Abstract:
The present disclosure provides a ray calibration device and a working method thereof, and a radiation imaging system and a working method thereof, and belongs to the field of radiation imaging technology. The present disclosure can solve the problems that the existing calibration devices have low calibration efficiency and require relatively large spaces. The ray calibration device of the present disclosure includes a driving part, a cam part and a calibration part, wherein the calibration part is located below the cam part; the driving part is adapted to drive the cam part to rotate; and the cam part is adapted to exert a force on the calibration part to enable the calibration part to move into a ray area downwards.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    The present disclosure belongs to the field of radiation imaging technology, and specifically relates to a ray calibration device and an operating method thereof, and a radiation imaging system and an operating method thereof. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    At present, in a ray imaging process, the performance of substance penetrated by rays needs to be calibrated to properly adjust the rays and image parameters to obtain a reasonable detection image. In the existing ray imaging technology, common ray calibration devices are divided into independent calibration devices and calibration devices integrated with accelerators (ray sources). The independent calibration device refers to that the calibration device is placed between the ray source and a detector, but this calibration device is generally relatively large in volume and weight, and is generally suitable for environments with relatively large spaces and sites. The calibration device integrated with the accelerator (the ray source) refers to that the calibration device and the accelerator (the ray source) are integrated into one part, so that the ray calibration device is compact in structure and is adaptive to the universal application of vehicle-mounted container detection systems and the calibration requirements of a variety of substances. 
         [0003]    Among the calibration devices integrated with the accelerators (the ray sources), stage-by-stage scanning calibration devices and layer-by-layer superimposition calibration devices are common, but in the structures thereof, lead screws are needed to provide driving forces to cause pressing blocks to reciprocate. Due to such structures that cause the pressing blocks to reciprocate, the calibration efficiency is low, and the necessary spaces are relatively large, which is even unfavorable to the reduction of the volumes of the accelerators. 
       SUMMARY OF THE DISCLOSURE 
       [0004]    In view of the problems that the existing calibration devices have low calibration efficiency and require relatively large spaces, the present disclosure provides a ray calibration device, which is compact in structure, small in space occupancy and high in calibration efficiency, and an operating method thereof, as well as a radiation imaging system and an operating method thereof. 
         [0005]    The technical solution adopted to solve the technical problems in the present disclosure is a ray calibration device, including a driving part, a cam part and a calibration part, wherein 
         [0006]    the calibration part is located below the cam part; 
         [0007]    the driving part is adapted to drive the cam part to rotate; and 
         [0008]    the cam part is adapted to exert a force on the calibration part to enable the calibration part to move into a ray area downwards. 
         [0009]    The calibration part includes a calibration connecting unit and a calibration block, and the calibration block is arranged below the calibration connecting unit and is fixedly connected with the calibration connecting unit; 
         [0010]    the cam part is adapted to exert the force on the calibration connecting unit to enable the calibration connecting unit to move downwards; and 
         [0011]    the calibration connecting unit is adapted to drive the calibration block to move into the ray area downwards. 
         [0012]    The calibration part further includes a reset part, and the reset part is located below the calibration connecting unit and is connected with the calibration connecting unit; and 
         [0013]    the reset part is adapted to provide an upward restoring force for the calibration connecting unit, so that the calibration connecting unit drives the calibration block to return to an initial position. 
         [0014]    The ray calibration device further includes a shielding part, the reset part includes a reset spring, one end of the reset spring is connected to the calibration connecting unit, and the other end of the reset spring is connected to the shielding part. 
         [0015]    The ray calibration device further includes a guide slide rail, a slide block is arranged on the calibration connecting unit to engage with the guide slide rail, and the calibration connecting unit is slidably connected with the guide slide rail through the slide block; and 
         [0016]    the calibration connecting unit moves on the guide slide rail along the vertical direction through the slide block. 
         [0017]    A roller is arranged on the calibration connecting unit; and 
         [0018]    the roller is adapted to rotate when the cam part exerts the force on the calibration connecting unit, in order to reduce the friction force between the calibration connecting unit and the cam part. 
         [0019]    The cam part includes at least one sub-cam, each sub-cam includes a base circle section and a basic block, the basic block is located on the base circle section, a front end of the basic block is of a slope structure, and a rear end of the basic block is of a slope structure; and 
         [0020]    the basic block is adapted to press the calibration connecting unit downwards. 
         [0021]    Each sub-cam further includes at least one additional block, the additional block is arranged on the base circle section and is located behind the basic block, the front end of the additional block is of an inverted slope structure for mating with the slope structure of the rear end of the basic block, and the rear end of the additional block is of a slope structure. 
         [0022]    The structures of the basic blocks of the sub-cams are identical. 
         [0023]    The structures of the additional blocks are identical. 
         [0024]    There is at least one calibration part, and each calibration part corresponds to one sub-cam. 
         [0025]    The cam part comprises a plurality of sub-cams, and the numbers of the additional blocks of the plurality of sub-cams are different. 
         [0026]    The ray calibration device further includes a driving shaft, and the base circle section is sleeved on the driving shaft, so that the sub-cam is arranged on the driving shaft. 
         [0027]    There is a plurality of sub-cams, and the plurality of sub-cams are sequentially arranged on the driving shaft. 
         [0028]    The driving part includes a motor, a driving chain wheel, a driven chain wheel and a transmission chain, the transmission chain is sleeved on the driving chain wheel and the driven chain wheel, and the driven chain wheel is sleeved on the driving shaft; and 
         [0029]    the motor is adapted to drive the driving chain wheel to rotate and drive the driven chain wheel to rotate through the transmission chain, to cause the driving shaft to rotate. 
         [0030]    As another technical solution, the present disclosure further provides a radiation imaging system, including a ray source and a ray calibration device, wherein the ray calibration device is any ray calibration device described above; and 
         [0031]    the ray source is adapted to emit rays to the calibration part, when the calibration part enters the ray area. 
         [0032]    As another technical solution, the present disclosure further provides a working method of a ray calibration device, wherein the ray calibration device includes a driving part, a cam part and a calibration part, the calibration part being located below the cam part, the working method including: 
         [0033]    driving, by the driving part, the cam part to rotate; and 
         [0034]    exerting, by the cam part, a force on the calibration part to enable the calibration part to move into a ray area downwards. 
         [0035]    The working method of the ray calibration device further includes: 
         [0036]    providing, by a reset part, an upward restoring force for a calibration connecting unit of the calibration part, so that the calibration connecting unit drives the calibration block to return to an initial position. 
         [0037]    As another technical solution, the present disclosure further provides a working method of a radiation imaging system, wherein the radiation imaging system includes a ray source and a ray calibration device; and the ray calibration device includes a driving part, a cam part and a calibration part, the calibration part being located below the cam part, the working method including: 
         [0038]    driving, by the driving part, the cam part to rotate; 
         [0039]    exerting, by the cam part, a force on the calibration part to enable the calibration part to move into a ray area downwards; 
         [0040]    emitting, by the ray source, rays to the calibration part, when the calibration part enters the ray area; and 
         [0041]    monitoring parameters of the radiation imaging system by the rays that penetrate through the calibration part. 
         [0042]    In the ray calibration device and the working method thereof, as well as the radiation imaging system and the working method thereof of the present disclosure, the ray calibration device includes the driving part, the cam part and the calibration part, the driving part is adapted to drive the cam part to rotate, the cam part is adapted to exert the force on the calibration part to enable the calibration part to move into the ray area downwards. No lead screw is needed to provide a driving force, and accordingly a pressing block does not need to reciprocate, thus the calibration efficiency is improved; and in addition, the lead screw is linear, and no lead screw needs to be arranged, so that the structure of the ray calibration device can be more compact, and the space occupation area is reduced. 
         [0043]    The ray calibration device of the present disclosure is suitable for the radiation imaging system in which the ray calibration device is integrated with an accelerator (the ray source). 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0044]      FIG. 1  is a schematic structural drawing of a ray calibration device in a first embodiment of the present disclosure; 
           [0045]      FIG. 2  is a schematic drawing of a working state of the ray calibration device in  FIG. 1 ; 
           [0046]      FIG. 3  is a front view of a cam part in  FIG. 1 ; 
           [0047]      FIG. 4  is a side view of the cam part in  FIG. 1 ; 
           [0048]      FIG. 5  is a schematic structural drawing of a sub-cam in  FIG. 1 ; 
           [0049]      FIG. 6  is a schematic structural drawing of a radiation imaging system in a second embodiment of the present disclosure; 
           [0050]      FIG. 7  is a schematic flow diagram of a working method of a ray calibration device in a third embodiment of the present disclosure; 
           [0051]      FIG. 8  is a schematic flow diagram of a working method of a ray calibration device in a fourth embodiment of the present disclosure; 
       
    
    
       [0052]    wherein reference signs are as follows:  1 . driving part;  11 . motor;  12 . driving chain wheel;  13 . transmission chain;  14 . driven chain wheel;  2 . cam part;  21 . sub-cam;  211 . base circle section;  212 . additional block;  213 . basic block;  3 . calibration part;  31 . calibration connecting unit;  311 . roller;  32 . calibration block;  33 . reset part;  4 . shielding part;  5 . guide slide rail;  6 . driving shaft;  100 . ray calibration device; and  200 . ray source. 
       DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0053]    In order that those skilled in the art better understand the technical solutions of the present disclosure, the present disclosure will be further described below in detail in combination with the accompany drawings and specific embodiments. 
       First Embodiment 
       [0054]    Referring to  FIGS. 1 to 5 , the embodiment provides a ray calibration device, including a driving part  1 , a cam part  2  and a calibration part  3 , wherein the calibration part  3  is located below the cam part  2 ; the driving part  1  is adapted to drive the cam part  2  to rotate; and the cam part  2  is adapted to exert a force on the calibration part  3  to enable the calibration part  3  to move into a ray area downwards. 
         [0055]    Preferably, the calibration part  3  includes a calibration connecting unit  31  and a calibration block  32 , and the calibration block  32  is arranged below the calibration connecting unit  31  and is fixedly connected with the calibration connecting unit  31 . 
         [0056]    It can be seen from  FIG. 1  that the calibration connecting unit  31  is arranged on one side close to the cam part  2  above the calibration block  32 . Of course, the calibration connecting unit  31  and the calibration block  32  can be two separate structures, and can also be an integral structure, namely being integrally formed, as long as the calibration connecting unit  31  and the calibration block  32  can fix to each other. 
         [0057]    The cam part  2  is adapted to exert the force on the calibration connecting unit  31  to enable the calibration connecting unit  31  to move downwards; and the calibration connecting unit  31  is adapted to drive the calibration block  32  to move into the ray area downwards. 
         [0058]    Since the calibration connecting unit  31  is arranged above the calibration block  32 , and the force exerted by the cam part  2  acts on the calibration connecting unit  31  earlier than the calibration block  32 , the calibration connecting unit  31  moves downwards earlier due to the force exerted by the cam part  2 . As the calibration connecting unit  31  is fixedly connected with the calibration block  32 , the calibration connecting unit  31  moves downwards and drives the calibration block  32  to move also downwards under the action of the force, so as to enter the ray area. 
         [0059]    Preferably, the calibration part  3  further includes a reset part  33 , and the reset part  33  is located below the calibration connecting unit  31  and is connected with the calibration connecting unit  31 . The reset part  33  is adapted to provide an upward restoring force for the calibration connecting unit  31 , so that the calibration connecting unit  31  drives the calibration block  32  to return to an initial position. The initial position herein refer to a position in which the calibration block  32  is away from the ray area and is not penetrated by the rays. 
         [0060]    Preferably, the ray calibration device further includes a shielding part  4 . The reset part  33  includes a reset spring. One end of the reset spring is connected to the calibration connecting unit  31 , and the other end of the reset spring is connected to the shielding part  4 . The reason why the reset spring is selected is that the reset spring is easy to compress and stretch and can automatically deform in response to the exertion and disappearance of the acting force, in order to provide the restoring force. Of course, the reset part  33  is not limited to the reset spring and can also adopt other structure, as long as the effect of providing the restoring force can be achieved, and this will not be described redundantly herein. 
         [0061]    Preferably, a roller  311  is arranged on the calibration connecting unit  31 ; and the roller  311  is adapted to rotate when the cam part  2  exerts the force on the calibration connecting unit  31 , in order to reduce the friction force between the calibration connecting unit  31  and the cam part  2 . 
         [0062]    Referring to  FIGS. 1 and 2 ,  FIG. 1  is a schematic drawing of a working state of the ray calibration device, and  FIG. 2  is a schematic drawing of another working state of the ray calibration device. When the ray calibration device works, the cam part  2  rotates clockwise under the drive of the driving part  1  and rotates from the position in  FIG. 1  to the position in  FIG. 2 . At this time, the cam part  2  is in contact with the roller  311  and exerts the force on the same to drive the calibration part  3  to move downwards, so the calibration block  32  moves downwards, and a section (that is the area exposed below the shielding part  4  in  FIG. 2 ) of the calibration block  32  enters the ray area, so that the rays penetrate through the section entering the ray area of the calibration block  32 . At this time, the reset part  33  deforms and is compressed. The driving part  1  continuously rotates clockwise to drive the cam part  2  to rotate until the tail end (one end away from the roller  311  in  FIG. 1 ) of the cam part  2  passes by the roller  311 . At this time, the cam part  2  does not exert the force on the calibration part  3  anymore, the reset part  33  recovers its initial shape without force. As the reset part  33  recovers its initial shape, it provides the upward restoring force for the calibration connecting unit  31 , so that the calibration connecting unit  31  drives the calibration block  32  to return to an initial position, namely the position in  FIG. 1 . That is to say, when the roller  311  is not stressed by the force of the cam part  2  anymore, the cam part  2  continuously rotates clockwise until rotating to the position in  FIG. 1 . 
         [0063]    Preferably, the ray calibration device further includes a guide slide rail  5 , a slide block is arranged on the calibration connecting unit  31  to engage with the guide slide rail  5 , and the calibration connecting unit  31  is slidably connected with the guide slide rail  5  through the slide block. The calibration connecting unit  31  is adapted to move on the guide slide rail  5  along the vertical direction through the slide block. 
         [0064]    The guide slide rail  5  is located on one side of the calibration part  3 . The slide block (not shown in the figures) is arranged on the calibration connecting unit  31  to engage with the guide slide rail  5 . The calibration connecting unit  31  is slidably connected with the guide slide rail  5  through the slide block. Of course, a rail identical as the guide slide rail  5  can also be arranged on the calibration connecting unit  31 , and one or more balls are arranged between the guide slide rail  5  and the rail on the calibration connecting unit  31 , thus the calibration connecting unit  31  can be slidably connected with the guide slide rail  5  through the balls. Sliding connection of the calibration connecting unit  31  and the guide slide rail  5  can be achieved in a variety of manners, as long as it can ensure the calibration connecting unit  31  moves on the guide slide rail  5  along the vertical direction through the slide block, and this will not be described redundantly herein. 
         [0065]    As shown in  FIG. 3 to 5 , preferably, the cam part  2  includes at least one sub-cam  21 , and each sub-cam  21  includes a base circle section  211  and a basic block  213 . The basic block  213  is located on the base circle section  211 . Front end of the basic block  213  is of a slope structure, and rear end of the basic block  213  is of a slope structure. The basic block  213  is adapted to press the calibration connecting unit  31  downwards. 
         [0066]    Preferably, each sub-cam  21  further includes at least one additional block  212 , and the additional block  212  is arranged on the base circle section  211  and is located behind the basic block  213 . The front end of the additional block  212  is of an inverted slope structure for mating with the slope structure of the rear end of the basic block  213 , and the rear end of the additional block  212  is of a slope structure. The additional block  212  is also adapted to press the calibration connecting unit  31  downwards. 
         [0067]    The basic block  213  is arranged in each sub-cam  21 , and the basic block  213  is located in front of the additional block  212 , that is to say, the basic block  213  is in contact with the roller  311  earlier than the additional block  212 . The front end of the basic block  213  is of the slope structure, in order to provide buffer, when the basic block  213  is in contact with the roller  311 . It is conceivable if the front end of the basic block  213  is a right angle, even if the basic block is in contact with the roller  311 , the roller  311  cannot “roll” from a vertical side of the basic block  213  to the surface of the basic block  213 . As both ends of the basic block  213  are configured as the slope structures, the situation that the roller  311  cannot “roll” to the surface of the basic block  213  can be avoided, and buffer is provided for enabling the roller  311  to “roll” to the surface of the basic block  213 . As the rear ends of the basic block  213  and the additional block  212  are configured as the slope structures, when the sub-cam  21  is provided with only one basic block  213 , or when a plurality of additional blocks  212  are arranged behind the basic block  213 , a buffer force can be provided for the roller  311  to leave the sub-cam  21 . 
         [0068]    Each sub-cam  21  includes a base circle section  211  and a basic block  213 , and the basic block  213  is located on the base circle section  211 , that is to say, the basic block  213  is fixedly arranged on the base circle section  211 . However, the number of the additional blocks  212  arranged on the base circle section  211  is variable, namely the number of the additional blocks  212  can be increased or decreased according to actual conditions. 
         [0069]    Preferably, the ray calibration device further includes a driving shaft  6 , and the base circle section  211  is sleeved on the driving shaft  6 , so that the sub-cam  21  is arranged on the driving shaft  6 . 
         [0070]    It should be noted that the cam part  2  is arranged on the driving part  1 , and the driving part  1  drives the cam part  2  to rotate around axis of the driving shaft  6 . The ray area is located below the shielding part  4 . The rays are emitted by the ray source. The area passed by rays is the ray area. The ray direction is perpendicular to the shielding part  4 , referring to  FIG. 1  and  FIG. 2 , the rays perpendicularly emit from the interior of a paper surface to the exterior of the paper surface. The shielding part  4  is adapted to shield the calibration part  3 , and is also used as a mounting frame of the ray calibration device for fixing various parts in the ray calibration device. 
         [0071]    Preferably, when there is a plurality of sub-cams  21 , the plurality of sub-cams  21  are sequentially arranged on the driving shaft  6 . Referring to  FIGS. 3 to 5 , the cam part  2  includes at least one sub-cam  21 , and the number of the sub-cams  21  can be adjusted according to actual demands. As shown in  FIG. 3 , 10 sub-cams  21  are sleeved on the driving shaft  6  side by side, the driving shaft  6  passes through the “hole” in the center of the base circle section  211  of each sub-cam  21 , so as to sequentially arrange the plurality of sub-cams  21  together. 
         [0072]    The number of the additional blocks  212  is related to the number of the sub-cams  21 . Take 10 sub-cams  21  as an example. Referring to  FIG. 3 , starting from the left side in the figure, the sub-cams  21  are sequentially numbered and are marked as the first sub-cam, the second sub-cam, . . . the tenth sub-cam. The ray calibration device of the embodiment calibrates the rays in the layer-by-layer superimposition mode, therefore until the last calibration block enters the ray area, the calibration blocks that previously enter the ray area should keep a state within the ray area. Specifically, the number of the additional blocks on the first sub-cam is equal to the total number of the sub-cams minus 1, namely at least 9 additional blocks should be arranged on the first sub-cam, so as to guarantee that when the calibration block corresponding to the tenth sub-cam enters the ray area, the calibration block corresponding to the first sub-cam is still within the ray area. Similarly, at least 8 additional blocks should be arranged on the second sub-cam, so as to guarantee that when the calibration block corresponding to the tenth sub-cam enters the ray area, the calibration block corresponding to the second sub-cam is still within the ray area, and so on. On the tenth sub-cam is at least arranged the basic block  213  and no additional block  212 . The number of the additional block(s)  212  needing to be arranged on each sub-cam can be obtained according to the above rule, and this will not be described redundantly herein. In  FIG. 3 , several additional blocks  212  close to the basic blocks  213  of the first sub-cam to the sixth sub-cam have passed by the corresponding calibration blocks, namely in the state that the calibration blocks are kept within the ray area, while the basic blocks  213  of the seventh sub-cam to the tenth sub-cam do not arrive at the top ends of the base circle sections  211 , and thus the heights of the seventh sub-cam to the tenth sub-cam are lower than those of the first sub-cam to the sixth sub-cam. 
         [0073]    Of course, if there are 10 sub-cams, but not all of the 10 sub-cams need to be used in actual operation, two solutions are available: one is that the unnecessary sub-cams are removed from the driving part  6 ; and the other is that the unnecessary sub-cams are not removed from the driving part  6 , namely all of the 10 sub-cams are retained, the basic blocks  213  and the necessary number of additional blocks  212  are arranged only on the sub-cams needing to be used, the number of the additional blocks  212  can be obtained according to the above rule, and thus this will not be described redundantly herein. 
         [0074]    The reason for such a configuration is that since the sub-cam  21  and the additional blocks  212  on the sub-cam  21  can be increased and decreased, the flexibility of use is improved. Preferably, the structures of the basic blocks  213  of the sub-cams  21  are identical, and the structures of the additional blocks  212  of the sub-cams  21  are identical. The structure herein includes shape, size and other parameters. The reason for such a configuration is that on the one hand, to guarantee that the heights of the sections entering the ray area of the calibration blocks  32  corresponding to each sub-cam  21  are unchanged, the thicknesses of the additional blocks  212  in the same sub-cam  21  should be identical, as shown in  FIG. 5 ; and on the other hand, the types of the parts to be added are simplified, that is to say, the basic blocks  213  on all sub-cams  21  are identical, and the additional blocks  212  on all sub-cams  21  are identical, therefore only three types of parts need to be prepared in use, namely identical basic blocks  213 , identical additional blocks  212  and one base circle section  211 . 
         [0075]    Preferably, there is at least one calibration part  3 , and each calibration part  3  corresponds to one sub-cam  21 . The number of the calibration parts  3  should be identical as the number of the sub-cams  21 , that is to say, in the embodiment, if there are 10 sub-cams  21 , 10 calibration parts  3  should be arranged correspondingly to the 10 sub-cams  21 . 
         [0076]    As mentioned above, when not all of the 10 sub-cams  21  need to be used in actual operation, no basic block  213  or additional block  212  is arranged in the sub-cams  21  that do not need to be used, in this way, as the sub-cam  21  is not provided with the basic block  213  or the additional block  212 , the roller  311  of the calibration part  3  will be not pressed downwards, and thus the calibration block  32  of the calibration part  3  will not be pressed into the ray area. 
         [0077]    Preferably, the driving part  1  includes a motor  11 , a driving chain wheel  12 , a driven chain wheel  14  and a transmission chain  13 , and the transmission chain  13  is sleeved on the driving chain wheel  12  and the driven chain wheel  14 . The motor  11  is adapted to drive the driving chain wheel  12  to rotate and drive the driven chain wheel  14  to rotate through the transmission chain  13 , so as to cause the driving shaft  6  to rotate. 
         [0078]    The motor  11  drives the driving chain wheel  12  to rotate and drives the driven chain wheel  14  to rotate through the transmission chain  13 . As the driven chain wheel  14  is located on the driving shaft  6 , the rotation of the driven chain wheel  14  can drive the driving shaft  6  to rotate, so as to drive the cam part  2  to rotate to exert the force on the calibration part  3 . 
         [0079]    The reason for such a configuration is that as this driving mode similar to a bicycle chain wheel is adopted, the arrangement of a lead screw device in the ray calibration device can be eliminated, so that the space occupation area can be effectively reduced, and the structure of the ray calibration device is more compact. 
         [0080]    The ray calibration device in the embodiment includes the driving part  1 , the cam part  2  and the calibration part  3 . The driving part  1  is adapted to drive the cam part  2  to rotate, and the cam part  2  is adapted to exert the force on the calibration part  3  to enable the calibration part  3  to move into the ray area downwards. No lead screw is needed to provide a driving force, and accordingly a pressing block does not need to reciprocate, thus the calibration efficiency is improved. In addition, as the lead screw is linear, and no lead screw needs to be arranged, the structure of the ray calibration device can be more compact, and the space occupation area is reduced. Meanwhile, the structures of the basic blocks  213  on the sub-cams  21  are identical, and the structures of the additional blocks  212  are also identical, thereby not only guarantee that the heights of the sections entering the ray area of the calibration blocks  32  corresponding to each sub-cam  21  are unchanged, but also simplify the types of the parts to be added. The basic blocks  213  on all sub-cams  21  are identical, and the additional blocks  212  on all sub-cams  21  are identical, therefore only three types of parts need to be prepared in use, namely identical basic blocks  213 , identical additional blocks  212  and one base circle section  211 . 
       Second Embodiment 
       [0081]    Referring to  FIG. 6 , the embodiment provides a radiation imaging system, including a ray source  200  and a ray calibration device  100 , wherein the ray calibration device  100  is the ray calibration device in the first embodiment; and the ray source  200  is adapted to emit rays to the calibration part  3 , when the calibration part  3  enters the ray area. 
         [0082]    The radiation imaging system in the embodiment includes the ray source and the ray calibration device. The ray calibration device includes the driving part, the cam part and the calibration part. The driving part is adapted to drive the cam part to rotate, and the cam part is adapted to exert the force to the calibration part to enable the calibration part to move into the ray area downwards. No lead screw is needed to provide a driving force, and accordingly a pressing block does not need to reciprocate, thus the calibration efficiency is improved. In addition, as the lead screw is linear, and no lead screw needs to be arranged, the structure of the ray calibration device can be more compact, accordingly, the integral structure of the radiation imaging system is more compact, and the space occupation area is reduced. Meanwhile, the structures of the basic blocks  213  on the sub-cams  21  are identical, and the structures of the additional blocks  212  are identical, thereby not only guarantee that the heights of the sections entering the ray area of the calibration blocks  32  corresponding to each sub-cam  21  are unchanged, but also simplify the types of the parts to be added. The basic blocks  213  on all sub-cams  21  are identical, and the additional blocks  212  on all sub-cams  21  are identical, therefore only three types of parts need to be prepared in use, namely identical basic blocks  213 , identical additional blocks  212  and one base circle section  211 . 
       Third Embodiment 
       [0083]    Referring to  FIG. 7 , the embodiment provides a working method of a ray calibration device, wherein the ray calibration device  100  includes a driving part  1 , a cam part  2  and a calibration part  3 , the calibration part  3  being located below the cam part  2 , the working method including: 
         [0084]    step  101 , the driving part  1  drives the cam part  2  to rotate. 
         [0085]    Specifically, the motor  11  drives the driving chain wheel  12  to rotate and drives the driven chain wheel  14  to rotate through the transmission chain  13 , and as the driven chain wheel  14  is located on the driving shaft  6 , the rotation of the driven chain wheel  14  can cause the driving shaft  6  to rotate, so as to drive the cam part  2  to rotate. 
         [0086]    Step  102 , the cam part  2  exerts a force on the calibration part  3  to enable the calibration part  3  to move into a ray area downwards. 
         [0087]    Step  103 , the reset part  33  provides an upward restoring force for the calibration connecting unit  31 , so that the calibration connecting unit  31  drives the calibration block  32  to return to an initial position. 
         [0088]    Specifically, referring to  FIGS. 1 and 2 , the entire operating method can be understood as follows: When the ray calibration device works, the cam part  2  rotates from the position in  FIG. 1  to the position in  FIG. 2  under the drive of the driving part  1 . At this time, the cam part  2  is in contact with the roller  311  and exerts the force on the same to cause the calibration part  3  to move downwards, and the calibration block  32  moves downwards, so that a section (that is the area exposed below the shielding part  4  in  FIG. 2 ) of the calibration block  32  enters the ray area, then the rays penetrate through the section entering the ray area of the calibration block  32 . At this time, the reset part  3  deforms and is compressed. The driving part  1  continuously rotates to drive the cam part  2  to rotate until the tail end of the cam part  2  passes by the roller  311 . At this time, the cam part  2  does not exert the force on the calibration part  3  anymore, and the reset part  33  recovers its initial shape without force. As the reset part  33  recovers its initial shape, it provides the upward restoring force for the calibration connecting unit  31 , so that the calibration connecting unit  31  drives the calibration block  32  to return to the initial position, namely the position in  FIG. 1 , and the current calibration is completed. 
         [0089]    The working method of the ray calibration device provided by the embodiment can be applied to the calibration work of the ray calibration device in the first embodiment, reference can be made to the first embodiment for detailed description, and this will not be described redundantly herein. 
         [0090]    According to the working method of the ray calibration device provided by the embodiment, the driving part  1  drives the cam part  2  to rotate, so that the cam part  2  exerts the force on the calibration part  3  to enable the calibration part  3  to move into the ray area downwards. After the force disappears, the reset part  33  provides the upward restoring force for the calibration connecting unit  31 , so that the calibration connecting unit  31  drives the calibration block  32  to return to the initial position. In the method, no lead screw is needed to provide a driving force, and accordingly a pressing block does not need to reciprocate, thus the calibration efficiency is improved. The cam part  2  is only controlled by the driving part  1  to rotate, so the operation method is simpler and more reliable, and the operation cost is low. 
       Fourth Embodiment 
       [0091]    Referring to  FIG. 8 , the embodiment provides a working method of a radiation imaging system, wherein the radiation imaging system includes a ray source  200  and a ray calibration device  100 ; and the ray calibration device  100  includes a driving part  1 , a cam part  2  and a calibration part  3 , the calibration part  3  being located below the cam part  2 , the working method including: 
         [0092]    Step  201 , the driving part  1  drives the cam part  2  to rotate. 
         [0093]    Step  202 , the cam part  2  exerts a force on the calibration part  3  to enable the calibration part  3  to move into a ray area downwards. 
         [0094]    Step  203 , the ray source  200  emits rays to the calibration part  3 , when the calibration part  3  enters the ray area. 
         [0095]    With respect to the specific methods of the above steps, reference can be made to the third embodiment, and this will not be described herein in detail. 
         [0096]    Step  204 , parameters of the radiation imaging system are monitored by the rays that penetrate through the calibration part  3 . 
         [0097]    After penetrating through the calibration part  3 , the rays will form an image in the radiation imaging system. The parameters of the radiation imaging system can be monitored according to the definition of the image, for example, if the image is unclear, a thinner calibration part  3  or the like can be selected and adjustment can be made according to actual conditions. 
         [0098]    The working method of the radiation imaging system provided by the embodiment can be applied to the calibration work of the radiation imaging system in the second embodiment, reference can be made to the second embodiment for detailed description, and this will not be described redundantly herein. 
         [0099]    According to the working method of the radiation imaging system provided by the embodiment, the parameters of the radiation imaging system can be monitored by the rays that penetrate through the calibration part  3 , so that the operation method is simpler and more reliable, and the operation cost is low. 
         [0100]    It can be understood that the above embodiments are merely exemplary embodiments adopted for illustrating the principle of the present disclosure, but the present disclosure is not limited hereto. Those of ordinary skill in the art can make a variety of modifications and improvements without departing from the spirit and the essence of the present disclosure, and these modifications and improvements shall all fall into the protection scope of the present disclosure.