With its 1928 × 1088 active-pixel array, the CMOS sensor delivers both low-light and high-dynamic-range scene performance.
By Murray Slovick, Contributing Editor
With insurance companies offering financial incentives for consumers using on-dash safety cameras, carmakers are now beginning to offer the product as standard equipment. To meet this demand, ON Semiconductor is now offering a fully AEC-Q100-qualified version of its AR0237AT 2.1 MP CMOS image sensor (see figure).
The 1/2.7-in. CMOS digital image sensor features an active-pixel array of 1928 × 1088. It can capture images in either linear or high-dynamic-range modes, with a rolling-shutter readout.Rolling shutter is a method of image capture in which each frame of a video is captured not by taking a snapshot of the entire scene at a single instant in time, but rather by scanning across the scene rapidly, either vertically or horizontally.
The image sensor includes such camera functions as in-pixel binning, windowing, and both video and single-frame modes. It’s designed for both low-light and high-dynamic-range scene performance, and is programmable through a simple two-wire serial interface. The part’s ability to capture both full HD video capture at 1080p/60 fps and single frames also makes it well-suited for a wide range of other applications, including surveillance and HD video.
ON Semi points out that the low-light performance of the AR0237AT can be further improved when it is coupled to the company’s Clarity+ enabled DVR processor. Clarity+ is an alternative filter where, in the standard Bayer Color Filter Array (CFA), the green spots are substituted with clear spots, allowing the entire visible spectrum to pass through. The implementation of Clarity+ requires post-processing of the raw signal to recalculate the missing green component. The image processor has to calculate the green component by subtracting the red and blue components from the clear pixels.
The advantage of this technology is an improvement of the signal-to-noise ratio (SNR) thanks to the fact that the sensor takes almost 2X the light compared to the standard configuration. This helps improve the quality of the image, especially in low-light conditions where the Clarity+ can use all of its potential.
Ross Jatou, Vice President and General Manager, Automotive Solutions Division of Image Sensor Group at ON Semiconductor, explained that the AR0237AT delivers the same performance as the non-automotive qualified part without the need for an IR-cut filter. He adds that “the high dynamic range means the sensor continues to perform even under changing light conditions. By moving the image processing off chip and qualifying the device to AEC-Q100, we have successfully developed a solution that gives automotive manufacturers more design flexibility, yet provides outstanding performance at a competitive price.”
The automotive qualified version can operate across the full automotive operating temperature range of −40 to +105°C. The AR0237AT is now available in an IBGA-80 package, measuring 10 × 10 mm.