Abstract:
A laser energy window arrangement especially usable in a tactical aircraft having night vision equipment-aided cockpit visual information input requirements. The laser energy window arrangement enables use of laser apparatus directed external to the aircraft for target designation or other purposes while minimizing the amount of energy from such laser returning spuriously inside the cockpit where it inherently acts a noise signal for night vision equipment. The laser energy window limits the portion of the aircraft windshield or canopy exposed to laser radiation and its effects to a relatively small area, an obscurable area generating significantly reduced amounts of spurious return energy in comparison with use of the laser directly through an unlimited windshield, canopy, or other type of transparency. Transmission of spurious return energy from the laser energy window to remaining portions of the windshield or canopy is precluded by interruption of transmission paths within the windshield or canopy material and transducing the interrupted path energy into heat dissipated within or outside of the aircraft and not affecting the remainder of the canopy. Potentially increased aircraft to target standoff range, reduce need for aircrew use of laser eye protection gear, reduced laser induced windshield or canopy degradation and other benefits are identified for aircraft uses of the invention. Use of the window invention in other non aircraft and non military aircraft settings is also contemplated.
Abstract:
System and method for in situ measurement of haze in a transparency, such as an aircraft windscreen, canopies, windows or the like are described which comprise an annular light source for illuminating a selected test area of the transparency along a selected optical axis, a photodetector, and a lens for projecting an image of the illuminated test area along the axis onto the photodetector.
Abstract:
System and method for measuring angular deviation in a transparency are described which comprise the steps of directing a large diameter collimated beam of light along an optical axis through a transparency, focusing a portion of the collimated beam, determining the position of the focus of the beam portion relative to the axis, repeating the above steps without the transparency, measuring any difference in position of the focus with and without the transparency, and calculating the vertical and horizontal components of angular deviation in the transparency according to relationships disclosed.
Abstract:
An optical instrument and method for measuring susceptibility to glare of a human vision system is described which comprises a glare light source of preselected intensity sufficient to generate glare in the vision system of a subject, an acuity target having first opaque or partially transparent areas and second translucent areas defining a pattern of recognizable indicia on the target, a housing supporting target and source side-by-side for simultaneous viewing by the subject, and a reflective surface within the housing for directing light from the source onto the back surface of the target for substantially uniform transillumination of the target with light from the source. Optional optical filters may be placed between the source and subject, target and subject, or source and reflective surface, for selectively filtering light viewed by the subject. A movable cover plate may be included for selectively exposing the source to the subject in certain glare susceptibility measurements.
Abstract:
An improved system for measuring absolute angular deviation through transparencies, such as aircraft windscreens, uses an incoherent light source and a target configuration in the form of an opaque slide with a transparent "L"-shaped pattern. The positions of images of the legs of the "L" after passing through the transparency are detected at separate times by a single CCD array through rotation of the image of the "L"-shaped pattern ninety degrees by rotation of a Pechan prism about the optical axis of the system. In such manner, horizontal (azimuth) and vertical (elevation) components of angular deviations is measured for each tested point on the transparency, uncontaminated by lateral displacement errors.
Abstract:
An apparatus for creating images of nonperiodic patterns, which patterns are variable in contrast with respect to a uniform and constant level of background luminance. Two beams of uniform luminance are projected through individual, orthogonally oriented linear polarizers, and then into a common cube beam splitter to be divided and interlaced. One combined output beam from the splitter is projected through a rotatable linear polarizer onto the image sensing optical detector undergoing test. The second beam is projected toward a detection system. The patterned region of the second beam passes through a second rotatable linear polarizer, synchronized to the first rotatable polarizer, and onto a CCD array detector system. Contrast between the pattern and the background is represented by the two electrical voltage levels in the array output, irrespective of the spatial frequencies in the pattern. Two unpatterned background regions from either of the interlaced beams are projected through individual and orthogonal linears polarizers to individual luminance detectors. Each detector, in turn, regulates its corresponding beam intensity to compensate for drift in the beam generating elements.
Abstract:
A cost considered arrangement for evaluating local illumination interference with operation of a night vision apparatus in for example the confines of an illumination inclusive aircraft cockpit. The evaluation is especially applicable to identifying interference between aircraft instrument lighting having infrared content for example, and night vision apparatus operation in the aircraft. The evaluation is cost is limited by use of a common household lamp night vision apparatus source calibrated with a common light measuring instrument operated at close range and with modification of the measured illumination through mathematical manipulation of the source operating distance to achieve the low light levels needed for night vision apparatus operation. A standard visual acuity chart and multiple operator interpretations of the chart resolutions achieved are included.
Abstract:
A self-contained, military usage compatible, stabilized illumination calibration system and method of using same to enable in-the-field accurate determination of the low-level light falling on the surface of a night vision apparatus resolution chart and attending adjustment of a night vision device. Use of such charts, such as the chart of U.S. Pat. No. 4,607,923, preferably includes known levels of illumination at several different expected night vision goggle compatible lower-levels in order to both evaluate and adjust the performance of a night vision device prior to its use or during extended use periods. The disclosed system is digital computer controlled and provides an accurate, easy to use, and low cost alternative to previous laboratory-like methods of determining night vision evaluation illumination. The disclosed system provides go or no go indications of achieved chart illumination.
Abstract:
A method for measuring optical distortion in a transparency is described which comprises the steps of acquiring an analog image of a grid board through the transparency, digitizing the analog image to form a digitized image comprising a multiplicity of pixels defining the shape of the grid board as viewed through the transparency, locating on the digitized image the pixels defining the grid and determining optical distortion of the transparency by comparing the shape of the grid in the digitized image to the actual grid shape on the grid board.
Abstract:
A system for measuring optical angular deviation in a transparency such as an aircraft or automobile windscreen, visor, optical lens or the like is described wherein orthogonal first and second incoherent light line images are combined and separately optically encoded, such as by wavelength or by polarization vector using suitable color or polarization filters or beamsplitters, and projected through a transparency under examination, the combined images then separated to detect simultaneously and separately the vertical and horizontal components of angular deviation at a specific location in the transparency.