This document reviews CMOS image sensors. It discusses the basic functions of image sensors including light collection, wavelength discrimination, photon detection, readout methods, timing and control electronics, and signal processing. It compares CCD and CMOS image sensors, noting that CCDs shift charge out while CMOS sensors use row and column decoders to read out charge. The document outlines various figures of merit for image sensors such as noise, sensitivity, dynamic range, and speed. It also includes diagrams of CMOS image sensor pixel architectures.
1. Review of CMOS
image sensors
CHIN CHUN-CHIEH
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5861-5872, 2010.
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2. Image sensor
An image sensor is a device that converts an optical image
into an electronic signal.
charge-coupled device (CCD)
complementary metal–oxide–semiconductor (CMOS) image
sensor
A CMOS image sensor
A CCD image sensor
http://en.wikipedia.org/wiki/Image_sensor http://en.wikipedia.org/wiki/CMOS_image_sensor
3. Image sensor
Basic functions
(1) Optical gathering of photons
(lens)
(2) Wavelength discrimination of
photons (filter)
(3) Detector for photons to
electrons conversion
(photodiode)
(4) A method to readout the
detector (CCD)
(5) Timing, control, and drive
electronics for the sensors
(6) Signal processing electronics Y. Huo, C. C. Fesenmaier, and P. B. Catrysse, "Microlens performance limits in sub-2µm pixel
(CDS - Correlated Double Sampling) CMOS image sensors," Opt. Express, vol. 18, pp. 5861-5872, 2010.
(7) Analog-to-digital conversion
(8) Interface electronics
4. CCD VS CMOS
Read out architecture
- for CCDs, charge is shifted out
- for CMOS image sensors, charge or voltage is read out using
row and column decoders
The main advantages of CCD and CMOS image sensors
M. Bigas, E. Cabruja, J. Forest, and J. Salvi, "Review of CMOS image sensors," Microelectronics Journal, vol. 37, pp. 433-451, 2006.
5. CCD VS CMOS
Dallmeier - CCD vs. CMOS-Chips Smearing-Effekte
6. CCD VS CMOS
Dallmeier - Einsatz von CMOS vs. CCD Chips in CCTV Kameras (Blooming
Effekt)
8. CMOS image sensors
readout done by transferring one row at a time to the column storage
capacitors, then reading out the row one (or more) pixel at a time using
the column decoder and multiplexer
9. (a) A photodiode- type APS
schematic
(b) A photodiode- type logarithmic
APS schematic,
(c) A photogate- type APS
schematic
(d) Photodiode- type shutter
(e) APS schematic TFA pixel
(f) A photodiode- type CAPS
schematic
(g) A photodiode- type Low FPN
CTIA APS schematic
(h) A photodiode- type High FPN
CTIA APS schematic.
10. Figures of merit
• Noise source
- Temporal noise
- Fixed pattern noise
• Sensitivity
- Fill factor (FF)
- Quantum efficiency (QE)
• Dynamic range (DR)
- The ratio of the saturation signal to the rms noise floor
• High speed market