Hyperspectral imaging technology refers to the use of a large number of continuous narrowband wavelengths to process image data and obtain detailed spectral information across many bands throughout the imaging process. It combines imaging and spectroscopy technology.
Short-Wave Infrared Explained
Shortwave infrared refers to the band 1-3 µm. Like visible light imaging, short-wave infrared imaging primarily uses light that is reflected on an object’s surface. The reflection spectrum properties of different substances vary, enabling the assessment and identification of these distinct characteristics.
Moreover, shortwave infrared has strong penetration and unique absorption properties for different substances. In some scenes, shortwave infrared lenses can uncover different visual characteristics than visible light lenses.
For instance, the absorption peak of water molecules in certain short-wave infrared bands is extremely strong. This spectral trait makes short-wave infrared particularly sensitive to meat, vegetables, fruits, and other objects, which is also a key application principle of SWIR technology in detection.
Combining short-wave infrared technology with a hyperspectral camera leverages the strengths of both technologies to provide a more detailed analysis of the observed target, which is crucial in various fields.
Applications of Short-Wave Infrared Hyperspectral Cameras
SWIR’s strong water absorption peak enables SWIR hyperspectral cameras to detect the ripeness of fruits and vegetables, check for foreign substances in meat, and track the health status of vegetation to examine drought conditions.
Additionally, the reflection spectra of different minerals in the shortwave infrared range follow specific patterns. Shortwave infrared spectroscopy can efficiently and quickly detect and classify various mineral species, significantly improving the efficiency of geological exploration.
Shortwave infrared hyperspectral cameras also have key applications in art analysis, archaeology, drug detection, and other fields.
Hyperspectral imaging optical system. Image Credit: Avantier Inc.
Hyperspectral Imaging Optical System
A SWIR hyperspectral camera comprises an objective lens, a spectroscopic system, and a sensor.
Dispersive hyperspectral cameras typically utilize a grating or prism to scatter light. The objective lens transfers the image of the target object to the spectrometer, which acquires continuous single-wavelength spectral data via the dispersion element and then transmits the image onto the sensor.
Ultimately, the collected spectral information is integrated and assessed by a computer.
Specifications
Source: Avantier Inc.
| |
|
| Wavelength range |
1000-2500 nm |
| F# |
2.8 |
| EFFL |
30 mm |
| FOV |
±15° |
Short-Wave Infrared lens. Image Credit: Avantier Inc.
The imaging lens is a crucial component of a hyperspectral camera. To acquire more spectral data, the objective lens of the general hyperspectral camera encompasses a wide band, and the volume is small, making it easier to integrate. The following is an example of a short-wave infrared hyperspectral camera lens.
This objective lens covers the band of 1000-2500 nm, and the glass material has a high transmittance in this band, which is appropriate for short-wave infrared use cases. Moreover, the design performance of the objective lens is near the diffraction limit, and the color difference correction is excellent.
MTF Performance at Different Temperatures
The Modulation Transfer Function (MTF) graph is an important indicator of a lens’s capacity to resolve fine details. Higher MTF values suggest superior performance in both image sharpness and contrast.
Lens Performance Evaluation at 20 °C
The following Modulation Transfer Function (MTF) graph demonstrates how the lens performs at a temperature of 20 °C. In particular, the MTF is a key indicator of the lens’s capacity to resolve fine details. A larger MTF value generally indicates superior image sharpness and contrast.
MTF@20 °C. Image Credit: Avantier Inc.
Performance Across Different Temperatures
Hyperspectral cameras are typically used in airborne settings and have a sizable operating temperature span. Therefore, the objective lens design must consider heat dissipation treatment. The design performance at various temperatures is as follows.
Chromatic focal shift. Image Credit: Avantier Inc.
Lens Performance at Extreme Temperatures
The following graphs demonstrate how the lens performs at extreme temperatures of -20 °C and 50 °C. Of particular note, the MTF values are indicative of the lens’s ability to maintain image quality across various spatial frequencies under different temperatures.
MTF@-20° C & 50 °C. Image Credit: Avantier Inc.
Versatility for SWIR Hyperspectral Camera Lenses
Measuring less than 50 mm in length, this SWIR Hyperspectral camera lens is compact and requires little space. It has a field of view of ±15 ° and a substantial scanning area.
It covers a wide band of 1000-2500 nm and is, therefore, appropriate for shortwave infrared use cases. Moreover, the thermal difference is corrected, making it adaptable to environments of various temperatures.
This SWIR hyperspectral camera lens is versatile and highly efficient, making it appropriate for a broad range of use cases, including agricultural monitoring, geological exploration, art analysis, and more.
Its capacity to produce sharp, high-contrast images in diverse conditions highlights its value in comprehensive spectral analysis, underscoring the crucial role of hyperspectral imaging technology in modern scientific and industrial fields.
This information has been sourced, reviewed and adapted from materials provided by Avantier Inc.
For more information on this source, please visit Avantier Inc.