Method for evaluating and correcting the image data of a camera system

1. A method for correcting the image data of a camera system for the inspection of colored printed products, comprising the steps of:

(a) providing an observation area adapted to receive and illuminate a printed product;

(b) providing a color camera adapted to generate first, second and third output signals for first, second and third separate color channels in the form of output signal vectors, said first, second and third output signals corresponding to image colors recorded;

(c) aiming said color camera at said printed product in said observation area;

(d) generating said first, second and third camera output signals corresponding to a recorded printed product image;

(e) multiplying said first camera output signal by a first color-channel dependant correction factor and adding the result to a first correction vector to generate a first camera corrected output signal vector;

(f) multiplying said second camera output signal by a second color-channel dependant correction factor and adding the result to a second correction vector to generate a second camera corrected output signal vector;

(g) multiplying said third camera output signal by a third color-channel dependant correction factor and adding the result to a third correction vector to generate a third camera corrected output signal vector;

(h) defining a camera corrected output signal vector matrix comprising said first, second and third camera corrected output signal vectors;

(i) defining a correction matrix comprising selected correction coefficients; said selected correction coefficients being selected by an iterative approximation process and compared to a reference color table; and

(j) multiplying said camera corrected output signal vector matrix with said correction matrix to generate a second corrected output signal vector.

2. The method for correcting the image data of claim 1 , wherein said correction matrix comprises a quadratic correction matrix.

3. The method for correcting the image data of claim 2 , wherein said correction matrix comprises a 3×3 quadratic correction matrix having the selected correction coefficients; said selected correction coefficients being selected by the iterative approximation process and compared to the reference color table of data representing an approximation of the color perception of a human eye.

4. The method for correcting the image data of claim 1 , wherein said color camera's first, second and third output signals are for red, green and blue separate color channels in the form of the output signal vectors, said first, second and third output signals corresponding to red, green and blue colors recorded.

5. The method for correcting the image data of claim 4 , wherein said camera corrected output signal vector matrix comprises red, green and blue camera corrected output signal vectors.

6. The method for correcting the image data of claim 1 , wherein said first, second and third color-channel dependant correction factors are selected to match color balance among red, green and blue colors.

7. The method for correcting the image data of claim 1 , wherein said first, second and third color-channel dependant correction factors are selected to correct contrast and brightness in said first, second and third camera corrected output signal vectors.

8. The method for correcting the image data of claim 1 , further comprising:

(k) assessing said second corrected output signal vector by placing a reference color table in said observation area and recording first, second and third reference color output signals and comparing said second corrected output signal vector with the reference color table data.

9. The method for correcting the image data of claim 8 , further comprising:

(l) selecting, in an iterative process, new values for said correction matrix's selected correction coefficients.

10. The method for correcting the image data of claim 9 , further comprising:

(m) again assessing said second corrected output signal vector when recording said first, second and third reference color output signals and again comparing said second corrected output signal vector with the reference color table data, to determine whether said new values for said selected correction coefficients have more nearly approximated said reference color table data with the newest iteration of said second corrected output signal vector.

11. The method for correcting the image data of claim 10 , further comprising:

(n) keeping said new values for said selected correction coefficients stored in a computer memory only if said new values for said selected correction coefficients have more nearly approximated said reference color table data with the newest iteration of said second corrected output signal vector.

12. The method for correcting the image data of claim 1 , further comprising:

(k) defining a pixel-by-pixel correction matrix comprising selected pixel correction coefficients; said the selected pixel correction coefficients being selected to match intensity values.

13. The method for correcting the image data of claim 12 , further comprising:

(l) multiplying said camera corrected output signal vector matrix with said pixel-by-pixel correction matrix to generate a third corrected output signal vector.

14. The method for correcting the image data of claim 12 , further comprising:

(m) defining a display compensating exponent for a selected image or video display's non-linear characteristics.

15. The method for correcting the image data of claim 14 , further comprising:

(n) generating a fourth corrected output signal vector by raising said third corrected output signal vector to the power of said display compensating exponent.

16. The method for correcting the image data of claim 14 , further comprising:

(o) displaying a fourth corrected output signal vector on said selected image or video display.

17. The method for correcting the image data of claim 1 , further comprising:

(k) selecting illumination source specific values for said correction matrix's selected correction coefficients to compensate for the characteristics of a selected illumination source illuminating said observation area, and assessing said second corrected output signal vector by placing the reference color table in said observation area and recording first, second and third reference color output signals and comparing said second corrected output signal vector with the reference color table data.

18. The method for correcting the image data of claim 17 , further comprising:

(l) selecting, in an iterative process, new values for said correction matrix's selected correction coefficients.

19. The method for correcting the image data of claim 18 , further comprising:

(m) again assessing said second corrected output signal vector when recording said first, second and third reference color output signals and again comparing said second corrected output signal vector with the reference color table data, to determine whether said new values for said selected correction coefficients have more nearly approximated said reference color table data with the newest iteration of said second corrected output signal vector; and

(n) keeping said new values for said selected correction coefficients stored in a computer memory only if said new values for said selected correction coefficients have more nearly approximated said reference color table data with the newest iteration of said second corrected output signal vector.

20. The method for correcting the image data of claim 1 , further comprising:

(k) selecting optical component specific values for said correction matrix's selected correction coefficients to compensate for the characteristics of a selected optical component used in recording said image, and assessing said second corrected output signal vector by placing a CIELAB reference color table in said observation area and recording first, second and third reference color output signals and comparing said second corrected output signal vector with CIELAB reference color table data;

(l) selecting, in an iterative process, new values for said correction matrix's selected correction coefficients;

(m) again assessing said second corrected output signal vector when recording said first, second and third reference color output signals and again comparing said second corrected output signal vector with CIELAB reference color table data, to determine whether said new values for said selected correction coefficients have more nearly approximated said CIELAB reference color table data with the newest iteration of said second corrected output signal vector; and

(n) keeping said new values for said selected correction coefficients stored in a computer memory only if said new values for said selected correction coefficients have more nearly approximated said CIELAB reference color table data with the newest iteration of said second corrected output signal vector.