Anti-reflective floor in motion lab

[Maria Prado]

Dear Biomch-L community,
We are using Vicon system to capture motion data in our laboratory. We are having problems with reflections from the infrared strobes of the cameras but also from the sun light. So we want to cover up the floor of the laboratory with an anti-reflective matting. Did anybody there have the same problem? Could anyone suggest which floor can we use?
Thanks in advance,

M Prado
Department of Mechanical Engineering
University of Malaga

[Edmund Cramp]

Re: Anti-reflective floor in motion lab

You don't say what sort of floor surface you have but on the assumption that it's a Linoleum or vinyl flooring of some sort - reflections are usually a result of polish on the floor. If this is the case, see if you can get a floor buffing machine with an abrasive pad to remove the polish from the surface to leave you with a matte surface.

I once installed a motion capture system for a hospital just outside New York and having spent a week setting it up and training everyone (this was back in the days when the Vicon software ran on a PDP-11/34), they signed off on the installation and everyone was happy. After I left the administrators announced that there would be an open house and demonstration day for the new system the following week and - without telling the lab staff - arranged for the hospital maintenance department to clean the lab - and polish the floor. I got a very panicky phone call when I got back into the office on Monday. Stripping the polish from the lab floor fixed the problems although the administrators were not happy,

[Drew Smith]

Re: Anti-reflective floor in motion lab

You should speak with your Vicon rep: my understanding is that they are now marketing their systems for outdoor use and I don't think there have been any radical changes to the hardware or software. It's all in the setup, I think.

[Ajit Chaudhari]

Re: Anti-reflective floor in motion lab

We have a Vicon system as well, and we used rubber matting similar to that often used in fitness centers and weight rooms. Each tile is 4ft x 4ft, and they interlock. It is heavy enough not to move on its own but easy enough to lift off if necessary. This is the link for the place we bought it: http://www.humanemfg.com/flooring.htm Hopefully you can find something similar where you are. I have also heard of another lab using a much larger piece of rubber mat that can be rolled out. It's the kind of material used for a "marley" on a dance floor (search Wikipedia for marley floor).

Good luck!

Ajit Chaudhari, PhD
Ohio State University
Columbus, OH

[Amanda Lin]

Re: Anti-reflective floor in motion lab

We have the same issue for our VICON. Each time we got a floor cleaning/polish done, the next day we're gonna have multiple large reflective spots. I use a fabric spread to cover the floor when I see them. It's ugly but perfect for killing the reflective noise.

Amanda Lin, DSc
Northwestern University

[Bruce MacWilliams]

Re: Anti-reflective floor in motion lab

With our old vinyl floor we used to hand buff spots with a pot scrubber every time the floor was cleaned. There is also software masking available in Nexus, but if the spots are large, you are simply eliminating large chunks of camera views this way. We upgraded our floor to a matte finished flooring product and have had no trouble with reflextions even at maximum strobe intensities as long as thresholds are appropriately set. If your lab setup is permanent I would reccomend changing the floor, it's worth the investment. Although I'm not a fan there are some labs that use carpeting, which would be a relatively cheap solution.

[Tim Wrigley]

Re: Anti-reflective floor in motion lab

I have done two labs now in Flotex carpet tiles. They're dense felt, thin, hard-wearing, don't reflect, don't move, and are comfortable to walk or run on even in bare feet. One floor was laid on wood, the other on concrete. The tiles can be cut easily to fit on force plates. We have 12 camera Vicon MX (visible red strobes).
Tim Wrigley
Director – Movement Research Laboratories
Centre for Health, Exercise and Sports Medicine (CHESM)
The University of Melbourne

[Andrew Ray]

Re: Anti-reflective floor in motion lab

Hello Maria,

As commented by others on this thread controlling the polishing done by maintenance workers on your floor is a key piece.

With respect to any new flooring; use a dull tile or linoleum for your floor surface. We recommend a conductive linoleum material to prevent static build up discharges during dry weather, which could disturb subjects or discharge through the force plate and cause analog data capture issues. The color of the floor does not affect system performance. You may wish to choose a color suitable to hide wear and tear and scuff marks.

With respect to any sun ingress; cover any windows or skylights to completely block out external light. We recommend hanging backed curtains to a length just above floor level. Use dark-colored curtains made from a non-shiny material.

As mentioned on here; you can control any noise from the area of interest by using the masking facility within Nexus for each camera. Other settings can also help such as the the aperture setting on the camera itself, the strobe intensity & camera thresholds for example. Vicon would be happy to talk this through with you, please feel free to use your support facility at www.vicon.com/support to set up a support session.

With respect to Vicon cameras being marketed as outdoor capable; this is indeed the case. All T series cameras can be made outdoor capable. Pre 2011 T series cameras do require a return to manufacturer for a hardware edit to make this function correctly, please contact your local Vicon representative for further information.

I hope this information helps.

Andy Ray
EMEA Sales and Support Manager
Vicon Motion Systems Ltd

[Christopher Stanley]

Re: Anti-reflective floor in motion lab

Kate from Denver Children's told me about a matte floor finish from Grainger that they used on their rubber flooring. However, Grainger only recommends that this product be used on wood flooring and did not believe it would stick to our vinyl composite tile (VCT). I have tried looking around a little, but does anyone know of a matte floor finish that works on VCT?

Chris Stanley
National Institutes of Health

[Dan India]

Re: Anti-reflective floor in motion lab

Hello Maria:

The discussion kind of drifted in an attempt to solve your problem. Buying new cameras is not your solution unless you cannot control its features.

Lets Start with the flooring: Get the medical center to completely strip the floor of its wax. They will nt like this but you with $100,000's of technology can do your job effectively so win the arguement. Any flooring can be painted once stripped and cleaned. If its concrete you can use a "concrete" dull finish matting paint that would bound well and avoid scuffing. Several recent Qualisys installations needed to strip their concrete flooring to do just this. The same scenario should be followed with a vinyl floor too.

Next work your cameras: Tilted and rotate them to optimize... also If the Vicon camera allows you to alter the camera's threshold, exposure (lighting) and aperture then do so. For example on the Qualisys cameras for either indoor and or outdoor use you have independent settings allowing you camera's sensor to receive more or less light via the exposure, threshold and manually adjusting the aperture to "close it down". Each camera company might call it slightly different so check the manual.

Next can you define your spatial volume and will the software allow you to create "virtual -area"? if so - do so. I am not sure in Vicon but in the Qualisys system you can set up your volume by defining the X,Y,Z corners of the Volume and to only accept data with in the volume and not reflections sitting outside of the area. In other words the cameras when digitizing the 2D data ignore data points outside your volume area.

Next does the Vicon software allow your cameras to alter the marker discrimination settings and or limiting the size of markers to be seen? That what its called in Qualisys but for instance if the cameras are seeking a 12.7 mm size marker but the shine of the floor causes a 10 cm hotspot due to camera red lights, can your software discriminate and reduce the size of the "blob or marker" to only accept and allow a 12.7 size marker to be captured? Beware of setting too low and missing actual marker data too! Also if available turn on your active filtering software which would negate such reflections.

Lastly another tool might be masking the hotspot with the software's masking tools. Again not sure if Vicon has this in your version but masking in the individual camera's 2D FOV allows you to create a black hole on the reflection. However, beware of placing masks in the critical 2D FOV like over a runway, platfoms etc since data entering the masked area is gone until coming out of the area.

Good luck and hopefully you can remove the reflections and capture data with your system.

My best to you.
Dan India

[Edmund Cramp]

Re: Anti-reflective floor in motion lab

You could always try a quick dusting of the offending area with a can of clear matte spray paint - under $10 at your local hardware store. You can find the offending area on the floor by watching the "live" camera view while someone moves a marker around in the general area.

[Gaspar Morey Klapsing]

Re: Anti-reflective floor in motion lab

Dear Maria,

I would say that most of the possible issues/solutions have been addressed. I will summarise them from my experience as a VICON user who has had these problems in different situations:

Setup solutions
- In case of the sunlight the easiest is to use a curtain or similar to darken the windows.
- In the case of strobe reflections:
- You can adjust strobe intensity and camera sensitivity. To do that I place markers in the zone each camera should cover and set sensitivity and strobe intensity as low as possible so that I still get the markers I need.
- You can change camera positions (usually you will get reflections from the camera in front of the problematic camera. You might try to "dis-align" the cameras.
- You can use MASKS to ged rid of small reflections (not reccomended for bigger reflections)

Flooring solutions
- When you have a non fixed setup, so it is a temporary issue, and the reflection is not inside the area where your subjects are moving, you can just place some fabric (a towel or whatever) on top of the floor at that place.
- If it is a fixed setup you should find a permanent solution. I ignore your budget, but the best solution is to get a non reflecting flooring (Painting could be a solution as well). Recently we have purchased a flooring to rise our walkway for 12 mm. We installed a puzzle-like floor from PAVIGYM (http://www.pavigym.com/). The floor is easily assembled and disassembled and has a very good quality. As you are located in Spain (same as me) ... I'll be glad to provide you with our contact. Just drop an email. They have many different finishings, hardness, thickness, etc.

Good luck,

Gaspar Morey

LAFC - INESCOP
(laboratory for funtional footwear analysis)
gmorey@inescop.es

Dear Biomch-L community,
We are using Vicon system to capture motion data in our laboratory. We are having problems with reflections from the infrared strobes of the cameras but also from the sun light. So we want to cover up the floor of the laboratory with an anti-reflective matting. Did anybody there have the same problem? Could anyone suggest which floor can we use?
Thanks in advance,

M Prado
Department of Mechanical Engineering
University of Malaga