JPH04348656A - Picture read method - Google Patents

Abstract

PURPOSE:To reduce the time till the start and end of the read of a succeeding original without need of new preliminary scanning. CONSTITUTION:A desired finish magnification is set, an optical system is adjusted to obtain an optical magnification close to the finished magnification, a reference board is subject to preliminary scanning based on the magnification to obtain a shading correction data and it is stored in a correction data memory 56. Shading correction is applied to a picture signal of the original resulting from main scanning by using the correction data, then an electric magnification circuit 58 applies electric magnification processing to obtain a desired finish magnification picture signal. When the finish magnification of the original to be read or the setting of a read range is revised, the revision in the adjustment of the optical system or the preliminary scanning is not implemented but the main scanning of the succeeding original is implemented at a preceding optical magnification and read position, the obtained picture signal is subject to shading correction by the preceding correction data, the corrected picture signal is subject to electric magnification processing and the picture signal with the desired finish magnification is generated.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an image reading method,
In particular, the present invention relates to a method of increasing the reading speed of multiple original documents while minimizing deterioration in image quality of read images.

0002

2. Description of the Related Art In explaining a conventional image reading method, the structure of the conventional image reading apparatus will first be explained with reference to an exploded perspective view from the rear of a general planar image reading apparatus shown in FIG.

[0003] A document table frame 2 is provided at the top of the image reading device. The document table frame 2 is provided with a transparent document table 4 made of a material such as glass, a reference plate 6 having a constant density elongated in the main scanning direction 5, and a document holding cover 8. The reference plate 6 is engraved with scales 3 for optical magnification measurement and focus adjustment. When reading the original 9, the original 9 is placed on the original placing table 4, and the original holding cover 8 is closed. This document table frame 2 is moved in the sub-scanning direction 12 or in the opposite direction 13 by a gear motor 10.
is moved one pitch at a time.

A rod-shaped light source 22 is provided below the document table frame 2 to illuminate the document 9 and the reference plate 6 in a line from below. This light source 22 is housed in a light source unit 24, and is prevented from leaking to the other side. Manuscript 9
The light reflected by the reference plate 6 is reflected by the reflection mirror 26 and formed into an image by the imaging lens 42. Imaging lens 4
The image formed by CCD line sensor 2 is received by CCD line sensor 44 and converted into an image signal representing the electrical density of the image. Note that the light source 22, the imaging lens 42, and the CCD
The line sensor 44 constitutes an optical system.

[0005] The document table frame 2 around the document table 4 has information such as the size of the document 9 and the main scanning direction 5 and sub-scanning direction 12 from the reference point O where the document 9 is placed on the document table 4. Measure parts 14 and 16 are provided for measuring positions and the like. Further, the operation panel 18 in front of the document table frame 2 (upper part of FIG. 2) includes a magnification setting key 72 and a magnification display 74.
, a trimming setting key 76, a numeric keypad 77, an enter key 78, a reset key 80, a start key 82, etc., and a display section 84 are provided.

To set the finishing magnification, operate the magnification setting key 72, input the finishing magnification value using the numeric keypad 77, and confirm the finishing magnification using the enter key 78. This finishing magnification is displayed on the magnification display 74 and stored in the RAM 62 of the control device 60. In this apparatus, the finishing magnification can be set within a range of 20% to 500%, for example. Further, a document table 86 and a digitizer 88 are provided on the left side of the document table frame 2 (right side in FIG. 2). By placing the original 9 in alignment with the origin O of the original platen 86 and operating the cursor on the digitizer 88, it is possible to set the finishing magnification, etc., in the same way as when operating keys.

When changing the optical magnification, the control device 6
0's CPU 64 searches for the finishing magnification stored in the RAM 62 according to a program stored in advance in the ROM 66, and operates the stepping motor 28 for adjusting the magnification.
A motor drive signal is output to the stepping motor 40 for focus adjustment. The stepping motor 28 rotates forward or backward depending on the motor drive signal. by this,
Conveyor belt 29 wrapped around stepping motor 28
is driven, the first movable base 32 moves on the slide rail 30 in the direction shown by arrow 46, and the second movable base 38 moves in the direction of arrow 46. Therefore, the imaging lens 42 and the CCD line sensor 44 move in the direction of the arrow 46, that is, in the sub-scanning direction 12 or in the opposite direction 13,
The relative distance to the original 9 and the reference plate 6 is changed, and the optical magnification is changed. Further, in accordance with the motor drive signal, the stepping motor 40 rotates forward or backward, and the imaging lens 42 moves in the direction shown by the arrow 48, that is, in the sub-scanning direction 12 or the opposite direction 13, and is brought into focus. . Then, the scale 3 on the reference plate 6 is viewed with the CCD line sensor 44, and fine adjustments are made to determine the focus and optical magnification.

Here, the range in which the imaging lens 42 and the CCD line sensor 44 can be moved in the sub-scanning direction 12 or the opposite direction 13 is limited to a certain range. For this reason,
In this device, the optical magnification is, for example, between 105% and 28%.
It is designed to be variable within a range of 0%. If the finishing magnification is set in the range of 105% to 280%, the optical magnification is set to a value approximately equal to the finishing magnification. Note that although the optical magnification is brought as close to the final magnification as possible, it cannot be made equal due to slack in the conveyor belt 29 and the like. Therefore, the difference between the finishing magnification and the optical magnification is determined by the image processing circuit 5.
The second electrical magnification circuit 58 thins out the image signal or increases the image signal to change the optical magnification to the final magnification. When the finishing magnification is in the range of 20% to 105%, the optical magnification is set to 105% to approximate the finishing magnification. When the finishing magnification is in the range of 280% to 500%, the optical magnification is set to 280% to approximate the finishing magnification. The difference between the final magnification and the optical magnification is stored in the RAM 62. Then, when reading the original 9, the control circuit 60 instructs the electrical magnification circuit 58 to eliminate the difference, and the electrical magnification circuit 58 changes the optical magnification to the final magnification. Note that the reason why the optical magnification is made close to the final magnification is to reduce the electrical magnification and to reduce deterioration in image quality.

When setting the reading range of the original 9, operate the trimming setting key 76 and press the numeric keypad 77.
to start reading position in main scanning direction 5 and sub-scanning direction 12 (X
1, Y1) and the reading end position (X2, Y2). Then, the user operates the enter key 78 to confirm the reading range. This reading range is displayed on the display section 84 and is also stored in the RAM 62. Furthermore, by placing the original 9 in alignment with the origin O of the original table 86 and operating the cursor on the digitizer 88, the reading range can be set in the same way as when operating keys.

When the reading range is set, in this device, the control circuit 60 adjusts the optical axis of the imaging lens 42 from the reading start position X1 and the reading end position X2 in the main scanning direction 5 stored in the RAM 62. is the reading position in the main scanning direction 5 (X
1+X2)/2 is output to the stepping motor 34. The stepping motor 34 rotates forward or backward in response to this motor drive signal. As a result, the conveyor belt 35 is driven, and the second moving base 38
moves on the slide rail 36 in the direction shown by the arrow 50. As a result, the imaging lens 42 and the CCD line sensor 44 move in the direction shown by the arrow 50, that is, in the main scanning direction 5 or in the opposite direction 7, and the optical axis of the imaging lens 42 moves to the reading position in the main scanning direction 5. It almost matches (X1+X2)/2. Then, the scale 3 on the reference plate 6 is viewed with the CCD line sensor 44, and fine adjustments are made to determine the reading position.

The purpose of changing the reading position is to align the optical axis of the imaging lens 42 with the reading position to minimize deterioration in image quality due to the cosine fourth law of the imaging lens 42. That is, the image becomes brighter toward the center (optical axis) of the imaging surface of the imaging lens 42, and becomes darker toward the periphery (see FIG. 3(2)). Therefore, the imaging lens 42
By aligning the optical axis of the document 9 with the reading position, the original 9 can be read with the highest quality.

Here, since the amount of light emitted from the light source 22 in the main scanning direction is not constant, as shown in FIG. 3(1), uneven illumination occurs. Furthermore, as described above, due to the cosine fourth power law of the imaging lens 42, the image becomes brighter toward the center of the imaging surface of the imaging lens 42, and becomes darker toward the periphery (see FIG. 3 (2)). . Further, the light receiving sensitivity of each light receiving element of the CCD line sensor 44 is not constant but different, as shown in FIG. 3(3). Due to these optical factors, when reading one line of a document with uniform density,
The output of the CCD line sensor 44 changes (Fig. 3 (4)
reference). Therefore, when document 9 is read, the CCD
If the image signal output from the line sensor 44 is left as it is, the image quality will deteriorate. In order to eliminate the influence of the phenomenon in which the output of the CCD line sensor 44 changes, a shading correction circuit 54 is provided in the image processing circuit 52. The shading correction circuit 54 is provided with a correction data memory 56 that stores correction data used for shading correction.

When obtaining correction data, a portion of the reference plate 6 where there is no scale 3 is prescanned, and the output of the CCD line sensor 44 is read for one line. Then, correction data is obtained (see FIG. 3(5)) so that when one line of an original with uniform density is read, the output does not change and remains at a constant level (see FIG. 3(6)). This correction data is stored in the correction data memory 56. Shading correction circuit 5
4, when reading the original 9, that is, when performing main scanning, the image signal output from the CCD line sensor 44 is based on the correction data stored in the correction data memory 56 in accordance with the command from the control circuit 60. and outputs the corrected image signal to the electrical magnification circuit 58.

[0014] In the conventional image reading method, when the finishing magnification of one original is read by changing the finishing magnification of the next original, or when the reading range of one original is changed and the reading range of the next original is read. was as follows.

For example, the original 9a has a size of 100 mm in the main scanning direction and 100 mm in the sub-scanning direction.
This entire range shall be read at a finishing magnification of 150%. The original 9b has a size of 15 in the main scanning direction.
0 mm, the size in the sub-scanning direction is 150 mm, and this entire range is read at a finishing magnification of 200%. Further, for convenience in setting the reading range, the reading start positions (X1, Y1) of the originals 9a and 9b are set to O, that is, (0, 0).

The operator sets the reading start position (0, 0) and the reading end position (100, 100) for the original document 9a, sets the finishing magnification of 150%, and operates the start key 82. In response to the key operation of the start key 82, the optical magnification and reading position are adjusted. That is, the light source 22 is turned on, the gear motor 10 is rotated, and the stepping motors 28 and 40 are rotated. Then, the scale 3 is read by the CCD line sensor 44, and the second base 38 is moved in the sub-scanning direction 12 or the opposite direction 13, and the imaging lens 42 is moved in the sub-scanning direction 12 or the opposite direction 13. . As a result, the optical magnification becomes approximately 150% and the focus is adjusted (see ■ in FIG. 5(1)). At this time, the actual optical magnification, for example 148%, is also measured. In addition, the stepping motor 34 is rotated to change the scale 3 to CC.
The image is read by the D line sensor 44, the second base 38 is moved in the sub-scanning direction 12 or the opposite direction 13, and the imaging lens 4
2 is aligned with the reading position 100/2=50 in the main scanning direction 5.

Then, the gear motor 10 is rotated to pre-scan the part of the reference plate 6 where there is no scale 3, and the CCD line sensor 44 reads it. Then, correction data (see ■ in FIG. 5(1)) is obtained from the image signal output from the CCD line sensor 44 (see ■ in FIG. 5(1)), and this correction data is stored in the correction data memory 56. .

Next, the gear motor 10 is rotated, and the original 9 is rotated.
a is actually scanned, and the image signal output from the CCD line sensor 44 is corrected using correction data (see Fig. 5 (1).
), obtain the corrected video signal. Since this corrected video signal has an optical magnification of 148%, it is converted into an image signal with a final magnification of 150% by the electrical magnification circuit 58 (
(See ■ in Figure 5 (1)).

In the conventional image reading method, the next original 9b is read in the same way as the original 9a.

That is, the operator selects the reading start position (0, 0) and the reading end position (150, 150) for the original 9b.
) and set the finishing magnification to 200%.
Operate the start key 82. In response to the key operation of the start key 82, the optical system is adjusted, the optical magnification becomes approximately 200%, and the focus is adjusted (
(See ■ in Figure 5 (2)). The actual optical magnification at this time is, for example, 198%. Further, the optical axis of the imaging lens 42 is adjusted to the reading position 150/2=75 in the main scanning direction 5.

Then, the gear motor 10 is rotated to pre-scan the portion of the reference plate 6 where there is no scale 3, and the CCD line sensor 44 reads it. Then, new correction data (see ■ in FIG. 5(2)) is obtained from the image signal output from the CCD line sensor 44 (see ■ in FIG. 5(2)), and the new correction data is stored in the correction data memory 56. to be memorized.

Next, the gear motor 10 is rotated, and the original 9 is rotated.
b is actually scanned, and the image signal output from the CCD line sensor 44 is corrected using correction data (see Figure 5 (2).
), obtain the corrected video signal. Since this corrected video signal has an optical magnification of 198%, it is converted into an image signal with a final magnification of 200% by the electrical magnification circuit 58 (
(See ■ in Figure 5 (2)).

[0023]

[Problems to be Solved by the Invention] However, in the conventional image reading method, the optical system is adjusted before the main scan of the next document, and furthermore, the correction for pre-scanning the reference plate and performing shading correction is required. Since data was being obtained, it took several tens of seconds, for example, to start reading the next document, and therefore it took a very long time to finish reading a plurality of documents.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image reading method capable of solving the above-mentioned technical problems and increasing the reading speed of a plurality of documents while minimizing deterioration of the read image quality.

[0025]

[Means for Solving the Problems] In order to solve the above-mentioned technical problems, the present invention takes the following configuration.

That is, the image reading method according to claim 1 sets a desired finishing magnification when reading an original, adjusts the optical system to obtain an optical magnification close to the finishing magnification, and reads the original. Beforehand, the reference plate is prescanned using the optical magnification, correction data for shading correction is obtained based on the image signal obtained by the prescan, and the main scan of the original is performed to obtain an image signal. In a device that performs shading correction on a signal using the correction data and performs electrical magnification processing on the corrected image signal to obtain an image signal with a desired finishing magnification, if the setting of the finishing magnification of the document to be read next has been changed. To do this, perform the main scan of the next document at the previous optical magnification without changing the adjustment of the optical system and without performing prescanning to obtain an image signal, and then shade this image signal with the previous correction data. The method is characterized in that the corrected image signal is subjected to electrical magnification processing to create an image signal with a desired finished magnification.

In the image reading method of claim 2, a desired finishing magnification and a reading range in the main scanning direction and sub-scanning direction of the document are set when reading the original, and the optical system is adjusted to obtain an optical image close to the finishing magnification. In addition to ensuring that magnification is obtained,
The reference plate is prescanned using the optical magnification and reading position before reading the document, and the reference plate is prescanned to match the set reading position approximately at the center of both ends in the main scanning direction, and based on the image signal obtained by the prescanning. Obtain correction data for shading correction, perform a main scan of the original to obtain an image signal, perform shading correction on this image signal using the correction data, and perform electrical magnification processing on the corrected image signal to obtain the desired image signal. If the finishing magnification setting of the next document to be read has been changed, or if the scanning range in the main scanning direction of the next document to be read has been changed, the optical system must be adjusted in order to obtain the final magnification image signal. Perform the main scan of the next document at the previous optical magnification and reading position without changing the , and without prescanning, obtain an image signal, perform shading correction on this image signal using the previous correction data, and perform correction. The image signal is electrically magnified to create an image signal with a desired finishing magnification.

[0028]

[Operation] In the image reading method of claim 1, if the setting of the finishing magnification of the document to be read next has been changed, the adjustment of the optical system is not changed and the pre-scan is not performed. Perform a main scan of the next document at an optical magnification of . In this case, the adjustment of the optical system is not changed, so
Previous correction data can be used as is. This eliminates the need for prescanning. Therefore, there is no time left until reading of the next document starts.

The next original is actually scanned to obtain an image signal with the previous optical magnification, the image signal is subjected to shading correction using the previous correction data, and the corrected image signal is subjected to electrical magnification processing to obtain the final magnification. Create an image signal. Therefore, the time required to finish reading the next document can also be shortened.

In the image reading method of claim 2, when the finish magnification setting of the next document to be read is changed or the reading range in the main scanning direction of the next document to be read is changed, the optical Perform main scanning of the next document at the previous optical magnification and reading position without changing system adjustment and without performing prescanning. In this case, since the adjustment of the optical system is not changed, the previous correction data can be used as is. This eliminates the need for prescanning. Therefore, there is no time left until reading of the next document starts.

The next document is actually scanned to obtain an image signal with the previous optical magnification, this image signal is subjected to shading correction using the previous correction data, and the corrected image signal is subjected to electrical magnification processing to obtain the desired image signal. Create an image signal at the final magnification. Therefore, the time required to finish reading the next document can also be shortened.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an image reading method according to an embodiment of the present invention.

In this image reading method, when reading by changing the finishing magnification of one original and the finishing magnification of the next original, or when reading by changing the reading range of one original and the reading range of the next original, , do it as follows.

For comparison with the conventional image reading method, it is assumed that the document 9a has a size of 100 mm in the main scanning direction and 100 mm in the sub-scanning direction, and that the entire range is read at a finishing magnification of 150%. In addition, the manuscript 9b is
The size is 150mm in the main scanning direction and 150mm in the sub-scanning direction, and the entire area is completed at a magnification of 200%.
It shall be read as follows. Further, for convenience in setting the reading range, the reading start positions (X1, Y1) of the originals 9a and 9b are set to O, that is, (0, 0).

The document 9a to be read first is the same as the conventional image reading method. That is, the operator sets the reading start position (0, 0) and the reading end position (100, 100) for the original 9a, and also sets the finishing magnification 1.
Set 50% and operate the start key 82. In response to the key operation of the start key 82, the optical magnification and reading position are adjusted. That is, the light source 22 is turned on, the gear motor 10 is rotated, and the stepping motors 28 and 40 are rotated. Then CC the scale 3
The second base 38 is moved in the sub-scanning direction 12 or the opposite direction 13 based on the reading by the D-line sensor 44, and the imaging lens 42 is moved in the sub-scanning direction 12 or the opposite direction 13. By doing this, the optical magnification becomes approximately 150% and the focus is adjusted (see ■ in Figure 1 (1))
. At this time, the actual optical magnification, for example 148%, is also measured. Also, the stepping motor 34 is rotated, the scale 3 is read by the CCD line sensor 44, and the second base 3
8 in the sub-scanning direction 12 or the opposite direction 13, and move the optical axis 42a of the imaging lens 42 to the reading position 10 in the main scanning direction 5.
Set to 0/2=50.

Then, the gear motor 10 is rotated to pre-scan the portion of the reference plate 6 where there is no scale 3, and the CCD line sensor 44 reads it. At this time, the CCD line sensor 44 also sees images in ranges α2 and α3, in addition to the reading range α1 from the reading start position X1=0 to the reading end position X2=100 in the main scanning direction 5 centered on the reading position 50. ing. Therefore, the CCD line sensor 44 receives an image signal β1 for the reading range α1 and an image signal β for the range α3.
3 (see ■ in Figure 1 (1)). Correction data γ1, γ2, γ3 (see (1) in FIG. 1(1)) are obtained from this image signal and stored in the correction data memory 56. Note that the correction data created based on the image signal β1 is γ1, and the correction data created based on the image signal β2 is γ.
2, and the correction data created based on the image signal β3 is γ3.

Next, the gear motor 10 is rotated, and the original 9 is rotated.
A is scanned one pitch at a time in the sub-scanning direction 12, a main scan is performed, and the image signal output from the CCD line sensor 44 is corrected with correction data (see ■ in FIG. 1 (1)),
Obtain a corrected video signal. Note that the reading range α of the original 9a
The image signal δ1 of 1 is corrected using the correction data γ1, but the image signals δ2 and δ3 of the ranges α2 and α3 are not necessary and are therefore discarded without being corrected. Since this corrected video signal has an optical magnification of 148%, it is converted into an image signal with a final magnification of 150% by the electrical magnification circuit 58 (see (1) in FIG. 1).

When reading the next document 9b, reading is performed in a completely different manner from the conventional image reading method.

The operator sets the reading start position (0, 0) and reading end position (150, 150) for the original 9b, sets the finishing magnification of 200%, and operates the start key 82.

The optical magnification remains unchanged at 148%. Also, the image reading position remains the same as 100/2.
=50. That is, the imaging lens 42 and the CCD
The line sensor 44 is not moved at all, and the optical magnification and reading position are not changed (■ in FIG. 1(2)). Therefore, the shading state is kept the same as in the case of reading the original document 9a. As a result, the correction data γ1, γ2,
γ3 can be used as is (■ in Figure 1 (2))
. Therefore, time for adjusting the optical system and time for pre-scanning are no longer required. Note that this correction data includes correction data γ2 corresponding to the range α2 in addition to correction data γ1 corresponding to the reading range α1 for the original document 9a. This correction data γ2 includes correction data γ4 corresponding to the increased reading range α4 of the document 9b to be read this time. Therefore, the correction data can be used effectively as is, and there is no need to perform prescanning again.

Therefore, in response to the key scan of the start key 82, the original scan of the document 9b is immediately performed. That is, the gear motor 10 is rotated, the document 9b is actually scanned, and the image signal outputted from the CCD line sensor 44 is corrected using correction data (see (2) in FIG. 1) to obtain a corrected video signal. Note that the reading range α1 of the original 9b
, α4 image signals δ1 and δ4 are corrected data γ1
, γ4, but the image signals δ2 and δ5 in the ranges α2 and α5 are not necessary and are therefore discarded without being corrected. This corrected video signal has an optical magnification of 148
%, the electric magnification circuit 58 sets the final magnification to 200.
% of the image signal (see ■ in FIG. 1 (2)).

In this case, the adjustment amount due to the electrical magnification is 58%, which is the difference between the final magnification of 200% and the optical magnification of 148%, which is increased compared to the conventional magnification of 2%. Further, the reading position 50 is shifted from the original reading position 75. For this reason, image quality deteriorates compared to conventional reading methods. However, even if the reading position deviates, the original scan 9b is actually scanned approximately around the optical axis 42a, so there is little deterioration in image quality due to the deviation of the reading position. Furthermore, the above-mentioned changes in finishing magnification and reading range belong to the extreme category, and in most cases the change in finishing magnification is a slight change, and in most cases the change in reading range is also small. Therefore, the deterioration in image quality is not noticeable.

Note that a selection switch or the like may be provided so that the conventional image reading method and the image reading method of the present invention can be selected. In this case, by operating this selection switch, the conventional image reading method is used when high image quality is required, and the image reading method of the present invention is used when high image quality is not required.

[0044]

[Effect of the Invention] In the image reading method of claim 1, when the finish magnification setting of the document to be read next has been changed, the adjustment of the optical system is not changed and the prescan is not performed. Perform the main scan of the next document at the previous optical magnification. In this case, since the adjustment of the optical system is not changed, the previous correction data can be used as is. This eliminates the need for prescanning. Therefore, there is no time left until reading of the next document starts.

The next original is actually scanned to obtain an image signal with the previous optical magnification, the image signal is subjected to shading correction using the previous correction data, and the corrected image signal is subjected to electrical magnification processing to obtain the final magnification. Create an image signal. Therefore, the time required to finish reading the next document can also be shortened.

In the image reading method of claim 2, when the finishing magnification setting of the next document to be read is changed or the reading range in the main scanning direction of the next document to be read is changed, the optical Perform main scanning of the next document at the previous optical magnification and reading position without changing system adjustment and without performing prescanning. In this case, since the adjustment of the optical system is not changed, the previous correction data can be used as is. This eliminates the need for prescanning. Therefore, there is no time left until reading of the next document starts.

The next document is actually scanned to obtain an image signal with the previous optical magnification, this image signal is subjected to shading correction using the previous correction data, and the corrected image signal is subjected to electrical magnification processing to obtain the desired image signal. Create an image signal at the final magnification. Therefore, the time required to finish reading the next document can also be shortened.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an image reading method according to an embodiment of the present invention in a flat image reading device.

FIG. 2 is an exploded perspective view of a general planar image reading device seen from the rear.

FIG. 3 is a diagram for explaining shading correction.

FIG. 4 is a diagram for explaining a conventional image reading method.

[Explanation of symbols]

6...Reference plate 9 (9a, 9b)...Manuscript 42...Imaging lens 44...CCD line sensor

Claims (2)

[Claims] Claim 1: A desired finishing magnification is set when reading an original, an optical system is adjusted to obtain an optical magnification close to the finishing magnification, and a reference plate is set using the optical magnification before reading the original. prescanning, obtaining correction data for shading correction based on the image signal obtained by the prescanning, performing main scanning of the document to obtain an image signal, and performing shading correction on this image signal using the correction data, In an image reading method in which the corrected image signal is subjected to electrical magnification processing to obtain an image signal with a desired finishing magnification, if the setting of the finishing magnification of the document to be read next has been changed, adjust the optical system. unchanged, and
A main scan is performed on the next document at the previous optical magnification without prescanning to obtain an image signal, this image signal is subjected to shading correction using the previous correction data, and the corrected image signal is subjected to electrical magnification processing. An image reading method comprising: creating an image signal with a desired finishing magnification. [Claim 2] A desired finishing magnification when reading a document and a reading range in the main scanning direction and sub-scanning direction of the document are set, and the optical system is adjusted so that an optical magnification close to the finishing magnification can be obtained. At the same time, the reference plate is prescanned using the optical magnification and reading position before reading the document, and the image signal obtained by the prescanning is obtain correction data for shading correction based on the correction data, perform a main scan of the document to obtain an image signal, perform shading correction on this image signal using the correction data,
In an image reading method in which the corrected image signal is subjected to electrical magnification processing to obtain an image signal with a desired finishing magnification, when the setting of the finishing magnification of the next document to be read has been changed, or when the main scanning of the next document to be read is If the reading range in the direction has been changed, perform the main scan of the next document at the previous optical magnification and reading position without changing the adjustment of the optical system and without performing prescanning to obtain the image signal. and perform shading correction on this image signal using the previous correction data,
An image reading method characterized by performing electrical magnification processing on the corrected image signal to create an image signal with a desired finishing magnification.