THZ MEASURING DEVICE AND THZ MEASUREMENT METHOD FOR MEASURING TEST OBJECTS, IN PARTICULAR PIPES

Abstract

The invention relates to a THz measuring device (2) for measuring a test object (8), in particular a pipe (8), including a first THz transceiver (3) which outputs a first THz beam (10) with a first polarization plane along an optical axis (A) through a measuring chamber (7), a first polarization mirror (4) designed to reflect the first THz beam (10) passing through the measuring chamber (7) back to the first THz transceiver (3) along the optical axis (A), a second THz transceiver (5), designed to output a second THz beam (11) which is polarized in a second polarization plane that is different, in particular orthogonal, from the first polarization plane, a second polarization mirror (6), designed to reflect the second THz beam (11) passing through the measuring chamber (7) along the optical axis (A) through the measuring chamber (7) back to the second Transceiver (5), wherein the THz beams pass through the respective other polarization mirrors without being substantially influenced, and the measuring signals (S1, S2) of the THz transceivers (3, 5) are correlated with each other so as to determine layer thicknesses (d1, d2) and/or a refractive index (n) of the tested object (8).

Claims

1-17. (canceled)

18. A THz measuring device for measuring a test object, in particular a pipe, the THz measuring device comprising: a first THz transceiver designed to output a first THz beam with a first polarization plane along an optical axis in a first direction through a measuring chamber of the measuring device, a second THz transceiver designed to emit a second THz beam, polarized in a second polarization plane different from the first polarization plane, along the optical axis, a first polarization mirror designed to reflect the first THz beam, which has travelled through the measuring chamber along the optical axis, back to the first THz transceiver, and to allow the second THz beam to pass, at least in part, a second polarization mirror designed to reflect the second THz beam, which has travelled through the measuring chamber, along the optical axis back to the second transceiver, and to allow the first THz beam to pass, at least in part, an evaluation unit designed to receive a first measuring signal of the first THz transceiver and a second measuring signal of the second THz transceiver, determine first measuring peaks of the first measuring signal and second measuring peaks of the second measuring signal and layer thicknesses and/or a refractive index of the tested object.

19. The THz measuring device of claim 18, wherein the first polarization plane of the first THz beam and the second polarization plane of the second THz beam run orthogonally in relation to one another, and/or a first polarization plane of the first polarization mirror which is active for reflections and a second polarization plane of the second polarization mirror which is active for reflections run orthogonally in relation to one another.

20. The THz measuring device of claim 18, wherein the first beam direction of the first THz beam and a second beam direction of the second THz beam are opposite, and/or the first THz transceiver and the second THz transceiver are arranged opposite one another with the measuring chamber in-between them.

21. The THz measuring device of claim 20, wherein the first polarization mirror is arranged between the second THz transceiver and the measuring chamber, and/or the second polarization mirror is arranged between the first THz transceiver and the measuring chamber.

22. The THz measuring device of claim 18, wherein in addition to the first and second THz transceivers, further THz transceivers are provided, directed along further optical axes, in particular centrally through an axis of symmetry or a middle region of the measuring chamber.

23. The THz measuring device of claim 18, wherein the first and second THz beams are formed in overlapping or identical frequency bands, in particular, between 10 GHz and 50 THz, preferably between 50 GHz and 10 THz, e.g., between 50 GHz and 4 THz, in particular, as a direct time-of-flight measurement, for frequency modulated measurements and/or pulsed radiation.

24. The THz measuring device of claim 18, wherein the evaluation unit correlates the two measuring signals with each other, e.g., correlates corresponding first and second measuring peaks of the two measuring signals with each other and/or carries out an averaging across measuring peaks or across time differences between measuring peaks of the two measuring signals, that correspond to identical layer thicknesses.

25. The THz measuring device of claim 24, wherein the evaluation unit is designed to, control the THz transceiver for carrying out measurements coordinated with one another, and/or trigger a calibration measurement of both THz transceivers without a test object contained inside, and to correlates this with the subsequent measurement of the test object, so as to determine both layer thicknesses and a refractive index.

26. A measuring arrangement consisting of a THz measuring device according to claim 18 and a test object received in the measuring chamber, in particular a profile, e.g., rectangular profile, or pipe, made of a material at least partially transparent for the THz beam, e.g., plastics, paper, organic material, or rubber.

27. The measuring arrangement of claim 26, wherein the test object comprises at least one region transparent for THz radiation of different polarizations.

28. The measuring arrangement of claim 26, further comprising a conveyor means is provided for transporting the tested object through the measuring chamber in a direction orthogonal to the optical axis, for continuous temporal measuring of the tested object.

29. A THz measuring method for measuring a test object, in particular a pipe, including the following steps: emitting a first THz beam which is polarized in a first polarization plane along an optical axis through a measuring chamber with a test object and subsequently to a first polarization mirror, on which the first THz beam is reflected back along the optical axis, along the optical axis through the measuring chamber and towards the first THz transceiver which outputs a first measuring signal, at the same time or at least partially overlapping in time, putting out a second THz beam which is polarized in a second polarization plane unequal to the first polarization plane, from a second THz transceiver along the optical axis through the measuring chamber with the test object and towards a second polarization mirror which reflects the second THz beam back along the optical axis towards the second THz transceiver which outputs a second measuring signal, evaluating the first measuring signal and the second measuring signal, where at least one layer thickness and/or a refractive index of the tested object is determined.

30. The THz measuring method of claim 29, wherein the first THz beam and the second THz beam are output in opposite beam directions along the optical axis.

31. The THz measuring method of claim 29, wherein the first polarization plane of the first THz beam runs orthogonal in relation to the second polarization plane of the second THz beam.

32. The THz measuring method of claim 29, wherein the first THz beam output by the first THz transceiver first passes through the second polarization mirror and subsequently through the measuring chamber with the test object, and the second THz beam output by the second THz transceiver first passes through the first polarization mirror and subsequently through the measuring chamber with the test object, wherein the first polarization beam is not or not to a relevant extent reflected on the second polarization mirror due to the first polarization plane, and whereby the second polarization beam is not or not to a relevant extent reflected on the first polarization mirror due to the second polarization plane.

33. The THz measuring method of claim 29, wherein the two measuring signals are evaluated together, whereby the measuring signals are correlated with each other.

34. The THz measuring method of claim 33, wherein the first measuring signal first partial reflection peaks of the first THz beam at boundary layers of the tested object are detected or determined, and a main reflection peak on the first polarization mirror is detected or determined, and correspondingly, in the second measuring signal second partial reflection peaks at the boundary surfaces of the tested object and a main reflection peak on the second polarization mirror are detected, and at least certain one of the partial reflection peaks of the two measuring signals are correlated with each other or equated, in particular, for averaging a layer thickness from the two measurements.

Description

[0022] The invention is further illustrated below by means of the attached drawings by means of certain embodiments. It is shown in:

[0023] FIG. 1 a measuring arrangement consisting of a measuring device and a pipe as test object, depicting the signal amplitudes of the measuring signals;

[0024] FIG. 2 a first polarized electromagnetic wave;

[0025] FIG. 3 a second polarized wave oriented orthogonally in relation to FIG. 2;

[0026] FIG. 4 a representation of the superimposition of the polarized waves;

[0027] FIG. 5 the effect of the polarization mirrors on the THz radiation.

[0028] FIG. 1 shows a measuring arrangement 1 comprising a THz measuring device 2 which in turn comprises a first THz transceiver 3 and a first polarization mirror 4 as well as a second THz transceiver 5 and a second polarization mirror 6.

[0029] In-between the THz transceivers 3 and 5 as well as the polarization mirrors 4 and 6 a measuring chamber 7 is formed in which a test object, in this case a pipe 8, is received and continuously transported along its pipe axis B, i.e., perpendicular to the plane of the drawing.

[0030] The first THz transceiver 3 emits a first THz beam 10 along an optical axis A which is polarized in a first polarization plane and passes through the second polarization mirror 6—substantially without any relevant attenuation. The first THz beam 10 subsequently runs through the measuring chamber 7 and the measured object 8 along the optical axis A, thereby passing through the boundary surfaces 8a through 8d of the tested object 8 creating partial reflection peaks (measuring peaks). Thereafter, the first THz beam 10 reaches the first polarization mirror 4 on which it is reflected, owing to its polarization, back along the optical axis A and again passes through the measuring chamber 7 with the test object 8. Subsequently, the first THz beam 10 runs through the second polarization mirror 6 through which it passes again, owing to its polarization, essentially without significant attenuation, and will subsequently be received by the first first THz transceiver 3 which thereupon generates a first signal amplitude S1.

[0031] Accordingly, the second THz transceiver 5 outputs a second THz beam 11 running along the optical axis A and in a direction opposite that of the first THz beam 10, i.e., in FIG. 1, from right to left. The second THz beam 11 is polarized again, with a polarization plane orthogonal in relation to the first polarization of the first THz beam 10. Therefore, the second THz beam 11 passes, without any relevant attenuation, through the first polarization mirror 4 thereafter through the measuring chamber 7 and through the boundary surfaces 8a through 8d of the tested object 8 while creating partial reflection peaks (measuring peaks), and, having passed through the measuring chamber 7, strikes the second polarization mirror 6 on which it is reflected, owing to its polarization, and travels along the optical axis A back through the measuring chamber 7, the test object 8, as well as the first polarization mirror 4 and is again detected by the second THz transceiver 5 which thereupon generates a second signal amplitude S2.

[0032] Upon passing through the boundary surfaces 8a and 8b of the wall region of the pipe 8 facing it, the first THz beam 10 generates corresponding measuring peaks (signal peaks) P1-a and P1-b in the first signal amplitude S1, then subsequently, having passed the interior space of the pipe 8, upon passing through the boundary surfaces 8c and 8d of the rear wall region of the pipe 8 again corresponding measuring peaks (signal peaks) P1-c, P1-d.

[0033] Subsequently, in the first signal amplitude S1 a first total reflection peak P4 is generated by the total reflection on the first polarization mirror 4. Thereafter, upon re-passing through the measuring chamber 7, reflections in the first signal amplitude S1 are generated on the boundary surfaces, which will not be described in further detail at this point.

[0034] Accordingly, upon passing through the measuring chamber 7, the second THz beam 11, by partial reflections on the boundary surfaces 8d, 8c, and, upon passing through the interior space of the pipe 8, on the boundary surfaces 8b, 8a generates corresponding measuring peaks (signal peaks) P2-d, P2-c, P2-b and P2-a and, thereafter, upon total reflection on the second polarization mirror 6, again a second total reflection peak P6.

[0035] Owing to the different polarization, the first and second measuring signal S1, S2 do not or not to a relevant extent influence one another so that, here, firstly separate measurements on the optical axis A and also on the same wall regions and boundary surfaces can be carried out which do not disturb one another but can be correlated with each other.

[0036] The two signal amplitudes S1 and S2 are plotted in the signal diagram of FIG. 1 at the bottom, for illustration purposes, in such a way with opposite temporal directions that the measuring peaks P1-a and P2-a as well as the further measuring peaks on identical boundary surfaces 8a through 8d correspond. This illustrates the reflection characteristics on the boundary surfaces 8a b through is 8d as well as the polarization mirrors 4 and 6.

[0037] Here, the respective electrical field E is being viewed for the polarization planes and the reflection characteristics; the magnetic B field extends perpendicular hereto, i.e., substantially in the plane of the electrical field of the respective other THz beam. FIG. 2 and FIG. 3 show electromagnetic radiation or THz radiation with polarization planes perpendicular or orthogonal respectively in relation to one another, FIG. 4 shows the combined path of the two THz beams.

[0038] FIG. 5 shows the functioning of the polarization mirrors 4 and 6 while depicting the polarization planes of the THz beams 10 and 11. Thus, the polarization mirrors 4 and 6 are arranged at an angle of 90° in relation to one another and may, in particular, by formed by grooves or lines in a metal surface.

[0039] The THz transceivers 3, 5 may be combined or, respectively, integrated transmitters and receivers sein; however, they may also each comprise a transmitter and receiver separately, with semi-transparent mirrors. The THz beams 10, 11 may be output for a direct time-of-flight measurement, frequency modulated measurements and/or pulsed radiation, whereby the polarized radiation in turn is preferably generated by the internal or, respectively, upstream polarization filter provided in the transceivers 3, 5 which allow only THz radiation of the respective polarization to pass.

[0040] An evaluation unit 16 show in FIG. 1 receives the first measuring signal S1 of the first THz transceiver 3 and the second measuring signal S2 of the second THz transceiver 5 auf and correlates the measuring signals with each other so as to allow for a common evaluation. To that end, the evaluation unit 16, in particular, according to the schematic representation of the signal amplitudes in FIG. 1, convert the measuring signals S1, S2 into a temporal progression that is inverse to one another, thereby correlating the partial reflection peaks on the boundary surfaces 8a, 8b, 8c, 8d with each other.

[0041] Thus, it is possible, in the combined measuring signal from the total reflection peaks P4 on the first polarization mirror 4 and P6 on the second polarization mirror 6 to determine even the distance between the polarization mirrors 4 and 6, e.g., for a calibration measurement with an empty measuring chamber 7 and subsequent measurement with a test object 8 contained therein, thereby allowing for a more precise determination of both layer thicknesses and the refractive index.

[0042] According to the invention it is possible to determine a layer thickness d1 of the front wall region between the boundary surfaces 8a and 8b, a layer thickness d2 of the rear wall region between the boundary surfaces 8c and 8d, and the internal diameter as a layer between the boundary surfaces 8b and 8c, as well as the refractive index n of the material of the test pipe 8.

[0043] Thus, when the refractive index n is known, the layer thicknesses d1, d2 can be determined directly from the temporal distance of the partial reflection peaks of a measuring signal S1 or S2, or even, so as to increase accuracy, from averaged values of these two measurements based on the formula

d=c8*Δt=c0/n*Δt,

where d=layer thickness, c0=speed of light in a vacuum, n=refractive index of the material of the pipe 8, c8=speed of light in the material of the test pipe 8, Δt time difference between the measuring peaks, e.g., difference P1-a and P1-b or P2-a and P2-b, or from these averaged values. Further, it is also possible to determine the diameter of the interior space of the pipe 8, i.e., the layer between the boundary surfaces 8b and 8c, as well as the exterior diameter of the pipe 8.

[0044] In a measurement with supplementary calibration measurement or, respectively empty measurement, prior to introducing the tested object 8 into the measuring chamber 7, the time of the total reflection peak P4 of the first THz beam 10 on the first reflection mirror 4 and, correspondingly, the time of the total reflection peaks P6 of the second THz beam 11 on the second reflection mirror 6 is determined, and thereafter, with a test pipe 8 contained therein, the time delay of the measuring peaks P4 and P6 in relation to the calibration measurement is determined so as to determine the total temporal delay upon travelling through the wall regions of the tested object 8 so that both layer thicknesses and refraction indexes can be determined from the calibration measurement and the subsequent measurements.

LIST OF REFERENCE NUMERALS

[0045] 1 measuring arrangement [0046] 2 THz measuring device [0047] 3 first THz transceiver [0048] 4 first polarization mirror [0049] 5 second THz transceiver [0050] 6 second polarization mirror [0051] 7 measuring chamber [0052] 8 test object, in this case a pipe [0053] 8a through 8d boundary surfaces, surfaces of the pipe 8 [0054] 10 first THz beam with first polarization plane [0055] 11 second THz beam with second polarization plane [0056] S1 first signal amplitude [0057] S2 second signal amplitude [0058] A optical axis [0059] B pipe axis [0060] P1-a through P1-d first measuring peaks, partial reflection peaks of the first THz beam 10 on the boundary surfaces 8a through 8d [0061] P2-a through P2-d second measuring peaks, partial reflection peaks of the second THz beam 11 on the boundary surfaces