Research On Embedded Laser Beam Quality Analyzing System

The paper did researches on laser beam quality analyzing system systematicaly based on the project whose number is 20070325 from Jilin province science and technology bureau and the project called laser XXXXXX system from 31 military base, discussed the corresponding theory and evaluation method about laser beam quality measurement, expounded the embedded image processing technology in detail and the construction of image processing platform for the embedded laser beam quality analyzing system, analyzed how each unit's performance affected the measurement precision and introduced the development and the action of laser beam quality analyzing system.Analyzed the significance of research on laser beam quality measurement and the common methods used in laser beam quality measurement, proposed the beam quality factor method which is also called M~2 method as evaluation method for the system designed in the paper by comparing their using range, advantages and disadvantages, the method proposed in the paper had advantages such as high evaluation precision, synthetical consideration including laser beam near field characteristic and far field characteristic synthetically and so on.The paper stated fundamental theories and methods for transmitting characteristical parameter's measurement of laser beam based on reviewing and summarizing Gauss beam transmitting and transformation properties, introduced conception and physical meaning for second order moment, product of laser parameter, diffraction limitation multiplying factor and beam transmitting factor, presented laser beam parameter measurement procedure, evaluation methods and the corresponding calculation formula which were provided by ISO standard file.The paper provided array digital CCD technology, embedded technology combining special integrated circuit technology to realize the embedded laser beam quality analyzing system based on researches on beam quality evaluation theory. The paper did researches on embedded image processing technology, introduced applications of embedded image processing system, embedded Linux operation system and embedded image user interface, and mainly discussed the key technique for QT/Embedded programming. Finally the paper designed image processing platform for the embedded laser beam quality analyzing system on the premise of combining the above key techniques , which included building embedded cross compiling circumstance, transplanting boot loader program, pruning and transplanting Linux and so on. After analyzing the major factor affecting the laser spot image quality in the system, the paper laid special stress on how embedded processor run filter algorithm such as image middle value, grey scale shaking, average frame and so on to process the image information to decrease the measurement error.Development of system hardware included designing of optical attenuation, focusing, and reflecting optical system, development of accurate mechanic unit, controlling of step motor, image data sampling, storing and transmitting unit, image processing and display, etc. The paper solved the key technique such as Field Programmable Gate Array as cache in the image data sampling and transmitting, direct memory access and so on. After the system's assembling, debugging and testing, it was shown that this system could measure the laser beam quality accurately and fastly, which gave the values of M~2 factor, beam waist diameter, beam waist position, divergence angle, two-dimension and three-dimension distribution of laser light intensity, spot shape and so on directly. The paper improved the system's real time by means of using the embedded operation system technique, therefore, system designed by this paper can measure the laser beam quality fastly, which actually realized real time measurement.Above all, the paper did researches on Gauss beam's transmitting, transforming property and property parameter when Gauss beam passes through thin lens by using the matrix method, especially discussed the evaluation and measurement for beam quality, adoptsed measurement suggestion established by international standard, built up a laser beam quality analyzing system which used digital CCD as detector, combined embedded processor and FPGA technique. Finally, applied the system to measure quality of He-Ne laser, gave the light intensity distribution, calculated the beam parameter by two order moment integral method, imitated the hyperbolic curve of laser beam transmitting to obtain the complete light intensity distribution information by using background subtract method to elimate noise, multi-frame average to remove trembling and Gauss imitation.System designed by the paper proposed an effective tool for laser beam quality detesting, provided theoretical reasoning and practical basis for the carry easily and small volume of measurement instrument. The embedded laser beam quality analyzing system was used to test some lasers' quality, data showed that the system had advantages such as small random error, small repeatability error, strong recurring ability and so on, measurement precision of M~2 factor was less than 4% at beam waist position.