

• Must be done electronically• Example to grab image of 500x500 dot

with 256 grey levels requires 6.25MB per sec.

• Require lots of resources

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Processing 7

Image Scanner

• Flat bed• Hand-held• for still images only• mechanical accuracy can be a problem

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Processing 8

Charge-Coupled Device (CCD)

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Processing 9

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

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Processing 10

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