JPS60249130A - Optical system of copying machine - Google Patents

Abstract

PURPOSE:To shorten the time required for changin a magnification, to make a device small in size and inexpensive, an also to obtain easily sufficient accuracy by turning a rack frame by 180 degrees around the axis. CONSTITUTION:A ball 31 is engaged with an engaging hole 32 provided on a rack frame 25, by which the rack frame 25 is positioned, and an optical axis of a zoom lens 7 is matched accurately with a center axis 191 of an optical path 19. In case copying of unmagnification, namely, magnification 1 is executed, the zoom lens 7 makes a center point ''0'' conform with a middle point M, and in case magnified copying is executed, the rack frame 25 is set to a full line position, and the zoom lens 7 is moved to a position corresponding to the magnification by rotating a feed screw 22. Subsequently, in case reduced copying is executed, when the rack frame 25 is rotated around an axis 27, the zoom lens 7 occupies the position of the reduction side as shown by a chain line, and in accordance with necessity, a fine adjustment by a difference of the magnification may be executed. Especially, in case of executing the reduced copying of 1/m times after executing the magnified copying of (m) times (m>1), the rack frame 25 may be rotated by 180 degrees.

Description

[Detailed description of the invention]

Industrial Application Field The present invention is directed to projecting an original image using an optical system.1. The present invention relates to a copying machine that makes copies, and particularly relates to a copying machine that uses a zoom lens as an optical system lens. BACKGROUND TECHNOLOGY Conventionally, in a copying machine having a scanning optical system, a document 71 placed on a platen glass is irradiated with a power of 1 watt from a light source lamp, while the document and the light source lamp are moved relative to each other. The reflected light is guided onto a photoreceptor by an optical system consisting of a successive mirror and a lens, and an image is formed on the photoreceptor. In this case, in order to focus the image of the original on the photoreceptor surface, Vc5 is determined by the distance from the original to the lamp, the distance from the lens to the photoreceptor, and the total path length from the original to the photoreceptor surface, the focal length of the lens, and the copying magnification. Each defined length must be strictly maintained. Therefore, when changing the magnification such as enlargement or reduction using a fixed focus lens, both the mirror and lens must be moved to determine the total path length, document-lens distance, and lens-
The value was changed to an appropriate value depending on the distance between the sensor and the body and the magnification (vc), but this required a complicated mechanism. However, in order to change the length of the image, the manuscript table must also be moved, which is troublesome. By changing the focal length Z of the lens, the total path length F
- Since a constant C can be maintained, there is no need to move the mirror, original table, or physical body as described in Q above. However, the lamp position must be moved according to the magnification, and since the zoom lens has a large mass, special consideration must be taken to ensure smooth movement and positional accuracy. For example, to increase the positional accuracy by 7, high-precision screws such as ball screws β
However, even if a wire-based drive method is used, high tension is required to ensure precision.
C, the friction decreases by 7 again fT,...? B required many ball bearings, which resulted in a higher cost. Furthermore, since the mass is large, the moving time, that is, the time required to change the magnification becomes long. Problems to be Solved by the Invention Accordingly, the present invention provides an optical system including 7 zoom lenses in which the zoom lens can be positioned with high precision using a relatively small and inexpensive device.

[2] The objective is to shorten the time required to move the lens. Means and Effects for Solving the Problems Therefore, in the present invention, seven midpoints of the optical path of the zoom lens element system are provided on a frame that is rotatable around an axis perpendicular to the optical path. The frame is mounted movably on one radius extending from the axis of the frame. According to the present invention, there is one line around the axis and line of the frame frame.
By rotating the lens by 80 degrees, for example, the lens moves from the enlargement side to the reduction side all at once, so the time required to change the magnification can be shortened. In addition, the length of drive guide members such as screws and wires that move the lens linearly along the optical path is equal to half of the total required movement distance of the lens, so the length of the part that requires precision 7 is short. Therefore, the device is small, inexpensive, and easy to install with sufficient precision. Ladies and gentlemen, please explain the present invention using the attached drawings. First, with reference to FIG. 3, an example of a copying machine equipped with the optical system of the present invention will be briefly explained. In FIG. 3, reference numeral 1 indicates a copying machine main body 2, which is stretched over the top surface of the main body 1, and a document 3 is placed on a platen glass 2. platen glass 2
An optical system 8 consisting of a light source lamp 4, a mirror 5.6, and a zoom lens 7 is disposed below, and an image of the document surface illuminated in a slit shape by the light source lamp 4 is transferred to a drum-shaped photoreceptor by the optical system 8. Projected onto the circumferential surface of 9. 19 is an optical system 80 source. The mirror 5.6 is fixed to the main body 1, so the total length of the optical path from the irradiation point 10 on the original 3 to the projection point 11 on the circumferential surface of the photoreceptor 90 is always constant.
By changing the focal length of the zoom lens 7 and moving it along the Z optical path, the copying magnification is changed. The original 3 moves from right to left in the figure, and in conjunction with this, the drum-shaped photoreceptor 9 rotates clockwise, and an electrostatic latent image of the original is formed on the circumferential surface of the photoreceptor 90. This electrostatic latent image is developed with toner in a developing device 12 and transferred onto a sheet of paper in a transfer device 13. 14 is a cleaner, 15 is a charger, and 16 is a fixing device. The paper is transferred from the paper feed tray 17 through the transfer device 13 and the fixing device 16 to the paper discharge tray 18. FIG. 1 is an enlarged view 17 showing a cross section of the zoom lens 7 disposed in the optical system 8 and its mounting device as described above. The zoom lens 7 is designed to continuously change the focal length by moving a portion of the lens system back and forth along the optical axis, and is provided with a zoom ring operating motor 20 for this purpose. This zoom lens 7 is screwed onto a feed screw 22 by a nut 21, and when the feed screw 22 is rotated by a feed screw drive motor n, the entire zoom lens 7 moves back and forth along the feed screw 22, that is. It is designed to move left and right in the figure. Both ends of the feed screw 220 are pivotally supported by the frame frame 5 via 24 bearings. A pivot 26 is provided protruding from the frame 25, and this pivot 26
The frame frame 5 is pivotally supported on the copying machine main body 1 via a hinge. The axis 27 of the pivot 26 is the central axis (original axis) of the optical path 19
19. The central axis 19. is perpendicular to the center point M of the optical path 19, which bisects the entire path from the irradiation point 10 to the projection point 1 in FIG. It intersects with The end of the pivot 26 is connected to the frame drive motor name,
The frame 2!5 is connected to the motor 28vc, as shown by the chain line in the figure, and has an engaging part consisting of a spring 30 and a ball 31 so as to be able to rotate by 180' around the axis 27. By engaging the engagement holes 32 and 2 balls 31 provided in the zoom lens 7, the frame frame B is positioned.
0 optical axis is the central axis 19. of the optical path 19. It is designed to match precisely. Since the zoom lens 7 in this embodiment is mounted as described above, when copying is to be performed at the same magnification, that is, the magnification is +17), the center point of the zoom lens 7 is 0, and the midpoint MVc does not match, and the enlarged copy cannot be made. When performing VC, set the frame 25 to the solid line position in Figure 1 and rotate the feed screw 22.
Move it to the position corresponding to the magnification (the left side of the diagram is the document side and the right side is the photoconductor side). Next, make a reduced copy at line 5 o'clock V
When the frame 2!5 is rotated around the fire axis 27, the zoom lens 7 occupies the position on the reduction side, as shown by the chain line in the second figure, and the zoom lens 7 occupies the position on the reduction side, and if necessary, the zoom lens 7 Just perform adjustment 2. In particular, if you are making an enlarged copy of m times ('', > 1) and a reduced copy of 2 times more, simply use a frame with a frame of 25 rs.
Just rotate o'. FIG. 2 schematically shows the optical system 8, where A is an object point corresponding to the irradiation point 10, B is an image point corresponding to the projection point 11, and the optical path length between A and E is shown. L1 is constant as described above. It is sufficient if the focal length of the lens is "fow-" when the Qenz intermediate point M device is used for the same-magnification copying.When making an enlarged copy with a magnification of m (m>1), the lens position moves by QVc, but the - lens's focal length is As can be easily derived from the basic equation, the following equation holds true regarding lens position 0 at this time: -Li1f...(1) O0-77 Lon-(+l)f...(2 ) i-mu f ... (3) m f is the required focal length when the lens is at the 0 point, f-υ7
・-(4). As can be seen from these formulas, when the magnification m is specified, the lens position O and focal length f are uniquely determined, so
Feed screw movement motor and zoom ring operation motor addition and 7al
It is sufficient to operate by an amount corresponding to the above formula according to 'mVC. Furthermore, as can be seen from equation (4), the V lens focal length f required to perform reduction copying of /l@rate -' is (9+1)L, and the focal length f at magnification m is etc. (2. It is the same as in the case of further reading. Therefore, when making a reduced copy 7 of the magnification m'Cm'< 1), find the reciprocal of m' 7, and use this as m for the feed screw motor and the zoom ring operation motor 20. Activated by J5,
The frame 25 may be rotated 180 degrees toward the object point B, that is, toward the photoreceptor 9. Although one embodiment of the present invention has been described and explained above, the present invention is not limited to this embodiment, and many modifications are possible within the scope of the present invention. t7 may be moved by a wire device instead of the screw 22. The optical system of the present invention is not limited to a scanning optical system for moving an original, but also for a scanning optical system for a fixed original.
Of course, it is also possible to use the optical system of the present invention as a full-surface exposure type optical system. Effects of the Invention As described above, in the present invention, two midpoints of the optical path of the zoom lens 2 optical system are provided on a frame that is rotatable around an axis perpendicular to the optical path, and extend from the axis of the frame. Since it is mounted so that it can be moved freely in one radius, the time required to move the lens when changing the copying magnification is shortened, and the length of linear movement of the lens is shortened. Not only can high accuracy be obtained, but the device can also be made smaller and cheaper.

[Brief explanation of the drawing]

Fig. 1 is a side view of an embodiment 2 of the zoom lens mounting device according to the present invention, showing a cross section of the control section, Fig. 2 is an explanatory diagram of the optical system of the present invention, and Fig. 3 is a side cross section showing the entire copying machine. It is a diagram. ■... Copying machine body, 3... Document, 7... Zoom lens, 8... Optical system, 19... Optical path, 5... Frame, 27... Axis line. Agent: Patent attorney Nozomi Ehara, 2 people

Claims (1)

[Claims] In a copying machine that projects and copies an original image using an optical system having a zoom lens, the frame is rotatable around an axis that passes through the middle point of an optical path between the zoom lens and the optical system and is perpendicular to the optical path. An optical system for a copying machine, characterized in that the frame is mounted movably on one radius extending from the axis of the frame.