Design and analysis of wide-band transmission spheres for multiwavelength interferometers

A design of high-precision 4-in. transmission spheres that can work in wide-band interferometric measurement is proposed. A motorized precision rotation mount is used to drive one of the lenses in the design to make the transmission sphere work at any wavelength in the wavelength range of 532 to 1550 nm, where the F-number of the transmission sphere remains constant during the movement of the lens. OpticStudio software is utilized to verify the design under F-numbers of 1.0, 2.2, and 3.3, and the results show that a transmission sphere with an F-number of 1.0 to 3.3 can be designed based on our model. The tolerance analysis and the secondary adjustment results show that the peak-to-valley transmission wavefront error of the transmission sphere can be controlled within λ / 20 in actual machining and assembly, which meets the requirement of high-precision interferometric measurement.