ABSTRACT

Photothermal radiometry with an infrared camera allows the contactless temperature measurement of multiple surface pixels simultaneously. A short light pulse heats the sample. The heat propagates through the sample by diffusion and the corresponding temperature evolution is measured at the surface of the sample by an infrared camera. The main drawback in radiometric imaging is the loss of the spatial resolution with increasing depth due to heat diffusion, which results in blurred images for deeper lying structures. We circumvent this information loss due to the diffusion process by using blind structured illumination, combined with a nonlinear joint-sparsity reconstruction algorithm. The structured illumination is realised by parallel laser lines from a vertical-cavity surface-emitting laser (VCSEL) array controlled by a random binary pattern generator. By using 150 different patterns of structured illumination and our iterative joint-sparsity algorithm, it was possible to resolve 1 mm thick lines at a distance down to 0.5 mm, which results in a resolution enhancement of approximately a factor of four compared to the resolution of 5.9 mm for homogeneous illuminated thermographic reconstruction.

摘要

使用红外热像仪进行光热辐射测量，可以同时测量多个表面像素的非接触式温度。短暂的光脉冲会加热样品。热量通过扩散传播通过样品，并且通过红外热像仪在样品表面测量相应的温度变化。辐射成像的主要缺点是由于热扩散而导致的空间分辨率随深度增加而损失，这会导致较深的结构图像模糊。我们通过使用盲结构照明和非线性联合稀疏重建算法来避免由于扩散过程而造成的信息丢失。结构化照明是由来自垂直腔表面发射激光器（VCSEL）阵列的平行激光线实现的，该阵列由随机二进制图案发生器控制。通过使用150种不同模式的结构化照明和我们的迭代联合稀疏算法，可以在低至0.5 mm的距离上分辨1 mm的粗线，与之相比，分辨率提高了大约四倍。 5.9毫米，用于均匀照明的热成像重建。