Etching a substrate: processes – Forming or treating optical article
Reexamination Certificate
2001-10-16
2003-09-16
Alanko, Anita (Department: 1765)
Etching a substrate: processes
Forming or treating optical article
C216S026000, C216S067000, C216S080000, C065S017400, C219S121600, C219S121690, C427S579000, C134S001000
Reexamination Certificate
active
06620333
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Endeavor
The present invention relates to optics and more particularly to a system that mitigates the growth of damage in an optic.
2. State of Technology
U.S. Pat. No. 4,667,101 for predicting threshold and location of laser damage on optical surfaces by Wigbert Siekhaus, patented May 19, 1987 provides the following description, “Modern day applications of laser devices call for increasingly powerful and precise beams. Such applications require high resolution optical devices such as lenses, filters, and mirrors. The application of large intensities of laser energy to these devices frequently destroys them during operation. Often the level of intensity required for experimental applications (such as the Projects Nova and Novette at the Lawrence Livermore National Laboratory) is so high that pretesting of the optical device at the required intensities would be impractical. The level of effort required to prepare for and execute the desired experiments, however, is very high and so an effective means of pretesting such devices is desirable. Presently there are no commercially available devices capable of “stress testing” a particular optical device. U.S. Pat. No. 3,999,865, issued Dec. 28, 1976 to Milam et al., teaches an instrument capable of analyzing the cause of damage to optical devices. It provides for subjecting the device to a damaging energy and intensity and then analyzing the damage from the standpoint of time and applied power in order to determine the one or more of several reasons for the laser induced damage. While Milam is helpful in improving system design or production techniques, it requires that damage actually occur and only indirectly identifies flaws through analysis of the parameters of the damaging event. The tested device clearly can no longer be used.”
U.S. Pat. No. 5,143,533 for a method of producing amorphous thin films by Raymond M. Brusasco, patented Sep. 1, 1992 provides the following description, “Disclosed is a method of producing thin films by sintering which comprises: a. coating a substrate with a thin film of an inorganic glass forming parulate material possessing the capability of being sintered, and b. irridiating said thin film of said particulate material with a laser beam of sufficient power to cause sintering of said material below the temperature of liquidus thereof. Also disclosed is the article produced by the method claimed.”
U.S. Pat. No. 5,472,748 for permanent laser conditioning of thin film optical materials by Wolfe et al., patented Dec. 5, 1995, provides the following description: “The performance of high peak power lasers, such as those used for fusion research and materials processing, is often limited by the damage threshold of optical components that comprise the laser chain. In particular, optical thin films generally have lower damage thresholds than bulk optical materials, and therefore thin films limit the output performance of these laser systems. Optical thin films are used as high reflectors, polarizers, beam splitters and anti-reflection coatings. The Nova project at Lawrence Livermore National Laboratory is designed to study the use of lasers to produce fusion by inertial confinement. The 1.06 &mgr;m wavelength Nova laser output is limited, in part, by the damage threshold of large aperture (approximately 1 m diameter) dielectric thin films coated on flat substrates. Proposed future fusion lasers require optical coatings with laser induced damage thresholds that exceed a fluence of 35 J/cm 2 in 10 ns pulses at the 1.06 &mgr;m wavelength. Fluence is defined in the specification and claims for a pulsed laser of a specified wavelength and specified pulse length as the energy per unit area delivered by a single pulse. Prior to the invention, the highest damage thresholds were in the range from 10-20 J/cm2 in a 10 ns pulse at the 1.06 &mgr;m wavelength. Therefore, a method of increasing the laser damage threshold of dielectric optical thin films (or coatings) is needed.”
U.S. Pat. No. 5,796,523 for a laser damage control for optical assembly by John M. Hall, patented Aug. 18, 1998 provides the following description, “Protection methods and apparatus for optical equipment have been attempted for providing protection from laser energy that could otherwise damage optical radiation detectors, including the human eye. The most common technique of providing protection involves optical filtering elements, which offer substantial protection but only over a limited, fixed spectral color range. Standard dielectric coatings are the most common form of filters, and flat plates with these “notch” coatings can be easily inserted into or outside many common optical assemblies. As noted above, however, these filters are useful only over a limited range of wavelengths, and also have the added disadvantage of blocking even non-harmful radiation within the designed spectral region. Typical military magnifying optical assemblies such as telescopes, periscopes, and binoculars vary widely, and typically have magnifying powers ranging from 4×to 10×, with entrance aperture diameters going from 20 mm to 60 mm or more. As the magnifying power increases, the angular resolution increases, and thus the farther away a given target can be recognized. The larger apertures are required to gather sufficient light energy to allow good contrast for far-away targets. These magnifying optical systems are commonly designed for use with the human eye, but can also easily perform similar tasks when connected to standard television camera equipment. Given the harsh nature of military environments, these optical systems do not lend themselves easily to the use of attachments to perform laser protection functions. All magnifying optical assemblies of the kind found in telescopes, periscopes, and binoculars can be characterized as consisting of an objective lens set, followed by an eyepiece assembly, with either a real or virtual focal plane between, as well as a variety of intervening prism assemblies (almost always porro prisms) to keep the image orientation proper. The magnifying power is defined as the ratio of the objective focal length divided by the eyepiece focal length. Typical fields of view for these systems range from 2° to 10°, depending upon the magnification. In the prior art for all these systems, the focal planes between the objective and eyepiece sections, or between any intervening relay optics, is not well corrected for aberrations. This does not affect the overall system performance, because the aberrations of the objective can be compensated by those of the eyepiece. It is much more difficult to design both objective and eyepiece optics to each have diffraction limited focal planes, and therefore this feature is not normally embraced by the current art. Additionally, since the magnifying power is the ratio of the objective and eyepiece focal lengths, it is desirable to have a relatively short focal length eyepiece to minimize the objective focal length for a given magnification. This reduces the overall size of the system, but does not offer much room between the eyepiece assembly and the intermediate focal plane. Because of this, prior art designs do not usually allow elements other than thin transmissive reticle plates to occupy the space in or near the intermediate focal plane. The prior art in developing laser protective devices offers many techniques, including sacrificial mirrors, transmissive optical power limiters, liquid cells, etc. These devices are generally designed to operate passively within an optical system until indicent optical radiation is of sufficiently high energy to activate the protective mechanism. In order to set the activation threshold below the damage threshold of the detector (human eye, TV camera, etc.), it is desirable to place the power limiter in or near a well corrected, diffraction limited focal plane. Additionally, the optical system must be able to accommodate the volume of the power limiter device, and be able to provide proper image orientation sho
Brusasco Raymond M.
Butler James A.
Governo George K.
Grundler Walter
Penetrante Bernardino M.
Alanko Anita
Scott Eddie E.
The Regents of the University of California
Thompson Alan H.
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