Research On Dynamically Generating A Point Source Generator Of An Ideal Array Of Interference Point Sources

Optical free-form surface has the advantages of improving the imaging quality of optical system,decreasing the number of lens,reducing the size of the system,so it is widely used in lighting,aerospace,biomedical and other fields.But because of its large surface gradient changes,making the shape of the field of detection into a major problem in the field of optics.At present,the Tilted-Wave-Interferometry(TWI)has attracted wide attention in free-form surface measurement because of its wide dynamic range,high detection precision and versatility.The point source generator is a key component of the tilted-wave-interferometry system and generates a spherical wave source array for compensating the local gradient of the device under test.At present,the point source generator consists of a pinhole array,a lens array and a dynamic mask plate.However,because of the spherical aberration of a single lens which constitutes the lens array,the beam emitted by the single lens is not ideal,and then leads to the introduction of the error in the measurement of the tilted-wave-interferometry system.Secondly,after the lens array is completed,it can not dynamically generate the point source array according to the shape of the measured object,which restricts the detection universality of the tilted-wave interferometer system.In this paper,a novel scheme of point source generator based on fiber array is proposed,which solves the above problems of point source generator based on lens array.The design method of point source generator based on optical fiber array is studied,and each key device is developed.A fiber array point source generator is designed for the tilted-wave interferometer system,then a point source generator based on fiber array for the tilted-wave-interferometry system is formed.In order to ensure the coherence of the tilted-wave interferometer system,polarization maintaining technique is adopted in the design of the fiber array based point source generator,to ensure the coherence between any two spot light sources emitted by the point source generator.In this paper,coherent detection device based on Fizeau interference principle is designed.The coherence of the fabricated fiber array point source generator is measured and it is proved that the coherence of the device meet the requirements of the tilted-wave-interferometry system.In this paper,the influence of the fiber-optic point source spacing error on the tilted-wave surface interference system is analyzed.The conclusion is that the fiber-to-core spacing error must be controlled within 15 ?m to make the wavefront error of the TWI system less than?/10.At the same time,the optical fiber array core spacing measurement system is designed and built,and the spot pattern of two light beams emitted by the point source generator is obtained by imaging method.The ellipse fitting method is used to determine the center position of the spot and calculate the core spacing,the core spacing error of the developed point source generator is 1.75 ?m,which meets the precision requirement of the inclined wave surface interference system.In this paper,the influence of the optical path difference between any two point sources based on fiber-array-based point source generator on the measurement results of TWI system is analyzed.The all fiber Mach-Zehnder interferometry system based on fraction coincidence method is designed and built.The optical path difference between the point sources of the fiber-array point source generator is measured.The corresponding error data matrix is calculated and stored as an inherent error into the tilted-wave-interferometry system to eliminate the influence of the optical path difference between the point sources on the accuracy of the TWI system.