WO1999030200A1 - Dispositif de diffraction a effets tridimensionnels - Google Patents

Dispositif de diffraction a effets tridimensionnels Download PDF

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Publication number
WO1999030200A1
WO1999030200A1 PCT/AU1998/001014 AU9801014W WO9930200A1 WO 1999030200 A1 WO1999030200 A1 WO 1999030200A1 AU 9801014 W AU9801014 W AU 9801014W WO 9930200 A1 WO9930200 A1 WO 9930200A1
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WO
WIPO (PCT)
Prior art keywords
eye
images
diffractive
image
dimensional
Prior art date
Application number
PCT/AU1998/001014
Other languages
English (en)
Inventor
Xiaoping Yang
Original Assignee
Commonwealth Scientific And Industrial Research Organisation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Commonwealth Scientific And Industrial Research Organisation filed Critical Commonwealth Scientific And Industrial Research Organisation
Priority to AU16479/99A priority Critical patent/AU738289B2/en
Priority to EP98960872A priority patent/EP1038200A1/fr
Publication of WO1999030200A1 publication Critical patent/WO1999030200A1/fr

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/18—Diffraction gratings
    • G02B5/1842—Gratings for image generation

Definitions

  • This invention relates to a diffractive device with three-dimensional effects. It relates particularly to a diffractive optically variable device (OVD) which, under appropriate illumination and observation conditions, generates one or more images which appear to be three-dimensional.
  • ODD diffractive optically variable device
  • OVDs are useful in a number of different applications, particularly as anti- forgery security devices on banknotes, credit cards, cheques, share certificates and other similar documents. In general, good OVDs are easily viewed and verified by the colour and pattern variation of images which they generate.
  • Patent 5,428,479) and EXELGRAMTM diffraction technology (PCT AU94/00441) which appeared first on the Australian opal stamps and Vietnam bank cheques issued in 1995 and which appeared on AmexTM travellers cheques and on Hungarian banknotes in 1997.
  • PCT AU90/00395 and PCT AU94/00441 both in the name of the present applicant, are hereby incorporated herein by reference.
  • PIXELGRAMTM and EXELGRAMTM technologies are able to generate a range of optical effects including moving guilloche and graphic effects.
  • PIXELGRAMTM and EXELGRAMTM technologies also have the ability to display high resolution portraiture effects that change from positive tone to negative tone images as the angle of view is changed.
  • Printed high resolution portraiture has long been used on banknotes as a security feature because of the particular ability of the human eye to notice errors or defects in an image of the human face. This was one of the reasons that the PIXELGRAMTM and EXELGRAMTM technologies were developed to include portraiture OVD effects.
  • VISATM cards are based on a two-dimensional imaging process, and images generated by the effect of illumination on these devices are two dimensional.
  • the hologram OVDs on VISATM cards generate images which appear to be three dimensional, but as stated above they blur under normal light conditions.
  • An object of the present invention is to provide an OVD which generates a three-dimensional image which can be clear and easily viewed on illumination by a normal fluorescent tube, a lamp or daylight.
  • a diffractive device having a surface relief structure which, when illuminated by a light source, generates two or more diffraction images which, when observed by an observer from an appropriate range of viewing angles, appear as one or more three- dimensional images.
  • a person with normal eyesight perceives an object or scene as three- dimensional by capturing two simultaneous but slightly different images of the object or scene through the person's left eye and right eye, and processing the two images with the person's brain to derive a feeling of depth and perspective based on the differences in the two images.
  • the invention preferably works by generating a left-eye image and a right-eye image, which possess slight differences simulating the differences between the left-eye and right-eye images which are observed in viewing an actual three-dimensional object or scene.
  • the diffractive device may generate a centre image which is visible to both eyes.
  • Separate left-eye and right-eye images may be generated as a result of any suitable characteristics of the surface relief structure.
  • separate images may be generated as a result of differing orientation of surface regions of the diffractive structure, with a left-eye diffraction image being generated by light diffracted from a plurality of surface regions each of which has a diffractive structure with a first orientation, and a right-eye diffraction image being generated by light diffracted from a plurality of surface regions each of which has a second orientation which differs in angle from the first orientation, so that the left-eye image and the right-eye image are observable from locations which are separated by a distance equivalent to the distance between a person's eyes.
  • a left-eye image of a particular colour (such as green) may be generated by light diffracted from a plurality of surface regions each of which has a diffractive structure with a first spatial frequency
  • a right- eye image of a different colour (such as red) may be generated by light diffracted from surface regions with a second spatial frequency
  • the observer may use optical filters of matching frequencies (such as glasses with a green left lens and a red right lens) to ensure that the observer's left eye sees the left-eye image and the right eye sees the right-eye image.
  • the diffractive device may generate one or more full colour three-dimensional images. This can be done by allocating surface regions to generate three or more left-eye primary colour images (such as a red image, a green image and a blue image) and three or more right-eye primary colour images, which together create a full colour three dimensional image. Because the colour sensitivity of human eye is relatively imprecise, in some arrangements it is possible to convey the impression of a full colour three-dimensional image without the necessity of three colour images for each eye.
  • the invention will hereafter be described in greater detail with reference to the attached drawings which show example forms of the invention. It is to be understood that the particularity of those drawings does not supersede the generality of the preceding description of the invention.
  • Figure 1 is a schematic illustration of an object and the location of an observer's eyes.
  • Figure 2 is a representation of some regions of a diffractive surface structure according to the invention, divided into left-eye and right-eye "channels".
  • Figure 3 is a schematic illustration of the mechanics of illuminating and viewing a diffractive device according to the invention.
  • Figure 4 is a representation of a region of a diffractive structure according to the invention showing curved diffractive structures with left-eye and right-eye "channels".
  • Figure 5 is a representation of a similar region with structures which are short and straight rather than curved.
  • Figure 6 is a representation of some regions of a diffractive surface structure according to the invention, divided into left-eye, right-eye and centre "channels”.
  • Figure 7 is a representation of some regions of a full-colour diffractive surface structure according to the invention, with red, green and blue left-eye and red, green and blue right-eye "channels”.
  • Figures 8 and 9 show two different images which were encoded into a diffractive device according to the invention.
  • Figure 10 shows a combination of the two images of Figures 8 and 9, which appears to be three-dimensional when the diffractive device is viewed.
  • a diffractive device 1 has a surface relief structure 2 which, when illuminated by a light source 3, generates two or more diffraction images which, when observed by an observer 4 from an appropriate range of viewing angles, appear as one or more three- dimensional images.
  • the invention preferably works by generating a left-eye image, perceived by the observer at left-eye observation point 5, and a right-eye image, perceived by the observer at right-eye observation point 6.
  • the two images possess slight differences simulating the differences between the left-eye and right-eye images which are observed in viewing an actual three-dimensional object or scene.
  • OTDs optically variable devices
  • diffractive devices of which diffractive devices according to the invention form a subset
  • the present invention is based on the application to diffractive devices of techniques for synthesising three-dimensional images from a two-dimensional substrate. For example, three-dimensional movies are displayed on a two-dimensional screen, and three-dimensional photo pictures are a pair of flat images viewed in a three- dimensional viewer. These photo pictures create a convincing illusion of a three- dimensional scene.
  • Two-dimensional and three-dimensional images The difference between two-dimensional and three-dimensional images is that the two-dimensional image is constructed from the same image for both human eyes; but in the three-dimensional real world a normal person's two eyes give two slightly different images. This is because they are in two different positions in space, separated horizontally by an amount of about 6.5 cm for an average adult human. The brain accepts the small horizontal separation between those two images, and in return gives a single image with accurate depth perception. This ability is known as stereoscopy. Because of stereoscopy, humans experience a real sense of three-dimensional depth or location of objects. This is illustrated in Figure 1 , which shows a left eye 5 and a right eye 6, together with objects 7, 8 and 9. The images of those objects perceived by left eye 5 clearly differs from that perceived by right eye 6.
  • object 9 obscures object 7 apart from a small part of object 7 to the left of object 9; whereas in the image perceived by right eye 6, object 9 obscures object 7 apart from a small part of object 7 to the right of object 9.
  • the observer's brain processes this information so that the observer becomes aware that object 9 is closer than object 7 and slightly smaller.
  • a preferred process of producing a three-dimensional OVD according to the invention is quite similar to a standard process for creating a three-dimensional photo picture.
  • the first step is to create two normal images for left and right eyes respectively, i.e., a stereo pair. This may be achieved simply by taking two photos, or observing images, in the human left eye and right eye positions respectively. As indicated above, for a normal adult human the separation is about 6.5 cm. This can also be done by means of a commercial three-dimensional camera. Alternatively, a suitable pair of images can be calculated and generated by computer software. It is also possible to mix images taken by a camera with images created by computer. In this process the base (distances of about 6.5 cm) may be increased or decreased relatively to the scale of the scene in order to have an appropriate significant stereo effect.
  • the next step is to design regional surface relief structures, each of which has the function of generating (under appropriate illumination conditions) one or more components of the stereo pair of images.
  • Two channel "palettes”, each consisting of a discrete number of different regional surface relief structures, can be employed for the two images. Some care is required in choosing the channel palettes, and consideration has to be given to how a stereo pair of images is to be reconstructed by the individual regional surface relief structures. If appropriate regional surface relief structures are not selected, there is a significant risk of cross-talk between the two channels which can reduce or even cancel the stereo three-dimensional effect.
  • diffractive regional surface relief structures is shown in Figure 2.
  • the structures consist of grooves or gratings.
  • diffractive structures may consist of dots or any other structure with appropriate periodicity, and suitable structures are not limited to line gratings.
  • Information for the left-eye and right-eye images is coded into two channel grating structures.
  • the regional surface relief structures which contribute to the left-eye image are marked L, and the structures which contribute to the right-eye image are marked R.
  • the image information is concentrated in the broader grating regions 10, whereas the inter-grating regions 11 can be used to enhance the contrast of the images generated.
  • FIG. 3 An arrangement for observing the three-dimensional diffractive device 1 is shown schematically in Figure 3.
  • the device is illuminated by light source 3. Clearest results are obtained if the light source approximates a point source, but good results are still available under diffuse illumination such as fluorescent tube lighting because images generated by diffractive devices of the present type are typically significantly sharper than the images generated by commonly known credit card holograms.
  • a first order diffraction image for the left eye is generated at location 5, and a first order diffraction image for the right eye is generated at location 6.
  • the brain of the observer processes these two images and perceives the overall image as a three-dimensional one. If the left-eye and right-eye positions of the observer are reversed, the observer may perceive an "inverted depth" image, in which closer objects appear to be further away, and further objects appear to be closer.
  • the best stereo three-dimensional effect is generated if the information for the left eye and right eye is deflected into left eye and right eye respectively without cross-talk between the two.
  • each eye sees only its own image which is created by the first order diffraction of incident illumination, observed at the observation distance (typically 25 cm to 50 cm).
  • a three-dimensional image produced according to the method described above is able to be viewed ("free- view"), in most cases, without the requirement of a special viewer.
  • the embodiment described above is therefore unlike three-dimensional movies which have to be viewed with polarisation glasses. This has been achieved by having a particular orientation of regional surface relief structures for all left-eye image information, and a slightly different orientation for all right-eye image information.
  • Figure 4 is a representation of a surface relief structure region which has curved structures, the left half of which are designated “left", and the right half being designated “right".
  • the curvature of the structures causes the diffractive effect generated by the structures to be observable from a broader range of viewing angles than is the case for straight-line structures.
  • the "left” structures contribute to the "left- channel” image which is viewed by the observer's left eye, and the "right” structures contribute to the "right-channel” image which is viewed by the observer's right eye.
  • Figure 5 is a representation of a region similar to that of Figure 4, but with each "left” and “right” structure being divided into three substantially straight structures. The overall effect is similar to that provided by the curved structures of Figure 4.
  • the foregoing embodiment relates to a diffractive device which generates a three-dimensional image from a stereo pair of images.
  • a three-dimensional image also can be coded into a stereo triple of images.
  • the stereo triple of images can be obtained by means of a 3-lens stereo camera, three separate photographs, computer processing of one or more two-dimensional or three-dimensional computer images, or any one of various other known techniques.
  • a three- dimensional image is then reconstructed from these three images which include a stereo pair of images as described with reference to the preceding embodiment (diffracted with a surface relief structure relative orientation angle of ⁇ , and each observed by one eye only) and the third image which is viewed by both eyes (diffracted with a surface relief structure relative orientation angle of zero).
  • An example of suitable surface relief structure regions for this "three-channel" embodiment is shown in Figure 6.
  • a three-dimensional image created by a stereo triple of images can be finer in three-dimensional depth and image resolution than an image created by a stereo pair.
  • a three-dimensional image can be reconstructed from a stereo 2N or 3N (oo ⁇ ⁇ X l ) channel diffractive device.
  • Each of the left , right and middle channel may be divided into N ( ⁇ > N > 1 ) sub-channels.
  • N may be the number of three- dimensional depth levels or the orientation of objects.
  • N images are coded into the diffractive device in construction of a three-dimensional image.
  • the left-eye and right-eye channels can be coded into two colours.
  • Monochrome (grey) three- dimensional images can be observed with a pair of glasses made from two different colour filters, for example, red and blue.
  • a full range of colours can be reconstructed with three primary colours.
  • Red, Green and Blue can be chosen as primary colours, although it is known that other combinations are equally suitable.
  • Any full colour image can be decomposed into three colour images in the three primary colours.
  • Each pixel of a full colour image has a particular hue and brightness which can be expressed as the sum of a brightness level for each of the three primary colours.
  • a diffractive device creates a full colour image in a similar way to the way in which a monitor displays a portrait or image on a screen.
  • the image is composed of an array of pixels.
  • Each of the pixels contains three sub-pixels which provide intensity levels for the three primary colours respectively as the effect of the first order diffraction of incident illumination by surface relief regions which are designed for that purpose. This mechanism therefore allows for the production of a full range of true colours with various hue and brightness values.
  • the diffractive surface relief structure uses only a single spatial frequency, the OVD produces mono-colour images.
  • a light source illuminates the OVD with a particular incidence angle and the observer views the image from a particular observation angle.
  • the viewing angle ⁇ is thereby determined. It is possible to determine from equation (2.1) the appropriate periodicity or spatial frequency of a surface relief structure region in order to generate diffracted light of a given wavelength at the viewing angle.
  • a diffractive relief structure region a sub-pixel
  • An example of the diffractive surface relief structure of six regions which together make up a pixel of a full colour three- dimensional image is shown in Figure 7.
  • Intensity characteristics associated with each surface relief structure region may be adjusted as required by varying grating depth, grating profile, area of gratings or grating curvatures.
  • Typical steps in a process of manufacturing diffractive devices which generate a full colour three-dimensional image may include:
  • each palette containing a discrete number of different regional surface relief structures, wherein each structure in a given palette is designed to generate the same colour at a different intensity in the image;
  • FIGS 8 to 10 illustrate a transparent multi-layer OVD.
  • Figure 8 shows a first example of artwork, consisting of the words "CSIRO 3D".
  • Figure 9 shows a map of Australia, with different areas appearing in different colours.
  • Figure 10 shows a two-dimensional composite image; however, because it is not possible to reproduce the stereoscopic effect in a single printed representation, Figure 10 does not show the effect which is observed by viewing the diffractive device.
  • the observed effect is that the words "CSIRO 3D" are semi-transparent and appear to be floating in space about 2cm in front of the map of Australia. The effect is observed only from a limited range of viewing angles; from another range of angles, only the words "CSIRO 3D" are observable, and from another range of angles only the map of Australia is observable.
  • a three-dimensional diffractive device is capable of providing an increased level of security.
  • the degree of security of an optically variable device (OVD) is proportional to the ratio of spatial variation to the dimension.
  • a three-dimensional image can have 2N or 3N (N is an integer) channels within 30 micron. It is clear that the three-dimensional diffractive device has a greater degree of surface variation, which results in an increased degree of security. Furthermore, an additional security feature is present because the channels are not independent, and the information in them is combined to form one image.

Abstract

L'invention concerne un dispositif de diffraction comprenant une structure à reliefs superficiels qui, lorsqu'elle est éclairée par une source lumineuse, produit deux ou plusieurs images de diffraction. Lorsqu'un observateur voit ces images sous une plage appropriée d'angles d'observation, elles apparaissent sous forme d'une ou plusieurs images tridimensionnelles. L'image de diffraction oeil gauche est, de préférence, produite par une lumière diffractée à partir d'une pluralité de zones superficielles, chacune ayant une structure de diffraction sous une première orientation. L'image de diffraction oeil droit est produite par une lumière diffractée à partir d'une pluralité de zones superficielles, chacune ayant une structure de diffraction d'une seconde orientation présentant une différence angulaire par rapport à la première orientation. Les images de diffraction, vues par un observateur à partir d'une plage appropriée d'angles de vison, donnent un effet d'image tridimensionnelle.
PCT/AU1998/001014 1997-12-09 1998-12-09 Dispositif de diffraction a effets tridimensionnels WO1999030200A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU16479/99A AU738289B2 (en) 1997-12-09 1998-12-09 A diffractive device with three-dimensional effects
EP98960872A EP1038200A1 (fr) 1997-12-09 1998-12-09 Dispositif de diffraction a effets tridimensionnels

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPP0817 1997-12-09
AUPP0817A AUPP081797A0 (en) 1997-12-09 1997-12-09 A diffractive device with three dimensional effects

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WO1999030200A1 true WO1999030200A1 (fr) 1999-06-17

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EP (1) EP1038200A1 (fr)
AU (1) AUPP081797A0 (fr)
WO (1) WO1999030200A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001027664A1 (fr) * 1999-10-14 2001-04-19 Commissariat A L'energie Atomique Dispositif optique de commande, en particulier de mise en forme, d'un faisceau de lumiere coherente
WO2006066732A2 (fr) * 2004-12-15 2006-06-29 Giesecke & Devrient Gmbh Image reticulaire stereoscopique et procede permettant de la produire
WO2008110239A1 (fr) * 2007-03-15 2008-09-18 Carl Zeiss Smt Ag Composant diffractif, agencement d'interféromètre, procédé de qualification de réseau de diffraction double, procédé de fabrication d'un élément optique, et procédé d'interférométrie
EP2676802B1 (fr) 2012-06-22 2015-09-16 OVD Kinegram AG Elément de sécurité à structure diffractive
CN108431671A (zh) * 2016-01-04 2018-08-21 奥崔迪合作公司 3d显示装置

Citations (2)

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Publication number Priority date Publication date Assignee Title
US5032003A (en) * 1988-12-12 1991-07-16 Landis & Gyr Betriebs Ag Optially variable surface pattern
US5784200A (en) * 1993-05-27 1998-07-21 Dai Nippon Printing Co., Ltd. Difraction grating recording medium, and method and apparatus for preparing the same

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5032003A (en) * 1988-12-12 1991-07-16 Landis & Gyr Betriebs Ag Optially variable surface pattern
US5784200A (en) * 1993-05-27 1998-07-21 Dai Nippon Printing Co., Ltd. Difraction grating recording medium, and method and apparatus for preparing the same

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DERWENT ABSTRACT, Accession No. 95-188084/25, Class W03; & JP 7104211 A (TOPPAN PRINTING CO. LTD) 21 April 1995. *
PATENT ABSTRACTS OF JAPAN, (P-1505), page 20; & JP 4028372 A (TOPPAN PRINTING CO. LTD) 4 November 1992. *

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001027664A1 (fr) * 1999-10-14 2001-04-19 Commissariat A L'energie Atomique Dispositif optique de commande, en particulier de mise en forme, d'un faisceau de lumiere coherente
WO2006066732A2 (fr) * 2004-12-15 2006-06-29 Giesecke & Devrient Gmbh Image reticulaire stereoscopique et procede permettant de la produire
WO2006066732A3 (fr) * 2004-12-15 2006-10-12 Giesecke & Devrient Gmbh Image reticulaire stereoscopique et procede permettant de la produire
WO2008110239A1 (fr) * 2007-03-15 2008-09-18 Carl Zeiss Smt Ag Composant diffractif, agencement d'interféromètre, procédé de qualification de réseau de diffraction double, procédé de fabrication d'un élément optique, et procédé d'interférométrie
EP2676802B1 (fr) 2012-06-22 2015-09-16 OVD Kinegram AG Elément de sécurité à structure diffractive
CN108431671A (zh) * 2016-01-04 2018-08-21 奥崔迪合作公司 3d显示装置
CN108431671B (zh) * 2016-01-04 2021-06-29 奥崔迪合作公司 3d显示装置

Also Published As

Publication number Publication date
AUPP081797A0 (en) 1998-01-08
EP1038200A1 (fr) 2000-09-27

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