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Dec 6, 2015, 1:14:04 PM12/6/15

to openkinect

Looking at a binary blob I got off of the intel realsense F200 camera

I found numbers in the upper triangle matrix format typically used for

intrinsic calibration.

(A)

1.487056 0.000000 0.012773

0.000000 1.982741 0.029860

0.000000 0.000000 1.000000

This doesn't match numbers from a manual calibration I did a while

ago, and I'm trying to figure out if this is some kind of equivalent

form.

My manual calibration

(B)

475.310051 0.000000 335.282418

0.000000 474.440685 242.982056

0.000000 0.000000 1.000000

If I take the top left number from A which should be a focal length to

pixel size number, and multiply it by half the width of the image 320

I get

475.85792 = 1.487056 * 320

Which is about the size of the number in B.

Similarly if I take the middle number from A, and multiply it by half

the height of the image I get.

475.85784 = 1.982741×240

The last two significant numbers I can't make any sense of how to convert them.

0.012773 should be a number for the X center of the image

0.029860 should be the Y center.

I'm hoping someone with more experience with the math can help.

--

teknotus (Take Notice)

I found numbers in the upper triangle matrix format typically used for

intrinsic calibration.

(A)

1.487056 0.000000 0.012773

0.000000 1.982741 0.029860

0.000000 0.000000 1.000000

This doesn't match numbers from a manual calibration I did a while

ago, and I'm trying to figure out if this is some kind of equivalent

form.

My manual calibration

(B)

475.310051 0.000000 335.282418

0.000000 474.440685 242.982056

0.000000 0.000000 1.000000

If I take the top left number from A which should be a focal length to

pixel size number, and multiply it by half the width of the image 320

I get

475.85792 = 1.487056 * 320

Which is about the size of the number in B.

Similarly if I take the middle number from A, and multiply it by half

the height of the image I get.

475.85784 = 1.982741×240

The last two significant numbers I can't make any sense of how to convert them.

0.012773 should be a number for the X center of the image

0.029860 should be the Y center.

I'm hoping someone with more experience with the math can help.

--

teknotus (Take Notice)

Jan 18, 2016, 8:40:44 AM1/18/16

to openk...@googlegroups.com, tekn...@gmail.com

Hello Daniel,

this has been sitting here for a while, but I've just had a look at

these values for my F200 and got very similar results. Would it be

possible that they just use a different convention for the origin?

Normally, it's in the lower left image corner, so the principal point is

somewhere around (resX/2,resY/2). However, if the convention here is to

use the image center as origin, then if you multiply the values with

res/2, you get something on the order of 5-10 pixels which would fit

pretty well...

Best, Florian

SENT FROM MY DEC VT50 TERMINAL

this has been sitting here for a while, but I've just had a look at

these values for my F200 and got very similar results. Would it be

possible that they just use a different convention for the origin?

Normally, it's in the lower left image corner, so the principal point is

somewhere around (resX/2,resY/2). However, if the convention here is to

use the image center as origin, then if you multiply the values with

res/2, you get something on the order of 5-10 pixels which would fit

pretty well...

Best, Florian

Jan 21, 2016, 5:15:59 PM1/21/16

to Florian Echtler, openkinect

On Mon, Jan 18, 2016 at 5:40 AM, Florian Echtler <fl...@butterbrot.org> wrote:

> Hello Daniel,

>

> this has been sitting here for a while, but I've just had a look at

> these values for my F200 and got very similar results. Would it be

> possible that they just use a different convention for the origin?

>

> Normally, it's in the lower left image corner, so the principal point is

> somewhere around (resX/2,resY/2). However, if the convention here is to

> use the image center as origin, then if you multiply the values with

> res/2, you get something on the order of 5-10 pixels which would fit

> pretty well...

>

> Best, Florian

Intel just released an open sourced (apache license) library that
> Hello Daniel,

>

> this has been sitting here for a while, but I've just had a look at

> these values for my F200 and got very similar results. Would it be

> possible that they just use a different convention for the origin?

>

> Normally, it's in the lower left image corner, so the principal point is

> somewhere around (resX/2,resY/2). However, if the convention here is to

> use the image center as origin, then if you multiply the values with

> res/2, you get something on the order of 5-10 pixels which would fit

> pretty well...

>

> Best, Florian

extracts the factory calibration, and converts it to a point cloud. I

assume the knowledge can be found in the source, but there is too much

for me to have read, and understood it all at this point. There seems

to be some parts marked TODO in the temperature compensation code so

it may still not be a 100% ready solution for the F200. I think the

R200 internally corrects for temperature.

https://github.com/IntelRealSense/librealsense

--

teknotus (Take Notice)

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