Image forming apparatus, and current control method

Abstract

To improve image quality in image formation.SOLUTION: An image forming device is equipped with an input portion that inputs input image data, a detecting portion that detects pixels becoming an edge among pixels configuring the input image data, a converting portion that converts the density of the edge to generate conversion pixels, an image forming portion that uses a light source emitting light on the basis of the conversion pixels to perform image formation, and an adjusting portion that adjusts a current flowing to the light source and adjusts the light amount of the light.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a current control method.

Background Art

[0002] An image forming apparatus including a light source that applies light to a photoreceptor drum to form a latent image on the photoreceptor drum is known.

[0003] Then, the image forming apparatus detects a boundary region between a normal pixel and an overexposed pixel. Next, the image forming apparatus converts the pixels in the boundary region into turn-off pixels where the light source is turned off. In this way, the image forming apparatus makes some of the normal pixels in the boundary region into overexposed pixels and converts the remaining pixels into turn-off pixels in image formation. That is, the image forming apparatus sets turn-off pixels between normal exposure and overexposure. Thereby, a technique is known that can accurately correct overshoot current and undershoot current (see, for example, Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0004] The technique disclosed in Patent Document 1 may not be able to correct the density or the like at the edge to prevent the edge effect or the like. Therefore, the conventional technique has a problem of poor image quality at the edge or the like.

[0005] An object of the present invention is to improve the image quality in image formation.

Means for Solving the Problems

[0006] To solve the above problems, an image forming apparatus according to an aspect of the present invention includes an input unit that inputs input image data, a detection unit that detects pixels that become edges among the pixels constituting the input image data, a conversion unit that converts the density of the edge to generate converted pixels, An image forming unit that forms an image using a light source that emits light based on the converted pixels, an adjustment unit that adjusts the amount of light by adjusting the current flowing through the light source, and the adjustment unit determines an overshoot current or an undershoot current based on an operation mode and when the operation modes are different, the correction processes for the edges are different This is the gist of the invention.

Advantages of the Invention

[0007] According to the present invention, image quality can be improved in image formation.

Brief Description of the Drawings

[0008]

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Figure 11

Figure 12

Modes for Carrying Out the Invention

[0009] Hereinafter, specific examples will be described with reference to the accompanying drawings. Note that the embodiments are not limited to the specific examples described below.

[0010] [Example of Image Forming Apparatus] FIG. 1 is a diagram showing an example of an image forming apparatus 10. For example, the image forming apparatus 10 includes a photoreceptor 11, a lens 12, a polygon mirror 13, a polygon control device 14, a laser diode 15 (which may also be referred to as "LD"), and the like. The image forming apparatus 10 also includes a detection device 16, a light source driving device 17, a data generation device 18, an image processing device 19, and the like. Hereinafter, the image forming apparatus 10 is assumed to include two of each hardware resource as shown in the figure.

[0011] The photoreceptor 11 forms a latent image. Specifically, when the photoreceptor 11 is irradiated with the light emitted by the laser diode 15, a latent image is formed on the irradiated portion. Then, toner is transferred to the latent image portion. That is, a latent image indicating an image to be formed on a recording medium is formed on the photoreceptor 11.

[0012] The lens 12 and the polygon mirror 13 are examples of optical members. Note that there may be other optical members. The lens 12 is, for example, an Fθ lens. When the light transmitted through the lens 12 hits the photoreceptor 11, a latent image is formed on the photoreceptor 11.

[0013] The polygon mirror 13 reflects the light emitted by the laser diode 15. When the polygon mirror 13 rotates, the light scans in one direction (the left - right direction in the figure. Hereinafter referred to as the "main scanning direction").

[0014] The polygon control device 14 is a device that controls an actuator or the like for rotating the polygon mirror 13.

[0015] The laser diode 15 is an example of a light - emitting light source device. For example, the laser diode 15 is a semiconductor LD or the like.

[0016] The detection device 16 is installed on the extension of the photoreceptor 11 in the main scanning direction. Then, the detection device 16 outputs a detection signal when it receives light. The detection signal output in this way indicates the reference timing. For example, the detection signal is used to align the writing positions of the image data, etc.

[0017] The light source driving device 17 performs control such as turning on or off the laser diode 15 based on the data (hereinafter referred to as "lighting data") generated by the data generation device 18.

[0018] The data generation device 18 generates lighting data based on the input image data 20, etc.

[0019] The image processing device 19 inputs the input image data 20, etc. from an external device such as a Personal Computer (PC) or a scanner. Note that the image processing device 19 may perform image processing and data conversion, etc. on the input image data 20.

[0020] Note that the image forming apparatus 10 is not limited to the hardware configuration shown above. Therefore, the image forming apparatus 10 may be provided with hardware resources other than those shown above, either internally or externally.

[0021] [Processing Example] Hereinafter, for the sake of simplicity, the description will focus on the processing of edge detection and correction. However, the image forming apparatus 10 may further perform processing other than that described below.

[0022] FIG. 2 is a diagram (part 1) showing a processing example. Hereinafter, the input image data 20 shown in FIG. 2(A) will be described as an example.

[0023] In FIG. 2(A), the pixels for image formation are shown in black. On the other hand, in FIG. 2(A), the pixels that do not perform image formation are shown in white (that is, the point where the color of the recording medium remains).

[0024] For example, based on the input image data 20, the image forming apparatus 10 generates the image data shown in FIG. 2(B) (hereinafter referred to as "first image data 21") and the image data shown in FIG. 2(C) (hereinafter referred to as "second image data 22"). Note that the processing is mainly performed by the image processing apparatus 19.

[0025] The first image data 21 is the same data as the input image data 20.

[0026] The second image data 22 is data indicating the result of detecting the edge 30.

[0027] The edge 30 is detected, for example, by comparing the density of the pixel of interest and the surrounding pixels. Specifically, the image forming apparatus 10 sets a threshold value in advance. Next, the image forming apparatus 10 determines whether the density of the pixel of interest and the surrounding pixels changes by more than the threshold value, that is, whether it is a point where the density changes abruptly. Then, when the image forming apparatus 10 determines that the pixel of interest is a pixel where the density changes abruptly, it determines that it is the edge 30.

[0028] In the example shown in FIG. 2(A), when white and black pixels are adjacent in the vertical direction or the horizontal direction, the edge 30 is detected. Note that the edge 30 is not limited to the vertical direction and the horizontal direction, and may be detected in an oblique direction or the like.

[0029] Note that the detection of the edge 30 may be performed by processing other than the above. For example, the edge 30 may be detected by filter processing or the like. Further, the edge 30 may be detected by widely considering not only adjacent pixels but also pixels existing around the pixel of interest.

[0030] As described above, by performing the process of detecting the edge 30 on the input image data 20, the image forming apparatus 10 generates the second image data 22. Next, based on the second image data 22 and the like, the image forming apparatus 10 converts the density of the edge 30 as follows.

[0031] FIG. 3 is a diagram (part 2) showing a processing example. The figure shows an example of data (hereinafter referred to as "third image data 23") after converting the density of edge 30 based on first image data 21 and second image data 22.

[0032] The third image data 23 has a different density of edge 30 compared to the first image data 21. Specifically, the third image data 23 is generated by converting the density of the pixels detected as edge 30 among the pixels for forming an image shown by the first image data 21 (that is, the black pixels in the first image data 21).

[0033] The edge 30, that is, the pixel to be converted, is the pixel shown by the second image data 22. Hereinafter, the pixel of the edge 30, that is, the pixel to be converted is referred to as "conversion pixel 31". On the other hand, for the pixels other than the conversion pixel 31, the image forming apparatus 10 maintains the density and the like from the first image data 21.

[0034] In the illustrated example, the image forming apparatus 10 is an example of converting so that the density of the edge 30 becomes lower. For example, the density is converted to a preset value or the like. Thus, how to convert the density of the edge 30 is preset.

[0035] As described above, when the third image data 23 is generated, based on the third image data 23, the image forming apparatus 10 performs Pulse Width Modulation (PWM) conversion or the like. For example, the PWM conversion is mainly performed by the data generation device 18. Specifically, the third image data 23 shown in FIG. 3 is converted as follows.

[0036] FIG. 4 is a diagram (part 3) showing a processing example. Hereinafter, an example will be described with respect to the first line 41, the second line 42, and the third line 43 among the lines constituting the third image data 23.

[0037] FIG. 4(B) shows an example of the PWM conversion result. Specifically, the 11th signal SIG11 is an example of a signal generated by performing PWM conversion on the first line 41. Similarly, the 12th signal SIG12 is an example of a signal generated by performing PWM conversion on the second line 42. Also, the 13th signal SIG13 is an example of a signal generated by performing PWM conversion on the third line 43.

[0038] For the 11th signal SIG11, the 12th signal SIG12, and the 13th signal SIG13, the concentration is the time when the light source is lit. That is, for pixels with a higher concentration, the width of the High level is wider. On the other hand, for pixels with a lower concentration, the width of the High level is narrower. Thus, by PWM conversion, a signal indicating the concentration by the width of the time when the light source is lit is generated. Next, the signals shown in FIG. 4(B) are converted by phase control, for example, as shown in FIG. 4(C).

[0039] FIG. 4(C) shows an example of the phase control result. Phase control is, for example, control that shifts the phase toward the side with larger dots when there are large dots before and after.

[0040] Among the 21st signal SIG21, the 22nd signal SIG22, and the 23rd signal SIG23, the 21st signal SIG21 and the 23rd signal SIG23 are the same before and after the phase control.

[0041] On the other hand, the 22nd signal SIG22 is different in that it is converted to shift the phase. Thus, phase control is a process of combining small dots and large dots into one dot. When image formation is performed with a signal subjected to such phase control, a stable image can be obtained.

[0042] On the other hand, when the concentrations of adjacent pixels are about the same, in phase control, the process of shifting the phase is not performed.

[0043] Through the above processing, the image forming apparatus 10 generates lighting data as shown in FIG. 4(C), for example. Based on the lighting data generated in this way, the light source is controlled.

[0044] FIG. 5 is a diagram showing a circuit configuration example.

[0045] The light source driving device 17 includes a drive signal generation circuit 171, a switch 172, a D / A converter (hereinafter referred to as "DAC173"), a current source 174, and the like.

[0046] The drive signal generation circuit 171 inputs the lighting data 51. Then, based on the lighting data 51, the drive signal generation circuit 171 generates drive signals such as a bias signal SIG31, an overshoot signal SIG32, and a lighting signal SIG33.

[0047] The lighting signal SIG33 is the signal indicated by the lighting data 51.

[0048] The switch 172 switches the ON / OFF of the current supplied from the power source based on the bias signal SIG31, the overshoot signal SIG32, the lighting signal SIG33, and the like.

[0049] The DAC173 converts the current data 53 into an analog quantity. Then, the DAC173 inputs the analog quantity to the current source 174.

[0050] When the switch 172 is ON, the current source 174 sends the current indicated by the analog quantity to the laser diode 15.

[0051] Hereinafter, the current flowing through the current source 174 based on the lighting signal SIG33 is referred to as "switching current Isw". The current flowing through the current source 174 based on the overshoot signal SIG32 is referred to as "overshoot current Iov". The current flowing through the current source 174 based on the bias signal SIG31 is referred to as "bias current Ib".

[0052] And the current flowing through the laser diode 15 is referred to as "total current It". Note that the total current It may also be referred to as a drive current or the like.

[0053] The current data 53, that is, the current flowing through the current source 174, is set by, for example, the setting data 52 or the like. Note that the setting data 52 may be determined by, for example, the operation mode or the like.

[0054] [Example of light amount adjustment] FIG. 6 is a diagram showing an example of light amount adjustment. For example, the image forming apparatus 10 adjusts the light amount of the light emitted from the laser diode 15 based on the signal shown in FIG. 6(A). Note that the adjustment is mainly performed by the light source driving device 17.

[0055] The delay signal SIG41 is a signal obtained by delaying the lighting signal SIG33. For example, the delay signal SIG41 is generated by inputting the lighting signal SIG33 to a delay element or the like.

[0056] The bias signal SIG31 is a signal through which a bias current Ib flows when it becomes a High level. Hereinafter, it is assumed that each signal is a High Active signal in which the High level is “ON” and the Low level is “OFF”.

[0057] The bias current Ib is a current that is flowed to smoothly start the light emission of the laser diode 15. Therefore, the bias current Ib is a current at a level where the laser diode 15 does not emit light. For example, the bias current Ib is set to ON (High level in the figure) while the image forming apparatus 10 is being driven. Also, the bias current Ib is set in advance according to the characteristics of the laser diode 15 or the like.

[0058] The overshoot signal SIG32 is a signal that detects the rising edge of the lighting signal SIG33, that is, the overshoot. For example, the overshoot signal SIG32 is a signal that detects the rising edge and turns ON when the lighting signal SIG33 is at the High level and the delay signal SIG41 is at the Low level. In this way, by using the lighting signal SIG33 and the delay signal SIG41, the rising edge of the signal can be detected.

[0059] When detecting a fall, the image forming apparatus 10 detects the timing at which the lighting signal SIG33 is at the Low level and the delay signal SIG41 is at the High level. In this way, by using the lighting signal SIG33 and the delay signal SIG41, the fall of the signal can be detected.

[0060] As shown in FIG. 6(B), the total current It is adjusted. In this way, it is desirable to adjust the light amount by adjusting the current. Specifically, as a result of the adjustment as shown in FIG. 6(B), the light amount becomes as shown in FIG. 6(C).

[0061] As shown in FIG. 6(B), when the bias signal SIG31 becomes ON, the bias current Ib flows through the total current It. Further, when the lighting signal SIG33 becomes ON, the switching current Isw is added to the total current It. Similarly, when the overshoot signal SIG32 becomes ON, the overshoot current Iov flows through the total current It. For the total current It determined in this way, the light amount has a relationship as shown in FIG. 6(C).

[0062] At the first timing T1, since the lighting signal SIG33 rises, the overshoot signal SIG32 becomes ON. Therefore, from the first timing T1 until the overshoot signal SIG32 is ON, the total current It becomes a current as shown in the following equation (1).

[0063] It = Ib + Isw + Iov (1)

[0064] As shown in the above equation (1), the total current It is adjusted so that the overshoot current Iov flows at the first timing T1. In this way, the overshoot current Iov is a current that flows in addition to the bias current Ib and the switching current Isw. Hereinafter, the light amount after being adjusted by the overshoot current Iov or the like is referred to as "adjusted light amount La". In the figure, the adjusted light amount La is shown by a solid line.

[0065] If the overshoot current Iov is not allowed to flow, the amount of light tends to be like the light amount Lb before adjustment (the light amount indicated by the dotted line in the figure). A phenomenon such as the light amount Lb before adjustment is caused by parasitic capacitance and the like existing in the light source and the substrate on which the light source is mounted.

[0066] Parasitic capacitance is also called stray capacitance or floating capacitance. Parasitic capacitance is, for example, the capacitance possessed by electronic components and the like.

[0067] During rise and the like, current flows through the parasitic capacitance until the parasitic capacitance is charged. Therefore, the current flowing through the light source decreases by the amount that has flowed through the parasitic capacitance, and the light amount tends to be dull like the light amount Lb before adjustment. Therefore, assuming that current flows through the parasitic capacitance, an overshoot current Iov is added to the total current It.

[0068] When adjusted to allow the overshoot current Iov to flow, the current flowing through the parasitic capacitance is compensated, and at the first timing T1, the light amount can rise steeply like the light amount La after adjustment.

[0069] When the light amount is increased, the amount of toner adhering to the latent image increases. Therefore, in order to reduce the edge effect on the edge 30 and the like, the image forming apparatus 10 converts the density of the edge 30 to decrease it. However, when the conversion to decrease the density is performed, the edge 30 tends to become thinner. Therefore, by adjustment such as flowing the overshoot current Iov, the image forming apparatus 10 adjusts the light amount so that the edge effect hardly occurs and the toner amount becomes optimal. In this way, the density and the toner amount are optimized. And by optimizing the toner amount, the image forming apparatus 10 can improve the image quality.

[0070] Note that the time required to form one dot may vary depending on the speed at which image formation is performed (which may also be referred to as the "printing speed" or "linear speed", etc.). In such a case, the ratio of the overshoot current Iov occupied in the formation of one dot also varies. Therefore, it is desirable that the overshoot current Iov be determined according to the speed of image formation or the like. In this way, when the image forming apparatus 10 determines the overshoot current Iov according to the speed of image formation or the like, image processing and current control suitable for the speed of image formation can be performed.

[0071] [First Modified Example] The image forming apparatus 10 may have the following configuration.

[0072] FIG. 7 is a diagram showing a circuit configuration example in the first modified example. Compared with FIG. 5, the circuit configuration shown in FIG. 7 is different in that there are two current sources 174 for overshoot. Hereinafter, the description will be centered on the differences, and the overlapping descriptions will be omitted.

[0073] Hereinafter, based on the first overshoot signal SIG321, the current flowing through the current source 174 is referred to as the "first overshoot current Iov1". Based on the second overshoot signal SIG322, the current flowing through the current source 174 is referred to as the "second overshoot current Iov2".

[0074] Also, in the first modified example, the switching current Isw flows when the delay signal SIG41 becomes ON.

[0075] FIG. 8 is a diagram showing an example of adjusting the light amount in the first modified example. Compared with FIG. 6, the difference is that the second delay signal SIG42 is added. Also, the overshoot signal SIG32 becomes the first overshoot signal SIG321 and the second overshoot signal SIG322. Hereinafter, the same signals will be denoted by the same reference numerals, and the description will be omitted.

[0076] The first overshoot signal SIG321 is a signal similar to the overshoot signal SIG32 in FIG. 6. That is, the first overshoot signal SIG321 is a signal indicating the rising edge of the delay signal SIG41.

[0077] For example, the first overshoot signal SIG321 is a signal that turns ON when the delay signal SIG41 is at a high level and the second delay signal SIG42 is at a low level. In this way, by using the delay signal SIG41 and the second delay signal SIG42, the rising edge can be detected.

[0078] Similar to FIG. 6, the first overshoot signal SIG321 is controlled to pass a first overshoot current Iov1 at a first timing T1.

[0079] The second delay signal SIG42 is a signal obtained by further delaying the lighting signal SIG33 by a delay element or the like compared to the delay signal SIG41.

[0080] The second overshoot signal SIG322 is a signal indicating the falling edge of the delay signal SIG41.

[0081] For example, the second overshoot signal SIG322 is a signal that turns ON when the lighting signal SIG33 is at a low level and the delay signal SIG41 is at a high level. In this way, by using the lighting signal SIG33 and the delay signal SIG41, the falling edge can be detected.

[0082] At a second timing T2 when the second overshoot signal SIG322 turns ON, a second overshoot current Iov2 flows.

[0083] Therefore, in the first modification, at the first timing T1, the total current It is as shown in the following equation (2).

[0084] It = Ib + Isw + Iov1 (2)

[0085] Also, at the second timing T2, the total current It is as expressed by the following equation (3).

[0086] It = Ib + Isw + Iov2 (3)

[0087] As described above, the image forming apparatus 10 adjusts the current rise with the first overshoot current Iov1, and also adjusts with the second overshoot current Iov2 immediately before the light source turns off. By adjusting in this way, the image forming apparatus 10 can adjust to increase the light amount at both timings of the current rise and the current fall, such as the adjusted light amount La.

[0088] For example, in the case of the edge 30 as shown in FIG. 2, the image forming apparatus 10 can optimize the toner amount at both the edge 30 located at the left end and the edge 30 located at the right end.

[0089] [Second Modified Example] FIG. 9 is a diagram showing a circuit configuration example in the second modified example. Compared with the first modified example, the second modified example is different in that an undershoot current source 174 or the like is added. Hereinafter, the description will focus on the differences from the first modified example.

[0090] Hereinafter, the current flowing through the current source 174 based on the undershoot signal SIG5 is referred to as the "undershoot current Iud". That is, when the undershoot signal SIG5 is turned ON, the undershoot current Iud flows.

[0091] The undershoot current Iud is a current that flows in a direction opposite to the current for causing the light source such as the first overshoot current Iov1 to emit light.

[0092] FIG. 10 is a diagram showing an example of adjusting the light amount in the second modified example.

[0093] The undershoot signal SIG5 is a signal indicating the fall of the delay signal SIG41.

[0094] For example, the undershoot signal SIG5 is a signal that turns ON when the delay signal SIG41 is at the Low level and the second delay signal SIG42 is at the High level. In this way, by using the delay signal SIG41 and the second delay signal SIG42, the fall can be detected.

[0095] Without the undershoot current Iud, the charge held in the parasitic capacitance and the like flows to the light source, and the light amount is likely to decay like the light amount Lb before adjustment.

[0096] On the other hand, if it is adjusted to flow the undershoot current Iud, the light amount can fall steeply like the light amount La after adjustment.

[0097] As described above, the image forming apparatus 10 adjusts the rise of the current with the first overshoot current Iov1, and also adjusts it with the second overshoot current Iov2 immediately before the light source turns off.

[0098] If it is slow to turn off the light source like the light amount Lb before adjustment, unnecessary dots may be formed at the boundary between the position where image formation is performed and the position where image formation is not performed.

[0099] Therefore, the image forming apparatus 10 adjusts so that the current falls steeply at the boundary like the light amount La after adjustment. By doing so, it is possible to prevent unnecessary toner from adhering and improve the image quality. Also, it is possible to prevent unnecessary toner from adhering and optimize the toner amount.

[0100] [Example of processing based on the operation mode etc.] The image forming apparatus 10 desirably performs processing in consideration of the operation mode etc. as follows, for example.

[0101] The operation mode is information indicating, for example, the use of image formation performed by the image forming apparatus 10 such as copying or printing. For example, the operation mode is set by a user operation.

[0102] When the operation mode is different, the required image quality often differs. Therefore, the image forming apparatus 10 performs different image processes depending on the operation mode. For example, when the operation mode is different, the correction process for the edge 30 is different.

[0103] Therefore, when the current is adjusted based on the operation mode, the image forming apparatus 10 can perform more optimal image processing and current control.

[0104] Also, similar to the operation mode, when conditions such as the speed of image formation, image quality, or type of recording medium for image formation are different, the required image quality may be different. Therefore, when the image forming apparatus 10 adjusts the current based on conditions such as the speed of image formation, image quality, or type of recording medium for image formation, the image forming apparatus 10 can perform more optimal image processing and current control.

[0105] [Functional Configuration Example] FIG. 11 is a diagram showing a functional configuration example. For example, the image forming apparatus 10 includes an input unit 10F1, a detection unit 10F2, a conversion unit 10F3, an image forming unit 10F4, an adjustment unit 10F5, and an image forming unit 10F7, etc. Note that the image forming apparatus 10 preferably further includes an operation mode setting unit 10F6 as shown in the figure. Hereinafter, the illustrated functional configuration will be described as an example.

[0106] The input unit 10F1 performs an input procedure for inputting the input image data 20. For example, the input unit 10F1 is realized by an input device or the like included in the image processing apparatus 19.

[0107] The detection unit 10F2 performs a detection procedure for detecting pixels that become edges among the pixels constituting the input image data 20. For example, the input unit 10F1 is realized by an arithmetic device or the like included in the image processing apparatus 19.

[0108] The conversion unit 10F3 performs a conversion procedure for converting the density of the edge to generate converted pixels. For example, the conversion unit 10F3 is realized by an arithmetic device or the like included in the image processing apparatus 19.

[0109] The image forming unit 10F4 performs an image forming procedure for forming an image using a light source that emits light based on the converted pixels. For example, the image forming unit 10F4 is realized by a light source driving device 17 or the like.

[0110] The adjustment unit 10F5 performs an adjustment procedure for adjusting the amount of light by adjusting the current flowing through the light source. For example, the adjustment unit 10F5 is realized by a light source driving device 17 or the like.

[0111] The operation mode setting unit 10F6 performs an operation mode setting procedure for setting the operation mode. For example, the operation mode setting unit 10F6 is realized by an input device or the like included in the image processing device 19. The input device receives the operation mode and the like by a user operation or the like.

[0112] The image forming unit 10F7 includes, for example, a laser diode 15, a photoreceptor 11, and the like.

[0113] The image forming apparatus 10 forms an image on a recording medium and outputs printed matter or the like.

[0114] With the above configuration, the image forming apparatus 10 can perform correction to lower the density to a level that prevents edge effects by converting the density of the edges. That is, in the conventional technology, there are cases where the density cannot be lowered to a level that can prevent edge effects. On the other hand, with the configuration as in the present application, the image forming apparatus 10 can sufficiently perform correction to lower the density to a level that prevents edge effects and the like. Therefore, the image forming apparatus 10 can prevent edge effects and the like and improve the image quality.

[0115] FIG. 12 is a diagram showing an example of an edge effect. For example, when performing image formation as shown in FIG. 12(A) or FIG. 12(B), image formation may be performed using signals as shown in FIG. 12(C) and FIG. 12(D).

[0116] When using such a signal, a phenomenon occurs where toner adheres uselessly at the edge positions, namely the so-called edge effect. To prevent the occurrence of such an edge effect, the image forming apparatus 10 corrects to lower the density at the edge. For example, the image forming apparatus 10 performs processing as shown in FIG. 3. Then, the image forming apparatus 10 forms an image based on the converted pixels.

[0117] When forming an image, the image forming apparatus 10 adjusts the current flowing through the light source at the rising and falling edges of the current, etc., to adjust the amount of light emitted by the light source. In this way, when adjusting the light amount with the current, fine adjustment is possible.

[0118] Also, in the conventional technology, when the density is lowered so much that the edge effect can be suppressed, the image quality may deteriorate. On the other hand, in the image forming apparatus 10 shown above, even when the density is lowered, since the current is adjusted to adjust the light amount, the toner amount can be optimized to improve the image quality.

[0119] [Other Embodiments] The current control method described above may be realized by, for example, a program such as firmware for some of the processing. That is, the current control method is a method executed by a computer by operating the arithmetic unit, storage unit, input unit, output unit, and control unit in cooperation based on a program. Also, the program may be written and distributed in a storage device or a storage medium, etc., or distributed through an electric communication line, etc.

[0120] Each device described above does not have to be a single device. That is, each device may be a system composed of a plurality of devices.

[0121] The image forming apparatus may be, for example, a commercial printing machine (such as a large electrophotographic printer or an inkjet printer, etc.).

[0122] The recording medium is, for example, paper (also referred to as "plain paper", etc.). However, the recording medium may be coated paper, label paper, etc. other than paper, overhead projector sheets, films, or flexible thin plates, etc. Further, the recording medium may be roll paper, etc.

[0123] That is, the material of the recording medium may be a material such as ink droplets or a coating material such as toner to which the coating material can adhere, temporarily adhere, adhere and fix, or adhere and penetrate.

[0124] Specifically, the recording medium is a recording medium such as paper, film, or cloth, an electronic substrate, an electronic component such as a piezoelectric element (also referred to as a "piezoelectric member", etc.), a powder layer (also referred to as a "powder layer", etc.), an organ model, or a test cell, etc.

[0125] Thus, the material of the recording medium may be a material to which the coating material can adhere, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, or a combination thereof, etc.

[0126] Note that the present invention is not limited to the embodiments exemplified above, and various modifications are possible without departing from the technical gist thereof, and all technical matters included in the technical idea described in the claims are the subject of the present invention. The above embodiments show preferred examples, but those skilled in the art can realize various modified examples from the disclosed content. Such modified examples are also included in the technical scope described in the claims.

Explanation of Reference Numerals

[0127] 10: Image forming apparatus 10F1: Input unit 10F2: Detection unit 10F3: Conversion unit 10F4: Image forming unit 10F5: Adjustment unit 10F6: Operation mode setting unit 20: Input image data 30: Edge 31: Transformed Pixel Ib: Bias Current Iov: Overshoot Current Iov1: First Overshoot Current Iov2: Second Overshoot Current Isw: Switching Current It: Total Current Iud: Undershoot Current La: Adjusted Light Quantity Lb: Light Quantity before Adjustment SIG32: Overshoot Signal SIG321: First Overshoot Signal SIG322: Second Overshoot Signal SIG5: Undershoot Signal T1: First Timing T2: Second Timing

Prior Art Documents

Patent Documents

[0128]

Patent Document 1

Claims

1. An input unit for inputting input image data; A detection unit that detects pixels that become edges among the pixels constituting the input image data; A conversion unit that converts the density of the edge to generate a converted pixel; An image forming unit that forms an image using a light source that emits light based on the converted pixel; An adjustment unit that adjusts the amount of light by adjusting the current flowing through the light source; Comprising; The adjustment unit, Based on the operation mode, determines an overshoot current or an undershoot current, When the operation mode is different, the correction process for the edge is different Image forming apparatus.

2. The adjustment unit, Based on the speed of image formation, image quality, or type of recording medium, determines an overshoot current to be additionally flowed in addition to the bias current and the switching current The image forming apparatus according to claim 1.

3. Further comprising an operation mode setting unit for setting an operation mode, The adjustment unit, Based on the operation mode, determines an overshoot current to be additionally flowed in addition to the bias current and the switching current The image forming apparatus according to claim 1 or 2.

4. The adjustment unit, Adjustment is performed at the rising and falling timings of the signal for controlling the current The image forming apparatus according to any one of claims 1 to 3.

5. The adjustment unit, At the falling timing of the signal for controlling the current, adjusts to flow an undershoot current flowing in the direction opposite to the direction in which the light source emits light The image forming apparatus according to any one of claims 1 to 4.

6. A current control method performed by an image forming apparatus, An input procedure in which the image forming apparatus inputs input image data; A detection procedure in which the image forming apparatus detects pixels that become edges among the pixels constituting the input image data; A conversion procedure in which the image forming apparatus converts the density of the edge to generate a converted pixel; An image forming procedure in which the image forming apparatus forms an image using a light source that emits light based on the converted pixel; An adjustment procedure in which the image forming apparatus adjusts the current flowing through the light source to adjust the amount of light of the light Having, In the adjustment procedure, Based on the operation mode, determines an overshoot current or an undershoot current, When the operation mode is different, the correction process for the edge is different Current control method.

Images