JPH1013671A - Image reading device - Google Patents

Abstract

(57) [Problem] To appropriately perform shading correction even if a platen roller becomes dirty. A groove (11) is formed at an end of a platen roller (10) and in an area outside the paper passage. Thereby, the bottom surface of the groove 11
Since the platen roller 10 does not come into contact with the original and the contact glass 3 and the bottom surface of the groove 11 does not become dirty even if the surface of the platen roller 10 becomes dirty with time, the light source 4
The output will fluctuate in proportion to only the light intensity fluctuation of
Since it is possible to detect light quantity fluctuations, based on the results,
The shading waveform can be corrected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus applied to a facsimile apparatus, an image scanner, a copying machine, and the like.

[0002]

2. Description of the Related Art Conventionally, as this kind of technology, there are an image reading apparatus described in Japanese Patent Application Laid-Open No. 4-134960 and an image forming apparatus described in Japanese Patent Application Laid-Open No. 64-70738.

According to the image reading apparatus described in Japanese Patent Application Laid-Open No. 4-134960, light reflected at a position defocused upward from the reading position by slightly shifting the position of the platen roller with respect to the reading position. By reading the shading correction data, the value and sensitivity are reduced as compared with the data for shading correction in the light reflected at the focus position, so that erroneous shading correction can be prevented.

According to the image forming apparatus described in Japanese Patent Application Laid-Open No. Sho 64-70738, the document is brought into close contact with the document table downstream of the transport rotating body that transports the document onto the document table and upstream of the guide plate. By providing the means, it is possible to suppress the rising of the moving document and to prevent the light amount unevenness in reading the image.

FIG. 7 is a side view showing the internal structure of a contact type image reading apparatus having a platen roller. FIG. 8 is a perspective view showing the appearance of the image reading apparatus shown in FIG. Platen roller, 3 is contact glass, 4
Denotes a light source, 5 denotes a selfoc lens array (hereinafter, referred to as SLA) in which a plurality of selfoc lenses are arranged in the main scanning direction, and 6 denotes a CCD (Cherge Couple) which is a photoelectric conversion element.
ed Device), 7 is a bracket, and 8 is a guide plate for a document.

The contact reading unit 1 includes a platen roller 2, a contact glass 3, a light source 4, and a SLA
5, is configured by mounting the CCD 6. The contact reading unit 1 is installed in a main body of a device such as a facsimile machine with a contact glass 3 exposed from a part of a guide plate 7. Furthermore, contact glass 3
The platen roller 2 is disposed in close contact with the platen roller. At this time, the platen roller 2 is at the image reading position of the contact reading unit 1.

The document is passed through a nip portion between the platen roller 2 and the contact glass 3 and is conveyed while being in close contact with the contact glass 3 by the rotation of the platen roller 2. At this time, the original is irradiated with light by the light source 4, and the reflected light is focused by the SLA 5,
The image of the original is read by receiving the light by D6.

[0008]

A system using a platen roller as in the image reading apparatuses shown in FIGS.
Since the adhesion between the contact glass surface and the document is good and the speed of the document is not easily influenced by floating of the document or external factors, it is often used when a contact sensor having a small depth of focus is applied to the reading unit.

There is also a configuration in which the platen roller also serves as a white substrate for performing shading white correction. In this case, a white platen roller is used.
However, although the white platen roller has good transportability of the original, the white platen roller is in direct contact with the contact glass and the original, so that dust and dirt on the original easily adhere to the platen roller surface and are very easily stained. FIG. 9 shows CC when the roller surface before the platen roller was stained was read.
FIG. 10 shows the output waveform of the CCD when the roller surface is read after a lapse of time. As described above, the roller surface becomes dirty due to the contact between the platen roller and the document or the contact glass, and the output waveform of the CCD changes as shown in FIGS. 9 and 10, making it difficult to perform normal shading white correction.

Further, as a shading white correction function, there is a function of correcting the light amount of the light source by changing the light amount with time. The temporal variation of the light source can be roughly divided into two: a decrease in the absolute light quantity and a decrease in the flatness at the right and left ends of the light source. However, as described above, it is not possible to distinguish whether the fluctuation of the shading level is due to the contamination of the roller or the fluctuation of the light source amount over time due to the contamination of the platen roller with time. Is not always possible.

[0011] The present invention solves such problems,
It is an object of the present invention to provide an image reading apparatus that can always perform proper shading correction even if a platen roller becomes dirty.

[0012]

In order to solve the above problems, the present invention illuminates an image of an original on a contact glass with a light source, and receives the reflected light to a photoelectric conversion element via an optical system. And a white platen roller disposed on the contact glass and passing a document while keeping the original in close contact with the contact glass surface. It is characterized in that a groove that is concave from the surface of the paper passing area is provided in the outer area and at least one end. With such a configuration, even if the platen roller becomes dirty, the groove portion is not stained. Therefore, by reading the surface of the groove portion, it is possible to correct the variation of the light source light amount over time.

Further, a white tape is wound around the surface of the groove. Further, the surface of the groove is painted white. With such a configuration, it is possible to prevent the influence of the discoloration of the groove portion of the platen roller.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front view showing the structure of a platen roller according to a first embodiment of the present invention. Reference numeral 10 denotes a white platen roller, and reference numeral 11 denotes a groove formed at one end of the platen roller 10. . In the first embodiment, the platen roller 2 in the conventional example shown in FIG. 7 is replaced with a platen roller 10 shown in FIG.

When the platen roller 10 is installed, a region outside the paper passage that is in contact with the contact glass 3 but does not contact the original when the paper is passed is formed at both ends of the platen roller 10. The groove 11 is formed at one end of the platen roller 10 and in a region outside the paper passing area, and is more concave than the surface of the platen roller 10 in the paper passing area. By providing the groove 11 in this manner, the bottom surface of the groove 11 does not come into contact with the document or the contact glass 3.

Next, the correction of the shading waveform will be described. First, a shading waveform obtained by reading the surface of the platen roller 10 while the platen roller 10 is clean, such as when the product is shipped, is stored. FIG. 2 shows a shading waveform when the platen roller 10 is in a clean state.

If the surface of the platen roller 10 becomes dirty over time, the shading waveform becomes unstable as shown in FIG. However, since only the bottom surface of the groove 11 is not contaminated, the output of the bottom surface portion of the groove 11 fluctuates in proportion to only the light amount fluctuation of the light source 4. For example, assuming that the initial output of the bottom of the groove 11 is y1, if the light quantity decreases by 10%, the output y2 of the bottom of the groove 11 is y2 = y
Since it is 1 × 0.9, it is only necessary to reduce the peak output by 10% with a waveform similar to the stored shading waveform as it is.
This makes it possible to correct the fluctuation of the shading waveform caused by the output fluctuation of the light amount of the light source 4.

According to the apparatus of the first embodiment configured as described above, the groove 11 is provided in the platen roller 10 and the surface which does not contact the original and the contact glass 3 is formed. This makes it possible to detect, and even if the platen roller 10 becomes dirty, it is possible to correct fluctuations in the shading waveform caused by fluctuations in the output of the light amount of the light source 4 over time. As a result, appropriate shading correction can always be performed.

By the way, as time passes, not only the peak output of the light source light quantity but also the output fluctuation of the light source light quantity at the left and right ends become large. Therefore, the correction of the shading waveform based on the light amount at one end as in the first embodiment can cope with the fluctuation of the peak output, but it is difficult to cope with the fluctuation of the both ends. The second embodiment described below has been made in consideration of this point.

FIG. 4 is a front view showing the structure of a platen roller according to a second embodiment of the present invention. Reference numeral 20 denotes a white platen roller; 21, a groove formed at one end of the platen roller 20; Denotes a groove formed on the other end of the platen roller 20. In the second embodiment, the platen roller 10 in the first embodiment shown in FIG. 1 is replaced with a platen roller 20 shown in FIG. That is, in the first embodiment, the groove 11 is formed at one end of the platen roller 10, but in the second embodiment, the grooves 21 and 22 are formed at both ends of the platen roller 20 and outside the paper passing area. Are formed.

Regarding the correction of the shading waveform, the first is
This is almost the same as the embodiment. First, a shading waveform as shown in FIG. 5 is stored, and output correction is performed at both left and right ends by comparing both the left and right outputs with the initial output with time. For example, if the light amount of the light source 4 decreases by 10% at one end and by 5% at the other end, the shading waveform is also corrected accordingly.

According to the apparatus of the second embodiment configured as described above, the flatness of the light amount of the light source can be corrected by comparing the output of the left and right ends, so that proper shading can be always performed.

FIG. 6 is a front view showing the structure of a platen roller according to a third embodiment of the present invention. Reference numeral 30 denotes a white tape that is hardly discolored. In the third embodiment, the tape 30 is attached to the bottom surfaces of the grooves 21 and 22 formed at both ends of the platen roller 20 in the second embodiment shown in FIG.
Is a white bottom.

With this construction, the material of the platen roller 20 may be discolored with time due to rubber, but a white tape 30 that is not easily discolored is adhered to the bottom surfaces of the grooves 21 and 22. This can prevent a change in the color of the bottom surfaces of the grooves 21 and 22.

The configuration according to the third embodiment may be applied to the groove 11 of the platen roller 10 shown in FIG. Furthermore, instead of the tape 30, a paint that is hardly discolored is
22 may be painted white.

[0027]

According to the present invention configured as described above, the following effects can be obtained.

According to the first aspect of the present invention, since the surface which does not contact the original or the contact glass is formed, it is possible to detect the output fluctuation of the light amount of the light source. Fluctuations in the light source light amount can be corrected. As a result, proper shading can always be performed.

According to the configuration of the second and third aspects, it is possible to prevent a change in the color of the bottom surface of the groove due to the time-dependent color change of the platen roller.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a configuration of a platen roller according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a shading waveform when a platen roller is in a clean state.

FIG. 3 is an explanatory diagram showing a shading waveform over time.

FIG. 4 is a front view illustrating a configuration of a platen roller according to a second embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a shading waveform when the platen roller shown in FIG. 4 is in a clean state.

FIG. 6 is a front view illustrating a configuration of a platen roller according to a third embodiment of the present invention.

FIG. 7 is a side view showing the internal configuration of a conventional contact type image reading apparatus having a platen roller.

FIG. 8 is a perspective view illustrating an appearance of the image reading apparatus of FIG. 7;

FIG. 9 is a CCD output waveform when the roller surface before the platen roller is soiled is read.

FIG. 10 shows CC when the roller surface is read after a lapse of time.
7 is an output waveform of D.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Contact reading unit, 2, 10, 20 ... Platen roller, 3 ... Contact glass, 4 ... Light source, 5 ... Selfoc lens array (SLA), 6 ... CCD, 7 ... Bracket, 8 ... Guide plate, 11, 21 , 22… groove, 30…
tape.

Claims (3)

[Claims] 1. A reading means for reading an image by irradiating an image of a document on a contact glass with a light source and receiving a reflected light of the reflected light by a photoelectric conversion element via an optical system, and arranging the reading means on the contact glass. And a white platen roller for passing a document while keeping the original in close contact with a contact glass surface, wherein the platen roller has a sheet passing area outside the sheet passing area and at least one end thereof. An image reading device provided with a concave groove that is lower than the surface. 2. The image reading apparatus according to claim 1, wherein a white tape is wound around the surface of the groove. 3. The image reading apparatus according to claim 1, wherein the surface of the groove is painted white.