Systems for spectral multiplexing of source images to provide a composite image, for rendering the composite image, and for spectral demultiplexing the composite image, which achieve increased dynamic range in a recovered source image

• US 20040071366A1
• Filed: 10/09/2002
• Published: 04/15/2004
• Est. Priority Date: 10/09/2002
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Zhang, Yeqing, Loce, Robert P., Harrington, Steven J., Sharma, Gaurav
• Granted Patent: US 7,155,068 B2
• Time in Patent Office: Days
• US Class Current: 382/284
• CPC Class Codes: H04N 1/4446 Hiding of documents or document information

Abstract

Methods and apparatus for spectrally-encoding plural source images and for providing the spectrally-encoded plural source images in a composite image, for rendering the composite image in a physical form, or for recovering at least one of the encoded source images from the rendered composite image such that the recovered source image is made distinguishable. The composite image is generated using an image-dependent dynamic range determination so as to provide a maximum usable contrast in a recovered source image.

Claims

1. A method of processing a plurality of source images, comprising the steps of:

encoding the plurality of source images in a composite image according to an image-dependent dynamic range determination so as to provide a maximum usable contrast in at least one recovered source image;

rendering the composite image on a substrate by use of a plurality of colorants; and

recovering the at least one of the encoded source images from the rendered composite image, such that the recovered source image is made distinguishable, by subjecting the rendered composite image to a narrow-band illuminant that is preselected to reveal the source image.

2. The method of claim 1, wherein the recovered source image is made visually detectable by an observer.

3. The method of claim 1, wherein the source image encoding step further comprises the step of mapping values representative of each source image pixel to a corresponding pixel value in a respective colorant image plane.

4. The method of claim 3, wherein the mapped values are determined according to at least one of the following:

(a) the trichromacy of human visual response to colorant/illuminant interaction;

(b) the spectral characteristics of the colorants selected for rendering the composite image, and (c) the spectral characteristics of the narrow-band illuminant(s) used for recovering the source image.

5. The method of claim 3, wherein the source image encoding step further comprises the steps of:

converting at least one source image to a monochromatic separation image; and

mapping the monochromatic separation image to a corresponding colorant image plane in the composite image.

6. The method of claim 5, wherein a narrow band colorant is assigned to a respective colorant image plane of the composite image, and the mapped values in the respective colorant image planes represent the relative amounts of the narrow band colorant to be deposited in the rendered composite image.

7. The method of claim 1, wherein the composite image is rendered as pattern of deposited narrow band colorants, each of which narrow band colorants exhibiting a predefined spectral reflectance characteristic.

8. The method of claim 7, wherein the selected narrow band colorant exhibits a predefined narrow band absorption characteristic.

9. The method of claim 8, wherein the selected narrow band colorant is selected from the group of cyan, magenta, and yellow colorants.

10. The method of claim 1, wherein the narrow band illuminant is selected from the group of red, green, and blue illuminants.

11. The method of claim 1, wherein the rendered composite image is rendered using a digital color electrophotographic printer.

12. An imaging system, comprising:

a spectral multiplexer for receiving image data representative of plural source images and for processing the image data to encode the source images in a composite image according to an image-dependent dynamic range determination so as to provide a maximum usable contrast in at least one recovered source image, and for providing a composite image data signal;

an image rendering device which is responsive to the spectral multiplexer for receiving the composite image data signal and for rendering the composite image on a substrate; and

a demultiplexer for subjecting the rendered composite image on the substrate to illumination by a narrow band illuminant having a selected spectral power distribution, such that the at least one of the encoded source images is made detectable.

13. A system for spectral multiplexing of plural source images, comprising a spectral multiplexer for receiving image data representative of a plurality of source images and for processing the image data to encode the plurality of source images into a composite image data signal according to an image-dependent dynamic range determination so as to provide a maximum usable contrast in at least one recovered source image, wherein values representative of each source image pixel are mapped to a corresponding pixel value in a respective colorant image plane.

14. The system of claim 13, wherein the mapped values are determined according to at least one of the following:

(a) the trichromacy of human visual response to colorant/illuminant interaction;

(b) the spectral characteristics of the colorants selected for rendering the composite image, and (c) the spectral characteristics of the narrow-band illuminant(s) used for recovering the source image.

15. A system for rendering a composite image, comprising an image recording device for receiving the composite image generated according to an image-dependent dynamic range determination so as to provide a maximum usable contrast in a recovered source image, the composite image been provided in the form of a composite image data file, and for rendering the corresponding composite image as a rendered composite image in a plurality of narrow band colorants on a substrate.

16. The system of claim 15, wherein the image recording device is provided in the form of a printer for printing the composite image on a substrate.

17. The system of claim 16, wherein the printer include narrow band colorants selected for their apparent darkness when exposed to at least one of red, green, and blue illuminants.

18. A system for spectral demultiplexing of a rendered composite image having encoded therein a plurality of source images generated according to an image-dependent dynamic range determination so as to provide a maximum usable contrast in at least one recovered source image, comprising a demultiplexer for subjecting the rendered composite image to illumination by a narrow band illuminant having a selected spectral power distribution, such that at least one of the encoded source images is made distinguishable.

19. The system of claim 18, wherein the composite image is formed from colorants selected from the group of cyan, magenta, and yellow colorants, and wherein the demultiplexer further comprises a controller and an illuminant source responsive to control by illuminant source control signals provided by the controller, and wherein the narrow band illuminant is selected from the group of red, green, and blue illuminants.

20. The system of claim 19, wherein the controller further comprises a computer, operable according to control programs for generating one or more of the illuminant source control signals, and wherein the illuminant source further comprises a CRT display responsive to the illuminant source control signals for generating a defined field of illumination of narrow band illuminant, whereby a rendered composite image on a substrate may be located within the field of illumination and thereby subjected to illumination by the narrow band illuminant.