Optical Engineering

Optical Engineering

  • Happiness xu added an answer:
    How can I measure the azimuth angle of an elliptically polarized light?

    I want to measure the azimuth angle of a elliptically polarized light. Could you give me some suggestions?

    Happiness xu · China University of Mining Technology

    Thank you very much for your suggestions! However, according to these suggestions, the principle axis of a optical fiber ( x or y axis) should be determined firstly, which is difficult.

  • Parviz Parvin added an answer:
    Is it possible to perform some experiment to understand if LASER is based on 3 level or 4 energy level model?

    If it is possible, can anyone suggest an experiment which can allow understanding if laser is based on 3 level or 4 energy level model? For example, for LASER Nd:YVO4. Thank you in advance.

    Parviz Parvin · Amirkabir University of Technology

    "Gain is linear in 4-level system" Alexandr wrote:

    To which parameter is the gain linear? pumping rate, input intensity, or dopant concentration ?

  • Haiwei Chen added an answer:
    Can anyone recommend best books in terms of quality and simplicity of explanations for liquid crystal tunable lens design?

    I would like to know what is being done in this area to understand if that can be relevant to my research.Thank you in advance!

    Haiwei Chen · University of Central Florida

    http://onlinelibrary.wiley.com/doi/10.1002/9781118270080.ch6/summary

    check this one. it was written by H. Ren and S.T. Wu.

  • Gwendal Beauvois added an answer:
    What is the influence of pre-irradiation defects on RIA of optical fibres?

    The prep-irradiation defects like some impurities can enlarge the linear attenuation of the fibre.
    But how this defect impact on the RIA?

    thx

    Gwendal Beauvois · Université de Perpignan

    so, can i imagine to put a maximum defects while the fabrication in order to maximise the sensibility of my finer ? if yes, how can i control during the drawing for this.

  • Parviz Parvin added an answer:
    Is it possible to make a simple optical set-up to reduce the spectral width of a laser source?

    Laser light is not fully monochromatic so is it possible to reduce its spectral width without using any monochromator?

    Parviz Parvin · Amirkabir University of Technology

    Tunable lasers handbook, I do not have the other!

  • Sara Liyuba Vesely added an answer:
    What is the physical meaning of the modulation transfer function (MTF)?

    Can somebody explain in the simple terms the physical meaning of the MTF?
    How does a turbulence in the air (atmosphere) affects on the MTF?
    How does the optical aberrations affect on the MTF?

    Sara Liyuba Vesely · itb cnr

    In my opinion, when stars are observed, the OTF is equivalent to the Airy disk. The latter corresponds to the first diffraction maximum of the telescope aperture. When the lens forms an image of a nearby object on a screen, its aperture forms a diffraction image on the same screen.

    MTF is a generalization of OTF -- valid for frequencies other than the optical range -- in the same way as an effective aperture is associated to a horn or reflector antenna.

    I suppose that your second question draws on an analogy of light with sounds. In that case a small paper disk is used to measure the direction of a sound field. In that analogy turbulence, as well as aberration cause distortion.

  • Yoon-Soo Jang added an answer:
    What's the working principle of micro channel plates (MCP) Photomultiplier tube (PMT)?

    Why it's so special compared to traditional PMT? Why it can't respond to high repetition rate (tens of MHz) and need to be pulse picked to low down the repetition rate (~ tens of kHz)?

    Yoon-Soo Jang · Korea Advanced Institute of Science and Technology

    It takes a time to multiply photon in MCP.

  • Maria Dienerowitz added an answer:
    Can anyone recommend best books in terms of quality and simplicity of explanations for optics implementation in the LABVIEW?

    Most of the simulations I perform in the MATLAB, so I almost not familar with LABVIEW, but It is a tool that can be very useful. I am mainly interested in the books describing the implementation of the Imaging (3D imaging, Hyperspectral imaging and Holography) in the LABVIEW. Thank you in advance!

    Maria Dienerowitz · University of Glasgow

    Hi Vladimir,

    for inspiration you can take a look at our group's software page. We have used LABVIEW extensively to run our optical trapping experiments but also to analyse data. It might not be directly your field but maybe worth a look.

    http://www.gla.ac.uk/schools/physics/research/groups/optics/research/opticaltweezers/software/

    Maria

  • Mina Esmaeelpour added an answer:
    How can I obtain the Fundamental Mode in an Octagonal solid core Photonic Crystal Fiber?

    I am simulating an Octagonal Photonic Crystal Fiber by Comsol. It is desired to extract some properties such as Dispersion, Confinement Loss and Effective Area vs. wavelength. For this purpose, I should obtain the Effective Refractive Index and Field Distribution for the Fundamental Mode. The Structure is a Solid-Core PCF (silica core n=1.45 and air holes n=1).
    How I can reach to the Fundamental Mode?

    Mina Esmaeelpour · Lehigh University

    Normally, fundamental mode has the highest group velocity, meaning the lowest n_eff. I recommend chapter 09 of the book below which is made available online by the authors.

  • Vladimir Farber asked a question:
    What are the limitations of the Linear Canonical Transformation (LCT) in the practical optical system modeling?

    Linear canonical transformation is the useful tool for the light propagation description. When we prefer to use it for light propagation description? And when we prefer not to use it?When it is valid and when not? Thank you in advance.

  • David Compertore added an answer:
    Can somebody answer on few clarifying questions about Hartmann-Shack sensor?

    I have a few clarifying questions, that I want to ask:

    1)Which exactly aberrations can be measured by Hartmann-Shack sensor?

    2)If there are differences between aberrations which can be measured if wavefront is spherical and not plane wave?If we will add lens in the acquisition process which additional aberrations we will able to identify?

    3)Data (about aberrations) that we aquired by Hartmann-Shack sensor how it is practically can be used to improve the aberrations?

    4) Can we improve all aberrations that identified by Hartmann-Shack sensor or only part of them?

    David Compertore · Lumetrics, Inc.

    A set of Zernike coefficients has no meaning unless the Zernike aperture over which the analysis was completed is provided. I don’t know exactly how the Thorlabs software works, but once a set of Zernike coefficients are available points beyond the Zernike circle can be calculated. If the points are beyond the Zernike radius reported by the software, those points are extensions beyond the original data set and should be viewed as estimates. This is the case where the Zernike analysis circle is selected to fit completely inside the detector.
    If the original Zernike fit was made using the furthest available data point, typically along the diagonal, then the original fix contains the full set of available data. There is a disadvantage to this method, too. If the Zernike radius was set by the diagonal of the data then the coefficients were calculated with holes in the data set where no centroid information exists. The four area of the circle where the arc of the circle extends beyond the detector’s rectangular area have no data, but are inside the Zernike analysis. This is the case where the Zernike analysis circle is made large enough to cover the detector area.
    To analyze the physical size of your measurement you must scale by the aperture. Normalization is achieved by dividing the distance away from the center of analysis by the Zernike radius, which is often defined as the maximum distance from the center for which data exists. Multiply by the Zernike aperture to return to physical coordinates. In fact, determining the Zernike radius can be complicated. It is affected by the criteria for selecting the outer most area of interest. It is not necessarily just the coordinates of furthest from the analysis center centroid’s center of mass. Often, the size of the area of interest needs to be considered. Again sometimes averaging of data along edge points can be employed to calculate the Zernike radius. Of course if the Zernike radius is set by the user the existing data is used to calculate the best fit regardless of coverage, and the operator should review the residual fit error to ensure it is acceptable.
    A zonal fit to the data does not rely on the Zernike fit process. It provides a map of the difference from your reference surface for all data points gathered. It is good for mapping, but does not provide a simple set of coefficients for later analysis.

  • H. T. Basavarajappa added an answer:
    Can somebody recommend a paper describing the use of the Nonlinear optics for hyperspectral imaging?

    I would like to know what is being done in this area to understand if that can be relevant to my research.Thank you in advance!

    H. T. Basavarajappa · University of Mysore

    High Resolution images 

  • Serge Grabtchak added an answer:
    Can anybody recommend a paper describing the use of the Nonlinear optics for 3D imaging?

    I would like to know what is being done in this area to understand if that can be relevant to my research.Thank you in advance!

    Serge Grabtchak · University of Prince Edward Island

    How about a book?

    Handbook of Biological Nonlinear Optical Microscopy

    Editor Barry R. Masters, Peter So

    Oxford University Press, June 1, 2008.

    Also, you may want to take a look at papers from Pavone's lab:

    http://www.lens.unifi.it/bio/people.php

  • Oliver Friedrich added an answer:
    Which techniques are used for three-dimensional imaging outside the visible light?

    Since conventional optics does not always work in the range outside the visible light (UV, IR) , it is very interesting how 3D imaging can be applied in this range.

    Can somebody give relevant references?

    Thank you in advance. 

    Oliver Friedrich · Friedrich-Alexander Universität Erlangen-Nürnberg

    Dear Vladimir, non-linear multiphoton microscopy, either fluorescence based or second-/third-harmonic generation microscopy is ideally suited for 3D imaging in single cells and tissues using infrared pulsed lasers. Please refer to work from our lab (Friedrich et al. 2010, Biophys J; Buttgereit et al. 2013 J Pathol; Schürmann et al. 2013, Gastroenterology; Vielreicher et al. 2013, J R Soc Interf) or from the labs of Schenke-Layland, Pavone, Ralston, for example.

  • Anatoly Smolovich added an answer:
    Which methods can you recommend for a speckle noise reduction in acquisition stage in the holography?

    I am interested in the methods to reduce the speckle noise in acquisition stage, but I am also interested in the speckle noise reduction in post-processing stage. Do you have any references?

    Anatoly Smolovich · Kotel'nikov Institute of Radioengineering and Electronics

    A speckle noise reduction is a hard problem. I can recommend a time average. Many years ago I received an impressive result using a laser illumination through a cuvette with milk. I suppose that a liquid crystal can be used instead of milk.  

  • Paul C Colby added an answer:
    How to numerically solve nonlinear coupled mode equations?

    I have read the paper "Nonlinear coupled-mode equations on a finite interval: a numerical procedure"  a few times, but I don't have a clue how to write the code in Matlab. There are two main equations for integration: 

    yn+1/2 = yn +h[a21f(xn,yn) + a22f(xn+1/2,yn+1/2) + a23f(xn+1,yn+1)],

    yn+1 = yn +h[a31f(xn,yn) + a32f(xn+1/2,yn+1/2) + a33f(xn+1,yn+1)]

    subscripts are not integers, I don't know how to implement it in Matlab. 

    The link is the paper. 

    Paul C Colby · Lockheed Martin Corporation

    I guess I don't follow the problem. What is wrong with defining an array X(n) where X(2k) corresponds to xk and X(2*k+1) to xk+1/2 ?? Are not all sample steps in integral units of h/2?

  • Huaping Gong added an answer:
    What caused noise at the end of a fiber optic at OTDR display?
    Can someone explain to me what caused noise at the end of a fiber optic at OTDR display?
    And is there any formula to calculate the length of the noise?
  • Mazin Ali A. Ali added an answer:
    Can anyone tell me how to generate a bending laser beam in free space or underwater?

    I want to generate a bending of laser beam propagation in free space  or underwater, I think an underwater occurrence of a bending of beam under conditions such as turbidity, increase of water temperature. I need some ideas to apply this phenomenon  

    Mazin Ali A. Ali · Al-Mustansiriya University

    My Dear Salam, I spoke in free space (without fiber)  

  • Jose A Diaz added an answer:
    Is there are others (similar or more effective) ways to describe aberrations except Zernike polynomials?

    In all literature describing aberrations which I met, I usually saw their relation to the Zernike polynomials? Is there are other methods describing aberrations with the same efficiency?

    Jose A Diaz · University of Granada

    Dear Vladimir,

    Zernike polynomials represents optimum balanced aberrations in the circular pupil and the expansion coefficients do not show crosslink, as it is orthonormal set of functions (for any other pupil geometries a set of useful polynomials can be obtained). Further, they provide useful optical information of the wavefront. several of these polynomials are well related with optimum balanced third order classical aberrations having minimum wavefront variance, and thus maximizing Strehl ratio.

    You can use any other orthonormal polynomial set but their optical usefulness has to be demonstrated. Mathematically, you can expand the wavefront aberration in any of these sets and get an accurate approximation. However, it is true that Zernike polynomials are widely used in the optical community as a standard specification and characterization.

    Hope this helps you.

    José Antonio

  • Mark L. Gurari (Gourari) added an answer:
    How do I calculate the power delivered by a white light source at each wavelength where the total power and the spectrum of the source is known?

    I have an optical source which covers the UV to infrared region. I know the relative intensity distribution and total power of the output. I need find out the power distribution at each wavelength.  

    A Solution of the task doesn't exist. If the mixture more than a one component one has an one equation with several unknowns.

  • Maria teresa Melis added an answer:
    Can anyone recommend the best books in terms of quality and simplicity of explanations for hyperspectral imaging?

    Hyperspectral imaging plays important role in my research, but my knowledges in this theme mainly based on a set of articles. I want to expand and orgonize my knowledge in this field. So, which books can be used as the bible for Hyperspectral imaging?

    Maria teresa Melis · Università degli studi di Cagliari

     Shunlin Liang- Quantitative Remote Sensing of Land Surfaces- Wiley

  • Florian Bryce Soulard added an answer:
    Is 3D shape-from-texture reconstruction using a speckle pattern possible?

    I would like to do a 3D reconstruction from a scene on which I project a speckle pattern (speckle grain size can be tuned). I was thinking about using the shape from texture method, can anyone help me with that?

    Florian Bryce Soulard · Durham University

    I believe the book "Digital Holography" by Ulf Schnars and Werner Jueptner would give you some hints. Two techniques in particular could be applied to your case.
    The first one is called "Electronic Speckle Pattern Interferometry" or "Digital Speckle Pattern Interferometry" (Chapter 7.1), and consists in subtracting a deformed speckle pattern from a reference speckle pattern, resulting in dark and bright fringes on the speckle pattern related to displacement/shape.
    The second one is called "Digital Speckle Photography" (Chapter 7.3), and is also about the processing of a deformed speckle pattern with a reference speckle pattern. In this case, the local displacement is found by cross-correlation of a small moving sub-image with itself (an illustration on page 134 will give you a better idea).

    Good luck!

    http://link.springer.com/book/10.1007%2Fb138284

  • Faramarz E. Seraji added an answer:
    How can I extract the "effective Area" in Photonic Crystal Fibers?

    I am simulating an octagonal PCFs and need to extract its "effective Area" curve vs. "wavelength" and then "non-linear coefficient". Which software can be used?

    Faramarz E. Seraji · Iran Telecommunication Research Center

    The best way is to use solvers such as FDTD or FEM.

  • Miles John Padgett added an answer:
    What are the applications of the Hartmann-Shack sensor?

    In one of the courses I met the Hartmann-Shack sensor, but I want to extend the knowledge about it in order to understand whether it can be used in my research.

    For which aims the the Hartmann-Shack sensor  can be used? How does it work?

    Links to relevant papers/documents are welcome.

    Miles John Padgett · University of Glasgow

    Imaging a plane wave incident upon a single lens.  This wave is focussed to a single point in the focal plane of the lens.  If the plane wave changes direction then the focal point moves sideways.   Here we can think of the position of the focal point as telling us about the direction of the wave.

    Now consider a rectangular array of lenses.  A single plane wave incident upon the lenslet array will produce a rectangular array of spots, with exactly the same spacing as the lenses themselves.  Indeed if this array of spots is perfectly regular then this is a demonstration that the incoming light was indeed a perfect plane wave.

    Now consider what happens with the incoming light is NOT a plane wave.  At each lenslet the local wave direction is defined and a spot is produced. BUT because the local wave directions are different, the array of spots produced is no longer regular.  The more the local tilt of the wave, the more the spot is moved sideways.  Looking at all the spot directions allows one to reconstruct the overall shape of the incoming wavefront (the spatial resolution of this reconstruction matches spacing of the lenslet array).

    One advantage of a Hartmann-Shack sensor is that it is not subject to the fringe ambiguity associated with interferometry.  Consequently it is a good technique for measuring bad, multi wavelength scale aberrations.  This is very useful for measuring the aberrations associated with a turbulent atmosphere.

  • Gwendal Beauvois asked a question:
    What is the stoechiometry of an Co-Fe-Al optical fiber?

    I need to make an optical fiber for distributed dosimeter. I see in one article (kim, 2013,Radiation-induced optical attenuation of Co/Fe co-doped alumino-silicate optical fiber for dosimeter application) that he used a new fiber with this 3 dopant.

    But I don't know the stoechiometry of each dopant.  I want to know what is usually the %mol. used with Co, Fe and Al like a dopant in optical fiber.

  • Gwendal Beauvois added an answer:
    How can i link properly a fiber optic with a 1500 um core diameter with an other with a 50 um core diameter?

    Hi all.

    I need to couple a maximum light power from a big fiber in small. But i dont know how i can link them without loss more energy.

    Gwendal Beauvois · Université de Perpignan

    ok.

    Thanks for all for your answers!

  • Mohan Ranganathan added an answer:
    What are the factors affecting subsurface damage? How can we calculate SSD in optical components?

    We don't have any facility related to TEM, and I am working on blanks (Disc 25 mm).

    Mohan Ranganathan · University of Tours

    subsuracfe damage could be the creation of microcracks. If there is one domiant crack you could use fracture mechanics concepts

  • Sanjay Kumar Mishra added an answer:
    Does the focal point of an ideal lens vary with different phase fronts from the incident beam?
    The planar phase front and the spherical phase front may change the focal point of an ideal micro-lens ( having min aberration). This fact may be enhanced drastically for an incident distorted wavefront.
    Sanjay Kumar Mishra · Defense R&D Organisation

    Dear parvin

    I hope discussion has deviated justlike focal point shifts l

  • Christophe Martinsons added an answer:
    Can wavefront shaping techniques be useful to measure BRDF of surfaces at "large" scale? Could W.S. be used to produce a given light distribution?

    In architectural lighting design, BRDF determine light distribution in buildings and indoor spaces. BRDF are not easy to measure with a spatial resolution of about 10 cm². Could wavefront shaping based on spatial light modulators be used to measure BRDF ?

    Inversely, Would it be possible to "taylor" a certain angular light distribution using wavefront shaping technique? A controlable light diffusing device?

    Christophe Martinsons · Centre Scientifique et Technique du Bâtiment

    Thank you Noël and Jacopo.

    Noel : I agree about the restrictions of the notion of BRDF. But, it is still a very comprehensive parameter, that would need to be coupled with texture to give a full understanding of the reflection of an incident wave of an arbitrary surface. I am more interested in measuring BRDF without using conventional equipments (complex mechanical goniometers)...

    Jacapo : the idea is to have a device that would reflect or transmit an incoherent light beam (emitted by an LED for instance) with a given angular distribution (a single lobe or a combination of several lobes), without mechanical equipment (no scanner, no moving prism, no variable lens, etc.). Ideally, the light would be broadband in the visible range (white light) but coloured LED would be fine too (5 to 10 nm wide).

    The concept would be somehow similar to a controlable light diffuser. I have never used SLM so far. Are you aware of such applications of SLM ?

    Christophe

  • Leonid A. Skvortsov added an answer:
    What wavelength can be absorbed by the blood?

    I need  to use a laser to measure the percentage of sugar in the blood directly, and I want to know which wavelength can be used in this case?

    Leonid A. Skvortsov · Polyus Research & Development Institute

    Dear Rajaa, the same answer was given 28 days ago.

    Best regards, Leonid 

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