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Elsa Fonseca
Unidade de Deteo Remota, Universidade da Beira Interior, Covilh, Covilha, Portugal

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Journal article
Published: 09 July 2021 in IEEE Transactions on Multimedia
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Recently, more interest in the different plenoptic formats, including digital holograms, has emerged. Aside from other challenges that several steps of the holographic pipeline, from digital acquisition to display, have to face, visual quality assessment of compressed holograms is particularly demanding due to the distinct nature of this 3D image modality when compared to regular 2D imaging. There are few studies on holographic data quality assessment, particularly with respect to the perceptual effects of lossy compression. This work aims to study the quality evaluation of digital hologram reconstructions presented on regular 2D displays in the presence of compression distortions. As there is no established or generally agreed on compression methodology for digital hologram compression on the hologram plane with available implementations, a set of state-of-the-art compression codecs, namely, HEVC, AV1, and JPEG2000, were used for compression of the digital holograms on the object plane. Both computer-generated and optically generated holograms were considered. Two subjective tests were conducted to evaluate distortions caused by compression. The first subjective test was conducted on the reconstructed amplitude images of central views, while the second test was conducted on pseudovideos generated from the reconstructed amplitudes of different views. The subjective quality assessment was based on mean opinion scores. A selection of objective quality metrics was evaluated, and their correlations with mean opinion scores were computed. The VIFp metrics appeared to have the highest correlation.

ACS Style

Hadi Amirpourazarian; Antonio Pinheiro; Elsa Fonseca; Mohammed Ghanbari; Manuela Pereira. Quality evaluation of holographic images coded with standard codecs. IEEE Transactions on Multimedia 2021, PP, 1 -1.

AMA Style

Hadi Amirpourazarian, Antonio Pinheiro, Elsa Fonseca, Mohammed Ghanbari, Manuela Pereira. Quality evaluation of holographic images coded with standard codecs. IEEE Transactions on Multimedia. 2021; PP (99):1-1.

Chicago/Turabian Style

Hadi Amirpourazarian; Antonio Pinheiro; Elsa Fonseca; Mohammed Ghanbari; Manuela Pereira. 2021. "Quality evaluation of holographic images coded with standard codecs." IEEE Transactions on Multimedia PP, no. 99: 1-1.

Journal article
Published: 07 November 2019 in Applied Optics
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Digital holography is an emerging imaging technique for displaying and sensing three-dimensional objects. The perceived image quality of a hologram is frequently corrupted by speckle noise due to coherent illumination. Although several speckle noise reduction methods have been developed so far, there are scarce quality assessment studies to address their performance, and they typically focus solely on objective metrics. However, these metrics do not reflect the visual quality perceived by a human observer. In this work, the performances of four speckle reduction algorithms, namely, the nonlocal means–the Lee, the Frost, and the block-matching 3D filters, with varying parameterizations–were subjectively evaluated. The results were ranked with respect to the perceived image quality to obtain the mean opinion scores using pairwise comparison. The correlation between the subjective results and 20 different no-reference objective quality metrics was evaluated. The experiment indicates that block-matching 3D and Lee are the preferred filters, depending on hologram characteristics. The best-performing objective metrics were identified for each filter.

ACS Style

Elsa Fonseca; Paulo Fiadeiro; Marco Bernardo; Antonio Pinheiro; Manuela Pereira. Assessment of speckle denoising filters for digital holography using subjective and objective evaluation models. Applied Optics 2019, 58, G282 -G292.

AMA Style

Elsa Fonseca, Paulo Fiadeiro, Marco Bernardo, Antonio Pinheiro, Manuela Pereira. Assessment of speckle denoising filters for digital holography using subjective and objective evaluation models. Applied Optics. 2019; 58 (34):G282-G292.

Chicago/Turabian Style

Elsa Fonseca; Paulo Fiadeiro; Marco Bernardo; Antonio Pinheiro; Manuela Pereira. 2019. "Assessment of speckle denoising filters for digital holography using subjective and objective evaluation models." Applied Optics 58, no. 34: G282-G292.

Journal article
Published: 06 November 2019 in Photonics
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The pseudophakic eye lacks the ability to produce a refractive change in response to object proximity. Thus, individual anatomical features such as the pupil size play an important role in achieving functional vision levels. In this work, the range of pupil sizes at varying object distance was measured in pseudophakic participants. Furthermore, the impact of the measured values on eye optical quality was investigated using a computer simulation model. A binocular eye-tracker was used to measure the participants’ pupil sizes at six object distances, ranging from 0.33 m (i.e., vergence of 3.00 D) to 3.00 m (i.e., vergence of 0.33 D), while observing a Maltese cross with a constant angular size of 1 ∘ . In total, 58 pseudophakic participants were enrolled in this study (age mean ± standard deviation: 70.5 ± 11.3 years). The effects of object distance and age on pupil size variation were investigated using linear mixed effects regression models. Age was found to have a small contribution to individual variability. The mean infinite distance pupil size (intercept) was 4.45 ( 95 % CI: 2.74, 6.17) mm and the mean proximal miosis (slope) was − 0.23 ( 95 % CI: −0.53, 0.08) mm/D. The visual acuity (VA) estimation for a distant object ranged from − 0.1 logMAR (smallest pupil) to 0.04 logMAR (largest pupil) and the near VA ( 0.33 m) when mean proximal miosis was considered ranged from 0.28 logMAR (smallest pupil) to 0.42 logMAR (largest pupil). When mean distance pupil was considered, proximal miosis individual variability produced a variation of 0.04 logMAR for the near object and negligible variation for the distant object. These results support the importance of distance pupil size measurement for the prediction of visual performance in pseudophakia, while suggesting that proximal miosis has a negligible impact in VA variability.

ACS Style

Elsa Fonseca; Paulo Fiadeiro; Renato Gomes; Angel Sanchez Trancon; António Baptista; Pedro Serra. Pupil Function in Pseudophakia: Proximal Miosis Behavior and Optical Influence. Photonics 2019, 6, 114 .

AMA Style

Elsa Fonseca, Paulo Fiadeiro, Renato Gomes, Angel Sanchez Trancon, António Baptista, Pedro Serra. Pupil Function in Pseudophakia: Proximal Miosis Behavior and Optical Influence. Photonics. 2019; 6 (4):114.

Chicago/Turabian Style

Elsa Fonseca; Paulo Fiadeiro; Renato Gomes; Angel Sanchez Trancon; António Baptista; Pedro Serra. 2019. "Pupil Function in Pseudophakia: Proximal Miosis Behavior and Optical Influence." Photonics 6, no. 4: 114.

Conference paper
Published: 03 October 2019 in Fourth International Conference on Applications of Optics and Photonics
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In pseudophakia, the eye is unable accommodate so proximal objects can be properly focused. Achieving functional vision levels relies on individual anatomical features, notably, the pupil size. This study measured the range of pupil sizes found in a population of pseudophakes, for an object placed at different distances, and modeled the optical quality associated to pupil variation. The pupil size of 58 pseudophakic eyes (age mean ± standard deviation: 70.5 ± 11.3 years) was measured using a binocular eye-tracker. The participants observed on a monitor a circular white patch subtending 5° with a cross on its center. The object was placed at 3.0, 1.0, 0.66, 0.5, 0.4, 0.33 m. The pupil size variation as a function of object distance was modelled using a linear mixed effects model. The mean and 95% confidence interval (CI) were calculated for a far object and the slope of the function, indicative of the proximal myosis. The effect of object distance on the image quality was modeled using a pseudophakic model eye for the pupil size data. The mean distance pupil sizes were 4.45 (95%CI: 2.74, 6.17) mm and the mean proximal myosis was -0.23 (95%CI: -0.53, -0.08) mm/D. The VA estimation for a distance object ranged from -0.1 logMAR for the smallest pupil to 0.08 logMAR and the near VA when mean myosis was considered ranged from 0.28 logMAR to 0.65 logMAR. These results support the importance of distance pupil size measurement for the prediction of visual performance in pseudophakia, while suggesting that myosis has a negligible impact in VA variability.

ACS Style

Elsa Fonseca; Paulo Fiadeiro; Renato Gomes; Angel Sanchez Trancon; António M. G. Baptista; Pedro M. Serra. Influence of pupil function in pseudophakia. Fourth International Conference on Applications of Optics and Photonics 2019, 11207, 112071N .

AMA Style

Elsa Fonseca, Paulo Fiadeiro, Renato Gomes, Angel Sanchez Trancon, António M. G. Baptista, Pedro M. Serra. Influence of pupil function in pseudophakia. Fourth International Conference on Applications of Optics and Photonics. 2019; 11207 ():112071N.

Chicago/Turabian Style

Elsa Fonseca; Paulo Fiadeiro; Renato Gomes; Angel Sanchez Trancon; António M. G. Baptista; Pedro M. Serra. 2019. "Influence of pupil function in pseudophakia." Fourth International Conference on Applications of Optics and Photonics 11207, no. : 112071N.

Conference paper
Published: 01 June 2019 in 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX)
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The perceived image quality of a digital hologram of macroscopic objects is affected by its reduced depth of focus and by speckle noise due to coherent illumination. Several filtering techniques have been proposed for speckle noise reduction of digital holograms but there are scarce quality assessment studies regarding phase-shifting digital holograms. Typically, the performance of these filters on experimental holograms is assessed using no reference objective metrics. However, these metrics do not reflect the subjective visual quality perceived by a human observer. In this work, the performance of four speckle reduction algorithms, namely the non-local means, the Lee, the Frost and the block matching 3D filters, using five different parametrizations for each case, are subjectively compared. Due to a large amount of testing data, the subjective test was divided in two: 1) one phase where the effects of the parametrization of each method are evaluated, 2) a second phase where the best parametrization results are compared between them. The results are ranked with respect to the perceived image quality to obtain the Mean Opinion Scores for each filter/parameter combination. As in this case there is no reference image and double stimulus is desirable, the subjective evaluation was achieved using full paired comparison. The experiment indicates that BM3D and Lee are the preferred filters, and reveals a strong dependence of filter performance on hologram characteristics.

ACS Style

Elsa Fonseca; Paulo Fiadeiro; Vahid Hajihashemi; Marco Bernardo; Antonio Pinheiro; Manuela Pereira. Perceptual evaluation of speckle noise reduction techniques for phase shifting holograms. 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX) 2019, 1 -6.

AMA Style

Elsa Fonseca, Paulo Fiadeiro, Vahid Hajihashemi, Marco Bernardo, Antonio Pinheiro, Manuela Pereira. Perceptual evaluation of speckle noise reduction techniques for phase shifting holograms. 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX). 2019; ():1-6.

Chicago/Turabian Style

Elsa Fonseca; Paulo Fiadeiro; Vahid Hajihashemi; Marco Bernardo; Antonio Pinheiro; Manuela Pereira. 2019. "Perceptual evaluation of speckle noise reduction techniques for phase shifting holograms." 2019 Eleventh International Conference on Quality of Multimedia Experience (QoMEX) , no. : 1-6.

Conference paper
Published: 01 March 2019 in 2019 Data Compression Conference (DCC)
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In previous work, a digital hologram compression scheme for representation on the object plane was proposed. Compression on object plane for experimental holograms and Computer-Generated Holograms (CGH) proves to be a very efficient model that outperforms the compression on the hologram plane. However, the compression gain is more relevant in CGHs. The difference between experimental holograms and CGHs is related to the fact that CGHs are less affected by speckle noise that is a characteristic of experimental holograms. In the current work, to improve the coding efficiency of the hologram compression scheme is proposed the reduction of speckle noise of experimental holograms. The compression scheme defines a base layer where a 2D version of the object is coded with an image codec standard. The efficiency of this step is much higher in case of CGH when compared to experimental holograms. However, after performing speckle noise reduction before any compression a similar compression efficiency is found. Since the speckle noise reduction is performed only on amplitude data without affecting the phase, is still possible to render 3D features such as depth map, multi-view or to recover holographic interference patterns for further 3D visualization.

ACS Style

Marco Bernardo; Elsa Fonseca; Antonio M. G. Pinheiro; Paulo T. Fiadeiro; Manuela Pereira. Speckle Reduction for Efficient Coding of Experimental Holograms. 2019 Data Compression Conference (DCC) 2019, 557 -557.

AMA Style

Marco Bernardo, Elsa Fonseca, Antonio M. G. Pinheiro, Paulo T. Fiadeiro, Manuela Pereira. Speckle Reduction for Efficient Coding of Experimental Holograms. 2019 Data Compression Conference (DCC). 2019; ():557-557.

Chicago/Turabian Style

Marco Bernardo; Elsa Fonseca; Antonio M. G. Pinheiro; Paulo T. Fiadeiro; Manuela Pereira. 2019. "Speckle Reduction for Efficient Coding of Experimental Holograms." 2019 Data Compression Conference (DCC) , no. : 557-557.

Conference paper
Published: 17 September 2018 in Applications of Digital Image Processing XLI
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Digital holography is a growing field that owes its success to the provided three-dimensional imaging representation. This is achieved by encoding the wave field transmitted or scattered by an object in the form of an interference pattern with a reference beam. While in conventional imaging systems it is usually impossible to recover the correct focused image from a defocused one, with digital holography the image can be numerically retrieved at any distance from the hologram. Digital holography also allows the reconstruction of multiple objects at different depths. In a previous study, the benchmark of the main available image coding standard solutions JPEG, JPEG-XT, JPEG 2000 and the HEVC intra mode was performed for digital holographic data represented on the object plane. The HEVC intra main coding profile outperforms the other standards while JPEG 2000 results in very similar compression performance. In the current work, a scheme based on the HEVC intra mode codec for holographic information compression on the object plane is proposed. In the base layer, a 2D version of the object (amplitude information on object plane) is coded with HEVC intra main coding profile. Previously was observed that the phase information requires much higher bit rates than the amplitude information, as standardized codecs are not adapted for the compression of this type of information. In this paper we propose a model where the amplitude information is encoded with the HEVC intra mode codec, while the phase is represented by encoding the real information and the signal of the imaginary information. The real information is also encoded using the HEVC intra mode as it already revealed appropriate for compression of this type of information. The imaginary information signal is encoded with JBIG. The advantage of this scheme is that the amplitude information provides a direct 2D representation of the hologram while the phase information can be considered as a 3D enhancement layer. The results show that the proposed scheme outperforms the state of the art in holography compression, while allowing compatibility with the current standards and direct 2D visualization.

ACS Style

Antonio M. G. Pinheiro; Manuela Pereira; Elsa Fonseca; Paulo Fiadeiro; Marco V. Bernardo. A digital hologram compression scheme for representation on the object plane. Applications of Digital Image Processing XLI 2018, 10752, 107520J .

AMA Style

Antonio M. G. Pinheiro, Manuela Pereira, Elsa Fonseca, Paulo Fiadeiro, Marco V. Bernardo. A digital hologram compression scheme for representation on the object plane. Applications of Digital Image Processing XLI. 2018; 10752 ():107520J.

Chicago/Turabian Style

Antonio M. G. Pinheiro; Manuela Pereira; Elsa Fonseca; Paulo Fiadeiro; Marco V. Bernardo. 2018. "A digital hologram compression scheme for representation on the object plane." Applications of Digital Image Processing XLI 10752, no. : 107520J.

Journal article
Published: 23 August 2018 in Signal Processing: Image Communication
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Digital holography allows the recording, storage and subsequent reconstruction of both amplitude and phase of the light field scattered by an object. This is accomplished by recording interference patterns that preserve the properties of the original object field essential for 3D visualization, the so-called holograms. Digital holography refers to the acquisition of holograms with a digital sensor, typically a CCD or a CMOS camera, and to the reconstruction of the 3D object field using numerical methods. In the current work, the different representations of digital holographic information in the hologram and in the object planes are studied. The coding performance of the different complex field representations, notably Amplitude-Phase and Real-Imaginary, in both the hologram plane and the object plane, is assessed using both computer generated and experimental holograms. The HEVC intra main coding profile is used for the compression of the different representations in both planes, either for experimental holograms or computer generated holograms. The HEVC intra compression in the object plane outperforms encoding in the hologram plane. Furthermore, encoding computer generated holograms in the object plane has a larger benefit than the same encoding over the experimental holograms. This difference was expected, since experimental holograms are affected by a larger negative influence of speckle noise, resulting in a loss of compression efficiency. This work emphasizes the possibility of holographic coding on the object plane, instead of the common encoding in the hologram plane approach. Moreover, this possibility allows direct visualization of the Object Plane Amplitude in a regular 2D display without any transformation methods. The complementary phase information can easily be used to render 3D features such as depth map, multi-view or even holographic interference patterns for further 3D visualization depending on the display technology.

ACS Style

Marco V. Bernardo; Pedro Fernandes; Angelo Arrifano; Marc Antonini; Elsa Fonseca; Paulo Fiadeiro; Antonio Pinheiro; Manuela Pereira. Holographic representation: Hologram plane vs. object plane. Signal Processing: Image Communication 2018, 68, 193 -206.

AMA Style

Marco V. Bernardo, Pedro Fernandes, Angelo Arrifano, Marc Antonini, Elsa Fonseca, Paulo Fiadeiro, Antonio Pinheiro, Manuela Pereira. Holographic representation: Hologram plane vs. object plane. Signal Processing: Image Communication. 2018; 68 ():193-206.

Chicago/Turabian Style

Marco V. Bernardo; Pedro Fernandes; Angelo Arrifano; Marc Antonini; Elsa Fonseca; Paulo Fiadeiro; Antonio Pinheiro; Manuela Pereira. 2018. "Holographic representation: Hologram plane vs. object plane." Signal Processing: Image Communication 68, no. : 193-206.

Journal article
Published: 20 September 2016 in Applied Optics
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Numerical reconstruction of digital holograms relies on a precise knowledge of the original object position. However, there are a number of relevant applications where this parameter is not known in advance and an efficient autofocusing method is required. This paper addresses the problem of finding optimal focusing methods for use in reconstruction of digital holograms of macroscopic amplitude and phase objects, using digital in-line phase-shifting holography in transmission mode. Fifteen autofocus measures, including spatial-, spectral-, and sparsity-based methods, were evaluated for both synthetic and experimental holograms. The Fresnel transform and the angular spectrum reconstruction methods were compared. Evaluation criteria included unimodality, accuracy, resolution, and computational cost. Autofocusing under angular spectrum propagation tends to perform better with respect to accuracy and unimodality criteria. Phase objects are, generally, more difficult to focus than amplitude objects. The normalized variance, the standard correlation, and the Tenenbaum gradient are the most reliable spatial-based metrics, combining computational efficiency with good accuracy and resolution. A good trade-off between focus performance and computational cost was found for the Fresnelet sparsity method.

ACS Style

Elsa S. R. Fonseca; Paulo T. Fiadeiro; Manuela Pereira; António Pinheiro. Comparative analysis of autofocus functions in digital in-line phase-shifting holography. Applied Optics 2016, 55, 7663 .

AMA Style

Elsa S. R. Fonseca, Paulo T. Fiadeiro, Manuela Pereira, António Pinheiro. Comparative analysis of autofocus functions in digital in-line phase-shifting holography. Applied Optics. 2016; 55 (27):7663.

Chicago/Turabian Style

Elsa S. R. Fonseca; Paulo T. Fiadeiro; Manuela Pereira; António Pinheiro. 2016. "Comparative analysis of autofocus functions in digital in-line phase-shifting holography." Applied Optics 55, no. 27: 7663.

Conference paper
Published: 05 July 2007 in European Conferences on Biomedical Optics
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The estimation of optical properties of highly turbid and opaque biological tissue is a difficult task since conventional purely optical methods rapidly loose sensitivity as the mean photon path length decreases. Photothermal methods, such as pulsed or frequency domain photothermal radiometry (FD-PTR), on the other hand, show remarkable sensitivity in experimental conditions that produce very feeble optical signals. Photothermal Radiometry is primarily sensitive to absorption coefficient yielding considerably higher estimation errors on scattering coefficients. Conversely, purely optical methods such as Local Diffuse Reflectance (LDR) depend mainly on the scattering coefficient and yield much better estimates of this parameter. Therefore, at moderate transport albedos, the combination of photothermal and reflectance methods can improve considerably the sensitivity of detection of tissue optical properties. The authors have recently proposed a novel method that combines FD-PTR with LDR, aimed at improving sensitivity on the determination of both optical properties. Signal analysis was performed by global fitting the experimental data to forward models based on Monte-Carlo simulations. Although this approach is accurate, the associated computational burden often limits its use as a forward model. Therefore, the application of analytical models based on the diffusion approximation offers a faster alternative. In this work, we propose the calculation of the diffuse reflectance and the fluence rate profiles under the δ-P1 approximation. This approach is known to approximate fluence rate expressions better close to collimated sources and boundaries than the standard diffusion approximation (SDA). We extend this study to the calculation of the diffuse reflectance profiles. The ability of the δ-P1 based model to provide good estimates of the absorption, scattering and anisotropy coefficients is tested against Monte-Carlo simulations over a wide range of scattering to absorption ratios. Experimental validation of the proposed method is accomplished by a set of measurements on solid absorbing and scattering phantoms.

ACS Style

E. S. R. Fonseca; M. E. P. De Jesus. Estimation of biomedical optical properties by simultaneous use of diffuse reflectometry and photothermal radiometry: investigation of light propagation models. European Conferences on Biomedical Optics 2007, 66310C -66310C-17.

AMA Style

E. S. R. Fonseca, M. E. P. De Jesus. Estimation of biomedical optical properties by simultaneous use of diffuse reflectometry and photothermal radiometry: investigation of light propagation models. European Conferences on Biomedical Optics. 2007; ():66310C-66310C-17.

Chicago/Turabian Style

E. S. R. Fonseca; M. E. P. De Jesus. 2007. "Estimation of biomedical optical properties by simultaneous use of diffuse reflectometry and photothermal radiometry: investigation of light propagation models." European Conferences on Biomedical Optics , no. : 66310C-66310C-17.

Proceedings article
Published: 09 February 2006 in Biomedical Optics 2006
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A novel method for measuring the optical properties of highly absorbing and scattering biological media is described. The method combines frequency-domain photothermal radiometry (FD-PTR) with spatially resolved diffuse reflectance (SR-DR) techniques aimed at improving sensitivity on the determination of both scattering and absorption coefficients. Simulation results with Monte-Carlo and Diffusion Theory approaches that assess the scope and feasibility of the method are presented. An optical fiber probe for SR-DR measurements was constructed for operations at small source-detector separations and an FD-PTR system was adapted for quasi-simultaneous operation with the probe. Several experiments on epoxy phantoms that illustrate the validity and potential of the method are presented.

ACS Style

E. S. R. Fonseca; M. E. P. De Jesus. Combined photothermal-photometric method for the determination of tissue optical properties. Biomedical Optics 2006 2006, 6084, 1 .

AMA Style

E. S. R. Fonseca, M. E. P. De Jesus. Combined photothermal-photometric method for the determination of tissue optical properties. Biomedical Optics 2006. 2006; 6084 ():1.

Chicago/Turabian Style

E. S. R. Fonseca; M. E. P. De Jesus. 2006. "Combined photothermal-photometric method for the determination of tissue optical properties." Biomedical Optics 2006 6084, no. : 1.

Journal article
Published: 19 February 2004 in IEEE Transactions on Geoscience and Remote Sensing
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Reconstruction of the backscatter and extinction coefficients is a crucial step in many quantitative remote sensing applications, such as radar, light detection and ranging (lidar), and sonar. We present a novel stochastic filtering approach for the estimation of the backscatter and extinction coefficients from time-range elastic-backscatter lidar data. The Bayesian perspective is adopted; we take as prior a causal first-order autoregressive Gauss-Markov random field tailored to enforce smoothness on time and range dimensions. By using a reduced-order state-space representation of the prior, we derive a suboptimal stochastic filter that recursively computes the backscatter and extinction coefficients at each range-time inversion cell. The estimator is a kind of adaptive extended Kalman filter, being efficient from the computational point of view. A set of experiments illustrates the effectiveness of the proposed approach, namely its advantage over the classical Klett deterministic approach.

ACS Style

José Bioucas-Dias; José Leitão; Elsa Fonseca. Reconstruction of Backscatter and Extinction Coefficients in Lidar: A Stochastic Filtering Approach. IEEE Transactions on Geoscience and Remote Sensing 2004, 42, 443 -456.

AMA Style

José Bioucas-Dias, José Leitão, Elsa Fonseca. Reconstruction of Backscatter and Extinction Coefficients in Lidar: A Stochastic Filtering Approach. IEEE Transactions on Geoscience and Remote Sensing. 2004; 42 (2):443-456.

Chicago/Turabian Style

José Bioucas-Dias; José Leitão; Elsa Fonseca. 2004. "Reconstruction of Backscatter and Extinction Coefficients in Lidar: A Stochastic Filtering Approach." IEEE Transactions on Geoscience and Remote Sensing 42, no. 2: 443-456.

Conference paper
Published: 22 October 1999 in SPIE's International Symposium on Optical Science, Engineering, and Instrumentation
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Lidar receivers perform time and/or space averaging to decrease the variance of the optical power estimates. In this paper we study an Avalanche PhotoDiode based receiver. The number samples to reach a given minimum variance depends on the receiver transfer function. Herein, we review the linear receiver and derive the number of samples for the logarithmic pre-amplifier. Comparing the two receivers, we show that the signal variance for the logarithmic case is degraded by a factor that vanishes as the receiver aperture increases. These results can be readily applied to the problem of estimating log-power returns in the context of Differential Absorption lidar systems. As an application example, we study two different log-power estimators and compare their performance.

ACS Style

José Bioucas-Dias; Elsa Fonseca; David P. Resendes. Time and range averaging of lidar echoes using APD-based receivers. SPIE's International Symposium on Optical Science, Engineering, and Instrumentation 1999, 158 -166.

AMA Style

José Bioucas-Dias, Elsa Fonseca, David P. Resendes. Time and range averaging of lidar echoes using APD-based receivers. SPIE's International Symposium on Optical Science, Engineering, and Instrumentation. 1999; ():158-166.

Chicago/Turabian Style

José Bioucas-Dias; Elsa Fonseca; David P. Resendes. 1999. "Time and range averaging of lidar echoes using APD-based receivers." SPIE's International Symposium on Optical Science, Engineering, and Instrumentation , no. : 158-166.

Conference paper
Published: 04 October 1999 in SPIE's International Symposium on Optical Science, Engineering, and Instrumentation
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This paper addresses the joint estimation of backscatter and extinction coefficients from range/time noisy data under a nonlinear stochastic filtering setup. This problem is representative of many remote sensing applications such as weather radar and elastic-backscatter lidar. A Bayesian perspective is adopted. Thus, in addition to the observation mechanism, relating in a probabilistic sense the observed data with the parameters to be estimated, a prior probability density function has to be specified. We adopt as prior a causal first order auto-regressive Gauss-Markov random field. By using a reduced order state-space representation of the prior, we derive a nonlinear stochastic filter that recursively computes the backscatter and extinction coefficients at each site. A set of experiments based on simulated data illustrates the potential of the proposed approach.

ACS Style

José Bioucas-Dias; Elsa Fonseca. Nonlinear stochastic filtering technique for radar/lidar inversion. SPIE's International Symposium on Optical Science, Engineering, and Instrumentation 1999, 51 -62.

AMA Style

José Bioucas-Dias, Elsa Fonseca. Nonlinear stochastic filtering technique for radar/lidar inversion. SPIE's International Symposium on Optical Science, Engineering, and Instrumentation. 1999; ():51-62.

Chicago/Turabian Style

José Bioucas-Dias; Elsa Fonseca. 1999. "Nonlinear stochastic filtering technique for radar/lidar inversion." SPIE's International Symposium on Optical Science, Engineering, and Instrumentation , no. : 51-62.