A Smart Image Sensor in Eye-Sage Band with Demodulation Function

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An image sensor with an in-pixel demodulation function for detecting modulated light is proposed and demonstrated. The pixel has two floating diffusion regions, one of which stores charges produced by static illumination, and the other stores charges produced by both static and modulated illumination. By subtracting the two outputs, images produced only by the modulated illumination can be obtained. Based on the proposed circuit, an image sensor with 64 x 64 pixels is lubricated using a 0.6μm 2-poly 3-metal CMOS technology. Using this sensor, we successfully demonstrate the extraction of the modulated component of images under constant illumination conditions. In addition, for the application of motion capture, we demonstrate that a marker, which is a modulated light source, can be extracted from a captured image under several light conditions by using this sensor. Finally, means of improving the characteristics of charge transfer efficiency are discussed.We have also demonstrated an image sensor using SiGe BiCMOS fabrication process for detecting object illuminated by light in "eye-safe" band. The fabrication process is general 0.8μm 2-poly 2-metal SiGe BiCMOS process for RF application. SiGe-Si photodiodes and Si-SiGe-Si hetero-phototransistors as well as Si homojunction photodiodes and phototransistors have been fabricated and measured. The gain of the hetero-phototransistor was around 100. There was little difference between the sensitivity characteristics of SiGe and Si photodetectors. An image sensor with 32x32 pixels has been fabricated using a phototransistor as a detector, which of the base is made of SiGe layer. The dynamic range was 23 dB and the minimum detectable light intensity was 10 lux. We have successfully quired images by using this image sensor. The future issues to use SiGe BiCMOS process for image sensors are discussed.