Method of forming a retroreflective material via light interference fringe patterns
First Claim
1. A method of making a retroreflective material comprising the steps ofa. providing a sheet-like photosensitive medium which after selective exposure to light may be developed to provide on one surface thereof a surface relief pattern corresponding to the light source areas,b. recording in said medium by directing thereat two interfering light beams an optical element consisting of a light interference fringe pattern having associated therewith a given focal length,c. changing the position of the photosensitive medium with respect to the two light beams and repeating the recording step to record a plurality of said optical elements in the medium,d. developing the medium to provide on a surface thereof a relief pattern corresponding to the plurality of optical elements,e. providing a transparent medium having a thickness equal to the focal length of the interference pattern,f. pressing the surface relief pattern of the developed photosensitive medium onto the transparent medium to provide an array of corresponding interference fringe patterns therein, andg. providing a reflective surface on the opposite side of the transparent medium corresponding to the back focal plane defined by said focal length,whereby light directed from a source onto the pressed surface of the transparent medium is transmitted through the medium, reflected from the opposite side and retroreflected back towards the source.
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Abstract
Retroreflective material including a medium containing a plurality of diffraction elements comprising light interference fringe patterns is formed by pressing a first medium having on a surface thereof a plurality of light interference fringe patterns defining an array of phase modulated fresnel zone plates onto a surface of a copy medium having a thickness equal to a given focal length associated with the fresnel zone plates and a reflective material is coated on the opposite surface of the copy medium. In making other embodiments a plurality of fringe patterns is recorded throughout the volume of a photosensitive medium.
68 Citations
11 Claims
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1. A method of making a retroreflective material comprising the steps of
a. providing a sheet-like photosensitive medium which after selective exposure to light may be developed to provide on one surface thereof a surface relief pattern corresponding to the light source areas, b. recording in said medium by directing thereat two interfering light beams an optical element consisting of a light interference fringe pattern having associated therewith a given focal length, c. changing the position of the photosensitive medium with respect to the two light beams and repeating the recording step to record a plurality of said optical elements in the medium, d. developing the medium to provide on a surface thereof a relief pattern corresponding to the plurality of optical elements, e. providing a transparent medium having a thickness equal to the focal length of the interference pattern, f. pressing the surface relief pattern of the developed photosensitive medium onto the transparent medium to provide an array of corresponding interference fringe patterns therein, and g. providing a reflective surface on the opposite side of the transparent medium corresponding to the back focal plane defined by said focal length, whereby light directed from a source onto the pressed surface of the transparent medium is transmitted through the medium, reflected from the opposite side and retroreflected back towards the source.
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11. A method of making a retroreflective material comprising the steps of
a. providing a sheet-like photosensitive medium which after selective exposure to light may be developed to provide on one surface thereof a surface relief pattern corresponding to the light source areas, b. recording in said medium by directing thereat two interfering light beams an optical element consisting of a light interference fringe pattern having associated therewith a given focal length, c. changing the position of the photosensitive medium with respect to the two light beams and repeating the recording step to record a plurality of said optical elements in the medium, d. developing the medium to provide on a surface thereof a relief pattern corresponding to the plurality of optical elements, and e. providing a reflective surface on the opposite side of the medium corresponding to the back focal plane defined by said focal length, whereby light directed from a source onto the developed surface of the medium is transmitted through the medium, reflected from the opposite side and retroreflected back towards the source.
Specification