# US 10,371,952 B2 · Fresnel lens with dynamic pitch > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,952 B2 - Document ID: US10371952B2 - Status: Granted - Kind: B2 - Application number: 15/594,485 - Filed: 2017-05-12 - Published: 2018-03-15 - Granted: 2019-08-06 - Earliest claimed: 2016-09-13 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Brian Wheelwright; Ning Yueng Chan; Jacques Gollier - Web page: https://patentgrep.com/patent/US10371952B2 ## CPC - G02B 27/0172: {characterised by optical features} - G02B 3/08: with discontinuous faces, e.g. Fresnel lens {(diffractive Fresnel lenses G02B5/1876)} - G02B 27/0176: {characterised by mechanical features} - G02B 5/1876: {Diffractive Fresnel lenses; Zone plates; Kinoforms (G02B5/1842, G02B5/1847 take precedence; optical systems having diffractive correction means G02B27/0037; Fresnel lenses operating by refraction G02B3/08)} - G02B 27/0093: {with means for monitoring data relating to the user, e.g. head-tracking, eye-tracking} - G02B 2027/011: {comprising device for correcting geometrical aberrations, distortion} - G02B 2027/0152: {involving arrangement aiming to get lighter or better balanced devices} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A lens includes an optically transparent substrate having a first lens surface and a second lens surface opposite to the first lens surface. The first lens surface includes a plurality of Fresnel structures. A respective Fresnel structure of the plurality of Fresnel structures includes a slope facet and a draft facet. The respective Fresnel structure of the plurality of Fresnel structures is characterized by a representative pitch. The representative pitch of the respective Fresnel structure is based on a distance of the respective Fresnel structure from a reference axis of the lens. A display device that includes the lens and an electronic display coupled with the lens for outputting light through the lens and a method for transmitting light from an electronic display toward the lens are also described. ## Claims ### Claim 1 A lens for directing light from an electronic display toward a first reference pupil through a first medium, the lens comprising: an optically transparent substrate having a first lens surface and a second lens surface opposite to the first lens surface, wherein: the first lens surface includes a plurality of Fresnel structures, wherein a respective Fresnel structure of the plurality of Fresnel structures is characterized by a representative pitch; the representative pitch of the respective Fresnel structure is based on a distance of the respective Fresnel structure from a reference axis of the lens; the respective Fresnel structure of the plurality of Fresnel structures includes a slope facet and a draft facet; the draft facet is characterized by a draft angle, relative to an optical axis of the lens, that is between a first angle for the respective Fresnel structure and a second angle for the respective Fresnel structure, the first angle for the respective Fresnel structure corresponding to an angle between the optical axis of the lens and a direction of a chief ray, in the first medium, incident upon the slope facet of the respective Fresnel structure, wherein the chief ray: is transmitted from a reference off-axis position on the electronic display, located away from the optical axis of the lens, and is transmitted through the slope facet of the respective Fresnel structure and propagates toward a center of the first reference pupil; the second angle for the respective Fresnel structure corresponding to an angle between the optical axis of the lens and a direction of the chief ray, in the optically transparent substrate, that is transmitted through the slope facet of the respective Fresnel structure and propagates toward the center of the first reference pupil; the draft angle of the respective Fresnel structure is distinct from the first angle and the second angle for the respective Fresnel structure; and the draft angle of the respective Fresnel structure is a predefined weighted average of the first angle and the second angle. ### Claim 2 (depends on 1) The lens of claim 1, wherein: the first medium is air. ### Claim 3 (depends on 1) The lens of claim 1, wherein: the draft angle is between a third angle and a fourth angle, the third angle corresponding to an angle between the optical axis of the lens and a direction of the chief ray, in the first medium, incident upon the slope facet of the respective Fresnel structure, wherein the chief ray: is transmitted from a reference off-axis position on the electronic display, located away from an optical axis of the lens, and is transmitted through the slope facet of the respective Fresnel structure and propagates toward the center of a second reference pupil; the fourth angle corresponding to an angle between the optical axis of the lens and a direction of the chief ray, in the optically transparent substrate, that is transmitted through the slope facet of the respective Fresnel structure and propagates toward the center of the second reference pupil; the first reference pupil is located at a first distance from the optically transparent substrate; the second reference pupil is located at a second distance from the optically transparent substrate; and the second distance is greater than the first distance. ### Claim 4 (depends on 3) The lens of claim 3, wherein: the first reference pupil is rotatable about a reference center of rotation; and the second reference pupil defines a reference plane that includes the reference center of rotation. ### Claim 5 (depends on 1) The lens of claim 1, wherein: the plurality of Fresnel structures includes a first Fresnel structure and a second Fresnel structure; the first Fresnel structure is characterized by a first representative pitch; and the second Fresnel structure is characterized by a second representative pitch, distinct from the first representative pitch. ### Claim 6 (depends on 5) The lens of claim 5, wherein: the second Fresnel structure is positioned further away from the reference axis of the lens than the first Fresnel structure; and the second representative pitch is smaller than the first representative pitch. ### Claim 7 (depends on 5) The lens of claim 5, wherein: the first Fresnel structure is characterized by a first depth; and the second Fresnel structure is characterized by a second depth, distinct from the first depth. ### Claim 8 (depends on 7) The lens of claim 7, wherein: the second Fresnel structure is positioned further away from the reference axis of the lens than the first Fresnel structure; and the second depth is greater than the first depth. ### Claim 9 (depends on 5) The lens of claim 5, wherein: the first Fresnel structure is characterized by a first draft angle; and the second Fresnel structure is characterized by a second draft angle, distinct from the first draft angle. ### Claim 10 (depends on 9) The lens of claim 9, wherein: the second Fresnel structure is positioned further away from the reference axis of the lens than the first Fresnel structure; and the second draft angle is greater than the first draft angle. ### Claim 11 (depends on 1) The lens of claim 1, wherein: a lateral distance from a peak of the slope facet of the respective Fresnel structure to a valley of the slope facet of the respective Fresnel structure is based on the distance of the respective Fresnel structure from the reference axis of the lens. ### Claim 12 (depends on 1) The lens of claim 1, wherein: a lateral distance from a peak of the draft facet of the respective Fresnel structure to a valley of the draft facet of the respective Fresnel structure is based on the distance of the respective Fresnel structure from the reference axis of the lens. ### Claim 13 (depends on 1) The lens of claim 1, wherein: a lateral distance from a valley of the draft facet of the respective Fresnel structure to a valley of the slope facet of the respective Fresnel structure is based on the distance of the respective Fresnel structure from the reference axis of the lens. ### Claim 14 (depends on 1) The lens of claim 1, wherein: the lens is configured to focus light impinging on the first lens surface. ### Claim 15 (depends on 1) The lens of claim 1, wherein the lens, in which a first Fresnel structure in the plurality of Fresnel structures has a first representative pitch and a second Fresnel structure in the plurality of Fresnel structures has a second representative pitch that is distinct from the first representative pitch, has a lower draft facet visibility than a lens having a plurality of Fresnel structures in which a respective Fresnel structure has a same representative pitch. ### Claim 16 (depends on 1) A display device, comprising: the lens of claim 1; and an electronic display coupled with the lens for outputting light through the lens. ### Claim 17 (depends on 16) The display device of claim 16, wherein the display device is a head-mounted display device. ### Claim 18 A method, comprising: transmitting light from an electronic display toward a lens comprising an optically transparent substrate having a first lens surface and a second lens surface opposite to the first lens surface, wherein: the lens is configured for directing the light from the electronic display toward a first reference pupil through a first medium; the first lens surface includes a plurality of Fresnel structures, wherein a respective Fresnel structure of the plurality of Fresnel structures is characterized by a representative pitch; the representative pitch of the respective Fresnel structure is based on a distance of the respective Fresnel structure from a reference axis of the lens; the respective Fresnel structure of the plurality of Fresnel structures includes a slope facet and a draft facet; the draft facet is characterized by a draft angle, relative to an optical axis of the lens, that is between a first angle for the respective Fresnel structure and a second angle for the respective Fresnel structure, the first angle for the respective Fresnel structure corresponding to an angle between the optical axis of the lens and a direction of a chief ray, in the first medium, incident upon the slope facet of the respective Fresnel structure, wherein the chief ray: is transmitted from a reference off-axis position on the electronic display, located away from an optical axis of the lens, and is transmitted through the slope facet of the respective Fresnel structure and propagates toward the center of the first reference pupil; the second angle for the respective Fresnel structure corresponding to an angle between the optical axis of the lens and a direction of the chief ray, in the optically transparent substrate, that is transmitted through the respective Fresnel structure and propagates toward the center of the first reference pupil; the draft angle of the respective Fresnel structure is distinct from the first angle and the second angle for the respective Fresnel structure; and the draft angle of the respective Fresnel structure is a predefined weighted average of the first angle and the second angle.