FOV and lens question

Discussion related to "under the hood" OpenMV topics.
psih
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Joined: Thu Feb 15, 2018 7:45 am

FOV and lens question

Postby psih » Thu Feb 15, 2018 8:50 am

Can't understand, how the 115° FOV was get with standard lens (2.8mm? and 1/4" sensor)
Also 185° with 1.7mm lens.
These values looks like true only for 1/2.5", but OV77725 is 1/4".
On my OpenMV Cam i get something looking like 60° of horizontal FOV with stock lens
and about 90° with widerange lens I have. (1.8mm 1/2.5")

Markings of cam:
OpenMV3 R2 US-MF-002 OV7725-M7 05/20/2017

Does somebody tried 1.7mm lens from openmv site?
Or, maybe, could explain me, if I am wrong somewhere.
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kwagyeman
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Joined: Sun May 24, 2015 2:10 pm

Re: FOV and lens question

Postby kwagyeman » Thu Feb 15, 2018 11:06 am

Hi, the 115 degree is what was quoted by the lens provider. Yeah, I agree its likely less given what I see. I guess I can work the math to get the real FoV for our given setup. The 1.7mm lens does provide a much wider field of view than the default one. Anyway, the info on the website is just the quoted FoV from the lens spec.
Nyamekye,
ser
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Joined: Tue Jun 19, 2018 10:50 pm

Re: FOV and lens question

Postby ser » Mon Jul 09, 2018 4:34 am

Considering the sensor image area as 3984 x 2952 µm (from OV7725 datasheet), focal length of 2.8 mm and using the formula from Edmund Optics
(https://www.edmundoptics.com.au/resourc ... ld-of-view)
the field of view for the infinity would be:

horz = 2 * atan( h / (2*f) ) = 2 * atan(3.98 / (2*2.8)) = 70.8 degrees
vert = 2 * atan( v / (2*f) ) = 2 * atan(2.95 / (2*2.8)) = 55.6 degrees
(In fact a bit less because of inactive pixels at the sensor border)

Could you please check if my calculations are correct and update the information on the product page? I think that providing FOV values from the lens manufacturer without taking in account the sensor size is somewhat misleading.
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kwagyeman
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Re: FOV and lens question

Postby kwagyeman » Mon Jul 09, 2018 1:28 pm

Will update. Mmm, we have no way of tracking bugs for this kind of stuff... Mmm, um, can you create a bug tracker on the OpenMV media GitHub repo. Like, make the issue there and I will deal with it.
Nyamekye,
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kwagyeman
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Re: FOV and lens question

Postby kwagyeman » Mon Jul 09, 2018 11:49 pm

Updated.
Nyamekye,
fabianschilling
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Joined: Tue Nov 27, 2018 5:33 am

Re: FOV and lens question

Postby fabianschilling » Tue Nov 27, 2018 5:37 am

Hi, could you confirm that the ultra wide-angle lens has the quoted 99/81.9 horizontal/vertical FOV?
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kwagyeman
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Re: FOV and lens question

Postby kwagyeman » Tue Nov 27, 2018 11:57 am

Hi, yes, it does with the OV7725.
Nyamekye,
fabianschilling
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Joined: Tue Nov 27, 2018 5:33 am

Re: FOV and lens question

Postby fabianschilling » Wed Feb 06, 2019 6:32 am

I equipped the OpenMV Cam M7 (which has the OV7725 sensor) with the ultra-wide angle lens (https://openmv.io/collections/products/ ... angle-lens) and I am measuring the following effective fields of views: HFOV=115° and VFOV=86°.
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kwagyeman
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Re: FOV and lens question

Postby kwagyeman » Wed Feb 06, 2019 12:24 pm

Hmmm, the numbers online are from working the math for the FoV equation given the sensor size and focal length. These numbers are less than the numbers quoted by the lens manufacturer which I originally had online. The customer above complained to me about this and I reduced the numbers. Now you are telling me the opposite.

So, I'm not sure what to do here...
Nyamekye,

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