中文摘要：

当固定光强的红外光透射厚度不相同的手指时，会在图像传感器上呈现质量不一的静脉图像，产生曝光过强或过暗的现象。为采集到质量一致的手指静脉图像，设计一种自动调光电路，可根据红外透射光的强度自动调整红外发射光强，以保证红外透射光强度维持在一个相对稳定的范围。同时设计了一种基于USB2．0和CMOS图像传感器的手指静脉采集系统。实验结果表明，该系统采集的手指静脉纹路图像清晰、质量稳定。

英文摘要：

Because each figure has different thickness, the sensor will get different quality of fingers vein images through the fixed infrared intensity light. That means the exposure of these images will be too strong or too dark. In order to get consistency quality finger vein images, auto-dimming circuit is designed which can automatically adjust intensity of the crossing infrared light and keep it relatively stable. At ＂the same time, a finger vein image collection system is designed based on USB2.0 and CMOS. Experimental results show that the finger vein image collected by this system can be clear and stable quality.