An ultra-compact concentric catadioptric imaging spectrometer with large relative aperture and long slit is proposed. It consists of three optical components integrated monolithically in a concentric layout. Its astigmatism theory is discussed through tracing its chief ray and its athermalization is realized by optimizing lens materials. A high-speed (F/2.25) long-slit (48mm) VNIR design with high imaging quality and small distortions is presented. Results show a 10× reduction in volume than classic designs based on Offner-Chrisp configuration and a 1.9× reduction in length than Dyson configuration. Moreover, the design shows superior thermal adaptability with negligible decline in imaging quality while operating temperature changes between −30 ℃ and 70 ℃.

To improve the swath width and quantitative accuracy of hyperspectral payloads on a geostationary orbit, a long-slit polarization-insensitive imaging spectrometer is designed and demonstrated in this paper. For the wide swath, several long-slit spectrometers with the same specification have been designed and compared. The result shows that the Wynne-Offner spectrometer has advantages in increasing slit length and reducing volume, and it is suitable for being spliced for ultra-wide swath. To solve the problem of inaccurate radiation measuring caused by the polarization of imaging spectrometers, the requirement for linear polarization sensitivity (LPS) is theoretically analyzed and assessed. As diffraction grating is the main polarization-sensitive element in an imaging spectrometer, we propose to increase the apical angle of the grating groove to reduce its LPS and compensate its residual polarization by specially polarized optical films coated on lens surfaces, thus the polarization-insensitive system is achieved. At last, a VNIR spectrometer with superior spatial and spectral performance is developed, and its slit is 61.44 mm long. The maximum LPS of this system is reduced from 10.0% to 2.3% (test 2.5%) after the depolarization design, which greatly reduces the uncertainty of the measuring radiation caused by polarization. The developed imaging spectrometer can play a role in quantitative hyperspectral remote sensing, especially in wide-swath applications on geostationary orbit.

The optical system of an imaging spectrometer working on a geostationary earth orbit (GEO) covering a full optical spectrum of 0.3–12.5 μm is analyzed and designed. It enables a ground coverage of 400 × 400 km by internal scanning and achieves a high spatial resolution of 25 m. The full spectrum is divided into five sub-bands, and each band adopts four spectrometers to splice in the field of view to achieve the ultra-long slit required by the wide swath. The total length of the slit is up to 241.3 mm. This paper focuses on compact spectrometers with long slits that can meet the splicing requirements and points out that low spectral distortions, low stray light, high signal-to-noise ratio, and uniform spectral response are necessary for high-fidelity performance. The Offner and Wynne–Offner high-fidelity spectrometers based on convex blazed gratings are designed, and prototypes of each band are developed as well. The properties of long slits and convex blazed gratings are presented. The maximum length of a single slit is 61.44 mm. The groove density of gratings for five bands ranges from 8.8 lp/mm to 312.1 lp/mm, and the peak efficiency is up to 86.4%. The alignment and test of the spectrometers are introduced. Results show that the developed spectrometers have high fidelity and fulfill all requirements.

This paper presents a UAV-based hyperspectral imaging system that can simultaneously capture a frame image and three hyperspectral images, providing an efficient and precise approach to hyperspectral data acquisition. By utilizing the frame image to preserve relative pose information across consecutive frames, the system simplifies geometric correction and eliminates the need for high-precision directional geo-referencing devices, ground control points, or gimbal systems. At the same time, the system employs a multi-slit time-sharing sampling strategy to enable repeated spectral measurements while reducing sampling loss and maintaining data authenticity. A matched geometric correction algorithm, which combines single-slit image mosaicking and multi-slit fusion, is proposed to ensure precise spatial alignment even under challenging conditions. Furthermore, a robust radiometric calibration framework, incorporating cross-calibration and real-time corrections via a downwelling radiance measurement device, mitigates errors caused by variable solar illumination. These features enable reliable reflectance measurements and high-quality hyperspectral images. A rigorous evaluation framework, including both ground-based and UAV-based experiments, is conducted to comprehensively assess system performance. The results demonstrate superior sampling efficiency, improved geometric alignment accuracy, and greater radiometric consistency compared to conventional methods. The proposed system offers a cost-effective, lightweight, and versatile solution for hyperspectral imaging applications in agriculture, environmental monitoring, target exploration, and other fields, effectively addressing key limitations of existing technologies.

The increasing demand for accurate imaging spectral information in remote sensing detection has driven the development of hyperspectral remote sensing instruments towards a larger view field and higher resolution. As the core component of the spectrometer slit, the designed length reaches tens of millimeters while the precision maintained within the μm level. Such precision requirements pose challenges to traditional machining and laser processing. In this paper, a high-precision air slit was created with a large aspect ratio through MEMS technology on SOI silicon wafers. In particular, a MEMS slit was prepared with a width of 15 μm and an aspect ratio exceeding 4000:1, and a spectral spectroscopy system was created and tested with a Hg-Cd light source. As a result, the spectral spectrum was linear within the visible range, and a spectral resolution of less than 1 nm was obtained. The standard deviation of resolution is only one-fourth of that is seen in machined slits across various view fields. This research provided a reliable and novel manufacturing technique for high-precision air slits, offering technical assistance in developing high-resolution wide-coverage imaging spectrometers.