Head-mounted display device and computer program

A non-transitory computer readable medium storing a computer program for a head-mounted display device including an image display having an optical element to transmit light from an outside scene and a display element to display an image, a camera, and a memory configured to store data of a marker image, the computer program causing a processor to perform a method comprising:

• displaying an image on the image display based at least on the data;
• and
• deriving at least one of a camera parameter of the camera and a spatial relationship, the spatial relationship being between camera and the image display, based at least on an image that is captured by camera in a condition that allows a user to visually perceive that the marker image displayed by the image display and a real marker corresponding to the marker image align at least partially with each other, the real marker being captured in the image by the camera, wherein:
• the real marker includes a first set of feature elements within a rectangle, the first set of feature elements arranged along intersecting diagonal lines connecting four peaks of the rectangle, and
• the marker image includes a second set of feature elements, the second set of feature elements corresponding to the first set of feature elements such that an alignment of the second set of feature elements with the first set of feature elements results in a calibration of the head-mounted display device.