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Journal ArticleDOI

Real-time edge detection by cyclic-path polarization interferometer

01 Feb 2014-Applied Optics (Optical Society of America)-Vol. 53, Iss: 4, pp 727-730
TL;DR: In a triangular path cyclic interferometer employing a polarizing beam splitter, using a linear polarizer in the path of the orthogonally polarized imaging beams, it is possible to achieve amplitude subtraction between the two images, resulting in an edge-enhanced image of the sample.
Abstract: In a triangular path cyclic interferometer employing a polarizing beam splitter (PBS), the two counterpropagating beams are orthogonally polarized. A sample placed almost equidistant from the PBS is imaged by a lens placed in the path of the emerging beams so that two defocused images of the sample are recorded on a CCD. Using a linear polarizer in the path of the orthogonally polarized imaging beams, it is possible to achieve amplitude subtraction between the two images, resulting in an edge-enhanced image of the sample. The proposed real-time edge-enhancement technique is experimentally demonstrated.
Citations
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Journal ArticleDOI
TL;DR: It is shown that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.
Abstract: Using polarization as an additional parameter apart from amplitude and phase in spatial filtering experiments offers additional advantages and possibilities. An S-waveplate that can convert a linearly polarized light into radially or azimuthally polarized light can also be used for isotropic edge enhancement. For anisotropic edge enhancement, introduction of a polarizer at the output was recommended and edge selection was done by orientation of the polarizer. But the full potential of the S-waveplate as a spatial filter has not been exploited so far. Unlike the standard amplitude and phase-based Fourier filters, which are independent to the state of polarization of the illuminating beam, the S-waveplate acts in a different way depending on the state of polarization. The edge selection does not need to be carried out by changing the orientation of the polarizer. With a fixed polarizer at the output, we show that either isotropic or anisotropic edge enhancement in any desired orientation can be performed by operating the same spatial filter setup in different illuminating polarization states.

41 citations


Cites methods from "Real-time edge detection by cyclic-..."

  • ...Among the polarization-based filtering methods, image subtraction is one of the methods to extract the edges [27]....

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Journal ArticleDOI
TL;DR: In this article, a method for generating carrier fringes and a nonconventional rotational shear in a triangular cyclic-path interferometer, while simultaneously suppressing the presence of typical lateral and radial shearing, is presented.
Abstract: This work presents a method for generating carrier fringes and a nonconventional rotational shear in a triangular cyclic-path interferometer, while simultaneously suppressing the presence of typical lateral and radial shearing. To carry out this method, a 4f optical system is implemented into the cyclic interferometer. The most important contributions of this paper are its demonstration of the linear dependence of the movable mirror displacement with the carrier frequency introduced, and the realization of a nonconventional rotational shearing interferometer. Additionally, we think that one of its possible potential applications is the observation of the angular derivative of parallel projections of a phase object placed at the output plane, generating a great advantage in edge-enhancement optical tomography. In this paper, we develop a theoretical model and show experimental results.

6 citations


Cites methods from "Real-time edge detection by cyclic-..."

  • ...Introduction A cyclic path optical configuration (CPOC) has been used extensively to measure many physical quantities in many fields in science and technology [1-21]....

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Journal ArticleDOI
TL;DR: Experimental results presented in this Letter could provide an insight into the momentum change associated with the energy redistribution in the fundamental phenomenon of optical interference.
Abstract: A scheme to study the effect of residual phase gradients in an optical interference between two out-of-phase Gaussian beams is proposed. In a Sagnac interferometer configured to provide a null output, a variable linear phase swept across the null point unfolds an optical field rotation due to an apparently negligible residual phase gradient present orthogonal to the linear phase sweep. As the optical beam that rotates around its propagation axis carries orbital angular momentum, the experimental results presented in this Letter could provide an insight into the momentum change associated with the energy redistribution in the fundamental phenomenon of optical interference.

5 citations

Journal ArticleDOI
TL;DR: In this article, a cyclic interferometric configuration is chosen to maintain the stability of the operation against external vibrations, and a wave plate is inserted into the common paths to introduce an intrinsic phase difference between the orthogonal polarized beams.
Abstract: An alternative polarization phase-shifting technique is proposed to determine the thickness of transparent thin-films. In this study, the cyclic interferometric configuration is chosen to maintain the stability of the operation against external vibrations. The incident light is simply split by a non-polarizing beam splitter cube to generate test and reference beams, which are subsequently polarized by a polarizing beam splitter. Both linearly polarized beams are orthogonal and counter -propagating within the interferometer. A wave plate is inserted into the common paths to introduce an intrinsic phase difference between the orthogonal polarized beams. A transparent thin-film sample, placed in one of the beam tracks, modifies the output signal in terms of the phase retardation in comparison with the reference beam. The proposed phase-shifting technique uses a moving mirror with a set of “fixed” polarizing elements, namely, a quarter-wave retarder and a polarizer, to facilitate phase extraction without rotating any polarizing devices. The measured thicknesses are compared with the measurements of the same films acquired using standard equipment such as the field-emission scanning electron microscope and spectroscopic ellipsometer. Experimental results with the corresponding measured values are in good agreement with commercial measurements. The system can be reliably utilized for non-destructive thickness measurements of transparent thin -films.

3 citations


Additional excerpts

  • ...In this study, a cyclic interferometric configuration, which is less prone to the instability due to environmental disturbances, is chosen [16, 17]....

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Proceedings ArticleDOI
01 Dec 2015
TL;DR: In this paper, a scheme to sense the residual phase gradients in an optical interference of two out-of-phase Gaussian beams is proposed, which is implemented using a Sagnac interferometer configured to provide a null output.
Abstract: A scheme to sense the residual phase gradients in an optical interference of two out-of-phase Gaussian beams is proposed. Its implementation by detecting the residual phase gradient as an optical field rotation in a Sagnac interferometer, configured to provide a null output is presented.

3 citations

References
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Journal ArticleDOI
Robert W. Lewis1

15 citations


"Real-time edge detection by cyclic-..." refers methods in this paper

  • ...For real-time processing of incoherently illuminated objects, the object is displayed in a transmissive spatial light modulator (SLM) placed in the object plane of the coherent image processing setup [2]....

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Journal ArticleDOI
TL;DR: A self-adaptive optical Fourier processing system using photoinduced dichroism in a bacteriorhodopsin film was experimentally demonstrated for medical image processing and it may be possible to develop a low-cost rugged battery operated portable signal-enhancing magnifier.
Abstract: Optical image processing techniques are inherently fast in view of parallel processing. A self-adaptive optical Fourier processing system using photoinduced dichroism in a bacteriorhodopsin film was experimentally demonstrated for medical image processing. Application of this powerful analog all-optical interactive technique for cancer diagnostics is illustrated with two mammograms and a Pap smear. Microcalcification clusters buried in surrounding tissue showed up clearly in the processed image. By playing with one knob, which rotates the analyzer in the optical system, either the microcalcification clusters or the surrounding dense tissue can be selectively displayed. Bacteriorhodopsin films are stable up to 140 degrees C and environmentally friendly. As no interference is involved in the experiments, vibration isolation and even a coherent light source are not required. It may be possible to develop a low-cost rugged battery operated portable signal-enhancing magnifier.

14 citations


"Real-time edge detection by cyclic-..." refers methods in this paper

  • ...Electrically and optically addressed SLMs located in the Fourier plane have also been used as dynamic spatial-frequency filters [3,4]....

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Journal ArticleDOI
TL;DR: In this paper, a birefringent lens is used for producing two images of the test transparency with different amount of defocus on a grating which are subsequently subtracted by optical means.

13 citations

Journal ArticleDOI
TL;DR: The fundamental architectures and the potential applications of optical processing techniques in medical imaging are introduced and the medical image processor in the foreseeable future may be a hybrid device, namely, a programmable optical architecture.
Abstract: In this report we introduce the fundamental architectures and the potential applications of optical processing techniques in medical imaging. Three basic optical processing architectures were investigated for digital and analog radiography. The processors consist of a module that converts either the analog or the digital radiograph into a coherent light distribution; a coherent optical processing architecture that performs various mathematical operations; a programmable digital-optical interface and other accessories. Optical frequency filters were implemented for mammographic and other clinical feature enhancement. In medical image processing, digital computers offer the advantages of programmability and flexibility. In contrast, optical processors perform parallel image processing with high speed. Optical processors also offer analog nature, compact size, and cost effectiveness. With technical advances of digital-optical interface devices, the medical image processor, in the foreseeable future, may be a hybrid device, namely, a programmable optical architecture.

12 citations

Journal ArticleDOI
TL;DR: Real-time optical image subtraction and edge enhancement based on a speckle modulation technique is carried out by using ferroelectric liquid-crystal polarization switches and a ferro Electric spatial light modulator as a real-time and multiple-exposure optical device.
Abstract: We carried out real-time optical image subtraction and edge enhancement based on a speckle modulation technique by using ferroelectric liquid-crystal polarization switches and a ferroelectric liquid-crystal spatial light modulator. A ferroelectric liquid-crystal spatial light modulator is employed as a real-time and multiple-exposure optical device, and successful results are obtained from three-exposure images modulated by speckles. Thus, image subtraction and edge enhancement are realized in real time. The whole operation is performed within several milliseconds with modest operating conditions. Because the spatial light modulator has a high resolution of greater than 100 line pairs/mm and can store fine speckle patterns, the image qualities we obtained are quite satisfactory.

12 citations