Projection optical system and image projection apparatus
A technology of projection optical system and positive refraction, which is applied in the direction of optics, projection devices, optical components, etc., and can solve the problem of size increase
Active Publication Date: 2014-06-04
RICOH KK
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Problems solved by technology
Thus, the lens diameter of the lens near the concave mirror and the size of the concave mirror will be further increased
Method used
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[0220] According to at least one exemplary embodiment of the present invention, it is possible to reduce the lens diameter of the lens close to the concave mirror or the size of the concave mirror to reduce the overall size of the projection optical system.
[0221] According to at least one exemplary embodiment of the present invention, it is possible to provide a compact projection optical system when super-short distance projection is realized.
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Disclosed is a projection optical system, including a first lens group configured to include at least one lens and have a positive refractive power, a second lens group configured to include at least one lens and have a positive refractive power, a third lens group configured to include at least one lens and have a negative refractive power, a fourth lens group configured to include at least one lens configured to have an aspheric surface or a free-form surface, and a concave mirror, wherein the first lens group, the second lens group, the third lens group, the fourth lens group, and the concave mirror are arranged in order and the projection optical system is a non-telecentric optical system.
Description
technical field [0001] An aspect of the present invention relates to at least one of a projection optical system and an image projection device. Background technique [0002] Image projection devices are known which can be placed closer to the screen than conventional devices. Such an image projection device is called a close-range projector. Proximity projectors are capable of avoiding the glare of incident projected light on the eyes of a speaker (such as a presenter or lecturer) standing near the screen, which is the projection surface on which the image is projected. In addition, a close-range projector can project an enlarged image without placing the projector near an audience listening to a speaker's utterance, so that exhaust gas or noise from such an image projection device does not affect the audience when used. [0003] The projection optical system contained in the close-range projector is set so that the angle of view of the traditional (coaxial or rotationall...
Claims
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IPC IPC(8): G02B17/08G02B13/18G02B7/02
CPCG03B21/28G02B13/16G02B17/08G02B21/28G03B21/147
Inventor 辰野響
Owner RICOH KK