Mechanical Shutter Research Articles

ZEROES: Robust Derivative-Based Demodulation Method for Optical Camera Communication

Most of Optical Camera Communication (OCC) systems benefit from the rolling shutter mechanism of Complementary Metal-Oxide Semiconductor (CMOS) cameras to record the brightness evolution of the Light-Emitting Diode (LED) through dark and bright strips within images. While this technique enhances the maximum achievable data rate, the main difficulty lies in the demodulation of the signal extracted from images, subject to blooming effect. Thus, two main approaches were proposed to deal with this issue, using adaptive thresholds whose value evolves according to amplitude changes or detecting signal variations with the first-order derivative. As the second method is more robust, a new demodulation method based on the detection of the zeros of the first-order derivative of the extracted signal was proposed in this paper. Obtained results clearly show an improvement in the extracted signal demodulation compared to other methods, achieving a raw Bit Error Rate (BER) of 10−3 around 50 cm in a Line-Of-Sight scenario, and increasing the maximum communication distance by 43.5%, reaching 330 cm in the case of a Non-Line-Of-Sight transmission.

Long-Term Radiometric Stability of Uncooled and Shutterless Microbolometer-Based Infrared Cameras

Uncooled and shutterless microbolometer cameras are good candidates for infrared imaging systems installed on small satellites or small unmanned aerial vehicles: they are light and passive since no cooling system or mechanical shutter is required and they can be operated at ambient temperatures. However, the radiometric compensation has to be carefully performed to make the system compatible with applications where the radiometric accuracy of the images is mandatory. In this paper, we study the impact of the camera environment to the radiometric accuracy of the images. We propose and test hardware and software solutions to improve this accuracy and the quality of the radiometric images. We show that the radiometric calibration of the camera with our model is valid over a long time period— about 3 years—using in-door experiments.

Detection of vague object signatures on deep learning surveillance devices

The deep learning of object detection has become a breakthrough in recent years. Many papers demonstrated that this method records significant reliability results. However, the question arises whether objects that were successfully detected are initially conditioned clear in daylight. The object being detected is in the form of a photographic product that has numerous problems. It can be distant or have low-contrast so that their signatures are challenging to recognize, especially detection of persons in surveillance systems for dark-environments. This paper contributes to proving the deep learning method capable of detecting night-person (NP) with high precision and recall in the dark without image enhancement, by using ordinary cameras which operate on day-night or visible-near infrared spectrum runs on embedded systems. For that, an infrared-cut filter mechanical shutter is designed to block for the day or deliver infrared light for the night. The NP signatures are illuminated by an external infrared light source, providing three-channel high-resolution images. The distance of a NP from the camera becomes a decisive successful detection. The external infrared light source makes objects under or overexposed affecting the object being recognized. The validation with thoroughly new data of the NP constantly provides high precision and recall.

Demonstration of symbol timing synchronization for rolling shutter-based optical camera communication

Optical camera communication (OCC) provides license-free communication channels without radio waves. The rolling shutter mechanism is expected to enhance the capacity of wireless links in OCC. However, signal erasure occurs due to waiting times between frames in consecutive signal transmission. To address this issue, we propose a symbol timing synchronization for OCC using a rolling shutter camera. The receiver camera synchronizes to the transmitter with additional waiting time which is computed based on the defined preamble signals. We analyzed the performance to clarify the theoretical limit. The feasibility of the proposed idea was confirmed with experimental results.

HYPSTAR: a hyperspectral pointable system for terrestrial and aquatic radiometry

Optical Earth observation satellites provide vast amounts of data on a daily basis. The top-of-atmosphere radiance measured by these satellites is usually converted to bottom-of-atmosphere radiance or reflectance which is then used for deriving numerous higher level products used for monitoring environmental conditions, climate change, stock of natural resources, etc. The increase of available remote sensing data impacts decision-making on both regional and global scales, and demands appropriate quality control and validation procedures. A HYperspectral Pointable System for Terrestrial and Aquatic Radiometry (HYPSTAR®) has been designed to provide automated, in-situ multiangular reflectance measurements of land and water targets. HYPSTAR-SR covers 380–1020 nm spectral range at 3 nm spectral resolution and is used at water sites. For land sites the HYPSTAR-XR variant is used with the spectral range extended to 1680 nm at 10 nm spectral resolution. The spectroradiometer has multiplexed radiance and irradiance entrances, an internal mechanical shutter, and an integrated imaging camera for capturing snapshots of the targets. The spectroradiometer is mounted on a two-axis pointing system with 360° range of free movement in both axes. The system also incorporates a stable light emitting diode as a light source, used for monitoring the stability of the radiometric calibration during the long-term unattended field deployment. Autonomous operation is managed by a host system which handles data acquisition, storage, and transmission to a central WATERHYPERNET or LANDHYPERNET server according to a pre-programmed schedule. The system is remotely accessible over the internet for configuration changes and software updates. The HYPSTAR systems have been deployed at 10 water and 11 land sites for different periods ranging from a few days to a few years. The data are automatically processed at the central servers by the HYPERNETS processor and the derived radiance, irradiance, and reflectance products with associated measurement uncertainties are distributed at the WATERHYPERNET and LANDHYPERNET data portals.

FriiTriga, a triggered controller with an optical beam shutter using a hard disk drive voice-coil actuator

We present in this article the complete setup to build a triggered controller with a mechanical optical shutter. The system is a low cost, Do-It-Yourself, and easy to implement setup with three functionalities: Manual mode, direct mode with TTL signal command and Triggered mode with a TTL signal command. Our setup is primarily intended to be integrated in optical setup where one needs to control the opening time of a light path, but can be used also for any other setup where one wants to send a TTL signal to command another subsystem (in our case the shutter is that subsystem). The shutter used here is hard disk drive voice-coil actuator, which was already demonstrated to have interesting potentialities to be a mechanical shutter.In the Manual mode, this setup achieves an opening and closing time of 3 ms. In Direct mode with TTL signal command, the setup has a delay response time of 19 ms and a minimum open pulse time of 23 ms. This low cost device which can be made with less than 50€, have similar characteristics with commercial ones which can be twenty times more expensive.

Application of thermotropic ferroelectric liquid crystals in electrical vehicle

This intermediate phase between solid and liquid enables liquid crystal engineers for various interesting yet fascinating thermo-optical applications. One such application of exploited for electric vehicle safety is optical shutter realized using thermotropic liquid crystals. Optical shutters are essential components in various optical systems, in providing control over the transmission of visible light. These shutters are categorized into various types of mechanical shutters, electro-optical shutters, liquid crystal optical shutters (LCOS) etc. liquid crystal cells and polarizing elements to quickly change the transmittance of light, making them ultimate for applications such as imaging and precision illumination. In this work, we explored the experimental techniques, key specifications, features, and applications of an optical shutter developed using liquid crystalline material LCOS.

Creation of a three-dimensional model of a landscape of the left bank of the Akhangaran reservoir using a phontom 4 pro quadrocopter

The purpose of the work under study is to create a three-dimensional model of a landslide on a dangerous section of the left bank of the Akhangaran reservoir, which is located in the Angren district, Tashkent region of the Republic of Uzbekistan, using unmanned aerial photography. In order to display the landslide area in as much detail and accuracy as possible, aerial photography was carried out by a Phontom4 pro multi-rotor unmanned aerial vehicle (Chinese company DJI) with a 4K camera and an object tracking function. camera DSC-RX1R with a focal length of 35 mm over an area of 162 hectares. Four 1:500 scale aerials were completed on site, with a longitudinal overlap of 70% and a transverse overlap of 50%. Aerial photography was carried out at an altitude of 70 meters. The total number of aerial photographs was 936. The length of all air routes was 122.7 km. The article examines in great detail the functions of the quadcopter, the uniqueness of its camera, which is capable of shooting video in 4K format (4096 by 2160 pixels) at a speed of 60 frames/sec, as well as taking 14 photos per second in burst mode, and at the same time broadcasting video picture to a synchronized tablet or phone. For the first time in a DJI camera of this size, a mechanical shutter is used, which allows you to shoot dynamic scenes without the “jelly effect”, and it is also noted that an improved battery with a capacity of 5350 mAh increased the drone’s flight time to almost 30 minutes. The paper notes the purpose of the Agisoft Metashape software, in which aerial photography materials were processed, and also describes the technology for creating a 3D model for the landslide section of the left bank of the Akhangaran reservoir.

An economical single-shot pulse picker without nonlinear effect and dispersion.

An economical and stable single-shot pulse picker design without dispersion, nonlinear effect, and limitation on wavelength is proposed. This design is composed of a periodic pulse blocker (PPB), a control unit, and a mechanical shutter. It has successfully beenapplied to the commercial high-fluence femtosecond laser with 11-mm beam diameter, 2-mJ pulse energy, and 1-kHz repetition rate. Significantly, by incorporating commercial optical choppers equipped with custom-designed chopper blades in the PPB, this design can accommodate lasers with fluences reaching 610 mJ/cm2 and the standard 1kHz repetition rate typical of high-fluence lasers. Furthermore, the proposed design provides a cost-effective substitute compared to using electro-optic modulators or acousto-optic modulators.

Leveraging a smartphone to perform time-gated luminescence measurements.

Empowered by advanced on-board sensors, high-performance optics packages and ever-increasing computational power, smartphones have democratized data generation, collection, and analysis. Building on this capacity, many platforms have been developed to enable its use as an optical sensing platform for colorimetric and fluorescence measurements. In this paper, we report the ability to enable a smartphone to perform laboratory quality time-resolved analysis of luminescent samples via the exploitation of the rolling shutter mechanism of the native CMOS imager. We achieve this by leveraging the smartphone's standard image capture applications, commercially available image analysis software, and housing the device within a UV-LED containing case. These low-cost modifications enable us to demonstrate the smartphone's analytical potential by performing tasks ranging from authentication and encryption to the interrogation of packaging, compounds, and physical phenomena. This approach underscores the power of repurposing existing technologies to extend the reach and inclusivity of scientific exploration, opening new avenues for data collection and analysis.

Thermal imaging spatial noise removal via deep image prior and step-variable total variation regularization

The imaging quality of an uncooled long wave infrared camera suffers severely from time-drifted spatial noises if not regulated by a thermoelectric cooler (TEC). These noises can be categorized within the frequency domain as either fixed pattern noise (FPN) or low-frequency noise (LPN). The time-drifted FPN is primarily governed by the temperature fluctuations of the focal plane array (FPA), whereas the LPN predominantly originates from non-uniform background radiations. Most existing methods have been proposed to address the FPN or LPN independently rather than from a unified perspective. In this paper, a self-supervised convolution neural network (CNN) is proposed to remove these two types of noise simultaneously. Because of the combination of the deep image prior (DIP) architecture and the total variation (TV) regularizer, this method is named TV-DIP. With the assumption that the spatial noises are constant in a short period of time, the spatial noise pattern is extracted directly from multiple continuous raw frames without ground-truth noise-free images. In this way, the noise pattern can be updated periodically during running time, without requiring the use of a mechanical shutter. Besides, the original TV regularizer is extended with a variable step, which shows a significant enhancement on the LPN denoising task. Furthermore, both simulation and experimental results have demonstrated that this approach achieves better performance in terms of the removal of spatial noise, the preservation of detail, and the suppression of artifacts. The source code and dataset are available on the website: https://github.com/brunolinux/TV-DIP

Unmanned-aerial-vehicle based optical camera communication system using light-diffusing fiber and rolling-shutter image-sensor.

We put forward and demonstrate a light-diffusing fiber equipped unmanned-aerial-vehicle (UAV) to provide a large field-of-view (FOV) optical camera communication (OCC) system. The light-diffusing fiber can act as a bendable, lightweight, extended and large FOV light source for the UAV-assisted optical wireless communication (OWC). During UAV flying, the light-diffusing fiber light source could be tilted or bended; hence, offering large FOV as well as supporting large receiver (Rx) tilting angle are particularly important for the UAV-assisted OWC systems. To improve the transmission capacity of the OCC system, one method based on the camera shutter mechanism, which is known as rolling-shuttering is utilized. The rolling-shuttering method makes use of the feature of complementary-metal-oxide-semiconductor (CMOS) image sensor to extract signal pixel-row by pixel-row. The data rate can be significantly increased since the capture start time for each pixel-row is different. As the light-diffusing fiber is thin and occupies only a few pixels in the CMOS image frame, Long-short-term-memory neural-network (LSTM-NN) is used to enhance the rolling-shutter decoding. Experimental results show that the light-diffusing fiber can satisfactorily act as an "omnidirectional optical antenna" providing wide FOVs and 3.6 kbit/s can be achieved, accomplishing the pre-forward error correction bit-error-rate (pre-FEC BER = 3.8 × 10-3).

Evaluation and comparison of effects of recycling on the shutter mechanism and shear bond strength (SBS) of various self-ligating brackets: An in vitro study

Introduction The procedures like sandblasting and direct flaming to remove the residual composite from brackets may affect the material properties of brackets, including the shutter mechanism and it’s shear bond strength. This study focuses on the comparison of these properties in new brackets and recycled brackets of various commercially available self-ligating brackets. Objectives To compare the effects of recycling on shutter mechanism and shear bond strength of different manufacturing companies of self-ligating brackets. Methodology Teeth will be mounted on acrylic blocks of different colors and the self-ligating brackets will be bonded on them. These brackets will be debonded by using universal testing machine and the shear bond strength and opening and closing force of shutter will be measured. The debonded brackets will be rebonded after recycling by sandblasting and flaming and the SBS and shutter mechanism force will be measured again and then will be compared with above mentioned group. Expected results The force of closing and opening the shutter mechanism of different commercially available self-ligating brackets will increase. There will be a decrease in the shear bond strength of the different self-ligating brackets available on the market. Conclusion We will be able to determine the quality of commercially available brackets despite recycling by examining the force necessary for opening and closing the shutters of self-ligating brackets, as well as their shear bond strength to ensure that even after recycling, the brackets retain their mechanical integrity and bond strength.

In-orbit recalibration of Longwave Infrared Camera onboard Akatsuki

Akatsuki has been in operation since Venus orbit insertion-revenge 1 (VOI-R1) in December 2015 and has been making observations of Venus’ cloud-top temperature with Longwave Infrared Camera (LIR) since the start of nominal observations in April 2016. LIR was originally designed to maintain its performance for at least 4 years after the VOI originally planned in December 2010. Although the operation time of LIR has exceeded its designed lifetime as of August 2022, it is still functioning normally. The mechanical shutter plate has been kept at a normal temperature and used as a hot reference in determining the brightness temperature of objects when in the closed position. Since the observed temperature of the background deep space is merely a value representing the output for no radiation input, it should be the same in any observation. This was around 180 K just after the launch of Akatsuki in May 2010; however, it has gradually increased to approximately 200 K by February 2022. Average Venus disk temperatures also show a slight increasing trend. The increases of the background and Venus’ disk temperatures are most likely due to degradation of the sensitivity of the bolometer array used in LIR as an image sensor. These temperatures have apparently been increasing since LIR was activated in October 2016. While LIR is activated, the bolometer temperature is kept at 40 °C and a moderate baking effect may have accelerated degassing in the bolometer package, and the resulting increase of thermal conductivity or decrease of transmittance of the window contaminated by evaporated components may have degraded the sensitivity of the bolometer. A sensitivity degradation of 5% from October 2016 to February 2022 is estimated from the increasing trend of the background temperature. A correction has been made to the LIR data to keep the background temperature constant. The corrected data show no increasing trend in either the background or Venus’ disk temperature. The corrected data are open to the public as a more reliable dataset for investigating the long-term variability of thermal condition at cloud-top altitudes.Graphical

Performance assessment of an evacuated tube solar-electric hybrid dryer for lotus seeds drying: Moisture removal behavior, GHG emission and thermodynamic analysis

A novel evacuated tube solar-electric hybrid dryer (ETSED) was developed and evaluated to contribute to global food security from the perspective of optimized processing while reducing energy consumption and greenhouse gas (GHG) emissions. The performance of the ETSED was assessed compared with solar heating drying (SHD), and mixed heating drying (MHD) at temperatures of 55, 65 and 75 °C by studying the drying behavior of the samples as well as the thermodynamic analysis and GHG emissions of the system. Results revealed that under all studied experimental conditions, the evacuated tube solar collector provided more than 60% of the thermal supply in the drying process, and significantly improved the fluid exergy. Moreover, the roller shutter mechanism and the heating tube were used together to achieve precise control of the drying temperature. In terms of thermodynamic analysis, the heating tube further enhanced the ETSED performance by providing high quality energy in combination with solar energy in MHD mode. Furthermore, compared with SHD, MHD-65 and 75 °C shortened the drying time by 10.4 and 28.2%, improved the drying efficiency by 0.7% and 6.29%, and increased the drying chamber's exergy by 14.99 and 19.36%, respectively. Remarkably, the lowest emissions of CO2 (872.06 g/kg removed water), SO2 (0.13 g/kg removed water) and NOx (0.19 g/kg removed water) were seen in the case of SHD. Based on the obtained results, the increased drying temperature in the MHD led to higher CO2, SO2 and NOX emission levels. Interestingly, when the lotus seeds were dehydrated, the accumulated electric energy generated by the photovoltaic cells almost met the electric consumption of mechanical energy. The results of this study identified the potential of ETSED equipment for food industrial production.

Si-based mid-infrared photodetector with dynamic Schottky barrier height modulation applicable for synchronous detection

We have proposed an electrical shutter operation of a nano-antenna infrared photodetector using Schottky barrier height (SBH) modulation, where the SBH is modulated by a reverse bias voltage V b applied to the detector. The inhomogeneity of the Schottky junction may be dominant in the mechanism of barrier height reduction. Compared to the photocurrent i ph obtained by modulating the frequency of on–off of the incident light, the proposed method yields almost the same value. Therefore, it can be concluded that the proposed method is capable of synchronous detection measurement. In addition, since the proposed method does not require a mechanical shutter, it is a compact system that can be used in very small electrical equipment.

Micro-vibration Modeling and Verification of Shutter Mechanism of Survey Space Telescope

The scientific research mission of the Survey Space Telescope (also known as the China Space Station Telescope, CSST) imposes rigorous requirements on the observation precision. However, microvibrations generated by the shutter mechanism can seriously affect the performance of the highly precise and sensitive instruments onboard. This study presents a dynamic model and verifies its performance using experimental results. Indeed, a five-degree-of-freedom nonlinear dynamic model that considers all interference sources and bearing nonlinearity is established. The validity of the proposed model is verified using experimental measurements of the microvibration characteristics. The obtained results proved that the proposed dynamic model can accurately predict the characteristics of the microvibrations caused by the shutter mechanism in the design stage and provide a theoretical basis for the development of CSST.

High-Resolution UAV RGB Imagery Dataset for Precision Agriculture and 3D Photogrammetric Reconstruction Captured over a Pistachio Orchard (Pistacia vera L.) in Spain

A total of 248 UAV RGB images were taken in the summer of 2021 over a representative pistachio orchard in Spain (X: 341450.3, Y: 4589731.8; ETRS89/UTM zone 30N). It is a 2.03 ha plot, planted in 2016 with Pistacia vera L. cv. Kerman grafted on UCB rootstock, with a NE–SW orientation and a 7 × 6 m triangular planting pattern. The ground was kept free of any weeds that could affect image processing. The photos (provided in JPG format) were taken using a UAV DJI Phantom Advance quadcopter in two flight missions: one planned to take nadir images (β = 0°), and another to take oblique images (β = 30°), both at 55 metres above the ground. The aerial platform incorporates a DJI FC6310 RGB camera with a 20 megapixel sensor, a horizontal field of view of 84° and a mechanical shutter. In addition, GCPs (ground control points) were collected. Finally, a high-quality 3D photogrammetric reconstruction process was carried out to generate a 3D point cloud (provided in LAS, LAZ, OBJ and PLY formats), a DEM (digital elevation model) and an orthomosaic (both in TIF format). The interest in using remote sensing in precision agriculture is growing, but the availability of reliable, ready-to-work, downloadable datasets is limited. Therefore, this dataset could be useful for precision agriculture researchers interested in photogrammetric reconstruction who want to evaluate models for orthomosaic and 3D point cloud generation from UAV missions with changing flight parameters, such as camera angle.

A low-cost shutter driver and arbitrary waveform generator for optical switching using a programmable system-on-chip (PSoC) device.

We have developed a low-cost mechanical shutter driver with integrated arbitrary waveform generation for optical switching and control using a programmable system-on-chip device. This microcontroller-based device with configurable digital and analog blocks is readily programmed using free software, allowing for easy customization for a variety of applications. Additional digital and analog outputs with arbitrary timings can be used to control a variety of devices, such as additional shutters, acousto-optical modulators, or camera trigger pulses, for complete control and imaging of laser light. Utilizing logic-level control signals, this device can be readily integrated into existing computer control and data acquisition systems for expanded hardware capabilities.

Vapor–Liquid Transition‐Based Broadband Light Modulation for Self‐Adaptive Thermal Management

AbstractConsiderable research efforts have aimed to control indoor temperatures to improve daily life and industrial production. However, current strategies, which involve active regulation of energy input or passive regulation of sunlight transmission, cannot control indoor temperatures under all weather conditions. Herein, a self‐adaptive thermal management device (STMD) that uses solar energy (heating) and radiative cooling (cooling) by exploiting the temperature differences across the device is reported. The adaptive heating and cooling functions are achieved by modulating sunlight transmittance and reflectance using a porous SiO2 coating separated/merged with a refractive index‐matched liquid which serves as a shutter. As a result, the STMD in the opaque mode exhibits low transmittance and in the transparent mode exhibits sufficiently high solar transmittance. Taking advantage of this self‐regulated shuttering mechanism, the developed STMD enables i) an increase of ≈10 °C relative to the ambient temperature under a solar intensity of 400 W m−2 in cold weather and ii) a temperature reduction of ≈5 °C under a solar intensity exceeding 900 W m−2 in hot weather. The described design strategy offers an approach for constructing smart light‐controlling devices and thermal‐controlling building materials.