Chlorophyll fluorescence (ChlF) is an important signature of photosynthesis to evaluate plant response to the environment. We explored an approach to estimate an important leaf ChlF-derived parameter, the intrinsic efficiency of photosystem II photochemistry (Fv/Fm), using spectral indices calculated from leaf reflectance measured by a hyperspectral radiometer. It is observed that leaf chlorophyll content closely related to Fv/Fm in nonstressed leaves, thus the indices developed for chlorophyll estimation were successfully used to estimate Fv/Fm. For leaves under short-term stress, Fv/Fm dropped dramatically while leaf chlorophyll content remained almost the same. Compared to leaf chlorophyll content, reflectance was more sensitive to Fv/Fm variations. As Fv/Fm decreased, the slope of reflectance in the spectrum range of 700 to 900 nm obviously increased, and the first derivative reflectance in the red edge and infrared (NIR) regions was highly correlated with Fv/Fm. The indices using longwave red edge and NIR reflectance (NDRE740 and CI740) worked well for Fv/Fm retrieval in both stressed and nonstressed leaves with the coefficients of determination (R2) above 0.72 and normalized root-mean-square errors below 0.16. Note that the relationships NDRE740 and CI740 versus Fv/Fm were significantly different between nonstressed and stressed leaves, which may give a good implication to detect short-term stress occurrence.
KEYWORDS: Proteins, Molecules, Molecular energy transfer, Data analysis, Fluorescence resonance energy transfer, Luminescence, Resonance enhancement, Resonance energy transfer, Neodymium, Signal processing
When timescale of the molecule kinetics faster than the bin time of millisecond order, the commercial single- molecule fluorescence resonance energy transfer (smFRET) data analysis tools may not clearly separate different states. We proposed a novel method to obtain the analysis result from smFRET raw data in microsecond scale. We introduced Akaike information criterion and non-stationarity measure in the fitting procedure to give an objective estimate about the number of states and populations. The results were used as initial values to make parameter estimation about equilibrium populations and transition rates from the photon trajectories based on an iterative optimizing procedure.
In this paper, we will present a smart structure based on an electrically controlled liquid crystal (LC) Fabry-Perot to achieve terahertz (THz) filter, which has extremely potential in THz communication. This proposed structure doesn’t need any mechanical movements because of adapting LC as a key material to compose the Fabry-Perot device. The THz filter based on LC, which is smart, light and cheap, can be realized to solve that common problem of short of tunable devices in THz radiation. The chosen LC material is E7, which has very stable and good transmissions in THz range. Under the external applied voltage, the alignment of the nematic LC allows the refractive index of the device to be tuned. Because of this feature, the resonant peaks could be shifted by changing the applied voltage. Especially, when the alignment is changed from planar to phototropic, the maximum value of the shift could be realized. The simulation result of the proposed device could be got. And the optimal structural parameters could be also got. Numerical analyses results have shown that the proposed structure has a high narrow transmission band and very sharp edges. This THz filter is novel for compact and smart features, so this kind of proposed THz filter is very attractive in many applications, such as THz communication, and THz spectral imaging.
Based on a proposed electrically tunable liquid crystal (LC) micro-lens array (MLA) instead of a commonly used microlens array with fixed focal length in a conventional type, a new prototyped Shack-Hartmann sensor is reported. The LCMLA with 128 × 128 elements is fabricated by the methods of photolithography and hydrochloric acid etching. Composed of the proposed LC-MLA and a CCD, a new type Shack-Hartmann wavefront sensor is got. This kind sensor can solve problems of the tradition wavefront sensor that the larger measurement range and high measurement accurate can't be realized by the same device. Except for adaptive switching the two working modes, this wavefront sensor also has a dual-mode imaging feature with obtaining wavefront information of the target and it's two-dimensional optical intensity image at the same time. In order to verify it's characteristics, an extreme experiment is designed, which introduces a distortion wavefront. At this circumstanc, the traditional wavefront sensor can't get anything. However, with proposed wavefront sensor, this situation can be solved by adjusting the applied voltage of LC-MLA to change it's focal length. With a reconstruction method, the three-dimensional information of the wavefront can be got. At the same time, the two-dimensional optical intensity image is also got. From the experiments, we can prove that it can effectively improve detection sensitivity and dynamic measurement range of wavefront. Results of the prototype demonstrated qualitatively verify this feasibility. This kind new type wavefront sensor will have a wide variety of applications in adaptive optics.
The photoelectrical response properties of a linear high-temperature (high-Tc) superconducting sensor coupled with a refractive microlens array are investigated. The theoretical analysis and measurements demonstrate that the photoelectrical response uniformity of superconducting sensors is not always improved simultaneously with the enhancement of the common photoelectrical performances of superconducting sensors, such as the responsivity, the noise equivalent power, and the detectivity, after coupling cylinder microlenses with them. A linear 8-pixel high-Tc YBa2Cu3O7-δ superconducting thin film sensor and a quartz microlens array of 32×64, are designed and then fabricated and finally coupled for detection infrared radiation in the wavelength range of 1 to 5 μm. The superconducting sensors are characterized through a common measurement method.
A smart spectral imaging detection method based on the integration of an electrically tunable liquid-crystal Fabry-Pérot microstructure and a focal plane array is discussed. The layout of the spectral device is designed effectively and prototypes with working wavelengths in the range of 800 to 900 nm were fabricated using ultraviolet photolithography and wet etching. Measurements were carried out with careful analysis. Based on the results, this paper proposes a smart spectral imaging array device structure that can potentially obtain the image of many spectral bands simultaneously in one picture frame. Some key issues concerning such structures for imaging applications and calibration are discussed. Without any mechanical parts, this kind of spectral component exhibits some advantages such as low cost and compact integration.
In this paper GPU based data parallel technique is used to reduce calculating time in diffractive optics elements (DOE)
design. By using compute unified device architecture (CUDA) framework, comparison of acceleration radio of some
major methods using in DOE design, including Gerchberg Saxton algorithm for global optimization in conjunction with
Rayleigh-Sommerfeld diffractive integrating transformation, genetic algorithm with a finite-difference time-domain
method and simulated annealing algorithm, is made with demonstrational DOE-lens design, whose focal spot size is 0.5
μm, incident light wavelength is 650 nm, focal length is 3mm, DOE aperture size is 2mm.
A liquid crystal (LC) cylindrical lens array with electrically tunable focal length is proposed, which is first fabricated.
And its optical focusing characteristics are got in tests. The LC cylindrical lens array is driven by applied voltage. It
composes of two ITO glasses substrates and LC layer. The top electrode pattern is fabricated by the methods of
lithography and hydrochloric acid etching, which has 128×128 elements. Every element is a 60μm×200μm rectangle.
The 20μm-thickness-spacer is used to control the LC thickness. When the external electric field is applied, the LC
molecules begin to rotate. Then the gradient refractive index forms in the LC cell. The LC cylindrical lens array is a
convergent lens array. The parallel white light is used to test its optical characteristics. It comes to a conclusion that the
focal length of the LC cylindrical lens array and the external applied voltage has an inverse proportion relationship. The
range of the focal length is from 60μm to 450μm, when the applied voltage varies from 1.54 Vrms to 5.0 Vrms. And the
response time is up to sub-microsecond. The unique focusing phenomenon of LC cylindrical lens array is that the
focusing beams in the top and bottom of every element rectangle are like the image "V".
Traditional mechanically tunable imaging spectrometry, including those based on MEMS technology, can only obtain continuous spectral image data in a fixed spectral order, which was restricted by the moving mechanism of the mechanical device. But spectrum absorption peakof materials is not continuous, especially in hyperspectral
scale. To overcome such shortages, a smart spectral imaging detection method based on the integration of electrically tunable liquid-crystal (LC) Fabry-Perot (FP) microstructure array and a non-continuous wavelength choosing strategy to operation the device are proposed. With a tunable LC-FP array composed by many working units arranging in two dimensions, the device can image in hundreds of spectral bands simultaneity within milliseconds in a calibrated system, and making correct detection for certain objects in one shot.
A new LC micro-lens array of 128×128 elements circular hole top electrode is proposed, which is fabricated by both the
lithography and HCL etching methods. Some valuable results are got in tests. The focal length of LC micro-lens array is
50μm~400μm under operating voltage from 0.2VRMS to 5.0VRMS. The lowest operating voltage of LC micro-lens array
is 0.2VRMS. The size of focus is about 10μm. And the PSF of LC micro-lens array is close to the theory values. The
optical multiple images which are got by LC micro-lens array are clear.
A smart spectral imaging detection method based on the integration of electrically tunable liquid-crystal(LC)
Fabry-Perot(FP) microstructure array is proposed. It has very broad application in many fields with advantages
of low cost, highly compact integration and working without mechanical part. The device can get hundreds of
spectral bands simultaneously in one frame of picture in theory. This paper proposes the structure of smart
spectral imaging array device, and analyses some key issues of liquid crystal Fabry-Perot structures for imaging
application and calibration. Prototypes of 4 × 4 LC-FP array with the cavity thickness ranging from 4 to 20
μm for the working wavelength in the range of 800~900nm, are made by lithography and wet etching. Test is
carried out and analysed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.