As an efficient detection instrument, an imaging spectrometer can simultaneously acquire two-dimensional spatial image information and one-dimensional spectral information of an observation target. With the rapid development of unmanned aerial vehicle (UAV) technology and the concept of the “low-altitude economy”, the application of UAV is rapidly expanding in agriculture, environmental protection, disaster emergency response, and other fields. As an important strategy to promote high-quality economic development, the low-altitude economy aims to build a new economic model by integrating the upstream and downstream of the industrial chain through the development and utilization of low-altitude resources. Among these, the R&D and manufacturing of UAV-related airborne equipment are also key components. Carrying an imaging spectrometer on the UAV platform combines the advantages of both to enable fast, flexible, and efficient observation of the ground. However, traditional airborne imaging spectrometers are currently characterized by large size, heavy weight, small field of view, high cost, and other limitations, which results in small ground coverage, low monitoring efficiency in a single mission, short range, and difficulty in being used by the general public. Therefore, the development of a miniaturized, lightweight, and low-cost unmanned airborne imaging spectrometer is of great strategic significance for supporting the development of the low-altitude economy and promoting the application of imaging spectrometers. To address the above problems, we design a miniature and low-cost unmanned airborne imaging spectrometer.

During the design of the imaging spectrometer, the front telescope system adopts a transmissive structure, with the double Gauss structure used as the initial design for optimization. In the optimization, it is found that due to the wide working band of the system, there are significant chromatic aberration and secondary spectra. The secondary spectra are corrected by introducing binary optical elements, which also make the structure of the front telescope system lighter and smaller. The rear spectrometer system adopts a symmetrical planar grating structure similar to the Offner structure. The collimation and focusing systems are integrated, sharing a positive lens and a refractive lens, which simplifies the overall structure and makes it easier to install and adjust. At the same time, using a plane grating as the spectroscopic element reduces the processing difficulty and cost of the grating. Finally, the whole system design combines the front telescope system with the rear spectrometer system. Since both systems have achieved good imaging quality, the integrated design optimization only requires fine-tuning of the overall optical system structure, resulting in the final design of the imaging spectrometer.

We design a miniature and low-cost unmanned airborne imaging spectrometer with the structure shown in Fig. 11. Light first enters the front telescope system and then passes through the slit into the rear spectrometer system. Upon reaching the rear spectrometer system, the light is collimated by the collimation system, then divided by the plane grating, converged by the convergence system, and finally reaches the detector. The collimation and convergence systems use an integrated design, which makes the structure compact and easy to install and adjust. The optical design specifications of the imaging spectrometer system are shown in Table 1. The design and analysis results show that the imaging spectrometer operates in the wavelength band of 400?1000 nm. At the Nyquist frequency of 36 lp/mm, the modulation transfer function (MTF) for each band is higher than 0.7. The root mean square (RMS) of the full-field-of-view dispersive spot for each band is less than 6.5 μm, and the spectral resolution is better than 3 nm. The volume of the optical system is 100 mm×45 mm×50 mm. The imaging quality is good, and all indexes meet the design requirements.

We focus on the research on microminiature and low-cost unmanned airborne imaging spectrometers. We design and optimize an imaging spectrometer with features such as structural microminiaturization, a large field of view, and low cost. It meets the needs of low-altitude remote sensing applications that require lightweight, miniaturized, and cost-effective imaging spectrometers. In the study, through the design optimization of the front telescope system and the rear spectrometer system, the secondary spectrum of the front telescope system is corrected using binary optical elements, and the microminiaturization of the rear spectrometer system is realized by adopting an Offner-like structure. The final design results meet the design requirements. The design scheme proposed in this paper provides a practical solution for the development of an unmanned airborne imaging spectrometer that is microminiaturized, low-cost, and has a large field of view, which is expected to be widely used in related fields.