Research of precision conditioning circuit in laser differential confocal sensor

Laser differential confocal sensor (LDCS) is a high precision and high integrated measurement system. In order to meet the demand of the LDCS, a novel implementation method of high precision conditioning circuit is studied. This circuit consists of photoelectric conversion, secondary amplification and signal operation. The photoelectric conversion is designed to detect the light intensity signal and transform it into a voltage signal. In order to adapt the test for different samples, the magnification is adjustable in secondary amplification unit. The two-way light intensity signals of the LDCS are differentially subtracted in signal operation unit. The noise characteristics of the photoelectric conversion unit were analyzed and the methods for decreasing noise were presented. The experimental results show that signal to noise ratio (SNR) of the conditioning circuit is better than 1160 and the sensitivity of LDCS reaches 2.168V/μm, which has the advantages of low noise, high stability and high integration and can widely used in many kinds of high precision photoelectric measurement systems.