Development of a tool to analyze back-focus characteristics of fix-focal cameras

Sammanfattning: Fix-focal cameras require careful alignment of the sensor relative to the lens during assembly in order to produce a sharp image. Axis developed wide- and fish-eye network cameras are, for a number of reasons, focused at infinity when aligned. This thesis develops the software for a new inhouse tool to be used at Axis to analyze the back-focus effect on the camera’s focus characteristics. The tool is a machine called Modus, which uses a variable focus collimator to measure the sharpness of objects at distances not limited to infinity. The main purpose of this new tool is to answer the following questions: • How can knowledge of the back-focus effects for a given camera be harnessed to decide on back-focus offsets to achieve desired focus characteristics during alignment? • What are the sensor placement tolerances to achieve a certain image sharpness? Can this information be used to decide between active or passive alignment? A fish-eye camera, Koi, is analyzed with the new software written for Modus. The results show that the focus moves from infinity to 0.3 m within a back-focus window of 5 µm, with focus changes of ± 0-5%. The depth of focus for a number of image sharpness levels is also measured. The limitation of the applicability of the results for the Koi camera lie in the sample size. In this thesis only one unit of the camera is analyzed. In order to draw conclusions about appropriate back-focus offsets a larger sample size in needed.