CA1290848C - Optical memory - Google Patents

Abstract

OPTICAL MEMORY
ABSTRACT

Disclosure is made of an optical memory wherein a cylindrical information carrier having a recording coat-ing applied on a tubular base and disposed in a sta-tionary cylindrical container provided with a window in the lateral surface thereof. A lens is secured in said window of said cylindrical container to let through a radiation flux from a source of modulated coherent radiation. The cylindrical container is filled with a liquid or gaseous medium transparent for the radiation flux and is twice as long as the recording coating applied on the tubular base of the cylindrical in-formation carrier equipped with drives for rotation and axial movement.

Description

OP~IOAL ~ ORY
This inve~tlon relates to i~form~tion storage devices and? in particular, to optlcal memories.
~ he present in~r~ntion can be u~ed in computers, video and sound recordi~g device~, information storag~ ~nd pro~
ces~ing system~, in particular9 in external memories for ccmputers.
Intolli~enc~ of computers is largely ~ependent o~ the ~ophi~tication of their ext~rllal memory. At presen~, the overall spe~d of oomputers is low~r by two or three orders tha~ that o~ their corG~uti~g units precisely becaus~
OI inadequate exter~al memori~. Basic technic~l charac-teristics of external memories includ~ informa~ion capacity, recording de~sity, access time, inf ormation excha~ge speed, and storage r~liability. Optical external memorie~
possess certain advantage~ a~ contrasted to magpetic external memories, such as lar~er capa~ity, great~r den~ity an~ reliabilit~ and ~r9 therefore mor~ promising.
~ now~ in the axt is an optical memory (JEE~ Spectrum, 1979 7 ~ 2, pp9 33-38) comprising a source oi mo~ulat2d coherent radlation including a laser and a modulator a~d optically connected with a mo~able information carrier mad~ as a ~aaled optical di~k~ a recordi~ medium being coated on the internal ~urface~ of tra~sp~rent wall~ of the diskp and an i~for~atio~ addre~sin~ un~t.
Howev~r thi~ ~ptical mo~ory i~ ~e~ t in ~hat it i~ not v~ry r~liable and its resording density is not su~ ientl~ high. It i8 ~ot reliable b~c~u3e th~ optiGal dis~ is rather fr~gils and, al~o, bec~u~ the wo~kin~
~urfa~ o~ th~ optical disc tend to d~orm by chan~e~

in the atmospheric pressure. Low recording deasi~y i9 due to variations in recording density for stora~e tracks having different radii~ '~he resolution of the "dry"
ob~ectiv~ lens in the movable optical head is low which ~dds to this disdvantage, the numerical aperture of the lens cannot be larger than one~
'rhe closest prior art, both technically and by the result obtained, i8 an optical me~ory (GB, A, 1 580 3~8) comprising optically con~ected eleme~ts: a source of modulat~d coherent radiation and a cylindrical inforulation carrier equipped with a rotational driv~. The cylindrical in~ormation carrier is a rigid nontransparent cyli~der whose external surface is covexed by a recording coating and which carries, by means o~ separating rings, an exter-nal relatively thin protective transparent cylinder, In the process o~ operation the external pl~tective transpa-rent cylinder rotate~ with the rigid nontrasparent cy-linder. 'I`he internal ~pace of the cylindrical infor~ation carrier is conmunicated with the atmosphere in order to avoid de~ormation of the external protective cylinder by changes in the atmospheric pressure.
But this optical inemory also has several disadvantages.
Its recordin~ ~ensity is low and it is not sufficiently reliable. Low r~cording de~sity i5 due to the fact that the recording coatin~ used to register information ca~ be applied only on the e~ternal surface of the ri~id no~transparent cylinder and, also, due to the uss of a "~ry" objective lens having a low nu,nerical aperture.

This optical ~emo~ is ~ot reli~ble b~cau~e the internal space o~ the cylindrical inforlllation carrier ~s not sealed oXf ~rom the environment and, when the temperature conditions of the carxier cha~lg~ in the process of operation i~ relation to th~ temperature of the enviFonment~ this carrier "breathe~" in or out. The internal space suck~ in large amounts of dust, moi3tllre, and other ~oreign bodies which a:re depo~ited o~ the surface of the recording coating, which substantiall~
reduces reliability of in~ormation readin~s-recording.
The reliability OI this prior art raemory devicc i~ also a~fecited because the surfac~ o~ the pro tective c;ylinder is ofterl dama~sed in the process o~ its fa~t rotation.
It i~ an obj~ct of this invention to provide ~
optical m~mory ha~i~g a higher recor~ ; density and reliabi lit;y.
~ rhese objects are achieved in that in ~n optical memo~ coLprising a ~ource of ~odulated coh~rent radiati-on, which is opticall7 con~ected to a cylindrical i~-~ormation carrier equipped with a drive for rotat~ on, a~d provided with a recording coating applied on the sub~trate o~ the cyli~drical in~or~ation carrier~
accordi~g to the in~ention, the cylindrical information carrier i~ disposed i~ a stationaIy ~ylindrical container having, i~ ~e ~ide wall thereof, a window wheroin a lens i~ placed to tran~mit modulated coherent radiation, said cyli~ldricaL container bei~g fille~ with a liquid ~ 4 or gaseous medium ~or th~ radiation fLux ~rom ~he source of modulat~d coherent radiation and th~ length OI said cylindric al container heing at l~ast twice as lar~se as that of the recording coati~g applied on thc substrate of the cylindrical information carrier equipped with a dri.Ye Ior axial ~llotion.
Since the proposed optical memory makes u~e o~ a stationary len~, it permits ,~uch bette~ adjustment o~
the optical sys~m9 the ~harpness o~ focu~i~g the flux of mo~ulated coherent radiatio~ on the sur~ace o~
the recording coati~g o~ th~ cylindrical in~ormation carrier ca~ be drastically improved. Si~ce the cylindrical i~formation carrier is arra~ed inside a stationar~ cy-lindrical container9 i t i~ well protected from da~age an~ dirt, thu~ ~aking i~ormation stor~ge more reliableO
The len~ is plaçed in a window in the wall oY the sta-tionary cylindrical container and, during addressing, the cylindrical carrier has to be axially moved in re-lation to the statio~ary contalner. The len~th o~ the inn~r space of the cyli~drical contai~er should, there-fore~ be equal to or exceed the double length o~ the recording coating o~ tho c~rlindrical information carrier.
Advisably, when the cyli~drical c ontainer is b~in~;
~illed with a ~aseous medium, th~ axial ~ive of the cylindrical information carrier shoul~ be the el~ctric linea;r ~rive who~e stationary part i9 ~isposed o~ the lateral wall OI the c~lindrical container, utlile the mo~abl~ part thereof i9 placed on at least one butt ~ g~3 container 3 i5 fllled with a gaseous medillm, e.g. air.
Butt facos o~ th9 cylindrical ~ontainer 3 are provided with openings 6 to which is conneGted a pipe-line 7 equipped ~ith a bidirectional pump 8 of th~ pneumatic drive uhich is~ in this embodi~en~, the drive ~or axial motio~ of the cylindrical lnformation carrier 2, ~ile th~ cy-lindriGal i~ormation carrier 2 performs as a piston o~
this pneumatic driv~. The cyli~der of this pneumatic drive is the c~lindrical container 3.
The cylindrical in~ormatio~ carrier 2 com~rls~s a tubular bas~ 9 tra~sparent for the radiat~on flux of the ~ource 1 of ~odulat~d coherent radiatio~ A recording coatirlg 12 i~ applied el the ~xternal and intern~l sur-fa~e3 10 and 11 of the tubular ba~ 9. It is possible that the recording layer 12 may be applie~ to only one ~ur~aco 10 or 11 o~ th~ tubular base 9. A protectiva coati~g 13 is al~o àpplied over the rscording coating 12.
The recordin~3 coating 12 on the tubular bas~ ~ may, for example, be a chalcogenid~ yer, while the protective coatin~; 13 ma~ be made from metallic oxides, e.g. ferric o~id~ ~23D
A radial impermeable partition 14 is ~ecured on one of the butt faces OI the tubular base 9. A rotor 15 o~
'`"~? motor ~or rotatin&s the cylindrical imorL~ation carrier 2 is i~stalled on this radial parti~,ion 14, while a 3tator 16 of thi~ ~o~or is installed on tho lateral surfac~ o~ the cylindrical container 3. ~he length o~ the cylindrical co~tainer 3 i9 at least t~ice as long in the worki~g fluid m~dium.
The inventio~ will now be de~cribed in mor~ detail with re~erence to specific embodilsonts thereo~ a~d ac-compa~ying drawings wherein:
Fî~. 1 shows a goneral sec~ion vlew o~ an optical memory accor~ing to the inYention;
Fi~. 2 shows a vlew of an optical memory equipped with a drive for axial motion o~ ~he cyli~drical .in-~ormation carrier9 which is made as an electric linear dri~re, according to the invention;
Fig. 3 shows a view of an optical memo~ rein th~ cylindrical contai~er is ~illed with a liquid medium and th~ drive for axial motion o~ the cylindrical'~
foxmation carrier provided wlth one i~p~rmeable radial partition is a bidirectional hydraulic drive, according to ths invention;
Fi~; . 4 sho~s the vi ew o~ Fig . 3 wherein ~e cy-lindrical information carrier is fitte~ with two impermoabl~
radial partitions, according to the invention.
An optical memo~ comprises~ according to the i~ven~ion, a sourc~ 1 of modulated coherent radiation and, optically conn cted ~hereto, a ¢ylindrical i~formation carrier 2 dispose~ i~ a statiorlar;y cylindrical container 3 made o~ a non-transparent material, 9 wh as metal " alloy3 pla~tic. A wi~ow 4 is provided in the lat~ral sur~ae~ o~
the containel 3 and a lens 5 i5 secured thero~ to let through the radiatio~l flux from th~ source 1 of modulated coherent radiatiorl. The inner spac~ o~ ~he cylindrical . 7 ~ac~ o~ the cylindrica1 movable information ~arrier.
It i~ al~o advisa~1e that, whe~ the c~lin~rical co~tainer i~ bein~ filled with a liquid medium, the drive ~or axial motion o~ the cyli~drical inPormatio~ c~rrler should be a reversible h~draulic driv~ who~e piston is the cyli~drical in'.'ormation carri~r and who~e eylinder is the cylindrical containert while the working fluid i8 the liq~i~ medium ~hich is deoirably a low-vi~cosity im-mer~ion oll.
It is desirable that at lea~t o~e impermeab1e ra~ia p~rtition should be pla~ed in the internal space of the cyli~drlcal information carrier.
It is also advisable that a protective coating ~hould be applied on the recording coatin~; provided on the base OI the cyli~drical inform~tion carrier.
Si~ce the cylindrical information carrier of the propo~ed optical memory i~ disposed within a ~ylindriGal Go~tai~er ~illed with im~ersion oil, the ~u~erical ap0rture o~ the objective lens ca~ be ~igni~icantly increased and the sharpnes~ of ~ocusing ~f the radiation ~lux can, thare~ore, be sub~ta~tially improYed. ~he axial hydraulic driva becomes extremely convenient for addres~i~
information. The cyli~drical in~ormatio~ carrier i~ pro-vided with impermeable radial partitio~ order to incre~e it~ h~dr~ulic resistance an~ improve the ef~iciency OI the hydraulic driv~. The purpose of ~he protective coating i~ to prolong the service life of the re~ording coating on the cylindrical i~ormatio~ G~rrier . 8 as the length o~ the recording coating 12 appl~ed on ~ne tubular ba~ 9.
~ he source 1 of modulat~d coherent ~adi~tion comprl-S~8 a laser 17, an optlcal modulator 18, and a polariza-tion divi~er 19, all optically connected. One output o~
the polarization divider 19 ls optically coupled, via a g.uarter wa~e plate 20, with the lons 5, while the other output of the polarization di~ider 19 is opt~cally coupled, via a lens 21, wit~ a photoreceiver ~2.
The optical memory cla~ med i~ this description ope-rates a~ follow~. Referanco tracks and servicc in~ormatio~ar~ recorded on the cylindrical in~ormation c~rrier 2 prior to pla~ing it into the cylindriGal container 3.
~hen the pipe-line 7 o~ th~ pneumatic drive ~or axial mo-tion o~ the cyli~drical in~ormation carrier 2 is con~ected to openi~g3 6 i~ ghe`~utt fac~ of the qtationary cy-lindrical container 3. The optical memory is ready for operation. When operatlng, the cylindric~l in~ormatio~
carrier 2 is rotated b~ the motor to a speci~ic speed, the 80urcæ 1 of modulated Goherent radiation e;~ts a low-power unmodulated radiation ~lux which corresponds to readout process. Tha radiation flux i8 r~flected frem th~ ¢ylindrieal in~ormation carrier 2 and i~ ,~odulated by ~ervice in~ormation recorded in the information track under the lens 5. The reflected radiation flu~ passes th~ quarter waYe plate 20 twicc, in th~ direct and rever~e directions. The polarizatioQ plan~ of the ~lux i5 cha~ged by 90, the radiation flu¢ is admitt0d to ~he polarization divid~r and~ further o~ to the photor~-~ - 9 ceivsr 22 wher~ the optical signal is converted into ~
electrical sig~al to be supplied to a control unit ~not shown~in the drawin~s for simplicity). ~he control unit proeesses the read out s0rvice informatio~ a~d extracts information o~ the numb~r of the tra¢k hit by the ra-diation flux. Thi~ in~or~ation is compared with Ghe n~mber of the in~ormatio~ track corresponding to a given add~ess a~d the control unlt i~tructs the pneumAtiG
drive ~or axial motion of the c~lindrical carrier 2 to switch o~er to a specific infor~ation track, Since the lens 5 is secur~d stationa~y on the cylindrical container 3, addressing process in the claime~ optical memory ia perfor~.ied by axial`.notions of the ~cylindrical i~ormatio~
carrier 2 in relation to the cylindrical container 3.
It is for this reason that the in~er space o~ the cy-Ilndrical contai~er 3 shoul~ be twice as long or even longer than the recording coating 12 on the cylindrical for~ation carrier 2. If necessary, an instruction ca~
be proàuced to re-focus the radiation ~lu~ ~rom th~
recordlng coatin~ 12 on the external surface 10 of the tubular base ~ to the recording coating 12 applied on the internal surface 11 or vise versa. When the control unit deter.~nes that th~ desired track is hit by tha radiation ~lux, i-t starts processing the readout service in~ormation to separate data on the n~nber of sector under the le~s 5. A~ter the control unit is satisfied that the desired address is ~ound, thereadout pro-cess is started to obtain the required in~ormatio~ or 1~

_ IO

recording of i~onrLation ~ed ~rom the control unit. To record, the si~;nal to be recorded is supplied to the optical modulator 18 and the inten~ity or some other quality of the radiation flux o~ the laser 17 is modulated.
Si~ce in -thi~ optical i~emory lens 5 through which the radiatio~ flux hi'is ~he recordin~ coating 12 is stationary on the Iixed cylindrical container 3, the optical system ca~ be very finel~ adjusted ~nd ~OCU~3 becoLaes m~ch ~ore sharp as co~pared to prior art de~ce~.
Besides, the cylin~rical co~ta:lner 3 protect~ the cylindrical in~ormation carri~r 2 ~rom dirt arld ~anage.
The cylindriGal information carrier 2 is still more protecte~ becauso the p~eui~atic syste~ is sealed of~.
~hi~ makes the recording and readout processes in ths proposed optical memory extremely reliable.
In another embodime~t OI the i~ention, a cyli~drical in~or~ation carrier 23 (Fig. 2 ) i9 s~aled by installing two impermeable radial partitions 24 a~d 25 in th~
butt ends of the tubular base 9.
In this embodiLQent, the recordin~ coa~ing 12 is applied onl~ on the int~rnal surface ll transpare~t for the radiation flux e~itted by the source 1 of ~odulated coherent radiation. A moving part 26 o~ an electric ~
drive ~or linear motion i~ ~ecured on the partition 24, while a stationary part 27 thereof is secured on the lateral surface of the cylindrical container 3. ~hc el~ctric drive for linear motion i9 at the ~ ~ time the drive for axial motio~ of the cyli~rical lr~orma-tion carrier 23. A rotor 28 of the electrlc motor i3 secured on th~ partition 25, while a stator 29 of the motor i9 secured or~ the lateral qurf~ce o~ t;he cylindric~l co~tai~er 3 and envelops the rotor 28., The motor is rotational drive o~ the cylindrical informatiozl carrier 23.
Butt f ac~s of the cylindrical co~tainer 3 ar~ provide~
with openi~g~ 6, a~ in the former embodimerlt of tho optical memory, but in thi~ case they are intended afi air inlets and outlets during a~ial motion6 o~ the cy-lindrical informatioll carrier 23. In all other respects the optical ~nemory o~ Fig. 2 i3 ~imilar to that o~ Fig. 1.
The operation of the optic~l memory of Fig. 2 is so~ewhat different. Since tha recording coati~g 12 is avai lable only on the i~ternal surf ac~ 11 o~ the transpare~t tub~}ax base ~, no com~arlds are required to switch over to the othor reco~ding coati~. In ali other respect~
the optical memor;~r o~ E`ig. 2 is analogous to that of Fig. 1.
In still another embo~lime~t o~ optical me~ory according to the inve~tion there is provided a bidirec-tio~al hydraulic driv~ for axial motion o~ a cylindrical information carrier 30 ~Fig, 3). In this ca~e, a pipe-line 31 i~ cons~ect~d to the cyli~drical container 3 via the opening~ ~ availabl~ in tho butt f ace~ thereof . Tha pipelille 31 is connected to a bidirectional h~ydraulic pUt~lp 32 o~ the bidirectio~al ~ydraulic drive. The cy-lindrical contairler 3 i8 filled with a flui~, c.g.

_ low-visco~it~ n~irsion oil 33, and has a len~ 5 secu~ed on tho lateral surface thereof. ~rhe cylindrical in-~orinatiorl carri0r 30 is arraLig~d within the cylindrical container 3. ~otors 34 o~ the motor for rotatiing the cylindrical information ci~rrier 30 axe i~stalled orl the hutt ~nds ther~o~ ? while stators 35 of tho motor are installed on the lateral ~urfaced o~ th~ cylindrici~
container 3, each stator 35 enveloping its rotor 34.
A recording coatin~ 12 and a proteCtiYe coating 13 ~ie applied on the exteril~l sur~acie 10 o~ a tubular base 36~ which is non-transparent for the radlation flux emitted by the source 1 of modulate~ coherent ra-diatiorl. Arl impermeable radial partition 37 i~; inst~led in the in~ier space o~ th~ tubuls~ bas~ 360 ~he c~ n~ri -cal container 3, lilce ii~ the other eilibodiiments, is at least twice as lon~ as the recording coating 12 on tho tubular base 36. ~h~ source 1 of modulate~ coherent ra~iation is oiimil~r to that of the optical memory o~
Figi~ 1~ In this embo~iment, the ii~mer~ion oil 33 is the workini~ fluid of the bidirei~tional hydraulic drive for axial ~otion of the cylindrical infori~ation carrier 3û, where the funGtion o~ th~ pi~ton is per~ormed by th~
c;ylinarical information carrier 30 and the ~unctio~
of the cylinder by the cos~tainer 3.
The optical ~emory according to the inv~ntion operates a~ ~ollowq~, During recor~ing, a radiatio~ L, in the visible or near i~frared r~nge~ is modulated and p~ojected by ~.~9~ 8 the l~n~ 5 o~ the recordin~ ~oatillg lZ of the ~ealed c;ylindrical i~for~atiorl carrier 30. ~hi~ modulated flux records informatiQn i~ t ~ desired addre~ he addressin~s proces~ is per~ormed by rotating tho ~ylindrlcal i~-for~ation carri~r 30 about it~ side the sta-tio~ry cyli~rlc~l co~tainer 3 ~d~ also, by its axial ilotions ~ected by thc bid~rectional h;ydraulic dri~e for axial moveme~lt~.
Durin~; readout, a radiatio~ ~lux i~ r~ot mo~ulated and weakened by the optica} modulator 18. ~he lens 5 proj~cts thi3 radiatio~ flux on the c;rli~drical in~or~
matio~ carri~r 30 whose ~oveme~ts ~re e~fected liks durin~ recording. ~he reYle~ted radiation îlu~ is mo-dulated by the signal recorded on the cylindrical in-formation carrier 30 and is ~upplied to th~ photorecei-ver 22 where it is conv~rted i;lto an electrical repro-duction signal.
The immersion oil 33 of low vi~cosit~9 which is fillin~; the cylindrlcal container 3 wherei~ the cyli~dri-cal in~ormation carrier 30 i9 placed, per.nit~ a higher numerical aperture of the len~ 5. Irhe ~radi atio~ flux i~ mo:re sharply focused on the recor~ing coating 12, thus increasing the information re~ording denRity.
Si~ce in this e~odiment the cylindric~l in~ormatio~
carrior 30 rotate~ in a low-viscosity Yluid ~edium 33 which can be compre~sed much less than air~ radial wobbling o~ th~ carrier c~linder during rotation i significantl;sr reduced. Thi~3 adds to a more sharp focus . . .

o~ the radiation ~lux.
In one more 0Inbodiment of the invention9 the optical memor~ ca~ be equipped with a b~ire¢t:Lonal hydr~ulic drl~e wherein a cyli~drical i~formation carri~r 38 (Fig.4) i8 pro~ided with two imper~eable radial partitions 39 lnstalled in the butt ends o~ a transpare~t tubular base 4~, the reoording coating 12 being applie~ onto ~he i~ternal surfa~e 11 thereo~.
In all other respects the desi~ o~ the optical me~ory as shown i~ Fig. 4 is a~alo~ous to that o~ Fig. 3.
In this embodiment the raliability o~ recording is still rnore improved because the re¢ording coatin~ 12 is not exposed to the immersi.on fluid 33. .lloreove~ ~ a dirt layer which rrlay occur on tho e~t~nal surface 10 o~
the tubular transpar0n~ base 40 i~ out~ide the ~OCU5 o~ the lens 5 and has no practical e~ect on the ope-ration of the optical memor;y accordin~ to the in~en tion~
~ o summarize, an optical merrlory described herein-above and its ~mbodiments can enslire more sharp focu~
o~ the inforr~ation-car~ring radiation flux anl a sub-~tantial re~pective rise in the recording densit;y"
In addition it makes reco~inæ more reliable.

Claims (7)

1. An optical memory comprising: a source of mo-dulated coherent radiation; a stationary cylindrical container provided in the lateral surface thereof with a window wherein a lens is fixedly secured to transmit a radiation flux from said source of modulated coherent radiation and filled with a liquid or gaseous medium transparent for the radiation flux; a cylindrical information carrier equipped with drives for rotational and axial motion, which is disposed in said cylindri-cal container and made as a tubular base, a recording coating being applied of at least one surface thereof;
the length of said cylindrical container is at least twice as large as that of said recording coating applied on said tubular base of said cylindrical information carrier.

2. An optical memory as claimed in claim 1, wherein, during filling of said stationary cylindrical container with a gaseous medium, said drive for axial motion of said cylindrical information carrier is an electrical linear drive whose stationary part is disposed on the lateral surface of said cylindrical container, while a moving part thereof is disposed of at least one of the butt faces of said cylindrical is information carrier,

3. An optical memory as claimed is claim 1, wherein, during filling of said stationary cylindrical container with said liquid medium, said drive for axial motion of said cylindrical information carrier is a bidirectional hydraulic drive whose piston is said cylindrical in-formation carrier, whose cylinder is said stationary cylindrical container, and the working fluid is said liquid medium.

4. An optical memory as claimed in claim 3, wherein said liquid medium is immersion fluid.

5. An optical memory as claimed in claim 3, wherein at least one impermeable radial partition is placed in the internal space of said cylindrical information carrier.

6. An optical memory as claimed in claim 1, wherein a protective coating is applied on said recording coating on said tubular base of said cylindrical in-formation carrier.

7. An optical memory as claimed in claim 3, wherein a protective coating is applied on said recording coat-ing on said tubular base of said cylindrical informa-tion carrier.