Optical sensing system

Abstract

An optical sensing system includes an optical film and a transceiver configured to at least one of emit and receive first light that propagates along a propagation direction in air at a first angle greater than about 20 degrees from a normal to the optical film toward an object through the optical film. The first light has a first infrared wavelength in an infrared wavelength range extending from about 800 nm to about 2000 nm. For incident light incident on the optical film in air and having the first infrared wavelength, and for at least one of first and second mutually orthogonal polarization states, the optical film reflects at least 60% of the incident light incident at an incident angle less than about 5 degrees, and transmits at least 40% of the incident light incident at an incident angle substantially equal to the first angle.

Description

Technical Field

[0001] This disclosure generally relates to optical sensing systems, and more specifically to optical films configured to be incorporated into windows and optically transparent to light detection and ranging (LiDAR). Background Technology

[0002] Cars are increasingly moving towards autonomous driving. Newer vehicles include features like adaptive cruise control and parking assist systems that allow the car to automatically maneuver into parking spaces. Efforts are underway to create almost fully autonomous vehicles that can operate with minimal direct human input. Information and data about the surroundings of autonomous vehicles are acquired from external sources using sensing systems such as LiDAR and other near-infrared (NIR) sensors. These external sources can include sensors connected to vehicles, pedestrians, cyclists, etc., in front and oncoming, or sensors mounted on structures such as traffic lights and bridges. Sensing systems can be configured to be installed either externally or internally within the vehicle. Sensing systems located inside the vehicle's cabin can avoid exposing sensors to environmental conditions such as inclement weather. Summary of the Invention

[0003] Some aspects of this disclosure relate to an optical sensing system comprising an optical film including a plurality of polymer layers, the plurality of polymer layers totaling at least 20. Each of these polymer layers has an average thickness of less than about 500 nm. The optical sensing system includes a transceiver having at least one of a transmitter and a receiver, and is configured to transmit and receive at least one of first light passing through the optical film toward an object along a propagation direction at a first angle greater than about 20 degrees. The first light has a first infrared wavelength in an infrared wavelength range extending from about 800 nm to about 2000 nm. For incident light incident on the optical film in air having the first infrared wavelength, and for at least one of a first polarization state and a second polarization state that are mutually orthogonal, the plurality of polymer layers reflect at least 60% of the incident light incident at an angle of incidence of less than about 5 degrees, and transmit at least 40% of the incident light incident at an angle of incidence substantially equal to the first angle.

[0004] Some other aspects of this disclosure relate to an optically transparent window configured as a vehicle window, the optically transparent window comprising an optical film disposed between and bonded to a first substrate layer and a second substrate layer, the optical film comprising a plurality of alternating polymer layers of different first and second layers, totaling at least 20. Each of the first and second layers has an average thickness of less than about 500 nm. The first and second layers have corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to the first and second directions. For a first infrared wavelength between about 800 nm and about 2000 nm, nx1-nx2 > 0.1, ny1-ny2 > 0.1, and nz1 and nz2 differ from each other by less than about 20%. For incident light in air that is incident on the optical film and has the first infrared wavelength, and for each of the first and second polarization states that are orthogonal to each other, the window reflects at least 60% of the incident light incident at an angle of incidence of less than about 5 degrees and transmits at least 40% of the incident light incident at an angle of incidence of greater than about 30 degrees.

[0005] Some other aspects of this disclosure relate to a flexible optical structure configured to be incorporated into a window. The flexible optical structure includes an optical film bonded to and extending substantially co-located with a first adhesive layer in length and width, the first adhesive layer being configured to be incorporated into a first substrate of the window. The optical film comprises a plurality of alternating polymer layers, each a first and second layer, totaling at least 20. Each of the first and second layers has an average thickness of less than about 500 nm. The first and second layers have corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to the first and second directions. For a first infrared wavelength between about 800 nm and about 2000 nm, nx1 - nx2 > 0.1, and nz1 and nz2 differ from each other by less than about 20%. For incident light incident in air having the first infrared wavelength, and for each of a first orthogonal polarization state and a second polarization state, for the first infrared wavelength, the optical film reflects at least 60% of the incident light at a first incident angle of less than about 5 degrees and transmits at least 40% of the incident light at a second incident angle of greater than about 30 degrees. For each of the first and second incident angles, the first adhesive layer has an optical transmittance greater than about 80%. For incident light incident in air having the first infrared wavelength, and for each of a first orthogonal polarization state and a second polarization state, for the visible light wavelength range between about 420 nm and about 680 nm, each of the optical film and the first adhesive layer has an average optical transmittance greater than about 70% (or 80%). The flexible optical structure is configured to bend with a radius of less than about 10 cm without causing or minimal damage to the flexible optical structure.

[0006] Other aspects of this disclosure relate to a vehicle that includes a window and an optical sensing system according to one or more embodiments of this disclosure. The window includes an optical film embedded therein, and a transceiver is disposed in the interior compartment of the vehicle such that the optical film is disposed between the transceiver and the outer surface of the window. Attached Figure Description

[0007] Various aspects of this disclosure will be discussed in more detail with reference to the accompanying drawings, in which,

[0008] Figure 1 An optical sensing system according to some embodiments of the present disclosure is schematically illustrated;

[0009] Figure 2 The structure of the optical film of an optical sensing system according to some embodiments is schematically shown;

[0010] Figures 3 to 5 The transmission spectrum of the optical film is shown graphically when light is incident on it at different incident angles.

[0011] Figure 6 A vehicle having an optical sensing system according to one or more embodiments is schematically shown;

[0012] Figure 7 The diagram schematically illustrates a conductive optically transparent electrode configured to be mounted on a vehicle window.

[0013] Figure 8 The transmission spectra of the first and second substrate layers of the window according to some embodiments are illustrated graphically.

[0014] Figures 9 to 22 The transmission spectra of optical films with different designs under different incident light angles are illustrated graphically.

[0015] The figures are not necessarily drawn to scale. Similar numbers used in the figures refer to similar parts. However, it should be understood that using numbers to refer to parts in a given figure is not intended to restrict parts to be labeled with the same numbers in another figure. Detailed Implementation

[0016] Reference is made in the following description to the accompanying drawings, which form part of the invention and in which various embodiments are illustrated by way of example. It should be understood that other embodiments are conceivable and may be practiced without departing from the scope or spirit of this specification. Therefore, the following detailed description should not be considered limiting.

[0017] External LiDAR sensing systems are exposed to adverse weather conditions such as icing, condensation, raindrops, and road contamination, all of which can interfere with their operation. Mounting the LiDAR system inside the vehicle cabin, such as behind the windshield, protects it from external environmental influences. However, solar control films on the windshield may largely or completely block near-infrared or infrared wavelengths (typically 850nm to 950nm or 1400nm to 1700nm, wavelengths at which LiDAR sensing systems operate), potentially rendering the system inoperable. The implementation described herein addresses these and other challenges.

[0018] Some embodiments of this disclosure describe an optical sensing system including a multilayer optical film (MOF) that is transparent to LiDAR and can provide a reduction in solar thermal load. The angular offset characteristics of the MOF can be utilized so that, upon oblique incidence, the infrared blocking band of the MOF is offset beyond the operating wavelength of the LiDAR, enabling transmission.

[0019] Some implementations of the optical sensing system (300) are in Figure 1 As shown in the figure. The optical sensing system (300) includes an optical film (10) and a transceiver (20). The transceiver (20) may include at least one of a transmitter (21) and a receiver (22). In some aspects, the transceiver (20) may include at least one transmitter (21) and at least one receiver (22). The transceiver (20) may be an optical transceiver configured to emit (23) and receive (24) at least one of first light passing through the optical film (10) toward the object (30) along the propagation direction (23a, 24a). In some aspects, the transmitter (21) may include a laser source and the receiver (22) may include an optical detector. In some cases, the receiver (22) may include a camera. In some embodiments, the transceiver (20) may be a LiDAR transceiver.

[0020] In some aspects, the optical sensing system (300) may further include a first substrate layer (60) and a second substrate layer (61). For example... Figure 8 As shown, each of the first substrate layer (60) and the second substrate layer (61) may have an average optical transmittance greater than about 50%, or greater than about 60%, or greater than about 70%, or greater than about 80%, or greater than about 85%, or greater than about 90% in a wavelength range extending from about 700 nm to about 1600 nm. In some embodiments, at least one of the first substrate layer (60) and the second substrate layer (61) may comprise glass. In other cases, each of the first substrate layer (60) and the second substrate layer (61) may comprise glass. In some aspects, the optical sensing system (300) may include a conductive optically transparent electrode (100). As shown in the illustrated embodiment, the conductive optically transparent electrode (100) may be disposed between the optical film (10) and the first substrate layer (60). The optically transparent electrode (100) may have an optical transmittance greater than about 70%, or greater than about 80%, or greater than about 90% at at least one visible wavelength between about 420 nm and about 680 nm.

[0021] In some aspects, the optical film can be disposed between and bonded to the first substrate layer and the second substrate layer (60, 61). For example, the optical film (10) can be bonded to the first substrate layer (60) and the second substrate layer (61) via respective first adhesive layer (70) and second adhesive layer (71). At least one of the first adhesive layer and the second adhesive layer (70, 71) may contain one or more of polyvinyl butyral (PVB), pressure-sensitive adhesive (PSA), ethylene vinyl acetate (EVA), polyolefin, or polyurethane.

[0022] In some aspects, in a wavelength range extending from about 700 nm to about 1600 nm, at least one region of each of the first adhesive layer and the second adhesive layer (70, 71) may have an average optical transmittance greater than about 50%, or greater than about 60%, or greater than about 70%, or greater than about 80%, or greater than about 85%, or greater than about 90%. In other aspects, for the visible light wavelength range between about 420 nm and about 680 nm, each of the optical film (10) and the first adhesive layer (70) may have an average optical transmittance greater than about 70% or greater than about 80%.

[0023] In some aspects, the transceiver (20) may be configured to emit (23) first light along the propagation direction (23a) and form a first angle (α1) with the normal (40) of the optical film (10) in air. The transceiver (20) may be further configured to receive (24) first light along the propagation direction (24a) and form a second angle (α2) with the normal (40) of the optical film (10) in air. In some embodiments, the first angle (α1, α2) may be greater than about 20 degrees. For example, the first angle (α1, α2) may be about 25 degrees, or about 30 degrees, or about 35 degrees, or about 40 degrees, or about 45 degrees, or about 50 degrees, or about 55 degrees, or about 60 degrees, or about 65 degrees.

[0024] like Figures 3 to 5 As shown, the first light may have a first infrared wavelength (25) in an infrared wavelength range extending from about 800 nm to about 2000 nm. In some cases, the first infrared wavelength (25) may be between about 850 nm and about 950 nm, or between about 900 nm and about 950 nm. In some cases, the first infrared wavelength (25) may be between about 1400 nm and about 1700 nm, or between about 1500 nm and about 1600 nm. In some cases, the first light may include a pulsed laser. In other cases, the first light may include a continuous laser. In some cases, the continuous laser may be at least one of phase modulation and frequency modulation.

[0025] In some embodiments, the optical film (10) may be a multilayer optical film (MOF) comprising multiple layers (11, 12), such as Figure 2 As shown. In some aspects, the optical film may include multiple polymer layers (11, 12). In some embodiments, the multiple polymer layers may include multiple alternating first layers (11) and second layers (12) of polymers. For example, the optical film (10) may include alternating first layers (11) and second layers (12) of polymers, which include at least one birefringent polymer (e.g., an oriented semi-crystalline polymer) and a second polymer.

[0026] In other embodiments, the materials of the first and second layers (11, 12) may be composed of polymers, such as polyesters. For example, an exemplary polymer used as the first birefringent layer (11) may be polyethylene naphthalate (PEN). Other semi-crystalline polyesters suitable as birefringent polymers, as the first birefringent layer (11) in a multilayer polymer film, may include, for example, polybutylene 2,6-naphthalene dicarboxylate (PBN), polyethylene terephthalate (PET), etc. The second layer (12) may be made of various polymers whose glass transition temperature is compatible with that of the first birefringent polymer layer (11) and whose refractive index is similar to the isotropic refractive index of the first birefringent polymer layer (11). Examples of other polymers suitable for optical films (particularly the second polymer layer (12)) may include olefin polymers and copolymers derived from monomers such as vinylnaphthalene, styrene, maleic anhydride, acrylates, and methacrylates. Examples of such polymers used for the second polymer layer (12) include polyacrylates, polymethacrylates (such as poly(methyl methacrylate) (PMMA)), and isotactic or syndiotactic polystyrene. Other polymers include condensation polymers such as polysulfones, polyamides, polyurethanes, polyamic acids, and polyimides. Additionally, the second polymer layer (12) may be formed from homopolymers and copolymers of polyesters, polycarbonates, fluoropolymers, and polydimethylsiloxanes, and blends thereof. These layers may be selected to achieve reflection of electromagnetic radiation with a specific bandwidth.

[0027] In one embodiment, the materials of the plurality of layers (11, 12) may have different refractive indices. In some embodiments, the optical film (10) may comprise a copolymer (coPMMA) of PET as the first optical layer (11) and PMMA as the second optical layer (12), or any other polymer (including copolyesters, fluorinated polymers) or combinations thereof with low refractive indices. The transmission and reflection properties of the optical film (10) may be based on the coherent interference of light caused by the difference in refractive indices between the layers (11, 12) and the thickness of the layers (11, 12). According to some embodiments, the first and second layers (11, 12) have corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to the first and second directions. In some cases, at least for the first infrared wavelength (25), nx1-nx2 > 0.1, and nz1 and nz2 may differ from each other by less than 20%. In some embodiments, ny1-ny2 > 0.1. In some other cases, nx1-nx2 > 0.15, or nx1-nx2 > 0.2. In some cases, ny1-ny2 > 0.15, or ny1-ny2 > 0.2.

[0028] In some cases, the total count of the plurality of polymer layers (11, 12) may be at least 10 or 20. In some cases, the total count of the plurality of polymer layers (11, 12) may be at least 50, or at least 100, or at least 200, or at least 300, or at least 400, or at least 500. Each of the polymer layers (11, 12) may have an average thickness of less than about 500 nm, or less than about 400 nm, or less than about 300 nm, or less than about 200 nm, or less than about 150 nm. In some embodiments, the number of layers of the optical film (10) may be selected for reasons of film thickness, flexibility, and economy to achieve the desired optical properties using the minimum number of layers.

[0029] In other respects, the optical film may further include at least one surface layer (13) disposed on the plurality of polymer layers (11, 12). The surface layer (13) may have an average thickness greater than about 500 nm. In some cases, the average thickness of the surface layer (13) may be greater than about 750 nm, or greater than about 1000 nm, or greater than about 1250 nm, or greater than about 1500 nm. In some embodiments, the optical film (10) may be physically continuous.

[0030] In some respects, since MOFs shift to shorter wavelengths as the incident angle increases, the reflection bands of MOFs can be designed to be offset beyond the LiDAR transmission wavelength at oblique incident angles, thereby allowing the transmission of LiDAR wavelengths. Figures 3 to 5 The transmission spectra of the MOF are shown when light is incident on it at different incident angles. The transmission spectra of three different MOF designs are also shown. Figures 3 to 5 Different lines are used to represent them.

[0031] According to some embodiments, incident light (50) can be incident on the optical film (10) in air at an incident angle (β). In some aspects, for incident light (50) incident on the optical film (10) at an angle (β) of less than about 5 degrees and having a first infrared wavelength (25), and for at least one or each of a first (x-axis) polarization state and a second (y-axis) polarization state that are orthogonal to each other, the plurality of polymer layers (11, 12) can reflect (R1) at least 60%, or at least 70%, or at least 80%, or at least 90% of the incident light (50), such as Figure 3As shown. In some aspects, for incident light (50) incident at an angle (β) substantially equal to the first angle (α1, α2) and having a first infrared wavelength (25), and for at least one or each of a first (x-axis) polarization state and a second (y-axis) polarization state that are mutually orthogonal, the plurality of polymer layers (11, 12) can transmit (T1) at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80% of the incident light (50), such as Figure 4 and Figure 5 As shown.

[0032] refer to Figures 3 to 5 In some embodiments, for incident light (50) incident on the optical film (10) in air, the plurality of polymer layers (11, 12) may include transmission passbands (80, 80'). The transmission passbands (80, 80') may include a left band edge (LBE) (81, 81') on the short wavelength side of the transmission passband and a right band edge (RBE) (82, 82') on the long wavelength side of the transmission passband. At the left band edge (LBE) (81, 81') on the short wavelength side of the transmission passband (80, 80'), the transmittance of the optical film (10) generally increases with increasing wavelength. At the right band edge (RBE) (82, 82') on the short wavelength side of the transmission passband (80, 80'), the transmittance of the optical film (10) generally decreases with increasing wavelength.

[0033] The transmission passband (80, 80') may include the full width at half maximum (FWHM) (83, 83'). For example... Figure 3 As shown, when incident light (50) is incident on the optical film (10) at an angle (β) of less than about 5 degrees, the first infrared wavelength (25) is outside the FWHM (83). Figure 4 As shown, when the incident light (50) is incident on the optical film (10) at an angle (β) that is substantially equal to the first angle (α1, α2), the first infrared wavelength (25) is within the FWHM (83').

[0034] In some other embodiments, for incident light (50) incident on the optical film (10) in air, the plurality of polymer layers (11, 12) may include transmission stopbands (90, 90'). The transmission stopbands (90, 90') may include a left band edge (LBE) (91, 91') on the short wavelength side of the transmission stopbands (90, 90') and a right band edge (RBE) (92, 92') on the long wavelength side of the transmission stopbands (90, 90'). At the left band edge (LBE) (91, 91') on the short wavelength side of the transmission stopbands (90, 90'), the transmittance of the optical film (10) generally decreases with increasing wavelength. At the right band edge (RBE) (92, 92') on the long wavelength side of the transmission stopbands (90, 90'), the transmittance of the optical film (10) generally increases with increasing wavelength.

[0035] The transmission stopband (90, 90') can include the full width at half maximum (FWHM) (93, 93'). For example... Figure 3 As shown, when the incident light (50) is incident on the optical film (10) at an angle (β) of less than about 5 degrees, the first infrared wavelength (25) is within the FWHM (93). Figure 5 As shown, when the incident light (50) is incident on the optical film (10) at an angle (β) that is substantially equal to the first angle (α1, α2), the first infrared wavelength (25) is outside the FWHM (93').

[0036] An optical sensing system according to one or more embodiments of this disclosure may be provided in a vehicle. For example... Figure 6As shown, the vehicle (400) may include a window (410) configured as an optically transparent window. For example, the window (410) may be the windshield of the vehicle (400). A flexible optical structure (411) including an optical film (10) may be configured to be incorporated into the window (410). In some embodiments, the optical film (10) may be embedded in the window. In other embodiments, the optical film (10) may be incorporated into a first adhesive layer (70) configured to be incorporated into a first substrate (60) of the window (410). For example, the first substrate (60) may comprise glass. The optical film (10) may extend substantially co-located with the first adhesive layer (70) in length and width. In other respects, the optical film (10) may be further incorporated into a second adhesive layer (71) opposite to the first adhesive layer (70). The second adhesive layer (71) may be configured to be incorporated into a second substrate (61) of the window. For example, the second substrate (61) may comprise glass. The optical film (10) can extend substantially together with the second adhesive layer (70) in both length and width. In some embodiments, the flexible optical structure (411) can be configured to be bent with a radius of less than about 10 cm, or 9 cm, or 8 cm, or 6 cm, or 5 cm without causing or with little damage to the flexible optical structure (411).

[0037] The flexible optical structure (411) can be configured such that for incident light (50) incident in air and having a first infrared wavelength (25), and for each of the mutually orthogonal first (x-axis) polarization state and second (y-axis) polarization state, for the first infrared wavelength (25), the optical film (10) can reflect (R1) at a first incident angle (β) of less than about 5 degrees of the incident light (50) at at least 60%, at least 70%, at least 80%, or at least 90%. The flexible optical structure (411) can be further configured such that for incident light (50) incident in air and having a first infrared wavelength (25), and for each of a first (x-axis) polarization state and a second (y-axis) polarization state that are orthogonal to each other, for the first infrared wavelength (25), the optical film (10) can transmit (T1) at a second incident angle (β) of at least 40%, at least 50%, at least 60%, at least 70%, or at least 80% of the incident light (50). In some embodiments, the second incident angle can be greater than about 30 degrees, or greater than about 40 degrees, or greater than about 50 degrees, or greater than about 55 degrees.

[0038] In some respects, the flexible optical structure (411) can be configured such that the first adhesive layer (70) has an optical transmittance greater than about 80% for each of the first and second incident angles. In other respects, for the visible light wavelength range between about 420 nm and about 680 nm, each of the optical film (10) and the first adhesive layer (70) can have an average optical transmittance greater than about 70% or greater than about 80%.

[0039] The transceiver (20) can be disposed in the interior compartment (420) of the vehicle (400), such that the optical film (10) can be disposed between the transceiver (20) and the outer surface of the window (410). According to the illustrated embodiment, the transceiver (20) can be disposed on or near the interior rearview mirror (430) of the vehicle. For example, the transceiver (20) can be a LiDAR transceiver disposed behind the rearview mirror (430).

[0040] In some embodiments, the window (410) may further include a conductive optically transparent electrode (100), such as Figure 1 As shown, the conductive optically transparent electrode is disposed on or therein for heating the window (410). The optically transparent electrode (100) may have an optical transmittance greater than about 70%, or greater than about 80%, or greater than about 90% for at least one visible light wavelength between about 420 nm and about 680 nm. Figure 7 As shown, the conductive optically transparent electrode may include a metal mesh (110) having a plurality of intersecting conductive traces (111) to form a plurality of closed opening regions (112). In some aspects, the window may further include an optical filter for blocking at least a portion of incident light with wavelengths (25) in the infrared wavelength range extending from about 800 nm to about 2000 nm.

[0041] The optical film (10) can be designed to shift towards shorter wavelengths as the incident angle (β) increases. In some embodiments, the optical film can be designed such that the reflection band is shifted at an oblique incident angle beyond the LiDAR transmission wavelength, which is at least between 900 nm and 950 nm. Since vehicle windshields typically have a high tilt angle (the angle between the tilted windshield and the vertical), incident light (50) can be incident on the optical film (10) embedded in the windshield (410) at an incident angle (β) of up to 60 degrees.

[0042] For example, according to some embodiments, for incident light (50) incident in air at an angle (β) of less than about 5 degrees onto the optical film (10) and having a first infrared wavelength (25), and for each of a first (x-axis) polarization state and a second (y-axis) polarization state that are orthogonal to each other, the window (410) can reflect (R1) at least 60%, or at least 70%, or at least 80%, or at least 90% of the incident light (50), such as Figure 3 As shown. In some aspects, for incident light (50) incident at an angle (β) greater than about 30 degrees, or about 40 degrees, or about 50 degrees, or about 55 degrees, or about 60 degrees and having a first infrared wavelength (25), and for each of a first (x-axis) polarization state and a second (y-axis) polarization state that are mutually orthogonal, the window (410) can transmit (T1) at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80% of the incident light (50), such as Figure 4 and Figure 5 As shown.

[0043] Figures 9 to 18 Transmission spectra of different optical film designs according to this disclosure are shown. For example, Figure 9 and Figure 10 The transmission spectra of 3M's Ultra Clear Solar Film (UCSF) are shown at different incident angles (β) of 0°, 40°, 60° and 80°. Figures 11 to 14 The transmission spectra of the optical film with notch filter are shown at different incident angles (β) of 0°, 40°, 60° and 80°. Figure 15 and Figure 16 The transmission spectra of the optical film with a narrow bandpass filter at different incident angles (β) of 0°, 40° and 60° are shown. Figure 17 and Figure 18 The transmission spectra of the optical film with a blue-shifted bandpass filter design at different incident angles (β) of 0°, 40° and 60° are shown.

[0044] Figure 19 and Figure 20 The transmission spectra of optical films with different designs are shown in comparison at an incident angle of 0 degrees. Figure 21 The transmission spectra of optical films with different designs are compared at an incident angle of 40 degrees. Figure 22 The transmission spectra of optical films with different designs are compared at an incident angle of 60 degrees.

Claims

1. An optical sensing system, comprising: An optical film comprising a plurality of polymer layers, the optical film comprising a total count of at least 20 polymer layers, each polymer layer having an average thickness of less than 500 nm, wherein the plurality of polymer layers comprises a plurality of alternating polymer first and second layers, the first and second layers having corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to the first and second directions; as well as A transceiver, comprising at least one of a transmitter and a receiver, and configured to transmit and receive at least one of first light passing through the optical film toward an object along a propagation direction at a first angle greater than 20 degrees, the first light having a first infrared wavelength in an infrared wavelength range extending from 800 nm to 2000 nm. Such that for incident light incident on the optical film in air having the first infrared wavelength, and for at least one of a first polarization state and a second polarization state that are orthogonal to each other, the plurality of polymer layers reflect at least 60% of the incident light incident at an angle of incidence of less than 5 degrees and transmit at least 40% of the incident light incident at an angle of incidence equal to the first angle.

2. The optical sensing system of claim 1, wherein the transmitter comprises a laser light source, and wherein the receiver comprises an optical detector.

3. The optical sensing system of claim 1, wherein for incident light incident on the optical film in air, the plurality of polymer layers include a transmission passband, the transmission passband including a left band edge on the short wavelength side of the transmission passband and a right band edge on the long wavelength side of the transmission passband, wherein at the left band edge on the short wavelength side, the transmittance of the optical film increases with increasing wavelength; and at the right band edge on the long wavelength side, the transmittance of the optical film decreases with increasing wavelength, the transmission passband including a full width at half maximum (FWHM) such that when the incident angle is less than 5 degrees, the first infrared wavelength is outside the FWHM, and when the incident angle is equal to the first angle, the first infrared wavelength is inside the FWHM.

4. The optical sensing system of claim 1, wherein for incident light incident on the optical film in air, the plurality of polymer layers include a transmission stopband, the transmission stopband including a left band edge on the short wavelength side and a right band edge on the long wavelength side of the transmission stopband, wherein at the left band edge on the short wavelength side, the transmittance of the optical film decreases with increasing wavelength; and at the right band edge on the long wavelength side, the transmittance of the optical film increases with increasing wavelength, the transmission stopband including a full width at half maximum (FWHM) such that when the incident angle is less than 5 degrees, the first infrared wavelength is within the FWHM, and when the incident angle is equal to the first angle, the first infrared wavelength is outside the FWHM.

5. A vehicle comprising: window; as well as According to the optical sensing system of claim 1, wherein the window includes the optical film embedded therein, and the transceiver is disposed in the interior compartment of the vehicle such that the optical film is disposed between the transceiver and the outer surface of the window.

6. An optically transparent window configured as a vehicle window, the optically transparent window comprising an optical film disposed between and bonded to a first substrate layer and a second substrate layer, the optical film comprising a plurality of alternating polymer layers of different first and second layers, each of the first and second layers having an average thickness of less than 500 nm. The first and second layers have corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to both the first and second directions, such that for a first infrared wavelength between 800 nm and 2000 nm, nx1 - nx2 > 0.1, ny1 - ny2 > 0.1, and nz1 and nz2 differ from each other by less than 20%. Such that for incident light incident on the optical film in air having the first infrared wavelength, and for each of the mutually orthogonal first and second polarization states, the window reflects at least 60% of the incident light incident at an angle of incidence of less than 5 degrees and transmits at least 40% of the incident light incident at an angle of incidence of greater than 30 degrees.

7. The optically transparent window of claim 6, wherein the optical film is bonded to the first substrate layer and the second substrate layer via respective first adhesive layer and second adhesive layer, and wherein at least one region of each of the first adhesive layer and the second adhesive layer has an average optical transmittance of greater than 50% in a wavelength range extending from 700 nm to 1600 nm.

8. A flexible optical structure configured to be incorporated into a window, the flexible optical structure comprising an optical film bonded to and extending coexisting with the first adhesive layer in length and width, the first adhesive layer being configured to be bonded to a first substrate of the window, the optical film comprising a plurality of alternating polymer first and second layers, each of the first and second layers having an average thickness of less than 500 nm. The first and second layers have corresponding refractive indices nx1 and nx2 along a first direction in the same plane, corresponding refractive indices ny1 and ny2 along a second direction in a plane orthogonal to the first direction, and corresponding refractive indices nz1 and nz2 along a third direction orthogonal to the first and second directions, such that for a first infrared wavelength between 800 nm and 2000 nm, nx1 - nx2 > 0.1, and nz1 and nz2 differ from each other by less than 20%. For incident light in air having the first infrared wavelength, and for each of the mutually orthogonal first and second polarization states: For the first infrared wavelength, the optical film reflects at least 60% of the incident light incident at a first incident angle of less than 5 degrees and transmits at least 40% of the incident light incident at a second incident angle of greater than 30 degrees, and the first adhesive layer has an optical transmittance greater than 80% for each of the first and second incident angles; and For the visible light wavelength range between 420 nm and 680 nm, each of the optical film and the first adhesive layer has an average optical transmittance greater than 70%. This allows the flexible optical structure to be bent with a radius of less than 10 cm without damaging it.

9. The flexible optical structure of claim 8, wherein the first substrate comprises glass.

10. The flexible optical structure of claim 8, wherein the optical film is further bonded to a second adhesive layer opposite to the first adhesive layer and extends in length and width together with the second adhesive layer, the second adhesive layer being configured to be bonded to a second substrate of the window.

Images