Conoscopic holography I Basic principles and physical basis

Sirat, Gabriel Y.

doi:10.1364/josaa.9.000070

Cited by 51 publications

(18 citation statements)

References 8 publications

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“…The resulting interference patterns are the conoscopic holograms and these contain the distance information that we are interested in. For a more detailed explanation of the principle with a mathematical foundation refer to (Sirat, G., 1992).…”

Section: Principle Of Operationmentioning

confidence: 99%

3d Reconstruction Methods, a Survey

2006

Proceedings of the First International Conference on Computer Vision Theory and Applications

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3D reconstruction technologies have evolved over the years. In this paper we try to highlight the evolution of the scanning technologies. The idea of a survey came up with our decision to look at 3D reconstruction methods. Little has been written about the methods in general, yet many developments have taken place in this area. This survey will prove useful for those intending to embark on research in 3D reconstruction technologies or are considering acquiring a 3D scanner. The survey takes a look at the major reconstruction methods, which are; Laser triangulation, Stereoscopy, Conoscopic holography and Moiré Interferometry. A review of the major producers of scanning technology for 3D reconstruction is also carried out.

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Section: Principle Of Operationmentioning

confidence: 99%

3d Reconstruction Methods, a Survey

2006

Proceedings of the First International Conference on Computer Vision Theory and Applications

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“…At present, cheap conoscopic systems, well adapted to work in the field, are available. Conoscopic holography has already been described in depth many times [9,10], here we present only what is necessary to understand the following discussion. Conoscopic holography is a simple implementation of a particular type of polarized light interference process, which uses a birefringent crystal.…”

Section: Conoscopic Holography and Conoscopic Range-findermentioning

confidence: 99%

Determination of the sequence of line crossings by means of 3D laser profilometry

Spagnolo

Simonetti

Cozzella

2005

Optical Security Systems

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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".

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“…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.…”

Section: Introductionmentioning

confidence: 99%

Surface micro-profilometry for the assessment of the effects of traditional and innovative cleaning treatments of silver

Daffara¹,

Gaburro²,

Marchioro³

et al. 2017

Proceedings of the International Conference LACONA XI

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In the complex procedure for the conservation of a work of art, the effective monitoring of the surface treatment is an important step in order to establish a conservation protocol. The evaluation of the effects of the cleaning requires the inspection of the outermost layer with complementary diagnostic techniques to obtain information on both materials and surface morphology. In this interdisciplinary work, a custom optical micro-profilometry device based on laser conoscopic holography was used for testing the performance of different mechanical procedures for the cleaning of silver alloy objects. Tarnishing is the main alteration phenomenon for silver alloy artworks. Even if such modification does not affect the long-term preservation of the objects, it heavily influences aesthetical features, making the removal of tarnishing one of the most important conservation treatments of the case. The mechanical cleaning procedure based on abrasive powders suspended in a liquid matrix is of widespread use. Recently, a novel dry cleaning procedure based on the use of erasers was proposed as alternative method and tested for both the efficacy of tarnishing removal and effects on the surface appearance using optical microscopy and scanning electron microscopy. However, the employed laboratory techniques cannot provide an objective measure of the roughness at micrometric scale over the sample. In this work, the effects on the surface structure of traditional and innovative silver treatments was investigated with multiscale profilometry, using scanning conoscopic holography and atomic-force microscopy. 3D surface metrology was carried out using standard areal amplitude parameters and a multiscale approach. Preliminary results are presented, addressing two aspects: 1) the validation of laser optical micro-profilometry for the diagnostics of silver objects, which are challenging due to the highly specular surface; 2) the validation of the dry-cleaning treatment based on rubbers, by adding to the previous study the complimentary analysis of the micro-surface. The results obtained on silver mockups confirm that the proposed dry cleaning methods produce surface variations less or similar to traditional methods. The optical micro-profilometry results are of particular significance since this technique is portable with wide field capability, thus allowing an in-situ use and a real monitoring of actual artwork surfaces.

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Conoscopic holography I Basic principles and physical basis

Cited by 51 publications

References 8 publications

3d Reconstruction Methods, a Survey

3d Reconstruction Methods, a Survey

Determination of the sequence of line crossings by means of 3D laser profilometry

Surface micro-profilometry for the assessment of the effects of traditional and innovative cleaning treatments of silver

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