Optical: systems and elements – Lens – With multipart element
Reexamination Certificate
2000-11-07
2003-04-22
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Lens
With multipart element
C359S666000
Reexamination Certificate
active
06552860
ABSTRACT:
BACKGROUND FIELD OF INVENTION
This invention relates to optical surfaces commonly referred to as Fresnel surfaces. Fresnel surfaces are commonly used to direct and/or focus light in desirable ways and have remained largely unchanged since their invention nearly 200 years ago. Such surfaces commonly consist of a multitude of equidistant grated protrusions formed on a flat rigid material. They are commonly structured in concentric circles in a first embodiment or in parallel rows in a second embodiment such that both embodiments direct light in desirable ways. Fresnel gratings can perform transmissive diffraction, reflective diffraction, refraction, and/or reflection. The general advantages of Fresnel optics include the performance simulation of optical lenses, prisms, and mirrors with significant reductions in material, thickness and consequently dramatically lighter weight and less bulky optics.
BACKGROUND DESCRIPTION OF PRIOR ART
Heretofore, the designs of flattened Fresnel type lens, prism, and mirror structures have always been rigid and have not been variable regarding angular pitch and surface curvature. Commonly these devices were cut or molded into transparent plastic or glass in the case of transmissive members or coated with reflective materials in the case of reflective members. The angles and curves once cut thereon not being variable. Adding angular and curvature adjustability to Fresnel structures as described herein is a significant advancement now possible due to the present novel structures which utilize the many advances in the transparency and elasticity of polymer technology. Transparent or reflective, highly elastic extrusions welded and assembled to form a Fresnel optical membrane as described herein are angularly tunable by actuating a first rigid member relative to a second rigid member. Curves formed by the Fresnel optical membrane are tunable by varying fluid pressure in communication with the optical membrane. Tunable angles and curves formed by the optical membrane as described herein causes light to be refracted, reflected and/or diffracted predictably and reliably. In the transmissive embodiments, curves formed by the Fresnel optical membrane surfaces and a fluid with an index of refraction in communication therewith, cause light to be redirected as desired through the processes of refraction and/or diffraction. In the reflective embodiments, identical Fresnel membrane structures in conjunction with reflective properties or in communication with a reflective material and operated identically forms reflective surfaces whereby electromagnetic energy is redirected by the process of reflection and/or reflective diffraction.
Prior art teaches the use of flexible membranes such as is depicted in
FIG. 1
from U.S. Pat. No. 5,684,637 (Floyd, 1997). The membranes are actuated to form a convex lens of desired focal length by varying a fluid with a refractive index contained there between. This structure and those abundantly found in prior art that are similarly actuated when used in small applications can reliably provide a range of focal lengths and coherent focal points. In many applications however, especially where the volume, physical size and weight of fluid are a consideration, an alternate approach utilizing Fresnel structures to provide coherent variable focal lengths is needed. The present invention achieves these objects with significantly reduced thickness, weight and volume.
Prior art teaches the use of a flexible mirror membrane actuated by fluid pressure such as is depicted in
FIG. 2
from U.S. Pat. No. 4,890,903 (Treisman et al, 1990). Such a fluid mirror membrane can be used in some small applications where thickness is not a factor. In larger applications or where absolute mirror thickness is a consideration, the variable membrane mirror composed of Fresnel surfaces as disclosed herein is a useful unanticipated advancement over the prior art.
Prior art teaches the use of actuating rigid structures to reliably alter the path of electromagnetic energy.
FIG. 3
from U.S. Pat. No. 5,166,831 (Hart, 1992) discloses the actuation of rigid planar members to vary a liquid prism angle. This and similar prior art is useful for some small applications. In large applications, the volume, physical size and weight of fluid required in these structures makes them prohibitive engineering problems. To eliminate the engineering problems of prior art, an alternate approach utilizing variable Fresnel structures to variably alter the course of electromagnetic radiation is required. Additionally, the Hart structure can not achieve a variable focal length (nor did Hart intend it to). Whereas the present invention can reliably achieve a coherent variable focal length.
Prior art discloses the use of variable lenslets.
FIG. 4
from U.S. Pat. No. 5,774,273 (Bornhorst, 1998) depicts a hexagonal grid and a transmissive membrane. This system uses fluid pressure to push the membrane through the grid and thereby produces an array of variable lenslets. This lenslet array can not achieve a truly coherent focal point. Nor can this structure reliably deliver a single variable focal point. Additionally, due to the grid structure, much of the electromagnetic radiation is lost into the grid. The hexagonal structure is used to minimize the light loss due to absorption by the grid structure (if the grid had round holes, the grid would absorb even more energy). But the hexagonal structure introduces the problem of lenslet distortion because the curvature of the membrane will be distorted into a rippled curve (caused by non uniform stretching when conforming to the hexagonal shape) when being stretched through anything other than a round structure. The round hole and smooth curve are required for imaging optics when used in conjunction with and elastic membrane. The Bornhorst grid structure forces a compromise between the loss of optical integrity when using a hexagonal grid and loss of optical efficiency when using a round grid. The present invention can achieve the objects of a variable coherent focal point and length with nearly one hundred percent efficiency and with nearly no distortion. For all of these reasons, the new art embodied in the variable Fresnel structure disclosed in the present application is a significant unanticipated advancement over prior art.
Prior art
FIG. 5
from U.S. Pat. No. 5,774,273 (Bornhorst, 1998) incorporates several independently variable arrays of fluid pressure variable lenslets into one collective structure. Again, the structure disclosed can not deliver a truly coherent focal point. Nor can it produce a variable focal length. This structure and the actuation methodology is not adequate for the purposes of a coherent variable lens with variable focal point and focal length. Each of these independent lenslet arrays can be directed into a similar direction but their grid shapes and positioning prohibit usage in any imaging optics applications. The new art disclosed in the present application avoids the problems associated with the lenslet formed by fluid pressure forcing a membrane through a grid structure. Further all of the new structures of the present invention can be used together to produce a coherent optic with variable focal length and a true focal point. These are all significant advancements unanticipated, unaddressed, and unachievable by prior art.
The variable prismatic surface of prior art
FIG. 6
from U.S. Pat. No. 5,774,273 (Bornhorst, 1998) can incoherently simulate a focal point. This may be adequate for some imprecise lighting applications but is not adequate for any coherent applications. Specifically since the riser of the structure is not parallel to the light source, (but instead forms a second surface in the path of the light) a high percentage of light is either absorbed, reflected, or refracted by the secondary angle formed by the riser. This causes light rays to travel in undesired directions and further increases waste within the system. Waste of energy may be tolerable where excess energy can be pumped into the sy
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