JP2015095888A - Image recorder and light quantity adjustment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily read an image even from a thick document, by optimally adjusting the balance of a quantity of light while shading correction has been made.SOLUTION: A CIS unit is moved to the position of a white reference plate by moving means. Light is emitted to the white reference plate by a plurality of light sources. Light reflected by the white reference plate is received by an imaging part and thereby image data are generated. Shading correction is made to the image data thus formed. Then, while the CIS unit is moved by the moving means to the position of a member provided next to the white reference plate and having recesses and projections opposite a plurality of light sources, light is emitted to the member by the light sources. Light reflected by the member is received by the imaging part and image data are generated. Then, on the basis of the image data, lighting duty for each of the light sources is adjusted.

Description

  The present invention relates to an image reading apparatus and a light amount adjusting method, and more particularly to an image reading apparatus and a light amount adjusting method for optically reading an image of a document placed on a platen glass using a CIS unit.

  Some conventional image reading apparatuses that optically read an image of an original use an LED array in which a plurality of LEDs are arranged in an array as a light source of a reading sensor. In such an apparatus, if the LED array is only arranged at a certain angle from one side with respect to the reading line, a shadow is formed on the document by a convex portion, and the shadow is read by the reading sensor. As a result, the quality of the output image is deteriorated. Therefore, a contact image sensor (CIS) in which LEDs are arranged symmetrically is used for reading a document with unevenness compared to the conventional technique (for example, Patent Document 1). .

JP-A-8-279885

  However, in the above conventional example, when adjusting the light intensity balance of each LED, it is common to adjust the light intensity based on the brightness level of the white reference plate, so the shadow level when reading a three-dimensional original is optimal. The adjustment was not made. For this reason, if the light intensity balance is not optimal, when reading a thick original, there may be a difference in brightness between the leading and trailing edges, or the unevenness on the surface of the paper will be reflected in the read image, which may be noticeable. is there.

  In addition, with the conventional light amount adjustment based on the brightness level of the white reference plate, the light amount adjustment cannot be reflected in the shading correction, and the light amount adjustment under conditions significantly different from normal image reading in a state where the shading correction is performed. There was a problem that could only be done.

  The present invention has been made in view of the above-described conventional example, and performs an optimal light amount balance adjustment in a state where shading correction is performed, and an image reading apparatus and a light amount adjustment capable of performing good image reading even with a thick original. It aims to provide a method.

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

  That is, an original table glass on which an original is placed, and a plurality of light sources on the side opposite to the side on which the original is placed and provided with a predetermined angle with respect to the original table glass and irradiating light A reading unit including an imaging unit that receives light and performs photoelectric conversion to generate image data; a moving unit that moves the reading unit in a predetermined direction; and an end of the original platen glass. A white reference plate, a member provided on the side of the white reference plate along the predetermined direction, and having an unevenness facing the plurality of light sources, and the reading unit is moved to the white reference plate by the moving unit. Correction means for performing shading correction on image data generated by irradiating the white reference plate with light from the plurality of light sources and receiving light reflected by the white reference plate by the imaging unit And the transfer Based on image data generated by irradiating light to the member by the plurality of light sources and receiving light reflected by the member by the imaging unit while moving the reading unit to the position of the member by means of And adjusting means for adjusting the lighting duty of each of the plurality of light sources, and storage means for storing the lighting duty of each of the plurality of light sources adjusted by the adjusting means.

  In another aspect of the present invention, the document table glass on which the document is placed and the side opposite to the side on which the document is placed are provided at a predetermined angle with respect to the document table glass. A reading unit including a plurality of light sources for irradiating light, an image pickup unit that receives the light and photoelectrically converts the light to generate image data, a moving unit that moves the reading unit in a predetermined direction, and the document A light amount adjustment method in an image reading apparatus provided with a white reference plate provided at an end of a table glass, wherein the reading unit is moved to the position of the white reference plate by the moving unit, and the plurality of light sources A correction step of performing shading correction on image data generated by irradiating light to the white reference plate and receiving light reflected by the white reference plate by the imaging unit, and the reading unit by the moving unit, Previous Irradiating the member with light by the plurality of light sources while moving to the position of the uneven member facing the plurality of light sources, provided next to the white reference plate along a predetermined direction, An adjustment step of adjusting the lighting duty of each of the plurality of light sources based on image data generated by receiving the light reflected by the member by the imaging unit.

  Therefore, according to the present invention, for example, even a thick original with conspicuous surface irregularities can be read satisfactorily.

1 is a side sectional view showing a configuration of an image reading apparatus that is a typical embodiment of the present invention. FIG. 2 is a side sectional view illustrating a configuration of a shadow reading unit of the image reading apparatus illustrated in FIG. 1. It is a block diagram which shows the structure of the control circuit of an image reading apparatus. It is a flowchart which shows the light quantity adjustment process of LED. It is a figure which shows the change of the luminance value regarding the subscanning direction obtained by reading the light quantity adjustment member. It is the figure which showed the change of the average brightness | luminance of the area | region A and the area | region B when the value of D1 increases. It is a flowchart which shows the process of the light quantity adjustment before image reading. It is the figure which showed the relationship between the lighting duty (D1) of the illumination part and the maximum luminance value (Imax) in the light quantity adjustment before image reading.

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

<Outline of Image Reading Apparatus (FIGS. 1 to 4)>
FIG. 1 is a side sectional view showing a configuration of an image reading apparatus (scanner apparatus) 1 which is a typical embodiment of the present invention.

  The image reading device 1 reads an image of a document by irradiating the document with light using a CIS unit, receiving reflected light from the document, and photoelectrically converting the light to generate an electrical signal.

  As shown in FIG. 1, the CIS unit 13 includes an illumination unit 131 (first illumination unit), an illumination unit 132 (second illumination unit), an optical lens 133, and an imaging unit 134, and a document placement side. Is arranged in close contact with the platen glass 14 on the opposite side. The illuminating unit 131 and the illuminating unit 132 each include a white type light guide tube provided with three red LEDs, green LEDs, and blue LEDs as light sources, and the original is viewed from a direction inclined by a predetermined angle with respect to the original table glass 14. Illuminate.

  The optical lens 133 is composed of a SELFOC lens (registered trademark) or the like. The optical lens 133 guides the light emitted from the illumination unit 131 and the illumination unit 132 and reflected from the document surface to a predetermined imaging position, and from the image document. Read the reflected light at the same magnification.

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 of a 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 mounted on the drive belt 16 and moves along the guide rail 17 in the direction of the arrow H when the driving force of the motor 18 is transmitted via the drive belt 16.
The image reading apparatus 1 moves the CIS unit 13 in the direction of the arrow H (sub-scanning direction) by the driving force of the motor 18 while moving the CIS unit 13 in the direction perpendicular to the paper (generally intersecting) (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 motor 18. Further, at the time of image reading, the white reference plate 12 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 light amount adjusting member 11 having a step due to a dent is attached to the side of the white reference plate 12 on the side facing the CIS unit 13, and the function thereof will be described later.

  In the above configuration, when an image of a document placed on the platen glass 14 is read, shading correction using the white reference plate 12 is performed in advance. At the same time, the light amount of the LED light source is adjusted to keep the exposure amount constant. The amount of LED light is adjusted by changing the duty ratio of PWM control for the lighting time for each line in the main scanning direction.

  FIG. 2 is a side sectional view showing the configuration of the shadow reading unit of the image reading apparatus 1.

  As shown in FIG. 2, a light amount adjusting member 11 having a step due to a dent is attached to the upper part of the document table glass 14, thereby partially irradiating light emitted from each of the illumination unit 131 and the illumination unit 132. It is configured to block. That is, the light amount adjusting member 11 has a shape capable of generating a shadow having unevenness and steps, and by reading this, the shadow image of the light amount adjusting member 11 is read, and image data reflecting the shadow is obtained. Can be acquired. 2A shows a case where the light emitted from the illumination unit 131 is blocked and shaded, and FIG. 2B shows the case where the light emitted from the illumination unit 132 is blocked and shaded. Shows the case.

  FIG. 3 is a block diagram showing the configuration of the control circuit of the image reading apparatus 1.

  The CIS unit 13 reads the image of the document in accordance with the lighting time performed by adjusting the light amount of the illumination unit 131 and the illumination unit 132 for each line in the main scanning direction in the LED drive circuit (driver) 3. The LED drive circuit 3 can turn on the illumination unit 131 and the illumination unit 132 with an arbitrary PWM duty.

  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 A configuration necessary for A / D conversion including the A / D conversion circuit 22 is collectively referred to as a conversion unit. The image processing unit 6 performs image processing on the digital image data converted by the A / D conversion circuit 22. The image storage unit 7 stores the image data sent from the image processing unit 6, and can transfer the image by connecting to an inkjet printer, a laser beam printer using an electrophotographic system, or an interface with an external device.

  The timing generation circuit 4 can vary the PWM duty for each line in the main scanning direction according to the setting of the CPU 5, and adjusts the light amount of the LED by sending an LED ON / OFF control signal to the LED drive circuit 3. Is possible. The CPU 5 includes a ROM 52 that stores a program executed by the CPU 5 and a RAM 51 that is used as a work area for executing the program.

  Next, processing up to light amount adjustment and image reading of the illumination unit 131 and the illumination unit 132 of the image reading apparatus 1 configured as described above will be described with reference to FIGS.

  Adjustment (light amount adjustment) for making the light amounts of the illumination unit 131 and the illumination unit 132 uniform is performed, for example, at the time of factory shipment of the image reading device 1 or during maintenance after the image reading device 1 is installed. Alternatively, the user may be able to adjust the light quantity uniformity at an arbitrary time.

  FIG. 4 is a flowchart showing LED light amount adjustment processing.

  When the light amount adjustment of the illumination unit 131 and the illumination unit 132 is started, in step S101, the value of the lighting duty (D1) of the illumination unit 131 is set to 0%, and the lighting duty (D2) of the illumination unit 132 is set to 50%. To turn on the LED of each illumination unit. In this state, in step S102, the CIS unit 13 is moved by driving the motor 18 to a position where the imaging unit 134 can read the white reference plate 12, and the white reference plate 12 is irradiated with light from the illumination unit 131 and the illumination unit 132.

  Next, in step S103, luminance data acquired by reading the white reference plate 12 is stored in the image storage unit 7, and shading correction is performed based on the luminance data. Further, in step S104, after the shading correction is performed, the lighting unit 131 and the lighting unit 132 are turned on without changing their lighting duty (D1, D2), and the light amount adjusting member 11 is read while moving in the direction B shown in FIG. Do.

  5 to 6 are diagrams showing changes in luminance values in the sub-scanning direction obtained by reading the light amount adjusting member.

  5 to 6, the vertical axis represents the average luminance obtained by averaging the luminance data for one line in the main scanning direction, and the horizontal axis represents the position in the sub-scanning direction indicating the position of the CIS unit 13. 5 to 6, the position (first position) in the sub-scanning direction of the CIS unit 13 where the irradiation light from the illumination unit 131 is blocked is a region A, and the CIS where the irradiation light from the lighting unit 132 is blocked. A sub-scanning position (second position) of the unit 13 is defined as a region B.

  FIG. 5A is obtained by reading the light amount adjusting member 11 when the lighting duty (D1) of the lighting unit 131 is set to D1 = 0% and the lighting duty (D2) of the lighting unit 132 is set to D2 = 50%. It shows the change in the average brightness. In the case of FIG. 5A, since the illumination unit 131 is not lit, luminance data is not affected in the region A where the irradiation light from the illumination unit 131 is blocked. On the other hand, since only the illumination unit 132 is lit in the region B where the irradiation light from the illumination unit 132 is blocked, the luminance data is much lower than in other regions.

Returning to FIG. 4 and continuing the description, in step S105, the average of the luminance data of the areas A and B is calculated. In step S106, the two are compared to determine whether the average luminance level (MB _A ) in region _A is higher than the average luminance level (MB _B ) in region B. Here, if it is determined that MB _A ≦ MB _B (when the average luminance level of region B is high), the process proceeds to step S108. In step S108, the lighting duty (D1) of the lighting unit 131 at that time is stored as D1m, the lighting duty (D2) of the lighting unit 132 at that time is stored as D2m, and the process ends.

On the other hand, when it is determined that MB _A > MB _B (when the average luminance level is lower in region B than in region A), the process proceeds to step S107. In step S107, the lighting duty (D1) of the illumination unit 131 is set to be larger by 10%, and then the process returns to step S102. Each time this process is repeated, the lighting duty (D1) of the illumination unit 131 increases the amount of light by 10%, and the process is repeated until the average luminance level of the region B exceeds that of the region A.

  5B shows a case where D1 = 10% and D2 = 50%, FIG. 5C shows a case where D1 = 20% and D2 = 50%, and FIG. 5D shows D1 = 30%. , D2 = 50%, respectively. As described above, increasing the duty of D1 increases the influence on the region A where the illumination unit 131 is blocked. On the other hand, the influence of the region B where the illumination unit 132 is blocked is weakened, and the average luminance of the region B increases and the average luminance of the region A decreases as the value of D1 increases.

  FIG. 6 is a diagram showing a change in average luminance in the region A and the region B when the value of D1 increases. According to FIG. 6, when D1 = 20% and D2 = 50%, the area B has a higher average luminance than the area A. Accordingly, it can be determined that the average luminance of the region A and the region B at this timing is the closest. Therefore, it is determined that the lighting duty at this time, that is, the values of D1 = 20% and D2 = 50% is the optimal light amount balance, and this is stored in the nonvolatile memory (for example, EEPROM) of the CPU 5.

  Next, light amount adjustment before image reading will be described.

  FIG. 7 is a flowchart showing a light amount adjustment process before image reading.

  In step S201, the CIS unit 13 is moved by driving the motor 18 to a position where the imaging unit 134 can read the white reference plate 12 as in the above-described shading operation (step S103). In this state, the light amount is adjusted based on the lighting duty (D1m) of the lighting unit 131 and the lighting duty (D2m) of the lighting unit 132 stored in step S108.

  In step S202, the values of D1m and D2m are compared. In step S203, it is checked whether D1m> D2m. Then, by comparing D1m and D2m, the larger lighting duty is adjusted to be the maximum light amount, and the smaller one is controlled so as to maintain the optimum ratio of D1m and D2m for the shadow calculated by the above light amount adjustment processing. To do.

  That is, when D1m> D2m, the process proceeds to step S203, the lighting duty (D1) of the lighting unit 131 is set to 100%, and the lighting duty (D2) of the lighting unit 132 is set to a ratio of D1m and D2m to D1. Calculate so that D2 holds. On the other hand, when D1m ≦ D2m, the process proceeds to step S205, the lighting duty (D2) of the lighting unit 132 is set to 100%, and the lighting duty (D1) of the lighting unit 131 is a ratio between D1m and D2m. Is calculated so that D1 and D2 hold.

  In step S206, the respective lights are turned on with the lighting duty (D1) of the lighting unit 131 and the lighting duty (D2) of the lighting unit 132 adjusted in step S204 or step S205.

  Next, in step S207, the white reference plate 12 is read in this state, and the maximum luminance value (Imax) is acquired. Furthermore, in step S208, in order to prevent saturation of the luminance value of the image data due to the light amount being too high, a threshold (Iref) relating to the maximum luminance value obtained by the white reference plate 12 determined in advance is compared with Imax. In step S209, it is checked whether Iref> Imax.

  Here, if Imax ≧ Iref, the process proceeds to step S211, and the lighting duty (D1) of the lighting unit 131 and the lighting duty (D2) of the lighting unit 132 are optimally adjusted to the shadow by the light amount adjustment processing. Reduction processing is performed while maintaining the ratio of D2m. That is, 10% of the values of the lighting duty (D1) of the lighting unit 131 and the lighting duty (D2) of the lighting unit 132 adjusted in steps S204 to S205 are respectively subtracted. Thereafter, the process returns to step S206, and light amount adjustment before reading the document is repeatedly performed until Iref> Imax. On the other hand, if Iref> Imax, the process proceeds to step S210, shading correction is performed, and then image reading is started in step S212.

  FIG. 8 is a diagram showing the relationship between the lighting duty (D1) of the illumination unit 131 and the maximum luminance value (Imax) in the light amount adjustment before image reading.

  In this way, since the optimal light amount related to the shadow can be calculated as the duty, it is possible to adjust the light amount balance separately from the light amount adjustment for securing the necessary light amount for noise. As a result, it is possible to shorten the time for the light amount adjustment processing for the shadow.

  Therefore, according to the embodiment described above, after the white reference plate is read and shading correction is performed, the light amount adjustment member reflecting the influence of the thick original is read to adjust the light amount. In this way, the light amount can be adjusted under the same conditions as when reading a document. As a result, it is possible to accurately perform the optimum light amount adjustment considering the shadow of the document. Accordingly, for example, a thick document can be prevented from having a luminance difference between the leading end and the trailing end thereof, and the influence of shading due to paper unevenness on the document reading can be reduced, and high-quality image reading can be realized.

  Furthermore, in order to prevent saturation of the luminance value of the image data due to the light amount being too high while maintaining an optimal light amount balance among a plurality of light sources, the maximum luminance value can be adjusted and then image reading can be performed. it can. Thereby, it is possible to realize image reading with an optimum light amount.

  Further, in the above-described embodiments, the image reading apparatus is described as an independent scanner apparatus as a single function apparatus, but the present invention is not limited thereto. For example, a copying machine in which the above-described image reading apparatus is incorporated as an image reading unit may be used, or a multifunction machine in which a facsimile function is added to the copying machine. Furthermore, the image forming unit of the copying machine may be an apparatus including a printer engine that employs an ink jet recording system as well as a printer engine that conforms to an electrophotographic system.

Claims (11)

A platen glass on which a document is placed;
A plurality of light sources that are provided on a side opposite to the side on which the original is placed and are provided at a predetermined angle with respect to the original platen glass and irradiate light, and photoelectrically convert the image data by receiving the light. Reading means including an imaging unit to generate;
Moving means for moving the reading means in a predetermined direction;
A white reference plate provided at an end of the platen glass;
A member provided on the side of the white reference plate along the predetermined direction, and having a concavo-convex facing the plurality of light sources;
The reading unit is moved to the position of the white reference plate by the moving unit, the white reference plate is irradiated with light by the plurality of light sources, and the light reflected by the white reference plate is received by the imaging unit. Correction means for performing shading correction on the generated image data;
Image data generated by irradiating light to the member by the plurality of light sources and receiving light reflected by the member by the imaging unit while moving the reading unit to the position of the member by the moving unit. Adjusting means for adjusting the lighting duty of each of the plurality of light sources based on
An image reading apparatus comprising storage means for storing lighting duty of each of the plurality of light sources adjusted by the adjusting means. The plurality of light sources each include a first illumination unit and a second illumination unit each made of an LED,
The adjusting means includes
With respect to the predetermined direction, image data generated at a first position where the irradiation light from the first illumination unit is blocked by the unevenness of the member, and the second illumination unit by the unevenness of the member. Comparing means for comparing with image data generated at a second position where the irradiation light of
The lighting duty of the first lighting unit and the second lighting unit is changed by changing the lighting duty of either the first lighting unit or the second lighting unit based on the result of comparison by the comparison unit. The image reading apparatus according to claim 1, wherein the image reading apparatus is adjusted. The correction means includes
Set the lighting duty of the LED for the first illumination unit and the second illumination unit,
Using the set lighting duty, turn on the LEDs of the first illumination unit and the second illumination unit, perform shading correction,
The adjusting means includes
3. The image according to claim 2, wherein the adjustment of the lighting duty of the LEDs of the first illumination unit and the second illumination unit is started using the lighting duty used when the shading correction is performed. Reader. The image data is a luminance value,
The adjusting means includes the first illumination unit and the second illumination when the level of the luminance value generated at the first position and the level of the luminance value generated at the second position are balanced. The image reading apparatus according to claim 2, wherein the lighting duty of each unit is an adjusted lighting duty.   The correction means turns on the LEDs of the first illumination unit and the second illumination unit using the adjusted lighting duty, and generates image data based on the light reflected by the white reference plate 5. The shading correction is performed after the adjusted lighting duty is adjusted so that the maximum brightness value is obtained from the image and the obtained maximum brightness value falls below a predetermined threshold value. Image reading apparatus.   The adjustment of the adjusted lighting duty is performed by maintaining the ratio between the lighting duty of the first lighting unit adjusted by the adjusting unit and the lighting duty of the second lighting unit. The image reading apparatus according to claim 5, wherein adjustment is performed so that a lighting duty and a lighting duty of the second illumination unit are reduced.   The image reading apparatus according to claim 2, wherein the LEDs of the first illumination unit and the second illumination unit each include a red LED, a green LED, and a blue LED. The moving means is
A motor for applying a driving force to move the reading means;
A guide rail for moving the reading means in the predetermined direction;
The image reading apparatus according to claim 7, further comprising a belt that transmits a driving force of the motor.   The image reading apparatus according to claim 1, wherein the imaging unit of the reading unit includes a CMOS sensor. A platen glass on which a document is placed; a plurality of light sources on the side opposite to the side on which the document is placed and provided at a predetermined angle with respect to the document table glass; A reading unit including an imaging unit that receives and photoelectrically converts and generates image data, a moving unit that moves the reading unit in a predetermined direction, and a white reference provided at an end of the platen glass A light amount adjustment method in an image reading apparatus comprising a plate,
The reading unit is moved to the position of the white reference plate by the moving unit, the white reference plate is irradiated with light by the plurality of light sources, and the light reflected by the white reference plate is received by the imaging unit. A correction step for performing shading correction on the generated image data;
While moving the reading means by the moving means to the position of a member having an unevenness facing the plurality of light sources, provided on the side of the white reference plate along the predetermined direction, Adjusting the lighting duty of each of the plurality of light sources based on image data generated by irradiating the member with light by the light source and receiving the light reflected by the member by the imaging unit. A method for adjusting the amount of light.   The light quantity adjusting method according to claim 10, further comprising a storing step of storing, in a memory, a lighting duty of each of the plurality of light sources adjusted in the adjusting step.

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