1. An improvement in a method for tomographic imaging of a fluid flow using phase-resolved functional optical coherence tomography (F-OCT) comprising:
extracting a Doppler bandwidth above a certain threshold level from the standard deviation of the frequency shift as a linear function of flow velocity by use of an optical probing beam; and
imaging the flow velocity component transverse to the optical probing beam.
2. The improvement of claim 1 where an interferometer with a sample arm having an optical objective with a effective numerical aperture is used to extract the Doppler bandwidth, and where extracting the Doppler bandwidth as a linear function of flow velocity extracts the Doppler bandwidth as a linear function with a slope determined by the effective numerical aperture of the optical objective in the sample arm.
3. The improvement of claim 1 where the optical probing beam extracts the Doppler bandwidth from the standard deviation and where extracting the Doppler bandwidth above a certain threshold level from the standard deviation of the frequency shift is performed without the precise determination of flow direction when the Doppler flow angle is within \xb115 degrees perpendicular to the probing beam.
4. The improvement of claim 1 where extracting a Doppler bandwidth as a linear function of flow velocity is performed as defined by
B
d
=
4
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
NA
eff
\u03bb
where Bd is the Doppler bandwidth, V is the flow velocity, \u03bb is the wavelength of the probing beam, \u03b8 is the Doppler angle and, NAeff is the effective numerical aperture and the Doppler bandwidth.
5. The improvement of claim 4 where the optical probing beam is a Gaussian beam and where the standard deviation, \u03c3, of the frequency shift is performed as defined by
\u03c3
=
\u03c0
\u2062
\u2003
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
NA
eff
8
\u2062
\u03bb
.
6. The improvement of claim 5 where the standard deviation, \u03c3, of the frequency shift is performed as defined by
\u03c3
=
\u03c0
\u2062
\u2003
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
NA
eff
8
\u2062
\u03bb
+
b
where b accounts for bandwidth spectrum broadening from contributions from Brownian motion and other factors that are independent of the macroscopic flow velocity.
7. The improvement of claim 1, further comprising:
measuring a Doppler frequency shift proportional to a flow velocity component axial to the probing beam; and
determining a flow direction from the flow velocity component axial to the probing beam and the flow velocity component transverse to the probing beam.
8. An improvement in an apparatus for tomographic imaging of a fluid flow using phase-resolved functional optical coherence tomography (F-OCT) comprising:
means for extracting a Doppler bandwidth above a certain threshold level from the standard deviation of the frequency shift as a linear function of flow velocity by use of an optical probing beam; and
means for imaging the flow velocity component transverse to the optical probing beam.
9. The improvement of claim 8 where the means for extracting comprises an interferometer with a sample arm having an optical objective with a effective numerical aperture is used to extract the Doppler bandwidth, and where the means for extracting the Doppler bandwidth as a linear function of flow velocity extracts the Doppler bandwidth as a linear function with a slope determined by the effective numerical aperture of the optical objective in the sample arm.
10. The improvement of claim 8 where the means for extracting comprises an optical probing beam and where the means for extracting the Doppler bandwidth above a certain threshold level from the standard deviation of the frequency shift performs without the precise determination of flow direction when the Doppler flow angle is within \xb115 degrees perpendicular to the probing beam.
11. The improvement of claim 10 where the optical probing beam is a Gaussian beam and where means for extracting generates a standard deviation, \u03c3, of the frequency shift is performed as defined by
\u03c3
=
\u03c0
\u2062
\u2003
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
N
\u2062
\u2003
\u2062
A
eff
8
\u2062
\u2003
\u2062
\u03bb
.
12. The improvement of claim 11 where the means for generating the standard deviation, \u03c3, of the frequency shift performs as defined by
\u03c3
=
\u03c0
\u2062
\u2003
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
N
\u2062
\u2003
\u2062
A
eff
8
\u2062
\u2003
\u2062
\u03bb
+
b
where b accounts for bandwidth spectrum broadening from contributions from Brownian motion and other factors that are independent of the macroscopic flow velocity.
13. The improvement of claim 8 where the means for extracting a Doppler bandwidth as a linear function of flow velocity performs as defined by
B
d
=
4
\u2062
V
\u2062
\u2003
\u2062
sin
\u2062
\u2003
\u2062
\u03b8
\u2062
\u2003
\u2062
NA
eff
\u03bb
where Bd is the Doppler bandwidth, V is the flow velocity, \u03bb is the wavelength of the probing beam, \u03b8 is the Doppler angle and, NAeff is the effective numerical aperture and the Doppler bandwidth.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A metal-layer-free multilayer film with a weight per unit area of \u226633 gm2 and with an at least six-layer structure comprising:
(a) a layer (a) composed of at least one thermoplastic olefin homo- or copolymer, as one of the external layers;
(b) a non-peelable adhesion-promoter layer (b) optionally having a plurality of sublayers;
(c) a layer (c) composed of at least one homo- andor copolyamide and optionally having a plurality of sublayers;
(d) at least one internal gas-barrier layer (d) which adjoins the layer (c) and which optionally has a plurality of sublayers and which differs at least in the composition of the polymer component(s) from the layer (c) and a layer (e);
(e) the layer (e) which adjoins the gas-barrier layer (d) and which optionally has a plurality of sublayers and is composed of at least one homo- andor copolyamide; and
(i) a layer (i) composed of at least one homo- andor copolyamide as one of the external layers;
wherein shrinkage of the multilayer film, determined as dimensional change in accordance with DIN 53377, is \u226610% at 90\xb0 C., both in machine direction and perpendicular to the machine direction, where the multilayer film comprises no metal foil and no vapor-deposition layer made of a metal or of a metal compound.
2. The metal-layer-free multilayer film as claimed in claim 1, with weight per unit area \u226633 gm2 and with an at least nine-layer layer structure comprising:
(a) a layer (a) composed of at least one thermoplastic olefin homo- or copolymer, as one of the external layers;
(b) a non-peelable adhesion-promoter layer (b) optionally having a plurality of sublayers;
(c) a layer (c) composed of at least one homo- andor copolyamide;
(d) at least one internal gas-barrier layer (d) which adjoins the layer (c) and which differs at least in the composition of the polymer component(s) from the layers (c) and (e);
(e) a layer (e) which adjoins the gas-barrier layer (d) and which is composed of at least one homo- andor copolyamide;
(f) an adhesion-promoter layer (f) optionally having a plurality of sublayers;
(g) at least one internal layer (g) composed of at least one thermoplastic olefin homo- or copolymer;
(h) a non-peelable adhesion-promoter layer (h) optionally having a plurality of sublayers;
(i) a layer (i) composed of at least one homo- andor copolyamide as one of the external layers;
wherein shrinkage of the multilayer film, determined as dimensional change in accordance with DIN 53377, is \u226610% at 90\xb0 C., both in machine direction and perpendicular to the machine direction.
3. The multilayer film as claimed in claim 1, wherein the weight per unit area of the multilayer film is \u226631 gm2.
4. The multilayer film as claimed in claim 1, wherein the total thickness of the multilayer film is at most 30 \u03bcm.
5. The multilayer film as claimed in claim 1, wherein the average density of the multilayer film is at most 1.1 gcm3.
6. The multilayer film as claimed in claim 1, wherein the shrinkage of the multilayer film, determined as dimensional change in accordance with DIN 53377, is \u22667%, both in machine direction and perpendicular to the machine direction.
7. The multilayer film as claimed in claim 1, wherein the gas-barrier layer (d) is composed of at least one ethylene-vinyl alcohol copolymer, at least one polyvinyl alcohol, at least one polyvinylidene chloride, at least one homo- or copolyamide, or a mixture of at least two of these polymers.
8. The multilayer film as claimed in claim 1, wherein the puncture resistance of the multilayer film is at least 100 N, determined in accordance with DIN 53373.
9. The multilayer film as claimed in claim 1, which exhibits a helium transmission of at most 3000 cm3(m2\xb724 h\xb7bar), determined in accordance with DIN 53380-2 at 23\xb0 C. and 0% humidity.
10. The multilayer film as claimed in claim 1, which exhibits an oxygen transmission of at most 8 cm3(m2\xb724 h\xb7bar), determined in accordance with DIN 53380-2 at 23\xb0 C. and 0% humidity.
11. The multilayer film as claimed in claim 1, wherein the layer (a) is composed of at least one ethylene homo- or copolymer.
12. The multilayer film as claimed in claim 2, wherein the layer (g) is composed of at least one ethylene homo- or copolymer andor of at least one propylene homo- or copolymer.
13. The multilayer film as claimed in claim 2, wherein the layers (a)-(i) are present in the stated sequence.
14. The multilayer film as claimed in claim 2, wherein the multilayer film also has at least one internal layer (j) and optionally at least one further internal layer (k), optionally respectively, being identical or different from one another, composed of at least one thermoplastic olefin homo- or copolymer or as a sublayer of the adhesion-promoter layer (b) having a plurality of sublayers andor of the adhesion-promoter layer (f) having a plurality of sublayers.
15. The multilayer film as claimed in claim 1, wherein the multilayer film has an at least ten-layer layer structure.
16. The multilayer film as claimed in claim 1, wherein the multilayer film is sealable.
17. The multilayer film as claimed in claim 1, wherein the multilayer film has been printed andor colored.
18. The multilayer film as claimed in claim 1, wherein the multilayer film is at least to some extent transparent and optionally colored.
19. The multilayer film as claimed in claim 1, wherein the multilayer film can be produced by the blown-film-coextrusion process.
20. A method of using a multilayer film as claimed in claim 1 for the production of a buoyancy body.
21. The method as claimed in claim 20, wherein the buoyancy body is at least a component of an aircraft, preferably of an airship, a hot-air balloon, a free balloon, a captive balloon, a pilot balloon, or a research balloon.
22. The method as claimed in claim 20, wherein the buoyancy body is a balloon.
23. The method as claimed in claim 20, wherein the buoyancy body is a flotation body which is optionally a component of a buoy, lifejacket, floating platform, or of a landing stage, or of a boat, or of a marine hovercraft.
24. A buoyancy body comprising a multilayer film as claimed in claim 1.
25. A balloon comprising the multilayer film as claimed in claim 1.
26. A balloon as claimed in claim 25, wherein the balloon is composed of at least two optionally identically designed segments, connected by a seal seam, of the multilayer film, and has a gas-supply duct, and also optionally has a gas-inlet and -outlet valve.
27. The balloon as claimed in claim 25, wherein the inflated balloon has any desired shape, and has optionally been printed with motifs.