JP2006262073A - Original reader and copying machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the irregularity of received light quantity in each line even though a reading clock frequency is in a different mode. <P>SOLUTION: This original reader having an original illuminating light source 102, a lighting means 205 that is lit and driven in accordance with a lighting timing signal CKinv, a photoelectric conversion means 107 for converting original reflected light into an image signal, reading the image signal and serially outputting the image signal in synchronization with a read clock ϕ, and A/D conversion means 113 to 118 for digitally converting the image signal into image data, is provided with a frequency division means 212; for generating a lighting timing signal CKinv of a frequency being the integer multiple m of the cycle of the clock ϕ in synchronization with the clock ϕ and outputting the lighting timing signal CKinv to the lighting means 205. Whether the lighting timing signal CKinv obtained by multiplying the cycle of the clock ϕ by how many times m is prepared beforehand for each reading mode, The how many times m is switched by a reading mode to thereby supply a proper lighting timing signal CKinv to a light source lighting device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a document reading apparatus and a copying apparatus using the same, and can also be used for a facsimile apparatus having a communication function and a multifunction copying machine.

Japanese Patent Application Laid-Open No. 09-009007 JP 09-098262 A JP 2001-45231 A Japanese Patent Laid-Open No. 2004-72606 JP 2004-357136 A.

In Patent Document 1, a clock having an inverter frequency f _INV is generated by a timing generator 60, and the clock is further _{divided by} a second frequency _dividing circuit 66 to obtain a one-line capture signal (LD signal of frequency f _LD ). And an inverter frequency f _INV is added to the inverter 11 to control the high frequency lighting of the fluorescent tube 10, while the LD signal is added to the CCD drive circuit 15 to control the exposure timing of the CCD line sensor 14. A scanner is described. Thus the operating frequency f _INV by a natural number multiple of one line of the incorporation frequency FLD, the exposure timing of the a period of the luminance change of the fluorescent tube 10 due to the high frequency lighting CCD line sensor 14 accumulates charge Are fully synchronized. As a result, unevenness in received light amount for each line received by the CCD line sensor 14 is eliminated.

  In Patent Document 2, image light of a document is converted into an image signal by the photoelectric conversion element array 3, and the start signal 11 is input and transferred in synchronization with the clock signal 12, and the operation mode of the photoelectric conversion element array 3 is controlled and arranged. The light source control signal 15 for controlling the light emission timing of the light source is output to the light emitting diode array 1 by the carry-out signal 13 from the end of the photoelectric conversion element driver 4 that sequentially reads the accumulated charge as the output line signal 14 and the start signal 11 of the next line. An image reading device is described. The conveyance control signal generator 6 generates a conveyance control signal 16 that sets the timing so as not to overlap the light source control signal 15 and controls the conveyance timing of the external conveyance means.

  Patent Document 3 describes an image input device in which a CCD image sensor control unit 16 outputs a count pulse signal CS to a CCD image sensor 26 and also to a light source control unit 14.

  In Patent Document 4, when an original is irradiated with an exposure lamp and the reflected light is received by a photoelectric conversion element, an electric signal for the original image is read line by line. An image reading apparatus is described which is controlled in synchronization with a line synchronization signal that defines the reading start timing, and sets the oscillation frequency of the inverter so that the number of lamp lighting pulses per one line period is constant.

  Patent Document 5 discloses a light source that irradiates light on a document, a light source lighting unit that turns on the light source by applying a driving voltage to the light source, and a reflected light or transmitted light of the light from the document. An image reading apparatus comprising: a photoelectric conversion unit that converts the charge into an image signal; and a charge transfer unit that transfers the charge to convert the charge into an image signal, and reads the rarely drawn image as the image signal. Shift control signal generating means for generating a shift control signal for controlling the timing at which the charge is shifted; and lighting control signal generating means for generating a lighting control signal for controlling the timing at which the drive voltage is applied; And an image reading apparatus in which the waveform of the lighting control signal is such that the same waveform repeats with one cycle of the shift control signal as a repeating unit.

  The above-mentioned Patent Document 1 states that “the lighting frequency for high-frequency lighting of the fluorescent tube is multiplied by a natural number of the capture frequency of the capture signal of one line” so that the received light amount unevenness of each reading line is not present. It is. In other words, one line acquisition period can be set only by a multiple of the lighting period of the fluorescent tube, and there is a restriction on the one line acquisition period setting. On the other hand, if the lighting period of the fluorescent tube is set to a natural number multiple after the preferential determination of the capturing period of one line, it may not match the light source well.

  On the other hand, an image reading apparatus having a color reading mode and a monochrome reading mode may be designed as follows. In other words, in the color reading mode, the image quality is given priority by allowing a long time for one line processing, and in the monochrome reading mode, the time for one line processing is shortened to give priority to productivity (number of readings per unit time). is there. In the case of a high-speed machine, EMI (electromagnetic induction noise) and other characteristics may be advantageous if the clock frequency to be processed is lowered as much as possible. Therefore, in color reading, the amount of time allowed for a long processing time for one line is the clock frequency. Can be reduced. In this case, in order to “increase the time for one line processing” in the prior art, it is necessary to “lower the lighting frequency”.

  However, since the fluorescent tube and its lighting device are generally designed to light up efficiently at a certain frequency, the intended amount of light is not output when lighting at a frequency significantly different from that frequency. Or worse, it may be in a bad state that does not light up completely.

  Therefore, an object of the present invention is to prevent unevenness in the amount of received light for each reading line even in an image reading apparatus having modes with different reading clock frequencies.

Therefore, in the present invention, it is prepared in advance for each reading mode how many times the cycle of the reading clock is to be supplied to the light source lighting device. An appropriate lighting timing signal (CKinv) is supplied to the light source lighting device by switching it according to the reading mode. This is performed by the next document reading apparatus.
(1) A light source (102) for irradiating a document with light, lighting means (205) for driving the light source in response to a lighting timing signal (CKinv), and image information of light reflected from the document as an electrical image signal A photoelectric conversion means (107) that serially outputs in synchronization with a read clock (φ) that is converted and divided into pixels, and an A / D conversion means that digitally converts an electrical image signal output from the photoelectric conversion means into image data and outputs the image data (113-118)
Frequency dividing means (212) for generating a lighting timing signal (CKinv) having a cycle of an integral multiple (m) of the cycle of the read clock (φ) in synchronization with the read clock (φ) and outputting the same to the lighting means (205). An original reading apparatus comprising:

  In addition, in order to make an understanding easy, the symbol of the corresponding element or the corresponding matter of the Example which is shown in drawing and mentioned later in parentheses is attached for reference as an example. The same applies to the following.

  The lighting timing signal (CKinv) input to the lighting means for turning on the light source is synchronized with the reading cycle of the photoelectric conversion means, and the reading clock divided by m according to the reading mode is supplied to the lighting device. Thus, the lamp can be driven under stable conditions (frequency), and the same amount of received CCD light can be obtained for each line.

  (2) The document reading apparatus according to (1), further comprising means (206) for setting a period of an integral multiple (m) of the period of the reading clock (φ) of the frequency dividing means (212). .

  (3) The frequency dividing means (212) is given the integer multiple value (m) as a preset value, counts the read clock (φ) and counts the preset value (m), and then a new preset value A circulation counter (213) that starts counting, and a flip-flop (214) that inverts the indicated level of the lighting timing signal (CKinv) each time the circulation counter (213) counts a preset value (m). The document reading device according to (1) above.

  (4) The document reading apparatus according to (3), further comprising preset means for supplying data representing the value of the integer multiple (m) to a preset data input terminal of the circulation counter (213).

  (5) The frequency dividing means (212) is means for initializing the circulation counter (213) in synchronization with the switching (SH0) of the line through which the photoelectric conversion means (107) serially outputs the electric image signal. (215) and means (216) for initializing the flip-flop (214); The document reading apparatus according to (3) or (4) above.

  (6) The lighting timing which is the output of the flip-flop (214) by clearing or setting the flip-flop (214) immediately after switching of the serial output line (SH0) according to the polarity instruction signal (PL) The document reading apparatus according to any one of (3) to (5), further including: start level setting means (216a-216c) that sets the instruction level of the signal (CKinv) to non-instruction or instruction level.

(7) A printer (200) that forms an image represented by image data on a sheet;
Document reading device (100, 120) according to any one of claims 1 to 6; and
A copying apparatus comprising: image data processing means (302) for converting image data generated by the document reading device (100, 120) into image data suitable for image formation of the printer.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

  FIG. 1 shows the external appearance of a full-color digital multi-function copier MF1 according to the first embodiment of the present invention. The full-color copying machine MF1 is roughly constituted by units of an automatic document feeder (ADF) 120, an operation board 10, a color scanner 100, and a color printer 200. The operation board 10 and the color scanner 100 with the ADF 120 are units that can be separated from the printer 200. The color scanner 100 has a control board having a power device driver, sensor input, and controller, and an engine controller ( CPU 301: Directly or indirectly communicates with FIG. 3) to read the document image under timing control.

  A controller board (400: FIG. 3) to which a scanner 100, a printer 200, and an engine (300: FIG. 3) including an image input / output device (302: FIG. 3) are connected is connected to a LAN (Local Area Network) connected to a personal computer PC. Is connected, and a facsimile control unit (FCU 417: FIG. 3) is connected to a switch PBX connected to a telephone line PN (facsimile communication line).

  FIG. 2 shows a document image reading mechanism of the scanner 100 of the multifunction copying machine MF1 and the ADF 120 attached thereto. The original placed on the contact glass 101 of the scanner 100 is illuminated by the illumination lamp 102, and the reflected light (image light) of the original is reflected by the first mirror 103 in parallel with the sub-scanning direction y. The illumination lamp 102 and the first mirror 103 are mounted on a first carriage (not shown) that is driven at a constant speed in the sub-scanning direction y. Second and third mirrors 104 and 105 are mounted on a second carriage (not shown) that is driven in the same direction as the first carriage, and the image light reflected by the first mirror 103. Is reflected downward (z) by the second mirror 104, reflected in the sub-scanning direction y by the third mirror 105, converged by the lens 106, irradiated to the CCD 107, and converted into an electrical signal. That is, it is converted into RGB color image signals.

  The first and second carriages are driven forward (original scanning) and backward (return) in the y direction using the traveling body motor 108 as a drive source. As described above, the scanner 100 is a flatbed reading original scanner that scans the original on the contact glass 101 with the lamp 102 and the mirror 103 and projects the original image on the CCD 107, but the first carriage is in the home position (standby position). It is also possible to stop at the HP and perform sheet-through reading.

  In order to perform sheet-through reading, an automatic document feeder (ADF) 120 is mounted on the scanner 100, and the sheet is placed at the reading visual field position of the first mirror 103 when the first carriage is stopped at the home position HP. There is a glass 132 that is a through reading window, and a transport drum (platen) 125 of the ADF 120 faces the glass 132.

  Documents stacked on the document tray 121 of the ADF 120 are detected by the filler sensor 130. The document size is determined based on whether the switch group 131 that detects the set position of the side plate that forces the document to a predetermined posture is on or off. At the time of sheet-through reading, the uppermost one of the documents stacked on the document tray 121 of the ADF 120 is sent to the registration roller 125 by the pickup roller 122 and the feeding rollers 123 and 124, and sent from the registration roller 125 to the window glass 132. At this time, the image on the original is reflected by the second mirror 104 and projected onto the CCD 107 by the first mirror 103 at the home position HP, and the CCD 107 photoelectrically converts the projected image to generate an image signal. That is, RGB color image signals are generated.

  In this embodiment, the home position HP is a sheet-through reading position of the image reading optical system, and is a first carriage driving start point (= return end point) of flat bed reading. In the case of flat bed reading, the first carriage is driven from the home position HP, and reading of a document image is started from a position advanced by a distance of A + B from HP (right end of the scale plate scp: reading start point). That is, the image signal generated by the CCD 107 is validated. Between the home position HP and the reading start point, there are a base point sensor 109 for detecting the first carriage and a reference white plate rwp. The reference white plate rwp is in close contact with the upper surface of the left end portion of the contact glass 101. Although the reference white plate rwp has read a document having a uniform density due to variations in individual light emission intensities of the illumination lamp 102, variations in the main scanning direction x, sensitivity unevenness for each pixel of the CCD 107, and the like. It is prepared for correcting the phenomenon in which read data varies (shading correction). It is also used for image signal amplification gain adjustment (AGC).

  At the time of flat bed reading, the sub-scan driving of the first carriage and the tracking of the sub-scan position are started from the home position HP. When the reference white plate rwp is in the reading field of the first carriage, the image signal of the CCD 107 (image data obtained by digital conversion) is read into the image signal processing circuit 111 (FIG. 3). When the first carriage crosses the base point sensor 109, the first carriage is started and the scanning speed converges to the set value. When the sub-scanning position reaches the reading start end (A + B: right side of the right end of the scale plate scp), the image signal valid signal (frame synchronization signal: FGATE) is switched to a significant level. In the flat bed reading, the first carriage is sub-scanned to the front end (right end) of the document on the contact glass 101, and when it is turned back to return driving, it temporarily stops at the home position HP. The sensor 109 detects the first carriage, and the sub-scanning position is initialized to the base point position data (set value) at the time of detection. The first carriage is temporarily stopped at the home position HP and then driven to the document size detection position (A + B + C), where it waits.

  The base body 135 of the ADF 120 is hinge-coupled (hinge-connected) to the base body of the scanner 100 on the back side (the back side of FIG. 2), and has a handle 136 on the front side of the base body 135 (the front side of the paper surface of FIG. 2). By raising the substrate 135, the ADF 120 can be raised (opened). On the back side of the base body 135 of the ADF 120, there is a pressure plate switch that detects opening and closing of the ADF 120. In this embodiment, when the ADF 120 is raised from the prone posture shown in FIG. 1 to the standing posture, the lower surface of the pressure plate (document pressing plate) 137 is set at an angle of about 30 degrees with respect to the document placement surface of the contact glass 101. The pressure plate switch is switched from OFF indicating pressure plate closing to ON indicating pressure plate opening, and the lower surface of the pressure plate 137 is placed on the document placement surface of the contact glass 101 in the process of falling from the standing posture to the flat posture. On the other hand, when the angle is equal to or smaller than the set angle, the pressure plate switch is switched from ON indicating pressure plate opening to OFF indicating pressure plate closing.

  The reason why the switching angle of the pressure plate switch open / close detection is set to a wide angle of about 30 degrees is that the original size detection position (FIG. 2) is set in advance when the angle is smaller than the set angle. The illumination lamp 102 on the positioned first carriage is turned on to illuminate the original on the contact glass 101, the original image is projected onto the CCD 107, and the boundary between the original and the background based on the image signal of the CCD 107, that is, the original side This is to detect the edge (the width of the document in the main scanning direction x). When the ADF 120 is tilted by about 10 degrees or more, the light from the illumination lamp 102 is reflected by the original on the contact glass 101 and reaches the CCD 107 and is detected brightly by the CCD 107, but the light outside the original is detected by the pressure plate 137. Although reflected from the lower surface, since the lower surface is inclined, it almost goes outside the optical field of view of the CCD 107, so that the outside of the original is detected darkly by the CCD 107. A document size detection 48 (FIG. 4), which will be described later, detects the size of the document on the contact glass 101 in accordance with such a difference in brightness.

In this embodiment, the following modes of document image reading can be performed:
1. Manual Document Reading The user raises the ADF 120 and places the document on the contact glass 101. The user scans the document with the pressure plate 137 by tilting the ADF 120, and performs the above-described flat bed type document scanning (flat bed reading). When the first carriage passes directly below the reference white plate rwp, shading correction data is generated based on the read image data of the reference white plate rwp, and the shading correction data in the memory is updated to the one obtained this time. When the flatbed reading is finished, the user raises the ADF 120 and takes out the document. When the user sets a document on the contact glass 101 and closes the ADF 120, the document size detection 48 (FIG. 4) detects the size of the document on the contact glass 101.
2. Sheet-through reading The document on the document tray 121 is transferred by the ADF 120 and the above-described sheet-through reading is performed. When a single document is fed from the tray 121, the first carriage is driven to the position of the reference white plate rwp and returned to the home position HP. When the first carriage is directly below the reference white plate rwp, the read image data of the reference white plate rwp is displayed. Based on this, the shading correction data is generated, and the shading correction data in the memory is updated to the one obtained this time. This reading is performed for each of the documents on the document tray 121.

  FIG. 3 shows the configuration of the image processing system of the multifunction copying machine MF1 shown in FIG. The multi-function copier MF1 includes an engine 300 that performs document image reading and color printing, a controller board 400, and an operation board 10. The engine 300 includes a CPU 301 that controls image reading and printing processes, the above-described color scanner 100, the above-described printer 200, and an image input / output processing 302 that includes an ASIC (Application Specific IC).

  The reading unit 110 of the scanner 100 includes a CPU, a ROM, and a RAM, and the CPU 100 controls the entire scanner 100 by writing a program stored in the ROM and executing the program. Further, it is connected to the process control CPU 301 via a communication line, and performs an operation instructed by transmission / reception of commands and data. The CPU in the reading unit 110 performs detection and ON / OFF control of a filler sensor (document detection sensor), a base point sensor, a pressure plate switch, a cooling fan, and the like. In the reading unit 110, a scanner motor driver is driven by a PWM output from the CPU, generates an excitation pulse sequence, and drives a pulse motor for scanning a document.

  The document image is illuminated by the light output of the halogen lamp 102 (FIG. 2) energized by the lamp regulator, and the reflected light of the document, that is, the optical signal, passes through the plurality of mirrors 103 to 105 and the lens 106 to read R, G, and B. The image is formed on a CCD 107 including three line sensors. The 3-line CCD 107 outputs an analog image signal of each pixel of each RGB to the digital processing circuit (AFE) 111. The AFE 111 is an image signal processing unit that amplifies an image signal, digitally converts it into image data, and performs shading correction.

  The controller board 400 includes a CPU 402, a document storage control 403 constituted by an ASIC, a hard disk device (hereinafter referred to as HDD) 401, a local memory (MEM-C) 406, a system memory (MEM-P) 409, North Bridge (hereinafter referred to as NB) 408, South Bridge (hereinafter referred to as SB) 415, NIC 410 (Network Interface Card), USB device 411, IEEE 1394 device 412, Centronics device 413 and others. The operation board 10 is connected to the document accumulation control 403 of the controller board 400. A facsimile control unit (FCU) 417 is also connected to the document storage control 403 by a PCI bus.

  The CPU 402 can transmit / receive document information to / from a personal computer PC connected to the LAN via the NIC 410 or another personal computer PC via the Internet. In addition, it is possible to communicate with a personal computer, a printer, a digital camera, or the like using the USB 411, IEEE 1394 412, and Centronics 413.

  The SB 415, the NIC 410, the USB device 411, the IEEE 1394 device 412, the Centronics device 413, and the MLB 414 are connected to the NB 408 via a PCI bus. As described above, the MLB 414 is a board connected to the engine 300 via the PCI bus. The MLB 414 converts the document data input from the outside into image data (image data), and outputs the converted image data to the engine 300.

  The local memory 406, the HDD 401, and the like are connected to the document storage control 403 of the controller board 400, and the CPU 402 and the document storage control 403 are connected via the NB 408 of the CPU chipset. The document accumulation control 403 and the NB 408 are connected via an AGP (Accelerated Graphics Port).

  The CPU 402 performs overall control of the multifunction function copying machine MF1. The NB 408 is a bridge for connecting the CPU 402, system memory 409, SB 415, and document storage control 403. A system memory 409 is a memory used as a drawing memory or the like of the multifunction copying machine MF1. The SB 415 is a bridge for connecting the NB 408 to the PCI bus and peripheral devices. The SB 415 is connected to a card IF 418 for reading and writing an external ROM and an SD memory card (hereinafter referred to as an SD card). The card IF 418 is connected to an SD card read / write device (card reader), and can read data from an SD card attached to the card reader, and can write data to the SD card.

  The local memory 406 is a memory used as a copy image buffer and a code buffer. The HDD 401 is a memory for storing image data, document data, programs, font data, forms, LUT (Look Up Table), and the like. The operation board 10 is an operation unit that receives an input operation from the user and performs display for the user.

  FIG. 3 shows the flow of image data exchanged between the scanner 100 and printer 200 and the image input / output processing 302. The image input / output processing 302 includes scanner image processing 303 that performs reading γ correction, MTF correction, and the like for each of R, G, and B image data generated when the color original scanner 100 reads an original image. Printer image processing 304 that converts R, G, B image data into c, m, y, k recording color data (print data) that matches the image expression characteristics of the C, M, Y, K color writing of the printer 200. In addition, there is an image processing I / F (Interface circuit) 305 that outputs document read image data RGB to the document storage control 403 and supplies the image data RGB output from the document storage control 403 to the printer image processing 304.

  In the case of monochrome copying, the G image data is output from the scanner image processing 303 to the image processing I / F 305, the image processing I / F 305 outputs the G image data to the printer image processing 304, and the printer image processing 304 is the G image data. Is converted into k recording color data, and if necessary, scaling, image processing, printer γ conversion and gradation processing are performed, and the result is output to the C writing unit 212 of the printer 200. The writing unit 212 modulates or turns on / off the current supplied to the laser light emitting diode of the optical scanning unit 203 (FIG. 4) according to the k recording color data output from the image processing 304.

  For color copying, RGB image data output by the scanner image processing 303 is temporarily stored in the local memory 406 or the HDD 401 or registered in the HDD 401 and read out via the image processing I / F 305 and the image storage control 403. Used for copying or printing, or sent to the outside.

  When printing registered image data by the printer 200 or image data received from the outside, the image data is given to the printer image processing 304 via the image accumulation control 403 and the image processing I / F 305. The printer image processing 304 converts the image data into cmyk recording color data, performs scaling, image processing, printer γ conversion and gradation processing as necessary, and outputs the result to the writing unit 212.

  The detection signal lines of the pressure plate switch of the reading unit 110 and the filler sensor 130 of the ADF 120, the key operation detection signal line of the power key switch 21 of the operation board 10, and the reception detection signal line of the facsimile controller 417 are the states of the controller board 400. The change detection circuit ACD is connected. While the main power switch is on, the state change detection circuit ACD is applied with the operating voltage + 5VE continuously output even when the power supply circuit 80 is in the sleep mode. As long as + 5VE is applied, if there is a signal change in any of the signal lines connected to the detection circuit ACD, a change detection signal indicating this is given to the CPU 402. In response to this signal, the CPU 402 switches the power supply circuit 80 to the standby mode.

  The state change detection circuit ACD has a power-on reset circuit that generates a reset pulse when the operation voltage + 5VE in the sleep mode is applied (when the main power switch 79 is switched from off to on), and reset by the reset pulse. Then, there is a latch (flip-flop; its Q output is the power-on mode signal POD) that sets the power-on mode signal POD as the output to a low level L (“0”). When the CPU 402 switches the power supply circuit 80 from the sleep mode to the standby mode, this latch is set to switch the power-on mode signal POD as the output to the high level H (“1”). “0” of the power-on mode signal POD means that the power supply circuit 80 is in the standby mode by switching the main power switch 79 from off to on, and “1” of the power-on mode signal POD is It means that it has switched from hibernation mode to standby mode. This power-on mode signal POD is generated when the operation voltage is applied to the document scanner 100 by the document scanner 100 when the operation voltage is applied by turning on the main power switch 79 or by the CPU 402 from the sleep mode to the standby mode. Referenced to determine whether or not.

  FIG. 4 shows an outline of the image signal processing function of the sensor board unit SBU and the AFE 111 of the color document scanner 100. The CCD 107 divides the R, G, and B image signals into even-numbered pixel columns and odd-numbered pixel columns and outputs them in parallel. The even-numbered pixel row and the odd-numbered pixel row of each color image signal are individually amplified by the buffer amplifier and output to the image output corrections 113 to 118 of the AFE 111, respectively. FIG. 4 shows only the functional configuration of the image output correction 113 that converts even-numbered pixel columns of the R image signal into digital data, but the functional configurations of the other image output corrections 114 to 118 are also those of the image output correction 113. It is the same. Hereinafter, the function of the image output correction 113 will be described.

  The analog image signal of the R even-numbered pixel row output from the CCD 107 is driven by the Re buffer amplifier on the SBU and sampled and held by the sampling circuit 31 to remove high frequency components such as reset noise. The variable gain amplifier 32 is an amplifier whose gain can be controlled by the control voltage Vg applied to its control terminal, and the offset setting circuit 33 is a positive or negative offset level by the control voltage Vof applied to its control terminal. It has the function to provide. Vg and Vof are voltages determined by the CPU 42 by operating the D / A conversion circuit 37. For example, if the D / A conversion circuit 37 is 8 bits, the CPU 42 sets any value from 0 to 255 to the D / A conversion circuit 37, and the D / A conversion circuit 37 outputs a corresponding voltage.

  The A / D conversion circuit 34 converts the analog image signal into a digital image signal, that is, image data with a predetermined resolution (for example, 8 bits) based on the upper limit reference value Vrefd / Vrefw and the lower limit reference value Vrefb. This image data is input to the offset level detection circuit 39 and the offset level subtraction circuit 35. Here, the CPU 42 determines the upper limit reference value Vrefw / Vrefd and the lower limit reference value Vrefb by operating the D / A conversion circuit 37. The upper limit reference value outputs Vrefw and Vrefd of the D / A conversion circuit 37 are input to the selector 38. The selector 38 reads Vrefw when reading the reference white plate rwp, Vrefd when reading the original, and the upper limit reference value. To the A / D conversion circuit 34.

  The CCD 107 has a sensor unit that is physically shielded, called an optical black (OPB) pixel, and then a sensor unit that outputs a voltage proportional to the amount of incident light, called an effective pixel. The data of the OPB pixel and the effective pixel are repeatedly output every main scanning period.

  The offset level detection circuit 39 has a function of capturing and storing the output of the A / D conversion circuit 34 corresponding to the OPB pixel of the CCD 107 during the period when the xopb signal is asserted. The offset level is an average value obtained by capturing a plurality of OPB pixels, and is stored for each output system of the CCD 107. The offset level subtraction circuit 35 is a circuit that subtracts the offset level stored in the offset level detection circuit 39 from the output value of the input A / D conversion circuit 34. The white peak detection circuit 41 stores a peak value of image data input within a period in which an xlgate signal representing an effective pixel section during document reading and a SMPL signal representing a reading period during reference white plate reading are asserted. It is. The CPU 42 can obtain the latest offset level value and peak value by accessing the offset level detection circuit 39 and the white peak detection circuit 41.

  The shading data storage 40 is a circuit that sequentially stores the values read from the reference white plate rwp while performing processing such as averaging for each pixel. The shading correction circuit 36 stores the image data obtained by reading the image as shading data storage. 40 is a circuit for converting into shading-corrected image data using the correction data stored in 40. The CPU 42 stores the image data for reading the reference white plate in the line memory in the shading data storage 40 for temporarily storing the image data for the inter-line averaging of the image data, and then stores the specific pixel (reference white plate rwp). Image data at a certain position in the main scanning direction x) can be read.

  The output of the A / D conversion circuit 34 causes a predetermined delay when A / D conversion is performed. xopb is an offset level data range instruction signal that is designed to be asserted for a predetermined period at the timing of the A / D conversion output corresponding to the read analog signal of the OPB pixel. In general, it has been found from experience that the latter half of the read analog signal of the OPB pixel has less noise, and this setting is also made in this embodiment. xlgate is a signal that is asserted in the area where the original in the effective pixel portion is read, and is used to specify a reading range when a white peak is detected.

  WTGT is a signal asserted when the CCD 107 reads the reference white plate rwp, and is used as a selector switching signal. The selector 38 selects Vrefw when WTGT is asserted, and selects Vrefd when negated and applies it to the A / D conversion circuit 34. SMPL is asserted during a part of the timing when the CCD 107 reads the reference white plate rwp (WTGT), and instructs the timing for taking the reference white plate data into the shading data FIFO.

-Adjustment of gain, etc. AGC-
In “adjustment AGC such as gain”, the CPU 42 first applies the upper reference voltage Vrefw to the A / D conversion circuit 34 when the first carriage moves to the position of the reference white plate rwp in accordance with the operation program read from the ROM 43a and written to the RAM 43b. Given, the peak data Dwp of the reference white plate reading is read. Next, it is checked whether the peak data Dwp is within a predetermined range Dp ± B. Dp is an adjustment target value, which is a value at which the peak value of the analog image signal input to the A / D conversion circuit 34 does not exceed the upper reference voltage Vrefw (for example, about 80% of the upper reference voltage Vrefw considering the margin). is there. This is because the performance of the A / D conversion circuit is sufficiently extracted to extract a highly accurate digital signal. B is an adjustment tolerance.

  When the peak data Dwp is within the predetermined range Dp ± B, the control voltage Vg, the lower reference voltage Vrefb, and the upper reference voltages Vrefw and Vrefd which are being set at this time are stored in the RAM 43b. When the peak data Dwp is not within the predetermined range Dp ± B, the set value Svg (Dvg of the D / A conversion circuit 37 for outputting the control voltage Vg (D / A output) for determining the gain is entered so as to enter. / A input). It is determined whether Svg of the calculation result is within a settable range (SvgL to SvgH) of the D / A conversion circuit 37. For example, if the D / A conversion circuit 37 is an 8-bit D / A conversion circuit, the settable range is 0 to 255. If it is within the settable range, it is actually set and the peak data Dwp is read again. If Svg is outside the range that can be set in the D / A conversion circuit 37, a value SvgL or SvgH close to the calculated value within the settable range is set, the peak data Dwp is read again, and the same check is performed.

When the peak data Dwp is not within the predetermined range Dp ± B, the CPU 42 calculates the upper reference voltage Vrefw of the A / D conversion circuit 34 when reading the reference white plate rwp. The relationship between the set value (input data) of the D / A conversion circuit 37 and the reference voltage Vrefw (output voltage) is represented by Vrefw = f (Srefw), and the inverse function of f (Srefw) is Srefw = g (Vrefw). If there is, the input data Srefw of the D / A conversion circuit 37 for Vrefw to be changed is
Srefw = g (Dwp / Dp / (f (Stp) -f (Stb))-f (Stb))
Indicated by here,
Dp: Peak data expected after changing the set value Srefw given to the D / A conversion circuit 37 addressed to Vrefw,
Stp: Set value Srefw given to the D / A conversion circuit 37 when the peak value Dwp is obtained.
Stb: set value Srefb of the D / A conversion circuit 37 addressed to Vrefb,
It is.

  It is checked whether the calculation result Srefw is within the settable range (SrefwL to SrefwH) of the D / A conversion circuit 37. For example, if 43 is an 8-bit D / A conversion circuit, the settable range is from 0 to 255. If it is within the settable range, it is actually set and the peak data Dwp is read again. If the calculation result Srefw is outside the settable range of the D / A conversion circuit 37, an error is detected, but a value close to the calculated value is set within the settable range, and the process ends. However, this error occurs only when a hardware problem such as pattern disconnection occurs.

Since the reference white plate reading reference voltage Vrefw is changed, the size of the image data after shading correction is changed unless the document reading reference voltage Vrefd is also changed. When the reference white plate reading reference voltage Vrefw before and after the change is Vrefwb and Vrefwa, the original reading reference voltage Vrefd before and after the change is Vrefdb and Vrefda, and the lower reference voltage is Vrefb, respectively.
(Vrefwb-Vrefb) / (Vrefwa-Vrefb)
= (Vrefdb-Vrefb) / (Vrefda-Vrefb)
Change Vrefd so that That is, the document reading reference voltage Vrefd of the D / A conversion circuit 37 is set to Vrefda that satisfies the above equation.

  Next, the CPU 42 sets a setting value for outputting the Vrefda addressed to Vrefd and a setting value for outputting the Vrefwa addressed to Vrefw. The upper reference voltages Vrefw and Vrefd set in this way, and the control being set at this time The set values Srefw, Srefd, Svg, and Srefb of the voltage Vg and the lower reference voltage Vrefb are stored in the RAM 43b, and the adjustment AGC such as gain is ended. Each set value obtained by this gain adjustment is transferred to the controller board 400, and the time at that time is registered in the setting data table addressed to the AFE 111 of the HDD 401, which is a nonvolatile memory, together with the previous execution time. Update writing). This is performed in step 26 shown in FIG.

  The CPU 42 of the AFE 111 of the scanner 100 acquires the setting values of the HDD 401 from the controller board 400 (the HDD 401) and writes them into the RAM 43b immediately after the power is turned on to the scanner 100 (and the ADF 120). It is set in each part in the image output corrections 113 to 118 shown in FIG. This is performed in steps 24 and 27 of FIG. This setting is shown below.

-Settings such as gain-
The CPU 42 registers in the setting data table of the HDD 401 of the controller board 400 when proceeding to a standby state (standby mode or low power mode: described later) waiting for a document image reading instruction from the power-off or energy-saving mode (pause mode: described later). The above-mentioned various set values such as the adjustment gain are read out, written into the RAM 43b, and stored (set) in the latch (register) of the D / A conversion circuit 37 for each image output correction. That is, the CPU 42 gives the set value Srefd for Vrefd registered in the HDD 401 which is a non-volatile memory to the D / A conversion circuit 37 and supplies the D / A conversion output voltage Vrefd to the A / D conversion circuit 34 via the selector 38. It is given as a reference voltage. Further, the set values Svg and Srefb of Vg and Vrefb are also given to the D / A conversion circuit 37. When the image signal is input to the image output correction 113 after such setting, the A / D conversion circuit 34 converts the analog image signal for document reading into a predetermined range between the lower reference voltage Vrefb and the upper reference voltage Vrefd. A / D conversion is performed on image data divided into the number of divisions.

−Shading correction data setting−
When setting the shading correction data when the first carriage is directly below the reference white plate rwp, the CPU 42 performs image reading processing in which each setting value such as a gain adjustment value is set in the D / A conversion circuit 37 as described above. Then, the reference white plate rwp is read, and shading correction data for one main scanning line is generated based on the image data and stored in the shading data storage 40.

-Original size detection-
When the first carriage is at the document detection position and the ON / OFF signal of the pressure plate switch indicates a change from opening to closing of the pressure plate 137, the CPU in the reading unit 110 (FIG. 3) turns on the illumination lamp 102 and turns on the first lamp. One carriage is driven to the home position HP, and the CPU 42 of the AFE 111 instructs the document size detection 48 to detect the document size. The document size detection 48 is a continuous process from the reading start point of the image data of each line in the main scanning direction x to the end point (the side end on the back side of the contact glass 101 with the pressure plate 137 opened as shown in FIG. 3). The number of white pixels is counted, and the average value of the count values of several lines is encoded (encoded) into the document size and output to the CPU. When a predetermined number of continuous white pixels cannot be obtained, the document size detection 48 outputs a no document code to the CPU 42.

-Image output correction-
When reading a document image, each image output correction 113 to 118 of the AFE 111 executes image processing according to each setting value read from the setting data table of the HDD 401 which is a non-volatile memory and set in the D / A conversion circuit 37, and variable gain The amplifier 32 amplifies the image signal by the set gain Vg, and the A / D conversion circuit 34 converts the image signal into image data representing the image signal divided by a predetermined number of divisions between the lower reference voltage Vrefb and the upper reference voltage Vrefd. / D conversion. Since the analog image signal is A / D converted into image data using the reference voltage values Vrefw and Vrefd set in the above-described “adjustment AGC of gain and the like” and written in the nonvolatile memory 43, the light amount fluctuates with time. However, the accuracy of the image data output from the A / D conversion circuit 34 is high and stable.

  The shading correction circuit 36 applies shading correction to the image data based on the data stored in the shading data storage 40. As a result, the image data of each point (image) in the main scanning direction x is corrected and output so that the image data has substantially the same value for the same white level.

  The image data of the R even-numbered pixel row subjected to the shading correction by the image output correction 113 as described above is combined with the image data of the R even-numbered pixel row similarly shaded by the image output correction 114 by the line synthesis 45 to one line row. The images are combined and output to the scanner image processing 303. Through similar image signal processing, the G and B image data combined into one line is output from the line combination 46 and 47 to the scanner image processing 303.

  The shading correction in the case of flat bed reading will be described. When the user places a document on the contact glass 101 and closes the ADF 120, the pressure plate switch is switched from open to closed. At this time, the first carriage is at the document size detection position, and the reading unit 110 lights the illumination lamp 102. Thus, the return drive of the first carriage to the home position HP is started. The document size detection 48 of the AFE 111 detects the document size on the contact glass 101 based on the G image data output from the image output correction 115. When the base point sensor 109 detects the first carriage, the reading unit 110 updates the sub-scanning position data to indicate the sub-scanning position (fixed value data) of the base point sensor 109. During the sub-scan driving of the first carriage, the reading unit 110 synchronizes with the driving pulse of the pulse motor that drives the first carriage, and the sub-scan driving (forward driving: forward driving: FIG. 2) of the first carriage. And from left to right), the sub-scan position data is incremented (driving pulse is counted up), and decremented (driving pulse is counted down) during driving in the return direction (right to left in FIG. 2). The reading unit 110 monitors the sub-scanning position, positions the first carriage at the home position, and turns off the illumination lamp 102.

  When the user operates the start key 17, the reading unit 110 turns on the illumination lamp 102 and starts the sub-scan driving of the first carriage for flat bed reading. When the sub-scanning position becomes the region of the reference white plate rwp, the shading data storage 40 (FIG. 4) starts reading the read image data of the reference white plate rwp, calculates the average value of a plurality of lines, A multiplication coefficient value necessary for setting the average value of the image data addressed to the pixels to the reference white level image data (for example, about 255 or about 80% thereof) is calculated and stored in the FIFO memory inside the data storage 40.

  While the sub-scanning position is in the document area from the beginning to the end of the document, the data storage 40 sequentially reads out the multiplication coefficient value for each pixel on one line from the FIFO memory and gives it to the shading correction 36. The shading correction 36 simultaneously gives the image data of each pixel of each line for document reading and the multiplication coefficient value addressed to the same pixel to the read address of the ROM in the shading correction 36. Since the ROM stores image data after shading correction representing the product of the image data given as an address and the multiplication coefficient value, the image data obtained by shading correction of the image data given as the address is read from the ROM. And output to the line synthesis 45 in the next stage.

  Next, shading correction in the case of sheet-through reading will be described. When the user loads a document on the document tray 121 and operates the start key 17, the reading unit 110 starts feeding the document from the document tray 121, turns on the illumination lamp 102, and turns on the first carriage. The sub-scan driving for reading the flat bed is started. When the sub-scanning position becomes the area of the reference white plate rwp, the shading data storage 40 (FIG. 4) starts reading the read image data of the reference white plate rwp, calculates the average value of a plurality of lines, and calculates each pixel on one line. A multiplication coefficient value necessary to make the average value of the addressed image data as reference white level image data is calculated and stored in the FIFO memory inside the data storage 40. When this is finished, the reading unit 110 starts the return drive of the first carriage to the home position HP, and positions the first carriage to the home position HP. This ends until the leading edge of the document fed from the document tray 21 reaches the window glass 132.

  While reading the document while the leading edge of the document enters the imaging field of view of the first carriage at the home position HP and the tail end of the document leaves the imaging field of view, the data storage 40 is multiplied by one line from the FIFO memory to each pixel. The coefficient values are read out sequentially and given to the shading correction 36. The shading correction 36 outputs the image data subjected to the shading correction to the line composition 45.

  When there is an original on the original tray 121 when the tail end of the original passes through the imaging field of view of the first carriage, the reading unit 110 starts to send out the original and starts reading the reference white plate rwp. Subsequent reading control is the same as the above-described first document reading.

  The scanner control circuit 206 of the reading unit 11 controls the lamp control circuit 205, the timing control circuit 211, and the motor control unit 207 in accordance with instructions from the CPU 301. The lamp control circuit 205 controls on / off of the exposure lamp 102 that is a discharge tube in accordance with an instruction from the scanner control CPU 206.

  The motor control unit 207 controls the sub-scanning drive motor 108 and the ADF motor in accordance with instructions from the scanner control CPU 206. A rotary encoder (E) is connected to the drive shaft of the sub-scanning drive motor 108. The position sensor detects whether the movable part of the scanner and the ADF is at the reference position.

  The timing control circuit 211 generates various signals in accordance with instructions or control signals from the scanner control CPU 206, the CPU 42, and the CPU 301 of the engine 300. Upon receiving a reading start instruction from the CPU 301, the scanner control CPU 206 controls the timing control circuit 211 to start reading the CCD image sensor 107, turns on the exposure lamp 102, and starts driving the sub-scanning drive motor 108.

  The CCD 107 is supplied with a drive clock output from the timing control circuit 211 via a driver (not shown), and outputs analog voltages (even-numbered pixels e, odd-numbered pixels o) that are substantially proportional to the amount of received light. Here, the drive clock indicates a series of signals necessary for CCD drive, such as a clock for transferring charges from the light-receiving pixel column to the analog shift register, and a clock for driving the analog shift register (see FIG. 6).

  The timing control circuit 211 generates a clock under conditions instructed by the scanner control CPU 206 and outputs the clock to the reading unit SBU and the lamp driving circuit 205. Here, the conditions instructed to the CPU are one main scanning clock number, clock frequency, and the like.

  The timing control circuit 211 generates a main scanning signal (φ to CP in FIG. 6), a sub scanning signal (SH), a light source lighting clock (CKinv), and the like related to reading of the CCD driving clock (φ) and the like. In the timing control circuit 211, the clock output from the oscillator is input to the multiplication circuit, and a high-frequency clock such as 200 MHz is generated. Based on this clock, various clocks for driving the CCD are generated. Various clocks related to the reading of the CCD drive clock itself have a frequency of about 25 MHz, but a high frequency clock of this level is required to satisfy the phase and duty between the drive clocks. The clock (CKinv) for turning on the light source is configured to count a clock related to reading (for example, a clock having the same frequency as the φ clock) and to invert the clock after a predetermined count.

  The inputs of the lamp driving circuit 205 are a power supply (24V), GND, a lamp driving clock (CKinv), and a lighting permission signal cnt. The lamp driving circuit 205 is controlled with respect to lighting by the lighting permission signal cnt and the lamp driving clock CKinv. The lamp driving clock CKinv is a timing clock for generating a lamp driving voltage that is an output of the lamp driving circuit 205, and a high voltage is applied from the lamp driving circuit 205 to the lamp at the rise of CKinv shown in FIG. The lighting permission signal cnt is a signal that permits lighting when it is at the Low level, and does not light even when the lamp driving clock CKinv is input when it is at the High level (see FIG. 7).

  Thus, normally, the lamp driving clock CKinv is inputted to the lamp driving circuit 205, and the CPU can easily perform the ON / OFF control for activating the lighting permission signal: cnt when an image reading request is made. Of course, there is no problem with the present invention even in a configuration without the lighting permission signal: cnt (power supply, GND, lamp driving clock: CKinv).

  FIG. 7 shows a CCD drive clock (generally driven by inputting SH, φ, / φ, RS, CP) and a lamp drive clock: Ckinv. One line capture signal SH is a signal for transferring the charge accumulated in the light receiving portion of the CCD to the shift register inside the CCD, and in FIG. 6, the transfer is performed during the High period. φ, / φ, RS, CP are clocks for transferring charges in the shift register and finally outputting them as voltage signals.

  Here, the reading time for one line, which is the unit reading amount in the image reading apparatus, is defined by the optical accumulation time (Tint) shown in FIG. This time is determined by the frequency of the φ clock: f and the number of clocks: n. That is, Tint = n × 1 / f. The lamp drive clock Ckinv is shown as an example in which m clocks corresponding to the frequency of the read clock φ are inverted. A frequency dividing circuit 212 that performs this is in the timing control circuit 211.

  FIG. 5 shows the configuration of the frequency dividing circuit 212. The frequency dividing circuit 212 includes a counter 213 and a flip-flop 214, and is configured to input a signal SH0, a clock CK0, and an initial value (preset data m). The one-line synchronization signal SH0 is a signal having the same cycle as the one-line time Tint for reading, and CK0 is a clock having the same frequency as the φ clock. The counter 213 takes in the count initial value m via the NOR gate 215 when a one-line synchronization signal SH0 or a carry of the counter 213 (preset value count over) occurs, and counts down the clock CK0 from the initial value m. The flip-flop 214 is configured to invert the level of the output (lamp drive clock CKinv) by the carry of the counter 213. In this configuration, the cycle of the lamp driving clock CKinv can be set by the count initial value m. This set value m is a value previously stored in the memory of the scanner control CPU 206 and is held (stored) for each mode such as color reading / monochrome reading mode. The scanner control CPU 206 corresponds to the designated reading mode. The read value (m) is read and reflected by setting it in the register (latch) of the timing control circuit 211. That is, it is applied to the preset data input terminal of the preset circulation counter 213. In the example of FIG. 5, since the synchronization signal SH0 for one line is input to / CLR of the flip-flop 214, the level of the lamp drive clock CKinv is forced to be Low at the line start end where the line synchronization signal SH0 arrives. .

  FIG. 8 shows the configuration of the frequency divider of the second embodiment. The frequency dividing circuit 212 in FIG. 8 has a function of setting the output of the flip-flop 214 to forced low or high when the synchronization signal SH0 of one line is input. The polarity instruction signal PL is an instruction for this, and when PL = Low and High, the output of the flip-flop 214 is forced to High and Low via the inverter 216c and the gates 216a and 216b, respectively. This polarity instruction signal PL is a value written (held) in advance in the memory of the scanner control CPU 206, and is determined for each mode such as color reading / monochrome reading mode. The scanner control CPU 206 The value corresponding to the read mode being read is read and set in the register of the timing control circuit 211 to be reflected.

  Thus, by setting the counter initial value m when generating the lamp driving clock and the polarity instruction signal PL in synchronization with SH0 for each mode such as the color reading / monochrome reading mode, the color reading / monochrome reading mode, etc. Even when the read clock frequency is changed for each mode, the same frequency of the lamp drive clock CKinv can be obtained.

FIG. 2 is a longitudinal sectional view showing an outline of the mechanism of the multifunction copy machine MF1 according to the first embodiment of the present invention. FIG. 2 is an enlarged longitudinal sectional view of a color scanner 100 and an ADF 120 shown in FIG. FIG. 2 is a block diagram showing a configuration of an image processing system in the copying machine MF1 shown in FIG. FIG. 4 is a block diagram showing functional configurations of a reading unit 11 and an image signal processing circuit (AFE) 111 shown in FIG. 3. FIG. 5 is a block diagram showing a configuration of a frequency dividing circuit 212 in the timing control circuit 211 shown in FIG. 4. 5 is a time chart showing several types of drive signals of the CCD 107 shown in FIG. 4 and waveforms of lighting timing signals CKinv. 5 is a time chart showing a lighting instruction signal cnt and a lighting timing signal CKinv given to the lamp driving circuit 205 shown in FIG. It is a block diagram which shows the frequency divider circuit 212 of 2nd Example of this invention.

Explanation of symbols

101: contact glass 102: illumination lamp 103: first mirror 104: second mirror 105: third mirror 106: lens 107: CCD 108: pulse motor 109: base point sensor rwp: reference white plate scp: scale 112: pressure plate switch 121: Document tray 125: Conveying drum 126: Conveying belt 130: Filler sensor 131: Side plate position detection switch 132: Glass 137: Pressure plate

Claims (7)

A light source for irradiating the document with light, a lighting unit for lighting the light source in response to a lighting timing signal, and serially synchronizing with a reading clock for converting image information of light reflected from the document into an electrical image signal and dividing it into pixels. In a document reading apparatus having photoelectric conversion means for outputting, and A / D conversion means for digitally converting an electrical image signal output by the photoelectric conversion means into image data and outputting the image data,
A document reading apparatus comprising: frequency dividing means for generating a lighting timing signal having a cycle that is an integral multiple of the read clock cycle and outputting the same to the lighting means in synchronization with the reading clock.   The document reading apparatus according to claim 1, further comprising: a unit that sets a period that is an integral multiple of the period of the reading clock of the frequency dividing unit.   The frequency dividing means is provided with the integer multiple value as a preset value, counts the read clock and counts the preset value, and starts counting the preset value again, and the cycle counter is preset. The document reading apparatus according to claim 1, further comprising: a flip-flop that inverts an instruction level of the lighting timing signal every time the value is counted.   4. The document reading apparatus according to claim 3, further comprising preset means for giving data representing the integer multiple value to a preset data input terminal of the circulation counter.   The frequency dividing means includes means for initializing the circulation counter and means for initializing the flip-flop in synchronization with switching of a line through which the photoelectric conversion means serially outputs an electrical image signal. The document reading device according to 3 or 4.   According to the polarity instruction signal, the flip-flop immediately after switching of the serial output line is cleared or set, and the instruction level of the lighting timing signal that is the output of the flip-flop is set to the non-instruction or instruction level setting. 6. The document reading device according to claim 3, further comprising: means. A printer that forms an image represented by the image data on paper;
The document reading device according to any one of claims 1 to 6, and
A copying apparatus comprising: image data processing means for converting image data generated by the document reading device into image data suitable for image formation of the printer.

Images