SmartSpectrometer-Embedded Optical Spectroscopy for Applications in Agriculture and Industry.

The ongoing digitization of industry and agriculture can benefit significantly from optical spectroscopy. In many cases, optical spectroscopy enables the estimation of properties such as substance concentrations and compositions. Spectral data can be acquired and evaluated in real time, and the results can be integrated directly into process and automation units, saving resources and costs. Multivariate data analysis is needed to integrate optical spectrometers as sensors. Therefore, a spectrometer with integrated artificial intelligence (AI) called SmartSpectrometer and its interface is presented. The advantages of the SmartSpectrometer are exemplified by its integration into a harvesting vehicle, where quality is determined by predicting sugar and acid in grapes in the field.

Basic angles in microelectromechanical system scanning grating spectrometers.

Modern miniaturized scanning grating spectrometers (SGSs) are often based on microelectromechanical system devices. In contrast to classical spectrometers, such systems exhibit additional design constraints, like a symmetrical motion of the grating with a limited deflection. A detailed mathematical analysis of typical SGS configurations based on the grating equation considering these constraints is presented. Equations that relate the basic angles on a scanning grating to the grating properties and the attainable wavelength range of a spectrometer are derived, and the solution set is examined. Furthermore, the analytical description can be used to optimize SGSs with symmetrically moving gratings. The attainable spectral range for a given deflection amplitude of the grating can be calculated. Alternatively, the required grating properties can be determined for a given spectral range.

Design of an all-reflective unobscured optical-power zoom objective.

A novel design for an all-reflective unobscured optical-power zoom (OPZ) objective with a zoom factor of 3 is presented. In contrast to OPZ objectives based on liquid lenses, all-reflective objectives use only reflective elements and are therefore free of chromatic aberrations. Thus, they can be used for a wide spectral range or in combination with image sensors that differ in their spectral characteristics. To avoid a decrease in image contrast encountered in on-axis designs with central obscuration, an unobscured off-axis or "Schiefspiegler" approach is adopted. The effective focal length of the objective is changed by two deformable mirrors, each with one actuator only. The simulated final design shows adequate image quality over the whole zooming range. Before starting the complex and cost-intensive development of deformable mirrors with the size, curvature, and dynamic range needed, the optical design should be evaluated first with respect to the practical achievable optical performance. Therefore, optomechanical setups with ultraprecision-manufactured solid mirrors were realized for three different focal lengths.

Design of a micro-opto-electro-mechanical-system-based near-infrared hyperspectral imager.

We present the development of an imaging spectrometer for the near infrared (NIR) using a micro-opto-electromechanical system. A diffraction grating has been etched into the surface of a micromechanical scanning mirror made of silicon and is used to scan the object space and to disperse the NIR radiation simultaneously. Beginning with the specific requirements of NIR hyperspectral imaging, a detailed analysis of the system approach resulting in an all-reflective optical design for the hyperspectral imager is presented. The investigation includes a thorough consideration of spectral and spatial distortion occurring by scanning the scene with a grating. Minimization of these aberrations leads to an improved spectrometer design.

Near-Infrared Grating Spectrometer for Mobile Phone Applications.

Near-infrared (NIR) spectroscopy is a well-established technique for the chemical analysis of organic and inorganic matter. Accordingly, spectroscopic instrumentation of different complexity has been developed and is currently commercially available. However, there are an increasing number of new mobile applications that have come into focus and that cannot be addressed by the existing technology due to size and cost. Therefore, a new miniaturized scanning grating spectrometer for NIR spectroscopy has been developed at Fraunhofer IPMS. It is based on micro-electro-mechanical systems (MEMS) technology, and has been designed to meet the requirements for mobile application, regarding spectral range, resolution, overall size, robustness, and cost. The MEMS spectrometer covers a spectral range from 950 nm to 1900 nm at a resolution of 10 nm. The instrument is extremely small and has a volume of only 2.1 cm(3) Therefore, it is well suited for integration, even into a mobile phone. A first sample of the new spectrometer has been manufactured and put into operation. The results of a series of test measurements are in good agreement with the requirements and specifications.