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intro_cmos [2026/08/11 10:53] – [Passive pixel sensor (PPS)] xhoana.likmeta.extintro_cmos [2026/09/22 14:18] (current) – [Front side illmunation (FSI) and Bask side illumination (BI)] antoine
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 //Passive Pixel Sensor (PPS)// is a basic CMOS image sensor pixel architecture. Is an early type of digital image sensor. Each pixel uses a photodiode and a single transistor switch to transfer charges without in-pixel amplification.  //Passive Pixel Sensor (PPS)// is a basic CMOS image sensor pixel architecture. Is an early type of digital image sensor. Each pixel uses a photodiode and a single transistor switch to transfer charges without in-pixel amplification. 
 ==== Active pixel sensor (APS)  ==== ==== Active pixel sensor (APS)  ====
-**Active Pixel Sensor (APS):** Each pixel includes active components, typically an amplifier, enabling local charge-to-voltage conversion and multiplexed readout+//Active Pixel Sensor (APS)//:Each pixel includes active components, typically an amplifier, enabling local charge-to-voltage conversion and multiplexed readout
  
-**3T-APS: ** pixel normally contains a photodiode and three transistors: a reset transistor, a source-follower amplifier, and a row/pixel selection transistor.+//3T-APS//: pixel normally contains a photodiode and three transistors: a reset transistor, a source-follower amplifier, and a row/pixel selection transistor.
 It operates through three phases  It operates through three phases 
 1. Reset transistor  1. Reset transistor 
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 4. Photodiode as the light-sensitive element  4. Photodiode as the light-sensitive element 
  
-**4T-APS** adds a transfer gate and uses a pinned (buried) photodiode instead of a basic p-n junction photodiode.+//4T-APS// adds a transfer gate and uses a pinned (buried) photodiode instead of a basic p-n junction photodiode.
 adds one extra transistor compared with 3T APS: adds one extra transistor compared with 3T APS:
 1. Reset transistor  1. Reset transistor 
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 </figure> </figure>
 ====  Digital pixel sensor (DPS) ==== ====  Digital pixel sensor (DPS) ====
- +//Digital Pixel Sensor (DPS)// is a CMOS pixel architecture in which analog-to-digital conversion is performed at the pixel level. 
-Digital Pixel Sensor (DPS) is a CMOS pixel architecture in which analog-to-digital conversion is performed at the pixel level. +
 Each pixel contains a dedicated analog-to-digital converter controlled by reset and select signals. Instead of sending an analog voltage to column circuitry for later conversion, each pixel outputs a digital signal.  Each pixel contains a dedicated analog-to-digital converter controlled by reset and select signals. Instead of sending an analog voltage to column circuitry for later conversion, each pixel outputs a digital signal. 
 ===== Types of illumination ===== ===== Types of illumination =====
  
-==== Front side illmunation (FSI) and Bask side illumination (BI) ====+==== Front side illmunation (FSI) and Back side illumination (BI) ====
 More for early sensors [(Advances_on_CMOS)] More for early sensors [(Advances_on_CMOS)]
 Since its invention in 1993, CMOS image technology has evolved. The first architectures were front-illuminated, meaning the microlens and color filter were on top, followed by metal wiring for interconnects and the photodiode on the bottom. Since light enters the image sensor through the metal layers, some light information is reflected and lost before reaching the photodiode. This affected the performance of front-illuminated sensors, but Sony Corporation solved the problem by moving the photodiode to the top, next to the color filter. This architecture is known as the back-illuminated (BI) CMOS image sensor, which greatly improved the sensor’s performance.  Since its invention in 1993, CMOS image technology has evolved. The first architectures were front-illuminated, meaning the microlens and color filter were on top, followed by metal wiring for interconnects and the photodiode on the bottom. Since light enters the image sensor through the metal layers, some light information is reflected and lost before reaching the photodiode. This affected the performance of front-illuminated sensors, but Sony Corporation solved the problem by moving the photodiode to the top, next to the color filter. This architecture is known as the back-illuminated (BI) CMOS image sensor, which greatly improved the sensor’s performance.