JPS6043639A - Optical system for dichroic copying device - Google Patents

Abstract

PURPOSE:To set an enlargement and a reduction rate large without increasing the size of a device, and also to reduce the scattering and falling of a developer by making an exposure scan so that the 3rd mirror of an exposure scanning optical system approaches an image-forming lens. CONSTITUTION:The 1st-the 3rd mirros 3-5 run from left to right to make an exposure scan. When an enlarged copy is taken, original scan distance is shorter than in life-size copying operation. Even when a lens 6 moves to a position 6' during enlargement copying operation, the current scan distance of the 3rd mirror 5 is short, so the 3rd mirror 5 and a lens 6' do not interfere with each other. Therefore, the enlargement rate is made larger than that of a conventional system which scans the 3rd mirror 5 away from the lens 6. Further, developing devices 21 and 35 can be arranged right upper photosensitive drums 11 and 12, so the reduction rate is also made larger, which is advantageous to a problem such as the falling and scattering of the developer.

Description

TECHNICAL FIELD The present invention relates to an optical system of a two-color copying apparatus that copies an original drawn in two colors, black and a chromatic color such as red, in those two colors.

BACKGROUND OF THE INVENTION In office documents such as administrative documents and research reports, sentences and drawings written in black are often underlined or framed in red to draw attention. If this could be copied in its original color, it would be convenient since there would be no need to color that part of the copy.

For this purpose, a \-7 mirror is placed behind the imaging lens of the original exposure scanning optical system to divide the reflected light beam from the original into two parts: a light beam transmitted by the half mirror and a reflected light beam. Each of the divided light beams is projected onto a different photoreceptor for image-forming exposure, and electrostatic latent particles corresponding to the black image area, red image area, etc. on the document are created on each photoreceptor through a predetermined process. A toner image is formed by forming an image, and each of the images is developed with black toner and red toner, and a toner image is formed on the photoreceptor so that the toner images on these two photoreceptors are transferred in the same positional relationship as on the original. A two-color copying apparatus is known in which a two-color copy is obtained by sequentially overlapping and transferring images onto transfer sheets that are conveyed in an overlapping manner.

A schematic configuration of this system of red and black two-color copying apparatus will be explained with reference to FIG. The optical system 100 of this copying apparatus includes a contact glass 1, an exposure lamp 2 that illuminates a document placed thereon, and a first mirror 3 that is integrated with the exposure lamp and performs exposure scanning at a predetermined speed. and second and third mirrors 4 that move in the same direction at half the speed in synchronization with the first mirror 3.
. The original is illuminated by an exposure lamp 2, and the reflected light beam is transmitted to a first mirror 6, a second mirror 4, and a third mirror 5.
, after passing through an imaging lens 6, it reaches a half mirror 7. The light beam is divided by the half mirror 7 into a reflected light beam and a transmitted light beam, and the reflected light beam passes through the fourth mirror 8 and the fifth mirror 9 and is projected onto the first solo drum 11'2 for image formation and exposure.

On the other hand, the half-mirror transmitted light beam is reflected by the sixth mirror 1o, and then projected onto the second photoreceptor drum 12+2 for image formation and exposure.

The first photoreceptor drum 11 on which the light beam reflected by the half mirror 7 is projected is made of a composite photoreceptor and is a red photoreceptor drum, and the second photoreceptor drum 12 on which the light transmitted from the half mirror 7 is projected is a black photoreceptor drum. It is a photoconductor and a tram. of\
A large number of red filters 15 are inserted into the optical path of the light transmitted through the -7 mirror 7. On each drum, electrostatic latent images corresponding to the red and black image areas on the document are formed through a predetermined process in the units described below, and are developed with toner of the respective colors to produce red images. and a black toner image is formed.

A primary charging device 17 and a secondary charging device 1 are provided around the first photosensitive drum 11 as a unit for forming a red toner image.
8. Exposure position 19A1 Eraser 20, Red developing device 2
1 is provided.

Further, around the second photoreceptor drum 12, a charging device 33 and an exposure 0 position 1 are installed as a unit for forming a black toner image.
9B1 green LED eraser 64, black developing device 1f3
5 are provided.

The red and black toner images formed on the photoreceptor drums 11, '12-, and L are sequentially transferred to the photoreceptor drums 11, 12-, and L because the transfer paper fed from the paper feed section 200 is not conveyed by the conveyor bell l-400. 11.12, and each toner image is sequentially transferred to the transfer paper by the transfer chargers 28' and 58 provided opposite the respective photoreceptor drums 11.12 at that position.
- is transferred to the original image while maintaining the same relationship as the original. After the transfer, the transfer paper is fixed by a fixing device 700 and discharged outside the machine.

Now, in order for the red and black toner image to be transferred to the transfer paper while maintaining the same relative position as the original image, as shown in FIG. The distance is tl, and the transfer position 28 of the first photosensitive drum 11 is
The distance from t to the transfer position 38 of the second photoreceptor drum 12 is t.
2. When the creepage distance from the exposure position 19A to the transfer position 28 of the first photosensitive drum 11 is t3, it is necessary to satisfy the following condition: AI=A2 +A3 (1).

Incidentally, variable magnification has recently become essential for copying machines, and the variable magnification ratio has gradually become available over a wider range. When changing the magnification with the aperture system having the configuration shown in Figure 2, if the magnification ratio is nl and the focal length of the imaging lens is f, then the optical path length in front of the lens (on the object side) is a lens. If the optical path length at the rear (image side) is b, then a2(1+-)f ・Concave ・(2) b = (1+m) f... Lens 6 and the second and second lenses are arranged to form the curve (6). It is well known that it is only necessary to displace the six mirrors 4°5.

That is, when enlarging, the lens 6 is moved to the right in the direction indicated by the broken line 6', and the second and third mirrors 4 and 5 are moved to the position 41.51, and when reducing, the lens 6 is moved to the left. 6″
The second and third mirrors may be moved to the right as in the case of magnification. The positions of the lenses indicated by 6' and 6'' in FIG. 1 are the positions at a magnification of 1,154 times and a reduction ratio of 0,647, respectively.

Further, the positions of the lens 6 and the first, second, and third mirrors 3, 4.5 shown by solid lines in FIG. 1 are scanning start positions (q positions), and the positions shown by chain lines indicate exposure scanning end positions. [2+1 also,
In this example, the sixth mirror 5 travels in a direction away from a position close to lens B to perform exposure scanning. The exposure start position is the position shown by the solid line, but in order to stabilize the normal travel, the first mirror 6 performs an approach run of 20 to 33 m1. Therefore, the scanning start position of the second and third mirrors 4 and 5 is located 10 to 15 mm further to the left from the position indicated by the solid line.

From the above, the maximum magnification is achieved under the condition that the lens 6 does not interfere with the sixth mirror 5 at the scanning start position.

The maximum reduction ratio is achieved under the condition that the lens 6 does not interfere with the half mirror 7.

In addition, in order to properly image the light beam divided by the half mirror 7 onto the photoreceptor drum 11.12, the optical path length from the half mirror 7 to the mirror 1° must be set to t4, and from the mirror 1o to the mirror 1o, as shown in FIG. Second photoreceptor drum 12'' second imaging point 19B
Z the length up to! The length from half mirror 7 to mirror 8 is 46, the length from mirror 8 to mirror 9 is 4, and the imaging point of first photoreceptor drum 114 from mirror 9 is 19.
If the length up to A is t8, '4 + Ls' = A6 + 1γ + t8 ...... (
4) must be satisfied.

From the above equations (1) and (4), the photosensitive drums 11 and 12
are arranged quite close to each other, and because of the mirror 8, the developing device 35 is arranged so that the developing roller 65, = 1, of the photoreceptor drum 12 is pushed to the side of the photoreceptor drum 12, and as a result, , problems such as developer falling and scattering occur. In addition, as a result of the arrangement in which the developing device 65 is pushed to one side of the photoreceptor drum 12, there are eight units in which the distance between the half mirror 7 and the mirror 10 is approximately equal to that of the half mirror. 7 had to be placed close to lens A, and therefore had the disadvantage that it was not possible to obtain a sufficiently large reduction ratio. According to my correspondence, the space occupied by the developing device became smaller, and the developer container could not be made larger. In addition, the conventional 114
Even if the focal length of the imaging lens is increased, the magnification ratio will be lower.
Although a large reduction ratio can be achieved, this inevitably increases the size of the entire device, which is not preferable.

In view of the above-mentioned drawbacks of the optical system of a two-color copying apparatus having a conventional configuration, the present invention has been made to increase the magnification and reduction without increasing the focal length of the lens and without increasing the size of the apparatus. It is an object of the present invention to provide an optical system for a two-color copying apparatus that can achieve a high ratio and can provide a developing device arrangement with less developer falling and toner scattering.

Configuration The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 4 shows an embodiment of the present invention. The same members as in the conventional example shown in FIG. 1 are given the same symbols.

Comparing this with the example of the conventional apparatus shown in FIG. 1, the structure of the exposed fiber 100 is the same, but the left and right arrangement is reversed. However, the first and second sensing drums 11.
12 and its surrounding process equipment arrangement, paper feeding device 20
The paper feeding direction from 0, the position of the fixing device 700, and the paper ejection direction are the same as those of the conventional apparatus shown in FIG. Therefore, the exposure scanning of the first, second, and sixth mirrors 3, 4.5 is performed by traveling from left to right. The positions of the mirrors 3, 4.5 indicated by solid lines in the figure are exposure start positions, the positions indicated by chain lines on the left are travel start positions, and the positions indicated by chain lines on the right are exposure end positions. In this example, the transmitted light beam divided by the half mirror 7 becomes the red image light beam, and the reflected focus becomes the black image light beam. Therefore, the red filter 15 is inserted into and out of the optical path of the reflected light beam.

In this case as well, it is necessary to satisfy the relationships of equations (1) to (4) above. In order to satisfy this relationship, the image positions 19A, 1'9B of the transmitted light beam and the reflected light beam divided by the two-half mirror 7 are formed on the photoreceptor drum 11.12 as in the conventional case.
is set within a range of one half on the opposite side of the opposing semicircular surfaces of the photosensitive drums 11 and 12.

First, considering the case of enlarged copying, the document scanning distance during enlargement is shorter than when it is at full size. For example, if you want to copy an A3 size document at the same size, the scanning distance will be the length of A3, but if you want to enlarge an A4 size document to A3 size by 1,414 times, you only need to scan the length of A4. That is clear.

Therefore, even if the lens 6 is at the 6' position during magnification, it will not interfere with the lens at the 6' position because the scanning distance of the fifth lens 5-5 is short. Therefore, compared to the conventional method in which the third mirror 5 scans in a direction away from the lens 6, a larger magnification can be obtained.

Next, considering the case of reduction, as shown in Fig. 4, by setting the imaging positions of both light beams divided by the half mirror 7 as described above, there is a space at the upper right of the photoreceptor drums 11 and 12. As a result, the developing device 21.35 can be placed without taking a large distance from the half mirror 7 to the mirror 10, and therefore the distance from the lens 6 to the half mirror 7 can be longer than before. I can do it.

Therefore, the reduction ratio can be made larger than before.

Further, since the position of the mirror 8 is changed from that of the conventional device, the 11'L position of the developing roller 55-1 of the developing unit 35 is located in the diagonal -L direction of the photosensitive drum 12, which prevents developer from scattering and Specific design H that is more advantageous than conventional models against falling
To give an example: Enlargement ratio Reduction ratio Conventional lens with f=230 1.154 0.647
In the present invention, f = 210 y 1.414 0.5, and both the magnification and reduction ratios were impressive with a short focal length lens.

Effects As described above, according to the present invention, it is possible to increase the magnification and reduction ratios without increasing the focal length of the lens or increasing the size of the device. Since it can be disposed obliquely above the drum, it is advantageous for problems such as developer falling and scattering.

Further, since the space occupied by the developing device can be increased, the capacity of the developer can be increased, and the life of the developer can be extended.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an example of a conventional device, Fig. 2 is a schematic diagram illustrating the positional constraints of the drum for aligning the transfer positions of red and black toner images onto transfer paper 2, and Fig. 3. The figure is a schematic diagram illustrating the constraint conditions of the optical system for correctly forming an image on the photosensitive drum, and FIG. 4 is a sectional view showing an embodiment of the present invention. 1... Original table 3... First mirror 4... Second
Mirror 5...Third mirror 6...Imaging lens 7...Half mirror (light beam splitting means) 8.9.10.
... Mirror 11 ... Photoreceptor drum for red 12 ... Photoreceptor drum for black 28. 32 ... Transfer charger agent Patent attorney Takehisa Ito

Claims (2)

[Claims] (1) An original placing table, a first mirror that scans the original placed on it at a constant speed, and second and sixth mirrors that move in synchronization with the first mirror halfway through the first mirror. A light beam splitter is installed behind the imaging lens of the exposure 0-scanning optical system to split the reflected light beam from the document placed on the document table and drawn with black and a second color, which is a chromatic color. The divided light beams are image-formed and exposed at predetermined projection positions on different photoreceptor drums, and each photoreceptor drum is subjected to a predetermined process to form a black image area and a second image on the original. forming electrostatic latent images corresponding to the color image portions, developing each electrostatic latent image with black toner and a second color toner to form a toner image;
The toner images on these two photoreceptor drums are transferred in the same positional relationship as on the original document, and are transferred to the transfer paper that is conveyed overlappingly on the photoreceptor drum in order to obtain a two-color copy. In the optical system for a two-color copying device, the third mirror performs exposure scanning from a side far from the imaging lens to a side approaching the imaging lens. system. (2) The predetermined projection position at which the reflected light beam and the transmitted light beam split by the light beam splitting means form images on each photoreceptor drum is located on the opposite side of the mutually opposing semicircular surfaces of the photoreceptor drum. The two-color copying device according to claim 1, wherein the two-color copying device is set on a semicircular surface that is farther away from the transfer paper contact position indicated by -1-. .