Optical Design Procedures Research Articles

Deep‐Learned Broadband Encoding Stochastic Filters for Computational Spectroscopic Instruments

AbstractComputational spectroscopic instruments with broadband encoding stochastic (BEST) filters allow the reconstruction of the spectrum at high precision with only a few filters. However, conventional design manners of BEST filters are often heuristic and may fail to fully explore the encoding potential of BEST filters. The parameter constrained spectral encoder and decoder (PCSED)—a neural network‐based framework—is presented for the design of BEST filters in spectroscopic instruments. By incorporating the target spectral response definition and the optical design procedures comprehensively, PCSED links the mathematical optimum and practical limits confined by available fabrication techniques. Benefiting from this, a BEST‐filter‐based spectral camera presents a higher reconstruction accuracy with up to 30 times enhancement and a better tolerance to fabrication errors. The generalizability of PCSED is validated in designing metasurface‐ and interference‐thin‐film‐based BEST filters.

Thin‐Metal‐Film‐Based Transparent Conductors: Material Preparation, Optical Design, and Device Applications

AbstractTransparent conductors are essential elements in an array of optoelectronic devices. The most commonly used transparent conductor – indium tin oxide (ITO) suffers from issues including poor mechanical flexibility, rising cost, and the need for annealing to achieve high conductivity. Consequently, there has been intensive research effort in developing ITO‐free transparent conductors over the recent years. This article gives a comprehensive review on the development of an important ITO‐free transparent conductor, that is based on thin metal films. It starts with the background knowledge of material selection for thin‐metal‐film‐based transparent conductors and then surveys various techniques to fabricate high‐quality thin metal films. Then, it introduces the spectroscopic ellipsometry method for characterizing thin metal films with high accuracy, and discusses the optical design procedure for optimizing transmittance through thin‐metal‐film‐based conductors. The review also summarizes diverse applications of thin‐metal‐film‐based transparent conductors, ranging from solar cells and organic light emitting diodes, to optical spectrum filters, low‐emissivity windows, and transparent electromagnetic interference coatings.

Optimization of prism-based stereoscopic imaging systems at the optical design stage with respect to required 3D measurement accuracy.

We address the optical design procedure of prism-based stereoscopic imaging systems. Conventional approach includes two sequential stages: selection of the hardware and development of the proper digital image processing algorithms. At each of these stages, specific techniques are applied, which are almost unrelated to each other. The main requirements to the imaging system include only the key parameters and the image quality. Therefore, the insufficient measurement accuracy may be revealed only after the prototype is assembled and tested. In this case, even applying complex time-consuming image processing and calibration procedures does not ensure the necessary precision. A radical solution of this issue is to include the measurement error estimation into the optical design stage. In this research, we discuss a simplified implementation of this approach and demonstrate the capabilities of optical design software for this purpose. We demonstrate the effectiveness of this approach by the analysis and optimization of a prism-based stereoscopic imager with respect to required 3D measurement accuracy. The results are meaningful for the development of 3D imaging techniques for machine vision, endoscopic and measurement systems.

Radiometric versus geometric, linear, and nonlinear vignetting coefficient

We analyze the vignetting phenomenon both for optical systems with objects placed at finite distances and for systems with objects at infinity. Four of the possible definitions of the vignetting coefficient k, only two of them existing in the literature, are discussed. We propose two new definitions, i.e., a nonlinear geometric coefficient that is, in part, an analytical model of the vignetting characterization using optical software and a radiometric vignetting coefficient. The object space of each type of optical systems is studied first, defining its characteristic light circles and cones. Several simplifying assumptions are made for each of the two cases considered to derive analytical equations of the vignetting coefficient and thus to determine the best definition to be used. A geometric vignetting coefficient with two expressions, a linear classical and easy-to-use one and a nonlinear, that we propose for both types of systems is obtained. This nonlinear geometric vignetting coefficient proves to be more adequate in modeling the phenomenon, but it does not entirely fit the physical reality. We finally demonstrate that the radiometric vignetting coefficient we define and derive as a view factor for both types of optical systems is the most appropriate one. The half vignetting level, necessary in most optical design procedures to obtain a satisfactory illumination level in the image plane, is also discussed.

Optical design procedure for duplicating wavefront errors of an optical instrument

A new optical design procedure for designing an optical device that will duplicate the wavefront errors of another optical instrument over the full field of view is described in this paper. We call this optical design procedure the inside-out method. It was devised to design an optical instrument that generated wavefronts simulating those of the Hubble Optical Telescope assembly (OTA). As is now common knowledge, during fabrication the OTA primary mirror was made using a defective null-test device; therefore the oTa wavefronts showed perceptible spherical aberration. With the inside-out method it was possible to design an instrument called Red-2 Stimulus that matched the OTA aberrated wavefronts to less than 0.0005? (638 nm) peak to valley on axis and 0.006 X maximum over the full field of view. The inside-out method is described, and two illustrative examples are given.

Strong atom-cavity coupling over large volumes and the observation of subnatural intracavity atomic linewidths.

Standard classical optical design procedures along with the intuitive concept of hour-glass-type optical modes are employed to produce cavities that provide strong atom-cavity coupling for atoms spread over a relatively large spatial region. Such cavities may be employed to provide macroscopic environments in which ordinarily microscopic quantum optical phenomena play an essential role. Concepts are tested through explicit cavity fabrication combined with an experimental study of cavity-mediated perturbations to the frequency and width of a spontaneous emission line in atomic barium. Manifestly subnatural emission linewidths are observed.