JPH03114355A - Original illumination device - Google Patents

Abstract

PURPOSE:To make the device compact and to reduce the cost of components by devising the device such that sufficient luminous quantity is obtained with a shorter LED light source than a conventional device with respect to a required read width. CONSTITUTION:Both end faces of a light collecting rod lens 8e are not cut at a face orthogonal to an axial line of the rod lens 8e but cut off with a tilt, surface treatment such as chromium plating is applied to the cut face 8j and the lens 8e is fixed so that a reflecting face of the cut face 8j is opened toward the lighted both thereby the luminous flux striking on the cut face 8j through the lens is reflected in the lens and passes through the lighted body. Thus, sufficient luminous quantity is obtained with a shorter LED light source 8 than a conventional device with respect to the required read width. Thus, the device is made compact and the material cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a document illumination device used in facsimiles and the like, which illuminates a document in order to read the document image.

[Prior Art] Conventionally, the illumination light source for image reading devices such as facsimile machines has been fluorescent tubes, xenon tubes, and other devices that produce a large amount of light, but recently, light-receiving elements such as CCDs have also become more sensitive. Go on,
Light emitting elements with a small amount of light, especially those using LEDs arranged in an array, are beginning to appear.

This is because LEDs do not require an inverter for lighting like fluorescent tubes or xenon tubes, so they can be made smaller and lower in cost, and because they do not require high-frequency lighting, they do not generate high-frequency noise. This is also because they have advantages such as stable rise characteristics and temperature characteristics compared to fluorescent tubes and xenon tubes.

The above description is about the cross-sectional direction of the device, but the reading line direction, that is, the longitudinal direction is as follows.

The light reflected from the original is read by a light receiving element via a lens. It is desirable that the illumination intensity on the document surface be uniform over the entire reading width. Also, due to the cos'θ law of the lens, even if the original illumination level is uniform, the area near the optical axis will be 100%
If this is the case, it will drop to 60-70% in the periphery. Therefore, on the document surface, it is desirable that the amount of light be large at the ends of the reading line in the longitudinal direction.

However, in fluorescent lamps and the like that are used numerically, the amount of light at the periphery decreases to about 80% of the amount of light near the center of the tube, so it is difficult to increase the amount of light at the periphery. Furthermore, in order to improve the uniformity in the reading width region, the tube is lengthened and only the uniform portion, that is, the central portion of the tube, is used. - Numerically speaking, fluorescent lamps require an extra length of approximately 10 G++m compared to the reading width, including the unused portions on both sides.

The same can be said about LED lighting. L
ED lighting has better conditions than fluorescent lighting, but the above-mentioned extra length is 20 to 50 mm longer on both sides. Unlike fluorescent lamps, there is no difference in the light intensity of the light emitting body itself in the longitudinal direction, but due to the distance from the object to be illuminated, there is only an LED chip in the center that corresponds one-to-one with the object to be illuminated. This is because it is also illuminated by surrounding LED chips. On the other hand, at the ends, it is not possible to secure enough light from one side.

In the past, the idea was to take a little extra time and make the LED longer, or
Increasing the number of chips by reducing the pitch of the chips at the edges, etc.
The current value is increased only in the end blocks (one block is made up of several LED chips) to increase the luminous intensity.

[Problem D to be Solved by the Invention] However, in the above conventional example, in order to improve the amount of light at the end, it is necessary to take an extra length, narrow the LED chip pitch at the end, or increase the light intensity at the end. There are problems with this, such as increasing the current value of the block, which requires sacrificing space or resulting in a high-cost component.

The present invention aims to solve the above problems. That is, an object of the present invention is to provide a document illumination device that can obtain a sufficient amount of light for a required reading width with an LED light source that is shorter than conventional ones, and can make the device more compact and reduce the cost of components. This is the purpose.

[Means for Solving the Problems] In order to achieve the above object, the document illumination device of the present invention includes:
An illumination device that illuminates one line of a document, and includes a number of rows of LED chips arranged in the width direction of the document, a printed board on which the LED chips are mounted, and a rod-shaped device that focuses the light of the front LED chip. a lens, and both ends of the rod-shaped lens in the longitudinal direction are cut non-orthogonally to the lens axis, and the lens is fixed at an angle open toward the object to be illuminated, and the lens The end face of the mirror was surface-treated.

[Function] According to the present invention, both end surfaces of the condensing lens are formed into rod-shaped lenses! [It is not cut perpendicularly to the h line, but diagonally, and the cut surface has a surface such as chrome plating I
Fix the lens so that the reflective surface of the cut surface opens toward the object to be illuminated so that the light beam that passes through the lens and hits the cut surface is reflected into the lens and passes toward the object to be illuminated. Therefore, the light beams at both ends of the lens are also effectively used for illuminating the corresponding portions of the document.

[Embodiment] 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 FIG. 2, reference numeral E denotes a document conveyance/reading system, and a plurality of originals g42, which are stacked with the original surface facing down on a document placing table 1 which also serves as a device cover, is connected at both ends to 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, while the document 2 separated one by one is transported at a constant speed by a pair of transport rollers 6a, 6b and a pair of discharge rollers 7a, 7b, it is irradiated with light by an LED array light source 8.
The reflected light passes through mirror 9 and lens 10 to CCD
The photoelectric conversion element 11 converts the signal into an electrical signal, and this signal is transmitted to a predetermined recording system.

In addition, the recording system F is a photoelectric conversion element 11 from another device or from the own device.
When a recording signal converted into an electric signal is inputted, the platen roller 12 rotates in the direction of arrow a, and the recording head 13, which has a plurality of heating elements 13a that generate heat in accordance with the image signal, is driven to generate heat. It is configured as follows.

As a result, a predetermined image is recorded on the roll-shaped thermal recording paper 14, and the thermal recording paper 14 after recording is cut from the trailing edge of the recorded image by a cutter 15, and is 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 such as a start key, 18b is a tact switch, 18C is an electric circuit printed board for the panel 18, 18d is a display such as an LCD, and 18e is a drive circuit printed board for the display 18d. ,1
8f is a transparent cover provided on the cover of the display device 18d, and the display contents can be confirmed through this cover 18f. Furthermore, 19 is a power supply, 20 is a system control circuit printed board, 21 is a top cover, 22 is a bottom cover/structure, 23 is a sheet metal cover that protects the back side of the printed board 20, and 24 is a stack for loading ejected originals. This is the paper output tray.

FIG. 3 shows the portion D in FIG. 2 in detail.

In FIG. 3, 31 is a lower document table, 31a is a reading blank fixed to the lower document table 31, 32a and 32b are lower document plates, 33 is a glass document table, 34 is a reflector, G is an optical axis, and R
indicates the reading position.

Further, reference numeral 8a denotes a substrate of the LED array, which is made of a material such as aluminum, glass, or epoxy, and the LED chip 8b is bonded onto the substrate 8a. 8c, 8d
are reflective walls on the left and right of the LED chip array. 8e is a rod-shaped lens for condensing light, and 8f is a holding member for the light source 8 that also serves as a heat radiation effect. In addition, ■ is a perpendicular line indicating a direction perpendicular to the substrate 8a.

In the above configuration, the original 2 is illuminated by the LED array light source 8, and reflected light is incident on the photoelectric conversion element 11 via the mirror 9 and lens 10, and is read as an image.

FIG. 1 is a perspective view of an LED array light source 8 according to the present invention. Here, 8g is the mounting hole, 8h is the power lead wire,
Reference numeral 81 indicates a resistor for limiting the block current, and reference numeral 8j indicates slopes provided at both ends of the rod-shaped lens 8e. The slope 8j has a mirror finish to improve reflection efficiency.

4 is a sectional view taken in the direction of the arrow in FIG. 3, that is, along the cutting line A-A, and FIG. 6 is a similar sectional view of a conventional LED light source.

In detail, FIGS. 4 and 6 show an enlarged view of one end of the LED light source, and FIG. 5 shows a cross-sectional view in relation to a diagram showing the light distribution on the surface of the read document. There is.

In FIG. 4, the arrow coming out from the LED chip 8b represents an approximate luminous flux. Here, the light beam directed toward the slope 8j is reflected by the slope 8j and heads toward the reading position as shown in the figure.

Therefore, the amount of light in portion B increases. Note that the light beam indicated by the two-dot chain line accurately represents the refraction at the boundary surface.

In the conventional example shown in FIG.
' However, the light flux Y is usually attenuated due to poor reflection efficiency. Furthermore, since the end face of the lens 8e is perpendicular, the light flux Y' exceeds a critical angle of about 41.8' and does not reach the reading position when exiting from the lens 8e. Therefore, there was no effect on increasing the amount of light.

In the embodiment of the present invention shown in FIG. 4, the angle θ of the slope 8j
was shown at approximately 75°. However, it is possible to optimize the angle θ using the position and dimension parameters of each element shown in the figure.

In FIG. 4, L is the distance between the LED chip 8b and the bottom of the rod-shaped lens 8e, H is the distance between the LED chip 8b and the reading position, H2 is the distance between the bottom of the rod-shaped lens 8e and the LED chip 8b, and φ is the diameter (thickness) of the rod-shaped lens 8e.

Further, the slope of the lens holding frame (part of the seal) corresponding to the slope 8j at the end of the rod-shaped lens 8e is coated with a material that enhances reflection efficiency in cooperation with the slope 8j, for example, black, to create a mirror effect. Then, there is an additional reflective effect. Further, a reflective effect can be obtained by plating the slope 8j with metal such as chrome or pasting an aluminum film on it.

Note that the rod-shaped lens 8e does not have to have a circular cross section, but as long as it is rod-shaped, the same effect can be obtained.

By adopting the configurations shown in FIGS. 1 to 4, the effects shown in FIG. 5 can be obtained.

The solid line in FIG. 5 shows the degree of illumination of the document surface by the conventional LED light source. The width dimension ■ is the reading width, for example,
For A4 size, B4 size, etc., the length of the LED must take into account the left and right margin Z, which is 2×z#20 to 50+n+n, as described above.

According to the present invention, the reading width can be expanded to the width dimension J by increasing the amount of light at portion B in FIG.

Therefore, for the required reading width, L is shorter than before.
A sufficient amount of light can be obtained with the ED light source, and the device can be made more compact and the cost of materials etc. can be reduced.

[Effects of the Invention] As explained above, according to the present invention, both end surfaces of a rod-shaped lens for condensing light are not cut on a plane perpendicular to the axis of the lens, but are cut obliquely, and Surface treatment is applied to the cut surfaces to make them mirror-like, and the reflective surface of the cut surfaces is directed toward the object to be illuminated so that the light beam that passes through the lens and hits the cut surface is reflected into the lens and passes toward the object to be illuminated. Since the rod-shaped lens is fixed so as to be open, the luminous flux at both ends of the lens is also effectively used for illuminating the corresponding portion of the object to be illuminated. Therefore, according to the present invention, a sufficient amount of light can be obtained for the required reading width with an LED light source that is shorter than conventional ones, making it possible to downsize the device and reduce the cost of materials and the like.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an LED light source according to an embodiment of the present invention, Fig. 2 is a sectional view of a facsimile machine using the light source of Fig. 1, and Fig. 3 shows a part of Fig. 2 in detail. FIG. 4 is a partially enlarged sectional view taken along cutting line A-A in FIG. 3, FIG. 5 is an explanatory diagram of the effect, and FIG. be. 8... LED array light source 8b... LED chip 8e... Rod-shaped lens 8g... Mounting hole 81... Resistor 8a... Substrate 8c, 8d... Reflection wall 8f... Holding member 8h...Power lead wire 8j...Slope and 4 others Figure 3

Claims (1)

[Claims] 1. Illumination means that illuminates one line of a document, which includes an appropriate number of rows of LED chips arranged in the width direction of the document, a printed board on which the LED chips are mounted, and a rod-shaped lens that focuses the amount of light from the LED chips. and both ends of the rod-shaped lens in the longitudinal direction are cut non-orthogonally to the lens axis, and the lens is fixed at an angle open toward the object to be illuminated, and the end surface of the lens is A document illumination device characterized by having a mirror-like surface treatment.