GB2097945A - Variable magnification photocopier - Google Patents

Abstract

A variable magnification line-by- line photocopier employs a moving original in the form of a microfilm 11, a fixed focal length lens 14, fixed mirrors 15 and 18, movable mirrors 16 and 17 and photoconductive drum 19, mirrors 16 and 17 being movable simultaneously in a direction at right angles to the optical axis of the lens to change the length of the optical path (necessitated by movement of the lens along its optical axis to change the magnification). Lens 14 may be replaced by a lens 14' of different fixed focal length. <IMAGE>

Description

SPECIFICATION Copying machine capable of continuously varying magnification The present invention is directed to a copying machine and more specifically to a copying machine utilizing a fixed focus projecting lens in a continuously variable magnification system.

Such a copying machine has a light source from which the light is directed through a condenser lens to an original microfilm copy. The light passed through the original microfilm copy then passes through a projecting lens which is freely movable up and down and then is reflected in sequence from four mirrors onto the surface of a photosensitive drum. The photosensitive drum has been charged before an optical image is formed thereon. As the drum is rotated an exposure process and a development process are successively carried out and a toner image is formed on the drum. The toner image is transferred onto a belt carried sheet which is conveyed along a path indicated by the dot-dash chain line. After being heated and fixed in the unit, the sheet is delivered into a discharge tray thereby completing the copying operation.

Microfilm copying machines for enlarging and copying a picture recorded on a microfilm are old and well known in the art. Most microfilm copying machines are so designed that a copying magnification is selected since the size of the picture recorded on a microfilm is considerably different from the size of the desired copy. In conventional copying machines, different lenses are provided for different magnifications and each lens specifically provided for a selected magnification is set at a predetermined position in the optical system to perform the copying operation Therefore, as the number of desirable magnifications is increased the number of lenses to be prepared in advance must be increased accordingly. This substantially increases the manufacturing cost of the copying device.

Even if a copying device has,a large number of lenses, it is still impossible to fine tune or precisely change the set magnification and, accordingly, it is impossible in practice to achieve an enlarged picture of a precise desired size.

In order to overcome the aforementioned difficulties it has been proposed to vary the lens back focus in order to continuously vary the copying magnification.

It is also known in the art to use a zoom lens in a copying machine to vary magnification.

However, such copying machines suffer from many disadvantages. The zoom lens is very expensive and the movement of the lens groups is intricate and rather troublesome since the movement must be carried out with precision.

In use where a variable magnification system is employed, the operator selects a copying magnification for the copying machine. A central processing unit or microcomputer provides instruction signals to move the projecting lens and the mirrors, which are movable, predetermined distances respectively, according to the copying magnification thus selected. According to the instruction signals a drive mechanism is operated to move the projecting lens and the movable mirrors so that the exposure process is carried out with the desired magnification. In the above-described copying machine the distance between the microfilm surface of the original microfilm copy and the surface of the projecting. lens must be adjusted precisely to the order of several microns whenever the copying magnification is changed.A suitable driving arrangement for the lens, in order to achieve a very precise magnification, is not available for use with a known copying machine which is used to copy microfilms.

The object of the present invention is to provide a new and improved copying machine which is relatively simple in construction since a fixed focus projecting lens is employed in a system for continuously varying the magnification.

According to the present invention there is provided a copying machine comprising image projecting means including at least one projecting lens having a fixed focus and a magnification varying drive means for moving said projecting lens along the optical axis thereof, a parallel reflection optical system for reflecting an incident light beam from said image producing means in parallel opposite directions along a path having a predetermined length and optical path length adjusting means including drive means for moving said parallel reflection optical system parallel to the direction of said incident light beam to continuously vary magnification.

The invention will now be described in the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings in which; Figure 1 is a schematic diagram of the optical system for a copying machine constructed in accordance with the present invention.

Figure 2 is a sectional view of a projecting lens back focus controlling device of the machine; Figure 3 is a perspective view of the driving and driven cam members which are employed in the device shown in Figure 2.

Figure 4 is a schematic view of the cam elements illustrating the control principle of the device.

Figure 5 is a perspective view of an alternative device for moving the fixed focus projecting lens, Figure 6 is a perspective view showing the mechanism for alternately locating different projecting lenses in the optical system, and Figure 7 is a perspective view of a mechanism for adjusting the optical path length as illustrated in Figure 1.

Figure 1 shows a microfilm copying machine in essentials. The machine has a light source 10 which directs a light beam through a condenser lens 12 and through an original microfilm copy 11. An image of this is produced and projected through a projecting lens 14 which is movable in the direction of the arrow 13, as will be described to adjust the back focus, that is in the direction of the optical axis of this lens. The image is reflected in sequence from four mirrors 1 5, 1 6, 1 7 and 1 8 two of which can be moved, and onto the surface of a photosensitive drum 1 9 which has been charged before an optical image is formed upon it.The drum is rotated and an exposure process followed by a developing process is carried out in succession and a toner image is formed on the drum 1 9. A sheet to which the image is to be transferred travels on a belt along a path indicated by chain dot lines, at 41. This sheet comes into contact with the drum 1 9 and the image is transferred to it. The sheet is afterwards heated and fixed in a unit 42 and is delivered to a discharge trav.

A back focus controlling device for the projecting lens 14 is shown in Figure 2 wherein the lens 14 is supported by means of a cylindrical lens support 1 4A which is arranged in an upright position below a conventional microfilm scanning stand (not shown). The lower end portion of the lens support 1 4A is fitted precisely into a supporting cylindrical stand 23 which is secured to a lens stand 21 by means of screws 22. A vertically elongated hole 23A is cut into the supporting cylindrical stand 23.

The head of a lens rotation stopping pin 20 which is secured to the side of the lens support 1 4A is loosely inserted into the vertically elongated hole 23A. The lens support 1 4A has a flange 1 4B located substantially at the middle level. A cylindrical cam 25 is mounted on the flange 1 4B by means of screws 24. A plurality of pins 26 are provided at equal intervals on the outer wall of the cylindrical cam 25 in such a manner that they extend horizontally therefrom. Each of the pins 26 has a groove 26A adjacent the end portion thereof and a tension coil spring 28 is connected between each groove 26A and a respective screw 27 which is secured into the lens stand 21 directly beneath each groove 26A.A second cylindrical cam 29 is rotatably supported on the support stand 23 directly below the cylindrical cam 25 in such a manner that the cam surface 25A of the cylindrical cam 25 abuts against the cam surface 29A of the cylindrical cam 29 as a result of the elastic force exerted by the coil springs 28. A circumferentially extending flange 29B protrudes from the outer side wall of the cylindrical cam 29 and is provided with a plurality of gear teeth 29C around the periphery thereof. The gear teeth 29C are engaged with a pinion gear 32 which is directly coupled to the rotary shaft of a stepping motor 31. The stepping motor 31 is coupled to a motor driving circuit 33 which is connected to a magnification setting unit 34.

After an original microfilm 11 has been placed upon its stand in alignment with a light source and the focusing lens in the manner shown in Figure 1 the magnification is selected by the operator in accordance with the arrangement shown in Figure 2. The magnification setting means 34 may be comprised of a multiple key input unit having a central microprocessor unit incorporated therein which calculates the amount of movement necessary for the lens 14 to move from a previous setting to a new setting in order to achieve the desired degree of magnification. The magnification setting unit 34 supplies a control signal representative of the desired amount of movement through the connector 35 to the motor drive circuit 33.In response to the control signal the pulse motor driving circuit 33 applies a pulse signal having a predetermined number of pulses through the connector 36 to the stepping motor 31. In response to the number of pulses in the pulse signal, the pulse motor 31 turns the pinion gear 32 thereby rotating the cylindrical cam 29 through a predetermined angle to a new setting where it is stopped.

As the cylindrical cam 29 is rotated in the direction of the arrow 37 as shown in Figure 3 the cylindrical cam 25 is forced to move vertically in the direction of the arrow 38 due to the location of the rotation stopping pin 20 in the hole 23A and the sliding engagement of the cam surface 25A on the cam surface 29A. At the same time the lens support 1 4A is moved with the cylindrical cam 25 in the same direction while sliding along the inner wall of the cylindrical support stand 23. Since the cylindrical cam 25 is biased toward the cylindrical cam 29 by the coil springs 28, the cylindrical cam 25 can precisely follow the cylindrical cam 29 regardless of the direction in which the cylindrical cam 29 is rotated. Thus, the angle of rotation of the cylindrical cam 29 can be finally adjusted and precisely set by the gear drive mechanism.Since the outer wall of the lens support 1 4A is precisely fitted within the inner wall of the cylindrical support stand 23 and the cam surfaces 25A and 29A are in contact with each other continuously through a predetermined range, the tilting of the lens support due to the movement of the lens 14 can be limited to an extremely small value.

As is apparent from the foregoing description, the end faces of the cams are utilized thereby allowing the lens support to be telescopically located within the cams and the back focus is adjusted according to the rotational angle of the cam driven by the motor 31. Thus, the device can be very compact in size.

While a stepping motor 31 has been disclosed as the drive means for the cylindrical cam 29 the stepping motor may be replaced by other driving means such as for instance a servo motor.

In the alternative arrangement shown in Figures 5 and 6 the projecting lens 1 4 is secured within a lens barrel 46 having external threads thereon. The lens barrel 46 is disposed in threaded engagement with internal threads on a collar 47 which is rotatably mounted in a support frame 48 as best seen in Figure 6. The collar 47 is provided with an integral gear 50 disposed in meshing engagement with a spur gear 52 which is driven by a micromotor 54 as best seen in Figure 5. In order to prevent rotation of the lens barrel 46, a groove 56 is formed in the lens barrel 46 and a stop member 58 is inserted into the groove 56.The stop member 58 is then secured in a stationary manner to the support frame 48 so that upon rotation of the collar 47 by means of the micromotor 54 the lens barrel 46 will be raised and lowered relative to the collar 47 depending upon the direction of rotation of the micromotor 54.

In addition to the projecting lens 14 another projecting lens 14' having a different focal length from that of the lens 14 is secured within a lens barrel 46' which is disposed in threaded engagement with a collar 47'. The collar is rotatably mounted in a support frame 48' identical to the support frame 48. The two support frames 48 and 48' are each secured at one end to a common drive chain 60 in spaced apart parallel relation to each other with the opposite ends of each support frame being guided upon a guide rail 62 by means of rollers 64 and 64', respectively. The drive chain 60 is entrained about a pair of spaced apart pulleys 66 and 68 one of which is driven by a micromotor 70 to shift the lens in opposite directions along the guide rail 62 depending upon the direction of rotation of the motor 70.

In operation of this form of the machine, a projecting lens 14 or 14' having the desired magnification is selected and the selected lens is moved into axial alignment with the light source 10 condenser lens 1 2 and microfilm 11 by operating the micromotor 70 in the proper direction.

The mirrors 1 6 and 1 7 are arranged at right angles relative to each other so that a projected light beam incident to the mirror 1 6 is reflected by the mirror 1 7 parallel to but in the opposite direction to the projecting light beam incident on the mirror 1 6. The mirrors 1 6 and 1 7 form an optical path length adjusting optical system 78 and are carried by a movable support member 80 which is best seen in Figure 7. The support member 80 is moved parallel to the direction of the projecting light beam incident to the mirror 1 6 so that the mirrors 1 6 and 17 may be moved from the position illustrated in solid lines in Figure 1 to the dotted line position.In the situation where a magnification M, is selected, the distance (S1) between the film 11 and the drum 19 is S1=f(1 +1/M,)+f(1 +M,) and in the case where a magnification M2 is employed, the distance (S2) between the film 11 and the drum 19 is S2=f(1 +1/M2)+f(1 +M2). Therefore, the amount of movement (L) of the mirrors is:

The optical path length adjusting optical system 78 is moved by the system shown in Figure 7. A pair of spaced apart parallel bores 82 and 84 are formed in the support member 80. The bore 82 is provided with internal threads which cooperate with an externally threaded drive rod 86 which is rotated by means of an electric motor 88 through a drive belt 90. The bore 84 is smooth and cooperates with a smooth guide rail 92 which extends therethrough.Upon rotation of the rod 86 in one direction the optical system 78 will be moved from the solid line position to the dotted line position shown in Figure 1 and upon rotation of the threaded rod 86 in the opposite direction the optical system 78 will be moved from the dotted line position to the solid line position.

While the selected projecting lens 14 or 14' is moved to the desired predetermined position along the axis of the projecting light beam by means of the motor 31 or micromotor 54, the micromotor 88 is operated to move the optical path length adjusting optical system 78 to the desired position to obtain a predetermined optical path length. While the copying machine thus described is simple in construction the magnification can be continuously varied and the magnification variation range can be changed into a wider magnification variation range when required. Therefore, copies of a predetermined size can be obtained from various microfilms of different sizes thereby facilitating the maintenance and control of copies and copying sheets.

Claims (11)

Claims

1. A copying machine comprising image projecting means including at least one projecting lens having a fixed focus and a magnification varying drive means for moving said projecting lens along the optical axis thereof, a parallel reflecting optical system for reflecting an incident light beam from said image producing means in parallel opposite directions along a path having a predetermined length and optical path length adjusting means including drive means for moving said parallel reflection optical system parallel to the direction of said incident light beam to continuously vary magnification.

2. A copying machine as claimed in Claim 1, wherein said image producing means is comprised of a light source, a condenser lens, a microfilm station and said projecting lens disposed in operative coaxial alignment with each other.

3. A copying machine as claimed in claim 1 or claim 2 wherein the projecting lens has a first cylindrical cam having a cam face formed on at least one end thereof, a second cylindrical cam having a cam face on one end thereof slidably disposed in contact with said first cam face over a predetermined range, the lens being secured to said second cylindrical cam, stop means operatively engageable with said lens to prevent rotation while allowing reciprocation of said lens means along the optical axis thereof and drive means for rotating said first cylindrical cam relative to said second cylindrical cam.

4. A copying machine as claimed in claim 3 including spring means normally biasing said second cylindrical cam into engagement with said first cylindrical cam.

5. A copying machine as claimed in claim 3 or claim 4 wherein said drive means is comprised of a stepping motor and electronic control means for controlling said stepping motor.

6. A copying machine as claimed in Claim 1, wherein the projecting lens has an externally threaded lens barrel supporting said projecting lens therein, an internally threaded collar means disposed in threaded engagement with said lens barrel, drive means for rotating said collar means and stop means engaging said lens barrel to prevent rotation of said lens barrel so that upon rotation of said collar means, said projecting lens will be moved axially along the optical axis thereof.

7. A copying machine as claimed in any one of the preceding claims, further comprising a second projecting lens, first and second support means for supporting said projecting lenses with the optical axes thereof disposed in spaced apart parallel relation and drive means for alternately shifting said lenses into and out of alignment with said image producing means.

8. A copying machine as claimed in any one of the preceding claims wherein said parallel reflection optical system is comprised of movable support means and first and second reflecting mirrors carried by said support means at right angles to each other.

9. A copying machine as claimed in Claim 8, further comprising a third reflecting mirror disposed in alignment with the optical axis of said projecting lens for directing an incident light beam from said projecting lens to said first reflecting mirror, a photosensitive drum and a fourth reflecting mirror for directing the light beam reflected by said second reflecting mirror onto said photosensitive drum.

1 0. A copying machine substantially as hereinbefore described with reference to and as shown in Figures 1 to 4 and 7 of the accompanying drawings.

11. A copying machine substantially as hereinbefore described with reference to and as shown in Figures 5 and 6 of the accompanying drawings.