JP2020157567A - Image formation apparatus and control method thereof - Google Patents

Abstract

To provide a technique of shaping a light emission waveform highly accurately even when using a light-emitting element with a high load.SOLUTION: An image formation apparatus includes: an image station which generates a toner image on a photoreceptor; an exposure unit which exposes a surface of the photoreceptor; an optical sensor 210 which detects a light amount of the exposure unit; a waveform shaping unit 203 which shapes a current to be supplied to the exposure unit; and a control unit 50 which controls the waveform shaping unit 203. The control unit 50 shapes the current to be supplied to the exposure unit with a shaping signal output by the waveform shaping unit 203, causes the exposure unit to emit light with a first light amount at a first frequency and a first light emission duty ratio, causes the exposure unit to emit light with a second light amount at a second frequency different from the first frequency and the first light emission duty ratio, causes the optical sensor to detect the first light amount and the second light amount, and adjusts the shaping signal on the basis of the difference between the first light amount and the second light amount.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to an image forming apparatus, and more specifically to adjusting the amount of light in an exposed portion.

A high-load light emitting element may be used in the exposed portion of the image forming apparatus. When a high-load light emitting element is made to emit light by ON / OFF control of a constant current, the light emission waveform does not have an ideal rectangle, and a so-called "light emission waveform summary" that emits light slowly occurs. In an image forming apparatus that is driven at high speed, the "emission waveform summary" causes deterioration of image quality. Therefore, there is a need for a technique for suppressing the emission waveform summary or driving the emission element at high speed.

Regarding the suppression of the emission waveform summary, for example, Japanese Patent Application Laid-Open No. 2011-216843 (Patent Document 1) states, "By correcting the drive signal according to the emission state of the light source, pulse thinning and waveform dullness are improved, and the light source is used. It discloses a "high-speed, high-precision" semiconductor laser drive device that reduces variations in the amount of light between the two and has excellent gradation reproducibility, especially at low densities (see [Summary]).

Further, Japanese Patent Application Laid-Open No. 2012-23109 (Patent Document 2) states that "a first current supply circuit that starts supplying a drive signal to a light emitting element in response to a drive signal and a light emitting element in response to the drive signal". The second current supply circuit is provided with a second current supply circuit for starting the supply of the auxiliary current, and the second current supply circuit stops the supply of the auxiliary current by detecting that the voltage applied to the light emitting element has reached the threshold voltage. The drive circuit is disclosed (see [Summary]).

Japanese Unexamined Patent Publication No. 2011-216843 Japanese Unexamined Patent Publication No. 2012-23109

According to the techniques disclosed in Patent Documents 1 and 2, it is not possible to shape the emission waveform with high accuracy when a high-load light emitting element is used. Therefore, there is a need for a technique for shaping the emission waveform with high accuracy even when a high-load light emitting element is used.

The present disclosure has been made in view of the above background, and an object in a certain aspect is to provide a technique for shaping an emission waveform with high accuracy even when a high-load light emitting element is used. ..

An image forming apparatus according to an embodiment includes an image station that generates a toner image on the photoconductor, an exposure unit that exposes the surface of the photoconductor, an optical sensor that detects the amount of light in the exposure unit, and a current supplied to the exposure unit. It is provided with a waveform shaping unit for shaping the waveform and a control unit for controlling the waveform shaping unit. The control unit shapes the current supplied to the exposed unit by the shaping signal output by the waveform shaping unit, causes the exposed unit to emit light with the first amount of light at the first frequency and the first emission duty ratio, and first. With a second frequency and a first emission duty ratio different from the frequency of, the exposed part is made to emit light with a second amount of light, the first amount of light and the second amount of light are detected by an optical sensor, and the first amount of light and the first amount of light are detected. The shaping signal is adjusted based on the difference in the amount of light of the second amount of light.

In a certain aspect, the control unit sets the shaping signal so that the light amount difference between the first light amount and the second light amount is within a predetermined range.

In one aspect, shaping the current involves shaping the current multiple times while setting the shaping signal. The control unit causes the exposed unit to emit light at the first frequency and the first emission duty ratio for each setting of the shaping signal, and further causes the exposed unit to emit light at the second frequency and the first emission duty ratio to perform shaping. For each signal setting, the light sensor emits light from the exposed unit at the first frequency and the first emission duty ratio, and the exposure unit that emits light at the second frequency and the first emission duty ratio. The fourth light amount and the light amount difference between the third light amount and the fourth light amount are obtained for each setting of the shaping signal, and the light amount difference between the third light amount and the fourth light amount is within a predetermined range. Set the shaping signal so that

In some aspects, the first frequency is higher than the second frequency. In the control unit, the amount of light in the exposed unit is increased based on the fact that the amount of light in the first unit is smaller than the amount of light in the second and the difference between the amount of light in the first amount and the amount of light in the second amount is less than a predetermined range. As described above, the shaping signal setting is changed so that the first light amount is larger than the second light amount, and the light amount difference between the first light amount and the second light amount exceeds a predetermined range. Change the shaping signal setting so that the amount of light in the exposed area is small.

In a certain aspect, changing the setting of the shaping signal so that the amount of light in the exposed portion is increased includes increasing the voltage at the rising edge of the current supplied to the exposed portion.

In a certain aspect, changing the setting of the shaping signal so that the amount of light in the exposed portion is reduced includes reducing the voltage at the rising edge of the current supplied to the exposed portion.

In a certain aspect, the control unit sets the second frequency to an integral fraction of the first frequency by the frequency divider of the control unit.

In one aspect, the emission duty ratio of the current supplied to the exposed area is between 20 percent and 90 percent.

In some aspects, the image forming apparatus further comprises a waveform shape portion that deforms the shaping signal by a delay circuit. The control unit controls the waveform of the shaping signal by switching between the waveform shape section and the shaping signal line.

In some aspects, the image forming apparatus further comprises a bias voltage source for applying a bias voltage to the shaping signal.

In one aspect, the control unit selects a constant voltage source or a constant current source to generate a shaping signal.

In one aspect, the control unit adjusts the width of the shaping signal by switching between a constant voltage source or a constant current source.

According to other embodiments, a method of adjusting the amount of light in the exposed area is provided. This method uses a shaping signal to shape the current supplied to the exposed portion that exposes the surface of the photoconductor, and causes the exposed portion to emit light with a first amount of light at a first frequency and a first emission duty ratio. A step, a step of causing the exposed portion to emit light with a second amount of light at a second frequency different from the first frequency and a first emission duty ratio, and a step of detecting each of the first amount of light and the second amount of light. And the step of adjusting the shaping signal based on the difference between the light amount of the first light amount and the light amount of the second light amount.

In one aspect, the method further comprises setting the shaping signal so that the light intensity difference between the first light intensity and the second light intensity is within a predetermined range.

In one aspect, shaping the current involves shaping the current multiple times while setting the shaping signal. The method includes, for each setting of the shaping signal, a step of causing the exposed portion to emit light at the first frequency and the first emission duty ratio, and further causing the exposed portion to emit light at the second frequency and the first emission duty ratio. For each setting of the shaping signal, the third light amount of the exposed part that emits light at the first frequency and the first emission duty ratio, and the fourth light amount of the exposed part that emits light at the second frequency and the first emission duty ratio. A step of acquiring the light amount, a step of obtaining the light amount difference between the third light amount and the fourth light amount for each shaping signal setting, and a predetermined range of the light amount difference between the third light amount and the fourth light amount. It further includes a step of setting the shaping signal so that it is inside.

In some aspects, the first frequency is higher than the second frequency. The method is such that the light amount of the exposed portion is increased based on the fact that the first light amount is smaller than the second light amount and the light amount difference between the first light amount and the second light amount is less than a predetermined range. Based on the step of changing the setting of the shaping signal and the fact that the first light amount is larger than the second light amount and the light amount difference between the first light amount and the second light amount exceeds a predetermined range. Further includes a step of changing the setting of the shaping signal so that the amount of light in the exposed portion is reduced.

In one aspect, the method involves changing the setting of the shaping signal so that the amount of light in the exposed area is increased, increasing the voltage at the rising edge of the current supplied to the exposed area.

In one aspect, the method involves changing the setting of the shaping signal so that the amount of light in the exposed area is reduced, reducing the voltage at the rising edge of the current supplied to the exposed area.

In some aspects, the method further comprises setting the second frequency to an integral fraction of the first frequency.

In one aspect, the emission duty ratio of the current supplied to the exposed area is between 20 percent and 90 percent.

In some aspects, the method further comprises controlling the waveform of the shaped signal by switching between the waveform shape portion and the line of the shaped signal.

In some aspects, the method further comprises applying a bias voltage to the shaping signal.

According to this technology, it is possible to shape the emission waveform at low cost and with high accuracy.
The above and other objectives, features, aspects and advantages of the invention will become apparent from the following detailed description of the invention as understood in connection with the accompanying drawings.

It is a figure which shows one configuration example of the image forming apparatus 100 according to a certain embodiment. It is a figure which shows an example of the circuit 200 from the control unit 50 to the exposure unit 3. It is a figure which shows an example of the name of the light emission waveform 301. It is a figure which shows an example of the structure of the optical waveform shaping part 203. It is a figure which shows an example of the generation procedure of a drive signal 210. It is a figure which shows an example of the evaluation method of the setting of the optical waveform shaping unit 203. It is a figure which shows an example of the influence of the overshoot and the overshoot for each emission frequency. It is a figure which shows an example of the internal structure of the control part 50 for generating the light emission waveform 301 which has the same light emission duty ratio but different frequencies. It is a figure which shows an example of the relationship between the light emission duty ratio of a light emission waveform 301, and the name and overshoot. It is a flowchart which shows an example of the process of requesting the setting of the optical waveform shaping unit 203. It is a figure which shows an example of simultaneous evaluation of a plurality of settings of an optical waveform shaping unit 203. It is a flowchart which shows an example of the process of simultaneous evaluation of a plurality of settings of an optical waveform shaping unit 203.

Hereinafter, embodiments of the technical concept according to the present disclosure will be described with reference to the drawings. In the following description, the same parts are designated by the same reference numerals. Their names and functions are the same. Therefore, the detailed description of them will not be repeated.

[First Embodiment]
<A. Device configuration>
First, the apparatus configuration of the image forming apparatus 100 according to the present embodiment will be described. In the following, as a typical example, the image forming apparatus 100 mounted as a multi-function peripheral (MFP) will be described. The image forming apparatus 100 is, for example, a color image forming apparatus, but the application target of the technical idea according to the present embodiment is not limited to the color image forming apparatus, and the technical idea is applied to the monochrome image forming apparatus. Is also applicable.

FIG. 1 is a diagram showing a configuration example of an image forming apparatus 100 according to the present embodiment. With reference to FIG. 1, the image forming apparatus 100 includes an image station 10, a document reading unit 120, and an ejection tray 130.

The image station 10 is an image station 10C, 10M, 10Y, 10K (hereinafter, “image station 10”) that generates toner images of cyan (C), magenta (M), yellow (Y), and key plate (K), respectively. The intermediate transfer belt 12, the intermediate transfer body drive rollers 14, 16 and the belt cleaning unit 18, the transfer rollers 20 and 21, the fixing unit 22, and the paper feed unit 30. The delivery roller 32, the transfer rollers 34 and 36, the control unit 50, and the storage unit 51 are included. The image station 10 includes a photoconductor 1, a charging unit 2, an exposure unit 3, and a developing unit 4 (4C, 4M, 4Y, and 4K corresponding to the color of the toner image generated by the corresponding image station 10, respectively. Included), a cleaning unit 5, and an intermediate transfer member contact roller 6. The document reading unit 120 includes an image scanner 122, a document feeding table 124, an automatic document feeding device 126, and a document discharging table 128.

The image station 110 performs a printing process on the medium 40 in the paper feeding unit 30. The medium 40 is conveyed from the paper feed unit 30 by the delivery roller 32. Further, the medium 40 is conveyed to the transfer rollers 20 and 21 by the transfer rollers 34 and 36. After the toner image is transferred to the medium 40 by the transfer rollers 20 and 21, the fixing process 22 performs the fixing process and discharges the medium 40 to the discharge tray 130.

Each image station 10 and the intermediate transfer belt 12 generate a toner image to be transferred to the medium 40. The charging unit 2 uniformly charges the surface of the photoconductor 1. The exposure unit 3 exposes the surface of the photoconductor 1 according to a designated image pattern by laser writing or the like to form an electrostatic latent image on the surface. The developing unit 4 develops an electrostatic latent image formed on the photoconductor 1 which is an image carrier as a toner image.

The toner image formed on the surface of the photoconductor 1 is transferred to the intermediate transfer belt 12 by the intermediate transfer body contact roller 6. Toner images are sequentially transferred from each photoconductor 1 onto the intermediate transfer belt 12, and toner images of four colors are superimposed. The superimposed toner images are transferred from the intermediate transfer belt 12 to the medium 40 by the transfer rollers 20 and 21.

The document reading unit 120 reads the document and outputs the scanning result as an input image for the image station 110. The image scanner 122 scans a document placed on a platen glass. The automatic document feeder 126 continuously scans documents arranged on the document paper feed tray 124. The documents arranged on the document feeding table 124 are fed one by one by a feeding roller (not shown), and are sequentially scanned by an image sensor arranged in an image scanner 122 or an automatic document feeding device 126. The scanned original is ejected to the original paper ejection table 128.

The control unit 50 controls the entire image forming apparatus 100. The storage unit 51 stores the firmware and various settings of the image forming apparatus 100. The control unit 50 refers to necessary data and programs from the storage unit 51.

FIG. 2 is a diagram showing an example of a circuit 200 from the control unit 50 to the exposure unit 3. The circuit 200 includes a control unit 50, a switching unit 201, a light source 202, an optical waveform shaping unit 203, and an optical sensor 204.

The control unit 50 switches (opens and closes) the switching unit 201 by the video signal 206, and generates the switching signal 207 from the current of the current source 205. Further, the control unit 50 outputs the video signal 206 and the shaping control signal 208 to the optical waveform shaping unit 203.

The optical waveform shaping unit 203 generates a shaping signal 209 based on the video signal 206 and the shaping control signal 208. The light source 202 is an optical element used in the exposure unit 3, and emits light by a drive signal 210 obtained by superimposing a shaping signal 209 and a switching signal 207 to expose the surface of the photoconductor 1 in the image station 10. ..

The light sensor 204 detects the light amount of the light source 202 and outputs a light amount signal 211 including the light amount information of the detected light source 202 to the control unit 50. The control unit 50 adjusts the shaping control signal 208 based on the light amount signal 211 input from the optical sensor 204.

In a certain aspect, the optical sensor 204 may be, for example, a PD (Photo Diode) sensor. The circuit 200 shown in FIG. 2 is mainly an example of peripheral circuits from the control unit 50 to the light source 202 of the exposure unit 3, and may include a configuration not illustrated in FIG.

FIG. 3 is a diagram showing an example of a summary of the emission waveform 301. When the drive signal 210 is supplied to the light source 202 of FIG. 2, and the light source 202 is a laser diode or LED (Light Emitting Diode) having a large output and a high load, the light emission waveform 301 of the light source 202 is shown in FIG. As shown in 3, the waveform does not become an ideal rectangle but gradually rises. Such a symptom is called "Namari". The “namari” of the emission waveform 301 causes unevenness in the exposure of the surface of the photoconductor 1 and causes deterioration of the printed image. Therefore, it is necessary to effectively suppress the "namari" of the emission waveform 301.

FIG. 4 is a diagram showing an example of the configuration of the optical waveform shaping unit 203. The optical waveform shaping unit 203 includes a bias voltage source 401, a constant voltage source 402, a constant current source 403, and a waveform shape unit 404. The shaping control signal 208 input from the control unit 50 to the optical waveform shaping unit 203 includes a bias voltage control signal 405, a shaping width signal 406, a selection signal 407, a constant voltage control signal 408, and a constant current control signal 409. , The waveform shape control signal 410 and the like.

The constant voltage source 402 is a power source for generating the shaping signal 209. When the shaping signal 209 is generated by the constant voltage control, the control unit 50 controls the constant voltage source 402 by the constant voltage control signal 408.

The constant current source 403 is a power source for generating the shaping signal 209. When the shaping signal 209 is generated by the constant current control, the control unit 50 controls the constant current source 403 by the constant current control signal 409.

The control unit 50 switches the switch circuit for switching between the constant voltage source 402 and the constant current source 403 by the selection signal 407. Further, the control unit 50 controls ON / OFF of the switch circuit on the path of the shaping signal 209 by the shaping width signal 406, and adjusts the pulse width of the shaping signal 209 generated by the constant voltage source 402 or the constant current source 403. To do.

The bias voltage source 401 is a circuit that applies a bias voltage to the shaping signal 209. The control unit 50 controls the bias voltage source 401 by the bias voltage control signal 405. Further, the video signal 206 controls ON / OFF of the switch circuit on the output side of the bias voltage source 401.

The corrugated shape portion 404 includes a plurality of circuits of resistors and capacitors connected to the ground (GND) inside the corrugated shape portion 404. Each circuit changes the shape of the shaping signal 209 by being connected to the path of the shaping signal 209. The control unit 50 controls the changeover switch circuit on the output path of the waveform shape unit 404 by the waveform shape control signal 410, and changes the waveform of the shaping signal 209.

Next, with reference to FIGS. 5 and 6, details of the emission waveform 301 generated by using the circuit 200 and how the image density changes by shaping the emission waveform 301 will be described.

<B. Emission waveform 301 and image density>
FIG. 5 is a diagram showing an example of a procedure for generating the drive signal 210. The control unit 50 generates a rectangular video signal 206. While the video signal 206 is HIGH, the switching unit 201 is turned on. Therefore, ideally, the switching signal 207 is generated.

Further, the control unit 50 generates a shaping width signal 406. While the shaping width signal 406 is HIGH, the switch circuit on the path of the shaping signal 209 is turned on, and a rectangular shaping signal 504B is generated.

Further, the control unit 50 deforms the shaping signal 504B by connecting the internal circuit of the waveform shape section 404 to the path of the shaping signal 209 by the waveform shape control signal 410, and generates the shaping signal 504C. The circuit inside the waveform shape portion 404 is a delay circuit consisting of a resistor and a capacitor. By connecting the delay circuit to the path of the shaping signal 209, the control unit 50 causes a delay in the shaping signal 209 and mainly changes the shape of the edge of the shaping signal 209.

Further, the control unit 50 controls the bias voltage source 401 by the bias voltage control signal 405, and superimposes the bias voltage 504A on the shaping signal 504C. By superimposing these bias voltage 504A and shaping signal 504C, the shaping signal 209 is obtained. The shape of the shaping signal 504C changes depending on the internal circuit of the waveform shape portion 404 connected to the path of the shaping signal 209.

The drive signal 210 is generated by superimposing the shaping signal 209 and the switching signal 207. The light emission waveform 301 shows the state of light emission of the light source 202 when the drive signal 210 is supplied to the light source 202. The start edge 506A of the emission waveform 301 is deformed by the bias voltage 504A and the shaping signal 504C. Further, the end edge 506B of the emission waveform 301 is deformed by the bias voltage 504A. As shown in FIG. 5, the start edge 506A of the emission waveform 301 may start from a position higher than the rectangle, and this phenomenon is referred to as “overshoot”.

As shown in FIG. 5, the control unit 50 can mainly adjust the bias voltage 504A and the shaping signal 504C to adjust the summary of the emission waveform 301 and bring it closer to a rectangle.

FIG. 6 is a diagram showing an example of an evaluation method for setting the optical waveform shaping unit 203. The control unit 50 causes the light source 202 to emit light at different frequencies while keeping the emission duty ratio of the light source 202 constant. The optical sensor 204 can detect an appropriate setting of the optical waveform shaping unit 203 by comparing each amount of light of the light source 202 that emits light at these different frequencies. Hereinafter, a comparison between the high frequency emission waveform 301 emitted from the light source 202 and the low frequency emission waveform 301 will be described as an example.

First, it is assumed that the control unit 50 generates an emission waveform 301 having a period of 604 and an emission duty ratio of 50% by the light source 202. The emission waveform 301 is generated by the drive signal 210 on which the switching signal 207 and the shaping signal 209 are superimposed. The emission waveform 301 can be any of a waveform 601 that is close to a square wave, a waveform 602 that has a gap, and a waveform 603 that is overshooted.

When the emission waveform 301 is a waveform 601 close to a rectangle, the amount of light of the light source 202 detected by the light sensor 204 is 621A. The light amount 621A is the average light amount of the waveform 601 detected by the light sensor 204.

When the light emission waveform 301 is a waveform 602 with a summary, the amount of light of the light source 202 detected by the light sensor 204 is the amount of light 620A. The light amount of 620A is smaller than that of the light amount of 621A. This is because the magnitude of the amount of light of the light source 202 is proportional to the area of the HIGH region of the emission waveform 301 of the light source 202. In the waveform 602, the area of the HIGH region of the light emission waveform 301 is smaller than that in the waveform 601 due to the occurrence of the sumi, and as a result, the light amount 620A is smaller than the light amount 621A.

When the emission waveform 301 is the overshoot waveform 603, the amount of light of the light source 202 detected by the light sensor 204 is the amount of light 622A. The light amount 622A is larger than the light amount 621A. This is because the waveform 603 has a larger area of the HIGH region of the emission waveform 301 than the waveform 601 due to the occurrence of the overshoot.

As described above, it can be seen that the amount of light of the light source 202 detected by the light sensor 204 differs depending on the summary and overshoot of the emission waveform. Therefore, if the control unit 50 adjusts the setting of the optical waveform shaping unit 203 while detecting the amount of light of the light source 202 by the optical sensor 204, the influence of the name and the overshoot can be removed from the light emission waveform 301.

However, in reality, there is no absolute reference for the amount of light, and the control unit 50 can appropriately adjust the setting of the optical waveform shaping unit 203 only by detecting the amount of light of the emission waveform 301 having a single emission frequency. Can not. This is because the control unit 50 can adjust the amount of light of the light source 202 by the light waveform shaping unit 203, but cannot determine whether or not the name or overshoot can be removed from the light emission waveform 301.

Therefore, as a comparison target, the control unit 50 generates an emission waveform 301 having a period 614 different from the period 604 and an emission duty ratio of 50% by the light source 202. In the example shown in FIG. 6, the period 614 is three times the period 604, but the period of the emission waveform 301 is not limited to this. Further, although the emission duty ratio of each emission waveform 301 will be described by taking 50% as an example, the emission duty ratio that can be set is not limited to this. The emission waveforms 301 to be compared may have the same emission duty ratio.

The density of the image is generally proportional to the emission duty ratio of the emission waveform 301. For example, a double density difference occurs between an image generated by an emission waveform 301 having an emission duty ratio of 40% and an image generated by an emission waveform 301 having an emission duty ratio of 80%.

On the other hand, when the emission duty ratio is constant, the difference in frequency of the emission waveform 301 does not affect the image density unless a summary and an overshoot occur. This is because even if the frequencies of the emission waveforms 301 are different, the emission duty ratio in one cycle of the emission waveforms 301 does not change, and images having the same density as a whole are generated. However, when namari or overshoot occurs, the difference in frequency may cause a difference in density in the generated image. Hereinafter, each emission waveform 301 having a period 604 and a period 614 will be described as an example.

It can be seen that the light emission waveform 301 of the cycle 614 has one-third the number of rising edges of the signal within the same time as the light emission waveform 301 of the cycle 604. While the rising edge of the emission waveform 301 of the cycle 614 is generated twice, the rising edge of the emission waveform 301 of the cycle 604 is generated six times. Further, since the signal namari and overshoot occur at the rising edge of the signal, the emission waveform 301 having a low frequency period 614 is more affected by the namari and overshoot than the emission waveform 301 having a high frequency period 604. It turns out to be difficult.

It is assumed that the control unit 50 has generated an emission waveform 301 having a period of 614 and an emission duty ratio of 50% for comparison with the emission waveform 301 having a period of 604. When the light emission waveform 301 is a waveform 612 with a summary, the amount of light of the light source 202 is 620B. Here, when the light amount 620B and the light amount 620A are compared, it can be seen that the light amount 620B is larger than the light amount 620A. This is because the period 614 is lower than the period 604, so that the influence of blunting is small, and as a result, the amount of decrease in the amount of light of the emission waveform 301 is small.

On the other hand, when the emission waveform 301 is an overshoot waveform 613, the amount of light of the light source 202 is 622B. Here, when the light amount 622B and the light amount 622A are compared, it can be seen that the light amount 622B is smaller than the light amount 622A. This is because the period 614 is lower than the period 604, so that the influence of overshoot is small, and as a result, the amount of increase in the amount of light of the emission waveform 301 is small.

Further, when the emission waveform 301 is a waveform 611 close to a rectangle, the amount of light of the light source 202 is 621B. Here, when the light amount 621B and the light amount 621A are compared, it can be seen that the light amount 621B and the light amount 621A are substantially equal. This is because when the emission waveform 301 is a rectangular wave, the amount of light is the same regardless of the emission frequency as long as the emission duty ratio is the same.

As described above, if the emission waveform 301 is a waveform close to a square wave, the amount of light does not change even if the emission frequency is changed, as long as the emission duty ratio is the same. Therefore, the control unit 50 compares the light amounts of the light emission waveforms 301 having the same light emission duty ratio and different frequencies, and the light when the light amounts of the light emission waveforms 301 are equal to or close to each other. By using the setting of the waveform shaping unit 203, it is possible to generate an emission waveform 301 without a duty cycle and an overshoot.

FIG. 7 is a diagram showing an example of the influence of the name and overshoot for each emission frequency. With reference to FIG. 7, the influence of the summarization and overshoot of the emission waveform 301 on the density of the toner image will be described.

The toner images 701A to 703A are halftone toner images formed on the photoconductor 1 exposed by the emission waveform 301 having a period of 604, respectively. Further, the toner images 701A to 703A are a toner image when the emission waveform 301 has a summary, a toner image when the emission waveform 301 is rectangular, and a toner image when the emission waveform 301 is overshooting, respectively.

The toner images 701B to 703B are halftone toner images formed on the photoconductor 1 exposed by the emission waveform 301 having a period of 614, respectively. Further, the toner images 701B to 703B are a toner image when the emission waveform 301 has a summary, a toner image when the emission waveform 301 is rectangular, and a toner image when the emission waveform 301 is overshooting, respectively.

Further, the emission duty ratios of the light sources 202 when forming the toner images 701A to 703A and the toner images 701B to 703B are all the same. Further, the settings of the optical waveform shaping unit 203 when forming the toner image 701A and the toner image 701B are the same. Similarly, the settings of the optical waveform shaping unit 203 when forming the toner image 702A and the toner image 702B are the same. Further, the settings of the optical waveform shaping unit 203 when forming the toner image 703A and the toner image 703B are also the same.

Comparing the toner images 701A and 701B when the emission waveform 301 is blunted, it can be seen that the toner image 701A is thinner than the toner image 701B. This is because the waveform 602 is more affected by the blunting and the amount of light is smaller than that of the waveform 612. As a result, the area of the exposed portion of the photoconductor 1 according to the waveform 602 becomes smaller than the area of the exposed portion of the photoconductor 1 according to the waveform 612, and the difference in the area of the exposed portion appears as the density difference of the toner image.

On the contrary, when the toner images 703A and 703B when the emission waveform 301 is overshooting are compared with each other, it can be seen that the toner image 703A is darker than the toner image 703B. This is because the waveform 603 is more affected by the overshoot and the amount of light is larger than that of the waveform 613. As a result, the area of the exposed portion of the photoconductor 1 according to the waveform 603 becomes larger than the area of the exposed portion of the photoconductor 1 according to the waveform 613, and the difference in the area of the exposed portion appears as the density difference of the toner image.

Comparing the toner images 702A and 702B when the emission waveform 301 is close to a rectangular wave, it can be seen that the densities of the toner image 702A and the toner image 702B are the same or close to each other. This is because the waveforms 601, 611 are not affected by the namari and the overshoot, and the emission duty ratios are the same, so that the areas of the exposed portions of the photoconductor 1 are substantially equal.

As described above with reference to FIGS. 6 and 7, the control unit 50 generates emission waveforms 301 having the same emission duty ratio and different frequencies, and compares the light amounts of these emission waveforms 301. To do. Then, the control unit 50 adjusts the setting of the optical waveform shaping unit 203 so that the light amounts of these light emission waveforms 301 are the same or close to each other, so that the influence of the name and overshoot from the light emission waveform 301 is appropriately applied. Can be removed.

FIG. 8 is a diagram showing an example of the internal configuration of the control unit 50 for generating emission waveforms 301 having the same emission duty ratio and different frequencies. The control unit 50 includes an image memory 805 and a frequency dividing counter 801. The frequency division counter 801 generates a frequency division clock 804 in which the main clock 802 of the control unit 50 is divided into 1 / N based on the frequency division setting 803. The control unit 50 generates the video signal 206 based on the frequency division clock 804. The configuration of the control unit 50 shown in FIG. 7 is an example, and the configuration of the control unit 50 is not limited to this.

FIG. 9 is a diagram showing an example of the relationship between the emission duty ratio of the emission waveform 301 and the namari and overshoot. The emission duty ratio of the emission waveform 301 is the ratio at which the output of the emission waveform 301 becomes HIGH in one cycle of the emission waveform 301.

When the emission duty ratio is "0%" or "100%", the rising edge of the emission waveform 301 is only once or 0 times. Therefore, even if the control unit 50 detects the amount of light of the light emission waveform 301 having a light emission duty ratio of “0%, 100%”, it cannot detect the influence of the name and overshoot on the light emission waveform 301.

Further, when the emission duty ratio is extremely low as in "10%", the influence of the name and overshoot on the emission waveform 301 becomes too large. Therefore, even if the control unit 50 detects the amount of light of the light emission waveform 301 having an extremely low light emission duty ratio, it may not be possible to accurately detect the influence of the name and overshoot on the light emission waveform 301.

Therefore, it is desirable that the control unit 50 sets the emission duty ratio to a range in which it is easy to detect the influence of the name and overshoot on the emission waveform 301 such as “20 to 90%”. The emission duty ratio "20 to 90%" is an example, and the setting range of the emission duty ratio is not limited to this.

<C. Signal shaping process flow>
FIG. 10 is a flowchart showing an example of a process for requesting the setting of the optical waveform shaping unit 203. The control unit 50 may read the program for performing the process of FIG. 10 from the storage unit 51 and execute it.

In step S1010, the control unit 50 sets the shaping control signal 208 output to the optical waveform shaping unit 203 to a predetermined value. More specifically, various signals included in the shaping control signal 208 shown in FIG. 4 are set to predetermined values. The predetermined value may be, for example, an intermediate value that can be taken by the shaping control signal 208, but the setting of the shaping control signal 208 is not limited to this.

In step S1020, the control unit 50 causes the light source 202 to emit light with drive signals 210 having the same emission duty ratio and different frequencies. For example, the light amount of the light emission waveform 301 of the light emission frequency A1 is defined as the light amount D1, and the light amount of the light emission waveform 301 of the light emission frequency A2 lower than the light emission frequency A1 is defined as the light amount D2. Further, the control unit 50 detects the light amounts D1 and D2 by the light sensor 204.

In step S1030, the control unit 50 compares the light amounts D1 and D2 detected in step S1020 to obtain the difference in the light amount. When the light amount D1 exceeds the light amount D2, the light amount difference becomes a positive value such as "1, 2, 3 ...". On the contrary, when the light amount D1 is less than the light amount D2, the light amount difference becomes a negative value such as "-1, -2, -3 ...". Note that these light intensity differences are examples and do not necessarily have to be expressed as integers.

When the control unit 50 determines that the light amount D1 is smaller than the light amount D2 and the light amount difference is less than the predetermined light amount difference lower limit Dmin (determined in step S1030 as "light amount difference <Dmin"). , Transfer control to step S1040.

When the control unit 50 determines that the light amount D1 and the light amount D2 are within a predetermined range (determined as "Dmin <light amount difference <Dmax" in step S1030), the control unit 50 shifts the control to step S1050.

When the control unit 50 determines that the light amount D1 is larger than the light amount D2 and the light amount difference exceeds a predetermined light amount difference upper limit Dmax (determines in step S1030 that "light amount difference> Dmax"). , Control is transferred to step S1060.

In step S1040, the control unit 50 changes the setting of the optical waveform shaping unit 203 to the overshoot side (the side where the amount of light increases), and shifts the control to step S1020.

In step S1050, the control unit 50 saves the current setting of the optical waveform shaping unit 203 in the storage unit 51, and uses the saved setting for the next and subsequent printing processes.

In step S1060, the control unit 50 changes the setting of the optical waveform shaping unit 203 to the normal side (the side where the amount of light becomes smaller), and shifts the control to step S1020.

As described above with reference to FIG. 10, the control unit 50 has the same emission duty ratio, compares the amount of light between the emission waveforms 301 of different frequencies, and the difference in the amount of light is within a predetermined range. Adjust the setting of the optical waveform shaping unit 203 so that it fits. By doing so, the control unit 50 can suppress the occurrence of the name and overshoot of the light emission waveform 301, and can suppress the deterioration of the image quality.

[Second Embodiment]
<D. Simultaneous evaluation of settings of multiple optical waveform shaping units 203>
Next, a second embodiment will be described. In the second embodiment, the control unit 50 shortens the time for adjusting the settings of the optical waveform shaping unit 203 by simultaneously comparing the plurality of settings of the optical waveform shaping unit 203.

FIG. 11 is a diagram showing an example of simultaneous evaluation of a plurality of settings of the optical waveform shaping unit 203. The control unit 50 generates an emission waveform 301 having a different frequency without changing the emission duty ratio for each of a plurality of settings of the optical waveform shaping unit 203. In the example of FIG. 11, the control unit 50 generates a high frequency emission waveform 301 and a low frequency emission waveform 301 by using each of the settings “1 to 5” of the optical waveform shaping unit 203.

Next, the control unit 50 determines the amount of light of the high-frequency emission waveform 301 having the same emission duty ratio and the amount of light of the low-frequency emission waveform 301 generated by using the same settings for each setting of the optical waveform shaping unit 203. And calculate the difference in the amount of light. Finally, the control unit 50 selects the setting of the optical waveform shaping unit 203 in which the light amount difference is within a predetermined range. In the example shown in FIG. 11, the setting of the optical waveform shaping unit 203 has been described in five stages, but this is an example, and the setting of the optical waveform shaping unit 203 is not limited to this.

FIG. 12 is a flowchart showing an example of processing for simultaneous evaluation of a plurality of settings of the optical waveform shaping unit 203. The control unit 50 may read the program for performing the process of FIG. 12 from the storage unit 51 and execute it. In the following description, the setting of the optical waveform shaping unit 203 will be described assuming that there are settings “1 to 5” as in FIG. The setting "1" is a setting in which the emission waveform 301 produces the least amount of light (the amount of light is the smallest). The setting "5" is a setting in which the light emission waveform 301 causes the largest overshoot (the amount of light is the largest). Note that these settings are examples, and the settings of the optical waveform shaping unit 203 are not limited to these.

In step S1210, the control unit 50 sets the setting of the optical waveform shaping unit 203 to the setting "1" in which the light emission waveform 301 is most vulnerable. In step S1220, the control unit 50 causes the light source 202 to generate emission waveforms 301 having different frequencies without changing the emission duty ratio. Further, the control unit 50 detects the amount of light of the emission waveform 301 for each frequency by the optical sensor 204.

In step S1230, the control unit 50 stores in the storage unit 51 the amount of light of the light emission waveform 301 for each frequency detected in step S1220 for each setting of the optical waveform shaping unit 203.

In step S1240, the control unit 50 determines whether or not the current setting of the optical waveform shaping unit 203 is the maximum value “5”. When the control unit 50 determines that the current setting of the optical waveform shaping unit 203 is the maximum value "5" (YES in step S1240), the control unit 50 shifts the control to step S1260. If not (NO in step S1240), the control unit 50 shifts control to step S1250.

In step S1250, the control unit 50 raises the current setting of the optical waveform shaping unit 203 by one step toward the overshoot side (for example, setting "1" to setting "2", setting "2" to "3", etc.). Regarding the process of FIG. 11, the control unit 50 may start the process from the setting “5” and lower the setting step by step in step S1240.

In step S1260, the control unit 50 refers to the amount of light of each emission waveform 301 stored in the storage unit 51, and for each setting of the optical waveform shaping unit 203, the amount of light between the emission waveforms 301 having the same emission duty ratio and different frequencies. Find the difference. Then, the control unit 50 searches for the setting of the optical waveform shaping unit 203 in which the light amount difference is in a predetermined range (Dmin <light amount difference <Dmax).

In step S1270, the control unit 50 saves the setting of the optical waveform shaping unit 203 obtained in step S1260 in the storage unit 51 and uses it for printing from the next time onward.

As described above with reference to FIGS. 11 and 12, the control unit 50 generates an emission waveform 301 with the same emission duty ratio and a different frequency in the light source 202 for each of a plurality of settings of the optical waveform shaping unit 203. Then, the light amount of each light emission waveform 301 is compared. By doing so, the control unit 50 can shorten the time for obtaining the setting of the optical waveform shaping unit 203.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications are included in the meaning and scope equivalent to the scope of claims.

1 Photoreceptor, 2 charged part, 3 exposed part, 4 developing part, 5 cleaning part, 6 intermediate transfer member contact roller, 10,10C, 10K, 10M, 10Y image station, 12 intermediate transfer belt, 14,16 intermediate transfer body Drive roller, 18 belt cleaning unit, 20, 21 transfer roller, 22 fixing unit, 30 feeding unit, 32 sending roller, 34, 36 transport roller, 40 media, 50 control unit, 51 storage unit, 100 image forming device, 120 Document reader, 122 image scanner, 124 document feeder, 126 automatic document feeder, 128 document ejector, 130 eject tray, 200 circuits, 201 switching unit, 202 light source, 203 optical waveform shaping unit, 204 optical sensor, 205 current source, 206 video signal, 207 switching signal, 208 shaping control signal, 209, 504B, 504C shaping signal, 210 drive signal, 211 light intensity signal, 301 emission waveform, 401 bias voltage source, 402 constant voltage source, 403 constant current Source, 404 waveform shape part, 405 bias voltage control signal, 406 shaping width signal, 407 selection signal, 408 constant voltage control signal, 409 constant current control signal, 410 waveform shape control signal, 504A bias voltage, 506A start edge, 506B end Edge, 601,602,603,611,612,613 waveform, 604,614 period, 620A, 620B, 621A, 621B, 622A, 622B light intensity, 701A, 701B, 702A, 702B, 703A, 703B toner image, 801 division Counter, 802 main clock, 803 division setting, 804 division clock, 805 image memory.

Claims (22)

An image station that produces a toner image on the photoconductor,
An exposed portion that exposes the surface of the photoconductor and
An optical sensor that detects the amount of light in the exposed area,
A waveform shaping unit that shapes the current supplied to the exposed unit, and
A control unit that controls the waveform shaping unit is provided.
The control unit
The current supplied to the exposed unit is shaped by the shaping signal output by the waveform shaping unit.
At the first frequency and the first emission duty ratio, the exposed portion is made to emit light with the first amount of light.
At a second frequency different from the first frequency and the first emission duty ratio, the exposed portion is made to emit light with a second amount of light.
The first light amount and the second light amount are detected by the light sensor, and the light amount is detected.
An image forming apparatus that adjusts the shaping signal based on the difference between the first light amount and the second light amount. The image forming apparatus according to claim 1, wherein the control unit sets the shaping signal so that the light amount difference between the first light amount and the second light amount is within a predetermined range. Shaping the current includes shaping the current a plurality of times while setting the shaping signal.
The control unit
For each setting of the shaping signal, the exposed portion is made to emit light at the first frequency and the first emission duty ratio, and further, the exposed portion is emitted at the second frequency and the first emission duty ratio. Let me
For each setting of the shaping signal, the light sensor emits light at the first frequency and the first emission duty ratio, the third light amount of the exposed portion, the second frequency, and the first emission. Obtaining the fourth amount of light emitted from the exposed portion at the duty ratio,
For each setting of the shaping signal, the light amount difference between the third light amount and the fourth light amount is obtained.
The image forming apparatus according to claim 1 or 2, wherein the shaping signal is set so that the light amount difference between the third light amount and the fourth light amount is within the predetermined range. The first frequency is higher than the second frequency,
The control unit
The light amount of the exposed portion is based on the fact that the first light amount is smaller than the second light amount and the light amount difference between the first light amount and the second light amount is less than the predetermined range. Change the shaping signal setting so that it becomes larger.
The light amount of the exposed portion is based on the fact that the first light amount is larger than the second light amount and the light amount difference between the first light amount and the second light amount exceeds the predetermined range. The image forming apparatus according to any one of claims 1 to 3, wherein the setting of the shaping signal is changed so as to be smaller. The image forming apparatus according to claim 4, wherein changing the setting of the shaping signal so that the amount of light of the exposed portion is increased includes increasing the voltage at the rising edge of the current supplied to the exposed portion. .. The image forming apparatus according to claim 4, wherein changing the setting of the shaping signal so that the amount of light in the exposed portion is reduced includes reducing the voltage at the rising edge of the current supplied to the exposed portion. .. The image forming apparatus according to any one of claims 1 to 6, wherein the control unit sets the second frequency to an integral fraction of the first frequency by a frequency divider of the control unit. .. The image forming apparatus according to any one of claims 1 to 7, wherein the emission duty ratio of the electric current supplied to the exposed portion is between 20% and 90%. Further provided with a waveform shape portion that deforms the shaping signal by a delay circuit,
The image forming apparatus according to any one of claims 1 to 8, wherein the control unit controls the waveform of the shaping signal by switching between the waveform shape section and the shaping signal line. The image forming apparatus according to any one of claims 1 to 9, further comprising a bias voltage source for applying a bias voltage to the shaping signal. The image forming apparatus according to any one of claims 1 to 10, wherein the control unit selects a constant voltage source or a constant current source and generates the shaping signal. The image forming apparatus according to claim 11, wherein the control unit adjusts the width of the shaping signal by switching the constant voltage source or the constant current source. It is a method of adjusting the amount of light in the exposed area.
The step of shaping the current supplied to the exposed part that exposes the surface of the photoconductor by the shaping signal,
A step of causing the exposed portion to emit light with a first amount of light at a first frequency and a first light emission duty ratio.
A step of causing the exposed portion to emit light with a second amount of light at a second frequency different from the first frequency and the first emission duty ratio.
The step of detecting each of the first light amount and the second light amount, and
A method including a step of adjusting the shaping signal based on the difference in light intensity between the first light intensity and the second light intensity. 13. The method of claim 13, further comprising setting the shaping signal so that the difference in light intensity between the first light intensity and the second light intensity is within a predetermined range. Shaping the current includes shaping the current a plurality of times while setting the shaping signal.
For each setting of the shaping signal, the exposed portion is made to emit light at the first frequency and the first emission duty ratio, and further, the exposed portion is emitted at the second frequency and the first emission duty ratio. Steps to make
For each setting of the shaping signal, light was emitted at the first frequency and the third emission duty ratio of the exposure unit, and at the second frequency and the first emission duty ratio. The step of acquiring the fourth light intensity of the exposed portion, and
For each setting of the shaping signal, a step of obtaining the light amount difference between the third light amount and the fourth light amount, and
The method according to claim 13 or 14, further comprising the step of setting the shaping signal so that the difference between the third light amount and the fourth light amount is within the predetermined range. The first frequency is higher than the second frequency,
The light amount of the exposed portion is based on the fact that the first light amount is smaller than the second light amount and the light amount difference between the first light amount and the second light amount is less than the predetermined range. The step of changing the shaping signal setting so that it becomes larger,
The light amount of the exposed portion is based on the fact that the first light amount is larger than the second light amount and the light amount difference between the first light amount and the second light amount exceeds the predetermined range. The method according to any one of claims 13 to 15, further comprising a step of changing the setting of the shaping signal so as to be smaller. The method according to claim 16, wherein changing the setting of the shaping signal so that the amount of light of the exposed portion is increased includes increasing the voltage at the rising edge of the current supplied to the exposed portion. The method according to claim 16, wherein changing the setting of the shaping signal so that the amount of light in the exposed portion is reduced includes reducing the voltage at the rising edge of the current supplied to the exposed portion. The method of any one of claims 13-18, further comprising the step of setting the second frequency to a fraction of an integer of the first frequency. The method according to any one of claims 13 to 19, wherein the emission duty ratio of the current supplied to the exposed portion is between 20% and 90%. The method according to any one of claims 13 to 20, further comprising a step of controlling the waveform of the shaping signal by switching between the waveform shape portion and the line of the shaping signal. The method according to any one of claims 13 to 21, further comprising the step of applying a bias voltage to the shaping signal.

Images