JP2003060859A - Image reader and image forming apparatus - Google Patents

Abstract

(57) Abstract: An image reading apparatus capable of minimizing an image change before and after a scanning stop due to a change in light amount of a light source without a reflection reference member having a uniform reflection characteristic in a sub-scanning direction. provide. An image memory for storing image information read by a color CCD, and a document scanning operation is temporarily stopped when a storable capacity of the image memory becomes equal to or less than a predetermined remaining amount. When the remaining amount has returned to the preset capacity, the image reading apparatus having the SCU 7 for restarting the original scanning is used to read the reflected light amount of the original pressing plate 20-1 other than the original reading area with time, and read the reflected light. A correction value for the light amount fluctuation of the light source while the original scanning operation is stopped is calculated based on the light amount, and the light amount fluctuation of the light source is corrected by the SBU 10, VIOB 31, and SCU 7.

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 reading an image, such as a copying machine or a facsimile machine, and an image forming apparatus for visualizing the read image to form a visible image on an image forming medium. The present invention relates to an image reading apparatus characterized by correction of light amount fluctuation of a light source during reading and an image forming apparatus using the reading apparatus.

[0002]

2. Description of the Related Art In a conventional image reading apparatus (hereinafter referred to as an image scanner), the illuminance of a light source easily changes with time, and when reading an image, the brightness of the illumination depends on the position of the scanner in the sub-scanning direction. May change,
The influence on the read image was a problem. For example,
With mercury fluorescent lamps, it takes several minutes from the start of lighting until the light quantity stabilizes, and even with a more stable Xe lamp, it tends to stabilize in a short time. The variation, that is, the slope of the time-light amount is large, which affects the image brightness.

Furthermore, in the case of a white fluorescent lamp, the respective RGB fluctuation amounts vary even over the same time, causing a color difference between the front and rear images within one frame.

On the other hand, the image scanner is usually provided with a buffer memory (storage means) for accumulating image data in the apparatus itself. The image scanner is usually connected to a PC or a network line as an input device, but depending on the data processing capacity of the output destination or the data transfer speed to the output destination, the balance between the scan capacity and the transfer speed. However, the data is accumulated in the buffer memory in the scanner. When the memory is full, the document cannot be transferred even if it is read, so the scanner stops the scanning operation and waits for the data in the memory to be transferred. If the stop time is several seconds or more, the influence of the light amount fluctuation on the brightness and the color difference becomes noticeable on the image. In particular, since the brightness of the image greatly changes at the joints of the images before and after the scanning is stopped, this change is noticeable and the image quality is lowered.

[0005]

In order to deal with such a problem, conventionally, the change of the luminous intensity of the light source is corrected with time. This correction first requires a reflection reference member having a uniform reflection characteristic in the sub-scanning direction, irradiates the reference reflection member while scanning, detects the light amount fluctuation of the reflected light, and then The reading result (image data) is corrected, or when any change is made, feedback is applied to correct the correction.

In such a correction method, the detection position of the reflected light is always at a different position in the sub-scanning direction, and a strict level of reflection uniformity in the scanning direction required for the reference reflector is required. Therefore, the control by the reference reflection plate cannot guarantee the accuracy when the reference reflection plate becomes dirty over time. That is, this method is vulnerable to noise such as stains over time.

As a method without correction, if the lamp is turned on after the power switch SW-ON of the scanner is left on, the light amount stable area is entered several minutes after the power is turned on.
After that, since there is little variation, there is a method in which scanning is performed after entering the light quantity stable region. However, in this method, the lighting becomes long except for the scan use time,
It cannot be denied that the lamp life will be shortened. Further, as a matter of course, the amount of light fluctuation immediately after lighting is large and the image during this period is greatly affected as described above.

Therefore, Japanese Patent Laid-Open No. 10-308849 discloses an invention in which a reference reflecting member is provided in the sub-scanning direction so that stray light of reflected light from an original is blocked so that light quantity correction is appropriately performed. Has been done. According to the present invention, the illuminance is monotonically decreased or increased from the reading start side to the reading side, so that the displacement or displacement of the optical system can be prevented.
It is said that the reading correction error can be reduced.

However, even with this known invention, the various problems due to the above-described change of the light amount with time have not been solved.

The present invention has been made in view of the circumstances of the prior art as described above, and an object thereof is to provide a light amount variation of a light source without a reflection reference member having a uniform reflection characteristic in the sub-scanning direction. An object of the present invention is to provide an image reading device capable of minimizing the change in image before and after scanning is stopped.

Another object of the present invention is to provide an image reading apparatus capable of more accurately correcting the fluctuation of the light quantity of the light source and minimizing the image change before and after the scanning is stopped due to the fluctuation of the light quantity of the light source. It is in.

Still another object of the present invention is to provide an image forming apparatus using an image reading apparatus capable of minimizing the image change before and after the scanning is stopped due to the fluctuation of the light source.

[0013]

To achieve the above object, a first means is a storage means for storing image information read by an optical reading means, and a storage capacity of the storage means set in advance. In the image reading apparatus having a control means for temporarily stopping the document scanning operation when the state becomes equal to or less than the amount, and then restarting the document scanning when the remaining amount returns to a preset capacity, A correction means for reading the reflected light amount of the document pressing plate other than the area over time, calculating a correction value for the light amount variation of the light source while the document scanning operation is stopped based on the read light amount, and correcting the light amount variation of the light source. It is characterized by having.

According to a second means, in the first means, the correcting means reads the reflected light quantity at least twice at different timings while the scanning is stopped, and the output of the optical reading means is based on the read reflected light quantity. It is characterized in that the amplification amount of the signal is changed.

According to a third means, in the first means, the correcting means reads the reflected light quantity at least twice at different timings while the scanning is stopped, and the analog-digital conversion circuit is based on the read reflected light quantity. It is characterized by changing the comparison voltage of.

A fourth means is characterized in that, in the second or third means, the change by the correcting means is performed based on the difference in the reflected light amount read.

A fifth means is characterized in that, in the first means, the original pressing plate is white.

According to a sixth aspect of the present invention, in the first means, when the correction means does not reach the preset value of the read data of the reflected light amount of the document pressing plate,
Instead of reading the reflected light amount of the document pressing plate, a document is read and the light amount fluctuation of the light source is corrected based on the peak value of the read data.

The seventh means comprises the image reading device according to the first to sixth means, and an image forming means for forming a visible image based on the image data read by the image reading device. It is characterized by

The first means has a storage means for storing image information of an image read by an optical reading means (for example, a line CCD), and the storage capacity of the storage means is in a near full state, that is, the remaining amount. In the image reading apparatus, the document scanning operation is temporarily stopped when the remaining amount is almost eliminated, and the scanning is resumed when the remaining amount returns to the preset remaining amount. Since the means is provided, the change in the image before and after the scanning is stopped can be minimized even during the period in which the light amount varies largely after the lighting lamp is turned on until the light amount is stabilized. At that time, it is not necessary to provide a reflection reference member having a uniform reflection characteristic in the sub-scanning direction, and it is possible to obtain a high-quality scanner image with less variation between machines.

In the second means, the amount of reflected light from the document pressing plate is measured at least twice while changing the timing while the scanning is stopped, data calculation is performed based on the measured value, and the optical reading means (line CCD) is used. Since the variation of the light amount of the light source is corrected by changing the amplification amount of the signal after the output of, the change of the image before and after the scanning is stopped can be minimized, and the reflection reference with uniform reflection in the sub-scanning direction can be obtained. It is possible to obtain a high-quality scanner image with little variation between machines without using any member.

In the third means, the amount of reflected light from the document pressing plate is measured at least twice with the timing changed while the scanning is stopped, data calculation is performed based on the measured value, and the comparison voltage of the analog-digital conversion circuit is calculated. The change in the light amount of the light source is corrected by changing the value of (1) to (2), so that the change in the image before and after the scanning is stopped can be minimized, and there is no reflection reference member having uniform reflection in the sub-scanning direction. You can obtain a high-quality scanner image with less variation.

In the fourth means, since the light amount fluctuation is calculated by the data difference (relative value) of the read reflected light amount, it is not necessary to provide a reflection reference member having a uniform reflection characteristic in the sub-scanning direction, and the accuracy is always maintained. Good correction can be performed.

In the fifth means, since the color of the original pressing plate is white, the accuracy of the data calculation before and after the scanning is stopped becomes high, and the correction can always be performed with high accuracy.

According to the sixth means, when the data on the document pressing plate has not reached the predetermined data, the data in the read document is measured and the data is calculated, so that the setting condition of the document is not affected. It is possible to always perform accurate correction.

The seventh means can provide an image forming apparatus having the effects of the first to sixth means.

In the following embodiments, the optical reading means is the first mirror 3, the second mirror 5, the third mirror 4, the imaging lens 1, and the color CCD 42, and the storage means is an image memory (not shown). SDRAM), the correction means corresponds to SBU10, VIOB31 and SCU7.

[0028]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

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

In FIG. 1, the color scanner SC has two functions: a sheet-through method for reading a document image and a flat-bed method for reading a document. Whichever function is used to read the original, the reflected light reflected by the original enters the imaging lens 1 through the first mirror 3, the second mirror 5, and the third mirror 4, and S
An image is formed on the light receiving surface of the CCD on the BU 10.

When reading an original by the flat bed method, the original is placed between the first original pressing plate 20-1 and the original table glass 8 and the placed original is integrated with the first mirror 3. It is illuminated by the constructed illumination lamp 2 and reflected by the document. The reflected light reflected by the document surface is scanned by the first mirror 3, the second mirror 5 and the third mirror 4 which are integrally formed. After that, the reflected light is focused by the lens 1,
It is photoelectrically converted into RGB by irradiating and forming an image on the SBU 10 equipped with a color CCD. First mirror 3,
The illumination lamp 2, the second mirror 5, and the third mirror 4 are movable in the left-right (sub-scanning) direction in the figure by using the traveling body motor 9 as a drive source.

In the case of reading by the sheet-through method, the reading optical system is fixed at the position shown in FIG. 1, and the original passing through the upper surface of the DF original glass 6 is illuminated by the illumination lamp 2 to make the first and the first. 2 and 3rd mirror 3, 5, 4
The reflected light is guided to the image forming lens 1 to form a read image on the light receiving surface of the CCD on the SBU 10, and is photoelectrically converted into RGB as described above to read the image.

Above the color scanner SC, in other words, the automatic double-sided document feeder ARDF is placed on the above-mentioned document glass plate 20-1, and the document is automatically fed and fed. The document is read.

In the ARDF, the document guide 1 on the document table 11
When the single-sided original reading is selected, the originals stacked along the line 2 are called by the calling roller 14, the feeding roller 15 by the paper feeding belt 16, the separating roller 17, and the DF original glass 6 and the second feeding roller 18 by the first feeding roller 18. After passing through the reading position between the document pressing plate 20-2 and the document pressing plate 20-2, the document is fed to the second transport roller 21 and the paper discharge roller 23, and the document is extracted. On the other hand, when the double-sided original reading is selected, first, the front side of the original is read in the same manner as when the single-sided original reading is selected. In the case of double-sided document reading, there are front side reading and back side reading.

In the case of reading the front surface of the document, the calling roller 14, the feeding roller 15 by the paper feeding belt 16, the separating roller 17, and the first feeding roller 18 are used to move the space between the DF original glass 6 and the reflection guide plate 20. After passing through the reading position, it is sent to the second transport roller 21 and the paper discharge roller 23,
The branch claw 24 is switched to the lower side without discharging the document,
It is transferred onto the reversing table 26 by the reversing roller 25. After the trailing edge of the document passes through the discharge roller 23, the branching claw 2
4 is switched upward and the reversing roller is once stopped.

When reading the back side of the original, once
The original is conveyed from the inversion table 26 toward the first conveying roller 18 by rotating the stopped reverse roller 25 in the opposite direction to the above, and the first conveying roller 18 is further conveyed.
After passing through the reading position between the DF original glass 6 and the second original pressing plate 20-2, the original is ejected to the second conveying roller 21 and the paper ejection roller 23, and then the original is ejected. It

The original is driven by the traveling motor 9 when passing through the reading position between the DF original glass 6 and the second original pressing plate 20-2 for reading the front surface and the back surface, and the original position is read. Illuminated by the illumination lamp 2 mounted on the first carriage moving in the vicinity, and reflected light thereof is mounted on the first mirror 3 and the second carriage, and is integrally configured as a second mirror 5 and a third mirror. 4 is scanned. After that, as described above, the reflected light is focused by the lens 1, irradiates the SBU 10 equipped with the color CCD, and is photoelectrically converted into RGB colors.

The sheet feeding mechanism including the ARDF calling roller 14, the sheet feeding belt 16, the conveying roller 15 and the separating roller 17 is driven by a sheet feeding motor (not shown).
Further, the transport mechanism including the first transport roller 18, the second transport roller 21, the paper discharge port 23, and the reversing roller 25 is driven by a transport motor (not shown).

Further, in the ARDF, a set sensor 13 for detecting whether a document is set on the document table 11 for detecting the document, a width size detection substrate 28 for detecting the document size, and the first document. A length sensor 29, a second document length sensor 30, and a document trailing edge sensor 27 for detecting the trailing edge of the document are mounted.

Here, the original and the first original pressing plate 20-1
14 is as shown in FIG. That is, in the case of reading using the original platen, the originals placed on the original platen glass 8 along the original platen glass 8 have a relationship as shown in FIG. For example, although the maximum reading size of the original document is A3 size here, the first original document pressing plate 20-1 is larger than the A3 size and is installed so as to overlap the A3 original document.

The relationship between the original and the second original pressing plate 20-2 is as shown in FIG. In reading using ARDF, the white of the original passes through the reading position between the DF original glass 6 and the second original pressing plate 20-2. First
The maximum document reading size is A3 size like the original pressing plate 20-1, but the second original pressing plate 20-
2 is larger than the A3-size main scan (297 mm), and is set so as to overlap the A3-size main scan (297 mm).

The scanner SC main body is equipped with an SCU 7 for controlling the operation of the color image reading device including the scanner SC main body and ARDF. 2 is a block diagram showing the overall configuration of the image reading device according to the present invention, and FIG. 3 is a diagram showing the image data flow of the image reading device according to the present invention. The flow of image data in the present invention will be described with reference to FIGS. 2 and 3.

The reflected light of the original entering the color CCD on the SBU 10 is converted into an analog signal of each color of RGB having a voltage value according to the intensity of the light in the color CCD. RG
The analog signal of each color B is divided into odd bits and even bits and output. The color CCD on the SBU 10 has a resolution of 600 pixels per inch in this embodiment. In addition, the number of pixels is 7200 pixels per line, and
Approximately 305 mm can be read in excess of 297 mm in three sizes.

The analog image signal of the SBU 10 is V
The dark potential portion is removed by the analog processing circuit 32 on the IOB 31, and the odd bit and the even bit are combined. After this synthesis, the gain is adjusted to a predetermined amplitude, and it is input to the A / D converter 33 and converted into a digital signal. The digitized image signal is subjected to shading correction by the shading ASIC 34, and after being subjected to image processing such as gamma correction and MTF correction by the RIPU 35 on the SCU 7 from the VIOB through the SCU 7, as a video signal together with the synchronization signal and the image clock. Is output.

The video signal output from the RIPU 35 is output to the OIPU 36. The video signal output to the OIPU 36 is subjected to predetermined image processing in the OIPU 36, and is input to the SCU 7 again. SCU again
The video signal input to 7 is input to the VIDEO input switching circuit 37. VIDEO input switching circuit 3
The other input of 7 is a video signal output from the RIPU 35, and the OIPU 36 can select whether to perform image processing.

The video signal output from the VIDEO input switching circuit 37 is the image data storage means (SDR).
It is input to SIBC2 (38) that manages AM) and SD
It is stored in an image memory composed of RAM. The image data stored in the image memory is the SCSI controller 3
9 and transferred to an external device such as a personal computer or a printer. CPU (not shown), ROM on the SCU 7
(Not shown), RAM (not shown) are mounted,
The CPU controls the SCSI controller 39 to execute S
It communicates with external devices such as personal computers through the CSI interface.

Further, the CPU sends the video signal output from the VIDEO input switching circuit 37 to the IEEE.
E1394 controller: IEEE via ISIC40
E1394 interface, network scanner controller: Communicates with an external device such as a personal computer or a printer by a network I / F via the NIC 41.

Further, the CPU (not shown) is the scanner S.
A traveling body motor 9 including a stepping motor of the C main body,
The timing control of the ARDF paper feed motor (not shown) and the transport motor (not shown) is also performed. ADU42
Has a function of relaying the power supply of the electrical components used in the ARDF unit.

The input port connected to the CPU (not shown) on the SCU 7 is connected to the main body operation panel: SOP43 via the VIOB 31. On the main body operation panel: SOP43, a start switch (not shown) and an abort switch (not shown) are mounted. When each switch is pressed, CP is sent via the input port.
U (not shown) detects that the switch is turned on.

FIG. 4 is a block diagram showing the processing arrangement of the image reading processing in the scanner SC main body. In the figure, image reading is performed by SBU10, RIPU35, S
It is performed and processed by the IBC2 (38), the SCSI controller 39, and the CPU 45. That is, the image processing LSI (RIPU) 35 outputs image data from the SBU 10 by outputting LSYNC (main scanning line synchronization signal) and LGATE (main scanning line data output period) to the SBU 10 which is a CCD driving unit.
The flow of image data is SBU10 → RIPU35 → memory control LSI (SIBC2) 38 → SCSI controller 39 → external (personal computer or the like). Further, ON / OFF of image output from the CPU 45 is controlled by rewriting an internal register provided inside an image processing LSI (RIPU) 35 (not shown). An interrupt signal from the memory control LSI SIBC2 (38) is generated (this interrupt is generated when the memory state becomes full, near full or empty, and is not shown in the figure).
(SIBC2) 38 is provided inside the register, and its state can be distinguished by a register) and is input to the CPU 45. Also, C
The PU 45 also controls the motor 46 for moving the traveling body. The RIPU 35 and SIBC2 (3
Since the technique of 8), etc., which performs the control and the determination in the state of the register provided in the LSI, is a known technique, the description thereof is omitted here.

FIG. 5 is a timing chart showing the timing of stopping the output of image data in the present embodiment, FIG. 6 is a timing chart showing the timing of restarting the output of image data, and FIGS. 7 to 9 are shown in FIGS. It is a flow chart which shows a processing procedure of different timing.

In FIGS. 5 and 7, first, the traveling body is started (step S101), and the reading is started (step S102). When the memory near full (slightly before the memory is full) is detected during reading (step S103), LGATE output inhibition is set (step S104), and the traveling body is stopped (through down) (step S105). Next, the motor is rotated in the reverse direction to move the traveling body from the stop position to the restart position (step S106).

The details of this step S106 are shown in FIG. In this return control of the traveling body, the same through-up data as that used for stopping the traveling body is used, and the traveling body starts in the reverse direction (step S201) and ends the slew-up (step S20).
Along with 2), the same through-up data is used again to slew down (step S203). 30m by this operation
m, but as shown in Fig. 6, slowly start at 3
It may be returned by 0 mm.

Next, a rereading start process is performed (FIG. 9). In the rereading start process, an interrupt is generated when the memory becomes empty, and after the interrupt (memory empty interrupt) is generated (step S301), the traveling body is restarted (step S302), and at the end of the slew-up (step S303). ) Is set to restart LGATE output and the reading of the original is restarted (step S304).

There is also a known technique of reading the main body without reading the traveling body even during slewing up / down, but the concept of intermittent reading is the same, and a description thereof will be omitted here.

On the other hand, the intermittent reading in ARDF is also read during this slewing up / down. That is, ARD
The intermittent reading operation of F is as follows.

FIG. 10 is a timing chart showing the timing of the speed change of the carry motor in the flatbed type image reading operation in ARDF, and FIG. 11 is the speed change of the carry motor (not shown) and the image when the intermittent operation occurs. FIG. 12 is a timing chart showing the reading timing, and FIG. 12 is a flowchart showing the operation procedure of the intermittent reading operation.

As shown in FIG. 12, in the intermittent operation of ARDF, in order to convey a document, a conveyance motor (not shown) is slewed up (steps S401-T1001), and when the slew-up is completed (step S402), reading is performed. The speed is kept constant (step S403-T100).
2) The reading is started after the reading start position is reached (step S404). SI of SCU7 after a while
Near-full interrupt signal from BC2 (38) (Memory usage is almost full, and there is a remaining memory capacity that will not be full even if you continue to read image data until the transport motor is slewed down and stopped.) At steps S405 and S410, the carry motor is slewed down (step S411-T1003) and stopped (steps S412, S413-T1004).

Although the image data is read during the slew-down, the speed becomes slow as shown in FIG. 11 so that the image data is read by thinning it out, and the reading is interrupted when the conveyance motor (not shown) is stopped. The personal computer reads the data (image data) from the SCSI interface and
Empty interrupt signal from C2 (38) (remaining memory 0%: the amount of empty can actually be adjusted.)-The CPU (not shown) again causes the carry motor (not shown) to slew up by step S415. (Step S41
5-T1005), and the reading is restarted. During the slew-up, thinning-out reading of the image data is performed, and when the slew-up ends (step S416) and the reading speed becomes constant (step S417), normal image reading is performed (T1006). The carrying motor stoppage period during intermittent operation is affected by the processing capacity of the personal computer. When the reading end position is reached (step S405-Y), the image reading is stopped, the conveyance motor is slewed down (step S406), and when the slew down is completed (step S407), the original is ejected (step S408) and conveyed. A motor (not shown) is slewed down and stopped (steps S409-T10).
07).

The operation described with reference to FIGS. 5 to 12 is for the flat bed method, and the original is fed onto the original glass 8 and is stopped and the illumination lamp 2, the first to the second lamps are used. This is a case where the traveling body equipped with the third mirrors 3, 4, and 5 moves, but when the traveling original is read by the traveling body at the position of the DF document glass 6 by the above-described sheet-through method, The moving speed and the stopping of the movement of the document are performed in the same manner as the traveling body. That is,
The relationship between the original and the traveling body is relative, and when the original moves, the control of the original and the traveling body is reversed.

FIG. 13 is a block diagram showing a light source fluctuation correction circuit.

This correction circuit includes SBU10 and VIOB3.
1 and SCU7. The SBU 10 comprises a color CCD 42 and a buffer 43, and the SCU 7 comprises a RIPU 35 and a CPU 45. Also, VIOB
Reference numeral 31 includes an RGB analog processing circuit 32, a D / A converter 44, an A / D converter 33, and a shading ASIC 34.

In this correction circuit, the analog video signal photoelectrically converted into odd bits and even bits by the color CCD 42 on the SBU 10 is input to the VIOB 31 via the buffer 43 on the SBU 10. Odd bits,
The analog video signal for each even bit is input to the analog processing circuit 32 on the VIOB 31. The signal input to the analog processing circuit 32 is combined with the even bit and the odd bit through a gain amplifier (not shown) that can finely change the output level for each of the odd bit and the even bit, and is output as an analog video signal.

Two channels of the D / A converter 44 are connected to the gain control terminal of the gain amplifier. By varying the output voltage of the D / A converter 44 in an analog manner, the gain for the analog video signal of the output is an even number bit. And can be changed for each odd bit.

The output voltage of the D / A converter 44 is set by the CPU 45 on the SCU 7. D / A converter 44
Since the reference voltage is 5V and the number of bits is 8 bits, the CPU 45 can set the output voltage to 0 to 5V in 255 steps. The setting of the CPU 45 is digital (integer) of 0 to 255.

The analog video signal which is obtained by synthesizing even and odd numbers from the analog processing circuit 32 is input to the A / D converter 33. The A / D converter 33 converts this analog video signal into a 12-bit digital video signal. A D / A converter 44 is connected to the reference setting terminal of the A / D converter 33 similarly to the analog processing circuit 32. By changing the output voltage of the D / A converter 44 in an analog manner, the A / D converter 33.
The digital output value of can be changed. The digital video data digitally converted by the A / D converter 33 is input to the shading ASIC 34. The shading ASIC 34 mainly performs shading correction, but in addition to this, there is a peak detection unit (not shown) that can detect the peak value of one line in the main scanning direction. The peak detector has a function of storing the peak value of one line. The CPU 45 on the SCU 7 can read the stored peak value of one line.

Further, the peak detection section can set the peak detection gate at an arbitrary position in one line, and detects the peak value during this peak detection gate period. The peak detection gate period is set by the CPU 45 on the SCU 7. The peak detection period is set to a position corresponding to the first document pressing plate 20-1 when reading a document placed on the document table within one line, that is, in the case of the flat bed method.
In addition, when the document is moved by the ARDF for reading, that is, in the case of the sheet through method, the second document pressing plate 2 is used.
Set to the position corresponding to 0-2.

The original pressing plate 20-1 or 20-2
Is read at least twice at different timings. First, the buffer (image memory) for storing image data becomes near full, and the reading operation is interrupted.
Immediately after interrupting (stopping) the reading operation, the CPU 45 on the SCU 7 issues a command to the shading ASIC 34 to set the peak detection gate period and start the peak detection. During the peak detection gate period, the first document holding plate 2
0-1 position or the second original pressing plate 2
Set to the position corresponding to 0-2. Shading AS
The peak detecting portion of the IC 34 is the first document pressing plate 20-
1 or the second original pressing plate 20-
The peak value in one line of the main scanning at the position corresponding to 2 is detected and the value is stored. After that, the CPU 45 reads the stored peak value DO from the shading ASIC 34.

The near-full state of the image buffer is released,
Immediately before resuming the reading operation, the CPU 45 performs the same operation as described above to read the peak value Dl. The ratio between the peak value DO and the peak value Dl corrects the gain as the light source fluctuation while the scanning is stopped.

Here, the concept of the analog video signal which is an input to the analog processing circuit and the correction amount to the CPU 45 will be described.

The analog video signal is Vin, and the analog video signal (output signal of the analog processing circuit) amplified by the constant gain value G which is the analog processing circuit is Vou.
If t, then Vout = G × Vin. Further, the A / D converter 33 performs digital conversion by using the reference voltage (reference voltage) as the maximum output, and when the reference voltage is Vref, the 12-bit digital output value D is D = (Vout / Vref) × 4095.

Vin changes due to the change in the light amount while the scanning is stopped,
Vout changes at the change ratio. Naturally, the digital output value D also changes similarly. In the latter embodiment, Vout is kept constant even if Vin is changed by changing G.

If Vin before light intensity variation is Vin0, Vin after light intensity variation is Vin1, gain before light intensity variation is G0, and gain after light intensity variation is G1, Vout is constant, so Vout = G0 × Vin0 = G1 It may be × Vin1. Since the peak value D0 before the light amount change and the peak value D1 after the light amount change are values at G = G0, G1 can be calculated by G1 = G0 × (D0 / D1) (1). Therefore, Vout = G0 × Vin0 = G1 × Vin1 = G0 × (D0 / D1) × Vin1.

The relationship between the gain control voltage V of the analog processing circuit 32 connected to the analog output of the D / A converter 44 and the gain G of the analog processing circuit is defined as G = V (2). The relationship between the analog output V of the D / A converter 44 and the digital input value C of the D / A converter 44 is D
From the number of bits of the / A converter 44 and the reference voltage of 5V, V = (C / 255) × 5 = C / 51 (3)

The digital input value of the D / A converter 44 before the light amount change is C0, and the digital input value after the light amount change is C1.
Then, from the above equations (1), (2) and (3), (C1 / 51) = (C0 / 51) × (D0 / D1) C1 = C0 × (D0 / D1) 44 against C
It is sufficient to write a value obtained by multiplying 0 by (D0 / D1).

By performing such a series of operations independently for R, G, and B, it is possible to absorb the difference in the light amount fluctuations of R, G, and B. Although the color has been described here, the idea is the same because data of any of RGB is used even in monochrome.

At the measurement positions of D0 and D1, the running body is stopped, so the same positions are read. Further, since the peak comparison calculation value uses the amount of change between intermittent stops, the first document pressing plate 20-1 and the second document pressing plate 20-
The correction control is possible without the need for accuracy such as density and uniformity of 2.

If the data of D0 and D1 is large,
The larger the value, the higher the accuracy of (D0 / D1).
Original pressing plate 20-1 and second original pressing plate 20-2
Is white.

Here, the light amount of the reflected light is measured at different times at least twice while the scanning is stopped, data calculation is performed based on the light amount, and the signal amplification amount after CCD output is changed to change the light source. Although the variation is corrected, the light intensity of the reflected light is measured at different times at least twice while the scanning is stopped, the light intensity data is determined, the data operation is performed, and the comparison voltage of the analog-digital conversion circuit is calculated. It is also possible to correct the variation of the light source by changing. This example will be described below.

In this example, first, when the buffer (image memory) for storing image data becomes near full, the reading operation is interrupted. Immediately after interrupting the reading operation, S
The CPU 45 on the CU 7 uses the shading ASIC 34
Then, the peak detection gate period is set and the peak detection start command is issued. The peak detection gate period is set at a position corresponding to the first original pressing plate 20-1 or a position corresponding to the second original pressing plate 20-2. The peak detection unit of the shading ASIC 34 detects a peak value in one line of the main scanning at a position corresponding to the first document pressing plate 20-1 or a position corresponding to the second document pressing plate 20-2, Store that value. After that, CPU45
Stores the stored peak value D0 in the shading ASIC3
Read from 4.

The near-full state of the image buffer is released,
Immediately before restarting the reading operation, the CPU 45 performs the same operation as described above to read the peak value D1. Based on the ratio of the peak value D0 and the peak value D1, the gain is corrected as the light source variation while the scanning is stopped. Here, the analog video signal input to the analog processing circuit 32 and the CPU 4
The concept of the correction amount to 5 is as follows.

Here, the A / D converter 33 digitally converts the reference voltage (reference voltage) as the maximum output value, and assuming that the reference voltage is Vref, the 12-bit digital output value D is D = (Vout / Vref) × 4095.

Vout changes due to the fluctuation of the light amount while the scanning is stopped, and the 12-bit digital output value D changes according to the change ratio. In this example, Vref is varied to make D constant even if Vout varies.

If the Vout before the light quantity change is Vout0, the Vout after the light quantity change is Vout1, the reference voltage before the light quantity change is Vref0, and the reference voltage after the light quantity change is Vref1, the 12-bit digital output value D is constant. = (Vout0 / Vref0) × 4095 = (Vout1 / Vref1) × 4095

Since the peak value D0 before the light amount variation and the peak value D1 after the light amount variation are values at Vref = Vref0, Vref1 can be obtained by Vref1 = Vref0 × (D1 / D0) (4) You can Therefore, D = (Vout0 / Vref0) × 4095 = (Vout1 / (Vref0 × (D1 / D0))) × 4095.

The relationship between the analog output V of the D / A converter 44 and the digital input value C of the D / A converter 44 with respect to Vref is calculated from the equation (3) based on the number of bits of the D / A converter 44 is 8 and the reference voltage is 5V. Thus, Vref = (C / 255) × 5 = C / 51 (3), and the digital input value of the D / A converter 44 before the light amount change is C2, and the digital input value after the light amount change is C3. Then, from the equations (3) and (4), (C3 / 51) = (C2 / 51) × (D1 / D0) C3 = C2 × (D1 / D0). Therefore, the CPU 45 uses the D / A converter 4
It is only necessary to write a value obtained by multiplying C2 by (D1 / D0) with respect to 4.

By performing such a series of operations independently for R, G, and B, it is possible to absorb the difference in the light amount fluctuations of R, G, and B.

At the measurement positions of D0 and D1, the same position is read because the moving body is stationary. Further, since the peak comparison calculation value uses the amount of change between intermittent stops, the first document pressing plate 20-1 and the second document pressing plate 20-
The correction control is possible without the need for accuracy such as density and uniformity of 2.

If the data of D0 and D1 is large,
The larger the value, the higher the accuracy of (D0 / D1).
Original pressing plate 20-1 and second original pressing plate 20-2
Is white.

Although the amount of light can be corrected in this way, in the case of reading using a flat bed type document table, a document placed on the document table glass 8 along the document table glass 8 is usually When viewed from the original platen glass 8 in an upward direction, the positional relationship is as shown in FIG. 14, and for example, the maximum original reading size is A3 size, but the first original pressing plate 20-1 is provided larger than A3 size. Is
The A3 originals are installed so as to overlap each other. However, there is no restriction on the size of the original placed on the original glass 8 and the main scanning direction may be A3 size or larger. At this time, the original may be larger than the first original pressing plate 20-1. The peak detection gate period is set at a position corresponding to the first original pressing plate 20-1, but when the original is larger in size, it means that the original is actually read. . Therefore, if the original density is high and the RGB D0 value is low, (D0 / D
The accuracy of l) becomes worse.

Therefore, when D0 of RGB has a threshold value of 256 out of 12-bit data and D0> 256, the peak detection gate period is the first original pressing plate 2 during the peak detection gate period.
When the position is set to a position corresponding to 0-1 and D0 of RGB is D0 ≦ 256, the first original pressing plate 2 is in the peak detection gate period.
The position corresponding to 0-1 is changed to the A3 size including the original.

That is, in the state shown in FIG. 17, the A3 original is placed on the original glass 8 and the peak detection gate is set at the position of the first original pressing plate 20-1 as shown in FIG. , Peak data is detected (step S50).
1). Then, it is checked whether D0 of RGB is 256 or less (step S502), and if D0 is 256 or less (step S502-N), the peak detection gate is set at the document position (step S503), and
If D0 is larger than 256 (step S502-
7) and calculate the peak data respectively (step S5
04) Return.

In this way, the document placing position and the document table glass 8 are set.
The peak detection gate position is changed to the A3 size including the original pressing plate position and the original according to the relative positional relationship between the original pressing plate 20-1 and the first original pressing plate 20-1. As a result, when the first original pressing plate 20-1 is read, the peak values when the original pressing plate 20-1 is read are compared, and when the A3 size including the original is read, the A3 size is read. The peak values at the time of the comparison are compared. In this way, even when the A3 size including the original is compared with the peak value when it is read, since the comparison is performed at the same pixel position, the correction can be reliably performed.

By performing the processing as described above, it is possible to always perform accurate correction without depending on the setting condition of the original.

[0095]

As described above, according to the present invention, the data of the document pressing plate other than the document reading area is read, the time data is measured, and the light amount of the light source when the document scanning operation is stopped is based on the measured time data. Since the correction means for calculating the correction value for the fluctuation to correct the fluctuation of the light quantity is provided, the scanner which stops in the memory full (near full) state has the reflection reference member having uniform reflection in the sub-scanning direction. Therefore, it is possible to provide an image reading apparatus that can minimize the image change before and after the scanning is stopped due to the light source variation.

Further, it is possible to provide an image reading apparatus capable of correcting the fluctuation of the light amount of the light source with higher accuracy and minimizing the image change before and after the scanning is stopped due to the fluctuation of the light amount of the light source.

Further, it is possible to provide an image forming apparatus using an image reading apparatus capable of minimizing the image change before and after the scanning is stopped due to the light source variation.

[Brief description of drawings]

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

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

FIG. 3 is a diagram showing an image data flow of the image reading apparatus according to the embodiment of the present invention.

FIG. 4 is a block diagram showing the image reading processing configuration of the scanner body.

FIG. 5 is a timing chart showing a timing at which output of image data is stopped in the embodiment of the present invention.

FIG. 6 is a timing chart showing a timing of restarting output of image data according to the embodiment of the present invention.

FIG. 7 is a flowchart showing a processing procedure for the timings shown in FIGS. 5 and 6.

8 is a flowchart showing a processing procedure for the timings shown in FIGS. 5 and 6. FIG.

9 is a flowchart showing a processing procedure for the timings shown in FIGS. 5 and 6. FIG.

FIG. 10 is a timing chart showing the timing of the speed change of the carry motor in the ADF image reading operation.

FIG. 11 is a timing chart showing a change in speed of the carry motor and an image reading timing when an intermittent operation occurs.

FIG. 12 is a flowchart showing an operation procedure of an intermittent reading operation.

FIG. 13 is a block diagram showing a light source variation correction circuit.

FIG. 14 is a diagram showing a relationship between a document table and a document according to the present embodiment.

15 is a timing chart showing a detection state of a peak detection gate signal in the case of FIG.

FIG. 16 is a flowchart showing a processing procedure for adjusting the relationship between the peak detection gate and the document position.

FIG. 17 is a diagram showing the relationship between the document table and the document when the document size is larger than the document table glass size or when the document is placed on the opposite side of FIG.

[Explanation of symbols]

7 SCU 10 SBU 31 VIOB 32 analog processing circuit 33 A / D converter 34 Shading ASIC 35 RIPU 38 SIBC2 39 SCSI controller 42 color CCD 43 buffers 44 D / A converter 45 CPU 46 motor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 1/107 H04N 1/40 101A 1/401 F term (reference) 5B047 AA01 AB04 BA02 BB02 BC11 BC14 CA07 CB04 CB22 CB25 DA01 DA03 DB01 DC02 DC06 5C072 AA01 BA19 CA02 EA05 FB13 FB15 FB18 LA07 LA15 RA16 TA07 UA05 UA06 XA01 5C077 LL04 MM27 PP06 PP10 PP44 PP72 PQ12 PQ20 SS01

Claims (7)

[Claims] 1. A storage unit for storing image information read by an optical reading unit, and a document scanning operation is temporarily stopped when the storable capacity of the storage unit is equal to or less than a preset remaining amount,
After that, when the remaining amount returns to a preset capacity, an image reading apparatus having a control means for restarting the original scanning, the amount of reflected light of the original pressing plate other than the original reading area is read and read with time. Calculate a correction value for the light amount variation of the light source while the original scanning operation is stopped based on the light amount,
An image reading apparatus comprising a correction unit that corrects a light amount variation of the light source. 2. The correction means reads the reflected light quantity at least twice at different timings while the scanning is stopped, and changes the amplification amount of the output signal of the optical reading means based on the read reflected light quantity. Claim 1
The image reading device described. 3. The correction means reads the reflected light amount at least twice at different timings while the scanning is stopped, and changes the comparison voltage of the analog-digital conversion circuit based on the read reflected light amount. The image reading device according to claim 1. 4. The image reading apparatus according to claim 2, wherein the change by the correction unit is performed based on a difference in the amount of reflected light that has been read. 5. The image reading apparatus according to claim 1, wherein the original pressing plate is white. 6. The correcting means, when the read data of the reflected light amount of the original pressing plate has not reached a preset value, reads the original instead of reading the reflected light amount of the original pressing plate. The image reading apparatus according to claim 1, wherein the light amount variation of the light source is corrected based on the peak value of the data. 7. An image reading device according to claim 1, and an image forming unit for forming a visible image based on image data read by the image reading device. An image forming apparatus characterized in that