SBIR-STTR Award

Picometrix proposes to demonstrate the feasibility of using differential time domain terahertz imaging methods to enhance the contrast and detectability of features such as kissing disbonds and cracks that in conventional THz imaging only weakly reflect or scatter the THz pulses. The goal of the project is to develop methods of shearographic loading of the samples, and use the penetrating THz pulses to detect the subsurface deformation of the defects in the differential THz images with better contrast than traditional THz imaging. In a "kissing" disbond there is a region where the two sides of the material are not adhered, but the space between the two sides are essentially in perfect optical contact. When the space between the two interfaces is so optically "thin," the reflections of the THz pulses from the top and bottom surfaces cancel each other out. The defect signature is only weakly detectable compared to when the spacing is greater than the minimum THz wavelength (approx. 50-150 microns), the shearographic loading will microscopically deform defects, changing the small THz reflections in the loaded vs. unloaded state. The differential images should subtract all background clutter and highlight the microscopic subsurface distortion of the defects under loading.

Potential NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) Time-domain terahertz reflection imaging is a proven NDE technology for imaging sub-surface features, flaws, and defects within space flight structures such as thermal protection systems (ablative resin honeycomb, TUFI, SOFI), inflatable space habitats, composite overwrap pressure vessels, radomes, and other dielectric components. THz pulses (0.1 to 3 THz) penetrates these materials, and can be used to generate sub-surface images. THz NDE can detect voids, disbonds, and damage such as tearing and micro-meteorite impact. Material examples include Kevlar, Zylon, and other non-conductive polymer matrix composites. Differential THz imaging should improve the detectability of defects in each of these applications.

Potential NON-NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) Time-domain terahertz gages are used in industry to measure the thickness of multi-layer sheet materials such as plastic film, insulation, foam sheets, roofing, paper, and other similar products that are extruded in presses. THz gages are used to measure the thickness of aerospace coatings, when dry or wet. The proposed differential imaging method and shearographic loading techniques should enhance the detectability of interfaces and delaminations in the manufacturing of these materials. THz instrumentation has significant potential in the research and development, government, and industrial markets for use in on-line and off-line inspection, communications, and test and measurement.

Technology Taxonomy Mapping:
(NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.) Nondestructive Evaluation (NDE; NDT)

In Phase II, Picometrix proposes to design, construct, test, characterize, and deliver a prototype differential time domain terahertz shearographic imaging system. The differential imaging methods developed in Phase I will be improved and the methods implemented in turn-key software and hardware. In Phase I the feasibility of using differential time domain THz imaging methods to enhance the contrast and detectability of features such as disbonds was demonstrated. Kissing disbonds and cracks may only weakly reflect the THz pulses in conventional THz imaging. The Phase I project developed the methods of shearographic loading of the samples, and used penetrating THz pulses to detect the subsurface deformation of the defects with better contrast than traditional THz imaging. In a disbond there is a region where the two sides of the material are not adhered, and the space between the two sides are essentially so close that THz interface reflection pulses from the non-adhered region may be partially cancelled out.. The defect signature may be only weakly detectable compared to when the spacing is greater than the minimum THz wavelength. The differential images null background clutter and highlight the subsurface distortion of the defects under loading.

Potential NASA Commercial Applications:
(Limit 1500 characters, approximately 150 words) THz reflection imaging is a proven NDE technology for imaging sub-surface features, flaws, and defects within space flight structures such as thermal protection systems (ablative resin honeycomb, TUFI, SOFI), inflatable space habitats, composite overwrap pressure vessels, and radomes. THz NDE can detect voids, disbonds, and damage such as tearing and micro-meteorite impact. Material include Kevlar, Zylon, and other non-conductive composites. Differential THz imaging should improve the detectability of defects in each of these applications.



Potential NON-NASA Commercial Applications:
:
(Limit 1500 characters, approximately 150 words) THz gages are used in industry to measure the thickness of multi-layer sheet materials: plastic film, insulation, foam sheets, roofing, paper, and other products that are extruded in presses. THz gauges are used to measure the thickness of aerospace coatings. The differential imaging method will improve the detectability of interfaces and delaminations in the manufacturing of these materials.

Technology Taxonomy Mapping:
(NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.) Air Transportation & Safety Analytical Instruments (Solid, Liquid, Gas, Plasma, Energy; see also Sensors) Coatings/Surface Treatments Composites Joining (Adhesion, Welding) Lasers (Measuring/Sensing) Materials & Structures (including Optoelectronics) Nondestructive Evaluation (NDE; NDT) Optical/Photonic (see also Photonics) Quality/Reliability