Cat's eye retro-reflector array coding device and method of fabrication

[0001] This application claims benefit under 35 USC 119(e) for the priority date of provisional patent application No. 60/494,749 filed on Aug. 13, 2003.

[0002] Not applicable

[0003] Not applicable

[0004] This invention relates to lenses, specifically cat's eye retro-reflective lenses manufactured with ink-jet printing technology to form lens arrays that provide coded information at short, long and intermediate distances.

[0005] The cat's eye retro-reflector lens shown in FIG. 1 is well known to one skilled in the art. It displays the features that a light beam incident onto the lens as illustrated in FIG. 1 is reflected back in the same direction as the incident beam as long as the angle θ is less than approximately 50 degrees. It got its name from the observation that shining a light onto a cat the light reflects back toward you from the cat's eyes. References are included that goes into more detail about the cat's eye retro-reflector lens.

[0006] In this invention the cat's eye retro-reflector array is fabricated using data-driven, ink jet micro-dispensing technology. Using ink jet technology to fabricate microlenses and larger lenses have be described in detail in U.S. Pat. Nos. 5,498,444 and 5,707,684, we want to incorporate by reference these patents into this application.

[0007] The objects and advantages of the present patent are:

• • [0008] a) to provide a cat's eye retro-reflector lens array that provides coded data about an object that does not require target proximity to access the information;
  • [0009] b) to provide a cat's eye retro-reflector lens array that provides unique coded data about an object because of the number of points within an array is unlimited;
  • [0010] c) to provide a cat's eye retro-reflector lens array that is manufactured using dispensing of lens materials;
  • [0011] d) to provide a cat's eye retro-reflector lens array that conveys unique coded data to an interrogator through conventional means of altering adsorption, emission, spectra, frequency, or wavelength characteristics of an electromagnetic wave.

[0012] Further objects and advantages are to provide a cat's eye retro-reflector lens array capable of providing identification information by analyzing materials presented to specific points on the array. Ink-jet printing can populate an array with numerous lens interrogation points as needed by the end user.

[0013] The invention relates to apparatus, the methods for providing and coding the apparatus, and the method of optically reading the apparatus over a wide range of distances. It can be read as a security badge less than one inch from the reading device or it could be read using a powerful telescope from a satellite. The coded information can be used to identify an object (people and things). For this case a pattern of optical signals would identify the object. This could be the pattern of signals themselves or specific information coded in each of the signals. Information encoded into each signal could be wavelength dependent or absorption dependent. The absorption dependence or wavelength dependence nature of the array makes it useful as a gas or biological sensor.

[0014] The invention consists of two arrays of lenses aligned on opposite sides of a substrate. Each pair is a cat's eye retro-reflector lens. The lens on the back side is metallized to reflect the light. An incoming beam of light impinging on the front side lens is focused onto the back side lens and the signal is returned into the same direction from which it came. For this type of lens system this is true if the incoming beam is within approximately 50 degrees from normal. In this invention the cat's eye retro-reflector array is fabricated using data-driven, ink jet micro-dispensing technology. Because of the data driven nature of the technology, the array pattern on the front side of the array can be pattern, a different pattern for every array. The back side would have 100% of the lenses present. When light impinges onto the array only locations where the front side lenses are present would reflect light back to the sending instrument. The instrumentation would detect the pattern that was originally printed onto the array.

[0022] In a typical embodiment of the device according to the invention is shown in FIGS. 1, 2, 3, 4, and 5. There is at least one cat's eye retro-reflector lens that consists of a substrate (1) made out of an optically transparent material that has an index of refraction close to that of the microlenses printed on both sides of the substrate. A larger microlens R2 (2) is on the back side of the substrate. This lens is metallized (3) so that it reflects light impinging on it from the front side. This metallization (3) could be deposited by various means including evaporation, sputtering, organometallic conversion, etc. One skilled in the art could easily apply various meads to metallize this surface. The other lens with lens radius R1 (4) is shown on the front side as seen in FIG. 2.

FIGS. 3A–C,—METHOD OF MANUFACTURE

[0023] The method of fabricating the cat's eye retro-reflector lens is shown in FIG. 3. In the first step (FIG. 3a) a Micro-jetting Device (5) is positioned over the appropriate location on the substrate. Droplet(s) (7) of lens material is dispensed through an orifice (6) onto the substrate (1) to form the microlens (2). This process is documented in U.S. Pat. No. 5,498,444 and U.S. Pat. No. 5,707,684 that are incorporated by reference into this application. After dispensing the correct number of droplets (7) the lens would be converted to a solid lens structure by one of many conversion processes. In this embodiment a UV curing process followed by a thermal cure is used. The second step in the process is metallizing the back surface of the back side lens (2). One method is shown in the FIG. 3b, where a metallization source (8) is shown schematically. This source would project a metal vapor stream (9) toward the lens. This process will deposit a reflective metal film (3) onto the lens surface. In FIG. 3c the same process is repeated with a small volume of fluid dispensed to create the front side microlens (4).

[0024] FIG. 4 shows a top view of a larger substrate (10) with an array of microlenses printed on both sides. This figure shows back side microlenses (2) printed at every location and front side microlenses (4) printed into a predetermined pattern. This is done by stepping the micro-jetting device only over certain predetermined locations to form front side microlenses. This stepping process is documented in the patents incorporated into this application. The pattern of front side microlenses printed can be a specific code for identification.

FIG. 5—METHOD OF OPERATION

[0025] FIG. 5 illustrates how this type of a coded cat's eye retro-reflector array works. A targeting light source (11) is made to shine onto the array. The arrows pointing from left to right in this figure illustrates this. If the light beam is aligned to the array within the allowed angle then the full cat's eye retro-reflector lenses will send the signal back to the targeting area. The arrows pointing away from the array, right to left show this. The returning light code (12) depends upon the location of the front side microlenses. The data driven nature of the precision microdispensing technology enables individual codes to be printed from a set of data patterns.

FIGS. 6,7—ADDITIONAL EMBODIMENTS

[0026] FIG. 6 illustrates a variation of this method of coding. FIG. 6 shows front side microlenses printed with different materials. These materials may have absorptive dyes in the lens material, so that the color of each would be different. Material A (13) could be the one used in FIG. 5; Material B (14) may have a dye present that changes the light absorbed and gives a color to the returning light, Material C (15) would have a different dye and therefore a different color. By using more that one material a more complex coding could be developed.

[0027] FIG. 7 illustrates a variation of this method of coding that can be use to make remote sensors. In this case, the different materials would be sensor materials sensitive to different gas molecules. In this application the front side microlenses would be printed with polymers sensitive to different gas modules. These lenses would change properties in a detectable way if the gas if a particular gas is present Microlens (16) would be sensitive to Gas A; Microlens (17) would be sensitive to Gas B and microlenses (18) would be sensitive to Gas C. The remote sensing system would be looking for changes to the optical signals that would indicate that a particular gas was present. Changes in the optical signal could arise from changes in absorption of the lens materials, swelling of the polymer lens that would change the focal length of the lens, or other optical changes.

[0028] The same type sensor system shown in FIG. 7 could indicate the presence of specific bio-molecules if the appropriate indicator chemistry was present in the microlenses.

[0029] As will be apparent to those skilled in the art from the description herein contained, the apparatus and method of fabrication may be embodied in other patterns, forms or arrangements and use other materials without departing form the scope of the invention.

[0030] Advantages

[0031] From the description above a number of advantages of this cat's eye retro-reflector lens array manufactured through ink-jet dispensing:

• • [0032] (a) numerous lens pairs may be easily and quickly created with a data driven process.
  • [0033] (b) a myriad of lens materials or sensor materials may be printed as lenses within a given array
  • [0034] (c) ink-jet printing of the lenses enables creating lenses of diameters and geometries to suit a range of interrogation distances
  • [0035] (d) ink-jet printing allows tailoring of the optical characteristics of each lens pair unavailable with standard lens array methods.