JPH08310044A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device which can form an excellent image having no irregularity in density without taking much labor. CONSTITUTION: An image forming device comprises a photosensitive body 40 and an exposure device 30, as an exposure means, having a plurality of exposure elements arranged in the vertical direction with respect to the moving direction of the photosensitive body 40. There is also provided a chaos generating device 20 as a light quantity adjusting means for irregularly changing the light emitting quantities of the exposure elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus applied to an image forming apparatus such as a copying machine, a printer, a facsimile, etc., which uses an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, an exposure apparatus using a semiconductor laser optical system has been widely used in digital copying machines and printers.

However, the exposure apparatus using a semiconductor laser often uses a laser beam deflecting device, an imaging optical system and the like, which are practically impossible to reduce in size more than those of the present time. Has a limit.

Further, there is a limit to the accuracy of a polygon mirror often used as a deflecting device and a folding mirror incorporated in an optical system, and in a true sense, a laser beam is accurately positioned on a latent image carrier. I know that I can't lead to.

This means that it is extremely disadvantageous as an exposure device for a high-speed printer or a color printer using a plurality of laser beams, for example.

For this reason, so-called solid-state light-emitting devices, which do not have movable parts such as LED heads, have been used as exposure apparatuses, especially in small printers.

As shown in FIG. 7A, the LED head has a base 130 on which an LED array chip 1301 and an LED driver chip 1302 arranged in a straight line are mounted.
3 and a self-hoc lens array 1304.

FIG. 7B is an enlarged view of the LED array chip 1301 shown in FIG. 7A, in which each LED element 1301a has a pixel density pitch (for example, 300 dp).
i).

Since the light emitted from the LED element 1301a has a property of diffusing, the self-hook lens array 13
An image is formed on the photoconductor via 04.

The self-hook lens array 1304 is small in size, uniform in the axial direction, and forms an erecting equal-magnification real image. Therefore, the self-hoc lens array 1304 is widely used as an image forming system for an exposure apparatus of a printer using a solid-state light emitting element. .

[0011]

However, the LED
Due to the nature of the semiconductor process, the elements 1301a differ in the amount of emitted light. Therefore, the LED array chip 1301
It is not possible to form a product having exactly the same performance in all the longitudinal directions.

Especially in the electrophotographic process, LE
Since the variation of the exposure light amount of the D element 1301a directly changes the image density, the variation of the emission intensity is
Image density becomes uneven, which is a bottleneck for improving image quality.

In order to adjust the variation in the emitted light amount of the LED element 1301a, the emitted light amount is monitored one by one,
It is necessary to change the current to flow according to the amount of emitted light,
For example, if the resolution is 300 dpi, 300 adjustments will be made per inch, which requires enormous labor and time.

The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an image forming apparatus capable of providing a good image having no image density unevenness without trouble. To do.

[0015]

In order to achieve the above object, the present invention provides a photoconductor and an exposure means having a plurality of exposure elements arranged in a direction perpendicular to the moving direction of the photoconductor. In the image forming apparatus having, the light amount adjusting means for irregularly changing the emitted light amount of the exposure element is provided.

The light amount adjusting means may randomly change the light emitting amount of each of the plurality of exposure elements.

It is preferable that the light quantity adjusting means can select whether or not to use.

It is effective that the exposure element has a resolution of 600 dpi or more.

The exposure element may be an LED element.

[0020]

In the image forming apparatus constructed as described above, the light quantity adjusting means for irregularly changing the light quantity of the light emitted from the exposure element is provided, so that the difference in the light quantity emitted from the exposure element is reduced.

The light amount adjusting means irregularly changes the emitted light amount for each of the plurality of exposure elements,
The difference in the amount of emitted light between the individual exposure elements is reduced.

The light amount adjusting means can correspond to an image to be formed by selecting whether or not to use it.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

(Embodiment 1) FIG. 1A is a diagram showing an image forming process in an image forming apparatus of the present invention.

In FIG. 1A, 10 is an LED driver circuit, 20 is a chaos generator (light quantity adjusting means), 30 is an exposure device (exposure means) using an LED head, 40 is a photoconductor, and 50 is a charging device. Is. 60 is a developing device,
Toner is developed and visualized from the formed electrostatic latent image.

FIG. 1B is a circuit diagram showing a circuit of the chaos generator 20 of the simplest principle.

In FIG. 1B, 201 is an oscillator for oscillating a periodic signal. 202 is a resistance from 5Ω to 100
0Ω, 203 is a coil, 1μH to 1000μ
An H-type device and a diode 204 are provided.

In this chaos generator 20, when the terminal 205 is connected as a signal terminal and the other terminal 206 is connected as a ground terminal, chaos does not occur in the frequency component, but chaos in the amplitude component as shown in FIG. Occurs.

The LED heads applied to the exposure apparatus 30 have LEs arranged in a straight line as shown in FIG.
Substrate 303 on which D array chip 301 and LED driver chip 302 are mounted, and selfoc lens array 304
It consists of

FIG. 3B is an enlarged view of the LED array chip 301 shown in FIG. 3A, in which each LED element (exposure element) 301a has a pixel density pitch (for example, 3).
00 dpi).

Since the light emitted from the LED element 301a has a property of diffusing, the self-hook lens array 304
An image is formed on the photoconductor 40 via.

Now, the chaos output is input to the LED driver circuit 10 by the chaos generator 20, and the light emitting current control circuit is modulated, whereby each LED element 301
It was possible to give fluctuation to the amount of light emitted from a.

This will be described below.

FIG. 4A is an image simulation in the case where there is uneven light quantity. In this image simulation, there is a large dot row in the third row from the right and a small dot row in the next fourth row, so there is a relatively large difference in dots. This difference is due to the difference in the amount of light emitted from the LED element 301a.

As can be seen from FIG. 4 (a) at a slightly distant position, it seems that there is a white / black boundary between the third and fourth columns. That is, this is the image density unevenness.

Therefore, the chaos output is input from the chaos generator 20 to the exposure device 30 via the LED driver circuit 10 to cause fluctuations in the amount of light emitted from each LED element 301a. This fluctuation is random with no periodicity (not patterned). The image after this processing is shown in FIG.

In FIG. 4B, the dot size changes in the vertical direction due to the above fluctuation. Also, this change is controlled to be different for each column,
Therefore, unevenness does not occur in the vertical direction.

As can be seen from FIG. 4 (b) at a slightly distant position, the boundary between white and black between the third and fourth columns from the right is no longer felt, and the image density unevenness is visually recognized. Could be reduced.

Since these attached simulation patterns are produced at a low resolution, the effect is difficult to understand, but the effect becomes more remarkable as the image becomes a higher resolution gradation image.

In FIG. 4A, as the resolution increases, the unevenness in the horizontal direction gradually becomes difficult to understand, but since the unevenness remains in the vertical direction as a whole, the low frequency component in the horizontal direction is always recognized as unevenness. Will be done.

However, in (b), since noise of high frequency component is added to the whole, the feeling of roughness is increased at a low resolution, but the feeling of roughness is reduced by increasing the frequency of the whole, Furthermore, the unevenness in the vertical direction can be masked.

Further, by incorporating it as a device in the image forming process of electrophotography, not in image processing, a larger effect can be obtained.

This is because the electrophotographic process is a system in which interference between pixels is large, and therefore high frequency noise pulls and smoothes peripheral pixels.

(Embodiment 2) In Embodiment 1, fluctuations are input to all pixels, but in Embodiment 2, fluctuations are added to the reference operating current for each line.

FIG. 5A shows an image when there is uneven light amount. By adding the fluctuation component, the result is as shown in FIG. 5 (b).

In the attached simulation, the image of (b) is more noticeable in a rough feeling, but the higher the resolution of this pattern is, the more the visual uniformity becomes (b). ) Is getting better.

In the second embodiment, unlike the first embodiment, the control is not performed differently for each column, and there is a possibility that some unevenness may occur in the vertical direction. Since the control is not performed differently depending on the column of, the control becomes easy.

(Embodiment 3) Embodiment 3 is a combination of Embodiment 1 and Embodiment 2, in which fluctuations are introduced into the reference operating current for each line, and all exposure elements (L
Fluctuation was added to the ED element 301a).

FIG. 6A shows an image when there is uneven light amount. By adding the fluctuation component, the result is as shown in FIG. 6 (b).

The higher the resolution of this pattern, the more remarkable the effect.

(Embodiment 4) The sharpness of an image may be impaired by performing the processing as in the above Embodiments 1 to 3.

For example, in a character image, sharpness is very important.

The fluctuation process is effective in the case of a gradation image in which the smoothness of the image is important, but this can be solved by a method in which the fluctuation process is not executed in the case of a character image in which sharpness is important. .

Regarding the use of the chaos generator 20 as the above-mentioned light amount adjusting means, depending on the image to be formed, for example, the user does not use it in the case of a character image but uses it in the case of a gradation image. It can be selected, or can be detected and selected in the apparatus.

In the above-described Examples 1 to 4, the LED element 301a was applied as the exposure element, but this LED element 301a has been used conventionally, and its performance, manufacturing method, etc. are known, and Easy to control and easy to control.

With the constitutions of Examples 1 to 4, it is possible to easily form a good image having no image density unevenness without the enormous amount of time and labor required in the conventional case.

[0057]

According to the present invention having the above-mentioned structure and operation, the light quantity adjusting means for irregularly changing the light quantity emitted from the exposure element is provided, so that the difference in the light quantity emitted from the exposure element can be alleviated. It is possible to easily form a good image without unevenness in image density without applying the image.

The light amount adjusting means irregularly changes the emitted light amount for each of the plurality of exposure elements,
It is possible to reduce the difference in the amount of emitted light among the individual exposure elements, and it is possible to form a good image with no image density unevenness.

Since the light quantity adjusting means can be selected whether or not to use it, it can be used depending on the image to be formed, for example, not using a character image but using a gradation image.

In case of high resolution such as 600 dpi,
Especially effective.

When the exposure element is an LED element, it is easy to manufacture and control, and the cost is reduced.

[Brief description of drawings]

1A is a schematic diagram showing an image forming apparatus according to an embodiment of the present invention, and FIG. 1B is a circuit showing a simplest circuit of a chaos generator applied to the image forming apparatus. It is a figure.

FIG. 2 is a diagram showing an example of a chaotic waveform generated by a chaotic generator.

FIG. 3 (a) is a perspective view showing an exposure device applied to the image forming apparatus of the present invention, and FIG. 3 (b) is a schematic view showing an LED element in this exposure device.

FIG. 4A and FIG. 4B are diagrams showing a simulation example of an output image pattern in the first embodiment of the present invention,
(A) shows before processing and (b) shows after processing.

5 (a) and 5 (b) are diagrams showing a simulation example of an output image pattern in Embodiment 2 of the present invention,
(A) shows before processing and (b) shows after processing.

6 (a) and 6 (b) are diagrams showing a simulation example of an output image pattern in Embodiment 3 of the present invention,
(A) shows before processing and (b) shows after processing.

7A is a perspective view showing an exposure apparatus applied to a conventional image forming apparatus, and FIG. 7B is a schematic view showing an LED array in the exposure apparatus.

[Explanation of symbols]

 20 Chaos Generator (Light Amount Adjusting Means) 30 Exposure Device (Exposure Means) 40 Photoreceptors 301a, 1301a LED Element (Exposure Element)

Claims (5)

[Claims] 1. An image forming apparatus comprising: a photoconductor; and an exposure unit having a plurality of exposure elements arranged in a direction perpendicular to a moving direction of the photoconductor, wherein an amount of light emitted from the exposure element is irregular. An image forming apparatus comprising a light amount adjusting means for changing the light amount. 2. The image forming apparatus according to claim 1, wherein the light amount adjusting unit irregularly changes the emitted light amount individually for each of the plurality of exposure elements. 3. The image forming apparatus according to claim 1, wherein the light amount adjusting unit can select whether to use the light amount adjusting unit. 4. The image forming apparatus according to claim 1, wherein the exposure element has a resolution of 600 dpi or more. 5. The image forming apparatus according to claim 1, wherein the exposure element is an LED element.