JPH0337350B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an illumination device suitable as a light source for a reading device such as a facsimile machine or a copying machine.

As shown in FIG. 1, this type of conventional illumination device condenses light from fluorescent lamps 1 and 2 arranged at predetermined intervals with lenses 3 and 4 and projects it onto a document 5.
The reflected light from the surface of the original 5 is condensed by a lens 6 and made to enter a photoelectric conversion element 7, so that an image of the projection portion of the original 5 is formed on the photoelectric conversion element 7. It's summery.

However, the tube diameter of the fluorescent lamps used here is about 15 mm even if it is small, and the illuminance decreases near both longitudinal ends and it becomes dark, so the tube length is longer than the required illumination length. The overall size of the reading device has become a hindrance to making it more compact.

Further, fluorescent lamps have a short lifespan and must be replaced during the service life of the reading device, which is disadvantageous in terms of maintenance, and in particular requires a dedicated power supply circuit for lighting.

Furthermore, this fluorescent lamp had the disadvantages that it took a long time to start up and the brightness decreased at low temperatures.

An object of the present invention is to provide a lighting device that uses a plurality of light emitting diodes as a light source and solves all of the above problems.

The present invention will be explained below by way of examples. Second
In the figure, reference numeral 8 denotes an upper table through which the original passes through a gap, and a non-transparent printed circuit board 9 is exposed in an opening 8a at the center of the upper table. A plurality of high-intensity light emitting diodes 10 are arranged along both longitudinal edges of the slit 9a. Note that the light emitting diodes 10 in the rows on both sides face each other, or
Or rather, the number is almost the same on both sides. Reference numeral 11 denotes a stay for adjusting the position of a light guiding element, which will be described later, located below the slit 9a.

FIG. 3 is a diagram showing the main part of the cross section of FIG. 2,
A transparent resin 13
is filled. Note that the guide hole 12a has a tapered inner wall so that the inner diameter increases as it goes downward. This guide hole 12
A large diameter hole 12b is formed in communication with the lower part of a, and a light guiding element 14 whose position can be adjusted by the stay 11 is installed therein, and the lower part of the light guiding element 14 is provided with a large diameter hole 12b. A plurality of photoelectric conversion elements 7 are arranged side by side in the direction in which the light emitting diodes 10 are arranged. 15 is the lower stand. Note that the inner wall of the slit 9a of the printed circuit board 9 is coated with a light absorbing agent.

In the apparatus of this embodiment, the original 5 is placed on the upper surface of the upper table 8 with a gap therebetween, and all the light emitting diodes 10 are made to emit light, so that the light reflected from the lower surface of the original 5 by the light from the light emitting diodes 10 is enters the light guiding element 14 through the slit 9a and the guide hole 12a. In this case, since the guide hole 12a is tapered, stray light does not occur even if it is long. The light guide element 14 then reaches the photoelectric conversion element 7, where a portion of the document 5 is imaged. Furthermore, slit 9
An auxiliary slit 9a' may be used for a. According to this, it is possible to further block stray light.

Further, the printed circuit board 9 has a light emitting diode 10
In order to dissipate the heat generated, it is preferable to use a substrate with excellent thermal conductivity such as a ceramic board or an aluminum-based printed circuit board.

As described above, the present invention uses a plurality of light emitting diodes as a light source, which are arranged in a row on both sides of a slit. Therefore, the length of the array of light emitting diodes becomes the effective light emitting length, and the light emitting Since unnecessary parts are eliminated, the length in that direction can be shortened, and the height can also be made extremely low compared to fluorescent lamps, reducing the gap between the light emitting diode and the document surface. It is also possible to make the size of the reading device about mm, and from the above, it becomes possible to realize an extremely miniaturized reading device.

Further, since the light source is a diffused light source using a light emitting diode, it is easy to adjust the displacement between the light source, the light guide element, and the photoelectric conversion element in the longitudinal direction.

Furthermore, light emitting diodes have a long lifespan and are therefore easy to maintain, do not require a dedicated power source unlike fluorescent lamps, and have no problem starting up at low temperatures.

Furthermore, according to the present invention, since the light source is covered and the transparent resin is filled from the slit to the inside of the guide hole, it is possible to prevent dust and moisture from entering the device and achieve an even longer lifespan of the light emitting diode. At the same time, the light guide effect of the transparent resin prevents light from being diffused, eliminating the need for a strictly sealed structure, which simplifies the structure. Furthermore, since the guide hole is formed in a slit shape, stray light can be prevented and efficient light transmission can be achieved. Furthermore, since the light guide element used in the present invention can be adjusted in position with a stay, the image formation on the photoelectric conversion element can be easily adjusted.

Therefore, according to the present invention, by combining the various advantages described above, when applied to a reading device such as a facsimile machine or a copying machine, it contributes to improving the reliability of the device and making the entire device more compact. be able to.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional illumination device for a reading device. FIG. 2 is an external perspective view of a reading device having an illumination device according to an embodiment of the present invention. Figure 3 shows
FIG. 3 is an enlarged sectional view taken along the line - in FIG. 2; 5... Original; 7... Photoelectric conversion element; 8... Upper stand; 8a... Opening; 9... Printed circuit board; 9a...
... slit; 9a'... auxiliary slit; 10... light emitting diode; 11... stay for adjusting the position of the light guide element; 12... support portion; 12a... guide hole;
13...Transparent resin; 14...Light guiding element; 15...
...Lower platform.

Claims (1)

[Claims] 1 Using a plurality of light emitting diodes arranged in two rows as a light source, the irradiated light is irradiated onto the document surface, and the reflected light is focused on a photoelectric conversion element arranged in a straight line through a slit provided between the rows of the light emitting diodes. In the illumination device configured to emit light, a transparent resin is provided that covers the light source and fills a tapered guide hole in the optical path from the slit to the photoelectric conversion element,
A lighting device characterized in that the transparent resin is used as a light guide that guides the reflected light to a photoelectric conversion element.