JPS6331050Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a dimming device for an overhead projector.

In an overhead projector, when the lamp is on, the surface of the document is very bright, and it is very dazzling when the user performs operations such as changing or writing on the document. For this reason, when performing such operations, it is common practice to reduce the amount of light using a dimming device to prevent too much glare. A device that lowers the voltage using an electrical switch is generally used as a dimming device. However, since such devices use transformers, resistors, semiconductors, etc., they are heavy, cause power loss, and also generate noise when switching, which is output as noise from the speakers. There are drawbacks such as slow movement. In addition to this,
Mechanical dimming devices using ND filters, comb filters, etc. are also known, but they have the disadvantage of a large loss in light quantity. Also, overhead projectors are usually used in dark rooms, so
The periphery of the device is dark in contrast to the very bright surface of the document, making it difficult to replace the document or use or check materials placed in the periphery.

The object of this invention is to provide an overhead projector dimmer device with less electrical or light loss.

A further object of this invention is to provide such a dimming device that does not generate noise due to electrical changeover switches.

A further object of this invention is to provide the above-mentioned dimming device which can also illuminate the periphery of the device body during dimming.

The overhead projector dimmer device according to this invention includes a semi-transparent reflective member that can enter and retreat into an optical path between an original irradiation lamp and an original table glass, and the semi-transparent reflective member enters into the optical path. When the apparatus is in use, the transmitted light illuminates the document surface above or below the document table glass, and the reflected light illuminates the periphery of the apparatus main body.

Hereinafter, embodiments of this invention will be described with reference to the accompanying drawings. In FIG. 1, inside the overhead projector main body 1, there is a document irradiation lamp 3 equipped with a reflector 2 at the bottom, a Fresnel lens and document table glass 5 at the top, and a pin 6 on one side. A swingable transflective member 7 and a diffuser plate 8 are provided at the side opening on the opposite side thereof. Above the document table glass 5, a projection mirror 10 is held on a stand (not shown).

During projection, the transflective member 7 is retracted from the optical path between the original irradiation lamp 3 and the original platen glass 5 as shown in the figure, and the original placed on the original platen glass 5 is exposed to the projection lens 9 and the original platen glass 5. Projection mirror 10
projected onto the screen by When dimming the light for exchanging originals, the transflective member 7 swings around the pin 6 and enters the optical path between the lamp 3 and the original platen glass 5, as shown in FIG. The transmitted light illuminates the document table glass 5 to facilitate document exchange and writing operations, and the reflected light is diffused by the diffuser plate 8 to widely illuminate the periphery of the apparatus body 1, thereby illuminating the surrounding area. Facilitate the use or confirmation of exchange manuscripts and materials kept in the department.

For this purpose, the transflective member 7 has means for selectively positioning it in two positions, indicated by a solid line and a broken line. The simplest example of this positioning means can consist of a manual lever or manual knob provided on the pin 6 and a stopper against which the transflective member 7 can rest in both positions. As the transflective member 7, in addition to the generally widely known half mirror, a comb-shaped total reflection mirror as shown in FIG.
A transparent substrate on which a striped reflective film 7a as shown in the figure is formed by vapor deposition or the like can be used. The semi-transparent reflective member 7 can also be moved in and out by linear movement or the like. Further, the light reflected from the transflective member 7 may directly illuminate the periphery of the device main body 1, or may be reflected again by a normal total reflection mirror so that the direction thereof can be freely changed.

Fig. 5 shows an example in which this invention is applied to a reflective overhead projector, in which a transparent original placed on a Fresnel reflector 11 which also serves as an original table glass is viewed from above by a reflector 2 and a lamp 3. When illuminated, the Fresnel reflector 11
The reflected image thereof is projected onto the screen by the upper projection lens 9 and projection mirror 10. Instead of the Fresnel reflector 11, if a special manuscript glass, such as a bead sheet made of many transparent spheres arranged closely together, is used in combination with a Fresnel lens plate, it is possible to read opaque originals such as ordinary paper. You can use this by placing it below.

The transflective member 7 is swingably provided around the pin 6 so that it can enter and retreat into the optical path between the lamp 3 and the Fresnel reflector 11. A plate or mirror 12 is arranged. In normal use, the transflective member 7 is retracted from the optical path of the lamp 3, as shown in FIG. 5, and when the light is dimmed,
As shown in FIG. 6, part of the light from the lamp 3 enters the optical path and passes through the Fresnel reflector 1.
A part of the reflected light is reflected by a diffuser plate or a mirror 12 and illuminates the peripheral lower part of the main body of the apparatus.

In this way, according to this invention, the transflective member is moved in and out of the optical path to attenuate the light and illuminate the periphery of the device body, so there is no electrical or light loss, and there is no noise caused by the electrical changeover switch. This further improves operability.

[Brief explanation of drawings]

Figure 1 is a schematic diagram showing an example in which this invention is applied to a transmission type overhead projector, Figure 2 is an explanatory diagram of the operation of the device shown in Figure 1, and Figures 3 and 4 are illustrations of this invention. FIG. 5 is a schematic diagram showing an example of applying this invention to a reflective overhead projector, and FIG. 6 is a diagram showing the device shown in FIG. 5. FIG. 1...Device body, 2...Reflector, 3...
Original irradiation lamp, 4... Fresnel lens, 5...
Original table glass, 6... Pin, 7... Transflective member, 8... Diffusion plate, 9... Projection lens, 10...
projection mirror.

Claims (1)

[Scope of utility model registration request] Equipped with a semi-transparent reflective member that can enter and retreat into the optical path between the document irradiation lamp and the document table glass,
When the transflective member enters the optical path, the transmitted light illuminates the document surface above or below the document table glass, and the reflected light illuminates the periphery of the main body of the apparatus. light device.