Voßgrag, LeonardLeonardVoßgragKießling, JensJensKießlingSeyler, TobiasTobiasSeylerBertz, AlexanderAlexanderBertzCarl, DanielDanielCarlBreunig, IngoIngoBreunig2024-03-142024-03-142024https://publica.fraunhofer.de/handle/publica/46416310.1117/12.3001619Multi-wavelength holography is a convenient method for the inline inspection of industrially machined parts. Compared with the single-wavelength approach, the unambiguity range can be extended by orders of magnitude. This is typically achieved by using multiple lasers. The smaller their wavelength difference, the larger is the unambiguity range. Reaching the centimeter or even meter range is difficult with individual lasers because of their relative wavelength drift. Here, we demonstrate multi-wavelength holography with 37.5 cm unambiguity range using only one single laser. The wavelength shifts are achieved with acousto-optic modulators driven at 200 MHz and 1 GHz. This provides unambiguity ranges of 37.5 and 7.5 cm respectively. Importantly, the perturbation caused by a possible long-term drift of the laser is significantly reduced. For a proof-of-concept demonstration, we determine the shape of a metallic object comprising height differences between 1 and 100 mm. The scheme can be extended to larger frequency shifts, i.e. better axial resolution, by using electro-optic modulators. This would enable to conveniently select the measurement range between some millimeters and meters although only one laser is used.enDigital holographyAcousto-optic modulationElectro-optic modulationSecond-harmonic generationconference paper