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Conoscopic holography. I. Basic principles and physical basis
Journal of the Optical Society of America A
Abstract
Conoscopic holography is an incoherent holographic technique based on the properties of crystal optics. More precisely, for each point of the object, the interference pattern between the ordinary and the extraordinary rays is presented. The pattern is a Gabor-zone-lens pattern, with a scale parameter that is a function of the distance of the point. The superposition of the Gabor zone lens from each point of the object is the hologram, which contains information on the shape of the object through the scale-parameter dependence of each point is presented. I present a simplified version of the theory of conoscopic holography. The point-spread function and the transfer function of the conoscopic system are presented by using simple arguments, and the conoscopic hologram is defined. The basic schemes for reconstruction, i.e., retrieving, optically or numerically, this three-dimensional information about the object from the recorded hologram, are presented. Finally, the resolution of the system is quantified.
... Conoscopic holography is another notable advancement in the optical architectures for recording holograms with incoherent and partially incoherent light sources [13,[52][53][54][55]. The optical configuration of a conoscopic holography system is shown in Fig. 10. ...
... By using the approximation developed in [52], the intensity in the sensor plane is given by ...
... The conoscopic holography technique was implemented for recording incoherent digital holograms [52][53][54][55]. Unlike the triangle interferometer, the conoscopic holography technique enables the development of compact on-axis digital holography. ...
Self-interference holography is a common technique to record holograms of incoherently illuminated scenes. In this review, we survey the main milestones in the topic of self-interference incoherent digital holography from two main points of view. First, we review the prime architectures of optical hologram recorders over more than 50 years. Second, we discuss some of the key applications of these recorders in the field of imaging in general, and for 3D super-resolution imaging, fluorescence microscopy, partial aperture imaging, seeing through a scattering medium, and spectral imaging in particular. We summarize this overview with a general perspective on this research topic and its prospective directions.
... Other methods which attracted attention for the recovery of phase objects with incoherent light include the selfinterference incoherent digital holography techniques [42][43][44][45][46][47][48][49]. These techniques are based on the principle that each point on the object emits light that only interferes with its counter point. ...
... Different imaging features are introduced by the object information present in both interfering waves. Methods such as Fourier and Fresnel digital holography are developed in recent years involving Fourier incoherent single channel holography [42], conoscopic holography [43], Fresnel incoherent correlation holography (FINCH) [44], and coded aperture correlation holography [45,46]. These incoherent holography methods record the incoherent hologram using intensity patterns, which then use to obtain the object information in using phase shifts. ...
Ghost diffraction involves the use of non-local spatial correlations to image objects with light, which has not interacted with them. Here, we propose and experimentally demonstrate a new technique for first-order correlation measurement in ghost diffraction and retrieval of two-dimensional phase objects from inversion of the experimentally measured two-point complex correlation function in a first order interferometer. The ghost diffraction scheme is experimentally implemented by a specially designed experimental setup wherein one of the orthogonal polarization components of the transversely polarized light interacts with the object and the other polarization component of the light remains intact and directly reaches the detector. The Fourier spectrum of the object is encoded into the two-point spatial correlation of these two orthogonal polarization components which is experimentally detected in an interferometer with a radial shearing in the Sagnac geometry. We experimentally demonstrated imaging of spatially varying phase objects and results are presented for three different cases.
... The temporal coherence can be improved by trading off some light using a spectral filter. In this line of research, there have been many interesting architectures, such as rotational shearing interferometer [6][7][8], triangle interferometer [9,10], and conoscopic holography [11,12]. The modern-day incoherent holography approaches based on SLM [6][7][8][9][10][11][12] are Fresnel incoherent correlation holography (FINCH) [13,14] and Fourier incoherent single-channel holography [15,16], developed by Rosen and team. ...
... In this line of research, there have been many interesting architectures, such as rotational shearing interferometer [6][7][8], triangle interferometer [9,10], and conoscopic holography [11,12]. The modern-day incoherent holography approaches based on SLM [6][7][8][9][10][11][12] are Fresnel incoherent correlation holography (FINCH) [13,14] and Fourier incoherent single-channel holography [15,16], developed by Rosen and team. The field of incoherent holography rapidly evolved with advancements in optical configuration, recording, and reconstruction methods through the contributions of many researchers, such as Poon, Kim, Tahara, Matoba, Nomura, Nobukawa, Bouchal, Huang, Kner, and Potcoava [17,18]. ...
Coded aperture 3D imaging techniques have been rapidly evolving in recent years. The two main directions of evolution are in aperture engineering to generate the optimal optical field and in the development of a computational reconstruction method to reconstruct the object’s image from the intensity distribution with minimal noise. The goal is to find the ideal aperture–reconstruction method pair, and if not that, to optimize one to match the other for designing an imaging system with the required 3D imaging characteristics. The Lucy–Richardson–Rosen algorithm (LR2A), a recently developed computational reconstruction method, was found to perform better than its predecessors, such as matched filter, inverse filter, phase-only filter, Lucy–Richardson algorithm, and non-linear reconstruction (NLR), for certain apertures when the point spread function (PSF) is a real and symmetric function. For other cases of PSF, NLR performed better than the rest of the methods. In this tutorial, LR2A has been presented as a generalized approach for any optical field when the PSF is known along with MATLAB codes for reconstruction. The common problems and pitfalls in using LR2A have been discussed. Simulation and experimental studies for common optical fields such as spherical, Bessel, vortex beams, and exotic optical fields such as Airy, scattered, and self-rotating beams have been presented. From this study, it can be seen that it is possible to transfer the 3D imaging characteristics from non-imaging-type exotic fields to indirect imaging systems faithfully using LR2A. The application of LR2A to medical images such as colonoscopy images and cone beam computed tomography images with synthetic PSF has been demonstrated. We believe that the tutorial will provide a deeper understanding of computational reconstruction using LR2A.
... The temporal coherence can be improved by trading-off some light using a spectral filter. In this line of research, there have been many interesting architectures such as rotational shearing interferometer [6][7][8] triangle interferometer [9,10] and conoscopic holography [11,12]. The modern-day incoherent holography approaches based on SLM [6][7][8][9][10][11][12] are Fresnel incoherent correlation holography (FINCH) [13,14] and Fourier incoherent single channel holography [15,16] developed by Rosen and team. ...
... In this line of research, there have been many interesting architectures such as rotational shearing interferometer [6][7][8] triangle interferometer [9,10] and conoscopic holography [11,12]. The modern-day incoherent holography approaches based on SLM [6][7][8][9][10][11][12] are Fresnel incoherent correlation holography (FINCH) [13,14] and Fourier incoherent single channel holography [15,16] developed by Rosen and team. The field of incoherent holography rapidly evolved with advancements in optical configuration, recording and reconstruction methods by the contributions of many researchers such as Poon, Kim, Tahara, Matoba, Nomura, Nobukawa, Bouchal, Huang, Kner and Potcoava [17,18]. ...
Coded aperture 3D imaging techniques have been rapidly evolving in the recent years. The two main directions of evolution are in aperture engineering to generate the optimal optical field and in development of computational reconstruction to reconstruct the object’s image from the intensity distribution with a minimal noise. The goal is to find the ideal aperture-reconstruction method pair and if not, to optimize one to match the other for designing an imaging system with required 3D imaging characteristics. Lucy-Richardson-Rosen algorithm (LR2A), a recently developed computational reconstruction method was found to perform better than its predecessors such as matched filter, Weiner filter, phase-only filter, Lucy-Richardson algorithm and non-linear reconstruction (NLR) for certain apertures when the point spread function (PSF) is a real and symmetric function. For other cases of PSF, NLR performed better than the rest of the methods. In this tutorial, LR2A has been presented as a generalized approach for any optical field along with MATLAB codes for reconstruction of any image when the PSF is known. The common problems and pitfalls in using LR2A has been discussed. Simulation and experimental studies for common optical fields such as spherical, Bessel, vortex beams and exotic optical fields such as Airy, scattered and self-rotating beams have been presented. From this study, it can be seen that it is possible to transfer the 3D imaging characteristics from non-imaging type exotic fields to indirect imaging systems faithfully using LR2A. The application of LR2A to medical images such as colonoscopy images and cone beam computed tomography images with synthetic PSF has been demonstrated. We believe that the tutorial will provide a deeper understanding of computational reconstruction using LR2A.
... Conforme descrito por Sirat, 1992, ao passar pelo polarizador, o feixe de luz é dividido em dois feixes, com ângulos de fase ortogonais entre si. Em seguida, estes feixes são propagados através do cristal birrefringente. ...
O objetivo deste trabalho foi realizar uma revisão das normas regulamentadoras vigentes, artigos e literatura em conjunto com um estudo de caso, que tratou da análise das condições do ambiente de trabalho de uma indústria, tendo como foco os trabalhadores expostos aos agentes químicos na fabricação de produtos e ferramentas de corte de metal-duro. O método utilizado nesta pesquisa se deu de forma qualitativa. Visitas técnicas e registros dos setores da fábrica foram realizadas. Com a inspeção realizada no local de trabalho, se faz necessário conhecer o Fator de Proteção Mínimo Requerido para aerodispersóides, poeiras respiráveis, variando de 0,1 a 10 micra e escolher o Equipamento de Proteção Respiratório correto, que possua Fator de Proteção Atribuído maior que a dose de exposição. O valor do limite de tolerância, 5 μg.m-3, para exposição de pós-metálicos de metal-duro proposto pela ACGIH, em 2016, representa um grande avanço para a higiene ocupacional e segurança do trabalho, sendo possível a realização da avaliação quantitativa da concentração média dos aerodispersóides de metais-duros. A doença do metal-duro ocorre devido as exposições elevadas de concentrações de aerodispersóides e identificou-se neste trabalho, a necessidade e a importância do treinamento dos trabalhadores na indústria, mas não apenas dos que atuam diretamente com o produto, mas das equipes multidisciplinares da gestão, segurança e medicina do trabalho.
Palavras-chave: Aerodispersóides, Metais-duros; Exposição ocupacional, Medidas preventivas e doenças ocupacionais.
... In IDH, the hologram is formed by self-interference, where light from an object point is split into two, differently modulated and interfered. Achieving self-interference requires complicated optical configurations such as rotational-shearing interferometry, 4,5 multiple viewpoint projection methods, 6,7 conoscopic holography, 8,9 optical scanning holography, 10,11 Fresnel incoherent correlation holography 12,13 and coded aperture correlation holography (COACH). 14 The recorded hologram can be processed using computational algorithms to obtain 3D image of the object. ...
... Hence, IDH requires two beam interference, resulting in complicated optical configurations and bulky, heavy optical systems. Some notable optical configurations of IDH are rotationalshearing interferometry [6,7], multiple viewpoint projection methods [8,9], conoscopic holography [10,11], optical scanning holography [12,13], Fresnel incoherent correlation holography [14,15] and coded aperture correlation holography (COACH) [16]. As implied from the above discussion, indirect imaging requires a complicated system, and the imaging procedure involves multiple steps in comparison to conventional imaging. ...
Direct imaging systems that create an image of an object directly on the sensor in a single step are prone to many constraints, as a perfect image is required to be recorded within this step. In designing high resolution direct imaging systems with a diffractive lens, the outermost zone width either reaches the lithography limit or the diffraction limit itself, imposing challenges in fabrication. However, if the imaging mode is switched to an indirect one consisting of multiple steps to complete imaging, then different possibilities open. One such method is the widely used indirect imaging method with Golay configuration telescopes. In this study, a Golay-like configuration has been adapted to realize a large-area diffractive lens with three sub-aperture diffractive lenses. The sub-aperture diffractive lenses are not required to collect light and focus them to a single point as in a direct imaging system, but to focus independently on different points within the sensor area. This approach of a Large-Area Diffractive lens with Integrated Sub-Apertures (LADISA) relaxes the fabrication constraints and allows the sub-aperture diffractive elements to have a larger outermost zone width and a smaller area. The diffractive sub-apertures were manufactured using photolithography. The fabricated diffractive element was implemented in indirect imaging mode using non-linear reconstruction and the Lucy–Richardson–Rosen algorithm with synthesized point spread functions. The computational optical experiments revealed improved optical and computational imaging resolutions compared to previous studies.
... Hence, IDH requires two beam interference, resulting in complicated optical configurations and bulky, heavy optical systems. Some notable optical configurations of IDH are rotationalshearing interferometry [6,7], multiple viewpoint projection methods [8,9], conoscopic holography [10,11], optical scanning holography [12,13], Fresnel incoherent correlation holography [14,15] and coded aperture correlation holography (COACH) [16]. As implied from the above discussion, indirect imaging requires a complicated system, and the imaging procedure involves multiple steps in comparison to conventional imaging. ...
Direct imaging systems that create an image of an object directly on the sensor in a single step are prone to many constraints as a perfect image is required to be recorded within this step. In designing high resolution direct imaging systems with a diffractive lens, the outermost zone width either reaches the lithography limit or the diffraction limit itself imposing challenges in fabrication. However, if the imaging mode is switched to an indirect one consisting of multiple steps to complete imaging, then different possibilities open up. One such methods is the widely used indirect imaging method with Golay configuration telescopes. In this study, a Golay-like configuration has been adapted to realize a large area diffractive lens with three sub-aperture diffractive lenses. The sub-aperture diffractive lenses are not required to collect light and focus them to a single point as in a direct imaging system but to focus independently on different points within the sensor area. This approach of Large Area Diffractive lens with Integrated Sub-Apertures (LADISA) relaxes the fabrication constraints and allows the sub-aperture diffractive elements to have a larger outermost zone width and smaller area. The diffractive sub-apertures were manufactured using photolithography. The fabricated diffractive element has been implemented in indirect imaging mode using non-linear reconstruction and Lucy-Richardson-Rosen algorithm with synthesized point spread functions. The computational optical experiments revealed an improved optical and computational imaging resolutions compared to previous studies.
... Conforme descrito por Sirat, 1992, ao passar pelo polarizador, o feixe de luz é dividido em dois feixes, com ângulos de fase ortogonais entre si. Em seguida, estes feixes são propagados através do cristal birrefringente. ...
... Conforme descrito por Sirat, 1992, ao passar pelo polarizador, o feixe de luz é dividido em dois feixes, com ângulos de fase ortogonais entre si. Em seguida, estes feixes são propagados através do cristal birrefringente. ...
O e-Book "Materiais metálicos: Composição, fabricação, propriedades e desempenho" traz uma coletânea de 26 capítulos e aborda a relação entre as fundamentações teóricas (revisões) e suas aplicações e relações com a formação nas engenharias.
O e-Book, no formato PDF, tem o acesso e a distribuição livres (gratuito) e é destinado para os profissionais e alunos das áreas cobertas pela Rede PDIMat, como, por exemplo, processos de fabricação e corrosão, tribologia e engenharia de superfície, educação em engenharia e indústria 4.0, metalurgia física e seleção de materiais e outras áreas correlatas.
A coletânea é fruto dos artigos de revisão apresentados no "I Congresso de Engenharia da rede PDIMat (engBRASIL2021)".
Sobre a Rede PDIMat:
Rede de cooperação em pesquisa, desenvolvimento e inovação em materiais e equipamentos para setor industrial brasileiro (Rede PDIMat) visa a agregação dos diferentes atores (pesquisadores, empresários, indústrias, instituições de ensino, instituições de pesquisa, órgãos governamentais, associações, engenheiros, técnicos, inspetores, estudantes, entre outros) e, ao mesmo tempo, o estímulo à cooperação, interinstitucional e multidisciplinar, como ferramenta de otimização do uso de infraestrutura laboratorial, de estímulo ao intercâmbio técnico-científico, da discussão sobre a formação de mão de obra, do uso adequado de recursos (fomentos) e de suporte às demandas dos setores industriais brasileiros, tais como os de petróleo e gás (P&G), construção naval, mineração, siderúrgico, metalomecânico, automobilístico, energia renovável, químico e petroquímico, outros.
... Laser conoscopic holography is a non-contact and noninvasive technique [15] that provides an interferometric measurement of distances within a versatile working range maintaining a micrometric accuracy [16]. The potentiality of the technique was proved on different heritage applications, e.g., in archeology [14,17], as complementary analysis in painting conservation [18,19], up to the recent 3D printing of artworks for tactile fruition [20]. ...
The analysis of surface roughness in highly reflective metal artworks is challenging and requires contactless devices capable to measure regions with high micrometer accuracy in both depth and lateral directions. We demonstrate optical profilometry based on scanning conoscopic holography for micrometer measurement of silver samples treated with different hand-made cleaning processes. The technique is shown effective in acquiring shiny and smooth metal samples providing high-resolution and high-accurate dataset ( $$0.1\,\upmu \hbox {m}$$ 0.1 μ m depth and $$5\,\upmu \hbox {m}$$ 5 μ m lateral resolution) that is a reliable representation of the microsurface structure. From a statistical point of view, the cleaning treatments have the same nature of the low-abrasion, but the underlying mechanical processes are different. This fact suggested a more in-depth study of both the amplitude and the hybrid areal roughness parameters. It is proposed a workflow for a dual integrated multiscale roughness analysis for surface characterization: a scale inspection to detect possible texture non-homogeneity, and a signals separation to outline the most significant texture components. The scale-limited components allowed to discriminate the different surface processes. The results on silver samples demonstrate the potential of multiscale roughness analysis by conoscopic holography as a new tool for treatment monitoring in metal artworks.
... The proposed method opens a new direction where deterministic fields and structured light can be engineered for rapid 3D imaging with a low photon budget, high lateral, and axial resolutions. The evolution of incoherent holography over the years from the complicated architectures such as rotational shearing interferometer 26 , conoscopic holography 27 , and FINCH 2,3 , to this version of holography with deterministic SALCAD fields using Lucy-Richardson-Rosen algorithm is interesting. We believe that the proposed method will compete with the existing coherent holography methods such as MIR digital holography and holographic interferometry using quantum cascade laser 28 , single shot Raman holography 29 , and label-free second harmonic phase imagers 30 . ...
In recent years, there has been a significant transformation in the field of incoherent imaging with new possibilities of compressing three-dimensional (3D) information into a two-dimensional intensity distribution without two-beam interference (TBI). Most of the incoherent 3D imagers without TBI are based on scattering by a random phase mask exhibiting sharp autocorrelation and low cross-correlation along the depth. Consequently, during reconstruction, high lateral and axial resolutions are obtained. Imaging based on scattering requires an astronomical photon budget and is therefore precluded in many power-sensitive applications. In this study, a proof-of-concept 3D imaging method without TBI using de-terministic fields has been demonstrated. A new reconstruction method called the Lucy-Richardson-Rosen algorithm has been developed for this imaging concept. We believe that the proposed approach will cause a paradigm-shift in the current state-of-the-art incoherent imaging, fluorescence microscopy, mid-infrared fingerprinting, astronomical imaging, and fast object recognition applications.
... color, lighting, reflection characteristic, transparency etc. The variety of optical sensors reaches from one dimensional up to full three dimensional sensors with versatile measurement principles such as the autofocus sensor [18], the triangulation laser [13], conoscopic holography [19], and the chromatic white light sensor [13]. ...
... It is well known that the two refracted waves transmit with different paths in the crystal [31]. However, a simplified representation of birefringence, assuming that the two refracted waves travel along the same path [32], is accurate enough to observe interference patterns. Thus, a simplified representation is chosen to estimate the incident angle on the surface of the electro-optic crystal in this paper. ...
To implement high-resolution and low-light sensitive three-dimensional (3D) imaging for long-range applications while simplifying data collection and reducing collection time, a polarization-modulated 3D imaging structure, using a large-aperture electro-optic modulator (EOM) and electron-multiplying CCD (EMCCD), is proposed in this paper. As the EMCCD camera itself has no ability of time resolution and high-speed gating due to the time integration mechanism, large-aperture EOMs are used to provide time resolution and high-speed shutter simultaneously for the EMCCD cameras to obtain the polarization-modulated images from which a 3D image can be reconstructed. A narrow field of view was designed to match the divergence of laser beam for long-range imaging, and therefore through the receiver, the incident angle on the EOM would still be limited to within a small angle, which would not degrade the modulation performance significantly during electro-optic modulation. Ultimately, we found that the polarization-modulated 3D imaging lidar showed very promising performance on time-resolved imaging in a field of view of 0.9 mrad.
... In this work, we used a newly developed optical micro-profilometer based on 3D scanning conoscopic holography that can be brought in the place where artefacts are conserved for an in-situ monitoring [9]. Laser conoscopic holography is a non-contact technique that has been developed in the last decades [10]. It provides distance measurements in non-invasive way in a versatile working range allowing the acquisition of artwork surfaces at different scales with micrometric resolution. ...
... Conoscopic holography is discovered by G.sirat and D.Psaltis in 1985 [5,6]. Optical path of it is shown in Figure 1. ...
A kind of interference measurement system with crystal is designed, which is not influenced much by other factors such as vibration for the property of common path. For the distance measurement, the phase of fringes is calculated on the oblique incident holography to avoid effects of fringe curvature, backup and light fluctuation. But the measurement result is affected by the uniformity of the crystal, and another method of adjusting position based on normal incident holography is also discussed. B-splines function is used to calculate zero position in normal incident holography, which is fitted over the patch image around gray extreme points of the stripes obtained by gray projection. Experiment results show that combining the normal and oblique incident holography reduce the repeatability error of the system and improve the measurement precision effectively.
... This imposes an additional requirement on the acquisition device to deconvolve the diffracted optical field, and is commonly implemented via a lens system in traditional two-dimensional (2D) optical imaging. In the more general case of threedimensional (3D) imaging, the deconvolution of the diffraction effect is known as the wavefront reconstruction, and can be implemented by using either interferometric [1][2][3][4] or noninterferometric holographic devices [5][6][7]. ...
A retroemission device (REM) is an incoherent holographic device that represents a lenslet array situated on a substrate containing fluorescent material. Each lenslet focuses each wavelet of an optical wavefront incident on the REM device into a diffraction-limited volume (voxel) in the fluorescent material, so that the voxel coordinates encode the angle of incidence and curvature of the wavelet. The back-propagating fraction of the excited fluorescence is collected by the lenslet and quasi-collimated into a back-propagating wavelet. All wavelets are combined to reconstruct the incident wavefront propagating in the backward direction. We present a theoretical model of REM based on Fresnel–Kirchhoff approximation describing the reconstructed 3D image characteristics versus the thickness of the fluorescence film at the focal plane of the lenslets. Results of the computer simulations of the REM-based images of a point source, two axially separated point sources and an extended object (a circular rim) situated in the sagittal plane are presented. These results speak in favor of using a fluorescence film of minimum diffraction-limited thickness at the lenslet back focal plane. This REM structure minimizes the fluorescence background and improves the 3D imaging resolution in virtue of the exclusion of out-of-voxel fluorescence contributions to the reconstructed wavefront.
... The conoprobe passes the reflected light through a polarizer and crystal, and the resulting phase changes and interference pattern can be used to calculate the distance to the object [28,29]. When optically tracked, the conoscopic laser can be swept across an organ surface to obtain a 3D point cloud [30]. ...
Purpose:
Organ-level registration is critical to image-guided therapy in soft tissue. This is especially important in organs such as the kidney which can freely move. We have developed a method for registration that combines three-dimensional locations from a holographic conoscope with an endoscopically obtained textured surface. By combining these data sources clear decisions as to the tissue from which the points arise can be made.
Methods:
By localizing the conoscope's laser dot in the endoscopic space, we register the textured surface to the cloud of conoscopic points. This allows the cloud of points to be filtered for only those arising from the kidney surface. Once a valid cloud is obtained we can use standard surface registration techniques to perform the image-space to physical-space registration. Since our methods use two distinct data sources we test for spatial accuracy and characterize temporal effects in phantoms, ex vivo porcine and human kidneys. In addition we use an industrial robot to provide controlled motion and positioning for characterizing temporal effects.
Results:
Our initial surface acquisitions are hand-held. This means that we take approximately 55 s to acquire a surface. At that rate we see no temporal effects due to acquisition synchronization or probe speed. Our surface registrations were able to find applied targets with submillimeter target registration errors.
Conclusion:
The results showed that the textured surfaces could be reconstructed with submillimetric mean registration errors. While this paper focuses on kidney applications, this method could be applied to any anatomical structures where a line of sight can be created via open or minimally invasive surgical techniques.
... G. Y. Sirat and D. Psaltis invented Conoscopic Holography at the California Institute of Technology in 1985 [1]. Further development was carried on at California Institute of Technology [2] and at École Nationale Supérieure des Telecommunications in Paris345 Based on crystal optics, Conoscopy is a simple implementation of a particular type of polarized light interference process [6, 7]. In the basic interference set-up a light beam is projected on a diffusive object. ...
1 Abstract Conoscopic Holography is a simple implementation of a particular type of polarized light interference process, Conoscopic Holography. It is based on crystal optics. In the basic interference set-up a point of light is projected on a diffuse object. This point creates a light point, which diffuses light in every direction. In a conoscopic system a complete solid angle of the diffused light is analyzed by the system. The measurement process corresponds to the retrieval of the distance of the light point from a fixed reference plane. Three-dimensional measurement systems based on Conoscopic Holography are steadily gaining ground against older techniques. Conoscopic systems have evolved from an exotic solution to the first choice for all measurement problems not covered by triangulation techniques. The ConoProbe is found today on more then sixty applications of Q.C. measurements, digitizing, reverse engineering and in-process inspection. A review the principle of Conoscopic Holography will be presented in the first part of the talk. The specificities of Conoscopic Holography and its differentiation from triangulation techniques will be reviewed. The actual ConoProbe and the newest version, the Smart ConoProbe, released these days, will be presented in the second part of the talk. A new system, the Smart ConoLine, will also be presented in the talk. It integrates a specific Smart ConoProbe head with a scanning resonant mirror to create a high speed line system. Finally, several examples of applications, which were not realizable, using older techniques, will be described. 2 Introduction Conoscopic Holography is a holographic technique based on light propagation effects in uniaxial crystals. Since its discovery it was targeted as a general-purpose three-dimensional optical sensor for precise non-contact distance measurement. In the last decade, the emphasis was shifted from applied scientific research laboratories to industrial realization of measurement systems based on conoscopic holography technologies. In the basic interference set-up a light beam is projected on a diffusive object. The reflected beam creates a light point source, which disperses light in all directions. A complete solid angle of the diffused light is analyzed with the conoscopic optical system. The measurement process corresponds to the retrieval of the distance of the illuminated point from a fixed reference plane. The first sensor developed for industrial purposes was the ConoProbe, which was made available commercially in early 1999. The ConoProbe is a high precision, non-contact point sensor. It is used today on many industrial applications, ranging from quality control of fine mechanics as turbine blades, gears, machine tools, molds and soft materials, to in-process inspection of thickness, shape and angles, and copy and milling on CNC machines. The commercial success of the ConoProbe is due to a combination of technical performances that distinguish it from other three dimensional point sensors. Recently the Smart ConoProbe, which is the new version of the ConoProbe, was introduced. The weight and the volume have been reduced by a factor of 2. The performances in terms of the sampling rate have been improved by at least 50-70%, reaching the 3 KHz mark instead of 850 Hz. It should be pointed out that all the controls and computational electronics are implemented and integrated inside this volume. (System on chip). A scanning version of the Smart ConoProbe, designated as the Smart ConoLine, is currently under development. It uses a resonant mirror to deflect the measuring point along a line, reaching rates of ten KHz. Following is a brief description of the physical principles of Conoscopic Holography followed by the ConoProbe's functional description, pointing out its distinctive attributes compared to other non-contact optical sensors.
... A measurement principle that combines accuracy comparable to laser triangulation with the ease of laparoscopic deployment of endoscopic imaging is conoscopic holography. Conoscopic holography is a low-cost, commercially available technology based on polarized light interference (24,25). The advantages over laser triangulation are that the send and receive paths of the laser light are collinear, and that distance measurements are derived from a solid angle (i.e. a cone of light), rather than from a single ray. ...
Background:
Registered medical images can assist with surgical navigation and enable image-guided therapy delivery. In soft tissues, surface-based registration is often used and can be facilitated by laser surface scanning. Tracked conoscopic holography (which provides distance measurements) has been recently proposed as a minimally invasive way to obtain surface scans. Moving this technique from concept to clinical use requires a rigorous accuracy evaluation, which is the purpose of our paper.
Methods:
We adapt recent non-homogeneous and anisotropic point-based registration results to provide a theoretical framework for predicting the accuracy of tracked distance measurement systems. Experiments are conducted a complex objects of defined geometry, an anthropomorphic kidney phantom and a human cadaver kidney.
Results:
Experiments agree with model predictions, producing point RMS errors consistently < 1 mm, surface-based registration with mean closest point error < 1 mm in the phantom and a RMS target registration error of 0.8 mm in the human cadaver kidney.
Conclusions:
Tracked conoscopic holography is clinically viable; it enables minimally invasive surface scan accuracy comparable to current clinical methods that require open surgery.
Conoscopic holography is an interferometric technique based on light propagation in crystals. Conoscopic optical probes overcome the main limitations of 3D optical measurement, namely complexity, unreliability, and low precision. Although some systems were designed before, conoscopic probes are operational today as industrial items due to the availability of new improved optical components and the new capacities of low cost numerical processing.
The Development of Scientific Approaches to Implementation of the Holographic Interferometry in Medicine
Convoluted rough surfaces involving overhanging features can be a natural consequence of laser additive manufacturing and other spray techniques or can be generated deliberately by laser surface texturing, e.g., to aid osseointegration. Overhanging features add an extra level of complexity to the topography of a rough surface and can have a substantial effect on wettability, etc. However, features of this type are invisible to traditional surface roughness measurement techniques. This work presents a computer-based surface analysis method that gives useful information about the presence and nature of overhanging features on rough technical surfaces. The technique uses micro-computer tomography to generate a typical cross section of the surface under investigation. The angles of the vectors normal to the surface can then be analyzed to reveal the presence of overhanging features, which can also be indicated by the standard deviation of the normal vector distribution. Titanium surfaces generated by six different techniques were compared. The characteristics of these surfaces varied strongly, as did the shapes of the overhangs involved. These variations are reflected by different statistical distributions of the normal vectors.
Art conservators have adopted optical technologies to improve conservation efforts; laser triangulation, stereophotogrammetry, structured light, laser scanners, and time of flight sensors have been deployed to capture the 3D information of sculptures and architectures. Optical coherence tomography (OCT) has introduced new imaging methods to study the surface features and subsurface structures of delicate cultural heritage objects. However, the field of view of OCT severely limits the scanning area. We present a hybrid scanning platform combined with an effective algorithm for real-time sampling and artifact removal to achieve macroscopic OCT (macro-OCT) imaging and spectral 3D reconstruction of impressionist style oil paintings.
The techniques in surface metrology with the largest diversity are based on electrodynamics, more precise on the interaction of electromagnetic waves with the surface of the workpiece. State-of-the-art camera technology, proper attention to the internal optical design, light sources, and computing capabilities have led to impressive optical metrology systems with considerable specifications. The most relevant techniques are discussed in the following Sects. 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, and 5.10.
Changes of temperature and relative humidity of the environment where the artefact is stored can cause deformations of the surface that can harm the object or affect the repeatability of the measurement. Currently, there are very few techniques and approaches that allow studying non-invasively the surface deformations of objects of different sizes maintaining accuracy of the order of micrometres. To address this problem, three different systems based on a conoscopic holography sensors have been tested on hygroscopic samples. Moreover, we implemented a low-cost apparatus for controlling relative humidity. Eventually, we investigated procedures that use reference standards, insensitive to thermal and hygrometric variations with the scope to assess short and long-term drifts of the instrumental set-up. We tested the approach on samples of paper and lambskin parchment and on a wooden icon.
Surface metrology of artworks requires the design of suitable devices for in-situ non-destructive measurement together with reliable procedures for an effective analysis of such non-engineered variegate objects. To advance the state-of-the-art it has been implemented a versatile optical micro-profilometry taking advantage of the adapt- ability of conoscopic holography sensors, able to operate with irregular shapes and composite materials (diffusive, specular, and polychrome) of artworks. The scanning technique is used to obtain wide field and high spatially resolved areal profilometry. The prototype has a modular scheme based on a set of conoscopic sensors, extending the typical design based on a scanning stage and a single probe with a limited bandwidth, thus allowing the collection of heights data from surface with different scales and materials with variegate optical response. The system was optimized by characterizing the quality of the measurement with the probes triggered in continuous scanning modality. The results obtained on examples of cultural heritage objects (2D paintings, 3D height-relief) and materials (pictorial, metallic) demonstrate the versatility of the implemented device.
The characterization of the surface morphology and the material layers stratigraphy is a pivotal step in several stages of the conservation process of the artwork. Generally, optimal characterization of the surface cannot be achieved using a single technique but is not always possible to find techniques that can be coupled effectively. Surface maps were retrieved using acoustic microscopy and conoscopic laser holography over a set of reference samples. The surface maps compared for showing possible way to better characterize the surface morphology when their information is combined. The final data give us a more complete surface and subsurface digitalization while the results obtained are discussed highlighting the main pros and cons of the two techniques. Thus besides having insights on the effectiveness and on the performance of the processes, it is also evident that uncertainties associated with the measurement can be overcome and a single more accurate representation of the surface can be derived using both scanning methods
Conoscopic holography, which consists of two linear polarizers and two wave plates, and an uniaxial crystal, is incoherent holographic technology for three-dimensional display. In the uniaxial crystal, the wave from object divides into extraordinary and ordinary waves and phase difference between two waves is caused by the different refractive index of two waves. Four intensity patterns, which are made by phase difference, are obtained using LCLV(liquid crystal light valve) and conoscopic holography system. By combining four intensity patterns, the complex hologram without bias and conjugate image. In this paper, we propose the optimized system, which consists of a wave plate and a linear polarizer, and uniaxial crystal. In the proposed system, it doesn't need LCLV. By adjusting the azimuth angle of a linear polarizer and a wave plate, we derive four intensity patterns in recording plane. We demonstrate theoretically that the complex hologram with bias and a conjugate image is obtained using the proposed system.
Fast and precise 3D inspection system is in great demand in modern manufacturing processes. At present, the available sensors have their own pros and cons, and hardly exist an omnipotent sensor to handle the complex inspection task in an accurate and effective way. The prevailing solution is integrating multiple sensors and taking advantages of their strengths. For obtaining a holistic 3D profile, the data from different sensors should be registrated into a coherent coordinate system. However, some complex shape objects own thin wall feather such as blades, the ICP registration method would become unstable. Therefore, it is very important to calibrate the extrinsic parameters of each sensor in the integrated measurement system. This paper proposed an accurate and automatic extrinsic parameter calibration method for blade measurement system integrated by different optical sensors. In this system, fringe projection sensor (FPS) and conoscopic holography sensor (CHS) is integrated into a multi-axis motion platform, and the sensors can be optimally move to any desired position at the object's surface. In order to simple the calibration process, a special calibration artifact is designed according to the characteristics of the two sensors. An automatic registration procedure based on correlation and segmentation is used to realize the artifact datasets obtaining by FPS and CHS rough alignment without any manual operation and data pro-processing, and then the Generalized Gauss-Markoff model is used to estimate the optimization transformation parameters. The experiments show the measurement result of a blade, where several sampled patches are merged into one point cloud, and it verifies the performance of the proposed method.
Measuring high-reflective surfaces using optical method is always a big challenging problem. This paper presents a high-reflective surface measurement method based on conoscopic holography technology using a 4D motion platform equipped with a conoscopic holography optical probe. There are two key problems needed to solve before the automate scan of the complex shape surface: the coordinate calibration and the path planning. To improve the calibration efficiency and accuracy, the coordinate calibration is divided into two parts: the rough calibration and the accurate registration. The path planning consists of two aspects including: the path points generation and the path points verification. In addition, by scanning the objects having high-reflective surfaces, such as the metal blades, coins and other work-pieces, the efficiency of the measurement method has been verified.
Conoscopic holography, which consists of two circular polarizers and an uniaxial crystal, is incoherent holographic technology for three-dimensional display and non-contact diagnosis. In this paper, we derive the longitudinal and lateral intensities from point-source hologram made by conoscopic holography. Also, the longitudinal and lateral resolutions of conoscopic holography will be obtained from the longitudinal and lateral intensities, respectively, according to Rayleigh criterion.
We present a new technology within the scope of distance measurements. It is based upon a particularly rugged holography technique using incoherent light. Unlike the triangulation technique, it resorts to a wavefront reconstruction and thus a limited on-axis optical aperture. These probes enter fields from metres down to nanometres (3D microscopy). They can be conveniently coupled to optical scanners, video cameras, colorimeters, etc. They can access places which are unreachable using conventional techniques and can measure surfaces with up to an angle. Multipurpose rangefinders with a 1/4000 point precision are starting to be manufactured in series for in-line inspection and 3D digitzation.
Nous pr?sentons une nouvelle technologie dans le domaine de la mesure de distance. Elle se fonde sur une technique particuli?rement robuste dite d'holographie en lumi?re incoh?rente. Au contraire des techniques de triangulation, elle a recours directement ? une reconstruction de front d'onde et n?cessite ainsi une ouverture limit?e sur l'axe. Les palpeurs r?alis?s suivant ce principe peuvent aborder des champs de mesure allant du m?tre au nanom?tre. On peut facilement les coupler ? des syst?mes de balayage optique, des cam?ras vid?o, des colorim?tres etc. Ils peuvent atteindre des endroits inaccessibles par d'autres moyens et peuvent mesurer sur des surfaces inclin?es jusqu'? . Des t?l?m?tres multiusages d'une pr?cision de 4000 points commencent ? ?tre produit en s?rie pour l'inspection industrielle en ligne ainsi que la num?risation tridimensionnelle de formes.
Non-contact measurement based on conoscopic holography is a kind of interferometry with common path, so it is not influenced much by other factors such as vibration. But the measurement result is affected by the uniformity of the crystal, which is analyzed in this paper, and corresponding method of adjustment based on image is discussed. And B-splines function is used to calculate zero position in measurement image, which is fitted over the patch image in the neighborhood of gray extreme points of the stripes, which is important to reduce the repeatability error, optimize design, and improve the accuracy of system.
Conoscopic holography is a fringe generation method widely used to reconstruct surface profiles with high precision. By means of linear fringe method, it is possible obtaining a depth analysis with resolution better than 1 μm. This depth allows utilizing conoscopic holography also to aid the forensic handwriting expert.In fact manuscripts have 3D characteristics, which can be acquired only with systems having a high level of details in the z dimension. In particular, this peculiarity has been used for analyzing line crossing cases, some of the more controversy during signature association in trials. Sometimes the analysis of the only 3D profile is not sufficient to clearly associate a signature to a specific person. In this article, a method to generate a pressure profile by means of a linear conoscopic holography System, which can identify a person from a template generated by this profile, in a way similar to biometric voice recognition systems is proposed.
The determination of the sequence of line crossings is still a current problem in the field of forensic documents examination. This paper presents the potentiality of the 3D micro-topography to resolve the writing order of signatures (if partially superimposed), to detect the tampering of manuscripts (if the added inscription superimposes itself on parts already written), to analyze pressure variation, and to identify strokes in handwritten. The system used, in this paper for creating 3D micro-topography, is based on conoscopic holography. It is a non-contact three-dimensional measuring system that allows producing holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. This technique is suitable to obtain 3D micro-topography with high resolution also on surfaces with unevenness reflectivity (which is usual on the surface of the handwritten document). The proposed technique is able to obtained 3D profile in non-invading way. Therefore, the original draft do not be physically or chemically modified, allowing the possibility of multi-analysis in different time, also in case of forensic analysis with the necessity to preserving the original sample. The experiments performed with line crossings data base show that the proposed method is able of "positive identification" of writing sequence in the majority of the tests. When we have not had a positive identification, the result has been "inconclusive". The proposed technique, if correctly used, does not supply "false positive" or "probable" identifications. The possible results are only: "positive identification" and "inconclusive".
Suggested is a new method to obtain a holograms, based on the use of optically-active-media properties. The light wave scattered by each object point is linearly polarized and transmitted through an optically active medium. The more is the spreading angle of the given wave area, the more becomes its way through the optically active media and consequently the more becomes the rotation angle for its polarization plane. Further the light wave passes through a polarizator. Behind the polarizator a Gabor-zone-lens pattern is formed. Each circle, dark or light is a geometrical place for points of beams with equal angle of polarization plane rotation. Superposition of the Gabor zone lens from each object point is the hologram. Application of this method permits to obtain the holograms without interferometry. So the suggested method allows the use of noncoherent waves for registration of the holograms.
Contrast to gain phase information from the conoscopoc hologram, detecting laser intensity of conoscopic hologram by non-contact measurement based on conoscopic holography is influenced by laser fluctuation easily. To eliminate the conjugate image by phase-shifting devive, phase-shifting error is also included in the intensity of conoscopic hologram. On the basis of theoretic analysis and experiments, the method of incremental phase measurement is proposed, which makes up the shortage of laser intensity measurement and improves measurement precision. This is important to optimize system design and enhance the accuracy of system.
Volume imaging, holography, and conoscopy are methods of recording three-dimensional images. We show that the dependence of the resolution cell size on distance is different for each system and determines the gray-level requirements of the detection and recording system in each case. Expressions are developed for the total number of resolution cells in the observable object volume. This is of interest in determining the total amount of data that must be processed by an electronic imaging system. Tables of performance figures are given for ideal and realistic conditions.
Recent advancements and some emerging trends in the methods and instruments used for surface and near surface characterisation are presented, considering the measurement of both topography and physical properties. In particular, surfaces that present difficulties in measurement or require new procedures are considered, with emphasis on measurements approaching the nanometre scale. Examples of new instruments and promising innovations for roughness measurement and surface integrity characterisation are presented. The new needs for tolerancing, traceability and calibration are also addressed.
Selective Laser Sintering (SLS) permits to manufacture physical models, suitable to be used as sand moulds in the casting processes. SLS presents some technological limits as regards the dimensional precision and surface roughness, which require an accurate assessment. Unfortunately contact methods are not able to carry out these measurements.This paper investigates the possibility of using a new non-contact instrument based on conoscopic holography to measure both microgeometry and macrogeometry of SLS samples. The reliability of measures and its influence on roughness parameters is discussed. A procedure for characterising and identifying the sample edges is introduced.
One of the most powerful applications of the World Wide Web (WWW) is the storage and distributuion of multimedia, integrating text, images, sound, videos and hyperlinks. In cultural heritage this is of particular interest, because best methods to convey a complex knowledge in the field of cultural heritage, to experts and non-experts, are the visual representation and visual interaction. In this work we propose 3D acquisition and digitizing techniques for the virtualized reality of small cultural heritage objects (virtual gallery). The system used for creating 3D shape is based on the conoscopic holograph. This technique is a non-contact three-dimensional measuring technique that makes possible to produce holograms, even with incoherent light, with fringe periods that can be measured precisely to determine the exact distance to the point measured. It is suitable to obtain 3D profile with high resolution also on surface with unevenness reflectivity (this situation is usual on the surface of the cultural heritage objects). By conoscopic holography, high-resolution D model can be obtained. Howver, accurate representation and high-quality display are fundamental requirements to avoid misinterpretation of the data. Therefore, virtual gallery can be obtained through a procedure involving 3D acquisition, D model and visualization.
The work concerns alternate versions of non-damaging optical monitoring of laser engraved flexo plates including (1) image acquisition of made by Computer-to-Plate technique masks using optics-analogue of flatbed scanners and mobile CCD microscope with calculation of halftone screen parameters and (2) measurement of flexo plate relief formed by direct laser engraving and by CtP technique using laser triangulation profilometry.
Conoscopic holography was discussed with simplifying assumptions in a companion paper [J. Opt. Soc. Am. A. 9, 70 (1992)]. These assumptions are removed, and the conclusions of the simplified analysis of the companion paper are proved by more exact calculations.
Metrology in production engineering must be fast, accurate, robust and automated, and ideally integrated into the production line. In many respects, optical methods seem to fulfil these requirements. Although optical methods have a long tradition in dimensional metrology, the rapid progress in the development of optoelectronic components and availability of increased computational power makes many new technical approaches possible. This paper provides a technical overview of the optical methods available for dimensional metrology. Methods for the measurement of length, angle, surface form and spatial co-ordinates are described. The paper summarises both the metrological characteristics and the technical limitations of the methods. Furthermore, it presents some new and promising approaches that, in the future, may play an important role in dimensional metrology for production.
For legal purposes there is a requirement for the validation of signatures and handwritten documents. A helpful method in this respect is the so-called superposed strokes analysis, based on the observation of some characteristics in the writing, such as some letters and their dynamics.
This paper introduces a promising new technique for superposed strokes analysis based on conoscopic holography. Through a non-contact 3D measure a 3D profile is created of the superposed strokes that allows the writing dynamics to be determined, such as, for example, if a stroke was drawn clockwise or counterclockwise.
We propose a 3D analysis by an opto-electronic system, in order to improve the graphology analysis for off-line signature verification.
The analysis of holograms obtained using a Conoscopic setup is a very complex subject, given their nature. Holograms contain the 3D depth information about an object whose surface is to be measured and later reconstructed. The recovery of depth information has so far been carried out using mathematical transforms in combination with linear regression techniques. Here the Hough transform, a useful Computer Vision technique for detecting features in images is adapted to the analysis of holograms in order to establish distance relationships for a given object. The captured images of holograms are pre-processed and subsequently analyzed for characteristic patterns that are later used in finding the distance to an object. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 10–13, 2009
In many applications such as three-dimensional (3-D) data acquisition, the scanning of 3-D objects or 3-D display, it is necessary to understand how an imaging system can be used to obtain information on the structure of an object in the direction perpendicular to the image plane, i.e. depth information. In certain cases the formation of a 3-D image can be described by a theory based on optical transfer functions (OTF): the image intensity distribution is given by the 3-D convolution of the object and a 3-D point spread function (PSF); equivalently, in 3-D Fourier space the image spectrum is the product of the object spectrum and a 3-D OTF. This paper investigates the 3-D PSFs and OTFs that are associated with different pupil functions of the imaging system.
Conoscopic holography was discussed with simplifying assumptions in a companion paper [J. Opt. Soc. Am. A. 9, 70 (1992)]. These assumptions are removed, and the conclusions of the simplified analysis of the companion paper are proved by more exact calculations.
A Huygens’ principle for uniaxially anisotropic media is developed using a plane-wave representation of the electromagnetic field. The field emanating from an illuminated aperture in a uniaxial medium (with an optic axis which is arbitrarily oriented with respect to the axis of the aperture) may be represented as the superposition of a transverse-electric (or TE) field and a transverse magnetic (or TM) field with respect to the optic axis of the medium. For the TE field, the field at an observation point and the aperture field distribution are related in the same manner as in isotropic media. An exact, closed-form expression is derived for the TM field, specifying the field at an observation point in terms of the field distribution over the aperture. A Huygens’ principle for anisotropic media emerges as a special case of this expression. The interpretation arrived at is that the field at an observation point is obtained by superposition of elliptical wavelets emanating from the aperture, with due regard to their phase differences when they reach the point in question.
L’holographie conoscopique est une nouvelle méthode d’’enregistrement d’hologrammes en lumière incohérente compatible avec
les systèmes de numérisation et de traitement d’image. Les auteurs présentent le principe de base de Vholographie conoscopique,
puis décrivent les systèmes expérimentaux mis en œuvre et enfin ils étudient les possibilités de traitement numérique des
hologrammes conoscopiques et, en particulier les algorithmes de reconstruction.
Conoscopic holography is a new method for forming holograms in coherent light which may be a solution to the design of a simple
holographic system compatible with microcomputers and numerical processing. We present the basic principles of conoscopic
holography and experimental setup of conoscopic cameras. The paper focuses on the possibilities of numerical processing of
conoscopic holograms and, more specially, we describe algorithms for numerical reconstructions.
Mots clésHolographie-Lumière incohérente-Numérisation-Reconstruction image
Key wordsHolography-Non coherent light-Digitizing-Image reconstruction
Conoscopic holography is an incoherent method for optically recording three dimensional objects using light propagation in birefrigent crystals. Three separate methods for reconstructing conoscopic holograms are presented and experimentally demonstrated.
Streibl [Optik 66, 341-354 (1984)] has shown that afocal telecentric imaging systems are shift invariant in three dimensions. We show that afocal telecentric imaging systems are the only imaging systems that are shift invariant in three dimensions. In addition, we present a model that allows any imaging system to be modeled as an afocal telecentric imaging system preceded and succeeded by simple coordinate transformation operators. The model is derived for diffraction-limited imaging systems where the Fresnel approximation is valid. It is assumed that the object distribution is incoherently radiating and that multiple scattering and absorption within the object distribution are negligible. A physical analogy is given that provides insight into the mathematical model. Finally, a comparison with the work of Frieden is given.
Optical configurations for performing holography with light of limited coherence are analyzed. Such configurations, which may employ mirrors and gratings in preference to lenses and prisms, are space invariant in that the optical pathlength of a ray between object and hologram recording planes depends only on its intial direction, not on its location in the object plane. Holograms of arbitrary size made from object transparencies of arbitrary size and containing an arbitrary number of fringes may be produced with light of limited coherence.
In this paper we present an holographic system based on the properties of optical propagation in birefrigent media. We have called it conoscopic after the conoscopic figures which are obtained when a spherical wave propagating through a birefrigent crystal, is observed through crossed polarizers. The idea can be summarized by saying that we replace the object and reference beams of coherent holography by the ordinary and extraordinary beams propagating in birefrigent media, two beams that are naturally coherent one with the other.
Monochromatic incoherent light holography
- G Sirat
- D Psaltis
G. Sirat and D. Psaltis, "Monochromatic incoherent light holography," U.S. patent 4,602,844 (July 29, 1986).
Pro-ced6 et dispositif holographique perfectionn6 en lumiere inco-herente
- G Sirat
- D Charlot
- E Dufresne
- A D Maruani
G. Y Sirat, D. Charlot, E. Dufresne, and A. D. Maruani, "Pro-ced6 et dispositif holographique perfectionn6 en lumiere inco-herente," French patent 88-1725 (December 22, 1988).
Dispositif holo-graphique perfectionn6 en lumiere incoh6rente
- P Chavel
- E Dufresne
- G Sirat
P. Chavel, E. Dufresne, and G. Y Sirat, "Dispositif holo-graphique perfectionn6 en lumiere incoh6rente," French patent 89-05344 (April 21, 1989).
Holographie conoscopique
- E Dufresne
E. Dufresne, "Holographie conoscopique," nouvelle these, (Ecole Nationale Sup6rieure des Tel6communications, 46 rue Barrault, Paris, 1990).