EXPRESS: A Low-Cost 3D-Printed Ocular Microspectrophotometer for Teaching Visible Spectroscopy

Visible microspectrophotometry enables the non-destructive acquisition of spectral information from microscopic regions and constitutes a valuable tool for the experimental teaching of spectroscopy, microscopy, and optical instrumentation. This work presents the design, fabrication, and evaluation of a low-cost ocular microspectrophotometer (OMP), developed using 3D printing and designed for integration with conventional optical microscopes. The device incorporates a diffraction grating, optical apertures, and a CMOS sensor to acquire continuous spectra over the 433–827 nm wavelength range from microscopic regions approximately 40 µm in diameter. In addition, a Python-based algorithm was developed to convert spectral images into transmittance vectors and calibrate the pixel-to-wavelength relationship. The system achieved a spectral resolution of approximately 0.84 nm/pixel and was validated using reference optical filters. Its educational potential was demonstrated through the spectral characterization of the RGB subpixels of a smartphone LCD screen and the analysis of the transmittance of a plant leaf. These activities provide an effective means of introducing concepts such as additive color synthesis, spatial resolution, light–matter interaction, and digital image processing. The OMP constitutes an accessible and reproducible platform that integrates additive manufacturing, digital image processing, and hands-on experimentation for teaching spectroscopy, microscopy, and the design of scientific instrumentation.