Dark-frame subtraction

About: Dark-frame subtraction is a research topic. Over the lifetime, 1216 publications have been published within this topic receiving 20763 citations.

Image noise removing apparatus and image noise removing method

Abstract: An image noise removing apparatus which removes, after removal of noise from a first image, noise included in a second image includes: a spatial noise removing unit executing an operation for removing the noise included in the second image using a pixel value included in the second image, thereby generating a spatial noise-free image; a reliability calculating unit calculating a reliability indicating how dynamic the second image is, based on the spatial noise-free image, the second image, and a first noise-free image which is generated from the first image with the noise therein removed; and a temporal blending unit performing, based on the reliability, a weighted summation on the second image and the first noise-free image, thereby removing the noise included in the second image.

Image enhancement using joint transform correlation

Abstract: An efficient technique for restoring the original from a blurred noise corrupted image using the concept of fringe- adjusted joint transform correlation is proposed. This technique employs Fourier plane apodization using the reference image power spectrum and noise power spectrum to suppress the effects of blur as well as input scene noise. The performance of the proposed technique has been enhanced significantly by employing the Fourier plane image subtraction especially for blurred noisy input scenes involving multiple identical objects. The image subtraction technique eliminates the unwanted zero-order term and crosscorrelation terms produced by similar input scene objects while alleviating the detrimental effects of blur and noise that may be present in the unknown input scene. Computer simulation results using blurred noise corrupted grey level input scenes are presented to verify the performance of the proposed technique.

Method for reducing image noise

Abstract: A method for reducing image noise is provided. The procedure of the method is provided in the following steps. First, the color level scale of a scanned image of a document is reduced by a plurality of bits in order to subtract a noise level from the scanned image. Then the color level scales of all pixels of the image are recombined by a halftone pattern method in order to recover the color level scales. Finally the missing codes of the image are filled out by bit enhance method. Because of the color level scales of the proceeding image are not reduced, the scanned image quality does not be blurred by the method. Because the method does not minimize the color level of the proceeding image, the image noise can be reduced without blurring the scanned image and the quality of the image can be increased after the process thereof. And because each color level of the pixel in the image is subtracted by a noise level, some of the bits are removed and the capacity of the image file is decreased.

CCD noise effects on position accuracy of star sensor

Abstract: Measurement accuracy of star point is an important character of star sensor accuracy,and it is restricted by optical system error,CCD image sensor noise,circuit noise,arithmetic,etc.Image sensor noise is not negligible,but it is studied rarely.So noise of TH7890M CCD chip,which was used for developing star sensor,was calculated quantitatively.Then based on the subpixel centroid arithmetic,RMS error of different noises was deduced respectively according to respective different noises distribution regular.At last,CCD centroid position accuracy model was received by synthesis.The results show that TH7890M CCD chip has three main noises,i.e.readout noise,photon shot noise and random noise caused by photoresponse nonuniformity,and the preceding two are the main factors which affect star sensor accuracy.For star position estimation,CCD noises can achieve accuracy level of 1/40 pixel for a 6 magnitude stars.

Hit noise reduction in some x-ray images

Abstract: The imaging system we have investigating suffer from the appearance of scattered bright points. A usual solution to reduce this noise can be achieved by an increase in exposure but it is very difficult to prevent the hits. In present study, we have investigating algorithms to reduce noise with out an increase in exposure by adopting four digital filters for noise reduction and comparing between efficiency of each filter to determine an efficient method. The resulting images and fidelity criteria showed that the median filter smoothes hit noise while maintaining edge information, but the mean filter image is a blurred version of the noisy image.