Method for calibrating a color sorting apparatus

Claim 1

A method of calibrating a plurality of cameras to produce substantially uniform measures of color of imaged objects, the method comprising the steps of: imaging a color standard reference of a same color with each camera and producing color signals from each camera; in a processor, transforming said color signals produced by each said camera in response to said color standard reference into a single hue value, such that said hue value is the same for each said camera imaging said color standard reference said hue value being selectable to define said calibration in a color space, wherein said processor performs a further transformation to provide a stable hue value under predetermined circumstances, wherein said hue value is a function of an angle defined by a predetermined relationship of red, green and blue signals from an imaging device, wherein said further transformation shifts an axis according to angles of each position in a plane, such that said hue value is determined from a position in a line defined by said angle, said position being substantially insensitive to errors to thereby generate a stable hue value, wherein said further transformation produces a hue value, h', defined as: ##EQU7## where ##EQU8## Q=the angle of the position on the UV or V.sub.α V 1 ! V 2 V 1 plane Q 0 =constant 0 ≦π Q 1 =constant 0 ≦π γ.sub. = constant -255 ≦γ 0 ≦255 χ 0 =constant -255 ≦χ 0 ≦255 α=offset -π≦α≦π.

Claim 2

A method of calibrating a plurality of cameras to produce substantially uniform measures of color of imaged objects, the method comprising the steps of: imaging a color standard reference of a same color with each camera and producing color signals from each camera; in a processor, transforming said color signals produced by each said camera in response to said color standard reference into a single hue value, such that said hue value is the same for each said camera imaging said color standard reference said hue value being selectable to define said calibration in a color space, wherein said processor performs a further transformation to provide a stable hue value under predetermined circumstances, wherein said hue value is a function of an angle defined by a predetermined relationship of red, green and blue signals from an imaging device, wherein said further transformation shifts an axis according to angles of each position in a plane, such that said hue value is determined from a position in a line defined by said angle, said position being substantially insensitive to errors to thereby generate a stable hue value, wherein said further transformation produces a hue value, h', defined as: ##EQU7## where ##EQU8## Q=the angle of the position on the UV or V.sub.α V 1 ! V 2 V 1 plane Q 0 =constant 0 ≦π Q 1 =constant 0 ≦π γ.sub. = constant -255 ≦γ 0 ≦255 χ 0 =constant -255 ≦χ 0 ≦255 α=offset -π≦α≦π.

Claim 3

A method of calibrating a plurality of cameras to produce substantially uniform measures of color of imaged objects, the method comprising the steps of: imaging a color standard reference of a same color with each camera and producing color signals from each camera; in a processor, transforming said color signals produced by each said camera in response to said color standard reference into a single hue value, such that said hue value is the same for each said camera imaging said color standard reference said hue value being selectable to define said calibration in a color space, wherein said processor performs a further transformation to provide a stable hue value under predetermined circumstances, wherein said further transformation shifts an axis according to angles of each position in a plane, such that said hue value is determined from a position in a line defined by said angle, said position being substantially insensitive to errors to thereby generate a stable hue value, wherein said further transformation produces a hue value, h', defined as: ##EQU9## where ##EQU10## Q =the angle of the position on the UV or V 2 V 1 plane Q 0 =constant 0≦π Q 1 =constant 0≦π γ.sub. = constant -255≦γ 0 ≦255 χ 0 =constant -255≦χ 0 ≦255 α=offset -≦α≦π.

Claim 4

A method of calibrating a plurality of cameras to produce substantially uniform measures of color of imaged objects, the method comprising the steps of: imaging a color standard reference of a same color with each camera and producing color signals from each camera; in a processor, transforming said color signals produced by each said camera in response to said color standard reference into a single hue value, such that said hue value is the same for each said camera imaging said color standard reference said hue value being selectable to define said calibration in a color space, wherein said processor performs a further transformation to provide a stable hue value under predetermined circumstances, wherein said further transformation shifts an axis according to angles of each position in a plane, such that said hue value is determined from a position in a line defined by said angle, said position being substantially insensitive to errors to thereby generate a stable hue value, wherein said further transformation produces a hue value, h', defined as: ##EQU9## where ##EQU10## Q =the angle of the position on the UV or V 2 V 1 plane Q 0 =constant 0≦π Q 1 =constant 0≦π γ.sub. = constant -255≦γ 0 ≦255 χ 0 =constant -255≦χ 0 ≦255 α=offset -≦α≦π.