Design Of Measurement Objective For Underwater Docking Of Spacecraft

The technology of underwater optical measurement is based on the technology of underwater imaging.Specialized optical design of the imaging objective complete the high-precision underwater position measurement.This subject is based on the project background of simulating a zero-gravity environment in space on the underwater to and innovatively proposes the application of underwater optical measurement objectives to the relative position measurement of targets.By using the telescopic additional lens and the combined objective of the telecentric structure in the image space,the demand for high-precision underwater measurement is realized.Underwater optical measurement technology has extremely broad prospects in many civil and military aspects such as the measurement of the shape and size of underwater targets,underwater monitoring,and underwater archaeology.This article mainly discusses the design of underwater measuring objective and the theory of underwater imaging.The main contents are as follows:1)Discuss the optical characteristics of water and the effect of water on optical imaging.The object medium is water is the main characteristic of underwater measurement objectives,it is different from other types of measurement objectives.So it is necessary to understand the optical characteristics of water and the effect of water on imaging quality.And according to the optical characteristics of water,the working band of the underwater measurement objective is determined to be the blue-green light band.The measurement objective is a telescopic additional lens and a telecentric structure in the image space.2)Designed an underwater measuring objective.The diagonal field of view of the underwater measurement objective reaches 54.8°,the distortion is less than 0.25%,the MTF is greater than 0.5 at 90lp/mm,the working distance is 1m-5m,the position measurement error within the working range is less than 6mm,and the angle measurement error is less than 0.06°.The image quality evaluation of the objective shows that the imaging quality is good and the aberration of the objective is corrected.When the object distance is adjusted to the actual working distance,the imaging quality slightly changes,but the measurement accuracy is not affected.3)Tolerance analysis and stray light analysis is carried out on the measuring objective.The overall tolerance distribution of the measurement objective is relatively loose,but the imaging quality is still guaranteed.The loose tolerance distribution improves the reliability of the system’s processing and assembly.The stray light analysis of the measurement objective shows that although the hood is not designed,the PST of the system is still relatively low due to the rear aperture stop.Especially in the large off-axis field of view,the PST of the system is reduced to 10^-7.