Method and device for generating a synthetic wavelength
In a method for generating a synthetic wavelength, particularly for an interferometric distance measuring setup, with a primary laser source defining a primary frequency υ 0 and at least a first sideband frequency υ 1 of the primary frequency υ 0 , laser radiation with the first sideband frequency υ 1 and a corresponding first wavelength is provided wherein the first sideband frequency υ 1 is continuously shifted, particularly by modulating the primary laser source. The synthetic wavelength is generated by combining the first wavelength and a second wavelength which is defined by the primary laser source, particularly by superposition.
1. A method for generating a synthetic wavelength with a primary laser source defining a primary frequency υ 0 and at least a first sideband frequency υ i of the primary frequency υ 0 , comprising:
providing laser radiation with the first sideband frequency υ 1 and a corresponding first wavelength; and
generating the synthetic wavelength by combining the first wavelength and a second wavelength which is defined by the primary laser source, wherein the first sideband frequency υ 1 is continuously shifted.
2. The method according to claim 1 , wherein the synthetic wavelength is generated by combining the first wavelength and a second wavelength which is defined by the primary laser source by superposition, wherein the first sideband frequency υ 1 is continuously shifted by modulating the primary laser source.
3. The method according to claim 1 , wherein at least one first laser source emits laser radiation with the first wavelength and the at least one first laser source is injection-locked on the first sideband frequency υ 1 .
4. The method according to claim 1 , wherein the second wavelength corresponds to the primary frequency υ 0 .
5. The method according to claim 1 wherein:
laser radiation with a second sideband frequency υ 2 of the primary frequency υ 0 is generated; and
a second laser source emitting laser radiation with the second wavelength is injection-locked on the second sideband frequency υ 2 .
6. The method according to claim 1 , wherein:
laser radiation with a second sideband frequency υ 2 of the primary frequency υ 0 is generated as the second wavelength by a second laser source; and
the primary laser source is injection-locked on the second sideband frequency υ 2 .
7. The method according to claim 6 , wherein the first and second sideband frequencies υ 1 and υ 2 are the first lower and upper sideband frequencies of the primary frequency υ 0 .
8. The method according to claim 6 , wherein:
the first and second laser sources are distributed-feedback-lasers; and
the primary laser source is an intensity modulated laser or a vertical cavity surface emitting laser, wherein a modulation frequency of the electro-absorption laser and a current applied to the first and second laser sources are varied synchronously in order to adapt the locking range of the distributed-feedback-lasers to the sideband frequencies υ 1 and υ 2 .
9. The method according to claim 1 , wherein:
the laser radiation with the first sideband frequency υ 1 and a second sideband frequency υ 2 of the primary frequency υ 0 as the second wavelength are generated by the primary source; and
laser radiation with the primary frequency υ 0 is suppressed.
10. A two- or multiple-wavelength interferometric method for measuring distances with variable synthetic wavelength wherein the synthetic wavelength is generated by the method according to claim 1 , comprising:
generating and emitting laser light with variable synthetic wavelength according to claim 1 ; and
a step for measuring distances with variable synthetic wavelength.
11. A two- or multiple-wavelength interferometric method for measuring distances with variable synthetic wavelength wherein the synthetic wavelength is generated by the method according to claim 1 according to the superheterodyne principle, comprising:
generating and emitting laser light with variable synthetic wavelength according to claim 1 and according to the superheterodyne principle; and
a step for measuring distances with the variable synthetic wavelength.
12. A device for generating a synthetic wavelength, comprising:
a primary laser source defining a primary frequency υ 0 and at least a first sideband frequency υ i with a first wavelength of the primary frequency υ 0 ; and
a component for generating the synthetic wavelength by combining the first wavelength and a second wavelength defined by the primary laser source, wherein the primary laser source is adapted to continuously shift the first sideband frequency υ i .
13. The device according to claim 12 , wherein the component for generating the synthetic wavelength by combining the first wavelength and a second wavelength is defined by the primary laser source by superposition, wherein the primary laser source is adapted to continuously shift the first sideband frequency υ 1 by modulating the primary laser source.
14. The device according the claim 12 , wherein:
the primary laser source is a distributed-feedback-laser;
the laser radiation with the first sideband frequency υ i and a second sideband frequency υ 2 of the primary frequency υ 0 as the second wavelength are generated by the primary source;
the laser radiation of the primary source is coupled into a Mach-Zehnder-interferometer setup with an electro-optical modulator in one of the interferometer arms; and
the interferometer setup is adapted to be operated synchronously with the shift of the first sideband frequency υ 1 .
15. The device according to claim 12 , wherein:
the primary laser source is an intensity-modulated electro-absorption laser or vertical cavity surface emitting and the first laser source is a distributed-feedback-laser.
16. The device according claim 12 , wherein at least one first laser source for emitting laser radiation emits the first wavelength, wherein the primary laser source and the first laser source are connected in a master-slave-laser-setup and the first laser source is injection-locked on the first sideband frequency υ 1 .
17. The device according to claim 12 , wherein the primary laser source and the first laser source are connected by a wavelength demultiplexer and a circulator, wherein the second wavelength corresponds to the primary frequency υ 0 .
18. The device according to claim 12 , wherein the primary laser source and a second laser source for emitting radiation with the second wavelength are connected in a master-slave-laser-setup wherein the second laser source is injection-locked on a second sideband frequency υ 2 .
19. The device according to claim 12 , wherein the primary laser source and a second laser source for emitting radiation with the second wavelength and a second sideband frequency υ 2 are connected in a master-slave-laser-setup wherein the primary laser source is injection-locked on the second sideband frequency υ 2 .
20. The device according to claim 19 , wherein the first and second sideband frequencies υ 1 and υ 2 are the first lower and upper sideband frequencies of the primary frequency υ 0 .
21. The device according to claim 20 , wherein the second laser source is a distributed-feedback-laser.
22. The device according to claim 12 , wherein the primary laser source is a gas-stabilized laser.
23. The device according to claim 12 , wherein the primary laser source is an acetylene-stabilized distributed-feedback-laser.
24. A two-wavelength interferometric device for measuring absolute distances comprising:
a device for generating synthetic wavelengths according to claim 12 ; and
means for measuring absolute distances.
25. A two-wavelength interferometric device for measuring absolute distances according to the superheterodyne principle comprising:
a device for generating synthetic wavelengths according to claim 12 ; and
means for measuring absolute distances according to the superheterodyne principle.