the origin of Depth

[KMiya7]

Could you tell me exactly where the origin of depth of Real sense D415/D435 is?

Experimentally I knew the approximate position, but I'd like to know the exact position if possible.

Although I confirmed the D415/D435 spec sheet, I couldn't find it.

[MartyG]

The 0,0,0 origin of the 400 Series cameras is the 'baseline' centerpoint between the left and right imagers. The link below describes the origin.

https://github.com/IntelRealSense/librealsense/wiki/Projection-in-RealSense-SDK-2.0# point-coordinates Projection in RealSense SDK 2.0 · IntelRealSense/librealsense Wiki · GitHub

[KMiya7]

Hi Marty

Thank you for your quick response.

I understood [0,0,0] referring to the center of the physical imager. However, I still don't know where the imager is located inside 400 Series cameras. Do you have any information regarding the exact imager position inside D415/D435 module.

I referred to the following spec sheet, but it seems it doesn't mention to the Z position of the imager.

https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/Intel-RealSense-D400-Series-Datasheet.pdf https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/Intel-RealSen…

* P87-P96

[MartyG]

You can download official CAD files for the full range of 400 Series cameras and modules from here:

https://www.intel.com/content/www/us/en/support/articles/000026841/emerging-technologies/intel-realsense-technology.html Intel® RealSense™ D400 Series Production CAD Files

[KMiya7]

That is exactly what I want. I would like to express my gratitude. Thank you so much.

[MartyG]

Thanks very much, you're very welcome. I'm glad you got what you needed. Have a great day!

[KMiya7]

There's one more thing I'd like to ask you.

You wrote " The 0,0,0 origin of the 400 Series cameras is the 'baseline' centerpoint between the left and right imagers" in the previous message. However, document mentions "Each stream of images provided by this SDK is also associated with a separate 3D coordinate space, specified in meters, with the coordinate [0,0,0] referring to the center of the physical imager."

https://github.com/IntelRealSense/librealsense/wiki/Projection-in-RealSense-SDK-2.0# point-coordinates https://github.com/IntelRealSense/librealsense/wiki/Projection-in-RealSense-SDK-2.0# point-coordinates

In our experiment, it seems depth coordinate is based on the coordinate [0,0,0] referring to the center of left IR imager. Could you tell me if my understanding is correct?

[MartyG]

The 400 Series' data sheet document defines the baseline as "The distance between the center of the left and right imagers". The data sheet adds: "The left and right imagers capture the scene and sends imager data to the depth imaging processor, which calculates depth values for each pixel in the image by correlating points on the left image to the right image and via shift between a point on the Left image and the Right image"..

The sentence ""Each stream of images provided by this SDK is also associated with a separate 3D coordinate space, specified in meters" is easier to understand when read in context in the original documentation. The paragraph before that sentence talks about the 2D image coordinate system. So it is saying that there are 2D coordinates based on the pixels on the image, and also a 3D coordinate system based on the world coordinates of what the camera is seeing.

The baseline distance between the imagers is 55 mm on the D415 and 50 mm on the D435.

[KMiya7]

Thank you always for quick reply.

We understood the meaning of the baseline and what documents described. But, I am still confused the sentences which you were telling me at first.

- "The 0,0,0 origin of the 400 Series cameras is the 'baseline' centerpoint between the left and right imagers."

Do you mean The 0,0,0 origin of the 400 Series depth is the 'baseline' centerpoint between the left and right imagers."? In our experiment, it seems depth coordinate is based on the coordinate [0,0,0] referring to the center of left IR imager. Please look at the attached images.

Sorry again for asking such a same thing.

[Depth Image]

[IR left image]

[IR left image overlaid with depth image]

[IR right image]

[IR right image overlaid with depth image]

[MartyG]

The baseline is between the left and right imagers. However, RealSense stereo cameras tend to rely on the left imager to generate the image. The dynamic calibration guide for the 400 Series says: "Assume left camera is the reference camera and is located at world origin."

https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/RealSense_D400_Dyn_Calib_Programmer.pdf https://www.intel.com/content/dam/support/us/en/documents/emerging-technologies/intel-realsense-technology/RealSense_D40…

[KMiya7]

Thank you. It is clear now.