The VCSEL-Array - a Novel High-Power Light Source for (Photo) Thermal Imaging
- Within the field of optically excited thermography, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers or to find inhomogeneities such as voids or cracks. Classical light sources, such as flash lamps (impulse heating) or halogen lamps (modulated heating), are hereby specifically used. This has led to the different testing methods lock-in and flash thermography. The VCSEL array promises to merge these excitation methods. Vertical Cavity Surface Emitting Lasers (VCSELs) are laser diodes emitting light perpendicular to their surface. Due to the vertical structure they can be arranged in large arrays of many thousand individual lasers and still be controlled like ordinary diode lasers. Recently a high-power albeit very compact version of such a VCSEL-array became available which offers both the fast timing behavior of lasers and large illumination areas. Moreover, it allows a spatial and temporal control of the heating because individualWithin the field of optically excited thermography, full-field thermal imaging is used to characterize materials, to determine thicknesses of layers or to find inhomogeneities such as voids or cracks. Classical light sources, such as flash lamps (impulse heating) or halogen lamps (modulated heating), are hereby specifically used. This has led to the different testing methods lock-in and flash thermography. The VCSEL array promises to merge these excitation methods. Vertical Cavity Surface Emitting Lasers (VCSELs) are laser diodes emitting light perpendicular to their surface. Due to the vertical structure they can be arranged in large arrays of many thousand individual lasers and still be controlled like ordinary diode lasers. Recently a high-power albeit very compact version of such a VCSEL-array became available which offers both the fast timing behavior of lasers and large illumination areas. Moreover, it allows a spatial and temporal control of the heating because individual parts of the VCSEL-array can be controlled arbitrarily in frequency, amplitude, and phase. Although the VCSEL-array has a high potential for a new range of applications, it is too early to proclaim them. As one out of very few labs, we already adopted to this new VCSEL technology and show a thorough characterization and first results obtained with a 2.4 kW device. Specifically, we will discuss - the linearity between control voltage and optical output - the minimal pulse duration - the maximal applicable modulation frequency - optical projection and its influence on the optical output - spatial control of the illumination and thermal wave shaping Our results indicate that a VCSEL-array can be used for conventional impulse (aka flash) thermography whereas pulse duration and power are instantaneously accessible compared to flash lamp excitation. In case of lock-in thermography, we can apply frequencies in excess of 200 Hz without a loss in amplitude or an after glowing of the source, making it attractive for photo thermal applications. Consequently, this means that the VCSEL-array is able to merge the two main excitation methods lock-in and impulse thermography.…
Autor*innen: | Erik Thiel |
---|---|
Koautor*innen: | Taarna Studemund, Mathias Ziegler |
Dokumenttyp: | Posterpräsentation |
Veröffentlichungsform: | Präsentation |
Sprache: | Englisch |
Jahr der Erstveröffentlichung: | 2016 |
DDC-Klassifikation: | Naturwissenschaften und Mathematik / Chemie / Analytische Chemie |
Freie Schlagwörter: | Active Thermography; Thermal Wave; VCSEL |
Veranstaltung: | 57th Course on Photoacoustic & Photothermal Phenomena |
Veranstaltungsort: | Erice, Italy |
Beginndatum der Veranstaltung: | 19.10.2016 |
Enddatum der Veranstaltung: | 26.10.2016 |
Verfügbarkeit des Dokuments: | Datei im Netzwerk der BAM verfügbar ("Closed Access") |
Datum der Freischaltung: | 27.10.2016 |
Referierte Publikation: | Nein |