Line Structured Light Sensor Signal Processing Systems Design Based On FPGA

Line structured light sensor is a key research component of three-dimensional laser scanning topography measurement technology, which are usually based on the principle of laser triangulation and light sectioning. Using cameras and frame grabbers to continuously acquire laser stripe modulated by surface and then transfer the images computer by cable. After that we always use the software program to process these images and detect the center position of each light streak of each frame and then draw a three-dimensional point cloud data of the object under measured. Some key technologies such as light stripe center extraction and calibration will be used during the process and they are always for off-line. However, the image data transferred to the computer in addition to the characteristic information further includes an outer large amount of redundant information, this also leads to lower data transmission efficiency, low system integration, and makes high demands for post-processing software.In view of the shortcoming of traditional scheme like high cost, low integration, and poor real-time, In order to achieve rapid and accurate detection of the position of laser stripe center, this design of FPGA-based structured light sensor use CMOS digital image sensor for acquisition front, FPGA programmable logic device for controlling and processing core, combined with SDRAM mass storage unit to complete online real-time acquisition and processing of laser stripe image, finally the results will be uploaded to computer via serial port. Acquisition module constituted by a single-chip CMOS image sensor not only improves the integration of the system, reduces system size and cost, and the digitized collection and transmission also has a strong anti-jamming capability. Using FPGA hardware to complete image processing algorithms instead of computer greatly improves the processing speed of the system, and also meets the requirements of embedded systems.For hardware design, this paper presents the overall design of structured light sensor, introduces the main chips used in the system and the design process of each module of the hardware circuit; for software design, using the Verilog hardware description language to complete design of modules including image sensor configuration, image data acquisition and storage, SDRAM controller,image filtering, threshold segmentation and centerline extraction in the Quartus II development environment, then simulate each module in Modelsim simulation software to verify the correctness of the function. At last, the paper combine hardware design and logic design, debugs the entire system in the actual environment. Using a plane as a reference standard to analyze the extraction accuracy of laser stripes and discussing the various factors affecting the accuracy of extraction. The experimental results basically meet the design requirements with high real-time performance and stability.