X-rite Gmbh

William R Given

Bernard J Berg

Mark A Cargill

David R Bowden

A densitometer apparatus (200) is disclosed and is adapted to provide color density measurements of opaque materials. The densitometer apparatus (200) comprises a light source unit (202) having a source light (204) projecting light through a collimating lens (206). Light rays transmitted through the collimating lens (206) project through an aperture (208). The rays are projected onto an irradiated area surface of an object sample (212) under test. Electromagnetic radiation in the form of reflected light rays (214) are reflected from the sample (212). The reflected light rays are directed through a spectral filter apparatus (216) and impinge on receptor surfaces of photo-voltaic sensor cells (232, 234, 236). The sensors (232, 234, 236) generate electrical currents having magnitudes proportional to the intensities of the sensed light rays. The electrical signals are applied as input signals to amplifiers (244, 246, 248), with the amplified signals applied as input signals to a multiplexer (256) for time multiplexing each of the output signals from the amplifiers. The resultant multiplexed signal is applied as an input signal to an A/D converter (264) to convert the analog multiplexed signal to a digital signal. The digital output signal from the A/D converter (264) is applied as a parallel set of binary information signals to a central processing unit (266). Actual measurements of color reference patches are processed so as to solve for unknown constants of a set of equations representing correction or compensation factors functionally dependent on actual reflectance measurements. The correction factors are then utilized by the densitometer apparatus (200) to compensate measurements of actual object samples.

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Kentwood, MI, United States of America

William R Given