Display system with diffractive off-axis collimation layer

Abstract

A display system includes a display including a plurality of pixels where each pixel includes a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display. The diffractive off-axis collimation layer includes diffractive regions configured to diffractively transmit light and non- diffractive regions configured to non-diffractively transmit light. The diffractive and non-diffractive regions are arranged relative to the subpixels so that the diffractive off-axis collimation layer at least partially collimates light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display.

Description

[0001] PA102986W002

[0002] DISPLAY SYSTEM WITH DIFFRACTIVE OFF-AXIS COLLIMATION LAYER

[0003] TECHNICAL FIELD

[0004] The present description relates generally to display systems.

[0005] BACKGROUND

[0006] A display system can include a display panel, such as an organic light emitting diode (OLED) display panel, with light emitting pixels.

[0007] SUMMARY

[0008] In some aspects, the present description provides a display system including a display that includes a plurality of pixels where each pixel includes a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display. The diffractive off-axis collimation layer includes diffractive regions configured to diffractively transmit light and non-diffractive regions configured to non- diffractively transmit light. The diffractive and non-diffractive regions can be arranged relative to the subpixels so that the diffractive off-axis collimation layer at least partially collimates light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display.

[0009] In some aspects, the present description provides a display system including a display including a plurality of pixels where each pixel includes a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display. The diffractive off-axis collimation layer includes diffractive regions configured to diffractively transmit light and non- diffractive regions configured to non-diffractively transmit light. The diffractive and non-diffractive regions can be arranged relative to the subpixels so that: at least a portion of light emitted by the subpixels at a first oblique angle is non-diffractively transmitted by the diffractive off-axis collimation layer and exits the display system substantially along the first off-axis direction (e.g., within a FWHM of a peak in brightness along the first off-axis direction); and at least a portion of light emitted by the subpixels substantially along the thickness direction (e.g., within 25, 20, 15, 10, or 5 degrees of the thickness direction and along a direction making an angle with the thickness direction of less than 0.4, 0.3, 0.2, or 0.1 times the first oblique angle) is diffractively transmitted by the diffractive off-axis collimation layer and exits the display system substantially along the first off-axis direction.

[0010] In some aspects, the present description provides a display system including a display having a display surface including a plurality of pixels where each pixel includes a plurality of subpixels and each subpixel has a subpixel centroid in a top plan view; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction. The first off-axis direction and a thickness direction of the display defines a first plane. The diffractive off-axis collimation layer including diffractive regions configured to diffractively transmit light and non- diffractive regions configured to non-diffractively transmit light. The diffractive regions include diffractive features spaced apart from the display surface along the thickness direction by an average distance S 1. The diffractive and non-diffractive regions can be arranged relative to the subpixels so that in the top plan view and for each non-diffractive region, a distance between a centroid of the non-diffractive region and a subpixel centroid closest thereto is DI, such than an angle al= atan(Dl / Sl) is in a range of 5 to 70 degrees and at least a portion of light emitted from the display surface at the angle al relative to the thickness direction in the first plane exits the display system substantially along the first off-axis direction after being non-diffractively transmitted by the diffractive off-axis collimation layer.

[0011] In some aspects, the present description provides a display system including a display including a plurality of pixels where each pixel includes a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display. The first off-axis direction and the thickness direction define a first plane. The diffractive off-axis collimation layer includes diffractive regions configured to diffractively transmit light and non-diffractive regions configured to non-diffractively transmit light. The diffractive and non-diffractive regions can be arranged relative to the subpixels so that the diffractive off-axis collimation layer increases a brightness of the display along the first off-axis direction by at least about 10 percent while decreasing an on -axis brightness of the display.

[0012] 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.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG. 1 is a schematic cross-sectional view of a portion of a display system, according to some embodiments.

[0015] FIGS. 2A-2B are schematic plots of brightness versus viewing angle, according to some embodiments.

[0016] FIGS. 3A-3C are plots of normalized brightness versus viewing angle, according to some embodiments.

[0017] FIG. 4A is a schematic illustration of a coordinate space, according to some embodiments.

[0018] FIG. 4B is an exemplary conoscopic plot of normalized brightness corresponding to the brightness versus viewing angle profiles of FIG. 3B, according to some embodiments.

[0019] FIGS. 5-9 are schematic top plan views of display systems, according to various embodiments.

[0020] FIGS. 10-12 are schematic cross-sectional views of illustrative unit cells of diffractive elements that may be used in diffractive regions, according to some embodiments.

[0021] FIG. 13 is a schematic cross-sectional view of light emitted from a subpixel and redirected by a diffractive off-axis collimation layer substantially along a first off-axis direction, according to some embodiments. FIG. 14 is a schematic plan view of a detection area corresponding to a single pixel, according to some embodiments.

[0022] FIGS. 15A is a plot of detected irradiance when a single subpixel of a control display system that does not include a diffractive off-axis collimation layer is illuminated.

[0023] FIGS. 15B is a plot of detected irradiance when a single subpixel of a display system that includes a diffractive off-axis collimation layer is illuminated, according to some embodiments.

[0024] DETAILED DESCRIPTION

[0025] 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.

[0026] Diffraction gratings have been used with organic light emitting diode (OLED) displays for various purposes. A diffraction grating can be placed over an organic light emitting diode (OLED) display panel to correct off-axis color shift as described in U.S. Pat. No. 10,991,765 (Freier et al.), for example. Diffractive structures can be disposed on an emissive layer of an OLED device within an evanescent zone of the emissive layer to improve extraction of light that would otherwise be trapped in the OLED device as described in U.S. Pat. Appl. Pub. No. 2010 / 0110551 (Lamansky et al.), for example. In each of these cases, a diffractive layer is placed over an entire emissive layer of the OLED device. Patterned diffractive layers including diffractive and non-diffractive regions have been used to improve axial brightness as described in International Appl. Pub. No. WO 2024 / 033838 (DeSutter et al.), for example.

[0027] According to some embodiments of the present description, it has now been found that suitably selectively patterned diffractive layers used in emissive displays, such as OLED or micro-LED displays, can provide collimation along predetermined non-axial direction(s). Collimation along non-axial directions may be desired in applications where viewers are not directly in front of the display. For example, in automotive applications, it may be desired that light from a center display be collimated in a first direction towards a driver and in a different second direction towards a passenger while the display has a lowered axial brightness. Alternatively, it may be desired to collimate light in a single direction (e.g., toward the driver but not the passenger, or toward the passenger but not the driver). According to some embodiments of the present description, the diffractive layer can be patterned to provide collimation primarily in one or at least one (e.g., two) directions by suitable arrangement of the diffractive and non-diffractive regions relative to subpixels (e.g., diffractive regions covering subpixels and non-emissive regions on one side, but not an opposite side, of the subpixels) and / or by suitable selection of the diffractive elements (e.g., asymmetric gratings). FIG. 1 is a schematic cross-sectional view of a portion of a display system 100, according to some embodiments. In some embodiments, a display system 100 includes a display 151 including a plurality of pixels, where each pixel includes a plurality of subpixels 110; and a diffractive off-axis collimation layer 150 disposed on the display 151 and configured to at least partially collimate light along a first off-axis direction 241 making an angle al' of at least 5, 6, 8, 10, 12, 14, 16, 18, or 20 degrees with a thickness direction (z-direction) of the display. The angle al' can be up to 80, 70, 60, 50 or 40 degrees, for example. Light emitted by the display 151 at an angle al exits the display system 100 at an angle al' (angle between direction 241 and thickness direction) which may differ from al due to refraction (e.g., at an interface between the display system and air). The angle al may be in any of the ranges described from the angle al', though the angle al may be smaller than the angle al' in some embodiments. For example, the angles al and al' can be in a range of 5 to 80 degrees or 10 to 70 degrees. The diffractive off-axis collimation layer 150 can be configured to at least partially collimate light along more than one direction: for example, along first and second directions 241 and 242 towards respective first and second viewers 109a and 109b. In some embodiments, the diffractive off-axis collimation layer 150 includes diffractive regions 152 configured to diffractively transmit light and non -diffractive regions 154 configured to non-diffractively transmit light. In some embodiments, the diffractive and non-diffractive regions arranged relative to the subpixels 110 so that: at least a portion 141 of light emitted by the subpixels at a first oblique angle al is non-diffractively transmitted (as light 141') by the diffractive off- axis collimation layer 150 and exits the display system substantially along the first off-axis direction 241; and at least a portion of light 140 emitted by the subpixels substantially along the thickness direction (z- direction) is diffractively transmitted (as light 140') by the diffractive off-axis collimation layer 150 and exits the display system substantially along the first off-axis direction 241. For example, for diffractive regions using symmetric diffractive elements (e.g., elements extending in an x-direction, for example, and being symmetric for plus and minus y-directions, for example), the diffractive regions may be disposed symmetrically about the subpixels 110 to achieve collimation primarily along two desired directions or asymmetrically about the subpixels (e.g., covering subpixels 110 and one, but not the other, of adjacent non-emissive regions 120 on each side of the subpixel) to achieve collimation primarily along a single desired direction. As another example, for diffractive regions symmetrically disposed about the subpixels, asymmetric diffractive elements may be used to achieve collimation primarily along a single desired direction. In some embodiments, a combination of asymmetric diffractive elements and diffractive regions disposed asymmetrically about the subpixels are utilized. Partially collimated light generally has a peak in a brightness distribution in at least one plane. The off-axis directions along which light is collimated generally refer to directions of a center of a peak in brightness.

[0028] In some embodiments, the diffractive and non-diffractive regions are arranged relative to the subpixels 110 so that at least a portion 142 of light emitted by the subpixels 110 at a second oblique angle a2 is non-diffractively transmitted (as light 142') by the diffractive off-axis collimation layer and exits the display system along the second off-axis direction 242. In some embodiments, the diffractive and non- diffractive regions are arranged relative to the subpixels 110 so that at least a portion of light 140 emitted by the subpixels substantially along the thickness direction (z-direction) is diffractively transmitted (as light 140") by the diffractive off-axis collimation layer 150 and exits the display system 100 substantially along the second off-axis direction 242. The second off-axis direction 242 can make an angle a2' of at least 5, 6, 8, 10, 12, 14, 16, 18 or 20 degrees with a thickness direction (z-direction) of the display 151. The angle a2' can be up to 80, 70, 60, 50 or 40 degrees, for example. The second oblique angle a2 may be in any of the ranges described for the angle a2'. For example, the angles a2 and a2' can be in a range of 5 to 80 degrees or 10 to 70 degrees.

[0029] In some embodiments, light emitted by the subpixels along the thickness direction is not diffracted into the desired collimation direction. In some embodiments, light emitted by the subpixels along at least two different oblique angles that differ by at least 5, 10, 15, or 20 degrees are diffracted by the diffractive off-axis collimation layer into a substantially same desired collimation direction.

[0030] The light diffractive layer 150 can include first and second layers 150a and 150b. In some embodiments, the first layer 150a is formed on a substrate (e.g., a polymeric substrate or another layer) using a cast and cure process where diffractive structures are fabricated from a tool by casting a polymerizable resin composition onto the substrate and curing the resin in contact with a structured surface of the tool. Such cast and cure methods are described in U.S. Pat. Nos. 5,175,030 (Lu et al.) and 5,183,597 (Lu) and in U.S. Pat. Appl. Pub. No. 2012 / 0064296 (Walker, JR. et al.), for example. The structured surface of the tool can be selected to define light diffractive regions and light non-diffractive regions, or the tool can define light diffraction structures throughout the structured surface of the first layer 150a and then portions of the light diffractive structures can be filled in in a subsequent coating step with a same material as used to form the first layer 150a in the cast and cure process, or a different material with a similar refractive index (e.g., substantially closer in refractive index to the cast and cure material than to the material of the second layer 150b), in order to define light non-diffractive regions. The second layer 150b can be a (e.g., planarizing) backfill layer coated over the structured surface defined in first layer 150a. The first and second layers 150a and 150b typically have different refractive indices na and nb, respectively, for at least a same first wavelength (e.g., about 550 nm) in a wavelength range of 420 nm to 680 nm, for example. In some embodiments, the difference |nb-na| can be at least about 0.03, 0.05, 0.07, 0.09, or 0.1, for example, for at least the first wavelength. In some such embodiments, or in other embodiments, the difference |nb-na| can be up to about 2, 1.5, 1, 0.8, 0.6, 0.5, or 0.4, for example, for at least the first wavelength. In some embodiments, the second layer 150b has a higher refractive index (nb) than that (na) of the first layer 150a. In some embodiments, the non- diffractive regions 154 include a structured interface and the difference in refractive index across the structured interface can be less than about 0.08, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01, for example, for at least the first wavelength. In some embodiments, the diffractive layer 150 includes more than 2 materials or layers. For example, the diffractive layer 150 can include a thin (e.g., substantially thinner than the grating height) overcoat layer at the grating interface that may have a high refractive index (e.g., the refractive index can be at least about 2, such as a refractive index of about 2.5, for example) for at least the first wavelength. In some embodiments, at the first wavelength, the layer 150a has a refractive index of about 1.4 to about 1.55, and the layer 150b has a refractive index of about 1.6, 1.65, 1.7, or 1.75 to about 1.85. If a wavelength is not otherwise specified, refractive indices can be understood to be for a wavelength of about 532 nm.

[0031] The average spacing SI can be in a range of about 20 to 1000 microns, the layer 150a can have a thickness of about 10 to 20 microns, and the layer 150b can have a thickness of about 5 to about 15 microns, for example. The average spacing SI may be in a range of about 20 to about 30 microns in cell phone applications, for example, and may be in a range of about 30, 35, 40, 45, 50, 60, 70, 80, or 90 microns to about 1000 microns in television applications, for example. In some embodiments, the light diffractive layer 150 is formed separately and then disposed on the layer 151, which can be or include an emissive layer of a display, with an optional air gap therebetween or the light diffractive layer 150 can be laminated to the emissive layer.

[0032] The light diffractive and light non -diffractive regions 152 and 154 can be patterned by any other suitable means. In some embodiments, the light diffractive and light non -diffractive regions 152 and 154 can be patterned by inkjet printing, photolithography, masking, or other suitable patterning technologies. In some embodiments, the patterning technology determines the placement of an index matching (e.g., difference in refractive index (e.g., at 550 nm) less than about 0.08, 0.06, 0.05, 0.04, 0.03, 0.02, or 0.01, for example) material to define the location of the light non-diffractive region 154. In some embodiments, the patterning technology determines the placement of an index mismatching (e.g., difference in refractive index (e.g., at 550 nm) at least about 0.03, 0.05, 0.07, 0.09, or 0.1 for example) material to define the light diffractive regions 152. In some embodiments, the patterning technology defines the exposure region over which the grating is preferentially fabricated or removed by, for example, etching or scribing. In some embodiments, the light diffractive layer 150 can be formed on the surface of another layer already present in the display system by etching or scribing where the process of etching or scribing is patterned as to define the light diffractive and light non-diffractive regions 152 and 154. Other methods of patterning known in the art may alternatively be utilized.

[0033] FIGS. 2A-2B are schematic plots of brightness 200a and 200b, respectively, versus viewing angle (angle relative to thickness direction), according to some embodiments. The viewing angle of FIGS. 2A-2B can be in the yz-plane of FIG. 1 and the brightness 200a can correspond to the brightness of display system 100, for example. The brightness 200b can correspond to the brightness of a display system 100 modified as described elsewhere herein to provide collimation primarily along a single off- axis direction in the yz-plane, according to some embodiments. FIGS. 3A-3B are plots of normalized brightness versus viewing angle for exemplary displays for green subpixels with diffractive and non- diffractive regions of the diffractive off-axis collimation layer 150 arranged symmetrically (FIG. 3 A) or asymmetrically (FIG. 3B) relative to the subpixels 110, as described further elsewhere herein. The gratings of FIG. 2A-3B were symmetric gratings. FIGS. 3C is a plot of normalized brightness versus viewing angle for an exemplary display for green subpixels with diffractive and non -diffractive regions of the diffractive off-axis collimation layer 150 arranged symmetrically (see, e.g., FIG. 5) but with a blazed grating (see, e.g., FIG. 12). Positive and negative viewing angles in FIGS. 3A-3C refer to viewing angles in the yz-plane having positive and negative y-components, respectively (e.g., in this context, in FIG. 1 al is a positive viewing angle and a2 is a negative viewing angle). Normalized brightness is the brightness (luminance) divided by the brightness (luminance) at a zero degree viewing angle (along the thickness direction) of the display without the diffractive off-axis collimation layer 150.

[0034] In some embodiments, the diffractive off-axis collimation layer 150 is configured to at least partially collimate light along a first off-axis direction 241 such that a brightness distribution 200a, 200b of the display includes a first peak 341 along the first off-axis direction 241. In some embodiments, the diffractive off-axis collimation layer 150 is configured to at least partially collimate light along a second off-axis direction 242 different from the first off-axis direction 241 such that a brightness 200a distribution of the display includes spaced apart first and second peaks 341 and 342 along the respective first and second off-axis directions 241 and 242. The peaks in the brightness distribution may be present in one viewing plane (e.g., yz-plane) while the brightness distribution may be approximately flat in an orthogonal viewing plane (e.g., xz-plane).

[0035] In some embodiments, the first off-axis direction 241 and the thickness direction (z -direction) define a first plane (e.g., yz-plane or the y'z-plane depicted in FIG. 9, for example) and a brightness distribution 200a, 200b of the display in the first plane has a first peak 341 along the first off-axis direction. In some embodiments, the first peak 341 has a first peak brightness Bpl, and may also have a corresponding full width at half maximum FWHM. The FWHM may be understood to be a local FWHM (e.g., the width at half of a difference between the first peak brightness Bpl and a valley or plateau adjacent to the peak). The first peak brightness Bpl may be a global maximum of the brightness distribution in the first plane. In some embodiments, the brightness distribution in the first plane is free of any second peak spaced apart from the first peak by at least 30 degrees and having a second peak brightness greater than about 85, 80, 75, 70, 65, 60, 55, 50, 45, or 40 percent of the first peak brightness. In some embodiments, the brightness distribution in the first plane is free of any second peak spaced apart from the first peak by at least 0.5, 0.6, 0.7, 0.8, 0.9, or 1 times the FWHM and having a second peak brightness greater than about 85, 80, 75, 70, 65, 60, 55, 50, 45, or 40 percent of the first peak brightness.

[0036] In some embodiments, the diffractive and non-diffractive regions are arranged relative to the subpixels so that the diffractive off-axis collimation layer 150 increases a brightness of the display along the first off-axis direction 241 by at least about 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 percent while decreasing an on-axis brightness of the display. In some such embodiments, or in other embodiments, the diffractive off-axis collimation layer 150 decreases the on-axis brightness of the display system by at least about 10, 15, 20, 25, 30, 35, 40, or 45 percent. The brightness of the display along the first off-axis direction 241 may be increased by up to about 300, 250, 200, 150, or 100 percent, for example. The brightness of the display with and without the diffractive off-axis collimation layer 150 can be determined for all subpixels being illuminated or for all subpixels of a same color (e.g., red, green, blue) being illuminated.

[0037] FIG. 4A is a schematic illustration of a coordinate space 600 defined by first and second angles Ayz and Axz in respective first and second planes (yz- and xz-planes) orthogonal to one another and parallel to the thickness direction (z-direction), according to some embodiments. The coordinate space 600 generally includes angles Ayz and Axz extending from -90 degrees to +90 degrees. A rectangular region 640 of the coordinate space 600 is schematically illustrated. FIG. 4B is an exemplary conoscopic plot of normalized brightness corresponding to the example of FIG. 3B, according to some embodiments. The rectangular region 640 of the coordinate space 600 may correspond to a substantially rectangular region 640' in the conoscopic plot.

[0038] The display system 100 includes the diffractive off-axis collimation layer 150 and the display 151. In some embodiments, the display 151 (without the diffractive off-axis collimation layer) has an on- axis brightness B0, and for a rectangular region 640 of a coordinate space defined by first and second angles Ayz and Axz in respective first and second planes (yz- and xz-planes) orthogonal to one another and parallel to the thickness direction (z-direction), with the rectangular region 640 substantially centered on the first off-axis direction 241 and comprising a range of the first angle Ayz at least 5 degrees wide and a range of the second angle Axz at least 30 degrees wide, the display system 100 has an average brightness B 1, a maximum brightness Bmax and a minimum brightness Bmin. In some embodiments, B1 / B0 is at least about 1.2, 1.3, 1.4, 1.5, or 1.6. In some such embodiments, or in other embodiments, Bmin / Bmax is at least 0.7, 0.72, 0.74, 0.76, 0.8, 0.82, 0.84, 0.86, 0.88, or 0.9. In some such embodiments, or in other embodiments, the display system 100 has an average brightness B2 for an entire region of the coordinate space 600 outside of the rectangular region 640, where B2 / B0 is no more than 0.98, 0.96, 0.94, 0.92, 0.9, 0.88, 0.86, 0.84, 0.82, 0.8, 0.78, or 0.76. The range of the first angle Ayz can be 5 to 25, or 6 to 15, or 7 to 15 degrees wide, for example. The range of the second angle Axz can be 30 to 90 degrees wide, or 40 to 80 degrees wide, or 50 to 70 degrees wide, for example. For example, the range of the first angle Ayz can be from about -15 degrees to about -25 degrees and the range of the second angle Axz can be from about -30 degrees to about 30 degrees. The display system can have any of B1 / B0, Bmin / Bmax, and B2 / B0 in any of these ranges for all subpixels being illuminated or for all subpixels of a same color (e.g., red, green, or blue) being illuminated.

[0039] FIGS. 5-9 are schematic top plan views of display systems 100, according to various embodiments.

[0040] In FIG. 5, the non-diffractive regions 154 are disposed symmetrically about rows of subpixels 110 while the diffractive regions 152 substantially cover the rows of subpixels 110 and a portion of the region between adjacent rows. The arrangement of FIG. 5 will generate collimation primarily along two off-axis directions (positive and negative viewing angles in the yz -plane) as schematically illustrated in FIGS. 1, 2A, and 3 A, for example. In FIG. 6. the non-diffractive regions 154 are disposed asymmetrically about rows of subpixels 110 while the diffractive regions 152 substantially cover the subpixels 110 and much of the regions between subpixels. The arrangement of FIG. 6 will generate collimation primarily along one off-axis direction (negative viewing angle in the yz-plane) as schematically illustrated in FIGS. 2B and 3B, for example.

[0041] In FIG. 7, the non-diffractive regions 154 are disposed asymmetrically about rows of subpixels 110 while the diffractive regions 152 substantially cover the subpixels 110 and much of the regions between subpixels. In FIGS. 5-6, the diffractive elements are approximately equal width and equally spaced elements extending along the x-direction. In FIG. 7, the spacing and widths of adject elements vary which may further increase the asymmetry provided by the arrangement of diffractive regions to further collimate primarily along a single direction (e.g., negative viewing angle in the yz-plane).

[0042] The diffractive regions 152 may include linear diffractive elements or two-dimensional diffractive elements, for example. In some embodiments, the subpixels 110 are arranged into rows of the subpixels extending along a first in-plane direction (x-direction) and arranged along an orthogonal second in-plane direction (y-direction), and the diffractive regions 152 of the diffractive off-axis collimation layer 150 include linear diffractive elements extending along the first in -plane direction and arranged along the second in -plane direction, such that in atop plan view, the non -diffraction regions 154 of the diffractive off-axis collimation layer 150 extend along the first in-plane direction and are off set (e.g., distance DI from center of subpixels to center of non-diffractive region 154) from the rows of subpixels along the second in-plane direction.

[0043] In FIGS. 8 and 9, a two-dimension grating is utilized to provide collimation primarily along a single first off-axis direction. In FIGS. 6-8, the first off-axis direction is in the yz-plane and has a negative y-component (i.e., makes an angle greater than 90 degrees with the +y direction or, equivalently, less than 90 degrees with the minus y-direction). In FIG. 9, the first off-axis direction is in the y'z-plane and makes an angle greater than 90 degrees with the +y' -direction, referring to the illustrated x'-y'-z coordinate system with is rotated about the z-axis relative to the x-y-z coordinate system.

[0044] In some embodiments, in a top plan view: the diffractive regions 152 cover at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 or 100 percent of a total area of the subpixels 110. In some such embodiments, or in other embodiments, in the top plan view, at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 percent of a total area of the non-diffractive regions 154 cover non-emissive areas 120 of the display. In some such embodiments, or in other embodiments, the display 151 has a display surface 101 for forming an image 107 thereacross for viewing by a viewer 109a, 109b, where the display surface 101 includes an emissive area defined by the subpixels 110 and a non-emissive area 120 being a total remaining portion of the display surface 101. In some such embodiments, or in other embodiments, in the top plan view, the diffractive regions 152 cover less than 65, 60, 55, 50, 45, 40, 35, 30, 25, or 20 percent of the non- emissive area. In some such embodiments, or in other embodiments, in the top plan view, the diffractive regions 152 cover at least 50, 55, 60, 65, 70, 75, or 80 percent of the non-emissive area. The off-axis direction can be selected by suitably selecting a distance D 1 between pixels and adjacent non-diffractive regions 154 and a distance SI between the diffractive features and the display surface 101.

[0045] In some embodiments, a display system 100 includes a display 151 including a display surface 101 including a plurality of pixels, where each includes a plurality of subpixels 110 and each subpixel 110 has a subpixel centroid 333 in a top plan view; and a diffractive off-axis collimation layer 150 disposed on the display 151 and configured to at least partially collimate light along a first off-axis direction 241, where the first off-axis direction 241 and a thickness direction (z-direction) of the display

[0046] 151 defines a first plane (e.g., yz-plane or y'z-plane). The diffractive off-axis collimation layer 150 typically includes diffractive regions 152 configured to diffractively transmit light and non-diffractive regions 154 configured to non-diffractive ly transmit light. In some embodiments, the diffractive regions

[0047] 152 include diffractive features spaced apart from the display surface 101 along the thickness direction by an average distance SI. In some embodiments, the diffractive and non-diffractive regions 152 and 154 are arranged relative to the subpixels 110 so that in the top plan view and for each non-diffractive region 154, a distance between a centroid 334 of the non-diffractive region and a subpixel centroid 333 closest thereto is DI, such than an angle al= atan(Dl / Sl) is in a range of 5 to 70 degrees and at least a portion of light emitted from the display surface at the angle al relative to the thickness direction in the first plane exits the display system substantially along the first off-axis direction (e.g., along a direction within the FWHM of the peak in brightness corresponding to the first off-axis direction) after being non- diffractively transmitted by the diffractive off-axis collimation layer. The angle al' between the first off- axis direction 241 and the thickness (z-direction) can differ from the angle al due to refraction. The angle al=atan(Dl / Sl) can be in any range described elsewhere herein for the angle al' between the first off-axis direction 241 and the thickness direction (z-direction). For example, the angle al may be in a range of 5 degrees to 80 degrees, or 8 degrees to 70 degrees, or 10 degrees to 60 degrees, or 14 degrees to 50 degrees, or 18 degrees to 50 degrees, or 20 degrees to 50 degrees.

[0048] In some embodiments, at least a portion (e.g., a portion 140' of light 140 in FIG. 1) of light emitted from the display surface 101 at a second angle (e.g., 0 degrees in FIG. 1) relative to the thickness direction in the first plane exits the display system 100 substantially along the first off-axis direction 241 after being diffractively transmitted by the diffractive off-axis collimation layer 150, where the second angle is different from the first angle by at least about 5, 10, 15, or 20 degrees. In some embodiments, at least another portion (e.g., a portion 140" of light 140 in FIG. 1) of light emitted from the display surface 101 at the second angle relative to the thickness direction in the first plane exits the display system 100 substantially along the second off-axis direction 242 after being diffractively transmitted by the diffractive off-axis collimation layer 150.

[0049] As is known in the art, light diffractive structures of a light diffractive layer can be selected to diffract light into desired directions when the light is transmitted through the light diffractive layer. The light diffractive region 152 can include any suitable diffractive structures that result in light diffraction into suitable directions. For example, the light diffractive region 152 can include phase gratings, amplitude gratings, blazed gratings, one -dimensional gratings (e.g., including substantially parallel linear diffractive elements), two-dimensional gratings (e.g., on a square, rectangular, or hexagonal lattice), subwavelength structures, metasurface structures, and / or other diffractive structures known in the art. In some embodiments, the light diffractive structures form a grating, and the geometry and refractive indices of the light diffractive structures can be related to the desired directions by a diffraction grating equation, for example. Illustrative diffractive structures described by diffraction grating equations can be found in “Design and fabrication of binary slanted surface-relief gratings for a planar optical interconnection”, Miller et al., Applied Optics, Vol. 36, No. 23, 1997 and “Formulation for stable and efficient implementation of the rigorous coupled-wave analysis of binary gratings”, Moharam et al., J. Opt. Soc. Am. A, Vol. 12, No. 5, 1995, for example. In some embodiments, the light diffractive structures form a metasurface (which can be considered to be a diffractive surface) that provides suitable steering into desired directions. Illustrative metasurfaces for beam steering are described in U.S. Pat. Appl. Publ. No., 2021 / 0109364 (Aieta et al.) and “Free-Form Diffractive Metagrating Design Based on Generative Adversarial Networks”, Jiang et al., ACS Nano, 13, 8872-8878, 2019, for example. The geometry of the diffractive elements can be selected, in part, based on the geometry of the pixel and subpixel layout and / or in part on desired luminance profdes along a horizontal direction (e.g., in xz-plane) and / or along a vertical direction (e.g., in yz-plane).

[0050] FIGS. 10-12 are schematic cross-sectional views of illustrative unit cells of diffractive elements that may be used in diffractive regions 152, according to some embodiments. The unit cells may be repeated along the y-direction to define a grating and may include a patterned layer 551 disposed between protective layers 552 and 553. In some embodiments, the diffractive regions 152 include one or more of a symmetric grating 459 or an asymmetric grating 463 (such as a blazed grating 461, for example). In some embodiments, each diffractive region 152 includes a symmetric grating 459. In some embodiments, each diffractive region 152 includes a blazed grating 461. In some embodiments, each diffractive region 152 includes an asymmetric grating 463. In some embodiments, the asymmetric grating 463 includes at least first and second structures 463a and 463b having different respective first and second sizes. In some embodiments, the first off-axis direction 241 and the thickness direction (z-direction) define a first plane (yz-plane) and the asymmetric grating includes a plurality of structures extending along a first in-plane direction (x-direction) substantially orthogonal to the first plane, where the plurality of structures include at least first and second structures 463a and 463b having different respective first and second widths along a second in-plane direction (y-direction) orthogonal to the first in-plane direction. Here, in-plane directions refer to directions in the plane (xy-plane) of the layer 150.

[0051] In some embodiments, the diffractive elements are such that when light from a subpixel 110 is redirected by the diffractive off-axis collimation layer 150 substantially along the first off-axis direction, most of the redirected light is within a FWHM of a first off-axis direction 241 FIG. 13 is a schematic cross-sectional view of light emitted from a subpixel 110a (of pixel 449) and redirected by a diffractive off-axis collimation layer 150 substantially along a first off-axis direction 241, according to some embodiments. A camera 443 can be disposed along the first off-axis direction to detect light from the subpixel 110a. The pixel 449 can include subpixels in addition to subpixel 110a that are disposed along the plus and / or minus x-direction from the cross-section of FIG. 13.

[0052] FIG. 14 is a schematic plan view of a detection area 449' corresponding to a single pixel 449 (including three subpixels), according to some embodiments. The detection area 449' includes a region 110a' corresponding to the subpixel 110a. Dashed outlines corresponding to other subpixels of the pixel 449, according to some embodiments, area schematically illustrated. The detected irradiance can be primarily in the region 451 for example. In some embodiments, when a first subpixel 110a is illuminated and irradiance along the first off-axis direction 241 is measured by a camera 443 disposed along the first off-axis direction 241, at least about 60, 65, 70, 75, 80, 85, 90, or 95 percent of the detected irradiance is within a detection area 449' corresponding to a single pixel that includes the first subpixel 110a. The detection area 449' corresponding to a single pixel is the area in the detection plane of the camera filled by the single pixel and by no other pixels of the display. The area in the detection plane filled by the single pixel may be the same as an area of the single pixel or may differ from the area of the single pixel by a geometric factor such as a cosine of an angle between the detection plane and the plane of the pixels, for example. In some embodiments, when a first subpixel 110a is illuminated and irradiance along the first off-axis direction 241 is measured by a camera 443 disposed along the first off-axis direction 241, at least 90, 92, 94, 96, 98, 99, 99.5 or even 100 percent of the detected irradiance is within a detection area 469' corresponding to a display area 469 including the single pixel and having a length and width each being twice a respective length and width of the single pixel (an illustrative pixel 449 and corresponding display area 469 are schematically shown in FIG. 5, for example). In some embodiments, when a first subpixel 110a is illuminated and irradiance along the first off-axis direction 241 is measured by a camera 443 disposed along the first off-axis direction 241, at least about 60, 65, 70, 75, 80, 85, 90, or 95 percent of the detected irradiance is within a detection area 449' corresponding to a single pixel that includes the first subpixel 110a and at least 90, 92, 94, 96, 98, 99, 99.5 or even 100 percent of the detected irradiance is within a detection area 469' corresponding to a display area 469 including the single pixel and having a length and width each being twice a respective length and width of the single pixel. In some embodiments, when a first subpixel 110a is illuminated and irradiance along the first off-axis direction 241 is measured by a camera 443 disposed along the first off-axis direction 241, at least 50, 55, 60, 65, or 70 percent of the detected irradiance is within a detection area 559' corresponding to a display area 559 (see, e.g., FIG. 5) including the first subpixel 110a and having a length and width each being twice a respective length and width of the first subpixel 110a. In some embodiments, when each subpixel of a first pixel 449 is illuminated and irradiance along the first off-axis direction is measured by a camera 443 disposed along the first off-axis direction 241, at least about 60, 65, 70, 75, 80, 85, or 90 percent of the detected irradiance is within a detection area 449' corresponding to the first pixel 449. In some embodiments, at least 90, 92, 94, 96, 98, 99, 99.5, or even 100 percent of the detected irradiance is within a detection area 469' corresponding to a display area 469 including the first pixel 449 and having a length and width each being twice a respective length and width of the first pixel 449.

[0053] EXAMPLES

[0054] Examples 1-2

[0055] Display systems generally as illustrated in FIGS. 5 and 6 (Examples 1 and 2, respectively) were modeled using conventional ray tracing techniques. The diffractive gratings were simulated via rigorous coupled wave analysis (RCWA) and the scattering information was then compiled for utilization during the ray trace. The pixels were arranged at a 210 micrometer pitch (e.g., center of red subpixel to center of red subpixel of an adjacent pixel) and the subpixels were square shaped with a 30 micrometer width. The gap between adjacent subpixels of a pixel was 40 micrometers. The diffractive off-axis collimation layer was modeled as including a layer 150a having a refractive index of about 1.5 and having a rectangular grating profile including ridges having a height of 900 nm and a width of 840 nm. The ridges were arranged at a pitch of 1200 nm and defined gaps between adjacent ridges that were 360 nm wide. A layer 150b having a refractive index of about 1.72 was disposed on layer 150a with the material of the layer 150b filling in the gaps between adjacent ridges. The emission profiles of the subpixels were modeled as Lambertian. The distance SI was 110 micrometers. For Example 1, the diffractive off-axis collimation layer utilized a symmetric grating disposed symmetrically about the subpixels (see, e.g., FIG. 5) and was adapted to collimate light primarily along first and second off-axis directions having azimuths of about 90 degrees relative to a horizontal direction of the display. For Example 2, the diffractive off-axis collimation layer utilized a symmetric grating disposed asymmetrically about the subpixels (see, e.g., FIG. 6) and was adapted to collimate light primarily along a first off-axis directions having an azimuth of about 90 degrees relative to a horizontal direction of the display. Results for the display system as generally depicted in FIG. 5 (Example 1) are shown in FIG. 3 A for green illuminated subpixels. Results for the display system as generally depicted in FIG. 6 (Example 2) are shown in FIGS. 3B and 4B for green illuminated subpixels. The quantities B1 / B0, Bmin / Bmax and B2 / B0, which are described elsewhere herein, were calculated for a rectangular region 640 defined by -30 degrees < Axz < 30 degrees and -15 degrees > Ayz > -25 degrees. Results for red, green, and blue subpixels for Example 2 are provided in the table below: For Example 1, a single green subpixel of a single pixel was illuminated and irradiance along the first off-axis direction was determined by an optically modeled camera disposed along the first off-axis direction. Most (99 %) of the detected irradiance was within an area of the single pixel. Additionally, 73 % of the detected irradiance was within an area of 60 micrometers x 60 micrometers (the area had a length and width each being twice a respective length and width of the illuminated green subpixel). FIGS. 15A-15B are plots of the detected irradiance for a control display that did not include the diffractive off- axis collimation layer and for the display system of Example 1, respectively.

[0056] Example 3

[0057] A display system was modeled as in Example 1 except that a blazed grating was used. The grating profile had a pitch of 1.2 micrometers, a height of 3 micrometers, and a blaze angle of 74 degrees. The blazed grating included a backfill having a refractive index of about 1.85 disposed on a structured layer having a refractive index of about 1.52. Results are shown in FIG. 3C.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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. A display system, comprising: a display comprising a plurality of pixels, each pixel comprising a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display, the diffractive off-axis collimation layer comprising diffractive regions configured to diffractively transmit light and non-diffractive regions configured to non-diffractively transmit light, the diffractive and non-diffractive regions arranged relative to the subpixels so that: at least a portion of light emitted by the subpixels at a first oblique angle is non-diffractively transmitted by the diffractive off-axis collimation layer and exits the display system substantially along the first off-axis direction; and at least a portion of light emitted by the subpixels substantially along the thickness direction is diffractively transmitted by the diffractive off-axis collimation layer and exits the display system substantially along the first off-axis direction.

2. The display system of claim 1, wherein the diffractive off-axis collimation layer is configured to at least partially collimate light along a second off-axis direction different from the first off-axis direction such that a brightness distribution of the display comprises spaced apart first and second peaks along the respective first and second off-axis directions.

3. The display system of claim 1, wherein the first off-axis direction and the thickness direction define a first plane, a brightness distribution of the display in the first plane comprising a first peak along the first off-axis direction, the first peak comprising a first peak brightness being a global maximum of the brightness distribution in the first plane, the brightness distribution in the first plane free of any second peak spaced apart from the first peak by at least 30 degrees and having a second peak brightness greater than about 85% of the first peak brightness.

4. The display system of claim 1, wherein the first off-axis direction and the thickness direction define a first plane, a brightness distribution of the display in the first plane comprising a first peak along the first off-axis direction, the first peak comprising a first peak brightness and a corresponding full width at half maximum FWHM, the first peak brightness being a global maximum of the brightness distribution in the first plane, the brightness distribution in the first plane free of any second peak spaced apart from the first peak by at least 0.5 times the FWHM and having a second peak brightness greater than about 85% of the first peak brightness.

5. The display system of claim 1, wherein in a top plan view:the diffractive regions cover at least 50 percent of a total area of the subpixels; and at least 50 percent of a total area of the non -diffractive regions cover non -emissive areas of the display.

6. The display system of claim 5, wherein the display comprises a display surface for forming an image thereacross for viewing by a viewer, the display surface comprising an emissive area defined by the subpixels and a non-emissive area being a total remaining portion of the display surface, wherein in the top plan view, the diffractive regions cover less than 65 percent of the non-emissive area.

7. The display system of claim 5, wherein the display comprises a display surface for forming an image thereacross for viewing by a viewer, the display surface comprising an emissive area defined by the subpixels and a non-emissive area being a total remaining portion of the display surface, wherein in the top plan view, the diffractive regions cover at least 50 percent of the non-emissive area.

8. The display system of claim 1, wherein the subpixels are arranged into rows of the subpixels extending along a first in-plane direction and arranged along an orthogonal second in-plane direction, the diffractive regions of the diffractive off-axis collimation layer comprising linear diffractive elements extending along the first in-plane direction and arranged along the second in-plane direction, such that in a top plan view, the non-diffraction regions of the diffractive off-axis collimation layer extend along the first inplane direction and are off set from the rows of subpixels along the second in-plane direction.

9. The display system of claim 1, wherein when a first subpixel is illuminated and irradiance along the first off-axis direction is measured by a camera disposed along the first off-axis direction, at least about 60% of the detected irradiance is within a detection area corresponding to a single pixel comprising the first subpixel.

10. The display system of claim 1, wherein when a first subpixel is illuminated and irradiance along the first off-axis direction is measured by a camera disposed along the first off-axis direction, at least about 50% of the detected irradiance is within a detection area corresponding to display area including the first subpixel and having a length and width each being twice a respective length and width of the first subpixel.

11. The display system of claim 1, wherein the diffractive off-axis collimation layer increases a brightness of the display along the first off-axis direction by at least about 10 percent while decreasing an on-axis brightness of the display.

12. A display system, comprising: a display comprising a display surface comprising a plurality of pixels, each pixel comprising a plurality of subpixels, each subpixel having a subpixel centroid in a top plan view; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction, the first off-axis direction and a thickness direction of the display defining a first plane, the diffractive off-axis collimation layer comprising diffractive regions configured to diffractively transmit light and non-diffractive regions configured to non-diffractively transmit light, the diffractive regions comprising diffractive features spaced apart from the display surface along the thickness direction by an average distance SI, the diffractive and non-diffractive regions arranged relative to the subpixels so that in the top plan view and for each non-diffractive region, a distance between a centroid of the non-diffractive region and a subpixel centroid closest thereto is DI, such than an angle al= atan(D 1 / S 1) is in a range of 5 to 70 degrees and at least a portion of light emitted from the display surface at the angle al relative to the thickness direction in the first plane exits the display system substantially along the first off-axis direction after being non-diffractively transmitted by the diffractive off-axis collimation layer.

13. The display system of claim 12, wherein at least a portion of light emitted from the display surface at a second angle relative to the thickness direction in the first plane exits the display system substantially along the first off-axis direction after being diffractively transmitted by the diffractive off-axis collimation layer, the second angle different from the first angle by at least about 5 degrees.

14. A display system, comprising: a display comprising a plurality of pixels, each pixel comprising a plurality of subpixels; and a diffractive off-axis collimation layer disposed on the display and configured to at least partially collimate light along a first off-axis direction making an angle of at least 5 degrees with a thickness direction of the display, the first off-axis direction and the thickness direction defining a first plane, the diffractive off-axis collimation layer comprising diffractive regions configured to diffractively transmit light and non-diffractive regions configured to non-diffractively transmit light, the diffractive and non- diffractive regions arranged relative to the subpixels so that the diffractive off-axis collimation layer increases a brightness of the display along the first off-axis direction by at least about 10 percent while decreasing an on-axis brightness of the display.

15. The display system of claim 14, wherein the display has an on-axis brightness BO, and for a rectangular region of a coordinate space defined by first and second angles in respective first and second planes orthogonal to one another and parallel to the thickness direction, the rectangular region substantially centered on the first off-axis direction and comprising a range of the first angle at least 5 degrees wide and a range of the second angle at least 30 degrees wide, the display system has an averagebrightness B 1, a maximum brightness Bmax and a minimum brightness Bmin, B 1 / BO at least about 1.2, Bmin / Bmax at least 0.7.

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