An objact of this invention is to disclosa tha projactiαn of an image utilizing tha raflsctad light from an αbjact such as that sasπ in the real world. According to this as act of tha invention, tha objact .is conventionally illumiπatad, for axampla aithar by

Ξ front illumination in the case αf an opaqua αbjact or by rear illu¬ mination in the casa of a translucent objact.Light from tha object is projected through a symmetrical imaging device. Tha symmetrical imaging davica has a rsfarsncs plana uihare light incidsnt upon the davioa has its direction changad and tha light with changed 0 direction is transmitted from tha device. All points cn the reference lane ars active over tha surface αf tha reference plane in accor¬ dance ωith tha following rule.

The symmetrical imaging davica relative to tha rafarsnca plana has optical properties restricting tha transmitted ray from the symme- 5 trical imaging davica to a normal plana containing tha incident ray and the normal to the reference plane to tha point αf iπoidaπca. The angle αf incidence is equal to tha angle αf transmission but is contained an tne same side αf tha normal (where tha a.ngia αf incideπcs is tha angle between the iπcidaπt light ray and a normal Q and che angia αf transmission i3 the angle between the reflected light ray and a normal).

Images from objects prαjectad further apart from the devica than the object versus distance -co the devica will also become visible and appear to be ravsrssd left-right and upsidsdown.

5 Other than for viewing or projecting images, the devices can bs used far the multiple functions usually performed by lenses and parabolic mirrors.

A furtπer abject o f tnis inventions is to disclose a screen far transmitting from ana side of the screen an image of an object to the opposite side of tπascrasπ. This is previously called the deflec¬ tive form αf the device. In this aspect αf the i<-.ventiαπ, tha image from tha device is a precise reciprocal of the object αf the device. Tor axampla, an imaga αf what is essentially a convex human contour

wαuld appear reciprocally as an image of a cαπcava human contour.

An advantage of this invention is that tha image, unlike that prσα'ucad through a positive spherical lens or parabolic mirror, is at the same distance from tha retroimaging device as the object whan the refaranca plans is reflected. ^■ •

Thus, by increasing the distance of the object from the retro- imaging device, one can increase the distance from the image and retroimaging device, "or axampla, utilizing this i-iventiαn a three- dimensional reciprocal image of an object can be easily cast out into the street through a storafrαπt window.

A further advantage is that by using reciprocal objects, one can cast an image αf a -real world αbjact. For example, by imaging tha concave features αf the human mask, one can image with reverse parity tha exterior of a human faca.

A further function αf one part αf this invention is to adapt a beam splittar to a retroreflecting screen to the casting of such images. According to this aspect αf the invention, the beam split¬ tar is placed at an angla between an illuminated object and a retro¬ reflecting screen. Light impinging upon the beam splittar from the retroreflecting screen is datαured outwardly and away from tha screen oath back to tha abject. 3eing so detaurea ^" , a reciprocal imaga i3 formed. T e formed reciprocal 'ii ^* nage may then be viewed as being real, and out in space in front of the viewer.

Other objects, features and advantages at this invention will be- come mαra apparent after referring to the following specification and attached drawings;

Fig. 1 is a t.raa-di aπsionai view of the projection device in this invention utilizing a retroreflecting screen and beam splitter to create a specular reciprocal image of the letters "A3C";

fig. 2 is a side perspective view of fig. 1 illustrating the pro¬ perty αf the invention wπersby the image is thrown some distance from the projection devica;

fig. 3 is an embodiment αf this invention si.milar to fig. 1, tha embo _d iment therein illustrating a rstroprσjβctiαn devica, which retrαprojectiαn device throws the reciprocal αf the letters to a naw location;

figs. 4.,..5, 6. are ..all embodiments αf specialized screens which can be used with the embodiment of fig. 3;

fig. 7 is an embodiment of the invention wherein two symmetrical imaging devices ara used . sα as to project the image of the object (leftmost face) into space sα that the imags (rightmost faca) appears the same as the object.

Referring to fig. 1, an object 100 is illuminated by a light source 99 which light source is only schematically shown. In the view αf fig.1, the object happens to be transparent or translucent. The light thus can be projected from the rear thereof.

Referring to the view of fig, 2, the light from the object passes to a retroreflecting screen 20 mountad an the base αf a three-sided box 22. Light from the retroreflecting screen returns directly to the object 10C. As those having skill in the art know: , a retro¬ reflecting screen returns tha light, impinging upon it with the precise angularity as the light is received from an objact. Thus, and assuming no beam splitter 24. intermediate the object 100 and retroreflecting screen 20, one would expect that tha light would reflect back upcn and enhance precisely with a real image the real world object 1QQ. Interposition of the beam splittar 24. at a prs- ferred 45 degree angle changes this. Specifically, the beam split¬ ter causes at least some of the converging light to be dβtoured to an imags plans 101. At tha imaga plane 101 the image of tha object (here shown as the letters "A3C") is recreated. As tha ima¬ ga is recreated, a viewer having a perspective from a solid angle αf projection equal to tha solid angla of projection αf the retro¬ reflecting screen and the beam splittar can see the letters A3C projected in space. In actual fact, the retroreflecting screen could be mounted on the and wail 25 αf tha box 22. However, in this location a viewer αf the imaga 101 such as that schematically shown

by the eye 30 would in fig. 2 have a bright and illuminated back - ground against which to view the image. As a bright and illuminated background would detract from the intensity of the image,it is usual¬ ly preferred to oαnt the retroreflacting screen 20 so that the via- wer has light passad to his view with a relatively dark background. Typically end wall 25 is -painted with a dark, light atisαrbative coating such as non-glossy black paint and the like. It is also important to distinguish this invention from that αf the conventional l3w of reflection. Taking the case of a retroimaging screen, it will be understood that the screen has a theoretical reference plane in which light changes its direction. This screen has optical properties restricting the transmitting ray to the re¬ troreflecting screen to a normal plane containing the incident ray and tha normal to the reference plane within the screen at the point of incidence. The angle of incident is equal to the angle of trans¬ mission, but is contained an the same 3idβ of the normal. The angle of incidence i3 defined as tha angla between the incident light ray and a normal and tha angla αf transmission or reflection is defined as the angle between the reflected ray and a normal.

It is important to disti-tguish this projection systam from that αf a conventional lens. Specifically, in the case αf a ians, a reci¬ procal image moves, liihera tha object is far away, the image moves to the focal point αf the lens. Conversely, where tine objact approaches the fαcai length αf the lens, tha i.maga i's projected at increasing distances. A reciprocal relationship results. Here, be¬ tween the image and the object there is a direct relationship. Specifically, the relationship is that the object to symmetry ima¬ ging device distance will always ramain tha same as tha image to symmetry imaging devica distance.li/heπ the symmetry of plane is chosen to be παπreflectiπg, e.g. by use αf curved beam splitter, or by use af a curved rear deflector, the image will be deformed according to the same ruias af symmetry. This iattar ruia -producas on imaςas some effects which are nor im adiataly apparent. Take, far instance, the image αf a human face. Typically, the nose of a human face will be closer to the projection screen than the ears of tha human face.

The projection αf a reciprocal imaga will give an αpposita result. Specifically, the human imaga will have the nose clαsar to the pro¬ jection device than tha ears. Thus, images projected by tha device will be reciprocal. It will be as if one is viewing a mask from the inside.An expedient to correct this reversal of distance parity is to utilize for the object a mask. Thereaf er, ^' tha projacted ^" 'image will be a real life image.

As will hereinafter be briefly discussed, and in the case αf ste¬ reoscopic projection, it is necessary to reverse the right-left parity to prevent pseudαscσpic images.

Having discussed an embodiment of this invention utilizing a retroreflecting screen, attention now can be given to the projection of an image using rstroprojsction devices such as illustrated in Figs. 4, 5 and δ. This will first be αiscussad with respect to Fig. 3.

Referring to Fig. 3, .a light source 103 illuminates an object in the farm af letters A3C deflective re a projection. A device 104 is iliustratad. The property af device 104 is exactly similar to that of the retroreflecting screen 2 ^Q « Specifically, reflected αr emanating light will diverge from each point on object .

(letters A3C). It will impinge upon tha screaπ device 104. Light will be projected from the screen device 104, converging to an image 105 αf tha letters A3C in the 3ame, exact and identical an¬ gularity as light projected from the letters A3C onto the screen device 104. There results projected in spaca a reciprocal imaga αf letters A3C.

The construction αf the projection device 104 can take several forms, which forms can all ba easily uπdarstcod with reference to Figs. 4, 3, and 5,

Referring to Fig. 4, a device 105 is shown consisting of glass bead lenses 40 aligned in a matrix 41 in one side of screen 50 and glass baad lenses 50 aligned in a matrix 51 an the opposite side af screen 50. A rear projection screen 50 sits intermediate the lens matrixes 41, 51.

The resulting projection system is easy to understand. Specifically, light from all angles is imaged through matrix 41 απto the rear projection screen SO. At the rear projection screen SO, the light is then seen by the matrix of lenses 51 and each individual lens 5Q causes light to e aπata from tha rear side αf the rear projection screen SO. with the exact same and precise angularity as the light was received. There will result a recreation αf the images as de¬ scribed. The same effect can be produced using pinhαles. A device utilizing pinholes is illustrated in Fig. 5.

In Fig. 5, a rear projection screen SO is shown having a series of individual pinhαlas 42 aligned in a matrix 43.Conversely and at the opposite side there are pinholes 52 aligned in a matrix 53. The result is tha same. Speci ically, light enters and forms an imaga on the rear projection screen 50. This image is seen at aach of the pinholes with the light exiting through the pinholes. T e angularity assigned to an outgoing ray is the reciprocal of the light to an incoming ray. Therefore, an iiii-age can be formed in the rπaππar iiiustratad in Fig. 3. ,

It will ba apparent that if matrixes differ in siza, enlargement is possible. Therefore, it is mentioned that the idea must be in¬ terpreted as wide as possible.

Referring to Fig. 5, yet another e odimβπt is iiiustratad. In par- ticuair, a matrix αf positive spherical lenses 51 is illustrated, ach lens is aligned between paired pinholes 44 towards tha object and 54 towards the imaga. As before, these respective lenses 5 , pinhαles 44, 54 are aligned in respective matrixes, 45, 33. It will be seen that tha separation between the matrix αf pi.nhoies 45 and the matrix αf pinholes 55 is chosen to be the exact focal length αf aacπ αf the lenses 51 of the lens matrix 55. _ith this property, the light rays pass along the illustrated path and each entering light ray enters with an angla equal and opposite to eacπ exiting iignt ray.Again, the screen illustrated in Fig. 5 will pro¬ duce a symmetry imaging characteristic such as that previously iiiustratad.

Reviawiπg the device af Figs. 4, 5 and 5, again it can be seen how the generic definition of symmetrical imaging devices aptly describe their function. Each device has a plane where the light changes direction. The symmetrical imaging device relative to its reference plane has optical properties restricting the transmitted ray from

- the symmetrical imaging- de-vice to. a normal plans containing the .. . incident ray and the normal tα tha reference plane at the point of the incidence. The angla of incideπcs is equal to tha angle of transmission, but is contained on tha same side af the normal. The angle αf incidence is the angle between the incident light ray and the normal and the angla αf transmission is tha angle between the transmitted ray and a normal, '..hare transmission αf a light imags αf the abject occurs from one sids af the device to the opposite side af the device, it will be seen that there results an image. It will be seen and realized that the images created are not those conventionally created by spherical lenses. Plαreαver, the imaga is to ba distinguished frcm any illuminated object merely placed in front αf a retroreflecting screen, where an illuminated object is placed in front of a retroreflecting screen, an imags αf that object is cast right back precisely upon the object itself. Hera and in this invention, the image of the object must be cast somewhere other than back upon the αbjact itself. It is the realization that tha image exists that is one of the important asoscts af this invention.

Referring to Fig. 7, a symme-ricai imaging devica far transmitting an imaga is shown. An abject 107, hers in the form af the human face, is placed on one sids of a first transmission device 103. It casts a reciprocal imags in tne farm of a mask 109 on tha opposite side thereof. The image αf mask 109 is than taken by a second image transmission device 110. This image transmission device forms an imags αf the human faca at 111. It can ba seen that with the above- described reciprocal imaging device, the devica αf the face may ba reproduced. It is seen that as the objact 107 is moved toward the right the imaga 111 will also move toward the right. Further, bαtπ abject and image will move at the same speed.

I nave just finished illustrating with respect to Fig. 7 two symmetrical imaging devices wherein an image from an αoject on one sid3 of the device is reiayeα to the opposite side. This image

-α— is in turn rs-rslayβd by a second symmetrical imaging device to produce a real parity image. Those having skill in tha art will realize that the retroreflecting scheme that I have illustrated with respect to Figs. 1 and 2 could as wall be used twice to restore parity to the imaga.

It will be apparent to those that the invention contained herein is limited only by the following claims.