JPS5822175Y2 - overhead projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an overhead projector that can be used interchangeably with various projection lenses having different focal lengths.

More specifically, by arbitrarily changing the ratio of the amount of elevation of the projection head with respect to the material placement stage and Fresnel lens and the amount of elevation of the light source with respect to the material placement stage and Fresnel lens, the projection head can have different focal lengths. An overhead projector in which various projection lenses can be used interchangeably, so that the magnification of an image can be changed by the above-mentioned vertical movement of the projection head and light source section and by exchange of the projection lens. - related to.

FIG. 3 is an explanatory diagram of the principle of a general overhead projector 30, in which numeral 31 indicates an original image mounting stage and numeral 32 indicates a Fresnel lens.

A light source 33 placed below the Fresnel lens 32 illuminates the original image 31a on the stage 31, and the image is projected onto the screen 35 by the projection lens 34a of the projection head 34 above.
projected on.

In the above, the separation distance 11 between the projection head 34 and the light source section 33 is determined by the focal length of the projection lens 34a.

In other words, once the position of the projection head 34 is determined, the separation distance 12 between the Fresnel lens 32 and the light source section 33 is determined by the focal length of the projection lens 34a.

For example, if the light source section 33 is positioned so that the convergence point A of the light beam emitted from the light source section 33 matches the position a of the projection lens 34a as shown in the figure, the folded image will be clear and free of chromatic aberration. becomes.

By the way, when changing the magnification of an image in this type of overhead projector, it is generally done by moving the projection head 34 and the light source section 33 up and down at a constant ratio with respect to the Fresnel lens 32.

According to such a means, the projection lens 34a and the light source section 33 are brought close to or separated from the Fresnel lens 32, so if this proximity or separation is achieved beyond a certain level, the screen 3
A problem arises in that distortion, chromatic aberration, etc. occur in the image projected onto the screen 5, and the image becomes unclear.

On the other hand, as another means of changing the magnification of the image, the entire overhead projector 30 may be moved and the screen 35 may be moved.
It is conceivable to perform the projector in close proximity to or at a distance from the overhead projector.
30 itself has to be moved every time the magnification is changed, which is troublesome. Furthermore, if the overhead projector 30 is separated from the screen 35 by a certain amount or more, the amount of light rays irradiated to the screen 35 decreases, making it difficult to obtain clear magnification. There are problems such as not being able to obtain an image.

In view of the above-mentioned problems, the present inventor devised the present invention in order to effectively solve the problems.

The purpose of this invention is to use various projection lenses with different focal lengths in the projection head by arbitrarily changing the ratio of the amount of elevation of the projection head to the amount of elevation of the light source with respect to the material mounting stage and Fresnel lens. to be able to
This makes it possible to change the magnification of the image both by changing the magnification by moving up and down the projection head and the light source, and by changing the magnification by changing the projection lens. An object of the present invention is to provide an overhead projector that can move up and down within a range that provides the best image quality and can obtain a desired projected image without causing chromatic aberration.

Therefore, an object of the present invention is to provide a light source using a support lever that moves up and down integrally with the projection head, one end of which is rotatably pivoted, and the other end of which is slidably supported by a movable block. The light source is slidably supported at the center of this support lever, which is disposed adjacent to the projection head and rotates around the movable block as a fulcrum when the projection head moves up and down. An overhead projector in which the ratio of the amount to the amount can be arbitrarily changed by moving the support lever 20 forward and backward in the length direction of the support lever 20.
is to provide.

Figure 1 shows an overhead projector according to the present invention.
1 and 2 are enlarged views of the support mechanism of the light source section, respectively.

2 indicates a box-shaped casing, and the upper surface of the casing 2 holds a transparent original image mounting stage 3.

Directly below this stage 3, a Fresnel lens 4 is fixedly installed parallel to this 3, and below this Fresnel lens 4, a light source box 5 is supported by a pair of guide rods 6, 6 so as to be vertically movable.

A coil spring 7.7 is wound around this guide rod 6.6, and the lower limit of the light source box 5 is limited by this spring 7.7.

A light source section 8 consisting of an upper condenser lens 8a, an intermediate light source lamp 8b, and a lower condensing reflector 8C is fixedly installed in the light source box 5.

The light source section 8 is disposed so as to coincide with the optical axis of the Fresnel lens 4, and vertically moves up and down in line with the optical axis as the light source box 5 moves up and down.

A column 9 is vertically erected from the left side surface 2a of the casing 2,
A head frame 10 is attached to this support 9 so as to be movable up and down, and a projection head 11 is integrated at the tip of this head frame 10.

A projection lens 12 is fixed to this head 11, and this projection lens 12 is made up of an input lens 12a, a reflecting mirror 12b, and an output lens 12C, and is arranged to coincide with the optical axis.

A roller 13 having a high coefficient of friction, such as rubber, is rotatably provided inside a base 10a inserted through the support 9 of the frame 10, and the outer periphery of this roller 13 is brought into contact with the side surface 9a of the support 9.

A leaf spring 14 is disposed on the inner surface of the base 10a with both upper and lower ends fixed.

This plate spring 14 is provided so as to be inclined in the direction of the support column 9 as shown in the figure, so that the roller 13 is constantly pressed in the direction of the support column 9 by this plate spring 14.

By doing this, the roller 13 can be rotated by rotating the handle.
When the support column 9 is rotated, the roller 13 is frictionally engaged with the support column 9 and reliably rolls in the vertical direction, whereby the head frame 1
0 and the head 11 integrated therewith are moved up and down.

A cross-sectional support plate 15 is fixed inside the right side surface 2b of the casing 2 so as to face the column 9.

The support portion 15a of the support plate 15 that protrudes in the horizontal direction holds and fixes the U-shaped bracket 16 laterally.

A threaded rod 17 is rotatably suspended horizontally on the left and right support pieces 16a and 16b of the bracket 16, and the right end of this 17 is extended to the outside from the right side surface 2b, and an operator 17 is attached to this extended end.
Fix b.

A moving block 18 is screwed into the screw rod 17 between the left and right support pieces 16 a and 16 b, and the moving block 18 is screwed onto the screw rod 17 .
By rotating 7b, this block 18 is moved forward and backward in a direction perpendicular to the optical axis.

The upper end 19a of the lever 19 is engaged with the lower surface 10b of the frame base 10a, and the lever 19 is extended downward.

A support lever 20 is horizontally mounted on the lower end of the lever 19 and the moving block 18 so as to be separated from the light source box 5.

Specifically, the left end of the support lever 20 shown in the figure is connected to the pin 19b.
is rotatably pivoted to the lower end of the lever 19, and
The elongated hole 20a at the right end is slidably attached to the moving block 18 via a pin 18a.

A pin 5a is slidably inserted into a long hole 20b formed in the center of the support lever 20, and the pin 5a is integrated into the light source box 5.

Thereby, the light source box 5 is slidably supported at the center of the support lever 20.

The support lever 20 rotates in the vertical direction about the pin 18a as a fulcrum when the projection head 11 moves up and down, so that the light source box 5 can be moved up and down and closed.

The magnification of the image is changed by the vertical movement of the projection head 11 and the light source box 5, that is, the light source unit 8 disposed inside this 5.

Incidentally, the ratio between the lifting amount 1 of the projection head 11 and the lifting amount 13 of the light source section 8 is determined by the focal length of the projection lens 12.

Therefore, when using various projection lenses with different focal lengths and changing the magnification of the image using both the exchange of the projection lenses and the above-mentioned vertical movement, the above ratio must be changed according to the focal length of the projection lenses. No.

The operation for changing this ratio will be described below.

The screw rod 17 is rotated by the rotation operation of the operator 17b, and the movable block 18 screwed into the screw rod 17 moves back and forth in the length direction of the support lever 20 as shown by the two-dot chain line in FIG. (only one shown).

Along with this, the pin 18 integrated into the moving block 18
A also moves in and out of the elongated hole 20a in the same manner.

This pin 18a, which becomes a fulcrum, and pin 1 on the left end
9b can be arbitrarily changed from S to, for example, Sl.

By changing the position of the fulcrum (pin 18a) in this manner, the rotation angle of the support lever 20 can be arbitrarily set to be large or small when the projection head 11 moves up and down by a certain amount.

Therefore, the light source box 5 supported by this support lever 20
The light source section is also vertically moved up and down while being guided by the left and right guide rods 6, 6 by an amount corresponding to the rotation angle of the support lever 20 due to the movement of the pin 18a. The lifting amount 13 of 8 is the fulcrum (pin 18a
) can be changed arbitrarily by moving.

Thus, the amount of elevation l of the projection head 11 and the amount of elevation 13 of the light source section 8 are determined by the focal length of the projection lens.
Since the ratio can be variously changed depending on the focal length of the projection lens used, various projection lenses having different focal lengths can be attached to the projection head 11 and used.

Therefore, it becomes possible to change the magnification of an image by using both means of changing the magnification by replacing the projection lens and changing the magnification by moving the projection head 11 and the light source section 8 up and down.

As is clear from the above, according to the present invention, the light source section is supported by a support lever that rotates as the projection head moves up and down, and the fulcrum of this support lever can be changed arbitrarily. The ratio between the amount of light and the amount of elevation of the light source can be arbitrarily changed by changing the above-mentioned fulcrum, and this allows the use of various projection lenses with different focal lengths in the projection head, improving the versatility of this type of device. In addition to this, it is possible to plan to change the magnification of an image by both means of changing the magnification by replacing the projection lens and changing the magnification by moving the projection head and the light source unit up and down, which is extremely effective. .

Furthermore, according to the present invention, since the projection lens can be replaced as described above, the conventional inconvenience caused when the projection head and light source section are moved up and down beyond a certain level can be solved by replacing the lens, and chromatic aberration can be reduced. This provides various effects such as being able to prevent this and obtain the best projected image.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, with Fig. 1 being a vertical side view of an overhead projector, Fig. 2 being an enlarged view of the support mechanism of the light source, and Fig. 3 explaining the principle of the overhead projector. It is a diagram. In the drawing, 1 is an overhead projector, 13 is a material mounting stage, 4 is a Fresnel lens, 8 is a light source unit, 1
1 is a projection head, 18 is a moving block, 18a is a pin serving as a fulcrum, 19 is a lever, and 20 is a support lever.

Claims (1)

[Scope of utility model registration request] In an overhead projector comprising a projection head above a material placement stage and a Fresnel lens, and a light source below which can be raised and lowered, one end of a support lever is attached to the lower end of the lever that moves up and down integrally with the projection head. A long hole is formed at the other end of the support lever, and a pin is implanted in the long hole in a movable block that moves forward and backward in the length direction of the support lever by rotating the operator. and a pin implanted in the light source part is engaged with a long hole formed in the center of the support lever, so that the swinging of the support lever and the vertical movement of the light source part are linked. overhead projector