A Software-Controlled Pixel-Level A-D Conversion Method

Summary

A pixel-level analog-to-digital (A-D) conversion method suitable for digital vision chips is proposed. In this method, each quantization boundary is compared by determining whether the signal level integrated for a certain time has reached a certain voltage, where both the time and voltage are properly controlled by software for each boundary. We derive an algorithm to generate an optimal controlling schedule to realize an arbitrary A-D conversion scale subject to the condition that noise is minimized. Experimental results show that images with given A-D characteristics can be obtained with low noise.

Fig. 1: Images of a grayscale chart obtained with linear characteristics. The proposed method can overcome the tradeoff that existing methods have between image noise and lower detection limits.


Fig. 2: Images obtained with different characteristics. The results show that the proposed method can achieve wide dynamic range imaging by realizing adequate A-D conversion scales.

Reference

1. Shingo Kagami, Takashi Komuro, Masatoshi Ishikawa: A Software-Controlled Pixel-Level A-D Conversion Method for Digital Vision Chips, 2003 IEEE Workshop on Charge-Coupled Devices and Advanced Image Sensors (Elmau, Germany, 2003.5.17) / Proceedings, 2003. [PDF (644KB)] ^*IEEE

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