Automatic Adjustment Technology Of Light Intensity And Its Application In Palmprint Recognition System

In recent years, palmprint recognition technology has been rapidly developed and caught more widely attention. The related palmprint identifiction equipment tends to be mature and was gradually applied into the market. The palmprint identification equipment which based on the CCD is the most widely used at present. Due to the influence by the change of environment light, the electronic components ageing of the cature device itself, such as LED and the differences in the process of production, would lead to the change of the light intensity which will effect the quality of the palmprint image. All of these situations will finally influence the key points location in the preprocessing, the feature extraction, the matching of feature and recogniton.The sub-module implemented in this research mainly including the equipment acquisition module, image quality assessment module and adaptive adjustment module of light intensity.The equipment acquisition module adds a set of light source which used for intensity compensation on the basis of the original equipment. It uses the PWM control function of the MSP430 MCU on the acquisition equipment to implement the adjustment of light intensity.Image quality assessment module mainly using the algorithm evaluation the reference index of palmprint image quality. According to the light characteristics real impactions on the palmprint image, from the image grayscale average and variance, the Gabor features and direction contrast these three indicators to make quality evaluation of the palmprint image.Adaptive adjustment module of light intensity is the hub to connect the above two sub modules. Through the quality assessment of the collected palmprint images to determine whether the image achieve the optimal quality under current compensation light.The optimal intensity range is determined through the experiment. The experimental results show that palm recognition result ha s the smallest equal error rate in this intensity range and the error rate that can’t locate the key point is also reduced. The adaptive dimming system greatly improves the quality of the palmprint image and solve the problems that can’t locate the key points under complex external light environment.