JP2001053936A - Image reading device and its method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time required for reading continuously the original images by reading properly the shading correction data in an initial transient phenomenon of a xenon lamp not by reading the shading correction data for every original when the original images are continuously read. SOLUTION: A xenon lamp 6 has a transient area for several minutes after it is lit to change its quantity of light and then keeps a stable state. It is not required to perform a shading correction read operation for every original to shorten the processing time as long as the shading correction is carried out in the proper timing accordant with the change of quantity of light of the lamp 6 that is caused in the several minutes. In this connection, a read timing table 21a is prepared to store the read timing of a white reference plate when the originals are continuously read out into ROM 21. Then a CPU 20 performs a shading correction read operation according to the read timing of the table 21a.

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 equipped with a sheet feeder type automatic feeder and using a xenon lamp as an exposure lamp, and an image reading method.

[0002]

2. Description of the Related Art Sheet feeder type (sheet feed type)
An image reading device equipped with an automatic supply device and using a xenon lamp as an exposure lamp has been put to practical use.

In such an image reading apparatus, when an original image is read, the original is exposed by an exposure lamp for reading the original, and the reflected light from the original is input to a CCD line sensor to be processed. I have. At this time, if the amount of light of the exposure lamp changes over time before exposing the document, the read image is usually affected. Therefore, a reference color (white or black) attached to a correction plate for the purpose of performing the correction is used. ) Is exposed, an electric signal obtained by the CCD line sensor by this exposure is stored as correction data, and shading correction is performed to correct the electric signal obtained by the CCD line sensor at the time of reading a document with the correction data.

In an image reading apparatus equipped with the above-mentioned sheet feeder type automatic feeding apparatus, a carriage equipped with a xenon lamp moves between two points, a document reading position and a correction plate reading position. Before reading the document, the correction plate is moved (positioned) to the reading position, and after irradiating the correction plate with reading light, the position is moved (moved) to the document reading position, and the document is read.

When a plurality of originals are fed by the automatic feeder, when the original image is continuously read, the correction plate is read and the original is read each time the original is read (each time). Of the carriage (moving between two points of the document reading position and the reading position of the correction plate) accompanying the reading of the document.

For this reason, when performing continuous reading of an original image, correction data for shading correction is read for each original every time one original is read (each time). The time required is long.

[0007]

According to the present invention, when performing continuous reading of a document image, correction data for shading correction is read for each document each time a document is read (each time). It eliminates the disadvantage that the time required for continuous reading of the original image is long, and when using a xenon lamp as the exposure lamp, the amount of light becomes stable after the initial transition range. When performing continuous reading of a document image by taking advantage of the above, instead of reading correction data for shading correction for each document, it is appropriate to set the initial transient phenomenon region time of the xenon lamp (according to the change in light amount in the initial transient region). By reading the correction data for shading correction (at the timing), the time required for continuous reading of the original image can be reduced. And its object is to provide an image reading apparatus and an image reading method.

[0008]

According to the present invention, there is provided an image reading apparatus comprising: a xenon lamp for irradiating light; a conveying unit for conveying a plurality of documents one by one via a document irradiation position of the xenon lamp; A white reference plate provided in the vicinity of the position, a moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate, and a photoelectric conversion device for converting light reflected by the xenon lamp into an electric signal. The conversion unit moves the irradiation position of the light by the xenon lamp to the position with respect to the white reference plate by the moving unit, and sets the electric signal for the reflected light from the white reference plate output from the photoelectric conversion unit as a shading correction value. First reading means for reading, moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means. Second reading means for reading, as image data, an electric signal for the document at the document irradiation position output from the photoelectric conversion means, and shading obtained by reading the image data read by the second reading means by the first reading means. Correction means for correcting by a correction value, and shading correction by the first reading means at a timing corresponding to a light quantity change in an initial transition region by the xenon lamp when a plurality of documents are sequentially conveyed by the conveyance means. The document is read continuously by the second reading means in a state where the light irradiation position of the xenon lamp is moved to the document irradiation position except at this timing. Is corrected by the shading correction value.

An image reading apparatus according to the present invention includes a xenon lamp for irradiating light, a conveying unit for conveying a plurality of originals one by one through an original irradiation position of the xenon lamp.
A white reference plate provided in the vicinity of the document irradiation position, moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate, the reflected light of the xenon lamp to an electric signal Photoelectric conversion means for converting, moving the irradiation position of light by the xenon lamp by the moving means to a position with respect to the white reference plate,
First reading means for reading, as a shading correction value, an electric signal for the reflected light from the white reference plate output from the photoelectric conversion means, and moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means A second reading unit that reads, as image data, an electric signal for the document at the document irradiation position output from the photoelectric conversion unit;
Reading means, correcting means for correcting the image data read by the second reading means with the shading correction value read by the first reading means, and when a plurality of documents are sequentially conveyed by the conveying means. The shading correction value is read by the first reading unit at a timing of each of a plurality of elapsed times during which the xenon lamp is lit according to a change in the amount of light in the initial transition region by the xenon lamp. While the irradiation position of the light by the xenon lamp is moved to the irradiation position of the original, the second reading unit continuously reads the original, and the read image data is corrected by the shading correction value. It is configured.

An image reading apparatus according to the present invention comprises: a xenon lamp for irradiating light; a conveying unit for conveying a plurality of originals one by one via an original irradiation position of the xenon lamp;
A white reference plate provided in the vicinity of the document irradiation position, moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate, the reflected light of the xenon lamp to an electric signal Photoelectric conversion means for converting, moving the irradiation position of light by the xenon lamp by the moving means to a position with respect to the white reference plate,
First reading means for reading, as a shading correction value, an electric signal for the reflected light from the white reference plate output from the photoelectric conversion means, and moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means A second reading unit that reads, as image data, an electric signal for the document at the document irradiation position output from the photoelectric conversion unit;
Reading means, correcting means for correcting the image data read by the second reading means with the shading correction value read by the first reading means, and when a plurality of documents are sequentially conveyed by the conveying means. Reading the shading correction value by the first reading means at a timing for each of the plurality of originals in accordance with a change in the amount of light in the initial transition region by the xenon lamp; The document is continuously read by the second reading means in a state where is moved to the document irradiation position, and the read image data is corrected by the shading correction value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image reading apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a schematic configuration of a scanner section 1 as an image reading apparatus according to the present invention.

The scanner unit 1 comprises a main body 2 having a built-in reading optical system, and a sheet feeder type automatic feeding device 3 mounted on the main body 2.

A transparent glass 4 is provided on the upper surface of the main body 2.
A white reference plate (shading correction plate) 5 for reading a reference value for shading correction is provided below the left end of the glass 4. A document irradiation position 4a for reading a document is located on the right glass 4 surface of the white reference plate 5.
It has become.

In the main body 2, a xenon lamp 6 as an exposure lamp, and a carriage 8 having a mirror 7 mounted thereon
Are provided so as to be movable (in the document conveying direction). The movement of the carriage 8 causes the irradiation position of the xenon lamp 6 to move between the document irradiation position 4 a and the reading position of the white reference plate 5.
The position is moved (moved) to the reading position of the white reference plate 5, and after the reading irradiation on the white reference plate 5, the position is moved (moved) to the document irradiation position 4a. When reading a document, the irradiation position of the xenon lamp 6 is fixed to the document irradiation position 4a.

The position of the xenon lamp 6 when reading the original is the position indicated by the solid line in FIG. 1, and the position of the xenon lamp 6 when reading the white reference plate 5 is the position indicated by the broken line in FIG. .

The irradiation position by the xenon lamp 6 is
At the document irradiation position 4a, the xenon lamp 6 emits light having a certain width as a document reading portion in the main scanning direction (the length direction of the xenon lamp 6) with respect to the document irradiation position 4a. Is exposed.

In the main body 2, a mirror 9, CC
A D line sensor 10 is provided. Mirror 9
Is fixed to the main body 2. Thereby, the reflected light from the xenon lamp 8 from the white reference plate 5 or the document irradiation position 4a is guided to the CCD line sensor 10 via the mirrors 7, 9 and the imaging lens (not shown). . The above CCD line sensor 10
Is to photoelectrically convert incident reflected light and output an electric signal corresponding to the reflected light. The electric signal output from the CCD line sensor 10 is transmitted to a signal processing unit 11.
Supplied to The signal processing unit 11 performs processes such as amplification, A / D conversion, and shading correction.
Output is made to an external device such as a C (personal computer) or a printer.

The automatic feeder 3 includes an original mounting table 12 on which a plurality of originals are mounted, and a single original (in the sub-scanning direction) of the originals on the original mounting table 12 fetched and conveyed to the original irradiating position. The transport system 13 includes a transport system 13 such as a transport roller that transports the original through the original 4a, and a tray 14 that is transported by the transport system 13 and discharges the original after passing through the original irradiation position 4a.

FIG. 2 shows a control system of the scanner unit 1.

That is, the scanner unit 1 has a CPU 20 for controlling the whole, and an RO for storing a control program and the like.
M21, a RAM 22 for storing various data, a regulator 23 for controlling lighting of the xenon lamp 6, a CCD driver 24 for driving the CCD line sensor 10, a motor driver 25 for driving a motor (not shown) for moving the carriage 8, a transport system The signal processing unit 11 includes a motor driver 26 that drives a motor (not shown) that rotates the motor 13. In the ROM 21,
There is provided a read timing table 21a that stores the read timing of the white reference plate 5 when reading a document continuously.

As shown in FIG. 3, the read timing table 21a stores, for example, a time of 35 seconds or less as t1, a time of 83 seconds or less as t2, and 1 as t3.
A time of 66 seconds or less and a time of 300 to 320 seconds or less are stored as t4.

The signal processing section 11 includes an amplifier 2 for amplifying an analog signal supplied from the CCD line sensor 10.
7. An A / D conversion circuit 28 for converting an analog signal amplified by the amplifier 27 into a digital signal, and correcting an electric signal from the CCD line sensor 10 due to a temporal change by the xenon lamp 6 using a shading correction value. And a shading correction circuit 29 to be used. A / D conversion circuit 28, shading correction circuit 2
Numeral 9 is connected to the CPU 20 to exchange data.

The above-mentioned shading correction value is obtained by an electric signal from the CCD line sensor 10 based on the amount of reflected light from the white reference plate 5 before reading the original at the original irradiation position 4a.

The reading process of the white reference plate 5 for obtaining the shading correction value is performed each time before reading an original when reading one original at a time, and when reading a plurality of originals continuously. , Based on the read timing stored in the read timing table 21a.

Next, a xenon lamp 6 is used as an exposure lamp.
The following describes a method that actively utilizes the characteristics of this method and is different from the conventional shading correction method.

That is, when performing shading correction, when a document is automatically fed, a reading for correction is usually performed every time the document is changed. By using a xenon lamp 6 which has many advantages and is increasing in demand as a successor to a halogen lamp, a method different from the conventional shading correction method is proposed by actively utilizing its characteristics.

One of the advantages of the xenon lamp 6 is that it has excellent temperature characteristics and extremely good light intensity stability. Ideally, reading should be continued without performing shading correction reading. Nevertheless, a transient region exists for several minutes (5 to 10 minutes) and a change in the amount of light occurs. After that, the region becomes a stable region.

In the conventional practice, the shading correction is performed every document, but it is not intentionally performed. Therefore, if the shading correction is performed at an appropriate timing in accordance with the temporal change of the light amount for 5 minutes, the shading correction is performed every time the document is processed. There is no need to perform reading for shading correction, and the effect of shortening the processing time can be obtained.

With respect to the timing time of the shading correction in accordance with the transient phenomenon of the xenon lamp 6, the characteristic diagram of the illuminance change with the lapse of time (t) as the transient phenomenon of the xenon lamp 6 shown in FIG. 4 and FIG. This will be described with reference to a characteristic diagram of an output change of the CCD line sensor 10 over time (t).

The maximum of the CCD line sensor 10 (MA
X) As an output at the input light amount, when the illuminance of the xenon lamp 6 is "70 k1x (lux)", the output of the CCD line sensor 10 is set to "750 mV" (70 k
1x → 750 mV (1)).

In this case, assuming that the allowable range of the output of the CCD line sensor 10 is about “± 50 mV” (750 mV
± 50 mV), the output of the CCD line sensor 10 “800
mV "corresponds to 100% illuminance of the xenon lamp 6.

As a result, 100% of the xenon lamp 6
The output of the CCD line sensor 10 for the illuminance of “80”
0 mV ”, the output of the CCD line sensor 10 for the initial illuminance of 105% of the xenon lamp 6 is“ 840 ”.
mV ".

As a result, the correction range Vo for the output of the CCD line sensor 10 is the output value “84” at 105%.
The value “40 mV” obtained by subtracting the output value “800 mV” at the time of 100% from “0 mV” corresponds.

In the reading process of the original image, if the illuminance of 1000 lux changes in the reading process of one sheet (1000
lx / 1 step), which affects the read image.
The allowable range of the output of the CCD line sensor 10 in the sheet reading processing (1 step) is about 10 m according to the above (1).
V.

Thus, the parameter is V = 30 mV,
By setting the voltage to 20 mV and 10 mV, and applying the equation in the transient region in C / R based on the definition of the electrical transient, the timing time of the shading correction along with the transient is calculated as described below.

V = Vo · ε− ^{t /} TV / Vo = ε− ^{t / T} InV / Vo = −t / T−lnV / Vo = t / T (−lnV / Vo) × T = t T = t / (-LnV / Vo), and t is 5 minutes (30
0s), t = 300, and V is 5% down (0.0%).
Assuming that the slope approaches 0 in 5), V = 0.05, Vo is an initial value of 100%, and when Vo = 1, T = 300 / (− ln0.05 / 1) = 100.14 Here, the value of T is Since it has been obtained, when it is transformed into an expression for obtaining t when V is a parameter in the transient region, t = (− lnV / Vo) × T = (− lnV / 40) × 100, and the parameter V is V = 30, 20 When t = 10, t1 = 29, V = 20 t2 = 69, V = 10 t3 = 139 when V = 30. As a result, the timing time of the shading correction along with the transient phenomenon becomes t1 29 seconds, t2 is 69 seconds, t3 is 1
It is calculated as 39 seconds.

Assuming that the calculated timing time is 100%, each allowable timing time of ± 20% is shown in FIG.

Therefore, when reading for shading correction is performed at a timing time of 120% with a margin from the calculated timing time, (1) Initialization shading is performed within 0.5 seconds or less after the xenon lamp 6 is turned on. (2) A second reading process for shading correction is performed for 35 seconds or less after the xenon lamp 6 is turned on. (3) 83 seconds or less after the xenon lamp 6 is turned on. A third shading correction reading process is performed at a time. (4) A fourth shading correction reading process is performed at a time of 166 seconds or less after the xenon lamp 6 is turned on. (5) A xenon lamp 6 is turned on. After 300 seconds to 320 seconds or less, 5
The second reading processing for shading correction is performed.

This timing time is registered in the read timing table 21a in advance.

In the above-described configuration, a reading process when reading a document continuously will be described with reference to flowcharts shown in FIGS. At this time, the white reference plate 5 is read based on the timing time stored in the read timing table 21a.

That is, a plurality of documents are placed on the document table 12.
After being placed on the scanner, a reading start key (not shown) is turned on or a reading start signal is supplied from an external device.
The CPU 20 turns on the xenon lamp 6 (ST1), and moves the carriage 8, that is, the xenon lamp 6, to the reading position of the white reference plate 5.

As a result, the reflected light from the white reference plate 5 becomes C
Guided by the CD line sensor 10, the CCD line sensor 1
The electric signal from 0 is output via the amplifier 27 and the A / D conversion circuit 28, and the shading correction value based on the output data from the A / D conversion circuit 28 is stored in the RAM 22 (ST2).

The reading processing for initializing shading correction is performed within 0.5 second or less after the xenon lamp 6 is turned on.

Next, the CPU 20 moves the carriage 8, that is, the xenon lamp 6, to a document reading position corresponding to the document irradiation position 4a.

After this movement, the CPU 20 drives the transport system 13 so that the original taken out from the original placing table 12 is conveyed, passed over the original irradiation position 4a, and then discharged onto the tray 14. .

Thus, the reflected light from the original is guided to the CCD line sensor 10, and the electric signal from the CCD line sensor 10 is output to the shading correction circuit 29 via the amplifier 27 and the A / D conversion circuit 28. In the shading correction circuit 29, output data obtained by correcting image data from a document with the shading correction value read from the RAM 22 is stored in the RAM 22 as a read result or output to an external device (ST3).

After the first document, the second and subsequent documents are sequentially taken out of the document table 12, conveyed, and passed over the document irradiation position 4a. Is performed in the same manner as the first document (ST6, ST7).

When reading the original continuously, the CPU 20 determines whether or not the elapsed time from turning on the xenon lamp 6 reaches 35 seconds during the reading processing of the next original. (ST5). As a result of this judgment, 3
When it is determined that the time reaches 5 seconds, the CPU 20 performs a reading process for shading correction.

That is, the CPU 20 stops the conveyance system 13 to stop the conveyance of the original, and moves the carriage 8, that is, the xenon lamp 6, to the reading position of the white reference plate 5.

As a result, the reflected light from the white reference plate 5 becomes C
Guided by the CD line sensor 10, the CCD line sensor 1
The electric signal from 0 is output via the amplifier 27 and the A / D conversion circuit 28, and the shading correction value based on the output data from the A / D conversion circuit 28 is stored in the RAM 22 (ST8).

Next, the CPU 20 moves the carriage 8, ie, the xenon lamp 6, to a document reading position corresponding to the document irradiation position 4a.

After this movement, the CPU 20 returns to the transport system 1 again.
By driving the document 3 and restarting the conveyance of the document, the document passes through the document irradiation position 4a and is then discharged onto the tray 14.

As a result, the reflected light from the document is guided to the CCD line sensor 10, and the electric signal from the CCD line sensor 10 is output to the shading correction circuit 29 via the amplifier 27 and the A / D conversion circuit 28. In the shading correction circuit 29, output data obtained by correcting image data from a document with the shading correction value read from the RAM 22 is stored in the RAM 22 as a read result or output to an external device (ST9).

Further, when reading the original continuously (ST10), the CPU 20 sets the elapsed time from turning on the xenon lamp 6 to 8 during the reading of the next original.
It is determined whether the time reaches three seconds (ST11). As a result of this determination, when it is determined that the time reaches 83 seconds, the CPU 20 performs the reading process for shading correction and restarts the reading process of the original as in steps 8 and 9 (S
T12, 13).

Further, when reading the original continuously (ST14), the CPU 20 determines that the elapsed time from turning on the xenon lamp 6 during the reading processing of the next original is one.
It is determined whether the time reaches 66 seconds (ST15). When it is determined that the time reaches 166 seconds, the CPU 20
After performing the shading correction reading process as in the steps 8 and 9, the document reading process is restarted (ST16 and ST17).

Further, while reading the original continuously (ST18), the CPU 20 sets the elapsed time from turning on the xenon lamp 6 to 3 during the reading of the next original.
It is determined whether the time reaches between 00 seconds and 320 seconds (S
T19). As a result of this determination, when it is determined that the time has been reached, the CPU 20 performs the reading process for shading correction and restarts the reading process of the document as in steps 8 and 9 (ST20 and ST21).

Thereafter, since the characteristics of the xenon lamp 6 are stabilized, the shading correction is performed with the same shading correction value as that at the time of the reading process in step 21 described above.

In the above processing, the document table 12
When the upper manuscript is gone (ST4, 7, 10, 14,
18, 20), the CPU 20 turns off the xenon lamp 6 (ST23), and stops the transport system 13.

As described above, the use of a xenon lamp as an exposure lamp takes advantage of the advantage that the amount of light becomes stable after the initial transition region, and when performing continuous reading of a document image, shading correction is performed for each document. Instead of reading the white reference plate for shading, read the white reference plate for shading correction appropriately at the time of the initial transient phenomenon area of the xenon lamp, and thereafter perform continuous reading without correction. This enables image reading. By doing so, it is possible to reduce the time required for reading scanning for each document when reading the document images continuously, which leads to a reduction in the time of the reading process, and is extremely effective.

That is, in a case where a xenon lamp is used as an exposure lamp in an image reading apparatus equipped with a sheet feeder type automatic feeder, even when a document is continuously read, even in a transitional region in which the amount of light decreases due to the temperature characteristics of the xenon lamp. As a means for performing shading correction so that stable image reading can be performed, a shading correction value is read at an appropriate time interval so that a transient phenomenon which is an electrical event is used to compensate for the decrease in light amount. It was made.

Further, by taking into account the stability of light quantity when a xenon lamp is used as an exposure lamp, the light quantity at the time of instability in the initial transient phenomenon area, which is the light quantity characteristic of the xenon lamp, is corrected, so that the shading is performed every time a document is read. By reading the shading correction value in a range that does not affect the image only in the initial transition area, instead of reading the correction value, the shading correction value is not read in the continuous image reading after the initial transition area. This has the effect of increasing the document reading speed as compared with the normal case. That is, the image processing speed can be significantly reduced.

In the above embodiment, a sheet feeder type automatic feeder is mounted, and the original conveyed from the automatic feeder is read by the optical system having a fixed xenon lamp when reading the original. However, the present invention is not limited to this case. Documents conveyed one by one from the automatic document feeder are placed on a document glass, and the document is read by an optical system that moves along the document glass. In this case, it can be carried out in the same manner as described above. In this case, a white reference plate is provided below the document glass, and the reading of the white reference plate by the optical system is performed before reading the document. In other cases, only document reading is performed, and the moving distance of the optical system can be reduced, and as a result, time can be reduced.

In the above-described embodiment, the time is used as the timing according to the change in the light amount in the initial transition region by the xenon lamp. However, the present invention is not limited to this, and the number of continuously read originals may be used. good. In this case, the number of documents is stored in the timing table 21a. The number of documents is, for example, 35 seconds (t1)
For the following, the corresponding number of documents for continuous reading is shown.

[0065]

As described above in detail, according to the present invention, when a xenon lamp is used as an exposure lamp, the characteristic that the amount of light becomes stable after the initial transition region is taken advantage of, and the original image When performing continuous reading, instead of reading the correction data for shading correction for each document, the shading correction is performed appropriately (at a timing corresponding to the light amount change in the initial transient area) at the time of the initial transient phenomenon area of the xenon lamp. By reading the correction data, it is possible to provide an image reading apparatus and an image reading method that can reduce the time required for continuous reading of a document image.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram schematically showing a control system of the image reading apparatus.

FIG. 3 is a view showing a reading timing table in which reading timings of a white reference plate when reading a document continuously are stored.

FIG. 4 is a diagram showing characteristics of a change in illuminance of a xenon lamp over time.

FIG. 5: CCD with irradiation time of xenon lamp
FIG. 9 is a diagram illustrating a change characteristic of an output voltage value of the line sensor.

FIG. 6 is a diagram showing a read timing time of a white reference plate for obtaining a shading correction value.

FIG. 7 is a flowchart for explaining a reading process when reading a document continuously.

FIG. 8 is a flowchart for explaining a reading process when reading a document continuously.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Automatic supply apparatus 4a ... Document irradiation position 5 ... White reference plate 6 ... Xenon lamp 8 ... Carriage 10 ... CCD line sensor 11 ... Signal processing unit 20 ... CPU 21a ... Read timing table 29 ... Shading correction circuit

Claims (6)

[Claims] A xenon lamp for irradiating light; a conveying means for conveying a plurality of documents one by one via a document irradiation position by the xenon lamp; and a white reference plate provided near the document irradiation position. Moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; photoelectric conversion means for converting reflected light from the xenon lamp into an electric signal; First reading means for moving an irradiation position of light by the xenon lamp to a position with respect to the white reference plate, and reading an electric signal for reflected light from the white reference plate output from the photoelectric conversion means as a shading correction value; Moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means, and outputting the light from the photoelectric conversion means; A second reading means for reading, as image data, an electric signal with respect to the document at the document irradiation position, and correcting the image data read by the second reading means with a shading correction value read by the first reading means. Correction means; and, when a plurality of documents are sequentially conveyed by the conveyance means, the shading correction value is read by the first reading means at a timing corresponding to a light amount change in an initial transition region by the xenon lamp. At times other than this timing, the document is continuously read by the second reading means while the light irradiation position of the xenon lamp is moved to the document irradiation position, and the read image data is used as the shading correction value. An image reading apparatus, comprising: processing means for performing correction by: 2. A xenon lamp for irradiating light, a transport unit for transporting a plurality of documents one by one via a document irradiation position by the xenon lamp, and a white reference plate provided near the document irradiation position. Moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; photoelectric conversion means for converting reflected light from the xenon lamp into an electric signal; First reading means for moving an irradiation position of light by the xenon lamp to a position with respect to the white reference plate, and reading an electric signal for reflected light from the white reference plate output from the photoelectric conversion means as a shading correction value; Moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means, and outputting the light from the photoelectric conversion means; A second reading means for reading, as image data, an electric signal with respect to the document at the document irradiation position, and correcting the image data read by the second reading means with a shading correction value read by the first reading means. When a plurality of originals are sequentially conveyed by the conveying unit, at the timing of each of a plurality of elapsed times during which the xenon lamp is turned on in accordance with a change in the amount of light in the initial transition region by the xenon lamp. The shading correction value is read by the first reading means, and the document is continuously read by the second reading means with the light irradiation position of the xenon lamp moved to the document irradiation position except for this timing. Processing means for correcting the read image data with the shading correction value. Image reading apparatus characterized by a. 3. A xenon lamp for irradiating light, a transport unit for transporting a plurality of documents one by one through a document irradiation position of the xenon lamp, and a white reference plate provided near the document irradiation position. Moving means for moving the light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; photoelectric conversion means for converting reflected light from the xenon lamp into an electric signal; First reading means for moving an irradiation position of light by the xenon lamp to a position with respect to the white reference plate, and reading an electric signal for reflected light from the white reference plate output from the photoelectric conversion means as a shading correction value; Moving the light irradiation position of the xenon lamp to the document irradiation position by the moving means, and outputting the light from the photoelectric conversion means; A second reading means for reading, as image data, an electric signal with respect to the document at the document irradiation position, and correcting the image data read by the second reading means with a shading correction value read by the first reading means. A correcting unit, wherein when the plurality of originals are sequentially conveyed by the conveying unit, the first reading unit performs the timing for each of the plurality of originals in accordance with a change in the amount of light in an initial transition region by the xenon lamp. The shading correction value is read, and the document is continuously read by the second reading means while the irradiation position of the light by the xenon lamp is moved to the document irradiation position except at this timing. Processing means for correcting image data with the shading correction value, wherein: Location. 4. A xenon lamp for irradiating light, a transport unit for transporting a plurality of documents one by one through a document irradiation position of the xenon lamp, and a white reference plate provided near the document irradiation position. Moving means for moving a light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; and a photoelectric conversion means for converting light reflected by the xenon lamp into an electric signal. In the apparatus, when a plurality of documents are sequentially conveyed by the conveyance unit, the light irradiation position of the xenon lamp is set to the white position by the moving unit at a timing corresponding to a light amount change in an initial transition region by the xenon lamp. Move to a position with respect to the reference plate, and shape an electric signal for reflected light from the white reference plate output from the photoelectric conversion means. The light irradiation position of the xenon lamp is moved to the document irradiation position by the moving means while the light irradiation position of the xenon lamp is moved to the document irradiation position except for the timing. An image reading method, comprising: reading out, as image data, an electric signal for a document at the document irradiation position output from a photoelectric conversion unit, and correcting the read image data with the shading correction value. 5. A xenon lamp for irradiating light, conveying means for conveying a plurality of documents one by one through a document irradiation position of the xenon lamp, and a white reference plate provided near the document irradiation position. Moving means for moving a light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; and a photoelectric conversion means for converting light reflected by the xenon lamp into an electric signal. In the apparatus, when a plurality of originals are sequentially conveyed by the conveyance unit, the xenon lamp is turned on at a timing of each of a plurality of elapsed times in which the xenon lamp is turned on in accordance with a light amount change in an initial transition region by the xenon lamp. The light irradiation position of the xenon lamp is moved to a position with respect to the white reference plate by a moving means, and the light output from the photoelectric conversion The electric signal corresponding to the reflected light from the white reference plate is read as a shading correction value. The light emitted by the xenon lamp is moved by the moving means in a state where the irradiation position of the light by the xenon lamp is moved to the irradiation position of the original document except for the timing described above. Moving the irradiation position of the document to the document irradiation position, reading an electric signal for the document at the document irradiation position output from the photoelectric conversion means as image data, and correcting the read image data with the shading correction value. An image reading method comprising: 6. A xenon lamp for irradiating light, conveying means for conveying a plurality of documents one by one through a document irradiation position of the xenon lamp, and a white reference plate provided near the document irradiation position. Moving means for moving a light irradiation position of the xenon lamp to the document irradiation position and a position with respect to the white reference plate; and a photoelectric conversion means for converting light reflected by the xenon lamp into an electric signal. In the apparatus, when a plurality of originals are sequentially conveyed by the conveyance unit, the moving unit uses the xenon lamp at a timing for each of the plurality of originals in accordance with a change in the amount of light in an initial transition region by the xenon lamp. The light irradiation position is moved to a position with respect to the white reference plate, and the reflected light from the white reference plate output from the photoelectric conversion unit is output. The electric signal corresponding to the light is read as a shading correction value, and the light irradiation position of the xenon lamp is moved to the document irradiation position by the moving means with the light irradiation position of the xenon lamp moved to the document irradiation position except for the timing. An image reading method, comprising: moving, reading, as image data, an electric signal for the document at the document irradiation position output from the photoelectric conversion unit, and correcting the read image data with the shading correction value.