Method and apparatus for sorting objects by color including stable color transformation

A system for sorting objects by color comprising:

• a camera responsive to an object to be imaged to produce color signals;
• a processor responsive to said color signals to execute a transformation of said color signals to a hue value for said object;
• a plurality of color standard references representing an anticipated range of colors of said objects, each of said color standard references when imaged producing color signals from said camera;
• a memory to store hue values for said color standard references;.
• a control system responsive to said hue values of said objects to be sorted to sort said objects into user defined categories, said categories being defined by ranges of hue values around said hue values of said color standard references, wherein each of said range of hue values corresponds to an approximately linear interpolation of hue values between said hue values for each of said pair.

An apparatus for sorting by color items delivered to thereto comprising:

• a plurality of color standard references spanning a range of colors for sorting said items;
• a camera positioned to receive light from said color standard references and subsequently from said items;
• a color processor receiving from said camera color standard signals for each of said color standard references and color signals for each of said items being sorted, said color processor determining a hue value for each said color standard reference and each said item according to a predetermined transform said hue value combining a measure of color and a measure of intensity of said color;
• a memory for storing said hue value for each of said color standard references;
• processing means for comparing said hue value for each said item to said stored hue values and categorizing said item into a sorting category defined by said stored hue values.

An apparatus for sorting by color items delivered to thereto comprising:

• a plurality of color standard references spanning a range of colors for sorting said items;
• a camera positioned to receive light from said color standard references and subsequently from said items;
• a color processor receiving from said camera color standard signals for each of said color standard references and color signals for each of said items being sorted, said color processor determining a hue value for each said color standard reference and each said item according to a predetermined transform;
• a memory for storing said hue value for each of said color standard references;
• processing means for comparing said hue value for each said item to said stored hue values and categorizing said item into a sorting category defined by said stored hue values, wherein said interpolated hue values approximately form a linear interpolation between said points, wherein said memory stores a hue value curve, said hue value curve having points representing measured hue values for each of said color reference standards and interpolated hue values between said points.

An apparatus for sorting by color items delivered to thereto comprising:

• a plurality of color standard references spanning a range of colors for sorting said items;
• a camera positioned to receive light from said color standard references and subsequently from said items;
• a color processor receiving from said camera color standard signals for each of said color standard references and color signals for each of said items being sorted, said color processor determining a hue value for each said color standard reference and each said item according to a predetermined transform;
• a memory for storing said hue value for each of said color standard references;
• processing means for comparing said hue value for each said item to said stored hue values and categorizing said item into a sorting category defined by said stored hue values, wherein at least some of said color standard references are positioned in a sequence such that color contrast between adjacent ones of said at least some is below a predetermined amount.