JPS59162513A - Variable power optical device - Google Patents

Abstract

PURPOSE:To perform the focusing and variable power positioning of a zoom lens cooperatively by varying the focal length simultaneously and cooperatively with a shift in lens position by a rack and pinion mechanism. CONSTITUTION:The optical device is provided with the zoom lens 11 which varies in focal length by the rotation of a zoom ring 15 fitted around the outer circumference, a lens supporting member 21 which holds the zoom lens 11, a guide member which guides the member 21 in a constant direction, a driving pulley 32 which displaces the lens holding member 21 along the guide member as a driving means. Further, a rack 42 is held movable on the lens holding member 21 and a cam plate 45 has a rack guiding cam groove 45a provided at a specific angle to the guide member; and a gear part 15c provided to the outer circumference of the zoom ring 15 is engaged with the gear of the rack 42.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable power optical device using a zoom lens.

2. Description of the Related Art A variable magnification optical device conventionally used in an image forming apparatus such as a copying machine uses a fixed focus lens. However, in an optical system that uses a fixed focal length lens, when changing the magnification, the optical path length is inevitably longer than when the magnification is constant, so the lens position must be displaced and 7 to 2 of the mirrors that make up the optical system must be moved. It is necessary to correct the optical path length by displacing the

As an example of a copying machine with a fixed document table, there are two methods for correcting the optical path length: a method of displacing a movable optical mirror, and a method of displacing a fixed mirror. However, both of these methods require a precise and complicated mechanism because the amount of displacement of the mirror must correspond to the amount of lens movement. Furthermore, a space must be provided in anticipation of the amount of mirror movement predicted in advance, resulting in an increase in the size of the apparatus.

On the other hand, an optical system using a zoom lens has the advantage that the optical path length does not change with respect to each magnification because only the lens position is displaced in terms of space, which leads to miniaturization of the apparatus. Furthermore, as a result, the mirror position does not change at each magnification, so the mechanism itself is simplified.

However, with a zoom lens, the focal length must be set to match each zoom. That is, it is necessary to change the focal length as well as the lens magnification position to match the magnification.

The present invention has been made in view of the above, and it is an object of the present invention to provide a variable magnification optical device for a copying machine using a zoom lens that can simultaneously change the focal length of the lens while changing the lens position. purpose.

Next, the present invention will be explained based on examples and with reference to the drawings.

FIG. 1 is an example of an optical system for a copying machine using a zoom lens.

An illumination lamp is disposed below the end of the document table glass inside the case A (lower left in the figure).

A first mirror 3, a second mirror 3,
and a third mirta are arranged.

The illumination lamp λ and the first mirror 3 move together in the direction of the arrow x, and the second mirror and the third mirror move together as the first mirror! move in the same direction at 1/2 the speed of Furthermore, a zoom lens B, a fixed mirror 7, and a photosensitive drum are arranged in the case A, and each of these members (3, G, left,
7) is optical path I! l -1-J2-, e3, l! 4-
J5.

The zoom lens B is placed in the optical path 14, and the photosensitive drum g is placed at the end of the thread on the left side of the optical path. Each of these members <2.3°4, ! i
The original image is projected onto the photosensitive drum g by an optical system consisting of -, B, and W). In this optical system, zoom lens O indicates the lens position when copying at the same magnification, and lens position O
and Ob (indicated by broken lines) indicate the lens positions at the time of reduction and enlargement, respectively.

As can be seen from FIG. 1, only the lens position changes and the mirror position does not change with respect to each magnification change.

An embodiment of the zoom lens used in the present invention will be described with reference to FIGS. 2 and 3.

A zoom lens // basically has a fixed lens barrel /2 and two inner barrels /3a and /3b fitted inside the fixed lens barrel /2.

It consists of two collars /4a, /gb attached to the inner cylinders /3a, /3b, respectively, and a zoom ring /2 fitted to the outer surface of the outer cylinder /2. This zoom lens //
Since it is a transmission type, the inner cylinders /3a and /3b are arranged at symmetrical positions with respect to each magnification. Two cam grooves //a and //b which are inclined in the longitudinal direction and extend in the circumferential direction are completely symmetrically provided in the fixed lens barrel /2 at symmetrical positions with respect to the longitudinal center. Collars/gu a and /4b are cam grooves/'
formed to be able to move along /a and //b;
In addition, long grooves are drilled at symmetrical positions on the zoom ring.
3a and 15b, respectively. The collar/II'a is fixed to the inner tube/3a, and the collar/&b is fixed to the inner tube/3b. A gear portion/c is formed on a part of the outer periphery of the zoom ring/S.

By configuring as described above, the zoom ring/3
When the lens rotates on the fixed lens barrel /2, the collars /&a and /qb move along the aforementioned cam grooves a and //b, so that the positions of the inner barrels /3a and /3b are displaced. In this way, the lenses /, 2a and /, 2b supported by the fixed lens barrel /2 and the lenses /3a', /3 supported by the inner barrels /3a, /3b
a", /3b/, and 73 dl change to ensure focus during each zooming. In other words, the zoom ring/left rotation amount is rotated by a certain amount in response to the positional change of the entire lens. If this is done, the magnification and focus will be guaranteed at the same time during each zooming.The zoom lens shown in Figures 2 and 3 has cam grooves //a and //1) that extend from the beginning to the end. The camera is set to continuously focus up to the subject.

An embodiment of a variable magnification device for a copying machine using the zoom lens described in FIGS. 2 and 3 will be described with reference to FIGS.

Zoom lens // is a lens support member! / is fixed by two screws 2xa, 22b. Lens support member '2/ bears on the guide shaft 23, 7qa and 2gb
be smoothly guided through. The guide shaft 23 is supported at both ends by shaft support plates 27 and 27 fixed to the base and 2S. A roller 2g is attached to the other end of the lens support member 2/
are arranged so as to be slidable, and the weight of 0.2 g can smoothly roll on the base 2S.

A single wire 29 is fixed in a loop shape at both ends to the lower part of the lens support system 2/2/a.

One end of the loop-shaped wire 29 is fixedly wound around a drive pulley 32 via a guide pulley 3/ which rotates smoothly on a shaft 30 fixed to a shaft support plate, and the other end is fixedly wound around a drive pulley 32. is guided by a guide pulley 3 (left) that rotates smoothly on a shaft 3 fixed to a boom plate 33. Therefore, the rotation of the drive pulley 32 causes the lens support member 1/
moves along the guide shaft 23. As is clear from FIG. 9, the clockwise rotation of the drive pulley 3 causes the lens support member 2/ to move leftward in the figure, and the counterclockwise rotation of the pulley 32 causes the lens support member 2/ to move rightward in the figure. Driven. A sensor plate qB is disposed on the lens support member 2/, and a sensor plate qB is fixedly mounted on the left side of the base 2. The drive pulley 32 smoothly rotates on a shaft 3 fixed to a support stand 3 disposed on the left side of the base 2. A stepping motor (pulse motor) 3g is further fixed to the support stand 3B, and a form gear 3q is fixed to its output shaft. The worm gear 39 meshes with the worm wheel qO, and the wall wheel qO rotates integrally with the drive pulley 32 on the shaft 3. Therefore, the rotation of the motor 3g is transmitted to the drive pulley 32 via the worm gear 3q and the wall wheel 0.

As a result, the lens // is guided along the guide axis 23.

The lens support member 2/ has q guide logs/a, da/
b, g/c, and g/d are rotatably arranged so that rack q can be guided smoothly and without play.

A plate gg to which a pin 3 is fixed is fixed to one end (lower end in the figure) of the rack q. The pin q3 smoothly slides within the groove 4'5a of the cam plate g5 fixed to the left side of the base 2.

That is, when the lens support member 23 is guided along the guide shaft 23 by the rotation of the motor 3g, the pin 4t is guided along the guide shaft 23.
2 is guided along the groove 45a of the cam plate <3-. 9th
As is clear from the figure, since the guide shaft 23 and the cam plates g and 1 are arranged at a certain angle, the lens support member 2
The rack 11= is displaced in the vertical direction as / is moved in the left-right direction.

Now, as shown in FIGS. 2 and 3, a gear portion /SC is provided on a part of the left outer periphery of the zoom ring of the zoom lens //. As is clear from Fig. S, the gear part 15C is connected to the rack 11
It meshes with the second gear part 2a. Therefore, as the lens moves, the position of the rack 112 relative to the support member 2/ is continuously displaced, and as a result, the zoom ring 15 is rotated. In this way, when the lens position changes when changing the magnification, the zoom ring rotates by the necessary amount in conjunction with the movement, making it possible to always maintain optimal focus.

As described in FIGS. 2 and 3, the zoom lens of this embodiment has cam grooves //a,
/b is provided, so this cam groove //a, /'/k
) with a certain correlation between the guide shaft 23 and the cam plate &5.
By setting the angle with , it is possible to construct a continuous heating one-stage guest multiplier mechanism.

An example of actual magnification changing operation will be described with reference to FIG. Assuming that a predetermined magnification is selected from an operation unit or the like (not shown), the motor 3g first rotates to move the lens support member 2/ to the left in the figure. A sensor plate qB is disposed on the lens support member λ/, and the motor 3g continues to rotate until the sensor plate qB blocks the sensor 4t7 fixed to the base 25. When the sensor plate 3 blocks the sensor 3g, the rotation of the motor 3g stops, and the lens support member,
2/ moves further to the left due to inertia. After stopping the motor 3g for a certain period of time, the motor is then rotated in the opposite direction. At this time, the lens support member 2/ does not immediately move forward to the right. That is, the worm gear 39 and the worm wheel qO
The play between rank q2 and Gaitoko oil/a, 4
t/b, 41/c.

The play between ≠/d and the like is absorbed first. Once all the play has been absorbed, the lens support member 2/ starts moving to the right. From the time when sensor plate qB opens sensor j7 (this is taken as a reference point), motor 3g rotates by a predetermined number of necessary pulses. The required number of pulses here corresponds to the distance from the reference point to which the tube is moved to the position corresponding to the selected magnification.Next, when another magnification is selected, the above-mentioned A new lens position is determined by the same operation as .

In the embodiment shown in Fig. 7, when assembling the lens to the rack, the position of the bin q3 can be adjusted in the longitudinal direction of the rack together with the plate g+ so that the tooth tip of the rack q and the tooth tip of the zoom ring do not interfere with each other. It becomes. In other words, when assembling the lens, if the tip of the rack teeth and the tip of the zoom ring interfere, turning the zoom ring will disrupt the relationship between magnification and focus. I have to move it. At this time, if ping 3 and rank q2 are completely integrated, they cannot move, so it is necessary to temporarily release the connection between ping 3 and ranks q and 2.

This relationship will be explained in detail using FIG. As mentioned above, bin q3 is integrally connected to plate 11.9. Rack '12 is provided with an elongated hole q2b at the end, and the bin q
3 is the cam groove g5a of the cam plate 45 through this elongated hole q2b.
You will be guided sliding inside. There is still an elongated hole 4tga in plates i&4, and a screw g connects plate q4t and rack 4t through this elongated hole IJga. By loosening the screw g, the rack q2 can be moved in the left-right direction (in FIG. 4) within the range of the elongated holes g' and 2b.

In this way, when tooth tip interference occurs between the zoom ring/3 and the rack 112, only the rack 4t2 can be moved without rotating the zoom ring/3 to ensure gear meshing. Once the engagement between the rack q and the zoom ring/ri is guaranteed, tighten the screw ttg and the rack is ready! The zoom ring can be rotated in conjunction with the displacement of the zoom ring.

The elongated hole q2b of the rack 41.2 described above can also be used for other purposes. For example, when adjusting the optical assembly, in order to determine the center position of the lens, move the lens // to the lens support member 2.
/ When moving the lens parallel to / (moving the lens vertically in the drawing in Figure q), the boom ring must be rotated, so in this case as well, loosen the screw qg to adjust the amount of parallel lens movement. The rack can be moved by an amount commensurate with the amount. Needless to say, the screw gg is tightened when the center positioning of the lens is completed.

As explained above, according to the present invention, a simple rack
By employing a pinion mechanism, the focal length of the lens can be changed simultaneously with changing the lens position, that is, the focusing of the zoom lens and the positioning of the zoom lens can be performed in conjunction with each other.

In the embodiments of the present invention, a stepless variable magnification optical device has been described, but the present invention is not particularly limited to this, and the same mechanism can be adopted for a stepwise variable magnification optical device having multiple stages. At that time, it is only necessary to change the shape of the cam groove of the lens fixing chain portion and the cam groove of the cam plate 4tS through which the pin 3 is guided, if necessary.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the configuration of a variable magnification copying machine using a zoom lens, and FIG. 2 is a perspective view of the zoom lens used in the present invention.
FIG. 3 is a longitudinal sectional view of FIG. 2, and FIG. q is a side view of the present invention.
FIGS. S and 4 are partial details of FIG. 7. //...Zoom lens 15...Zoom ring/3c...Gear portion 2/...Lens holding member 23...Guide shaft, :l 4ta, , 24' b-a receiver 29...
Wire 32... Drive pulley 39... Worm gear qg... Worm wheel 4t, 2... Rack q left... Cam plate g left a... Cam groove @111 Fig. 2

Claims (1)

[Claims] A zoom lens configured to be able to change its focal length by rotating a zoom ring fitted on its outer periphery, a lens holding member that holds the zoom lens, and a guide that guides the lens holding member in a fixed direction. a member, a driving means for displacing the lens holding member along the guide member, a rack member movably held on the lens holding member, and a rack member disposed at a constant angle with the guide member. and a cam member having the rack member guiding cam groove, and further comprising a gear portion disposed on the outer periphery of the zoom ring and a gear portion disposed on the rack member. Double optical device.