OCT measuring device and oct measuring method

Patent metadata

Field	Value
Publication number	US-11408722-B2
Application number	US-202117241125-A
Country	US
Kind code	B2
Filing date	Apr 27, 2021
Priority date	Jun 3, 2020
Publication date	Aug 9, 2022
Grant date	Aug 9, 2022

Abstract

OCT measuring device in the present exemplary embodiment includes: wavelength sweep light source that emits light of which a wavelength is swept; optical interferometer that divides the light into measurement light and reference light, emits measurement light toward measurement surface of measuring target object, and generates an optical interference intensity signal indicating an intensity of interference between measurement light reflected from measurement surface and reference light; electro-optic element which is a phase modulator arranged in a light path of optical interferometer; measurement processor which is a signal generator that derives a position of measurement surface and generates a phase amount indicator signal that indicates a phase amount of phase modulator based on the optical interference intensity signal; and electro-optic element controller which is a phase amount controller that controls the phase amount given to the light that is transmitted through phase modulator.

First claim

What is claimed is:

1. An optical coherence tomography (OCT) measuring device comprising:
a wavelength sweep light source that emits light of which a wavelength is swept;
an optical interferometer that divides the light into measurement light and reference light, emits the measurement light toward a measurement surface of a measuring target object, and generates an optical interference intensity signal indicating an intensity of interference between the measurement light reflected from the measurement surface and the reference light;
a phase modulator arranged in a light path of the optical interferometer;
a signal generator that derives a position of the measurement surface and generates a phase amount indicator signal that indicates a phase amount of the phase modulator based on the optical interference intensity signal; and
a phase amount controller that controls the phase amount given to the light that is transmitted through the phase modulator based on the phase amount indicator signal, wherein:
the signal generator calculates linear instantaneous phase change data that linearly changes from an instantaneous phase value of first data to an instantaneous phase value of last data in a section between a first wave number in the first data of the instantaneous phase change data and a last wave number in the last data of the instantaneous phase change data, calculates phase compensation data by taking a difference between the instantaneous phase change data and the linear instantaneous phase change data, and generates the phase compensation data as the phase amount indicator signal, and
the phase amount controller calculates a compensation voltage control signal based on the phase compensation data and a phase modulation control coefficient that controls a phase modulation amount, which is set in the phase modulator and a phase amount controller, and controls the phase amount by the compensation voltage control signal.

2. The OCT measuring device of claim 1 , wherein the phase modulator is an electro-optic element.

3. The OCT measuring device of claim 1 , wherein the phase modulator is arranged in a reference light path through which the reference light is transmitted.

4. The OCT measuring device of claim 1 , further comprises a reference mirror that reflects modulated light from the phase modulator back to the phase modulator.

5. An optical coherence tomography (OCT) measuring method comprising:
detecting an optical interference intensity signal indicating an intensity of interference between measurement light emitted toward a measurement surface of a measuring target object and reflected from the measurement surface and reference light in a state in which a phase modulator arranged in a light path of an optical interferometer that generates the optical interference intensity signal indicating an intensity of interference with the reference light gives a phase to light transmitted through the light path based on a predetermined compensation voltage control signal, and calculating instantaneous phase change data indicating an instantaneous phase value at a wave number of the light emitted from a wavelength sweep light source that emits the light of which a wavelength is swept;
calculating linear instantaneous phase change data that linearly changes from an instantaneous phase value of first data to an instantaneous phase value of last data in a section between a first wave number in the first data of the instantaneous phase change data and a last wave number in the last data of the instantaneous phase change data;
calculating phase compensation data by taking a difference between the instantaneous phase change data and the linear instantaneous phase change data;
calculating a compensation voltage control signal based on the phase compensation data and a phase modulation control coefficient that controls a phase modulation amount, which is set in the phase modulator and a phase amount controller that controls the phase amount given to the light transmitted through the phase modulator;
storing the compensation voltage control signal in a controller;
giving a phase to the light transmitted through the light path using the compensation voltage control signal output from the controller based on the compensation voltage control signal in accordance with a wavelength sweep timing of the light emitted from the wavelength sweep light source by the phase modulator; and
deriving a position of the measurement surface based on the optical interference intensity signal.

6. The OCT measuring method of claim 5 , wherein, in the calculating of the instantaneous phase change data, the optical interference intensity signals each being the optical interference intensity signal are acquired a plurality of times, and the instantaneous phase change data are calculated based on each of the optical interference intensity signals, and data obtained by averaging the plurality of instantaneous phase change data is used as new instantaneous phase change data.

7. The OCT measuring method of claim 6 , wherein, in the giving of the phase to the light transmitted through the light path, the light that is transmitted through the light path, to which the phase is given, is the reference light.

8. The OCT measuring method of claim 7 , wherein, in the calculating of the compensation voltage control signal, after calculating the compensation voltage control signal at least once or more times, a new compensation voltage control signal is calculated and the compensation voltage control signal is updated while giving the phase to the light transmitted through the light path using the compensation voltage control signal.

9. The OCT measuring method of claim 5 , wherein the phase modulator is an electro-optic element.

Assignees

• Panasonic Ip Man Co Ltd

Inventors

• Takechi Yohei
• Yokoyama Jun

Classifications

• G01B9/02004

  using frequency scans · CPC title

• G01B9/02091 Primary

  Tomographic interferometers, e.g. based on optical coherence · CPC title

• G01J9/02

  by interferometric methods (using interferometers for measuring optically the linear dimensions of objects G01B9/02) · CPC title

• G01B2290/40

  Non-mechanical variable delay line · CPC title

• G01B9/02067

  by electronic control systems, i.e. using feedback acting on optics or light · CPC title