scholarly journals A Straightness Error Compensation System for Topography Measurement Based on Thin Film Interferometry

Photonics ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 149
Author(s):  
Hang Su ◽  
Ruifang Ye ◽  
Fang Cheng ◽  
Changcai Cui ◽  
Qing Yu
Keyword(s):  
Phase Shift ◽  
Error Compensation ◽  
Incident Light ◽  
Digital Camera ◽  
Image Processing Algorithm ◽  
Measurement Capability ◽  
Motion Stage ◽  
Straightness Error ◽  
Value Measurement ◽  
Measurement Deviation

Straightness error compensation is a critical process for high-accuracy topography measurement. In this paper, a straightness measurement system was presented based on the principle of fringe interferometry. This system consisted of a moving optical flat and a stationary prism placed close to each other. With a properly aligned incident light beam, the air wedge between the optical flat and the prism would generate the interferogram, which was captured by a digital camera. When the optical flat was moving with the motion stage, the variation in air wedge thickness due to the imperfect straightness of the guideway would lead to a phase shift of the interferogram. The phase shift could be calculated, and the air wedge thickness could be measured accordingly using the image processing algorithm developed in-house. This air wedge thickness was directly correlated with the straightness of the motion stage. A commercial confocal sensor was employed as the reference system. Experimental results showed that the repeatability of the proposed film interferometer represented by σ was within 25 nm. The measurement deviation between the film interferometer and the reference confocal sensor was within ±0.1 µm. Compared with other interferometric straightness measurement technologies, the presented methodology was featured by a simplified design and good environment robustness. The presented system could potentially be able to measure straightness in both linear and angular values, and the main focus was to analyze its linear value measurement capability.

scholarly journals Colour Constancy for Image of Non-Uniformly Lit Scenes

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2242
Author(s):  
Md Akmol Hussain ◽  
Akbar Sheikh-Akbari ◽  
Iosif Mporas
Keyword(s):  
Light Source ◽  
State Of The Art ◽  
Incident Light ◽  
Digital Camera ◽  
Input Image ◽  
Absolute Difference ◽  
Light Sources ◽  
Colour Constancy ◽  
Adjustment Factors ◽  
Camera Sensors

Digital camera sensors are designed to record all incident light from a captured scene, but they are unable to distinguish between the colour of the light source and the true colour of objects. The resulting captured image exhibits a colour cast toward the colour of light source. This paper presents a colour constancy algorithm for images of scenes lit by non-uniform light sources. The proposed algorithm uses a histogram-based algorithm to determine the number of colour regions. It then applies the K-means++ algorithm on the input image, dividing the image into its segments. The proposed algorithm computes the Normalized Average Absolute Difference (NAAD) for each segment and uses it as a measure to determine if the segment has sufficient colour variations. The initial colour constancy adjustment factors for each segment with sufficient colour variation is calculated. The Colour Constancy Adjustment Weighting Factors (CCAWF) for each pixel of the image are determined by fusing the CCAWFs of the segments, weighted by their normalized Euclidian distance of the pixel from the center of the segments. Results show that the proposed method outperforms the statistical techniques and its images exhibit significantly higher subjective quality to those of the learning-based methods. In addition, the execution time of the proposed algorithm is comparable to statistical-based techniques and is much lower than those of the state-of-the-art learning-based methods.

scholarly journals Gamma Precorrection and Phase Error Compensation Methods Based on Three-Frequency with Three-Phase Shift

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Wei Feng ◽  
Shaojing Tang ◽  
Shinan Xu ◽  
Tong Qu ◽  
Daxing Zhao
Keyword(s):  
Phase Shift ◽  
Error Compensation ◽  
Phase Error ◽  
Three Dimensional ◽  
Harmonic Component ◽  
Measurement Technology ◽  
Compensation Methods ◽  
Three Phase ◽  
Phase Calculation ◽  
Fringe Patterns

Digital fringe projection measurement technology has been widely used in computer vision and optical three-dimensional (3D) measurement. Considering the phase error caused by the gamma distortion and nonlinear error, the active gamma precorrection and phase error compensation methods based on the three-frequency with three-phase shifts are designed to reversely solve the initial phase and accurately compensate phase error. On the one hand, the gamma coefficient of the measurement system depends on precoding two groups of fringe sequences with different gamma coefficients to calculate the corresponded proportional coefficient of harmonic component. On the other hand, the phase error compensation method is designed to compensate the phase error and improve the accuracy and speed of phase calculation after gamma correction. Experiments show that the proposed precalibration gamma coefficient method can effectively reduce the sinusoidal error in nearly 80 percent which only needs fewer fringe patterns. Compared with the traditional three-frequency with four-phase shift method, the proposed method not only has higher phase accuracy and better noise resistance but also has good robustness and flexibility, which is not limited to the gamma distortion model.

Effect analysis of surface metal layer on step height standard

2021 ◽  
pp. 2140006
Author(s):  
Xiaodong Zhang ◽  
Suoyin Li ◽  
Zhiguo Han ◽  
Lin Zhao ◽  
Yanan Feng ◽  
...  
Keyword(s):  
White Light ◽  
Metal Layer ◽  
Step Height ◽  
Measuring Instrument ◽  
Effect Analysis ◽  
Measurement Capability ◽  
White Light Interferometer ◽  
Surface Metal ◽  
Measuring Machine ◽  
Measurement Deviation

In order to improve the measurement accuracy of the step height measuring instrument, a semiconductor process was used to prepare the step height standard for calibrating the instrument. Aiming at the problem of deviation in the white light interferometer measuring step height standard, the cause of the measurement deviation was theoretically analyzed, combining the optical theory and the principle of instrument. In addition, referring to the semiconductor sputtering process, a method of sputtering metal layer on the surface of the step structure was proposed, and a set of universal step height standards with a nominal value of [Formula: see text] nm were developed for the step height measuring instrument. Finally, the step height standards with the sputtered metal layer were compared and measured, using the white light interferometer and nanometer measuring machine (NMM). The measurement error of the white light interferometer can be effectively controlled within 1%, which is beneficial to verify the measurement capability of the step height measuring instrument.

Research on the Compensation Method of Installation Errors in Guideway Straightness Measurement with PSD

2012 ◽  
Vol 630 ◽  
pp. 389-395
Author(s):  
Rui Fan ◽  
Di Zhang
Keyword(s):  
Significant Influence ◽  
Error Compensation ◽  
Measurement Accuracy ◽  
Compensation System ◽  
Compensation Method ◽  
Error Angle ◽  
Compensation Theory ◽  
Straightness Error ◽  
After Error

Influence and Compensation Theory of Installation Errors in Guideway Straightness Measurement with PSD Is Analyzed. it Shows that Pincushion Distortion Affects PSD’s Accuracy, while Angle θ between Laser and Guideway, Error Angle Caused by Straightness Error and Angle β Generated when PSD Rotates about the Guideway Have Significant Influence on System Measurement Accuracy. PSD’s Pincushion Distortion Could Be Corrected and Installation State Can Be Determined by Measuring on Site and Calibrating with Laser Tracer. after Error Compensation, System Measurement Accuracy Is Greatly Improved.

scholarly journals Using digital photography to implement the McFarland method

2012 ◽  
Vol 9 (73) ◽  
pp. 1892-1897 ◽  
Author(s):  
L. Lahuerta Zamora ◽  
M. T. Pérez-Gracia
Keyword(s):  
Light Intensity ◽  
Calibration Curve ◽  
Incident Light ◽  
Digital Camera ◽  
Imaging Method ◽  
Bacterial Cells ◽  
Liquid Media ◽  
The Public ◽  
Public Domain Software ◽  
Bacterial Concentrations

The McFarland method allows the concentration of bacterial cells in a liquid medium to be determined by either of two instrumental techniques: turbidimetry or nephelometry. The microbes act by absorbing and scattering incident light, so the absorbance (turbidimetry) or light intensity (nephelometry) measured is directly proportional to their concentration in the medium. In this work, we developed a new analytical imaging method for determining the concentration of bacterial cells in liquid media. Digital images of a series of McFarland standards are used to assign turbidity-based colour values with the aid of dedicated software. Such values are proportional to bacterial concentrations, which allow a calibration curve to be readily constructed. This paper assesses the calibration reproducibility of an intra-laboratory study and compares the turbidimetric and nephelometric results with those provided by the proposed method, which is relatively simple and affordable; in fact, it can be implemented with a digital camera and the public domain software I mage J.

Engineering Realization of Dual-Target DPVS on Expressway Fog Detection

2014 ◽  
Vol 587-589 ◽  
pp. 2089-2095
Author(s):  
Qin Guan
Keyword(s):  
Image Processing ◽  
Detection Method ◽  
Detection System ◽  
Digital Camera ◽  
Anhui Province ◽  
Processing Algorithm ◽  
Image Processing Algorithm ◽  
Main Components ◽  
Dual Target ◽  
Fog Detection

Digital photographic visibility system (DPVS) based on binocular targets is a method using digital camera and image processing technology for visibility detection. In order to obtain accurate results, the function and installation methods for main components of video visibility detection system including artificial objects, cameras and other parts are designed delicately. Also the article explains the image processing algorithm. From this analysis, the detection system engineering and implementation are not complicated. In 2013, this video visibility detection method has been applied to enhance foggy area security system in Anhui Province, Bengbu - Huainan expressway, and achieved good results.

Z-TRANSFORM METHOD FOR OPTIMIZATION OF ADD-DROP CONFIGURATION SYSTEM

2015 ◽  
Vol 74 (8) ◽  
Author(s):  
Suzairi Daud ◽  
Kashif Tufail Chaudary ◽  
Mahdi Bahadoran ◽  
Jalil Ali
Keyword(s):  
Phase Shift ◽  
Gaussian Beam ◽  
Communication Technology ◽  
Input Signal ◽  
Ring Resonator ◽  
Incident Light ◽  
Dark Soliton ◽  
Transform Method ◽  
New Approaches ◽  
Configuration System

This paper presents the new approaches of optimization the add-drop configuration system by using Z-transform method. Dark soliton was chosen as the input signal and Gaussian beam was chosen as the control signal for the model proposed. The incident light was said to achieve the maximum resonance with the ring resonator when the phase shift, . The derivation, analyzation, and optimization of the system are typically very important especially for the communication technology.

scholarly journals Automated Enumeration of Groups of Marine Picoplankton after Fluorescence In Situ Hybridization

2003 ◽  
Vol 69 (5) ◽  
pp. 2631-2637 ◽  
Author(s):  
Jakob Pernthaler ◽  
Annelie Pernthaler ◽  
Rudolf Amann
Keyword(s):  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
North Sea ◽  
Incident Light ◽  
Digital Camera ◽  
Automated System ◽  
Cell Counting ◽  
Microbial Cells ◽  
Relative Abundances

ABSTRACT We describe here an automated system for the counting of multiple samples of double-stained microbial cells on sections of membrane filters. The application integrates an epifluorescence microscope equipped with motorized z-axis drive, shutters, and filter wheels with a scanning stage, a digital camera, and image analysis software. The relative abundances of specific microbial taxa are quantified in samples of marine picoplankton, as detected by fluorescence in situ hybridization (FISH) and catalyzed reporter deposition. Pairs of microscopic images are automatically acquired from numerous positions at two wavelengths, and microbial cells with both general DNA and FISH staining are counted after object edge detection and signal-to-background ratio thresholding. Microscopic fields that are inappropriate for cell counting are automatically excluded prior to measurements. Two nested walk paths guide the device across a series of triangular preparations until a user-defined number of total cells has been analyzed per sample. A backup autofocusing routine at incident light allows automated refocusing between individual samples and can reestablish the focal plane after fatal focusing errors at epifluorescence illumination. The system was calibrated to produce relative abundances of FISH-stained cells in North Sea samples that were comparable to results obtained by manual evaluation. Up to 28 preparations could be analyzed within 4 h without operator interference. The device was subsequently applied for the counting of different microbial populations in incubation series of North Sea waters. Automated digital microscopy greatly facilitates the processing of numerous FISH-stained samples and might thus open new perspectives for bacterioplankton population ecology.

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