JP2008183866A - Image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form an excellent image without reducing productivity when a monochromatic image which keeps a color image mixed with the monochrome image and is processed by a monochromatic image processing mode is outputted by a color image formation mode. <P>SOLUTION: This device comprises a solid scanning type optical writing unit having a configuration consisting of a plurality of optical modulators arranged in a main scan direction and a control unit having the function of controlling optical writing by the solid scanning type optical writing unit, wherein the control unit controls exposure energy so as to provide n<n' in the case of increasing the exposure energy n' times by one pixel of the optical modulator to form one dot as compared with the case of exposure by n pixels of the optical modulators to form a dot. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine and a printer, and more particularly to an image forming apparatus having a solid scanning optical writing device that performs exposure for each color by light emission lighting driving or light modulation.

  In an image forming apparatus such as a copying machine or a printer, an electrostatic latent image is formed according to exposure based on image data, the electrostatic latent image is developed to form a toner image, and the toner image is transferred onto a recording sheet. There is something to do.

  In the image forming apparatus that forms an electrostatic latent image / toner image by performing such exposure, the image carrier is irradiated with laser light in the main scanning direction, and the image carrier is in the main scanning direction. There is a type that irradiates light from a solid-state scanning optical writing device having a longitudinal direction of.

  Here, the solid-state scanning optical writing device is either a light emitting / lighting drive for each pixel such as an LED array, or a combination of a light source that continuously modulates a light modulation element that performs modulation for each pixel. Shall also be included.

In recent years, there has been an increasing demand for forming high-definition images, and at least some monochrome image output devices have high-definition monochrome output.
As an example of this type of image forming apparatus, each color of Y (yellow), M (magenta), and C (cyan) is provided with a light modulation element of 600 dpi (600 dots / 25.4 mm) in the main scanning direction, and K (black). ) Include a light modulation element of 1200 dpi (1200 dots / 25.4 mm) in the main scanning direction.

  In the color image formation mode, the resolution in the sub-scanning direction is increased to improve the gradation of the recorded image. In YMC, image formation is performed in the main scanning direction of 600 dpi × sub-scanning direction of 2400 dpi, and in K, the main scanning direction is 1200 dpi.times. Image formation is performed in the sub-scanning direction 2400 dpi.

  On the other hand, in the monochrome image of only K in the monochrome image formation mode, the image formation is performed in the main scanning direction 1200 dpi × sub-scanning direction 1200 dpi with an emphasis on high-speed image formation. In this color image formation mode and monochrome image formation mode, image formation is executed with different image formation speeds (process speeds).

  By the way, when the color image and the monochrome image are different jobs, there is no problem because they operate in the color image processing mode and the color image forming mode, and the monochrome image processing mode and the monochrome image forming mode, respectively.

However, when color pages and monochrome pages are mixed in one job, the following problems may occur in a certain type of color image forming apparatus.
When a scanner unit reads a plurality of originals mixed with color images / monochrome images, the color / monochrome automatic selection function treats each document as a color image / monochrome image, and the image processing unit performs image processing (color image processing / monochrome image). Image processing).

  Here, the resolution of the YMC image data in the color image is converted to 600 dpi × 1200 dpi and the resolution of the K image data is 1200 dpi × 2400 dpi according to the color image processing mode. On the other hand, the resolution of the K image data in the monochrome image is converted to 1200 dpi × 1200 dpi in the monochrome image processing mode.

  In other words, whether the color image is handled in the color image processing mode or the monochrome image is handled in the monochrome image processing mode, the resolution in the K sub-scanning direction is treated as a different value.

The same problem occurs when color pages and monochrome pages are mixed, not only when reading a document with a scanner, but also with a printer.
Here, if the process speed is changed between the color image and the monochrome image and the color image formation mode and the monochrome image formation mode are switched, the image formation is executed without any problem.

However, since it takes a certain time to change the process speed in the image forming apparatus, a problem arises that productivity (the number of images formed per unit time) decreases.
Therefore, when color images / monochrome images are mixed, a monochrome image processed in the monochrome image processing mode is formed in the color image formation mode.

  However, the resolution (number of recorded pixels) in the sub-scanning direction of the monochrome image processed in the monochrome image processing mode is ½ of the color image in the color image processing mode, and the monochrome image processed in the monochrome image processing mode is If the image is formed as it is as a monochrome image in the color image formation mode, the exposure energy per unit area is insufficient and the image quality is significantly deteriorated.

  In addition, if the image processing in the color image processing mode is applied to the monochrome image when the color image / monochrome image is mixed as in the case of the color image, the above problem can be solved, but the image processing is switched according to the result of determination of the mixture. There is a problem that control becomes troublesome, such as necessity.

Here, image forming apparatuses that handle different recording densities include those described in Patent Document 1 and Patent Document 2 below.
Japanese Unexamined Patent Publication No. 2000-108406 (first page, FIG. 1) Japanese Patent Laying-Open No. 2005-114563 (first page, FIG. 1)

  In the invention described in Patent Document 1 above, in the high image quality mode, the process speed is set to ½ that in the standard image quality mode, the input image is doubled in the sub-scanning direction, and the resolution is doubled. To do. At this time, it is described that the exposure amount of one dot in the high image quality mode is set to 1/2 or more of the standard image quality mode. In this case, it is assumed that the process speed is switched, and in the case of mixed color / monochrome, a decrease in productivity becomes a problem.

  Further, in Patent Document 2 described above, as a color image forming apparatus that performs high-resolution recording only for K, it is described that a plurality of laser beams more than YMC are generated at K. This patent document 2 is different in that a laser beam is used.

  Further, neither Patent Document 1 nor Patent Document 2 described above gives any consideration to the difference in resolution between the monochrome image included in the color mode and the monochrome image in the monochrome mode.

  By the way, assuming that the resolution in the sub-scanning direction of the monochrome image in the color image forming mode is n times the resolution in the sub-scanning direction of the monochrome image in the monochrome image forming mode, the monochrome image processing mode is set without changing the process speed. When forming an image-processed monochrome image as a monochrome image in the color image formation mode, it is conceivable that the exposure energy per pixel is multiplied by n to make the total exposure energy equal.

  However, the inventors have conducted intensive experiments. As a result, in an image forming apparatus that forms an image by optical writing, n pixels are recorded with standard energy, and 1 pixel is recorded with n times the energy. In the case of performing, it was newly found that dots having the same diameter are not finally formed.

  As a result, when a monochrome image processed in the monochrome image processing mode is recorded in the color image formation mode, the same density and dot diameter as those of the K image that is processed in the color image processing mode and recorded in the color image formation mode are obtained. In addition, it was newly found that the same density and dot diameter as those of a monochrome image processed in the monochrome image processing mode and recorded in the monochrome image forming mode cannot be obtained, and a good image quality cannot be obtained.

  The present invention has been made in view of the above problems. In an image forming apparatus using a solid scanning optical writing apparatus, a color image and a monochrome image are mixed and processed in a monochrome image processing mode. An object of the present invention is to realize an image forming apparatus capable of forming a good image without reducing productivity even when an image is output in a color image forming mode.

That is, the present invention for solving the above problems is as described below.
(1) The invention according to claim 1 is a solid scanning optical writing device having a configuration in which a plurality of light modulation elements are arranged in the main scanning direction, and optical writing by the solid scanning optical writing device. A control unit having a function of controlling the exposure, wherein the control unit generates exposure energy in one pixel of the light modulation element as compared with a case where dots are formed by exposure with n pixels of the light modulation element. In the image forming apparatus, the exposure energy is controlled to satisfy n <n ′ when one dot is formed by multiplying by n ′.

  (2) The invention according to claim 2 is provided for each color, each of which has a configuration in which a plurality of light modulation elements are arranged in the main scanning direction, and each of the solid scanning A control unit having a function of controlling optical writing by a type optical writing device, and the pixel recording resolution of the light modulation element of a certain color is n times the pixel recording resolution of the light modulation element of another color In the case where the control unit forms one dot by multiplying the exposure energy by n ′ with one pixel of the light modulation element as compared with the case where the dot is formed by exposure with the n pixel of the light modulation element. , N <n ′, the exposure energy is controlled to be n <n ′.

  (3) The invention according to claim 3 is characterized in that the control unit controls at least one of a light amount per pixel and an exposure time of one pixel as the exposure energy. Item 5. The image forming apparatus according to Item 2.

  (4) According to the invention of claim 4, as the solid-state scanning optical writing device, YMCK color modulation elements are provided, and the control unit forms different images in a monochrome image formation mode and a color image formation mode. When performing monochrome image formation in the color image formation mode by performing control at a speed, compared to the case of forming dots by exposing the light modulation element of K to n pixels of the light modulation element, 4. The exposure energy is controlled so that n <n ′ when one dot is formed by multiplying the exposure energy by n ′ in one pixel of the light modulation element. The image forming apparatus according to any one of the above.

According to each of the above inventions, it is possible to obtain the effects listed below.
(1) In the invention of the image forming apparatus according to the first aspect, the exposure energy is multiplied by n ′ with one pixel of the light modulation element as compared with the case of forming dots by exposing with n pixels of the light modulation element. In the case of forming one dot, by controlling the exposure energy so that n <n ′, the diameter of the dot generated by the image formation between the n pixel exposure and the one pixel exposure of the light modulation element can be reduced. When a monochrome image processed in the monochrome image processing mode is recorded in the color image forming mode, a good image quality can be obtained.

  In other words, color images and monochrome images coexist, and even when a monochrome image processed in the monochrome image processing mode is output in the color image formation mode, a good image can be formed without reducing productivity. An image forming apparatus can be realized.

  (2) In the invention of the image forming apparatus according to claim 2, the pixel recording resolution of a light modulation element of a certain color is n times the pixel recording resolution of a light modulation element of another color, and n pixels of the light modulation element Compared to the case where dots are formed by exposure, the exposure energy is controlled so that n <n ′ when one dot is formed by multiplying the exposure energy by one pixel of the light modulation element. Therefore, it is possible to make the diameters of dots generated by image formation equal to each other in n pixel exposure and 1 pixel exposure of the light modulation element, and a monochrome image processed in the monochrome image processing mode can be processed in the color image formation mode. When recording, good image quality can be obtained.

  In other words, color images and monochrome images coexist, and even when a monochrome image processed in the monochrome image processing mode is output in the color image formation mode, a good image can be formed without reducing productivity. An image forming apparatus can be realized.

  (3) In the invention of the image forming apparatus according to claim 3, the exposure energy is multiplied by n ′ with one pixel of the light modulation element as compared with the case where the dot is formed by exposing with n pixels of the light modulation element. When one dot is formed, it is generated by image formation by controlling exposure energy while controlling at least one of the light amount per pixel and the exposure time of one pixel so that n <n ′. When the monochrome image processed in the monochrome image processing mode is recorded in the color image formation mode when the monochrome image / color image is mixed, the color image is processed in the color image processing mode. Good image quality equivalent to the case of recording in the formation mode or the case of image processing in the monochrome image processing mode and recording in the monochrome image formation mode can be obtained.

  (4) In the invention of the image forming apparatus according to claim 4, the solid-state scanning optical writing device is provided with light modulation elements of each color of YMCK, and is controlled at different image forming speeds in the monochrome image forming mode and the color image forming mode. When performing monochrome image formation in the color image formation mode, the light modulation is compared with the case where the K light modulation element is exposed to n pixels of the light modulation element to form dots. When one dot of an element is multiplied by n ′ to form one dot, the exposure energy is controlled so that n <n ′, thereby making the diameters of dots generated by image formation equal. When a monochrome image processed in the monochrome image processing mode is recorded in the color image formation mode when the monochrome image / color image is mixed, the image processing is performed in the color image processing mode. Color to image processing in the case or monochrome image processing mode for recording in the image forming mode so that an equivalent good quality to the case of recording the monochrome image forming mode is obtained.

  In other words, color images and monochrome images coexist, and even when a monochrome image processed in the monochrome image processing mode is output in the color image formation mode, a good image can be formed without reducing productivity. An image forming apparatus can be realized.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the drawings.
It should be noted that even if the image forming apparatus (copying apparatus) has a function of reading and copying the contents of a copy object as image information by a document reading section (scanner), the image forming apparatus does not have a document reading section (scanner). Even so, the present invention can be applied. The present invention can also be applied to an image forming apparatus such as a multifunction machine having a facsimile function.

<First Embodiment>
First, the basic components of the present embodiment will be described with reference to FIG. 1, and then the mechanical configuration of the overall configuration of the apparatus to which the image forming apparatus of the embodiment is applied will be described with reference to FIG.

<Electrical configuration of image forming apparatus>
First, the electrical configuration of the image forming apparatus will be described by function with reference to FIG. In this embodiment, an image forming apparatus that reads an image of a document to generate image data, performs image processing on the image data in an image processing unit, and performs image formation on the basis of the image data. Used as a specific example of the form. In addition, here, an image forming apparatus that forms an image with four colors of an electrophotographic system is used as a specific example.

  An image forming apparatus 100 according to this embodiment includes a control unit 101 configured by a CPU or the like as a control unit that controls exposure in addition to controlling the entire image forming apparatus, and an image reading unit that reads an original and generates image data. 110, a scanner processing unit 120 that performs necessary processing such as color conversion on the image data obtained by the image reading unit 110, and various image processing necessary for image formation on the image data generated by the scanner processing unit 120 An image processing unit 130, a memory 140 used for image processing in the image processing unit 130, an LPH control unit 150 that performs light emission lighting driving or light modulation control of an LED print head (LPH) that performs exposure for each color, and The memory 160 for each color used in the control by the LPH control unit 150 for each color and the light emission by the LPH control unit 150 It comprises an LED print head (LPH) 170 as a light-emitting element array (LED light-emitting element array) for each color, which is an assembly of LED light-emitting elements that are exposed for each color by being driven by a lamp or light-modulated. Yes.

  In this embodiment, the image reading unit 110 generates RGB image data by reading RGB, and the scanner processing unit 120 converts the RGB image data into YMCK image data in accordance with the image formation color.

  Further, in this embodiment, as a specific example of a light emitting element that performs exposure for each color, an LED is used, and light emission lighting driving or light modulation is performed for each element by on / off control such as light emission / non-light emission. What we do is used as a specific example.

  In this embodiment, the LPH 170 is an example of the solid scanning optical writing device in the claims, and is provided for each color, and each has a configuration in which a plurality of light modulation elements are arranged in the main scanning direction. Is. In addition, as the solid-state scanning optical writing device, it is possible to use a continuous lighting light source combined with a light modulation element.

  Further, in this embodiment, the control unit 101 and the LPH control unit 150 constitute a control unit in the claims, and have a function of controlling optical writing by each solid-state scanning optical writing device.

In the following description of the embodiments, the light emission lighting driving of the light emitting element or the light modulation of the light modulation element is collectively referred to as light modulation.
<Mechanical configuration of image forming apparatus>
Here, the mechanical configuration of the image forming apparatus will be described with reference to FIG. Here, an image forming apparatus that performs image formation based on image data with the image processing unit and the image forming unit as the center is used as a specific example of this embodiment. In addition, here, an image forming apparatus that forms an image with four colors of an electrophotographic system is used as a specific example.

  In FIG. 2, an image processing unit 130 executes various types of image processing such as scaling and density necessary for image formation on given image data, and LPH control units 150Y, 150M, 150C, and 150K for each color. In contrast, image data of each color that has undergone image processing is supplied.

  The LPH control units 150Y to 150K convert the image data of each color from the image processing unit 130 into drive data for exposure using the memories 160Y to 160K, and perform light modulation of the LED print heads (LPH) 170Y to 170K for each color. Do.

  Then, the respective color photoconductor drums 180Y to 180K are exposed by the respective color LED print heads (LPH) 170Y to 170K, and electrostatic latent images corresponding to the image data are formed on the surfaces of the respective photoconductor drums 180Y to 180K. It is formed. Here, the surfaces of the photosensitive drums 180Y to 180K for the respective colors are charged to a predetermined voltage by the chargers 181Y to 181K.

  The electrostatic latent images on the surfaces of the photosensitive drums 180Y to 180K for the respective colors are developed by the developing devices 182Y to 182K, and become toner images for the respective colors. The toner images for the respective colors are color-synthesized on the transfer belt 190 and then transferred onto a recording sheet.

<Description of Operation of the Present Embodiment (1)>
The operation of the image forming apparatus as described above will be described. In the following description of the operation, problems newly found by the inventor of the present application and solutions for the problems will be described.

In this embodiment, a unit representing (dpi) the number of dots per 25.4 mm is used as the resolution for reading and image formation.
Here, as an example of the image forming apparatus, each color of Y (yellow), M (magenta), and C (cyan) includes an LED print head as a light modulation element of 600 dpi in the main scanning direction, and a main color in K (black). A specific example is one having an LED print head as a light modulation element of 1200 dpi in the scanning direction.

  In the image forming apparatus according to this embodiment, the image reading unit 110 reads the image data with an input resolution of 600 dpi × 600 dpi to generate image data. Also, image data with a resolution of 600 dpi × 600 dpi is received from an external device via a printer controller or the like.

  In the color image formation mode, in order to improve the resolution in the sub-scanning direction in order to improve the gradation of the recorded image, the YMC converts the image data to 600 dpi in the main scanning direction × 2400 dpi in the sub-scanning direction, and 600 dpi in the main scanning direction. Image formation is performed in the sub-scanning direction 2400 dpi. Similarly, K included in the color image is converted into image data of main scanning direction 1200 dpi × sub-scanning direction 2400 dpi, and image formation is performed in the main scanning direction 1200 dpi × sub-scanning direction 2400 dpi. In this case, the image forming speed is, for example, 280 mm / s.

  On the other hand, in the monochrome image forming mode, in order to improve the image forming speed, the image forming speed is set to 350 mm / s, K is converted into image data of 1200 dpi × sub-scanning direction 1200 dpi, and main scanning direction 1200 dpi × sub-scanning direction. Image formation is performed at 1200 dpi.

  FIG. 6 shows the case where the above-described color image job and monochrome image job are different jobs. In this case, there is no problem because the color image and the monochrome image are separate jobs and operate in the color image processing mode and the color image formation mode, and the monochrome image processing mode and the monochrome image formation mode, respectively.

  In some cases, a monochrome image and a color image are mixed in the same job. This is shown in FIG. In this case, the color image YMC mixed with the monochrome image, the color image K mixed with the monochrome image, and the monochrome image K mixed with the monochrome image are the same as those in FIG.

  However, in a certain type of color image forming apparatus, when a color page and a monochrome page are mixed in one job by a color / monochrome automatic selection (auto color selection; ACS) function, that is, a plurality of color images / monochrome images are mixed. When a document is read by the scanner unit, it is handled as a color image / monochrome image by the color / monochrome automatic selection function, and image processing (color image processing / monochrome image processing) is performed by the image processing unit.

  Here, the YMC component image data in the color image is converted in resolution to 600 dpi × 1200 dpi, and the K component image data is converted to 1200 dpi × 2400 dpi in the color image processing mode. On the other hand, K image data in a monochrome image is resolution-converted to 1200 dpi × 1200 dpi in the monochrome image processing mode regardless of whether the image is a monochrome single image or a color / monochrome mixed image.

  In other words, whether the color image is handled in the color image processing mode or the monochrome image is handled in the monochrome image processing mode, the resolution in the K sub-scanning direction is treated as a different value. The same problem occurs when color pages and monochrome pages are mixed, not only when reading a document with a scanner, but also with a printer.

  Here, if the process speed is changed between the color image and the monochrome image and the color image formation mode and the monochrome image formation mode are switched, the image formation is executed without any problem. However, since it takes a certain time to change the process speed in the image forming apparatus, in the case of a color / monochrome mixed image as one job, productivity (the number of images formed per unit time) decreases. A new problem arises. Therefore, when color images / monochrome images are mixed, a monochrome image processed in the monochrome image processing mode is formed in the color image formation mode.

  However, the resolution (recording pixel number) in the sub-scanning direction of the monochrome image processed in the monochrome image processing mode, that is, the portion indicated by hatching in FIG. 7 is ½ of the color image in the color image processing mode. If image formation is performed with a monochrome image processed in the monochrome image processing mode as it is as a monochrome image in the color image formation mode, the exposure energy per unit area is insufficient and the image quality is significantly deteriorated.

  In addition, if the image processing in the color image processing mode is applied to the monochrome image when the color image / monochrome image is mixed as in the case of the color image, the above problem can be solved, but the image processing is performed according to the mixed determination result. There is a problem that the control becomes troublesome, such as necessity of switching.

  In the following, processing of a monochrome image that is processed in the monochrome image processing mode and that is formed in the color image formation mode as shown by hatching in FIG.

  Here, when image data having a resolution of 1200 × 1200 dpi converted by monochrome image processing is formed in a color image formation mode of 1200 × 2400 dpi, one dot at 1200 dpi in the sub-scanning direction is 2400 dpi in the sub-scanning direction. It is conceivable that the exposure energy is doubled so as to be equal to two dots. That is, it is conceivable to form one dot by multiplying the exposure energy by one pixel n times compared to the case where dots are formed by exposure with n pixels.

  FIG. 3 is a characteristic diagram schematically illustrating the light intensity (exposure energy) of 2 dots of 2400 dpi in the sub-scanning direction. The light intensity of one dot formed by combining these 2400 dpi 2 dots (2 pixels) is as shown in FIG. 4 (thick solid line).

  On the other hand, when the light intensity (exposure energy) in a dot in which the light intensity (exposure energy) is doubled by one pixel of 1200 dpi in the sub-scanning direction is schematically shown, the characteristic is as shown by a thin solid line in FIG. . In this case, since there is no spread corresponding to a positional shift in 2 pixels of 2400 dpi, the energy is concentrated near the center even if the total energy amount is equal.

  When a toner image is formed on the photoconductive drum, the portion above the broken line (toner image formation threshold) in FIG. 4 depends on the electrostatic latent image potential and the toner potential in the developing device. A toner image is formed. That is, according to the difference in the light intensity characteristics due to the exposure of FIG. 4, the dot synthesized by two pixels of 1200 × 2400 dpi has a diameter of D0, whereas the light intensity of 1200 × 1200 dpi is doubled 1 The dot generated by the pixel has a diameter D1. This means that even if the total exposure energy is equal, the diameter of the toner image differs depending on the distribution pattern.

  In other words, compared to the case where dots are formed by exposure with n pixels, even if one dot is formed by multiplying the exposure energy by 1 pixel, only a small toner image is generated and the density is lowered. I mean.

  Here, when the inventor of the present application conducted an experiment, it was found that the characteristics shown in FIG. 5 exist. Here, it is assumed that energy when forming dots by exposure with n pixels is E0, and energy when forming one dot by multiplying exposure energy by n 'for one pixel is E1. Further, the dot diameter when forming dots synthesized by exposure with n pixels is D0, and the dot diameter when forming one dot by multiplying the exposure energy by n 'for one pixel is D1.

  In the case of the above specific example, a case where dots are formed by combining two pixels having exposure energy 1 and a case where dots are formed by one pixel having exposure energy 2, that is, E1 / E0 = 2/2 = 1. As is clear from FIG. 5, D1 / D0 = 0.87.

  That is, if the dot diameter when combining two pixels with exposure energy 1 to form a dot is 1, the dot diameter when forming a dot with one pixel with exposure energy 2 is 0.87, and the density is about 87. It turns out that it will fall to%.

Therefore, in FIG. 5, in order to set D1 / D0 = 1.0, it is necessary to set the exposure energy ratio E1 / E0 = 1.5.
Therefore, in order to form dots equivalent to the case where dots are formed by exposure with n pixels, n <n ′ is set when one dot is formed by multiplying the exposure energy by n ′ in one pixel. In the example of the experimental results in FIG. 5, in order to obtain a dot equivalent to the case where dots are formed by exposure with two pixels, one dot is formed by multiplying the exposure energy by one pixel (2 × 1.5). There is a need to. As a result, as shown by the thick solid line in FIG. 8, the exposure energy is multiplied by n ′ by 1 dot, and the dot diameter is set to D0, which can be equal to the case of n-dot synthesis (thick broken line in FIG. 8). .

  In this case, since the exposure energy is a product of the light amount per pixel and the exposure time of one pixel, the light amount 3 · time 1, the light amount 2 · time 1.5, the light amount 1.5 · time 2, and the light amount 1 Any combination such as time 3 may be used.

It was confirmed that the above-mentioned relationship of n <n ′ was established, although there were some fluctuations depending on the properties of the photoreceptor used and the specific values of the exposure energy.
Therefore, the control unit 101 and the LPH control unit 150K determine the exposure energy and adjust the light intensity as described above, so that a color image and a monochrome image are mixed and processed in the monochrome image processing mode. Even when a monochrome image is output in the color image formation mode, it is possible to form a good image without reducing productivity.

<Other embodiment (1)>
In the description of the above embodiment, a case where color pages and monochrome pages are mixed in one job by the color / monochrome automatic selection (auto color selection; ACS) function in the color image forming apparatus has been described as a specific example. However, the present invention is not limited to this, and in various image formations in which a dot is formed by exposure with n pixels and various cases in which one dot is formed by multiplying the exposure energy by n ′ in one pixel. It is possible to realize good image quality and productivity improvement by applying the control of n <n ′.

  Further, not only in a color image forming apparatus but also in a monochrome image forming apparatus, similarly, various cases of forming dots by exposing n pixels to form dots by multiplying the exposure energy n 'by one pixel. It is possible to realize good image quality and productivity improvement by applying a control of n <n ′ in various image formations in which cases are mixed.

  Similarly, in color image forming apparatuses and monochrome image forming apparatuses, exposure is performed with n pixels not only for K but also for other colors of YMC and other special colors (RGB and the like). Good image quality by applying the control of n <n ′ in various image formations in which a case where dots are formed and various cases where one pixel is formed by multiplying the exposure energy by n ′ is mixed. It is possible to improve productivity.

The above-described specific examples relating to the resolution of image processing and image formation are merely examples for explanation, and other numerical values can be used. For example, the same effects can be obtained when n = 3 or n = 4.
<Other embodiment (2)>
In the above embodiment, by setting the dot diameter ratio D1 / D0 to 1.0, a dot is formed by exposure with n pixels, and one dot is formed by multiplying the exposure energy by n ′ with one pixel. It has been explained that the dot diameter is the same as that in the case of performing the same, and the same density can be obtained.

  However, when the exposure energy is increased as shown by the thick solid line characteristic in FIG. 8, the energy is concentrated at the central portion, and the toner is concentrated. It has been newly found that the dots of the toner image tend to spread when the toner is fixed by the fixing unit.

  Therefore, the dot diameter of the final toner image on the paper is equal when the dot diameter ratio D1 / D0 = 1.0 in FIG. is there. This is caused by the exposure energy ratio, the properties of the toner to be used, the properties of the photosensitive member, and the like, and therefore it is desirable to make adjustments with various actual image forming apparatuses.

  However, the control of n <n ′ is performed in various image formations in which exposure is performed by n pixels to form dots and various cases in which exposure energy is multiplied by n ′ by 1 pixel to form one dot. It can be applied to achieve good image quality and productivity improvement.

1 is a functional block diagram illustrating an electrical configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a configuration diagram illustrating an electrical and mechanical configuration of an image forming apparatus according to an exemplary embodiment of the present invention. FIG. 6 is a characteristic diagram illustrating characteristics of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 6 is a characteristic diagram illustrating characteristics of the image forming apparatus according to the exemplary embodiment of the present invention. FIG. 6 is a characteristic diagram illustrating characteristics of the image forming apparatus according to the exemplary embodiment of the present invention. It is explanatory drawing which shows the operation mode of the image forming apparatus of embodiment of this invention. It is explanatory drawing which shows the operation mode of the image forming apparatus of embodiment of this invention. FIG. 6 is a characteristic diagram illustrating characteristics of the image forming apparatus according to the exemplary embodiment of the present invention.

Explanation of symbols

101 Control Unit 110 Image Reading Unit 120 Scanner Processing Unit 130 Image Processing Unit 140 Memory 150 LPH Control Unit 160 Memory 170 LPH
180 Photosensitive drum

Claims (4)

A solid scanning optical writing device having a configuration in which a plurality of light modulation elements are arranged in the main scanning direction;
A control unit having a function of controlling optical writing by the solid-state scanning optical writing device;
With
When the control unit forms one dot by multiplying the exposure energy by n ′ with one pixel of the light modulation element as compared with the case where the dot is formed by exposure with n pixel of the light modulation element, controlling the exposure energy so that n <n ′.
An image forming apparatus. A solid-state scanning optical writing device provided for each color, each having a configuration in which a plurality of light modulation elements are arranged in the main scanning direction;
A control unit having a function of controlling optical writing by each of the solid scanning optical writing devices;
With
The pixel recording resolution of the light modulation element of a certain color is n times the pixel recording resolution of the light modulation element of another color;
When the control unit forms one dot by multiplying the exposure energy by n ′ with one pixel of the light modulation element as compared with the case where the dot is formed by exposure with n pixel of the light modulation element, controlling the exposure energy so that n <n ′.
An image forming apparatus. The control unit controls at least one of a light amount per pixel and an exposure time of one pixel as the exposure energy.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. As the solid scanning optical writing device, YMCK color modulation elements are provided,
The control unit performs control at different image forming speeds in the monochrome image forming mode and the color image forming mode,
When performing monochrome image formation in the color image forming mode, the light modulation element of K is compared with the case where the light modulation element of K is exposed to n pixels of the light modulation element to form dots. When forming one dot by multiplying the exposure energy by n ′ in a pixel, the exposure energy is controlled so that n <n ′.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

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