What are the advantages of off-axis reflection parallel light tubes?

As a typical optical calibration system, parallel optical tube optical system is a necessary tool to measure the parameters of optical system. Its main function is to provide a beam of parallel light to simulate an infinite target, and different optical devices can be placed at the focal plane position to detect the performance parameters of different systems under test, such as placing a divider to measure the focal length of the system under test, placing a discrimination rate board, a star plate and other measurement system resolution and other imaging quality.

The parallel light tube is divided into transmission type and reflection type two kinds, transmission type parallel light tube due to the uniformity of material and color difference and other factors, the aperture can not be too large; The reflective parallel light tube is not limited by the material, no color difference, easy to achieve large aperture, high system transmittance; The reflective parallel light tube is divided into two forms: coaxial and off-axis. The coaxial reflection parallel optical tube has small field of view and central blocking, which will have a great influence on the imaging quality. Off-axis parallel optical tube because of the off-axis structure, the focus is led outside the main mirror, there is no central blocking, can avoid energy loss, the use of multi-reverse structure, the light path can be folded, compact structure, conducive to reducing the volume of the system, while the back of the mirror can also be lightweight structure, easy to reduce the quality of the system.

The reflection surface of the off-axis reflection parallel optical tube is usually aspherical, which can improve the image quality well, but the aspherical surface is difficult to process and the cost is high. In recent years, due to the development of numerical control technology and the emergence of deterministic polishing technology, the processing efficiency of aspherical surface has been increasing and the processing cost has gradually decreased, and the cost of off-axis reflection parallel optical tube has also decreased, so that off-axis reflection parallel optical tube has gradually been widely used in various fields.

Off-axis reflection parallel light tube