Color measuring apparatus

A method of making a measurement with illumination angle error compensation in a color measurement device, the measurement device including at least one illumination assembly having a nominal illumination direction with respect to a measurement spot of a measurement object, the illumination assembly including at least two illumination subassemblies each including a light source and having illumination sub-directions which are angularly offset to each other by an angle (Δε) of 4°-8° and enclosing the nominal illumination direction between them, a pick-up assembly for capturing the measurement light radiated back from the measurement spot along an observation direction and for converting the same into corresponding electrical signals, and adjustment parameters for the illumination subassemblies stored in a data storage, the adjustment parameters comprising individual activation durations for each subassembly weighted to provide illumination for a weighted illumination measurement that corrects for the difference between the actual illumination angle and the nominal illumination angle said method comprising:

• activating the pick-up assembly for a first time window;
• individually controlling activation durations of at least two of the illumination subassemblies within one illumination assembly in accordance with the adjustment parameters and within the first time window;
• and
• obtaining a first weighted illumination measurement from the pick-up assembly measurement including two or more illumination sub-directions of an illumination assembly.

A method of making a measurement with illumination angle error compensation in a color measurement device, the measurement device including at least one illumination assembly, the illumination assembly including at least two illumination subassemblies each including a light source, the illumination assembly being oriented with an actual illumination direction with respect to a measurement spot of a measurement object and a nominal illumination direction, each illumination subassembly illuminating the measurement spot from illumination sub-directions that differ from the actual illumination direction by angles of no more than 4° and having a measurement summation weighting factor to correct for the difference between the actual illumination angle and the nominal illumination angle, a pick-up assembly for capturing the measurement light radiated back from the measurement spot along an observation direction and for converting the same into corresponding electrical signals, said method comprising:

• making a first measurement by activating the pick-up assembly for a first time window and individually controlling an activation of a first illumination subassembly within the first time window;
• making a second measurement by activating the pick-up assembly for a second time window and individually controlling an activation of a second illumination subassembly within the second time window;
• weighting each measurement according to each sub assembly's weighting factor;
• and
• summing the weighted measurements to obtain a measurement corrected to the nominal illumination angle.

A color measurement device with illumination angle error compensation for measuring reflectance of a measurement spot of a measurement object, the measurement device comprising:

• at least one illumination assembly having a first actual illumination direction with respect to the measurement spot of the measurement object, the first actual illumination direction corresponding to a first nominal illumination direction, the illumination assembly including at least two illumination subassemblies each including a light source and having illumination sub-directions which are angularly offset from the first actual illumination direction by an angle of no more than 4° and enclosing the first nominal illumination direction between them;
• a pick-up assembly for capturing the measurement light radiated back from the measurement spot along an observation direction and for converting the same into corresponding electrical signals;
• a data storage having adjustment parameters for the illumination subassemblies stored therein, the adjustment parameters including weightings which correct for any difference between the actual illumination angle and the nominal illumination angle;
• a control operatively connected to the at least one illumination assembly, the pick-up assembly, and the data storage, the control operating the illumination assembly and receiving electrical signals from the pick-up assembly in accordance with the adjustment parameters to obtain a weighted measurement.