The 2014 Nobel Prize in Chemistry is an award to praise the development of super-resolution microscopy, which has pushed the fluorescence microscopy to a new summit. However, there still exist challenges for further application of super-resolution: (1) Better spatial resolution is always preferred especially at no additional cost; (2) Deeper imaging depth inside the scattering specimen; and (3) Richer biological information.
The pixel size of a charge-coupled device (CCD) camera plays a major role in the image resolution, and the square pixels are attributed to the physical anisotropy of the sampling frequency. We synthesize the high sampling frequency directions from multiple frames acquired with different angles to enhance the resolution by 1.4 × over conventional CCD orthogonal sampling. To directly demonstrate the improvement of frequency-domain diagonal extension (FDDE) microscopy, lens-free microscopy is used, as its resolution is dominantly determined by the pixel size. We demonstrate the resolution enhancement with a mouse skin histological specimen and a clinical blood smear sample. Further, FDDE is extended to lens-based photography with an ISO 12233 resolution target. This method paves a new way for enhancing the image resolution for a variety of imaging techniques in which the resolution is primarily limited by the sampling pixel size, for example, microscopy, photography, and spectroscopy.
Graded index (GRIN) lenses focus light through a radially symmetric refractive index profile. It is not widely appreciated that the ion-exchange process that creates the index profile also causes a radially symmetric birefringence variation. This property is usually considered a nuisance, such that manufacturing processes are optimized to keep it to a minimum. Here we show that this birefringence can be harnessed as a basis of a versatile and expandable vectorial state manipulator. Using standard GRIN lenses in cascade with other optical components, we generate various states, including full Poincaré beams that also contain orbital angular momentum. The combination of highly-symmetrical graded refractive index and corresponding birefringence – which benefit from the mature technology of the ion-exchange process – permit precise, simultaneous, phase and polarization modulation, which – when combined in a cascade structure with other elements – forms the basis for several applications. The non-pixelated nature of the birefringence of the lens, optical efficiency of the lens, and complex geometric phase inside the lens may also benefit future applications such as precision beam generation and quantum manipulation. All of these complex vectorial beam manipulations are achieved using off-the-shelf, inexpensive, passive optical components.
This work is a result of an exploration in response to the following observation: though reconstruction methodology of SIM image since its origin is carried out in frequency domain, recent works in this field, specially when it comes to SIM reconstruction using lesser than 9 raw images, have ventured into reconstruction methodologies that operate directly in the spatial domain. This work formulates and demonstrates a frequency domain reconstruction of SIM image using four raw images – one wide-field image and three SIM images. One of the chief feature of the presented reconstruction algorithm is that it employs the standard ‘tools and tricks’ used by the conventional 9-frame SIM reconstruction algorithm. Results indicate that the presented reconstruction algorithm provides high resolution reconstructions successfully as long as the noise level in the raw images is lower than 10%. For higher level of noise, the reconstruction result shows little resolution enhancement.
Super-resolution optical fluctuation imaging (SOFI) is a fast and low-cost live-cell optical nanoscopy for extracting subdiffraction information from the statistics of fluorescence intensity fluctuation. As SOFI is based on the fluctuation statistics, rather than the detection of single molecules, it poses unique requirements for imaging detectors, which still lack a systematic evaluation. Here, we analyze the influences of pixel sizes, frame rates, noise levels, and different gains in SOFI with simulations and experimental tests. Our analysis shows that the smaller pixel size and faster readout speed of scientific-grade complementary metal oxide semiconductor (sCMOS) enables SOFI to achieve high spatiotemporal resolution with a large field-of-view, which is especially beneficial for live-cell super-resolution imaging. Overall, as the performance of SOFI is relatively insensitive to the signal-to-noise ratio (SNR), the gain in pixel size and readout speed exceeds the loss in SNR, indicating sCMOS is superior to electron multiplying charge coupled device in context to SOFI in many cases. Super-resolution imaging of cellular microtubule structures with high-order SOFI is experimentally demonstrated at large field-of-view, taking advantage of the large pixel number and fast frame rate of sCMOS cameras.
Because of its optical property of photostability, Nitrogen-Vacancy center (NV center) is desired to be applied for biomedical staining for super-resolution microscopy. In this paper, we report the sub-diffraction imaging of NV centers in nano-diamond and bulk materials. The resolution of ~65nm is achieved in the FND sample with our home built CW STED system.
Confocal laser scanning microscopy (CLSM) has become one of the most important biomedical research tools today due
to its noninvasive and 3-D abilities. It enables imaging in living tissue with better resolution and contrast, and plays a
growing role among microscopic techniques utilized for investigating numerous biological problems. In some cases, the
sample was phase-sensitive, thus we introduce a novel method named laser oblique scanning optical microscopy
(LOSOM) which could obtain a relief image in transparent sample directly.
Through the LOSOM system, mouse kidney and HeLa cells sample were imaged and 10x, 20x and 40x magnify
objective imaging results were realized respectively. Also, we compared the variation of pinhole size versus imaging
result. One major parameters of LOSOM is the distance between fluorescence medium and the sample. Previously, this
distance was set to 1.2 mm, which is the thickness of the slide. The experiment result showed that decreasing d can
increase the signal level for LOSOM phase-relief imaging. We have also demonstrated the application of LOSOM in
absorption imaging modality, when the specimen is non-transparent.
Fluorescent microscopy has become an essential tool to study biological molecules, pathways and events in living cells, tissues and animals. Meanwhile even the most advanced confocal microscopy can only yield optical resolution approaching Abbe diffraction limit of ~200 nm. This is still larger than many subcellular structures, which are too small to be resolved in detail. These limitations have driven the development of super-resolution optical imaging methodologies over the past decade.
In stimulated emission depletion (STED) microscopy, the excitation focus is overlapped by an intense doughnut-shaped spot to instantly de-excite markers from their fluorescent state to the ground state by stimulated emission. This effectively eliminates the periphery of the Point Spread Function (PSF), resulting in a narrower focal region, or super-resolution. Scanning a sharpened spot through the specimen renders images with sub-diffraction resolution. Multi-color STED imaging can present important structural and functional information for protein-protein interaction.
In this work, we presented a two-color, synchronization-free STED microscopy with a Ti:Sapphire oscillator. The excitation wavelengths were 532nm and 635nm, respectively. With pump power of 4.6 W and sample irradiance of 310 mW, we achieved super-resolution as high as 71 nm. Human respiratory syncytial virus (hRSV) proteins were imaged with our two-color CW STED for co-localization analysis.
Fluorescence microscopy has become an essential tool to study biological molecules, pathways and events in living cells,
tissues and animals. Meanwhile, the conventional optical microscopy is limited by the wavelength of the light. Even the
most advanced confocal microscopy or multiphoton microscopy can only yield optical resolution approaching the
diffraction limit of ~200 nm. This is still larger than many subcellular structures, which are too small to be resolved in
detail. These limitations have driven the development of super-resolution optical imaging methodologies over the past
The stimulated emission depletion (STED) microscopy was the first and most direct approach to overcoming the
diffraction limit for far-field nanoscopy. Typically, the excitation focus is overlapped by an intense doughnut-shaped
spot to instantly de-excite markers from their fluorescent state to the ground state by stimulated emission. This
effectively eliminates the periphery of the Point Spread Function (PSF), resulting in a narrower focal region, or super-resolution.
Scanning a sharpened spot through the specimen renders images with sub-diffraction resolution. Multi-color
STED imaging can present important structural and functional information for protein-protein interaction.
In this work, we presented a dual color, synchronization-free STED stimulated emission depletion (STED) microscopy
with a Ti:Sapphire oscillator. The excitation wavelengths were 532nm and 635nm, respectively. With pump power of 4.6
W and sample irradiance of 310 mW, we achieved super-resolution as high as 71 nm. We also imaged 200 nm
nanospheres as well as all three cytoskeletal elements (microtubules, intermediate filaments, and actin filaments), clearly
demonstrating the super-resolution resolving power over conventional diffraction limited imaging. It also allowed us to
discover that, Dylight 650, exhibits improved performance over ATTO647N, a fluorophore frequently used in STED.
Furthermore, we applied synchronization-free STED to image fluorescently-labeled intracellular viral RNA granules,
which otherwise cannot be differentiated by confocal microscopy. Thanks to the widely available Ti:Sapphire oscillators
in multiphoton imaging system, this work suggests easier access to setup super-resolution microscope via the
synchronization-free STED A series of biological specimens were imaged with our dual-color STED.
We reported recently that laser oblique scanning optical microscopy (LOSOM) is able to obtain a relief image in
transparent sample directly. To optimize the performance of LOSOM, the parameters such as numerical aperture, the
distance between the specimen and the fluorescent medium and the pinhole size are investigated in this work. A beam
blocker is introduced in light path which enhances dramatically the visualization of local phase difference.
A portable video-rate confocal laser scanning microscope (CLSM) is implemented with polygon mirror and
galvanometric mirror employed as the fast and slow axis scanner, respectively. The system can be applied for
noninvasively imaging skin and other tissue. The dimension of this real-time CLSM is only 33×20×12cm3 with weigh of
1.780 kg. Here we used a single Complex Programmable Logic Device (CPLD) to generate the control and
synchronization signals for real time confocal microscopy. Utilizing NI image acquisition card, the CLSM system can
acquire and store the real-time images. So that high resolution confocal microscopy is achieved simultaneously.
It is necessary to apply the spectral-domain optical coherence tomography (SD-OCT) to image the whole eye segment
for practically iatrical application, but the imaging depth of SD-OCT is limited by the spectral resolution of the
spectrometer. By now, no result about this research has been reported. In our study, a new dual channel dual focus OCT
system is adopted to image the whole eye segment. The cornea and the crystalline lens are simultaneously imaged by
using full range complex spectral-domain OCT in one channel, the retina is detected by the other. The new system was
successfully tested in imaging of the volunteer' eye in vivo. The preliminary results presented in this paper
demonstrated the feasibility of this approach.
An adaptive pulse shaper controlled by multiphoton intrapulse interference phase scanning (MIIPS) was used, together with a prism-pair, to measure and cancel high-order phase distortions introduced by a high-numerical-aperture objective and other dispersive elements of a two-photon laser-scanning microscope. The delivery of broad-bandwidth (~100 nm), sub-12-fs pulses was confirmed by interferometric autocorrelation measurements at the focal plane. A comparison of two-photon imaging with transform-limited and second-order-dispersion compensated laser pulses of the same energy showed a 6-to-11-fold improvement in the two-photon excitation fluorescence signal when applied to cells and tissue, and up to a 19-fold improvement in the second harmonic generation signal from a rat tendon specimen.
Ultrashort <15 fs pulses are shown to provide higher fluorescence intensity, deeper sample penetration, and
single laser selective excitation. To realize these advantages chromatic dispersion effects must be
compensated. We use multiphoton intrapulse interference phase scan (MIIPS) to measure and then
eliminate high-order distortions on pulses with a bandwidth greater than 100nm FWHM. Once
compensated, the transform limited pulses deliver higher signal intensity, and this translates into deeper
optical penetration depth with a high signal-to-noise ratio. By using a pulse shaper and taking advantage of
the broad spectrum of the ultrafast laser, selective excitation of different cell organelles is observed due to
the difference in nonlinear optical susceptibility of different chromophores without the use of an emission
Shorter pulses, in theory, should be favorable in nonlinear microscopy and yield stronger signals. However, shorter
pulses are much more prone to chromatic dispersion when passing through the microscope objective, which significantly
broadens its pulse duration and cancels the expected signal gain. In this paper, multiphoton intrapulse interference phase
scan (MIIPS) was used to compensate chromatic dispersion introduced by the 1.45 NA objective. The results show that
with MIIPS compensation, the increased signal is realized. We also find that third and higher order dispersion
compensation, which cannot be corrected by prism pairs, is responsible for an additional factor of 4.7 signal gain.
The depth-resolved autofluorescence ofrabbit oral tissue, normal and dysplastic human ectocervical tissue within l20μm depth were investigated utilizing a confocal fluorescence spectroscopy with the excitations at 355nm and 457nm. From the topmost keratinizing layer of oral and ectocervical tissue, strong keratin fluorescence with the spectral characteristics similar to collagen was observed. The fluorescence signal from epithelial tissue between the keratinizing layer and stroma can be well resolved. Furthermore, NADH and FADfluorescence measured from the underlying non-keratinizing epithelial layer were strongly correlated to the tissue pathology. This study demonstrates that the depth-resolved fluorescence spectroscopy can reveal fine structural information on epithelial tissue and potentially provide more accurate diagnostic information for determining tissue pathology.
The depth-resolved autofluorescence of normal and dysplastic human ectocervical tissue within 120um depth were investigated utilizing a portable confocal fluorescence spectroscopy with the excitations at 355nm and 457nm. From the topmost keratinizing layer of all ectocervical tissue samples, strong keratin fluorescence with the spectral characteristics similar to collagen was observed, which created serious interference in seeking the correlation between tissue fluorescence and tissue pathology. While from the underlying non-keratinizing epithelial layer, the measured NADH fluorescence induced by 355nm excitation and FAD fluorescence induced by 457nm excitation were strongly correlated to the tissue pathology. The ratios between NADH over FAD fluorescence increased statistically in the CIN epithelial relative to the normal and HPV epithelia, which indicated increased metabolic activity in precancerous tissue. This study demonstrates that the depth-resolved fluorescence spectroscopy can reveal fine structural information on epithelial tissue and potentially provide more accurate diagnostic information for determining tissue pathology.
Endogenous fluorophores, such as NAD(P)H/FAD and collagen/elastin, have been regarded as in vivo quantitative fluorescence biomarkers for precancerous changes of epithelial tissue. However, the fluorescence signal measured by conventional spectroscopy is a mixture of autofluorescence from the epithelium and deep structures. The dominant fluorescence of collagen/elastin from connective tissue in deep layers creates serious challenge for extracting the epithelial fluorescence of NAD(P)H/FAD that is weak, but important for the characterization of tissue pathology. In this work, we instrumented a confocal fluorescence spectroscopy system and a two-photon excited fluorescence spectroscopy system to measure the depth-resolved single- and two-photon fluorescence spectra from the rabbit esophageal tissues. The excitation wavelengths were 349 nm and 735 nm, respectively. Both systems provided good optical sectioning. The information obtained from depth-resolved fluorescence was generally consistent with the histology of the examined tissue sample. The NAD(P)H signals from epithelial layers were clearly separated from the collagen signal from deep layers. In addition, strong second harmonic generations given by collagen fibers were observed. This work demonstrates that depth-resolved fluorescence spectroscopy may produce more accurate information on the diagnosis of tissue pathology.
We describe a new kind of symmetric color separation grating (SCSG), which can be applied to separate the frequency-tripling (3ω)light from the basic (1ω) and frequency-doubling (2ω)lights. The profile of the proposed SCSG is a three-level symmetric structure in one period, thus it is easy to fabricate it with the much improved tolerance of mask misalignment without the decrese of the efficiency of the frequency-tripling light. We have analyzed the principles of the SCSGs by employing the scalar diffraction theory and fabricated them experimentally by means of binary optics technology. The theoretical and experimental results demonstrated that the proposed SCSGs can be made in a comparatively easy way for the symmetric structure that can effectively avoid the effect of the fabrication error due to mask misalignment, thus higher manufacturing yield and lower cost can be achieved.
In fabrication of a fine optical element, femtosecond laser is an attractive experimental tool because it avoids the splutter effect to damage the nearby lines. However, the wavelength of the usual Ti:sapphire laser is insensitive to the widely-used photoresist in microlithographic industry. In this paper, we introduce a new method with femtosecond doubled-frequency laser by use of a BBO crystal to fabricate optical gratings and chromium photomasks. The laser source is the Ti:sapphire laser with a central wavelength of 790 nm and its doubled-frequency laser is obtained through the BBO crystal whose wavelength (395nm) is within the sensitive exposure range of the photoresist. This enables us to fabricate fine optical elements with the normal photolithographic technique. In the experiment, we use a translator that is controlled by a computer to accurately move for fabrication of optical elements with high precision. In contrast to the other techniques, our approach has the higher quality and precision, for femtosecond laser works faster than the material’s thermal diffusion, i.e., without splutter effect that yields the clear edge of the optical element. Moreover, it also makes the fabrication processing simplified. Experiments are given to verify that this method should be highly interesting for the fabrication of fine binary optical elements.
Inductively Coupled Plasma (ICP)can achieve high density plasma in low pressure,so it has a number of significant advantages such as improved etching rates,better profile control,improved uniformity, greatly increased selectivity and a dramatic reduction in radiation damage and contamination. In optics,quartz is an ideal optical material with transmitting spectral range from deep ultraviolet to far infrared.So we systematically studied the etching characteristics
of quartz by using a Inductively Coupled Plasma (ICP)etching system.In the xperim nts,the gas was the mixture of CHF3,O2 and Ar,and the chamber pressure was about 10 mTorr.Th influences of gas flow rate and the power of the
radio frequency on etching rate were optimized. The uniformity and repeatability of the etching technology were also studied. After residue mask material was removed by wet chemical solution, no polymer was observed on the surfaces of samples,and the surfaces of the fabricated quartz elements were smooth and clean. The optimized etching process is important for the fabrication of micro-optical lements based on quartz. Using this etching process, many gratings such as Dammann grating, rectangular groove grating, and optical disk grating can be fabricated successfully.
Proc. SPIE. 5225, Nano- and Micro-Optics for Information Systems
KEYWORDS: Nanotechnology, Optical microscopes, Moire patterns, Optical signal processing, Sensors, Photoresist materials, Near field scanning optical microscopy, Near field, Near field optics, Diffraction gratings
The high-density grating is routinely used in spectral expansion of optical information processing system. But usually it is hard to examine such gratings directly. The well-used Moire interferential pattern method can only obtain the overall coarse result. While in practice,the local quality of a grating is highly interesting. In this paper we use a nano-probe fiber to scan the near field of a grating. With the Talbot effect of a grating,we can take a picture of 5 x 5 square-micron area for analyzing the local quality. In our experimental setup,the Talbot image of a grating is coupled into a fiber detector with the fiber tip of 50 nanometers. With the Talbot effect, the surface profiles of the gratings are detected. Three gratings are examined in our experiment with the line widths of 600 lines per millimeter for all gratings. From the experimental results we can see that a well made grating can yield a sharp image at the Talbot distance. Experimental results demonstrate that this nanotechnology-based Talbot detection method can be widely applied in grating examination.
Laser beam scanning has wide applications in laser printer, laser tracking, etc.. The previous phase coding method is the micro-lens array method, which is difficult to fabricate because of the extreme fine linewidth at the outer part of the array lens. We propose a new scanning method based on the Talbot phase coding method. The Talbot phase codes come from the natural phase codes of the self-imaging effect of a grating for array illumination. A pair of two complementary Talbot encoded phase plates is used to replace the previous micro-lens array. Compared with the previous microlens array method, this method overcomes the shortcoming of the extreme fine linewidth of the previous method by replacing the equal linewidth of the encoded phases. This method overcomes the shortcoming of the continuous phase levels requirement of the previous method by using a limited phase-level number. This method overcomes the shortcoming of the continuous movement of the previous method by taking the equal-step movement. Therefore, our design of Talbot encoded scanner is more easily fabricated with binary optics and more reliable in practical use.
In this paper, we use diffractive superresolution technology to design a pure-phase plate for realizing the smaller spot size than the usual Airy spot size. We have calculated 2,3,4,5 circulation zones for optimizing the highest energy compression (Strelratio) with the constraint of the Firstzero value G=0.8. Numerical results show that the 2-circular zone pure-phase plate can yield the highest Strelratio (S=0.59) with the constraint of G=0.8.The 3-circular zone pure-phase plate with the respective phases of φ1φ2φ3 has also been calculated. At the same time the 4,5 circular zone binary phase (0,π) plates are calculated to yield the result of S = 0.57 with G=0.8. The usage of the superresolution phase plate aims to realize the smaller spot size instead of the usage of the higher numerical aperture lens, which is the main advantage of this superresolution technology. Therefore, in this constraint of G=0.8, we have selected the 2-circular zone with binary phase for ease of fabrication. At last, we use a 50 nanometer fiber tip detector to scan the diffractive superresolution light spot in order to compare it with the Airy spot. Detailed experiments are presented.
Hexagonal array devices are widely used in optical communication and optical computing. Near field Talbot array illuminator is an ideal method for the illumination of these devices. Ultrafast pulse provides high transmission bit-rate and high peak energy, thus it is favorable for optical communication, diffractive optics, and other applications. In this paper we studied the hexagonal array Talbot effect under ultrafast pulse illumination. Ultrafast pulse has wide wavelength spectra range, and each spectral component corresponds to a unique wavelength that is directly relating to the Talbot distance. Thus the Talbot effect of hexagonal array is different from those of continuous wave in a whole. From the experimental result we can see that, comparing with that of the monochromic illumination, the efficiency and contrast of ultrafast pulse illumination are decreased. The result should be highly interesting for ultrafast fiber communication as well as other optical devices.
Over the past years great efforts have been made to find the optimization methods for synthesizing computer-generated holograms, e.g., kinoforms. The simulated annealing (SA) method is widely used in programing to approach the global optimization. But the drawback of the SA is it is time consuming. It is not possible to use the SA for some large computational optimization problems. So there is a strong need of the fast and effective algorithm. In this paper we propose a new optimization method, based on the modified Gerchberg-Saxton (G-S) algorithm, for synthesizing the large-scale kinoforms. Both phase and amplitude freedoms are used in this method. This method is especially suitable for the optimization of the large-scale kinoforms. It takes much less computational time than SA and the obtained image quality is also comparable to that of the SA. Another advantage of this method is that the reconstructed image quality is adjustable to meet the different requirements by controlling the noise parameter. The diffractive efficiency or the uniformity of the reconstructed image can be enhanced selectively to satisfy the different needs by the adjustment of the noise parameter. Using this method we have obtained several large-scale kinoforms with fast speed. The pattern of a binary kinoform is transferred into the glass plate by inductive coupled plasma (ICP) technology. Experimental results are also given in this paper to show the effectiveness of our methods.
In this paper we propose a space multiplexed diffractive optical device based on Talbot effect. Several different diffractive optical elements (DOEs) with the same size and physical aspect, such as Dammann grating, computergenerated hologram (CGH), are arranged interleavely and periodically in the DOE plane to form a multifacet DOE. Then it is illuminated by the corresponding Talbot illuminator. Each of the DOEs in the multifacet DOE can be triggered respectively by the irradiance of the Talbot illuminator. In our experimental setup, two CGHs with the period size of 0.5x0.5mm and pixel size of 5x5µm are incorporated into one multiplexed hologram according to the specific encoding periodic pattern that can be realized with a Talbot array illuminator. The corresponding reconstructed images have been obtained selectively when the relative position of the Talbot illuminator and the multifacet DOE is properly changed, which confirm the feasibility of our method. This device can be used in optical information and optical interconnection.
Talbot array illuminator (TAIL) based on fractional Talbot effect is useful for illuminating very large array, the number of phase levels of TAIL is a very important factor for estimation of practical fabrication complexity and cost. Based on the symmetry of the phase distribution, we can obtain the maximum phase level number for a given fractional Talbot distance. But because of the redundant equal phase, the exact phase level number is still unpredictable for an arbitrary opening ratio (1/M) of the illumination array. In this paper, we'll show that there is a simple decomposing rule to predict the number of phase levels of two-dimensional Talbot array illuminator (2D-TAIL) with the opening ratios (1/Mx), (1/My) in two dimensions, respectively. In the condition that the output array is alternatively (pi) -phase-modulated, there are similar simple relations. These results are generally applicable and should be interesting for practical use. Based on the joint-Talbot effect, we realized a separable 2D-TAIL by using two crossly placed 1D-TAIL. The 1D-TAIL is fabricated with the usual binary-optics technique and the number of phase levels in this experiment can be well explained by our theoretical results.
Pulse-width of ultrashort laser is a very important parameter for the wide applications of ultrashort pulse. Various methods have been proposed to measure pulse-width, such as second harmonic generation method, third harmonic generation method and frequency resolved optical gating method. Despite of the benefits they hold, they share a vital drawback: they all employ nonlinear effects of ultrashort pulse, which means that the input power must be large enough to generate nonlinear effect, and the central wavelength of the pulse must correspond to the sensitivity range of nonlinear crystal. In this paper we present a new method of measuring pulse-width based on the Talbot effect of ultrashort laser pulse. The ultrashort pulse can be treated as a series of waves of different wavelengths, so at certain Talbot distances, the diffraction of the ultrashort laser pulse reshapes the energy distribution. Thus it gives us the possibility to determine the pulse-width by means of the diffraction. Taking advantages of Talbot effect, the method has the features of large measuring wavelength range, accurate measurement and simple structure. As the basis of the method is diffraction rather than nonlinear effect, all the problems related to nonlinear effect are avoided, such as high incident power and wavelength requirement. Both single and multiple shot pulse are suitable for this method. Numerical analysis has shown that pulse-width from 1 to 100fs can be measured with error of less than 1fs, at wavelength of 800nm. As there is just one Talbot grating between the light source and the detector, we can make the conclusion that this very simple method of pulse-width measuring should be highly interesting for practical application.
Random phase is usually assigned to the amplitude of the desired image to synthesis the phase-only computer-generated hologram(CGH). As a matter of fact, the CGH can be obtained directly if proper phase is assigned. But it is rather difficult since there are infinite ways of phase assignment. Based on the symmetry, a new deterministic binary phase coding technique is introduced in this paper. According to this method, the amplitude of the desired image is coded by a binary array derived form the desired image itself. The coarse CGH can be obtained by applying inverse discrete Fourier transform of the previous result. In order to get higher diffraction efficiency the usual iterative method is used to optimize the CGH. Using this method we have obtained several CGHs with high diffraction efficiency. The pattern of the binary CGH is transferred into the glass plate by inductive coupled plasma (ICP) technology. Experimental results are also given in this paper.
Zernike phase-contrast method is proposed for its application to optical pickup head for the two-layer optical disk. The most attractive feature of this proposed approach is that a very simple architecture can be fabricated for simultaneous readout of both layers with only one objective lens. After giving the basic theoretical analyses of Zernike phase-contrast method, we constructed one feasible system based on this method and discussed the influences caused by the possible phase change of the high order spectrum and the finite aperture. The experimental demonstration of the proposed system is given.
Inductively coupled plasma (ICP) equipment is a new advanced version of dry-etching equipment that has not been widely reported to produce micro-optical elements before. The obvious structural improvement of ICP over the usual widely-used Reactive Ion Etching (RIE) is that two Radio Frequency (RF) power sources are used in ICP, while only one RF power source is used in RIE. This structural improvement of ICP results in the features of high-density plasma, low pressure and good directionality of ions, thereby bringing us the advantages over RIE technology as the weaker surface damage, better vertical profile of the etched surface, smaller linewidth and more freedoms to control the etching process. In this paper we report our detailed experimental results of using the new ICP setup for producing micro-optical elements. Experimental results support the view that ICP is a new advanced version of dry etching equipment for producing micro-optical elements. Phase gratings made with ICP have wide applications in micro-optical elements and systems. It is believed that use of ICP is the new developing direction for fabrication of micro- optical elements and systems in the future.
Arbitrary-phase-modulated array illuminator (APM-AIL) based on Talbot effect means that arbitrary-phase-modulated phase plate may generate the specific intensity distribution at the specific fractional Talbot distance. The previous understanding is that only the specific phase modulated Talbot illuminator is possible for this purpose. In this paper, we discussed how the condition of APM-AIL can be fulfilled. We found that APM-AIL is also a position- selective Talbot array illuminator, which is usually impossible to realize for the conventional Talbot illuminator. We have given two-dimensional experimental example of Talbot illuminator. We also present some of other experimental examples fabricated by binary-optics technology, e.g., nonseparable hexagonal illumination, random-intensity simulation of sky stars, optical square- beam transformation, and 1x3 beam splitting for readout of optical disk.
An equation is given to study the time dependence of the Fresnel diffraction field of a grating illuminated by an ultrashort pulsed-laser beam. Through numerical calculation, we find the temporal Talbot effect is both time-dependent and distance-dependent. For the width of the input pulse (Delta) (tau) within a few decade femtoseconds, the shorter Talbot distance, and/or the longer length of the input pulse, the more similar the outline of the temporal intensity distribution to that of the input pulse. While for (Delta) (tau) within a few thousand femtoseconds, the outline of the temporal intensity distribution is almost the same as that of the input pulse except for a time-delay.
Lateral vehicle control is a nonlinear control problem. Because there exists many uncertain factors (e.g., imprecision of vehicle modeling and information measurement), it is limited to take advantage of the traditional control method based on a precise mathematical model to design a controller for lateral vehicle control. During the past several years, fuzzy control has emerged as one of the most active areas for research in dealing with the nonlinear control problem and has made many achievements. We designed a fuzzy logic controller for the road following of the autonomous land vehicle. The main sensor we used is the video camera that can provide the environment information around the vehicle. We have implemented this controller in the simulation. The controller drove the vehicle to follow the curved road and we got good tracking accuracy. In comparing with the PID controller, the fuzzy logic controller does not need a precise vehicle model and has better adaptability to parameter variation of the vehicle than the PID.
Proc. SPIE. 2300, Image Algebra and Morphological Image Processing V
KEYWORDS: Digital signal processing, Digital filtering, Zinc, Interference (communication), Signal processing, Image filtering, Very large scale integration, Binary data, Filtering (signal processing), Samarium
In this paper, we give some results of threshold decomposition of soft morphological (SM's) filters. Some of new properties of SM have been developed by means of these results. We give the necessary and sufficient condition for the SM's operators to be the morphological operators in the sense of complete lattice. We propose the binary SM, which simplify the analysis of SM. An algebraic approach to bounded signal processing has been given. The VLSI implementation of SM's filters have been discussed.
In this paper, we propose a novel fuzzy morphology (FM) which is induced by threshold decomposition. Its operators are the measures on a (sigma) _ring in range space of the membership functions of fuzzy sets, which depend upon the ordinary binary morphological operators of threshold sets of fuzzy sets. Some of the characteristic of these FM are similar to those of the traditional morphology. All the operators of these FM prove to be the morphological operators in the sense of complete lattice. It is shown how one can use binary morphological operators, thresholding techniques and stacking properties to implement these FM's operators. The VLSI implementation is simple and fast. The concept of fuzzification of set_intersection is introduced. This paper also presents a general algebraic approach to analysis fuzzy morphological operators on the space of fuzzy sets.