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Understanding BSI Sensors and its Current Applications

March 19, 2019

What’s a BSI Sensor?

A back-illuminated sensor (BI or BSI) refers to a modern type of imaging sensor used for digital cameras. Imaging sensors serve as a vital component for cameras and responsible for converting photon energy into electrical energy to produce images.

The Birth of BSI Sensors

Earlier models of cameras were equipped with a traditional sensor with a matrix of transistors in front of the lenses and joined with other components such as small loops of wires. As light enters the camera through the loops of wire and electronics before reaching the lenses, the results produced are low-quality images. Due to the components, some portion of the light is either being blocked or bounced back by the obstacles that hinder its path.

The low image quality paved the way for the development of a new type of sensor that we now know as the back- side illuminated sensor. Unlike its predecessor, the design is concise positioning of specific components that allow a more considerable amount of light to pass through as most of the wirings and transistors are in the back as opposed to the front of the lenses. The configuration enables for better quality images due to its promising optimization on the low-light performance feature as well as minimizing the digital noise.

Applications of BSI

During the integration of this new sensor, many have thought its design was quite too complicated at the time hence manufacturing it in the market was only limited to microscopes, security cameras, astronomy sensors, and among others that require specialized usage on catching images during low light.

However, companies eventually took notice of its potential and decided to develop a plan that can make them produce the sensors on a  larger scale. Their efforts bore fruits when the 5-megapixel BI CMOS sensor was finally brought to the public in 2009 and ever since then, BSI sensors became a commonplace on portable devices such as compact cameras and smartphones.

It’s promising capabilities

Back-side illuminated sensors have been known to provide an 8dB improvement, which can be considered to be a significant breakthrough in the field of image sensor development. Most cameras boasting BSI sensors have undergone several tests conducted by DxOMark labs that suggests some substantial improvement in lowering the digital noise levels. The effect is observed among higher end cameras which boasts advanced features such as JPEG noise reduction. Capturing images with amazing quality that ranges around ISO 400 or higher are not an impossibility anymore.


Now that BSI’s have become more available through the production of CMOS sensors, it is now quite a golden era for every photography enthusiast to avail an image-capturing device equipped with such sensors that can help capture a picture with a quality truly deserved!