Optical filter and optical system

Abstract

The optical filter has an average light transmittance of greater than about 50% in the visible wavelength range (e.g., wavelengths from about 420 nm to about 550 nm) and an optical density of greater than about 1.5 in the infrared wavelength range (e.g., wavelengths from about 650 nm to about 800 nm). The optical filter may have sharp band edges between the visible and infrared ranges. For example, a change in percent transmittance of at least about 30% may occur over a wavelength range about 10 nm or less wide, and / or the slope of the band edges may be greater than about 5% / nm. The optical system includes an optical filter disposed between a light-emitting display and an optical sensor.

Description

[Background technology]

[0001] Optical films can include alternating polymer layers and can be used to transmit or reflect light in a desired wavelength range.

[0002] The display system may include a fingerprint sensor behind the display panel. Summary of the Invention

[0003] The present specification relates to optical filters and optical systems including optical filters. The optical filters can have an average light transmission of more than about 50% in the visible wavelength range (e.g., wavelengths from about 420 nm to about 550 nm) and an optical density of more than about 1.5 in the infrared wavelength range (e.g., wavelengths from about 650 nm to about 800 nm). In some cases, high optical density (e.g., more than about 1.5, or more than about 2) is achieved with a low total average thickness (e.g., about 60 micrometers or less). The optical filters can have sharp band edges between the visible and infrared ranges (e.g., a percent transmission change of at least about 30% can occur over a wavelength range about 10 nm wide or less, and / or the gradient of the band edges can be more than about 5% / nm). The optical filters can be optical stacks including a first optical filter disposed on a second optical filter. For example, a first optical filter can include alternating polymer layers, while a second optical filter can include dyes and / or pigments to provide an absorptance peak. Alternatively, or in addition, dyes and / or pigments can be incorporated into one or more of the alternating polymer layers to provide an absorptance peak. The optical system can include an optical filter disposed between a light-emitting display and an optical sensor. For example, the optical system can be an organic light-emitting diode (OLED) display system, the optical sensor can be an optical fingerprint detector, and the optical filter can be configured to pass visible light to the fingerprint detector (e.g., substantially transmit wavelengths in at least a range of 450 nm to 550 nm) while blocking near-infrared ambient light (e.g., substantially block wavelengths in at least a range of 650 nm to 800 nm). The optical filter has been found to significantly improve the signal-to-noise ratio of the sensor. These and other aspects will become apparent from the detailed description that follows. In no event, however, should this brief summary be construed as limiting the claimed subject matter. [Brief description of the drawings]

[0004] [Figure 1]FIG. 2 is a schematic cross-sectional view of an optical filter. [Diagram 2] 1 is a plot of the transmission spectrum of an optical filter. [Diagram 3] 1 is a plot of the transmission spectrum of an optical filter. [Figure 4] 1 is a plot of the optical density of an optical filter. [Diagram 5] 1 is a plot of the transmission spectrum of the optical filter of Example 1. [Figure 6] 1 is a schematic cross-sectional view of an optical system; [Figure 7] 1 is a plot of layer thickness for a multilayer film. [Figure 8] 1 is a plot of the transmission spectrum of the optical filter of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0005] In the following description, reference is made to the accompanying drawings which form a part hereof, and in which various embodiments are shown by way of illustration. The drawings are not necessarily to scale. It is to be understood that other embodiments are contemplated and may be made without departing from the scope or spirit of the specification. Accordingly, the following detailed description is not to be taken in a limiting sense.

[0006] Optical filters according to some embodiments herein can have high transmission (e.g., at least 50%, or at least 70%) in the visible wavelength range (e.g., from 420 nm or 450 nm to 550 nm or 560 nm), high optical density (e.g., greater than about 1.5, or greater than about 2) or low optical transmission (e.g., less than about 5%, or less than about 1%, or less than about 0.6%) in the infrared wavelength range (e.g., from about 650 nm to about 800 nm), and a sharp transition between high and low transmission ranges (e.g., a percent transmission change of at least 30% over a range of about 10 nm or less, and / or a slope of more than about 5% / nm). In some cases, these optical properties are achieved with thin optical filters (e.g., about 60 micrometers thick or less). Optical filters can be used to increase the signal-to-noise ratio in optical systems that include, for example, an optical sensor behind a light-emitting display.

[0007] Optical filters can include multilayer optical films that include a plurality of alternating polymer layers.As known in the art, multilayer optical films that include alternating polymer layers can be used to provide desired reflection and transmission bands by suitable selection of layer thickness.Multilayer optical films and methods for making multilayer optical films are described in, for example, U.S. Patent No. 5,882,774 (Jonza et al.), U.S. Patent No. 6,179,948 (Merrill et al.), U.S. Patent No. 6,783,349 (Neavin et al.), U.S. Patent No. 6,967,778 (Wheatley et al.), and U.S. Patent No. 9,162,406 (Neavin et al.).

[0008] FIG. 1 is a schematic cross-sectional view of an optical filter 100 including a plurality of alternating first and second polymer layers 10 and 20. The optical filter may have more layers than are shown in FIG. 1. The number of first and second polymer layers is typically at least 50 in total (e.g., 50-600 layers in total, or 100-500 layers in total). Each of the first and second polymer layers may have an average thickness (average value across the layers of thickness) of less than about 500 nm or less than about 400 nm. The optical filter 100 may further include thicker (e.g., greater than about 1 micrometer) layers 15 and / or 17, which may be included as protective boundary layers between packets or stacks of alternating polymer layers, or as outer protective skin layers. In some embodiments, the optical filter 100 includes a first optical filter 110 and a second optical filter 80. The second optical filter 80 may be disposed on the first optical filter 110 (e.g., directly or indirectly via one or more additional layers, such as an adhesive layer). The second optical filter 80 may optionally be omitted. In embodiments in which the second optical filter 80 is included and disposed on the first optical filter 110, the optical filter 100 may be referred to as an optical stack. In some such cases, FIG. 1 may be described as a schematic, partially exploded view in which the second optical filter 80 is shown disposed away from the first optical filter 110 for ease of illustration.

[0009] The optical filter 110 can reflect and transmit light primarily by optical interference, while the optical filter 80 can include one or more absorption bands. For example, the optical filter 110 can have a reflection band with left (lower wavelength) and right (higher wavelength) band edges, and the optical filter 80 can include an absorption band near the left band edge and / or an absorption band near the right band edge to mitigate the shift in the band edges for obliquely incident light. The optical filter 80 can include, for example, dyes and / or pigments dispersed in a polymer film or coating.

[0010] If it is desired to include one or more absorption bands, the absorption bands may be provided using a layer of the first optical filter 110 instead of, in addition to, or including the second optical filter 80 (e.g., the first optical filter 110 may provide a first absorption band and the second optical filter 80 may provide a different second absorption band). For example, in some embodiments, at least one layer of the multiple alternating first polymer layers 10 and second polymer layers 20 has an absorptance peak (e.g., at the peak absorption wavelength of the absorption band). As another example, in some embodiments, at least one of layers 15 and / or 17 has an absorptance peak. Any suitable dyes and / or pigments may be used to provide the absorptance peak. For example, the dyes described in U.S. Patent Application Publication Nos. 2015 / 0378077 (Haag et al.) and 2018 / 0172888 (Johnson et al.) may be used.

[0011] 2-3 are plots of transmission spectra of optical filters according to some embodiments. FIG. 2 shows the percent transmission for angles of incidence of 0 degrees, 45 degrees, and 60 degrees for an optical filter according to some embodiments. FIG. 3 shows the transmission (expressed as a percentage) for angles of incidence of 0 degrees, 45 degrees, and 60 degrees for another optical filter according to some embodiments. The transmission can be described for the visible range (e.g., 70 or 170), which can be, for example, about 400 nm or about 420 nm or about 450 nm to at least about 550 nm, for the (near) infrared range (e.g., 71), which can be, for example, about 650 nm to at least about 800 nm, and for the far infrared range (73 or 173, etc.). The far infrared range can be at least about 100 nm wide and can be positioned such that the near infrared wavelength range is between the visible wavelength range and the far infrared wavelength range. The far infrared range can be, for example, about 950 nm to at least about 1050 nm. As used herein, the term infrared range refers to a wavelength range that includes infrared wavelengths and may optionally include wavelengths up to about 650 nm. As used herein, the terms near infrared wavelength range and far infrared wavelength range refer to relatively lower and relatively higher wavelength infrared ranges, respectively. The far infrared wavelength range may be located, for example, below 2000 nm or below 1500 nm.

[0012] In some embodiments, the optical filter 100 includes a plurality of alternating first polymer layers (10) and second polymer layers (20), totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, thereby providing a uniform optical filter for substantially normally incident light 30 (e.g., within 30 degrees, or 20 degrees, or 10 degrees of normal, or nominally normally incident), and for a visible wavelength range 70 spanning from about 420 nm to about 550 nm and an infrared wavelength range 71 spanning from about 650 nm to about 800 nm, and for a first orthogonal polarization (e.g., polarization along the x-axis) state and a second orthogonal polarization (e.g., polarization along the y-axis) state. For each of the polarized light (polarized along) states, the first polymer layer 10 has a refractive index (e.g., refractive index n1) greater than the second polymer layer 20 (e.g., refractive index n2) for at least one visible wavelength in the visible wavelength range 70, the average light transmittance of the optical filter 100 in the visible wavelength range 70 is greater than about 50%, the optical filter 100 has an optical density greater than about 1.5 in the infrared wavelength range 71, and the transmittance of the optical filter 100 varies by at least about 30% over a first wavelength range 72 that is disposed between the visible wavelength range (70) and the infrared wavelength range (71) and is less than or equal to about 10 nm in width. For example, a variation in transmittance by at least 30% can mean, for example, T1-T2≧30% where T1 and T2 are transmittances at two different wavelengths expressed as percentages (see, for example, FIG. 2), or T1-T2≧0.3 where T1, T2 are transmittances at two different wavelengths expressed as percentages (see, for example, FIG. 3). In some embodiments, the average light transmission of optical filter 100 in the visible wavelength range 70 for substantially normally incident light 30 is greater than about 60%, or greater than about 70%, or greater than about 80%. In some embodiments, first wavelength range 72 is less than or equal to about 8 nm wide. First wavelength range 72 can be, for example, from about 1 nm to about 10 nm wide, or from about 2 nm to about 8 nm wide.

[0013] The refractive index of a polarization state is the refractive index along the direction of the electric field associated with the polarization state. For example, for normally incident light polarized along the x-axis, the refractive index of the polarization state is the refractive index along the x-axis. In some embodiments, for at least one visible wavelength in the visible wavelength range 70, the first polymer layer 10 has a refractive index n1x along the x-axis and a refractive index n1y along the y-axis, and the second polymer layer 20 has a refractive index n2x along the x-axis and a refractive index n2y along the y-axis. In some embodiments, n1x-n2x>0.05, and n1y-n2y>0.05. In some embodiments, the first polymer layer 10 is birefringent. For example, the first polymer layer 10 can be biaxially oriented such that n1x≈n1z>n1z, where n1z is the refractive index of the first polymer layer 10 in the thickness direction (z-direction) for at least one visible wavelength. In some embodiments, 1 / 2(n1x+n1y)-n1z>0.05. In some embodiments, the second polymer layer 20 is substantially isotropic such that n2x≈n2y≈n2z, where n2z is the refractive index of the second polymer layer 20 in the thickness direction (z-direction) for at least one visible wavelength. In some embodiments, the first polymer layer 10 is birefringent and the second polymer layer 20 is substantially isotropic.

[0014] Optical density is the intensity of light incident on an optical filter. Degree , divided by the transmitted light intensity base 10 logarithm of4 is a plot of the optical density corresponding to the normal incidence transmittance shown in FIG. 2. In some embodiments, the optical density of the optical filter is greater than about 1.5, or greater than about 2, or greater than about 2.2, or greater than about 2.4 in a wavelength range (e.g., near infrared wavelength range 71). The wavelength range can range, for example, from about 650 nm to about 800 nm, to at least about 800 nm, or to at least about 850 nm (e.g., to about 850 nm or to about 900 nm). The optical density can be any of these ranges across the entire wavelength range, or the average optical density within the wavelength range can be any of these ranges. In some embodiments, the optical filter has an average light transmittance of less than about 5%, or less than about 2%, or less than about 1%, or less than about 0.6% in a wavelength range ranging from about 650 nm to at least about 800 nm or at least about 850 nm.

[0015] In some embodiments, the optical filter 100 or the first optical filter 110 has an average thickness (average thickness value along the z-direction over the area of ​​the filter) of about 100, 80, 70, 60, 50, or 40 micrometers or less. For example, the average thickness can be about 60 micrometers or less, or about 20 micrometers to about 60 micrometers. A relatively thin (e.g., about 40 micrometers thick or less) optical filter that also has a desired optical density (e.g., greater than about 1.5) can be made using polyethylene naphthalate (PEN) as the high index layer and polymethyl methacrylate (PMMA) as the low index layer. This provides a relatively high difference between the refractive index of the high and low index layers to achieve high optical density in thin films. Thin optical filters are desired in some applications, such as display applications where a thin display may be desired.

[0016] The optical filter may have one or more absorptance peaks, or may have substantially no absorptance peaks. In some embodiments, at least one of the plurality of alternating first and second polymer layers has an absorptance peak (e.g., 82 or 282) within a wavelength range of about 600 nm to about 900 nm, or about 700 nm to about 900 nm. For example, dyes and / or pigments can be incorporated into one or both of the first or second layers to provide an absorptance peak. In some embodiments, the transmittance of the optical filter varies by at least about 30% over a second wavelength range (e.g., 74 or 174) that is about 100 nm or less wide, where the infrared wavelength range is disposed between the first and second wavelength ranges, or between the visible and second wavelength ranges. In some embodiments, at least one of the plurality of alternating first and second polymer layers 10 and 20 has a first absorptance peak 182 at a wavelength closer to the first wavelength range 72 than to the second wavelength range 74 (e.g., in some cases, the first absorptance peak 182 can be within the first wavelength range 72). In some embodiments, at least one of the plurality of alternating first and second polymer layers 10 and 20 has a second absorptance peak 82 at a wavelength closer to the second wavelength range 74 than to the first wavelength range 72 (e.g., in some cases, the second absorptance peak 82 can be within the second wavelength range 74).

[0017] The optical filter whose transmission spectrum is shown in Figure 2 was formed similarly to that of Example 1 described elsewhere herein. The transmission spectrum of Figure 3 was calculated using conventional optical modeling techniques in which a dye dispersion was included in the high index layers of alternating polymer layers to provide an absorptance peak 282.

[0018] In some embodiments, the optical filter has a sharp left band edge. In some embodiments, the optical filter has a sharp right band edge. The band edges can be made sharp by suitable selection of the layer thickness profile of the alternating polymer layers. Optical films with sharp band edges are known in the art and are described, for example, in U.S. Pat. No. 6,967,778 (WheAtley et al.). Figure 5 is a transmission spectrum of an optical filter according to some embodiments, in which the first band edge 60 and the second band edge 61 have slopes, respectively, represented generally by s1 and s2, one or both of which may be greater than about 5% / nm or greater than about 7%. As used herein, the slopes s1 and s2 are positive quantities. In some embodiments, for substantially normally incident light 30, the optical transmittance of the optical filter (e.g., 100 or 110) decreases from about 70% of the average optical transmittance of the optical filter in the visible wavelength range to about 20% of the average optical transmittance of the optical filter in the visible wavelength range with a slope s1 of more than about 5% / nm or more than about 7% / nm. The slope can be determined, for example, from a linear least squares fit to the optical transmittance versus wavelength in the range from about 70% of the average optical transmittance of the optical filter in the visible wavelength range to about 20% of the average optical transmittance of the optical filter in the visible wavelength range. In some embodiments, for substantially normally incident light 30 and for a far-infrared wavelength range spanning from about 950 nm to at least about 1050 nm (e.g., 73), the optical filter has a second band edge 61 between the near-infrared wavelength range and the far-infrared wavelength range, whereby the optical transmittance of the optical filter increases from about 20% of the average optical transmittance of the optical filter in the far-infrared wavelength range to about 70% of the average optical transmittance of the optical filter 200 in the far-infrared wavelength range with a slope s2 of more than about 5% / nm or more than about 7% / nm.

[0019] In some embodiments, the optical stack 100 includes a first optical filter 110 and a second optical filter 80. The first optical filter 100 includes a plurality of alternating first polymer layers (10) and second polymer layers (20), totaling at least 50, each of which may have an average thickness of less than about 500 nm. For substantially normally incident light 30, and for a visible wavelength range 70 ranging from about 420 nm to about 550 nm and an infrared wavelength range 71 ranging from about 650 nm to about 800 nm, and for at least a first polarization (e.g., polarization along the x-axis and / or polarization along the y-axis) state, the first optical filter 110 has an average light transmittance of greater than about 50% in the visible wavelength range 70, an average light reflectance of greater than about 90% in the infrared wavelength range 71, and a light reflectance of greater than about 80% at a first wavelength greater than about 650 nm (e.g., 81 or 181 or 281). The second optical filter 80 is disposed on the first optical filter 110 and includes a first peak absorption (e.g., 82 or 182 or 282) at a first wavelength 81 or 281. In some embodiments, the first wavelength is in a range of about 600 nm to about 900 nm, or about 700 nm to about 900 nm. In some embodiments, the second optical filter 80 further includes a second peak absorption (e.g., 82) at a wavelength (e.g., 81) that is at least 100 nm greater than the first wavelength (e.g., 181). In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average optical transmittance is greater than about 60%, or greater than about 70%, or greater than about 80% in the visible wavelength range 70. In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average optical reflectance is greater than about 95%, or greater than about 98% in the infrared wavelength range 71. In some embodiments, for substantially normally incident light 30 and for at least a first polarization state, the optical reflectance is greater than about 90% at the first wavelength.

[0020] In some embodiments, the optical filter 110 includes a plurality of alternating first polymer layers (10) and second polymer layers (20), totaling at least 50, each polymer layer may have an average thickness of less than about 500 nm, such that for substantially normally incident light 30, and for a visible wavelength range 70 spanning from about 420 nm to about 550 nm, a near-infrared wavelength range 71 spanning from about 650 to about 800 nm, and a far-infrared wavelength range 73 spanning from about 950 nm to at least about 1050 nm, and for at least a first polarization state, the optical filter 110 has an average light transmittance of greater than about 50% in each of the visible wavelength range (70) and the far-infrared wavelength range (73), an average light transmittance of less than about 5% in the near-infrared wavelength range 71, and a light transmittance 383 at a first wavelength 83 between the near-infrared wavelength range (71) and the far-infrared wavelength range (73) that is about 50% of the average light transmittance of the optical filter in the far-infrared wavelength range. In some embodiments, at least one of the multiple alternating first and second polymer layers 10 and 20 has an absorptivity peak 82 at a second wavelength 81 between the near infrared wavelength range (71) and the far infrared wavelength range (73). In some embodiments, for light 34 incident on the optical filter 110 at an incidence angle θ (angle relative to normal) of at least about 45 degrees, the first wavelength 83 is shifted to a third wavelength 84 that is smaller than the second wavelength 81. In other words, at an incidence angle θ, the wavelength at which the optical transmittance is equal to the optical transmittance 383 is shifted to the wavelength 84 as represented diagrammatically by the arrow 384 for an incidence angle of 60 degrees in FIG. 2. The incidence angle θ can be, for example, about 45 degrees or about 60 degrees. In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average light transmission is greater than about 60%, or greater than about 70%, or greater than about 80% in each of the visible wavelength range (70) and the far-infrared wavelength range (73). In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average light transmission is less than about 2%, or less than about 1%, or less than about 0.6% in the near-infrared wavelength range 71.

[0021] In the embodiment of FIG. 2, the average light transmittance in the visible wavelength range 70 is about 82.5%, the average light transmittance in the near infrared range 71 is about 0.2%, the average light transmittance in the far infrared range of about 950 nm to 1050 nm is about 80%, the first wavelength 83 is about 900 nm, the second wavelength 81 is about 850 nm, and the third wavelength 84 is about 755 nm for an incidence angle of about 60 degrees.

[0022] In some embodiments, the optical filter 110 includes a plurality of alternating first polymer layers (10) and second polymer layers (20), totaling at least 50, each of which may have an average thickness of less than about 500 nm, thereby providing a substantially uniform optical filter 110 for substantially normally incident light 30, as well as a visible wavelength range 170 ranging from about 450 nm to about 550 nm, a near infrared wavelength range 71 ranging from about 650 to about 800 nm, and a near infrared wavelength range 72 ranging from about 800 nm to about 900 nm, and a far infrared wavelength range (173). ), and for at least a first polarization state, the optical filter 110 has an average light transmittance greater than about 75% in each of the visible and far-infrared wavelength ranges, an average light transmittance less than about 45% in the near-infrared wavelength range, and a light transmittance at a first wavelength 183 between the near-infrared and far-infrared wavelength ranges that is about 10% of the average light transmittance of the optical filter in the visible wavelength range. In some embodiments, at least one of the plurality of alternating first and second polymer layers 10 and 20 has an absorptance peak 282 at a second wavelength 281 in a range of about 650 nm to about 900 nm. In some embodiments, for light 34 incident on the optical filter 110 at an incidence angle θ of at least about 45 degrees, the first wavelength shifts to a third wavelength 184 that is smaller than the second wavelength 281. In other words, at an incidence angle θ, the wavelength where the optical transmittance is equal to the optical transmittance 483 is shifted to wavelength 184 as shown generally in FIG. 3 for an incidence angle of 45 degrees. The incidence angle θ can be, for example, about 45 degrees or about 60 degrees. In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average optical transmittance is greater than about 80% in each of the visible wavelength range 170 and the far infrared wavelength range 173. In some embodiments, for substantially normally incident light 30 and for at least the first polarization state, the average optical transmittance is less than about 40%, or less than about 30% in the near infrared wavelength range 71.

[0023] In the embodiment of FIG. 3, the average light transmittance in the visible wavelength range 170 is about 85%, the average light transmittance in the near infrared range 71 is about 36.5%, the average light transmittance in the far infrared range of 1350 nm to 1450 nm is about 87%, the first wavelength 183 is about 860 nm, the second wavelength 281 is about 800 nm, and the third wavelength 184 is about 741 nm for an incidence angle of about 45 degrees.

[0024] In some embodiments, the far-infrared wavelength range spans about 2000 nm or less, or about 1800 nm or less, or about 1600 nm or less, or about 1500 nm or less. In some embodiments, for substantially normally incident light and for at least a first polarization state, the optical filter 110 has an average light transmittance of less than about 5%, or less than about 2%, or less than about 1%, or less than about 0.6% in a second near-infrared wavelength range 175 located between the near-infrared wavelength range (71) and the far-infrared wavelength range (173) and at least 100 nm wide. For example, the second near-infrared wavelength range can be from about 1000 nm to about 1200 nm. In the embodiment of FIG. 3, the average light transmittance in the second near-infrared wavelength range 175 is about 0.5%.

[0025] In any embodiment in which the transmission, absorption, or reflection of light is described for at least one polarization state, the optical stack or optical filter may satisfy the conditions described for one polarization state or for each of two orthogonal polarization states. For example, the reflection band provided by an optical filter may be for one polarization state (e.g., a reflective polarizer) or for two orthogonal polarization states (e.g., a mirror).

[0026] In some embodiments, the optical system includes optical filter 100 or first optical filter 110. The optical system can be a display system including a light-emitting display (e.g., an OLED display), an optical sensor (e.g., a fingerprint sensor), and an optical filter disposed between the light-emitting display and the optical sensor.

[0027] 6 is a schematic cross-sectional view of an optical system 300 including an emissive display 40 configured to emit a visible image 31 in a visible wavelength range (e.g., 70) that may span at least about 420 nm to about 550 nm, and an optical sensor 50 configured to receive and sense a first visible light 32 in the visible wavelength range and a second infrared light 33 in an infrared wavelength range (e.g., 71) that spans at least about 650 nm to about 800 nm through the emissive display 40. An optical filter 200 is disposed between the emissive display 40 and the optical sensor 50 such that for substantially normally incident light 30, the optical filter 200 has a first band edge 60 between the visible wavelength range 70 and the infrared wavelength range 71, and the optical transmittance of the optical filter decreases from about 70% of the average optical transmittance of the optical filter 200 in the visible wavelength range 70 to about 20% of the average optical transmittance of the optical filter in the visible wavelength range 70 at a gradient of more than about 5% / nm. The optical filter 200 may correspond to, for example, the optical filter 100 or the optical filter 110. In some embodiments, the gradient is greater than about 7% / nm. In some embodiments, the optical transmittance of the optical filter 200 varies by at least about 30% over a first wavelength range (e.g., 72) that is about 10 nm wide or less, or about 8 nm wide or less, where the first wavelength range is disposed between the visible and infrared wavelength ranges. In some embodiments, the optical system 300 further includes imaging optics 90 including at least a first lens 91 for imaging light incident on the emissive display 40 onto the optical sensor 50. The imaging optics 90 may include a plurality of microlenses, for example, as described in U.S. Patent Application Publication Nos. 2009 / 0179142 (Duparre et al.) and 2018 / 0045860 (Kawanishi et al.).

[0028] In some embodiments, for substantially normally incident light 30 and for a far-infrared wavelength range spanning from about 950 nm to at least about 1050 nm (e.g., 73), the optical filter 200 has a second band edge 61 between the near-infrared wavelength range and the far-infrared wavelength range, whereby the optical transmittance of the optical filter increases from about 20% of the average optical transmittance of the optical filter 200 in the far-infrared wavelength range to about 70% of the average optical transmittance of the optical filter 200 in the far-infrared wavelength range with a gradient of greater than about 5% / nm or greater than about 7% / nm.

[0029] Working Example Example 1 Multilayer optical film optical filters including alternating first and second layers were prepared by coextrusion and biaxial orientation as described in US Patent Application Publication No. 2001 / 0013668 (Neavin et al.), with the following exceptions: The first layer was formed from polyethylene naphthalate (PEN) homopolymer (100 mole % naphthalene dicarboxylate with 100 mole % ethylene glycol) having a Tg of 121-123°C. The second layer was formed from poly(methyl methacrylate) or PMMA (PMMA having a Tg of 100°C is available, for example, from Arkema, Pasadena, TX, USA). The PEN layer had a refractive index of about 1.75-1.8 at 550 nm, and the PMMA layer had a refractive index of about 1.5 at 550 nm. The polymers for use in the skin layers were formed from the same materials as those used in the first layer.

[0030] The materials were fed from separate extruders into a multi-layer coextrusion feedblock where they were assembled into alternating layers. Skin layers were added to the structure in a manifold dedicated to that purpose, resulting in a final structure with 227 layers. The multi-layer melt was then cast through a film die onto a chill roll in the conventional manner for polyester films and quenched as it was cast. The cast web was then stretched in a commercial scale biaxial tenter with a temperature and stretch profile similar to that described in US Patent Application Publication No. 2001 / 0013668 (Neavin et al.). The layer thickness profile (layer thickness vs. layer number) was measured by atomic force microscopy and is shown in FIG. 7. The transmission spectrum for normal incidence light is shown in FIG. 5. The physical thickness of the film was measured using an Ono-Sokki DG-925 Micrometer and was measured by capacitance meter to be approximately 33 micrometers.

[0031] Example 2 A multilayer optical film optical filter was made generally as described for Example 1, except that polyethylene terephthalate (PET) was used for the high refractive index layer (first layer), while PMMA was still used for the low refractive index layer (second layer), and the film included 425 layers with the layer profile shown in FIG. 7. The PET layers had a refractive index of about 1.65 to 1.7 at 550 nm. The transmission spectrum for normally incident light is shown in FIG. 8. The thickness of the film was about 60 micrometers.

[0032] Terms such as "about" will be understood by those of skill in the art in the context in which they are used and described herein. If the use of "about" as applied to quantities describing feature sizes, quantities, and physical properties is not clear to those of skill in the art in the context in which it is used and described herein, "about" will be understood to mean within 10 percent of a particular value. A quantity given as about a particular value may be exactly that particular value. For example, if it is not clear to those of skill in the art in the context in which it is used and described herein, an amount having a value of about 1 means that the amount has a value between 0.9 and 1.1, and the value may be 1.

[0033] All references, patents, or patent applications referenced above are hereby incorporated by reference in their entirety. In the event of any inconsistency or contradiction between any portion of the incorporated reference and this application, the information in the foregoing description shall take precedence.

[0034] Descriptions of elements in a figure should be understood to apply equally to corresponding elements in other figures unless otherwise indicated. Although specific embodiments have been illustrated and described herein, those skilled in the art will appreciate that the specific embodiments illustrated and described may be replaced by various alternative and / or equivalent embodiments without departing from the scope of the present disclosure. The present application is intended to cover any adaptations or variations or combinations of the specific embodiments discussed herein. Accordingly, the present disclosure is intended to be limited only by the claims and the equivalents thereof. In the following, exemplary embodiments are presented. [Item 1] 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, thereby providing a substantially normal incidence optical filter for a visible wavelength range ranging from about 420 nm to about 550 nm and an infrared wavelength range ranging from about 650 nm to about 800 nm, and for each of a first orthogonal polarization state and a second orthogonal polarization state. the first polymer layer has a greater refractive index than the second polymer layer for at least one visible wavelength in the visible wavelength range; the average light transmittance of the optical filter in the visible wavelength range is greater than about 50%; the optical filter has an optical density of greater than about 1.5 in the infrared wavelength range; An optical filter, the transmittance of which varies by at least about 30% over a first wavelength range disposed between the visible and infrared wavelength ranges and which is about 10 nm or less in width. [Item 2] 2. The optical filter according to claim 1, wherein the optical density of the optical filter is greater than about 1.5 in a wavelength range spanning from about 650 nm to at least about 850 nm. [Item 3] 2. The optical filter according to claim 1, wherein the optical density of the optical filter is greater than about 2 within a wavelength range spanning from about 650 nm to at least about 850 nm. [Item 4] 4. The optical filter according to any one of items 1 to 3, having an average thickness of about 60 micrometers or less. [Item 5] 5. The optical filter according to any one of items 1 to 4, wherein the first wavelength range is about 8 nm or less in width. [Item 6] 6. The optical filter according to any one of items 1 to 5, wherein at least one of the plurality of alternating first polymer layers and second polymer layers has an absorptance peak in a wavelength range of about 600 nm to about 900 nm. [Item 7] 7. The optical filter according to any one of items 1 to 6, wherein the transmittance of the optical filter varies by at least about 30% over a second wavelength range having a width of about 100 nm or less, and the infrared wavelength range is disposed between the first wavelength range and the second wavelength range. [Item 8] 8. The optical filter of claim 7, wherein at least one of the plurality of alternating first and second polymer layers has a first absorptance peak at a wavelength closer to the first wavelength range than to the second wavelength range. [Item 9] 9. The optical filter of claim 7 or 8, wherein at least one of the plurality of alternating first and second polymer layers has a second absorptance peak at a wavelength closer to the second wavelength range than to the first wavelength range. [Item 10] a light emitting display configured to emit visible images in the visible wavelength range spanning at least about 420 nm to about 550 nm; an optical sensor configured to receive and sense a first visible light in the visible wavelength range and a second infrared light in an infrared wavelength range spanning at least about 650 nm to about 800 nm through the light emitting display; an optical filter disposed between the light emitting display and the optical sensor, the optical filter having a first band edge between the visible and infrared wavelength ranges for substantially normally incident light, wherein a light transmittance of the optical filter decreases from about 70% of an average light transmittance of the optical filter in the visible wavelength range to about 20% of the average light transmittance of the optical filter in the visible wavelength range with a slope of greater than about 5% / nm; An optical system comprising: [Item 11] Item 11. The optical system of item 10, further comprising imaging optics including at least a first lens for imaging light incident on the emissive display onto the optical sensor. [Item 12] a first optical filter including a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that for substantially normally incident light, and for a visible wavelength range spanning from about 420 nm to about 550 nm and an infrared wavelength range spanning from about 650 nm to about 800 nm, and for at least a first orthogonal polarization state, the first optical filter has an average light transmittance of greater than about 50% in the visible wavelength range, an average light reflectance of greater than about 90% in the infrared wavelength range, and a light reflectance of greater than about 80% at a first wavelength greater than about 650 nm; a second optical filter disposed over the first optical filter and having a peak absorptance at the first wavelength; and An optical laminate comprising: [Item 13] Item 13. The optical laminate according to item 12, wherein the first wavelength is within a range of about 700 nm to about 900 nm. [Item 14] 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that the optical filter is capable of detecting a wavelength distribution for substantially normally incident light over a visible wavelength range of about 420 nm to about 550 nm, a near infrared wavelength range of about 650 to about 800 nm, a far infrared wavelength range of about 950 nm to at least about 1050 nm, and for at least a first polarization state. an average light transmittance of greater than about 50% in each of the visible and far infrared wavelength ranges; an average light transmittance of less than about 5% in the near infrared wavelength range; and a light transmittance at a first wavelength between the near infrared wavelength range and the far infrared wavelength range that is about 50% of the average light transmittance of the optical filter in the far infrared wavelength range; 11. An optical filter comprising: at least one of the plurality of alternating first and second polymer layers having an absorptivity peak at a second wavelength between the near infrared wavelength range and the far infrared wavelength range, wherein the first wavelength is shifted to a third wavelength less than the second wavelength for light incident on the optical filter at an angle of incidence of at least about 45 degrees. [Item 15] 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that the optical filter is optically transparent for substantially normally incident light, for a visible wavelength range spanning from about 450 nm to about 550 nm, a near infrared wavelength range spanning from about 650 to about 800 nm, a far infrared wavelength range disposed such that the near infrared wavelength range is between the visible and far infrared wavelength ranges and having a width of at least about 100 nm, and for at least a first polarization state. an average light transmittance of greater than about 75% in each of the visible and far infrared wavelength ranges; an average light transmittance of less than about 45% in the near infrared wavelength range; and a light transmittance at a first wavelength between the near infrared wavelength range and the far infrared wavelength range that is about 10% of the average light transmittance of the optical filter in the visible wavelength range; 1. An optical filter, wherein at least one of the plurality of alternating first and second polymer layers has an absorptivity peak at a second wavelength in a range of about 650 nm to about 900 nm, and wherein the first wavelength is shifted to a third wavelength smaller than the second wavelength for light incident on the optical filter at an angle of incidence of at least about 45 degrees.

Claims

1. 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, thereby providing a substantially normally incident optical filter for a visible wavelength range ranging from about 420 nm to about 550 nm and an infrared wavelength range ranging from about 650 nm to about 800 nm, and for each of a first orthogonal polarization state and a second orthogonal polarization state: the first polymer layer has a greater refractive index than the second polymer layer for at least one visible wavelength in the visible wavelength range; the average light transmittance of the optical filter in the visible wavelength range is greater than about 50%; the optical filter having an optical density greater than about 1.5 in the infrared wavelength range; An optical filter, the transmittance of which varies by at least about 30% over a first wavelength range disposed between the visible and infrared wavelength ranges and which is about 10 nm or less in width.

2. 10. The optical filter of claim 1, wherein the optical density of the optical filter is greater than about 1.5 in a wavelength range spanning from about 650 nm to at least about 850 nm.

3. 10. The optical filter of claim 1, wherein the optical density of the optical filter is greater than about 2 within a wavelength range spanning from about 650 nm to at least about 850 nm.

4. The optical filter of any one of claims 1 to 3, having an average thickness of about 60 micrometers or less.

5. The optical filter of any one of claims 1 to 4, wherein the first wavelength range is less than or equal to about 8 nm wide.

6. 6. The optical filter of claim 1, wherein at least one of the plurality of alternating first and second polymer layers has an absorptance peak in the wavelength range of about 600 nm to about 900 nm.

7. 7. The optical filter of claim 1, wherein the transmittance of the optical filter varies by at least about 30% over a second wavelength range that is about 100 nm or less wide, and the infrared wavelength range is located between the first wavelength range and the second wavelength range.

8. 8. The optical filter of claim 7, wherein at least one of the plurality of alternating first and second polymer layers has a first absorptance peak at a wavelength closer to the first wavelength range than to the second wavelength range.

9. 9. The optical filter of claim 7 or 8, wherein at least one of the plurality of alternating first and second polymer layers has a second absorptance peak at a wavelength closer to the second wavelength range than to the first wavelength range.

10. a light emitting display configured to emit a visible image in the visible wavelength range spanning at least about 420 nm to about 550 nm; an optical sensor configured to receive and sense a first visible light in the visible wavelength range and a second infrared light in an infrared wavelength range spanning at least about 650 nm to about 800 nm through the light emitting display; an optical filter disposed between the light emitting display and the optical sensor, the optical filter having a first band edge between the visible and infrared wavelength ranges for substantially normally incident light, wherein a light transmittance of the optical filter decreases from about 70% of an average light transmittance of the optical filter in the visible wavelength range to about 20% of the average light transmittance of the optical filter in the visible wavelength range with a slope of greater than about 5% / nm; An optical system comprising:

11. The optical system of claim 10 , further comprising imaging optics including at least a first lens for imaging light incident on the emissive display onto the optical sensor.

12. a first optical filter including a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that for substantially normally incident light, and for a visible wavelength range spanning from about 420 nm to about 550 nm and an infrared wavelength range spanning from about 650 nm to about 800 nm, and for at least a first orthogonal polarization state, said first optical filter has an average light transmittance of greater than about 50% in the visible wavelength range, an average light reflectance of greater than about 90% in the infrared wavelength range, and a light reflectance of greater than about 80% at a first wavelength greater than about 650 nm; a second optical filter disposed over the first optical filter and having a peak absorptance at the first wavelength; and An optical laminate comprising:

13. The optical stack of claim 12, wherein the first wavelength is in the range of about 700 nm to about 900 nm.

14. 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that for substantially normally incident light, and for a visible wavelength range spanning from about 420 nm to about 550 nm, a near infrared wavelength range spanning from about 650 to about 800 nm, a far infrared wavelength range spanning from about 950 nm to at least about 1050 nm, and for at least a first polarization state, the optical filter: an average light transmittance of greater than about 50% in each of the visible and far infrared wavelength ranges; an average light transmittance of less than about 5% in the near infrared wavelength range; and a light transmittance at a first wavelength between the near infrared wavelength range and the far infrared wavelength range that is about 50% of the average light transmittance of the optical filter in the far infrared wavelength range; 11. An optical filter comprising: at least one of the plurality of alternating first and second polymer layers having an absorptivity peak at a second wavelength between the near infrared wavelength range and the far infrared wavelength range, wherein the first wavelength is shifted to a third wavelength less than the second wavelength for light incident on the optical filter at an angle of incidence of at least about 45 degrees.

15. 1. An optical filter comprising a plurality of alternating first and second polymer layers totaling at least 50, each polymer layer having an average thickness of less than about 500 nm, such that for substantially normally incident light, and for a visible wavelength range spanning from about 450 nm to about 550 nm, a near infrared wavelength range spanning from about 650 to about 800 nm, a far infrared wavelength range disposed such that the near infrared wavelength range is between the visible and far infrared wavelength ranges and having a width of at least about 100 nm, and for at least a first polarization state, the optical filter: an average light transmittance of greater than about 75% in each of the visible and far infrared wavelength ranges; an average light transmittance of less than about 45% in the near infrared wavelength range; and a light transmittance at a first wavelength between the near infrared wavelength range and the far infrared wavelength range that is about 10% of the average light transmittance of the optical filter in the visible wavelength range; 1. An optical filter comprising: at least one of the plurality of alternating first and second polymer layers having an absorptivity peak at a second wavelength in a range from about 650 nm to about 900 nm, wherein the first wavelength is shifted to a third wavelength less than the second wavelength for light incident on the optical filter at an angle of incidence of at least about 45 degrees.

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