Image forming device

Abstract

To acquire required densities in an image forming apparatus having a plurality of control means.SOLUTION: First control means transmits designation information on density correction processing to second control means. The second control means acquires a parameter related to an image forming apparatus. The second control means estimates densities corresponding to a tone level specified according to the designation information based on the parameter related to the image forming apparatus, and transmits the estimated densities to the first control means.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a technique for adjusting image density in an image forming apparatus. [Background technology]

[0002] Image density (tone characteristics) is one measure of image quality formed by an image forming apparatus. Patent Document 1 proposes a first tone correction that corrects tone by forming a patch image, and a second tone correction that corrects tone without forming a patch image. Patent Document 2 proposes a method for obtaining a lookup table for a wide color gamut print mode in an image forming apparatus having a normal print mode and a wide color gamut print mode. Such a lookup table is sometimes called a tone correction table or a density correction table. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-174231 A [Patent Document 2] JP 2019-020521 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, an image forming apparatus may have a first controller that performs tone correction using a lookup table and a second controller that controls an image forming engine. When multiple lookup tables exist for tone correction depending on the control mode or image processing mode of the image forming apparatus, the density (estimated result) required for each lookup table differs. In other words, a method is required for the second controller to appropriately assist the first controller in obtaining the required density. Therefore, an object of the present invention is to obtain the required density in an image forming apparatus having multiple control means. [Means for solving the problem]

[0005] The present invention relates to, for example, a first control means for performing density correction processing on image data to generate an image signal; an image forming means for forming an image on a recording medium based on the image signal; A second control means for controlling the image forming means, The first control means a designation unit that transmits designation information regarding the density correction process to the second control unit; The second control means An acquisition means for acquiring parameters related to an image forming apparatus; an estimation means for estimating densities of a plurality of images corresponding to a tone level specified by the designation information transmitted from the first control means based on the parameters acquired by the acquisition means and transmitting the densities to the first control means; death, The first control means has a creating means for creating or updating density correction data serving as a reference for the density correction process based on the densities of the plurality of images estimated by the estimating means. The present invention provides an image forming apparatus comprising: Effect of the Invention

[0006] According to the present invention, in an image forming apparatus having a plurality of control units, the required density can be obtained. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram illustrating an image forming apparatus. [Diagram 2] Diagram explaining the controller [Diagram 3] Diagram explaining the video controller [Figure 4] Diagram explaining the engine controller [Diagram 5] FIG. 13 is a diagram illustrating the relationship between a test image and density. [Figure 6] A diagram explaining a concentration estimation method [Figure 7] Diagram explaining how to specify tone levels [Figure 8] Flowchart showing a concentration estimation method [Figure 9] Diagram explaining how to specify tone levels [Figure 10] Diagram explaining how to specify tone levels [Figure 11] Diagram explaining how to specify tone levels [Figure 12] Flowchart showing a concentration estimation method [Figure 13] Diagram explaining the video controller [Figure 14] Diagram explaining the engine controller [Figure 15] Diagram explaining the video controller [Figure 16] Diagram explaining the engine controller DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.

[0009] <Example 1> Image forming equipment As shown in Fig. 1, image forming apparatus 100 is a printer, copier, or multifunction machine that forms an image on a sheet P. Here, an electrophotographic method is adopted as the image forming method, but the image forming method may be an inkjet method, a thermal transfer method, or the like. The reference symbols shown in Fig. 1 are suffixed with Y (yellow), M (magenta), C (cyan), and K (black) indicating the toner color. The letters YMCK are omitted when matters common to the four colors are explained.

[0010] The image forming unit 1 forms a full-color image on the sheet P by superimposing each toner image of YMCK. The photosensitive drum 5 is an image carrier that rotates while carrying an electrostatic latent image or a toner image. The charger 6 uniformly charges the surface of the photosensitive drum 5 using a charging voltage. The exposure device 10 irradiates the photosensitive drum 5 with light according to an image signal to form an electrostatic latent image on the surface of the photosensitive drum 5. The developing roller 9 of the developing device 8 adheres toner to the electrostatic latent image using a developing voltage to form a toner image. The primary transfer roller 4 transfers the toner image from the photosensitive drum 5 to the intermediate transfer belt 12 using a primary transfer voltage. Here, the toner images of YMCK are transferred in order to the intermediate transfer belt 12 to form a full-color image. The intermediate transfer belt 12 transports the toner image to the secondary transfer unit. The intermediate transfer belt 12 may be a transport belt that carries and transports the sheet P. In this case, the toner image 71 is transferred from the photosensitive drum 5 to the sheet P. The photosensitive drum 5, the charger 6 and the developing device 8 may be integrated into a cartridge 7.

[0011] The sheet cassette 21 can store a plurality of sheets P. The pickup roller 22 feeds the sheets P one by one from the sheet cassette 21 toward the conveying path 23. The conveying roller 24 conveys the sheet P along the conveying path 23, and the registration roller 24 conveys the sheet P along the conveying path 23. 25 The sheet P is then delivered to the secondary transfer section. The registration rollers 25 transport the sheet P along the transport path 23 and deliver the sheet P to the secondary transfer section. The secondary transfer rollers 26 provided in the secondary transfer section transfer the toner image 71 transported by the intermediate transfer belt 12 onto the sheet P. A secondary transfer voltage is applied to the secondary transfer rollers 26 to promote the transfer of the toner image 71 here. The fixing unit 27 applies heat and pressure to the toner image and the sheet P to fix the toner image to the sheet P. The paper discharge rollers 28 discharge the sheet P onto the paper discharge tray 29.

[0012] The density sensor 30 measures the optical image density (hereinafter simply referred to as density) of the toner image 71 carried on the intermediate transfer belt 12. The density measurement result is used for density adjustment (e.g., gradation correction) of the toner image. The temperature sensor 32a measures the temperature inside the image forming apparatus 100. The humidity sensor 33 measures the humidity inside the image forming apparatus 100. The temperature sensor 32a and the humidity sensor 33 are disposed in close proximity to each other, and may be housed in a single housing, for example. The temperature sensor 32b measures the temperature around the cartridge 7. These temperatures and humidities are called environmental parameters, and are used to estimate the density of the toner image 71 without forming a test image.

[0013] ● Controller As shown in FIG. 2, the image forming apparatus 100 includes two control circuits or control boards, a video controller 202 and an engine controller 203. The video controller 202 is a controller that receives image data and a print command from a host computer 201 via a communication line 204. The video controller 202 may be called a print controller or an image processing controller. The communication line 204 may be, for example, a wired LAN (local area network) or a wireless LAN. The video controller 202 converts image data into an image signal (video signal 206) in a predetermined format and transmits it to the engine controller 203. The video controller 202 transmits a command corresponding to the command received from the host computer 201 to the engine controller 203.

[0014] The engine controller 203 mainly controls the image forming unit 1 (which may also be called a printer engine). The communication circuit 211 of the engine controller 203 is a circuit that communicates with the video controller 202. The CPU 208 controls the image forming unit 1 according to a control program stored in the memory 209. The memory 209 may include one or more of a RAM (random access memory), a ROM (read only memory), a HDD (hard disk drive), and an SSD (solid state drive). The CPU 208 is connected to the drive circuits 215a, 215b, and 215c, the input circuits 217a and 217b, and the high-voltage power supply 216 via a bus 214 and an I / O port 213.

[0015] The driving circuit 215a drives the laser 75 of the exposure device 10 according to the video signal 206 input from the video controller 202 via the I / O port 213. The driving circuit 215b drives the scanner 76 that rotates the rotary polygon mirror according to a command from the CPU 208. The scanner 76 includes a motor and the like. The driving circuit 215c drives the motor M1 according to a command from the CPU 208. The motor M1 drives a plurality of rotating bodies that constitute the image forming unit 1. The rotating bodies are, for example, the pickup roller 22, the conveying roller 24, the registration roller 25, the secondary transfer roller 26, the photosensitive drum 5, and the intermediate transfer belt 12. A plurality of motors may be provided as the motor M1. The pickup roller 22 may be driven by a solenoid or the like.

[0016] The input circuit 217a includes a circuit for amplifying a detection signal output by the density sensor 30 that detects the density of the toner image 71. The input circuit 217a reports the detection result (actual measurement value) of the density to the CPU 208 via the I / O port 213. The input circuit 217b includes a circuit for amplifying and outputting the detection signal from the temperature sensors 32a and 32b and the detection signal from the humidity sensor 33. The input circuit 217b reports the detection results (actual measurement values) of the temperature and humidity to the CPU 208 via the I / O port 213. Hereinafter, the detection result of the density and the estimated result of the density may be expressed as density ΔE. The CPU 208 transmits the density ΔE to the video controller 202 via the communication circuit 211.

[0017] The high-voltage power supply 216 is a power supply circuit that generates high voltages such as a charging voltage, a developing voltage, a primary transfer voltage, and a secondary transfer voltage in accordance with commands from the CPU 208. The system timer 212 is used by the CPU 208 to measure time and monitor various control timings.

[0018] ●Video controller functions 3 shows the functions of the video controller 202. The CPU 308 communicates with the host computer 201 via a communication circuit 301. The CPU 308 communicates with the engine controller 203 via a communication circuit 321. The CPU 308 realizes various functions by executing control programs stored in the ROM area of ​​the memory 309. The memory 309 includes storage devices such as a ROM and a RAM.

[0019] The RIP 311 is a raster image processor that converts image data expressed in a language such as PostScript into image data in a bitmap format. The color space conversion unit 312 converts the color space (e.g., RGB) of the image data input from the RIP 311 into the color space (e.g., YMCK) of the toner. The gradation correction unit 313 corrects the gradation characteristics of the image data using a lookup table (LUT 330) stored in the memory 309. This makes the gradation characteristics of the original image and the gradation characteristics of the image formed on the sheet P match. The LUT 330 is corrected according to the state of the image forming apparatus 100 (e.g., the installation environment, the degree of wear of parts), thereby maintaining the reproducibility of the gradation.

[0020] The mode selection unit 315 selects an operation mode of the image forming apparatus 100. The CPU 308 has a plurality of operation modes corresponding to the type of the sheet P (plain paper, coated paper, thick paper, thin paper, recycled paper, etc.). The mode selection unit 315 selects an appropriate operation mode corresponding to the type of the sheet P. The LUT selection unit 316 selects the LUT 330 suitable for the operation mode selected by the mode selection unit 315 and sets it in the gradation correction unit 313. The LUT 330 and the operation mode may be stored in the memory 209 in association with each other. The start determination unit 317 determines whether a start condition for starting the correction process of the LUT 330 is satisfied. The start condition is held in the memory 309 and is defined based on one or more of, for example, the number of images formed, environmental parameters (e.g., temperature, humidity), and the period during which the image forming apparatus 100 was in a pause state.

[0021] The first correction unit 318 corrects the LUT 330 based on an actual measurement value acquired by detecting the density of a test image actually formed on the intermediate transfer belt 12 with the density sensor 30. The first correction unit 318 outputs the video signal 206 of the test image to the engine controller 203, and updates or creates the LUT 330 based on the actual measurement value of the density.

[0022] The second correction unit 319 corrects (updates or creates) the LUT 330 based on estimated values ​​of density obtained without forming a test image. The second correction unit 319 can save toner because it does not form a test image. On the other hand, the first correction unit 318 uses actual measured values, so the correction accuracy of the LUT 330 is high.

[0023] The tone designation unit 320 designates, to the engine controller 203, a tone level that is useful for identifying a density estimation target. This allows the CPU 308 to designate various tone levels to the engine controller 203. The multiple LUTs 330 include an LUT that is corrected based on a small number of estimated densities and an LUT that is corrected based on a larger number of estimated densities. Alternatively, even if the number of estimated densities required is the same, there may be multiple LUTs with different positions of the estimated densities (tone levels). Therefore, the estimation target may differ for each LUT. Therefore, if the video controller 202 designates an estimation target according to the LUT 330 to be corrected, the engine controller 203 can efficiently obtain the required estimation target.

[0024] ●Engine controller functions 4 shows functions realized by the CPU 208 of the engine controller 203. The actual measurement unit 401 acquires the measurement result (detection result) of the test image from the density sensor 30, performs calculations, and reports the result to the video controller 202 via the communication circuit 211. The test image is a patch image or a pattern image. callThe acquisition unit 402 acquires parameters that affect the image density of the toner image. Examples of such parameters include environmental parameters, control parameters, and state parameters. The environmental parameters include, for example, the temperature detected by the temperature sensors 32a and 32b, the relative humidity detected by the humidity sensor 33, and the absolute moisture content calculated from the detection results of the temperature sensor 32a and the humidity sensor 33. The control parameters include, for example, the charging voltage, the developing voltage, the primary transfer voltage, and the secondary transfer voltage. The state parameters include, for example, the remaining amount of toner contained in the developing device 8, and the remaining amount of the surface layer of the photosensitive drum 5 (drum remaining amount). The consumption monitoring unit 405 monitors the remaining amount of toner and the remaining amount of the surface layer of the photosensitive drum 5. The consumption monitoring unit 405 may acquire the remaining amount of toner using a remaining amount sensor (not shown), or may obtain the amount of toner used from image data and acquire the remaining amount based on the amount used. The wear monitoring unit 405 may obtain the remaining amount of the surface layer based on the rotation distance of the photoconductor drum 5. The rotation distance may be obtained based on the time during which the photoconductor drum 5 has rotated and the rotation speed (circumferential speed) of the photoconductor drum 5.

[0025] The tone setting unit 403 sets a tone level in the estimation unit 404 based on designation information received from the video controller 202. The estimation unit 404 estimates an image density based on the tone level designated by the designation information and the parameters acquired by the acquisition unit 402. For example, the estimation unit 404 may refer to an estimation table 411 stored in the memory 209 to find a density corresponding to a pair of a tone level and a parameter. The estimation table 411 holds densities corresponding to a plurality of pairs of a tone level and a parameter.

[0026] The tone set 410 is a set having a plurality of tone levels. Each of the plurality of tone sets 410 is distinguished by identification information. When the video controller 202 transmits this identification information, the tone setting unit 403 can read out the tone set 410 associated with the identification information from the memory 209. The tone setting unit 403 sets the plurality of tone levels included in the tone set 410 to the estimation unit 404. The estimation unit 404 transmits the estimation result of the image density to the video controller 202 via the communication circuit 211.

[0027] ●LUT correction based on actual measurements The first correction unit 318 of the video controller 202 corrects, updates, or creates the LUT 330 based on the actual measured value of the density of the test image formed on the intermediate transfer belt 12. Here, the LUT 330 is a lookup table that indicates the relationship between the tone level and the density.

[0028] Fig. 5(A) shows four test images 501a to 501d formed on the surface of the intermediate transfer belt 12. Fig. 5(B) is a diagram showing the relationship between the test images 501a to 501d and density ΔE.

[0029] When the first correction unit 318 starts correcting the LUT 330, the first correction unit 318 transmits a command to the engine controller 203 to instruct the engine controller 203 to detect (measure) the test images 501a to 501d. The first correction unit 318 starts outputting the video signal 206 corresponding to the test images 501a to 501d.

[0030] Upon receiving the command, the measurement unit 401 controls the image forming apparatus 100 to form the test images 501a-501d on the intermediate transfer belt 12. Furthermore, the measurement unit 401 controls the density sensor 30 to read the test images 501a-501d and obtains the actual measurement values ​​(density ΔE) of the densities of the test images 501a-501d. Finally, the measurement unit 401 transmits the densities ΔE of the test images 501a-501d to the video controller 202.

[0031] The first correction unit 318 of the video controller 202 creates the LUT 330 based on each density ΔE of the test images 501a to 501d. Here, since the first correction unit 318 generates the video signal 206 for forming the test images 501a to 501d, it knows the tone levels Ta to Td corresponding to the test images 501a to 501d. Therefore, as shown in FIG. 5B, the first correction unit 318 creates the LUT 330 by mapping the tone levels Ta to Td and the densities ΔEa to ΔEd corresponding to the test images 501a to 501d. The LUT 330 is stored in the memory 309.

[0032] LUT correction based on estimated density values As already described, the second correction unit 319 corrects, creates, or updates the LUT 330 based on the density (estimated value) estimated by the video controller 202 without forming a test image. Here, since a test image is not formed, the engine controller 203 cannot specify which tone level corresponds to which density should be estimated. Therefore, the tone designation unit 320 designates or notifies the engine controller 203 of the tone level associated with the density to be estimated.

[0033] The tone setting unit 403 sets the designated N tone levels in the estimation unit 404. The estimation unit 404 estimates N densities corresponding to the designated N tone levels based on the parameters acquired by the acquisition unit 402 and the wear monitoring unit 405. The estimation unit 404 transmits the estimated N densities ΔE to the second correction unit 319 of the video controller 202. At this time, the estimation unit 404 may transmit the designated tone level T and the estimated density ΔE as a pair to the video controller 202. This allows the second correction unit 319 to easily determine the relationship between the tone level T and the estimated density ΔE. The second correction unit 319 corrects, updates, or creates the LUT 330 based on the N tone levels and the N densities ΔE.

[0034] In this way, by correcting the LUT 330 using the estimated density value, toner consumption is reduced. In addition, downtime is reduced. Downtime is a period during which a user image cannot be formed due to the formation of a test image. A user image is an image formed on a sheet P in response to an instruction from the host computer 201 (i.e., at the user's request).

[0035] FIG. 6A shows an example of parameters that can be used for density estimation. In this example, the environmental parameters are temperature (e.g., 23° C), relative humidity (e.g., 50%), and absolute moisture content (e.g., 10.3 g / m^3). m^3 indicates cubic meters. The control parameters are charging voltage (e.g., −1000 V), developing voltage (e.g., −500 V), and primary transfer voltage (e.g., 300 V). The status parameters are remaining toner amount (e.g., 40%) and remaining drum amount (e.g., 35%). The estimation unit 404 estimates the density ΔE using these parameters, the tone level, and the estimation table 411.

[0036] FIG. 6B shows an LUT 330 created based on the estimated density E and the specified tone level T. The curve of the LUT 330 changes depending on the parameters shown in FIG. 6A. The LUT 330a is determined based on the parameters shown in FIG. 6A. When the environmental parameters shown in FIG. 6A change to low temperature and low humidity, the LUT 330b is obtained. When the charging voltage changes in the negative direction (e.g., charging voltage=−1200V) among the parameters shown in FIG. 6A, the LUT 330c is obtained.

[0037] In the above description, the LUT 330 is created by the second correction unit 319, but it may be created in the engine controller 203. The CPU 208 creates the LUT 330 based on the specified N tone levels and the estimated N densities ΔE, and transmits the LUT 330 to the video controller 202.

[0038] According to the LUT 330a in FIG. 6B, when the tone level is 60h, the density ΔE is 50 (32h). According to the LUT 330b, when the tone level is 60h, the density ΔE is 55 (37h). According to the LUT 330c, when the tone level is 60h, the density ΔE is 43 (2Bh).

[0039] Also, according to LUT 330a, when the tone level is A0h, the density ΔE is 130 (82h). According to LUT 330b, when the tone level is A0h, the density ΔE is 137 (89h). According to LUT 330c, when the tone level is A0h, the density ΔE is 120 (78h). In this way, even at the same tone level, the density ΔE will be different if the parameters are different.

[0040] How to specify tone levels When it is desired to stabilize the density over a wide range of gradations, the video controller 202 specifies a wide range of tone levels. To reduce the number of specified tone levels, the intervals between the specified tone levels may be wide. On the other hand, when it is desired to stabilize the density in the intermediate tones of the image, the video controller 202 specifies a narrow range of tone levels, which is the intermediate tone region. In other words, the intervals between the specified tone levels are narrowed.

[0041] In this way, the positions and total number of tone levels required to create the LUT 330 differ for each operation mode of the video controller 202. For this reason, the video controller 202 specifies to the engine controller 203 the tone levels corresponding to the concentration ΔE to be estimated.

[0042] 7A shows the tone levels and the total number N of tone levels required to create the LUT 330 for a mode in which an image is printed on plain paper. The total number N is 4 points. Tone level 1 is 20h. Tone level 2 is 50h. Tone level 3 is 80h. Tone level 4 is B0h. These four tone levels are useful for stabilizing density over a relatively wide range of gradations.

[0043] FIG. 7B shows the tone levels and total number N of tone levels required to create a LUT 330 for a mode in which an image is printed on gloss paper. The total number N is 4 points. Tone level 1 is 40h. Tone level 2 is 60h. Tone level 3 is 80h. Tone level 4 is A0h. These four tone levels help to stabilize the density in the midtone area.

[0044] Comparing FIG. 7(B) with FIG. 7(A), the minimum and maximum values ​​of the specified tone levels and the interval between two adjacent tone levels are different. In FIG. 7(A), the difference between the minimum and maximum values ​​of the tone levels is large, so the specified range of tone levels is wide. The interval between two adjacent tone levels is 30h, which is relatively wide. In FIG. 7(B), the difference between the minimum and maximum values ​​of the tone levels is small, so the specified range of tone levels is narrow. The interval between two adjacent tone levels is 20h, which is relatively narrow.

[0045] FIG. 7C shows the tone levels required in LUT 330 for a mode in which detailed color adjustment is instructed by the user, and the total number N of tone levels. The total number N is 8 points. Tone level 1 is 40h. Tone level 2 is 50h. Tone level 3 is 60h. Tone level 4 is 70h. Tone level 5 is 80h. Tone level 6 is 90h. Tone level 7 is A0h. Tone level 8 is B0h. By specifying a large number of tone levels over a wide range in this way, with narrow intervals (10h in this example), the image density is stabilized across the entire gradation range.

[0046] Incidentally, the tone levels used in the LUT correction based on actual measurements may be the same as or different from the tone levels used in the LUT correction based on estimated values. In addition, both the total number N of tone levels and the N tone levels may be specified, or only the N tone levels may be specified.

[0047] Flowchart 8 is a flowchart showing a density estimation method executed by the CPU 208 of the engine controller 203. When the image forming apparatus 100 is supplied with power from a commercial power source and starts up, the CPU 208 executes a control program. Ta Therefore, the following process is executed.

[0048] In S801, the CPU 208 (tone setting unit 403) receives the total number N of tone levels from the video controller 202. In S802, the CPU 208 (tone setting unit 403) receives the tone levels from the video controller 202. The CPU 208 stores the received total number N and the tone levels in the RAM of the memory 209. In S803, the CPU 208 (tone setting unit 403) determines whether all the tone levels have been received. For example, the tone setting unit 403 may determine whether all the tone levels have been received by comparing the number of received tone levels (count value) with the total number N. If all the tone levels have not been received, the CPU 208 returns to S802 and receives the next tone level. If all the tone levels have been received, the CPU 208 proceeds to S804.

[0049] In S804, the CPU 208 determines whether or not a start condition for density estimation is satisfied. The start condition may be, for example, that an amount of change in an environmental parameter exceeds a threshold value at every predetermined time or every predetermined number of images formed. The start condition may also be that a start command is received from the video controller 202. In this case, the CPU 208 may report information required for determining the start condition, such as the number of images formed or the environmental parameters, to the video controller 202. This causes the start determination unit 317 of the video controller 202 to determine whether or not the start condition is satisfied, and transmit a command based on the determination result. When the start condition is satisfied, the CPU 208 proceeds to S805.

[0050] In S805, the CPU 208 (acquisition unit 402) acquires parameters necessary for density estimation. In S806, the CPU 208 (estimation unit 404) estimates the density ΔE corresponding to the specified tone level using the specified tone level and the parameters. 7 The CPU 208 (estimation unit 404) then transmits the estimated density ΔE corresponding to the specified tone level to the video controller 202.

[0051] In Fig. 8, the total number N of tone levels and the tone levels are received, but as shown in Fig. 9(A) to Fig. 9(C), the tone level number and the tone level may be received in pairs. Alternatively, as shown in Fig. 10(A) and Fig. 10(B), the start value of the tone level (the minimum value of the designated tone levels), the end value (the maximum value of the designated tone levels), and the tone level interval may be specified.

[0052] The tone setting unit 403 can specify the four tone levels shown in FIG. 10C based on the start value (20h), end value (B0h) and tone level interval (30h) shown in FIG. 10A. Similarly, the tone setting unit 403 can specify the four tone levels shown in FIG. 10C based on the start value (00h), end value (FFh) and tone level interval (01h) shown in FIG. 10B. D ) can identify 256 tone levels.

[0053] 8, the tone level is specified immediately after the video controller 202 is started, but this is merely an example. The video controller 202 may specify the tone level at the timing when the engine controller 203 executes the concentration estimation.

[0054] <Example 2> A plurality of image forming apparatuses sold as different products on the market may be equipped with a common (identical) engine controller 203. On the other hand, these plurality of image forming apparatuses may be equipped with different video controllers 202. Some video controllers 202 provide many functions to the image forming apparatus 100, while others provide fewer functions. For example, there are SFPs (single function printers) having only a print function and MFPs (multifunction printers) having a print function and an image reading function on the market. It is easy to imagine that the video controller 202 for the SFP and the video controller 202 for the MFP are different. These different video controllers 202 have different image density processes, and therefore different methods for creating the LUT 330. If the image density processes differ, the appropriate LUT 330 also differs. Therefore, the video controller 202 must specify the tone level required to create the appropriate LUT 330 to the engine controller 203.

[0055] In the second embodiment, tone levels that can be specified by the video controller 202 are stored in advance in the engine controller 203 for each type of the video controller 202. The tone setting unit 403 of the engine controller 203 acquires a tone level corresponding to the type information from the memory 209 based on the type information of the video controller 202 transmitted from the video controller 202. Note that the video controller 202 may not transmit type information. In this case, the tone setting unit 403 uses a default tone level stored in the memory 209.

[0056] FIG. 11 shows tone level sets held in memories 209 and 309. When type information (type code) is 01, the type of video controller 202 is I, and four tone levels (20h, 50h, 80h, B0h) are specified. When type information is 02, the type of video controller 202 is II, and four tone levels (40h, 60h, 80h, A0h) are specified. When type information is 03, the type of video controller 202 is III, and eight tone levels (40h, 50h, 60h, 70h, 80h, 90h, A0h, B0h) are specified. CPU 308 (tone designation unit 320) transmits type information to CPU 208 (tone setting unit 403), so that CPU 208 (tone setting unit 403) can read out tone levels corresponding to the type information from memory 209.

[0057] Fig. 12 is a flowchart showing concentration estimation executed by the CPU 208 of the engine controller 203. Explanation of matters common to those explained in Fig. 8 will be omitted. More specifically, S804 to S807 executed after S1202 and S1204 are as explained in the first embodiment.

[0058] In S1201, the CPU 208 (tone setting unit 403) determines whether type information has been received from the video controller 202. If type information has been received, the CPU 208 proceeds to S120. 2 In S1202, CPU 208 (tone setting unit 403) acquires a tone level corresponding to the type information from memory 209, and sets it in estimation unit 404. On the other hand, if type information has not been received in S1201, CPU 208 proceeds to S1203.

[0059] In S1203, CPU 208 (tone setting unit 403) determines whether the reception waiting time measured by system timer 212 has exceeded a threshold. If the reception waiting time has not exceeded the threshold, CPU 208 returns to S1201. If the reception waiting time has exceeded the threshold, CPU 208 proceeds to S1204. In S1204, CPU 208 (tone setting unit 403) obtains a default tone level from memory 209 and sets it in estimation unit 404.

[0060] In this way, a tone level set having a plurality of tone levels is specified based on the designation information (type information) transmitted from the video controller 202. In the second embodiment, the tone level set is specified based on the type information of the video controller 202, but this is merely an example. For example, when the video controller 202 has a plurality of image density processes, identification information of the tone level set may be transmitted instead of the type information. This may enable an appropriate tone level to be set for each image density process. Note that the identification information is sufficient as long as it can identify the tone level set, and may be identification information of the image density process linked to the tone level set.

[0061] <Example 3> In the first and second embodiments, the engine controller 203 specifies the density for which tone level to estimate based on the designation information transmitted from the video controller 202. However, it is not essential for the video controller 202 to transmit the designation information. For example, the engine controller 203 may estimate several densities in advance and transmit them to the video controller 202 without relying on the designation information. The video controller 202 may select and use the density that is actually required from the several densities received from the engine controller 203.

[0062] Fig. 13 shows a video controller 202 according to the embodiment 3. Fig. 14 shows an engine controller 203 according to the embodiment 3. The same reference numerals are given to the components described in the embodiments 1 and 2, and the descriptions thereof are incorporated herein by reference.

[0063] 13, the video controller 308 has a selection unit 1300. The selection unit 1300 selects M concentrations to be actually used in the second correction unit 319 from among the N concentrations estimated by the engine controller 203, and provides the M concentrations to the second correction unit 319. Here, N and M are integers, and N is equal to or greater than M. When N is less than M, the MN concentrations may be obtained by an interpolation calculation by the CPU 308 using at least two or more concentrations from among the N concentrations.

[0064] As shown in FIG. 14, the memory 209 stores tone information 1400. The tone information 1400 holds, for example, N densities likely to be required by the second correction unit 319, and N tone levels corresponding to the N densities. The tone setting unit 403 reads the tone information 1400 from the memory 209, acquires the N tone levels included in the tone information 1400, and sets them in the estimation unit 404. As described above, the estimation unit 404 estimates N densities corresponding to the N tone levels based on the parameters acquired by the acquisition unit 402. The estimation unit 404 transmits the N densities to the video controller 202 via the communication circuit 211. Here, the estimation unit 404 may transmit the estimated densities and identification information indicating the tone levels in pairs to the video controller 202. This allows the video controller 202 to easily identify which estimated densities correspond to which tone levels. In this manner, in the third embodiment, the video controller 202 can obtain the N densities required by the second corrector 319 without using the designation information.

[0065] <Example 4> In the first to third embodiments, the image density is estimated in the engine controller 203. However, the estimation unit 404 may be provided in the video controller 202. In this case, it is not necessary to transmit designation information from the video controller 202 to the engine controller 203.

[0066] Fig. 15 shows a video controller 202 according to the embodiment 4. Fig. 16 shows an engine controller 203 according to the embodiment 4. The same reference numerals are given to the components described in the embodiments 1 and 2, and the descriptions thereof are incorporated herein by reference.

[0067] 15, the CPU 308 of the video controller 202 has an estimation unit 404. The memory 309 has an estimation table 411. The estimation unit 404 receives parameters from the engine controller 203 via the communication circuit 321. The estimation unit 404 estimates an image density corresponding to a tone level designated by a tone designation unit 320 based on the received parameters. The estimation unit 404 passes the image density, which is the estimation result, to a second correction unit 319.

[0068] 16, the CPU 208 of the engine controller 203 has an acquisition unit 402. The acquisition unit 402 transmits the acquired parameters to the video controller 202 via the communication circuit 211. As described above, the parameters may be parameters related to the image forming apparatus that indirectly or directly affect the image density of the toner image. In this way, in the fourth embodiment, the image density can be estimated without transmitting designation information from the video controller 202 to the engine controller 203.

[0069] <Summary> [Point 1] The video controller 202 is an example of a first control means that applies density correction processing to image data to generate an image signal. The image forming unit 1 is an example of an image forming means that forms an image on a recording medium based on an image signal. The engine controller 203 is an example of a second control means that controls the image forming means. The tone designation unit 320 is an example of a designation means that designates the density of a plurality of images to be estimated by the estimation means to the second control means. The tone designation unit 320 functions as a designation means that transmits designation information capable of identifying a tone level to the second control means. The tone designation unit 320 may also function as a designation means that transmits designation information related to density correction processing to the second control means. The CPU 208 and the acquisition unit 402 function as an acquisition means that acquires parameters related to the image forming apparatus (e.g., parameters that affect the density of an image). The CPU 208 and the estimation unit 404 function as an estimation means that estimates the density of a plurality of different images based on the parameters acquired by the acquisition means. The CPU 208 and the estimation unit 404 may estimate the density of a plurality of different images, which is a density corresponding to a tone level identified by the designation information transmitted from the first control means, based on the parameters acquired by the acquisition means. The estimation unit 404 may transmit the estimated densities of the multiple images to the first control unit (the video controller 202). This allows the required densities to be efficiently acquired in an image forming apparatus having multiple control units.

[0070] [Points 2-4] The second control means (e.g., engine controller 203) may specify the densities of the multiple images to be estimated based on the tone levels transmitted from the first control means. The designation information may include the tone levels themselves. The estimation unit 404 may estimate the densities corresponding to the tone levels included in the designation information. The second control means (e.g., engine controller 203) may specify the densities of the multiple images to be estimated based on the identification information (e.g., tone level numbers) of the tone levels transmitted from the first control means. That is, the designation information may include the identification information of the tone levels. The estimation unit 404 estimates the densities corresponding to the tone levels specified by the identification information included in the designation information. The second control means (e.g., engine controller 203) may specify the densities of the multiple images to be estimated based on the tone levels corresponding to each density transmitted from the first control means and the total number of the tone levels. The designation information may include the tone levels and the total number of the tone levels. The CPU 208 may determine whether or not all the tone levels required by the estimation means have been received from the first control means based on the total number of the tone levels. [Points 5 and 6] The second control means (e.g., engine controller 203) may specify the densities of the multiple images to be estimated based on information transmitted from the first control means (e.g., video controller 202). For example, the densities of the multiple images to be estimated may be specified based on a first tone level (e.g., start value), a second tone level (e.g., end value), and a coefficient (e.g., tone level interval). That is, the second control means (e.g., CPU 208) may specify multiple tone levels based on the first tone level, the second tone level, and a coefficient. Here, the coefficient is used by a calculation to specify tone levels that exist between the first tone level and the second tone level. For example, the coefficient may be the interval between two adjacent tone levels in three or more tone levels required by the estimation unit 404. Alternatively, the coefficient may be the total number N of tone levels that specify the densities of the multiple images to be estimated. In this case, the CPU 208 can calculate the tone level interval by dividing the difference between the end value and the start value by N-1. This makes it possible to specify the remaining tone levels.

[0071] [Points 8 and 9] As described in the second embodiment, the memory 209 functions as a storage means for storing a plurality of tone level sets including a tone level that specifies the density of an image to be estimated. The memory 209 may function as a storage means for storing a plurality of tone level sets each including a plurality of tone levels. The second control means may specify the density of a plurality of images to be estimated based on a tone level set specified by the first control means among the plurality of tone level sets stored in the storage means. That is, the second control means may specify a plurality of tone levels required by the estimation means based on a tone level set specified by the specification information among the plurality of tone level sets stored in the storage means. The tone level set may be specified by, for example, identification information (e.g., type information) that identifies the type of the first control means. Note that the tone level set may be specified by a control mode applied to an image among the plurality of control modes provided in the image forming apparatus 100. In this case, in the memory 209, the identification information of the control mode and the tone level set are linked.

[0072] [Points 10-13] The parameter, the detected environment of the image forming apparatus (which may be called the internal environment) may be at least one of the output value of the high voltage used in the image forming apparatus and the usage amount of the consumables constituting the image forming apparatus. The detected environment of the image forming apparatus includes at least one of the temperature, the relative humidity, and the absolute moisture content. The high voltage of the image forming apparatus may be a charging voltage used to charge the image carrier. The high voltage of the image forming apparatus may be a developing voltage used to develop an electrostatic latent image that is the source of the image. The high voltage of the image forming apparatus may be a transfer voltage used to transfer a toner image that is the source of the image to an intermediate transfer body or a recording medium. The usage amount of the consumables includes at least one of the usage amount of the toner (e.g., the remaining amount of toner) and the usage amount of the image carrier provided in the image forming apparatus (e.g., the remaining amount of the drum).

[0073] [Point 14] The second correction unit 319 functions as a creating unit that creates or updates density correction data (e.g., LUT 330) that is the standard for density correction processing based on the densities of multiple images estimated by the estimating unit. According to the first and second embodiments, it becomes possible to transmit the designation of the density required to create or update the density correction data between multiple control units. As a result, it becomes possible to create or update the density correction data more accurately than before.

[0074] [Point 15] The density correction data may be a lookup table (e.g., LUT 330) that converts the gradation characteristics of the image signal. As described above, the LUT 330 holds the relationship between the tone level and the image density, and is used for gradation correction (image density correction).

[0075] [Points 16, 17] As can be understood from the first correction unit 318 and the second correction unit 319, the first control means (e.g., video controller 202) may have an accuracy priority mode and a resource saving mode. The accuracy priority mode is a mode in which density correction data is updated or created based on the detection result of a test image formed on an image carrier or a recording medium provided in the image forming means. The resource saving mode is a mode in which density correction data is updated or created based on the estimation result of the estimation means without forming a test image. The resource saving mode may be executed more frequently than the accuracy priority mode. This saves resources such as toner.

[0076] [Point 18] 4, the memory 209 may function as a second storage means for storing the correspondence between the tone level, the parameters, and the image density (e.g., the estimation table 411). The estimation unit 404 may read out the image density corresponding to the tone level specified by the designation information and the parameters acquired by the acquisition means from the second storage means.

[0077] [Point 19] a first control means for performing density correction processing on image data to generate an image signal; an image forming means for forming an image on a recording medium based on an image signal; A second control means for controlling the image forming means, The second control means is An acquisition means for acquiring parameters related to an image forming apparatus; An estimation means for estimating densities of N images that may be required by the first control means based on the parameters acquired by the acquisition means; The first control means is a selection means for selecting M image densities that are actually required from the N image densities estimated by the estimation means. An image forming apparatus comprising:

[0078] [Point 20] a first control means for performing density correction processing on image data to generate an image signal; an image forming means for forming an image on a recording medium based on an image signal; A second control means for controlling the image forming means, The second control means is An acquisition means for acquiring parameters related to an image forming apparatus; A transmission means for transmitting the parameters acquired by the acquisition means to the first control means, The first control means is A receiving means for receiving the parameters acquired by the acquiring means; and estimating means for estimating densities of a plurality of images based on the parameters acquired by the receiving means.

[0079] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0080] 202: video controller, 1: image forming unit, 203: engine controller

Claims

1. a first control means for performing density correction processing on image data to generate an image signal; an image forming means for forming an image on a recording medium based on the image signal; A second control means for controlling the image forming means, The first control means a designation unit that transmits designation information regarding the density correction process to the second control unit; The second control means An acquisition means for acquiring parameters related to an image forming apparatus; an estimation means for estimating densities of a plurality of images corresponding to tone levels specified by the designation information transmitted from the first control means based on the parameters acquired by the acquisition means, and transmitting the densities to the first control means; The image forming apparatus according to the present invention, wherein the first control means has a creating means for creating or updating density correction data serving as a reference for the density correction process based on the densities of the plurality of images estimated by the estimating means.

2. The designation information includes the tone level itself, 2. The image forming apparatus according to claim 1, wherein the estimation means estimates a density corresponding to the tone level included in the specification information.

3. The designation information includes identification information of the tone level, 3. The image forming apparatus according to claim 2, wherein the estimation means estimates a density corresponding to a tone level specified by the identification information included in the specification information.

4. The designation information includes a tone level and a total number of the tone levels; 2. The image forming apparatus according to claim 1, wherein the second control means determines whether or not all of the tone levels required by the estimation means have been received from the first control means based on the total number of tone levels.

5. The designation information is A first tone level; A second tone level; and and coefficients used by the calculation to identify tone levels lying between the first tone level and the second tone level; 2. The image forming apparatus according to claim 1, wherein the second control means specifies a plurality of tone levels based on the first tone level, the second tone level and the coefficient.

6. 6. An image forming apparatus according to claim 5, wherein said coefficient is a distance between two adjacent tone levels among three or more tone levels required by said estimation means.

7. 7. An image forming apparatus according to claim 6, wherein said coefficient is a total number of said tone levels.

8. The second control means a first storage means for storing a plurality of sets of tone levels each including a plurality of tone levels; The image forming apparatus according to claim 1, characterized in that the second control means identifies a plurality of tone levels required by the estimation means based on a tone level set specified by the designation information, from among the plurality of tone level sets stored in the first storage means.

9. 9. The image forming apparatus according to claim 8, wherein the tone level set is specified by identification information that identifies the type of the first control means, or is specified by a control mode that is applied to the image among a plurality of control modes provided in the image forming apparatus.

10. 10. An image forming apparatus according to claim 1, wherein the parameter is at least one of a detection environment of the image forming apparatus, a high voltage output value used in the image forming apparatus, and a usage amount of consumables constituting the image forming apparatus.

11. 11. The image forming apparatus according to claim 10, wherein the detection environment of the image forming apparatus includes at least one of a temperature, a relative humidity, and an absolute moisture content.

12. 12. The image forming apparatus according to claim 10, wherein the high voltage of the image forming apparatus includes at least one of a charging voltage used to charge an image carrier, a developing voltage used to develop an electrostatic latent image that is the source of the image, and a transfer voltage used to transfer a toner image that is the source of the image to an intermediate transfer body or the recording medium.

13. 13. The image forming apparatus according to claim 10, wherein the usage amount of the consumables includes at least one of a usage amount of a toner and a usage amount of an image carrier provided in the image forming apparatus.

14. 14. The image forming apparatus according to claim 1, wherein the density correction data is a lookup table for converting a gradation characteristic of the image signal.

15. The first control means an accuracy priority mode in which the density correction data is updated or created based on a detection result of a test image formed on an image carrier provided in the image forming means or on the recording medium; a resource saving mode in which the density correction data is updated or generated based on the estimation result of the estimation means without forming the test image; 15. The image forming apparatus according to claim 1, further comprising:

16. 16. The image forming apparatus according to claim 15, wherein the resource saving mode is executed more frequently than the accuracy priority mode.

17. Further comprising a second storage means for storing a correspondence relationship between the tone level, the parameter, and the density of the image; An image forming apparatus according to any one of claims 1 to 16, characterized in that the estimation means reads out from the second storage means an image density corresponding to a tone level specified by the specified information and the parameters acquired by the acquisition means.

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