US 12,248,255 B2
Differential measurement system
Hubert Matthieu Richard Steijns, Veldhoven (NL); and Pulkit Aggarwal, Veldhoven (NL)
Assigned to ASML NETHERLANDS B.V., Veldhoven (NL)
Appl. No. 17/916,730
Filed by ASML Netherlands B.V., Veldhoven (NL)
PCT Filed Mar. 9, 2021, PCT No. PCT/EP2021/055884
§ 371(c)(1), (2) Date Oct. 3, 2022,
PCT Pub. No. WO2021/204478, PCT Pub. Date Oct. 14, 2021.
Claims priority of application No. 20168356 (EP), filed on Apr. 7, 2020.
Prior Publication US 2023/0152718 A1, May 18, 2023
Int. Cl. G03F 7/00 (2006.01); G01F 1/06 (2006.01); G01F 1/86 (2006.01); G01M 3/38 (2006.01)
CPC G03F 7/7085 (2013.01) [G01F 1/065 (2013.01); G01F 1/86 (2013.01); G01M 3/38 (2013.01); G03F 7/70908 (2013.01); G03F 7/70975 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A system comprising:
first and second coaxial members configured to have an axis of rotation substantially parallel to a light path,
wherein:
the first member comprises a first pattern and is arranged to rotate with a first speed of rotation, wherein the first speed of rotation of the first member is configured to be based on a flow rate of a first target,
the second member comprises a second pattern and is arranged to rotate with a second speed of rotation, wherein the second speed of rotation of the second member is configured to be based on a flow rate of a second target, and
the first and second patterns have an angular variation and are configured to generate an interference pattern from a light beam traveling along the light path based on their interaction with the light beam and in response to the first and second members having a relative difference in their rotational speeds, the interference pattern being indicative of a magnitude of this difference; and
a fluid circulation system having a fluid inlet and a fluid outlet,
wherein the system is configured to measure a difference between flow rates of the fluid inlet and the fluid outlet.