Patent Number: 
Section: claims

1. An X-ray examination method using an X-ray examination apparatus for examining an examining portion of an object by X-ray irradiation, the apparatus including a detection surface for detecting an intensity distribution of an X-ray set and entered to a position specified out of predetermined positions, an X-ray source capable of moving an X-ray focal position on a target surface and generating the X-ray, and a storage device for storing history information on generation of the X-ray at the position on the target surface as the X-ray focal position, the method comprising the steps of:setting the X-ray focal position corresponding to a position of the detection surface specified out of a plurality of first predetermined positions and the examining portion;detecting that an X-ray radiation dosage generated from the set X-ray focal position has exceeded a predetermined amount based on the history information of the storage device;changing and setting a specified position of the detection surface to one of a plurality of second predetermined positions different from the plurality of first predetermined positions according to the detection result;moving the X-ray focal position to a position reset according to the changed detection surface, and generating the X-ray; anddetecting an intensity distribution of the X-ray transmitted through the examining portion on the detection surface. 2. An X-ray examination method according to claim 1, wherein the step of setting the X-ray focal position includes a step of determining the X-ray focal position on the target surface so that the X-ray transmits through the examining portion and enters the detection surface. 3. An X-ray examination method according to claim 1, whereinthe step of changing and setting the specified position includes a step of specifying a plurality of detection surfaces for detecting the X-ray out of the plurality of second predetermined positions;the step of generating the X-ray includes steps of:determining each of the plurality of X-ray focal positions on the target surface so that the X-ray transmits through the examining portion and enters the plurality of detection surfaces, andmoving an irradiating position applied with an electron beam of the X-ray source to the each determined X-ray focal position, and generating the X-ray; andthe method further comprises a step of:reconstructing image data of the examining portion based on data of the detected intensity distribution. 4. An X-ray examination method according to claim 3, wherein the step of detecting that the X-ray radiation dosage has exceeded the predetermined amount includes a step of detecting that at least an accumulated time in which the X-ray is generated from the set X-ray focal position has elapsed a predetermined time. 5. An X-ray examination method according to claim 4, wherein the step of determining each of the plurality of X-ray focal positions includes a step of determining the X-ray focal position excluding a position applied with the electron beam beyond the predetermined time. 6. An X-ray examination method according to claim 4, wherein the step of determining each of the plurality of X-ray focal positions includes a step of determining the X-ray focal position out of a position applied with the electron beam beyond the predetermined time excluding a range determined based on an area coefficient corresponding to a size of an X-ray focus. 7. An X-ray examination method according to claim 1, wherein the step of generating the X-ray includes a step of changing an irradiation position applied with an electron beam on the target surface by deflecting the electron beam, and moving the X-ray focal position. 8. An X-ray examination apparatus for examining an examining portion of an object with X-ray, the X-ray examination apparatus comprising:an X-ray detector having a plurality of detection surfaces for detecting the X-ray, the X-ray detector including a detection position changing part for changing the positions of the plurality of detection surfaces from a plurality of first predetermined positions to a plurality of second predetermined positions different from the plurality of first predetermined positions;an output controller for controlling an output process of the X-ray, the output controller including:a starting point setting part for setting, on the plurality of detection surfaces, each starting point of X-ray emission so that the X-ray transmits through the examining portion of the object and enters the each detection surface,a storage part for storing the each starting position and history information on emission of the X-ray from the each starting position in correspondence to each other, anda detection part for detecting that an accumulated irradiation time has elapsed a predetermined time on the set starting point position based on the history information in the storage part, and outputting the detection result to allow the detection position changing part to change,the starting point setting part resets the each starting point position when change is made by the detection position changing part, the apparatus further comprising:an X-ray output part for moving an X-ray focal position of an X-ray source to the each starting position and generating the X-ray; anda reconstruction part for reconstructing image data of the examining portion based on data of an intensity distribution of the X-ray transmitted through the examining portion detected on the plurality of detection surfaces. 9. An X-ray examination apparatus according to claim 8, wherein the X-ray output part includes a part for deflecting an electron beam and moving an irradiation position on the target surface to move the X-ray focal position. 10. An X-ray examination apparatus according to claim 8, wherein the detection position changing part includes:a rotatable base arranged with the plurality of detection surfaces on a circumference having a predetermined axis as a center; anda rotating part for rotating the rotatable base with the axis as the center;whereinthe positions of the plurality of detection surfaces are changed from the plurality of first predetermined positions to the plurality of second predetermined positions by rotating the rotatable base by a constant angle according to the detection result of the detection part. 11. An X-ray examination apparatus according to claim 8, wherein the starting point setting part sets the each starting point position excluding the position associated with an irradiation time that has elapsed the predetermined time based on the history information. 12. An X-ray examination apparatus according to claim 8, wherein the output part further includes a specifying part for specifying an examining portion of the object.