Patent ID: 11892620
Assignee: INSTITUT NATIONAL D'OPTIQUE
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 17:
18. A target device for characterizing a terahertz imaging system under test using terahertz radiation, the target device comprising:
a terahertz resolution pattern having spatially distributed resolution features configured to transmit or to reflect the terahertz radiation;
at least one prism assembly coupled to the terahertz resolution pattern, each of the at least one prism assembly being arranged in a Frustrated Total Internal Reflection (FTIR) configuration and comprising:
a first prism made of a material having a first refractive index n1 for said terahertz radiation, the first prism having outer interfaces and a first FTIR interface i1, one of the outer interfaces of the first prism defining an input interface of said prism assembly, said input interface being positioned to receive an incident terahertz radiation beam; and
a second prism made of a material having a second refractive index n2 for said terahertz radiation, the second prism having outer interfaces and a second FTIR interface i2,
wherein the FTIR configuration comprises the first FTIR interface i1 and the second FTIR interface i2 facing each other and separated by a gap having a variable width, and
wherein the terahertz resolution pattern is provided along one of the outer interfaces of the second prism of each of the at least one prism assembly and extends across a path of a transmitted radiation beam corresponding to a portion of the incident terahertz radiation beam transmitted through the input interface and then transmitted through the gap by evanescent-wave coupling, the spatially distributed resolution features reflecting the transmitted radiation beam;
whereby when in use to characterize the terahertz imaging system under test with said terahertz radiation, said target device provides contrast images of the resolution features with a variable contrast determined by the variable width of the gap.