Research On Laser Spot All-angle Evaluation And Pointing Stability Measurement Technology

The evaluation and measurement of laser beam spatial performance have been key issues in the development and application of laser.Due to the influence of various factors such as the laser itself and the environment,the beam emitted by the laser has the phenomenon of asymmetry and instability,which affects the quality and precision of work in the fields of laser guidance and laser processing.The incomplete evaluation of such phenomenon hinders the expansion of laser application.Aiming at the evaluation of laser spot asymmetry,an all-angle evaluation method is proposed.The method extends the traditional method of obtaining the spot width in the horizontal and vertical directions to an arbitrary angle direction through the process of constructing the coordinate system for spot image and obtaining the quadruple second-order moments of the laser intensity distribution.Then select the effective pixels in the spot image and draw the spot profile that reflects the intensity distribution characteristics of the actual spot.Aiming at the measurement of laser beam instability,a measurement method of pointing stability is proposed.The method uses the angle-displacement transform imaging characteristics of the F-theta lens,eliminating the effect of tangent error in traditional measurement.And the way to obtain the minimum envelope circle of the point group of beam shift positions is used to evaluate the pointing shift.A measurement system with a CCD camera as the image acquisition unit is built.Using the Visual C++ platform and MFC framework,the measurement system operating software is developed to realize the real-time acquisition of lase spot image,pre-processing,display of laser intensity distribution and calculation of the parameter measurement results.Multiple groups of actual measurements are performed with the system,which prove the feasibility of the two methods.The main error sources of parameter measurement in two aspects are analyzed.For the all-angle evaluation,the measurement of the laser spot width in each typical angle direction with an interval of 15o for one single spot image is realized,and the measurement error is less than 0.6%.For beam pointing stability measurement,a pointing angle resolution of 1.2?rad is realized,and the measurement error is less than 0.27%.The evaluation direction in the evaluation of spot spatial performance is extended while the positioning precision and evaluation accuracy of the laser beam in the measurement of pointing stability are improved,which are beneficial to the comprehensive,high-speed,and accurate evaluation of the spatial performance of the laser beam.