This paper presents a high-speed CMOS image sensor whose frame rate exceeds 2000 frames/sec (fps). The pixel includes a photodiode, a charge-transfer amplifier, and circuitry for correlated double sampling (CDS) and global electronic shuttering. Reset noise, which is the major random noise factor, is reduced by the CDS combined with the charge-transfer amplifier. The total number of devices in the pixel is 11 transistors and 2 MOS capacitors. Test circuits were fabricated using the 0.25 um CMOS process. The sensitivity of the 20 x 20 um2 pixel using the floating diffusion capacitor of 6.2 fF and the photodiode area of 15 x 12.7 um^2 is 34 V/lux-sec. At 1000 fps, noise level is 2.43 mVrms (dark). The noise level and the sensitivity are greatly improved compared to the non-charge-transfer pixel without global shutter (3Tr-type) implemented with the same technology, and to a previous version of the APS with in-pixel CDS.
The conventional color video image was regarded as a compound image representing energy distributions of three wavelengths such as R.G.and B. These wavelengths were convenient to reconstruct the natural color images. However each of these representative wavelengths could not have clear information concerning self-luminescence events like combustion phenomena. A high-speed video optical system, so called “Multi-Spectral Optics” which had four optical paths for objective wavelengths was developed. The principle of the optics was a new simple multi-spectral beam splitting optics to obtain four images of different wavelengths. By setting the wavelengths as to correspond to representative wavelengths of self-luminescence event, many kinds of information could be derived by image-analysis of among four images captured by this system. The optical system developed here and its feasibility study in combustion analysis are reported in this paper.
This paper presents a high-speed CMOS image sensor of whose frame rate exceeds 2000 frames/s. The pixel includes a photodiode, a charge-transfer amplifier, and circuitry for correlated double sampling (CDS) and global electronic shuttering. Reset noise, which is a major random noise factor, is greatly reduced by the CDS combined with the charge-transfer amplifier. The total number of devices in the pixel is 11 transistors and 2 MOS capacitors. Test circuits were fabricated using a 0.25μm CMOS process. The sensitivity of the 20 x 20μm2 pixel using the floating diffusion capacitor of 6.2fF and the photodiode area of 15 x 12.7μm2 is 34V/lux-sec. At 1000frames/sec, noise level is 2.43mVrms (dark). The noise level and the sensitivity are greatly improved compared with a 3Tr. type APS implemented with the same technology and a previous version of the APS with in-pixel CDS.
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