Image Correction And Reconstruction Of Optical Holograms

Abstract:Images captured from optical holograms printed on goods, documents, personal identity cards, and etc. would be distorted due to quality of the imaging system and influence of shooting conditions. The reconstruction image will be severely blurred or even impossible to identify, if the distortion hologram is numerically reconstructed directly. So, before the numerical reconstruction is implemented the distortion must be corrected. At present, the research of corrections for the ordinary image distortion is more at home and abroad, but the study of correction for the hologram distortion has not yet been conducted.A distortion correction method for the captured optical holograms is proposed in this paper. Firstly, an image pre-processing technique is used to extract the target hologram and the boundary of the target hologram is determined. Then four vertexes and midpoint positions of the hologram and the ideal corresponding points can be sought automatically. The holograms with the projection distortion and non-linear distortion are corrected by using different polynomial models. Compared with the other methods, the proposed one is simpler and faster, as it does not need the high-precision calibrating objects and the images shot from different angles as many other self-calibration do and deals with a hologram object only.The experiments show that the method proposed in this paper is productive to the correction of the distortion for hologram and encrypted hologram. The correction hologram can be reconstructed clearly. The distortion encrypted hologram after corrected by the proposed method can be decrypted and the reconstructed hologram can show the information concealed in encrypted hologram.From the experiments, it can be shown that the corrected holograms can be recognized clearly. The proposed method has the advantages of high efficiency, fast and high-recognition rate.