JPH0923318A - Image reading device - Google Patents

Abstract

(57) [Summary] [Object] To provide an image reading apparatus capable of obtaining a high-quality image without image distortion with a simple configuration. [Structure] The solid-state imaging device 1 other than the document placement area
The image reading main scanning direction is set to the Y axis in the area that maintains an optically conjugate relationship with the light receiving surface of 06 and the imaging lens 105.
When the image reading sub-scanning direction is the X axis, the main scanning reference line 1 that defines the parallelism of the Y axis is set on the original platen glass 101.
It was integrated with.

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 for reading image information of an original with a solid-state image sensor.

[0002]

2. Description of the Related Art Conventionally, various image reading apparatuses using a solid-state image pickup device (hereinafter referred to as CCD) as a reading device have been proposed.

FIG. 12 is a schematic view of a main portion of this type of image reading apparatus. In the figure, a document 107 placed on a document table glass 101 is illuminated with an illumination light beam from a light source 100, and a reflected light beam from a document 107 is reflected by mirrors 102, l.
CCD 1 through imaging lens 105 through 03, 104
The image is formed on the image plane 06. At this time, the light source 10
0, mirrors 102 to 104, imaging lens 105, CCD
The optical unit 20 in which many of the main parts of the apparatus such as 106 are integrated is placed in the apparatus on two scanning rails l09 and 110 arranged in parallel to the platen glass 101 (the scanning rails l09 and l10). Are arranged in parallel on the front side and the back side with appropriate intervals in the drawing),
A driver (not shown) is used to scan in a direction (hereinafter, referred to as a sub-scanning direction or an X-axis direction) perpendicular to an element array direction of the CCD 106 (hereinafter, referred to as a main scanning direction or a Y-axis direction). By moving on the rails 109 and 110, the reading position can be scanned on the surface of the document 107. In FIG. 12, reference numeral 108 denotes a document pressure plate which presses the document 10 on the document table glass 101. Also,
A main scanning white reference plate 111 regulates the white level of image reading and also serves as a document setting reference in the X-axis direction.

Further, such an image reading apparatus is shown in FIG.
The main-scanning white reference plate 11 and the sub-scanning light amount correction reference plate 112 as shown in FIG.
It is common to place them in. Main scanning white reference plate 11
The reference planes of 1 and the sub-scanning light amount correction reference plate 112 are white with the same spectral characteristics, and both are outside the document mountable area and are optically conjugate with the light receiving surface of the CCD 106 and the imaging lens 105. Each reference plate 111,
The reference surface 112 is arranged in close contact with the surface of the platen glass 10l.

The main scanning white reference plate 111 has the following functions.
Before the original image reading is started, the original image output value is normalized by sampling the output of each pixel of the CCD 106 when a uniform white plate is read in advance, and at the same time,
As a device, it plays a role of determining a white level with a constant reflectance. The function of the sub-scanning light amount correction reference plate ll2 is to reproduce a white color having a constant reflectance as the same white color with respect to a light amount variation of the light source 100 when the reading position is scanned in the sub-scanning direction. While the reflected light of the sub-scanning light amount correction reference plate ll2 is read by the CCD 106, it is electrically corrected so that a white color having a constant reflectance is always reproduced as the same white color.

[0006]

However, in the above-mentioned conventional example, the amount of shift in the Y-axis direction reading position in the XY plane accompanying the scanning of the optical unit 20 in the X-axis direction is clear in FIG. In addition, there is a problem that it largely depends on the bending amount d of the scanning rails 109 and 110. Ie CC
If the original image output start pixel of D106 is the nth pixel,
When the scanning rails 109 and 110 are most curved, the read position is displaced by d in the Y-axis direction.

More specifically, the alternate long and short dash line 10 in FIG.
6S is a scanning locus of the CCD 106, and this CCD 10
A locus of the reading position on the surface of the original 107 optically conjugate with the scanning locus 106S of No. 6 is shown by a dotted line S. At this time, CC
D106 and the image reading position a ′ have a conjugate relationship during a certain scanning. In this way, the locus S of the reading position on the surface of the original 107 has a curved shape, and a distorted output image is formed. In FIG. 14, the same parts as those in FIG. 13 are designated by the same reference numerals.

Therefore, conventionally, in order to solve the above-mentioned problems, the amount of curvature d of the scanning rails 109 and 110 is reduced,
It has been generally practiced to improve the scanning accuracy of the optical unit 20. Specifically, the diameter of the cylinder is increased, and a scanning rail having high rigidity and high straightness is used, which causes another problem such as an increase in the cost of the main body and an increase in the weight of the main body.

Even if the distortion of the scanning rails 109 and 110 can be completely eliminated, the main scanning white reference plate lll or the original platen glass 101 integrally bonded to the main scanning white reference plate lll. If the mechanical Y-axis of is not adjusted in parallel with the element arrangement direction of the CCD 106 at the start of image reading, one scanning line of the image reading on the platen glass 101 is inclined as indicated by a in FIG. Main scanning white reference plate 111 and sub-scanning light amount correction reference plate 1
There was a problem that the 12 correct functions could not be performed. 15, the same parts as those in FIG. 14 are designated by the same reference numerals.

FIG. 1 shown to explain the conventional example has been described above.
2 to 15 are all conceptual diagrams in which the inside of the apparatus is viewed from the upper surface of the platen glass 101.

The present invention has been made in view of the above-mentioned problems of the above-mentioned prior art, and an object thereof is to provide an image reading apparatus capable of obtaining a high-quality image without image distortion with a simple structure. That is.

[0012]

In order to achieve the above object, an image reading apparatus according to a first aspect of the present invention is an image reading apparatus having a document placing table, an imaging lens and a solid-state image sensor, except for a document placement area. Further, when the image reading main scanning direction is the Y axis and the image reading sub-scanning direction is the X axis in a region that maintains an optically conjugate relationship with the light receiving surface of the solid-state imaging device and the imaging lens, A main scanning reference line that defines the parallelism of the Y-axis by being read by an image pickup device is provided integrally with the document placing table.

To achieve the same object, an image reading apparatus according to a second aspect of the present invention is the image reading apparatus according to the first aspect, wherein the main scanning reference line is at least two reference points on the main scanning reference line. It is characterized by being an imaginary straight line determined by points.

In order to achieve the same object, an image reading apparatus according to a third aspect of the present invention is the image reading apparatus according to the first or second aspect, wherein the arrangement direction of the solid-state image pickup elements is the It is characterized in that it is parallel to the main scanning reference line.

In order to achieve the same object, an image reading apparatus according to a fourth aspect of the present invention is the image reading apparatus according to the first, second or third aspect, in which the main scanning reference line is located on the upper surface of the document placing table, that is, It is characterized in that it is arranged on the document placing side.

In order to achieve the same object, an image reading device according to a fifth aspect of the present invention is the image reading device according to the first to third or fourth aspects, in which a white reference plate that also serves as a document setting reference in the X-axis direction is provided. The main scanning reference line is arranged on the upper surface of the document placing table, that is, on the document placing side, and the main scanning reference line is integrally provided between the document placing table and the white reference plate.

In order to achieve the same object, an image reading apparatus according to a sixth aspect of the present invention is an image reading apparatus having a document mounting table, an imaging lens and a solid-state image pickup device, which is located in a region other than the document mounting area and is the above-mentioned. A sub-scanning reference line that defines the parallelism of the X-axis by being read by the solid-state image sensor is provided in a region that maintains an optically conjugate relationship with the light-receiving surface of the solid-state image sensor and the imaging lens. It is characterized in that it is provided integrally with the table.

In order to achieve the same object, an image reading apparatus according to a seventh aspect of the present invention is the image reading apparatus according to the sixth aspect, wherein the length in the X-axis direction of the document placing area is L.
In this case, the length L ′ of the sub-scanning reference line is L ′ ≧ L
Is satisfied.

In order to achieve the same object, an image reading apparatus according to an eighth aspect of the present invention is the image reading apparatus according to the sixth or seventh aspect, in which the sub-scanning reference line is placed on the upper surface of the original placing table, that is, the original placing. It is characterized by being placed on the storage side.

In order to achieve the same object, an image reading device according to a ninth aspect of the present invention is the image reading device according to the sixth, seventh or eighth aspect, in which the fluctuation of the light amount in the sub-scanning direction of image reading is corrected and A light amount correction reference plate, which also serves as a Y-axis document setting reference in the image scanning main scanning direction, is arranged on the upper surface of the document mounting table, that is, on the document mounting side, and the sub-scanning reference line is used for the document mounting table and the light amount correction. It is characterized by being integrally provided between the reference plates.

In order to achieve the same object, an image reading device according to a tenth aspect of the present invention is the image reading device according to the eighth or ninth aspect, in which the read signal for at least one color of the sub-scanning reference line is applied to the leading edge of the image. The digital image data for one line of main scanning that is used as a positioning signal is characterized in that the pixel which is a fixed amount A pixels ahead of the image leading edge positioning signal is always the image leading edge.

In order to achieve the same object, an image reading apparatus according to claim 11 of the present invention is the image reading apparatus according to claim 6 to 9 or 10, wherein the main scanning reference line and the sub-scanning reference line are perpendicular to each other. It is characterized by being.

[0023]

FIG. 1 is a block diagram showing an embodiment of the present invention.
~ It demonstrates based on FIG.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view of a main part of the image reading device according to the first embodiment of the present invention, taken along a cross section parallel to the sub-scanning direction (X-axis direction). In FIG. 1, the same parts as those in the above-mentioned conventional FIG. 12 are designated by the same reference numerals.

In FIG. 1, a document 107 placed on a document table glass 101 is illuminated with an illumination light beam from a light source 100, and reflected light beams from the document 107 are reflected by mirrors 102 and 1.
CCDl through the imaging lens 105 through 03, 104
The image is formed on the 06 plane. The optical unit 20 incorporating the above components is placed on the two scanning rails 109 and 110 (the scanning rails 109 and 110 are arranged in parallel on the front side and the back side in the drawing with appropriate intervals), An element array direction of the CCD 106 (hereinafter, referred to as a main scanning direction or a Y-axis direction) using a driving device (not shown)
Direction perpendicular to (hereinafter referred to as sub-scanning direction or X axis)
By moving on the scan rails 109 and 110, the image reading position can be scanned on the surface of the document 107.

FIG. 2 is a schematic cross-sectional view of a main part of the image reading apparatus according to the first embodiment of the present invention, taken along a cross section parallel to the main scanning direction (Y-axis direction). In FIG. 2, FIG.
The same reference numerals are given to the same parts.

The main-scanning white reference plate 11l in FIG. 1 and the sub-scanning light amount correction reference plate 112 in FIG. 2 are located outside the original mountable area and on the light receiving surface of the CCD 106 and the imaging lens 1.
The reference surface of each of the reference plates 111 and 112 is arranged in close contact with the surface of the document glass 106 in a region that maintains an optically conjugate relationship with respect to 05. The CCD 106 has a larger number of pixels than the number of pixels required to read the original reading width and the sub-scanning reference width. However, the functions of the main-scanning white reference plate 11l and the sub-scanning light amount correction reference plate l12 have been described in the above-mentioned "Prior Art", and therefore will be omitted here.

In FIG. 1, the main scanning reference line 1 is provided between the main scanning white reference plate 11 and the original platen glass 101. In this embodiment, the main scanning white reference plate 11 is coated with black paint of several 10 μm. It is assumed that it is formed by painting in parallel with the Y axis with a line width of. Similarly, in FIG. 2, the sub-scanning reference line 2
Is provided between the sub-scanning light amount correction plate 112 and the platen glass 101, and black paint is applied to the sub-scanning light amount correction plate 112 by several 10
It shall be formed by coating with a line width of μm parallel to the X axis.

The main scanning reference line l provided as described above,
When the sub-scanning reference line 2 is illuminated by the light source 100, the reflected light having the position information of the reference line is reflected by the mirrors 102 to 105,
An image with the best focus is formed on the light receiving surface of the CCD 106 via the image forming lens 105.

Next, an example of a method for assembling and adjusting the image reading apparatus according to this embodiment will be briefly described. In the image reading apparatus according to the present embodiment, first, the optical unit 20 alone is optically adjusted in focus, magnification, etc., and then the optical unit 2 is adjusted.
0 is incorporated in the apparatus on the scanning rails 109 and 110 arranged in parallel to the document mounting surface of the document table glass 101.
Finally, when incorporating the platen glass 101 in the outer frame of the main body,
After adjusting the original table glass 101 by moving in the X-axis direction, the Y-axis direction and rotating in the XY plane so that the main scanning reference line 1 is detected as a signal in the entire Y-axis direction while taking the output of the CCD 106. , Fix it. By arranging in this way, the CCD 106 adjusted by the optical unit 20 alone
This means that the element arrangement direction of is adjusted with the mechanical Y axis of the platen glass 101.

FIG. 3 shows the upper surface of the platen glass 101 at this time. In FIG. 3, the same parts as those in FIGS. 1 and 2 are designated by the same reference numerals. The platen glass 10 of FIG.
CCD 106 when 1 is installed in the outer frame of the main body and fixed
4 shows the output of the CCD 106 at the image reading scanning line a on the surface of the original 107 optically conjugate with each pixel of FIG.

With the above arrangement, the Y axis of the original platen glass 101 and the element arrangement direction of the CCD 106 can be easily adjusted in parallel.

Next, the original 107 is actually placed on the original glass 1
Document table glass 10 when the image is read by placing it on 01.
The upper surface of No. 1 is shown in FIG. In FIG. 5, the same parts as those in FIG. 3 are designated by the same reference numerals.

Since the parallelism in the element arrangement direction of the CCD 106 and the main scanning reference line 1 is maintained by performing the above-described adjustment, the main scanning reference line 1 and the CCD 106 have a perpendicular relationship on the XY plane. The sub-scanning reference line 2 is C as shown in FIG.
The element array direction of the CD 106 and the reading direction at the start of reading are substantially vertical. After the output variation correction (shading correction) in the main scanning direction is performed with the signal obtained by reading the main scanning white reference plate 111, if one scanning line of the image reading when the document is scanned is a ′, then the CCD 106 at that time.
Output is as shown in FIG. In FIG. 6, when the signal b is the image leading edge positioning signal and the entire area of the original 107 is read,
Image leading edge positioning signals for the number of scanning lines are obtained. Signal b
Among them, the pixel in which the high / low boundary of the output (one of the front and rear) is detected is set as the image signal positioning pixel.

Output image data is created by using a pixel of a fixed amount A from the image leading edge positioning pixel, the preceding pixel as the image leading edge, and the signals of the number of pixels corresponding to the reading width from here as the image signal. However, since the CCD 106 has a sufficient number of pixels as described above, there is no fear that the image signal of the original document 107 is lost.

The scanning rail 1 is configured as described above.
Even when 09 and 110 are curved, since the read position is corrected based on the reference line, a high-quality image without image distortion can be obtained with a simple configuration.

In this embodiment, the reference lines are provided for both the main scanning and the sub scanning, but it goes without saying that only one of them may be provided.

(Second Embodiment) In the first embodiment, the reference lines are provided for both the main scanning and the sub-scanning, but it goes without saying that either one may be used.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a top view of the document table glass 101 when the document 107 is actually placed on the document table glass 101 and the image is read in the image reading apparatus according to the second embodiment. The same parts as those in FIG. 3 in the above-described first embodiment are designated by the same reference numerals. In the second embodiment of the present invention, the main scanning reference line 1
Is an imaginary straight line connecting the two reference points 3a and 3b in FIG. The other structure is the same as that of the first embodiment described above. Also, at the time of assembly adjustment, the image reading scanning line a
FIG. 8 shows the output of the CCD 106 when is aligned with the main scanning reference line 1.

With the above structure, the same effect as that of the first embodiment can be obtained.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. 9 to 11. FIG. 9 shows an actual document 1 in the image reading apparatus according to the third embodiment.
7 is a top view of the platen glass 101 when the image is read by placing 07 on the platen glass 101, in which the same parts as those in FIG. 3 in the above-described embodiment are denoted by the same reference numerals. is there. In the third embodiment of the present invention, the main scanning reference line 1 is the six lines 4 parallel to the X-axis direction in FIG.
An imaginary straight line connecting the overlapping portions of a, 4b, 4c, 4d, 4e, and 4f. The other configuration is the same as that of the first embodiment.

FIG. 11 shows six lines 4a, which are parallel to the X-axis direction.
4f shows an enlarged view of FIG. Further, at the time of assembly adjustment, the CCD when the image reading scanning line a is aligned with the main scanning reference line 1
The output of 106 is shown in FIG.

With the above-mentioned structure, the first embodiment
An effect equivalent to that of the form is obtained. Further, the main scanning reference line 1 is not limited to each of the above-described embodiments, but various patterns are conceivable, and an appropriate pattern can be selected according to the adjustment method and the like.

(Fourth Embodiment) In the fourth embodiment, the length in the X-axis direction of the document mountable area in the configuration of the first embodiment described above is L, and the length of the sub-scanning reference line. L '
Then, the following formula 1 should be satisfied.

L'≥L (1) With the above-described structure, the same effect as the effect of the first embodiment can be obtained in the entire document mountable area.

(Fifth Embodiment) In the fifth embodiment, the line widths of the main scanning and sub-scanning reference lines in the configuration of the above-described first embodiment are uniquely determined from t and the device resolution. When one pixel size on the original 107 surface is c, the following 2
Make the formula satisfied.

T ≧ 2c (2) With the above configuration, the contrast of the CCD output signal can be increased, and highly accurate adjustment can be performed. Moreover, the effect of the first embodiment is realized. The same effect as can be obtained.

(Sixth Embodiment) In the sixth embodiment, the main scanning and sub-scanning reference lines in the structure of the first embodiment described above are black pattern surfaces having an area to some extent. In this case, the pixel at the boundary between the CCD output signal of the black pattern portion and the CCD output signal of the main scanning white reference plate or the sub-scanning light amount correction plate is used as the pixel of the pixel leading edge positioning signal, so that the first embodiment The same effect as the form is obtained. However, the color of the main scanning, sub-scanning reference line or the surface is not limited to black in each of the above embodiments.

(Seventh Embodiment) In the configuration of the first embodiment described above, the main scanning and sub-scanning reference lines are formed by vapor deposition on the platen glass.

With the above configuration, the perpendicularity of the main scanning and sub-scanning reference lines is improved, the reading accuracy is further improved, and the same effect as the effect of the first embodiment can be obtained.

[0051]

As described in detail above, according to the image reading apparatus of the present invention, it is possible to obtain a high quality image with no image distortion with a simple structure.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of main parts of an image reading apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a main part of the image reading device according to the first embodiment.

FIG. 3 is a top view of a document table glass in the image reading apparatus according to the first embodiment.

FIG. 4 is a diagram showing a CCD output in the image reading apparatus according to the first embodiment.

FIG. 5 is a top view of a document table glass in the image reading apparatus according to the first embodiment.

FIG. 6 is a diagram showing CCD output in the image reading apparatus according to the first embodiment.

FIG. 7 is a top view of a document table glass in an image reading apparatus according to a second embodiment of the present invention.

FIG. 8 is a diagram showing a CCD output in the image reading apparatus according to the second embodiment.

FIG. 9 is a top view of a document table glass in an image reading apparatus according to a third embodiment of the present invention.

FIG. 10 is a diagram showing a CCD output in the image reading device according to the third embodiment.

FIG. 11 is an enlarged view of a D circle portion and an E circle portion of FIG. 9.

FIG. 12 is a schematic cross-sectional view of a main part of a conventional image reading device.

FIG. 13 is a top view of a document table glass in the conventional image reading apparatus.

FIG. 14 is a top view of a document table glass for explaining a first problem in the conventional image reading apparatus.

FIG. 15 is a top view of a platen glass for explaining a second problem in the conventional image reading apparatus.

[Explanation of symbols]

 l Main-scanning reference line 2 Sub-scanning reference line 3a Reference point 3b Reference point 4c Line 4d line 4e Line 4f Line 20 Optical unit 100 Light source 101 Manuscript table glass (manuscript table) 102 Mirror 103 Mirror 104 Mirror 105 Imaging lens 106 CCD (Solid-state image sensor) 107 Document 108 Pressure plate 109 Scan rail 110 Scan rail 111 Main scanning white reference plate 112 Sub scanning light amount correction reference plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04N 1/19

Claims (11)

[Claims] 1. An image reading apparatus having a document placing table, an imaging lens, and a solid-state image sensor, which is optically conjugate with a light-receiving surface of the solid-state image sensor and the imaging lens in a region other than the document placement area. In the region where the image reading main scanning direction is set to the Y axis and the image reading sub scanning direction is set to the X axis, the main scanning reference line that defines the parallelism of the Y axis by the solid-state image sensor is read. An image reading device characterized by being provided integrally with a mounting table. 2. The image reading apparatus according to claim 1, wherein the main scanning reference line is an imaginary straight line determined by at least two reference points on the main scanning reference line. 3. The image reading apparatus according to claim 1, wherein the array direction of the solid-state image pickup elements is parallel to the main scanning reference line at the start of image reading. 4. The image reading apparatus according to claim 1, wherein the main scanning reference line is arranged on an upper surface of the document mounting table, that is, on the document mounting side. 5. A white reference plate also serving as a reference for setting the original in the X-axis direction is arranged on the upper surface of the original placing table, that is, on the original placing side, and the main scanning reference line is provided between the original placing table and the white reference plate. It is integrally provided in the
The image reading device described in 3 or 4. 6. An image reading apparatus having a document placing table, an imaging lens and a solid-state imaging device, which is optically conjugate with a light receiving surface of the solid-state imaging device and the imaging lens in a region other than the document placing area. An image reading apparatus, wherein a sub-scanning reference line that defines the parallelism of the X-axis by being read by the solid-state image sensor is provided integrally with the document placing table in a region where such a relationship is maintained. 7. When the length of the document mountable area in the X-axis direction is L, the length L ′ of the sub-scanning reference line is:
7. The image reading apparatus according to claim 6, wherein L'≥L is satisfied. 8. The image reading apparatus according to claim 6, wherein the sub-scanning reference line is arranged on the upper surface of the document mounting table, that is, on the document mounting side. 9. A light amount correction reference plate which corrects fluctuations in light amount in the sub-scanning direction of image reading and also serves as a reference for setting a document on the Y-axis which is the main scanning direction of image reading, is provided on the upper surface of the document mounting table, that is, the document mounting table. 9. The image reading apparatus according to claim 6, 7 or 8, wherein the sub-scanning reference line is disposed on the side, and the sub-scanning reference line is integrally provided between the document placing table and the light amount correction reference plate. 10. Digital image data for one main-scanning line created by using a read signal for at least one color of the sub-scanning reference line as an image leading-edge positioning signal is always a fixed amount of A pixels from the image leading-edge positioning signal. 10. The image reading apparatus according to claim 6, wherein a pixel ahead of the minute is used as an image front end. 11. The image reading apparatus according to claim 6, wherein the main scanning reference line and the sub scanning reference line are perpendicular to each other.