Axial resonance of periodic patterns by using a Fresnel biprism.

This paper proposes a method for the generation of high-contrast localized sinusoidal fringes with spatially noncoherent illumination and relatively high light throughput. The method, somehow similar to the classical Lau effect, is based on the use of a Fresnel biprism. It has some advantages over previous methods for the noncoherent production of interference fringes. One is the flexibility of the method, which allows the control of the fringe period by means of a simple axial shift of the biprism. Second is the rapid axial fall-off in visibility around the high-contrast fringe planes. And third is the possibility of creating fringes with increasing or with constant period as the light bea…

THREE-DIMENSIONAL INTEGRAL MICROSCOPY WITH ENHANCED RESOLUTION AND DEPTH OF FIELD

In this contribution we explain two new techniques developed by our group, which permit to increase the two-dimensional spatial resolution of the computed depth images in integral microscopy.

Three-dimensional imaging system with both improved lateral resolution and depth of field considering non-uniform system parameters

In this paper, we propose a new 3D passive image sensing and visualization technique to improve lateral resolution and depth of field (DoF) of integral imaging simultaneously. There is a resolution trade-off between lateral resolution and DoF in integral imaging. To overcome this issue, a large aperture and a small aperture can be used to record the elemental images to reduce the diffraction effect and extend the DoF, respectively. Therefore, in this paper, we utilize these two pickup concepts with a non-uniform camera array. To show the feasibility of our proposed method, we implement an optical experiment. For comparison in details, we calculate the peak signal-to-noise ratio (PSNR) as th…

Free-depths reconstruction with synthetic impulse response in integral imaging

Integral Imaging provides spatial and angular information of three-dimensional (3D) objects, which can be used both for 3D display and for computational post-processing purposes. In order to recover the depth information from an integral image, several algorithms have been developed. In this paper, we propose a new free depth synthesis and reconstruction method based on the two-dimensional (2D) deconvolution between the integral image and a simplified version of the periodic impulse response function (IRF) of the system. The period of the IRF depends directly on the axial position within the object space. Then, we can retrieve the depth information by performing the deconvolution with compu…

Time-multiplexing Integral Microscopy

Conventional microscopes do not capture the 3D information of thick specimens. In order to avoid this limitation Integral Microscopy was proposed. An integral microscope is implemented by inserting a microlens array between the microscope objective and the camera sensor. Although this device captures multiperspective information of the specimen, the small number of microlenses limits the lateral resolution. In this paper we propose to improve the resolution by time multiplexing. Specifically, we propose an electrically addressable device that permits to obtain three sheared versions of the microscopic plenoptic map. Digital processing algorithm applied to the maps provides images with resol…

Large Depth-of-Field Integral Microscopy by Use of a Liquid Lens

Integral microscopy is a 3D imaging technique that permits the recording of spatial and angular information of microscopic samples. From this information it is possible to calculate a collection of orthographic views with full parallax and to refocus computationally, at will, through the 3D specimen. An important drawback of integral microscopy, especially when dealing with thick samples, is the limited depth of field (DOF) of the perspective views. This imposes a significant limitation on the depth range of computationally refocused images. To overcome this problem, we propose here a new method that is based on the insertion, at the pupil plane of the microscope objective, of an electrical…

Three-Dimensional Integral Imaging and Display

Resolution enhancement in integral microscopy by physical interpolation

Integral-imaging technology has demonstrated its capability for computing depth images from the microimages recorded after a single shot. This capability has been shown in macroscopic imaging and also in microscopy. Despite the possibility of refocusing different planes from one snap-shot is crucial for the study of some biological processes, the main drawback in integral imaging is the substantial reduction of the spatial resolution. In this contribution we report a technique, which permits to increase the two-dimensional spatial resolution of the computed depth images in integral microscopy by a factor of √2. This is made by a double-shot approach, carried out by means of a rotating glass…

Non-Homogeneity of Lateral Resolution in Integral Imaging

We evaluate the lateral resolution in reconstructed integral images. Our analysis takes into account both the diffraction effects in the image capture stage and the lack of homogeneity and isotropy in the reconstruction stage. We have used Monte Carlo simulation in order to assign a value for the resolution limit to any reconstruction plane. We have modelled the resolution behavior. Although in general the resolution limit increases proportionally to the distance to the lens array, there are some periodically distributed singularity planes. The phenomenon is supported by experiments.

Algorithms for transforming an integral photography into a plenoptic picture

We report a simple algorithm for transforming the set of elemental images captured with an integral-photography set up, into the set of micro-images ready to be projected into an integral-imaging monitor. The method is based in the transposing relation between an integral photography and a plenoptic picture. The reported technique permits to adapt the integral images to the resolution and size of the monitor.

Resolution improvements in integral microscopy with Fourier plane recording

Abstract: Integral microscopes (IMic) have been recently developed in order to capture the spatial and the angular information of 3D microscopic samples with a single exposure. Computational post-processing of this information permits to carry out a 3D reconstruction of the sample. By applying conventional algorithms, both depth and also view reconstructions are possible. However, the main drawback of IMic is that the resolution of the reconstructed images is low and axially heterogeneous. In this paper, we propose a new configuration of the IMic by placing the lens array not at the image plane, but at the pupil (or Fourier) plane of the microscope objective. With this novel system, the spa…

Elemental images for integral-imaging display

One of the differences between the near-field integral imaging (NInI) and the far-field integral imaging (FInI), is the ratio between number of elemental images and number of pixels per elemental image. While in NInI the 3D information is codified in a small number of elemental images (with many pixels each), in FInI the information is codified in many elemental images (with only a few pixels each). The later codification is similar that the one needed for projecting the InI field onto a pixelated display when aimed to build an InI monitor. For this reason, the FInI cameras are specially adapted for capturing the InI field with display purposes. In this contribution we research the relation…

Integral imaging with Fourier-plane recording

Integral Imaging is well known for its capability of recording both the spatial and the angular information of threedimensional (3D) scenes. Based on such an idea, the plenoptic concept has been developed in the past two decades, and therefore a new camera has been designed with the capacity of capturing the spatial-angular information with a single sensor and after a single shot. However, the classical plenoptic design presents two drawbacks, one is the oblique recording made by external microlenses. Other is loss of information due to diffraction effects. In this contribution report a change in the paradigm and propose the combination of telecentric architecture and Fourier-plane recordin…

View images with unprecedented resolution in integral microscopy

Integral microscopy is a novel technique that allows the simultaneous capture of multiple perspective images of microscopic samples. This feature is achieved at the cost of a significant reduction of the spatial resolution. In fact, it is assumed that in the best cases the resolution is reduced by a factor that is not smaller than ten, what poses a hard drawback to the utility of the technique. However, to the best of our knowledge, this resolution limitation has never been researched rigorously. For this reason, the aim of this paper is to explore the real limitations in resolution of integral microscopy and to obtain optically, without the need of any image-processing algorithm, perspecti…

Depth rendering of large incoherent scenes from integral images

Integral imaging is a technique that provides the spatial and angular information of three-dimensional (3D) scenes through a single shot. Taking advantage of this capability, different applications have been developed. Some of these applications are the 3D display and digital post-processing, in particular depth-reconstruction from integral images.

Free segmentation in rendered 3D images through synthetic impulse response in integral imaging

Integral Imaging is a technique that has the capability of providing not only the spatial, but also the angular information of three-dimensional (3D) scenes. Some important applications are the 3D display and digital post-processing as for example, depth-reconstruction from integral images. In this contribution we propose a new reconstruction method that takes into account the integral image and a simplified version of the impulse response function (IRF) of the integral imaging (InI) system to perform a two-dimensional (2D) deconvolution. The IRF of an InI system has a periodic structure that depends directly on the axial position of the object. Considering different periods of the IRFs we …

Optical sectioning with a Wiener-like filter in Fourier integral imaging microscopy

Non-scanning, single-shot, 3D integral microscopy with optical sectioning is presented. The method is based on the combination of Fourier-mode integral microscopy with a 3D deconvolution technique. Specifically, the refocused volume provided by a regular back-projection algorithm is 3D deconvolved with a synthetic 3D impulse response function that takes into account the number and positions of the elemental images. The use of this hybrid technique provides a stack of true-color depth-refocused images with significant gain of optical sectioning. The stack can be used, among other applications, to inspect inside the thick microscope specimen, to calculate collections of perspective views wit…

FIMic: design for ultimate 3D-integral microscopy of in-vivo biological samples

In this work, Fourier integral microscope (FIMic), an ultimate design of 3D-integral microscopy, is presented. By placing a multiplexing microlens array at the aperture stop of the microscope objective of the host microscope, FIMic shows extended depth of field and enhanced lateral resolution in comparison with regular integral microscopy. As FIMic directly produces a set of orthographic views of the 3D-micrometer-sized sample, it is suitable for real-time imaging. Following regular integral-imaging reconstruction algorithms, a 2.75-fold enhanced depth of field and [Formula: see text]-time better spatial resolution in comparison with conventional integral microscopy is reported. Our claims …

3D Integral Microscopy based in far-field detection

Lately, Integral-Imaging systems have shown very promising capabilities of capturing the 3D structure of micro- scopic and macroscopic scenes. The aim of this work is to provide an optimal design for 3D-integral microscopy with extended depth of field and enhanced lateral resolution. By placing an array of microlenses at the aperture stop of the objective, this setup provides a set of orthographic views of the 3D sample. Adopting well known integral imaging reconstruction algorithms it can be shown that the depth of field as well as spatial resolution are improved with respect to conventional integral microscopy imaging. Our claims are supported on theoretical basis and experimental images …

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