Even in dark places through photomultiplication
High-gradation color images

Panasonic Corporation announced today that it has developed a CMOS image sensor (APD-CMOS) in which avalanche photodiodes (APD) *1 are applied to each pixel. The company succeeded in obtaining an electrical signal amplified 10,000 times by multiplying photoelectrons generated in the photodetector using an APD.
This enables the capture of clear color images even under starlight with an illumination of about 0.01 lux or in similarly dark places.

*1 A photodiode capable of acquiring a large amount of electrical signal from weak illumination (a small number of photons). A high-power signal can be obtained by multiplying the photoelectrons generated in the photoelectric conversion layer.
*2 Comparison with image sensors without magnification function (Panasonic's own research results, February 3, 2016)


Panasonic’s newly introduced image sensor enables the capture of high-sensitivity video by utilizing photomultiplication to produce high-gradation color images even in dark environments without the need to increase exposure time. In addition, photomultiplication can be rapidly controlled by changing the voltage applied to the APD according to the illumination level during shooting, thereby allowing images to be captured in various illumination levels ranging from bright to dark. This solution is expected to be applicable to products such as surveillance cameras requiring wide dynamic range color video capture and industrial cameras requiring ultra-high sensitivity video.

This product features high-sensitivity color imaging of 40 million lux·sec·μm2 (10,000 times that of a standard device) and a wide dynamic range of 100 dB (more than 40 dB compared to a standard CMOS image sensor).

The development was realized based on the following technology. An APD pixel design technology was applied to the photoelectric conversion unit, which combines an avalanche photodiode and a charge storage to simultaneously multiply and accumulate photoelectrons containing color information generated. By controlling the voltage applied to the APD, multiplication is controlled within 1/1000th of a second, providing variable sensitivity technology that enables 30-fps video recording that changes according to changes in illumination.

In the case of conventional image sensors, photoelectric conversion of photoelectrons can drop below noise levels while capturing images in dark environments, which means images could only be captured under conditions similar to moonlight (illumination of 0.1 lux). This is why shooting using near-infrared light sources and photomultiplier tubes is performed. However, near-infrared light sources cannot capture color images, and photomultiplier tubes require a large power supply, which has the disadvantage of increasing the size of the camera.

The results of this development were presented at the 2016 International Solid-State Circuits Conference held in San Francisco on February 1, 2016.