JPH067615Y2 - Image reader - Google Patents

Description

TECHNICAL FIELD The present invention relates to an image reading device for reading an image from a document such as a facsimile device.

(Prior Art) Conventionally, a light source such as a fluorescent lamp is used as a light source of an image reading apparatus that sets a white level on the surface of a document based on the illuminance of light from a light source reflected by a white tape for white level setting reference. A tubular light source was used.

However, when a light source such as a fluorescent lamp is used, there is a problem that the image reading device cannot be downsized because the light source in the image reading device and an accessory device of the light source occupy a large volume.

Further, in order to solve this problem, a light emitting diode (LED) array has been used as a light source in recent years. However, when a light emitting diode of a diffused type is used as a light source of an image reading apparatus, a fluorescent lamp or the like is used. Since the illuminance becomes insufficient as compared with the light source, it is necessary to use a condensing type light emitting diode that emits parallel rays as the light source of the image reading apparatus.

However, since the condensing type light emitting diode 1 has the illuminance distribution as shown in FIG. 5, the light of the light source reflected by the reflecting surface P ₁ of the white tape 2 for white level setting reference is When used as a light source of an image reading device for correcting the white level of the surface P ₂ of the original 3 based on the illuminance, the optical axis of the light emitting diode ₁ is aligned with the reflecting surface P ₁ of the white tape 2 (see FIG. 6). ), The illuminance on the reflection surface P ₁ of the white tape 2 is maximized, but the illuminance on the surface P ₂ of the original 3 is extremely reduced (see FIG. 5), and the photoelectric conversion element 4 for image reading is used.
The output level of the white level signal in the above is different between the reflection surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 (see FIG. 7),
When the image of the original 3 is halftone, the margin of the leading edge of the original 3 is read as black.

When the optical axis of the light emitting diode 1 is aligned with the surface P _{2 of the} original 3 (see FIG. 6), the illuminance on the surface P ₂ of the original 3 is maximized, but the illuminance on the reflection surface P ₁ of the white tape 2 is increased. When the output level of the white level signal in the photoelectric conversion element 4 is extremely lowered (see FIG. 5), the reflection surface P of the white tape 2 is reduced.
₁ and the front surface P _{2 of the} original 3 (see FIG. 8), the left and right margins of the original 3 are read as black when the image of the original 3 is halftone.

Therefore, if the illuminance of the reflection surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 are made equal, the reflection surface P ₁ of the white tape 2 is set.
Light emitting diode array for illuminating ₁ and the surface P _{2 of the} original 3
This requires a light-emitting diode array for illuminating the light source, which increases the number of parts of the image reading apparatus and the number of manufacturing steps, and also raises the manufacturing cost.

(Object of the Invention) It is an object of the present invention to provide an image reading apparatus capable of illuminating the reflecting surface of a white tape and the surface of a document with the same illuminance by one light emitting diode array.

(Structure of the Invention) The present invention is designed so that the optical axis of the light-emitting diode array arranged in the light-emitting diode array passes through the midpoint between the reflective surface of the white tape on the scanning line and the surface of the original. , Attached to the image reading device.

Embodiment An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the structure of a specific example in one embodiment of the present invention. The same reference numerals as those in FIG. 6 denote the same parts, and the illuminance distribution shown in FIG. In a light emitting diode array (not shown) in which condensing light emitting diodes 1 for emitting parallel light rays are arranged, the optical axis of the light emitting diodes 1 is such that the reflecting surface P ₁ of the white tape 2 on the scanning line and the surface P _{2 of the} original 3 are arranged. It is attached to the image reading device so as to pass through the midpoint P ₀ of

In this specific example configured as described above, the light emitting diode 1
If the optical axis of is passing through the midpoint P ₀ , the light emitting diode 1
Even if the angle θ formed between the optical axis of the light emitting diode and the scanning line changes, the distance between the optical axis of the light emitting diode 1 and the reflecting surface P ₁ of the white tape 2,
Since the distance between the optical axis of the light emitting diode 1 and the surface P ₂ of the original 3 is always the same, the illuminances of the reflecting surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 are always the same (see FIG. 2). The output level of the white level signal in the photoelectric conversion element 4 becomes equal on the reflection surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 (see FIG. 3).

By the way, the reflective surface P ₁ of the white tape 2 and the surface P of the original 3
_For the illuminance of ₂ , when the angle θ is reduced or the distance H ₁ between the reflective surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 is reduced, the optical axis of the light emitting diode 1 and the reflective surface P of the white tape 2 are reduced. ₁
And the optical axis of the light emitting diode 1 and the surface P of the original 3
The interval between the _two and the illuminance is reduced, and the illuminance is improved.

Further, in order to reliably and clearly read the image on the surface P ₂ of the original 3 with the photoelectric conversion element 4, the illuminance on the reflecting surface P ₁ of the white tape 2 and the surface P ₂ of the original 3 is about 90% of the maximum illuminance. Although necessary, the width of the region where the illuminance of about 90% of the maximum illuminance of the light emitting diode 1 is obtained is about 1 mm (see FIG. 2).

Further, H ₁ is the interval of the transport path required to transport the document 3, and this interval H ₁ is a value determined in consideration of the thickness of the document 3.

Therefore, if the illuminance area of the maximum illuminance of the light emitting diode 1 is determined, the width of the illuminance area is automatically determined, and the interval H ₁ is a simple design value. You will be able to decide. Further, as the angle θ becomes smaller, the illuminance on the reflecting surface P ₁ of the white tape 2 and the surface P ₂ of the original 3 becomes closer to the maximum illuminance of the light emitting diode 1, so that the light emitting diode array and the photoelectric conversion element 4 are brought closer to each other. It will be possible to install them, or to form them together.

It should be noted that H ₂ is the passing position of the front surface P ₂ of the original 3 and the guide plate 5.
If a conveyance roller (not shown) for the original 3 is installed in the vicinity of the original reading section at an interval of, the original 3 is lifted from the guide plate 5 and H ₂ > 0 (see FIG. 1).
However, if the original 3 is brought into contact with the guide plate 5 and conveyed,
H ₂ = 0.

FIG. 4 shows the structure of another specific example of the embodiment of the present invention, in which the same reference numerals as those in FIG. 1 denote the same parts, and 6 denotes the refractive index n, The contact glass has a thickness of T, and this contact glass 6 is used in place of the guide plate 5 of the specific example shown in FIG.

In this specific example configured as described above, the light emitted in parallel from the light emitting diode 1 is refracted by the contact glass 6 and is incident on the reflecting surface P ₁ of the white tape 2 and the surface P ₂ of the original 3. However, since the incident angle of light from the light emitting diode 1 to the contact glass 6 and the emitting angle of light from the contact glass 6 to the reflecting surface P ₁ of the white tape 2 and the surface P _{2 of the} original 3 are equal, The installation position is the first because the light is refracted by the contact glass 6.
The other conditions are exactly the same as those of the specific example shown in FIG. 1, except that the light emitting diode 1 of the specific example shown in the drawing is closer to the scanning line than the installation position.

(Effect of the Invention) As described above, according to the present invention, the light emitting diode array can illuminate the reflecting surface of the white tape and the surface of the original document with the same illuminance. This has the effect of reducing man-hours and manufacturing costs. Further, the closer the installation position of the light emitting diode is to the scanning line, the more the illuminance between the reflecting surface of the white tape and the surface of the original is improved. Therefore, the volume occupied by the image reading unit is reduced, and the image reading apparatus can be miniaturized. In addition, if the light emitting diode array and the photoelectric conversion element are integrally formed,
Further, the number of parts and the number of manufacturing steps of the image reading apparatus are reduced, the manufacturing cost is reduced, and the volume occupied by the image reading unit is reduced, so that the image reading apparatus can be downsized.

[Brief description of drawings]

FIG. 1 is a block diagram of a specific example of an embodiment of the present invention,
FIG. 2 is an illuminance distribution chart of the light emitting diode in one embodiment of FIG. 1, FIG. 3 is an output waveform chart of a white level signal in one embodiment of FIG. 1, and FIG. 4 is an embodiment of the present invention. FIG. 5 is a configuration diagram of another specific example, FIG. 5 is an illuminance distribution diagram of a light emitting diode attached to a conventional image reading device, and FIG. 6 is a configuration diagram of an image reading unit in the conventional image reading device, FIGS. 7 and 8. FIG. 7 is an output waveform diagram of a white level signal in a conventional image reading device. 1 ... Light emitting diode, 2 ... White tape, 3 ... Original,
4 ... Photoelectric conversion element, P ₁ ... Reflective surface of white tape 2, P
₂ ... front of manuscript 3, P ₀ ... midpoint.

Claims (2)

[Scope of utility model registration request] 1. The light source and the photoelectric conversion element, based on the illuminance of the light of the light source reflected by the reflecting surface of the white tape for white level setting reference arranged along the scanning line of the photoelectric conversion element. In an image reading apparatus that corrects the white level of the surface of an original that passes between the white tape and the white tape, the optical axis of the light source having an illuminance of a normal distribution with a narrow dispersion is conveyed at a predetermined interval with respect to the white tape. The light source is arranged so as to pass through the midpoint between the surface of the original and the reflecting surface of the white tape, and the illuminance of the light irradiating the reflecting surface of the white tape and the surface of the original is made equal. An image reading device characterized by the above. 2. The image reading apparatus according to claim (1), wherein the light source is an array of light emitting elements for emitting parallel rays.