Unconventional Image‐Sensing and Light‐Emitting Devices for Extended Reality

Abstract

Extended reality (XR) refers to a space where physical and digital elements coexist and comprises three elements, namely, environment, human, and computer, which interact with each other. Image sensors and displays are the core elements of XR systems because visual information is important for recognizing and judging objects. Recently, new features of image sensors and displays that are useful for developing next‐generation XR systems have been reported. For example, a miniaturized version of image sensors with the superb object detection and recognition capability offers new opportunities for machine vision technology. Furthermore, transparent and deformable displays are the key components of XR systems because they not only provide highly realistic virtual image information but also serve as efficient user interfaces. Herein, the recent progresses in such unconventional image sensors and display technologies are reviewed. First, image sensors with features of wavelength‐selective photodetection for color discrimination, neuromorphic image acquisition for facile pattern recognition, and curved image sensor designs inspired by biological eyes for miniaturization and unconventional imaging performances are discussed. Then, light‐emitting device technologies focusing on devices with transparency and deformable form factors are described. Finally, the review is concluded with a brief summary and a future outlook.

Soft Bioelectronics Based on Nanomaterials

“…Optical sensors convert light into electrical signals, and their biomedical applications include photo­plethysmography (PPG) and retinal prosthesis (Figure E). − Recently, flexible and wearable PPG sensors have been actively studied due to their capability for continuous noninvasive monitoring of the blood pressure. − The PPG sensor optically monitors changes in the blood volume underneath the skin by measuring the amount of light absorbed or reflected by the blood vessel. , Red or near-infrared (IR) light has been known to feature deepest penetration into skin and thus is widely used for the light source of the transmissive PPG sensor. Green light cannot penetrate deeply, but shows the largest modulation of the reflected signals and a high signal-to-noise ratio even under movement artifacts, compared to red or near-IR light. , The pulse oximetry can also be performed using the PPG signals by irradiating multiple wavelength lights since the oxygen saturation level can be calculated by the optical absorption of hemoglobin.…”

Bio-Inspired Electronic Eyes and Synaptic Photodetectors for Mobile Artificial Vision

“…1(c)] [29]. Because conventional imaging devices are based on flat image sensors fabricated on rigid silicon wafers, optical aberrations should be caused by the mismatch between the flat image sensor and curved focal plane formed by a single lens [10]. To avoid such optical aberrations, multilens optical systems (e.g., double Gauss lens) are required.…”

Integration of synaptic phototransistors and quantum dot light-emitting diodes for visualization and recognition of UV patterns

“…However, because of the high noise level of the original UV image data, the residual background noise often remains even after the conventional in-sensor preprocessing step. Therefore, a novel UV imaging system is demanded to achieve high-accuracy image recognition with minimum image filtering during the backend processing step (39)(40)(41). Besides, visualization strategies of the preprocessed UV images for human vision are required.…”