Practical Kinect Stereo Calibration for the Highest Accuracy

I’ve been meaning to write up this post for a while, but I’ve been putting it off 🙂

The release of the Kinect sensor by Microsoft spawned a plethora of research in robotics, computer vision and many other fields. Many of these attempts involved using Kinect for purposes other that what it was originally meant for! That pretty much involves anything other than gesture recognition and skeleton tracking.

Even though Kinect is a very capable device, many people (including us!) don’t get the fact that Kinect was simply not designed for being used as an all-purpose depth and RGB camera. This observation is further bolstered by the fact that the Kinect was not released with a public API, and the official SDK which was released much later was missing a lot of functionality critical to various computer vision applications. For instance, the SDK does not provide a built-in functionality for getting color camera and depth camera calibration values, extrinsics and distortion models. Rather conveniently, the SDK designers simply chose to provide the users with simple functionality, like mapping pixels from world coordinates to RGB coordinates (but no way to do a backproject an image or depth point to ray). Needless to say that in many practical computer vision applications, one needs to constantly re-calibrate the camera in order to minimize the error caused by the mis-calibration of the camera.

Nevertheless, the choice by the SDK designers is understandable: there are proprietary algorithms and methods that are implemented in the Kinect software layer and it may not always be possible to give public access to them. Also, 3rd party open source libraries (such as libfreenect) have tried to reverse-engineer many of the innerworkings of the Kinect sensor and supply the end user with a set of needed functionalities.

With all this, let’s get started! (If you are impatient, feel free to jump to the list of tips I have compiled for you at the end of this post). I have also included PDFs containing checkerboards suitable for printing on large sheets, PVC or aluminum dibond.

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