JP2001094737A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image reader that can read image information of an original with high accuracy by enhancing read accuracy of a gray scale reference member provided on an original continuous read glass section and correcting a gain of an image signal with high accuracy in the image reader having a continuous read function. SOLUTION: In the image reader that has a 1st image read means reading image information of an original placed on an original mount glass section and a 2nd image read means that read image information of the original while sequentially feeding originals on an upper part of the original continuous read glass section, a gray scale reference member is placed to an end of the original continuous read glass section, a center of an original lighting section is matched to a middle or about the middle between the arranged position of the gray scale reference member and an edge position opposite to the arranged position. The image read stein reads the gray scale reference member, and an output obtained by the image read section is used to correct a temporal change in the luminance of the original lighting section in the main scanning direction and the image information of the original is read.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus having a flow scanning function (flow scan), and more particularly to an image reading apparatus in which image information of a document is read by reading means such as a line sensor (CCD). It is.

[0002]

2. Description of the Related Art Conventionally, image information of a document or the like is line-scanned in the sub-scanning direction, the image information is imaged on a line sensor (CCD) surface as reading means, and an output signal obtained from the line sensor is output. There have been proposed various image reading apparatuses that read image information of the original by utilizing the image reading apparatus.

FIG. 4 is a schematic view of a main part of a conventional image reading apparatus of this kind, and FIG. 5 is a top view of the main part when the original placing glass part and the original moving reading glass part are viewed from above.

In FIG. 4, an illumination light source (linear light source) 4 is shown.
The image information of the original 40 on the original placing glass part (original placing glass table) 41 illuminated by the scanner 4 passes through the slit 45 and the first, second, and third mirrors 46, 47, and 4 for scanning.
An image is formed on the surface of the line sensor 50 by the image forming lens 49 via the image sensor 8, and the image information of the document 40 is read digitally.

In FIG. 1, as a method of scanning the image information of the document 40 in the sub-scanning direction, for example, the first, second, and third mirrors 46, 47, and 48 for scanning are moved in the direction of arrow A in FIG. Direction) while maintaining a constant relationship. At this time, the scanning speed of each scanning mirror is set so that, for example, when the speed of the first mirror 46 is V, the scanning speed of the second and third mirrors 47 and 48 is V / 2. I have.

In such a configuration, the line sensor 5
The image information formed on the 0 plane is converted into an electric signal and sent to, for example, an output device to output the image information as a print output, or sent to a storage device to store the input image information. There are various cases and the like, which are used as information of each image reading apparatus.

In the image reading apparatus shown in FIG. 4, data on the density of the shading plate 43 between the front name plate 42 and the document placing glass portion 41 is scanned and stored before the image information of the document 40 is read. By comparing the data with image data relating to the density of the document 40, unevenness in the light amount distribution in the apparatus, unevenness in the sensitivity of the CCD,
Then, output fluctuations and the like are corrected, and the image information of the document 40 is read with high accuracy.

[0008]

In such a conventional image reading apparatus, image information of a document can be read with high accuracy without any problem if the normal configuration shown in FIG. 4 is used.

However, an image reading apparatus provided with this image reading apparatus and having a flow reading function for reading image information of the original while sequentially feeding the original has the following problems.

FIG. 6 is a schematic view of a main part of the image reading apparatus having the flow reading function, and FIG. 7 is a top view of the main part when the document placing glass part and the document moving reading glass part are viewed from above.
FIG. 6 shows a configuration in which a portion (document flow reading unit) for reading a document while sequentially feeding the document is added to the leading end portion of the image reading apparatus in FIG.

Before the original 70 is read, the operation of the original flow reading section is as follows: the light source 44, the slit 45, the first, second, and third mirrors 46, 47, and 48 for scanning, the imaging lens 49, and An image reading section 61 such as a line sensor (CCD) 50 moves to a lower portion of the original reading glass section 71.

Next, an automatic document feeder (not shown)
Also called "DF". ), The original 70 is sequentially sent, and passes through the upper part of the original flow reading glass unit 71 when the light source 4
4, the original 70 is illuminated, and the reflected and diffused light beam from the illuminated original 70 passes through the slit 45, and passes through the first, second, and third mirrors 46, 47, and 48 for scanning. The image information of the original 70 is read by forming an image on the surface of the line sensor 50. And manuscript 7
Since 0 passes through the document flow reading glass portion 71 at a constant speed, the image information of the document 70 is read by obtaining a signal based on the image information of the document 70 during that time.

As described above, the automatic reading of the original is possible by providing the original flow reading unit at the end of the image reading apparatus and providing a simple DF at the end of the original pressure plate.

However, in an image reading apparatus for reading a document in a flowing manner, when the document is read, the light source is turned on and is stationary. For example, when a xenon lamp or the like is used as the light source, the time of illumination Fluctuations have become a problem. As shown in FIG. 8, there is a problem that the illumination light amount of the xenon lamp decreases as the lighting time increases. For example, in the case of a flow-reading image reading apparatus that reads an A4 document at 15 sheets / minute, the number of documents to be read is 30
In the case of sheets, as shown in FIG. 8, the illumination light amount when reading the last document is reduced by about 5 to 6% as compared with the illumination light amount when reading the first document. There is a problem that the original is read dark.

The present invention provides a flow reading function (flow scan).
In the image reading apparatus having the following, when using the drift reading function, the density reference member disposed outside the document reading effective area in the main scanning direction of the document drift reading glass portion, the arrangement position of the density reference member, and An image reading unit in which the center of the document illuminating unit and / or the optical axis of the image forming optical system is aligned with or substantially in the middle of the document reading effective area of the document flow reading glass unit on the opposite side of the arrangement position, or approximately the middle. Using the output obtained by the reading unit, the temporal change of the illumination light amount in the main scanning direction of the document illuminating unit is corrected, so that the reading accuracy of the density reference member is improved, and the gain of the image signal is increased. An object of the present invention is to provide an image reading apparatus capable of always reading image information of a document with high accuracy by performing correction with high accuracy regardless of the number of documents to be read.

[0016]

According to a first aspect of the present invention, there is provided an image reading apparatus for illuminating an original, and forming an image of a light beam from the original illuminated by the original illuminator at a predetermined position. The original placed on the original placing glass unit by an image reading unit having an imaging optical system and reading means arranged at a predetermined position of the imaging optical system in the main scanning direction. A first image reading means for reading the image information by scanning the original and the image reading section relatively in the sub-scanning direction; and A second image in which the image reading unit is moved to a lower portion of the document flow reading glass unit and the image reading unit reads image information of the document in the main scanning direction by sequentially feeding the document to the upper portion of the document flow reading glass unit; Reading means, comprising:
When the density reference member is arranged outside the original reading effective area in the main scanning direction of the original flow reading glass portion, and when reading is performed by the second image reading means, the arrangement position of the density reference member and the arrangement position of the density reference member are determined. The center of the document illuminating unit is centered or substantially halfway with the end position of the document reading effective area of the document flow reading glass unit on the opposite side, and the density reference member is read by the image reading unit. It is characterized in that the output obtained by the reading unit is used to correct the temporal change of the illumination light amount in the main scanning direction of the document illuminating unit, and the image information of the document is read.

According to a second aspect of the present invention, there is provided an image reading apparatus comprising: a document illuminating section for illuminating a document; an image forming optical system for forming a light beam from the document illuminated by the document illuminating section at a predetermined position;
A reading unit having a reading unit disposed at a predetermined position of the image forming optical system in the main scanning direction, and image information of the document placed on the document loading glass unit is read by the document. A first image reading means for relatively scanning the image reading section in the sub-scanning direction and reading the image reading section; and a document flow reading glass section provided at a position off the sub-scanning direction of the document placing glass section. Second image reading means for moving the image reading unit to a lower portion and reading image information of the document in the main scanning direction by the image reading unit while sequentially sending the document to an upper portion of the document flow reading glass portion. In the image reading device, when a density reference member is disposed outside the original reading effective area in the main scanning direction of the original flow reading glass portion, when reading is performed by the second image reading unit,
The optical axis of the imaging optical system is aligned with or substantially halfway between the position where the density reference member is arranged and the end position of the original reading effective area of the original flow reading glass portion opposite to the arrangement position. The density reference member is read by the image reading section, and the output obtained by the image reading section is used to correct a temporal change in the illumination light amount of the document illuminating section in the main scanning direction, thereby obtaining image information of the document. Is read.

According to a third aspect of the present invention, there is provided an image reading apparatus, comprising: a document illuminating section for illuminating a document; an image forming optical system for forming a light beam from the document illuminated by the document illuminating section at a predetermined position;
A reading unit having a reading unit disposed at a predetermined position of the image forming optical system in the main scanning direction, and image information of the document placed on the document loading glass unit is read by the document. A first image reading means for relatively scanning the image reading section in the sub-scanning direction and reading the image, and a document flow reading glass section provided at a position off the sub-scanning direction of the document placing glass section. Second image reading means for moving the image reading unit to a lower portion and reading image information of the document in the main scanning direction by the image reading unit while sequentially sending the document to an upper portion of the document flow reading glass portion. In the image reading device, when a density reference member is disposed outside the original reading effective area in the main scanning direction of the original flow reading glass portion, when reading is performed by the second image reading unit,
The center of the document illuminating section and the image forming point are intermediate or substantially intermediate between the arrangement position of the density reference member and the end position of the effective original reading area of the original flow reading glass section opposite to the arrangement position. The optical axis of the optical system is aligned, the density reference member is read by the image reading unit, and the output obtained by the image reading unit is used to correct the temporal change of the illumination light amount in the main scanning direction of the document illumination unit. The image information of the original is read.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a schematic view of a main part of Embodiment 1 of the present invention, and shows an optical system when reading an image using, for example, a flow scan. . FIG. 2 is a main part top view of the original placing glass part and the original moving reading glass part when viewed from above. FIG. 2 shows a case where an A3-size original is read.

In FIG. 1, reference numeral 1 denotes a document placing glass portion on which a document 30 is placed. Reference numeral 2 denotes a front original abutting nameplate, 3 denotes a shading plate, and 4 denotes a light source as an original illuminating unit, which is formed of a fluorescent tube such as a xenon lamp. Although the light source 4 in this embodiment is a linear light source such as a fluorescent tube, it may be a point light source such as a light emitting diode (LED). Reference numeral 5 denotes a slit which is long in the main scanning direction and blocks stray light from the document surface. Reference numerals 6, 7, and 8 denote scanning first, second, and third mirrors, respectively, which guide a light beam reflected from the document surface to an image forming lens described later. Reference numeral 9 denotes an image forming lens as an image forming optical system, which reduces image information of a document at a fixed magnification and forms an image on a line sensor surface described later. Reference numeral 10 denotes a line sensor (C
CD) and a reading unit (a plurality of reading elements) in the main scanning direction.
Has been arranged. Each element such as the light source 4, the slit 5, the first, second, and third mirrors 6, 7, 8 for scanning, the imaging lens 9, and the line sensor 10 constitutes one element of the image reading unit 21. are doing. As shown in FIG. 1, the image reading section 21 moves to a lower portion of a document flow reading glass section 11, which will be described later, when reading an image using a flow scan. It moves to the lower part of the placing glass part 1.

Reference numeral 11 denotes a document flow reading glass portion, which is disposed at a position off the document placing glass portion 1 in the sub-scanning direction. Reference numeral 12 denotes a paper feeding device. Reference numeral 13 denotes a density reference member, which is made up of a white reference member (hereinafter also referred to as a "white reference member"), and has an original reading effective area (a + b shown in FIG. 2) in the main scanning direction of the original flow reading glass portion 11. )
It is located outside. In the present embodiment, the white reference member 13 is read by the image reading unit 21 and the output from the line sensor 10 corresponding to the white reference member 13 is monitored so that the monitored output is always constant as a signal output. The signal output from the line sensor 10 is corrected by changing the gain of the electric circuit on the way.

In this embodiment, when performing normal image reading, the original 30 placed on the original placing glass unit 1 is illuminated by the original illuminating unit 4 and the illuminated light beam from the original 30 is slit. 5, first, second and third for scanning through
An image is formed on the surface of the line sensor 10 by the image forming lens 9 via the mirrors 6, 7, 8 of the image forming apparatus.
1 is relatively scanned in the sub-scanning direction and is read (first image reading means).

On the other hand, when reading an image using the flow scan, the original 20 is sequentially fed to the upper part of the original flow reading glass part 11 provided at a position deviated from the original placing glass part 1 in the sub-scanning direction. The image information of the document 20 is read in the main scanning direction by the image reading unit 21 moved to a lower portion of the document flow reading glass unit 11 (second image reading unit).

Here, the image reading section 21 scans the white reference member 13 provided at the end of the document flow reading glass section 11, and the line sensor 10 corresponding to the white reference member 13 is scanned.
The means for correcting the output signal from the device will be described.

As described above, the amount of illumination of the xenon lamp 4 as a light source gradually decreases as the lighting time elapses as shown in FIG. Therefore, when the image information of the document 20 is read in a state where the xenon lamp 4 located below the document flow reading glass portion 11 is lit and still, the output signal from the line sensor 10 increases as the number of documents 20 increases. There is a problem that the temperature gradually decreases.

In this embodiment, as described above, as shown in FIG. 2, the white reference member 1 as a density reference member is provided outside the document reading effective area (a + b) of the document flow reading glass portion 11.
3, the white reference member 13 is read by the image reading unit 21 and the output from the line sensor 10 corresponding to the white reference member 13 is monitored so that the monitored output is always constant as a signal output. The signal output from the line sensor 10 is corrected by changing the gain of the electric circuit on the way. As a result, even if the illumination light amount of the xenon lamp 4 changes with time, the final image signal output is, for example, if the density of the original 20 is the same, the original 20 is automatically fed first and the read original 20 is automatically fed last. It is possible to set the same image output signal level even in the read original 20.

However, for example, a white original 20
The output from the line sensor 10 in the main scanning direction is usually
The output waveform is as shown in FIG. 3 due to a drop in the light amount at the end of the illumination light and a drop in the light amount due to the cos4 law of the imaging lens. As can be seen from the drawing, the drop in the amount of light is particularly remarkable near the end portion in the main scanning direction.

Normally, in an image reading apparatus having only the original placing glass section 1, the center of the original illuminating section (light source) 4 is located on the A axis (the center of the effective original reading area in the main scanning direction) as shown in FIG. The distances a and b from the A-axis to both ends 11a and 11b of the original reading effective area are a = b = 148.
5 mm.

However, since the white reference member 13 provided on the original flow reading glass portion 11 needs to be provided outside the effective document reading area, for example, the distance e (a + c ') from the A axis to the white reference member 13 is required. ) Is e = 156.
It is provided at a position separated by 5 mm. Therefore, when the center of the document illuminating unit 4 is the A-axis, the white reference member 13 is further away from the end 11a of the document reading effective area by a distance c ′ = 8.
mm, and a position where the amount of light at the end suddenly decreases as shown in FIG. 3, for example.

Therefore, in the present embodiment, the center of the document illuminating section 4 is not on the A-axis, but, for example, the position of the white reference member 13 on the document flow-reading glass section 11 and the effective area of the document reading effective area on the reflection side of the position. It is aligned with the B axis that is intermediate or substantially intermediate with the end position 11b. That is, in the present embodiment, the center of the document illuminating unit 4 is set to the B axis, and at this time, c = d = 15
By setting the distance to 2.5 mm, it is possible to avoid the position of the end portion where the light amount sharply decreases, thereby accurately correcting the gain of the image signal.

As described above, in the present embodiment, as described above, the intermediate position between the arrangement position of the white reference member 13 and the end position 11b of the original reading effective area of the original document reading glass portion 11 on the opposite side of the arrangement position. Alternatively, by adjusting the center of the document illuminating section 4 approximately at the center, the drop in the amount of light at the end portion is improved, the reading accuracy of the white reference member 13 is increased, and the gain of the image signal is corrected with high accuracy. 20 image information is always read with high accuracy regardless of the number of originals to be read.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described.

The present embodiment differs from the first embodiment in that the position of the white reference member 13 and the end position 11b of the effective document reading area of the original document reading glass section 11 on the opposite side of the arrangement position are different. This means that the optical axis L of the imaging optical system 9 is adjusted to the middle or almost the middle. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, in the present embodiment, the intermediate position between the arrangement position of the white reference member 13 and the end position 11b of the original reading effective area (a + b) of the original document reading glass portion 11 on the opposite side of the arrangement position, or By aligning the optical axis L of the imaging optical system (imaging lens) 9 approximately in the middle, the end of the document reading effective area can be set inside, thereby the light amount at the end as in the first embodiment. And the resolution of the edges has been improved.

(Embodiment 3) Next, Embodiment 3 of the present invention will be described.

The present embodiment is different from the first embodiment in that the position of the white reference member 13 and the end position 11b of the original reading effective area of the original flow reading glass portion 11 on the opposite side of the arrangement position. That is, the center of the document illuminating unit 4 and the optical axis L of the image forming optical system 9 are aligned at the middle or almost the middle. Other configurations and optical functions are substantially the same as those of the first embodiment, and thus, similar effects are obtained.

That is, in this embodiment, the position between the arrangement position of the white reference member 13 and the end position 11b of the original reading effective area (a + b) of the original document reading glass portion 11 on the opposite side of the arrangement position, or Since the center of the document illuminating unit (light source) 4 and the optical axis L of the imaging optical system (imaging lens) 9 are aligned approximately in the middle, further effects can be obtained as compared with the first and second embodiments. I have.

[0038]

According to the present invention, in the image reading apparatus having the flow reading function (flow scan) as described above, when the flow reading function is used, the document reading in the main scanning direction of the document flow reading glass portion is effective. The density reference member arranged outside the area is placed at the middle or almost at the middle of the position where the density reference member is arranged and the end position of the original reading effective area of the original document reading glass section opposite to the arrangement position. The image is read by an image reading unit in which the center of the unit or / and the optical axis of the image forming optical system is aligned, and the temporal change of the illumination light amount in the main scanning direction of the document illumination unit is determined using the output obtained by the image reading unit. By performing the correction, the reading accuracy of the density reference member is improved, and the gain of the image signal is corrected with high accuracy.
It is possible to achieve an image reading apparatus that can always read with high accuracy regardless of the number of originals from which image information of the original is read.

[Brief description of the drawings]

FIG. 1 is a schematic view of a main part of a first embodiment of the present invention.

FIG. 2 is a top view of a main part when FIG. 1 is viewed from above.

FIG. 3 is an explanatory diagram showing an output from a line sensor according to the first embodiment of the present invention.

FIG. 4 is a schematic diagram of a main part of a conventional image reading apparatus.

5 is a top view of a main part when FIG. 4 is viewed from above.

FIG. 6 is a schematic diagram of a main part of a conventional image reading apparatus having a document flow reading unit.

7 is a top view of a main part when FIG. 6 is viewed from above.

FIG. 8 is an explanatory diagram showing a time change of the illumination light amount of a xenon lamp.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Original mounting glass stand 2 Leading original abutting nameplate 3 Shading plate 4 Original illumination part (light source) 5 Slit 6 First mirror 7 Second mirror 8 Third mirror 9 Imaging optical system 10 Reading means (Line sensor) 11) Document reading glass table 12 Paper feeder 13 Density reference member 20 Document 21 Image reading section

Claims (3)

[Claims] 1. A document illuminator for illuminating a document, an image forming optical system for forming a light beam from the document illuminated by the document illuminator at a predetermined position, and a predetermined position of the image forming optical system And a reading unit having a reading unit arranged in the main scanning direction, and sub-scans the image information of the document placed on the document loading glass unit between the document and the image reading unit. First image reading means for scanning and reading relatively in the direction, and moving the image reading section to a lower portion of the original flow reading glass section provided at a position off the sub-scanning direction of the original placing glass section. A second image reading means for reading the image information of the document in the main scanning direction by the image reading unit while sequentially feeding the document to the upper portion of the document flow reading glass unit. Density outside the effective document reading area in the main scanning direction on the glass When the reference member is arranged and read by the second image reading means, the arrangement position of the density reference member and the end position of the original reading effective area of the original flow reading glass portion on the opposite side of the arrangement position The document illuminating section is centered at, or substantially in between, the density reference member is read by the image reading section, and the output of the image reading section is used to perform main scanning of the document illuminating section. An image reading apparatus wherein a temporal change in the amount of illumination light in a direction is corrected to read image information of the document. 2. A document illuminator for illuminating a document, an image forming optical system for forming a light beam from the document illuminated by the document illuminator at a predetermined position, and a predetermined position of the image forming optical system. And a reading unit having a reading unit arranged in the main scanning direction, and sub-scans the image information of the document placed on the document loading glass unit between the document and the image reading unit. First image reading means for relatively scanning in the direction of reading, and moving the image reading section to a lower portion of the original flow reading glass section provided at a position deviated in the sub-scanning direction of the original placing glass section. A second image reading means for reading the image information of the document in the main scanning direction by the image reading unit while sequentially feeding the document to the upper portion of the document flow reading glass unit. Density outside the effective document reading area in the main scanning direction on the glass When the reference member is arranged and read by the second image reading means, the arrangement position of the density reference member and the end position of the original reading effective area of the original flow reading glass portion on the opposite side of the arrangement position The optical axis of the image forming optical system is aligned with or substantially in between, the density reference member is read by the image reading unit, and the output obtained by the image reading unit is used to control the illumination of the original illuminating unit. An image reading apparatus, wherein a temporal change in the illumination light amount in the main scanning direction is corrected, and image information of the document is read. 3. A document illuminator for illuminating a document, an image forming optical system for forming a light beam from the document illuminated by the document illuminator at a predetermined position, and a predetermined position of the image forming optical system. And a reading unit having a reading unit arranged in the main scanning direction, and sub-scans the image information of the document placed on the document loading glass unit between the document and the image reading unit. First image reading means for relatively scanning in the direction of reading, and moving the image reading section to a lower portion of the original flow reading glass section provided at a position deviated in the sub-scanning direction of the original placing glass section. A second image reading means for reading the image information of the document in the main scanning direction by the image reading unit while sequentially feeding the document to the upper portion of the document flow reading glass unit. Density outside the effective document reading area in the main scanning direction on the glass When the reference member is arranged and read by the second image reading means, the arrangement position of the density reference member and the end position of the original reading effective area of the original flow reading glass portion on the opposite side of the arrangement position The center of the original illuminating unit and the optical axis of the image forming optical system are aligned in the middle or approximately the middle of the document reading unit, the density reference member is read by the image reading unit, and the output obtained by the image reading unit is used. An image reading device that corrects a temporal change in the amount of illumination light in the main scanning direction of the document illuminating section and reads image information of the document.