Optical Engineering

Optical Engineering

  • Elena Stoykova 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?

    Elena Stoykova · Korea Electronics Technology Institute

    I would recommend the paper

    F. Yaras, H. Kang, and L. Onural, "Real-time phase-only color holographic video display system using LED illumination," Appl. Opt.  48, H48-H53 (2009).

    I used LED to illuminate sinusoidal phase grating recorded as an analog thin hologram or generated by a SLM to produce sinusoidal fringes with reduced speckle noise for optical metrology.

    Regards,

    Elena Stoykova 

  • Jingjiang Xu asked a question:
    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)?

  • Vladimir Farber 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?

    Vladimir Farber · Ben-Gurion University of the Negev

    I have additional subquestion.

    I performed some simple experiment with Thorlab's Shack-Hartman sensor. Some of it's  software outputs are 15 first Zernike coefficients and some image describing wavefront.

    I performed simulation, to reconstruct wavefront, but since Zernike polynomials defined in the normalized circle of radius 1, then I reconstructed the wavefront inscribed in the circle and not inscribed into the square as in image from Thorlabs' software.

    Which corrections I must perform to obtain exactly the same inscribed in the square image?

    How influences of the fact that there are differences between representations on Zernike coefficients?

  • 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?
  • Huaping Gong 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?

  • 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:
    If 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 

  • Mauro Elias added an answer:
    How can I modify the OH stoichiometry in an optical fiber?

    I saw in some articles that OH stoichiometry can modify the RIA of some fibers. But I never find any informations in the fabrication cycle that can modify the OH stoichiometry.

    Thank you in advance for your advice and answer.

    Mauro Elias · Centro de Tecnologia da Informação Renato Archer

    During preform manufacturing process, an outer OH-barrier and an inner
    OH-barrier free of P205 can be deposited respectively between
    the substrate tube and a cladding layer and between the
    cladding layer and a core layer during a deposition process (we are talking about MCVD process). There are other methods to produce OH-free fibers.  SM fibers produced by state-of-the-art vapor axial deposition (VAD) process lack OH absorption peak,  

  • Kuppuraj Rajamanickam added an answer:
    How do shadowgraphy velocity values and PIV velocity values differ? Which method is better?
    Which method is better for spray characterization of velocity- PIV (particle image velocimetry) or shadowgraphy?
    Kuppuraj Rajamanickam · Indian Institute of Science

    PIV is a opt method to measure the velocity and also flow pattern. Shawdowgraphy doesn't give that much accurate results, however it give accurate results on other parameters like cone angle, spray structure, instability / surface waves. If possible go for PDPA  since it give droplet size and velocity rather than PIV. 

  • Christophe Martinsons added an answer:
    What polymers can be used to manufacture infrared lenses working at around 10µm?

    I am investigating plastic optical parts that could be produced by injection molding, hot embossing, or other techniques, in order to work between 7 and 14µm (long wave infrared - LWIR).

    Christophe Martinsons · Centre Scientifique et Technique du Bâtiment

    Sure ! Military applications doesn't really need low cost materials... That 's the difference with mainstream applications in building automation. No missile involved, just millions of cheap IR modules to detect, count and locate people !

    Christophe

  • F. Q. Jia added an answer:
    Is there any cost effective PM Tapered fibre boudles supplier ?

    Is there any cost effective PM Tapered fibre boudles supplier ?

    F. Q. Jia · Xiamen University

    Many thanks !

  • Sayan Saha added an answer:
    How do I prepare the TiO2 interlayer for tandem solar cells?

     What precursor do I use for this layers and how can the high temperature step be avoided?

    Sayan Saha · Intel

    You can use ALD TiO2 deposition using tetrakis-dimethyl-amido titanium or Ti isopropoxide precursors and H2O. the reference to look at - http://scitation.aip.org/content/aip/journal/jap/102/8/10.1063/1.2798384.

    Alternatively you can use e-beam evaporation of 1-2nm of Ti and oxidize it by exposure to air and repeat. the reference to look at - 

    http://pubs.acs.org/doi/abs/10.1021/nn5038509

  • Charlotte Bennett added an answer:
    Which software is most suitable for Photonic Crystal Fiber analysis?
    Dispersion vs wavelength, MD vs lambda.
    Charlotte Bennett · QinetiQ

    It depends on what sort of PCF you are investigating. If it is a standard low air-filling fraction with circular holes and one hole missing for the solid core then there are quite a few publications providing approximate dispersion and mode field diameter. These are based on the effective index model; the main issue is chosing a size for the core diameter otherwise you can model as a step-index fibre. If it has 7 or more holes missing then you can still use a similar method.

    If the air-filling fraction is large or the holes are not circular then you need to model the structure with either finite element software (I have used COMSOL Multiphysics in the past) or FDTD. Even then you will probably find that the approximate solution is not that different.

  • Mazin Ali A. Ali added an answer:
    What is the obstacle for underwater optical wireless communications?

    Water have complicated nature, water acts as a big obstacle in the propagation optical light which ends up with reduction of the optical transmittance in very short ranges which can be in the order of a few tens of meters. on the other hand, we can use the visible band of the electromagnetic spectrum (450nm-550nm), where water is relatively transparent to light and absorption takes its minimum value.

    Mazin Ali A. Ali · Al-Mustansiriya University

    thank u for comments

  • Gintaras Tamosauskas added an answer:
    Semiconductor laser flashes but there is no continuous wave radiation. What's going on?

    I have worked with quite a few laser diodes, but this one is proving rather mysterious. It is a non-coated LD. There is no lasing at the specified threshold current or operating current, just fluorescence.  However, there is a flash of, what looks to be, laser light when the current cable is simply connected to the diode with the expected mode shape (but not when using the on/off switch of the current supply).  There seems to be a momentary surge of current that creates the laser flash — nothing new, but it does suggest that the diode is not completely dead. The obvious thing to do is just keep ramping up the current until  there is complete failure (or lasing), which I will most likely do. I am curious to know if anyone has seen this kind of behaviour before. Maybe something is happening in the chip that prevents a stable cavity. The spec sheets weren't dated, so I don't know how old the chips are (the light is red, but this is likely to be inconsequential). 

    Gintaras Tamosauskas · Vilnius University

    Hello,

    looks like you have the supply with current stabilization. In that case, when the cable is unplugged, voltage is increased to max value (preset max voltage limit). However, output small capacitors (which typically are present) and cables (also small capacitance) are charged. The stored charge is discharged via LD producing short peak of current when you connect the cable of the LD to the supply . The supply instantly switched from voltage limiting to current stabilization which takes place at lower voltage level and everything starts to work "normally". But damage is already done - LD, even if it was OK before, may be damaged due to short current peak.

  • be Ravand asked a question:
    Does anyone know how to do simulation of MLL with optisystem software?

    Doese anyone know how do simulate external cavity mode lock laser (MLL) with optisystem?

    I want simulate a 10 GHz MLL operating at 0.001 W at 1555nm gaussian pulse which is used as a clock pulse .

  • Karnam Raghunath added an answer:
    Can anyone recommend any Photon Discriminator Devices for Photon Counting?

    I am using Photon Counting with Hamamatsu PMT, photon discriminator and ni-DAQ for Laser Scanning Microscopy.

    My previous photon discriminator system were custom-designed and it has begun to go wrong so I should replace it. 

    Actually, recently I found the Photon counting unit of Hamamatsu, but it only supports 1 channel. (Links attatched,C9744) (I need at least 2 channel)

    Can you suggest another company or products that can alternate to C9744? 

    I hope that it can support up to 2 channel, and price is reasonable. 

    Karnam Raghunath · National Atmospheric Research Laboratory

    Stand alone Discriminators from Phillips Scientific are one option. Another option is licel which has an integrated system

  • Yariv Shamir added an answer:
    Any people know how to stripe a GTWave fibre ?

    In my fibre laser setup,one broken point was investigate in the fibre, so  I have to recleave the fibre and resplice the fibre. However the first step is sperate this two fibres and then do the left work. Hopefully, some people could give me some suggestions. Thanks a lot !

    Yariv Shamir · SNRC

    Sulpuric acid or HF will do the work, also arc discharge from a splicing machine could help, if you can somehow mound a fiber section and drive it through. Not sure how clean you need it, soince some of these methods can leave microscopic debris...they may be lethal in case high intensity is applied...

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Optical engineering is the field of study that focuses on applications of optics.

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