New structure low intensity x-ray image system is mainly made of a plane plate mode x-ray intensifier of single proximity focus, a CCD data acquisition and a processing subsystem. This paper presents noise source inside the x-ray image system and its characteristics. By analyzing its components, image noise source of the system is found to contain quantum noise, particulate noise and dark noise of CCD. Thus a new combination method of "multi-frame mean with morphological transform filter" is studied in this paper for imaging noise elimination in the low intensity x-ray image system. Firstly, some frames of images are superimposed for mean image calculation based on the principle of noise non-correlation. Secondly, different with traditional methods of morphological transform filtering algorithm, difference image information is referred in the algorithm for source image de-noising. Based on multi-scale morphological principle, the difference image, obtained from the source image, contains both image noise and characters. After subsequent processing of wavelet translation and fuzzy algorithm, the noise of the difference image is eliminated. Thus when the processed difference image is added onto the last filtered image by the multi-scale morphological filter, the advanced image without noise is achieved which still keeps the source image characters.
New structure low intensity x-ray image system is mainly made of plane plate mode x-ray intensifier of single proximity focus and CCD data acquisition and processing system. The paper explains the noise source and characteristic of the low intensity x-ray image system. By the system composition, the image noise source of low x-ray imaging system is constituted with quantum noise, particulate noise and dark noise of CCD. Then the compound methods of the "multi-frame mean + morphological transform filter" is submitted which deals with the imaging noise. Firstly, some frame images is superimposed, then mean image is calculated from those images, which is under the principle of noise non-correlation. Secondly, distinguishing with the conventional ways of morphological transformation filtering algorithm, the differential image information is referred to de-noising. Under the multi-scale morphological thought, the differential image which is obtained from the source image includes noise and some image details. After the noise of the differential image is cut off by the wavelet translation, the differential image is added to the last filtered image by the multi-scale morphological filter, then the clean image is achieved which has no noise but keeps the image details.
A New type of X-ray imaging intensifier was studied and developed. This intensifier combined with a little focal spot X-ray tube and a miniature high voltage power supply. Our product had performances of small volume, light weight, portable, high luminosity, Low X-ray radiation density and real-time imaging in daylight. The Lixiscope had also characteristics of simple structure, simple process, long lifetime, low cost and easy to application and promotion. The qualification of the imaging tube and the system: field range 50 mm, brightness 15 - 20 Cd/m2, screen resolution greater than or equal to 5 lp/mm, X-ray tube current 0.05-0.10 mA, target voltage 40 - 60 KV (continuous adjustable), DC/AC available, portable 2.5 Kg. To improve the X-ray imaging intensifier, we adopted several technologies as below. The little focal spot X-ray tube (0.5 mm2) and X-ray collimator was used to increase the resolution, maximum 10 lp/mm, the fiber faceplate or light cone output window to increase brightness and field range, nd the large area and high resolution MCP to increase field range. So, the developed X-ray imaging intensifier had found the widely application.
Microchannel plate (MCP) is a device of two-dimension array electron multiplier. The detection ability to 40 - 60 KeV X-ray for MCP was increased by coating the halide such as CsI, CsBr and KBr on input plate of MCP, that forming a reflection X-ray sensitive film in the channel with depth of 2 - 3 times of diameter below the input plate. Experiment results show that the output response of MCP with variable density structure CsI to X-ray is about 5 - 6 times higher than that with constant density structure, and of one order of magnitude stronger than that without coating the film. Comparatively, the output response of MCP with CsI sensing film is best, CsBr medium and KBr bad. The response characteristics of MCP with CsI to X-ray related to film materials, structure, component distribution and process. Several experiment curves denoted the response characteristics to X-ray at different target voltage and current. The results basically accorded with the theory about quantum detection efficiency of reflection X-ray cathode. This new MCP reflection X-ray sensitive film of variable density halide has been successfully applied in X-ray imaging detecting devices. The corresponding detection system will find widely and potential applications in the field of medical diagnosis, nondestructive evaluation and security inspection, etc.
A silicon microchannel plate (Si-MCP), with 15-25 aspect ratio of the microchannel, 6-20 microns diameter and 6-8 microns space, was prepared by Inductively Coupled Plasma (ICP) and LPCVD. The inner surface topography of microchannel was surveyed, the bulk resistance 7.3 mega ohm and electron gain 110 of MCP were tested by ultraviolet optoelectronic method. The plasma-etching lag in processing the microchannel array was analyzed and discussed. Finally, we compared the electron gain of silicon microchannel plate with traditional glass one. Our work proved the feasibility of making Si-MCP by microfabrication and semiconductor process.