Application Of Improved Edge Method In Measurement Of Modulation Transfer Function Of Security Surveillance Lens

In the field of security video surveillance,the image quality of video surveillance equipment is an important factor to evaluate the performance of the system.In the production process of fixed-focus products,which have the majority of output,it is still necessary to focus artificially and determine the resolution artificially to ensure the image quality of the products.The resolution method is not only easy to be affected by the quality of drawing printing and screen resolution,but also can only rely on subjective judgment,reading,can not be digitized,will cause misjudgment of production line workers.MTF(Optical Modulation Transfer Function)is an accurate,objective and quantitative image quality evaluation index.It is recognized as the most effective and comprehensive method in the current image quality evaluation of optical systems.Therefore,using MTF can evaluate the imaging quality of optical system more intuitively and scientifically.Through extensive investigation and analysis,MTF is calculated by edge method.The various processing methods in every key process of the edge method are sorted out.Through theoretical analysis and simulation test,from the point of view of improving calculation accuracy and stability,the influence of various processing methods on evaluation accuracy and calculation stability is compared and analyzed,and the algorithm optimization strategy is proposed.The main works of this paper are as follows:(1)The centroid method used in edge detection by traditional edge method is easy to be disturbed by image noise,which will lead to the inaccuracy of the final calculation of MTF.In this paper,an improved Canny operator is used to detect edge edges,and an adaptive smoothing filter is used instead of Gaussian filter.This method not only has better denoising effect,but also can effectively preserve the edge information of edge images.Furthermore,the maximum inter-class variance method is used to automatically extract the image threshold and effectively reduce the false edge information.(2)Cubic spline interpolation is used to extract ESF(Edge Spread Function)curve in traditional edge method,which can effectively reduce the interference of blind pixels and noise.The ESF curve is smoothed by using smoothing filter,which reduces the error of LSF(Line Spread Transfer Function).(3)The influence of external potential factors on the stability of edge-edge method is validated,and the shot quality is judged by setting MTF threshold at a specific frequency,and the algorithm is applied to practical production.