JP3674799B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus such as a digital color copying machine.
[0002]
[Prior art]
For example, in a digital color copying machine, an original image is scanned by an image sensor in a color original reading apparatus, and RGB (red, green, blue) primary color signals are output. This RGB signal is converted into a digital RGB signal and then subjected to processing such as shading correction and masking. It is converted into a YMC (yellow, magenta, cyan) color material signal, and further, a K (black) color material signal is generated from this YMC signal, and finally a YMCK signal is obtained. The YMCK signal is supplied to a color image output apparatus, and a yellow, magenta, cyan, and black toner image is transferred onto a recording material such as paper to form a color image.
[0003]
In such a digital color copying machine, in order to faithfully reproduce the original image, a color image output device forms a reference gradation pattern on the recording material before outputting the actual original. The gradation pattern is read by a color original reading apparatus, and the image forming conditions in the color image output apparatus are adjusted based on the read gradation pattern.
[0004]
However, even in an image forming apparatus that adjusts image forming conditions using such a gradation pattern, when the image forming apparatus is used for a long period of time, it is corrected by a change over time such as deterioration of the image carrier. The characteristic is different from the initial state, and there is a problem that the image quality is deteriorated.
[0005]
In order to solve such a problem, Japanese Patent Application Laid-Open No. 7-264411 discloses that correction characteristics are calibrated at an arbitrary time. This calibration is started, for example, by pressing a mode setting button called automatic gradation correction provided on the operation unit.
[0006]
When this mode setting button is pressed, a patch pattern is output on the paper in each color, and a first test print is generated. The image forming conditions at this time are initial conditions. The first test print is read by the image reading unit, and the density value of each pattern is detected. Based on the density value, an optimum contrast potential (difference between the developing bias potential and the surface potential of the photosensitive drum) is obtained, and an optimum grid potential and developing bias potential are obtained from the contrast potential. Next, a gradation pattern is output on the paper in each color to generate a second test print. This second test print is also read by the image reading unit, and the density value of each gradation of each pattern is detected. Then, a γ conversion table is created so that the detected density matches the target density. In this way, the image forming conditions are set, and automatic gradation correction is appropriately performed.
[0007]
[Problems to be solved by the invention]
However, in the image forming apparatus described in the above publication, the adjusted image forming conditions cannot be canceled when the user who performed the adjustment fails to obtain a satisfactory result for the adjustment. For this reason, there is a problem in that the user must perform the subsequent image forming operation under the adjusted unintentional image forming conditions, or repeat the adjustment until a satisfactory result is obtained.
[0008]
Therefore, an object of the present invention is to make it possible to easily return the image forming conditions to the original state when satisfactory results are not obtained by the adjustment.
[0009]
[Means for Solving the Problems]
The image forming apparatus of the present invention includes a pattern forming unit that forms a gradation pattern on a recording material, a gradation pattern reading unit that reads a gradation pattern formed by the pattern forming unit, and the gradation pattern reading unit. In an image forming apparatus comprising correction means for automatically correcting gradation characteristics based on a read gradation pattern, a setting condition for setting whether to apply the automatically corrected gradation characteristics during image formation is set. If it is set to apply the automatically corrected gradation characteristic with reference to the condition setting means and the setting condition at the time of image formation, the gradation is set based on the automatically corrected gradation characteristic at the time of image formation. Tone correction that performs tone correction and performs tone correction based on the tone characteristics in the initial state at the time of image formation when it is set not to apply the automatically corrected tone characteristics A stage provided, the condition setting means, in the case of setting the setting condition of applying the automatic corrected gradation characteristics at the time of image formation, characterized in that it is a specifiable its scope. As the application range, only a copy operation and either a copy operation or a printer operation can be selected.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a schematic sectional view of a digital color copying machine to which an image forming apparatus of the present invention is applied.
[0011]
FIG. 1 is a schematic configuration diagram of a digital color copying machine to which an image forming apparatus of the present invention is applied. FIG. 2 is a block diagram showing an image processing unit of the copying machine shown in FIG.
[0012]
In FIG. 1, 1 is an original, 2 is an original platen glass on which the original 1 is placed, 3 is an original illumination device, 4 is an imaging lens, and 5 is a reduced CCD color image sensor.
[0013]
First, the copying process will be described. When a copy start key (not shown) is pressed, the illumination device 3 irradiates the document 1, and the reflected light from the document is imaged on the CCD color image sensor 5 by a reduction optical system composed of a mirror and an imaging lens. The CCD color image sensor 5 has three one-dimensional CCDs corresponding to red, green and blue colors. In the CCD color image sensor 5, the reflected light from the original is photoelectrically converted and output as red (R), green (G), and blue (B) dot-sequential analog signals. As shown in FIG. 2, the analog signal from the CCD color image sensor 21 is converted into a digital signal by the A / D converter 22 and further subjected to shading correction by the shading correction unit 23. For the signal after shading correction, as basic image processing, color conversion processing by the equivalent neutral brightness conversion unit 24, the first color conversion unit 25, and the second color conversion unit 30, a black plate generation processing unit 31 is subjected to black plate generation, MTF processing by the digital filter 32, output tone correction by the recording system gamma correction unit 33, and further subjected to processing for reproducing halftones by the halftone processing unit 34, and then yellow ( Y), magenta (M), cyan (C), and black (K) signals are generated and supplied to the printer unit 35. The printer unit 35 includes an electrophotographic image forming apparatus centering on the laser scanning optical system 8 and the photosensitive drum 7 shown in FIG.
[0014]
The digital signal of the image obtained in this way is passed through a screen generator built in the intermediate processing section 34 on the negatively charged photosensitive drum 7 shown in FIG. As a result, an electrostatic latent image is formed on the photosensitive drum 7.
[0015]
The electrostatic latent image obtained in this way is developed by a rotary developing machine 9 that sequentially develops four colors. The developed image is fed from the paper tray 17 and transferred onto the copy paper wound on the transfer drum 10, and the residual toner on the photosensitive drum is scraped off by the cleaner 11.
[0016]
This process from charging to transfer is repeated four times in the order of black, yellow, magenta, and cyan, and then output as a color copy through the fixing device 12.
[0017]
Next, details of the operation of the image processing unit shown in FIG. 2 will be described.
[0018]
The image signals separated into blue, green and red from the reduced CCD color image sensor 21 are digitized by the A / D converter 22 and the white level is corrected by the shading correction unit 23. Next, the image reflectances of blue, green and red are converted from the reflectance data ref (B, G, R) to the brightness data enL (B, G, R) by the equivalent neutral brightness converter 24, The data is input to the first color conversion unit 25.
[0019]
In the first color conversion section 25, the output of the first color conversion unit 25 which masking processing is performed to convert the BGR signal to a standard color signal ^{L * a * b * L *} , a *, b * is This is supplied to the second color conversion unit 30.
[0020]
Thereafter, the conversion from the standard color signal L ^* a ^* b ^* to the color material density signal YMC by the second color conversion unit 30, the black plate generation by the black plate generation processing unit 31, and the MTF (modulation transfer function) processing by the digital filter 32 After the output tone is corrected by the recording system gamma correction unit 33 and further subjected to processing for reproducing the halftone by the halftone processing unit 34, yellow (Y), magenta (M), cyan (C) , A black (K) signal is generated and supplied to the printer unit 35. The printer unit 35 prints an image corresponding to the original image on a sheet.
[0021]
FIG. 3 is a block diagram of a basic electric circuit of the digital color copying machine described above.
[0022]
An operation panel 42 for inputting various instructions to the copier and displaying the operation state of the copier, etc., the CPU 43 for controlling the operation of the entire copier, and the CPU 43 are operated. A RAM 44 used as a work area and the like, a ROM 45 in which a control program and the like are written, are connected. An image reading device 47 that reads an image of a document and converts it into image data between the CPU bus 41 and the image data bus 46, an image processing device 48 that performs various image processing on the image data, and a post-image processing device. An image output device 49 for outputting an image on a sheet based on the image data is connected.
[0023]
The CPU 43 executes the control program written in the ROM 45 while using the RAM 44 as a work area. When an instruction to start copying is given from the operation panel 42, the image reading device 47 reads the image of the document and generates image data. Then, after predetermined image processing is performed on the image data in the image processing device 48, the image output device 49 outputs an image corresponding to the image of the document on the paper.
[0024]
Next, the automatic gradation correction operation in the digital color copying machine will be described with reference to the flowchart of FIG. Note that the program corresponding to the flowchart of FIG. 4 is executed by the CPU 48a, RAM 48b, ROM 48c, and the like built in the image processing apparatus 48.
[0025]
First, the operation of the digital color copying machine is changed to the tool mode. The change to the tool mode is performed by pressing the operation buttons provided on the operation panel 42 in an order not normally operated, or by turning on the power while pressing a specific operation button (step 101). If it is not the tool mode, that is, if it is the normal mode, a normal copy operation is performed (step 102).
[0026]
When the tool mode is entered, a main menu of the tool mode as shown in FIG. 5 is displayed on the display device 42 (step 103). In the main menu, a plurality of buttons for selecting various tool functions including an “automatic gradation correction” button and an “end button” are displayed. When a button other than “automatic gradation correction” is selected, processing corresponding to each button is executed (steps 104 and 105).
[0027]
When the “automatic gradation correction” button is selected from the main menu, an automatic gradation correction menu screen as shown in FIG. 6 is displayed (step 106). When the “original output” button is selected from the automatic gradation correction menu screen (step 107), a screen indicating that a correction original is being output as shown in FIG. 7 is displayed (step 109). At the same time, a signal for instructing the output of the correction document is supplied to the image output device 47. The image output device 47 prints a predetermined gradation pattern on the paper and generates a correction document (step 108). .
[0028]
FIG. 8 is an explanatory diagram showing an example of a correction document. A plurality of color patches each having a predetermined color and density are arranged in a grid pattern on the paper. Y, M, C, and K in the figure indicate yellow, magenta, cyan, and black, and the numerical value indicates the patch density with the maximum density being 100%. YMC represents process black formed by mixing yellow, magenta, and cyan. The color patches formed at the four corners are magenta and black color patches for position confirmation, and the other color patches are gradation color patches.
[0029]
When the output of the correction document is completed normally (step 110), after the operation of the copying machine is stopped, a correction execution instruction input screen as shown in FIG. 9 is displayed (step 111). In the case of abnormal termination, a screen for notifying abnormality is displayed (step 112), and after the abnormality factor is canceled, the screen returns to the automatic gradation correction menu screen.
[0030]
Next, when the correction document is placed on the platen of the image reading apparatus and the “execution start” button is selected on the correction execution instruction input screen shown in FIG. 9 (step 113), as shown in FIG. A screen indicating that correction is being performed is displayed (step 115), and an automatic gradation correction operation is performed (step 114). If the “cancel” button is selected on the screen of FIG. 9 (step 113), the screen returns to the automatic gradation correction menu screen shown in FIG. While the tone correction operation is in progress, a bar indicating the progress of tone correction as shown in FIG. 11 is displayed (step 115).
[0031]
FIG. 12 is a flowchart showing the automatic gradation correction operation. First, the correction document placed on the platen glass 2 is read by the image reading device 47, and the positions of the M patches and K patches for position confirmation formed at the four corners of the correction document are measured (step 201). Then, the CPU 48a built in the image processing apparatus determines the quality of the position of the correction document (step 202). When the position of the correction document is appropriate (step 203), the gradation color patch of the correction document is measured (step 204), and the measurement result is transferred from the image processing device 48 to the system and stored in the nonvolatile memory. (Step 205). As the nonvolatile memory, a part of the RAM 44 backed up by a battery or a dedicated nonvolatile memory can be used. Next, the measurement result and the target value in the nonvolatile memory of the system are transferred to the image processing device 48 (step 206), and the automatic gradation correction lookup table is calculated in the image processing device 48 (step 207). The obtained automatic gradation correction lookup table is developed in the RAM 48b of the image processing device 48 (step 208). This automatic gradation correction lookup table determines gradation characteristics in the recording system gamma correction unit 33 shown in FIG. The RAM 48b also stores a through lookup table when automatic gradation correction is not performed. If it is determined in step 202 that the position of the correction document is inappropriate, the operation is stopped after the fact is displayed on the operation panel 42 (step 207).
[0032]
When the gradation correction operation ends normally (step 116), after the operation of the copying machine is stopped, a “confirm” button as shown in FIG. 13 is displayed (step 117). By this gradation correction operation, an image forming condition that is considered appropriate is set based on the correction document, and data on the image forming condition is stored in, for example, a RAM built in the microprocessor 45. In the case of abnormal termination, a screen for notifying abnormality as shown in FIG. 14 is displayed (step 118). Here, when the “execution start” button is selected (step 119), the screen returns to the screen of FIG. 10 and gradation correction is executed again. When the “cancel” button is selected on the screen of FIG. 14 (step 119), the screen returns to the automatic gradation correction menu screen shown in FIG.
[0033]
When the “Confirm” button shown in FIG. 13 is selected after the gradation correction operation has been completed normally (step 120), the automatic adjustment correction screen is exited and the screen returns to the main menu shown in FIG.
[0034]
Next, an operation for performing test printing based on the image forming conditions set as described above will be described.
[0035]
When the “print output” button is selected on the automatic adjustment correction screen shown in FIG. 6 (step 107), a screen indicating that the gradation confirmation print as shown in FIG. 15 is being output is displayed (step 122). ) And a gradation confirmation print is output based on the set image forming conditions (step 121). When the printing operation is normally completed, the operation of the copying machine is stopped and then the screen returns to the automatic gradation correction menu screen shown in FIG. In the case of abnormal termination, a screen for notifying abnormality is displayed, and after canceling the abnormality factor, the screen returns to the automatic gradation correction menu screen shown in FIG.
[0036]
Next, an operation for designating the application range of automatic gradation correction, which is a feature of the present invention, will be described.
[0037]
When the “application range designation” button is selected on the automatic gradation correction menu screen shown in FIG. 6 (step 107), an application range designation screen as shown in FIG. 16 is displayed (step 123). On the application range specification screen, a “Copy / Printer” button and “Copy only” button to apply the gradation correction results, a “Copy / printer” button to which the gradation correction results are not applied, and an “End” button are displayed. Is done.
[0038]
When the “copy / printer” button to apply the gradation correction result is selected (step 124), a flag indicating that the gradation correction result is applied to both the copy and the printer is turned on (step 124). 125) When the “copy only” button to apply the result of gradation correction is selected, a flag indicating that the result of gradation correction is applied only to the copy is turned on (step 126). When a “copy printer” button that does not apply the result of gradation correction is selected, a flag indicating that the result of gradation correction is applied to the copy and the printer is turned off (step 127). When the “end button” is selected on the application range designation screen shown in FIG. 16 (step 127), the screen returns to the automatic gradation correction menu screen shown in FIG. The state of the gradation correction application flag indicating whether or not to apply these gradation correction results at the time of image formation is stored, for example, in the built-in memory of the microprocessor 45 shown in FIG.
Next, processing when the copy operation is performed after returning to the normal operation mode will be described with reference to the flowchart of FIG.
[0039]
When the copy start button of the copying machine is pressed (step 201), it is determined whether or not the previously performed image quality adjustment is effective (step 202). That is, the state of the gradation correction application flag stored in the microprocessor 45 is referred to. Then, when the flag is on, image quality adjustment is performed based on the result of the previous correction (step 202), and when the flag is off, image quality adjustment is not performed. That is, when the image quality adjustment is valid, the automatic gradation correction lookup table in the RAM 48b of the image processing device 48 is used, the automatic gradation correction is performed in the recording system gamma correction unit 33, and the image quality adjustment is performed. If valid, the through look-up table of RAM 48b is used and no automatic tone correction is performed.
[0040]
【The invention's effect】
As described above, even when the user does not obtain a satisfactory result with respect to the adjustment of the image forming conditions, an image in the initial state where the adjustment is not performed can be obtained at a minimum. As a result, even when the image quality after adjustment becomes worse than the image quality before adjustment, it can be easily restored to the original state, and significant deterioration of the image quality can be prevented.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a digital color copying machine to which an image forming apparatus of the present invention is applied.
FIG. 2 is a block diagram showing an image processing unit of the copying machine shown in FIG.
FIG. 3 is a block diagram of an electric circuit for performing automatic gradation correction in the digital color copying machine described above.
FIG. 4 is a flowchart for explaining an automatic gradation correction operation in a digital color copying machine.
FIG. 5 is an explanatory diagram showing a main menu screen in a tool mode.
FIG. 6 is an explanatory diagram showing an automatic gradation correction menu screen.
FIG. 7 is an explanatory diagram showing a screen indicating that a correction document is being output.
FIG. 8 is an explanatory diagram illustrating an example of a correction document.
FIG. 9 is an explanatory diagram showing a correction execution instruction input screen.
FIG. 10 is an explanatory diagram showing a screen indicating that correction is being performed.
FIG. 11 is an explanatory diagram showing a screen on which a bar indicating the progress of gradation correction is displayed.
FIG. 12 is a flowchart showing an automatic gradation correction operation.
FIG. 13 is an explanatory diagram showing a screen when the gradation correction operation is normally completed.
FIG. 14 is an explanatory diagram showing a screen for notifying abnormality.
FIG. 15 is an explanatory diagram showing a screen indicating that a gradation confirmation print is being output.
FIG. 16 is an explanatory diagram showing an application range designation screen.
FIG. 17 is a flowchart for explaining processing when a copy operation is performed;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Original, 2 ... Original platen glass, 3 ... Original illumination apparatus, 4 ... Imaging lens, 5 ... CCD color image sensor, 6 ... Charge corotron, 7 ... Photosensitive drum, 8 ... Laser scanning optical system, 9 ... Rotary development 10 ... transfer drum, 11 ... cleaning device, 12 ... fixing device, 13 ... paper peeling corotron, 14 ... static corotron, 15 ... transfer corotron, 16 ... charged corotron, 21 ... CCD color image sensor, 22 ... A / D Converter: 23 ... Shading correction unit 24 ... Equivalent neutral brightness conversion unit 25 ... First color conversion unit 30 ... Second color conversion unit 31 ... Black plate generation unit 32 ... Digital filter 33 ... Recording system Gamma correction unit, 34 ... halftone processing unit, 35 ... printer unit, 41 ... CPU bus, 42 ... operation panel, 43 ... CPU, 44 ... RAM, 45 ... ROM, 4 6 ... Image data bus, 47 ... Image reading device, 48 ... Image processing device, 49 ... Image output device

Claims (2)

A pattern forming unit that forms a gradation pattern on a recording material, a gradation pattern reading unit that reads a gradation pattern formed by the pattern forming unit, and a gradation pattern that is read by the gradation pattern reading unit In the image forming apparatus provided with a correction unit that automatically corrects the gradation characteristics,
Condition setting means for setting a setting condition as to whether or not to apply the automatically corrected gradation characteristics at the time of image formation;
When it is set to apply the automatically corrected gradation characteristic with reference to the setting condition at the time of image formation, gradation correction is performed based on the automatically corrected gradation characteristic at the time of image formation, When it is set not to apply the automatically corrected gradation characteristic, a gradation correction unit that performs gradation correction based on the gradation characteristic in an initial state at the time of image formation is provided ,
2. An image forming apparatus according to claim 1, wherein when the condition setting means sets a setting condition for applying the automatically corrected gradation characteristic at the time of image formation, the application range can be specified . The image forming apparatus according to claim 1, wherein only the copy operation can be selected as the application range, and either the copy operation or the printer operation can be selected.

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