Abstract An optical reader for a plurality of narrow wavelength radiation bands, for example those derived from coded inks with narrow band photoluminescent materials as the coding components, comprises two independently adjustable spherical mirrors of radius of curvature R arranged side by side and a planoconvex lens of focal length R with the convex side toward the mirrors and arranged so that the normal to the lens passes symmetrically between the two mirrors and so that the lens and mirrors are separated by a distance R. In the planar surface of the lens are situated a clear entrance aperture and several interference filters, the interference filters being arranged in one or more rows and each one passing the narrow band radiation corresponding to the photoluminescent bands of the different coding components. The spherical half mirrors are adjusted so that the entrance aperture is reflected back and forth to produce images centered on each interference filter. When an image of the entrance aperture is imaged onto a portion backed by an interference filter, the filter passes only one band of wavelengths, reflecting the others back onto the mirrors. Two of the images involve only one reflection and other sets, two, three, four, etc. With a total of four possible reflections, eight coding components can be accommodated. Behind each interference filter is a detector sensitive to light of that particular wavelength.
An optical reader for polychromatic beams containing one or more narrow band colors, comprising in combination, a. pair of spherical half mirrors having identical radii of curvature, b. a planoconvex lens of focal length equal to the mirror radii positioned so that its normal passes symmetrically between the two half mirrors and spaced from the mirrors by a distance equal to its focal length, the convex side of the lens being toward the mirrors, c. an entrance aperture in the cEnter of the planoconvex lens and narrow band interference filters arranged in at least one row on the planar surface of the lens, d. the spherical mirrors being positioned to produce a plurality of images on the planar surface of the lens, one pair by single reflection and other pairs by multiple reflections, each image being centered on a particular interference filter, whereby an image containing the color passed by the interference filter passes through it and all other colors are reflected back to the mirrors.
Claim 2
Dependent Claim
166 words
An optical reader for polychromatic beams containing one or more narrow band colors, comprising in combination, a. pair of spherical half mirrors having identical radii of curvature, b. a planoconvex lens of focal length equal to the mirror radii positioned so that its normal passes symmetrically between the two half mirrors and spaced from the mirrors by a distance equal to its focal length, the convex side of the lens being toward the mirrors, c. an entrance aperture in the cEnter of the planoconvex lens and narrow band interference filters arranged in at least one row on the planar surface of the lens, d. the spherical mirrors being positioned to produce a plurality of images on the planar surface of the lens, one pair by single reflection and other pairs by multiple reflections, each image being centered on a particular interference filter, whereby an image containing the color passed by the interference filter passes through it and all other colors are reflected back to the mirrors.
Claim 3
Dependent Claim
38 words
A device according to claim 1 in which the interference filters are in two rows, staggered with respect to each other, and the entrance aperture is between the center pair of interference filters in one of the rows.
Claim 4
Dependent Claim
30 words
A device according to claim 2 in which the row having the entrance aperture is composed of four interference filters and the other row is also composed of four filters.