Systems and method for optical scatter imaging of latent image plates

• US 20090244636A1
• Filed: 04/13/2009
• Published: 10/01/2009
• Est. Priority Date: 09/08/2005
• Status: Active Grant

• Current Assignee: X-Rite Incorporated (Danaher Corporation)
• Original Assignee: X-Rite Incorporated (Danaher Corporation)
• Inventors: Richardson, Thomas M., Weber, Michael J., Nisper, Jon Kenneth
• Granted Patent: US 8,237,138 B2
• Time in Patent Office: Days
• US Class Current: 358/3.260
• CPC Class Codes: B41C 1/1083 Mechanical aspects of off-press plate preparation B41C1/1008 - B41C1/1066 take precedence
• CPC Class Codes: G06T 2207/20036 Morphological image processing
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/50 using two or more images, e.g. averaging or subtraction
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: G06T 5/92 based on global image properties
• CPC Class Codes: G06T 7/136 involving thresholding

Abstract

Computer-implemented systems and methods for processing image data of a process-free plate are provided according to the present disclosure. The systems and methods may, generally, include a data acquisition step/means for receiving image data using one or more channels of a imaging system, each channel functioning to image the same target region of a process-free plate using a different wavelength of light, and a data processing step/means for filtering the image data using at least one of: (i) self-filtering, (ii) Fourier shrinkage and (iii) Wavelet shrinkage. When the image data is received using a plurality of channels, the received image data may advantageously be combined so as to optimize contrast-to-noise performance. The disclosed systems and methods may advantageously perform the operations of image de-noising, contrast enhancement, and thresholding, and may further involve compensation techniques, e.g., for minimizing distortion and blurring effects.

Claims

1. A computer-implemented method for processing image data of a process-free plate, the method comprising:

(a) a data acquisition step of receiving image data using one or more channels of an imaging system, each channel functioning to image the same target region of a process-free plate using a different wavelength of light;

(b) when image data is received using a plurality of channels, a data processing step of combining the image data from the plurality of channels; and

(c) a data processing step of filtering the image data using at least one of;

(i) self-filtering, (ii) Fourier shrinkage and (iii) Wavelet shrinkage.

2. The method of claim 1, wherein each wavelength of light is around the crosslinking wavelength for the process-free plate.

3. The method of claim 1, further comprising an initial data processing step of general image calibration of the image data received for each of the one or more channels.

4. The method of claim 1, further comprising a preliminary data processing step of computing the logarithm of the image data received for each of the one or more channels.

5. The method of claim 1, wherein the combining the image data from the plurality of channels includes computing a weighted sum of the image data from the plurality of channels.

6. The method of claim 1, wherein self-filtering is used in connection with one or more of:

(i) an anti-blurring compensation technique, and (ii) an anti-distortion compensation technique.

7. The method of claim 6, wherein the anti-blurring compensation technique includes multiplying each filter component by a magnitude of frequency.

8. The method of claim 6, wherein the anti-distortion compensation technique includes at least one of (i) a local anti-distortion compensation technique, and (ii) a global anti-distortion compensation technique.

9. The method of claim 8, wherein the local anti-distortion compensation technique includes applying a local maximum filter to the self-filter and wherein the global anti-distortion compensation technique includes truncating each self-filter magnitude above a defined value to maximum value equal to a fixed fraction of the maximum magnitude of the self-filter.

10. The method of claim 1, wherein Fourier shrinkage includes one of:

(i) soft thresholding, and (ii) hard thresholding.

11. The method of claim 1, wherein an estimate for a threshold value for soft thresholding or hard thresholding is provided as a fixed multiple of an estimate of noise.

12. The method of claim 11, wherein the estimate of noise is determined based on an analysis of the Fourier components outside the known frequency response of a particular screening method used for the process-free plate.

13. The method of claim 1, wherein Fourier shrinkage is used in connection with one or more of:

(i) de-blurring compensation, and (ii) band-pass filtering.

14. The method of claim 1, wherein self-filtering and Fourier shrinkage are used only for process-free plates having a patterned image with a limited range frequency components.

15. The method of claim 1, further comprising a data processing step of threshholding the filtered image data into binary image data based on a threshold value.

16. The method of claim 15, wherein the threshold value is determined using one of:

(i) Otsu'"'"'s method, (ii) Entropy thresholding, and (iii) a direct search of a histogram of the filtered image values for a local minimum between two local maxima.

17. The method of claim 16, wherein Entropy thresholding is used in connection with an error checking function for checking whether the determined threshold value is between the two peaks for a bimodal distribution of filtered image values.

18. The method of claim 15, wherein the imaging system displays a histogram of the filtered image and allows a user to assess potential threshold values.

19. The method of claim 1, further comprising a data processing step of threshold smoothing of the filtered image data.

20. The method of claim 19, wherein threshold smoothing includes one or more morphological operations selected from the group consisting of:

(i) erosion, (ii) dilation, (iii) opening, and (iv) closing.

21. The method of claim 1, wherein the filtered image data is used for at least one of (i) computing dot coverage of the target region of the process-free plate, and (ii) rending the target region of the process-free plate on a display.

22. The method of claim 1, wherein each of the data processing steps is performed by means of a processor.

23. The method of claim 1, wherein, the received image data is specular-excluded image data.

24. The method of claim 1, wherein, the received image data is scatter image data.

25. The method of claim 1, wherein the target region of the process-free plate is illuminated by a band of light around the crosslinking wavelength.

26. An imaging system for processing image data of a process-free plate, the system comprising:

a. one or more channels configured to receive image data, each channel adapted to image the same target region of a process-free plate using a different wavelength of light,

b. processor-implemented means for combining the image data from the plurality of channels so as to optimize contrast-to-noise;

c. processor-implemented means for filtering the image data using at least one of;

(i) self-filtering, (ii) Fourier shrinkage, and (iii) Wavelet shrinkage.