光学组件中心偏的自动测试

介绍光学组件中心偏的测试原理，给出了测量系统和光路的设计方案，详细地介绍了中心偏的自动测试的设计过程。     

Optical shifter for a three-dimensional image by use of a gradient-index lens array

We propose a new function of the two-dimensional lens array that is composed of many gradient-index lenses. The array forms three-dimensional (3D) images. The characteristics of the 3D images depend on the length of the gradient-index lens. Especially, if the length of the lens is an odd-integer multiple of the half period of the optical path, 3D images are pseudoscopic with a reversed depth. The two lens arrays are positioned at a suitable distance, so that orthoscopic 3D images with the correct depth are formed in front of the lens array.     

Optical field study of near-field optical recording with a solid immersion lens

The use of a solid immersion lens (SIL) is an important technique for increasing areal density in optical recording. Here an approximate method is presented for analyzing the optical fields in a SIL above a half-space and a SIL above a multilayer recording medium. Both propagating and evanescent components are included in the distribution of fields below the SIL. An approximate closed-form expression is given for the decay of the intensity away from the SIL surface above a half-space. In the case of a SIL above a recording medium the model describes the strong oscillations that are observed in the reflected Kerr rotation and ellipticity as the medium spacing is varied. These oscillations are attributed to standing waves in the propagating field component.     

Optical performance of frequency-selective bolometers

Frequency-selective bolometers (FSBs) are a new type of detector for millimeter and submillimeter wavelengths that are transparent to all but a narrow range of frequencies as set by characteristics of the absorber itself. Therefore stacks of FSBs tuned to different frequencies provide a low-loss compact method for utilizing a large fraction of the light collected by a telescope. Tests of prototype FSBs indicate that the absorption spectra are well predicted by models, that peak absolute absorption efficiencies of the order of 50% are attainable, and that their out-of-band transmission is high.     

Imaging performance of widefield solid immersion lens microscopy

We investigate the performance of a widefield imaging system employing an aplanatic solid immersion lens. Off-axis imaging quality is examined theoretically at different radii and thicknesses of the aplanatic solid immersion lens. It is found that field curvature is the major aberration affecting the imaging quality. Aberrations are measured experimentally, and the results are in very good agreement with those obtained from simulations and demonstrate the situations where high quality images can be obtained with the aplanatic solid immersion lens.     

Optical performance of a burst-mode multikilowatt CO(2) laser

A unique advancement in the flexibility of high-power lasers is presented. Operation of a 20-kW, continuous-wave, CO(2) laser with a burst excitation technique produces a broad range of optical output characteristics. A detailed discussion of the discharge excitation of this system demonstrates some unique features of the process. Control of burst frequency and duty cycle provides a convenient means to alter the time-varying nature of the output beam. Laser output can be varied from distinct, independent pulses through to a continuous wave. Optical pulse shape varies from triangular to square in profile. The primary focus of this study lies in the regime with distinct, separate pulses. Empirical relationships that summarize the dependence of optical duty cycle and peak laser power on discharge control parameters are developed. Use of these relations imparts control of the optical parameters of importance in deep penetration welding.     

Optical tunneling effect calculation of a solid immersion lens for use in optical disk memory

A solid immersion lens (SIL) has the advantage of easily decreasing the spot size for high data density in optical recording. To accurately obtain the optical tunneling effect for a high-N.A. SIL, we calculated the optical tunneling beam characteristics, using electromagnetic theory. Tunneling beam spot-size dependence on polarization direction and energy-transfer efficiency are also clearly shown.     

Numerical optimization of integrating cavities for diffraction-limited millimeter-wave bolometer arrays

Far-infrared to millimeter-wave bolometers designed to make astronomical observations are typically encased in integrating cavities at the termination of feedhorns or Winston cones. This photometer combination maximizes absorption of radiation, enables the absorber area to be minimized, and controls the directivity of absorption, thereby reducing susceptibility to stray light. In the next decade, arrays of hundreds of silicon nitride micromesh bolometers with planar architectures will be used in ground-based, suborbital, and orbital platforms for astronomy. The optimization of integrating cavity designs is required for achieving the highest possible sensitivity for these arrays. We report numerical simulations of the electromagnetic fields in integrating cavities with an infinite plane-parallel geometry formed by a solid reflecting backshort and the back surface of a feedhorn array block. Performance of this architecture for the bolometer array camera (Bolocam) for cosmology at a frequency of 214 GHz is investigated. We explore the sensitivity of absorption efficiency to absorber impedance and backshort location and the magnitude of leakage from cavities. The simulations are compared with experimental data from a room-temperature scale model and with the performance of Bolocam at a temperature of 300 mK. The main results of the simulations for Bolocam-type cavities are that (1) monochromatic absorptions as high as 95% are achievable with <1% cross talk between neighboring cavities, (2) the optimum absorber impedances are 400 ohms/sq, but with a broad maximum from approximately 150 to approximately 700 ohms/sq, and (3) maximum absorption is achieved with absorber diameters > or = 1.5 lambda. Good general agreement between the simulations and the experiments was found.     

Nonparaxial diffraction-limited propagation of light in a graded-index planar medium with a hyperbolic secant refractive-index profile

Nonparaxial diffraction-limited propagation of light with amplitude distribution in hyperbolic functions through an inhomogeneous planar medium with a hyperbolic secant refractive-index profile is studied by means of the stationary phase method. The irradiance distribution at geometrical shadow, edge of shadow, and a geometrically illuminated region is analyzed for a particular case.     

Optical inspection of periodic structures using lens arrays and moire magnification

Abstract

This paper describes a technique that uses the phenomenon of moire magnification, developed recently for the measurement and inspection of periodic structures. Moire magnification occurs when an array of lenses is used to view an array of identical objects situated at the focal plane of the lenses. As the lens array is aligned with the object array, a moire pattern is observed in which each moire fringe consists of a magnified image of the repeat element of the object array. As the arrays are rotated with respect to each other, the magnification and orientation of the image changes.

The moire magnifier builds up an image from a large number of components of an array and therefore gives a representation of the average unit. It is a very simple and robust device and may well be more convenient to use, for example in an industrial production environment, than a microscope. A large number of components used in electronic imaging systems are periodic in nature and can conveniently be inspected using this technique. Examples are shown.     

Optical lens design based on metallic nanoslits with variant widths

Designs of optical lenses based on metallic nanoslits are carried out based on the phase and amplitude modulation by tuning the slit widths. The slits are perforated on thin metallic film, and the width of each slit is achieved by simulated annealing algorithms, which is connected with both the amplitude and phase modulation. Two kinds of focal lenses, which can realize one or two focus points, have been designed. The finite-difference time-domain method is employed to check the performance of the designed lenses. Simulation results show that the designed lenses can perform the preset functions well. Using this method, multiple optical elements with different functions can be conveniently achieved in subwavelength scale.     

Optical pressure sensor based on the combined system of a variable liquid lens and a point diffraction interferometer

We propose an experimental efficient optical pressure sensor based on a variable liquid lens and a modified point diffraction interferometer. The working principle of the sensor is based on the fact that a variation in pressure induces a change in lens curvature and hence in its focal length, which can be tracked and measured with the interferometer. The pressure is then measured by recording and processing the interferometric images. The sensor in this proposal can change its dynamic range by the simple axial movement of one of the components of the optical system. In this work we show the performance of the system within three working ranges: from 0 to 1 kPa with accuracy of approximately 0.01 kPa, from 0 to 7 kPa with 0.05 kPa accuracy, and from 0 to 30 kPa with 0.3 kPa accuracy.     

Optical behaviour of display performance enhancement films

Abstract

The optical properties of holographic display screen enhancement films are investigated. Experimental data show that the on-axis scattering from such films is significantly stronger than the off-axis scattering. The results are modelled using the beam propagation method in two dimensions. Good qualitative comparisons between experimental and theoretical results are obtained.     

微型紫外光纤光谱仪的光学系统设计及性能检测

采用非对称交叉的切尼尔-特纳(C-T)光路结构,设计了一种微型紫外光纤光谱仪的光学系统.用ZEMAX对光路进行仿真、像质评价和优化,对各类像差进行校正.同时,对不同狭缝尺寸和光栅常数的光谱仪理论分辨率进行了分析.当采用30μm狭缝和1 800线/mm光栅时,模拟光学系统在180~270nm光谱范围内整体分辨率优于0.5nm,在180nm附近最高分辨率达到0.1nm.最后,基于该光学设计研制了一台光谱仪样机,在使用交流电弧激发金属纯铁样品的条件下,对原子发射光谱进行了检测.     

Superresolution performance of an absorbing glass positive lens element

Superresolution performance of a plano-convex lens made of absorbing glass is analyzed numerically. It was found that a reduction of the radius of the Airy disk depends solely on the center transmittance of the lens (a zero edge thickness is assumed) for any reasonable ratio of radius of curvature of the convex surface and the lens radius. The modest decrease in the size of the central diffraction peak is followed by a large decrease of its energy content and a rapid brightening of the diffraction rings. The most that can be achieved with such a lens is a reduction of the radius of the Airy disk to 71% of the corresponding clear aperture value, followed by approximately 78% of the energy being diverted into diffraction rings.     

Optical analysis of time-averaged multiscale Bessel beams generated by a tunable acoustic gradient index of refraction lens

Current methods for generating Bessel beams are limited to fixed beam sizes or, in the case of conventional adaptive optics, relatively long switching times between beam shapes. We analyze the multiscale Bessel beams created using an alternative rapidly switchable device: a tunable acoustic gradient index (TAG) lens. The shape of the beams and their nondiffracting, self-healing characteristics are studied experimentally and explained theoretically using both geometric and Fourier optics. By adjusting the electrical driving signal, we can tune the ring spacings, the size of the central spot, and the working distance of the lens. The results presented here will enable researchers to employ dynamic Bessel beams generated by TAG lenses.     

Nearly diffraction-limited signal generated by a lower beam-quality pump in an optical parametric oscillator

The beam quality of an optical parametric oscillator (OPO) within a singly resonant, confocal-positive branch unstable resonator is investigated. Resonator configurations have been found in which the beam quality of the outgoing signal exceeds the beam quality of the pump. Cavity magnification and pump-pulse duration are found to determine the signal beam quality. It is shown that signal M2 decreases with increasing pump-pulse duration for a given cavity magnification. In an experimental demonstration of a LiNbO3 OPO within an unstable resonator, pumped by a multitransversal mode beam, a signal beam with an almost-single transversal mode has been generated, whereas the multitransversal mode behavior of the pump beam is projected on the idler beam.     

Optical and thermal performance of a three-dimensional compound parabolic concentrator for spherical absorber

For medium range temperature applications, focusing type collectors like Compound Parabolic Concentrator (CPC) are most commonly used. Considerable research work has been carried out to improve the performance of the two-dimensional compound parabolic concentrator (2D CPC). The three-dimensional compound parabolic concentrator (3D CPC) was found to be more efficient than 2D CPC because of the higher concentration ratio. In the present work a 3D CPC was fabricated with a half acceptance angle of 4° for a spherical absorber of radius 100 mm. UV stabilized aluminized polyester foil having high reflectivity (0·85) was pasted on the reflector for a total height of 441mm and an aperture width of 540 mm. The optical efficiency was estimated theoretically and compared with the experimental value. Experimentally determined values of optical and thermal efficiencies were in good agreement with theoretically predicted value. The experimental results shown that the optical efficiency obtained from the 3D CPC (0·626) was significantly higher than that of the 2D CPC (0·570) of similar dimensions. Since the optical efficiency of the 3D CPC was increased, the thermal efficiency of the collector was also increased. In addition to that, time constant of the concentrator was also calculated. The time constant of the 3D CPC (431 s) was fairly high when compared with the 2D CPC (110 s). An attempt was made to generate low pressure steam using 3D CPC in the in situ steam generation mode. The efficiency of the steam generation was about 38%, which was one of the possible applications of 3D CPC module.     

Optical performance of axisymmetric edge-ray concentrators and illuminators

The optical performance of axisymmetric radiation concentrators and illuminators that are derived when two-dimensional edge-ray designs are rotated about their optic axis is investigated. Of particular interest are devices with spherical and cylindrical absorbers or light sources, for which the inherent ray rejection can be substantial. From the principle of etendue (phase-space) conservation, a lower bound for ray rejection can be established. With computer ray tracing, we demonstrate that this bound underestimates the actual ray rejection by only a few percent at most. Hence, to a good approximation, it can be used as an equality in analytic predictions of characteristic efficiency-concentration curves. By designing for absorbers or sources with a bald spot, the full range of efficiency and flux concentration values can be realizedand the trade-off between them can be quantified. The optical performance of these edge-ray designs is also compared against fundamental upper bounds on the flux concentration and efficiency of axisymmetric devices.     

Optical performance of absorber structures for thermal detectors

The concept of absorption by a metal-dielectric-metal structure is reexamined. The absorber system is modeled as a transparent medium between two absorbing films. We study the conditions for the parameters that ensure null reflectance and transmittance for a fixed wavelength of the incident radiation, and we present explicit expressions for the absorptance in each film. The absorption optimum conditions in a range of wavelengths are also analyzed.