Dr. Guan Chen Profile

Dr. Guan Chen

at Qilu Univ of Technology

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Publications (4)

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Proceedings Article | 24 November 2023 Paper

Design of a compact single-photon LiDAR optical system for aerosol detection

Guan Chen, Xiaofei Wang, Xiaolei Zhang, Dongjie Ju, Haobo Li, Hua Fan

Proceedings Volume 12935, 1293549 (2023) https://doi.org/10.1117/12.3007954

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A compact single-photon detection LiDAR optical system for aerosol detection with the bistatic and off-axis structure has been designed. This design overcomes the signal crosstalk associated with the transceiver optical system. The working wavelength of the telescope optical system is 1.55 μm. The transmitting telescope optical system has a clear aperture of 74 mm, an effective focal length of 17.780 mm, an object space NA of 0.09. Besides, its wavefront aberration RMS is 0.0000λ (λ=632.8 nm) which indicates that the light becomes nearly collimated after passing through the transmitting telescope optical system. The receiving telescope optical system has a clear aperture of 100 mm, an effective focal length of 271.106 mm, and an image space NA of 0.1814. Its root mean square radii are close to the diffraction limit, indicating minimal optical system aberrations and excellent imaging performance. Based on the design result, a prototype LiDAR system was constructed, and experiments have verified that the system can detect aerosols at distances of up to 7 km with signal-to-noise ratios of the echo photons greater than 1:1. The system exhibited stable and reliable operation.

Proceedings Article | 24 November 2023 Paper

Autofocus optical imaging system based on image processing

Teng Teng, Chen Guan, Xiaofei Wang, Hua Fan, Dongjie Ju, Zhaojuan Chi

Proceedings Volume 12935, 1293531 (2023) https://doi.org/10.1117/12.3007706

KEYWORDS: Image sharpness, Image processing, Imaging systems, Image analysis, Image filtering, Gaussian filters, Cameras, Image enhancement, Tunable filters, Sensors

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Autofocus optical imaging systems are widely used in industrial inspection, medical diagnosis, drone photography, machine vision and other fields. Image-based autofocus algorithms typically consist of two key steps: image sharpness evaluation and search strategy. In this study, we propose an advanced image-based autofocus algorithm specifically designed for industrial image measurement. In order to improve the accuracy of the clarity assessment, we improve the existing method by introducing Gaussian filtering and threshold controlled Laplace operators. This improvement effectively reduces the effects of noise and light intensity changes, improving the reliability of clarity measurements. In addition, we propose a novel distance adjustment strategy combining coarse and fine tuning as part of the search strategy. This strategy reduces the interference of local peaks, allowing the algorithm to accurately identify the best image focus. The proposed image-based autofocus algorithm has several advantages, e.g. high focusing accuracy, high repeatability, and stability under light intensity changes. These advantages make it ideal for industrial image measurement applications. To verify the effectiveness of our method, we build an experiment setup in a lab using ADLINK PCI-9114-DG board and a custom-designed lens. The results show that the sensitivity and performance of the autofocus system meet certain requirements. In summary, the image-based autofocus algorithm that we developed enables accurate and reliable focusing. It overcomes some challenges such as noise and light intensity changes to ensures optimal image focus, and improves overall image quality. The successful implementation of our autofocus system can benefit industrial inspection, medical diagnostics and many other applications.

Proceedings Article | 6 November 2023 Paper

Accuracy improvement of optical 3D measurement sensor with optics method

Xiaofei Wang, Hua Fan, Xiaolei Zhang, Chen Guan, Teng Teng, Dongjie Ju, Haobo Li

Proceedings Volume 12921, 1292127 (2023) https://doi.org/10.1117/12.2689307

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Laser based 3D measurement sensor are widely used in industrial applications because of its advantage of robust and easy to be employed. However higher measurement accuracy and faster speed are always demanded by more precise and faster fabrication process. This presentation will address this point with optics method. Laser based 3D measurement sensor consists of laser line projector, imaging optics and image process unit with algorithms. This presentation will show an customized imaging optics which based on Scheimpflug principle. It can tilt the focal plane to cover the height measurement range. With this method it can be assured that every image is in focus, and it helps to improve the measurement accuracy.

Proceedings Article | 16 December 2022 Presentation + Paper

Design of an adjustable working distance Bessel lens for femtosecond laser cutting

Chen Guan, Xiaolei Zhang, Xiaofei Wang, Hua Fan

Proceedings Volume 12312, 123120B (2022) https://doi.org/10.1117/12.2642139

KEYWORDS: Bessel beams, Axicons, Laser cutting, Gaussian beams

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An adjustable working distance Bessel lens for high-precision femtosecond laser cutting is designed. The system is composed of an axicon and a bi-telecentric optical system. By adjusting the distance between the axicon and the bitelecentric optical system, a zero-order Bessel beam with continuously adjustable working distance within a certain range can be obtained. Compared with the traditional Gaussian beam, when the central core diameter of the Bessel beam and the beam width of the Gaussian beam are the same, the non-diffracting propagation distance of the Bessel beam is much larger than the Rayleigh length of the Gaussian beam. The focusing accuracy can be effectively reduced, and a larger processing dynamic range can be achieved in laser processing. Ultra-short pulse Bessel beam generated by this method in laser cutting has longer laser focal field length and smaller light field axial intensity distribution gradient, which can provide a high-quality light source for laser cutting. In this paper, the spatial intensity distribution of Bessel beam is simulated by MatLab software. The simulation results show that, by the incidence of a femtosecond pulsed Gaussian beam whose central wavelength is 1030 nm with a certain diameter on the Bessel lens, a Bessel beam with a central core diameter of 6.7 μm, a non-diffracting propagation distance of 3.40 mm, and a continuously variable working distance from 18 mm to 21 mm can be obtained.

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