CA1293548C - Optical encoder - Google Patents
Optical encoderInfo
- Publication number
- CA1293548C CA1293548C CA000586745A CA586745A CA1293548C CA 1293548 C CA1293548 C CA 1293548C CA 000586745 A CA000586745 A CA 000586745A CA 586745 A CA586745 A CA 586745A CA 1293548 C CA1293548 C CA 1293548C
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- reticle
- moving unit
- transparent
- light
- window
- Prior art date
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Abstract
An optical encoder having a concentric cylindrically disposed reticle and moving unit with each having alternating transparent and opaque regions. A light emitter is located in each of two windows on one side of the reticle and moving unit while a light sensor is located on the other. The spacing of transparent and opaque regions in the reticle relative to that in the moving unit is such that when the transparent regions in one window are aligned those in the other unit are sufficiently non-aligned to produce quadrature and enable detection of both motion and direction of motion.
Description
35 ~
OP~ICAL ENCODER
BACKGROUND OF THE INVENTION
The present invention relates to an optical encoder for generating output pulses in number proportional to the amount of preselected movement of a coupled analog component.
An encoder is an electromechanical device to measure the position, velocity, acceleration, etc. of an operating mechanism to which the encoder is coupled. Optical encoders utilize light as a means for transmitting information about mechanical movement to a detector which outputs a number of electrical pulses dependent on the amount of movement of the operating mechanism.
Encoders may be linear or rotary. Both utilize a moving unit having alternating strips of transparency and opacity to the light path. The size, shape and fre~uency of theses areas determines the number and rate of the output pulses for a given movement of the operating mechanism. ~ common moving unit is in the form of a disc having a plurality of short radially directed spaced apart openings around its periphery. A light emitting diode (LED) directs light onto the disc and a photosensor located in the opposite side of the disc detects transmitted light giving an output proportional to the intensity of light transmitted through each open region. Such an encoder in combination with a counter for storing the number of sensor output pulses measures only the magnitude of movement, the speed, etc. but not the direction. Moreover, such discs provide a resolution of less than 50 lines per inch around the disc periphery. Greater resolution is possible using chrome on glass but at a greatly increased cost.
Mylar (trade-mark) film can also be used to obtain higher resolution but offers poor mechanical, thermal and humidity stability and is easily damaged by handling.
~' lLZq335'~
Resolution ~ay be improved by using a reticle having a pattern of transparent and opaque areas which ~re optically mated to those patterns on the ~oving unit. As ~he moving unit moves relative to the reticle which is ~ationary, alternating alignment and non-alignment of the transparent regions cau~es the transmitted light intensity to rise and fall. If the ~ize of the transparent and opaque regions are equal then the degree of fluctuation of the transmitte~ light will be maximized.
In order to determine direction of movement of t~e moving unit one can locate two LED'~ and two corre~ponding sensors with one ~ensor detecting light transmitted through a first reticle opening and a second 6ensor detecting light transmitted through a ~econd reticle opening. By ~hifting the 6econd reticle opening such that it is 1/4 cycle from the pattern in the first reticle a phase shift in the output from the second detector relative to the first is achieved. This phase shift reverses when the direction of the moving unit reverses .
There has been a 6evere problem in attempting to make high resolution encoder~ capable of quadrature at a rea~onable cost. This difficulty arises because o~ many requirements.
First, the spacing between the ~oving unit and reticle ~ust be a~ ~mall as possible and 6hould not vary. The thickness of the moving unit and reticle must be ~mall enough to ~ini~ize diffraction along the edges ~nd yet be thick enough to cut down light tranmission ~ignificantly. The tolerance in spacing of the transparent and opague region~ must be low. The material u~ed ~u~t be ~table against changes in hu~idity, have a low temperature coe~ficient of expansion ~nd be suf~iciently rugged to w~th~tand handling. Hitherto, rotary encoders ~aving a lar~e number of line6 per inch (400 or more) ~eeting the ~bove requirement~ have only been built with great difficulty and ~Z~354~
usually individual adjustment.
Optical encoders have been utilized in track balls which consist of a large steel ball rotatably mounted on a caæing. Clutch di6c6 contact the ball at orthogonal positions relative to the center of the ball and couple to a pair of respective rotary encoders which employ a disc. Because of the use of the disc the height of the casing is necessarily relatively large to accommodate the diameter of the disc.
Moreover, only a cimple encoder i~ used. A 6imilar encoder is used in a "mouse" which is a casin~ having a large ball which is adapted to roll over a table top. To date these have been the only known units for generating input control data for a computer using optical encoders.
Accordingly, it is an object of the present invention to provide an improved low cost optical encoder.
It is a further object of the invention to provide an ~ncoder Gf 6ubstantially higher resolution than those used in present computer analog input devices and capable of quadrature.
It i~ yet a further object of the invention to provide an improved joystick which has a low profile and capable of high resolution and able to generate information as to motion and direction of ~otion.
S~MMARY OF THE INVENTION
~ ccording to the i~vention there i~ pro~ided ~n optical encoder or generating input control data for a proces60r or comput~r. The encoder include~ a ba~e, a rotor rctatably attached to th~ base and a pair of window chambers affixed to the ba6e. A reticle having alternating transparent ~nd opague 3~
areas i~ ~ounted in a cylindrically di~po~ed position on the base. A moving unit cylindrically disposed ~o and concentric with the reticle al~o having alternating transparent and opaque areas is Attached to the rotor. The moving unit i6 ~ovable with respect to the reticle ~uch that alternating opa~ue and transparent regions o~ he moving unit and the reticle come into and out of alignment. A light emitting ~eans i~ located in each of the chambers and light ~ensing means ~re also in each o~ the chamber~ Oh a side of the reticle and moving unit opposite to that of the light emitting means. ~s the moving unit i5 mov~d relative to the reticle, the transparent regions of the moving unit move into full alignment with the transparent regions of the reticle in one of the windows while in the other of the windows the transparent regions of the moving unit are ~ufficiently non-aligned with those of the reticle such that light transmission through the other window is substantially reduced ~rom that in the one window.
Advantageously, the transparent and opaque regions are linear, of con~tant width and transverse to the length of the associated ~oving unit and reticle.
~; Prefera~ly, the reticle and moving unit are each strips of photographic film having alternating exposed and unexposed linear regions transverse to the length t~ereof forming the : transparent and opaque regions. The thickness o~ each of the ~Eilms i~ approxiloately 5/1000 of ~n inch.
Utilization of high resolution optical encoding in the environ~ent of a joystick is hitherto not known, possibly due to the dif.~iculties in achieving ~tabillty, mechanical reliability ~nd dimensions which are suffi~iently ~mall to allow their inclusion in the restricted dimensions of ~ joystick case all at a relatively low co~t. ~y uging a cylindrical geometry a ~ore ~9~5~1 preferred location of the optical components may be employed to achieve relatively small dimen~ions. By employing ph~tographic film with alternating ~xposed and unexposed linear bands transver#e to the length sf the film ~trip it i~ possible to achieve a large number of lines per inch of exposed regions at minimal cost. M~reover, such fil~ can be made to contact an adjacent fil~ with essentially no air gap between the interface so as to avoid undesirable reflections therefr~. A ~ilm thickness of 0.005 inches is ~ufficient to reduce the transmission of light through unexposed regions to a ~uffi~ient extent so that clear resolution betw~en aligned and unaligned regions of the film i~ possible. Utilizing ~ csnstant ~pacing between the exposed and unexposed regions on each ~ilm with a pre-selected spacing on each film maximizes the di~ference in light transmission between aligned and non-aligned regions in each window. As the moving unit film is caused to rotate relative to the reticle in first one window and then the other window the resultant signal by the light sensing detectors in each window produces a wave form that is periodic. A hardened film on the strips between their contacting 6urfaces avoids ~cratches.
In another aspect of the invention there is provid~d a joystick which includes a casi~g, operating means coupled to the casing for developing ~ovement translatable into two dimensions a~d an optical encoder aPfixed to the casing. The optical encoder ha~ a base, a rotor rotatably attached to the base and coupled to the operating means and a pair of window cha~bers ~ixed to the base. A reticle is mounted on th2 base in a cylindrically disposed position traversing each o~ the ~indow cha~bers and having alternating ~ransparent and opaque areas. A
~oving uni~ mounted on the rotor i6 al60 cylindrically disposed and concentric wit~ ~nd juxtaposed to the reticle. T~e moving unit has a}ternating transparent and opa~ue areas ~ubstantially 6 ~Z9~S4~3 matching those of the reticle but ~paced ~uch that alternatiny opaque and transparent region~ of the moving unit and reticle come into and out of alignment and such tha~ as ~aid ~oving unit is moved past 6aid reticle, a periodic ouput response by each light sensing means results with the transparent region~ of the moving unit becoming fully aligned with those o~ the reticle in one ~f the window~ and 90 degrees out of alignment in ~nother of the windows. Light emitting means are located in each window to direct light onto the reticle and moving unit and li~ht 6ensing means are located on an opposite side of the ret~cle and m~ving means to detect transmitted light in each window. The coupling between the operating means and t~e optical encoder is ~uch as to rotate the rotor through an angle substantially linearly proportional to an angle of pivoting of the lever in a predetermined plane.
~RIEF DESCRIPTION QF THE DRAWINGS
i The novel features believed characteristic of the invention are set forth in the appended claims. The inv~ntion itself, however, as well as other features and advantages thereof, will be best understood by reference to the detailed : description which follows, read in conjunction with the accompanying drawings, wherein:
Fig. 1 is a per~pective view showing the casing and the handle in exploded form.
Fig. 2 i~ a front elevation view of the handle and handle collar:
Fig. 3 is a ~ide elevation view of the handle with the collar in 6ection;
7 :~9~S48 Fig. ~ is a bottom view of the ca6ing assembly ~howing the gimbal plates and printed circuit board;
; Fig. 5 i~ a plan view of the base plate and printed circuit board;
Fig. 6 is a plan view ~howing the spring as~emblies and tensioning ring as mounted in a bott~m casing section;
Fig. 7 is a bottom view of the casing assembly showing the gimbal plates and printed circuit board with the rotary : devices in place;
Fig. 8 is a plan view of the base plate and printed circuit board with the rotary devices in place:
Fig. 9 is a plan view in ~ection of a portion of the rotor;
Fig. 10 is an elevation view of a strip of film having alternately exposed and unexposed regions;
Fig. 11 is a plan view of a window chambers showing alignment of-exposed regions in one window and non-alignment in the other; and A
Fig. 12 are two ~et~ of output wave forms from the two deteckors in the windows corresponding to clockwi8e ~nd counterclockwise xotation for re~pective left and right detector~.
g3S'~8 DETAILED DESCRIPTION WITH REFERE:NCE TO THE DRAWINGS
The present invention i5 particularly u6eful in a joystick, an example o~ which is hown in Figures 1-6.
The joystick ~s shown in Fig . 1, ~ n exploded ~orm, consist of a handle 10 coupled to a casing 12 having an upper casing section 13 and a bottom casing section ~1. The handle lo includes a padded handle grip 11, a thumb button housing 19 at the top of which is lo~ated a thumb microswitçh button 18.
8elow the handle grip 11 is a handle housing 41 which supports a handle ball 36 having two oppositely disposed ball pins 42 and a gimbal ring actuating sphere 38.
An annular handle collar 34 fits between hand~e housing 41 and handle ball 36. Collar 34 includes a pair o:E o~positely disposed ball pin collar sl~ts or keyways 40 which ~lidably receive ball pins or keys 42. As shown in Fig. 3, collar 34 has a sloped interior surface 23 which abut~ ball 36 and permit~
pivotal ~otion of the handle lO in a spherical arc but prevents rotation thereof when the pins 42 are engaged with slots 40~
Casing 12 houses a base plate 44 (see Figs. 4 and 5) which has a collar receptable 22 formed on an upper 6urface thereof and a ball base plate contact ~urface 24 which contacts ball 36. Contact ~urface 24 has formed therein two oppositely dispo~ed ball pin ba~e plate ~lots or keyways 26 dimensioned and positioned to slidably receive ball pins or Xeys 42. Below the base plate 44 is mounted a pair of gimbal plates 27 and 29 (see ~g. 4). Annular gimbal ring or bushing 52 i5 mounted between a pair o~ overlapping central plate openings 51 and 53 as ~hown.in FigO ~. Ackuating sphere 38 passes into annular ring 52 and engage6 the latter.
9 ~93S'~13 Collar 34 has a plurality of radially spaced apart receptacle keys 43 which are positioned and dimensioned to be snugly ~lidably received in receptacle keyways 35. A pair o~
firing buttons 14 and 16 are ~ounted on the casing to actuate microswitches 136 and 138 (see Fig. 5) located within the c~sing 1~. A cabl 32 ho~sing a plurality of electrical leads passes in to the casin~ 12 through a cable guard 37 that prevents movement of the ~able 32 into or out of the casing 12. The tensioning wheel 30 i8 rotatably mounted w:ithin the casing 12 and extends through slots 81 and 83 in the latter to provide adjusting surface portions thereof.
As shown in Fig. 4, a base plate 44 is mounted as an upper casing section 13 by means of a locate lip or positioning tab 110 snugly, ~lidably insertable into a lip or tab receptacle 116 in casing section 134 and ~ locate or positioning plug 112 snugly, slidably insertable into a plug receptacle 114. At one end of the base plate 44 there is affixed a printed circuit board 118 having three rotary wheel apertures 127, 128 and 131.
The bottom edge of the upper casing section 13 has an upper casing rim 15 which extend~ bel~w an upp~r casing shoulder 17 adjac~nt to, but interior with respect to the rim 15.
Thre~ rim slots 120, 122 and 124 are formed oppo6ite the corresponding rotary wheel apertures 127, 129 and 131, respectively.
The bottom surface of base plate 44 has four radially di~posed ~heel guide pins 108. Also formed in the bottom of ba~e pl~te 44 are a plurality of radially outwardly directed base plate pring wall~ 90, 92, 94 and 96. Intermediate paced apart walls 90 and 92 ~re central positioning ribs 98 and 100, respectively. A pair o~ orthogonally disposed gi~bal plates 27 ~nd 29 ¢ach have a pair of arcuate ~lots 64 and 62, and 58 and ~ 9354~3 60, respectively formed therein. Posts 66, 68, 70 and 72, respectively, slidably ~it through corresponding slots 58, 60, 62 and 64, respectively. Thus, the gimbal plates 27 and 29 are orthogonally 81 idable with re~pect to one another. Each o~
gimbal plates 27 ~nd 29 has a pair vf opposed rectangular ~lots 86 and 88, and 82 and 84, respectively. Along an ~dge parallel to the direction of ~liding movement on each of corresponding gimbal plates 27 and 29 i~ ~ormed a U-shaped ~lot 78 and 80, respectively, which ~lots are adapted to slida~ly receive an end of lever arms 74 and 7Ç, respectiYely. Lever arms 74 ~nd 76 are coupled to the wiper arms of potentiometers 132 and 134 as shown in Fig. 5. Thus, rotation of the the lever arms 74 and 75 causes movement of corresponding wiper arms of potentiometers 132 and 134, respectively.
Lower gimbal plate 29 has a central outer opening 61 and a concentric slightly smaller inner opening 51 joined by a lower gimbal plate ~houlder 56. Similarly, a spaced apart upper gimbal plate 27 has an upper gimbal plate ~houlder 54 joining an outer opening 55 and a concentric inner opening 53.
: ~i~bal ring or bushing 52 has a pair of opposit~ly disposed small sleeves 46 and a single central large sleeve 48.
Large ~leeve 48 is ~lidable on ~houlders 54 and 56, respectively. Four posts 210, 212, 214 and 216 are ~paced proximate the corner of upper casing 6ection 13. A hole 106 in ~a~e plate 44 provides an access ~upport for le~ding electrical cable from one ~ide of plate ~4 to the other.
. The upper ~urface o base plate 44, a~ illustrated in Fig. 5, contains a cylindrical collar receptacle wall 33 forming a collar receptacle wall 33 and accommodates receptacle keys 43 Lvcate or po~itioning plug 112 i~ formed so as to Z93~4~
accommodate an adjusting ~crew 45 between two ~pacing legs 140.
On a threaded end of ~crew 45 is registered a nut 47 having a fork end 49. Fork end 49 fit into a slot (not shown) in a post 57 which prevents rotational ~ovement of nut 47 in response to rotation of screw 45. Post ~7 is integral with a ~leeYe 59 capturing potentiometer 134 in a firm, non slipping engagement.
A si~ilar arrangement (not shown) is used with respect to lorate lip or positioning tab 110 and potentiometer 132.
Printed circuit board 118 has mo~mted thereto a pair of microswitches 138 and 136 on top of which are placed firing buttons 16 and 14, respectively. Rotary wheel switches 121, 123 and 125 having wheel axles 144, 146 and 148, respectively are mounted against the printed circuit board 118 with the axles 144, 146 and 148 slidably inserted through apertures 127, 129 and 131, respectively. A pair of contacts on each wheel 121, 123 and 125 (not shown) are used to contact a set o~ three different pads ~not 6hown) on printed circuit board 118~
On the periph~ry of base plate 44 ~as shown in Figs. 4 and 5) is a tension ring button 65 formed at the end o~ a finger in the base plate 44.
The tensioning wheel 30 is sh~wn in Fig. 6 as it is mounted on a bottom casing section 21. An upper annular surface of wheel 30 rotates around the outside of wheel guide pin6 lOg on base plate 44 as 6hown in Fig. 4 and around corresponding ridges (not shown) in the bottom casing ~ection 21. On the interior cylindrical surface ~f the tensioning wheel 30 there is 8 set of four radiaIly ~paced integral cams t 58, 160, 162 and 164 having gen~rally 6erpentine cam ~urfaces. On the bottom ca6ing there i5 form~d a ~et of four equally, radially ~paced ~part ~pring wells 171, 173, 175 ~nd 177, generally directed toward a center of the tensioning wheel 30 and interior 12 ~L~Z93S~E~
thereof. Spring well 171 is formed by vertical walls 150, ~51 and 153; spring well 173 is for~ed by vertical wallB 152 ~ 155 and 157; 6pring well 175 is ~oxmed by vertical walls 154, 159 and 161; while spring well 177 i~ formed by vertical walls 156, 163 and 16S. The walls 150 and 151 align with wall6 30 on the base plate; walls 152 and 155 align with ~lalls g6: wall~ 154 and 159 align with walls 92; and walls 156 and 163 align with walls 94. Sufficient space i8 allowed be~ween t~he sets of aligned walls to permit gimbal plates 27 and 29 to ~lide back and forth. Spring wells 171, 173, 175 and 177 each have spring cups 182, 184, lB6 and 188 ~lidably contained therein. Coil springs 174, 176, 178 and 180 are inserted into corresponding respective cups 182, 184, 1~6 and 188 and at an opposite end contact ball bearings 166, 168, 170 and 172, respectively. Radial edges of cams 158 and 162 contact walls 152 and 163, respectively, at one end of the adjustment position. The wheel 309 is rotatable in a clockwise direction as ~hown in Fig. 6. Casing 21 has an interior bottom casing rim 31 which extends beyond a bottom casing shoulder 25 and abuts top casing rim 15. Three rotary wheel bottom ~ection rim slots 126, 128 and 130 are formed in bottom casing section 21 and coincide with corresponding slots 124, 122 and 120, respectively, ~f the top casing ~ection 13.
Three rotary switch ~upport walls 190, 192 and 194 each forming a portion of a cylindrical wall, are located proximate coresponding slots 126, 128 and 130, respectively. Each support wall has three notches 196, 198 and 200 formed therein at radially ~paced apart positions in the top edge thereof for contacting a corresponding detent i~ each o~ wheels 121, 123 and 125 in order to mark the three separate switch positions. (The det~nt in wheel~ 121, 123 ~nd 125 are not shown.) Four bottom casing posts 218, 220, 222 and 224 disposed proximate each of the four corners of the bottom casing ~ection 21 register with corre~ponding top casing posts 214, 212, 210 and 216, respectively. Screws passi~g through the posts 218, 220, 222 3S~1!3 and 22~ threadedly register with threaded hole~ in corresponding top casing posts 214, 212, 210 and 216, r~spectively. Base plate 44 is affixed to ~ottom ca~ing 21 by means of casing posts 202, 204, 206 ~nd 108 which register with ,gi~bal plate guide posts 68, 6~ 72 and 70, respectively are u~ed to affix the base plate 44 to the bottom casing section Zl. ~paced apart grooves 225, 2~6 and 227 in ~ top surface of tensioning wheel 30 successively engage tension ring bu~ton Ç5 on base plate 44 in the first three tension settings.
Formed in each long side of casing ~ection 21 are a pair of tensioning wheel slots 81 and 83 which are used to provide user access to the tensioning wheel 30.
In operation, when handle lO is tilted in ~ particular direction, ball 36 rotates against collar ball contact 6urface 23 and ball base plate contact surface 24. At the same time cylindrical pins 42 rotate and pivot vertically in ball pin base plate 610ts 26 and ball pin collar 810ts 40. Gimbal ring actuating sphere 38 forces g~mbal ring 52 against upper and lower gimbal plate openings 53 and 51, respectiv~ly. In response, gimb~l plates 27 and 29 each move in a direction determined by the movement of actuating sphere 38. Gimbal plate 27 is constrained to move in a linear direction as determined by the contact of gimbal plate 610ts 62 and 64 against guide posts 68 and 72, respectively. Similarly, gimbal plate 29 moves in a direction ~onstrained by the movement of ~lots 58 and 60 past guide posts 66 ~nd 70, respectively. Movement of gimbal plates 27 ~nd 29, in turn, result in U- haped ~lots 80 and 78 pivoting pot~ntiometer coupling arms 76 and 74 respecti~ely.
The l~tter pivoting ~rms are coupled to the wiper 2rms (not ~hown) of potentiometer6 134 ~nd 132, respectively. Thus, ~ove~ent O~ each wiper arm of each potenti~meter 132 ~nd 134 ~ay ~e obtained by adju~tment o~ a corresponding adjusting ~crew 45 1~ ~Z9354~3 such as that of potentiometer 134 ~hown in Fig. 5.
A~ screw 45 i~ rotated, nu~ 47 travels along the threaded portion thereof thereby moving the casing of potentiometer 134. ~he wiper arm at the 6ame time i~ held in a fixed position by means of th ~-~haped ~lot 890 of gimbal plate 27. A ~imilar adjustment i~ available ~or potentiometer 132.
In the event a user desires a change in biasing on the handle 10, this i~ ~ccomplished by rotation of tensioning wheel 30. As tensioning wheel 30 rotates in a clockwise position as shown in Fig. 6, cams 158, 160, 162 and 164 begin to engage ball bearings 166, 168, 170 and 172 respectively, forcinq the latter to compress associated springs 174, 176, 178 and 180, respectively. This in turn causes a compression force to be generated against associated spring cups 182, 184, 186 and 188, respectively. Spring GUpS 182 and 186 contact gimbal plate 29 at slots 82 and 84, respectively, thereby applying opposing biasing forces to the latter. Similarly, ~pring cups 184 and 188 contact gimbal plate 27 at 810ts 86 and 88, respectively.
The more tensioning wheel 30 i5 rotated in a clockwise direction, the more compression is applied to coil ~prings 174, 176, 178 and 180, thereby providing a greater biasing o$ gimbal plates 27 ~nd 29 when moved from the neutral position.
Alternatively, 6pring biasing can be disconnected altogether from the handle by ~imply rotating tension wheel 30 in a complete counterclockwise direction until cam ~urfaces 162 and 158 abut walls 163 and 152, respectively.
A~ een in Fig. 5, micr~switches 138 and 136 ~re ncluded to provide ~iring buttons. ~imilarly, button 18 a~
~h~wn in Fig. 1 ~t the top end of handle 10 i~ provided as a fire button operable by the thumb of a user of the ~a~ hand that i8 ueed to aanipulate handle 10. Button 18 actuates a ;
microswitch ~not shown~ looated inside thu~b button hou inq 19.
Handle 10 is hollow ts permit wires to connect to the latter microswitch (not ~hown).
Initially, rotary wheel awitches 121, 123 and 125 are rotatea to a desired p~sition depending on the particular ~achine with which the joy~tick i~ to be u~ed. Secondly, tensioning wheel 30 i6 adjusted to provide the desired biasing force to handle 10.
The Joystick of Figures 1-6 i~ modified by replacing p~tentiometers 132 and 134 by a rotary assembly 321 a~ shown in Figs. 7 and 8. Rotary assembly 321 has a fixed portion 319 fixed to the base plate 44 by ~ans of locate pins 323. The rotary portion 310 on each rotor assembly 321 i6 coupled to rotary arms 74 and 76, ~imilar to the potentiometer~ of Fig. 4, and received by U-shaped slots 78 and 80, respectively. The rotary p~rtions 310 are thus operated in a similar ~anner as potentiometer wiper arms.
Referring to Fig. 3, there is shown ~ top view of a portion of the rotor assemhly 321 which includes a ~ixed casing 312 and a rotor 31~ rotatable with respect to the casing 312.
Attached to the casing 312 are a pair of reticle guides 318 for capturing and positionin~ a reticle 316.
A pair ~f slot~ 322 in the periphery of the rotor 314 ~erve to receive ~nd m~intain in position a ~oving unit of film 320 contiguous to the reticle ~trip of fil~ 316. Both 6trips of film pa~s through window chamber~ 326 and 328 affixed to the casing 312. At one end of the chamber~ 326 ~nd 328 are located light-e~itting diodes 330 and 332 while ~t the other extremity, on an opposite ~ide of the film ~trips 316 ~nd 320, are located light detector~ 334 and 336.
16 ~Z93S'~3 As shown in Fig. lO, each o~ the fil~ strip6 corresponding to the reticle 316 and the ~ovins unit 320 have alternating transparent ~40 and opaque 3~2 regions correspo~ding to exposed 340 and une~posed 342 regions of the film ~trip 338.
Referring to Fig. ll, exposed regions 344 transparent to light and une~pose~ regions 346 are shown aligned in a right window chamber 32~ and only partially in left window chamber 3260 Consequently, light detected by light detector 336 in the right window chamber 328 gives rise to a ~aximum signal output whereas that in the left window chamber detected by light detector 334 gives ri~e to an intermediate value of signal.
As film trip 320 moves in a counter-clockwise direction relative to reticle 6trip 316 the exposed regions 344 in the right hand window chamber 328 move from maximum light transmission to a diminishing level of light transmission as the exposed regions gradually move away from exact alignment. At the ~ame time the exposed regions 344 in the left hand window chamber approach maximum transmission as the exposed regions enter into exact alignment. Thus, curve 348 in Fig. 12 describes the 6ituation as would occur in the left window chamber 326 whereas curve 350 would correspond to that in the right window chamber 328. However, for clockwi e rotation in which moving unit strip 320 moves in a cloc~wi~e direction or to the left as shown in Fig. ll, the transmission in the left window chamber r~ther than increasing would decrease to a ~inimum as the expo ed regions 344 moved toward complete non-overlapping positions. Thus, curve 352 would correspond to the l~ft window chamber 326 for clockwise rotation wh~reas curve 354 would correspond to that of the right hand window chamber and would be substantially the same as for counter-clockwi~e rotation in the latter case.
Z9~54~
It will be appreciated that there will alway~ be a certain level of light transmis~ion through the film but it has been found that a 5 ~il thickness of film iB Fufficently thick to make the difference between ~aximum and minimu~ light transmission through the film trips 316 2nd 320 aufficiently great to be able to distinguish between the two po~itions.
Curves ~howing the output of the two detectors as a function of rotor angle as ~hown in Fig. 12 assum~ an ideal detector respons~ in which the detector outputs are in the form of sawtooth waves. However, amplitude limiting causes the output to be as ~own in the dotted lines 355. By directing the output 350 or 354 to a counter (not shown) and counting the number of pulses one can determine position of one coordinate in a two coordinate system.
In detecting the phase difference between the signal from one of detectors 334 an~ 336 and that ~rom the other, one can determine the direction o~ rotation of the rotor and hence the direction Qf ~o~ement along one dimension. For exa~ple, if output 348 which lags output 350 corresponds to that ~rom detector 330, then ~uch an output indicates film 320 i6 ~oving to the right in Fig. 12. Similarly, output 352 corresponds to movement of film 320 to the le~t in Fig. 4 In addition, by recording the rate at which pulses are detected it i~ possible to measure velocity and acceleration.
As ~hown in Fi~. 13, the output pulses from the light detectors ~ay be run to a 6ignal processing unit which will include electronic counter , ~nalog to digital converters, 6witch~s, etc. to ~elect position, velocity or acceleration ~odes a~ well a~ performing many other functions. ~ypically, two rotor~ would be installed $n a ~ingle ~oystick casing so as to provide ~eparate outputs for each of the two coordinate 18 ~9~S~
axes. By utilizing the cylindrical ~ymmetry o~ the rotor it i~;
possible to incorporate two such roltors into a relativley 6mall, flat base ~3tructure. 2~oreover, the use of standard acetate photographic film permits one to obtain highly dense ~qui-spaced alternating transparent and opaque regions,. The use of two such film strips provide6 an inexpen6ive, compact, accurate optical encoding ~ystem. A standard commercially availabl~ ultra violet curable lubricant on the film protects it :Erom cratches and reduces the friction between the film strips. One can easily achieve 1200 counts ~or rotation through an angle of less than 70 with such a system.
Clearly, any kind of mechanical coupling between the joystick lever and each of the rotors can be implemented in order to effect rotational movement of the rotor in proportion to displacement along a selected corresponding axis.
Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various ~odifications of the illustrative embodiments, as well as other em~odiments of the invention9 will be apparent to persons ~killed in the art upon reference to this description. It is therefore contemplated that the ~ppended claims will cover any ~uch ~odifications or embodiments as fall within the true cope o~ the invention.
.
OP~ICAL ENCODER
BACKGROUND OF THE INVENTION
The present invention relates to an optical encoder for generating output pulses in number proportional to the amount of preselected movement of a coupled analog component.
An encoder is an electromechanical device to measure the position, velocity, acceleration, etc. of an operating mechanism to which the encoder is coupled. Optical encoders utilize light as a means for transmitting information about mechanical movement to a detector which outputs a number of electrical pulses dependent on the amount of movement of the operating mechanism.
Encoders may be linear or rotary. Both utilize a moving unit having alternating strips of transparency and opacity to the light path. The size, shape and fre~uency of theses areas determines the number and rate of the output pulses for a given movement of the operating mechanism. ~ common moving unit is in the form of a disc having a plurality of short radially directed spaced apart openings around its periphery. A light emitting diode (LED) directs light onto the disc and a photosensor located in the opposite side of the disc detects transmitted light giving an output proportional to the intensity of light transmitted through each open region. Such an encoder in combination with a counter for storing the number of sensor output pulses measures only the magnitude of movement, the speed, etc. but not the direction. Moreover, such discs provide a resolution of less than 50 lines per inch around the disc periphery. Greater resolution is possible using chrome on glass but at a greatly increased cost.
Mylar (trade-mark) film can also be used to obtain higher resolution but offers poor mechanical, thermal and humidity stability and is easily damaged by handling.
~' lLZq335'~
Resolution ~ay be improved by using a reticle having a pattern of transparent and opaque areas which ~re optically mated to those patterns on the ~oving unit. As ~he moving unit moves relative to the reticle which is ~ationary, alternating alignment and non-alignment of the transparent regions cau~es the transmitted light intensity to rise and fall. If the ~ize of the transparent and opaque regions are equal then the degree of fluctuation of the transmitte~ light will be maximized.
In order to determine direction of movement of t~e moving unit one can locate two LED'~ and two corre~ponding sensors with one ~ensor detecting light transmitted through a first reticle opening and a second 6ensor detecting light transmitted through a ~econd reticle opening. By ~hifting the 6econd reticle opening such that it is 1/4 cycle from the pattern in the first reticle a phase shift in the output from the second detector relative to the first is achieved. This phase shift reverses when the direction of the moving unit reverses .
There has been a 6evere problem in attempting to make high resolution encoder~ capable of quadrature at a rea~onable cost. This difficulty arises because o~ many requirements.
First, the spacing between the ~oving unit and reticle ~ust be a~ ~mall as possible and 6hould not vary. The thickness of the moving unit and reticle must be ~mall enough to ~ini~ize diffraction along the edges ~nd yet be thick enough to cut down light tranmission ~ignificantly. The tolerance in spacing of the transparent and opague region~ must be low. The material u~ed ~u~t be ~table against changes in hu~idity, have a low temperature coe~ficient of expansion ~nd be suf~iciently rugged to w~th~tand handling. Hitherto, rotary encoders ~aving a lar~e number of line6 per inch (400 or more) ~eeting the ~bove requirement~ have only been built with great difficulty and ~Z~354~
usually individual adjustment.
Optical encoders have been utilized in track balls which consist of a large steel ball rotatably mounted on a caæing. Clutch di6c6 contact the ball at orthogonal positions relative to the center of the ball and couple to a pair of respective rotary encoders which employ a disc. Because of the use of the disc the height of the casing is necessarily relatively large to accommodate the diameter of the disc.
Moreover, only a cimple encoder i~ used. A 6imilar encoder is used in a "mouse" which is a casin~ having a large ball which is adapted to roll over a table top. To date these have been the only known units for generating input control data for a computer using optical encoders.
Accordingly, it is an object of the present invention to provide an improved low cost optical encoder.
It is a further object of the invention to provide an ~ncoder Gf 6ubstantially higher resolution than those used in present computer analog input devices and capable of quadrature.
It i~ yet a further object of the invention to provide an improved joystick which has a low profile and capable of high resolution and able to generate information as to motion and direction of ~otion.
S~MMARY OF THE INVENTION
~ ccording to the i~vention there i~ pro~ided ~n optical encoder or generating input control data for a proces60r or comput~r. The encoder include~ a ba~e, a rotor rctatably attached to th~ base and a pair of window chambers affixed to the ba6e. A reticle having alternating transparent ~nd opague 3~
areas i~ ~ounted in a cylindrically di~po~ed position on the base. A moving unit cylindrically disposed ~o and concentric with the reticle al~o having alternating transparent and opaque areas is Attached to the rotor. The moving unit i6 ~ovable with respect to the reticle ~uch that alternating opa~ue and transparent regions o~ he moving unit and the reticle come into and out of alignment. A light emitting ~eans i~ located in each of the chambers and light ~ensing means ~re also in each o~ the chamber~ Oh a side of the reticle and moving unit opposite to that of the light emitting means. ~s the moving unit i5 mov~d relative to the reticle, the transparent regions of the moving unit move into full alignment with the transparent regions of the reticle in one of the windows while in the other of the windows the transparent regions of the moving unit are ~ufficiently non-aligned with those of the reticle such that light transmission through the other window is substantially reduced ~rom that in the one window.
Advantageously, the transparent and opaque regions are linear, of con~tant width and transverse to the length of the associated ~oving unit and reticle.
~; Prefera~ly, the reticle and moving unit are each strips of photographic film having alternating exposed and unexposed linear regions transverse to the length t~ereof forming the : transparent and opaque regions. The thickness o~ each of the ~Eilms i~ approxiloately 5/1000 of ~n inch.
Utilization of high resolution optical encoding in the environ~ent of a joystick is hitherto not known, possibly due to the dif.~iculties in achieving ~tabillty, mechanical reliability ~nd dimensions which are suffi~iently ~mall to allow their inclusion in the restricted dimensions of ~ joystick case all at a relatively low co~t. ~y uging a cylindrical geometry a ~ore ~9~5~1 preferred location of the optical components may be employed to achieve relatively small dimen~ions. By employing ph~tographic film with alternating ~xposed and unexposed linear bands transver#e to the length sf the film ~trip it i~ possible to achieve a large number of lines per inch of exposed regions at minimal cost. M~reover, such fil~ can be made to contact an adjacent fil~ with essentially no air gap between the interface so as to avoid undesirable reflections therefr~. A ~ilm thickness of 0.005 inches is ~ufficient to reduce the transmission of light through unexposed regions to a ~uffi~ient extent so that clear resolution betw~en aligned and unaligned regions of the film i~ possible. Utilizing ~ csnstant ~pacing between the exposed and unexposed regions on each ~ilm with a pre-selected spacing on each film maximizes the di~ference in light transmission between aligned and non-aligned regions in each window. As the moving unit film is caused to rotate relative to the reticle in first one window and then the other window the resultant signal by the light sensing detectors in each window produces a wave form that is periodic. A hardened film on the strips between their contacting 6urfaces avoids ~cratches.
In another aspect of the invention there is provid~d a joystick which includes a casi~g, operating means coupled to the casing for developing ~ovement translatable into two dimensions a~d an optical encoder aPfixed to the casing. The optical encoder ha~ a base, a rotor rotatably attached to the base and coupled to the operating means and a pair of window cha~bers ~ixed to the base. A reticle is mounted on th2 base in a cylindrically disposed position traversing each o~ the ~indow cha~bers and having alternating ~ransparent and opaque areas. A
~oving uni~ mounted on the rotor i6 al60 cylindrically disposed and concentric wit~ ~nd juxtaposed to the reticle. T~e moving unit has a}ternating transparent and opa~ue areas ~ubstantially 6 ~Z9~S4~3 matching those of the reticle but ~paced ~uch that alternatiny opaque and transparent region~ of the moving unit and reticle come into and out of alignment and such tha~ as ~aid ~oving unit is moved past 6aid reticle, a periodic ouput response by each light sensing means results with the transparent region~ of the moving unit becoming fully aligned with those o~ the reticle in one ~f the window~ and 90 degrees out of alignment in ~nother of the windows. Light emitting means are located in each window to direct light onto the reticle and moving unit and li~ht 6ensing means are located on an opposite side of the ret~cle and m~ving means to detect transmitted light in each window. The coupling between the operating means and t~e optical encoder is ~uch as to rotate the rotor through an angle substantially linearly proportional to an angle of pivoting of the lever in a predetermined plane.
~RIEF DESCRIPTION QF THE DRAWINGS
i The novel features believed characteristic of the invention are set forth in the appended claims. The inv~ntion itself, however, as well as other features and advantages thereof, will be best understood by reference to the detailed : description which follows, read in conjunction with the accompanying drawings, wherein:
Fig. 1 is a per~pective view showing the casing and the handle in exploded form.
Fig. 2 i~ a front elevation view of the handle and handle collar:
Fig. 3 is a ~ide elevation view of the handle with the collar in 6ection;
7 :~9~S48 Fig. ~ is a bottom view of the ca6ing assembly ~howing the gimbal plates and printed circuit board;
; Fig. 5 i~ a plan view of the base plate and printed circuit board;
Fig. 6 is a plan view ~howing the spring as~emblies and tensioning ring as mounted in a bott~m casing section;
Fig. 7 is a bottom view of the casing assembly showing the gimbal plates and printed circuit board with the rotary : devices in place;
Fig. 8 is a plan view of the base plate and printed circuit board with the rotary devices in place:
Fig. 9 is a plan view in ~ection of a portion of the rotor;
Fig. 10 is an elevation view of a strip of film having alternately exposed and unexposed regions;
Fig. 11 is a plan view of a window chambers showing alignment of-exposed regions in one window and non-alignment in the other; and A
Fig. 12 are two ~et~ of output wave forms from the two deteckors in the windows corresponding to clockwi8e ~nd counterclockwise xotation for re~pective left and right detector~.
g3S'~8 DETAILED DESCRIPTION WITH REFERE:NCE TO THE DRAWINGS
The present invention i5 particularly u6eful in a joystick, an example o~ which is hown in Figures 1-6.
The joystick ~s shown in Fig . 1, ~ n exploded ~orm, consist of a handle 10 coupled to a casing 12 having an upper casing section 13 and a bottom casing section ~1. The handle lo includes a padded handle grip 11, a thumb button housing 19 at the top of which is lo~ated a thumb microswitçh button 18.
8elow the handle grip 11 is a handle housing 41 which supports a handle ball 36 having two oppositely disposed ball pins 42 and a gimbal ring actuating sphere 38.
An annular handle collar 34 fits between hand~e housing 41 and handle ball 36. Collar 34 includes a pair o:E o~positely disposed ball pin collar sl~ts or keyways 40 which ~lidably receive ball pins or keys 42. As shown in Fig. 3, collar 34 has a sloped interior surface 23 which abut~ ball 36 and permit~
pivotal ~otion of the handle lO in a spherical arc but prevents rotation thereof when the pins 42 are engaged with slots 40~
Casing 12 houses a base plate 44 (see Figs. 4 and 5) which has a collar receptable 22 formed on an upper 6urface thereof and a ball base plate contact ~urface 24 which contacts ball 36. Contact ~urface 24 has formed therein two oppositely dispo~ed ball pin ba~e plate ~lots or keyways 26 dimensioned and positioned to slidably receive ball pins or Xeys 42. Below the base plate 44 is mounted a pair of gimbal plates 27 and 29 (see ~g. 4). Annular gimbal ring or bushing 52 i5 mounted between a pair o~ overlapping central plate openings 51 and 53 as ~hown.in FigO ~. Ackuating sphere 38 passes into annular ring 52 and engage6 the latter.
9 ~93S'~13 Collar 34 has a plurality of radially spaced apart receptacle keys 43 which are positioned and dimensioned to be snugly ~lidably received in receptacle keyways 35. A pair o~
firing buttons 14 and 16 are ~ounted on the casing to actuate microswitches 136 and 138 (see Fig. 5) located within the c~sing 1~. A cabl 32 ho~sing a plurality of electrical leads passes in to the casin~ 12 through a cable guard 37 that prevents movement of the ~able 32 into or out of the casing 12. The tensioning wheel 30 i8 rotatably mounted w:ithin the casing 12 and extends through slots 81 and 83 in the latter to provide adjusting surface portions thereof.
As shown in Fig. 4, a base plate 44 is mounted as an upper casing section 13 by means of a locate lip or positioning tab 110 snugly, ~lidably insertable into a lip or tab receptacle 116 in casing section 134 and ~ locate or positioning plug 112 snugly, slidably insertable into a plug receptacle 114. At one end of the base plate 44 there is affixed a printed circuit board 118 having three rotary wheel apertures 127, 128 and 131.
The bottom edge of the upper casing section 13 has an upper casing rim 15 which extend~ bel~w an upp~r casing shoulder 17 adjac~nt to, but interior with respect to the rim 15.
Thre~ rim slots 120, 122 and 124 are formed oppo6ite the corresponding rotary wheel apertures 127, 129 and 131, respectively.
The bottom surface of base plate 44 has four radially di~posed ~heel guide pins 108. Also formed in the bottom of ba~e pl~te 44 are a plurality of radially outwardly directed base plate pring wall~ 90, 92, 94 and 96. Intermediate paced apart walls 90 and 92 ~re central positioning ribs 98 and 100, respectively. A pair o~ orthogonally disposed gi~bal plates 27 ~nd 29 ¢ach have a pair of arcuate ~lots 64 and 62, and 58 and ~ 9354~3 60, respectively formed therein. Posts 66, 68, 70 and 72, respectively, slidably ~it through corresponding slots 58, 60, 62 and 64, respectively. Thus, the gimbal plates 27 and 29 are orthogonally 81 idable with re~pect to one another. Each o~
gimbal plates 27 ~nd 29 has a pair vf opposed rectangular ~lots 86 and 88, and 82 and 84, respectively. Along an ~dge parallel to the direction of ~liding movement on each of corresponding gimbal plates 27 and 29 i~ ~ormed a U-shaped ~lot 78 and 80, respectively, which ~lots are adapted to slida~ly receive an end of lever arms 74 and 7Ç, respectiYely. Lever arms 74 ~nd 76 are coupled to the wiper arms of potentiometers 132 and 134 as shown in Fig. 5. Thus, rotation of the the lever arms 74 and 75 causes movement of corresponding wiper arms of potentiometers 132 and 134, respectively.
Lower gimbal plate 29 has a central outer opening 61 and a concentric slightly smaller inner opening 51 joined by a lower gimbal plate ~houlder 56. Similarly, a spaced apart upper gimbal plate 27 has an upper gimbal plate ~houlder 54 joining an outer opening 55 and a concentric inner opening 53.
: ~i~bal ring or bushing 52 has a pair of opposit~ly disposed small sleeves 46 and a single central large sleeve 48.
Large ~leeve 48 is ~lidable on ~houlders 54 and 56, respectively. Four posts 210, 212, 214 and 216 are ~paced proximate the corner of upper casing 6ection 13. A hole 106 in ~a~e plate 44 provides an access ~upport for le~ding electrical cable from one ~ide of plate ~4 to the other.
. The upper ~urface o base plate 44, a~ illustrated in Fig. 5, contains a cylindrical collar receptacle wall 33 forming a collar receptacle wall 33 and accommodates receptacle keys 43 Lvcate or po~itioning plug 112 i~ formed so as to Z93~4~
accommodate an adjusting ~crew 45 between two ~pacing legs 140.
On a threaded end of ~crew 45 is registered a nut 47 having a fork end 49. Fork end 49 fit into a slot (not shown) in a post 57 which prevents rotational ~ovement of nut 47 in response to rotation of screw 45. Post ~7 is integral with a ~leeYe 59 capturing potentiometer 134 in a firm, non slipping engagement.
A si~ilar arrangement (not shown) is used with respect to lorate lip or positioning tab 110 and potentiometer 132.
Printed circuit board 118 has mo~mted thereto a pair of microswitches 138 and 136 on top of which are placed firing buttons 16 and 14, respectively. Rotary wheel switches 121, 123 and 125 having wheel axles 144, 146 and 148, respectively are mounted against the printed circuit board 118 with the axles 144, 146 and 148 slidably inserted through apertures 127, 129 and 131, respectively. A pair of contacts on each wheel 121, 123 and 125 (not shown) are used to contact a set o~ three different pads ~not 6hown) on printed circuit board 118~
On the periph~ry of base plate 44 ~as shown in Figs. 4 and 5) is a tension ring button 65 formed at the end o~ a finger in the base plate 44.
The tensioning wheel 30 is sh~wn in Fig. 6 as it is mounted on a bottom casing section 21. An upper annular surface of wheel 30 rotates around the outside of wheel guide pin6 lOg on base plate 44 as 6hown in Fig. 4 and around corresponding ridges (not shown) in the bottom casing ~ection 21. On the interior cylindrical surface ~f the tensioning wheel 30 there is 8 set of four radiaIly ~paced integral cams t 58, 160, 162 and 164 having gen~rally 6erpentine cam ~urfaces. On the bottom ca6ing there i5 form~d a ~et of four equally, radially ~paced ~part ~pring wells 171, 173, 175 ~nd 177, generally directed toward a center of the tensioning wheel 30 and interior 12 ~L~Z93S~E~
thereof. Spring well 171 is formed by vertical walls 150, ~51 and 153; spring well 173 is for~ed by vertical wallB 152 ~ 155 and 157; 6pring well 175 is ~oxmed by vertical walls 154, 159 and 161; while spring well 177 i~ formed by vertical walls 156, 163 and 16S. The walls 150 and 151 align with wall6 30 on the base plate; walls 152 and 155 align with ~lalls g6: wall~ 154 and 159 align with walls 92; and walls 156 and 163 align with walls 94. Sufficient space i8 allowed be~ween t~he sets of aligned walls to permit gimbal plates 27 and 29 to ~lide back and forth. Spring wells 171, 173, 175 and 177 each have spring cups 182, 184, lB6 and 188 ~lidably contained therein. Coil springs 174, 176, 178 and 180 are inserted into corresponding respective cups 182, 184, 1~6 and 188 and at an opposite end contact ball bearings 166, 168, 170 and 172, respectively. Radial edges of cams 158 and 162 contact walls 152 and 163, respectively, at one end of the adjustment position. The wheel 309 is rotatable in a clockwise direction as ~hown in Fig. 6. Casing 21 has an interior bottom casing rim 31 which extends beyond a bottom casing shoulder 25 and abuts top casing rim 15. Three rotary wheel bottom ~ection rim slots 126, 128 and 130 are formed in bottom casing section 21 and coincide with corresponding slots 124, 122 and 120, respectively, ~f the top casing ~ection 13.
Three rotary switch ~upport walls 190, 192 and 194 each forming a portion of a cylindrical wall, are located proximate coresponding slots 126, 128 and 130, respectively. Each support wall has three notches 196, 198 and 200 formed therein at radially ~paced apart positions in the top edge thereof for contacting a corresponding detent i~ each o~ wheels 121, 123 and 125 in order to mark the three separate switch positions. (The det~nt in wheel~ 121, 123 ~nd 125 are not shown.) Four bottom casing posts 218, 220, 222 and 224 disposed proximate each of the four corners of the bottom casing ~ection 21 register with corre~ponding top casing posts 214, 212, 210 and 216, respectively. Screws passi~g through the posts 218, 220, 222 3S~1!3 and 22~ threadedly register with threaded hole~ in corresponding top casing posts 214, 212, 210 and 216, r~spectively. Base plate 44 is affixed to ~ottom ca~ing 21 by means of casing posts 202, 204, 206 ~nd 108 which register with ,gi~bal plate guide posts 68, 6~ 72 and 70, respectively are u~ed to affix the base plate 44 to the bottom casing section Zl. ~paced apart grooves 225, 2~6 and 227 in ~ top surface of tensioning wheel 30 successively engage tension ring bu~ton Ç5 on base plate 44 in the first three tension settings.
Formed in each long side of casing ~ection 21 are a pair of tensioning wheel slots 81 and 83 which are used to provide user access to the tensioning wheel 30.
In operation, when handle lO is tilted in ~ particular direction, ball 36 rotates against collar ball contact 6urface 23 and ball base plate contact surface 24. At the same time cylindrical pins 42 rotate and pivot vertically in ball pin base plate 610ts 26 and ball pin collar 810ts 40. Gimbal ring actuating sphere 38 forces g~mbal ring 52 against upper and lower gimbal plate openings 53 and 51, respectiv~ly. In response, gimb~l plates 27 and 29 each move in a direction determined by the movement of actuating sphere 38. Gimbal plate 27 is constrained to move in a linear direction as determined by the contact of gimbal plate 610ts 62 and 64 against guide posts 68 and 72, respectively. Similarly, gimbal plate 29 moves in a direction ~onstrained by the movement of ~lots 58 and 60 past guide posts 66 ~nd 70, respectively. Movement of gimbal plates 27 ~nd 29, in turn, result in U- haped ~lots 80 and 78 pivoting pot~ntiometer coupling arms 76 and 74 respecti~ely.
The l~tter pivoting ~rms are coupled to the wiper 2rms (not ~hown) of potentiometer6 134 ~nd 132, respectively. Thus, ~ove~ent O~ each wiper arm of each potenti~meter 132 ~nd 134 ~ay ~e obtained by adju~tment o~ a corresponding adjusting ~crew 45 1~ ~Z9354~3 such as that of potentiometer 134 ~hown in Fig. 5.
A~ screw 45 i~ rotated, nu~ 47 travels along the threaded portion thereof thereby moving the casing of potentiometer 134. ~he wiper arm at the 6ame time i~ held in a fixed position by means of th ~-~haped ~lot 890 of gimbal plate 27. A ~imilar adjustment i~ available ~or potentiometer 132.
In the event a user desires a change in biasing on the handle 10, this i~ ~ccomplished by rotation of tensioning wheel 30. As tensioning wheel 30 rotates in a clockwise position as shown in Fig. 6, cams 158, 160, 162 and 164 begin to engage ball bearings 166, 168, 170 and 172 respectively, forcinq the latter to compress associated springs 174, 176, 178 and 180, respectively. This in turn causes a compression force to be generated against associated spring cups 182, 184, 186 and 188, respectively. Spring GUpS 182 and 186 contact gimbal plate 29 at slots 82 and 84, respectively, thereby applying opposing biasing forces to the latter. Similarly, ~pring cups 184 and 188 contact gimbal plate 27 at 810ts 86 and 88, respectively.
The more tensioning wheel 30 i5 rotated in a clockwise direction, the more compression is applied to coil ~prings 174, 176, 178 and 180, thereby providing a greater biasing o$ gimbal plates 27 ~nd 29 when moved from the neutral position.
Alternatively, 6pring biasing can be disconnected altogether from the handle by ~imply rotating tension wheel 30 in a complete counterclockwise direction until cam ~urfaces 162 and 158 abut walls 163 and 152, respectively.
A~ een in Fig. 5, micr~switches 138 and 136 ~re ncluded to provide ~iring buttons. ~imilarly, button 18 a~
~h~wn in Fig. 1 ~t the top end of handle 10 i~ provided as a fire button operable by the thumb of a user of the ~a~ hand that i8 ueed to aanipulate handle 10. Button 18 actuates a ;
microswitch ~not shown~ looated inside thu~b button hou inq 19.
Handle 10 is hollow ts permit wires to connect to the latter microswitch (not ~hown).
Initially, rotary wheel awitches 121, 123 and 125 are rotatea to a desired p~sition depending on the particular ~achine with which the joy~tick i~ to be u~ed. Secondly, tensioning wheel 30 i6 adjusted to provide the desired biasing force to handle 10.
The Joystick of Figures 1-6 i~ modified by replacing p~tentiometers 132 and 134 by a rotary assembly 321 a~ shown in Figs. 7 and 8. Rotary assembly 321 has a fixed portion 319 fixed to the base plate 44 by ~ans of locate pins 323. The rotary portion 310 on each rotor assembly 321 i6 coupled to rotary arms 74 and 76, ~imilar to the potentiometer~ of Fig. 4, and received by U-shaped slots 78 and 80, respectively. The rotary p~rtions 310 are thus operated in a similar ~anner as potentiometer wiper arms.
Referring to Fig. 3, there is shown ~ top view of a portion of the rotor assemhly 321 which includes a ~ixed casing 312 and a rotor 31~ rotatable with respect to the casing 312.
Attached to the casing 312 are a pair of reticle guides 318 for capturing and positionin~ a reticle 316.
A pair ~f slot~ 322 in the periphery of the rotor 314 ~erve to receive ~nd m~intain in position a ~oving unit of film 320 contiguous to the reticle ~trip of fil~ 316. Both 6trips of film pa~s through window chamber~ 326 and 328 affixed to the casing 312. At one end of the chamber~ 326 ~nd 328 are located light-e~itting diodes 330 and 332 while ~t the other extremity, on an opposite ~ide of the film ~trips 316 ~nd 320, are located light detector~ 334 and 336.
16 ~Z93S'~3 As shown in Fig. lO, each o~ the fil~ strip6 corresponding to the reticle 316 and the ~ovins unit 320 have alternating transparent ~40 and opaque 3~2 regions correspo~ding to exposed 340 and une~posed 342 regions of the film ~trip 338.
Referring to Fig. ll, exposed regions 344 transparent to light and une~pose~ regions 346 are shown aligned in a right window chamber 32~ and only partially in left window chamber 3260 Consequently, light detected by light detector 336 in the right window chamber 328 gives rise to a ~aximum signal output whereas that in the left window chamber detected by light detector 334 gives ri~e to an intermediate value of signal.
As film trip 320 moves in a counter-clockwise direction relative to reticle 6trip 316 the exposed regions 344 in the right hand window chamber 328 move from maximum light transmission to a diminishing level of light transmission as the exposed regions gradually move away from exact alignment. At the ~ame time the exposed regions 344 in the left hand window chamber approach maximum transmission as the exposed regions enter into exact alignment. Thus, curve 348 in Fig. 12 describes the 6ituation as would occur in the left window chamber 326 whereas curve 350 would correspond to that in the right window chamber 328. However, for clockwi e rotation in which moving unit strip 320 moves in a cloc~wi~e direction or to the left as shown in Fig. ll, the transmission in the left window chamber r~ther than increasing would decrease to a ~inimum as the expo ed regions 344 moved toward complete non-overlapping positions. Thus, curve 352 would correspond to the l~ft window chamber 326 for clockwise rotation wh~reas curve 354 would correspond to that of the right hand window chamber and would be substantially the same as for counter-clockwi~e rotation in the latter case.
Z9~54~
It will be appreciated that there will alway~ be a certain level of light transmis~ion through the film but it has been found that a 5 ~il thickness of film iB Fufficently thick to make the difference between ~aximum and minimu~ light transmission through the film trips 316 2nd 320 aufficiently great to be able to distinguish between the two po~itions.
Curves ~howing the output of the two detectors as a function of rotor angle as ~hown in Fig. 12 assum~ an ideal detector respons~ in which the detector outputs are in the form of sawtooth waves. However, amplitude limiting causes the output to be as ~own in the dotted lines 355. By directing the output 350 or 354 to a counter (not shown) and counting the number of pulses one can determine position of one coordinate in a two coordinate system.
In detecting the phase difference between the signal from one of detectors 334 an~ 336 and that ~rom the other, one can determine the direction o~ rotation of the rotor and hence the direction Qf ~o~ement along one dimension. For exa~ple, if output 348 which lags output 350 corresponds to that ~rom detector 330, then ~uch an output indicates film 320 i6 ~oving to the right in Fig. 12. Similarly, output 352 corresponds to movement of film 320 to the le~t in Fig. 4 In addition, by recording the rate at which pulses are detected it i~ possible to measure velocity and acceleration.
As ~hown in Fi~. 13, the output pulses from the light detectors ~ay be run to a 6ignal processing unit which will include electronic counter , ~nalog to digital converters, 6witch~s, etc. to ~elect position, velocity or acceleration ~odes a~ well a~ performing many other functions. ~ypically, two rotor~ would be installed $n a ~ingle ~oystick casing so as to provide ~eparate outputs for each of the two coordinate 18 ~9~S~
axes. By utilizing the cylindrical ~ymmetry o~ the rotor it i~;
possible to incorporate two such roltors into a relativley 6mall, flat base ~3tructure. 2~oreover, the use of standard acetate photographic film permits one to obtain highly dense ~qui-spaced alternating transparent and opaque regions,. The use of two such film strips provide6 an inexpen6ive, compact, accurate optical encoding ~ystem. A standard commercially availabl~ ultra violet curable lubricant on the film protects it :Erom cratches and reduces the friction between the film strips. One can easily achieve 1200 counts ~or rotation through an angle of less than 70 with such a system.
Clearly, any kind of mechanical coupling between the joystick lever and each of the rotors can be implemented in order to effect rotational movement of the rotor in proportion to displacement along a selected corresponding axis.
Accordingly, while this invention has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various ~odifications of the illustrative embodiments, as well as other em~odiments of the invention9 will be apparent to persons ~killed in the art upon reference to this description. It is therefore contemplated that the ~ppended claims will cover any ~uch ~odifications or embodiments as fall within the true cope o~ the invention.
.
Claims
WE CLAIM:
1. An optical encoder, having a base, comprising:
(a) a reticle having alternating transparent and opaque areas mountable in a cylindrically disposed position on said base;
(b) a pair of spaced apart window housings mounted on said base, each housing having a chamber which defines spaced apart light paths through said reticle;
(c) a light emitter in each of said window chambers on a given side of said reticle;
(d) a light detector in each of said window chambers on a side of said reticle opposite to said given side for detecting light from associated ones of said light emitters;
(e) a moving unit cylindrically disposed to and concentric with said reticle having alternating transparent and opaque areas substantially matching those of said reticle, and movable with respect to said reticle through said pair of window chambers intermediate said light emitters and light detectors such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment and such that as said moving unit is moved relative to said reticle a periodic variation in light transmission through said moving unit and reticle in each of said window chambers is produced and the transparent regions of said moving unit move into full alignment with the transparent regions of said reticle in one of said window chambers while in the other of said window chambers the transparent regions of said moving unit are non-aligned with those of a corresponding one of said reticles such that light transmission through the other window chamber is substantially reduced from that in said one window chamber and quadrature is achieved so as to permit detection of both motion and direction of motion;
and wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
2. An encoder according to claim 1, wherein the thickness of each of said strips is approximately 5 thousandths of an inch.
3. An encoder according to claim 2, wherein said strips of film are in contact throughout each of said windows.
4. An encoder according to claim 1, wherein said transparent and opaque regions are linear, of constant width and transverse to the length of each associated moving unit and reticle.
4. An encoder according to claim 1, wherein each of said strips are coated with a transparent hardened film to inhibit scratching of contacting surfaces of said strips.
6. An encoder according to claim 2, wherein said casing is opaque.
7. An encoder according to claim 1, wherein said light emitters are light emitting diodes in respective ones of said windows and said light detectors are photosensors mounted in respective ones of said window chambers on a side of said reticle and moving unit opposite to said light emitting diodes.
8. An optical encoder, comprising:
(a) a casing;
(b) operating means coupled to said casing for developing movement translatable into two dimensions;
(c) an optical encoder affixed to said casing having a base, a rotor rotatably attached to said base and coupled to said operating means and a pair of spaced apart window housings affixed to said base each housing defining a respective window chamber;
(d) a light emitter in each of said window chambers on a given side of said reticle;
(e) a light detector in each of said window chambers on a side of said reticle opposite to said given side for detecting light from associated ones of said light emitters;
(f) a reticle mounted on said base in a cylindrically disposed position traversing each of said window chambers and having alternating transparent and opaque areas;
(g) a moving unit mounted on said rotor, movable through said window chambers, concentric with and juxtaposed to said reticle, having alternating -transparent and opaque areas substantially matching those of said reticle but spaced such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment as said moving unit moves, and such that as said moving unit is moved past said reticle, a periodic variation of light transmitted through said reticle and moving unit results in the transparent regions of said moving unit becoming fully aligned with those of said reticle in one of said window chambers and being non-aligned in another of said window chambers;
wherein the coupling between said operating means and optical encoder is such as to rotate said rotor through an angle substantially linearly proportional to an angle of pivoting of said operating means in a predetermined plane; and wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
9. A joystick according to claim 8, wherein said reticle and moving unit are each strips of exposed photographic film with alternating exposed and unexposed regions corresponding to said transparent and opaque regions, respectively.
10. A joystick according to claim 9, wherein said reticle strip and moving unit strip are approximately 5 thousands of an inch in thickness.
11. A joystick according to claim 8, wherein said reticle strip is in contact with said moving unit strip through each of said windows.
12. A joystick according to claim 11, wherein the exposed regions on said reticle and moving unit are equi-spaced linear bands transverse to the length of each of said reticle and moving unit.
13. A joystick according to claim 12, wherein the spacing between adjacent transparent regions on said reticle are the same as those on said moving unit.
14. A joystick according to claim 13, wherein the width of transparent and opaque regions on each of said moving unit and reticle are equal.
15. A joystick according to claim 18, wherein said operating means is a lever.
16. A joystick, comprising:
(a) a casing;
(b) a lever pivotally coupled to said casing and pivotal about a point along the length thereof;
(c) a pair of optical encoders coupled to said lever so as to respond to a component of pivotal movement of said lever in each of two orthogonal planes with a first one of said pair providing a number of output pulses proportional to an angle of pivoting in one of said planes and a second one of said pair a number of output pulses proportional to an angle of pivoting in another of said planes wherein each encoder includes:
(d) a base;
(e) a rotor rotatably attached to said base and coupled to said lever;
(f) a pair of window housings affixed to said base said housings defining respective window chambers;
(g) a reticle mounted on said base in a cylindrically disposed position traversing each of said window chambers and having alternating transparent and opaque areas;
(h) a moving unit mounted on said rotor, concentric with and juxtaposed to said reticle movable relative to said reticle and having alternating transparent and opaque areas substantially matching those of said reticle but spaced such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment and such that as said moving unit is moved past said reticle, a periodic variation of light transmitted through said reticle and moving unit results with the transparent regions of said moving unit becoming fully aligned with those of said reticle in one of said windows and 90 out of full alignment in another of said windows;
(i) light emitting means in each of said chambers for directing light onto said reticle and moving unit; and (j) light sensing means in said window chambers for detecting light from a corresponding one of said light emitting means after its transmission through said reticle and moving unit;
wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
17. A joystick according to claim 16, wherein said reticle strip is in contact with said moving strip through each of said windows.
18. A joystick according to claim 17, wherein the exposed regions on said reticle and moving unit are equi-spaced linear bands transverse to the length of each of said reticle and moving unit.
19. A joystick according to claim 18, wherein the spacing between adjacent transparent regions on said reticle are the same as those on said moving unit.
20. A joystick according to claim 19, wherein the width of transparent and opaque regions on each of said moving unit and reticle are equal.
21. A joystick according to claim 17, wherein said reticle strip and moving unit strip are approximately 5 thousands of an inch in thickness.
1. An optical encoder, having a base, comprising:
(a) a reticle having alternating transparent and opaque areas mountable in a cylindrically disposed position on said base;
(b) a pair of spaced apart window housings mounted on said base, each housing having a chamber which defines spaced apart light paths through said reticle;
(c) a light emitter in each of said window chambers on a given side of said reticle;
(d) a light detector in each of said window chambers on a side of said reticle opposite to said given side for detecting light from associated ones of said light emitters;
(e) a moving unit cylindrically disposed to and concentric with said reticle having alternating transparent and opaque areas substantially matching those of said reticle, and movable with respect to said reticle through said pair of window chambers intermediate said light emitters and light detectors such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment and such that as said moving unit is moved relative to said reticle a periodic variation in light transmission through said moving unit and reticle in each of said window chambers is produced and the transparent regions of said moving unit move into full alignment with the transparent regions of said reticle in one of said window chambers while in the other of said window chambers the transparent regions of said moving unit are non-aligned with those of a corresponding one of said reticles such that light transmission through the other window chamber is substantially reduced from that in said one window chamber and quadrature is achieved so as to permit detection of both motion and direction of motion;
and wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
2. An encoder according to claim 1, wherein the thickness of each of said strips is approximately 5 thousandths of an inch.
3. An encoder according to claim 2, wherein said strips of film are in contact throughout each of said windows.
4. An encoder according to claim 1, wherein said transparent and opaque regions are linear, of constant width and transverse to the length of each associated moving unit and reticle.
4. An encoder according to claim 1, wherein each of said strips are coated with a transparent hardened film to inhibit scratching of contacting surfaces of said strips.
6. An encoder according to claim 2, wherein said casing is opaque.
7. An encoder according to claim 1, wherein said light emitters are light emitting diodes in respective ones of said windows and said light detectors are photosensors mounted in respective ones of said window chambers on a side of said reticle and moving unit opposite to said light emitting diodes.
8. An optical encoder, comprising:
(a) a casing;
(b) operating means coupled to said casing for developing movement translatable into two dimensions;
(c) an optical encoder affixed to said casing having a base, a rotor rotatably attached to said base and coupled to said operating means and a pair of spaced apart window housings affixed to said base each housing defining a respective window chamber;
(d) a light emitter in each of said window chambers on a given side of said reticle;
(e) a light detector in each of said window chambers on a side of said reticle opposite to said given side for detecting light from associated ones of said light emitters;
(f) a reticle mounted on said base in a cylindrically disposed position traversing each of said window chambers and having alternating transparent and opaque areas;
(g) a moving unit mounted on said rotor, movable through said window chambers, concentric with and juxtaposed to said reticle, having alternating -transparent and opaque areas substantially matching those of said reticle but spaced such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment as said moving unit moves, and such that as said moving unit is moved past said reticle, a periodic variation of light transmitted through said reticle and moving unit results in the transparent regions of said moving unit becoming fully aligned with those of said reticle in one of said window chambers and being non-aligned in another of said window chambers;
wherein the coupling between said operating means and optical encoder is such as to rotate said rotor through an angle substantially linearly proportional to an angle of pivoting of said operating means in a predetermined plane; and wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
9. A joystick according to claim 8, wherein said reticle and moving unit are each strips of exposed photographic film with alternating exposed and unexposed regions corresponding to said transparent and opaque regions, respectively.
10. A joystick according to claim 9, wherein said reticle strip and moving unit strip are approximately 5 thousands of an inch in thickness.
11. A joystick according to claim 8, wherein said reticle strip is in contact with said moving unit strip through each of said windows.
12. A joystick according to claim 11, wherein the exposed regions on said reticle and moving unit are equi-spaced linear bands transverse to the length of each of said reticle and moving unit.
13. A joystick according to claim 12, wherein the spacing between adjacent transparent regions on said reticle are the same as those on said moving unit.
14. A joystick according to claim 13, wherein the width of transparent and opaque regions on each of said moving unit and reticle are equal.
15. A joystick according to claim 18, wherein said operating means is a lever.
16. A joystick, comprising:
(a) a casing;
(b) a lever pivotally coupled to said casing and pivotal about a point along the length thereof;
(c) a pair of optical encoders coupled to said lever so as to respond to a component of pivotal movement of said lever in each of two orthogonal planes with a first one of said pair providing a number of output pulses proportional to an angle of pivoting in one of said planes and a second one of said pair a number of output pulses proportional to an angle of pivoting in another of said planes wherein each encoder includes:
(d) a base;
(e) a rotor rotatably attached to said base and coupled to said lever;
(f) a pair of window housings affixed to said base said housings defining respective window chambers;
(g) a reticle mounted on said base in a cylindrically disposed position traversing each of said window chambers and having alternating transparent and opaque areas;
(h) a moving unit mounted on said rotor, concentric with and juxtaposed to said reticle movable relative to said reticle and having alternating transparent and opaque areas substantially matching those of said reticle but spaced such that alternating opaque and transparent regions of said moving unit and said reticle come into and out of alignment and such that as said moving unit is moved past said reticle, a periodic variation of light transmitted through said reticle and moving unit results with the transparent regions of said moving unit becoming fully aligned with those of said reticle in one of said windows and 90 out of full alignment in another of said windows;
(i) light emitting means in each of said chambers for directing light onto said reticle and moving unit; and (j) light sensing means in said window chambers for detecting light from a corresponding one of said light emitting means after its transmission through said reticle and moving unit;
wherein each of said reticle and moving unit are photographic film strips with alternating exposed and unexposed bands transverse to the length of the strips corresponding to said opaque and transparent regions, respectively, wherein the bands on one of said film strips being of equal dimensions and equispaced and having the same dimensions and spacing as those on another of said film strips and said film strips are in sliding contact with one another so that reflections from surfaces of the film strips due to air gaps between the strips is substantially reduced.
17. A joystick according to claim 16, wherein said reticle strip is in contact with said moving strip through each of said windows.
18. A joystick according to claim 17, wherein the exposed regions on said reticle and moving unit are equi-spaced linear bands transverse to the length of each of said reticle and moving unit.
19. A joystick according to claim 18, wherein the spacing between adjacent transparent regions on said reticle are the same as those on said moving unit.
20. A joystick according to claim 19, wherein the width of transparent and opaque regions on each of said moving unit and reticle are equal.
21. A joystick according to claim 17, wherein said reticle strip and moving unit strip are approximately 5 thousands of an inch in thickness.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000586745A CA1293548C (en) | 1988-12-21 | 1988-12-21 | Optical encoder |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000586745A CA1293548C (en) | 1988-12-21 | 1988-12-21 | Optical encoder |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1293548C true CA1293548C (en) | 1991-12-24 |
Family
ID=4139353
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000586745A Expired - Fee Related CA1293548C (en) | 1988-12-21 | 1988-12-21 | Optical encoder |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1293548C (en) |
-
1988
- 1988-12-21 CA CA000586745A patent/CA1293548C/en not_active Expired - Fee Related
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