Laser Differential Confocal And Interference Measurement Method And Technology For Element Parameters

Spherical components are widely used in many high-tech systems, such as inertial confinement fusion system, extreme ultraviolet lithography system, for their excellent processing performance. However, the measurement accuracy of spherical components has become the technical bottleneck to improve their processing accuracy and quality. So the research of high-accuracy component parameters measurement technologies and instruments is of great significance.Supported by the National Instrumentation Program(NIP) of China “Development and application research for laser differential confocal imaging and testing instrument”(No. 2011YQ040136) and National Natural Science Foundation of China “Instrument development of laser differential confocal and interference measurement for multiple parameters of an element”(No. 61327010), the thesis carries out the research of laser differential confocal and interference measurement method and technology for multiple element parameters. The main creative contents are as follows.The theoretical analysis models of point spread function and transfer function are established for laser differential confocal and interference measurement system. Based on these models, the influences of the combination of laser differential confocal and phase-shift interference measurement light paths on measurements, of the aberrations on focusing and positioning, and of the positioning sensitivity are deeply analyzed. This offers theoretical guides for the designs of measurement light path and system.A laser differential confocal focal-length measurement method is proposed. With the help of a standard plane reflector, the method identifies the lens focus and vertex precisely by using differential confocal technology. Then, measurement of the precise distance between these two positions is achieved to determine the lens focal length. The relative expended uncertainty can reach 10 ppm.A compensation method for differential confocal radius and focal-length measurement is proposed by using the interference measurement results of spherical surface and lens wavefront distortion, respectively. This method is based on the established transfer function model of laser differential confocal radius and focal-length measurement. The compensation for the measurement error caused by the wave aberrations of measurement system and standard lens, test surface shape, and the wavefront aberration of test lens can be achieved, and the compensation accuracy is up to submicron scales.A laser differential confocal and interference measurement system for multiple element parameters is developed. Based on the system, the measurement experiments of spherical surface, spherical radius, lens wavefront aberration, and lens focal length are carried out, which verify the feasibility of the combination of laser differential confocal system and phase-shift interference system. The relative expended uncertainties of the spherical radius and lens focal length obtained by this system are both up to 10 ppm.