We developed a flexible endomicroscopy (FEM) in reflection geometry for quantitative phase imaging of unlabeled thick samples. FEM provides the phase information by wavefront modulation using chessboard grating and phase-shifting. FEM system features high lateral and axial resolutions of 1.2 and 8.3 μm, respectively, with a probe diameter of 2.5 mm. By testing pathologic slices and thick opaque mammalian tissue, FEM identifies normal and tumor glandular structures, secreta, and tomographic skin layers. With the potential for direct morphological and phase measurement, high resolution, and thin fiber tip, the label-free FEM could be an attractive tool for various clinical applications.
Polarized angle-resolved spectroscopy is introduced to measure transparent anisotropic films with back focal plane imaging by virtue of its rich information provided at various incident and azimuthal angles. The polarized angle-resolved spectroscopy provides a conoscopic interferogram and angle-resolved spectrum to deal with the complex characterization parameters of an anisotropic film, including the thickness, principal refractive index, and optical axis. Firstly, the optics model of a transparent anisotropic film is built by superpositioning the incoherent waves from the front and rear surfaces with coherency matrices formalism when the optical length is larger than the coherent length, and the incoherent issue arises. Then the optical axis of the anisotropic sample can be determined by the conoscopic interference image with the melatope, which marks zero phase difference between the ordinary and extraordinary waves. The measured angle-resolved reflectance spectrum and anisotropic interference phase are fitted to the optics model of the film with coherency matrix formalism, utilizing the Levenberg-Marquardt algorithm to calculate the thickness and dispersion principal refractive index within a single shot. The thickness and anisotropic refractive index are determined for sapphire and polyethylene terephthalate (PET) samples with our homemade polarized angle-resolved spectrometer. The thickness measurement results show that the relative error of the proposed method is less than 1.45%.
Quantitative Phase Imaging (QPI) has been widely applied in characterizing cells and tissues. Spatial light interference microscopy (SLIM) is a highly sensitive QPI method. However, as a phase-shifting technique, SLIM is limited in acquisition rate to at most 15 fps. On the other hand, Diffraction Phase Microscopy (DPM) is such a method, with the advantage of being common-path. However, laser-based DPM systems are plagued by spatial noise due to speckles and multiple reflections. Here, we propose using deep learning to produce SLIM-quality phase maps from DPM, single shot, images. We constructed a deep learning model based on U-Net and trained on over 1,000 pairs of DPM and SLIM images. From the test set, we observed that the model learned to remove the speckles in DPM and overcame the background phase noise. We implemented the neural network inference into the live acquisition software and allows us to acquire single-shot DPM images and infer from them SLIM images in real time.
As for chromatic confocal sensor system with limited computational capacity, a fast peak extraction algorithm with considerate accuracy is in urgent demand. However, current peak extraction algorithms such as the centroid algorithm (CA) and nonlinear fitting algorithms can not balance the accuracy and computational efficiency. Thus, we propose an accurate peak extraction algorithm with good computational efficiency called corrected differential fitting algorithm (CDFA). At first, the differential signal derived from the original axial response signal is linearly fitted for initial peak extraction. Then corresponding systematic error of this linear fitting operation is analyzed using a first-order linear nonhomogeneous differential equation. At last, error compensation, that is, the solution to this equation is implemented with an introduction of "sum differences of sampling intensity". The performance of CDFA is compared with two conventional peak extraction algorithms including the CA and Gaussian fitting algorithm (GFA) using Monte Carlo simulations. CDFA is found to have a comparable accuracy performance with GFA while have a much higher computational efficiency.
This paper discusses electromagnetic force actuator and configuration design of the aerostatic bearing stylus displacement sensor for the surface topography measurement. This stylus displacement sensor is designed based on the structure of direct metrology of stylus displacement, and aerostatic bearing is utilized to achieve the precise linear movement of stylus, with which the profiler measurement system has high precision without non-linear error. During the measurement process, the attitude of the stylus is adjusted by electromagnetic force to control the contact force between stylus and surface, thus the electromagnetic force analysis and implement is the key component to support the constant measurement force. The electromagnetic actuator combined permanent magnet with coils is designed to achieve the electromagnetic force precisely. The results of the numerical analysis and experiments indicate that the electromagnetic actuator can balance the gravity of stylus and keep a constant contacting force during the measurement. The surface topography measurement system based on aerostatic bearing stylus displacement sensor is constructed and the primarily experiment result is also given.
Piezoelectric ceramics with a flexible hinge guide was used for fine positioning at nanometer level, while a stepping motor was used for coarse positioning with a resolution at micrometer level, and their combination helped fulfillment of vertical scanning positioning with large range and nanometer resolution. A grating sensor was used for the real-time measurement of scanning displacement for close-loop positioning control. The properties of the flexible hinge guide was analyzed using ANSYS. Experimental results indicated the performance of the system was good. The system had a good application prospect in an optical profiler for surface measurement.
A new generation system for structured light is proposed here. This light has non-diffraction characteristic and is generated based on Mach-Zehnder interferometer together with optical wedge as the main optical element, which can realize phase shift easily. Theoretical analysis and ZEMAX simulation between the wedge angle and the strip phase shift are carried out. Experimental results show that the new structured light provided by this system has properties of long focal-depth, narrow strip-width, stable spatial sinusoidal density distribution and good contrast of fringe. The phase of the fringe can be shifted by adjusting the optical wedge’s position. The new structured light generated by this system has great advantages over traditional structured light on three-dimensional surface profile measurement which shows good application prospect.
KEYWORDS: Control systems, Digital signal processing, Particles, Magnetism, Control systems design, Resistance, Electromagnetism, Structural design, Metrology, Manufacturing
In tactile scanning profiler, the measuring force would change in a wide range when it was used for profile measurement in a large range, which could possibly destroy the measured surface. To solve the problem, measuring force control system for tactile scanning profiler was needed. In the paper, a voice coil motor-based measuring force control system for tactile scanning profiler was designed. In the design, a low stiffness coefficient spring was used to provide contact force, while a voice coil motor (VCM) to balance the spring force so that the contact force could be kept for constant measuring force. A VCM was designed specially, and for active measuring force control, a precision current source circuit under the control of a DSP unit was designed to drive the VCM. The performance of voice coil motor based measuring force control system had been tested, and its good characteristics were verified.
White light interference (WLI) optical profiler had been used widely for structured surface measurement. To achieve high measuring accuracy, piezoelectric ceramic (PZT) was usually used as the vertical scanning unit, which was normally less than 100um and only for small range structured surface measurement. With the development of advanced manufacturing technology, precision structured surfaces with large step height were appearing. To satisfy the measurement requirements of this kind of precision structured surfaces, WLI optical profiler with large range had to be developed. In this paper, an optical profiler was proposed, in which a coarse-fine vertical scanning system was adopted to expand its measurement range to 10mm while its resolution still at nanometer level.
Running-in is the initial phase of the entire wear process and significantly influences the performance and service life of wear components. Surface profile is an important feature of wear components, and researchers have made a lot of effort in investigation of running-in based on surface profile. However, surface profile merely contains the two-dimensional information about surface, which cannot represent the three-dimensional information. Due to the technology development of surface measurement and analysis, three-dimensional evaluation of surface topography can effectively extract comprehensive information about surface. Therefore, it is necessary to update the conclusions about running-in wear based on surface profile. This paper adopted areal surface evaluation parameters derived from surface topography instead of surface roughness parameters derived from surface profile to investigate a common phenomenon of running-in, which illustrates that the surface roughness after running-in is independent of the nature of initial roughness. The analysis of experiment result revealed that some properties of surface topography before running-in process are reserved after running-in.
Small angle measurement has been widely use for the alignment or error compensation of a mechanical system. In this paper a small angle dynamic measurement device based on laser interference technique is introduced, which consists of a reference module and a measuring module. The measuring module is fixed on the measured object. With the variation of the small tilt angle of the measured object, the phase difference between the two beams from prism1 and prism2 changes according to it. By analyzing the interference patterns, the variation of the small tilt angle can be obtained dynamically. Experimental setup has been established and the results show that the measurement range is 15' with the resolution of 0.08", the measurement error is less than 8″.
The accuracy of stylus profilometer sensor directly affects the performance of the profilometer. To ensure good status of the profilometer, the accuracy features of the profilometer sensor should be verified regularly. However by now, only standard samples with comprehensive parameters are adopted for verification of the total profilometer, and there is no verification device for stylus profilometer sensor, especially for that with large range and high resolution. In this paper, a special verification device for stylus profilometer sensor is introduced. The device consists of displacement generation unit, displacement measurement unit and data acquisition and feature analysis software unit. A motor and PZT are combined to be a large range and high resolution displacement generator in the displacement generation unit, and a grating interference displacement measurement unit gives standard value of the displacement. When a sensor should be verified, the displacement generation unit generates displacement within the measuring range of the stylus sensor, and the displacement is input to the sensor, the output of the senor is compared with the data measured by the grating interference displacement measurement unit, and the acquisition and feature analysis software unit shows the accuracy features of the stylus sensor. A double frequency laser interferometer is applied to the verification device for experimental testing, its high accuracy, stability, reliability and wide range is verified, which satisfies the large-scale verification requirement of stylus profilometer sensor.
A new optical configuration for amplified off-axis digital holographic microscopy is presented and applied to surface measurement. By symmetrical configurations in the optical path, aberration compensation for phase curvature can be avoided in the reconstructed process. Three dimensional surface texture of a grating plate is reconstructed via a single hologram and its parameters are verified.
White-light vertical scanning technique has been used for surface topography measurement because of its characteristics
of non-contact, high-accuracy and large range. In this technique, PZT is usually employed for high resolution vertical
scanning. Due to the nonlinearity and creep characteristics of PZT however, large scanning positioning error is inevitable
if direct interference image sampling without positioning metrology is adopted. Otherwise if positioning metrology is
adopted for every image sampling, measurement efficiency will be reduced greatly. To solve this problem in this paper,
the nonlinearity characteristic of PZT is analyzed and its local linearity is investigated, and based on the local linearity a
novel interference image sampling strategy is proposed. In this strategy, the whole scanning range is divided into many
sub-ranges, in which the non-linearity errors are small enough for direct interference image sampling. When white-light
vertical scanning measurement is conducted, in every sub-range, interference images are sampled directly at every
scanning position corresponding to equal driving voltage interval of PZT, while the end points of each sub-range are
measured by a positioning metrology system. Thus based on the local linearity of sub-range, the scanning positioning for
image sampling can have enough accuracy, while less positioning metrology is needed for high measurement efficiency.
Analysis and case study proves the improved scanning positioning accuracy and measurement efficiency through the
novel sampling strategy.
Surface topography is an important geometrical feature of a workpiece that influences its quality and functions such as
friction, wearing, lubrication and sealing. Precision measurement of surface topography is fundamental for product
quality characterizing and assurance.
Stylus scanning technique is a widely used method for surface topography measurement, and it is also regarded as the
international standard method for 2-D surface characterizing. Usually surface topography, including primary profile,
waviness and roughness, can be measured precisely and efficiently by this method. However, by stylus scanning method
to measure curved surface topography, the nonlinear error is unavoidable because of the difference of horizontal position
of the actual measured point from given sampling point and the nonlinear transformation process from vertical
displacement of the stylus tip to angle displacement of the stylus arm, and the error increases with the increasing of
measuring range.
In this paper, a wide range stylus scanning measurement system based on cylindrical grating interference principle is
constructed, the originations of the nonlinear error are analyzed, the error model is established and a solution to decrease
the nonlinear error is proposed, through which the error of the collected data is dynamically compensated.
KEYWORDS: Data modeling, Global Positioning System, System integration, Standards development, Tolerancing, Data storage, 3D imaging standards, Metrology, Manufacturing, Systems modeling
Geometrical Product Specifications is an international standard system regarding standardization of dimensional,
tolerancing, surface texture and related metrological principles and practices in the charge of ISO/TC213. Integrated
information system is necessary to encapsulate the knowledge in GPS to extend its application in digital manufacturing.
Establishing a suitable data structure for GPS data is one of the main works in building the integrated information system.
This paper is focused on cylindricity and the main points are as follows: proposes the complete verification operator and
the complete drawing indication for cylindricity consistent with GPS standard system; models the inter/intra
relationships between the elements of operations involved in cylindricity and integrates them by category theory; solves
the storage format and closure of query for the categorical data model by the pull-back structure and functor transform in
category theory respectively.
KEYWORDS: Global Positioning System, Manufacturing, Metrology, Standards development, Tolerancing, Fused deposition modeling, Communication engineering, Gaussian filters, System integration, Data acquisition
The next generation GPS (Dimensional and Geometrical Product Specification and Verification) is a very important basic
technique standard system for manufacturing that aims to enrich the GPS specification language to express the functional
requirements of the products, thus to reduce the correlation uncertainty and specification uncertainty, etc. On one facet, it
seems that the indication may be richer, precise, and therefore more verbose, and thus probably to take longer time for
design. And on another facet, the designer can't use the standards effectively even if he has a well comprehension of
them. To resolve the problem, this paper proposes a GPS information system, which will further help to reduce the
development cycle and the cost of the products greatly. Acquisition and representation of knowledge are one of the most difficult steps on successfully developing of the knowledge base of this GPS information system, because it affects the
development efficiency, speed, and maintenance of the system as data structure in ordinary programming. For
knowledge modeling of this GPS information system, a new modeling mechanism based on category theory is put
forward in this paper. The knowledge model based on category theory is called Geometrical Knowledge Model (GKM).
This information system is built up on the category theory due to its formality and high level of abstraction. Finally, the
basic knowledge structure of the next generation GPS roundness specification is given in the paper.
KEYWORDS: Global Positioning System, Data modeling, Fused deposition modeling, System integration, Metrology, Manufacturing, Standards development, Systems engineering, Systems modeling, Data processing
The next generation GPS (Geometrical Product Specification and Verification) is a very important basic technique standard system for manufacturing. It has been developing by ISO/TC 213 since 1996. But it is an intricate and abundant information system for engineering application and causes the problem of popularized usage. An integrated information system of the next generation GPS is proposed in this paper. For data modeling of next generation GPS information system, a new modeling method based on category theory is put forward and called GDM (Geometrical Data Model) in the paper. An important advantage of the method lies in its configurable semantics which can make the structure relationship clearly amongst the meta knowledge of standards issued or revised by the ISO/TC213, and by this method, features such as null values, uncertainty and temporal behavior can be added easily by selecting appropriate instance categories.
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.