IMAGE SENSORS

Andrew DillonDan Ehlke

April 21, 2008

Outline

Application Structure CCD vs CMOS Error & Loss Signal Conditioning Capturing an image Kodak KAF 8300

Application

Converts an optical image to an electric signal Converts photons into electrons Cameras, Scanners, Videocameras, Fax Machines

Major types CCD (charged coupled device) CMOS (Complementary metal–oxide–

semiconductor)

CCD versus CMOS

CCD CMOS

•Better light sensitivity•Superior Shuttering•More expensive•Made in non-standard process•More power consuming

•Lower light sensitivity•Cheaper•More energy efficient, ideal for battery operated devices•Creating better and better images as technology improves

CCD versus CMOS

CCD versus CMOS

Error & Loss

Dark Current: noise

Absorbtion Loss: optically insensitive areas on the pixel can’t absorb light.

Reflection Loss: silicon naturally reflects certain wavelengths

Transmission loss: very short & very large wavelengths may pass through pixel without generating an electron.

• increases with exposure time. • a function of the temperature of the sensor and associated electronics.

Signal Conditioning

Programs: Photoshop

Parameters

Operating Range: Decibels (dB), ratio or bits Sensitivity (Quantum efficiency)

color gamut/range of values Commonly respond to 70% of the incident light

(meaning a quantum efficiency of about 70%) Environmental Factors

Temperature: effects sensitivity Vibration / movement: blurry Too bright (blooming) / Too Dark

Overflow drains compensate for overfilling of wells.

Capturing an image

•Instead of film, a digital camera uses an image sensor

•On the surface of these chips are millions of photosensitive diodes, each of which captures a single pixel in the photograph to be

•Each pixel accumulates an electrical charge-the more light that hits a pixel, the higher the charge it records

•the charge from each pixel is measured and converted into a digital number

Capturing an image cont.•pixels on an image sensor only capture brightness, not color

•Color systems•Red, Blue and Green (RBG)•cyan, magenta, yellow and black (CMYK)

•Used in printers

•placing red, green, and blue filters over individual pixels on the image sensor can create color images

Kodak KAF 8300Full Frame CCD Image Sensor

FEATURES • High Resolution • High Dynamic Range • Low Noise Architecture

APPLICATIONS • Photography • Industrial Imaging • Medical Imaging

Architecture Full Frame CCD; with Square Pixels

Total Number of Pixels 3448 (H) x 2574 (V) = approx. 8.9M

Number of Effective Pixels 3358 (H) x 2536 (V) = approx. 8.6M

Number of Active Pixels 3326 (H) x 2504 (V) = approx. 8.3M

Pixel Size 5.4μm (H) x 5.4μm (V)

Saturation Signal > 25.5 K e-

Output Sensitivity 23 μV/e-

Quantum Efficiency, color 33%, 40 %, 33%

R(600nm), G(540nm), B(480nm)

Total Sensor Noise 16 e-

Linear Dynamic Range 64.4 dB

Linearity Error at 12ºC +/- 10%

Charge Transfer Efficiency 0.999995

Parameters above are specified at T = 60 °C and a data rate of 28 MHz unless otherwise noted

Kodak KAF 8300Parameters

Kodak KAF 8300Specifications

Kodak KAF 8300Typical Performance Curve

Bibliography

http://www.dalsa.com http://www.dalsa.com/sensors/products/productdetails.asp?ProductID=FTF

3041M http://www.clarkvision.com/imagedetail/

digital.sensor.performance.summary/ http://www.shortcourses.com/guide/ http://www.cambridgeincolour.com/tutorials/camera-sensors.htm http://www.dpreview.com/learn/?/Glossary/Camera_System/ http://www.kodak.com/global/en/business/ISS/Products/Fullframe/

index.jhtml?pq-path=11937/11938/12138

Questions?