The invention discloses an optical
system focal
distance detection method and belongs to the technical field of
optics. The method includes the following steps that moire fringes are formed after light of a
light source penetrates through a target board and change divergent light of the target light to parallel light after passing through a
collimator, and after the parallel light passes through a shot under a test, a target is image-formed on a focal plane of the shot under the test; a
time delay and integration charge coupled device (TDICCD) is configurated through a computer, driving frequency fT of a line transfer pulse
signal of the TDICCD is confirmed, from
image motion linear speed people can know that the driving frequency fT of the line transfer pulse
signal has a proportional relation to the
image motion linear speed, when the computer controls the TDICCD to start rotation from an initial position, the line transfer pulse
signal is sent, images are started to be recorded, when the TDICCD reaches to an ending position, the images are stopped being recorded, and the line transfer pulse signal is stopped being sent. Under the speed, a precise rotating platform is driven to take pictures for 4-5 times, and focal distance of the shot under the test is calculated. The optical
system focal
distance detection method is high in detection accuracy and widely applied to detection on focal distance of optical
system of
optical instrument equipment.