JPH0521070Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field This invention relates to an overhead projector that projects a transparent original placed on a reflective Fresnel lens.

BACKGROUND TECHNOLOGY In general, there are various types of overhead projectors of this type, but the arrangement of an illumination lamp and an imaging lens with respect to a reflective Fresnel lens is described, for example, in Japanese Utility Model Application Publication No. 180334/1983. The illumination lamp, the center of the reflective Fresnel lens, and the imaging lens are arranged on a straight line toward the screen to be projected so that it can be seen. Therefore,
The optical axis direction of the projected image coincides with the longitudinal axis of the overhead projector.

Problems to be Solved by the Invention As mentioned above, the optical axis of the overhead projector's image coincides with the longitudinal axis of the device, so it can be used while being set in the center of the room. many. In this case, it is difficult for people located at the rear of the device to see the image on the screen because the head of the overhead projector blocks the image. For this reason, consideration was given to setting the stand low so that the head would not get in the way.

Therefore, it is possible to set the overhead projector on one side of the room and project onto a screen located in the center, but in this case the screen is installed at an angle relative to the projected image. The problem is that the entire screen cannot be brought into focus.

Means for solving the problem: A rotating body is provided that rotates in a plane parallel to the reflective Fresnel lens with the center of the reflective Fresnel lens as an axis, and the rotating body is placed at a point symmetrical position with the center of rotation as the axis. An illumination lamp and imaging lens were attached to the.

Function When the positions of the illumination lamp and imaging lens change due to the rotation of the rotating body, the position of the projected image projected on the screen shifts to the left and right. Therefore, by rotating the rotating body, the overhead projector can be set in one corner of a room and projected onto a screen located in the center. Your head will not get in the way, and even if you set the overhead projector in a corner of the room and project onto a screen located in the center, the screen will not be tilted relative to the projected image. It allows you to focus on everything.

Embodiment An embodiment of this invention will be described based on the drawings. First, a reflective Fresnel lens 2 is provided on a rectangular and flat substrate 1. A pair of arms 3 are erected from the substrate 1 so as to be able to rise and fall freely, and a head 4 is supported by these arms 3.

This head 4 has an opening 5 formed therein.
A central shaft 7 supported by ribs 6 is provided at the center of this opening 5 . This central axis 7 is arranged on an axis centered on the center of the reflective Fresnel lens 2. A rotating plate 9 as a rotating body having a protrusion 8 that partially protrudes from the tip of the head 4 is attached to the central shaft 7, and is rotatably held by a nut 10.
On the rotating plate 9, an illumination lamp 11 and an imaging lens 12 are arranged point-symmetrically about the central axis 7.

Next, a reflecting mirror 1 is mounted above the head 4.
3 is attached so that it can be raised and lowered freely.

In such a configuration, a transparent original prepared in advance is placed on the reflective Fresnel lens 2, and the illumination lamp 11 is turned on. As a result, light transmitted through the transparent original and reflected by the reflective Fresnel lens 2 passes through the imaging lens 12 and the reflective mirror 13 and is imaged on the screen. In this case, the apparatus is set in one corner of the room and the screen is set in the center, but even in this state, the positions of the illumination lamp 11 and the imaging lens 12 are similar to that of the reflective Fresnel lens 2. The illumination lamp 11 and the imaging lens 12 are arranged point-symmetrically with respect to the center of the
Since these are displaced in the left-right direction, the optical axis of the reflected image is inclined with respect to the longitudinal axis of the device. Therefore, it is possible to project the image of the transparent original onto the screen located at the center without being out of focus.

As a result of projection in this manner, the device can be set in a corner of a room, and even if the head 4 is located high, it does not enter the field of view of the people behind it and does not get in the way. When the relative position with respect to the screen changes, the protrusion 8
is operated by hand to appropriately rotate the rotating plate 9. As a result, the positions of the illumination lamp 11 and the imaging lens 12 are changed around the center of the reflective Fresnel lens 2, and the projection angle of the optical image is changed to adjust to the most appropriate position.

Although only the minimum necessary structure of the head 4 has been described, a cooling fan, a condenser lens, a cold mirror, a heat ray absorption filter, etc. may be used as necessary.

Further, the illumination lamp 11 and the imaging lens 1
Regarding the heightwise arrangement position with respect to 2, it has been described that they are located in the same horizontal plane, but in actual practice, there is no problem even if their height positions are slightly different.

Effects of the invention As described above, this invention provides an overhead projector in which a transparent original to be projected superimposed on a reflective Fresnel lens is illuminated with an illumination lamp, and is projected using an imaging lens and a reflecting mirror. A rotating body is provided that rotates in a plane parallel to the reflective Fresnel lens with the center of the reflective Fresnel lens as an axis, and an illumination lamp and an imaging lens are mounted on this rotating body at point-symmetrical positions about the center of rotation. By rotating the rotary body and changing the position of the illumination lamp and imaging lens, the position of the projected image projected on the screen can be shifted to the left and right. The projector can be set in a corner of a room and used to project onto a screen located in the center of the room. The head of the overhead projector does not get in the way, and even if the overhead projector is set in a corner of the room and projects onto a screen located in the center, the This has the effect that the screen is relatively free of inclination with respect to the image, and the entire surface of the screen can be focused.

[Brief explanation of drawings]

The drawing shows one embodiment of this invention.
The figure is a plan view, FIG. 2 is a vertical front view, and FIG. 3 is a side view. 2...Reflection Fresnel lens, 11...Illumination lamp, 12...Imaging lens, 13...Reflection mirror.

Claims (1)

[Scope of utility model registration request] In an overhead projector in which a transparent original to be projected superimposed on a reflective Fresnel lens is illuminated with an illumination lamp and projected by an imaging lens and a reflective mirror, this A rotating body that rotates in a plane parallel to the reflective Fresnel lens is provided, and the illumination lamp and the imaging lens are attached to the rotating body at points symmetrical with respect to the center of rotation of the rotating body. Overhead projector.