JP2722045B2 - Overhead projector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead projector and, more particularly, to an overhead projector capable of directly projecting an opaque document as it is.

[0002]

2. Description of the Related Art Conventionally, there is an overhead projector (hereinafter, referred to as an OHP) which irradiates a transparent film with light, for example, from below and projects it on a screen or the like by a projection lens and a mirror. In such an OHP, an original is once copied onto a transparent film for OHP, and the original is enlarged and projected by irradiating the transparent film with light from a lamp. There is also a type called a reflection type in which strong light is applied to an original and the reflected light is projected by a lens.

[0003]

Since the conventional OHP projects an original as described above, an opaque original such as plain paper must be copied onto a transparent film, and an opaque original must be copied. The reflection type OHP used as it is has a problem that it is difficult to see in a bright place because the amount of light is insufficient because the light is projected by the reflected light from the original.
In addition, there is a problem in that any of the OHPs can project on a screen only in a preset black and white, for example, and cannot change the projection color. SUMMARY OF THE INVENTION It is an object of the present invention to provide an overhead projector capable of changing a color projected on a screen without having to copy a document onto a transparent film in order to solve the above problem.

[0004]

SUMMARY OF THE INVENTION The present invention provides an image pickup device for reading an original, a signal processing unit for converting an image signal output from the image pickup device into a liquid crystal drive signal, a lamp as a light source, a first and a second light source. In the second projection mode, the light from the lamp reflects predetermined color light and transmits light other than the predetermined color light. In the third projection mode, the light moves to a predetermined position and does not perform reflection and transmission. In the first and second projection modes, light other than light of a predetermined color from the first dichroic mirror enters, and in the third projection mode, light from a lamp enters. A liquid crystal panel that performs display based on a liquid crystal driving signal; and, in the first projection mode, light transmitted from the liquid crystal panel and light from a first dichroic mirror that does not transmit through the liquid crystal panel, are combined into projection light, and The third Second to morphism as projection light transmitted light of the liquid crystal panel is moved to a predetermined position when the mode
And a projection lens for projecting projection light onto a screen.

[0005]

According to the present invention, a document is imaged by an image sensor and converted into an image signal, and the image signal is converted into a liquid crystal drive signal by a signal processing section and output to a liquid crystal panel. Then, in the first projection mode, the first dichroic mirror reflects predetermined color light out of the light emitted from the lamp and transmits light other than the predetermined color light, and the second dichroic mirror transmits the first dichroic mirror. In addition, the light transmitted through the liquid crystal panel and the reflected light of the first dichroic mirror not transmitted through the liquid crystal panel are combined into projection light, and the projection light is projected on the screen by the projection lens. In the second projection mode, the second dichroic mirror moves, and only the light transmitted through the liquid crystal panel is used as the projection light. In the third projection mode, the first and second dichroic mirrors move, the light of the lamp is directly incident on the liquid crystal panel, and the transmitted light becomes projection light as it is.

[0006]

FIG. 1 is a block diagram of an OHP showing one embodiment of the present invention. 1 is an original, 2 is an original glass for setting the original 1, 3 is an original illumination such as a fluorescent lamp that illuminates the original 1, 4 is a total reflection mirror that reflects light from the original 1 over the entire visible region, and 5 is An image sensor 6 converts an incident light from the total reflection mirror 4 into an image signal, and a signal processor 6 converts an image signal output from the image sensor 5 into a liquid crystal drive signal.

[0007] Reference numeral 7 denotes a lamp as a light source for projection;
Is a cold mirror that reflects visible light of the light emitted from the lamp 7 and transmits infrared light. Reference numeral 9 denotes a first dichroic mirror, which reflects blue light, which is a predetermined color light, out of the light from the cold mirror 8 and transmits light other than the blue light in the first and second projection modes. It moves to a predetermined position A in the projection mode. Reference numeral 10 denotes a liquid crystal panel, 11 denotes a total reflection mirror that reflects light passing through the liquid crystal panel 10, and 12 denotes a total reflection mirror that reflects light from the dichroic mirror 9.

Reference numeral 13 denotes a second dichroic mirror, which reflects blue light from the total reflection mirror 12 and transmits light from the total reflection mirror 11 to combine them in the first projection mode. In the second and third projection modes, the light is moved to a predetermined position B and the total reflection mirror 11
Is used as the projection light. Reference numeral 14 denotes a total reflection mirror for reflecting the projection light, and reference numeral 15 denotes a projection lens for projecting the light from the total reflection mirror 14 onto a screen (not shown) or the like.

The OHP has first to third projection modes, in which dichroic mirrors 9 and 13 supported by a movable mechanism (not shown) move in accordance with the projection mode. In the mode, the dichroic mirror 13 moves to a predetermined position B, and in the third projection mode, the dichroic mirrors 9 and 13 move to predetermined positions A and B, respectively.

Next, the operation of such an OHP will be described for the first projection mode. First, the original 1 is set on the original glass 2 face down. The lower surface of the set original 1 is illuminated by the original illumination 3. The total reflection mirror 4 reflects light from the document 1 and causes the light to enter the image sensor 5.

Next, the contents of the original 1 are imaged by the image sensor 5 and converted into image signals. The signal processing unit 6 converts the image signal output from the image sensor 5 into a liquid crystal drive signal after inverting the density, and outputs the signal to the liquid crystal panel 10. Therefore, the content displayed on the liquid crystal panel 10 is the original 1
Is an image in which the black and white are reversed.

On the other hand, light emitted from a lamp 7 as a light source is guided to a dichroic mirror 9 by a cold mirror 8. The cold mirror 8 transmits harmful infrared rays and reflects only visible light. The dichroic mirror 9 reflects only the blue light in the visible light emitted from the lamp 7 and reflected by the cold mirror 8, and the total reflection mirror 12
Reflects this blue light and guides it to the dichroic mirror 13.

At the same time, the dichroic mirror 9 transmits light other than blue light from the cold mirror 8 and
0 is incident. The total reflection mirror 11 reflects the light passing through the liquid crystal panel 10 and reflects the dichroic mirror 1.
3 At this time, since the image displayed on the liquid crystal panel 10 has the black and white of the document 1 inverted as described above, light passes through only the black portion of the document, that is, the portion of characters and figures.

Next, the dichroic mirror 13 combines the light by reflecting the blue light from the total reflection mirror 12 and transmitting the light from the total reflection mirror 11. Since the light from the total reflection mirror 11 is light excluding the blue light, the black portion of the document becomes the original white light of the lamp 7 and the white portion of the document becomes the blue light by being combined.

The total reflection mirror 14 reflects this light and the projection lens 15 projects it. Therefore, a so-called blue-back document 1 in which the characters of the document are white characters and the background is blue is projected onto a screen (not shown) (hereinafter, such a combination is referred to as blue-back / white characters).

In this embodiment, the density of the image is inverted by the signal processing unit 6. However, the image signal output from the image pickup device 5 may be directly converted into a liquid crystal drive signal. Is blue character and the background is white (white background / blue character). Also, the dichroic mirrors 9 and 13 have been described as reflecting blue light as predetermined color light,
The predetermined color light may be light of a color other than blue light. For example, if the predetermined color light is green light, it can be a green background / white character or a white background / green character.

Accordingly, the original 1 can be enlarged and projected as it is, and in the first projection mode, the characters of the original and the color of the background are projected with a combination of the predetermined color reflected by the dichroic mirrors 9 and 13 and the white color of the lamp 7. be able to.

Next, a second projection mode in which the dichroic mirror 13 is moved to a predetermined position B will be described. FIG. 2 is a diagram in which the dichroic mirror 13 is moved to set the second projection mode in the OHP of FIG. 1. Here, only the OHP projection unit is shown.

The operation is almost the same as that of the first projection mode shown in FIG. 1, but the light of the total reflection mirror 11 does not enter the dichroic mirror 13 because the dichroic mirror 13 has moved to the predetermined position B. Also a total reflection mirror 1
Even if the light 2 enters the dichroic mirror 13, the reflected light does not enter the total reflection mirror 14. That is, the composition by the dichroic mirror 13 is not performed,
The light incident on the total reflection mirror 14 is only the light from the total reflection mirror 11, and if the predetermined color light is blue light, the light projected from the projection lens 15 is yellow light excluding the blue light.

Therefore, if the original 1 is black and white inverted by the signal processing section 6, black back and yellow characters are projected, and if the original 1 is left as it is, yellow back and black characters are projected. If the predetermined color light is changed to green light, black back and purple (magenta) characters or purple back and black characters can be obtained. Therefore, in the second projection mode, it is possible to project the color of the text and the background of the document in a combination of black and white color of the lamp 7 excluding predetermined color light reflected by the dichroic mirror 9.

Next, a third projection mode in which the dichroic mirror 9 is moved to a predetermined position A in addition to the dichroic mirror 13 will be described. FIG. 3 shows the OHP of FIG.
FIG. 11 is a diagram in which dichroic mirrors 9 and 13 are moved to set the third projection mode, and here, OHP is used.
Only the projection unit is shown.

In the third projection mode, white light from the lamp 7 directly enters the liquid crystal panel 10, and light transmitted through the liquid crystal panel 10 and reflected by the total reflection mirror 11 also directly enters the total reflection mirror 14. Therefore, the document 1 with black background and white characters or white background and black characters is projected on the screen. Therefore, in the third projection mode, the characters of the document and the color of the background can be projected using a combination of white and black of the lamp 7.

[0023]

According to the present invention, it is not necessary to copy an opaque plain paper original on a transparent film, and it is possible to directly enlarge and project the original with high clarity. Further, by providing the first, second, and third projection modes, the colors of the characters and the background of the document can be appropriately switched, and projection can be performed in various combinations of colors.

[Brief description of the drawings]

FIG. 1 is a block diagram of an OHP showing one embodiment of the present invention.

FIG. 2 is a diagram in which a second dichroic mirror is moved in order to set a second projection mode in the OHP of FIG. 1;

FIG. 3 is a diagram in which first and second dichroic mirrors have been moved to set a third projection mode in the OHP of FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original 5 Image sensor 6 Signal processing part 7 Lamp 8 Cold mirror 9 First dichroic mirror 10 Liquid crystal panel 11 Total reflection mirror 12 Total reflection mirror 13 Second dichroic mirror 14 Total reflection mirror 15 Projection lens

Claims (1)

(57) [Claims] 1. An image sensor for reading a document, a signal processing unit for converting an image signal output from the image sensor into a liquid crystal drive signal, a lamp as a light source, and a lamp in the first and second projection modes. A first dichroic mirror that reflects light of a predetermined color out of the light and transmits light other than the light of a predetermined color, moves to a predetermined position in the third projection mode, and does not perform the reflection and transmission; In the second projection mode, light other than the predetermined color light from the first dichroic mirror is incident, and in the third projection mode, the light of the lamp is incident, and based on the liquid crystal drive signal. A liquid crystal panel that performs display, and in the first projection mode, light transmitted from the liquid crystal panel and light from the first dichroic mirror that does not pass through the liquid crystal panel are combined into projection light, and second and third projections are performed. mode Overhead projector according to claim further comprising a second dichroic mirror to directly projected light to transmitted light of the liquid crystal panel is moved to a predetermined position, and a projection lens that projects the projection light to the screen when.