JP2000151914A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader that is made small and provided with a lighting system with excellent assembling performance where effect of a reflected light of an original is hardly caused independently of a characteristic of the original, the effect of light from an external environment and the effect of reflection of a case itself are reduced, a true luminous quantity of the light source is stably detected and the image quality to ensure the reproducibility is obtained. SOLUTION: In the image reader provided with an original glass sheet 3, a light source 6a and a luminous quantity sensor 17 or the like, the luminous quantity sensor 17 is placed at the outside of an original placing area on the original glass 3. Furthermore, a light shield member 22 is adhered to an area at a side of the original glass sheet 3 opposite to the luminous quantity sensor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus such as a printer or a computer.

[0002]

2. Description of the Related Art Conventionally, an image reading apparatus has been used as an input method and an input device of a printer and a computer. Recently, there has been an increasing demand for gradation in order to improve the reproducibility of an image.

However, when a fluorescent lamp is used as a light source, the amount of light fluctuates due to a rise in the temperature of the fluorescent lamp itself. Further, the amount of reflected light from the document varies depending on the difference in reflectance due to the difference in the material of the document itself, the type of characters and images on the document, and the like. Therefore, it is difficult to obtain image data with good reproducibility due to fluctuations in the amount of light during reading of one document and reflectance characteristics depending on the material of the document. As a countermeasure, measures such as providing a temperature sensor for detecting the temperature of the fluorescent lamp tube surface or providing a light amount sensor for detecting the light amount have been taken. An image reading apparatus having a light amount sensor is disclosed in
No. 4 has been proposed.

Hereinafter, a conventional image reading apparatus will be described. FIG. 4 is a top view of the illumination system of the conventional image reading device, FIG. 5 is a cross-sectional view of the illumination system of the conventional image reading device, and FIG. 6 is a side view of the conventional image reading device.

In FIG. 4, reference numeral 17 denotes a light quantity sensor, which is arranged at the center of the optical axis L and installed on the side of the light source 6a. There is also a mode in which a light amount sensor is installed on the side surface of the other light source 6b. Reference numeral 21 denotes a light source unit that houses the light amount sensor 17 and the light sources 6a and 6b.

In FIG. 5, reference numeral 2 denotes an original, and reference numeral 3 denotes an original glass. Reference numeral 18 denotes a reflector, 19 denotes a direct light beam emitted from the light source 6a, and 20 denotes a light beam emitted from the light source 6a.
It is a luminous flux that is reflected back.

In FIG. 6, reference numeral 1 denotes a housing of an image reading apparatus, 2 denotes an original, 3 denotes an original glass on which the original 2 is loaded, 4 denotes an original pressing plate that presses the original 2, and 5 denotes various parts to be described later. A frame 7 is a reflection mirror for causing the reflected light irradiated on the document 2 to reach an image forming lens 8 described later, and 8 is an image forming device for changing the reflected light irradiated on the document 2 to a predetermined magnification. Reference numeral 9 denotes a solid-state imaging device for converting an image of the document 2 formed by the imaging lens 8 into an electric signal;
Is driven in the sub-scanning direction B, 11 is a motor-side toothed pulley attached to the output shaft of the sub-scanning drive actuator 10, and 12 is a timing belt for transmitting the driving force of the sub-scanning drive actuator 10. A driving transmission member, 13 is a driven pulley on a driven side,
Reference numeral 14 denotes a guide member such as a shaft, and reference numerals 15 and 16 denote bearing members fixed to the frame 5 for guiding the guide member 14.

The operation of the conventional image reading apparatus configured as described above will be described below. First, the original 2 is placed on the original glass 3 by the original pressing plate 4,
The reflected light emitted from the light sources 6a and 6b passes through the original 2,
Further, the light reaches the image forming lens 8 via the reflection mirror 7, and the image forming lens 8 forms the image on the solid-state image pickup device 9 after changing the reflected light at a predetermined magnification. When reading the entire original 2, the frame 5 is moved by the sub-scanning direction drive actuator 10 in the direction indicated by the arrow B in the drawing according to the length of the original 2.
Are scanned through.

When a predetermined sensor detection voltage or current is reached with reference to the light amount received by the light amount sensor 17,
Start reading. The voltage or current applied to the light sources 6a and 6b is adjusted so that the output of the light amount sensor 17 does not fluctuate even during reading, and control is performed so that the light amount does not fluctuate in one read document.

[0010]

However, the configuration of the above-described conventional image reading apparatus has the following problems. That is, since the light amount sensor 17 is arranged at the center of the optical axis, the reflected light beam 20 of the document 2 is indirectly received, and the light amount from the true light source cannot be detected, and a higher output is detected. Was. While reading one original, the effect of light intensity fluctuations caused by characters and pictures
The reflected light beam 20 has a problem that a true amount of light cannot be received.

Further, the light amount sensor 17 receives the light from the external environment passing through the housing 1 of the image reading apparatus and the reflected light beam of the light source due to the reflection of the housing 1 itself, so that the true light source light beam can be detected. There was a problem that it was impossible. Further, since the light amount sensor 17 is disposed at the center position of the optical axis, the size of the light source unit 21 is increased.

Accordingly, the present invention solves the above-mentioned conventional problems, and makes it difficult to be affected by the reflected light of the original without depending on the characteristics of the original, and to reflect the light from the external environment and the reflection of the housing itself. To provide an image reading device with an illumination system that can realize stable detection of the true light amount of the light source, obtain image quality that can ensure reproducibility, can be further miniaturized, and have a good assemblability. It is intended to be.

[0013]

In order to solve the above-mentioned problems, an image reading apparatus according to the present invention comprises a document glass on which a document is placed, a light source for illuminating the document, and a light amount sensor for detecting a light amount of the light source. A solid-state imaging device for reading an original, and imaging means for forming an image of the original on a light-receiving surface of the solid-state imaging device, wherein the light amount sensor is arranged outside the original placing area on the original glass. .

According to this configuration, the influence of the reflected light of the original is hardly affected, the influence of the light from the external environment and the reflection of the housing itself is reduced without depending on the characteristic of the original, and the true light amount of the light source is reduced. It is possible to realize an image reading device that can realize stable detection, obtain an image quality that can ensure reproducibility, can be further reduced in size, and has an illumination system with good assemblability.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 is a document glass on which a document is placed, a light source for illuminating the document, a light amount sensor for detecting a light amount of the light source, and a solid-state image sensor for reading image information of the document. And an image forming means for forming a document image on the light receiving surface of the solid-state imaging device, wherein the light amount sensor is arranged outside the document placing area on the document glass.

According to this configuration, the influence of the reflected light of the original can be eliminated, and the arrangement at the end improves the miniaturization and the assemblability.

According to a second aspect of the present invention, in the image reading apparatus according to the first aspect, the light amount sensor is disposed at a position opposite to a document surface with a light source interposed therebetween.

With this configuration, it is possible to eliminate the influence of the reflected light from the horizontal direction of the document. The invention according to claim 3 is
3. The image reading apparatus according to claim 1, wherein a light shielding member is provided in a region facing the light amount sensor on a side portion of the document glass.

With this configuration, the original light amount of the light source can be detected while eliminating the influence of light from the external environment and the housing itself.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a side view of the illumination system of the light amount sensor output of the image reading device according to one embodiment of the present invention, FIG. 2 is a side view of the image reading device, and FIG. It is.

In FIG. 1, the light source 6a is a light source unit 21.
The original 2 is placed on an original glass 3. The document glass 3 is supported by the reading device housing 1. The light amount sensor 17 is disposed below the end of the light source 6 a on the opposite side of the original placing surface with the light source 6 a interposed therebetween, and is installed on the light source unit 21 on the surface facing the original 2. Further, a light shielding member 22 is attached to the reading device housing 1 facing the light amount sensor 17. The light-shielding member 22 is provided on the side of the original glass 3.
Is pasted in the area opposite to. FIG. 2 is an overall view of the image reading apparatus having the configuration shown in FIG.

FIG. 3 shows the temporal variation of the ordinary light source light quantity, and shows that the output of the light quantity sensor 17 fluctuates depending on the presence or absence of a document.

The operation of the image reading apparatus configured as described above will be described below. The light-shielding member 22 is attached to the reading device housing 1 facing the light amount sensor 17, so that the influence of the reflected light of the document 2 is eliminated and the influence of the sneaking light from the lateral direction is also reduced. Further, by attaching the light shielding member 22 to the housing 1, the influence of the reflected light from the housing 1 is removed, and light such as an interior light from the outside passes through the housing 1 and is input to the light amount sensor 17. Is eliminated, and it becomes possible to detect the true light amount of the light source.

When the light source 6a is turned on in response to the lighting start signal, the temperature of the light source 6a itself gradually rises to a stable tube surface temperature (about 70 to 80 degrees). Accordingly, the light amount also fluctuates, and increases until the temperature stabilizes. The light amount can be controlled by controlling the voltage or current of the light source 6a. Further, in FIG. 3, it is possible to suppress the fluctuation of the light amount due to the presence or absence of the document and to detect the true light amount.

As described above, the light amount sensor is set in a region deviated from the document placing position, and is disposed at a position facing the document of the light source, and a light shielding member is attached at a position facing the light amount sensor. Therefore, it is possible to realize the detection of the true light amount of the light source without being affected by extraneous light from a document or an external environment.

[0026]

As described above, according to the present invention, it is possible to detect a true light amount of a light source without being affected by extraneous light from a document or an external environment and reflected light of a housing itself. This makes it possible to provide an image reading apparatus capable of improving the accuracy of light amount control and obtaining image data with good reproducibility. In addition, it is possible to realize an image reading apparatus in which the position of the light amount sensor is reduced in size and which has good assemblability.

[Brief description of the drawings]

FIG. 1 is a side view of an illumination system of a light amount sensor output of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a side view of the image reading apparatus according to the embodiment of the present invention;

FIG. 3 is a diagram showing the progress of the light amount sensor output of the image reading apparatus according to the embodiment of the present invention;

FIG. 4 is a top view of an illumination system of the conventional image reading apparatus.

FIG. 5 is a sectional view of an illumination system of a conventional image reading apparatus.

FIG. 6 is a side view of a conventional image reading apparatus.

[Explanation of symbols]

 2 Document 3 Document glass 5 Frame 6a Light source 8 Imaging lens 9 Solid-state imaging device 17 Light intensity sensor 22 Light shielding member

Continued on the front page F term (reference) 2G065 AA04 AB22 AB26 AB27 BA04 BA36 BB19 BB21 BB49 BC35 CA05 CA07 CA21 DA17 2H108 AA02 CB01 JA11 2H109 AA02 AA23 AA83 5C072 AA01 BA13 CA02 CA14 DA02 DA15 EA05 LA04 RA06 UA13 X04

Claims (3)

[Claims] An original glass on which an original is placed, a light source for illuminating the original, a light amount sensor for detecting a light amount of the light source, a solid-state image sensor for reading image information of the original, and an original on a light receiving surface of the solid-state image sensor An image reading apparatus, comprising: image forming means for forming an image, wherein the light amount sensor is arranged outside a document placing area on the document glass. 2. An image reading apparatus according to claim 1, wherein said light amount sensor is arranged at a position opposite to a document placing surface with said light source interposed therebetween. 3. The image reading apparatus according to claim 1, wherein a light-shielding member is provided in a region of the side of the document glass facing the light amount sensor.