1. A method for detecting an obstacle by using two cameras, the obstacle being on a reference plane in a field of view common to the two cameras, the method comprising:
inputting a first image and a second image from the two cameras, respectively;
transforming the first image to a transformed image on a basis of image transform which is introduced from a geometrical relationship between a reference plane and the two cameras for transforming any given pixel in a reference plane region in the first image to a corresponding pixel in the second image;
obtaining a degree of similarity D indicating a similarity between an image in a processing region established in the second image and an image in a corresponding processing region established in the first image and being a function of position in the vertical direction of the image;
establishing, when any given image line in a specified region in the second image is a contact line of the obstacle with the reference plane, the processing region for an inter-image arithmetic operation between the first image and the second image, and a plurality of the processing regions being established with the image line being shifted in the vertical direction;
obtaining a degree of similarity P indicating a similarity between an image in the processing region established in the second image and an image in a corresponding processing region established in the transformed image and being a function of position in the vertical direction of the image;
establishing the processing region for an inter-image arithmetic operation between the second image and the transformed image, and a plurality of the processing regions being established with the image line being shifted in the vertical direction;
detecting the obstacle on a basis of the degree of similarity D and the degree of similarity P on a reference plane region; and
obtaining a difference K between the degree of similarity D and the degree of similarity P both obtained as being on the reference plane region;
judging that the obstacle is at a position where the difference K is large; and
determining a width and a height of the processing region on the basis of a position in the vertical direction on the second image.
2. The method as claimed in claim 1, further comprising:
carrying out threshold value processing of the difference K with a threshold value equal to or more than zero, in which the difference K is given as K(y) as a function of y the direction of which is taken as the vertical direction of the image and a result of the threshold value processing of K(y) is taken as Kth(y);
judging that there is none of the obstacle in a case when Kth(y) satisfies
\u2211
y
\u2062
\u2062
K
th
\u2061
(
Y
)
=
0
;
and
judging that a y0 that minimizes
\uf603
\u03b1
\u2062
\u2211
y
\u2062
\u2062
K
th
\u2061
(
y
)
–
\u2211
y
y
0
\u2062
\u2062
K
th
\u2061
(
y
)
\uf604
is the position of the obstacle in the cases other than the above, where \u03b1 is any one of constants from 0 to 1.
3. The method as claimed in claim 1, further comprising:
selecting and outputting either a result of detection of a plurality of the obstacles or a position of an obstacle detected as being the closest to three or more cameras, wherein the two cameras are part of the three or more cameras.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A CT scanning system for generating a CT image of an object, the system comprising:
a multi-pixel x-ray source including a plurality of pixels disposed along a z-axis and adapted to be sequentially activated, each pixel configured to controllably emit x-rays in response to incident electrons, when activated;
a detector array including one or more rows of x-ray detectors, the detectors configured to detect x-rays that are emitted from the pixels and that have traversed the object, and to generate data from detected x-rays; and
an image reconstruction system configured to generate the CT image of the object from the data generated by the x-ray detectors;
wherein the detector array has a number of detector rows, N1, that is reduced compared to a multi-detector row CT scanning system that has a single pixel x-ray source;
wherein the multi-pixel x-ray source and the N1 detector rows are positionable and the activation sequencing of the multi-pixel x-ray source is controllable to provide the same x-ray beam coverage along the z-axis compared to a multi-detector row CT scanning system that has a single pixel x-ray source and a detector array with N rows of detectors, where N is greater than N1.
2. The CT scanning system of claim 1, further comprising a support for the multi-pixel x-ray source and the detector array, the support constructed and arranged so as to rotate the source and the detectors array about the z-axis while the object is being scanned by the CT scanning system; and
wherein the CT scanning system is a third generation helical CT scanning system.
3. The CT scanning system of claim 1, further comprising a controller configured to sequentially activate the pixels, the controller further configured to control timing of the sequential activation of the pixels, as well as duration, intensity, and energy level of x-ray emission by each one of the pixels.
4. The CT scanning system of claim 2, wherein the controller is further configured to sequentially activate the plurality of pixels so as to substantially achieve a same x-ray beam coverage along the z-axis and to generate similar data coverage for a helical reconstruction algorithm that is used in the image reconstruction system, compared to the x-ray beam coverage along the z-axis and the data coverage achieved by a multi-detector row CT helical scanning system that has a single pixel x-ray source.
5. The CT scanning system of claim 1, wherein the CT scanning system includes a single row of x-ray detectors, and the multi-pixel x-ray source includes a plurality N of pixels; and wherein the CT scanning system is adapted and configured to provide the same x-ray coverage along the z-axis as a multi-detector row CT scanning system having N rows of x-ray detectors and a single pixel x-ray source.
6. The CT scanning system of claim 1, wherein the detector array includes a number N1 of rows of x-ray detectors, and the multi-pixel x-ray sources includes a plurality N2 of pixels, where N1\xd7N2=N; and
wherein the CT scanning system is adapted to provide the same x-ray beam coverage along the z-axis as a multi-detector row CT scanning system having a single pixel x-ray source and N rows of x-ray detectors.
7. The CT scanning system of claim 1, wherein the multi-pixel x-ray source is a carbon nanotube field emission x-ray tube; and
wherein the carbon nanotube field emission x-ray tube comprises multiple carbon nanotube field emission cathodes, each of which provides one pixel of electron beam targeting at one anode location to generate one pixel of x-ray beam.
8. The CT scanning system of claim 1, wherein the multi-pixel x-ray source comprises a plurality of vacuum enclosures, each of which comprises an anode and a cathode and each of which is a pixel of the x-ray source.
9. The CT scanning system of claim 1, wherein the multi-pixel x-ray source comprises a plurality of cathodes, and a single anode within one vacuum enclosure.
10. A method of reducing the number of x-ray detector rows in a third generation CT scanning system without affecting x-ray beam coverage along a z-axis, wherein the z-axis is a traveling direction of the object, the method comprising:
providing a multi-pixel x-ray source having a plurality N1 of pixels, and a number N2 of rows of x-ray detectors; and
sequentially activating the pixels along a direction substantially parallel to the z-axis, so as to provide the same x-ray beam coverage as a multi-row detector CT scanning system having a single pixel source and a plurality M of rows of x-ray detectors;
wherein M=N1\xd7N2.
11. A CT system configured to generate a CT image of an object, the CT system comprising:
a multi-pixel x-ray source including a plurality of pixels disposed along a z-axis, each pixel configured to be sequentially activated and to controllably emit x-rays in response to incident electrons, when activated;
a detector array comprising a plurality of rows of x-ray detectors, the detector array stationary with respect to the multi-pixel x-ray source in a direction parallel to the z-axis, the detectors configured to detect x-rays that are emitted from the pixels and that have traversed the object, and to generate data from detected x-rays; and
an image reconstruction system configured to generate the CT image of the object from the data generated by the x-ray detectors;
wherein each pixel is configured to have x-ray beam coverage of the entire detector array, when activated.
12. The CT scanning system of claim 11, further comprising a support for the multi-pixel x-ray source and the detector array, the support constructed and arranged so as to rotate the multi-pixel x-ray source and the detector array about the z-axis while the object is being scanned.
13. The CT scanning system of claim 12, further comprising a controller configured to sequentially activate the pixels, the controller further configured to control timing of the sequential activation of the pixels, as well as duration, intensity and energy level of x-ray emission by each one of the pixels.
14. The CT system of claim 13, wherein the controller is further configured to control the pixels in the multi-pixel x-ray source so that data completeness conditions for an exact reconstruction algorithm that is used in the image reconstruction system is satisfied.
15. The CT system of claim 13, wherein the controller is further configured to activate the pixels in the multi-pixel x-ray source in such a way as to implement a scanning geometry in which a saddle trajectory is implemented for the multi-pixel x-ray source, and in which neither the x-ray source, nor the detector array, nor the scanned object engages in any motion along the z-axis during scanning.
16. The CT system of claim 15, wherein a mathematical parametrization of the saddle trajectory comprises:
\u03b1(\u03bb)=R cos \u03bb, R sin \u03bb, h cos 2\u03bb,
wherein \u03b1(\u03bb) is the source trajectory, \u03bb is the view angle, R is the source to isocenter distance, and h is the half distance of the multi-pixel x-ray source coverage in Z. and wherein hcos2\u03bb specifies the source activation timing with respect to the view angle \u03bb.
17. A method of enhancing image quality in a single rotation single organ CT scan, the method comprising:
providing a multi-pixel x-ray source having a plurality pixels disposed along a z-axis, and a detector array including a plurality of rows of x-ray detectors; wherein each pixel is constructed and arranged to have x-ray coverage of the entire detector array, when the pixel is activated;
rotating the multi-pixel x-ray source and the detector array about the z-axis while the object is being scanned; and
sequentially activating the pixels so that each activated pixel controllably emits x-rays in response to incident electrons, in a way that data completeness conditions for an exact reconstruction algorithm that is used in the image reconstruction system are satisfied.
18. A method of implementing a saddle trajectory in a CT system without tilting rotational gantry or translational conveyor or having the x-ray source, detector array, or the scanning object involving any motion along the z-axis during scanning, the method comprising:
providing a multi-pixel x-ray source having a plurality pixels, and a detector array including a plurality of rows of x-ray detectors; wherein each pixel is constructed and arranged to have x-ray coverage of the entire detector array, when the pixel is activated;
rotating the multi-pixel x-ray source and the detector array about the z-axis while the object is being scanned; and sequentially activating the pixels according to the parameterization formula of hcos2\u03bb which specifies the source activation timing with respect to the view angle \u03bb where h is the half distance of the multi-pixel x-ray source coverage in Z.
19. A stationary CT system with a rectangular opening for generating a CT image of an object, the CT system comprising:
a multi-pixel x-ray source including a plurality of pixels disposed on three sides of the rectangular opening, which is perpendicular to the object translational direction (or z-axis), each pixel configured to be sequentially activated and to controllably emit x-rays in response to incident electrons, when activated;
a detector array that is not rotatable with respect to the multi-pixel x-ray source, the detector array including a plurality of rows of x-ray detectors that are configured to detect x-rays that are emitted from the pixels and that have traversed the object, and to generate data from detected x-rays;
wherein the detectors of each row are disposed on the three sides of the rectangular opening;
a conveyor configured to translate the object along the z-axis during the scan;
an image reconstruction system configured to generate the CT image of the object from the data generated by the x-ray detectors;
wherein two opposite sides of the rectangular opening have both x-ray pixel sources and x-ray detectors; and
wherein one of the remaining sides of the rectangular opening has only x-ray pixel sources, and the other remaining side of the rectangular opening has only x-ray detectors.
20. The system of claim 19, wherein the stationary CT scanning system is usable for screening checked baggage for potential threats at airports.
21. The system of claim 19, wherein the stationary CT scanning system is usable for screening carry-on baggage for potential threats at checkpoints of airports.