Densitometer for an electrophotographic printer using focused and unfocused reflecting beams
AssigneeXerox Corporation
InventorFrank C. Genovese
Life of this patent
Estimating the term…
Abstract
An apparatus measures the reflectivity of a selected region of a surface. A first light beam is reflected from the selected region and substantially focused on a photodetector. A second light beam is reflected from the selected region and is substantially unfocused on the photodetector. A signal is derived representative of the direct reflectance of light reflected from the surface onto the photodetector as a function of the intensities of the focused light beam and the unfocused light beam detected by the photodetector.
Claims16
An apparatus for measuring the reflectivity of a selected region of a surface, comprising:
- means for creating first and second light beams reflected from the selected region;
- a photodetector;
- a focusing lens positioned to focus the first light beam reflected from the selected region of the surface onto the photodetector through the axis of the focusing lens with the second light beam being reflected from the selected region and transmitted to the photodetector in a substantially unfocused manner;
- and
- processor means, operatively associated with the photodetector, for deriving a signal representative of the direct reflectance of a light beam reflected from the selected region of the surface into the photodetector as a function of the focused reflected light and the unfocused reflected light detected by the photodetector.
A method for measuring the reflectivity of a selected region of a surface, comprising the steps of:
- reflecting a pair of light beams through a focusing lens from the selected region of the surface;
- detecting focused light from one of the pairs of light beams and unfocused light from the other of the pair of light beams;
- and
- deriving a signal representative of the direct reflectance of a light beam reflected from the surface into the photodetector as a function of the focused and unfocused light detected in the detecting step.
Dependencies are inferred from the claim text.