ABSTRACT
Aiming at the difficulty of detecting the modulation transfer function (MTF) of Bayer color cameras during focusing, the traditional scheme is modified in this paper. First, through analysis, it is found that the MTF of the Bayer detector decreased substantially compared to the monochromatic detector, which was caused by the loss of a large amount of light from the Bayer detector. When the MTF is calculated for the color image after de-mosaicing, the degradation of image quality leads to the inability to obtain the full-frequency MTF curve. Therefore, this paper proposes a solution to detect the MTFs of the three primary colors in the Bayer image individually, and then weight the MTFs of each primary color to obtain the MTF of the color image based on the calibration results of the light source. Then, considering the steps of differentiation and Fourier transform in the slanted-edge method, this paper solves the problem of non-uniform sampling of edge spread function by using the modification of the slanted-edge method with non-uniform Fourier transform. Finally, the optimal imaging position of a certain type of Bayer color camera is determined using the methods proposed in this paper. Simulation and test results verify the effectiveness and accuracy of the methods in this paper.
ABSTRACT
Bayer filter color cameras are more and more widely used in the field of aerospace remote sensing, but the Bayer filter causes great degradation in image quality; therefore, obtaining a means of achieving the high-precision measurement of the modulation transfer function (MTF) of Bayer filter color cameras is an urgent problem. In order to solve this problem, this paper develops a slanted-edge method via three steps: the detection of the slanted edge, the acquisition and processing of the edge spread function (ESF), and the acquisition and processing of the line spread function (LSF). A combination of the Canny operator and Hough transform is proposed for the detection of the slanted edge, which improves the fitting accuracy and anti-interference ability of the algorithm. Further, the Canny operator is improved by constructing an adaptive filter function and introducing the Otsu method, which can more effectively smooth the image and remove its false edges. A method of processing ESF data by combining cubic spline interpolation and Savitzky-Golay (SG) filtering is proposed, which reduces the effects of noise and the non-uniform sampling of ESF on MTF. A method of LSF processing using Gaussian function fitting is proposed to further reduce the effect of noise on MTF. The improved algorithm is verified by the MTF measurement test applied to a specific type of Bayer filter color space camera. The simulation and test results show that the improved slanted-edge method discussed in this paper has greater precision and a better anti-interference ability, and it can effectively solve the difficult problem associated with MTF detection in Bayer filter color space cameras.
ABSTRACT
Crystals of the title complex, C(3)H(7)NO(2).C(8)H(8)O(3).0.5H(2)O, were obtained from an aqueous solution containing racemic mandelic acid and (S)-alanine. The unit cell includes two independent molecular complexes and one water molecule. The structure formed by (R)-mandelic acid and (S)-alanine in a 1:1 molar ratio shows the successful optical separation of racemic mandelic acid. Strong hydrogen bonding, with a rather short O...O separation of 2.494 (3) A, is observed between the carboxyl and carboxylate groups. A structural comparison suggests that the strong hydrogen bonding affects the neighbouring covalent bond.
ABSTRACT
The title chiral compound, 3-aminocarbonyl-1,2,2-trimethylcyclopentane-1-carboxylic acid, C(10)H(17)NO(3), was prepared from (1R,3S)-camphoric acid. The five-membered ring adopts a conformation which is intermediate between a twist and an envelope. Elongations of the C-C bonds and contractions of the C-C-C bond angles are observed within the five-membered ring. A (1)H NMR spectrum was recorded to assist in distinguishing the amide group from the carboxyl group.
