JPH0553415A - Screen device of electronic photographing device - Google Patents

Abstract

PURPOSE:To eliminate need of a mechanical structure to move a liquid crystal panel, i.e., a screen filter, to prevent the generation of noise owing to provision of the structure and the occurrence of a mechanical trouble, to prevent an influence from being exercised by temperature and humidity, to perform stable operation, and to improve reliability. CONSTITUTION:A screen filter to form a screen pattern to provide an image, formed by an electronic photographing device, with gradient is composed of a liquid crystal panel 32. A control device 34 causes the liquid crystal panel 32, driven by a liquid crystal driver 33, to perform operation to form a pattern and operation to erase a screen pattern and to perform only transmission of light.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screen device for an electrophotographic apparatus provided in an optical system of an electrophotographic apparatus such as a full color copying machine in order to improve the gradation of an image to be formed.

[0002]

2. Description of the Related Art For example, in an electrophotographic full-color copying machine, gradation is emphasized in order to reproduce faithful colors, and the screen method is adopted as one of the methods for obtaining good gradation. Has been done. This screen method provides a screen filter near the surface of the photoconductor that decomposes the light reflected from the document and incident on the photoconductor into a linear shape, and imparts gradation to the copied image according to the line width of the screen filter. It is a method to do.

On the other hand, if the exposure optical system is always provided with a screen filter, when a document image consisting of characters and line drawings is copied, the obtained image is unclear and difficult to read. Therefore, when the exposure mode is set to the screen mode in which the gradation is important and copying is performed, a screen filter is arranged in the optical path of the exposure optical system, and the exposure mode is set such that characters or the like are displayed rather than the gradation. When copying is performed in the normal mode, which emphasizes sharpness, the screen filter is removed from the optical path of the exposure optical system.

The above structure will be described with reference to FIG. 3. In a full-color copying machine, a document 52 placed on a document table 51.
Is optically scanned by the light source lamp 55 of the exposure optical system 54, and the reflected light thereof is reflected by a plurality of reflecting mirrors 56 and a lens 57.
It is adapted to be guided to the surface of the belt-shaped photoconductor 53 via. The screen filter 58 is arranged in the vicinity of the photoconductor 53, and constitutes a screen device 60 together with a mechanical drive device 59.

The screen filter 58 is driven by the driving device 59, and is arranged in the optical path of the exposure optical system 54 when the exposure mode is the screen mode, and when the exposure mode is the normal mode. It is designed to be removed from the optical path 54. The screen filter 58 is made of a photographic film in which a large number of parallel thin lines are formed at regular intervals in the A direction, which is the traveling direction of the photoconductor 53.

[0006]

However, in the above-mentioned conventional screen device 60, since the screen filter 58 is made of a photographic film, the expansion and contraction rates of the base film and the film on which the fine line is formed are different, and And the screen filter 58 is warped due to the influence of humidity. For this reason, the function of the screen filter 58 is partially changed, and uneven density occurs. Further, since the drive device 59 is mechanical, noise is generated when the screen filter 58 is driven, and the drive device 59 itself is liable to be mechanically damaged, and high reliability cannot be ensured. Have a point.

[0007]

In order to solve the above-mentioned problems, a screen device for an electrophotographic apparatus of the present invention develops an electrostatic latent image formed by exposing a photoconductor to obtain a predetermined image. Provided in the electrophotographic apparatus, having a screen filter in the vicinity of the photoconductor in the optical path of light for exposing the photoconductor,
In the screen device of the electrophotographic device, in which a screen pattern for imparting gradation to an image formed by the electrophotographic device is formed on the screen filter, the screen filter is composed of a liquid crystal display device. Liquid crystal driving means for driving the device based on a control signal of the control means, and a control signal for causing the liquid crystal display device to perform the operation of forming the above-mentioned screen pattern and the operation of erasing the screen pattern and simply transmitting light. Is output to the liquid crystal drive device.

[0008]

According to the above construction, the screen filter is
The liquid crystal display device is composed of a liquid crystal display device, and the liquid crystal display device is controlled by the control means to form a screen pattern for imparting gradation to an image formed by the electrophotographic device, and the screen pattern is erased to simply display light. Can be transmitted. Therefore, a liquid crystal display device, that is, a mechanical structure for moving the screen filter becomes unnecessary, and problems such as noise generation and mechanical failure due to the structure are solved. Further, the liquid crystal display device is less affected by temperature and humidity as compared with the photographic film and can perform stable operation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 2, a full-color copying machine (hereinafter, simply referred to as a copying machine) as an electrophotographic apparatus has a transparent original placing table 1 on its upper surface. An exposure optical system 3 that optically scans a document 2 and exposes a photoconductor 4 to be described later is arranged below the document table 1. The exposure optical system 3 includes a light source lamp 3a for irradiating the original 2 placed on the original placing table 1 with light, and reflected light from the original 2 on a photoconductor 4 as indicated by a chain line in the figure. It includes a plurality of reflecting mirrors 3b for guiding, an image forming lens 3c arranged in the optical path of the reflected light, and a color separation filter 3d having color filters of three primary colors of red, green and blue.

Below the exposure optical system 3, a belt-shaped photosensitive member 4 is provided. The photosensitive member 4 is rotatably driven by being stretched over two rollers 5 and 6 arranged at regular intervals. Around the roller 6 side of the photoconductor 4, a charger 7 that charges the photoconductor 4, a cleaning device 8 that removes toner remaining on the photoconductor 4, and the like are provided.

A liquid crystal panel 32, which is a liquid crystal display device of the screen device 31, is provided above the incident position of the reflected light from the original 2 on the photoconductor 4 and in proximity to the photoconductor 4. Above the photoconductor 4, four developing tanks 9 to
A developing device 13 having 12 is arranged in a non-contact state with the photoconductor 4. In this developing device 13, the developing tanks 9 to 1
Reference numeral 1 separately stores toners as yellow, magenta, and cyan color developers that are complementary colors of the color filters in the color separation filter 3d, while the developing tank 12 stores black toner.

Below the photoconductor 4, paper feed cassettes 14 and 15 of different sizes are arranged vertically. In the paper output direction of the paper feed cassettes 14 and 15, the conveyance rollers 16 and
17 are provided. A belt-shaped transfer intermediate 18 driven by three rollers 19 to 21 is provided on the roller 5 side of the photoconductor 4. Transfer intermediate 1
The toner image on the photosensitive member 4 is transferred around the transfer intermediate member 18
A transfer roller 22 for transferring the toner image on the transfer intermediate body 18, a cleaning device 23, and a transfer roller 24 for transferring the toner image on the transfer intermediate 18 to a transfer sheet are arranged. A transfer belt 25 and a fixing device 26 for thermally fixing the toner on the transfer paper to the transfer paper are provided in the paper output direction of the transfer intermediate 18.

As shown in FIG. 1, the screen device 31 has a transmissive liquid crystal panel 32 functioning as a screen filter, a liquid crystal driver 33 as liquid crystal driving means for driving the liquid crystal panel 32, and the liquid crystal driver. A control device 34 as control means for controlling the operation of the liquid crystal panel 32 via 33.

The liquid crystal panel 32 is 1 to 2 m from the photoconductor 4.
It is provided parallel to the photoconductor 4 at a position above m. The control device 34 controls the liquid crystal panel 32 to function as a screen filter when the exposure mode is set to the screen mode, and controls the liquid crystal panel 32 to the original 2 when the exposure mode is set to the normal mode. The panel is controlled so that the reflected light from the panel is simply transmitted. The above screen mode is selected for copying originals such as full-color originals and photographic originals that emphasize gradation, and the normal mode is for originals such as text originals that emphasize line sharpness rather than gradation. It is selected in the case of copying. When the liquid crystal panel 32 functions as a screen filter, as shown in FIG.
A fine line pattern composed of a large number of fine lines 32a, which are parallel to each other and are arranged at regular intervals, is formed in the A direction, which is the traveling direction of the photoconductor 4. Further, in the present embodiment, the copying machine sets the exposure mode to the screen mode when the full-color copy and the photo original copy are selected, and sets the exposure mode to the normal mode when the black-and-white copy selected as the copy of the character is selected. , And each shall be set automatically.

In the above structure, when full-color copying is selected on the copying machine side, the exposure mode is set to the screen mode and the control device 34 of the screen device 31 is set.
Controls the liquid crystal panel 32 to function as a screen filter. As a result, the thin line pattern is formed on the liquid crystal panel 32.

When the copy start button is turned on, the light source lamp 3a of the exposure optical system 3 irradiates the original 2 placed on the original placing table 1 with light, so that optical scanning is performed three times. Be seen. The reflected light from the original 2 is incident on the color separation filter 3d via the reflecting mirrors and the image forming lens 3c, and is separated into color components by the color separation filter 3d.

This light is further radiated through the reflecting mirrors 3b and 3b and the liquid crystal panel 32 on which the fine line pattern is formed onto the photosensitive member 4 uniformly charged by the charger 7 to expose it. To do. As a result, an electrostatic latent image for each color component corresponding to the image of the original 2 is formed on the photoconductor 4.

The electrostatic latent images described above are developed by the developing device 13 with the toners of yellow, magenta, and cyan, which are the complementary colors of the color filters in the color separation filter 3d, and are visualized to form toner images. These toner images for each color component are sequentially transferred to the transfer intermediate 18 by the transfer roller 22, and one color toner image is formed by superposing the toner images for each color component. The color toner image is transferred by the transfer roller 24 onto the transfer paper supplied from one of the paper feed cassettes 14 and 15. After that, the transfer paper is transferred to the conveyor belt 25.
Is introduced into the fixing device 26, and the color toner image is thermally fixed on the transfer paper. As a result, a full-color image with good gradation can be obtained on the transfer paper.

On the other hand, when black-and-white copying is selected on the copying machine side, the exposure mode is set to the normal mode, and the control device 34 of the screen device 31 erases the thin line pattern of the liquid crystal panel 32 and the liquid crystal panel 32. Controls so that the panel simply transmits the reflected light from the original 2.

When the copy start button is turned on, the exposure optical system 3 scans the original 2 once, and the reflected light from the original 2 does not pass through the color separation filter 3d. , Liquid crystal panel 3 with thin line pattern erased
2 is simply transmitted to irradiate the photoconductor 4 to expose it. The electrostatic latent image formed by this is developed with black toner in the developing tank 12 to be visualized into a toner image, and this toner image is transferred to the transfer paper via the transfer intermediate 18. The toner image on the transfer paper is thermally fixed on the transfer paper by the fixing device 26, and a clear black and white image is obtained on the transfer paper.

As described above, the present screen device 31 controls the liquid crystal panel 32 so that the fine line pattern is formed and erased without moving the liquid crystal panel 32. Since no special structure is required, noise is generated due to the structure.
Also, problems such as occurrence of mechanical failure due to repeated use are solved. Further, the liquid crystal panel 32 is less affected by temperature and humidity as compared with a photographic film, and can perform stable operation.

In the screen device 31 of this embodiment, the pattern formed on the liquid crystal panel 32 is composed of a large number of fine lines 32a ... Although it is a fine line pattern,
Without being limited to this, it is possible to form an arbitrary screen pattern on the liquid crystal panel 32 by selecting the configurations of the liquid crystal panel 32, the liquid crystal driver 33, and the control device 34.

[0023]

As described above, in the screen device of the electrophotographic apparatus of the present invention, the screen filter for imparting gradation to the image formed by the electrophotographic apparatus is composed of the liquid crystal display device. Liquid crystal driving means for driving the device based on a control signal of the control means, and a control signal for causing the liquid crystal display device to perform the operation of forming the above-mentioned screen pattern and the operation of erasing the screen pattern and simply transmitting light. Is output to the liquid crystal drive device.

This eliminates the need for a liquid crystal display device, that is, a mechanical structure for moving the screen filter, and solves the problems of noise and mechanical failure due to the structure. You can Further, the liquid crystal display device is less affected by temperature and humidity as compared with the photographic film and can perform stable operation, so that the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a screen device showing an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a full color copying machine including the screen device shown in FIG.

FIG. 3 is an explanatory diagram showing a conventional screen device provided in a copying machine.

[Explanation of symbols]

 4 Photoreceptor 31 Screen Device 32 Liquid Crystal Panel (Liquid Crystal Display Device) 33 Liquid Crystal Driver (Liquid Crystal Driving Means) 34 Control Device (Control Means)

Claims (1)

[Claims] 1. A screen filter is provided in an electrophotographic apparatus for developing an electrostatic latent image formed by exposing a photosensitive member to obtain a predetermined image, and a screen filter is provided near the photosensitive member in an optical path of light for exposing the photosensitive member. In this screen filter, in the screen device of the electrophotographic device in which a screen pattern for imparting gradation to the image formed in the electrophotographic device is formed, the screen filter is a liquid crystal display device,
Liquid crystal driving means for driving the liquid crystal display device based on the control signal of the control means, and for causing the liquid crystal display device to perform the operation of forming the above-mentioned screen pattern and the operation of erasing the screen pattern and simply transmitting light. And a control means for outputting the control signal of 1. to the liquid crystal driving device.