Charles John Reilly

US Patent:

44127448, Nov 1, 1983

Filed:

Jun 1, 1981

Appl. No.:

6/268707

Inventors:

Jerald D. Lee - Mendenhall PA
Charles D. Reilly - Wilmington DE

Assignee:

E. I. Du Pont de Nemours & Co. - Wilmington DE

International Classification:

G01J 342

US Classification:

356319

Abstract:

An improved spectrophotometer having a light source, a scanning type monochromator that provides light beams of different wavelengths over a light spectrum being scanned, and an object photometer for measuring the intensity of reflected light from an object being tested and generating an electrical signal proportional to the intensity of the light measured and connected to means for recording the signal as a function of wavelength measured, the improvement used therewith comprising: (a) a beam splitter that divides the beam exiting from the monochromator into first and second light beams, whereby the first beam is incident upon the object; (b) a reference photometer that measures the flux of the second light beam and generates an output electrical signal proportional to the intensity of the light measured; and (c) a light source control, connecting the reference photometer and the light source, which receives the electrical signal from the reference photometer and generates a feedback electrical signal to adjust the intensity of the light source to maintain the reference photometer output electrical signal level constant across the light spectrum that is being scanned. The spectrophotometer is useful for determining standard color values for coatings on substrates or for any colored surface.