JP2002199253A - Lighting device for original for use in camera for paintings and calligraphy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact camera for paintings and calligraphy built in a liquid crystal projector that can prevent a lighting light from being imprinted. SOLUTION: Each of lighting sections 1, 1 is formed through the arrangement of 3-rows and 10-columns of white light emitting diodes each having a lens whose lighting angle is about 40 degrees. A light diffusion plate 2 is shaped to be an inverse quadrangular pyramid whose apex is a focus of an image pickup lens 4a to surround a field angle of the image pickup lens 4a without a bottom face where a rectangular glass original platen 3 is equivalent to the bottom face, the four side faces are shaped to connect four triangles each having a notch to avoid the image pickup lens 4a and the inner face with knurl is painted in white. Furthermore, a rectangular lighting light transmission notch window 2a is made nearly in the middle of narrow width faces of the light diffusion plate 2 opposed to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to illumination of a document camera, and more particularly to a reflection type document illuminating device using light emitting diodes.

[0002]

2. Description of the Related Art In a liquid crystal projector having a plain paper OHP (overhead projector) function by incorporating a document camera in a housing, an original is placed on a transparent glass plate with its original surface facing down. The document is placed on the liquid crystal projector, and light emitted from a lighting device in the housing of the liquid crystal projector is irradiated from below the glass plate, and an image of the document is taken by a document camera.

FIG. 2 shows a conventional document camera section of a liquid crystal projector incorporating such a document camera. In FIG. 2, reference numerals 7 and 7 denote a pair of left and right illumination light sources, 8 and 8 denote reflectors, 9 denotes a transparent glass plate on which a document is placed, 10 denotes an imaging lens 10a, a CCD element 10b, and an aperture. An image pickup unit 10c and a shielding plate 11 constitute a document camera. The illumination light sources 7, 7
It is arranged symmetrically with respect to the optical axis of the imaging means 10.
Reference numeral 12 denotes an imaging range of the imaging lens 10a, 13 denotes an imaging light incidence range (a range in which a light beam reflected by the glass plate 9 as a reflection surface enters the imaging lens), and 14 denotes a range occupied by the housing of the liquid crystal projector. Such a document camera irradiates the document surface from both sides with light radiated from each lighting device, and captures an image of the document by an imaging unit.

When an image is taken, when the illumination light source 7 is arranged inside the imaging light incidence range 13, reflected light emitted from the illumination light source 7 and reflected by the glass plate 9 is taken by the imaging lens 1.
0a. As a result, the reflected light overlaps the captured image, the portion becomes white, and the image quality deteriorates.
Such a phenomenon is called “reflection”, and conventionally, in order to prevent the reflection, the illumination light source 7 is arranged so as to be located outside the imaging light incidence range 13.

As described above, in the conventional document camera, in order to prevent the reflected light emitted from the illumination light source 7 and reflected by the glass plate 9 from being reflected, the illumination light source 7 is set to be higher than the imaging light incidence range 13. It was necessary to arrange it outside. For this reason, since the illumination light source 7 must be located outside the glass plate 9, in other words, outside the end of the imaging range 13, the size of the entire apparatus 14 is inevitably increased, and as a result, the apparatus is downsized. There was a problem that can not be converted.

Several techniques have been devised to solve this problem. One of them is JP-A-8-18736.
There is an image input device disclosed in Japanese Unexamined Patent Application Publication No. H10-260, 1993. This technology is
As shown in FIG. 3, the light sources 2 of the two lighting devices 20 and 20
1, 21 are symmetrical with respect to the optical axis 19 of the imaging lens 16 of the document camera, outside the viewing angle 18a of the imaging lens 16 which is folded back with the original 17 on the original table 15 as a reflection surface, and the reflected light incident range. 18b, and the reflector 2 with respect to the light sources 21 and 21.
2, 22 are provided with light shielding plates 23, 23. Light shield plate 2
Reference numerals 3 and 23 are located inside the reflected light incident range 18b and block light reflected from the document surface 17 among the light from the light sources 20 and 20.

The reflection plates 22, 22 are located outside the reflected light incident range 18b, reflect the light emitted from the light sources 20, 20, and are reflected by the light shielding plates 23, 23 from the light sources 21, 21. The light is guided to the area of the document surface 17 where the light is blocked. That is, by covering the area shielded by the light-shielding plates 23, 23 with the area irradiated by the reflection of the reflection plates 22, 22, the influence of the light-shielding plates 23, 23 is eliminated, and the entire imaging area of the document surface 17 is reduced. Light source 2
Irradiation with light from 0 and 20 is performed. According to such a structure, since the light sources 20 and 20 can be arranged inside the reflected light incident range 18b, there is an advantage that the interval between them can be narrowed and the size of the entire apparatus can be reduced.

[0008]

However, in this image input apparatus, it is necessary to dispose the reflection plates 22, 22 so as to be located outside the reflected light incident area 18b (in the case of the inside, the reflection plates 22, 22). The reflected light reflected by the light source enters the imaging lens 15 and is reflected on the image), which is a limitation in reducing the overall size of the device as in the conventional device shown in FIG.

The light shielding plates 23, 23 are connected to the light sources 20, 20.
In the case where an image of an imaging target having a high reflectivity is taken, the light shielding plates 23 and 23 are reflected and the image quality is reduced. Furthermore, since it does not cover the viewing angle 18a of the imaging lens 16, the light source 20,
When light from other than 20, for example, an illumination lamp installed on the ceiling exists within the viewing angle 18a of the imaging lens 16,
When the light is reflected on the document surface 17 and enters the imaging lens 16, the light is reflected on the image, so that there is a problem that the image quality is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a document for a liquid crystal projector built-in which can prevent the reflection of illumination light and can reduce the size of the apparatus. An object of the present invention is to provide a document illumination device for a camera.

[0011]

A document illuminating device for a document camera according to the present invention is a liquid crystal with a document camera having a transparent glass plate on which a document is placed and image pickup means for picking up the document surface of the document from below. A document illuminating device for a projector, comprising: an illuminating unit in which a plurality of white light emitting diodes for illumination are arranged in a matrix; and an inner surface embossing arranged to surround an angle of view of the document camera for imaging the document surface. A light diffusion plate made of a white plate, and a notch window for transmitting illumination light from the illumination unit is formed in the center of the position opposite to the light diffusion plate, and the illumination unit is provided with a notch window. It is located outside and on the inside of the end of the imaging range, and is arranged so as to be substantially parallel to the glass plate. The illumination light of the illumination unit irradiates only the light diffusion plate through the cutout window. It is characterized by doing That.

According to the document camera document illuminating device of the present invention, an illuminating portion in which a plurality of white light emitting diodes for illumination are arranged in a matrix surrounds the angle of view of the document camera for imaging the document surface. It is located outside the light diffusion plate consisting of a white plate with an inner surface with a cutout window for transmitting the illumination light that is arranged like this, and inside the end of the imaging range. The document camera of the projector can be housed in the housing. Further, the illuminating unit is disposed outside the light diffusing plate so as to be substantially parallel to the transparent glass plate on which the original is placed, and irradiates only the light diffusing plate. Reflection can be prevented.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is a schematic side view of a document camera illumination device according to the present invention, and FIG. 1B is a top view of the document camera illumination device. In the figure, 1, 1
Is a light diffuser made up of a plurality of white light emitting diodes for illumination arranged in a matrix, 2 is a light diffusing plate made of a white plate with an inner surface embossed, and 2a is a light diffusing plate 1 A cutout window for transmitting illumination light, 3 is a rectangular glass platen serving as a transparent glass plate on which a document is placed, 4 is an image pickup unit of a document camera serving as image pickup means for picking up the document from below.
a is an imaging lens, 4b is a CCD element, 5 is a housing area of a document camera housing unit, 6 is a state in which light emitted from the illumination units 1 and 1 is scattered to uniformly illuminate the glass platen 3. Show. Note that reference numeral 3 also indicates an imaging range of the imaging unit 4.

The configuration of such a document camera document illumination device will be described. The illuminating units 1 and 1 are each configured by arranging 30 rows and 10 columns of white light-emitting diodes with a lens having an irradiation angle of about 40 degrees. The light diffusing plate 2 has an inverted quadrangular pyramid shape having the focal point of the imaging lens 4a as an apex so as to surround the angle of view of the imaging lens 4a, and having no bottom surface but a rectangular glass platen 3 corresponding to the bottom surface. Then, the four side surfaces have a shape in which four triangles provided with cutouts so as to avoid the imaging lens 4a are connected, and the inner surface is white with a grain. Here, the inner surface is made white with embossed
The white color reflects light, and the grain is fine irregularities. The irregularities reflect the illumination light from the illumination units 1 and 1 on the inner surface to uniformly scatter the light.

Further, a rectangular cutout window 2a for transmitting illumination light is formed in the middle of the opposed narrow surface of the light diffusion plate 2.
The illuminating units 1 and 1 are located outside the light diffusing plate 2 and inside the imaging range, and are arranged so as to be directed substantially horizontally to the glass platen 3. The light diffusion plate 2 is installed so as to irradiate the opposite surface through the window 2a. When installing the illumination units 1 and 1, a glass platen 3
Also, care should be taken not to irradiate the imaging lens 4a directly. This consideration is for avoiding reflection. With this configuration, the light emitted from the illumination units 1 and 1 spreads at an angle of about 40 degrees and is irregularly reflected on the surface of the light diffusing plate 2. Illuminate evenly and uniformly.

Next, the operation of the document camera lighting device of the present invention will be described. First, a document is placed on a glass platen 3 with the document face down. Then, the power of the document projector built-in liquid crystal projector is turned on, and the document is enlarged and projected. At this time, the illumination units 1 and 1 are turned on to illuminate the document surface. Here, the brightness of the document surface is adjusted by adjusting the brightness adjustment units of the illumination units 1 and 1 (not shown) so that the document camera imaging unit 4 can capture the document in the most visible state.

Since the brightness of the white light emitting diodes constituting the lighting units 1 and 1 can be controlled by the current flowing through the light emitting diodes, the brightness can be easily and freely adjusted by adjusting the power supply voltage applied to the light emitting diodes. be able to.
Therefore, unlike the illumination by the conventional cathode ray tube, this brightness adjustment function does not require the adjustment of the aperture of the imaging lens of the document camera. This is because, in the case of illumination by a cathode ray tube, it is difficult to stably change the brightness little by little when changing the brightness of the cathode ray tube. In contrast, in the case of lighting with a light emitting diode as in the present invention, if the brightness is changed as described above, the power supply voltage is adjusted as desired to adjust the brightness of the lighting. This is because it is possible to change the stability itself stably. This is particularly effective when projecting a three-dimensional object because the shadow of the three-dimensional object can be finely adjusted.

[0018]

According to the present invention, all the illuminating devices can be arranged inside the glass platen when the liquid crystal projector with a built-in document camera is viewed from above, so that the housing dimensions of the liquid crystal projector with a built-in document camera can be minimized. It is possible to design a small size. In addition, unlike the conventional cathode ray tube, the white light emitting diode group for illumination used in the present invention can adjust the illuminance by adjusting the power supply voltage for lighting, so that the light amount adjusting aperture of the imaging unit can be omitted. As a result, the cost can be reduced and the weight of the lens can be reduced. Furthermore, since the lighting device reflector of the prior art is installed near the light source for lighting,
While the installation required fine adjustment of the angle,
That the light diffusion plate of the present invention utilizes diffuse reflection of light,
Since the light diffusion plate is installed at a place distant from the light source, uniform document illumination can be easily obtained without fine adjustment of the light diffusion plate installation angle.

[Brief description of the drawings]

FIG. 1 is a schematic side view and a plan view of a document camera illumination device showing an embodiment of the present invention.

FIG. 2 is a schematic side view showing an example of a conventional document camera illumination device.

FIG. 3 is a schematic side view showing an example of a conventional document camera illumination device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 white light emitting diode group for illumination 2 light diffusion plate formed of white plate with grain 2 a cutout window for transmission of illumination light 3 glass platen 4 imaging unit of document camera 4 a imaging lens 4 b CCD element 5 liquid crystal projector housing area 6 irradiation A state in which light is scattered to uniformly illuminate a glass platen 7 Illumination light source 8 Reflector plate 9 Transparent glass plate on which a document is placed 10 Imaging means 10a Imaging lens 10b CCD element 10c Aperture 11 Shielding plate 12 Imaging range 13 Imaging Light incident range for use 14 Range occupied by housing of liquid crystal projector 15 Document table 16 Imaging lens of document camera 17 Document 18a Viewing angle 18b Reflected light incident range 19 Optical axis 20 Illumination device 21 Light source 22 Reflector 23 Light shield

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Claims (1)

[Claims] 1. An original illuminating device for a liquid crystal projector with a built-in document camera having a transparent glass plate on which an original is placed and an image pickup means for imaging the original surface of the original from below, wherein a plurality of white light sources for illumination are provided. An illuminating unit in which diodes are arranged in a matrix, and a light diffusing plate that is a white plate with an inner surface embossed and disposed so as to surround the angle of view of the document camera that images the document surface; A notch window for transmitting illumination light from the illumination unit is formed at the center of the opposing position, and the illumination unit is located outside the notch window and inside the end of the imaging range. A document illumination device for a document camera, wherein the illumination light from the illumination unit is illuminated only through the light diffusion plate through the cutout window.