While the equipment of Micro-jet wave-guided laser was assembled, high-precision of concentricity and coaxiality between nozzle and cavity are required, which directly or indirectly influent the laser coupling precision of nozzle, the micro-jet stability and the steady length of micro-jet as well. As a result, the measurement of concentricity and coaxiality is important to improve the processing quality of Micro-jet wave-guided laser Through the new digital universal tool microscope measuring both ends of micro nozzle and diameter of nozzle, more resolution the other hand, the backlight detection the edge of nozzle is utilized. When the position of the center of a circle is indirect measured and then find out the concentricity through the uncertainty of the measurement and calculation method. V shaped groove is utilized to make certain its position. Otherwise, digital imaging through setting fixture and the use of new digital universal tool microscope and processed by software, which will cause to reduce measurement human error in tradition, after that, error theory analysis will be carried out, uncertainty theory will be utilized to make the experiment more sure at the same time. Above all, the reliability of data is obtained, compared with the traditional measurement methods are more accurate. Therefore, the processing quality of laser drilling will be enhanced significantly.
An improved Canny operator based on the method of Maximum Classes Square Error is adopted to get a self-adaptive threshold for grain recognition. First, a grinding wheel surface was measured by using a vertical scanning white light interferometric (WLI) system and reconstructed with an improved centroid algorithm; then the grains were extracted using the proposed method based on the fact that the peak intensity difference (ΔI) between maximum and minimum intensities on interferometric curve from diamond is larger than that from bond due to different reflective characteristics of different materials; third the grain protrusion parameters are investigated for grinding performance analysis. The experiments proved that the proposed grain recognition method is effective and assessment parameters are useful for understanding grinding performance.
In order to precisely locate the position of zero optical path difference (ZOPD) between the measuring light beam and the reference light beam in Vertical Scanning White-light Interferometer and then realize accurate surface measurement, the Particle Swarm Optimization (PSO) was used to process the interferometry data captured by a CCD camera. The envelope line of series of intensities of every pixel was supposed to be approximated by a Gaussian curve first. Then its parameters were optimized to find the best Gaussian curve as well as the position of ZOPD by the PSO with an objective function which minimized the residual sum of squares between the measured data and theoretical fitting curve. Finally, the measured surface can be reconstructed according to a series of best positions of ZOPD obtained by the proposed method. The simulation data and sampled data of two standard samples with different kinds of reticles from repetitive test show that the PSO is suitable for precisely locating the ZOPD with low requirements of step sampling and a small amount of pictures. Therefore, without reducing the precision, the PSO can be used in data processing of the white-light interferometry system with relatively low requirements for stepping hardware.
A comprehensive 3-dimensional measurement and characterization method for grinding tool topography was developed. A stylus instrument (SOMICRONIC, France) was used to measure the surface of a metal-bonded diamond grinding tool. The sampled data was input the software SurfStand developed by Centre for Precision Technology (CPT) for reconstruction and further characterization of the surface. Roughness parameters pertaining to the general surface and specific feature parameters relating to the grinding grits, such as height and angle peak curvature have been calculated. The methodology of measurement has been compared with that using an optical microscope. The comparison shows that the three-dimensional characterization has distinct advantages for grinding tool topography assessment. It is precise, convenient and comprehensive so it is suitable for precision measurement and analysis where an understanding of the grinding tool and its cutting ability are required.
The topograpgy characterization of grinding wheel grain is indispensable for precision grinding, it depends on accurate edge detecting and recognition of abrasive grains from wheel bond to a large extent. Due to different reflective characteristics arising among different materials, difference between maximum and minimum intensity (Δ ) of diamond is larger than that of bond. This paper uses a new method for grain edge detection of resin-bonded diamond grinding wheel that combines the improved Canny operator in Method of Maximum Classes Square Error (called as OTSU) with ΔI obtained by the white light interferometry (WLI). The experimental results show that the method based on improved Canny operator can effectively detect the edge of diamond grain.
The axial resolution of parallel confocal measurement can be improved as the laser source added into the system, but extreme monochromaticity of laser beam will produce the Talbot effect, which is an effect of many images of point light array appear along the optical path direction, and it causes to distinguish the true in-focus image from lots of Talbot images difficultly, which means the confocal measurement can’t be carried on. The author researched factors of the influences for Talbot distance, and developed some methods to weaken the impact of the Talbot effect. A LED was added into the laser parallel confocal measurement system to find the in-focus image, and there were no Talbot images nearby to impede positioning, and then the laser beam was lead into the system to measure with high precision. The difference of location of the two in-focus images with laser and LED was about 11μm in the experiment, which was shorter than one Talbot distance in the system, and the result indicated that the in-focal could be distinguished with this method.
KEYWORDS: Diamond, 3D metrology, 3D image processing, Data fusion, Signal to noise ratio, Interferometry, Image fusion, Digital filtering, Reflection, Microscopes
It is necessary to stitch small area of images together for large surface analysis while the measurement instrument used with a limited measurement area, e.g. White-light Interferometry (WLI)-based system. A new stitching method is proposed in this paper for diamond grinding wheel surface analysis. The images are captured by a WLI-based system and the 3D images’ stitching requires an overlapping region of 30%~50%. First, two-step intensity correlation matching method is used to obtain several pairs of matched points fast and the RANSAC (Random Sample Consensus) algorithm is adopted to screen them to get exact pairs of matched points. Then the measurement errors are adjusted and a stitched topography is got after data fusion. Experiments show that this method can effectively stitch 3D images of diamond grinding wheel together in less than 4 minutes with a correlation coefficient above 0.9 for two horizontal overlapping regions after adjustment.
Laser is widely used in processing and measurement because of its fine directivity and concentrated energy. The quality
of processing and measurement are mostly determined by the location of laser spot. However, it is difficult to locate its
center. A new algorithm, based on Hough Transform and sub-pixel methods, is proposed to locate laser spot center at a
sub-pixel level. In this algorithm, Hough Transform is utilized to detect the profile, center and radius of circle spot at a
pixel level, and the centroid method and curve fitting method are utilized to locate the center to sub-pixel level.
Simulation and experimental results show that the algorithm offers great accuracy in position locating for laser spot. This
method can be used in laser processing and measuring system.
Photoacoustic imaging is attracting increasing interests in biomedical imaging. The comparing between the traditional
piezoelectric detections and optical detections is described. Three kinds of all-optical detection photoacoustic imaging
systems, including system based on optical reflectance at a glass-liquid interface, system based on FP polymer film and
the system based on POISe, are introduced and compared in this paper. Because these methods are difficult to realize
measuring the photoacoustic signal on a 2D plane with the backward detection mode, a new kind of photoacoustic
imaging system based on Electronic Speckle Pattern Interferometry (ESPI) is proposed. An ESPI outside displacement
measurement system is adopted to detect the surface displacement of sample. Since the exposure time of a standard CCD
which is of the order of tens of milliseconds, the temporal resolution to sample an acoustic field at MHz frequencies is
achieved by interrogating the sensor with a short laser pulse whose bandwidth is about 20ns. After measuring and
disposing the displacement data of the sample at a series detecting time, the photoacoustic image will be reconstructed
by a delay and sum beam-forming algorithm or by a reconstruction algorithm based on the decomposition. In principle,
the system will realize noncontact and backward-mode inspection and smaller element sizes of the receiver in the
photoacoustic imaging application.
The shape and energy distribution of laser beam directly define its applications in laser processing. In order to cater for
different laser processing requirements, the input beam always needs to be transformed. The transformation between the
solid beam and ring beam can be realized by the axicon-based optical devices. A beam transformation optical system,
which uses a pair of positive axicon and negative axicon is designed and analyzed. The novelty of the optical system is
not only that they can focus the laser beam on a ring pattern or solid beam pattern, but also that they can change the
diameter of patter easily by adjusting the separation of the two conical lenses. The optical system is analyzed based on
the geometry optical theory. By adjusting the separation of the convergent conical lens and the divergent conical lens,
different shapes and the energy distributions are gained. At last, a measurement method of the beam profile is introduced
which based on charge coupled device (CCD) The results show that the axicon-based beam transformations raise the
effectiveness of laser and have a wide application prospect in laser processing field.
A novel scheme is proposed to achieve all-optical SPM-based wavelength conversion in a bismuth oxide-based highly
nonlinear photonic crystal fiber. It consists of erbium-doped fiber amplifier, optical circulator, Fiber Fabry-Perot filters,
photonic crystal fiber and fiber Bragg grating. Owing to SPM, a recirculating configuration is designed to induce the
further spectral broadening and wavelength conversion is achieved with a tunable Fiber Fabry-Perot filter. The
simulation results of bismuth oxide-based photonic crystal fiber indicate that the effective index of the fundamental
mode increases monotonically with the increase in the hole pitch, or the decrease in the ratio of the hole diameter to the
hole pitch. The mode effective area steadily increases with the hole pitch. The nonlinear coefficient, which is beneficial
to shorten the fiber length and reduce the required optical power, is expected to be 1100W-1km-1 by using bismuth
oxide-based glass with high nonlinear refractive index and reducing the effective core area with holey microstructure.
The mode-field diameter of bismuth oxide-based is estimated to be 1.98μm and the predicted small effective core area is
3.3μm2. The propagation loss at 1550nm is about 0.8dB/m. The obtained results show that SPM-based PCF-WC has a
potential of wide conversion bandwidth, high response time, simple configuration and low insertion loss etc.
All-optical wavelength conversion plays a major role in providing the wavelength flexibility in optical communication networks. All-optical wavelength converters (AOWCs) based on cross-gain modulation (XGM) and cross-phase modulation (XPM) in semiconductor optical amplifiers (SOAs) have attracted considerable research interest. In this paper, we propose a novel scheme for cascaded wavelength conversion based on cross-gain modulation and cross-phase modulation in SOAs. The wavelength conversion operation in the proposed scheme includes two stages, that is, XGM in the first stage followed by the stage of XPM, and thus is expected to have a high ER and a large input power dynamic range simultaneously.
A simple architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is proposed, which consists of an erbium-doped fiber amplifier, a polarization controller, a nonlinear medium
PCF, two tunable fiber Fabry-Perot filters and an optical isolator. Self-phase modulation is utilized to induce spectral
broadening for all-optical wavelength conversion. The desired dispersion properties can be tailored by the parameters of
bismuth oxide-based PCF microstructure. The propagation loss at 1550nm is about 0.8dB/m. The nonlinear coefficient is
expected to be 1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field
diameter of PCF is estimated to be 1.98μm and the predicted effective core area is 3.3μm2. The intermediate high
numerical aperture fibers between bismuth oxide-based PCF and single-mode fibers are considered to reduce the splicing
loss. The obtained results show that the all-optical wavelength converter has a potential of high conversion efficiency,
wide conversion bandwidth, ultrafast response time, compact configuration and low insertion loss etc.
A novel architecture of all-optical wavelength conversion in a highly nonlinear bismuth oxide-based photonic crystal
fiber (PCF) is demonstrated. Self-phase modulation is utilized to induce spectral broadening for the all-optical
wavelength converter. A recirculating configuration is designed to obtain the twice spectral broadening. Therefore,
wavelength conversion is achieved. The design and the simulation of PCF are demonstrated. The desired dispersion
properties can be tailored by the parameters of bismuth oxide (Bi2O3) PCF microstructure. The propagation loss at
1550nm is about 0.8dB/m. The simulation results of PCF indicate the relationship of the effective index of the
fundamental mode, the mode effective area and the holes pitch of PCF. The nonlinear coefficient is expected to be
1100W-1km-1 by using bismuth oxide-based glass and reducing the effective core area. The mode-field diameter of PCF
is estimated to be 1.98μm and the predicted small effective core area is 3.3μm2. The design of Bi2O3-based PCF and the
intermediate high numerical aperture fibers between Bi2O3-based PCF and single-mode fibers are considered to reduce
the splicing loss. The obtained results show that the wavelength converter has a potential of wide conversion bandwidth,
high response time, simple configuration and low insertion loss etc.
In this paper, we demonstrated for the first time variable 1.5μm wavelength conversion through cascaded second order
nonlinear processes "SHG+DFG" by fan-out grating in lithium niobate waveguide. We fabricated the waveguide by
annealed proton exchange in periodically poled LiNbO3 (PPLN). The device used in this experiment is 4 cm long, has a
QPM period from 14.8μm to 15.2μm, waveguide width of 12μm, proton exchange depth of 0.7μm, and was annealed for
32h at 350°C. After proton exchange in pure benzoic acid using a SiO2 mask, the substrate was annealed in an oxygen
atmosphere. The wavelength of signal light was set at 1551.3 nm. The wavelengths of tunable pump lights we used in
experiment were 1543.2 and 1556.2 nm, and the corresponding grating periods were 14.87 μm and 15.03 μm,
respectively. The temperature was set at 100.5°C to avoid photo refractive damage and to match the QPM peaks to the
pump wavelengths. The conversion efficiency was about 10dB to be expected with the pump power 175mW in a similar
device with a slightly different QPM period and operated at 125°C.
All-optical wavelength converters (AOWCs) that utilize nonlinearities in semiconductor optical amplifiers (SOAs) have
attracted considerable research interest. AOWCs based on cross gain modulation (XGM) have a large dynamic range of
the input optical signal power but a low extinction ratio (ER) and a high chirp, whereas AOWCs based on cross phase
modulation (XPM) provide a low chirp and a high ER but suffer from a relative small input power dynamic range. We
point out that there seems to be some complementarity between XGM and XPM. Based on this, we propose a novel
scheme for cascaded wavelength conversion based on cross gain modulation and cross phase modulation in SOAs thus is
expected to have a high ER and a large input power dynamic range simultaneously. The wavelength conversion
operation includes two stages, that is, XGM in the first stage followed by the stage of XPM. In the XGM stage, we use a
band pass filter to increase the frequency response of the SOA. In the XPM, we use the bidirectional input scheme for
MZI to improve the response of XPM and cancel XGM-induced intensity unbalance to get a relative perfect interference.
A novel high-speed magneto-optic (MO) modulator which consists of an integrated wire grid polarizer (WGP), Bi-YIG
waveguide with cladding layer and conducting micro-strip line is proposed. With the integrated WGP, this MO
modulator is faster, more accurate and more stable because it is not only completely driven by electric signals but also
has no mechanically moving parts. Moreover, it is compact-structured and low-cost. Large Faraday rotation is obtained
with specific arrangement of the directions of the bias magnetic field and the modulation RF magnetic field. Optical
route and optic-electrical detect circuit are also designed and analyzed.
All-optical wavelength converters (AOWCs) are considered to be important components in future wavelength-division-multiplexed
(WDM) networks. Cross gain modulation schemes in semiconductor optical amplifiers (SOA) are promising
candidates for an all-optical wavelength conversion application due to the simple implementation and effective
conversion. However, the slow gain recovery time of SOA limits the maximum operation speed and causes unwanted
pattern effects. This paper provides a novel scheme for wavelength conversion enables ultra-fast conversion speed. On
the one hand, we utilize a three-wavelength-device (TWD) to reduce the recovery time of the SOA. On the other hand,
we use an optical band pass filter (OBF) which central wavelength is blue shifted with respect to the central wavelength
of the probe beam to increase the frequency response. The combination of a reduction of the SOA recovery time and an
increase of the frequency response enables conversion speed potentially to achieve 160 Gb/s or even faster.
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.