Research And Implementation Of Automatic Test System For ROSA Focal Length

At present,most of the production and testing of photodetectors and detector components still rely on manual methods,in which the detector focal distance testing requires the operator to find the focus manually,and the efficiency is low.Many automation equipment in foreign countries have been applied to the automatic testing and coupling package of optical devices and modules.However,there are few photoelectric enterprises using automatic equipment testing and coupling in China,and most of them are coupled under the condition of uncounted optical fiber distribution,which can not guarantee the efficiency of receiving light.The main innovation of the dissertation is to present an efficient algorithm for finding focus automatically by analyzing the light intensity distribution rule when the fiber end is connected to the device.Compared to general-purpose intelligent search algorithms,the paper's variable-step cross-scan method takes advantage of the existence of a connection between the largest point in the plane and any point,making the focal length test time shorter and improving the efficiency of automated coupling testing.In addition,the paper also proposes a variety of methods to improve the accuracy of the test results.In software,the local extrema is taken into account in the cross scan,and the focal length results are obtained by fitting the sampling points;in the hardware,the current and mechanical errors are reduced from the circuit and the system level.The main research work of this paper is as follows:(1)The study and implementation of stable laser light source.The main factors affecting the stability of the laser light source are analyzed.The negative feedback loop scheme is adopted,and the automatic light power control circuit and the automatic temperature control circuit are designed to ensure the stability of the light output light power.At the same time,the power supply circuit of the light source module is optimized to ensure the stable operation of the laser.(2)Research and implementation of low noise photoelectric detection module.Based on the analysis of the influence of circuit components on the SNR of the detection circuit,the design principles of the circuit module and low-noise anti-interference measures are proposed to realize the photocurrent detection circuit of the system.Besides,the system's cable noise,power supply noise and suppression methods are also analyzed to reduce the noise that affects the weak photocurrent detection.(3)Research and implement an efficient algorithm for automatically measuring the focal length.Firstly,the key to improve the focal length testing efficiency is to reduce the scanning point,avoid falling into local extreme points,and optimize the motor motion parameters and the device movement trajectory.Then do experiments to collect data to analyze the distribution law of the photoelectric conversion efficiency values in the three-dimensional space,and find the connection between any point in the space and the best point.Then according to the spatial characteristics of the best point,the spiral back shape scanning is carried out in the area with small photoelectric conversion efficiency,and cross scanning is carried out in the main light receiving area.Finally,from theoretical analysis and experimental point of view,it is proved that the motion method of finding focus in this paper is superior to the traditional methods.The test results of the system prove that the focal length error of the ROSA focal length automatic test system designed in this paper is less than 50 um,and the test time is 15 s.It can greatly improve work efficiency and meet practical application needs.