A PMP System Based On C6000 Series DSP

Phase measuring profilometry (PMP)is an important technique in the 3-D shape measurement, which is based on fringe patterns projection and phase measurement. It has been widely used in industrial inspection, machine vision, inverse engineering etc because of its merits of noncontact, full-field, high-precision and high-speed.In PMP measurement system, the digital projector is often adopted to produce the phase-shift sinusoid fringes through the computer VGA video interface, and a special image captured card embedded in computer must be applied to obtain the corresponding deformed patterns , because the display and projector share a VGA video interface, while a phase-shift Sinusoid fringe need to be projected onto the measured object ,both the digital projector and the display are producing the information which makes the computer difficult to operate the measuring software and capture image data at the same time. Usually, there are two methods to solve this conflict problem, One is to adopt another computer specially for controlling the projector so as to let the master computer operate the application software and accomplish the image data captured and processed, this kind of system is unsuitable to be instrument; The other is to adopt special-purpose display card, controlling the display with VGA interface, and controlling the projector with DVI interface, besides the special-purpose application software is required to realize the separated display of the projector and computer display, because this kind of system needs to adopt the special-purpose hardware and special-purpose software, it may not be compatible enough. So an improved PMP measuring system of making use of the high-performance image processing chip of TI Company's TMS320C6000 series DSP named TMS320DM642 has been developed instrumentally in which the projector is connected to the video display port of DM642 rather than the computer, and CCD is linked to the video capture port of DM642 without any other image captured card. Some instrumental design has been researched. The main tasks are as follows:1. Having compared several kinds of structure of PMP system, the improved PMP system has been proposed.2. The key modules based on DSP of the improved PMP system have been developed such as the video image capture control, the phase-shift sinusoid fringes generator realization and UART communication program design. Finally, the related algorithms and self-starting program in this system have been accomplished.3. In order to analyze the accuracy of PMP system, the intensity transmit . function (ITF) is used to improve the quality of the projected sinusoidal fringe, experimental results show its feasibility.4. Because of the unstable projected field caused by pixel scanning, which may influence the precision of PMP system ,a faster image data processing method with several frames mean arithmetic has been done inside of the high performance DM642 to reduce the instability of the field. Contrastive experiments have been proved that the measuring precision has been improved remarkably.