JPH0254992B2 - - Google Patents

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is an electrophotographic printer that forms a latent image on a photoreceptor by exposing it to spot light from a light emitting source. The present invention relates to an electrophotographic printer that can perform printing, and particularly relates to an electrophotographic printer that can print at both an integral multiple and a non-integer multiple of the resolution ratio relative to the highest resolution.

Electrophotographic printers are widely used because they can print on plain paper and can print various patterns. Such an electrophotographic printer uses a laser light source as an exposure source, and is constructed as shown in the overall configuration diagram in FIG. 15 and the optical system configuration diagram in FIG. 16.

That is, a charger 5, a developer 6, a transfer device 7, a static elimination unit 8, and a cleaner 9 are arranged around a photoconductor drum 4 having a photoconductor (photoreceptor) on its surface to constitute an electrophotographic unit. 12, a collimating lens 13, a polygon mirror 14, an F-θ (imaging) lens 16, and a mirror 17 constitute an exposure optical unit, and furthermore, a paper hopper 1, a feeding roller 2, a conveying roller 3, a fixing roller 10, The stacker 11 constitutes a paper handling unit. In such an electrophotographic printer, a laser beam modulated according to a written image from a laser diode 12 as a laser source passes through a collimating lens 13 to a polygon mirror rotated by a spindle motor (servo motor) 15. 14, the photosensitive drum 4 charged by the charger 5 is exposed via the F-θ lens 16 and the mirror 17. As a result, a latent image is formed on the photosensitive drum 4, which is developed by the developing device 6. The sheet is fed out from the paper hopper 1 by the feeding roller 2, and then sent to the transfer section by the conveyance roller 3.
The developing device is transferred to the CP by the transfer device 7.
Thereafter, the paper CP is fixed by the fixing device 10 and stored in the stacker 11, while the photosensitive drum 4 is neutralized by the static eliminating unit 8, cleaned by the cleaner 9, and used for the next latent image formation.

In such a laser printer, as shown in FIG. 16, the optical system includes a laser source 12, a polygon mirror (scanning mirror) 14, and a spindle motor 15.
is provided, and the spindle motor 15 rotates the polygon mirror 14 with the spot light from the laser source 12, thereby scanning the photosensitive drum 4 rotated by the motor 4a in the X direction in FIG. 17A, that is, in the main scanning direction. form an image. This laser source 12 is driven by a modulation signal LEDS corresponding to the written image, and a dot array of light corresponding to the modulation signal LEDS is generated from the laser source 12, so that a written image is formed on the photosensitive drum 4. become.

Therefore, as shown in FIG. 17A, the spot diameters of the laser beams from the laser source 12 are set so that they overlap each other at positions X1 to Xm on each main scanning line, and the rotation of the drum 4 causes the beams to move in the sub-scanning lines Y1 to Yn. conduct.

A latent image is formed on the photosensitive drum 4 by the spot light from the laser source 12 in the following manner. For example, as shown in FIG. 17B, when the modulation signal is on, off, and on, spot light S1 is irradiated at position X1 and spot light S3 is irradiated at position X3. If the threshold hold is T, then the threshold hold T
The charge in the above portion disappears, and a latent image SI is formed as shown in the figure. When performing normal development, the charging potential Vc
If a toner of opposite polarity (minus) is applied, a visible image similar to DI can be obtained. That is, the part where the modulation signal is off becomes a black pattern, and the unit line width is d.

In such an electrophotographic printer, the unit line width d depends on the spot diameter and is constant. However, there is a need or desire to change the unit line width.

For example, when applying such a printer to a facsimile machine, the data (content) to be printed is sent from the sending side at various resolutions (dot densities) depending on the content of the transmitted document, so the data is printed according to this resolution. Similarly, when printing enlarged characters, etc., this can be achieved by changing the resolution, so it is necessary to print according to the resolution.

In other words, in the case of high resolution (e.g. 400dpi),
The dot spacing in the main scanning direction is as small as db1, and the dot spacing (cotton density) in the sub-scanning direction is also small accordingly.
The dot spacing in the main scanning direction is as small as db1, but in the case of low resolution (for example, 300 dpi) the dot spacing in the main scanning direction is large as db2, and the dot spacing in the sub-scanning direction is correspondingly large.
It will be as large as db2. For this reason, it is necessary to set the unit line width to d ₁ for high resolution, and to set the unit line width to d ₂ for low resolution.

[Conventional technology]

Conventionally, in order to adjust the line width, the optical spot diameter of the light beam is expanded to increase the line width from d _1.
There are known methods to change the spot diameter to _d2 , and conventional methods have been proposed to change the spot diameter by providing multiple laser sources (light emitting sources) with different spot diameters or by changing the focal length by moving the optical system. has been done.

On the other hand, a method is also known in which the modulation width in the main scanning direction is changed and the line width is adjusted using an oval beam.

[Problem that the invention seeks to solve]

The former conventional method described above has the problem that it requires an extra laser source for the resolution and a complicated optical system, making the device itself complicated and expensive. In addition, although the latter method allows adjustment in the main scanning direction, the spot diameter does not change in the sub-scanning direction and line width adjustment in the sub-scanning direction cannot be adjusted, so there is a problem that the image is distorted, and the maximum resolution There was a problem that printing was not possible when the resolution ratio was a non-integer multiple.

[Means for solving problems]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic printer that can easily change the resolution and print regardless of whether the resolution ratio to the highest resolution is an integral multiple or a non-integer multiple.

For this reason, the present invention provides a photoreceptor, a charger for charging the photoreceptor, a light emitting source for writing an image in accordance with a modulation signal on the photoreceptor at a predetermined spot diameter, and control of the light emission intensity of the light emitting source. an optical scanning section that optically scans the photoreceptor with spot light from the light emitting source; an n-fold section that generates n times as many dots in the main scanning direction; and the intensity control section and the n-fold section. and when the resolution ratio n of the specified resolution is a non-integer multiple of the highest resolution, the control section controls the intensity control section to change the light emission intensity of the light source, and When the resolution ratio n of the specified resolution is an integral multiple of the maximum resolution, the control section controls the n-fold section to generate a modulation signal of n times as many dots and output it repeatedly n times. It is a feature.

[Effect]

In the present invention, when the resolution ratio is an integer multiple, n times as many dots are generated and outputted n times to write one pixel as n ² dots, and when the resolution ratio is a non-integer multiple, the dots are Since it is not possible to combine them, the apparent diameter of the spot can be expanded,
Writing is performed by changing the dot diameter.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

Fig. 2 is a diagram explaining the principle of the present invention, and the maximum resolution of Fig. 2 D is 400 dpi (dots per inch), and the resolution ratio is 100 dpi, which is an integral multiple of 1:4, and 1:2.
200dpi and the resolution ratio is a non-integer multiple of 1:1.3
An example of printing at 300 dpi is shown.

In the present invention, a unit pixel with a maximum resolution of 400 dpi is
If it is represented by a dot and its diameter is S1, then at an integer multiple resolution, the resolution ratio is n and the unit pixel is n ²
Writing is performed using dots of the same diameter. That is, at 100 dpi with n=4, 16 dots are written in the main scanning direction and 4 in the sub-scanning direction, as shown in FIG. 2A, and at 200 dpi with n=2, as shown in FIG. The image is written using four dots: 2 in the horizontal direction and 2 in the sub-scanning direction. That is, the number of dots is changed and the image is enlarged by n times in the vertical and horizontal directions for printing.

On the other hand, if the resolution ratio is a non-integer multiple, this cannot be achieved by changing the number of dots, so as shown in Figure 2C, the dot diameter is changed as shown in S2,
The sub-scanning interval is also changed to print at a non-integer multiple of 300 dpi. For this reason, it is necessary to change the spot diameter of the light beam, but in the present invention,
This is achieved by changing the light emission intensity of one light source by changing the apparent spot diameter without changing the optical spot diameter. This will be explained with reference to FIG. 3, which shows the principle of line width (dot diameter) adjustment by changing the resolution, FIG. 4, which shows line width adjustment characteristics, and FIG. 5, which shows line width adjustment.

As shown in the intensity level distribution diagram of the light beam in FIG. 3A, if the optical spot diameter of the light beam L1 with intensity P ₁ is D, the apparent spot diameter as seen from the photoreceptor is the threshold of the photoreceptor. The part above hold T becomes D ₁ . Here, the optical spot diameter is the intensity
It is 1/e ² of P ₁ , that is, 0.13·P ₁ . On the other hand, when the optical spot diameter D, that is, the focal length is the same, and the intensity level is increased to _P2 , the light beam L2 becomes similar to the light beam L1 as shown in the figure, and the optical spot diameter is equal to D. However, the apparent spot diameter is larger than the threshold T of the photoreceptor.
It becomes D ₂ and expands.

Therefore, when the light beam L2 of intensity P ₂ is irradiated as shown in FIG. 3B in the same manner as in FIG. The unit line width (dot diameter) of the image becomes smaller. In this way, the apparent spot diameter is changed by changing the intensity of the light beam, and the dot diameter is adjusted.

That is, since the amount of laser light and the line width are inversely proportional as shown in FIG. 4, in order to obtain the desired line width, it is sufficient to drive the laser source 12 with the corresponding amount (intensity) of the laser light.

Therefore, in order to change the line width according to the resolution, at high resolution the laser intensity must be increased as shown in Figure 5A.
For a small beam like P ₁ and low resolution,
If we change the intensity according to the resolution so that the laser intensity becomes a large light beam P ₂ as shown in Figure 5B, we can obtain the corresponding unit line widths (dot diameters) d ₁ and d ₂ . Become.

In this way, the laser intensity is switched when the resolution ratio is a non-integer multiple, but when the laser intensity is increased, a bleeding phenomenon occurs and the image quality deteriorates. To compensate for this, charge voltage switching is performed.

This operation will be explained with reference to the overexposure phenomenon diagram shown in FIG. 6, the density characteristic diagram shown in FIG. 7, and the charging potential control diagram shown in FIG.

First, to explain the bleeding phenomenon caused by overexposure with reference to FIG. 6, when a photoreceptor with a certain charging potential vH is exposed with an appropriate amount of laser light, the unexposed area will overlap with the exposed area as shown in FIG. 6A. The boundaries are clear,
This results in a rectangular potential distribution. On the other hand, if the laser light intensity is increased as in the case of 300 dpi, overexposure occurs, and the resistance value of the exposed area becomes extremely small, resulting in a type of halation phenomenon. For this reason, as shown in FIG. 6B, in the potential between the exposed and non-exposed areas, the potential of the non-exposed areas flows into the exposed areas,
In this area, the image appears as splatter and smearing.
For this reason, when the laser power is increased, the image quality deteriorates.

On the other hand, as shown in FIG. 7, the relationship between the charging potential and the printing density is such that the increase in the charging potential is proportional to the increase in the printing density.

Therefore, in the present invention, when the amount of laser light is large (low resolution), the charged potential is reduced as shown in vL in FIG.
If the printing density is set to a low charging potential, the bleeding due to the above-mentioned scattering will be minimized, and eventually the bleeding can be suppressed to a minimum. In this case, the print density will be large at high resolution and small at low resolution,
As mentioned above, in the case of low resolution, the unit line width becomes large, so the appearance does not change.

Next, a specific example of the present invention will be explained with reference to FIG.

FIG. 1 is a configuration diagram of an embodiment of the present invention. In the figure, the same parts as shown in FIGS. 15 and 16 are indicated by the same symbols, and 20 is a high-voltage power source for charging. , a predetermined charging voltage (strength) is applied to the charger 5.
21 is a laser drive circuit (intensity control unit) that drives the laser source 12 with the intensity according to the intensity designation signal SD, which will be described later, in accordance with the modulation signal (video signal) LEDS; 22 is a motor drive unit , which drives the motor 15 at a speed according to the speed designation signal VD, and 23 is a control section that controls the intensity designation signal SD, charging voltage designation signal ST, and modulation speed corresponding to the resolution switching signal DS given from the outside. Something that generates the designated signal LS and speed designated signal VD,
24 is a charging control unit, which generates a control voltage Vc in accordance with a charging voltage designation signal ST given from the control unit 23 in response to resolution switching, as will be described later, and controls the charger 5.
25 is an image memory in which the pattern to be written is stored; 26 is an n-fold circuit that controls the modulation speed designation signal;
A buffer memory 27 multiplies the pattern read out from the image memory 25 according to LS by n, which stores write data for one scanning line and supplies it to the laser drive circuit 21 as a video signal (modulation signal). It is.

Next, regarding the operation of the embodiment configuration shown in FIG.
The explanation will be based on the control explanatory diagram in FIG. 1 and the modulation signal explanatory diagram in FIG.

Here, in response to the high resolution designation signal DS of 400 dpi, the control unit 23 generates a strength designation signal SD, a charging voltage designation signal ST, and a modulation speed designation signal corresponding to the high resolution.
LS and a speed designation signal VD, and the laser drive circuit 21 modulates the light emitting source 12 with a modulation signal LEDS at a beam intensity P ₁ for high resolution (Figs. 3 and 5A).
The motor drive unit 22 drives the spindle motor 15 at a speed V ₁ of 400 dpi to rotate the polygon mirror 14 at this speed, and rotates the light emitting source 12 at a predetermined optical scanning (main scanning) speed V _{1 .} scan the laser beam.

At this time, the control unit 23 stores the 14th image in the image memory 25.
Given the clock CL4 in figure A, this clock CL4
The pattern in the image memory 25 is read out at a speed of
Since the n-times circuit 26 is specified with a modulation period of 400 dpi, n=1, that is, the buffer memory 2 is
given to 7. Buffer memory 27 is a clock
It is driven at a speed of CL4 and provides a modulation signal LEDS to the laser drive circuit 21.

Therefore, writing is performed on the photosensitive drum 4 with a dot diameter as shown in FIG. 2D, that is, with a unit line width _d1 .

Next, when the resolution designation signal DS is switched to 300dpi, the control unit 23 outputs a strength designation signal corresponding to 300dpi.
SD, charging voltage designation signal ST, and speed designation signal VD are generated. Thereby, the laser drive circuit 21 drives the light emitting source 12 according to the modulation signal LEDS at a beam intensity P ₂ for 300 dpi as shown in FIGS. 3 and 5B. At this time, the control section 23 reads out the image memory 25 using the clock CL3 (which has a longer cycle than the clock CL4), and the n-times circuit 26 supplies this to the buffer memory 27 through the specified modulation of 300 dpi.
Buffer memory 27 operates with clock CL3.
Therefore, the period of the modulation signal LEDS (readout clock)
Also, as shown in db2 in FIG. 17B, the light becomes long for 300 dpi and reaches the laser drive circuit 21.

On the other hand, the motor drive unit 22 changes the speed to 300 dpi.
V ₂ to drive the spindle motor 15,
Rotating the polygon mirror 14 at such a speed,
The laser beam from the light emitting source 12 is scanned at an optical scanning speed V ₂ for 300 dpi.

That is, the resolution in the sub-scanning direction is determined by the rotational speed (sub-scanning speed) of the photosensitive drum 4, but in this example, the main scanning speed of the polygon mirror 14 is changed without changing the rotational speed of the photosensitive drum 4. The rotational speed in the scanning direction is changed equally.

Therefore, the unit line width d ₂ corresponding to 300 dpi is set, and writing by the light emitting source 12 is performed.

In addition, the control unit 23 increases the laser intensity (300 dpi).
When this is specified, the charging voltage designation signal ST is specified to be small, and when the laser intensity is specified to be small (400 dpi), the charging voltage specification signal ST is specified to be large to the charging control unit 24. As a result, the charging control section 24 changes the control voltage Vc,
By controlling the charging voltage of the high voltage power supply 20, the charging potential on the photosensitive drum 4 is adjusted according to the laser intensity as shown in FIG.
Set to vH (low laser intensity, 400 dpi) or vL (high laser intensity, 300 dpi).

In this way, when the resolution ratio is 300 dpi, which is a non-integer multiple, printing at 300 dpi is performed as shown in FIG. 2C by changing the laser intensity, charging voltage, scanning speed, and readout period as shown in FIG.

On the other hand, 200dpi or
When switching to the 100 dpi resolution designation signal DS, the control unit 23 outputs the intensity designation signal as shown in FIG.
SD, charging voltage designation signal ST and speed designation signal VD are
Specify the same values as in the case of 400 dpi, the laser intensity is P ₁ , the charging potential is VH, and the optical scanning speed is V ₁ .

Then, in order to multiply the frequency by n in both the main scanning direction and the sub-scanning direction as shown in FIGS. 2A and B, the control unit 23 stores the clock CL2 having half the frequency of the clock CL4 in the image memory 25 for 200 dpi, and the clock CL for 100 dpi.
At 200 dpi, the clock CL1 with a frequency of 1/4 of 4 is applied to read and drive the
For 100dpi, specify 4x. As a result, as shown in Fig. 14B, at 200 dpi, the output out2 has twice the number of dots, and at 100 dpi, the output out 2 has four times the number of dots.
4 is created from the dots read out from the image memory 25 marked with circles, and a video output with n times the number of dots in the main scanning direction is obtained. This output is sent to the buffer memory 27, driven by the same clock as 400 dpi, and supplied to the laser drive circuit 21 as a video (modulation) signal. Next, change the sub-scanning direction to n
In order to double the image memory 25, the control unit 23
By specifying the reading period for one scanning line of 200 dpi twice as much as 400 dpi, and 100 dpi as four times as much as 400 dpi using the modulation speed designation signal LS, the writing of the contents of the buffer memory 27 can be made twice as much as 200 dpi. ,
If it is 100dpi, it should be done at four times the frequency. In other words, at 400 dpi, it is read once every one scanning line, but at 200 dpi, it is read out twice every two scanning lines.
At 100 dpi, the same data is read out four times in the time of four scanning lines, and the modulation signal LEDS is
It is output twice at 200 dpi and four times at 100 dpi, meaning that the same data is written twice and four times, respectively.

In this way, n ² times as many dots are written as shown in FIGS. 2A and 2B.

Next, the laser drive circuit 21 and charging voltage control section 24 configured in FIG. 1 will be described in detail.

FIG. 9 shows a laser drive circuit 2 having the configuration of the embodiment shown in FIG.
1, in which the same parts as shown in Fig. 1 are indicated by the same symbols, and 12
a is a laser diode that operates as a light emitting source; 12b is a monitor diode;
A device that receives the light from the laser diode 12a and converts it into an electric signal; 210 is a modulation circuit that performs a switching operation according to the modulation signal LEDS to flow a driving current; 211 is an amplifier that converts the output current of the monitor diode 12b; something that amplifies, 21
2 is a gain change circuit, which changes the feedback gain according to the intensity designation signal SD, and is composed of resistors R ₁ and R ₂ and a transistor Q1; 213 is a comparison circuit, which changes the feedback gain according to the intensity designation signal SD; Feedback signal and modulation signal from circuit 212
The bias current ic flowing through the laser diode 12a is changed by comparing it with the LEDS.

Next, regarding the operation of the embodiment configuration shown in FIG.
This will be explained using the waveform diagram of each part in the figure and the laser diode drive explanatory diagram of Figure 11.

First, the strength specification signal SD is turned off (400, 200,
100 dpi), transistor Q1 is off. On the other hand, the modulation signal LEDS is input to the modulation circuit 210, and the laser diode 12a is controlled by the bias current IC.
It is driven with a drive current that has a modulation signal added to it. As shown in FIG. 11, the characteristics of a laser diode are non-linear in terms of drive current versus laser light amount. Therefore, the bias current ic is used to maintain the voltage close to the threshold T, and the modulation signal LEDS is added to this for driving.

In addition, in order to keep the laser power constant, the light emission state is monitored by the monitor diode 12b, feedback is provided via the amplifier 211 and the gain change circuit 212, and the modulation signal LEDS is compared with the feedback signal FS in the comparison circuit 213, and the bias current is IC is controlled to keep the laser power constant.

On the other hand, SD is on (300dpi) and line width (strength)
When the designation of changes, transistor Q1 turns on,
Since the voltage is divided by the resistor R ₂ , the gain decreases, and therefore the level of the feedback signal FS from the monitor diode 12b decreases. Therefore, when comparing it with the modulation signal LEDS, the comparator circuit 213 considers that the laser power has decreased by this level reduction, and increases the bias current as ic. As a result, the laser power (light amount) is P ₁
to _P2 , the luminous intensity increases, the apparent spot diameter increases, and the line width becomes _d2 for 300 dpi.

FIG. 12 shows the charging control section 24 of the embodiment configuration shown in FIG.
This is a detailed circuit diagram of 240. In the figure, the same parts as shown in FIG.
241 is an adder that adds a base voltage and an additional voltage, which will be described later, to create a control voltage Vc;
is a base voltage generation circuit, which generates a base voltage (Vc ₁ + Vc ₂ ) for low resolution,
R ₃ and R ₄ are their output resistances, and 242 is an additional voltage applying circuit, which has resistors R ₁ and R ₂ and a transistor QT1, and when the charging designation signal ST is off (400,
200, 100 dpi), the transistor QT1 is turned off and an additional voltage Vc ₃ is generated from the midpoint between the resistors R ₁ and R ₂ .

Next, the operation of the embodiment configuration shown in FIG. 12 will be explained.

When the charged voltage designation signal ST is on (300 dpi), the transistor QT1 is on, so no additional voltage is generated from the additional voltage generation circuit 242, so the control voltage Vc, which is the output of the adder 240, is equal to the base voltage (Vc ₁ +Vc ₂ ), a corresponding charging voltage is generated from the high-voltage power supply 20, and the charging potential of the photoreceptor 4 is set to vL in FIG.

On the other hand, if the charging voltage designation signal ST is off (400,
200, 100dpi), the transistor QT1 is off, so the additional voltage is generated from the additional voltage generation circuit 242.
Vc ₃ is generated, and the control voltage Vc which is the output of the adder 240 is the base voltage (Vc ₁ +Vc ₂ ) and the additional voltage Vc ₃
A corresponding charging voltage is generated from the high-voltage power supply 20, and the charging potential of the photoreceptor 4 is determined as shown in FIG. 8B.
Let vH be

In the above-mentioned embodiment, a laser diode is used as a light emitting source, but the light source is not limited to this, and any type that can have variable intensity may be used, and the optical scanning system is not limited to that in the embodiment.

Alternatively, the speed in the sub-scanning direction may be changed by changing the rotational speed of the photosensitive drum 4.

Although the present invention has been described above using one embodiment, the present invention can be modified in various ways according to the gist of the present invention, and these are not excluded from the present invention.

〔Effect of the invention〕

As described above, according to the present invention, a photoreceptor, a charger for charging the photoreceptor, a light emitting source for writing an image in accordance with a modulation signal on the photoreceptor with a predetermined spot diameter, and an intensity control unit that controls the light emission intensity of the light source; a light scanning unit that optically scans the photoreceptor with spot light from the light source; an n-times unit that generates n times as many dots in the main scanning direction; and a control unit that controls the n-fold part, and the resolution ratio n of the designated resolution.
When is a non-integer multiple of the maximum resolution, the control section controls the intensity control section to change the light emission intensity of the light source, and when the resolution ratio n of the specified resolution is an integer multiple of the maximum resolution. The control section controls the n-fold section so that n
It generates a modulated signal with twice as many dots as n
The feature is that the dots are output repeatedly, so by controlling the dot diameter or the number of dots according to the resolution ratio, printing with integer multiples and non-integer multiples of resolution can be achieved with one device. In addition, since only one light emitting source is required and electrical control is used, the structure is not complicated and can be realized at low cost, making it extremely useful in practice.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is an explanatory diagram of the principle of the present invention, Fig. 3 is a diagram of the principle of dot diameter adjustment according to the present invention, Fig. 4 is a diagram of the laser light amount versus line width characteristic, Figure 5 is an explanatory diagram of dot diameter adjustment according to the present invention;
Figure 6 is an explanatory diagram of the bleeding phenomenon caused by overexposure, Figure 7
The figure is a charging potential vs. printing density characteristic diagram, Figure 8 is a diagram explaining charging potential control, Figure 9 is a detailed configuration diagram of the laser drive circuit in the configuration shown in Figure 1, Figure 10 is a waveform diagram of each part of the configuration in Figure 9, FIG. 11 is a characteristic diagram of the laser diode in the configuration shown in FIG. 9, FIG. 12 is a detailed configuration diagram of the charging control section in the configuration shown in FIG.
14 is an explanatory diagram of the modulation signal in the configuration shown in FIG. 1, FIG. 15 is a configuration diagram of an example of an electrophotographic printer to which the present invention is applied, and FIG. 16 is an optical diagram of the configuration shown in FIG. 15. FIG. 17 is a diagram illustrating the recording principle in electrophotography, and FIG. 18 is a diagram illustrating the necessity of line width adjustment. In the figure, 4... photosensitive drum (photosensitive body), 5... charger, 12... light emitting source, 14... polygon mirror, 15... spindle motor, 20... high voltage power supply, 21... laser drive circuit ( strength control section), 2
2...Motor drive unit, 23...Control unit, 24...
Charging control section, 25... image memory, 26... n-times circuit.

Claims (1)

[Claims] 1. A photoreceptor, a charger that charges the photoreceptor, a light emitting source that writes an image in accordance with a modulation signal on the photoreceptor with a predetermined spot diameter, and an intensity control unit that controls the emission intensity of the light emitting source. , an optical scanning section that optically scans the photoreceptor with spot light from the light emitting source, an n-fold section that generates n times as many dots in the main scanning direction, and a control section that controls the intensity control section and the n-fold section. and when the resolution ratio n of the specified resolution is a non-integer multiple of the highest resolution,
The control unit controls the intensity control unit to change the light emission intensity of the light emitting source, and when the resolution ratio n of the designated resolution is an integral multiple of the highest resolution, the control unit controls the n-fold part. An electrophotographic printer characterized in that it generates a modulation signal of n times as many dots and repeatedly outputs it n times.