Method for measuring focal length and rotation angle using Fabry-Perot etalon

The invention discloses a method for measuring a focal length and a rotation angle using a Fabry-Perot etalon. The method for measuring the focal length comprises steps that monochromatic light is transmitted by the Fabry-Perot etalon and then a group of standard cone light beams with accurate cone angle [theta]i rules, the group of cone light beams is reflected by a rotary mirror and then passes through an object mirror, and a group of concentric circles are formed on the surface of an area array photoelectric device on a focal plane of the object mirror; a plurality of point domains are selected on each circle, and one-dimension pixels in each point domain are subdivided; by means of the diameter Di of the concentric circles of the cone light beams and the standard difference sDi thereof, and according to the cone angle [theta]i distribution rule, fi/W is calculated by the formula Di=2(fi/w)tan[theta]i, fi/W is a ratio of the focal length fi calculated by the single circle diameter Di to the average pixel s