Optical encoders are commonly used for high accuracy position measurement, both linear and angular. In order to determine the position, the optical encoder generates two electrical signals that are combined using the arctangent algorithm. There are a number of situations, optical, mechanical and electronic, that affect these signals and produce an error in the position measurement. In this work, we analyze the error produced in optical encoders when the electrical signals vary from their nominal values. By using a linear expansion, simple expressions for the error estimation are obtained which can be used to improve the design of the optical encoders. In addition, an experimental verification of the theoretical results is performed.

https://iopscience.iop.org/article/10.1088/0957-0233/19/11/115104/pdf

Metrological errors in optical encoders

An apparatus for producing structured light comprises a first optical arrangement which comprises a microlens array comprising a multitude of transmissive or reflective microlenses which are regularly arranged at a lens pitch P and an illumination unit for illuminating the microlens array. The illumination unit comprises an array of light sources for emitting light of a wavelength L each and having an aperture each, wherein the apertures are located in a common emission plane which is located at a distance D from the microlens array. For the lens pitch P, the distance D and the wavelength L, the following equation applies P 2=2LD/N, wherein N is an integer with N≧1. High-contrast high-intensity light patterns can be produced.

Apparatus for producing patterned illumination including at least one array of light sources and at least one array of microlenses

We introduce a modulation mechanism for negative index materials (NIM) in the GHz frequency range by means of photoconductive coupling. This leads the way to a monolithically integrated modulable NIM achieved by conventional microfabrication techniques. The photosensitive material is deposited in the gap of the split ring resonator (SRR) structure and the response in terms of S-parameters is simulated using a high frequency structure simulator (HFSSTM) program. Only a single SRR particle is simulated to demonstrate total suppression of resonance amplitude and without any loss of generality the concept is applicable to a NIM comprising of both negative permeability and negative permittivity. This simple modulation of refractive indices can lead to novel optical device developments with the potential to dramatically improve the performance of existing phased array antennas, optical beam-forming networks, antenna remoting and transportation of RF power through fiber.

Switching between positive and negative permeability by photoconductive coupling for modulation of electromagnetic radiation

Holography offers unique advantages over conventional photography or traditional photogrammetric techniques in the recording of three-dimensional objects over a large depth of field. However, there are several fundamental problems in recording and replay that must be understood and overcome. The authors discuss the techniques of in-line and off-axis holography, and the problems that are encountered in practice. They present a review of several applications in particulate recording, bubble chamber holography, fuel-rod 'hologrammetry', endoscopy etc. The emphasis is on precision three-dimensional coordinate measurements from holographic images.

Precision coordinate measurements using holographic recording

Under certain circumstances, Voigt waves can propagate in a biaxial composite medium even though the component material phases individually do not support Voigt wave propagation. This phenomenon is considered within the context of the strong-permittivity-fluctuation theory. A generalized implementation of the theory is developed in order to explore the propagation of Voigt waves in any direction. It is shown that the correlation length—a parameter characterizing the distributional statistics of the component material phases—plays a crucial role in facilitating the propagation of Voigt waves in the homogenized composite medium. (Some figures in this article are in colour only in the electronic version)

Correlation length facilitates Voigt wave propagation

On the exact first order ellipsometric calculations of the optical constants of thin films

The effects of spectral width and size of source on the quality of multiple images have been investigated theoretically and experimentally. It has been shown that, under the validity of Fourier optics, the physical size of the source has no influence on image resolution, but the spectral width of the source has. The relationship between the image resolution and the spectral width of the source shows that for high resolution multiple imaging, a high pressure Hg lamp can be used in conjuction with a suitable interference filter.

Effects of Spectral Width and Size of Source on Multiple Images Produced by Sampling of Spatial Frequencies

The production and the diffraction properties of holographically produced multidirectional phase gratings have been discussed. Theoretical interpretations of the experimental results have been outlined. Some practical applications of these gratings have been mentioned.

Multidirectional holographic phase gratings: I. Production and diffraction properties

A new approach to the problem of transmission of holographic data via TV is considered. It is proposed to transmit the equivalent of holographic data by transmitting the sampled Fourier spectrum of the object wave using a holographic recording technique. In this approach, the limited resolution of the TV channel does not pose a serious problem and, it seems, some essential properties of the holographic data, for example, their usefulness for reconstructing 3-D perspective, can be transmitted without radical modification of the conventional TV pick-up camera. Results of a limited optical simulation experiment are presented.

S. C. Som

Papers

On the exact first order ellipsometric calculations of the optical constants of thin films

Effects of Spectral Width and Size of Source on Multiple Images Produced by Sampling of Spatial Frequencies

Multidirectional holographic phase gratings: I. Production and diffraction properties

A New Scheme for Holographic Data Transmission via TV

Comments on the paper “Best proximity point results for p-proximal contractions”