JPH0990264A - Illuminator for projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the illuminance of a projection surface to a value proximate to a light distribution theoretical value and to obtain an excellent image. SOLUTION: A fluorescent lamp 26 is housed in a lamp case 25 and light outgoing from the lamp 26 is condensed by a cylindrical lens 27 and guided to the projection surface of a subject 5. Reflectors 28a to 28c reflecting the light from the lamp 26 and guiding it to the projection surface are arranged in the case 25, and a reflector 30 is arranged between the ends of two lamps 26. Thus, the illuminance of the periphery part of the projection surface is increased and the illuminance proximate to the light distribution theoretical value is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention places an object on a transparent glass plate, irradiates light through the glass plate from below to image the projection surface of the object, and magnifies and projects the image on the screen. The present invention relates to a lighting device suitable for application to a projector or the like.

[0002]

2. Description of the Related Art Generally, in an overhead projector using plain paper (hereinafter referred to as plain paper OHP), a copying machine, or the like, an opening provided in a frame 2 forming an upper surface of a device body 1 as shown in FIG. 3 is covered with a transparent glass plate 4, and a subject 5 such as an original is placed on the glass plate 4 with its surface to be projected (projection surface) facing down. The light is emitted from the light source 6 provided in the above, and the image is taken by the camera 7. At this time, the subject 5 is fixed so as not to be displaced, and the light transmitted through the subject 5 and the light from the light source 6 transmitted through the portion of the glass plate 4 not covered by the subject 5 leaks to the surroundings or is exposed to the outside. In order to prevent light from entering, the object 5 is covered by the cover 8.
And covers the glass plate 4. In addition, 9 is a reflection mirror, and 10 is a hood having a frame-shaped body and an inner surface of which is black so that reflected light does not enter the camera 7.

As the light source, a halogen lamp is usually used because it is necessary to illuminate the entire projection surface of the subject 5 with a desired illuminance. Halogen lamps have been widely used as lighting devices for copying machines and the like since they are small in size, have high brightness, have good light color (color temperature of 3000 to 3400K), have excellent color rendering properties, and have a long life. . However, since the halogen lamp generates a large amount of heat, it requires a cooling device, and the lamp itself is expensive.

Therefore, recently, a fluorescent lamp has been proposed as a light source, and the light is condensed by a cylindrical lens to illuminate the projection surface 5a of the subject 5.

[0005]

However, in an illuminating device using a fluorescent lamp, the illuminance distribution of the fluorescent lamp is the brightest and the central portion in the axial direction of the fluorescent lamp (length 280 mm) as shown in FIG. There is a problem that desired light distribution characteristics cannot be obtained because the light becomes darker as the distance from the portion increases. That is, the theoretical light distribution value (ideal value) of the projection surface is 100% as shown in FIG.
When set to (%), it becomes a large value along the outer peripheral portion. The theoretical light distribution value is 260 mm × 195
The values in each area when the mm projection surface is divided into 25 in a matrix are shown. Therefore, a fluorescent lamp cannot obtain a light distribution characteristic close to a theoretical value of light distribution, and a good image cannot be obtained.

The present invention has been made in order to solve the above-mentioned conventional problems, and an object thereof is to make the illuminance on the projection surface close to a theoretical value of light distribution, thereby obtaining a good image. An object of the present invention is to provide a lighting device such as a projector which is designed to obtain

[0007]

In order to achieve the above object, the present invention is directed to a pair of fluorescent lamps provided on both lower sides of a subject through glass plates, and the light emitted from the fluorescent lamps is collected to collect the subject. It is characterized by comprising a cylindrical lens for guiding to the projection surface, and reflectors provided corresponding to both ends and a central portion of the fluorescent lamp in the axial direction, respectively, for reflecting light emitted from the fluorescent lamp and guiding it to the projection surface. Further, the present invention is characterized by including a reflector provided between both ends of the pair of fluorescent lamps to reflect the light from the fluorescent lamps toward the projection surface. Further, the present invention is characterized in that the fluorescent lamp is displaced from the center of the optical axis of the cylindrical lens to the side opposite to the center side of the glass plate. Furthermore, the present invention is characterized in that the cylindrical lens is tilted so as to be directed toward the center of the glass plate.

In the present invention, the light emitted from the fluorescent lamp is condensed by the cylindrical lens and guided to the projection surface of the subject. The illuminance of the peripheral portion on the projection surface is increased by reflecting the light from the fluorescent lamp by the reflection plates provided corresponding to both ends and the center of the fluorescent lamp. In addition, the light from the fluorescent lamp is reflected by the reflection plate provided between the end portions of the two fluorescent lamps to increase the illuminance of the peripheral portion on the projection surface. When the fluorescent lamp is displaced from the optical axis center of the cylindrical lens and the cylindrical lens is tilted so that it is directed toward the center of the glass plate, the amount of light around the center of the optical axis decreases and the amount of light in the peripheral area increases. Let

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. 1 is an external perspective view showing an embodiment in which the present invention is applied to plain paper OHP, FIG. 2 is a perspective view of an illuminating device, and FIG. 3 is a side view of the illuminating device.
It should be noted that the same members as those shown in the section of the prior art in the figure are denoted by the same reference numerals, and detailed description thereof will be omitted. The plain paper OHP 20 includes a box-shaped device body 1. A camera 7, a reflection mirror 9, a hood 10, an illumination device 21 that illuminates the subject 5, and the like, and a projection optical system (not shown) that projects an image captured by the camera 7 onto a screen are incorporated in the device body 1. There is. A frame 2 forming the upper surface of the apparatus body 1 is provided with a transparent glass plate 4 on which a subject 5 is placed, and an openable / closable cover 8 for covering the subject 5. A lens barrel portion 22 of the projection optical system is provided on the frame 2 on the right side of the glass plate 4, and a projection lens 23 is provided on the front surface of the lens barrel portion 22 so as to face the outside.

The plain paper OHP 20 optically picks up characters or the like written on a subject 5 made of plain paper by an original image pickup device including an image pickup camera 7 and a mirror 9, and the image signal thereof is not shown in the liquid crystal panel. Is a device for projecting an image on a screen by using a projection optical system, and an example of this type of device is Japanese Patent Application No. 5-198.
Since it is described in detail in Japanese Patent Publication No. 849, etc., a detailed description thereof will be omitted here.

The illuminating device 21 includes a pair of left and right lamp cases 25 arranged below and adjacent to the ends of the glass plate 4 on the long side, and the fluorescent lamps 2 housed in the lamp cases 25.
6 and a cylindrical lens 27 that covers the front opening of the lamp case 25. As the fluorescent lamp 26,
For example, one having a length of 260 mm is used.

The lamp case 25 is formed in an elongated box shape and has a reflector 28 (28a, 28b, 28) described later.
Black paint is applied to the entire inner surface except the portion where c) is attached. Therefore, the case 25 forms a black box. This is to prevent the light emitted from the fluorescent lamp 26 from hitting the inner surface and being reflected. Further, as shown in FIG. 3, the two lamp cases 25 are inclined outward with a required angle (θ) with respect to the front and back surfaces of the glass plate 4 so that the distance between the front opening side and the rear end side becomes smaller. In addition, it is arranged outside the viewing angle of the camera 7. The inclination angle θ is about 42 °. For this reason,
The optical axis center L of the cylindrical lens 27 is also inclined with respect to the glass plate 4 by an angle θ. Although the lamp case 25 is shown in parallel with the glass plate 5 in FIG. 2 for the sake of convenience, it is actually arranged so as to be inclined as shown in FIG.

The axis of the fluorescent lamp 26 is the transparent glass plate 4
It is housed horizontally in the lamp case 25 so as to be parallel to the surface of the lamp. Further, the two fluorescent lamps 26 are parallel to each other and housed in the upper inside of each lamp case 25, so that they are displaced above the optical axis center L of the cylindrical lens 27. Fluorescent lamp 26 and cylindrical lens 2
The reason why it is displaced from the optical axis center L of No. 7 is to reduce the amount of light around the optical axis center and increase the amount of light in the peripheral portion. That is, the fluorescent lamp 26 is replaced by the cylindrical lens 27.
When it is arranged on the center L of the optical axis, the amount of light near the center of the optical axis is larger than the amount of light in the peripheral portion, and the amount of light that illuminates the end portion of the projection surface 5a of the subject 5 closest to the fluorescent lamp 26 can be increased. Can not. Therefore, when the fluorescent lamp 26 is displaced upward from the optical axis center L of the cylindrical lens 27, the amount of light around the optical axis center L decreases and the amount of light that irradiates the end portion of the projection surface 5a closest to the fluorescent lamp. Can be relatively increased. It should be noted that if the displacement is made below the optical axis center L, the central portion of the subject 5 becomes relatively bright, which is not preferable. The displacement X from the optical axis center L is 15 mm
It is a degree. Such a cylindrical lens 27 is
A rod-shaped body having a D-shaped cross section is formed of synthetic resin or glass. The focal length of the cylindrical lens 27 is, for example, 26 mm.
The distance between the fluorescent lamp 26 and the fluorescent lamp 26 is about 5 mm.

The reflection plate 28 reflects the light emitted from the fluorescent lamp 26 in the direction of the projection surface 5a, and is made of white acrylic resin or the like, and the reflection surface forms a diffusion surface by forming irregularities or the like. ing. Such a reflector 28 is
The fluorescent lamp 26 is divided into three parts, which are provided at positions corresponding to both ends and the center of the fluorescent lamp 26, respectively. Of the three reflectors 28, the reflectors 28a and 28c on both sides are formed longer than the reflector 28b in the central portion. This is to increase the illuminance at the end portion as compared with the central portion.

Further, a reflector plate 30 for reflecting the light from the fluorescent lamps 26 toward the projection surface is provided between both ends of the two fluorescent lamps 26. Similar to the reflector 28, the reflector 30 is made of white acrylic resin or the like, and its reflection surface forms a diffusion surface by forming irregularities or the like. Such reflectors 30 are provided on the inner side surfaces of the hood 10 that face each other in the direction orthogonal to the optical axis of the fluorescent lamp 26.

According to the illuminating device 21 having the above-described structure, the reflecting plates 28 and 30 are provided, the optical axis center L of the cylindrical lens 27 is inclined with respect to the glass plate 4, and the fluorescent lamp 26 is arranged in the cylindrical lens 27. Since it is displaced above the optical axis center L, the projection surface 5 of the subject 5
A can be satisfactorily irradiated, and the light distribution characteristic close to the theoretical light distribution value of the projection surface shown in FIG. 10 can be obtained. That is, FIG. 4 is a table showing measured values of the illuminance distribution on the projection surface 5a when the reflection plates 28a, 28b, 28c, 30 are provided. As is clear from this table, the illuminance at the peripheral portion of the projection surface is significantly improved, and the value of each area can be made close to the theoretical value of light distribution shown in FIG. Therefore, a good image can be obtained.

Further, FIG. 5 shows reflectors 28a, 28b, 28.
9 is a table showing measured values of illuminance distribution when only c is used and the reflection plate 30 between the fluorescent lamps 26 is not used. In this case, although there is a region where the difference from the theoretical light distribution value is large, there is no problem in practical use because the value is close to the theoretical light distribution value as a whole.

FIG. 6 shows reflectors 28a and 28c and a fluorescent lamp 26.
It is a table which shows the measured value of the illuminance distribution in the case of using the reflector plate 30 in between and not using the reflector plate 28b. In this case, the illuminance at the corner of the projection surface is not sufficiently secured, which is not suitable for practical use. FIG. 7 is a table showing the measured values of the illuminance distribution when the reflector 30b between the reflector 28b and the fluorescent lamp 26 is used and the reflectors 28a and 28c are not used. Even in this case, the illuminance at the corner of the projection surface is not sufficiently improved,
Not suitable for practical use.

Although the above-described embodiment has been described as applied to the plain paper OHP provided with the transparent glass 4, the present invention is not limited to this.
It can be directly applied to an illuminating device when photographing a catalog, a book or the like with a V camera.

[0020]

As described above, the illuminating device such as the projector according to the present invention is provided with a pair of fluorescent lamps provided over the glass plate below both sides of the subject and the light emitted from the fluorescent lamps. Since the cylindrical lenses that guide the projection surface of the subject and the reflectors that are provided at both ends and the center of the fluorescent lamp in the axial direction are provided to reflect the light emitted from the fluorescent lamp and guide the projection surface to the projection surface, It is possible to improve the illuminance at the outer peripheral portion of the. Further, according to the present invention, since the reflectors for reflecting the light from the fluorescent lamp toward the projection surface are provided between both ends of the pair of fluorescent lamps, the light distribution characteristic of the lighting device can be further improved. Further, the present invention, while displacing the fluorescent lamp outward from the optical axis center of the cylindrical lens,
Since the cylindrical lens is inclined so as to be directed toward the center of the glass plate, it is possible to obtain a light distribution characteristic close to the theoretical value of light distribution on the projection surface, and it is possible to obtain a good image.

[Brief description of drawings]

FIG. 1 is an external perspective view showing an embodiment in which the present invention is applied to plain paper OHP.

FIG. 2 is a perspective view of a lighting device.

FIG. 3 is a side view of the lighting device.

FIG. 4 is a table showing actually measured values of illuminance distribution on a projection surface.

FIG. 5 is a table showing measured values of illuminance distribution on the projection surface.

FIG. 6 is a table showing actually measured values of the illuminance distribution on the projection surface.

FIG. 7 is a table showing actually measured values of the illuminance distribution on the projection surface.

FIG. 8 is a schematic configuration diagram showing a conventional example of plain paper OHP.

FIG. 9 is a diagram showing an illuminance distribution of a fluorescent lamp.

FIG. 10 is a table showing theoretical light distribution values on a projection surface.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Device main body, 2 ... Frame, 3 ... Opening part, 4 ... Glass plate, 5 ... Subject, 5a ... Projection surface, 6 ... Light source, 7 ... Camera, 9 ... Mirror, 25 ... Lamp case, 26 ... Fluorescent lamp,
27 ... Cylindrical lens, 28, 28a, 28b,
28c ... Reflector, 30 ... Reflector.

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[Procedure amendment]

[Submission date] January 9, 1996

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Brief description of drawings

[Correction method] Change

[Correction contents]

[Brief description of drawings]

FIG. 1 is an external perspective view showing an embodiment in which the present invention is applied to plain paper OHP.

FIG. 2 is a perspective view of a lighting device.

FIG. 3 is a side view of the lighting device.

FIG. 4 is a chart showing measured values of illuminance distribution on a projection surface.

FIG. 5 is a chart showing measured values of illuminance distribution on a projection surface.

FIG. 6 is a chart showing measured values of illuminance distribution on a projection surface.

FIG. 7 is a chart showing measured values of illuminance distribution on a projection surface.

FIG. 8 is a schematic configuration diagram showing a conventional example of plain paper OHP.

FIG. 9 is a diagram showing an illuminance distribution of a fluorescent lamp.

FIG. 10 is a chart showing theoretical light distribution values on a projection surface.

[Explanation of Codes] 1 ... Device body, 2 ... Frame, 3 ... Opening part, 4 ... Glass plate, 5 ... Subject, 5a ... Projection surface, 6 ... Light source, 7 ... Camera, 9 ... Mirror, 25 ... Lamp case, 26 ... Fluorescent lamp,
27 ... Cylindrical lens, 28, 28a, 28b,
28c ... Reflector, 30 ... Reflector.

Claims (4)

[Claims] 1. A pair of fluorescent lamps provided on both lower sides of a subject through glass plates, a cylindrical lens that collects light emitted from the fluorescent lamp and guides the light to a projection surface of the subject, and both ends in the axial direction of the fluorescent lamp. An illuminating device such as a projector, which is provided with a reflecting plate which is provided corresponding to each of the central portion and the central portion and reflects the light emitted from the fluorescent lamp and guides the light to the projection surface. 2. An illumination device such as a projector according to claim 1, further comprising: a reflector provided between both ends of the pair of fluorescent lamps for reflecting light from the fluorescent lamps toward a projection surface. Lighting equipment such as projectors. 3. An illumination device such as a projector according to claim 1, wherein the fluorescent lamp is displaced from the center of the optical axis of the cylindrical lens to the side opposite to the center side of the glass plate. Lighting equipment. 4. An illumination device such as a projector according to claim 1, 2 or 3, wherein a cylindrical lens is inclined so as to be oriented in a central direction of the glass plate.