JPS63254470A - Copying device - Google Patents

Abstract

PURPOSE:To set the density of a copy image to a desired level by detecting the light quantity of an exposing light from a plate document or an original, and controlling the light quantity or a developing bias voltage applied to a developing device provided in the vicinity of an image carrying body, based on a detecting signal. CONSTITUTION:The titled copying device has a regular original copying mode for placing an original on an original platen and copying it, and a plate document copying mode for projecting an image of a plate document to an image reading position on the original platen and copying it. A light quantity detector S is arranged in an optical path of an image light radiated to a photosensitive drum. A detecting signal of the detector S is inputted to a control circuit 20 through an A/D converter 19. The circuit 20 compares it with a reference light quantity level which has been set in advance, executes a control so that the light quantity of a lamp 4 for illuminating a plate document becomes a reference value, in the case of plate document copying, and also, controls a developing bias voltage applied to a developing device 25. Moreover, in the case of original copying, in the same way, the light quantity of the lamp 6 is controlled, and also, the developing bias voltage applied to the developing device 25 is controlled. In such a way, the density of a copying image can be set to a desired level.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides an image written on a board and a;
The present invention relates to a copying apparatus that can selectively copy any of the images of a printed original.

(Prior Art) Conventionally, in a device capable of copying image information written on three sides of a board, a planar scanning method using a CCD sensor as a solid-state image sensor is used as a method for reading the writing on the board, and a thermal recording method is used as a recording method. is common. This type of digital method not only cannot copy the image information on old boards onto plain paper, but also has a low recording speed, so it takes time to copy a large number of sheets, and the resulting recording density is about 6 dots/■.
It remains at the level of a layer.

Therefore, recently, an apparatus has been proposed for recording image information written on a board using an electrophotographic method. This type of device involves directly forming an image of image information written on a board onto the belt or drum-shaped image carrier of a conventional electrophotographic copying machine, and converting it into a plain paper transfer material using a known electrophotographic process. A copying device and image information written on a board are once imaged on a field lens provided on a manuscript table, and the formed image is formed on an image carrier via an optical system in an electrophotographic copying machine. There are devices that transfer and copy onto a transfer material using a known process.

Both methods are capable of copying originals placed on a manuscript table and copying image information written on a board onto plain paper, and have improved recording density compared to conventional digital methods. Even when obtaining multiple copies, after copying one board document,
If the transfer material obtained by the copying is used as a copy original for secondary copying, no time is wasted due to copying speed. It is also used to paste large manuscripts such as newspaper spreads or AI-sized blueprinted drawings onto the above-mentioned board, and then reduce and copy them.

(Problems to be Solved by the Invention) However, the above-mentioned conventional technology does not have a means for adjusting the amount of exposure light from the board onto the image carrier.
For example, when copying newspaper letters pasted on a board or an image with a dark background such as blueprint, rather than an ordinary image written with a felt marker, the background part of the copied image There was a problem in that fogging occurred and proper images could not be obtained.

In addition, if the exposure amount decreases due to dirt on the board or optical system, or deterioration of the lamp that illuminates the board,
Since there is no means for adjusting the exposure amount, there is a problem in that the copied image becomes unclear and a suitable IE image cannot be obtained.

Therefore, the present invention has been made to solve the above problems of the prior art, and its purpose is to select either an image written on a board or an image of a document placed a on a document table. It is an object of the present invention to provide a copying apparatus which has a flexible copying section and can always obtain proper copied images.

(Means for Solving the Problems) In order to achieve the above object, one aspect of the present invention is to provide an image that is either an image written on a writable board or an image of a manuscript placed on a manuscript table. In a copying apparatus equipped with an image forming means that selectively exposes an image carrier to one side and forms an image on a transfer material using an electrophotographic method, detection detects the amount of exposure light from the board document or the original document. The apparatus is configured to control at least one of the amount of light and a developing bias voltage applied to a developing device provided near the image carrier based on a signal obtained by the detecting means.

(Function) In the present invention, the amount of exposure light from a board document or a document placed on a document table is detected by a detection means, and the amount of light or the amount of exposure light from an image carrier is determined based on a signal obtained by the detection means. By controlling at least one of the developing bias voltages applied to a nearby developing device to a preset value, the density of the copied image can be set to a desired level.

(Embodiment) Fig. 1 is a perspective view showing an embodiment of the present invention, and Fig. 2 is a side view of the same embodiment. It is a flexible sheet member, and is stretched between rollers 2 and 3. This sheet member
Board A.

B is substantially flat in the vertical direction and is movable by rotating the rollers 2 and 3 in the direction of the arrow, and image information written at this time is scanned and projected onto the photoreceptor by an optical system to be described later. On the side indicated by A on the sheet member 1, an image of location → is written down with an appropriate writing instrument such as a felt-tip pen, and this written image information is converted into a board document A by the rotation of rollers 2 and 3. The board is illuminated and scanned by the surface illumination lamp 4 at the position of the board B on the opposite side.

Reference numeral 5 denotes an electrophotographic image forming means, which has a photosensitive drum 7 inside a box 6 that rotates in the direction of the arrow. Along the rotation path around the photosensitive drum 7, in addition to the developing device 25, a primary charger, a transfer charger, and a cleaner (not shown) are provided. Means for supplying the material and a fixing device for fixing the toner image transferred to the transfer material are also provided at predetermined positions.

A movable document table 8 is attached to the upper part of the box body 6.

In the original copy mode, a document to be copied is placed on the original table 8, and the original table 8 is moved forward in a direction substantially perpendicular to the moving direction of the sheet member 1 to scan the original.

When the document scanning is completed, the document table 8 returns to the home position.

During document scanning, the document placed on the document table 8 is illuminated by the document illumination lamp L, and this light image is exposed to light by an imaging optical system consisting of mirrors 9, 11 and a lens 10 arranged inside the box body 6. An image is formed on the body drum 7 and exposed. The imaging optical system projects an image of the document portion located at position C, which is a fixed position relative to the box 6, onto the photosensitive drum 7.

On the other hand, in the board copy mode, the field lens 12 is placed in contact with or close to the document table 8 at the C position. Also, on manuscript table 8! 2! In the original copy mode, the field lens 12 is retracted from the above position. That is, the field lens 12 includes a sheet member l, rollers 2 and 3, a lamp 4, and a first . Second mirror 13, 14. It is attached to a retractable optical path cover 17 such as a bellows attached to a board box 16 that houses a lens 15, and is lowered and placed in the upper position in the board copying mode, and raised in the original copying mode. Then, it is evacuated from the movement path of the document table 8.

The image of the board B scanned by the board Bgs is projected onto the field lens 12, and its optical system is based on the first. It has second mirrors 13 and 14 and a lens 15. The first mirror 13 is arranged in the upper direction, and the lamp 4
The light from the illuminated board B is reflected laterally along the board B, and the second mirror 14 reflects the light image from the first mirror 13 downward along the board B.

Then, the lens 15 receives the light from the second mirror 14,
The image on the plate Δ plane B is focused on the field lens 12.

The image formed on the field lens 12 is transferred to the photoreceptor drum 7 at the same position as in the original copying mode by the imaging optical system consisting of the mirrors 9, 11 and the lens 1O. be done.

As described above, in this embodiment, the Jf
There is a normal original copying mode in which the original image is copied onto a recording paper by placing an It is possible to select either a board copy mode in which the image of document B is copied onto recording paper.

However, one function that utilizes blackboard writing is to paste a dark-based manuscript with a large screen such as newspaper on the blackboard and make a reduced copy of this manuscript, but in this case, the background part of the image Since the blackish portion appears as a background fog in the formed image, there is a problem in that the image becomes very difficult to look at.

Therefore, in this embodiment, in addition to the above configuration, a light amount detector S such as a photodiode is provided in the optical path of the image light irradiated onto the photoreceptor drum 7 to detect the amount of light. Based on the detection signal, the image density is controlled as described below. By the way, this image density is determined by the difference (contrast potential) between the developing bias potential applied to the developing device 25 and the charging potential (WI image potential) on the photosensitive drum 7.
In general, the higher the contrast potential, the higher the density. On the other hand, even if the developing bias potential remains unchanged, the greater the amount of light irradiated onto the photoreceptor drum 7, the more the potential of the latent image on the photoreceptor drum 7 decreases, and thus the density increases. Therefore, the concentration is controlled by the light amount detector S.
In this embodiment, the third detection signal is
The configuration shown in the block diagram in the figure was adopted. That is, to explain the control operation based on the same figure, first, the light-
The amount of exposure light from the board is detected by the jI''L detector S, and the image density signal obtained by photoelectric conversion is converted into a digital value by the A/D converter 19 and then input to the control circuit 20. This control circuit 20 compares it with a preset reference light intensity level, and outputs a digital signal based on the difference so that the lamp 4 that illuminates the board reaches the above reference value. It is controlled through a D/A converter 21 and a lamp regulator 22 based on a signal from.

Furthermore, when controlling the developing bias voltage applied to the photoreceptor drum 7, the high voltage is The developing unit 25 is controlled by operating the unit 24.

Furthermore, in the original copy mode, the amount of exposure light from the original placed on the original platen 8 is detected by the light amount detector S, and a signal from the control circuit 20 is detected as in the above-mentioned board copy mode. Based on this, the light amount of the document illumination lamp L is controlled through the D/A converter 26 and the lamp regulator 27, or the developing unit 25 is controlled through the D/A converter 23 and the high voltage unit 24.

In the embodiment having the above configuration and operation, the light amount detector S detects the amount of exposure light from the board B or the document placed on the document table 8, and the amount of exposure light obtained by the light amount detector S is detected. By controlling at least one of the light amount or the developing bias voltage applied to the photoreceptor drum 7 to a preset value based on the signal, the density of the copied image can be set to a desired level. , there is no fog in the image even for originals with a dark background such as newspaper,
A proper copy image can be obtained. Also, board document A,
Even when the amount of light is reduced due to stains on the H, a proper copy image can be obtained without making the image unclear.

In this embodiment, when copying the image written on the board A onto the transfer material, the image is formed on the field lens 12, and the copying is performed using the formed image. It may be configured such that the written image information is directly imaged and exposed on the image carrier, that is, as shown in FIG.
The image written on the image is illuminated by a lamp 34, and the light image thereof is reflected by mirrors 35, 36 and formed onto a photoreceptor drum 38 by an imaging lens 37. At this time, the amount of exposure from the board 31 is detected by the detection means 40 provided in the image forming means 39, and the amount of light from the lamp 34 or the amount of light from the developing device provided near the photoreceptor drum 38 is detected as in the case of the first embodiment. The developing bias voltage applied to the device 25 is controlled to a preset value.

In addition, in the first embodiment, the light amount detector S is arranged near the lens 1O, but it is not limited to the vicinity of the lens 1O as long as it is at a position where the amount of exposure from the board document B and the copy document can be detected. do not have.

Further, in the first embodiment, the light intensity of the board illumination lamp 4 or document illumination lamp L or the developing bias voltage applied to the developing device 25 is controlled based on the signal obtained by the detection means S. However, in each mode, both the light intensity of the lamp and the developing bias voltage may be controlled. In this case, the density of the copied image can be finely adjusted, making it possible to obtain a copied image of even higher quality. becomes possible.

(Effects of the Invention) As described above, in the present invention, the detection means detects the ag! 11. detecting the amount of exposure light from the original document, and controlling at least one of the amount of light or a developing bias voltage applied to a developing device provided near the image carrier based on a signal obtained by the detection means; According to
Since the density of the copied image can be set to a desired level, it is possible to obtain a proper copied image without fogging the image even for originals with a dark background such as newspaper. Furthermore, even when the exposure amount is reduced due to stains on the board, there is an effect that a proper copy image can be obtained without making the image unclear.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a copying apparatus according to an embodiment of the present invention, FIG. 2 is a side sectional view of the same embodiment, and FIG. 3 is a block diagram showing a control system for exposure amount or developing bias voltage. FIG. 4 is a schematic configuration diagram showing a copying apparatus according to another embodiment of the present invention. Explanation of symbols

Claims (1)

[Claims] Image formation in which either an image written on a writable board or an original image placed on a document table is selectively exposed onto an image carrier and an image is formed on a transfer material using an electrophotographic method. The copying apparatus includes a detection means for detecting the amount of exposure light from the board document or the original document, and detects the light amount or the amount of exposure light provided near the image carrier based on the signal obtained by the detection means. A copying apparatus characterized in that at least one of the developing bias voltages applied to the developing device is controlled.