Image sensors and optical devices

What is the main advantage of a backside-illuminated (BSI) CMOS image sensor?

  1. AIt can reduce the number of pixels
  2. BLight reaches the photodiode without passing through the wiring layers, making it easier to increase sensitivity
  3. CIt no longer needs color filters
Show answer and explanation

Answer: B. Light reaches the photodiode without passing through the wiring layers, making it easier to increase sensitivity

In conventional front-side illumination, light reaches the photodiode through gaps in the wiring layers, so wiring blocks or reflects some of it. In backside illumination, the wafer is thinned and light enters from the side opposite the wiring, so light is captured efficiently and sensitivity is easier to maintain even with small pixels.

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More Image sensors and optical devices questions

  1. What mainly determines the emission color (wavelength) of an LED?
  2. Compared with CCD image sensors, which is a general advantage of CMOS image sensors?
  3. In a Bayer color filter array, which color appears most often in each 2×2 block of pixels?
  4. Why do fast-moving subjects appear distorted with the rolling shutter method of CMOS image sensors?
  5. What is the role of the microlens placed over each pixel of an image sensor?