Distance calculation device, distance calculation method, and distance calculation program

A distance calculation method comprising:

• emitting detection light from a first light source and a second light source that are arranged in positions different from each other and applying the detection light to an eyeball of a subject, wherein the emitting comprises emitting the detection light from the first light source and the second light source alternately;
• by an imaging unit, capturing, at respective different timings of emission from the first light source and the second light source, images of the eyeball to which the detection light is applied;
• based on the images of the eyeball captured at the respective different timings of emission, calculating a position of a first cornea reflection center according to the detection light from the first light source and a position of a second cornea reflection center according to the detection light from the second light source;
• calculating a center-center distance between the first cornea reflection center and the second cornea reflection center based on a number of pixels between the position of the first cornea reflection center and the position of the second cornea reflection center of the image of the eyeball;
• setting a given constant for a cornea curvature radius of the eyeball;
• and
• based on the center-center distance and the cornea curvature radius of the eyeball, calculating an object distance between the imaging unit and the eyeball.

A non-transitory computer readable recording medium storing therein a distance calculation program that causes a computer to execute

• a process of emitting detection light alternately from a first light source and a second light source that are arranged in positions different from each other and applying the detection light to an eyeball of a subject;
• a process of, by an imaging unit, capturing images of the eyeball to which the detection light is applied at respective different timings of emission from the first light source and the second light source;
• a process of, based on the images of the eyeball captured at the respective different timings of emission, calculating each of a position of a first cornea reflection center according to the detection light from the first light source and a position of a second cornea reflection center according to the detection light from the second light source;
• a process of calculating a center-center distance between the first cornea reflection center and the second cornea reflection center based on a number of pixels between the first cornea reflection center and the second cornea reflection center of the image of the eyeball;
• a process of setting a given constant for a cornea curvature radius of the eyeball;
• and
• a process of, based on the center-center distance and the cornea curvature radius of the eyeball, calculating an object distance between the imaging unit and the eyeball.