US3873189A

US3873189A - Adjustable-position optical system

Info

Publication number: US3873189A
Application number: US371459A
Authority: US
Inventors: Raymond Whitaker; Bryan S Haslam
Original assignee: Rank Xerox Ltd
Current assignee: Xerox Ltd
Priority date: 1972-06-23
Filing date: 1973-06-19
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25

Abstract

A movable lens for plural magnification is provided with positive stops at predetermined points corresponding to the several magnifications. The lens carriage actuates switches to control solenoids which position the stops into and out of the path of the lens carriage.

Description

United States Patent [191 Whitaker et al.

ADJUSTABLE-POSITION OPTICAL SYSTEM Inventors: Raymond Whitaker, Leeds; Bryan S. Haslam, Harrogate, both of England Assignee: Rank Xerox Limited, London,

England Filed: June 19, 1973 Appl. No; 371,459

Foreign Application Priority Data June 23, 1972 United Kingdom 39651/72 U.S. Cl 350/255, 350/l87, 355/55,

355/58 Int. Cl. G02b 7/02 Field of Search 350/183, 187, 252, 245,

[ Mar. 25, 1975 [56] References Cited UNlTED STATES PATENTS I 3,594,068 7/1971 Kirstein 350/255 3,623,790 ll/l97l Buckstud 3,682,072 8/1972 Hess 3,701,309 l0/l972 Thiele. 3,782,808 l/l974 Hohl 350/30l Primary E.\'aml'ner-Ronald L. Wibert Assistant Examiner-Michael J. Tokar Attorney, Agent, or Firm-Robert J. Bird [57] ABSTRACT A movable lens for plural magnification is provided with positive stops at predetermined points corresponding to the several magnifications. The lens carriage actuates switches to control solenoids which position the stops into and out of the path of the lens carriage.

8 Claims, 8 Drawing Figures PATENTEDMARZSIHYS SHEET 1 [IF 7 Q NDW PATENTED MAR 2 5 I975 SHEET 2 :1

PATENTEU W 2 5 5 SHEET 7 BF 7.

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j 3% 3% H H v \IQMWQ V m L M JJMWQ L h E; mm H71 swm him 3% km Mm wmw Nxwi w wgm Ri w 5% Nmmim Qmw haw Tl Pwfi H mm n @R F mt Eu; h m L U elm; EQ wkg FAQ 30% 3% tax IQ; Elm. 125 mt 3E wwdm m hm a we 1 ADJUSTABLE-POSITION OPTICAL SYSTEM This invention relates to a method and apparatus, for positioning an optical assembly particularly, although not exclusively, the lens assembly of a variablemagnification copying machine.

In copending patent application Ser. No. 371,654, there is described an electrostatographic copying machine in which copies of original documents may be made in any one of three different magnification modes. In order to change the magnification of the optical system, a projection lens is moved between three different positions along the optical path through the lens. Moving a lens in this way presents the problem that it is very difficult to relocate the lens very precisely, as is necessary on each magnification change.

It is an object of the present invention to provide a method and apparatus for positioning an optical assembly in which this problem is overcome.

According to the present invention there is provided a method of positioning an optical assembly in one of a plurality of predetermined positions along its optical path comprising driving the optical assembly always in one direction against a selected one of a plurality of stops each of which is operable to bring it into the path of the assembly for positive engagement by the assembly, the assembly if approaching one of the predetermined positions from said one direction being driven directly against the operated stop, and if approaching the predetermined position from the direction opposite to said one direction, being driven past the selected stop while the stop is not operated and then reversed and driven directly against the stop which is operated on reversal of the assembly.

The invention also provides an apparatus for carrying out the method of claim 1.

An optical system in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional elevation of an optical assembly;

FIG. 2 is a diagrammatic plan view of the mechanical control and drive systems of the optical assembly;

FIG. 3 is a simplified diagram illustrating the action of the system of FIG. 2;

FIG. 4 is a side elevation, partly in section, of a part of the system of FIG. 2;

FIGS. 5 to 8 are portions of the circuit diagram of the machine described in copending patent application Ser. No. 371,654 which are relevant to the present invention.

Referring to FIG. 1, there is shown an optical assembly capable of projecting an image in any one of three magnification modes, while maintaining a constant conjugate length between the object and image.

The three magnification modes are a 100% mode, in which the image is substantially the same size as the object; and two reduction modes, in which the image is respectively 70 and 50% of the size of the object. In the 70% mode only the main lens 21 is used, whereas in the 100% mode, add-lens 22 is swung into the optical path as the main lens 21 is moved to a position closer to a first mirror 262. In the 50% mode, the main lens 21 is used in conjunction with add-lens 23, which is moved into the optical path as the main lens is moved towards a second mirror 263. The add-lenses 22 and 23 are swung into and out of the optical path as the main lens moves by means of ramp cams.

Referring now to FIGS. 1 and 2, the main lens 2] and the add-lenses 22 and 23 are mounted on a lens carriage 264. The lens carriage 264 is mounted for sliding motion parallel with the optical path through the main lens on

shafts

265 and 266 that are mounted in the optical system casting. Shaft 265 is fixed relative to the optical system casting, whereas shaft 266 is mounted for angular movement about its longitudinal axis for reasons to be described below. The lens carriage 264 may be driven along the

shafts

265 and 266 by means of a lead screw 267 which is mounted for rotation about its longitudinal axis, which is parallel to the

shafts

265 and 266, relative to the optical system casting. The lead screw may be rotated in either direction by means of a reversable drive motor MOT 5, through a toothed pulley 268 secured to the lead screw 267, and a toothed belt 269.

In order to position the main lens for the three magnification modes, positive stops are provided on the opticalsystem casting. Furthermore, in order to ensure that inaccuracies in positioning do not arise due to backlash between the lead screw and its co-operating lead-screw nut 287 (carried by the lens carriage) the lens carriage 264 is always driven in the same direction against the stops whenever it is repositioned. Since the lens carriage is driven by a motor, stopping the motor at the appropriate time, and taking account of motor over-run are essential to proper operating of the optical system, otherwise rapid wear or damage would result. Referring now to FIGS. 2 and 4, the lens carriage 264 has a lateral extension 286 which supports the lead-screw nut 287. The lead-screw nut 287 is threaded onto the leadscrew 267, and is slidably mounted within the lateral extension 286. The end of the lead-screw nut 287 nearest the 100% position terminates in a wide flange 288, whilst the other end (nearest the 50% position) carries a pair of locking nuts 289. A compression spring 290 acts between the nuts 289 and the lateral extension 286 so as to urge the flange, in the absence of any other constraints, into contact with the adjacent face of the extension 286.

When the lens carriage is being brought into any one of its three positions, an abutment surface 291 of the extension 286 encounters the appropriate stop, e.gv stop 292 (the stop) which has been brought into position by solenoid SOL 18. The lens carriage 264 is accordingly positively positioned, but the motor MOT 5 has not yet stopped. The motor is stopped as follows. The lead-screw nut 287 continues to move (compressing spring 290) until microswitch MS 16 (carried by the extension 286) is deactuated by its actuating pin 293. Pin 293 is carried by the flange 288 of the leadscrew nut. Microswitch MS 16 switches off the motor, and motor over-run further compresses the spring 290. Should microswitch MS 16 fail, a backing switch MS 14 is actuated just before the spring 290 is completely compressed.

The way that lens position changes are achieved will now be described with particular reference to FIG. 3. In the following discussion, movement of the lens in the direction from its mode position to its 50% mode position will be referred to as the forward" direction. Assuming that the lens is in the 100% mode-initially, the case will first be-considered where the lens is to be moved into the 70% mode position. The lens carriage 264 is first driven forward until an activating edge 293 carried by the extension 286 actuates a microswitch MS 17, positioned just forward of the 70% mode position, which reverses the direction of motor MOT 5, causing the lens carriage to be driven in the reverse direction. At the same time a 70% position solenoid SOL 18 is actuated to place a stop 292 in the path of the backward-travelling lens carriage. The microswitch MS 16 is deactuated as a result ofthe lens carriage extension 286 encountering the stop, thereby switching off the motor MOT 5, and stopping the lens carriage in positive engagement with the stop.

A similar procedure is followed when it is desired to change the lens position from the 70% to the 50% mode. The lens carriage is driven forwards until the actuating edge 293 encounters microswitch MS 18, positioned just forwards of the 50% mode position, which reverses the direction of motion of the lens carriage, and at the same time operates solenoid SOL 19 to bring a stop 294 into the path of the backward-moving lens. The microswitch MS 16 is deactuated, as explained above, thereby stopping the lens in the 50% mode position, in positive engagement with the stop. The same procedure is followed when it is desired to move the lens from the 100% mode position to the 50% mode position; In these circumstances, however, microswitch MS 17 is inhibited so that the lens carriage can travel straight from the 100% mode position to the 50% mode position.

In order to return the lens from the 50% mode position to the 70% mode position, the lens carriage is driven forward until the actuating edge 293 actuates microswitch MS 18. This causes reversal of the motion of the lens, but this time solenoid SOL 19 is inhibited and solenoid SOL 18 is actuated to bring the stop into position at the 70% mode position. The lens accordingly travels up to the 70% mode position, until the microswitch MS 16 is deactuated as a result of the lens carriage 264 encountering the stop 292.

When it is desired to move the lens back into the 100% mode position, from either the 70% or the 50% mode positions, the motor MOT 5 is first driven forwards until the actuating edge 293 actuates either microswitch MS 17 (70% mode) or MS 18 (50% mode). This reverses motor MOT 5 and drives the lens backwards, either solenoid SOL 18 or both of solenoids SOL l8 and SOL 19 being inhibited. The lens, which always approaches the 100% mode position from the same direction, is stopped when microswitch MS 16 is deactuated as a result of the lens carriage encountering a fixed stop 295.

Returning to FIG. 2, the 70 and 50% stops 292 and 294 are mounted respectively on sliding members 296 and 297 that are operated by solenoids SOL 18 and SOL 19. In the Figure, SOL 18 is in the operated position (i.e. the lens carriage 264 is in the 70% position) the sliding member 296 having moved, in relation to its guide 298, towards the solenoid. In moving across, the draw-bar 299 actuates microswitch MS 43, which is the 70% lens position microswitch, and also extends a tension spring 300. When power is removed from solenoid SOL 18, however, the fact that the lens carriage was driven against stop 292 holds the sliding member 296 in the operated position, and keeps MS 43 actuated. Only when the lens position is changed is sliding-member 296 released, so that stop 292 is removed under the action of the spring 300. Exactly similar considerations apply in the case of solenoid SOL 19, its'stop 294, and the 50% lens position microswitch MS 44. In FIG. 2,

SOL 19 is, of course, shown in its non-operated condious position in a fowards direction.

A description of the electrical control circuitry for the above arrangement now follows with reference to FIGS. 5 to 8.

SELECT 70% POSITION WITH LENS STARTING FROM THE 100% POSITION Switch S 4 is pressed, thereby calling two relays, RL 26 and RL 10. RL 26-2 drives the lens change motor MOT 5 in a forward direction (as defined above). RL 10-1 acts as a hold path for RL 10, 24 volts being supplied via RL 17-3 and MS 16. RL 10-2 primes the lens stop solenoid circuit. As the lens moves from the l00% position, MS 16 changes over, and supplies 24 volts to relays in the lens position circuit. At a position :just after passing the 70% position, microswitch MS 17 is made, and relay RL 27 is called via contact RL 12-3. RL 27-1 acts'as a hold path for RL 27. RL 27-2 is a change-over contact, and upon its operation, the lens motor MOT 5 is driven in the reverse direction towards the 70% (home) position. RL 27-3 initiates the lens stop solenoid SOL 18 which was previously primed by contact RL 10-2. SOL 18 places a physical stop in the lens path, and on contact with this, MS 16 (which is mounted on the lens carriage) changes over, and deenergises relays RL 26, RL 10 and RL 27. It also deenergises the lens drive motor MOT 5, and the solenoid SOL 18. Since the lens carriage is driven hard against the stop, the solenoid plunger remains in the operated position: the position has now been reached.

SELECT 50% POSITION WITH LENS STARTING FROM OR 70% POSITION The same general sequence of events takes place when the 50% mode is selected. S 5 is pressed which calls relays RL 26 and RL 12. RL-l2-l acts as a hold path for RL l2, and RL 12-2 primes the 50% lens stop solenoid SOL 19. Motor reversal at the 70% position is inhibited by RL 12-3, and the lens only reverses on reaching microswitch MS 18 at a location forwardly of the 50% position. A physical stop is placed in the 50% mode position by means of the solenoid SOL 19.

SELECT 70% POSITION WITH LENS STARTING FROM 50% POSITION Switch S 4 is pressed which calls relays RL 26 and RL 10. RL 26-2 drives the lens motor in a forward direction. RL 10-1 acts as a hold path for RL 10, 24 volts being supplied by RL 17-3 and MS 16. RL 10-2 primes the lensstop solenoid SOL l8 circuit, and as the lens moves from the 50% position MS 16 changes over and supplies 24 volts to the relays in the lens position circuit. On reachingthe 50% position, microswitch MS 18 is made,and RL 27 is called. Relay contacts RL 27-1, -2 and -3, operate as described above, so that the lens comes to-rest in the 70% (home) position.

SELECT 100% POSITION WITH LENS STARTING FROM 70% OR 50% POSITION On selecting the 100% mode a similar sequence occurs as in the case just described, where the 70% position is selected starting from the 50% position. The lens moves off the stop in a forward direction (towards the 50% position) and then reverses to come to rest against the 100% position stop.

Thus, whichever mode is selected, the lens always starts to drive in a forward direction (i.e. towards the 50% position), and always approaches the programmed position from the same direction (towards the 100% position).

In case any of the position microswitches fail, MS 14 and MS 15 are provided, being overtravel switches which isolate the motor to prevent damage to the mechanism.

What we claim is:

1. An apparatus for positioning an optical assembly in one of a plurality of predetermined positions along its optical path comprising means for driving the optical assembly in one direction and in the opposite direction along the optical path, a plurality of stops which are individually operable to directly engage the optical assembly and stop it in said predetermined positions, and in the case where the assembly is to change position in said one direction means to actuate said drive means to bring the assembly directly against a selected, operated, one of said stops, and in the case where the assembly is to change position in the opposite direction, means to actuate the drive means to drive the assembly in said opposite direction past the stop, and means to operate the selected stop and reverse the drive means when the assembly has travelled past the stop, whereby in operation of the apparatus, the assembly always engages one of said stops in said one direction.

2. The apparatus of claim 1 wherein said stops are operated by solenoids to bring them into position for engagement by said optical assembly.

3. The apparatus of claim [wherein the means to operate the stop and reverse the drive means of the optical assembly is a microswitch actuable by the assembly.

4. The apparatus of claim 1 wherein the optical assembly carries a lead-screw nut, and is driven by a motor-driven lead-screw which engages the lead-screw nut.

5. The apparatus of claim 4 wherein the lead-screw nut engages the optical assembly via a compression spring, and a switching means is arranged on the assembly to be normally actuated by the lead-screw nut, whereby in operation of the apparatus, when the assembly is stopped by a stop, the lead-screw continues to drive, compressing said spring, until the switching means is deactuated to stop the motor driving the leadscrew.

6. Apparatus for positioning an optical assembly in one of a plurality of predetermined positions along its optical axis including:

a frame,

a lens carriage including a lens assembly and being mounted for movement relative to said frame along said optical axis,

a drive member operatively connected to and springbiased relative to said lens carriage,

a bi-directional motor operatively connected to said drive member to cause said drive member to motivate said lens carriage in either direction along said optical axis,

abutment means mounted on said frame and selectively positionable in the path of said lens carriage to positively stop said lens carriage,

switch means operatively connected to said motor to switch said motor off when said lens carriage traveling in a first direction meets said abutment means, said drive member absorbing any overtravel of said motor by means of said spring bias relative to said lens carriage.

7. Apparatus as defined in claim 6 and further including switch means to reverse said motor when said lens carriage passes said abutment means traveling in a second direction opposite to said first direction and to position said abutment means in the path of said lens carriage as it travels back in said first direction to meet said abutment means.

8. Apparatus for positioning an optical assembly in one of a plurality of predetermined positions along its optical axis, including: i

a frame,

a drive screw and nut mechanism operatively connected to said lens carriage, said nut being resiliently spring mounted to said lens carriage,

a bi-directional motor operatively connected to said drive screw to rotate the same in either direction to motivate said lens carriage in either direction along said optical axis,

a plurality of abutment means mounted on said frame corresponding to said plurality of predetermined positions and selectively positionable in the path of said lens carriage to positively stop said lens carriage in a first direction of its travel,

first switch means to switch said motor off when said lens carriage meets one of said abutment means, said resiliently mounted nut absorbing any over travel of said motor and said drive screw,

second switch means to reverse said motor when said lens carriage passes a predetermined one of said abutment means traveling in a second direction opposite to said first direction,

third switch means to signal the positioning of said predetermined abutment means into the path of said lens carriage as it travels back in said first direction to meet said abutment means.

l =t l

Claims

3. The apparatus of claim 1 wherein the means to operate the stop and reverse the drive means of the optical assembly is a microswitch actuable by the assembly.

5. The apparatus of claim 4 wherein the lead-screw nut engages the optical assembly via a compression spring, and a switching means is arranged on the assembly to be normally actuated by the lead-screw nut, whereby in operation of the apparatus, when the assembly is stopped by a stop, the lead-screw continues to drive, compressing said spring, until the switching means is deactuated to stop the motor driving the lead-screw.

6. Apparatus for positioning an optical assembly in one of a plurality of predetermined positions along its optical axis including: a frame, a lens carriage including a lens assembly and being mounted for movement relative to said frame along said optical axis, a drive member operatively connected to and spring- biased relative to said lens carriage, a bi-directional motor operatively connected to said drive member to cause said drive member to motivate said lens carriage in either direction along said optical axis, abutment means mounted on said frame and selectively positionable in the path of said lens carriage to positively stop said lens carriage, switch means operatively connected to said motor to switch said motor off when said lens carriage traveling in a first direction meets said abutment means, said drive member absorbing any overtravel of said motor by means of said spring bias relative to said lens carriage.

8. Apparatus for positioning an optical assembly in one of a plurality of predetermined positions along its optical axis, including: a frame, a lens carriage including a lens assembly and being mounted for movement relative to said frame along said optical axis, a drive screw and nut mechanism operatively connected to said lens carriage, said nut being resiliently spring mounted to said lens carriage, a bi-directional motor operatively connected to said drive screw to rotate the same in either direction to motivate said lens carriage in either direction along said optical axis, a plurality of abutment means mounted on said frame corresponding to said plurality of predetermined positions and selectively positionable in the path of said lens carriage to positively stop said lens carriage in a first direction of its travel, first switch means to switch said motor off when said lens carriage meets one of said abutment means, said resiliently mounted nut absorbing any overtravel of said motor and said drive screw, second switch means to reverse said motor when said lens carriage passes a predetermIned one of said abutment means traveling in a second direction opposite to said first direction, third switch means to signal the positioning of said predetermined abutment means into the path of said lens carriage as it travels back in said first direction to meet said abutment means.