Looking for projector/laser pointer help

[shankar2017]

Hi everyone, excited to have found this group and hoping that someone can point me in the right direction. I have an application where I am taking multiple images of an object from different angles so that I can use standard computer vision techniques to reconstruct the 3D shape of the object. The reconstruction relies on surface texture, which becomes a problem if we have shiny surfaces. The workaround is to spray such surfaces with a fine powder, e.g. talc spray or paint, so that some artificial texture is created. See the attached images for an example of a shiny metallic surface with a fine speckling made by spraying black and white paints. While this works, it introduces additional processing steps to create and remove the texture and often this is a huge problem.

As an alternative, I was wondering if we could project a random texture on to the part, similar to the one in the figure, using some sort of a projector. Colour is not relevant, but the projected pattern needs to be in the visible range since I cannot use IR cameras. The pattern can be of any colour and it is also okay if the native surface is seen between the projected dots. I am mainly interested in cutting down the specular reflection and obtaining a random texture optically. Pico projectors will probably work, but they are not small enough or cheap enough for our application. Instead, I was wondering if we could modify low-cost laser pointers that throw patterns on the screen. Can these be tweaked to throw random user-defined patterns instead of the systematic patterns they usually project? Plus, their intensity also drops from the center to the edge, can this be avoided? Or, if there are other inexpensive ways of doing this, I would be very grateful to hear about them.

Thanks.
Shankar

 

[hakzaw1]

what????

we often go to the profile page--& yours is lacking...needs more--like location..
and an 'intro' thread placed in our 'welcome' section is ALSO considered to be just good manners.

did you try our search at the bottom?

you remind me of a person who was once a member..
so welcome..or
welcome back....hk

 

[paul1598419]

There are several options you have besides paint, which is difficult to remove. If you can build a static charge on the surface it would attract many things like baby powder or paper clippings. If this doesn't work and there are no plastics that acetone could ruin, you might try fingernail polish as it is easily removed with acetone. I'm sure there are other option as well.

 

[shankar2017]

what????

we often go to the profile page--& yours is lacking...needs more--like location..
and an 'intro' thread placed in our 'welcome' section is ALSO considered to be just good manners.

did you try our search at the bottom?

Looks like I have committed the cardinal noob sin, it appears, even though I was trying my best not to! I am really sorry, had no intention of being rude here. I have taken your advice and posted a short 'Welcome' note as well as added biographical details.

I did search here prior to posting, but did not find anything of direct relevance. I did find a DIY solution, but I am looking for a compact, commercial solution which I can use directly and in scale.

Thanks.

 

[shankar2017]

Yes, we have tried baby powder before, it is quite easy to apply and remove. But, we will likely be processing thousands of parts like this on a manufacturing floor, so such a solution is not viable beyond the prototyping stage. That's why I am looking for an optical, non-contact solution. Besides, we don't want to add stuff to the surface that would change the surface geometry signifjcantly. The end goal is to reproduce the geometry very accurately, sometimes to within 0.002", which makes an optical projection method more desirable than a physical speckling method.

Thanks.

 

[paul1598419]

Maybe I don't understand what you are trying to do. If you need to take a projection for 3D printing, one will do it. Why would you want to do this with every piece on a production floor? It makes no sense to me.

 

[shankar2017]

Maybe I don't understand what you are trying to do. If you need to take a projection for 3D printing, one will do it. Why would you want to do this with every piece on a production floor? It makes no sense to me.

Let me explain it a bit more. What we are trying to do is to provide a service to a manufacturer, who produces many units of a certain part. Our service is to provide 3-D measurements of each actual unit produced, we are not trying to 3D print a part. The first step in making the measurements is to construct a 3D point cloud of each manufactured unit from several overlapping images taken with a regular camera. For the overlap to work well, we need to have some texture on the surface, which is an issue with smoooth, reflective parts. This is what I need help with. Since the number of units manufactured can run into several thousands, if not more, I am looking to project speckles on to the surface optically and save myself all the prep of physically applying and removing physical texture.

Please let me know if something is still not clear.

Thanks.

 

[diachi]

Let me explain it a bit more. What we are trying to do is to provide a service to a manufacturer, who produces many units of a certain part. Our service is to provide 3-D measurements of each actual unit produced, we are not trying to 3D print a part. The first step in making the measurements is to construct a 3D point cloud of each manufactured unit from several overlapping images taken with a regular camera. For the overlap to work well, we need to have some texture on the surface, which is an issue with smoooth, reflective parts. This is what I need help with. Since the number of units manufactured can run into several thousands, if not more, I am looking to project speckles on to the surface optically and save myself all the prep of physically applying and removing physical texture.

Please let me know if something is still not clear.

Thanks.

Sounds like what the Microsoft Kinect does, it projects a pattern using IR lasers and then analyzes that pattern to create a 3D "image".

Not sure how accurate it is with that method, but sounds like something that could be applicable to your case. It'll require some R&D to figure it out I'd imagine, seeing as the MS technology is proprietary. Might try seeing what others have done with the Kinect.

 

[paul1598419]

Not sure this is my area of expertise. I'll follow and add where I can.

 

[shankar2017]

Sounds like what the Microsoft Kinect does, it projects a pattern using IR lasers and then analyzes that pattern to create a 3D "image".

Not sure how accurate it is with that method, but sounds like something that could be applicable to your case. It'll require some R&D to figure it out I'd imagine, seeing as the MS technology is proprietary. Might try seeing what others have done with the Kinect.

Yes, I did go down that path and found these guys: Structured light with extremely low zero-order

I am talking to them now and will come back and post if it works.

Thanks.