用二次触发法改进接触式传感器线阵相机的曝光性能

Improvement of exposure performance of linear array CIS camera by two-trigger method

针对外触发接触式图像传感器(CIS)线阵相机的扫描图像灰度值受外触发信号频率变化影响的问题,提出了一种新的曝光控制方法——二次触发法。首先,分析了外触发信号频率变化对图像灰度值影响的原因。然后,介绍了二次触发法:该方法将一个外触发信号转变为两次触发信号,第一次触发信号用于控制曝光,第二次触发信号用于控制CIS输出数据。最后,从理论上说明了该方法可以提升图像质量。将该方法成功应用于1.6m长线阵零畸变CIS相机,实验结果表明:在不同的触发频率下,扫描图像的灰度值波动范围减小了75%,消除了图像上的横条纹。在智能视觉十字绣数码喷印机的应用上,绣布上1mm×1mm的孔成像清晰、灰度值均匀。提出的方法有效地解决了外触发信号频率影响图像质量的问题,成功地提高了图像的质量。

As the frequency changing of external trigger signal from an external trigger Contact Image Sensor（CIS） camera will cause the nonuniform of a scanned image gray value, a new exposure meth- od- two-trigger method was proposed. First, the reason that the frequency changing of external trigger signal affects the image gray value was analyzed. Then, the two-trigger method was intro- duced. With the method, an external trigger signal was converted to two trigger signals, the first one was used to control the exposure and the second one was used to control the CIS to output data. Final- ly, it explained that the method can improve the image quality theoretically. A 1.6 meter non-distor- tion long-term array CIS camera was fabricated based on this method. The experimental results show that the fluctuation range of scanned image gray value is reduced by 75%, and the horizontal stripes on the image is eliminated at different trigger frequencies. When it is applied to an intelligent visionstitch digital printing machine, the image of 1 mmX 1 mm hole in the embroidered cloth is clear. It concludes that the proposed method reduces the effect of the frequency changing of external trigger signal on images effectively and improves the image quality successfully.