Abstract: There is provided a visual line detection device including at least one light source configured to radiate light to an eyeball of a user observing a display surface through at least one optical member, and an imaging unit configured to acquire a captured image of the eyeball used to detect a visual line of the user on the display surface by detecting reflected light of the light from the eyeball. The reflected right from the eyeball passes through at least the optical member installed in an optical path along which the light from the display surface travels from the display surface to the eyeball of the user, and is incident on the imaging unit.

Abstract: An eyepiece optical system includes: a first lens having a biconvex shape in optical axis center and having positive refractive power; a second lens having negative refractive power; a third lens having positive refractive power; and a fourth lens having positive refractive power. The first to fourth lenses are arranged in order from an image to be observed. The following conditional expression is satisfied, 0.47<f3/f4<3.00 ??(1) where f3 is a focal length of the third lens, and f4 is a focal length of the fourth lens.

Abstract: There is provided a visual line detection device including at least one light source configured to radiate light to an eyeball of a user observing a display surface through at least one optical member, and an imaging unit configured to acquire a captured image of the eyeball used to detect a visual line of the user on the display surface by detecting reflected light of the light from the eyeball. The reflected right from the eyeball passes through at least the optical member installed in an optical path along which the light from the display surface travels from the display surface to the eyeball of the user, and is incident on the imaging unit.