Full-Color See-Through Three-Dimensional Display Method Based on Volume Holography

We propose a full-color see-through three-dimensional (3D) display method based on volume holography. This method is based on real object interference, avoiding the device limitation of spatial light modulator (SLM). The volume holography has a slim and compact structure, which realizes 3D display through one single layer of photopolymer. We analyzed the recording mechanism of volume holographic gratings, diffraction characteristics, and influencing factors of refractive index modulation through Kogelnik’s coupled-wave theory and the monomer diffusion model of photopolymer. We built a multiplexing full-color reflective volume holographic recording optical system and conducted simultaneous exposure experiment. Under the illumination of white light, full-color 3D image can be reconstructed. Experimental results show that the average diffraction efficiency is about 53%, and the grating fringe pitch is less than 0.3 μm. The reconstructed image of volume holography has high diffraction efficiency, high resolution, strong stereo perception, and large observing angle, which provides a technical reference for augmented reality

Effects of Blood-cooling and Stasis-removing Formula on Hemorheology in Rats with Acute Blood Stasis

Objective: To investigate the effects of blood-cooling and stasis-removing formula on hemorheology in rats with acute blood stasis induced by mutifactor stimuli. Methods: The selected SD rats orally took blood-cooling and stasis-removing granule for six days, then the model of acute blood stasis was prepared on the fifth day by injection of epinephrine combined with ice-water bath. The variations of blood-cooling and stasis-removing granule on hemorheology were detected. Results: The high-dose group of blood-cooling and stasis-removing formula can decrease plasma viscosity in rats with acute blood stasis, and obviously reduce the blood viscosity under the condition of shear rates (200s-1, 30s-1, 5s-1, 1s-1) (P < 0.01, P < 0.05). The middle-dose group can decrease the blood viscosity under the condition of shear rate (30s-1) (P < 0.05). Conclusion: Blood-cooling and stasis-removing formula can improve abnormal hemorheology in rats with acute blood stasis

Correction: Wu et al. Full-Color See-Through Three-Dimensional Display Method Based on Volume Holography. Sensors 2021, 21, 2698

The authors make the following corrections to the published paper [...

Crosstalk-Reduced Double-Layer Half-Divided Volume Holographic Concentrator for Solar Energy Concentration

A new double-layer sunlight concentration system, where each layer is divided into two regions, is proposed, and the system has four volume holograms. Since the four holograms convert light in different directions, the interlayer crosstalk is reduced, and the system has a high concentration ratio. The simulation results show that the concentration system can achieve a 30° operation angle range. The holograms are fabricated on photopolymer substrates, and the left half of the system is implemented using two holograms. The characteristics of the left half of the system are assessed. The agreement of the simulation and experimental results on diffraction efficiency validates the proposed method. The tested monochromatic concentration ratio can achieve a record of 418.8, and the concentration ratio under sunlight is 5.38. The experiment results of light use efficiency are close to the simulation with non-crosstalk, which indicates that the interlayer crosstalk is small

Optical Encryption Based on Computer Generated Holograms in Photopolymer

An optical encryption method based on computer generated holograms printing of photopolymer is presented. Fraunhofer diffraction is performed based on the Gerchberg-Saxton algorithm, and a hologram of the Advanced Encryption Standard encrypted Quick Response code is generated to record the ciphertext. The holograms of the key and the three-dimensional image are generated by the angular spectrum diffraction algorithm. The experimental results show that large-size encrypted Quick Response (QR) code and miniature keys can be printed in photopolymers, which has good application prospects in optical encryption. This method has the advantages of high-density storage, high speed, large fault tolerance, and anti-peeping

Establishing Reference Intervals for Normal Fetal Lung Biological Parameters at 21–40 Weeks of Gestation in the Chinese Population: A Cross-Sectional Study

(1) Background: There is no reliable way to assess antenatal fetal pulmonary hypoplasia; however, the biological parameters of the fetal lung can help in evaluating fetal lung development. This study aimed to establish the reference intervals for normal fetal lung biological parameters at 21–40 weeks among the Chinese population. (2) Methods: This was a cross-sectional study of Chinese groups, and included a total of 1388 normal single pregnant women at 21–40 weeks’ gestation. We selected 2134 images of a standard four-chamber view (4CV). ImageJ software (Release 2.14.0) was used to measure the left and right lung areas using a manual tracing method; the elliptic function key was used to measure the fetal thoracic circumference (TC), thoracic area (TA), head circumference (HC), heart area (HA), and abdominal circumference (AC). Based on the above measurements, the following parameters were calculated: lung area to head circumference ratio (LHR), total lung area (TLA), TLA/Weight (mm2/g), cardiothoracic ratio (CTR), lung–thoracic area ratio (TLA/TA), lung–heart area ratio (TLA/HA), TC/AC, and TC/HC. (3) Results: The left and right lung areas and LHRs positively correlated with gestational age (R2 = 0.85, 0.88, 0.66, 0.71, p 2/g) was weakly correlated with gestational age, while CTR, TLA/TA, TLA/HA, TC/AC, and TC/HC had no significant correlation with gestational age. There was no statistically significant difference in fetal lung parameters between different genders of newborns, p > 0.05. (4) Conclusions: Our study establishes the reference intervals for normal Chinese fetal lung biological parameters at 21–40 weeks. Moreover, the reference intervals apply to fetuses of different genders. This paper can provide a reference for the prenatal non-invasive assessment of fetal pulmonary hypoplasia