Image Acquisition and Digitization Image Sensing IMAGE ACQUISITION

Image Acquisition and Digitization

Image Sensing

IMAGE ACQUISITION AND DIGITIZATION Energy source Sensor Analog image Digitization (A/D) Digital image

Energy Source

Electromagnetic Spectrum

VISIBLE LIGHT wavelength 400 -700 nm

INFARED BAND wavelength 10 -6 -10 -4 m Microprocessor (60 x) Washington D. C. area Hurricane images

MICROWAVE BAND ความยาวคลน 10 -4 -10 -2 m Radar image of mountains

RADIO BAND Magnetic Resonance Image (MRI) Ultrasonic image

ULTRAVIOLET BAND wavelength 10 -8 -10 -7 m Fluorescence microscope image Normal corn cell Infected corn cell

X-RAY wavelength 10 -10 m Chest X-ray Head cross-section Circuit board

GAMMA RAY wavelength 10 -12 Bone scan m Reactor valve

Image Sensing

Sensor Single Sensor Row Sensor Array Sensor

Non-overlap Layout Overlap Layout CCD Sensor

Analog signal from image sensor Sampling A/D convertor Quantization Digital Image Binary representation Analog-to-Digital Image

Sampling Quantization Binary representation Analog-to-Digital Image

Sampling effect Nyquist theorem Sampling Rate >= 2 ความถสงสดของสญญาณ If Sampling rate < 2 x f. High

aliasing Sampling

Quantization Real number represent in 7 8 (3 bits) Desired Integer 0. 875 3 7 2 6 1 5 0 4 0 3 -1 2 -2 1 -3 0

Quantization คณภาพของภาพ & จำนวน bit ในการทำ quantize ระดบสญญาณไฟฟาทได 3 3. 0625 2 2. 6250. . . 2. 625 1. 750 1 0. 875 Quantize 2 bits 0 – 3. 5000 3. 500 0. 000 อยท 0 0. 8750 0. 4375 0. 0000 7 6 5 4 3 2 1 0 Quantize 3 bits

Binary Representation

452 374 CAT projection image : gray levels Quantization 25 6 12 8 64 32 16 8 4 2

Category of Digital Image • Binary Image or Black and White Image

Digital Image (Gray-level Intensity example)

Indexed Image

Color Image or RGB Image