Enhanced depth of field of computer‐generated holographic stereograms by twice close‐range capturing with occlusion processing

2021 ◽  
Author(s):  
Piao Dai ◽  
Guoqiang Lv ◽  
Zi Wang ◽  
Xin Gong ◽  
Qibin Feng
Keyword(s):  
Depth Of Field ◽  
Close Range ◽  
Holographic Stereograms

scholarly journals DoF-Dependent and Equal-Partition Based Lens Distortion Modeling and Calibration Method for Close-Range Photogrammetry

Sensors ◽  
2020 ◽  
Vol 20 (20) ◽  
pp. 5934
Author(s):  
Xiao Li ◽  
Wei Li ◽  
Xin’an Yuan ◽  
Xiaokang Yin ◽  
Xin Ma
Keyword(s):  
Optical Axis ◽  
Focal Length ◽  
Calibration Method ◽  
Depth Of Field ◽  
Model Parameters ◽  
Lens Distortion ◽  
Camera Model ◽  
Distortion Model ◽  
Manual Adjustment ◽  
Close Range

Lens distortion is closely related to the spatial position of depth of field (DoF), especially in close-range photography. The accurate characterization and precise calibration of DoF-dependent distortion are very important to improve the accuracy of close-range vision measurements. In this paper, to meet the need of short-distance and small-focal-length photography, a DoF-dependent and equal-partition based lens distortion modeling and calibration method is proposed. Firstly, considering the direction along the optical axis, a DoF-dependent yet focusing-state-independent distortion model is proposed. By this method, manual adjustment of the focus and zoom rings is avoided, thus eliminating human errors. Secondly, considering the direction perpendicular to the optical axis, to solve the problem of insufficient distortion representations caused by using only one set of coefficients, a 2D-to-3D equal-increment partitioning method for lens distortion is proposed. Accurate characterization of DoF-dependent distortion is thus realized by fusing the distortion partitioning method and the DoF distortion model. Lastly, a calibration control field is designed. After extracting line segments within a partition, the de-coupling calibration of distortion parameters and other camera model parameters is realized. Experiment results shows that the maximum/average projection and angular reconstruction errors of equal-increment partition based DoF distortion model are 0.11 pixels/0.05 pixels and 0.013°/0.011°, respectively. This demonstrates the validity of the lens distortion model and calibration method proposed in this paper.

scholarly journals EXPERIMENTS ON CALIBRATING TILT-SHIFT LENSES FOR CLOSE-RANGE PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B5 ◽  
pp. 99-105 ◽  
Author(s):  
E. Nocerino ◽  
F. Menna ◽  
F. Remondino ◽  
J.-A. Beraldin ◽  
L. Cournoyer ◽  
...  
Keyword(s):  
Optical Axis ◽  
National Research Council ◽  
Image Plane ◽  
Limiting Factors ◽  
Depth Of Field ◽  
Small Object ◽  
Digital Cameras ◽  
Close Range Photogrammetry ◽  
Object Distance ◽  
Close Range

One of the strongest limiting factors in close range photogrammetry (CRP) is the depth of field (DOF), especially at very small object distance. When using standard digital cameras and lens, for a specific camera – lens combination, the only way to control the extent of the zone of sharp focus in object space is to reduce the aperture of the lens. However, this strategy is often not sufficient; moreover, in many cases it is not fully advisable. In fact, when the aperture is closed down, images lose sharpness because of diffraction. Furthermore, the exposure time must be lowered (susceptibility to vibrations) and the ISO increased (electronic noise may increase). In order to adapt the shape of the DOF to the subject of interest, the Scheimpflug rule is to be applied, requiring that the optical axis must be no longer perpendicular to the image plane. Nowadays, specific lenses exist that allow inclining the optical axis to modify the DOF: they are called tilt-shift lenses. In this paper, an investigation on the applicability of the classic photogrammetric model (pinhole camera coupled with Brown’s distortion model) to these lenses is presented. Tests were carried out in an environmentally controlled metrology laboratory at the National Research Council (NRC) Canada and the results are hereafter described in detail.

Optimal Camera Configuration for 3D Scanning of Human Hand

2019 ◽  
Author(s):  
Yusheng Yang ◽  
Willemijn S. Elkhuizen ◽  
Tao Hou ◽  
Tessa T. W. Essers ◽  
Yu Song
Keyword(s):  
3D Reconstruction ◽  
Spatial Configuration ◽  
Low Cost ◽  
Absolute Error ◽  
Depth Of Field ◽  
Human Hand ◽  
Spatial Configurations ◽  
Close Range ◽  
3D Printed ◽  
3D Scans

Abstract Fast, accurate and low-cost 3D scans are the key in designing personalized products. In this paper, using close-range photogrammetry technique, we aim at finding the “just enough” number of cameras and their spatial configurations for a full 3D reconstruction of the human hand. Given an object, we establish a mathematical model to describe the 3D constructible ratio based on the field of the view and the depth of field of each camera, as well as the visibility of each part of the object in the view of each camera. Furthermore, we introduce spatial constrains to arrange cameras along two rings for: 1) solving the problem of the large number of parameters in the unconstrained optimization, and 2) the feasibility and flexibility in the construction. Based on the found number of cameras and the spatial configuration of each camera, a prototype scanner was built to verify the effectiveness of the proposed method. The mean absolute error between the 3D scan of a 3D printed hand and its original CAD model was found to be 0.38mm, which is smaller than that (0.52mm) of using the conventional setup. Besides, the distribution of errors is smaller as well, which implicates a better full 3D reconstruction of the scanned hand.

scholarly journals EXPERIMENTS ON CALIBRATING TILT-SHIFT LENSES FOR CLOSE-RANGE PHOTOGRAMMETRY

2016 ◽  
Vol XLI-B5 ◽  
pp. 99-105 ◽  
Author(s):  
E. Nocerino ◽  
F. Menna ◽  
F. Remondino ◽  
J.-A. Beraldin ◽  
L. Cournoyer ◽  
...  
Keyword(s):  
Optical Axis ◽  
National Research Council ◽  
Image Plane ◽  
Limiting Factors ◽  
Depth Of Field ◽  
Small Object ◽  
Digital Cameras ◽  
Close Range Photogrammetry ◽  
Object Distance ◽  
Close Range

One of the strongest limiting factors in close range photogrammetry (CRP) is the depth of field (DOF), especially at very small object distance. When using standard digital cameras and lens, for a specific camera – lens combination, the only way to control the extent of the zone of sharp focus in object space is to reduce the aperture of the lens. However, this strategy is often not sufficient; moreover, in many cases it is not fully advisable. In fact, when the aperture is closed down, images lose sharpness because of diffraction. Furthermore, the exposure time must be lowered (susceptibility to vibrations) and the ISO increased (electronic noise may increase). In order to adapt the shape of the DOF to the subject of interest, the Scheimpflug rule is to be applied, requiring that the optical axis must be no longer perpendicular to the image plane. Nowadays, specific lenses exist that allow inclining the optical axis to modify the DOF: they are called tilt-shift lenses. In this paper, an investigation on the applicability of the classic photogrammetric model (pinhole camera coupled with Brown’s distortion model) to these lenses is presented. Tests were carried out in an environmentally controlled metrology laboratory at the National Research Council (NRC) Canada and the results are hereafter described in detail.

The Broad Applications of the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 20-21
Author(s):  
C. T. Nightingale ◽  
S. E. Summers ◽  
T. P. Turnbull
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscopy ◽  
Surface Topography ◽  
Great Depth ◽  
Resolving Power ◽  
Depth Of Field ◽  
Pictorial Representations ◽  
Scanning Electron

The ease of operation of the scanning electron microscope has insured its wide application in medicine and industry. The micrographs are pictorial representations of surface topography obtained directly from the specimen. The need to replicate is eliminated. The great depth of field and the high resolving power provide far more information than light microscopy.

Visualization of Internal Skin Structures with the Scanning Electron Microscope

1969 ◽  
Vol 27 ◽  
pp. 46-47
Author(s):  
Emil Bernstein
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Great Depth ◽  
Hair Follicles ◽  
Depth Of Field ◽  
Pig Skin ◽  
Realistic Picture ◽  
Main Components ◽  
Scanning Electron

An interesting method for examining structures in g. pig skin has been developed. By modifying an existing technique for splitting skin into its two main components—epidermis and dermis—we can in effect create new surfaces which can be examined with the scanning electron microscope (SEM). Although this method is not offered as a complete substitute for sectioning, it provides the investigator with a means for examining certain structures such as hair follicles and glands intact. The great depth of field of the SEM complements the technique so that a very “realistic” picture of the organ is obtained.

Computer Assisted Image Reconstruction of Oligomer Structure

1976 ◽  
Vol 34 ◽  
pp. 472-473
Author(s):  
A.M. Jones ◽  
A. Max Fiskin
Keyword(s):  
Three Dimensional ◽  
Depth Of Field ◽  
Computer Assisted ◽  
Projection Data ◽  
Two Dimensional ◽  
Single Particles ◽  
Dimensional Reconstruction ◽  
Computer Assisted Image ◽  
The Fourier Transform ◽  
Space Approach

If the tilt of a specimen can be varied either by the strategy of observing identical particles orientated randomly or by use of a eucentric goniometer stage, three dimensional reconstruction procedures are available (l). If the specimens, such as small protein aggregates, lack periodicity, direct space methods compete favorably in ease of implementation with reconstruction by the Fourier (transform) space approach (2). Regardless of method, reconstruction is possible because useful specimen thicknesses are always much less than the depth of field in an electron microscope. Thus electron images record the amount of stain in columns of the object normal to the recording plates. For single particles, practical considerations dictate that the specimen be tilted precisely about a single axis. In so doing a reconstructed image is achieved serially from two-dimensional sections which in turn are generated by a series of back-to-front lines of projection data.

Sem/X-Ray Applications to the Forensic Science Field

1976 ◽  
Vol 34 ◽  
pp. 390-391
Author(s):  
K. Culbreth
Keyword(s):  
Forensic Science ◽  
Depth Of Field ◽  
Surface Phenomena ◽  
Criminal Cases ◽  
Forensic Evidence ◽  
Science Field ◽  
X Ray ◽  
Hit And Run ◽  
Evaluation Of Evidence ◽  
Scanning Electron

The introduction of scanning electron microscopy and energy dispersive x-ray analysis to forensic science has provided additional methods by which investigative evidence can be analyzed. The importance of evidence from the scene of a crime or from the personal belongings of a victim and suspect has resulted in the development and evaluation of SEM/x-ray analysis applications to various types of forensic evidence. The intent of this paper is to describe some of these applications and to relate their importance to the investigation of criminal cases.The depth of field and high resolution of the SEM are an asset to the evaluation of evidence with respect to surface phenomena and physical matches (1). Fig. 1 shows a Phillips screw which has been reconstructed after the head and shank were separated during a hit-and-run accident.

Cryomicroscopy of crotoxin complex crystals at 400 KV

1989 ◽  
Vol 47 ◽  
pp. 826-827
Author(s):  
Jaap Brink ◽  
Wah Chiu
Keyword(s):  
Signal To Noise Ratio ◽  
3D Structure ◽  
Three Dimensional ◽  
Carbon Films ◽  
Depth Of Field ◽  
Basic Subunit ◽  
Ewald Sphere ◽  
Diffraction Patterns ◽  
Complex Crystals ◽  
Acidic Subunit

The crotoxin complex is a potent neurotoxin composed of a basic subunit (Mr = 12,000) and an acidic subunit (M = 10,000). The basic subunit possesses phospholipase activity whereas the acidic subunit shows no enzymatic activity at all. The complex's toxocity is expressed both pre- and post-synaptically. The crotoxin complex forms thin crystals suitable for electron crystallography. The crystals diffract up to 0.16 nm in the microscope, whereas images show reflections out to 0.39 nm2. Ultimate goal in this study is to obtain a three-dimensional (3D-) structure map of the protein around 0.3 nm resolution. Use of 100 keV electrons in this is limited; the unit cell's height c of 25.6 nm causes problems associated with multiple scattering, radiation damage, limited depth of field and a more pronounced Ewald sphere curvature. In general, they lead to projections of the unit cell, which at the desired resolution, cannot be interpreted following the weak-phase approximation. Circumventing this problem is possible through the use of 400 keV electrons. Although the overall contrast is lowered due to a smaller scattering cross-section, the signal-to-noise ratio of especially higher order reflections will improve due to a smaller contribution of inelastic scattering. We report here our preliminary results demonstrating the feasability of the data collection procedure at 400 kV.Crystals of crotoxin complex were prepared on carbon-covered holey-carbon films, quench frozen in liquid ethane, inserted into a Gatan 626 holder, transferred into a JEOL 4000EX electron microscope equipped with a pair of anticontaminators operating at −184°C and examined under low-dose conditions. Selected area electron diffraction patterns (EDP's) and images of the crystals were recorded at 400 kV and −167°C with dose levels of 5 and 9.5 electrons/Å, respectively.

Going Beyond 3-D Imaging: Automated 3-D Montaged image Analysis of Cytological Specimens

1996 ◽  
Vol 54 ◽  
pp. 282-283
Author(s):  
Badrinath Roysam ◽  
Hakan Ancin ◽  
Douglas E. Becker ◽  
Robert W. Mackin ◽  
Matthew M. Chestnut ◽  
...  
Keyword(s):  
Image Analysis ◽  
Structural Changes ◽  
Sampling Methods ◽  
Spatial Clustering ◽  
Three Dimensional ◽  
Field Of View ◽  
Cell Counting ◽  
Depth Of Field ◽  
Tissue Cell ◽  
Tissue Organization

This paper summarizes recent advances made by this group in the automated three-dimensional (3-D) image analysis of cytological specimens that are much thicker than the depth of field, and much wider than the field of view of the microscope. The imaging of thick samples is motivated by the need to sample large volumes of tissue rapidly, make more accurate measurements than possible with 2-D sampling, and also to perform analysis in a manner that preserves the relative locations and 3-D structures of the cells. The motivation to study specimens much wider than the field of view arises when measurements and insights at the tissue, rather than the cell level are needed.The term “analysis” indicates a activities ranging from cell counting, neuron tracing, cell morphometry, measurement of tracers, through characterization of large populations of cells with regard to higher-level tissue organization by detecting patterns such as 3-D spatial clustering, the presence of subpopulations, and their relationships to each other. Of even more interest are changes in these parameters as a function of development, and as a reaction to external stimuli. There is a widespread need to measure structural changes in tissue caused by toxins, physiologic states, biochemicals, aging, development, and electrochemical or physical stimuli. These agents could affect the number of cells per unit volume of tissue, cell volume and shape, and cause structural changes in individual cells, inter-connections, or subtle changes in higher-level tissue architecture. It is important to process large intact volumes of tissue to achieve adequate sampling and sensitivity to subtle changes. It is desirable to perform such studies rapidly, with utmost automation, and at minimal cost. Automated 3-D image analysis methods offer unique advantages and opportunities, without making simplifying assumptions of tissue uniformity, unlike random sampling methods such as stereology.12 Although stereological methods are known to be statistically unbiased, they may not be statistically efficient. Another disadvantage of sampling methods is the lack of full visual confirmation - an attractive feature of image analysis based methods.

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