Chromatic aberration calibration and validation system

A system for chromatic aberration and geometry calibration and validation of virtual reality head mounted displays (VR HMDs) comprising:

• a left eye display and a right eye display,
• a measurement device configured in a way that an HMD to be calibrated or validated is attachable to it in a way as such an HMD would be removably attached to the head of a user;
• wherein the measurement device comprises:
• a left and a right camera, wherein each camera is intrinsically and extrinsically calibrated, and
• a control unit connected to the two cameras as well as configured to deliver control signals to the HMD when removably attached to the measurement device and when a camera inter pupillary distance (IPD) is manually or automatically adjusted to a prechosen HMD IPD,
• wherein the control unit is configured to execute steps comprising:
• a.) setting a virtual IPD equal to the value of camera IPD,
• b.) creating a virtual target object for the displays, the virtual target object having an image center identifying element and a plurality of predetermined points within a field of view (FOV) of the cameras,
• c.) calculating and transmitting images of said virtual target object to the displays of the HMD,
• d.) taking the images of the displays through the HMD lenses with the cameras,
• e.) detecting the virtual object and the image center identifying element within the images,
• f.) determining a shift, for each camera, for the plurality of predetermined points of the virtual object in relation to the image center identifying element,
• wherein the control unit is further configured for
• g.) determining said shift for each color channel of a plurality of color channels, and using the shift between one of the color channels and another for calculating a distortion of the predetermined points within the FOV of the cameras, creating a chromatic aberration heatmap for the HMD based on the shift between the two colors, and determining the chromatic aberration validation or denying the chromatic aberration validation, if a predetermined number of points of the predetermined heatmap is inside or outside a predetermined heatmap threshold of the HMD, respectively;
• and
• h.) determining said shift for the plurality of predetermined points colored black on a white background, or for the plurality of predetermined points colored white on a black background, using the shift for creating a geometry heatmap for the HMD, and determining the geometry validation or denying the geometry validation, if a predetermined number of points of the geometry heatmap is inside or outside a predetermined heatmap threshold of the HMD, respectively,
• wherein the virtual target object a black cylinder portion with vertical lines in a color or white to be taken separately by each camera with the image center identifying element being a centrally arranged line for each camera and the virtual camera being arranged on the center axis of the cylinder portion, or a black cylinder portion with horizontal lines in a color or white to be taken separately by each camera with the image center identifying element being a centrally arranged line for each camera and the virtual camera being arranged on the center axis of the cylinder portion.