LIQUID CRYSTAL COMPOUNDS AND COMPOSITIONS FOR TUNABLE LENSES
20230212458 · 2023-07-06
Inventors
- Huiyang Deng (Cupertino, CA, US)
- Jeffrey G. Koller (Cupertino, CA, US)
- Jiaqi Jiang (Cupertino, CA, US)
Cpc classification
C07C25/24
CHEMISTRY; METALLURGY
C09K19/18
CHEMISTRY; METALLURGY
C07C25/18
CHEMISTRY; METALLURGY
G02F1/29
PHYSICS
International classification
C09K19/30
CHEMISTRY; METALLURGY
C07C25/24
CHEMISTRY; METALLURGY
C07C25/18
CHEMISTRY; METALLURGY
Abstract
The disclosure is generally directed to compounds and compositions that can be used as liquid crystal materials in adjustable ophthalmic lenses.
Claims
1. A compound having the structure of Formula (I): ##STR00011## wherein R.sub.1 is selected from hydrogen, a saturated C.sub.1-10 alkyl, halogen, and pseudohalogen; R.sub.2 and R.sub.3 are each independently selected from hydrogen, a halogen, and a pseudohalogen; R.sub.4 is selected from Formula (II) and Formula (III): ##STR00012## m is an integer from 1 to 5; R.sub.5 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy; n is an integer from 1 to 5; and R.sub.6 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy.
2. The compound of claim 1, selected from a structure of Formulae (IV), (V), and (VI): ##STR00013## wherein R.sub.1 is selected from hydrogen, a saturated C.sub.1-10 alkyl, a halogen, and a pseudohalogen; R.sub.2 and R.sub.3 are each independently selected from hydrogen, a halogen, and a pseudohalogen; R.sub.7 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy; R.sub.8 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy; and R.sub.9 is saturated C.sub.1-C.sub.10 alkyl.
3. The compound of claim 2, wherein the compound has the structure of Formula (IV).
4. The compound of claim 3, wherein R.sub.1 is a pseudohalogen.
5. The compound of claim 4, wherein R.sub.1 is NCS.
6. The compound of claim 3, wherein R.sub.2 and R.sub.3 are each independently selected from H and F.
7. The compound of claim 3, wherein R.sub.7 is selected from C.sub.2H.sub.5, C.sub.4H.sub.9, and C.sub.2H.sub.5O.
8. The compound of claim 2, wherein the compound has the structure of Formula (V).
9. The compound of claim 8, wherein R.sub.1 is a pseudohalogen.
10. The compound of claim 9, wherein R.sub.1 is NCS.
11. The compound of claim 8, wherein R.sub.2 and R.sub.3 are each independently selected from H and F.
12. The compound of claim 8, wherein R.sub.8 is selected from C.sub.3H.sub.7 and C.sub.5H.sub.11.
13. The compound of claim 2, wherein the compound has the structure of Formula (VI).
14. The compound of claim 14, wherein R.sub.1 is a pseudohalogen.
15. The compound of claim 15, wherein R.sub.1 is NCS.
16. The compound of claim 14, wherein R.sub.2 and R.sub.3 are each independently selected from H and F.
17. The compound of any claim 14, wherein R.sub.9 is selected from C.sub.2H.sub.5 and C.sub.4H.sub.9.
18. A composition comprising a first compound and a second compound each according to claim 1, wherein the first compound and second compound are different.
19. A liquid crystal cell comprising: a first transparent substrate and a second transparent substrate on opposing sides of a liquid crystal layer, the liquid crystal layer comprising a compound according to claim 1.
20. The liquid crystal lens comprising a first liquid crystal cell, a second liquid crystal cell, and a third liquid crystal cell, each of the first liquid crystal cell, second liquid crystal cell, and third liquid crystal cell is according to claim 20.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] Non-limiting aspects of the disclosure are described by reference to the drawings and descriptions.
[0034]
[0035]
[0036]
[0037]
[0038]
[0039]
OPHTHALMIC LENSES
[0040] The disclosure is directed to ophthalmic lenses having liquid crystal compounds or compositions included herein.
[0041] A cross-sectional side view of an illustrative ophthalmic lens is shown in
[0042] At each location of electrode strips 38 in component 22, a voltage can be applied across liquid crystal layer 34 by supplying a first voltage to electrode 38 and a second voltage (e.g., a ground voltage) to common electrode 36. The liquid crystal between the two electrodes will receive an applied electric field with a magnitude that is proportional to the difference between the first and second voltages on the electrodes. By controlling the voltages on electrodes 38 and common electrode 36, the index of refraction of liquid crystal layer 34 of component 22 can be dynamically adjusted to produce customized lenses.
[0043] In the example of
[0044] When an electric field is applied to the liquid crystals of layer 34, the liquid crystals change orientation. The speed at which a given liquid crystal material can be reoriented is limited by factors such as the thickness of layer 34 (e.g., thickness T1 of
[0045] Lens component 22 can include two or more liquid crystal cells 40 stacked on top of one another. This type of arrangement is illustrated in
[0046] As shown in
[0047] The cell gap of each liquid crystal cell 40 in module 44 can be less than that of liquid crystal cell 40 of
[0048] At each location of finger electrode 38 in component 22, a voltage can be applied across each liquid crystal layer 34 by supplying a first voltage to finger electrode 38 and a second voltage (e.g., a ground voltage) to common electrode 36. The liquid crystal between the two electrodes will receive an applied electric field with a magnitude that is proportional to the difference between the first and second voltages on the electrodes. By controlling the voltages on electrodes 38 and common electrode 36, the index of refraction of each liquid crystal layer 34 of component 22 can be dynamically adjusted to produce customized lenses. Because finger electrodes 38 extend along the X-dimension, the phase profile of each liquid crystal cell 40 can be modulated in the Y-dimension by applying the desired voltages to each finger electrode 38.
[0049] Overlapping portions of the two liquid crystal layers 34 in module 44 can be controlled using the same or different voltages to achieve the desired index of refraction at that portion of module 44. For example, finger electrode 38A of upper liquid crystal cell 40 in module 44 can overlap finger electrode 38B of lower liquid crystal cell 40 in module 44. A first voltage V1 can be applied across a portion of upper liquid crystal layer 34 overlapping finger electrode 38A, and a second voltage V2 can be applied across a portion of lower liquid crystal layer 34 overlapping finger electrode 38B. Voltages V1 and V2 can be different or can be the same. Control circuitry 26 can determine the ratio of V1 to V2 based on the desired index of refraction at that portion of the liquid crystal module 44.
[0050]
[0051]
[0052] In
[0053] In various aspects, the compounds and compositions of the disclosure can be used in the liquid crystal lenses described in U.S. Pat. No. 11,086,143, which is incorporated herein by reference in its entirety.
[0054] The disclosure is directed to devices including a tunable liquid crystal lens. In various aspects, liquid crystals can be designed to have properties including but not limited to a lower viscosity, higher elastic constant (K33), and more polarizable compounds. Liquid crystal lenses using the compounds and compositions as liquid crystal materials thereby provide for improve tunable lenses in the visible spectrum (400 nm-750 nm). The lenses can be used in, for example, automated presbyopia glasses and AR/VR glasses.
Compounds
[0055] Liquid crystal cells described herein include a liquid crystal layer comprising the compounds or compositions of the disclosure.
[0056] In one variation, the compound has the structure of formula (I):
##STR00006##
[0057] wherein
[0058] R.sub.1 is selected from a hydrogen, saturated C.sub.1-10 alkyl, halogen, and pseudohalogen;
[0059] R.sub.2 and R.sub.3 are each independently selected from hydrogen, a halogen, and a pseudohalogen;
[0060] R.sub.4 is selected from the structure of Formula (II) or Formula (III):
##STR00007##
[0061] m is an integer from 1 to 5;
[0062] R.sub.5 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy;
[0063] n is an integer from 1 to 5; and
[0064] R.sub.6 is saturated C.sub.1-C.sub.10 alkyl or saturated C.sub.1-C.sub.10 alkoxy.
[0065] The substituents can be selected from a range of possible options.
[0066] In some variations, R.sub.1 is hydrogen. In some variations, R.sub.1 is a saturated C.sub.1-10 alkyl. In some variations, R.sub.1 is a saturated C.sub.1-5 alkyl. In some variations, R.sub.1 is a saturated C.sub.1-2 alkyl. In some variations, R.sub.1 is ethyl. In some variations, R.sub.1 is methyl. In some variations, R.sub.1 is a halogen. In some variations, R.sub.1 is a pseudohalogen. In some further variations, R.sub.1 is a cyano substituent. In some further variations, R.sub.1 is a thioisocyanate substituent.
[0067] In some variations, R.sub.2 and R.sub.3 are each independently selected from hydrogen or a halogen. In some variations, R.sub.2 and R.sub.3 are both hydrogen. In some variations, R.sub.2 and R.sub.3 are both a halogen. In some variations, the halogen is fluorine. In some variations, R.sub.2 and R.sub.3 are both fluorine. In some variations, R.sub.2 is hydrogen and R.sub.3 is a halogen.
[0068] When R.sub.4 is Formula (II), in some variations m is 1. In some variations, m is 2. In some variations, m is 3. In some variations, m is 4. In some variations, m is 5. Further, when R.sub.4 is Formula (II), R.sub.5 is a saturated alkyl. In some variations, R.sub.5 is a saturated straight chain C.sub.1-C.sub.10 alkyl. In some variations, R.sub.5 is a saturated straight chain C.sub.1-C.sub.5 alkyl. In some variations, R.sub.5 is n-butyl. In some variations, R.sub.5 is n-propyl. In some variations, R.sub.5 is ethyl. In some variations, R.sub.5 is methyl. In some variations, R.sub.5 is a C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.5 is a saturated C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.5 is cyclohexyl. In some variations, R.sub.5 is a saturated C.sub.1-C.sub.10 alkoxy. In some variations, R.sub.5 is a saturated C.sub.1-C.sub.5 alkoxy.
[0069] When R.sub.4 is Formula (III), in some variations n is 1. In some variations, n is 2. In some variations, n is 3. In some variations, n is 4. In some variations, n is 5. Further, when R.sub.4 is Formula (III), R.sub.6 is a saturated alkyl. In some variations, R.sub.6 is a saturated straight chain C.sub.1-C.sub.10 alkyl. In some variations, R.sub.6 is a saturated straight chain C.sub.1-C.sub.5 alkyl. In some variations, R.sub.6 is n-butyl. In some variations, R.sub.6 is n-propyl. In some variations, R.sub.6 is ethyl. In some variations, R.sub.5 is methyl. In some variations, R.sub.6 is a C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.6 is a saturated C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.6 is cyclohexyl. In some variations, R.sub.6 is a saturated C.sub.1-C.sub.10 alkoxy. In some variations, R.sub.6 is a saturated C.sub.1-C.sub.5 alkoxy. In various aspects, R.sub.4 can be combined with any structure or variable herein, in any combination.
[0070] In some variations, the compound has the structure of Formula (IV):
##STR00008##
[0071] wherein R.sub.1, R.sub.2, and R.sub.3 can be as described herein, in any combination, and R.sub.7 is a saturated alkyl. In some variations, R.sub.7 is a saturated straight chain C.sub.1-C.sub.10 alkyl. In some variations, R.sub.7 is a saturated straight chain C.sub.1-C.sub.5 alkyl. In some variations, R.sub.7 is n-butyl. In some variations, R.sub.7 is n-propyl. In some variations, R.sub.7 is ethyl. In some variations, R.sub.7 is methyl. In some variations, In some variations, R.sub.7 is a saturated C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.7 is cyclohexyl. In some variations, R.sub.7 is a saturated straight chain C.sub.1-C.sub.10 alkoxy. In some variations, R.sub.7 is —OC.sub.2H.sub.5, —OC.sub.4H.sub.9, or —OC.sub.5H.sub.11.
[0072] In some variations, the compound has the structure of Formula (V):
##STR00009##
[0073] wherein R.sub.1, R.sub.2, and R.sub.3 can be as described herein, in any combination, and R.sub.8 is a saturated alkyl. In some variations, R.sub.8 is a saturated straight chain C.sub.1-C.sub.10 alkyl. In some variations, R.sub.8 is a saturated straight chain C.sub.1-C.sub.5 alkyl. In some variations, R.sub.8 is n-butyl. In some variations, R.sub.8 is n-propyl. In some variations, R.sub.8 is ethyl. In some variations, R.sub.8 is methyl. In some variations, R.sub.8 is a saturated C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.8 is cyclohexyl. In some variations, R.sub.8 is a saturated straight chain C.sub.1-C.sub.10 alkoxy. In some variations, R.sub.8 is —OC.sub.2H.sub.5, —OC.sub.4H.sub.9, or —OC.sub.5H.sub.11.
[0074] In some variations, the compound has the structure of Formula (IV):
##STR00010##
[0075] wherein R.sub.1, R.sub.2, and R.sub.3 can be as described herein, in any combination, and R.sub.9 is a saturated alkyl. In some variations, R.sub.9 is a saturated straight chain C.sub.1-C.sub.10 alkyl. In some variations, R.sub.9 is a saturated straight chain C.sub.1-C.sub.5 alkyl. In some variations, R.sub.9 is n-butyl. In some variations, R.sub.9 is n-propyl. In some variations, R.sub.9 is ethyl. In some variations, R.sub.9 is methyl. some variations, R.sub.9 is a saturated C.sub.5-C.sub.10 cycloalkyl. In some variations, R.sub.9 is cyclohexyl.
Intramolecular Properties
[0076] The compounds of the disclosure have properties that improve their use in liquid crystals.
Rigid Core and Bridging Group
[0077] The rigid core containing phenyl substituents and optional pi bond bridges can provide higher polarizability. Connecting multiple pi bonds in succession can provide for delocalized electrons over a longer intramolecular distance. Larger number of phenyl substituents and pi-containing bridges can increase the polarizability of the compound. The delocalized electrons thereby can result in a super-linear increase in polarizability of the compound.
[0078] The difference in refractive index along the long axis and transverse axis of the compound corresponds to the difference in polarizability. Increased polarizability results in increased tunability of the liquid crystal.
[0079]
[0080] A macroscopic change in refractive index can be achieved by rotation of the molecule. As such, the relative long axis to the transverse axis corresponds to the polarizability of light incident on the liquid crystal. This property can be measured as Δn for wavelengths in the visible spectrum, determined by difference in polarizability along the long axis versus the transverse axis.
Polar Groups
[0081] A polar groups can be at the terminal end of the compounds of the disclosure (e.g., a halogen or pseudohalogen as R.sub.1 in the compounds of Formula (I)), creating a permanent dipole moment of the compound. In some variations, the polar group can be a halogen. In some variations, the polar group can be a pseudohalogen. The polar group can be a cyano moiety, or alternatively the polar group can be a thioisocyanate moiety.
[0082] In some variations, the polar group is an NCS moiety. The NCS moiety remains polarizable, but has a reduced permanent dipole moment, thereby having a lower likelihood of forming dipole-dipole interactions. Dimerization results in increased viscosity and consequent worse responsiveness when used as a liquid crystal-based high-speed tunable lens, for example. In some variations, the compounds of the disclosure include optional transverse moieties (e.g., R.sub.2 and R.sub.3 in the compounds of Formula (I)). These transverse moieties are outside central axis of the compound. The transverse moieties provide a repulsive force that increases the space between compounds, thereby further decreasing viscosity.
Terminal Group
[0083] As described herein, saturated terminal substituents opposite the polar group (e.g. substituent R.sub.5 in Formula (II), R.sub.6 in Formula (III), R.sub.7 in Formula (IV), R.sub.8 in Formula (V), or R.sub.9 in Formula (VI)) can increase intermolecular distances between compounds, thereby further reducing intermolecular interactions in the composition. In some variations, the non-polar terminal group is a saturated alkyl group. In further variations, the saturated alkyl group can be a C.sub.1-10 saturated alkyl group or alternatively a C.sub.1-5 saturated alkyl group. In further variations, the alkyl group can be a C.sub.1-10 saturated cycloalkyl group, for example a cyclohexyl group. The length or size of the saturated alkyl group can reduce the viscosity of the compound or composition. Reducing viscosity of the compounds when used as a liquid crystal improves the response speed of liquid crystal tunable lens in the visible spectrum. Reduced viscosity also can provide for a larger tuning range and aperture of the lens given the same figure of merit in the visible spectrum, as discussed herein.
Compositions
[0084] In some variations, the disclosure is directed to a composition including multiple compounds described herein. By combining multiple compounds into a composition, the melting point of the liquid crystal can be reduced such that the liquid crystal composition has a lower melting point. Further, the clearing temperature can be increased such that the composition does not become isotropic.
[0085] Any number of compounds can be used in the composition. In some non-limiting variations, the composition can include any number between 1-20 compounds disclosed herein. In some variations, the composition can include any number between 1-15 compounds disclosed herein. In some variations, the composition can include any number between 1-10 compounds disclosed herein. In some variations, the composition can include any number between 1-5 compounds disclosed herein. The relative amounts of different compounds in the composition can be in any amount, and do not have to be in equal amounts.
[0086] The melting temperature of the liquid crystal can be further reduced by combining different compounds of the disclosure to form the disclosed compositions. The resulting eutectic composition has a lower effective melting point temperature as compared to the melting point of a single compound. The composition can include multiple compounds having different chemical compositions.
[0087] By reducing intermolecular interactions between compounds, the viscosity and melting point of the composition can be reduced, while maintaining or increasing the clearing point. Reducing viscosity while increasing the rotational elastic constant (K33) provides for reduced response time of the liquid crystal materials. Intermolecular interactions that increase viscosity include dipole-dipole interactions. Smaller compounds (e.g., two rings) can reduce the melting point and reduce viscosity. Larger compounds with delocalized electrons over a longer intramolecular distance can increase the polarization of the composition.
[0088] In some variations, the polar group can be selected to reduce dimerization of the compounds. With reference to the compound of Formula (I), R.sub.1 can be a substituent such as thioisocyanate, which is polarizable but has a reduced permanent dipole moment, and therefore and lower likelihood of forming dipole-dipole interactions.
[0089] In the composition, different compounds with different levels of electron delocalization are provided. Different types of compositions defined by Formulae (IV), (V), and (VI) are in the composition. Different combinations of transverse substituents R.sub.2 and R.sub.3 reduce intermolecular interactions by providing a repulsive force to other molecules. Tables 1A-1C show a combination of a non-limiting example composition.
TABLE-US-00001 TABLE 1A Number Compound R7 R2 R3 Mole Percent 1 Formula (IV) C.sub.2H.sub.5 F H 21% 2 Formula (IV) C.sub.4H.sub.9 F H 23% 3 Formula (IV) C.sub.5H.sub.11 F H 7% 4 Formula (IV) C.sub.2H.sub.5O F F 5% 5 Formula (IV) C.sub.4H.sub.9O F F 6% 6 Formula (IV) C.sub.5H.sub.11O F F 5%
TABLE-US-00002 TABLE 1B Number Compound R.sub.8 R.sub.2 R.sub.3 Mole Percent 7 Formula (V) C.sub.3H.sub.7 F F 6% 8 Formula (V) C.sub.5H.sub.11 F F 5%
TABLE-US-00003 TABLE 1C Number Compound R.sub.8 R.sub.2 R.sub.3 Mole Percent 7 Formula (VI) C.sub.2H.sub.5 F H 8% 8 Formula (VI) C.sub.4H.sub.9 F H 14%
[0090] In some variations, the composition includes a compound having the structure of Formula (IV), a compound having the structure of Formula (V), and a compound having the structure of Formula (VI) as described herein. In further variations, the composition includes more than one compound having the structure of Formula (IV), compound having the structure of Formula (V), and/or compound having the structure of Formula (VI).
[0091] In some variations, in the compound having the structure of Formula (IV), R.sub.1 is NCS, R.sub.2 is H or F, R.sub.3 is H or F, and R.sub.7 is selected from C.sub.2H.sub.5, C.sub.4H.sub.9, and C.sub.2H.sub.5O. In some variations, R.sub.2 is F. In further variations, in the compound having the structure of Formula (IV), R.sub.1 is NCS, R.sub.2 is F, R.sub.3 is H or F, and R.sub.7 is selected from —OC.sub.2H.sub.5, —OC.sub.4H.sub.9, and —OC.sub.5H.sub.11. In further variations, the composition includes from 1-6 of the compounds of Table 1A. In still further variations, the composition includes each compound of Table 1A.
[0092] In some variations, in the compound having the structure of Formula (V), R.sub.1 is NCS, R.sub.2 is H or F, R.sub.3 is H or F, and R.sub.8 is selected from C.sub.3H.sub.7 and C.sub.5H.sub.11. In some variations, R.sub.2 and R.sub.3 are F. In further variations, in the compound having the structure of Formula (V), R.sub.1 is NCS, R.sub.2 is F, R.sub.3 is H or F, and R.sub.8 is selected from C.sub.3H.sub.7 and C.sub.5H.sub.11. In further variations, the composition includes two compounds having the structure of Formula (V), wherein in the first compound R.sub.1 is NCS, R.sub.2 and R.sub.3 are F, and R.sub.8 is C.sub.3H.sub.7, and in the second compound R.sub.1 is NCS, R.sub.2 and R.sub.3 are F, and R.sub.8 is C.sub.5H.sub.11 (as in Table 1B).
[0093] In some variations, in the compound having the structure of Formula (VI), R.sub.1 is NCS, R.sub.2 is H or F, R.sub.3 is H or F, and R.sub.9 is selected from C.sub.2H.sub.5 and C.sub.4H.sub.9. In some variations, R.sub.2 is F and R.sub.3 is H or F. In some variations, R.sub.2 is F and R.sub.3 is H. In further variations, the composition includes two compounds having the structure of Formula (VI), wherein in the first compound R.sub.1 is NCS, R.sub.2 is F, R.sub.3 is H, and R.sub.9 is C.sub.2H.sub.5, and in the second compound R.sub.1 is NCS, R.sub.2 is F, R.sub.3 is H, and R.sub.9 is C.sub.4H.sub.9 (as in Table 10).
Liquid Crystal Materials
[0094] As described herein, individual compounds in the composition have reduced intermolecular interactions, a reduced permanent dipole moment as compared to substituents with a CN polar substituent, and increased intermolecular distances. The combination of these properties reduces the rotational viscosity γ1, while increasing the K33 and Δn (refractive index proportional to polarizability) in the visible spectrum to improve the response speed and tunability of liquid crystal tunable lenses. The reduced rotational viscosity also can provide for a larger tuning range and aperture of the lens.
[0095] Table 2 provides a comparison of the properties of the composition of Tables 1A-1C to two conventional Reference Compositions 1 and 2.
TABLE-US-00004 TABLE 2 Reference Reference Liquid Crystal Composition Composition Composition of Property 1 2 Table 1A-C Δn 0.257 0.2188 0.39 γ1 (mPa sec, rotational 160 233 190 velocity) K33 (pN, Bend) 14.9 17.1 29.8 Figure of Merit (μm.sup.2s.sup.−1) 6.151 3.513 23.8
[0096] Δn corresponds to the net change in refractive index between long axis and transverse axis of the molecules. The Δn of 0.39 for wavelengths in the visible spectrum is substantial increase over Reference Compositions 1 and 2.
[0097] In some variations, the compounds and compositions have a higher K33. A higher K33 improves tunability of the lens. A higher K33 also has a larger energy barrier for thermal fluctuation, thereby reducing scattering of light incident on the liquid crystal materials that include the compounds or compositions in the visible spectrum. The K33 of 29.8 is substantially increased over Reference Compositions 1 and 2.
[0098] The compounds and compositions have a lower rotational viscosity than the composition of Tables 1A-1C. Lower rotational viscosity allows faster tuning of the liquid crystal. The Figure of Merit (FoM) in the visible spectrum for liquid crystal ophthalmic lenses, which is equal to Δn.sup.2*K33/γ1, is substantially larger than the composition described in Table 1A-1C than for conventional Reference Compositions 1 and 2 for wavelengths in the visible spectrum.
[0099] Having described several embodiments, it will be recognized by those skilled in the art that various modifications, alternative constructions, and equivalents can be used without departing from the spirit of the disclosure. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the embodiments disclosed herein. Accordingly, the above description should not be taken as limiting the scope of the document.
[0100] Those skilled in the art will appreciate that the presently disclosed embodiments teach by way of example and not by limitation. Therefore, the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the method and system, which, as a matter of language, might be said to fall there between.