LD Coupling Lens Focal Spot Position Detection System

Laser Diodes(LD)light source is widely used in communication,measurement,military,medical and other fields because of its good monochromaticity,good coherence,simple modulation,small size,and low cost.In the process of coaxial packaging and production of laser diodes,it is necessary to perform focal length testing,die cap and die welding,and coupling and welding of fiber adapter and laser.At present,the laser diode focal spot position test in the industry mainly uses an optical power meter for manual blind search and measurement,which has disadvantages such as low measurement efficiency,introduction of human error,and single acquisition parameters.Therefore,this paper proposes a set of online automatic detection methods based on the principle of image vision measurement,and designs an LD coupling lens focal spot position detection system.The system consists of a telecentric lens,a ring LED light source,a stepping motor and an industrial CMOS camera,which is used for LD coupling lens focus.Spot position detection.The focal length of the LD is defined as the distance from the surface of the LD package base to the focal point of the laser converged by the cap lens.The detection system first automatically locates the outer end surface of the base and detects the additional size of the base.Then,through the automatic focusing method,the CMOS camera is moved to find the center position of the laser focal spot of the coupling lens,thereby measuring the LD coupling lens Focal length and LD eccentricity.The method and device can be widely used for LD focal spot detection in different wavelength bands.In order to improve the detection efficiency,this paper proposes an improved automatic focusing algorithm.The algorithm uses the Brenner definition evaluation function.In the same batch of LD detection,some samples are first selected for rough measurement,and the improved adaptive step change is used in the rough measurement stage.Long hill climbing algorithm.Perform fine measurement on the basis of rough measurement,and perform Gaussian fitting on the result of fine measurement to obtain the beam waist position,which is the focal spot position of the LD.The experimental data show that the standard deviation of the LD eccentricity measurement with a wavelength of 1330 nm is less than 5?m,and the focal length measurement standard deviation is less than ±0.1mm.It can accurately obtain the relative position relationship between the focus spot and the base circle center.The experimental results are accurate and the measurement efficiency is high.