Instrument Development: 4-D Near-Infrared Chemical Imaging Using Snapshot Tomography

在化学系化学测量和成像计划的支持下，威斯康星大学密尔沃基分校(UWM)的Sung教授开发了用于近红外(NIR)范围内的4维(4D)化学成像的新仪器。近红外高光谱成像已被广泛应用于无损质量检测，然而，现有的方法无法检测具有复杂内部结构的样品，也无法检测埋藏在三维体积中的化学杂质，因为记录的二维投影图像中丢失了深度信息。传统的三维层析成像方法需要一种扫描机制，这大大增加了数据采集的时间和仪器的复杂性。宋教授和他的团队正在开发使用一种名为快照断层扫描的技术的仪器，这种技术可以在一次快照中获得3D断层图像。通过结合各种波长扫描策略，新仪器可以以高速和良好的空间分辨率获取4-D高光谱数据。这种仪器一旦开发出来，可能会对许多行业产生潜在影响，因为它可以对制药、化工、石化或农产品进行无损质量检查。例如，通过检测假药来改善人类健康，或者用于太阳能电池或微电子机械系统(MEMS)设备中的3-D集成电路芯片的故障分析，这些应用是可以预见的。宋教授致力于为本科研究人员和K-12学生、未来一代科学家和工程师提供培训机会。他还致力于将尖端科学融入课程材料，并积极参与许多校园项目，以招募更多女性和少数族裔学生加入他的团队。宋教授正在开发一种4D近红外吸收和折射率成像技术，其中将波长扫描光源与通过微透镜阵列和数字全息实现的快照层析成像技术相结合。采用共路设计以进一步提高对环境振动的稳健性，并采用空间光调制器来主动补偿色差。对于4-D近红外发射成像，可调带通滤光器或傅里叶变换光谱与另一种用于发光的快照层析成像技术相结合。将要开发的理论框架被认为将衍射层析成像的应用扩展到更一般的吸收样本类别，并通过在图像形成和重建模型中包括波的性质和光的部分相干性来提高发射层析成像的准确性。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Chemical Measurement and Imaging Program in the Division of Chemistry, Professor Sung at University of Wisconsin-Milwaukee (UWM) develops new instruments for 4-dimensional (4D) chemical imaging in the near-infrared (NIR) range. NIR hyperspectral imaging has been widely used for nondestructive quality inspection; however, existing methods cannot examine a specimen with a complicated internal structure or detect the chemical impurities buried deep inside a 3-D volume because the depth information is lost in the recorded 2-D projection images. Traditional approaches to 3-D tomographic imaging require a scanning mechanism, which significantly increases the data acquisition time and the complexity of an instrument. Professor Sung and his group is developing instruments using a technique called snapshot tomography, which can acquire the 3-D tomogram in a single snapshot. By incorporating various wavelength-scan strategies, the new instruments can acquire the 4-D hyperspectral data at a high speed and good spatial resolution. The instruments, once developed, could potentially impact many industries by allowing nondestructive quality inspection of pharmaceutical, chemical, petrochemical, or agricultural products. Applications such as improving human health by detecting counterfeit medicines or being used in failure analysis of 3-D integrated-circuit chips in solar cells or micro-electro-mechanical system (MEMS) devices are envisioned. Professor Sung strives to provide training opportunities to undergraduate researchers and K-12 students, the future generation of scientists and engineers. He also works on incorporating cutting-edge science into course materials and is actively engaged in many on-campus programs to recruit more women and minority students into his group.Professor Sung is developing a 4D NIR absorption and refractive index imaging where a wavelength-scanning light source is combined with a snapshot tomography technique that is enabled by a micro-lens array and digital holography. A common-path design is incorporated to further increase the robustness to environmental vibrations and a spatial light modulator to actively compensate for the chromatic aberration. For 4-D NIR emission imaging, a tunable bandpass filter or Fourier transform spectroscopy is combined with another snapshot tomography technique for luminescence light. The theoretical frameworks to be developed is believed to extend the application of diffraction tomography to more general classes of absorbing specimens and increase the accuracy of emission tomography by including the wave nature and the partial coherence of light in the image formation and reconstruction models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.