Panasonic takes an image step with the development of the new CMOS sensor (APD-CMOS)

It uses avalanche photodiodes (APD) in each pixel, allowing electrical signals to be multiplied 10,000 times.

Panasonic announced at the 2016 International Solid State Circuits Conference, held last week in San Francisco, that it is completing the development of the CMOS image sensor (APD-CMOS) that uses avalanche photodiodes (APD) in each pixel.

The company was successful in obtaining electrical signals multiplied 10,000 times by APD multiplication of photoelectrons generated by photoelectric conversion in the photodetector. This allows images with sharp colors even under starlight (illuminance of 0.01 lux) or in other dark places.

This new image sensor allows the generation of highly sensitive images through the multiplication of photoelectrons, obtaining high-gradation color images without the need to increase the exposure time even in dark places. Furthermore, photoelectron multiplication can be controlled instantaneously by changing the voltage applied to the APDs depending on the illuminance at the time of imaging, allowing imaging at various illuminances from bright to dark locations. Its expected applications include surveillance cameras that demand color images with a wide dynamic range and industrial cameras that demand ultra-sensitive imaging.

This development would allow highly sensitive color images to be achieved (40 mill./lux・sec・μm^2, 10,000 times more sensitive compared to conventional devices) and with a high dynamic range (100 dB, 40 dB higher compared to conventional CMOS image sensors)

This development is based on two technologies. On the one hand, the design technology of APD photography elements where avalanche photodiodes and charge storages are incorporated in the photoelectric converter not only to multiply but also to accumulate photoelectrons that contain generated color information.

On the other hand, the variable sensitivity technology in which the multiplication is controlled in a thousandth of a second by controlling the voltage applied to the APD, obtaining a 30 frames per second video image that can follow changes in illuminance.

With conventional image sensors, the photoelectrons that are converted by photoelectricity during imaging in dark locations can be below the noise level and thus limit the imaging environment to no less than moonlight (0.1 lux illuminance). This is why it was possible to capture images under the illumination of a near-infrared light source and through the use of photographic multipliers.

However, near-infrared light sources have the disadvantage of their inability to capture color images, while photographic multipliers have the disadvantage of forcing cameras to increase in size due to the need for a higher capacity power source.