Why do the D435 has such a wide distance range from 15mm - 10000mm?

[HDiet]

to calculate the maximum distance a stereo camera can measure I used this formula:

d = f * b /(PixelSize * Disparity)

• d = maximum Distane
• f = focal length
• b = baseline
• Disparity = 1Px

Let´s look at the maximum distance of the D435, which is calculated with this formula:

D435 Specs (focal length = 1.93 mm, PixelSize = 3 µm/px, Baseline b = 50 mm). The maximum distance for the D435 should be, with the formula above d ~ 320 mm (with disparity = 1 Pixel). Why is the D435 able to measure such a wide distance range (up to 10000mm) ? With my calculations it should only reach max. 320 mm.

Can someone please explain this to me?

[MartyG · Accepted solution]

The 400 Series camera's minimum distance (MinZ) is determined with the formula shown in the image below. Please left-click on the image to view the information in full size.

As mentioned by the illustration in note 3, the maximum distance that the camera can depth-sense can be influenced by a factor called the Disparity Shift. When the Disparity Shift value is '0', the camera could theoretically see an infinite distance. As the Disparity Shift value is increased, its minimum sensing distance (MinZ) reduces, meaning that the camera can get closer to objects before the image starts to break up. But at the same time, the maximum distance that the camera can depth-sense (MaxZ) reduces.

In the example illustration below for the D415 camera model, at Disparity shift = '0', MinZ is 45 cm and MaxZ is infinite. If the Disparity Shift is increased to '50' then MinZ reduces to 30 cm but MaxZ also reduces from infinity to just 110 cm. Please left-click on the image to view it in full size.

This images above are taken from Intel's excellent illustrated 400 Series camera tuning guide, which can be viewed here:

https://realsense.intel.com/wp-content/uploads/sites/63/BKM-For-Tuning-D435-and-D415-Cameras-Webinar_Rev3.pdf?language=en_US

[HDiet]

Hello MartyG,

thx for your detailed answer. But there are a lot of things I don´t understand right now e.g. why do I can measure nearer objects, when I reduce the resolution or increase the disparity shift? Do you know, if there is a document out there which explains the fundamentals on how the D435 works?

[MartyG]

I believe that the minimum distance reduction when resolution is lowered is related to a change in pixel size at lower resolutions. The operating range is scaling with the X-Y resolution.

The D435's hardware technicals are covered in detail by the data sheet document for the 400 Series cameras.

https://www.intel.com/content/www/uk/en/support/articles/000026827/emerging-technologies/intel-realsense-technology.html