2D Optical Calibration

Search…

This version of the calibration system allows you to calibrate your headset with a single stereo camera

These Modules require python 3.7 in order to work
The realsense T265 & T261 can only be used with on application at a time, you'll have to close realsense viewer. 
Above: A video walking you through the 2D calibration process for northstar.
Setup
1.Download the realsense-integration branch of the following repo: 
https://github.com/BryanChrisBrown/ProjectNorthStar/tree/realsense-integration​
2.Setup python with the following dependencies: 
1) Pyrealsense2
2) opencv-contrib-python
3) numpy
3.Print the calibration stand and intel realsense t265 mount m3x12mm screws to mount the t265 itself.
4.If using a Deck X and t261 mount, use the intel realsense t261 mount instead, the screws are included in your Deck X Kit. 
Calibrating your headset
Run through the following steps to calibrate your headset. 
captureGraycodes.py - run python captureGraycodes.py to run this script
Ensure that your headset is placed on the calibration stand, with the stand's camera looking through it where the users' eyes will be.

On line 44 there is a line of code that changes the window offset for the graycode generator.  
 This example here moves the window 1920 pixels to the right, and 0 up and down. You'll want the X value (1920) to be your main monitor's width in pixels. cv2.moveWindow ("Graycode Viewport", 1920, 0) 

It helps to place a piece of cloth over the rig to shield the cameras + headset from ambient light.

The sequence of binary codes will culminate in a 0-1 UV mapping, saved to "./WidthCalibration.png" "./HeightCalibration.png" in your main folder.

calibrateGraycodes.py
Running this script will fit a 3rd-Degree 2D Polynomial to the left and right "eye"'s X and Y distortions.

This polynomial will map from each display's 0-1 UV Coordinates to rectilinear coordinates (where a 3D ray direction is just (x, y, 1.0)).
When you are finished, you may paste the output of the calibrateGraycodes.py into this diagnostic shadertoy to check for alignment. Additionally, ensure that your headset is plugged in and displaying imagery from your desktop. Running this script will display a sequence of gray codes on your North Star, capturing them at the same time.  
The shader toy should look like this when viewed through the headset
Additionally, there should be a NorthStarCalibration.json in this directory which you may use in the Unity implementation.
​

Bending Reality: North Star’s Calibration System

Next - Calibration

Calibration Stand Assembly Guide

Last modified 1yr ago

Export as PDF

Copy link

Contents

Setup

Calibrating your headset