JPH01944A - overhead projector - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overhead projector, and more specifically, the present invention relates to an overhead projector.
The present invention relates to an overhead projector having a projection optical system capable of projecting all images onto a screen with the same sharpness without moving the main body.

[Prior Art] As shown in FIG. 2, a conventional overhead projector of this type includes, for example, a condensing reflector 1i13 provided directly below a light source 12, and a Fresnel lens provided horizontally above the light source 12. 14, a stage 15 on which a projection original image, such as a transparence range 16, is placed, which is provided parallel to this Fresnel lens 4; a projection lens 17, which is located above this stage 15, and which is placed parallel to said stage 15;
, and an upper reflecting mirror 18. Note that 19 is a screen.

[Problems to be Solved by the Invention] In the conventional overhead projector configured as shown in FIG. 2, when the screen 19 is installed perpendicular to the optical axis of the projection optical system, the light source 12
, an optical system consisting of a Fresnel lens 14, a stage 15, and a projection lens 17 are sequentially arranged on a line perpendicular to the transparent range plane 16. A correct image 20 can be obtained on the screen 19 seen in FIG.

However, with this method, if the screen 19 is not installed perpendicularly to the optical axis of the projection optical system, the image 20 on the screen 19 will be greatly distorted and the image 20 will be distorted as shown in FIG. The present invention is intended to solve these problems.

[Means for Solving the Problem] The projection lens of the overhead projector is aligned with a straight line on the plane perpendicular to the optical axis of the projection lens passing through the intersection of the plane perpendicular to the optical axis of the projection lens and the optical axis of the projection optical system. It was set up so that it could rotate freely.

[Function] According to the present invention, the projection lens is rotatable about a straight line on the plane perpendicular to the optical axis of the projection lens passing through the intersection of the plane perpendicular to the optical axis of the projection lens and the optical axis of the projection optical system. Therefore, based on Scheinbruch's law, the extension surface of the transbearing range and the extension surface of the plane perpendicular to the optical axis of the projection lens intersect in a straight line, and the screen is symmetrical to the upper reflecting mirror surface. By setting the extended surface of the virtual screen to intersect with the intersection line when the screen is positioned, a transparent range can be seen on the screen even when the screen is not installed perpendicular to the axis of the projection optical system. All images are projected with the same sharpness.

[Embodiment] FIG. 1 shows an embodiment of the present invention. In FIG. 1, 1 is an overhead projector main body, 2 is a light source such as a halogen lamp, 3 is a condensing reflector that directs the light emitted from the light source 2 upward, and 4 is a condensing reflector that directs the light emitted from the light source 2 and the condensing reflector 3. A Fresnel lens for condensing the light onto a projection lens 7, which will be described later, 5 is a stage for supporting a transparent body such as a transbare range containing a projected image, 8 is an upper reflector, and 9 is a screen. be. The projection lens 7 is provided so as to be rotatable about a straight line on a plane perpendicular to the projection lens optical axis passing through the intersection of the plane perpendicular to the projection lens optical axis and the projection optical system optical axis. .

In the overhead projector configured as shown in FIG. It is illuminated by the light that passes through it. The light that has passed through the transparent range 6 is refracted by the projection lens 7, and then reflected at the upper part &! 8, the direction is changed and the image is projected onto a screen 9.

Here, if the image projected on the screen 9 is unclear over the entire surface, first, by moving the projection lens 7 and the upper reflecting mirror 8 in the optical axis direction of the projection optical system, a part of the projected image can be Adjust so that it is clear. Thereafter, by rotating the projection lens 7 about a straight line on a plane perpendicular to the projection lens optical axis passing through the intersection of the plane perpendicular to the projection lens optical axis and the projection optical system optical axis, The image becomes clearer throughout.

By repeating the above operation several times, an image with uniform clarity can be obtained over the entire surface of the screen 9, which is not installed perpendicularly to the optical axis of the projection optical system.

Another embodiment of the present invention is as follows. That is, in the embodiment shown in FIG.
This makes it possible to more easily operate the embodiment shown in the figures. That is, here, if the image projected on the screen 9 is unclear over the entire surface, first, by moving the projection lens 7 and the upper reflecting mirror 8 in the optical axis direction of the projection optical system, the central part of the projected image is Adjust the image so that it is clear, then turn the projection lens 7
By just performing two operations, rotating the lens around a straight line passing through the principal point of the projection lens and on the principal plane of the projection lens, a clear image similar to the center of the entire surface of the image being projected can be obtained. is obtained.

[Effects of the Invention] The present invention provides a projection lens rotatable about a straight line on a plane perpendicular to the projection lens optical axis passing through the intersection of the plane perpendicular to the projection lens optical axis and the projection optical system optical axis. Therefore, if the screen is not installed perpendicular to the axis of the projection optical system, the projection lens can be projected onto the screen simply by rotating the projection lens about the straight line. This has the effect of achieving uniform sharpness over the entire surface of the image.

[Brief explanation of the drawing]

FIG. 1 is a side sectional view showing one embodiment of the present invention, FIG. 2 is a side sectional view showing an example of the conventional technology, and FIG.
FIG. 3 is a side cross-sectional view showing the effect of the conventional technique shown in FIG. 1... Overhead projector - body 2... Light source 3... Condensing reflector 4... Fresnel lens 5... Stage 6... Transbare range - 7... Projection lens 8... Upper reflector 9...
screen

Claims (1)

[Claims] a light source, a stage supporting a transparent body containing a projected image, a projection head comprising a projection lens and a reflecting mirror, and a Fresnel condensing light from the light source to the projection lens to project the projected image onto an observation screen. In an overhead projector having a lens and a condensing reflector, the projection lens has a straight line on a plane perpendicular to the optical axis of the projection lens passing through the intersection of the plane perpendicular to the optical axis of the projection lens and the optical axis of the projection optical system. An overhead projector characterized by being rotatably provided.