For automotive applications requiring very low and very high ambient temperatures, scientists from the Fraunhofer institute for microelectronic systems (Duisburg, Germany) has developed a CMOS image sensor capable of working at an extended temperature range from -40 through 115 degrees Celsius.
Widespread image sensors based on CCD technology (Charge-Coupled Device) are operational at ambient temperatures of up to 60 degrees Celsius. The Fraunhofer Institute researchers claim they have developed a pixel architecture featuring an extremely low dark current. This residual current doubles with every 8 degrees of temperature increase, causing signal noise and reducing the available dynamic range of the device. The reduction of this current, which flows even in complete darkness, makes it possible to capture very high-quality images even in extreme heat, said Fraunhofer researcher Werner Brockherde.
The CMOS-based image sensor developed by Fraunhofer features a dynamic range or exposure latitude of 90 dB, resulting in high contrast and optimized detail reproduction in shadow as well as in very bright segments of the image. Its very high sensitivity and low noise makes the device suited for night vision gear, the researchers claim.
The device was developed within a customer project with somewhat unusual specifications: Despite its large size, the sensor features a resolution of only 256 x 256 pixel. “It was a customer-specific design,” said Brockherde. The excellent signal features of the device have been made possible by the relatively large geometries at semiconductor level: The device has been designed and manufactured with a feature size of 0,5microns.
Besides automotive applications, the image sensor could be used in process control and quality assurance applications in the chemical and steel industry, Brockherde said.
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