JPH08172530A - Image reader - Google Patents

Abstract

PURPOSE: To attain a high speed of the reader and to reduce the load on a control section by allowing a control section to control shading correction and image processing in the unit of blocks and designating a line in the block to adopt shading distortion data. CONSTITUTION: The reader is provided with a line unit control section 25 in addition to a system control section 1, the system control section 1 sets control data by prescribed plural lines to the line unit control section 25 altogether, the line unit control section 25 stores the control data altogether and provides the output of the data to a shading correction section 22 and a digital image processing section 23 sequentially in the unit of lines synchronously with a line synchronizing signal. The system control section 1 adopts block unit control in the unit of plural lines for the control of the shading correction section 22 and the digital image processing section 23 and the collection of shading distortion data is executed by using a shading distortion data collection means in which a prescribed line in the block is designated and a series of processing relating to the collection of the shading distortion data is conducted.

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 used in a facsimile machine, a digital copying machine, an image scanner or the like, and more particularly to shading correction thereof.

[0002]

2. Description of the Related Art FIG. 15 is a block diagram showing the basic structure of a general facsimile apparatus. In the figure, reference numeral 1 denotes a system control unit that performs control processing of each unit of the apparatus and processing of a facsimile transmission control procedure, and is realized by a CPU (central processing unit). 2 is a system memory that stores a control processing program executed by the system control unit 1 and various data necessary for executing the control processing program, and that constitutes a work area of the system control unit 1, and 3 is a G3 facsimile apparatus. Parameter memory 4 for storing various information unique to the scanner, 4 is a scanner (image reading device) for scanning an original at a predetermined resolution to read an image, and performing various predetermined image processing on the read image. A plotter 6 for recording image-processed image data or image data received from another facsimile apparatus at a predetermined resolution is an operation panel for operating this apparatus, and includes various operation keys and various display devices.

Reference numeral 7 is an encoding / decoding unit for encoding and compressing the read image data, or for decoding the encoded and compressed image data into the original image data, and 8 is the image data in the encoded and compressed state. Is an image storage device for storing the G3 facsimile device, and 9 is a device for realizing the modem function of the G3 facsimile device. The low-speed modem function (V.21 modem) for exchanging a transmission procedure signal and mainly the image data are stored. High-speed modem function for communicating (V.29 modem,
V. A modem 10 equipped with a 27 ter modem is used to connect the facsimile apparatus to a public line, and a network control unit (NCU; Network Cont
roll unit).

These system control unit 1, system memory 2, parameter memory 3, scanner 4, plotter 5,
The operation panel 6, the encoding / decoding unit 7, the image storage device 8, the modem 9, and the network control device 10 are connected to a system bus 11, and data is exchanged among these elements mainly in the system bus 11. However, data is exchanged directly between the modem 9 and the network control device 10.

FIG. 16 shows an example of the construction of an image reading apparatus in such a facsimile. In the figure, 12
Is a manuscript to be read, 13 is a contact glass for guiding the conveyance of the manuscript 12 and preventing dust and the like from entering the optical system, 14 is a light source for illuminating the manuscript 12, and 15 is a shading distortion correction caused by the optical system. A white reference member for reference, 16 is a mirror group for guiding the reflected light from the original 12 or the white reference member 15 by a predetermined optical path length (in the figure, collectively represented by one mirror), 17 is a mirror group 16 A lens for forming a document image guided by
Is an image sensor for photoelectrically converting the optical information formed by the lens 17 into an electric signal.

Reference numeral 19 denotes an operational amplifier (opamp) for amplifying an analog signal from the image sensor 18 at a predetermined magnification, and 20 denotes an image signal 1 amplified by the operational amplifier 19.
A peak detector that detects and holds the maximum value of the line, 21 is an A / D (analog / digital) converter that quantizes an image signal based on the peak level held by the peak detector 20, and 22 is an A / D A shading correction unit that corrects shading distortion caused by the characteristics of the optical system is applied to the image data quantized by the converter 21, and 23 is subjected to various image processes on the image data from which the distortion is removed by the shading correction unit 22. A digital image processing unit, 24 is a shading correction unit 22 and a digital image processing unit 23.
It is a line buffer that stores various data referred to in (1). The shading correction unit 22 and the digital image processing unit 23 are each controlled by the system control unit 1.

In the above arrangement, the system controller 1 turns on the light source 14 before reading the original 12. Light emitted from the light source 14 passes through the contact glass 13 and reaches the white reference member 15. Part of the irradiation light is reflected according to the reflectance of the white reference member 15, and part is transmitted (absorbed). The reflected light is classified into two types, specular reflection light and irregular reflection light, and a part of the irregular reflection light is guided through the mirror group 16 and is imaged on the image sensor 18 by the lens 17.
The image sensor output at this time is quantized by the A / D converter 21 via the operational amplifier 19, and is stored in the line buffer 24 as white reference data (shading distortion data) via the shading correction unit 22.

At the time of reading the original, since the original 12 enters the optical path, the irradiation light is reflected and transmitted by the original surface, and the diffuse reflection component is similarly imaged on the image sensor 18. At this time, the shading correction unit 22 reads the previously stored white reference data for each corresponding pixel and performs a predetermined correction calculation. The image data after the distortion correction is input to the digital image processing unit 23 and various image processing is performed.

The series of operations are controlled by software by the system controller 1. The system control unit 1 executes various line-unit control related to shading correction and image processing by using an interrupt generated for each line of main scanning as a trigger.

FIG. 17 is a flow chart showing an example of image data fetch control at the time of reading a document. When the reading of the original is started, the system control unit 1 determines whether the corresponding line data is valid or invalid according to the interrupt for each line (determination 1).
01, 102). If valid, data capture signal N
"1" is set to DRQ (process 103), and if it is invalid, "0" is set (process 104). The shading control unit 22 and the digital image processing unit 23 process the data of the corresponding line according to the set value of the data capture signal NDRQ. In the system control unit 1, the line-by-line intervention in the shading correction unit 22 and the image processing unit 23 is repeated until the reading of the document is completed (determination 10).
5 → decision 101).

As described above, in an image reading apparatus used for a facsimile or the like, a standard white member is usually scanned prior to reading a document to correct shading distortion caused by the optical transfer characteristics of the optical system. Data is sampled, and at the time of reading the original, various image processes are performed after distortion correction based on the data. Generally, the shading distortion data is collected by controlling a series of operations on a line-by-line basis by a software before reading a document.

FIG. 18 is a flow chart showing an operation example of such shading distortion data collection. The system control unit 1 first turns on the light source 14 (process 201) and starts the conveyance of the document (process 202). When the document reaches a predetermined position (decision 203), the document is stopped (process 204), synchronized with the line synchronization signal LNSYNC (decisions 205, 207, 209), the peak value is reset (process 206), and the peak value is detected (process 206). Software controls each operation of processing 208) and white reference data collection (processing 210).

FIG. 19 shows a conventional example of shading correction. It should be noted that the shading correction unit 22 shown in FIG.
Conversion etc. shall be included. The system control unit 1 is shown in FIG.
Based on the flowchart of FIG. 8, control signals for resetting the peak value, detecting the peak value, and collecting white reference data are output to the shading correction unit 22, and the shading correction unit 22 performs a predetermined operation according to these control signals. The white reference data is sequentially stored in the line buffer 24.

FIG. 20 shows an outline of this operation. In the peak value reset mode, the peak value (quantized reference level when white reference data is collected) Vp is set (reset) to a value sufficiently lower than the white reference member scanning signal Vw. In the peak value detection mode, the peak value Vp is set to a value sufficiently larger than the white reference member scanning signal Vw, the white reference member scanning signal Vw is quantized, and the maximum value at that time is detected and held. Then, in the white reference data collection mode, the peak value Vp is set to the maximum value of the white reference member scanning signal Vw previously detected, and the white reference member scanning signal Vw is quantized again. The quantized data is sequentially stored in the line buffer 24 as white reference data.

[0015]

As described above, in the conventional image reading apparatus, it is general to intervene software related to image processing including shading correction for each line of main scanning. . However, in recent years
With the shortening of the line cycle accompanying the speeding up of equipment, such software intervention for each line imposes a great load on the system control unit side, which is one of the factors that hinder the speeding up. Further, in the conventional device, when correcting the shading distortion, the original is conveyed to a predetermined position, the original is made to stand by at that position, and a series of operations related to the shading distortion data collection are mediated by software by the system control unit. I was doing it, but with the speedup of the equipment,
There were problems such as the load on the software control becoming heavy.

Further, when foreign matter such as paper dust exists on the scanning line when collecting the shading distortion data, the data whose level is lowered by the foreign matter is collected as white reference data. If the foreign matter itself deviates from the scanning line by itself, there is a problem that normal correction is not performed. On the other hand, JP-A-1-
No. 221062 discloses accurate shading correction by reading a plurality of positions on a white reference plate, storing a plurality of read data, comparing the respective data with each other, and selecting the data closest to the data representing white. It is proposed to be able to. However, in this case, the mechanism becomes complicated, and the data closest to white is simply selected from the plurality of data.
For example, when a foreign substance extends in the width direction of the white reference plate, accurate shading correction is not performed, and there arises a problem that a good image cannot be read.

The present invention has been made in order to solve such a problem, and it is possible to reduce the load on the control unit by reducing the intervention of software by the control unit and to speed up the equipment. An object is to provide an image reading device. Another object of the present invention is to provide an image reading apparatus capable of performing accurate shading correction even when an abnormality such as adhesion of foreign matter occurs and reading an excellent image.

[0018]

According to a first aspect of the present invention, a light source for irradiating a document to be read and a reflected light from the document illuminated by the light source are received via an optical system,
An image sensor that scans each pixel and converts it to an electrical signal, and a white reference member is scanned to collect shading distortion data due to the optical system for each pixel before reading the original. An image including a shading correction unit that corrects the distortion of the read image data based on the image processing unit, an image processing unit that performs various image processing on the shading-corrected image data, and a control unit that controls the shading correction unit and the image processing unit. In the reading device, control data for a plurality of main scanning lines are collectively set, line-line control means for sequentially outputting the set control data line by line to the shading correction unit and the image processing unit, and shading distortion data collection. Shading distortion data collection means for performing a series of such processes, and the control unit A predetermined plurality of lines of control data are collectively set in the line unit control means, and the shading correction unit and the image processing unit are controlled in block units in units of a plurality of lines. This is performed by the shading distortion data sampling means by designating a predetermined line in the block.

According to a second aspect of the present invention, a light source for irradiating a document to be read and reflected light from the document illuminated by the light source are received through an optical system and scanned for each pixel to generate an electric signal. Before scanning the image sensor and the document, the white reference member is scanned to collect the shading distortion data caused by the optical system for each pixel, and the distortion of the read image data is read based on the distortion data when reading the document. In an image reading apparatus including a shading correction unit that corrects, shading distortion data collecting means for performing a series of processes relating to shading distortion data collection, and when collecting shading distortion data, dealing with abnormal pixels due to foreign matter adhering to a scanning line And a foreign matter compensating means for interpolating the data.

According to a third aspect of the invention, the foreign matter compensating means detects foreign matter detecting means for detecting abnormal pixels due to the foreign matter adhering to the scanning line prior to sampling shading distortion data, and the detection result of the foreign matter detecting means. And an interpolation selection executing means for selectively executing the interpolation of the data corresponding to the abnormal pixel due to the foreign matter.

According to a fourth aspect of the present invention, the foreign matter detecting means compares the level difference between adjacent pixels with a foreign matter determination threshold value that can be set for a plurality of types to detect an abnormal pixel due to foreign matter adhesion. It is the one.

According to a fifth aspect of the present invention, when a plurality of kinds of main scanning read line densities are variable, a judgment threshold value switching means for changing the foreign matter judgment threshold value according to the main scanning read line density is provided. is there.

According to a sixth aspect of the present invention, when the foreign matter detection unit detects an abnormal pixel due to foreign matter adhesion, the abnormal pixel detection operation is performed again, and when the foreign matter detection occurs consecutively a predetermined number of times or more in the same pixel. Further, a control means for interpolating the corresponding data by the interpolation selection executing means is provided.

According to a seventh aspect of the present invention, the operation is performed when the foreign matter detecting means continuously detects an abnormal pixel in the same pixel or a region having a predetermined number of pixels over a plurality of shading distortion data sampling operations. It is provided with a control means for issuing a warning to a person.

[0025]

According to the structure of the first aspect, the line unit control means is provided separately from the control unit, so that the control unit performs software control relating to shading correction and image processing in blocks of a predetermined plurality of lines. Therefore, the frequency of software intervention by the control unit is reduced. Further, by providing a shading distortion data collecting means and controlling a series of shading distortion data collecting operations by hardware, the frequency of software intervention by the control unit is reduced. Further, by associating these with each other and designating the sampling timing of the shading distortion data by a predetermined line in the block, the frequency of software intervention by the control unit can be further reduced.

According to the second aspect of the present invention, by providing the shading distortion data collecting means and controlling the series of shading distortion data collecting operations by hardware, the frequency of software intervention is reduced, and
Since the foreign matter compensating means is provided, it is possible to interpolate the abnormal pixel data due to the foreign matter adhering to the scanning line.

According to the third aspect of the present invention, since the foreign matter compensating means is composed of the foreign matter detecting means and the interpolation selecting means, abnormal pixels due to the foreign matter adhering to the scanning line prior to the shading distortion data collection are detected. Detected, and if necessary, abnormal pixel data due to foreign matter is interpolated.

According to the structure of the fourth aspect, the foreign matter detecting means compares the level difference between adjacent pixels with a foreign matter determination threshold value, and if the level difference is larger than the determination threshold value, determines that the pixel is an abnormal pixel due to foreign matter adhesion. Further, since it is possible to set a plurality of types of foreign matter determination thresholds, it is possible to estimate the foreign matter adhesion position and the like.

According to the fifth aspect of the present invention, the determination threshold value switching means changes the foreign matter determination threshold value according to the read line density of the main scan, so that good foreign matter data interpolation can be performed regardless of the read line density.

According to the sixth aspect of the invention, when the abnormal pixel due to the foreign matter is detected, the abnormal pixel detection operation is performed again, and when the abnormal pixel due to the foreign matter is continuously detected for the same pixel a predetermined number of times or more. Since the abnormal pixel data is interpolated, excellent abnormal pixel data can be interpolated without following sudden noise.

According to the configuration of claim 7, when abnormal pixels are continuously detected in the same pixel or in a region having a predetermined number of pixels over a plurality of shading distortion data sampling operations, the operator is informed. A warning is issued to prompt the operator to maintain the equipment.

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration related to block unit control in an image reading apparatus according to an embodiment of the present invention, and the same reference numerals as those in FIG. 16 denote the same or corresponding portions. In the figure, reference numeral 25 is a line-unit control unit that sequentially outputs control data for a plurality of lines that are collectively set in line units.

The system control unit 1 sets the control data for a plurality of predetermined lines in the line unit control unit 25 at once.
Along with this, the software intervention from the system control unit 1 is reduced from the conventional line by the set line number interval.
The line-unit control unit 25 collectively holds the control data and sequentially outputs the control data to the shading correction unit 22 and the digital image processing unit 23 in line units in synchronization with the line synchronization signal LNSYNC. That is, conventionally, the system control unit 1
The line unit control unit 25 executes the control data setting operation which has been performed for each line by hardware by the hardware so that the system control unit 1 can change the conventional line unit control to the block unit control in units of a plurality of lines. As a result, the frequency of software intervention is reduced, the load on the system controller 1 side can be reduced, and the speed of the device can be increased.

FIG. 2 shows a configuration example of the line unit control section 25. In the figure, 25a is a control data holding register for storing control data set in block units, converting the data into line-by-line data and outputting the data, and 25b is a line synchronization signal LN.
A line number counter for counting SYNC and performing line management in the block, 25c sequentially selects control data for each line from the control data holding register 25a based on a signal from the line number counter 25b, and shading correction unit 22 and It is a multiplexer that outputs to the digital image processing unit 23.

Various control data relating to shading correction and image processing are collectively set in the control data holding register 25a in units of a plurality of lines. This control data is line-sequentially replaced in the register and output to the multiplexer 25c in the next stage. The line number counter 25b counts the line synchronization signal LNSYC and outputs the count value to the multiplexer 25c. The multiplexer 25c selects line control data corresponding to the relevant line in the block and outputs it to the shading correction unit 22 and the digital image processing unit 23. By providing the line unit control unit 25 as described above, the line unit control can be performed by the software intervention of the block unit.

FIG. 3 is a block diagram showing a configuration related to shading correction in the image reading apparatus according to the embodiment of the present invention, and the same reference numerals as those in FIG. 19 denote the same or corresponding portions. In the figure, reference numeral 26 is a peak value register for holding the peak value of the input image signal in a digital code, and 27 is a value (0 level or 0 level) for holding the value held in the peak value register 26 sufficiently lower than the image signal level at the time of scanning the white reference member. A peak value resetting unit for setting a predetermined offset level), a peak value detecting unit 28 for detecting and holding the maximum value of the image signal level during scanning of the white reference member,
Reference numeral 9 quantizes the white reference member scanning signal Vw with the peak value held by the peak value detecting unit 28 as a reference, and the quantized data is quantized data through the distortion correcting unit 22a.
The white reference data sampling unit 30 stores the peak value reset unit 27, the peak value detection unit 28, and the white reference data sampling unit 29 in sequence by a control signal from the system control unit 1.
Reference numeral 1 is a D / A converter for converting the digital peak code held by the peak value register 26 into an analog signal.
Here, the peak value register 26, the peak value resetting unit 27, the peak value detecting unit 28, and the white reference data collecting unit 29.
The sequence controller 30 constitutes a shading distortion data sampling means 22b that performs a series of processes related to shading distortion data sampling. In addition,
The distortion correction unit 22a corrects the shading distortion at the time of reading an image, and the distortion correction unit 22a and the shading distortion data sampling unit 22b constitute the shading correction unit 22.

When the system control unit 1 gives an instruction to collect white reference data, the sequence controller 30 first resets the value held in the peak value register 26 to a predetermined level by the peak value reset unit 27. Next, the peak value detector 28 sets the data of the peak value register 26 to, for example, full scale, quantizes the white reference member scanning signal Vw, and detects and holds the maximum value of the quantized data.

Thereafter, the white reference data sampling unit 29 quantizes the white reference member scan signal Vw using the peak value of the white reference member scan signal Vw as a reference, and the white reference data is distorted as white reference data normalized to the peak value. Correction unit 22
And is stored in the line buffer 24 via. When the reading of the original is started, the distortion correction unit 22 causes the line buffer 2
After reading the white reference data from No. 4 and performing a predetermined correction calculation on the input image data, various image processings are performed. In this way, by controlling the series of shading distortion data collection operations by hardware, the frequency of software intervention by the system control unit 1 is reduced, the load can be reduced, and the speed of the device can be increased. be able to.

The sequence controller 30 switches the operations of the peak value reset unit 27, the peak value detection unit 28, and the white reference data sampling unit 29 in synchronization with the line synchronization signal LNSYC, and determines the number of operating lines of each unit. By making it possible to set arbitrarily, control equivalent to software control can be performed by hardware.

According to the image reading apparatus of FIG. 3, the shading distortion data is collected only by the control signal from the system controller 1 to the sequence controller 30, so that it is not necessary to control the line unit as in the conventional case. .
Therefore, when the block unit control is performed as shown in FIGS. 1 and 2, the distortion data is sampled sequentially by setting only the line for collecting the shading distortion data, and the system control unit 1 It is possible to further reduce the frequency of software intervention. Therefore, the load on the system controller 1 can be significantly reduced, and the speed of the device can be sufficiently increased. In this case, the line unit controller 25 is provided between the system controller 1 and the sequence controller 30 shown in FIG. In addition, the system control unit 1 and the digital image processing unit 2
Illustration of the connection with 3 is omitted.

FIG. 4 shows an operation flowchart of the image reading apparatus (corresponding to claim 1) for performing block unit control with the above-described configuration of FIG. That is, when the operation is started, first, the number of lines in a block (LN = n) is set (process 30
1) After setting block control data for the set number of lines in the control data holding register 25a (process 30
2) The conveyance of the document is started (process 303). When the conveyance of the original is started, it is determined whether the line is a predetermined white reference data sampling line in synchronization with the line synchronization signal LNSYC (decision 304) (decision 305). If it is not the white reference data sampling line, the number of lines in the block LN is incremented (process 306), and the number of lines in the block L
It is determined whether or not N has become 0, and if it is not 0, the process returns to the process 304 and the subsequent processes are repeated. When the value becomes 0, the process returns to the first process 301 and the subsequent processes are repeated. On the other hand, if it is determined in the determination 305 that the line is the white reference data collection line, the process proceeds to step 308, the document conveyance is stopped, and the white reference data collection is instructed to the sequence controller 30 (process 309). A series of processing ends. After that, the sequence controller 30 controls execution of a series of processes related to shading distortion data collection.

Now, in the above-mentioned image reading device,
When the document is conveyed by transmitting the rotation of the stepping motor, if the motor is stopped while phase excitation is being performed when the white reference data is collected, the induced noise due to the excitation current will be superimposed on the white reference data. It is expected that there will be problems. Therefore, in the embodiment shown in the flow chart of FIG. 5, in order to prevent such a problem, the stepping motor is stopped at the time of collecting the white reference data, the phase excitation is also stopped, and the white reference data is set after the predetermined time has elapsed. The sampling prevents the induction noise from being superimposed on the white reference data. That is, in FIG. 5, when the stepping motor is stopped by the document conveyance stop process of process 408 in the same manner as the flow of FIG. 4, the phase excitation is also stopped in the next process 409. Then, after waiting for a predetermined time from the phase excitation stop (decision 410), white reference data is sampled (process 411).

In each of the above-mentioned image reading devices, strain data is uniquely sampled at a predetermined strain data sampling position. Therefore, even when there is abnormal data due to foreign matter such as dust adhering to the scanning line, this strain data is also collected. Cannot be identified and is taken in as correction data. If such a foreign substance deviates from the scanning line when the document is read, for example, due to the document transportation itself, the normal distortion correction is not performed on the pixel in which the abnormal data is taken in, and the image quality is deteriorated.
An image reading apparatus which prevents such a problem will be described below.

FIG. 6 shows an example of a problem when abnormal data due to a foreign substance adhering to a scanning line is taken in as distortion correction data. FIG. 6A shows a reference white waveform during normal operation and a white waveform after shading correction. The white waveform after correction has a uniform level, and the peak level Vp also follows the peak value of the image signal. On the other hand, FIG. 6B shows the waveforms before and after the distortion correction when the foreign matter adheres to the scanning line when the white reference data is collected and the foreign matter is removed when the document is read.
Since the white reference data of the foreign substance adhering portion is stored as a low level, it is corrected so as to be higher than other pixels when reading the original. However, if a foreign substance deviates from the scanning line during reading of the original, the level of the current signal will not drop, and the corrected image data will be overcorrected and projected. If the peak value Vp follows this protruding pixel, the peak value is excessively increased, and image deterioration such as background stain occurs.

FIG. 7 is a block diagram showing a configuration example relating to shading correction in the image reading apparatus according to claim 2, and the same reference numerals as those in FIG. 3 indicate the same or corresponding portions. As shown in the figure, the white reference data sampling unit 2
Reference numeral 9 has a foreign matter compensating means 29a, and the distortion correcting section 22
The white reference data stored in the line buffer 24 via a is detected by the foreign matter compensating means 29a.
After receiving the interpolation, it is stored in the line buffer 24. By including such foreign matter compensating means 29a, in addition to the effect of the embodiment of FIG. 3, abnormal pixel data due to foreign matter adhering to the scanning line can be interpolated, and good image reading can be performed. it can.

FIG. 8 is a block diagram showing a configuration example of the foreign matter compensating means 29a, which corresponds to claims 3 and 4. In the figure, 32 is a flip-flop (F / F1) that holds the digital data from the A / D converter 21 at a predetermined timing, and 33 is a flip-flop (F / F2) that holds the output data of the multiplexer 36 at a predetermined timing. ), 34 is a flip-flop (F / F2) 3
3, a subtractor for subtracting the value held by the flip-flop (F / F1) 32 from the value held by 3, a comparator 35 for comparing the output of the subtractor 34 with the threshold value TH from the system control unit 1, and a reference numeral 36 for the comparator 35. Flip-flop (F / F
1) A multiplexer that selects and outputs the value held in 32 or the flip-flop (F / F2) 33. here,
The subtractor 34 and the comparator 35 constitute the foreign matter detection means 37, and the flip-flop (F / F1) 32, the flip-flop (F / F2) 33 and the multiplexer 36 constitute the interpolation selection execution means 38.

In the white reference data collection mode, A / D
The digital data output from the converter 1 is the flip-flop (F / F1) 32 and the flip-flop (F / F1).
F2) 33 is sequentially held. Here, for the sake of convenience, the data held in the flip-flop (F / F1) 32 and the flip-flop (F / F2) 33 are an and an-1, respectively. These data are subtracted by the subtracter 34 (an-1
-An) is calculated, and the calculation result is input to the comparator 35. The comparator 35 compares the difference value from the subtractor 34 with a preset threshold value TH, and outputs, for example, an H level when the difference value is larger. This output signal is connected to the signal selection terminal of the multiplexer 36. When the signal level is H, an-1 is selected and output to the flip-flop (F / F2) 33. With this configuration, an abnormal pixel due to a foreign substance adhering to the scanning line is detected before the white reference data (shading distortion data) is collected, and the abnormal pixel data due to the foreign substance is interpolated as necessary. Therefore, good white reference data can be collected.

That is, when the white reference data an of the current pixel is lower than the white reference data an-1 of the previous pixel by a predetermined level or more, the white reference data of the current pixel is replaced with the white reference data of the previous pixel. By storing the white reference data in the line buffer 24, the white reference data of which the level is partially lowered due to adhesion of foreign matter or the like is performed. In the example of FIG. 8, the white reference data of two adjacent pixels are used as the determination target, but the number of target pixels, the determination algorithm, etc. can be changed according to the application. The determination threshold TH may be set by the system controller 1 or may be generated by hardware.

FIG. 9 shows an operation flowchart of the foreign matter compensation. Here, a case of reading 2048 pixels / line will be described as an example. First, in process 501, the pixel number n and the difference Δn are initialized, and a desired value is set as the foreign substance determination threshold TH. Next, the peak value reset unit 27, the peak value detection unit 28, and the white reference data sampling unit 29 are sequentially controlled via the sequence controller 30 to reset the peak value (process 502) and detect the peak value (process 50).
3) Each process of white reference data collection (process 504) is sequentially executed. When the white reference data is collected, the data an acquired this time is flip-flop (F / F1) 32
In the flip-flop (F / F2) 33 (process 5).
06). Next, the difference Δn = an−1 −an between the previous time and this time is calculated by the subtractor 34 (process 507), and the comparator 35 determines whether the obtained difference Δn is larger than the foreign matter determination threshold value TH.
(Judgment 508). If the difference Δn is larger than the foreign substance determination threshold value TH, it means that the foreign substance is detected, and the current sampling data an is the data due to the foreign substance. Therefore, the multiplexer 36 is controlled by the output of the comparator 35 to set the current data an to the previous one. Processing 509 for replacing with the data an-1 of. After that, flip-flop (F / F
2) The data an-1 held in 33 is stored in the line buffer 24 (process 510). If the difference Δn is not larger than the foreign substance determination threshold value TH, the foreign substance is not detected, and therefore the process 509 is skipped and the process proceeds to the process 510. Next, the pixel number n is incremented (process 51
1), it is determined whether or not the pixel number n becomes 2048 (determination 512). If n is not 2048, the process returns to step 504 and the steps from white reference data collection are repeated. If n = 2048, it means that all the pixels in the line have been checked, and the series of processing is terminated.

By the way, various factors such as paper dust and dust can be considered as the above-mentioned foreign matter. In addition, the contact position of the foreign matter may be on the lath 13, the white reference member 15, the mirror 16, or the like. Among these, the above-mentioned problems occur when the toner adheres to the vicinity of the document passing position, that is, on the contact glass 13 or the white reference member 15. The foreign matter adhering to the contact glass 13 is easily removed by the cleaning effect brought in by the document. Further, since the foreign matter attached to the white reference member 15 is blocked by the document, it will be out of the reading optical path. On the other hand, the foreign matter attached to the mirror 16 does not move unless a cleaning operation is performed. Therefore, it is preferable that the foreign matter is interpolated for the matters other than the mirror. The level variation of the white reference data due to the adhesion of foreign matter has the following characteristics.

The foreign matter adhering to the contact glass 13 or the like is in the vicinity of the reading position of the original document, and therefore is substantially focused on the image sensor 18. Therefore, the image of the foreign matter is clearly projected on the image sensor 18, and as a result, the level change of the sensor output becomes sharp. Meanwhile, the mirror 17
The foreign matter adhering to the top or the like is out of focus and is projected on the image sensor 18 in a blurred manner, so that the level change becomes gentle.

In the image reading apparatus of the above embodiment,
Since the determination threshold TH is variable, the foreign matter attachment position can be estimated by using the above characteristics. For example, foreign matter detection is performed with two types of determination thresholds THH and THL (THH> THL), and the contact glass 13 and the white reference member 15 are used for pixels in which THH and THL detect foreign matter.
It is determined that foreign matter is attached to the etc., and data is interpolated. It is judged that the foreign matter is attached to the mirror 17 for the pixel in which the foreign matter is detected only by THL, and the data is not interpolated. Further, since the foreign matter on the mirror 17 needs to be cleaned, a message to that effect is generated to the operator, so that the maintainability of the device can be improved.

FIG. 10 shows an operation flowchart for estimating the above-mentioned foreign matter adhesion position. In FIG. 10, process 6
The procedure up to 05 is almost the same as the procedure up to the step 507 in the flowchart of FIG. 9, but in the first step 601, two types of thresholds THH and THL (THH> THL), large and small, are set as foreign object determination thresholds. Then, when the difference Δn is obtained in the process 605, it is first determined whether or not the obtained difference Δn is larger than the smaller determination threshold THL (decision 6).
06), if larger, a flag FLGL indicating the determination result
Is set to "1" (process 607). Next, it is judged whether the difference Δn is larger than the larger judgment threshold value THH (decision 608), and if it is larger, the flag FLGH indicating the judgment result is set to "1" (process 609).
In the next judgment 610, it is judged whether or not the flag FLGH is "0" and FLGL is "1". If this condition is satisfied, it is presumed that foreign matter is attached to the mirror 17 from the above-mentioned characteristics, Since cleaning is required, the process moves to step 611 and a message to that effect is generated to the operator. Judgment 6
If the above condition is not satisfied in 10, the process proceeds to the next judgment 612. In this judgment 612, the flag FLGH is "1".
, And FLGL is "1", and if this condition is satisfied, the contact glass 13
Since it is estimated that foreign matter is attached to the data etc. and interpolation is required, after the processing 613 for replacing the current data an with the previous data an-1 in the same manner as the flowchart of FIG. 9, the data an- 1 is stored in the line buffer 24 (process 614). If neither of the above conditions is met, no foreign matter will be detected.
3 is not performed and the process proceeds to step 614. Similarly, the pixel number n is incremented (process 615), and the pixel number n
The processing 603 to the determination 616 are repeated until the number becomes 2048.

By the way, in the above-mentioned image reading apparatus, when the read linear density of the main scanning is variable, if foreign substances are detected by the same method for a plurality of kinds of linear densities, there is a difference in detection capability. Comes out. That is, when the read line density is high, the level difference between adjacent pixels is small (see FIG. 11). FIG. 11 shows an example in which the read line density is doubled. At this time, the level difference between pixels is theoretically 1/2. If TH = 3 is set for such white reference data, interpolation is performed when the pixel density is normal, but interpolation is not performed when the pixel density is double.

In order to improve such a problem, the foreign matter determination threshold value is changed according to the read line density (corresponding to claim 5). It is possible to perform good data interpolation even when the density changes. The switching of the determination threshold may be performed by the system control unit 1 in conjunction with the switching of the linear density, or may be switched by hardware. When the system control unit 1 performs the determination threshold value switching means by the system control unit 1, and when switching is performed by providing new hardware such as a variable resistor,
The determination threshold value switching means is realized by newly provided hardware such as a variable resistor.

Further, in order to improve the above-mentioned problems, the foreign matter determination threshold value is set to be the same, and the foreign matter detection target pixel interval is changed. More specifically, the larger the reading line density is, the wider the detection object pixel interval is. It is possible to perform good data interpolation even when is changed. At this time, with respect to the pixel in which the foreign matter is detected, good data interpolation can be performed by correcting the undetected pixel in the predetermined area near the pixel.

In the above-mentioned series of image reading devices, the influence of foreign matter adhering to the scanning line can be satisfactorily removed by hardware. However, in an actual device, transient level fluctuations such as various noises are easily mixed. If such noise is recognized as a foreign substance, the data interpolation unit may follow the noise, which may cause image deterioration. The embodiment described below has been made to prevent these problems, and corresponds to claim 6.

FIG. 12 shows an example of the structure relating to the shading correction of this embodiment. When collecting the white reference data, the foreign matter detecting means 37 (FIG. 8) which is a component of the foreign matter compensating means 29b is used.
When the foreign substance is detected by (see), the corresponding pixel is stored and the detection operation is continued. If there is a pixel in which a foreign substance is detected when the detection operation is completed for one line, the foreign substance detection operation is performed again. When a foreign substance is recognized in the same pixel as the previous line in the detection operation of the next line, it is determined that the foreign substance is attached to the corresponding pixel, and a predetermined interpolation operation is performed. If the foreign matter is not detected in the same pixel on the next line, it is determined that the previously detected foreign matter is transient such as noise, and data interpolation is not performed. An arbitrary value can be set for the number of lines that are determined to have foreign matter attached. By doing this,
Good interpolation of abnormal pixel data can be performed without following sudden noise.

In the embodiment of FIG. 12, the storage of the foreign matter detection result also serves as the shading correction data storage area of the line buffer 24. Since the shading correction data is stored after the foreign matter determination mode, the shading correction data can be freely accessed in the foreign matter detection mode, and the foreign matter can be determined without increasing the storage means. In this case, by expressing the foreign matter detection result with binary data corresponding to each pixel, the number of lines of the detection result that can be stored is equal to the accuracy (bit number) of the shading correction data. For example, 6
If the shading correction accuracy of bits is 6, 6 lines can be stored. This state is shown in FIG. In this way, by storing the foreign matter detection result in the shading correction data storage area by the number of lines corresponding to the correction accuracy (correction data bit number), the history of abnormality detection results is managed without increasing the storage means. Therefore, it is possible to perform good interpolation of abnormal pixel data without following sudden noise.

Further, the foreign matter detection pixel is stored every time the shading correction data is collected, and when the abnormal pixel is continuously detected from the history, the abnormal pixel is detected in the area of the same pixel or a predetermined number of pixels. By determining that there is a constant abnormality (dirt or deterioration) and generating a message to that effect to warn the operator, the maintainability of the device can be improved (corresponding to claim 7).

FIG. 14 shows an operation flowchart of the above embodiment. When the foreign matter detection is started, first, a foreign matter detection data storage line number LN is set in a process 701, a foreign matter detection flag DT and a pixel number n are initialized in a process 702, and it is determined whether a foreign matter is detected or not in a next determination 703. judge. If a foreign substance is detected, the process proceeds to step 704, the detection result is stored in the shading correction data storage area in the line buffer 24, and the foreign substance detection flag DT is set to "1" indicating the foreign substance detection in process 705. Proceed to 706. On the other hand, if no foreign matter is detected, the above processes 704 and 705 are not performed, and the determination 703 to the process 70 are performed.
Proceed to 6. In the process 706, the pixel number n is incremented, and in the next determination 707, it is determined whether or not the pixel number n is 2048, so that the determination 703 to determination are performed until the foreign substance detection of all the pixels in the line is completed. 7
07 is repeated. When the foreign matter detection of all the pixels is completed, the process proceeds to a determination 708 to determine whether or not the foreign matter detection flag DT is "1". If the foreign matter detection flag DT is not "1", it means that there is no foreign matter.
4, the white reference data is stored in the line buffer 24.

On the other hand, if the foreign matter detection flag DT is "1", it means that the foreign matter is detected by the above scanning, and the process proceeds to the next processing 709 to decrement the foreign matter detection data storage line number LN. Then, the next judgment 710
Then, it is determined whether or not the number LN of foreign substance detection data storage lines has become 0, and if it has not become 0, the process returns to the process 702 to initialize the foreign substance detection flag DT and the pixel number n, and then repeats the above process. In this repeated processing, when the foreign matter is no longer detected, the foreign matter detection flag DT remains "0", and therefore the process shifts from the determination 708 to the processing 714 to perform the white reference data storage processing. On the other hand, until the foreign substance detection data storage line number LN becomes 0, the foreign substance detection flag DT
If the state of = 1 continues, it is determined in step 711 that foreign matter is attached, and in step 712, predetermined foreign matter interpolation processing is performed. Then, in process 713, a message indicating that the optical system or the like has an abnormality such as stain or deterioration is generated to the operator, and in process 714, the white reference data storage process is performed and the series of processes is ended. The processing flow described above is controlled by the system control unit 1. Therefore, the control means of claims 6 and 7 is also the system control unit 1.
Is realized by.

[0063]

According to the first aspect of the present invention, the line unit control means is provided separately from the control unit, so that the control unit performs software control relating to shading correction and image processing in a plurality of predetermined lines. This can be done in block units with one block as a block, the frequency of software intervention by the control unit is reduced, the load on the control unit is reduced, and the speed of the device can be increased. Further, by providing a shading distortion data sampling means and controlling a series of shading distortion data sampling operations by hardware, the frequency of intervention of software by the control section is reduced, the load on the control section is reduced, and the device The speed can be increased. Furthermore, by associating these with each other and designating the sampling timing of the shading distortion data with a predetermined line in the block, the frequency of software intervention by the control unit can be further reduced. This has the effects of significantly reducing the load on the parts and sufficiently increasing the speed of the device.

According to the invention of claim 2, the same as above,
By providing a shading distortion data collection means and controlling a series of shading distortion data collection operations by hardware, the frequency of software intervention is reduced, software load is reduced, and equipment speed is increased. You can Further, since the foreign matter compensating means is provided, it is possible to interpolate the abnormal pixel data due to the foreign matter adhering to the scanning line, so that accurate shading correction can be performed and good image reading can be performed. There is.

According to the third aspect of the present invention, since the foreign matter compensating means is composed of the foreign matter detecting means and the interpolation selecting means, abnormal pixels due to the foreign matter adhering to the scanning line prior to the shading distortion data collection. Is detected and the abnormal pixel data due to the foreign matter is interpolated as necessary, so that there is an effect that the shading distortion data can be more favorably collected.

According to the fourth aspect of the invention, the foreign matter detecting means compares the level difference between adjacent pixels with a foreign matter determination threshold value and determines an abnormal pixel due to foreign matter adhesion. Since it is possible to make a determination and a plurality of types of foreign matter determination thresholds can be set, there is an effect that the foreign matter adhesion position and the like can be estimated.

According to the fifth aspect of the present invention, since the determination threshold value switching means changes the foreign substance determination threshold value according to the read line density of the main scan, good interpolation of abnormal pixel data can be performed regardless of the read line density. There is an effect that can be.

According to the sixth aspect of the present invention, when the abnormal pixel due to the foreign matter is detected, the abnormal pixel detection operation is performed again, and when the abnormal pixel due to the foreign matter is continuously detected for the same pixel a predetermined number of times or more. Since the abnormal pixel data is interpolated, there is an effect that good abnormal pixel data can be interpolated without following sudden noise or the like.

According to the seventh aspect of the present invention, when abnormal pixels are continuously detected in the same pixel or in a region having a predetermined number of pixels over a plurality of shading distortion data sampling operations, the operator is informed. Since the warning is issued by the operator, the operator can be prompted to perform maintenance of the device, and the maintainability of the device is improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration related to block unit control in an image reading apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example of a line unit control unit shown in FIG.

FIG. 3 is a block diagram showing a configuration related to shading correction in the image reading apparatus according to the embodiment of the present invention.

4 is an operation flowchart of the image reading apparatus that performs block-unit control with the configuration of FIG.

FIG. 5 is an operation flowchart of an embodiment in which phase excitation of a document conveying stepping motor is also stopped at the time of collecting white reference data.

FIG. 6 is a diagram showing an example of shading correction failure due to adhesion of foreign matter.

FIG. 7 is a block diagram showing another configuration example related to shading correction.

8 is a block diagram showing a configuration example of the foreign matter compensating means shown in FIG.

9 is a flowchart showing an operation example of foreign matter adhesion data interpolation by the foreign matter compensating means in FIG.

10 is an operation flowchart for estimating a foreign matter adhesion position in another operation example of foreign matter adhesion data interpolation by the foreign matter compensation means in FIG. 8;

FIG. 11 is a diagram showing an example of a change in level difference between adjacent pixels depending on the read line density.

FIG. 12 is a block diagram showing still another configuration example related to shading correction.

FIG. 13 is a diagram showing how abnormal pixel data is stored and determined.

FIG. 14 is an operation flowchart of an embodiment that deals with sudden noise and the like.

FIG. 15 is a basic configuration diagram of a facsimile device.

FIG. 16 is a block diagram showing a configuration example of a conventional image reading device.

FIG. 17 is a flowchart showing an example of conventional control for capturing image reading data.

FIG. 18 is a flowchart showing a conventional shading distortion data (white reference data) collection operation.

FIG. 19 is a block diagram showing a configuration example related to conventional shading correction.

FIG. 20 is a diagram showing an outline of an operation when collecting white reference data.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 System control unit 4 Scanner 12 Original document 13 Contact glass 14 Light source 15 White reference member 16 Mirror group 17 Lens 18 Image sensor 21 A / D converter 22 Shading correction unit 22a Distortion correction unit 22b Shading distortion data sampling unit 23 Digital image processing unit 24 line buffer 25 line unit control section 26 peak value register 27 peak value resetting section 28 peak value detecting section 29 white reference data collecting section 29a, 29b foreign matter compensating means 30 sequence controller 31 D / A converter 37 foreign matter detecting means 38 interpolation selection Means of implementation

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H04N 1/04 103 E

Claims (7)

[Claims] 1. A light source for irradiating a document to be read, an image sensor for receiving reflected light from the document illuminated by the light source through an optical system, scanning each pixel, and converting the pixel into an electric signal. Prior to reading the original, a white reference member is scanned to collect shading distortion data due to the optical system for each pixel, and at the time of reading the original, a shading correction unit that corrects the distortion of the read image data based on the distortion data, In an image reading apparatus including an image processing unit that performs various image processing on shading-corrected image data and a control unit that controls the shading correction unit and the image processing unit, control data for a plurality of main scanning lines are collectively received. A line-unit control hand that sequentially outputs the set control data to the shading correction unit and the image processing unit in line units. And a shading distortion data collecting unit that performs a series of processes related to shading distortion data collection, wherein the control unit collectively sets control data for a plurality of predetermined lines in the line unit control unit to perform the shading correction. The control for the image processing unit and the image processing unit is block unit control in units of a plurality of lines, and the shading distortion data sampling is performed by the shading distortion data sampling unit by designating a predetermined line in the block. Image reader. 2. A light source for irradiating a document to be read, an image sensor for receiving reflected light from the document illuminated by the light source through an optical system, scanning each pixel, and converting the pixel into an electric signal. Prior to reading the original, a white reference member is scanned to collect shading distortion data due to the optical system for each pixel, and at the time of reading the original, a shading correction unit that corrects the distortion of the read image data based on the distortion data is provided. In the provided image reading device, shading distortion data collecting means for performing a series of processes related to shading distortion data collection, and foreign matter for interpolating data corresponding to abnormal pixels due to foreign matter adhering to the scanning line when collecting shading distortion data An image reading apparatus comprising a compensating means. 3. The foreign matter compensating means detects foreign matter pixels that are abnormal due to foreign matter adhering to a scanning line prior to collecting shading distortion data, and detects foreign matter pixels that are abnormal due to foreign matter based on the detection result of the foreign matter detecting means. 3. The image reading apparatus according to claim 2, further comprising interpolation selection executing means for selectively executing interpolation of corresponding data. 4. The foreign matter detection unit detects an abnormal pixel due to foreign matter adhesion by comparing a level difference between adjacent pixels with a foreign matter determination threshold value that can be set for a plurality of types. The image reading device described. 5. The judgment threshold value switching means for changing the foreign matter judgment threshold value according to the main scanning read line density when a plurality of kinds of main scanning read line densities are variable. Image reader. 6. When the foreign matter detection unit detects an abnormal pixel due to foreign matter adhesion, the abnormal pixel detection operation is performed again, and when the foreign matter detection occurs consecutively a predetermined number of times or more in the same pixel, the interpolation selection execution unit The image reading apparatus according to claim 3 or 4, further comprising a control means for interpolating the corresponding data. 7. A warning is issued to an operator when the foreign matter detecting means continuously detects abnormal pixels in an area having the same pixel or a predetermined number of pixels over a plurality of shading distortion data sampling operations. An image reading apparatus according to claim 3 or 4, further comprising a control means for controlling the image reading means.