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14 pages, 5787 KiB

Open AccessArticle

by Liming Geng, Guohua Cao, Chunmin Shang and Hongchang Ding

Sensors 2024, 24(5), 1400; https://doi.org/10.3390/s24051400 - 22 Feb 2024

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With the application of encoders in artificial intelligence and aerospace, the demand for the miniaturization and high measurement accuracy of encoders is increasing. To solve this problem, a new absolute matrix encoder is proposed in this paper, which can realize 19-bit matrix coding [...] Read more.

With the application of encoders in artificial intelligence and aerospace, the demand for the miniaturization and high measurement accuracy of encoders is increasing. To solve this problem, a new absolute matrix encoder is proposed in this paper, which can realize 19-bit matrix coding by engraving two circles of matrix code, and has the advantages of fewer circles of code disk engraving and higher measurement accuracy. This article mainly focuses on the design of a new matrix code disk, encoding and decoding methods, decoding circuit design, Matlab simulation analysis, and experimental error analysis. The experimental results show that the encoder designed in this paper achieves ultra-small volume Φ30 mm × 20 mm, and the angle measurement accuracy is 2.57”. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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14 pages, 5047 KiB

Open AccessArticle

Optimization of Thermal Control Design for Aerial Reflective Opto-Mechanical Structure

by Huilin Wang, Yun Zhou, Xiaocun Jiang, Xiaozhou Zuo and Ming Chen

Sensors 2024, 24(4), 1194; https://doi.org/10.3390/s24041194 - 12 Feb 2024

Viewed by 525

Abstract

To improve the adaptability of aerial reflective opto-mechanical structures (mainly including the primary mirror and secondary mirror) to low-temperature environments, typically below −40 °C, an optimized thermal control design, which includes passive insulation and temperature-negative feedback-variable power zone active heating, is proposed. Firstly, [...] Read more.

To improve the adaptability of aerial reflective opto-mechanical structures (mainly including the primary mirror and secondary mirror) to low-temperature environments, typically below −40 °C, an optimized thermal control design, which includes passive insulation and temperature-negative feedback-variable power zone active heating, is proposed. Firstly, the relationship between conventional heating methods and the axial/radial temperature differences of mirrors with different shapes is analyzed. Based on the heat transfer analyses, it is pointed out that optimized thermal control design is necessary to ensure the temperature uniformity of the fused silica mirror, taking into account the temperature level when the aerial electro-optics system is working in low-temperature environments. By adjusting the input voltage based on the measured temperature, the heating power of the subregion is changed accordingly, so as to locally increase or decrease the temperature of the mirrors. The thermal control scheme ensures that the average temperature of the mirror fluctuates slowly and slightly around 20 °C. At the same time, the temperature differences within a mirror and between the primary mirror and the secondary mirror can be controlled within 5 °C. Thereby, the resolution of EO decreases by no more than 11.4%. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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13 pages, 18121 KiB

Open AccessArticle

Demonstration of a Transportable Fabry–Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes

by Clayton Forssén, Isak Silander, Johan Zakrisson, Eynas Amer, David Szabo, Thomas Bock, André Kussike, Tom Rubin, Domenico Mari, Stefano Pasqualin, Zaccaria Silvestri, Djilali Bentouati, Ove Axner and Martin Zelan

Sensors 2024, 24(1), 7; https://doi.org/10.3390/s24010007 - 19 Dec 2023

Viewed by 589

Abstract

Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology [...] Read more.

Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10–90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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19 pages, 21258 KiB

Open AccessArticle

Research on the Design and Alignment Method of the Optic-Mechanical System of an Ultra-Compact Fully Freeform Space Camera

by Yunfeng Li, Zongxuan Li, Tiancong Wang, Shuping Tao, Defu Zhang, Shuhui Ren, Bin Ma and Changhao Zhang

Sensors 2023, 23(23), 9399; https://doi.org/10.3390/s23239399 - 25 Nov 2023

Viewed by 794

Abstract

As space resources become increasingly constrained, the major space-faring nations are establishing large space target monitoring systems. There is a demand for both the number and the detection capability of space-based optical monitoring equipment. The detection range (i.e., field of view) and parasitic [...] Read more.

As space resources become increasingly constrained, the major space-faring nations are establishing large space target monitoring systems. There is a demand for both the number and the detection capability of space-based optical monitoring equipment. The detection range (i.e., field of view) and parasitic capability (lightweight and small size) of a single optical payload will largely reduce the scale and cost of the monitoring system. Therefore, in this paper, the optic-mechanical system of an ultra-lightweight and ultra-compact space camera and the optical alignment method are investigated around a fully freeform off-axis triple-reversal large field of view (FOV) optical system. The optic-mechanical system optimisation design is completed by adopting the optic-mechanical integration analysis method, and the weight of the whole camera is less than 10 kg. In addition, to address the mounting problems caused by the special characteristics of the freeform surface optical system, a dual CGH coreference alignment method is innovatively proposed. The feasibility of the method is verified by the mounting and testing test, and the test results show that the system wavefront difference is better than 1/10 λ. The imaging test of the space camera and the magnitude test results meet the design requirements of the optical system. The optic-mechanical system design method and alignment method proposed in this paper are instructive for the design and engineering of large field of view full freeform optical loads. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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16 pages, 6827 KiB

Open AccessArticle

Dynamic Characterization of Optical Coherence-Based Displacement-Type Weight Sensor

by Zhengchuang Lai, Zhongjie Ouyang, Shuncong Zhong, Wei Liang, Xiaoxiang Yang, Jiewen Lin, Qiukun Zhang and Jinlin Li

Sensors 2023, 23(21), 8911; https://doi.org/10.3390/s23218911 - 02 Nov 2023

Viewed by 788

Abstract

Dynamic characteristics play a crucial role in evaluating the performance of weight sensors and are essential for achieving fast and accurate weight measurements. This study focuses on a weight sensor based on optical coherence displacement. Using finite element analysis, the sensor was numerically [...] Read more.

Dynamic characteristics play a crucial role in evaluating the performance of weight sensors and are essential for achieving fast and accurate weight measurements. This study focuses on a weight sensor based on optical coherence displacement. Using finite element analysis, the sensor was numerically simulated. Frequency domain and time domain dynamic response characteristics were explored through harmonic response analysis and transient dynamic analysis. The superior dynamic performance and reduced conditioning time of the non-contact optical coherence-based displacement weight sensor were confirmed via a negative step response experiment that compared the proposed sensing method to strain sensing. Moreover, dynamic performance metrics for the optical coherence displacement-type weight sensor were determined. Ultimately, the sensor’s dynamic performance was enhanced using the pole-zero placement method, decreasing the overshoot to 4.72% and reducing the response time to 0.0132 s. These enhancements broaden the sensor’s operational bandwidth and amplify its dynamic response capabilities. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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12 pages, 3987 KiB

Open AccessArticle

The Design and Fabrication of Large-Area Under-Screen Fingerprint Sensors with Optimized Aperture and Microlens Structures

by Chih-Chieh Yeh, Teng-Wei Huang, You-Ren Lin and Guo-Dung Su

Sensors 2023, 23(21), 8731; https://doi.org/10.3390/s23218731 - 26 Oct 2023

Cited by 1 | Viewed by 910

Abstract

In this paper, we designed and fabricated an optical filter structure applied to the FoD (Fingerprint on Display) technology of the smartphone, which contains the microlens array, black matrix, and photodetector to recognize the fingerprint on a full touchscreen. First, we used optical [...] Read more.

In this paper, we designed and fabricated an optical filter structure applied to the FoD (Fingerprint on Display) technology of the smartphone, which contains the microlens array, black matrix, and photodetector to recognize the fingerprint on a full touchscreen. First, we used optical ray tracing software, ZEMAX, to simulate a smartphone with FoD and a touching finger. We then further discussed how the aperture and microlens influence the fingerprint image in this design. Through numerical analysis and process constraint adjustment to optimize the structural design, we determined that a modulation transfer function (MTF) of 60.8% can be obtained when the thickness of the black matrix is 4 μm, allowing successful manufacturing using photolithography process technology. Finally, we used this filter element to take fingerprint images. After image processing, a clearly visible fingerprint pattern was successfully captured. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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17 pages, 2527 KiB

Open AccessArticle

Nonlinearities in Fringe-Counting Compact Michelson Interferometers

by Jiri Smetana, Chiara Di Fronzo, Anthony Amorosi and Denis Martynov

Sensors 2023, 23(17), 7526; https://doi.org/10.3390/s23177526 - 30 Aug 2023

Cited by 1 | Viewed by 769

Abstract

Compact Michelson interferometers are well positioned to replace existing displacement sensors in the readout of seismometers and suspension systems, such as those used in contemporary gravitational-wave detectors. Here, we continue our previous investigation of a customised compact displacement sensor built by SmarAct that [...] Read more.

Compact Michelson interferometers are well positioned to replace existing displacement sensors in the readout of seismometers and suspension systems, such as those used in contemporary gravitational-wave detectors. Here, we continue our previous investigation of a customised compact displacement sensor built by SmarAct that operates on the principle of deep frequency modulation. The focus of this paper is the linearity of this device and its subsequent impact on sensitivity. We show the three primary sources of nonlinearity that arise in the sensor: residual ellipticity, intrinsic distortion of the Lissajous figure, and distortion caused by exceeding the velocity limit imposed by the demodulation algorithm. We verify the theoretical models through an experimental demonstration, where we show the detrimental impact that these nonlinear effects have on device sensitivity. Finally, we simulate the effect that these nonlinearities are likely to have if implemented in the readout of the Advanced LIGO suspensions and show that the noise from nonlinearities should not dominate across the key sub-10 Hz frequency band. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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14 pages, 6540 KiB

Open AccessArticle

Reconfiguration Error Correction Model for an FBG Shape Sensor Based on the Sparrow Search Algorithm

by Qiufeng Shang and Feng Liu

Sensors 2023, 23(16), 7052; https://doi.org/10.3390/s23167052 - 09 Aug 2023

Viewed by 807

Abstract

A reconfiguration error correction model for an FBG shape sensor (FSS) is proposed. The model includes curvature, bending direction error correction, and the self-correction of the FBG placement angle and calibration error based on an improved sparrow search algorithm (SSA). SSA could automatically [...] Read more.

A reconfiguration error correction model for an FBG shape sensor (FSS) is proposed. The model includes curvature, bending direction error correction, and the self-correction of the FBG placement angle and calibration error based on an improved sparrow search algorithm (SSA). SSA could automatically correct the placement angle and calibration direction of the FBG, and then use the corrected placement angle and calibration direction to correct the curvature and bending direction of the FSS, thereby improving the accuracy of shape reconfiguration. After error correction, the tail point reconfiguration errors of different shapes were reduced from 2.56% and 4.96% to 1.12% and 2.45%, respectively. This paper provides a new reconfiguration error correction method for FSS that does not require a complicated experimental calibration process, is simpler, more efficient, and more operable than traditional methods, and has great potential in FSS application scenarios. Full article

(This article belongs to the Special Issue Advanced Optical and Optomechanical Sensors)

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