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US5044744A
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Method and apparatus for distance measurement using electromagnetic waves
Assignee: Hamamatsu Photonics KK
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Filing: 1990-05-29
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Granted: 1991-09-03
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Expires: 2010-05-29
Abstract
Abstract Times t 1 and t 2 required for two electromagnetic waves having different wavelengths to propagate from a reference point to a target point are measured. Necessary meteorological conditions along the path are also measured to determine refractivities N 1 and N 2 of the path for the two electromagnetic waves as: N.sub.1 =α.sub.1 ·ρ.sub.s +β.sub.1 ·ρ w N.sub.2 =α.sub.2 ·ρ.sub.s +β.sub.2 ·ρ w where ρ s and ρ w are densities of dry air and water vapor in the path, respectively. Length of the path D is calculated using the following formula: D=[t.sub.1 +{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ s )·(t 2 -t 1 )}/{(α 1 +β 1 ·ρ w /ρ s )-(α 2 +β 2 ·ρ w /ρ s )}]·C. where C is the speed of an electromagnetic wave in vacuum.
Inventors
- 👤 Ichizo Ogawa
- 👤 Yoshihisa Warashina
- 👤 Yoshihiko Mizushima
- 👤 Koji Ichie
- 👤 Morio Takeichi
- 👤 Akira Takeshima
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 11:31
CPC Classifications
G; G01; G01S; G01S17/00; G01S17/02; G01S17/06; G01S17/08; G01C; G01C15/00; G01C15/002; G01S17/87; G01S7/00; G01S7/48; G01S7/497
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
184 words
A method for measuring a length of a path between a reference point and a target point using two electromagnetic waves having different wavelengths, comprising the steps of: measuring respective times t 1 and t 2 required for a first electromagnetic wave and a second electromagnetic wave to propagate from the reference point to the target point; measuring meteorological conditions along the path including a temperature, an atmospheric pressure and a relative humidity; determining respective refractivities N 1 and N 2 of the path for the first and second electromagnetic waves as: N.sub.1 =α.sub.1 ·ρ.sub.s +β.sub.1 ·ρ.sub.w N.sub.2 =α.sub.2 ·ρ.sub.s +β.sub.1 ·ρ.sub.w where ρ s and ρ w are densities of dry air and water vapor in the path, respectively, based on the measured meteorological conditions and where α 1 , α 2 , β 1 and β 2 are wavelength-dependent coefficients; and calculating the length of the path using a formula of: D=[t.sub.1 +{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)·(t.sub.2 -t.sub.1)}/{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)-(α.sub.2 +β.sub.2 ·ρ.sub.w /ρ.sub.s)}]·C where C is a speed of an electromagnetic wave in vacuum, or using an approximated expansion of the formula.
Claim 2
Independent Claim
184 words
A method for measuring a length of a path between a reference point and a target point using two electromagnetic waves having different wavelengths, comprising the steps of: measuring respective times t 1 and t 2 required for a first electromagnetic wave and a second electromagnetic wave to propagate from the reference point to the target point; measuring meteorological conditions along the path including a temperature, an atmospheric pressure and a relative humidity; determining respective refractivities N 1 and N 2 of the path for the first and second electromagnetic waves as: N.sub.1 =α.sub.1 ·ρ.sub.s +β.sub.1 ·ρ.sub.w N.sub.2 =α.sub.2 ·ρ.sub.s +β.sub.1 ·ρ.sub.w where ρ s and ρ w are densities of dry air and water vapor in the path, respectively, based on the measured meteorological conditions and where α 1 , α 2 , β 1 and β 2 are wavelength-dependent coefficients; and calculating the length of the path using a formula of: D=[t.sub.1 +{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)·(t.sub.2 -t.sub.1)}/{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)-(α.sub.2 +β.sub.2 ·ρ.sub.w /ρ.sub.s)}]·C where C is a speed of an electromagnetic wave in vacuum, or using an approximated expansion of the formula.
Claim 3
Independent Claim
189 words
An apparatus for measuring a length of a path between a reference point and a target pint using two electromagnetic waves having different wavelengths, comprising: means for measuring respective time t 1 and t 2 required for a first electromagnetic wave and a second electromagnetic wave to propagate from the reference point to the target point; means for measuring meteorological conditions along the path including a temperature, an atmospheric pressure and a relative humidity; and means for determining respective refractivities N 1 and N 2 of the path for the first and second electromagnetic waves as: N.sub.1 =α.sub.1 ·ρ.sub.s +β.sub.1 ·ρ.sub.w N.sub.2 =α.sub.2 ·ρ.sub.s +β.sub.1 ·ρ.sub.w where ρ s and ρ w are densities of dry air and water vapor int he path, respectively, based on the measured meteorological conditions and where α 1 , α 2 , β 1 and β 2 are wavelength-dependent coefficients; and for calculating the length of the path using a formula of: D=[t.sub.1 +{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)·(t.sub.2 -t.sub.1)}/{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)-(α.sub.2 +β.sub.2 ·ρ.sub.w /ρ.sub.s)}]·C where C is a speed of an electromagnetic wave in vacuum, or using an approximated expansion of the formula.
Claim 4
Independent Claim
189 words
An apparatus for measuring a length of a path between a reference point and a target pint using two electromagnetic waves having different wavelengths, comprising: means for measuring respective time t 1 and t 2 required for a first electromagnetic wave and a second electromagnetic wave to propagate from the reference point to the target point; means for measuring meteorological conditions along the path including a temperature, an atmospheric pressure and a relative humidity; and means for determining respective refractivities N 1 and N 2 of the path for the first and second electromagnetic waves as: N.sub.1 =α.sub.1 ·ρ.sub.s +β.sub.1 ·ρ.sub.w N.sub.2 =α.sub.2 ·ρ.sub.s +β.sub.1 ·ρ.sub.w where ρ s and ρ w are densities of dry air and water vapor int he path, respectively, based on the measured meteorological conditions and where α 1 , α 2 , β 1 and β 2 are wavelength-dependent coefficients; and for calculating the length of the path using a formula of: D=[t.sub.1 +{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)·(t.sub.2 -t.sub.1)}/{(α.sub.1 +β.sub.1 ·ρ.sub.w /ρ.sub.s)-(α.sub.2 +β.sub.2 ·ρ.sub.w /ρ.sub.s)}]·C where C is a speed of an electromagnetic wave in vacuum, or using an approximated expansion of the formula.
Claim 5
Dependent Claim
128 words
The apparatus according to claim 2, wherein the time measuring means comprises: transmitting means at the reference point for transmitting said first and second electromagnetic waves to the target; reflecting means at the target point for reflecting said first and second electromagnetic waves back to the reference point; detecting means at the reference pint for detecting said reflected first and second electromagnetic waves to produce corresponding said first and second detection electric signals; means for obtaining respective first and second phase differences of said first and second detection electric signals from a synchronizing signal; means for calculating the times t 1 and t 2 based on the obtained first and second phase differences; and means for providing the synchronizing signal to the transmitting means and the obtaining means.
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