Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating – Light polarizing article or holographic article
Reexamination Certificate
2001-05-10
2004-04-13
Vargot, Mathieu D. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Optical article shaping or treating
Light polarizing article or holographic article
C264S001900, C264S081000, C427S162000
Reexamination Certificate
active
06719928
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an optical lens structure and a means of manufacturing the same wherein the optical lens reflects light in a manner that is scattered while allowing a portion of the light striking the lens surface to pass through the lens in a coherent manner similar to that of a conventional eyeglass lens.
The basic theory behind a lens structure of this type is simply that a transparent medium, such as a window pane, will transmit light in a coherent or undistorted manner provided that both surfaces of the window pane, which are perpendicular to the light rays, are optically smooth and parallel to one another. If, however, one of the two surfaces is not optically smooth, that is to say, etched, scratched or sculptured in some manner, the light passing through the transparent medium will be distorted. Generally speaking, the more the surfaces are etched, the more the transmitted light will be distorted. This basic phenomena is commonly applied to the design glass of acrylic shower doors in which one side of the glass is typically textured while the other side remains smooth, the result being that an observer cannot clearly see through the shower door.
The texturing of the shower door, as described above, causes the light to be distorted simply because the refractive index of the transparent medium, such as glass, is different than that of air. In other words, the speed at which light travels through air is different than the speed at which light travels through glass. The fact that the speed of light will change as a function of the medium through which it is traveling is pertinent in that, on a microscopic level, as the light rays pass through an uneven surface of one transparent medium, the light rays will exit that transparent medium at slightly different times. This will cause the light rays that were previously moving together at the same rate to change speeds at slightly different times, in turn causing the light rays to become scattered.
A textured surface, as described above, is in effect made up of peaks and valleys. Such a surface is commonly referred to as a “relief pattern.” It is those peaks and valleys that cause the once coherent light rays to exit the transparent medium at different times, resulting in distortion. If another transparent medium, such as a liquid, for instance, having exactly the same refractive index as the glass, is applied to the textured surface of the glass (the side opposite the textured side of the glass being optically smooth), such that the liquid fills in the peaks and valleys of the textured surface, in turn providing an optically smooth surface, the light will once again pass through without distortion. If the refractive index of the liquid is the least bit different than that of the glass, the light will remain distorted. The degree to which the light remains distorted is directly proportional to the mismatch in refractive indices between the glass and the liquid. For example, water on the etched surface of a shower door will cause the door to become more transparent yet not as clear as a window pane, for example. The shower door does not become perfectly clear basically because water does not have the same refractive index as glass. However, the refractive index of water is closer to that of glass than the refractive index of air is to glass, and that is why the door becomes more clear. It is important to note that nearly every different type of transparent medium will have a unique refractive index.
Consider again a light transmitting substrate in which a first side of the substrate is optically smooth and a second side is textured. If a vacuum deposited reflective type coating, like the type of coatings used to create a mirrored sunglass lens, is applied to the textured side of the light transmitting substrate, the reflective coating will highlight the textured surface. Consider now an optically clear liquid applied to the reflective coated textured surface in which the liquid fills in the peaks and valleys of the textured surface and is made to provide a new surface which is optically smooth and parallel to the first side of the substrate. If the liquid has exactly the same refractive index as the transparent substrate, the newly constructed multi-layered substrate will once again allow light to pass through undistorted. At the same time, the reflective coating, which is sandwiched between the liquid and the substrate, will highlight the textured surface.
When creating an optical system such as this, the refractive index of the reflective coating does not need to be the same as the other light transmitting materials for two reasons. First, the reflective coating is very thin, in the order of angstroms. Second, it has, for all practical purposes, an even thickness at all points across the surface. Because of the reflective coating's substantially uniform thickness, the optically clear liquid can very closely, if not perfectly, match the textured surface of the substrate. Because it is very thin, the optically clear liquid can come within angstroms of contacting the textured surface of the substrate. As a result of these two conditions, light is able to pass through the reflective coating practically undisturbed.
By observing these basic principals, an optical lens, such as used for sunglasses, can be made in such a way as to reflect light in a scattered manner, while at the same time transmit light in a coherent manner. Such a lens is advantageous in that on the face of an eyeglass lens, decorative patterns, images, logos, etc. can be made apparent to an observer while presenting no adverse affect to the wearer of the lens.
U.S. Pat. No. 4,315,665 describes an optical lens structure comprised of a first transparent layer that has a relief pattern on one surface, a reflective coating applied to the relief pattern, and a second transparent layer applied to the reflective coating. The second transparent layer is described as being applied in a manner that fills in the surface variations of the reflective coated relief pattern. The objective of the three-layer structure is to reflect a portion of incident light in the form of an image created by the relief pattern, while allowing the remainder of the incident light to pass undistorted. The reference further teaches that the first and second transparent layers are to have substantially the same refractive index. This reference is silent, however, as to the means by which this is to be accomplished. More specifically, it does not teach any method by which the second transparent layer, having a similar refractive index as the first transparent layer, is adhered to the reflective coating. With regard to matching refractive indices, as described, the problem encountered is that lens elements that serve as structural substrates, such as thermo or thermoset plastics, typically do not have the inherent capability to adhere to materials such as those typically employed as reflective coatings. Therefore, to create a lens structure of the type described in this prior art reference, manufacturers typically rely on adhesives or epoxies to bond a second preformed transparent layer to the reflective coating. The term “preformed” relates to the idea of the transparent layer being a solid state substrate, such as a sheet of plastic, wherein the sheet is adhered to the adhesive by means of lamination.
The foregoing reference describes holography as being a suitable means for creating a surface relief pattern that will reflect images and or decorative light patterns. Moreover, holography is described as being the method of choice. Today, eyeglasses with holographic images on the eyeglass lenses are commonly available. These types of eyeglasses are typically considered to be novelty items. Adhesives are typically employed in manufacturing the holographic lenses used in these eyeglasses. An adhesive is applied to the surface of the reflective coating to facilitate transmission of light through the lens as well as to provide a binary layer to which an add
Hein William E.
Vargot Mathieu D.
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