CA1084321A - Photographic encoding system using lenticular graticule and synchronous motion - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An improved camera and process of coding images and a product produced thereby is described in which an image of graphics is scrambled by operation of a pseudoscopic camera. The graphics and focal plane-type shutter are moved simultaneously relative to .
an objective lens and a graticule so as to produce an image of the graphics which will appear inchoate to ordinary vision. The image can be unscrambled by viewing the same through a graticule of the same nature as that used in the scrambling process.

Description

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This invention relates to coding and decoding graphics and more particularly to a system an~ method of producing scrambled or coded images, typically in printed form and for decoding the same.
The term "graphics" as used herein shall mean an object of which a photographic image can be formed and generally includes - two and three dimensional objects including photograph~, patterns, logos, figures, indicia, line work including alpha-~ - numeric characters, signatures, solids, continuous tone and .~ half-tone ma~erials, etc. ~ :
ID U.S. Patent 3,937,565 issued on February 10, 19i6, on Process of Coding Indicia and Product Produced Thereby, I
,. . . . ., -~ described a system and method of coaing an image of graphi~s so that the image cannot be easily recognized nor reproduced and cannot be readily decoded without speci~ic ~nowledge of the ~-articulars of the encoding process~ The system and me hod escrîbed employs an autostereoscopic camera for photographing ~^ ~ Ithe artwork so as to produce a parallax panoramagram. Spe~ifi-- ally, the camera includes a lenticular screen whereby a photo-i`l `~ ensitive element is placed in the combined image plane of ~h~
mera formed by the objective lens and lenticular screen.
~he image of the graphics to be coded is initially ~ocussed on he photosensitive element in the image plane of the camexa, - ith the camera "wide open'i so as to provide a relatively small epth o~ focus. The lens system is then "stopped down" by making the aperture stop of the camera smaller so as to increase the . . .,.
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: ¦depth o~ focus. The lenticular scree!n and photosensitive .
element are then moved longitudinally along the optical axis of ¦the camera either toward or away from the objective lens of the ¦camera to the edge of but within the limits defining the depth of : ¦~ocus. The shutter of the camera is opened to expose the photo-¦sensitive element to the light projected from the graphicsO During .: ¦exposure, the lenticular screen and photosensiti~e element are . Imoved together relative to the objective lens of the samera to - ~ :
- ¦ expose successive portions of the photosensitive element under-¦ lying the screen.. me relative movements are such that tha ~
point image of the subject center of the graphics will be recorded .
in.the c~nter of the photosensitive element as a blurred spot ~ ¦ which is moved progressively in the course of the relàtive movement : -¦ of the objective lens, lenticular screen and photosensitive element -: . The resulting images formed on the photDseDsitlve element ; is a lenticular dissection of the image of the graphics as ell aa an image in which the displacement between the subject . .
center ana the second conjugate point introduces a scrambling . .... ~.
~ actor. The scrambled image is essentially unrecognizabie and ~ ;.
.. : . cannot.readily be identified by unaided vi~ion. ~ j . . . ~.
. In order to reconstru~t, unscramble, or decode the .
crambled image, a second transparent lenticular screen of the .
. ame nat~re as the ~irst screen used in the coding process is .
~ -- mployed. The secona screen is registered, i.e., the lenticules .~ f the screen are oriented in a direction so that they are.in the .' . ' ' ' " . . , i ~ : . . . , . . . ' '~, ' : ' . -:~ - -3-: . ,, . . .
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same r~lationship to the scrambled irnage as the ~irst screen was positioned to the photographic irnage o~ the original graphics.
Once the second screen is properly registered, the viewer can .
easily see the unscra~bled image by ]Looking through the second ~ . screen.
: . Although ~his process and system may be satisfactory ~or .~ elatively small scale production, the relatively long expo~ure.
. ime necessary to expose each photosensitive element in the auto- .
: stereoscopic camera inhibits large scale production of scramble~
~ ; maging ph~tographic reproduction. Additionally, sinoe each photo-,: ensitive element is exposed within the depth of focus but spaced rom the image plane, even though the scrambled image wh~n decoded . . is discernable, it will not be in sharp focus as it would be had : -~ xposure of the photosensitive element occurred in the image plane. :
: urther even though the scrambled image is difficult to discern wit he unaided eye, variations in shading and contrast of the scram- .
-- bled image suggests that a scrambled image is present. ~ ~ ~ . ~;
- Objects of the present inventisn theref~re are to provide ~
- n image coding or scrambling system, process and~product made :;
y the process which are impro~eme~ts over the system, procees : -~ nd product descrLbed in my U.S. Patent No. 3,937,565 which ~ :
equire relatively short exposure times for each artwork enabling elatively large ~cale production of scrambled printed sheets ith relatively sharper images, and which provides a scrambled mage having relatively less contrast and shading making it more :~ :
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difficult to recognize with unaided vision.
To effect the foregoing and other objects of the present invention, the scrambled image is preferably produced photo-graphically in a manner which scrambles the image of the ar~work, so that it cannot be directly identified, by u~ing a camera such as a pseudoscopic camera, the latter :being well known in the artO .
Pseudoscopic cameras of the type used in carrying out t~e ~:
principles of the present invention generally include a~ objective lens, preferably corrected to have a flat field (generaliy -defined as that surface in which the sharpest images are formed by a lens system when the viewed objeGt is at infinity- :
or the loci of all points of colllmated light imaged :
by the lens system). In.order to reduce or substantially .
eliminate marginal rays so as to improve image quality an ~ I
aperture stop, preferably in the form of an elongated-slit, is utilized to form a sllt lens. The slit should be wide enough ts .
avoid severe difraction and to allow enough light through the lens ~ ~ :
to form an image. The length of the slit is preferably e~l~al to th width of the lens. The "slit lens" may be any one o~ several types of lenses. For example, the slit lens may take the form of .
a simple convex convex lens which i9 provided with a light-opague ~ask having a slit, preferably horizontally oriented, in ront of the lens. Alternatively, the slit lens may be a relatively small ~longated block-shaped lens haviny at least one curved surface .
~o that the lens can be horizontally-positioned along its elongate ~irection with i~s curved surface focussing the incoming rays to .
the image plane (defined as that surface, generally referred to s a plane at which a lens system forms the sharpest image ~f the object whLch iS at some posltion in front of Lhe lens system) of the camera. Accordingly .,'., . .
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the t~rm " the elongate direction of the slit lens" shall include hereafter the elongate direction gene!rally defined by the slit of the mask or the elongate direction of. the blocX shaped lens depending upon the type of lens used~ .

-; The graticule can be in the form of a grid comprising narrow, .: substantially parallel opague s~rips sepaxated by narrower trans-. parent strips, or preferably in the form of a lenticular ~creencomprising substantially elongated, parallel, contiguous; hemi-cylindri~al lenticules. The graticule is located between the slit . . .
L0. lens and the image plane closely adjacent the image plane. The . strips or hemi-cylindrical lenticules are normally oriented i~ a .
dlrection perpendicular to the elongate direction of the sli~ lens, ; so that where the sli.t is horizontal the strips or lenticules of. .
. ~ the graticule are .vertically oriented. Further, the camera include L5 ~ a focal plane-type shutter,.positioned either directly in .
. front of or directly behind the objective lens. Such a shutter is usually an opaque curtain having an~elongated slit, :
~ - normally oriented parallel with the strips or lenticule~ of the :
.~ raticule and movable so that the slit travels in a directio~
;20 ~ . arallel (preferably horizontally) to the elongated direction o~
.. he slit lens~ :A photosensitive element such as a sensitized film . . s positioned at the combined image plane of the graticule and ~ :
: ~ bjective lens. During exposure of the preferred camera, the focal . lane-type shutter is operated so that the vertical sllt of the shu _ . er travels horizontally across the plane of th~ shutter so as t~
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expose successive portions of the photosensitive element. Since the objective lens is a slit lens with the elongate direction of the slit transversely oriented with respect to the slit of the shutter, movemen~ of the shutter has the effect of moving a square aperture across the width of the objective lens. As the slit of the shutter moves the angle of vie~w of the object changes which in turn changes the angle of acceptance through the . graticu~e. :;
- Due to the spacing between the lenS surfaces or strips of the graticule, a.light ray from a point near the center of the . subjec~ or scene photographed (hereinater called.the "subjec~ ~;
- . center") passing through the nodal point of the objective lens will .
fall upon the photosensitive element at progressively different . ~:
- points as the SlLt of the focal plane shutter is moved, so that S ~.~ different aspects of the subject are presented.to the lens and .
recorded by the photosensitive element as a parallax panoramagram.
~- In accordance with the present invention, the means are pro- .
.- . vided for moving the subject trans~ersely to.the optic axis of the ~ .: lens when the shutter is operated. This produces a photographic .
D image which is not only a lenticular dissection of thë.image .` . but one in which the displacement of each point of the image~
... of the subject is moved through a loci of points in the image .:
. pl~ne so as to introduce a scrambling factor. As in my prior . .S. Patent No. 3,937,565, this scramblea image can be recorded ..
. . on.film, preferably of the self-developing type. If multiple . ersions of the scrambled indicia are desired, screen positives ..; . can then be made from the photographic image provided by the . camera, which in tur.n can be used to prepare a printing plate.
The plate can then be used to produce a plurAlity of printed . sheets with the scrambled image. . ~

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The scrambled lenticular dissec:tions provided by the .
process of the present invention are essentially unrecognizable in the sense that the original form of the indicia or pattern cannot be identified by the unaided eye. The scrambled image - can be reconstructed in the same maImer as described in my U.S.
. Patent No. 3,937,565~ 5pecifically, assuming that there has no~
:. . been any posi~ive or negative magnification.of the image during . developing and/or printing, the scrambled image is decoded by .. positioning over the pri~ted or developed image, a transparent ~0 :, lanticular screen of the same nature as that used i~ the camera..-in te~ms o~ the number of lenticules per inch and the radius of ~ ~..
curvature of the lenticules, with the lenticular æcree~ positLoned : in the same relation to the scrambled image as it was positioned ;
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... with respect to the original recorded image during the coding . ..
~ process. Alternatively7-a ~iewing screen ha~ing a different pitch, . i.e., different numbers of lenticules, can.be used in d~coding .:
the scrl Icd irage by using a ~iever which can op~ cally size, ',~',' ~ . , . . ,. . ,,. .
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1~3;~:~ -i.a. magnify or mini~y the imagè to a.ny desired pitch. The scrambled image will thus appear as a. blur of variations of :~
shading and contra~t when viewed by the unaided eye. In accordance with the present invention, this shading and contrast of the scrambled image can even further be reduced by the utilization of a dot screen, preferably positioned between the lenticular screen .
and ~he photosensitive element during exposure o~ the photo- :
sensitive element~ The screen is provided with a dot pattern which approximates the tone of the ~inal scrambled image so a~
to mask the îmag~
The invention can thus be used for many purpose~ ~uch as backgrou~d patterns or documents which must be safeguarded against erasures, forgeries, counterfeitting and the like. The invention may also be used for games and eaucational purposes ~
where, for ex~mple~ test answers, scrambled or coded in accordance ~
with the present invention, can be put on the same test sheet as :::
that containing the questlons in uncoded form, .. .
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In one particular aspect the parent application, Canadian ApplLcation No. 274,794 filed March 25, 1977, is concerned with the provision of a camera system suitable for forming parallax panoramagra~ls of a sub~ect, and comprising; in combination:
lens means having a focal plane and including means for defining A llght transmitting slit;
a graticule dlsposed adjacent said focal plane ~o as to form wi~h said lens means a combined focal plane;
selectively operable exposure means for permitting formation, in operative cooperation with said means for defining said slit, an image of said sub~act at said combined focal plane; : I
supporting means for supporting said subject; and means for moving said supporting means relative to sait means for defining said slit, simultaneously with the operation of said exposure means so as to provide a scanning ;~
r aperture across the image plane defined by the lens means and --~ graticule and so as to simultaneously permit said-~formation of said image.
In another particular aspect the parent application, ~- .
Canadian Application No. 274,794 filed March 25, 1977, is concerned with the provision of a process of producing a ; parallax panoramagram of a coded or scrambled form of a subject using a camera of the type having a lens means having a focal~plane and comprising means for defining a ~ ~ -slit, a graticule positioned adjacen~ said focal plane so :~
as to define with said lens a combined image plane and a . shutter movable with respect to said lens means for exposlng the combined image plane to light traversing said lens means -~:
:~ and for providing a scanning aperture across said image plane, said process comprising~
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moving said qhutter to im~ge said subject within the depth of f OCU9 of said g~aticule and lens means;
simultaneo~lsly movin~ said s~b~ect t~ansversely to the optical axis of said lens means wlth motion of said shutter formin~ an image within said depth of focus; and exposing a photosensitive element to said for~ed image within said depth of focus.
The present appllcation, a d:ivision of aforementioned :. Canadian Application No. 274,794, i9 primarily.concerned with provision of a novel coded or scrambled form of an original artwork pattern made in accordance with the following steps:
forming an image of said original artwork pattern in the combined image plane of a camera comprising (a) lens means including means for defining a light transmitting slit and (b) a graticule having a plurallty of parallel contiguous ..
elongated elements; and exposing a photosensitive element to said image while simultaneously moving said original artwork pattern and the slit of a shutter of said camera in a plane adjacent said ` 20 slit means of said lens means, each transversely to the ::
.. elongated direction of said graticule elements.

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Other objects of the invention wili, in par-t~
appear obvious and will, in part, appear hereinafter. The invention accordingly comprises -the appara-tus possessing the construc-tion, combination of elements, and arrangement of parts, the methods comprising the several steps and the relation and order of one or more of such steps with respect to each of the others, and the products possessing the features, properties and relation of elements which are exemplified in the following detailed disclosure and - 10 the scope of the application all of which will be indicated in the claims.
For a further understanding of the nature and objects of the present invention, reference should be had ~`~ - to the following detailed description taken in connection with the accompanying drawings wherein:
Fig. 1 illustrates an example of an original or : unscrambled artwork;
- Figs~ 2A, 2B and 2C, which appear on a sheet ``j of drawings separate from the sheet of drawings bearing ~
Figs. 1 and 3 to 6, are top views, in schematic form, ~ -of a camèra system of the present invention showing the technique employed for forming a photographic scrambling image of the artwork of Fig. l;
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Fig. 3 illustrates the scrambled image of the artwork as provided by the method of the present invention;
` Fig~ 4 is an enlarged partial cross-section of the lenticular screen; - ~
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Fig. 5 shows the method of decoding the printed scrambled . ¦indicia using a transparent lenticular screen; and .
. I Fign 6 illustrates the decoded or unscrambled indicia as .
it appears to the viewer through the lenticular screen of Fiy. 4.
Referring to the drawings, wherein l~ke numerals refer .
¦to like parts, Fig. 1 illustrates an ex~mple of an original or :;~
unscrambled graphics or artwork which can be used with the present ¦invention. The artwork is shown as a pictorial design 14, disposec , ~.
: ¦in any kno~n manner ~n sheet 10, the latter having contrasting bac~ ~
: - ground 1~. Th~ ~in,~,~u~ contrast required ~e~ween design 14 an~: .' ; ~ac~:~round ~2 i, dependent on light~ng conditions un~er which the ~'. :
~ . . ~ma.~e'og des~ n 14 i,s to ~e recorded as well as the se~sitivity oE :,. the`p~bto$en~itive'sur~ce'of the'photosensitive ~lement 2'6 OD .~ . "
~i'c~:'t~e.'i~a~e,'o~ t~e'des:ign ;s to ~e recorded. '~ .
. Fi~. 2~sho'~.s,~'schematically, thb prior art camera 18 of ' ' :,: t~e''t~pe'de~cri~ed ~od~.~ied in accorda`nce with the pre~ent ' ; .. i~r,rventIon. '~Qre'$pecifically, the prior art.camera includes .~. oBjecti~e'sl~ lens 20, grat';cule'24 and shutter 22 for record- ~ -~
7~.n~ an im~ on ph.oto~ensit~ve'element 26.- . . ' ' . . ~ .' . , Alt~oug~ t~e'oDiect~ve'slit lens 20 is show,n for'purposes : ' .:, . of claxity only ~s a sin~le.'simple convex-convex lens, it should ~ , .' . be under~too~ t~'t th.e'o,~je~t~ve'lens may comprise any type of slit len~ including a single'lens or' combination o~ lenses or .: ' ~
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any other devices known which are capable of converging incoming.
light, such as the elongated block-shaped lens previously de-scribed, so th~t the light will be focused as an image in the image .
plane of the lens system. As shown :Lens 20 further includes a ..
light opaque mask 28 positioned adjacent to and preferably on .
the surface of the convex-convex lens. The mask 28 defines a .
light transmitting eLongated slit 30 which in the preferxed .
embodiment extends across the surface of the lens in a horizontal direction. .
In the preferred embodiment, graticule 24 is in the form of a lenticular screen which comprises substantially unidirectional contiguous longated cylindrical lenticules 34~ The number of lenticules per inch, the orientation and the radius of curvature : :.
of the len~icules is a matter of choice, although as.described in .
greater detail below, such factors must be known since they are : -. , . , . ..
critical in decoding or unscrambling the.coded image which is ~;;
being recorded. It should be understood.therefore that the len- : .
ticules of other ~onfigurationst such as spher.ical lenticules;.~ ~:
can be used so long as the specific configuration is known so. .
that the image c~n be decoded. In the preferred embodim~nt the nidirectiona1 lenticules are oriented in a vertical direction erpendicular to the direction of the slit 30 of mask 28. As ell known in the art a lenticulaL screen of the type.described ill act as a converging lens and thus when screen 24 is di~posed .
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between lens system 20 and the focal point of the lens system, the com~ined lens system 20 and screen 2~ will.focus the light at the new combined focal point, referred to at 36. As mentioned above, an i.mage of an ob~ect being focused by slit lens 20 and screen 24 will be focused in an image plane. This image plane will move from the focal plane ~which passes through the ~ocal point ~6) toward the screen 24 as the artwork object being viewed ` . . moves fxom infinity toward the c~mera. Thus, as shown in Figs.
2A, 2B and 2C when the artwork 10 is positioned in front of the ~10 camera at some finite distance, the image will be focused:i~ the image plane generally referre~ to at 38.. ; ~ -- .
. The shutter 32 is preferably of the focal plane type including : cur~ain 42 formed with slit 44. The shutter is positioned and the ~ slit is transversely oriented with respect to the elongate direo- ~
- tion of sllt 30 of the lens 20, preferably ln a vertical directlon, .
: so that the slit moves horizontally a~ross the optical axis either :~
: directly in-front of or behind the lens 20 when shutter 22 is -`; .
. driven by shutter drive mechanism 46. The latter is well knowh : . . to those skilled in the art and thus will not be aescribed in ~ .
.20: great detail. . ~
. The photosensitive element 26, which~may be photographic film of the self-developing type or the like, is positioned with . screen 24-behind shutter 24 with element 26 in image plane 38.
:~ . In this way, the camera îs said to be in ocus in which an image ~25 ¦oi ar k 10 can ~e recorded on el~ment 26.

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~ ~ 3Zl In accordance with the present :invention the camera is modified to further include mean6 fo:r moving artwork 10 sîmul-taneously with shutter 24 relative to slit lens 20. The means can comprise any type of device or moving graphics 10 and can .
i for example, as shown, include a platform 48 for supporting graphics 10. Platform 48 is provided w th a rack gear 50. A motor .
: 52, the operation of which is controlled by motor drive mechanism - 54 rotates pinion gear 5~, the latter engaging rack gear 5U. Thus, .
: . operation of motor 52 moves graphics 10 along a path relative to .
.1- slit lens 20. Motor drive mechamism S4 can be synchronized with shutter drive mechanism 46 as indicated generally by numeral 5 : in any known manner in the art, such as by differential gearing : . through a suitable drive train, or by electrical mean~ . -~
lthough it is preferred that graphics 10 travels along a : ~
.; . ath essentially parallel to the elongate direction of the ::
. lit lens it will be appreciated that the path does ~ot . :
. . ave to be parallel to the elongatè direction of the slit -: .; ens nor does the path have to be unidirectio~ but can be curved ~ r even in the opposite direction to the direction at which the i li~ of the shutter moves so long as the direction is transverse - . o the optical axis o~ the system. Further, the speed at which--` . he graphics moves need not necessarily be proportional to the . peed at which the slit of the shutter move~. .
::~ - Referring to Figs. 2Aj 2B and 2C the operation o~ camera : ~ as well as the method of the present invention is illustrated . n sequence~ Initially, an image of the graphics 10 is focused ,,.,,,,.,, . , , . , , ' ' ' . . ' ,. ' ' ' ~ 6 ~

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moves in a direction parallel to slit 30 of the slit lens 20. ,~
Simultaneously, graphics 10 also moves in a direction substantiall parallel to the direction in which the slit of the shutter moves. .
As the slit of the shutter moves horizontally across the plane . of the shutter through the successive first, second and third . ~
.; positions shown in Figs. 2A, 2B and 2C respectively, succe~sive :
portions of photosensitive element 26 are exposed. Since t~e . .
-. slit lens is defined by a horiæontal~slit, movement of the shutter .: - has the effect of a relatively small substantially square aper~ure - which moves acr~ss the objective lens. Due to the .
- spacings between the lenticules 34 of the screen 24, and the ;~ ~ movement of the graphics during exposure, a photographic image is provided on the photosensitive element 26 which is ~ot only - .
`: a lenticular dissection of the image, but one in which the displace ment o each point of the image of the artwork through a loci of ~
oints ln the imaga plane introduces a scrambling factor. ~- ~:
-- ?he photosensitive element 26 once exposed, can then be . rocessed so that a screen positive can be made as des~ribed i~ : .
ny U!S. Patent No. 3,937,565. As stated therein the pcsitive . - s then used to prepare a printing plate which in turn is used o print sheet material 26' shown in ~ig. 3 as having a coded or . crambled image 14' printed thereon. The printing plate may also ¦ ma From the negative e ~leme~e~.26 and that other printing ,, , , .' .',, . '. , . ...
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¦systems can be employed to produce printed multiple versions¦of the coded images on sheet material. As shown in Fig. 3, the ¦scrambled image 14' thus printed, is essentially unrecognizable ¦and cannot be identified by unaided vision. Even though the ¦scrambled image is unrecognizable, nevertheless, there are ¦~ariations in contrast which would indicate the presence of some ¦type of image. Accordingly, and in accordance with the present ¦ invention, this contrast can be substantially reduced so as to further make it difficult to recogni2e the scrambled image without the use of a lenticular screen and without effecting the decoding-¦ process of the image. Specifically, in accordance with the present ; I invention, a dot screen 60 is preferably positioned between lenti-cular screen 22 and photosensitive element 26 during exposure of the photosensitive element. Preferably the screen 60 is secured ; to the back of graticule 24. This screen is provided with a dot attern which approximates the tonal pattern of the image to be rovided so as to mask the formed image. Such screens are well nown in the art for use in lithography or p~inting half tone rints from Gontinuous tone prints. The screens o~ the type us~d erein are described a~ "halftone plates" in vvlume 10 of McGraw-ill Encyclopedia of Science and Technology, (1960), McGraw-Hill ook Company, Inc. pp. 611 and 612. Typically, the dots are provid y a transparent plate having a first array of etched parallel line xtending transversely to a second array of etched parallel lines esulting in the ~ormation o what appears to be a dot pattern of, or example, 10,000 dots per square inch. Generally, the screen 60 - rovides an overall tint which will cause the dissected and scram-led image to blend in with the background of the printed sheet so hat imaging screen 60 on photosensitive element 3S with the crambled image has the effect of masking the imageO

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. As shown in Fig. 4~ in order to reconstruct, unscramble or .
decode thP scrambled image 14l,~whether dot screen 60 is used in the coding process or not, a transparent lenticular screen 24' is employed in the same manner as described in my U.S. patent .
3,937~563. Assuminy that thexe has been no magnification, . either positive or negative of the printed form of the scrambled image with respect to the photographi.c image, the screen 24' is - .
; o~ the same nature as the screen 24 used in the camera 18 in . terms of the same nature as the screen 24 used in the camera 18 . in terms of the number of cylindrical lenticules 34' per inch and .
the radius of curavture of the lenticules. :The optical thickness .
of the screen 34' is made~as thick as the optical distance from ~ the lenticulated surface of the screen 24 to the photosensitive .
.~ . surface of element 26 when the photographic image was formed..
As shown in Fig. 5, by registering the lenticular screen .
.- : 4', i~e~ orienting the direction o~ the lenticules.34' in - he same relationship to the scrambled image 14' as the screen .
4 was positioned to the photographic image from which the . .
.~ rinting plates were made, the image 14' can be reconstructed, .
ecoded or unscrambled as illustrated in Fig. 6. ~ .
:~ It should be realized that the scrambled image 14' cannot .
- e easily reproduced. Such-reproduction would not only require :~
. ~. he same camera 18 and knowledge of the original artwork 10~
ut also, interalia, Xnowledge of the distance of the artwork . s placed ~rom the camera, the orientation of the lenticules 34 : ' ' ' . . . ' ';
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o~ screen 24, and the length and path directions of artwork 10.
Withou~ this knowledge, any attemptes~ reproduction of the scrambled image would be subject to detection.
It is noted that the longer the path over which artwork 10 moves during exposure, the greater the scrambling factor will be~ i.e. the more difficult it will be to determine from the scrambled image the nature of the original unscrambled image.
However, increasing ~he path length over which artwork 10 moves ~uring exposure, decreases the angle of acceptance (the angle 0 relative to the perpendiculra of the plane in which the image lies) through which the image can be viewed through Lenticular - screen 26. Further, the amount of scrambling can also be controlle by the resolution of the photosensitive element, the number of ; . - ., , .
lenticules per inch, the complexity of the subject, etc.
The Lnvention thus described provides a camera and technique which is much fas~er then that described in my prior patent No. 3,937,565 since the exposure time of the photosensitive ~ ;~

~ element 2~ using the p~eudoscopic camera 18 of the present ., . , , . ~ . . .
invention is relatively short in comparison to the excursion time required by a conventional autostereoscopic camera~ Further, since ~he artwork is focussed on the photosensitive element ~ during exposure, the resluting image ~Yill be superior in - sharpness in compaxison to the image provided by my prior art process of moving the photosensitive element away from the image 'S ~ lane. Finally, the use of dot screen 60 further reduces th~ ~
- contrast between the scrambled image and the background o~ the ~;
j printed sheet.
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While a particular preferred embodiment of the invention : has been described, it will be understood that various change .
and modifications can be made from the foregoing without departing from the spirit and scope of the claims. For example, if a further i scrambling factor i5 desired, and the sharpness of the image is not critical, the camera can be stopped down and the photosen~iti~
. element can be moved away from the image plane to a position withi the depth of focus prior to exposure. Alternatively, the scrambl-.~. ing factor can be increased by moving the graticule 24 relative to ) the slit lens during exposure of the photosensitive elemént 26.

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Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A novel coded or scrambled form of an original artwork pattern made in accordance with the following steps:
forming an image of said original artwork pattern in the combined image plane of a camera comprising (a) lens means including means for defining a light transmitting slit and (b) a graticule having a plurality of parallel contiguous elongated elements; and exposing a photosensitive element to said image while simultaneously moving said original artwork pattern and the slit of a shutter of said camera in a plane adjacent said slit means of said lens means, each transversely to the elongated direction of said graticule elements.