This PDF file contains the front matter associated with SPIE Proceedings Volume 11434, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists.

Optical tweezers is one of the commonly used technologies to research on protein force spectroscopy. However, whether optical tweezers system has the capability of force spectroscopy measurement at the molecular scale is vital to single molecule experiments. In this paper, we test the capability of our home-built dual-trap optical tweezers system by stretching polyprotein (NuG2)₈ which is made of eight identical tandem repeats of NuG2. With the constant velocity stretching and relaxation mode, we achieve a lot of experimental data and get the contour length increment of (NuG2)₈ rapidly from the unfolding processes after fitting these data. The result is consistent with existing reports, which demonstrates optical tweezers system has the force spectroscopy test ability and (NuG2)₈ can be used as a new standard sample to evaluate the test performance of optical tweezers. Using polyprotein (NuG2)₈ as standard sample has two advantages: stretching polyprotein can help improve the efficiency of data statistics and a large number of experiments can reduce the randomness of the system when testing.

Objective and accurate lesion assessment is one of the key factors for the optimal photodynamic therapy (PDT) of Port Wine Stains (PWS). The evaluation method based on 3D point cloud can effectively solve the problems. Comparing to the traditional point cloud registration algorithms such as ICP which tend to global registration, the feature description method is more suitable for facial point clouds fusion since each clouds is obtained from different angle and just overlap in certain area. In this paper, the method of fusion of multiple point clouds is applied, in which point cloud fusion is achieved by characterizing randomly selected sampling points. The point cloud fusion result is obtained by matching the public area between the two point clouds. Several fusion experiments are designed and conducted using the facial point cloud acquired by Artec Eva three-dimensional scanner. The experimental results show that it can accomplish the point cloud fusion of patient facial point cloud (including all the information on the skin lesions of PWS), which could be an efficient support for effective 3D lesion assessment.

In order to solve the problem that the large field of view and high resolution of the traditional single aperture optical system are difficult to realize at the same time, a curved compound eye system including a three-ring lens group is designed. Firstly, the relationship between the field of view of the sub-eye system and the total field of view is studied, and the arrangement of the sub-eyes is obtained. Then, according to the object image conjugate relationship between the incident window and the exit window, we obtained a geometric model of sub-eye stitching. The compound eye system designed by this method has a full field of view of 79.5°. The angular resolution of the central system is 0.01°, the edge system is 0.017°. The system is simulated and verified by the optical design software ZEMAX. Finally, the feature points of each sub-eye image are extracted by SIFT(Scale Invariant Feature Transform) algorithm. The extracted feature points are accurately matched by RANSAC(Random Sample Consensus) algorithm, Then we use a weighted average algorithm to splicing the image of the sub-eye. This research further promotes the application of bionic compound eye imaging systems.

Diffraction imaging flow cytometry is a new biological cell research method developed recently, which can get abundant information of 3D morphology inside the cell without staining. However, the pattern of diffraction image is non-intuitive, and cannot be directly classified by the observer. On the contrary, the bright field images obtained by microscope are clear enough to be directly perceived through the senses by researchers. This paper will introduce a new flow cell imaging design incorporating the merits of these two kinds of methods that can obtain diffraction image and bright field image of the same cell simultaneously, which is based on the infinite microscopic architecture with two optical paths. The first path gets the diffraction image by defocusing the shared object lens, meanwhile, the second path gets the bright-field microscopic image by adjustable lens compensating for the defocus. In the new system diffraction and microscopic images of yeasts were captured with illumination of 532nm laser and 450nm LED respectively. Two classification models were set up for recognition of yeast-budding-state with diffraction images and microscopic images independently by using GLCM (Grayscale Co-occurrence Matrix) feature extraction method, which got the highest 97% accuracy of classification with diffraction images compared to the 94% with microscopic images.

The spectrum is a crucial parameter to a petawatt laser which is adopting the chirped pulse amplification technique. In such complex systems with high gain and wide spectrum bandwidth, the shape of the spectrum is crucial to the final output pulse width. In daily operation, the width of the compressed pulse will have some abnormal fluctuation, and the shape of the spectrum before compressed is also changed at the same shot. It will mislead the power and intensity estimation in laser-matter interaction experiments. So far, no theory has been able to analyze the relationship between spectrum and pulse width completely. Because it is hard to describe the fluctuation of the compressed pulse width which the online measure spectral phase in the high power laser system is difficult. In this paper, we first found and analyzed the relation between spectral variation and pulse width in the petawatt laser. With the support of existing data, we establish an end-toend deep learning model to map the petawatt laser’s spectrum before the compressor to the compressed pulse width. The deep learning scheme which based on Bayesian Neural Network (BNN) can provide an estimate of uncertainty as a function of pulse width to improve the accuracy of the model. After 20000 iterations, the Mean Square Error (MSE) is reduced to 0.08 in the validation test. Under the experiment, the model realizes an effective predict of the compressed pulse width. With the help of deep learning, we can get more information on the spectrum rather than the center wavelength and spectrum width to predict the compressed pulse width. It should be emphasized that this method will help to avoid unstable pulse output caused by an abnormal spectrum and to improve the operating efficiency of the petawatt laser system.

Freeform optical surfaces can be characterized as nonsymmetric surfaces and they can offer much more degree of freedom for optical design. This kind of optical surface can be seen as a revolution in the optical design and plays a key role in the next generation of high-performance optical systems. Another trend in imaging optics is to use phase elements (such as diffractive elements and metasurface). In specific, the flat or planar phase element can effectively reduce the weight and volume of the total system. Easier-alignment of the system can also be achieved. In this paper, the point-by-point design method are applied to the design of three kinds of nonsymmetric imaging systems: consisting of only geometric freeform surfaces, only flat phase elements, and both of them (the generalized case). The entire design process begins from an initial system using simple geometric planes. Both the geometric freeform surfaces and the phase profiles or functions are generated point-by-point based on specific design requirements. The design results can be taken as good starting points for further optimization. The dependence on existing starting points is significantly reduced and advanced design skills are not required. In addition, three typical three-mirror folding geometries are employed and designed using the proposed method for all the three kinds of systems under same system specifications. The imaging performance and system volume of the different systems after final optimization are analyzed and compared. The results offer insight on the selection of optimal system folding geometry and types of imaging element for the nonsymmetric system design tasks.

As a kind of radial basis functions, the Gaussian function has local feature and therefore has an excellent surface description ability. In this paper, we proposed the design strategy of freeform unobscured three-mirror system using Gaussian radial basis functions surface type and demonstrate a design example. A novel and high-accuracy surface fitting algorithm of Gaussian radial basis functions is proposed for the freeform surface fitting. Successive optimization strategy is employed for the system after surface fitting. The final example system works at the long wave infrared band and has an 8°×6° field-of-view with an F-number of 1.9.

The superresolving pupil filters are utilized to modulate amplitude or phase, which can compress the central main lobe of the diffracted spot below the diffraction limit. The mature pupil filter is mainly made by binary optical processing technology or liquid crystal spatial light modulators. Compared with these two types, the superresolving pupil filters based on deformable mirror(DM) have the advantages of programmability, no wavelength and polarization limitation. In this paper, the design of superresolving continuous phase filters using DM eigenmodes as the basis function is studied by simulation. The DM eigenmodes are constructed by the coupling relationship between the actuators, and the first, sixth, fifteenth and 30th order eigenmodes are selected for interpolation to obtain the continuous phase function. Superresolution gain factor (G_t), Strehl ratio (S) and axial displacement of focus (U_F) are chosen as performance evaluation index. Using multi-objective optimization genetic algorithm to solve the constrained multi-objective optimization problem, the spot size is reduced by approximately 30% compared to the diffraction-limited spot, and the corresponding Strehl ratio is approximately 0.4. Using DM as the continuous phase filter, we analyzed the effects of defocus and astigmatism on the super-resolution performance of the filter. The fitting accuracy of pupil filters designed by DM eigenmodes and Zernike polynomials are also compared, which proves that the eigenmode-based superresolving pupil filters are more suitable for fitting with a deformable mirror.

Deformable mirror (DM) is a flexible wavefront modulator with a changeable surface. It is traditionally adopted in adaptive optical system for aberration correction. Recently applications in zoom imaging system and interferometer for freeform measurement have been proposed because the improvement in fabrication technique makes larger stroke amount and faster response possible. The order and accuracy of aberration correction are typical wavefront correction characteristics of DMs. Due to the non-linearity, hysteresis and creep characteristic of piezoelectric ceramics, accurate control of piezoelectric type DM remains a challenge. Generally, the surface shape of a DM is changed by altering the voltages applied to different actuators below the DM film. And the shape of the DM can be fitted with Zernike polynomial to better characterize the aberration. So accurate control of the DM surface shape requires a relationship between the control voltage vector and the Zernike coefficients of the surface shape. We adopt neural network for the foundation of the relationship. 3000 set of control-voltage-vector and Zernike-coefficient pairs are experimentally collected based on the data measured with an interferometer and fitted with Zernike polynomials. The neural network is constructed and trained, and the control voltage vectors of new surface shapes can be retrieved with the network. The accuracy of shape realization is finally demonstrated by comparison between measured and predicted voltages.

A depolarizer is usually used to reduce the polarization response of the spectrometer. On the basis of LYOT depolarizer, a depolarizer composed of two quartz crystals with the same wedge angle is designed and developed. Based on the matrix optics theory, this paper studies the relationship between the residual polarization degree of a LYOT depolarizer and the polarization angle of incident light, wavelength, spectral bandwidth, crystal central thickness. The residual polarization degree of a LYOT depolarizer is tested on the polarization sensitivity tester, and the test results are in good agreement with the theoretical analysis results. The LYOT quartz depolarizer can meet the requirements of spectral radiation measurement, and is of strong engineering practice.

Micro-focus x-ray sources have been wildly applied to more and more fields，such as medical treatment, industrial area and aerospace. As the core indicator of micro-focus x-ray sources, the focal spot size directly affects performance of application scenarios. The smaller the focal spot size, the higher the resolution of micro-focus x-ray sources. So it is vitally important of accurately measuring the focal spot size. Three classic measurement standards of x-ray focal spot size, including the EN 12543, the IEC 60336 and the ASTM E 1165, have been introduced in detail. And the measurement principles, adaptive range, application objects and processing method of tested data are analyzed and compared. Then on this basis of three classic measurement standards, several measurement methods, scanning method, pinhole camera radiographic method, slit camera radiographic method, edge method and measurement of the effective focal spot size of mini and micro focus x-ray tubes, are expatiated. Additionally, advantages and disadvantages of various methods are expounded to readers, and some references are offered to demanders.

Image stitching technology is an important technology for generating large field of view images, and it is also a research hotspot in the field of digital image processing. Binocular imaging technology is closely related to image stitching technology and is widely used in robot vision, 3D reconstruction and other fields. However, in the existing image stitching methods, when the image with the distant view and the near object are coexisted, due to the parallax, the near object often has partial missing or unnatural transition, which leads to the poor image stitching effect and low naturalness. Aiming at this problem, we uses the characteristics of the binocular camera that can obtain depth information, and regards the information as one of the basis of the seam positioning. A strategy based on the combination of geometry, color and depth features is proposed, and we constructed a seaming algorithm model for positioning the optimal seam. The comparison experiment results show that the stitching naturalness is improved by 37% according to the proposed seaming algorithm.

Framing camera is a powerful tool to investigate the ultrafast phenomena in chemical reaction process. Wavelength framing technique is one of the key technologies in the development of framing cameras. The wavelength resolution of the images generated by wavelength framing system determines the interval time of the wavelength framing camera, that is, the time resolution of the wavelength framing camera. In this paper, a wavelength framing system based on a diffractive optical element (DOE) and a band-pass filter (BPF) was set up. The wavelength characteristics of the wavelength framing system were simulated utilizing the theory of multi-beam interference. The central wavelength of each image got from the system, which varies with the position relationship between DOE and BPF, has been obtained. Experiments were carried out through imaging a target of 6 mm × 6 mm by using the wavelength framing system. The spectral characteristics of each image were also studied experimentally. The result we have got proves that the system we have generated can achieve 16-frame imaging, every image has different spectral properties. For the target with a size of 6 mm × 6 mm, the resolution of a single image got from the system is 610 × 610, and the central wavelength ranges from 784 nm to 814 nm. The average difference in central wavelength between adjacent images is 1.95 nm. If the dispersion of the incident pulse light source is 0.46 ps/nm, the time resolution of the system is 0.9 ps.

A common phase-type spatial light modulator (SLM) can only modulate the phase part of a complex-amplitude hologram calculated from an object image. To calculate a phase-only hologram, iterative methods such as the Gerchberg–Saxton algorithm can be employed. However, one-step non-iterative phase-only hologram calculation is more favorable for real-time applications. This paper proposes a novel scheme to optimize a shared phase mask from a set of training images. Then a phase-only hologram can be simply calculated by phase truncation after any given object image similar to the training samples is multiplied with the shared mask and Fresnel diffracted. The speckle noise in the reconstructed images can be significantly suppressed if our optimized phase mask is used instead of a conventional random phase mask.

Time-delay technology is widely used in machine vision, optical communication, laser radar (LIDAR), photoelectric detection and other fields. Compared with electric time-delay technology, optical fiber time-delay technology has many advantages under the condition of large delay time, such as high delay accuracy, good delay stability, small jitter, strong anti-electromagnetic interference ability, and less environmental impact, etc. It has attracted much attention in related fields. In order to achieve a larger delay time and a higher delay accuracy, this paper focused on the high-precision CNC (computerized numerical control) optical fiber delay system applied to laser echo simulator. The system consisted of 16 delay fibers, 16 optical fiber jumpers and 17 optical switches. By using binary gated mode, the delay of 0-64553ns was achieved and the laser echo of 0-5km was simulated. Using 10kHz-100MHz modulated laser, the actual length of 16 delay optical fibers was accurately measured by phase method, and the measurement error was less than 28.6mm. Aiming at the problem that the accuracy of long optical fiber cutting was poor in engineering, a compensation method for changing the delay resolution of the system is proposed, so that the delay precision of the whole system is controlled within 0.984 ns. The effects of temperature changes on the refractive index of the fiber and the length of the fiber on the system delay time are analyzed. The experimental device developed can achieve a delay of 0-64553 ns, a delay resolution of 0.984 ns, and a delay measurement accuracy of 0.14 ns. The system has been successfully applied.

Aiming at the requirements of gas detection in petroleum, petrochemical, power equipment and air pollution monitoring, some key technologies in passive uncooled gas leakage infrared imaging detection system are analyzed. Based on the gas absorption line intensity and absorption peak position in the standard infrared database, the key components such as MW and LW infrared optical lens and wide band uncooled infrared focal plane detector are optimized. Considering the imaging signal-to-noise ratio and signal contrast, the filter used in several typical gas detections is analyzed, and an online and handheld gas leakage infrared imaging detection system capable of detecting multiple gases is designed. Theoretically, it is possible to detect gas with characteristic absorption in the range of 3-14 μm. The imaging effects of carbon dioxide gas, methane gas and sulfur hexafluoride gas with absorption peaks in MW and LW bands were measured. The test results show that the uncooled infrared gas detection system designed in this paper not only has good imaging detection ability for sulfur hexafluoride gas and ethylene gas (near 10.5 μm) with large absorption intensity and absorption peak in conventional LW band, but also for methane gas (near 7.5μm or 3.3μm) and carbon dioxide gas (near 4.2 μm) with absorption peak in unconventional LW band. In the laboratory environment, with the black body as the background, the gas flow rate is controlled by the gas mass flow meter to observe the imaging detection effects under different temperature differences and different flow rates. When the target and background temperature difference is 5K, the gas detection ability is ≤100mL/min.

Wavefront coding is the most widely used method to extend the depth of field, because the wavefront coding system combines the advantages of optical imaging and image post-processing. This paper mainly discusses the principle, advantages, and application scenarios of wavefront coding and analyzes the greater than 20 existing types of phase masks. Specifically, these methods are discussed for the optimization of the phase mask parameters together with the generally used optimization algorithms. In addition, the fuzzy image recovery algorithms of image post-processing are also discussed. Finally, our recent work on the depth extension of existing optical imaging systems is introduced and we look forward to the future development of wavefront coding.

As an important ultra-precision measurement method, white light interferometry is widely used in 3D measurements with nanometer resolution. In this paper, a white light interferometer is designed with a random phase noise insensitive algorithm. A discrete interferogram is established by analyzing the phase noise, which is modelized by the combination of random noise and systematic deviation. After Fourier analysis, the mathematical expression of the discrete interferogram in frequency domain is derived, where the random noise can be estimated by least square method and then be corrected. As a result, a more accurate relationship between phase distribution and surface height is established. To set up an stable system, the scanner of white light interferometer is driven by a precision step motor with scanning range 100 mm, and the travel range of the object stage in x and y directions is 60 mm. In the experiment, a step height standard (VLSI, 182.7±2.0 nm) and the end face of a multi-mode optical fiber are tested, where the repeatability error for the step height is less than 0.28%, which proves the measurement accuracy and robustness of the system.

Refractive index is an important optical parameter of the liquids. Conventional liquid refractive index measurement instruments can be classified into refractometers and interferometers according to measurement methods. These methods are relatively simple. However, the liquid in the measurement instrument is usually in contact with air and is not suitable for measuring volatile and toxic liquids. In this paper, we propose a liquid refractive index (LRI) measurement instrument based on electrowetting lens. The instrument is composed of a light source, a collimating lens, a liquid measurement chamber, an electrowetting lens and an image sensor which is integrated in a cylindrical cavity. After adding the measured liquid, the refractive index of the measurement chamber changes, and the incident light cannot be focused on the image plane. By adjusting the driving voltage of the electrowetting lens, the curvature of the liquid-liquid interface changes to focus the incident light on the image plane. According to the voltage value, we can measure the refractive index of the liquid. The proposed LRI measurement instrument has no mechanical moving parts and the imaging surface remains stationary, which can make the measurement simply and accurately. The experiments show that the measurement range can be turned from ~1.3300 to ~1.4040. The instrument can be used to measure the optical properties of liquids and has widely potential applications in chemical reagent detection and pharmaceutical testing.

When the Satellite-borne very high infrared spectrometer performs atmospheric composition analysis, it needs to use the sun as a light source for occultation detection. The stability of the light source is related to the detection accuracy. In general, it is believed that the light distribution within the maximum solar intensity range is the most stable and it is necessary to accurately identify and track this range. However, due to the inhomogeneous atmosphere and the change of atmospheric density, the solar image will have deformation or block, which affects the accuracy of target recognition and tracking. This paper proposes a multi-objective clustering-based recognition method to solve the problem of accurate multi-target identification under the large dynamic light intensity range, and uses the hardware structure of FPGA+DSP to realize the imaging and tracking system.

High-resolution space observation is of great importance for scientific and military use. To get higher resolution, a larger imaging aperture is highly required. For example, to obtain one-meter ground sampling distance (GSD) in visible band on geostationary orbit (GEO), the pupil diameter of space telescope is around 25 meters. Trying to fabricate and launch so large monolithic mirror will meet many unconquerable obstacles. A feasible scheme is using sparse aperture imaging technique based on small satellites formation. This paper is focused on a sparse aperture telescope consisting of small sub-telescopes to form a Fizeau imaging interferometer. Each sub-telecope is based on a small satellite. Imaging performance of an annular structure consisting of 25 sub-apertures is evaluated by simulation. The influence of phasing error (including piston and tip/tilt) of subapertures on image quality is evaluated. The co-phasing error budget of sparse aperture telescope dependent on field of view is also analyzed. A co-phasing error detection and correction method based on wavefront sensorless adaptive optics (WSLAO) is proposed at last.

A novel method of droplet concentration measurement is presented based on analysis of angular distribution of elastic light scattering patterns, which provide a possible way to get the information of complex refractive index and inverse the liquid concentration for both absorbing and non-absorbing solutions. A mathematical model is established and an inverse algorithm corresponding to this model is also proposed which calculates the complex refractive index accurately. Experiments were carried out on both absorbing dye solutions and non-absorbing ethanol solutions with different concentrations. The results show a good agreement with the theoretical analysis and prove the potential use of this method.

A new method to remove metal artifacts utilizing virtual dual-energy CT image sets generated from monoenergetic CT images and dual-energy CT subtraction is presented in this work. CT images were derived from Optima CT580 (General Electric Company, Fairfield, Connecticut, USA). Optimized conversion model from CT numbers to linear attenuation coefficients (LAC) was applied to calculate an accurate LAC map at specific energy. According to mass attenuation coefficients (MAC) of base materials from the National Institute of Standards and Technology (NIST), a LAC map at another higher energy was obtained, and then a set of CT images was derived from the LAC map, which is at different but a known energy. Then, dual-energy subtraction was applied to remove metal artifacts. Results: Between the CT image sets of virtual high energy and the original, there is no significant difference in STD (standard deviation) (no more than 1.91%), while Merror (a parameter for quantification of the CT value differences between two images at the same position) varies from 58.83 to 101.6442. CNRs (Contrast-noise-ratio) in dual-energy subtracted CT images are 1.9% higher than those in the CT images processed by polar coordinate transformation. Conclusions: The Dual-energy subtraction is proved to be a better method for reduction of metal artifacts than the polar coordinate transformation scheme. Moreover, the dual-energy subtraction method is based on the reconstructed CT images obtained with a single energy CT scanner, which is more convenient for users not having access to the projection data.

Different from visible light, infrared optical systems need to consider various effects in order to change the F-number of the system, such as the effect of stray light in the system before and after variable F number, and the effect of cold reflection on the system, which are all effects to be considered. This paper analyzes the technology of infrared variable F number, summarizes the research progress, and the key technology of thermal aperture variable F-number.

Using a single detector to realize the detection of wind Lidar in the upper atmosphere is the simplest signal detection mode, but the disadvantage of single detector is that it would limit the dynamic range of wind Lidar. When the detection area is 30km, the linear dynamic range of electronic system is required to be 5~6 orders of magnitude. In this case, it is difficult to satisfy the demand by using analog sampling or photon counting alone. In order to extend the dynamic range of wind Lidar based on single detector, we developed a set of wind Lidar readout electronics in the upper atmosphere based on single detector which has large dynamic range. The system of the detector used analog measurement and photon counting measurement at the same time, namely, analog sampling is adopted to measure the strong echo signals and photon counting is adopted to measure the weak echo signals. At the same time, the calibration laser energy is obtained by using the integral channel to improve the accuracy of Lidar calibration. After signal acquisition, data of analog sampling channel and photon counting channel are splicing through FPGA, and finally transmitted to the upper computer through Ethernet and UART. The results of electronics test show that the linear dynamic range of readout electronics system can reach 5~6 orders of magnitude through the combination of two channel signals, which can meet the design requirements. In addition, the high integration of this electronic readout system can meet the demand of miniaturization of current wind Lidar.

To tackle with false recognition of the forged vasculars in vein recognition, a new vascular recognition method is proposed by photoacoustic anti-counterfeiting. An optical-resolution photoacoustic microscopy imaging system is built by use of the laser diode. Then, photoacoustic experiments were performed on the forged vasculars and isolated subcutaneous vasculars. To realize anti-counterfeiting of vasculars, the photoacoustic signal intensity is used to distinguish between forged and real vasculars. Meanwhile, the vascular recognition performance can be lifted on our established photoacoustic vascular library. The experiment results show that the proposed technique has the advantages of high anti-counterfeiting and high recognition rate, and can be applied in biometrics.

It is a hybrid design spectrometer with zooming and spectral imaging. The system realizes the searching in large field of view and recognition in small field of view which can resolve the difficulty that the target and background of spectrometer are not easy to distinguish in a single field of view. It also decreases the difficulty of spectral demixing and data dimension reduction. The new lenses can simultaneously obtain optical imaging and spectral data which provides a basis for the subsequent spectral analysis. The optical system realizes three times zoom from 55mm to 165mm. The simulation achieves the effect imaging result. Experiments show that the system has both imaging and spectral recognition capabilities.

Port wine stains is a congenital vascular malformation disease, which occurs mostly on the face and neck. Photodynamic therapy is an effective treatment for port wine stains, which utilizes photodynamic reaction between light, photosensitizer and oxygen in the tissue to produce phototoxic substance singlet oxygen to destroy the lesion. However, the irradiance dose is simply described by the irradiance on a specific plane instead of the irradiance on the lesion with curve shape. The clinician has little knowledge about the effective irradiance value on the lesion, which limits the understanding between the effect and the dosage. To get the effective irradiance on the lesion, a two-steps algorithm is proposed in this paper. Firstly, the point cloud data of lesion are constructed, and the normal vector of each point of the point cloud is calculated based on the least square method. Secondly, according to the first and second laws of irradiance, the effective irradiance on the lesion can be obtained when the parameters of the light source are available. Several typical port wine stains lesions are used to verify the difference between the irradiance on the plane and the lesion. The algorithm can not only help the clinician to make the preoperative planning of photodynamic therapy, but also provide a method for the study on the relationship between the effective irradiance dose on the lesions and the treatment effect of photodynamic therapy for port wine stains.

Introduces a real-time color imaging system can be operated at night and uses a low-cost, simple and convenient CMOS sensor. In this imaging system, the sensor is driven by the FPGA, the differential data output by the sensor is decoded by the FPGA, and a series of image processing algorithms are implemented in the hardware description language through FPGA programming to improve the imaging quality of the system at night. The main problems solved by this imaging system are as follows: (1) For night time light energy is weak, and after adding an IR cut filter, the sensor can capture the problem of insufficient light. This paper proposes an imaging method without an IR cut filter. This method requires a color correction algorithm in the FPGA to correct the color distortion caused by the transmission of near-infrared light. (2) The problem of low contrast and insufficient color saturation for night time imaging results. This paper combines the gamma correction algorithm and the defogging algorithm to propose a method that can effectively improve the image color saturation. The combination of the two algorithms can improve the brightness of the nighttime image and make the image more vivid. (3) When imaging a single color sensor at night, the details and brightness of the captured object still do not meet the needs of the human eye. In this paper, a mono and color dual-camera system is used to improve imaging quality. In this system, two sensors are simultaneously imaged, so that the imaging results retain both the color information of the color sensor and the clarity of the mono sensor.

To realize spectral diffuse reflectance scale in mid-infrared waveband in 0/d geometric condition at National Institute of Metrology in China (NIM), a facility based on auxiliary integrating sphere method has been built up. An integrating sphere (diameter 100mm) coated with gold and series of gold plate were used for calculating the reflectance. The uncertainty of spectral diffuse reflectance in NIM is approximately less than 3.0% (k = 2) in 3μm -14μm.

In order to research the imaging effect of the IRFPA ROIC, the imaging simulation system is developed which is the PC-DAQ system based on virtual instrument technology. The system uses powerful software and hardware resources of computer and high performance DAQ data acquisition card to complete the acquisition and display of IRFPA ROIC image signal. The hardware of the system is composed of signal source, junction box, drive circuit board, PCI MIO16E-1 data acquisition card and PC. According to the driving timing requirement of IRFPA imaging, the field synchronization signal is used to control the triggering start of the acquisition card, and the scanning clock signal is used as A/D clock to control the accurate sampling of each pixel. Video output signal, field synchronization signal, pre-trigger signal of data acquisition card and A/D clock signal are connected with data acquisition card through junction box. The time sequence control of the acquisition card is realized by software programming to complete the acquisition of one-dimensional ROIC signal. In the software platform, the signal is converted to display image in two-dimensional space. At the same time, ROIC image signal is processed by software system, such as background noise correction, invalid pixel compensation, gray histogram enhancement, pseudo-color coding and so on, so that users can choose image display mode. By the experiment of 128*128 HgCdTe IRFPA ROIC, it is valid that the system can visually simulate the imaging effect of ROIC image, and provide a good algorithm basis for the construction of IRFPA imaging system, and provide a reference for device quality evaluation.

Metasurfaces are widely applied to realize miniaturized optical devices with high performance, because of the high design freedom. Recently, with the help of optical design, cascaded metalenses with two-layered metasurface, which can correct monochromatic aberration have been proposed for a well-focused light spot in the focal plane at large incident angles. However, the focal length is fixed in these systems. In this paper, we report a wide-angle metalens with continuously tunable focus. Through the optical design method, we obtain a lens phase profile with large field of view. And referring to the principle of Moiré lens, a wide angle (±30°) and continuously zoomed metalens with well focusing at infrared wavelength (810nm) was designed, and its characteristics are verified by numerical simulations. Our metalens has great potential in areas where high imaging quality and tunability.

Optical design of an imager with wide field-of-view (FOV) and high-resolution utilizes a monocentric objective lens in conjunction with an array of secondary optical lenses to achieve good performance. An intermediate image with uniform residual aberration throughout a wide FOV is obtained on a curved surface by the monocentric objective lens and then relayed to a sensor array by the secondary optical lenses. In this paper, we focus on the study of the monocentric objective lens and the surface type of its obtained curved image. Firstly, the equation of focal length is determined by ray tracing. The achromatic condition is obtained through first-order aberration theory. Accordingly, the initial configuration of the monocentric objective lens is determined, including the surface radii and reasonable glass combination. Secondly, a detailed calculation of the image positions is performed. The results show that the image surface is spherical when the object distance is much larger than the focal length. But it is aspheric when the object distance is comparable to the focal length. Finally, a mono-centric lens is optimumly designed, with a visible working wavelength band of 480-640nm, a focal length of 100mm, a wide FOV of 140°, and a large f-number of 5. Through imaging simulation and the image performance evaluation with ZEMAX, the theoretical calculations are verified.

The main challenge and limitation of combustion diagnosis technique lies in the volumetric/spatial resolution. Frequently reported technique widely use laser bean scanning to get inner knowledge of combustion, however due to the line-of-sight nature, spatial resolution along the “path” is lacked. With the ability of 3-D tomography detection, CTC technique (computed tomography of chemiluminescence) shows advantage over other techniques; but not yet widely used in combustion science study. In CTC measurement, “dense projection” is required to make satisfying tomography reconstruction, but this is practically hard to meet for high cost and spatial limitation. At sparse projection conditions, tomography reconstruction is distorted with the appearance of geometric blur. The reason of occurrence of blur is analyzed in this paper, and an improved method for tomography reconstruction is proposed. Test results show that blur distortion could be effectively eliminated using the improved method at sparse projection conditions. Other factors and constraints that have influence on flame tomography measurement are discussed in this paper, and quantitative evaluations were made through tests.

The bionic polarization navigation sensor has important research and application value in the field of modern navigation. In this study, a new algorithm for calculating the solar meridian azimuth from imaging polarization navigation sensors is proposed. By analyzing the sky polarization distribution model,there is only one line with a polarization angle of 90° in the projection plane of the sensor, and the zenith point of the sky must be on this line, with which a novel method for extracting the solar meridian in the two-dimensional projection plane is proposed. A polarization measurement model is built based on the Stokes vector method. Gaussian smoothing filtering is performed on the polarization angle image to conduct image noise suppression. The preliminary positioning of the solar meridian is solved by a dual-threshold recursive method.Then, the accuracy of the meridian detection is promoted to the sub-pixel level by interpolation to detect the exact pixel points on the solar meridian. Finally, the least-squares fitting of the precisely positioned pixels are utilized to obtain an accurate azimuth angle.An outdoor verification experiment is carried out with an imaging bionic polarization navigation sensor with a high-precision turntable system.The experimental results show that the static repeatability measurement accuracy of the algorithm is 0.0554° (σ) . The dynamic maximum error is less than 0.95° . This indicates the effectiveness and feasibility of the direction angle calculation method. The method can provide accurate and no cumulative error heading information for the movement of the carrier and provides important technical support for the field of navigation.

Time-division-detected fiber-optic Mueller OCT system was developed for radiumdium. In this system, Mueller matrix was used to measure the polarization characteristics of the anisotropic scattering medium. There are four optical channels for different polarization types in reference arm: horizontal , vertical , 45° linearly polarized , and circular polarization. Meanwhile the sample arm uses rotary wave plate to achieve the four polarizations of light. The optical switches are used to select different channels in the reference arm, and the polarized light of each channel interfere with the polarized light backscattering from the sample. Therefore, the sixteen OCT images from different polarization were obtained to calculate Mueller matrix of sample. Finally, this OCT system was applied for quantitatively characterize isolated pig myocardium structure.

In the present of microscopic imaging technology, both the large imaging field of view (FOV), and high-resolution are required. The Fourier ptychographic microscopy (FPM) does not need to move the sample and can keep the original FOV unchanged. It can expand the frequency bandwidth and reconstruct high-resolution intensity and phase images by using the angle diversity and synthetic aperture. It has a very important application prospect in the field of biomedical detection. However, the LED, used as the illumination source in the FPM, is an extended light source, and the light emitting unit with a certain size will cause the image blurring. Therefore, a reconstruction algorithm based on Lucy-Richardson (L-R) deconvolution is proposed in this paper. The experimental results show that the proposed algorithm can solve the problem of image blurring in FPM imaging and improve the imaging quality.

When performing Three-dimension (3D) measurements with phase-shifting method, usually a digital projector, or a translation stage is used to generate phase-shifted fringe patterns. However, in these cases, errors like gamma distortion, lens distortion and random errors caused by mechanisms are inevitable. In order to reduce the effect caused by system errors, simplify calibration procedures as well as further minimizing, in this paper, phase-shifted fringes are generated by linear LED arrays and a Ronchi grating. Phase-shifting will be performed by switching one linear LED array to another. The advanced iteration algorithm which do not require the phase-shifting amount to be known and unified is employed to minimize the calculation error caused by un-unified phase-shifting amount, since the phase-shifting amount produced by this method depends on the distance to the grating plane, which could not be exact 2π/3. Experiment results suggest that the system has a measurement error less than 0.05mm at the working distance of 130mm.

The conventional method of alignment for the laser launching system is complicated and low precision, because the system contains several optical channels and interlaced dimensions. In the high-energy laser launching system, the laser has the very high energy and abnormal wavelength in addition. That is, the alignment method is limited to cases of human safety due to the personnel involved and the higher accuracy for the lager multipler. In this paper, we prose a new method based on the auto-collimation method to solve the questions of human safety and high accuracy. In this method, we built a novel optical model used assistant optical path. To verify this method, simulations and experiment are performed. In the end, the precision impression and error compound of the laser launching system are analyzed and compared. The analysis results show that the aiming precision can reach 10” without human in the light path, which is only 1’ when using the conventional method.

In this paper, the three-dimensional measurement technology of structured light is combined with high-speed photography to measure and reconstruct the surface deformation of aluminum alloy target under the condition of light gas gun loading. The test designed a structured light projection system based on the Kohler illumination structure, and adopted a self-developed high-speed photoelectric camera to receive the deformed fringe image. A 100ns magnitude time-resolved three-dimensional surface measurement of the deformation of the target during the process of the light gas gun pushing the projectile into the target plate is realized. By comparing the results of 3D surface reconstruction with numerical simulation results, the reliability of the proposed method for 3D measurement under high speed impact conditions is verified.

A novel approach to improve signal-to-noise (SNR) of full-waveform LiDAR based on differential optical path is proposed. Two avalanche photodiodes are placed on the before and after the focus of a focusing lens to detect backscattered full - waveform signal (BFWS) respectively. The two BFWSs are sent to a subtraction circuit to suppress background noise. The mathematical model of the differential BFWS is developed. A prototype is built and the effectiveness of the proposed approach has been validated by experiments. The results show that comparing with the traditional method, the proposed method can improve SNR, which verifies the validity of the proposed method.

The most widely used fingerprint recognition technology is to extract the texture information and features of the skin fingerprint, and then use the algorithm to match and identify, and finally confirm the identity. However, when there are dirt and water stains on the fingerprint of the skin, or when the fingerprint skin is worn or even peeled off, the generation of these factors will bring difficulties to the identification system. In this study, optical coherence tomography (OCT) was used to obtain the three-dimensional structure of the finger fingerprint, and the three-dimensional structure inside the fingerprint was identified. The three-dimensional structure image of the fingerprint obtained by the OCT system can not only observe the fingerprint skin information, but also acquire the image information of the internal structure of the fingerprint. Taking the acquired three-dimensional structure image of fingerprint as the research object, a three-dimensional convolutional neural network model is constructed based on the theory of deep learning, and the features of image data is extracted and trained to achieve the purpose of recognition.

With the development of robotics technology, people are gradually inclined to study robots that can imitate human specific behavior, such as writing and drawing robots. At present, there is less research on drawing robots, and the method has certain limitations. This paper designs and completes an innovative drawing method: spiral line method, that is, the method of spiral line superimposing sinusoidal curve to draw. And it is named I-Circle. Compared with the traditional methods, it has the advantages of simple control and strong expressiveness. This work chooses two-dimensional translation platform as hardware system, uses MATLAB to process image and generate path, and uses path coordinate points to generate G code. Then the code is sent to the lower computer through serial port, which controls the two-dimensional translation platform, makes the pen draw automatically on paper, and designs GUI interface, so that the operation process is simple and easy. Through the experiment, we succeeded in drawing pictures, which proved its feasibility. This work can also be expanded, such as replacing the penholder with a micro-drill for sculpture. Similarly, it can be made into cake mounting machine, coffee drawing machine and so on. It can also lay out a drawing robot in a specific place to create drawings on the spot, which can be participated by users, or make the drawing method into software. It has broad application prospects.

The method adopts the technique of information-processing to retrieve phase-information of light-ray, while it hat had been omitted after imaging. Phase is the information to develop spatial-information for virtualization and stereopsis. A way to mend the gap between Geometrical-Optics and Physical-Optics that is to welcome 5G ICT with mirroring-real-world, a virtual-space for displaying together with formulated phase-information, and also allowing full extent of AI processing inside.

The field of view (FOV) has always been a key indicator to measure the quality of the near-eye display (NED) system. How to expand the field of view of the system without reducing other system metrics has always been a key issue in the development of near-eye display systems. In recent years, with the booming development of process technology there have been various schemes for expanding the display field of view of near-eye display systems, including grating partitioning, grating layering, using curved or free-form surfaces optical structure, and others. Each method of expanding the field of view has its applicable conditions, for example grating partitioning and grating layering are suitable for use in a waveguide display system using a grating as a coupled input and output. While the free-form surface component as a light guiding structure not only can be used for the coupled input and output component of the waveguide display system, but also can directly replace the slab waveguide as the main optical path of the near-eye display system. This talk will systematically analyze the technical principles and features of the above methods, and prospect for the future development of each method. In addition, some near-eye display systems with large fields of view will be presented as examples to more fully demonstrate the technical principle and features. Furthermore, analysis and outlook across the NED system is included.

Spectroscopic measurement of methane gas concentrations using absorption lines in the near infra-red (the 1.67 μm region) has been demonstrated by several research teams. In this paper, a methane telemetry system based on tunable diode laser absorption spectroscopy (TDLAS) is proposed and demonstrated. The center wavelength of the laser is locked to the methane absorption peak and the second harmonic detection technology is used to realize the real time monitoring of the methane gas concentration. To receive more signal light and enhance the signal to noise ratio, a lens and its focal length, the spot size of the reflecting surface and a filter plate are used to optimizing the optical path. The experimental results show that after optimizing methane telemetry system the minimum detection limit can be enhance from 20000 ppm to 5000 ppm in the distance of 20 meters.

The atomic force microscopy (AFM) was proposed to characterize the surfaces of various materials with high sensitivity and resolution(sub-nanometer) since 1980s, but it intrinsically lacks amongst others chemical sensitivity. These limitations of AFM can be overcome by coupling with optical microscope, which allows to obtain more comprehensive characterization data by in-situ measurement. To integrate the AFM into the upright optical microscope easily, this paper proposed a novel design of AFM. The corresponding Raman-AFM system was developed which adopts the sample scanning structure with a self-developed ultra-thin AFM head. The AFM head employs an innovative multi-reflected laser beam to detect the deformation of the cantilever, which greatly reduces the Z-direction thickness of the head, making its Z-direction thickness smaller than the working distance of the objective lens. Therefore, the AFM probe can be directly mounted under the objective lens of the upright optical microscope without changing the existing optical path. To evaluate the performance of the proposed AFM system, a standard grid was imaged using the Raman-AFM system. Then, a sample of two-dimensional material, black phosphorus(BP)/molybdenum disulfide(MoS2) heterojunction, was characterized. The physicochemical information of the heterojunction was obtained by in-situ measurement of the surface topography and Raman spectra.

In recent years, because of its safety and effectiveness, photothermal therapy has also become an important way to treat malignant tumors. However, due to the photothermal conversion effect, the heat deposited in the lesion area will spread to other parts of the biological tissue in the way of heat conduction in the treatment process, which is likely to cause some damage to other normal tissues. Optical coherence tomography (OCT) can reconstruct internal high-resolution images to observe the extent of tissue injury. The image of tissue damage structure obtained by OCT system can observe not only the external damage of tissue, but also the internal damage of tissue. The OCT images of damage tissue are taken as the research object, and a semantic segmentation model of deep learning was constructed to separate and visualize the damage tissue, which can help to accurately identify the damage range quickly.

Laser imaging radar is the combination of four technologies, laser, radar, optical scanning control, and high-speed computer processing. It is extensively used in both military and civilian applications. Non-scanning imaging radar, which works without a scanning device, is characterized by high frame rate, wide field of view, and high reliability and has become the focus of research in recent years. The objective of this study is to firstly, elaborate the structure of non-scanning imaging laser radar and basic principle of plane array ranging. Next, it focuses on the latest developments in the non-scanning laser 3D imaging radar systems. Thereafter, it categorizes and summarizes various non-scanning laser 3D imaging radar systems, such as flash, polarization modulation, and gain modulation. From the comprehensive coverage of these systems presented in this study, it can be inferred that the laser 3D imaging has the advantages of high resolution, high energy utilization, and high signal-to-noise ratio. In addition, a discussion of their disadvantages is presented. Finally, this study concludes with some challenges and possible future research directions in this field.

Near-eye display, also known as head-mounted display, has emerged as a vital approach to give humans virtual images since its invention dating back to the last century. However,the typically poor performance impose limitations in the on-demand applications of near-eye display. In particular, for the ultimate realization of commercial near-eye display, it is necessary to provide an ultra-wide field of view (FOV), obvious depth cues and a compact form factor with acceptable weight. In recent years, various display methods have been proposed as potential solutions to these problems. Freeform surface elements can be a suitable way for the achievement of not only an impressive field of view but also an improved and lightened image, but its weight and volume can hardly be wearable. Potential solutions include but are not limited to:inserting reflective mirrors into the system, replacing the spherical lens group with a wedge-shaped freeform prism and applying gradient index lenses. Depth cues can be fulfilled by retinal projection, multi-focal, holographic displays and so on. Each of these technologies has unique disadvantages. For instance, it is most challenging to develop full-color,high-resolution holographic displays with acceptable price and FOV. Metasurface may be the possible solution.Multi-focal and vary-focal plane displays often comes at the cost of both time multiplexing and large data bandwidth. Retinal projection gives observer clear images with no relation to distance, however, the propagating light must pass through center of pupil. Here, we investigate recent developments in near-eye display, systematically classify vital problems in near-eye display systems and analyze technical principle of solutions to them. Meanwhile, prospect for the future development of each technology will be proposed.

In this paper, we provide a high-speed large-field DIC imaging method and corresponding system with sufficient scanning efficiency for real industry, which makes it applicable for in-line surface scratch detection of cellphone panel. The work mainly involves: 1. basic principles of traditional DIC methods and the line-scan improving scheme for high-speed large-field imaging: 2. key techniques of system integration such as motion control and data synchronized acquisition.

The 3D shape measurement technology based on structured-light with a single camera has many advantageous aspects on usability, such as non-contact, high precision, high speed etc. There are various kinds of software accepting its measurement results readily. That is why it has been widely used in reality. System calibration is the key step before it begins normal scanning, and the setting of parameters in calibration directly affects the accuracy of the measurement. Some problems exist in the process of its calibration, such as the process is complicated and hard to operate, always taking low accuracy for the scanning result. This paper aims to find methods to solve the problems. The 3D scanning system used in the research is composed of a Canada-made Point Grey CMOS industrial camera (FL3-U3-13Y3M-C) with a China-made lens, a Texas instrument projector DLP LightCrafter 4500 EVM.

The parameters that can be set in the process of system calibration are discussed in the paper, and the scanning results with parameter change are evaluated based on the indicators of camera and projector’s reprojection error, scanning resolution and point cloud’s uniformity. The research concludes that the distance between the projector and the calibration board is a key factor needs to be controlled. It can be set up properly based on the indicators for the quality of scanned data, which improves the speed of system calibration and keep the collected point cloud data more stable.

At present, the problem of population aging has become a hot spot of international concern, especially in China, and the international community urgently needs a universally applicable health care system for the elderly. Recent research shows that falling is the biggest threat to the health of the elderly. Based on thihe physiological and behavioral characteristics of the elderly, the paper discusses an algorithm for the recognition of motion state and fall detection of elderly applied to wearable devices to ensure timely rescue after a fall. The algorithm continuously acquires acceleration information during the movement of the elderly through a six-axis acceleration sensor. Firstly, the acceleration data is filtered, then the combined acceleration is calculated, and multiple features of the continuous data are extracted, and then the softmax method is used to classify the different motion states to realize the alarm of the fall. The algorithm extracts the feature vector by the magnitude of the combined acceleration, which solves the problem that the single acceleration in the traditional algorithm must solves the coordinate axis, which may waste much calculating time. The algorithm is validated by using the existing data set, and the accuracy of the algorithm is up to 89%. It is an effective way to detect falls.

Computer-generated hologram (CGH) method is a high-precision aspherical surface detection method. CGH produces wavefronts of any shape with extremely high precision and is adopted in null test. Liquid crystal CGH (LC-CGH) is a new type of CGH with short production cycle and low cost. It is a promising alternative to traditional CGH. In this paper, the overall process flow of LC grating preparation is presented. The influences of three process parameters, such as LC solution concentration, spin coating speed and time on the three physical quantities of LC grating diffraction efficiency, LC polymer film thickness and phase delay are studied. Based on the analysis, improvement measures are proposed for the preparation process. The research carried out in this paper has guiding significance for the processing and manufacturing of LC-CGH.

Metrological AFM (mAFM) has high-resolution three-dimensional measurement capability, and its measurement results can be traced back to the SI. Most of mAFMs utilize the optical beam deflection (OBD) method to detect the deflection of cantilever probe, which has simple structure and high sensitivity. A novel 3D traceable OBD system was designed based on the flatbed scanner. In the design, the propagation direction of the laser beam can always be parallel to the motion direction of the scanner so that the relative positions of the laser focal spot and the cantilever probe remain unchanged in any scanning range. All the scanners in the X, Y, Z directions are connected in series, and their motion directions are strictly orthogonal without mutual coupling. The application of the compensation scanner achieves the synchronous movement of the aspherical lens and the Z-direction scanner, which avoids the defocusing phenomenon of the cantilever probe during the large-stroke scanning with the Z-direction scanner. A series of experiments were performed to evaluate the proposed design, including the measurement of the laser tracking errors caused by the scanner motion and imaging results of a standard grid under contact mode. The results demonstrated the imaging capabilities of this system.

Graphene metamaterials have been theoretically demonstrated as an enabler for applications as perfect absorbers, photodetectors, directional light emitters, electro-absorption modulators, and tunable spintronic devices. We demonstrate the experimental realization of phototunable graphene metamaterials on diverse substrates by a scalable, transfer-free solution-phase deposition method. The optical properties of the metamaterials are tuned by controllable laser-mediated conversion of the graphene oxide layers into their graphene counterparts. We demonstrate the fabrication of functional photonic devices with the laser printing process, such as ultrathin flat lenses, perfect absorbers, selective photo absorber, colorful display, and devices integrated with semiconductor waveguide structures.

To implement Real-time segmentation for polarization-modulated 3D imaging system, an efficient segmentation method for multi-dimensional information fusion is proposed in this paper. Conventional 3D imaging Lidar systems use an avalanche photodiode (APD) array detector to measure time-of-flight of each pixel in the scene. Here we propose and experimentally demonstrate a super-resolution 3D imaging framework based on a new imaging sensor EMCCD (Electron Multiplying Charge Coupled Device). Due to its low bandwidth characteristics, the electro-optic modulators are applied to implement temporal (range) resolution, and meanwhile act as a fast shutter with sub-nanosecond-level. Consequently, range-gated 3D imaging can be achieved to improve the signal-to-noise ratio (SNR) performance in our framework. With dual EMCCDs structure, the depth map and intensity image can be reconstructed from adding the two modulated images. The iterative threshold algorithm method is applied to the target segmentation of high-resolution images, and image morphological erosion algorithm are used to improve the segmentation accuracy. The target’s pixel coordinate position obtained by image segmentation is mapped to 3D point cloud data to get the segmented target point cloud data. Experimental results show that the system can achieve high-precision flash imaging. Meanwhile, the segmentation method has a great improvement in time efficiency compared with traditional clustering algorithm, and can reduce the under-segmentation error rate. Ultimately, we found that the imaging method showed outstanding performance on high-precision imaging with an error less than 0.1m in a wide field-of-view of 0.9mrad. And the segmentation of target takes only 560ms.

Publisher’s Note: This paper, originally published on 12 March 2020 was replaced with a corrected/revised version on 10 April 2020. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance.