Spectral imaging captures data in three dimensions, including two spatial dimensions and one spectral dimension. Common two-dimensional detectors cannot access all data content simultaneously. Traditional scanning spectral imaging methods employ a time-dependent multiplexing detector to acquire partial dimensional information in one exposure and stitch multiple exposures to form a complete three-dimensional spectral image. Our study adopts a snapshot spectral imaging method based on microlens arrays, which captures three-dimensional spectral image information in a single exposure. By sacrificing some spatial and spectral resolution, temporal resolution is improved. This approach meets the need for high sensitivity and fast time resolution in observations.

Our study encompasses the theoretical analysis and practical implementation of a spectral imaging system based on microlens arrays. The system architecture is described, including the imaging lens, beam splitter, microlens array, collimator lens, wedge prism, focusing lens, and detector. The integral imaging principle of microlens arrays is derived analytically, with light tracing simulations performed to evaluate the integral spot size under varying incident light cone angles. The theoretical spectral resolution is examined by adopting both dispersive ray tracing simulations on the detector surface, and collimating and focusing lenses with different focal lengths, thus yielding the theoretical spectral resolution of the system. The system parameters are defined by integrating theoretical and simulation results, and bandpass filters are employed to calibrate the spot positions of each wavelength. Spatial resolution and three-dimensional spectral imaging tests are conducted by utilizing uniform stripes with varying spacing and 24-color checkers, validating the system’s three-dimensional spectroscopic observation capabilities.

The integration formula derivation for the microlens array indicates that the sub-pupil diameter is a single-valued function of the incident angle, increasing monotonically with the angle [Eq. (5)]. Optimal integration requires minimal light divergence post-imaging lenses (Fig. 3). Ray tracing simulations with collimating and focusing lens focal lengths of 30 mm/30 mm, 30 mm/50 mm, 40 mm/40 mm, and 50 mm/50 mm demonstrate that increasing the focusing lens focal length alone does not significantly enhance spectral resolving power (Fig. 6). In contrast, increasing the collimating lens focal length yields notable improvements in spectral resolving power (Fig. 7). The system’s theoretical optimal spectral resolution is 25 nm with 40 mm focal lengths for both lenses. Calibration of spot positions by employing bandpass filters with central wavelengths of 450, 500, 532, 589, 628, and 685 nm reveals that the spot interval for 450 and 685 nm is 16.2 pixel, corresponding to an actual distance of 38.9 μm on the detector, which is consistent with ray tracing results (Fig. 10). Spatial resolution tests employing uniform stripes with varying spacing indicate three-dimensional spectral image resolution of at least 1.2 m and two-dimensional spatial image resolution of at least 0.5 m at a target distance of 30 m (Fig. 12). Three-dimensional spectral imaging with a 24-color checker confirms the system’s ability to distinguish different color regions across six bands (Fig. 13), thus validating its three-dimensional spectral detection proficiency.

Our study presents the development of a snapshot spectral imaging system by utilizing microlens arrays for three-dimensional spectral imaging within the visible wavelength range. Theoretical analysis and light tracing simulations are conducted to elucidate and validate the factors influencing the integral spot size of microlens arrays and the effects of collimation and focusing lens focal lengths on the system’s spectral resolving power. The system employs microlens arrays as the integrating element, achieving spectral imaging across six bands within the 450?685 nm range. The spatial resolution for the three-dimensional spectral image reaches 1.2 mm, while that for the two-dimensional spatial image reaches 0.5 mm at a target distance of 30 m. Validation by adopting a 24-color checker produces spectral images across different wavelength bands, confirming the system’s proficiency in three-dimensional spectral imaging.