Optical film and optical system including the optical film for reducing chromatic aberration

Abstract

An optical film includes a plurality of optical repeat units including at least three first ORUs that have thicknesses within P1% of a same first thickness, where each first ORU is separated from each other first ORU by at least one ORU having a thickness differing from the first thickness by greater than P1%, and where P1% is in a range of about 1% to about 10%. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range. An optical system includes the optical film for reducing chromatic aberration by at least partially compensating for a chromatic dispersion of at least one optical component of the optical system.

Description

[0001] OPTICAL FILM AND OPTICAL SYSTEM INCLUDING THE OPTICAL FILM FOR REDUCING CHROMATIC ABERRATION

[0002] TECHNICAL FIELD

[0003] The present description relates generally to optical films, such as polymeric multilayer optical films, and to optical systems that utilize the optical films.

[0004] BACKGROUND

[0005] An optical film can include a plurality of polymeric layers arranged into optical repeat units. The optical film can be a reflective polarizer and can be used in an optical system such as a display system.

[0006] SUMMARY

[0007] In some aspects, the present description provides an optical film such that for an incident light incident on the optical film at a first incident angle, and for at least one polarization state, a reflection depth of the optical film from the same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range and / or over a visible wavelength range extending from about 420 nm to about 680 nm. The optical film can include a plurality of polymeric layers which may be or include a plurality of alternating polymeric first and second layers and / or which may be arranged into a plurality of optical repeat units. An optical system can include the optical film for reducing chromatic aberration by at least partially compensating for a chromatic dispersion of at least one optical component of the optical system.

[0008] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. The plurality of ORUs includes at least three first ORUs where each first ORU has a thickness within Pl% of a same first thickness, each first ORU being separated from each other first ORU by at least one ORU having a thickness differing from the first thickness by greater than Pl%, where Pl% is in a range of about l% to about 10%. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0009] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs includes at least a polymeric A layer and a different polymer B layer, such that for an incident light incident on the optical film at a first incident angle and for at least one polarization state: each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW) that can be in a range of about 300 nm to about 3000 nm; for a first wavelength disposed in a visible wavelength range extending from about 420 nm to about 680 nm, the optical film includes at least three first ORUs, each first ORU having an RW that is within Pl% of the first wavelength, each first ORU being separated from each other first ORU by at least one ORU having an RW that differs from the first wavelength by greater than Pl%, Pl% being in a range of about 1% to about 10%; and a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over the visible wavelength range.

[0010] In some aspects, the present description provides an optical film including a macrolayer and a plurality of optical repeat units (ORUs) numbering at least 10 in total disposed on a same first major surface of the macrolayer. The macrolayer and the plurality of optical repeat units can be coextruded and co-stretched with one another. The macrolayer can have an average thickness greater than about 500 nm. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. For an incident light incident on the optical film at a first incident angle and for at least a first polarization state, the plurality of ORUs has first, second, and third average reflection depths relative to the first major surface of the macrolayer in respective nonoverlapping first, second, and third wavelength ranges, where the second wavelength range is disposed between the first and third wavelength ranges; the second average reflection depth differs from each of the first and third average reflection depths by at least about 1.2 times a difference between the first and third average reflection depths; and each of the first, second, and third wavelength ranges is at least about 20 nm wide and disposed between about 380 nm and about 2000 nm. For the incident light incident on the optical film at the first incident angle and for at least the first polarization state, the optical film has an average reflectance in each of the first, second, and third wavelength ranges of at least about 60%.

[0011] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer, and where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that when in a scatter plot of the RWs of the ORUs versus depths of the ORUs relative to a same major side of the optical film, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth. The intersection points form a plurality of alternating peaks and valleys. A first one of the first lines of the plurality of first lines includes a plurality of first straight line segments collectively extending from a first valley of the plurality of alternating peaks and valleys to a first peak of the plurality of alternating peaks and valleys. Slopes of the first straight line segments have minimum and maximum slope magnitudes. The minimum slope magnitude can be at least about 5 nm / micron. The maximum slope magnitude is at least about 3 times greater than the minimum slope magnitude.

[0012] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer, and where the ORUs are sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that when adjacent data points in a scatter plot of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number. The intersection points form a plurality of alternating peaks and valleys. A first one of the first lines of the plurality of first lines includes a plurality of the first straight line segments collectively extending from a first valley of the plurality of alternating peaks and valleys to a first peak of the plurality of alternating peaks and valleys. Slopes of the first straight line segments have minimum and maximum slope magnitudes. The minimum slope magnitude can be at least about 0.5 nm per ORU number. The maximum slope magnitude is at least about 3 times greater than the minimum slope magnitude.

[0013] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW) and includes at least a polymeric A layer and a different polymer B layer, such that when in a scatter plot of the RWs of the ORUs versus depths of the ORUs relative to a same major side of the optical film, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth. The intersection points forming at least a first plurality of alternating peaks and valleys. For each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, a difference in ORU RWs of the peak and the valley can be greater than about 5 nm and less than about 200 nm.

[0014] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, where each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer, and where the ORUs are sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that when adjacent data points in a scatter plot of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number. The intersection points form at least a first plurality of alternating peaks and valleys. For each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, a difference in ORU thicknesses of the peak and the valley can be greater than about 3 nm and less than about 120 nm.

[0015] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. The ORUs in the plurality of ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that for non-overlapping first and second thickness ranges at least about 5 nm wide, a scatter plot of the thicknesses versus the numbers of the ORUs includes at least three nonoverlapping first groups of sequentially numbered ORUs of the plurality of the ORUs where each ORU of each of the first groups has a thickness in the first thickness range; and a second group of at least 8 ORUs of the plurality of the ORUs where each ORU of the second group has a thickness in the second thickness range. Each of the first groups includes at least three sequentially numbered ORUs in the plurality of ORUs. Each first group is separated from each other first group by at least two sequentially numbered ORUs of the plurality of ORUs having thicknesses not in the first thickness range. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from the same first major side of the optical film varies non- monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0016] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW) and includes at least a polymeric A layer and a different polymer B layer. The ORUs in the plurality of the ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that for non-overlapping first and second wavelength ranges at least about 15 nm wide, a scatter plot of the RWs versus the numbers of the ORUs includes at least three non-overlapping first groups of sequentially numbered ORUs of the plurality of the ORUs where each ORU of each of the first groups has an RW in the first wavelength range; and a second group of at least 8 ORUs of the plurality of the ORUs where each ORU of the second group has an RW in the second wavelength range. Each of the first groups includes at least three sequentially numbered ORUs in the plurality of ORUs. Each first group is separated from each other first group by at least two sequentially numbered ORUs of the plurality of the ORUs having RWs not in the first wavelength range. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from the same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0017] In some aspects, the present description provides an optical film including a macrolayer and a plurality of optical repeat units (ORUs) numbering at least 10 in total disposed on a same first major surface of the macrolayer. The macrolayer and the plurality of optical repeat units can be coextruded and co-stretched with one another. The macrolayer can have an average thickness greater than about 500 nm and each layer of each of the ORUs can have an average thickness less than about 500 nm. Each of the ORUs include comprising at least a polymeric A layer and a different polymer B layer. When adjacent data points in a scatter plot of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot includes a plurality of first lines where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number, such that for an incident light incident on the optical film at a first incident angle and for at least one polarization state: for a first wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, a reflection depth of the plurality of ORUs relative to the first major surface of the macrolayer is less than about 10 micrometers; and for a wavelength range at least 20 nm wide and substantially centered on the first wavelength, the plurality of ORUs has an average reflectance of greater than about 60%.

[0018] In some aspects, the present description provides an optical film including a macrolayer and a plurality of optical repeat units (ORUs) numbering at least 10 in total disposed on a same first major surface of the macrolayer. The macrolayer and the plurality of optical repeat units can be coextruded and co-stretched with one another. The macrolayer can have an average thickness greater than about 500 nm and each layer of each of the ORUs can have an average thickness less than about 500 nm. Each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW) and includes at least a polymeric A layer and a different polymer B layer. When in a scatter plot of the RWs of the ORUs versus depths of the ORUs relative to the first major surface of the macrolayer, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot includes a plurality of first lines where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth, such that for an incident light incident on the optical film at a first incident angle and for at least one polarization state: for a first wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, a reflection depth of the plurality of ORUs relative to the first major surface of the macrolayer is less than about 10 micrometers; and for a wavelength range at least 20 nm wide and substantially centered on the first wavelength, the plurality of ORUs has an average reflectance of greater than about 60%.

[0019] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. The ORUs in the plurality of the ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film. A scatter plot of the thicknesses versus the numbers of the ORUs includes at least three non-overlapping first groups of the ORUs. Each group of the first groups includes at least three of the sequentially numbered ORUs in the plurality of ORUs including first and second ORUs having respective maximum and minimum thicknesses among the at least three ORUs in the group, where the minimum and maximum thicknesses in the group are different from each other by at least 15%. For each of the first ORUs and the second ORUs in the at least three non-overlapping first groups of the ORUs, the thicknesses of the ORUs can be within about 10% of each other. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a wavelength range of about 420 nm to about 680 nm.

[0020] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. Each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW). A scatter plot of the RWs of the ORUs versus depths of the ORUs relative to a same major side of the optical film includes at least three non-overlapping first groups of the ORUs. Each group of the first groups includes at least 3 of the sequentially numbered ORUs in the plurality of ORUs including first and second ORUs having respective maximum and minimum RWs among the at least three ORUs in the group. The minimum and maximum RWs in the group are different from each other by at least 15%. For each of the first ORUs and the second ORUs in the at least three non-overlapping first groups of the ORUs, the RWs of the ORUs can be within about 10% of each other. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non- monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0021] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. The ORUs in the plurality of the ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that a scatter plot of the average thicknesses versus the numbers of the sequentially numbered ORUs in the plurality of the ORUs includes at least three non-overlapping groups of the ORUs, where each of the groups includes at least two of the sequentially numbered ORUs in the plurality of ORUs. For each pair of adjacent first and second groups in the at least three groups, the first group includes a first ORU closest to the second group and the second group comprises a second ORU closest to the first group, where the average thicknesses of the first and second ORUs are different by at least about 5%. For an incident light incident on the optical film at a first incident angle, and for at least one polarization state: for at least a first wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, the plurality of the ORUs and at least one of the groups in the at least three nonoverlapping groups have respective optical reflectances R and Rl; for at least a second wavelength in the visible wavelength range different from the first wavelength, the plurality of the ORUs and a group of at least three sequentially numbered ORUs not overlapping any of the at least three non-overlapping groups of the ORUs have respective optical reflectances R' and Rl'; and a reflection depth of the optical film from the same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over the visible wavelength range, where R > Rl > 10%, R / Rl > 1.1, Rl' > 50% and 1.25 > R7R1'.

[0022] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. The ORUs in the plurality of the ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. Each of the ORUs having a peak reflectivity at a corresponding resonant wavelength (RW), such that a scatter plot of the RWs versus depths of the ORUs relative to the first major side of the optical film includes at least three non-overlapping groups of the ORUs, where each of the groups including at least two of the sequentially numbered ORUs in the plurality of ORUs. For each pair of adjacent first and second groups in the at least three groups, the first group includes a first ORU closest to the second group and the second group includes a second ORU closest to the first group, where the RWs of the first and second ORUs are different by at least about 5%. For an incident light incident on the optical film at a first incident angle, and for at least one polarization state: for at least a first wavelength in a visible wavelength range extending from about 420 nm to about 680 nm, the plurality of the ORUs and at least one of the groups in the at least three non-overlapping groups have respective optical reflectances R and Rl ; for at least a second wavelength in the visible wavelength range different from the first wavelength, the plurality of the ORUs and a group of at least three sequentially numbered ORUs not overlapping any of the at least three non-overlapping groups of the ORUs have respective optical reflectances R' and Rl'; and a reflection depth of the optical film from the first major side of the optical film varies non- monotonically with increasing wavelength of the incident light over the visible wavelength range, where R > Rl > 10%, R / Rl > 1.1, Rl' > 50% and 1.25 > R7R1'. In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. The ORUs can be sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that for a first thickness range at least about 20 nm wide, a scatter plot of thicknesses versus the numbers of the ORUs includes at least first, second and third non-overlapping plots of the sequentially numbered ORUs with each ORU of each of the at least first, second and third non-overlapping plots having a thickness in the first thickness range. Each of the at least first, second and third non-overlapping plots includes at least 2 of the ORUs in the plurality of ORUs. Magnitudes of slopes of best linear fits to at least two of the at least the first through the third non-overlapping plots are different by at least about 20%. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from the first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0023] In some aspects, the present description provides an optical film including a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total. Each of the ORUs can have an average thickness of less than about 1500 nm and includes at least a polymeric A layer and a different polymer B layer. Each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that for a first wavelength range at least about 40 nm wide, a scatter plot of RWs of the ORUs versus depths of the ORUs relative to a same major side of the optical film includes at least first, second and third non-overlapping plots of the ORUs with each ORU of each of the at least first, second and third non-overlapping plots having a RW in the first wavelength range. Each of the at least first, second and third non-overlapping plots includes at least 2 of the ORUs in the plurality of ORUs and has a slope being a rate of change of the RW with respect to the depth at a same first RW. Magnitudes of the slopes of at least two of the at least the first through the third plots are different by at least about 20%. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from the first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

[0024] In some aspects, the present description provides an optical film including a plurality of polymeric layers stacked along a thickness direction of the optical film, such that when a substantially monochromatic first light ray having a first wavelength and an optical intensity li 1 is incident on the plurality of polymeric layers at a first incident angle of at least 5 degrees and a substantially monochromatic second light ray having a second wavelength different from the first wavelength and an optical intensity Ii2 < lil is incident on the plurality of polymeric layers at the first incident angle, the plurality of polymeric layers reflects the incident first light ray, but not the incident second light ray, as at least two spaced apart first reflected light rays having corresponding at least two first optical intensities where each of the at least two first optical intensities is greater than about 0.1 lil, and the plurality of polymeric layers reflects the incident second light ray as a second reflected light ray having a second optical intensity greater than about 0.5 Ii2, where the second optical intensity is greater than each of the at least two first optical intensities.

[0025] In some aspects, the present description provides an optical system including a display configured to form and emit an image; at least one optical component, where the at least one optical component has a chromatic dispersion; and an optical film of the present description in optical communication with each of the display and the at least one optical component. The optical film can be configured to at least partially compensate for the chromatic dispersion of the at least one optical component.

[0026] In some aspects, the present description provides an optical system including a display configured to form and emit an image comprising coincident first and second emitted image rays having respective first and second wavelengths at least about 20 nm apart, where the optical system can be configured to display a virtual image of the emitted image to a viewer; at least one optical component, where the at least one optical component has a chromatic dispersion; and an optical film including a plurality of polymeric layers and configured to at least partially compensate for the chromatic dispersion of the at least one optical component. Each layer of the plurality of polymeric layers can have an average thickness of less than about 500 nm. For an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range comprising the first and second wavelengths. The optical system can be such that an optical interaction between the at least one optical component and the coincident first and second emitted image rays laterally separates the first and second emitted image rays so that, when incident on the optical film, the first and second emitted image rays are separated by a first distance Gl. The plurality of polymeric layers reflects the incident first and second emitted image rays as respective reflected first and second image rays separated by a second distance G2. G2 is less than Gl by at least 10%.

[0027] These and other aspects will be apparent from the following detailed description. In no event, however, should this brief summary be construed to limit the claimable subject matter.

[0028] BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a schematic cross-sectional view of an optical film, according to some embodiments.

[0030] FIG. 2 is a schematic plot of optical repeat unit (ORU) thickness or ORU resonant wavelength (RW) versus ORU number or depth from a same major side of an optical film for at least a portion of the optical film, according to some embodiments.

[0031] FIG. 3 is a schematic plot of ORU thickness or RW versus ORU number or depth from a same major side of an optical film, according to some embodiments. FIGS. 4A-4B are schematic plots of ORU thickness or RW versus ORU number or depth from a same major side of an optical film for at least a portion of the optical film, according to some embodiments.

[0032] FIGS. 5A-5B are schematic plots of ORU thickness or RW versus ORU number or depth from a same major side of another optical film for at least a portion of the optical film, according to some embodiments.

[0033] FIG. 6 is a plot of resonant wavelength versus depth from a same major side of an optical film, according to some embodiments.

[0034] FIG. 7 shows polynomial fits to non-overlapping plots of portions of the plot of resonant wavelength versus depth of FIG. 6.

[0035] FIG. 8 is a plot of slopes of the non-overlapping plots of FIG. 7 versus resonant wavelength.

[0036] FIG. 9 is a plot of ORU thickness versus ORU number, according to some embodiments.

[0037] FIG. 10 shows linear fits to non-overlapping plots of portions of the plot of ORU thickness versus ORU number of FIG. 9.

[0038] FIG. 11A is plot of resonant wavelength versus depth from a same major side of another optical film, according to some embodiments.

[0039] FIG. 1 IB is a portion of the plot of FIG. 11A.

[0040] FIG. 12A is plot of ORU thickness versus ORU number for an optical film, according to some embodiments.

[0041] FIG. 12B is a portion of the plot of FIG. 12A.

[0042] FIGS. 13-14 are schematic plots of reflection depth from a same major side of an optical film versus wavelength, according to some embodiments.

[0043] FIG. 15 is a schematic illustration of reflection from an optical film, according to some embodiments.

[0044] FIG. 16 is a schematic plot of reflectivity versus wavelength for an optical repeat unit, according to some embodiments.

[0045] FIGS. 17-18 are plots of reflectance versus wavelength for optical films and non-overlapping groups of ORUs of the optical films, according to some embodiments.

[0046] FIG. 19 is a schematic cross-sectional view of an optical system, according to some embodiments.

[0047] DETAIUED DESCRIPTION

[0048] In the following description, reference is made to the accompanying drawings that 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 present description. The following detailed description, therefore, is not to be taken in a limiting sense. As is known in the art, multilayer optical films including a plurality of optical repeat units (e.g., alternating first and second polymeric layers) can be used to provide desired reflection and transmission in desired wavelength ranges by suitable selection of layer thicknesses and refractive index differences. Multilayer optical films and methods of making multilayer optical films are described in U.S. Pat. Nos. 5,882,774 (Jonza et al.); 6,783,349 (Neavin et al.); 6,949,212 (Merrill et al.); 6,967,778 (Wheatley et al.); 9,162,406 (Neavin et al.); and 11,493,677 (Haag et al.), for example. An optical repeat unit of a multilayer optical film is generally the smallest distinct unit of optical layers that repeats along a thickness direction of the optical film. An optical repeat unit generally includes at least two different layers (e.g., higher index first and lower index second layers) and may optionally include additional layers as described in U.S. Pat. Nos. 5,103,337 (Schrenk et al.); 5,360,659 (Arends et al.); 5,540,978 (Schrenk); and 6,207,260 (Wheatley et al.), for example, and in International Appl. Pub. No. WO 2022 / 195373 (Huseby et al.), for example.

[0049] Multilayer optical films can be interference stacks that reflect light by stacking together optical repeat units (e.g., a bi-layer unit cell including two quarter-wave layers) with refractive index contrast between layers of the optical repeat units. Each optical repeat unit can be characterized by a reflection band with intrinsic optical power and bandwidth determined by the index contrast and f-ratios of the optical repeat unit. An f-ratio of an optical repeat unit is an optical thickness of a layer of the optical repeat unit divided by the total optical thickness of the optical repeat unit. In the case of a bi-layer optical repeat unit, the f-ratio of the higher index layer of the bi-layer is taken to be the f-ratio of the optical repeat unit. More generally, the optical repeat unit can be characterized by n-1 independent f-ratios where n is the number of layers of the optical repeat unit. Because the intrinsic optical power and bandwidth of a single optical repeat unit are usually too weak and narrow for practical applications, many optical repeat units are typically stacked and graded to increase overall optical power and bandwidth. As a result, different wavelengths reflect at different depths within the multilayer optical film depending on which optical repeat units are on or off resonance. In many applications, this reflection-depth dispersion does not noticeably impact key performance metrics. In imaging optics applications, however, this characteristic can induce a lateral shift of rays of different wavelength and lead to chromatic aberration, pixel blur, loss of resolution and other artifacts. Other optical components, such as lenses, can also induce chromatic aberration and it is common in imaging systems to add a compensation lens to correct for the overall chromatic aberration.

[0050] It has been found, according to some embodiments, that the ability to tune and engineer a reflection-depth dispersion within the optical film, such as a reflective polarizer in a polarizing beam splitter or a folded-optics lens, could mitigate, and in some instances eliminate or substantially eliminate, chromatic aberration. For example, it has been found, according to some embodiments, that an optical system can include an optical film and at least one optical component that has a chromatic dispersion, where the optical film has a reflection depth from a same first major side of the optical film that varies non-monotonically with wavelength to correct the chromatic dispersion. For example, reflection depths for blue and red wavelengths can be similar while reflection depths for green wavelengths may be significantly different from the red and green reflection depths in order to correct the chromatic dispersion.

[0051] FIG. 1 is a schematic cross-sectional view of an optical film 300, according to some embodiments. The optical film 300 can include a plurality of optical repeat units (ORUs) 10. Each ORU 10 typically includes at least a polymeric A layer and a different polymer B layer and can optionally include additional layers. In some embodiments, the ORUs are coextruded and co-stretched with one another. In some embodiments, all layers of the optical film 300 are coextruded and co-stretched with one another. In some embodiments, the ORUs 10 number at least 10, 25, 50, 100, 150, 200, 250, 300, 350, 400, 450, 500 in total. The ORUs 10 can number up to 2000, 1500, 1000, 800, or 700, for example.

[0052] In some embodiments, each of the ORUs 10 has an average thickness of less than about 1500, 1250, 1000, 900, 800, 700, 600, 500, 450, 400, 350, or 300 nm. Each ORU 10 can have an average thickness greater than about 50, 75, 100, 150, or 175 nm, for example. The average thickness of a layer is the average (unweighted mean) over a total area of the layer of the thickness of the layer. The average thickness of an ORU is the average of the total thickness (sum of thicknesses of the layers of the ORU) of the ORU. The thickness of a layer or ORU can be understood to be the average thickness of the layer or ORU unless indicated otherwise or unless the context clearly indicates otherwise. In some embodiments, each layer (e.g., each of the A and B layers) of each of the ORUs 10 has an average thickness less than about 500, 450, 400, 350, 300, 250, or 200 nm. Each layer of each ORU 10 can have an average thickness of greater than about 10, 15, 20, 25, 30, 35, 40, 45, or 50 nm, for example. In some embodiments, the optical film 300 includes a plurality of polymeric layers (e.g., A and B layers) where each layer of the plurality of polymeric layers has an average thickness of less than about 500, 450, 400, 350, 300, 250, or 200 nm. Each of the layers of the plurality of polymeric layers can have an average thickness of greater than about 10, 15, 20, 25, 30, 35, 40, 45, or 50 nm, for example. The optical film 300 can have an average total thickness of at least about 10, 15, 20, 25, 30, 35, 40, 45, or 50 micrometers. The average total thickness of the optical film 300 can be up to about 400, 300, 250, 200, 175, 150, 125, or 100 micrometers, for example. In some embodiments, the plurality of optical repeat units 10 has an average total thickness (e.g., corresponding to S4 in FIG. 15) in any of these ranges. For example, the plurality of optical repeat units 10 can have an average total thickness in a range of about 10 micrometers to about 400 micrometers, or about 15 micrometers to about 300 micrometers, or about 20 micrometers to about 200 micrometers, for example.

[0053] The ORUs can be sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300. In some embodiments, the optical film 300 includes a plurality of polymeric layers (e.g., A and B layers). The plurality of polymeric layers can be stacked along a thickness direction (z-direction) of the optical film 300 and can be sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300. The layers of the optical repeat units 10 may be referred to as microlayers, optical layers, or interference layers. In some embodiments, the optical fdm 300 includes at least one additional layer 124, 125, 126. For example, in some embodiments, the optical fdm 300 includes at least one macrolayer 124, 126 where each macrolayer of the at least one macrolayer 124, 126 has an average thickness greater than about 500, 600, 750, 1000, 1500, or 2000 nm. The average thickness of each macrolayer 124, 126 can be up to 50, 30, 20 or 10 micrometers, for example. The at least one macrolayer 124, 126 can include outermost skin layers of the optical fdm 300 and / or can include protective boundary layers between adjacent packets of layers of the optical fdm 300, for example. Layer 125 may be a protective boundary layer and / or may be a macrolayer, for example. In some embodiments, the layer 125 is omitted. In some embodiments, the plurality of polymeric layers and / or the plurality of ORUs 10 is disposed on the at least one macrolayer 124, 126. In some embodiments, an optical fdm 300 includes a macrolayer 124 and a plurality of optical repeat units (ORUs) 10 numbering at least 10 (or in a range described elsewhere herein) in total disposed on a same first major surface 124a of the macrolayer 124. In some embodiments, the macrolayer 124 and the plurality of optical repeat units 10 are coextruded and co-stretched with one another. In some embodiments, the macrolayer 124 has an average thickness greater than about 500 nm (or in a range described elsewhere herein) and each of the ORUs has an average thickness of less than about 1500 nm (or in a range described elsewhere herein) and includes at least a polymeric A layer and a different polymer B layer. In some embodiments, each layer of each optical repeat unit 10 has an average thickness less than, or less than about 0.8, 0.6, 0.5, 0.4, or 0.3 times, the average thickness of the macrolayer 124.

[0054] In some embodiments, each of the A layers of the plurality of optical repeat units 10 has a same first composition and each of the B layers of the plurality of optical repeat units 10 has a same second composition different from the first composition. In some embodiments, the A layers are substantially birefringent (e.g., a birefringence greater than about 0.05, 0.07, 0.1, 0.15, or 0.2 for at least one wavelength in a range of about 450 nm to about 1500 nm; the birefringence can be up to about 0.4, 0.35, or 0.3, for example) and the B layers are substantially optically isotropic (e.g., a birefringence less than about 0.04, 0.03, 0.02, 0.015, 0.01, or 0.008 for the at least one wavelength in the range of about 450 nm to about 1500 nm). In some embodiments, the A and B layers have respective higher and lower average in-plane refractive indices for at least a first wavelength in a range of about 450 nm to about 1500 nm. Inplane refractive indices are indices along directions in the plane (x-y plane) of the optical film 300. The plane of the film can be understood to be a tangent plane in the case of a curved film. The average inplane refractive index is the average over all directions, or over two principal directions, in the plane of the layer. In some embodiments, the average in-plane refractive index can be higher for the A layers than the B layers by at least about 0.05, 0.07, 0.1, 0.15, or 0.2 for the at least one wavelength in the range of about 450 nm to about 1500 nm. The difference in the average in-plane refractive indices can be up to about 0.4, 0.35, or 0.3, for example. The at least one wavelength can be or include a wavelength of about 633 nm, for example. Suitable materials for the various layers of the optical film 300 include, for example, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycarbonate, polymethylmethacrylate (PMMA), copolyesters, and blends or copolymers thereof. Suitable copolymers of PEN include coPEN 90 / 10 (also referred to as Low-melt PEN or LmPEN) as described in U.S. Pat. No. 6,946,188 (Hebrink et al.). CoPEN 90 / 10 can be described a copolyester where carboxylate units of the copolyester comprises 90 mole percent naphthalate units and 10 mole percent terephthalate units. More generally, a copolyester can include other ratios of naphthalate and terephthalate units. For example, in some embodiments, carboxylate units of a coPEN copolyester can include about 60 to 95 mole percent naphthalate units and about 5 to 40 mole percent terephthalate units. Such copolyesters may be denoted coPEN N / 100-N where N is the mole percent naphthalate units and 100-N is the mole percent terephthalate units. In some embodiments, PEN or LmPEN can be used as a high index and / or birefringent layer (e.g., A layer) and PMMA or an optically isotropic coPEN can be used as a low index and / or optically isotropic layer (e.g., B layer), for example. As another example, PET can be used as a high index and / or birefringent layer (e.g., A layer) and coPMMA can be used as a low index and / or optically isotropic layer (e.g., B layer). Other suitable materials are described in the multilayer optical fdm references provided elsewhere herein.

[0055] In some embodiment, the optical fdm 300 is or includes a reflective polarizer. In some embodiments, for a substantially normally incident light (e.g., having an incident angle 0 less than about 30, 25, 20, 15, 10, or 8 degrees), the reflective polarizer reflects at least 60% of the incident light polarized along a first in-plane direction (e.g., x-direction) and transmits at least 60% of the incident light polarized along an orthogonal second in-plane direction (e.g., y-direction). In some embodiments, for the substantially normally incident light, the reflective polarizer reflects at least 70, 80, or 90% of the incident light polarized along the first in-plane direction and transmits at least 70, 80, or 85% of the incident light polarized along the second in-plane direction. In some embodiment, the optical film 300 is or includes an optical mirror or a partial mirror. In some embodiments, for a substantially normally incident light, the optical mirror or partial mirror reflects at least 40, 50, 60, 70, 80, or 90% of the incident light for each of two mutually orthogonal polarization states 101, 102.

[0056] In some embodiments, each of the optical repeat units (ORUs) 10 has a peak reflectivity (see, e.g., peak reflectivity Rp in FIG. 16) at a corresponding resonant wavelength (RW). The optical film 300 may be characterized by an ORU thickness distribution and / or by an ORU RW distribution. The distributions can be determined as functions of ORU number or depth from a same major side (one of 301 and 302) of the optical film 300. The resonant wavelength can be determined for at least one polarization state (e.g., at least one of polarization state 101 and 102). For example, for a reflective polarizer, the resonant wavelength can be determined for the block polarization state. The resonant wavelength can be determined for incident light at a first (or predetermined) incident angle 0. The angle 0 can be in a range of 0 degrees (normal incidence) to about 75, 70, 65, or 60 degrees, for example. The light can be incident on the optical film 300 from a specified medium such as air, glass or plastic. For example, the predetermined incident angle 0 can be about 45 degrees and the specified medium can be glass or plastic. Such incident angle and medium can be appropriate to describe a polarizing beam splitter (PBS) including the optical film 300 disposed between prisms, for example. As another example, the predetermined incident angle 0 can be less than about 10 degrees and the specified medium can be air.

[0057] FIG. 2 is a schematic plot of optical repeat unit (ORU) thickness or ORU resonant wavelength (RW) versus ORU number or depth from a same major side of an optical film 300 for at least a portion of the optical film, according to some embodiments. The ORUs can continue to the right in FIG. 2 as schematically illustrated in FIGS. 3 through 4B, for example. FIG. 3 is a schematic plot of ORU thickness or RW versus ORU number or depth from a same major side of an optical film 300, according to some embodiments. FIGS. 4A-4B are schematic plots of ORU thickness or RW versus ORU number or depth from a same major side of an optical film 300 for at least a portion of the optical film 300, according to some embodiments. In each of FIGS. 3 through 4B, a first plurality of ORUs have thicknesses or RWs in a range (e.g., range d2 schematically illustrated in FIG. 4B) intermediate between ranges (e.g., dl and d3) of other ORUs where the first plurality is disposed adjacent a first major side (e.g., 301) of the optical film 300. In other embodiments, the first plurality of ORUs is disposed adjacent the opposite second major side (e.g., 302) of the optical film 300. FIGS. 5A-5B are schematic plots of ORU thickness or RW versus ORU number or depth from a same major side of an optical film 300 for at least a portion of the optical film 300, according to some embodiments. Schematic plots of ORU thickness versus ORU number and of ORU RW versus depth, for example, can appear generally similar so that the same schematic plot may show ORU thickness or RW along the ordinate and ORU number or depth along the abscissa. Fines 24 and 25 refer to lines in a scatter plot of ORU thickness or RW versus ORU number or depth.

[0058] The ORU profiles may be selected such that or an incident light incident on the optical film at a first incident angle and for at least one polarization state (e.g., at least one of 101 and 102), a reflection depth of the optical film from a same first major side 301 of the optical film 300 varies non- monotonically with increasing wavelength of the incident light over a predetermined wavelength range (e.g., over the wavelength range of W1 to W6 as schematically illustrated in FIGS. 13-14). For example, in FIGS. 3-4B, the ORUs may be selected to provide a reflection depth from the first major side (side with lower ORU number or depth) of the optical film 300 for green wavelengths that is smaller than reflection depths for blue and red wavelengths (e.g., as schematically illustrated in FIG. 14), while in FIGS. 5A-5B, the ORUs may be selected to provide a reflection depth from the first major side of the optical film 300 for blue and red wavelengths that are similar and that are smaller than for green wavelengths (e.g., as schematically illustrated in FIG. 13). In some embodiments, the predetermined wavelength range is a visible wavelength range extending from about 400 nm to about 700 nm or from about 420 nm to about 680 nm.

[0059] It has been found, according to some embodiments, that using multiple stacks of ORUs over a same thickness or RW range can be advantageously utilized to produce a reflection depth that is similar for wavelengths throughout or substantially throughout the RW range. For example, in FIG. 4B, the group 34 (which includes stacks 34a, 34b and 34c) of the ORUs 10 can provide a substantially uniform reflection depth for wavelengths substantially throughout a range d2, while groups 31-33 and 135-137 of the ORUs 10 can provide a substantially uniform reflection depth for wavelengths substantially throughout ranges dl and d3, according to some embodiments. In some embodiments, the multiple stacks are arranged from a same major side of the optical fdm 300 to have decreasing slopes among the stacks and / or increasing the number of ORUs in the stacks (see, e.g., FIGS. 6-12B). It has been found, according to some embodiments, that decreasing slopes and / or increasing the number of ORUs in the stack provide a more uniform reflection depth since this can result in a lower reflectance for stacks closer to the same major side than for stacks farther from the same major surface so that, accounting for light reflected by stacks closer to the same major side, similar intensities of light are reflected by the different stacks.

[0060] In some embodiments, the plurality of ORUs 10 includes at least three first ORUs (e.g., zl-z3 in FIG. 2 or 4A; or one of xl-x3 or yl-y3 in FIG. 4A or 5 A) where each first ORU has a thickness within Pl% of a same first thickness (e.g., a in FIG. 2 or 4A; or one of al or a2 in FIG. 4A or 5A), and where each first ORU is separated from each other first ORU by at least one ORU, or at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, 20 ORUs each, having a thickness differing from the first thickness by greater than Pl%. In some embodiments, Pl% is at least about 1, 1.5, or 2%. In some such embodiments, or in other embodiments, Pl% is no more than about 10, 8, 6, 5, 4, 3, 2.5, or 2%. For example, in some embodiments, Pl% is in a range of about 1% to about 10%, or about 1% to about 5%, or about 1% to about 4%, or about 1% to about 3%, or about 1% to about 2%, or about 1.5% to about 8%, or about 2% to about 6%, or about 2% to about 4%, or about 2% to about 3%. In some embodiments, Pl% is about 1, 1.5, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, or 10 percent. In some embodiments, the thickness of each of the at least three first ORUs is within 2.5% of the first thickness and the thickness of each of the at least one ORU, or the at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, or 20 ORUs, that separates the first ORUs differs from the first thickness by greater than 3%. In some such embodiments, or in other embodiments, the thickness of each of the at least three first ORUs is within 2, 1.5, or 1 percent of the first thickness. In some such embodiments, or in other embodiments, the thickness of each of the at least one ORU, or the at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, or 20 ORUs, differs from the first thickness by greater than 3.5, 4, or 4.5 percent. In some embodiments, each first ORU is separated from each other first ORU by at least one ORU, or at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, or 20 ORUs each, having a thickness differing from the first thickness by greater than Pl% + 0.5%, or Pl% + 1%, Pl% + 1.5%, Pl% + 2%, Pl% + 2.5%, Pl% + 3%, Pl% + 3.5%, Pl% + 4%, Pl% + 4.5%, Pl% + 5%, Pl% + 6%, Pl% + 7%, Pl% + 8%, Pl% + 9%, or Pl% + 10%, or greater than 1.01, 1.03, 1.05, 1.07, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.8, or 2 times Pl%. For example, in some embodiments, the thickness of each of the at least one ORU differs from the first thickness by greater than Pl%+0.5%, where Pl% is in a range of about 1% to about 3%. As another example, in some embodiments, each first ORU is separated from each other first ORU by at least two ORUs that each having a thickness differing from the first thickness by greater than Pl% + 1%. In some embodiments, the plurality of ORUs lOincludes at least three second ORUs (e.g., the other of xl-x3 or yl-y3 in FIG. 4A or 5A) where each second ORU has a thickness within Pl% of a same second thickness (e.g., the other of al or a2), and where each second ORU is separated from each other second ORU by at least one ORU, or at least 2, 3, 4, 5, 6, 8, 10, 12, 15, or 20 ORUs each, having a thickness differing from the second thickness by greater than Pl%. In some embodiments, the second thickness is different from the first thickness by at least about 10, 15, 20, 30, 40, 50, 60, 70, 80, 90, or 100 nm. In some embodiments, the second thickness is different from the first thickness by at least about 1.2, 1.5, 1.8, 2, 2.2, 2.4, or 2.5 times Pl%. Each of the second ORUs is typically different from each of the first ORUs. In some embodiments, the thickness of each of the at least three second ORUs is within 2.5% of the second thickness and the thickness of each of the at least one ORU, or the at least 2, 3, 4, 5,

[0061] 6, 7, 8, 10, 12, 15, or 20 ORUs, differs from the second thickness by greater than 3%. In some such embodiments, or in other embodiments, each of the at least three second ORUs is within 2, 1.5, or 1 percent of the second thickness. In some such embodiments, or in other embodiments, the thickness of each of the at least one ORU, or the at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, or 20 ORUs, that separates the second ORUs differs from the second thickness by greater than 3.5, 4, or 4.5 percent.

[0062] The at least three first ORUs can be or include at least four first ORUs. In some embodiments, the at least three first ORUs includes up to 15, 12, 10, 8, 7, 6, 5, or 4 first ORUs. Similarly, the at least three second ORUs can be or include at least four second ORUs. In some embodiments, the at least three second ORUs includes up to 15, 12, 10, 8, 7, 6, 5, or 4 second ORUs.

[0063] The optical film 300 can be characterized in terms of ORU thicknesses as described above and / or as described elsewhere herein. Alternatively, or in addition, the optical film 300 can be characterized in terms of resonant wavelengths of the ORUs.

[0064] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10, such that for an incident light 100 incident on the optical film at a first incident angle 0 and for at least one polarization state (e.g., at least one of 101 and 102): each of the ORUs 10 has a peak reflectivity at a corresponding resonant wavelength (RW) in a range of about 300 nm to about 3000 nm; for a first wavelength (e.g., a, al or a2 - see, e.g., FIGS. 2, 4A, 5A) disposed in a visible wavelength range extending from about 420 nm to about 680 nm, the optical film 300 includes at least three first ORUs (e.g, zl-z3, xl-x3 or y l-y3) where each first ORU has an RW within Pl% of the first wavelength, and where each first ORU is separated from each other first ORU by at least one ORU, or at least 2, 3, 4, 5, 6,

[0065] 7, 8, 10, 12, 15, 20 ORUs each, having an RW that differs from the first wavelength by greater than Pl%; and a reflection depth of the optical film from a same first major side of the optical film varies non- monotonically with increasing wavelength of the incident light over the visible wavelength range. In some embodiments, Pl% is in a range of about 1% to about 10% or Pl% can be in any range described elsewhere herein. In some embodiments, the RW of each of the ORUs is at least about 320, 340, 360, 380, or 400 nm. In some such embodiments, or in other embodiments, the RW of each ORU is no more than about 2500, 2000, 1500, 1200, 1000, 900, 800, or 750 nm. In some embodiments, for the incident light 100 incident on the optical film at the first incident angle 0 and for the at least one polarization state: for a second wavelength (e.g., a2) different from the first wavelength (e.g., al) by at least 50, 100, or 150 nm and disposed in the visible wavelength range, the optical film 300 includes at least three second ORUs (e.g., yl-y3) where each second ORU has an RW within Pl% of the second wavelength. In some embodiments, each second ORU is separated from each other second ORU by at least one ORU, or at least 2, 3, 4, 5, 6, 7, 8, 10, 12, 15, 20 ORUs each, having an RW that differs from the second wavelength by greater than P 1 %.

[0066] The percentage differences between the RW of the first (or second) ORUs from the first (or second) wavelength and the percentage difference of the RW of the ORUs between the first (or second) ORUs can be in any of the corresponding ranges described for the ORU thicknesses. For example, in some embodiments, the RW of each of the at least three first ORUs is within 2.5, 2, 1.5, or 1% of the first wavelength and the RW of each of the at least one ORU differs from the first wavelength by greater than 3%. In some such embodiments, or in other embodiments, the RW of each of the at least one ORU differs from the first wavelength by greater than 3.5, 4, or 4.5%. In some embodiments, each first ORU is separated from each other first ORU by at least one ORU having a RW differing from the first wavelength by greater than Pl% + 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, or 10%. In some embodiments, each first ORU is separated from each other first ORU by at least 2, 3, 4, 5, 6, or 7 ORUs, where each of the at least 2, 3, 4, 5, 6, or 7 ORUs has an RW differing from the first wavelength by greater than Pl%. In some embodiments, each of the at least 2, 3, 4, 5, 6, or 7 ORUs has an RW differing from the first wavelength by greater than Pl% + 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, or 10%.

[0067] In some embodiments, as described further elsewhere herein, for an incident light 100 incident on the optical film 300 at a first incident angle 0 and for at least one polarization state (e.g., 101 and / or 102), a reflection depth of the optical film 300 from a same first major side (e.g., 301) of the optical film 300 varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range (e.g., a visible wavelength range of about 400 nm to about 700 nm or about 420 nm to about 680 nm). In some embodiments, for the incident light 100 incident on the optical film at the first incident angle 0 and for the at least one polarization state: the plurality of ORUs 10 has first, second, and third average reflection depths Fl, F2, F3 (see, e.g., FIGS. 13-14) relative to the same first major side 301 of the optical film 300 in respective non-overlapping first, second, and third wavelength ranges (W1 to W2, W3 to W4, and W5 to W6), where the second wavelength range is disposed between the first and third wavelength ranges. In some embodiments, the second average reflection depth F2 differs (e.g., V2) from each of the first and third average reflection depths Fl and F3 by at least about 1.2, 1.25, 1.3, 1.35, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 5, 6, 7, 8, 9, or 10 times a separation VI between the first and third average reflection depths. In some embodiments, the second average reflection depth F2 is less than about 10, 9, 8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, or 4 micrometers.

[0068] In some embodiments, as described further elsewhere herein, the plurality of ORUs 10 is disposed on a same first major surface 124a of a macrolayer 124 having an average thickness greater than about 500 nm (or in a range described elsewhere herein). In some embodiments, for the incident light 100 incident on the optical fdm 300 at the first incident angle 0 and for the at least one polarization state: for a first wavelength (e.g., W7 in FIG. 14; or between W1 and W2 or between W5 and W6 in FIG. 13; and / or а, al or a2 - see, e.g., FIGS. 2, 4A, 5A) in the predetermined wavelength range, a reflection depth of the plurality of ORUs relative to the first major surface of the macrolayer is less than about 10, 9, 8, 7.5, 7, б.5, 6, 5.5, 5, 4.5, 4 micrometers. The reflection depth can be at least about 0.25, 0.5, 1, or 1.5 micrometers, for example. The first wavelength can be a green wavelength (e.g., about 525 nm) in a range from about 490 nm to about 560 nm, for example. In some embodiments, for the incident light incident on the optical film at the first incident angle and for the at least one polarization state: for a wavelength range at least 20, 25, 30, 35, 40, 45, 50, 55, or 60 nm wide and substantially centered on the first wavelength (e.g., the first wavelength can be closer to the a center of the wavelength range than to either edge of the wavelength range), the plurality of ORUs has an average reflectance of greater than about 60, 70, 80, 85, 90, or 95%. The wavelength range can be from about 490 nm to about 560 nm, for example. In some embodiments, the wavelength range extends between first and second end wavelengths and has a center wavelength being a mean of the first and second end wavelengths. In some embodiments, an absolute value of a difference between the first wavelength and the center wavelength is less than about 25, 20, 15, 10 or 5 percent of an absolute value of a difference between the first and second end wavelengths. In some embodiments, the first wavelength is equal to or about equal to the center wavelength.

[0069] The optical film 300 can optionally include additional groups of the ORUs 10 not shown in FIGS. 2 through 5B. For example, one or more groups of ORUs can optionally be disposed between ORUs 36f and 37a in FIG. 4A, or after (higher ORU number or depth) ORU 36c in FIG. 4A, or between group 33 and ORU 39 in FIG. 5B. The additional groups of the ORUs may include at least one group for reflecting in different wavelength ranges (e.g., different from dl, d2, d3) and / or can include at least one additional groups reflecting in a same range as one or more of the illustrated groups (e.g., one or more of dl, d2, d3).

[0070] FIG. 6 is a plot of resonant wavelength versus depth from a same major side of an optical film 300, according to some embodiments. Non-overlapping plots 190 through 194 and 190' through 193' are illustrated in FIG. 6. FIG. 7 shows polynomial fits (best quadratic fits) 190a through 193a to the respective non-overlapping plots 190 through 193 of portions of the plot of resonant wavelength versus depth of FIG. 6. Similar polynomial fits can be constructed for the non-overlapping plots 190' through 193' and 194. FIG. 8 is a plot of slopes 190b through 193b of the respective fits 190a through 193a of FIG. 7 versus resonant wavelength. The resonant wavelengths of FIG. 6 were determined for light incident on the optical film from a glass having a refractive index of about 1.8 at a visible wavelength (e.g., about 633 nm).

[0071] FIG. 9 is a plot of ORU thickness versus ORU number for an optical film 300, according to some embodiments. The plot of FIGS. 6 and 9 can be for a same optical film. Non-overlapping plots 90 through 94 and 90' through 93' are illustrated in FIG. 9. FIG. 10 shows linear fits 90a through 93a to the respective non-overlapping plots 90 through 93 of portions of the plot of ORU thickness versus ORU number of FIG. 9. Similar linear fits can be constructed for the non-overlapping plots 90' through 93' and 94.

[0072] FIG. 11A is plot of resonant wavelength versus depth from a same major side of an optical film, according to some embodiments. FIG. 1 IB is a portion of the plot of FIG. 11A. FIG. 12A is plot of ORU thickness versus ORU number, according to some embodiments. FIG. 12B is a portion of the plot of FIG. 12A. The plot of FIGS. 11A-1 IB and 12A-12B can be for a same optical film.

[0073] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, such that for a first thickness range (e.g., dl or d3 in FIG. 5B or dl, d2, or d3 in FIG. 4B) at least about 20 nm wide, a scatter plot 20 of thicknesses versus the numbers of the ORUs comprises at least first, second and third non-overlapping plots (e.g., 90-93 and / or 9O'-94' in FIG. 9; or 90-93 in FIG. 12B) of the sequentially numbered ORUs, with each ORU of each of the at least first, second and third non-overlapping plots having a thickness in the first thickness range, and with each of the at least first, second and third non-overlapping plots comprising at least 2, 3, 4, 5, 6, or 7 of the ORUs in the plurality of ORUs 10. In some embodiments, magnitudes of slopes of best linear fits (e.g., best linear fits 90a-93a of FIG. 10 having respective slopes of about 9.5, 65, 1.7, and 0.85 nm per ORU number) to at least two of the at least the first through the third non-overlapping plots are different by at least about 20%, 30%, 40%, 50%, 75%, 100%, 250%, 500%, or different by at least a factor of about 5, 6, 7, 8, 9, 10, or 11. In some embodiments, the first thickness range is least about 30, 40, or 50 nm wide. The first thickness range can be up to about 200, 150, 100, or 75 nm wide, for example.

[0074] In some embodiments, for a second thickness range (e.g., a different one of dl or d3 in FIG. 5B or dl, d2, or d3 in FIG. 4B) at least about 20 nm wide and non-overlapping with the first thickness range, the scatter plot 20 of thicknesses versus the numbers of the ORUs comprises at least fourth, fifth, and sixth non-overlapping plots (e.g., different ones of 90-93 and / or 90' -94' in FIG. 9; or 90-93 in FIG. 12B) of the sequentially numbered ORUs, with each ORU of each of the at least fourth, fifth, and sixth nonoverlapping plots having a thickness in the second thickness range, and with each of the at least fourth, fifth, and sixth non-overlapping plots comprising at least 2, 3, 4, 5, 6, or 7 of the ORUs in the plurality of ORUs 10. In some embodiments, magnitudes of slopes of best linear fits to at least two of the at least the fourth through the sixth non-overlapping plots are different by at least about 20%, 30%, 40%, 50%, 75%, 100%, 250%, 500%, or different by at least a factor of about 5, 6, 7, 8, 9, 10, or 11. The width of the second thickness range can be in any of the ranges described elsewhere herein for the width of the first thickness range.

[0075] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that for a first wavelength range (e.g., dl or d3 in FIG. 5B or dl, d2, or d3 in FIG. 4B) at least about 40 nm wide, a scater plot 20 of RWs of the ORUs versus depths of the ORUs relative to a same major side (e.g., 301) of the optical film 300 includes comprises at least first, second and third non-overlapping plots (e.g., 190-193 and / or 190' - 194' in FIG. 6 or 190-193 in FIG. 1 IB) of the ORUs, with each ORU of each of the at least first, second and third non-overlapping plots having a RW in the first wavelength range, and with each of the at least first, second and third non-overlapping plots comprising at least 2, 3, 4, 5, 6, or 7 of the ORUs in the plurality of ORUs and having a slope (e.g., 190b-193b in FIG. 8) being a rate of change of the RW with respect to the depth (i.e., d(RW) / d(depth)) at a same first RW (e.g., first RW 95 in FIG. 8). The slopes can be determined from best polynomial (e.g., quadratic) fits (e.g., best quadratic fits 190a- 193a in FIG. 7). In some embodiments, magnitudes of the slopes (e.g., slope magnitudes of about 62, 42, 11, and 5.5 at the first RW 95) of at least two of the at least the first through the third plots are different by at least about 20%, 30%, 40%, 50%, 75%, 100%, 250%, or 500%, or different by at least a factor of about 5, 6, 7, 8, 9, 8, 9, 10, or 11. The slope magnitudes can be different by up to a factor of about 50, 40, 30, 20, or 15, for example. In some embodiments, the first wavelength range is at least about 50, 60, 70, 80, 90, or 100 nm wide. The first wavelength range can be up to about 500, 400, 300, 200, or 150 nm, for example.

[0076] In some embodiments, for a second wavelength range (e.g., another one of dl or d3 in FIG. 5B or dl, d2, or d3 in FIG. 4B) at least about 40 nm wide and non-overlapping with the first wavelength range, the scater plot 20 of RWs of the ORUs versus depths of the ORUs relative to the same major side (e.g., 301) of the optical film 300 includes comprises at least fourth, fifth and sixth non-overlapping plots (e.g., another one 190-193 and / or 190' - 194' in FIG. 6 or 190-193 in FIG. 1 IB) of the ORUs, with each ORU of each of the at least fourth, fifth and sixth non-overlapping plots having a RW in the second wavelength range, and with each of the at least fourth, fifth and sixth non-overlapping plots comprising at least 2, 3, 4, 5, 6, or 7 of the ORUs in the plurality of ORUs and having a slope (e.g., 190b-193b in FIG. 8) being a rate of change of the RW with respect to the depth (i.e., d(RW) / d(depth)) at a same first RW (e.g., first RW 95 in FIG. 8). In some embodiments, magnitudes of the slopes of at least two of the at least the fourth through the sixth plots are different by at least about 20%, 30%, 40%, 50%, 75%, 100%, 250%, or 500%, or different by at least a factor of about 5, 6, 7, 8, 9, 8, 9, 10, or 11. The slope magnitudes can be different by up to a factor of about 50, 40, 30, 20, or 15, for example. The width of the second wavelength range can be in any of the ranges described elsewhere herein for the width of the first wavelength range.

[0077] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that when in a scater plot 20 of the RWs of the ORUs versus depths of the ORUs relative to a same major side (e.g., 301) of the optical film 300, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines (e.g., first lines 24 in FIG. 3, 4A, or 5A) where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines (e.g., second lines 25 in FIG. 3, 4A, or 5A) where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth (note that the ORU number or depth could be taken from the opposite major side of the optical fdm 300 from any of the illustrated plots so that each line where ORU thickness or RW increases with increasing ORU number or depth would become a line where the ORU thickness or RW increases with decreasing ORU number or depth). The intersection points can form a plurality of alternating peaks and valleys (e.g., 36a-36c and 37a-37c in FIGS. 4A or 5A; or 36d-36f and 37d-37f in FIG. 3 or 4A). In some embodiments, a first one of the plurality of first lines 24 includes a plurality of first straight line segments collectively extending from a first valley (e.g., 37b) of the plurality of alternating peaks and valleys to a first peak (e.g., 36b) of the plurality of alternating peaks and valleys (i.e., the first straight line segments in combination extend from the first valley to the first peak), where slopes of the first straight line segments have minimum and maximum slope magnitudes (e.g., the minimum and maximum slope magnitudes can occur for respective straight line segments 24a and 24b in FIG. 4A or 5A, or corresponding straight line segments in FIG. 6). In some embodiments, the minimum slope magnitude is at least about 5, 6, 8, 10, 12, 15, 20, 25, 30, or 35 nm / micron. In some such embodiments, or in other embodiments, the maximum slope magnitude is at least about 3, 5, 7, 10, 12, 15, 20, or 25 times greater than the minimum slope magnitude. The minimum slope magnitude can be up to about 400, 300, 250, 200, 150, or 100 nm / micron, for example. The maximum slope magnitude can be up to about 500, 250, 200, 150, 100, 80, 60, or 50 times the minimum slope magnitude, for example. In some embodiments, the maximum slope magnitude is in a range of about 150 to 600 nm / micron, for example. In some embodiments, the plurality of alternating peaks and valleys comprises at least three peaks alternating with at least two valleys. In some embodiments, at least two of the first lines in the plurality of the first lines are substantially parallel (e.g., having slopes for corresponding ORU thicknesses or RWs with the same sign and with magnitudes within about 30, 20, 10, or 5% of one another). In some embodiments, at least two of the second lines in the plurality of the second lines are substantially parallel. For example, in FIG. 3, the first three first lines 24 (from 37d to 36d; from 37e to 36e; and from 37f to 36f) are substantially parallel and the first two second lines 25 (from 36d to 37e; and from 36e to 37f) are substantially parallel. As another example, in FIG. 5A, the first three first lines 24 (from 37a to 36a; from 37b to 36b; and from 37c to 36c) are substantially parallel and the first two second lines 25 (from 36a to 37b; and from 36b to 37c) are substantially parallel. Similarly, the first two first lines 24 and the first two second lines 25 in FIGS. 6 and 9, for example, are substantially parallel. In some embodiments, at least one of the first straight line segments (e.g., a first straight line segment 24b that has the maximum slope) extends over an ORU RW range of at least about 40, 50, 60, 70, 75, or 80 nm. The ORU RW range can be up to about 400, 300, 250, 200, 175, 150, or 125 nm, for example.

[0078] Others of the first lines can have similar slope magnitude minima and maxima. For example, in some embodiments, a second one, different from the first one, of the first lines of the plurality of first lines comprises a plurality of second straight line segments collectively extending from a second valley (different from the first valley) of the plurality of alternating peaks and valleys to a second peak (different from the first peak) of the plurality of alternating peaks and valleys, where slopes of the second straight line segments include second minimum and maximum slope magnitudes. The second minimum slope magnitude can be at least about 5 nm / micron (or in another range described for the minimum slope magnitude), and the second maximum slope magnitude can be at least about 3 (or another range described for the ratio of maximum to minimum slope magnitudes) times greater than the second minimum slope magnitude.

[0079] The terms “substantially increases” and “substantially decreases” should be understood to mean that the increase or decrease occurs in a general sense with the changing ORU number or ORU depth, while allowing for noise and / or process variations which may vary from the general trend. That is, while the RW or thickness may generally increase or decrease with changing ORU number or depth, one or more pairs of adjacent plot points may be reversed from the overall trend. The term “line” in the context of a continuous line plot formed from straight line segments between data points in a scatter plot of ORU thicknesses or RWs versus ORU number or depth should be understood to be a collection of adjacent straight line segments where the ORU thickness or RW in the straight line segments substantially increases with a same one of increasing and decreasing ORU number or depth. For example, in FIGS. 4A and 5 A, a line 24 between valley 37b and peak 36b includes the straight line segments 24a and 24b. A “line” in this context can be a straight or approximately straight line or can be a non-straight line (e.g., curved and / or including one or more bends).

[0080] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, such that when adjacent data points in a scatter plot 20 of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot includes a plurality of first lines (e.g., first lines 24 in FIG. 3, 4A, or 5A) where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines (e.g., second lines 25 in FIG. 3, 4A, or 5A) where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number. The intersection points can form a plurality of alternating peaks and valleys (e.g., 36a-36c and 37a-37c in FIGS. 4A or 5A; or 36d-36f and 37d-37f in FIG. 3 or 4A). In some embodiments, one of the first lines of the plurality of first lines 24 includes a plurality of first straight line segments (e.g., 24a, 24b) collectively extending from a first valley (e.g., 37b) of the plurality of alternating peaks and valleys to a first peak (e.g., 36b) of the plurality of alternating peaks and valleys, where slopes of the first straight line segments include minimum and maximum slope magnitudes (e.g., the minimum and maximum slope magnitudes can occur for respective first straight line segments 24a and 24b in FIG. 4A or 5A, or for corresponding first straight line segments of FIG. 9). In some embodiments, the minimum slope magnitude is at least about 0.5, 0.7, 0.9, 1, 1.1, 1.2, 1.3, 1.5, 1.7, 2, 2.5, 3, 4, 5, or 6 nm per ORU number. In some such embodiments, or in other embodiments, the maximum slope magnitude at least about 3, 5, 7, 10, 12, 15, 20, or 25 times greater than the minimum slope magnitude. The minimum slope magnitude can be up to about 100, 80, 60, 40, 30, 20, or 15 nm per ORU, for example. The maximum slope magnitude can be up to about 500, 250, 200, 150, 100, 80, 60, or 50 times the minimum slope magnitude, for example. In some embodiments, the maximum slope magnitude is in a range of about 20 to 100 nm per ORU, for example. In some embodiments, the plurality of alternating peaks and valleys comprises at least three peaks alternating with at least two valleys. In some embodiments, at least two of the first lines in the plurality of the first lines are substantially parallel. In some embodiments, at least two of the second lines in the plurality of the second lines are substantially parallel. In some embodiments, at least one of the first straight line segments (e.g., a first straight line segment 24b that has the maximum slope) extends over an ORU thickness range of at least about 20, 25, 30, 35, 40, 45, or 50 nm. The ORU thickness range can be up to about 300, 200, 150, 100, or 75 nm, for example.

[0081] Others of the first lines can have similar slope magnitude minima and maxima. For example, in some embodiments, a second one, different from the first one, of the first lines of the plurality of first lines comprises a plurality of second straight line segments collectively extending from a second valley (different from the first valley) of the plurality of alternating peaks and valleys to a second peak (different from the first peak) of the plurality of alternating peaks and valleys, where slopes of the second straight line segments include second minimum and maximum slope magnitudes. The second minimum slope magnitude can be at least about 0.5 nm per ORU number (or in another range described for the minimum slope magnitude), and the second maximum slope magnitude can be at least about 3 (or another range described for the ratio of maximum to minimum slope magnitudes) times greater than the minimum slope magnitude.

[0082] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that when in a scatter plot 20 of the RWs of the ORUs versus depths of the ORUs relative to a same major side (e.g., 301) of the optical film 300, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines 24 where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines 25 where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth. The intersection points can form at least a first plurality of alternating peaks and valleys (e.g., 36d-36f and 37d-37f in FIG. 3 or 4A), where for each pair of adjacent peak and valleys (e.g., 36d and 37e; or 36e and 37f) in the first plurality of alternating peaks and valleys, a difference in ORU RWs of the peak and the valley is greater than about 5 nm and less than about 200 nm. In some embodiments, for each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, the difference in ORU RWs of the peak and the valley is greater than about 6, 7, 8, 0, 10, 12, 15, 20, 25, or 30 nm. In some such embodiments, or in other embodiments, for each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, the difference in ORU RWs of the peak and the valley is less than about 180, 160, 140, 120, 100, 90, 80, or 70 nm. For a pair of peaks and valleys to be considered to be a pair of adjacent peaks and valleys in a plurality of alternating peaks and valleys, there should be no peak and no valley of the plurality of alternating peaks and valleys that is disposed between the peak and valley of the pair. In some embodiments, the intersection points form a second plurality of alternating peaks and valleys (e.g., 36a-36c and 37a-37c in FIG. 4A) not overlapping the first plurality of alternating peaks and valleys. In some embodiments, for at least one pair (e.g., 36a and 37b) of adjacent peak and valleys in the second plurality of alternating peaks and valleys, a difference in ORU RWs of the peak and the valley is greater than about 200, 220, 240, 260, or 280 nm. In some embodiments, for each pair of adjacent peak and valleys in the second plurality of alternating peaks and valleys, a difference in ORU RWs of the peak and the valley is greater than about 200, 220, 240, 260, or 280 nm. The difference can be up to about 3000, 2500, 2000, 1500, 1000, 800, 600, 500, or 400 nm, for example.

[0083] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, such that when adjacent data points in a scatter plot 20 of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot includes a plurality of first lines 24 where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines 25 where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number. The intersection points can form at least a first plurality of alternating peaks and valleys (e.g., 36d-36f and 37d-37f in FIG. 3 or 4A), where for each pair (e.g., 36d and 37e; or 36e and 37f) of adjacent peak and valleys in the first plurality of alternating peaks and valleys, a difference in ORU thicknesses of the peak and the valley is greater than about 3 nm and less than about 120 nm. In some embodiments, for each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, the difference in ORU thicknesses of the peak and the valley is greater than about 4, 5, 6, 7, 8, 0, 10, 12, 15, or 20 nm. In some such embodiments, or in other embodiments, for each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, the difference in ORU thicknesses of the peak and the valley is less than about 100, 90, 80, 70, 60, 50, or 40 nm. In some embodiments, the intersection points form a second plurality of alternating peaks and valleys (36a-36c and 37a-37c in FIG. 4A) not overlapping the first plurality of alternating peaks and valleys. In some embodiments, for at least one pair (e.g., 36a and 37b) of adjacent peak and valleys in the second plurality of alternating peaks and valleys, a difference in ORU thicknesses of the peak and the valley is greater than about 120, 125, 130, 135, 140, 145, or 150 nm. In some embodiments, for each pair of adjacent peak and valleys in the second plurality of alternating peaks and valleys, a difference in ORU thicknesses of the peak and the valley is greater than about 120, 125, 130, 135, 140, 145, or 150 nm. The difference can be up to about 1500, 1000, 750, 500, 400, 300, 250, or 200 nm, for example. In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where the ORUs in the plurality of ORUs 10 are sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, such that for nonoverlapping first and second thickness ranges (e.g., one of dl and d3, and d2 in FIG. 4B or 5B) at least about 5 nm wide, a scatter plot 20 of the thicknesses versus the numbers of the ORUs includes at least three non-overlapping first groups (e.g., one of 31-33 and 135-137) of sequentially numbered ORUs of the plurality of the ORUs, where each ORU of each of the first groups has a thickness in the first thickness range (one of dl and d3), each of the first groups includes at least three sequentially numbered ORUs in the plurality of ORUs, and each first group is separated from each other first group by at least two sequentially numbered ORUs of the plurality of ORUs having thicknesses not in the first thickness range. The scatter plot 20 further includes a second group (e.g., group 34 or 134) of at least 8, 10, 12, 15, 20, 30, 40, 50, 60, or 70 ORUs of the plurality of the ORUs, each ORU of the second group having a thickness in the second thickness range (e.g., d2). The plurality of ORUs 10 can include first and second ORUs 39 and 49 each having a thickness outside the second thickness range with the second group 134 disposed between the first and second ORUs 39 and 49. In some embodiments, each of the first and second thickness ranges is at least about 7, 10, 12, 15, 20, 25, or 30 nm wide. In some embodiments, for a third thickness range (the other of dl and d3) at least about 5 nm wide and non-overlapping with the first and second thickness ranges, the scatter plot of the thicknesses versus the numbers of the ORUs includes at least three non-overlapping third groups (e.g., the other of 31-33 and 135-137) of sequentially numbered ORUs of the plurality of the ORUs, where each ORU of each of the third groups has a thickness in the third thickness range, each of the third groups includes at least three sequentially numbered ORUs in the plurality of ORUs, and each third group is separated from each other third group by at least two sequentially numbered ORUs of the plurality of ORUs having thicknesses not in the third thickness range. In some embodiments, the third thickness range is at least about 7, 10, 12, 15, 20, 25, or 30 nm wide. The first, second, and / or third thickness range can be up to about 700, 500, 400, 300, 200, 150, or 100 nm wide, for example. In some embodiments, each of the first and second ORUs 39 and 49 has a thickness outside of each of the first, second, and third thickness ranges dl, d2, and d3. In some embodiments, an average slope magnitude of the scatter plot in each of first groups is greater than an average slope magnitude of the scatter plot in the second group by at least a factor of 1.2, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, or 10. The average slope magnitude is the average (unweighted mean) of the magnitude (absolute value) of the slope of the scatter plot (e.g., average over the straight line segments of the line 24 and / or 25 between adjacent ORUs in the group). In some embodiments, the optical film 300 includes no group of at least 8, 10, 12, 20, 30, 40, 50, 60, 70, 80, 90, or 100 sequentially numbered ORUs where each ORU in the group has a thickness in the second thickness range (e.g., d2) and where the group is nonoverlapping with the second group. In some embodiments, the ORUs of the second group are sequential in the sequentially numbered ORUs. In some embodiments, the ORUs of the second group are contiguous with one another. In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW) and where the ORUs in the plurality of the ORUs are sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film, such that for non-overlapping first and second wavelength ranges (e.g., one of dl and d3, and d2 in FIG. 4B or 5B) at least about 15 nm wide, a scatter plot 20 of the RWs versus the numbers of the ORUs includes at least three nonoverlapping first groups (e.g., one of 31-33 and 135-137) of sequentially numbered ORUs of the plurality of the ORUs, where each ORU of each of the first groups has an RW in the first wavelength range, each of the first groups includes at least three sequentially numbered ORUs in the plurality of ORUs, and each first group is separated from each other first group by at least two sequentially numbered ORUs of the plurality of the ORUs having RWs not in the first wavelength range. The scatter plot 20 further includes a second group (e.g., 34 or 134) of at least 8, 10, 12, 15, 20, 30, 40, 50, 60, or 70 ORUs of the plurality of the ORUs, where each ORU of the second group has an RW in the second wavelength range. The plurality of ORUs can include first and second ORUs 39 and 49 each having an RW outside the second wavelength range with the second group 134 disposed between the first and second ORUs 39 and 49. In some embodiments, each of the first and second wavelength ranges is at least about 20, 25, 30, 35, 40, 45, 50, 55, 60 nm wide. In some embodiments, for a third wavelength range (the other of dl and d3) at least about 15 nm wide and non-overlapping with the first and second wavelength ranges, the scatter plot of the RWs versus the numbers of the ORUs includes at least three non-overlapping third groups (e.g., the other of 31-33 and 135-137) of sequentially numbered ORUs of the plurality of the ORUs, where each ORU of each of the third groups has an RW in the third wavelength range, each of the third groups includes at least three sequentially numbered ORUs in the plurality of ORUs, and each third group is separated from each other third group by at least two sequentially numbered ORUs of the plurality of ORUs having RWs not in the third wavelength range. In some embodiments, the third wavelength range is at least 7, 10, 12, 15, 20, 25, or 30 nm wide. In some embodiments, the third wavelength range is at least about 20, 25, 30, 35, 40, 45, 50, 55, 60 nm wide. The first, second, and / or third wavelength range can be up to about 2000, 1000, 700, 500, 400, 300, or 250 nm wide, for example. In some embodiments, each of the first and second ORUs 39 and 49 has an RW outside of each of the first, second, and third wavelength ranges dl, d2, and d3. In some embodiments, the optical film 300 includes no group of at least 8, 10, 12, 15, 20, 30, 40, 50, 60, 70, 80, 90, or 100 sequentially numbered ORUs where each ORU in the group has an RW in the second wavelength range (e.g., d2) and where the group is non-overlapping with the second group. In some embodiments, the ORUs of the second group are sequential in the sequentially numbered ORUs. In some embodiments, the ORUs of the second group are contiguous with one another.

[0084] In some embodiments, an optical film includes a plurality of optical repeat units (ORUs) 10 where the ORUs in the plurality of the ORUs 10 are sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300. In some embodiments, a scatter plot 20 of the thicknesses versus the numbers of the ORUs includes at least three non-overlapping first groups of the ORUs (e.g., 31 and 135; 32 and 136; and 33 and 137 - see, e.g., FIGS. 4B and 5B), where each group of the first groups includes at least three of the sequentially numbered ORUs in the plurality of ORUs including first and second ORUs (e.g., 36a and 37a; 36b and 37b; and 36c and 37c - see, e.g., FIGS. 4A and 5A) having respective maximum and minimum thicknesses among the at least three ORUs in the group. In some embodiments, for each group of the first groups, the minimum and maximum thicknesses in the group are different ([maximum - minimum] / minimum times 100%) from each other by at least about 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70% (see, e.g., FIGS. 4A, 5A, 9). The minimum and maximum thicknesses in each group can be different by up to about 600, 500, 400, 300, 250, 200, 150, or 100%, for example. In some embodiments, for each of the first ORUs and the second ORUs in the at least three non-overlapping first groups of the ORUs, the thicknesses of the ORUs are within about 10, 9, 8, 7, 6, 5, or 4% of each other. The scatter plot 20 can further include at least one second group (e.g., 34 or 134 - see, e.g., FIGS. 4B and 5B) of the ORUs 10, where each second group is non-overlapping with each first group.

[0085] In some embodiments, the optical film 300 includes a plurality of optical repeat units (ORUs) 10 where each of the ORUs have a peak reflectivity at a corresponding resonant wavelength (RW). In some embodiments, a scatter plot 20 of the RWs of the ORUs versus depths of the ORUs relative to a same major side (e.g., 301) of the optical film 300 includes at least three non-overlapping first groups of the ORUs (e.g., 31 and 135; 32 and 136; and 33 and 137 - see, e.g., FIGS. 4B and 5B), where each group of the first groups includes at least 3 of the sequentially numbered ORUs in the plurality of ORUs including first and second ORUs (e.g., 36a and 37a; 36b and 37b; and 36c and 37c - see, e.g., FIGS. 4A and 5A) having respective maximum and minimum RWs among the at least three ORUs in the group. In some embodiments, for each group of the first groups, the minimum and maximum RWs in the group are different ([maximum - minimum] / minimum times 100%) from each other by at least 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or 70% (see, e.g., FIGS. 4A, 5A, 6). The minimum and maximum RWs in each group can be different by up to about 600, 500, 400, 300, 250, 200, 150, or 100%, for example. In some embodiments, for each of the first ORUs and the second ORUs in the at least three non-overlapping first groups of the ORUs, the RWs of the ORUs are within about 10, 8, 6, 5, or 4% of each other. The scatter plot 20 can further include at least one second group (e.g., 34 or 134 - see, e.g., FIGS. 4B and 5B) of the ORUs 10, where each second group is non-overlapping with each first group.

[0086] FIGS. 13-14 are schematic plots of reflection depth from a same major side of an optical film versus wavelength, according to some embodiments. FIG. 13 can correspond to the optical films of FIGS. 5A-5B, 6, or 9, for example. An example modeled optical film of FIGS. 6 and 9, for example, had average reflection depths of about 12. 4, 88.9, and 19.1 micrometers for respective wavelengths of 450, 525, and 615 nm, for example. FIG. 14 can correspond to the optical films of FIGS. 3, or 11A-12B, for example. An example modeled optical film of FIGS. 11A to 12B, for example, had average reflection depths of about 29.4, 3.7, and 48.9 micrometers for respective wavelengths of 450, 525, and 615 nm, for example. A related example that included a fourth stack (e.g., in addition to stacks 34a-34c in FIG. 4B) of ORUs for reflecting in a green wavelength range and that had a fewer total number of ORUs (75 instead of 300) had average reflection depths of about 7.1, 1.7, and 11.5 micrometers for respective wavelengths of 450, 525, and 615 nm, for example. The reflection depths in FIG. 14 for the wavelength ranges W1 to W2 and W5 to W6 may be made closer to one another by replacing the stacks of ORUs 10 producing the reflection in these ranges (see, e.g., FIG. 3) with multiple stacks for each range as schematically illustrated in FIGS. 4A-4B, for example. In some embodiments, W1 is about 300, 320, 340, 360, 380, 400, or 420 nm. In some embodiments, W6 is about 3000, 2500, 2000, 1500, 1200, 1000, 900, 800, 750, 700, 680, or 670 nm. In some embodiments, W2 is about 470 or 480 nm. In some embodiments, W3 is about 490 or 500 nm. In some embodiments, W4 is about 550, 560, or 570 nm. In some embodiments, W5 is about 580, 590, or 600 nm. In some embodiments, W7 is in a range of about 510 nm to about 540 nm, or about 520 to about 530 nm (e.g., W7 can be about 525 nm).

[0087] In some embodiments, the optical fdm 300 includes a macrolayer 124 and a plurality of optical repeat units (ORUs) 10 disposed on a same first major surface 124a of the macrolayer 124. The plurality of ORUs 10 is disposed on a same side of the macrolayer 124 and may be disposed between outermost first and second macrolayers 124 and 126. In some embodiments, for an incident light 100 incident on the optical film at a first incident angle 0 and for at least a first polarization state (e.g., polarization state 101 and / or 102): the plurality of ORUs 10 has first, second, and third average reflection depths F1-F3 relative to the first major surface 124a of the macrolayer 124 in respective non-overlapping first, second, and third wavelength ranges (e.g., W1-W2, W3-W4, and W5-W6), where the second wavelength range is disposed between the first and third wavelength ranges. In some embodiments, the second average reflection depth F2 differs (e.g., difference V2 or each of |F2-F 11 and |F2-F3|) from each of the first and third average reflection depths by at least about 1.2, 1.22, 1.24, 1.26, 1.28, 1.3, 1.35, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.25, 2.5, 2.75, 3, 3.5, 4, 5, 6, 7, 8, 9, or 10 times a difference (e.g., VI) between the first and third average reflection depths Fl and F3. In some embodiments, each of the first, second, and third wavelength ranges is at least about 20, 25, 30, 35, 40, 45, 50, 55, or 60 nm wide. In some embodiments, each of the first, second, and third wavelength ranges is disposed between about 380, 400, or 420 nm and about 3000, 2500, 2000, 1500, 1200, 900, 88, 700, and 680 nm. For example, in some embodiments, each of the first, second, and third wavelength ranges is disposed between about 380 nm and about 2500 nm, or between about 400 nm and about 700 nm, or between about 420 nm and about 680 nm. In some embodiments, the first, second and third wavelength ranges are respective blue, green, and red wavelength ranges. In some embodiments, the blue wavelength range extends from about 420 nm to about 480 nm, the green wavelength range extends from about 490 nm to about 560 nm, and the red wavelength range extends from about 590 nm to about 670 nm. In some embodiments, for the incident light 100 incident on the optical film at the first incident angle 0 and for at least the first polarization state (e.g., polarization state 101 and / or 102), the optical film has an average reflectance in each of the first, second, and third wavelength ranges of at least about 60, 70, 80, 85, 90, or 95%. In some embodiments, the second average reflection depth F2 is less than about 10, 9, 8, 7.5, 7,

[0088] 6.5, 6, 5.5, 5, 4.5, 4, 3.5, 3, 2.5, or 2 micrometers. In some embodiments, the first and third average reflection depths Fl and F3 are within about 23, 22.5, 22, 21.5, 21, 20.5, 20, 19.5, 19, 17, 15, 12, 10, 9, 8, 7, 6, or 5 micrometers of one another. In some such embodiments, or in other embodiments, the second average reflection depth F2 differs from each of the first and third average reflection depths F 1 and F3 by greater than about 23, 23.5, 24, 24.5, 25, 25.5, 26, 30, 35, 40, 45, 50, 55 or 60 micrometers. For example, in some embodiments, the first and third average reflection depths Fl and F3 are within about 21.5 micrometers of one another, and the second average reflection depth F2 differs from each of the first and third average reflection depths Fl and F3 by greater than about 24.5 micrometers. As another example, in some embodiments, the first and third average reflection depths Fl and F3 are within about 8 micrometers of one another, and the second average reflection depth F2 differs from each of the first and third average reflection depths Fl and F3 by greater than about 40 micrometers. In some embodiments, each of Fl, F2, and F3 is in a range of about 5% to about 95% or about 10% to about 90% of a total average thickness of the plurality of optical repeat units 10.

[0089] In some embodiments, as described further elsewhere herein, the plurality of ORUs 10 include at least three first ORUs (e.g., xl-x3, yl-y3, or zl-z3 - see, e.g., FIGS. 4A and 5A) that have thicknesses within Pl% of a same first thickness (e.g., al, a2, or a), where each first ORU is separated from each other first ORU by at least one ORU having a thickness differing from the first thickness by greater than Pl%, where Pl% is in a range of about 1% to about 10% or another range described elsewhere herein.

[0090] In some embodiments, the first incident angle 0 is less than about 30, 25, 20, 15, 10, or 5 degrees. In some embodiments, the first incident angle 0 is greater than about 5, 10, 15, 20, 25, or 30 degrees. In some such embodiments, or in other embodiments, the first incident angle 0 is less than about 75, 70, 65, 60, 55, 50, 45, 40, 35, or 30 degrees. The first incident angle 0 can be between about 5 degrees and about 75 degrees, or between about 10 degrees and about 70 degrees, or between about 30 degrees and about 60 degrees, for example.

[0091] In some embodiments, each of the ORUs 10 has a peak reflectivity at a corresponding resonant wavelength (RW), and for the incident light 100 incident on the optical film 300 at the first incident angle 0, for at least the first polarization state, and for a first wavelength (e.g., al or al - see, e.g., FIGS. 4A and 5A) in one of the first and third wavelength ranges, the optical film 300 includes at least three first ORUs (e.g., xl-x3 or yl-y3) that have RWs within 20, 15, 12, 10, 9, 8, 7, 6, 5, 4, 3.5, 3, 2.5, 2, 1.5, or 1% of the first wavelength. In some embodiments, the first ORUs are spaced apart from one another along a thickness direction (z-direction) of the optical film 300 by at least about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25,

[0092] 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 17, 18, 19, or 20 micrometers. For example, the first ORUs can be xl-x3 which can have respective depths bl-b3 (see, e.g., FIGS. 4A or 5A) and each of b2- bl and b3-b2 can be at least about 0.5 micrometers or another of these ranges. In some embodiments, the first ORUs are spaced apart from one another along the thickness direction of the optical film 300 by no more than about 150, 100, 50, 30, 20, 15, or 10 micrometers. For example, each of b2-bl and b3-b2 can be in a range of about 0.5 micrometers to about 100 micrometers or about 1 micrometer to about 50 micrometers. In some embodiments, for the incident light 100 incident on the optical fdm 300 at the first incident angle 0, for at least the first polarization state, and for a second wavelength in the other of first and third wavelength ranges, the optical film includes at least three second ORUs that have RWs within 20, 15, 12, 10, 9, 8, 7, 6, 5, 4, 3.5, 3, 2.5, 2, 1.5, or 1% of the second wavelength. In some embodiments, the second ORUs are spaced apart from one another along the thickness direction of the optical film by at least about 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.25, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 17, 18, 19, or 20 micrometers. For example, the second ORUs can be yl-y3 which can have respective depths cl-c3 (see, e.g., FIGS. 4A or 5A) and each of c2-cl and c3-c2 can be at least about 0.5 micrometers or another of these ranges. In some embodiments, the second ORUs are spaced apart from one another along the thickness direction of the optical film 300 by no more than about 150, 100, 50, 30, 20, 15, or 10 micrometers. For example, each of c2-cl and c3-c2 can be in a range of about 0.5 micrometers to about 100 micrometers or about 1 micrometer to about 50 micrometers.

[0093] In some embodiments, the optical film 300 includes a macrolayer 124 and a plurality of optical repeat units (ORUs) 10 disposed on a same first major surface 124a of the macrolayer 124. In some embodiments, when adjacent data points in a scatter plot 20 of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines 24 where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines 25 where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number, such that for an incident light 100 incident on the optical film 300 at a first incident angle 0 and for at least one polarization state (e.g., 101 and / or 102): for a first wavelength (e.g., a, al or a2 - see, e.g., FIGS. 4A and 5A) in a visible wavelength range extending from about 420 nm to about 680 nm, a reflection depth (e.g., F2) of the plurality of ORUs 10 relative to the first major surface 124a of the macrolayer 124 is less than about 10, 9, 8, 7.5, 7, 6.5, 6, 5.5, 5, 4.5, or 4 micrometers. The reflection depth can be at least about 0.25, 0.5, 1, or 1.5 micrometers, for example. In some embodiments, for the incident light 100 incident on the optical film 300 at the first incident angle 0 and for the at least one polarization state, for a wavelength range (e.g., W3 to W4 - see, e.g., FIGS. 13-14) at least 20, 25, 30, 35, 40, 45, 50, 55, or 60 nm wide and substantially centered on the first wavelength (e.g., W7), the plurality of ORUs 10 has an average reflectance of greater than about 60, 70, 80, 85, 90, or 95%. The wavelength range can be a green wavelength range extending from about 490 nm to about 560 nm, for example. In some embodiments, the first wavelength is in a wavelength range extending from about 490 nm to about 560 nm. In some embodiments, for the incident light 100 incident on the optical film 300 at the first incident angle 0 and for the at least one polarization state, a reflection depth of the optical film 300 from a same first major side 301 of the optical film 300 varies non- monotonically with increasing wavelength of the incident light 100 over the visible wavelength range.

[0094] In some embodiments, the optical film 300 includes a macrolayer 124 and a plurality of optical repeat units (ORUs) 10 disposed on a same first major surface 124a of the macrolayer 124 where each of the ORUs 10 has a peak reflectivity at a corresponding resonant wavelength (RW).

[0095] In some embodiments, when in a scatter plot 20 of the RWs of the ORUs versus depths of the ORUs relative to the first major surface 124a of the macrolayer 124, adjacent data points are connected with straight line segments to form a continuous line plot, then the continuous line plot includes a plurality of first lines 24 where the ORU RW in all of the first lines substantially increases with a same one of increasing and decreasing ORU depth, alternating with, and intersecting, a plurality of second lines 25 where the ORU RW in all of the second lines substantially decreases with the same one of increasing and decreasing ORU depth (see, e.g., FIGS. 3, 4A, 5A, 6, 1 IB). In some embodiments, the optical film 300 is such that for an incident light 100 incident on the optical film 300 at a first incident angle 0 and for at least one polarization state (e.g., 101 and / or 102): for a first wavelength (e.g., a, al, a2 or W7) in a visible wavelength range extending from about 420 nm to about 680 nm, a reflection depth of the plurality of ORUs relative to the first major surface of the macrolayer is less than about 10 micrometers (or in a range described elsewhere herein); and for a wavelength range at least 20 nm wide and substantially centered on the first wavelength, the plurality of ORUs has an average reflectance of greater than about 60%. In some embodiments, the wavelength range is at least 25, 30, 35, 40, 45, 50, 55, or 60 nm wide. The wavelength range can be a green wavelength range as described further elsewhere herein. In some embodiments, the first wavelength is in a (e.g., green) wavelength range extending from about 490 nm to about 560 nm. In some embodiments, the plurality of ORUs 10 has an average reflectance in the wavelength range of greater than about 60, 70, 80, 85, 90, or 95%. In some embodiments, for the incident light 100 incident on the optical film 300 at the first incident angle 0 and for the at least one polarization state, a reflection depth of the optical film 300 from a same first major side 301 of the optical film 300 varies non-monotonically with increasing wavelength of the incident light over the visible wavelength range.

[0096] FIG. 15 is a schematic illustration of reflection from an optical film 300, according to some embodiments. In some embodiments, an optical film 300 includes a plurality of polymeric layers (e.g., layers A and B) stacked along a thickness direction (z -direction) of the optical film 300, such that when a substantially monochromatic first light ray 110a having a first wavelength and an optical intensity lil is incident on the plurality of polymeric layers at a first incident angle 0 of greater than about 5 degrees (or in a range described elsewhere herein) and a substantially monochromatic second light ray 111 having a second wavelength different from the first wavelength and an optical intensity Ii2 < li 1 is incident on the plurality of polymeric layers at the first incident angle 0, the plurality of polymeric layers reflects the incident first light ray, but not the incident second light ray, as at least two spaced apart first reflected light rays 120a, 120b having corresponding at least two first optical intensities Ira, Irb where each of the at least two first optical intensities is greater than about 0.1 lil, and the plurality of polymeric layers reflects the incident second light ray as a second reflected light ray having a second optical intensity greater than about 0.5 Ii2, where the second optical intensity greater than each of the at least two first optical intensities. In some embodiments, each of the at least two first optical intensities is greater than about 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 times lil. In some such embodiments, or in other embodiments, the second optical intensity is greater than about 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.92, 0.94, 0.95, 0.96, or 0.97 times Ii2. In some such embodiments, or in other embodiments, at least one of the at least two first optical intensities is less than about 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45 times lil.

[0097] In some embodiments, a separation S2 between at least two adjacent reflected light rays in the at least two spaced apart first reflected light rays is greater than an average total thickness S 1 of at least 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, 18, 20, 25, 30, 35, 40, 50, 60, 70, 80, 90, or 100 sequentially stacked polymeric layers in the plurality of polymeric layers. In some embodiments, the polymeric layers in the plurality of polymeric layers have a total thickness S4, and a maximum separation S3 between the first reflected light rays and the second reflected light ray is less than about 2S4 or less than about 1.9, 1.8, 1.7, 1.6, 1.5, or 1.4 times S4. The substantially monochromatic light rays can have a spread in wavelengths sufficiently small (e.g., a full width at half maximum of less than about 15, 10 or 5 nm) that the separation S2 is negligibly different (e.g., less than about 15, 10, or 5 percent different) from that resulting from monochromatic light rays having no spread in wavelengths. Suitable substantially monochromatic light sources include lasers and laser diodes, for example.

[0098] FIG. 16 is a schematic plot of reflectivity versus wavelength for an optical repeat unit 10, according to some embodiments. A resonant wavelength (RW) of an optical repeat unit (ORU) can be defined as a wavelength at which the ORU exhibits peak reflectivity. The peak reflectivity, and thus the resonant wavelength, can be a function of incident angle and polarization. For example, for normally incident light, the resonant wavelength is generally two times an optical thickness of the ORU, while at oblique angles, the resonant wavelength is generally less than the resonant wavelength at normal incidence and furthermore it is in general different for s-polarized light and p-polarized light. In FIG. 16, the ORU has a peak reflectivity Rp at a corresponding resonant wavelength RW. As is known in the art, a stack of ORUs 10 can produce a reflection band by overlapping the reflectivities of the ORUs 10 in the stack.

[0099] FIGS. 17-18 are plots of reflectance versus wavelength for optical films and non-overlapping groups of ORUs of the optical films, according to some embodiments. Results are shown for an s- polarization state 102 for an incident angle 0 of 45 degrees where the light 100 is incident from glass having a refractive index of about 1.8 for at least one wavelength in a visible wavelength range of about 420 nm to about 680 nm. FIG. 17 was calculated using standard optical modeling techniques from the ORU thickness distribution of FIG. 9 with birefringent UmPEN used for the A layers and optically isotropic coPEN used for the B layers. Rs-1 refers to the reflectance from the combined group 90 and 90', Rs-2 refers to the reflectance from the combined group 91 and 91', Rs-3 refers to the reflectance from the combined group 92 and 92', Rs-4 refers to the reflectance from the combined group 93 and 93', Rs-5 refers to the reflectance from the group 94, and Rs-All refers to the reflectance from the optical film 300. FIG. 18 was calculated using standard optical modeling techniques from the ORU thickness distribution of FIGS. 12A-12B with birefringent LmPEN used for the A layers and optically isotropic coPEN used for the B layers. Rs-1 refers to the reflectance from the group 90, Rs-2 refers to the reflectance from the group 91, Rs-3 refers to the reflectance from the group 92, Rs-4 refers to the reflectance from the group 93, Rs-5 refers to the reflectance from the combined group 94 and 94', and Rs-All refers to the reflectance from the optical film 300.

[0100] In some embodiments, an optical film 300 includes a plurality of optical repeat units (ORUs) 10 where the ORUs in the plurality of the ORUs 10 are sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, such that a scatter plot 20 of the average thicknesses versus the numbers of the sequentially numbered ORUs in the plurality of the ORUs 10 includes at least three non-overlapping groups (e.g., 34a-34c, or combined groups 31, 135; 32, 136; and 33, 137 - see, e.g., FIGS. 3, 4B and 5B) of the ORUs, where each of the groups includes at least two of the sequentially numbered ORUs in the plurality of ORUs 10, and where for each pair of adjacent first and second groups in the at least three groups, the first group (e.g., 34a or the combined group 31, 135) includes a first ORU (e.g., 36d or 36a) closest to the second group (e.g., 34b or the combined group 32, 136) and the second group includes a second ORU (e.g., 37e or 37b) closest to the first group. In some embodiments, the average thicknesses of the first and second ORUs are different by at least about 5, 6, 7, 8, 9, 10, 15 20, 30, 40, 50, 60, 70, 80, 90, or 100%. The average thicknesses of the first and second ORUs can be different by up to about 600, 500, 400, 300, 250, 200, 150, or 100%, for example. In some embodiments, each of at least two of the at least three non-overlapping groups of the ORUs includes at least three of the sequentially numbered ORUs in the plurality of ORUs 10. In some embodiments, each of the at least three non-overlapping groups of the ORUs includes at least three of the sequentially numbered ORUs in the plurality of ORUs 10. In some embodiments, at least one of the at least three non-overlapping groups of the ORUs includes at least 4, 5, 6 of the sequentially numbered ORUs in the plurality of ORUs 10. In some embodiments, each of the at least three non-overlapping groups of the ORUs includes no more than 200, 150, 120, 100, 80, 60, 40, or 20 of the sequentially numbered ORUs in the plurality of ORUs 10. In some embodiments, the at least three non-overlapping groups of the ORUs include no more than 20, 15, 12, 10, 9, 8, 7, 6, 5 or 4 non-overlapping groups of the ORUs. In some embodiments, the at least three non-overlapping groups of the ORUs includes at least four non-overlapping groups of the ORUs 10.

[0101] In some embodiments, for an incident light 100 incident on the optical film 300 at a first incident angle 0, for at least one polarization state (e.g., 101 and / or 102), and for at least a first wavelength (e.g., Wa - see, e.g., FIGS. 17-18) in a visible wavelength range extending from about 420 nm to about 680 nm, the plurality of the ORUs 10 and at least one of the groups in the at least three non-overlapping groups have respective optical reflectances R and Rl, where R > R1 > 10%, and R / Rl > 1.1, 1.15, 1.2, 1.3, 1.4, 1.5, 1.75, 2, 2.5, 3, 4, 5, 6, 7, 8, 9, or 9.5. In some embodiments, R > Rl > 15, 20, 25, 30, 35, 40, 45, or 50%. In some embodiments, for the incident light 100 incident on the optical fdm 300 at the first incident angle 0, for the at least one polarization state, and for at least a second wavelength (e.g., Wb - see, e.g., FIGS. 17-18) in the visible wavelength range different from the first wavelength, the plurality of the ORUs 10 and a group of at least three, 5, 10, 20, 30, 40, 50, 60, or 70 sequentially numbered ORUs not overlapping any of the at least three non-overlapping groups of the ORUs have respective optical reflectances R' and Rl', where Rl' > 50, 60, 70, 80, 85, 90, 92, 94, 95, 96, or 97% and 1.25 > R' / Rl'. In some embodiments, R' / Rl' is less than 1.2, 1.15, 1.1, or 1.05. In some embodiments, R' > Rl'. In some embodiments, R' and Rl' are substantially equal (e.g., equal to within about 5, 4, 3, 2, or 1 percent). In some embodiments, for the incident light 100 incident on the optical film 300 at the first incident angle 0, and for the at least one polarization state, a reflection depth of the optical film from the same first major side 301 of the optical film 300 varies non-monotonically with increasing wavelength of the incident light 100 over the visible wavelength range.

[0102] In some embodiments, an optical film 300 includes a plurality of optical repeat units (ORUs) 10 sequentially numbered from a same first major side 301 of the optical film 300 to an opposite second major side 302 of the optical film 300, where each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), such that a scatter plot 20 of the RWs versus depths of the ORUs relative to the first major side 301 of the optical film 300 includes at least three non-overlapping groups of the ORUs (e.g., 34a-34c, or combined groups 31, 135; 32, 136; and 33, 137 - see, e.g., FIGS. 3, 4B and 5B), where each of the groups including at least two of the sequentially numbered ORUs in the plurality of ORUs, and where for each pair of adjacent first and second groups in the at least three groups, the first group (e.g., 34a or the combined group 31, 35) includes a first ORU (e.g., 36d or 36a) closest to the second group (e.g., 34b or the combined group 32, 136) and the second group includes a second ORU (e.g., 37e or 37b) closest to the first group. In some embodiments, the RWs of the first and second ORUs are different by at least about 5, 6, 7, 8, 9, 10, 15 20, 30, 40, 50, 60, 70, 80, 90, or 100%. In some embodiments, each of at least two of the at least three non-overlapping groups of the ORUs includes at least three of the sequentially numbered ORUs in the plurality of ORUs 10. The number of ORUs in the at least three non-overlapping groups of the ORUs and / or the number of the at least three nonoverlapping groups of the ORUs can be in any of the ranges described elsewhere herein. The optical reflectances (e.g., R, Rl, R' and Rl') for first and second wavelengths (e.g., Wa and Wb - see, e.g., FIGS. 17-18) for the for the plurality of the ORUs 10 and for the various groups of ORUs can be in any of the respective ranges described elsewhere herein.

[0103] FIG. 19 is a schematic cross-sectional view of an optical system 400, according to some embodiments. The optical system 400 can include the optical film 300 for reducing chromatic aberration. For example, the optical film 300 can be a reflective polarizer and including the optical film in place of a conventional reflective polarizer can reduce a magnitude of a chromatic aberration of the optical system 400 by at least about 5, 10, 15, or 20% compared to using the conventional reflective polarizer. In some embodiments, for an incident light at a first incident angle and for a first polarization state (e.g., polarization state 101 which may be a block polarization state for each of the optical film 300 and the conventional reflective polarizer): a reflection depth of the optical film 300 from a same first major side of the optical film 300 varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range, while a reflection depth of the comparative reflective polarizer from a same major side of the optical film 300 varies monotonically with increasing wavelength of the incident light over the predetermined wavelength range. An example conventional reflective polarizer is APF available from 3M Company, St. Paul, MN. Chromatic aberration is an optical aberration where a lateral and / or longitudinal focus of light varies with wavelength ass described in U.S. Pat. Appl. Pub. No. 2020 / 0341267 (Wong), for example. The chromatic aberration can be a longitudinal (also known as axial) aberration determined along an optical axis 290 of the optical system 400.

[0104] In some embodiments, the optical system 400 includes a display 200 configured to form and emit an image 201; at least one optical component 220, 221, where the at least one optical component has a chromatic dispersion; and any of the optical films 300 of the present description in optical communication with each of the display 200 and the at least one optical component 220, 221. In some embodiments, the optical film 300 is configured (e.g., via having a desired reflection depth versus wavelength) to at least partially compensate for the chromatic dispersion of the at least one optical component 220, 221. The term “optical communication” as applied to two objects or components means that light can be transmitted from one to the other either directly or indirectly using optical methods (e.g., direct transmission, reflection, diffraction, or refraction). The display 200 can be a liquid crystal display or an organic light emitting diode display, for example. The optical system 400 can be a folded optical system such as those generally described in U.S. Pat. Nos. 10,678,052 (Ouderkirk et al.); 11,156,814 (Steiner et al.); and 11,630,290 (Y un et al.), for example. In some embodiments, the optical system 400 has an optical axis 290 such that a light ray 291 propagating along the optical axis 290 passes through the at least one optical component 220, 221 and the optical film 300 (e.g., in a folded optical system, the light ray can be transmitted through the optical film 300 after first being reflected by the optical film 300) without being substantially refracted.

[0105] In some embodiments, an optical system 400 includes a display 200 configured to form and emit an image 201 comprising coincident first and second emitted image rays 203a, 203b having respective first and second wavelengths at least about 20, 30, 40, 50, or 60 nm apart. In some embodiments, the first and second wavelengths are within a visible wavelength range extending from about 420 nm to about 680 nm. In some embodiments, the first wavelength is a blue or red wavelength, and the second wavelength is a green wavelength. The optical system 400 can be configured to display a virtual image 202 of the emitted image 201 to a viewer 210. The optical system 400 includes at least one optical component 220, 221 where the at least one optical component has a chromatic dispersion; and an optical film 300 including a plurality of polymeric layers (e.g., A and B layers) and configured to at least partially compensate for the chromatic dispersion of the at least one optical component. Each layer of the plurality of polymeric layers can have an average thickness of less than about 500 nm (or in a range described elsewhere herein). In some embodiments, for an incident light 100 incident on the optical film 300 at a first incident angle 0 and for at least one polarization state (e.g., at least one of 101 and 102), a reflection depth of the optical film 300 from a same first major side (e.g., 301) of the optical film 300 varies non- monotonically with increasing wavelength of the incident light 100 over a predetermined wavelength range comprising the first and second wavelengths. In some embodiments, the predetermined wavelength range is from about 420 nm to about 680 nm, for example. In some embodiments, the optical system 400 is such that an optical interaction (e.g., refraction from material exhibiting chromatic dispersion) between the at least one optical component 220, 221 and the coincident first and second emitted image rays 203a, 203b laterally separates the first and second emitted image rays (the coincident first and second emitted image rays 203a and 203b become the laterally separated first and second emitted image rays 204a and 204b) so that, when incident on the optical film 300, the first and second emitted image rays 204a, 204b are separated by a first distance Gl, and the plurality of polymeric layers reflects the incident first and second emitted image rays as respective reflected first and second image rays 205a, 205b separated by a second distance G2, where G2 is less than Gl by at least 10% ([G1-G2] / G1 times 100% is at least 10%). In some embodiments, G2 is less than Gl by at least 20% or by at least 50%. In some embodiments, G2 is less than Gl by at least a factor of 2, 2.5, 3, 5, 7, 10, 20, 50, or 100.

[0106] In some embodiments, the first and second emitted image rays 203a and 203b have respective optical intensities II and 12 and the reflected first and second image rays 205a and 205b have respective optical intensities QI and Q2. In some embodiments, each of Ql / Il and Q2 / I2 is greater than about 0.15, 0.2, 0.3, or 0.4.

[0107] In some embodiments, the at least one optical component 220, 221 includes a metasurface. In some embodiments, the at least one optical component 220, 221 includes a diffractive surface. For example, the surface 222 of the optical component 221 can be a metasurface and / or a diffractive surface. In some embodiments, the at least one optical component includes a refractive optical lens (e.g., 220 and / or 221 can be or include a refractive optical lens). In some embodiments, the at least one optical component comprises at least two optical lenses (e.g., 220 and 221). In some embodiments, the at least one optical component is or includes a multilayer optical film. For example, element 221 or 240 can be a multilayer optical film appearing generally as schematically illustrated in FIG. 1. Element 240 can be a partial reflector that may be a multilayer optical film, for example.

[0108] In some embodiments, the optical film 300 is or includes a reflective polarizer, such that for a substantially normally incident light, the reflective polarizer reflects at least 60% of the incident light polarized along a first in-plane direction and transmits at least 60% of the incident light polarized along an orthogonal second in-plane direction. In some embodiments, for a substantially normally incident light in a visible wavelength range of about 420 nm to about 680 nm, the reflective polarizer has an average reflectance of greater than about 60, 70, 80, or 90 percent for a first polarization state 101 and an average transmittance of greater than about 60, 70, 80, or 85 percent for an orthogonal second polarization state 102.

[0109] In some embodiments, the optical system 400 further includes a partial reflector 240, such that for a substantially normally incident light and for each of mutually orthogonal polarization states 101 and 102, the partial reflector reflects at least 30% of the incident light and transmits at least 30% of the incident light. In some embodiments, for the substantially normally incident light and for each of the mutually orthogonal polarization states 101 and 102, the partial reflector reflects at least 40% of the incident light and transmits at least 40% of the incident light. The partial reflector 240 may be a half silvered mirror, for example, or may be a multilayer optical film, for example.

[0110] In some embodiments, the optical system 400 further includes a retarder layer 250. In some embodiments, the retarder layer 250 is disposed between the optical film 300 and the partial reflector 240. In some embodiments, the retarder layer 250 is configured to change a phase of a normally incident light having the first or second wavelengths by at least 20 degrees. In some embodiments, the retarder layer 250 is a quarter wave retarder for at least one wavelength in a visible wavelength range that comprises the first and second wavelengths. The retarder layer 250 can be a single layer (e.g., a birefringent film layer) or can include multiple layers (e.g., a multilayer achromatic retarder).

[0111] In some embodiments, the optical system 400 further includes an absorbing polarizer 260. In some embodiments, the absorbing polarizer 260 is such that for a substantially normally incident light, the absorbing polarizer absorbs at least 60% of the incident light polarized along a first in-plane direction and transmits at least 60% of the incident light polarized along an orthogonal second in-plane direction. In some embodiments, for the substantially normally incident light, the absorbing polarizer absorbs at least 70 or 80 percent of the incident light polarized along a first in-plane direction and transmits at least 70 or 80 percent of the incident light polarized along the second in-plane direction. In some embodiments, the absorbing polarizer 260 is disposed between the optical film 300 and the viewer 210. The absorbing polarizer 260 can include an iodine-stained polyvinyl alcohol layer, for example. The first in-plane direction for the absorbing and reflecting polarizers can be a same direction or can be aligned to within about 20, 15, 10, or 5 degrees, for example.

[0112] Terms such as “about” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “about” as applied to quantities expressing feature sizes, amounts, and physical properties is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, “about” will be understood to mean within 10 percent of the specified value. A quantity given as about a specified value can be precisely the specified value. For example, if it is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description, a quantity having a value of about 1, means that the quantity has a value between 0.9 and 1. 1, and that the value could be 1.

[0113] Terms such as “substantially” will be understood in the context in which they are used and described in the present description by one of ordinary skill in the art. If the use of “substantially” with reference to a property or characteristic is not otherwise clear to one of ordinary skill in the art in the context in which it is used and described in the present description and when it would be clear to one of ordinary skill in the art what is meant by an opposite of that property or characteristic, the term “substantially” will be understood to mean that the property or characteristic is exhibited to a greater extent than the opposite of that property or characteristic is exhibited.

[0114] All references, patents, and patent applications referenced in the foregoing are hereby incorporated herein by reference in their entirety in a consistent manner. In the event of inconsistencies or contradictions between portions of the incorporated references and this application, the information in the preceding description shall control.

[0115] Descriptions for elements in figures should be understood to apply equally to corresponding elements in other figures, unless indicated otherwise. Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and / or equivalent implementations can be substituted for the specific embodiments shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations, or variations, or combinations of the specific embodiments discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.

Claims

What is claimed is:

1. An optical film comprising a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, each of the ORUs having an average thickness of less than about 1500 nm and comprising at least a polymeric A layer and a different polymer B layer, wherein the plurality of ORUs comprises at least three first ORUs, each first ORU having a thickness within Pl% of a same first thickness, each first ORU being separated from each other first ORU by at least one ORU having a thickness differing from the first thickness by greater than Pl%, Pl% being in a range of about 1% to about 10%, and wherein for an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range.

2. The optical film of claim 1, wherein the plurality of ORUs comprises at least three second ORUs, each second ORU having a thickness within Pl% of a same second thickness, each second ORU being separated from each other second ORU by at least one ORU having a thickness differing from the second thickness by greater than Pl%, the second thickness different from the first thickness by at least 10 nm.

3. The optical film of claim 2, wherein the second thickness is different from the first thickness by at least about 1.5 times Pl%.

4. The optical film of claim 1, wherein the thickness of each of the at least one ORU differs from the first thickness by greater than Pl%+0.5%, Pl% being in a range of about 1% to about 3%.

5. The optical film of claim 1, wherein for the incident light incident on the optical film at the first incident angle and for the at least one polarization state: the plurality of ORUs has first, second, and third average reflection depths relative to the same first major side of the optical film in respective non-overlapping first, second, and third wavelength ranges, the second wavelength range disposed between the first and third wavelength ranges, the second average reflection depth differing from each of the first and third average reflection depths by at least about 1.2 times a separation between the first and third average reflection depths.

6. The optical film of claim 1, wherein the plurality of ORUs is disposed on a same first major surface of a macrolayer having an average thickness greater than about 500 nm, wherein for the incident light incident on the optical film at the first incident angle and for the at least one polarization state: for a first wavelength in the predetermined wavelength range, a reflection depth of the plurality of ORUs relative to the first major surface of the macrolayer is less than about 10 micrometers.

7. An optical film comprising a macrolayer and a plurality of optical repeat units (ORUs) numbering at least 10 in total disposed on a same first major surface of the macrolayer, the macrolayer and the plurality of optical repeat units being coextruded and co-stretched with one another, the macrolayer having an average thickness greater than about 500 nm, each of the ORUs having an average thickness of less than about 1500 nm and comprising at least a polymeric A layer and a different polymer B layer, wherein for an incident light incident on the optical film at a first incident angle and for at least a first polarization state: the plurality of ORUs has first, second, and third average reflection depths relative to the first major surface of the macrolayer in respective non-overlapping first, second, and third wavelength ranges, the second wavelength range disposed between the first and third wavelength ranges, the second average reflection depth differing from each of the first and third average reflection depths by at least about 1.2 times a difference between the first and third average reflection depths, each of the first, second, and third wavelength ranges being at least about 20 nm wide and disposed between about 380 nm and about 2000 nm; and the optical film has an average reflectance in each of the first, second, and third wavelength ranges of at least about 60%.

8. The optical film of claim 7, wherein the second average reflection depth is less than about 10 micrometers.

9. The optical film of claim 7, wherein each of the ORUs has a peak reflectivity at a corresponding resonant wavelength (RW), and wherein for the incident light incident on the optical film at the first incident angle, for at least the first polarization state, and for a first wavelength in one of the first and third wavelength ranges, the optical film comprises at least three first ORUs that have RWs within 20% of the first wavelength, the first ORUs being spaced apart from one another along a thickness direction of the optical film by at least about 0.5 micrometers.

10. An optical film comprising a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, each of the ORUs having an average thickness of less than about 1500 nm and comprising at least a polymeric A layer and a different polymer B layer, the ORUs sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that when adjacent data points in a scatter plot of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, aplurality of second lines where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number, the intersection points forming a plurality of alternating peaks and valleys, wherein a first one of the first lines of the plurality of first lines comprises a plurality of first straight line segments collectively extending from a first valley of the plurality of alternating peaks and valleys to a first peak of the plurality of alternating peaks and valleys, slopes of the first straight line segments comprising minimum and maximum slope magnitudes, the minimum slope magnitude at least about 0.5 nm per ORU number, the maximum slope magnitude at least about 3 times greater than the minimum slope magnitude.

11. An optical film comprising a plurality of optical repeat units (ORUs) coextruded and co-stretched with one another and numbering at least 10 in total, each of the ORUs having an average thickness of less than about 1500 nm and comprising at least a polymeric A layer and a different polymer B layer, the ORUs sequentially numbered from a same first major side of the optical film to an opposite second major side of the optical film, such that when adjacent data points in a scatter plot of thicknesses versus the numbers of the ORUs are connected with straight line segments to form a continuous line plot, then the continuous line plot comprises a plurality of first lines where the ORU thickness in all of the first lines substantially increases with a same one of increasing and decreasing ORU number, alternating with, and intersecting, a plurality of second lines where the ORU thickness in all of the second lines substantially decreases with the same one of increasing and decreasing ORU number, the intersection points forming at least a first plurality of alternating peaks and valleys, wherein for each pair of adjacent peak and valleys in the first plurality of alternating peaks and valleys, a difference in ORU thicknesses of the peak and the valley is greater than about 5 nm and less than about 120 nm.

12. The optical film of claim 1, wherein the intersection points form a second plurality of alternating peaks and valleys not overlapping the first plurality of alternating peaks and valleys.

13. An optical film comprising a plurality of polymeric layers stacked along a thickness direction of the optical film, such that when a substantially monochromatic first light ray having a first wavelength and an optical intensity li 1 is incident on the plurality of polymeric layers at a first incident angle of greater than about 5 degrees and a substantially monochromatic second light ray having a second wavelength different from the first wavelength and an optical intensity Ii2 < lil is incident on the plurality of polymeric layers at the first incident angle, the plurality of polymeric layers reflects the incident first light ray, but not the incident second light ray, as at least two spaced apart first reflected light rays having corresponding at least two first optical intensities where each of the at least two first optical intensities is greater than about 0.1 lil, and the plurality of polymeric layers reflects the incident second light ray as a second reflectedlight ray having a second optical intensity greater than about 0.5 Ii2, the second optical intensity greater than each of the at least two first optical intensities.

14. An optical system comprising: a display configured to form and emit an image; at least one optical component, the at least one optical component comprising a chromatic dispersion; and the optical film of any one of claims 1 to 13 in optical communication with each of the display and the at least one optical component, the optical film being configured to at least partially compensate for the chromatic dispersion of the at least one optical component.

15. An optical system comprising: a display configured to form and emit an image comprising coincident first and second emitted image rays having respective first and second wavelengths at least about 20 nm apart, the optical system configured to display a virtual image of the emitted image to a viewer; at least one optical component, the at least one optical component comprising a chromatic dispersion; and an optical film comprising a plurality of polymeric layers and configured to at least partially compensate for the chromatic dispersion of the at least one optical component, each layer of the plurality of polymeric layers having an average thickness of less than about 500 nm, wherein for an incident light incident on the optical film at a first incident angle and for at least one polarization state, a reflection depth of the optical film from a same first major side of the optical film varies non-monotonically with increasing wavelength of the incident light over a predetermined wavelength range comprising the first and second wavelengths; such that an optical interaction between the at least one optical component and the coincident first and second emitted image rays laterally separates the first and second emitted image rays so that, when incident on the optical film, the first and second emitted image rays are separated by a first distance Gl, the plurality of polymeric layers reflecting the incident first and second emitted image rays as respective reflected first and second image rays separated by a second distance G2, G2 less than Gl by at least 10%.

Images