Patent Number: 
Section: claims

1. An energy spectrum modulation method by using an energy spectrum modulation apparatus, wherein the energy spectrum modulation apparatus comprises a rotation shaft, a first energy spectrum part and a second energy spectrum part both coupled to the shaft, and the energy spectrum modulation method comprises the steps of:modulating by the first energy spectrum modulation part a first X-ray having a first energy spectrum; andmodulating by the second energy spectrum modulation part a second X-ray having a second energy spectrum different from the first energy spectrum;whereinthe first energy spectrum modulation part includes at least one first vane, and the second energy spectrum modulation part includes at least one second vane; andthe mass thickness of the first vane is smaller than or equal to that of the second vane in the direction of the X-rays. 2. The energy spectrum modulation method of claim 1, wherein the first vane is made of material having a first Z value, the second vane is made of material having a second Z value lower than the first Z value. 3. The energy spectrum modulation method of claim 2, wherein the first vane is made of at least one of Pb, W, U and Cu. 4. The energy spectrum modulation method of claim 2, wherein the second vane is made of at least one of B, C, polyethylene and any other hydrogen-rich organic material. 5. The energy spectrum modulation method of claim 2, wherein the first vane and the second vane are arranged alternately and can rotate. 6. A method of discriminating material using X-rays having different energy levels comprising the steps of:generating alternately a first X-ray having a first energy spectrum and a second X-ray having a second energy spectrum;performing energy spectrum modulation for the first X-ray and second X-ray respectively by the energy spectrum modulation method of claim 1;utilizing the modulated first X-ray and second X-ray to interact with an inspected object;collecting the first X-ray and the second X-ray after their interaction with the inspected object to obtain a first detection value and a second detection value; anddiscriminating a material of the inspected object based on the first detection value and the second detection value;wherein the discriminating step includes generating corresponding classification functions from the first detection value and the second detection value, and determining the material of the inspected object based on the classification functions, the classification functions is fitting functions of third and fourth detection values obtained after the first X-ray and the second X-ray interact respectively with predetermined known materials having varying mass thickness. 7. The method of claim 6, wherein the detection values are the transmission intensity of the X-rays after they penetrate through the inspected object. 8. The method of claim 6, wherein the known materials are different materials which represent organic matter, light metal, inorganic matter and heavy metal respectively and whose atomic numbers are known. 9. The method of claim 6 further comprises collecting the first X-ray and the second X-ray after their interaction with the inspected object by a variable gain detector. 10. The method of claim 9, wherein the gain of the detector at the time of collecting the first X-ray is different from that at the time of collecting the second X-ray. 11. A device for discriminating material using X-rays having different energy levels comprising:a ray generation apparatus for generating alternately a first X-ray having a first energy spectrum and a second X-ray having a second energy spectrum;an energy spectrum modulation apparatus for modulating the first X-ray and the second X-ray respectively, wherein the modulated first X-ray and the modulated second X-ray interact with the inspected object;a collecting apparatus for collecting the first X-ray and the second X-ray after their interaction with the inspected object to obtain a first detection value and a second detection value; anda material discrimination apparatus for discriminating a material of the inspected object based on the first detection value and the second detection value;wherein the discriminating apparatus is further adapted to generate corresponding classification functions from the first detection value and the second detection value, and determine the material of the inspected object based on the classification functions, the classification functions are fitting functions of third and fourth detection values obtained after the first and second X-rays interact respectively with predetermined known materials having varying mass thickness. 12. The device of claim 11, wherein the detection values are the transmission intensity of the X-rays after they penetrate through the inspected object. 13. The device of claim 11, wherein the known materials are different materials which represent organic matter, light metal, inorganic matter and heavy metal respectively and whose atomic numbers are known. 14. The device of claim 11, wherein the collecting apparatus has a variable gain. 15. The device of claim 14, wherein the gain of the collecting apparatus at the time of collecting the first X-ray is different from that at the time of collecting the second X-ray. 16. An image processing method comprising the steps of:utilizing a first X-ray having a first energy spectrum and a second X-ray having a second energy spectrum to interact with an inspected object, respectively, wherein the first X-ray and the second X-ray are modulated by the energy spectrum modulation method of claim 1;collecting the first X-ray and the second X-ray after the interaction to obtain a first detection value and a second detection value;comparing the first detection value and the second detection value with a threshold value respectively to judge mass thickness information of the inspected object; andbased on the mass thickness information, combining an image obtained from the first detection value and an image obtained from the second detection value with different weighting factors;for a material having a first mass thickness, the weighting factor for the image from the first detection value is smaller than that for the image from the second detection value; for a material having a second mass thickness larger than the first mass thickness, the weighting factor for the image from the first detection value is greater than that for the image from the second detection value. 17. The image processing method of claim 16, wherein the mass thickness information is determined based on the attenuation of the X-rays from the inspected object.