Optimal use of dynamic range of a white light video measurement system

Abstract

This paper describes a method to make optimal use of the dynamic range of a white light video measurement system. Since the exposure period of a CCD camera is reduced with high frame rate, dynamic measurement with a short exposure is intrinsically light intensity starved. Thus insufficiency in light intensity may introduce underexposure problem and leads to poor image quality. To overcome this problem, we have developed a simple method which enhances the light intensity detected by a high-speed camera using a white light source (WLS). As an example, we have implemented the system for vibration measurement using a liquid crystal display (LCD) projector and a high-speed camera. By incorporating the WLS, the measurement speed of the camera is effectively increased by a factor of 6. Discrepancy in the measured vibration amplitude is less than 2%. This experimental study shows a clear demonstration of the limitations of the performance of a CCD camera and the importance of matching the intensity of the image to be analyzed to the characteristics of the detector.