Minimal detect AprilTag (don't need tag ID) with better range?

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qschebdrap
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Joined: Mon Jul 08, 2019 5:03 pm

Minimal detect AprilTag (don't need tag ID) with better range?

Postby qschebdrap » Tue Jul 09, 2019 8:27 am

Here is the problem statement: there will be at most one AprilTag in view at all times and I need to find its approximate horizontal position in frame. The approximate size in frame of the tag might be useful but is not necessary. I don't need the tag ID, its pose, or any other information.

I have tried the find_apriltags function and it can get the job done, but the distance the tag can be seen from is pretty limited unsurprisingly. I'm wondering if there is a way to modify the algorithm or create a new one to only detect a tag rather than read it, and hopefully bump up the range a bit. I'm thinking of using something like a blob finding algorithm to locate the tag most of the time since the background should be somewhat regular. What sort of algorithm is recommended for this purpose? I've done some testing and the best I've done so far is comparable range to find_apriltags_w_lens_zoom.py, though the current background is more chaotic than the intended background.
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kwagyeman
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby kwagyeman » Tue Jul 09, 2019 2:45 pm

There's an example script which shows off how to us find_blobs() to do what you want at 640x480. it's under the AprilTag examples.

We will have a DRAM camera coming out soon which will have no limits on this.
Nyamekye,
qschebdrap
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby qschebdrap » Tue Jul 09, 2019 2:58 pm

I am thinking about the telephoto lenses, yes. I'm going to order them soon. I'm just worried that the smaller FOV might get in the way of other aspects of the project so I'm looking at other solutions too.

I did also test the blob AprilTag example but with the current chaotic setting its performance wasn't any better and it ran less than half the framerate. I'll test it out in the better environment too when I get a chance and hopefully it will do better.

When you say the DRAM camera is coming out soon, how soon? The project I'm working on will be at the point of no return in a couple weeks, but if the camera comes out in the next week or so I would gladly get one and try it out.
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kwagyeman
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby kwagyeman » Tue Jul 09, 2019 3:58 pm

Um, I just have dev units. If I get one working I could send it to you. Don't expect this to happen in a timely manner however.
Nyamekye,
qschebdrap
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby qschebdrap » Tue Jul 09, 2019 4:13 pm

Oh, if they're dev units they'd be better used by someone else so no worries. The H7 was a lucky enough find for us and I don't think we could do our project in the time we have without it. Thanks for doing the work so we don't have to!
ecdm2
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby ecdm2 » Fri Jul 12, 2019 7:51 am

Is this a DRAM camera like this:

https://hackaday.com/2014/04/05/taking- ... dram-chip/

Or is a DRAM module between the camera sensor and the mcu ?

If it is between the sensor and the mcu will it slot between either the rolling or global shutter modules or is it on a board with its own sensor ?

Best Wishes

Ed
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iabdalkader
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby iabdalkader » Sat Jul 13, 2019 3:44 pm

ecdm2 wrote:
Fri Jul 12, 2019 7:51 am
Is this a DRAM camera like this:

https://hackaday.com/2014/04/05/taking- ... dram-chip/

Or is a DRAM module between the camera sensor and the mcu ?

If it is between the sensor and the mcu will it slot between either the rolling or global shutter modules or is it on a board with its own sensor ?

Best Wishes

Ed
It's a new camera with SDRAM for the MCU.
ScottM
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Location: Ottawa, Canada

Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby ScottM » Fri Aug 16, 2019 7:59 pm

"We will have a DRAM camera coming out soon which will have no limits on this."

I'm really struggling trying to design my robot to detect April Tags on the floor and to navigate from one to another. The problem is the limited field of view because of the 64K memory limit. I want to place the tags no less than 4" apart and the camera needs to see several in the FOV so that it can see the next one. I bought a brand new printer, a Zebra ZD420 along with their 1" x 1" Poly 3000T plastic labels. I used your program to create 100 April tags, numbered 1 - 100. I then used another utility to crop the bottom 240 rows off because the text is too small. I then used Bartender software to create the labels, essentially 100 labels each with a different image on them, plus a serialized text field below to be the human readable text. The labels look great, with the April tag on top of a number label that shows what is encoded. I have been playing with both the stock lens and the ultra wide angle lens to come up with a FOV and distance that works. I don't want to have to move the camera too high up to get a bigger FOV. If I could get April Tag decoding with 640 x 480, I think that it would work.

I tried to use Code 39 barcodes instead with VGA and GRAYSCALE, but the decoder isn't as omnidirectional as it needs to be. If quality dips to 1 - 2, it misdecodes. It does this often when the barcode is at an angle other than 0 or 90, but that is a topic for another post.

If you have any sample cameras with more memory that would give me April Tag decoding with full VGA, I'd love to test it out and report my findings back to you.
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kwagyeman
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Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby kwagyeman » Fri Aug 16, 2019 8:11 pm

I'm working on the H7 with DRAM right now. I need to finish JPEG support for the OV2640 and OV5640. The dram camera will ship with the OV5640 5MP camera.
Nyamekye,
ScottM
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Location: Ottawa, Canada

Re: Minimal detect AprilTag (don't need tag ID) with better range?

Postby ScottM » Sat Aug 17, 2019 9:45 pm

Sounds exciting to go from VGA to 2MP and 5MP cameras. How long before you can field test them?

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