System for capturing graphical images using hyperspectral illumination

• US 20040141213A1
• Filed: 01/09/2004
• Published: 07/22/2004
• Est. Priority Date: 01/09/2003
• Status: Active Grant

• Current Assignee: Larry Kleiman
• Original Assignee: Larry Kleiman
• Inventors: Kleiman, Larry
• Granted Patent: US 7,583,419 B2
• Time in Patent Office: Days
• US Class Current: 358/474
• CPC Class Codes: G01J 3/2823 Imaging spectrometer
• CPC Class Codes: H04N 1/484 with sequential colour illumination of the original

Abstract

A graphical scanner for scanning a graphical image includes a source for producing an optical beam, a monochromator for dividing the optical beam into a plurality of component beams for hyperspectral bandpasses, a director for directing the component beams to illuminate portions of the graphical image, a sensor for measuring a light intensity for the one or illuminated portions, and a translator for transforming the measured light intensities for each of the one or more portions into hyperspectral traces each representing a spectral power distribution. The translator further transforms the hyperspectral traces into one or more device-independent representations of color.

Claims

1. A method for creating a digital master of a graphical image in a hyperspectral form, the method comprising the steps of:

dividing a light beam from an illumination source into a plurality of component beams each representing one of a plurality of hyperspectral bandpasses, wherein the plurality of hyperspectral bandpasses define a spectrum characterized by wavelengths ranging continuously between 360 and 830 nanometers, and wherein the component beam for each hyperspectral bandpass is characterized by a substantially unique and non-overlapping selection of continuous wavelengths from the spectrum;

successively illuminating one or more portions of the graphical image with each of the plurality of component beams;

measuring a light intensity with a sensor for each of the one or more illuminated portions of the graphical image with respect to each of the plurality of component beams;

transforming each measured light intensity into a relative light intensity based on minimum and maximum light intensities measured by the sensor; and

saving the relative light intensities in a buffer or data file as a hyperspectral trace representing a spectral power distribution.

2. The method of claim 1, further comprising the step of:

transforming the hyperspectral trace into coordinates representing a device-independent color space.

3. The method of claim 1, further comprising the step of:

transforming the hyperspectral trace into coordinates representing a device-dependent color space.

4. The method of claim 1, wherein the one or more portions comprise a plurality of pixels arranged along a first scan line, the illuminating step further comprising the steps of:

forming each of the plurality of component beams as a spot that illuminates a width of a slit defining the first scan line; and

sweeping each of the plurality of component beams across a length of the slit to successively illuminate each pixel in the first scan line.

5. The method of claim 4, further comprising the steps of:

moving the graphical image after successively illuminating each pixel in the first scan line to position a next scan line within the slit, the next scan line comprising a next plurality of pixels; and

sweeping each of the plurality of component beams across a length of the slit to successively illuminate each of the next plurality of pixels in the next scan line.

6. The method of claim 1, wherein the graphical image is a film-based graphical image.

7. The method of claim 4, wherein the transforming step further comprises the steps of:

establishing a linear photodynamic range for a plurality of elements of the sensor by determining a white point (WP_λ

) value and a black point (BP_λ

) value for each sensor element, wherein the WP_λ

value is indicative of a light intensity that saturates the sensor element and the BP_λ

value is indicative of a threshold electronic noise level of the sensor element.

8. An apparatus for creating a digital master of a graphical image in a hyperspectral form, the apparatus comprising:

an illumination source for producing an optical beam;

a hyperspectral bandpass creation apparatus for dividing the optical beam into a plurality of component beams each representing one of a plurality of hyperspectral bandpasses, wherein the plurality of hyperspectral bandpasses define a spectrum characterized by wavelengths ranging continuously between 360 and 830 nanometers, and wherein the component beam for each hyperspectral bandpass is characterized by a substantially unique and non-overlapping selection of continuous wavelengths from the spectrum;

a director for directing each of the plurality of component beams to one or more portions of the graphical image;

a sensor for measuring a light intensity for each of the one or more illuminated portions of the graphical image with respect to each of the plurality of component beams;

a translator for transforming each of the measured light intensities for each of the one or more portions into a relative light intensity based on minimum and maximum light intensities measured by the sensor; and

a buffer for storing each of the the relative light intensities as a hyperspectral trace representing a spectral power distribution.

9. The apparatus of claim 8, wherein the translator further transforms the hyperspectral trace into three-dimensional coordinates representing a location in a device-independent color space.

10. The apparatus of claim 8, wherein the translator further transforms the hyperspectral trace into three-dimensional coordinates representing a location in a device-dependent color space.

11. The apparatus of claim 8, wherein the hyperspectral bandpass creation apparatus is a monochromator.

12. The apparatus of claim 8, wherein the hyperspectral bandpass creation apparatus comprises an optical grating.

13. The apparatus of claim 8, further comprising a first optical device positioned between the illumination source and the hyperspectral bandpass creation device for controlling an intensity of the illumination source.

14. The apparatus of claim 8, further comprising a second optical device positioned between the hyperspectral bandpass creation device and the director for shaping each of the plurality of component beams to illuminate the one or more illuminated portions.

15. The apparatus of claim 8, wherein the director includes a scanning mirror controlled by a servo motor for directing each of the plurality of component beams to the one or more portions of the graphical image.

16. The apparatus of claim 8, further comprising a graphical image translation stage positioned between the director and the sensor for selectively positioning each of the one or more portions of the graphical image in a path of the plurality of component beams.

17. The apparatus of claim 16, further comprising a magnification stage positioned between the graphical image translation stage and the sensor for controlling a spatial scanning resolution of the sensor relative to the graphical image.

18. The apparatus of claim 8, further comprising a sensor translation stage for positioning the sensor to receive light transmitted by the one or more illuminated portions of the graphical image.

19. The apparatus of claim 8, wherein the sensor includes at least one region for actively measuring light intensity for at least one of the one or more portions, and at least one transfer buffer for transferring data indicative of the measured light intensities to the translator.

20. The apparatus of claim 19, wherein the graphical image has a plurality of portions and the at least one region includes a plurality of sensing elements for simultaneously measuring light intensity for each of the plurality of portions, each portion comprising a pixel of the graphical image.

21. The apparatus of claim 8, wherein the sensor and the translator are coupled to an analog to digital converter (ADC), and the ADC receives analog signals output by the sensor, converts the received analog signals into digital data, and inputs the digital data to the translator.

22. The apparatus of claim 21, wherein the sensor and the ADC are coupled via a multiplexer.

23. The apparatus of claim 8, wherein the translator comprises a digital signal processor (DSP), said DSP being equipped to perform parallel pipeline processing.

24. A computer-readable storage medium on which is recorded a program for enabling a host computer system to perform a method for calibrating a multi-element sensor for creating a digital master of a graphical image in a hyperspectral form, the method comprising the steps of:

controlling a director to direct an optical beam to one of one or more sensing elements in a sensor;

controlling an iris diaphragm to adjust an intensity of the optical beam;

measuring a white point (WP) value for the one sensing element, the WP value occurring at a lowest optical beam intensity sufficient to saturate the one sensing element;

determining a first setting of the iris diaphragm to produce the lowest optical beam intensity sufficient to saturate the one sensing element;

controlling a hyperspectral bandpass creation apparatus to divide the optical beam into a plurality of component beams each representing one of a plurality of hyperspectral bandpasses, wherein the plurality of hyperspectral bandpasses define a spectrum characterized by wavelengths ranging continuously between 360 and 830 nanometers, and wherein the component beam for each hyperspectral bandpass is characterized by a substantially unique and non-overlapping selection of continuous wavelengths from the spectrum;

setting the iris diaphragm to the first setting;

determining a white point (WP_λ

) value for the one sensing element value at one of the plurality of hyperspectral bandpasses;

closing the iris diaphragm; and

determining a black point (BP_λ

) value for the one sensing element value at the one hyperspectral bandpass.

25. The computer-readable storage medium of claim 24, wherein the method performed by the program further comprises the steps of:

repeating the determining step to determine a WP_λ

value for the one sensing element value at each of the others of the plurality of hyperspectral bandpasses;

storing the WP_λ

values in a white point buffer;

repeating the determining step to determine a BP_λ

value for the one sensing element value at each of the others of the plurality of hyperspectral bandpasses; and

storing the BP_λ

values in a black point buffer.

26. A computer-readable storage medium on which is recorded a program for enabling a host computer system to scan a graphical image for creating a master of the graphical image in a hyperspectral form, the method comprising the steps of:

controlling a hyperspectral bandpass creation apparatus to divide an optical beam into a plurality of component beams each representing one of a plurality of hyperspectral bandpasses, wherein the plurality of hyperspectral bandpasses define a spectrum characterized by wavelengths ranging continuously between 360 and 830 nanometers, and wherein the component beam for each hyperspectral bandpass is characterized by a substantially unique and non-overlapping selection of continuous wavelengths from the spectrum;

controlling a position of the graphical image;

controlling a director for directing each of the plurality of component beams to illuminate a portion of the graphical image;

controlling a position of a sensor to measure a light intensity of the illuminated portion of the image.

27. The computer-readable storage medium of claim 26, wherein the method performed by the program further comprises the step of:

controlling a first optical device to control an intensity of the optical beam.

28. The computer-readable storage medium of claim 26, wherein the method performed by the program further comprises the step of:

controlling a second optical device to shape each of the plurality of component beams for effectively illuminating the illuminated portion of the graphical image.

29. The computer-readable storage medium of claim 26, wherein the method performed by the program further comprises the step of:

controlling a magnification stage to control a spatial scanning resolution of the sensor relative to the graphical image.

30. The computer-readable storage medium of claim 26, wherein the director is controlled by controlling a servo motor that positions a scanning mirror.

31. A method for transforming light intensities measured by a sensor for a portion of a graphical image into a device-independent representation of color for the image portion, the method comprising the steps of:

receiving an output signal from the sensor indicative of a light intensity for the image portion for each of a plurality of hyperspectral bandpasses, wherein the plurality of hyperspectral bandpasses define a spectrum characterized by wavelengths ranging continuously between 360 and 830 nanometers, and wherein the component beam for each hyperspectral bandpass is characterized by a substantially unique and non-overlapping selection of continuous wavelengths from the spectrum;

converting each of the output signals for the plurality of hyperspectral bandpasses into a raw count digital data (RCT_λ

) value;

calculating a relative normalized intensity value (T_λ

) for each of the plurality of hyperspectral bandpasses as a function of the RCT_λ

value, a white point (WP_λ

) value and a black point (BP_λ

) value, wherein the WP_λ

value is indicative of a light intensity that saturates the sensor and the BP_λ

value is indicative of a threshold electronic noise level of the sensor;

storing the T_λ

value for each of the plurality of hyperspectral bandpasses as a hyperspectral trace representing a spectral power distribution;

calculating bandpass delineated intermediate values (T_λ

S_λ

{overscore (x)}_λ

, T_λ

S_λ

{overscore (y)}_λ

, T_λ

S_λ

{overscore (z)}_λ

) for each of the plurality of hyperspectral bandpasses as a function of the T_λ

value, a user-selected Illuminant value (S_λ

) and user-selected Observer values ({overscore (x)}_λ

, {overscore (y)}_λ

, and {overscore (z)}_λ

);

calculating bandpass delineated sum values (ε

T_λ

S_λ

{overscore (x)}_λ

, T_λ

S_λ

{overscore (y)}_λ

, ε

T_λ

S_λ

{overscore (z)}_λ

) for the image portion by respectively summing each of the bandpass delineated intermediate values (T_λ

S_λ

{overscore (x)}, T_λ

S_λ

{overscore (y)}_λ

, T_λ

S_λ

{overscore (z)}_λ

) for all of the plurality of hyperspectral bandpasses;

calculating tristimulus values (X, Y, Z) for the image portion respectively as kε

T_λ

S_λ

{overscore (x)}_λ

, kε

T_λ

S_λ

{overscore (y)}_λ

, and kε

T_λ

S_λ

{overscore (z)}_λ

, where a constant k is calculated as 100/ε

S_λ

{overscore (y)}_λ

; and

storing the tristimulus values (X, Y, Z) for the image.

32. The method of claim 31, further comprising the steps of:

calculating image values for the image portion for one or more additional device-independent color space models as a function of the stored tristimulus values (X, Y, Z); and

storing the calculated image values for each of the one or more additional device-independent color space models as a computer-readable data file.

33. The method of claim 32, wherein the one or more additional device-independent color space models are selected from the group consisting of CIELAB, CIELUV and CIE xyY models.

34. The method of claim 31, further comprising the steps of:

calculating image values for the image portion for one or more device-dependent color space models as a function of the stored tristimulus values (X, Y, Z); and

storing the calculated image values for each of the one or more additional device-dependent color space models as a computer-readable data file.

35. The method of claim 34, wherein the one or more device-dependent color space models are selected from the group consisting of additive RGB and subtractive CMYK models.

36. The method of claim 31, wherein where the stored hyperspectral trace is used to recalculate alternate Tristimulus Values X, Y, and Z in conjunction with one or more alternatively selected Illuminant values (S_λ

) and alternatively selected Observer values ({overscore (y)}_λ

, {overscore (y)}_λ

, and {overscore (z)}_λ

).