JP2925348B2 - Copier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine in which a lens moves in a direction perpendicular to the direction of an optical axis, and more particularly to a device provided on a side of a lens for preventing light leakage.

[0002]

2. Description of the Related Art Conventionally, in an optical system using a lens of a copying machine or the like, a light-shielding member is provided on the side of the lens so that light passing through the side of the lens that has come off the lens does not reach the photosensitive member. ing. . In particular, in a variable-magnification copying apparatus, since the lens moves in accordance with the magnification, a space is easily created on the side of the lens. Have been.

[0003]

However, in the above-mentioned prior art, light passing through the side of the lens can be blocked in the vicinity of the lens even if the lens moves, but the entire light shielding member follows the movement of the lens. A gap is formed in the apparatus at the end of the light-shielding member opposite to the lens due to the movement with the lens. As a result, there is a problem that image light that is not image-formed enters the photosensitive member and adversely affects image exposure.

[0004]

According to the present invention, there is provided an image forming means comprising a lens for forming an image of a document on a photoreceptor and movable in a direction of an optical axis of the lens and in a direction perpendicular to the optical axis. And a lens hood that covers the top and sides of the imaging means so as not to block the movement of the imaging means and light incident on the lens toward the photoreceptor, and light leakage between the imaging means and the lens hood. And a light shielding member for preventing the light, the light shielding member is extendable and contractible, one end is fixed to the image forming means, and the other end is a free end. In this case, the lens hood is always in contact with the inner wall of the lens hood.

[0005]

FIG. 1 is a sectional view of a copying machine system to which the present invention can be applied. This copying machine system is roughly divided into three sections: an automatic document feeder section A, a copying machine body section B, and a sorter section C of a copy sheet post-processing apparatus.

Referring to FIG. 1, a process until a copy sheet on which a document image is reproduced is obtained will be briefly described.

When a document is set on a tray 101 of the automatic document feeder and a copy button is pressed, the document is automatically conveyed onto a document glass 102 and moved in the direction of an arrow while irradiating the document with an exposure device 103. Then, the entire surface of the document is scanned.

The light reflected by the exposure device is reflected by the second and third mirrors 104, passes through the zoom lens 1, is reflected again by the fourth mirror 105, and forms an image on the photosensitive drum 106.

Next, a method of forming an image on the photosensitive drum of light from the original surface in the plane direction and movement of the lens will be described with reference to FIG. FIG. 2 is a diagram showing lines of light that form an image on the photosensitive drum from the original surface. lm is the width of the original surface (A4 width: 297 mm in this case), l'm 'is the maximum width of the image forming surface that can be reproduced by this apparatus, and forms an image of the original having the lm width at the same magnification. It corresponds to the width of the surface. Copy magnification is 50%
The lens used is a zoom lens. In the coordinate system, the horizontal direction is x and the vertical direction is y as shown in the figure.

First, the equal magnification will be described. The lens moves to the position of point 0. This time 0 coincides with the image center line. The light of width lm irradiated by the exposure device is imaged on the photosensitive drum in the opposite direction as l'm 'due to the characteristics of the lens. In this embodiment, the document is configured to abut on the reference on the back side of the document glass.

Second, when trying to make a 200% copy, the lens moves from point 0 to point a. At this time, the light having a width of 1 m on the original surface should form an image with a width of l "m" on the photosensitive drum. However, since the width of the photosensitive drum is limited by the width of l'm ', The size of an original from which a 200% copy image can be actually obtained is ₁ m1. l
the width of the document m ₁ is the magnitude of l "m _1" on the photosensitive drum.

Third, in the case of 50% copy, the lens is at the point b.
Move up to. The light having a width of lm of the original is reduced to l "".
m ′ ″ ″.

Since the copy paper is used as a reference, the position of l ', l ", l""is unchanged regardless of the magnification of 100%, 200%, and 50% regardless of the copy paper used. Also moves only linearly between a and b.

However, when the original is placed on one side and the copy paper is fed on the basis of the center, the situation changes. As an example, assume that the original is A4 and the copy paper is B5. At this time B5
If there is a lens at the position where the same magnification image is formed on the copy paper, the lm light is imaged as p'q 'because the copy image is from the front of the copy paper, but the width of the photosensitive drum is limited. Therefore, it becomes p'm '. Similarly, for 200%, lm
Becomes p "q", and in the case of 50%, becomes p "'q"'. Up to now, the lens has only moved linearly between a and a. However, if the lens can be individually moved in the x direction and the y direction, the moving range of the lens is abcd, and the movable range of the lens is cebf. Expanding. Next, a light-shielding device corresponding to the enlarged movement range of the lens will be described.
FIG. 3 shows an embodiment of the present invention, and shows a plan view of a lens mount. The lens 1 is fitted to a lens moving shaft 3 whose both ends are supported by support plates 4a and 4b. The lens is moved in the x direction via the belt 6 by the stepping motor 5 attached to the support plate 4b, and moves for changing the magnification. The movement amount at that time is controlled by the number of steps from the photo interrupter 7. The above object is set on the lens stage 2. The lens stage itself moves in the y direction. The method of moving the lens stage is such that the stage can be moved in parallel with the stage moving shaft 8 via the bearing 9, and is moved by the stepping motor 10 via the belt 11. The moving amount at this time is also controlled by the number of steps of the photo interrupter. That is, in this apparatus, the lens is moved in accordance with an arbitrary magnification and a paper edge position by two motors, a zoom motor and a lens stage moving motor. The light blocking device for blocking light leaking from the lens side end includes first light blocking members 12 and 13 and second light blocking members 14 attached to the light amount correction plate of the lens, first bellows 15 provided on the near side in FIG. It is constituted by the second bellows 16. As shown in FIG. 4, the light-shielding plate 12 of the first light-shielding member is rotatably fixed to the light amount correction plate 30, and a light-shielding plate 13 is rotatably fixed to the tip of the light-shielding plate 12. The light shielding members 12 and 13 are extendable and contractible.
Torsion coil springs 22 and 23 are set at the respective rotation centers, and are set so as to generate a load in the direction of the arrow in FIG. The other end opposite to the light blocking members 12 and 13 fixed to the light amount correction plate of the lens as the image forming means is a free end, and this free end moves upon the image forming means and enters the lens and faces the photosensitive member. It is configured so as to abut on the inner surface A of the lens hood 20 covering the upper part and the side part of the imaging means so as not to block light, and to completely block light other than light passing through the lens.

As shown by the broken line in FIG. 3, the lens hood is located at a portion on the back side of a plane A perpendicular to the plane of FIG. 3 (the broken line in FIG. 3 because the optical apparatus is viewed from above). And a portion on the front side of a surface B perpendicular to the paper surface is bent so as to be parallel to a surface between the surfaces A and B. The lens hood is attached to the bottom surface of the optical device at the back portion of the surface A and the front portion of the surface B, and the lens between the surface A and the surface B parallel to the bottom surface of the optical device at the same magnification. 1 is covered. The lens stage 2 and the stage moving shaft 8 are hidden below the bottom of the optical device to which the lens hood is attached, and the lens 1 is located above the bottom of the optical device. The front side of the apparatus (the lower side in FIG. 3) is configured to block light with the first bellows 15, the second bellows 16, and the light shielding plate 14. Here, the first and second bellows 1
The ends of the lenses 5 and 16 are held by a lens stage and a stay attached to the lens base, and are arranged so as not to overlap in the vertical direction. The light shielding member 14 is also mounted such that the torsion coil spring 21 generates a load in the direction of the arrow (FIG. 3), and constantly presses the light shielding plate in the direction of the arrow. The light shielding plates 12, 13, 14 and the first and second bellows 15, 16 are formed of resin, and the light shielding plates and the bellows are further provided with a low friction elastic thin film 51 having good slidability. 52 (high-molecular polyethylene, taflite (trade name), etc.) are attached.

FIG. 5 is a diagram viewed from the direction of arrow L in FIG. This figure shows a state where the light shielding plate is fully spread. The low friction elastic thin film sheets 51, 5 described above
Reference numeral 2 is attached so as to be located above the light shielding plate. A configuration is provided so as to be slidable with the upper surface of the lens hood, which is a part of the light shielding device indicated by the broken line in FIG. C, so as not to generate a gap between the light shielding plate and the lens hood, and to further enhance the light shielding property. I am taking. In addition, this low friction elastic thin film sheet has antireflection on the surface side (photoconductor surface side) in FIG.

FIG. 6 is a perspective view schematically showing the light shielding device on the near side. The first bellows 15 and the second bellows 16 are fixed by thermal caulking between a stay 61 arranged on the lens stage side and a stay 62 arranged on the lens stage side. The light is shielded by extending or contracting in accordance with the movement of the lens stage in the y direction. Here, the bellows are made of PP (polypropylene) resin having a thickness of 1 mm, and have rigidity so as to fit in a predetermined position.
Further, a low friction elastic thin film sheet 53 is attached to the first bellows so as to be higher than the bellows as in the case of the light-shielding plate, and a gap with the lens hood is eliminated to improve the light-shielding performance.

Next, the movement of the light shielding plate when the lens moves to 200% will be described with reference to FIG. At this time, the lens moves to the point C in FIG. As described above, the lens and the lens stage are moved to predetermined positions by independent stepping motors. At that time, the light shielding plates 12 and 13
Slides on the inner wall A of the lens hood and is bent. At this time, the light shielding plate is configured to be pushed and spread in the direction of the arrow by each of the torsion coil springs. Therefore, no gap is generated between the lens hood and the light shielding plate. On the near side, the light-shielding plate 14 slides on the C-plane of the bellows stay, and shields light beside the lens. Beyond that, light is shielded by bellows 15 and 16 attached to the lens base via stays.

FIG. 8 shows a model diagram when the lens is moved to 50% for the third time. The mechanism by which the lens moves is as described above. Light shielding plates 12 and 13 as the lens moves
As shown in the figure, the light shielding plate is spread by the spring of the torsion coil spring and slides on the inner wall A of the lens hood so that no gap is formed between the lens hood and the light shielding plate. The front side is from the sliding surface C of the bellows stay to the inner wall B of the lens hood.
And no gap is generated.

As described above, the maximum (200%) and minimum (50%)
%), And the movement of the light-shielding device at the same-magnification position is shown as a representative example. However, at the magnification in between, the above-mentioned light-shielding device always moves so as not to generate a gap with the lens hood. Since light leakage at the side can be completely prevented in the lens hood, a good copy image can be obtained.

[0021]

As described above, by not fixing one end of the light shielding member to an immovable stay or the like, unnecessary light other than passing through the lens in accordance with the movement of the lens even if the movement range of the lens becomes large. There is an effect that light can be shielded.

[Brief description of the drawings]

FIG. 1 is a sectional view of a copying apparatus to which the present invention can be applied.

FIG. 2 is a diagram illustrating an optical path from a document surface to an image forming surface.

FIG. 3 is a plan view of an imaging optical system at an equal magnification position according to an embodiment of the present invention.

FIG. 4 is a plan view of the light shielding device.

FIG. 5 is a front view of the light shielding device.

FIG. 6 is a detailed view of a bellows light shielding member shown in FIG. 3;

FIG. 7 is a plan view of the imaging optical system at a 200% position.

FIG. 8 is a plan view of the imaging optical system at a 50% position.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Zoom lens 2 Lens stage 12 Shield plate 13 Shield plate 14 Shield plate 15 Bellows member 16 Bellows member

Claims (1)

(57) [Claims] An image forming means includes a lens for forming an image of a document on a photoreceptor and movable in an optical axis direction of the lens and in a direction orthogonal to the optical axis. A copying apparatus comprising: a lens hood that covers an upper portion and a side portion of the imaging unit so as not to block light directed to the body; and a light-blocking member that prevents light from leaking between the imaging unit and the lens hood. The light-shielding member is extendable and retractable, and one end is fixed to the image forming means, and the other end is a free end. This free end is always in contact with the inner wall of the lens hood even when the image forming means moves. Features a copying machine.