Error analysis of laser divergence angle measurement

In the product delivery process, deviation between the laser divergence angled calculated by hole-set method and CCD imaging method is usually large. In order to find the reason, theoretical analysis was carried out by ZEMAX simulaiton and experimental verification was done. The results show that:when using CCD imaging method to measure the laser spot size in white CCD sighting system, due to optical path difference between white light and laser, the influence of image error caused by optical path difference on the calculation of laser divergence angle should be eliminated. Laser spot size and distance are in accordance with the law of hyperbolic variation. In the near field conditions, there is not the linear relationship. Laser spot image measured by CCD imaging method is large and the calculated laser divergence angle is far more than the angle measured by hole-set method. In the far field conditions, there is approximately the linear relationship. The values of laser divergence angles calculated by hole-set method and CCD imaging method are in consistence. The study can eliminate the influence of optical path difference on divergence angle of laser beam and improve the measurement accuracy according to design parameters of the products.