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Papers by Carlos Ferreira

Advances in Imaging and Electron Physics, 2010

ABSTRACT

Frontiers in Optics 2012/Laser Science XXVIII, 2012

ABSTRACT

Journal of The Optical Society of America, 1996

The space -bandwidth product (SW) is fundamental for judging the performance of an optical system... more The space -bandwidth product (SW) is fundamental for judging the performance of an optical system. Often the SW of a system is defined only as a pure number that counts the degrees of freedom of the system. We claim that a quasi-geometrical representation of the SW in the Wigner domain is more useful. We also represent the input signal as a SW in the Wigner domain. For perfect signal processing it is necessary that the system SW fully embrace the signal SW.

Optics Letters, 2006

We present a superresolving approach that allows one to exceed the diffraction limit and recover ... more We present a superresolving approach that allows one to exceed the diffraction limit and recover highly resolved contours of moving targets from a sequence of low-resolution images. The presented approach is suitable for remote sensing applications. The resolution decoding algorithm that is used to recover the highresolution features of the target can be run partially via optical means and that way can be used to reduce the required computational complexity.

Optics Letters, 1993

A morphological optoelectronic image processor based on the threshold decomposition concept is de... more A morphological optoelectronic image processor based on the threshold decomposition concept is described and demonstrated. Binary slices of a gray-scale input image are optically convolved with a binary structuring element of arbitrary size and shape in a noncoherent convolver. The slices are displayed on a liquid-crystal spatial light modulator of 320 x 264 pixels. The kernels are implemented as modifications of the system impulse response. The processor's convolution patterns are recorded with a CCD camera and fed into a PC by a frame grabber. Subsequent elementary morphological operations are looped. Examples of processing an input image of 256 x 256 pixels and 16 gray levels with kernels of arbitrary size are presented.

Optics Communications, 2009

In this paper, we present an approach that can be used for transmission of 2D spatial information... more In this paper, we present an approach that can be used for transmission of 2D spatial information through space-limited systems capable of transmitting even only a single spatial pixel. The input 2D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixels into one point at its focal plane. Although the various spatial pixels were mixed together, since the random mask provided axial delay which was larger than the coherence length of the light source, the orthogonality between the spatial content of every pixel is preserved. The decoding system includes a lens that is positioned at the output of the resolution reduction system and it converts the output light into a plane wave containing all the spatial information of the original image mixed together in all of its pixels. By interfering this plane wave with the same plane wave after passing through the same random spatial coding mask, the spatial information of every pixel of the input object is recovered.

Optics Communications, 2000

A graphical representation of general non-absorbing polarization devices operating under normal p... more A graphical representation of general non-absorbing polarization devices operating under normal plane-wave incidence is presented. The representation is based on a four-dimensional spherical parametrization of the Jones matrix of this kind of polarization devices. The graphical representation takes the form of a solid cylinder. The projection of the point representing the device over the base of the cylinder gives the corresponding polarization eigenvectors represented in the complex plane, while the height of the point in the cylinder is the phase of its eigenvalue. Some simple examples like wave-plates and rotators are discussed. The representation may represent a useful tool to identify the operation regimes of polarization modifying elements, for instance electro-optic devices. In this sense, the representation is also applied to the case of a twisted nematic liquid crystal display. q larized light. In these two descriptions, polarization devices act as linear transformations, represented by Jones or Mueller matrices, respectively.

Optical Engineering, 1992

The feasibility of polychromatic object recognition by multichannel correlation is experimentally... more The feasibility of polychromatic object recognition by multichannel correlation is experimentally demonstrated. Objects whose shape changes with the wavelength of the illumination beam are used. Separate high-pass matched filters, each one recorded with a different wavelength, ...

Optical Engineering, 2000

A convenient relation between fractional Fourier transform patterns and diffraction patterns is o... more A convenient relation between fractional Fourier transform patterns and diffraction patterns is obtained by applying the Gauss equation of geometrical optics. Thus, Fresnel and fractional domains cannot be considered as independent domains, since one is just a geometrical image of the other, providing a physical and direct connection.

Journal of The Optical Society of America A-optics Image Science and Vision - J OPT SOC AM A-OPT IMAGE SCI, 2001

We present a novel method for achieving in real time a two-dimensional optical wavelet decomposit... more We present a novel method for achieving in real time a two-dimensional optical wavelet decomposition with white-light illumination. The underlying idea of the suggested method is wavelength multiplexing. The information in the different wavelet components of an input object is transmitted simultaneously in different wavelengths and summed incoherently at the output plane. Experimental results show the utility of the new proposed method.

Optics Express, 2007

A scale invariant 3D object detection method based on phase Fourier transform (PhFT) is addressed... more A scale invariant 3D object detection method based on phase Fourier transform (PhFT) is addressed. Three-dimensionality is expressed in terms of range images. The PhFT of a range image gives information about the orientations of the surfaces in the 3D object. When the object is scaled, the PhFT becomes a distribution multiplied by a constant factor which is related to the scale factor. Then 3D scale invariant detection can be solved as illumination invariant detection process. Several correlation operations based on vector space representation are applied. Results show the tolerance of detection method to scale besides discrimination against false objects.

Applied Optics, 1992

A shift-and scale-invariant version of morphological fringe-adjusted joint transform correlation ... more A shift-and scale-invariant version of morphological fringe-adjusted joint transform correlation (MFJTC) is proposed in this paper, which we call shift-and scale-invariant MFJTC (SIMFJTC). SIMFJTC is combination of MFJTC and conventional radial harmonic filter (RHF). Using computer simulation, we compare the output results of SIMFJTC with those of morphological radial harmonic correlation (MRHC) and SDF-based FPFJTC when input scene is corrupted by salt-and-pepper noise and cluttered background. Our results show that SIMFJTC has higher discriminability and displays better stability against salt-and-pepper noise and cluttered background. Moreover, scale-invariance of SIMFJTC is much stricter than MRHC and SDF-based FPFJTC.

* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery t... more * Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or longer. For further details, please see shipping policy. ... Listed below are the papers found in this volume. Click the paper title to view an abstract or to order an individual paper. ... Holographic methods for imaging into scattering volume media are described. The holography is carried out with light that has reduced coherence, either ...

Advances in Imaging and Electron Physics, 2010

ABSTRACT

Frontiers in Optics 2012/Laser Science XXVIII, 2012

ABSTRACT

Journal of The Optical Society of America, 1996

The space -bandwidth product (SW) is fundamental for judging the performance of an optical system... more The space -bandwidth product (SW) is fundamental for judging the performance of an optical system. Often the SW of a system is defined only as a pure number that counts the degrees of freedom of the system. We claim that a quasi-geometrical representation of the SW in the Wigner domain is more useful. We also represent the input signal as a SW in the Wigner domain. For perfect signal processing it is necessary that the system SW fully embrace the signal SW.

Optics Letters, 2006

We present a superresolving approach that allows one to exceed the diffraction limit and recover ... more We present a superresolving approach that allows one to exceed the diffraction limit and recover highly resolved contours of moving targets from a sequence of low-resolution images. The presented approach is suitable for remote sensing applications. The resolution decoding algorithm that is used to recover the highresolution features of the target can be run partially via optical means and that way can be used to reduce the required computational complexity.

Optics Letters, 1993

A morphological optoelectronic image processor based on the threshold decomposition concept is de... more A morphological optoelectronic image processor based on the threshold decomposition concept is described and demonstrated. Binary slices of a gray-scale input image are optically convolved with a binary structuring element of arbitrary size and shape in a noncoherent convolver. The slices are displayed on a liquid-crystal spatial light modulator of 320 x 264 pixels. The kernels are implemented as modifications of the system impulse response. The processor's convolution patterns are recorded with a CCD camera and fed into a PC by a frame grabber. Subsequent elementary morphological operations are looped. Examples of processing an input image of 256 x 256 pixels and 16 gray levels with kernels of arbitrary size are presented.

Optics Communications, 2009

In this paper, we present an approach that can be used for transmission of 2D spatial information... more In this paper, we present an approach that can be used for transmission of 2D spatial information through space-limited systems capable of transmitting even only a single spatial pixel. The input 2D object is illuminated with temporally incoherent illumination. The axial coherence length is very short and it equals only a few microns. Attached to the input object spatial random phase mask generates different axial shift for every pixel of the input. The temporal delays of the encoding (axial shifts) of every pixel are longer than the coherence length of the illuminating source. Therefore no temporal correlation exists between the various pixels of the input. A lens combines all spatial pixels into one point at its focal plane. Although the various spatial pixels were mixed together, since the random mask provided axial delay which was larger than the coherence length of the light source, the orthogonality between the spatial content of every pixel is preserved. The decoding system includes a lens that is positioned at the output of the resolution reduction system and it converts the output light into a plane wave containing all the spatial information of the original image mixed together in all of its pixels. By interfering this plane wave with the same plane wave after passing through the same random spatial coding mask, the spatial information of every pixel of the input object is recovered.

Optics Communications, 2000

A graphical representation of general non-absorbing polarization devices operating under normal p... more A graphical representation of general non-absorbing polarization devices operating under normal plane-wave incidence is presented. The representation is based on a four-dimensional spherical parametrization of the Jones matrix of this kind of polarization devices. The graphical representation takes the form of a solid cylinder. The projection of the point representing the device over the base of the cylinder gives the corresponding polarization eigenvectors represented in the complex plane, while the height of the point in the cylinder is the phase of its eigenvalue. Some simple examples like wave-plates and rotators are discussed. The representation may represent a useful tool to identify the operation regimes of polarization modifying elements, for instance electro-optic devices. In this sense, the representation is also applied to the case of a twisted nematic liquid crystal display. q larized light. In these two descriptions, polarization devices act as linear transformations, represented by Jones or Mueller matrices, respectively.

Optical Engineering, 1992

The feasibility of polychromatic object recognition by multichannel correlation is experimentally... more The feasibility of polychromatic object recognition by multichannel correlation is experimentally demonstrated. Objects whose shape changes with the wavelength of the illumination beam are used. Separate high-pass matched filters, each one recorded with a different wavelength, ...

Optical Engineering, 2000

A convenient relation between fractional Fourier transform patterns and diffraction patterns is o... more A convenient relation between fractional Fourier transform patterns and diffraction patterns is obtained by applying the Gauss equation of geometrical optics. Thus, Fresnel and fractional domains cannot be considered as independent domains, since one is just a geometrical image of the other, providing a physical and direct connection.

Journal of The Optical Society of America A-optics Image Science and Vision - J OPT SOC AM A-OPT IMAGE SCI, 2001

We present a novel method for achieving in real time a two-dimensional optical wavelet decomposit... more We present a novel method for achieving in real time a two-dimensional optical wavelet decomposition with white-light illumination. The underlying idea of the suggested method is wavelength multiplexing. The information in the different wavelet components of an input object is transmitted simultaneously in different wavelengths and summed incoherently at the output plane. Experimental results show the utility of the new proposed method.

Optics Express, 2007

A scale invariant 3D object detection method based on phase Fourier transform (PhFT) is addressed... more A scale invariant 3D object detection method based on phase Fourier transform (PhFT) is addressed. Three-dimensionality is expressed in terms of range images. The PhFT of a range image gives information about the orientations of the surfaces in the 3D object. When the object is scaled, the PhFT becomes a distribution multiplied by a constant factor which is related to the scale factor. Then 3D scale invariant detection can be solved as illumination invariant detection process. Several correlation operations based on vector space representation are applied. Results show the tolerance of detection method to scale besides discrimination against false objects.

Applied Optics, 1992

A shift-and scale-invariant version of morphological fringe-adjusted joint transform correlation ... more A shift-and scale-invariant version of morphological fringe-adjusted joint transform correlation (MFJTC) is proposed in this paper, which we call shift-and scale-invariant MFJTC (SIMFJTC). SIMFJTC is combination of MFJTC and conventional radial harmonic filter (RHF). Using computer simulation, we compare the output results of SIMFJTC with those of morphological radial harmonic correlation (MRHC) and SDF-based FPFJTC when input scene is corrupted by salt-and-pepper noise and cluttered background. Our results show that SIMFJTC has higher discriminability and displays better stability against salt-and-pepper noise and cluttered background. Moreover, scale-invariance of SIMFJTC is much stricter than MRHC and SDF-based FPFJTC.

* Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery t... more * Available as a photocopy reprint only. Allow two weeks reprinting time plus standard delivery time. No discounts or returns apply. ... Standard delivery in the US is 7 to 10 business days and outside the US delivery is 4 to 6 weeks or longer. For further details, please see shipping policy. ... Listed below are the papers found in this volume. Click the paper title to view an abstract or to order an individual paper. ... Holographic methods for imaging into scattering volume media are described. The holography is carried out with light that has reduced coherence, either ...