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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 general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities and compared with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter, which may be the most effective filtering methods at present.
Abstract: Filtering off speckle noise from a fringe image is one of the key tasks in electronic speckle pattern interferometry (ESPI) In general, ESPI fringe images can be divided into three categories: low-density fringe images, high-density fringe images, and variable-density fringe images In this paper, we first present a general filtering method based on variational image decomposition that can filter speckle noise for ESPI fringe images with various densities In our method, a variable-density ESPI fringe image is decomposed into low-density fringes, high-density fringes, and noise A low-density fringe image is decomposed into low-density fringes and noise A high-density fringe image is decomposed into high-density fringes and noise We give some suitable function spaces to describe low-density fringes, high-density fringes, and noise, respectively Then we construct several models and numerical algorithms for ESPI fringe images with various densities And we investigate the performance of these models via our extensive experiments Finally, we compare our proposed models with the windowed Fourier transform method and coherence enhancing diffusion partial differential equation filter These two methods may be the most effective filtering methods at present Furthermore, we use the proposed method to filter a collection of the experimentally obtained ESPI fringe images with poor quality The experimental results demonstrate the performance of our proposed method

23 citations

Patent
06 Oct 1978
TL;DR: Reference scenes stored in a filter set containing an array of sets of suimposed, holographic, matched filters are optically correlated with input images displayed on an optically-addressed, liquid crystal, light modulator.
Abstract: Reference scenes stored in a filter set containing an array of sets of suimposed, holographic, matched filters are optically correlated with input images displayed on an optically-addressed, liquid crystal, light modulator 34. In operation, a selected laser diode is energized to direct a polarized light beam through the collimating lens L1 to the reflecting surface of a polarizing beam splitter 35. After reflecting off the beamsplitter surface, the beam is expanded by positive lens L2 and passed to the liquid crystal modulator. There it is modulated by the input image and reflected; after which it is recollimated by positive lens L2, transmitted by the beamsplitter, and directed to a particular array location of the filter set dependent upon which particular laser diode is energized. The filter set is positioned to be in the back focal plane of lens L4 so that the Fourier-transform of the input image is incident on the particularly located, superimposed matched filter at 31. If the Fourier transformed input image corresponds to one of the superimposed matched filters the incident light beam is diffracted by that particular hologram matched filter to form a spot of light at a predetermined array location of a detector array. The optical correlator finds use as a terminal guidance system in guiding a missile to its target.

23 citations

Journal ArticleDOI
TL;DR: A heuristic development of the operation of a square root filter (one whose amplitude transmittance is proportional to the square root of position in frequency space) is presented and the use of this filter in phase image visualization systems is discussed.
Abstract: A heuristic development of the operation of a square root filter (one whose amplitude transmittance is proportional to the square root of position in frequency space) is presented. The output of a coherent optical processor utilizing this filter for phase image inputs is shown to be an intensity which is directly proportional to the derivative of the input phase function. The results of a digital filtering experiment which confirms this linear relationship are presented. The use of this filter in phase image visualization systems is also discussed.

23 citations

Journal ArticleDOI
TL;DR: The results demonstrate the ability to unambiguously associate a complicated scattering pattern with the particle size, shape, and orientation.
Abstract: This work combines digital holography with spatial filtering at two wavelengths to record the hologram and light-scattering pattern for a single particle using a color sensor. Particles 30-100 μm in size and with various shapes are considered. The results demonstrate the ability to unambiguously associate a complicated scattering pattern with the particle size, shape, and orientation.

23 citations

Proceedings ArticleDOI
S. Yoda1, H. Okabe1, J. Takagi1, T. Yamashita1
25 Sep 1995
TL;DR: In this paper, a road surface recognition sensor was realized by using an optical spatial filter, which transforms a street surface image into spatial frequency spectra, and ground velocity is shown by a filtered moving image.
Abstract: A road surface recognition sensor has been realized by using an optical spatial filter. The sensor transforms a road surface image into spatial frequency spectra. Frequency distribution depends on the road surface type. Ground velocity is shown by a filtered moving image. Experimental results show that five road surface types were recognized in cold districts. Both road surface condition and vehicle velocity can be detected by a noncontact sensor; therefore, the sensor is useful for active safety systems.

23 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202321
202265
202181
2020144
2019180
2018179