# US 7,609,386 B2 · Optical characteristic measuring apparatus

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- Number: US 7,609,386 B2
- Document ID: US7609386B2
- Status: Granted
- Kind: B2
- Application number: 12/277,032
- Filed: 2008-11-24
- Published: 2009-03-26
- Granted: 2009-10-27
- Earliest claimed: 2005-05-31
- Assignees: Yokogawa Electric Corporation
- Inventors: Takaaki Hirata; Minoru Maeda
- Web page: https://patentgrep.com/patent/US7609386B2

## CPC

- G01J 4/04: Polarimeters using electric detection means (G01J4/02 takes precedence)
- G01B 9/02003: using beat frequencies
- G01B 9/02004: using frequency scans
- G01B 9/02007: {Two or more frequencies or sources used for interferometric measurement (using only beat G01B9/02003)}
- G01J 3/453: by correlation of the amplitudes
- G01M 11/0235: {by measuring multiple properties of lenses, automatic lens meters}
- G01M 11/0292: {of objectives by measuring the optical modulation transfer function (photometry G01J)}
- G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence)
- H04J 14/0227: {Operation, administration, maintenance or provisioning [OAMP] of WDM networks, e.g. media access, routing or wavelength allocation}
- H04J 14/0246: {using one wavelength per ONU}
- H04J 14/06: Polarisation multiplex systems
- G01B 2290/45: Multiple detectors for detecting interferometer signals
- G01B 2290/70: Using polarization in the interferometer
- G01J 3/10: Arrangements of light sources specially adapted for spectrometry or colorimetry
- G01J 3/4338: {Frequency modulated spectrometry}
- G02B 27/283: {used for beam splitting or combining}
- H04J 14/0279: {WDM point-to-point architectures}
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical characteristic measuring apparatus includes: a light source section which sweeps wavelengths of a first input light and a second input light respectively, frequencies of the first and second input lights being different from each other and polarized states of the first and second input lights being perpendicular to each other, and outputs the first and second input light; an interference section which inputs one branched light of the first and second input lights to a measuring object, makes output light from the measuring object interfere with other branched light of the first and second input lights, and outputs a plurality of interference lights; a plurality of light receiving sections which are respectively provided for the interference lights, receives the interference lights respectively, and outputs signals in accordance with optical powers of the interference lights respectively; and a low-pass filter for filtering the outputted signals.

## Claims

### Claim 1

An optical characteristic measuring apparatus for measuring an optical characteristic of a measuring object, the optical characteristic measuring apparatus comprising:
a first wavelength variable light source which sweeps a wavelength of a first input light and outputs the first input light to an interference section;
a second wavelength variable light source which sweeps a wavelength of a second input light and outputs the second input light to the interference section, frequencies of the first input light and the second input light being different from each other and polarized states of the first input light and the second input light being perpendicular to each other;
the interference section which multiplexes and inputs the first input light and the second input light to the measuring object, makes output light from the measuring object interfere with at least one of the first input light and the second input light, and outputs a plurality of interference lights;
a detecting section for detecting a frequency difference of the first input light and the second input light from the first wavelength variable light source and the second wavelength variable light source; and
a control section for controlling a frequency difference of the first wavelength variable light source and the second wavelength variable light source based on the frequency difference detected by the detecting section.

### Claim 2 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, wherein at least one of the first wavelength variable light source and the second wavelength variable light source includes a surface emitting laser forming a resonator by a movable mirror being formed by a semiconductor micromachining technology.

### Claim 3 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, wherein at least one of the first wavelength variable light source and the second wavelength variable light source includes a surface emitting laser forming a resonator by a movable mirror being formed by a semiconductor micromachining technology, and
the first wavelength variable light source and the second wavelength variable light source are provided on a same substrate.

### Claim 4 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, wherein the interference section includes a polarization beam splitter which multiplexes the first input light and the second input light and outputs a multiplexed light to the measuring object.

### Claim 5 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, wherein the interference section includes:
a polarization beam splitter which multiplexes at least one of the first input light and the second input light with the output light from the measuring object, and branches a multiplexed light into s polarized light and p polarized light; and
a polarization plane rotating section which inclines at least one polarization plane of the first input light and the second input light by 45°, and outputs an inclined light to the polarization beam splitter.

### Claim 6 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, further comprising:
a plurality of light receiving sections which are respectively provided for the interference lights outputted from the interference section, receives the interference lights respectively, and outputs signals in accordance with optical powers of the interference lights respectively; and
a low-pass filter for filtering the signals outputted from the light receiving sections,
wherein the interference section branches each of the first input light and the second input light, inputs one branched light to the measuring object, makes the output light from the measuring object interfere with other branched light, and outputs the plurality of interference lights,
the plurality of interference lights includes:
a first interference light in which the first input light interferes with an output light in a first polarized state of the output light from the measuring object;
a second interference light in which the second input light interferes with the output light in the first polarized state of the output light from the measuring object;
a third interference light in which the first input light interfere with an output light in a second polarized state of the output light from the measuring object; and
a fourth interference light in which the second input light interferes with the output light in the second polarized state of the output light from the measuring object, and
the first polarized state of the output light and the second polarized state of the output light are perpendicular to each other.

### Claim 7 (depends on 6)

The optical characteristic measuring apparatus according to claim 6, wherein the low-pass filter passes a signal having a frequency lower than a difference of the frequencies of the first input light and the second input light.

### Claim 8 (depends on 1)

The optical characteristic measuring apparatus according to claim 1, wherein the interference section is an interferometer of a spatial light type.