Composing an image from sub-images

Claim 2

An image pick-up apparatus comprising a first and a second image sensor (2, 3) for converting a first and a second sub image into a first and a second electronic sub-image signal, respectively, and a combination unit for deriving an electronic image signal for a composite image from said first and second electronic sub-image signals, characterized in that the image pick-up apparatus comprises a correction unit for correcting brightness values, comprising a multiplier for multiplying brightness values of an image column of the first sub-image by a column gain factor, and brightness values of an image line of the second sub-image by a line gain factor.

Claim 3

An X-ray examination apparatus, comprising an X-ray source (8) for irradiating an object by means of an X-ray beam in order to form an X-ray image, an X-ray detector for deriving an optical image from the X-ray image, and an image splitter for deriving a first and second sub-image from the optical image, said X-ray examination apparatus comprising an image pick-up apparatus for deriving an electronic image signal of a composite image with corrected brightness values from the sub-images, characterized in that said image pick-up apparatus comprises a first and a second image sensor for converting said first and second sub-image into a first and second electronic sub-image signal, respectively, a combination unit for deriving an electronic image signal for said composite image from said first and second electronic sub-image signals, and a correction unit for correcting brightness values, comprising a multiplier for multiplying brightness values of an image column of the first sub-image by a column gain factor, and brightness values of an image lines of the second sub-image by a line gain factor.

Claim 4

An X-ray examination apparatus, comprising an X-ray source (8) for irradiating an object by means of an X-ray beam in order to form an X-ray image, an X-ray detector for deriving an optical image from the X-ray image, and an image splitter for deriving a first and second sub-image from the optical image, said X-ray examination apparatus comprising an image pick-up apparatus for deriving an electronic image signal of a composite image with corrected brightness values from the sub-images, characterized in that said image pick-up apparatus comprises a first and a second image sensor for converting said first and second sub-image into a first and second electronic sub-image signal, respectively, a combination unit for deriving an electronic image signal for said composite image from said first and second electronic sub-image signals, and a correction unit for correcting brightness values, comprising a multiplier for multiplying brightness values of an image column of the first sub-image by a column gain factor, and brightness values of an image lines of the second sub-image by a line gain factor.

Claim 7

A method as claimed in claim 3, characterized in that the column and line gain factors are derived from brightness values of a first and a second reference image picked up by the first image sensor and the second image sensor, respectively.

Claim 8

A method as claimed in claim 3, characterized in that column gain factors for individual image columns are formed as the quotient of mean brightnesses in corresponding image columns in the first reference image and the second reference image, and respectively, line gain factors for individual image lines are formed as the quotient of mean brightnesses in corresponding image lines in the second reference image and the first reference image, respectively.

Claim 9

A method as claimed in claim 5, characterized in that at least one of the column or line gain factors are derived from said mean brightness values by means of a bisection method.

Claim 10

A method as claimed in claim 3, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 11

A method as claimed in claim 4, characterized in that the first and second sub-images are used as the first and the second reference image, respectively, for calculation of the column and line gain factors, and the column and line gain factors are calculated from brightness values of the first and a second sub-image.

Claim 12

A method as claimed in claim 4, characterized in that column gain factors for individual image columns are formed as the quotient of mean brightnesses in corresponding image columns in the first reference image and the second reference image, respectively, and line gain factors for individual image lines are formed as the quotient of mean brightnesses in corresponding image lines in the second reference image and the first reference image, respectively.

Claim 13

A method as claimed in claim 9, characterized in that at least one of the column or line gain factors are derived from said mean brightness values by means of a bisection method.

Claim 14

A method as claimed in claim 4, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 15

A method as claimed in claim 5, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 16

A method as claimed in claim 6, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 17

A method as claimed in claim 9, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 18

A method as claimed in claim 10, characterized in that said column and line gain factors are stored in a memory, and said column and line gain factors are fetched from the memory for the correction of brightness values of the first and the second sub-image.

Claim 19

A method as claimed in claim 5, characterized in that the first and second sub-images are used as the first and the second reference image, respectively, for calculation of the column and line gain factors, and the column and line gain factors are calculated from brightness values of the first and a second sub-image.

Claim 20

A method as claimed in claim 6, characterized in that the first and second sub-images are used as the first and the second reference image, respectively, for calculation of the column and line gain factors, and the column and line gain factors are calculated from brightness values of the first and a second sub-image.

Claim 21

A method as claimed in claim 9, characterized in that the first and second sub-images are used as the first and the second reference image, respectively, for calculation of the column and line gain factors, and the column and line gain factors are calculated from brightness values of the first and a second sub-image.

Claim 22

A method as claimed in claim 10, characterized in that the first and second sub-images are used as the first and the second reference image, respectively, for calculation of the column and line gain factors, and the column and line gain factors are calculated from brightness values of the first and a second sub-image.