Monocentric lenses allow high resolution panoramic cameras, where imaging fiber bundles transport the hemispherical image surface to conventional focal planes. Refraction at the curved image surface limits the field of view coupled through a single bundle of straight fibers to less than ±34°, even for NA 1 fibers. Previously we have demonstrated a nearly continuous 128° field of view using a single lens and multiple adjacent straight fiber-coupled image sensors, but this imposes mechanical complexity of fiber bundle shaping and integration. However, a 3D waveguide structure with internally curved optical fiber pathways can couple the full continuous field of view onto a single focal plane. Here, we demonstrate wide-field imaging using a monocentric lens and a single curved fiber bundle, showing that the 3D bundle formed from a tapered fiber bundle can be used for relaying a 128° field of view from a curved input to the planar output face. We numerically show the coupling efficiency of light to the tapered bundle for different field of views depends on the taper ratio of the bundle as well as center of the curvature chosen for polishing of the fiber bundle facet. We characterize a tapered fiber bundle by measuring the angle dependent impulse response, transmission efficiency and the divergence angle of the light propagating from the output end of the fiber.
High resolution, wide field-of-view and large depth-of-focus imaging systems are greatly desired and have received much attention from researchers who seek to extend the capabilities of cameras. Monocentric lenses are superior in performance over other wide field-of-view lenses with the drawback that they form a hemispheric image plane which is incompatible with current sensor technology. Fiber optic bundles can be used to relay the image the lens produces to the sensor's planar surface. This requires image processing to correct for artifacts inherent to fiber bundle image transfer. Using a prototype fiber coupled monocentric lens imager we capture single exposure focal swept images from which we seek to produce extended depth-of-focus images. Point spread functions (PSF) were measured in lab and found to be both angle and depth dependent. This spatial variance enforces the requirement that the inverse problem be treated as such. This synthesis of information allowed us to establish a framework upon which to mitigate fiber bundle artifacts and extend the depth-of-focus of the imaging system.
Surveillance, detection, and tracking of multiple high-speed projectiles, particularly bullets, RPGs, and
artillery shells, can help military forces immediately locate sources of enemy fire and trigger countermeasures. The
traditional techniques for detection and tracing of fast moving objects typically employ various types of radar, which has
inherently low resolution for such small objects. Fast moving projectiles are aerodynamically heated up to several
hundred degree Kelvin temperatures depending on the speed of a projectile. Thereby, such projectiles radiate in the Mid-
Infrared (MWIR) region, where electro-optical resolution is far superior, even to microwave radars. A new passive
electro-optical tracker (or PET) uses a two-band IR intensity ratio to obtain a time-varying speed estimate from their
time-varying temperatures. Based on an array of time-varying speed data and an array of azimuth/ elevation angles, PET
can determines the 3D projectile trajectory and back track it to the source of fire. Various methods are given to
determine the vector and range of a projectile, both for clear and for non-homogeneous atmospheric conditions. One
approach uses the relative intensity of the image of the projectile on the pixels of a CCD camera to determine the
azimuthal angle of trajectory with respect to the ground, and its range. Then by using directions to the tracked projectile
(azimuth and elevation angles of the trajectory) and the array of instant projectile speeds, PET determines the distance to
the projectile at any point on its tracked trajectory or its predicted trajectory backwards or forwards in time. A second
approach uses a least-squares optimization technique over multiple frames based on a triangular representation of the
smeared image to yield a real-time trajectory estimate. PET's estimated range accuracy is 0.2 m and the azimuth of the
trajectory can be estimated within 0.2°.
In this paper, biologically-inspired optical imaging systems, including fish eye, bug eye, lobster eye, and RGB color
vision, are discussed as new lensing systems for military and homeland security applications. This new area of interest
includes UV, VIS, IR, and X-ray part of electromagnetic spectrum. In particular, recent progress at Physical Optics
Corporation will be discussed, including such applications as hyperspectral/multi-spectral imagery, video surveillance,
and X-ray inspection.
A universal method for precision lenght measurements, called "excess fractions" was proposed at the end of the 18th century for the precise calibration of gauges. In this method, the interferometer compares an unknown gauge with the number of known wavelengths. The array of φi; which consists of the remainders of an integer number of wavelengths in the length of the gauges, was obtained and analyzed. For the measurement of gauge lengths that were small enough, the integer number of wavelengths can be found heuristically. With the development of lasers technique, the possibility of applying this idea to the measurement of large distances, such as the distance to the moon, appeared. With the imminent number of wavelengths in the distance, the heuistic solution is not possible. In this paper the solution based on Chinese Remainder Theorem is proposed. The Chinese Remainder Theorem is developed for use in the case, when wavelengths are not mutually prime numbers, and metrological aspects of this solution will be analyzed.
In response to a pressing demand for tagging systems and technologies developing, Physical Optics Corporation (POC) proposes a novel Passive Optoelectronical (POET) Tag system. The POET tag is an omnidirectional (360° in azimuth), with up to 180° field-of-view in elevation, retroreflection optical system with a high frequency multiple quantum well (MQW) light intensity modulator for free space IR optical communication. The POET tag optical scheme is a compact, high quality generalized fish-eye lens with telecentric arrangement in image space. The telecentric arrangement in image space provides perfect omnidirectional retroreflection of a recall beam and an optimum divergent of light at the MQW providing maximum modulation contrast ratios. The important POET tag features are low power consumption, zero probability of jamming and intercepting (high security of communication,) because it operates in a passive retroreflection mode with a highly-directed optical beam.
The problem of multiextremum optimization is very general in optical design. Many efforts have been applied to finding approaches to its solution, but optical software developers are still far from finding a universal and reliable method. Solving the problem of finding the optimal angles of rotation of real components is a good way to test different approaches to the problem of multiextremum optimization. Compared with the general approach to optical-system design, multiextremum optimization is unconstrained optimization with an analytical test for the optimization criterion: the mean-square wavefront deformation. Finding the optimal angles of rotation shares many specific features with the general problem of optical-system design, such as having a large number of minimums. In addition, these minimums have a special character: they look like a “ravines”. The common optimization methods (gradient or Newtonian) easily can find the local minimums associated with an initial point, but they lack the ability to jump to another minimum. A genetic algorithm can find some point in the zone of attraction to another minimum, but it gets stuck in a “ravine” bottom line. An adaptive genetic algorithm together with local optimization methods can find a major number of minimums.
KEYWORDS: LIDAR, 3D displays, 3D image processing, Visualization, Optical sensors, Environmental sensing, 3D visualizations, Profilometers, Sensors, 3D vision
In this paper, LIDAR imaging sensors, 3D synthetic and natural object-centric environment, and temporal ATR are discussed in the context of Modeling and Simulation and Hardware-in-the-loop testing.
New approaches to light directionality and backlighting are described. They are discussed in the general context of the Liouville theorem and the second principle of thermodynamics; 3-D autostereoscopic applications are also discussed.
The double expansion of wavefront deformation in Zernike polynomials over pupil and field-of-view coordinates is a powerful tool for lens design, testing and alignment. It provides a compact description of wavefront deformation of centered and decentered optical systems over the field-of-view. Understanding the structure of this expansion provides a solution for determining the optimum position and minimum number of field-of-view points for wavefront approximation. This can significantly reduce the computational burden of lens design and is especially important for time consuming wavefront testing before lens alignment.
Physical Optics Corporation (POC) is developing an innovative light illumination system for a continuous wave imaging laser radar that is being investigated at the Army Research Laboratory. The illumination system will combine the output power from a number of laser diodes into one highly collimated beam with a divergence of three angular minutes. This will provide a 10-m diameter illumination spot at a distance of 5 km, and therefore, a high-power illumination field at the object of interest. The illumination system consists of several fiber-coupled laser diodes, mechanical and optical assemblies for focusing light from every fiber to a collimator focus point, and a non-imaging beam combiner-collimator with 180 degree acceptance aperture. The outgoing clear aperture of the combiner-collimator element is about 80 mm; overall the entire illuminator is compact, light-weight, and cost- effective in mass production.
Physical Optics Corporation has developed an automatic polarization sensitive multispectral imaging system for real-time object-to-background contrast enhancement. This system is built around an acousto-optic tunable filter and liquid crystal achromatic rotator of light polarization.
The smooth continuous wavefront deformation function (WDF) can be expanded into Zernike polynomials. The coefficients of polynomial expansion for Fizeau or Twyman-Green interferometry can be found with ease by applying the least-square approximation. In the Hartmann test, shearing interferometry methods, or the Ritchey-Common test, coefficients can be found by using the least-square approximation as well. In these cases, the measuring data is a result from applying a linear operator to the WDF (which is the differentiation operator in the Hartmann test). By applying this operator to Zernike polynomials, new polynomials can be found for the test data. The coefficients of test data expansion and WDF expansion are equal. As in lateral shearing interferometry, the data from several test pictures can be approximated in one step of the 'truss' approximation.
The double expansion of the wavefront deformation in Zernike polynomials over the pupil and the field-of-view coordinates is a powerful tool for lens design, testing, and alignment. It provides a compact description of the wavefront deformation of perturbed and unobscured optical systems over the field-of-view. The integral of the mean-square wavefront deformation over the field-of-view is simply the sum of the products of the norms of the polynomials and the squared global coefficients. Eight or ten global coefficients can provide a comprehensive centered system description. Only fourteen main additional global coefficients is sufficient for the description of perturbed and unobscured optical systems.
Vibration sensors provide very important information for an unattended ground sensor network. For this specific application, a vibration sensor must be extremely robust and must have very high sensitivity and very low power consumption. The authors experimentally demonstrated two schemes of fiber optic interferometric sensors capable of sensing vibrations with amplitudes of a few tens of picometers in the frequency range below 1 kHz. The proposed schemes consist of commercially available components and make possible fabrication of a ruggedized, highly sensitive sensor with low power consumption.
This presentation describes the major performance characteristics of the developed camera and demonstrates some results of target contrast enhancement in laboratory and field experiments.
By utilizing the unique AOTF feature of varying its spectral transmission according to the spectrum of the driving RF signal, Physical Optics Corporation developed an automatic hyperspectral system for real-time target contrast enhancement and target tracking.
The double expansion of wavefront deformation in Zernike polynomials over the pupil and the field-of-view is a promising approach for lens design, testing, and alignment. Conventional wavefront representation in Zernike polynomial expansion from the pupil coordinates makes it very cumbersome to consider the optical system condition over the field-of- view. Evaluating the properties of symmetry of centered and perturbed systems can provide a compact representation of wavefront deformation over the field-of-view. Even for complicated optical systems such as lithography objectives, 8 to 12 global coefficients can provide a comprehensive system description. Coefficients for centered and perturbed systems are independent.
Absolute distance interferometry is a promising technology for comprehensive investigation of optical component parameters, including measurement of radii and thicknesses. In special interferometric schematics, it is applicable to measuring parameters of surfaces after grinding and can simplify null corrector design or eliminate its implementation for final testing aspherical surfaces. A universal method for precision length measurement, called 'excess fractions,' was proposed at the end of the last century to calibrate gauges. In this method, the interferometer compares an unknown distance with magnitudes of several wavelengths. The array which consists of the remainders of integer parts of the phase shift between the reference branch of the interferometer and the measuring distance, will be obtained. The proposed consideration of the 'excess fraction' method is based on the Chinese Remainder Theorem. It will be shown that the confidence interval of the obtained distance is equal to the confidence interval of the fractions. Consideration of the finite precision will make the method independent of which units will express, and provides the intervals of unambiguity of the method.
The recently developed technology of spectrally-adaptive light filtering has been applied to create a spectrally-matched filter directly in the optical channel, to select a target with a known spectral signature over an ambient background. The approach to ATR described eliminates intensive computer post-processing of multispectral images, making real-time target detection with enhanced signal-to-clutter ratio possible.
A new approach to imaging colorimeter design has been demonstrated. This approach is based on the concept of spectrally adaptive filtering of images, which permits adjustment of the overall response of the system for measuring color coordinates to fit one of three color matching functions and to change its spectral response rapidly. The experiments conducted demonstrated high spatial resolution -- 512 by 512 pixels or more (for nonpixelated objects), capability of performing color coordinate measurements of an entire image in 1/30 second, and high measurement accuracy.
A technology of spectrally adaptive light filtering has been demonstrated, which allows changing the transmission curve of an optical filter in an octave-wide spectral interval with the kilohertz rate under full computer control. This technology utilizes the unique capability of acousto-optic tunable filters to transmit light in several spectral intervals simultaneously, driven by radio signals with complex spectra. A computer algorithm to synthesize the driving signal for an arbitrary given spectral transmission curve was developed. This algorithm has been used for various applications of this developed technology in the visible, SWIR, and MWIR spectral intervals.
Interferometric flatness testing of a large surface of 500 mm plus in diameter appears to be a complex problem which can be solved, in particular, by means of the oblique-incidence interferometer. The possibility of use of dumping least square method is considered in this paper. This method criteria are square sum minima both for wave front distortion function deviation and for mirror mounting errors in the three base points. The mathematical model has proved that the method proposed provides the original wave front reconstruction accuracy 2.5 ... 5 times better than by means of the former method depending on points number on a subaperture.
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