Browsing by Author "Lu, Jiawei"

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    Design and Fabrication of Snapshot Imaging Spectrometers for Biomedical and Remote Sensing Applications
    (2023-08-28) Lu, Jiawei; Tkaczyk, Tomasz
    In this work, two advanced snapshot field-integral hyperspectral imaging spectrometers are presented. The first system is based on image mapping mirrors and achieves significantly increased datacube size and dynamic range compared to previous generations. This benefits from a novel design and fabrication method for making the large-format multifaceted mapping mirrors based on the two-photon grayscale lithography (2GL) mode from a commercial two-photon polymerization(2PP) printer. The new fabrication technique can accelerate the fabrication process, increase facet density, eliminate edge eating, and reduce shadowing effects. Additionally, images combining the IMS and dual inverted selective plane illumination microscope (diSPIM) are demonstrated for high spatial and spectral resolution 5D imaging (x,y,z,λ,t). The second system is a fiber-based snapshot hyperspectral imaging spectrometer which can work in both visible (490 nm-732 nm) and short-wave infrared (1090 nm - 1310 nm) wave ranges. A customized relay system with a high numerical aperture (NA) and large field of view (FOV) is designed, fabricated, and then implemented in the spectrometer to overcome the light collection efficiency problems in previous systems. The new relay system enables imaging with a fast frame rate and/or under low illumination conditions. The aims of this work are to advance the two hyperspectral imaging techniques to broaden their applications in biomedical imaging and remote sensing.
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    Fabrication of a multifaceted mapping mirror using two-photon polymerization for a snapshot image mapping spectrometer
    (Optica Publishing Group, 2023) Lu, Jiawei; Ng, Xue Wen; Piston, David; Tkaczyk, Tomasz S.
    A design and fabrication technique for making high-precision and large-format multifaceted mapping mirrors is presented. The method is based on two-photon polymerization, which allows more flexibility in the mapping mirror design. The mirror fabricated in this paper consists of 36 2D tilted square pixels, instead of the continuous facet design used in diamond cutting. The paper presents a detailed discussion of the fabrication parameters and optimization process, with particular emphasis on the optimization of stitching defects by compensating for the overall tilt angle and reducing the printing field of view. The fabricated mirrors were coated with a thin layer of aluminum (93 nm) using sputter coating to enhance the reflection rate over the target wave range. The mapping mirror was characterized using a white light interferometer and a scanning electron microscope, which demonstrates its optical quality surface (with a surface roughness of 12 nm) and high-precision tilt angles (with an average of 2.03% deviation). Finally, the incorporation of one of the 3D printed mapping mirrors into an image mapping spectrometer prototype allowed for the acquisition of high-quality images of the USAF resolution target and bovine pulmonary artery endothelial cells stained with three fluorescent dyes, demonstrating the potential of this technology for practical applications.
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    Light-guide snapshot imaging spectrometer for remote sensing applications
    (The Optical Society, 2019) Wang, Ye; Pawlowski, Michal E.; Cheng, Shuna; Dwight, Jason G.; Stoian, Razvan I.; Lu, Jiawei; Alexander, David; Tkaczyk, Tomasz S.
    A fiber-based snapshot imaging spectrometer was developed with a maximum of 31853 (~188 x 170) spatial sampling and 61 spectral channels in the 450nm-750nm range. A compact, custom-fabricated fiber bundle was used to sample the object image at the input and create void spaces between rows at the output for dispersion. The bundle was built using multicore 6x6 fiber block ribbons. To avoid overlap between the cores in the direction of dispersion, we selected a subset of cores using two alternative approaches; a lenslet array and a photomask. To calibrate the >30000 spatial samples of the system, a rapid spatial calibration method was developed based on phase-shifting interferometry (PSI). System crosstalk and spectral resolution were also characterized. Preliminary hyperspectral imaging results of the Rice University campus landscape, obtained with the spectrometer, are presented to demonstrate the system’s spectral imaging capability for distant scenes. The spectrum of different plant species with different health conditions, obtained with the spectrometer, was in accordance with reference instrument measurements. We also imaged Houston traffic to demonstrate the system’s snapshot hyperspectral imaging capability. Potential applications of the system include terrestrial monitoring, land use, air pollution, water resources, and lightning spectroscopy. The fiber-based system design potentially allows tuning between spatial and spectral sampling to meet specific imaging requirements.
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    Radiometric and design model for the tunable light-guide image processing snapshot spectrometer (TuLIPSS)
    (Optical Society of America, 2021) Zheng, Desheng; Flynn, Christopher; Stoian, Razvan I.; Lu, Jiawei; Cao, Haimu; Alexander, David; Tkaczyk, Tomasz S.; Tkaczyk, Tomasz S.
    The tunable light-guide image processing snapshot spectrometer (TuLIPSS) is a novel remote sensing instrument that can capture a spectral image cube in a single snapshot. The optical modelling application for the absolute signal intensity on a single pixel of the sensor in TuLIPSS has been developed through a numerical simulation of the integral performance of each optical element in the The tunable light-guide image processing snapshot spectrometer (TuLIPSS) is a novel remote sensing instrument that can capture a spectral image cube in a single snapshot. The optical modelling application for the absolute signal intensity on a single pixel of the sensor in TuLIPSS has been developed through a numerical simulation of the integral performance of each optical element in the TuLIPSS system. The absolute spectral intensity of TuLIPSS can be determined either from the absolute irradiance of the observed surface or from the tabulated spectral reflectance of various land covers and by the application of a global irradiance approach. The model is validated through direct comparison of the simulated results with observations. Based on tabulated spectral reflectance, the deviation between the simulated results and the measured observations is less than 5% of the spectral light flux across most of the detection bandwidth for a Lambertian-like surface such as concrete. Additionally, the deviation between the simulated results and the measured observations using global irradiance information is less than 10% of the spectral light flux across most of the detection bandwidth for all surfaces tested. This optical modelling application of TuLIPSS can be used to assist the optimal design of the instrument and explore potential applications. The influence of the optical components on the light throughput is discussed with the optimal design being a compromise among the light throughput, spectral resolution, and cube size required by the specific application under consideration. The TuLIPSS modelling predicts that, for the current optimal low-cost configuration, the signal to noise ratio can exceed 10 at 10 ms exposure time, even for land covers with weak reflectance such as asphalt and water. Overall, this paper describes the process by which the optimal design is achieved for particular applications and directly connects the parameters of the optical components to the TuLIPSS performance.
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    Visible and short-wave infrared fiber-based snapshot imaging spectrometer with a custom high-throughput relay system
    (Optica Publishing Group, 2023) Lu, Jiawei; Zheng, Desheng; Stoian, Razvan-Ionut; Flynn, Christopher; Alexander, David; Tkaczyk, Tomasz S.
    This paper presents the design and fabrication of a fiber-based snapshot imaging spectrometer working in both visible (490 nm-732 nm) and short-wave infrared (1090 nm - 1310 nm) ranges. To maximize the light collection efficiency, a custom relay system with 0.25 NA and 20 mm field of view (FOV) was designed and integrated. The bench setup showed that the custom relay system could fully resolve 10 µm fiber cores over the entire FOV among visible and short-wave infrared ranges. The numerical aperture (NA) match provided a 2.07X fold throughout improvement in the visible range and about 10X fold in the SWIR range compared to the previous generations, enabling imaging with a fast frame rate and under low illumination conditions. The presented imaging spectrometer generated spectral datacubes with 35000 spatial samplings and 23 spectral channels. Spectral urban imaging results obtained by the spectrometer in both visible and SWIR ranges are presented. Finally, we collected spectral images of apple bruising to show potential applications in the food quality industry.