Image reading device

Abstract

To provide an image reading device that reduces noise generated by turning on a plurality of light sources at the same time.SOLUTION: An image reading device comprises: a plurality of light sources 73r, 73g, 73b that irradiate an object to be read with light; image reading means 70a (70b) that receives light from a conveyance medium S that is a document being the object to be read irradiated with light by the plurality of light sources and generates an image signal from the received light; and light quantity adjustment means that controls lighting sections of the plurality of light sources to adjust the quantity of the light received by the image reading means 70a. The light quantity adjustment means executes sequential lighting control of, when the first light source 73r of the plurality of light sources is turned off, turning on the second light source 73g of the plurality of light sources.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an image reading device.

Background Art

[0002] An image reading device (such as an image scanner, a copier, a facsimile device, etc.) reads a document conveyed by an automatic paper feeding mechanism (ADF: Auto Document Feeder) with a CIS (Contact Image Sensor). In order to sufficiently ensure gradation in the reading quality of the document, the lighting period of the light source per line is adjusted so that the output of the light receiving element does not saturate.

[0003] As the light source mentioned here, generally, light emitting diodes (hereinafter referred to as LEDs) of each color of R (red), G (green), and B (blue) are used.

[0004] Normally, when acquiring a color image, the lighting periods of each of the RGB LEDs are adjusted one color at a time, and each LED is sequentially lit in the adjusted lighting period to read the outputs of the RGB colors as a color image.

[0005] Also, when acquiring a gray image, generally, the lighting periods of each LED are adjusted one color at a time as in the case of color, and then each LED is lit simultaneously in the adjusted lighting period to read the output at that time as a gray output image.

[0006] However, when acquiring a gray image, since a plurality of LEDs are lit simultaneously, a sudden voltage displacement occurs. This voltage displacement may affect the image data (analog signal) being transferred to the ADC (Analog Digital Converter) as noise and may finally appear as streaks in the output image.

[0007] In contrast, Patent Document 1 discloses control for acquiring a gray image by sequentially lighting the RGB LEDs.

Prior Art Documents

Patent Documents

[0008] [Patent Document 1] Patent No. 6133199 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Patent Document 1 describes how to stabilize operation by sequentially lighting each RGB LED so that the lighting intervals of each LED do not overlap, and by providing a "standby interval" as the lighting interval for each LED. However, when each light source in a line is lit, some voltage change occurs, and there remains a possibility that noise will be generated in the image, so it is necessary to suppress the voltage change. [Means for solving the problem]

[0010] In contrast, the image reading device according to the present invention is Multiple light sources that illuminate the object to be read, An image reading means that receives light from the object to be read, which is irradiated with light by the plurality of light sources, and generates an image signal from the received light, A light intensity adjustment means that adjusts the amount of light received by the image reading means by controlling the lighting intervals of the plurality of light sources. Equipped with, The light intensity adjustment means is characterized by performing sequential lighting control, which involves turning on the second light source among the plurality of light sources when the first light source among the plurality of light sources is turned off. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress the generation of noise associated with the lighting of each light source and provide the image data desired by the user. [Brief explanation of the drawing]

[0012] [Figure 1] A cross-sectional view illustrating the structure of an image reading device. [Figure 2]A diagram for explaining the image reading unit. [Figure 3] Another diagram for explaining the image reading unit. [Figure 4] A diagram for explaining sequential lighting control. [Figure 5] A diagram for explaining the displacement of the power supply voltage when the light source is lit. [Figure 6] A diagram for explaining the drive circuit of the light source. [Figure 7] A diagram for explaining saturated lighting section control 1. [Figure 8] A diagram for explaining saturated lighting section control 2 [Figure 9] A diagram for explaining the controller. [Figure 10] A flowchart showing the process of adjusting the lighting section of the light source. [Figure 11] A flowchart showing the process of adjusting the lighting section of the light source. [Figure 12] A flowchart showing the switching process of saturated lighting section control and light reception amount adjustment means.

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are given the same reference numerals, and duplicate explanations are omitted.

[0014] <Structure of the Image Reading Apparatus> As shown in FIG. 1, the image reading apparatus 100 reads a document to be read conveyed by an ADF with a CIS to generate image data. The placement table 1 stacks one or more conveyance media S. The conveyance media S is, for example, a sheet such as OA paper, a check, or cards, and may be a thick sheet or a thin sheet. The cards are, for example, an insurance certificate, a driver's license, a credit card, etc. Further, the conveyance media S includes booklets such as a passport.

[0015] The first conveyance unit 10 is a feeding mechanism that feeds the conveyance media S to the path RT. The first conveyance unit 10 has a feed roller 11 and a separation roller 12 disposed opposite to the feed roller 11. The feed roller 11 and the separation roller 12 convey only one of the plurality of conveyance media S placed on the placement table 1 in the conveyance direction D1. The drive unit 3 is a motor or the like. The drive unit 3 transmits a driving force to the feed roller 11 via the transmission unit 4 to rotate the feed roller 11. The rotation direction of the feed roller 11 is counterclockwise (the direction of conveying the conveyance media S along the path RT). The transmission unit 4 is, for example, an electromagnetic clutch, and intermittently (cuts off / connects) the driving force from the drive unit 3 to the feed roller 11 according to an instruction from the control unit 8. The transmission unit 4 is in a state of transmitting the driving force normally, and cuts off the driving force when the conveyance media S is reversely conveyed. When the transmission of the driving force to the feed roller 11 is cut off by the transmission unit 4, the feed roller 11 becomes freely rotatable. When the feed roller 11 is driven only in one direction, the transmission unit 4 may be omitted.

[0016] The separation roller 12 is a roller for separating the plurality of conveyance media S one by one, and is pressed against the feed roller 11 with a constant pressure. To ensure this pressed state, the separation roller 12 is provided so as to be swingable and is biased toward the feed roller 11 by a spring or the like. The driving force is transmitted to the separation roller 12 from the drive unit 3 via the torque limiter 12a, and the separation roller 12 rotates in the counterclockwise direction. The driving force of the separation roller 12 is regulated by the torque limiter 12a. Therefore, when the separation roller 12 is in contact with the feed roller 11, the separation roller 12 rotates with the feed roller 11. As a result, the plurality of conveyance media S are separated from the feed roller 11 When the conveying medium S is transported to the contact area with the roller 12, only one conveying medium S is transported downstream, and the remaining conveying medium S is blocked from being transported downstream. In this embodiment, the separation mechanism is configured with the separation roller 12 and the feed roller 11, but this is just one example. The separation mechanism may be omitted, or a separation mechanism consisting of a separation pad that applies frictional force to the conveying medium S and the feed roller 11 may be adopted.

[0017] A second conveying section 20 is provided downstream of the first conveying section 10 in the conveying direction. The second conveying section 20 has a drive roller 21 and a driven roller 22 that moves with the drive roller 21. The second conveying section 20 further conveys the conveying medium S that has been conveyed from the first conveying section 10 to the downstream side. The drive roller 21 receives driving force from the drive section 3 and rotates counterclockwise. The driven roller 22 is pressed against the drive roller 21 with constant pressure and therefore rotates along with the drive roller 21. The driven roller 22 may be biased against the drive roller 21 by a biasing unit (not shown), such as a spring.

[0018] A third conveying section 30 is provided downstream of the second conveying section 20 in the conveying direction. The third conveying section 30 has a drive roller 31 and a driven roller 32 that moves with the drive roller 31. The third conveying section 30 conveys and discharges the conveying medium S conveyed from the second conveying section 20 to the discharge tray 2. The drive roller 31 receives driving force from the drive section 3 and rotates counterclockwise. The driven roller 32 is pressed against the drive roller 31 with constant pressure and rotates along with the drive roller 31. The driven roller 32 may be biased against the drive roller 31 by a biasing unit such as a spring.

[0019] In the route RT, image reading units 70a and 70b are positioned between the second transport unit 20 and the third transport unit 30. Image reading unit 70a reads the first surface of the transport medium S. Image reading unit 70b reads the second surface of the transport medium S. For image reading, the second transport unit 20 and the third transport unit 30 transport the transport medium S at a constant transport speed. This transport speed may always be set to be higher than or equal to the transport speed of the first transport unit 10. This prevents the following transport medium S from colliding with the preceding transport medium S.

[0020] The double-feed sensor 40 is positioned between the first transport unit 10 and the second transport unit 20. The double-feed sensor 40 detects double-feeding of the transport medium S. Double-feeding is a phenomenon in which multiple transport mediums S become attached to each other due to static electricity or the like, and pass through the first transport unit 10. Various types of double-feed sensors 40 can be used. For example, the double-feed sensor 40 may be an ultrasonic sensor. In this case, the double-feed sensor 40 has an ultrasonic transmitter 41 and a receiver 42. The amount of attenuation of the ultrasonic waves passing through the transport medium S differs depending on whether multiple transport mediums S are being transported or whether only one transport medium S is being transported. Double-feeding is detected based on this principle.

[0021] In the transport path RT, a medium sensor 50 is positioned downstream of the double-feed sensor 40 in the transport direction. The medium sensor 50 is positioned upstream of the second transport unit 20 and downstream of the first transport unit 10. The medium sensor 50 detects the position of the transport medium S being transported by the first transport unit 10. More specifically, the medium sensor 50 detects whether the end of the transport medium S has reached or passed the detection position of the medium sensor 50. Various types of medium sensors 50 can be used. For example, the medium sensor 50 may be an optical sensor. In this case, the medium sensor 50 has an illumination unit 51 and a light receiving unit 52. The light reception intensity of the light receiving unit 52 changes when the transport medium S reaches or passes through. The transport medium S is detected based on this principle. The medium sensor 50 is positioned downstream of the double-feed sensor 40 so that when the leading edge of the transport medium S is detected by the medium sensor 50, the transport medium S has reached a position where the double-feed sensor 40 can detect double-feeding. The medium sensor 50 may be a sensor capable of detecting the end of the transport medium S (e.g., an image sensor), or it may be a lever-type sensor protruding from the path RT.

[0022] The medium sensor 60 is positioned upstream of the image reading units 70a and 70b and downstream of the second transport unit 20. The medium sensor 60 detects the position of the transport medium S being transported by the second transport unit 20. Similar to the medium sensor 50, various types of medium sensors 60 can be used. Here, as an example, the medium sensor 60 is an optical sensor equipped with a light-emitting unit 61 and a light-receiving unit 62. In Figure 1, the medium sensors 50 and 60 are positioned upstream and downstream respectively in the transport direction of the second transport unit 20, but only one of them may be positioned.

[0023] The image reading units 70a and 70b are line sensors that, for example, optically scan the transport medium S along the main scanning direction for each reading line, convert the light from the transport medium S into an electrical signal, and generate an image signal. The image reading units 70a and 70b include a light source such as an LED, a light guide, a light receiving sensor array, etc. Only one of the image reading units 70a and 70b may be placed on one side of the path RT. In Figure 1, the image reading units 70a and 70b are placed opposite each other with the path RT in between, but this is just one example. The image reading units 70a and 70b may be placed spaced apart in the direction of the path RT.

[0024] When the control unit 8 receives an instruction to start image reading, the drive unit 3 starts driving the first transport unit 10, the second transport unit 20, and the third transport unit 30. The transport media S loaded on the platform 1 are transported one by one, starting from the transport media S at the bottom. During transport, the transport media S are checked by the double-feed sensor 40 to determine if there is a double feed. If it is determined that there is no double feed, the transport of the transport media S continues. If it is determined that there is a double feed, the control unit 8 stops the drive unit 3 and stops the transport of the transport media S. The control unit 8 initiates image reading of the transport medium S by the image reading units 70a and 70b at a timing corresponding to the detection result of the medium sensor 60. The control unit 8 converts the image signals output from the image reading units 70a and 70b into image data. The transport medium S is finally ejected into the discharge tray 2.

[0025] <Explanation of the structure of the image reading unit> Figure 2 is a perspective view of the image reading units 70a and 70b as seen from the path RT side. The image reading units 70a and 70b have a light source 73 that illuminates the original document with light. Since the structures of the image reading units 70a and 70b are the same, the structure of the image reading unit 70a will be described in detail here.

[0026] The light source 73 has a light-emitting element (e.g., an LED). The light source 73 is installed at at least one end of the light guide 71. In Figure 2, the light source 73 is installed at one end of the light guide 71, but it may also be installed at the other end of the light guide 71. This supplements the amount of light emitted. The light guide 71 mainly uses a light-transmitting material such as a translucent molded resin or glass. The light emitted from the light source 73 propagates inside the light guide 71. A reflector (not shown) is provided inside the light guide 71 to reflect the light towards the path RT. The reflector reflects the light from the light source 73 towards the path RT. Multiple reflectors may be installed at relatively narrow intervals. This allows light to be irradiated uniformly to the path RT in the main scanning direction. Furthermore, multiple light guides 71 may be provided.

[0027] Light emitted from the light guide 71 is reflected again from the surface of the transport medium S and incident on the light receiving sensor array 72. The light receiving sensor array 72 has multiple photoelectric conversion elements, such as CMOS (Complementary Metal Oxide Semiconductor) image sensors. The multiple photoelectric conversion elements are arranged along the main scanning direction, forming a line in the main scanning direction. Light that reaches the light receiving sensor array 72 is converted into an electrical signal on a line-by-line basis. Generally, the output value of the CMOS image sensor changes according to the amount of light acquired on a line-by-line basis. For example, if the amount of light emitted from the light source 73 is large, the output value will be large. However, even with the same amount of light emitted, if the scanning interval per line is long, the output value will be large. Finally, the electrical signals acquired on a line-by-line basis are converted into digital signals by an A / D converter (ADC) described later. By combining the digital signals of multiple lines, image data of the transport medium S is created.

[0028] Figure 3 is a cross-sectional view of the image reading units 70a and 70b as seen from the main scanning direction. As shown in Figure 3, the light source 73 consists of a red light source 73r (e.g., a red LED), a green light source 73g (e.g., a green LED), and a blue light source 73b (e.g., a blue LED). Light sources 73r, 73g, and 73b each emit light of a different wavelength. The illumination intervals of light sources 73r, 73g, and 73b may be controlled on a line-by-line basis. The illumination intervals of light sources 73r, 73g, and 73b are determined, for example, so that the output value of the light receiving sensor array 72 does not overflow.

[0029] The amount of light emitted by the light source 73 and the amount of light received by the light receiving sensor array 72 may be adjusted by controlling the current (current value) supplied to the light source 73. In this case, the amount of light emitted and the amount of light received can be controlled while maintaining a constant illumination interval for the light source 73. The current values ​​for light sources 73r, 73g, and 73b may be set individually. The light receiving sensor array 72 selectively receives light in the corresponding wavelength range using a spectral filter or the like. Here, there is a single light receiving sensor array 72, but a configuration with multiple sensor arrays that receive light in their respective wavelength ranges may also be adopted.

[0030] Furthermore, in addition to adjusting the lighting interval and current value, gain adjustment, which multiplies the received light amount by a predetermined correction coefficient, may also be incorporated. This can be achieved by multiplying the image data by a predetermined correction coefficient. Gain adjustment allows for a larger output value even in situations where the scanning interval per line is short and it is difficult to secure sufficient received light. There are several methods for gain adjustment. Specifically, there is analog gain adjustment, which multiplies the received light amount by a predetermined correction coefficient before digital conversion, and analog gain adjustment, which multiplies the received light amount by a predetermined correction coefficient after digital conversion. There is a digital gain adjustment that uses multiplication.

[0031] <Explanation of light intensity adjustment process and light source illumination control> The following describes the method for adjusting the amount of light received by the light receiving sensor array 72 when acquiring a grayscale image, and sequential lighting control, which sequentially lights up each light source 73r, 73g, and 73b while synchronizing the timing of when they turn off and when they turn on. In addition, saturation lighting section control is described as an example of control when the lighting interval of light sources 73r, 73g, and 73b becomes saturated during sequential lighting control.

[0032] ● Sequential lighting control Figure 4 shows an example of a sequence chart in sequential lighting control, where the lighting intervals for each color of light source 73r, 73g, and 73b are controlled when reading an image of one line.

[0033] The SP (Start Pulse) section 80, which corresponds to the pulse interval indicated by the label "SP," represents the scanning section (reading section) of image data for one reading line unit. Note that the SP section 80 does not have to strictly correspond to the pulse interval of "SP," and as shown in Figure 4, if a predetermined illumination prohibition section is provided immediately after pulse generation, it will correspond to any other section.

[0034] The labels "R", "G", and "B" represent light sources 73r, 73g, and 73b, respectively. Light source 73r lights up in the lit section 81r of SP section 80 and turns off in the off section 82r. Light source 73g lights up in the lit section 81g of SP section 80 and turns off in the off section 82g. Light source 73b lights up in the lit section 81b of SP section 80 and turns off in the off section 82b.

[0035] The lighting intervals 81r, 81g, and 81b are adjusted so that the amount of light received by the light receiving sensor array 72 reaches the target light intensity. The target light intensity is set to, for example, the amount of light received that maximizes the signal-to-noise ratio of the original image. For example, the target light intensity can be finely adjusted so that the reading result of the brightest original (the one that reflects the most light from the light source 73) is not saturated. Therefore, the lighting intervals are finely adjusted so that the amount of light received does not saturate and the signal-to-noise ratio is maximized.

[0036] Furthermore, the longer the continuous period of unlit sections 82r, 82g, and 82b in the SP section 80, the more localized the sampling section of the original image becomes, potentially causing aliasing and moiré patterns in the image. Therefore, in this embodiment, SP section division positions 83 are provided in the SP section 80, and the light sources 73r, 73g, and 73b are lit by dividing the lighting section within one line into multiple periods (lightable sections) with the SP section division positions 83 as one unit. By dividing the lighting section, the period in which the light sources 73r, 73g, and 73b are continuously unlit is reduced. This increases the sampling frequency of the original image, preventing the occurrence of moiré patterns. In Figure 4, the light sources 73r, 73g, and 73b are divided into six sections and lit. Here, the position and number of SP section division positions 83 provided in the SP section 80 are not particularly specified.

[0037] In sequential lighting control, at the timing of SP section division position 83, only light source 73r is lit, and after the 81r section has elapsed, it is turned off. Next, at the same timing as the start of turning off light source 73r, light source 73g is lit, and after the 81g section has elapsed, light source 73g is turned off. Furthermore, at the same timing as the start of turning off light source 73g, light source 73b is lit, and after the 81b section has elapsed, light source 73b is turned off. This is repeated each time the SP section division position 83 is reached. The advantages of this control are explained in Figures 5 and 6.

[0038] Figure 5 shows an image of the displacement of the power supply voltage applied to the image reading unit 70a (70b) when the light source is turned on. Normally, when light sources 73r, 73g, and 73b are turned on simultaneously at the light source lighting start position 84, disturbances in the power supply voltage appear as shown in Figure 5(a). This is because the light source drive circuits 633r, 633g, and 633b according to this embodiment, which will be described later in Figure 9, are configured as shown in Figure 6. That is, in Figure 6, each light source 73r, 73g, and 73b is supplied with current from the same power supply, and the lighting interval of each light source 73r, 73g, and 73b is controlled by switching the ON and OFF states of transistors Tr1, Tr2, and Tr3, which are examples of switching elements, by control signals Sr, Sg, and Sb from the control unit 8. At this time, when light sources 73r, 73g, and 73b are turned on simultaneously, a sudden current flows from the power supply, and as a result, disturbances occur in the power supply voltage. These disturbances in the power supply voltage can become noise for the analog signal. Therefore, by sequentially controlling the lighting of the light sources and aligning the timing of the start of the off state of light source r and the start of the on state of light source g at the green LED lighting start position 85, fluctuations in the power supply voltage become less likely to occur, as shown in Figure 5(b). As described above, by performing sequential lighting control, it is possible to prevent large changes in the current value flowing to the image reading unit 70a (70b), and the fluctuation of the power supply voltage applied to the image reading unit 70a (70b), as shown in Figure 5(a), can be reduced, thereby suppressing noise on the analog signal.

[0039] In sequential lighting control, Figure 4 shows the light sources 73r, 73g, and 73b being lit in that order, but the order in which each light source 73r, 73g, and 73b are lit is not limited to this.

[0040] ● Saturated lighting section control Using Figures 7 and 8, we will explain two types of control when the lighting intervals 81r, 81g, and 81b during sequential lighting control exceed the maximum lighting interval Tmax (lighting interval) for which the light source can be lit. These are saturation lighting interval control 1 and saturation lighting interval control 2.

[0041] Here, the relationship between the maximum interval Tmax and the lighting intervals 81r, 81g, and 81b when performing saturation lighting interval control is expressed by the following formula. (Note that the maximum interval Tmax here is equal to the interval between the SP interval division positions 83 mentioned above.)

number

[0042] Figures 7(a) and 8(a) illustrate the state described in equation (1). In Figures 7(a) and 8(a), the end position of lighting section 81r and the start position of lighting section 81g are aligned, and the end position of lighting section 81g and the start position of lighting section 81b are aligned. Therefore, it is necessary to control the system so that the sum of the total lighting sections 81r, 81g, and 81b does not exceed the maximum section Tmax.

[0043] <Saturated lighting section control 1> To explain the control when the maximum interval Tmax over which the light source can be lit is exceeded, saturation lighting interval control 1 is described using Figure 7. In saturation lighting interval control 1, each of the lighting intervals 81r, 81g, and 81b is first divided by the sum of the lighting intervals 81r, 81g, and 81b to calculate the ratio of each lighting interval. The calculated ratio of each lighting interval is multiplied by the maximum interval Tmax to obtain the lighting interval after saturation lighting interval control 1 (hereafter, lighting intervals 81r_new, 81g_new, and 81b_new, respectively). Equation 2 below shows the formulas for calculating 81r_new, 81g_new, and 81b_new.

number

[0044] Figure 7(b) shows the lighting intervals of each light source 73r, 73g, and 73b changed to the lighting intervals 81r_new, 81g_new, and 81b_new after saturation lighting interval control 1. Here, if the amount of light received falls below the target light amount due to changing the lighting intervals to 81r_new, 81g_new, and 81b_new, it is preferable to readjust the amount of light received using the correction coefficient in the gain adjustment described above in <Structure of Image Reading Device> or by increasing the current supplied to the light source 73, etc., using these light receiving amount adjustment means.

[0045] In this embodiment, after adjusting the lighting intervals of each light source 73r, 73g, and 73b, the amount of light received was readjusted using the light received amount adjustment means. However, if these adjustment processes can be calculated from the current value that increases the output value that changes due to the light received amount readjustment process, or from the gain adjustment correction coefficient, it is not necessarily required to adjust the amount of light received in multiple steps.

[0046] Furthermore, in this embodiment, the maximum interval Tmax is the maximum interval over which the light source can be lit, and is set to be equal to the interval between SP interval division positions 83, but it may be set to a shorter time. In addition, although the control when the lighting intervals 81r, 81g, and 81b during sequential lighting control exceed the maximum interval Tmax has been described, the lighting intervals may be similarly changed when the lighting intervals 81r, 81g, and 81b during sequential lighting control are smaller than the maximum interval Tmax. That is, the lighting intervals 81r, 81g, and 81b of each light source should be calculated based on Equation 2 so that the sum of the lighting intervals of each light source 73r, 73g, and 73b is equal to the maximum interval Tmax. In this case, if the amount of light received becomes too large, it is preferable to redo the light received amount adjustment process by reducing the correction coefficient in gain adjustment or the current supplied to the light source 73.

[0047] In any case, if the lighting intervals 81r, 81g, and 81b during sequential lighting control do not match the maximum interval Tmax, which corresponds to the length of one cycle when the SP interval 80 is divided into multiple lit intervals, the control unit 8 functions as a modification means to change the lighting intervals 81r, 81g, and 81b so that the total lighting time within the cycle (81r + 81g + 81b), which is the sum of the lighting intervals of each of the multiple light sources 73r, 73g, and 73b, matches the maximum interval Tmax, while maintaining the ratio of the lighting intervals of each of the multiple light sources.

[0048] This is preferable because it can suppress changes in the voltage supplied to each light source within each cycle, as well as changes in voltage at the switching timing between cycles.

[0049] <Saturated lighting section control 2> Next, we will explain the saturation lighting section control 2 as a control method when the maximum lighting section Tmax is exceeded, using Figure 8 and Equation 3.

number

[0050] In other words, saturation lighting section control 2 advances the start timing of lighting the second and subsequent light sources from the timing determined by sequential lighting control, and controls it so that the start timing of the last light source to light up coincides with the end position of the lighting-possible section.

[0051] In the case of saturation lighting section control 2, only the starting position of the lighting section for each light source is changed. Therefore, there is no change in the amount of light received by each light source, and there is no need to readjust the light intensity, thus shortening the time required for light intensity adjustment processing. However, because the starting position of the lighting section and the ending position of the lighting section of another light source are shifted, the noise reduction effect described above may be less with sequential lighting control compared to saturation lighting section control 1. Nevertheless, compared to the conventional technology where current is introduced from a state where no current is flowing to any light source, the noise reduction effect itself is still achieved by suppressing the ratio of change in current relative to the power supply.

[0052] ● Switching of saturation lighting section control <Switching between saturation lighting section control 1 and saturation lighting section control 2> As mentioned above, both saturation lighting control 1 and saturation lighting control 2 have their own advantages, and it is desirable to implement control that switches the processing when the required light level becomes saturated, according to the user's request.

[0053] Saturated lighting control 1 has the characteristic of producing an output image that is less susceptible to noise, while saturated lighting control 2 has the characteristic of reducing the time required for light intensity adjustment processing. Therefore, it is considered effective to switch between saturated lighting control 1 and saturated lighting control 2 depending on whether the user has entered a setting that prioritizes noise reduction.

[0054] The setting in which noise reduction is prioritized, as used here, includes cases such as when the moiré removal function using image processing is enabled. Here, the moiré removal function is just one example. For example, if the image smoothing process is enabled, the user may also decide that noise reduction is prioritized. Furthermore, if the image needs to be automatically processed by a subsequent system using existing technology such as OCR (Optical Character Reader), and it is desirable to prioritize avoiding the generation of noise in the image to avoid system malfunction, this can also be considered a case where noise reduction is prioritized. In this embodiment, these settings in which noise reduction is prioritized (selection of a specific mode) are input from an unillustrated control panel attached to the image reading device 100, or from a dialog screen that sets information regarding the image reading settings of the image reading device 100 via software from an unillustrated information processing device. However, the means are not limited to this, as long as the setting information can be notified to the image reading device 100. If these settings in which noise reduction is prioritized are selected by the user, saturation lighting section control 1 is adopted; otherwise, saturation lighting section control 2 is adopted. This configuration allows the image reading device 100 to be controlled according to the user's priorities, such as image quality and the speed of image output.

[0055] <Switching and execution sequence of light reception amount adjustment means in saturation lighting section control 1> If the amount of light received falls below the target amount after the saturation lighting section control 1, it is preferable to readjust the amount of light received using the light received amount adjustment means, such as increasing the correction coefficient in the gain adjustment described above in the <structure of the image reading device> or increasing the current supplied to the light source 73.

[0056] In this case, readjusting the amount of light received by increasing the current has the advantage of not reducing the signal-to-noise ratio of the output image and ensuring maximum gradation. Also, readjusting by gain adjustment has the advantage that the output image is less affected by noise compared to control by increasing the current. Therefore, in this embodiment, the switching of these light-receiving amount adjustment means is determined based on whether or not the user has input a setting that prioritizes ensuring the signal-to-noise ratio.

[0057] Settings that prioritize ensuring the signal-to-noise ratio (S / N ratio) include cases where, for example, the gamma curve setting due to image processing has been changed from the default value. Here, changing the gamma curve is just one example. For example, if the original document is a photograph or something similar where tonal gradation is important, it can also be determined that ensuring the S / N ratio should be prioritized. If the setting that prioritizes ensuring the S / N ratio is selected, the current supplied to the light source 73 is increased as a light-receiving amount adjustment means after saturation lighting section control 1. If it is not selected, the gain is increased (the correction coefficient is made larger) as a light-receiving amount adjustment means. In this way, the image reading device 100 can be controlled according to the content that the user has selected as their priority, similar to the switching between saturation lighting section control 1 and saturation lighting section control 2 described above. The selection of the light-receiving amount adjustment means is performed by the CPU functioning as the selection means.

[0058] Furthermore, although this embodiment describes the switching of saturation lighting section control 1, saturation lighting section control 2, and the light reception amount adjustment means in saturation lighting section control 1, control may be implemented to switch the execution order of these processes according to user settings.

[0059] The control flow for switching between saturation lighting section control 1 and saturation lighting section control 2, and for switching the light reception amount adjustment means in saturation lighting section control 1, will be described in detail later in Figure 12.

[0060] <Controller> Figure 9 shows details of the control unit 8 that controls the image reading device 100. The control unit 8 is, for example, a CPU (Central Processing Unit) that implements various functions by executing a control program stored in the ROM or RAM area of ​​the storage device 620. The mode control unit 601 switches the image acquisition method according to user instructions input from the input device of the operation unit 621. Here, mode settings such as grayscale and color during image reading, and resolution are instructed, and the lighting control of the light source 73 is switched based on these. The contents of the instructions are not limited to mode settings and resolution.

[0061] The lighting time control unit 602 functions as a lighting interval control means by adjusting the lighting intervals of the light sources 73r, 73g, and 73b so that the amount of light received by the light receiving sensor array 72 reaches the target light amount. The current control unit 603 adjusts the current values ​​of the light sources 73r, 73g, and 73b so that the amount of light received can reach the target light amount. The current values ​​may be set individually for the drive circuits 633r, 633g, and 633b. The drive circuits 633r, 633g, and 633b each supply the corresponding light sources 73r, 73g, and 73b with the set current value for the lighting interval set by the control unit 8. The gain control unit 604 adjusts the correction coefficient (gain) of the multiplier unit 641. The multiplier unit 641 adjusts the output by multiplying the output from the light receiving sensor arrays 72r, 72g, and 72b by the correction coefficient. The ADC 642 converts the input analog image signal into digital data and outputs it to the image data generation unit 610 in line units. The multiplication unit 641 may be provided before, after, or both of the ADC 642.

[0062] In addition to the multiplication unit 641 and ADC 642, the image reading unit 70a may also be provided with an offset addition unit (not shown) that adds a correction value to the output from the light receiving sensor arrays 72r, 72g, and 72b.

[0063] <Flowchart> Figures 10 and 11 are flowcharts illustrating the process of adjusting the lighting intervals so that the light received by light sources 73r, 73g, and 73b reaches the target light level when sequential lighting control is performed (hereinafter referred to as the dimming process). Here, we will explain the dimming process when reading a gray image.

[0064] In step S1000 of Figure 10, when the dimming process by the control unit 8 is started, in step S1001 the control unit 8 sets the gain of the multiplier unit 641 to an initial value. Here, the gain is applied commonly to the amount of light received by all light sources. However, this is just one example. For example, a configuration in which the gain value can be set individually for the output of each color, or a configuration in which the output of the light receiving sensor array is divided and each can be set. Also, the smaller the gain, the better the gradation of the reading result. For this reason, the initial value is set to approximately 1. However, this is just one example. For example, if it is known in advance that the amount of light received is small, a value greater than 1 may be set as the initial value of the gain. This shortens the adjustment interval (adjustment time).

[0065] In step S1002, the control unit 8 sets the illumination interval of the light source 73 to an initial value (e.g., the maximum value that can be set as the illumination interval). Here, the illumination interval of the light source 73 is adjusted for each color individually, so for example, when adjusting the illumination interval of light source 73r, the illumination intervals of the other light sources 73g and 73b are set to 0 (off). Setting the initial adjustment value to the maximum possible interval is just one example. Even if the illumination interval is not set to the maximum possible value, if it is already known that the amount of light received will reach the target light amount, the initial adjustment value of the illumination interval is set to a value smaller than the maximum value.

[0066] In step S1003, the control unit 8 controls the image reading unit 70a to acquire the amount of light received. Since the light source 73 adjusts the illumination interval for each single color, the amount of light received acquired in this step is the output value of the light source 73 whose illumination interval was set to its initial value (maximum value) in step S1002. Here, the amount of light received may also be the luminance value. Here, gain is applied to the amount of light received.

[0067] In step S1004, the control unit 8 determines whether the received light amount is equal to or greater than the target light amount. If the received light amount is equal to or greater than the target light amount, the gain setting value required for the currently adjusted light source 73 to reach the target light amount is determined. The control unit 8 then proceeds to step S1008. If the received light amount does not exceed the target light amount, the control unit 8 proceeds to step S1005.

[0068] In step S1005, the control unit 8 determines whether the current gain is less than the maximum possible value. If the gain is at the maximum value, the control unit 8 proceeds to step S1007 in Figure 11. If it is determined that the gain is less than the maximum value, the control unit 8 proceeds to step S1006.

[0069] In step S1006, the control unit 8 increases the gain by a predetermined value. Here, the predetermined value does not need to be constant; a larger predetermined value may be used so that the gain increases significantly if the difference between the amount of light received and the target amount of light is large. This shortens the adjustment interval (adjustment time). After that, the control unit 8 returns the process to step S1002.

[0070] In step S1007 of Figure 11, the control unit 8 outputs a notification indicating an error to the display device of the operation unit 621 or the like. The control unit 8 then proceeds to step S1017 of Figure 11 and terminates the process.

[0071] Meanwhile, in step S1008, the control unit 8 checks whether the determination in step S1004 has been performed for all colored light sources 73. If the determination for all colored light sources 73 is not complete, the process proceeds to step S1009. If it is complete, the gain setting values ​​for the outputs of all light sources 73 have been determined, and the process proceeds to step S1010 in Figure 11.

[0072] In step S1009, the control unit 8 changes the color of the light source 73, which sets an initial value (maximum value) for the lighting interval, and returns the process to step S1002.

[0073] The subsequent steps will be explained using Figure 11.

[0074] In step S1010, the control unit 8 performs the sequential lighting control described in <Explanation of light intensity adjustment process and light source lighting control>, adjusting the lighting interval for each single color of the light source 73. At this time, the gain setting value determined in step S1008 of Figure 8 is applied. After that, the process proceeds to step S1011.

[0075] In step S1011, the control unit 8 controls the image reading unit 70a to acquire the amount of light received. Then, the process proceeds to step S1012.

[0076] In step S1012, the control unit 8 determines whether the amount of light received has reached the target amount. If the amount of light received has not reached the target amount, the control unit 8 returns to step S1010. If the amount of light received has reached the target amount, the control unit 8 proceeds to step S1013.

[0077] In step S1013, the control unit 8 checks whether the determination in step S1012 has been made for the amount of light received by all the light sources 73 of all colors. If the determination has been made for the amount of light received by all the light sources 73 of all colors, the lighting interval for all the light sources 73 of all colors has been determined, and the process proceeds to step S1015. If the determination has not been made for the amount of light received by all the light sources 73 of all colors, the control unit 8 first changes the color of the light source 73 to be lit in step S1014, and then returns the process to step S1010.

[0078] In step S1015, the control unit 8 determines whether the sum of the illumination intervals of all the light sources determined in step S1013 is less than or equal to the illumination interval of the light source 73. If it exceeds the illumination interval, the process proceeds to step S1016. If it is less than or equal to the illumination interval, the process proceeds to step S1017 and the process ends.

[0079] In step S1016, the control unit 8 executes the saturation lighting interval control described above in <Explanation of light intensity adjustment process and light source lighting control>, and changes the lighting interval of the light source 73 to within the lighting interval. At this time, if changing the lighting interval to within the lighting interval may result in a significant shortage of light compared to the target light intensity, the process may be returned to step S1004 in Figure 10. After that, the process proceeds to step S1017 and the process is terminated.

[0080] Figure 12 is a flowchart illustrating the process of switching between saturation lighting section control 1, saturation lighting section control 2, and the light reception amount adjustment means.

[0081] In step S2000 of Figure 12, when the control unit 8 starts saturation lighting section control, in step S2001, the control unit 8 determines whether the user has entered a setting to prioritize noise reduction in the switching of saturation lighting section control using the method described above. If the setting to prioritize noise reduction has been entered, the process proceeds to step S2002. If the setting to prioritize noise reduction has not been entered, the control unit 8 proceeds to step S2003.

[0082] In step S2002, the control unit 8 performs saturation lighting section control 1 using the method described above in saturation lighting section control, and proceeds to step S2004.

[0083] In step S2003, the control unit 8 performs saturated lighting section control 2 using the method described above in saturated lighting section control, and proceeds to step S2007.

[0084] In step S2004, the control unit 8 determines, using the method described above, whether the user has entered a setting to prioritize securing the signal-to-noise ratio when switching the saturated lighting section control. If the setting to prioritize securing the signal-to-noise ratio has been entered, the control unit 8 proceeds to step S2005. If the setting to prioritize securing the signal-to-noise ratio has not been entered, the control unit 8 proceeds to step S2006.

[0085] In step S2005, the control unit 8 performs a light reception amount readjustment process using the current value in the manner described above in <Structure of the Image Reading Device>, and proceeds to step S2007.

[0086] In step S2006, the control unit 8 performs a light reception amount readjustment process using the gain as described above in the <structure of the image reading device>, and proceeds to step S2007.

[0087] In the embodiments described above, adjustment processing was explained using either the current value or the gain, but processing may also be performed using both. In that case, the method set by the user as their priority will be prioritized and processed first.

[0088] The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention as described above.

[0089] For example, in the embodiments described above, the document to be read is transported as a transport medium S to the image reading units 70a and 70b. However, the image reading unit may also move and irradiate light onto the document placed on the document table to read the image. In other words, the present invention can be applied to any method that reads a document that moves relative to the image reading unit, line by line.

[0090] Furthermore, in the embodiments described above, except for the saturation lighting section control 2 in the <Explanation of light intensity adjustment process and light source lighting control>, the rise time when lighting each light source is turned on and the fall time when turning off are described as being approximately 0, but in reality, there is a small amount of time. In contrast, one embodiment of the present invention is characterized by performing sequential lighting control in which the second light source among the multiple light sources is turned on when the first light source among the multiple light sources is turned off. In view of the problems of the present invention, although to varying degrees, if the rise time of the second light source is started during the fall time of the first light source, the voltage change, which is one of the effects of the present invention, can be suppressed. Therefore, "when the first light source is turned off" includes cases in which the lighting of the second light source is started during the transient state from the start of the off control of the first light source until the current flowing to the light source becomes 0 after the fall time. More preferably, the lighting control is performed so that the overall current is smoother by taking into account the fall time when turning off and the rise time when turning on. However, it is not necessary to control whether the fall time when the light is turned off and the rise time when it is turned on are zero. The timing of when the light is turned off and the timing of when it is turned on can be controlled to be the same. In that case, it becomes possible to easily configure the system without being dependent on the fall time and rise time, which tend to be unique to each element or configuration.

[0091] In the above-described embodiment, sequential lighting control was performed to control the lighting intervals of light sources 73r, 73g, and 73b. When the total lighting interval exceeds the available lighting interval, saturation lighting interval control was performed, and the current value and gain supplied to light sources 73r, 73g, and 73b were adjusted to compensate for the insufficient amount of light received. Here, while the lighting interval control allows for continuous adjustment of the lighting time, the current control unit 603 (driver) and gain control unit 604 (gain adjustment circuit) that control the current value are adjusted discretely. Therefore, in the present invention, saturation lighting interval control is performed based on the results of adjusting the lighting intervals by sequential lighting control, and if the amount of light received is insufficient, the current value and gain are adjusted. In addition, further adjustment of the lighting interval is performed based on the results, thereby ensuring the necessary amount of light received while also synchronizing the lighting start timing and the extinguishing start timing of each light source. [Explanation of Symbols]

[0092] 100 Image reading device S Conveying medium 70a Image Reading Unit 70b Image reading unit 71 Light guide 72 Light-receiving sensor array 73 Light source 73r (red) light source 73g (green) light source 73b (Blue) light source 80 SP section 81r Red LED illuminated section 81g Green LED lit section 81b Section with blue LEDs lit 82r Red LED off section 82g Green LED off section 82b Section where blue LEDs are off 81r_new (Red LED lighting section after saturation lighting section control 1) 81g_new (Green LED lighting section after saturation lighting section control 1) 81b_new (After saturation lighting section control 1) Blue LED lighting section Tmax Maximum Light-Up Range Light intensity values ​​exceeding Tover Tmax 83 SP section division position 84 Green LED illumination start position 85 Green LED illumination start position (Green LED illumination start position) 86 Tover's division value 601 Mode Control Unit 602 Lighting Section Control Unit 603 Current Control Unit 604 Gain Control Unit 633r drive circuit 633g drive circuit 633b Drive circuit

Claims

1. A plurality of light sources for irradiating light onto a reading object; an image reading unit that receives light from the object to be read that is irradiated with light by the plurality of light sources and generates an image signal from the received light; a light amount adjusting unit that adjusts the amount of light received by the image reading unit by controlling the lighting intervals of the plurality of light sources; The image reading device according to claim 1, wherein the light amount adjusting means executes sequential lighting control for lighting a second light source of the plurality of light sources when a first light source of the plurality of light sources is turned off.

2. the image reading means is a line sensor that reads the image of the object being read, which moves relatively, line by line; 2. The image reading device according to claim 1, wherein the light amount adjusting means divides a reading section in units of the reading line into a plurality of periods, and executes the sequential lighting control within each divided period.

3. 3. The image reading device according to claim 2, further comprising a modification means for modifying the lighting sections of the plurality of light sources so that the total lighting time within a cycle, which is the sum of the lighting sections of the plurality of light sources within the cycle, does not match the length of the cycle, while maintaining the ratio of the lighting sections of each of the plurality of light sources, so that the total lighting time within a cycle matches the length of the cycle.

4. a gain control unit that multiplies the amount of light received by the image reading means by a predetermined correction coefficient; 4. The image reading device according to claim 3, wherein when the amount of light received by the image reading means falls below a target amount of light due to a change in the lighting intervals of the plurality of light sources by the change means, a correction coefficient in the gain control unit is increased.

5. When the amount of light received by the image reading means falls below a target amount of light due to the change in the lighting intervals of the plurality of light sources by the change means, a selection means for selecting a gain adjustment process for multiplying a predetermined correction coefficient based on a user setting, or a light receiving amount readjustment process for controlling a current value output to a light source, 4. The image reading apparatus according to claim 3, wherein the selected light receiving amount readjustment process is switched and controlled.

6. 6. The image reading apparatus according to claim 5, wherein the light amount adjusting means includes a gain control section that performs control to multiply the amount of received light by a correction coefficient.

7. 6. The image reading apparatus according to claim 5, wherein the light amount adjusting means includes a current control section for controlling a current value output to the plurality of light sources.

8. 2. The image reading device according to claim 1, wherein when executing the sequential lighting control, if the total of the lighting periods of the multiple light sources exceeds the period during which the multiple light sources can be turned on, the timing at which the light sources that are turned on second or later are turned on is brought forward from the timing determined by the sequential lighting control, and the timing at which the light source that is turned on last is turned off is controlled so that it coincides with the end position of the period during which the light sources can be turned on.

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