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DLPLCR4500EVM: spatial resolution for small-scale experiment, camera type

Carlijn Snoek
Prodigy 20 points
Part Number: DLPLCR4500EVM

Hi,

I am speaking on behalf of my team of three MSc students Earth Sciences from the University of Amsterdam. We are participating in the Spin Your Thesis! campaign hosted by the European Space Agency. We will execute an experiment in a hypergravity simulator called the Large Diameter Centrifuge (LDC, link for more info below) in September 2018, with the aim of examining the influence of gravity on granular avalanches. We are simulating small-scale granular avalanches under varying gravity conditions and wish to use the DLP Lightcrafter 4500 to create a 3D profile of the avalanches. We were inspired by an article from Deetjen et al. (2017, the full reference can be found below), where they use the device to make high-speed surface reconstructions of a flying pigeon. To use in our own experiment, we have some questions regarding the application of the DLP Lightcrafter 4500 that we could not find in the user's guide.

  1. What is the minimum distance from the Lightcrafter to the object the laser grid will be projected on (the avalanche in our case)? We have limited space in the LDC gondola, so the DLP Lightcrafter 4500 would be placed about 30 centimeters max. from the surface. 

  2. Is it necessary to have a specific camera with the DLP Lightcrafter 4500? We have read something about the Fire Wire, but are wondering whether there is also the possibility of using for instance a regular Nikon or GoPro camera or any other options.

  3. Does the Lightcrafter have a minimum size of the studied object, or what kind of spatial resolution are we speaking of? Our avalanches will have height differences of less than 1 millimeter, which we would want to be visible in the laser grid.

Could you give us some advice?

Deetjen, M. E., Biewener, A. A., & Lentink, D. (2017). High-speed surface reconstruction of a flying bird using structured light. Journal of Experimental Biology, 220(11), 1956-1961.

More info on the LDC: https://www.esa.int/Education/Spin_Your_Thesis/The_Large_Diameter_Centrifuge2

Thanks in advance and kind regards,

Carlijn Snoek

  • 0
    TI__Mastermind 28005 points
    Carlijn,

    Welcome to the E2E forums, and thanks for your interest in our DLP technology. Let me try to answer each of your questions individually.

    1. What is the minimum distance from the Lightcrafter to the object the laser grid will be projected on (the avalanche in our case)? We have limited space in the LDC gondola, so the DLP Lightcrafter 4500 would be placed about 30 centimeters max. from the surface.

    The "out-of-the-box" working distance of this EVM is ~50 cm minimum, which is higher than what your design is calling for. However, you may be able to reduce this distance by adding additional optics. See this thread for more info:
    e2e.ti.com/.../305041

    2. Is it necessary to have a specific camera with the DLP Lightcrafter 4500? We have read something about the Fire Wire, but are wondering whether there is also the possibility of using for instance a regular Nikon or GoPro camera or any other options.

    The LightCrafter 4500's camera trigger function is compatible with industrial USB 2, USB 3, FireWire, and GigE CCD cameras from Point Grey Research, The Imaging Source, and other manufacturers. I believe you should be able to interface any camera that can properly operate based on the trigger signal from the 4500 EVM.

    3. Does the Lightcrafter have a minimum size of the studied object, or what kind of spatial resolution are we speaking of? Our avalanches will have height differences of less than 1 millimeter, which we would want to be visible in the laser grid.

    The achievable resolution of your system may be dependent on a number of factors, including the patterns used and light sources. The LightCrafter 4500 should provide at least 1mm spatial resolution. Generally the camera resolution will be greater than the projector resolution to ensure proper capture of the pixels (due to the Nyquist frequency). Assuming the camera resolution is higher, while data can be obtained for each pixel in the camera, there will be no unique depth information at every point as this is limited by the projector resolution (at least in one axis). Therefore, the spatial x and y resolution can be calculated with the below equations:

    x_res=(captured image width)/(min⁡(cam res width,DMD res width))
    y_res=(captured image height)/(min⁡(cam res height,DMD res height))

    I hope this helps.

    Best Regards,
    Philippe Dollo
  • 0 in reply to Philippe Dollo
    Prodigy 20 points

    Dear Philippe, thank you for your reply.

    Regarding Question 1:

    So if I understand correctly, we would just need to place a converging lens with a focal length of ~35-50 mm in front of the light engine? Does TI provide these kind of lenses that are compatible with the DLP Lightcrafter, or is it possible to use any lens with the suitable focal length and just place it in front? Do you have any recommendations? Or does it work differently, where we can replace the projection lens with the converging one? I know I am asking many questions at the same time, we're just not sure how to place this additional lens in the DLP design.

    Questions 2 and 3 are clear.

    Thank you for your time!

    Best regards,

    Carlijn Snoek

  • 0 in reply to Carlijn Snoek
    TI__Mastermind 28005 points
    Calijn,

    Unfortunately, TI does not provide these lenses. You can mount the additional lens right in front of the system, once it is designed properly. You would need to custom design or buy one off the shelf.

    Best Regards,
    Philippe Dollo