FOV and lens question

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psih
Posts: 2
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
Posts: 3
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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Joined: Sun May 24, 2015 2:10 pm

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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Joined: Sun May 24, 2015 2:10 pm

Re: FOV and lens question

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

Updated.
Nyamekye,

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