scispace - formally typeset
Search or ask a question
Topic

Spatial filter

About: Spatial filter is a research topic. Over the lifetime, 6170 publications have been published within this topic receiving 100451 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: A diffractive optical element for off-axis focusing of terahertz radiation that acts as both a spatial and a spectral filter is presented and the experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented.
Abstract: A diffractive optical element for off-axis focusing of terahertz radiation is presented. It was designed in a nonparaxial regime and manufactured in a metal slab by laser cutting of curved stripes. The optical function of the structure includes focusing and deflecting the illuminating beam of a chosen frequency in a particular place. Therefore, the element acts as both a spatial and a spectral filter; hence it is especially suitable for separating the terahertz signal from a broadband thermal load in passive detection devices. The experimental evaluation of the proposed diffractive lens by means of time-domain spectroscopy is presented and discussed.

26 citations

Journal ArticleDOI
TL;DR: In this paper, a simple analytic expression for the far-field diffraction pattern of a general high-order Laguerre-Gaussian mode from a circular aperture is derived, and the effect of the aperture as a spatial filter is discussed.

26 citations

Journal ArticleDOI
TL;DR: In this article, a 3D U-Shaped thin lens is proposed to capture the radiated fields over a broader range of incident angles compared to the prior flat lens, which is more effective at a closer distance.
Abstract: This letter presents a 28-GHz compact antenna array that employs a U-Shaped thin lens where a low-profile 1 × 4 antenna array is used as a feed source. The letter demonstrates that the proposed three-dimensional (3-D) U-Shaped lens designed by phase-shifting spatial filter arrays enables more than 3 dB peak gain enhancement even at the distance of less than half of the wavelength from the feed antenna. The first design step is to employ unit cells having a stable insertion loss and phase shift against the incident angle of electromagnetic waves without the gain degradation caused by undesired cavity effects, which is a critical bottleneck at such a short distance. In addition to this, the total gain is further enhanced by creating a novel 3-D U-Shaped architecture, enabling an increase in the effective aperture size because the U-Shaped thin lens can capture the radiated fields over a broader range of incident angles compared to the prior flat lens, which is more effective at a closer distance. This letter demonstrates that the proposed approach can achieve higher than 3.8 dB enhancement in peak gain compared to the antenna without the U-Shaped lens when the phase offset (PO) is 0°. When the levels of the PO are 45°, 90°, and 135°, gain enhancements of 3.4, 3, and 2 dB are also achieved, respectively.

26 citations

Journal ArticleDOI
TL;DR: The suitability of a low-cost liquid crystal TV to function as a spatial light modulator in an optical preprocessor for an electronic pattern recognition system is investigated and three optical edge enhancement methods are presented.
Abstract: The suitability of a low-cost liquid crystal TV to function as a spatial light modulator in an optical preprocessor for an electronic pattern recognition system is investigated. The application presented is optical edge enhancement. The liquid crystal TV performs reasonably well where high-quality images are not required. Three optical edge enhancement methods are presented: spatial filtering; image cancellation; and phase cancellation. The phase cancellation method was discovered during the course of this research.

26 citations

Journal ArticleDOI
TL;DR: In this article, the directional median (DiM) filter is proposed to separate short-length-scale bathymetric features from regional bathymetry, and the spatial distribution of variations in the DiM-based separation is evaluated by estimating their median absolute deviation at each data point.
Abstract: [1] We present a new spatial filter designed to separate short-length-scale bathymetric features from regional bathymetry. The directional median (DiM) filter divides a given filter circle into N “bow tie” sectors, allocates data points inside the filter circle to each sector based on their relative position within the circle, estimates a median for each sector, and returns the lowest of these N medians. This approach prevents DiM filtering from choosing the biased medians near the features on a sloping regional trend, which is a serious artifact of standard median filtering. As the bathymetry comprises diverse length-scale features, the separated results vary with the choice of filter width. Such variations are spatially distributed. Using a finite range of filter widths, we evaluate the spatial distribution of variations in the DiM-based separation by estimating their median absolute deviation (MAD) at each data point. The distribution of MAD values is indicative of uncertainties inherent in the separation. We demonstrate the effectiveness of DiM filtering with both synthetic and actual bathymetric data.

26 citations


Network Information
Related Topics (5)
Optical fiber
167K papers, 1.8M citations
88% related
Resonator
76.5K papers, 1M citations
85% related
Image processing
229.9K papers, 3.5M citations
84% related
Filter (signal processing)
81.4K papers, 1M citations
83% related
Wave propagation
55K papers, 1.1M citations
82% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202265
202181
2020144
2019180
2018179