KEYWORDS: Imaging systems, Sensors, Image processing, Error analysis, Spectral data processing, Imaging spectroscopy, Computer programming, Signal to noise ratio
Hadamard transform spectral imaging technology has high signal-to-noise ratio and the advantage in energy distribution. In recent decades, related works focus on dynamic coding Hadamard spectral imager instead of static coding ones. The latter has great potential value in spaceborne and airborne applications, but the accuracy of its restored spectral image data is poor at present. Therefore, it is necessary to further study the formation mechanism and correction method of errors in static coding Hadamard spectral imager. In this paper, the influencing mechanism and correction method of spectral overflow are studied. Firstly, the imaging and restoration process of the Hadamard coding spectral imager with spectral overflow is mathematically deduced, and the conclusion is compared with the simulated restoration results. Secondly, the simulated results are compared with the experimental data, verifying that spectral overflow is an important source of the error in experimental results. Finally, a correction method for eliminating spectral overflow errors under certain conditions is proposed, and the effectiveness of the method is verified by simulation. This paper can provide reference for the design and data restoration of static coding Hadamard spectral imager.
In order to meet the requirements of synchronous image acquisition in online industrial vision inspection, a new method based on image feature recognition is proposed. According to the method, the spatial characteristic information of sequence images has been calculated, and an algorithm under multi-constrained conditions which based on the trend of feature values of sequence images is established. The synchronous target image in online inspection is acquired by the trigger signal which was obtained by the algorithm under the condition of no dependence on external attachment. The method does not need to rely on the external position feedback device, and reduces the hardware cost. The algorithm has a better synchronization precision and adaptability, and has been successfully applied in practice.
To meet the actual demand, the linear CCD technology is applied to tunnel crack detection, and an edge detection algorithm is proposed to measure the crack width. Firstly, the application form of linear CCD imaging technology in tunnel crack detection is introduced concretely in this paper. Then, the key influencing parameters of measurement are discussed. Finally, an edge detection algorithm based on the change of gray level in linear direction is proposed and it is verified by experiments. Experimental results indicated that the linear CCD imaging technology in tunnel crack detection could obtain measurement data quickly and improve the efficiency of tunnel cracks’ measurement, and that the detection algorithm could be used for the crack width measuring.
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