RELATING TO DETECTORS

Abstract

A method for optimising detector performance in a dual-energy detector system including high-energy X-ray detection and low-energy X-ray detection. The method includes one or more steps from a group including: utilising different scanning rates for high-energy X-ray detection and low-energy X-ray detection; utilising different integration times for high-energy Xray detection and low-energy X-ray detection; and/or utilising different diode sizes for high-energy X-ray detection and low-energy X-ray detection.

Claims

1-51. (canceled)

52. A method for optimising detector performance in a dual-energy detector system comprising high-energy X-ray detection and low-energy X-ray detection, wherein the method comprises: (i) utilising different scanning rates for high-energy X-ray detection and low-energy X-ray detection; (ii) utilising different integration times for high-energy X-ray detection and low-energy X-ray detection; and/or (iii) utilising different diode sizes for high-energy X-ray detection and low-energy X-ray detection.

53. The method as claimed in claim 52 comprising either high-energy X-ray scanning at about 2 to about 32 times faster than low-energy X-ray scanning, or high-energy X-ray scanning at about 2 to about 8 times faster than low-energy X-ray scanning.

54. The method as claimed in claim 52 comprising either utilising different integration times from about 5 milliseconds (ms) to about 200 microseconds (s), or utilising different integration times from about 5 milliseconds to about 1 millisecond.

55. The method as claimed in claim 52 comprising combining an image created by high-energy X-ray detection with an image created by low-energy X-ray detection, so as to substantially precisely synchronise the images.

56. The method as claimed in claim 55 comprising improving synchronisation by utilising smaller diode sizes for high-energy X-ray detection, so as to compensate for a difference in photon flux at the different energy levels of high- and low-energy X-ray detectors.

57. The method as claimed in claim 52, wherein high-energy X-ray detection and low-energy X-ray detection are conducted in, either (i) substantially the same plane of detection, or (ii) substantially parallel planes.

58. The method as claimed in claim 52 comprising aligning focal point(s) of high-energy X-ray detection and low-energy X-ray detection.

59. The method as claimed in claim 58 comprising aligning the focal points at, either (i) a distance yl from a conveyor bed or object plane of an apparatus, or (ii) a distance y2 from an approximate top of an item to be scanned.

60. The method as claimed in claim 52 further comprising creating a pseudo X-ray image of an item to be scanned using laser height measurement means or laser height measurement means and one or more known or predicted properties of said item to be scanned, and comparing the pseudo X-ray image and at least one X-ray image, so as to improve foreign object detection.

61. The method as claimed in claim 60 comprising comparing the pseudo X-ray image with an image created by high-energy X-ray detection and an image created by low-energy X-ray detection.

62. The method as claimed in claim 60 comprising: (i) conducting X-ray detection and laser detection in a coplanar manner, and/or (ii) aligning the focal point(s) of X-ray detection and laser detection.

63. The method as claimed in claim 52 comprising zoning a food product by utilising: (i) laser height measurement means to determine a height profile of various parts of the food product, and selecting one or more zones for preferred data combinations; (ii) geometrical position data within about 30 mm, about 20 mm or about 10 mm of a periphery of the food product; (iii) X-ray greyscale data, as an alternative way of defining height, and/or (iv) identifying one or more edge regions of the food product and one or more central regions, so as to determine preferred data usage options selected from: laser height measurement data and low-energy X-ray data; dual-energy X-ray data; or laser height measurement data and dual-energy X-ray data.

64. A dual-energy detector system comprising high-energy X-ray detection and low-energy X-ray detection, wherein the system comprises: (i) means for utilising different scanning rates for high-energy X-ray detection and low-energy X-ray detection; (ii) means for utilising different integration times for high-energy X-ray detection and low-energy X-ray detection; and/or (iii) means for utilising different diode sizes for high-energy X-ray detection and low-energy X-ray detection.

65. The detector system as claimed in claim 64 further comprising laser height measurement means for creating a pseudo X-ray image of an item to be scanned and means for comparing the pseudo X-ray image and at least one X-ray image to improve foreign object detection.

66. The detector system as claimed in claim 64 wherein a high-energy X-ray detector, a low-energy X-ray detector and/or a laser height measuring means are mounted so as to be coplanar, in use.

67. An apparatus, for improving bone detection in poultry, the apparatus comprising: laser height measurement means, for creating a pseudo X-ray image of an item to be scanned; X-ray imaging means, for creating an X-ray image of said item; and means for comparing the pseudo X-ray image and the X-ray image, so as to improve foreign object detection in said item.

68. The apparatus as claimed in claim 67, wherein the laser height measurement means comprises means for creating the pseudo X-ray image from data supplied by the laser height measurement means and one or more known or predicted properties of said item to be scanned.

69. The apparatus as claimed in claim 67, wherein the laser height measurement-means and X-ray imaging means are mounted such that, in use, laser detection and X-ray detection are conducted in, either (i) substantially the same plane of detection, or (ii) substantially parallel planes.

70. The apparatus as claimed in claim 67, wherein the apparatus is configured such that a focal point of the laser height measurement means aligns with a focal point of the X-ray imaging means.

Description

[0097] The invention will now be disclosed, by way of example only, with reference to the following drawings, in which:

[0098] FIG. 1 is a schematic perspective view of a dual-energy X-ray and laser detector apparatus;

[0099] FIG. 2 is a schematic side-view of the detector apparatus of FIG. 1; and

[0100] FIG. 3 is a schematic end-view of the detector apparatus of FIG. 1.

[0101] FIG. 1 shows a dual-energy X-ray and laser detector apparatus, generally identified by reference 1. The apparatus 1 includes a conveyor 2 of a production line for supplying a plurality of food products 3 to be tested by the apparatus 1. The apparatus 1 further includes two X-ray detectors, in the form of a high-energy X-ray generator 4 and associated high-energy X-ray detector 5, and a low-energy X-ray generator 6 and associated low-energy X-ray detector 7. The apparatus further includes a laser height measurement detector, in the form of a laser source 8 and a laser profilometer 9. Both X-ray generators 4;6 and the laser profilometer 9 are mounted above the conveyor 2 in a coplanar relationshipthe laser source 8 is also mounted above the conveyor 2 (mountings not shown), such that sequential detection in provided as a food product 3 moves along the conveyor 2.

[0102] In an alternative to what is shown in FIG. 1, the apparatus may be provided by a single X-ray detector, being an X-ray generator and associated detector, in combination with a laser height measurement detector. As a further alternative, the apparatus may be provided by dual-energy X-ray detectors, in the form of a high-energy X-ray generator and associated high-energy X-ray detector and a low-energy X-ray generator and associated low-energy X-ray detector, without a laser height measurement detector.

[0103] General operation of X-ray detectors is known in the art and X-rays are passed through the food product 3 and are detected beneath the conveyor 2. General operation of the laser height measurement detector is also known in the art. Accordingly, neither require a detailed explanation. However, the present invention provides a number of differences to the set-up and operation of those detectors, which will now be further explained.

[0104] The approximate geometries of detection are shown in FIGS. 1 and 2, in particular. The geometry of high-energy X-ray detection is indicated by the region bounded by the dash-dot line having reference 20, the geometry of low-energy X-ray detection is identified by the region bounded by the dash-dot line having reference 21 and the geometry of laser height measurement detection is identified by the region bounded by the dash-dot line having reference 22. As can be noted from those Figures, the geometries of detection 20; 21; 22 are substantially aligned in the sense that the detectors are provided in-line such that a food product 3 passes individually through all detectors in a linear manner and in the sense that those geometries of detection 20; 21; 22 are approximately parallel to each other. In addition, focal points 10; 11 of the X-ray generators 4; 6 and a focal point 12 of the laser profilometer 9 are aligned as shown by line X-X in FIG. 2, and provided at the same path length or distance y2 from the food product 3and path length or distance y1 from the conveyor 2. The distances y2 and y1, where y1>y2, may be from about 300 mm to about 700 mm. FIG. 3, an end-view looking along the conveyor 2, shows alignment of the X-ray generators 4; 6 and the laser profilometer 9, and shows the respective distances y2 and y1, which are common for all of the detectors. This arrangement of geometries of detection 20; 21; 22 and alignment of focal points 10; 11; 12 makes correlation between images easier to calculate. Accordingly, detection of foreign objects in the food product 3 is improved.

[0105] The apparatus includes a system (not shown) having a processor and associated memory for capturing data from the detectors, analysing such data, and providing output images.

[0106] In use, laser height measurement allows one to create a pseudo X-ray imagei.e. an image calculated to show what an X-ray image of the food product 3 being tested would look like if it were pure muscle, with no bone. Such a pseudo X-ray image provides a good reference image against which to compare the true X-ray image or imageswhich image(s) may include bone. Of course, if the data from only one X-ray scan is utilised, the pseudo X-ray image is compared to a single true X-ray image, whereas, in the alternative, if the data from both X-ray scans is utilised, the pseudo X-ray image is compared to both true X-ray images. Comparing the pseudo X-ray and X-ray image(s) is, essentially a process of subtracting the pseudo X-ray image from the real X-ray image(s). If no bone is detected in the food product, there would be practically no difference in the images and a resulting image would be substantially black. However, if a bone is detected in the X-ray image(s), then a difference would be provided in a resulting image such that the bone would be identified by a white-ish region. Such a food product could then be diverted from the main production line for disposal or further review and rework.

[0107] Using chicken breasts as an example, it is often in the occluded regions that any bones will be located, for example, parts of the wishbone may be found in edge regions of the breast. Accordingly, the food product may be zoned so as to identify one or more edge regions in which occlusions may be expected and one or more central regions in which no occlusions are expected. In one example, zoning involves use of laser height measurement data in the system so as to select the one or more edge regions and the one or more central regions. Once zoned, the system determines the best combination of detector data for detecting bones in the one or more edge regions and one or more central regions, and then conducts further analysis. As such, in (typically) edge regions, where laser detection is occluded, the system uses dual-energy detection data. Whereas, in the (typically) central regions, where laser detection is not occluded, the system uses a combination of laser detection data and low-energy X-ray detection data. By way of alternatives, zoning could be achieved through analysis of geometrical data or X-ray detector data. Accordingly, the combinations of detector data described above provide optimum detection at the edges and centre of food products to be scanned.

[0108] Those skilled in the art will understand that aligning the geometries of detectors, whether X-ray or laser, to be coplanar and/or aligning the focal points of detectors makes image correlation easier and improves detection.

[0109] With respect to optimising detector performance in a dual-energy detector system comprising high-energy X-ray detection and low-energy X-ray detection, which can be also in combination with laser height measurement detection, energy discrimination in the two independent X-ray detectors (4; 5 and 6; 7) is achieved by means of, for high-energy, use of a selected scintillator and metal filter, and, for low-energy, use of a selected scintillator or direct conversion.

[0110] The high-energy X-ray generator 4 will operate at, at least, two times the kV of the low-energy generator 6, which will then provide an output photon flux of, at least, four times that of the low-energy generator 6. The high-energy detector (4; 5) will scan the food product 3 faster than the low-energy detector (6; 7) at, at least, four times the rate. This allows the system to combine the data from multiple rows of the high-energy detector (4; 5) in such a combination as to relatively precisely synchronise the image with the low-energy detector image to within +/0.25 of a pixel. The effects of such an arrangement are that: one can match the two detector outputs more accurately, which will optimise the use of the respective dynamic ranges; one can combine multiple rows of the high-energy X-ray detector, thereby improving the signal to noise ratio; and one can achieve more accurate synchronisation between the low- and high-energy X-ray images.

[0111] As an alternative to the above, or in addition, the two X-ray detectors may operate with different integration times, irrespective of the scanning interval, so as to provide a matching output that will optimise the dynamic ranges of the detectors.

[0112] In addition to either varying scanning rates and/or integration times of the two X-ray detectors, a smaller diode size may be used in the array of the high-energy detector 5, so as to help compensate for the difference in photon flux at the different energy levels of the high-energy and low-energy detectors (4; 5 and 6; 7). A combination of this with faster scanning rates for high-energy X-ray detection (i.e. over-scanning) will result in improved detection of metallic foreign bodies in the product. Although it is not wished to be bound by theory, it is well-known that higher-energy detection can result in improved detection of high-atomic number contaminants.

[0113] Other methods for optimising detector performance may be to alter the scintillator and/or metal filter.

[0114] Those skilled in the art will understand that such improved dual-energy X-ray detection may be conducted alone, or in combination with laser height measurement.