JPH02280564A - Original illumination device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application in Business A] The present invention relates to a light source for illumination using an LED array in a document reading device such as a facsimile image reader.

[Prior Art] Conventionally, in document reading devices such as facsimile image readers, a high-intensity fluorescent lamp with an aperture reflector has been used as an illumination light source. In addition, cold cathode tubes such as Xe (xenon) were used in some low-priced machines with slow reading speeds.

However, since these tubular light sources are made of glass tubes, they require careful handling and require expensive electrical circuits such as inverters for generating high voltage for discharge.

On the other hand, high-sensitivity types of elements such as CCDs for light reception have appeared, and L
I was told that it is possible to read even ED arrays.

However, the light intensity ratios of the light sources mentioned above are roughly as follows.

Fluorescent lamp = Xe tube: Attached LED: LED
l: 0.125: 0. O83: 0.
As shown in Figure 01, the lens-less LED array emits 0.016 times as much light as a fluorescent lamp. (LEDs are LED chips arranged at regular pitch intervals, and are reference values when comparing the original reflection intensity at the original reading position when reading with a CCD etc. through a lens.) Therefore, high sensitivity Even when using a CCD with a low reading speed, the amount of light is not sufficient, the S/N ratio of the CCD output is poor, noise affects the output, and the image quality deteriorates.

Further, FIG. 4 shows a general example of the arrangement of the optical system. It is preferable that the optical axis of the lens be perpendicular to the original, since it is less susceptible to the effects of shadow wrinkles, specular reflection, etc. of the original. Therefore, the light source illuminates the original from an oblique direction. The same applies when the lens optical axis is not vertical but is tilted by about 10°.

FIG. 5 is a cross-sectional light distribution diagram of the illuminance on the document surface when directly facing the original IRQ when the Xe tube S is used. It shows the light distribution characteristics in the direction orthogonal to the reading line. Figure 6 shows an LED with a lens T.
8. FIG. 7 shows an LED 8 without a lens.

FIG. 8 shows the illuminance on the document surface when the Xe tube is placed in the reading device as shown in FIG. 4 so as not to eclipse the lens light beam. FIG. 9 shows an LED with a lens, and FIG. 10 shows an LED without a lens.

As can be seen in Figures 8 to 10, compared to when using a Xe tube, the peak position point P of the light amount is shifted from the reading position R to the paper ejection side (arrow A side). This is because the light source The closer the lens is to the reading position R, the higher the amount of light becomes, but in the direction of arrow C, it is relatively easy to bring them close together, but in the direction of arrow B, in order to secure space for the lens luminous flux, it is not possible to bring them close together.

The position of the light beam from the lens is determined by the angle and precision of the mirror, the position of the CCD, etc.1 Usually, it is positioned within the thick broken line as an integrated unit with the light source. The dashed lines at both ends of the optical axis indicate the luminous flux range. If we remove this luminous flux, C
A partial dip occurs in the CD output, and a long shadow appears on the image. The alignment of the optical axis is normally performed with an accuracy of approximately ±1 mm, and taking into account deformation of the cylinder, etc., the distance from the optical axis to surrounding objects is usually at least 3 mm1i.

[Problem to be solved by the invention] In the case of the conventional LED array with the lens shown in Fig. 9, the amount of light is almost % of that of the Xe tube at the focused peak part, but the actual reading position is shifted from the peak. This is because variations in positioning accuracy between machines can cause large differences in the amount of light.
There were some good images and some bad images. Furthermore, even within the same machine area, if there is a misalignment between the axis of the light source and the reading line in the direction of the reading line, there will be a large difference in the amount of light between the left and right sides, resulting in poor S/N on one side and deterioration of the image. Furthermore, in order to compensate for the above-mentioned drawbacks, the reading position and the optical unit (the unit within the broken line) must be accurately aligned, resulting in a very expensive device.

In addition, in the case of an LED without a lens as shown in Fig. 10, the light distribution characteristics at the reading position are flat compared to those with a lens shown in Fig. 9, and although the reading position accuracy can be roughened, the absolute light intensity is It is even less of a waste than with a lens, and it is difficult to obtain a sufficient S/N even if a high-sensitivity CCD is used and the reading speed is slowed down << longer CCO reception (accumulation) time). , it was not put into practical use. In addition, to increase the amount of light, increase the number of LED chips in the reading line direction.
(by reducing the arrangement pitch, staggered delivery, or arranging in multiple rows), the amount of light was biased. In this case, L.E.
Not only does the D-array itself become expensive, but the capacity of the power supply becomes large, making it expensive, and the LEDs generate a lot of heat.

[Means for Solving the Problems] The present invention uses an LED array as a light source for a document reading device, and one of the upper ends of the reflective side walls on both sides of the LED chip row of the LED array is By cutting out the portion, it is possible to bring the LED array close to the reading position.

Further, the amount of illumination light is further improved by providing the LED array with a first reflecting surface having a large area and away from the original, and a second reflecting surface having a small area close to the original.

Hereinafter, a facsimile machine which is used in one embodiment of the present invention will be described as an example.

FIG. 2 is a side view of a facsimile machine to which an embodiment of the light source for document illumination of the present invention is applied.

In the figure, E is a document conveyance/reading system, and a plurality of documents 2, which are stacked with the document side facing down on a document placing table 1 which also serves as a device cover, are placed on both ends of the document by a sheet guide member 3.
The stacked documents 2 are guided by a preliminary conveyance roller 4 from the bottom, and are separated one by one by a separation roller 5. Note that 4a and 5a are pressing pieces. Then, the original 2 separated sheet by sheet is transferred to the pair of transport rollers 6a and 6b.
While being conveyed at a constant speed by a pair of discharge rollers 7a and 7b, the LED array light source 8 irradiates the light, and the reflected light passes through a mirror 9 and a lens 10 to a photoelectric conversion element 1 such as a CCD.
1 and is converted into an electrical signal, which is then transmitted to a predetermined recording system.

In addition, when the recording system F receives a recording No. from another device or is converted into an electric signal by its own photoelectric conversion element 11, the platen roller 12 rotates in the direction of arrow a and responds to the image signal. The recording head 13 having a plurality of heating elements 13a that generate heat is driven to generate heat. As a result, a predetermined image is recorded on the roll-shaped thermal recording paper 14, and the thermal recording paper after recording is cut from the trailing edge of the recorded image by a cutter 15 and stored in a reversing tray 16. Note that 17 is an opening for taking out the thermal recording paper 14 after recording.

Further, 18 is an operation panel, 18a is a key top (for example, a start key is shown), IBb is a tact switch, 18
C is the electric circuit printed board of panel IB, 18d is the display device such as LCD, 18e is the drive circuit printed board of LCD 18d, and 18f is the transparent cover provided on the cover of LCD 18d, and the display contents can be confirmed through this cover. can do. Furthermore, 19 is a power supply, 20 is a system control circuit printed board, 21 is a top cover, 22 is a bottom cover and structure, 23 is a sheet metal cover that covers the back side of the printed board 2o for protection, and 24 is a discharge paper on which discharged documents are loaded. It's a tray.

FIG. 1 shows a detailed view of the middle part of FIG. 2.

In FIG. 1, 31 is the lower document table, and 31a is the lower document table 3.
1 is a fixed reading white background, 32a and 32b are lower document stands, 3
3 is a document table glass, 34 is a reflecting plate G indicating an optical axis, and R is a reading position. 8a is an LED array substrate made of a material such as aluminum or glass epoxy;
Chip 8b is bonded onto substrate 8a. 8c
.

Reference numeral 8d indicates reflective side walls on the left and right sides of the LED chip row.

8e is a chamfered portion made on a part of the reflective side wall. 2 is a perpendicular line indicating a direction perpendicular to the LED board.

In the above configuration, the original 2 is illuminated by the LED light source device 8, and reflected light is incident on the ccott via the mirror 9 and the lens 10, and is read as an image.

[Other Examples] Although FIG. 1 shows an example of an LED without a lens, the same effect can be obtained in D with a lens attached with the Rocitron lens 8g shown in FIG. In this case, by chamfering the upper end surfaces of one side of the holding frames on the left and right sides of the LED chip rows that hold the lenses, it becomes possible to move the LEDs in the direction of arrow B in FIG. At this time, Δ in the diagram indicates the distance to the light beam, and there is a sufficient margin. Further, regardless of whether the lens is spherical or non-spherical, the same effect can be obtained by making the shape of the holding member as described above.

In addition, in FIGS. 1, 1i42, and 3, the reading position R and the perpendicular line V coincide with each other, but the same effect can be obtained even if ■ is shifted to the right or left.

Furthermore, as shown in FIG. 3, a density sensor 81 using a short focal length lens array 8h instead of the mirror reflection lens optical system can have the same effect.

FIG. 11 shows another embodiment in which a reflecting surface 34a34b formed by a reflecting plate 34a is provided opposite the LED chip 8b. This reflective surface has a large first reflective surface 34b at a position away from the document, and further has a small second reflective surface 34c at a location close to the document illumination position.

In particular, this small reflective surface 34c is located on the document side of the large reflective surface at an angle that guides light to the reading position, so it can be disposed without interfering with the light flux from the large reflective surface 34b, and this small reflective surface 34c The light source is located close to the illumination position of the document, and the above-mentioned improvement in illumination efficiency can be obtained in a light source using an LED chip.

Further, by cutting out the reflection side wall 8d on the side of the reflection optical axis G, it is possible to bring the document closer to the reflection plate 34a at the same time as the original, which is particularly effective for lighting devices using LED chip elements.

[Effects of the Invention] As described above, by cutting out a part of the upper end of the side wall on either side of the LED chip row of the LED array, it becomes possible to increase the amount of light at the reading position. It has become possible to provide an inexpensive illumination light source.

Furthermore, when the reflective surface described in FIG. 11 was used in combination, a decrease in illumination efficiency was observed.

The above improvement in lighting efficiency is due to improvement in the S/N ratio of image signals,
Effects such as stabilization of illumination light by the LED element, use of inexpensive LED elements, use of a light-receiving member with low sensitivity, and conversely improvement of reading speed can be obtained.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the present invention Fig. 2 is a cross-sectional view of a FAX using the present invention Fig. 3 is a cross-sectional view of another embodiment of the present invention Fig. 4 is an explanatory diagram of a conventional optical system Figure s5 is a vertical light intensity distribution diagram for an Xs tube. Figure 6 is a vertical light intensity distribution diagram for an LED with a lens. Figure 7 is a vertical light intensity distribution diagram for an LED without a lens. Figure 8 is a light intensity distribution diagram when the Xe tube is mounted diagonally. 10 is a light intensity distribution diagram when an LED with a lens is mounted in an oblique direction. FIG. 1t is a sectional view of another embodiment. ... Board 8b... LED chip 8C... Reflective side plate or lens holding frame 8d... Reflective side plate or lens holding frame 8e... Chamfered portion

Claims (2)

[Claims] (1) As a light source for line illumination of the document reading device, it has an LED chip arranged in the direction of the reading line, and reflects the luminous flux of the chip on both sides near the chip row;
What is claimed is: 1. A document illumination device comprising: a reflective side wall for condensing light near a reading position; and a notch formed on a ridge line outside a chip at an upper end of the side wall. (2) It has an LED chip arranged in the direction of the reading line as a light source for line illumination of the document reading device, and reflects the luminous flux of the chip on both sides near the chip row and focuses it near the reading position. A reflective side wall is provided, and a ridgeline at a corner outside the chip is cut out at the upper end of the side wall, and a reflective surface is provided to face the chip through the reflected light beam from the document, and this reflective surface A document illuminating device characterized in that a large first surface is provided at a position away from the document, and a small reflective surface is provided on a side close to the document to direct reflected light toward a reading device.