JP6555099B2 - Signal processing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a technology capable of eliminating the influence caused by differences in pulse widths of a plurality of pulse signals in a signal processing apparatus and an image forming apparatus that perform signal processing based on image data.

  As an image forming apparatus, a pulse signal is generated according to image data, and image formation of one line or several lines in the main scanning direction (first direction) is performed using the pulse signal, and each line in the main scanning direction is formed. It is known that image formation of one page is repeated in the sub-scanning direction (second direction) to form an image for one page.

  As an example, an electrophotographic image forming apparatus generates an image forming signal (PWM pulse signal by a PWM circuit) from image data, and scans a laser beam modulated in accordance with the PWM pulse signal in the main scanning direction. In parallel with this, an image is formed by the laser beam on an image carrier that rotates in the sub-scanning direction.

  By the way, in order to realize high-speed image formation, two systems of pulse generators are provided in a PWM circuit that generates PWM pulse signals, and generation of PWM pulse signals based on image data is executed alternately. There is a method of switching and selecting a PWM pulse signal generated by a system pulse generator and outputting a system of PWM signals. By doing in this way, the merit that the burden (processing capability) of a PWM circuit (pulse generation part) can be reduced occurs.

In addition, it is possible to further reduce the load on the PWM circuit for high-speed image formation by arranging more than one system of pulse generation units, not limited to two systems, and sequentially selecting and using them.
A plurality of pulse generators as described above generate a PWM pulse signal, switch a pulse generation source circuit in a certain period, and finally combine it as a single PWM pulse signal with a selector or a logical OR circuit. In a circuit that does not perform waveform shaping using a D flip-flop circuit or the like, for example, a phenomenon in which a pulse width characteristic is slightly different for each of a plurality of PWM pulse signals occurs due to variations in the distribution of processes, temperature, voltage, and the like inside the ASIC.

  In addition, as a technique relevant to this, it describes in the following patent documents etc., for example.

JP-A-8-265532

In the above Patent Document 1, it is proposed to detect the difference between the PWM pulse signal and an ideal value and correct the difference.
Further, regarding the difference in the pulse width of the PWM pulse signal by the plurality of pulse generators as described above, it is conceivable to measure and correct the difference.

  However, in order to correct a minute difference due to variations in the distribution of processes, temperature, voltage, and the like inside the ASIC, a high-resolution measurement circuit and a high-resolution correction circuit are required, which is expensive. Furthermore, even if correction is performed with high accuracy as described above, a certain residual due to measurement / correction error remains. Furthermore, there is a problem that real-time correction cannot be performed and cannot be handled when there is a time variation.

  If the difference between the PWM pulse signals as described above is generated, there is no problem if a high-frequency random image such as a photograph is drawn, but a pulse with a constant width (constant density) continues to be output. If they occur at the same position in the main scanning direction, there is a problem that the image is continuously (aligned) in the sub-scanning direction and the density is visually recognized.

Also, in the case of image formation that expresses light and shade on a screen, a light and dark difference occurs for each screen due to the difference in PWM pulse signals of dots used for the screen.
Even if the pulse width difference between the subtle PWM pulse signals as described above is collected, a certain number of such differences cause a reduction in spatial frequency and a situation where it is easy to see. It is thought that the difference can be easily grasped visually.

  Here, FIG. 7 schematically shows a state of pulses output by a PWM processing unit having two pulse generation units (a first pulse generation unit and a second pulse generation unit). A pulse generated by the first pulse generation unit is represented as “A”, and a pulse generated by the second pulse generation unit is represented as “B”. In FIG. 7, it is assumed that the pulse width is A> B. In FIG. 7, (1), (2), (3),... Represent the main scanning lines of the laser beam arranged in the sub-scanning direction.

  Here, when a plurality of pulse generators are selectively used, if a minute difference (A> B) in the pulse width remains in the pulse signal from each pulse generator, the difference is indicated in the sub-scanning direction. Will be aligned in the direction including Then, it can be seen that such a difference continues in the sub-scanning direction so that it is easy to grasp visually.

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to improve an adverse effect on image quality due to a minute difference in pulse width when a plurality of pulse generation units are selectively used. An object is to realize a possible signal processing apparatus and image forming apparatus.

In order to achieve at least one of the above objects, a signal processing apparatus and an image forming apparatus reflecting one aspect of the present invention are configured as follows.
(1) According to the present invention, a pulse signal corresponding to image data is generated, and an image is formed in the first direction using the pulse signal, and the image formation in the first direction is perpendicular to the first direction. A signal processing apparatus used in an image forming apparatus that forms a two-dimensional image according to image data by repeating in a direction, and generates a pulse signal according to the image data for each pulse signal. A plurality of pulse generators to be generated and the pulse signal sharing generation by the plurality of pulse generators are selectively switched, and the pulse signals generated by the plurality of selectively switched pulse generators are output. And a control unit that controls the switching order in the selection unit, and the control unit transmits the pulse signal in the first direction as the switching order in the selection unit. When repeating the output of said second direction, and controlled to a predetermined order including a different order, a reference position signal indicating that the image form a predetermined reference position in the first direction in the image forming apparatus The control unit controls the switching order in the selection unit to be a predetermined order including a different order each time the reference position signal is generated .

Further, the present invention generates a pulse signal corresponding to the image data, forms an image in the first direction using the pulse signal, and performs image formation in the first direction in a second direction orthogonal to the first direction. A plurality of pulse generators for generating a pulse signal corresponding to the image data in a shared manner for each pulse signal; A selection unit that selectively switches shared generation of the pulse signals by the plurality of pulse generation units, and outputs the pulse signals generated by the plurality of pulse generation units that are selectively switched; and the selection unit A control unit that controls the switching order in the control unit, wherein the control unit outputs the pulse signal in the first direction in the second direction as the switching order in the selection unit. When returning Ri, different controlled to be predetermined order including an order, the reference position signal indicating that a predetermined reference position in the first direction and image formation in the image forming apparatus is generated, the control unit Controls the order of switching in the selection unit so as to be a predetermined order including a different order each time the reference position signal is generated .

Oite (2) or more (1), wherein the control unit controls such that the predetermined order using a random number.
Oite in (3) above (1), wherein the predetermined order is generated in advance a storage unit stored as an ordered pattern, wherein the control unit uses the sequence pattern stored in the storage unit To control the predetermined order.

( 4 ) In the above (1) to ( 3 ), the image forming apparatus is configured to execute image formation in the first direction for a plurality of lines in parallel, and a plurality of the pulse generation units and the A selection unit and a combination are provided for each of the plurality of lines, and the control unit changes the order of switching in the selection unit in at least adjacent lines for the plurality of lines for performing image formation in parallel. Control is performed in a predetermined order.

In the signal processing apparatus and the image forming apparatus reflecting one aspect of the present invention, the following effects can be obtained.
(1) The present invention generates a pulse signal corresponding to image data, forms an image in the first direction using the pulse signal, and performs image formation in the first direction in a second direction orthogonal to the first direction. When the two-dimensional image formation according to the image data is performed by repeating the above, a plurality of pulses that are selectively switched are generated by sharing the generation of the pulse signal according to the image data for each pulse signal. When outputting the pulse signal generated by the generation unit and repeating the output of the pulse signal in the first direction in the second direction, a predetermined order including a different order as a switching order of the plurality of pulse generation units The switching order is controlled so that As a result, even when a plurality of pulse generators are selectively used, even if a minute difference in pulse width remains in the pulse signal from each pulse generator, the difference is aligned in the second direction. Therefore, it is possible to eliminate an adverse effect on image quality.

  (2) In the above (1), when a reference position signal such as an index signal indicating that a predetermined reference position in the first direction is image-formed is generated by the image forming unit, this reference position signal is selected. As the order of switching in the unit, every time the reference position signal is generated, by controlling so as to be a predetermined order including a different order, there is a small difference in the pulse width included in the pulse signal from each pulse generation unit. Since the difference is reliably distributed in the first direction, the difference is not aligned in the second direction, and it is possible to eliminate an adverse effect on the image quality.

  (3) In the above (1) to (2), by controlling to be in a predetermined order using a random number, a minute difference in pulse width included in the pulse signal from each pulse generation unit is converted into a random number. Therefore, the difference is no longer aligned in the second direction and the adverse effect on the image quality can be eliminated.

  (4) In the above (1) to (2), the pulse included in the pulse signal from each pulse generation unit is controlled by using the order pattern generated and stored in advance so as to be in a predetermined order. Since the minute difference in width is reliably distributed in the first direction based on the stored order pattern, the difference is not aligned in the second direction, and adverse effects on image quality can be eliminated. . When the influence on the image quality due to the difference in the pulse width still remains, it is possible to further reduce the adverse effect on the image quality by changing the order pattern.

  (5) In the above (1) to (4), when image formation in the first direction is executed in parallel for a plurality of lines in the image forming apparatus, a combination of a plurality of pulse generators and selectors is combined into a plurality of lines. Parallel execution is performed by controlling the switching order in the selection unit to be a predetermined order including a different order in at least adjacent lines corresponding to a plurality of lines that are provided for each part and perform image formation in parallel. Even in a plurality of lines, a minute difference in pulse width is reliably dispersed in the first direction, so that the difference is not aligned in the second direction in the plurality of lines, and an adverse effect on image quality can be eliminated. It becomes possible.

1 is a configuration diagram illustrating a configuration of an image forming apparatus having a signal processing apparatus according to an embodiment of the present invention. 1 is a configuration diagram illustrating a configuration of an image forming apparatus having a signal processing apparatus according to an embodiment of the present invention. 1 is a configuration diagram illustrating a configuration of an image forming apparatus having a signal processing apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of the signal processing apparatus of embodiment of this invention. It is explanatory drawing which shows the mode of the signal processing of an image forming apparatus. It is explanatory drawing which shows the mode of the signal processing of an image forming apparatus. It is explanatory drawing which shows the mode of the conventional signal processing.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments (embodiments) for implementing a signal processing apparatus and an image forming apparatus of the present invention will be described in detail with reference to the drawings.
[Configuration of signal processing apparatus and image forming apparatus]
Here, based on FIG. 1, the structure of the signal processing apparatus which can be used for image formation and the image forming apparatus 100 including the signal processing apparatus will be described in detail.

Note that description of general parts that are known as the signal processing apparatus and the image forming apparatus 100 and are not directly related to the characteristic operation and control of the present embodiment is omitted.
The image forming apparatus 100 includes a control unit 101 that controls each unit of the image forming apparatus 100, a communication unit 102 that communicates with an external device, an operation display unit 103 that receives an operation from a user and displays an apparatus state, and various setting data. A storage unit 104 for storing, an image data storage unit 110 for storing image data, an image processing unit 120 for performing various image processing on the image data, a PWM processing unit 130 for generating a pulse signal in pixel units in accordance with the image data, and PWM processing The image forming unit 140 is configured to form an image by irradiating the image carrier with a laser beam in accordance with a pulse signal output from the unit 130.

Further, the PWM processing unit 130 constitutes the signal processing device according to the present embodiment, and the generation of the pulse signal corresponding to the image data is generated by sharing a plurality of pulse generation units for each pulse signal. It is configured as follows.
That is, the PWM processing unit 130 distributes the generation of a pulse signal according to image data to a plurality of pulse generation units for each pulse signal, and generates the pulse signal according to image data for each pulse signal. A plurality of pulse generation units 132a and 132b to be shared, and an output side selection unit 133 that synthesizes a single pulse signal when the generation of a pulse signal according to image data is shared by a plurality of pulse generation units for each pulse signal. It is configured.

  Note that the input side selection unit 131 and the output side selection unit 133 control selection based on a selection control signal from the control unit 101. Here, the control unit 101 outputs pulse signals in the first direction (the main scanning direction in image formation of the image forming unit 140) as the switching order in the input side selection unit 131 and the output side selection unit 133. When repeating in the second direction (sub-scanning direction in image formation of the image forming unit 140), control is performed so that a predetermined order including a different order is obtained.

Here, when the image forming unit 140 generates a reference position signal such as an index signal indicating that the light beam has scanned a predetermined reference position in the main scanning direction (for example, a scanning start position in the main scanning direction). Each time the reference position signal is generated, the input side selection unit 131 and the output side selection unit 133 are controlled to have a predetermined order including a different order as the switching order. (For example, an M-sequence random number) is used to control the predetermined order in the above selection. Alternatively, a predetermined order is generated in advance and stored in the storage unit 104 as an order pattern, and the control unit 101 uses the order pattern stored in the storage unit 104 to obtain the predetermined order in the above selection. To control.

  In the specific example shown in FIG. 1, a specific example is shown in which two pulse generation units 132 a and 132 b are provided in the PWM processing unit 130. Here, the plurality is not limited to 2, and three pulse generators 132a, 132b, and 132c may be provided as shown in FIG. Further, as shown in FIG. 3, m pulse generation units 132a to 132m may be provided. In addition, by providing a plurality of pulse generators for generating pulse signals in this way and generating the pulse signals based on the image data in order, the pulse signals generated by these multiple pulse generators By switching and selecting and outputting one system of pulse signals, the burden (processing capability) of the pulse generation unit can be reduced.

  In addition, the image forming unit 140 uses a plurality of laser diodes arranged in the sub-scanning direction to simultaneously form a plurality of laser beams arranged in the sub-scanning direction in parallel and perform image formation in the main scanning direction. There is an image forming method called. For example, when the image forming unit 140 executes multi-beam image formation using n laser beams, the PWM processing unit 130-1 to the PWM processing unit 130-n are provided as the PWM processing unit 130, and main scanning is performed. For image formation in the direction, the image processing unit 120 distributes n columns in the sub-scanning direction to the PWM processing unit 130-1 to the PWM processing unit 130-n. In this case, each of the PWM processing units 130-1 to 130-n is provided with a maximum of a plurality of m pulse generation units 132a to 132m as shown in FIGS.

  In this case, the control unit 101 has a predetermined order including a switching order in which the input-side selection unit 131 and the output-side selection unit 133 switch in at least adjacent lines corresponding to a plurality of n lines that perform image formation in parallel. Control to be in order. That is, in the n PWM processing units 130-1 to 130-n, when 1 <i <n−1 and j = i + 1, the i-th PWM processing unit 130-i and the j-th PWM processing unit 130-n are set. The control unit 101 controls the PWM processing unit 130-j so that the switching order in the input side selection unit 131 and the output side selection unit 133 is a predetermined order including different orders.

[Operation (1)]
Here, based on FIG. 5, an operation in the image forming apparatus 100 including the PWM processing unit 130 including the two systems of pulse generation units 132a and 132b illustrated in FIG. 1 will be described.
Here, due to variations in the distribution of processes, temperature, voltage, and the like inside the PWM processing unit 130, a minute difference in pulse width characteristics may occur between the pulses generated by the plurality of pulse generation units 132a and 132b.

  In this case, the control unit 101 outputs a pulse signal in the main scanning direction every time an index signal is generated from the image forming unit 140 as the switching order in the input side selection unit 131 and the output side selection unit 133. The switching order in the input side selection unit 131 and the output side selection unit 133 is controlled so as to be a predetermined order including a different order with reference to a random number or an order pattern stored in the storage unit 104. .

Here, in FIG. 5, the pulse generated by the pulse generation unit 132 a is expressed as “A” pulse, and the pulse generated by the generation unit 132 b is expressed as “B”. In FIG. 5, it is assumed that the pulse width is A> B.
In this case, the order of selection is as follows:
・ A → B as a basic pattern A, B, A, B, A, B, A, B,...
・ B → A as a basic pattern B, A, B, A, B, A, B, A,...
Exists.

In FIG. 5, (1), (2), (3),... Represent the main scanning lines of the laser beam aligned in the sub-scanning direction.
Here, the switching order of the two pulse generation units 132a and 132b by the input side selection unit 131 and the output side selection unit 133 is a predetermined order including different orders (A → B and B → A). Since it is controlled, it will not continue in the sub-scanning direction for either A or B. Similarly, any one of A and B does not continue in a direction including the sub scanning direction (for example, an oblique direction between the main scanning direction and the sub scanning direction).

  As a result, even when a plurality of pulse generators 132a and 132b are selectively used, even if a minute difference in pulse width remains in the pulse signal from each pulse generator, the difference does not change in the sub-scanning direction. It becomes possible to eliminate the adverse effect on the image quality because it is no longer aligned in the direction of inclusion.

[Operation (2)]
Here, based on FIG. 6, the operation in the image forming apparatus 100 including the PWM processing unit 130 including the three systems of pulse generation units 132a, 132b, and 132c shown in FIG. 2 will be described. Here, due to variations in distribution of processes, temperature, voltage, and the like inside the PWM processing unit 130, a slight difference in pulse width characteristics may occur between the pulses generated by the plurality of pulse generation units 132a, 132b, and 132c.

  In this case, the control unit 101 outputs a pulse signal in the main scanning direction every time an index signal is generated from the image forming unit 140 as the switching order in the input side selection unit 131 and the output side selection unit 133. The switching order in the input side selection unit 131 and the output side selection unit 133 is controlled so as to be a predetermined order including a different order with reference to a random number or an order pattern stored in the storage unit 104. .

Here, in FIG. 6, the pulse generated by the pulse generation unit 132 a is expressed as “A”, the pulse generated by the pulse generation unit 132 b is expressed as “B”, and the pulse generated by the pulse generation unit 132 c is expressed as “C”. In FIG. 5, it is assumed that the pulse width is C>A> B.
In this case, the order of selection is as follows:
A, B, C, A, B, C,... With A → B → C as a basic pattern,
-B → C → A as a basic pattern B, C, A, B, C, A,...
The order of C, A, B, C, A, B,... With C → A → B as a basic pattern,
Exists.

It is possible to further increase the predetermined order by adding A → C → B, B → A → C, and C → B → A as basic patterns.
In FIG. 6, (1), (2), (3),... Represent the main scanning lines of the laser beam aligned in the sub-scanning direction.

  Here, the switching order of the two pulse generation units 132a, 132b, and 132c by the input side selection unit 131 and the output side selection unit 133 is different (A → B → C, B → C → A, C Since control is performed so that a predetermined order including A → B) is maintained, it is not possible to continue any of A, B, or C in the sub-scanning direction. Similarly, any one of A, B, and C does not continue in a direction including the sub-scanning direction (for example, an oblique direction between the main scanning direction and the sub-scanning direction).

  As a result, even when a plurality of pulse generators 132a and 132b are selectively used, even if a minute difference in pulse width remains in the pulse signal from each pulse generator, the difference does not change in the sub-scanning direction. It becomes possible to eliminate the adverse effect on the image quality because it is no longer aligned in the direction of inclusion.

[Other operations (1)]
Further, in addition to the above-described FIGS. 5 and 6, even in the case of image formation that expresses light and shade on a screen, the pulse width difference can be obtained by selecting the order as described above in the pulse signal of dots used on the screen. Will be dispersed, and the difference in shades between screens will not be noticeable.

[Other operations (2)]
In the above embodiment, since it is not necessary to correct a minute difference in pulse width, a high-resolution measurement circuit and a high-resolution correction circuit are not required, and cost does not increase. Further, even when there is a time variation and real-time correction cannot be performed, it is possible to cope with this embodiment.

[Other operations (3)]
In the above embodiment, as the predetermined order in selection, a random number (for example, an M-sequence random number) or an order pattern table generated in advance and stored in the storage unit 104 as an order pattern can be used.

  In this case, even if the predetermined order as described above is realized, if the influence on the image quality due to the difference in the pulse width still remains, the random number generation sequence is changed, or a plurality of order patterns are previously set. It is possible to further reduce the adverse effect on image quality by switching the order pattern table to be used while storing the table.

[Other operations (4)]
The image forming apparatus capable of using the image forming apparatus 100 is assumed to be an electrophotographic image forming apparatus, but is not limited to this. That is, the signal processing apparatus and the image forming apparatus 100 according to the above-described embodiments can be used for various types of image forming apparatuses that use pulse signals.

[Other operations (5)]
Although the case of a pulse signal by PWM has been described as a specific example as pulse generation, it is not limited to this. That is, the above embodiment can be applied to various pulses generated by other than PWM, for example, when a plurality of pulse signals that are not variable but have a constant width are generated and selected. Can be obtained.

DESCRIPTION OF SYMBOLS 100 Signal processing apparatus 101 Control part 102 Communication part 103 Operation display part 104 Storage part 110 Image data storage part 120 Image processing part 130 PWM processing part 140 Image formation part

Claims (5)

Image data is generated by generating a pulse signal corresponding to the image data, forming an image in the first direction using the pulse signal, and repeating the image formation in the first direction in a second direction orthogonal to the first direction. A signal processing apparatus used in an image forming apparatus for forming a two-dimensional image according to
A plurality of pulse generators that generate and generate pulse signals according to the image data for each pulse signal; and
A selector that selectively switches the shared generation of the pulse signals by a plurality of the pulse generators and outputs the pulse signals generated by the plurality of pulse generators that are selectively switched; and
A control unit for controlling the order of switching in the selection unit;
Have
The control unit, when switching the output of the pulse signal in the first direction in the second direction as a switching order in the selection unit, controls to be a predetermined order including a different order,
A reference position signal indicating that a predetermined reference position in the first direction has been imaged in the image forming apparatus is generated,
The control unit controls the selection unit to switch to a predetermined order including a different order each time the reference position signal is generated.
A signal processing apparatus. The control unit uses a random number to control the predetermined order.
The signal processing apparatus according to claim 1. A storage unit in which the predetermined order is generated in advance and stored as an order pattern;
The control unit controls the predetermined order using the order pattern stored in the storage unit .
The signal processing apparatus according to claim 1 . The image forming apparatus is configured to execute image formation in the first direction in parallel for a plurality of lines;
A combination of a plurality of the pulse generation unit and the selection unit is provided for each of the plurality of lines,
The control unit controls the switching order in the selection unit to be a predetermined order including a different order in at least adjacent lines for the plurality of lines that perform image formation in parallel .
The signal processing apparatus according to any one of claims 1 to 3 . A signal processing device according to any one of claims 1 to 4, comprising:
Forming an image with the pulse signal generated by the signal processing device according to image data;
An image forming apparatus.

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