Liquid lens based holographic camera for real 3D scene hologram acquisition using end-to-end physical model-driven network.

With the development of artificial intelligence, neural network provides unique opportunities for holography, such as high fidelity and dynamic calculation. How to obtain real 3D scene and generate high fidelity hologram in real time is an urgent problem. Here, we propose a liquid lens based holographic camera for real 3D scene hologram acquisition using an end-to-end physical model-driven network (EEPMD-Net). As the core component of the liquid camera, the first 10 mm large aperture electrowetting-based liquid lens is proposed by using specially fabricated solution. The design of the liquid camera ensures that the multi-layers of the real 3D scene can be obtained quickly and with great imaging performance. The EEPMD-Net takes the information of real 3D scene as the input, and uses two new structures of encoder and decoder networks to realize low-noise phase generation. By comparing the intensity information between the reconstructed image after depth fusion and the target scene, the composite loss function is constructed for phase optimization, and the high-fidelity training of hologram with true depth of the 3D scene is realized for the first time. The holographic camera achieves the high-fidelity and fast generation of the hologram of the real 3D scene, and the reconstructed experiment proves that the holographic image has the advantage of low noise. The proposed holographic camera is unique and can be used in 3D display, measurement, encryption and other fields.

Corneal confocal microscopy for assessment of diabetic peripheral neuropathy: a meta-analysis.

PURPOSE: To evaluate the diagnostic performance of corneal confocal microscopy (CCM) in assessing corneal nerve parameters in patients with diabetic peripheral neuropathy (DPN). METHODS: Studies in the literature that focused on CCM and DPN were retrieved by searching PubMed, Excerpt Medica Database (EMBASE) and China National Knowledge Infrastructure (CNKI) databases. RevMan V.5.3 software was used for the meta-analysis. The results are presented as weighted mean difference (WMD) with a corresponding 95% CI. RESULTS: 13 studies with a total of 1680 participants were included in the meta-analysis. The pooled results showed that the corneal nerve fibre density, nerve branch density and nerve fibre length were significantly reduced (all p<0.00001) in the patients with DPN compared with healthy controls ((WMD=-18.07, 95% CI -21.93 to -14.20), (WMD=-25.35, 95% CI -30.96 to -19.74) and (WMD=-6.37, 95% CI -7.44 to -5.30)) and compared with the diabetic patients without DPN ((WMD=-8.83, 95% CI -11.49 to -6.17), (WMD=-13.54, 95% CI -20.41 to -6.66) and (WMD=-4.19, 95% CI -5.35 to -3.04)), respectively. No significant difference was found in the corneal nerve fibre tortuosity coefficient between diabetic patients with DPN and healthy controls (p=0.80) or diabetic patients without DPN (p=0.61). CONCLUSIONS: This meta-analysis suggested that CCM may be valuable for detecting and assessing early nerve damage in DPN patients.

[Locally Dynamically Moving Average Algorithm for the Fully Automated Baseline Correction of Raman Spectrum].

The baseline correction is an, extremely important spectral preprocessing step and can significantly improve the accuracy of the subsequent spectral analysis algorithm. At present most of the baseline correction algorithms are manual and semi-automated. The manual baseline correction depends on the user experience and its accuracy is greatly affected by the subjective factor. The semi-automated baseline correction needs to set different optimizing parameters for different Raman spectra, which will be inconvenient to users. In this paper, a locally.dynamically moving average algorithm (LDMA) for the fully automated baseline correction is presented and its basic ideas.and steps are demonstrated in detail. In the LDMA algorithm the modified moving averaging algorithm (MMA) is used to strip the Raman peaks. By automatically finding the baseline subintervals of the raw Raman spectrum to divide the total spectrum range into multi Raman peak subintervals, the LDMA algorithm succeed in dynamically changing the window half width of the MA algorithm and controlling the numbers of the smoothing iterations in each Raman peak subinterval. Hence, the phenomena of overcorrection and under-correction are avoided to the most degree. The LDMA algorithm has achieved great effect not only to the synthetic Raman spectra with the convex, exponential, or sigmoidal baseline but also to the real Raman spectra.

[Spectral Smoothing with Adaptive Multiscale Window Average].

In order to smooth the spectra automatically and reliably, a spectral smoothing algorithm with adaptive multiscale window average (AWMA) is demonstrated. In this method, different positions of the spectra are smoothed by windows of different width, and the width of the windows will directly affect smoothing. The window with inappropriate width may cause excessive denoising (peak distortion or loss) or inadequate denoising (the flat region of the spectra still contains a lot of noise). So, how to get the right width of the window is the key of spectral smoothing. The algorithm optimized the width of windows by an iterative method, and verified whether the width is the best according to statistical Z-test. In order to increase the reliability of the algorithm, a comprehensive comparison of the thresholds of hypothesis according to simulation data of different SNR was performed. When the threshold is set to 1. 1, the denoising effect can be the best. In this work, the AMWA algorithm was tested by simulated spectra and real syectra, and it can automatically adapt to different spectral shape and different noise intensity. A comprehensive comparison of AMWA smoothing, Savitzky-Golay smoothing and moving average smoothing was performed in this paper, and the AMWA algorithm is better than the other two algorithms. Results show that the AMWA algorithm not only has better denoising effect, but also has higher accuracy and fidelity. This method has achieved great effect not only to simulated spectra but also to real spectra.

Overlapped optics induced perfect coherent effects.

For traditional coherent effects, two separated identical point sources can be interfered with each other only when the optical path difference is integer number of wavelengths, leading to alternate dark and bright fringes for different optical path difference. For hundreds of years, such a perfect coherent condition seems insurmountable. However, in this paper, based on transformation optics, two separated in-phase identical point sources can induce perfect interference with each other without satisfying the traditional coherent condition. This shifting illusion media is realized by inductor-capacitor transmission line network. Theoretical analysis, numerical simulations and experimental results are performed to confirm such a kind of perfect coherent effect and it is found that the total radiation power of multiple elements system can be greatly enhanced. Our investigation may be applicable to National Ignition Facility (NIF), Inertial Confined Fusion (ICF) of China, LED lighting technology, terahertz communication, and so on.

[General calculation method of diffraction efficiency of concave blazed gratings].

In order to make diffraction energy of concave gratings more concentrated in the desired order, the present paper puts forward that the concave blazed grating with variable groove angles could be fabricated on the concave substrates by mechanical ruling method, and the theoretical method of simultaneously calculating the diffraction efficiency in the main section and non-main section is deduced by using Fresnel-Kirchhoff's diffraction formula, which makes up the shortage of the diffraction efficiency calculated only in the main section. Finally, the diffraction efficiency curves varied with wavelength is simulated by Matlab software, and the variation laws of the diffraction efficiency are compared for different production methods and application parameters, which provides a valuable reference for the design and production of the concave gratings.

[Preparation by spin-coating technology and characterization of UV-enhanced Lumogen film].

As an effective way to increase the UV response for CCD/CMOS, the advantage of the Lumogen film is the simple process and low cost. In the present paper the Lumogen film was deposited onto fused silica slides by the spin-coating way, which has less damage than PVD physical vacuum deposition) way. The main test and analysis of the thin-film include transmission spectrum, absorption spectrum, and excitation and emission spectrum. It was showed that these coatings were transmitted well in visible region (lambda > 400 nm), and emitted a yellowish green glow centered at -525 nm together with a wide excitation spectrum range from 200 to 400 nm. The synthesis shows that Lumogen coatings match accurately with the detected spectrum of conventional silicon-based image sensors, which makes this kind of thin films an ultraviolet responsive coating for sensors.

Feasibility and safety of magnetic-controlled capsule endoscopy system in examination of human stomach: a pilot study in healthy volunteers.

OBJECTIVE: To assess the feasibility and safety of magnetic-controlled capsule endoscopy (MCE) system for examination of human stomach. METHODS: This pilot study enrolled 34 healthy volunteers. All subjects swallowed the MCE and gas-producing powder for gastric distention. An external robot was used to generate magnetic field to manipulate MCE inside the stomach. The primary measurements included safety, gastric preparation, maneuverability and visualization of gastric mucosa. RESULTS: Gastric preparation and examination was well accepted by subjects and there were no adverse events. The examination in the stomach takes 43.8±10.0min (27-60). The cleanliness was evaluated as good in the 30 (88.2%) subjects and as moderate in 4 (11.8%) subjects. The distention of gastric cavity was evaluated as good in the 29 (85.3%) subjects and moderate in 5 (14.7%) subjects. Maneuverability of the MCE to movements of the guidance magnet robot was graded as good in 29 (85.3%) subjects and moderate in 5 (14.7%) subjects. More than 75% gastric mucosa was visualized in 27 (79.4%) subjects and 50% to 75% in 7 (20.6%) subjects. Visualization of the gastric cardia, fundus, body, angulus, antrum and pylorus was subjectively assessed as complete in 82.4%, 85.3%, 100.0%, 100.0%, 100.0% and 100.0%, respectively. Polyp and erosive lesions were found in 7 subjects. CONCLUSION: Magnetic-controlled capsule endoscopy used for examination of the human stomach is feasible and safe.

[The characteristics of multicolor imaging system for logarithmic wavefront coding].

The wavefront coding extension the depth of field (DOE) of an imaging system is by insert a phase plate into the pupil plane of a spatially incoherent imaging system, the encoded image can be digitally restored to produce a final image with improved depth dependent detail. To study the multicolor imaging performance of a logarithmic wavefront coding system, the phase and chromatic aberration variation with wavelength are analyzed, and characteristics such as shape, distribution and width of two wavelengths' PSF are compared. The research results show that if the chromatic aberration is excellently corrected then the technology can be used for multicolor even broadband spectrum DOE imaging system. Otherwise, the encode image can not be effectively decoded.

[Preparation and spectral characterization of Lumogen coatings for UV-responsive CCD image sensors].

Traditional charge-coupled devices (usually front-illuminated CCDs) and complementary metal oxide semiconductor (CMOS) have lower response in ultraviolet region particularly. The reason is that polysilicon gate material absorbs the ultraviolet radiation highly, which leads to a barricade of the radiation penetrating the gate to the channel of CCD. To enhance the detective responsibility of CCD in the ultraviolet region, a feasible method is to coat the surface of CCD polysilicon gate with a thin film. The thin film should have the ability of converting the ultraviolet to visible in order to enable the UV radiation to "penetrate" the polysilicon gate. An organic coating to convert the UV radiation to visible has been developed in the present paper. Lumogen thin films were deposited on fused silica substrates by vacuum evaporation of an organic dye called Lumogen Yellow S0790. Analysis of organic functional groups was used to study the luminescence mechanism of Lumogen. The optical constants of coatings were calculated by spectroscopic ellipsometry. The results indicate that Lumogen exhibits photoluminescence continuously owing to four kinds of double bonds in each Lumogen molecule. The refractive index of Lumogen film was approximately 1.3, which indicates that this film could be considered an antireflection coating. Finally, the spectral properties of Lumogen coatings were characterized by transmission, absorption, photoluminescence emission, and excitation spectra. It is showed that these coatings were transmitted well in visible region (lambda > 470 nm), and emitted a yellowish green glow centered at approximately 523 nm together with a wide excitation spectrum field from 240 nm to 490 nm. The synthesis shows that Lumogen coatings match accurately with the detected spectrum of conventional silicon-based image sensors, which makes this kind of thin films an ultraviolet responsive coating for sensors.

[Investigation of multi-wavelength effect during the measurement of UV-enhanced film's emission spectrum].

The UV-responsive detector is a dual-use device for civilian and military after the laser and IR-responsive sensors. Typical image sensor coated with a layer of down-convert frequency thin film on it's photosurface to enhance UV response is the key technology of enhancing UV-response. The UV-enhanced thin film was made in the experimental laboratory using the Zn2SiO4:Mn phosphor by spin coating method. Two peaks at 520 and 560 nm respectively in the emission spectrum of the UV-enhanced film were found by SP1702 spectrograph when the excitation wavelength was 260 and 280 nm. The peaks were found in the process of experiment of measuring and counting the quantum efficiency of UV-enhanced thin film. But the light peaks at 520 and 560 nm are not the emission light peaks by the exciting light of 260 and 280 nm. The reason why the light at 520 and 560 nm is not the emission light was analyzed based on the measurement principle of grating spectrograph. The reasons for the multi-wavelength of light overlaps during the measurement of emission spectrum were also discussed. And the equipment used to separate the overlapped different wavelengths was designed, which will be used to resolve the problem of the overlap of multi-wavelength.

Preparation of high laser induced damage threshold antireflection film using interrupted ion assisted deposition.

Single layers and antireflection films were deposited by electron beam evaporation, ion assisted deposition and interrupted ion assisted deposition, respectively. Antireflection film of quite high laser damage threshold (18J/cm2) deposited by interrupted ion assisted deposition were got. The electric field distribution, weak absorption, and residual stress of films and their relations to damage threshold were investigated. It was shown that the laser induced damage threshold of film was the result of competition of disadvantages and advantages, and interrupted ion assisted deposition was one of the valuable methods for preparing high laser induced damage threshold films.

[Analysis for the near infrared spectrum characteristic of tea based on orthogonal wavelet packet].

According to the high co-linearity and dimension in the near infrared (NIR) spectrum of tea, the present paper describes quantitatively the characteristic of tea NIR spectra with wavelet packet by introducing the retained energy and number of zeros, based on the decorrelation capacity of orthogonal wavelet packet. Results show that the energy retained is as high as 99.98% after compressing, while the percentage for number of zeros is 95.87%. It was concluded that orthogonal wavelet packet has a good compressibility for NIR spectra, which has significance in storing, searching and processing the NIR spectrogram.