JP2004357074A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which easily and evenly adjusts image quality (density) by preventing occurrence of density difference on front and rear in the image forming apparatus provided with line sensors on both sides. <P>SOLUTION: There is provided a density sample wherein on the front surface of the sample density printing with four stages of density is previously performed, each density value is described on lower sides of each density printing, and on the rear surface of the sample, printing whose density is continuously changed is performed and corresponding density values and scales are described on its right side. The front surface (side A) of the density sample is read by a front surface reading part 9A (ST2), the rear surface (side B) of the density sample is similarly read by a rear surface reading part 9B (ST3). Next, multilevel data on the read side A is printed (ST4) and multilevel data of the read side B is printed (ST5). A density part of the side B with density equal to that of the side A is extracted by observing both prints, difference of density values described on each is calculated and the difference is set and inputted as a correction value (ST6). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a multifunction peripheral having multiple functions such as a facsimile function and a copying function.
[0002]
[Prior art]
Generally, in image forming apparatuses such as copiers, facsimile machines, and multifunction peripherals, there are machines that can read both sides at a time. However, usually, a manuscript once read is mechanically turned over and read again to realize double-sided reading. . As another method of double-sided reading, there is a method in which separate line sensors (CCD, CIS, etc.) are provided on the front and back to perform reading.
[0003]
By the way, in the past, regarding the two-sided reading, in order to correct the density distortion on the front and back sides during the two-sided printing, the same image was printed on both sides, the printed front side image and the back side image were read, respectively, and the automatic There has been disclosed a technique for performing dynamic correction (for example, Patent Document 1).
[0004]
[Patent Document 1]
JP-A-9-27879
[Problems to be solved by the invention]
In the above two-sided reading method, in the method of providing line sensors on the front and back sides, since the sensors are different on the front and back sides, there is a problem that it is difficult to adjust the image quality so that a density difference does not occur on both sides. In addition, the technique described in Patent Document 1 relates to a method of reading the front surface first, and then turning the front and back sides to read the back surface even in both-side reading. Therefore, it is difficult to directly adopt a method of providing a line sensor on the front and back sides. There's a problem.
[0006]
SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and in an image forming apparatus in which line sensors are provided on both sides, it is possible to prevent the occurrence of a density difference between front and back sides and to easily and uniformly adjust the image quality (density). It is intended to provide.
[0007]
[Means for Solving the Problems]
An image forming apparatus according to the present invention includes a double-sided reading unit having a reading line sensor on each of the front and back sides, a storage unit that reads and stores two density samples corresponding to a change in density and a density value with the double-sided reading unit, Means for printing the two stored density samples, means for inputting a density correction instruction when the correspondence between the print density and the density value of these print images differs between the two print images, Means for correcting image processing parameters corresponding to front side reading and / or back side reading in response to the instruction input.
[0008]
Further, the image forming apparatus of the present invention includes a double-sided reading unit that reads the same density sample by reading line sensors on the front and back surfaces, a storage unit that stores a relationship between a coordinate position of the density sample and the density in advance, and the front surface line sensor. Means for correcting parameters in image processing based on read data of a density sample according to the above and read data by a back surface line sensor.
[0009]
Further, the image forming apparatus of the present invention has a double-sided reading unit having reading line sensors on both sides of a document conveying path, a unit for setting a double-sided image quality adjustment mode, and a document read by the reading line sensor. Control means for printing the read image data, and control means for individually reading the front and back sides of the original by the reading line sensors on the front and back sides in the duplex image quality adjustment mode, and printing the read images on the front and back sides. The means automatically shifts to a mode for accepting a double-sided image quality adjustment operation in accordance with printing of a read image in the double-sided image quality adjustment mode.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a block diagram showing a configuration of a facsimile apparatus according to an embodiment of the present invention.
[0011]
As shown in FIG. 1, the facsimile apparatus according to this embodiment includes an NCU 1, a MODEM 2, a ROM 3, a RAM 4, an image memory 5, an MPU 6, a display unit 7, an operation unit 8, an image reading unit 9, A CODEC 10, a printer 11, and a bus 12 are provided.
[0012]
The NCU 1 has a function of controlling connection with the telephone line 13, a function of transmitting a telephone number (= a corresponding dial signal) of a destination, and a function of detecting an incoming call. MODEM2 conforms to ITU-T Recommendation T. 30 based on a facsimile transmission control procedure according to V.30. 17, V.I. 27ter, V.I. Modulation of transmission data and demodulation of reception data in accordance with 29 or the like. The ROM 3 stores a program for controlling the entire apparatus. The RAM 4 temporarily stores various information on the facsimile machine. The image memory 5 temporarily stores received image data and image data read by the image reading unit 9.
[0013]
The MPU 6 controls each unit constituting the device according to a program stored in the ROM 3. The display unit 7 displays various information such as an operation state of the apparatus, a message such as an operation procedure, and the like. The operation unit 8 includes ten keys, one-touch keys, a start key, and other keys. The image reading section 9 reads image data on a document and outputs black and white binary image data. The image reading unit 9 has a front surface reading unit 9A and a back surface reading unit 9B for simultaneously reading the front and back of a document. Each of the double-sided reading unit 9A and the back-side reading unit 9B has a line sensor for reading an image individually.
[0014]
The CODEC 10 encodes image data to be transmitted and decodes received image data. The printer 11 is formed of an electrophotographic printer, and records received image data and image data of a document read by the image reading unit 9 on a recording sheet in a copy operation. However, the hardware configuration of the facsimile apparatus according to the embodiment shown here is not particularly novel, and each circuit configuration itself is already well known.
[0015]
As shown in FIG. 2, the image reading unit 9 includes a front surface reading unit 9A and a back surface reading unit 9B. The front surface reading unit 9A includes a CCD line sensor 21A, an analog front end 22A, a shading correction circuit 23A, a shading RAM 24A, a gamma correction circuit (RAM) 25A, and a binarization circuit 26A. The back surface reading unit 9B has the same configuration.
[0016]
The CCD line sensors 21A and 21B read an image of one scanning line of a document, and sequentially read the next scanning line image at a predetermined interval. The CCD line sensor 21A reads the front side of the document, and the CCD line sensor 21B reads the back side of the document. The analog front ends 22A and 22B amplify the outputs of the CCD line sensors 21A and 21B in an analog manner, and output multi-valued digital data. The shading RAMs 24A and 24B store the outputs of the analog front ends 22A and 22B when the original is white paper for shading correction. The shading correction circuits 23A and 23B perform shading correction based on shading correction data stored in the shading RAMs 24A and 24B and output the outputs of the analog front ends 22A and 22B when reading the original. The gamma correction circuits 25A and 25B have predetermined input / output characteristics and perform gamma correction. The gamma correction circuits 25A and 25B are generally used for image quality adjustment. The binarization circuits 26A and 26B binarize the outputs of the gamma correction circuits 25A and 25B at a predetermined threshold. The binarization circuits 26A and 26B may be included in the gamma correction circuit 25.
[0017]
In the facsimile apparatus of this embodiment, one density sample on which the printing shown in FIGS. FIG. 3 shows the side A on which a density sample is printed. Here, density printing of four levels of density is performed, and each density value 200, 150, 100, 50 is provided below each density printing. Is written. FIG. 4 shows the B side on which the density sample is printed. Here, printing is performed in which the density is continuously changed, and the density value corresponding to the right side thereof is more clearly understood than the A side. , A scale of 10 density values is shown.
[0018]
In the facsimile apparatus of this embodiment, the density difference between the front and back sides is corrected using the density sample. The adjustment processing operation will be described with reference to the flowchart shown in FIG. First, in step ST1, it is determined whether or not the mode is the adjustment mode. If the user has set the adjustment mode using the operation unit 8, the determination is YES and the process proceeds to step ST2.
[0019]
In step ST2, the image of the surface A of the density sample set in the image reading section 9 is read by the CCD line sensor 21A. Further, in step ST3, the image on the surface B of the set density sample is read by the CCD line sensor 21B. Then, each is stored in the memory. Next, the process proceeds to step ST4.
[0020]
In step ST4, the image of the surface A of the density sample that has been read and stored is printed by the printer 11. In step ST5, an image of the surface B of the density sample, which is also read and stored, is printed. Next, the process proceeds to step ST6. Here, the user visually compares the printed density sample A surface and the printed density sample B surface. If the numbers are the same, they should print at the same density. However, since the characteristics of the sensor are different, it is considered that printing is performed at a different density. Therefore, a portion which is the same as the density sample (for example, 50) on the A surface is searched for on the B surface. The number found next to the same density that is found is the reading density of the B side with respect to the reading density of the A side. Assuming that the horizontal numerical value of the same density on the B side is, for example, 42, the density difference between the two is 8. In step ST6, the density difference 8 is set in the gamma correction circuit 25B from the operation unit 8 as, for example, a correction value. By setting the correction value, the gamma correction circuit 25B is corrected so that the output becomes 42 with respect to the input of the density 50. The same correction is performed for the densities 100, 150, and 200 on the other side A. FIG. 7 shows an example of the input / output density characteristics of the density sample A surface and the density sample B surface. Therefore, if the density of 50 on the B side is reduced to 42 from the density of 42 on the A side in the gamma curve, the density is corrected to the same level.
[0021]
Next, the processing at the time of actual double-sided printing after the correction will be described with reference to the flowchart shown in FIG. In step ST11, it is determined whether or not the mode is the duplex printing mode. If the user has set the double-sided print mode using the operation unit 8, the determination is YES and the process proceeds to step ST12. In step ST12, the surface A of the document set on the image reading section 9 is read by the line sensor 21A. In step ST13, the B side of the original set in the image reading section 9 is read by the line sensor 21B. Then, the read data is stored in the memory. Next, the process proceeds to step ST14. In step ST14, the set correction data is subtracted from the B-side data. Next, the process proceeds to step ST15.
[0022]
In step ST15, the surface of the read document A is printed by the printer 11. In step ST16, the surface of the read original B is printed by the printer 11.
[0023]
In the above embodiment, the different density samples printed on the front and back are read by the front and back line sensors, respectively, and the densities of those printed on the front and back are compared to determine the correction value. A single reading sample (for example, the density sample shown in FIG. 3) having the same density sample on both sides was prepared, and the same density sample on the front and back was read by the front and back CCD line sensors 21A and 21B, respectively. The correction data may be obtained from the multi-valued data.
[0024]
In this case, as shown in FIG. 8, the density difference calculation circuit 27 receives the density sample front surface data output from the shading correction circuit 23A and the density sample back surface data output from the shading correction circuit 23B. A density difference is calculated for each point of the sample XY coordinates. The calculated difference value is input to the gamma correction circuit having the larger density, and stored as correction data. For example, if the surface reading density is higher, the correction data is stored in the gamma correction circuit 25A. In actual printing, the correction data is subtracted from the data input to the gamma correction circuit 25A, and printing is performed with the input / output characteristics of the gamma correction circuits 25A and 25B aligned. As a method of aligning the input / output characteristics, 差 of the difference value is added to the input of the lower density so that the input value becomes the intermediate value of the reading density of the front and back, and the difference value of 1 is added from the input of the higher density. Correction for subtracting / 2 may be performed.
[0025]
According to another embodiment of the present invention, the reading line sensors are arranged on both sides of the document conveyance path, and the reading line sensors for the front surface and the back surface are of different reading systems (for example, CCD and CCD). If CIS) is adopted and the double-sided image quality adjustment mode is set, the reading of the front and back sides of the document may be individually performed by the front and back reading line sensors, and the read images of the front and back sides may be printed. Furthermore, in this embodiment, control is performed so as to automatically shift to a mode in which a double-sided image quality adjustment operation is accepted in accordance with printing of a read image in the double-sided image quality adjustment mode. Here, the transition to the reception mode is performed by displaying a reception screen. In addition, the double-sided image quality adjustment may include not only the density but also the color adjustment of the color. In addition, one sample original at the time of double-sided image quality adjustment may be read front and back at the same time, that is, by one conveyance, or the same sample original may be read for the first time using the front line sensor and for the second time using the back side. May be read by the line sensor.
[0026]
【The invention's effect】
According to the present invention, the density difference between the two surfaces is determined using a density sample prepared in advance, and the correction value is set so that the density on both surfaces is equal. Can be prevented from occurring.
[0027]
According to the invention, the same density sample is read by the reading line sensors on the front and back surfaces, and the parameters in the image processing are corrected based on the reading data of the density sample by the front line sensor and the reading data by the back line sensor. The correction value can be easily set without performing the operation for correction.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a facsimile apparatus according to an embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of an image reading unit of the facsimile machine.
FIG. 3 is a diagram showing an A-side surface of a density sample prepared in advance for use in the facsimile machine.
FIG. 4 is a diagram showing a surface B of the density sample.
FIG. 5 is a flowchart illustrating an adjustment process in the facsimile apparatus of the embodiment.
FIG. 6 is a flowchart illustrating double-sided printing processing in the facsimile machine of the embodiment.
FIG. 7 is a diagram showing input / output characteristics of a double-sided line sensor of the facsimile apparatus of the embodiment.
FIG. 8 is a circuit block diagram showing a part of an image reading circuit according to another embodiment of the present invention.
[Explanation of symbols]
1 NCU
2 MODEM
3 ROM
4 RAM
5 Image memory 6 MPU
7 display unit 8 operation unit 9 image reading unit 10 CODEC
11 Printer 21A, 21B CCD line sensor 22A, 22B Analog front end 23A, 23B Shading correction circuit 24A, 24B Shading RAM
25A, 25B Gamma correction circuits 26A, 26B Binarization circuit

Claims (3)

A double-sided reading unit having a reading line sensor on each of the front and back sides, a storage means for reading and storing two density samples corresponding to a change in density and a density value by the double-sided reading unit, and the stored two density samples Means for inputting a density correction instruction when the correspondence between the print density and the density value of these print images is different between the two print images. Means for correcting image processing parameters corresponding to reading and / or backside reading. A double-sided reading unit that reads the same density sample with the reading line sensors on the front and back, storage means for storing the relationship between the coordinate position of the density sample and the density in advance, read data of the density sample by the front line sensor and the back line Means for correcting a parameter in image processing based on data read by a sensor. A double-sided reading unit having reading line sensors on both sides of the document conveying path, a unit for setting a double-sided image quality adjustment mode, a unit for printing read image data of a document read by the reading line sensor, In the image quality adjustment mode, there is provided control means for reading the front and back surfaces of the document individually by the reading line sensors for the front and back surfaces and printing the read images on the front and back surfaces. An image forming apparatus, which automatically shifts to a mode for accepting a two-sided image quality adjustment operation along with printing of an image.

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