Patent Number: 
Section: claims

1. A filter, comprising:a plurality of filter plates configured to adjust an X-ray energy spectrum, wherein the plurality of filter plates comprises three filter plates;a plurality of rails for fixedly supporting the filter plates, the filter plates being provided in a laminated structure on guiders of the plurality of rails;a plurality of cams which are respectively provided with a groove curve on a surface thereof, wherein a surface of one of the cams comprises a second groove curve;a driving wheel configured to drive the plurality of cams; anda plurality of link levers comprising three link levers, each link lever being connected to one of the filter plates at a first end and being mounted to an axis at an opposite second end such that the link lever is rotatable about the axis, each link lever comprising a pin which is in cooperation with the groove curve of the corresponding cam so that the link lever proceeds with a reciprocating movement according to rotation of the corresponding cam to move the filter connected to it into or out of an X-ray passing space, wherein the plurality of cams are respectively located at a left side and a right side of the driving wheel to move the filter plates into the X-ray passing space from different directions, wherein the second groove curve of the one of the cams which is in cooperation with the pin on a third link lever. 2. A filter according to claim 1, wherein the groove curve on each cam is based by:where N is a number of filter thickness states that can be switched, a calculated minimum rotation angle of each cam in each thickness switch by 360°/N;a corresponding radius of the groove curve is set as minimum value when one of the plurality of filter plates is in an O region retreating from the X-ray passing space;the corresponding radius of the groove curve is set as a maximum value when the one of the plurality of filter plates is in a W region advancing into the X-ray passing space;a determination of whether the driving wheel is rotated clockwise or anticlockwise;a setting of the O region and W region of the filter plates according to a space size and structure of a collimator box; anda determination of whether the plurality of cams are located at a left side or a right side of the filter, wherein the O region represents the non X-ray passing space and the W region represents the X-ray passing space. 3. A filter according to claim 2, wherein the plurality of filter plates comprises a first filter plate having a first thickness and a second filter plate having a second thickness such that the filter has one of a first thickness that indicates that there is no filter in the X-ray passing space, a second thickness that indicates that the filter includes the first filter plate with the first thickness in the X-ray passing space, a third thickness that indicates that the filter includes the second filter plate with the second thickness in the X-ray passing and a fourth thickness that indicates that the filter includes the first filter plate and the second filter plate in the X-ray passing space, and wherein, corresponding to each thickness, the plurality of cams will be rotated by an angle of 90° such that the driving wheel is rotated anticlockwise and the plurality of cams are rotated clockwise. 4. A filter according to claim 2, wherein the plurality of filter plates comprises a first filter plate having a first thickness, a second filter plate having a second thickness, and a third filter plate having a third thickness, such that a thickness of the filter is one of zero, the first thickness, the second thickness, a sum of the first thickness and the second thickness, and the third thickness, wherein, corresponding to each thickness, the plurality of cams are rotated by an angle of 72° such that the driving wheel is rotated anticlockwise and the plurality of cams are located respectively at a left side and at a right side of the driving wheel are rotated clockwise, and wherein groove curves for respectively controlling the first filter plate and the third filter plate are respectively provided on a front surface and a back surface of the cam located at the right side. 5. A filter according to claim 2, wherein the plurality of filter plates comprises a first filter plate having a first thickness, a second filter plate having a second thickness, and a third filter plate having a third thickness, such that a thickness of the filter is one of zero, the first thickness, the second thickness, a sum of the first thickness and the second thickness, and a sum of the first thickness, the second thickness, and the third thickness, wherein, corresponding to each thickness, the plurality of cams are rotated by 72° such that the driving wheel is rotated anticlockwise and the plurality of cams located respectively at a left side and at a right side of the driving wheel are rotated clockwise, and wherein groove curves for respectively controlling the first filter plate and the third filter plate are respectively provided on a front surface and a back surface of the cam located at the right side. 6. A filter according to claim 3, wherein the plurality of filter plates are made of copper or tin, and the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm. 7. A filter according to claim 4, wherein the first filter plate and the second filter plate are made of copper or tin, the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm, and the third filter plate is made of tin or copper. 8. A filter according to claim 5, wherein the first filter plate and the second filter plate are made of copper or tin, the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm, and the third filter plate is made of tin or copper. 9. An X-ray imaging apparatus comprising:an X-ray irradiating device configured to emit X-rays; anda filter arranged such that the X-rays pass therethrough, the filter comprising:a plurality of filter plates configured to adjust an X-ray energy spectrum, wherein the plurality of filter plates comprises three filter plates;a plurality of rails for fixedly supporting the filter plates, the filter plates being provided in a laminated structure on guiders of the plurality of rails;a plurality of cams which are respectively provided with a groove curve on a surface thereof, wherein a surface of one of the cams comprises a second groove curve;a driving wheel configured to drive the plurality of cams; anda plurality of link levers comprising three link levers, each link lever being connected to one of the filter plates at a first end and being mounted to an axis at an opposite second end such that the link lever is rotatable about the axis, each link lever comprising a pin which is in cooperation with the groove curve of the corresponding cam so that the link lever proceeds with a reciprocating movement according to rotation of the corresponding cam to move the filter connected to it into or out of an X-ray passing space, wherein the plurality of cams are respectively located at a left side and a right side of the driving wheel to move the filter plates into the X-ray passing space from different directions, wherein the second groove curve of the one of the cams is in cooperation with the pin on a third link lever. 10. An X-ray imaging apparatus according to claim 9, wherein the groove curve on each cam is based by:where N is a number of filter thickness states that can be switched, a calculated minimum rotation angle of each cam in each thickness switch by 360°/N;a corresponding radius of the groove curve is set as minimum value when one of the plurality of filter plates is in an O region retreating from the X-ray passing space;the corresponding radius of the groove curve is set as a maximum value when the one of the plurality of filter plates is in a W region advancing into the X-ray passing space;a determination of whether the driving wheel is rotated clockwise or anticlockwise;a setting of the O region and W region of the filter plates according to a space size and structure of a collimator box; anda determination of whether the plurality of cams are located at a left side or a right side of the filter, wherein the O region represents the non X-ray passing space and the W region represents the X-ray passing space. 11. An X-ray imaging apparatus according to claim 10, wherein the plurality of filter plates comprises a first filter plate having a first thickness and a second filter plate having a second thickness such that the filter has one of a first thickness that indicates that there is no filter in the X-ray passing space, a second thickness that indicates that the filter includes the first filter plate with the first thickness in the X-ray passing space, a third thickness that indicates that the filter includes the second filter plate with the second thickness in the X-ray passing and a fourth thickness that indicates that the filter includes the first filter plate and the second filter plate in the X-ray passing space, and wherein, corresponding to each thickness, the plurality of cams will be rotated by an angle of 90° such that the driving wheel is rotated anticlockwise and the plurality of cams are rotated clockwise. 12. An X-ray imaging apparatus according to claim 10, wherein the plurality of filter plates comprises a first filter plate having a first thickness, a second filter plate having a second thickness, and a third filter plate having a third thickness, such that a thickness of the filter is one of zero, the first thickness, the second thickness, a sum of the first thickness and the second thickness, and the third thickness, wherein, corresponding to each thickness, the plurality of cams are rotated by an angle of 72° such that the driving wheel is rotated anticlockwise and the plurality of cams are located respectively at a left side and at a right side of the driving wheel are rotated clockwise, and wherein groove curves for respectively controlling the first filter plate and the third filter plate are respectively provided on a front surface and a back surface of the cam located at the right side. 13. An X-ray imaging apparatus according to claim 10, wherein the plurality of filter plates comprises a first filter plate having a first thickness, a second filter plate having a second thickness, and a third filter plate having a third thickness, such that a thickness of the filter is one of zero, the first thickness, the second thickness, a sum of the first thickness and the second thickness, and a sum of the first thickness, the second thickness, and the third thickness, wherein, corresponding to each thickness, the plurality of cams are rotated by 72° such that the driving wheel is rotated anticlockwise and the plurality of cams located respectively at a left side and at a right side of the driving wheel are rotated clockwise, and wherein groove curves for respectively controlling the first filter plate and the third filter plate are respectively provided on a front surface and a back surface of the cam located at the right side. 14. An X-ray imaging apparatus according to claim 11, wherein the plurality of filter plates are made of copper or tin, and the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm. 15. An X-ray imaging apparatus according to claim 12, wherein the first filter plate and the second filter plate are made of copper or tin, the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm, and the third filter plate is made of tin or copper. 16. An X-ray imaging apparatus according to claim 13, wherein the first filter plate and the second filter plate are made of copper or tin, the first thickness and the second thickness are respectively approximately 0.1 millimeters (mm) and 0.2 mm, and the third filter plate is made of tin or copper.