Simple Optical System Research Articles

Configurable multiple virtual lenses conjugated with singlet physical lens for achromatic extended depth-of-field imaging.

An achromatic extended depth-of-field (EDOF) system can obtain clear scene information that is crucial for target recognition, dynamic monitoring, and other applications. However, the imaging performance of most optical systems is depth-variant and wavelength-variant, which leads to the generation of chromatic aberrations. Traditional optical design and image post-processing algorithms cannot effectively eliminate these chromatic aberrations. Here, we propose a deep configurable multiple virtual lenses optimization method that embeds four virtual lenses in parallel conjugated with a real lens. Combined with a lens fusion recovery network (LFRNet), it compensates for chromatic aberrations at different depths to achieve achromatic EDOF imaging. Trainable virtual optics can eliminate chromatic aberrations and overcome the limitations of traditional optics. The proposed framework reduces the optical design complexity and improves the imaging quality of a simple optical system. We validate our method using a singlet lens, and the experimental results show that the reconstructed images have an average peak signal-to-noise ratio (PSNR) improvement of 12.1447 dB and an average structural similarity index measure (SSIM) improvement of 0.2465. The proposed method opens a new avenue for ultra-compact, high-freedom, high-efficiency, and wholly configurable deep optics design, and empowers various advanced applications, such as portable photography and other complex vision tasks.

Real-time data processing in colorimetry camera-based single-molecule localization microscopy via CPU-GPU-FPGA heterogeneous computation.

Because conventional low-light cameras used in single-molecule localization microscopy (SMLM) do not have the ability to distinguish colors, it is often necessary to employ a dedicated optical system and/or a complicated image analysis procedure to realize multi-color SMLM. Recently, researchers explored the potential of a new kind of low-light camera called colorimetry camera as an alternative detector in multi-color SMLM, and achieved two-color SMLM under a simple optical system, with a comparable cross-talk to the best reported values. However, extracting images from all color channels is a necessary but lengthy process in colorimetry camera-based SMLM (called CC-STORM), because this process requires the sequential traversal of a massive number of pixels. By taking advantage of the parallelism and pipeline characteristics of FPGA, in this paper, we report an updated multi-color SMLM method called HCC-STORM, which integrated the data processing tasks in CC-STORM into a home-built CPU-GPU-FPGA heterogeneous computing platform. We show that, without scarifying the original performance of CC-STORM, the execution speed of HCC-STORM was increased by approximately three times. Actually, in HCC-STORM, the total data processing time for each raw image with 1024 × 1024 pixels was 26.9 ms. This improvement enabled real-time data processing for a field of view of 1024 × 1024 pixels and an exposure time of 30 ms (a typical exposure time in CC-STORM). Furthermore, to reduce the difficulty of deploying algorithms into the heterogeneous computing platform, we also report the necessary interfaces for four commonly used high-level programming languages, including C/C++, Python, Java, and Matlab. This study not only pushes forward the mature of CC-STORM, but also presents a powerful computing platform for tasks with heavy computation load.

Surface plasmon resonance microscopy for optical EHL measurement systems

This study investigates the suitability and limitations of surface plasmon resonance (SPR) microscopy for optical elastohydrodynamic lubrication (EHL) measurement systems. SPR microscopy developed in this study can quantify the lubricant density distribution in contact region with high spatial-temporal resolution using simple total reflection optical systems. It means that, if either the temperature or pressure distribution can be estimated, the other can be calculated. To examine the practicalities, we determined specific optical setting conditions such as the incident angle and thickness of each film layer for surface plasmon excitations under EHL conditions based on numerical calculations and demonstration experiments.

Curriculum learning for ab initio deep learned refractive optics

Deep optical optimization has recently emerged as a new paradigm for designing computational imaging systems using only the output image as the objective. However, it has been limited to either simple optical systems consisting of a single element such as a diffractive optical element or metalens, or the fine-tuning of compound lenses from good initial designs. Here we present a DeepLens design method based on curriculum learning, which is able to learn optical designs of compound lenses ab initio from randomly initialized surfaces without human intervention, therefore overcoming the need for a good initial design. We demonstrate the effectiveness of our approach by fully automatically designing both classical imaging lenses and a large field-of-view extended depth-of-field computational lens in a cellphone-style form factor, with highly aspheric surfaces and a short back focal length.

Analysis of the zoom system of a microscope condenser and its modification using variable focus lenses

A detailed theoretical analysis and optimization of the classical three-element zoom (pancratic) microscope condenser according to a patent from the 1930s [Reichspatentamt Nr. 713188 (29 10 1936)] is performed and formulas are derived for calculating basic parameters and the displacement of lenses during zooming. Furthermore, the modification of the classical zoom microscope condenser is investigated using a simpler optical system of two lenses with variable focal lengths and fixed positions. The relations for the calculation of the focal lengths of both variable focus lenses and the basic parameters of the zoom system have been described. The proposed two-element zoom system consisting of a system of two lenses with variable focal lengths maintains a constant distance between the object and image planes and fixed position of both lenses during zooming. The basic parameters and third-order aberration coefficients of such a system are calculated using an example.

Colorimetric Sensor Array for Simultaneous Assay of Catecholamine Neurotransmitters Using Various-Sized Citrate-Capped Gold Nanoparticles

Driven by the need to in situ monitoring of the endogenous substances in biological matrices, a simple, rapid and sensitive optical nanoarray system has been designed for determination and visual discrimination of four important catecholamine neurotransmitters: dopamine (DA), epinephrine (EP), norepinephrine (NE) and levodopa (LD). To fabricate this platform, spherical citrate-capped gold nanoparticles (AuNPs) in the size range of 13–42 nm have been employed as sensing elements. For each catecholamine different responses toward the AuNPs was obtained indicating unique aggregation kinetics. When the sensor array exposed to different catecholamines (CAs), both the color and UV–Vis absorbance spectra changed due to the interaction of analytes and AuNPs, creating a unique fingerprint-like pattern for each analyte which can be visually detected by naked eye. To analyze response profiles, we employed unsupervised chemometric algorithms including hierarchical cluster analysis (HCA) and principal component analysis (PCA) and satisfactory class separations were achieved. Furthermore, the sensitive RGB based color difference patterns were generated providing easily monitored visual output. Based on this sensor array, the set of four catecholamine neurotransmitters have been correctly identified and classified in the spiked real urine samples. The target analytes have been well distinguished at low concentrations of 0.3 − 4 μM DA, 0.8 − 10 μM EP, 0.8 − 8 μM NE, and 0.3 − 10 μM LD using the proposed “chemical nose” strategy. We believe that the established optical sensor array can be potentially employed as an efficient discrimination tool for diagnostic and therapeutic applications in the future.

Aberration pre-correction for a simple optical system of HMDs.

Head-mounted displays (HMDs) are becoming increasingly popular as a crucial component of virtual reality (VR). However, contemporary HMDs enforce a simple optical structure due to their constrained form factor, which impedes the use of multiple lens elements that can reduce aberrations in general. As a result, they introduce severe aberrations and imperfections in optical imagery, causing visual fatigue and degrading the immersive experience of being present in VR. To address this issue without modifying the hardware system, we present a novel, to the best of our knowledge, software-driven approach that compensates for the aberrations in HMDs in real time. Our approach involves pre-correction that deconvolves an input image to minimize the difference between its after-lens image and the ideal image. We characterize the specific wavefront aberration and point spread function (PSF) of the optical system using Zernike polynomials. To achieve higher computational efficiency, we improve the conventional deconvolution based on hyper-Laplacian prior by adopting a regularization constraint term based on L2 optimization and the input-image gradient. Furthermore, we implement our solution entirely on a graphics processing unit (GPU) to ensure constant and scalable real-time performance for interactive VR. Our experiments evaluating our algorithm demonstrate that our solution can reliably reduce the aberration of the after-lens images in real time.

Telephoto achromatic camera based on optical–digital co-design

Due to the difficulty of correcting chromatic aberration (CA) in telephoto cameras, recent studies have combined image algorithms with simple optical structures, such as single-spherical lenses, for high-quality photography, moving away from complex optics. However, this approach often struggles to comprehensively address compounded issues arising from optical aberrations of simple optical systems, including defocus blur and multi-channel misalignment. To tackle this challenge, this manuscript presents an approach for developing a telephoto imaging system by leveraging the distinct characteristics of axial and lateral chromatic aberrations (ACA, LCA) over the visible spectrum. The optical design is limited to a specific wavelength range to preserve high-frequency information of the green channel. A cross-channel fitting method is presented to suppress the LCA. Subsequently, the powerful capabilities of deep learning are utilized to correct ACA, defocus blur, and other residual optical aberrations. Simulation experiments demonstrate the effectiveness of the proposed approach in mitigating the CA inherent in telephoto systems, thereby delivering high-quality imaging results over the whole visible waveband.

Probing exciton dynamics with spectral selectivity through the use of quantum entangled photons.

Quantum light is increasingly recognized as a promising resource for developing optical measurement techniques. Particular attention has been paid to enhancing the precision of the measurements beyond classical techniques by using nonclassical correlations between quantum entangled photons. Recent advances in the quantum optics technology have made it possible to manipulate spectral and temporal properties of entangled photons, and photon correlations can facilitate the extraction of matter information with relatively simple optical systems compared to conventional schemes. In these respects, the applications of entangled photons to time-resolved spectroscopy can open new avenues for unambiguously extracting information on dynamical processes in complex molecular and materials systems. Here, we propose time-resolved spectroscopy in which specific signal contributions are selectively enhanced by harnessing nonclassical correlations of entangled photons. The entanglement time characterizes the mutual delay between an entangled twin and determines the spectral distribution of photon correlations. The entanglement time plays a dual role as the knob for controlling the accessible time region of dynamical processes and the degrees of spectral selectivity. In this sense, the role of the entanglement time is substantially equivalent to the temporal width of the classical laser pulse. The results demonstrate that the application of quantum entangled photons to time-resolved spectroscopy leads to monitoring dynamical processes in complex molecular and materials systems by selectively extracting desired signal contributions from congested spectra. We anticipate that more elaborately engineered photon states would broaden the availability of quantum light spectroscopy.

Improving the two-step two-frequency upconversion luminescence of Er3+ in 70TeO2–20ZnO–10GeO2 glass ceramic by doping CaF2

The investigation of efficiency enhancement in TSTF UCL materials through near-infrared (NIR) light excitation has important implications for volumetric three-dimensional (3D) imaging. Here, we developed the TSTF UCL process of the tellurite glass 70TeO2–20ZnO–10GeO2 doped with Er3+ and CaF2. Under dual-mode excitation with 1550 nm and 850 nm NIR lasers, a strong photon-excited synergistic effect was exhibited in these glass ceramics. Through the UCL spectra analysis, it can be found that CaF2 plays an important role in improving UCL intensity. The optimized glass ceramics are selected and a simple optical display system is designed to achieve a good 3D volumetric imaging effect. Moreover, we levitate the 3D image in the air using a levitation display technology, which can be utilized to display and distinguish objects in medicine, military, or commercial applications. Such an improving TSTF UCL intensity strategy by doping fluoride nanocrystals is generally applicable for many other glass ceramics.

Low-cost and simple optical system based onwavefront coding and deep learning.

With the development of computational imaging, the integration of optical system design and digital algorithms has made more imaging tasks easier to perform. Wavefront coding (WFC) is a typical computational imaging technique that is used to address the constraints of optical aperture and depth of field. In this paper, we demonstrated a low-cost and simple optical system based on WFC and deep learning. We constructed an optimized encoding method for the phase plate under the framework of deep learning, which reduces the requirement for aberration correction in the full field of view. Optical coding was achieved with just a double-bonded lens and a simple cubic phase mask, and digital decoding used the deep residual UNet++ network framework. The final image obtained has good resolution, whereas the depth of field of the system expanded by a factor of 13, which is of great significance for the high-precision inspection and attaching of small parts of machine vision.

A Resonant-Type Thin Plate Piezoelectric Actuator Inspired by Koala's Locomotion

Imitating the behavioral traits or structures of biological organisms can provide new ideas and operating principles for designing micro actuators. Inspired by the locomotion of koalas, a lightweight self-locomotion piezoelectric actuator (SLPA) is developed. Based on the hybrid of the longitudinal and bending vibration modes, the proposed SLPA is able to obtain linear locomotion. The configuration of the SLPA is designed based on a thin metal plate with miniature size of 19.5×19.5×1.1mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> . The operating principle is verified through the finite element analysis (FEA) simulation. The experimental results show that the prototype achieves maximum speed of 61.68 mm/s and slope angle of 20° when the excitation frequency and voltage are 19.75 kHz and 50 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p-p</sub> , which demonstrates the validity of the proposed SLPA climbing on slopes and the effectiveness of the proposed operating principle. Furthermore, the step displacement resolution of 2.2 μm is obtained by the proposed SLPA under the resonant working state. Finally, a simple optical focusing system is established to verify the feasibility of potential application of micro piezoelectric actuator.

Quasi-analytic solution for real-time multi-exposure speckle imaging of tissue perfusion.

Laser speckle contrast imaging (LSCI) is a widefield imaging technique that enables high spatiotemporal resolution measurement of blood flow. Laser coherence, optical aberrations, and static scattering effects restrict LSCI to relative and qualitative measurements. Multi-exposure speckle imaging (MESI) is a quantitative extension of LSCI that accounts for these factors but has been limited to post-acquisition analysis due to long data processing times. Here we propose and test a real-time quasi-analytic solution to fitting MESI data, using both simulated and real-world data from a mouse model of photothrombotic stroke. This rapid estimation of multi-exposure imaging (REMI) enables processing of full-frame MESI images at up to 8 Hz with negligible errors relative to time-intensive least-squares methods. REMI opens the door to real-time, quantitative measures of perfusion change using simple optical systems.

Narrowband and Broadband Dual‐Mode Perovskite Photodetector for RGB Detection Application

AbstractWavelength‐selective light detection is becoming more and more prevalent as new sectors emerge, such as imaging, wearable electronic devices, the Internet of Things, machine vision, and biosensing. Traditional narrowband RGB detection necessitates several separate devices for different colors by changing the active layer materials or applying color filters ahead of the broadband detector, which increases the architectural complexity and limits the quality of color sensing. Here, this work devises a novel dual‐mode perovskite photodetector with both narrowband and broadband light sensing based on the imbalance transportation of carriers in the perovskite: Rhodamine B (RhB) active layer. In Mode 1, under light illumination from ITO, a narrowband response in 600–700 nm is obtained with a specific detectivity (D*) of 6.7 × 1011Jones, responsivity (R) of 7.6 mA W−1, and a full‐width at half‐maximum (FWHM) of 80 nm. In Mode 2, under light illumination from Ag, the visible broadband response of 400–700 nm is achieved with a D* of 1012Jones and R over 80 mA W−1. Furtherly, by designing a simple optical system and signal processing, RGB light signals are detected independently and panchromatic image sensing and rebuilding are realized. This work will give inspiration to architecture design for multi‐band integrated photodetectors.

Object Detection through Fires Using Violet Illumination Coupled with Deep Learning

Fire accidents threaten public safety. One of the greatest challenges during fire rescue is that firefighters need to find objects as quickly as possible in an environment with strong flame luminosity and dense smoke. This paper reports an optical method, called violet illumination, coupled with deep learning, to significantly increase the effectiveness in searching for and identifying rescue targets during a fire. With a relatively simple optical system, broadband flame luminosity can be spectrally filtered out from the scattering signal of the object. The application of deep learning algorithms can further and significantly enhance the effectiveness of object search and identification. The work shows that this novel optics–deep learning combined method can improve the object identification accuracy from 7.0% with the naked eye to 83.1%. A processing speed of 10 frames per second can also be achieved on a single CPU. These results indicate that the optical method coupled with machine learning algorithms can potentially be a very useful technique for object searching in fire rescue, especially considering the emergence of low-cost, powerful, compact violet light sources and the rapid development of machine learning methods. Potential designs for practical systems are also discussed.

Design and Performance Analysis of Simple WDM Optical Fiber Communication System

WDM (wavelength division multiplexing) is used in this project to simultaneously send data over several channels at high speed. Single mode fiber is favored over Multimode fiber for long-distance communication. As data rate and optical fiber length grow, the quality factor falls. Dispersion effects on an 8-channel dense WDM system at a high data rate will be examined using the Optisystem 10 simulator. A dispersion compensation fiber (DCF) and an Erbium doped fiber amplifier (EDFA) are used to compensate for the dispersion and attenuation in the transmitted optical signal, respectively. Bit error rate (BER) and eye diagram analyzers were used to evaluate the optical communication system's performance.

The endpoint detection method using moiré pattern in CMP’s EPD system

We have developed a technique for observing fine wiring patterns using moiré patterns generated by interference between wiring patterns and reference patterns in endpoint detection (EPD) of the CMP. With this technique, wiring pattern images of patterned wafers can be evaluated with a simple and low magnification optical system to observe large moiré patterns. In this process, the large moiré pattern is calculated from the device wiring and other reference pattern layouts. As a result, EPD signals can be detected.

A combination interferometric and morphological image processing approach to rapid quality assessment of additively manufactured cellular truss core components

Advanced manufacturing (AM) processes such as laser powder bed fusion (LPBF) are increasingly capable of fabricating components with useful and unprecedented mechanical properties by incorporating complex internal bracing structures. From the standpoint of quality control and assessment, however, internally complex assemblies present significant build-verification challenges. Here we propose a hybrid approach to the inspection involving the application of computer-aided speckle interferometry (CASI) and morphological image processing as a rapid, inexpensive, and facile method for AM quality control. The described methodology has low capital equipment costs, is full-field and non-contact, can be used in an industrial setting, and has very low requirements in terms of operator training and expertise. Consisting primarily of the combination of image processing software with a simple optical system of variable sensitivity, the method is shown to be effective for inspection of a titanium honeycomb component subjected to differential pressure. Results are compared to those achieved with computed tomography (CT), immersion ultrasound testing (UT), and optical holographic interferometry. Lastly, we propose several possible processing strategies for automated quality assessment based on this powerful hybrid approach.

Sensing Algorithm to Estimate Slight Displacement and Posture Change of Target from Monocular Images.

Various types of displacement sensors, which measure position changes of object, have been developed depending on the type and shape of the object under measurement, measurement range of the amount of displacement, required accuracy, and application. We are developing a new type of displacement sensor that is image-based, capable of measuring changes in 6DOF (3D position and orientation) of an object simultaneously, and is compact and low-cost. This displacement sensor measures the 6DOF of an object using images obtained by a monocular vision system. To confirm the usefulness of the proposed method, experimental measurements were conducted using a simple and inexpensive optical system. In this experiment, we were able to accurately measure changes of about 0.25 mm in displacement and 0.1 deg in inclination of the object at a distance of a few centimeters, and thus confirming the usefulness of the proposed method.

CIAO: An on-the-shelf adaptive optics system for astronomers

Since 1990, adaptive optics are used in astronomy to remove the effects of atmospheric turbulence, and then retrieve diffraction-limited images, even in bad seeing conditions. Thanks to its strong knowledge in Shack-Hartmann wavefront sensing and deformable mirror, Imagine Optic has developed a simple and affordable adaptive optics system for astronomers. We present the current prototype as well as first experimental results on both natural stars and extended sources, with the main goal of allowing an effective correction in all sky conditions regardless of the object.