Method and camera (apparatus) for optically capturing a screen

• US 7,706,634 B2
• Filed: 07/19/2005
• Issued: 04/27/2010
• Est. Priority Date: 01/20/2003
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Kostka, Guenther, Schmitt, Peter, Behrendt, Rolf, Schmidt, Dieter
• Primary Examiner(s): Johns; Andrew W
• Assistant Examiner(s): Thomas; Mia M
• Application Number:
  US11/185,658
• Publication Number:
  US 20060023078A1
• Time in Patent Office: 1,743 Days
• Field of Search: 382/294, 382/293, 382/287, 382/276, 382/284, 382/286, 382/275, 348/222.1, 348/207.99, 348571-721
• US Class Current: 382/294
• CPC Class Codes: H04N 23/30 for generating image signals from X-rays
• CPC Class Codes: H04N 5/32 Transforming X-rays cameras or camera modules for generating image signals from X-rays H04N23/30; circuitry of SSIS for transforming X-rays into image signals H04N25/30

Abstract

A camera for optically capturing a screen, wherein the screen has an area and wherein a predetermined overall resolution is provided for the optical capture, comprises a camera support with an array of camera mounts, an array of optical individual cameras as well as an image processing device for processing digital individual images of the array of optical individual cameras to generate the optical capture of the screen with the predetermined overall resolution. The image processing device is effective to reduce a correction of the individual images with regard to alignment inaccuracies and/or parameter variations, wherein for correction purposes a correction resolution is used, which is higher than the overall resolution, and wherein for every individual camera an individual correction rule is used for the correction. After the correction has been performed, the corrected overall image is brought to the predetermined overall resolution by combining adjacent pixels. Thereby, with inexpensive individual cameras, an image of a large-format screen is obtained efficiently, inexpensively and with little artifacts.

Claims

1. A camera for optically capturing a screen, wherein the screen has an area, and wherein a predetermined overall resolution is intended for the optical capture, comprising:

a camera support with an array of camera mounts, which are effective to build an optical arrangement comprising;

an array of optical individual cameras, wherein every optical individual camera is fixed on an associated camera mount, wherein an optical individual camera has a light sensor and an optical imaging device, wherein the light sensor and the optical imaging device are effective to capture a partial area of the screen area with an individual resolution, which is higher than the predetermined overall resolution, wherein the light sensor and the optical imaging device are arranged such that the partial areas of the optical individual cameras partially overlap each other; and

an image processing device for processing digital individual images of the array of optical individual cameras to generate the optical capture of the screen that has an area, with the predetermined overall resolution,

wherein the image processing device is effective to subject the digital individual images to a correction to reduce alignment inaccuracies and parameter variations including scaling variations in the array of optical individual cameras, wherein a correction rule determined for an individual image during calibration is used for the correction, and wherein the correction results in corrected digital individual images having a correction resolution which is higher than the predetermined overall resolution and lower than or equal to the individual resolution used used when capturing the partial areas of the screen area;

wherein the image processing device is effective to assemble, with overlapping areas of the corrected individual images eliminated, the corrected individual images to obtain a corrected overall image having the correction resolution, and

wherein the image processing device is effective to combine adjacent pixels of the corrected overall image to reduce the resolution thereof down to the predetermined overall resolution.

2. The camera according to claim 1, wherein the optical individual The cameras are mounted on the camera support such that the shortest distances of the optical individual cameras to the screen are substantially constant and only vary within a tolerance range.

3. The camera according to claim 2, wherein the image processing device is configured to perform, within the correction, a geometrical correction on the digital individual images after the binning such that the digital individual images maintain the intermediate resolution.

4. The camera according to claim 1, wherein the optical individual cameras are mounted on their associated camera mounts such that they are mechanically adjusted in relation to each other with regard to a rotation of the light sensor around an optical axis of the optical individual camera, which the light sensor comprises, so that a straight line extending across partial areas of the screen area is imaged in individual pixels of the individual cameras, which image the partial areas, as parallel partial straight lines.

5. The camera according to claim 4, wherein the image processing device performs a vertical and/or horizontal displacement of the optical individual images of the individual cameras in relation to each other as correction rule, and to discard a remaining overlapping area in the individual images of the adjacent individual cameras.

6. The camera according to claim 1, wherein the image processing device performs, by pixel address or pixel value manipulations, a vertical and/or horizontal displacement of the individual images, of the optical individual cameras in relation to each other, a rotation and a scaling of the digital individual images as a correction rule, and to discard a remaining overlapping area of the individual images of adjacent optical individual cameras such that, when the corrected individual images are assembled to obtain the corrected overall image, the digital individual images are vertically, horizontally, rotationally and regarding scale adapted to each other.

7. The camera according to claim 1, wherein the image processing device corrects deviating reductions in the optical imaging device of the optical individual cameras.

8. The camera according to claim 1, wherein the image processing device uses a look-up table as the correction rule, wherein an optical individual look-up table is associated to an individual camera.

9. The camera according to claim 1, wherein the optical imaging device of an optical individual camera causes a reduction by a factor of less than 5.

10. The camera according to claim 1,

wherein a number of pixels of the optical capture is equal to a number of pixels of a partial area, and

wherein an individual image has a resolution which is substantially equal to the overall resolution multiplied with the number of optical individual cameras.

11. The camera according to claim 10, wherein the resolution of an individual image is higher than 15 times the overall resolution of the optical capture and the number of the optical individual cameras is higher than 15.

12. The camera according to claim 1, wherein the light sensor of an individual camera is a CCD sensor, which is effective to reduce a maximum resolution of the CCD sensor in integer steps to the individual resolution in an analog way in a binning mode.

13. The camera according to claim 1, wherein the screen is a scintillator screen.

14. The camera according to claim 1, wherein a protective pane, which is X-ray absorbing and optically transparent, is arranged between the screen and the optical imaging device.

15. The camera according to claim 14, wherein the protective pane can be heated during or after radiation with X-rays.

16. The camera according to claim 1, wherein the image processing device comprises:

an individual image memory for every optical individual camera, wherein the image processing device is effective to store a sequence of individual images of the optical individual camera in the image memory for the optical individual camera.

17. The camera according to claim 16, wherein every optical individual camera has an A/D converter on the output side, whose conversion depth is more than 8 bit.

18. The camera according to claim 1, wherein the optical arrangement comprises one or several lenses, mirror optics, fiber optics or a combination of said optical arrangements.

19. The camera according to claim 1, wherein the image processing device is configured to perform the assembling by putting together non-overlapping portions of the corrected individual images.

20. The camera according to claim 1, wherein the image processing device is configured to perform, within the correction

binning on the digital individual images to reduce the individual resolution to obtain the corrected individual images with an intermediate resolution between the individual resolution and the predetermined overall resolution.

21. The camera according to claim 1, wherein the image processing device is effective to perform the the assembling by aligning the corrected individual images in relation to each other under overlapping area elimination, with the overlapping area elimination comprising discarding whole rows and columns in the corrected individual images.

22. A method for optically capturing a screen, wherein the screen has an area, and wherein a predetermined overall resolution is provided for the optical capture, comprising the steps of:

capturing the screen via an array of optical individual cameras, wherein every individual camera is fixed on a camera mount of a camera support, wherein an optical individual camera comprises a light sensor and an optical imaging device, wherein the light sensor and the optical imaging device are effective to capture a partial area of the screen area with an individual resolution, which is higher than the predetermined overall resolution, wherein the light sensor and the optical imaging device are arranged such that the partial areas of the optical individual cameras partially overlap each other; and

processing digital individual images of the array of optical individual cameras to generate the optical capture of the screen with the predetermined overall resolution, wherein the step of processing comprises the following substeps;

correcting the digital individual images to reduce alignment inaccuracies and parameter variations including scaling variations in the array of optical individual cameras, wherein in the step of correcting a correction rule determined for an individual image during calibration is used, and wherein the correction results in corrected individual images having a correction resolution, which is higher than the predetermined overall resolution and lower than or equal to the individual resolution dual images;

assembling, with overlapping areas of the corrected individual images eliminated, the corrected individual images to obtain a corrected overall image having the correction resolution; and

combining adjacent pixels of the corrected overall image to reduce the resolution thereof down to the predetermined overall resolution.