Laser protection optical devices

Abstract

A laser protection optical device ("LPOD") includes a polarization rotator and a wavelength selective polarizer. The polarization rotator is configured to act on incident polarized narrowband radiation having a peak wavelength and a first polarization to produce rotated narrowband radiation having a second polarization different from the first. The wavelength selective polarizer receives and substantially blocks the rotated narrowband radiation having the second polarization.

Description

LASER PROTECTION OPTICAL DEVICESCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to, and any other benefit of, U.S. Provisional Patent Application Serial No. 63 / 614,670, entitled LASER PROTECTION OPTICAL DEVICES, filed December 26, 2023, the entire disclosure of which is fully incorporated herein by reference.TECHNICAL FIELD

[0002] The present disclosure relates to optical devices that provide protection from high intensity narrowband radiation, and in particular, to optical devices capable of absorbing or reflecting laser light while allowing some non-polarized broad band light to be visible.BACKGROUND

[0003] Variable transmission optical devices, e.g., glasses, goggles, visors, windows, sensors, filters, cameras, or the like, that can quickly change between a high-transmission “clear” state and a low-transmission “dark” state have many advantages over fixed transmission optical devices. An especially useful feature is the ability to make this quick change occur on demand, whether manually (e.g., at the touch of a button by the user), or automatically, e.g., under the control of a light sensor and an electronic circuit.

[0004] Optical devices can potentially offer protection from intense light, e.g., from narrow beam light sources such as lasers. For example, the military, police, first responders, pilots and others can face threats from laser light wielded by hostile persons or devices. Defending against laser light has been difficult and solutions to date have been largely unsatisfactory. For example, a common approach (for green lasers) has been simply to provide a static green-light absorbing strip at a top portion of a face shield. This only provides protection if the person wearing it has their head properly angled. Furthermore, the system will continue to block that region of the spectrum regardless of the presence or absence of the threat. This can lead to color distortions which may not meet the optical requirements for some uses. In the case of pilots, a static tinted film that blocks the green laser is undesirable because it can also dim aviator vision and filter out cockpit displays and additionally, impair the pilot’s ability to properly view PAPI (PrecisionApproach Path Indicator) or VAST (Visual Approach Slope Indicator) lights which require red / white or rcd / grccn differentiation.

[0005] Variable transmission optical devices can also provide some protection from intense light. However, it has been difficult to formulate such devices to have sufficient optical density for satisfactory protection against lasers. For some applications, it is important that a scene viewed through the optical device is not obscured when the device is activated to protect against laser light. To reach sufficient optical densities to protect against lasers (e.g., having an Optical Density “OD” of 1 or more at the laser wavelength), the scene becomes unacceptably dim overall in wavelength regions outside the laser wavelength.

[0006] Thus, there is a need to provide an optical system (e.g., filters, lenses, goggles, visors, face shields, windows, windshields, cockpits, AR or VR glasses, or the like) that can protect against intense narrow band light while maintaining sufficient light transmission spectral regions other than the laser light.SUMMARY

[0007] In accordance with some embodiments, laser protection optical device (“LPOD”) includes a polarization rotator and a wavelength selective polarizer. The polarization rotator is configured to act on incident polarized narrowband radiation having a peak wavelength and a first polarization to produce rotated narrowband radiation having a second polarization different from the first. The wavelength selective polarizer receives and substantially blocks the rotated narrowband radiation having the second polarization. In some embodiments, the polarization rotator may be an electronic polarization rotator.BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1 is a schematic view of a non- limiting example of a Laser Protection Optical Device (LPOD).

[0009] FIGS. 2 A and 2B are schematic views of a non-limiting example of a VT-LPOD.

[0010] FIGS. 3A and 3B are schematic views of a non-limiting example of another VT-LPOD.

[0011] FIGS. 4A and 4B are schematic views of a non-limiting example of another VT-LPOD.

[0012] FIGS. 5A and 5B are schematic views of a non-limiting example of another VT-LPOD.

[0013] FIG. 6 is a schematic view of a non-limiting example of another LPOD.

[0014] FIGS. 7A and 7B are schematic diagrams of non-limiting examples of electronic polarization rotators.DETAILED DESCRIPTION

[0015] Lasers and some other high intensity narrowband radiation sources are typically not polarization independent and are often polarized to a large degree. As described in the present application, it has been found that this polarization dependence can be leveraged in novel ways to create a laser protection optical device that can still have excellent light transmission properties in spectral regions outside of the laser light region. Further, the present devices can be operative against incident laser light or other polarized high intensity narrowband radiation regardless of their incident polarization properties or even if such properties changes as a function of time or incident angle. That is, a priori knowledge of the polarization properties of the incident laser is not necessary and devices of the present disclosure can be effective against incident laser light of arbitrary polarization.

[0016] Note that various embodiments are often described with reference to lasers, but this is simply for convenience and such embodiments also generally apply to other polarized high intensity narrowband radiation sources. For example, the devices and methods of the present application may protect a user or a device from an LED, a surface-mounted diode (SMD), or the like.

[0017] Regarding various concepts described herein relating to polarization rotators, wavelength selective polarizers, liquid crystal devices, guest-host systems, and laser protection, reference is made to U.S. Patent Nos. 9,304,333, 11,500,255, International Patent Application Publication No. WO2023 / 086426, and U.S. Patent Application Publication No. 2024 / 0077777, the entire contents of each are incorporated herein by reference for all purposes.

[0018] A few descriptions and definitions are provided below to aid in the discussion of various embodiments. Wherever any conflict may exist, the description found in the embodiments supersedes.

[0019] Unless specifically defined otherwise herein, the definitions for optical parameters such as linear, circular and unpolarized light are the same as those in “Principles of Optics Electromagnetic Theory of Propagation, Interference and Diffraction of Light”, Max Born, et al., Cambridge University Press; 7th edition (October 13, 1999). Similarly, all liquid crystalterminology which is not specifically defined herein is to have the definition as used in Liquid Crystals Applications and Uses, vol.3, edited by B. Bahadur, published by World Scientific Publishing Co. Pte. Ltd., 1992 (“Bahadur”).

[0020] A “wavelength selective polarizer” (“WSP”) is a polarizer configured to block (absorb, reflect, or both) narrowband radiation of a selected polarization and wavelength range. A WSP may be absorptive or reflective.

[0021] An “absorptive WSP” or “absorptive polarizer” as used herein is a polarizer that is configured to have a narrow band absorption band of a selected polarization of light. In some cases, an absorptive WSP polarizer may have two axes, an absorptive axis and a transmissive axis, which are at right angles to each other. The polarization of the light that is parallel to the axis of the absorptive polarizer is absorbed more than the orthogonal polarization component. For example, an “absorptive polarizer with an axis in the x-direction” means that the polarizer will substantially absorb the x-direction polarization of light while substantially allowing y- polarization to propagate (or vice versa). It should be noted that absorptive circular polarizers may be constructed by using a linear polarizer in combination with a quarter wave retarder. Once light is polarized by the polarizer, the quarter wave plate induces a p / 2 phase retardation which turns a linear polarization to a circular polarization. In some cases, an absorptive polarizer may include a liquid crystal host and a dichroic light-absorbing guest provided with a particular alignment.

[0022] A “reflective polarizer” or “reflective WSP” as used herein is a polarizer that will reflect a selected polarization of narrowband radiation more than the other. For example, a “reflective polarizer with a reflective axis in the x-direction” means that the reflective polarizer will reflect the x-direction polarization of incident light more than the other y-direction polarization (or vice versa). In some cases, a reflective polarizer will reflect right-handed circularly or elliptically polarized narrowband radiation more than the left-handed component which may be transmitted (or vice versa). In some cases, a reflective polarizer may include a cholesteric liquid crystal (CLC) material.

[0023] A “passive polarizer”, “passive WSP”, or “static polarizer” refers to a polarizer whose properties are generally fixed and not electronically controllable, e.g., by an electric field. Apassive polarizer may be an absorptive polarizer or a reflective polarizer. In some case, a reflective polarizer may be referred to as a static CLC.

[0024] An “active polarizer” or “active WSP” or “electronic Polarizer on Demand” (“e-POD”) refers to a polarizer that can alter its absorption or reflection of the selected polarization of light depending on the applied voltage. In some preferred embodiments, an active WSP is an active absorptive WSP. In some cases, when in an unenergized (low or no voltage) condition, the polarizer will not preferentially absorb either polarization and will transmit light of both polarizations. In this case, the active polarizer is in a “non-activated state”. Alternatively, in other embodiments, when in an unenergized (low or no voltage) condition, the polarizer may preferentially absorb one polarization and will transmit light of the other polarization. In such case, the active polarizer is considered to be in its “activated state”. A controller coupled with the active polarizer controls the polarization: in one embodiment, the polarizer can be operated in an ON or OFF state. In other embodiments, the polarizer can be set to apply a variable polarization absorption level with the controller setting a selected polarization level. In some examples, the polarization level of the active absorptive polarizer is selected by controlling the voltage applied to the active absorptive polarizer. Thus, the device can further include a controller for application of voltage to the device and the controller is coupled with the active absorptive polarizer. As mentioned, “activated state” does not necessarily mean application of a voltage. In some cases, a voltage is applied to create an activated state, but in other cases, an activated- state voltage may be at or near zero volts and a voltage is instead applied to “deactivate” the polarization (to the non-activated state).

[0025] An “active polarization rotator” or an “electronically tunable polarizer” or an “electronic polarization rotator” (“EPR”) are synonymous terms referring to a device where application of a voltage to the device alters the polarization properties of incident polarized radiation. For example, it may alter the direction of two linearly polarized components of the incoming light by a value between 0 and 90 degrees, changing it so that light exiting the polarizer rotator is changed from a first direction polarization to a second direction polarization within a selected wavelength region. Thus, for example, polarized light having polarization angle 01 entering the polarizer rotator will be turned into polarized light having polarization angle 62. In some cases, the rotator may turn linearly polarized light to elliptical / circular polarized light.The active polarization rotator may function in various ways: in some examples, polarization rotation occurs when the rotator is in the energized (V is not 0) state, in other examples, polarization rotation occurs when the rotator or device is in an unenergized (V=0) state.

[0026] A “passive polarization rotator” or “static polarization rotator” refers to a device that rotates or otherwise alters the polarization properties of incident radiation. Unlike the active polarization rotator mentioned above, such rotation is fixed and not electronically controllable, e.g., by an electric field.

[0027] “Arbitrary polarization” of incident narrowband radiation generally means any polarization. Devices of the present disclosure can be made effective independent of the incident polarization properties or angle.

[0028] “ Narrow Band Absorption” as used herein, is defined as a spectral absorption band width with a Full Width at Half Max (FWHM) that is less than or equal to 175 nm, or alternatively less than or equal to 165 nm, 155 nm, 120 nm, lOOnm, 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30 nm, 20 nm, or 10 nm where the entire spectral absorption band is typically measured within the visible region of 400 - 700 nm, or alternatively 380 nm - 780 nm.

[0029] ‘ ‘Ultra-Narrow Band Absorption” is a subset of “narrow band absorption” and as used herein is defined as a spectral absorption band width with FWHM that is less than or equal to 88 nm, or alternatively less than or equal to 80 nm, 70 nm, 60 nm, 50 nm, 40 nm, 30nm, 20 nm, or 10 nm or less where the entire spectral absorption band is typically measured within the visible region of 400 - 700 nm, or alternatively 380 nm - 780 nm.

[0030] ‘ ‘Narrowband radiation” refers to radiation incident on the present optical device 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, bandwidth may correspond to a full-width-at- half-max (FWHM) of a spectrum of relative radiant power vs. wavelength. “Ultra-narrowband radiation is a subset of narrowband radiation and refers to the incident light having a bandwidth of 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 optionally be ultra-narrowband radiation, may in some cases include light produced from a laser (laser radiation or laser light), surface-mounted diodes (SMDs) or some LEDs and the like. In some cases, narrowband radiation may have a peakwavelength in the visible spectrum, e.g., 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.

[0031] ‘‘Optical Density” or OD generally refers to the apparent absorbance of radiation measured at a particular wavelength, e.g., at a peak dye absorption wavelength or a peak narrowband radiation wavelength. Percent transmittance (%T) is related to the overall OD at the particular wavelength through: %T = 10(’OD)x 100%.

[0032] ‘ ‘Polarizer” refers to a material, layer, or component that absorbs or reflects one polarization of incident light more than the orthogonal polarization.

[0033] ‘ ‘Transmission” and “Transmittance” are used interchangeably and mean the percentage of light that is transmitted through a mixture or device, and which may be referred to herein as a %T.

[0034] “Photopic transmittance” or “photopic transmission” refers to the percent transmission of visible light weighted by the spectral response of the day-adapted human eye.

[0035] ‘ ‘Visible light” refers to a wavelength range of about 400 nm to about 700 nm, or alternatively about 380 nm to about 780 nm.

[0036] FIG. 1 is a schematic view of a non-limiting example of a Laser Protection Optical Device (LPOD). For additional perspective, arbitrary XYZ axes are also illustrated. LPOD 100 includes a polarization rotator (PR) 120 and a wavelength selective polarizer (WSP) 140. Although shown as spaced apart components, the PR and WSP may be laminated together, optionally with an optical adhesive. In some embodiments, PR 120 may be an “active” electronic polarization rotator, but in some other cases the PR 120 may be a passive polarization rotator. In some embodiments, WSP 140 may be an “active” electronic polarization rotator, but in other cases, WSP 140 may be passive. WSP may be an absorptive polarizer or a reflective polarizer. In some embodiments, the LPOD is a variable transmission optical device (VT-LPOD) where at least one of the PR or WSP is an electronically active component, or optionally both are active. In some alternative embodiments, the LPOD may be passive (P-LPOD) where both the WSP and PR are passive. Although not shown, the LPOD (e.g., a VT-LPOD or a P-LPOD) may be used in conjunction with another optical device which may have its own variable transmission characteristics.

[0037] Incident non-polarized light 160, e.g., non-threat broadband radiation from an ambient environment or scene, is received by the PR and transmitted to the WSP as non-polarized intermediate light 162. PR 120 may be designed to transmit a substantial amount of the incident non-polarized light 160, e.g., at least 20%, 30%, 40%, 50%, 60%, 70%, or more. While the PR may in some cases have a tint and absorb or reflect some of the incident non-polarized light 160, in other cases, it may be substantially clear to such light. In some preferred embodiments, the incident non-polarized light 160 is visible light.

[0038] In some cases, in addition to the non-polarized ambient light, high intensity narrowband radiation 170 such as a polarized laser (laser radiation 170) may be incident upon the PR 120. Laser radiation 170 may be characterized by a peak wavelength and a first polarization 170pl. As a non-limiting example, laser radiation 170 may be from a green laser and have a peak wavelength of 532 nm. As illustrated, laser radiation 170 may propagate in a direction parallel to the Z axis. In some cases, the first polarization 170pl may be characterized by a first angle 0i about its propagation axis. PR 120 acts on the incident narrowband radiation to produce rotated narrowband radiation 172 having a second polarization 172p2 different from the first. In particular, the second polarization may be a rotated to a second angle 02. As illustrated, the second polarization 172p2 may be rotated so that it is aligned parallel to the X axis. As mentioned, the axes are arbitrary and not limiting.

[0039] The WSP 140 receives both the rotated narrowband radiation 172 and the nonpolarized intermediate light 162. The WSP 140 is capable of substantially blocking (absorbing or reflecting or both) narrowband radiation having the second polarization 172p2 (e.g., at least 80%, 85%, 90%, 95%, 99%, 99.5%, or 99.9%, optionally up to 99.99%), but is significantly less blocking for radiation having a polarization orthogonal to 172p2 (e.g., along the Y axis in this illustration). For example, the ratio of blocking for radiation polarized along the Y axis relative to the X axis may be less than or equal to 0.5, 0.3, 0.2, 0.1, 0.05, 0.02, or 0.01. WSP 140 is designed to transmit incident non-polarized wavelengths away from the peak wavelength of the narrowband radiation (or peak absorbance of the WSP). For example, the WSP may transmit at least 20%, 30%, 40%, 50%, 60%, or 70% of incident non-polarized visible light at wavelengths at least 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 80 nm, 100 nm, or 120 nm away from the peak wavelength of the narrowband radiation. The WSP may also transmit a portion of the non-polarized radiation at or near the peak wavelength that is not aligned with the second polarization axis, c.g., up to 50%, 40%, 30%, 20%, 10%, 5%, or 1% of the non-polarizcd radiation.

[0040] Thus, only a small amount of the incident laser light is transmitted through the LPOD as transmitted narrowband radiation 175. That is, the intensity of transmitted narrowband radiation 175 may, relative to incident narrowband radiation 170, be reduced by at least 80%, 90%, 95%, 99%, 99.5%, 99.9%, 99.95%, or 99.99%, or alternatively, by at least 1 OD, 2 OD, 3 OD, or 4 OD. In some cases, the LPOD may be capable of blocking up to 99.99% of incident narrowband radiation. On the other hand, a useful amount of the incident non-polarized visible light is allowed through the LPOD as transmitted non-polarized light 165. Thus, a viewer or a device receiving the transmitted light / radiation 165 or 175 is not harmed by the laser and can still view the ambient scene. In some embodiments, at least 10% of incident non-polarized visible light is transmitted through the LPOD, alternatively at least 20%, 30%, or 40%, and preferably at least 50%, 60%, 70%, or 80%. In some embodiments, the LPOD is characterized by a photopic transmission of at least 10%, alternatively at least 20%, 30%, or 40%, and preferably at least 50%, 60%, 70%, or 80%.

[0041] FIGS. 2A and 2B are schematic views of a VT-LPOD according to some embodiments. FIGS. 2A and 2B show VT-LPOD 200 in its non-activated state and activated state, respectively. VT-LPOD 200 includes a passive PR 220 and an active WSP 240. In some embodiments, WSP 240 may be an absorptive active polarizer such as an e-POD. Passive PR 220 may include a static reflective polarizer 222 (e.g., a static CLC) and a static quarter waveplate 224. Incident non-polarized light 260, e.g., non-threat broadband radiation from an ambient environment or scene, is received by the PR and transmitted to the WSP as non-polarized intermediate light 262. Although there may be some reflective losses, e.g., for a portion of the non-polarized light that happens to have wavelength and polarization properties that are reflected by reflective polarizer 222, a substantial amount of the incident non-polarized light 260 is transmitted as non-polarized intermediate light 262. WSP 240 is in a state such that its polarization axis 242 for absorbing light is set to substantially transmit any polarization. This may sometimes be referred to as “clear” state or “transmissive” state or “non-activated” state. The state can be determined by a voltage V applied across the WSP 240. In some cases, a clear state may have V at or near zero.However, in some other cases, a clear state may require a voltage to be applied. Tn this nonactivated state, WSP 240 substantially transmits the non-polarizcd intermediate light as transmitted non-polarized light 265.

[0042] FIG. 2B shows VT-LPOD 200 in its activated state, for example, in the presence of incident laser radiation 270. Incident laser radiation may have a first polarization 270pl and the PR 220 is designed to reflect a first portion 270r of the laser radiation, e.g., having a first handedness, and to transmit a second portion 271 having a second handedness orthogonal to the first. The second portion of laser radiation 271 is received by the quarter wave plate to produce rotated laser radiation 272 having a second polarization 272p2. Regardless of the polarization 270pl, only the second polarization will be substantially transmitted to WSP 240. The voltage across WSP 240 can be altered to change it from a clear state to a darkened state having a polarization axis 242p2 for absorbing polarized radiation now strongly aligned with the second polarization 272p2. In some cases, WSP 240 can be altered even before any incident laser radiation is detected, e.g., when there is a threat of potential high energy narrowband radiation. In some cases, the darkened (activated) state may require application of a voltage, but in some other cases, a darkened (activated) state may have a voltage at or near zero. In this way, even if there is an unexpected power failure, the VT-LPOD can still provide laser protection. In its activated state, WSP 240 may absorb a minor portion of the non-polarized intermediate light 262, e.g., a portion at or near its peak absorption having the second polarization, but a substantial amount is transmitted.

[0043] Thus, in its activated state only a small amount of the incident laser light is transmitted through the VT-LPOD 200 as transmitted narrowband (laser) radiation 275. On the other hand, a useful amount of the incident non-polarized visible light is allowed through the VT-LPOD, even in its activated state, as transmitted non-polarized light 265’. Thus, a viewer or a device receiving the transmitted light / radiation 265’ or 275 is not harmed by the laser and can still view the ambient scene with relatively minor reductions in ambient light intensity or color fidelity. Further, when there is no threat of incident laser radiation and the VT-LPOD is placed in its nonactivated state, the ambient light or scene can be advantageously viewed with good intensity and high color fidelity.

[0044] FIGS. 3 A and 3B are schematic views of a VT-LPOD according to some embodiments. FIGS. 3A and 3B show VT-LPOD 300 in its non-activatcd state and activated state, respectively. VT-LPOD 300 includes an active, electronic polarization rotator 320 (EPR 320) and a passive WSP 340. In some embodiments, WSP 340 may be an absorptive passive polarizer configured to absorb narrowband radiation along a fixed polarization axis 342p2. Incident non-polarized light 360, e.g., non-threat broadband radiation from an ambient environment or scene, is received by the EPR and substantially transmitted to the WSP as non-polarized intermediate light 362. WSP 340 receives and may absorb a portion of the non-polarized intermediate light 362, e.g., a small portion at or near its peak absorption having the second polarization, but a substantial amount of the non-polarized intermediate light as transmitted non-polarized light 365.

[0045] Incident laser radiation 370 having a first polarization 370pl may also be incident on EPR 320. Since VT-LPOD 300 is not in its activated state (FIG. 3A), the laser radiation may be transmitted as intermediate (non-rotated) laser radiation 371 still characterized by the first polarization 370pl. Since the polarization axis 342p2 of passive WSP 340 is not aligned to the first polarization, a substantial and potentially harmful amount of intermediate laser radiation passes through as transmitted laser radiation 375.

[0046] FIG. 3B shows VT-LPOD 300 in its activated state where, for example, a voltage has been altered relative to the non-active state so that EPR 320 now acts on incident laser radiation 370 to produce rotated laser radiation 372 having a second polarization 372p2. Second polarization 372p2 generally matches the polarization axis 342p2 of WSP 340 allowing most of the rotated laser radiation to be absorbed. As a result, transmitted laser radiation 375’ in the activated state has a much lower intensity than transmitted laser radiation 375 in the nonactivated state. The EPR may in some cases include a polarization-rotating liquid crystal cell and activation of the device may include changing a voltage applied across the polarization-rotating liquid crystal cell.

[0047] The VT-LPOD 300 may include or be in communication with a polarization detector for adjusting the amount of rotation by EPR 320 to ensure a good match with the WSP polarization. In some cases (not shown), a photodetector may be shown to receive transmitted laser radiation 375’ which provides intensity feedback to the EPR for tuning the rotation.

[0048] Thus, in its activated state only a small amount of the incident laser light is transmitted through the VT-LPOD 300 while a useful amount of the incident non-polarizcd visible light is allowed through. Thus, a viewer or a device receiving the transmitted light / radiation 365 or 375’ is not harmed by the laser and can still view the ambient scene with relatively minor reductions in ambient light intensity or color fidelity.

[0049] FIGS. 4A and 4B are schematic views of a VT-LPOD according to some embodiments. FIGS. 4A and 4B show VT-LPOD 400 in its non-activated state and activated state, respectively. VT-LPOD 400 is similar to VT-LPOD 300 except that the passive WSP is a reflective polarizer (e.g., a static CLC). VT-LPOD 400 includes an active, electronic polarization rotator 420 (EPR 420) and a passive reflective WSP 440. The reflective WSP may be designed to transmit polarized light having a first handedness but substantially reflect polarized light having a second handedness orthogonal to the first. Incident non-polarized light 460, e.g., non-threat broadband radiation from an ambient environment or scene, is received by the EPR and substantially transmitted to the WSP as non-polarized intermediate light 462. WSP 440 receives and may reflect a portion of the non-polarized intermediate light 462, e.g., a small portion at select polarization wavelengths, but a substantial amount of the non-polarized intermediate light passes through as transmitted non-polarized light 465.

[0050] Incident laser radiation 470 having a first polarization 470pl may also be incident on EPR 420. Since VT-LPOD 400 is not in its activated state (FIG. 4A), the laser radiation may be transmitted as intermediate (non-rotated) laser radiation 471 still characterized by the first polarization 470pl. A significant amount of transmitted laser radiation 475 propagates through VT-LPOD 400 in the non-activated state, for example, a portion having the first handedness. Another portion may be reflected as reflected laser radiation 471r having the second handedness. The reflected portion, however, is insufficient to provide protection for a viewer or device.

[0051] FIG. 4B shows VT-LPOD 400 in its activated state where, for example, a voltage has been altered relative to the non-activated state so that EPR 420 now acts on incident laser radiation 470 to produce rotated laser radiation 472 having a second polarization 472p2 characterized by the second handedness that is strongly reflected by the reflective WSP as reflected laser radiation 471r’. As a result, very little laser light propagates through the reflective WSP. Transmitted laser radiation 475’ in the activated state has a much lower intensity thantransmitted laser radiation 475 in the non-activated state. The EPR may in some cases include a polarization-rotating liquid crystal cell and activation of the device may include changing a voltage applied across the polarization-rotating liquid crystal cell.

[0052] The VT-LPOD 400 may include or is in communication with a polarization detector for adjusting the amount of rotation by EPR 420 to ensure a good match with the reflective passive WSP 440 polarization. In some cases (not shown), a photodetector may be shown to receive transmitted laser radiation 475’ which provides intensity feedback to the EPR for tuning the rotation.

[0053] Thus, in its activated state only a small amount of the incident laser light is transmitted through the VT-LPOD 400 while a useful amount of the incident non-polarized visible light is allowed through. Thus, a viewer or a device receiving the transmitted light / radiation 465 or 475’ is not harmed by the laser and can still view the ambient scene with relatively minor reductions in ambient light intensity or color fidelity.

[0054] FIGS. 5A and 5B are schematic views of a VT-LPOD according to some embodiments. FIGS. 5A and 5B show VT-LPOD 500 in a non-activated state and in an activated state respectively. VT-LPOD 500 includes an active, electronic polarization rotator 520 (EPR 520) that may be similar to EPR 420 or 320 described elsewhere herein. VT-LPOD further includes an active WSP 540 that may be similar to active WSP 240 described elsewhere herein. In some embodiments, WSP 540 may be an absorptive active polarizer such as an e-POD.

[0055] Incident non-polarized light 560, e.g., non-threat broadband radiation from an ambient environment or scene, is received by the EPR and substantially transmitted to the active WSP as non-polarized intermediate light 562. WSP 540 is in a state such that its polarization axis 542 for absorbing light is set to substantially transmit any polarization. This may sometimes be referred to as “clear” state or “transmissive” state. The state can be determined by a voltage V applied across the WSP 540 as previously discussed. In this non-activated state, WSP 540 substantially transmits the non-polarized intermediate light 562 as transmitted non-polarized light 565. In some cases, this can be with relatively high transmittance and color fidelity.

[0056] Since both EPR 520 and WSR 540 are active components, VT-LPOD has multiple activated states. However, engaging just one of the WSR or EPR alone may have relatively low effect on potentially hostile incident narrowband radiation. FIG. 5B shows VT-LPOD 500 in anactivated state where both the WSP 540 and EPR 520 have been electronically adjusted to counteract laser radiation. For example, a voltage has been altered relative to the non-activc state so that EPR 520 acts on incident laser radiation 570 having a first polarization 570pl to produce rotated laser radiation 572 having a second polarization 572p2. Second polarization 570p2 generally matches the polarization axis 542p2 of WSP 540, now in an electronically adjusted state (darkened state), allowing most of the rotated laser radiation to be absorbed. As a result, there is very little transmitted laser radiation 575’. In its activated state, WSP 540 may absorb a portion of the non-polarized intermediate light 562, e.g., a minor portion at or near its peak absorption having the second polarization, but a substantial amount is transmitted.

[0057] The VT-LPOD 500 may include or be in communication with a polarization detector for adjusting the amount of rotation by EPR 520 and / or adjustment of the WSP to ensure a good match with the WSP polarization or a desired laser absorption. In some cases (not shown), a photodetector may be shown to receive transmitted laser radiation 575’ which provides intensity feedback to the EPR for tuning the rotation.

[0058] Thus, in its activated state only a small amount of the incident laser light is transmitted through the VT-LPOD 500 while a useful amount of the incident non-polarized visible light is allowed through. Thus, a viewer or a device receiving the transmitted light / radiation 565 or 575’ is not harmed by the laser and can still view the ambient scene with relatively minor reductions in ambient light intensity or color fidelity. Further, when there is no threat of incident laser radiation and the VT-LPOD is placed in its non-activated state, the ambient light or scene can be advantageously viewed with good intensity and high color fidelity.

[0059] FIG. 6 is a schematic view of another LPOD according to some embodiments. Here, LPOD 600 may include a passive PR 220 (as described elsewhere herein with respect to FIGS. 2A and 2B) and a passive, absorptive WSP 340 (as described elsewhere herein with respect to FIGS. 3 A and 3B). In operation, incident laser radiation 670 may have a first polarization 670pl and the PR 220 is designed to reflect a portion 670r of incident laser radiation, e.g., having a first handedness, and to transmit a second portion 671 having a second handedness orthogonal to the first. The second portion of laser radiation 671 is received by the quarter wave plate to produce rotated laser radiation 672 having a second polarization 672p2. Regardless of the polarization 670pl, only the second polarization will be substantially transmitted to WSP 340. Secondpolarization 672p generally matches the polarization axis 342p2 of WSP 340 allowing most of the rotated laser radiation to be absorbed. As a result, there is very little transmitted laser radiation 675.

[0060] Incident non-polarized light 660, e.g., non-threat broadband radiation from an ambient environment or scene, may be received by the PR and transmitted to the WSP as non-polarized intermediate light 662. Although there may be some reflective losses, e.g., for a portion of the non-polarized light that happens to have wavelength and polarization properties that are reflected by static reflective polarizer 222, a substantial amount of the incident non-polarized light 660 is transmitted as non-polarized intermediate light 662. WSP 340 receives and may absorb a portion of the non-polarized intermediate light 662, e.g., a small portion at or near its peak absorption having the second polarization, but a substantial amount of the non-polarized intermediate light as transmitted non-polarized light 665.

[0061] Thus, only a small amount of the incident laser light is transmitted through the LPOD 600 while a useful amount of the incident non-polarized visible light is allowed through. Thus, a viewer or a device receiving the transmitted light / radiation 665 or 675’ is not harmed by the laser and can still view the ambient scene with relatively minor reductions in ambient light intensity or color fidelity. While some active VT-LPOD embodiments may be able to produce higher light transmission and color fidelity of transmitted non-polarized broadband light, LPOD 600 has an advantage of manufacturing and operational simplicity.

[0062] The structure of an EPR can be such that it can alter an arbitrary polarization of an incident narrowband radiation to a desired polarization. The operation depends on the layers used and the location of the incident and transmitted light on the Poincare Sphere. FIG. 7A is a schematic diagram of an electronic polarization rotator, EPR 720A, according to some embodiments. In this configuration, a stack of 2 static quarter waveplates 724 and 725 whose axis are at 90 degrees to each other sandwiches an electronically controllable waveplate 726 with the axis at 45 degrees to the principal axis of the two quarter waveplates. The electronically controllable waveplate may include electronically controllable polarization-rotating liquid crystal cell disposed. Such devices are known in the art and sometimes referred to as an electronically controlled birefringence (ECB) liquid crystal device. Application of the voltage to theelectronically controllable waveplate will act on the arbitrary linear polarization of incident light to produce a desired (rotated) linear transmitted polarized radiation that is received by the WSP.

[0063] If incident narrowband radiation is circular or elliptical, an alternative construction can be made as shown in FIG. 7B as EPR 720B. In this embodiment, the first static quarter waveplate can be replaced with another voltage controlled waveplate 727. In this case, if the incident light has circular or elliptical polarization, the waveplate can be tuned to impart any phase (including, but not limited to, 0 degrees) to the incident light to produce the desired rotated polarized radiation.

[0064] Applications

[0065] The LPODs of the present disclosure have a wide variety of potential uses. For example, these devices may be directly fabricated into or laminated onto “wearable” products such as eyewear (such as prescription and non-prescription glasses and sunglasses), visors, goggles, face shields, near-eye displays, sensor optics, cameras, and AR / VR headsets to name a few. Alternatively, they may be directly fabricated into or laminated onto other products including, but not limited to, windows (vehicles, buildings, aircraft, etc.), windshields, cockpits, sunroofs, heads-up displays, camera filters, and optical instruments. Such products and devices may be further equipped with power supplies, batteries, sensors or the like. In some embodiments, the sensor(s) can provide information or data that is used in the operation of the LPOD. Some non-limiting examples of sensors include a light sensor, an imaging sensor, and a laser warning receiver.

[0066] Still further embodiments herein include the following enumerated embodiments.

[0067] Enumerated embodiment 1. A laser protection optical device (“LPOD”) including: a polarization rotator configured to act on incident polarized narrowband radiation having a peak wavelength and a first polarization to produce rotated narrowband radiation having a second polarization different from the first polarization; and a wavelength selective polarizer that receives and substantially blocks the rotated narrowband radiation having the second polarization.

[0068] Enumerated embodiment 2. The LPOD of enumerated embodiment 1, wherein at least 10% (or optionally at least 20%, 30%, 40%, 50%, 60%, or 70%) of incident non-polarized visible light is transmitted through the LPOD.

[0069] Enumerated embodiment 3. The LPOD of enumerated embodiment 1 or 2, wherein the wavelength selective polarizer is capable of blocking least 80% (optionally at least 85%, 95%, 99%, 99.5%, or 99.9%) of the rotated narrow band radiation.

[0070] Enumerated embodiment 4. The LPOD according to any of enumerated embodiments 1- 3, wherein the wavelength selective polarizer is capable of blocking up to 99.99% of the rotated narrowband radiation.

[0071] Enumerated embodiment 5. The LPOD according to any of enumerated embodiments 1- 4, wherein an intensity of the narrowband radiation transmitted through the LPOD is reduced by at least 1 OD (or optionally by at least 2 OD, 3 OD, or 4 OD) relative to an incident intensity.

[0072] Enumerated embodiment 6. The LPOD according to any of enumerated embodiments 1- 5, wherein an intensity of the narrowband radiation transmitted through the LPOD is reduced by at least 90% (or optionally by at least 95%, 99%, 99.5%, 99.9%, 99.95%, or 99.99%) relative to an incident intensity.

[0073] Enumerated embodiment 7. The LPOD according to any of enumerated embodiments 1- 6, wherein the LPOD transmits at least 50% (optionally at least 55%, 60%, 65%, 70%, 75%, or 80%) of incident non-polarized visible light at wavelengths at least 100 nm away from the peak wavelength.

[0074] Enumerated embodiment 8. The LPOD according to any of enumerated embodiments 1- 7, wherein up to 50% (optionally up to 40%, 30%, 20%, 10%, or 5%) of incident non-polarized light at the peak wavelength is transmitted through the LPOD.

[0075] Enumerated embodiment 9. The LPOD according to any of enumerated embodiments 1- 8, wherein the wavelength selective polarizer is a reflective polarizer that optionally includes a liquid crystal material.

[0076] Enumerated embodiment 10. The LPOD of enumerated embodiment 9, wherein the reflective polarizer is a passive polarizer that optionally includes a cholesteric liquid crystal material.

[0077] Enumerated embodiment 11. The LPOD according to any of enumerated embodiments 1 - 8, wherein the wavelength selective polarizer is an absorptive polarizer that optionally includes a liquid crystal material.

[0078] Enumerated embodiment 12. The LPOD of enumerated embodiment 11 , wherein the absorptive polarizer is an electronic polarization rotator that optionally includes a guest-host system including a liquid crystal host and a dichroic dye guest.

[0079] Enumerated embodiment 13. The LPOD of enumerated embodiment 11, wherein the absorptive polarizer is a passive polarizer.

[0080] Enumerated embodiment 14. The LPOD according to any of enumerated embodiments 1 - 13, wherein the first polarization is linear, circular, or elliptical.

[0081] Enumerated embodiment 15. The LPOD according to any of enumerated embodiments 1 - 14, wherein the second polarization is linear.

[0082] Enumerated embodiment 16. The LPOD according to any of enumerated embodiments 1 - 15, wherein the polarization rotator is a passive polarization rotator.

[0083] Enumerated embodiment 17. The LPOD of enumerated embodiment 16, wherein the passive polarization rotator includes a static reflective polarizer and a static quarter waveplate, wherein the static reflective polarizer optionally includes a cholesteric liquid crystal.

[0084] Enumerated embodiment 18. The LPOD according to any of enumerated embodiments 1 - 15, wherein the polarization rotator is an electronic polarization rotator.

[0085] Enumerated embodiment 19. The LPOD of enumerated embodiment 18, wherein the electronic polarization rotator includes an electronically controllable polarization-rotating liquid crystal cell disposed between two quarter waveplates.

[0086] Enumerated embodiment 20. The LPOD of enumerated embodiment 19, wherein at least one of the quarter waveplates is electronically adjustable.

[0087] Enumerated embodiment 21. The LPOD of enumerated embodiment 19, wherein the two quarter waveplates are passive quarter waveplates.

[0088] Enumerated embodiment 22. The LPOD according to any of enumerated embodiments 1 - 21, wherein the first polarization of the incident narrowband radiation varies as a function of time.

[0089] Enumerated embodiment 23. The LPOD according to any of enumerated embodiments 1 - 22, further including a detector to characterize the first polarization direction.

[0090] Enumerated embodiment 24. The LPOD according to any of enumerated embodiments 1 - 23, wherein the incident narrowband radiation is ultra-narrowband radiation.

[0091] Enumerated embodiment 25. The LPOD according to any of enumerated embodiments 1 - 24, wherein the narrowband radiation includes laser light.

[0092] Enumerated embodiment 26. The LPOD according to any of enumerated embodiments 1 - 25, wherein the peak wavelength is in the visible spectrum.

[0093] Enumerated embodiment 27. An article of manufacture including the LPOD according to any of enumerated embodiments 1 - 26, wherein the article of manufacture includes a camera filter, eyewear, a visor, goggles, a face shield, an AR / VR headset, a near-eye display, a window, a windshield, a sunroof, a heads-up display, or an optical instrument.

[0094] While various embodiments have been discussed with respect to the visible spectrum for polarized narrowband radiation and non-polarized broadband radiation, the methods and devices can be applied to narrowband wavelengths and broadband spectra in the infrared or ultraviolet.

[0095] The specific details of particular embodiments may be combined in any suitable manner without departing from the spirit and scope of embodiments of the invention. However, other embodiments of the invention may be directed to specific embodiments relating to each individual aspect, or specific combinations of these individual aspects.

[0096] The above description of example embodiments of the invention has been presented for the 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 teaching above.

[0097] In the preceding description, for the purposes of explanation, numerous details have been set forth in order to provide an understanding of various embodiments of the present technology. It will be apparent to one skilled in the art, however, that certain embodiments may be practiced without some of these details, or with additional details.

[0098] Having described several embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of the invention. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the present invention. Additionally, details of any specific embodiment may not always be present in variations of that embodiment or may be added to other embodiments.

[0099] Unless otherwise noted, a phrase that recites a range of values is inclusive of the end values, for example, “between X and Y,” “range of X to Y,” “from X to Y,” “from X - Y”, each includes X and Y. Similarly, unless otherwise noted, the phrase “up to Y” includes Y and the phrase “down to X” includes X. Statements such as “at least X, Y, or Z” or “at least any of X, Y, or Z” are to be interpreted as “at least X, at least Y, or at least Z”. That is, the modifier “at least” (or “at most”, “less than”, “greater than”, or the like) is applied to all of the listed values. Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither, or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit 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.

[0100] 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 “the layer” includes reference to one or more layers and equivalents thereof known to those skilled in the art, and so forth. The invention has now been described in detail for the purposes of clarity and understanding. However, it will be appreciated that certain changes and modifications may be practiced within the scope of the appended claims.

[0101] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes. None is admitted to be prior art.

[0102] Listing of Reference Numerals in Figures100 - Laser Protection Optical Device (LPOD)120 - polarization rotator (PR)140 - wavelength selective polarizer (WSP)160 incident non-polarized light162 - non-polarized intermediate light165 - transmitted non-polarized light170 - high-intcnsity narrowband radiation (c.g., laser radiation)170pl - first polarization172 - rotated narrowband radiation172p2 - second polarization175 - transmitted narrowband radiation200 - VT-LPOD220 - passive PR222 - static reflective polarizer224 - static quarter waveplate240 - active WSP242 - polarization axis (non-activated state)242p2 - polarization axis (activated state)260 - incident non-polarized light262 - non-polarized intermediate light265 - transmitted non-polarized light265’ - transmitted non-polarized light270 - incident laser radiation270pl - first polarization27 Or - reflected first portion of laser radiation271 - second portion of laser radiation received by the quarter wave plate272 - rotated laser radiation272p2 - second polarization275 - transmitted narrowband (laser) radiation300 - VT-LPOD320 - electronic polarization rotator (EPR)340 - passive WSP342p2 - fixed polarization axis360 - incident non-polarized light362 - non-polarized intermediate light365 - transmitted non-polarized light370 - incident laser radiation370pl - first polarization371 - intermediate (non-rotated) laser radiation372 - rotated laser radiation372p2 - second polarization375 - transmitted laser radiation375’ - transmitted laser radiation400 - VT-LPOD420 - electronic polarization rotator (EPR)440 -passive reflective WSP460 - incident non-polarized light462 - non-polarized intermediate light465 - transmitted non-polarized light470 - incident laser radiation470pl - first polarization471 - intermediate laser radiation47 Ir - reflected laser radiation47 lr’- reflected laser radiation472 - rotated laser radiation472p2 - second polarization475 - transmitted laser radiation475’ - transmitted laser radiation500 - VT-LPOD520 - electronic polarization rotator (EPR)540 - active WSP542 - polarization axis542p2 - polarization axis560 - incident non-polarized light562 - non-polarized intermediate light565 - transmitted non-polarized light570 - incident laser radiation570pl - first polarization572 - rotated laser radiation572p2 - second polarization575’ - transmitted laser radiation600 - LPOD660 - incident non-polarized light662 - non-polarized intermediate light665 - transmitted non-polarized light670 - incident laser radiation670pl - first polarization670r - reflected laser radiation671 - second portion of laser radiation received by the quarter wave plate672 - rotated laser radiation672p2 - second polarization675’ - transmitted laser radiation720 A - electronic polarization rotator (EPR)720B - electronic polarization rotator (EPR)724 - static quarter waveplate725 - static quarter waveplate726 - electronically controllable waveplate727 - electronically controllable waveplate

Claims

CLAIMSWc claim:

1. A laser protection optical device (“LPOD”) comprising: a polarization rotator configured to act on incident polarized narrowband radiation having a peak wavelength and a first polarization to produce rotated narrowband radiation having a second polarization different from the first polarization; and a wavelength selective polarizer that receives and substantially blocks the rotated narrowband radiation having the second polarization.

2. The LPOD of claim 1, wherein at least 10% of incident non-polarized visible light is transmitted through the LPOD.

3. The LPOD of claim 1, wherein the wavelength selective polarizer blocks at least 80% of the rotated narrow band radiation.

4. The LPOD of claim 1, wherein the wavelength selective polarizer is capable of blocking up to 99.99% of the rotated narrowband radiation.

5. The LPOD of claim 1, wherein an intensity of the narrowband radiation transmitted through the LPOD is reduced by at least 1 OD relative to an incident intensity.

6. The LPOD of claim 1, wherein an intensity of the narrowband radiation transmitted through the LPOD is reduced by at least 90% relative to an incident intensity.

7. The LPOD of claim 1, wherein the LPOD transmits at least 50% of incident nonpolarized visible light at wavelengths at least 100 nm away from the peak wavelength.

8. The LPOD of claim 1, wherein up to 50% of incident non-polarized light at the peak wavelength is transmitted through the LPOD.

9. The LPOD of claim 1, wherein the wavelength selective polarizer is a reflective polarizer that optionally comprises a liquid crystal material.

10. The LPOD of claim 9, wherein the reflective polarizer is a passive polarizer that optionally comprises a cholesteric liquid crystal material.

11. The LPOD of claim 1, wherein the wavelength selective polarizer is an absorptive polarizer that optionally comprises a liquid crystal material.

12. The LPOD of claim 11 , wherein the absorptive polarizer is an electronic polarization rotator that comprises a guest-host system comprising a liquid crystal host and a dichroic dye guest.

13. The LPOD of claim 11, wherein the absorptive polarizer is a passive polarizer.

14. The LPOD of claim 1, wherein the first polarization is linear, circular, or elliptical.

15. The LPOD of claim 1, wherein the second polarization is linear.

16. The LPOD of claim 1, wherein the polarization rotator is a passive polarization rotator.

17. The LPOD of claim 16, wherein the passive polarization rotator comprises a static reflective polarizer and a static quarter waveplate, wherein the static reflective polarizer comprises a cholesteric liquid crystal.

18. The LPOD of claim 1, wherein the polarization rotator is an electronic polarization rotator.

19. The LPOD of claim 18, wherein the electronic polarization rotator comprises an electronically controllable polarization-rotating liquid crystal cell disposed between two quarter waveplates.

20. The LPOD of claim 19, wherein at least one of the quarter waveplates is electronically adjustable.

21. The LPOD of claim 19, wherein the two quarter waveplates are passive quarter waveplates.

22. The LPOD of claim 1, wherein the first polarization of the incident narrowband radiation varies as a function of time.

23. The LPOD of claim 1, further comprising a detector to characterize the first polarization direction.

24. The LPOD of claim 1, wherein the incident narrowband radiation is ultranarrowband radiation.

25. The LPOD of claim 1, wherein the narrowband radiation comprises laser light.

26. The LPOD of claim 1, wherein the peak wavelength is in the visible spectrum.

27. An article of manufacture comprising the LPOD of claim 1 , wherein the article of manufacture includes a camera filter, eyewear, a visor, goggles, a face shield, an AR / VR headset, a near-eye display, a window, a windshield, a sunroof, a heads-up display, or an optical instrument.

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