JPS63198041A - Anamorphic variable power copying machine - Google Patents

Abstract

PURPOSE:To easily execute copying by bringing an original image to variable power only in its one direction, by correcting a variation of a projection optical path length caused by varying an intersection angle, by moving one or plural mirrors in a projection optical system. CONSTITUTION:In a copying machine for executing a slit exposure onto a photosensitive body 2 by a scan of a projection optical system 4, at least one mirror 23 in the projection optical system is provided so that an angle can be adjusted, so that an intersection angle of a projection optical axis and the original surface or the exposure surface is variable, and a variation of a projection optical path length caused by varying the intersection angle is corrected by moving one or plural mirrors 24, 25 in the projection optical system 4. In such a way, at the time of executing the variable power by a ratio of a scan speed and a moving speed of the exposure surface of the photosensitive body 2, a special optical member or a new optical member is not required, and deterioration of the copy picture quality caused by a difference of a movement of the projected image and a movement of the exposure surface can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an analog magnification copying machine that can reproduce an original image by varying its magnification in only one direction.

(Prior Art) This type of copying machine is known from US Pat. No. 3,445,161 (Conventional Example 1) and Japanese Patent Publication No. 53-28087 (Conventional Example 2).

In Conventional Example 1, the image of a moving original is slit-exposed onto a moving photoreceptor, but the copy image formed on the photoreceptor is determined by the ratio of the moving speed of the original to the moving speed of the exposure surface of the photoreceptor. is enlarged or reduced in the direction of movement of the photoreceptor.

Conventional Example 2 performs anamorphic magnification using the same method as Conventional Example 1, but exposes the photoreceptor to slit light through a cylindrical lens, thereby eliminating the movement of the projected image and exposure that would otherwise occur when using the anamorphic magnification method. This eliminates the misalignment with the movement of the body and prevents blurring in the direction of movement of the copied image.

Furthermore, a method using a special lens that changes the projection magnification in only one direction has been proposed (Conventional Example 3).

(Problems to be Solved by the Invention) In Conventional Example 1, there is a misalignment between the movement of the projected image and the movement of the exposure surface, causing blur in the copied image, and the maximum range of magnification is limited to about 5%. Although the conventional example 2 eliminates the drawbacks of the conventional example 1, it is expensive because an extra long cylindrical lens must be provided. Although conventional example 3 does not require additional optical members, it is still expensive because it uses a special projection lens.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a copying machine that performs slit exposure on a photoreceptor by scanning a projection optical system. is provided so that the angle of intersection between the projection optical axis and the original surface or the exposure surface is variable, and one or more mirrors in the projection optical system are used to adjust the projection optical path length by changing the intersection angle. This feature is characterized by a curve that corrects the movement of the image.

(Function) When the original image is slit-exposed onto the photoreceptor by scanning with the projection optical system, if the moving speed of the exposure surface of the photoreceptor is equal to the moving speed of the projection optical system, a copy image of the same size will be produced in the direction of movement. If the moving speed is slower than that of the projection optical system, a reduced copy image will be obtained, and if it is faster than the moving speed, an enlarged copy image will be obtained. The copying magnification in the direction perpendicular to the moving direction corresponds to the projection magnification set by the projection optical system.

The intersection angle between the projection optical axis and the document surface or exposure surface is relative to the exposure range of the document image exposed within the slit width in slit exposure. By adjusting the angle of one or more mirrors of the projection optical system so that the ratio between the slit width and the exposure range matches the ratio of the scanning speed of the projection optical system and the moving speed of the exposure surface of the photoreceptor, a special The difference between the movement of the projected image and the movement of the exposure surface can be suppressed without using a new optical member or a new optical member, and blurring of the copied image due to the difference can be prevented.

The optical path length of the projection optical system changes by adjusting the angle of the mirror, but this optical path length change can be corrected by moving one or more mirrors of the projection optical system.

Note that the projection optical axis is tilted with respect to the original surface or exposure surface (and the focal plane is tilted from the original surface or exposure surface by that amount, causing a shift in focus. However, this shift is shallow and is due to the projection lens normally used in the projection optical system. It is well within the depth of focus range at normal magnifications, and there is no problem of deterioration in image quality due to out of focus.

Further, when the projection optical system performs a magnification change operation, if it is used alone, it becomes possible to perform analog magnification change in a direction perpendicular to the direction of movement of the exposure surface. If magnification is changed based on the ratio of the scanning speed and the moving speed of the exposure surface, magnification can be changed in two directions. When changing magnification in two directions, it is also possible to freely set the magnification for each direction.

(Embodiment) To explain the first embodiment of the present invention shown in FIGS. 1 and 2, as shown in FIG. A photosensitive drum 2 is provided, and an image of an original 27 placed on the original placing glass 3 on the upper surface of the machine body 1 is slit-exposed onto the photosensitive drum 2 by a projection optical system 4 under the original placing glass. ing.

Around the photoreceptor drum 2, there is a charger 5 for forming an electrostatic latent image by the slit exposure, a toner developing device 6 for developing the latent image, and a toner image visualized on the photoreceptor drum 2. A transfer charger 7 that transfers the toner onto a copy sheet, a cleaning device 8 that removes toner remaining on the photosensitive drum 2 after copying, and the like are provided.

An automatic paper feed section 9 is provided below the photosensitive drum 2 for feeding copy sheets one by one to the transfer section, and a manual paper feed section 10 is provided outside the machine body 1. A pair of registration rollers 11 are provided midway along a common paper feed path from each of the paper feed sections 9, 10 to the transfer section to determine the timing of paper feed to the transfer section. Further, a fixing device 13 for fixing the transferred copy sheet is provided in the middle of the paper discharge path from the transfer section to the paper discharge tray 12 outside the machine body 1.

The projection optical system 4 includes an illumination light source 22 and a first mirror 23 provided on a first moving table 21 forming a scanner, and a second and second mirror 23 provided on a second moving table 24 for correcting the optical path length during scanning. 3 mirrors 25, 26, a projection lens 28 that forms an image of the light from the document 27 that has passed through the first, second, and third mirrors 23, 25, and 26 onto the photoreceptor drum 2, and a projection optical path that passes through the projection lens 28. and a fourth mirror 29 that bends the photoreceptor drum 2 toward the photoreceptor drum 2.

The projection magnification of the projection lens 28 can be adjusted by adjusting its position in the optical axis direction, and at this time the fourth mirror is moved to correct the optical path length. In the slit exposure method, the projection magnification does not affect the scan direction, and only changes the magnification in the direction perpendicular to the scan direction. The magnification in the scanning direction is changed by changing the ratio between the scanning speed and the circumferential speed of the photosensitive drum 2. It is possible to perform magnification changes in both directions at the same time, or to perform analog magnification changes in only one of them.

These various magnification changing operations and copying operations are controlled by a microcomputer (hereinafter referred to as "microcomputer"), not shown, according to the operator's selections.

As shown in FIG. 1, the first mirror 23 on the first movable table 21 is pivoted by a shaft 31 to allow one angle adjustment, and the angle is adjusted by an eccentric cam 33 connected to a stepping motor 32. be. A spring 34 is attached to the first mirror 23.
The eccentric cam 33 is driven by the eccentric cam 33.

By adjusting the angle of the first mirror 23, the intersection angle θ between the projection optical axis X and the surface of the original 27 can be varied as shown in FIG. This eliminates the blurring of the copied image due to the difference between the moving speed and the moving speed of the projected image.

To explain this in detail, when changing the magnification in the scanning direction, the scanning speed of the first mirror 23 is set to ■.

, when the circumferential speed of the photoreceptor drum 2 is , the ratio of the thickness of the image exposed on the photoreceptor drum 2 to the size of the image on the original 27 in the scanning direction is V r /
It becomes a Vo relationship. Therefore, when vI)>vP, the exposed image is reduced, and when v8<V, the exposed image is enlarged.

However, during this exposure, a shift occurs between the movement of the exposure surface and the movement of the projected image, resulting in a decrease in image quality. For example, in the case of reduced copying, since V, > V, the image A on the original 27 is placed on the exposed surface of the photoreceptor drum 2 on the side of one edge 34a of the slit 34, as shown in FIG. From the position projected as,
While moving at a relative speed VD by the slit width l to the position A'' projected as the image a' on the edge 34b side of the slit 34, the image a on the exposure surface moves only VP/voxl and It only reaches the position a'' in front of the image a°.

Therefore, while the image A of the document 27 is projected within the slit width l, the projected image is displaced only on the photosensitive drum 2, and the image is blurred in the scanning direction. Ultimately, this is because the movement of the exposure surface is slower than the movement of the projected image.

Although not shown, ■. 〉■In the case of enlarged copying (2),
The movement of the exposure surface is faster than the movement of the projected image, and the moving image a'' of image a on the exposure surface will lead the original projected image a'' at position A by an amount D, and the scanning will also be performed by that amount. Blurred direction occurs.

On the other hand, if the angle of the first mirror 23 is adjusted as shown by the broken line in FIG. 1, and the intersection angle θ of the projection optical axis The exposure range of the image of the original 27 is lo shown in FIG. 4, and θ=9.
In the state indicated by the broken line in the figure, which is 0°, the exposure range increases slightly compared to the case where the exposure range remains at 2.

This increasing exposure range is 2"=□ sin θ, in other words, the image on the exposure surface is slit width l
During the movement, the original image moves by lo.

Therefore, if the relationship between V and V is Vo It, then the difference between the movement of the projected image and the movement of the exposure surface, and the resulting difference between the images a'' and a on the exposure surface.

The copy magnification in the scanning direction is set to V without any deviation.

/v.

Therefore, the stepping motor 32 is controlled by the microcomputer so that the projection optical axis X has an appropriate intersection angle θ with respect to the surface of the original 27 in accordance with the setting of VP/Vl.

At this time, the focal plane Y, which is perpendicular to the projection optical axis X, is tilted with respect to the surface of the original 27, resulting in a focus shift of a distance X. However, if the depth of focus of the projection lens 28 is within the range of normally used projection magnification, the image quality will not be affected and there will be no problem.

In addition, the first mirror 2 in the case of full-size copying is shown by a broken line in FIG.
For position 3, θ without changing the scan start position
In order to obtain <90@, it is necessary to move the first mirror 23 to the solid line position. Therefore, the projection optical path length becomes longer by ΔL. This ΔL is expressed as follows, where L is the optical path length from the first mirror 23 to the original in the case of full-size copying.

In order to correct this ΔL, in accordance with the position adjustment of the first mirror 23 by the movement of the first moving table 21, as shown by the broken line in FIG. 25 and 26, and these controls are also performed by a microcomputer.

Adjusting the angle and position of the first mirror 23 changes the relationship between the slit exposure position of the original 27 and the illumination direction regulated by the reflective shade 30 of the illumination light source 22, impairing the illumination effect.

In order to deal with this, in this embodiment, another eccentric cam 35 is connected to the stepping motor 32, and the passive piece 30a of the reflective shade 30 is driven by the eccentric cam 35 by the biasing force of the spring 36. 1st by 32
At the same time as adjusting the angle of the mirror 23, the direction of the reflective shade 30 is changed with respect to the illumination light source 22. As a result, the slit exposure position on the document 27 and the illumination position by the illumination light source 22 match.

Of course, one of the mirrors 23, 25, 26, and 29 of the projection optical system 4 is used to change the intersection angle θ between the projection optical axis
This can be done freely by adjusting the angle or moving one or more of them.

Various other methods may be used to adjust the angles of the first mirror 23 and the reflective shade 30.

In the above case, we have described how to reduce the copy size in the scanning direction. However, in the case of enlarged copying, the intersection angle of the projection optical axis
By setting the intersection angle with the exposure surface to θ<90@, the completely opposite relationship to the above can be achieved.

(Effects of the Invention) Since the present invention has the above-described structure and operation, special optical members or new optical members are not required to change the magnification depending on the ratio of the scanning speed and the moving speed of the exposure surface of the photoreceptor. A variable magnification copying machine capable of preventing deterioration in copy image quality due to the difference between the movement of the projected image and the movement of the exposure surface can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a side view showing a part of the document side of the projection optical system in an analog copier showing an embodiment of the present invention, FIG. 2 is a side view showing the internal structure of the entire analog copier, and FIG. 3 is a projection A state explanatory diagram when there is a difference between the movement of the image and the movement of the exposure surface,
FIG. 4 is an explanatory diagram showing the relationship between the scan width and the projection range of the original image when the intersection angle between the projection optical axis and the original surface is changed.

Claims (1)

[Claims] (1) In a copying machine that performs slit exposure on a photoconductor by scanning a projection optical system, at least one mirror in the projection optical system is configured to have a variable intersection angle between the projection optical axis and the document surface or exposure surface. An analog magnification variable copying machine, characterized in that the angle is adjustable, and a change in the projection optical path length caused by changing the crossing angle is corrected by moving one or more mirrors in the projection optical system.