12 Mega-pixel, 1,000 fps Visible Camera with a Nanowatt A/D Converter at Each Pixel

摘要

A large format, area array, digital visible light camera was developed based on A/D conversion at each pixel. Production CMOS technology was used in the development of a monolithic front side illuminated photo diode pixel. Each pixel includes a one loop MOSAD, (Multiplexed Oversample A/D) converter, photo diode, and buffered output to support a very large array format operating at high frame rates. MOSAD is a modification of the delta sigma approach to A/D conversion. The 12 megapixel sensor consists of a 4,000X3,000 pixel array capable of up to 1,000 frames per second sample rate. Alternate approaches to satisfy the 1,000 fps sample rate with up to 10 bits dynamic range were analyzed. To approximately fit a 35 millimeter optics format, a pixel size of 8.5 μm was selected. There are no operational amplifiers required at the pixel to perform the A/D function, thus allowing a high fill factor. With this pixel size, a 48% fill factor and 38% photo diode area was achieved. A single process run was completed yielding five 8 inch wafers each containing 27 camera die. The single poly, three metal AMIS 0.35 μm CMOS process was used in the fabrication process. Selected die were directly mounted on a specially designed carrier daughter board. Camera support electronics were designed and fabricated to allow sampling of the camera output using commercial standard Camera Link interfacing. Off the shelf 35 Millimeter optics was used to validate imaging capabilities of the sensor. Tests show that the first iteration sensor chip design works to the fundamental requirements and can image.