JPH0421869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic apparatus using the so-called Carlson process for copying an image of a document surface onto plain paper.

Structure of a conventional example and its problems FIG. 1 shows a schematic structure of a main part of an example of a conventional electrophotographic apparatus using the Carlson process. In FIG. 1, photoreceptor 10 is rotating in the direction of arrow 12 when copying is performed, and first, a uniform charge is applied to the surface by corona discharge from charger 14. The document surface 18 of the document 16 is irradiated by a fluorescent lamp 20 serving as document irradiation means, and a reflected image thereof is formed on the photoreceptor 10 through an imaging optical system such as an optical fiber 22 having a lens effect. The document surface 18 is rotated in synchronization with the rotation of the photoreceptor 10.
The document surface image is sequentially exposed onto the photoreceptor 10 from the right end to the left end. In the developing device 24, toner adheres to the photoreceptor 10 according to the charge distribution of the electrostatic latent image generated on the photoreceptor 10 by exposure of the original surface image, and a developed image is formed on the photoreceptor 10. This developed image is transferred onto the plain paper 11 by the transfer charger 25 to form a copy image, and one of the main factors that determines the density of the copy image is the size of the residual charge of the electrostatic latent image. It is well known that this residual charge is determined by the amount of exposure to the photoreceptor 10.

On the other hand, when obtaining a copy image, there is a demand for image control such as adjusting the density or erasing a specific part (that is, bringing the image density of a specific part close to zero). It is conceivable to control the copied image by adjusting the amount of exposure. However, in the conventional electrophotographic apparatus, the light source for exposing the photoreceptor is only a single fluorescent lamp 20, and moreover, the exposure from this fluorescent lamp 20 is the exposure of the reflected image from the document surface 18; There is no irradiation means for irradiating the photoreceptor 10. Therefore, although it is possible to reduce the amount of exposure to the photoreceptor 10, increasing the amount of exposure requires a significant increase in the amount of light emitted from the fluorescent lamp 20, which is not practical. Because it always contains information corresponding to the original surface image, for example, even if you try to erase a specific part of the original surface image, the exposure that includes the information corresponding to the original surface image will not work even if you increase the exposure amount somewhat. Essentially, there are limits to the range of exposure adjustment and image control, such as the inability to erase the original surface image.

Furthermore, it is usually convenient to perform image control by extracting a specific image portion of the document surface 18 and selectively controlling the image density. It is necessary to selectively adjust the exposure amount to specific image parts according to this detected image information, but conventional electrophotographic devices do not have a function to detect image information, and There are problems in that it is difficult to adjust the exposure amount to a specific image portion according to the image information using a light source, and it has been difficult to control the copied image as described above.

Purpose of the Invention The present invention solves such problems in the conventional example, and reads image information on the surface of a document to be copied, adjusts the amount of exposure to a photoreceptor according to the read image information, and It is an object of the present invention to provide an electrophotographic apparatus in which the density of a copied image can be controlled based on the above-mentioned image information.

Structure of the Invention The electrophotographic apparatus of the present invention includes an original irradiation unit that irradiates the original surface with light, and a plurality of detection elements that read image information corresponding to the density distribution of the original image on the original surface in the width direction of the photoreceptor. A detection means provided in an array, a photoreceptor, an imaging optical system for forming an image of the document surface on the photoreceptor, and a plurality of light emitters for irradiating the photoreceptor surface with light. The photoconductor irradiation means includes a photoconductor irradiation means arranged in an array in the width direction of the photoconductor, and a control means for controlling the amount of light that the photoconductor irradiation means irradiates the photoconductor surface, and a plurality of the photoconductor irradiation means are provided. The light emitters are configured such that the amount of emitted light can be individually controlled by the current supplied to the control means, and the resolution of the photoreceptor irradiation means for dividing the photoreceptor surface into a plurality of pixel areas is n, the original When the resolution of the detection means for reading the image information of the image is m, and k is an integer satisfying k≧1, the photoreceptor surface is divided into a plurality of surfaces corresponding to the number of the light emitters so that m=kn or n=km. The document irradiation means and the imaging optical system are configured to irradiate the photoconductor into a plurality of pixel regions, each of which is controlled to have a required amount of light by the control means. In addition to the first exposure of the original image to the photoreceptor by the photoreceptor, a photoreceptor irradiation means is applied to the image portion of the original surface to be copied according to the image information corresponding to the density distribution of the original image by the detection means. By superimposing the second exposure on the photoreceptor by the second exposure, the image density of the image portion of the document surface to be copied is controlled for each pixel area.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a perspective view of essential parts showing the structure of an embodiment of the electrophotographic apparatus of the present invention, and FIG. 3 is a block diagram showing the relationship of the main parts in the embodiment of FIG. Second
In the figure, when copying, a photoreceptor 10 rotates in the direction of an arrow 12, a charger 14 is placed around the photoreceptor 10, and an original surface of an original 16 placed on an original placing surface 28 of an original platen 26. A fluorescent lamp 20 as an original irradiating means A for irradiating the document 18 with light, and an optical fiber 22 having a lens effect as an imaging optical system are provided. The document table 26 moves in the direction of an arrow 30 in synchronization with the rotation of the photoreceptor 10,
As a result, the image of the document surface is sequentially exposed onto the photoreceptor 10 from the right end to the left end of the document surface 18 placed on the document placement surface 28 .

The document surface image exposure section described above corresponds to the area surrounded by the broken line in FIG. 3, and is similar to the document surface image exposure section in a conventional electrophotographic apparatus. Also,
Similar to a conventional electrophotographic apparatus, an electrostatic latent image is formed by applying an electrostatic charge to the photoreceptor 10 and exposing the image on the document surface, and the charge distribution of the electrostatic latent image is changed by the developing device 24. Accordingly, toner is attached to the photoreceptor 1.
In this embodiment, the above-mentioned photoreceptor irradiation means B for directly irradiating the photoreceptor 10 with light is provided between the charger 14 and the optical fiber 22. A plurality of light emitting diodes 32 having a size that can divide the photoreceptor 10 into a plurality of divided areas in the width direction of the photoreceptor 10 are provided in an array along the width direction of the photoreceptor 10. The amount of light emitted from each light emitting diode 32 is
A control unit 34 constituting a control means C for controlling the amount of current applied to the light emitting diode 32 is connected to the light emitting diode 32 via a flexible wiring board 33. has been done. The control section 34 further includes a document surface 18.
An image sensor 36 serving as a detection means D for reading image information is connected via a flexible wiring board 35. The image sensors 36 are arranged in an array in the width direction of the photoreceptor 10 in the same way as the light emitting diodes 32, and the original 16 is arranged along the arrow 30.
As the document is fed in the direction, image information from the right end to the left end of the document surface 18 can be sequentially read. The read image information is transmitted to the control unit 34 and stored in a memory medium attached to the control unit 34. Further, the control section 34 includes, for example: - Selectively erase portions of the original image whose density is less than a specified density.

●Selectively erases parts of the original image that have a density higher than the specified density.

●All original image areas are adjusted to approximately constant copy image density.

An instruction button 38 is provided for selecting and instructing a desired form of copy image control.

Here, the image information on the document surface 18 needs to be read before the photoreceptor 10 is exposed to light by the light emitting diode 32.

FIG. 4 schematically shows the positional relationship of the image sensor 36, light emitting diode 32, and optical fiber 22 with respect to the document surface 18 and the photoreceptor 10. In FIG. 4, portion G of the document surface 18 is the photoreceptor 10.
Assuming that the exposure corresponds to the upper H portion,
The position of the image sensor 36 with respect to the G portion is set in the moving direction 30 of the original 16 or the photoreceptor 10 relative to the position of the light emitting diode 32 with respect to the H portion.
By placing it on the front side with respect to the rotational direction 12, image information on the document surface 18 can be read prior to exposure of the photoreceptor 10 by the light emitting diode 32 as described above. Further, as described above, the light emitting diodes 32 have a size that allows the photoreceptor 10 to be divided into a plurality of divided areas in the width direction of the photoreceptor 10, and are arranged in an array along the width direction of the photoreceptor 10. The second exposure amount can be controlled for each pixel length with one or more light emitting diodes as one pixel length, and the amount of light emitted from the light emitting diode 32 can also be controlled in the direction of rotation of the photoreceptor 10. By making it possible to change the pixel length at a required time interval, it is possible to form a pixel length corresponding to this time interval. It becomes possible to divide the surface of the photoreceptor 10 into pixel regions of a required size and control the second exposure amount for each pixel region.

Next, the copying operation will be explained using the electrophotographic apparatus of this embodiment configured as described above, taking as an example a case where a copy image is formed by selectively erasing the portion of the original image with a density below a specified density. do. As shown in FIGS. 2, 3, and 4, first, the image sensor 36 sequentially reads the document surface 18, and outputs an image information signal corresponding to the density distribution of the document surface image to the control unit. The information is stored in a memory medium attached to 34. The control unit 34 receives the required copy image control mode for erasing the portion of the original image having a specified density or less and the specified density using an instruction button 38 or the like, and selects the specified density based on the image information signal described above. The following image portions to be erased are calculated, and the positions on the photoreceptor 10 corresponding to the image portions to be erased are calculated. When the photoreceptor 10 whose surface is charged by the charger 14 rotates in the direction of the arrow 12 and the portion of the photoreceptor corresponding to the image portion to be erased comes to the position of the light emitting diode 32, this Light emitting diode 3 corresponding to the erased part
2 is emitted with a sufficient amount of light to eliminate the static charge on the photoreceptor 10, using the above-mentioned pixel area as a unit size.
Perform exposure. When the photoreceptor 10 rotates further and comes to the position of the optical fiber 22, the document 1
6 also moves in the direction of the arrow 30 in synchronization with the rotation of the photoreceptor 10 to close the optical fiber 22.
The document surface image including the erased portion is sequentially exposed to the photoreceptor 10 for the first time. The photoreceptor 10, on which the electric charge corresponding to the document image portion having a density lower than the specified density is eliminated by the second exposure, and an electrostatic latent image corresponding to the document surface image formed by the first exposure, is processed by the developing device 24. The document is then developed and a developed image is formed, but the portion of the document image below the specified density is erased and does not appear as an image during the development.

Here, the image sensor 36 detects the original surface 18.
According to this image information, the light emitting diode 3 corresponding to the image portion of the document surface whose density is below the specified density is read.
2, the light emitting timing of the light emitting diode 32 is determined by reading image information from the image sensor 36 for a time Δt determined by the distance between the image sensor 36 and the light emitting diode 32 and the rotational circumferential speed of the photoreceptor 10. During this time, it is necessary to store the image information read by the image sensor 36 in the memory medium. There is no problem if the storage capacity of the memory medium is sufficiently large, but if the storage capacity is limited and the distance between the image sensor 36 and the light emitting diode 32 is large, a large amount of image information must be stored. This may cause the storage capacity of the memory medium to be exceeded. Therefore, the light emitting diode 32 is provided on the side closer to the image sensor 36 with respect to the optical fiber 22, and the second exposure using the light emitting diode 32 is performed first.
It is convenient to perform the first exposure of the document surface image after a certain time and to reduce the distance between the image sensor 36 and the light emitting diode 36, since the storage capacity of the memory medium can be reduced.

Next, when the image sensor 36 has a resolution of m lines per 1 mm for reading image information on the document surface, and the light emitting diode 32 has a resolution of n lines per 1 mm for dividing the photoreceptor 10 into pixel areas, ideally both of the above It is desirable to make the resolution sufficiently large and to control the second exposure amount to a unit pixel area with respect to unit image information by setting m = n. However, in the case of m≠n, k should be set by a positive value. m=kn or n= as an integer of
It is best to set it to km. In this way, an integral number of pixel areas correspond to a unit of image information, or an integral number of image information corresponds to a unit of pixel area, and the image sensor 36 and light emitting diode 32 It is convenient to form them in an array so that the image information units and the pixel areas correspond to each other continuously.

Effects of the Invention As is clear from the above description, the electrophotographic apparatus of the present invention includes: an original irradiation unit that irradiates the original surface with light; a detection unit that reads image information corresponding to the density distribution of the original image on the original surface; and a photoreceptor irradiation means for irradiating the surface of the photoreceptor with light, the photoreceptor irradiation means being a plurality of light emitters, and a control means individually controlling the amount of current applied to the plurality of light emitters. At the same time, the photoreceptor surface is divided into a plurality of pixel areas corresponding to the number of the light emitters, and the photoreceptor is irradiated with a required amount of light by the control means for each of the plurality of pixels. In addition to the first exposure of the document surface image onto the photoreceptor by the document irradiation means and the imaging optical system, the document surface image portion to be copied is exposed to
By superimposing the second exposure of the photoreceptor by the photoreceptor irradiation means on the photoreceptor according to the image information corresponding to the density distribution of the original surface image by the detection means, a desired area of the image to be copied can be detected with a simple structure. It is possible to erase the electrostatic latent image on the photoreceptor, and the second exposure is bias exposure to the photoreceptor (to obtain a clear copy image without causing "fogging", which will be described later). It acts as a uniformly applied exposure to erase the charge in the electrostatic latent image area on the photoreceptor corresponding to the area), and prevents fogging of the copied image (for example, the color of the "ground" of a newspaper is clear white). Automatically and selectively removes a state in which the "ground" part of the copied image is slightly darker than white, which occurs when a document other than the original is copied, according to the image density information from the detection means. be able to. Also, the photoreceptor surface is divided into n pixel areas,
Resolution m at which the detection means reads image information of the document surface image
In contrast, by configuring the photoreceptor irradiation means and the detection means so that m = kn or n = km, and by controlling the amount of light irradiated on the photoreceptor by the photoreceptor irradiation means for each pixel, A required amount of second exposure is performed on the photoconductor corresponding to a part of the image within the document surface of the document according to the image density within the document surface of the document having image information, and the photoconductor irradiation means or Copy image control can be carried out according to the lower resolution of the sensing means.

[Brief explanation of drawings]

FIG. 1 is a schematic front view of main parts showing an example of a conventional electrophotographic apparatus, FIG. 2 is a perspective view of main parts showing the structure of an embodiment of the electrophotographic apparatus of the present invention, and FIG. FIG. 4 is a block diagram showing the relationship of the main parts in the embodiment. FIG. 4 is a schematic diagram showing the positional relationship of the main parts in the embodiment of FIG. 10... Photoreceptor, 14... Charger, 16... Original, 18... Original surface, 20... Fluorescent lamp, 22...
Optical fiber, 24... Charger, 25
...Transfer charger, 26...Document table, 28...Document placement surface, 32...Light emitting diode, 34...Control unit, 36...Image sensor, 38...Instruction button
A... Original irradiation means, B... Photoreceptor irradiation means, C
...control means, D...detection means.

Claims (1)

[Scope of Claims] 1. An original irradiation unit that irradiates the original surface with light, and a plurality of detection elements that read image information corresponding to the density distribution of the original image on the original surface, arranged in an array in the width direction of the photoreceptor. a photoconductor, an imaging optical system for forming an image of the document surface on the photoconductor, and a plurality of light emitters for irradiating the photoconductor surface with light, each of which has a width of the photoconductor. The photoreceptor irradiation means includes a photoreceptor irradiation means arranged in an array in the direction, and a control means for controlling the amount of light that the photoreceptor irradiation means irradiates the photoreceptor surface, and the plurality of light emitters of the photoreceptor irradiation means , the amount of emitted light can be individually controlled by the current flowing through the control means, and the resolution at which the photoreceptor irradiation means divides the surface of the photoreceptor into a plurality of pixel areas is n, and the image information of the original image is adjusted. When the resolution of the detection means for reading is m and k is an integer such that k≧1, m=kn or n=
km, the photoreceptor surface is divided into a plurality of pixel areas corresponding to the number of the light emitters, and the photoreceptor is controlled to a required light amount by the control means for each of the plurality of pixel areas. irradiation, and in addition to the first exposure of the original image to the photoreceptor by the original irradiation means and the imaging optical system,
The second exposure of the photoreceptor by the photoreceptor irradiation means is superimposed on the image portion of the document surface to be copied, according to the image information corresponding to the density distribution of the original image by the detection means. An electrophotographic apparatus characterized in that image density control is performed for each pixel region of a copy image density of an image portion of a document surface. 2. The control means includes a storage means for storing the image information of the document surface read by the detection means, from the reading of the image information by the detection means to the second exposure of the photoreceptor by the photoreceptor irradiation means. During this period, the image information is held in the storage means, and the photoreceptor irradiation means first performs a second exposure, and then the original irradiation means displays the image of the document surface on the photoreceptor. 2. The electrophotographic apparatus according to claim 1, wherein the electrophotographic apparatus is configured to perform first exposure to an image.