In an image projection device including a laser beam source and a diffractive optical element provided on an optical path of a laser beam L from the laser beam source, a transparent member having a refractive index higher than that of an area ahead of an emission surface on the optical path of the laser beam L and a diffractive optical element is formed on an emission surface of the transparent member. The laser beam L is obliquely incident on the diffractive optical element. The diffractive optical element generates a diffraction image in an area which is not overlapped with zeroth order light LR of the laser beam L and an area occupied by a conjugate image, and is arranged in a direction to irradiate a screen with diffracted light forming the diffraction image while substantially eliminating the zeroth order light and the diffracted light forming the conjugate image.

A dome screen projection system includes a dome screen unit and two sets of projectors. The dome screen unit includes a top side, two opposite lateral sides extending downward from two opposite ends of the top side, and a curved projection surface extending downwardly from the top side between the opposite lateral sides. Each of the two sets of projectors are disposed on the top side proximally to one of the lateral sides. The two sets of projectors are directed toward the curved projection surface.

A dome screen projection system includes a dome screen unit and two sets of projectors. The dome screen unit includes a top side, two opposite lateral sides extending downward from two opposite ends of the top side, and a curved projection surface extending downwardly from the top side between the opposite lateral sides. Each of the two sets of projectors are disposed on the top side proximally to one of the lateral sides. The two sets of projectors are directed toward the curved projection surface.

Disclosed is a starry sky reproducing sheet containing: N laminated light reducing sheets stuck together, each of which has homogeneous light reducing effects (where N is two or larger); the starry sky reproducing sheet containing, with M and L being two mutually different integers that are one or larger and N or smaller (M>L): L-layer transmission holes that are formed through L light reducing sheets stuck together, so that light beams pass therethrough; and M-layer transmission holes that are formed, through M light reducing sheets stuck together including the L light reducing sheets, at different positions from those of the L-layer transmission holes; wherein light beams incident on one face of the starry sky reproducing sheet pass through the L- and M-layer transmission holes while being attenuated at mutually different light reduction ratios to become L- and M-layer transmitted beams respectively which are visibly recognizable as transmitted-light stars having mutually different brightnesses.

Disclosed is a starry sky reproducing sheet containing: N laminated light reducing sheets stuck together, each of which has homogeneous light reducing effects (where N is two or larger); the starry sky reproducing sheet containing, with M and L being two mutually different integers that are one or larger and N or smaller (M>L): L-layer transmission holes that are formed through L light reducing sheets stuck together, so that light beams pass therethrough; and M-layer transmission holes that are formed, through M light reducing sheets stuck together including the L light reducing sheets, at different positions from those of the L-layer transmission holes; wherein light beams incident on one face of the starry sky reproducing sheet pass through the L- and M-layer transmission holes while being attenuated at mutually different light reduction ratios to become L- and M-layer transmitted beams respectively which are visibly recognizable as transmitted-light stars having mutually different brightnesses.

The present invention implements the movement of an object in an image projected onto a dome-shaped screen while maintaining an original resolution without increasing the resolution of a video projector as a projection device. In a device for projecting an image onto the dome-shaped screen D, an aggregate of two or more video projectors 1A, 1B for projecting a moving image is disposed in a dome such that the range of projection from the aggregate covers the whole sphere, and the aggregate is mounted on a stand 2 having two or more rotating shafts.

The present invention implements the movement of an object in an image projected onto a dome-shaped screen while maintaining an original resolution without increasing the resolution of a video projector as a projection device. In a device for projecting an image onto the dome-shaped screen D, an aggregate of two or more video projectors 1A, 1B for projecting a moving image is disposed in a dome such that the range of projection from the aggregate covers the whole sphere, and the aggregate is mounted on a stand 2 having two or more rotating shafts.

Disclosed is a starry sky reproducing sheet containing: N laminated light reducing sheets stuck together, each of which has homogeneous light reducing effects (where N is two or larger); the starry sky reproducing sheet containing, with M and L being two mutually different integers that are one or larger and N or smaller (M>L): L-layer transmission holes that are formed through L light reducing sheets stuck together, so that light beams pass therethrough; and M-layer transmission holes that are formed, through M light reducing sheets stuck together including the L light reducing sheets, at different positions from those of the L-layer transmission holes; wherein light beams incident on one face of the starry sky reproducing sheet pass through the L- and M-layer transmission holes while being attenuated at mutually different light reduction ratios to become L- and M-layer transmitted beams respectively which are visibly recognizable as transmitted-light stars having mutually different brightnesses.

Disclosed is a starry sky reproducing sheet containing: N laminated light reducing sheets stuck together, each of which has homogeneous light reducing effects (where N is two or larger); the starry sky reproducing sheet containing, with M and L being two mutually different integers that are one or larger and N or smaller (M>L): L-layer transmission holes that are formed through L light reducing sheets stuck together, so that light beams pass therethrough; and M-layer transmission holes that are formed, through M light reducing sheets stuck together including the L light reducing sheets, at different positions from those of the L-layer transmission holes; wherein light beams incident on one face of the starry sky reproducing sheet pass through the L- and M-layer transmission holes while being attenuated at mutually different light reduction ratios to become L- and M-layer transmitted beams respectively which are visibly recognizable as transmitted-light stars having mutually different brightnesses.

Provided is a quick-responsive voice control technique even in use in a planetarium. A control device of a projector of a planetarium includes: a storage unit that stores a plurality of commands for controlling the projector, flags indicating whether or not the respective commands can be executed, and keywords associated with the respective commands; a voice acquisition unit that acquires voice data; a control unit that controls the control device; and a communication unit that communicates with the projector. The control unit determines whether or not each of the commands for the projector can be executed on the basis of state information of the projector, the state information being acquired through the communication unit, updates the flags on the basis of the determination result, generates character string information from voice data acquired by the voice acquisition unit, acquires a command in which an executable flag is set from the storage unit using the character string information as a search key, and transmits the acquired command to the projector.