Acronym · Automotive
CIS (CMOS Image Sensor)
The silicon imager at the heart of every vehicle camera. Automotive variants prioritise wide dynamic range, LED flicker mitigation, low-light sensitivity, functional safety features and grade 2 temperature operation over raw megapixel count.
- Also known as
- Image sensor, CMOS image sensor, APS
- Type
- Acronym
- Domain
- Automotive, Sensing
- Also relevant to
- Photonics, MEMS & Sensors
Notes
onsemi, Sony, OmniVision and ST hold most automotive share; resolution is climbing from 2 MP toward 8 MP for front sensing.
Overview
A CIS (CMOS image sensor) is a chip that turns light into a digital image using an array of photodiode pixels made in a CMOS process, with amplifiers and analogue-to-digital converters on the same die. It is the imager in phone cameras, webcams and most digital cameras, and in the cameras that cars use for driver assistance and monitoring. Automotive sensors are judged less on pixel count than on dynamic range, LED flicker mitigation, low-light sensitivity, temperature grade and safety features.
How it works
Each pixel collects charge in a pinned photodiode during the exposure. In the common four-transistor pixel, a transfer gate moves that charge to a small floating node, which is buffered onto a column line and then reset; sampling the node before and after the transfer cancels much of the noise. Columns are read in parallel and digitised on chip, so the sensor outputs digital data. A colour filter and a microlens sit over each pixel.
Most sensors read row by row with a rolling shutter, which can skew fast-moving objects; global shutter designs store each pixel's charge so that the whole frame is captured at once, at a cost in pixel area and noise. In a back-side illuminated (BSI) sensor the wafer is thinned and turned over so that light reaches the photodiodes without passing through the metal wiring. Stacked sensors go further, bonding the pixel layer to a separate logic layer, and in some designs a memory layer.
Car cameras face scenes that range from dark tunnels to direct sunlight, so automotive sensors offer high dynamic range, with figures of up to 120 dB quoted. LED traffic lights and signs flicker, and a short exposure can catch them while they are off; LED flicker mitigation techniques, such as overflow capacitors in each pixel, keep them visible to the driver assistance system.
Related terms
Part of the Automotive glossary, with every term in the topic and the lifecycles, tools and standards that use them.
Where it appears on the Hub
Used on 20 pages of the Hub. In each group, the pages that mention it most come first.
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Last reviewed . Written by The Semiconductor Hub editorial team. The full glossary