A Method for Measuring the Focal Length of Long Focal Length Lens Based on Moiré Fringe Matching

Abstract

The invention discloses a long-focus lens focus distance measuring method based on moire fringe matching. According to the long-focus lens focus distance measuring method based on the moire fringe matching, divergent light is adopted to serve as a light source, a moire fringe is collected firstly through a charge coupled device (CCD) camera when a long-focus lens to be measured focus is not added, focus distance between the light source to an initial divergent beam of the first Lang grating, the light source is moved forward and backward after the long-focus lens to be measured focus is added until a present moire fringe collected by the CCD camer is the same as the first moire fringe, combined focal distance between a new divergent beam and the lens to be measured is the same as the focus distance of the initial divergent beam, and then the focus distance of the long-focus lens to be measured is obtained. The long-focus lens focus distance measuring method based on the moire fringe matching has the advantages that focus distance of the long-focus lens (focus distance can be several meters to tens of meters) with a heavy caliber can be measured accurately, uniqueness is achieved by using a moire fringe angle as a criterion, measurement of an included angle between grating lines of two gratings is not needed, and error of the moire fringe angle caused by installation of an imaging system is avoided.

Description

technical field [0001] The invention belongs to the field of optical testing, in particular to a method for measuring the focal length of a long focal length lens based on moiré fringe matching. Background technique [0002] Inertial confinement nuclear fusion is an effective way for humans to use lasers to control nuclear fusion, so that nuclear fusion can release corresponding energy according to human needs, so as to obtain controllable nuclear fusion energy, so that human beings can completely get rid of the trouble of energy shortage. The long focal length lens is a very critical basic component in inertial confinement nuclear fusion, and it is playing an increasingly important role, and the required focal length is getting longer and the aperture is getting larger and larger. In large systems, such as the National Ignition Facility, long focal length lenses are the key light-gathering elements, and these lenses have a focal length of tens of meters. The use of long fo...

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Problems solved by technology

[0003] In 2011, the applicant applied for an invention patent with the patent application number 201110252061.3 and the name "A High-precision Long-focus Lens Focal Length Detection Device". The specification of the patent mentioned a focal length detection method. Measure the angle between the grid lines of the first Ronchi grating and the second Ronchi grating to calculate the focal length of the long focal length lens to be measured, but the accuracy of the measurement of the angle between the grid lines of the first Ronchi grating and the second Ronchi grating limits the Improvement of focal length measurement accuracy

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