# US 10,768,361 B1 · System for monitoring grating formation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,768,361 B1 - Document ID: US10768361B1 - Status: Granted - Kind: B1 - Application number: 16/054,943 - Filed: 2018-08-03 - Granted: 2020-09-08 - Earliest claimed: 2018-08-03 - Assignees: Facebook Technologies, LLC - Applicants: Facebook Technologies, LLC - Inventors: Matthieu Charles Raoul Leibovici; Kavous Jorabchi; Austin Lane - Web page: https://patentgrep.com/patent/US10768361B1 ## CPC - G02B 6/02123: {characterised by the method of manufacture of the grating (photolithography G03F7/0005)} - G01M 11/00: Testing of optical apparatus; Testing structures by optical methods not otherwise provided for - G02B 5/1847: {Manufacturing methods} - G02B 6/02133: {using beam interference} - G02B 6/02195: {characterised by means for tuning the grating} - G02B 6/34: utilising prism or grating {(G02B6/293 takes precedence)} - G02B 27/44: Grating systems; Zone plate systems (G02B27/46 takes precedence) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR ## Abstract A monitoring system monitors changes in an index of refraction of the grating over a time interval that includes the period of time. The monitoring system includes a light source assembly, a probing assembly, a power meter (e.g., a diffraction and/or a transmittance power meter), and a controller. The light source assembly emits a probe beam. The scanning assembly scans the probe beam over an area of the grating. The power meter measures power of a portion of the probe beam that interacts (e.g., is transmitted by or diffracted from) with the area of the grating. The controller determines changes in grating parameters (may be as a function of time) for the grating being formed based in part on measured power readings over the time interval. ## Claims ### Claim 1 A manufacturing system comprising: a grating manufacturing system configured to form a grating over a period of time; a monitoring system configured to monitor changes in an index of refraction of the grating as a function of time over a time interval that includes the period of time, the monitoring system comprising: a light source assembly configured to emit a probe beam; a probing assembly configured to scan the probe beam over an area of the grating; a beam splitter configured to split a reference portion from the probe beam; a reference power meter configured to measure reference power of the reference portion; a diffraction power meter configured to measure diffraction power of a diffraction portion of the probe beam that is diffracted in the area of the grating; a transmittance power meter configured to measure transmittance power of a transmittance portion of the probe beam that is transmitted through the area of the grating; and a controller configured to determine changes in the index of refraction as a function of time for the grating being formed based in part on the measured diffraction power, the measured transmittance power, and the measured reference power over the time interval. ### Claim 2 (depends on 1) The manufacturing system of claim 1, wherein the controller is further configured to: determine a length of time for the grating to complete formation based at least in part on the determined changes in the index of refraction; and provide the length of time to the grating manufacturing system, wherein the grating manufacturing system is configured to adjust the period of time to the length of time for formation of subsequent grating. ### Claim 3 (depends on 1) The manufacturing system of claim 1, wherein the controller is further configured to: determine that the grating is formed based at least in part on the determined changes in the index of refraction; and responsive to the determination that the grating is formed, instruct the manufacturing system to stop formation of the grating, and start formation of a different grating. ### Claim 4 (depends on 1) The manufacturing system of claim 1, wherein the diffraction portion of the probe beam that is diffracted passes through the beam splitter before reaching the diffraction power meter. ### Claim 5 (depends on 1) The manufacturing system of claim 1, wherein the grating is selected from a group consisting of: a phase grating, Bragg grating, a surface relief grating, and a liquid crystal grating. ### Claim 6 (depends on 1) The manufacturing system of claim 1, wherein the probing assembly is configured to scan the probe beam in one or more dimensions over the area of the grating. ### Claim 7 (depends on 1) The manufacturing system of claim 1, wherein the probing assembly is configured to scan the probe beam over the area of the grating at a rate that is faster than the time period, wherein the time period is a time over which the grating is formed. ### Claim 8 (depends on 7) The manufacturing system of claim 7, wherein the rate is approximately 200 Hz and the time over which the grating is formed is approximately 50 ms. ### Claim 9 (depends on 1) The manufacturing system of claim 1, wherein the controller is configured to: generate a report describing the change in the index of refraction for the grating; and provide the report to a user of the manufacturing system. ### Claim 10 A monitoring system comprising: a light source assembly that is configured to emit a probe beam; a probing assembly that is configured to scan the probe beam over an area of a grating being formed over a period of time by a grating manufacturing system; a beam splitter configured to split a reference portion from the probe beam; a reference power meter configured to measure reference power of the reference portion; a diffraction power meter configured to measure diffraction power of a diffraction portion of the probe beam that is diffracted in the area of the grating; a transmittance power meter configured to measure power of a transmittance portion of the probe beam that is transmitted through the area of the grating; and a controller configured to determine changes in an index of refraction as a function of time for the grating being formed based in part on measured power readings over a time interval that includes the period of time, the measured power readings including the power measured by the reference power meter, the diffraction power meter, and the transmittance power meter. ### Claim 11 (depends on 10) The monitoring system of claim 10, wherein the controller is further configured to: determine a length of time for the grating to complete formation based at least in part on the determined changes in the index of refraction; and provide the length of time to the grating manufacturing system, wherein the grating manufacturing system is configured to adjust the period of time to the length of time for formation of subsequent grating. ### Claim 12 (depends on 10) The monitoring system of claim 10, wherein the controller is further configured to: determine that the grating is formed based at least in part on the determined changes in the index of refraction; and responsive to the determination that the grating is formed, instruct the manufacturing system to stop formation of the grating, and start formation of a different grating. ### Claim 13 (depends on 10) The monitoring system of claim 10, wherein the portion of the probe beam that is diffracted passes through the beam splitter before reaching the diffraction power meter. ### Claim 14 (depends on 10) The monitoring system of claim 10, wherein the probing assembly is configured to scan the probe beam in 2-dimensions over the area of the grating. ### Claim 15 (depends on 10) The monitoring system of claim 10, wherein the probing assembly is configured to scan the probe beam over the area of the grating at a rate that is faster than the time period, wherein the time period is a time over which the grating is formed. ### Claim 16 (depends on 15) The monitoring system of claim 15, wherein the rate is approximately 200 Hz and the time over which the grating is formed is approximately 50 ms. ### Claim 17 (depends on 10) The monitoring system of claim 10, wherein the controller is configured to: generate a report describing the change in the index of refraction for the grating as a function of time; and provide the report to a user of the manufacturing system.