Abstract: Disclosed is a head mounted display device. The head mounted display device includes a head mount unit wearable on a head of a user, a display unit supported on the head mount unit and sending an image to eyes of the user, and a position adjustment unit coupled to the head mount unit, connected to the display unit, and moving the display unit relative to the head mount unit such that a position of the display unit varies with respect to the eyes of the user.

Abstract: A direct-type reflective diffusion lens and a lighting installation including the reflective diffusion lens. The reflective diffusion lens includes a first reflective surface concave and having a longitudinal cross-section with a parabola shape or normal distribution shape to totally reflect incident light, and a bottom surface comprising a light incident surface concave toward the first reflective surface. The reflective diffusion lens includes a second reflective surface having a longitudinal cross-section inclined by a first angle with respect to a central axis of the lens to totally reflect incident light and a refractive surface connecting the first reflective surface with the bottom surface. The refractive surface includes a first refractive surface having a longitudinal cross-section inclined by a second angle with respect to the central axis and a second refractive surface having a longitudinal cross-section inclined by a third angle with respect to the central axis.

Abstract: Embodiments of the present disclosure relate to a direct-type reflective diffusion lens and a lighting installation including the reflective diffusion lens. The reflective diffusion lens includes a first reflective surface concave and having a longitudinal cross-section with a parabola shape or normal distribution shape to totally reflect incident light, a bottom surface comprising a light incident surface concave toward the first reflective surface, and a second reflective surface having a longitudinal cross-section inclined by a first angle with respect to a central axis of the lens to totally reflect incident light and a refractive surface connecting the first reflective surface with the bottom surface and comprising a first refractive surface having a longitudinal cross-section inclined by a second angle with respect to the central axis and a second refractive surface having a longitudinal cross-section inclined by a third angle with respect to the central axis.

Abstract: A reflective diffusion lens may include a bottom surface concave toward a reflective surface, a longitudinal cross section of the bottom surface being formed in a parabolic shape or normal distribution shape such that light incident upon the bottom surface is incident upon the reflective surface, and the reflective surface concave toward the bottom surface. The reflective surface may include a concave surface having a longitudinal cross section formed in a parabolic shape or normal distribution shape to totally reflect the light transmitted from the bottom surface and incident upon the reflective surface. A lighting installation may include at least one light source to emit light, a reflective diffusion lens to collect light emitted from the light source, and a reflective plate positioned at a lower portion of the light source and adapted to adjust a direction or amount of light reaching the reflective plate.