Method and apparatus for sensing color of articles

A method for sensing color of articles, comprising steps of:

• selecting a first pair of wavelengths on a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, wherein said first pair of wavelengths delimits a first range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said first range of wavelengths;
• illuminating with light comprising said first pair of wavelengths a first area of one of said articles;
• measuring light reflected from said first area of one of said articles at said first pair of wavelengths to obtain detected light reflection values corresponding to said first pair of wavelengths;
• producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• selecting at least one secondary wavelength on said reflected light wavelength spectrum;
• illuminating with light comprising said at least one secondary wavelength a second area of said one of said articles;
• measuring light reflected from said second area at said at least one secondary wavelength on said reflected light wavelength spectrum to produce a secondary signal;
• said secondary signal being further indicative of the color of said one of said articles;
• selecting at least one tertiary wavelength on said reflected light wavelength spectrum, said at least one tertiary wavelength having a substantially different value compared to said at least one secondary wavelength;
• illuminating with light comprising said at least one tertiary wavelength said first area of said one of said articles;
• and
• measuring light reflected from said first area at said at least one tertiary wavelength to produce a tertiary signal, said tertiary signal being further indicative of the color of said one of said articles.

A method for sensing the color of articles, comprising steps of:

• selecting a first pair of wavelengths on a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, wherein said first pair of wavelengths delimits a first range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said first range of wavelengths;
• illuminating with light comprising said first pair of wavelengths a first area of one of said articles;
• measuring light reflected from said first area of one of said articles at said first pair of wavelengths to obtain detected light reflection values corresponding to said first pair of wavelengths;
• producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• selecting a second pair of wavelengths on said plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, said second pair of wavelengths delimiting a second distinct range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said second range of wavelengths;
• illuminating with light comprising said second pair of wavelengths said first area of said one of said articles;
• measuring light reflected from said first area of one of said articles at said second pair of wavelengths to obtain detected light reflection values corresponding to said second pair of wavelengths;
• and
• producing a second primary signal representing a resulting difference between said detected light reflection values, said second signal being further indicative of the color of said one of said articles.

A method for sensing the color of articles, comprising steps of:

• selecting a first pair of wavelengths on a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, wherein said pair of wavelengths delimits a first range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said first range of wavelengths;
• illuminating with light comprising said first pair of wavelengths a first area of one of said articles;
• measuring light reflected from said first area of one of said articles at said first pair of wavelengths to obtain detected light reflection values corresponding to said first pair of wavelengths;
• producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• selecting a second pair of wavelengths on said plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, said second pair of wavelengths delimiting a second range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said second range of wavelengths;
• illuminating with light comprising said second pair of wavelengths a second area of said one of said articles;
• measuring light reflected from said second area at said second pair of wavelengths to obtain detected light reflection values corresponding to said second pair of wavelengths;
• and
• producing a second primary signal representing a resulting difference between said detected light reflection values, said second signal being further indicative of the color of said one of said articles.

A method for sensing color of articles, comprising steps of:

• selecting a first pair of wavelengths on a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, wherein said first pair of wavelengths delimits a first range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said first range of wavelengths;
• illuminating with light comprising said first pair of wavelengths a first area of one of said articles;
• measuring light reflected from said first area of one of said articles at said first pair of wavelengths to obtain detected light reflection values corresponding to said first pair of wavelengths;
• producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• selecting at least one secondary wavelength on said reflected light wavelength spectrum;
• illuminating with light comprising said at least one secondary wavelength said first area of said one of said articles;
• measuring light reflected from said first area at said at least one secondary wavelength to produce a secondary signal;
• said secondary signal being further indicative of the color of said one of said articles;.
• selecting at least one tertiary wavelength on said reflected light wavelength spectrum, said at least one tertiary wavelength having a substantially different value compared to said at least one secondary wavelength;
• illuminating with light (98, 120) comprising said at least one tertiary wavelength said first area (101, 128) of said one of said articles (82);
• and
• measuring light reflected (100, 126) from said first area (101, 128) at said at least one tertiary wavelength to produce a tertiary signal, said tertiary signal being further indicative of the color of said one of said articles (82).

An apparatus for sensing color of articles comprising:

• means for placing each of said articles at a viewing location in said apparatus;
• illumination means providing a light output comprising a pair of wavelengths, said light output being directed toward said viewing location for illuminating an area of one of said articles passing at said viewing location, said pair of wavelengths being selected from a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, said pair of wavelengths delimiting a range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said range of wavelengths;
• means for measuring light reflected from said one of said articles at a said first pair of wavelengths to obtain detected light reflection values corresponding to said pair of wavelengths;
• and
• a spectrophotometer for producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles.

An apparatus for sensing color of articles comprising:

• means for placing each of said articles at a viewing location in said apparatus;
• illumination means providing a light output comprising a pair of wavelengths, said light output being directed toward said viewing location for illuminating an area of one of said articles passing at said viewing location, said pair of wavelengths being selected from a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, said pair of wavelengths delimiting a range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said range of wavelengths;
• means for measuring light reflected from said one of said articles at a said first pair of wavelengths to obtain detected light reflection values corresponding to said pair of wavelengths;
• and
• means for producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• wherein said illumination means comprises a first light source providing said light output, and at least one other light source providing at least one further light output, two of said light outputs comprising a respective wavelength of said pair of wavelengths, and at least two optical bandpass filters for receiving a respective one of said light outputs, at least two of said at least two optical bandpass filters having a bandwidth being centered to a respective one of wavelengths of said pair of wavelengths;
• said measuring means comprising at least two photodetectors for receiving a respective reflected light beam corresponding to said at least two of said light outputs and for detecting said light reflection values.

An apparatus for sensing color of articles comprising:

• means for placing each of said articles at a viewing location in said apparatus;
• illumination means providing a light output comprising a pair of wavelengths, said light output being directed toward said viewing location for illuminating area of one of Said articles passing at said viewing location, said pair of wavelengths being selected from a plurality of light reflection curves in terms of a reflected light wavelength spectrum, said curves being associated with a plurality of said articles constituting a sample representative of a color range to be sensed, said pair of wavelengths delimiting a range of wavelengths corresponding to light reflection values in said curves, said light reflection values in each of said curves being in a substantially linear relationship over said range of wavelengths;
• means for measuring light reflected from said one of said articles at a said first pair of wavelengths to obtain detected light reflection values corresponding to said pair of wavelengths;
• and
• means for producing a primary signal representing a resulting difference between said detected light reflection values, said signal being indicative of the color of said one of said articles;
• wherein said light output is further directed toward said viewing location for illuminating at least one other area of one of said articles passing at said viewing location, said apparatus further comprising:
• means for producing at least one other primary signal representing a resulting difference between said detected light reflection values;
• means for accumulating a number of primary signals thereby produced corresponding to said areas of one of said articles;
• and
• means for dividing a sum of said primary signals by the number of signals produced, whereby to produce an average signal which is indicative of the color of said one of said articles.