optical filter
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Horticulturae ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 77
Author(s):  
Christian Höing ◽  
Sharvari Raut ◽  
Abozar Nasirahmadi ◽  
Barbara Sturm ◽  
Oliver Hensel

The state-of-the-art technique to control slug pests in agriculture is the spreading of slug pellets. This method has some downsides, because slug pellets also harm beneficials and often fail because their efficiency depends on the prevailing weather conditions. This study is part of a research project which is developing a pest control robot to monitor the field, detect slugs, and eliminate them. Robots represent a promising alternative to slug pellets. They work independent of weather conditions and can distinguish between pests and beneficials. As a prerequisite, a robot must be able to reliably identify slugs irrespective of the characteristics of the surrounding conditions. In this context, the utilization of computer vision and image analysis methods are challenging, because slugs look very similar to the soil, particularly in color images. Therefore, the goal of this study was to develop an optical filter-based system that distinguishes between slugs and soil. In this context, the spectral characteristics of both slugs and soil in the visible and visible near-infrared (VNIR) wavebands were measured. Conspicuous maxima followed by conspicuous local minima were found for the reflection spectra of slugs in the near infrared range from 850 nm to 990 nm]. Thus, this enabled differentiation between slugs and soils; soils showed a monotonic increase in the intensity of the relative reflection for this wavelength. The extrema determined in the reflection spectra of slugs were used to develop and set up a slug detector device consisting of a monochromatic camera, a filter changer and two narrow bandpass filters with nominal wavelengths of 925 nm and 975 nm. The developed optical system takes two photographs of the target area at night. By subtracting the pixel values of the images, the slugs are highlighted, and the soil is removed in the image due to the properties of the reflection spectra of soils and slugs. In the resulting image, the pixels of slugs were, on average, 12.4 times brighter than pixels of soil. This enabled the detection of slugs by a threshold method.


Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 89
Author(s):  
Bowen Zhang ◽  
Nuo Chen ◽  
Xinda Lu ◽  
Yuhang Hu ◽  
Zihao Yang ◽  
...  

A chip-scale tunable optical filter is indispensable to meeting the demand for reconfigurability in wavelength division multiplexing systems, channel routing, and switching, etc. Here, we propose a new scheme of bandwidth tunable band-pass filters based on a parity-time (PT) symmetric coupled microresonator system. Large bandwidth tunability is realized on the basis of the tuning of the relative resonant frequency between coupled rings and by making use of the concept of the exception point (EP) in the PT symmetric systems. Theoretical investigations show that the bandwidth tuning range depends on the intrinsic loss of the microresonators, as well as on the loss contrast between the two cavities. Our proof-of-concept device confirms the tunability and shows a bandwidth tuning range from 21 GHz to 49 GHz, with an extinction ratio larger than 15 dB. The discrepancy between theory and experiment is due to the non-optimized design of the coupling coefficients, as well as to fabrication errors. Our design based on PT symmetry shows a distinct route towards the realization of tunable band-pass filters, providing new ways to explore non-Hermitian light manipulation in conventional integrated devices.


2022 ◽  
Author(s):  
Shayan Mookherjee

Summary of a Project Outcomes report of research funded by the U.S. National Science Foundation under Project Number 0925133. A two-section optical filter is studied which can achieve tunable passband width and high extinction ratio.


Author(s):  
Jun Ushida ◽  
Tadashi Murao ◽  
Akemi Shiina ◽  
Tsuyoshi Horikawa

Abstract Crosstalk among channels in wavelength division multiplexing (WDM) filters must be suppressed to enhance receiver sensitivity in direct-detection-based optical communication systems. We present a systematic method to identify the maximum crosstalk and upper limit of the transmission spectrum bandwidth of a highly multi-staged Mach-Zehnder interference (MZI) lattice optical filter with a number of cascade N (N=1,2,…,∞). The scattering matrix including the wafer-level-measurement-based coupling coefficients of directional couplers is used to calculate the transmittance from the input to each output channel and the result is exactly extrapolated to infinite N. This method can be used to design, characterize, and evaluate $N$-cascaded MZI lattice optical filters that must meet strict WDM specifications.


2021 ◽  
pp. 127855
Author(s):  
Yang Yan ◽  
Jinpeng Yuan ◽  
Lirong Wang ◽  
Liantuan Xiao ◽  
Suotang Jia

2021 ◽  
Vol 191 ◽  
pp. 106521
Author(s):  
Xinzhi Liu ◽  
Jun Yu ◽  
Toru Kurihara ◽  
Ke Li ◽  
Zhao Niu ◽  
...  

2021 ◽  
Vol 2127 (1) ◽  
pp. 012032
Author(s):  
A S Beliaeva ◽  
G E Romanova

Abstract Designing systems with an acousto-optical filter requires considering its small numerical aperture and crystal size. These features lead to the low efficiency of using the luminous flux, which may be crucial in practical applications of such systems for spectral analysis. The article discusses ways to increase the energy efficiency in different types lighting systems based on acousto-optic filtration.


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