MXPA00006439A - Composite holographic multifocal lens - Google Patents

Abstract

The invention provides an optical lens having a combination volume holographic optical element that provides a diffractive optical power. The optical lens has a programmed activating angle in which the holographic optical element provides a diffractive optical power. The invention also provides a method for producing a multilayer holographic element suitable for the optical lens.

Description

MULTIFOCAL COMPOSITE HOLOGRAPH LENS The present invention relates to a ultifocal lens that contains a holographic element, and that provides at least two optical powers. There are several bifocal lens design concepts available for ophthalmic lenses, which are placed over or inside the eye to correct visual defects, for example, contact lenses and infraocular lenses. A conventional bifocal ophthalmic lens design is the type of concentric simultaneous vision. Another conventional bifocal ophthalmic lens design is the type of simultaneous diffraction vision. Yet another conventional bifocal ophthalmic lens design is the type of translation. A translation lens has two different localized view sections that have different optical powers. The position of the bifocal lens over the eye must change from one section to the other when the user wants to see objects that are located at a different distance from the objects he is currently focusing on. Recently, actively controllable approaches have been proposed to provide a bifocal function in an ophthalmic lens. An example is a bifocal lens of simultaneous vision type having sectionally applied thermochromic coatings. There remains a need for an ophthalmic lens that reliably provide multifocal functions without the deficiencies of the multifocal lenses of the prior art. There also remains a need for an adequate process to produce this multifocal lens. According to the present invention, there is provided an optical lens having a holographic optical element in volume, which provides an optical power, and the holographic optical element in volume is a combination or composite holographic element. The optical lens has a programmed activation angle, wherein the holographic optical element provides an optical diffraction power. The invention also provides a method for producing a multi-layer holographic element suitable for the optical lens. The method has the steps of providing a beam of light from the first source; dividing the light beam of the first source into first and second light beams; providing a recordable holographic element having first and second opposingly located surfaces, wherein the surfaces are flat, concave, or convex; directing the first and second light beam towards the first and second surface, respectively, of the recordable holographic element; providing a light beam from a second source; divide the light beam of the second source into a third and fourth beam of light; and directing the third and fourth light beam towards the first and second surface, respectively, of the holographic element recordable, wherein the first and third light beams, and the second and fourth light beams, have appropriate phase relationships to register grating structures, desirably grid structures in volume, in the recordable holographic element. The invention further provides a method in sequence for producing a composite holographic element. The method in sequence has the steps of providing a first fluidizable polymeric material or crosslinkable in a first mold; registering a first grid structure in volume in the optical material, thereby forming a first non-fluid holographic optical element layer; providing a second mold, wherein the second mold has a larger cavity volume than the first holographic optical element layer, and which contains the first holographic optical element layer on a surface thereof; providing a second polymerizable or crosslinkable fluid optical material in the second mold on the first holographic optical element layer; and registering a second grid structure in volume in the second optical material, thereby forming a second non-fluid holographic optical element layer, wherein the first and second holographic optical element layers are joined in a coherent manner. The present invention provides an activatable multifocal optical lens having a volume holographic optical element in combination. The holographic optical element in volume in combination allows the optical element to have a small angular change between activated and inactivated states, as well as reducing dispersion and chromatic aberrations.

Figure 1 illustrates an active ophthalmic lens of the present invention. Figure 2 illustrates the diffraction function of the holographic optical element for an active lens of the present invention. Figure 3 illustrates an active ophthalmic lens of the present invention. Figure 4 illustrates the transmission function of the holographic optical element. Figure 5 illustrates the diffraction function of the holographic optical element when the element is activated. Figure 6 illustrates an exemplary method for producing the holographic optical element. Figure 7 illustrates the optical power of the holographic optical element. Figures 8-8B illustrate a holographic optical element in combination of the present invention. Figure 9 illustrates a telescope composite lens of the present invention. Figure 10 illustrates an exemplary method for producing a combination holographic optical element. Figure 11 illustrates another example method for produce a combination holographic optical element.

The present invention provides active multifocal ophthalmic lenses. The present invention additionally provides active multifocal lenses for spectacles. Hereinafter, the term "optical lenses" is used to indicate both ophthalmic lenses and spectacle lenses, unless otherwise indicated. The active optical lens of the invention provides more than one optical power. More specifically, the lens provides at least one optical power and at least one additional optical power that can be activated. Unlike conventional bifocal lenses, the present active multifocal lens can be controlled in an active and selective manner to provide a desired optical power at a time without, or substantially without, optical interference from the other optical powers of the lens. The active optical lens contains a holographic optical element (HOE), and the holographic optical elements suitable for the active lens are holographic optical elements in transmission volume. A holographic optical element in volume contains patterns of interference fringes that are programmed or recorded as a periodic variation in the Refractive Index of the optical material. The periodic variation in the Refractive Index creates planes of peak refractive index, that is, grid structure in volume, inside the optical material. The planes of the pattern of interference fringes in the holographic optical element are further described below. Turning to Figure 1, the figure illustrates an active bifocal lens of Example 10 of the present invention. It should be noted that the invention is disclosed herein with reference to a bifocal optical lens for purposes of illustration, although the active optical lens of the present invention may have more than two optical powers. The lens 10 is a contact lens having a first optical element 12 and a holographic optical element 14. The holographic optical element 14 is embedded or encapsulated in the first optical element 12 to form the composite lens 10, such that the The holographic optical element 14 is moved in conjunction with the lens 10. The first optical element 12 provides a first optical power, which corrects the ametropia, for example myopia. Alternatively, the first optical element 12 can be a flat lens that functions as a carrier for the holographic optical element 14. As for the holographic optical element 14, the optical element is designed to modify the light path only when the light in the holographic optical element 14 at a pre-programmed angle, or within a pre-programmed angle range, that is, the activating angle, which activates the optical element. According to above, when the light enters an angle that is outside the activation angle, the holographic optical element 14 transmits completely or substantially completely the input light without modifying it in a significant way, or without modifying the path of the light. Said in an alternative way, the holographic optical element 14 can act as a flat lens, except when the incident angle of the input light comes within the previously programmed activating angle. When the holographic optical element 14 is activated, the fringe patterns or the grid structure in programmed volume in the holographic optical element 14, modify the path of the light, to provide an optical power that is different from the first optical power of the lens 10. In addition to the activatable optical power, the holographic optical element 14 can also provide an optical power resulting from the shape of the holographic optical element 14 and the refractive index of the composition of the holographic optical element 14. This additional optical power complements to the first optical material, to provide the first optical power to the active lens 10 when the input light enters the lens 10 at an angle that does not activate the holographic optical element 14. The term "activating angle", as used herein, indicates an incident angle of input light, which is defined by the angle formed by the direction of the input light ance and the normal axis to the element surface holographic optic, which satisfies the Bragg condition, such that the input light is diffracted by the interference fringe grating structure of the holographic optical element, which is further discussed further below. It should be noted that the activating angle does not have to be of a single value, and it can be a range of angles. When the Bragg condition is satisfied, up to 100 percent of the input light can be coherently diffracted. Figure 2 further illustrates the function of the holographic optical element 14 of the bifocal active lens 10 of Figure 1. The z-axis, which is normal to the flat surface of the holographic optical element 14, and the direction of advance of the input light R , they form the incident angle s. When the input light R enters the holographic optical element 14 at an incident angle that is within the activating angle of the holographic optical element 14, the light R is diffracted by the pattern of previously programmed interference fringes, i.e., the grating structure in volume, of the holographic optical element 14, and leaves the holographic optical element 14 as the output light S, with an output angle p, which is different from the incident angle s. Figure 3 illustrates another embodiment of the active bifocal lens of the present invention. The bifocal active lens 16 is a composite lens having a first optical lens 17, and a holographic optical element lens 18, which completely covers to the first optical lens 17. Alternatively, the lens of the holographic optical element 18 can be of a size that covers only the pupil of the eye. The first optical lens 17 and the lens of the holographic optical element 18 can be manufactured separately, and can be attached, for example, in an adhesive or thermal manner. In an alternative way, the first optical lens 17 and the lens of the holographic optical element 18 can be manufactured in sequence or simultaneously one above the other, such that a composite lens is produced. This sequential or simultaneous approach is particularly suitable when the first optical lens and the lens of the holographic optical element are produced from a basic material or from two chemically compatible materials. Although the active lens 16 is illustrated with a lens having a first optical lens of the inner half and a holographic optical element lens of the outer half, other combinations of different optical elements according to the present invention can be produced. Still another embodiment of the active bifocal lens is a bifocal lens of an active non-composite holographic optical element. In this embodiment, the bifocal active lens of the active holographic optical element is produced from an optical material that forms a holographic optical element. The combination of the active lens shape and the refractive index of the holographic optical element material, provides a first optical power, and the grid structure in volume programmed into the lens of the holographic optical element provides a second optical power. This non-composite active holographic optical element lens embodiment is particularly suitable when the holographic optical element material employed is a biocompatible material, and therefore, does not interact adversely with eye tissues of the eye. The term "biocompatible material", as used herein, refers to a polymeric material that does not appreciably deteriorate, and that does not induce a significant immune response or a deleterious reaction of the tissue, for example, a toxic reaction or an irritation. significant, over time, when implanted within, or placed adjacent to, the biological tissue of a subject. Exemplary biocompatible materials that can be used to produce a holographic optical element suitable for the present invention are disclosed in U.S. Patent No. 5,508,317 to Beat Müller, and in International Patent Application PCT Number / EP96 / 00246 to Mühlebach, whose patent and patent application are incorporated herein by reference, and are discussed further below. Suitable biocompatible optical materials are highly photocrosslinkable or photopolymerizable optical materials including derivatives and copolymers of a polyvinyl alcohol, polyethylene imine, or polyvinylamine. The present holographic optical element is designed or programmed to have an activating angle or a range of activating angles within which the holographic optical element is activated, and the holographic optical element diffracts the input light to focus the light on a desired location. Figures 4 and 5 illustrate the function of the holographic optical element 21 of the composite active lens 20, which contains a holographic optical element lens element that is programmed to focus light originating from a close distance. When the light 22 from a distant object enters the lens at an angle that does not activate the holographic optical element 21, the light 20 is focused according to the optical power of the first optical element 23 of the lens 10, in combination with the optical power of the lens. lens of the eye (not shown), to a focal point 24 on the retina of the eye, more specifically on the fovea. For example, the first optical element 23 can have a corrective power in the range between +10 diopters and -20 diopters. It should be noted that the lens of the holographic optical element 21 can have an inherent optical power that comes from the lens e of the holographic optical element 21, and the refractive index of the composition of the holographic optical element. Accordingly, the lens of the holographic optical element 21 can contribute to the refractive optical power of the active lens 20. Independently of the foregoing, subsequently in the present, the inherent optical power of the lens of the holographic optical element 21 is ignored, in order to simplify the illustration of the diffraction function of the present holographic optical element lens, since the inherent optical power can easily be factored into the teaching of the present invention. When the lens of the holographic optical element 21 is not activated, the lens of the holographic optical element 21 does not interfere with the light 22 in its path in the normal refractive path caused by the first optical lens element 23. However, when the light enters the lens of the holographic optical element 21 at an angle that activates the lens of the holographic optical element 21 (i.e., enters the activating angle), the light is diffracted by the lens of the holographic optical element 21. As illustrated in the Figure 5, when the entrance light enters the active lens 25 at an angle that activates the lens of the holographic optical element 26, the lens, in conjunction with the first optical lens 27, and the crystalline lens of the eye, focus the light on the retina , more specifically on the fovea. For example, the light 28 originating from a nearby object 29, forms an image 30 on the fovea, when the light enters the lens of the holographic optical element 26 at an angle that is within the programmed activation angle. The incident angle of the entrance light with respect to the active bifocal lens, more specifically to the portion of the holographic optical element of the active lens, can be changed by different means. For example, the active lens can be tilted to change the incident angle of the entrance light, that is, the lens user can change the incident angle of the downward looking light, while maintaining the position of the head. Alternatively, the active lens can have a position that controls the mechanism, which can be actively controlled by the lens user with one or more muscles of the eye. For example, the active lens can be configured to have a ballast, in such a way that the movement of the lens with the lower eyelid can be controlled. It should be noted that the activating angle of the active lens 25 illustrated in Figure 5 is exaggerated, to more easily explain the present invention, and consequently, the activating angle of the active lens need not be as large as the inclined angle illustrated in FIG. Figure 5. In fact, the holographic optical elements suitable for the present invention can be programmed to have a wide range of different trigger angles, according to the programming methods of the holographic optical element known in the holographic technique. According to the above, the degree of movement required for the active lens to change from one optical power to another can be easily changed depending on the design criteria and the needs of each lens user.

Although the active lens of the present invention provides more than one optical power, the active lens forms clearly perceptible images that are focused by one optical power at a time. Consequently, the active lens does not produce hazy or blurry images, unlike conventional bifocal lenses, such as concentric simultaneous bifocal lenses. Returning to Figure 5, when the active lens 25 is positioned to see a nearby object 29 (ie, the incident angle of the light originating from the object 29 is within the lens activating angle of the holographic optical element 26), the light from the object 29 is focused by the lens of the holographic optical element 26, in conjunction with the first optical lens 27 and the crystalline lens of the eye, on the fovea 30. At the same time, the incident angle of the light originating from distant objects, it is not within the activating angle of the active lens 25. According to the above, the path of the input light from distant objects is not modified by the lens of the holographic optical element 26, but the path of the input light from distant objects, i.e., refracted, by the first optical lens 27 and the crystalline lens of the eye. The entrance light from the distant objects, therefore, is focused to form an image in an area 31 that is outside the fovea. Consequently, the focused images of near and distant objects are not concentrically or axially aligned. HE has found that the image, which is formed outside the fovea 31, is not clearly perceived by the user of the active lens 25. and is easily overlooked as peripheral vision. Accordingly, the user of the active lens 25 can clearly see the near object 29 without having fuzzy interference from the light originating from the distant objects. In a similar manner, when the active lens is placed to view a distant object, for example, as illustrated in Figure 4, the light 22 from the distant objects enters the lens outside the activating angle of the holographic optical element 21. Accordingly , the path of the light is not affected by the holographic optical element 21, and is only affected by the first optical element 23 and the crystalline lens of the eye, thus forming an image of the distant object on or near the fovea 24. At the same time, light originating from a nearby object is diffracted and focused by the holographic optical element 21, and is projected onto an area outside the fovea. According to the above, the user of the active lens clearly sees the distant object without significant interference. The advantage that the present active lens is not blurred is a result of the design of the active lens that uses the inherent anatomy of the eye. It is known that the concentration of retinal receptors outside the fovea is drastically lower than inside the fovea. Consequently, any image Focusing substantially outside the fovea is not clearly perceived, because the image is subsampled by the retina and easily passed through the brain of the user of the lens as peripheral vision or images. In fact, it has been found that the visual acuity of a human eye falls to approximately 20/100 for objects only 8 degrees out of line of sight. In the active control manner described above, the present active lens provides clear images from one optical power at a time, using the inherent anatomy of the eye. The use of the inherent anatomy of the eye's retinal receiver, and the ability to program different ranges of activating angles in the lens of the holographic optical element, the present active lens provides in an exclusive and selective way, clear images of the objects that are located at different distances. In contrast to different simultaneous bifocal lenses, the active lens provides clear images without impediments, and in contrast to the translational bifocal lenses, the active lens can be easily designed to require only a small movement of the lens to selectively provide images from different distances. The holographic optical elements suitable for the present invention can be produced, for example, from a polymerizable or crosslinkable optical material, especially a fluid optical material. The materials of the optical element holographic polymerizable and crosslinkable materials are discussed further below. Hereinafter, for purposes of illustration, the term "polymerizable material" is used to indicate both polymerizable and crosslinkable materials, unless otherwise indicated. An exemplary process for producing a holographic optical element of the present invention is illustrated in Figure 6. The light from the dot source object 32 projects to a photopolymerizable optical material 33 (ie, photopolymerizable holographic optical element), and the reference light simultaneously collimated 34 is projected towards the photopolymerizable holographic optical element 33, in such a way that the electromagnetic waves of the light of the object 32 and the reference light 34 form patterns in interference fringes, which are recorded in the material polymerizable as it is polymerized, thereby forming a grid structure in volume in the lens 33. The photopolymerizable holographic optical element 33 is a photopolymerizable material that is polymerized by both the light of the object and the reference light. Preferably, the light of the object and the reference light are produced from a light source, using a beam splitter. The two divided portions of the light are projected onto the holographic optical element 33, where the path of the light portion of the object, of the divided light, is modified to form a point source light 32. The light of the object from source point 32 can be provided, for example, by placing a conventional convex optical lens at some distance from the photopolymerizable holographic optical element 33, such that the light is focused over a desirable distance from the holographic optical element 33, ie on the position of the point source light 32. A preferred light source is a laser source, and an ultraviolet laser source is more preferred. Although the appropriate wavelength of the light source depends on the type of holographic optical element employed, the preferred wavelength ranges are between 300 nanometers and 600 nanometers. When the photopolymerizable holographic optical element 33 is exposed and fully polymerized, the resulting holographic optical element contains a refractive index modulation pattern, i.e., the grid structure in volume 35. In addition, when a polymerizable optical material is used fluid to produce the holographic optical element, the light source transforms the fluid optical material to a non-fluid holographic optical element, while forming the grid structure in volume. The term "fluid" as used herein, indicates that a material can flow as a liquid. Turning to Figure 7, the polymerized holographic optical element 36 has a focal point 38 which corresponds to the light position of the object of the point source 32 of Figure 6, when light 39 enters the holographic optical element 36 from the opposite side of the focal point, and engages, or substantially engages, with the inverted path of the collimated reference light 34 of Figure 6. Figures 6 and 7 provide an example method for producing a holographic optical element. which has a positive corrective power. As can be seen, the holographic optical elements that have a negative corrective power can also be produced with the holographic optical element production setup described above, with minor modifications. For example, a convergent object light source that forms a focal point on the other side of the holographic optical element from the light source, can be used in place of the light of the dot source object to produce a holographic optical element that have a negative corrective power. In accordance with the present invention, active multifocal lenses having different corrective powers can be easily and simply produced., to correct different atrophic conditions, for example, myopia, hyper etropia, presbyopia, regular astigmatism, irregular astigmatism, and combinations thereof. For example, the corrective powers of the holographic optical elements can be changed by changing the distance, position, and / or path of the object's light, and the activating angle of the holographic optical elements can be changed, changing the positions of the holographic optical elements. the light of the object and the reference light.

According to the present invention, suitable holographic optical elements can be produced from polymerizable and crosslinkable optical materials that can be light-cured and photo-reticular relatively quickly. A rapidly polymerizable optical material allows to create a periodic variation in the refractive index inside the optical material, thereby forming a grid structure in volume, while the optical material is being polymerized, to form a solid optical material. An example group of polymerizable optical materials suitable for the present invention is disclosed in U.S. Patent No. 5,508,317 to Beat Müller. A preferred group of polymerizable optical materials, as described in U.S. Patent No. 5,508,317, is that of those having a basic structure of 1,3-diol, wherein a certain percentage of the units of 1,3-diol to 1,3-dioxane, which has in position 2 a radical which can be polymerized, but which does not polymerize. The polymerizable optical material is preferably a derivative of a polyvinyl alcohol having a weight average molecular weight, MM, of at least about 2,000, which, based on the number of polyvinyl alcohol hydroxyl groups, comprises about 0.5 percent to approximately 80 percent of units of formula I: wherein: R is lower alkylene having up to 8 carbon atoms, R1 is hydrogen or lower alkyl, and R2 is an olefinically unsaturated copolymerizable electron attracting radical, preferably having up to 25 carbon atoms. R2 is, for example, an acyl radical. olefinically unsaturated of the formula R3-CO-, wherein R3 is an olefinically unsaturated copolymerizable radical having from 2 to 24 carbon atoms, preferably from 2 to 8 carbon atoms, particularly preferably from 2 to 4 carbon atoms; carbon. In another embodiment, the radical R2 is a radical of the formula II: -CO-NH- (R4-NH-CO-0) q-R5-0-CO-R3 di] where: q is 0 or 1; R4 and R5 are each independently lower alkylene having from 2 to 8 carbon atoms, arylene having from 6 to 12 carbon atoms, a saturated divalent cycloaliphatic group having from 6 to 10 carbon atoms, arylenealkylene, or alkylenearylene which it has from 7 to 14 carbon atoms, or arylenenalkylenearylene having from 13 to 16 carbon atoms; and R3 is as defined above.

R as lower alkylene preferably has up to 8 carbon atoms, and can be straight or branched chain. Suitable examples include octylene, hexylene, pentylene, butylene, propylene, ethylene, methylene, 2-propylene, 2-butylene, and 3-pentylene. Preferably, R as lower alkylene has up to 6, and especially preferably up to 4 carbon atoms. Methylene and butylene are especially preferred. R1 is preferably hydrogen or lower alkyl having up to 7, especially up to 4 carbon atoms, especially hydrogen. As for R 4 and R 5, R 4 or R 5 as lower alkylene preferably has from 2 to 6 carbon atoms, and is especially straight chain. Suitable examples include propylene, butylene, hexylene, dimethylethylene, and especially preferably ethylene. R4 or R5 as arylene, is preferably phenylene which is unsubstituted or substituted by lower alkyl or lower alkoxy, especially 1,3-phenylene or 1,4-phenylene or methyl-1,4-phenylene. R 4 or R 5 as a saturated divalent cycloaliphatic group is preferably cyclohexylene or lower cyclohexylenealkylene, for example cyclohexylenemethylene, which is unsubstituted or is substituted by one or more methyl groups, such as, for example, trimethylcyclohexylenemethylene, for example the divalent isophorone radical . The arylene unit of alkylenearylene or arylenenalkylene in R4 or R5, it is preferably phenylene, unsubstituted or substituted by lower alkyl or lower alkoxy, and the alkylene unit thereof is preferably lower alkylene, such as methylene or ethylene, especially methylene. These radicals R4 or R5 are therefore preferably phenylenemethylene or methylenephenylene. R 4 or R 5, as arylene-alkylene-arylene, is preferably phenylene-lower alkylene-phenylene having up to 4 carbon atoms in the alkylene unit, for example phenylene-ethylene-phenylene. The radicals R4 and R5 are each independently preferably lower alkylene having from 2 to 6 carbon atoms, phenylene, unsubstituted or substituted by lower alkyl, cyclohexylene, or lower cyclohexyalkylene, unsubstituted or substituted by lower alkyl, lower phenylene alkylene, lower phenylene alkylene , or lower phenylene-alkylene-phenylene.

The polymerizable optical materials of the formula I can be produced, for example, by the reaction of a polyvinyl alcohol with a compound III: wherein R, R1, and R2 are as defined above, and R 'and R "are each independently hydrogen, lower alkyl, or lower alkanoyl, such as acetyl or propionyl Desirably, between 0.5 and about 80 percent of the hydroxyl groups of the resulting polymerizable optical material are replaced by compound III Another exemplary polymerizable optical material suitable for the present invention is disclosed in International Patent Application Number PCT / EP96 / 00246 to Mühlebach. Suitable optical materials disclosed therein include derivatives of a polyvinyl alcohol, polyethylene imine, or polyvinylamine containing from about 0.5 to about 80 percent, based on the number of hydroxyl groups in the polyvinyl alcohol, or in the number of imine or amine groups in polyethyleneimine or polyvinylamine, respectively, of units of formulas IV and V: wherein Ri and R2 are, independently of one another, hydrogen, an alkyl group of 1 to 8 carbon atoms, an aryl group, or a cyclohexyl group, wherein these groups are unsubstituted or substituted; R3 is hydrogen or an alkyl group of 1 to 8 carbon atoms, and is preferably methyl; and R4 is a bridge -O- or -NH-, and preferably is -0-. The alcohols polyvinyl, polyethylene imines, and polyvinylamines suitable for the present invention, have a number average molecular weight of between about 2,000 and 1,000,000, preferably between 10,000 and 300,000, more preferably between 10,000 and 100,000, and most preferably between 10,000 and 50,000. A particularly suitable polymerizable optical material is a water-soluble derivative of a polyvinyl alcohol having between about 0.5 and about 80 percent, preferably between about 1 and about 25 percent, more preferably between about 1.5 and about 12 percent, based on the number of hydroxyl groups in the polyvinyl alcohol, of formula IV, having methyl groups for Ri and R2, hydrogen for R3, -O- (ie, an ester bond) for R4 . The polymerizable optical materials of formulas IV and V can be produced, for example, by the reaction of an azalactone of formula VI: where Ri, R2, R3 are as defined above, with a polyvinyl alcohol, a polyethylene imine, or a polyvinylamine, at an elevated temperature, between about 55 ° C and 75 ° C, in a suitable organic solvent, optionally in the presence of a suitable catalyst. Suitable solvents are those which dissolve the base structure of the polymer, and include polar aprotic solvents, for example formamide, dimethylformamide, hexamethylphosphoric triamide, dimethyl sulfoxide, pyridine, nitromethane, acetonitrile, nitrobenzene, chlorobenzene, trichloromethane, and dioxane. The suitable catalyst includes tertiary amines, for example triethylamine, and organotin salts, for example dibutyltin dilaurate. Other groups of holographic optical elements suitable for the present invention can be produced from recording means of conventional holographic optical transmission elements. As the polymerizable materials described above for the holographic optical elements, the light of the object and the collimated reference light are projected simultaneously onto a recording medium of holographic optical element, in such a way that the electromagnetic waves of the object and reference light form patterns in interference fringes. The patterns in interference strips, that is, the grid structure in volume, are recorded in the middle of the holographic optical element. When the recording medium of the optical element is completely exposed holographic, the medium of the registered holographic optical element is developed according to a known holographic optical element development method. Suitable recording means of the holographic optical transmission element include commercially available holographic photographic recording materials or plates, such as dichromatic gelatins. Holographic photography record materials are available from different manufacturers, including Polaroid Corp. When using photographic recording materials such as the holographic optical element, however, the toxicological effects of the materials on the ocular environment must be considered. Accordingly, when a conventional photographic holographic optical element material is used, it is preferred that the holographic optical element be encapsulated in a biocompatible optical material. The biocompatible optical materials useful for encapsulating the holographic optical element include optical materials that are suitable for the first optical element of the present active lens, and these suitable materials are discussed further below. As known in the ophthalmic art, an ophthalmic lens must have a thin dimensional thickness to promote the comfort of the lens user. According to the above, a dimensionally thin holographic optical element is preferred for the present invention. However, in order to provide an optical element When holographic has a high diffraction efficiency, the holographic optical element has to be optically thick, that is, the light must be diffracted by more than one plane of the pattern in interference fringes. One way to provide an optically thick and dimensionally thin optical holographic optical element is to program the pattern into interference fringes in a direction that is inclined toward the length of the holographic optical element. This grid structure in inclined volume causes the holographic optical element to have a large angular deviation between the incident angle of the entrance light and the exit angle of the exit light. However, a holographic optical element having a large angular deviation may not be particularly suitable for an optical lens. For example, when a holographic optical element is used in an ophthalmic lens, and the holographic optical element is activated, the active line of sight doubles significantly away from the normal straight line of vision. As a preferred embodiment of the present invention, this angular limitation in the design of a holographic optical element lens is solved using a holographic optical element in combination of multiple layers, especially a holographic optical element in two layers. Figure 8 illustrates a multilayer holographic optical element of example 40 of the present invention. Two dimensionally thin holographic optical elements are manufactured that have a large angular deviation, in a holographic optical element in combination, to provide a dimensionally thin holographic optical element having a small angular deviation. The holographic optical element in combination 40 has a first dimensionally thin holographic optical element 42, and a second thin holographic optical element 44. The first holographic optical element 42 is programmed to diffract the input light, such that when the light enters the optical holographic element at an activation angle a, the light emerging from the holographic optical element 42 forms an exit angle ß, which is greater than the incident angle a, as shown in Figure 8A. Preferably, the first holographic optical element has a thickness of between about 10 microns and about 100 microns, more preferably between about 20 microns and about 90 microns, and most preferably between about 30 microns and about 50 microns. The second holographic optical element 44 is programmed to have an incident incident angle ß, which is coupled with the exit angle ß of the first holographic optical element 42. In addition, the second holographic optical element 44 is programmed to focus the entrance light at a focal point 46, when the light enters the activating angle ß. Figure 8B illustrates the second holographic optical element 44. Preferably, the second holographic optical element has a thickness of between about 10 microns and about 100 microns, more preferably between about 20 microns and about 90 microns, and most preferably between about 30 microns and about 50 microns. When the first holographic optical element 42 is placed next to the second holographic optical element 44, and the input light is directed at an angle corresponding to the activating angle of the first holographic optical element 42, the light coming out of the holographic optical element in multiple Layers focus the light towards the focal point 46. By utilizing a holographic optical element in combination of multiple layers, a dimensionally thin holographic optical element having a high diffraction efficiency and a small deflection angle can be produced. In addition to the advantages of high diffraction efficiency and small angular deviation, the use of a multi-layer holographic optical element provides additional advantages, including the correction of distortion aberration and chromatic aberration. A single holographic optical element can produce images that have scattering and chromatic aberrations, because the visual light consists of a spectrum of electromagnetic waves that have different wavelengths, and the differences in the wavelengths can make the electromagnetic waves they are diffracted in a different way by the holographic optical element. It has been found that a holographic optical element of multiple layers, especially of two layers, can counteract to correct these aberrations that can be produced by a single-layer holographic optical element. According to the above, a holographic optical element in combination of multiple layers is preferred as the component of the holographic optical element of the active lens. The holographic optical element in combination of multiple layers can be produced from holographic optical element layers produced separately. The layers of the holographic optical element in combination are manufactured and then permanently bonded, in an adhesive or thermal manner, to have a coherent contact. In an alternative way, the holographic optical element in combination can be produced by recording more than one layer of holographic optical elements on an optical material. Preferably, the multiple layers of holographic optical elements are recorded simultaneously. As a preferred embodiment, Figure 10 illustrates a simultaneous recording method for producing a holographic optical element in combination. The simultaneous registration configuration 60 has a first light section and a second light section. The first light section has a first light source 62, a beam splitter 64, a first mirror 66, a second mirror 68, and an optical material holder 70, which holds a polymerizable optical material. The light source 62, preferably one laser source, provides a beam 63 of light to beam splitter 64, and beam splitter 64 divides beam 63 into two portions, preferably two equal portions. The two mirrors 66 and 68 are placed on two opposite sides of the beam splitter 64, such that a divided portion of the light beam, which continues the original path of the light beam 63, is directed towards the first mirror 66, and the reflected portion is directed towards the second mirror 68. The two mirrors direct the two light beams to enter the optical material at an appropriate phase, to register a grid structure in volume from one side (i.e., the first flat surface) of the optical material holder 70. The second light section has the same components as the first light section, i.e., a light source 72, a beam splitter 74, a third mirror 76, a fourth mirror 78, and the Optical material holder 70, which is shared with the first section of light. The components of the second light section are configured in such a way that the divided light beams enter the optical material, which is stopped by the optical material holder 70, from the opposite side of the first light section (i.e. the second surface of the fastener), and in an appropriate registration phase to register a grid structure in volume from the second surface. The resulting polymerized holographic optical element has two layers of holographic optical element.

As another preferred embodiment, Figure 11 illustrates a second method of simultaneous recording to produce a holographic optical element in combination. The second simultaneous registration configuration 80 also has a first light section and a second light section. A bidirectional emission light source 71 provides coherent light beams towards the two light sections. For the first light section, a light beam 83 from the light source 81 is reflected by a mirror 82 to a beam splitter 84. The light beam 83 is divided into two beams, preferably two equal portions, 85 and 87. The first beam 85 is allowed to traverse the path of the light beam 83, and the second beam 87 is directed towards the opposite direction of the first beam 85. Both beams 85 and 87 are reflected by the mirrors 86 and 88, respectively, and they are directed towards a fastener of optical material 90. The fastener of optical material 90, which is a mold containing a polymerizable optical material, and has two flat or relatively flat surfaces, is positioned in such a way that the two light beams 85 and 87 enters the optical material holder 90 from the opposite flat surfaces. Based on the illustration of Figure 11, the first light beam 85 enters the optical material holder 90 from the right flat surface, and the second light beam 87 enters the optical material holder 90 from the left flat surface. The second section of light also has the same components that the first light section: a mirror 92, a beam splitter 94, a pair of mirrors 96 and 98, and the optical material holder 90, which is shared by the two light sections. The beam splitter 94 of the second light section provides two light beams, that is, a third light beam 95 and a fourth light beam 97, and the pair of mirrors 96 and 98 direct the light beams to enter the light beam. fastener of optical material 90 from the two flat surfaces. The first light beam 85 and the second light beam 95 are coherent, and enter the optical material holder 90 at an appropriate stage, to register a grid structure in volume in the optical material held in the holder 90, starting from the optical material located near the flat entrance surface. The second beam of light 87 and the fourth beam of light 97 are also coherent, and enter the optical material holder 90 from the other flat surface. The two light beams are in an appropriate phase to register a grid structure in volume in the optical material, starting from the optical material located near the flat entrance surface. Preferably, the register configuration 80 additionally has light polarizers that polarize the first and third light beams towards a coherent and polarized direction, and the second and fourth light beams towards another coherent and polarized direction, such that both pairs of light beams do not interfere with each other. In addition, for both previous simultaneous recording methods, it is preferred that each pair of light beams have sufficient polymerization influence on only half of the optical material in the optical material holder, which are located closer to the input flat surface, thus forming efficiently two layers of different optical holographic element. It should be noted that, although the present invention is illustrated above with a fastener of optical material, or a mold having two flat surfaces receiving the recording light beams, the surfaces may have other configurations, including concave and convex surfaces, and combinations thereof. The simultaneous recording methods are particularly suitable for producing holographic optical elements from the polymerizable or crosslinkable optical materials previously disclosed. A polymerizable or crosslinkable optical material is placed in a fastener of enclosed optical material that can transmit light, i.e., a mold. Molds suitable for the simultaneous recording configuration include conventional lens molds to produce contact lenses. A typical lens mold is produced from a transparent thermoplastic or can transmit ultraviolet, and has two mold halves, i.e. one mold half having the first surface of the lens, and the other mold half having the second lens surface.

When the optical material is placed in a mold, the registration configuration is activated to polymerize the optical material and simultaneously record two grid structures in volume in the optical material from the two opposite surfaces defined by the two halves of the mold. Optionally, after the optical element forms the grid structures in volume, the setting of registration light is deactivated, and the optical element is subjected to a subsequent curing step, to ensure that all of the fluid optical material is completely polymerized. mold. For example, the reference light source alone is activated to subsequently cure the optical material. With the simultaneous registration method, a holographic optical element can be produced in combination in a relatively simple manner, and a wide variety of holographic optical elements can be produced having different activation angles, changing the positions and angles of the mirrors and of the beam splitters in the configuration. Preferably, an effective amount of a light absorbing compound (e.g., an ultraviolet absorber when an ultraviolet laser device is used) is added to the polymerizable optical material in the mold, such that light beams entering from one side of the mold (ie, the first surface defined by the mold) does not have a strong polymerization influence on the optical material that is locate closer to the second side of the mold. The addition of the light absorber ensures that different layers of holographic optical elements are formed, and that the polymerization light entering from one side of the mold does not interfere with the polymerization light entering from the other side. The effective amount of a light absorber varies depending on the efficiency of the light absorber, and the amount of the light absorber should not be so high as to interfere in a meaningful way with the proper polymerization of the optical material. Although preferred light absorbers are biocompatible light absorbers, especially when the present invention is used to produce ophthalmic lenses, non-biocompatible light absorbers can be used. When a non-biocompatible light absorber is used, the resulting holographic optical element can be removed to remove the light absorber after the holographic optical element is completely formed. Exemplary ultraviolet absorbers for optical materials include o-hydroxyphene derivatives, o-hydrophenyl salicylates, and 2- (o-hydroxyphenyl) benzotria-zoles, benzenesulfonic acid, and hindered amine. Particularly suitable ultraviolet absorbers include locally acceptable ultraviolet absorbers, for example 2,4-dihydroxybenzophenone, 2,2'-dihydro-4,4-dimethoxybenzophenone, 2-hydroxy-4-methoxybenzophenone, and the like. One type of example uses between 0.05 and 0.2 weight percent of an ultraviolet absorbent, preferably a benzenesulfonic acid derivative, for example 2, 2 '- ([1, 1' -biphenyl] -4,4 '-di -ildi-2, l-etendi-yl) bis-disodium of benzenesulfonic acid. As another embodiment of the present invention, the holographic optical element in combination can be produced by a sequential recording method. A closed mold assembly, having a pair of two mold halves, containing a polymerizable or fluid crosslinkable optical material, is subjected to a volume grid registration process, and then the mold assembly is opened while leaves the formed holographic optical element layer adhered to the optical surface of the first mold half. An additional amount of the polymerizable optical material or a second chemically compatible polymerizable optical material is placed on the first layer of the holographic optical element. Then, a new half of couple mold is coupled, having a cavity volume larger than half the mold previously removed, with the mold half having the first holographic optical element layer. The new mold assembly is subjected to a second registration process of grid structure in volume to form a second layer of holographic optical element on the first holographic optical element layer. The resulting holographic optical element is a holographic optical element in combination that has two layers of holographic optical element formed in sequence and together. According to the present invention, the holographic optical elements of the present invention preferably have a diffraction efficiency of at least about 70 percent, more preferably at least about 80 percent, and most preferably at least 95 percent. one hundred, over all, or substantially all wavelengths within the spectrum of visible light. The holographic optical elements especially suitable for the present invention have a diffraction efficiency of 100 percent over all wavelengths of the visible light spectrum. However, holographic optical elements that have a diffraction efficiency lower than that specified above, can also be used for the present invention. Additionally, the preferred holographic optical elements for the present invention have an acute transition angle between the activated and non-activated stages, and have no gradual transition angles, such that the activation and deactivation of the holographic optical element can be achieved by a small movement of the active lens, and in such a way that no transition images are formed, or are minimal, by the holographic optical element, during the movement between the activated and deactivated stages. As for the first optical material of the active lens, an optical material suitable for a lens can be used hard, a gas permeable lens, or a hydrogel lens. Polymeric materials suitable for the first optical element of the active ophthalmic lens include hydrogel materials, rigid gas permeable materials, and rigid materials, which are known to be useful for producing ophthalmic lenses, for example contact lenses. Suitable hydrogel materials typically have a crosslinked hydrophilic network, and contain between about 35 percent and about 75 percent, based on the total weight of the hydrogel material, of water. Examples of suitable hydrogel materials include copolymers having 2-hydroxyethyl methacrylate, and one or more comonomers, such as 2-hydroxyl acrylate, ethyl acrylate, methyl methacrylate, vinylpyrrolidone, N-vinylacrylamide, hydroxypropyl methacrylate, isobutyl methacrylate, styrene, ethoxyethyl methacrylate, triethylene glycol methoxy methacrylate, glycidyl methacrylate, diacetone acrylamide, vinyl acetate, acrylamide, hydroxytrimethylene acrylate, methoxymethyl methacrylate, acrylic acid, methacrylic acid, glyceryl ethacrylate, and acrylate of dimethylaminoethyl. Other suitable hydrogel materials include copolymers having methyl vinylcarbazole or dimethylaminoethyl methacrylate. Another group of suitable hydrogel materials include polymerizable materials, such as modified polyvinyl alcohols, polyethylene imines, and polyvinylamines, for example, as disclosed in U.S. Patent Number 5,508,317, issued to Beat Müller, and in International Patent Application Number PCT / EP96 / 01265. Still another group of highly suitable hydrogel materials include silicone copolymers, disclosed in International Patent Application Number PCT / EP96 / 01265. Rigid gas permeable materials suitable for the present invention include cross-linked siloxane polymers. The network of these polymers incorporates appropriate crosslinking agents, such as N, N '-dimethyl-bis-acrylamide, ethylene glycol diacrylate, trihydroxypropane triacrylate, pentaerythritol tetra-acrylate, and other similar polyfunctional acrylates or methacrylates, or vinyl compounds, by example, N, m-ethylaminodivinylcarbazole. Suitable rigid materials include acrylates, for example methacrylates, diacrylates, and dimethacrylates, pyrrolidones, styrenes, amides, acrylamides, carbonates, vinyls, acrylonitriles, nitriles, sulfones, and the like. Of the suitable materials, hydrogel materials for the present invention are particularly suitable. According to the present invention, the first optical element and the holographic optical element can be laminated, or the holographic optical element can be encapsulated in the first optical element to form the active lens, when practicing one of the active lens modalities. compound. In addition, when an active ophthalmic lens is produced using a non-biocompatible holographic optical element, the holographic optical element is preferably encapsulated in the first optical element, such that the holographic optical element does not make direct contact with the ocular environment, because the holographic optical element can adversely affect long-term corneal health. Alternatively, as discussed above, the active lens can be produced from a biocompatible holographic optical element, such that a holographic optical element can provide both the diffraction and refractive function, for example, the first and second optical powers, of the active lens. Figure 9 illustrates another embodiment of the present invention. A bifocal eyeglass lens 50 is formed by laminating a layer of a first optical material having a first optical power 52, which provides an optical power, and a layer of a holographic optical element 54, which provides a second optical power . The two layers are manufactured separately, and then bonded, for example, in a thermal or adhesive manner. Composite lenses can be machined subsequently to fit a spectacle frame, in order to provide a pair of bifocal glasses. The first optical material 52 is a conventional optical material that has been used to produce glasses, for example glass, polycarbonate, polymethyl methacrylate, or the like, and the holographic optical element is any holographic optical material that can be programmed to focus the input light, as described above. Alternatively, the bifocal eyeglass lens can be produced from a holographic optical element configured in such a way that the optical shape of the holographic optical element provides a refractive power when the holographic optical element is not activated, and the structure of grid in volume of the holographic optical element provides a diffraction power when activated. The present multifocal optical lens can be controlled in an active and selective manner to provide a desired optical power at a time without, or substantially without, optical interference from the other optical powers of the lens, unlike conventional bifocal lenses. In addition, the programmable nature of the holographic optical element of the active lens, makes the lens highly suitable for correcting atrophic conditions, which are not easily accommodated by conventional corrective optical lenses. For example, the active lens can be programmed to take corrective measures for the unequal and distorted corneal curvature of an irregular astigmatic condition, by the specific design of the object and reference light configurations. The present invention is further illustrated with The following examples. However, the examples should not be construed to limit the invention to them.

EXAMPLES Example 1: Approximately 0.06 milliliters of a Nelfilcon A monomer lens composition are deposited in the central portion of a female mold half, and a male coupling mold half is placed on the female mold half, forming a mold assembly of lens. The male mold half does not touch the female mold half, and they are separated by approximately 0.1 millimeters. The lens mold halves are made of quartz, and are masked with chrome, except for the central circular portion of the lens of approximately 15 millimeters in diameter. Briefly, Nelfilcon A is a crosslinkable modified polyvinyl alcohol product containing approximately 0.48 millimoles / gram of an acrylamide crosslinker. Polyvinyl alcohol has approximately 7.5 mole percent acetate content. Nelfilcon A has a solid content of approximately 31 percent, and contains approximately 0.1 percent of a photoinitiator, Durocure® 1173. The closed lens mold assembly is placed under a laser apparatus. The laser apparatus provides two coherent collimated ultraviolet laser beams having a wavelength of 351 nanometers, wherein a beam is passed through an optical convex lens, such that the focal point is form 500 millimeters from the lens mold assembly. The focused light serves as a point source object light. The angle formed between the light trajectories of the object and the reference light is approximately 7 degrees. The apparatus provides a holographic optical element that has an aggregate corrective power of two diopters. The monomeric lens composition is exposed to laser beams having approximately 0.2 watts for about 2 minutes, to completely polymerize the composition, and to form patterns of interference fringes. Because the lens mold is masked except for the central portion, the lens monomer exposed in the circular center portion of the mold is subjected to the light of the object and the reference light and polymerized. The mold assembly opens, leaving the lens attached to the male mold half. Again, approximately 0.06 milliliters of the Nelfilcon A monomer lens composition is deposited in the central portion of the female mold half, and the male mold half with the formed lens is placed on the female mold half. The male and female mold halves are separated by approximately 0.2 millimeters. The closed mold assembly is again exposed to the laser apparatus, except that the convex optical lens of the object light apparatus is removed. The monomeric composition is again exposed to the laser beams for approximately 2 minutes, to completely polymerize the composition, and to forming a second layer of patterns of interference fringes. The resulting composite lens has an optical power based on the shape of the lens and the refractive index of the lens material, and an additional activatable corrective power of +2 diopters.

Example 2: Example 1 is repeated, except that the laser apparatus for the second layer is modified. For the second layer, the grid structure record for the first layer is repeated. The resulting holographic optical element is a combination holographic optical element having two layers of grid structures in volume. When the cross section of the holographic optical element is studied under an electron microscope, two distinct layers of grid structures in volume are clearly observed.

Example 3: A programming of the holographic optical element is used as discussed above in conjunction with Figure 11, to produce a holographic optical element in combination. The programming facility has the object light and reference light sections equally configured. The light source provides a collimated ultraviolet laser beam that has a wavelength of 351 nanometers, and the light source provides enough energy to deliver 1 to 2 mW / cm2, when each beam of light enters the beam. fastener of optical material. Two flat quartz slides, which are separated by approximately 50 microns, are used as the fastener of optical material, and a sufficient amount of an optical crosslinkable material is placed in the optical material to form a circular cylinder that is 14 millimeters in diameter. The crosslinkable optical material used is Nelfilcon A modified with ultraviolet absorber. Nelfilcon A is modified by adding 0.1 weight percent of Stilbene 420, which is available in Exitron, and which is the salt 2,2 '- ([1, 1' -biphenyl] -4,4 '-di-ildi - 2, 1-etendy-yl) bis-disodium of benzenesulfonic acid. The optical material in the mold is irradiated from both sides by the object and reference laser beams for four minutes, to record two layers of the grid structures in volume from both flat surfaces of the mold.

The resulting combination holographic optical element is a flexible hydrogel holographic optical element having two distinct layers of holographic optical element. Each of the two layers of holographic optical element occupies about half the thickness of the holographic optical hydrogel element.

Claims (20)

1. CLAIMS 1. An optical lens comprising a first optical element and a holographic optical element in transmission volume, wherein the first optical element provides a first optical power at a first focal point, and the holographic optical element provides a second optical power at a second focal point, wherein the holographic optical element is a holographic optical element in combination, and diffracts up to 100 percent of the input light when the Bragg condition is satisfied. The optical lens of claim 1, wherein the holographic optical element in combination has two layers of holographic elements. 3. The optical lens of claim 2, wherein the two layers of holographic elements are separately manufactured layers. 4. The optical lens of claim 2, wherein the two layers of holographic elements are simultaneously recorded layers. 5. The optical lens of claim 1 which is biocompatible. 6. The optical lens of claim 1 which is a contact lens. 7. The optical lens of claim 1 which is a spectacle lens. 8. A method for producing a holographic element in two layers, which comprises the steps of: h) providing a beam of light from a first source, i) dividing this beam of light from the first source into first and second light beam, ) providing a recordable holographic element having a first and second opposingly located surface, said surfaces being flat, concave, or convex, k) directing the first and second light beam towards the first and second surface, respectively, of the recordable holographic element, 1) providing a beam of light from a second source, m) dividing the light beam from the second source into a third and fourth beam of light, and n) directing the third and fourth beam of light towards the first and second surface, respectively, of the recordable holographic element, wherein: the first and third light beams have appropriate phase relationships to register a grid structure from the first surface of the holographic element re gistrable, and the second and fourth light beams have appropriate phase relationships to register a grid structure from the second surface of the recordable holographic element. The method of claim 8, wherein the recordable holographic element comprises an optical material crosslinkable or polymerizable. 10. The method of claim 9, wherein the recordable holographic element is a fluid optical material that forms a non-fluid optical material when exposed to light beams. The method of claim 9, wherein the recordable holographic element further comprises an ultraviolet absorber. The method of claim 9, wherein this method further comprises the step of subsequently curing the registered optical element with the reference beams. 13. An optical lens comprising a holographic optical element in transmission volume, this optical element having a programmed activating angle, wherein the optical element provides a first optical power for light to enter the optical element at an angle outside the activating angle , and provides a second optical power for light to enter the optical element at an angle within the activating angle, and wherein the holographic optical element is a holographic optical element in combination. The optical lens of claim 13, wherein the optical lens is an ophthalmic lens. 15. The optical lens of claim 13, wherein the optical lens is a contact lens. 16. The optical lens of claim 13, wherein the holographic optical element in combination has at least two layers of holographic elements. 17. A method for producing a composite holographic element, which comprises the steps of: q) providing a first polymeric fluidizable or crosslinkable optical material in a first mold; r) registering a first grid structure in volume in the optical material, thereby forming a first non-fluid holographic optical element layer; s) providing a second mold, this second mold having a larger cavity volume than the first layer of the holographic optical element, and maintaining this first layer of holographic optical element on a surface thereof; t) providing a second polymerizable or crosslinkable fluid optical material in the second mold on the first holographic optical element layer; and u) registering a second grid structure in volume in the second optical material, thereby forming a second non-fluid holographic optical element layer, wherein: the first and second holographic optical element layer are joined in a coherent manner. The method of claim 17, wherein the first and second fluid optical material are the same fluid optical material. 19. The method of claim 17, wherein the first and second fluid optical material are chemically compatible optical materials. 20. A method for producing a holographic element in two layers, which comprises the steps of: t) providing a recordable holographic element having an opposing first and second surface, u) providing a beam of light from a first source, v ) dividing the light beam of the first source into first and second hz of light,) directing the first and second light beams towards the first surface of the recordable holographic element, x) providing a beam of light from a second source, and) dividing the light beam of the second source into third and fourth light beam, and z) directing the third and fourth light beam towards the second surface of the recordable holographic element, wherein: the first and second beam of light have phase relationships suitable for registering a grid structure from the first surface of the recordable holographic element, and the third and fourth beam of light have appropriate phase relationships to register a structure grating from the second surface of the recordable holographic element.