Hello, i want to build a stereo camera.I choosed this camera -> https://de.ids-imaging.com/store/ui-3241le.htmlBut now i need to know which lens i should take. It should have a S-Mount M12 screw thread.The lens should have 120° viewing angle or not? Becaus the vertical viewing angle of the oculus rift dk2 is 120°???I want to see from a distance: 0,15m - 5m. Is it possible? And witch lens is good enough for my requierments?Thanks!

Hi,I have used a similar camera from IDS. The problem is that you will need a camera with a really short focal length to match the Oculus FOV.The FOV calculations can be made like this:Horizontal FOV = 2*ARCTAN(SH /(2*FL))Vertical FOV = 2*ARCTAN(SV /(2*FL))FL = Focal length of lensSH = Sensor horizontal (width)SV = Sensor vertical (height)The IDS cameras you link use a 1/1.8" sensor which gives the sensor size of 7.176 mm x 5.319 mmUsing the above calculations gives that the needed Focal length will be approx. 2 mm to be able to capture a 120 deg horizontal FOV.

First thanks for your help.This mean only my sensor and focal length is important for the FOV?My sensor has the following SV=5.427 and SH=6.784. When i take a focal length of 1.55 my FOV is 2.28°???Isn't the field Angle important? In our case its 120° or not?When i want to rebuild the human eye i need 120°?Soruce: willsteptoe.com/post/67399683294/ar-rift-camera-selection-part-2

"GermanStudent" wrote:This mean only my sensor and focal length is important for the FOV?Yes, for the field of view only the sensor size and focal length matter. But you seem to have messed up your calculations.The camera you linked in your first post have a 1/1.8 sensor, this means that the sensor diagonal is 1/1.84 inch. This gives a sensor size of 7.176 mm horizontal and 5.319 mm vertical (assuming you use the cameras in landscape mode).If you use a lens with focal length of 1.5 mm you will get the following field of view:HFOV = 2*ARCTAN(SH /(2*FL)) = 2 * ARCTAN ( 0.007176 / (2 * 0.0015)) = 2,35 radians = 135 degreesVFOV = 2*ARCTAN(SV /(2*FL)) = 2 * ARCTAN ( 0.005319 / (2 * 0.0015)) = 2,11 radians = 121 degrees

Hi,"pixelminer" wrote:Vertical FOV = 2*ARCTAN(SV /(2*FL))This only works if the lens is rectilinear though, which is most probably not the case at these values.You would need to know the radial distortion parameters of the lens or the mapping function. Note that in the general case the sensor "size" value indicated in specs (like 1/1.8" here) is more of a "category" than a physical value. (1" sensors are not 1" in any dimension).The imaging area is also smaller than the whole sensor, due to dark rows, etc. The product sheet for the linked camera indicates 6.784 mm x 5.427 mm (still unclear if this is the whole pixel array or the usable array).Another thing to take into account is the crop factor. The lens will project an image circle of a given diameter on the focal plane. Depending on the sensor size, the image rectangle will be entirely or partly inscribed in the circle. This will change the field of view imaged by the sensor. You will only get the full field of view of the lens in all dimensions if you have the entire circle into the image, in which case you won't use all the pixels. The imaged diagonal field of view will match the lens FOV only if the lens projects a circle that perfectly match the sensor diagonal. M12 lenses usually have a "sensor size" rating that you can use to match your sensor.

"joan" wrote:This only works if the lens is rectilinear though, which is most probably not the case at these values.You would need to know the radial distortion parameters of the lens or the mapping function. You are correct, shorter focal length normally means greater distortions and as we approach fish eye lenses linear formulas have greater errors."joan" wrote:Note that in the general case the sensor "size" value indicated in specs (like 1/1.8" here) is more of a "category" than a physical value. (1" sensors are not 1" in any dimension).The imaging area is also smaller than the whole sensor, due to dark rows, etc. The product sheet for the linked camera indicates 6.784 mm x 5.427 mm (still unclear if this is the whole pixel array or the usable array).I missed the specified sensor size in the data sheet. But the specified pixel size (5.3 μm) multiplied with the resolution gives the same values, so it looks as this is the usable array that is specified.Anyhow... Since this is quite expensive cameras I hope that OP's camera dealer can help him/her with selecting a lens with the desired FOV.

Stereo Camera | Meta Community Forums

17 Replies

GermanStudent
Honored Guest
10 years ago
Ok i solved the Problem now i want to Set the brightness is IT possible to Set IT on Auto?
GermanStudent
Honored Guest
10 years ago
@pixelminer

Do you know how i can set the contrast and brightness with open cv?
In my current stream its very bright so its impossible to see details.
Vrally
Protege
10 years ago
"GermanStudent" wrote:
@pixelminer

Do you know how i can set the contrast and brightness with open cv?
In my current stream its very bright so its impossible to see details.

Hi,

OpenCV have some functions for controlling brightness, contrast, gain and exposure:
http://docs.opencv.org/modules/highgui/ ... apture-set

The problem with VideoCapture properties in OpenCV is that not all are actually implemented for each camera type. So if you are unlucky setting the brightness, contrast, gain and/or exposure will have no effect. You have to try out which of these functions that work. In worst case none of them will work. Then you will have two options: Either implement your own IDSCamera->OpenCV wrapper that support the functions you need. Your other option is to use a physical image filter between your lens and the sensor:
http://en.wikipedia.org/wiki/Neutral_density_filter
GermanStudent
Honored Guest
10 years ago
Okay i tried it with a filter, but it was only anoter layer over my picture and was sensless.

Now i try to work with the IDS Api.

With this function i can set the brightness, but it dosent effect my picture...

double soll = 0;
is_SetAutoParameter (0, IS_SET_AUTO_REFERENCE, &soll, 0);

Do i forget something?
There are no errors or warnings that means the libs are correctly implemented.

Ok i think the exposure time is the reason that its so bright. Now i want to set him to auto with this function

double soll = 0;
is_SetAutoParameter (m_hCam, IS_SET_AUTO_REFERENCE, &soll, 0);
Vrally
Protege
10 years ago
"GermanStudent" wrote:
Okay i tried it with a filter, but it was only anoter layer over my picture and was sensless.

Now i try to work with the IDS Api.

With this function i can set the brightness, but it dosent effect my picture...

I cannot really say why your code is not working. In my own inteface with the IDS camera I handle the setup like this:
http://github.com/bjornblissing/osgueye ... p#L98-L197
GermanStudent
Honored Guest
10 years ago
hm okay i think i would take your project can you upload the whole project? because i dont understand how i can start it.
Vrally
Protege
10 years ago
"GermanStudent" wrote:
hm okay i think i would take your project can you upload the whole project? because i dont understand how i can start it.

It already is the whole project. But the project is dependent of OpenSceneGraph, which is a OpenGL scene graph library. You can download the latest stable version from:
http://github.com/openscenegraph/osg/tr ... raph-3.2.1

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Stereo Camera

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