JP6130756B2 - Image reading apparatus and image forming apparatus having the same - Google Patents

Description

  The present invention relates to an image reading apparatus that reads a document as an image and generates image data, and more particularly to an image reading apparatus that can reduce switching loss when a light source that illuminates the document is turned on and off, and an image including the image reading apparatus. The present invention relates to a forming apparatus.

  In general, in an image reading apparatus, light from a light source is irradiated onto a document surface, and reflected light from the document surface is imaged on an image pickup surface of a reading sensor using an optical system such as a lens, whereby the document is converted into an image. Read. In order to suppress the temperature rise of the light source, to prevent saturation of the detection signal of the reading sensor, and to reduce power consumption, etc., the light source is turned on by the PWM method in synchronization with the scanning period at the time of image reading. An image reading apparatus to be controlled is known.

  For example, Patent Document 1 below discloses an image reading apparatus that adjusts the timing of turning on and off a light source so that the lighting time of the light source becomes constant in synchronization with a document conveyance signal. Patent Document 2 below discloses an image reading apparatus that prevents a temperature rise of a light source by adjusting a pulse width of a driving voltage for turning on the light source by PWM control according to the temperature of the light source.

JP 2010-161719 A JP 2012-138879 A

  In the case of PWM control of lighting of the light source, the switching element (FET or transistor, etc.) included in the light source drive unit performs on and off operations for each scanning period, so that switching loss (power consumption) due to the switching element of the drive unit is reduced. There is a big problem.

  FIG. 1 shows a timing chart of PWM control of a conventional light source. The signal SH is a synchronization signal used to synchronize the scanning of the document surface by the radiated light from the light source (LED) and the operation of the line sensor (CCD) that receives the reflected light and generates an electrical signal. is there. The signal S1 is a signal for controlling turning on and off the light source. The light source is turned on (ON) while the signal S1 is at a high level, and turned off (OFF) while the signal S1 is at a low level. The signal S2 is a signal for driving the CCD. The CCD can accumulate charges while the signal S2 is at a high level, accumulates charges while the light source is ON (period ts when S1 is at a high level), and accumulates charges when the signal S2 is at a low level. Then, the data is output to a subsequent circuit (A / D conversion circuit or the like).

  In the image reading apparatus, the light source is turned on and off in accordance with the periodic signal SH in FIG. That is, the light source is turned on when the switching element in the light source is turned on, and the light source is turned off when the switching element is turned off. The signal P schematically indicates the power consumption of the light source. The oval part of the broken line in FIG. 1 indicates the power consumption when the switching element is on and off. In a transient period when a switching element such as an FET or a transistor is turned on, power is consumed by a current and a voltage generated between terminals of the switching element. Thereafter, substantially constant power is consumed during lighting. Similarly, when the switching element is turned off, the power consumption becomes 0 after the power is similarly consumed. In FIG. 1, the switching element is turned on once and turned off once in each period. For this reason, in order to reduce the power consumption of the light source, it is preferable to reduce the number of times the switching element is turned on and off.

  However, neither of Patent Documents 1 and 2 described above can reduce the number of times the switching element is turned on and off.

  Accordingly, an object of the present invention is to provide an image reading apparatus capable of reducing switching loss of a switching element for turning on and off a light source, and an image forming apparatus including the image reading apparatus.

  An image reading apparatus according to the present invention is an image reading apparatus that generates image data by irradiating a document with light, and includes a light emitting unit that emits light, and a synchronization signal generation unit that generates a synchronization signal having a predetermined period. A control unit that controls turning on and off of the light emitting unit in synchronization with the synchronization signal, and a one-dimensional array of pixel signals for receiving reflected light from the document irradiated with light by the light emitting unit and generating image data The control unit is configured to generate a pixel signal by the light emitting unit and the light receiving unit while changing the position on the document to which the light from the light emitting unit is irradiated in synchronization with the synchronization signal. The control unit turns on the light emitting unit when the first time has elapsed from the start of the synchronization signal in one cycle of the repeated scanning, and keeps the light emitting unit on while maintaining the lighting of the one cycle. The synchronization signal is opened in the next cycle. A second time turns off the light emitting unit when the elapsed from.

  Preferably, the control unit turns on the light-emitting unit when the first time has elapsed from the start of the synchronization signal in one cycle of scanning repetition in the entire period from the start to the end of scanning of one original. While the lighting of the light emitting unit is maintained, the light emitting unit is turned off when the second time has elapsed from the start of the synchronization signal in one cycle following the one cycle.

  More preferably, the control unit turns on the light emitting unit from the start of the synchronization signal in each cycle of scanning until the predetermined time elapses from the start of scanning of one original, and starts from the start of lighting. When the time 3 has elapsed, the light emitting unit is turned off, and after a predetermined time has elapsed from the start of scanning of the original, the first time has elapsed from the start of the synchronization signal in one cycle of scanning. The light emitting unit is turned on, and the light emitting unit is turned off when the second time has elapsed from the start of the synchronization signal in one cycle following the one cycle while the light emitting unit is kept on.

  More preferably, the control unit emits light when the first time elapses from the start of the synchronization signal in one cycle of scanning repetition until a predetermined time elapses from the start of scanning of one original. Is turned on and the light emitting unit is turned off when the second time has elapsed from the start of the synchronization signal in one cycle following the one cycle while the light emitting unit is kept on, and the predetermined period from the start of scanning of the document. After the elapse of time, the light emitting unit is turned on from the start of the synchronization signal in each cycle of scanning repetition, and the light emitting unit is turned off when the third time has elapsed from the start of lighting.

  An image forming apparatus according to the present invention includes the above-described image reading device and an image forming unit that forms an image on a recording paper, and the image forming unit performs an image on the recording paper according to image data generated by the image reading device. Form.

  According to the present invention, it is possible to reduce the number of times of turning on and off the switching element for turning on and off the light source (light emitting unit) of the image reading apparatus as compared with the conventional art. Therefore, the switching loss (power consumption) of the light source can be reduced, and the temperature rise of the light source due to heat generation accompanying the switching loss can be suppressed. Moreover, it can suppress that the lifetime of the switching element of a light source becomes short.

It is a timing chart which shows lighting control of the light source in the conventional image reading apparatus. 1 is a cross-sectional view illustrating a schematic configuration of an image forming apparatus equipped with an image reading apparatus according to a first embodiment of the present invention. FIG. 2 is a block diagram illustrating a schematic configuration of the image forming apparatus in FIG. 1. 1 is a block diagram showing a schematic configuration of an image reading apparatus according to a first embodiment of the present invention. It is a flowchart which shows the control structure of the lighting control program of the light source in the image reading apparatus which concerns on the 1st Embodiment of this invention. It is a timing chart which shows the control signal produced | generated by the program of FIG. It is a flowchart which shows the control structure of the lighting control program of the light source in the image reading apparatus which concerns on the 2nd Embodiment of this invention. It is a timing chart which shows the control signal produced | generated by the program of FIG. It is a flowchart which shows the control structure of the lighting control program of the light source which changed the program of FIG. 10 is a timing chart showing control signals generated by the program of FIG. It is a flowchart which shows the control structure of the lighting control program of the light source in the image reading apparatus which concerns on the 3rd Embodiment of this invention. It is a timing chart which shows the control signal produced | generated by the program of FIG. It is a flowchart which shows the control structure of the lighting control program of the light source which changed the program of FIG.

  In the following embodiments, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

(First embodiment)
Referring to FIG. 2, image forming apparatus 100 equipped with image reading apparatus 90 according to the first embodiment of the present invention forms an image on recording paper in accordance with image data generated by reading a document. . The image forming apparatus 100 includes a main body device 110 and an automatic document feeder 120. The main body device 110 includes an image reading device 90, an optical scanning device 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, and paper discharge. A tray 91 is provided.

  The image reading device 90 is disposed on the upper part of the main body device 110. A document placing table 92 made of transparent glass (platen glass) on which a document is placed is provided above the image reading device 90. An automatic document feeder 120 is attached to the upper side of the document table 92. The automatic document feeder 120 automatically conveys the document on the document table 92. The automatic document feeder 120 is attached to the image reading apparatus 90 by a hinge (not shown) on one side on the back side. When the front portion of the automatic document feeder 120 is raised, the document placing table 92 is opened, and a document can be placed thereon.

  The image data handled in the image forming apparatus 100 is decomposed into color image data using each color of black (K), cyan (C), magenta (M), and yellow (Y), that is, these four color components. Image data. Accordingly, four sets of the developing device 2, the photosensitive drum 3, the charger 5, and the cleaner unit 4 are provided so as to form four types of latent images corresponding to the respective colors.

  The charger 5 is a device for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. The optical scanning device 1 is a laser scanning unit including a laser emitting unit and a reflection mirror. The optical scanning device 1 forms an electrostatic latent image corresponding to the image data on the surface of the photosensitive drum 3 by exposing the charged photosensitive drum 3 according to the input image data. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toner of four colors (YMCK). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 disposed above the photosensitive drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, and an intermediate transfer roller 64. Four intermediate transfer rollers 64 are provided corresponding to each color of YMCK.

  As described above, the electrostatic images visualized according to the hues on the photosensitive drums 3 are stacked on the intermediate transfer belt 61. The laminated image information (toner density distribution) is transferred onto the recording paper by the transfer roller 10 disposed at a contact position between the recording paper and the intermediate transfer belt 61 by rotating the intermediate transfer belt 61.

  The paper feed cassette 81 is a tray for storing recording paper used for image formation. Recording paper used for image formation can also be placed in the manual paper feed cassette 82. The paper discharge tray 91 is a tray for collecting printed recording sheets face down, that is, with the printing surface facing down.

  In the main body apparatus 110, the recording paper conveyance path S is set in a substantially vertical direction in order to send the recording paper of the paper feeding cassette 81 and the manual paper feeding cassette 82 to the paper discharge tray 91 via the transfer roller 10 and the fixing unit 7. Is formed. In the vicinity of the recording paper transport path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, pickup rollers 11a and 11b, a plurality of transport rollers 12a to 12d, a registration roller 13, a transfer roller 10, and A fixing unit 7 and the like are arranged.

  The pickup roller 11 a picks up the recording paper one by one from the paper feed cassette 81 and supplies it to the recording paper transport path S. The pickup roller 11b picks up the recording paper one by one from the manual paper feed cassette 82 and supplies it to the recording paper transport path S. The conveyance rollers 12a to 12d are rollers for promoting and assisting the conveyance of the recording paper. The registration roller 13 temporarily holds the recording paper conveyed through the recording paper conveyance path S, and conveys the recording paper to the transfer roller 10 at a timing when the leading edge of the toner image on the photosensitive drum 3 coincides with the leading edge of the recording paper. To do.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72. The heat roller 71 and the pressure roller 72 rotate with the recording paper interposed therebetween. The heat roller 71 is set to a predetermined fixing temperature by a control unit based on a signal from a temperature detector (not shown). Recording is performed by thermocompressing the toner to the recording paper together with the pressure roller 72. The multicolor toner image transferred to the paper is heat-fixed on the recording paper.

  The image reading device 90 and the automatic document feeder 120 will be described. The image reading device 90 includes a document placing table 92, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, and a CCD 48 which is a line sensor.

  The first scanning unit 45 includes a light source. The light source is composed of, for example, a plurality of LEDs arranged in a line. The arrangement direction of the LEDs is parallel to the main scanning direction (direction perpendicular to the paper surface of FIG. 2). The first scanning unit 45 exposes the document on the document table 92 with the emitted light from the light source while moving in the sub-scanning direction (left and right direction in FIG. 2) at a constant speed according to the document size. The reflected light is reflected by the reflecting mirror and guided to the second scanning unit 46. As a result, the image on the surface of the document is scanned in the sub-scanning direction. The second scanning unit 46 includes a plurality of reflection mirrors. The second scanning unit 46 reflects the reflected light from the document by a plurality of reflecting mirrors and guides it to the imaging lens 47. The imaging lens 47 condenses the reflected light from the document on the CCD 48 and forms an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the image of the document in the main scanning direction and outputs an analog image signal (pixel signal for one line) for one main scanning line each time scanning is performed.

  The first scanning unit 45 and the second scanning unit 46 are provided with pulleys (not shown). A wire (not shown) is laid over the pulley, and the wire is driven by a stepping motor, whereby the first scanning unit 45 and the second scanning unit 46 move.

  The image reading device 90 can read not only a stationary document on the document table 92 but also an image on the surface of the document conveyed by the automatic document feeder 120. In this case, the first scanning unit 45 and the second scanning unit 46 are moved to the reading area below the document reading glass 84 (state shown in FIG. 2). In this state, the automatic document feeder 120 starts conveying the document.

  In the automatic document feeder 120, the document on the document tray 56 is drawn by the pickup roller 55 and conveyed by the conveyance roller, and the leading edge of the document is abutted against the registration roller 85 to align the leading edge of the document. Then, the original is passed between the original reading glass 84 and the reading guide plate, and the original is discharged from the discharge roller 58 to the discharge tray 49.

  While the original passes between the original reading glass 84 and the reading guide plate, the light source of the first scanning unit 45 illuminates the original surface through the original reading glass 84, and the reflected light from the original surface The light is guided to the imaging lens 47 by the reflecting mirrors of the first scanning unit 45 and the second scanning unit 46. Reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47, and an image on the document surface is formed on the CCD 48. As a result, the document surface is read as an image.

  In this way, the document read by the CCD 48 is output as an analog image signal from the CCD 48, and the analog image signal is A / D converted to generate a digital image signal. The digital image signal is input to the optical scanning device (laser exposure device) 1 of the image forming apparatus 100 after being subjected to various image processing, and as described above, an image is formed on the recording paper and discharged.

  Referring to FIG. 3, the image forming apparatus 100 includes a control unit (hereinafter referred to as a CPU) 130 that controls the entire image forming apparatus 100, a ROM (Read Only Memory) 132 for storing a program, and the like, and a volatile property. A random access memory (RAM) 134, an HDD (Hard Disk Drive) 136, which is a non-volatile storage device that retains data even when power is turned off, and a bus 140. The ROM 132 stores programs and data necessary for controlling the operation of the image forming apparatus 100.

  The CPU 130, ROM 132, RAM 134, and HDD 136 are connected to the bus 140. Data (including control information) is exchanged between the units via the bus 140. The CPU 130 reads a program from the ROM 132 onto the RAM 134 via the bus 140 and executes the program using a part of the RAM 134 as a work area. That is, the CPU 130 controls each part of the image forming apparatus 100 according to a program stored in the ROM 132 and realizes each function of the image forming apparatus 100.

  The image forming apparatus 100 further includes an automatic document feeder 120, an image reading device 90, an image forming unit 150, an image processing unit 152, an image memory 154, a paper feeding unit 156, and an operation unit 160. These are also connected to the bus 140.

  The operation unit 160 receives an input such as an instruction to the image forming apparatus 100 by the user. The operation unit 160 includes an operation panel and an operation key unit (both not shown). The operation panel includes a display panel configured by a liquid crystal panel and the like, and a touch panel that is disposed on the display panel and detects a touched position. In order to operate the image forming apparatus 100, soft keys are displayed on the display panel, and hard keys are arranged on the operation key unit. The CPU 130 monitors user operations on these keys. The user can press or touch these keys to instruct the image forming apparatus 100 to copy a document and input document reading conditions and image forming conditions. Selection of the key displayed on the display panel is performed by touching a corresponding portion on the touch panel superimposed on the display panel.

  When the operation unit 160 is operated by the user and a copy of the document is instructed, the image reading device 90 reads the document as described above to generate image data, and the generated image data is temporarily stored in the image memory 154. Memorized. The image processing unit 152 executes various image processes on the image data stored in the image memory 154. The image data is stored in the HDD 136 as necessary.

  The paper feed unit 156 includes the paper feed cassettes 81 and 82 and holds recording paper for image formation. The image forming unit 150 includes the photosensitive drum 3, the charger 5, the optical scanning device 1, the developing device 2, the transfer roller 10, the fixing unit 7, and the like. The image data read from the image memory 154 or the HDD 136 is As described above, it is formed on the recording paper conveyed from the paper supply unit 156.

  The control of the light source in the image reading device 90 will be described. Referring to FIG. 4, the image reading apparatus 90 includes a sensor unit 200 (including the CCD 48), a sensor driving unit 202, a lighting control unit 204, a light source driving unit 206, and a light source 208. These operate according to the same clock signal.

  Under the control of the CPU 130, the sensor driving unit 202 is a synchronization signal that is a reference signal for synchronizing each unit in order to scan in the sub-scanning direction while repeating scanning in the main scanning direction to acquire image data of the document. SH is generated. A period (period) for acquiring pixel data of one line along the main scanning direction is also referred to as a “line period”. The sensor driving unit 202 generates a control signal for controlling the sensor unit 200 based on the generated synchronization signal SH and outputs the control signal to the sensor unit 200. The output signal of the sensor unit 200 is A / D converted as described above, and then stored in the RAM 134 via the bus 140. In addition, the sensor driving unit 202 outputs a synchronization signal SH to the lighting control unit 204.

  The lighting control unit 204 detects the start point (for example, the rising edge of the signal) of the input synchronization signal SH, and determines whether the detected start point corresponds to odd-numbered or even-numbered line synchronization. Then, a control signal S 1 corresponding to the determination result is generated and output to the light source driving unit 206. Here, it is assumed that the lighting control unit 204 includes a microcomputer (including a memory and the like). Note that the order of the synchronization signals is counted from the line cycle in which the light source 208 is turned on in order to obtain the first one line of pixel data when each original is read.

  The light source driving unit 206 controls on / off of the switching element of the light source 208 in accordance with the input control signal S1, and controls lighting / extinguishing of the light source 208. The light source driving unit 206 turns on the light source 208 if the control signal S1 is high level, and turns off the light source 208 if the control signal S1 is low level.

  Hereinafter, it will be described in more detail with reference to FIG. The program for controlling lighting of the light source shown in FIG. 5 is executed by the microcomputer of the lighting control unit 204. Here, it is assumed that the total number of scans in the main scanning direction (total number of line cycles) when reading a document is an even number.

  When the image forming apparatus 100 is turned on, in step 300, the lighting control unit 204 executes initial setting. Specifically, the lighting control unit 204 reads out parameters C1 and C2 relating to a counter to be described later from the HDD 136 and stores them in the internal memory.

  In step 302, the lighting control unit 204 determines whether a scan start instruction has been acquired from the CPU 130. When the user sets a document on the image forming apparatus 100 and presses a start key displayed on the operation unit 160 and instructing execution of copying, the CPU 130 issues a scan start instruction, a lighting control unit 204, and a sensor driving unit 202. And the like are transmitted to each section related to scanning of the original. If the range to be scanned (document type (A4 or B5, etc.) or the vertical and horizontal dimensions of the area), resolution (in dpi), and the like are designated, the CPU 130 also sends the information to the lighting control unit 204. To transmit.

  In step 304, the lighting control unit 204 sets the counter I of the repetition process to “0”. The lighting control unit 204 uses a predetermined area of a memory provided in the microcomputer as a storage area of the counter I.

  In step 306, the lighting control unit 204 determines whether or not the rising of the input synchronization signal SH has been detected. As shown in FIG. 6, the input synchronization signal SH is a pulse signal whose signal level changes between a low level and a high level at a constant cycle. If it is determined that a rising edge has been detected, control proceeds to step 308. Otherwise, step 306 is repeated.

  In step 308, the lighting control unit 204 adds “1” to the counter I. That is, the counter I set to “0” at the start of scanning increases by “1” every time the rising edge of the synchronization signal is detected. Therefore, the counter I is also a synchronization signal number during document scanning.

  In step 310, the lighting control unit 204 resets the internal clock counter C to an initial value (for example, “0”). The clock counter counts the number of input clock signals with a certain period (for example, the clock counter increases by “1” at every rising edge of the clock). Therefore, the value of the clock counter is reset to the initial value when the rising edge of the synchronization signal is detected for the first time after the document scan is instructed.

  In step 312, the lighting control unit 204 determines whether or not the counter I is an odd number. If it is determined that the number is odd, control proceeds to step 314; otherwise (if it is even), control proceeds to step 318.

  In step 314, the lighting control unit 204 determines whether or not the value of the clock counter C is smaller than a predetermined value C1. If it is determined that C <C1, step 314 is repeated. Otherwise (C ≧ C1), control proceeds to step 316.

  In step 316, the lighting control unit 204 turns on the light source 208. Specifically, the lighting control unit 204 changes the control signal S1 input to the light source driving unit 206 from a low level to a high level. Accordingly, the light source driving unit 206 outputs a signal at a level at which the switching element of the light source 208 is turned on, and the light source 208 is turned on.

  When the counter I is an even number, in step 318, the lighting control unit 204 determines whether or not the value of the clock counter C is smaller than a predetermined value C2. If it is determined that C <C2, step 318 is repeated. Otherwise (C ≧ C2), control proceeds to step 320.

  In step 320, the lighting control unit 204 turns off the light source 208. Specifically, the lighting control unit 204 changes the control signal S1 input to the light source driving unit 206 from a high level to a low level. Accordingly, the light source driving unit 206 outputs a signal at a level at which the switching element of the light source 208 is turned off, and the light source 208 is turned off.

  In step 322, the lighting control unit 204 determines whether or not to scan the next line, that is, whether or not the entire scan target area has been scanned. Specifically, the lighting control unit 204 can determine whether or not the counter I is the maximum value Imax (I corresponding to the last scan). The lighting control unit 204 can determine the maximum value Imax of the counter I from the scan range and resolution information acquired from the CPU 130 in step 302.

  If it is determined that there is a next line scan, control returns to step 306. Otherwise control passes to step 324.

  In step 324, the lighting control unit 204 determines whether an end instruction has been received. The end instruction is transmitted from the CPU 130 when the power of the image forming apparatus 100 is turned off, for example. If an instruction to end is received, this program ends. Otherwise, control returns to step 302.

  Thus, the signal S1 shown in FIG. 6 is generated. In FIG. 6, the odd period is a period in which the counter I is an odd number, and the even period is a period in which the counter I is an even number. In the odd period, the control signal S1 is at the low level during the period (t1) until the value of the clock counter C becomes C1, and after the value of the clock counter C becomes C1, the control signal S1 becomes high level. As a result, the light source 208 is turned on (step 312 → step 314 → step 316).

  The even period starts from a state in which the light source 208 is turned on in the preceding odd period. In the even period, the control signal S1 is at a high level during the period (t2) until the value of the clock counter C becomes C2, and after the value of the clock counter C becomes C2, the control signal S1 becomes a low level. As a result, the light source 208 is turned off (step 312 → step 318 → step 320).

  In the power consumption P of the light source shown in FIG. 6, the number of switching losses (power consumption) (the elliptical portion of the broken line in FIG. 6) that accompanies turning on and off of the switching element of the light source is two in two periods. This is ½ of the prior art (see FIG. 1), and as a result, switching loss associated with turning on and off the light source can be reduced. Further, the period during which the light source is turned on is the same as in the prior art. By reducing the number of times of switching, the amount of heat generated by switching can be reduced, and the temperature rise of the light source can be suppressed.

  Here, it is preferable that the light source lighting time (period in which the signal S1 is high) in the odd period and the even period are set to be equal (t3 = t2). When the off period Δt of the licensor control signal S2 cannot be ignored, it is preferable to set so that t3 = t2−Δt.

(Second Embodiment)
In the first embodiment, the timing for turning on the light source is delayed in an odd period during the entire period of document scanning, but the present invention is not limited to this. The image reading apparatus according to the second embodiment turns on the light source at the same timing as before in the initial stage of scanning, and delays the timing of turning on the light source in an odd period from the middle of scanning.

  The image reading apparatus according to the second embodiment is configured in the same manner as in FIG. 4, and only the program executed by the lighting control unit 204 is different.

  The program executed by the lighting control unit of the image reading apparatus according to the second embodiment shown in FIG. 7 is different from the program of FIG. 5 only in that Steps 500 to 508 are added.

  In step 500, the lighting control unit 204 determines whether or not the counter I is equal to or greater than a predetermined even value I0. If it is determined that I ≧ I0, the control proceeds to step 312. Otherwise (I <I0), control proceeds to step 502. Therefore, step 502 is executed while 1 ≦ I <I0, and step 312 is executed while I0 ≦ I ≦ Imax. The processing when step 312 is executed is the same as in the first embodiment.

  In step 502, the lighting control unit 204 determines whether or not the clock counter C is smaller than a predetermined value C0. If it is determined that C <C0, step 502 is repeated. Otherwise (C ≧ C0), control proceeds to step 504. This is a process for turning off the light source 208 during a period until the sensor unit 200 is driven after the rising edge of the synchronization signal is detected (a period t0 until charge accumulation is started).

  In step 504, the lighting control unit 204 turns on the light source 208. Specifically, the lighting control unit 204 changes the control signal S1 input to the light source driving unit 206 from a low level to a high level. As a result, the light source driving unit 206 turns on the light source 208 while the control signal S1 is at a high level.

  In step 506, the lighting control unit 204 determines whether or not the clock counter C is smaller than a predetermined value C2. If it is determined that C <C2, step 506 is repeated. Otherwise (C ≧ C2), control proceeds to step 508.

  In step 508, the lighting control unit 204 turns off the light source 208. Specifically, the lighting control unit 204 changes the control signal S1 input to the light source driving unit 206 from a high level to a low level. As a result, the light source driving unit 206 turns off the light source 208 while the control signal S1 is at a low level.

  With the above processing, the signal S1 shown in FIG. 8 is generated. In FIG. 8, the light source 208 is turned on and off within each line period in a predetermined period (period of 1 ≦ I <I0) from the start of scanning. During the period of I ≧ I0, the same processing as that of the first embodiment is executed. If I = I0 + 1, that is, if the counter I becomes an odd number, steps 314 and 316 are executed, and the light source 208 is turned on. Then, in the next even cycle, the light source 208 is turned off. Thereafter, the light source 208 is turned on in the odd period, and the light source 208 is turned off in the even period.

  Therefore, in FIG. 8, the number of times the switching element of the light source 208 is turned on and off in the period of 1 ≦ I <I0 is the same as that in the prior art, but in the period of I0 ≦ I ≦ Imax, The number of on / off times is ½ of the conventional number. For example, if I0 = Imax / 2 is set, the power consumption associated with turning on and off the switching element can be reduced to 3/4 of the conventional one. In addition, the amount of heat generated by switching can be reduced, and the temperature rise of the light source 208 can be suppressed.

  In the above, the light source is turned on at the same timing as before in the initial stage of document scanning, and the timing for turning on the light source in the odd period is delayed from the middle of the scan. The light source may be turned on at the same timing as before, after a delay and a predetermined time has elapsed. For example, the program shown in FIG. The only difference between the program of FIG. 9 and the program of FIG. 7 is that step 500 is replaced by step 520.

  In step 520, the lighting control unit 204 determines whether or not the counter I is equal to or less than a predetermined even value I0. If it is determined that I ≦ I0, control proceeds to step 312. Otherwise (I> I0), control proceeds to step 502. Therefore, step 312 is executed while 1 ≦ I ≦ I0, and step 502 is executed while I0 <I ≦ Imax.

  The signal S1 shown in FIG. 10 is generated by the above processing. In FIG. 10, during a predetermined period from the start of scanning (period of 1 ≦ I ≦ I0), the light source is turned on in the odd period and the light source is turned off in the even period, as in the first embodiment. During the period of I> I0, the light source is turned on and off in each line cycle.

  Therefore, in FIG. 10, the number of times the switching element of the light source is turned on and off is ½ of that in the period of 1 ≦ I ≦ I0, and the switching element of the light source is turned on in the period of I0 <I ≦ Imax. And the number of times of OFF is the same as the conventional one. For example, if I0 = Imax / 2 is set, the power consumption associated with turning on and off the switching element can be reduced to 3/4 of the conventional one.

(Third embodiment)
In the third embodiment, the timing for turning on the light source is delayed for an arbitrary period during scanning of the document. The image reading apparatus according to the third embodiment is configured in the same manner as in FIG. 4, except that the program executed by the lighting control unit 204 is different.

  The program executed by the lighting control unit of the image reading apparatus according to the third embodiment shown in FIG. 11 is different from the program of FIG. 7 only in that step 500 is replaced by step 530.

  Here, the line cycle for delaying the timing of turning on the light source is designated in advance and stored in the HDD 136. When the scan start is instructed in Step 302, the CPU 130 reads out from the HDD 136 and transmits it to the lighting control unit 204. . The line cycle for delaying the timing for turning on the light source may be directly specified by the cycle number (counter) I. Further, for example, a condition for calculating the cycle number I may be specified such as I = 4n + 1 (n is an integer of 0 or more). The line period for delaying the timing for turning on the light source may be specified according to the scanning range, resolution, and the like.

  In step 530, the lighting control unit 204 determines from the CPU 130 whether or not it is a cycle for delaying the lighting of the light source 208. Specifically, the lighting control unit 204 determines whether or not the counter I corresponds to the cycle number acquired in step 302. If it is determined that the cycle of delaying lighting of the light source 208 is reached, the control proceeds to step 312. Otherwise control passes to step 502.

  Thereby, a signal S1 shown in FIG. 12 is generated. In FIG. 12, the light source is turned on in the odd period and the light source is turned off in the even period, as in the first embodiment, only during the designated period. In the period not instructed, the light source is turned on and off in each line cycle. Therefore, in the instructed period, the number of times the switching element of the light source is turned on and off is ½ of the conventional number, and power consumption due to turning on and off of the switching element during document reading can be reduced.

  In the first to third embodiments described above, the case where the passage of time is detected by counting the number of clocks has been described, but the present invention is not limited to this. The elapsed time may be measured by a timer or the like.

  In the second embodiment, the case where the same process is repeated after the process of delaying the lighting of the light source once in an odd period has been described, but the present invention is not limited to this. After the process of delaying the lighting of the light source in the odd period is executed, the light source may be turned on again without delay as in the conventional case after a predetermined period has elapsed.

  In the first to third embodiments, the timing for delaying the lighting of the light source is set in advance, but the present invention is not limited to this. The timing for turning on the light source may be set by the CPU 130, for example. For example, in step 302 of FIG. 5 and the like, the lighting control unit 204 acquires parameters C1 and C2 of timing for turning on and off the light source in addition to the scan start instruction, the range to be scanned, and the resolution information from the CPU 130. To do.

  Further, during the scanning of the document, the CPU 130 may instruct the lighting control unit 204 whether or not to delay the lighting of the light source. For example, in step 530 of FIG. 11, whether or not to delay lighting may be determined based on whether or not an instruction to delay lighting of the light source is received from the CPU 130.

  Further, the process for designating whether or not the lighting of the light source is delayed by the CPU 130 during the scanning of the document may be a process as shown in FIG. FIG. 13 is different from FIG. 11 only in that step 312, step 318 and step 320 are deleted and step 532 to step 540 are added.

  If the lighting control unit 204 determines in step 530 that it has not received an instruction to delay the lighting of the light source 208 from the CPU 130, steps 502 to 508, which are the same processes as in the prior art, are executed. In step 530, when the lighting control unit 204 determines that an instruction to delay lighting of the light source 208 has been received from the CPU 130, the lighting control unit 204 executes step 314 and step 316.

  In step 532, the lighting control unit 204 determines whether or not it is the last line scan (last one cycle). If it is determined that this is the last line scan, steps 502 to 508 are executed.

  Otherwise, i.e., if there are more line scans to be performed, steps 314 and 316 are performed. Thereafter, in step 534, the lighting control unit 204 determines whether or not the rising of the input synchronization signal SH has been detected. If it is determined that a rising edge has been detected, control proceeds to step 536. Otherwise, step 534 is repeated.

  In step 536, the lighting control unit 204 adds “1” to the counter I.

  In step 538, the lighting control unit 204 determines whether or not the value of the clock counter C is smaller than a predetermined value C2. If it is determined that C <C2, step 536 is repeated. Otherwise (C ≧ C2), control proceeds to step 540.

  In step 540, the lighting control unit 204 turns off the light source 208. Thereafter, the processes in and after step 306 are repeated until it is determined in step 322 that there is no next line scan.

  Thus, if there is an instruction from the CPU 130 to delay the lighting of the light source, the light source 208 is turned on in the previous one of the two consecutive cycles, and the light source 208 is turned off in the subsequent one. Therefore, the CPU 130 does not necessarily need to output an instruction to delay the lighting of the light source at an odd cycle timing, and can output an instruction to delay the lighting of the light source at an arbitrary timing.

  In the above-described programs of FIGS. 5, 7, 9, and 11, the total number of scans (total number of line periods) is an even number, but the total number of scans may be an odd number. In such a case, the determination process of step 532 shown in FIG. 13 and steps 502 to 508 for performing conventional light source control when the determination is the last scan in step 532 are included. Change the program.

  The present invention has been described above by describing the embodiment. However, the above-described embodiment is an exemplification, and the present invention is not limited to the above-described embodiment, and is implemented with various modifications. be able to.

90 image reader 200 sensor unit 202 sensor driving unit 204 lighting control unit 206 light source driving unit 208 light source

Claims (5)

An image reading apparatus for generating image data by irradiating light on a document,
A light emitting means for emitting light;
Synchronization signal generating means for generating a synchronization signal of a predetermined period;
Control means for controlling lighting and extinguishing of the light emitting means in synchronization with the synchronization signal;
Light receiving means for receiving reflected light from the original irradiated with light by the light emitting means, and generating a one-dimensional array of pixel signals for generating the image data;
The control unit performs irradiation of light by the light emitting unit and generation of the pixel signal by the light receiving unit while changing a position on the original to which the light from the light emitting unit is irradiated in synchronization with the synchronization signal. Repeat the scan,
The control means turns on the light-emitting means when a first time has elapsed from the start of the synchronization signal in one cycle of the scanning repetition, and maintains the lighting of the light-emitting means, and continues to the next of the one cycle. An image reading apparatus characterized in that the light emitting means is turned off when a second time elapses from the start of the synchronization signal in one cycle.   The control means turns on the light-emitting means when the first time has elapsed from the start of the synchronization signal in one cycle of the scanning in the entire period from the start to the end of the scan for one original. The light-emitting means is turned off when the second time has elapsed from the start of the synchronization signal in one cycle following the one cycle while the light-emitting means is kept on. The image reading apparatus described in 1. The control means includes
The third time from the start of the synchronization signal in each cycle of the scan is repeated from the start of the scan for one document until a predetermined time in units of one cycle of the synchronization signal elapses. The light emitting means is turned on when it has elapsed, and the light emitting means is turned off when a fourth time has elapsed from the start of the lighting,
After the predetermined time from the start of the scanning of the document has passed, it turns on the light emitting means when said first time from the start of the synchronizing signal in one period of repetition of the scan has passed, the light emitting means 2. The image reading according to claim 1, wherein the light emitting unit is turned off when the second time has elapsed from the start of the synchronization signal in one period following the one period while the light is kept on. apparatus. The control means includes
The first time from the start of the synchronization signal in one cycle of the scan repeats until a predetermined time in units of one cycle of the synchronization signal elapses from the start of the scanning of one original. The light-emitting means is turned on when the light-emitting means has elapsed, and the light-emitting means is turned off when the second time has elapsed from the start of the synchronization signal in one cycle following the one cycle while the light-emitting means is kept on. Let
After the predetermined time from the start of the scanning of the document has passed, in each cycle of repetition of the scanning, turns on the light emitting unit when the third time from the start of the synchronizing signal has elapsed, the lighting The image reading apparatus according to claim 1, wherein the light emitting unit is turned off when a fourth time has elapsed from the start. An image reading apparatus according to any one of claims 1 to 4,
Image forming means for forming an image on recording paper,
The image forming apparatus, wherein the image forming unit forms an image on a recording sheet in accordance with image data generated by the image reading apparatus.

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