Thermal Imaging Metrology Using High Dynamic Range Near-Infrared Photovoltaic-Mode Camera

The measurement of a wide temperature range in a scene requires hardware capable of high dynamic range imaging. We describe a novel near-infrared thermal imaging system operating at a wavelength of 940 nm based on a commercial photovoltaic mode high dynamic range camera and analyse its measurement uncertainty. The system is capable of measuring over an unprecedently wide temperature range; however, this comes at the cost of a reduced temperature resolution and increased uncertainty compared to a conventional CMOS camera operating in photodetective mode. Despite this, the photovoltaic mode thermal camera has an acceptable level of uncertainty for most thermal imaging applications with an NETD of 4–12 °C and a combined measurement uncertainty of approximately 1% K if a low pixel clock is used. We discuss the various sources of uncertainty and how they might be minimised to further improve the performance of the thermal camera. The thermal camera is a good choice for imaging low frame rate applications that have a wide inter-scene temperature range.

Неохлаждаемые фотодиоды для регистрации импульсного инфракрасного излучения в спектральном диапазоне 0.9-1.8 мкм

Uncooled GaSb/GaAlAsSb photodiodes for detecting pulsed infrared radiation in the spectral range of 0.9-1.8 µm have been developed. Active GaSb layer was grown using lead as a neutral solvent in order to reduce the concentration of natural acceptors. The capacity of the photodiodes with a diameter of photosensitive area of 300 µm was 115−135 pF with no bias and 62−70 pF at U=−1.5 V. The photodiode speed of response measured using an InGaAsP/InP laser with a wavelength of 1.55 µm reached tau=42−60 ns in the photovoltaic mode. It is shown experimentally that the photodiodes can be used without cooling to detect the pulsed radiation of lasers and LEDs in the near-infrared region of the spectrum.

Experimental Characterization of RGB LED Transceiver in Low-Complexity LED-to-LED Link

This paper proposes a low-complexity and energy-efficient light emitting diode (LED)-to-LED communication system for Internet of Things (IoT) devices with data rates up to 200 kbps over an error-free transmission distance up to 7 cm. The system is based on off-the-shelf red-green-blue (RGB) LEDs, of which the red sub-LED is employed as photodetector in photovoltaic mode while the green sub-LED is the transmitter. The LED photodetector is characterized in the terms of its noise characteristics and its response to the light intensity. The system performance is then analysed in terms of bandwidth, bit error rate (BER) and the signal to noise ratio (SNR). A matched filter is proposed, which optimises the performance and increases the error-free distance.

Effect of the Front and Back Illumination on Sub-Terahertz Detection Using n-Channel Strained-Silicon MODFETs

Plasma waves in semiconductor gated 2-D systems can be used to efficiently detect Terahertz (THz) electromagnetic radiation. This work reports on the response of a strained-Si Modulation-doped Field-Effect Transistor (MODFET) under front and back sub-THz illumination. The response of the MODFET has been characterized using a two-tones solid-state continuous wave source at 0.15 and 0.30 THz. The DC drain-to-source voltage of 500-nm gate length transistors transducing the sub-THz radiation (photovoltaic mode) exhibited a non-resonant response in agreement with literature results. Two configurations of the illumination were investigated: (i) front side illumination in which the transistor was shined on its top side, and (ii) back illumination side where the device received the sub-THz radiation on its bottom side, i.e., on the Si substrate. Under excitation at 0.15 THz clear evidence of the coupling of terahertz radiation by the bonding wires was found, this coupling leads to a stronger response under front illumination than under back illumination. When the radiation is shifted to 0.3 THz, as a result of a lesser efficient coupling of the EM radiation through the bonding wires, the response under front illumination was considerably weakened while it was strengthened under back illumination. Electromagnetic simulations explained this behavior as the magnitude of the induced electric field in the channel of the MODFET was considerably stronger under back illumination.

Study of the photo-adjustability of pn-junctions in photovoltaic mode coupled to photoconductors

We propose a photo-adjustable arrangement that electrically combines a pn-junction operating in photovoltaic mode to a suitably designed photoconductor in order to keep the output current, voltage, or both, fixed. The characteristic I-V curves of a pn-junction under different light intensities do not intersect each other, resulting in different operational points for a given load. However, the resistivity of the photoconductor also changes with light, and by connecting it in parallel to the photovoltaic cell, and exposing both to the same level of irradiance, it is possible to find a design that alters the I-V curves of the cell in such a way that they will intersect at a chosen point. That could offer an alternative solution for a stable supply to autonomous DC loads. This paper presents an example case for a silicon pn-junction, considering the presence of parasitic components.

The Feasibility Study of Distributed Photovoltaic Power Generation System in Western Region of China

Due to the natural environment, geographic location, the technical conditions and restrictions of many factors, centralized parallel operation of power grid the west extension and popularization in our country with high difficulty and feasibility. The distributed photovoltaic power generation possesses the following advantages: less investment, flexibility and compatibility. The joint operation of DG with power grid brings tremendous variation in control and operation for modern power system, ultimately the stability of power supply is enhanced and the life quality of residents is improved in western region of China. This paper explores the operation mode of distributed photovoltaic power generation in remote areas, and introduces the concrete operation mode of the project, analyzes the adaptability of distributed photovoltaic mode. Finally, the feasibility of the application of the distributed photovoltaic power generation in the western region of China is analyzed in this paper.