We present a reduced cost, field portable and compact prototype of lensless holographic microscope based on multi-illumination and single holographic recording for sperm sorting and analysis of the three dimensional trajectories.
In aerospace industry, the structure of the aircraft is assembled using small parts or a combination of them that are made
with different materials, such as for instance aluminium, titanium, composites or even 3D printed parts. The union
between these small parts is a critical point for the integrity of the aircraft. The quality of this union will decide the
fatigue of adjacent components and therefore the useful life of them. For the union process the most extended method is
the rivets, mainly because their low cost and easy manufacturing. For this purpose it is necessary to made drill holes in
the aeronautical surface to insert the rivets.
In this contribution, we present the preliminary results of a 3D inspection system [1] for drill holes analysis in
aeronautical surfaces. The system, based in optical triangulation, was developed by the Group of Optoelectronic Image
Processing from the University of Valencia in the framework of the Airbus Defence and Space (AD&S), MINERVA
project (Manufacturing industrial - means emerging from validated automation). The capabilities of the system permits
to generate a point cloud with 3D information and GD&T (geometrical dimensions and tolerances) characteristics of the
drill hole. For the inner surface defects detection, the system can generate an inner image of the drill hole with a scaled
axis to obtain the defect position. In addition, we present the analysis performed for the drills in the wing station of the
A-400 M. In this analysis the system was tested for diameters in the range of [10 – 15.96] mm, and for Carbon Fibre.
KEYWORDS: Digital holography, Microscopy, Interferometry, Super resolution, Holography, Multiplexing, Imaging systems, Image acquisition, Digital recording, Sensors, Diffraction, Charge-coupled devices, Image resolution, Holograms, RGB color model
Digital in-line holographic microscopy (DIHM) relates with the capability to achieve microscopic imaging working without lensless in the regime of holography. In essence, DIHM proposes a simple layout where a point source of coherent light illuminates the sample and the diffracted wavefront is recorded by a digital sensor. However, DIHM lacks high numerical aperture (NA) due to both geometrical distortion and the mandatory compromise between the illumination pinhole diameter, the illumination wavelength, and the need to obtain a reasonable light efficiency. One way to improve the resolution in DIHM, is by allowing superresolution imaging by angular multiplexing using tilted beam illumination. This illumination allows the on-axis diffraction of different spatial frequency content of the sample’s spectrum, different in comparison to the case when on-axis illumination is used. And after recover this additional spectral content, a synthetic numerical aperture (SNA) expanding up the cutoff frequency of the system in comparison with the on-axis illumination case can be assembled in a digital post-processing stage. In this contribution, we present a method to achieve one-dimensional (1-D) superresolved imaging in DIHM by a SINGLE SHOT illumination, using color-coded tilted beams. The method has been named as L-SESRIM (Lensless Single-Exposure Super-Resolved Interferometric Microscopy). Although the technique was previously presented showing very preliminary results [34], in this contribution we expand the experimental characterization (USAF resolution test target) as well as derive the theoretical frame for SNA generation using different illumination wavelengths.
Image registration techniques are used among different scientific fields, like medical imaging or optical metrology. The straightest way to calculate shifting between two images is using the cross correlation, taking the highest value of this correlation image. Shifting resolution is given in whole pixels which cannot be enough for certain applications. Better results can be achieved interpolating both images, as much as the desired resolution we want to get, and applying the same technique described before, but the memory needed by the system is significantly higher. To avoid memory consuming we are implementing a subpixel shifting method based on FFT. With the original images, subpixel shifting can be achieved multiplying its discrete Fourier transform by a linear phase with different slopes. This method is high time consuming method because checking a concrete shifting means new calculations. The algorithm, highly parallelizable, is very suitable for high performance computing systems. GPU (Graphics Processing Unit) accelerated computing became very popular more than ten years ago because they have hundreds of computational cores in a reasonable cheap card.
In our case, we are going to register the shifting between two images, doing the first approach by FFT based correlation, and later doing the subpixel approach using the technique described before. We consider it as ‘brute force’ method. So we will present a benchmark of the algorithm consisting on a first approach (pixel resolution) and then do subpixel resolution approaching, decreasing the shifting step in every loop achieving a high resolution in few steps. This program will be executed in three different computers. At the end, we will present the results of the computation, with different kind of CPUs and GPUs, checking the accuracy of the method, and the time consumed in each computer, discussing the advantages, disadvantages of the use of GPUs.
Holography dates back to the year when Dennis Gabor reported on a method to avoid spherical aberration and to improve image quality in electron microscopy. Gabor’s two-step holographic method was pioneer but suffered from three major drawbacks: the reconstructed image is affected by coherent noise, the twin image problem of holography that also affects the final image quality, and a restricted sample range (weak diffraction assumption) for preserving the holographic behavior of the method. Nowadays, most of those drawbacks have been overcome and new capabilities have been added due to the replacement of the classical recording media (photographic plate) by digital sensors (CCD and CMOS cameras). But in the Gabor’ regime, holography is restricted to weak diffraction assumptions because otherwise, diffraction prevents an accurate recovery of the object's complex wavefront. In this contribution, we present an experimental approach to overcome such limitation and improve final image resolution. We use the phase-shifting Gabor configuration while the CCD camera is shifted to different off-axis positions in order to capture a bigger portion of the diffracted wavefront. Thus, once the whole image set is recorded and digitally processed for each camera's position, we merge the resulting band-pass images into one image by assembling a synthetic aperture. Finally, a superresolved image is recovered by Fourier transformation of the information contained in the generated synthetic aperture. Experimental results are provided using a USAF resolution test target and validating our concepts for a gain in resolution of close to 2.
KEYWORDS: 3D modeling, Clouds, Cameras, Chemical analysis, 3D image processing, 3D image reconstruction, 3D acquisition, Fringe analysis, Calibration, Statistical analysis
Deterioration of artwork, in particular paintings, can be produced by environmental factors such as temperature
fluctuations, relative humidity variations, ultraviolet radiation and biological factors among others. The effects of these
parameters produce changes in both the painting structure and chemical composition. While well established analytical
methodologies, such as those based in Raman Spectroscopy and FTIR Spectroscopy require the extraction of a sample
for its inspection, other approaches such as hyperspectral imaging and 3D scanning present advantages for in-situ, noninvasive
analysis of artwork. In this paper we introduce a novel system and the related methodology to acquire process,
generate and analyze 4D data of paintings. Our system is based on non-contact techniques and is used to develop
analytical tools which extract rich 3D and hyperspectral maps of the objects, which are processed to obtain accurate
quantitative estimations of the deterioration and degradation present in the piece of art. In particular, the construction of
4D data allows the identification of risk maps on the painting representation, which can allow the curators and restorers
in the task of painting state evaluation and prioritize intervention actions.
The SYDDARTA project is an on-going European Commission funded initiative under the 7th Framework Programme. Its main objective is the development of a pre-industrial prototype for diagnosing the deterioration of movable art assets. The device combines two different optical techniques for the acquisition of data. On one hand, hyperspectral imaging is implemented by means of electronically tunable filters. On the other, 3D scanning, using structured light projection and capturing is developed. These techniques are integrated in a single piece of equipment, allowing the recording of two optical information streams. Together with multi-sensor data merging and information processing, estimates of artwork deterioration and degradation can be made. In particular, the resulting system will implement two optical channels (3D scanning and short wave infrared (SWIR) hyperspectral imaging) featuring a structured light projector and electronically tunable spectral separators. The system will work in the VIS-NIR range (400-1000nm), and SWIR range (900-2500nm). It will be also portable and user-friendly. Among all possible art work under consideration, Baroque paintings on canvas and wooden panels were selected as the project case studies.
Single Exposure Super Resolved Interferometric Microscopy (SESRIM) has been recently proposed as a way to achieve
one dimensional super resolved imaging in digital holographic microscopy. SESRIM uses Red-Green-Blue (RGB)
multiplexing for illuminating the sample having different propagation angles for each one of the three illumination
wavelengths and it has been experimentally validated considering color (A. Calabuig, V. Mico, J. Garcia, Z. Zalevsky,
and C. Ferreira, “Single-exposure super-resolved interferometric microscopy by red–green–blue multiplexing,” Opt.
Lett. 36, 885-887, 2011) and monochrome (A. Calabuig, J. Garcia, C. Ferreira, Z. Zalevsky, and V. Mico, “Resolution
improvement by single-exposure superresolved interferometric microscopy with a monochrome sensor,” J. Opt. Soc.
Am. A 28, 2346-2358, 2011) digital sensors for holographic recording. In this contribution, we will first review some of
the characteristics of the previously reported SESRIM approaches and second, we will present preliminary results for the
extension of SESRIM to the field of lensless holographic microscopy. Experimental results are reported validating this
new kind of superresolution imaging method named as lensless SESRIM (L-SESRIM).
We present a method capable to improve the resolution limit of an imaging system in digital lensless Fourier holographic
configuration. The method is based on angular- and time-multiplexing of the object's spatial frequency information. On
one hand, angular multiplexing is implemented by using tilted beam illumination to get access to high order spectral
frequency bands of the of the object's spectrum. And, on the other hand, time multiplexing is needed to cover different
directions at the spatial frequency domain. This combination of angular- and time- multiplexing in addition with
holographic recording allows the complex amplitude recovery of a set of elementary apertures covering different
portions of the object's spectrum. Finally, the expanded synthetic aperture (SA) is generated by coherent addition of the
set of recovered elementary apertures. Such SA expands up the cut-off frequency limit of the imaging system and allows
getting a superresolved image of the input object. Moreover, if a priori knowledge about the input object is available,
customized SA shaping is possible by considering the addition of those elementary apertures corresponding with only the
directions of interest and, thus, reducing the whole consuming time of the approach. We present experimental results in
concordance with theoretical predictions for two different resolution test objects, for different SA shapes, and
considering different resolution gain factors.
KEYWORDS: 3D acquisition, 3D modeling, Projection systems, Scanners, Chemical elements, Systems modeling, Cameras, 3D metrology, Computing systems, Chemical analysis
In this paper it will be presented a case study of the optical technologies applicated to archaeology. This case study is
centered in the main actions executed on an extraordinary rest appeared in the excavations of the Roman forum of
Lucentum (Alicante, Spain) in 2005. This rest is a fragment of a bronze sculpture, and is catalogued as a Unicum (that is,
a sample that presents some singular elements with no comparison with other samples, in this case of the Roman Art).
That sample represents the only part that is conserved so far of that statue. This paper will explain briefly the main 3D
digitizing systems and, after that, will focus in the process of identification and documentation of the rest. In particular, it
will be widely described the 3D digitizing process of the rest and the post-processing of the information obtained on it,
showing the main steps of the work and the results obtained, used subsequently in other processes.
KEYWORDS: Computer aided design, Finite element methods, Solid modeling, 3D acquisition, 3D modeling, 3D metrology, Reverse modeling, Chemical elements, Systems modeling, Manufacturing
Conventional techniques applied to three dimensional (3D) acquisition of information has significant limitations
depending on the features of the piece under test. Thus, complex curvatures, deeper concavities and higher volumes are
some examples of critical factors in which contact digitising systems are not suitable to undertake such kind of task. In
these cases, the usage of optical 3D digitization systems implies a more appropriate way to obtain 3D information about
the sample. In particular, structured illumination by means of white light provides point-to-point object acquisition with
accuracy and resolution that are always below the manufactured tolerances. Moreover, when the object under test is too
large, structured illumination can be mixed with photogrammetrical techniques in order to avoid errors by means of the
delimitation of the overall working volume. This proceeding presents several real cases applied to mould industry in
which 3D shape measurement using white light structured illumination is combined with finite element method (FEM)
and laser cladding techniques to allow the repair of the mould.
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