JP2018078425A - Image reading device and method for generating shading data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading device that obtains a color image by switching a plurality of light sources with different wavelengths every one line and that can shorten movement operation to acquire shading data on each color.SOLUTION: An image reading device limits data acquired by movement shading to a color component from one light source, and calculates shading data on remaining color components from shading data on the color component, an average value of an amount of light corresponding to one line of the other color components, and an average value of an amount of light corresponding to one line of black. Because the movement shading is performed with only one color component like this, movement operation to acquire shading data can be shortened. Furthermore, noise of the device is suppressed, and a time until reading start can be shortened.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an image reading apparatus and a method for generating shading data, and more particularly to an image reading apparatus for optically reading an image recorded on a document placed on a document table and a method for generating shading data thereof. .

  In a copying machine, a facsimile machine, a multifunction machine having a copying function and a facsimile function, and the like, generally, when reading a document, the document is placed on the document table so that the reading surface faces downward. Then, the image reading is executed by irradiating the original with light, receiving the light reflected by the original while scanning the reading unit, and outputting an image signal obtained by photoelectrically converting the light.

  Conventionally, white shading has been performed in order to adjust variations in image signals before image reading. White shading is a white calibration process using a reading value of a reference white plate. By executing the white shading, the entire read image can be corrected so as to have an average uniform brightness. Specifically, reading is performed in a state where the light source is turned on in a certain region of the reference white plate, and white level correction data is generated. When the image is read, the white level of the image signal of the read image is corrected using the white level correction data.

  Shading includes fixed shading and moving shading. Fixed shading is a process in which a reading operation for obtaining white level correction data is performed at one location in the reference white plate. On the other hand, moving shading is obtained by scanning the reading unit at a plurality of locations in the reference white plate while moving the reading unit in the direction (sub-scanning direction) orthogonal to the document width direction (main scanning direction). In this process, the average value of the obtained image signals is used as correction data. In particular, since moving shading performs reading while moving the reading unit, the reference white plate needs a scanning width of a certain level or more.

  When shading processing is performed by an image reading device that acquires a color image by switching light sources that irradiate a plurality of lights, such as a plurality of light sources having different wavelengths, data for several lines is acquired for each color component. The average value is used as correction data. When reading a color image composed of three color components of R (red), G (green), and B (blue), a reference white that takes into account that the reading unit has a moving distance three times that of reading a monochrome image A plate was required, and there were problems such as an increase in the cost of the device and an increase in the size of the device.

  For this reason, an image reading apparatus that can output image signals subjected to shading correction without increasing the width of the reference white plate, and switches between a plurality of light sources having different wavelengths for each line to acquire color image data is proposed. (See Patent Document 1).

Japanese Patent Laid-Open No. 11-341237

  However, in the shading correction method as in the above conventional example, it is necessary to repeat the movement of the reading unit in different directions in order to obtain a plurality of shading data of three color components. For this reason, there are problems such as noise of the image reading apparatus during the shading operation and a long shading operation time.

  The present invention has been made in view of the above conventional example, and provides an image reading apparatus capable of shortening the time for acquiring each shading data when reading an image using a plurality of light sources, and a method for generating shading data. For the purpose.

  In order to achieve the above object, the image reading apparatus of the present invention has the following configuration.

  That is, an irradiation unit that irradiates a plurality of lights, a plurality of photoelectric conversion elements arranged in a predetermined first direction, and a plurality of lights irradiated from the irradiation unit are received by a common photoelectric conversion element. First shading data is acquired based on a reading unit including an imaging unit and capable of optically reading a document image and reflected light from a reference member by at least one of the plurality of irradiated lights A first acquisition unit that performs the first acquisition unit that corresponds to the irradiation light that is not included in the reflected light among the plurality of irradiation light based on the first shading data acquired by the first acquisition unit. And generating means for generating 2 shading data.

  Therefore, according to the present invention, there is an effect that the moving operation for obtaining the shading data can be shortened.

1 is a side cross-sectional view illustrating a configuration of an image reading apparatus that optically reads an image of an original that is a typical embodiment of the present invention. FIG. 2 is a block diagram illustrating a control configuration of the image reading apparatus illustrated in FIG. 1. 6 is a flowchart illustrating a color image reading operation. It is a flowchart which shows the shading operation | movement of a color reading. It is the figure which showed the arrangement | sequence of shading data. It is a figure which shows the relationship between the shading data by the difference of LED lighting pattern, and the position of a main scanning direction.

  Hereinafter, preferred embodiments of the present invention will be described more specifically and in detail with reference to the accompanying drawings.

  In this specification, the “sheet (or recording medium)” is not limited to image original paper and photographic paper used in a general image reading apparatus, but is widely used for cloth, plastic film (OHP), It includes media that can record images, such as metal plates, wood, and leather.

<Outline of Image Reading Apparatus (FIGS. 1-2)>
FIG. 1 is a side sectional view showing a schematic configuration of an image reading apparatus 1 that optically reads an image of an original such as a cut sheet, which is a typical embodiment of the present invention. The image reading apparatus 1 uses the CIS unit 13 to irradiate light on the original, receives light reflected from the original, and photoelectrically converts this to generate an electrical signal, thereby reading the image of the original and generating image data. To do.

  As shown in FIG. 1, the CIS unit 13 includes an illuminating unit 131, an optical lens 133, and an imaging unit 134, and is disposed so as to be in close contact with the document table glass 14 on the side opposite to the document placement side. The illumination unit 131 includes a white type light guide tube including three red LEDs, green LEDs, and blue LEDs as a light source, and illuminates the document from a direction inclined by a predetermined angle with respect to the document table glass 14. A platen cover (not shown) is provided on the top of the platen glass 14.

  The optical lens 133 is composed of a SELFOC (registered trademark) lens or the like, and guides the light emitted from the illumination unit 131 and reflected by the document surface to a predetermined imaging position, and the reflected light from the document is magnified by an equal magnification. Read with.

  The imaging unit 134 includes a plurality of photoelectric conversion elements and the like, and images light guided to a predetermined imaging position by the optical lens 133. In this embodiment, it is assumed that the imaging unit 134 is a CMOS sensor. Image data generated from the document imaged by the imaging unit 134 is stored in an image storage unit (described later). The CIS unit 13 having such a configuration is attached to the driving belt 16 and moves along the guide rail 17 by transmitting the driving force of the scanner motor 18 through the driving belt 16 in the sub-scanning direction.

  The image reading apparatus 1 moves the CIS unit 13 in the sub-scanning direction (arrow H direction) by the driving force of the scanner motor 18 while moving the CIS unit 13 in a direction (generally intersecting) with the paper surface (main scanning direction). The image of the document 15 is read by scanning electrically. In general, a stepping motor, a DC motor, or the like is used as the scanner motor 18. At the time of image reading, the reference white plate 11 provided at the end of the platen glass 14 is irradiated with light, and a reference signal for performing shading correction is obtained from the reflected light. A document abutting plate 12 is attached to the side of the reference white plate 11 so that the user can abut the document 15 on the reference end position. The document abutting plate 12 is disposed on the upper surface of the document table glass 14.

  In the above configuration, when reading an image of a document placed on the platen glass 14, shading correction using the reference white plate 11 is performed in advance.

  The arrow F indicates the forward direction in the sub-scanning direction, and the arrow B indicates the backward direction.

  FIG. 2 is a block diagram showing a control configuration of the image reading apparatus 1 shown in FIG.

  The CIS unit 13 reads the image of the document 15 in accordance with the lighting time performed by adjusting the light amount of the illumination unit 131 for each line in the main scanning direction by the LED driving circuit (driver) 3. The LED drive circuit 3 can turn on the illumination unit 131 with an arbitrary PWM duty.

  Furthermore, the illumination unit 131 of the CIS unit 13 includes three light sources, a red LED 1311, a green LED 1312, and a blue LED 1313, and white light can be generated by these three light sources.

  The amplifier (AMP) 21 amplifies the electrical signal output from the CIS unit 13, and the A / D conversion circuit 22 performs A / D conversion on the amplified electrical signal. For example, each pixel has a 16-bit luminance value. The digital image data expressed as The configuration necessary for A / D conversion including the A / D conversion circuit 22 is collectively referred to as a conversion unit. The image signal for one line output from the CIS unit 13 is obtained by sequentially turning on the red LED 1311, the green LED 1312, and the blue LED 1313. The A / D conversion circuit synchronizes with the main scanning synchronization signal line by line. 22 is input.

  Digital image data (hereinafter referred to as image data) output by the A / D conversion circuit 22 is input to the digital processing unit 6, and the digital processing unit 6 performs image processing on the image data. A memory 61 included in the digital processing unit 6 stores image data, and transfers images by connecting to an interface with a printing apparatus such as an ink jet printer or a laser beam printer using an electrophotographic system, or another external apparatus. be able to. Examples of this interface include a serial interface such as USB and a network interface of a wired / wireless network. The image reading device 1 executes an image reading operation in response to an instruction from an external device connected via an interface. Alternatively, an image reading operation is executed in response to a user operation on an operation unit (not shown) provided in the image reading apparatus 1.

  The operation unit includes a display unit such as a display and an input operation unit such as an input key, and provides a function as a user interface. On the display of the display unit, a message for notifying the user of the state of the device or guiding the user to input operation is displayed. Further, the user operates the input keys to input necessary instructions.

  The timing generation circuit 4 changes the PWM duty for each line in the main scanning direction in accordance with the setting of the CPU 5, and transmits the LED lighting ON / OFF control signal to the LED driving circuit 3 to adjust the light amount of the LED. Is possible. Specifically, the LED light amount can be adjusted by transmitting a control signal for turning on / off the red LED 1311, the green LED 1312, and the blue LED 1313 included in the illumination unit 131 to the LED drive circuit 3.

  The CPU 5 controls the entire image reading apparatus 1. Therefore, the CPU 5 executes the control by executing the control program stored in the ROM 52 using the RAM 51 as a work area.

  The memory 61 of the digital processing unit 6 stores image data and shading reference data. The shading correction unit 62 of the digital processing unit 6 performs shading correction on the image data converted by the A / D conversion circuit 22 based on the shading reference data stored in the memory 61.

  Next, a color image original reading and shading correction method performed by the image reading apparatus 1 having the above configuration will be described.

  FIG. 3 is a flowchart showing a color image original reading operation.

  First, in step S101, it is checked whether or not a user has instructed color image reading. Here, if there is no such reading instruction, the process ends as it is, but if there is a color image reading instruction, the process proceeds to step S102.

  In step S102, color shading processing is executed. Details of the processing will be described later.

  In step S103, the red LED 1311, the green LED 1312, and the blue LED 1313 included in the illumination unit 131 are switched on a line-by-line basis in the main scanning direction and sequentially turned on. In step S104, the scanner motor 18 is driven to move the CIS unit 13, and reading of the image of the document 15 placed on the document table glass 14 is started. In the reading, the three LEDs included in the illumination unit 131 are switched on and turned on line by line, and red (R) data, green (G) data, blue ( B) Transfer the data to the digital processing unit 6. At this time, each transferred color component data is corrected using the shading coefficient calculated by the color shading processing by the shading correction unit 62.

  Since the moving distance of the CIS unit 13 varies depending on the size of the read document specified in advance, it is checked in step S105 whether or not the image reading has been completed. Proceed to step S106. Until the image reading is completed, the LED lighting of the illumination unit 131, the movement of the CIS unit 13, and the acquisition of image data are repeated.

  In step S106, the LED of the illumination unit 131 is turned off. In step S107, the CIS unit 13 is moved below the reference white plate 11, and the process is terminated in a standby state so that the next image reading can be immediately executed.

  Next, details of the color shading process will be described with reference to FIGS.

  FIG. 4 is a flowchart showing details of the color shading process in step S102 shown in FIG.

  FIG. 5 is a diagram conceptually showing the arrangement of shading data.

First, in step S201, the CIS unit 13 is moved to the lower part of the reference white plate 11, and the imaging unit 134 makes the reference white plate 11 readable and stops the movement. Next, in step S <b> 202, all the LEDs included in the illumination unit 131 are turned off so that no light enters the imaging unit 134. Further, in step S203, the reference white plate 11 is read in a state where the LEDs are completely turned off to obtain black shading data BK _SHD , which is stored in the memory 61. Also, the luminance value indicated by the black shading data BK _SHD is averaged in the main scanning direction, and this is stored in the memory 61 as the black average value BK _AVE .

As shown in FIG. 5, the black shading data BK _SHD (i) is a one-dimensional matrix, and is composed of N data corresponding to each pixel in the main scanning direction. Here, i = 1 to N (N is a natural number).

Returning to FIG. 4, the description is continued. In step S <b> 204, the green LED 1312 is turned on, and the light of the green LED 1312 enters the imaging unit 134. In step S205, the reference white plate 11 is read to obtain green shading data, the luminance value is averaged in the main scanning direction, and this is stored in the memory 61 as the green average value _GAVE .

In step S <b> 206, the blue LED 1313 is turned on so that the light of the blue LED 1313 is incident on the imaging unit 134. In step S207, blue shading data is acquired, the luminance value is averaged in the main scanning direction, and this is stored in the memory 61 as a blue average value B _AVE . Further, in step S208, the red LED 1311 is turned on so that the light of the red LED 1311 enters the imaging unit 134. Then, in step S209, red shading data is acquired, the luminance value is averaged in the main scanning direction, and this is stored as the red average value R _AVE in the memory 61.

In step S210, the luminance magnification Gain (G) with respect to the red (R) component of the green (G) component is obtained using equation (1). Formula (1) is expressed as follows. That is,
Gain (G) = (G _AVE -BK _AVE ) / (R _AVE -BK _AVE ) (1)
It is. According to Equation (1), in order to calculate the luminance magnification by excluding the black offset component, the magnification is calculated from the difference between the green average value G _AVE and the red average value R _{AVE, and the} black average value BK _AVE. ing.

Similarly, in step S211, the luminance magnification Gain (G) with respect to the red (R) component of the blue (B) component is obtained using equation (2). Equation (2) is expressed as follows. That is,
Gain (B) = (B _AVE −BK _AVE ) / (R _AVE −BK _AVE ) (2)
It is.

In step S212, the reference white plate 11 is read while moving the CIS unit 13 while the red LED 1311 is lit, and R component data for M lines is acquired in the sub-scanning direction. The acquired R component data is a two-dimensional array as shown in FIG. On the other hand, the red shading data R _SHD is a one-dimensional array.

In step S213, an average value in the sub-scanning direction is obtained from the acquired R component data for M lines, and red shading data R _SHD data is calculated. That is, the R component data for one line consisting of N in the main scanning direction is acquired, and the R component data acquired up to M lines in the sub scanning direction is added to the data at the same position in the main scanning direction. Divide by M to find the average value. The average value is stored as red shading data R _SHD in the memory 61 for each position in the main scanning direction.

In step S214, green shading data G _SHD is generated using the following three elements. The three elements are red shading data R _SHD , luminance magnification Gain (G) for the red component of the green component, and black shading data BK _SHD . Specifically, the green shading data G _SHD is calculated using Equation (3). Equation (3) is expressed as follows. That is,
G _SHD = (R _SHD −BK _SHD ) × Gain (G) + BK _SHD (3)
It is. In Equation (3), BK _SHD is subtracted from R _SHD to remove the black offset, and the product of the value and the luminance magnification Gain (G) of green (G) is calculated, and the black offset, BK _SHD is calculated. to add. Here, Gain (G) is a constant. As shown in FIG. 5, the green shading data G _SHD is a one-dimensional matrix like the red shading data R _SHD, and is composed of N data corresponding to each pixel in the main scanning direction. Therefore, G _SHD (i) (i = 1 to N) is calculated using the values of R _SHD and BK _SHD corresponding to the coordinates in the main scanning direction. After the calculation, the green shading data G _SHD is stored in the memory 61.

Similarly, in step S215, blue shading data B _SHD is generated using equation (4). Equation (4) is expressed as follows. That is,
B _SHD = (R _SHD -BK _SHD ) × Gain (B) + BK _SHD (4)
It is.

  This completes the color shading process.

  FIG. 6 is a diagram showing the relationship between the shading data of each color component and the position in the main scanning direction.

  As shown in FIG. 6, the luminance value level output from the imaging unit 134 varies depending on the position in the main scanning direction. Most of the causes of this variation are due to variations in sensor sensitivity, lens variations, and illumination light quantity variations. In this embodiment, since the light guide tube is used for the illumination unit 131, the relative light quantity variation in the main scanning direction by the used LED does not change. The same applies to sensor sensitivity and lenses. Although the absolute value of the luminance value of the shading data of each color component shown in FIG. 6 is different, the characteristics and tendency of variation are similar.

  For this reason, it is possible to obtain the respective light quantity ratios from the average value of the data generated by turning on the red LED 1311, the green LED 1312 and the blue LED 1313 and reading the reference white plate 11, and obtain the shading data of each color according to the ratio It becomes.

In this embodiment, as shown in FIGS. 4 to 5, green shading data G _SHD and blue shading data B _SHD are calculated and obtained based on red shading data R _SHD . That is, the luminance magnification with respect to the R component of the G component and the luminance magnification with respect to the R component of the B component are obtained, and the shading data for green and blue are obtained by applying these luminance magnifications to the shading data of the R component. Actually, the CIS unit is moved to perform shading only when the red shading data R _SHD is acquired.

  Therefore, according to the embodiment described above, it is possible to reduce the operation of moving the CIS unit in order to acquire shading data for each color component, and it is possible to acquire shading data for all color components in a shorter time. As a result, the time required for the CIS unit to move due to the shading operation is reduced, and this has the effect of reducing the time for generating noise and the time for starting image reading.

  In the above-described embodiment, the green shading data and the blue shading data are calculated based on the red shading data. However, the color component data used for the reference is not limited to red, and may be blue or green. Component data can also be referenced.

  In the above-described embodiment, the other shadings are calculated based on the shading data of one color using the light sources of three different colors of red, blue, and green. However, it is not necessary to limit to different colors. For example, when two green light sources are used, one shading data can be used to calculate the other shading data.

  In the above-described embodiment, the shading data is acquired by reading the reference white plate while moving the CIS unit in the sub-scanning direction. However, the present invention is not limited to this. For example, instead of moving shading, the same configuration may be used when generating a plurality of shading data from the reading result of one main scanning line.

  Furthermore, in the above-described embodiments, a single-function image reading device (scanner device) has been described as an example, but the present invention is not limited thereto. The present invention can be applied to, for example, a copier system in which an image reading apparatus (scanner apparatus), an image forming apparatus (LBP), and an ADF apparatus are integrated, or a combined system in which a facsimile function is added to the copier system. good. The image forming unit of these systems may include not only a printer engine that conforms to an electrophotographic system, but also a printer engine that employs an ink jet recording system.

1 image reading device, 3 LED drive circuit, 4 timing generation circuit, 5 CPU,
6 digital processing unit, 11 reference white plate, 12 document abutting plate,
13 CIS unit, 14 platen glass, 15 document, 16 drive belt,
17 guide rail, 18 motor, 21 amplifier (AMP), 22 A / D conversion circuit,
61 memory, 62 shading correction unit

Claims (9)

An irradiation unit that irradiates a plurality of light, a plurality of photoelectric conversion elements arranged in a predetermined first direction, and an imaging unit that receives a plurality of lights irradiated from the irradiation unit by a common photoelectric conversion element Reading means capable of optically reading a document image;
First acquisition means for acquiring first shading data based on reflected light from a reference member by at least one of the plurality of irradiated light;
Generation that generates second shading data corresponding to irradiation light that is not included in the reflected light among the plurality of irradiated light based on the first shading data acquired by the first acquisition means And an image reading apparatus. The irradiation unit has a plurality of light sources that emit light of different colors,
Irradiating a plurality of light from each of the plurality of light sources, further comprising a calculation means for calculating a ratio of the irradiation light from each of the plurality of light sources based on reflected light from the reference member;
The image reading apparatus according to claim 1, wherein the generation unit generates the second shading data based on the first shading data and the ratio. A moving unit capable of moving the reading unit in a second direction different from the first direction;
The first acquisition means irradiates light from one of the plurality of light sources, and moves the reading means by the moving means to acquire the first light based on the reflected light from the reference member. The image reading apparatus according to claim 2, wherein the shading data is acquired. A second acquisition unit that receives reflected light from the reference member in a state in which all of the plurality of light sources are turned off, and acquires data corresponding to a black offset for shading correction;
4. The image reading apparatus according to claim 2, wherein the calculation unit further calculates the ratio using data corresponding to the black offset acquired by the second acquisition unit. 5.   The said calculation means calculates the said ratio using the average value of each data acquired when the light from each of these several light sources is irradiated to the said reference member, The ratio of Claim 4 characterized by the above-mentioned. Image reading device.   The image reading apparatus according to claim 5, further comprising storage means for storing the average value.   The generation means uses the ratio calculated using the average value and the average value of the data corresponding to the black offset acquired by the second acquisition means to determine the color corresponding to the other data. The image reading apparatus according to claim 5, wherein shading data is generated.   The image reading apparatus according to claim 2, wherein the plurality of light sources are a red LED, a green LED, and a blue LED. An irradiation unit that irradiates a plurality of light, a plurality of photoelectric conversion elements arranged in a predetermined first direction, and an imaging unit that receives a plurality of lights irradiated from the irradiation unit by a common photoelectric conversion element A method for generating shading data in an image reading apparatus including a reading unit capable of optically reading a document image,
An acquisition step of acquiring first shading data based on reflected light from a reference member by at least one of the plurality of irradiated lights;
A generating step of generating second shading data corresponding to irradiation light not included in the reflected light among the plurality of irradiated light based on the first shading data acquired in the acquisition step; A method for generating shading data, comprising:

Images