Image forming apparatus

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 Art

[0002] Image density (tone characteristics) exists as one measure of the image quality formed by an image forming apparatus. In Patent Document 1, a first tone correction for forming a patch image and correcting the tone, and a second tone correction for correcting the tone without forming a patch image are proposed. In Patent Document 2, a method for obtaining a lookup table for a wide color gamut printing mode in an image forming apparatus having a normal print mode and a wide color gamut print mode is proposed. Such a lookup table may also be referred to as a tone correction table or a density correction table.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in an image forming apparatus, there may be a first controller that performs tone correction using a lookup table, and a second controller that controls an image forming engine. When there are a plurality of lookup tables for tone correction according to the control mode or image processing mode of the image forming apparatus, the density (estimated result) required for each lookup table is different. That is, a method for the second controller to appropriately assist the first controller in obtaining the required density is needed. Therefore, an object of the present invention is to obtain the required density in an image forming apparatus having a plurality of control means. [Means for solving the problem]

[0005] The present invention, for example, An image forming apparatus, A first control means that generates an image signal by performing density correction processing on image data, Image forming means for forming an image on a recording medium based on the aforementioned image signal, It includes a second control means for controlling the image forming means, The second control means is The aforementioned A means for acquiring parameters related to an image forming apparatus, Each of the N tone levels used in the density correction process by the first control means corresponds to N pieces of An estimation means for estimating the concentration based on the parameters obtained by the acquisition means, It has, The first control means is the N number estimated by the estimation means of Of the concentrations Select M concentrations (where N and M are integers) to be used to create or update concentration correction data, and the selected M pieces of concentration The invention is characterized by having a creation means for creating or updating the concentration correction data that serves as the basis for the concentration correction process. To provide an image forming apparatus. [Effects of the Invention]

[0006] According to the present invention, in an image forming apparatus with multiple control means, the required density can be obtained. [Brief explanation of the drawing]

[0007] [Figure 1] Diagram illustrating an image forming apparatus. [Figure 2] Diagram explaining the controller [Figure 3] Diagram illustrating the video controller. [Figure 4] Diagram explaining the engine controller [Figure 5] A diagram illustrating the relationship between test images and density. [Figure 6] Diagram illustrating the method for estimating the concentration. [Figure 7] Diagram explaining how to specify tone levels. [Figure 8] Flowchart showing the concentration estimation method [Figure 9] Diagram explaining the method of specifying the tone level [Figure 10] Diagram explaining the method of specifying the tone level [Figure 11] Diagram explaining the method of specifying the tone level [Figure 12] Flowchart showing the 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

Mode for Carrying Out the Invention

[0008] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiments, not all of these plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the accompanying drawings, the same or similar configurations are denoted by the same reference numerals, and redundant explanations are omitted.

[0009] <Example 1> ●Image forming apparatus As shown in FIG. 1, the image forming apparatus 100 is a printer, a copier, or a 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. At the end of the reference numerals shown in FIG. 1, Y (yellow), M (magenta), C (cyan), and K (black) indicating the color of the toner are assigned. The characters YMCK are omitted when matters common to the four colors are described.

[0010] The image forming unit 1 superimposes the YMCK toner images to form a full-color image on the sheet P. The photoreceptor drum 5 is an image carrier that rotates while carrying an electrostatic latent image or toner image. The charger 6 uniformly charges the surface of the photoreceptor drum 5 using a charging voltage. The exposure device 10 irradiates the photoreceptor drum 5 with light corresponding to the image signal to form an electrostatic latent image on the surface of the photoreceptor drum 5. The developing roller 9 of the developer unit 8 uses a developing voltage to deposit toner onto the electrostatic latent image, forming a toner image. The primary transfer roller 4 uses a primary transfer voltage to transfer the toner image from the photoreceptor drum 5 to the intermediate transfer belt 12. Here, the YMCK toner images are transferred sequentially 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 also be a transport belt that carries and transports the sheet P. In this case, the toner image 71 is transferred from the photoreceptor drum 5 to the sheet P. The photoreceptor drum 5, charger 6, and developer 8 may be integrated into a single cartridge 7.

[0011] The sheet cassette 21 can accommodate multiple sheets P. The pickup roller 22 feeds the sheets P one by one from the sheet cassette 21 toward the transport path 23. The transport roller 24 transports the sheets P along the transport path 23 and passes them to the register roller 25. The register roller 25 transports the sheets P along the transport path 23 and passes them to the secondary transfer section. The secondary transfer roller 26, located in the secondary transfer section, transfers the toner image 71, which has been transported by the intermediate transfer belt 12, to the sheets P. A secondary transfer voltage is applied to the secondary transfer roller 26 to facilitate the transfer of the toner image 71. The fuser unit 27 fixes the toner image to the sheets P by applying heat and pressure to the toner image and the sheets P. The paper discharge roller 28 discharges the sheets P into 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 supported on the intermediate transfer belt 12. The density measurement results are used for density adjustment of the toner image (e.g., gradation correction). The temperature sensor 32a measures the internal temperature of the image forming apparatus 100. The humidity sensor 33 measures the internal humidity of the image forming apparatus 100. The temperature sensor 32a and the humidity sensor 33 are located in close proximity and may, for example, be housed in a single enclosure. The temperature sensor 32b measures the ambient temperature around the cartridge 7. These temperature and humidity values ​​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 Figure 2, the image forming apparatus 100 is equipped with 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 print commands from the host computer 201 via a communication line 204. The video controller 202 may also 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 the 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 commands to the engine controller 203 that correspond to the commands received from the host computer 201.

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

[0015] The drive circuit 215a drives the laser 75 of the exposure apparatus 10 according to the video signal 206 input from the video controller 202 via the I / O port 213. The drive circuit 215b drives the scanner 76, which rotates a rotating polyhedron mirror according to instructions from the CPU 208. The scanner 76 includes a motor, etc. The drive circuit 215c drives the motor M1 according to instructions 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 transport roller 24, the resist roller 25, the secondary transfer roller 26, the photoreceptor drum 5, and the intermediate transfer belt 12. Multiple motors may be provided as motor M1. The pickup roller 22 may be driven by a solenoid or the like.

[0016] Input circuit 217a includes a circuit that amplifies the detection signal output by the density sensor 30, which detects the density of the toner image 71. Input circuit 217a reports the density detection result (measured value) to the CPU 208 via I / O port 213. Input circuit 217b includes a circuit that amplifies and outputs the detection signals from temperature sensors 32a and 32b and the detection signal from humidity sensor 33. Input circuit 217b reports the temperature and humidity detection results (measured values) to the CPU 208 via I / O port 213. Hereinafter, the density detection result and density estimation result may be denoted as density ΔE. The CPU 208 transmits density ΔE to the video controller 202 via communication circuit 211.

[0017] The high-voltage power supply 216 is a power supply circuit that generates high voltages such as charging voltage, developing voltage, primary transfer voltage, and secondary transfer voltage according to instructions 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 Figure 3 shows the functions of the video controller 202. The CPU 308 communicates with the host computer 201 via the communication circuit 301. The CPU 308 communicates with the engine controller 203 via the communication circuit 321. The CPU 308 implements various functions by executing control programs stored in the ROM area of ​​the memory 309. The memory 309 includes storage devices such as ROM and RAM.

[0019] RIP311 is a raster image processor that converts image data expressed in PostScript or other languages ​​into bitmap image data. The color space conversion unit 312 converts the color space of the image data input from RIP311 (e.g., RGB) to the toner color space (e.g., YMCK). The gradation correction unit 313 corrects the gradation characteristics of the image data using a lookup table (LUT330) held in memory 309. This ensures that the gradation characteristics of the original image match those of the image formed on the sheet P. The LUT330 is corrected according to the state of the image forming apparatus 100 (e.g., installation environment, degree of wear of parts) to maintain gradation reproducibility.

[0020] The mode selection unit 315 selects the operating mode of the image forming apparatus 100. The CPU 308 has multiple operating modes, for example, depending on the type of sheet P (plain paper, coated paper, thick paper, thin paper, recycled paper, etc.). The mode selection unit 315 selects the appropriate operating mode according to the type of sheet P. The LUT selection unit 316 selects a LUT 330 suitable for the operating mode selected by the mode selection unit 315 and sets it in the gradation correction unit 313. The LUT 330 and the operating mode may be associated and stored in the memory 209. The start determination unit 317 determines whether the start conditions for starting the correction processing of the LUT 330 are met. The start conditions are stored in the memory 309 and are defined based on one or more of the following, for example, the number of images to be formed, environmental parameters (e.g., temperature, humidity), and the period during which the image forming apparatus 100 was in a dormant state.

[0021] The first correction unit 318 corrects the LUT 330 based on measured values ​​obtained by detecting the density of the test image actually formed on the intermediate transfer belt 12 using the density sensor 30. The first correction unit 318 outputs the video signal 206 of the test image to the engine controller 203, or updates or creates the LUT 330 based on the measured density values.

[0022] The second correction unit 319 corrects (updates or creates) the LUT 330 based on estimated density values ​​acquired without forming a test image. Since the second correction unit 319 does not form a test image, toner can be saved. On the other hand, the first correction unit 318 uses measured values, resulting in higher correction accuracy for the LUT 330.

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

[0024] ● Engine controller functions Figure 4 shows the functions implemented by the CPU 208 of the engine controller 203. The measurement unit 401 acquires the measurement results (detection results) of the test image from the density sensor 30, performs calculations, and reports them to the video controller 202 via the communication circuit 211. The test image may also be called a patch image or pattern image. The acquisition unit 402 acquires parameters that affect the image density of the toner image. Such parameters include, for example, environmental parameters, control parameters, and state parameters. Environmental parameters include, for example, the temperature detected by temperature sensors 32a and 32b, the relative humidity detected by the humidity sensor 33, and the absolute moisture content obtained from the detection results of the temperature sensor 32a and the humidity sensor 33. Control parameters include, for example, the charging voltage, developing voltage, primary transfer voltage, and secondary transfer voltage. State parameters include, for example, the remaining amount of toner contained in the developer unit 8, and the remaining amount on the surface of the photoreceptor drum 5 (drum remaining amount). The consumption monitoring unit 405 monitors the remaining amount of toner and the remaining amount of toner on the surface of the photoreceptor drum 5. The consumption monitoring unit 405 may acquire the remaining amount of toner using a remaining amount sensor (not shown), or it may determine the amount of toner used from image data and acquire the remaining amount based on the amount used. The consumption monitoring unit 405 may also acquire the remaining amount of toner on the surface based on the rotation distance of the photoreceptor drum 5. The rotation distance may be acquired based on the time the photoreceptor drum 5 has been rotating and the rotation speed (peripheral speed) of the photoreceptor drum 5.

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

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

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

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

[0029] When the first correction unit 318 starts correcting the LUT 330, it sends a command to the engine controller 203 to instruct it to detect (measure) the test images 501a to 501d. The first correction unit 318 then starts outputting a 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 test images 501a to 501d on the intermediate transfer belt 12. Furthermore, the measurement unit 401 controls the density sensor 30 to read the test images 501a to 501d and obtains the measured density values ​​(density ΔE) of the test images 501a to 501d. Finally, the measurement unit 401 transmits the density ΔE of the test images 501a to 501d to the video controller 202.

[0031] The first correction unit 318 of the video controller 202 creates a LUT 330 based on the respective densities ΔE of the test images 501a to 501d. Here, since the first correction unit 318 generates the video signal 206 to form 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 Figure 5(B), the first correction unit 318 creates the LUT 330 by mapping the tone levels Ta to Td with 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 concentration values As already explained, 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 no test image is formed, the engine controller 203 cannot determine which tone level's 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 specified N tone levels in the estimation unit 404. The estimation unit 404 estimates N densities corresponding to the specified N tone levels based on the parameters acquired by the acquisition unit 402 and the consumption 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 also transmit the specified tone level T and the estimated densities ΔE as pairs 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 densities 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, correcting the LUT330 using estimated density values ​​reduces toner consumption. Downtime is also reduced. Downtime refers to the period during which user images cannot be formed due to the formation of test images. User images are images formed on sheet P according to instructions from the host computer 201 (i.e., according to the user's wishes).

[0035] Figure 6(A) 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 / m³). m³ represents cubic meters. The control parameters are charging voltage (e.g., -1000V), developing voltage (e.g., -500V), and primary transfer voltage (e.g., 300V). The state parameters are toner level (e.g., 40%) and drum level (e.g., 35%). The estimation unit 404 estimates the density ΔE using these parameters, along with the tone level and estimation table 411.

[0036] Figure 6(B) shows the LUT330 created based on the estimated concentration E and the specified tone level T. The curve of LUT330 changes depending on the parameters shown in Figure 6(A). LUT330a is determined based on the parameters shown in Figure 6(A). If the environmental parameter among the parameters shown in Figure 6(A) changes to low temperature and low humidity, LUT330b is obtained. If the charging voltage among the parameters shown in Figure 6(A) changes in the negative direction (e.g., charging voltage = -1200V), LUT330c is obtained.

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

[0038] According to LUT330a in Figure 6(B), when the tone level is 60h, the density ΔE is 50 (32h). According to LUT330b, when the tone level is 60h, the density ΔE is 55 (37h). According to LUT330c, when the tone level is 60h, the density ΔE is 43 (2Bh).

[0039] Furthermore, according to LUT330a, when the tone level is A0h, the density ΔE is 130 (82h). According to LUT330b, when the tone level is A0h, the density ΔE is 137 (89h). According to LUT330c, when the tone level is A0h, the density ΔE is 120 (78h). Thus, even at the same tone level, the density ΔE will differ if the parameters are different.

[0040] ● How to specify tone level To stabilize density across a wide range of tonal gradations, the video controller 202 specifies multiple tone levels spanning a wide range. To reduce the number of specified tone levels, the intervals between these multiple tone levels may be wider. On the other hand, to stabilize density in the midtones of an image, the video controller 202 specifies multiple tone levels within a narrow range, namely the midtone region. In other words, the intervals between these multiple tone levels become narrower.

[0041] Thus, the position and total number of tone levels required to create the LUT 330 differ depending on the operating mode of the video controller 202. Therefore, the video controller 202 specifies to the engine controller 203 the tone level corresponding to the density ΔE to be estimated.

[0042] Figure 7(A) shows the tone levels and the total number of tone levels N required to create LUT330 for printing images on plain paper. The total number of tone levels 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 help stabilize density over a relatively wide range of tonal gradations.

[0043] Figure 7(B) shows the tone levels and the total number of tone levels N required to create LUT330 for the mode of printing an image on gloss paper. The total number of tone levels 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 stabilize the density in the midtone range.

[0044] Comparing Figure 7(B) and Figure 7(A), we see that the minimum and maximum values ​​of the specified tone levels, as well as the interval between two adjacent tone levels, are different. In Figure 7(A), the difference between the minimum and maximum values ​​of the tone levels is large, resulting in a wide range of specified tone levels. The interval between two adjacent tone levels is 30h, which is relatively wide. In Figure 7(B), the difference between the minimum and maximum values ​​of the tone levels is small, resulting in a narrow range of specified tone levels. The interval between two adjacent tone levels is 20h, which is relatively narrow.

[0045] Figure 7(C) shows the tone levels required for LUT330 in a mode where the user can provide detailed color adjustment instructions, and the total number of tone levels N. 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 across a wide range at narrow intervals (10h in this example), the image density is stabilized across the entire tonal range.

[0046] Incidentally, the tone levels used in LUT correction based on measured values ​​and the tone levels used in LUT correction based on estimated values ​​may or may not match. Also, both the total number of tone levels N and N tone levels may be specified, or only N tone levels may be specified.

[0047] ●Flowchart Figure 8 is a flowchart showing the density estimation method performed by the CPU 208 of the engine controller 203. When the image forming apparatus 100 is powered by the commercial power supply and starts up, the CPU 208 performs the following processes according to the control program.

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

[0049] In S804, the CPU 208 determines whether the conditions for starting density estimation have been met. The conditions for starting density estimation may be, for example, every predetermined time, every predetermined number of image formations, or when the amount of change in environmental parameters exceeds a threshold. Alternatively, the conditions for starting density estimation may be when a start command is received from the video controller 202. In this case, the CPU 208 may report to the video controller 202 the information necessary for determining the conditions for starting density estimation, such as the number of image formations or environmental parameters. Based on this, the start determination unit 317 of the video controller 202 determines whether the conditions for starting density estimation have been met and sends a command based on the determination result. If the conditions for starting density estimation have been met, the CPU 208 proceeds to S805.

[0050] In S805, the CPU 208 (acquisition unit 402) acquires the 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 parameters. In S807, the CPU 208 (estimation unit 404) transmits the estimated density ΔE corresponding to the specified tone level to the video controller 202.

[0051] Figure 8 shows that the total number of tone levels N and the tone levels are received, but as shown in Figures 9(A) and 9(C), the tone level number and tone level may be received as a pair. Alternatively, as shown in Figures 10(A) and 10(B), the start value of the tone level (the minimum value among the specified tone levels), the end value (the maximum value among the specified tone levels), and the tone level interval may be specified.

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

[0053] In Figure 8, the tone level is specified immediately after the video controller 202 starts up, but this is just one example. The video controller 202 may also specify the tone level at the time the engine controller 203 performs density estimation.

[0054] <Example 2> Multiple image forming machines sold as different products in the market may be equipped with a common (identical) engine controller 203. On the other hand, these multiple image forming machines may each be equipped with different video controllers 202. Some video controllers 202 provide many functions to the image forming machine 100, while others provide fewer functions. For example, the market includes SFPs (single-function printers) that only have printing functions, and MFPs (multi-function printers) that have printing and image reading functions. It can be imagined that the video controller 202 for SFPs and the video controller 202 for MFPs are different. Because these different video controllers 202 have different image density processing, the method of creating LUTs 330 will also differ. Different image density processing means that the appropriate LUT 330 will also differ. Therefore, the video controller 202 must specify the tone level required to create the appropriate LUT 330 to the engine controller 203.

[0055] In Example 2, the tone levels that can be specified by the video controller 202 are pre-stored in the engine controller 203 for each type of video controller 202. The tone setting unit 403 of the engine controller 203 obtains the 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 the type information. In this case, the tone setting unit 403 uses the default tone level stored in the memory 209.

[0056] Figure 11 shows the tone level sets held in memories 209 and 309. When the 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 the type information is 02, the type of video controller 202 is II, and four tone levels (40h, 60h, 80h, A0h) are specified. When the 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. The CPU 308 (tone specification unit 320) transmits the type information to the CPU 208 (tone setting unit 403), allowing the CPU 208 (tone setting unit 403) to read the tone levels corresponding to the type information from memory 209.

[0057] Figure 12 is a flowchart showing the concentration estimation performed by the CPU 208 of the engine controller 203. Explanations of matters common to those described in Figure 8 are omitted. More specifically, S804 to S807, which are performed after S1202 and S1204, are as described in Example 1.

[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 S1202. In S1202, the CPU 208 (tone setting unit 403) obtains the tone level corresponding to the type information from the memory 209 and sets it in the estimation unit 404. On the other hand, if type information has not been received in S1201, the CPU 208 proceeds to S1203.

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

[0060] In this way, a tone level set having multiple tone levels is identified based on the designation information (type information) transmitted from the video controller 202. In Example 2, the tone level set is identified based on the type information of the video controller 202, but this is only one example. For example, if the video controller 202 has multiple image density processing functions, identification information for the tone level set may be transmitted instead of the type information. This may allow an appropriate tone level to be set for each image density processing function. The identification information only needs to be able to identify the tone level set, and may also be identification information for the image density processing function associated with the tone level set.

[0061] <Example 3> In Examples 1 and 2, the engine controller 203 identifies which tone level density should be estimated based on the specified information transmitted from the video controller 202. However, it is not mandatory for the video controller 202 to transmit the specified 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 specified information. The video controller 202 may then select and use the density that is actually needed from among the density values ​​received from the engine controller 203.

[0062] Figure 13 shows the video controller 202 of Embodiment 3. Figure 14 shows the engine controller 203 of Embodiment 3. The same reference numerals are used for the components described in Embodiments 1 and 2, and their descriptions are incorporated herein by reference.

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

[0064] As shown in Figure 14, the memory 209 stores tone information 1400. The tone information 1400 contains, for example, N densities that may be needed by the second correction unit 319, and holds N tone levels corresponding to each of the N densities. The tone setting unit 403 reads the tone information 1400 from the memory 209, obtains the N tone levels contained in the tone information 1400, and sets them in the estimation unit 404. As described above, the estimation unit 404 estimates the N densities corresponding to the N tone levels based on the parameters obtained 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 also transmit the estimated densities and identification information indicating the tone level as a pair to the video controller 202. This will allow the video controller 202 to easily identify which estimated densities correspond to which tone levels. Thus, in Example 3, the video controller 202 can acquire the N required concentrations in the second correction unit 319 without using specified information.

[0065] <Example 4> In Examples 1 to 3, 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 becomes unnecessary to transmit specification information from the video controller 202 to the engine controller 203.

[0066] Figure 15 shows the video controller 202 of Embodiment 4. Figure 16 shows the engine controller 203 of Embodiment 4. The same reference numerals are used for the components described in Embodiments 1 and 2, and their descriptions are incorporated herein by reference.

[0067] As shown in Figure 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 the image density corresponding to the tone level specified by the tone specification unit 320 based on the received parameters. The estimation unit 404 passes the estimated image density to the second correction unit 319.

[0068] As shown in Figure 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 Embodiment 4, the image density can be estimated without transmitting specified information from the video controller 202 to the engine controller 203.

[0069] <Summary> [Perspective 1] The video controller 202 is an example of a first control means that generates an image signal by applying density correction processing to image data. The image forming unit 1 is an example of an image forming means that forms an image on a recording medium based on the image signal. The engine controller 203 is an example of a second control means that controls the image forming means. The tone specification unit 320 is an example of a specification means that specifies the density of a plurality of images to be estimated by the estimation means to the second control means. The tone specification unit 320 functions as a specification means that transmits specification information that can identify the tone level to the second control means. The tone specification unit 320 may also function as a specification means that transmits specification information related to density correction processing to the second control means. The CPU 208 and acquisition unit 402 function as acquisition means that acquire parameters related to the image forming apparatus (e.g., parameters that affect the density of an image). The CPU 208 and estimation unit 404 function as estimation means that estimate the density of a plurality of different images based on the parameters acquired by the acquisition means. The CPU 208 and estimation unit 404 may estimate the density of a plurality of different images, which corresponds to the tone level identified by the specification information transmitted from the first control means, based on the parameters acquired by the acquisition means. The estimation unit 404 may transmit the estimated density of multiple images to the first control means (video controller 202). This allows for the efficient acquisition of the required density in an image forming apparatus with multiple control means.

[0070] [Perspectives 2-4] The second control means (e.g., engine controller 203) may identify the density of 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 density corresponding to the tone levels included in the designation information. The second control means (e.g., engine controller 203) may identify the density of multiple images to be estimated based on the tone level identification information (e.g., tone level number) transmitted from the first control means. In other words, the designation information may include tone level identification information. The estimation unit 404 estimates the density corresponding to the tone levels identified by the identification information included in the designation information. The second control means (e.g., engine controller 203) may identify the density of 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 such tone levels. The designation information may include the tone levels and the total number of such tone levels. The CPU 208 may determine whether all the tone levels required by the estimation means have been received from the first control means based on the total number of tone levels. [Perspectives 5, 6] A second control means (e.g., engine controller 203) may identify the density of multiple images to be estimated based on information transmitted from the first control means (e.g., video controller 202). For example, the density of multiple images to be estimated may be identified 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). In other words, the second control means (e.g., CPU 208) may identify multiple tone levels based on the first tone level, the second tone level, and the coefficient. Here, the coefficient is used in a calculation to identify the tone levels present between the first and second tone levels. 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 density 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 identify the remaining tone levels.

[0071] [Perspectives 8, 9] As described in Example 2, the memory 209 functions as a storage means for storing multiple tone level sets, each containing a tone level that specifies the density of an image to be estimated. The memory 209 may also function as a storage means for storing multiple tone level sets, each containing multiple tone levels. The second control means may identify the densities of multiple images to be estimated based on the tone level set specified by the first control means from among the multiple tone level sets stored in the storage means. In other words, the second control means may identify the multiple tone levels required by the estimation means based on the tone level set specified by the specification information from among the multiple tone level sets stored in the storage means. The tone level set may be specified, for example, by identification information (e.g., type information) that identifies the type of the first control means. The tone level set may also be specified by the control mode applied to the image from among the multiple control modes provided by the image forming apparatus 100. In this case, the control mode identification information and the tone level set are linked in the memory 209.

[0072] [Perspectives 10-13] The parameters include the sensing environment of the image forming apparatus (which may also be called the internal environment), which may be at least one of the following: the output value of the high voltage used in the image forming apparatus, and the amount of consumables used in the image forming apparatus. The sensing environment of the image forming apparatus includes at least one of temperature, relative humidity, and absolute moisture content. The high voltage of the image forming apparatus may be the charging voltage used to charge the image carrier. The high voltage of the image forming apparatus may be the developing voltage used to develop the electrostatic latent image that will become the image. The high voltage of the image forming apparatus may be the transfer voltage used to transfer the toner image that will become the image to an intermediate transfer medium or recording medium. The amount of consumables used includes at least one of the following: the amount of toner used (e.g., remaining toner) and the amount of image carriers used in the image forming apparatus (e.g., remaining drum).

[0073] [Perspective 14] The second correction unit 319 functions as a creation means for creating or updating density correction data (e.g., LUT 330) that serves as a reference for density correction processing, based on the densities of multiple images estimated by the estimation means. According to Examples 1 and 2, it becomes possible to transmit the specification of densities necessary for creating or updating density correction data between multiple control means. As a result, it becomes possible to create or update density correction data more accurately than in the conventional method.

[0074] [Perspective 15] Density correction data may also be a lookup table (e.g., LUT330) that converts the tonal characteristics of the image signal. As mentioned above, LUT330 maintains the relationship between tone level and image density and is used for tonal correction (image density correction).

[0075] [Perspectives 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 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 frequency of execution of the resource saving mode may be higher than the frequency of execution of the accuracy priority mode. This saves resources such as toner.

[0076] [Perspective 18] As illustrated in Figure 4, the memory 209 may function as a second storage means that holds the correspondence between tone levels, parameters, and image density (e.g., estimation table 411). The estimation unit 404 may read the image density corresponding to the tone level specified by the specified information and the parameters acquired by the acquisition means from the second storage means.

[0077] [Perspective 19] A first control means that generates an image signal by performing density correction processing on image data, Image forming means for forming an image on a recording medium based on an image signal, It includes a second control means for controlling the image forming means, The second control means is, A means for acquiring parameters related to an image forming apparatus, An estimation means estimates the concentrations of N images that may be required by the first control means, based on parameters obtained by the acquisition means, The first control means is a selection means that selects the concentrations of M images that are actually needed from the concentrations of N images estimated by the estimation means. An image forming apparatus characterized by having the following features.

[0078] [perspective 20] A first control means that generates an image signal by performing density correction processing on image data, Image forming means for forming an image on a recording medium based on an image signal, It includes a second control means for controlling the image forming means, The second control means is, A means for acquiring parameters related to an image forming apparatus, It includes a transmission means for transmitting parameters acquired by an acquisition means to a first control means, The first control means is, A receiving means that receives parameters acquired by the acquisition means, An image forming apparatus characterized by having an estimation means for estimating the density of multiple images based on parameters acquired by a receiving means.

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

[0080] 202: Video controller, 1: Image forming unit, 203: Engine controller

Claims

1. An image forming apparatus, A first control means that generates an image signal by performing density correction processing on image data, Image forming means for forming an image on a recording medium based on the aforementioned image signal, It includes a second control means for controlling the image forming means, The second control means is An acquisition means for acquiring parameters related to the image forming apparatus, The system includes an estimation means that estimates N concentrations corresponding to N tone levels used in the concentration correction process by the first control means, based on the parameters acquired by the acquisition means, The image forming apparatus is characterized in that the first control means selects M concentrations (N and M are integers) from the N concentrations estimated by the estimation means to be used to create or update concentration correction data, and creates or updates the concentration correction data which serves as the basis for the concentration correction process based on the selected M concentrations.

2. The image forming apparatus according to claim 1, wherein the parameters include environmental parameters based on the environment of the image forming apparatus, control parameters used to control the image forming apparatus, or state parameters indicating the state of consumable members of the image forming apparatus.

3. The image forming apparatus according to claim 1 or 2, wherein, when obtaining M concentrations from the N concentrations estimated by the estimation means, if N is less than M, the first control means obtains the missing M-N concentrations from the M concentrations by interpolation calculation based on at least two concentrations from the N concentrations.

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