Research

This study examined the effects of a glyphosate-based herbicide on early life stages of Nile tilapia, revealing dose-dependent reductions in hatching rates, increased mortality, and developmental deformities. Using OCT, we non-invasively visualized structural abnormalities, while biochemical assays showed reduced acetylcholinesterase expression and digestive enzyme activity, indicating neurotoxicity and metabolic disruption. The findings highlight the ecological risks of glyphosate and demonstrate the value of OCT for aquatic toxicology.

    Since 2015, we have continuously developed a compact OCT microscope prototype tailored for field assessments in aquatic animal study. Specifically, it is used to evaluate pesticide exposure in freshwater fish. The prototype, comprising exclusively commercial optical components, achieves imaging depths up to 2 mm from a sample's surface at a rate of 20 frames per second and boasts resolutions of 10 microns both laterally and in depth. We demonstrated its utility by imaging African catfish exposed to the herbicide 2,4-D dimethylammonium, comparing these with control samples. We performed in vivo 3D imaging, using the developed prototype, on each catfish throughout its hatching and embryonic development period, comparing the 2,4-D exposure with the control. The results show significant deviations in the exposed group from the typical developmental patterns observed in the control group. This confirms the capability of OCT to assess the effects of herbicides on aquatic organisms. 

    The effective spectral resolution of a spectrometer that utilizes dispersive optics is normally limited by either the size of the sensor pixels or the optical resolution of the focusing optics. Therefore, achieving optimal optical alignment is crucial to maximize the spectrometer's effective spectral resolution. In this paper, we introduce a laboratory method for real-time assessment of spectrometer alignment by measuring the modulation transfer function (MTF). The modulation on spectral signal is generated using an interferometer, allowing control of the modulation frequency by adjusting the optical path difference. The results show that the proposed technique can provide useful information about the alignment of the spectrometer, which can be used to obtain the optimum alignment of the spectrometer. The accuracy of the proposed method was confirmed by comparing the MTF measurement, and hence the resolution evaluation, with the specifications of a commercial spectrometer. In addition, we demonstrate the use case of the proposed method by performing a through-focus MTF measurement on a custom-built spectrometer with known misalignments.