Freeform Optics

A special issue of Photonics (ISSN 2304-6732).

Deadline for manuscript submissions: closed (20 October 2022) | Viewed by 13487

Special Issue Editors


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Guest Editor
School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Interests: freeform optics design; optical system development; astronomical optics; computational imaging
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Guest Editor
Institute of Applied Physics, Friedrich-Schiller University Jena, 07745 Jena, Germany
Interests: lens design; general simulation of optical systems

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Guest Editor
College of Intelligence Science and Technology, National University of Defense Technology, Changsha 410073, China
Interests: optical testing; ultra-precision machining and measurement

Special Issue Information

Dear Colleagues,

Freeform optics is an emerging technology that brings an evolutionary development for both imaging and non-imaging optics.

New fabrication techniques can fabricate optical surfaces with no axis of rotational symmetry, which open an expansive new space for optical systems. Particularly enabled systems include illumination systems, head-worn displays, mid- and long-wave pervasive surveillance systems, extreme ultraviolet lithography, solar concentrators, space optics, mobile displays, manufacturing, remote sensing, and medical and biosensing technologies.

However, the technology requires expertise in bringing together cross-disciplinary fields of design, simulation, fabrication, testing, and assembly into one process. Concurrent freeform optics technologies are still facing many issues, such as new representations of freeform surfaces, metrology of MSF errors for freeform surfaces, design methods for all-reflective multi-mirror unobscured freeform systems, the application of freeform optics in spectrometers,  new freeform optics manufacturing technologies, additive manufacturing technologies of freeform optics, Alvarez-like lenses, molding technologies of freeform optics, and novel metrology methods of freeform optics to reduce cost.

This feature issue will highlight significant contributions in both academia and industry with regards to the evolution of freeform optical systems in design, fabrication, metrology, and novel applications, as well as artificial intelligence and machine learning techniques.

Prof. Dr. Donglin Ma
Prof. Dr. Herbert Gross
Prof. Dr. Shanyong Chen
Guest Editors

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Keywords

  • freeform optical design
  • freeform optical system simulation
  • freeform surface representations
  • manufacturing of freeform optics
  • tolerancing of freeform optics
  • mid-spatial frequency mitigation, removal, and tolerancing
  • freeform surface testing
  • assembly techniques of freeform optical systems
  • machine learning techniques for optical design, fabrication, assembly, and optical metrology of freeform optics
  • applications of freeform optics

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Published Papers (5 papers)

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17 pages, 13835 KiB  
Article
Optical Design of an LCoS-Based 1 × 10 WSS with High Coupling Efficiency and Compact Light Paths
by Huiru Ji, Yuefan Shan, Yan Mo, Zhihao Chen and Donglin Ma
Photonics 2023, 10(10), 1107; https://doi.org/10.3390/photonics10101107 - 30 Sep 2023
Cited by 4 | Viewed by 2257
Abstract
In the field of communication, the utilization of Liquid Crystal On Silicon (LCoS) in Wavelength Selective Switch (WSS) systems holds great promise. However, the lack of research on the optical path design of LCoS-based WSS makes it challenging to realize high-port-count and perfect [...] Read more.
In the field of communication, the utilization of Liquid Crystal On Silicon (LCoS) in Wavelength Selective Switch (WSS) systems holds great promise. However, the lack of research on the optical path design of LCoS-based WSS makes it challenging to realize high-port-count and perfect performance with a compact structure. In this paper, the conceptual optical path design method of a compact LCoS-based 1 × 10 WSS system working in C-band (1529 nm–1568 nm) is proposed, where there exists 1 input port and 10 output ports in the same array. The optical powers in both the wavelength and deflection directions have been meticulously considered separately, while the polarization-independent structure has been designed novelty, which boost system compactness and lowers manufacturing costs. Finally, a high fiber-to-fiber coupling efficiency of an idealized system ranging from 95.07 to 99.18% with only five components is achieved. Furthermore, a brief tolerance analysis to demonstrate the instrumentation feasibility is also conducted and the additional losses that will be introduced by real experiments are discussed. Our work is pioneering in providing a more straightforward methodology and conceptual model for WSS system design and offering reference significant for high-port-count systems. Full article
(This article belongs to the Special Issue Freeform Optics)
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14 pages, 3429 KiB  
Article
Desensitization Design Method for Freeform TMA Optical Systems Based on Initial Structure Screening
by Zichang Qin, Yunsheng Qi, Chengming Ren, Xiaodong Wang and Qingyu Meng
Photonics 2022, 9(8), 544; https://doi.org/10.3390/photonics9080544 - 3 Aug 2022
Cited by 11 | Viewed by 2255
Abstract
Achieving aberration correction can improve the imaging quality of an optical system, and reducing the error sensitivity of system can improve the realizability of the system. In order to obtain an off-axis three-mirror optical system with high image quality and low error sensitivity, [...] Read more.
Achieving aberration correction can improve the imaging quality of an optical system, and reducing the error sensitivity of system can improve the realizability of the system. In order to obtain an off-axis three-mirror optical system with high image quality and low error sensitivity, a design method is proposed which obtains the initial structure of the three-mirror anastigmatic (TMA) optical system with low error sensitivity through a nondominated sorting genetic algorithm II (NSGA-II). Combining the comprehensive evaluation function of image quality and error sensitivity, this method iteratively selects multiple freeform surface types to determine the combination with the lowest error sensitivity and obtains the freeform TMA optical system with optimal overall performance. A freeform TMA optical system is designed by the method proposed in this paper, and the error sensitivity of the optical system is analyzed. The results show that the image quality of the freeform optical system is effectively improved and the error sensitivity is effectively reduced with the same error applied, which verifies the correctness and practicality of the method. Full article
(This article belongs to the Special Issue Freeform Optics)
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11 pages, 1894 KiB  
Article
Design Method of Freeform Off-Axis Multi-Mirror Optical Systems
by Xinyu Liu and Jun Zhu
Photonics 2022, 9(8), 534; https://doi.org/10.3390/photonics9080534 - 30 Jul 2022
Cited by 4 | Viewed by 2347
Abstract
A data point calculation method that does not require the use of Fermat′s principle and a simple and general design method of starting points of freeform off-axis multi-mirror optical systems are proposed in this paper, which aim to promote the realization of high-performance [...] Read more.
A data point calculation method that does not require the use of Fermat′s principle and a simple and general design method of starting points of freeform off-axis multi-mirror optical systems are proposed in this paper, which aim to promote the realization of high-performance reflective systems containing freeform surfaces. Taking a planar system and the required parameters as the input, a good starting point for a freeform off-axis multi-mirror system can be automatically obtained using the proposed method. The design of a freeform off-axis five-mirror system with a low F-number is taken as an example to show the effectiveness of the proposed method. The method can also be used for the design of freeform reflective systems with other numbers of mirrors. Full article
(This article belongs to the Special Issue Freeform Optics)
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14 pages, 3590 KiB  
Article
Spatial Three-Mirror Off-Axis Freeform Optical System without Any Symmetry
by Yilin Tan and Jun Zhu
Photonics 2022, 9(5), 326; https://doi.org/10.3390/photonics9050326 - 9 May 2022
Cited by 6 | Viewed by 2866
Abstract
In this manuscript, we have launched a study on the completely nonsymmetric freeform optical system with neither rotational symmetry nor planar symmetry. An off-axis three-mirror freeform optical system with nonsymmetric geometry is proposed and a direct design method is developed for the nonsymmetric [...] Read more.
In this manuscript, we have launched a study on the completely nonsymmetric freeform optical system with neither rotational symmetry nor planar symmetry. An off-axis three-mirror freeform optical system with nonsymmetric geometry is proposed and a direct design method is developed for the nonsymmetric freeform optical system. The design field points are sampled across the full FOV to control the imaging quality and object–image relationship. In this system, the center of the image plane is greatly away from the plane determined by the centers of the three mirrors. This nonsymmetric system with F/1.3, a focal length of 50 mm, and an 8° × 6° field of view can achieve imaging quality close to the diffraction limit. This work provides a feasible nonsymmetric system design idea for the optical community. Full article
(This article belongs to the Special Issue Freeform Optics)
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11 pages, 3991 KiB  
Opinion
Design of a Multi-Channel High-Power Color-Mixing Optical System Based on RGB LED Arrays
by Yvang Chen, Yuncui Zhang, Xufen Xie, Long Liu, Minjv Fan, Changcheng Sun, Yan Wang and Shuhan Yan
Photonics 2022, 9(12), 904; https://doi.org/10.3390/photonics9120904 - 26 Nov 2022
Cited by 2 | Viewed by 2013
Abstract
This paper presents a design method for a high-power optical system with multiple channels to achieve high-quality color-mixing and uniform lighting. The high-power optical system consists of a multi-channel reflector and a color-mixing component. The optical systems with different parameters are simulated to [...] Read more.
This paper presents a design method for a high-power optical system with multiple channels to achieve high-quality color-mixing and uniform lighting. The high-power optical system consists of a multi-channel reflector and a color-mixing component. The optical systems with different parameters are simulated to analyze the color-mixing performance. Simulation results show that the illumination uniformity of all optical systems is greater than 0.77, and the maximum color difference is 0.014. This optical system can be introduced into applications, such as illumination of machine vision, simulating daylight, smart lighting, and so on. Full article
(This article belongs to the Special Issue Freeform Optics)
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