System for capturing graphical images using hyperspectral illumination
First Claim
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.
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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.
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Citations
36 Claims
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1. A method for creating a digital master of a graphical image in a hyperspectral form, the method comprising the steps of:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. An apparatus for creating a digital master of a graphical image in a hyperspectral form, the apparatus comprising:
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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. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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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:
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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 (WPλ
) value for the one sensing element value at one of the plurality of hyperspectral bandpasses;
closing the iris diaphragm; and
determining a black point (BPλ
) value for the one sensing element value at the one hyperspectral bandpass. - View Dependent Claims (25)
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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:
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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. - View Dependent Claims (27, 28, 29, 30)
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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:
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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 (RCTλ
) value;
calculating a relative normalized intensity value (Tλ
) for each of the plurality of hyperspectral bandpasses as a function of the RCTλ
value, a white point (WPλ
) value and a black point (BPλ
) value, wherein the WPλ
value is indicative of a light intensity that saturates the sensor and the BPλ
value is indicative of a threshold electronic noise level of the sensor;
storing the Tλ
value for each of the plurality of hyperspectral bandpasses as a hyperspectral trace representing a spectral power distribution;
calculating bandpass delineated intermediate values (Tλ
Sλ
{overscore (x)}λ
, Tλ
Sλ
{overscore (y)}λ
, Tλ
Sλ
{overscore (z)}λ
) for each of the plurality of hyperspectral bandpasses as a function of the Tλ
value, a user-selected Illuminant value (Sλ
) and user-selected Observer values ({overscore (x)}λ
, {overscore (y)}λ
, and {overscore (z)}λ
);
calculating bandpass delineated sum values (ε
Tλ
Sλ
{overscore (x)}λ
, Tλ
Sλ
{overscore (y)}λ
, ε
Tλ
Sλ
{overscore (z)}λ
) for the image portion by respectively summing each of the bandpass delineated intermediate values (Tλ
Sλ
{overscore (x)}, Tλ
Sλ
{overscore (y)}λ
, Tλ
Sλ
{overscore (z)}λ
) for all of the plurality of hyperspectral bandpasses;
calculating tristimulus values (X, Y, Z) for the image portion respectively as kε
Tλ
Sλ
{overscore (x)}λ
, kε
Tλ
Sλ
{overscore (y)}λ
, and kε
Tλ
Sλ
{overscore (z)}λ
, where a constant k is calculated as 100/ε
Sλ
{overscore (y)}λ
; and
storing the tristimulus values (X, Y, Z) for the image. - View Dependent Claims (32, 33, 34, 35, 36)
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Specification