High-resolution three-dimensional (3-D) imaging (stereo imaging) by endoscopes in minimally invasive surgery, especially in space-constrained applications such as brain surgery, is one of the most desired capabilities. Such capability exists at larger than 4-mm overall diameters. We report the development of a stereo imaging endoscope of 4-mm maximum diameter, called Multiangle, Rear-Viewing Endoscopic Tool (MARVEL) that uses a single-lens system with complementary multibandpass filter (CMBF) technology to achieve 3-D imaging. In addition, the system is endowed with the capability to pan from side-to-side over an angle of ±25 deg, which is another unique aspect of MARVEL for such a class of endoscopes. The design and construction of a single-lens, CMBF aperture camera with integrated illumination to generate 3-D images, and the actuation mechanism built into it is summarized.
We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named “iLocater.” The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 μm), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R~150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use “extreme” adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.
We report on the design, tolerancing, and laboratory breadboard of an imaging spectrometer for the Earth Science Decadal Survey Hyperspectral and Infrared Imager (HyspIRI) mission. The spectrometer is of the Offner type but with a much longer slit than typical designs, with 1600 resolvable spatial elements along the slit for a length of 48 mm. Two such spectrometers cover more than the required swath while maintaining high throughput and signal-to-noise thanks to the large pixel size (30 μm), relatively high speed (F/2.8) and small number of reflections. We also demonstrate a method for measuring smile using a linear array, and use the method to prove the achievement of negligible smile of less than 2% of a pixel over the entire 48 mm slit. Thus we show that this high-heritage, all-spherical mirror design can serve the requirements of the HyspIRI mission.
Studies have shown that stereo images improve surgeons' visuomotor tasks and therefore constructively affect the outcome of a minimally invasive surgery. Stereo images are captured by a stereo endoscope, which consists commonly of duplicate lens systems. However, stereo images can also be captured by a single lens system following a dual aperture scheme (DAS). DAS creates two spatially separated optical channels by placing a dual aperture plate in the limiting aperture of a single lens system. This paper describes efforts to miniaturize the DAS-based imaging system for use in minimally invasive surgery. To demonstrate feasibility, a prototype was fabricated using lens elements 3 mm in diameter and was tested for its stereo depth effect (SDE). The SDE of the prototype was then compared to a duplicate lens system that was constructed theoretically in the same diameter as the 3-mm prototype. The results show that the prototype yields 4/7 of the SDE of the theoretical model. However, the SDE of the prototype provides sufficient SDE, in a viewing range of 1 to 2.5 cm from the lens, for minimally invasive surgery.
We present a technique for imaging full-color 3-D images with a single camera in this paper. Unlike a typical 3-D-imaging system comprising two independent cameras each contributing one viewpoint, the technique presented here creates two viewpoints using a single-lens camera with a bipartite filter whose bandpass characteristics are complementary to each other. The bipartite filter divides the camera's limiting aperture into two spatially separated apertures or viewpoints that alternately image an object field using filter-passband matched, time-sequenced illumination. This technique was applied to construct a 3-D camera to image scenes at a working distance of 10 mm. We evaluated the effectiveness of the 3-D camera in generating stereo images using statistical comparison of the depth resolutions achieved by the 3-D camera and a similar 2D camera arrangement. The comparison showed that the complementary filters produce effective stereopsis at prescribed working distances.
In an effort to miniaturize a 3D imaging system, we created two viewpoints in a single objective lens camera. This was
accomplished by placing a pair of Complementary Multi-band Bandpass Filters (CMBFs) in the aperture area. Two key
characteristics about the CMBFs are that the passbands are staggered so only one viewpoint is opened at a time when
a light band matched to that passband is illuminated, and the passbands are positioned throughout the visible
spectrum, so each viewpoint can render color by taking RGB spectral images. However, each viewpoint takes a
different spectral image from the other viewpoint hence yielding a different color image relative to the other. This
color mismatch in the two viewpoints could lead to color rivalry, where the human vision system fails to resolve two
different colors. The difference will be closer if the number of passbands in a CMBF increases. (However, the number
of passbands is constrained by cost and fabrication technique.) In this paper, simulation predicting the color mismatch
is reported.
There are many advantages to minimally invasive surgery (MIS). An endoscope is the optical system of choice by the
surgeon for MIS. The smaller the incision or opening made to perform the surgery, the smaller the optical system needed.
For minimally invasive neurological and skull base surgeries the openings are typically 10-mm in diameter (dime sized)
or less. The largest outside diameter (OD) endoscope used is 4mm. A significant drawback to endoscopic MIS is that it
only provides a monocular view of the surgical site thereby lacking depth information for the surgeon. A stereo view
would provide the surgeon instantaneous depth information of the surroundings within the field of view, a significant
advantage especially during brain surgery.
Providing 3D imaging in an endoscopic objective lens system presents significant challenges because of the tight
packaging constraints. This paper presents a promising new technique for endoscopic 3D imaging that uses a single lens
system with complementary multi-bandpass filters (CMBFs), and describes the proof-of-concept demonstrations
performed to date validating the technique. These demonstrations of the technique have utilized many commercial off-the-
shelf (COTS) components including the ones used in the endoscope objective.
KEYWORDS: Near field optics, National Ignition Facility, Systems modeling, Optical design, Relays, Laser systems engineering, Laser optics, Software development, Optical filters, Spatial filters
The optical model of a National Ignition Facility beamline will be described and illustrated. The complexity ofthe optical design will be evident. The benefits of having an Endto-End optical model will be presented.
Axial astigmatism can be introduced into the nominal design of an optical system by tilted and tilted-wedged plates. The pupil images in the National Ignition Facility experience many such components. Some ramifications will be explored.
The Injection Laser System (ILS) optical design of the National Ignition Facility (NIF) laser system is described, covering design functions, requirements and constraints, various approaches and options, and the resultant configuration. The front end compromises approximately 70 optical elements per beamline, and 8300 elements total, whose characteristic dimensions are from two to six inches. Individual beamlines span a distance of approximately 15 meters. A variety of optical element types are used: spherical and aspheric lenses, mirrors, polarizers, multi-order waveplates, Faraday rotators, and laser rods. The front end performs multiple functions, namely to: image the pupil of the NIF laser system; amplify the beam's energy with a gain of approximately 104; magnify the beam size by 30x; split the beam four-fold; provide back-reflection isolation; and adjust the pupil location, along with arrival time of the pulse, on a beam-by-beam basis. Due to the high-energy nature of the beam, particular attention is paid to minimizing peak fluence throughout the system, thus reducing the likelihood of optical damage. The front end must deliver wavefront with no more than approximately a wave of P-V aberration (at 1.053 micrometer). This demanding wavefront requirement requires optics' surfaces and transmitted wavefronts to be of relatively high quality, typically 1/10 wave P-V (at 0.633 micrometer).
The optical design of the main laser and transport mirror sections of the National Ignition Facility are described. For the main laser the configuration, layout constraints, multiple beam arrangement, pinhole layout and beam paths, clear aperture budget, ray trace models, alignment constraints, lens designs, wavefront performance, and pupil aberrations are discussed. For the transport mirror system the layout, alignment controls and clear aperture budget are described.
The National Ignition Facility (NIF), being designed and constructed at Lawrence Livermore National Laboratory, comprises 192 laser beams. The lasing medium is neodymium in phosphate glass with a fundamental frequency (1ω) of 1.053μm. Sum frequency generation in a pair of conversion crystals (KDP/KD*P) will produce 1.8 megajoules of the third harmonic light (3ω or λ= 0.351μm) at the target. The purpose of this paper is to provide the lens design community with the current lens design details of the large powered optics in the Main Laser. This paper describes the lens design configuration and design consideration of the Main Laser. The Main Laser is 123 meters long and includes two spatial filters: one 23.5 meters and one 60 meters. These spatial filters perform crucial beam filtering and relaying functions. We shall describe the significant lens design aspects of these spatial filter lenses which allow them to successfully deliver the appropriate beam characteristic onto the target.
A statistical methodology used to judge optical material interpolation models is presented in this paper. A quality- of-fit criterion related to probable performance impact in lens design is used. This treatment was developed as a way to judge the acceptability in lens design of low and medium precision data so that material model developed from this type of data could be used to some level of confidence in a wide assortment of lens designs--in other words, judging whether the material model is universally applicable. The results will show that a universal acceptability criterion is very demanding on the statistics of the data. However, the method developed lends itself to a wider use in judging material models for less demanding lens designs, too. Therefore, the initial criteria goal may rule out some fit models for universal utility in lens design, but the same material models may be usable for less demanding lens design performance situations.
Protective windows and domes on air vehicles such as aircraft and missiles must be efficient aerodynamically, and also they must be acceptable from an optical standpoint. Flat windows have essentially no effect to the optical performance, however they are extremely blunt and not efficient aerodynamically. Concentric domes are reasonably efficient aerodynamically, and if the imaging sensor optics gimbals around the center of curvature of the concentric dome, then the optical aberrations can be easily and effectively corrected for all fields of regard away from the nose. For high speed applications such as with missiles, concentric domes have been a standard for many years. Unfortunately, for extremely high speed applications where aerodynamically induced drag is a problem, concentric domes are simply not adequate, and more aerodynamically efficient shapes such as tangent ogives, must be used. For many applications using today's state of the art IR focal plane arrays the optical performance must be close to diffraction limited. While correction of the residual optical aberrations of a concentric dome is quite trivial, the highly aspheric shape of a tangent ogive introduces significant asymmetrical aberrations which change dramatically with field of regard. In this paper we discuss some recent developments using binary optics for correcting these optical aberrations. With the approaches outlined herein, the heretofore impossible task of imaging through a tangent ogive pointed dome is now shown to be possible.
An all acousto-optic infrared scene projector (IRSP) has been developed for use in evaluating thermal-imaging guidance systems at the Kinetic Kill Vehicle Hardware-in-the-Loop Simulator (KHILS) facility located at Elgin AFB, Florida. The IRSP is a laser source based projector incorporating Scophony illumination and scanning methods to produce 96 X 96 pixel multi-wavelength images at very high frame rates (400 Hz). The IRSP is composed of five functionally similar optical trains, four of which are fed with a different `color' infrared laser. The separate scenes from each optical train are then combined and projected simultaneously into the imaging guidance system.
The index of refraction is a measure of the speed of light in matter. The dispersion, or change of the refractive index with wavelength, can be represented mathematically many different ways for use in optical design. What is covered in this paper is not what the index of refraction is, but how it is represented and how well it is represented over the transmission band of a material. More specifically, the emphasis of this paper is on how the dispersion characterization of a material (particularly in the infrared) effects the chromatic performance of a lens design and the development of a refractive-index interpolation fit criterion based on dispersion.
The sensitivity of infrared optical designs to errors in dispersion is explored through the use of examples. The main cause for a high sensitivity to dispersion tolerances in achromatic designs is explained. Conditions for alerting the optical designer to the need for including dispersion tolerances in the design process as well as to suspect raw refractive-index data for an infrared material are provided. 2. OVERVIEW OF CONCEPTS Dispersion tolerances (dV) rarely limit the performance of optical systems used in the visible spectral band. An optical designer might consider dispersion tolerances on the glasses in a visible-band design when the design has a very high-performance specification and/or when there is very little performance margin for tolerances. In infrared (IR) designs dispersion tolerances are even more rarely considered for the materials. It is also unusual to tolerance the bulk refractive index change (index tolerance dn) for an IR design. The need for dispersion tolerances are analyzed in this paper to highlight for the optical designer the situations and motivations for including dispersion tolerances in the evaluations of optical designs especially in the infrared. Achromatic optical systems in the infrared show a wide range of sensitivity to changes in dispersion. The sensitivity is driven by V-number difference (LV) of the materials used to achieve achromatization and to some extent by aperture diameter and f-number. Therefore the sensitivity to change in dispersion of the materials
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