Calibration and error correction in multi-channel imaging

1. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

a) producing a sub-image in each channel of the system using a predetermined wavelength;

b) dividing each sub-image produced by the system into a plurality of sub-regions;

c) measuring a geometric distortion introduced by the system in each sub-region of each sub-image by measuring a spatial displacement with respect to a predetermined reference position of an image feature in each sub-region of each sub-image produced by the system using a cross-correlation algorithm for each sub-region of each sub-image;

d) determining a correction factor corresponding to said geometric distortion introduced by the system in each sub-region of each sub-image by calculating correction factors as required to negate said spatial displacement in each sub-region of each sub-image produced by the system;

e) using said correction factor for each sub-region of each sub-image to establish a correction coefficient for each sub-image pixel and to produce a corresponding geometric correction matrix for each sub-image; and

f) applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system.

2. The method of claim 1 , wherein a surface equation is fit through said correction factors and said correction coefficient is obtained from the surface equation.

3. The method of claim 2 , wherein said surface equation is a polynomial.

4. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

a) producing a sub-image in each channel of the system using a predetermined wavelength;

b) measuring a geometric distortion introduced by the system in each sub-image;

c) determining a geometric correction matrix corresponding to said geometric distortion introduced by the system in each sub-image; and

d) applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system;

wherein said geometric distortion is measured using one of said sub-images as a reference.

5. The method of claim 4 , further including the step of repeating steps (a) through (c) using a different wavelength prior to carrying out step (d).

6. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

producing a sub-image in each channel of the system using a predetermined wavelength;

measuring a geometric distortion introduced by the system in each sub-image;

determining a geometric correction matrix corresponding to said geometric distortion introduced by the system in each sub-image;

measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-image;

determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels;

applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system; and

applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system.

7. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

a) producing a sub-image in each channel of the system using a predetermined wavelength;

b) dividing each sub-image produced by the system into a plurality of sub-regions;

c) measuring a geometric distortion introduced by the system in each sub-region of each sub-image;

d) determining a correction factor corresponding to said geometric distortion introduced by the system in each sub-region of each sub-image; and

e) using said correction factor for each sub-region of each sub-image to establish a correction coefficient for each sub-image pixel and to produce a corresponding geometric correction matrix for each sub-image;

f) measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-region of said sub-image;

g) determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels in each sub-region of said sub-image;

h) applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system; and

i) applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system.

8. The system of claim 4 , wherein said measuring means includes:

means for dividing each sub-image produced by the system into a plurality of sub-regions;

means for measuring a geometric distortion introduced by the system in each sub-region of each sub-image;

means for determining a correction factor corresponding to said geometric distortion introduced by the system in each sub-region of each sub-image; and

means for using said correction factor for each sub-region of each sub-image to establish a correction coefficient for each sub-image pixel and to produce a corresponding correction matrix for each sub-image.

9. The system of claim 8 , wherein said measuring means further includes means for measuring a spatial displacement with respect to a predetermined reference position of an image feature in each sub-region of each sub-image produced by the system; and said determining means includes means for calculating correction factors as required to negate said spatial displacement in each sub-region of each sub-image produced by the system.

10. The system of claim 4 , further including means for fitting a surface equation through said correction factors and for obtaining said correction coefficient from the surface equation.

11. The system of claim 10 , wherein said surface equation is a polynomial.

12. A multi-channel imaging system, comprising:

a) means for producing a sub-image in each channel of the system using a predetermined wavelength;

b) means for measuring a geometric distortion introduced by the system in each sub-image;

c) means for determining a geometric correction matrix corresponding to said geometric distortion introduced by the system in each sub-image; and

d) means for applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system;

wherein said means for measuring said geometric distortion utilizes one of said sub-images as a reference.

13. The system of claim 4 , further including means for changing said wavelength.

14. A multi-channel imagine system, comprising:

means for producing a sub-image in each channel of the system using a predetermined wavelength;

means for measuring a geometric distortion introduced by the system in each sub-image;

means for determining a geometric correction matrix corresponding to said geometric distortion introduced by the system in each sub-image;

means for applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system;

means for measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-image;

means for determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels; and

means for applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system.

15. A multi-channel imaging system, comprising:

means for producing a sub-image in each channel of the system using a predetermined wavelength;

means for dividing each sub-images produced by the system into a plurality of sub-regions;

means for measuring a geometric distortion introduced by the system in each sub-region of each sub-image;

means for determining a correction factor corresponding to said geometric distortion introduced by the system in each sub-region of each sub-image;

means for using said correction factor for each sub-region of each sub-image to establish a correction coefficient for each sub-image pixel to produce a corresponding correction matrix for each sub-image;

means for measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-region of said sub-image;

means for determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels in each sub-region of said sub-image;

means for applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system; and

means for applying said geometric correction matrix to remove geometric distortion from measurement sub-images produced by the system.

16. A method of correcting measurement phase data obtained from a multi-channel interferometric imaging system, comprising the steps of:

a) producing a set of sub-images, each sub-image in said set corresponding to a channel of the system;

b) calculating a phase map from said set of sub-images;

c) repeating steps (a) and (b) a plurality of times, each time introducing a phase offset in said set of sub-images, thereby producing a plurality of additional phase maps;

d) averaging said phase map and said additional plurality of phase maps to produce a corrected phase map.

17. The method of claim 16 , wherein said phase offset is random.

18. The method of claim 16 , wherein said phase offset is introduced in a reference path length.

19. The method of claim 1 , further including the following steps:

measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-image;

determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels; and

applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system.

20. The method of claim 4 , further including the following steps:

measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-image;

determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels; and

applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system.

21. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

producing a sub-image in each channel of the system using a predetermined wavelength;

measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-image;

determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels; and

applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system.

22. A method of correcting measurement data obtained from a multi-channel imaging system, comprising the steps of:

a) producing a sub-image in each channel of the system using a predetermined wavelength;

b) dividing each sub-image produced by the system into a plurality of sub-regions;

c) measuring an intensity distortion introduced by the system in a plurality of pixels in each sub-region of said sub-image;

d) determining a transfer-function correction matrix to produce a uniform intensity response across each of said plurality of pixels in each sub-region of said sub-image; and

e) applying said transfer-function correction matrix to remove intensity distortion from measurement sub-images produced by the system.