JP2020204702A - Image forming apparatus - Google Patents

Abstract

To provide a technology to accurately determine the consumption of developer on the basis of a corrected image signal.SOLUTION: An image forming apparatus comprises: means that, on the basis of gradation value correction information according to the position in a main scanning direction of a photoreceptor, corrects the gradation values of pixels of first image data according to the positions of pixels in the photoreceptor to output second image data; means that generates an image signal according to a clock frequency on the basis of the second image data; means that scans the photoreceptor with light that is emitted from a light source and the scan speed of which changes according to the position in the main scan direction to form a latent image; means that controls the clock frequency according to the position of the photoreceptor being scanned; and counting means that, when the image signal has a value to turn on the light source at a count timing according to a count frequency, increases a count value. The counting means controls the amount of increase in the count value according to the position of the photoreceptor being scanned.SELECTED DRAWING: Figure 15

Description

The present invention relates to a technique for predicting the consumption of a developer in an image forming apparatus.

The electrophotographic image forming apparatus has an optical scanning apparatus for exposing the photoconductor. The optical scanning apparatus scans and exposes the photoconductor by emitting a light beam based on image data, reflecting the emitted light beam with a rotating multifaceted mirror, and transmitting the emitted light beam through a scanning lens having fθ characteristics. The fθ characteristic is an optical characteristic in which the scanning speed of the photoconductor by the light beam becomes constant when the rotating multifaceted mirror is rotated at a uniform angular velocity. However, scanning lenses having fθ characteristics are expensive and large in size. Therefore, it is considered that the scanning lens itself is not used, or a scanning lens having no fθ characteristic is used.

Patent Document 1 discloses a configuration in which the clock frequency is changed so that the pixel width formed on the photoconductor is constant even when the scanning speed of the photoconductor by the light beam is not constant. In Patent Document 2, the gradation value (pixel value) of each pixel indicated by the image data is corrected according to the image height, and halftone processing is performed based on the corrected gradation value, so that the exposure is caused by fluctuations in scanning speed. It discloses a configuration that suppresses the amount of exposure per unit area of the body from changing according to the image height. Patent Document 3 discloses a configuration in which the consumption amount of a developer is estimated by counting the number of on (pixel count) of an image signal that controls the on / off of a light source of an optical scanning apparatus.

Japanese Unexamined Patent Publication No. 58-125064 JP-A-2017-209965 Japanese Patent No. 4822578

Here, when using an optical scanning apparatus in which the scanning speed is not constant, in order to suppress a change in the exposure amount per unit area of the photoconductor due to the image height, the gradation value is set as disclosed in Patent Document 2. It shall be corrected according to the image height. In this case, even if the exposure amount is the same, the corrected gradation values of the pixels having different image heights are different. Therefore, the image signal (signal for turning on / off the light source) generated by halftone processing the corrected gradation value also differs depending on the image height. This means that even if the exposure amount of the pixels is the same, the pixel count value differs depending on the image height. On the other hand, the amount of developer consumed correlates with the amount of exposure per unit area of the photoconductor. Therefore, in this case, the amount of developer consumed cannot be determined based on the pixel count value.

The present invention provides a technique for accurately determining the consumption amount of a developer based on a corrected image signal.

According to one aspect of the present invention, the image forming apparatus determines the gradation value of each pixel of the first image data based on the photoconductor and the correction information of the gradation value according to the position of the photoconductor in the main scanning direction. A density correction means that corrects according to the pixel position in the main scanning direction of the photoconductor and outputs the second image data, a generation means that generates an image signal according to the clock frequency based on the second image data, and the image. It has a light source whose blinking is controlled by a signal, and scans the photoconductor in the main scanning direction with light emitted by the light source and whose scanning speed changes according to the position of the photoconductor in the main scanning direction. A scanning means for forming a latent image on the photoconductor, a clock frequency control means for controlling the clock frequency according to the position of the photoconductor being scanned by the scanning means in the main scanning direction, and a counting frequency. When the image signal is a value that turns on the light source at the counting timing according to the above, the counting means includes a counting means for increasing the count value, and the counting means is the main of the photoconductor being scanned by the scanning means. It is characterized in that the increase amount of the count value is controlled according to the position in the scanning direction.

According to the present invention, the consumption amount of the developer can be accurately determined based on the corrected image signal.

The block diagram of the image forming apparatus by one Embodiment. The block diagram of the optical scanning apparatus according to one Embodiment. The figure which shows the relationship between the image height and a partial magnification by one Embodiment. The block diagram of the image signal generation part by one Embodiment. The figure which shows the dither matrix and the position control matrix by one Embodiment. Explanatory drawing of halftone processing by one Embodiment. Explanatory drawing of PWM signal generation by one Embodiment. The figure which shows the relationship between the gradation value and the exposure area by one Embodiment. Explanatory drawing of partial magnification correction and density correction processing by one Embodiment. The figure which shows the exposure pattern of the solid image by one Embodiment. The figure which shows the exposure pattern of the image including the isolated pixel by one Embodiment. The figure which shows the density correction information by one Embodiment. The figure which shows the exposure control composition by one Embodiment. The figure which shows the image data and the VDO signal in a different region by one Embodiment. A flowchart of counting processing according to an embodiment. The figure which shows the 1st correction coefficient of the count value by one Embodiment. A flowchart of counting processing according to an embodiment. The figure which shows the relationship between the partial magnification and the 2nd correction coefficient by one Embodiment.

Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The following embodiments do not limit the invention according to the claims. Although a plurality of features are described in the embodiment, not all of the plurality of features are essential to the invention, and the plurality of features may be arbitrarily combined. Further, in the attached drawings, the same or similar configurations are designated by the same reference numbers, and duplicate description is omitted.

<First Embodiment>
FIG. 1 is a configuration diagram of an image forming apparatus A according to the present embodiment. The image forming apparatus A forms an image on the sheet 10 based on the image data received from the host computer (PC) 500, for example. At the time of image formation, the photoconductor 1 is rotationally driven in the clockwise direction shown in the figure. The charging unit 2 charges the surface of the photoconductor 1 to a uniform potential. The laser driving unit 300 of the optical scanning device 400 scans and exposes the photoconductor 1 with the scanning light 208, and forms an electrostatic latent image on the photoconductor 1. The laser drive unit 300 emits scanning light 208 based on the image signal from the image signal generation unit 100 and the control signal from the control unit 200. The image signal is a pulse width modulation signal (PWM signal), and is a signal for controlling blinking of the light source 401 (FIG. 2) of the optical scanning apparatus 400. In this embodiment, the image signal is also referred to as a VDO signal. The VDO signal is a signal synchronized with the clock signal for the image signal. That is, the cycle of the VDO signal (PWM signal) follows the cycle of the clock signal. The developing unit 5 develops the electrostatic latent image of the photoconductor 1 with toner (developer) to form a toner image (developer image) on the photoconductor 1. The transfer roller 9 transfers the toner image of the photoconductor 1 to the sheet 10 which is fed from the paper feed unit 8 and conveyed to the position facing the photoconductor 1 by the roller 7. The blade 3 of the cleaning unit 4 is not transferred to the sheet 10, and the toner remaining on the photoconductor 1 is removed from the photoconductor 1 and recovered.

After transferring the toner image, the sheet 10 is conveyed to the fixing portion 6. The fixing unit 6 heats and pressurizes the sheet 10 to fix the toner image on the sheet 10. The sheet 10 on which the toner image is fixed is discharged to the outside of the image forming apparatus A by the paper ejection roller 11. The photoconductor 1, the charging unit 2, the cleaning unit 4, and the developing unit 5 are integrally configured as a process cartridge B that can be attached to and detached from the main body of the image forming apparatus A. The process cartridge B is provided with a non-volatile memory 12 in which a count value or the like, which will be described later, is stored.

FIG. 2 is a configuration diagram of the optical scanning device 400 according to the present embodiment. Note that FIG. 2A shows a cross-sectional view in the main scanning direction, and FIG. 2B shows a cross-sectional view in the sub-scanning direction. The scanning light 208 emitted by the light source 401 is shaped into an elliptical shape by the aperture diaphragm 402 and is incident on the coupling lens 403. The scanning light 208 that has passed through the coupling lens 403 is converted into substantially parallel light and incident on the anamorphic lens 404. The substantially parallel light includes weakly convergent light and weakly divergent light. The anamorphic lens 404 has a positive refractive power in the main scanning cross section and converts the incident light flux into convergent light in the main scanning cross section. Further, the anamorphic lens 404 concentrates the luminous flux in the vicinity of the reflecting surface 405a of the deflector 405 in the sub-scanning cross section, and forms a long line image in the main scanning direction.

Then, the scanning light 208 that has passed through the anamorphic lens 404 is reflected by the reflecting surface 405a of the deflector (polygon mirror) 405. The scanning light 208 reflected by the reflecting surface 405a passes through the imaging lens 406 and forms an image on the surface of the photoconductor 1 to form a predetermined spot-like image (hereinafter referred to as a spot). By rotating the deflector 405 in the direction of the arrow Ao at a constant angular velocity by a driving unit (not shown), the spot moves in the main scanning direction on the scanned surface 407 of the photoconductor 1, and is electrostatically charged on the scanned surface 407. A latent image is formed. The main scanning direction is a direction parallel to the rotation axis of the photoconductor 1. Further, the sub-scanning direction corresponds to the circumferential direction of the photoconductor 1 orthogonal to the main scanning direction.

The beam detect (hereinafter referred to as BD) sensor 409 and the BD lens 408 are synchronous optical systems that determine the timing of writing an electrostatic latent image on the scanned surface 407. The scanning light 208 that has passed through the BD lens 408 enters the BD sensor 409 including the photodiode and is detected by the BD sensor 409. The timing of writing the electrostatic latent image on the photoconductor 1 is controlled based on the timing at which the scanning light 208 is detected by the BD sensor 409. The light source 401 of the present embodiment has one light emitting unit, but the light source 401 may include a plurality of light emitting units that can independently control light emission.

As shown in FIG. 2, the imaging lens 406 has two optical surfaces (lens surfaces), an incident surface 406a and an exit surface 406b. In the present embodiment, the imaging lens 406 does not have the so-called fθ characteristic. That is, when the deflector 405 is rotating at a constant angular velocity, the spot does not move at a constant velocity on the surface to be scanned 407. By using the imaging lens 406 having no fθ characteristic, the imaging lens 406 can be arranged close to the deflector 405 (at a position where the distance D1 is small). Further, the imaging lens 406 having no fθ characteristic can have a smaller length (width LW) in the main scanning direction and a length (thickness LT) in the optical axis direction than the imaging lens having the fθ characteristic. Therefore, the size of the optical scanning device 400 can be reduced. Further, in the case of a lens having fθ characteristics, there may be a sharp change in the shape of the entrance surface and the exit surface of the lens when viewed in the main scanning cross section, and if there is such a shape restriction, a good result is obtained. Image performance may not be obtained. On the other hand, the imaging lens 406, which does not have the fθ characteristic, obtains good imaging performance because there is little sharp change in the shape of the incident surface and the exit surface of the lens when viewed in the main scanning cross section. be able to. The imaging lens 406 may be a lens that has fθ characteristics in a part of the main scanning direction and does not have fθ characteristics in other regions.

FIG. 3 shows the relationship between the image height and the partial magnification according to the present embodiment. The image height of 0 means that the spot is on the optical axis of the imaging lens 406, and is hereinafter referred to as the on-axis image height. Further, the image height other than the on-axis image height is hereinafter referred to as an off-axis image height. Further, the maximum value of the absolute value of the image height is called the most off-axis image height. The image height can also be read as the position in the main scanning direction of the photoconductor 1. As shown in FIG. 2A, the position of the most off-axis image height on the scanned surface 407 is W / 2. In FIG. 3, for example, when the partial magnification of the image height is 30%, it means that the scanning speed at the image height is 1.3 times the scanning speed at the image height where the partial magnification is 0%. In the example of FIG. 3, the scanning speed at the axial image height is the lowest, and the larger the absolute value of the image height, the faster the scanning speed. Therefore, if the pixel width in the main scanning direction is determined at a fixed time interval determined by the clock period of the VDO signal (PWM signal), the pixel density will differ between the on-axis image height and the off-axis image height. Therefore, in the present embodiment, partial magnification correction is performed. Specifically, the clock frequency is adjusted according to the image height so that the pixel width becomes substantially constant regardless of the image height.

Further, the time required to scan the unit length of the photoconductor 1 becomes shorter as the partial magnification becomes higher. Therefore, assuming that the emission brightness of the light source 401 is constant, the total exposure amount per unit length decreases as the partial magnification increases. Therefore, in order to obtain good image quality, it is necessary to perform density correction in addition to the above-mentioned partial magnification correction.

FIG. 4 is a configuration diagram of the image signal generation unit 100. The image data from the host computer 500 is stored in the memory 110. In this example, the image data indicates the gradation of each pixel with 8 bits. The density correction processing unit 101z of the image processing unit 101 performs density correction processing on the image data of the memory 110, and outputs the image data (8 bits) after the density correction to the halftone processing unit 101a. The details of the density correction processing will be described later. The halftone processing unit 101a performs halftone processing on the image data after density correction, and outputs image data indicating the gradation of each pixel in 5 bits.

Hereinafter, a line of processing in the halftone processing unit 101a will be described. As shown in FIG. 5A, in the present embodiment, a total of nine pixels a to i, three pixels in the main scanning direction (horizontal direction in the figure) and three pixels in the sub-scanning direction (vertical direction in the figure). Use the configured dither matrix. FIG. 6 shows a level represented by 5 bits and a threshold value applied to image data input to determine the level for each of the pixels a to i in FIG. 5A. The halftone processing unit 101a determines which of the pixels a to i of FIG. 5A corresponds to the pixel of the input image data, and determines the gradation value of the input image data and the gradation value of FIG. The corresponding level is output by comparing with the threshold of the corresponding pixel in the table. The threshold value in the table of FIG. 6 means a range that is equal to or higher than the threshold value and one level is less than the large threshold value. Therefore, for example, when the input gradation value of the pixel a is 151, the halftone processing unit 101a outputs 3 as a level. When there are a plurality of levels having the same threshold range, the halftone processing unit 101a outputs the largest level. Therefore, when the input gradation value of the pixel a is 181 or more, the halftone processing unit 101a outputs 31 as a level.

Returning to FIG. 4, the position control unit 101b adds 2-bit position control data indicating the growth direction to the image data indicating the 5-bit level output by the halftone processing unit 101a to the PWM control unit. Output to 101c. Hereinafter, the details of the processing in the position control unit 101b will be described. FIG. 5B shows the position control matrix in this example. Each square of the position control matrix of FIG. 5 (B) is one pixel, and corresponds to the pixel of the dither matrix of FIG. 5 (A). According to FIG. 5B, "R" is set for the pixels a, d and g, "C" is set for the pixels b, e and h, and "L" is set for the pixels c, f and i. It is set. Note that "R", "C" and "L" are encoded by 2 bits. For example, "R" = "01", "C" = "00", "L" = "10". The position control data indicates the growth direction of the dots in the pixel. Specifically, "R" indicates that dots grow from the right end to the left side of the pixel. Further, "C" indicates that dots grow from the center of the pixel in both the left and right directions. Further, "L" indicates that the dots grow from the left end to the right side of the pixel.

The PWM control unit 101c generates a VDO signal, which is a PWM signal, based on the 7-bit image data to which the position control data is added, and outputs the VDO signal to the laser drive unit 300. FIG. 7 is an explanatory diagram of the generation of the PWM signal by the PWM control unit 101c. The PWM control unit 101c extracts 5 bits indicating the level of one pixel and 2 bits of position control data. Then, the PWM signal shown in FIG. 7 is generated based on the position control data and the level. In the present embodiment, as shown in FIG. 7, when the level is 0 to 17, the high level period (hereinafter, pulse width) of the PWM signal increases as the level increases. In this embodiment, the light source 401 of the optical scanning device 400 emits scanning light 208 while the PWM signal is at a high level. That is, the high level period of the PWM signal indicates the exposed area in the pixel. As shown in FIG. 7, when the position control data is "C", the exposure area is increased in order from the center of the pixel. Similarly, when the position control data is "L", the exposure area is increased in order from the left end of the pixel, and when the position control data is "R", the exposure area is increased in order from the right end of the pixel. The PWM value indicates the pulse width of the PWM signal, and the value 255 means that the entire pixel is exposed. As shown in FIG. 7, when the level exceeds 17, the pulse width decreases from level 18 to level 24 as the level increases. Further, above level 24, the pulse width increases again. As described above, in the present embodiment, the halftone processing unit 101a, the position control unit 101b, and the PWM control unit 101c perform halftone processing on the image data after the density correction processing to determine the exposure area of each pixel. It functions as a generator that generates an image signal.

FIG. 8 is a diagram showing the relationship between the gradation value and the exposure region when all nine pixels in the dither matrix have the same gradation value. The black part in the figure corresponds to the exposed area. From the gradation value 0 to the gradation value 29 of the dither matrix, the exposure area of only the pixel e increases as the gradation value increases. After that, the exposure area of the pixel b increases up to the gradation value 57. After that, the exposure area of the pixel h increases up to the gradation value 86. Further, the exposure areas of the pixels d and f increase up to the gradation value 143. In the gradation value 143, the entire region of the pixels b, d, e, f and h is exposed. On the other hand, up to the gradation value 143, the pixels a, c, g and i remain unexposed.

When the gradation value exceeds 143, the exposure area of the pixels a, c, g and i is increased up to the gradation value 171 but the exposure area of the pixels b, d, e, f and h is decreased. Let me. Since the exposed area as a whole increases, the density increases. At the gradation value 171 all pixels are exposed by the area corresponding to the PWM value 150. After that, as the gradation increases toward the gradation value 255, the exposure area of each pixel increases, and at the gradation value 255, the entire region of all the pixels is exposed.

Subsequently, the density correction processing in the density correction processing unit 101z will be described. As described above, the optical scanning apparatus 400 of the present embodiment has a faster scanning speed of the off-axis image height than the on-axis image height. Therefore, in the present embodiment, the clock speed is adjusted, and partial magnification correction is performed to suppress fluctuations in the width of one pixel in the main scanning direction due to the image height. Specifically, as shown in FIG. 9, the frequency (clock frequency) of the clock signal at the on-axis image height is set to 100%, and the clock frequency is increased toward the off-axis image height. In the optical scanning apparatus 400 according to the present embodiment, since the partial magnification of the outermost image height is 35%, the clock frequency at the outermost image height is set to 135%.

By adjusting the clock frequency as partial magnification correction, fluctuations due to the image height (main scanning position) of the pixel width can be suppressed. However, due to the change in scanning speed, the total exposure amount per unit length varies depending on the image height, and therefore the density varies depending on the image height. In the present embodiment, in order to suppress this density fluctuation, the gradation value of each pixel indicated by the image data is corrected according to the pixel position in the main scanning direction of the pixel photoconductor 1. FIG. 9 shows the gradation values after the density correction processing when the gradation values of all the pixels in the main scanning direction are 255. In the present embodiment, the main scanning direction is divided into seven regions A to G, and correction is performed for each region. In the regions A and G including the off-axis image height, the corrected gradation value remains 255. The corrected gradation value of the regions B and F on the axial image height side of the regions A and G is 228. Further, the corrected gradation value of the regions C and E on the axial image height side of the regions B and F is 200. The corrected gradation value of the region D including the on-axis image height is 171. As described above, in the present embodiment, the gradation value is lowered as the scanning speed becomes slower, based on the out-of-axis image height. As a result, the density fluctuation due to the image height is suppressed. The density correction information for each region used by the density correction processing unit 101z for density correction is obtained in advance based on the exposure sensitivity characteristics of the photoconductor 1 and the development characteristics of the toner, and is stored in the density correction processing unit 101z.

FIG. 10 is an explanatory diagram of an exposure state of an image having a gradation value of 255 for all pixels. Note that FIG. 10 shows the range of nine dither matrices. As shown in FIG. 9, the gradation value after the density correction processing is 255 in the area A, 228 in the area B, 200 in the area C, and 171 in the area D. The areas E, F and G are the same as the areas C, B and A. In the region A, each pixel is exposed with a PWM value of 255. In the region B, some pixels are exposed at a PWM value of 150. In the area C, some pixels are exposed at the PWM value 150, but more pixels than the area B are exposed at the PWM value 150. On the other hand, in the area D, all the pixels are exposed at the PWM value of 150.

FIG. 11 is an explanatory diagram of an exposure state of another image. In the example of FIG. 11, the image data in which the gradation value of the three pixels is 255 and the gradation value of the other pixels is 0 is shown. The position where the gradation value is 255 is as shown in FIG. Similar to FIG. 10, the gradation value 255 is corrected to 255 in the area A, 228 in the area B, 200 in the area C, and 171 in the area D by the density correction process. Similar to FIG. 10, in the region A, all three pixels are exposed with a PWM value of 255. In region B, two pixels are exposed by PWM225 and one pixel is exposed by PWM150. In region C, one pixel is exposed with a PWM value of 255 and two pixels are exposed with a PWM value of 150. On the other hand, in the area D, all three pixels are exposed with a PWM value of 150.

Subsequently, the density correction information held by the density correction processing unit 101z will be described. FIG. 12 shows an example of density correction information. According to FIG. 12, with respect to the minimum value (0) to the maximum value (255) of the gradation value before correction, the gradation value after correction linearly changes from the minimum value (0) to the maximum value for each region. I am trying to increase it. In the density correction information of FIG. 12, the gradation value after correction rises linearly with respect to the gradation value before correction, so that an image showing continuous gradation characteristics is formed. In the present embodiment, the scanning region in the main scanning direction is divided into seven regions A to G and the density correction processing is performed. However, in order to improve the correction accuracy, the region is further divided and the density correction is performed. It can also be configured to perform processing. Further, the density correction information is not limited to the form in which the gradation value after correction is linearly changed with respect to the gradation value before correction, and may be changed in a non-linear manner.

FIG. 13 shows an exposure control configuration. Partial magnification information is stored in the memory 304 of the laser drive unit 300. The partial magnification information is information indicating the partial magnification at each image height. Information indicating the scanning speed at each image height can also be used as partial magnification information. The partial magnification information stored in the memory 304 may be information measured for the optical scanning device 400 having the memory 304 or information indicating a typical partial magnification of the plurality of optical scanning devices 400.

The CPU 201 of the control unit 200 acquires the partial magnification information from the memory 304 via the serial communication 311. Then, the CPU 102 notifies the CPU 102 of the image signal generation unit 100 of the partial magnification information. The CPU 102 notifies the image processing unit 101 of the partial magnification information via the bus 103. The image processing unit 101 generates a VDO signal 114 at a clock frequency corresponding to the image height based on this partial magnification information. Further, the CPU 102 acquires the density correction information from the image processing unit 101 via the bus 103, and notifies the CPU 201 of the density correction information. The CPU 201 notifies the pixel counting unit 202 of the density correction information and the partial magnification information via the bus 211.

When the image signal generation unit 100 is ready to output the VDO signal 114, the image signal generation unit 100 instructs the control unit 200 to start image formation via the serial communication 113. When the control unit 200 starts light emission of the light source 401 and rotational drive of the deflector 405 and is ready for image formation, the control unit 200 transmits the TOP signal 112 which is the sub-scanning synchronization signal and the BD signal 111 which is the main scanning synchronization signal. It is output to the image signal generation unit 100. The TOP signal 112 is a signal output before forming an image on each sheet 10. Further, the BD signal 111 is a signal output before scanning each scanning line. The TOP signal 112 and the BD signal 111 are output to the image processing unit 101 and the pixel counting unit 202. Upon receiving these synchronization signals, the image signal generation unit 100 outputs the VDO signal 114 at a predetermined timing. As described above, the clock frequency of the VDO signal 114 changes according to the image height according to the partial magnification information. That is, the image processing unit 101 functions as a clock frequency control unit, and the PWM control unit 101c outputs a VDO signal 114 according to the clock frequency. Further, the gradation value that is the source of the VDO signal 114 is corrected by the density correction processing unit 101z as described above. The laser driver IC 301 controls the on / off of the light source 401 based on the VDO signal 114. The emission intensity of the light source 401 is controlled by the control signal 310 output by the control unit 200. As a result, an electrostatic latent image is formed on the photoconductor 1.

The pixel counting unit 202 receives the VDO signal 114 and counts when the VDO signal 114 is at a high level at a predetermined sampling frequency (hereinafter, counting frequency). That is, the pixel counting unit 202 increases the counting value when the VDO signal 114 indicates a value for lighting the light source 401 at the counting timing according to the counting frequency. While the VDO signal 114 is at a high level, the light source 401 emits light to emit scanning light 208. The count frequency is higher than the clock frequency of the VDO signal 114, and can be, for example, about 11 times the clock frequency at the axial image height.

Here, for example, as shown in FIG. 14, it is assumed that an image having a gradation value of 255 is formed in each of the regions A, D, and G. As described with reference to FIG. 9, images having the same density are formed in the regions A, D, and G by the partial magnification correction and the density correction, and thus the toner consumption is the same. On the other hand, by the correction processing by the density correction processing unit 101z, the gradation values of the regions A, D and G indicated by the corrected image data become the gradation values 255, 171 and 255, respectively. Further, as described above, the frequency of the VDO signal 114 in the regions A and G becomes higher than the frequency of the VDO signal 114 in the region D due to the partial magnification correction. That is, the period of the VDO signal 114 in the areas A and G is shorter than the period of the VDO signal 114 in the area D. Therefore, in each of the regions A, D, and G, the period during which the VDO signal 114 is at a high level is the black part in FIG. Therefore, the count value of the pixel count unit 202 in the areas A and G is the same, but the count value of the pixel count unit 202 in the area D is different from the count value in the areas A and G. Specifically, even if the density is the same, the exposure area differs depending on the image height, and the high level period of the VDO signal 114 changes. Therefore, in order to accurately determine the toner consumption from the count value counted by the pixel counting unit 202, it is necessary to correct the count value according to the image height.

FIG. 15 is a flowchart of the counting process of the VDO signal 114 performed by the pixel counting unit 202. The process of FIG. 15 is started by inputting the TOP signal 112. Further, the loop processing from S101 to S113 in the flowchart of FIG. 15 is repeated every cycle of the count frequency. Further, at the start of the process of FIG. 15, the count value W is initialized to 0.

After the input of the TOP signal 112, the input of the VDO signal 114 to the pixel counting unit 202 is started in S100.

In S101, the pixel counting unit 202 acquires the partial magnification information of the scanning position (image height) of the scanning light 208. The pixel counting unit 202 can determine the scanning position of the scanning light 208 based on the elapsed time from the input of the BD signal 111.

In S102, the pixel counting unit 202 determines the counting frequency based on the partial magnification information of the scanning position. Specifically, assuming that the count frequency when the image height is 0 is the reference frequency F, the count frequency F'at the image height where the partial magnification is L% is F'= Fx (1 + L / 100). Therefore, the count frequency at an image height of 35% partial magnification is 1.35 times the reference frequency, and the count frequency at an image height of 20% partial magnification is 1.2 times the reference frequency. As a result, the change in the clock frequency due to the image height of the VDO signal 114 is canceled out. In this way, the pixel counting unit 202 functions as a counting frequency control unit.

The pixel counting unit 202 determines the level of the VDO signal 114 in S103, and determines the value of X. In this embodiment, X is set to 1 when the VDO signal 114 is at a high level, and X is set to 0 when the VDO signal 114 is at a low level. The value of X when the VDO signal 114 is at a high level can be any value other than 0.

In S104, the pixel counting unit 202 acquires information on a region corresponding to the scanning position (image height) of the scanning light 208. The information of the area can be determined by the elapsed time from the input of the BD signal 111. Further, the relationship between the scanning position and the region is included in the density correction information.

In S105 to S107, the pixel counting unit 202 determines which of the areas A to G is the area corresponding to the scanning position. The pixel counting unit 202 advances the processing to S108 when the region corresponding to the scanning position is the region A or G, advances the processing to S109 when it is the region B or F, and advances the processing to S110 when it is the region C or E. If it is the area D, the process proceeds to S111.

In the pixel counting unit 202, the value obtained by multiplying X by 1 in S108 is defined as Y, the value obtained by multiplying X by 1.12 in S109 is defined as Y, the value obtained by multiplying X by 1.28 in S110 is defined as Y, and X is defined in S111. Let Y be the value multiplied by 1.40. The value multiplied by X in S108 to S111 is the first correction coefficient according to the region of the photoconductor 1 being scanned by the optical scanning apparatus 400. FIG. 16 shows the first correction coefficient for each region. The first correction coefficient is the ratio of the gradation value before the density correction to the gradation value after the density correction, and is generated based on the density correction information. As shown in FIG. 16, the first correction coefficients in the regions A, B, C and D are 1, 1.12.1.28 and 1.49, respectively. Multiplying the first correction coefficient by X corresponds to controlling or changing the amount of increase in the count value according to the region. That is, Y obtained in the processes of S108 to S111 corresponds to the amount of increase in the count value when the VDO signal 114 is at a high level. More generally, based on the density correction information, the pixel counting unit 202 uses the increase amount Y as a reference value at an image height in which the gradation value of the second image data is N times the gradation value of the first image data. Make it 1 / N times X.

In S112, the pixel counting unit 202 updates the count value W by adding Y to the count value W up to that point. In S113, the pixel counting unit 202 determines whether a predetermined time has elapsed from the input of the TOP signal 112. The predetermined time corresponds to the output period of the VDO signal 114 on one sheet 10. That is, in S113, the pixel counting unit 202 determines whether the output of the VDO signal 114 for forming the image on one sheet 10 is completed. As described above, the pixel counting unit 202 repeats the process from S101 every cycle of the counting frequency while the VDO signal 114 for forming an image on one sheet 10 is output. That is, at each count timing (sampling timing) indicated by the count frequency (sampling frequency), the processes from S101 to S113 are performed.

When a predetermined time has elapsed from the input of the TOP signal 112, the pixel counting unit 202 stores the count value W at that time in the non-volatile memory 12 in S114, and ends the process of FIG. In the process of FIG. 15, the count value W for one sheet 10 is individually stored in the non-volatile memory 12. However, when an image is formed on a plurality of sheets 10 by one job, the total of the count values W of each sheet 10 of the job can be continuously counted and stored in the non-volatile memory 12. Further, in order to reduce the amount of data to be recorded in the non-volatile memory 12, a value obtained by reducing the count value W to 1/10 or 1/100 may be recorded in the non-volatile memory 12. The control unit 200 determines the amount of toner consumed or the remaining amount based on the total value of the individual count values W recorded in the non-volatile memory 12. For example, when the recorded total value exceeds the threshold value, the control unit 200 determines that the remaining amount of toner is less than the predetermined value or runs out of toner, and notifies the user to replace the process cartridge B. Do.

In this embodiment, the amount of increase in the count is controlled or corrected according to the region of the photoconductor 1 being scanned by the optical scanning apparatus 400. However, the amount of increase in the count value in each region is set as a reference value, for example, 1, and when the count in one region is completed, the count value in the region is multiplied by the first correction coefficient in the region and integrated. Even if it is the same.

As described above, by changing the count frequency according to the image height and correcting the increase amount of the count value according to the image height, the VDO signal 114 generated by performing the density correction and the partial magnification correction is used. The amount of developer consumed can be determined accurately.

<Second embodiment>
Subsequently, the second embodiment will be described focusing on the differences from the first embodiment. FIG. 17 is a flowchart of counting processing according to the present embodiment. In the first embodiment, in S102, the pixel counting unit 202 determines the counting frequency according to the image height based on the partial magnification information. Then, the high level period of the VDO signal 114 was counted by the counting frequency corrected according to the image height. In the present embodiment, the pixel counting unit 202 performs counting processing at a constant reference frequency F. As in the first embodiment, the process of FIG. 17 is started by inputting the TOP signal 112. Further, the loop processing from S201 to S213 in the flowchart of FIG. 17 is repeated every cycle of the count frequency. As described above, in the present embodiment, the count frequency is constant at the reference frequency F. Further, at the start of the process of FIG. 17, the count value W is initialized to 0.

After the input of the TOP signal 112, the input of the VDO signal 114 to the pixel counting unit 202 is started in S200. The pixel counting unit 202 determines the level of the VDO signal 114 in S201, and sets X to 1 when the VDO signal 114 is high level and 0 when the VDO signal 114 is low level. The value of X when the VDO signal 114 is at a high level can be any value other than 0.

In S202, the pixel counting unit 202 acquires the partial magnification information of the scanning position (image height) of the scanning light 208. The scanning position can be determined by the elapsed time from the input of the BD signal 111, and thus the partial magnification information can be determined by the elapsed time from the input of the BD signal 111.

In S203, the pixel counting unit 202 corrects the reference value X of the increase amount of the count value according to the partial magnification L (%) of the image height to obtain the increase amount Y. In the present embodiment, instead of performing the count processing at the count frequency corresponding to the partial magnification correction, the fluctuation of the count value due to the partial magnification correction is suppressed by correcting the increase amount of the count value. Specifically, the increase amount Y of the count value is obtained by multiplying the reference value X (1 in this example) by the second correction coefficient. The second correction coefficient of the image height is determined based on the partial magnification of the image height. For example, as shown in FIG. 18, the second correction coefficient for the image height with a partial magnification of 35% is 1.35, and the second correction coefficient for the image height with a partial magnification of 25% is 1.25. More generally, the second correction factor at an image height with a partial magnification of L% is (1 + L / 100). Therefore, the pixel counting unit 202 obtains the corrected increase amount Y at the image height where the partial magnification is L% as Y = X × (1 + L / 100).

In S204, the pixel counting unit 202 acquires information on a region corresponding to the scanning position (image height) of the scanning light 208. The information of the area can be determined by the elapsed time from the input of the BD signal 111. Further, the relationship between the scanning position and the region is included in the density correction information.

The processing of S205 to S213 is the same as the processing of S105 to S113 of FIG. However, the pixel counting unit 202 obtains the corrected increase amount Z in S208 to S211 by multiplying the increase amount Y obtained in S203 by the first correction coefficient according to the region. The first correction coefficient and the second correction coefficient can also be combined. In this case, the gradation value of the second image data is N times the gradation value of the first image data, and the pixel counting unit 202 increases the increase amount Z at the image height at which the clock frequency is M times the reference frequency. Make it M / N times the reference value.

When the partial magnification information shows the same partial magnification in a certain range in the main scanning direction, the amount of increase in the count value is set to 1 and the count value for each predetermined section is first corrected as described in the first embodiment. The same applies even if correction is made based on the coefficient and the second correction coefficient. The predetermined section is a section in which each of the first correction coefficient and the second correction coefficient is constant.

As described above, by counting at a constant count frequency and correcting the count value according to the image height, the consumption of the developer is accurately measured by counting the VDO signal 114 generated by performing density correction and partial magnification correction. Can be determined.

[Other Embodiments]
The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

The invention is not limited to the above embodiments, and various modifications and modifications can be made without departing from the spirit and scope of the invention. Therefore, a claim is attached to make the scope of the invention public.

1: Photoreceptor, 101z: Density correction processing unit, 101a: Midtone processing unit, 101b: Position control unit, 101c: PWM control unit, 400: Optical scanning device, 101: Image processing unit, 202: Pixel counting unit

Claims (15)

Photoreceptor and
Based on the correction information of the gradation value according to the position of the photoconductor in the main scanning direction, the gradation value of each pixel of the first image data is corrected according to the pixel position in the main scanning direction of the photoconductor. A density correction means that outputs the second image data,
A generation means for generating an image signal according to a clock frequency based on the second image data, and
A light source whose blinking is controlled by the image signal, the light source emits light, and the scanning speed of the photoconductor changes according to the position of the photoconductor in the main scanning direction. A scanning means for forming a latent image on the photoconductor by scanning the light source.
A clock frequency control means that controls the clock frequency according to a position in the main scanning direction of the photoconductor being scanned by the scanning means.
When the image signal is a value for lighting the light source at the count timing according to the count frequency, a counting means for increasing the count value and a counting means for increasing the count value.
With
The counting means is an image forming apparatus that controls an increase amount of the count value according to a position in the main scanning direction of the photoconductor being scanned by the scanning means. The image forming apparatus according to claim 1, further comprising a count frequency control means for controlling the count frequency according to a position in the main scanning direction of the photoconductor being scanned by the scanning means. .. The image forming apparatus according to claim 2, wherein the counting means controls the increase amount based on the correction information according to the position in the main scanning direction. The counting means according to claim 2 or 3, wherein the increase amount increases as the ratio of the gradation value of the second image data to the gradation value of the first image data becomes smaller. Image forming device. At the position in the main scanning direction where the gradation value of the second image data is N times the gradation value of the first image data, the counting means sets the increase amount to 1 / N times the reference value. The image forming apparatus according to claim 4. The image forming apparatus according to any one of claims 2 to 5, wherein the count frequency control means controls the count frequency according to the scanning speed of the photoconductor by the scanning means. The image forming apparatus according to claim 6, wherein the count frequency control means increases the count frequency as the scanning speed of the photoconductor by the scanning means increases. The image forming apparatus according to any one of claims 2 to 5, wherein the count frequency control means increases the count frequency when the clock frequency control means increases the clock frequency. The image forming apparatus according to claim 1, wherein the counting means controls the increase amount based on the correction information and the clock frequency according to the position in the main scanning direction. The image forming according to claim 9, wherein the counting means increases the amount of increase as the ratio of the gradation value of the second image data to the gradation value of the first image data becomes smaller. apparatus. The image forming apparatus according to claim 9, wherein the counting means increases the amount of increase as the clock frequency becomes faster. At the position in the main scanning direction in which the gradation value of the second image data is N times the gradation value of the first image data and the clock frequency is M times the reference frequency, the counting means is described. The image forming apparatus according to any one of claims 9 to 11, wherein the amount of increase is M / N times a reference value. A developing means for developing the latent image formed on the photoconductor with a developing agent,
A determination means for determining the amount of the developer consumed by the developing means or the remaining amount of the developer in the developing means based on the count value.
The image forming apparatus according to any one of claims 1 to 12, further comprising. The image forming apparatus according to any one of claims 1 to 13, wherein the generation means generates the image signal by halftone processing the second image data. The clock frequency control means is any one of claims 1 to 14, wherein the clock frequency control means controls the clock frequency so as to suppress fluctuations in the pixel width due to fluctuations in the scanning speed of the photoconductor by the scanning means. The image forming apparatus according to.