Super-resolution techniques were applied to infrared thermographic temperature measurement for the
improvement of spatial resolution of the infrared image with limited number of imaging pixels. In the
proposed super-resolution technique, a high resolution image was produced from plural low resolution
images with sub-pixel displacements. The super-resolution scheme was developed based on the
displacement analyses in the sub-pixel level for low resolution images based on the image correlation and
subsequent interpolative reassignment of the pixel values from low resolution images to the high resolution
image. The practicability of the developed super-resolution infrared thermography was experimentally
Recently, deterioration of concrete structures before their design life has become a serious social problem in Japan. Nondestructive inspection techniques are required, for detecting defects and damages in concrete structures, such as subsurface void or delamination. As one of these techniques, the thermographic NDT can be applied as an effective NDT technique to inspect large area of the objective structure from distant place. In addition, it does not require any chemicals and application of physical excitation for inspection. However, the thermographic NDT has a shortcoming that the measurement results are affected by the reflection of atmospheric radiation due to the sunlight, sky or surrounding materials. Since most of the buildings in Japan are covered with luster materials with low emissivity, such as tile or mortal, infrared reflection on the surface is difficult to be neglected. To reduce the influence of these reflection noises, the infrared thermography with detectable wavelength from 5 to 8 μm, which coincides with absorption range of moisture, is utilized. In this research, a new infrared thermography with 5 to 8 μm wavelength range by applying a band pass filter and an uncooled microbolometer infrared array detector. Further, a new signal to noise (S/N) ratio improvement technique has been developed in order to compensate a deterioration of sensitivity due to the band pass filter.
Diagnosing the reinforced concrete structures by using infrared thermography has become considerable in Japan. Infrared thermography has potential for detecting the defects, but is challenging due to unwanted thermal signals caused by surface roughness dirt, etc. To prevent from misdiagnosing, an innovative concept of merged thermal with visible images is proposed. Several key issues exist to capture the merged images: (1) alignment for the optical axes of an infra-red camera and digital still camera, (2) parallax correction between the thermal and visible images, (3) aberration correction for the lenses, and (4) adjustment of the image view angles. An experimental setup demonstrates an efficient diagnosing using the merged images.