In the field of CMOS image sensors research, the design and application of Low-Voltage Differential Signaling (LVDS) drivers are key to achieving efficient video signal transmission. As the frequency of LVDS signals continues to increase, issues of signal loss and attenuation during long-distance cable transmission have become more prominent, posing greater challenges to the performance stability of LVDS drivers. This paper establishes a model for CMOS image sensor LVDS drivers and transmission lines, detailing the attenuation mechanisms of LVDS transmission lines and their impact on differential signal transmission. The study focuses on methods for matching the design of LVDS drivers with transmission line characteristics, while also analyzing the interaction mechanisms between the operating states of MOS transistors in the circuit and key variables of the RLGC transmission line model. Using 1Gbps LVDS data and a 20cm flexible transmission ribbon cable as an example, the effectiveness of the matching method was validated through simulation experiments. This method provides technical support for the reliable design of high-speed LVDS drivers in image sensors or other chips, and offers useful references for the engineering selection of LVDS high-frequency transmission lines.
The pixel array of BSI CMOS image sensor is a kind of photoelectric device to obtain 2D image information. The image quality was evaluated by the modulation transfer function (MTF) of BSI CMOS image sensor pixel at Nyquist frequency. With the decreasing pixel size of BSI CMOS image sensor and the increasing spatial resolution, it is more and more difficult to improve the MTF at Nyquist frequency. According to the theoretical analysis, MTF is composed of aperture MTF and diffusion MTF, the comprehensive MTF function is usually obtained by the multiplication relationship between the two MTFs in the frequency domain. Aperture MTF and diffusion MTF have different influence factors and calculation functions, but they are related to the size of the opening. The opening here represents the sensitivity aperture and photo-sense region respectively. The smaller the opening of the detector pixel, the larger MTF will be. In this paper, the theoretical mechanism of MTF function is analyzed in detail, and the calculation results of MTF of BSI CMOS image sensor pixel under 8 typical optical wavelengths in 300nm-1000nm spectral band are listed.
Based on the working mechanism and characteristics of spaceborne hyperspectral Fourier transform infrared spectrometer, the computer and software were used as data acquisition and processing tools in this paper to study and simulate the various processes in photoelectric information processing of spectrometer. Analytical models including functional modules such as interference signal generation, effective signal detection, spectral data inversion and instrument error correction was established, then a visualization software system was developed. Finally, the accuracy of the model was calculated and optimized with experiments, the verification results show that this resolving system can process the interference data with high spectral resolution non-destructively, significantly improve the smoothness of the restored spectrum without distortion, and the measured spectral resolution of an instrument is better than 0.03cm-1 . This digital model could provide useful support for the design and parameter optimization of the aerospace Fourier transform infrared spectrometer.
The readout chain circuits for time delay integration charge coupled device camera imaging system include CCD focal plane driving circuit, analog-to-digital conversion circuit, high-speed digital data transmission circuit and other parts together. The parasitic factors such as the quality of high frequency clock, high speed data transmission error rate and the aging of printed circuit board will induce more noise to image data of camera. As the longer time circuits working, the noise of readout chain becomes bigger and bigger, then the signal-to-noise becomes worse. This paper proposed a method to make circuit system check its noise as the circuit is working, which is based on pseudo CCD-signal to check the Signal-to-Noise of readout chain of TDICCD, and sends the result to control core of the system. The paper combines the theory calculation and actual measurement as the method for testing. High precision pseudo CCD signal source is used to test the onboard circuit and circuit SNR results of readout chain, harmonic frequency, noise floor and other related parameters are automatic processed.
The Low level light sensor has evolved from early ICCD device to EMCCD that appeared at the beginning of this century. With the continuous progress of CMOS technology, the scientific CMOS sensors were developed, which have been used for industrial cameras in high sensitivity imaging. This article described a low level light CMOS detector and its associated camera, which were developed by Beijing Institute of Space Mechanics and Electricity (BISME) in cooperation with a domestic detector manufacturer. We had an in-depth discussion of the chip's high sensitivity design techniques and analyze the weak charge transfer optimization mechanism. Then both the CMOS and EMCCD detector were combined with lens and video processing circuits to conduct a laboratorial test, finally low light detection performance of them were compared and analyzed. The SNR of CMOS imaging circuits was basically equal to the EMCCD imaging circuits when the camera's entrance pupil radiance was less than 0.5E-05 W/m2 /sr, when the radiance was up to 2E-05 W/m2 /sr, the SNR of CMOS circuits was about 2dB better than the EMCCD circuits.
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