The present invention relates to color registration adjustment in an image formation apparatus.
Tandem-type image forming apparatuses, which form color images by superimposing images of respective colors, have an advantage in that images can be formed quickly. However, color misregistration will occur if the timings at which the paper is fed, the images are formed, and so on are not controlled accurately. For this reason, image forming apparatuses carry out color registration adjustment. In color registration adjustment, an image forming apparatus forms a plurality of color patterns onto, for example, an intermediate transfer belt, and then uses a sensor to detect the relative positions of the color patterns of each color. The image forming apparatus then controls the image forming conditions so as to reduce misregistration between the relative positions of the images of the respective colors (an amount of the color misregistration).
The sensor emits light toward the intermediate transfer belt on which the plurality of color patterns are formed, and outputs a detection signal corresponding to the intensity of the reflected light. The image forming apparatus compares the detection signal from the sensor with a threshold, and determines the relative positions of the color patterns of the respective colors. Here, if the density of the color pattern is uniform, the waveform of the detection signal of each color pattern will be symmetrical relative to a center position of the color pattern. If the waveform of the detection signal is symmetrical, the image forming apparatus can detect the relative positions of the plurality of color patterns with a high level of accuracy, regardless of the threshold. However, if the density of the color pattern is not uniform, the waveform of the detection signal will be asymmetrical relative to the center position of the color pattern. There has thus been a risk that, depending on the threshold, the image forming apparatus cannot accurately detect the relative positions of the plurality of color patterns. The image forming apparatus according to Patent Document 1 ensures that the output times of signals, obtained by converting detection signals of color patterns of respective colors on the basis of a threshold, are the same time, by adjusting the threshold. According to Patent Document 1, detection error can be reduced even when the waveform of the detection signal is asymmetrical relative to the center position of the color pattern.
The image forming apparatus disclosed in Patent Document 1 must control the threshold for each color pattern passing a detection area of the sensor. However, it is possible that the change in the threshold will not occur in time between when a color pattern of a first color has passed the detection area and when the color pattern of a second color reaches the detection area. For example, if a color pattern enters the sensor detection area before the threshold stabilizes at a target threshold, error will arise in the output time of the signal obtained by converting the detection signal of the color pattern on the basis of the threshold. In other words, the threshold at the timing when the front end of the color pattern in a conveyance direction passes the detection area is different from the threshold at the timing when the back end of the color pattern in the conveyance direction passes the detection area. Error arises in the output time of the detection signal as a result. This in turn produces error in the detection of the relative positions of the plurality of color patterns.
PTL 1: Japanese Patent Laid-Open No. 2013-25184
According to one aspect of the present invention, an image forming apparatus includes: a plurality of image forming units that form images, each having a different color, an intermediate transfer member that rotates in a predetermined direction, a sensor that measures reflected light from a color pattern formed on the intermediate transfer member, a comparator that compares an output value from the sensor with a threshold value, and a controller. The controller executes: a first image formation task that forms a plurality of first color patterns having different colors by controlling the plurality of image forming units; a first measurement task that measures the plurality of first color patterns by controlling the sensor; a determination task that, on the basis of a first output value corresponding to a measurement result of the plurality of first color patterns output from the sensor, determines a threshold value corresponding to each of a plurality of second color patterns having different colors; a second image formation task that forms the plurality of second color patterns by controlling the plurality of image forming units; a second measurement task that measures the plurality of second color patterns by controlling the sensor; a detection task that detects an amount of the color misregistration related to a relative position between a color pattern, among the plurality of second color patterns, that has a reference color and a color pattern, among the plurality of second color patterns, that has another color different from the reference color, on the basis of a result of the comparator comparing a second output value corresponding to a measurement result of the second color patterns output from the sensor with a threshold value corresponding to each of the second color patterns; and a correction task that corrects color misregistration between an image of the reference color and an image of the other color on the basis of the amount of the color misregistration. In the second measurement task, the controller controls whether or not to set the threshold value to the threshold value corresponding to each of the plurality of second color patterns on the basis of the first output value output from the sensor in the first measurement task.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
The appended drawings, which are included in and constitute part of the specification, illustrate embodiments of the present invention, and along with those descriptions serve to illustrate the principles of the present invention.
Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are to be taken as examples only, and the present invention is not intended to be limited by the embodiments. Note also that constituent elements not necessary for the descriptions of the embodiments have been omitted from the drawings.
The intermediate transfer belt 8 is stretched upon rollers 10, 11, and 21, and is rotationally driven in the direction indicated by the arrow in the drawing when an image is formed. As the intermediate transfer belt 8 rotates, the toner image transferred onto the intermediate transfer belt 8 is conveyed to a position opposite a secondary transfer unit 22. Meanwhile, a sheet S placed in a cassette 17 or a tray 13 is conveyed to a position opposite the secondary transfer unit 22 to coincide with the timing at which the toner image transferred onto the intermediate transfer belt 8 arrives at the position opposite the secondary transfer unit 22. The secondary transfer unit 22 transfers the toner image on the intermediate transfer belt 8 to the sheet S by outputting a secondary transfer bias. Toner that has not been transferred onto the sheet S, and which remains on the intermediate transfer belt 8, is removed by a cleaning unit 12. The sheet S onto which the toner image has been transferred is conveyed to a fixing unit 23. The fixing unit 23 fixes the toner image to the sheet S by heating and compressing the sheet S. The sheet S onto which the toner image has been fixed is discharged to a tray 25. The image forming apparatus 1 also includes a sensor 40 for detecting an amount of the color misregistration. The sensor 40 is provided between the photosensitive member 2d and the roller 10, opposite the intermediate transfer belt 8.
Color registration adjustment will be described next with reference to
For example, when the relative positional relationship between the magenta detection pattern and the yellow detection pattern is being successfully controlled to an ideal positional relationship, m1 and m2 are equivalent to corresponding target values. However, if the magenta detection pattern is misregistered in the sub scanning direction relative to the yellow detection pattern, m1 and m2 will be values different from the corresponding target values. Note that when the magenta detection pattern is misregistered toward the + side in the sub scanning direction illustrated in
Returning to
As illustrated in
In step S13, the threshold setting unit 711 finds differences between the bottom levels Vy, Vm, Vc, and Vk and the level B (the detection signal value corresponding to the intermediate transfer belt 8), and determines whether or not any of the differences are within a third predetermined value. Normally, regularly-reflected light from a pattern is weaker than regularly-reflected light from the surface of the intermediate transfer belt 8. Accordingly, when the differences between the bottom levels Vy, Vm, Vc, and Vk and the level B are within the third predetermined value, it is possible that a problem has arisen in the formation, detection, or the like of the threshold setting patterns. Thus in such a case, the threshold setting unit 711 determines, in step S14, whether or not the process of step S11 has already been carried out twice. If the process of step S11 has not been carried out twice, the threshold setting unit 711 moves the process to step S11. However, if in step S14 the process of step S11 has already been carried out twice, the threshold setting unit 711 makes an error notification in a display unit, which is not shown, and ends the threshold setting process. Note that the third predetermined value is set in advance through experiments. The third predetermined value is stored in the storage unit 73. On the other hand, if none of the differences between the bottom levels Vy, Vm, Vc, and Vk and the level B are within the third predetermined value in step S13, the threshold setting unit 711 determines the thresholds for the respective colors in step S15. Note that the determined thresholds are stored in the storage unit 73.
yellow threshold=(B−Vy)×0.5+Vy (1)
The above Expression (1) sets a median value (50%) between the detection signal for the intermediate transfer belt 8 (the level B) and the detection signal for the yellow threshold setting pattern 901 (the bottom level Vy) as the threshold for yellow. Note that the threshold for the yellow color registration patterns 801 and 811 need not be the median value as long as it is a value between the detection signal for the intermediate transfer belt 8 (the level B) and the detection signal for the yellow threshold setting pattern 901 (the bottom level Vy). In step S21, the threshold setting unit 711 determines whether the absolute value of the difference between the detection signal for the yellow threshold setting pattern 901 (the bottom level Vy) and the detection signal for the magenta threshold setting pattern 902 (the bottom level Vm) is less than or equal to a second predetermined value. This is a process for determining whether or not a switch between the thresholds will be in time if the yellow color registration pattern 801 and the magenta color registration pattern 802, which is adjacent to the yellow color registration pattern 801, are measured in sequence by the sensor 40. This is also a process for determining whether or not a switch between the thresholds will be in time if the yellow color registration pattern 811 and the magenta color registration pattern 812, which is adjacent to the yellow color registration pattern 811, are measured in sequence by the sensor 40. If the absolute value of the difference between the bottom level Vy and the bottom level Vm is less than or equal to the second predetermined value, in step S22, the threshold setting unit 711 sets the threshold for binarizing the detection signals for the magenta color registration patterns 802 and 812 as follows. The threshold for binarizing the detection signals for the magenta color registration patterns 802 and 812 is found by replacing the bottom level Vy with the bottom level Vm in Expression (1). On the other hand, if the absolute value of the difference between the yellow bottom level Vy and the magenta bottom level Vm is not less than or equal to the second predetermined value, it is determined that the switch in the thresholds will not be in time. Accordingly, in step S23, the threshold setting unit 711 sets the threshold for the magenta color registration patterns 802 and 812 to the same level as the threshold for the yellow color registration patterns 801 and 811. Thereafter, in the same manner, the threshold setting unit 711 determines, in step S24, whether or not the absolute value of the difference between the detection signal for the magenta threshold setting pattern 902 (the bottom level Vm) and the detection signal for the cyan threshold setting pattern 903 (the bottom level Vc) is less than or equal to the second predetermined value. If the absolute value of the difference between the bottom level Vm and the bottom level Vc is less than or equal to the second predetermined value, in step S25, the threshold setting unit 711 sets the threshold for the cyan color registration patterns 803 and 813 as follows. The threshold for binarizing the detection signals for the cyan color registration patterns 803 and 813 is found by replacing the bottom level Vy with the bottom level Vc in Expression (1). On the other hand, if the absolute value of the difference between the magenta bottom level Vm and the cyan bottom level Vc is not less than or equal to the second predetermined value, it is determined that the switch in the thresholds will not be in time. Accordingly, in step S26, the threshold setting unit 711 sets the cyan threshold to the same level as the magenta threshold. Here, if the threshold for the magenta color registration patterns 802 and 812 is set to the same value as the threshold for the yellow color registration patterns 801 and 811, the threshold for the cyan color registration patterns 803 and 813 is set to the same value as the yellow threshold. Furthermore, the threshold setting unit 711 determines, in step S27, whether or not the absolute value of the difference between the detection signal for the cyan threshold setting pattern 903 (the bottom level Vc) and the detection signal for the black threshold setting pattern 904 (the bottom level Vk) is less than or equal to the second predetermined value. If the absolute value of the difference between the bottom level Vc and the bottom level Vk is less than or equal to the second predetermined value, in step S28, the threshold setting unit 711 sets the threshold for the black color registration patterns 804 and 814 as follows. The threshold for binarizing the detection signals for the black color registration patterns 804 and 814 is found by replacing the bottom level Vy with the bottom level Vk in Expression (1). On the other hand, if the absolute value of the difference between the cyan bottom level Vc and the black bottom level Vk is not less than or equal to the second predetermined value, it is determined that the switch in the thresholds will not be in time. Accordingly, in step S29, the threshold setting unit 711 sets the threshold for the black color registration patterns 804 and 814 to the same level as the threshold for the cyan color registration patterns 803 and 813. Here, if the threshold for the cyan color registration patterns 803 and 813 is set to the same level as the threshold for the magenta color registration patterns 802 and 812, the threshold for the black color registration patterns 804 and 814 is set to the same value as the magenta threshold. Furthermore, if the threshold for the magenta color registration patterns 802 and 812 is set to the same level as the threshold for the yellow color registration patterns 801 and 811, the threshold for the black color registration patterns 804 and 814 is set to the same value as the yellow threshold.
Hereinafter, a configuration in which a toner image of a second color is formed upstream, in the rotation direction of the intermediate transfer belt 8, from a color registration pattern of a first color, will be described as an example. The threshold setting unit 711 determines whether or not to change the threshold for detecting the color registration pattern of the second color on the basis of a difference between the detection signal value of a threshold setting pattern formed using toner of the first color and the detection signal value of a threshold setting pattern formed using toner of the second color. For example, the threshold setting unit 711 determines whether or not to change the threshold for detecting the magenta color registration patterns 802 and 812 on the basis of whether or not the absolute value of the difference between the bottom level Vy and the bottom level Vm is less than or equal to the second predetermined value. If the absolute value of the difference between the bottom level Vy and the bottom level Vm is less than or equal to the second predetermined value, the threshold setting unit 711 determines the threshold for the magenta color registration patterns 802 and 812 from the bottom level Vm and the level B, on the basis of Expression (1). This is because it is possible that the detection waveform of the detection pattern of the first color will be analogous to the detection waveform of the detection pattern of the second color. When the threshold is set on a color-by-color basis to, for example, a median value of the detection signal value pertaining to the intermediate transfer belt 8 (the level B) and the detection signal value pertaining to the threshold setting pattern for each color (the bottom level), the determination unit 713 can find the amount of the color misregistration with a high level of accuracy. On the other hand, if the absolute value of the difference between the bottom level Vy and the bottom level Vm is greater than the second predetermined value, the threshold setting unit 711 sets the threshold for the magenta color registration patterns 802 and 812 on the basis of the bottom level Vy and the level B corresponding to the intermediate transfer belt 8. In other words, the threshold setting unit 711 does not change the threshold for the color registration pattern of the second color from the threshold for the color registration pattern of the first color. This is because the threshold may not be switched in time between when the color registration pattern of the first color passes through the detection position of the sensor 40 to when the detection pattern of the second color arrives at the detection position. In other words, when the absolute value of the difference between the bottom level of the threshold setting pattern of the first color and the bottom level of the threshold setting pattern of the second color is greater than the second predetermined value, the threshold setting unit 711 determines that the threshold will not be switched in time, and prohibits the threshold from being changed. Additionally, the configuration may be such that when the absolute value of the difference between the bottom level Vm and the bottom level Vc is greater than the second predetermined value, the threshold setting unit 711 sets the threshold for the cyan color registration pattern 803 to the same value as the threshold for the yellow color registration pattern 801. Furthermore, the configuration may be such that when the absolute value of the difference between the bottom level Vc and the bottom level Vk is greater than the second predetermined value, the threshold setting unit 711 sets the threshold for the black color registration pattern 804 to the same value as the threshold for the magenta color registration pattern 802.
As described above, the comparator 72 binarizes the detection signal from the sensor 40 using the threshold controlled by the RC circuit 77. While the color registration pattern of the first color is passing through the detection area of the sensor 40, the threshold setting unit 711 outputs a PWM signal corresponding to the threshold for the color registration pattern of the first color. The RC circuit 77 smoothes the PWM signal, and controls the threshold of the comparator 72 to the threshold for the color registration pattern of the first color. Then, after the color registration pattern of the first color has passed through the detection area of the sensor 40, the threshold setting unit 711 outputs a PWM signal corresponding to the threshold for the color registration pattern of the second color. As a result, the RC circuit 77 changes the threshold of the comparator 72 from the threshold for the color registration pattern of the first color to the threshold for the color registration pattern of the second color. However, it takes some time for the threshold of the comparator 72 to converge on the threshold for the color registration pattern of the second color. When the difference between the threshold for the color registration pattern of the first color and the threshold for the color registration pattern of the second color is great, the color registration pattern of the second color may arrive at the detection area of the sensor 40 before the threshold of the comparator 72 converges on the threshold for the color registration pattern of the second color. In this case, the threshold at the timing when the binary signal corresponding to the color registration pattern of the second color changes from low-level to high-level is different from the threshold at the timing when the binary signal changes from high-level to low-level. This produces error in the binary signal, and the amount of the color misregistration therefore cannot be found with a high level of accuracy.
Note that the difference between the threshold for the color registration pattern of the first color and the threshold for the color registration pattern of the second color, which is found through Expression (1), is half the difference between the bottom level of the detection signal pertaining to the threshold setting pattern of the first color and the level of the detection signal pertaining to the intermediate transfer belt 8. The second predetermined value is assumed to be, for example, a value less than or equal to twice a maximum amount of variation (a first predetermined value) at which the output from the RC circuit 77 can stabilize in the time from when the color registration pattern of the first color passes through the detection area of the sensor 40 to when the color registration pattern of the second color arrives at the detection area of the sensor 40. In this case, if the difference between the bottom level of the detection signal pertaining to the threshold setting pattern of the first color and the bottom level of the detection signal pertaining to the threshold setting pattern of the second color is less than or equal to the second predetermined value, the difference between the threshold for the first color and the threshold for the second color found through Expression (1) will be less than the first predetermined value. Accordingly, the output from the RC circuit 77 finishes changing from the threshold for the first color to the threshold for the second color between when the following end of the color registration pattern of the first color passes through the detection area of the sensor 40 to when the leading end of the color registration pattern of the second color arrives at the detection area of the sensor 40. On the other hand, if the difference between the bottom level of the detection signal pertaining to the threshold setting pattern of the first color and the bottom level of the detection signal pertaining to the threshold setting pattern of the second color is greater than the second predetermined value, the difference between the threshold for the first color and the threshold for the second color found through Expression (1) will be greater than the first predetermined value. In this case, the output from the RC circuit 77 does not finish changing from the threshold for the first color to the threshold for the second color between when the following end of the color registration pattern of the first color passes through the detection area of the sensor 40 to when the leading end of the color registration pattern of the second color arrives at the detection area of the sensor 40. Accordingly, if the difference between the bottom level of the detection signal pertaining to the threshold setting pattern of the first color and the bottom level of the detection signal pertaining to the threshold setting pattern of the second color is greater than the second predetermined value, the threshold setting unit 711 sets the threshold for the second color to the same value as the threshold for the first color. In other words, the threshold setting unit 711 does not change the PWM signal input to the RC circuit 77, so that the threshold is not changed. As a result, the comparator 72 converts the detection signal of the color registration pattern of the second color to a binary signal on the basis of the threshold for the first color. Accordingly, detection error arising as a result of the threshold changing while the color registration pattern of the second color is being detected can be suppressed.
Expression (1) sets the median value between the level B of the detection signal pertaining to the intermediate transfer belt 8 and the bottom level Vy of the detection signal pertaining to the threshold setting pattern as the threshold, and thus the second predetermined value is set to a value less than or equal to twice the first predetermined value. However, if the multiplier of 0.5 in Expression (1) is set to 0.25, the second predetermined value will be of value less than or equal to four times the first predetermined value. In other words, the second predetermined value is a value found on the basis of a relationship between the first predetermined value and the multiplier in Expression (1). Note that the first predetermined value corresponds to the maximum amount of variation at which the output from the RC circuit 77 can stabilize during the detection interval of the color registration pattern.
Meanwhile, if the difference between the bottom level of the detection signal pertaining to the threshold setting pattern of the first color and the bottom level of the detection signal pertaining to the threshold setting pattern of the second color is greater than the second predetermined value, the threshold for the second color may be set to a value obtained by increasing/reducing the threshold for the first color by a value equivalent to less than or equal to the first predetermined value. In other words, it is sufficient for the difference between the threshold for the color registration pattern of a given color, and the threshold for the color registration pattern of another color formed upstream from the color registration pattern of the given color, to be less than or equal to the first predetermined value. The threshold setting unit 711 can determine whether to increase or reduce the threshold for the first color by the first predetermined value on the basis of the magnitude relationship between the bottom level of the detection signal pertaining to the threshold setting pattern for the first color and the bottom level of the detection signal pertaining to the threshold setting pattern for the second color. Specifically, when the absolute value of the bottom level Vm is greater than the absolute value of the bottom level Vy, the threshold setting unit 711 reduces the threshold for the color registration patterns 802 and 812 from the threshold for the color registration patterns 801 and 811 by an amount equivalent to the first predetermined value. In other words, the threshold for the color registration patterns 802 and 812 is shifted, toward the bottom level Vm side, from the threshold for the color registration patterns 801 and 811. Conversely, when the absolute value of the bottom level Vm is less than the absolute value of the bottom level Vy, the threshold setting unit 711 increases the threshold for the color registration patterns 802 and 812 from the threshold for the color registration patterns 801 and 811 by an amount equivalent to the first predetermined value. In other words, the threshold for the color registration patterns 802 and 812 is shifted, toward the level B side, from the threshold for the color registration patterns 801 and 811.
In the flowchart of
In step S30, the determination unit 713 forms the color registration patterns (
As described thus far, the threshold setting unit 711 sets the threshold so that variation in the threshold, arising as the patterns of the respective colors pass through the detection area of the sensor 40, is less than or equal to a predetermined value, which makes it possible to suppress detection error in the color registration adjustment with a low-cost configuration.
The present embodiment will be described next, focusing on the differences from the first embodiment. In the first embodiment, the threshold is set in a color-by-color basis. However, the differences between the bottom levels Vy, Vm, and Vc of the detection signals pertaining to the threshold setting patterns 901, 902, and 903 for the chromatic colors are not particularly great. On the other hand, the difference between the bottom levels Vy, Vm, and Vc and the bottom level Vk is great. Accordingly, in the threshold setting process according to the present embodiment, only two thresholds, namely a threshold for the color registration patterns 801, 802, 803, 811, 812, and 813 of the chromatic colors and a threshold for the black color registration patterns 804 and 814, are determined. In this case, the threshold setting unit 711 finds an average Vymc of the bottom levels Vy, Vm, and Vc, and takes a value found by replacing the bottom level Vy in Expression (1) with the average Vymc as the threshold for the color registration patterns 801, 802, 803, 811, 812, and 813 of the chromatic colors. Then, on the basis of a difference between the average Vymc and the bottom level Vk, the threshold setting unit 711 sets the threshold for the black color registration patterns 804 and 814 to the bottom level Vk, or to the same threshold as the threshold for the color registration patterns of the chromatic colors. In the determination process of
As described thus far, the threshold setting unit 711 sets the threshold so that variation in the threshold, arising as the patterns of the respective colors pass through the detection area of the sensor 40, is less than or equal to a predetermined value, which makes it possible to suppress detection error in the color registration adjustment with a low-cost configuration.
The threshold setting unit 711 according to the first embodiment determines the thresholds for the color registration patterns 801 to 814 on the basis of the bottom levels Vy, Vm, Vc, and Vk of the detection signals corresponding to the threshold setting patterns 901, 902, 903, and 904. The threshold setting unit 711 according to the second embodiment determines the threshold on the basis of the bottom levels of the detection signals corresponding to the threshold setting patterns of the chromatic colors and the bottom level of the detection signal corresponding to the black threshold setting pattern.
The threshold setting unit 711 according to the present embodiment compares durations of the binary signals obtained by conversion from the detection signals for the threshold setting patterns 901, 902, 903, and 904, and determines the thresholds for the color registration patterns 801 to 814 on the basis of the comparison result. In other words, the threshold setting unit 711 converts the threshold setting patterns 901, 902, 903, and 904 to the binary signal on the basis of a threshold TH set in advance. The threshold setting unit 711 calculates a time Time, for which the high-level signal is output on the basis of the binary signal, for each of the threshold setting patterns 901, 902, 903, and 904. Then, the threshold setting unit 711 determines whether or not the absolute value of a difference between a time Time_y corresponding to the threshold setting pattern 901 and a time Time_m corresponding to the threshold setting pattern 902 is longer than a predetermined amount of time. If the absolute value of the difference between the time Time_y and the time Time_m is longer than the predetermined amount of time, the threshold setting unit 711 sets the threshold for the magenta color registration patterns 802 and 812 to the threshold for the yellow color registration patterns 801 and 811. Note that the threshold for the yellow color registration patterns 801 and 811 is determined on the basis of the bottom level Vy and the level B, using Expression (1) described in the first embodiment. The threshold determined here is also set as the threshold for the magenta color registration patterns 802 and 812.
On the other hand, if the absolute value of the difference between the time Time_y and the time Time_m is not longer than the predetermined amount of time, the threshold setting unit 711 determines the threshold for the magenta color registration patterns 802 and 812 on the basis of the bottom level Vm and the level B. Note that the threshold for the yellow color registration patterns 801 and 811 is determined on the basis of the bottom level Vy and the level B, using Expression (1) described in the first embodiment. On the other hand, the threshold for the magenta color registration patterns 802 and 812 is determined on the basis of the bottom level Vm and the level B, using Expression (1) described in the first embodiment.
Likewise, the threshold setting unit 711 determines whether or not the absolute value of a difference between the time Time_m corresponding to the threshold setting pattern 902 and a time Time_c corresponding to the threshold setting pattern 903 is longer than a predetermined value. If the absolute value of the difference between the time Time_m and the time Time_c is longer than the predetermined amount of time, the threshold setting unit 711 sets the threshold for the cyan color registration patterns 803 and 813 to the threshold for the magenta color registration patterns 802 and 812. The threshold for the cyan color registration patterns 803 and 813 is set to the same value as the threshold for the magenta color registration patterns 802 and 812.
On the other hand, if the absolute value of the difference between the time Time_m and the time Time_c is not longer than the predetermined amount of time, the threshold setting unit 711 determines the threshold for the cyan color registration patterns 803 and 813 on the basis of the bottom level Vc and the level B, using Expression (1) according to the first embodiment.
Likewise, the threshold setting unit 711 determines whether or not the absolute value of a difference between the time Time_c corresponding to the threshold setting pattern 903 and a time Time_k corresponding to the threshold setting pattern 904 is longer than a predetermined value. If the absolute value of the difference between the time Time_c and the time Time_k is longer than the predetermined amount of time, the threshold setting unit 711 sets the threshold for the black color registration patterns 804 and 814 to the threshold for the cyan color registration patterns 803 and 813. In other words, the threshold for the black color registration patterns 804 and 814 is set to the same value as the threshold for the cyan color registration patterns 803 and 813.
On the other hand, if the absolute value of the difference between the time Time_c and the time Time_k is not longer than the predetermined amount of time, the threshold setting unit 711 determines the threshold for the black color registration patterns 804 and 814 on the basis of the bottom level Vk and the level B, using Expression (1) according to the first embodiment.
As described thus far, the threshold setting unit 711 sets the threshold so that variation in the threshold, arising as the patterns of the respective colors pass through the detection area of the sensor 40, is less than or equal to a predetermined value, which makes it possible to suppress detection error in the color registration adjustment with a low-cost configuration.
Additionally, the image forming apparatus 1 is not limited to a configuration in which the functions of the threshold setting unit 711, the determination unit 713, and the light emission control unit 714 are realized by the CPU 70. For example, the functions of the threshold setting unit 711, the determination unit 713, and the light emission control unit 714 may be at least partially realized by an ASIC different from the CPU 70. Alternatively, all of the functions of the threshold setting unit 711, the determination unit 713, and the light emission control unit 714 may be realized by an ASIC different from the CPU 70. The number of ASICs is not limited to 1. In other words, the image forming apparatus 1 may be configured such that an ASIC for realizing the function of the threshold setting unit 711, an ASIC for realizing the function of the determination unit 713, and an ASIC for realizing the function of the light emission control unit 714 are different ASICs. Additionally, the functions of the threshold setting unit 711, the determination unit 713, and the light emission control unit 714 may be at least partially realized by a processor different from the CPU 70. Alternatively, all of the functions of the threshold setting unit 711, the determination unit 713, and the light emission control unit 714 may be realized by a processor different from the CPU 70. The number of processors different from the CPU 70 is not limited to 1. In other words, the image forming apparatus 1 may be configured such that a processor for realizing the function of the threshold setting unit 711, a processor for realizing the function of the determination unit 713, and a processor for realizing the function of the light emission control unit 714 are different processors.
Additionally, the image forming apparatus 1 according to the first embodiment, the second embodiment, and the third embodiment includes the intermediate transfer belt 8. However, the image forming apparatus 1 is not limited to a configuration that includes the intermediate transfer belt 8, and the image forming apparatus 1 may instead be configured so as to include an intermediate transfer drum. The intermediate transfer belt 8, the intermediate transfer drum, and the like are called intermediate transfer members. The intermediate transfer member can rotate in a predetermined direction and convey a pattern to the detection area of the sensor 40.
According to the present invention, in an image forming apparatus that carries out color registration adjustment by using thresholds of respective colors to determine the positions of toner images, error in the detection of the positions of the toner images can be reduced.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
Number | Date | Country | Kind |
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2016-231851 | Nov 2016 | JP | national |
This application is a Continuation of International Patent Application No. PCT/JP2017/042315, filed Nov. 27, 2017, which claims the benefit of Japanese Patent Application No. 2016-231851, filed Nov. 29, 2016, both of which are hereby incorporated by reference herein in their entirety.
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Number | Date | Country | |
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Number | Date | Country | |
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Parent | PCT/JP2017/042315 | Nov 2017 | US |
Child | 16416349 | US |