JP3150185B2 - Image reading device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus for photoelectrically reading a document image.

[0002]

2. Description of the Related Art In digital copiers and facsimile apparatuses, an image reading apparatus having a photoelectric conversion element such as a CCD is used to photoelectrically read an original image. Such an image reading apparatus is provided with a processing function called so-called shading correction in order to read the image density uniformly.

Conventionally, in shading correction, a standard white plate having a known density is arranged outside a document reading area, the standard white plate is read before reading a document, and the read signal is stored in a first memory. Then, based on the accumulated data, shading correction is performed on the read data at the time of reading the original.

Generally, a reading device reads a document in a main scanning direction using a one-dimensional CCD, and reads the document in a direction orthogonal to the main scanning direction.
The configuration is such that sub-scanning reading is performed by mechanically moving a reading line by a CCD, and a standard white plate is arranged at a reading start position in the sub-scanning direction.

In the shading correction, a multiplication coefficient for obtaining the light amount data from the standard white plate for each pixel stored in the first memory into a light amount value corresponding to a known density value of the standard white plate is obtained for each pixel. , Stored in the second memory.

Then, at the time of reading the original, a multiplication coefficient corresponding to the read pixel is read from the second memory and multiplied by the original reading signal to perform shading correction.

[0007]

In the above conventional example,
Since the original is placed on the platen glass, the read signal of the original is a signal transmitted through the platen glass. On the other hand, since the standard white plate is made by painting a thin metal plate, it is not always arranged at the same height as the document surface, but is often the height of the lower surface of the platen glass. In particular, when the automatic document feeder is placed on the original platen glass, the standard white plate cannot be arranged on the platen glass because the original feed is hindered. Therefore, the standard white plate is provided on the side opposite to the original surface of the platen glass, that is, inside the reader. For this reason, the standard white plate is located close to the illumination lamp.

Further, while the original is covered by the platen glass, the reading surface of the standard white plate made of paint is exposed to the light source and the CCD sensor. Therefore, when used for a long time, the standard white plate which is exposed to illumination is significantly faded compared to the original, and greatly differs from the initially set known density value.

Further, the standard white plate becomes extremely dirty due to the adhesion of dust and oil vapor inside the apparatus.

Therefore, since the shading correction is based on the premise that the standard white plate has a known density, the original read signal subjected to the shading correction deviates from a predetermined value due to a change in the density of the standard white plate. As a result, the original reading signal becomes lighter or darker. G. FIG. The balance of each color separation signal of B is lost, and the color and gray balance cannot be guaranteed.

As a known technique for compensating for a density change of a standard white plate, there is US Pat. No. 4,888,492. this is,
An all-white original is set as a reference on a platen glass, and an attempt is made to compensate for a change in density of a standard white plate based on read data of the all-white original.

[0012] However, since this is usually performed by a serviceman placing the all-white paper on the platen, the work is troublesome and the standard white plate is not used while the serviceman does not come or does not perform this work. If the density is changed, there is a disadvantage that the read image quality deteriorates.

[0013]

According to the present invention, there is provided an image reading apparatus comprising: a platen on which a document is placed; and a platen on which the document is placed. Reading means for reading an image of a placed document and outputting an image signal; a first standard member used for measuring non-uniformity of the output of the reading means; and a second standard member having a predetermined reference density And a first standard signal obtained by reading the first standard member by the reading means and a reference density obtained by reading the reference original having a predetermined reference density placed on the platen by the reading means. A correcting means for correcting non-uniformity of an image signal obtained by reading the image of the document by the reading means on the basis of the signal and a second standard member obtained by reading the second standard member by the reading means. Compensation by the correction means based on a standard signal And having a compensating means for compensating the operation.

Further, the image reading apparatus according to the ninth aspect of the present invention provides
A platen on which a document is placed, reading means for reading an image of the document placed on the platen and outputting an image signal, and a first standard used for measuring the non-uniformity of the output of the reading means A first mode having a member, a second standard member having a predetermined reference density, and correcting means for correcting non-uniformity of the image signal obtained by reading the image of the document by the reading means. Wherein the correction unit reads a first standard signal obtained by reading the first standard member by the reading unit and a reference document having a predetermined reference density placed on the platen by the reading unit. A target value is determined based on the obtained reference density signal, and the non-uniformity of the image signal is corrected by using the determined target value. The first obtained by reading the first standard member The target value is compensated based on the standard signal and the second standard signal obtained by reading the second standard member by the reading means, and the non-uniformity of the image signal is reduced using the compensated target value. It is characterized by correction.

[0015]

[0016]

[0017]

FIG. 2 shows an image reading apparatus using the present invention.

Reference numeral 200 denotes a recirculating document feeder for supplying a plurality of documents to the scanner unit 201. The image scanner unit 201 reads the fed document and performs digital signal processing.

In the transport device 201, reference numeral 1 denotes a document tray on which an operator places a document s. Reference numeral 2 denotes a document stopper against which the leading end of the document is abutted. Reference numeral 3 denotes a half-moon roller for separating the leading edge of the document and conveying the lowermost sheet of the document. Reference numeral 4 denotes a weight, which drops when the document does not easily enter the separation section and presses it from above the half-moon roller 3 to assist in transporting the document. Reference numeral 5 denotes a separation restricting plate for preventing a bundle of originals from being pushed. Reference numeral 6 denotes a paper feed roller which separates the lowermost document from the document bundle in cooperation with separation roller pairs 7 and 8 and a separation belt 9 described below. The tip of the upper guide 10 guides the document so that the document easily enters the registration nip formed by the registration roller 11 and the reversing roller 12. Reference numeral 13 denotes an inner guide plate, and reference numeral 14 denotes a middle guide, each of which forms a document conveyance path and guides the document onto the platen 15. The original is transported onto the platen 15 by the transport belt 18 stretched between the driving roller 16 and the tongue roller 17 and the roller 19 pressed from the back thereof, and stopped.
When the reading operation is stopped, the reading operation is performed, and after the reading operation is completed, the transport belt 18 is rotated in reverse, and the document is scooped by the jump table 20, passes through the path formed by the lower guide 21 and the middle guide 14, and further opens / closes the guide 22. The sheet is reloaded on the tray 1 by the discharge roller pair 24 through the upper portion of the upper guide 10 and the upper portion of the flapper 23, between the reversing roller 12, and the reversing roller 12.

When reading a double-sided original, the flapper 23 is deflected, and the original passes under the flapper and passes through the registration rollers 1.
1. The sheet is again conveyed onto the platen by the reversing roller 12.

In the image scanner unit 201, 20
2 is a standard white plate. The standard white plate 202 is used to mount the jump stand 20 below the upper surface of the platen 15.
It is attached below the jump table 15, that is, below the upper surface of the platen 15. Therefore, the jumping stand 20 is mounted on the outer surface of the device housing, and the white plate 202 is mounted on the inner surface of the housing, and is affected by dust, heat, oil vapor and the like inside the device. The document s placed on the platen 15 and transported and fixed by the transport device 200 is
Irradiation at 5. The reflected light from the document 204 is reflected on the mirror 20.
6, 207, and 208, and further incident on a line sensor (hereinafter referred to as a CCD) 210 by a lens 209. C
The output of the CD 210 is sent to the signal processing unit 211 as an original reading electric signal.

The ramp 205 and the mirror 206 have a speed v
The mirrors 207 and 208 scan the entire surface of the document by mechanically moving at a speed of 1/2 V in a direction perpendicular to the electrical scanning direction of the line sensor.

The signal processing unit 211 performs shading correction on the read signal and outputs the signal as a Video signal.

FIG. 1 shows the configuration of the signal processing unit 211.

The read signal CV from the CCD 210 is amplified by the amplifier 101 and then converted to a digital video signal DV by the A / D converter 102. An oscillator 103 generates a pixel clock CLK of the CCD. A line counter 104 generates a CCD address CCD-ADR for identifying a read pixel of the CCD 210.

In this embodiment, since a CCD having approximately 5000 pixels is used, the CCD-ADR repeatedly counts from 0 to 4999.

Reference numeral 105 denotes an address decoder, which is a CCD
Decoding the ADR signal and outputting a CD signal such as a shift pulse, a reset pulse, and a transfer clock for driving the CCD;

A control CPU 106 controls a motor 107 for moving an optical system (lamp 205, mirrors 206, 207, and 208) in the sub-scanning direction via a motor driver 108. Further, the lighting control of the document illumination lamp 205 is performed by the lamp driver 109. The external memories 110 and 111 are accessed by the address bus CPU-ADR and the data bus DATA. The CPU 106 internally has a program memory (ROM) for these controls.

An address selector 112 selects an address of the memories 110 and 111.

Reference numeral 110 denotes a first memory for taking in one line of data from the CCD 210, and reference numeral 111 denotes a second memory for outputting a multiplication coefficient for each pixel.

Reference numeral 112 'denotes a multiplier which multiplies the digital image signal DV from the CCD 210 by the multiplication coefficient EV from the second memory 111, and outputs a shading-corrected image signal Video.

An operation panel 113 includes a document reading start key 114 and a standard white plate density measurement key 115, and further includes a numeric keypad, a display, and the like as necessary.

[Original Reading Operation] When the CPU 106 detects that the reading start key 114 is pressed, the transporting device 200 is driven to stop transporting the original onto the platen 15. Thereafter, the illumination lamp 205 is turned on to move the first mirror 206 to the position of the standard white plate 202. And P ₀ , P ₁
The signal is set to L level, and a read signal for one line of the standard white plate 202 is written to addresses 0 to 4999 of the memory 110. After that, the P ₁ signal is set to the H level to complete the writing, and then the P ₀ signal is set to the H level, and the data from the addresses 0 to 4999 of the memory 110 is read one by one.

It is assumed that the read data obtained by reading the standard white plate from the address X of the CCD is Bx. In the shading correction, the read value Bx from the standard white plate is corrected to a light amount conversion value Bd of a known standard white plate density, so that the CCD read data corresponding to the address X is converted to Bd / B.
x times.

The multiplier 112 'is a well-known digital multiplier. When the EV signal of 8 bits is EV = 0, it is 0 times.
When EV = 128, the DV signal is multiplied by 1 and when EV = 255, the DV signal is multiplied by (1 + 127/128) times.

That is, the multiplication coefficient e is e = EV / 12
It becomes 8. Therefore, the CPU 106 sets the P ₂ signal to the L level, and writes the EVx corresponding to e = Bd / Bx at the address X of the memory 111.

That is, EVx = 128 × e = 128 × (Bd / Bx)

By repeating this from address 0 to address 4999, the CPU 106 stores the CCD 2 in the memory 111.
The multiplication coefficient corresponding to each pixel of 10 is written.

At the time of subsequent document reading, the CPU 106
_{The 0} signal is set to the L level again, and the P ₂ signal is set to the H level, so that the memory 111 outputs a multiplication coefficient corresponding to each pixel of the CCD 210. Then, shading correction is performed by multiplying each pixel of the image signal DV output by reading the document by the multiplier 112 'by a multiplication coefficient, and further, the optical system is advanced at a predetermined speed V to read the entire surface of the document. Do.

(Standard White Plate Density Measurement Mode) FIG. 3 is a schematic diagram relating to the measurement of the density of the standard white plate 202. FIG. 4 shows a flowchart of the measurement procedure.

In FIG. 3, reference numeral 301P denotes a reference patch, which is an original reading area OG on the platen glass 15.
It is affixed to the area indicated by oblique lines inside the readable range of the CCD 210 outside E.

The density of the patch 301P is about 0.1, is located at a point B which is 10 cm away from the standard white plate reading position A in the sub-scanning direction, and is attached to the rear end in the main scanning direction.
The size is 4 from the address 4744 in the CCD address.
The size is 256 pixels or more that always sufficiently covers the address 999.

As described above, the reference patch 301P
Is a structure in which the exposure is performed by the lamp 205 via the original platen glass 15 without exposing the lamp 205 and the CCD 210. Therefore, the patch 301P is located at a position corresponding to the actual document mounting surface, and its discoloration and contamination are unlikely to occur, and its density does not fluctuate for a long period of time. The signal can be used as a reference white with a density of 0.1 on the platen 15.

In the density measurement mode of the standard white plate 202 shown in the flowchart of FIG. 4, the density Bd1 of the standard white plate 202 is measured from the read data from the standard white plate 202 and the read data of the reference white original on the platen. .

In this mode, the operator puts some commonly used copy sheets on the platen glass 15 of the platen.
The sample (SMP) key 115 is depressed while being overlaid on top. The copy sheet immediately after opening has a stable reflection density of about 0.05, and can be handled as a reference white document.

When the press of the SMP key 115 is detected, the CP
U106 enters the measurement mode of the standard white plate 202.

First, the CPU 106 drives the optical system to move the mirror 206 to a point B located 10 cm from the standard white plate (step 402). And the lamp 205
Is turned on (step 403).

[0048] Next, the P ₀ signal to L level, given the CCD-ADR to the memory 110, also to the P ₁ signal to L level, the memory 110 one line of read signal DV output from CCD210 (Step 40)
4).

Thereafter, the CPU 106 sets the P ₀ signal and the P ₁ signal to the H level, and stores the contents of the first memory 110 at 2500.
The address is read from address 2755.

The address 2500 substantially corresponds to the center of the original platen 15 in the main scanning direction, and the average value Wave of the read data of 256 pixels at the center is obtained (step 40).
6).

Next, the 47 of the first memory 110
The addresses from 44 to 4999 are read. This data is read data from the reference patch P,
The average value Pave of the read data of 256 pixels is obtained (step 407).

Next, the CPU 106 moves the optical system again to bring the mirror 206 to the position A of the standard white plate 202 (step 408). Then, the P ₀ and P ₁ signals are changed to L
The image signal DV for one line from the standard white plate 202 is written to the memory 110 (step 409). Then, after returning the P ₀ and P ₁ signals to the H level, the average value Bave1 of the data from address 2500 to address 2755 in the memory 110 is obtained as in the case of the copy sheet (steps 410 and 411).

This Bave 1 is a CCD for which a Wave is obtained.
Since the value is a read value from the standard white plate by the same pixel as the pixel, the ratio between Bave1 and Wave is the ratio of the density of the standard white plate 202 and the light intensity conversion value of the density of the copy paper CPP.

Next, from memory address 4744 to address 4744,
An average value Bave2 of data up to address 999 is obtained (step 412).

This Bave2 is a CCD for which Pave is obtained.
Since the value is a read value from the standard white plate 202 by the same pixel as the pixel, the ratio between Bave2 and Pave is
2 and the ratio of the density of the reference patch 301P in the light amount conversion value.

The output DV of the A / D converter 102 is an 8-bit multi-value light quantity signal, and the CPU obtains the density value of the standard white plate 202 based on the ratio between the Wave signal and the Wave1 signal.

That is, when the light quantity conversion value of the density of 0.05 of the copy paper is normalized to the level of 255 by the 8-bit multi-level signal, the light quantity conversion value Bd1 of the density of the standard white plate is obtained.
Is Bd1 = 255 × (Bave1 / Wave).

Since the standard white plate 202 is painted almost uniformly, the density value Bd1 obtained using 256 pixels can be applied to the entire surface of the standard white plate 202.

The CPU 106 obtains this Bd1 (step 413), and outputs Wave, Pave, Bave1, and Bav1.
The values of e2 and Bd1 are stored in the non-volatile battery backup RAM 116.

In the original reading immediately after the standard white plate density measurement mode executed by the SMP key 115, the above-described shading correction is performed with Bd = Bd1.

(Standard White Plate Density Correction Mode)
When the reading operation is performed for a long time, the density on the standard white plate 202 and the document table is reduced to 0. 0 due to dust or oil vapor contained in the outside air.
The density ratio Bd with the copy paper CPP No. 05 changes. That is, Bd obtained in the standard white plate density measurement mode
1 and the actual Bd value will be different. As a result, correct shading correction is not performed, and the output Vid
The eo data becomes darker or lighter than the actual document density. This is corrected in the standard white plate density correction mode shown in FIG.

In this mode, the reference patch 301 affixed on the original platen 15 without the copy paper CPP having the standard density of 0.05 being placed on the original platen 15
By sampling the read data of P and the standard white plate 202, the ratio Bd1 'of the light intensity conversion value of the density between the standard white plate 202 and the copy paper on the original platen 15 at that time is equivalently obtained.

This mode is automatically performed during use as a normal document reading apparatus. In this embodiment, this mode is executed prior to the first document reading after the power is turned on.

As described above, this mode is for compensating for relatively long-term changes in the optical system such as contamination of the reading optical system. There is no effect, and it only takes time for the reading operation to execute this mode. Therefore, in this embodiment, this mode is executed only once after the power is turned on.

In order to prevent the apparatus from operating at a timing unintended by the operator by executing this mode, this mode is executed by pressing the first reading start key 114 after the power is turned on. This is also to prevent a serviceman or an operator from being injured by suddenly operating the input system when the power is turned on when the reading optical system is exposed, such as during maintenance of the apparatus.

FIG. 6 shows a control flowchart of the CPU for controlling the reading operation.

After the power is turned on, the correction operation flag preset in the internal memory of the CPU 106 is cleared to 0 (step 601). Then, it waits for a key input from the operation panel 113 (step 602).

When the SMP key 115 is pressed, the
Is executed (step 603), and the process returns to step 602 again.

When the reading start key 114 is input, it is checked whether the correction operation flag is 0 (step 604).
In the case of 0, since the standard white plate density correction mode is not executed, the standard white plate density correction mode of FIG. 5 is executed (step 605), and the correction operation flag is set to 1 (step 606). Thereafter, an original reading operation is performed (step 607).

When the correction operation flag is 1, the original is read because the standard white plate density correction mode has already been executed. Then, the process returns to step 602.

The operation of the standard white plate density correction mode will be described below with reference to the flowchart of FIG.

When the power is turned on, a standard white plate density correction mode is entered.
Move to a point B with P (step 502). Then, the illumination lamp 205 is turned on (step 50).
3).

Then, the CCD-ADR is supplied to the memory 110 with P ₀ = Low and P ₁ = Low, and the read signal DV for one line output from the CCD is written in the memory 110 (step 504). Thereafter, the CPU sets the P ₀ signal and the P ₁ signal to the H level (step 505), and reads the contents of the first memory 110 from addresses 4744 to 4999 (step 506). This data is read data from the reference patch 301P.
An average value Pave 'of the read data of six pixels is obtained.

Next, the CPU moves the optical system to bring it to the point A of the standard white plate 202 (step 507). Then, the P ₀ and P ₁ signals are set to L level, and the standard white plate 202 is set.
Is written into the memory 110 (step 508).

After returning the P ₁ and P ₀ signals to the H level (step 509), an average value Bave2 ′ of data from addresses 4744 to 4999 of the memory 110 is obtained (step 510).

Even if the brightness of the illumination changes due to dust or oil vapor, as long as the shading shape of the illumination does not change, the Wave measured at addresses 2500 to 2755 and the Pave measured at reference patch 301P are not affected. The ratio does not change. Therefore, if the value when reading the copy paper having a density of 0.05 on the original platen in the illumination state at the time of execution of this mode is Wave ′, Wave ′ =
(Pave ′ / Pave) × Wave.

Similarly, since the ratio between Bave1 and Bave2 does not change, the values from the standard white plate in the illumination state during execution of this mode and the state of the dirty standard white plate, which are obtained from addresses 2500 to 2755, are obtained. If Bave1 ', Bave1' = (Bave2 '/ Bave2) .times.B
ave1 is calculated.

In addition, even when the standard white plate and the illumination are in this mode, the target value for correcting the read value from the standard white plate by shading correction to correct the value Wave 'of the white paper on the original plate to 255. Bd1 'is Bd1' = 2
55 × (Bave1 ′ / Wave ′).

By substituting Wave1 'and Wave' into the above equation, the following equation is obtained.

[0080]

[Outside 1]

This means that Bd1 is corrected using the change rate of Bave2 and the change rate of Pave.

The ratio Bave2 / Pave of the measured value Bave2 of the standard white plate and the measured value Pave of the patch at the CCD pixel corresponding to the reference patch 301P obtained in the standard white plate density measuring mode, and the standard white plate density Ratio Ba between Bave2 'and Pave' found in correction mode
By using ve2 '/ Pave', it also means that Bd1 is corrected to obtain a target value Bd1 'for shading correction from the standard white plate when this mode is executed.
Therefore, in this embodiment, data of the ratio of Pave to Bave2 may be stored in the battery backup RAM.

The CPU calculates Bd1 '(step 511), and ends the standard white plate density correction mode.

In the subsequent document reading, the above-described shading correction is performed by setting the light quantity conversion value of the standard white plate density to Bd = Bd1 '.

Also in this case, when a copy sheet having a density of 0.05 placed on the document platen 203 is read with shading correction, the Video signal from each pixel of the CCD 210 is normalized by a standard white plate density measurement mode of 255. The set value is obtained.

In this embodiment, the standard white plate density correction mode is performed before the original reading operation after the power is turned on.
In order to speed up the start of document reading, it may be performed after the document reading operation immediately after the power is turned on. In addition, the start of document reading is not limited to key input, but may be a communication command such as a document reading start command from an external video signal capturing device (not shown).

In the above embodiment, the standard white plate density correction mode is executed in synchronization with the first original reading after the power is turned on. Sometimes it is complicated. In the following embodiment, such a case is taken into consideration, and the operation panel is provided with a standard white plate density correction mode execution permission key.

FIG. 7 shows an operation panel 113 used in this embodiment.
The details are shown below.

In FIG. 7, the same components as those in FIG. 1 are denoted by the same reference numerals. A correction mode key 701 is used to turn ON / OFF the execution of the standard white plate density correction mode described in the above embodiment.
Is a key for designating whether or not the standard white plate density correction mode is currently permitted. When the LED 702 is ON, it means that the permission is given.

FIG. 8 shows a control flow of the CPU relating to the control of the reading operation in this embodiment.

After turning on the power, the CPU 106 clears the correction operation flag (step 801). Thereafter, the correction permission flag is checked (step 802). If the flag is 1, the LED 70 is turned on (step 803). If the flag is 0, the LED 702 is turned off (step 804). This correction permission flag is stored in the nonvolatile battery backup RAM 11 accessed by the CPU.
6 and holds the setting state before the power is turned off.

Next, a key input from the operation unit is checked (step 805). When the SMP key 115 is input, the standard white plate density measurement mode shown in FIG. 4 is executed (step 806).

If the reading start key 114 has been input, the correction permission flag is checked (step 80).
7). When the correction permission flag is OFF (non-permission), an original reading operation is performed (step 811). If the correction permission flag is ON (permitted), the correction operation flag is checked (step 808), and after the power is turned on, the standard white plate density correction mode is executed only for the first document reading (step 809).

When the correction mode key 701 is input, the correction permission flag is inverted (step 813), and the process returns to steps 802, 803, and 804, and the lighting control of the LED 702 is performed according to the state of the correction operation flag.

As described above, this embodiment has ON / OFF means for automatically executing the standard white plate density correction mode.

In this embodiment, similarly to the above-described embodiments, the start of document reading is not limited to key input, but may be a command through communication such as a command from an external device.

As described above, if the standard white plate density correction mode is executed in synchronization with the first reading of the original after the power is turned on, that is, every time the power is turned on, the reading of the original in a hurry may be complicated. . Further, in a reading apparatus which is used while the power is continuously turned on, since the power-on operation is not performed, the standard white plate density correction mode is not executed.

The following embodiment takes such a case into consideration, and the operation panel is provided with a standard white plate density correction mode execution key. Then, when the operator presses this key, the standard white plate density correction mode is executed.

FIG. 9 shows an operation panel 113 used in this embodiment.
The details are shown below.

In FIG. 9, the same components as those in FIG. 1 are denoted by common numbers. A correction mode key 901 is a key for designating execution of the standard white plate density correction mode described in the above embodiment.

FIG. 10 shows a control flow of the CPU relating to the control of the reading operation in this embodiment. As shown in the figure, a standard white plate density measurement mode, a document reading operation, and a standard white plate density correction mode are respectively executed in response to key inputs of the SMP key 114, the reading start key 115, and the correction mode key 901.

Note that the standard white plate density correction mode is executed based not only on the input of the correction mode key but also on the basis that the standard white plate density measurement mode is not being executed or that the original is not being read.

In this embodiment, as in the previous embodiment, the start of document reading is not limited to key input, but may be a command by communication such as a command from an external device. Similarly, it may be a command by communication such as a command from an external device.

As described above, when the standard white plate density correction mode is executed in synchronization with the first document reading after the power is turned on, the power-on operation of the reading apparatus used while the power is continuously turned on is not performed. Since this is not performed, the standard white plate density correction mode is not executed.

The following embodiment takes such a case into consideration, and executes the standard white plate density correction mode when the number of document readings exceeds a predetermined number. In this embodiment, as an example, the standard white plate density correction mode is executed every time 100 or more originals are read.

The operation panel in this embodiment is the same as that in the embodiment shown in FIG.

FIG. 11 is a control flowchart of the CPU relating to the control of the reading operation in this embodiment. After turning on the power, the CPU 106 determines a key input (step 11).
01). If the SMP key 115 is pressed, the standard white plate density measurement mode is executed (step 1102). Since the density value of the standard white plate is measured on a paper having a density of 0.05 on the platen, the cumulative copy count is calculated. The data value is cleared to zero (step 1107).

When the reading start key 1103 is input, the document is read (step 1103). In this case, the document is read by the number of times specified by, for example, a reading number specifying unit (not shown) such as a numeric keypad.

Next, the cumulative copy count data is increased by the number of times of reading this time (step 1104). This accumulated copy count data is set on the nonvolatile battery backup RAM 116 accessed by the CPU, and retains the set state even when the power is turned off. The value of the cumulative copy count data is the number of document readings since the previous execution of the standard white plate density measurement mode or the standard white plate density correction mode.

Next, the cumulative copy count data after the end of the series of document reading operations is checked (step 110).
5). Here, when the value of the cumulative copy count data is equal to or more than a predetermined value (100 times), it is determined that the density level of the image data has fluctuated due to the influence of the contamination of the reading optical system, and the standard white plate density correction mode is used. (Step 110)
6) Then, the value of the accumulated copy count data is cleared to zero (step 1107).

On the other hand, if the value of the cumulative copy count data is 1
If the key does not reach 00, the flow waits for a key input in step 1101 again.

In this embodiment, as in the previous embodiment, the start of document reading is not limited to key input, but may be a command through communication such as a command from an external device.

In this embodiment, when the value of the cumulative copy count data becomes equal to or more than a predetermined number, the standard white plate density correction mode is not immediately executed, but the cumulative copy count data is read before the next original reading operation. The count data value is checked, and if the count data is equal to or greater than a predetermined value at this point, the standard white plate density correction mode is executed, and then the original may be read. At this time, the value of the accumulated copy count data is checked, and if the value is equal to or more than a predetermined value at this time, the standard white plate density correction mode may be executed.

Also, in this embodiment, a means for determining whether or not the standard white plate density correction mode can be executed as described in the embodiment shown in FIG. 7 is provided. Even if the value has reached, the standard white plate density correction mode may not be executed. Here, when the value of the cumulative copy count data has reached the predetermined value and the standard white plate density correction mode is not executed, the value of the cumulative copy count data is not cleared to zero.

In the embodiment shown in FIG. 11, the standard white plate density correction mode is executed when the number of document readings exceeds a predetermined number. However, even if the apparatus is left in a state where the power is turned on without performing document reading, dust in the outside air may enter the reading apparatus due to operation of a fan for cooling an illumination lamp, for example, and the optical system may not operate. May get dirty. As a result, as described above, a difference occurs between the level of the read image signal and the actual document density. In this embodiment, such a case is taken into consideration, and the standard white plate density correction mode is executed when the cumulative energization time to the apparatus has exceeded a predetermined time.

In this embodiment, 10 hours (36000 seconds)
The standard white plate density correction mode is executed for each of the cumulative energizing times described above.

FIG. 12 shows a control block in this embodiment. Here, a timer 1201 attached to the CPU 106 is added to that of FIG. This timer 1
201 is a one-second clock SC from the oscillator 1202.
Count LK. And the port P4 of the CPU 106
Reset by the output, the count value of the timer 1201 is read by the CPU 106. The operation panel 113 in this embodiment is the same as that in the embodiment of FIG.

FIG. 13 shows a control flow of the CPU 106 relating to the control of the reading operation in the present embodiment. After turning on the power, the CPU 106 resets the timer 1201 (step 1301). Then, a key input is determined (step 1302).

When the SMP key 115 is input, the standard white plate density measurement mode is executed (step 1303).
By measuring the current correct density of the standard white plate 202, the value of the later-described cumulative timer count data is cleared to zero (step 1304).

When the reading start key 114 is input, the CPU 106 reads the value of the timer 1205 (step 1305) and resets the timer 1201. Then, the value of the accumulated timer count data is increased by the currently read timer value (step 1306).

This accumulated timer count data is stored in the CPU
The power OF is set on a nonvolatile battery backup RAM 116 accessed by the
Even if F is set, the setting state is maintained. The value of the accumulated timer count data is the accumulated energizing time since the previous execution of the standard white plate density measurement mode or the standard white plate density correction mode.

Next, the value of the accumulated timer count data is checked (step 1307). Here, if the value of the accumulated timer count data exceeds a predetermined value (36000 seconds), it is determined that the density level of the image data has fluctuated due to the influence of contamination of the reading optical system, and the standard white plate density The correction mode is executed (step 1308), and the value of the accumulated copy count data is cleared to zero (step 130).
9).

On the other hand, if the value of the cumulative copy count data is 3
If the time does not reach 6000 seconds, the original is read (step 1310).

In this embodiment, as in the previous embodiment, the start of document reading is not limited to key input, but may be a communication command such as a command from an external device.

Also, in this embodiment, instead of checking the value of the accumulated timer count data and executing the standard white plate density correction mode before reading the original, the value of the accumulated timer count data is not changed at the end of the original reading operation. Is checked, and if it is equal to or more than a predetermined value at this time, the standard white plate density correction mode may be executed.

Similarly, in step 1302, the accumulated timer count data may be updated during the key input judgment, and the standard white plate density correction mode may be executed irrespective of the original reading.

Also in this embodiment, a means for determining whether or not the standard white plate density correction mode described in the previous embodiment can be executed is provided. If the standard white plate density correction mode cannot be executed, the value of the accumulated timer count data has reached a predetermined value. However, the standard white plate density correction mode may not be executed. Here, when the value of the accumulated timer count data has reached the predetermined value and the standard white plate density correction mode is not executed, the value of the accumulated timer count data is not cleared to zero.

In the embodiment shown in FIG. 9, the operation panel is provided with a standard white plate density correction mode execution key. Then, when the operator presses this key, the standard white plate density correction mode is executed.

In the following embodiment, similarly to the embodiment shown in FIG. 11, it is detected that the number of document readings has exceeded a predetermined number, and it is necessary for the operator or an external This is to notify the connected device. That is,
In the present embodiment, as an example, the need to execute the standard white plate density correction mode is notified every time 100 or more originals are read.

FIG. 14 shows the operation panel 11 used in this embodiment.
3 is shown in detail.

In the figure, the same components as those in FIG. 1 are denoted by common numbers. The correction mode key 901 is a key for designating execution of the standard white plate density correction mode described in the embodiment of FIG. The LED 1401 is an LED for notifying the operator of the execution of the standard white plate density correction mode. The LED 1401 is turned on at the time of the notification, and goes off when the standard white plate density measurement mode or the standard white plate density correction mode is executed.

FIG. 15 shows a control flow of the CPU 106 relating to the control of the reading operation in this embodiment. After the power is turned on, in steps 1501, 1502, and 1503, the lighting of the LED 1401 is controlled according to the value of the accumulated copy count data. Then, as shown, SMP key 1
15, reading start key 114, correction mode key 901
Steps 1505 and 150 corresponding to each key input of
In steps 6 and 1508, a standard white plate density measurement mode, an original reading operation, and a standard white plate density correction mode are executed.

After reading the document, the value of the cumulative copy count data is increased by the number of times of reading the document in step 1507.
In step 1501, lighting control of the LED 1401 is performed according to the result.

After executing the standard white board density measurement mode and the standard white board density correction mode in steps 1507 and 1508, the value of the accumulated copy count data is cleared in step 1508.

Here, the cumulative copy count data is shown in FIG.
This is equivalent to that of the embodiment shown in FIG.

In this embodiment, as in the previous embodiment, the start of document reading is not limited to key input, but may be a command by communication such as a command from an external device. The notification of necessity is not limited to LED display, but may be notification by communication of status information or the like to an external device.

In addition, the notification here indicates the necessity of the standard white plate density correction mode, but also the necessity of the standard white plate density measurement mode. Therefore, the operator or the external connection device may execute the standard white plate density measurement by the key input or the command of the communication unit by the notification.

In the embodiment shown in FIG. 15, the necessity of executing the standard white plate density correction mode is notified based on the cumulative number of read originals. In the present embodiment, as in the embodiment shown in FIG. Notifies that the standard white plate density correction mode needs to be executed. In this embodiment, the operation unit shown in FIG. 14 is used. The control block shown in FIG. 12 is used.

FIG. 16 shows a control flow of the CPU 106 in this embodiment. Here, the cumulative timer count is equivalent to that used in FIG.

After the power is turned on, the timer 1201 is reset in step 1601. Then, step 1602,
In step 1603, the count value (second unit) of the timer 1201 is read, and the value of the accumulated timer count data is updated. In steps 1604, 1605, and 1606, lighting control of the LED 1401 is performed based on the value of the accumulated timer count data.

Next, in step 1607, a key input is determined, and a process according to the input key is performed. If there is no key input, the process returns to step 1602 to update the value of the accumulated timer count data.

After executing the standard white board density measurement mode and the standard white board density correction mode in steps 1508 and 1510, the value of the accumulated timer count data is cleared in step 1611.

In this embodiment, as in the previous embodiment, the start of document reading is not limited to key input, but may be a command by communication such as a command from an external device. The notification of necessity is not limited to LED display, but may be notification by communication of status information or the like to an external device.

As described above, a reference patch having a predetermined density is provided outside the document reading area, and means for measuring a change in a read signal from this patch and a read signal of a standard density plate (standard white plate) are provided. An interval for the operator to clean the optical system by providing a means for controlling the execution of the measuring means and measuring the brightness of the standard density plate at a necessary and sufficient frequency without affecting the reading operation. And the stability of the device is improved.

Further, the standard white plate density correction mode is executed in accordance with the actual degree of contamination of the apparatus, and the necessity of the standard white plate density correction mode and the standard white plate density measurement mode is notified. Accordingly, the unusable time for correcting the reading device can be minimized, and the running cost of the device can be reduced.

As described above, the first standard member obtained by reading the first standard member provided outside the platen on which the original is placed is obtained.
In the configuration for correcting the non-uniformity of the image signal obtained by reading the image of the original based on the standard signal of the above, based on the second standard signal obtained by reading the second standard member provided on the platen In addition, the compensation operation for the non-uniformity of the image signal is compensated, and the compensation operation is appropriately permitted, so that the non-uniformity of the image signal can always be corrected well without wasting time.

FIG. 17 is a schematic diagram relating to the measurement of the density of the standard white plate 202 in another embodiment using the present invention. FIG. 18 shows a flowchart of the measurement procedure.

In the embodiment shown in FIG. 17, a total of four reference patches are provided before and after in the main scanning direction and before and after in the sub-scanning direction.

P1 is the rear side in the main scanning direction (main scanning addresses 4744 to 4744) similarly to the patch 301P of the embodiment of FIG.
999) on the front side in the sub-scanning direction (B position at 10 cm in the sub-scanning direction from the standard white plate). P2 is located at the same position as P1 in the main scanning direction, and on the rear side in the sub-scanning direction (30c from B).
m rearward (C position). P3 is on the front side in the main scanning direction (main scanning address 0 to 255) and on the front side in the sub-scanning direction (position B). P4 is on the front side in the main scanning direction (main scanning address 0 to 255) and on the rear side in the sub-scanning direction (position C).

In this embodiment, by providing the reference patches P1 to P4 at the four points described above, it is possible to cope with differences in stains of the optical system and the standard white plate 202 in the main scanning direction and differences in illumination conditions in the sub-scanning direction. Standard white plate 202
In the density correction mode.

(Standard White Plate Density Measurement Mode) As in the embodiment of FIG. 4, in this mode, the operator presses the SMP key 115 on the copy plate having a reflection density of 0.05 which is usually used, on the original platen 15.

When the press of the SMP key 115 is detected,
The PU turns on the lamp 205 in the same manner as in the above-described embodiment,
The mirror 206 is moved to the position B, and the average value Pa of the read signals from the patches P1, P3 and the copy paper CPP is moved.
ve1, Pave3, and Wave1 are obtained (Step 7)
01-707).

Next, the CPU moves the optical system again, and
The mirror 206 is moved to the position C, and the patches P2, P4,
Average value Pav of read signal from each copy paper CPP
e2, Pave4, and Wave2 are obtained by the same method as in the above-described embodiment (steps 708 to 712).

Next, the CPU moves the optical system to the position (position A) of the standard white plate 202 in the same manner as in the above-described embodiment, and averages the read signals of the main scanning addresses 0 to 255 corresponding to the patches P3 and P4. The value Bave3 is obtained.

Further, the average value Bave1 of the read signals at the main scanning addresses 2500-2755 corresponding to Wave1 and Wave2 is obtained. Further, the average value Bave2 of the read signals of the main scanning addresses 4744 to 4999 corresponding to the patches P1 and P2 is obtained (steps 713 to 717).

Here, the ratio of Wave1 to Wave1 is the ratio of the density of the standard white plate and the density of the copy paper at the B position in the light amount conversion value, as in the first embodiment. When the light quantity conversion value of the density of 0.05 of the copy paper is normalized to a level of 255 by an 8-bit digital signal, the light quantity conversion value Bd11 of the density of the standard white plate becomes Bd11 = 255 × (Bave1 / Wave1).

Further, the light quantity conversion value B of the density of the standard white plate from the read value Wave2 value of the copy sheet at the C position in the sub-scanning direction
D12 is Bd12 = 255 × (Bave2 / Wave2).

When the optical system is scanned in the sub-scanning direction, the mirrors 206, 207, and 208 may have slight deviation in parallelism,
Due to the misalignment of the mirror, even if the same original is read, the read signal value is not always the same before and after in the sub-scanning direction.

For this reason, in this embodiment, a read signal from a copy paper having a density of 0.05 is obtained from two points in the sub-scanning direction, and a light quantity conversion value of the density of the standard white plate 202 of Bd11 and Bd12 is obtained from each. The average value is defined as the density value Bd1 of the standard white plate.

The CPU operates in the same manner as in the above-described embodiment.
1, Wave2, Pave1, Pave2, Pave
3, Pave4, Bave1, Bave2, Bave
3 and Bd1 are stored in the nonvolatile memory (step 71).
9).

Then, in the same manner as in the above-described embodiment, in the original reading immediately after the standard white plate density measurement mode, the shading correction is performed with Bd = Bd1.

(Standard White Plate Density Correction Mode) As described above, if the reading operation is performed for a long time, the Bd value changes due to dust and oil vapor. Further, the dirt on the mirror is not always uniform in the main scanning direction.

Bd in the main scanning direction due to the uneven dirt
In this mode, in order to optimally correct the change in the reading state in the sub-scanning direction due to the change in the value and the variation in the mounting accuracy of the mirror system, the read value Pave1 from the current four patches P1, P2, P3, and P4. ', Pave2', Pave
3 ', Pave4' and read value Bave from standard white plate
2 ′, Bave 3 ′ and Wa stored in the nonvolatile memory
ve1, Wave2, Pave1, Pave2, Pav
e3, Pave4, Bave1, Bave2, Bave
3 and Bd1, the ratio Bd1 'of the light intensity conversion value of the density between the standard white plate and the copy paper at that time is equivalently obtained according to the procedure shown in FIG.

That is, in the same manner as in the previous embodiment, when the power is turned on, the standard white plate density measurement mode is entered, and the four-point patch P1
To P4 and the read value from the standard white plate 202 are obtained.

First, the CPU turns on the illumination lamp 205, moves the mirror 206 to the position B,
The average values Pave1 'and Pave3' of the read values of 256 pixels in the main scanning direction from P1 and P3 are obtained (step 8).
01-806).

Next, the CPU moves the mirror 206 to the position C to obtain the average values Pave2 'and Pave4' of the read values of 256 pixels in the main scanning direction from the patches P2 and P4 (steps 807 to 810).

Then, the CPU brings the mirror 206 to the position A of the standard white plate 202. And patches P1, P2
Is obtained, the average value Bave2 'of the read signals at the main scanning addresses 4744 to 4999 is obtained.

Further, the average value Bave3 'of the read signals of the main scanning addresses 0 to 255 corresponding to the patches P3 and P4 is obtained (steps 811 to 814).

Thereafter, the measured value Pave1 'from the position B is obtained.
And Pave3 ', the value Wave1 of the copy sheet of density 0.5 on the original platen 15 in the same manner as in the above-described embodiment.
1 ′ and Wave 13 ′ are obtained.

Wave11 'obtained by calculation from Pave1' is Wave11 '= (Pave1' / P
ave1) × Wave1, and Wave13 ′ obtained by calculation from Pave2 ′ is Wave13 ′ =
(Pave2 ′ / Pave2) × Wave1.

The patch measurement values at two different points in the main scanning direction at the B position are based on the illumination state at each patch position. Since the degree of dirt on the optical mirror between the patch P1 and the patch P3 often changes slowly, the density of the current density on the original platen 203 is set to 0.
The value Wave1 'of the copy paper CPP of No. 5 is Wave1.
It may be regarded as the average value of 1 'and Wave 13'. Therefore, Wave1 ′ = １ ／ (Wave11 ′ + Wave1)
3 ').

Similarly, the current value B at the center of the standard white plate
ave1 'is a calculated value Bave12' from Bave2 '
And the average value of the calculated values Bave13 'from Bave3'.

In the same manner as in the embodiment of FIG.
2 ′ and Bave 13 ′ are obtained by Expression 2.

[0174]

[Outside 2]

From this average value, Bave1 '= 1/2
(Bave12 '+ Bave13').

Calculated value Wa of Wave 1 obtained at position B
Ve1 ′ and the above calculated value Bave1 ′, a density of 0.5
In order to perform the shading correction so that Wave1 ′ corresponding to the original of No. becomes 255, the shading correction is performed so that the read value from the standard white plate 202 becomes the value of Bd1B ′ in Expression 3.

[0177]

[Outside 3]

This is the ratio Pa of the read values of the patches P1 and P3 obtained in the standard white plate density measurement mode to the current read value.
Vave1 '/ Pave1, Pave3' / Pave3, and ratio Bave2 '/ Bave of the read values of the standard white plate 202
2, Bave3 '/ Bave3) means that Bd1 is corrected to obtain the current shading correction target value Bd1B'.

After Bd1B 'is obtained from the measured value of the patch at the position B, similarly, the target value Bd1C' for shading correction is obtained from the measured value of the patch from the position C by the following equation.

[0180]

[Outside 4]

The rate of change of the amount of light from the patch read at the B position and the rate of change of the amount of light from the patch read at the C position are not constant due to the parallelism of the mirror and the change in the mounting angle that vary depending on the sub-scanning position. Therefore, in the present embodiment, the target values of the shading correction from two points (the B position and the C position) in the sub-scanning direction are separately calculated and averaged.

That is, from Bd1B 'and Bd1C', the correction target value Bd1 'for shading correction of the read data from the standard white plate 202 is Bd1' = 1/2 (Bd1B '+ Bd1C').

In the subsequent document reading, shading correction is performed with Bd = Bd1 'as in the previous embodiment.

Although the embodiment described above is a mono-black reading apparatus, an example in which the present invention is applied to a color reading apparatus will be described below.

FIG. 21 is a cross-sectional view of the color reading apparatus used in this embodiment, which is basically the same as the reading apparatus shown in FIG. 2, except that the photoelectric conversion element 210 is provided with R, G, and R for color reading.
It is a monolithic CCD 1001 of B3 line. The configuration of the CCD 1001 is shown in FIG.

CCD sensors 1103, 1104, 110
5 are formed on the same chip 1102 in parallel at an interval of 180 μm. A red (R) filter is applied to the sensor 1103, a green (G) filter is applied to the sensor 1104, and a blue (B) filter is applied to the sensor 1105.

The number of pixels of each CCD sensor is about 5,000 pixels, and 297 mm in the longitudinal direction of an A4 document is 400 dots.
It can be read at a resolution of s / inch.
Reference numeral 1106 is an enlarged view of the sensor portion, where one pixel width is 10 μm.
m, and the distance between the sensors is 180 μm.

FIG. 20 shows a signal processing section in this embodiment. It has basically the same configuration as the embodiment of FIG.
Corresponds to the three systems, the amplifier, the A / D converter, the first memory, the second memory, and the multiplier have three systems.

(Original Reading Operation) The original reading is basically the same as that of the above-described embodiment, and the shading correction operation is also performed.
It operates independently for each of the R, G, and B color signals.

The target value Bd for correcting the read signal from the standard white plate 202 by shading correction is also set independently for the three colors R, G, and B, and becomes BdR, BdG, and BdB, respectively.

(Standard White Plate Density Measurement Mode) In this mode, the same measurement as in the previous embodiment is performed for each of the three colors R, G, and B. The procedure is shown in FIG.

According to the read value Wave from the copy paper having the density of 0.05 in the above-described embodiment, R, G, B
WaveR, WaveG, and WaveB are measured and calculated (Steps 1201 to 1206).

Similarly, PaveR, PaveG, and PaveB are measured corresponding to the read value Pave from the patch P.
It is calculated (step 1207).

Similarly, Bave from standard white plate 202
Rave 1, Bave2, R1, G, B
R, Bave2R, Bave1G, Bave2G, Ba
ve1B and Bave2B are measured and calculated (step 1).
208-1212).

Since the copy paper is white with a density of 0.05, the light amount conversion value of the 8-bit multivalued signal is R,
Both G and B are normalized to a level of 255.

As a result, the light quantity conversion values Bd1R, Bd1G, and Bd1B of the densities of the standard white plates of R, G, and B are given by Equation (5).

[0197]

[Outside 5]

The CPUs are WaveR, WaveG, and Wa.
veB, PaveR, PaveG, PaveB, Bav
e1R, Bave1G, Bave1B, Bave2R,
Bave2G, Bave2B, Bd1R, Bd1G, B
d1B is replaced with a nonvolatile battery backup RAM 116
(Step 1214).

In reading a document immediately after the standard white plate density measurement mode executed by the SMP key 115, BdR = Bd1
The above-described shading correction is performed with R, BdG = Bd1G and BdB = Bd1B.

(Standard White Plate Density Correction Mode) This mode is also executed for each of the three colors R, G, and B in the same manner as in the above-described embodiment.

PaveR 'and PavR' correspond to read data Pave 'from patch 301P in the embodiment of FIG.
eG 'and PaveB' are measured and obtained (step 13).
01 to 1306).

Then, corresponding to Bave2 ', Bave
2R ', Bave2G', and Bave2B 'are measured and calculated (steps 1307 to 1310).

The calculated value of the 0.05 density copy paper on the original platen 203 in the illumination state when this mode is executed is R,
G and B are each obtained by Expression 6.

[0204]

[Outside 6]

Similarly, the values from the standard white plate 202 can be obtained by R, G, and B using Equation (7).

[0206]

[Outside 7]

The standard white plate 202 during the execution of this mode
The value of the blank paper on the platen is WaveR ', W
Both aveG 'and WaveB' are corrected to 255. Therefore, the target values for correcting the read value from the standard white plate 202 by shading correction are R, G, and B, respectively, as shown in Equation 8 (Step 1311).

[0208]

[Outside 8]

The above-described Bave1R ', Bave1G',
Wave1B ', WaveR', WaveG ', Wav
By substituting the expression of eB ′, Expression 8 becomes Expression 9.

[0210]

[Outside 9]

As in the above-described embodiment, in reading the original after executing this mode, BdR = Bd1R ', BdG = Bd1G',
The above-described shading correction is performed with BdB = Bd1B ′.

As a result, when the copy paper having a density of 0.05 on the original platen 203 is read with shading correction, the video from each pixel of the R, G, and B color CCDs is obtained.
The signal is output as 255 normalized values.

As shown in FIG. 17, it is also possible to provide a plurality of patches and perform the processing for each of R, G, and B for each color.

In the above-described embodiment, the reference of the density is copy paper immediately after unsealing at a density of 0.05 placed on the platen 203 of the document table. However, if the density of the patch is strictly controlled, a signal read from the patch can be used as a reference for the density of the apparatus.

In this case, in the standard white plate density measurement mode, Bave1 and Wave measured at addresses 2500 to 2755 in the main scanning address are replaced with Bave.
2 and Pave are used. That is, when the patch density is 0.05, the 8-bit light amount conversion value corresponds to 255, so that Bd1 = 255 × Bave2 / Pave. When the density of the patch is 240 in terms of the light amount conversion value, Bd1 = 240 × Bave2 / Pave.

In the standard white plate density correction mode, a correction target value Bd1 'for shading correction for a signal read from the standard white plate is obtained by equation (10).

[Equation 10] Bd1 ′ = Bd1 × (Bave2 ′ / Pave ′) / (Bave2 / Pave) = 255 × (Bave2 ′ / Pave ′)

In this case, the same process is performed in the standard density plate density correction mode and the standard white plate density measurement mode.

In this embodiment, the target value Bd1 for shading correction is determined using only the ratio between the signal value read from the standard white plate and the signal value read from the patch.

As described above, a reference patch of a predetermined density is provided outside the original reading area, and the brightness of the standard white plate is measured from the read signal from this patch and the change in the read signal of the standard white plate. Even if the standard white plate or the optical system changes due to dirt or the like, a document of a predetermined density on the document table is always automatically calibrated to a signal value corresponding to the density. As a result, there is an effect that the interval at which the operator cleans the optical system becomes longer, and the operability and stability of the apparatus are improved.

[0221]

As described above, according to the present invention,
Good image signal non-uniformity can always be corrected without being affected by aging or contamination of the standard member.

[Brief description of the drawings]

FIG. 1 is a signal processing circuit diagram according to an embodiment of the present invention.

FIG. 2 is an apparatus configuration diagram of a reading apparatus according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a standard white plate density measurement in an example of the present invention.

FIG. 4 is a control flowchart of a standard white plate density measurement according to the embodiment of the present invention.

FIG. 5 is a control flowchart of a standard white plate density correction according to the embodiment of the present invention.

FIG. 6 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 7 is a diagram of an operation unit according to the embodiment of the present invention.

FIG. 8 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 9 is a diagram of an operation unit according to the embodiment of the present invention.

FIG. 10 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 11 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 12 is a signal processing block diagram according to an embodiment of the present invention.

FIG. 13 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 14 is a diagram of an operation unit according to the embodiment of the present invention.

FIG. 15 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 16 is a control flowchart of the reading apparatus according to the embodiment of the present invention.

FIG. 17 is a schematic view of a standard white plate density measurement according to another embodiment of the present invention.

FIG. 18 is a control flowchart of a standard white plate density measurement according to another embodiment of the present invention.

FIG. 19 is a control flowchart of a standard white plate density correction according to another embodiment of the present invention.

FIG. 20 is a block diagram of a signal processing circuit diagram device according to another embodiment of the present invention.

FIG. 21 is a diagram showing the configuration of a reading apparatus according to another embodiment of the present invention.

FIG. 22 is a configuration diagram of a color CCD used in another embodiment of the present invention.

FIG. 23 is a control flowchart of a standard white plate density measurement according to another embodiment of the present invention.

FIG. 24 is a control flowchart of a standard white plate density correction according to another embodiment of the present invention.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/401

Claims (13)

(57) [Claims] 1. A platen on which a document is placed, reading means for reading an image of the document placed on the platen and outputting an image signal, and a measuring means for measuring the non-uniformity of the output of the reading means. The first
A second standard member having a predetermined reference density, and a first standard member obtained by reading the first standard member with the reading means.
An image of the document is obtained by reading the image of the document by the reading unit based on the standard signal of the reference document and a reference density signal obtained by reading the reference document having a predetermined reference density placed on the platen by the reading unit. Correcting means for correcting the non-uniformity of the image signal; and a second means for reading the second standard member by the reading means.
And a compensating means for compensating the correcting operation by the correcting means based on the standard signal. 2. The image reading apparatus according to claim 1, wherein the second standard member is provided at a position having an environmental condition in which the rate of change in density is lower than that of the first standard member. . 3. The image reading apparatus according to claim 2, wherein the second standard member is provided on the platen. 4. The image reading apparatus according to claim 2, wherein the first standard member is provided inside a housing of the reading apparatus. 5. The image reading apparatus according to claim 1, further comprising a feeding unit for feeding a document onto the platen. 6. The method according to claim 1, wherein the correction unit determines a target value based on the first standard signal and the reference density signal, and corrects the non-uniformity of the image signal using the determined target value. The image reading device according to claim 1. 7. The image reading apparatus according to claim 6, wherein the compensating means compensates the target value used for correcting nonuniformity of the image signal based on the second standard signal. 8. The apparatus according to claim 6, wherein said correction means includes a nonvolatile storage means for storing a target value determined based on said first standard signal and said reference density signal.
The image reading device according to claim 1. 9. A platen on which a document is placed, reading means for reading an image of the document placed on the platen and outputting an image signal, and a measuring means for measuring the non-uniformity of the output of the reading means. The first
A standard member having a predetermined reference density; and a correction unit configured to correct non-uniformity of the image signal obtained by reading the image of the document by the reading unit. In the mode, the correction unit includes a first standard signal obtained by reading the first standard member by the reading unit, and a reference document having a predetermined reference density placed on the platen by the reading unit. A target value is determined based on the reference density signal obtained by reading the target value, and the determined target value is used to determine the target value.
Correcting the non-uniformity of the image signal, and in the second mode,
The correction means includes: a first standard signal obtained by reading the first standard member by the reading means;
Based on the second standard signal obtained by reading the standard member of
Compensating the target value and using the compensated target value to generate the image
An image reading device for correcting non-uniformity of a signal . 10. The image reading apparatus according to claim 9, wherein the second standard member is provided at a position having an environmental condition in which the rate of change in density is lower than that of the first standard member. . 11. The image reading apparatus according to claim 10, wherein the second standard member is provided on the platen. 12. The image reading device according to claim 10, wherein the first standard member is provided inside a housing of the reading device. 13. The image reading apparatus according to claim 9, further comprising a feeding unit for feeding a document onto the platen.