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Ding YQ, Luo ZY, Borjigin G et al. Breaking the optical efficiency limit of virtual reality with a nonreciprocal polarization rotator. Opto-Electron Adv 7, 230178 (2024). doi: 10.29026/oea.2024.230178
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Breaking the optical efficiency limit of virtual reality with a nonreciprocal polarization rotator
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Abstract
A catadioptric lens structure, also known as pancake lens, has been widely used in virtual reality (VR) displays to reduce the formfactor. However, the utilization of a half mirror (HM) to fold the optical path thrice leads to a significant optical loss. The theoretical maximum optical efficiency is merely 25%. To transcend this optical efficiency constraint while retaining the foldable characteristic inherent to traditional pancake optics, in this paper, we propose a theoretically lossless folded optical system to replace the HM with a nonreciprocal polarization rotator. In our feasibility demonstration experiment, we used a commercial Faraday rotator (FR) and reflective polarizers to replace the lossy HM. The theoretically predicted 100% efficiency can be achieved approximately by using two high-extinction-ratio reflective polarizers. In addition, we evaluated the ghost images using a micro-OLED panel in our imaging system. Indeed, the ghost images can be suppressed to undetectable level if the optics are with antireflection coating. Our novel pancake optical system holds great potential for revolutionizing next-generation VR displays with lightweight, compact formfactor, and low power consumption. -
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References
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Ding YQ, Luo ZY, Borjigin G et al. Breaking the optical efficiency limit of virtual reality with a nonreciprocal polarization rotator. Opto-Electron Adv 7, 230178 (2024). doi: 10.29026/oea.2024.230178
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Figure 1.
Concept of pancake optics systems. (a) Device configuration and (b) operation mechanism of conventional pancake optics system. (c) Configuration and (d) operation mechanism of double path pancake optics system. LCP, RCP, and LP represent left-handed circular polarization, right-handed circular polarization, and linear polarization.
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Figure 2.
Schematic of reciprocal and nonreciprocal polarization rotators. Polarization rotation in (a) a reciprocal polarization rotator during forward propagation and (b) backward propagation. Polarization rotation in (c) a nonreciprocal polarization rotator through forward propagation and (d) backward propagation.
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Figure 3.
Working principle of the proposed novel pancake optics system. (a) Polarization conversion process in the proposed novel pancake optic system with a FR. (b) A possible configuration of the proposed novel pancake optics. (c) Polarization conversion process in the proposed novel pancake optic system without a FR.
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Figure 4.
Experiments using a laser source. The folded beams in pancake optics system (a) without FR, (b) with FR.
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Figure 5.
Characterization of the FR in the novel pancake optics system. (a) Transmission spectrum of the FR. (b) Measurement setup for characterizing polarization rotation. LP stands for linear polarizer. (c) Measured and calculated normalized transmission spectra (zero means perfect polarization rotation) of the FR.
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Figure 6.
Experiments using a micro-OLED panel. (a) Original image. (b) 0th order folded image and (c) 1st order image in the pancake system without a FR. (d) 1st order image in the pancake system with a FR operating in 510-550 nm. (e) Original image. (f) 0th order folded image and (g) 1st order image in the pancake system without a FR. (h) 1st order image in the pancake system with a FR operating in 603–663 nm.
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Figure 7.
Mechanism of ghost images in the novel pancake optics system. (a) Light path of ghost images generated by the transmission of the RPs in block state. (b) Ghost images (c) and suppressed ghost images by an extra linear polarizer captured at its own focal plane. (d) Light path of ghost images caused by surface reflection of FR. (e) Light path of ghost images produced from imperfect polarization rotation in FR. (f) Light path of ghost images induced by panel reflection and reflection of the RPs in transmission state.
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Figure 8.
Achieving broadband FR. (a) 1st order white image in the pancake system with a FR operating in 510-550 nm. (b) Broadband FR design of sequences of FRs and QWPs. (c) Spectrum of polarization rotation ability using a single piece FR, two sequences of FRs and QWPs and three sequences of FRs and QWPs.
