THz measurement method and THz measurement device for surveying a measurement object, in particular a pipe

A THz measuring device for measuring a measured object comprising:

• a THz sensor arrangement including at least one first THz sensor, the THz sensor arrangement adapted to carry out at least one first THz measurement at a first measuring position by emitting a first THz transmission beam and receiving first reflected radiation and one second THz measurement at a second measuring position by emitting a second THz transmission beam and receiving second reflected radiation, the first and second measuring positions being separated by an empty path;
• and
• a controller and evaluating device for controlling the sensor arrangement and receiving at least one measuring signal of the sensor arrangement, said controller and evaluating device being configured to determine, from the at least one measuring signal:
• during a calibration, the empty path, from an empty time of flight of the at least one THz transmission beam through the empty path without a measured object, and
• a total time of flight of the at least one THz transmission beam through a measured object introduced into the empty path from (1) a first and second exterior time of flight of the at least one THz transmission beam between the measuring positions and an exterior surface of a measured object, (2) a first and second wall time of flight of the at least one THz transmission beam in a first wall region and a second wall region of the measured object and (3) an interior time of flight of the at least one THz transmission beam in an interior space of the measured object, and
• from the determined times of flight and the speed of light in the empty path, a first wall thickness of the first wall region, and a second wall thickness of the second wall region of the measured object introduced in the empty path,
• wherein the THz sensor arrangement is configured to emit the first THz transmission and the second THz transmission beam at different times and in different frequency ranges, and/or in different polarity, so as to avoid mutual interference of the two THz transmission beams.

A THz measuring method for measuring a measured object, the method including

• a preparatory step, providing a THz sensor arrangement for emitting and/or reflecting THz transmission beams from at least one first measuring position of a measuring region and from a second measuring position of the measuring region, the measuring positions being separated by an empty path,
• a calibrating step, measuring of an empty time of flight of at least one THz transmission beam through the empty path without the measured object and determining the empty path,
• positioning a measured object inside the measuring region between the first measuring position and the second measuring position,
• carrying out a first THz measurement from the first measuring position using a THz transmission beam along a first optical axis while measuring a first exterior time of flight up to an exterior surface of the measured object, a first wall time of flight through a first wall region of the measured object and an interior time of flight through an interior space of the measured object,
• carrying out a second THz measurement from the second measuring position along a second optical axis while measuring a second exterior time of flight between the second measuring position and the exterior surface of the measured object and a second wall time of flight through a second wall region of the measured object,
• determining a total time of flight through the measuring region with the measured object, and
• determining a first wall thickness of the first wall region and a second wall thickness of the second wall region from the measured times of flight,
• wherein the THz sensor arrangement comprises at least two THz sensors arranged around the measuring region at the measuring positions, emitting the at least two THz transmission beams, and carrying out the at least two THz measurements,
• and wherein the THz sensor arrangement comprises THz-sensors received pivotably in their measuring positions lying, in an initial position, on a common optical axis and being respectively pivoted in their measuring positions from this initial position to an adjusted position thereby producing an adjustment angle formed between a respective optical axis of each THz-sensor in the adjusted position and their common optical axis axes, where the THz-sensors are pivoted away from the initial position subsequent to the calibrating step and/or prior to some of the THz measurements.