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Need a camera with constant focus

asked 2013-07-16 23:29:48 -0500

Pouyan gravatar image

updated 2013-07-16 23:33:37 -0500

Hello,

I use a usb camera to localize NAO robot by tracking a marker placed on its head (using ar_pose marker tracker). My problem is with the camera autofocus which results in the poor performance when there are other moving objects in the environment.

Is there a camera with constant focus you could suggest me to buy? (I need a camera with a wide field of view and a long data cable as the camera is placed in the ceiling in my scenario) or whether it is possible to set the autofocus of usb camera off?

Thanks, Pouyan

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I think all cheap webcam's are constant focus, only the expensive ones have autofocus. Finding a wide angle is harder.

davinci gravatar imagedavinci ( 2013-07-17 01:35:16 -0500 )edit

you need to specify a price range - there's a whole host of cameras that do not auto focus

2ROS0 gravatar image2ROS0 ( 2017-09-22 18:18:47 -0500 )edit

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answered 2017-09-29 15:51:28 -0500

chrisalbertson gravatar image

Your problem is physics related. What you are asking for is a camera and lens that have a depth a focus from some minimum out to infinity. such that the target will never be closer than the minimum focus. Of course this can be done but there is a trade off.

A camera that has a wide depth of focus will have three features you may not want: A wide angle lens, physically small sensor size and numerically high f-stop number. I camera like this typically has poor low light performance and has a bit of "noise" or grain in the image. Most of the things engineers can do to improve the image alto reduce the depth of focus. They make up for this by using a focus motor on the lens. So it is a trade off, one thing for another.

One way you can solve the grain and noise problem is by seriously increasing the amount of light. Double the lighting power for every loss of 1 f-stop. A fixed focus lens operating at (say) f/5.6 needs 4 times as much light as the same lens at f/2.8 and 8 times as much as one at f/2.0 Image quality improves quite a lot as you add light, does wonders for the signal to noise ratio (because you are adding signal)

You also have a limit if you are using a USB 2 interface to the camera. You can't get uncompressed 1080P at 60 fps trough a USB cable. USB lacks the required bandwidth.

All that said. A good solution is the USB web cam that was made for the Sony Playstation II It was VERY inexpensive, under $10. They are used by many people for computer vision, especially video because that can to 480P at 60 fps. They are fixed focus and there is a two step manual zoom but even the wide setting is not very wide. This will be a problem if used for survilence. You would need to attach an auxiliary lens There is also a good quality microphone array on the camera.

wikipedia.org/wiki/PlayStation_Eye

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answered 2017-09-22 05:49:30 -0500

I'm not exactly sure which camera the Nao uses, but most webcams with a autofocus feature are UVC-compliant, so the autofocus is often configurable via software. See for instance here or this video. I'm writing "often" because I've seen various cases where the UVC standard is not followed correctly, in which case the controls might not work, even if they are available.

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answered 2017-09-22 18:21:15 -0500

2ROS0 gravatar image

FLIR (formerly pointgrey) cameras are really good in my experience and come in many configurations. There's a ROS driver pointgrey_camera_driver that's plug-and-play which will get you up and running in a couple hours.

Obviously they're not in the same price range as the best-selling webcams on Amazon.

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answered 2017-09-21 12:46:29 -0500

If you need to do this on a budget then buy a cheap webcam with no auto-focus and glue one of the wide angle lenses you can get for mobile phones over the top of it. This will give you a good field of view but the quality will not be great.

The best camera I've used it a GoPro 4 but it's not easy to feed it into a computer live. I believe some of the knock off GoPro like cameras you can buy can be used as USB web-cams directly so that's probably worth looking into.

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answered 2017-09-29 10:11:21 -0500

The Axis F-Series IP security cameras are very nice:

https://www.axis.com/us/en/products/a...

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Asked: 2013-07-16 23:29:48 -0500

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Last updated: Sep 29 '17