Wider FOV than 58 degree lenses?

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The_Nomad
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Wider FOV than 58 degree lenses?

Post by The_Nomad » Mon Sep 10, 2012 10:11 am

Heya!

I'm just wondering - would it be possible to use an even wider FOV with Optitrack and Arena than the 3.5mm M12 lenses you sell?

I'm specifically talking about usage with a v100 here - I notice that it's possible to acquire 2.1mm lenses with an 80-ish degree field of view. Would Arena and Optitrack cope with that sort of FoV well, or is there a technical reason why 58 degrees is the maximum?

NaturalPoint - Mike
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Re: Wider FOV than 58 degree lenses?

Post by NaturalPoint - Mike » Mon Sep 10, 2012 4:38 pm

Hello -

There's no stock lenses that we sell with that field of view. It's possible that you could get an M12 lens that would fit and work with the camera, however it's not guaranteed that the lens would calibrate properly. Additionally, using an 80 degree field of view lens would create quite a bit of marker bloom at closer distances, and would limit the range of the camera significantly.

mikewarren
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Re: Wider FOV than 58 degree lenses?

Post by mikewarren » Thu Oct 11, 2012 1:08 pm

A wider FOV lens is something I'd be interested in as well. Has anyone tried using one? It's something I'd like to encourage NP to investigate.

I'm doing tracking in VR display system (for instance, CAVEs and display walls) where the cameras are relatively close to the tracked bodies. I'm finding I have to go overboard on cameras to get adequate overlapping coverage.

Can NP point to a source of decent M12 lenses? This might be something I can try myself.


Mike

Seth Steiling
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Re: Wider FOV than 58 degree lenses?

Post by Seth Steiling » Thu Oct 11, 2012 4:00 pm

We're currently developing a new camera (the Prime 17W) with a very wide FOV. In the interim, and for users looking to modify current camera models, here is the situation:

When using a wide FOV third party lens with any of our cameras, the effective FOV is impacted by the lens itself, the FOV/aiming of the LEDs, and how well the lens' image circle matches the size/shape of the imager.

We custom design our own lenses so both the FOVs of the lens/LED and the sizes of the image circle/imager meet up as perfectly as possible. This enables us to utilize the full area of the lens FOV. Along with many other factors, these optimizations are part of why our lenses perform better in motion capture applications than any other.

If you use a very wide FOV third party lens that isn't specified for our cameras, any of the following could reduce the quality of data and effective FOV:


The extra FOV of the lens is insufficiently illuminated because the LED FOV and aiming don't accommodate that particular lens.

The imager size and the lens image circle don't match up, resulting in either wasted pixels on the imager or wasted FOV in the outer edge of the lens frustum.

The lens isn't properly treated for IR imaging, decreasing light transmission and effective range.

For V100 cameras--the wide FOV lens' distortion blooms the markers too much, creating merging problems between markers. (Our lenses are designed to be super low distortion, but often other COTS lenses are not, exacerbating this problem.)Having said all of that, it is definitely possible to install third party lenses on our cameras and enjoy good tracking results. The SLIM camera, in particular, is designed to accommodate M12, C, and CS lenses--including third party models. If you have a particular lens you'd like feedback on, post a link and we'll happily take a look at it and let you know what we think.
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Jim
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Re: Wider FOV than 58 degree lenses?

Post by Jim » Sat Oct 13, 2012 5:19 pm

Hello:

Thanks for the feedback on the need for wider FOV lenses.

I agree that for smaller capture volumes, a wider FOV would be very useful. Too add to what Seth said above, we do try to match our FOV to the IR LED FOV and also to the resolution of the sensor (pixels per degree) and the distance to the tracked object.

The Prime 17W will be for motion capture setups, not ideally suited for CAVES. Getting this feedback helps us decide product direction for that market, which is one we care about a lot.

mikewarren
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Re: Wider FOV than 58 degree lenses?

Post by mikewarren » Tue Oct 16, 2012 7:26 am

I don't generally buy camera lenses, so I'd have idea how to evaluate a quality lens. If you know of one you could recommend trying (no guarantee of success), please post a link.

Mike

Seth Steiling
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Re: Wider FOV than 58 degree lenses?

Post by Seth Steiling » Tue Oct 16, 2012 9:45 am

Hi Mike,

What camera + lens do you currently have?
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mikewarren
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Re: Wider FOV than 58 degree lenses?

Post by mikewarren » Tue Oct 16, 2012 10:19 am

We have V100:R2 cameras. Also, just purchased a 12 camera Flex 13, so I'd be interested in application to both.

Mike

Seth Steiling
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Re: Wider FOV than 58 degree lenses?

Post by Seth Steiling » Tue Oct 16, 2012 11:41 am

Are you using the 3.5mm lens on the V100:R2 cameras?

Also: can you elaborate on the application? Specifically, what's your setup area, and what objects are you tracking?
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mikewarren
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Re: Wider FOV than 58 degree lenses?

Post by mikewarren » Wed Oct 17, 2012 10:28 am

Sorry. It's the 58 deg lens on the V100:R2 cameras.

My latest display setup is a single screen projection wall: 18'x8'. The tracking area is the 6' in front of the screen.

I have eight cameras (V100:R2, 58 deg lenses) positioned around the screen. Four are at the top (~8') at ~0', 5', 13', 18'. Four at the bottom of the screen (~18") at the same positions.

We are tracking a pair of stereographic glasses and an XBox controller. Cameras are aimed give some coverage to the entire area but optimize coverage of a person near the center of the display.

It's only challenging because the tracking area is so shallow. If I could get users farther away from the screen, it would be easy. Unfortunatly, we do a lot of VR system where users are physically surrounded by screens, limiting distances.

Mike

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