Limpa - 16 December 2009 02:12 PM

Hey!
Just tested my new lens and i am having trouble getting blobs at the edges working fine in the middle. Running on 6 fps right now aswell. Dunno why actually.
Shit! Depressing!

Limpa, first thing I reckon is to check that you’re running at a decent resolution and frame rate. I use 640x480 (30fps), this gives me the best image with minimal noise artifacts.

Next, I’d look at your LED setup in terms of uniformity of IR distribution. Is there enough IR getting to the edges? If not, you might need to acquire additional IR strobe lights or reposition them to cover the edges better. My table just barely works with 4 - ideally I would use 6.

Also look at the CCV configuration - in particular image threshold (mine’s at 1) and blurring (14). Both these parameters affect the sensitivity.

I’m currently investigating whether the diffusion layer affects IR transmission - it shouldn’t in theory, but worth a try.

Hey! Damn i have no time for testing. The thing is i have à dsi setup and a pretty even light over the surface . Still I have no or very week blobdetection in the corners. Gotta do some more testing I guess. Someone else having this problem?

Limpa: I also had problems detecting blobs on sides with my 2.1mm lens, what I did, I just increased the distance from camera to screen to have less angle of view, now it get better detection on the edges

Ei! Thanks for the reply. I built a coffetable though and can’t move te camera away from the screen. Not without changing or remaking the table anyway.
Dsi is a good way to get a even illumination but it creates very week blobs and therfour very sensitive to distoration from widelens .

if you use mirror, maybe you can point a camera through mirror, that will give you also narrower angle..

NICE SET-UP!

Is there any way I can ask you to elaborate on the construction of your box?  I’m no carpenter, and I’m kind of stuck on what materials I should use.  I’ve built a frame for prototyping out of cheap wood.  Serves its purpose for now, but man its ugly. LOL

Absolutely Beautiful, well done on the construction

emerex - 04 January 2010 10:47 PM

NICE SET-UP!


Is there any way I can ask you to elaborate on the construction of your box?  I’m no carpenter, and I’m kind of stuck on what materials I should use.  I’ve built a frame for prototyping out of cheap wood.  Serves its purpose for now, but man its ugly. LOL

Thanks guys.

I looked at two options when designing the box: wood and acrylic. The pros/cons I thought up for each were:

Wood
Pros:
- Cheaper for materials
- Easy to mount internal components
- Suited to a less modern interior (softer in appearance)
- Lighter, unless using something like hardwood

Cons:
- Expensive if purchasing own tools (this would however be offset with successive units)
- Requires painting and/or surfacing (and skill in this art to get it to look good)
- Susceptable to environmental damage and discolouration

Acrylic
Pros:
- Strong construction
- Visually appealing in a modern setting (clean lines, glossy appearance)
- Can achieve interesting effects such as edge rounding
- Highly resistant to environmental damage

Cons:
- Expensive, regardless of whether an external fabricator is employed
- Almost impossible to make structural changes once built
- Hard to fix internal components in a professional manner (i.e. without using acrylic cement so they are removable in case of failure)

Good to see you actually constructing a prototype! Mine consisted of two chairs, the acrylic projection surface on top and a couple of mirrors..just enough to make sure I could project the image.

My recommendation? Acrylic. Simply because it was so easy to prepare a design for a local fabricator and have them cut and assemble it down to the millimetre, as well as polish edges. Essentially making it production-ready. Depending on what you want to get out of this project though, you might choose wood if say, you want the challenge of actually building your box yourself. Personally, I wasn’t prepared to pit my inexperience in woodwork against potential failure.

To those with problems picking up blobs, I would suggest looking at reducing the thickness of the diffuser material. Changing mine from 5mm to 3mm made a whole lot of difference to the amount of IR transmitted. If you are doubtful, you could try a simple sheet of baking paper on top of the clear perspex to see if this improves the situation.

Thanks for the tip and excellent response!  You have an excellent point, buying tools and dealing with the learning curve would most likely make my costs skyrocket.  It will probably be a better idea to have a professional make the box.  This way at least, it will be a nice piece of furniture and won’t run the risk of my wife tossing it out the back! lol

Peter K - 07 December 2009 05:40 AM

kolinko - Thanks mate. I’ll outline the issue I have experienced with UV/IR light:

- When the surface is illuminated by sunlight, it increases the ambient IR levels picked up by the camera. This is exacerbated by the fact that I have the camera’s exposure control set to manual (as auto doesn’t yield good results). Therefore, when this occurs CCV has trouble distinguishing fingers from the ambient levels of IR.
- Sunlight as you know contains a very broad spectrum of radiation, not just visible light. Therefore direct sunlight on your table can have a negative effect, as explained above.
- For a good explanation of this, refer to the Environmental Factors section on page 25 of http://www.microsoft.com/downloads/details.aspx?familyid=CACC79C7-42E4-41DB-BD23-4E0D849F56B5&displaylang=en.

So how to address the issue?
- Close curtains to eliminate direct sunlight
- Attempt to use auto-exposure control to mitigate changing levels of IR

Hope this helps,

Peter

Peter, can you give me detail on how you built the cabinet? i saw you already posted dimensions and mentioned its all acrylic, but do you have any pics of the build process?

EDIT: nevermind, just noticed you had already posted thorough details on the construction of it.

nice job!! lets see some videos of that table in action!!

Beautiful table. I love the low form factor.
Is there any chance you could post a more detailed side view/diagram for us to be able to see the angles and positioning of your projector and mirrors?

Keep up the good work.

Once again, very nice work Peter!