CMOS sensors see in the dark

28 Aug 2007

OmniVision Technologies has released two CMOS sensors that are sensitive to near-infrared light.

The latest CMOS CameraChip image sensors from OmniVision Technologies (OVT), US, are sensitive to near-infrared (NIR) light up to 1050 nm. The company is targeting its OV7710 and OV7950 products at automotive and security applications where it says a single dual-mode sensor will simplify system designs and reduce costs.

Night vision CMOS

"The sensor records the interior of the car for security applications," Inayat Khjasha, Product Director at OVT told optics.org. "For pedestrian detection and other 'forward-looking' applications, the sensor is placed behind the rear-view mirror. This technology is being evaluated by a significant number of top-tier suppliers (that provide sensor modules to OEMs) in the US, Europe and Japan."

OVT says that a number of undisclosed 'process-level' enhancements have expanded the sensor's spectral sensitivity. "There is a level of NIR detection inherent in CMOS to start with, which we have further enhanced so that low power LEDs may be used and the resulting image quality is much improved," commented Khjasha.

The dual-mode nature of the sensors means that a standard color image is produced in daylight conditions and then as ambient light levels fall, the sensor switches automatically to a black-and-white night vision mode.

"NIR is used when the visible light goes below 1 lux," said Khjasha. "When the target cannot be seen in visible light, the switch to the NIR mode is executed. There is no need to operate both modes simultaneously."

Both the OV7710 and OV7950 sensors are commercially available and Khjasha says that all new releases for the automotive and security markets will feature NIR capability. He adds that the visible and the NIR images are the same size in terms of the number of pixels and are acquired at the same frame rate for both sensors.

When asked to elaborate on the 'process-level' enhancements, Khjasha was unable to give anything away. "Our process level enhancements are significantly better than those offered by anyone else and we cannot divulge more information at this stage for commercial reasons," he said.

Author
Jacqueline Hewett is editor of Optics & Laser Europe magazine.