03. Trichromatic theory - 2011

03. Trichromatic theory - 2011 - ECE 638: Principles of...

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Unformatted text preview: ECE 638: Principles of Digital Color Imaging Systems Lecture 3: Trichromatic theory of color Synopsis Continue development of mathematical framework for trichromatic theory Review: foundations for trichromatic theory Color matching experiment Grassmans laws for color matching Spectral models for color Surface-illuminant interaction model Review: color matching experiment Review: spectral representation of color R ( ) I ( ) S ( ) Illuminant Stimulus Reflective Surface S ( ) = R ( ) I ( ) Key Result: Development of trichromatic theory Sensor model Reinterpretation of conditions for color match Metamerism Linearity of sensor model Response to monochromatic stimuli Chromaticity diagram Trichromatic sensor model are spectral response functions that characterize the sensor R S = S ( ) Q R ( ) d G S = S ( ) Q G ( ) d B S = S ( ) Q B ( ) d Q B ( ) Q G ( ) Q R ( ) Q R ( ), Q G ( ), Q B ( ) Trichromatic sensor model (cont.) With suitable choices for the spectral response functions , this model applies to the HVS, as well as color capture devices, such as digital cameras and scanners. The 3-tuple response vector represents the system output for color capture devices and an internal signal for the HVS. The subscript S refers to the particular stimulus, in this case Q R ( ), Q G ( ), Q B ( ) ( R S , G S , B S ) S ( ) Trichromatic sensor model for HVS When used to model the HVS, it is common to use the following terminology: Red (R) Long (L) Green (G) Medium (M) Blue (B) Short (S) In this case, the sensor response vector is called the tristimulus vector ( R S , G S , B S ) Color matching condition Two stimuli will match to a human viewer if and only if they have identical tristimulus (vector) values, i.e. where and and are the spectral power distributions corresponding to the stimuli and C 1 = C 2 ( R 1 , G 1 , B 1 ) = ( R 2 , G 2 , B 2 ) R 1 = S 1 ( ) Q R ( )d G 1 = S 1 ( ) Q G ( )d B 1 = S 1 ( ) Q B ( )d R 2 = S 2 ( ) Q R ( )d G 2 = S 2 ( ) Q G ( )d B 2 = S 2 ( ) Q B ( )d S 1 ( ) S 2 ( ) C 1 C 2 Example 1 Ideal block sensor Find response to two different stimuli InkSurvey Quiz: Find response of sensor to S 2 ( ) Example 1 (cont.) Example 1 (cont....
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This note was uploaded on 02/19/2012 for the course ECE 638 taught by Professor Staff during the Fall '08 term at Purdue University-West Lafayette.

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03. Trichromatic theory - 2011 - ECE 638: Principles of...

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