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25–29 June 2017
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2017 Symposium ChairsContents

Bernard C. Kress,
Microsoft Corp.
(United States)

10335: Digital Optical Technologies . . . . . . . .  3-27

Wolfgang Osten,
Univ. Stuttgart(Germany)

H. Paul Urbach,Technische Univ. Delft(Netherlands)

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Conference 10335:
Digital Optical Technologies
Monday - Wednesday 26–28 June 2017
Part of Proceedings of SPIE Vol. 10335 Digital Optical Technologies 2017

10335-1, Session 1

insufficient backlight suppression of non-emissive microdisplays.

See-through 3D technology foraugmented reality (Invited Paper)
Byoungho Lee, Seungjae Lee, Gang Li, Changwon Jang,
Jong-Young Hong, Seoul National Univ. (Korea, Republicof)Augmented reality (AR) is recently attracting a lot of attention as one of
the most spotlighted next-generation technologies. In order to achieve
realization of ideal AR, we need to integrate 3D virtual information into
real world. This integration should not be noticed by users, blurring theboundary between the virtual and real worlds. Thus, the ultimate device
for AR should reconstruct and superimpose 3D virtual information on thereal world that is not distinguishable, which is referred to as see-through3D technology. Here, we introduce our recent researches to combine seethrough displays and 3D technologies using emerging optical combiners:
holographic optical elements and index matched optical elements.
Holographic optical elements are volume gratings that have angularand wavelength selectivity. Index matched optical elements are partiallyreflective elements using a compensation element for index matching.
Using these optical combiners, we could implement see-through 3D
displays based on typical methodologies including integral imaging,
digital holographic displays, multi-layer displays, and retinal projection.
Some of these methods are expected to be optimized and customized forhead-up displays, head-mounted or wearable displays. We conclude withdemonstration and analysis of fundamental researches for head-mounted
see-through 3D displays.

10335-2, Session 1

OLED microdisplays in near-to-eye
applications: challenges and solutions
Uwe Vogel, Fraunhofer-Institut für Organische
Elektronik, Elektronenstrahl- und Plasmatechnik(Germany); Bernd Richter, Philipp Wartenberg, Peter
Koenig, Fraunhofer Institute for Organic Electronics,
Electron Beam and Plasma Technology FEP (Germany);
Olaf R. Hild, Fraunhofer-Institut für Organische
Elektronik, Elektronenstrahl- und Plasmatechnik FEP(Germany); Karsten Fehse, Matthias Schober, Elisabeth
Bodenstein, Fraunhofer-Institut für Organische
Elektronik, Elektronenstrahl- und Plasmatechnik(Germany); Beatrice Beyer, Fraunhofer-Institut
für Organische Elektronik, Elektronenstrahl- undPlasmatechnik FEP (Germany)
The prominent emissive microdisplay technology on the market is OLEDon-silicon. A single-crystalline silicon CMOS chip provides the activematrix circuitry to address and drive the millions of individual pixels (pixel
cell circuitry also known as the backplane). Since the silicon substrateitself is intransparent in the visible spectrum, a top-emission OLED setup
is required (emitting away from substrate). OLED microdisplays coverby far the major portion of emissive microdisplays on the market today
as they are well-suited for extremely small form-factor and low-power
consuming optical engines. Due to the size, power, contrast and colorspace advantages, NTE applications represent the largest opportunity
for OLED microdisplays. This relates to both personal viewers (PV) andelectronic viewfinders (EVF). PV are either see-through data glasses used
for mixed- and augmented reality (AR) applications, or non-see-through/immersive video glasses used for entertainment or virtual reality (VR)applications in gaming, training or entertainment. Due to their emissive
nature OLED microdisplays are specifically suited for see-through/AR smart glasses, since they prevent a virtual grey-shaded monitorlike perception inside the user’s field of view, which is caused by the

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OLED-on-Silicon microdisplay technology might be best suited tobi-directional microdisplay techniques too, which combine both image
display and image acquisition in a single chip. That is mainly due to thefact that there is no intrinsic saturation of photodetectors embedded
inside the microdisplay backplane caused by the external illuminationof “modulating” displays (in contrast to the top-emission here), though,optical cross-talk inside the emissive microdisplay device should befactored in. Image sensor elements, for example, pn-junction CMOS
photodiodes, are arranged in a fixed matrix/pixel pattern correlated tothe image display pixel matrix/pattern. In a common case, both arrays
have become intersected to each other; one photodetector pixel per
one display pixel. Other design arrangements are feasible and should
be adapted to the application. Moreover, optical crosstalk effects can belimited or avoided by design, driving scheme and technological means.
For smart glasses application that feature can add eye-tracking capability
for enabling hands-free user-interaction with the virtual display content,e.g., via gaze-controlled virtual buttons.
Luminance and lifetime are two critical performance parameters for OLED
microdisplays, specifically under high-temperature conditions. For costreasons, achieving low-pixel pitch is important, since it directly translates
into die size and chip cost. For immersive environments (for example,
non-see-through or EVF and NTE applications), usually luminance up to
500 cd/m? and lifetime >10,000 hours are sufficient, whereas current
see-through optics and consideration of sunlight conditions easily
demand >5,000 cd/m? of luminance and beyond, regularly combinedwith elevated temperature operation. The challenge at high luminanceis to supply and modulate the forward voltage at dynamic range levelsof 2V up to 7 V (or even more, depending on OLED stack architecture)
toward each OLED pixel; this requires integrated driving transistors
able to withstand voltage swing of 5 V or more. That’s a high-voltage
for advanced mixed-signal CMOS processes at minimum feature sizes(usually referenced by minimum transistor channel length), for example,
in the range of 0.25 to 0.11 µm at core voltages of about 1.2 to 2.5 V. Suchhigh-voltage transistors require more die area, whereas smaller featuresize CMOS processes typically provide even fewer options for HV devices,
i.e., shrinking pixel cell size remains limited.
There are plenty of NTE applications which demand long battery life
above frame rate and resolution. For such applications it becomes
sufficient to display simple graphics (e.g., symbols) and text. Even more,
the alteration frequency of screen content is often rather low (<5Hz).
Therefore image data can be stored in a static random access memory
SRAM-like pixel cell architecture, and the direct pixel-wise addressing
scheme enables much lower bandwidth for the display interface as well.
That approach allows to drastically reduce display power consumption
by minimizing the backplane consumption. Consequently, OLED power(and its efficiency) now determines the overall power consumption.
At moderate display resolution and frame rate there is even a power
advantage for video display.
To summarize: Advancing near-to-eye applications of microdisplays
demand improved parameters and extended features, such as full-color
high-brightness, low-power and embedded sensors for user interaction.
OLED micro-patterning for achieving R, G, B sub-pixels appears to be an
inevitable approach, though remaining unsolved for commercialization
yet. That will require further technology progress - electron-beampatterning might potentially contribute to that. Moreover, low-power
backplane architectures will enable significantly longer battery operationin those NTE applications, that do not require high-resolution full-frame
video capability.

10335-3, Session 1

Time multiplexing for increased FOV andresolution in virtual reality
Juan C. Minano, Pablo Benítez, Univ. Politécnica deMadrid (Spain) and Limbak (Spain); Dejan Grabovickic,
Pablo Zamora, Marina Buljan, Bharathwaj A. Narasimhan,
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We introduce a time multiplexing strategy to improve the density of
pixels or the Field of View (or both) of the virtual image seen in a VR or
AR headset. A given virtual image is displayed by generating a successionof partial real images, each representing part of the virtual image andtogether representing the virtual image. Each partial real image uses
the full set of physical pixels available in the display. The partial real
images are imaged to form a part of the virtual image viewable from aneye position. Each one of these different parts (called sub-images) are
shown during a fraction of the frame time called a sub-frame slot. The
union of all sub-frame slots is the frame display time and the union of all
sub-images forms the full image shown on the virtual screen. The opticalsystem contains different channels, each one imaging the physical display
in one sub-image. Every optical channel entrance sees the display. Each
optical channel is only used during the sub-frame slot corresponding
to its sub-image. When using displays with wide angular emission,
such as OLED displays, for instance, then the system must prevent lightentering the wrong channel since this light will image a portion of thevirtual image in the wrong place. For the purpose of controlling the lightentering the active channel, shutters are used (high-speed, high-contrast
active shutters such as the ones used in 3D glasses). Alternatively to theuse of shutters, LCD displays may use directional backlights such that thebacklight sends light only to the active optical channel entrances. Since
VR and AR applications require very compact designs, in general, at least
some of the sub-images (images of the partial real images) are occupying
overlapping positions. This optical overlapping diminishes slightly the
resolution/FOV gains due to time multiplexing.
The sub-images, which are successively formed, combine spatially andtemporally to form a virtual image viewable from the eye position so thatsaid overlapping portions of different partial real images from different
portions of the virtual image. This time multiplexing strategy needs
real images be shown at high frame rates. Available display and lightchanneling (shutters, etc.) technologies are discussed with regard to pixel
density and frame rate. Several optical designs for achieving this time
multiplexing scheme in a compact format are shown.
This time multiplexing scheme allows increasing the resolution /FOV of
the virtual image not only by increasing the physical pixel density but also
by decreasing the pixels switching time, a feature that may be simpler toachieve in certain circumstances.

10335-4, Session 1

Phase space methods in HMD systems
James Babington, Qioptiq Ltd. (United Kingdom)
Unoccluded head mounted display (HMD) systems, such as freeformprisms or pupil replicating waveguide geometries provide good examples
of augmented reality technology, where digital images are overlaid
onto the real world. Since the optical systems used to implement thisnecessarily involve a different type of complexity, it is a worthwhile
venture to try and understand them using alternative methods of analysis
and design. In this paper we consider using phase space techniques andmethods in analysing and understanding HMD geometries. The pointof view taken here is to understand the global nature of the imaging
problem, where the phase space coordinates are the fundamental
variables from which physical quantities and observables can beconstructed. In this paper we consider firstly how phase space provides a
global map of the physical ray trace data. As such, this gives a complete
optical history of the entire ray trace data propagating through thesystem. Phase space methods originally were the domain of classicaldynamics, where Hamiltonian mechanics is naturally formulated. However,classical optical imaging also provides a natural stage to employ phasespace techniques, albeit as a constrained system.
Two example geometries are considered in some detail in this paper.
Firstly, the well known shark tooth freeform geometry is presented
that embodies much more complexity in its optical surfaces. A second
example of a waveguide geometry that replicates a pupil in one
dimension is also shown. The complexity here lies in the multiple copiesof the exit pupil that propagate out to an external eye box. In both
examples, ray trace data is recorded on a number of well defined surfacesthat capture both the parabasal and the global regions. Using this data,
one can subsequently look at how ray aberrations can be extracted
numerically from the phase space diagrams. This is of particular relevancefor the example of a freeform imaging prism. An important point to4

note here is that this gives direct access to the second order aberrations
that arise due to the system only having one plane of symmetry.
Standard third order aberration theory is insufficient in capturing the rayaberrations of the freeform surfaces. This is consistent with the nodal
aberration theory approach, where titled optical surfaces can introduce
different nodal structure at the image plane. In the example of the
waveguide geometry, phase space diagrams provide a way of illustrating
how replicated pupils behave at the eyebox and what these imply fordesign considerations. In particular, one can see with this approach how
the field of view is limited by the spectral bandwidth and field of view ofthe system. Ray aberrations are manifest in the phase space diagrams of
the replicated pupils, for example, due to imperfect optical tolerances of
the waveguide structure itself.

10335-5, Session 1

Comparison of different designs of head
mounted displays with large field of view
Bo Chen, Alois M. Herkommer, Univ. Stuttgart (Germany)
Head mounted displays (HMD), as one type of wearable virtual reality
device, are nowadays rather popular in aviation, 3D gaming, training, andmany other applications. There are already many optical design concepts
for these systems in the literature. Takahashi (1997) [1] presented one
prism HMD optics which is small in size and light in weight with one totalinternal reflection (TIR) surface. In contrast A. Bauer and J. P. Rolland(2014) [2] depicted two freefrom HMDs, which contain only mirrors.
The HMDs are required to be light in weight, small in size, offering awide field of view and high imaging quality. In nearly all the designs,
freeform surfaces are employed with the advantage to effectively
correct aberrations while reducing the number of lenses. Also in thispaper, anamorphic aspheric surfaces are used for the description of thefreeform.
The TIR prism type described by Takahashi [1] represents a basic design
type of HMD optics, which is widely applied by others. This patent andone similar TIR prism HMD designed by our own will be employed as areference in this paper. The goal of our investigation is to find alternate
design form with potentially better performance. Therefore we havedesigned one catadioptric HMD (consisting of a lens and two mirrors),
and one prism with different folding geometry for comparison. These
two types of HMDs are seldom studied and may have mechanicaldisadvantages, however the optical performance of these two alternate
types are quite good.
SPECIFICATIONS AND DESIGN PROCESS:
For fair comparison, the specifications of all the systems designed are thesame as the patent lens [1]. The specifications are depicted in Table 1 andthe layout of the patent lens is presented in Fig. 1.
FOV vertical 30º, horizontal 40º In order to find competitive design forms
a specific process has been developed, stating from on-axis systems
which are modified to form valid off-axis geometries. During design
the paraxial focal length calculation is non-trivial and cannot be usedduring optimization. As a substitute the numerical aperture at the image
is applied to constrain the size of the systems. In addition obscurationand escaping of rays needs to be avoided during design. To correct theserious aberrations, anamorphic freeform surfaces (Eq. (1)) are applied forthese tilted and decentered systems. Additionally, up to 15 fields of angle
are applied during the optimization to minimize the distortion since theoff-axis system allows for large distortion.
where z is the sag, cx and cy represent the curvatures in the orthogonal
directions x and y, respectively, kx and ky denote the conic constants,
and Ai and Bi are the higher order symmetric and asymmetric terms,
respectively.
RESULTS:
Several forms of head mounted display optics are designed andcompared. One is a prism HMD, which is similar to the patent lens shownin Fig. 1. Another is a catadioptric system with one lens and two mirrors
shown in Fig. 2. Besides, an alternate prism without TIR surface anddifferent folding geometry is depicted in Fig. 3.
1) TIR head mounted display
2) Catadioptric head mounted display

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Conference 10335:
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3) Prism head mounted display without TIR surface
References:[1] K. Takahashi, “Head or face mounted image display apparatus.” U.S.
Patent No. 5,701,202. 23 Dec. 1997.
[2] A. Bauer and J. P. Rolland, “Visual space assessment of two allreflective, freeform, optical see-through head-worn displays.” Opt.
Express 22, 13155-13163 (2014).

10335-6, Session 2

Designing optics to reduce digitalprocessing and communication incomputational sensors and imagers: a
new approach to low-power sensing(Invited Paper)David G. Stork, Rambus Inc. (United States)
No Abstract Available

10335-7, Session 2

Computational wavelength resolution for
in-line lensless holography: phase-coded
difraction patterns and wavefront groupsparsity
Vladimir Y. Katkovnik, Tampere Univ. of Technology(Finland); Igor A. Shevkunov, Nikolay V. Petrov, ITMO
Univ. (Russian Federation); Karen O. Egiazarian, Tampere
Univ. of Technology (Finland)
In-line lensless holography is considered with a random phase modulation
at the object plane. The forward wavefront propagation is modelledusing the Fourie transform with the angular spectrum transfer function.
The multiple intensities (holograms) recorded by the sensor are random
due to the random phase modulation and noisy with Poissonian
noise distribution. In computational imaging sparse and redundant
representations have been successfully developed the last years as
a general concept. It is based on the assumption that there exists a
small number of items such that image can be represented exactly
or approximately with a good accuracy. In term of statistics, a sparse
representation can be thought as a low-order parametric approximation.
The group (or structured) sparsity has appeared artificially by specialgrouping of observations. In particular, for 2D images a small similar 2D
patches are grouped in 3D array processed independently. The similarityof the grouped patches enables a high-level sparsity of the grouped dataand high efficiency of small size their approximations. The main featuresof these techniques are originated from the work on Block Matching 3D(BM3D) filtering, which is a well established technique enabling the stateof the art performance for various imaging problems.
The sparsity and group sparsity for optics is a nontrivial developmentof the standard concepts because of the complex-valued objects ofinterest with phase and amplitude. The Sparse Phase and Amplitude
Reconstruction (SPAR) algorithm is proposed in this paper using
the group sparsity (BM3D) as the main tool for noise suppression
and super-resolution imaging. The algorithm is designed for optimalphase/amplitude reconstruction from Poissonian data. It is shown bycomputational experiments that high-accuracy reconstructions can beachieved with resolution going up to the quarter of the wavelength, ?/4.
With respect to the sensor pixel size it is a 32? super-resolution.
Some qualitative effects of the basic ingredients (modulation phasemasks and group sparsity) used in the algorithm are demonstrated inFig. 1. The first left image shows the true phase. The next completely
destroyed image is obtained by the Gerchberg-Saxton algorithm fromthe experiment with no phase modulation and without the sparsemodeling for phase and amplitude. The next third image is obtained froma single experiment where the phase modulation is employed but nosparse filtering. This modulation makes the main features of the phase

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distribution at least visible but quite noisy. This noise is a result of theused phase modulation. The last fourth image in this set of experiments
is obtained by the SPAR algorithm, i.e. for the data with the phasemodulation and sparse imaging for the phase and amplitude. It showsnear perfect reconstruction of the object phase. These 512?512 images are
obtained for the very low noise level. For a larger number of experiments
the accuracy of the phase reconstruction with the phase modulation is
improving quickly both for processing with (SPAR) and without sparsefiltering (GS).

10335-8, Session 2

Fast physical optics-based simulation of
waveguide displays for mixed and virtual
reality applications
Daniel Asoubar, LightTrans International UG (Germany);
Christian Hellmann, Wyrowski Photonics UG (Germany);Frank Wyrowski, Friedrich-Schiller-Univ. Jena (Germany)
Various displays for mixed or virtual reality applications consist of one
or several waveguides for guiding light from an image generation unit
to the human eye. On the waveguides holographic or surface gratings
are located for coupling light into, between and out of the waveguides
as well as expanding the exit pupil of the imaging system. For therealistic simulation of such waveguide displays the propagation of entire
wavefronts through the macroscopic waveguide as well as stray lightcaused by zero and higher diffraction orders at the microscopic grating
structures must be analyzed. Thus in this presentation we introduce a
non-sequential field tracing approach, which enables a physical optics
based system analysis. It is shown that this field tracing computation
includes all relevant physical effects like refraction, speckle, interferences,spatial and temporal coherence as well as polarization. Furthermore field
tracing provides a calculation speed advantage compared to conventional
Monte-Carlo ray tracing. To ensure that diffraction efficiency andpolarization effects can be taken into account correctly even for grating
periods in the region of the wavelength of light, a rigorous Fourier modal
method (FMM) is applied. Simulation results of several simple waveguidedisplays are shown to demonstrate the flexibility and performance of the
discussed modeling concepts.

10335-9, Session 2

Real-time augmented reality overlay foran energy-efficient car study
Peter Wozniak, Hochschule Offenburg (Germany);
Nicolas Javahiraly, ICUBE (France); Dan S. Curticapean,
Hochschule Offenburg (Germany)
Our university carries out various research projects. Among others the
project “Schluckspecht” is an interdisciplinary work on different ultraefficient car concepts for different international contests. Besides theengineering work, one part of the project deals with real-time datavisualization. In order to increase the efficiency of the vehicle, an online
monitoring of the runtime parameters is necessary.
The driving parameters of the vehicle are transmitted to a processing
station via a wireless network connection. We plan to use an augmented
reality (AR) application to visualize different data on top of the view of
the real car.
By utilizing a mobile Android or iOS device a user can interactively
view various real-time and gathered statistical data. The car andits components are meant to be augmented by various additional
information, whereby that information should appear at the correct
position. An engine e.g. could show the current rpm and consumption
values. A battery on the other hand could show the current charge level.
The goal of this paper is to evaluate different possible approaches,
their suitability and to expand our application to other projects of ouruniversity.

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10335-10, Session 3

The ideal imaging AR waveguideDavid Grey, WaveOptics (United Kingdom)
From 2016 onwards we have seen an unprecedented pull for near-toeye AR displays declared by leaders of major consumer companies.
WaveOptics believe that imaging waveguides will provide the key
component as a solution to achieve this mass market adoption. The whole
field of imaging waveguides is a very challenging technical area withworldwide interest in AR continuing to grow and a constant search for
new IP that will secure a commercial route forward. Our experience ofworking in this area for much longer than the subject has been of generalinterest has given us a real insight into the problems and requirements fora scalable solution. This paper first considers the ideal imaging waveguidedevice then looks at what we and others have achieved towards this goal.
The ideal imaging AR waveguide description will vary for a given
application, implementation and cost requirement however in our view,
the solution has to have the following aims:
1. Highly scalable manufacturing process
2. Maintain high angular (over say 90+ degrees field of view) andchromatic (full visible spectrum) image information from a display
projector without introducing any optical aberrations.
3. No tinting of outside world image ( 100% transmission)
4. Create a large eyebox from a small input projector aperture to allow
best form factor for a given eye relief to allow different size head/IPD use
and movement of AR headset
5. Introduce no distractions for the user, for example diffractive colour
effects.
6. Maximize the use of light to ensure optimum battery life.
7. Low weight – minimize thickness and area of waveguide
Current real solutions suffer from not being able to solve all of theserequirements. These solutions are restricting the adoption of thetechnology in enterprise applications and cannot approach low-cost
consumer applications which require a readily scalable solution.
Imaging waveguides are a key development that are helping to create
this Augmented Reality revolution. WaveOptics are at the forefront of thisAR technology and have developed and demonstrated a radically new
approach based on photonic crystal 2D pupil expansion.
One of our key PCT patent applications covers our design concept ofan imaging waveguide which has a single input diffraction grating anda single output area photonic crystal lattice. We have a regular array ofnanostructures in the output which in conjunction with the input grating
design provide full angular and chromatic correction as well as provide
pupil expansion. We have developed this concept through prototype
stages and it now gives a field of view beyond 40 degrees, large eyebox,
full colour, outside world transmission >80%, and a HD+ resolution display.
We will demonstrate our latest display and roadmap to take ourtechnology forward in 2017 where we are looking to increase the fieldof view towards 60 degrees whilst maintaining or improving all of theother specifications. We will present our view of the ideal imaging AR
waveguide, the current status (June 17) of our technology and review
existing imaging waveguide technologies against the ideal component.
The future of AR with the potential for mass market adoption for the firsttime is here.

10335-11, Session 3

Thin combiner optics utilizing volume
holographic optical elements (vHOEs)
using Bayfol® HX photopolymer film
Friedrich-Karl Bruder, Thomas Faecke, Rainer Hagen,Sven Hansen, Christel Manecke, Enrico Orselli, Christian
Rewitz, Thomas Rölle, Günther Walze, Covestro AG(Germany)

images and information. Besides real-time head-tracking and roomscanning capabilities the combiner optics, which optically merge thenatural with the artificial visual information, represent a key component
for those systems. Various types of combiner optics are known to theindustry, all with their specific advantages and disadvantages. Beside thewell-established solutions based on refractive optics or surface gratings,
Volume Holographic Optical Elements (vHOEs) are a very attractive
alternative in this field. The unique characteristics of these diffractive
grating structures – being lightweight, thin and flat – make them perfectly
suitable for use in integrated and compact combiners. For any consumer
application it is paramount to build unobtrusive and lightweightaugmented reality displays, for which those holographic combiners are
ideally suited.
In contrast to other diffractive solutions, like surface gratings,
rainbow effects can be suppressed and vHOEs are also completelytransparent in off-Bragg condition. Due to processing challenges of(historic) holographic recording materials, that did not allow mass
production of vHOE holographic combiners, they only found use inmilitary applications by now. The new Bayfol® HX instant developing
holographic photopolymer films provide an ideal technology platform
to optimize the performance of vHOEs in a wide range of applications.
Bayfol® HX provides full color capability and adjustable diffraction
efficiency as well as an unprecedented optical clarity when compared toclassical holographic recording materials like Silver Halide emulsions or
Dichromate Gelatin.
Bayfol® HX is an industrially available product, with optional tailoredproperties for various diffractive performance and integration methods.
Those films are easy to process without the need for chemical or thermal
development steps offering simplified contact-copy mass production
schemes.

10335-12, Session 3

Folded optics with birefringent reflective
polarizers
Timothy Wong, Zhisheng Yun, Gregg Ambur, Jo Etter,
3M Co. (United States)
Folded optics with curved reflective polarizers provide optical design
freedom and enable important capabilities for head-mounted and nearto-eye displays.
Polymeric, birefringent reflective polarizers have been used to produce
compact, mid-FOV eyepieces and wide field-of-view optics forvirtual reality (VR) head-mounted displays using the “pancake” lensconfiguration. In these folded systems a quarter-wave retarder is disposed
between a 50:50 beamsplitter and the reflective polarizer. The retarderenables polarization conversion such that the imaging light is firstreflected by the polarizer and subsequently transmitted, or vice-versa.
The beamsplitter also is used in both reflection and transmission in theimaging system.
Catadioptric imaging systems have well known advantages over solely
refractive systems including a more compact form, lighter weight andimproved aberration control. Using partial reflectors in catadioptric
systems eliminates obscurations and enables the optics to be useful foreye-pieces and head-mounted displays.
Deploying a birefringent reflective polarizer in this scheme hasadvantages. Current research and development includes forming
polymeric films to have reflective optical power and integrating them
onto the curved surface of lenses. Polymeric reflective polarizers havehigh transmission efficiency critical to visual contrast. Additionally, thepolymeric reflective polarizers have good environmental stability and do
not need to be protected from corrosion.
Multiple configurations for pancake lens systems are discussed as are
their advantages and disadvantages relative to refractive systems.
Polarization control is an important consideration and the polarizing
effects of different components are discussed. Designs for mid-FOV,
wide-FOV and ultra-wide FOV are presented and additional benefits ofusing folded optics for virtual reality systems are explored.

The main function of any augmented reality system is to seamlessly
merge the real world perception of a viewer with computer generated

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10335-13, Session 3

Subwavelength optics for new optical
combiners: beyond diffractive optics’limitations
Guillaume Basset, Giorgio Quaranta, Frédéric Zanella,
Angélique Luu-Dinh, Ctr. Suisse d’Electronique et deMicrotechnique SA (Switzerland)
Until recently, resonant subwavelength gratings have been successfully
industrialized only in the field of optical document security andbiochemical sensing. Due to their subwavelength structure, resonant
waveguide-gratings (RWG) support only very few diffraction modes,
and present eventually no diffraction except Zero-order transmission/reflection filtering. Recent developments have demonstrated their ability
to redirect light with a very high selectivity and tunability, opening
great promises to use them as optical combiners for augmented andmixed reality systems. Due to their subwavelength structures, the typicallimitations of Diffractive Optical elements can be overcome, especially
their chromatic aberrations, limited transparency and “rainbow” effect.

be focused on the fovea. Additionally, 90% of all eye movements occur
within less than 15 degs from the normal direction.
We apply this design approach to multiple architectures, and threedesign examples will be presented: an axisymmetric diffractive singlet,
an axisymmetric two-element lens, and a multichannel freeform lens that
perform a squeezed segmented mapping between display pixels and VR
pixels. Compared to a conventional lens design for a QHD (2560x1440)
display (for both eyes) and FOV = 100 degs, those examples achieve thesame FOV but a resolution gain in pixels/deg of 1.35, 1.50 and 1.75 at thecenter of the central area of the FOV. Alternatively, for a given resolutionof the VR pixels, our novel optics can provide a much larger field ofview than a conventional lens. A design example of this type achieves
a FOV=130 degs with the same resolution of a conventional lens of
FOV=100 degs.

The proposed presentation will introduce resonant/subwavelength
gratings and present their strength and weaknesses.

We have also developed a prototype, whose experimentally measured
performance will be shown too. It is a two-element design, manufactured
in PMMA and PS by direct cut with a single-point diamond tool, which
does not only produce 1.50 times the resolution of a conventional design,
but also a good correction of chromatic aberration. This prototype lens,
if used with a mobile-based headset with a QHD (2560x1440) display
and using our lenswill show 19 pixels/deg, the same VR resolution
obtained with a 4K UHD (3840x2160) display and the conventional lens.
Experimental measurements (EFL, FOV, distortion, MTF) of the lens show
a good agreement with the expected design values.

A short word will be given about their application today in different
products and their successful industrialization and production of
hundreds millions of units per year.

10335-15, Session 4

Finally example of use of see-through optical combiners based on
RWG will be presented in different configurations. A first example willshow very thin and highly transparent optical combiners providing highresolution, and large field-of-view RGB images. A second one will present
opportunities for light-field display see-through optical combining.

Mass production of holographictransparent components for augmented
and virtual reality applications
Juan Manuel Russo, Fedor Dimov, Joy Padiyar, Seth A.
Coe-Sullivan, Luminit LLC (United States)

10335-14, Session 3

Super-resolution optics for virtual reality
Dejan Grabovickic, Limbak (Spain); Pablo Benítez, Juan
C. Minano, Limbak (Spain) and Univ. Politécnica deMadrid (Spain); Pablo Zamora, Marina Buljan, Bharathwaj
A. Narasimhan, Limbak (Spain); Milena I. Nikolic, CeDIntUPM (Spain); Jesus Lopez, Limbak (Spain); Eduardo
Sanchez, CeDInt-UPM (Spain)
Resolution perceived in VR is still limited, since the Nyquist frequencyof the VR pixels (typically 10-15 pixels/deg) is well below the angularfrequencies the human eye can resolve (60 pixels/deg). We present
here a novel optics that approach to dramatically increase the perceived
resolution of the VR keeping the large FOV required for VR.
Our optical design approach is based on two main features. First, we take
into account the eye rotations in order to pay special attention to therays that will be focused on the fovea (where the human vision acuity is
maximum). This permits us to optimized for the sharpest image of a VR
pixel to be obtained when it is directly gazed (so the eye images it on
the fovea), and relax the resolvable angular frequency when the eye ispositioned so that VR pixel is seen obliquely (imaged outside the fovea).
This allows the best use of the limited degrees of freedom in the design.
Note that all this is done at the optical design stage, and no eye tracker isneeded in the headset.
Secondly, we design with variable magnification to make VR pixels denser
where they can be gazed, and coarser in the highly peripheral regions.
This variable magnification implies that the lens will present a strong
distortion, which must be compensated for the displayed contents bysoftware (in the same way as it is done for conventional lenses too).
The variable magnification is precisely adapted to the resolution andmovements of the human eye, so the user does not detect that the VR
pixels in the periphery are not as small as those in the central region. This
strategy is effective because the aperture stop of VR optics is also theexit pupil and is located only 15-20 mm from the eye pupil, which implies
that, for a FOV=100 lens measured with the eye is looking forwards,
the user can gaze only up 30-35 degs from the frontward direction, so
the VR pixels from that angle to the rim of the FOV (50 deg) will never

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Diffractive optics such as holographic optical elements (HOE) can provide
transparent, and narrow band components with arbitrary incident anddiffracted angles for near to eye commercial electronic products foraugmented (AR), virtual reality (VR), and smart glass applications. In thispaper, we will summarize the operational parameters and general opticalgeometries relevant for near to eye displays, the holographic substrates
available for these applications, their performance characteristics andease of manufacture.
Compared to HOEs, conventional optics present several disadvantages
for these applications, including refractive optical materials that areheavy or bulky reflective optical train designs. Since traditional opticalelements are limited to the laws of refraction and reflection, cumbersome
custom optical elements that are difficult to fabricate are required
to form a usable image in the wearer’s visual field. These limitations
result in a device that fails to be ergonomic and lightweight and hence,
unacceptable. HOEs are thin and can be custom fabricated for ergonomic
input and output angles with relative ease. The flexibility provided by
HOE fabrication allows production of an attractive, conformable, usefuland easy to use consumer electronic product.
In this application space, narrow angular and spectral performance isoften referred to as transparency. In other words, the wearer has anunobstructed view of the environment (AR) or of another display (VR)while the optical system overlays specific images and information.
Volume HOEs operating in the thick regime are especially suited toprovide the required transparency while overlaying the images withhigh efficiency. Although surface relief diffractive optical elements areeasy to manufacture by embossed replication, they add scattering andmultiple diffraction orders, causing ghosting, reducing efficiency andcompromising see through operation. Conversely, thick volumetric HOEs
can be designed to diffract in only one order with minimal scattering,eliminating ghosting, and maximizing efficiency and see throughtransparent performance.
We will compare the holographic substrates available in terms offabrication, manufacturability and end-user performance characteristics.
Like surface relief structures, volume HOEs can be manufactured in amaster and replication schemes. These applications provide an importantavenue for diffractive optical element penetration into the consumer
electronics markets with high part volume and reliability requirements.
This is because, based on recent market research reports, combined·

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Conference 10335:
Digital Optical Technologies
revenues of up to $120B by 2020 have been forecast. The projected
revenue is divided into 70% for AR, 18% for VR, 5% for HUD. Volume HOEs
are particularly crucial for the AR and HUD segments where transparency
is necessary in terms of performance and cosmetic appearance.

Both have only two lenslets and use (for each eye) a 2” 16:9 display. Theirrespective eye pupil to display distance is only 30 mm and 36 mm (to becompared to 65-80 mm in most conventional headsets), while displaying
12 pixels/deg resolution of the VR and FOV = 94x75 degs.

Luminit is currently emplacing the manufacturing capacity to serve
this market, and this talk will discuss the capabilities and limitations of
this unique facility. Three-color, tunable, holographic grade lasers formastering and roll-to-roll replication will be emplaced, with throughput
and capacity to well-serve the AR, smart glass, and HUD markets.

Additionally, two other designs (whose prototypes are underconstruction) will be presented. One has with 4 light-folding lenslets fora 2” 1:1 display per eye which will show 13 pixels/deg and a round FOV =100 degs, similar or better than the main commercial VR headsets, butwhose eye pupil to display distance is only 26 mm. The other design,
which has been developed under the EU project LOMID, uses two 0.93”
microdisplays per eye, and has been designed to achieve 22 pixels/deg
with FOV =100x85 degs, targeting high end applications.

10335-16, Session 4

Advanced freeform optics enabling ultracompact VR headsets
Pablo Benítez, Juan C. Miñano, Limbak (Spain) and Univ.
Politécnica de Madrid (Spain); Pablo Zamora, Dejan
Grabovickic, Marina Buljan, Limbak (Spain); Milena I.
Nikolic, Univ. Politécnica de Madrid (Spain); Bharathwaj
A. Narasimhan, Jorge Gorospe, Jesus Lopez, Limbak(Spain); Eduardo Sanchez, Univ. Politécnica de Madrid(Spain)At present commercial VR headsets are rather bulky and heavy, which
may be not comfortable enough to use for long periods of time. The
main reason for their volume is the distance required between theirconventional lenses and the displays.
We present novel advanced optical designs with a dramatically smaller
display to eye distance, excellent image quality and a large field ofview (FOV). This enables headsets to be much more compact, typicallyoccupying about a fourth of the volume of a conventional headset withthe same FOV.
The design strategy of these optics is based on a multichannel approach,which reduces the distance from the eye to the display and the display
size itself. The optical system splits the incoming bundle of rays in
different sub-bundles that are optically processed (independently) andthen recombined in a single outgoing bundle. This is obtained by meansof dividing a conventional optical system into several lenslets, each oneof which handles one sub-bundle of rays (and its corresponding part of
the total field of view). Each one of the sub-bundles is emitted by certain
sector of the display, then goes through one of the lenslet in the optics,
and then redirected towards the user’s eye. The addition of all the ray
sub-bundles arriving to the eye composes the virtual image that the user
perceives, with a total field of view equal to the addition of all the partial
fields of view provided by each of the sub-bundle. Unlike conventional
microlens arrays, which are also multichannel devices, our designs use
freeform optical surfaces to produce excellent imaging equality in theentire field of view, even operating in oblique incidences. Additionally, wetake into account the eye rotations, we optimized for the sharpest imageof the VR pixels to be obtained when they are directly gazed (so the eye
images them on the fovea).
We present two families of compact solutions that use different type oflenslets:(1) Refractive designs, whose lenslets are composed typically of two
refractive surfaces each (i.e. rays undergo a total of two refractions while
travelling from the display to the eye)(2) Light-folding designs that use prism-type three-surface lenslets, inwhich rays undergo four successive deflections when travelling fromthe display to the eye: refraction, reflection, total internal reflection andrefraction.
For both families of designs, the number of lenslets is not fixed, so
different configurations may arise, adaptable for flat or curved displayswith different aspect ratios. In the refractive designs the distance between
the optics and the display decreases with the number of lenslets, allowing
for displaying a light-field when the lenslet becomes significantly small
than the eye pupil. On the other hand, the correlation between numberof lenslets and the optics to display distance is broken in light-folding
designs, since their geometry permits achieving a very short display toeye distance with even a very small number of lenslets.
We have built two complete headset prototypes using two different
compact optics: one refractive-type and the other light-folding type.

810335-17, Session 4

High collimated coherent illumination
for reconstruction of digitally calculated
holograms: design and experimental
realization
Alexander V. Morozov, German Dubinin, Sergey
Dubynin, Igor Yanusik, SAMSUNG R&D Institute Rus.
(Russian Federation); Sun Il Kim, Chil-Sung Choi, Hoon
Song, Hong-Seok Lee, Samsung Advanced Institute ofTechnology (Korea, Republic of); Andrey Putilin, P.N.
Lebedev Physical Institute (Russian Federation); Sergey
Kopenkin, Yuriy Borodin, Moscow State Technical Univ.
of RadioTechnics, Electronics and Automatics (RussianFederation)
Future commercialization of glasses-free holographic real 3D displays
requires not only appropriate image quality but also slim design ofbacklight unit and whole display device.
In this paper we report coherent backlight unit (C-BLU) for 3D
holographic display with thickness comparable to commerciallyavailable 2D displays (cell phones, tablets, laptops, etc.). C-BLU forms
uniform, high-collimated and effective illumination of Complex Spatial
Light Modulator, which consists from two parts for simultaneous andindependent amplitude and phase modulation of an input wave field.
Active optical element then is used to form viewing zones.
Designed C-BLU consists from two light sources and two concave lenses,
one of each per eye, light guide plate (LGP), collimating hologram forlight collimating and redirecting (H1), which is placed on the back surfaceof light guide plate, and outcoupling hologram (H2) for light redirectingout of light guide plate towards viewer, this hologram is placed on bottom
surface of light guide plate.
Optical channels operate independently from each other. Light emitted bycoherent light source is transformed to diverging beam by concave lensand incoupled into LGP through side surface. Beam propagates in LGP
without reflection straight to opposite side surface. There it illuminates
H1 and diffracts on it. Collimated first order of diffraction propagatesinside of LGP without reflection straight to the bottom surface. Therebeam illuminates H2 and diffracts on it. Depending on H2 design firstorder of diffraction can stay collimated or become convergent beam. It
goes normally from H2 and outcouples from LGP through top surface.
Outcoupled light is uniform and coherent. It illuminates holographic
display with plane or convergent wavefront depending on outcoupling
hologram design.
H1 and both designs of H2 are produced by analog method that allows
recording them with high uniformity and high efficiency. Holograms arereflective volume type and were recorded on Bayer photopolymer. Suchmaterial was chosen because of dry post-processing with UV light.
First was carried out design preliminary numerical simulation of C-BLU
volume holograms. Simulations of diffraction efficiency and range ofpossible working angles were based on Kogelnik coupled wave theory.
Then schemes for holograms recording were elaborated. Schemes
are based on intersecting beams technique. Main challenge of such
scheme, which is elimination of ghost light due to multiple Fresnel
reflections near hologram plate, was successfully completed by opticalelements arrangement. After that experiments on holograms recording

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Conference 10335:
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were conducted. Goal was to find such combination of exposure timeand incident power that provides maximal diffraction efficiency while
recording as low noise as possible.
In result of this project several fully functional prototypes were assembled
and measured. Experimental prototypes have following parameters:
illumination area up to 130x80 mm2 (diagonal size 5.5”); thicknessof C-BLU is 10 mm; illumination uniformity 90% (measured by VESA
standard v2.0); collimation angle for backlight unit with plane wavefront
output is ±0.038°; for backlighting unit with converging wavefront
viewing zones are formed at distance 600mm with stereoscopic baseis 62mm; angle of divergence between two optical channels is 6°. Main
results were obtained for monochromic C-BLU realization, yet multi-color
holograms were recorded too and stay under our continuous research.
Experimental results prove that described design of backlight unit isfeasible for real-time slim holographic display.

10335-19, Session 4

Optical architecture of HoloLens mixed
reality headset
Bernard C. Kress, William J. Cummings, Microsoft Corp.
(United States)
The ultimate wearable AR system would address all aspects of a truly
forgettable device, to be worn throughout the entire day, such asprescription glasses or a smart watch. Comfort is king: therefore, dramatic
reductions in size, weight and power requirements and at the sametime increase in field of view, angular resolution, and reduction of visual
induced nausea are all required. Among these challenging hardware
requirements, optics is a critical one.
The human visual system is complex and dynamic, and has specifics
and limitations which scale differently when the system is a near to eye
display rather than a standard projection display or screen display. In
order to avoid over-designing optics for next generation AR and VR
systems, it is crucial to consider carefully such specifics and limitationsin the optical design process itself, and adapt existing or novel display
technologies to create the experience and comfort needed for the user.
Human-centric optical design is therefore emerging as a key to address
such stringent requirements for the ultimate AR/VR experience.

10335-20, Session 5

Metasurface polarization optics: chiral
holograms and elliptical polarization
beam splitters (Invited Paper)
Federico Capasso, Jan Philipp Balthasar Mueller, RobertCharles Devlin, Noah A. Rubin, Benedict Groever,
Harvard School of Engineering and Applied Sciences(United States)
We present a method allowing for the imposition of two independent andarbitrary phase profiles on any pair of orthogonal states of polarization—
linear, circular, or elliptical—relying only on simple, linearly birefringent
wave plate elements arranged into metasurfaces. This stands in contrast
to previous designs which could only address orthogonal linear, and to alimited extent, circular polarizations. Using this approach, we demonstratechiral holograms characterized by fully independent far fields for eachcircular polarization and elliptical polarization beam splitters, both in thevisible. This approach significantly expands the scope of metasurface
polarization optics.

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10335-21, Session 5

Novel fabrication methods fornanophotonics
Stephan Kress, Harvard Univ. (United States)
Light rarely interacts. Fortunately, light-matter-interaction may be
increased when light is confined to sub-wavelength scales. However,a prerequisite to gain control over light at such small scales is thatfabrication technologies exist for sub-wavelength features with evenlower surface roughness. To meet such requirements, we developed
two novel fabrication technologies: The first is a molding-technique tostructure thin films with nanoscale features and Angstrom-roughness. The
second is an ultra-high-resolution printing-technique to place functional
nanomaterials with nanometer-precision and sub-wavelength resolution.
For the patterning of thin films, we employ a technique termed ‘templatestripping’. This technique enables the structuring of polycrystalline thinfilms that typically show large roughness when processed using standard
techniques (such as lithography and etching). In template-stripping, astructured silicon-wafer is used as an ultrasmooth template onto whicha thin film (such as a metal) is deposited and then peeled off using an
epoxy-backing-layer. This reveals a surface that inherits the ultra-smooth
and well-defined features of the silicon-wafer-template. Since the silicontemplate remains unharmed, reproducible fabrication of high-fidelity
nanostructures is possible.
Another challenge for nanophotonic devices is the precise placement offunctional nanomaterials (such as colloidal quantum dots) into welldefined locations. Typically, multiple solvent- and lithography-steps are
involved to place nanocrystals. In contrast, we achieve the placement of
nanocrystals in a single-step involving an on-demand printing technique.
In this process, atto-liter-sized ink droplets containing nanocrystals areejected from an electrified printing nozzle. As for a desktop printer, thisallows to build up arbitrary patterns of colloidal quantum dots. However,far beyond desktop printers this technique can produce feature sizes
below Der h100 nm. This exceeds the resolution of a desktop printer by
three orders of magnitude and is equivalent to more than 200,000 dotsper-inch.
In a demonstration of our newly-acquired capabilities, we develop
quantum-dot plasmonic waveguides, resonators and spasers to gain
control over light at scales smaller than the diffraction limit. Thesewaveguides and resonators constitute state-of-the-art plasmonic circuitrythat routes and stores light in the form of surface plasmon polaritons(SPPs). Further, we show that by exploiting quantum dots as a gain
medium plasmonic losses may be fully compensated. As a result of thisplasmonic gain and feedback (by a plasmonic cavity), we observe thestimulated emission of SPPs – also known as spasing – at low pumping
thresholds and under ambient conditions. In sum, our results confirm thepromise of template-stripping and electro-hydrodynamic printing for
creating nanoscale circuits for light. More importantly, the capability ofthese techniques to define nanoscale features over wafer-scales should
impact technologies in digital optics that rely on sub-wavelength features
patterned over large areas.

10335-22, Session 5

Digital metasurface for wavefront
modulation
Yan Zhang, Capital Normal Univ. (China)
Metasurface is a kind of matematerials with only two-dimensional
distribution. By carefully arranging the shape and size of eachsubwavelength antenna, the amplitude, phase, and polarization ofreemitted light from the antenna can be artificially control. Eight antennas
with same amplitude modulation and different phase modulation are
selected to construct different devices. The phase modulations are
selected as in the range of 0 to 2π with a step of π/4. Several devices,such as lens, holograms, pure phase elements, are designed, fabricated,and characterized in the terahertz range. Experiment results demonstrate
the validity of this new approach. The insert loss can be reduced to 20%
with two layer metasurface devices.

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10335-23, Session 5

Global optimization of complex opticalstructures using Baysian optimization
based on Gaussian processes
Philipp-Immanuel Schneider, JCMwave GmbH
(Germany); Xavier Garcia Santiago, JCMwave GmbH
(Germany) and Karlsruher Institut für Technologie(Germany); Carsten Rockstuhl, Karlsruher Institut fürTechnologie (Germany); Sven Burger, JCMwave GmbH
(Germany) and Zuse Institute Berlin (ZIB) (Germany)
Advanced devices in micro- and nano-optics and -photonics include
structures on micron or nanometer scales.
Most of their relevant optical properties can be projected by solving thetime-harmonic, macroscopic Maxwell’s equations rigorously, i.e. without
simplifying the geometrical, material and source models.
We discuss how to approach challenging design tasks in this field withfinite element methods (FEM).
The general framework of FEM allows to employ adaptive, errorcontrolled numerical resolution and accurate geometry modelling forarbitrary shapes [1].
We also briefly report on application of these methods to recent
simulation and optimization tasks ranging from industrial applications(optical metrology, microcavity design, photovoltaics [2,3,4]) to academic
research (plasmonics, chiral metamaterials [5,6,7]).
[1] S. Burger, et al., Proc. SPIE 9424, 94240Z (2015).
[2] V. Soltwisch, et al., Phys. Rev. B 94, 035419 (2016).
[3] K. Jaeger, et al., Opt. Express 24, A569 (2016).
[4] M. Gschrey, et al., Nat. Commun. 6, 7662 (2015).
[5] P. Gutsche, et al., Photonics 3, 60 (2016).
[6] K. M. McPeak, et al., Adv. Mater. 27, 6244 (2015).
[7] J. Kaschke, et al., Opt. Express 22, 19936 (2014).

10335-78, Session 5

Slot silicon-gallium nitride waveguidein MMI structures based 1x8 wavelength
demultiplexer
Bar Baruch Ben Zaken, Tal Zanzury, Dror Malka, Holon
Institute of Technology (Israel)
A slot-waveguide is a structure that allows light to be propagated inside anarrow region (nanometer-scale) of low index material that is surroundedby two layers with high index material and also leads to a strong light
confinement. The fabrication of 1x4 intensity splitter based on MMI in
Silicon (Si)-Galliun Nitride (GaN) slot waveguide structures has been
demonstrated [1].
Multimode interference (MMI) demultiplexer devices based on slot
waveguide structures have been demonstrated the ability to separate twochannels (spacing of 250nm) [2] and four channels (spacing of 50nm)[3].
Choosing a slot material with lower-index value lead to a stronger
confinement inside the slot region. However, an MMI demultiplexer
component with closer spacing between ports is very sensitive to thevariation of the optical signals in the C-band (1530-1565nm) ,which
can influence on the MMI coupler size and the performance. In orderto overcome this problem, we choose GaN as the slot material. GaN
has a low-index value compered to Si material and is also high-index
value compared to alumina or silica. Thus, the MMI demultiplexer
component based Si-GaN slot waveguide is not very sensitive to thevariation of the effective refractive index that lead, the ability to separate
closer wavelengths in the C-band inside the MMI coupler with good
performances.
In this paper, we demonstrate a 1x8 wavelength MMI demultiplexer in slot
Si-GaN waveguide structure that divides 8-ports in the C-band range

10

with a spacing of 5nm between two ports. The operating wavelengths
are: 1530nm (port 2), 1535nm (port 8), 1540nm (port 4), 1545nm (port 6),1550nm (port 1), 1555nm (port 7), 1560nm (port 3) and 1565nm (port 5).
The device is based on 14 S-band, 7 units of 1x2 MMI couplers and 1 input
taper. Numerical optimizations were carried out on the slot-waveguidestructurer and the MMI coupler size in order to obtain a strong power
confinements inside the slot region and to find the optimal values of the
MMI coupler size.
Fig. 1 shows that the proposed device has low crosstalk ((-19.97)-(-13.77)dB) with a bandwidth range of 1.8-3.6nm. Therefore, this device can beused in optical networking systems that work on DWDM technology.
References[1] Malka, D.; Danan,Y.; Ramon, Y.; Zalevsky, Z. A Photonic 1 ? 4 Power
Splitter Based on Multimode Interference in Silicon–Gallium-Nitride Slot
Waveguide. Structures Materials. 2016, 9, 516.
[2] J. Itatani, Xiao, J.; Liu, X.; Sun, X. Design of an ultracompact MMI
wavelength demultiplexer in slot waveguide structures. Optics Express.
2007, 15, 8300-8308.
[3] Malka, D.; Sintov, Y.; Zalevsky, Z. Design of a 1 ? 4 silicon-alumina
wavelength demultiplexer based on multimode interference in slot
waveguide structures. Journal of Optics. 2015, 17, 1-9.

10335-24, Session 6

Short-wavelength infrared high resistive
photoconductor based on Chalcogenide
glasses for OASLM applications
Asi Solodar, Matvey Kalbanov, Ibrahim Abdulhalim, BenGurion Univ. of the Negev (Israel)In this work we have investigated highly resistive photoconductive
samples based on Lead (II) sulfide (PbS) and GePbS as an active
photosensitive layer for the SWIR spectrum range, obtained by thermal
vacuum evaporation. As highly resistive layer we used chalcogenide
As2S3 layer. In addition for OASLM applications the As2S3 layer can beutilized as a liquid crystal alignment layer instead of polymer spin coating
method.

10335-25, Session 6

Self-refraction in HMDs throughadjustable focus lenses (Invited Paper)
Rob Stevens, Adlens, Ltd. (United Kingdom)
No Abstract Available

10335-26, Session 6

A robust liquid crystal device withadjustable deflection and diffraction for
multiple applications
Neal Weinstock, Soliddd Corp. (United States)
Based on the invention of Dr. Richard A. Muller, professor of physics at
the University of California, Berkeley, the author’s company proceeded tobuild a number of LC cells according to the initial design. The first design
aimed at increasing pixel density equal to the inverse of the fill factor of a
specific OLED display. The OLED display featured a fill factor of 25% andwas run at a frame rate of 240Hz. The LC device featured a prism arraywith periodicity of 100 microns and height of 17 microns, which structure
was chosen to minimize diffraction and moire from interaction with theunderlying display. Light was deflected, as planned, in a sweep thatwas controllable by voltage ranging from 1V to 4V, by up to 2 degrees.
The above prism array was bonded to one side of a single cell structure
prepared with ITO coating, synchronized to the underlying display via thevertical sync signal. The desired four-times multiplied pixel density was

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Conference 10335:
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achieved with a constant deflection sweep of about 1 degree.
The system proved capable of highly accurate deflection at rates up to
1kHz and as low as 1Hz, with voltage which we found could be optimized
to about 100 millivolts. At extremely low frequency, the deflection of lightis easily apparent through the naked eye, and the device could be seen todisplace any underlying image to either left or right. Very high light andcolor transmissivity were exhibited, and were clearly suitable for criticaluse in displays and other optical applications.
The experiment proved the system capable of deflecting light to muchwider angles with the use of more acute prisms, thus removing the limit
to pixel density increase imposed by the fill factor of the underlying
display. When using a more complex wiring pattern to apply different
voltage to different areas of the LC cell, the system also proved to beeasily controllable for different degrees of deflection in different regions.
This would allow for the relatively simple application of correcting for
improper pixel alignment in the underlying display, or for inaccurate
manufacturing or assembly of the prism array located within the LC cell.
Our success in these adaptations led to development of two additional
adaptations of the same core technology. We have designed a cell thatincorporates a Fresnel prism array, with voltage activated in concentric
circles that are aligned with the Fresnel pattern. The goal of this system
is to create a lens for vision adjustment in the range of four positive
diopters. We expect to report on this ongoing development by the time
we deliver the paper.
Finally, our experiments in limiting diffraction potentially caused by
the system (which would be objectionable in our first application ofincreasing pixel density) have allowed us to understand how to adjust theamplitude and the frequency of the prism array. The potential, therefore,
for a multiplier effect in the frequency of a diffraction grating, as well as achanged pattern, clearly exists. We expect to report on developments inthis field by the time that we deliver the paper.

10335-27, Session 6

A high-resolution optical rangefinderusing tunable focus optics and spatial
photonic signal processing
Tariq Shamim Khwaja, Mohsin Ali Mazhar, Haris Khan
Niazi, Syed Azer Reza, Lahore Univ. of Management
Sciences (Pakistan)In this paper, we present the design of a proposed optical rangefinder
to determine the distance of a semi-reflective target from the sensor
module. The sensor module deploys a simple Tunable Focus Lens
(TFL), a Laser Source (LS) with a Gaussian Beam profile and a digital
beam profiler/imager to achieve its desired operation. We show that,
owing to the nature of existing measurement methodologies, previous
attempts to use a simple TFL in prior art to estimate target distancemostly deliver “one-shot” distance measurement estimates instead ofobtaining and using a larger dataset which can significantly reduce
the effect of some largely incorrect individual data points on the final
distance estimate. Using a measurement dataset and calculating averages
also helps smooth out measurement errors in individual data points
through effectively low-pass filtering unexpectedly odd measurement
offsets in individual data points. In this paper, we show that a simple
setup deploying an LS, a TFL and a beam profiler or imager is capable ofdelivering an entire measurement dataset thus effectively mitigating theeffects on measurement accuracy which are associated with “one-shot”
measurement techniques. The technique we propose allows a Gaussian
Beam from an LS to pass through the TFL. Tuning the focal length of
the TFL results in altering the spot size of the beam at the beam imager
plane. Recording these different spot radii at the plane of the beamprofiler for each unique setting of the TFL provides us with a means to
use this measurement dataset to obtain a significantly improved estimateof the target distance as opposed to relying on a single measurement. We
show that an iterative least-squares curve-fit on the recorded data allows
us to estimate distances of remote objects very precisely. We also showthat using some basic ray-optics-based approximations, we also obtain an
initial seed value for distance estimate and subsequently use this value toobtain a more precise estimate through an iterative residual reduction in
the least-squares sense. In our experiments, we use a MEMS-based Digital
Micro-mirror Device (DMD) as a beam imager/profiler as it delivers an

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accurate estimate of a Gaussian Beam profile. The proposed method, its
working and the distance estimation methodology are discussed in detail.
For a proof-of-concept, we back our claims with detailed experimental
results showing a less than 3% measurement error for different target
distances by using a reflective plane mirror as a target. We also
demonstrate multiple orders of magnitude improvement in measurement
accuracy when compared to existing techniques which deploy TFLs fortarget ranging applications.

10335-28, Session 6

Arbitrary shaping of ultrafast Bessel
beams with a phase-only spatial light
modulator
Ismail Ouadghiri Idrissi, FEMTO-ST (France); Remo Giust,
Luc Froehly, FEMTO-ST (France); Maxime Jacquot, Luca
Fufaro, FEMTO-ST (France); John M. Dudley, François
Courvoisier, FEMTO-ST (France)
A Bessel beam is a diffraction-resistant beam. It is defined as asuperposition of an infinite number of plane waves propagating at thesame angle with respect to the optical axis. Its transverse spatial profile
is featured by a hot central core with a width potentially below the
wavelength surrounded by several peripheral rings with lower intensities.
This diffraction-free nature and conical structure allow for propagation
invariant regimes, even for high power lasers, which is very advantageous
in many applications such as material processing and laser ablation. Dueto the spatial limitation of experimentally generated Bessel beams, theiron-axis intensity varies significantly along propagation.
In this context, arbitrary manipulation of their longitudinal propagationis necessary to control the peak intensity of the central core. We
specifically aim to generate Bessel beams with flat-top and linear ramp
on-axis intensity shapes. Theoretically, longitudinal beam shaping canbe performed from Fourier space. This consists in the computation of
the angular spectrum using a one-dimensional Fourier transform of thedesired complex axial envelop. Since these two profiles involve abrupt
intensity growth, they cannot be realized physically since this requires
infinite spatial frequencies. We analytically express this limitation interms of a convolution of the desired longitudinal intensity profile witha sinc-shaped function. We then show how to resolve this issue usingsmooth intensity profiles. In practice, arbitrary manipulation of the axial
propagation of Bessel beams requires the modulation of both the spatial
amplitude and phase of an incoming beam. In previous works, this has
solely been performed using an iterative technique to encode the desired
beam’s spatial spectrum on a phase only spatial light modulator (SLM).
Although this method allows for precise generation of target beam
shapes, it yields a very low energy conversion (about 1.5 %), which makes
it unsuitable for the application of Bessel beams in micro-nano machining.
In our work, we use a non-iterative technique to exactly encode theoptical field in a single SLM, from direct space, thus preserving highenergy throughput. This technique is based on the modulation of thephase wrapping of a computer generated hologram, which allows tocontrol the diffraction efficiency at each point of the phase mask. Our
experimental setup is based on a 4f system and the desired opticalfield is retrieved at the first diffraction order. In contrast with previous
works, our technique is generalized for arbitrary shapes of the incident
laser beam on the SLM. This enables the conservation of a high-energy
throughput by maintaining finite-size input illumination profiles of theSLM. In our experiments, we use a femtosecond laser source whosetransverse spatial profile is in the form of imperfect Gaussian. We
experimentally measure the intensity distributions along propagationof Bessel beams with different intensity profiles: a flat-top profile withparabolic leading and trailing edges; and linear ramp with a parabolic
trailing edge. Our experimental results are in excellent agreement withnumerical simulations. The measured energy conversion is typically ~10%, which is one order of magnitude higher than the one obtained using
Fourier-space beam shaping techniques. We anticipate this will open very
novel perspectives for nonlinear optics and laser material processing. We
acknowledge funding from the European Research Council (ERC) under
Horizon 2020 program (GA N° 682032-PULSAR) in cooperation with
Labex ACTION program, contract ANR-11-LABX-0001-01.

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10335-29, Session 6

Calibration and digital correction ofaberrations in combined optical systems
with interchangeable parts
Thomas Milde, Carl Zeiss AG (Germany)
For many optical systems, mainly in photography, the correction of
distortion and lateral colour aberration is a common step in the image
processing pipeline. It is based on images of calibration targets and thedetermination of coefficients for a correction model. These coefficientsare specific for the optical system which forms the aerial image for thesensor. If an exchange of the optical system is necessary, e.g. for offering
optics for several applications like macro mode, wide-angle or tele-photo,
the entire optical system is typically exchanged and not only parts of it.
Using an technique for digital identification of the optical system, e.g. via
an electronic interface, the corresponding correction coefficients can beobtained and applied. If the optical system to be exchanged is only a partof the entire optical system, the situation is more difficult. As an example,
this is the case in the field of digital microscopy, where the objective lenshas to be exchanged in order to offer a larger range of magnifications andresolutions. This objective lens is not an image forming optical system
and needs at least a tube lens to produce an image for sampling witha sensor. Both optical systems produce contributions to the resulting
overall aberrations, namely distortion and lateral colour aberration. For
a particular pairing, coefficients for a correction model can be calibrated
and applied. But in the case of an exchange of the objective, only a partof the optical system changes and a new calibration is needed. We willshow how this problem can be solved using a mathematical operationand individual calibration of the distinct parts of the optical system.
The advantage is, that the parts of the optical system can be arbitrarily
combined and the correction-model coefficients of the combination
can be computed from the corresponding coefficients of the individual
parts. Hence, there’s no need to calibrate every possible combinationor to manage a calibration process at the customer’s place. In addition,
the manufacturing and calibration of objectives and tube lenses may
take place at different locations. In addition, the optical design canbenefit from the digital aberration correction although it is made up ofinterchangeable components.

10335-51, Session 6

Adaptive digital stereo microscope
to support 3D vision: optomechanicaldesign and experimental validation
Carsten C. Reichert, Daniel Claus, Alois M. Herkommer,
Institut für Technische Optik (Germany)In this talk we present the opto-mechanical design and experimental
results of an adaptive imaging system to simulate the human eye ina digital stereo microscope. The system allows for digital recording
including the effects of accommodation and pupil shift, while offering atemporal resolution of better than 50ms (20Hz). Furthermore, a spatial
resolution under 50 microns and a field of view of 30x30 mm is realized,
which are common surgical microscope specifications. Special attention
was given to the optical design of the recording system to match theimaging parameters and quality of a conventional stereo microscope.
Important parameters, like NA, the position and size of the entrance
pupil and the field of view match a conventional stereo microscope. The
imaging performance of the recording system is good enough for during
a surgery. The MTF and Seidel aberration coefficients demonstrate a good
imaging performance of the adaptive digital stereo microscope.
In the digital stereo microscope accommodation is implemented via theaddition of two tunable lenses from the company Optotune AG, one
for each arm of the stereoscopic system. The optotune lens enables theapplication of a variable focal length of 80 mm to 200 mm. With this
optotune lens in place the refocusing range of our system is 55 mm.
Based on the latency of the human eyes with regards to changing pupil
position, the temporal requirement imposed is 50 ms (20 Hz). Therefore,
a conventional manual x-y stages were modified by the attachmentof two linear actuators from the company Nanotec Electronic GmbH12

& Co. KG, which enable a maximum speed of 140 mm / s. To cover thesame amount of shift at the entrance pupil in our adaptive digital stereo
microscope in comparison to the conventional system, the diaphragmmust be displaced by ±0.6 mm. However, the total amount of shift thatcan be applied without significant loss caused by vignetting is ± 7mm.
The camera employed (XIMEA MQ013MG-E2) has a pixel pitch of 5.3 µm.
To ensure sufficient sampling of the high-resolution elements the pixel
pitch was multiplied by factor of 2.5. The magnification of the system is0.25. Hence our system can deliver a maximum lateral resolution of 53µm.
To confirm this theoretically calculated resolution a USAF test target has
been employed. The resolution has been determined in accordance to thecontrast threshold defined by Rayleigh’s criterion applied to the averaged
cross section plot of the respective test target element. A maximum
spatial frequency of 17,96 line pairs / mm (Group 4, Element 2) could
be achieved, which corresponds to a lateral resolution of 55,68 µm. The
recovery of depth information as accomplished by the eye in the processof accommodation could be demonstrated using a cuboid. Applying
different voltage settings to the optotune lens enables the recovery
of different axial planes for the digital stereo microscope. Different
perspective images are obtained by means of moving the diaphragm. A
three-dimensional device has been printed. This device consists of twobars located at a distance of 70 mm to the in-focus object plane, which
project a shadow on the in-focus object plane. Changing the locationof the aperture in the intermediate pupil plane enables the recovery ofobject details which have previously been hidden by the shadow.

10335-30, Session 7

Large holographic 3D display for realtime computer-generated holography(Invited Paper)
Ralf Häussler, Norbert Leister, Hagen Stolle, SeeReal
Technologies GmbH (Germany)
SeeReal’s proprietary concept of real-time holography is based on SubHologram (SH) encoding and tracked Viewing Windows (VWs). A small
VW is located at the eye pupil and contains the holographic informationthat is required to see a 3D scene. A SH can be considered as a small
encoded lens function that reconstructs an object point in the 3D scene.
The SH is only as large as is required to illuminate a VW. The small VWsize and SH encoding, combined with other proprietary optimizationsof SeeReal, lead to significant reduction of pixel count and computation
effort compared to conventional holography concepts, thus making large
real-time holographic displays feasible.
SeeReal presented its patented concept and holographic displays alreadyseveral years ago. These displays used mainly off-the-shelve components.
Meanwhile, improved full-color holographic displays were built withdedicated components. The most recent display has 300 mm x 200 mm
active area.
Progress has been made on several components:
1) Lasers are used as light sources. They are more energy efficient, well
suited for diffractive elements in the display sandwich and provide larger
color gamut than the previously used LEDs.
2) A holographic display requires large-area collimated light. Parabolic
mirrors or large lenses are not an option for a commercial display.
Therefore, a flat backlight unit (BLU) was built that uses volume gratings(VG) to expand the light in compact size. The VGs are exposed in thinphotopolymer films.
3) The hologram is encoded on a spatial light modulator (SLM). The SLM
comprises a phase-modulating and an amplitude-modulating liquidcrystal display. The two displays were aligned pixel-to-pixel and laminatedas a sandwich. Thus, the SLM modulates amplitude and phase of light.
4) A field lens made up of two VGs focuses the light into the VW. Thislens replaces a bulky glass lens.
5) The holograms are calculated in real time on a computer graphics card
or FPGA system.
A camera was placed at the VW and photographs of holographic
reconstructed full-color 3D scenes were taken. Only the depth region
on which the focus of the camera lens is set is in focus while the otherdepth regions are out of focus. Selective focus is possible while the same

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Conference 10335:
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hologram is displayed. These photographs demonstrate that the 3D scene
is reconstructed in depth and that SeeReal’s holographic display supports
accommodation of the eye lenses. Hence, the display is a solution to
overcome the accommodation-convergence conflict that is inherent
for stereoscopic 3D displays. Other depth cues are also supported andcontribute to natural depth perception.
The main components, the progress and results of the holographic display
with 300 mm x 200 mm active area will be described in the presentation.
Furthermore, photographs of holographic reconstructed 3D scenes will beshown.

10335-31, Session 7

3D color reconstructions in single DMD
holographic display with LED source andcomplex coding scheme
Maksymilian Chlipala, Tomasz Kozacki, Warsaw Univ. ofTechnology (Poland)
Nowadays there is high demand on displays, which allows 3D imaging.
Several systems were proposed but most of them gives only theimpression of three-dimensionality by use of stereoscopy, polarization
effects, volumetric imaging and others. Among them only holographic
displays enable to obtain 3D object reconstruction with full perspective
and parallax. With recent and further improvement of display technology(smaller pixel size and higher frequencies of work) building color
holographic display is becoming more realistic.
Highest resolution of reconstructed holograms is achieved formonochromatic point source and it drops down when the source of
decreased coherence is used. Incoherent LED source limits the depth offocus and resolution of holographic display. However, such a source isinteresting one because it enables reconstruction of holograms with nospeckle noise, cause no eye hazard, has small size and is already widely
available in displays.
In the literature there are several color holographic displays based on SLM(Spatial Light Modulators) and LED sources[1-4]. In our previous work
we presented single SLM holographic display with white light LED, whichallows to reconstruct high quality 3D objects[5]. The phase-only SLM has
improved quality of reconstructed holograms. However its disadvantage
is long response time. Thus it has limited possibility of implementing time
multiplexing. For that reason many researchers decide to utilize DMD
modulators [6,7] in holographic displays and investigate possibilities ofcolor reconstruction [8] as well as using incoherent LED source [9].
In this work we decided to use our experience with holographic display
and incoherent sources. We propose holographic display setup with
DMD and LED source. We choose DMD since it has high speed response,
which allows to increase the resolution and obtain color reconstruction of
3D objects with time multiplexing. Additionally, illuminated with correct
angle DMD can work as blaze grating, which increase efficiency andallows to obtain large separation between diffraction orders.
In experimental part of this work we investigate the possibility of color
reconstructions of holograms with single DMD and incoherent LED
illumination. Our holographic display design employs complex coding
scheme achieved with frequency filtering in Fourier plane of 4F imaging
system, which allows to center reconstruction volume around display
surface. To reduce noise and improve the resolution of reconstructed
3D objects we utilize time multiplexing method. Since DMD is binary
modulator it is important to ensure correct binarization for RGB channels
in order to obtain proper color mixing. This work is accompanied withcomputer simulations where we investigate quality of reconstructed
holograms obtained for coherent and incoherent source as a function ofreconstruction distance. We analyze influence of temporal and spatial
coherence of source. During optical reconstructions we analyze qualityof reconstructed holograms for several distances from DMD plane andcompare display efficiency for each RGB color component. We show thatin presented holographic display it is possible to obtain color holographic
reconstructions of different content: 2D and 3D computer generated
hologram.

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10335-33, Session 7

Autonomous generation of extended
images of dynamic phase objects in a
depth volume sample using a simple
focusing criterion and K-means clustering
María-Luisa Cruz-López, Univ. Panamericana (Mexico);
Miguel Alcaraz-Rivera, Univ. Panamericana (Mexico);
Pinhas Girshovitz, Natan T. Shaked, Tel Aviv University(Israel); Bahram Javidi, University of Connecticut (UnitedStates)
The study of the movements of microscopic phase objects, like biologicalcells, is of high interest in the scientific community. In microbiology,
environment pollution and medicine it is important to analyze themovement pattern of cell or microparticles in real time with a noninvasive technique. Digital Holographic Microscopy (DHM) is a goodcandidate for this proposal. In the last years, it had been wide used foranalysis of phase objects with different interferometric setups. DHM
can record, in one shot, the whole sample complex field: amplitude andphase. Then the complex field is refocused in several planes for the 3D
sample reconstruction. The focus depth of the hologram is limited by
the focus depth of the system used in the recording process. In a thicksample, this condition arouses than only some of the retrieved object
are in focus. The entire sample is recovered propagating the field toeach object distance location or focus distance. When in the view field
there are several cells at different distances from the hologram plane,
the correct location of each cell is critical for the analysis of the sample.
There are diverse approaches for finding the optimal focusing distanceof a phase object. One of the most used is the criterion of look for a
maximum in the integrate intensity of the propagated wave for phaseobject and a minimum for the amplitude object. This method requires
the location in the view field and the definition of the analysis area foreach object. Some proposals had incorporated the use of complementary
segmentation methods to set these parameters automatically. However,the segmentation process is strongly linked to the object shape. In thecase of a biological sample, some cells change its shape as they swim
in the sample. We present the analysis of moving phase objects, using
an alternative focusing criterion that introduces the use different sized
windows it the analysis of the integrated intensity. The use of the various
sized windows allows detecting the object focus distance without todefine a specify analysis area for each object. The view field is divided
into a grid of sampling points, and the method is applied in each pointof the grid. With this criterion, we create a depth map with the focus
distance calculated for each point. The method measures the variationof the integrated intensity not only in the longitudinal direction but also
in the transversal direction. See Fig. 1, where a graph of the integrated
intensity of one point inside of a cell is analyzed with the different sized
windows for all the propagation distances. We set a threshold in thevariation of the integrated intensity as a criterion for the discrimination of
the phase objects from the background area in the depth map, see Fig. 2.
The depth map is segmented with the clustering K-means method, andeach cluster is analyzed to determine the optimal focusing distance foreach object. The method is implemented in the C++ language, and the
OpenCV libraries are used in the clustering analysis. For each cluster, weselect a focus distance. We propose two criterions to choose the focus
distance of each cluster. One is the median, and the other is the meanof the detected focus plane in the depth map. We present the results ofboth criteria in the selection of the cluster focus distance. The recovered
complex field is propagated to the focus distances detected, and using
the cluster zones as a reference, we segmented the complex field andcomposed an extended focus image of the sample in amplitude andphase. See Fig. 3. The phase is unwrapped before the segmentation. The
process is optimized with a multithreading routine in the focus detection
process and the composition of the extended image. The integrated
intensity analysis of each propagated plane is processed in a different
thread, and the results are recorded in one matrix. The reconstructionof each object is also assigned to different threads. These operations
reduce the processing time for the extended focus image generation. The
method can detect autonomously when a new cell enters the view fieldand calculate its focusing distance. The resulting images present all thecells in the sample well focused, and can be used for counting or tracking
purposes. We present simulated and experimental results.

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10335-34, Session 710335-36, Session 8

An optical method for compensatingphase discontinuity in a 360-degree
viewable tabletop digital holographic
display system

The promises and pitfalls of real-time
holographic display (Invited Paper)

Yongjun Lim, Keehoon Hong, Hayan Kim, Hyon-Gon
Choo, Minsik Park, Jin-Woong Kim, Electronics andTelecommunications Research Institute (Korea, Republicof)Recently, various methods for implementing 360-degree viewable
tabletop systems have been reported, and our proposed system
implementing the 360-degree viewable holograms was published in Optic
Express titled “360-degree tabletop electronic holographic display” in
October in 2016 [1]. Generally, many researchers interested in holographic
display systems have proposed or focused on methods for overcoming
low space bandwidth product of currently-available (or commerciallyavailable) spatial light modulators (SLMs). Representative techniques toovercome low space bandwidth product of SLMs are spatial multiplexing,
time-division (temporal) multiplexing and combination of those twotechniques. In our recently-published work, spatially-tiled digital micromirror devices (DMDs) are used to generate holograms to provide anincreased-size hologram.
In addition, lots of applications based on quantitative phase imaging
methods such as digital holography (DH) and transport of intensity
equation (TIE) have shown unprecedented ways to perform phaseimaging that can provide three dimensional images and views [2].
However, they are usually used to detect wavefront of optical waves
coming out of micron-sized or submicron-sized objects. In our proposed
work, we are going to present the feasibility of transport of intensity
equation technique to estimate holograms generated by a holographic
display system based on spatially-tiled digital micro-mirror devices(DMDs) which are used as spatial light modulators.
Specifically, in our 360-degree table-top electronic holographic display
system, to extend the size of the generated hologram, more than two
DMDs are used. To stitch those DMDs seamlessly in a resultant hologram
plane, it is necessary to establish well-aligned optical systems. However,
the imperfection in optical alignment causes the discontinuity in theboundary between two adjacent DMDs in an optically-tiled hologram
plane. Consequently, it is necessary to adopt an appropriate technique toestimate reconstructed holograms in using multiple numbers of DMDs,
and we are going to extract the phase profile of the generated hologramsby the use of the TIE method proposed by M. R. Teague [3]. Moreover,by comparing the extracted phase profile given by the TIE methodwith the conventional interferometric results based on a phase-shifting
DH technique, we are going to guarantee the accuracy of the phase
information obtained by the TIE technique. And then, after identifying
the phase discontinuity between two DMDs, we are going to suggest an
optical method to compensate for the phase discontinuity between them.
In our 360 degree table-top electronic holographic display system, thelaser with the wavelength of 532 nm is used as a light source, and the
DMD which has 1024 (horizontal) ? 768 (vertical) pixels is used as a spatial
light modulator to display binary patterns of the computer generated
holograms (CGHs). To remove unwanted signals in reconstructing
holograms, where the DMD is used as an SLM, 4-f optics configuration
composed of two lenses with the focal length of 180 mm and a spatial
filter is implemented. By optically aligning multiple numbers of the DMD
based on the 4-f configuration, it is possible to form a reimaged DMD
plane composed of more than two DMDs. The reconstructed holograms
are captured by a charge coupled device (CCD), and the position of the
CCD is adjusted to adopt the TIE method. After extracting phase profileof the reconstructed holograms, the phase discontinuity between two
adjacent DMDs are numerically estimated.

Joel S. Kollin, Microsoft Corp. (United States)
No Abstract Available

10335-37, Session 8

VR versus LF: towards the limitation-free3DTibor Balogh, Holografika Kft. (Hungary); Peter A. Kara,WMN Research Group, Kingston University (United
Kingdom)
The evolution of 3D technologies shows cyclical learning curve with seriesof hypes and dead-ends, with mistakes and consequences. 3D images
contain significantly more information than corresponding 2D. 3D display
systems should be built on more pixels, or higher speed components1. Fortrue 3D this factor is in the order of 100x, a real technology challenge. If
not fulfilled, 3D systems’ capabilities will be compromised: headgears will
be needed, or viewers should be positioned / tracked, single user devices,lack of parallax, missing cues, etc.
The temptation is always there: why to provide all the information,
just what the person absorbs that moment (subjective or objective
visualization). This leaded to the short-cut to 3D: 2x stereo, the 3DTV
hype (rather 2 x ?). The 3D the industry promised and what people
expected was not what they got. Was it a mistake? Yes, since 3DTV failed,
but we learnt a lot about the artifacts, camera rigs, view synthesis (depth/
disparity, inter /extrapolation), stereo content editing, audience reactions,etc.
VR glasses were around for more than two decades. With the latest
technical improvements and the market start signal by the 2B$
acquisition of Oculus, VR became the next hype. 3D immersion wasadded, as a new phenomenon, however VR represents an isolated
experience, requires headgears and a controlled environment (AR in thissense if different). Will VR/AR hype with the headgears be a mistake?
Might be. On the other hand it will be B$ business and we will learn that
3D requires more information (and more than 2 cameras). Although thegeometry of next-generation 3D systems may be different, as shown in
Figure 1., we will learn a lot about camera arrays, high-performance 3Dcomputation, immersive 3D content, complementing technologies, like 3D
tracking, motion platforms, haptic feedback, etc., and range of novel VR/
AR applications, areas, professions will be born.
“While VR headsets may sell better than smart glasses or 3D TV glasses,
also consider that using the technology may require a set of behavioral
changes that the majority of people do not want to make”2. Displays andtechnologies that restrict viewers, or cause any discomfort will not be
accepted on the long term.
The newer wave of 3D is forecasted to 2018-2020, answering the needfor unaided limitation-free 3D experience. Light Field (LF) systems
represent the next-generation in 3D. The HoloVizio3,4 system, having~100x capacity, offers natural, restrictions-free 3D on a full FOV, enabling
collaborative use for unlimited number of viewers even in a wider
immersive space. As a scalable technology, the display range goes frommonitor style units, through automotive 3D HUDs, screen-less solutions,
up to cinema systems and Holografika is working on interactive largescale immersive systems and glasses-free 3D LED walls.
Acknowledgment
This research is partly supported by the Optintegral project, funded under
the EU H2020 Programme, grant agreement# 643956
1. T. Balogh, The HoloVizio System, Stereoscopic Displays and Virtual
Reality Systems XIII, EI Proceedings, SPIE Vol. 6055, p. 60550U-1 60550U-12, (2006).
2. Deloitte: Virtual reality (VR): a billion dollar niche, Technology,
Media&Telecommunication Predictions 2016

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10335-38, Session 8

Volumetric graphics in liquid using
holographic femtosecond laser pulse
excitations
Kota Kumagai, Utsunomiya Univ. (Japan); Yoshio
Hayasaki, Utsunomiya Univ (Japan)
Volumetric display has paid much attention for three-dimensional (3D)
display in fields of optics and computer graphics. This display can renderthe 3D graphics that is observed from any surrounding viewpoints
without to wear any special devices and physiologic discomfort for
displaying visual information having binocular parallax. Volumetricdisplays are classified into two types, depending on the characteristics ofthe voxels: the light-reflecting type and the light-emitting type. Reflecting
types using projection rotating screen, water drops, and floating small
particles have been constructed. Light-emitting types using optical fibers,
3D cubic array of light-emitting diodes (LEDs), and laser irradiation havebeen demonstrated. The laser irradiation type has a wide viewing angle
and does not require any physical connection between the light source
and the display volume. Laser-irradiation-based volumetric displays havebeen demonstrated by using various media, such as air, liquids, and solids.
With these previous approaches, however, the number of voxels in thevolumetric display is not high enough for rendering practical volumetricimages because they are limited by the repetition frequency of the laser
and the speed of the 3D scanning system.
In our previous work, we demonstrated the volumetric display system
based on holographic parallel optical access and two-photon excitation
using a computer-generated hologram displayed on a liquid crystal
spatial light modulator, and the multilayer fluorescence screen. The
holographic method has not only increased the maximum number ofvoxels that can be rendered but also enabled the formation of brightervolumetric images. In addition, two-color display composed of red voxels
and blue-green voxels has been achieved using a fluorescence place
containing different fluorescence moolecules.
In this presentation, we demonstrated a volumetric display based onholographic femtosecond-laser induced micro bubbles. The volumetricdisplay system is generally composed of a light source, a modulatorof light, and a screen. In our system, the light source is an amplified
femtosecond pulse laser in order to excite a liquid screen via multi-photon
absorption. The modulators perform three-dimensional beam scanningof the focal points for a laser drawing of voxels. The screen is a liquidwith high-viscosity. The holographic parallel access technique based on
a computer-generated hologram displayed on a liquid crystal on silicone
spatial light modulator. First, the holographic technique is an effective
way to increase the number of voxels of the volumetric graphics per unit
time. Second, it controls the size and shape of voxels. Various shapesof beam like a line-focused beam and a focal point corrected sphericalaberration can be achieved. Third, it synthesizes different patterns in asingle beam. When a femtosecond laser is focused inside a liquid, bubbles
are formed via through nonlinear processes called breakdown. Our
motivation is achieving the volumetric display with femtosecond laserinduced bubbles.
We demonstrate two-dimensional and three-dimensional bubble graphics
rendered by femtosecond laser-induced micro bubbles. We also somefeatures of bubble graphics such as the relation between the structureand speed of bubbles for the irradiation energy of femtosecond laser
pulses, the voxel structure controlled with the holographic parallel
excitations, and color changes using a light projection.

10335-39, Session 8

Distortion-free 3D imaging using
wavefront shaping
Martin Teich, Jeremy Sturm, Lars Büttner, Jürgen W.
Czarske, TU Dresden (Germany)
3-dimensional imaging often requires substantial effort since information
along the optical axis is not straight forward gatherable. In many
applications it is aimed for depth information along the direction of view.
For example fluidic mixing processes and the environmental interaction

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on a microscopic scale are of particular importance for pharmaceuticalapplications [1] and often demand for 3D information. Beside micro- andnano-fluidic applications also surveillance systems usually exhibit a lag of
depth mapping ability [2]. This problem is often solved by stereoscopic
approaches, where two cameras are used in order to gather depth
information by triangulation technique. Another approach is to scan
the object through the focal plane in order to get sharp images of eachlayer, which is not suitable for every application. Since all the before
mentioned approaches require a lot of video data to be evaluated it
would be more convenient to get depth mapping within a single camera
recording and without scanning. Here we present a tunable 3D depthmapping camera technique in combination with dynamic aberration
control. It is a scan-free, shadow and fluorescence imaging technique for3D trajectory and velocity measurement of flow fields [3]. By using an
incoherent light source, only one camera and a spatial light modulator(LCoS-SLM) loaded with a spiral phase mask that generates doubleimages of the measurement object, it is a simply applicable and highly
scalable technique [4]. A double-helix point spread function (DH-PSF) is
generated for light emerging from the observed focal plane. Each object
appears as a double-image on the camera. Within the orientation of the
double-image, depth information along the optical axis is encoded. By
using an additional adaptive element (deformable mirror) the technique
is combined with wide-field aberration correction [5]. Here we combine atunable 3D depth camera with dynamic aberration control in one imaging
systems.
[1] Munson, M. S., Yager, P., “Simple quantitative optical method formonitoring the extent of mixing applied to a novel microfluidic mixer,”
Anal. Chim. Acta 507(1), 63–71 (2004).
[2] Berlich, R., Bräuer, A., Stallinga, S., “Single shot three-dimensional
imaging using an engineered point spread function,” Opt. Express 24(6),5946 (2016).
[3] Teich, M., Mattern, M., Sturm, J., Büttner, L., Czarske, J. W., “Spiralphase mask shadow-imaging for 3D-measurement of flow fields,” Opt.
Express 24(24), 27371–27381 (2016).
[4] Quirin, S., Piestun, R., “Depth estimation and image recovery using
broadband, incoherent illumination with engineered point spreadfunctions [Invited].,” Appl. Opt. 52(1), A367-76 (2013).
[5] Warber, M., Maier, S., Haist, T., Osten, W., “Combination of scenebased and stochastic measurement for wide-field aberration correction in
microscopic imaging.,” Appl. Opt. 49(28), 5474–5479 (2010).

10335-40, Session 8

Autostereoscopic image creation byhyperview matrix controlled single pixel
rendering
Armin Grasnick, FernUniv. in Hagen (Germany)
Just as the increasing awareness level of the stereoscopic cinema, so
the perception of limitations while watching movies with 3d glasses
has been emerged as well. It is not only that the additional glasses areuncomfortable and annoying; there are some tangible arguments foravoiding 3d glasses. These “stereoscopic deficits” are caused by the 3dglasses itself.
In contrast to natural viewing with naked eyes, the artificial 3d viewing
with 3d glasses introduces specific “unnatural” side effects. The mostof the moviegoers has experienced unspecific discomfort in 3d cinema,
which they may have associated with insufficient image quality.
Obviously, quality problems with 3d glasses can be solved by technicalimprovement. But this simple answer can -and already has- mislead somedecision makers to relax on the existing 3d glasses solution. It needs tobe underlined, that there are inherent difficulties with the glasses, which
can never be solved with modest advancement – as the 3d glasses initiatethem.
To overcome the limitations of stereoscopy in display applications, several
technologies have been proposed to create a 3d impression without
the need of 3d glasses, known as autostereoscopy. But even todays
autostereoscopic displays cannot solve all viewing problems and stillshow limitations. A hyperview display could be a suitable candidate, if itwould be possible to create an affordable device and also generate thenecessary content in an acceptable timeframe.

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Conference 10335:
Digital Optical Technologies
All autostereoscopic displays, based on the idea of lightfield, integral
photography or super-multiview could be unified within the conceptof hyperview. It is essential for functionality that every of these display
technologies uses numerousness of different perspective images to create
the 3d impression. Such a calculation of a very high number of views
will require much more computing time as for the formation of a simple
stereoscopic image pair.
The hyperview concept allows to describe the screen image of any 3dtechnology just with a simple equation. This formula can be utilized tocreate a specific hyperview matrix for a certain 3d display – independent
from the technology used. A hyperview matrix may contain the references
to loads of images and act as an instruction for a subsequent rendering
process of particular pixels. Naturally, a single pixel will deliver an image
with no resolution and does not provide any idea of the rendered scene.
However, by implementing the method of pixel recycling, a 3d image canbe perceived, even if all source images are different. It will be proven thatseveral millions of perspectives can be rendered with the support of GPU
rendering and benefit from the hyperview matrix.
In result, a conventional autostereoscopic display which is designed torepresented only a few perspectives can be used to show a hyperview
image by using a suitable hyperview matrix.
It will be shown that a millions-of-views-hyperview-image can bepresented on a conventional autostereoscopic display (designed for 5 or
8 images by default). For such an hyperview image it is required that all
pixels of the displays are allocated by different source images. Controlled
by the hyperview matrix, an adapted renderer can render a full hyperview
image in realtime.

10335-41, Session 9

Smart spin-orbit photonics using liquid
crystalsEtienne Brasselet, Univ. Bordeaux 1 (France)
Liquid crystals are well-known for their exquisite sensitivity to external
fields and their ability to tailor the amplitude, phase and polarizationof light fields. The interplay between the topological features of liquid
crystals and that of electromagnetic fields offers a playground for thedevelopment of self-engineered spin-orbit optical elements with uniquefunctionalities. Recent progresses will be reviewed.

10335-42, Session 9

Holographically generated structured
illumination for cell stimulation in
optogenetics
Felix Schmieder, Lars Büttner, Jürgen W. Czarske, TU
Dresden (Germany); Maria Leilani Torres, Leibniz Univ.
Hannover (Germany); Alexander Heisterkamp, Leibniz
Univ. Hannover (Germany) and Laser Zentrum Hannovere.V. (Germany); Simon Klapper, Volker Busskamp, DFGCtr. for Regenerative Therapies Dresden (Germany)
Computer generated holograms (CGH) cover a wide range of applications,e.g. the calculation of customized diffractive optics [1]. In conjunction
with a spatial light modulator (SLM), such a digital holographic system
can be used for holographic displays [2] or even adaptive beam forming
in material inspection systems [3]. A research field which has rousedmuch interest lately and will greatly benefit from digital holographic
systems is optogenetics [4]. Here cells, neurons or cardiac cells, aregenetically altered to produce for example the light-sensitive protein
Channelrhodopsin-2. Illuminating these cells induces action potentials orcontractions and therefore allows to control electrical activity. Thus, lightinduced cell stimulation can be used to gain insight to various biologicalprocesses. In our contribution, we present a digital holographic system
for the patterned, spatially resolved stimulation of cell networks. We
employ a fast ferroelectric liquid crystal on silicon SLM, which can display
computer generated holograms at a rate of up to 1.7 kHz. We calculate theholograms of our sparse patterns by convolving a Fresnel zone plate with16

the pattern, followed by two steps of error diffusion for the conversion
into a binary hologram. We employ a quasi-free-space holographic
setup to be able to use the light-efficient zero-order diffraction and to
somewhat alleviate the need for pseudo-random illumination patterns
reported in literature [4]. With an effective working distance of 33 mm,
we achieve a focus of 10 µm at a positioning accuracy of the individual
foci of about 8 µm. We utilized our setup for the optogenetic stimulationof clusters of cardiac cells derived from induced pluripotent stem cells
and were able to observe contractions correlated to both temporalfrequency and spatial power distribution of the light incident on the cellclusters. Thus, future single-cell-based optogenetics research will benefit
from the digital holographic system presented in our contribution, e.g. in
the probing of signal pathways in cell networks.
[1] S. Vorndran et al., “Broadband Gerchberg-Saxton algorithm forfreeform diffractive spectral filter design”, Opt. Express 23(24),A1512-A1527 (2015)[2] H. Yoshikawa, “Research activities on digital holographic displays inJapan”, Proc. of SPIE Vol. 8043 804305-1, 2011
[3] F. Schmieder, L. Büttner, J. Czarske, “Adaptive laser-induced
ultrasound generation using a micro-mirror array spatial light modulator”,
Opt. Express 24(20), 22536-22543 (2016).
[4] I. Reutsky-Gefen et al., “Holographic optogenetic stimulationof patterned neuronal activity for visional restoration”, Nature
Communications, 2013

10335-43, Session 9

Design and quality metrics of point
patterns for coded structured lightillumination with diffractive opticalelements in optical 3D sensors
Ralf Vandenhouten, Technische Hochschule Wildau(Germany); Andreas Hermerschmidt, HOLOEYE
Photonics AG (Germany); Richard Fiebelkorn, Technische
Hochschule Wildau (Germany)
Structured light has become a widespread technique for the developmentof camera-based 3D sensors. The structured illumination provides texture
to homogeneous objects and thus allows for the reliable determinationof the disparity of each object point in a stereo-camera setting. Even a
monocular 3D sensor is possible if the light projector has a fixed relative
position to the camera and if the structured light is coded, i.e. the position
within the whole light pattern can be reconstructed uniquely from a small
local window of the pattern, the uniqueness window. Coded patterns withsuch a uniqueness property are called Perfect SubMaps (PSM).
In principle, the PSMs can contain any number of brightness levels. The
maximum signal-to-noise ratio, however, which is particularly importantfor monocular 3D cameras, is achieved if only two brightness levels areused and if the light spots are isolated. In this case the PSM is a binary
grid pattern with code symbols that are either 0 or 1, and each 1 issurrounded by zeros. For most optical 3D sensors it is sufficient that only
a repeating part of the structured light pattern is a PSM, i.e. the complete
pattern consists of identical tiles that are toroidal PSMs (TPSM)., The
toroidal property ensures that the uniqueness property is not lost at theborder of the tiles. The most efficient way to build powerful structured
light projectors with a small size is to combine a collimated diode laser
with a diffractive optical element (DOE) that generates the PSM fromthe collimated laser beam. In applications, large projection angles,
high contrast, and a good suppression of the undesired undiffracted(zeroth-order) laser beam are required. This can be achieved only withbinary DOEs that are point-symmetric with respect to the 0th order ofdiffraction, i.e. the center of the pattern.
Therefore, in our paper we focus on the design and the evaluation ofsymmetric isolated binary toroidal PSMs (SIBTPSM) for structured light
DOEs. We define several quality metrics that are relevant for the practicaluse of PSMs in a 3D sensor: the size of the PSM, the size of the uniquenesswindow, the Hamming distance, the density, and the homogeneity.
We have created SIBTPSMs using our own dedicated algorithms and havedesigned and fabricated DOEs that produce these patterns with large fanangles of 61° x 47° when used with near-infrared diode lasers (?=830nm).

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Conference 10335:
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We analyze the influence of the above mentioned quality characteristics
on the 3D measurement process by theory, simulations, and experiments.
The patterns of publicly available DOEs based on SIBTPSMs are used forcomparison and reference.
Our results show that the width of the PSM, the size of the uniquenesswindow, the minimum and the average Hamming distance, and thehomogeneity have strong impact on either the speed or the quality of the
3D reconstruction, whereas the point density and the height of the PSM
are of minor importance.

10335-44, Session 9

Structured illumination 3D microscopyusing adaptive lenses and multimodefibersJürgen W. Czarske, Katrin Philipp, Nektarios Koukourakis,
TU Dresden (Germany)
Microscopic techniques with high spatial and temporal resolution are
required for in vivo studying biological cells and tissues. Adaptive lenses
exhibit strong potential for fast motion-free axial scanning. However,they also lead to a degradation of the achievable resolution because ofaberrations. This hurdle can be overcome by computational imaging. We
present a novel High-and-Low-frequency (HiLo) 3D-microscope using
structured illumination and an adaptive lens [1]. A uniform illumination
image is used to obtain optical sectioning for the high-frequency (Hi)components of the image, and a nonuniform illumination image is used
to obtain optical sectioning for the low-frequency (Lo) components of
the image. To generate the nonuniform illumination we use an opticalmultimode fiber [2]. The nonuniform illumination ensures stability
against optical aberrations of the adaptive lens. The depth-of-field of
our microscope can be adjusted a-posteriori by computational optics.
It enables to create flexible scans, which compensate for irregular axial
measurement positions. The adaptive HiLo 3D-microscope provides anaxial scanning range of 1 mm with an axial resolution of about 4 microns
and sub-micron lateral resolution over the full scanning range. In result,volumetric measurements with high temporal and spatial resolution
are provided. Demonstration measurements of zebrafish embryos with
reporter gene-driven fluorescence in the thyroid gland are presented.
Furthermore, we demonstrate how multimode fibers can be employed totransfer images with spatio-temporal resolution [2].
[1] K. Philipp, A. Smolarski, N. Koukourakis, A. Fischer, M. Stürmer, U.
Wallrabe, J.W. Czarske, “Volumetric HiLo microscopy employing anelectrically tunable lens”, Optics Express, 24(13), 15029 (2016)

through a MCF with a resolution dictated by the numerical aperture of thecores of the MCF.
A focus spot can be created through a MCF using wavefront shaping
techniques [3–6], where the wavefront of the laser beam entering the
MCF is properly modified using a spatial light modulator (SLM) in orderto focus light in a specific location in front of the optical fiber. In this work
we used digital phase conjugation (DPC) [7] as the wavefront shaping
technique. A calibration spot was focused in front of the MCF, and then bymeasuring the field at the other end of the fiber and phase conjugating it,a focus spot is recreated at the calibration position. The size of the spot
(or the point spread function – PSF – of the imaging system) depends on
the highest spatial frequency that can contribute in the specific location in
front of the fiber. In this case, it depends on the numerical aperture of thecores and not on the inter-core distance. For a large enough numericalaperture, the obtained PSF has, as a consequence, a resolution finer thanthe core-to-core spacing.
The focus spot can be shifted across the imaging plane by tilting theangle of the wavefront incident on the MCF [3], [5], [8]. This effect issimilar to the memory effect observed in scattering media [9], [10]. The
ability to focus and scan light in a regular grid (Figure 1(a)), enabled us
to image with a resolution finer than the core-to-core spacing (Figure1(b)). Also, thanks to the memory effect, the spots can be projected inseveral locations simultaneously. Combining several spots permitted
the projection of patterns with the same high-resolution determined by
the numerical aperture of the core. We demonstrate the projection of
simple patterns, such as the combination of several foci, and complex
patterns (Figure 1(c)), using the phase only SLM as amplitude and phasemodulator.
References[1] G. Oh, E. Chung, and S. H. Yun, “Optical fibers for high-resolution invivo microendoscopic fluorescence imaging,” Opt. Fiber Technol., vol. 19,
no. 6, Part B, pp. 760–771, Dec. 2013.
[2] B. A. Flusberg, E. D. Cocker, W. Piyawattanametha, J. C. Jung, E. L.
M. Cheung, and M. J. Schnitzer, “Fiber-optic fluorescence imaging,” Nat.
Methods, vol. 2, no. 12, pp. 941–950, Dec. 2005.
[3] A. J. Thompson, C. Paterson, M. A. A. Neil, C. Dunsby, and P. M. W.
French, “Adaptive phase compensation for ultracompact laser scanningendomicroscopy,” Opt. Lett., vol. 36, no. 9, pp. 1707–1709, May 2011.
[4] D. Kim et al., “Toward a miniature endomicroscope: pixelation-free anddiffraction-limited imaging through a fiber bundle,” Opt. Lett., vol. 39, no.
7, pp. 1921–1924, Apr. 2014.
[5] E. R. Andresen, G. Bouwmans, S. Monneret, and H. Rigneault, “Toward
endoscopes with no distal optics: video-rate scanning microscopy
through a fiber bundle,” Opt. Lett., vol. 38, no. 5, p. 609, Mar. 2013.

[2] Czarske, J. W., Haufe, D., Koukourakis, N., Büttner, L. „Transmission of
independent signals through a multimode fiber using digital optical phaseconjugation.” Optics Express, 24(13), 15128-15136 (2016).

[6] D. B. Conkey, N. Stasio, E. E. Morales-Delgado, M. Romito, C. Moser,
and D. Psaltis, “Lensless two-photon imaging through a multicore fiberwith coherence-gated digital phase conjugation,” J. Biomed. Opt., vol. 21,
no. 4, p. 045002, Apr. 2016.

10335-45, Session 9[7] I. N. Papadopoulos, S. Farahi, C. Moser, and D. Psaltis, “Focusing andscanning light through a multimode optical fiber using digital phaseconjugation,” Opt. Express, vol. 20, no. 10, p. 10583, May 2012.

Imaging and pattern projection throughmulticore fibers using the memory effect[8] N. Stasio, D. B. Conkey, C. Moser, and D. Psaltis, “Light control in a
multicore fiber using the memory effect,” Opt. Express, vol. 23, no. 23, p.
30532, Nov. 2015.

Nicolino Stasio, Donald B. Conkey, Christophe Moser,
Demetri Psaltis, Ecole Polytechnique Fédérale deLausanne (Switzerland)
Microendoscopy through optical fibers permits high-resolution opticalimaging inside tissues at depths not accessible using conventional
microscopy [1, 2], while also being minimally invasive. Clinically usedmicroendoscopes are usually made with multicore fibers (MCFs), opticalfibers consisting of a common cladding and several single mode (orfew modes) cores arranged in a quasi-periodic array. Each core probes
information for one pixel of the final image. Thus, the attained image
will be pixelated by the core spacing, which limits the resolution of theseendoscopes to a several micrometers. In fact, to avoid inter-core coupling,
the spacing between cores has to be sufficiently large, so that the
information carried by each core is independent from its neighbors. Here
we show how with a single calibration step, wavefront shaping enables
light control through a MCF at a resolution below the core-to-core
spacing. We demonstrate both imaging and complex pattern projection

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[9] S. Feng, C. Kane, P. A. Lee, and A. D. Stone, “Correlations andFluctuations of Coherent Wave Transmission through Disordered Media,”Phys. Rev. Lett., vol. 61, no. 7, pp. 834–837, Aug. 1988.
[10] I. Freund, M. Rosenbluh, and S. Feng, “Memory Effects in Propagationof Optical Waves through Disordered Media,” Phys. Rev. Lett., vol. 61, no.
20, pp. 2328–2331, Nov. 1988.

10335-18, Session PS2

Aerial 3D display by use of a 3D-shaped
screen with aerial imaging by retroreflection (AIRR)
Nao Kurokawa, Shusei Ito, Hirotsugu Yamamoto,
Utsunomiya Univ. (Japan)·

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Conference 10335:
Digital Optical Technologies[CONTEXT] One of the big dreams in imaging technology is to realize
a three-dimensional display that is floating in mid-air. One of theprospective techniques to realize such a floating display is aerial imaging
by retro-reflection(AIRR) [H. Yamamoto, Opt. Exp. 22, 26919 (2014)].
AIRR forms the real image of a source display plane-symmetricallyregarding a beam splitter by use of a retro-reflector to converge lights.
In order to avoid the loss of reflected and transmitted lights at the beam
splitter, polarization modulation has been introduced to AIRR. This setup
is called polarized AIRR (pAIRR) [M. Nakajima, Proc. CLEO-PR, 25B12 (2015)]. Previously reported systems formed a 2D screen in mid-air.
[OBJECTIVE] The purpose of this paper is to realize an aerial 3D display.
We design optical system that places a 3D-shaped screen and a projector
below a retro-reflector. [METHOD] Our proposed new optical system iscomposed of a 3D-shaped screen, a projector, a quarter-wave retarder,
a retro-reflector, and a reflective polarizer. Because AIRR forms aerial
images that are plane-symmetric of the light sources regarding thereflective polarizer, the shape of the 3D screen is the inverted shape of thedesired aerial 3D image. In order to expand view angle, the 3D-shaped
screen is surrounded by a retro-reflector. In order to separate the aerial
image from reflected lights on the retro-reflector surface, the retroreflector is tilted by 30 degrees. A projector is located below the retroreflector at the same height of the 3D-shaped screen. The optical axis of
the projector is orthogonal to the 3D-shaped screen. Scattered light on
the 3D-shaped screen forms the aerial 3D image. [RESULTS] A cornercube-shaped screen is used for the 3D-shaped screen. Its color is white.
Its area length is 100 mm. Thus, the aerial 3D image is a cube that is
floating above a reflective polarizer. We used a DLP projector (PT-DX820
made by Panasonic). The brightness of the projector is 7,000 lumens.
In order to confirm the optical design, an aerial green cube is formedby projecting a calculated image on the 3D-shaped screen. The green
cube image is digitally inverted in depth by our developed software. Our
software can adjust the projected image to the size, the direction, andthe location of the 3D-shaped screen. The side retro-reflectors have 340
mm height and 600 mm width. The central retro-reflector has 170 mm
height and 480 mm width. The formed aerial 3D image is floating at 150mm height from the reflective polarizer. Viewing positions are designed at
500 mm distance from the aerial 3D image and at 160 mm height. Thus,
we have succeeded to form aerial 3D image with our designed opticalsystem. Our optical system has overcome the following two problems.
The first problem is low luminance of the aerial image that is formed byscattered light on an object. The second problem is that aerial 3D image
depth is inverted. [NOVELTY] This is the first report on forming the 3D
aerial image by use of a 3D-shaped screen with AIRR.

10335-56, Session PS2

Real-time aberration correction
simulation of multimode beam by SPGD
algorithm
Qiong Zhou, Wenguang Liu, Baozhu Yan, Quan Sun,
Shaojun Du, National Univ. of Defense Technology(China)With the increase of the laser output power, heat effect and nonlinear
effect on the beam quality become increasingly serious, directly limit
the improvement of laser brightness output. Multimode laser has fewer
restrictions on the structure, so it can be able to withstand higher power
output. But the multimode beams with poor beam quality decline thebeam quality of imaging system and far field. As a result, improving
beam quality of the multimode beams by aberration control is of greatsignificance. In this paper, a real-time dynamic closed loop control
method of multimode beams is proposed that use the wave-front
aberration measurement data and phase correction device as the core.
It has a very good reference value for subsequent application in imaging
system in beam quality measurement.
In this paper, the physical properties of multimode beam are analysedby using the theory of partially coherent light. Based on the spatial
coherence measurement results of a multimode fiber laser, we provide
a theoretical basis for aberration correction for multimode beams. To
improve the beam quality of multimode lasers, phase correction ofmultimode laser based on a dual-phase-only liquid-crystal spatial light
modulator (LC-SLMs) is presented which is used as aberration correction
device. The phase distribution was optimized by the stochastic parallel

18

gradient descent (SPGD) algorithm. In this paper the power in thebucket (PIB) of the far field was used as the evaluation function and themultimode beam included multiple higher order Laguerre-Gaussian beammodes. The PIB of single high-order mode beam, coherent and incoherent
multimode beam are simulated respectively. According to the result of the
PIB, the parameters of SPGD algorithm can be adjusted and the efficiency
and practicability of the algorithm are determined.
In conclusion, the real-time dynamic closed loop aberration correction ofmultimode beam based on the SPGD algorithm can efficiently improve
the imaging quality, and it may be a useful means to preserve beam
quality both in fiber laser system and imaging system.

10335-58, Session PS2

CPU architecture for a fast and energysaving calculation of convolution neuralnetworks
Florian Knoll, Michael Grelcke, Fachhochschule
Westküste Heide (Germany); Vitali Czymmek,
Tim Holtorf, West Coast Univ. of Applied Sciences(Germany); Stephan H. Hussmann, Fachhochschule
Westküste Heide (Germany)
The increasing computing power in recent years allows more andmore complex algorithms for the implementation of adaptive artificial
intelligence. Deep Learning is one approach for adaptive intelligence. For
the task of pattern recognition the family of Convolution Neural Networks(CNN) is applied. The best example is the image search on the internet.
Here CNN are used for classifying 1000 different objects in one picture[1]. In addition these networks are used for example for autonomous
driving. These networks learn how to behave on the street and also therecognition of the road signs [2]. Another application is the detectionof human faces [3] and there emotions. The CNN is used as an interface
between humans and robots [4]. CNN can even be trained to calculate
the calories in a meal. The user only has to make an image of his meal
with a smartphone [5]. Another use of the CNN is to recognize emotionsin audio data or images [6]. The first CNN worked for optical character
recognition (OCR). Le Cun has developed networks with an accuracy of
about 98% [7]-[8].
In this paper a CNN is used for plant detection in organic farming. In
paper [9]-[10] the basics, the sensor-configuration and parts of theclassification task of the project were already presented. The biggest
problem is still the speed and power consumption of the algorithms.
Although large search engine companies own specially developed
hardware to provide the necessary computing power, for the conventionaluser only remains the state of the art method, which is the use of agraphic processing unit (GPU) as a computational basis. Althoughthese processors are well suited for large matrix computations, theyneed massive energy. Therefore a new processor on the basis of a field
programmable gate array (FPGA) has been developed and is optimized
for the application of deep learning. This processor is presented in thispaper as well. The processor can be adapted for a particular application(in this paper to an organic farming application). The power consumption
is only a fraction of a GPU application and should therefore be well suitedfor energy-saving applications.
To further increase the performance of the FPGA solution, the ALU should
be set up several times so that more calculations are possible at the sametime. Since we have only consumed about 3% of the FPGA’s required
resources at present, a multiplication of the ALU is not a big problem.
A further optimization is the implementation of a pipeline structure toeliminate unnecessary course times. We hope that we can present thenext generation of our CPU in the future.
REFERENCES[1] Krizhevsky, A., Sutskever, I. and Hinton, G.E. “ImageNet Classification
with Deep Convolutional Neural Networks”, Papers published at the
Neural Information Processing Systems Conference. 2012[2] Jung, S., Lee, U., Jung, J. and Shim, D. “Real-time Traffic Sign
Recognition system with deep convolutional neural network”, Ubiquitous
Robots and Ambient Intelligence (URAI), 2016 13th International
Conference on, IEEE Xplore 2016

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Conference 10335:
Digital Optical Technologies[3] Chen, L., Guo, X., and Geng, C., “Human face recognition based on
adaptive deep Convolution Neural Network”, Control Conference (CCC),
2016 35th Chinese, IEEE Xplore 2016
[4] Liu, H., Stoll, N., Junginger, S., Zhang, J., Ghandour, M. and Thurow, K.
“Human-Mobile Robot Interaction in laboratories using Kinect Sensor and
ELM based face feature recognition”, Human System Interactions (HSI),
2016 9th International Conference on, IEEE Xplore 2016[5] Pouladzadeh, P., Kuhad, P., Peddi, S. V. B., Yassine, A. andShirmohammadi, S. “Food calorie measurement using deep learningneural network”, Instrumentation and Measurement Technology
Conference Proceedings (I2MTC), 2016 IEEE International[6] Zhang, B., Quan, C. and Ren, F. “Study on CNN in the recognition ofemotion in audio and images”, Computer and Information Science (ICIS),
2016 IEEE/ACIS 15th International Conference on[7] Chen, L., Wang, S., Fan, W., Sun, J. and Naoi, S. “Beyond humanrecognition: A CNN-based framework for handwritten character
recognition”, Pattern Recognition (ACPR), 2015 3rd IAPR Asian
Conference on, IEEE Xplore 2016
[8] Le Cun, Y., Boser, B., Denker, J. S. and Henderson, D. “Handwritten
Digit Recognition with a Back-Propagation Network”, Papers published at
the Neural Information Processing Systems Conference. 1989
[9] Knoll, F., Holtorf, T. and Hußmann, S., “ Investigation of different sensor
systems to classify plant and weed in organic farming applications”, SAI
Computing Conference, p.p. 343 - 348, 2016.
[10] Knoll, F., Holtorf, T. and Hußmann, S., “Vegetation index
determination method based on color room processing for weed control
applications in organic farming”, I2MTC 2016, Proc. of the 33th Int. Conf.
on Inst. and Meas. Tec., IEEE Instrumentation and Measurement Society,p.p. 1024-1029, 2016.

generated in the setup in practice. We can create the 3D model of theseobjects that we can use in ray-tracing. During the ray tracing we can findthe areas of the object surfaces what produce certain elements in theimage patterns. We can assume what we would like to have in the image
pattern, so the next step is the synthesis of the object (the 3d-model)using the different fragments of the found surfaces. This can speed up thesynthesis procedure for the given image of the high self-similarity for the
setups of drug-free therapy.

10335-60, Session PS2

A study of wavefront coding techniqueapplied to next generation digital opticalsystem
Qi-Feng Lee, National Central Univ. (Taiwan); Yi Chin
Fang, National
Kaohsiung First Univ. of Science and Technology (Taiwan); Cheng-Mu Tsai,National Chung Hsing Univ. (Taiwan)In this research, we mainly focuses on
the development of wave-front coding digital algorithm and the design ofan optical system which conforms to wavefront coding system. Therefore,
we carried out two design, 1. Special design A phase plate is added to theoptical system, 2. Design a lens that only has a significant effect on the
defocus (the primary aberrations can not be too large), so the system canmeet the wavefront coding technology.
In addition, this study will use some methods to simulate the intermediate
image that is generated by defocus effect, and describe how to restore
the intermediate image to the near-diffraction limit imaging results.

10335-59, Session PS210335-61, Session PS2

Method of synthesis of abstract images
with high self-similarity

Analytic functions of optical choppers for
Gaussian laser beams

Nikolai V. Matveev, Sergey A. Shcheglov, Galina E.
Romanova, Tatiana A. Koneva, ITMO Univ. (RussianFederation)

Nicolina Pop, Politehnica Univ. of Timisoara (Romania);
Octavian Cira, Aurel Vlaicu Univ. of Arad (Romania);
Virgil-Florin Duma, Aurel Vlaicu Univ. of Arad (Romania)
and Politehnica Univ. of Timisoara (Romania)

Abstract image with high self-similarity could be used for drug-free stresstherapy. This based on the fact that a complex visual environment has ahigh affective appraisal. Comlex structure of the picture is constructedfrom the different complicated geometric shapes of different colors. The
pattern is projected to the dome for additional effect of immersion to thevisual environment.
To create such an image we can use the setup based on the three laser
sources of small power and different colors (Red, Green, Blue), theimage results resulting from reflecting and refracting by the object of
the complicated form placed into the laser ray paths. Using three laser
sources provides the possibility of different colors of the patterns,
the shape of the object defines the structure of the pattern. The more
complicated is the object surfaces the more complicated is the image
projected on the dome surface.
Different object forms were used for pattern forming, as a result theimages were obtained experimentally which showed the good therapy
effect on the group of volunteers. However, to find and to choose theobject which gives needed image structure requires many trials if itchosen experimentally because of the high non-linear structure of thenecessary image.
Of cause the design task can be solved using the non-imaging optics
methods. In fact this means obtaining the necessary irradiancedistribution on the given surface. In the given case this task is very
complicated because of the complicated structure of the illuminancedistribution and its high non-linearity.
The goal of the work is to develop a method and a procedure of finding
the object form which can provide the necessary structure of the image
when placed into the ray paths.
So we propose during the modeling of the optical system using ray
tracing technique to locate the object zones responsible for the area ofinterest in the future image. It means that we have a few objects withcomplex and highly non-linear surfaces, and the patterns that were

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The present paper is focused on achieving and analyzing the analytic
functions of optical choppers with disks with n symmetrical wings. A
Gaussian laser beam distribution of the light beam to be chopped anda light bundle of small diameter in the plane of the chopper have beenchosen. The functions of the transmitted flux and the transmission
coefficient of a device are obtained. This allows for the designingcalculus of choppers for different applications, taking into accountthe specific requirements to be met. A comparison between analyticalresults obtained in this work and the results from our previous modelingand simulations is shown – for different configurations of chopper
wheels. Selected References: [1] Duma, V. F., “Theoretical approach on
optical choppers for top-hat light beam distributions,” Journal of Optics
A: Pure and Applied Optics, 10(6), 064008 (2008). [2] Duma, V. F.,“Optical choppers with circular-shaped windows: Modulation functions,”
Communications in Nonlinear Science and Numerical Simulation (CNSNS)
16, 2218-2224 (2011). [3] Duma V.-F., Prototypes and modulation functionsof classical and novel configurations of optical chopper wheels, Latin
American Journal of Solids and Structures 10(1), 5-18 (2013).

10335-62, Session PS2

Adding polarimetric imaging to depth
map using improved light field camera
2.0 structure
Xuanzhe Zhang, Hefei Institutes of Physical Science(China) and National Univ. of Defense Technology(China) and Univ. of Science and Technology of China(China); Yi Yang, Shaojun Du, Yu Cao, National Univ. of
Defense Technology (China)·

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Conference 10335:
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Polarization information plays an important role in skylight navigation
under complicated weather, target identification under complex
background, and material identification from shot scene, while thecorrectness of depth information is the key to three-dimensional
imaging, obtaining them both can not only help to rebuild the 3D scene
comprehensively but also to improve the accuracy for each other. This
paper describe a polarimetric imaging system based on light field 2.0
camera structure, which can calculate the polarization angle and thedepth distance from reference plane for every objet point within a single
shot. In this optical structure, a 3-quadrants Polaroid which has rotational
symmetric polarizing angle in each quadrant is placed on pupil, and ahoneycomb-liked micro lens array with three different micro lens focal
lengths is placed near the system focal plane, at last a high resolution
CCD is place on image plane of micro lens array, at the same time, rotate
direction of the 3 quadrants is adjusted to match micro lens arrangement,
and the F-number of main aperture is designed to equal the F-numberof micro lens. By this means, main lens generates intermediate image,and micro lens array acts as camera array that focuses different patchesof intermediate image onto CCD, that is to say, every patch is “looked”
by a certain number of micro “eyes”, whose number depending on
how close the patch is to the camera, and every “eye” is equivalent to awindow on main aperture, having a definite polarization state. Therefore,
depth can be calculated by matching the relative offset of corresponding
image patch, while polarization can be calculated by its relative intensity
difference, and their resolution will be equal to each other. Wholealgorithm and one of the applications on navigation under different
weather conditions is proposed in next part, whose results show that thismethod has a high accuracy and strong robustness. Latest developments
in other applications are discussed at the end of the article.

out10335-63, Session PS2

Calibration between a 3D camera and an
aerial information screen

Modified 3D time-of-flight camera forobject separation in organic farming
Florian Knoll, Fachhochschule Westküste Heide(Germany); Tim Holtorf, West Coast Univ. ofApplied Sciences (Germany); Stephan H. Hussmann,
Fachhochschule Westküste Heide (Germany)
The increase of plant earnings (food or energy plants) with simultaneousconsideration of the protection of the environment will be a global task
in the future. The manual weed control, used in organic farming, withoutchemical or synthetical agriculturalpesticides is one way to protect ourenvironment. Manual weed elimination is very expensive. Our cooperation
partner Westhof Bio in Germany for example, spends over 170.000 EUR
per year for the manual weed elimination by human labor. Furthermore it
is more and more difficult to find human workers for this task. Hence theneed for research for automated non-chemical weed control systems isvery large. But up to now no commercial system is available.
A major problem in organic farming is to separate the plants. It has to be
detected which leaf belongs to which plant. This is not an easy task as
many leafs overlap each other.
Therefore 3D information of the plants is needed. A simple option tocreate a 3D picture is to use Time of Flight cameras or laser scanners.
Hence the used measurement setup and the 3D sensors tested arepresented in section II. Subsequently the problems with the presented
commercial 3D cameras from section II are described in in section III andthe carried out modification of the Kinect II 3D camera are described in
section IV. Finally in section V experimental results of the original andthe modified Kinect II are presented. A summary of the results is given in
section VI.
For the measurement recordings the mobile field robot BoniRob wasused. The complete measurement setup including the results is explainedin the paper.
The robot drove autonomously over the field at a rate of 20 mm/s.
At 1 frame per second this speed allows an uninterrupted view of the
field, with an overlap of the respective sensor data of around 20%. Theinteresting area, where the plants are growing on the wall has an averagewidth of about 15cm. This area has been recorded among others with
the Kinect II sensor, the CamCube 3 and the LMI Gocator 2350. All thesesensors are recording 3D images.
Using this data from the same plants on different days it shall be figured

20• Which sensors• Which configuration• Which growth stage
is the best for the seperation and classification of carrot plants and weed.
These sensors have the advantage over the stereo vision procedure, thatthe 3D image is created automatically without much computation time
Subsequently it is shown in practical measurements that 3D measurement
methods are suitable for the problem. But only the Kinect II showed
potential.
The camera is intended for recording the entire living room and serves as
an interface for the players of a video game.
About two-thirds of the resolution is wasted in our application. Onlya small strip of approximately 20 cm width is sufficient for the root
recognition. The Kinect II had to be reconstructed in order to use thefull resolution efficiently. Therefore, the camera was disassembled andprovided with a new lens. Due to the small aperture, the entire resolutionof 512 x 424 pixels can now be used on the small strip, where the rootsgrow.
In this article, we explained why 3D measurement procedures for plant
identifications are necessary. Subsequently, it is shown in practicalmeasurements that 3D measuring methods are suitable for the problem.
The original and the modified Kinect II are compar by different measuringmethods.

10335-64, Session PS2

Shusei Ito, Nao Kurokawa, Hirotsugu Yamamoto,
Utsunomiya Univ. (Japan)[CONTEXT] An interactive 3D interface system is gathering attention.
Direct handling of an aerial screen information can be realized by use of a
3D gesture recognition camera and an aerial screen. We have formed anaerial screen with aerial imaging by retro reflection (AIRR) [H. Yamamoto,Opt. Exp. 22, 26919 (2014)] and detected gestures of a user with a Kinect[Y. Tokuda, Proc. SIGGRAPH Asia’15, Emerging Technologies (2015)].
We faced a calibration problem. The calibration problem means thatthe coordinate systems of the aerial screen and the Kinect should bematched. In the previous demonstration, the calibration was conductedmanually when the position or/and the direction of the Kinect werechanged.
[OBJECTIVE] We propose a calibration method of a 3D gesturerecognition camera and an aerial information screen. The proposed
method is confirmed experimentally by use of our prototype aerial
display with AIRR.
[METHOD] Our aerial display is composed of a source display, a reflective
polarizer, a quarter-wave retarder, and a retro-reflector. The reflective
polarizer is placed in crossed nicols regarding the polarizer on thesource display. In this case, the light from the source display reflects at
the reflective polarizer. The reflected light retro-reflects at the retroreflector. The polarization angle of the retro-reflected light is rotated by
90 degrees after penetrating the quarter-wave retarder twice. Therefore,
the retro-reflected light transmits through the reflective polarizer andconverges into the plane symmetric position of the light source regarding
the reflective polarizer. We used a Kinect v2 as a 3D gesture recognition
camera. The Kinect detects positions of users’ hands. Our system detects
up to two users. We developed a calibration software and interactive
applications by using Unity, which is a commonly-used platform forinteractive software. In Unity, we prepared a camera for rendering,objects, and two squares that show hands’ positions. Displayed image isrendered by use of the camera in Unity. The objects are displayed in the
mid-air. In order to handle these aerial objects, our developed program
detects collision between one of the hands and one of the objects. The
collision is determined after calibration. The calibration is automaticallyconducted by adjusting the view angle and the position of the camera inUnity to match the Kinect. In the calibration process, a user is instructed
to place one of the hands on four corners of an aerial calibration pattern,
one after another. The x-coordinate and y-coordinate of the hand position

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Conference 10335:
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in the Kinect coordinate system are used to calibrate the central positionin Unity. The z-coordinate is used to judge collision because it shows the
distance from the hand to the aerial image.
[RESULTS] We have formed a 43-inch aerial screen. The aerial screen,
tilting by 30 degrees, is floating at 35 cm above a reflective polarizer.
We have realized interaction: when a user touches an object, color of theobject changes. Furthermore, we have created a balloon-popping game.
[NOVELTY] This is the first report on the calibration system by 3D gesturerecognition camera and AIRR.

10335-65, Session PS2

Power estimation of martial arts
movement using 3D motion capture
cameraMohamad Zubir Mat Jafri, Nurzaidi Azraai, Ahmad Afiq
Sabqi Awang Soh, Univ. Sains Malaysia (Malaysia)
Motion capture camera (MOCAP) has been widely used in many areas
such as biomechanics, physiology, animation, arts, etc. This project isdone by approaching physics mechanics and the extended of MOCAP
application through sports. Most researchers will use a force plate, but
this will only can measure the force of impact, but for us, we are keen
to observe the kinematics of the movement. Martial arts is one of the
sports that uses more than one part of the human body. For this project,martial art ‘Silat’ was chosen because of its wide practice in Malaysia.
2 performers have been selected, one of them has an experienced
in ‘Silat’ practice and another one have no experience at all so that
we can compare the energy and force generated by the performers.
Every performer will generate a punching with same posture whichin this project, two types of punching move were selected. Before themeasuring start, a calibration has been done so the software knows
the area covered by the camera and reduce the error when analyze byusing the T stick that have been pasted with a marker. A punching bagwith mass 60 kg was hung on an iron bar as a target. The use of thispunching bag is to determine the impact force of a performer when theypunch. This punching bag also will be stuck with the optical marker so
we can observe the movement after impact. 8 cameras have been usedand placed with 2 cameras at every side of the wall with different angle
in a rectangular room 270 ft2 and the camera covered approximately
50 ft2. We covered only a small area so less noise will be detected andmake the measurement more accurate. A Marker has been pasted on thelimb of the entire hand that we want to observe and measure. A passive
marker used in this project has a characteristic to reflect the infrared thatbeing generated by the camera. The infrared will reflected to the camera
sensor so the marker position can be detected and show in software.
The used of many cameras is to increase the precision and improve theaccuracy of the marker. Performer movement was recorded and analyzed
using software Cortex motion analysis where velocity and accelerationof a performer movement can be measured. With classical mechanics
approach we have estimated the power and force of impact and showsthat an experienced performer produces more power and force of impact
is higher than the inexperienced performer.

10335-66, Session PS2

Development of an optical radar for
distance learning crevices Mars
Leonid Smirnov, Victoria A. Ryzhova, Alexsandr S.
Grishkanich, ITMO Univ. (Russian Federation)
More recently, Mars became the object of research is associated primarily
with the development of techniques and technologies that allow adetailed way to explore the planet’s surface. These studies are quite
relevant, because humanity sees Mars as their new home. For potential
terraforming key factor is the presence of water on the red planet. At the
moment there are two ways to study the surface: contact and contactless.
For contactless electronic methods include the latest telescopes based on
Earth but telescopes do not provide accurate and detailed information,
which in turn does not accelerate and simplify the study the planet’s

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surface.
To contact methods include rovers, delivered to the surface of Mars.
Unfortunately rovers have fairly low speed, which greatly increases
the time spent on research alone, even a small portion of the surface.
Also cross-country rover is not high enough, it also affects the speed ofresearch.
At this time, none of the existing methods of probing the surface of Mars
is not able to look into the deep Martian crevices, which according topreliminary estimates and may be of Martian water reserves. Therefore, tosolve this problem will require the machine, orbiting Mars, which will be
used as a special rangefinder.
On the surface of the red planet water was found in two of its aggregate
states, namely water vapor and ice. However, September 29, 2015,
when the average Martian temperature rose to -23 degrees Celsius,
supersensitive equipment was able to detect a watery suspension.
Detailed spectral analysis showed that the aqueous slurry contains
impurities, the most striking is its components H2S and HCL. Therefore, as
the indicator substances, it was decided to select H2O, H2S and HCL.
Given the structure of Mars atmosphere, namely the fact that it consists of
CO2 (95%), Ar (1.6%), N2 (2.7%), O2 (0.13%) and CO (0.07%), and taking
into account the range of atmospheric transmittance should that the bestarea for sensing a UV range.
As a method for remote sensing of the most effective is the Raman
scattering method that allows to detect several substances indicators
without complicating the structure of the device, in contrast to themethod of differential absorption and scattering, as for the detection ofsubstances it requires two power sources, thus to detect three substances
required indicators I have enormous energy.
Taking the existing at this time «NOMAD», the best option would be touse the circuits of the monostatic lidar, which will minimize the size of thedevice, since the receiver is in the immediate vicinity of the source, andit reduces the costs associated with the development and maintenanceof such a device. So take a monostatic lidar scheme for constructing thebasis for the most suitable option.
The aim is to create a model of such a device, which in the future will leadto the development of a prototype that can find water on the red planet.

10335-67, Session PS2

Measuring the volume of brain tumourand determining its location in T2weighted MRI images using hidden
Markov random field: expectation
maximization algorithm
Mohamad Zubir Mat Jafri, Univ. Sains Malaysia(Malaysia); Hayder Saad Abdulbaqi, Univ. Sains Malaysia(Malaysia) and College of Education Al-Qadisiya (Iraq);
Kussay N. Mutter, Iskandar Shahrim Mustafa, Ahmad
Fairuz Omar, Univ. Sains Malaysia (Malaysia)
A brain tumour is an abnormal growth of tissue in the brain. Most
tumour volume measurement processes are carried out manually by
the radiographer and radiologist without relying on any auto program.
This manual method is a time-consuming task and gives results may
be inaccurate. Treatment, diagnosis, signs and symptoms of the brain
tumours mainly depend on the tumour volume and its location. In thispaper, an approach is proposed to improve volume measurement of brain
tumors as well as using a new method to determine the brain tumour
location. The current study presents a hybrid method that includes two
methods. One method is hidden Markov random field ?- expectation
maximization (HMRF-EM), which employs a positive initial ?classificationof the image. The other method employs the threshold, which enables
the final segmentation. In this method, ?the tumour volume is calculatedusing voxel dimension measurements. The accuracy of the proposedvolume estimation method was validated by comparing it with the gold
standard, which is obtained by using the water displacement method.
The brain tumour location was determined accurately in T2- weighted
MRI image using a new algorithm. According to the results, this process
was proven to be more useful compared to the manual method. Thus, it·

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Conference 10335:
Digital Optical Technologies
provides the possibility of calculating the volume and location of a brain
tumour.

10335-68, Session PS2

An efficient method to improve speed-offocus of electronically tunable lenses for
optical systems using Gaussian beams
Muhammad Assad Arshad, Friedrich-Schiller-Univ. Jena
(Germany); Ahsan Muhammad, Syed Azer Reza, Lahore
Univ. of Management Sciences (Pakistan)
Various applications in optical imaging, vision correction, microscopy,
sensing and target ranging deploy Tunable Focus Lenses (TFL) as part ofa working system design. Several of these systems require tuning these
TFLs to obtain a minimum spot size or the tightest focus of a Gaussian
Beam in various locations. Such spot size minimization is often used in
microscopes for a motion-free depth scan. Sometimes the knowledge of a
TFL focal length which results in a minimum beam spot is also the means
to determine the location of the plane where the minimum beam spot
forms. Such a sensing mechanism has been used to determine shapes ofobjects, liquid level, pressure in a closed chamber and terrain mapping.
Therefore, the use of TFLs to obtain a minimum spot size of a propagating
Gaussian Beam at different planes is critical for several optical imaging
and sensing applications. In general, the focal length of a TFL is controlled
by varying the amplitude of an input voltage or the current signal. Hence,
the response time of a TFL-based sensor or imaging system depends on
the required duration to scan the input signal amplitude until an optimal
amplitude value produces the required minimum beam spot size at agiven plane. Thus, it can be inferred that the system response time or
sampling rate depends on the number of voltage/current samples tocorrectly identify the TFL focal length value which yields a minimum
beam spot. For sensing and imaging applications, tuning the TFL to thedesired focal length by beginning the scan of the input signal amplitude
at any corner or random voltage/current value and incrementally
increasing or reducing it is highly inefficient as tuning to a minimum spot
requires several scan steps resulting in a slow sensor response. In thispaper, we propose an efficient method of scanning the focal length of
a TFL which results in a significant reduction in the number of voltage/current steps to obtain a minimum beam spot size at any plane ofobservation. We demonstrate the effectiveness of our proposed methodwith experimental results and validate our claims by significantly reducing
the required number of steps to tune a Gaussian Beam spot to a minimum
possible at various chosen observation plane locations.

10335-69, Session PS2

A MEMS and agile optics-based dualmode variable optical power splitter withno moving parts
Tariq Shamim Khwaja, Hamid Suleman, Syed Azer Reza,
Lahore Univ. of Management Sciences (Pakistan)In this paper, we present a novel design of an optical power splitter.
Owing to the inherent variable power split ratios that the proposed
design delivers, it is ideal for use in communications, sensing andsignal processing applications where variable power splitting is often
quintessential. The proposed power splitter module is dual mode as it
combines the use of a Micro-Electro-Mechanical Systems (MEMS) based
Digital Micro-mirror Device (DMD) and an Electronically Controlled
Tunable Lens (ECTL) to split the power of an input optical signal between
two output ports – the designated port and the surplus port. The useof a reflective Digital Spatial Light Modulator (DSLM) such as the DMD
provides a motion-free digital control of the split ratio between the two
output ports. Although the digital step between two possible successive
split ratios can be fairly minimal with the use of a high resolution DMD
but it is a challenge to correctly ascertain the exact image pattern on the
DMD to obtain any desired specific split ratio. To counter this challenge,
we propose the synchronized use of a circular pattern on the DMD, which
serves as a circular clear aperture with a tunable radius, and an ECTL. The

22

radius of the circular pattern on the DMD provides a digital control of the
split ratio between the two ports whereas the ECTL, depending on its
controller, can provide either an analog or a digital control by altering thebeam radius which is incident at the DMD circular pattern. The radius of
the circular pattern on the DMD can be minimally changed by one micropixel thickness. Setting the radius of the circular pattern on the DMD toan appropriate value provides the closest “ball-park” split ratio whereas
further tuning the ECTL aids in slightly altering from this digitally set
value to obtain the exact desired split ratio in-between any two digitallyset successive split ratios that correspond to any clear aperture radius of
the DMD pattern and its incremental minimal allowable change of one
micro-pixel. We provide a detailed scheme to calculate the desired DMD
aperture radius as well as the focal length setting of the ECTL to obtainany given split ratio. By setting tolerance limits on the split ratio, we also
show that our method affords diversity by providing multiple possible
solutions to achieve a desired optical power split ratio within the specified
tolerances. We also demonstrate the validation of the proposed concept
with initial experimental results and discussions. These experimental
results show a repeatable splitter operation and the resulting power split
ratios according to the theoretical predictions. With the experimental
data, we also demonstrate the effectiveness of the method in obtaining
any particular split ratio through different DMD and TFL configurations
with specific split ratio tolerance values.

10335-70, Session PS2

A multispectral telescopic systems with avariable magnification
Ivan Tarasov, Helen A. Tsyganok, ITMO Univ. (RussianFederation)
Telescopic system is one of the most widespread types of the opticalsystems. They can be used as a standalone system and as a component ofa more difficult system.
This type of the optical systems is applied in geodetic, astronomical,
observation, goniometric, ranging devices, expansion of laser radiation
systems, in high precision required systems, for example, in medicine
when carrying out operations, etc. Telescopic systems can conditionallybe divided like systems with constant, discretely or smoothly changing
magnification. The well-known telescopic systems are constructedaccording to Galilei or Kepler’s schemes belong to the first type ofsystems. In the telescopic system are created constructed according toGalilei’s scheme the positive optical system is used as a lens, and as an
eyepiece – negative is used. Advantages of the scheme of Galilei are
the direct image and smaller length in a comparison with the Kepler’s
scheme. In Kepler’s scheme a lens and an eyepiece is a positive opticalsystem. The lens creates the inverted real image in the lens back focal
plane of the lens. Shortcomings of the scheme of Kepler are: big lengthof optical system, the inverted image. For creation of the system with adiscretely changing magnification we can used the earlier described twocomponent telescopic systems with a constant magnification by the turnof the system in general is used to receive two values of magnification.
Or in the three component systems, each component is a group of lenses,
one of the components have to be moved, under strictly certain law which
will provide the magnification with the discrete step. The advantage ofsuch systems undoubtedly is relative simplicity of a calculation and arealization. And the impossibility of use of these systems in conditions
where a smooth magnification is required will be a shortcoming.
This work is devoted to receipt of the last type of telescopic systems withthe smooth variable magnification, with a possibility of their application ina wide range of wavelengths covering visible and near infrared area of arange, that today will be an urgent task, especially if it turns out to reachthe system of this sort, with highly resolving power. The main complexity
in case of synthesis of this type of the systems is stabilization not only
the planes of a subject and an image, but also preserving a positionof an entrance and an exit pupils, especially if the system is a part ofa more difficult system. Initially the shift of a component shall lead tochange of the size of the image, but also with preserving the plane of its
registration. Thus, calculating this type of the systems the following tasksarise:
1. The various realization of the primary scheme are possible because
it consists at least of three components. Originally it requires choosing
the optimum primary scheme which will be able to provide the higher

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Conference 10335:
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characteristics of the optical system. For providing required magnification
the moving component has to be chosen.
2. the optical materials, which will be able to provide a transmission of thewide spectral range, ought to be determined.
3. The design data of the optical system ought to be calculated.
4. The law of a movement of the moving component, for providing
required magnification has to be determined.
5. The analysis of quality of the received image, in case of all provisions of
the moving component.
6. Admissions for elements of the received optical system have to be
calculated.
7. Comparison of the received law of the movement of the chosen second
component, with an opportunity its implementation in a real frame of thedevice.
In the course to work various circuit decisions for further work andimplementation were considered. The three-component system with amoving negative central component containing the lens which is also
moving according to the separate law concerning the all component waschosen. Optical materials for further work and implementation whichhave high transmission capacity in visible and infrared spectral ranges andavailable from catalogs Schott and also which would be able to be madeat the Lytkarinsky factory of optical glasses were also chosen. Primarycalculation of the design data of components of the telescopic opticalsystem, taking into account the chosen optical materials is at the moment
carried out.

10335-71, Session PS2

Ghosting images processing methods for
dynamic aberration detection in imaging
systemsYi Yang, Hefei Institutes of Physical Science (China) andNational Univ. of Defense Technology (China) and Univ.
of Science and Technology of China (China); Quan Sun,
National Univ. of Defense Technology (China); Xuanzhe
Zhang, Hefei Institutes of Physical Science (China) andNational Univ. of Defense Technology (China) and Univ.
of Science and Technology of China (China); Shaojun
Du, Baozhu Yan, National Univ. of Defense Technology(China)For decades now, adaptive optics technique has played a tremendous rolein many areas, such as laser propagation in the atmosphere, astronomical
object imaging, eye medical treatment, etc. As a key component in theadaptive optics, the detecting errors of wavefront sensors is a major error
source.
Wavefront reconstruction is based on light-spots centroid location in
the application of conventional Hartmann-Shack (H-S) waveront sensor.
Nowadays, the design of optical system becomes more and more
complex with increasingly demanding on imaging performance andmultispectral imaging sometimes. That way, multiple reflections fromoptical elements, or paraxial stray light from operating environment
may cause double images (ghosting) in part of sub-aperture of H-S
wavefront sensor, resulting in centroid detection errors, and so loss of the
precision of wavefront reconstruction might occur. Of course, optimum
design of optical coating and opto-mechanical structure can generator
less ghosting to some extent, which can’t eliminate completely thehidden trouble nevertheless. On the other hand, a suitable image digitalprocessing technique can also diminish the effect of background noise or
ghosting. At present, the threshold method is commonly used. Ghosting
can been brought under effective control by this way, which leads to theloss of available information of light-spots in the meanwhile, especiallyhigh frequency information and leads to centroid detection errors.
This paper begins with the theoretical model analysis of various image
processing techniques, conventional threshold method, convolution
method, correlation algorithm and spectral-filter method included. And
then, a numerical simulation platform is established which aiming at the
research in the influence of ghosting images processing on wavefront
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relative slope measurement errors of wavefront are tested in thecomparative trials with different image processing algorithms. A improved
methods is proposed by combining several algorithms, and the simulation
results and practical application show that more available informationof light-spots are kept through this way, which improves the accuracy of
centroid detection and extends the applicability of H-S wavefront sensor.

10335-72, Session PS2

Optical power transmission in a polygon
mirror-based swept source opticalcoherence tomography system
Mike Everson, Univ. of Kent (United Kingdom); Virgil F
Duma, Universitatea Aurel Vlaicu (Romania); George M
Dobre, University. of Kent (United Kingdom)
Optical Coherence Tomography (OCT) has a broad range of applicationsin 2D and volumetric, non-invasive imaging of micron scale structures,
typically used to investigate the detail of tissue layers at different
depths (retina, eye anterior, skin, larynx etc.). This application requires
fast imaging speeds and high resolutions if it is to be used as a medical
diagnostics tool.
In Swept Source OCT (SS-OCT), generally favoured for its faster operating
speeds compared to Spectrometer Based OCT, the imaging speed
is governed by the sweeping frequency of the source and the axial
resolution is given by the total bandwidth generated.
We performed this study on a Polygon Mirror based SS-OCT system.
Our sweeping configuration employs a mechanical method that enables
a broad (100 nm) spectrum of light to be reduced to tunable narrowband windows of width ??, which are individually selected through theuse of a dispersive element (diffraction grating), a rotating polygon
mirror and two achromatic lenses arranged telescopically in a Littman
configuration (Fig. 1). After the polygon the beam is returned from a fixed
end retroreflector (mirror). The rotation of the polygon mirror ensuresthat only light in a small range of wavelengths is coupled back in theoriginating single mode fibre at any one time and that this condition issequentially fulfilled over the angular sweep range of the polygon.
Through theoretical development, ray-tracing modelling andmeasurement, this paper specifically addresses the geometric andradiometric vignetting associated with the spectrum reflected from anindividual polygon mirrored facet (Fig. 2) and how this may impose
limitations to the incident beam size and hence lead to variations andlosses in the peak power available in the tunable spectral line, as well as
the linewidth variation throughout the scanned spectral range.
Simulations were carried out using ZemaxTM ray-tracing software. The
incident spectrum was split into 11 equally spaced wavelength windows
over a bandwidth range of 125 nm centred at ?_c=1350 nm. Although
this range is greater than that of the Semiconductor Optical Amplifier
used in our system, its analysis offers an insight into the total wavelength
acceptance range of our optical design. For each wavelength window,
a suitably chosen polygon mirror angle maximised throughput at thatwavelength to the end reflector, ensuring normal incidence. This allows
the beam to return into the fibre along substantially the same path.
Calculations were also carried out on the beam propagation after
the diffraction grating, assisted by the tracing of beams centred atwavelengths from ?_max to ?_min and covering the entire spectrum,
through the Littman configuration in both directions. We found that,at the midfocal plane of the telescope, the function h(?) describing
the deviation of the chief ray of each constituent wavelength from thetelescope’s optical axis exhibits non-linearities.
Collimated light propagating through the telescope is subject to changes
in beam diameter dictated by the relative focal lengths of the lenses used.
This has an impact on the shape and size of the spot on the polygon
mirrors facets, which has an effect on the overall amount of vignetting
the system experiences in each wavelength window. Our theoreticaldevelopment of the function W_2 (?) gives the ideal beam width on thepolygon mirror facet based on the grating constant and the incident
beam diameter, W_0, exiting from the collimator prior to lens 1. Our
simulation agrees with the theoretically predicted beam cross-section
at lens 1 but differs non-linearly from those on lens 2 due to the inherent
aberrations experience by the light passing through lens 1. W_2 decreases·

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Conference 10335:
Digital Optical Technologies
and then increases again past a local minimum with a wavelength ?>?_c.
The beam strikes the polygon facet at an angle between 42° and 48°
producing an elliptical spot for a circular incident beam. When the beam
is not homogeneous the shape of the ellipse changes and contributes in avariable fashion to the amount of vignetting and hence to the proportionof light successfully reinserted back into the originating fibre.
Our results suggest that wavelengths near the centre of the spectrum
experience higher losses than those further out with the exception of thelight at the very edge of the spectrum, but this effect can be mitigatedby small axial adjustments in the location of the telescope lenses which
can be used to reshape the swept spectrum. However, we show that oursimple telescope design cannot, on its own, result in a spectral envelopewith a flat ceiling throughout the full range.
These non-linearities, in combination with facet vignetting and lensaberrations, contribute to a complex light coupling efficiency functionthat leads to light losses and non-uniformities in the swept spectrum, andalso a reduction in the effective swept range to around half of the initial
bandwidth of the Semiconductor Optical Amplifier.

10335-73, Session PS2

A digital filtering algorithm fast
implementation based on Catapult C
Zhang Ye, Beijing Institute of Space Mechanics andElectricity (China)
With the increasing complexity of the algorithm in optical remote sensing
camera video real-time data processing, direct design by hardware
description languages becoming more and more difficult. By using
EDA tools, directly convert complex algorithms described by high-level
language into RTL code as described in HDL language. The design
choices of Catapult C tool to complete the digital filtering algorithm fromthe C language to RTL design. Finally verify designed by Catapult for RTL
code with c, Matlab function consistent. After hardware implementation
performance, the design speed faster than the direct use of hardware
description language several times to several times.

10335-74, Session PS2

Medical photoacoustic beamforming
using minimum variance-based delay
multiply and sum
Moein Mozaffarzadeh, Ali Mahloojifar, Mahdi Orooji,
Tarbiat Modares Univ. (Iran, Islamic Republic of)
Photoacoustic (PA) imaging is a promising biomedical imaging modality
with the capability of providing Ultrasound (US) resolution and opticalcontrast. When a short duration laser pulse illuminates the tissue asa target of imaging, tissue induces US waves based on thermoelastic
expansion and reflected waves at the detectors can be used toreconstruct the optical absorption distribution. Since the receiving part of
PA consists of US waves, most of the US beamforming algorithms can beapplied on PA imaging. Due to the simple implementation and the robust
performance, Delay-And-Sum (DAS) is treated as the most common
beamforming algorithm in US imaging. However, it suffers from limited
resolution and high levels of sidelobe. To address these problems, a newalgorithm namely Delay-Multiply-And-Sum (DMAS) was introduced. In
DMAS, similar to DAS, corresponding samples for each element of arrayare calculated based on delays, but before the summation, samples
are combinatorially multiplied, which can be interpreted as the crosscorrelation of the received signal at the elements of the array. In thispaper, a modified version of DMAS beamforming algorithm is introduced
based on Minimum Variance (MV) adaptive beamforming method namely
Minimum Variance-Based DMAS (MVB-DMAS). It is shown that expanding
the DMAS algorithm results in some terms where every term contains a
DAS algebra. Since DAS is a simple algorithm with low levels of off-axis
signals rejection, it is proposed to use MV adaptive beamformer insteadof existing DAS algebra inside DMAS expansion. Numerical simulations for
one-point and two-point targets are presented using proposed algorithm,
DAS, DMAS and MV beamformers. Lateral variation for three depths of24

imaging in two cases of simulation is presented. Resolution and levelsof sidelobe are evaluated and it is shown that using MVB-DMAS leads
to valley of lateral variation reduction in all depths of imaging, which isregarded as the resolution enhancement. In other word, two points in
two-point target are more distinguished and pronounced using MVBDMAS in compare to other mentioned beamformers. In particular, forreconstructed image at depth of 70 mm, MVB-DMAS results in 26.96 dB,
20.55 dB and 17.88 dB reduction in case of valley of lateral variation incompare to DAS, DMAS and MV, respectively. Also, MVB-DMAS ends inlevels of sidelobe reduction which is regarded as contrast enhancement
and for another instance, for depth of 70 mm, it can be perceived thatlevels of sidelobe are reduced using MVB-DMAS for about 20 dB, 13 dB
and 12 dB in compare to DAS, MV and DMAS, respectively. To make aquantitative comparison of mentioned beamformers, Full-Width-HalfMaximum (FWHM) in -3dB, is presented. It is shown that MVB-DMAS
results in FWHM improvement in all depths of imaging. Considering depthof 60 mm, MVB-DMAS leads to 347 µm, while DAS, DMAS and MV resultin 3836 µm, 2217 µm and 349 µm, respectively. It should be noted that allthese enhancements are achieved at the expense of higher computationalburden.

10335-75, Session PS2

An adaptive weighted Lp metricfor optimal margin classification: atheoretical framework for optical remotesensing data
Sawon Pratiher, Indian Institute of Technology Kanpur(India); Vigneshram Krishnamoorthy, National Instituteof Technology, Tiruchirappalli (India); Paritosh
Bhattacharya, National Institute of Technology, Agartala(India)The rapid advancement in high-resolution remote sensing applications
escalated the complexity of data diversity and higher oder dimensionality
features. As such, the efficacy of any optical data sensing problems
depends on the adequacy of the distance metric used for inter-sample
distance computation of the remote sensing feature vectors, while
taking into account of the wide variety of probability distributions ofremote sensing data along with the inherent problems of optical source
separation, background noise and outliers. The challenges of optimal
mapping, varying feature index homogeneity and feature classificationby combining distance metrics stems from the work of Chen, Lei, andRaymond Ng’s time series analysis by fusion of metrics to handle local
time shifting while improving the accuracy and log-likelihood significanceof data correlations and noise disassociation by means of a linear
transformation is the sole motivation of this work.
In this contribution, a novel incremental learning methodology combining
the Mahalanobis and the Minkowski distance metrics along with cosine
similarity was proposed to exploit the prior statistical entropy anddiversity of optical remote sensing data for maximal inter-sample andminimal intra-sample separation. The robustness to outliers and scalevariation sensitivity, while accounting for the statistical heterogeneity
and non-isotropic reciprocity in the remote sensing feature componentsof hyperspectral imaging and remote sensing data have been explained.
The fact that the scale invariance Mahalanobis distance accounts for thecovariance of the feature vectors and rectify the data heterogeneity isused for disassociating the correlated feature components and weighing
the different dimensions according to their statistical feature variations
is used for generating the modified remote sensing feature space. Whilethe combination of the cosine similarity signifying the degree of featurecohesion within the data clusters and the Minkowski metric gives a
convex objective function subjected to convex constraints has been used
for learning an adaptive metric of the feature space for maximal marginclassification.
The conceptual architecture for the optimality criterion for learning
optimal feature weights and the optimal Minkowski exponent, ‘p’, with its
adaptiveness through semi-definite convex optimization for calculating
the upper and lower bounds of the objective function have been shown.
Theoretical proof of the optimal metric along with the optimal parameters
bounds validates the suitability of the proposed metric in optical remotesensing applications.

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Conference 10335:
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10335-76, Session PS2

Statistical classifiers on multifractal
parameters for optical diagnosis of
cervical cancer
Sabyasachi Mukhopadhyay, IISER Kolkata, India (India);
Sawon Pratiher, IIT Kanpur (India); Rajeev Kumar,
NIT Allahabad (India); Vigneshram Krishnamoorthy ,NIT Trichy (India); Asima Pradhan, IIT Kanpur (India);
Nirmalya Ghosh, Prasanta K. Panigrahi, IISER Kolkata(India)
The augmented multifractal parameters provide better noise immunity,stability and discrimination for segregation of normal and precancerous
elastic scattering spectroscopic data. The introduction of multiple
distortion features to characterize the multifractal spectrum supplement
the efficacy of MFDFA for heterogeneous dynamic of tissue abnormalities.
In this contribution, the adequacy of geometrical attributes of theMultifractal spectrum with a proposed set of novel features for apotential biomarker for optical diagnosis of cancer is performed.
Different classifiers are trained with the obtained features to compare
the sensitivity and specificity for cervical cancer detection. The statisticalclassifiers with accuracy of 84.17% validate the adequacy of multi-feature
MFDFA characterization of elastic scattering spectroscopy for cancer
diagnosis.

To resolve the above issues, recently we have developed a method
named Regenerated Phase-Shifted Sinusoids assisted EMD (RPSEMD)
which is very powerful for nonstationary signal processing. To meetwith the requirement of both accuracy and efficiency, we also extend
this algorithm to 2D space, i.e., the sinusoids-assisted bidimensional
EMD (SBEMD). These sinusoids-assisted EMD (SEMD) methods havebeen proved efficient and accurate for fringe analysis to retrieve phase.
Because the mode mixing problem is solved, a fringe pattern can be
decomposed into a series of intrinsic modes that carry clear physicalmeaning, and then different modes can be processed combined withdifferent frequency-spectra analysis. In this sense, we sufficiently used
these SEMD methods to construct the for practical SFPP system, whichis called SEMD profilometry (SEMDP): we propose a fast and convenientcalibration method based on the SBEMD fringe analysis; we also propose
a fast and robust phase unwrapping method based on the qualityguided maps using SBEMD combined spiral HT; furthermore, we try tocorrect the system error through the pre-code method also using thetime-frequency-spectra of the SBEMD combined with the HT. Comparedwith the PSP and FTP, the developed SEMDP shows much superiority forpractical use, such as high automation, high speed, satisfactory accuracy
and strong robustness.

10335-47, Session 1010335-35, Session 10

High-resolution LCOS microdisplay with
sub-kHz frame rate for high performance,high precision 3D sensor
Grigory Lazarev, Stefanie Bonifer, Philip Engel, HOLOEYE
Photonics AG (Germany); Daniel Höhne, GuntherNotni, Fraunhofer-Institut für Angewandte Optik undFeinmechanik (Germany)
We report the implementation of the LCOS microdisplay with 1920 by
1080 resolution and 720 Hz frame rate. The driving solution is FPGAbased. The input signal is converted from the ultrahigh-resolution HDMI
2.0 signal into HD frames, which follow with the specified 720 Hz frame
rate. Alternatively the signal is generated directly on the FPGA withpattern generator. The display is showing switching times below 1.5 ms(rise plus fall) for the selected working temperature. The bit depth of theaddressed image achieves 8 bit within each frame. The microdisplay isused in the 3D sensing system, implemented by Fraunhofer IOF.

10335-46, Session 10

Sinusoids-assisted empirical mode
decomposition profilometry
Chenxing Wang, Feipeng Da, Southeast Univ. (China)
Fringe projection profilometry has been a popular means for 3D surface
measurement. As some group published, phase-shifting profilometry(PSP) has already been mature to a certain extent. However, thismeasures is always constrained by the high-speed hardware equipment
if the measured object is moving. Single fringe projected profilometry(SFPP) has been researched for a long time, but the well-known Fouriertransform profilometry (FTP) can only measure the simply constructedsurface. To measure complex objects, the windowed FT (WFT), Wavelet
transform (WT) and etc. are researched to achieve better accuracy,
nevertheless these methods are either limited by the low efficiency
or constrained by poor ability of time-frequency analysis due to theuncertainty theory. Hilbert-Huang transform (HHT) is an effective timefrequency-spectra analysis tool, where the Empirical Mode Decomposition(EMD) is the core of this method providing as a spatial filtering. Recently
the EMD methods are frequently used in SFPP, especially for fringe
pattern analysis. Among the published methods the Trusiak’s automatedReturn to Contents

selective reconstruction based on enhanced fast EMD (ASR-EFEMD) is
outstandingly excellent because of the great efficiency and effectiveness.
However, this method needs many artificial interventions, and in addition,
it avoids solving the tricky mode mixing problem and hence can hardly be
used in practice for SFPP if the measurement environment is complicatedthat may cause low-frequency mode mixing.

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Phase unwrapping in fast fringe
projection profilometry
Haixia Wang, Rou Peng, Xicheng Yang, Zhejiang Univ. ofTechnology (China)
Fringe projection profilometry (FFP) has become one of the most popular
3D information acquisition techniques being developed over the past
three decades. In FFP, phase unwrapping is a critical step in acquiring thecorrespondence information for 3D reconstruction. Unlike traditional FFP
which uses methods such as temporal phase unwrapping, high-speed
real time measurement FFP systems require phase unwrapping of single
phase image probably with discontinuous objects. Phase unwrapping inFast FPP such brings three difficulties, the separation of discontinuous
wrapped phases, the unwrapping of each wrapped phase and theconnection of the discontinuous phases. During FFP measurement ofmultiple objects. They may be positioned in different depths but with
their phase maps located side by side. Object separation based on themodulation values could not well identify the discontinuous boundaries.
In this paper, the object separation based on phase modulation is adapted
first to remove the background and separate isolated wrapped phases.
For each isolated wrapped phase, discontinuous phase separation based
local orientation coherence is further used to identify the existence of
discontinuous boundaries. After the separation, spatial unwrapping
method is applied to each wrapped phase segments. We proposed anoriented unwrapping method that unwrap the phase along the direction
perpendicular to the fringe orientation to minimize the error caused
by noise. In the last, each continuous phase segments need to correct
identify their corresponding positions before used for 3D reconstruction.
A grid line is projected to establish the relative positions. Experimental
results show that our algorithm works well for multiple and overlapping
object measurement10335-48, Session 10

Feature selection from hyperspectral
imaging for guava fruit defects detection
Mohamad Zubir Mat Jafri, Sou Ching Tan, Univ. Sains
Malaysia (Malaysia)
Development of technology makes hyperspectral imaging commonlyused for defect detection. In this research, a hyperspectral imaging·

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Conference 10335:
Digital Optical Technologies
system was setup in lab to target for guava fruits defect detection. Guava
fruit was selected as the object as to our knowledge, there is fewer
attempts were made for guava defect detection based on hyperspectral
imaging. The common fluorescent light source was used to represent
the uncontrolled lighting condition in lab and analysis was carried out
in a specific wavelength range due to inefficiency of this particular lightsource. Based on the data, the reflectance intensity of this specific setup
could be categorized in two groups. Sequential feature selection withlinear discriminant (LD) and quadratic discriminant (QD) function wereused to select features that could potentially be used in defects detection.
Besides the ordinary training method, training dataset in discriminant was
separated in two to cater for the uncontrolled lighting condition. These
two parts were separated based on the brighter and dimmer area. Four
evaluation matrixes were evaluated which are LD with common training
method, QD with common training method, LD with two part training
method and QD with two part training method. These evaluation matrixes
were evaluated using F1-score with total 48 defected areas. Experimentshown that F1-score of linear discriminant with the compensated method
hitting 0.8 score, which is the highest score among all.

10335-50, Session 11

Axial-resolution in depth from focus
digital holography
Joseph van Rooij, Jeroen Kalkman, Technische Univ.
Delft (Netherlands)
Sub-mm single shot depth resolved digital holography. Digital holography
enables absolute distance measurements and full-field quantitative
depth resolving of objects from a single image capture. This has been
demonstrated in the past by calculating over a set of reconstruction
distances a focus metric, such as variance of the intensity, for each pixelof the image. The distance where the focus metric peaks is an estimate
for the distance from the object surface to the recording medium. This
enables full-field optical depth resolving from a single holographic image,over distances from a few centimetres up to the coherence length of alaser source, a range traditionally not accessible for techniques such as(white light) interferometry or optical coherence tomography. However,currently the limit on the depth resolution lies in the order of a centimeterand is an obstacle to application of this technique to microstructure
analysis. Furthermore, the limits of the resolution using this method havenot been investigated.
We demonstrate from theory and experiment that the resolution canreach to the sub-mm level. We analyse the dependence of the varianceas a function of the spatial frequency content of the object. The variancecurve as a function of reconstruction distance can be represented as
the sum of variance curves over all spatial frequencies contained in theintensity image. Due to the Talbot-effect, each individual curve associatedwith a single spatial frequency is periodic, hence, summation over allthese curves gives a single maximum which is well defined in the sub-mm
range. Based on our Talbot-representation, we also show that the focus
curve has an inherent broadness regardless of the spatial frequencies
present in the image, which defines the resolution limit of this depth
resolving method. We experimentally validate our findings by resolving
an object with multiple reflecting layers located at different depths. A
Michelson interferometer setup is used in the acquisition of the hologramsand 100 micron axial resolution is achieved. This is approximately 50
times better than previously reported and opens opportunities forcharacterising high resolution single shot surface topography of objects.
We envisage applications of this technique in the study of art objects andin machine vision quality control.

10335-52, Session 11

Optical sound wave recording by digitalholography with heterodyne technique
Xiangyu Quan, Sudheesh K. Rajput, Kouichi Nitta, Osamu
Matoba, Kobe Univ. (Japan); Yasuhiro Awatsuji, Kyoto
Institute of Technology (Japan)
Visualization technique gives us the important information to see the26

behavior and to understand the mechanism of the physical phenomena.
Sound wave is one of the invisible phenomena for human, but it isuseful for many applications such as communication, damage detection,
ultrasound imaging, sonar, SAW devices. Real-time measurement andvisualization of the propagating sound wave is a challenging theme for
optical sensing.
We proposed an optical voice recorder and a sound wave recorder basedon digital holography [1]. Sound wave propagation modulates temporally
and spatially the refractive index of the air. In proposed technique, thespatial and temporal phase distributions of an optical wave are recodedby an off-axis digital holography by a high-speed image sensor when
the optical wave is modulated by the sound wave propagation. In theprevious demonstration, a tuning fork operated at 440 Hz was recordedby an image sensor with a frame rate of 2000 frames per second (fps) [1].
To record the sound wave, it is required to use a high-speed image sensor
that can record the holograms with more than two times faster than thefrequency of the sound wave. This limits the observation frequency rangeof the sound wave. For engineering applications, the frequency up to
Megahertz is required to observe the propagation of ultrasound waves.
In this presentation, we propose a method that uses a heterodyne
technique for increasing the observation frequency range. For theheterodyne interferometer, the reference wave is modulated by apiezoelectric mirror. By tuning the frequency of the piezoelectric mirror,
the central frequency of the observed sound wave can be changed. In theexperiment, a tuning fork operated at 440 Hz is observed by an image
sensor operated at 10 fps. The experimental results indicate that thedifferent frequency can be obtained. We will present different frequencyof tuning forks and human voices.
Reference
1. O. Matoba, H. Inokuchi, K. Nitta, and Y. Awatsuji, “Optical voice recorderby off-axis digital holography,” Optics Letters, Vol. 39, Iss. 22, pp.
6549–6552 (2014).

10335-53, Session 11

Spectrally resolved digital holographyusing a white light LED
Daniel Claus, Giancarlo Pedrini, Dominic Buchta,
Wolfgang Osten, Univ. Stuttgart (Germany)
Several imaging techniques, such as OCT or digital light-in-flightholography, take advantage of low temporal coherence to examine
three-dimensional objects. The use of a short coherence source in digitalholography allows optical sectioning and hence enables the separationof light coming from different planes of the sample under investigation[1]. Due to the short coherence, the interference is just observed when
the optical path lengths of reference and object beams are matched.
In addition, shape measurement can be performed when selecting two
or more quantitative wavelength reconstructions in order to generate
a synthetic wavelength, which is of the magnitude of the object underinvestigation [2].
The spectral information can be used to study microscopic objects, suchas described in [3], where a supercontinuum fibre laser (wavelength
range 0.45 to 2 µm) has been employed.
We will demonstrate that digital holography using a broadband source(white light LED) can provide spectral information and also be used for
optical sectioning and metrology. Furthermore its application to biologicaltissues can provide the capability of cells or tissue discrimination.
A Mach-Zehnder setup has been used for recording spectrally resolved
digital holograms in combination with a white light LED source, see Fig.
1. The spatial coherence has been increased by placing a pinhole of 25µm diameter directly in front the emitting surface of the LED. The lightleaving the pinhole is divided into two arms (reference and object beam).
After interaction with the sample, the object beam is superimposed withthe light coming from the reference beam. Due to the large spectral
width of the white light LED (ranging from 400-700nm) interferenceis only observed within a short axial range of theoretically less than amicron, at which both path lengths are perfectly matched. After carefully
matching the optical path lengths of both interfering arms, a mirror
mounted on piezoelectric actuator is moved to introduce a path length
difference between the two beams. The length of the reference beam

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Conference 10335:
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is consecutively changed (typically step of 100 nm) by moving the PZT
and after each step a hologram is recorded. Typically more than 1000
holograms are recorded and stored in a stack. If we consider a single
pixel in each hologram and plot its value along the z-direction, a signal
describing the temporal changing interference is obtained, as shownin Fig. 2. Since the LED used has low temporal coherence only within asmall range an interference appears. The information about the spectrumof the light after passage through the sample can simply be obtained
via a Fourier transformation along the z-axis. The complex spectral
information is equally spaced with regards to the wavenumber, whichcorresponds to the reciprocal value of the wavelength. In that manner, awavelength or a wavelength range can be selected and by inverse Fouriertransform the amplitude and phase along the z-axis is obtained. This
process is repeated for each pixel of the stack, enabling the recovery ofspectrally resolved modulus and phase information for shape and spectral
measurement.
[1] L. Martínez-León, G. Pedrini, and W. Osten, “Applications of shortcoherence digital holography in microscopy,” Appl. Opt. 44, 3977-3984(2005)[2] D. Carl, M. Fratz, M. Pfeifer, D. M. Giel, H. Höfler, “Multiwavelength
digital holography with autocalibration of phase shifts and artificial
wavelengths,” Appl. Opt. 48, H1-H8 (2009)[3] G. Kalenkov, S. Kalenkov und A. Shtanko, „Hyperspectral holographic
fouriermicroscopy,“ Quantum Electronics, Bd. 45, Nr. 4, pp. 333-338, 2015.

10335-54, Session 11

Ptychographic phase retrieval byapplying hybrid input-output (HIO)
iterations sequentially
Sander Konijnenberg, Technische Univ. Delft(Netherlands); Wim Coene, ASML Netherlands B.V.
(Netherlands); Silvania Pereira, Hendrik P. Urbach,Technische Univ. Delft (Netherlands)
Coherent diffractive imaging (CDI) is a technique that can be used toimage an sample without having to use lenses. Especially for X-ray
imaging this may be useful, since the reconstructed image will not suffer
due to low-quality focusing optics. One particular method for CDI is
ptychography, in which the probe that illuminates the sample is shifted todifferent positions, and for each position a far-field diffraction pattern isrecorded.
To reconstruct the sample, the Ptychographical Iterative Engine (PIE)applies iterations of the Error Reduction (ER) algorithm for each probe
position sequentially. However, it is well known that the Hybrid InputOutput (HIO) algorithm outperforms ER. The difference between HIO and
ER is that HIO uses a feedback function that improves convergence tothe correct solution and avoids stagnation. Also, PIE is known to performbetter when the updates of the reconstruction are applied for each probe
position sequentially, rather than updating the entire reconstruction at
once each iteration.
In this research, we have designed a ptychographical algorithm (HIO-PIE)
in which HIO iterations are applied for each probe position sequentially.
The important insight is that for each probe position a separate HIOfeedback function needs to be introduced, which is to be stored
separately from the reconstructed image. With simulations we compared
our proposed algorithm (sequential HIO-PIE) to three other algorithms
that were already known from the literature: sequential PIE, simultaneous
PIE, and simultaneous HIO-PIE. We compared the algorithm for the noisefree case as well as for the case of shot noise. Also, we compared theirePIE (extended PIE) variants which reconstruct the object and the probe
simultaneously (thus making the image reconstruction robust against
unknown aberrations in the probe).

10335-55, Session 11

Imaging particles in full 3D parallax modewith two-wavelength off-axis Fresnel
holography
Pascal Picart, Univ. du Maine (France); Soumaya KaraMohammed, Univ. du Maine (France) and Univ. Ferhat
Abbas de Sétif (Algeria); Larbi L. Bouamama, Univ.
Ferhat Abbas de Sétif (Algeria)
Digital holography and digital holographic microscopy are techniques
for recording and reconstructing three-dimensional images of objects.
The principle is to directly recording a hologram with an image sensor
CCD sensor and then reconstructing it digitally with a computer. Actually,
holographic digital imaging provides a 2.5D image because it lacks
parallax by the fact that digital holography is not able to “see behind theobject”. In particular, this property is a limiting factor for the imagingof particles when the number of particles is high. It is then not fully
possible to discriminate 2 particles aligned along the axis of the sightview. An alternative approach is to increase the number of sight views
but without multiplying the number of sensors. In this context, Boucherit
et al described a two-view technique based on angular multiplexing
using a single reference beam which makes it possible to discriminate
along the propagation axis. The technique has the disadvantage that the
spatial multiplexing performed by the coherent mixing of the 3 waves (2views and a reference) does not always lead to a clear separation of thediffraction orders. In addition, in the Fresnel configuration, the distance
between sensor and particles has to be increased to permit a correct
separation of the orders. This leads to a decrease in the spatial resolutionof the reconstructed images of the particles. In order to overcome such
limitations; this paper proposes an approach based on 2 sight of views
and 2 wavelengths. The advantages of using two wavelength is that there
will be no cross mixing between diffraction orders and that the reference
waves can be adjusted separately. So, independent adjustment of thespatial frequencies of the two reference waves leads to a very good
separation of diffraction orders.
In this set-up, two wavelengths illuminate the region of interest (tankfilled with water and particles) along two orthogonal directions. Spatiochromatic multiplexing makes it possible to encode the information ona single two-color digital hologram. Recording of color holograms is
performed using a 3CCD sensor from Hamamatsu with 1024x1344 pixels
having pixel pitches at 6.45?m and 8-bit digitization. In the set-up the
distances from the useful area to the sensor depends on the wavelengthand they are not the same. So, digital holographic reconstructions mustbe performed for different wavelength. It follows that in order to provide
the full 3D location of any particle in the tank, the field of views must havethe same set of reference axis along the two views. In this set-up, the Yaxis must be the same along the two views, whereas the X axis is the 2nd
axis of the blue line and the Z axis that of the green line. Since the same
sensor is used to detect both wavelengths, sampling along X and Z axis
is rigorously identical. A calibration has to be carried out to ensure thatthe set of reference axis along the two view have the same (0,0,0) center
point. To do this we propose a calibration method based on the Fourier
modulation theorem to identify the position of any particle in a single
XYZ frame.
The set-up is applied to the study of 3D trajectory of particles moving in
the tank. Experimental results are provided and confirm the suitability ofthe proposed approach.

Simulations indicate that sequential HIO-(e)PIE tends to outperform (e)PIE even in the presence of shot noise, especially when the number ofprobe positions is small. Thus, this adaptation may reduce the numberof scan positions required for a successful image reconstruction, thereby
relaxing the constraints on an experimental setup.

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