Performance Test And Evaluation Of Optical Imaging System Based On Knife-Edge Method

Optical imaging systems play an indispensable role in modern technology,with widespread applications in medicine,aerospace,industry,security,and other fields.The performance of these systems directly impacts image quality and their effectiveness in various applications.Therefore,performance testing and evaluation of optical imaging systems is of paramount importance.Traditional knife-edge methods for measuring the modulation transfer function(MTF)have several disadvantages,including uneven sampling of the edge spread function and insufficient sampling,which result in larger MTF errors in the tested imaging systems.To address these issues,this paper proposes a novel measurement method,the tilted knife-edge method,and presents the associated algorithm.The main research contributions are as follows:(1)The common method of measurement and modulation and transfer function is studied.While the slit method offers high measurement accuracy,it imposes strict requirements on the system and can be difficult to implement for unconventional systems.The need to measure multiple directions increases the test’s complexity and duration.The contrast method for measuring MTF is heavily influenced by ambient light and requires additional processing to yield accurate results,making it less convenient for practical applications.In comparison,the knifeedge method exhibits high measurement accuracy,broad applicability,good repeatability,and is less affected by the signal-to-noise ratio than the slit method,making it a more reliable and widely used method for MTF measurement.(2)Analyze the measurement principles and methods of traditional knife mouth method,highlighting its limitations in practical application,such as low measurement accuracy and insufficient sampling.The tilted knife-edge method is introduced as a solution to these shortcomings.The paper presents a detailed explanation of the measurement principles and algorithms associated with the tilted knife-edge method and demonstrates,through comparison,that its measurement performance surpasses that of the traditional knife-edge method.The traditional knife-edge method utilizes a single line of data information,relying on detection and evaluation.However,due to the large sampling,a single line cannot accurately represent edge information,and the significant information loss at the edge is a clear disadvantage of the traditional knife-edge method.The tilted knife-edge method enables oversampling and adjusts the tilt angle to measure MTF in multiple directions,providing a more comprehensive and precise MTF curve.This method improves measurement accuracy and can accommodate optical systems of varying shapes and directions,including non-axisymmetric optical systems,offering considerable benefits for complex optical systems.Thus,the tilted knife-edge method is characterized by a reduced measurement error,enhanced measurement accuracy,and greater suitability for intricate systems.(3)The paper constructs an experimental optical path based on theoretical analysis and selects a system for testing.Both the traditional knife-edge method and the tilted knife-edge method are employed for measurement.The comparison of theoretical values demonstrates that the tilted knife-edge method outperforms the traditional knife-edge method.Subsequently,the experimental results obtained using the tilted knife-edge method are processed and analyzed,drawing conclusions regarding the influence of edge gradients and varying tilt angles on MTF.This analysis makes significant contributions to future research and successfully demonstrates the efficacy of the tilted knife-edge method in reducing errors.The tilted knife-edge method proposed in this paper exhibits higher measurement accuracy and reliability compared to the traditional knife-edge method.It can be effectively used to evaluate performance parameters such as resolution,image quality,and distortion of optical imaging systems.