JPH03289860A - Original lighting device - Google Patents

Abstract

PURPOSE:To prevent irregular reflection of light in a condenser lens by applying diffusion processing diffusing light to faces of the condenser lens except its light collecting face. CONSTITUTION:Surface rough treatment diffusing light is applied entirely to other faces than light collecting faces 50a, 50b of a condenser lens 8c to form the diffusion faces like frosted glass. Since the light radiating from an LED chip 8b strikes on the other faces than the light collecting faces 50a, 50b of the condenser lens 8c and is diffused on them, irregular reflection in the condenser lens 8c is prevented and adverse effect (noise) on reading a picture is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a document illumination device used in image reading devices such as facsimile machines and copying machines, which illuminates a document in order to read the document image.

(Prior art) Conventionally, fluorescent tubes, cannon tubes, and other devices with a large amount of light have been used as illumination light sources for image reading devices such as facsimiles, but recently, light receiving elements such as CCDs have 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.

Unlike fluorescent tubes and canon tubes, LEDs do not require an inverter for lighting, so they can be made smaller and lower in cost. Also, since 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.

FIG. 9 shows a schematic configuration of an image reading device 100 as a document illumination device.

In the figure, 101 is the upper document table, and 102 is the upper document table 10.
1 is a white reading background provided on the lower surface of the document 1, 103 and 104 are lower document plates, and 105 is a document plate glass. In addition, the document platen glass 1
05, a substrate 106 and a light receiving member such as a photoelectric conversion element (not shown) are arranged. This substrate 106 is tilted approximately 20'' to 40' with respect to the document table glass 105 and directly faces the illumination position 107 of the document.

On the upper surface of the substrate 106, there are a plurality of LEDs as light emitting elements.
Chips 108 are arranged in a straight line along the longitudinal direction (width direction of the document), and a light converging surface 10 is arranged above the chips 108.
A condenser lens 109 having 9a and 109b is arranged. There are two types of condensing lenses 109: one type in which one condenser lens is arranged for each LED chip 108, and one rod-shaped type that covers all rows of LED chips 108. In addition, the optical path 2
In order to bring the substrate 106 close to the reading position 107 and secure the necessary amount of light, LE is placed on the document table glass 105.
It may be angled in a direction away from the D-chip 108. Note that the substrate 106 is fixed to a holding member 111 with a set screw 110.

In the document reading device 100 configured in this way, L
The ED chip 108 emits light and illuminates the reading position 107 of the original as shown in the optical path 200 indicated by a chain line, and the reflected light is guided to the light receiving member through the optical path 201 to read the image on the original. .

(Problem to be Solved by the Invention) However, in the above conventional example, the LED chip 1
Since the condenser lens 109 is disposed on the lens 08, there are drawbacks as shown below.

(2) In the document reading device 100 of the conventional example described above, each of the LED chips 108 can be considered as a point light source. The light emitted from the LED chip 108 passes through the condensing lens 10
9 condensing surface 109a.

109b and illuminates the document reading position 107, but some of the light is inside the condenser lens 109 and illuminates the condenser lens 109 or the side surface of the condenser lens 109 that is not directly involved in condensing light or the attachment of the condenser lens 109. There was diffuse reflection in some parts. In particular, this diffusely reflected light is closer to the optical path 201 than the LED chip 108
If the document leaks from the side closest to the platen glass 105,
Illumination position 1 from a direction more perpendicular to the surface of the document platen glass 105 than the direct light from the LED chip 108
07 will be illuminated. That is, the light emitted in the direction indicated by T is directed toward the condensing lens 109 from a surface other than the condensing surface 109a.
After T2, the light is repeatedly reflected along the path indicated by the two-dot chain line and exits in the L direction, and is regularly reflected on the lower surface of the document platen glass 105 and enters the optical path 201, which acts as noise on the image reading signal. However, this results in poor image reading. There is also an optical path in the M direction, and the document table glass 1
The specular reflection occurs on the upper surface of 05, causing a similar defect.

In some cases, this noise component may exceed 10% of the light reflected from the document surface.
It can reach ~20%.

Furthermore, since the strength of this noise varies depending on the arrangement of the rows of LED chips 108, the output of the CCD sensor does not include LEDs.
Wavy undulations corresponding to the 108th row of chips (solid dotted line)
There was a defect that caused vertical stripes with the same pitch as the pitch of the LED chip rows in the read image.

(2) Conventionally, in order to eliminate the influence of the diffusely reflected light, the substrate 106 having the LED chip 108 was placed at the illumination position 10.
7, the amount of light from the LEDs could not be used sufficiently, and the number of LED chips had to be increased, leading to an increase in cost. Furthermore, a space is required to separate the substrate 106 from the illumination position 107, resulting in an increase in the size of the entire device.

The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a document illumination device that can prevent diffused reflection of light within a condenser lens without increasing manufacturing costs or increasing the size of the device. Means for Solving the Problems) In order to achieve the above object, the present invention includes a light-emitting element and a condenser for guiding the light emitted from the light-emitting element to the illumination position on a substrate disposed facing the illumination position of the document. In a document illuminating device including a condensing lens with a surface, a diffusion process for diffusing light is applied to a surface of the condensing lens other than the condensing surface. This diffusion treatment may be performed on all surfaces other than the light condensing surface, or may be performed on some surfaces other than the light condensing surface.

(Function) The function of the present invention based on the above configuration is such that the light emitted from the light emitting element passes through the condensing surface of the condensing lens and reaches the illumination position of the original. It is a condensing lens, and light reaching areas other than the condensing surface is diffused.

(Embodiment) FIG. 2 is a side sectional view of a facsimile machine to which the present invention is applied.

In FIG. 2, F is a document conveyance/reading device (document illumination device), and a plurality of documents H, which are stacked with the document surface facing down on the document placement table 1 which also serves as a device cover, are guided at both ends by sheet guides. Guided by a member 3, sheets of the stacked documents H are conveyed from the bottom by a preliminary conveyance port 4, and separated one by one by a separation roller 5. Note that 4a and 5a are pressing pieces. Then, while the document H 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 chip (described later) as a light emitting element. The reflected light reaches a photoelectric conversion element 11 such as a CCD via a mirror 9 and a lens 1o, where it is converted into an electrical signal, and this signal is transmitted to a predetermined recording system.

When the recording system F receives a recording signal from another device or converted into an electric signal by its own photoelectric conversion element 11, the platen roller 12 rotates in the direction of arrow a and generates heat according to the image signal. The recording head 13 having a plurality of heating elements 13a is configured to be 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 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, and 23 is a sheet metal cover 24 that covers the back side of the printed board 20 to load discharged originals. This is the paper output tray.

1 and 3 show details of the document reading device F shown in FIG. 2. FIG.

In the figure, 31 is the upper document table, and 31a is the upper document table 3.
A reading white background fixed to 1, 32a.

32b is a lower document table, 33 is a document table glass, 34 is a reflection plate, G is an optical path, and R is an illumination position.

Further, reference numeral 8a denotes a substrate disposed facing the illumination position R, which is made of a material such as aluminum, glass, or epoxy, and an LED chip 8b as a light emitting element is placed on the substrate 8a in the longitudinal direction (of the document H) as shown in FIG. Bonding is performed in a straight line along the width direction. 8c is a condensing lens made of acrylic resin, and the condensing surface 50 is composed of upper and lower curved surfaces.
a, 50b and a base portion 51 that supports them are integrally molded, and are fixed by heat caulking the boss 52 protruding from the base portion 51 into the caulking hole 8g of the substrate 8a.

The portion of the outer circumferential surface of the condensing lens 8c shown by the slope in the figure, that is, the surface other than the condensing surfaces 50a and 50b, is textured to diffuse light over the entire surface, and becomes a fogged glass-like diffusion surface. ing. The grain treatment is simultaneously performed using a mold when manufacturing the condenser lens 8c by injection molding. 8d is a limiting resistor, which is shown as a plane-mounted chip resistor in the figure. 8e is a holding member that also serves as a heat sink, 8f is a substrate 8a
This is a set screw for fixing to the holding member 8e. Further, ▪ is an optical path indicating a direction perpendicular to the substrate 8a.

FIG. 4 is a perspective view of a substrate 8a according to the present invention, and FIG.
A perspective view of a state in which a condensing lens 8C is attached is shown. In the figure, 8g is a caulking hole for the condenser lens 8C, and 8h is a screw hole for screwing into the holding member 8C of the substrate 8a.

In the above configuration, the light from the LED chip 8b passes through the optical path (3) and reaches the illumination position R of the document H as shown in FIG. is read as .

Here, the light emitted from the LED chip 8b is the condensing lens 8C, which is the condensing surface 50a.

If the light is directed toward a surface other than 50b, it will be diffused, so that diffuse reflection within the condenser lens 8C can be prevented, and there will be no adverse effect (noise) on image reading. In other words, Fig. 3 shows an enlarged view of the vicinity of the condenser lens 8C, and the light T1 emitted toward the A surface, which is the diffusion-treated surface, is diffused in the directions of multiple arrows shown on the A surface, and is directed toward the T2 direction. This is because the light that travels to the L direction becomes extremely weak, and then diffuses at the B plane and then diffuses at the 0 plane as well, so that the light that finally exits in the L direction becomes extremely weak.

Here, an example of the light flux that becomes a noise component has been illustrated and explained, but the bonding position of the LED chip 8b and the substrate 8a
There is a possibility that there are other optical paths of the light flux that cause similar noise components due to manufacturing variations such as the mounting position of the
It is generally safe to apply the diffusion treatment to all surfaces other than the light condensing surfaces 50a and 50b as in this embodiment.

In the above embodiment, the condensing surface 50a of the condensing lens 8C.

Although diffusion treatment was applied to all surfaces other than substrate 50b,
If there are few manufacturing variations in itself or its attachment position to the image reading device, and if the optical path of the light beam that becomes a noise component is clear and relatively stable, the number of parts to be subjected to diffusion processing can be reduced. Examples are shown in FIGS. 6 and 7.

In these examples, diffusion processing is performed only on the A side and the B side, respectively, and the optical path beyond each side is cut off.

A unique effect can be obtained by limiting the portion to be subjected to diffusion processing to the necessary minimum. In the previous embodiment, for example, the surface indicated by N in FIG.
Direct light K from the D chip 8b is incident, and the same surface, which is a diffusing surface, becomes a secondary light source and emits light, and the diffused light is further transmitted to the surface C.
There is a possibility that it will be reflected and emitted as a noise component in the L direction, although it is weak. However, in the embodiments shown in FIGS. 6 and 7, the surface C and surface N are not diffusion surfaces, so the same problem does not occur.

Further, in the above embodiment, graining by mold treatment was used as the diffusion treatment, but for a condensing lens that has already been molded, a method of roughening it with a chemical such as sulfuric acid is also effective. According to this method, it is possible to perform the diffusion treatment even on areas that cannot be textured due to the structure of the mold.

Furthermore, applying sandpaper is also effective as another diffusion treatment method. Diffusing surface treatment can be easily applied to a molded condenser lens without the need for special equipment.

Further, in the present invention, since the diffusion treatment is directly applied to the surface of the condenser lens 8C other than the condensing surfaces 50a and 50b, it is possible to bring the substrate close to the illumination position, and the entire apparatus can be made compact.

Furthermore, there is no shortage of light quantity due to moving the substrate away from the illumination position, and there is no increase in cost due to an increase in the number of LED chips.

Figure 8 shows the photoelectric conversion element (CC) when reading an all-white original.
D), the horizontal axis represents time, ie, position in the main scanning direction, and the vertical axis represents output voltage, ie, light intensity.

The solid line is the output according to the present invention, and it can be seen that the waveform in the conventional example disappears and becomes a flat waveform.

(Effects of the Invention) Since the present invention is configured as described above, it is possible to prevent the light emitted from the light emitting element from being diffusely reflected when passing through the condenser lens.

Therefore, it is possible to prevent image reading defects when applied to an image reading device, for example.

Furthermore, in the present invention, since the diffusion treatment is directly applied to the surface of the condensing lens other than the condensing surface, it is possible to bring the substrate close to the illumination position, and the entire device can be made compact. Furthermore, unlike in the prior art, there is no shortage of light quantity due to placing the light emitting elements away from the illumination position, and there is no increase in cost due to an increase in the number of light emitting elements.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1 to 7 show embodiments of the present invention, and FIGS.
The figure is an enlarged front sectional view of the vicinity of the illumination position, Figure 2 is a schematic front sectional view of the present invention applied to a facsimile machine, Figure 4 is a perspective view of the board, and Figure 5 is light condensed above the board. FIG. 6 and FIG. 7 are front sectional views showing other configuration examples of diffusion processing, and FIG. 8 shows the relationship between the position of the light emitting element in the main scanning direction and the intensity of light. Graph, No. 9
The figure is a front sectional view of main parts showing a conventional example. R... Explanation of illumination position code 8a... Board 8b... LED chip (light emitting element) 8c...
. . . Condensing lenses 50a, 50b . . . Condensing surface 417- Fig. 3 Y W 'j? G floating woman

Claims (3)

[Claims] (1) In a document illumination device that includes a light emitting element and a condensing lens having a condensing surface that guides light emitted from the light emitting element to the illumination position on a substrate arranged to face the illumination position of the document. . A document illumination device, characterized in that it is a condensing lens, and a surface other than the condensing surface is subjected to a diffusion process to diffuse light. (2) The document illumination device according to claim 1, wherein the condensing lens has a diffusion treatment applied to all surfaces other than the condensing surface. (3) The document illumination device according to claim 1, wherein a portion of the condensing lens other than the condensing surface is subjected to a diffusion process.