We propose a volumetric display based on holographic parallel optical access and two-photon excitation using a computer-generated hologram displayed on a liquid crystal spatial light modulator and a multilayer fluorescent screen. The holographic parallel optical access increased the number of voxels of the volumetric image per unit time. This approach increased the total input energy to the volumetric display, that is, the total fluorescence power, because the maximum energy incident at a point in the multilayer fluorescent screen is limited by the damage threshold. The multilayer fluorescent screen was newly developed to display colored voxels. The thin layer construction of the multilayer fluorescent screen minimized the axial length of the voxels. A volumetric display with only blue-green voxels and a volumetric display with both blue-green and red voxels were demonstrated.

We present a method of rendering aerial and volumetric graphics using femtosecond lasers. A high-intensity laser excites physical matter to emit light at an arbitrary three-dimensional position. Popular applications can thus be explored, especially because plasma induced by a femtosecond laser is less harmful than that generated by a nanosecond laser. There are two methods of rendering graphics with a femtosecond laser in air: producing holograms using spatial light modulation technology and scanning of a laser beam by a galvano mirror. The holograms and workspace of the system proposed here occupy a volume of up to 1 cm 3 ; however, this size is scalable depending on the optical devices and their setup. This article provides details of the principles, system setup, and experimental evaluation, and discusses the scalability, design space, and applications of this system. We tested two laser sources: an adjustable (30--100fs) laser that projects up to 1,000 pulses/s at an energy of up to 7mJ/pulse and a 269fs laser that projects up to 200,000 pulses/s at an energy of up to 50μJ/pulse. We confirmed that the spatiotemporal resolution of volumetric displays implemented using these laser sources is 4,000 and 200,000 dots/s, respectively. Although we focus on laser-induced plasma in air, the discussion presented here is also applicable to other rendering principles such as fluorescence and microbubbles in solid or liquid materials.

Background Evidence exists on the clinical efficacy and safety of periodontally accelerated osteogenic orthodontics (PAOO) with “Piezocision”—a minimally invasive, flapless alternative to corticotomy for alveolar bone augmentation. Allograft has been extensively studied for alveolar bone augmentation in Piezocision; however, the use of deproteinized bovine bone mineral with 10% collagen (DBBM‐C) in Piezocision for PAOO has not been investigated. Methods This study is a prospective, observational, cohort study of 19 patients of Angle Class I malocclusion with a total of 692 teeth assessed for maintenance of health of the periodontal attachment apparatus. Patient‐centered pain, sensitivity, and satisfaction outcomes, digital photographs and radiographs, and changes in probing depth, clinical attachment level, width of keratinized tissue, percussion sensitivity, pulp vitality tests, radiographic pathology, and root‐crown‐ratio were all recorded. Results Overall treatment was significantly faster (5 to 7 days between clear aligner tray changes), periodontal parameters remained stable, and alveolar bone loss was not observed. Visual analog score for healing, sensitivity/duration, bleeding/duration, swelling/duration, appearance, and inflammation, demonstrated no significant differences between DBBM‐C and control (no bone graft) groups. Patient‐centered outcomes revealed high levels of satisfaction with Piezocision. Piezocision‐treated teeth with DBBM‐C tended to exhibit less root resorption, although it was not statistically significant (P = 0.074). Conclusions Within the limits of the study, our results show that the use of DBBM‐C with piezosurgically enhanced orthodontics is effective and safe. This study was not designed to demonstrate equivalence with other materials that might be used in Piezocision. To understand whether there is an advantage to using DBBM‐C, additional studies may be required.

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A volumetric display generates a graphics that can be viewed from 360$$^{\circ }$$ ∘ by representing the 3D information of an object as voxels in physical space. However, the natural properties of physical objects, such as 3D information and colors, and the seamless relationships between graphics and humans make it difficult to implement such displays. Here, we introduce a novel system that combines the spatial generation of femtosecond-laser-excited emission points using computer-generated holograms and beam scanning with the drawing space separation method. We demonstrate the drawing of volumetric graphics that can be color-expressed in voxel units in the air. This system enables the drawing of volumetric graphics in the air, accurate color representations, and robust graphics that are not destroyed by contact with users or objects. It also lays the foundation for the implementation of future volumetric displays.