JP2017183795A - Image reader, image forming apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader capable of highly accurately reading image signals formed by lights in different wavelength regions from a document, an image forming apparatus and a program.SOLUTION: Before lighting an infrared LED in fall timing (latch timing) To of a vertical transfer period of a CCD image sensor, a white LED is turned off prior to an afterglow disappearance time Tth until afterglow of a yellow fluorescent substance becomes a sufficiently little quantity of light after turning-off of the white LED. Thus, even in the case where the CCD image sensor is irradiated with light emission of the yellow fluorescent substance as afterglow by a slow response property in the case where the white LED is turned off, a color mixture state where a light of the white LED and a light of the infrared LED are combined is not provided.SELECTED DRAWING: Figure 12

Description

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

  Japanese Patent Application Laid-Open No. H10-260260 discloses a technique that enables reading of an image on a document and another image having a wavelength range different from that of the image by a single scan. In this technique, the visible image formed on the document and the invisible image are invisible by switching between receiving the reflected light of the document by the white light of the white light source and receiving the reflected light of the document by the infrared light of the infrared light source. Reading the image.

  Patent Document 2 discloses a technique that makes it possible to acquire both visible image information and infrared image information of a document in one sub-scan. In this technique, for each reading in the main scanning direction (main scanning), the lighting operation of the visible illuminating device and the infrared illuminating device is switched, so that the original and the imaging optical system are relative in one sub-scanning direction. Visible image information and infrared image information of the document are acquired by position change (sub-scanning).

JP 2007-243249 A JP 2006-333078 A

  In the present invention, when a plurality of light sources irradiating light having different wavelength ranges are alternately turned on and off, the light emitted from the light source is illuminated as compared with the case where the light emitted from the turned off light source is not considered. An object of the present invention is to provide an image reading apparatus, an image forming apparatus, and a program capable of suppressing the influence of light from the other light source when reading a document.

  In order to achieve the above object, the image reading apparatus according to claim 1 includes a light source that emits light in a first wavelength band and a light source that emits light in a second wavelength band different from the first wavelength band. When a light source that is lit is turned off and turned off alternately when a light source unit, a reading unit that reads a document illuminated with light emitted from the light source unit, and a light source of the light source unit are turned on and off alternately, the light source is turned off. Control means for controlling the light source unit to turn off the light source being turned on at a timing when the light amount emitted from the turned off light source is equal to or less than a predetermined light amount before the light source is turned on, It has.

  In the image reading apparatus according to a second aspect, in the image reading apparatus according to the first aspect, the amount of light emitted from the light source that is turned off is the amount of afterglow when the light source that is turned on is turned off.

  According to a third aspect of the present invention, in the image reading device according to the first or second aspect, the reading unit stores the charge accumulated in the charge coupled device that accumulates the charge according to the received light. A semiconductor element is provided which is extracted as an image signal by vertical transfer and horizontal transfer, and the control means controls to turn off the light source that is lit during the horizontal transfer period.

  The image reading device according to claim 4 is the image reading device according to any one of claims 1 to 3, wherein the first wavelength range is a visible wavelength range, and the second wavelength range is The near-infrared wavelength region.

  The image reading device according to claim 5 is the image reading device according to any one of claims 1 to 3, wherein the light source unit emits blue light and yellow light that is excited by the blue light. A white LED light source that emits white light in the visible wavelength region as light in the first wavelength region, and an infrared LED light source that emits light in the near infrared wavelength region as light in the second wavelength region. The control means is configured to turn on white light at a timing when the amount of yellow light emitted from the turned off white LED light source becomes equal to or less than a predetermined amount before turning on the turned off infrared LED light source. The light source unit is controlled to turn off the LED light source.

  An image forming apparatus according to claim 6 forms an image based on the image reading apparatus according to any one of claims 1 to 5 and an image signal output from the image reading apparatus. Forming means.

  The program according to claim 7 is illuminated with light emitted from a light source unit including a light source that emits light in a first wavelength range and a light source that emits light in a second wavelength range different from the first wavelength range. In order to read the original, when turning on and off the light source of the light source unit alternately, from the light source turned off before the timing of turning on the light source that is turned off, This is for causing the computer to execute processing including controlling the light source unit so that the light source that is turned on is turned off at a timing when the amount of light to be irradiated becomes equal to or less than a predetermined light amount.

  According to the first, sixth, and seventh aspects of the present invention, when a plurality of light sources that irradiate light having different wavelength ranges are alternately turned on and off, the light emitted from the turned off light sources As compared with the case where the above is not taken into consideration, the influence of the light from the other light source can be suppressed when the original illuminated with the light emitted from the light source is read.

  According to the second aspect of the present invention, it is possible to suppress the influence of afterglow when the lit light source is turned off, compared to the case where afterglow is not considered when the lit light source is turned off. it can.

  According to the third aspect of the present invention, it is possible to extract each of the image signals while suppressing the influence of the light from the other light source as compared with the case where the light source being turned on is not turned off during the horizontal transfer period.

  According to invention of Claim 4, a visible image and the image by an infrared absorption material can be read.

  According to the invention described in claim 5, when using a white LED light source and an infrared LED light source that emit white light from blue light and yellow light excited and emitted by the blue light, a white LED light source is used. Compared with the case where the afterglow of yellow light when the light is turned off is not considered, color mixture of light emitted from the light source unit can be suppressed.

1 is a schematic configuration diagram illustrating an example of an overall configuration of an image forming apparatus according to an exemplary embodiment. 1 is a schematic configuration diagram illustrating an example of a configuration of an image reading apparatus according to an embodiment. It is a schematic block diagram which shows an example of a structure of the illumination unit which concerns on this Embodiment. It is a schematic block diagram which shows an example of a structure of the light-receiving part which concerns on this Embodiment. It is a characteristic view which shows each wavelength characteristic of an illumination unit and a CCD image sensor. It is a schematic block diagram of an example of the control part which concerns on this Embodiment. It is a functional block diagram of an example of the control part which concerns on this Embodiment. It is a timing chart which shows an example which performs lighting and extinction of white LED and infrared LED concerning this embodiment in a vertical transfer period. It is explanatory drawing of the operation | movement which transfers the electric charge photoelectrically converted in the CCD image sensor which concerns on this Embodiment. It is a time chart for demonstrating an example of the afterglow of the yellow fluorescent substance in white LED which concerns on this Embodiment. FIG. 10 is a characteristic diagram illustrating an example of the effect of inking in a halftone patch of each color of YMCK by electrophotography. It is a time chart for demonstrating an example of lighting and extinction of white LED and infrared LED which concern on this embodiment. It is a flowchart which shows an example of the blink process in the illumination unit which concerns on this Embodiment.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an example of the configuration of the image forming apparatus according to the present embodiment.
As shown in FIG. 1, an image forming apparatus 10 according to the present embodiment is a multi-function apparatus that is provided with a copying function, a printing function, a facsimile function, and the like, and includes an image reading apparatus 12 and an image forming apparatus unit 14. And is composed of.

  First, the image forming apparatus unit 14 will be described. The image forming apparatus unit 14 according to the present embodiment includes an image forming unit 20 that forms an image based on image data of each color, a forming-side control unit 40 that controls the operation of the entire image forming apparatus 10, and a LAN (Local), for example. And a communication unit 44 that receives image data from an external device such as a personal computer (PC) via a network such as an area network (WAN), a wide area network (WAN), and the Internet. In addition, the image forming apparatus unit 14 according to the present embodiment preliminarily processes image data transferred from the facsimile (FAX) unit 46 that transmits and receives image data through a public line, the image reading device 12, the communication unit 44, and the like. An image processing unit 42 that performs predetermined image processing, and a U / I (user interface) unit 48 that receives instructions from the user and presents information related to image reading and image formation to the user. .

  The image forming unit 20 is a functional unit that forms an image by, for example, electrophotography, and includes four image forming units 21Y, 21M, 21C, and 21K arranged in parallel (hereinafter collectively referred to as image forming units). 21). Each image forming unit 21 includes, for example, a photosensitive drum 22 that forms an electrostatic latent image and holds a toner image, a charger 23 that charges the surface of the photosensitive drum 22 with a predetermined potential, and a charger 23. The print head 24 that exposes the charged photosensitive drum 22 based on the image data, the developing unit 25 that develops the electrostatic latent image formed on the photosensitive drum 22, and the surface of the photosensitive drum 22 after the transfer are cleaned. It is comprised with the cleaner 26 which carries out.

  The image forming unit 20 also includes an intermediate transfer body 27 onto which the color toner images formed on the photosensitive drums 22 of the image forming units 21 are transferred, and the color toner images from the image forming units 21 to the intermediate transfer body 27. A primary transfer roll 28 that sequentially transfers (primary transfer) to a toner image, a secondary transfer roll 29 that collectively transfers (secondary transfer) a toner image transferred and superimposed on the intermediate transfer body 27 to a recording material (recording paper P), And a fixing device 30 for fixing the secondary transferred image on the recording paper P.

  Each image forming unit 21 of the image forming unit 20 forms toner images of each color of yellow (Y), magenta (M), cyan (C), and black (K) by electrophotography. The respective color toner images formed by the respective image forming units 21 are sequentially electrostatically transferred onto the intermediate transfer body 27 by the primary transfer roll 28 to form a composite toner image in which the respective color toners are superimposed. The synthesized toner image on the intermediate transfer member 27 is conveyed to the area where the secondary transfer roll 29 is disposed as the intermediate transfer member 27 moves (in the direction of arrow A in FIG. 1), and is supplied from the sheet storage portions 31A and 321B. The images are electrostatically transferred collectively onto the recording paper P (in the direction of arrow B in FIG. 1). Thereafter, the synthetic toner image electrostatically transferred onto the recording paper P is fixed on the recording paper P by being subjected to a fixing process by the fixing device 30.

Next, the image reading device 12 of the present embodiment will be described.
FIG. 2 shows a schematic configuration of an example of the image reading apparatus 12 according to the present embodiment. The image reading device 12 according to the present embodiment includes an automatic document feeder 50 and an image reading processing unit 52 that reads an image formed on the surface of the document.

  The automatic document feeder 50 according to the present embodiment includes a document table 60 on which at least one document is placed, a document conveyance path 61 that conveys the document, and a discharge table 62 that ejects the document after reading the image. , Including.

  The document conveyance path 61 is formed in a U-shape, and around the document conveyance path 61, there are a sheet delivery roll 63, a delivery roll 64, a pre-positioning roll 65, a positioning roll 66, a platen roll 67, an out-roll 68, And a discharge roll 69 is provided. The paper feed roll 63 descends when the original is fed and picks up the original placed on the original table 60. The sending roll 64 supplies the document at the top of the documents sent from the paper sending roll 63 to the inside. The pre-positioning roll 65 temporarily stops the document sent from the sending roll 64 and corrects the skew feeding. The alignment roll 66 temporarily stops the document sent from the pre-alignment roll 65 and adjusts the reading timing. The platen roll 67 causes the document passing through the document transport path 261 to face the second platen glass 74. The out roll 68 and the discharge roll 69 discharge the read original document to the discharge table 62.

  The image reading apparatus 12 according to the present embodiment has a function of scanning and reading the surface of the document sent from the document table 60 by the automatic document feeder 50 and a function of reading the surface of the document placed on the first platen glass 70. And.

  The image reading processing unit 14 according to the present embodiment includes a CCD image sensor 88 and a reading side control unit 90 in a housing 75. In addition, the image reading device 12 is stationary at the reading position of the second platen glass 74 in the housing 75, or a full-rate carriage 76 that reads an image while scanning the entire first platen glass 70. A half rate carriage 78 for guiding light obtained from the full rate carriage 76 to the CCD image sensor 88 is provided.

  As shown in FIG. 2, the surface of the housing 75 facing the automatic document feeder 50 is being conveyed by the first platen glass 70 on which a document for reading an image is placed, the white reference plate 72, and the automatic document feeder 50. In order to read the original, a second platen glass 74 serving as an opening for irradiating the original with light is provided.

  The full-rate carriage 76 includes an illumination unit 80 having a light source for irradiating light on the document, a diffuse reflection member 83 that reflects the light emitted from the illumination unit 80 while diffusing the light toward the document surface, and a reflection obtained from the document surface. A first mirror 82 that reflects light toward the half-rate carriage 78 is provided.

  The half rate carriage 78 includes a second mirror 85 and a third mirror 84 that guide the light obtained from the full rate carriage 76 to the CCD image sensor 88.

FIG. 3 shows a schematic configuration of an example of the illumination unit 80 according to the present embodiment.
The lighting unit 80 of the present embodiment includes a substrate 87, a plurality of white light emitting diodes (LEDs: hereinafter referred to as white LEDs) 81A as light sources, and a plurality of infrared light emitting diodes (hereinafter referred to as infrared LEDs). ) 81B. The white LED 81A emits white light including red (R), green (G), and blue (B). The infrared LED 81B emits infrared light including infrared (IR). The white LED 81A and the infrared LED 81B are alternately arranged along the longitudinal direction, that is, the main scanning direction of the document. In the present embodiment, the conveyance direction of the intermediate transfer body 27 (the direction of arrow A in FIG. 1) is the sub-scanning direction, and the direction intersecting this is the main scanning direction.

  The white LED 81A is configured by laminating a blue LED chip and a transparent resin containing a yellow fluorescent material. The yellow fluorescent material around the chip is excited by the blue light emitted from the blue LED chip to generate yellow fluorescence. Thereby, blue and yellow having complementary colors are added (synthesized) to generate white light.

  FIG. 4 shows a schematic configuration of an example of a CCD (Charge Coupled Device) image sensor 88 as an example of a light receiving unit according to the present embodiment.

  As shown in FIG. 1, the CCD image sensor 88 of the present embodiment photoelectrically converts an optical image formed by an imaging lens 86 that optically reduces the optical image obtained from the half-rate carriage 78. It has a function of accumulating charges as R (red), G (green), and B (blue) color signals (image signals). The CCD image sensor 88 photoelectrically converts the reflected light from the document in units of pixels and outputs R, G, and B analog image signals.

  As shown in FIG. 4, the CCD image sensor 88 of the present embodiment has a configuration in which one-dimensional line sensors for R, G, and B colors are arranged in a set of three rows as an example. Specifically, the CCD image sensor 88 has a rectangular sensor substrate 88a and three pixel columns (a plurality of pixel columns) 88R, 88G, and 88B on the sensor substrate 88a. In the following description, these three pixel columns 88R, 88G, and 88B are referred to as a red pixel column 88R, a green pixel column 88G, and a blue pixel column 88B, respectively. The red pixel row 88R, the green pixel row 88G, and the blue pixel row 88B are arranged in parallel in a direction (main scanning direction) orthogonal to the document transport direction. Each of the red pixel column 88R, the green pixel column 88G, and the blue pixel column 88B is configured by arranging, for example, k photodiodes PD each having a size of 10 μm × 10 μm on a straight line. In the present embodiment, the reading resolution in the main scanning direction by the red pixel row 88R, the green pixel row 88G, and the blue pixel row 88B (hereinafter referred to as the main scanning direction resolution) is, for example, 600 spi (sample per inch). The distance between the blue pixel line 88B and the green pixel line 88G and the distance between the green pixel line 88G and the red pixel line 88R are each two lines in the sub-scanning direction.

  Here, the red pixel row 88R, the green pixel row 88G, and the blue pixel row 88B are provided with color filters for transmitting different wavelength components, respectively. It functions as a pixel row, a pixel row for green (G), a pixel row for blue (B), that is, a color sensor. Each color filter mounted on the red pixel row 88R, the green pixel row 88G, and the blue pixel row 88B transmits infrared light in a predetermined wavelength region in addition to the corresponding visible light. ing. For this reason, the red pixel column 88R, the green pixel column 88G, and the blue pixel column 88B also function as infrared (IR: InfraRed) pixel columns.

FIG. 5 shows the wavelength characteristics of the illumination unit 80 and the CCD image sensor 88.
FIG. 5A shows the wavelength-light emission characteristics of the white LED 81A and the infrared LED 81B.
The white LED 81A includes a blue-violet light emitting diode having a light emission wavelength in the blue region (for example, 405 nm) and a phosphor material of red, green, and blue, and from the blue region (near 400 nm) to the green region (near 550 nm). ), And outputs light having a continuous wavelength up to the red region (near 800 nm). The white LED 81A hardly emits light in the near infrared region (800 nm to 1000 nm). On the other hand, the infrared LED 81B is configured by an infrared light emitting diode having a light emission wavelength in the infrared region (center wavelength 850 nm). However, the infrared LED 81B emits little light in the visible region (400 nm to 800 nm). Therefore, the white LED 81A outputs light in the visible region as the first wavelength region, and the infrared LED 81B outputs light in the infrared region as the second wavelength region.

  In the present embodiment, the white LED 81A having the above-described configuration is used, but the present invention is not limited to this. FIG. 5A also shows the light emission characteristics of a white LED 81A manufactured by combining a blue LED, a green LED, and a red LED. Thus, it is also possible to generate white light by combining three of the blue LED, the green LED, and the red LED. Even when white light is obtained in this way, the emission spectrum in the near-infrared region does not exist or is weak even if it exists. If the white LED 81A has an emission spectrum in the near infrared region and adversely affects the characteristics of the color image, it is necessary to separately arrange an infrared cut filter that blocks the infrared component close to the white LED 81A. There is. In this case, the infrared cut filter is laid out so as not to enter the optical path of the infrared LED 81B.

FIG. 5B shows the wavelength-transmission characteristics of the color filters provided in the red pixel column 88R, the green pixel column 88G, and the blue pixel column 88B.
The color filter of the blue pixel row 88B transmits light having a wavelength in the blue region, but substantially blocks light having wavelengths in the green region and the red region. The color filter of the green pixel row 88G transmits light having a wavelength in the green region, but substantially blocks light having wavelengths in the blue region and the red region. Further, the color filter of the red pixel row 88R transmits light having a wavelength in the red region, but substantially blocks light having wavelengths in the blue region and the green region. However, the color filters provided in the red pixel row 88R, the green pixel row 88G, and the blue pixel row 88B are appropriate for light in the near-infrared region (specifically, around 850 nm). Has high permeability.

  The reading-side control unit 90 has a function of controlling the operation of the entire image reading device 12, and the reading-side control unit 90 of the present embodiment is an image signal of each color from the CCD image sensor 88. It has a function of processing (R, G, B) to generate image data. The reading-side control unit 90 is connected to the forming-side control unit 40 and the image processing unit 42 of the image forming apparatus unit 14 through signal lines, and transmits / receives control signals and read image data to / from each other.

FIG. 6 shows a schematic configuration of an example of the reading-side control unit 90 according to the present embodiment.
The reading side control unit 90 according to the present embodiment includes a CPU 93, a RAM 94, a ROM 95, an NVM (Non Volatile Memory) 97, and an I / F unit 98. The CPU 93, RAM 94, ROM 95, NVM 97, and I / F (interface) unit 96 are connected so that information and the like are exchanged via a bus 99 such as a control bus or a data bus.

  The CPU 93 has a function of executing digital arithmetic processing according to a predetermined processing program when processing an image signal generated by reading a document. The RAM 94 secures a work area when the CPU 93 executes the program 96. The ROM 95 stores various setting values used for processing by the CPU 93, various processing programs 96, and the like. In the present embodiment, the program 96 is executed by the CPU 93, whereby a blinking process in the lighting unit 80, which will be described in detail later, is performed. The NVM 97 is a flash memory or the like backed up by a battery that retains data even when power supply is interrupted. The I / F unit 98 controls input / output of signals to / from respective components such as the formation side control unit 40 and the image processing unit 42 of the image forming apparatus unit 14 connected to the signal processing unit 100. .

  In the present embodiment, the program 96 is stored in advance. However, the present invention is not limited to this, and the program 96 may be installed in the ROM 95 from an external device (not shown). Further, the program may be transmitted to the signal processing unit 100 via a network such as the Internet and installed in the ROM 95 of the signal processing unit 100. Furthermore, it may be configured to be installed in the ROM 95 from an external recording medium such as a DVD-ROM, a flash memory, or a USB.

Next, functions of the reading side control unit 90 according to the present embodiment will be described in detail.
FIG. 7 shows an example of blocks into which the reading side control unit 90 according to the present embodiment is functionally classified.

  The reading side control unit 90 of this embodiment includes a signal processing unit 100 and an apparatus control unit 120. The reading side control unit 90 includes a signal processing unit 100 and a device control unit 120. Here, the signal processing unit 100 performs processing on the image data input from the CCD image sensor 88 (specifically, the blue pixel row 88B, the green pixel row 88G, and the red pixel row 88R). Further, the device control unit 120 controls the operation of the image reading device 12.

  First, the signal processing unit 100 includes a preprocessing unit 102, a visible post-processing unit 104, an infrared post-processing unit 106, and a data synthesis unit 108.

  The preprocessing unit 102 converts each image data (analog data) input from the blue pixel row 88B, the green pixel row 88G, and the red pixel row 88R of the CCD image sensor 88 into digital data. Further, the preprocessing unit 102 outputs each image data converted into digital data by separating it into image data for invisible images and image data for visible images.

  Specifically, in the preprocessing unit 102, each data from the blue pixel row 88B, the green pixel row 88G, and the red pixel row 88R of the CCD image sensor 88 is subjected to analog correction such as gain / offset adjustment. After that, it is converted into digital data. Here, the data acquired from the CCD image sensor 88 includes data acquired when the white LED 81A (see FIG. 2) is turned on and data acquired when the infrared LED 81B (see FIG. 2) is turned on. Therefore, the pre-processing unit 102 converts the data converted into digital data into visible data (image data for visible image) acquired by lighting the white LED 81A and infrared data (for invisible image) acquired by lighting the infrared LED 81B. Image data) and output. That is, the LED lighting switching signal is input from the light source control unit 128 to the preprocessing unit 102, and the preprocessing unit 102 performs a separate output operation of infrared data and visible data based on the LED lighting switching signal. Therefore, the pre-processing unit 102 outputs the separated visible data to the visible post-processing unit 104 and outputs the infrared data to the infrared post-processing unit 106.

  The visible post-processing unit 104 performs predetermined image processing on the input image data for visible image, and outputs it as image information.

  Specifically, the visible post-processing unit 104 samples (samples) the analog image signals (R, G, B) of the respective colors from the CCD image sensor 88 and holds (holds) the sample for a predetermined period. For the analog image signals (R, G, B) that have been read, the output corresponding to black of the read original (hereinafter referred to as read original) matches the black level of the output of the image reading device 12 (including substantially the same). It has a function to adjust so as to. The visible post-processing unit 104 amplifies the analog image signal (R, G, B) after black level adjustment, A / D converts the amplified analog image signal (R, G, B), It has a function of converting into image data (R, G, B) which is digital data. Further, the visible post-processing unit 104 corrects unevenness of the read output caused by the illumination unit 80 and the CCD image sensor 88 for the A / D converted image data (R, G, B), and also reads the read document. Shading correction for adjusting the white level of the image and the white level of the output of the image reading device 12 to match (including substantially the same), and one-dimensional lines for R, G, and B constituting the CCD image sensor 88 It has a function of correcting, for example, R image data as a reference, using a delay circuit or the like, for a reading time difference between the respective image data caused by a positional shift of the sensor in the sub-scanning direction.

  Then, the visible post-processing unit 104 uses the color conversion parameters (color conversion coefficient group) to convert the RGB color space (first color space: device-dependent color space) image data (R, G, B) to the luminance color difference. It has a function of performing color conversion processing for converting into image data (L *, a *, b *) in an L * a * b * color space (second color space: device-independent color space) that is a color space. Here, the “color conversion parameter” refers to, for example, converting RGB color space image data (R, G, B) into L * a * b * color space image data (L *, a *, b *). In this case, it defines the correspondence between image data (R, G, B) and image data (L *, a *, b *). Examples of the color conversion process include, but are not limited to, a method using a matrix operation or a multi-dimensional (three-dimensional) lookup table (DLUT (Direct Look-Up Table)).

  The image data (L *, a *, b *) subjected to color conversion processing by the visible post-processing unit 104 is transferred to the image processing unit 42 provided in the image forming apparatus unit 14 via the data synthesis unit 108. Then, color conversion processing to image data (C, M, Y, K) in the CMYK color space (device-dependent color space) that is an output color space is performed. The image processing unit 42 that performs color conversion processing to image data (C, M, Y, K) in the output color space may be provided inside the image reading device 12.

  Therefore, in the visible post-processing unit 104, after the three analog image signals (R, G, B) from the CCD image sensor 88 are sampled, the black level is adjusted and further amplified to a predetermined signal level. The The amplified analog image signals (R, G, B) are A / D converted to generate image data (R, G, B) which is digital data. These image data (R, G, B) are made to correspond to the sensitivity variation of the one-dimensional line sensor constituting the CCD image sensor 88 and the light quantity distribution characteristic of the optical system based on the image data read from the white reference plate 72. Correction is applied. The image data (R, G, B) is converted into image data (L *, a *, b *) in the L * a * b * color space after the positional deviation in the sub-scanning direction is corrected, and the data composition The data is output via the unit 108.

  The infrared post-processing unit 106 performs image analysis on the input image data for the invisible image, and extracts and outputs identification information included in the invisible image. Note that the infrared post-processing unit 106 may output image data obtained by performing image processing on the input image data for an invisible image.

  Specifically, the infrared post-processing unit 106 has a function of analyzing identification information from the code image included in the input infrared data and outputting the obtained identification information via the data synthesis unit 108. ing. The infrared post-processing unit 106 can acquire infrared shading data used for shading correction of infrared image data of a document. For example, for the input infrared data (each color of R, G, B), the variation in sensitivity of the photodiode PD in each of the corresponding blue pixel row 88B, green pixel row 88G, and red pixel row 88R Correction according to the light quantity distribution characteristic of the LED light source (in this case, the infrared LED 81B) can be performed.

  The data synthesis unit 108 synthesizes (associates) the identification information output from the infrared post-processing unit 106 and the image information output from the visible post-processing unit 104 and outputs the resultant information to the image forming apparatus unit 14. Note that the data synthesis unit 108 may output the data to an electronic device such as a PC (Personal Computer) provided at a later stage.

Next, the device control unit 120 will be described.
The apparatus control unit 120 according to the present embodiment includes an overall control unit 122, a CCD control unit 126, a light source control unit 128, a scan control unit 130, and a document conveyance control unit 132.

  The overall control unit 122 has a function of controlling the reading of the document instructed by the U / I unit 48 and the like and controlling the entire image reading device 12.

  The CCD control unit 126 has a function of controlling driving of the CCD image sensor 88. The light source control unit 128 has a function of controlling the illumination unit 80 in accordance with the reading timing of the document. In this embodiment, the white LED 81A and the infrared LED 81B are turned on based on an instruction from the overall control unit 122. And a function of controlling the turn-off. The scan control unit 130 has a function of controlling the scan operation by controlling the moving speed of the full rate carriage 76 and the half rate carriage 78. The document conveyance control unit 132 has a function of controlling the operation of the automatic document feeder 50. Control signals are output from the CCD control unit 126, the light source control unit 128, the scan control unit 130, and the document conveyance control unit 132 to the automatic document feeder 50 and the image reading processing unit 52, respectively, and based on the control signals. A document reading operation is performed.

  For example, when a reading format for reading a document placed on the first platen glass 70 is instructed in the image reading device 12 of the present embodiment, a user operation from the U / I unit 48 of the image forming device unit 14 is performed. Based on the instruction, the formation-side control unit 40 of the image forming apparatus unit 14 instructs the apparatus control unit 120 to read the document placed on the first platen glass 70.

  In this case, the reading side control unit 90 moves the full rate carriage 76 and the half rate carriage 78 in the scanning direction (direction of arrow C in FIG. 2). Further, the illumination unit 80 of the full rate carriage 76 emits light, and the original surface is irradiated. By the irradiation, the reflected light from the document is guided to the imaging lens 86 through the first mirror 82, the second mirror 85, and the third mirror 84. The light guided to the imaging lens 86 is imaged on the light receiving surface of the CCD image sensor 88. The CCD image sensor 88 processes one line for each of R, G, and B colors substantially simultaneously. Then, the reading in the line direction is executed by scanning over the entire document size, thereby reading the document for one page. The image signals (R, G, B) obtained by the CCD image sensor 88 are transferred to the reading side control unit 90, and the signal processing unit 100 generates image data (L *, a *, b *) for identification. Information is associated and output to the image processing unit 42.

  In reading a document, in the illumination unit 80, one of the white LED 81A and the infrared LED 81B is turned on while the other LED is turned off. That is, when reading a visible image from a document, the infrared LED 81B is turned off while the white LED 81A is turned on. On the other hand, when acquiring identification information from a document, the white LED 81A is turned off while the infrared LED 81B is turned on. Thereby, it can process substantially simultaneously by switching irradiation of white LED81A and infrared LED81B about one line of CCD image sensor 88. FIG.

  Note that when the image reading device 12 instructs the reading format for reading the document placed on the document table 60, the forming side control unit 40 of the image forming device unit 14 similarly sends the document to the reading side control unit 90. An instruction to read the document placed on the table 60 is given, and image data associated with the identification information is output.

  Here, in the image reading apparatus 12 according to the present embodiment, in order to acquire a visible image and an invisible image (identification information) from the document, one of the white LED 81A and the infrared LED 81B is turned on and the other is turned off. The turning on and off of the white LED 81A and the infrared LED 81B will be described.

First, operation | movement of the illumination unit 80 which is a light source is demonstrated.
FIG. 8 is a timing chart showing an example in which the white LED 81A and the infrared LED 81B are turned on and off during the vertical transfer period VT.
In FIG. 8, in the order from the upper stage to the lower stage, the CCD control unit 126 controls the CCD image sensor 88 to operate (CCD drive clock), the control signal to operate the white LED 81A, and the light emission luminance characteristics of the blue LED chip in the white LED 81A ( Response performance), the light emission luminance characteristic (response performance) of the yellow fluorescent substance in the white LED 81A, a control signal for operating the infrared LED 81B, and the light emission luminance characteristic (response performance) of the infrared LED 81B are shown.

  In the example shown in FIG. 8, the transfer period of image information in one line in the main scanning direction is a charge accumulation period in the CCD image sensor 88, and the transfer period includes a vertical transfer period VT and a horizontal transfer period HT. In the example shown in FIG. 8, in the vertical transfer period VT, lighting of the light source in the illumination unit 80 is switched from the white LED 81A to the infrared LED 81B, or from the infrared LED 81B to the white LED 81A.

  That is, as shown in FIG. 8, the control signal for operating the white LED 81A is turned on in synchronization with the falling timing of the vertical transfer period VT, and turned off in synchronization with the rising timing of the vertical transfer period VT. The On the other hand, the control signal for operating the infrared LED 81B is switched alternately between the on state and the off state in synchronization with the falling timing of the vertical transfer period VT so that the white LED 81A and the infrared LED 81B are not turned on simultaneously.

  When the control signal for operating the white LED 81A is turned on, the blue LED chip in the white LED 81A emits light, and the white light emitted from the yellow fluorescent material is emitted to the CCD image sensor 88. In addition, when the control signal for operating the infrared LED 81B is turned on, the infrared LED 81B emits light and the CCD image sensor 88 is irradiated with infrared light.

Next, operations (vertical transfer and horizontal transfer) in the CCD image sensor 88 will be described.
FIG. 9 is an explanatory diagram of the operation of transferring the photoelectrically converted charges in the CCD image sensor 88. In FIG. 9, one of the three pixel columns 88R, 88G, and 88B (see FIG. 4) arranged on the sensor substrate 88a is shown as an example.

  In FIG. 9, the photodiode PD corresponds to one pixel when the image is read by the image reading device 12. When the photodiode PD is irradiated with light, photoelectric conversion occurs and charges are accumulated in the photodiode PD. The amount of charge accumulated is proportional to the accumulation time (accumulation period) and the amount of light emitted. In the photodiode PD, charges are accumulated in a predetermined accumulation period, and the accumulated charges are taken out as an electric signal. At this time, the general CCD image sensor 88 extracts charges (electrical signals) by performing vertical transfer and horizontal transfer. The charge accumulated in the photodiode PD is first vertically transferred and sent to the charge transfer unit D, which is a semiconductor element made up of a CCD (Charge Coupled Device). The charges transferred in the vertical direction are further transferred from the charge transfer unit D in the horizontal direction to be taken out as an image signal for one line.

  The charge accumulated in the photodiode P is transferred vertically from the photodiode P to the charge transfer portion D in the vertical transfer period VT (FIG. 8). Thereafter, in the horizontal transfer period HT (FIG. 8), horizontal transfer in the charge transfer unit D is performed. Note that horizontal transfer is sequentially performed pixel by pixel in accordance with the on / off state of the CCD drive clock until all charges for one line are transferred horizontally. Further, during the vertical transfer and the horizontal transfer, the next one-line charge is photoelectrically converted and accumulated in the photodiode PD.

  By the way, when the white LED 81A and the infrared LED 81B are turned on and off, the illumination of the white LED 81A and the infrared LED 81B that has been turned off remains, which may affect the illumination of the turned on. . For example, when the white LED 81A is turned off and the infrared LED 81B is turned on, the afterglow of the turned off white LED 81A is received by the CCD image sensor 88. The afterglow of the white LED 81A is added to the amount of received light obtained by turning on the infrared LED 81B, and causes SN degradation of the acquired infrared data. In such a case, it may be difficult to read the document normally.

  Specifically, the light emission characteristics of the blue LED chip in the white LED 81A may be different from the light emission characteristics of the yellow fluorescent material. In the example shown in FIG. 8, the response characteristic of the yellow fluorescent material is slower than the response characteristic of the blue LED chip with respect to the on / off state of the white LED 81A (tb <VT <ty). Here, due to the slow response characteristic when the white LED 81A is turned off, the light emission of the yellow fluorescent material is irradiated to the CCD image sensor 88 as afterglow. When the afterglow due to the yellow fluorescent material remains beyond the vertical transfer period VT, a color mixture state synthesized with the light emitted by the infrared LED 81B is obtained. That is, the CCD image sensor 88 is irradiated with a mixture of the afterglow of the yellow fluorescent material and the light emitted from the infrared LED 81B. For this reason, the CCD image sensor 88 detects afterglow of the yellow fluorescent material as noise.

  Therefore, in the present embodiment, the illumination unit 80 is controlled so that the light of the white LED 81A, specifically, the afterglow of the yellow fluorescent material and the emitted light of the infrared LED 81B are not mixed. That is, the infrared LED 81B is caused to emit light after the afterglow of the yellow fluorescent material is sufficiently reduced.

  After the white LED 81A is turned off, the value indicating the amount of light with sufficiently little afterglow of the yellow fluorescent material can be determined as follows.

  Generally, it is known that the afterglow time of the yellow phosphor in the white LED 81A used in the line scan type image reading apparatus is several μs to several tens μs. On the other hand, since the sensor output of the CCD image sensor 88 is proportional to the exposure amount (integrated value of the light amount and the exposure time), the line cycle of the CCD image sensor 88 becomes shorter as the scanning operation speed increases, and the afterglow component. The effect of is relatively increased.

FIG. 10 is a time chart showing an example of the afterglow of the yellow phosphor in the white LED 81A.
In FIG. 10, the control signal for operating the white LED 81A in the order from the top to the bottom, the light emission luminance characteristic (response performance) of the blue LED chip in the white LED 81A, and the light emission luminance characteristic (response performance) of the yellow fluorescent substance in the white LED 81A. It is shown. For example, when scanning at 600 dpi and a process speed of 500 mm / s, the line period is 84.6 μsec. In this case, although the afterglow component after the white LED 81A is extinguished gradually, color mixing may be caused by the afterglow exceeding 10% during the afterglow time.

  In addition, when an image is formed using toner of each color of YMCK by electrophotography, inking is generally performed. Inking is a process of replacing a part of the common amount of YMC with K color in the image data converted into each color of YMC in the image processing.

FIG. 11 shows an example of the effect of inking in a half-tone patch of each color of YMCK by electrophotography.
As shown in FIG. 11, even when the RGB read values are equal (for example, [RGB] = [0,0,50] in the normalized output), the color value changes depending on the inking rate (differs visually). Color). In other words, there are different colors even if the RGB output values are the same. That is, since the RGB output values handle only the three values determined by the spectral characteristics of the CCD image sensor 88 and the convolution of the spectral reflection light from the original, the spectral reflection light having the same convolution value for different spectral incidences. There can be a plurality of distributions.

  For example, for image data ([YMC] = [20, 10, 30]) converted to each color of YMC, a part of the common amount of YMC (for example, [5]) is replaced with K color ([YMCK] = [ 15,5,25,5]). The maximum value that can be replaced with K color in this image data is 10, but 50% of 5 is the inking amount. Since the spectral characteristics of each toner are different, the color changes when it is replaced with K color, but the total amount of toner can be suppressed by appropriately controlling the inking, so inking in consideration of color changes To do.

  As shown in FIG. 11, when a color profile (color conversion parameter) is created without considering the amount included in the K plate, a large error may occur. For example, when the inking rate is 60%, the amount of change in the color value is about 20, and the error (delta-E / inking rate) is about 0.33 (= 20/60). Here, when creating the color profile of the image reading device, if the color profile of the image reading device is created for each image forming device, that is, the color profile for the image reading device including the amount of inking of each image forming device. By creating the, accuracy can be ensured. However, it is not practical to create a color profile for an image reading apparatus that includes the amount of inking of each image forming apparatus because it involves a huge amount of work. It is preferable that the image reading apparatus can cope with different image forming apparatuses (different inking amounts) with only a unique color profile.

  For example, if it is desired to suppress the change amount of the color value due to an error to less than a certain value (delta-E <1), it is only necessary to detect the inking rate with an accuracy of 3% or less. Actually, the amount of inking (K toner amount) can be obtained, so the condition that maximizes the error is when the ink mixing rate is 100% and the color mixing error is 3%, and the inking amount is detected with an error of 3% or less. I can do it. Therefore, it is preferable to suppress the color mixture of visible light to infrared light to 3% or less.

  In color conversion, there are errors due to nonlinearity between the RGB space and the L * a * b * space, errors due to SN, and the like. In reality, it is desired that the color difference (delta-E <3) allowed by the human eye is suppressed by color mixing (delta-E is less than about 1). It is reasonable to suppress the content to 3% or less.

  Therefore, in the present embodiment, at the falling timing (latch timing) of the vertical transfer period VT of the CCD image sensor 88, the integrated value due to the afterglow of the fluorescent component when the white LED 81A is extinguished is less than 3%. The lighting signal of the white LED 81A is turned off before the timing. By previously deriving the time until the integrated value due to the afterglow of the fluorescent component when the white LED 81A is turned off falls below 3%, the lighting signal of the white LED 81A can be turned off before the latch timing. . Note that by controlling the current value of the white LED 81A, the illumination brightness may be increased to compensate for the shortened lighting time. Since an increase in luminance due to current value control causes a change in the color (spectral) of illumination, it is preferable to obtain the parameters of the color conversion equation under the conditions for shortening the lighting time.

FIG. 12 is a timing chart showing an example of turning on and off the white LED 81A and the infrared LED 81B according to this embodiment.
In FIG. 12, as in FIG. 8, the CCD control unit 126 controls the CCD image sensor 88 to operate the CCD image sensor 88, the control signal to operate the white LED 81A, and the blue LED in the white LED 81A in the order from the top to the bottom. The light emission luminance characteristics (response performance) of the chip, the light emission luminance characteristics (response performance) of the yellow fluorescent substance in the white LED 81A, the control signal for operating the infrared LED 81B, and the light emission luminance characteristics (response performance) of the infrared LED 81B are shown. ing.

  In the example shown in FIG. 12, at the falling timing (latch timing) To of the vertical transfer period VT of the CCD image sensor 88 that turns on the infrared LED 81B, the integrated value due to the afterglow of the fluorescent component when the white LED 81A is turned off is a predetermined value. The lighting signal of the white LED 81A is turned off in advance so as to be lower than a value (for example, 3%).

  That is, as shown in FIG. 12, the control signal for operating the white LED 81A is turned on in synchronization with the falling timing of the vertical transfer period VT, and turned off after a predetermined time has elapsed. On the other hand, after the white LED 81A is turned off, the control signal for operating the infrared LED 81B is switched to the on state after the afterglow of the yellow fluorescent material becomes sufficiently small.

  Specifically, when the white LED 81A is turned off, an afterglow disappearance time Tth equal to or longer than the afterglow time ty due to the response characteristic of the slow yellow fluorescent material is determined in advance compared to the response characteristic of the blue LED chip. . Then, the white LED 81A is turned off before the afterglow disappearance time Tth from the latch timing To for turning on the infrared LED 81B. Accordingly, due to the slow response characteristic when the white LED 81A is turned off, even if the light emission of the yellow fluorescent material is irradiated to the CCD image sensor 88 as the afterglow, the afterglow by the yellow fluorescent material is sufficient. Since the light emitted from the infrared LED 81B is emitted after the amount of light is reduced, the mixed color state where the light from the white LED 81A and the light from the infrared LED 81B are combined is not caused. Therefore, the CCD image sensor 88 does not detect the afterglow of the yellow fluorescent material as noise.

Next, the blinking process (of the white LED 81A and the infrared LED 81B) in the illumination unit 80 of the image reading apparatus 12 of the present embodiment will be described. In the present embodiment, a case where the light source of the white LED 81A and the light source of the infrared LED 81B are alternately turned on and off as the blinking process will be described.
FIG. 13 shows an example of the flow of blinking processing in the illumination unit 80, which is executed by the light source control unit 128 according to the present embodiment. The blinking process in the illumination unit 80 is executed when the U / I unit 48 receives an instruction to read a document from the user.

  In step S100, the afterglow disappearance time Tth is derived by obtaining a document reading instruction from the overall control unit 122. The afterglow disappearance time Tth is stored in advance in the NVM 97, or the response characteristic of the blue LED chip of the white LED 81A and the response characteristic of the yellow fluorescent material are obtained from the overall control unit 122, and the amount of afterglow is sufficiently small Is obtained, and an afterglow disappearance time Tth longer than that time is derived. The time until the afterglow reaches a sufficiently small light amount is the time when the exposure amount (integrated value) due to the afterglow after the white LED 81A is turned off is less than 3%, for example.

  In the next step S102, a CCD drive clock signal is acquired, and in the next step S104, it is determined whether the CCD drive clock signal has reached the falling timing (latch timing) of the vertical transfer period VT. In step S104, a negative determination is repeated until the CCD drive clock signal reaches the falling timing (latch timing) of the vertical transfer period VT. If the latch timing comes, an affirmative determination is made, and the process proceeds to step S106. In step S106, the white LED 81A is turned on and the infrared LED 81B is turned off. That is, the white LED 81A is turned on (control signal is turned on) so that the white LED 81A is turned on, and the infrared LED 81B is turned off (control signal) so that the infrared LED 81B is turned off. Off).

  In the next step S108, it is determined whether the CCD drive clock signal has reached the previous time by the afterglow disappearance time Tth derived in step S100 from the falling timing (latch timing To) of the next vertical transfer period VT. In step S108, the negative determination is repeated until the CCD drive clock signal reaches the time before the afterglow disappearance time Tth from the latch timing To. In step S110, the white LED 81A is turned off. That is, the white LED 81A is controlled to be turned off (the control signal is turned off) so that the white LED 81A is turned off, and the process proceeds to step S112.

  In step S112, it is determined whether the CCD drive clock signal has reached the falling timing (latch timing To) of the vertical transfer period VT. In step S112, the negative determination is repeated until the CCD drive clock signal reaches the latch timing To, and when the latch timing To is reached, an affirmative determination is made, and the process proceeds to step S114 to turn on the infrared LED 81B. That is, the lighting of the infrared LED 81B is controlled (the control signal is turned on) so that the infrared LED 81B is turned on.

  In the next step S116, it is determined whether the CCD drive clock signal has reached the falling timing of the next vertical transfer period VT. In step S116, a negative determination is repeated until the CCD drive clock signal reaches the next latch timing, and if it reaches, an affirmative determination is made, and the process proceeds to step S118. In step S118, it is determined whether to end the blinking process. If the determination is negative, the process returns to step S106. On the other hand, if the determination in step S118 is affirmative, this process ends.

  As described above, the image reading device 12 of the image forming apparatus 10 according to the present embodiment has a slow yellow fluorescent material compared to the response characteristic of the blue LED chip when the white LED 81A is turned off. An afterglow disappearance time Tth equal to or longer than the afterglow time ty according to the response characteristics is determined in advance. Then, the white LED 81A is turned off before the afterglow disappearance time Tth from the latch timing To for turning on the infrared LED 81B. Thereby, due to the slow response characteristic when the white LED 81A is turned off, the afterglow by the yellow phosphor is sufficient even when the light emission of the yellow phosphor is applied to the CCD image sensor 88 as afterglow. The infrared LED 81B emits light after the amount of light becomes very small. For this reason, there is no mixed color state in which the light of the white LED 81A and the light of the infrared LED 81B are combined. Further, the CCD image sensor 88 does not detect the afterglow of the yellow fluorescent material as noise.

  Thus, in this embodiment, afterglow disappearance time Tth is determined according to the response characteristics of the blue LED chip of the white LED 81A and the response characteristics of the yellow fluorescent substance, and the afterglow disappearance time is longer than when the infrared LED 81B is turned on. Prior to Tth, the white LED 81A is turned off. Accordingly, even when the response characteristics of the blue LED chip of the white LED 81A and the response characteristics of the yellow fluorescent substance are slow and afterglow occurs after the light is turned off, the light of the white LED 81A and the light of the infrared LED 81B are mixed. Invisible image data and visible image data can be obtained with high accuracy.

  In the present embodiment, when the white LED 81A is turned off and the infrared LED 81B is turned on, the amount of light (integrated value) due to the afterglow of the fluorescent component when the white LED 81A is turned off is at a timing such that it falls below a predetermined value. The case where the lighting signal of the white LED 81A is turned off before the infrared LED 81B is turned on has been described. Thus, turning off the white LED 81A and turning on the infrared LED 81B means that when the white LED 81A is turned off, the infrared LED 81B is turned on after the amount of light due to the afterglow of the fluorescent component of the white LED 81A falls below a predetermined value. May be.

  The configuration, operation, blinking processing, and the like of the image forming apparatus 10, the image reading apparatus 12, the image forming apparatus unit 14, and the like described in the present embodiment are examples, and depending on the situation without departing from the scope of the present invention. Needless to say, it will change.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Image reading apparatus 14 Image forming apparatus part 80 Illumination unit 81A White LED
81B infrared LED
88 CCD image sensor 90 Control unit 122 Overall control unit 128 Light source control unit

Claims (7)

A light source that includes a light source that emits light in a first wavelength range, and a light source that emits light in a second wavelength range different from the first wavelength range; and
Reading means for reading a document illuminated by light emitted from the light source unit;
When alternately turning on and off the light source of the light source unit, the amount of light emitted from the turned off light source is predetermined before turning on the turned off light source. Control means for controlling the light source unit so as to turn off the light source that is turned on at a timing that is less than or equal to the light amount,
An image reading apparatus comprising: The amount of light emitted from the turned off light source is the amount of afterglow when the turned on light source is turned off.
The image reading apparatus according to claim 1. The reading means includes a semiconductor element that takes out the charge accumulated in the charge-coupled element that accumulates the charge according to the received light as an image signal by vertical transfer and horizontal transfer.
The control means controls to turn off the light source that is lit during the horizontal transfer period,
The image reading apparatus according to claim 1. The image reading apparatus according to claim 1, wherein the first wavelength range is a visible wavelength range, and the second wavelength range is a near-infrared wavelength range. The light source unit includes a white LED light source that emits white light in a visible wavelength region as light in the first wavelength region by blue light and yellow light that is excited and emitted by the blue light, and a near-infrared wavelength region. Including an infrared LED light source that irradiates light of the second wavelength range as light in the second wavelength range,
The control means is configured to turn on the white LED that is turned on at a timing when the amount of yellow light emitted from the turned off white LED light source becomes equal to or less than a predetermined amount before the timing of turning on the turned off infrared LED light source. The image reading apparatus according to claim 1, wherein the light source unit is controlled so that the light source is turned off. An image reading apparatus according to any one of claims 1 to 5,
Image forming means for forming an image based on an image signal output from the image reading device;
An image forming apparatus. In order to read a document illuminated with light emitted from a light source unit including a light source that emits light in a first wavelength range and a light source that emits light in a second wavelength range different from the first wavelength range, the light source When alternately turning on and off the light source of the unit, if the light source that is on is turned off, the amount of light emitted from the turned off light source is determined in advance before the timing of turning on the light source that is turned off A program for causing a computer to execute processing including controlling the light source unit to turn off a light source that is turned on at the following timing.

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