JPS6149652B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical device for an electrophotographic copying machine with variable copying magnification.

In conventional copying machines, the original and the copied image are
Normally, one-to-one copying is performed at the same size, but it is convenient for organizing documents if the copying magnification is varied so that originals of various sizes can be copied onto the same size copy paper. be.

To convert the copying magnification, let the optical path length from the document surface to the lens be a, the optical path length from the lens to the exposure surface be b, the focal length of the lens be f, and the desired magnification be n, then 1/a+1/b ] This is done by moving the lens and mirror to positions a and b that satisfy the equation 1/f b/a=n. Furthermore, in a slit exposure type copying machine, magnification conversion in the scanning direction must be performed by setting the ratio of the scanning speed of the document to the exposure speed to 1/n.

The conventional apparatus shown in FIGS. 1 to 4 will be explained below.

FIG. 1 shows an example of a magnification conversion optical system of a copying machine using a fixed slit exposure type copying machine. The original 1 to be copied is placed on the original platen glass 2, and the first mirror M1 scans the original from below in the right direction in the figure, and the reflected light of the original is scanned in the same direction at 1/2 the speed of the first mirror M1. The light is reflected by the second mirror M2, which moves to , and is imaged on the outer peripheral surface of the photosensitive drum 3 via the lens L and the third and fourth mirrors M3 and M4.

When the first magnification n ₁ is, for example, 1/1, the lens L and the third and fourth mirrors M3 and M4 are at the G and g positions, respectively, and in this case, 1/a ₁ +1/b ₁ = 1/f b ₁ /a ₁ =n ₁ (=1), that is, a ₁ =b ₁ =2f is satisfied. The scanning speed of the first mirror M1 is 1/n ₁ of the peripheral speed of the photosensitive drum 3.
(=1) times.

Next, in the case of the second magnification n ₁ (<n ₁ ), in order to satisfy the above formula, the lens L is a ₂ = (1+1/n ₂ )
At f, the third and fourth mirrors M3 and M4 move to the h position because the total optical path length (a ₂ +b ₂ ) increases to (1+n ₂ )(1+1/n ₂ )f.

At this time, in order to keep the image forming position on the photosensitive drum 3 constant in the circumferential direction, the lens L includes its optical axis and moves in a plane perpendicular to the screen in FIG. 1, and the third and fourth mirrors M3 - M4 must integrally move in parallel within a plane bisecting the angle formed by the incident light beam on the third mirror M3 and the reflected light beam from the fourth mirror M4. The ratio of the original scanning speed of the first mirror M1 to the circumferential speed of the photosensitive drum 3 is set to 1/n ₂ , but since it is undesirable to change the circumferential speed of the photosensitive drum 3 due to the image creation process, etc., the photosensitive drum 3
The peripheral speed of is kept the same as in the case of the first magnification n ₁ , and
Generally, the document scanning speed of the mirror M1 is set to n ₁ /n ₂ times.

In the case of the _third magnification n3, the lens L and the third and fourth mirrors M3 and M4 similarly move to the positions I and i, respectively, and the first mirror M1 moves at the circumferential speed of the photosensitive drum 3.
Scan the original at ₃ times the speed of n ₁ /n.

FIG. 2 is an expanded view of the optical path in FIG. 1, looking in the longitudinal direction of the slit. When performing magnification conversion copying, it is preferable to place the original in a fixed manner and copy it onto copy sheets of various sizes. On the other hand, copy paper is separated from the photosensitive drum regardless of its size.
When paper is fed, one edge parallel to the direction of paper movement is often kept at a constant position. In that case, one side edge 4a of the original 4 (this one side edge 4a is set in alignment with the same reference position both when making a full-size copy and when making a reduced copy) is placed at a fixed position on the photosensitive drum 3 regardless of the magnification. Since the images 5G to 5I are being formed, it is necessary to move the lens L not only in the direction of its optical axis but also in a direction perpendicular to the optical axis.

Now, when converting from the magnification n ₁ to the magnification n ₂ , if the lens L is moved by Δl ₁₂ in the direction perpendicular to the optical axis, the distance S ₁₂ from the fixed position of the photosensitive drum 3 to the edge of the image at that time is S ₁₂ = n ₁ · l ₁ − {n2 (l 1 + △l ₁₂ ) + △l ₁₂ } (1) (l ₁ is the distance between the optical axis position of the original and the reference edge when the magnification is n ₁ . ) becomes. Therefore, as mentioned above, one side edge 4 of the original 4
In order to image a at a certain position on the photosensitive drum 3,
It is sufficient to determine Δl ₁₂ so that S ₁₂ =0, and its value becomes Δl ₁₂ = (n ₁ - n ₂ ) l ₁ / (1+n ₂ ) (2) from equation (1).

As shown in FIGS. 3a to 3c, using the above method, it is possible to copy magnification-converted images 5G to 5I on copy sheets P ₁ to _{P 3} of different sizes fed from one side edge as a reference.

The above is a conventional optical device for a copying machine with a variable copying magnification. Generally, the copying magnification is divided into 1:1 copying where the original and the copied image are in a 1:1 relationship, and reduced copying where the copied image is smaller than the original. There are many things that are now possible.

By the way, in a type of copying machine that separates the side edge of the copy paper from the photosensitive drum using a separation belt, etc., in order to prevent the image from becoming distorted or smudged, a distance of several mm to 10 mm is placed on the reference side corresponding to the separation belt, etc. A non-image forming part is provided in which no image is formed in the width. Therefore, the document information corresponding to this part is not copied. This poses almost no practical problem in the case of full size copying, but becomes a problem in the case of reduced copying. That is, as shown in FIG. 4, the width of the non-image forming section 6 is W.
Then, in the case of full-size copying, the width of the original that is not copied by the non-image forming section 6 is also W, but in the case of reduced copying, if the magnification is n, the width of the original that is not copied by the non-image forming section 6 is W. /n(>W), and a wider portion will not be copied. This cannot be ignored in practice, as the smaller the magnification, the wider the area that will not be copied.

The present invention aims to solve the above problems.

An embodiment of the present invention will be described below with reference to FIGS. 5 and 6. FIG. 5 shows an example in which the present invention is applied to a magnification conversion optical system of a slit exposure type copying machine, and is a diagram showing the optical path developed and viewed in the longitudinal direction of the slit. As is clear from the comparison with the conventional example shown in FIG. 2, in the case of full-size copying, the image of the original 4 is formed at a fixed position 5G on the drum by the lens L at the G position, as in the conventional case. That is, the image of the one side edge 4a of the original 4 is formed so as to coincide with the photosensitive drum position corresponding to the one side edge of the copy paper on the side where no image is formed over the predetermined width W as described above. . However, in the case of reduction copying, the lens L is moved to the positions H' and I' so that the original 4 is imaged 5H' and 5I' in areas other than the non-image forming area (image forming area). be. The amount of movement of the lens in the direction perpendicular to the optical axis at this time is the one side edge 4a of the original 4 (this one side edge 4a).
The imaging position of the image (which is set in alignment with the same reference position both during full-scale copying and reduced-size copying) is set at the boundary between the non-image area and the image area. For example, when moving the lens L to the H' position, the amount of movement △l ₁₂ ' in the direction perpendicular to the optical axis is S ₁₂ =W in equation (1) above, where W is the width of the non-image area. Δl ₁₂ ′ = {(n ₁ −n ₂ )l ₁ −W}/(1+n ₂ ). In addition, when using standard copy paper, the magnification at this time is a ₂ ′, so that it can be copied on the copy paper.
This determines b ₂ ′, which is slightly smaller than that in the example in Figure 2. Incidentally, when moving the lens L to the I' position, the same procedure is used.

By the above method, images 5G, 5H', and 5I' can be copied onto copy sheets P1 to P3 as shown in FIGS. 6a to 6c.

In other words, the copy sheets P1, P2, and P3 are advanced with one side edge parallel to the direction of travel aligned with a fixed position, and a non-image forming area of a predetermined width W is provided on the one side edge side of the copy sheet. 6, and in this non-image forming section 6, the original 4 is separated from the photosensitive drum by a separation belt or the like as described above, and one side edge 4a of the original 4 is imaged as shown in FIG. Therefore, part of the image on the one side edge 4a of the original 4 is missing in the non-image forming area 6 when copying at the same size (FIG. 6a), but when copying in reduced size (FIGS. 6b and c) The image up to one side edge 4a of the original 4 is copied without being missing.

As described above, according to the present invention, the copy paper is advanced with one side edge parallel to the traveling direction aligned with a fixed position, and a non-image forming portion of a predetermined width is provided on the side of the one side edge of the copy paper. In an electrophotographic copying machine in which copy paper is separated from a movable photoreceptor by a separating member in a non-image forming section, when copying at the same size, a part of the document is missing and copied by the non-image forming section as before. During reduced copying, where the same amount of information is concentrated in a smaller area as during full-size copying, the above-mentioned omissions can be avoided, and the above-mentioned conventional problems can be solved, and this type of copying This is an effective and appropriate improvement for the machine.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of the magnification conversion optical system, Figure 2 is a developed view of the optical path of the magnification conversion optical system of a conventional copying machine, and Figure 3 is an explanatory diagram of the magnification conversion optical system.
Figures a, b, and c are explanatory diagrams of the relationship between copy paper and copy image,
Figures 4a, b, and c are the same diagrams when there is a non-image forming part, Figure 5 is a developed view of the optical path of the magnification conversion optical system of the copying machine of the present invention, and Figures 6a, b, and c are copies thereof. An explanatory diagram of the relationship between an image and copy paper. 1 is the original, L is the lens, M1, M2, M3, M
4 is the first, second, third, and fourth mirrors, 2 is the document table glass, 3 is the photosensitive drum, and 6 is the non-image area.

Claims (1)

[Scope of Claims] 1. The copy paper is advanced with one side edge parallel to the traveling direction aligned with a fixed position, and a non-image forming part of a predetermined width is provided on the side of the one side edge of the copy paper. An electrophotographic copying machine that separates a copy paper from a movable photoreceptor by a separation member in a non-image forming part, and is capable of copying by selecting at least one reduction ratio other than the same magnification, and also when copying at the same magnification. In an electrophotographic copying machine that aligns one side edge of the original to the same reference position even when making a reduced copy, when making a full-size copy, place the one side edge of the original on the one side edge of the copy paper. Position the lens so that the image is aligned with the corresponding photoreceptor position, and when making a reduction copy, place the above-mentioned one side edge of the document on the photoreceptor corresponding to the boundary between the non-image forming area and the image forming area of the copy paper. An optical device for an electrophotographic copying machine, characterized in that a lens is positioned so as to form an image in accordance with a body position.