Abstract: In this projection display device, which can display 3D images, it is possible to support lens shift and zooming without providing excess additional parts and without increasing the number or output of light-emitting elements when mounting a light-emitting element such as an infrared beam light-emitting element to the main body of the projection display device. The projection display device (1) is able to display 3D images, projects from a projection lens (16) light emitted from a light source device (10) with an internal total reflection prism (15), wherein two prisms are disposed facing each other, therebetween, and is provided with an infrared beam light-emitting element (17). The infrared beam light-emitting element (17) is disposed in a manner so that an infrared beam enters the internal total reflection prism (15), the infrared beam is reflected at the internal total reflection surface (15c) of the internal total reflection prism (15), and is projected via the projection lens (16).

Abstract: For the purpose of providing a staircase which has a lightweight structure, high efficiency in manufacturing and constructing, and creates a sense of lightness in weight, a staircase is composed with a pair of right and left stringers made of truss structural members (10), and treads (12). The truss structural members (10) are composed of the upper chord members (1) and the lower chord members (2) inclined with the slope of the staircase, and a plurality of lattice members (4) for linking the upper chord members (1) and the lower chord members (2), and between the truss structural members (10) are fixed a plurality of linking members (11) which are laid horizontally at each riser height and on which the treads (12) are fixedly supported.