Optical paper detector
AssigneeThe United States of America as represented by the Secretary of the Treasury
InventorKenneth R. Duvall
Life of this patent
Estimating the term…
Abstract
An optical paper detector for use in conjunction with a printing press for sensing the undesirable condition of more than a single sheet of paper being simultaneously fed to the press. The optical paper detector is comprised of an array of wide angle phototransistors connected in parallel which uniformly sense light transmittance through the paper over a relatively large and continuous area to provide an averaging effect so that the optical paper detector is relatively insensitive to local variations in light transmittance. The optical paper detector is equipped with a flat cover that permits flush mounting and provides a self-cleaning wiping action.
Claims8
In an improved optical paper control assembly wherein a light source and an optical paper detector are adapted to sense the presence of more than a single sheet of paper to be printed wherein said improvement comprises an improved optical paper detector, said improved detector comprising a planar array of photosensors having individual sensing angle .alpha., substantially equal to 75 degrees, said photosensors being spaced from each other a first distance substantially equal to s and from said paper a second distance d substantially equal to 0.65s where d and s are related to .alpha. by the following relationship
- d=s/2 tan (90.degree.-.alpha./2)
- where said array is responsive to light transmittance through a continuous area of said paper which is substantially coincident with the physical area of said planar array.
Dependencies are inferred from the claim text.