公开(公告)号：US20230288247A1

公开(公告)日：2023-09-14

申请号：US18017025

申请日：2020-07-28

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kenji ISHIKAWA ,  Yoshifumi SHIRAKI ,  Takehiro MORIYA ,  Kenichi HITACHI ,  Atsushi ISHIZAWA ,  Katsuya OGURI

IPC: G01H9/00 ,  G01B9/02001 ,  H04R23/00

CPC classification number: G01H9/00 ,  G01B9/0201 ,  H04R23/008

Abstract: An optical phase modulation amount measurement technology using sound without being affected by noise included in an average light intensity is provided. A sound measurement method includes an interference light generation step of obtaining first light including light subjected to light phase modulation by a sound measurement unit and second light including light subjected to light phase modulation by the sound measurement unit, which differs from the first light, from light emitted from a light source, a first light detection step of obtaining a first electrical signal from the first light, a second light detection step of obtaining a second electrical signal from the second light, and a differential signal generation step of obtaining a differential signal that is a difference between the first electrical signal and the second electrical signal, wherein a phase of the light subjected to light phase modulation included in the first light and a phase of the light subjected to the light phase modulation included in the second light are in an inverted relationship, and an optical phase modulation amount φs by sound is measured as a current Δi of the differential signal expressed by an equation Δi=βIA cos (φs+φ0) (where β is a predetermined constant, IA is an amplitude of an interference fringe, and φ0 is an optical phase modulation amount by an element other than sound).

公开(公告)号：US20240410741A1

公开(公告)日：2024-12-12

申请号：US18702396

申请日：2021-10-28

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kenji ISHIKAWA ,  Yoshifumi SHIRAKI ,  Takehiro MORIYA ,  Atsushi ISHIZAWA ,  Kenichi HITACHI ,  Katsuya OGURI

IPC: G01H9/00

Abstract: Provided is a measurement technology of an optical phase modulation amount due to sound without being affected by noise included in average light intensity. The measurement technology includes: an interference light generator that obtains first light including light subjected to optical phase modulation by a sound measurement unit and second light different from the first light and including light subjected to optical phase modulation by the sound measurement unit from light emitted from a light source; a first photodetector that obtains a first electrical signal from the first light; a second photodetector that obtains a second electrical signal from the second light; a differential signal generator that obtains a differential signal that is a difference between the first electrical signal and the second electrical signal; and an optical phase modulation amount adjuster that adjusts an optical phase modulation amount φ0 due to an element other than sound by fixing an interferometer such that a phase of an interference fringe is in mid-fringe by using the differential signal as an error signal, in which the optical phase modulation amount φs due to sound is measured as a current Δi of the differential signal, and the first photodetector and the second photodetector are adjusted such that output voltages are saturated when light that causes a phase fluctuation exceeding a predetermined range around mid-fringe is input.

公开(公告)号：US20240305932A1

公开(公告)日：2024-09-12

申请号：US18578272

申请日：2021-07-20

Applicant: NIPPON TELEGRAPH AND TELEPHONE CORPORATION

Inventor： Kenji ISHIKAWA ,  Yoshifumi SHIRAKI ,  Takehiro MORIYA

IPC: H04R23/00 ,  H04R29/00

CPC classification number: H04R23/008 ,  H04R29/001 ,  H04R2217/03

Abstract: A technique for accurately measuring acoustic characteristics of a parametric array is provided. A first calculation unit that calculates a complex amplitude d of an optical phase at a frequency fd from an amount of change φs of the optical phase caused by demodulated sound S, assuming that qdiff(ξ′, η′) is a function defined using a Gaussian beam expansion method, a second calculation unit that calculates a function value qdiff(ξ, η) at a point X and a line integral value ∫Lqdiff(ξ′, η)dξ′ of the function qdiff(ξ′, η) along the optical path L, and a third calculation unit that calculates a complex amplitude p of the demodulated sound with the frequency fd at the point X using the complex amplitude d, the function value qdiff(ξ, η), and the line integral value ∫Lqdiff(ξ′, η)dξ′ are included.