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What kind of electronics is need for depth perception of objects? I know that having 2 cameras is one method, but what about ultrasonic? Can I determine depth through that? In my project I am dealing with computer vision, and I require depth perception without the additional camera. Still a little stumped on what to do....

more specifically I'm trying to build a robot with computer vision using a single camera. I need to deal with depth specifically in object recognition. Typical object recognition training requires for the object to be set in an environment with a clean blank background. But with depth perception this isn't necessary. However since I'm limited to a single wireless camera, I have limited means of accomplishing this.

So essentially if I could use a kinect all my problems would be solved, unfortunately there are various restrictions that limits me to a simple wireless camera.

thanks!

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    \$\begingroup\$ For quality answers we really need to know more about constraints. How accurate, how many FPS, so forth so on. We need all the details to approach an issue. \$\endgroup\$
    – Kortuk
    Commented Sep 21, 2011 at 2:01
  • \$\begingroup\$ I've been hesitant to add anything else to this since it seems like my post has been taken over.... as for accuracy, I need enough so that I can determine a particular object as separate from the background. FPS isn't too big of an issue, 30fps is about what I'm dealing with. \$\endgroup\$
    – mugetsu
    Commented Sep 21, 2011 at 18:13
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    \$\begingroup\$ Your post has been taken over? Can you expand on what you mean, either here or in chat? Please edit your question to include details of what you are trying to accomplish, currently it is very open ended and valid answers that do not help your situation could occur. Lets try to get you both the best help and help related to your specific issues. If you are referring to my retag, I just changed your tag to computer-vision as this question does not seem to have any direct relation to robotics, although it could be used for such. \$\endgroup\$
    – Kortuk
    Commented Sep 21, 2011 at 21:19
  • \$\begingroup\$ I meant all the edit wars going on on the page \$\endgroup\$
    – mugetsu
    Commented Sep 21, 2011 at 21:21
  • \$\begingroup\$ That is nothing to worry about, it was constrained to that answer and of no significance. Please update your question with all the juicy details! \$\endgroup\$
    – Kortuk
    Commented Sep 21, 2011 at 21:23

2 Answers 2

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Yes, an ultrasonic range finder can give you an approximate depth reading in air out to a few meters. They work by emitting a short click and then measuring how long it takes to hear that click echoing off of an object in front of it; the longer the delay, the further the object must be.

The advantage of these devices is that you often don't need to do any additional processing, they produce a value that can be converted directly do a range. They're also very cheap and small.

Some downsides of using this kind of range-finder is that they don't work well for long distances (the linked part has a maximum range of 6.5 meters), and they can measure the depth of only a single point; generating large point-clouds of depth information from these devices would be slow and inaccurate. They also get "confused" when there's several other range-finders operating in the same space, or if the nature of the reflecting surface is such that it doesn't return a nice echo; they'll walk right into curtains.

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It takes sound about 3 ms to travel one meter in normal air. Polaroid once did a auto-focus mechanism based on that principle.

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