FOV at various resolutions

[bmegli]

Related to #13, HVS#8

From Realsense datasheet (May 2020 Table 3-42. Depth Camera SKU properties:

type	D415	D435
Depth FOV HD	H:65±2 / V:40±1 /D:72±2	H:87±3 / V:58±1 /D:95±3
Depth FOV VGA	H:50±2 / V:40±1 /D:61±2	H:75±3 / V:62±1 /D:89±3
IR Projector FOV	H:67 / V:41 / D:75	H:90 / V:63 / D:99
Color Camera FOV	H:69±1 /V:42±1/D:77±1	H:69±1 /V:42±1/D:77±1

Table 4.3 repeats this information with additions:

• Depth FOV specified at 2 meters
• Due to mechanical tolerances of +/-5%, Max and Min FOV values can vary from lens to
  lens and module to module by ~ +/- 3 degrees

Also:

• 4.4 gives formula for Depth FOV at any distance
• 4.5 has information about Invalid Depth Band

What I am missing is:

• FOV at other resolutions (probably kept with aspect)
• IR imagers FOV
• Color Camera FOV at various resolutions

All those properties may be calculated from intrinsics.

[bmegli]

The FOV can be calculated from intrinsics and resolution:

This would give as FOV in radians, multiply by 180/PI for result in degrees.

[bmegli]

By running the program that calculates FOV from intrinsics we may tabulate FOV.

Note that exact results depend on particular camera (mechanical tolerances + factory calibration)

D435

Depth

• we have three groups related to aspect.
• VGA has highest vertical FOV

resolution	hfov	vfov
1280x720	89.6272	58.3975
640x360	89.6272	58.3975
-	-	-
848x480	89.6272	58.7039
424x240	89.6272	58.7039
-	-	-
640x480	79.2447	63.6762

Color

• we have three groups related to aspect.
• vertical FOV never changes

resolution	hfov	vfov
1920x1080	69.2096	42.4216
1280x720	69.2096	42.4216
960x540	69.2096	42.4216
640x360	69.2096	42.4216
320x180	69.2096	42.4216
-	-	-
848x480	68.8742	42.4216
424x240	68.8742	42.4216
-	-	-
640x360	54.7216	42.4216
320x240	54.7216	42.4216