Auto Focus Measurement System For Aspheric By Planar PSD

The high speed development of designing and machining aspheric parts raises a much higher demand in their measurement. In this article, using planar array sensitive photoelectric device PSD (Position Sensitive Device) as the sensor, designed an auto-focusing system for noncontact measurement. Grating measuring technique is applied in this system to obtain precise aspheric shape data. This paper is on the basis of linear array PSD measurement platform, using planar array PSD to achieve three-dimensional aspheric measurement, mainly includes the optical path design of PSD, the design of hardware and controlling software.The article includes such contents as below:(1)Introduction and comparison the development and application of aspheric measurement, planar array photoelectric position sensitive device PSD and CCD, ways of auto-focusing measurement on aspheric measurement.(2) The principle of optical path for auto-focusing system. And make comparison of the designed paths.(3) The design of processing circuit of PSD and grating, the communication between PC and singchip.(4) The component and function of each part for this system.(5) Program of two singchips and controlling software.(6) The conclusion and its possible future research aspects.The keystone of the article is the design of optical path and controlling software. Though experiment was not carried out with perfect background, it does prove this method is feasible to get accuracy data. The advantage of the method is:(1)Using PSD as sensitive device not only increases the sampling speed, but also decrease the cost. (2) Apply AF to precise measurement, and use grating to get much higher accuracy and improve its reliability.(3) It is Convenient to get photoelectric signal. Using serial port to send and receive data of PSD and display the result and grating signal on PC, easy to inspect state and extend functions.