JPH0662252A - Digital image generating device - Google Patents

Abstract

PURPOSE:To easily select a gradation characteristic desirable for a user by preparing a third gradation curve between the two kinds of gradation curves selected out of plural stored gradation curves by the user. CONSTITUTION:Sometime, the user does not satisfy the selected gradation curve although it is selected. Then, a fine selection mode is provided to select arbitrary first and second gradation curves out of the plural previously stored data for gradation correction and to calculate plural intermediate target curves between those two curves. The number of steps can be set by the user. The gradation correction data corresponding to these intermediate curves are not stored in a data ROM 203. Therefore, the gradation correction data are arithmetically calculated, and the arithmetic result is stored in a RAM 204. Further, a trial printing mode is provided to facilitate the selection of the user at the time of selecting any intermediate gradation curve, and trial printing is performed to one part of a source image with plural gradations.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to gradation control of a digital image forming apparatus such as a digital printer or a digital copying machine.

[0002]

2. Description of the Related Art In an electrophotographic process in a digital printer, a digital copying machine or the like, laser emission is modulated in accordance with the original reading density (multivalued digital value) to reproduce an image. In image reproduction, the density of the output image is preferably proportional to the original reading density (digital value). The gradation characteristic, which is the relationship between the output image density and the document reading density, is a factor that greatly affects the impression of a pictorial image. Therefore, the input document density is processed to correct the light emission characteristics so that the density of the formed image is proportional to the input document density. This is called gradation correction. In color image reproduction, it is basically required that the output image changes linearly with the density of the original, and therefore, stabilization of the image is required. The gradation characteristics slightly change due to changes in the photoconductor sensitivity, surface potential, developing bias potential, developing characteristics, etc. in the electrophotographic process. Therefore, the image reproduction is stabilized by automatic density control and gradation correction. In the digital image forming apparatus, the density of the read original is
Although it is converted into a multi-valued digital value, non-linear conversion of multi-valued data is easy by a look-up table process, etc., so various stabilization controls are possible in the digital image forming apparatus (for example, according to the applicant). JP-A-3-271
764).

[0003]

However, in reality, since the image stabilization is not perfect, the quality of the reproduced image by the stabilization control may be unsatisfactory for some professional users. Further, as a digital equalizer function, if the user can arbitrarily select the gradation characteristic, the user can realize a desired image tone. Therefore, it is considered that if the user is allowed to positively change the gradation characteristics, the user can be satisfied. In addition,
In order to allow the user to change the gradation characteristics, it is necessary to operate the gradation correction and the image stabilization system in conjunction with each other, and a process control system corresponding to each image generation process is required. By the way, in the selection by the user, even if the target gradation curve is selected, it may not feel good. In such a case, if the gradation curve can be set more finely, it becomes easier to obtain a desired image.
It is considered that if a finer intermediate gradation can be set within the selectable range, the gradation desired by the user can be easily obtained. Further, when such a large number of gradations can be realized, it is convenient if the user can easily select the gradation.

An object of the present invention is to provide a digital image forming apparatus which allows a user to easily select a desired gradation characteristic.

[0005]

A first digital image forming apparatus according to the present invention includes a storage unit for storing a plurality of gradation curves and an arbitrary first gradation curve stored in the storage unit. And a selection means for selecting the second gradation curve, a gradation curve calculation means for calculating a third gradation curve from the first second gradation curve, and a third gradation curve described above. And a light emission control means for emitting light with a light emission characteristic corresponding to. Preferably, the apparatus further comprises input means for inputting a division number for dividing the first and second gradation curves by an arbitrary number (N), and the gradation curve calculation means is The first and second gradation curves are continuously divided into N steps to calculate new N gradation correction curves. A second digital image forming apparatus according to the present invention selects storage means for storing a plurality of gradation curves and arbitrary first and second gradation curves from the plurality of gradation curves stored in the storage means. Selecting means, a gradation curve calculating means for calculating the third gradation curve from the first and second gradation curves, and a trial copy of the created gradation curve.
Print control means for repeatedly performing output processing on the same copy paper by using the gradation curve obtained by calculation for the portion.

[0006]

In the first digital image forming apparatus according to the present invention, the third gradation curve is provided in the middle of the two kinds of gradation curves selected by the user from the plurality of gradation curves stored in the storage means. Let me create. By storing the third tone curve in the storage device, the obtained tone curve can be repeatedly used. Furthermore, by inputting the number of divisions for dividing the first and second gradation curves by an arbitrary number (N), a plurality of gradation curves that change continuously between both curves can be obtained. It can be created by calculation. Further, in the second digital image forming apparatus according to the present invention, one or more third gradation curves are created from the first and second gradation curves, and the created gradation is set for one part of the original image. Using the curve, the same image with different gradation is repeatedly output on the same copy paper, and the created gradation curve is trial copied.

[0007]

Embodiments of the present invention will be described below in the following order with reference to the drawings. (A) Configuration of digital color copying machine (b) Image signal processing (c) Image stabilization (d) Gradation control (e) Gradation selection (f) Use of external storage device (g) Image quality of gradation curve switching Monitor (h) Synthesis of target gradation curve (i) Fine selection of target gradation curve (j) Trial baking mode (k) Calculation of gradation correction data (l) Printer control flow

(A) Configuration of Digital Color Copying Machine FIG. 1 is a sectional view showing the overall configuration of a digital color copying machine according to an embodiment of the present invention. The digital color copying machine is roughly divided into an image reader unit 100 that reads an original image and a printer unit 200 that reproduces the image read by the image reader unit. Image reader unit 100
The scanner 10 of FIG.
A rod lens array 13 that collects the reflected light from the original,
And a contact-type CCD that converts condensed light into an electric signal
The sensor 14 is provided. The scanner 10 is driven by the motor 11 at the time of reading an original, moves in the direction of the arrow (sub scanning direction), and scans the original placed on the platen 15. As shown in FIG. 3, the image reader unit 100
Are controlled by the image reader control unit 101. The image reader control unit 101 controls the exposure lamp 12 via the drive I / O 103 according to a position signal from the position detection switch 102 indicating the position of the document on the platen 15, and also drives I / O 103 and parallel I.
The scan motor driver 105 is controlled via the / O 104. The scan motor 11 is driven by the scan motor driver 105.

Returning to FIG. 1 and continuing the description, the image of the original surface illuminated by the exposure lamp 12 is photoelectrically converted by the CCD sensor 14. The red (R), green (G), and blue (B) multi-valued electrical signals obtained by the CCD sensor 14 are
By the read signal processing unit 20, yellow (Y), magenta
(M), cyan (C), and black (K) are converted into 8-bit gradation data and output to the printer control unit 201. As shown in FIG. 3, the image control unit 106 includes a CCD
The color image sensor 14 and the image signal processing unit 20 are connected to each other via a bus. The image signal from the CCD color image sensor 14 is input to the image signal processing unit 20 and processed. As shown in FIG. 2, in the image signal processing unit 20, the image signal photoelectrically converted by the CCD sensor 14 is converted into multi-valued digital image data of R, G, B by the A / D converter 21, To
Shading correction is performed in the shading correction circuit 22. Since the shading-corrected image data is the reflected light data of the document, the log conversion circuit 23 performs log conversion to convert it into actual image density data. Further, the undercolor removal / blackening circuit 24 removes an unnecessary black color and generates true black data K from R, G, B data. Then, the masking processing circuit 25 converts the data of the three colors of R, G and B into the data of the three colors of Y, M and C. After the density correction circuit 26 performs density correction processing for multiplying the Y, M, and C data thus converted by a predetermined coefficient, the spatial frequency correction processing is performed in the spatial frequency correction circuit 27, and then the image is displayed in the printer control unit 201. Output as a density signal.

Returning to FIG. 1, in the printer section 200, the print head section 31 performs gradation correction according to the gradation characteristics of the photoconductor on the input gradation data, and then The corrected image data is D / A converted to generate a laser diode drive signal, and the semiconductor laser 264 (FIG. 4) is caused to emit light by this drive signal. The laser beam generated from the print head unit 31 by modulating the emission intensity corresponding to the gradation data passes through the polygon mirror,
Photoreceptor drum 41 that is rotationally driven via reflecting mirror 37
To expose. The photoconductor drum 41 is irradiated with an eraser lamp 42 before being exposed for each copy, and is uniformly charged by a charging charger 43. When exposed in this state, an electrostatic latent image of the original is formed on the photosensitive drum 41. Only one of the cyan, magenta, yellow, and black toner developing devices 45a to 45d is selected to develop the electrostatic latent image on the photosensitive drum 41. On the other hand, the copy paper is fed from the paper cassette 50 and wound around the transfer drum 51. The developed toner image is transferred to copy paper by the transfer charger 46. The above printing process is repeated for four colors of yellow (Y), magenta (M), cyan (C), and black (K). At this time, the photosensitive drum 41 and the transfer drum 51
The scanner 10 repeats the scanning operation in synchronization with the above operation. After that, the copy paper is separated from the transfer drum 51 by operating the separation claw 47, is fixed through the fixing device 48, and is discharged to the paper discharge tray 49.

(B) Printer Control Unit and Image Signal Processing FIGS. 3 and 4 are block diagrams of the entire control system of the digital color copying machine. The printer unit 200 includes a printer control unit 201 that controls general print operations. A printer control unit 201 including a CPU includes a control ROM 202 storing a control program and a data ROM 20 storing various data (gradation correction data and the like).
3 and RAM 204 are connected. Printer control unit 2
Reference numeral 01 controls the printing operation according to the data in the ROM and RAM. The printer control unit 201 includes a V ₀ sensor 44, an AIDC sensor 210, and an ATDC sensor 21.
1, analog signals from the temperature sensor 212 and the humidity sensor 213, and signals from the fog input switch 214, the color balance switch 216, and the photoconductor lot switch 218 are input. Here, the V ₀ sensor 44 detects the potential on the surface of the photoconductor. In addition, the AIDC sensor 210 is
For each color, the toner amount of the reference toner image on the photoconductor developed under the standard image forming conditions (photoconductor surface potential V ₀ , development bias potential V _B , exposure amount) is detected, and V ₀ , V _B , and exposure are performed. Set amount to optimum. Further, various data is input to the printer control unit 201 via the parallel I / O 222 by a key input on the panel CPU 150 that receives a key input from the operation panel 221 described later. Similarly,
A tablet editor 232 (see FIG. 13) which will be described in detail later.
The input value of (see) is also input to the printer control unit 201 via the panel CPU 150.

The printer control unit 201 controls the copy control unit 231 according to the contents of the control ROM 202 by various input data, and further, the grid potential V _{G of the} charger 43 via the parallel I / O 241 and the drive I / O 242. High voltage unit 24 for generating V _G
3 and controls the V _B generated high-voltage unit 244 that generates a developing bias voltage V _B of the developing unit 45a to 45d. The printer control unit 201 also includes the image reader unit 100.
The image data processing unit 20 is connected to the image data processing unit 20 via an image data bus, and data in which a gradation correction table is stored, as will be described later, based on the image density signal input via the image data bus. The light emission level is determined by referring to the contents of the ROM 203, and the drive I / O 261 and parallel I
The semiconductor laser driver 263 is controlled via / O262. The semiconductor laser 264 is driven to emit light by the semiconductor laser driver 263. The gradation expression is
This is performed by modulating the emission intensity of the semiconductor laser 264.

FIG. 5 shows the appearance of the operation panel 221.
Here, the LCD display unit 301 displays the mode set by the operation, explains the operation procedure to the user, and displays the status such as the jam display and the copy operation display. The panel reset key 302 is a key for initializing all modes. A key 303 is a ten-key for setting the number of copies and a clear key for clearing. The start key 304 is a key for instructing the start of copying. Image quality menu key 305
When is pressed, a menu for image quality adjustment is displayed on the LCD display unit 301. The user can adjust the image quality by operating this. Create menu key 30
When 6 is pressed, the LCD display unit 301 displays a setting menu for various create functions. By operating this, the user can set various functions and modes. The enter key 307 is used as an enter key and a next screen key in the operation screens of the image quality menu and the create menu described above. River ski 30
Reference numeral 8 is used as a cancel key and a previous screen key.
A cursor key 309 is a key for selecting a cursor on a menu and setting a level on each operation screen. The multifunction key 310 is used for the LCD display unit 301.
This is a key whose meaning can be changed according to each selection menu displayed in. This panel has IC card insertion ports 311 and 312 so that up to two IC cards can be inserted at the same time. A program call / registration key 313 and an IC card ejection key 314 are provided corresponding to each insertion slot. The bar code reader pen 315
With, it is possible to scan a barcode and set various modes.

FIG. 6 is a block diagram of image data processing in the printer control unit 201. Here, the image data (8 bits) from the image signal processing unit 20 is input to the first-in / first-out memory (hereinafter referred to as a FIFO memory) 252 via the interface unit 251. The FIFO memory 252 is a line buffer memory capable of storing gradation data of an image for a predetermined number of rows in the main scanning direction, and absorbs a difference in operating clock frequency between the image reader unit 100 and the printer unit 200. It is provided to do. The data in the FIFO memory 252 is then input to the γ correction unit 253. Data ROM 2
The various γ correction data of 03 is sent to the γ correction unit 253 by the printer control CPU 250, and the γ correction unit 253 corrects the input data and sends the emission level to the D / A conversion unit 254. The data ROM 203 stores various gradation correction data. The analog voltage converted from the light emission level (digital value) by the D / A converter 254 is
In the gain switching unit 255, the switches SW1, SW2, ... (corresponding to different powers P1, P2, ...) Are switched and set by the gain switching signal generation circuit unit 256 in accordance with the gain setting value from the printer control unit 201. After being amplified by the gain, it is sent to the semiconductor laser driver 263 via the drive I / O 261, and the semiconductor laser 26
4 is made to emit light with the light intensity of that value. On the other hand, the printer control CPU 250 sends a signal to the clock switching circuit 257 to select the clock generating circuit 258 or 259, and to output the clock signal generated by the clock generating circuit in parallel I.
It is sent to the semiconductor laser driver 263 via / O262 and the image data is modulated by the clock. By selecting the clock generation circuit, the duty ratio (pattern) of the light emission signal is changed (for example, 100% and 80%), and the reproducibility of gradation can be selected. When the duty ratio is 100%, it corresponds to normal light emission, but when the duty ratio is 80%, light emission is performed during 80% of the normal light emission period.

(C) Image Stabilization Gradation characteristics are basically the sensitivity characteristics of the photoconductor, the development characteristics,
Also, it is determined by setting the charging potential V ₀ , the developing bias potential V _B , and the attenuation potential V _S of the electrostatic latent image. An image that is basically formed in color image reproduction (output image)
Is required to change linearly with the original density.
For this reason, stabilization of the image is required. Although the present invention allows the user to select the gradation characteristic, the gradation control system operates in conjunction with the image stabilization system to constantly supply the selected gradation characteristic in a stable manner. Must be one.

Before describing image stabilization, a brief overview of the electrophotographic process is provided. FIG. 7 schematically shows the arrangement of the charging charger 43 and the developing device 45r around the photosensitive drum 41. Here, a charging charger 43 having a discharge potential V _G is installed opposite to the photoconductor 41. The grid of the charger 43 includes a grid potential generation unit 24.
3, the negative grid potential V _G is applied. The relationship between the grid potential V _G and the surface potential V ₀ of the photosensitive drum is
Since it can be regarded that V ₀ = V _G , the potential V _{0 on the} surface of the photosensitive drum 41 can be controlled by the grid potential V _G. The surface potential V ₀ is detected by the V ₀ sensor 44 which is a surface potential meter. First, before laser exposure, a negative surface potential V ₀ is applied to the photosensitive drum 41 by the charger 43, and a low negative development bias potential V ₀ is applied to the roller of the developing device 45r by the developing bias generating unit 244. _B (| V _B | <| V ₀ |) is given. That is, the developing sleeve potential of the developing device 45r is V _B. The laser exposure lowers the potential of the irradiation position on the photosensitive drum 41, and the surface potential V ₀ changes to the attenuation potential V _S of the electrostatic latent image. When the decay potential V _S becomes lower than the developing bias potential V _B, the negatively charged toner carried to the sleeve surface of the developing device 45r adheres onto the photosensitive drum 41.

Here, if the difference between V ₀ and V _B is too large, carrier adhesion to the non-exposed area occurs, and if it is too small, toner fog occurs, so it is neither too large nor too small. The toner adhesion amount increases as the development potential difference ΔV = | V _B −V _S | increases. On the other hand, the attenuation potential V _S changes as the surface potential V ₀ changes even with the same exposure amount. Therefore, if the surface potential V ₀ and the developing bias potential V _B are changed while maintaining the difference between V ₀ and V _B within a certain range, for example, keeping the difference constant, the difference between V _B and V _S changes. Therefore, the toner adhesion amount can be changed and the density can be controlled (see, for example, Japanese Patent Laid-Open No. 3-271764). Further, the gain of laser emission is determined by the V ₀ sensor 44.
It is switched according to the sensitivity information of the photoconductor obtained by.

Further, since the electrophotographic process handles static electricity, it is affected by the environment. Therefore, the development characteristics and the photoreceptor characteristics mainly change, and this compensation is necessary. Therefore, for each of the four colors, the amount of toner adhering to the reference toner image developed under the standard image forming condition is calculated as AI.
It is detected by the DC sensor 210. That is, a reference toner image, which is the basis of density control, is formed outside the image area on the photoconductor drum 41, and an AI provided near the photoconductor drum 41 is formed.
The DC sensor 210 detects the toner amount. In accordance with this detected value, the developing bias potential V _B and the grid potential V _G are changed, the developing potential difference (ΔV) is selected, and automatic density control for keeping the toner adhesion amount at the maximum density level constant is performed. You can It is also necessary to remove the background fog.

(D) Gradation Control Next, the standard gradation correction in which the value of the input image signal and the density of the actually printed image are linear will be described.
Particularly in color images, basically linear characteristics are required. FIG. 8 is a diagram of sensitometry in reversal development. The value of the image signal input from the image reader (image input level OD) is output linearly with respect to the original density. When the laser emission amount P (Lx) is linearly changed with respect to this image input level value Lx, gradation characteristics (image density actually printed (output image density ID)
To the image input level OD) becomes non-linear.
The surface potential V _S of the photosensitive member is attenuated in response to the laser emission. That is, the surface potential gradually and non-linearly attenuates as the laser emission amount increases. The developing bias potential V _B is set with respect to the photoconductor charging potential V ₀ so as to remove the background fog, and the developing potential difference (V _B −V
_The output image density ID (V _S ) is obtained corresponding to _S (Lx), but this developing characteristic also exhibits non-linearity. Therefore, instead of linearly changing the laser emission amount P, the nonlinearity of each of the photoconductor characteristic and the developing characteristic is corrected so that the output image density becomes linear with respect to the input level, which will be described later. Thus, the light emission characteristic is corrected non-linearly. This allows the output image density to be linear with the image input level.

FIG. 9 is a diagram showing how to obtain gradation correction data that realizes standard gradation characteristics that makes the output image density ID linear with the image input level OD. When the image input data is directly converted without conversion and exposed by linearly converting it into the laser exposure amount as shown in the lower side, the gradation curve (the relationship between the image input level and the output image density) shown in the upper side is as shown by the broken line. It becomes non-linear. The emission characteristic for converting this to the target gradation curve shown by the solid line is the curve shown by the solid line in the lower part of the figure. That is, in order to convert the point A (image input level L ₁ ) on the dotted line in the figure to the point A ′ on the solid line, the laser exposure amount P at the point A ″ on the broken line having the same output image density as the point A ′ is obtained.
(L ₁ ) may be output corresponding to the input image data L ₁ . Similarly, in order to convert the point B on the dotted line to the point B'on the target solid line, the laser exposure amount P (L ₂ ) at the point B "on the broken line having the same output image density as the point B'is output. In this way, the laser exposure amount with respect to the image input level, that is, the gradation correction data is obtained.

(E) Gradation Selection In the above, it has been explained that a standard gradation curve that outputs the image density linearly with respect to the input image data is realized in order to obtain an output that is faithful to the original image. In this embodiment, the user can select a different gradation curve in addition to the standard linear gradation curve. In selecting the target gradation curve,
In this embodiment, in order to facilitate the selection by the user,
It is specified by two levels of input of the shape of the gradation curve and the degree of change of the shape.

FIG. 10 schematically shows the concept of the shape of the target gradation curve and the stages of the shape change. The following four types (a) to (d) can be considered as combinations of selection of the gradation curve based on the relative relationship with the standard curve. Also,
An infinite gradation curve can be realized by changing the change level (level) of each shape. In the low density emphasis type (a),
Make the gradation curve convex upward. A solid feeling can be obtained by using this gradation curve. In the high density emphasis type (b),
Make the gradation curve convex downward. A pastel feeling can be obtained by using this gradation curve. In addition, it is possible to correct a totally dark image. In the halftone density portion emphasizing type (c), the gradation curve is largely convex on the high level side, but is small convex on the low level side. Using this gradation curve gives a feeling of “colorful” or “sharp”. In the half tone density part non-emphasized type (d), the gradation curve is
On the low level side, it is slightly convex upward, but on the high level side, it is largely convex downward. Using this gradation curve gives a feeling of "moist" or "smooth". The point where the gradation curves of the halftone density area emphasis type (c) and the halftone density area non-emphasized type (d) intersect with a linear straight line may be the same as in the case of the standard gradation curve (FIG. 8), for example. .

Next, selection of these gradation curves and a specific method will be described. First, the operation panel 2 shown in FIG.
The selection of the gradation curve by 21 will be described. In the setting of the operation panel 221, selection is made by two-step input of selection of a gradation curve and degree of change of its shape. A screen for selecting a gradation curve is called up on the display unit 301 by operating the key 306. FIG. 11 is a diagram of a selection screen displayed on the display unit 301. In the selection screen, the standard gradation curve and each kind of gradation curve shown in FIG. 10 represent the characteristics of the gradation curve (“standard”, “smooth”, “colorful”, “bright”). , "Heavy"). A desired gradation curve is selected from the displayed five gradation curves by a key 310 provided below the display unit 301. When one of the gradation curves is selected by the key 310, next, as shown in FIG. 12, the words (“weak”, “standard”, “strong”) indicating the degree of change of the gradation curve are displayed. It is displayed on 301. The user sets the degree of change by selecting one with the key 310 as in the previous case. That is,
Three levels of change can be selected, and "strong"
Is selected, the gradation curve shape of the type selected in FIG. 11 is selected, and the gradation curve farthest from the standard gradation curve shown in FIG. 10 is selected. The closest gradation curve is selected, and when "Standard" is selected, the intermediate gradation curve is selected.

In the above selection, after the desired gradation curve type is selected, a display prompting the input of the gradation curve level is output. When the level is not input, the level "0" is set as the standard target. The curve is selected. The gradation curve can also be selected using the tablet editor 232 shown in FIG. FIG. 13 shows the appearance of the tablet editor 232. In the coordinate input section 320, by pointing with the coordinate input pen 321, the position on the original can be specified. As a result, partial editing can be designated among various editing functions. Also, this coordinate input unit 3
The group 20 has mode setting key groups 322 and 323. That is, the mode setting keys 322 and 323, the gradation curve setting unit 324 and the color palette 325 are printed on the coordinate input unit 320, and the setting function causes
It can be used as a mode setting part or level setting part. The mode setting keys 322 and 323 are keys for setting various modes, respectively, and can be set by pressing the coordinate input pen 321. Therefore, it is possible to select the type and degree of the gradation curve using the key groups 322 and 323.

(F) Utilization of External Storage Device Furthermore, the gradation curve can be input from an external storage device such as an IC card. The operation panel 221 shown in FIG.
Individual IC cards can be inserted into the insertion ports 311 and 312.
The memory configuration of the IC card is configured according to the type of main body. 14 and 15 show the external appearance and internal configuration of the IC card. Here, the conductive portion 1 is provided on the IC card body 130.
31 is printed. Power can be supplied from the outside through the conductive portion 131, or data can be transmitted and received by a serial interface with the outside. The control CPU 132 in the IC card uses the E ² PR
It manages the OM 133 and controls the interface with the outside. The data is held in the E ² PROM 133.

FIG. 16 shows the structure of the internal data 134 stored in the IC card. The internal data 134 is divided into blocks 135 of variable length. Then, program data (mode setting) can be written in each block. With this, it is possible to register a plurality of programs in one IC card. One block 135 is composed of various data as described below. That is, the "header" contains a code indicating whether the program is registered or not registered and the type of the program. The "program name" contains the user registration name of the program, and based on this, the user can easily know the program creator, the purpose of the program, and the like.
The "model code" contains the code of the model that created the program. The "model characteristic information" contains more detailed characteristic information of the model for which the program is created in order to use the IC card between different models. The "various mode memory" stores various copy modes that can be set on the operation panel. By reading this, the mode setting state when this program was created can be faithfully reproduced. As an example, the ROM 2 of the main body of the copying machine is stored in the mode memory.
03 gradation curve which is different from the built-in gradation curve, and a curve number indicating which gradation curve is selected from among several kinds of gradation curves built in the ROM 203 of the copying machine body. One or both of 137 and 137 are included. Since the model code is also stored in this manner, it becomes possible to store the code information of the insertable machine and the target gradation curve correction information corresponding to each machine in the IC card. Therefore, the target gradation data can be supplied to a plurality of machines.

FIG. 17 shows the configuration of the control system of the operation panel 221. The panel CPU 150 integrally controls the operation panel 221 while controlling the various input / output devices 151 to 158. The copy mode set on the operation panel 221 is sent as an instruction signal to another CPU through the interface. Operation keys 302 on the operation panel
˜310, 313, 314 form a key matrix 151, and the ON / OFF state is read by searching the key matrix 151. The LCD interface 152 is an LCD controller, a video RA.
M, a character generator, etc., and displays the display data set by the main CPU 150 on the display unit 30.
The data is converted into data to be displayed on the first LCD module 153 and displayed on the LCD module 153. IC
The card interface unit 154 controls two IC card units (IC card readers / writers) 155 and 156 corresponding to the IC card insertion ports 311 and 312,
The IC card insertion detection and IC card ejection are performed.
Since data is transmitted and received to and from the IC card through the serial interface, the IC card interface unit 154 controls the interface and the panel CP.
The burden on U150 is lightened. The tablet interface unit 157 is the same as the tablet editor 232 described above.
Controls data transmission and reception with. The bar code interface unit 157 analyzes the data read by the bar code reader pen 315 and sent to the panel CP.
Convert to a data format that U150 can easily process.

The selection of gradation data from the IC card will be described. FIG. 18 shows a gradation curve selection screen displayed on the display unit 301 when one IC card is set. Eight kinds of arbitrary gradation curves created by the user can be registered for each program in the IC card. Then, on this screen, the user can select from a total of nine types of gradation curves, four of which and five stored in the ROM 203 of the main body. FIG. 19 shows a gradation curve selection screen when two IC cards are set.
On this screen, four types of gradation curves registered in each IC card are displayed in a menu, and a gradation curve can be selected from them.

(G) Image quality monitor with gradation curve switching An image quality monitor mode is provided to facilitate the selection by the user when selecting a gradation curve. As shown in FIG. 20, the image quality monitor creates, for example, eight types of sample copies with different image forming conditions on a part of the image previously designated by the tablet editor 232 on one sheet of paper, and This function makes it easy to select an image that suits the user's taste. In this embodiment,
By switching the gradation curves, sample copies with different gradation curves are created on the paper. 21 and FIG.
The example of the gradation curve corresponding to the eight images of is shown. The user can easily select a copy of different image quality obtained by switching the gradation curve by referring to the sample copy.

FIG. 22 shows an operation screen on the display unit 301 of the operation panel 221 for making an image quality monitor sample copy in the image quality monitor mode. When the center of the area to be monitored is designated on the tablet editor 232 according to this operation screen and the original is set and the start key 304 is pressed, a sample copy shown in FIG. 20 is created for the area to be monitored. Image numbers 1 to 8 are printed on the top of each image. When the copying is completed, the image number selection screen shown in FIG. 23 is displayed. Figure 2
By selecting an arbitrary image number from the menu of No. 3, the gradation curve corresponding to it is selected. This allows the user to easily select a desired image quality.

(H) Synthesis of Target Tone Curve A tone curve can also be created by synthesizing from a plurality of stored tone curves. FIG. 24 shows an operation screen for synthesizing gradation curves. In this screen, a menu for selecting two curves, that is, a first curve and a second curve for performing composition is displayed. Here, the first curve is a gradation curve stored in the main body, and the second curve is an IC
It is a gradation curve stored in the card. The user selects between those two curves. Further, as described above, the gradation curve includes the gradation curve built in the main body and the gradation curve in the IC card. Then, depending on the insertion state of the IC card,
It is also possible to switch the selection menu in this operation screen and perform gradation curve synthesis by the gradation curve in the IC card.

Next, FIG. 25 shows an operation screen displayed next to the operation screen of FIG. Then, on this gradation curve composition screen, the composition method of the gradation curve can be selected from the following three selection branches.
(I) Average. (Ii) High density = first curve, low density = second curve
curve. (Iii) High density = second curve, low density = first curve. Therefore, in the first case, the two curves are averaged to obtain a combined curve. In the second and third cases,
A synthetic curve is obtained by connecting two curves.

(I) Fine selection of target gradation curve Although the user has selected a gradation curve as shown in FIG. 10, there are cases where the selected gradation curve is not satisfactory. In such a case, if the gradation curve can be set more finely, it becomes easier to obtain a desired image. Therefore, in this embodiment, a fine selection mode is provided, and arbitrary first and second gradation curves are selected from a plurality of gradation correction data stored in advance, and a plurality of ( An intermediate target curve with the number of steps N) can be calculated. The number of steps is set by the user. The gradation correction data corresponding to the intermediate curve thus obtained is not stored in the data ROM 203. Therefore, the gradation correction data must be calculated. This calculation is the first curve ID which is the target curve data shown in FIG. 10 from the first and second input curves.
_The division between _A (L) and the second curve ID _B (L) is performed evenly by the following equation, for example. The following equation represents the i-th curve in the number of steps N. Here, L represents the level of the input image density.

[Number 1] ID (i, L) = i × {ID A (L) -ID B (L)} / (N + 1) + ID B (L) calculation result is stored in the RAM 204. Alternatively, it may be stored in an IC card.

As described above, the user can select a favorite image from the eight types of image samples having different gradation curves by the image quality monitor function by switching the gradation curves. However, when actually used, there are cases where it is desired to switch the gradation curves more finely to obtain an image that suits the taste. Therefore, the "select tone curve of image quality monitor" function fulfills this desire. FIG. 26 shows an operation screen of this function. Here, the user selects the first and second curves for switching the gradation curves in the image quality monitor function.
Then, when the start key is pressed to start the image quality monitor copy, the machine side divides the two selected curves as shown in FIG. 27, and creates an image sample with each curve. Thus, it is possible to easily select an image that suits the taste. The setting is performed by the tablet editor 232. A fine selection mode can be set in the mode selection key groups 322 and 323. In this mode, selection of the first curve, selection of the second curve, and input of the number of steps are sequentially performed. The selection of the first curve and the second curve,
It is performed in the same manner as described above. The number of steps N is input by pointing the displayed number with the coordinate input pen 132. The setting input may be input from the operation panel 221.

(J) Trial Burning Mode Further, in order to facilitate selection by the user when selecting an intermediate gradation curve, a trial burning mode for performing trial burning is provided, similar to the image monitor mode. , A part of the output image of the original image is printed on the same paper as a trial with a plurality of gradations. For example, if the first and second target curves are divided by six intermediate curves, the image using both curves is the same as the created image using the six intermediate curves. It is printed on paper. The user can easily select a desired gradation by viewing the plurality of partial output images.

(K) Calculation of gradation correction data In this embodiment, the toner adhesion amount detected by the AIDC sensor 210 is hierarchically divided into 28 levels, and the developing bias potential V _B and the photosensitivity are classified according to this level. Body surface potential V ₀
(Grit potential V _G of charging charger 43) is set. Therefore, since the image forming condition is changed according to the level of the AIDC sensor 210, tone correction data under the image forming condition corresponding to each level of 28 is required. Further, when a plurality of gradation correction curves can be selected, for example, a total of 13 kinds of gradation correction curves of 4 × 3 kinds of gradation correction curves and standard gradation correction curves shown in FIG. 10 can be selected. In this case, it is necessary to store the gradation correction data corresponding to the Y, M, C, K and 28 levels of the print color for each gradation correction curve. That is, it is necessary to store 13 × 28 × 4 = 1456 sets of gradation correction data. However, in order to store all such a large number of gradation correction data, a large storage capacity is required even if the polygonal line approximation is used. Therefore, in the present embodiment, only a small number of basic gradation curves (original gradation curves) are stored, and gradation correction data is calculated each time in accordance with the shape of the selected gradation curve. As a result, it is not necessary to store all the gradation correction data, and the memory capacity can be reduced. If these data are stored by the polygonal line approximation, the storage capacity can be further reduced.

FIG. 28 is a diagram showing the concept of gradation control of this embodiment. In the data ROM 203, 28 original gradation curves before correction are stored for each color of C, M, Y, and K corresponding to the detection level of the AIDC sensor 210, and 4 × 3 + 1 = shown in FIG. 13 kinds of settable gradation curves are also stored. In this embodiment, as the original gradation curve, the gradation curve when the value of the input image signal is linearly converted into the exposure amount and printing is performed at each level of the AIDC sensor 210 is stored. ing. First, (A) the user operates the operation panel 22.
1 sets the gradation curve. The setting may be performed by the tablet editor 232. on the other hand,
(B) Call the original tone curve corresponding to the detection value levels 1-28 of the AIDC sensor 210. Next, (C) the gradation correction data is calculated from the called original gradation curve and the set gradation curve in the same manner as in the case of the standard gradation curve of FIG. FIG. 29 is a graph showing the procedure of calculating this gradation correction data. In FIG. 29, an AI
The original gradation curve at the DC level is indicated by. Is a non-linear original gradation curve when the laser exposure amount is linear with respect to the image input level OD (a straight line shown by a dotted line on the lower side), and is called from the ROM 203. Further, is a gradation curve set by the operator from the operation panel 221. Next, a calculation procedure for obtaining gradation correction data for realizing a set gradation curve using these two curves will be described.

The case of the image input level L11 will be described. When the image input level L11 is given, it is necessary to print with the image density indicated by the point C ′ in the set gradation curve. It is understood that the point on the original gradation curve that reproduces the same image density as this point C ′ is point C ″, and this point C ″ is reproduced when the laser exposure amount is P (L11). Therefore, when the image input level L11 is given, if the laser exposure amount of P (L11) is used for the printing, the printing is performed with the gradation characteristics indicated by the set gradation curve. In this way, other image input levels are also converted, and tone correction data showing the relationship between the image input level and the laser exposure amount for realizing the set tone curve is calculated. (D) The correction curve thus obtained is stored in the RAM 204 and is reused when the same gradation is set.

(L) Printer Control Flow FIG. 30 shows the main flow of the printer control unit 201. First, after performing initial settings (S1), the operation panel 2
21 is performed (S2, see FIG. 31), and the start key 304 of the operation panel 221 is waited for being pressed (S3). When the start key is pressed, sensor input processing is performed (S4). Next, the operation panel 221
Input signals from various switches of the printer control unit 201
It is taken into the internal RAM (S5). Next, the gain of the gain switching circuit 255 in FIG. 5 is switched according to the set values obtained in steps S4 and S5, and the semiconductor laser 264
The light intensity level of is set (S6).

Next, the AIDC measurement process is executed and the AI
The toner amount can be obtained by the DC sensor 210 (S
7). In this AIDC process, a reference toner image is formed on a photoconductor, the image reproduction density is detected by the AIDC sensor 210 based on the toner adhesion amount of the image pattern, and is captured in the RAM 204 in the printer control unit 201. Next, based on the density detection level corresponding to the measured toner adhesion amount, the grid potential correction value, the developing bias potential correction value, and the code of the original gradation curve which are set in advance corresponding to this level are selected. (S8, FIG.
reference). Next, based on the code (original tone curve) selected in step S8 and the tone curve input in step S2, the operation described in FIG. 29 is performed to obtain tone correction data (S9). . Next, the grid potential V _G and the developing bias potential V _B selected in the above step S8.
Then, based on the gradation correction table obtained by the calculation in step S9, the known electrophotographic copying operation is executed until the end (S10, S11). In the case of a color image, one copy is sequentially processed in the order of cyan, magenta, yellow and black. Therefore, the main flow described above is repeated for each color.

FIG. 31 shows a flow of the key input process (FIG. 30S2). First, it is determined whether the fine selection mode is set (S21). If it is the fine selection mode (S21
YES), the fine selection routine is executed (S22, see FIG. 32). If it is not the fine selection mode (N in S21
O), the shape of the gradation curve is input (S23), and then the level of the shape is input (S24). Finally, other set values are input (S25), and the process returns.

FIG. 32 shows a fine selection routine (FIG. 31S2).
The flow of processing in 2) is shown. First, the user selects the shape and level of the first gradation curve (S1).
01, S102). Next, the user selects the shape and level of the second gradation curve (S103, S10).
4). Next, the number of curves to be calculated (the number of steps N) is set by the user (S105). Next, the shape of the intermediate curve is calculated by interpolation calculation from these input data (S106), and the RAM 204 (or IC card).
And the intermediate gradation curve is displayed on the display screen 301 (S107). In this example, an intermediate gradation curve is obtained by dividing the first and second input curves by the number of steps N. Next, it is determined whether or not it is the trial baking mode (S108). If you are in trial burn mode,
The trial baking mode is set (S109, see FIG. 33),
If it is not the trial baking mode, the user selects the intermediate curve level i from these curves (S11).
0). Then return.

FIG. 33 shows a processing flow in the trial baking mode. First, V based on the AIDC sensor output
_G , V _B and the original gradation curve are selected (S201). Then, the selected original gradation curve and step S10
Based on the intermediate curve and the first and second curves stored in 7, N + 2 gradation correction curves are calculated and stored in the RAM (S202). Next, one of the N + 2 curves of the input curve and the intermediate curve is selected (S203), and a sample copy is printed (S204). Next, the number of trial firings becomes N + 2 (S
Until YES in 205), the process returns to S203, the next curve is selected, and the same image with different gradation is printed on different portions of the same paper (S204). This process is performed for all these curves.

FIG. 34 shows a flow of V _G , V _B and gradation data selection (FIG. 30S8). Based on the detection value of the AIDC sensor 210, the grid voltage V _G , the developing bias potential V
_B is selected (S41). Then, selecting the code tone correction curve corresponding to _{(V G, V B) (} S42), the process returns.

[0045]

According to the present invention, the user can himself create an intermediate gradation characteristic among several gradation characteristics copied by trial copying, and an original gradation curve can be prepared. It is possible to reduce erroneous copying by continuously performing trial copying and selecting N gradation curves.

[Brief description of drawings]

FIG. 1 is a sectional view showing the overall configuration of a digital color copying machine.

FIG. 2 is a block diagram of an image signal processing unit.

FIG. 3 is a block diagram of a part of a printer control unit.

FIG. 4 is a block diagram of a part of a printer control unit.

FIG. 5 is a perspective view of an operation panel.

FIG. 6 is a block diagram of image data processing in a printer control unit.

FIG. 7 is a diagram schematically showing an arrangement of a charging charger and a developing device around a photosensitive drum.

FIG. 8 is a diagram of sensitometry in reversal development.

FIG. 9 is a diagram showing how to obtain standard gradation correction data.

FIG. 10 is a diagram schematically showing a concept of a target gradation curve shape and a step of enhancing the shape.

FIG. 11 is a diagram of a screen for selecting a type of gradation curve.

FIG. 12 is a diagram of a screen for selecting a level of a gradation curve.

FIG. 13 is a diagram of a panel of a tablet editor.

FIG. 14 is an external view of an IC card.

FIG. 15 is a diagram of an internal configuration of an IC card.

FIG. 16 is a diagram showing a structure of internal data stored in an IC card.

FIG. 17 is a diagram of a configuration of a control system of an operation panel.

FIG. 18 is a diagram showing an example of a gradation curve selection screen.

FIG. 19 is a diagram showing an example of a gradation curve selection screen.

FIG. 20 is a diagram of an output image on the image quality monitor.

FIG. 21 is a diagram showing switching of a gradation curve on the image quality monitor.

FIG. 22 is a diagram of an operation screen in the image quality monitor mode.

FIG. 23 is a diagram showing an image number selection screen in the image quality monitor mode.

FIG. 24 is a diagram of a curve selection screen for synthesizing gradation curves.

FIG. 25 is a diagram of an operation screen for setting a gradation curve synthesizing method.

FIG. 26 is a diagram of a curve selection screen on the image quality monitor.

FIG. 27 is a diagram showing a situation of gradation curve division.

FIG. 28 is a diagram showing storage of various correction data for gradation correction.

FIG. 29 is a diagram for explaining correction of a gradation curve.

FIG. 30 is a diagram of a main flow of a printer control unit.

FIG. 31 is a flowchart of key input processing.

FIG. 32 is a flowchart of a process in a fine selection mode.

FIG. 33 is a flowchart of processing in a trial baking mode.

FIG. 34 is a flowchart for selecting V _G , V _B and gradation data.

[Explanation of symbols]

201 ... Printer control unit, 203 ... Data ROM,
204 ... RAM, 210 ... AIDC sensor, 232 ...
Tablet editor, 253 ... γ correction unit, 322, 3
23 ... Mode setting key.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location G03G 15/04 116 G06F 15/68 310 9191-5L (72) Inventor Yoshinobu Hada Osaka City Central 2-3-13 Azuchi-cho, Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hiroyuki Ideyama 2-3-3 Azuchi-cho, Chuo-ku, Osaka City, Osaka Prefecture International Building Minolta Camera Co., Ltd.

Claims (3)

[Claims] 1. A storage unit for storing a plurality of gradation curves, and a first arbitrary unit selected from the plurality of gradation curves stored in the storage unit.
And a selecting means for selecting a second gradation curve, a gradation curve calculating means for calculating a third gradation curve from the first and second gradation curves, and a third gradation curve. And a light emission control unit that emits light according to a light emission characteristic corresponding to the digital image forming apparatus. 2. The digital image forming apparatus according to claim 1, further input a division number for dividing the first and second gradation curves by an arbitrary number (N). An input means is provided, and the gradation curve calculation means calculates new N gradation correction curves obtained by continuously dividing the first and second gradation curves into N stages. Digital image forming apparatus. 3. An image forming apparatus capable of selecting an arbitrary gradation curve from a plurality of gradation curves and forming an image with the selected gradation curve, the image corresponding to a part of a document image. And a print control means for repeatedly performing output processing while switching gradation curves on the same copy paper.