Thermal Imaging Lenses Research Articles

Ga2S3-SnS2-CsI chalcohalide glasses for mid-infrared Optics

Chalcogenide and chalcohalide glasses have been considered promising host materials for thermal imaging lenses and mid-infrared (MIR) optical fibers. In this paper, a novel Ga2S3-SnS2-CsI chalcohalide glass system, with environment-friendly constituent elements, was proposed. The glass forming region was explored, and the physical properties were investigated. The glasses show high transmittance (>60%) over the 1–12 μm spectral range and exhibit relatively high microhardness, making them competitive candidates for manufacturing thermal imaging lenses. Furthermore, the MIR emission property of Dy3+-doped Ga2S3-SnS2-CsI glass was also studied. With strong emissions and high quantum efficiencies at 3.00 μm and 4.38 μm wavelengths, the glass can be potentially used as gain media for MIR lasers.

EFFECT OF DEVIATION FROM AN ASPHERICAL SURFACE ON THE MODULATION TRANSFER FUNCTION OF A THERMAL IMAGING LENS IN CONTRAST ESTIMATION ON A COLLIMATION INSTALLATION

This article discusses the Chinese lens with a focal length of F50 and its analogue, developed by me at the production enterprise LLC “Doksard” for the overall dimensions of the body already delivered to the stream, with high-precision manufacture of aspherical surfaces: with a deviation accuracy of up to 0.1 microns and with an accuracy of up to 1 mm. The quality of the obtained image from the lens is analyzed. The purpose of the work was to determine the necessary error. The TAS-7T software, CDT15120HR collimation unit and the World TCB 4.5 kit are used. The worlds are located in a revolver mechanism, the lens is assembled, installed in a collimation installation, after which an image from the sight is displayed on the computer and the picture is fixed when observing different worlds. As a result of the conducted research, it is possible to draw conclusions about the dependence of the manufacturing accuracy and how well the quality of modern thermal imaging lenses can be determined using collimation installations. The data proposed in this paper on the results of the quality of optical sights: the dependence of the modulation transfer function on the accuracy of the manufacture of aspherical surfaces. The results of these studies will help to form the basic technical requirements for the design of thermal imaging sights during the transition of the Russian market to radiation receivers of the next generation of 14 and 12 mkm.

Optical setup for evaluating image quality of thermal imaging lenses working in the spectral region of 8÷12 µm

In this paper, we demonstrate a homemade setup and an image processing algorithm to evaluate the image quality of optical systems working in the spectral region of 8-12 µm. The working principle of our approach relies on measuring the line spread function (LSF) and the modulation transfer function (MTF). All components in the setup are carefully designed and manufactured, and we strictly follow quality control to limit measurement errors. The setup can determine the LSF and MTF of a thermal imaging lens with a focal length of f' ≤ 500 mm and pupil diameter D ≤ 100 mm. A number of objective samples have been studied using our setup, and the experimental results indicate that our setup can work reliably with high accuracy.

Recognition of big mammal species in airborne thermal imaging based on YOLO V5 algorithm.

Unmanned aerial vehicle (UAV) technology, artificial intelligence, and the relevant hardware can be used for monitoring wild animals. However, existing methods have several limitations. Therefore, this study explored the monitoring and protection of Amur tigers and their main prey species using images from UAVs by optimizing the algorithm models with respect to accuracy, model size, recognition speed, and elimination of environmental interference. Thermal imaging data were collected from 2000 pictures with a thermal imaging lens on a DJI M300RTK UAV at the Hanma National Nature Reserve in the Greater Khingan Mountains in Inner Mongolia, Wangqing National Nature Reserve in Jilin Province, and Siberian Tiger Park in Heilongjiang Province. The YOLO V5s algorithm was applied to recognize the animals in the pictures. The accuracy rate was 94.1%, and the size of the model weight (total weight of each model layer trained with the training set) was 14.8 MB. The authors improved the structures and parameters of the YOLO V5s algorithm. As a result, the recognition accuracy rate became 96%, and the model weight was 9.3 MB. The accuracy rate increased by 1.9%, the model weight decreased by 37.2% from 14.8 MB to 9.3 MB, and the recognition time of a single picture was shortened by 34.4% from 0.032 to 0.021 s. This not only increases the recognition accuracy but also effectively lowers the hardware requirements that the algorithm relies on, which provides a lightweight fast recognition method for UAV-based edge computing and online investigation of wild animals.

Research on Pest Image Processing Method Based on Android Thermal Infrared Lens

Agricultural pests and diseases seriously affect the yield and quality of crops. In order to study the incidence of pests and diseases, and improve the utilization rate of pesticides, an Android rapid processing system of Android-based insect pest thermal infrared image was designed and implemented. In this paper, maize tumor powdery mildew was used as the research object, infrared thermal imaging lens based on Android system was used to obtain corn disease images. Meanwhile, OpenCV technology was used for image processing. Moreover, in order to better achieve the thermal infrared segmentation effect, the image segmentation effect based on the traditional Otsu algorithm (Otsu) and the Otsu single-threshold segmentation method based on the bare bones fireworks algorithm (BBFWA) was analyzed. Importantly, the results showed that the method of Otsu single-threshold segmentation based on BBFWA had the best effect on thermal infrared image segmentation. Since thermal infrared images are greatly influenced by the ambient temperature, the shooting needs to be performed under cloudy or cloudy conditions. Finally, the ratio value between the total number of pixels in the white area and the total number of pixels in the divided binary image was calculated to determine the degree of pest infestation, which can provide data reference for the UAV spraying amount to some extent.

Современные тенденции в разработках инновационных тепловизионных объективов и проблемные вопросы их промышленного производства

Современные тенденции в разработках инновационных тепловизионных объективов и проблемные вопросы их промышленного производства

In brief

PAGE 1146 A team working in Australia have achieved wideband gain enhancement of a slot antenna by placing a quarter-wavelength-thick unprinted dielectric slab above it. In addition to having a high gain with a large bandwidth, the antenna is easy to fabricate and has a low vertical profile, with a total height of 0.593λ0. PAGE 1140 The specific differential attenuation reflectivity, phase and reflectivity exhibited by large rand drops and melting hail have been computed and studied by a team from the USA. The work addresses the ‘hot spots’ in C-band polarimetric radar observations in storms. The measured peak gain is 16.95 dBi and the 3dB gain bandwidth is 16.25% PAGE 1172 Gerald Küstler, working in Germany, reports on a simultaneous inline triple levitation system using permanent magnets. The system allows for the inline levitation of three different bodies without energy input or feedback control, and could find application in seismometers or accelerometers after further study. Melting hailstones take the form of a water torus surrounding an ice core PAGE 1170 A team from the USA and Korea build on their previous work by investigating surface plasmon resonant splitting and merging due to infrared incidence through a thermal imaging lens. The team analyse the transmission of a plasmonic perforated gold film (PGF) against the incident light in both polar and azimuth angles. The future challenge is to characterise the system response behaviour PAGE 1132 A team working in China have achieved adjustable electromagnetically induced transparency (EIT) using a slotted circle ring structure. EIT can create a narrow transmission window in a wide absorption band, and such structures that create this effect can be used as angle modulators or state sensors. The sample was fabricated with a PGF on a semi-insulating GaAs substrate The proposed structure can also be used in frequency selective surface design

Surface plasmon resonant splitting and merging due to infrared incidence through thermal imaging lens

In previous work, the present authors discovered the resonant splitting phenomenon of a plasmonic perforated gold film (PGF), as the incident light comes in the polar angle. However, in reality, the light through the imaging lens could be incident on the PGF not only in the polar angle but also in the azimuth angle. The transmission of a PGF against the incident light is analysed in both polar and azimuth angles in spherical coordinates. To mimic the incidence through the lens, a PGF sample is rotated by simultaneously varying both types of angles as normal incidence arrives. For the measurement, the sample has been fabricated with a PGF on a semi-insulating gallium arsenide (GaAs) substrate. The measured transmission spectra show both resonant splitting and merging under TM and TE polarisations as the azimuth angle is increased. Results drawn from this work will pave the way to fully understanding the interaction between the imaging lens and the plasmonic structure (PGF).

On the ultra-precision diamond machining of chalcogenide glass

Chalcogenide glasses are important materials for components in thermal imaging systems (IR-optics). While suitable for molding, the machining characteristics of these brittle materials are largely unknown. In this paper, ultra-precision machining data for a common chalcogenide glass (As40Se60) is presented. Data acquired from orthogonal cutting experiments show a transition in cutting mechanics at an uncut chip thickness of approximately one micrometer. This data is used to identify parameters for high-speed milling, and results are used to produce a thermal imaging lens. This paper demonstrates that the milling process is suitable for prototyping and low-batch production of IR-optics in this glass.

Generation of Parabolic and Toroidal Surfaces on Silicon and Silicon-Based Compounds Using Diamond Cup Grinding Wheels

This paper presents the methods and experimental results using diamond cup wheels and CNC machining centers for grinding parabolic and toroidal surfaces made of Si and SiC, the former for use as a thermal imaging lens and the latter for synchrotron radiation facilities. Generation of aspheric surfaces, by zonal material removal, on Si using cup grinding wheels and a 5-axis machining center was investigated. Theoretical and experimental investigation of the grinding and material parameters that influence ductile grinding are discussed. Ductile grinding is possible with wheels having small grit size and with proper combination of feed and unit normal load; a resinoid bonded wheel promotes this more easily than a metal bonded wheel, though at the expense of profile accuracy. Profile analysis, surface integrity, and examination of grinding swarf using digital imaging are discussed. Also, generation of toroidal surfaces on SiC using metal-bonded cup wheels, a 3-axis machining center and a micro-displacement table with piezoelectric actuators was studied. Toroidal SiC mirrors were ground with good shape accuracy, mirror finish, and low surface roughness. The time consumed in the process is very short. The machines used are inexpensive and not specially designed for ultra-precision grinding.

The Use of Simple Relationships between Wavefront Aberration and Wavelength to Approximate the Polychromatic Optical Transfer Functions of 8 to 12 µm Thermal Imaging Lenses

Abstract Two methods are described which can be used to predict polychromatic optical transfer functions (OTFs) of thermal imaging lenses to good accuracy from only one finite ray trace. These methods offer some saving in calculation time and could be used to predict polychromatic OTFs from monochromatic test data provided suitable paraxial data and spectral details are available.

An automated MTF measurement system for use in the 8-12μm spectral region

A microprocessor-based MTF lens evaluation system involving direct measurement of the IR line spread function is described. The microprocessor controls the instrument during the signal location and data acquisition phases and in addition carries out the data processing. The relative merits of different methods of evaluating the inverse Fourier transform are discussed. Results obtained with both finite conjugate and afocal thermal imaging lenses are presented.