Iterative point indexing

A head-mounted display (HMD) device comprising:

• an eye tracking device having;
• an image sensor;
• and
• one or more processors configured to at least:
• acquire with the image sensor, at least one optical target image from an optical target, wherein the optical target contains image points in a pattern;
• index image points within the optical target image;
• input indexed image points into an optimization algorithm that calculates a hardware calibration of the HMD unit;
• and
• writing hardware calibration values calculated from the optimization algorithm to the HMD unit;
• wherein the image points are indexed by:
• selecting a rigid region of the optical target image;
• assigning indices to image points within the rigid region;
• fitting a fitted model function to at least one column and one row of the image points of the region;
• predicting the location of at least one image point using the fitted model function;
• and
• assigning the predicted image point an index.

A non-transitory computer-readable storage medium storing instructions which, when executed by a head-mounted device (HMD) cause the HMD to carry out the steps of:

• acquiring with the HMD, at least one optical target image from an optical target, wherein the optical target contains image points in a pattern;
• indexing image points within the optical target image;
• inputting indexed image points into an optimization algorithm that calculates a hardware calibration of the HMD;
• and
• writing hardware calibration values calculated from the optimization algorithm to the HMD unit;
• wherein the image points are indexed by:
• selecting a rigid region of the optical target image;
• assigning indices to image points within the rigid region;
• fitting a fitted model function to at least one column and one row of the image points of the region;
• predicting the location of at least one image point using the fitted model function;
• and
• assigning the predicted image point an index.