TW202534409A - Laser-protection variable transmission optical device - Google Patents

Abstract

A laser protection variable transmission optical device (“LP-VTOD”) includes first and second cells, each capable of changing from a state of higher light transmittance to a state of lower light transmittance. The first cell is characterized by a narrow band absorption having a first peak absorption wavelength and a first FWHM of 175 nm or less, and the second cell is characterized by a narrow band absorption having a second peak absorption wavelength and a second FWHM of 175 nm or less. In some cases, the second peak absorption wavelength may be within 5% of the first peak absorption wavelength. The LP-VTOD is capable of switching from a clear state to a darkened state having a darkened state transmittance %T _DS-Pthat is equal to or less than 10% for at least one of the first or second peak absorption wavelengths.

Description

Laser protected variable transmission optical device

The present disclosure relates to optical devices, and more particularly, to variable transmission optical devices that can be reversibly switched between a clear state and a darkened state to block, inter alia, narrowband radiation such as laser light.

Variable transmission optical devices ("VTODs") (e.g., glasses, goggles, visors, windows, sensors, filters, cameras, or the like) that can rapidly change between a high-transmission "clear" state and a low-transmission "dark" state offer many advantages over fixed-transmission optical devices. A particularly useful feature is the ability to perform this rapid change on demand, either manually (at the touch of a button by the user) or automatically (under the control of a light sensor and electronic circuitry).

Optical devices can potentially provide protection against intense light, such as narrow-beam light sources like lasers. For example, the military, police, emergency personnel, pilots, and others may face the threat of laser light emitted by enemy personnel or devices. Protecting against laser light is difficult, and solutions to date have been largely unsatisfactory. For example, one common approach (for green lasers) is to simply place a static green-light absorbing strip on the top portion of the visor. This only provides protection against green lasers, and only if the head of the person wearing the strip is angled correctly. Furthermore, the system will continue to block that area of the light spectrum regardless of whether the threat is present or not. This can result in color distortion and thus does not meet optical requirements for general use. In the case of pilots, a static tint that blocks the green laser is undesirable because it can also dim the pilot's vision and filter cockpit displays, and further impair the pilot's ability to correctly see the Precision Approach Path Indicator (PAPI) or Visual Approach Slope Indicator (VASI) lights, which require red/white or red/green discrimination.

Variable transmission optics can also provide some protection against glare. However, it can be difficult to configure these devices to have sufficient optical density for satisfactory protection against lasers. For some applications, it is important that the scene viewed through the optics is not obscured as the device moves between its clear and various dimmed states. To achieve sufficient optical density to protect against lasers (e.g., an optical density (OD) of 1 or greater at the laser wavelength), the scene becomes unacceptably dark overall in wavelengths outside the laser's range.

Therefore, it is desirable to provide a variable transmission optical system (e.g., a filter, lens, goggles, visor, mask, window, windshield, AR or VR glasses, or the like) that can resist strong narrowband light while maintaining sufficient transmission of a spectral region of light other than laser light.

According to some embodiments, a laser protected variable transmission optical device ("LP-VTOD") includes a first unit and a second unit. The first unit includes a first electro-optical material provided between a first pair of substrates. The first electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a first wavelength region upon a change in a first electric field applied to the first electro-optical material. The first unit is characterized by having a narrowband absorption having a first peak absorption wavelength and a first full width at half maximum (FWHM) of 175 nanometers or less. The second unit is in optical communication with the first unit, and the second unit includes a second electro-optical material provided between a second pair of substrates. The second electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a second wavelength region upon a change in a second electric field applied to the second electro-optical material. The second unit is characterized by having a narrowband absorption having a second peak absorption wavelength and a second full width at half maximum (FWHM) of 175 nm or less. The first peak absorption wavelength and the second peak absorption wavelength may be the same or different. In some cases, the second peak absorption wavelength may be within 5% of the first peak absorption wavelength. With respect to light passing through the LP-VTOD, the LP-VTOD is capable of switching from a clear state to a darkened state, wherein the darkened state has a darkened state transmittance %T _DS-P equal to or less than 10% for at least one of the first peak absorption wavelength or the second peak absorption wavelength.

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to and any other benefits of U.S. nonprovisional patent application No. 18/505,144, filed on November 9, 2023, entitled “LASER-PROTECTION VARIABLE TRANSMISSION OPTICAL DEVICE,” the entire disclosure of which is fully incorporated herein by reference.

It should be understood that the embodiments include various aspects that can be combined in different ways. The following description is provided to list components and describe some embodiments of the present application. These components are listed using specific embodiments; however, it should be understood that they can be combined in any manner and in any number to create additional embodiments. The various described examples and embodiments should not be interpreted as limiting the embodiments of the present application to only the systems, techniques, and applications explicitly described. It should be understood that the drawings are for the purpose of illustrating the concepts of the present disclosure and may not be drawn to scale.

The terms "about" and "substantially" may be used to include any value that may vary without changing the basic function of that value. When used in the context of a range, "about" and "substantially" also disclose the range defined by the absolute values of the two endpoints, for example, "about 2 to about 4" also discloses the range of "2 to 4".

As used in this specification and claims, the terms "comprise/comprises," "include/includes," "having," "has," "may," "contain/contains," and variations thereof as used herein are intended to be open transition phrases, terms, or words that require the presence of named elements, components, or steps and permit the presence of additional elements, components, or steps.

The present disclosure may include one or more of the following terms, the meanings of which may be as described below.

As used herein, "absorption" may define the percentage of light absorbed by a mixture, cell, or optical device.

An "absorption band" defines the wavelength in the optical spectrum where absorption occurs.

As used herein, "clear state" or "clear state transmission" may refer to a state in which the LP-VTOD exhibits high or maximum light transmittance.

"Darkened state" or "darkened state transmission" may refer to a state in which the VTOD exhibits reduced light transmittance relative to the clear state.

A "dichroic dye," or "DC dye," is a light-absorbing dye moiety that typically has a rod-like shape and exhibits unique anisotropy, with its light absorption properties occurring parallel ( _α∥ ) and perpendicular ( _α⊥ ) to the molecule. This is characterized by a dichroic ratio (DR) = _α∥ / _α⊥ . Any molecule with a dichroic ratio (DR) is considered "dichroic."

The "dye order parameter" or "S _dye " refers to the order parameter of the transition dipole of each dichroic dye with respect to the director.

The "dichroic ratio" of a dye mixture, or _Dmix, refers to the dichroic ratio of a guest-host mixture, which may contain one or more DC dyes, at the peak absorption wavelength of the mixture or dye, as applicable.

As used herein, "narrowband absorption" is defined as having a spectral absorption bandwidth having a full width at half maximum (FWHM) less than or equal to 175 nm, or alternatively less than or equal to 165 nm, 155 nm, 120 nm, 100 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm, wherein the entire spectral absorption band is typically measured in the visible region of 400 to 700 nm, or alternatively, 380 nm to 780 nm. Narrowband absorption can, in some cases, have high color chromaticity.

"Ultra-narrowband absorption" is a subset of "narrowband absorption" and, as used herein, is defined as having a spectral absorption bandwidth of less than or equal to 88 nm, or alternatively less than or equal to 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm or less, with the entire spectral absorption band typically measured in the visible region of 400 nm to 700 nm, or alternatively, 380 nm to 780 nm. Ultra-narrowband absorption can, in some cases, have high color chromaticity.

A "narrowband mixture" refers to a guest-host liquid crystal mixture (ultra-narrowband mixture) that can be used in a narrowband cell to produce narrowband absorption (which may be ultra-narrowband absorption).

A "narrowband unit" refers to a device that can produce narrowband absorption (which may be ultra-narrowband absorption).

"Narrowband radiation" refers to radiation incident on the LP-VTOD having a wavelength bandwidth less than 88 nm, alternatively less than 80, 70, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 nm. In some cases, the bandwidth may correspond to the full width at half maximum (FWHM) of the optical spectrum relative to the power of the radiation and the wavelength. "Ultra-narrowband radiation" is a subset of narrowband radiation and refers to incident light having a bandwidth less than 40 nm, alternatively less than 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1 nm. Narrowband radiation (which may be ultra-narrowband radiation) may in some cases include light produced by lasers (laser radiation or laser light), surface-mounted diodes (SMDs), or some LEDs and the like.

The "nematic-isotropic transition temperature," or _TNI, is the temperature at which a liquid crystal undergoes a nematic-to-isotropic transition, from an orientationally ordered nematic phase to a completely disordered isotropic phase. As used herein, _TNI refers to the nematic-isotropic transition temperature of a guest-host mixture.   

The "order parameter of a guest-host mixture" or "S _mix " refers to the order parameter of the guest-host mixture at the mixture's peak absorption wavelength. The mixture may contain one or more dyes and other dopants.

Optical density, or OD, typically refers to the apparent absorption of radiation measured at a specific wavelength, such as the wavelength of peak dye absorption or peak narrowband radiation. Percent transmittance (%T) is related to the total OD at a specific wavelength by: %T = 10 ^(-OD) × 100%.

"Photopic transmittance" or "photopic transmission" refers to the percentage of visible light transmitted weighted by the spectral response of the day-adapted human eye.

Polarization dependence is a measure of a material's response to two orthogonal polarizations, i.e., where the optical properties of the material (such as refractive index or absorption/transmittance) experienced by incident light depend on the polarization of the incident light.

Polarization sensitivity is a relative measure of a material's response between two orthogonal polarizations. In the ideal theoretical limit, zero percent (0%) polarization sensitivity refers to a completely polarization-insensitive device, and 100% polarization sensitivity refers to a completely polarization-sensitive device, as obtained using a polarizer.

"Polarizer" refers to a material, layer, or component that absorbs or reflects one polarization of incident light more than the orthogonal polarization.

"Transmittance" and "transmittance" are used interchangeably and mean the percentage of light transmitted through a mixture or device and may be referred to herein as %T. In some cases, transmittance may refer to a specific wavelength. For example, an LP-VTOD may be characterized by transmittance at the peak absorption wavelength in the clear state (%T _CS-P ) or by transmittance at the peak absorption wavelength in the darkened state (%T _DS-P ). In some cases, transmittance may refer to the average or integral across a range of wavelengths. For example, an LP-VTOD may be characterized by photopic transmittance in the clear state (PT _CS ) or by photopic transmittance in the darkened state (PT _DS ).

"Transmission swing" refers to the difference in transmission between the clear state and the dark state. For example, if the clear state transmission is 65% and the dark state transmission is 15%, the transmission swing is 65 - 15 = 40%. The transmission swing of an optical device (at a wavelength or across a range of wavelengths) can be determined using a spectrophotometer or other specialized equipment, such as the "Haze-Gard Plus" device from BYK-Gardner (USA) or equivalent.

A "tinted" or "tinted" state refers to a condition in which the guest-host mixture exhibits some light absorption relative to the clear state, which may be narrowband (<175 nm bandwidth) or broadband (≥ 175 nm). The tinted state may correspond to a color state, or alternatively, may correspond to a low color chromaticity state.

"Uniform retardation" refers to a plastic substrate with a retardation variation of less than ±20%. "Resistance" is defined as the change in optical phase experienced by incident light of different polarizations.

“Visible light” refers to the wavelength range of about 400 nm to about 700 nm, or alternatively, about 380 nm to about 780 nm.

As used herein, "broadband absorption" may refer to a spectral absorption band greater than 175 nm, and preferably greater than 180 nm, 185 nm, 190 nm, 195 nm, or 200 nm, wherein the entire spectral absorption band is contained within the visible wavelength range, typically assumed to be 400 nm to 700 nm, or alternatively 380 nm to 780 nm. Broadband absorption may, in some cases, have low color chromaticity.

"Broadband unit" refers to a device that can produce a wide absorption band.

"Broad-band hybrid" refers to a guest-host liquid crystal mixture that can be used in a wide-band cell.

It should be noted that the terms "transmittance" and " transmissivity " are generally used interchangeably herein.

FIG1 is a cross-sectional view of a non-limiting example of a laser-protected variable transmission optical device ("LP-VTOD") according to some embodiments. It should be noted that the term "laser-protected" is used for convenience and is non-limiting. While an LP-VTOD may protect a user or device from laser light in some cases, in other cases, it may protect a user or device from some other narrowband radiation, such as that generated by an LED, SMD, or another light source.

In some embodiments, the LP-VTOD 10 may include a first unit 11 in optical communication with a second unit 31 such that incident light 26 may be modulated by the first unit, the second unit, or both and pass through the device as transmitted light 27. The incident light 26 may include a lower-intensity component 26' comprising light of various wavelengths, such as broadband radiation spanning most of the visible spectrum. The incident light 26 may also include a higher-intensity narrowband radiation component 26" , such as light from a laser or LED. Depending on how the LP-VTOD modulates the light, the transmitted light 27 may include a transmitted lower-intensity component 27' corresponding to the portion of 26' that passes through the device and a transmitted narrowband radiation component 27" corresponding to the portion of 26" that passes through the device. The first and second cells are visibly separated by layer 50 , which may comprise, for example, an optically transparent adhesive, a polymer film, a glass layer, or an optical object such as a lens, a polarization rotator, a half-wave plate, a quarter-wave plate, a window, a sunshade, or the like. In some embodiments, layer 50 may be selected to reduce insertion loss associated with the interface. It should be noted that the designations of "first" and "second" cells are arbitrary and interchangeable, i.e., in the embodiments described herein, the second cell may instead receive incident light first, rather than the first cell.

Each cell may include a pair of substrates, 12a and 12b for the first cell and 32a and 32b for the second cell. As discussed in more detail below, the substrates may be independently selected and may include, for example, a polymer material, glass, or ceramic. Each cell may include a pair of transparent conductive layers, 14a and 14b for the first cell and 34a and 34b for the second cell, which may be disposed or coated on each corresponding substrate surface within the cell. In some embodiments, an optional passivation layer (which may in some cases be referred to as an insulating layer or "hard coat") 16a , 16b , 36a , 36b may be provided over the corresponding transparent conductive layers. The passivation layer may comprise, for example, a non-conductive oxide, a sol-gel, a polymer, or a composite. Optionally, alignment layers 18a , 18b , 38a , 38b may be provided above the passivation layer or the transparent conductive layer. As a non-limiting example, the alignment layer may comprise polyimide. In some embodiments, the alignment layer may function as the passivation layer. In some embodiments, the alignment layer may be brushed as is known in the art to help orient the electro-optical material, such as an LC host, near the surface. In some embodiments, both alignment layers of a cell are brushed. In some embodiments, a cell may comprise only one brushed alignment layer.

In some embodiments, the alignment layer of the first cell may have an orientation that is rotated, for example, 70 to 110 degrees, alternatively 80 to 110 degrees, or alternatively 85 to 95 degrees, relative to the alignment layer of the second cell. For example, Figure 2A is a schematic plan view of the alignment layer 18a showing the alignment brush lines 18a-BL oriented generally vertically. Figure 2B is a schematic plan view of the alignment layer 38a showing the alignment brush lines 38a-BL oriented generally horizontally (i.e., at approximately 90 degrees relative to the alignment layer 18a ). This type of configuration may, in some cases, be able to absorb more light in its darkened state. Although not theoretically bound, a first cell may absorb more of one polarization than another cell, but by rotating the alignment, the second cell may be configured to absorb more of the other polarization. In some alternative embodiments, instead of using an alignment layer orientation (or in addition to using an alignment layer orientation), a polarization rotator, such as a half-wave plate, may be positioned between the first cell and the second cell (e.g., such as layer 50 ). For example, both the first cell and the second cell may absorb light having a first polarization to a greater extent than a second polarization (e.g., substantially orthogonal to the first polarization). However, the presence of the polarization rotator acts to rotate the second polarization light transmitted through the first cell to have the first polarization. That is, the half-wave plate configures the second cell to absorb the second polarization. In some other embodiments, the electro-optical materials of the first and second cells may be selected such that the first cell is configured to absorb the first polarization to a greater extent, and the second cell is configured to absorb the second polarization to a greater extent (e.g., substantially orthogonal to the first polarization).

The first cell 11 includes a first electro-optical material 25 , such as a first liquid crystal guest-host mixture, provided between a pair of substrates 12a , 12b of the first cell. The substrates and any overlying layers define a first cell gap 20. Upon changing a first electric field applied to the first electro-optical material, the first electro-optical material can change from a higher transmittance state to a lower transmittance state in a first wavelength region. The first electric field can be varied, for example, by varying a voltage applied between a pair of transparent conductive layers 14a , 14b of the first cell. In some embodiments, the first electro-optical material and/or the first cell in its lower transmittance state can be characterized by narrowband absorption having a first peak absorption wavelength and a first full width at half maximum (FWHM). In some embodiments, the narrowband absorption of the first cell can be ultra-narrowband absorption, as previously described.

Similarly, the second cell 31 includes a second electro-optical material 45 provided between a pair of substrates 32a and 32b of the second cell, for example, a second liquid crystal guest-host mixture that may be the same as or different from the first liquid crystal guest-host mixture. Upon changing the second electric field applied to the second electro-optical material, the second electro-optical material can change from a higher transmittance state to a lower transmittance state in a second wavelength region that may be substantially the same as or different from the first wavelength region. The second electric field can be changed, for example, by changing the voltage applied between a pair of transparent conductive layers 34a and 34b of the second cell. In some embodiments, the second electro-optical material and/or the second cell in its lower transmittance state may be characterized by narrowband absorption having a second peak absorption wavelength and a second full width at half maximum (FWHM). In some embodiments, the narrowband absorption of the second cell can be ultra-narrowband absorption as previously described. In some preferred embodiments, one or both of the first peak absorption wavelength and the second peak absorption wavelength are in the range of 380 to 780 nm, or alternatively, in the range of 400 to 700 nm. The substrate and any overlying layers define a second cell gap 40. The second cell gap 40 can be the same as or different from the cell gap 20. To help maintain this separation, optional spacers (not shown) (such as glass or plastic rods or beads) can be inserted between the respective substrates of each cell.

In some cases, the first and second cell structures may be enclosed by a sealing material 13 , 33 (such as a UV-curable optical adhesive or other sealant known in the art). The sealing materials 13 and 33 may be the same or different. FIG. 1 shows the sealing materials of the first and second cells as separate, but in some embodiments, a single common sealing material layer may alternatively seal both cells. It should be understood that the sealing material 13 , 33 may be provided at any location to create a seal for the electro-optical material 25 , 45 between the substrates 12a , 12b , 32a , 32b . By way of example and not limitation, the sealing material may be placed between the substrates 12a , 12b , 32a , 32b and any overlying layer. In some embodiments, the sealing material may include spacers for maintaining the cell gaps 20 , 40 .

The conductive layers of each cell 14a , 14b , 34a , 34b can be electrically connected to a controller 55. Controller 55 can include one or more variable voltage supplies, schematically represented by circles _V1 and _V2 , for the first and second cells, respectively. FIG1 shows the first cell power circuit with its switch 28 open so that no voltage is applied. When switch 28 is closed, a variable voltage or electric field can be applied to the liquid crystal guest-host mixture 25. Similarly, the second cell power circuit is shown with its switch 48 in the open position so that no voltage is applied. When switch 48 is closed, a variable voltage or electric field can be applied to the liquid crystal guest-host mixture 45 . In some embodiments, the electric field applied to the first cell can be controlled independently of the electric field applied to the second cell. Independent control can, in some cases, allow for more options in how the VTOD filters light. In other embodiments, the electric fields applied to the first and second cells are controlled jointly, for example by simultaneously applying the same voltage profile to each set of electrodes in the first and second cells. In some embodiments, one electrode of the first cell is electrically connected to one electrode of the second cell, and another electrode of the first cell is electrically connected to another electrode of the second cell. Joint control can, in some cases, be simpler and allow for the use of a lower-cost controller.

In some embodiments (not shown), instead of including layer 50 , the second and first cells may share a substrate (e.g., substrate 12b ), such that transparent conductive layer 34a (and optionally other layers 36a and/or 38a ) is provided on a substrate surface opposite the substrate surface having transparent conductive layer 14b of the first cell. In some cases, such a structure can reduce potential light loss. It should be noted that any or all of the substrates 12a , 12b , 32a , 32b may be the same or different, any or all of the transparent conductive layers 14a , 14b , 34a , 34b may be the same or different, any or all of the passivation layers 16a , 16b , 36a , 36b , if applicable, may be the same or different, and any or all of the alignment layers 18a , 18b , 38a , 38b , if applicable, may be the same or different. In some embodiments, one or both cells include only one alignment layer. Electro-optical Materials

An electro-optic material is a material that changes its light absorption profile upon application of an electric field. In some embodiments, the electro-optic material comprises a guest-host system having an LC host and a DC dye (guest) dissolved or dispersed therein, or alternatively, a dichroic light-absorbing moiety covalently attached to the LC host (all considered guest-host mixtures). Unless otherwise indicated, the term "DC dye" includes any DC light-absorbing material, whether provided as a small molecule or as a moiety attached to a polymer, oligomer, or LC host.

Guest-host systems can be used to generate electro-optical effects. These systems involve a mixture of a dichroic dye (guest) and a liquid crystal (LC) (host), where the dichroism is modulated within a voltage-controllable LC cell. In an isotropic host, the molecules are randomly oriented, and the effective absorption is a weighted average: α _eff = (2α⊥ + α∥)/3. In anisotropic LC host materials designed for polarization-independent operation, the absorption can be increased to α _eff = (α⊥ + α∥)/2 or decreased to α⊥, depending on the desired effect.

In some embodiments, the liquid crystal guest-host comprises a mixture of a liquid crystal host and a dye material (also referred to herein as a DC dye composition). The DC dye composition can be characterized as having dichroic properties and, as described below, can include a single DC dye or a mixture of DC dyes to provide these properties. In some embodiments, the liquid crystal guest-host mixture can be formulated as a "narrowband mixture." In some embodiments, at least one cell 11 , 31 includes a narrowband mixture as the electro-optical material 25 , 45. It should be noted that in the context of guest-host materials, the term "mixture" is generally used broadly herein and can refer to a DC light-absorbing moiety covalently attached to the LC host. The guest-host mixture can be, but need not be, a simple combination of a single dye and liquid crystal molecules.

In some embodiments, the first and second cells comprise narrowband blends having substantially identical optical performance (i.e., peak absorption wavelength, full-width-at-height (FWHM) absorption band, and total absorptivity). In these embodiments, one cell is configured to substantially absorb one polarization or eigenmode of light, while the other cell is configured to substantially absorb another (orthogonal) polarization or eigenmode of light.

For example, at least 90 weight % of the chemical composition of the first electro-optical material may have the same molecular/polymer structure as at least 90 weight % of the composition of the second electro-optical material (excluding the chiral dopant). In some cases, the elemental analysis of each element of the first electro-optical material may differ from the elemental analysis of the second electro-optical material by 10% (atomic % or weight %). In some cases, the spectral properties of the first and second units may be substantially the same. For example, the first peak absorption wavelength may differ from the second peak absorption wavelength by 10% or 5%, or the first FWHM may differ from the second FWHM by 10% or 5%. The advantage of this combination is that the system can be extremely effective in blocking, for example, the target wavelength from the laser, regardless of its polarization. Alternatively, it is possible to increase the total absorptivity, thereby overcoming the potential solubility limitations in each unit. It has been found that stacking two similar cells together can be more effective than attempting to double the cell gap or dye concentration because it can resolve both eigenmodes. For example, it has been found that using two cells with substantially identical mixtures can provide an optical density of at least 1.0, alternatively at least 1.5, 2.0, 2.5, 3.0, 3.5, or even higher. Such levels can be particularly important for blocking high-intensity narrowband light, such as laser light.

In some embodiments, each unit comprises a narrowband mixture that differs in some respect from the other unit (one or both of which may be ultra-narrowband mixtures, as the case may be). Generally speaking, different mixtures are mixtures that are "substantially" not "identical" as described above. For example, the first DC dye composition may be different from the second DC dye composition. In some cases, different chromophores or different chromophore mixtures may be used. In some cases, the first peak absorption wavelength differs from the second peak absorption wavelength by, for example, at least 5 nm or 10 nm, or alternatively, by at least 5% or 10%, or the first FWHM may differ from the second FWHM by, for example, at least 5 nm or 10 nm, or alternatively, by at least 5% or 10%. In some cases, the peak absorption wavelengths differ so that each unit absorbs different regions of the spectrum (e.g., one unit absorbs red light and another unit absorbs green light, or any other color combination, as appropriate). In some cases, a different host material may be used for the first electro-optic material than for the second electro-optic material. The advantage of using two different cells is that the VTOD can block multiple wavelengths simultaneously, such as from red and green lasers. LC Host

In some embodiments, the host comprises a chiral nematic or cholesteric liquid crystal material (collectively referred to as "CLC"), which may have a negative dielectric anisotropy ("negative CLC") or a positive dielectric anisotropy ("positive CLC"). In some embodiments of CLC, the liquid crystal material is cholesteric, or it comprises a nematic liquid crystal in combination with a chiral dopant. The CLC material has a twisted or helical structure. The periodicity of the twist is referred to as its "pitch"("p"). The orientation or order of the liquid crystal host can be changed upon application of an electric field and, in combination with a dye material, can be used to control or partially control the optical properties of the cells 11 , 31. In some embodiments, the CLC may be further characterized by its chirality, i.e., right-handed or left-handed.

A variety of CLC materials are available and have potential utility in various embodiments of the present disclosure.

In some embodiments, the LC host is a nematic LC (zero chirality) or is ferroelectric or smectic and may have positive or negative dielectric anisotropy. It should be noted that non-zero d/p can be achieved by using a suitably rubbed surface as known in the art. Dye Materials

In some embodiments, the dye material may further include a small amount of an existing absorbing dye, for example to provide a desired overall color tone to the device in the clear state. In some embodiments, the dye composition includes essentially only DC dye. DC Dye

Dichroic dyes typically have an elongated molecular shape and exhibit anisotropic absorption (i.e., the absorption of light varies depending on the polarization direction). In the present system, absorption is higher along the long axis of the molecule, and these dyes can be referred to as "positive dyes," or dyes exhibiting positive dichroism. Positive DC dyes are typically used herein. In some embodiments, the dichroic ratio of a DC dye (as measured in an LC host) can be at least 5.0, alternatively at least 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20.

The visible light absorption level of a DC dye can be a function of the dye type and the LC host. In the disclosed optical devices, the apparent visible light absorption can also be a function of voltage. The orientation or long-range order of the LC can be a function of the electric field or voltage across the thickness of the cell. The DC dye exhibits a certain alignment with the LC host, allowing the application of voltage to alter the apparent darkness of the cell.

In some embodiments, the DC dye may comprise a small molecule type of material. In some embodiments, the DC dye may comprise an oligomeric or polymeric material. It is also possible to add a polymer component to the dye mixture. The chemical moiety responsible for light absorption may be, for example, a pendent group on the main chain. Multiple DC dyes may be used as appropriate, for example to tune the light absorption envelope, or to improve the overall unit performance with respect to lifetime or some other property. The DC dye may comprise functional groups that may improve solubility, miscibility with the LC host, or bonding to the LC host. Some non-limiting examples of DC dyes may include azo dyes, for example, azo dyes having 2 to 10 azo groups, or alternatively 2 to 6 azo groups. Other DC dyes are known in the art, such as anthraquinones, perylenes, triphenol diols, and the like. Examples of dyes include oxazine, quinoline yellow, and boron-dipyrromethene (BODIPY) dyes. Generally, any molecule with dichroic properties can be used. For some applications, DC dyes with a FWHM absorption band of 175 nm or less are preferred. Alternatively, DC dyes may have a FWHM absorption band of less than 150 nm, 125 nm, 100 nm, 90 nm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm.

It should be noted that one or more DC dyes can be used in narrowband mixtures, that is, can be used to produce narrowband absorbing guest-host liquid crystal mixtures in narrowband cells. Other cell characteristics Substrate

Referring again to FIG. 1 , in some embodiments, substrates 12a , 12b , 32a , 32b may be independently selected and may comprise plastic, glass, ceramic, or some other material. The choice of material and its specific properties depend in part on the intended application. For many applications, the substrate should be at least partially transmissive to visible light. In some embodiments, the substrate may have a transmittance greater than 45% for visible radiation between wavelengths of 400 nm and 700 nm, alternatively, a transmittance greater than 50%, 60%, 70%, 80%, 90%, or 95%. In some embodiments, the substrate may have high optical clarity so that a person or sensor can clearly see through the LP-VTOD 10. In some embodiments, the substrate may have a color or hue. In some embodiments, the substrate may have an optical coating on the exterior of the cell. The substrate can be flexible or rigid.

As some non-limiting examples, the plastic substrate may include polycarbonate (PC), polycarbonate and copolymer blends, polyether sulfone (PES), polyethylene terephthalate (PET), cellulose triacetate (TAC), polyamide, p-nitrophenyl butyrate (PNB), polyetheretherketone (PEEK), polyethylene naphthalate (PEN), polyetherimide (PEI), polyarylate (PAR), polyvinyl acetate, cycloolefin polymer (COP), or other similar plastics known in the art. In some non-limiting examples, flexible glass, including materials such as Corning® Willow® glass and the like, may be used as the substrate. The substrate may include multiple materials or have a multi-layer structure.

In some embodiments, the thickness of the substrate can be in the range of 10-20 μm, 20-30 μm, 30-40 μm, 40-50 μm, 50-75 μm, 75-100 μm, 100-150 μm, 150-200 μm, 200-250 μm, 250-300 μm, 300-350 μm, 350-400 μm, 400-450 μm, 450-500 μm, 500-600 μm, 600-800 μm, 800-1000 μm, or greater than 1 mm, or any combination of ranges thereof.

In some embodiments, the LP-VTOD 10 does not use a polarizer .

By "transparent" conductive layer, it is meant that the conductive layer 14a , 14b , 34a , 34b allows at least 45% of incident visible light to pass through. A transparent conductive layer can absorb or reflect a portion of visible light and still be useful. In some embodiments, the transparent conductive layer may comprise a transparent conductive oxide (TCO), including but not limited to ITO, AZO, or FTO. In some embodiments, the transparent conductive layer may comprise a conductive polymer, including but not limited to PEDOT:PSS, poly(pyrrole), polyaniline, polyphenylene, or poly(acetylene). In some embodiments, the transparent conductive layer may comprise a partially transparent metal thin layer or metal nanowire, for example, formed of silver, copper, aluminum, or gold. In some embodiments, the transparent conductive layer may comprise graphene.

Narrowband light source

In some embodiments, the wavelength bandwidth of the narrowband radiation can be less than 88 nm, alternatively less than 80, 70, 60, 50, 40, 30, 20, 15, 10, 9, 8, 7, 6, 5, 4, 3, or 2 nm, or a bandwidth equal to 1 nm. In some cases, the bandwidth can correspond to the full width at half maximum (FWHM) of a spectrum relative to radiation power and wavelength. In some embodiments, the narrowband radiation can be ultra-narrowband radiation, such as coherent laser light, for example, derived from one or more pulsed or continuous wave lasers. In some cases, the narrowband radiation can be non-coherent and originate from one or more laser diodes, LEDs, micro-LEDs, superluminescent diodes (SLDs), surface-mount diodes (SMDs), or laser- or LED-pumped phosphor devices. Alternatively, the narrowband radiation can originate from a xenon, mercury, or other high-intensity lamp, whose light output is routed through a color filter element and, optionally, a collimating lens. In some embodiments, the narrowband radiation can originate from a laser or diode based on GaN, GaAs, or InP.

Generally speaking, the peak narrowband radiation wavelength can be anywhere in the electromagnetic spectrum between 100 nm and 1 mm. In some embodiments, at least one peak narrowband radiation wavelength is in the visible spectrum, i.e., in the range of 380 nm to 780 nm, or alternatively, 400 nm to 700 nm. In some cases, at least one narrowband radiation wavelength is in the range of greater than 400 nm up to and including 500 nm, greater than 500 nm up to and including 600 nm, or greater than 600 nm up to and including 700 nm. In other embodiments, at least one peak narrowband radiation wavelength is in the infrared (IR) or ultraviolet (UV) region. IR wavelengths include near IR (700 nm to 1,300 nm), mid IR (1,300 nm to 3,000 nm), or far IR (3,000 nm to 1 mm) radiation. UV wavelengths include peak radiation wavelengths within the range of 100 to 380 nm, or alternatively, 100 to 400 nm.

When there are multiple narrowband radiation sources, the second (or additional) peak narrowband radiation wavelength may be in the visible range, such as the UV or IR range described above. In some cases, the second (or additional) peak narrowband radiation wavelength may be in a range greater than 100 nm, 200 nm, or 240 nm up to (and including) 380 nm, greater than 780 nm up to (and including) 1,300 nm, or greater than 1,300 nm up to (and including) 3,000 nm, greater than 3,000 nm up to (and including) 1 mm, or any range therebetween. In some embodiments, the narrowband radiation is laser light having a peak intensity wavelength of about 257 nm, 266 nm, 343 nm, 355 nm, 405 nm, 450 nm, 473 nm, 473 nm, 488 nm, 515 nm, 520 nm, 532 nm, 589 nm, 593 nm, 635 nm, 638 nm, 650 nm, 660 nm, 670 nm, 694 nm, 914 nm, 1030 nm, 1047 nm, 1064 nm, 1319 nm, 1342 nm, 1444 nm, 1645 nm, 2000 nm, 2100 nm, 2940 nm, or some other wavelength. LP-VTOD Embodiments and Properties

The following describes some device embodiments for improving visibility while protecting against narrowband, intense light sources such as lasers. Compared to static films used for laser protection, the described devices offer the following advantages: (a) they are absorptive only when needed, thus minimizing impairment of the user's vision or color perception when not needed, and (b) their narrow absorption bands are designed to absorb only the wavelengths of light necessary for protection, thereby increasing the overall system's photopic transmittance.

Figures 3A through 3D are a series of cross-sectional schematic diagrams illustrating non-limiting examples of LP-VTODs according to some embodiments. LP-VTOD 310 includes a first cell 311 having a first guest-host mixture, including a negative first LC host 322 and a first dye composition 324 , which may include at least one positive DC dye. The host and dye molecules are depicted to illustrate general orientation. The first cell is in optical communication with a second cell 331 having a second guest-host mixture, including a negative second LC host 342 and a second dye composition 344 , which may include at least one positive DC dye different from the first DC dye composition 324. For clarity, other components of cells 311 and 331 are not shown, but may be described as described with respect to Figure 1 and its variations. In some embodiments, each unit can be independently controlled by power circuits _V1 and _V2 provided in controller 355 .

In this embodiment, the first cell absorbs light in a first wavelength region, and the second cell absorbs light in a second wavelength region different from the first wavelength region. In FIG3A , both power circuits _V1 and _V2 are disconnected, i.e., no voltage is applied to cells 311 and 331. Both the first and second cells are in a relatively high light transmission state (which may be at or near their maximum light transmission state), and LP-VTOD 310 is in a clear state (which may be at or near its maximum light transmission state), wherein a significant amount of incident light 326 passes through as transmitted light 327a . Incident light 326 may include broadband light 326′ , which may correspond to light from a typical environment (e.g., a room, outdoors, or the like) typically composed of various wavelengths across some or all of the visible spectrum.

Incident light 326 may further include first narrowband radiation 326-1″ having a peak intensity at a first peak narrowband radiation wavelength. In some cases, the incident light may also include second narrowband radiation 326-2″ having a peak intensity at a second peak narrowband radiation wavelength that differs from the first narrowband radiation wavelength by at least 5 nm or at least 5%. The first and second narrowband radiation may be derived from lasers or other narrowband light sources as described above and may have an intensity higher than that of broadband light 326′ , for example, sufficient to disrupt or even damage the function of a person's vision or a sensor (such as a camera sensor). In FIG. 3A , the transmitted light 327 a may include transmitted broadband light 327 a ′ , transmitted first narrowband radiation 327 - 1 a ″, and transmitted second narrowband radiation 327 - 2 a ″ .

The VTOD can be configured such that each cell has a different transmittance at the peak absorption wavelength compared to the total (photopic) absorptivity of the entire system. For example, in some embodiments, the clear state photopic transmittance (PTCS ₎ of at least one cell in the clear state can be at least 40% (alternatively, at least 50%, 60%, 70%, 80%, 90%, or 95%). In some cases, the device can be characterized by a clear state transmittance (%TCS-P) of 1 to 5%, or alternatively, at least 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90% for at least one cell at the peak absorption wavelength. %TCS _{-P can} refer to the first peak absorption wavelength (%TCS _-P1 ) or the second peak absorption wavelength (%TCS _-P2 ).

In Figure 3B, the power circuit _V2 of the second cell remains open (no voltage applied), but the power circuit _V1 of the first cell is closed and a voltage is applied that is higher than the threshold voltage sufficient to significantly reorient the LC host 322 and DC dye composition 324. Light absorption in the first wavelength region increases as the voltage increases. Light transmission can vary based on the applied voltage up to a certain point, beyond which increasing the voltage has little effect. In FIG3B , the LP-VTOD is in a first colored state (also referred to herein as a first darkened state), wherein the first cell 311 is in a relatively low-transmittance state in a first wavelength region (optionally at or near its minimum light transmission state), causing some absorption of incident visible light 326 in the first wavelength region, thereby generating transmitted light 327b . Specifically, the first cell blocks a significant amount of narrowband radiation 326-1″ , which is transmitted at a significantly reduced intensity as 327-1b″ . Activating the first unit also blocks some of the broadband radiation 326' , but because the first unit has narrowband absorption, most of 326' passes through as transmitted broadband radiation 327b' , allowing the user or sensor to still fully view the scene or environment without substantial distortion. Blocking narrowband radiation while still maintaining acceptable viewing conditions for the scene or environment provides additional safety for users, particularly those in hazardous situations, operating vehicles, aircraft, or the like. For example, a user or sensor can detect narrowband radiation 326-1" , such as intense 532 nm laser light, and activate the unit (manually or automatically). However, in this configuration, if any second narrowband radiation 326-2″ exists, it may be transmitted as second narrowband radiation 327-2b″ .

In Figure 3C, the power circuit _V1 of the first cell is open, meaning no voltage is applied, while the power circuit _V2 of the second cell is closed and a voltage is applied that is higher than the threshold voltage sufficient to significantly reorient the LC host 342 and DC dye composition 344. Light absorption in the second wavelength region increases with increasing voltage. Light transmission can vary based on the applied voltage up to a certain point, beyond which increasing the voltage has little effect. In FIG3C , the LP-VTOD is in a second colored state (also referred to herein as a second darkened state), wherein the second cell is in a relatively low light transmittance state in the second wavelength region (optionally at or near its minimum light transmission state), so that some amount of incident visible light 326 in the second wavelength region is absorbed, thereby generating transmitted light 327 c . Specifically, the second cell blocks a significant amount of narrowband radiation 326 - 2 ″ , which is transmitted at a significantly reduced intensity as 327 - 2 c ″ . Activating the second unit also blocks some of the broadband radiation 326' . However, because the second unit has narrowband absorption, most of the broadband radiation 326' passes through as transmitted broadband radiation 327c' , allowing the user or sensor to still fully view the scene or environment without substantial distortion. Blocking narrowband radiation while still maintaining acceptable viewing conditions for the scene or environment provides additional safety for users, particularly those in hazardous situations, operating vehicles, aircraft, or the like. For example, a user or sensor can detect narrowband radiation 326-2" , such as intense 635 nm laser light, and activate the unit (manually or automatically). However, in this configuration, if any first narrowband radiation 326-1″ exists, it may be transmitted as first narrowband radiation 327-1c″ .

In FIG3D , the power circuits _V1 and _V2 of the first and second cells are both closed and a voltage (above the threshold voltage) is applied to both cells, allowing each cell to operate as generally described with respect to FIG3B and FIG3C , respectively, causing incident light 326 to pass through as transmitted light 327 d . Here, both the first narrowband radiation 326 - 1 ″ and the second narrowband radiation 326 - 2 ″ are substantially blocked, with these radiations being transmitted as 327 - 1 d ″ and 327 - 2 d ″, respectively, with significantly reduced intensities. Furthermore, while there may be some reduction or filtering of broadband radiation 326' , most of it advantageously passes through in the form of transmitted broadband radiation 327d' so that a user or sensor can still fully view the scene or environment without substantial distortion, as previously explained.

When the cell is activated to its lower transmittance state, the LP-VTOD may be characterized by a darkened state having a transmittance (%T DS-P ) of typically no more than 10% at the corresponding peak absorption wavelength, alternatively no more than 5%, 3%, 2%, 1%, 0.5%, 0.2%, 0.1%, 0.05%, 0.02%, 0.01%, or even less. In some cases, the ratio of %T _{DS -P} / %T _CS-P may be no more than 0.5, alternatively no more than 0.4, 0.3, 0.2, 0.1, 0.05, or 0.02. It should be noted that values and metrics related to %T _DS-P may refer to the first peak absorption wavelength when the first unit is activated (%T _DS-P1 ), or the second peak absorption wavelength when the second unit is activated (%T _DS-P2 ), or the combined peak absorption wavelength when both units are activated.

When the cell is activated to its lower transmittance state, the LP-VTOD may in some cases be characterized by a darkened state having an optical density (OD) of at least 1.0, preferably at least 1.5, more preferably at least 2.0, 2.5, 3.0, 3.5, 4.0, or even higher at the corresponding peak absorption wavelength. In some embodiments, the change between the clear state transmittance (%T _CS-P ) and the dark state transmittance (%T _DS-P ) at the peak absorption wavelength may correspond to an optical density difference (ΔOD) greater than 0.5 OD, 0.75 OD, 1 OD, or, in some examples, greater than 1.5, 2, 2.5, 3, 3.5, or 4 OD.

In some cases, the darkened state of the LP-VTOD can be characterized by a photopic transmittance, PT _DS , of at least 10%, alternatively at least 20%, 30%, 40%, 45%, 50%, 55%, or 60%. In some cases, PT _CS is greater than PT _DS by more than 20 percentage units, alternatively 25 percentage units, 30 percentage units, 35 percentage units, or 40 percentage units. In some embodiments, the ratio of PT _DS / PT _CS is at least 0.25, alternatively 0.3, 0.4, 0.5, 0.6, or 0.7. It should be noted that the aforementioned metrics related to PT _DS may refer to metrics when only the first unit is in a lower transmittance state ( FIG. 3B ), when only the second unit is in a lower transmittance state ( FIG. 3C ), or when both the first unit and the second unit are in a lower transmittance state ( FIG. 3D ).

The specific dye composition chosen can be based in part on which narrowband radiation wavelength is desired to be blocked. Generally speaking, the highest blocking occurs when the peak absorption wavelength is close to the narrowband radiation peak intensity wavelength, for example, within 40 nm, preferably within 30 nm, 20 nm, 15 nm, or more preferably within 10 nm. In some embodiments, at narrowband radiation wavelengths (which may include ultra-narrowband radiation), the LP-VTOD may be capable of providing an optical density of at least 1.0, preferably at least 1.5, more preferably at least 2.0, 2.5, 3.0, or even higher.

It should be noted that, depending on whether the LC host has negative anisotropy, the system will be absorbing ("dark" state) when voltage is applied and clear when no voltage is applied. Conversely, when using an LC host with positive anisotropy, the system will be dark when no voltage is applied and transition to clear when voltage is applied. The examples and descriptions provided cover devices using negative LC, but each system or device can also be configured to use a positive LC host (i.e., LC with positive dielectric anisotropy).

Figures 4A and 4B are cross-sectional schematic diagrams of non-limiting examples of LP-VTODs according to some embodiments. In this embodiment, two cells are configured to provide narrowband absorption. LP-VTOD 410 includes a first cell 411 having a first guest-host mixture comprising a negative first LC host 422 and a first dye material comprising a positive first DC dye composition 424. The host and dye molecules are drawn to illustrate general orientation. The first cell is in optical communication with a second cell having a second guest-host mixture comprising a negative second LC host 442 and a second dye material comprising a positive second DC dye composition 444 or a dye mixture. In some cases, the hosts and/or dye compositions of the first and second cells can be substantially identical. For clarity, other components of cells 411 and 431 are not shown, but may be viewed as described with respect to FIG. 1 and its variations. In some embodiments, each cell may be independently controlled by power circuits _V1 and _V2 provided in controller 455. In other embodiments, the voltages applied to the first and second cells may be controlled jointly.

In this embodiment, both the first and second narrowband cells absorb light having a peak wavelength in the visible, UV, or IR regions of the optical spectrum. In some embodiments, the first cell and the second cell absorb light in a first wavelength region and a second wavelength region, respectively, wherein the second wavelength region is substantially identical to the first wavelength region. The wavelength region substantially identically absorbed by the first and second cells can be a wavelength region of the spectrum characterized by a %T within 10% units, alternatively within 5% units, for each wavelength within the relevant wavelength region when dimmed to the same photopic transmittance. For example, when the wavelength region is visible light, the wavelength range is at least 450 to 650 nm, alternatively 400 to 700 nm, or alternatively 380 to 780 nm. In some cases, the substantially identical wavelength region may include a wavelength region where the first peak absorption wavelength and the second peak absorption wavelength are within 5%, or where the first FWHM and the second FWHM are within 5%, or both. Alternatively, the substantially identical wavelength region may include a wavelength region where the first peak absorption wavelength and the second peak absorption wavelength are within 5 nm, or where the first FWHM and the second FWHM are within 5 nm, or both.

In some embodiments, substantially identical wavelength regions can produce CIE 1931 x-y chromaticities for each cell that are within 0.07 units (x and y) (in the cell's darkened state).

The CIE 1931 xy chromaticity, or XYZ color space, refers to a colorimetric standard established by the International Commission on Illumination (CIE). In FIG4A , both power circuits _V1 and _V2 are disconnected, meaning no voltage is applied to either cell 411 or 431. Both the first and second cells are in a relatively high light transmission state (which may be at or near their maximum light transmission state), and the LP-VTOD 410 is in a clear state (which may be at or near its maximum light transmission state), wherein a significant amount of incident visible light 426 passes through as transmitted light 427a . Incident light 426 may include broadband light 426' , which may correspond to light from a general environment (e.g., a room, outdoors, or the like) that is typically composed of various wavelengths across some or all of the visible spectrum.

Incident light 426 may further include narrowband radiation 426' having a peak intensity at a first peak narrowband radiation wavelength. Narrowband radiation may be from a laser or other narrowband light source and may have a higher intensity than broadband light 426' , for example, sufficient to disrupt or even damage the function of a person's vision or sensors (such as camera sensors).

In FIG4B , the power circuits _V1 and _V2 of the first and second cells are both closed (under independent or common control), and a voltage is applied that is higher than the threshold voltage of both cells, sufficient to significantly reorient the LC hosts 422 , 442 and the DC dye compositions 424 , 444. Light absorption in the first and second wavelength regions (which can be identical) increases as the voltage increases. Light transmission can vary based on the applied voltage up to a certain point, beyond which increasing the voltage has less effect. In Figure 4B , the LP-VTOD is in a darkened state, wherein both first unit 411 and second unit 431 are in a relatively low transmittance state (optionally at or near minimum light transmission) in the first/second wavelength region. This results in absorption of some incident visible light 426 in the first/second wavelength region, thereby generating transmitted light 427b . Specifically, the first and second units together block a significant amount of narrowband radiation 426″ , which is then transmitted at a significantly reduced intensity as 427b″ . Activating the first and second cells also blocks some of the broadband radiation 426' , but because the cells have narrowband absorption, most of 426' passes through as 427b' , allowing the user or sensor to still adequately view the scene or environment without substantial distortion. Blocking narrowband radiation while still maintaining acceptable viewing conditions for the scene or environment provides additional safety for users, particularly those in hazardous situations, operating vehicles, aircraft, or the like. For example, a user or sensor can detect narrowband radiation 426" , such as intense 532 nm laser light, and activate the cells (manually or automatically).

Figures 4C and 4D are schematic cross-sectional views of an LP-VTOD 410c similar to the LP-VTOD of Figures 4A and 4B , but including a third cell 451. In some embodiments, third cell 451 may comprise, for example, a broadband electro-optical material having a third guest-host mixture comprising a negative third LC host 462 and a third dye composition 464 , which may include two or more different positive DC dyes. The host and dye molecules are depicted to illustrate general orientation. The third cell is in optical communication with the first and second cells. In some embodiments, the third cell may be controlled independently of the first and second cells by a power circuit _V3 in controller 455 . As shown in FIG4C , power circuit _V3 is closed, and a voltage is applied that is above the threshold voltage sufficient to significantly reorient LC host 462 and DC dye composition 464. Light absorption in the first wavelength region increases as the voltage increases. Light transmission can vary based on the applied voltage up to a point, beyond which increasing the voltage has little effect. In FIG4C , third cell 451 is depicted in an intermediate darkened state. For example, third cell 451 could correspond to an electronic sunglass that reduces transmission across most or all of the visible spectrum.

Referring to FIG4C , power circuits _V1 and _V2 are disconnected, i.e., no voltage is applied to either cell 411 or 431. Both the first and second cells are in a relatively high light-transmitting state (which may be at or near their maximum light-transmitting state), while the third cell 451 is in an intermediate, darkened state. A substantial amount of incident light 426c incident on LP-VTOD 410c passes through the first and second cells but is partially absorbed by the third cell, producing transmitted light 427c . Incident light 426c may include broadband light 426c′ , which may correspond to light from a typical environment (e.g., a room, outdoors, or the like) typically composed of various wavelengths across some or all of the visible spectrum, which is partially absorbed and transmitted as 427c′ . In some cases, the third cell may be colorimetrically neutral in its light absorption and impart no noticeable color hue to the transmitted broadband light 427c' relative to 426c' . The colorimetrically neutral state may be characterized as having both neutral and low color chromaticity.

Referring to FIG. 4D , incident light 426d may include both broadband light 426d′ and narrowband radiation 426d″ . During operation, a sensor or user may detect narrowband radiation 426d″ , such as intense 532 nm laser light, and (manually or automatically) activate first unit 411 and second unit 431 to their lower transmittance states as described elsewhere. This may substantially reduce the intensity of transmitted narrowband radiation 427d″ . Although there may be some additional reduction or filtering of broadband radiation 426d' (in addition to the intentional dimming caused by cell 451 ), the transmitted broadband radiation 427d' is sufficient so that a user or sensor can still adequately view the scene or environment without substantial distortion, as previously explained. In some embodiments, detecting narrowband radiation can further cause broadband cell 451 to change the applied voltage _V3 so that it can be further dimmed or alternatively made less dim.

To further illustrate how wideband and narrowband units can be used together, FIG5 shows a set of transmittance spectra according to some embodiments. Transmission spectrum 561 may correspond to the clear state of LP-VTOD 410c , in which all three units ( 411 , 431 , and 451 ) are in their higher transmittance states. In some cases, transmission spectrum 561 may be colorimetrically neutral, or have low color chromaticity as shown here. Transmission spectrum 563 may correspond to activating the first and second narrowband units ( 411 , 431 ) to their lower transmittance states, while the third wideband unit 451 remains in its higher transmittance state. This state can be used, for example, to absorb a particular laser light (e.g., green, as described here, or some other laser light). Transmission spectrum 565 corresponds to the darkened state produced by the third wideband unit 451 as previously described. This darkened state can be a chromatically neutral first or second darkened state (or low color chroma), or even chromatically neutral, or with low color chroma, depending on the situation. Transmission spectrum 565 can be produced, for example, when the LP-VTOD is as shown in FIG4C. Transmission spectrum 567 corresponds to a darkened state, in which all three units are in a lower transmittance state. The darkened state can be used to block laser light while also providing the user with reduced total transmittance in wavelength regions other than the laser wavelength.

Turning to FIG. 6 , in some embodiments, when incident light 426c (or broadband radiation 426c′ ) is illuminant C light, transmitted light 427c may have a chromaticity falling within the neutral region 602 of the CIE 1931 xy chromaticity diagram 600. In the Munsell color system, the neutral region 602 corresponds to the equivalent chromaticity 2 point at a Munsell chromaticity value of 5 (neutral region 602 may be referred to herein as chromaticity 2 at Munsell chromaticity value 5). In the Munsell color system, under illuminant C, a Munsell chromaticity value of 5 is associated with a visual reflectance Y equivalent (percentage) of approximately 20%. It should be further noted that the neutral region 602 is also similar to the neutral region of some military specifications for light-darkening goggles (e.g., see FIG. 1 of MIL-PRF-32432A, published September 11, 2018, the entire contents of which are incorporated herein by reference for all purposes).

Although not shown, two or more cells may be used instead of just a single cell 451 for dimming broadband radiation, for example, as described in U.S. Non-Provisional Patent Application No. 18/369,843, which is incorporated herein by reference.

In some cases, to detect narrowband radiation incident on or near the LP-VTOD, a sensor may be added to the LP-VTOD itself, to a frame or housing that may support the unit, or to some other location. For example, if the LP-VTOD is being used by a pilot, the aircraft or windshield may house the sensor. The sensor may be provided on any vehicle operated by the LP-VTOD user or even on a piece of clothing or equipment. The sensor may communicate with the LP-VTOD controller either wired or wirelessly. The sensor may be a light sensor. Alternatively, the sensor may detect a secondary electromagnetic signature that indicates the use of a nearby laser.

In some embodiments, the LP-VTOD may include or interface with additional variable transmission optics. For example, the LP-VTOD may include additional units that are wideband VTODs, narrowband VTODs, photochromic devices, electrochromic devices, or hybrid VTODs that may include PC dyes and/or PCDC dyes.

In some embodiments, one cell of the LP-VTOD may include an LC host with right-handed chirality, and the other cell of the LP-VTOD may include an LC host with left-handed chirality. In some embodiments, the light absorption curves of the two cells may have significant overlap. By varying the chirality of the LC, the polarization dependence in the overlapping region (although typically small in this guest-host system) can be further reduced, which can lead to a beneficial increase in transmission swing. This effect can be strongest in the case of overlap in the green region of the visible spectrum (where the human eye has highest sensitivity), such as in the blue/yellow-orange and red/cyan first/second cell combinations.

The chirality of the host material gives rise to an intrinsic spacing p of the liquid crystal host material. The ratio of the cell gap thickness d to this spacing is referred to as d/p. In some embodiments, the d/p of the liquid crystal host can be equal to 0. In some embodiments, the d/p of the liquid crystal host can be greater than 0. In some embodiments with low d/p and birefringence, referred to as " in the Mauguin limit ," the polarization of light follows the polarization of the liquid crystal. Alternatively, the light propagation eigenmode of the device that is not in the Mauguin limit is elliptical. In some cases, the host liquid crystal can cause the device to have a relatively low polarization sensitivity, i.e., less than 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, or 10% polarization sensitivity.

In some embodiments, the thickness to pitch ratio (d/p) of a cell of the LP-VTOD may be at least 0.01, alternatively at least 0.1, 0.2, 0.3, 0.4, or 0.5. In some embodiments, d/p is less than or equal to 3.0, or alternatively less than or equal to 2 or 1. In some embodiments, d/p may be in the range of 0.01 to 0.2, 0.2 to 0.3, 0.3 to 0.4, 0.4 to 0.5, 0.5 to 0.6, 0.6 to 0.7, 0.7 to 0.8, 0.8 to 0.9, 0.9 to 1.0, 1.0 to 1.5, 1.5 to 2.0, 2.0 to 2.5, 2.5 to 3.0, or any combination thereof.

In some embodiments, LP-VTODs may use plastic substrates having photoresist that varies less than ±20% in uniformity across the area of the device, alternatively less than ±15% or less than ±10%.

In some embodiments, cells of the LP-VTOD may have individually selected cell gaps within the range of 3-5 microns, 5-7 microns, 7-10 microns, 10-15 microns, 15-20 microns, 20-25 microns, 25-30 microns, 30-35 microns, 35-40 microns, or 40-50 microns, or any combination of ranges thereof.

In some embodiments, the guest-host mixture has a nematic-isotropic transition temperature, TNI, greater than 40° C. In other embodiments, the TNI is greater than 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., or 90° C.

The order parameter of the mixture can be determined by optical measurements of the light transmission in the rest and energized states using linearly and/or circularly polarized light at several wavelengths both inside and outside the absorption spectrum. The order parameter can then be determined by numerically fitting the experimental data using liquid crystal optical simulation methods such as those developed by Berreman (Berreman D. W. 1972, Optics in Stratified and Anisotropic Media: 4×4-Matrix Formulation. Journal of the Optical Society of America, 62(4), 502) or Odano (Allia, P., Oldano, G., and Trossi, L., 1986, 4×4 Matrix approach to chiral liquid-crystal optics. Journal of the Optical Society of America B, 3(3), 424). These simulation methods are used by those skilled in the art or through commercial programs such as Kelly's Twisted Cell Optics (Kelly, J., Jamal, S., and Cui, M., 1999, Simulation of the dynamics of twisted nematic devices including flow. Journal of Applied Physics, 86(8), 4091).

In some embodiments, one or more units of the LP-VTOD include a guest-host _mixture having an order parameter Smix at a peak absorption wavelength greater than or equal to 0.65, 0.7, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77 , or 0.78, alternatively greater than or equal to 0.79 or 0.80.

LP-VTODs have a variety of potential applications. For example, these devices can be manufactured directly into or laminated onto "wearable" products such as eyewear (prescription and over-the-counter glasses and sunglasses), visors, goggles, face shields, near-eye displays, sensor optics, cameras, and AR/VR headsets (to name a few). Alternatively, they can be manufactured directly into or laminated onto other products, including but not limited to windows (for vehicles, buildings, aircraft, etc.), windshields, sunroofs, head-up displays, camera filters, and optical instruments. These products and devices may further be equipped with a power supply, battery, sensor, or the like. In some embodiments, one or more sensors may provide information or data used in the operation of the LP-VTOD. Some non-limiting examples of sensors include light sensors, imaging sensors, and laser warning receivers.

In some embodiments, one or more cells of an LP-VTOD can be divided into discrete, individually addressable regions to allow different regions of the LP-VTOD to display different states. In some cases, these regions can be formed by patterning a transparent conductive layer, optionally combined with spacers to separate the electro-optical material into different sub-cells within the cell. Example Embodiments

LP-VTODs can be fabricated according to protocols similar to those described herein. Each cell can be fabricated using an isotropic substrate of 3 mil polycarbonate coated with indium tin oxide (ITO), a transparent conductor. On top of the ITO, a polyimide coating, such as Nissa 5661 (Nissan Chemical Industries, Ltd., Tokyo, Japan), can be applied. This polyimide coating acts as an alignment layer designed to induce strong vertical alignment of the liquid crystal molecules. Plastic spheres, such as 6.2 micron spheres, can be sprayed onto one of the substrates to act as spacers. A thin bead of UV-curable adhesive, such as Loctite 3106 (Henkel AG & Co. KGaA, Dusseldorf, Germany), can be applied around the perimeter of one of the substrates, leaving a gap that will serve as the fill port. The two substrates are assembled, pressed together against spacers to create a uniform gap between the substrates, and then exposed to UV light to cure the adhesive.

An appropriate guest-host mixture of the first and second cells can be prepared. The cells can be laminated together using an optically clear, pressure-sensitive adhesive. Each cell can be individually connected to a driver circuit that can be used to apply, for example, a 60 Hz square wave voltage. Alternatively, the cells can be connected together to the driver circuitry so that a common voltage can be applied to both cells.

An LP-VTOD was constructed in which the first and second cells were substantially identical in their overall design and chemical composition. Each cell was filled with the LC-dye mixture AMI #905NC (AlphaMicron, Inc., Kent, OH). The DC dye composition included a BODIPY (boron dipyrromethene) dye with a narrow-band light-absorbing moiety having the properties shown in Table 1. The first and second cells had a peak absorption wavelength of approximately 522 nm. Some electro-optical properties are reported in Table 1 and Figure 7. Table 1. Voltage (V) PT% 522 nm 532 nm FWHM %T OD %T OD 0 68.2 25 0.6 32 0.5 n/a 16 49.7 0.6 2.2 1.0 2.0 ~49 nm

Figure 7 shows plots of the optical density of the LP-VTOD as a function of wavelength at 0 V (clear state; dashed line) and 16 V (dark state, solid line). Based on these spectra, the photopic transmittance (PT%) can be calculated and reported in Table 1. The optical density at the peak absorption wavelength (522 nm) and the nearby common laser wavelength (532 nm) is also reported in Table 1. It can be seen that at 522 nm and even 532 nm, a significant increase in optical density (%T decrease) can be achieved with the LP-VTOD while still maintaining high photopic transmittance. This is due in part to the low FWHM of the dye composition in its reduced transmittance state, which is only approximately 49 nm. It should be noted that even in the clear state, the LP-VTOD has some absorption of light around 522 nm. Although this can impart a slight magenta tint, in many applications this would be undesirable. If necessary, this clear state tint can be at least partially corrected by adding complementary light absorbing features, such as non-dichroic dyes or pigments, to the electro-optical mixture or as a separate layer to the LP-VTOD.

Still other embodiments herein include the following. Example 1. A laser protected variable transmission optical device ("LP-VTOD") comprising: a first unit comprising a first electro-optical material provided between a first pair of substrates, wherein upon a change in a first electric field applied to the first electro-optical material, the first electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a first wavelength region, and wherein the first unit is characterized by having a first peak absorption wavelength and a first FWHM of 175°C. nm or less; and a second unit in optical communication with the first unit, the second unit comprising a second electro-optical material provided between a second pair of substrates, wherein the second electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a second wavelength region upon a change in a second electric field applied to the second electro-optical material, and wherein the second unit is characterized by having a second peak absorption wavelength and a narrowband absorption with a second Full Width At Half Maximum (FWHM) of 175 nm or less, wherein for light passing through the LP-VTOD, the LP-VTOD is capable of switching from a clear state to a darkened state, the darkened state having a darkened state transmittance %T _DS-P equal to or less than 10% for at least one of the first peak absorption wavelength or the second peak absorption wavelength. Example 2. The LP-VTOD of Example 1, wherein the first peak absorption wavelength is different from the second peak absorption wavelength. Example 3. The LP-VTOD of Example 1 or 2, wherein the first electro-optical material comprises a first LC host and a first DC dye composition, the second electro-optical material comprises a second LC host and a second DC dye composition, and the second DC dye composition is different from the first DC dye composition. Example 4. The LP-VTOD of any one of Examples 1 to 3, wherein the first electro-optical material comprises a first narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow-band absorption, the second electro-optical material comprises a second narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow-band absorption, and the second narrow-band guest-host liquid crystal mixture is different from the first narrow-band guest-host liquid crystal mixture. Example 5. The LP-VTOD of Example 4, wherein the first narrowband guest-host liquid crystal mixture and the second narrowband guest-host liquid crystal mixture have different optical properties selected from one of the following: peak absorption wavelength, full width half maximum (FWHM) absorption band, total absorptivity, or a combination thereof. Example 6. The LP-VTOD of Example 1, wherein the first peak absorption wavelength and the second peak absorption wavelength are substantially the same, optionally wherein the second peak absorption wavelength differs from the first peak absorption wavelength by less than 5%, or optionally wherein the second peak absorption wavelength differs from the first peak absorption wavelength by less than 5 nm. Example 7. The LP-VTOD of Example 1 or 6, wherein the first electro-optic material comprises a first LC host and a first DC dye composition, the second electro-optic material comprises a second LC host and a second DC dye composition, and the second DC dye composition is substantially the same as the first DC dye composition. Example 8. The LP-VTOD of any one of Examples 1, 6, or 7, wherein the first electro-optic material comprises a first narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow band absorption, the second electro-optic material comprises a second narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow band absorption, and the second narrow-band guest-host liquid crystal mixture is substantially the same as the first narrow-band guest-host liquid crystal mixture. [0015] Example 9. The LP-VTOD of Example 8, wherein the first narrowband guest-host liquid crystal mixture and the second narrowband guest-host liquid crystal mixture have substantially the same optical properties selected from one of the following: peak absorption wavelength, full width half maximum absorption band, total absorptivity, or a combination thereof. [0016] Example 10. The LP-VTOD of any one of Examples 1 to 9, wherein the first peak absorption wavelength and the second peak absorption wavelength are independently selected from the following ranges: 100 to 380 nm, 380 to 780 nm, 780 to 1300 nm, 1300 to 3000 nm, or 3000 nm to 1 mm. [0017] Example 11. The LP-VTOD of any one of Examples 1 to 10, wherein the first peak absorption wavelength or the second peak absorption wavelength is in a range of 380 to 780 nm. Example 12. The LP-VTOD of any one of Examples 1-11, wherein the first peak absorption wavelength and the second peak absorption wavelength are both within a range of 380 to 780 nm, or optionally 400 to 700 nm. Example 13. The LP-VTOD of any one of Examples 1-12, wherein the clear state has a clear state transmittance %TC _S-P of at least 20%, or optionally at least 40%, for at least one peak absorption wavelength. [0014] Example 14. The LP-VTOD of any one of Examples 1-13, wherein at each of the first peak absorption wavelength and the second peak absorption wavelength, the LP-VTOD is capable of switching from a clear state having a %T _CS-P of at least 20%, or optionally at least 40%, to a darkened state having a %T _DS-P of no more than 2.0%, or optionally no more than 1.0%. [0015] Example 15. The LP-VTOD of any one of Examples 1-14, wherein for at least one of the first peak absorption wavelength or the second peak absorption wavelength, switching between the clear state and the darkened state corresponds to an optical density change, ΔOD, of at least 1.0. [0014] Example 16. The LP-VTOD of Example 15, wherein ΔOD is at least 1.5, or optionally at least 2.0. [0015] Example 17. The LP-VTOD of any of Examples 1 to 16, wherein the clear state is characterized by a photopic transmittance PT _CS of at least 40%, or optionally at least 60%, and the darkened state is characterized by a photopic transmittance PT _DS of at least 10%, or optionally at least 20%. [0016] Example 18. The LP-VTOD of Example 17, wherein PT _CS is greater than PT _DS by more than 20 percentage points, or optionally more than 30 percentage points. [0015] Example 19. The LP-VTOD of Example 17 or 18, wherein a ratio of PT _DS /PT _CS is at least 0.25, or optionally at least 0.35, or optionally at least 0.5. [0016] Example 20. The LP-VTOD of any one of Examples 1 to 19, wherein the darkened state is characterized by an optical density of at least 2.0 measured at 532 nm, or optionally an optical density of at least 2.5 measured at 532 nm. [0017] Example 21. The LP-VTOD of any one of Examples 1 to 20, wherein at least one of the first FWHM and the second FWHM is 88 nm or less, or optionally 80 nm or less, or optionally 70 nm or less, or optionally 60 nm or less. [0014] Example 22. The LP-VTOD of any one of Examples 1 to 21, wherein the first cell comprises a first alignment layer, and the second cell comprises a second alignment layer, and wherein an orientation of the first alignment layer is rotated 70 to 110 degrees relative to an orientation of the second alignment layer. [0014] Example 23. The LP-VTOD of any one of Examples 1 to 22, wherein the first cell is configured to absorb a first polarization to a greater extent than a second polarization, and the second cell is configured to absorb the second polarization to a greater extent than the first polarization, wherein the second polarization is substantially orthogonal to the first polarization. [0015] Example 24. The LP-VTOD of any one of Examples 1 to 23, further comprising a third unit in optical communication with the first unit and the second unit, the third unit comprising a third electro-optical material provided between a third pair of substrates, wherein the third electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a third wavelength region upon a change in a third electric field applied to the third electro-optical material. [0016] Example 25. The LP-VTOD of Example 24, wherein the third unit is characterized by having a narrowband absorption having a third peak absorption wavelength and a third FWHM of 175 nm or less. [0017] Example 26. The LP-VTOD of Example 25, wherein the third FWHM is 88 nm or less, or optionally 80 nm or less. Example 27. The LP-VTOD of Example 25 or 26, wherein the third peak absorption wavelength is in a range of 380 nm to 780 nm. Example 28. The LP-VTOD of Example 25 or 26, wherein the third peak absorption wavelength is in a range of 100 to 380 nm or 780 nm to 1 mm. Example 29. The LP-VTOD of Example 24, wherein the third unit is characterized by having a broadband absorption having a third FWHM greater than 175 nm. [0066] Example 30. The LP-VTOD of Example 29, wherein the lower transmittance state of the third cell has a photopic transmittance that is at least 20%, or optionally at least 40%, lower than a photopic transmittance of the higher transmittance state of the third cell. [0067] Example 31. The LP-VTOD of Example 29 or 30, wherein the lower transmittance state of the third cell is colorimetrically neutral. Example 32. The LP-VTOD of any one of Examples 24 to 31, further comprising a fourth unit in optical communication with the first unit, the second unit, and the third unit, the fourth unit comprising a fourth electro-optical material provided between a fourth pair of substrates, wherein the fourth electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a fourth wavelength region upon a change in a fourth electric field applied to the fourth electro-optical material. Example 33. The LP-VTOD of Example 32, wherein the fourth unit is characterized by having a broadband absorption having a fourth FWHM greater than 175 nm. Example 34. The LP-VTOD of Example 32 or 33, wherein the third unit and the fourth unit operate cooperatively in their respective lower transmittance states to produce a combined photopic transmittance that is at least 20% lower, and optionally at least 40% lower, than a photopic transmittance produced when the third unit and the fourth unit are in their respective high transmittance states. Example 35. The LP-VTOD of Example 34, wherein the combined photopic transmittance is colorimetrically neutral. [0014] Example 36. An article comprising the LP-VTOD of any one of Examples 1 to 35, wherein the article comprises a camera filter, glasses, a sun visor, goggles, a mask, an AR/VR headset, a near-eye display, a window, a windshield, a sunroof, a head-up display, or an optical instrument. [0014] Example 37. A method of operating the LP-VTOD device of any one of Examples 1 to 29, the method comprising varying the first electric field to switch the first unit from a higher transmittance state to a lower transmittance state. [0015] Example 38. The method of Example 37, further comprising changing the second electric field to switch the second unit from a higher transmittance state to a lower transmittance state. [0016] Example 39. The method of Example 38, wherein the first electric field and the second electric field are independently controlled. [0017] Example 40. The method of Example 38, wherein the first electric field and the second electric field are jointly controlled. [0018] Example 41. The method of any one of Examples 37 to 40, further comprising detecting the presence of laser light incident on or near the LP-VTOD by a sensor, wherein the sensor is provided for wired or wireless communication with the LP-VTOD. [0066] Enumerated embodiment 42. The method of embodiment 41, wherein sensing triggers a change in one or both of the first electric field or the second electric field. [0067] Enumerated embodiment 43. The LP-VTOD of any one of embodiments 1 to 35, further comprising a polarization rotator disposed between the first unit and the second unit, wherein the polarization rotator comprises a half-wave plate or a quarter-wave plate.

The specific details of a particular embodiment may be combined in any suitable manner without departing from the spirit and scope of the embodiments of the present invention. However, other embodiments of the present invention may be directed to specific embodiments related to each individual aspect or specific combinations of these individual aspects.

The above description of example embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the above teaching.

In the foregoing description, for the purpose of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present invention. However, one skilled in the art will appreciate that certain embodiments may be practiced without some of these details or with other additional details.

After describing several embodiments, those skilled in the art will recognize that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the present invention. Furthermore, many well-known processes and components have not been described to avoid unnecessarily obscuring the present invention. Furthermore, details of any particular embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

Where a range of values is provided, it is understood that each intervening value between the upper and lower limits of that range is also specifically disclosed, to the tenth of the unit of the lower limit, unless the context clearly dictates otherwise. Each smaller range between any stated or intervening value in the stated range, as well as any other stated or intervening value in the stated range, is encompassed. The upper and lower limits of such smaller ranges may independently be included or excluded in the range, and ranges where either, no, or both limits are included in the smaller range are also encompassed within the invention, subject to any specifically excluded limits in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a method" includes a plurality of such methods, and reference to "a layer" includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth. The present invention has been described in detail for purposes of clarity and understanding. However, it should be understood that certain variations and modifications may be practiced within the scope of the appended claims.

All publications, patents, and patent applications cited herein are incorporated by reference in their entirety for all purposes. No admission is made that any of them is prior art.

10, 310, 410, 410c: LP-VTOD 11, 311, 411: First cell 12a, 12b, 32a, 32b: Substrate 13, 33: Sealing material 14a, 14b, 34a, 34b: Transparent conductive layer 16a, 16b, 36a, 36b: Passivation layer 18a, 18b, 38a, 38b: Alignment layer 18a-BL, 38a-BL: Alignment brush lines 20: First cell gap 25: First electro-optical material 26, 326, 426, 426c, 426d: Incident light 26': Lower intensity component 26'': Higher intensity narrowband radiation component 27,327a,327b,327c,327d,427a,427b,427c,427d: Transmitted light 27': Transmitted lower-intensity component 27'': Transmitted narrowband radiation component 28,48: Switch 31,331,431: Second cell 40: Second cell gap 45: Second electro-optical material 50: Layer separating the first and second cells 55,355,455: Controller 322,422: First LC host 324,424: First dye composition 326',426',426c',426d': Broadband light 326-1'': First narrowband radiation 326-2'': Second narrowband radiation 327a', 327b', 327c', 327d', 427a', 427b', 427c', 427d': Transmitted broadband light 327-1a'', 327-1b'', 327-1c'', 327-1d'': Transmitted first narrowband radiation 327-2a'', 327-2b'', 327-2c'', 327-2d'': Transmitted second narrowband radiation 342, 442: Second LC host 344, 444: Second dye composition 426'', 426d'': Narrowband radiation 427a'', 427b'', 427d'': Transmitted narrowband radiation 451: Third unit 462: Third LC host 464: Third dye composition 561, 563, 565, 567: Transmitted spectrum 600: Chromaticity diagram 602: Neutral region

[ FIG. 1 ] is a cross-sectional view of a non-limiting example of a laser protected variable transmission optical device (“LP-VTOD”) according to some embodiments.

2A and 2B are schematic plan views illustrating the relative orientation of alignment layers between different cells according to some embodiments.

3A-3D are a series of cross-sectional schematic diagrams of non-limiting examples of LP-VTOD according to some embodiments.

4A-4B are cross-sectional schematic diagrams of a non-limiting example of another LP-VTOD according to some embodiments.

4C-4D are cross-sectional schematic diagrams of non-limiting examples of another LP-VTOD according to some embodiments.

FIG5 is a graph of various light transmission spectra illustrating the effect of adding a wideband unit to an LP-VTOD according to some embodiments.

[Figure 6] illustrates a portion of the CIE 1931 x-y color space chromaticity diagram according to some embodiments.

[Figure 7] Optical density spectra illustrating clear and dark states of a non-limiting example of LP-VTOD.

10: LP-VTOD

11: Unit 1

12a,12b,32a,32b:Substrate

13,33: Sealing materials

14a, 14b, 34a, 34b: Transparent conductive layer

16a, 16b, 36a, 36b: Passivation layer

18a,18b,38a,38b: Alignment layer

20: First unit gap

25: First electro-optical material

26: Incident Light

26': Lower strength

26": High-intensity narrowband radiation component

27: Transmitted Light

27': Transmitted lower intensity component

27": Transmitted narrowband radiation component

28,48: Switch

31: Unit 2

40: Second unit gap

45: Second electro-optical material

50: Layer separating the first unit from the second unit

55: Controller

Claims (22)

A laser protected variable transmission optical device ("LP-VTOD") comprising: a first unit comprising a first electro-optical material provided between a first pair of substrates, wherein the first electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a first wavelength region upon a change in a first electric field applied to the first electro-optical material, and wherein the first unit is characterized by having a first peak absorption wavelength and a first full width at half maximum (FWHM) of 175°C. and a second unit in optical communication with the first unit, the second unit comprising a second electro-optical material provided between a second pair of substrates, wherein the second electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a second wavelength region upon a change in a second electric field applied to the second electro-optical material, and wherein the second unit is characterized by having a second peak absorption wavelength within 5% of the first peak absorption wavelength and a narrowband absorption with a second full width at half maximum (FWHM) of 175 nm or less, wherein for light passing through the LP-VTOD, the LP-VTOD is capable of switching from a clear state to a darkened state, the darkened state having a darkened state transmittance %T _DS-P equal to or less than 10% for at least one of the first peak absorption wavelength or the second peak absorption wavelength. . The LP-VTOD of claim 1 , wherein the first peak absorption wavelength and the second peak absorption wavelength are independently selected from the following ranges: 100 to 380 nm, 380 to 780 nm, 780 to 1300 nm, 1300 to 3000 nm, or 3000 nm to 1 mm. The LP-VTOD of claim 1, wherein for the at least one peak absorption wavelength, the clear state has a clear state transmittance %TCS _-P of at least 20%. The LP-VTOD of claim 3, wherein at each of the first peak absorption wavelength and the second peak absorption wavelength, the LP-VTOD is capable of switching from a % T _CS-P of at least 30% to a % T _DS-P of no more than 1.0%. The LP-VTOD of claim 1 , wherein for at least one of the first peak absorption wavelength or the second peak absorption wavelength, switching between the clear state and the darkened state corresponds to an optical density change ΔOD of at least 1.0. The LP-VTOD of claim 1, wherein the first peak absorption wavelength and the second peak absorption wavelength differ by less than 5 nm. The LP-VTOD of claim 1, wherein the clear state is characterized by a photopic transmittance PT _CS of at least 40%, and the darkened state is characterized by a photopic transmittance PT _DS of at least 10%. The LP-VTOD of claim 7, wherein a ratio of PT _DS /PT _CS is at least 0.35. The LP-VTOD of claim 1, wherein the first electro-optic material comprises a first narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow-band absorption, and the second electro-optic material comprises a second narrow-band guest-host liquid crystal mixture having a narrow or ultra-narrow-band absorption. The LP-VTOD of claim 9, wherein the first narrowband guest-host liquid crystal mixture and the second narrowband guest-host liquid crystal mixture have substantially the same optical performance selected from the group consisting of FWHM absorption band, total absorptivity, or a combination thereof. The LP-VTOD of claim 1, wherein the darkened state is characterized by an optical density of at least 2.0 measured at 532 nm. The LP-VTOD of claim 1, wherein the first peak absorption wavelength and the second peak absorption wavelength are both within a range of 380 to 780 nm. The LP-VTOD of claim 1 , wherein at least one of the first FWHM and the second FWHM is 60 nm or less. The LP-VTOD of claim 1 further comprises a third unit in optical communication with the first unit and the second unit, the third unit comprising a third electro-optical material provided between a third pair of substrates, wherein the third electro-optical material is capable of changing from a higher transmittance state to a lower transmittance state in a third wavelength region after a third electric field applied to the third electro-optical material changes. The LP-VTOD of claim 14, wherein the third unit is characterized by having a narrowband absorption with a third peak absorption wavelength and a third full width at half maximum (FWHM) of 175 nm or less. The LP-VTOD of claim 14, wherein the third unit is characterized by having a broadband absorption with a third FWHM greater than 175 nm. The LP-VTOD of claim 16, wherein the lower transmittance state of the third unit has a photopic transmittance that is at least 30% lower than a photopic transmittance of the higher transmittance state of the third unit. The LP-VTOD of claim 16, wherein the lower transmittance state of the third unit is colorimetrically neutral. The LP-VTOD of claim 1 , wherein the first unit is configured to absorb a first polarization light to a greater extent than a second polarization light, and the second unit is configured to absorb the second polarization light to a greater extent than the first polarization light, wherein the second polarization light is substantially orthogonal to the first polarization light. The LP-VTOD of claim 1, wherein the first unit includes a first alignment layer, and the second unit includes a second alignment layer, and wherein an orientation of the first alignment layer is rotated 70 to 110 degrees relative to an orientation of the second alignment layer. The LP-VTOD of claim 1 , further comprising a polarization rotator disposed between the first unit and the second unit. An article comprising the LP-VTOD of claim 1, wherein the article comprises a camera filter, glasses, a sun visor, goggles, a mask, an AR/VR headset, a near-eye display, a window, a windshield, a sunroof, a head-up display, or an optical instrument.