Distance calculation device, distance calculation method, and distance calculation program
A distance calculation device includes a first light source and a second light source that emit detection light from positions different from each other and that apply the detection light to at least one of eyeballs of a subject; an imaging unit that captures an image of the eyeball of the subject to which the detection light is applied; a position calculator that, based on the image of the eyeball of the subject that is captured by the imaging unit, calculates 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 center-center distance calculator that calculates a center-center distance between the position of the first cornea reflection center and the second cornea reflection center; and an object distance calculator.
1 . A distance calculation device comprising:
a first light source and a second light source that emit detection light from positions different from each other and that apply the detection light to an eyeball of a subject;
an imaging unit that captures an image of the eyeball to which the detection light is applied;
a position calculator that, based on the image of the eyeball, calculates 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 center distance calculator that calculates a center-center distance between the position of 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; and
an object distance calculator that sets 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 of the subject, calculates an object distance between the imaging unit and the eyeball,
wherein the first light source and the second light source emit the detection light alternately, and the position calculator calculates the position of the first cornea reflection center and the position of the second cornea reflection center based on images captured at respective timings of emission.
2 . The distance calculation device according to claim 1 , wherein
the position calculator calculates the position of the first cornea reflection center based on a first image, of the images, that is captured at a timing at which the detection light is emitted from the first light source and calculates the position of the second cornea reflection center based on a second image, of the images, that is captured at a timing at which the detection light is emitted from the second light source.
3 . 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.
4 . 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.