JP2014233057A - Image reading device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device that can read a document at an appropriate light intensity even with a light source the light intensity of which has not reached a target value after the adjustment of a pulse width in a period during which the light source can be lit, and an image forming apparatus.SOLUTION: An image reading device 10 includes a plurality of light sources 21, light intensity adjustment unit 40, light detection unit 22, control unit 30, and density reference member 50. The control unit 30 controls the light intensity adjustment unit 40 and light detection unit 22. The control unit 30 controls the detection unit period of the light detection unit 22 on the basis of a density reference member detection light intensity indicating the light intensities detected by the light detection unit 22, the light intensities of a plurality of rays of color light emitted from the plurality of light sources 21 to the density reference member 50.

Description

  The present invention relates to an image reading apparatus and an image forming apparatus.

  The image reading apparatus is used not only as a scanner, but also as an image forming apparatus such as a multifunction peripheral, a copying machine, or a component of a FAX apparatus. The image reading device reads a document image by detecting light emitted from a light source and reflected on the document by a photodetector.

  Even when the image reading apparatus reads the same document, the amount of light detected by the photodetector may vary for each reading operation. For example, the amount of light detected by the photodetector varies depending on the surrounding conditions or variations of the light source, optical system and / or photodetector. For this reason, the image reading apparatus generally performs shading correction using the result of reading the white reference plate with a preset amount of light, and suppresses fluctuations in the reading result due to fluctuations in the amount of light.

  The image reading apparatus disclosed in Patent Document 1 can obtain a good image without density unevenness by performing PWM control within a unit time with a time corresponding to an accumulation time for one line as one unit.

JP 2003-338904 A

  However, there are cases where the target light quantity cannot be obtained even if PWM control is performed within a unit time. As a result, proper reading may not be possible.

  The present invention has been made in view of the above problems, and its purpose is to read a document with an appropriate light amount even for a light source whose light amount has not reached the target value even when the pulse width is adjusted in the lighting-enabled period. Another object of the present invention is to provide an image reading apparatus and an image forming apparatus.

  An image reading apparatus according to the present invention includes a plurality of light sources, a light amount adjustment unit, a light detection unit, a control unit, and a density reference member. The plurality of light sources are lit during a lighting period within each lighting-enabled period and emit a plurality of color lights. The light amount adjustment unit adjusts the light amounts of the plurality of color lights emitted from the plurality of light sources. The light detection unit detects the plurality of color lights emitted from the plurality of light sources within a detection unit period including the lighting-enabled period. The control unit controls the light amount adjustment unit and the light detection unit. The control unit detects the light detection unit based on density reference member detection light amounts respectively indicating the light amounts of the plurality of color lights emitted from the plurality of light sources to the concentration reference member and detected by the light detection unit. Control the unit period.

  An image forming apparatus according to the present invention includes the image reading apparatus described above and an image forming unit. The image forming unit forms an image based on image data read by the image reading device.

  The image reading apparatus according to the present invention controls the detection unit period of the light detection unit based on the light amounts of the plurality of color lights emitted from the plurality of light sources to the density reference member and detected by the light detection unit. Therefore, it is possible to read a document with an appropriate amount of light even for a light source that has not reached the target value in the detection unit period before adjustment.

1 is a schematic diagram illustrating an image reading apparatus according to an embodiment of the present invention. It is a schematic diagram which shows the photon detection part of the image reading apparatus which concerns on embodiment of this invention. 1 is a schematic block diagram illustrating an image reading apparatus according to an embodiment of the present invention. 6 is a timing chart illustrating an image reading operation of the image reading apparatus according to the embodiment of the present invention. 6 is a graph showing a relationship between a pulse width and a light amount in the image reading apparatus according to the embodiment of the present invention. (A), (b), and (c) are timing charts showing an image reading operation at the time of pulse width adjustment of the image reading apparatus according to the embodiment of the present invention. (A), (b), and (c) are timing charts showing an image reading operation at the time of pulse width adjustment of the image reading apparatus according to the embodiment of the present invention. 6 is a flowchart illustrating a light amount adjustment method by the image reading apparatus according to the embodiment of the present invention. 1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention.

  Embodiments of an image reading apparatus and an image forming apparatus according to the present invention will be described below with reference to the drawings. However, the present invention is not limited to the following embodiments.

  An embodiment of an image reading apparatus 10 according to the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic diagram showing an image reading apparatus 10 according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing the light detection unit 22 of the image reading apparatus 10 according to the embodiment of the present invention.

  The image reading apparatus 10 includes a light source 21 (a red light source 21r, a green light source 21g, and a blue light source 21b), a light amount adjustment unit 40, a light detection unit 22, and a control unit 30. Typically, the image reading apparatus 10 further includes a document table 11. The image reading device 10 reads the document M placed on the document table 11 and obtains an input image. In the present embodiment, the image reading apparatus 10 is a scanner, and the document M is paper.

  The light source 21 and the light detection unit 22 are provided below the document table 11. The light source 21 and the light detection unit 22 are attached to the carriage 23.

  The light source 21 extends in the main scanning direction. Here, the main scanning direction is parallel to the direction perpendicular to the paper surface of FIG. 1, and the sub-scanning direction is the Y direction. The light source 21 is, for example, a light emitting diode (LED). The plurality of light sources 21 include a red light source 21r, a green light source 21g, and a blue light source 21b. The red light source 21r emits red light, the green light source 21g emits green light, and the blue light source 21b emits blue light.

  The light detection unit 22 will be described in detail with reference to FIG. The light detection unit 22 includes a plurality of light receiving elements 22 a and a shift register 24. The light detection unit 22 further includes an output unit 26. In the present embodiment, the light detection unit 22 is a monochrome sensor. The light detection unit 22 is, for example, a CMOS (Complementary Metal Oxide Semiconductor) image sensor. Each of the plurality of light receiving elements 22a generates charges from the received light. The charge generated in the light receiving element 22a is transferred to the shift register 24 every time a shift pulse signal SP described later with reference to FIG. The charges are sequentially transferred through the shift register 24 by a clock signal passing through the wiring 25 and output from the output unit 26. One pixel is output for one cycle of the clock signal. All charges transferred to the shift register 24 must be output from the shift register 24 before the charges generated in the light receiving element 22a are transferred next time.

  When the image reading apparatus 10 reads the document M, the carriage 23 to which the light source 21 is attached moves along the sub-scanning direction Y. Since the light detection unit 22 is a monochrome sensor, the light source 21 switches the light source 21 that is sequentially turned on in the order of the red light source 21r, the green light source 21g, and the blue light source 21b, irradiates the document M with light, and reads the entire document M. To get the input image.

  The light emitted from the light source 21 is reflected by the document M or the density reference member 50 and reaches the light detection unit 22. The light detection unit 22 generates an analog electrical signal from the light that has reached the light detection unit 22. Thereafter, in the analog front end 70 (not shown in FIG. 1), the analog signal is converted into a digital signal. The digital signal is input to the control unit 30.

  When the image reading apparatus 10 reads the density reference member 50, the light source 21 irradiates the density reference member 50 with light. For example, the density reference member 50 extends in a plate shape along the main scanning direction. The density reference member 50 is a white reference member. When the image reading apparatus 10 reads the white reference member (density reference member 50), white reference data (density reference data) corresponding to the position of the pixel region in the main scanning direction is acquired.

  The control unit 30 performs shading correction based on the density reference data. Note that the shading correction is a result of reading the document M in order to reduce deterioration of the read image due to non-uniform light quantity of the light source 21 or non-uniform sensitivity of the light detection unit 22. To be done. Shading correction is performed for each reading operation of the document M.

  The lighting periods of the red light source 21r, the green light source 21g, and the blue light source 21b are controlled by PWM (Pulse Width Modulation) control. For example, the red light source 21r, the green light source 21g, and the blue light source 21b emit red light, green light, and blue light, respectively, during a period when the pulse signal is High. In the following description of the present specification, a period in which the pulse signal is high may be referred to as a pulse width. The light amounts of the red light source 21r, the green light source 21g, and the blue light source 21b are proportional to the period during which the pulse signal is High, that is, the lighting period of the light source 21.

  When reading the document M, it is preferable that the light amounts of the red light source 21r, the green light source 21g, and the blue light source 21b are appropriately adjusted. The image reading apparatus 10 adjusts the light amounts of the red light source 21r, the green light source 21g, and the blue light source 21b by adjusting the pulse width so that the white reference data approaches the target value. The image reading apparatus 10 can appropriately read the document M by turning on the red light source 21r, the green light source 21g, and the blue light source 21b with the adjusted pulse width.

  An embodiment of the image reading apparatus 10 according to the present invention will be described with reference to FIG. FIG. 3 is a schematic block diagram showing the image reading apparatus 10 according to the embodiment of the present invention.

  The image reading apparatus 10 includes a light source 21, a light detection unit 22, a control unit 30, a light amount adjustment unit 40, a density reference member 50 (not shown in FIG. 3), and an analog front end 70. The control unit 30 and the light amount adjustment unit 40 are mounted on an ASIC 31 (Application Specific Integrated Circuit).

  The light source 21 includes a red light source 21r, a green light source 21g, and a blue light source 21b. The plurality of light sources 21 are lit during a lighting period within each lighting-enabled period, and emit a plurality of color lights.

  The light amount adjustment unit 40 adjusts the light amounts of the plurality of color lights emitted from the plurality of light sources 21.

  The light detection unit 22 detects a plurality of color lights emitted from the plurality of light sources 21 within a detection unit period including a lighting possible period. A detailed description of the lighting enabled period and the detection unit period will be described later with reference to FIG.

  The control unit 30 controls the light amount adjustment unit 40 and the light detection unit 22. The control unit 30 determines the detection unit period of the light detection unit based on the concentration reference member detection light amount respectively indicating the light amounts of the plurality of color lights emitted from the plurality of light sources 21 to the concentration reference member 50 and detected by the light detection unit. Control.

  Within the adjusted detection unit period, the light detection unit 22 outputs an analog signal based on the detected charge from the shift register 24 to the analog front end 70. The controller 30 changes the frequency of the clock signal input to the shift register 24 so that the analog signal is output from the shift register 24 to the analog front end 70 within the adjusted detection unit period.

  An embodiment of the image reading apparatus 10 according to the present invention will be described with reference to FIGS. FIG. 4 is a timing chart showing the image reading operation of the image reading apparatus 10 according to the embodiment of the present invention. Although details will be described later, the intervals of the pulses of the shift pulse signal SP are equal, and the detection unit periods Tsr, Tsg, and Tsb are equal to each other.

  The shift pulse signal SP is a signal input to the light detection unit 22. The pulse signal R_LED, the pulse signal G_LED, and the pulse signal B_LED are signals input to the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. The read signal RD_DATA is a signal output from the light detection unit 22.

  Immediately before the rise of the shift pulse signal SP is a lighting prohibition period of the light source 21. Periods Tlr, Tlg, and Tlb are periods during which the red light source 21r, the green light source 21g, and the blue light source 21b can be turned on. The pulse widths Pr, Pg, and Pb are the pulse widths of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. The pulse widths Pr, Pg, and Pb are adjusted so as to fall within the lighting possible periods Tlr, Tlg, and Tlb, respectively. The red light source 21r, the green light source 21g, and the blue light source 21b are lit during a period in which the pulse signal is High, that is, a period of pulse widths (pulse widths Pr, Pg, and Pb).

  The shift pulse signal SP becomes High three times when reading one line of data. During the period (period Tsr, Tsg, and Tsb) from the rising edge of a certain pulse of the shift pulse signal SP to the rising edge of the next pulse (periods Tsr, Tsg and Tsb), the light reflected from the light source 21 and reflected on the document M is detected by the plurality of light receiving elements 22a Is generated. The charge generated by the light receiving element 22a is transferred to the shift register 24 every time the shift pulse signal SP becomes High. In this specification, the period from the rising edge of a certain pulse of the shift pulse signal SP to the rising edge of the next pulse may be referred to as a detection unit period. In the detection unit periods Tsr, Tsg, and Tsb, the light detection unit 22 detects red light, green light, and blue light emitted from the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. In FIG. 4, the detection unit periods Tsr, Tsg, and Tsb are equal.

  The charges detected by the light detection unit 22 during the detection unit period are output from the light detection unit 22 to the analog front end 70 during the detection unit period of the next color. For example, the charge detected by the light detection unit 22 by turning on the red light source 21r during the period of the pulse width Pr in the detection unit period Tsr (time t0 to t1) is detected in the green detection unit period Tsg (time t1 to t2). It is output from the light detection unit 22 and output to the analog front end 70.

  When reading the document M, it is preferable that the light amounts of the red light source 21r, the green light source 21g, and the blue light source 21b are appropriately adjusted. However, even if the pulse width (lighting period of the light source 21) is set to the limit of the lightable period of the light source 21, the target light quantity may not be obtained. When the target light amount cannot be obtained, the control unit 30 calculates a pulse width necessary for obtaining the target light amount. With reference to FIG. 5, a method for calculating a missing pulse width in the embodiment of the image reading apparatus 10 according to the present invention will be described.

  FIG. 5 is a graph showing the relationship between the pulse width and the amount of light in the image reading apparatus 10 according to the embodiment of the present invention. The horizontal axis indicates the pulse width input to the light source 21, and the vertical axis indicates the amount of light detected by the light detection unit 22 when the density reference member (white reference member) 50 is read. The light quantity Qt is a target value of the light quantity. In the present embodiment, the target value is, for example, 240 in 256 gradations (0 to 255). The pulse width Pi indicates the initial value of the pulse width, and the light quantity Qi indicates the light quantity at the pulse width Pi. The pulse width Pa indicates the value after adjusting the pulse width, and the light quantity Qa indicates the light quantity when the pulse width Pa is set.

  The control unit 30 adjusts the pulse width within the lighting period of the light source 21 so that the light amount approaches the target value Qt. However, although the pulse width is adjusted to the pulse width Pa which is the limit of the lighting possible period of the light source 21, the light amount reaches only the light amount Qa and does not reach the target value Qt. If the light amount does not reach the target value Qt even if the pulse width is adjusted to the limit of the lighting possible period of the light source 21, the control unit 30 calculates the pulse width necessary for obtaining the target light amount.

  The control unit 30 calculates the light intensity gradient a with respect to the pulse width from the initial value pulse width Pi, the initial light quantity value Qi, the adjusted pulse width Pa, and the adjusted light quantity Qi. An arithmetic expression is shown in Expression 1 below.

  a = (Qa-Qi) / (Pa-Pi) (Formula 1)

  Further, the control unit 30 calculates a pulse width Pc necessary for obtaining a target light amount. An arithmetic expression is shown in Expression 2 below.

  Pc = Qt / a-Pa (Formula 2)

  Here, Equation 2 is derived on the assumption that the graph of the relationship between the pulse width and the light amount passes through the origin, but it does not necessarily have to be derived on the assumption that the graph passes through the origin.

  As shown in the graph of FIG. 5, there is a light source 21 in which a target light amount cannot be obtained even if the pulse width (lighting period of the light source 21) is set to the limit of the light source 21 can be turned on. There may be a light source 21 that can obtain a target light amount within the lighting-enabled period. In this specification, even if the pulse width (lighting period of the light source 21) is set to the limit of the lightable period of the light source 21, the light source 21 in which the target light quantity cannot be obtained is described as a target unachieved light source. In addition, the light source 21 that can obtain a target light amount within the lighting-enabled period of the light source 21 may be described as a target reaching light source.

  An embodiment of the image reading apparatus 10 according to the present invention will be described with reference to FIG. FIGS. 6A, 6B, and 6C are timing charts showing an image reading operation when adjusting the pulse width of the image reading apparatus 10 according to the embodiment of the present invention. 6A shows a timing chart before adjusting the pulse width, FIG. 6B shows a timing chart in which the pulse width is adjusted within the light amount lighting period, and FIG. 6C shows the result after the pulse width distribution. A timing chart is shown. Detailed description of the contents overlapping with those described above with reference to the timing chart shown in FIG. 4 will be omitted.

  In FIG. 6A, periods Tsri, Tsgi, and Tsbi indicate initial values of detection unit periods of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. The periods Tlri, Tlgi, and Tlbi are initial values of periods in which the red light source 21r, the green light source 21g, and the blue light source 21b can be turned on. The pulse widths Pri, Pgi, and Pbi indicate initial values of the pulse widths of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively.

  The pulse widths of the pulse signals R_LED, G_LED, and B_LED are set to initial values within each lighting enabled period. The control unit 30 controls the light amount adjusting unit 40 to adjust the light amount by adjusting the pulse widths of the pulse signals R_LED, G_LED, and B_LED.

  In FIG. 6B, pulse widths Pra, Pga, and Pba indicate pulse widths after adjustment of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. The pulse width Pra of the pulse signal R_LED is shorter than the lighting possible period Tlri, and there is a margin period of the period Tdr with respect to the lighting possible period Tlri. Similarly, the pulse width Pba of the pulse signal B_LED is shorter than the lighting possible period Tlbi, and there is a margin period of the period Tdb with respect to the lighting possible period Tlbi. On the other hand, as for the pulse width Pga of the pulse signal G_LED, the light amount does not reach the target value even if the pulse width Pga is adjusted until the lighting possible period Tlgi. The lighting possible period Tlgi and the pulse width Pga are equal. The red light source 21r and the blue light source 21b are target reaching light sources, and the green light source 21g is a target unsuccessful light source.

  As described above with reference to FIG. 5, the control unit 30 calculates the pulse width Pc necessary for the target unreachable light source to obtain the target light amount by calculating Expression 2. The control unit 30 distributes the margin period of the target reaching light source to the pulse width of the target unreachable light source in order to ensure the pulse width Pc necessary for the target unreachable light source to obtain the target light amount.

  In FIG. 6C, periods Tsrb, Tsgb, and Tsbb indicate values after pulse width distribution in the detection unit periods of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. Further, periods Tlri, Tlgi, and Tlbi indicate values after pulse width distribution in the turn-on periods of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively. The pulse widths Prb, Pgb, and Pbb indicate the pulse widths after the pulse widths of the red light source 21r, the green light source 21g, and the blue light source 21b, respectively.

  The margin period Tdr (= Tlri-Pra) of the red light source 21r is distributed to the pulse width of the green light source 21g. As a result, the detection unit period Tsrb and the lighting possible period Tlrb of the red light source 21r are shortened by the allocated amount (Tsrb = Tsri−Tdr, Tlrb = Tlri−Tdr). The pulse width Prb after distribution is equal to the pulse width Pra after adjustment. Further, the pulse width Prb after the distribution is equal to the lighting possible period Tlrb.

  A part of the margin period Tdb (= Tlbi−Pba) of the blue light source 21b is distributed to the pulse width of the green light source 21g. As a result, the detection unit period Tsbb and the lightable period Tlbb of the blue light source 21b are shortened by the allocated amount (Tsbb = Tsbi−Tdb, allocated portion, Tlbb = Tlbi−Tdb allocated portion). The assigned pulse width Pbb is equal to the adjusted pulse width Pba. Further, the pulse width Pbb after the distribution is shorter than the lighting-enabled period Tlbb.

  The pulse width Pgb of the green light source 21g is a period in which the pulse width necessary for the target unreachable light source to obtain the target light amount is added to the adjusted pulse width Pga (Pgb = Pga + Pc). The detection unit period Tsgb and the lightable period Tlgb of the green light source 21g become longer by the amount allocated from the red light source 21r and the blue light source 21b (Tsgb = Tsgi + Pc, Tlgb = Tlgi + Pc). By increasing the pulse width Pgb of the green light source 21g, a target amount of light can be obtained.

  The initial values of the detection unit periods (periods Tsri, Tsgi, and Tsbi) are all the same, but the detection unit periods after distribution (periods Tsrb, Tsgb, and Tsbb) are different. The total of the detection unit periods of one line of the red light source 21r, the green light source 21g, and the blue light source 21b is equal to the initial value and the value after the distribution (Tsri + Tsgi + Tsbi = Tsrb + Tsgb + Tsbb).

  Since the detection unit period is changed, the control unit 30 changes the frequency of the clock signal output to the shift register 24 of the light detection unit 22 so that the number of pixels of each color becomes a predetermined number of pixels. For example, in the period from time t1 to t2 (the period for reading the electric charges generated by the red light source 21r), the reading period becomes longer, so the frequency of the clock signal is made lower than before the adjustment. On the other hand, at times t2 to t3 (the readout period of charges generated by the green light source 21g) and from t3 to t4 (the readout period of charges generated by the blue light source 21b), the readout period is shortened, so the frequency of the clock signal is , Make it higher than before adjustment. The frequency of the clock signal is switched based on the rising or falling edge of the SP signal.

  In FIG. 6, the margin period Tdr of the red light source 21r is all allocated to the pulse width of the green light source 21g, and a part of the margin period Tdb of the blue light source is allocated to the pulse width of the green light source 21g. It is not limited to. For example, the margin period Tdb of the blue light source may be all allocated to the pulse width of the green light source 21g, and a part of the margin period Tdr of the red light source may be allocated to the pulse width of the green light source 21g. Alternatively, a part of the margin period Tdr of the red light source 21r may be allotted to the pulse width of the green light source 21g, and a part of the margin period Tdb of the blue light source may be allocated to the pulse width of the green light source 21g.

  In FIG. 6, the margin period of the target reaching light source is longer than the pulse width necessary for obtaining the target light amount for the target unreachable light source. A case where the pulse width is shorter than that necessary for obtaining the above will be described with reference to FIG. 7A, 7B, and 7C are timing charts showing an image reading operation at the time of pulse width adjustment of the image reading apparatus 10 according to the embodiment of the present invention. FIG. 7 (a) shows a timing chart before adjusting the pulse width, FIG. 7 (b) shows a timing chart in which the pulse width is adjusted within the light amount lighting period, and FIG. 7 (c) shows after the pulse width distribution. A timing chart is shown. Detailed description of the contents overlapping with those described above with reference to the timing charts shown in FIGS. 4 and 6 will be omitted.

  In FIG. 7A, as in FIG. 6A, the pulse widths of the red light source 21r, the green light source 21g, and the blue light source 21b are set to initial values Pri, Pgi, and Pbi, respectively.

  In FIG. 7B, the pulse width Pra of the pulse signal R_LED is shorter than the lighting possible period Tlri, and there is a margin period of the period Tdr with respect to the lighting possible period Tlri. The period Tdr in FIG. 7B is shorter than the Tdr in FIG. Further, the pulse width Pba of the pulse signal B_LED is shorter than the lighting possible period Tlbi, and there is a margin period of the period Tdb with respect to the lighting possible period Tlbi. The period Tdr in FIG. 7B is shorter than the period Tdr in FIG.

  In FIG. 7C, similarly to FIG. 6C, the pulse widths are distributed from the red light source 21r and the blue light source 21b, which are target reaching light sources, to the green light source 21g, which is a target unreachable light source. The margin period Tdr (= Triri-Pra) of the red light source 21r and the margin period Tdb (= Tlbi-Pba) of the blue light source 21b are distributed to the pulse width of the green light source 21g. The pulse width Pgb of the green light source 21g is a period obtained by adding the margin period Tdr of the red light source 21r and the margin period Tdb of the blue light source 21b to the adjusted pulse width Pga (Pgb = Pga + Tdr + Tdb).

  The initial values (Tsri, Tsgi, and Tsbi) of the detection unit periods are all the same, but the detection unit periods after distribution (Tsrb, Tsgb, and Tsbb) are different. The total of the detection unit periods of one line of the red light source 21r, the green light source 21g, and the blue light source 21b is equal to the initial value and the value after the distribution (Tsri + Tsgi + Tsbi = Tsrb + Tsgb + Tsbb).

  The green light source 21g does not reach the target value of the light amount, but the light amount is adjusted so as to be closer to the target value than before the pulse width distribution.

  Since the detection unit period is changed, the control unit 30 changes the frequency of the clock signal output to the shift register 24 of the light detection unit 22 as described above with reference to FIG.

  6 and 7 show one target unachieved light source, but there may be two.

  With reference to FIG. 1, FIG. 6, and FIG. 8, a light amount adjustment method by the image reading apparatus 10 according to the present invention will be described. FIG. 8 is a flowchart showing a light amount adjustment method by the image reading apparatus 10 according to the embodiment of the present invention. In the light quantity adjustment method of this embodiment, as shown in FIG. 8, the light quantity (pulse width) is adjusted by performing Steps S100 to S120. Thereafter, when reading the document M, the light source 21 is turned on based on the set light amount. The pulse width setting value is set, for example, in 256 steps. The pulse width setting value converges by repeatedly adding and subtracting α to the initial setting value. The initial value and α are set so that the density reference data obtained by irradiating the density reference member 50 with the light source 21 using the converged pulse width setting value approaches the target value. For example, here, the initial setting value is set to 100 and α is set to 40.

  Step S100: Set the pulse width setting value to the initial setting value. As shown in FIG. 6A, the pulse widths of the red light source 21r, the green light source 21g, and the blue light source 21b are set to the pulse widths Pri, Pgi, and Pbi of the initial setting values. Here, the pulse width setting value is set to the initial setting value of 100.

  Step S102: Density reference data (density reference member detected light amount) is acquired by irradiating the density reference member 50 (white reference member) with the light source 21. The first acquisition of density reference data is acquired by irradiating the density reference member 50 (white reference member) with the light source 21 using the initial value of the pulse width set in step S100.

  Step S104: The control unit 30 determines whether or not the output value (density reference data) acquired in S102 is equal to the target value. When the output value is equal to the target value (step S104: Yes), the light amount adjustment process proceeds to step S116. When the output value is not the target value (step S104: No), the light amount adjustment process proceeds to step S106.

  Step 106: The control unit 30 determines whether or not the output value is smaller than the target value (output value> target value). If the output value> the target value (step S106: Yes), the light amount adjustment process proceeds to step S108. If the output value is not greater than the target value (step S106: No), the light amount adjustment process proceeds to step S110.

  Step S108: If output value> target value in step 106 (step S106: Yes), the pulse width is larger than the pulse width corresponding to the target value, indicating that the output value is larger than the target value. . Therefore, the control unit 30 performs a calculation process of pulse width set value = pulse width set value−α to reduce the pulse width. Here, the pulse width setting value = 100−40 = 60. An initial value is set as α. Here, α is set to 40. Then, the light amount adjustment process proceeds to step S112.

  Step S110: If the output value is not greater than the target value in Step 106 (Step S106: No), the pulse width is smaller than the pulse width corresponding to the target value, indicating that the output value is smaller than the target value. Therefore, the control unit 30 performs a calculation process of pulse width setting value = pulse width setting value + α to increase the pulse width. Here, the pulse width setting value = 100 + 40 = 140. An initial value is set as α. Here, α is set to 40. Then, the light amount adjustment process proceeds to step S112.

  Step S112: The control unit 30 determines whether α is smaller than 1 (α <1). If α <1 (step S112: Yes), the light amount adjustment process proceeds to step S116. If α <1 is not satisfied (step S112: No), the light amount adjustment process proceeds to step S114.

  Step S114: The control unit 30 sets α to α / 2. Here, 20 is set, which is a half of the initial value 40 of α. Thereafter, the light quantity adjustment process returns to S102, and the density reference data is acquired again by irradiating the density reference member with the pulse width reset in step S108 or S110.

  The pulse width is adjusted so that the output value approaches the target value by repeating steps S102 to S114. When the control unit 30 determines in step S104 that the output value is equal to the target value (step S104: Yes) or until the control unit 30 determines in step S112 that α <1 (step S112: Yes). Steps S102 to S114 are repeated, and the pulse width is adjusted as shown in FIG. Here, α changes to 1/2 by repeating steps S102 to S114 from the initial value of 40 to 20, 10 and 5, respectively.

  Even if the pulse width is adjusted in steps S100 to S112, the output value may not reach the target value. In that case, in step S116 to step S120, the pulse width is distributed between the target reaching light source and the target unachieved light source so that the output values of all the light sources 21 approach the target value.

  Step S116: The control unit 30 reads the pulse width adjusted in step S100 to step S114 and the output value at that pulse width.

  Step S118: The control unit 30 calculates a pulse width necessary for obtaining a target light amount in the target unreachable light source and a margin period in the target reach light source. Then, the control unit 30 assigns the margin period of the target reaching light source to the target unachieved light source. Further, the control unit 30 adjusts the detection unit period of the light detection unit 22.

  Step S120: The control unit 30 changes the frequency of the clock signal output to the shift register 24 based on the detection unit period adjusted in step S118.

  As described above with reference to FIGS. 1 to 8, in the image reading apparatus 10, the densities respectively indicating the light amounts of the plurality of color lights emitted from the plurality of light sources 21 to the density reference member 50 and detected by the light detection unit 22. The detection unit period of the light detection unit 22 is controlled based on the reference member detection light amount. Therefore, the original M can be read with an appropriate amount of light even for the light source 21 that has not reached the target value in the detection unit period before adjustment.

  The control unit 30 also turns on the lighting periods of the plurality of light sources so that the light amounts of the plurality of color lights emitted from the plurality of light sources 21 to the density reference member 50 and detected by the light detection unit 22 approach the target amounts, respectively. Adjust within the lighting period. Therefore, the original M can be read with an appropriate amount of light.

  In addition, the control unit 30 identifies the target reaching light source and the target unreachable light source from the plurality of light sources 21, and the target unreachable light source lighting period is within the target unreachable light source lighting period. And the light amount adjustment unit are controlled so as to be a period in which at least a part of the difference between the target arrival period and the target achievement period is added. Therefore, the lighting period of the target unachieved light source can be adjusted efficiently.

  Further, the control unit 30 changes the frequency of the clock signal output to the shift register 24 based on the results of controlling the detection unit periods of the light detection unit 22. Therefore, appropriate reading can be performed.

  The light source 21 is not limited to the red light source 21r, the green light source 21g, and the blue light source 21b, and there may be four or more types of light sources 21.

  FIG. 9 is a schematic diagram showing an image forming apparatus 100 according to the embodiment of the present invention. Hereinafter, in the present embodiment, the image forming apparatus 100 is a copying machine. The image forming apparatus 100 includes an image reading device 10 and an image forming unit 60. The image forming unit 60 includes a fixing device 110, a paper feed cassette 120, an image forming unit 130, a toner replenishing device 140, a paper discharge unit 150, and a paper transport unit 160. The image forming unit 60 forms an image based on the image data read by the image reading device 10.

  The paper feed cassette 120 contains printing paper P. When copying, the paper P in the paper feed cassette 120 is transported by the paper transport unit 160 so as to be discharged from the paper discharge unit 150 via the image forming unit 130 and the fixing device 110.

  The image forming unit 130 forms a toner image on the paper P. The image forming unit 130 includes a photoreceptor 131, a developing device 132, and a transfer device 133.

  An electrostatic latent image is formed on the photoreceptor 131 by a laser based on an electronic signal of an original image generated by the image reading apparatus 10. The developing device 132 has a developing roller 121. The developing roller 121 forms a toner image on the photosensitive member 131 by supplying toner to the photosensitive member 131 and developing the electrostatic latent image. The toner is supplied from the toner supply device 140 to the developing device 132.

  The transfer device 133 transfers the toner image formed on the photoconductor 131 onto the paper P.

  In the fixing device 110, the unfixed toner image formed in the image forming unit 130 is melted and fixed on the sheet P by heating and pressing the sheet P by the fixing member 111 and the pressure member 112.

  In the image reading apparatus 10, the light detection unit 27 is a CMOS (Complementary Metal Oxide Semiconductor) image sensor, but the light detection unit 27 may be a CCD (Charge Coupled Device).

  The document M read by the image reading device 10 is not limited to paper. For example, it may be a cloth or a thick three-dimensional object.

  Further, the image forming apparatus 100 is not limited to a copying machine. It can be a copying machine, a printer, a facsimile machine, or a multifunction machine having these functions.

  The image reading apparatus according to the present invention is suitably used for an image reading apparatus that performs reading by sequentially switching on and off a plurality of light sources.

M Document P Paper Y Sub-scanning direction 10 Image reading device 11 Document table 20 Image reading unit 21r Red light source 21g Green light source 21b Blue light source 22 Light detection unit 22a Light receiving element 23 Carriage 24 Shift register 25 Wiring 26 Output unit 30 Control unit 40 Light quantity Adjustment unit 50 Density reference member 60 Image forming unit 70 Analog front end 100 Image forming device 110 Fixing device 111 Fixing member 112 Pressing member 120 Paper feed cassette 130 Image forming unit 131 Photoconductor 132 Developing device 133 Transfer device 140 Toner replenishing device 150 Paper discharge unit 160 Paper transport unit

Claims (9)

A plurality of light sources that illuminate in a lighting period within each litable period and emit a plurality of colored lights;
A light amount adjusting unit for adjusting the light amounts of the plurality of color lights emitted from the plurality of light sources,
A light detection unit that detects the plurality of color lights emitted from the plurality of light sources, respectively, within a detection unit period including the lighting-enabled period;
A control unit for controlling the light amount adjustment unit and the light detection unit;
A concentration reference member,
The control unit detects the light detection unit based on density reference member detection light amounts respectively indicating the light amounts of the plurality of color lights emitted from the plurality of light sources to the concentration reference member and detected by the light detection unit. An image reading apparatus that controls a unit period.   The image reading apparatus according to claim 1, wherein the control unit adjusts the lighting periods of the plurality of light sources within the lighting-enabled period so that the density reference member detection light amount approaches a target amount. The controller is
From the plurality of light sources, a target reaching light source in which the light amount detected by the density reference member reaches the target amount by adjusting the lighting period is specified, and the density reference member detection is performed even if the lighting period is adjusted to the lightable period. Identify the target unreachable light source whose light intensity does not reach the target amount,
The controller is
The lighting period of the target reaching light source is a target reaching period for causing the density reference member detection light amount to reach the target amount, and the lighting period of the target unreachable light source is the lighting possible period of the target unreachable light source. The image reading apparatus according to claim 2, wherein the light amount adjustment unit is controlled to be a period in which at least a part of a difference between the turn-on enabled period of the target reaching light source and the target reaching period is added.   Based on the relationship between the lighting period of the light source and the detection result of the light detection unit, the control unit determines a lighting period necessary for the light amount of the density reference member detected by the light source not reaching the target to reach the target amount. The image reading device according to claim 3, wherein the image reading device calculates. The light detection unit is
A plurality of light receiving elements each for generating charge from the received light;
A shift register that receives charges generated by the plurality of light receiving elements from the plurality of light receiving elements;
The image reading apparatus according to claim 1, wherein the control unit outputs a clock signal for reading out the electric charge received by the shift register to the shift register.   The image reading apparatus according to claim 5, wherein the control unit changes a frequency of a clock signal output to the shift register based on a result of controlling the detection unit period of the light detection unit. The controller is
When controlling the detection unit period of the light detection unit to be short, increase the frequency of the clock signal,
The image reading apparatus according to claim 6, wherein when the detection unit period of the light detection unit is controlled to be long, the frequency of the clock signal is lowered. The plurality of light sources are
A red light source that emits red light within a red lighting enabled period;
A green light source that emits green light within the green lighting period;
The image reading apparatus according to claim 1, further comprising a blue light source that emits blue light within a blue littable period. An image reading apparatus according to any one of claims 1 to 8,
An image forming apparatus comprising: an image forming unit that forms an image based on image data read by the image reading apparatus.

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