JP2000050063A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide images with excellent and stable image quality without making striped artifacts or the like appear in an image reader using a TDI(time delay and integration) sensor. SOLUTION: This image reader is provided with the read elements 1610 and 1612 of a time delay and integration system for reading original images irradiated by a light source and converting them to electric signals, an integration stage number control means 1616 for controlling the integration stage number of the delay integration of the read elements corresponding to the light quantity of the light source, a storage means for storing reference data for shading correction corresponding to the integration stage number controlled by the integration stage number control means and a correction means for correcting output signals from the read elements based on the reference data.

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 using a time delay integration type reading element (TDI sensor).

[0002]

2. Description of the Related Art Conventionally, TDI (Time-Delay and Int
Egration) sensors are known as image reading devices of the time delay integration type, and are used as reading devices in copiers and the like. The TDI sensor is characterized in that it has higher sensitivity than a generally used one-dimensional CCD line sensor.

FIG. 20 is a diagram schematically showing a TDI sensor 800. Such a TDI sensor 800 is applied to, for example, reading of a document of a copying machine. As shown in FIG. 20, the TDI sensor 800 includes a photosensitive unit 810 and a reading unit 820.

The photosensitive section 810 is composed of n rows of photodiodes 810X in which m photodiodes PT are arranged in the X direction (main scanning direction) in the Y direction (sub scanning direction).

[0005] The reading section 820 has a plurality of registers RT arranged similarly to the photodiodes PT in the photosensitive section 810. That is, m registers RT are arranged in the X direction, thereby forming an X direction register column 820X. The X direction register row 820X is arranged in n rows in the Y direction. For example, a value of about 5000 as the value of m and a value of about 100 as the value of n are often used.

The original P moves in the Y direction above the photosensitive portion 810 while being illuminated by a light source (not shown). Thus, the sub-scanning of the document P is performed. Each photodiode PT reads the intensity of light corresponding to the density of the image of the document P and converts it into signal charges. The signal charge stored in each photodiode PT is transferred to a register RT corresponding to each pixel. Each X direction register column 820X (8
20X1, 820X2,... 820Xn) transfer the signal charge output from each photodiode PT in the X direction. Thus, the main scanning of the document P is performed.

Each X-direction register column 820X transfers its signal charge in the Y-direction for each read line. Transfer timing, that is, each X-direction register column 820X
The speed of shifting in the direction is synchronized with the moving speed of the document P. Therefore, the signal charges for the image at the same position on the document P are transferred in the Y direction while being integrated. That is, the signal charges are shifted n times, which is the same numerical value as the number n of columns in the Y direction of the X direction register column 820X, and thereby added n times. When the shift is performed n times, the signal charge of each pixel of the document P is output from the last column of the X-direction register column 820Xn.

Since the signal charges output at this time are added n times, the amount becomes larger than when a single CCD line sensor is used. Therefore, when the TDI sensor 800 is used, the sensitivity is improved as compared with the case where a single CCD line sensor is used, and the original can be read clearly with a light amount of a small amount of light.

On the other hand, since the TDI sensor 800 has high sensitivity as described above, if the light amount of the light source becomes larger than a predetermined amount for some reason, the TDI sensor 8 has a high sensitivity.
00 output signal may be saturated.

As a method of preventing the output of the TDI sensor 800 from being saturated, there is a method of controlling the number of times of adding signal charges, that is, the number of integration stages. The method of controlling the number of integration stages is, for example, to reduce the number of effective columns of the photodiode array 810X, that is, to reduce the number of integration stages when the light amount increases. This can lower the sensitivity of the TDI sensor 800 and prevent saturation.

In controlling the number of integration stages, whether or not it is necessary to reduce the number of integration stages is determined when the reference white plate is read before the image of the document is read. If the output signal obtained when reading the reference white plate is larger than a predetermined value, the number of integration stages is determined so that the output signal does not become larger than the predetermined value.

The integration of the signal charge when reading the original image is as follows:
Since the determination is performed based on the determined number of integration stages, the original image is read in a state where the output of the TDI sensor 800 is not saturated.

[0013]

In the TDI sensor 800, the photodiodes PT are two-dimensionally arranged. Therefore, each photodiode PT
The variation in the sensitivity distribution of the TDI sensor 800 caused by the difference in the sensitivity is also two-dimensional.

In the case where the number of integration stages is changed as described above, shading correction is performed based on shading correction data obtained by reading the reference white plate using the number of integration stages before the determined number of integration stages. Become.

The variation in the sensitivity distribution of the TDI sensor 800 is two-dimensional, and the shading correction is performed based on shading correction data obtained by the number of integration stages different from the number of integration stages when reading the image of the document. This can cause streak-like artifacts in the resulting image.

FIG. 21 is a diagram for comparing an image with streak-like artifacts and a document. When the document shown in FIG. 21B is read by the TDI sensor 800 with the direction indicated by the arrow as the main scanning direction, the document shown in FIG.
A streak-like artifact as shown in FIG.

As shown in FIG. 21A, streak-like artifacts are streak-like or band-like vertical stripes that do not exist in a document. Its color is black or white, and its direction is a direction perpendicular to the main scanning direction of the TDI sensor 800.

Even if the number of integration stages is not changed, this type of streak-like artifact may appear when a defective line is present in any of the photodiode rows 810X.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made in an image reading apparatus using a TDI sensor.
It is an object of the present invention to provide an image reading apparatus capable of obtaining a stable and high quality image without streak-like artifacts.

[0020]

According to a first aspect of the present invention, there is provided an image reading apparatus, comprising: a read element of a time delay integration type for reading an image and converting the read image into an electric signal; Control means for controlling the number of stages of integration, and correction means for correcting an output signal from the reading element using reference data for shading correction corresponding to the number of integration stages controlled by the number of integration stages control means. .

According to a second aspect of the present invention, there is provided an image reading apparatus comprising:
A light source for irradiating the original, wherein the integration stage number control means,
The number of integration stages is controlled in multiple stages according to the light amount of the light source.
According to a third aspect of the present invention, in the image reading apparatus, the correction unit includes a storage unit that stores the reference data corresponding to the number of integration stages controlled by the integration stage number control unit.

According to a fourth aspect of the present invention, there is provided an image reading apparatus comprising:
The correction unit includes a storage unit that stores reference data for shading correction corresponding to each of the number of integration stages in the delay integration, and is controlled by the integration stage number control unit among the reference data stored in the storage unit. An output signal from the read element is corrected using the reference data corresponding to the number of integration stages.

According to a fifth aspect of the present invention, there is provided an image reading apparatus comprising:
A reference white plate is provided, and data obtained by reading the reference white plate with the reading element is used as the reference data.

According to a sixth aspect of the present invention, there is provided an image reading apparatus comprising:
A plurality of line sensors, a delay element for delaying output signals of the plurality of line sensors, an averaging circuit for averaging outputs from the plurality of line sensors delayed by the delay element, and the plurality of line sensors A switching element for switching whether or not to input the output signal of the averaging circuit, and a control circuit for controlling the switching element so that the output signal of the defective line sensor is not input to the averaging circuit, Having.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] FIG. 1 shows an image reader IR as an example of an image reading apparatus according to the present invention.
FIG. 2 is a sectional front view showing the entire configuration of a copying machine 1 to which the present invention is applied.
FIG. 3 is an enlarged view of the image reader IR.

As shown in FIG. 1, the copying machine 1 is a digital copying machine comprising an image reader IR and a page printer PRT. The main body of the image reader IR scans the original placed on the original platen glass 18 into pixels. The scanning system 10 reads the original. The photoelectric conversion signal output from the scanning system 10 is a signal corresponding to various image forming modes. It comprises an image signal processing unit 20 for performing processing and a memory unit 30 for storing image data corresponding to a document. An automatic double-sided document feeder (ADFR) 500, which is an additional device also serving as a document cover, is attached to the upper part of the main body so as to be openable and closable about its rear end.

Referring also to FIG. 2, the scanning system 10 is a line scanning type image reading mechanism, and includes a scanner 19, fixed mirrors 13a and 13b, a condenser lens 14, a sensor unit 16 including a TDI sensor 161; It comprises a scan motor M2 for driving the scanner 19, and a cooling fan F1 for preventing a rise in temperature due to the document irradiation lamp 11.
The scanner 19 has a document irradiation lamp 1 for irradiating the document.
1, a heater 191 for heating the document irradiation lamp 11, a temperature sensor 192 including a thermistor, etc., and a reflection shade 19
3 and a mirror 12 are provided.

The ADFR 500 conveys the original set on the original stacker 510 onto the original platen glass 18 by the feed roller 501, the sandwiching roller 502, the conveying roller 506a, and the reading roller 505, and discharges the original after reading. The document is discharged onto a document discharge tray 511 by a roller 509. The ADFR 500 is provided with a document scale, a document sensor for detecting the presence or absence of a document, a document size sensor for detecting the size of a document, and a discharge sensor. Illustration of the original scale and each of these sensors is omitted.

For example, when copying a plurality of originals, the operator sets the originals with the front surfaces thereof facing upward. Each document on the document stacker 510 is pulled out one by one from the lowermost document, and passes through the reading position YT on the document table glass 18 with the front surface facing downward. At this time, the original is read. Then, in the case of the single-sided original mode, after the reading is completed, the original is conveyed by the conveying rollers 506b and 506c and the paper discharging roller 509 over the switching claw 508b, and is discharged so that the upper surface becomes the back surface. .

In the case of the double-sided original mode, the original conveyed by the conveying rollers 506b and 506c after the reading of the front side is completed is caused by the left end of the switching claw 508c moving rightward. Is conveyed toward the reading position YT by the conveyance roller 506d under the switching claw 508c. At this time, the front side and the back side of the document are reversed. The reading roller 505 rotates in the direction opposite to the direction in which the front side of the document is read, thereby reading the back side of the document. After the reading of the back side is completed, the document passes above the switching claw 508a and is conveyed by the conveying rollers 506e and 506.
f, 506c, and is discharged by a paper discharge roller 509 such that the upper surface is on the back surface.

The page printer PRT includes a print processing unit 40 for outputting an exposure control signal, a print head 60 using a semiconductor laser 62 as a light source, a developing / transfer system 70A including a photosensitive drum 71 and its peripheral devices, and a fixing roller pair 84. Fixing / discharging system 70B having a sheet replenishing unit 600 and a fixing / discharging system 70B having a discharging roller 85 and the like.
And the like, and prints a copied image by an electrophotographic process based on the image data transferred from the image reader IR. At the bottom of the page printer PRT,
Two paper cassettes 80 capable of storing several hundred sheets of paper
a, 80b, paper size sensors SE11 and SE12, and a paper feed roller group.

The laser beam emitted from the semiconductor laser 62 is deflected by the polygon mirror 65 in the main scanning direction.
The light is guided to the exposure position of the photosensitive drum 71 via the main lens 69 and various mirrors 67a, 68, 67c. The surface of the photoconductor drum 71 is uniformly charged by the charging charger 72. The latent image formed by the exposure is
, And the toner image is transferred onto a sheet by a transfer charger 74 at a transfer position (copying position). Then, the sheet is separated from the photosensitive drum 71 by the separation charger 75, sent to the fixing roller pair 84 by the transport belt 83, and discharged face-up.

The re-feed unit 600 is mounted on the side of the page printer PRT as an additional device for automating double-sided copying. The re-feed unit 600 temporarily stores the sheet discharged from the page printer main body by the discharge roller 85, and performs switchback. It has the function of transporting and sending it back to the page printer body.

In the one-sided copy mode, the paper is discharged onto the paper discharge tray 621 without passing through the paper re-feed unit 600. On the other hand, in the duplex copy mode,
The left end of the switching claw 601 is moved upward by a solenoid (not shown), and the paper discharged from the discharge roller 85 reaches the forward / reverse roller 603 through the transport roller 602. When the trailing edge of the sheet reaches the sheet sensor SE61, the forward / reverse roller 603 is inverted. As a result, the sheet is returned to the page printer main body. The returned paper is sent to the timing roller 82 through the horizontal transport rollers 86a to 86c in order and waits. Here, when a plurality of sheets are continuously fed, each sheet is conveyed one after another with a predetermined sheet interval so that the sheets do not overlap each other, and the sheet is fed again to the re-feed unit 600.
Sent to. Since the paper transport path length is constant,
The number of sheets in one circulation by the re-feeding unit 600 and the horizontal transport rollers 86a to 86c (the maximum number of circulations) depends on the sheet size.

In FIG. 2, the original on the original platen glass 18 is illuminated by an original illuminating lamp 11, and the reflected light is transmitted via a mirror 12, fixed mirrors 13 a and 13 b and a condenser lens 14 to a sensor section 16. An image is formed on the light receiving surface of the TDI sensor 161 at.

The sensor section 16 converts the intensity of light corresponding to the density of the image of the original image formed on the photosensitive section of the TDI sensor 161 into a signal charge, and outputs image data S4. Sub-scanning of a document (reading in a direction perpendicular to the main scanning direction) is performed as follows. That is, when the automatic paper feed mode is activated by activating the ADFR 500, the scanner 19 is disposed below the reading position YT, and the document itself is moved above the reading position YT by the rotation of the transport roller 505. When the manual mode is set without operating the ADFR 500, the scanner 19 is set to the reading position YT.
By moving to the right.

In the vicinity of the reading position YT, a reference white plate 1
5 are provided. The reference white plate 15 is read by the scanner 19 before reading the original, and shading correction is performed based on the reference white plate data obtained at this time. That is, shading correction that is caused by uneven brightness of the document irradiation lamp 11 and variation in sensitivity of each pixel of the TDI sensor 161 is performed.

The image data S4 is subjected to signal processing according to various image forming modes by the image signal processing section 20, and is output as image data D2. Image data D2
Are stored in the memory unit 30 and output to the page printer PRT.

FIG. 3 is a block diagram showing the structure of the sensor section 16. As shown in FIG. As shown in FIG. 3, the sensor unit 16
DI sensor 161, amplification section 162, black level clamp 1
63, AD converter 164, and clock driver 1
65.

The TDI sensor 161 converts the intensity of light corresponding to the density of the image of the original image formed on the photosensitive portion into a signal charge and outputs it as an image signal S1. Amplifier 162
Is an amplifier circuit composed of an operational amplifier and the like, which amplifies the image signal S1 and outputs a signal S2.

The black level clamp 163 changes the position of the reference level of the signal S2 and outputs a clamp signal S3.
The AD converter 164 outputs the analog clamp signal S3
Is quantized and converted into 8-bit digital image data S4. The range of quantization in the AD converter 164 depends on the reference white plate 1 without shading correction.
5 and the minimum density to be read when reading the document.

The clock driver 165 inputs a drive clock to the TDI sensor 161 to make
The sensor 161 can read a document at a desired reading speed.

Next, the configuration and operation of the TDI sensor 161 will be described with reference to FIGS. FIG. 4 shows TD
FIG. 5 is a block diagram showing a configuration of the I sensor 161, FIG. 5 is a block diagram showing an integration stage number control circuit 1616, and FIG. 6 is a timing chart showing an operation of the TDI sensor 161.

As shown in FIG. 4, the TDI sensor 16
1 denotes a photosensitive unit 1610, a Y-direction shift register 161
2. Transfer gate 1613, X-direction shift register 161
4, output amplifier 1615, integration stage number control circuit 1616,
Input terminals 1617a to 1617d, an output terminal 1618, and a reset terminal 1619 are provided.

The photosensitive section 1610 and the Y-direction shift register 1612 correspond to a reading element in the present invention, and the integration stage number control circuit 1616 corresponds to an integration stage number control means in the invention.

In FIG. 4, the X direction is the main scanning direction, and the Y direction is the sub scanning direction. The photosensitive unit 1610
A photodiode array DX in which m photodiode PDs are arranged in one row in the direction is arranged so as to be adjacent to each other in n columns in the Y direction.
A two-dimensional set of D is formed.

As an example of specific values of the variables m and n, for example, when reading the short side (297 mm) of an A3 document at 400 dpi, the value of m is: m = 4000 dots / 25.4 mm × 297 mm = 46
77, which is approximately 5000 (pixels). the value of n, ie Y
The number of rows in the direction is determined according to the required sensitivity. For example, a 96-row TDI sensor is known. In this case, the total number of photodiodes PD used is about 48000 from 96 × 5000 = 480,000.
It becomes zero.

Referring also to FIG. 5, Y-direction shift register 1612 has a plurality of registers RT, and the arrangement and total number thereof are the same as the arrangement and total number of photodiodes PD of photosensitive section 1610. . That is, in the above-described example, the X-direction register row RX (RX1 to RX9) having about 5000 registers RT per row in the X-direction.
6) to form a Y-direction register row RY having 96 registers RT per row in the Y-direction. Therefore, a total of about 480000 registers RT are two-dimensionally arranged.

Each of the registers RT is associated with each of the photodiodes PD, and the signal charge of the intensity of light corresponding to the density of the image of the original image formed on each photodiode PD is: , To the register RT.

From each photo die array DX, each X
The signal charges are sent to the direction register row RX.
From each photo die auto row DX to each X direction register row RX
Are sequentially transferred (shifted) in the Y direction in read line units by the control signals φYSR1 to φYSR4 input from the input terminal 1617b. The transfer timing is synchronized with the movement of the document. That is, when the document has moved by a predetermined distance corresponding to one pixel in the Y direction, a one-stage shift is performed in the Y direction. In the above-described example of the TDI sensor 161 having 96 rows, after the shift is performed 96 times, the signal charge corresponding to the light amount from the document is output from the X-direction register row RX96 at the final stage.

The signal charge in each X-direction register row RX is Y
Since the speed of shifting in the direction is synchronized with the moving speed of the document, the signal charge corresponding to the light amount from an arbitrary pixel of the document is added 96 times.

That is, in the TDI sensor 161,
The signal charges generated in the photodiodes at the same position along the main scanning direction (X direction) are sequentially integrated in the sub-scanning direction, so that the reading sensitivity increases and the S / N ratio increases.

The number of additions, that is, the number of Y-direction register arrays RY to be used is determined by the integration stage number control circuit 1616. In the above example, since the pixel is configured with 96 pixels (96 shift registers) in the Y direction, the maximum number of additions is 96.

The integration stage number control circuit 1616 is connected to the input terminal 1
The number of integration stages (the number of additions) in the Y direction is determined by the control signal φIT input to the Y-direction shift register 1612.
Set to.

As shown in FIG. 5, the integration stage number control circuit 1616 is composed of switching elements SW1 to SW96 and a selector SL. Switching element SW
1 to SW96 each have an X-direction register row RX.
1 to RX96. Switching element SW
The other ends of SW1 to SW96 are connected to a common discharge unit EA. The selector SL controls on / off of these switching elements SW1 to SW96 based on the control signal φIT.

For example, the switching elements SW1, SW3
Is turned on, the signal charges in the X-direction register rows RX1 and RX3 are discharged. This means that the number of X-direction register rows RX to be integrated along the Y-direction is changed, and the number of stages of integration is changed. The processing content of the integration stage number control will be described later.

The setting of the number of integration stages is performed before the reading of the original is started. By changing the number of integration stages, the sensitivity of the TDI sensor 161 is changed. Note that the number of integration stages may be changed during reading of the document. In this case, the number of integration stages is set according to the density of the original to be read and the density of the portion to be reproduced. By changing the number of integration stages during reading, the sensitivity of the TDI sensor 161 can be changed in real time. X-direction register row RX96 at the last stage
From this, the signal charge S11 obtained by integrating the set number of integration stages is output.

The transfer gate 1613 has an input terminal 1617
This is a gate circuit that is opened by a control signal φTCK input from c, and when the gate is opened, outputs a signal charge S11 from the final row of the X-direction register row RX96 as a signal charge S12 to the X-direction shift register 1614. .

The X-direction shift register 1614 controls the control signals φXSR1 and φX input from the input terminal 1617d.
This is a shift register that transfers signal charges in the X direction by SR2.

The output amplifier 1615 amplifies the signal charge S13 output from the X-direction shift register 1614,
It is output from the output terminal 1618 as a time-series image signal S1.

In FIG. 6, control signals φYSR1 to φYSR4
Is a signal for transferring the signal charges of the X-direction register rows RX1 to RX96 in the Y-direction. As shown, the control signal φYSR1, the control signal φYSR3, and the control signal φYSR
2 and the control signal φYSR4 are signals whose “H” and “L” levels are inverted from each other. When the levels of these signals change, the signal charges input from each photodiode row DX to each X-direction register row RX shift by one stage in the Y-direction. The level changes of control signals φYSR1 to φYSR4 are performed when control signal φTCK is at “H” level.

The control signal φTCK is a signal for controlling the transfer gate 1613 that moves the signal charge from the Y-direction shift register 1612 to the X-direction shift register 1614. In this example, when the control signal φTCK is “H”,
The signal charges move to the X-direction shift register 1614.

Control signals φXSR1 and φXSR2 are signals for driving X-direction shift register 1614. Control signal φXSR1 and control signal φXSR2 are “H” with each other.
This is a pulse signal having an inverted “L” level, and each time the “H” or “L” level of each of the control signals φXSR1 and φXSR1 changes, the signal charge in the X-direction shift register 1614 is shifted by one stage in the X direction shift. When control signal φXSR1 is “L” and φXSR2 is “H”, transfer gate 16
The signal charges S12 sent from the signal 13 are output as signal charges S13.

Each pulse signal of control signals φXSR1 and φXSR2 is stopped while control signal φTCK is at “H”. When the signal charge moves to the final stage 1614E of the X-direction shift register 1614, the signal charge
615.

The reset signal φRES is output from the final stage 1614
This is a pulse signal that resets the signal charge remaining in the output amplifier 1615 for each pixel before the next signal charge output from E is converted into a voltage. The rising of reset signal φRES is set so as to be synchronized with the rising of control signal φXSR1 or the falling of control signal φXSR2.

The image signal S 1 is output from the output amplifier 1615. The image signal S1 is output when the pulse of the control signal φXSR1 is “L” level, that is, when the pulse of the control signal φXSR2 is “H” level. In the figure, the lower the image signal S1 is, the more light is received by the photosensitive unit 1610.

FIG. 7 is a block diagram showing the internal configuration of the image signal processing section 20. As shown in FIG. 7, the image signal processing unit 20 includes a digital image processing unit 200, a correction data storage unit 220, a timing control unit 210, a histogram generation unit 206, a CPU 102, a CPU 103, and a CPU 1.
07 and a tube wall temperature light amount table 211.

The digital image processing section 200 includes a shading correction section 201, an MTF correction section 202, a gamma correction section 203, a scaling processing section 204, and a binarization processing section 205.

The digital image processing section 210 sequentially performs the following processes on the image data S4 and outputs the image data D2 to the memory unit 30. That is, the shading correction unit 201 performs shading correction on the image data S4 output from the sensor unit 16, and outputs the image data S5. Shading correction unit 201
Corresponds to the correcting means in the present invention. The MTF correction unit 202 performs MTF correction on the image data S5,
The image data S6 is output. The gamma correction unit 203
The gamma correction is performed on the image data S6, and the image data S7 is output. The scaling unit 204 performs processing on the image data S7
Is subjected to enlargement processing or reduction processing, and the image data S8
Is output. The binarization processing unit 205 performs a binarization process on the image data S8, and outputs image data D2.
The correction data storage unit 220 stores the obtained shading correction data for white shading correction and black shading correction. Correction data storage unit 220
Corresponds to the storage means in the present invention.

The histogram generation unit 206 generates a histogram of a read image for performing automatic density adjustment.
The timing control unit 210 controls the digital image processing unit 20
0, and outputs various synchronization signals SY1 to SY5, SY6, and SY7 to the correction data storage unit 220 and the sensor unit 16, respectively.

CPU 102, CPU 103, and CPU
107 performs the following control in response to an external command. That is, the CPU 107 controls the ADFR 500. The CPU 102 sends a reading start control signal and the like to the digital image processing unit 200. CPU103
Performs drive control of the scanning system 10. For example, by controlling a document irradiation lamp control circuit (not shown), turning on and off the document irradiation lamp 11 and adjusting the light amount are performed. The heater 1 used for the document irradiation lamp 11
The controller 91 controls the cooling fan F1, controls the scan motor M2, and the like.

The CPU 103 reads the digital image processing unit 200 based on the tube wall temperature information obtained from the thermistor for sensing the tube wall temperature of the document irradiation lamp 11 and the tube wall temperature light amount table 211. Outputs operation prohibition / permission information. Note that the CPU 103 operates the document irradiation lamp 11 when the power is turned on or while reading is not performed.
Is turned on.

The tube wall temperature light amount table 211 stores rewritable data for calculating the light amount of the document irradiation lamp 11 based on the tube wall temperature of the document irradiation lamp 11. When the image reader IR is shipped from the factory, various data measured at the factory for the image reader IR are stored. However, since the relationship between the light amount and the tube wall temperature changes with time, the contents of the tube wall temperature light amount table 211 are changed. It needs to be rewritten.

The rewriting of the contents of the tube wall temperature light amount table 211 is performed every fixed accumulation lighting time of the original irradiating lamp 11. The light amount is calculated from the gain adjustment value, the maximum value of the reference white plate 15 at the time of gain adjustment, and the sensitivity value of the sensor unit 16,
It is created according to the tube wall temperature at that time. It may be rewritten at the time of gain adjustment performed for each reading.

FIG. 8 is a block diagram showing the internal configuration of the memory unit 30. The memory unit 30 includes a multi-port input image memory 301 and an output image memory 3
2, an image memory unit 300 including a compressor 303, a decompressor 304, and a multiport code memory 305 is provided.

The flow of image data D2 or code data D2C from the input image memory 301 to the code memory 305 via the compressor 303 is the compressed transfer line DL1 at the time of reading, and separately from the compressed transfer line DL1. The image data D is directly stored in the code memory 305 from the memory 301.
2 is provided with an uncompressed transfer line DL2. The flow of image data D3 or code data D3C from the code memory 305 via the decompressor 304 to the output image memory 302 is a compression transfer line DL3 at the time of reading, and is separate from the compression transfer line DL3. 305 directly to the output image memory 302 to store the image data D
3 is provided with an uncompressed transfer line DL4.

The CPU 106 controls the image memory unit 300 in accordance with the procedure of the program stored in the ROM 116. Parameters for operating the program are stored in the RAM 126. The RAM 126 stores a code management table MT. CPU10
6, a serial I / F 146 is connected, and the CPU 101 and the CPU 10 are connected through the serial I / F 146.
2 and other control blocks such as commands or statuses can be exchanged. Timer 136
Is a timer that performs a count operation at a constant cycle, and is used for time measurement. The timer 136 is provided with a two-channel timer, and operates as a timer 1 or a timer 2, respectively.

The image signal of the original read by the image reader IR is processed by the image signal processing section 20 and is taken into the input image memory 301 as image data D2.

The image data D2 stored in the input image memory 301 is compressed by the compressor 303 and stored in the code memory 305 as code data D2C. At the same time, without passing through the compressor 303, the input image memory 3
01 is transferred to the code memory 305 by DMA, and the uncompressed image data D2 is stored in another area of the code memory 305. That is, the image data D2 stored in the input image memory 301 is divided into a compressed transfer line DL1 and a non-compressed transfer line DL2.
The transfer is started at the same time by the various methods, and the storage in the code memory 305 is started at the same time.

Then, when the transfer by one of the compressed transfer line DL1 and the non-compressed transfer line DL2 is completed first, the transfer by the other is stopped and terminated.
Thereafter, as described below, a process for copying is performed using the image data D2 or the code data D2C for which transfer has been completed first.

That is, the code data D2C that has been compressed and stored in the code memory 305 is read out as necessary as code data D3C, decompressed by the decompressor 304 to become image data D3, and is output to the output image memory 302. It is memorized. This is the compression transfer line DL3. Also,
The image data D2 stored in the code memory 305 without being compressed is read out as needed as image data D3, and stored in the output image memory 302 as it is.
This is the uncompressed transfer line DL4. The image data D3 stored in the output image memory 302 is read and transferred to the print processing unit 40, where the print processing is performed.

Note that an instruction to start the reading process to the image reader IR is sent from the memory unit 30 to the data D0.
This is performed by issuing a command to the CPU 102 and the CPU 103 through the line. Also, in the printing process, the CPU transmits the data D0 through the line.
This is performed by issuing a command to the CPU 104 and the CPU 105. The control itself by exchanging these commands is the same as the control in a conventionally known printer or digital copying machine.

Next, the process of controlling the number of integration stages will be described. FIG. 9 is a diagram comparing dark outputs when the number of integration stages in the TDI sensor 161 is changed to M and N stages. FIGS. 9A and 9B show dark outputs when the number of integration stages is M or N, respectively.
FIG. 9C shows the difference between the dark output when the number of integration stages is M and the dark output when the number of integration stages is N. Note that M and N are natural numbers different from each other.

FIG. 10 is a diagram comparing the white output when reading the reference white plate 15 by changing the number of integration stages in the TDI sensor 161 to M and N stages. FIG.
10A shows a case where the number of integration stages is M, and FIG. 10B shows a case where the number of integration stages is N.

In these figures, the horizontal axis represents the pixel position of TDI sensor 161. The vertical axis represents the size of the image data S4 output from the sensor unit 16. The black shading correction data for the black shading correction is obtained by quantizing the dark output obtained in a state where the document irradiation lamp 11 is turned off by the AD converter 164, and is stored in the correction data storage unit 220. You. Note that the correction data storage unit 220 may store the analog value as it is using an analog memory.

The white shading correction data for the white shading correction is an output signal obtained by reading the reference white plate 15 with the original irradiation lamp 11 turned on.
It is obtained by quantization by the AD converter 164 and stored in the correction data storage unit 220. Note that the correction data storage unit 220 may store the analog value as it is using an analog memory.

In this embodiment, the black shading correction data for the dark output read with the same number of integration steps as the number of integration steps determined when reading the reference white plate 15 is used.

That is, with the original irradiation lamp 11 turned off, the number of stages of delay integration is variously changed, and black shading correction data is obtained for each changed number of stages of delay integration. To memorize. Next, the reference white plate 15 is read with the document irradiation lamp 11 turned on, and the number of integration stages is determined. The determination of the number of integration stages at this time is performed so that the maximum value of the read data when reading the reference white plate 15 becomes a predetermined specified value. At the same time, white shading correction data is obtained and stored in the correction data storage unit 220. The black shading correction data of the number of integration stages corresponding to the determined number of integration stages is acquired from the correction data storage unit 220, and the shading correction is performed on the image data S4 using this and the white shading correction data of the number of integration stages.

As described above, when the number of integration stages is changed, shading correction is performed based on white and black shading correction data obtained by the same number of integration stages. For this reason, when a document is read, a high-quality image signal without streak-like artifacts in the read image can be obtained.

If shading correction is performed by using black shading correction data and white shading correction data obtained by different numbers of integration stages,
For example, when the reference white plate 15 is read and the black shading correction data is generated based on the dark output of N stages, although the number of integration stages to be used is determined to be M stages, FIG. There is a possibility that streak-like artifacts as shown in FIG.

The prescribed value R in FIGS. 10A and 10B is
This is a set value of a photoelectric conversion signal obtained when the reference white plate 15 is read, and is incorporated in the control program. For example, in the case where the photoelectric conversion signal is represented by 8 bits and 0 to 255 steps, by setting the specified value R to 200, the density reproduction range of the read original is 255/200 = 1.275 of the reference white plate 15. It is possible to read a document having a double reflectance.

As shown in FIGS. 10A and 10B, since the actual output of the TDI sensor 161 is not uniform, the number of integration stages is determined so that the maximum value of the read photoelectric conversion signal becomes a prescribed value. I do. This specified value does not affect the quality of the image.

Next, an original reading process according to the present invention will be described with reference to a flowchart. FIG. 11 is a flowchart showing a document reading process according to the present invention.

In FIG. 11, the document irradiating lamp 11 is turned off (# 1). The scanner 19 is moved to a position where black shading correction data is obtained (# 2). By changing the number of integration stages, L sets (L is an integer) of black shading correction data are obtained (# 3). The black shading correction data obtained in step # 3 is stored in the correction data storage unit 22.
0 is stored (# 4). The document irradiation lamp 11 is turned on (# 5). The scanner 19 is moved to a position where the gain adjustment and the white shading correction data are obtained (the position of the white reference plate 15) (# 6). The number of integration stages is changed so that the data value obtained by reading the white reference plate 15 becomes a specified value, and the number of integration stages to be adopted is determined (# 7). The white reference plate 15 is read to obtain white shading correction data (# 8).
The white shading correction data obtained in step # 8 is stored in the correction data storage unit 220 (# 9). The shading correction unit 2 converts the white shading correction data and the black shading correction data according to the number of integration stages to be used.
01 (# 10). Scan the original (# 1
1). The image data S5 is output while performing white and black shading correction (# 12).

It should be noted that the number of stages to be integrated is i to k (i, k
In the case where the fluctuation of the black shading correction data is small within the range of (integer), the storage capacity of the correction data storage unit 220 can be reduced by representing the black shading correction data with, for example, constant numerical data. The values of i and k are set according to the magnitude of the fluctuation of the black shading correction data.

FIG. 12 is a flowchart showing a document reading process according to another embodiment of the present invention. 12, first, the document irradiation lamp 11 is turned off (# 2).
1). The scanner 19 is moved to a position where the black shading correction data is obtained (# 22). The number of integration stages is set to the number of integration stages used in the previous reading, and black shading correction data is obtained (# 23). The acquired black shading correction data is stored in the correction data storage unit 220 (# 24). The document illumination lamp 11 is turned on (# 2
5). The scanner 19 is moved to a position where the gain adjustment and white shading correction data are obtained (the position of the white reference plate 15) (# 26). The number of integration stages is changed so that the data value obtained by reading the white reference plate 15 becomes a specified value, and the number of integration stages to be employed is determined (# 27). Read the white reference plate 15,
The white shading correction data is obtained (# 28). The white shading correction data obtained in step # 28 is stored in the correction data storage unit 220 (# 29). The shading correction unit 201 converts the white shading correction data
(# 30). The document irradiation lamp 11 is turned off (# 31). The scanner 19 is moved to a position where the black shading correction data is obtained (# 32). Step #
The number of integration stages determined in step 27 is set (# 33). The black shading correction data is obtained, and the obtained black shading correction data is stored in the correction data storage unit 220 (# 34). The white shading correction data and the black shading correction data corresponding to the number of integration stages to be used are input to the shading correction unit 201 (# 35). The original is read (# 36). The image data S5 is output while performing white and black shading correction (# 37).

When the number of integration stages to be selected varies,
Since the storage capacity of the correction data storage unit 220 becomes large,
According to this alternative form of reading processing, the storage capacity can be reduced.

In the two reading processes shown in FIGS. 11 and 12, the reference white plate 15 is read, and the number of integration stages K1 is determined so that the maximum value of the white output at the time of reading becomes the specified value R. I do. Here, K1 is an integer having a predetermined value.

Next, the reference white plate 15 is read again. The number of integration stages at this time is the integration stage number K determined earlier.
It is one. The white shading correction data is generated from a white output read using the number of integration stages K1. As the black shading correction data, data generated from the dark output read by the integration stage number K1 is used. As described above, the white shading correction data and the black shading correction data used are generated with the same number of integration stages K1.

When the original is read by the number of integration stages K1, shading correction is performed using the white and black shading correction data generated by the number of integration stages K1.

Therefore, even when the number of integration stages of the TDI sensor 161 is changed, the changed number of integration stages K1
, The shading correction is performed using the white and black shading correction data, so that a signal causing a streak-like artifact is not superimposed on the image signal. [Second Embodiment] Next, an image reader IRA according to a second embodiment will be described.

FIG. 13 is a block diagram showing the configuration of the image reader IRA of the second embodiment. Although not shown, the image reader IRA also has a reference white plate, a document irradiation lamp, and the like, and is applied to a copying machine, like the image reader IR.

The image reader IRA is a reading device having a reading element for performing delay integration using a plurality of line sensors, and can obtain a high quality image signal by not taking in the output of a defective line sensor. In addition,
For ease of explanation, the number of line sensors used is assumed to be three.

In FIG. 13, the image reader IRA
Are line sensors 711-3, delay line 721-
2, switch circuits 731-73, buffer amplifier 741-
3, resistors 744-6, an averaging circuit 750, an AD converter 760, a timing generation circuit 770, a DA converter 771, a CPU 780, and a storage device 790.

The line sensors 711 to 711 are each composed of a photodiode array, and photoelectrically convert an optical signal obtained from an original image to output photoelectrically converted signals S711 to S711. The arrangement interval of each of the line sensors 711 to 3 is a width of two lines.

Each of the delay lines 721 and 2 comprises a CCD shift register or a BBD shift register. The delay line 721 has a delay of six lines to match the phase with the photoelectric conversion signal S713 output from the line sensor 713. Delay line 7
Reference numeral 22 has a delay of three lines to match the phase with the photoelectric conversion signal S713 output from the line sensor 713. These line sensors 711-3 and delay lines 721-2 constitute a time delay integration type reading element.

Each of the switch circuits 73-1 to 3-3 is composed of an analog switch or the like. Each of these outputs is connected to a ground potential discharge section E1 via resistors 744-6. The switch circuit 731 is opened by the timing signal S771 when the line sensors 712 to 3 are subjected to the inspection process shown in the flowchart below or when the photoelectric conversion signal S721 is an abnormal signal. When the other line sensors 712 to 3 are not inspected and when the image signal S721 is a normal signal, the line sensor is closed and outputs the image signal S731. The same applies to the switch circuits 732 to 3.

The buffer amplifiers 741 to 743 output the image signals S731 to S733 to the averaging circuit 750 while maintaining their voltages. FIG. 14 shows an averaging circuit 750.
FIG.

As shown in FIG. 14, the averaging circuit 75
0 comprises an operational amplifier 751, a feedback resistor 752, and addition resistors 753-5. Averaging circuit 750
For example, when all of the image signals S731 to S733 are input, they are added and further averaged. A resistance element controlled by a voltage such as an FET is used as the feedback resistor 752 so that the averaging can be controlled by the output voltage S778 (H level) from the DA converter 771.

The timing generation circuit 770 generates the following signals and supplies them to each component. That is, for each of the line sensors 711 to 311, a drive pulse signal S774 for driving them and the like for the delay lines 721 to 2, and a drive pulse signal S775 for driving them are sent to each switch circuit 731 to 3. On the other hand, control signals S771 to S773 for controlling them are controlled by DA converter 771, control signal S776 for controlling the averaging coefficient in averaging circuit 750, and control for controlling the output of AD converter 760. The signal S777 is generated and supplied.

The control signal S776 is determined by the CPU 780 in accordance with the line sensor to be inspected or the number of input image signals.
Is generated in accordance with the data and the timing of the combination of the switch circuits 731 to 733 to be set to the closed state.

FIG. 15 is a flowchart showing a line sensor inspection process in the image reader IRA, and FIG. 16 is a timing chart showing an operation of the line sensor inspection process in the image reader IRA. In the figure, each line sensor 711-3 and each delay line 721, 7
The number written in the output signal of No. 22 indicates the reading position (scanning line). Here, an example will be described in which a reference white plate is read and defects of the line sensors 711 to 711 are checked.

In FIG. 15, each line sensor 711-
3 allows the reference white plate to be read (# 41). C
The PU 780 sends a signal to the timing generation circuit 770 to close the switch circuit 731 and open the switch circuits 732 and 733 (# 42). The CPU 780 sends the timing generation circuit 770 a signal from the DA converter 776 to the averaging circuit 7.
The averaging coefficient given to 50 is set to a predetermined value (# 43). At this time, the value to be set is a value at which the averaging circuit 750 does not saturate.

Then, the image data S4a is read (#
44). Inspection of the read image data S4a is performed (#
45). The inspection criterion is that when the output for a certain pixel or the entire line sensor is about 1/3 or less of the output obtained from the other pixel or the entire line sensor, respectively,
In addition, a case where the variation of several lines is extremely large is determined to be a defect. If there is a defect in step # 45, the CPU 780 records the position of the defective pixel or the defective line in the storage device 790 (# 46).

The switch circuit 732 is closed and the switch circuits 731 and 733 are opened (# 47), and steps # 43 to # 43 are performed.
The same processing as the processing of 46 is executed (# 48). The switch circuit 733 is closed, and the switch circuits 731 and 732 are opened (# 49), and the same processing as the processing of steps # 43 to # 46 is executed (# 50).

FIG. 17 is a flowchart showing a document reading process in the image reader IRA. In FIG. 17, at the start of document reading, the CPU 780 reads data of a defective portion from the storage device 790 and writes a control signal for controlling the timing of opening and closing each of the switch circuits 731 to 3 in the timing generation circuit 770 (# 6).
1). Document reading is started (# 62). At the time of reading the original, the timing generation circuit 770 detects that each line sensor 71
And drive pulse signals for each of the delay lines 721 and 722, and each switch circuit 731 to
3 is opened and closed. The averaging coefficient is set in the averaging circuit 750 through the DA converter 771. The control of the opening and closing of the switch circuits 731 to 3 and the setting of the averaging coefficient need to be changed and followed at the same speed as the drive pulse signals of the line sensors 711 to 3 because a defect may occur for each pixel. (# 62). Averaging circuit 75
The signal processed at 0 is quantized by the AD converter 770 and sent to a downstream image signal processing circuit (not shown) (#
64).

FIG. 18 is a timing chart showing the operation of reading a document in the image reader IRA. FIG. 18 shows a state in which part of the output of the line sensor 711 is defective, all of the outputs of the line sensor 712 are defective, and the output of the line sensor 713 is normal. In the figure, the shaded portion indicates a defective portion. [Third Embodiment] Next, an image reader IRB according to a third embodiment will be described.

FIG. 19 is a block diagram showing the configuration of the image reader IRB of the third embodiment. Each of the line sensors 711, 712, 71 is replaced by an image reader IRB instead of the AD converter 760 in the image reader IRA.
3, AD converters 7601 to 7603 are provided immediately after, and the averaging circuit 750
0a and a division circuit 750b, the switching elements 731b, 732b, and 733b serve as each switching circuit in the image reader IRA and a buffer amplifier corresponding to each of these switching circuits. The configuration is the same as that of the image reader IRA except that the image reader 771 is omitted.
The same reference numerals are given as.

In the image reader IRB, the photoelectric conversion signals output from the line sensors 711 to 711 are converted into digital signals and sent to the subsequent stage. The inspection process of the line sensor and the reading process of the original are the same as those of the image reader IRA.

In the image readers IRA and IRB, when any one of the line sensors 711 to 711 has a defect, the output of the defective line sensor is output from a switch circuit connected to the line sensor. Accordingly, the averaging circuit 750 does not perform the averaging process. Therefore, the influence of the output of the defective line sensor on the read image signal is reduced. Therefore,
Even if any of the line sensors has a defect, a high-quality image signal can be obtained.

In the above-described embodiment, the image readers IR, IRA, and IRB are applied to a copying machine, but can be applied to a facsimile and other various devices. Other devices include, for example, a scanning digital camera. The scanning digital camera has a configuration in which an image to be imaged is scanned by a scanning mirror such as a galvanometer mirror, and the scanned image is incident on an image sensor. In a line scan type digital camera, it is effective to increase the scanning speed in order to prevent camera shake, but if the scanning speed is increased, it is not possible to obtain a large amount of light incident on the image sensor. Therefore, it is effective to apply the above-described TDI sensor as an image sensor. Further, in a digital camera, since an image is taken outdoors or an image is taken indoors, it is expected that the amount of light at the time of reading an image changes greatly. Therefore, it is effective to make the number of integration stages of the TDI sensor variable as described above.

In the above embodiment, the configuration of the image readers IR, IRA, IRB or the copying machine 1 as a whole or of each unit, the content of processing, the order, and the like can be appropriately changed in accordance with the gist of the present invention.

[0123]

According to the present invention, in an image reading apparatus using a TDI sensor, it is possible to obtain a good and stable image with no streak-like artifacts.

[Brief description of the drawings]

FIG. 1 is a sectional front view showing a copying machine to which an image reading apparatus according to the present invention is applied.

FIG. 2 is an enlarged view showing an image reader.

FIG. 3 is a block diagram illustrating a configuration of a sensor unit.

FIG. 4 is a block diagram showing a main part of the TDI sensor.

FIG. 5 is a block diagram illustrating an integration stage number control circuit.

FIG. 6 is a timing chart showing the operation of the TDI sensor.

FIG. 7 is a block diagram illustrating an internal configuration of an image signal processing unit.

FIG. 8 is a block diagram showing an internal configuration of a memory unit.

FIG. 9 is a diagram comparing dark outputs output by changing the number of integration stages in the TDI sensor.

FIG. 10 is a diagram comparing white outputs when a reference white plate is read by changing the number of integration stages in the TDI sensor.

FIG. 11 is a flowchart illustrating a document reading process according to the present invention.

FIG. 12 is a flowchart illustrating a document reading process according to another embodiment of the present invention.

FIG. 13 is a block diagram illustrating a configuration of an image reader according to a second embodiment of the present invention.

FIG. 14 is a diagram illustrating a configuration of an averaging circuit.

FIG. 15 is a flowchart illustrating inspection processing of a line sensor.

FIG. 16 is a timing chart showing an operation of a line sensor inspection process.

FIG. 17 is a flowchart illustrating a document reading process.

FIG. 18 is a timing chart illustrating an operation of a document reading process.

FIG. 19 is a block diagram illustrating a configuration of an image reader according to a third embodiment of the present invention.

FIG. 20 is a diagram schematically showing a TDI sensor.

FIG. 21 is a diagram for comparing an image in which streak-like artifacts appear and a document.

[Explanation of symbols]

IR, IRA, IRB Image reader (image reader) 11 Original illumination lamp (light source) 15 Reference white plate 1610 Photosensitive section (reading element) 1612 Y direction shift register (reading element) 1616 Integration stage number control circuit (integration stage number control means) 201 Shading correction unit (correction unit) 220 Correction data storage unit (storage unit) 711, 712, 713 Line sensor 721, 722 Delay line (delay element) 731, 732, 733 Switch circuit (switching element) 731b, 732b, 733b Switching element 731b, 732b, 733b Switching circuit (switching element) 750 Averaging circuit 750a Adder (averaging circuit) 750b Divider (averaging circuit) 770 Timing generation circuit (control circuit) 780 CPU (control circuit)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C072 AA01 BA08 CA14 EA04 RA16 RA20 UA02 UA11 UA20 XA01 5C077 LL04 MM02 MM27 PP06 PP10 PP48 PP72 PQ08 PQ18 PQ23 SS03

Claims (6)

[Claims] A time delay integration type reading element for reading an image and converting it into an electric signal; an integration stage number control means for controlling the number of integration stages of the delay integration of the reading element in multiple stages; and an integration stage number control means. An image reading apparatus, comprising: correction means for correcting an output signal from the reading element using reference data for shading correction corresponding to the controlled number of integration stages. 2. An image reading apparatus according to claim 1, further comprising a light source for irradiating the original, wherein said integration stage number control means controls the number of integration stages in multiple stages according to the light amount of said light source. 3. The image reading apparatus according to claim 1, wherein said correction means includes storage means for storing said reference data corresponding to the number of integration stages controlled by said integration stage number control means. 4. The method according to claim 1, wherein the correction means includes storage means for storing reference data for shading correction corresponding to each of the number of integration stages in the delay integration, and the control means controls the number of integration stages among the reference data stored in the storage means. 4. The image reading apparatus according to claim 3, wherein an output signal from the reading element is corrected using the reference data corresponding to the number of integration stages controlled by the means. 5. The image reading apparatus according to claim 1, further comprising a reference white plate, wherein data obtained by reading the reference white plate with the reading element is used as the reference data. 6. A plurality of line sensors, a delay element for delaying output signals of the plurality of line sensors, an averaging circuit for averaging outputs from the plurality of line sensors delayed by the delay elements, A switching element for switching whether or not output signals of the plurality of line sensors are input to the averaging circuit; and controlling the switching element so that output signals of the defective line sensor are not input to the averaging circuit. An image reading apparatus, comprising: a control circuit configured to perform the following.