Specular diffuse balance correction method
AssigneeXerox Corporation
InventorPatricia Joanne Donaldson
Life of this patent
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Abstract
According to the invention, a method is provided for calculating a Fractional Area Coverage (FAC) for determining the density of toner to evaluate the effectiveness of a xerographic printing process. The amount of diffuse light being reflected at the specular angle is determined during densitometer calibration and subsequent specular sensor readings are corrected by subtracting a fraction of the diffuse sensor signal from the specular sensor signal. Also provided is a computer readable media having stored computer executable instructions, wherein the computer executable instructions, when executed by a computer, directs a computer to perform a method for calculating a FAC for determining the density of toner to evaluate the effectiveness of a xerographic printing process.
Claims28
A method of calculating a Fractional Area Coverage (FAC) for determining the solid developed mass per unit area (DMA) to evaluate the effectiveness of a xerographic printing process, the method comprising:
- (a) measuring a plurality of test patterns having varying predetermined toner or ink densities formed thereon using a sensing system, the sensing system comprising:
- an illuminator configured to emit a beam of light at a point on a target, thereby producing a generally specular reflectance at a specular angle and generally diffuse reflectance at a diffuse angle;
- a specular sensor configured to detect the generally specular reflectance at the specular angle;
- a diffuse sensor configured to detect the generally diffuse reflectance at the diffuse angle;
- and
- a processor configured to process the generally specular reflectance detected by the specular sensor and the generally diffuse reflectance detected by the diffuse sensor;
- (b) for each of the test patterns measured, calculating a measured FAC value (mFAC) from the specular and diffuse sensor readings for that test pattern;
- (c) calculating the true Fractional Area Coverage (FAC) for each measured test pattern as a function of alpha (α), representing a fraction of diffuse reflectance at the specular angle,
- wherein alpha is calculated as a function of:
- (i) a maximum mFAC value determined from the measurements of the test patterns (SpecFACmax);
- or
- (ii) a slope measured from the maximum mFAC value to the mFAC value corresponding to a highest DMA value in a sweep (SpecSLOPE).
A non-transitory computer readable media having stored computer executable instructions, wherein the computer executable instructions, when executed by a computer, directs a computer to perform a method for calculating a Fractional Area Coverage (FAC) for determining the density of toner to evaluate the effectiveness of a xerographic printing process using a sensing system comprising:
- (a) an illuminator configured to emit a beam of light at a point on a target, thereby producing a generally specular reflectance at a specular angle and generally diffuse reflectance at a diffuse angle;
- (b) a specular sensor configured to detect the generally specular reflectance at the specular angle;
- (c) a diffuse sensor configured to detect the generally diffuse reflectance at the diffuse angle;
- and (d) a processor configured to process the generally specular reflectance detected by the specular sensor and the generally diffuse reflectance detected by the diffuse sensor;
- the method comprising:
- (a) receiving measurements for a plurality of test patterns having different predetermined toner or ink densities formed thereon from the sensing system,
- (b) for each of the test pattern measurements, calculating a measured FAC value (mFAC) from the specular and diffuse sensor readings for that test pattern;
- (c) calculating the true Fractional Area Coverage (FAC) for each measured test pattern as a function of alpha (α), representing a fraction of diffuse reflectance at the specular angle for each measurement,
- wherein alpha is calculated as a function of:
- (i) a maximum mFAC value determined from the measurements of the test patterns (SpecFACmax);
- or
- (ii) a slope measured from the maximum mFAC value to the mFAC value corresponding to a highest DMA value in a sweep (SpecSLOPE).
Dependencies are inferred from the claim text.