On The Measuring Precision Of Non-metric Digital Color Cameras

Digital industrial photogrammetry is a high-precision, 3-dimension-coordinate measuring technology which uses digital pictures shot by cameras. Digital cameras, used as industrial photogrammetric sensors, are playing an important role in precise measuring area.This paper, based on the non-metric color digital camera structure, has done further researches on error factors and calibration methods and has put forward reasonable and constructive ideas on how to improve the precision of this kind of camera efficiently. The main contents are summarized as follows:(1) The characteristic of industrial photogrammetry is particularly analyzed. The development tendency of domestic and overseas industrial photogrammetric systems and the important role played by the digital cameras are put forward. Aiming at the situation that metric cameras are expensive, the measuring precision of non-metric color digital cameras is dug deeply to build high cost performance ratio measuring systems.(2) The camera calibration method called finite element grid method is analyzed. Classical 10-parameter method, finite element grid method and the combination method which put 10-parameter and finite element grid together are compared. And the highest precision of these methods is the combination method through theoretical analysis and experimental results.(3) The imaging mechanism of CCD and CMOS and camera stability are discussed. The calculating method of the angle between CCD plane and camera's primary optic axis is put forward independently, which provides a feasible method to adjust the camera's primary optic axis precisely.(4) The chromatic aberration effect is focused on. The results show that using only homochromatism information can improve photogrammetric precision.(5) Different formats of pictures are analyzed. The results show that different formats of pictures can affect measuring precision.(6) A new image compression method which combinate run-length coding and Huffman coding together is brought forward. The compression ratio of this new method can reach 30:1, which may help to transfer iamges with high efficiency.