We present, as a different perspective on optimization, an expert system for optimization of optical systems that can be used in conjunction with damped least squared methods to find minima for specific design forms. Expert system optimization differs from global optimization in that it preserves the basic structure of the optical system and limits its search for a minima to a relatively small portion of the design space. In general, the high density of local minima obscures the general trend of the merit function in the region of interest for systems with a large number of variables and constraints. Surprisingly, there may be a potential decrease of an order a magnitude in the merit function for a region of solution space. While global optimization is well-suited to identifying design forms of interest, expert system optimization can be used for in-depth optimization of such forms. An expert system based upon such techniques was used to obtain the winning entry for the 2002 IODC lens design problem. The expert system used is discussed along with other design examples.
Recent investigation demonstrated the feasibility of using stacks of microlenslet arrays for optical imaging applications. Many applications driving our research require ultra-compact magnifying imaging systems. In this investigation we demonstrate that a magnifying system based on a stack of two dissimilar microlenslet
arrays is feasible.
Optical design tools are presented to provide automatic generation of reflective optical systems for educational use. The tools are graphical in nature and use an interactive slider interface with freely available optical design software. Operation of the sliders provides input to adjust first-order and other system parameters (e.g. focal length), while appropriate system construction parameters are automatically updated to correct aberrations. Graphical output is also presented in real-time (e.g. a lens drawing) to provide the opportunity for a truly visual approach to optical design. Available systems include two- and three-mirror telescopes, relays, and afocal systems, either rotationally symmetric or having just a plane of symmetry. Demonstrations are presented.
We discuss a surprising new feature of the merit function landscape in optical system design. When certain conditions are satisfied, the set of local minima forms a network in which all nodes are connected. Each link between two neighboring minima contains a special type of saddle point (more precisely, a saddle point having a Morse index. On this basis, a new global optimization method that takes advantage of this feature is proposed. The central component of the new method, the algorithm for saddle point detection, works in a parameter space of arbitrary dimensionality, and uses only the local optimization engine of the optical design program. For a simple global optimization search (the symmetric Cooke triplet) the network of the corresponding set of local minima is presented.
We propose the implementation of improved Fresnel type diffractive optical elements (DOEs) on spatial light modulators with a limited phase modulation capability. For the design of our elements we developed a method of design, that starts with an element formed by the phase function of a pixelated lens (PL), modulated by the phase of a lenslet array. The design is subject to a large number of phase levels in a limited range (smaller than 2π). We show that the undesirable effects produced by the complex modulation of a spatial light modulator (specifically, a twisted nematic liquid crystal display) can be minimized when improved Fresnel type DOEs are used. Simulation and optical reconstructions corroborate our proposal.
Three new polarimeters are described which represent advances in polarization metrology capabilities. Two are at a new polarization laboratory started at the University of Arizona’s Optical Sciences Center, (1) a Fiber Optic Spectropolarimeter and (2) a High Speed Mueller Matrix Imaging Polarimeter. The third is a new visible Mueller Matrix Spectropolarimeter for optical component test from a startup company, Axometrics, which is useful for detailed characterization of optical components and thin films via spectra of diattenuation, retardance, and depolarization.
In this paper we present a normalized method of deriving a phase pupil function to extend the focal depth of imaging systems specially used for small object tracking. The method is based on the concept that the intensity distribution in the vicinity of the focal plane can be controlled and redistributed by means of a phase pupil function. This phase pupil function allows the peak intensity of a point-spread function (PSF) of the imaging system to remain relatively uniform, and the profile of the PSF to be approximately fitted to a Gaussian function in an extended range of the focal depth. A rotational symmetric aspheric phase plate has been designed and fabricated. The imaging system incorporating this pupil plate has extended the focal depth more than twofold compared with a conventional imaging system. Theoretical analyses and experimental results are also presented in support of this method.
Aperture size imposes, by way of diffraction, a fundamental limit on the spatial resolution that can be attained with an imaging system that operates at a given distance from a target. It is therefore natural to seek to improve image resolution by increasing the size of the collection aperture of a remote sensing system. On the other hand, as aperture size increases it becomes technically more difficult, and financially much more expensive, to maintain a figure quality that holds geometrical aberrations to a level that is negligible compared to diffraction effects. This paper presents an analysis of an approach that combines active optics with what has been called a post-detection phase diversity technique [R. A. Gonsalves, "Phase retrieval and diversity in adaptive optics," Opt. Eng. 21, 829-832 (1982)]. The basic concept is to allow for variable focus as an inherent system capability, in order to acquire multiple defocused images, each one of which has slightly different, and complementary, spatial frequency content. The proper deconvolution and merging of these images produces a composite image that is superior to the image that can be acquired at any single focal setting. This paper presents the theoretical basis of this approach, and numerical simulations that include the effects of noise and various levels of third order spherical aberration.
There has recently been an increased interest in software that can propagate complex fields through optical systems. This type of optical software gives the user the ability to analyze and tolerance two main categories of coherent optical systems: (1) metrology systems and (2) systems used to propagate coherent optical signals. In order to demonstrate the methodology of modeling and analyzing coherent systems, a software model of a Fizeau interferometer was constructed. The model extended from the laser source through a 256 x 256 pixel detector with 8-bit gray level resolution. The reference mirror in the model is moved to create four, 90-degree phase shifted interferograms in the form of ASCII files. These four ASCII files are then input into another software code that calculates and unwraps the phase to determine the surface error. The peak-to-valley and RMS surface errors are calculated and the surface is fit to Zernike polynomials. This Fizeau model was and used to study the effects on surface measurement accuracy of the first surface of a test lens due to unwanted reflections from the second surface of the lens. This is the type of study for which non-sequential, coherent field propagation software has some advantage relative to geometrical ray trace codes.
A new class of optical telescope is required to obtain high resolution spectra of many faint, distant galaxies. These dim objects require apertures approaching 30 meters in addition to many hours of integration per object, and simultaneous observation of as many galaxies as possible. Several astronomical telescopes of 20, 30, 50, even 100 meters are being proposed for general purpose astronomy. We present a different concept here with a 30-m telescope optimized for wide field, multi-object spectroscopy. The optical design uses a fully steerable, quasi-Cassegrain telescope in which the primary and secondary mirrors are parts of concentric spheres, imaging a 3° field of view onto a spherical surface. The spherical aberration from the mirrors is large (about 2 arc minutes) but it is constant across the field. Our system design uses numerous correctors, placed at the Cassegrain focus, each of which corrects over a small field of a few arc seconds. These can be used for integral field spectroscopy or for direct imaging using adaptive optics. Hundreds of these units could be placed on the focal surface during the day to allow all-night exposures of the desired regions. We believe that this design offers an economical system that can be dedicated for several important types of astronomical observation.
Single point diamond turning of optical surfaces is becoming more commonly used, especially in infrared systems. However, the process introduces its own peculiar forms of figure error that can compromise performance. These errors include tool misalignment error, thermal effects, low frequency surface ripple, and mounting effects. Techniques have been developed to model these effects in Monte Carlo simulations using conventional optical design codes to predict the changes in optical performance.
A method for transfer of Finite Element Analysis (FEA) results to the optical design program CODE V1 has been developed, although the method can be readily adapted to other optical design codes that support Zernike surfaces. This method is an improvement in many ways over the methods used in commercial codes written to perform this data transfer. The method assumes the surface nodal displacements are purely in the direction of the sag (z-axis) at the radial location of the displaced node point. This eliminates the approximations necessary when transferring the deformations as pseudo-interferograms, and eliminates the approximations made in the ray tracing of interferograms. Special techniques have been included to remove the inaccuracies introduced in the FEA program. The method has been validated on a series of test cases.
We have developed the Optical Fiber Imaging Laser Radar based on the focal plane array detection using the small number of detectors less than the number of the focal plane array resolution. For this focal array detection, first, we made the optical fiber dissector which has one vertical cross section of the 35 x 35 optical fibers square array at one end to receive the reflected laser pulse from an object and 25 vertical cross sections of the 7 x 7 optical fibers array extracted from the 35 x 35 optical fibers square array at 25 other ends to guide the dissected laser pulse to the 25 InGaAs photodiode pulse detectors of the 25 channels of the parallel pulse counter. The 7 x 7 optical fibers arrays are the mode (5,5) residual classes from the 35 x 35 optical fibers square array. Second, we shaped the most of Erbium doped optical fiber laser pulse into the laser pulse with the beam of the elliptic cross section that falls into one 5 x 5 area of the vertical cross section of the 35 x 35 optical fibers square array when it is received. And we made a mask with a window of a size 5 x 5 optical fibers’ cross section to ensure no cross talk in the receiver of the Optical Fiber Imaging Laser Radar. Then, we controlled the direction of the shaped laser pulse to scan and reconstruct the received data from the 25 channels of the parallel pulse counter to the actual order data of the Imaging Laser Radar. The developed Imaging Laser Radar shows that the image resolution between the range image and the object is within one pixel difference and that the range resolution is under 15cm.
We propose a design of a compact HD-DVD pickup head, where a lensed penta-prism is used to replace the mirror and the collimating lens in a conventional one to shorten the geometrical size but keep the whole optical path length unchanged.
In this paper, a white light interferometer has been designed to measure the distributed polarization coupling in high birefringence fibers. The limitations to the measurement accuracy have been analyzed. The main structure is a Michelson interferometer. A superluminescent diode (SLD) has been adopted as the broadband source in the white light interferometer. Corner mirrors have been adopted to reflect the light beams in both arms of the Michelson interferometer. To enlarge the measurement range, the light beam in the scanning arm of the Michelson interferometer is reflected three times. Thus the scanning range of the interferometer is doubled for a certain linear motion rail. The full width half maximum (FWHM) spectrum of the SLD is 50 nm, and its central wavelength is 1300 nm. If the modal birefringence of the HBF is 6 X 10-4, a spatial resolution of 56 mm can be achieved. A high sensitivity photo detector and a high-resolution analog to digital converter (ADC) have been adopted. These devices are capable of testing a coupling point with accuracy up to -80 dB.
Birefringent interleaving filters are very useful in DWDM, but it is quite difficult to design the birefringent interleavers with the frequency spacing smaller than 50GHz. Because of the small birefringence of all the natural and synthesized crystals, the sizes of birefringent plates in this use become impossible large. This paper proposes an analog birefringence structure, which is suitable for such a task. The structure consists of a pair of double-refraction plates for splitting and combination, respectively, and in between a set of two optical plates of different indices of refraction. An incident beam is first divided into two separated beams by the first plate, which then pass through the individual plates to delay with different refraction. Finally the two delayed beams are combined spatially into a single beam by the second plate. It can be understood that this structure has the function just the same as a birefringent plate. The difference of the refractive indices of the two optical plates can be very large (up to 0.8), so that the analog birefringence structure is not only practically possible but also very compact. As usual, a cascade of analog birefringence structures will form a flat-passband interleaver. The detailed designs are given. The experiment on an analog birefringence structure is demonstrated as well.
The performance of Q-switch DPL output giant pulse can be optimized by utilized the site of maximum diffraction efficiency of acousto-optic Q-switch. Based on the model of spot acoustic source, spatial distribution of ultrasound field in acousto-optic crystal is studied by numerical calculation with considering the factor of acoustic attenuation. Distribution of diffraction efficiency in acousto-optic crystal is obtained by analysis it. So the site of maximum diffraction efficiency is found, and the same outcome is obtained in experiment. The channel selection technology is put forward based on the study on spatial distribution of diffraction efficiency in acousto-optic crystal that is benefit to obtain optimal parameters (which include the peak power, pulse width, etc) in DPL.
In this paper, we design microlens arrays for the improvement of the optical power coupling efficiency of 8x8 planar lightwave circuit (PLC) devices. Eight fiber array input and output are considered for integrated packaging with 8x8 PLCs. A variety of core pitches matching are achieved from 25μm to 127μm between integrated optical chips and fiber array. We presented a simple formula, which is useful for microlens arrays design. Our proposed microlens arrays
provide versatility in a micro-optics package for optical communication. Our results are helpful for low-cost packaging,
monolithic integration optics modularization, and minimization of the optical power coupling loss between fiber array and array module.
Polarization propagation of a monochromatic plane wave through layered thin film dielectric media is described using an electric and magnetic field component spinor while the transformation of fields at a dielectric interface is effected using the characteristic matrix for each layer. The characteristic matrix is rendered in a representation of the Pauli spin matrices and expressions constructed for the change of polarization field components. The matrix representation describes a pseudo-spinor rotation of the field components the magnitude of which is given by the phase thickness of the stack and the direction of rotation given by a vector expressed in terms of an optical admittance dependent on the index of refraction and angle of incidence. This method provides a useful and simple calculation procedure for polarization propagation phenomena in optical problems along with potential applications to surface characterization.
We present a simple and effective method of reducing the background noise of a full-field optical coherence tomography system that improves the image quality of the system. The system is based on a modified Michelson interferometer providing such new features as a tilted cubic beam-splitter and a spatial filter incorporated in the back focal plane of an imaging lens. The new arrangement reduces background noise significantly. The effects of the tilted beam-splitter and spatial filter on the optical image are also studied, and experimental results are provided.
In fabrication of a fine optical element, femtosecond laser is an attractive experimental tool because it avoids the splutter effect to damage the nearby lines. However, the wavelength of the usual Ti:sapphire laser is insensitive to the widely-used photoresist in microlithographic industry. In this paper, we introduce a new method with femtosecond doubled-frequency laser by use of a BBO crystal to fabricate optical gratings and chromium photomasks. The laser source is the Ti:sapphire laser with a central wavelength of 790 nm and its doubled-frequency laser is obtained through the BBO crystal whose wavelength (395nm) is within the sensitive exposure range of the photoresist. This enables us to fabricate fine optical elements with the normal photolithographic technique. In the experiment, we use a translator that is controlled by a computer to accurately move for fabrication of optical elements with high precision. In contrast to the other techniques, our approach has the higher quality and precision, for femtosecond laser works faster than the material’s thermal diffusion, i.e., without splutter effect that yields the clear edge of the optical element. Moreover, it also makes the fabrication processing simplified. Experiments are given to verify that this method should be highly interesting for the fabrication of fine binary optical elements.
A novel method for phase gradient extraction from fringe patterns is described. We use the sine and cosine of the phase as they are obtained with phase shifting techniques or Fourier methods. The phase gradient is approximated using simultaneously forward and backward phase differences. The resulting set of simultaneous linear equations is solved using iterative procedures. This avoids solving for the phase as a previous step to obtain the searched phase derivatives, decreasing processing time. The method is noise tolerant, incorporating regularization terms to constrain the solution to be smooth. The recovered phase derivatives may be used in surface strain analysis or for the purposes of phase recovery.
In this paper, the principle and characteritics of an optical critical angle sensor based on the internal-reflection effect are introduced. Then, the method to design the optical parameters of the critical angle prisms and the relationship between these parameters and the system character are discussed with analytical and simulation results. These parameters include the initial angle of incidence, non-parallelism errors of the two parallel faces, and the surface flatness of the reflection faces. A pair of custom-built critical angle prisms providing three internal-reflections is used in our simulation. With the initial angle error is 20 arcsec, the matched non-parallelism errors of the prisms are 30 arcsec and the surface flatness is λ/8, the sensitivity of the system is better than 0.05 arcsec and the nonlinearity is less than 0.3%.
In this paper, the present status and developing tendency of night vision device of helmet are reviewed. The research intention and design principle of CY-1R night vision goggle are explained which fills the gaps in active-passive combined night vision field in our country. The structure, composition, mechanism and overall performance of the goggle are analyzed. Based on these characteristics, the sensitivity of the system is high and the image observed is very clear. Taking advantage of it, we can complete the military operation under any atrocious weather conditions.
We demonstrated a flat-surface magneto-optic spatial light modulator (MOSLM) without physically isolated pixels and an external bias coil. The flat-surface MOSLM, which was fabricated by a simple process, was designed as a compact system with a high resolution and very low driving current. Flat-surface pixels for the novel MOSLM were magnetically isolated and produced by the combinatory use of the local annealing effect that reduced magnetization 4πMs of pixel areas and the stress effect that produced sharp variations of magnetic anisotropy in a magnetic garnet film under the edge of a metal layer. The novel MOSLM can provide a higher resolution, a simpler fabrication process, more compact systems and a lower driving current than the conventional MOSLM.
Wide application of Zernike’s orthogonal polynomials at lens design and optical engineering generates a need of more detailed study of their properties, assemblage new results and results received previously. In this connection we bring results of our researches on study of properties of Zernike's polynomials, revealing their interrelation with other special functions, obtaining recurrence relations, formulas of differentiation of Zernike's radial polynomials, decomposition of the ratio of two radial polynomials in continuous fractions and so on.