Machine vision system

Abstract

A fluorescing marker is used in order to mark (for example) a leaf of a multi-leaf collimator and/or the reference points within the field of view. The markers are illuminated with light tuned to cause the markers to fluoresce at a wavelength different to that of the illuminating light. The fluorescence is then detected by a camera. This method allows the image to be captured by the camera with increased contrast. Accordingly, the present invention provides a multi-leaf collimator for a radiotherapeutic apparatus, comprising at least one leaf having a fluorescent marker. The fluorescent marker will usually emit light of a wavelength longer than the incident light, allowing suitable filters to be provided in order to distinguish the light emitted by the markers. A suitable material for use in the fluorescent markers is ruby. The present invention also provides a radiotherapeutic apparatus comprising a multi-leaf collimator as defined above, and a camera arranged to view the fluorescent markers. A source of illumination for the fluorescent markers is ideally monochromatic, or nearly so. The camera can have a filter arranged to substantially prevent light of the wavelength emitted by the source of illumination from entering the camera, thereby improving the contrast of the image. The radiotherapeutic apparatus can also comprise a source of illumination that is optically co-located with a radiation source, to allow the radiation field that will be emitted to be checked visually by an operator. The co-located source is preferably substantially monochromatic, emitting substantially no light at the wavelength of the fluorescent markers. A filter can then be placed over an output of the radiotherapeutic apparatus, for blocking light of the wavelength of the fluorescent markers and thereby enhancing the contrast of the image that is taken of the fluorescent markers.

1 . A leaf for a multi-leaf collimator for a radiotherapeutic apparatus, having a fluorescent marker. 
     
     
         2 . A multi-leaf collimator for a radiotherapeutic apparatus, comprising at least one leaf having a fluorescent marker. 
     
     
         3 . The multi-leaf collimator according to  claim 2  in which substantially all the leaves of the collimator have a fluorescent marker. 
     
     
         4 . The multi-leaf collimator according to  claim 2  in which at least one leaf has a plurality of markers. 
     
     
         5 . The multi-leaf collimator according to  claim 4  in which a plurality of leaves have a plurality of markers, each leaf carrying the markers in a configuration that is different to the configuration of the other leaves. 
     
     
         6 . The multi-leaf collimator according to  claim 2  in which the leaves are mounted on a frame, and the frame has at least one fluorescent marker. 
     
     
         7 . The multi-leaf collimator according to  claim 6  in which the frame has a plurality of fluorescent markers which collectively indicate a maximum field of view of the collimator. 
     
     
         8 . The multi-leaf collimator according to  claim 2  in which the fluorescent marker is arranged to emit light of a wavelength longer than the incident light. 
     
     
         9 . The multi-leaf collimator according to  claim 2  in which the fluorescent marker comprises ruby. 
     
     
         10 . The multi-leaf collimator according to  claim 2  in which the fluorescent marker is spherical. 
     
     
         11 . The multi-leaf collimator according to  claim 2  in which the fluorescent marker is cylindrical. 
     
     
         12 . A radiotherapeutic apparatus comprising the multi-leaf collimator according to  claim 2 , the apparatus further comprising a camera arranged to view the fluorescent markers. 
     
     
         13 . The radiotherapeutic apparatus according to  claim 12  further comprising a source of illumination for the fluorescent markers. 
     
     
         14 . The radiotherapeutic apparatus according to  claim 13  in which the camera has a filter arranged to substantially prevent light of the wavelength emitted by the source of illumination from entering the camera. 
     
     
         15 . The radiotherapeutic apparatus according to  claim 13 , further comprising a radiation source, wherein the source of illumination is optically co-located with the radiation source. 
     
     
         16 . The radiotherapeutic apparatus according to  claim 15  in which the co-located source of illumination is substantially monochromatic. 
     
     
         17 . The radiotherapeutic apparatus according to  claim 15  in which the co-located source of illumination is a point source. 
     
     
         18 . The radiotherapeutic apparatus according to  claim 15  in which the co-located source emits substantially no light at the wavelength of the fluorescent markers. 
     
     
         19 . The radiotherapeutic apparatus according to  claim 15  comprising a filter over an output thereof for blocking light of the wavelength of the fluorescent markers. 
     
     
         20 . An apparatus comprising at least one moveable element to which is attached a fluorescent marker, a source of illumination at an excitation frequency for the fluorescent marker, and a camera arranged to view the moveable element and capable of sensing light at the fluorescence frequency of the marker. 
     
     
         21 . The apparatus according to  claim 20  in which the fluorescent marker comprises ruby. 
     
     
         22 . The apparatus according to  claim 20  in which the camera has a filter arranged to substantially prevent light of the wavelength emitted by the source of illumination from entering the camera. 
     
     
         23 . The apparatus according to  claim 20  in which the source is substantially monochromatic. 
     
     
         24 . The apparatus according to  claim 23  in which the source emits substantially no light at the wavelength of the fluorescent markers.