Optical Analysis System Research Articles

Millimeter-Level-Spatial-Resolution Brillouin Optical Correlation-Domain Analysis Based on Broadband Chaotic Laser

We propose and demonstrate a millimeter-level-spatial-resolution Brillouin optical correlation-domain analysis system based on a broadband chaotic laser, where the spatial resolution only depends on chaotic signal bandwidth. By adjusting the bandwidth of chaos, the single correlation peak has been compressed to be extremely narrow. The Brillouin gain spectrum was obtained by replacing a previous optical power meter with a lock-in amplifier. Thus, the signal-to-noise ratio improved and the data acquisition time reduced effectively. This experiment is the first in that the distributed tensile strain was observed via a chaotic Brillouin optical correlation-domain analysis system with a 3.5-mm spatial resolution over 165-m measurement range. The standard deviation in the reconstructed Brillouin frequency shift was ±2 MHz. To the best of our knowledge, the proposed system is a broadband-source optical sensing system with the highest reported spatial resolution.

Methods of collection, extender type, and freezability of semen collected from creole bulls raised in the tropical highlands of Ecuador.

This study was conducted to determine the best combination between two collection method and two extenders in the cryopreservation of semen from creole bulls adapted to highlands of the Ecuadorian Andes. Sixty ejaculates from three adult Creole bulls were evaluated after collection by artificial vagina (AV) and electroejaculation (EE). Semen samples were split into two aliquots and diluted with a soy lecithin extender (Andromed®; A) or an egg yolk-containing extender (Triladyl®; T) and packed in straws of 0.25ml with 20 × 106 sperms. Optical microscopy and computer-assisted semen analysis system (CASA) were used to evaluate semen quality characteristics. The effects of collection methods and extender type as well as its interaction were evaluated by a factorial ANOVA and Bonferroni's test. Semen samples collected with EE and frozen with T (EE-T) and A (EE-A) had greater proportion of spermatozoa with optical assessed individual progressive motility (IPM), plasmatic membrane intact (HosT), and lower tail abnormalities than those obtained with AV and frozen with the same extenders (AV-T and AV-A); however, differences were significant only between EE-A and AV-T. CASA assessment indicated that the total mobility (TM) was greater (P < 0.05) in semen samples diluted with T, although these samples had a greater proportion (P < 0.05) of sperms with local motility (LM) and fewer immobile sperms (IS), than those extended with A. Generally, semen samples obtained with EE or AV and diluted with T seems to be the best option to ciopreserve gametes of Creole bulls raised in highlands of Ecuadorian Andes.

Three-Dimensional Density Estimation of Flame Captured From Multiple Cameras

Optical combustion measurement and analysis systems using multiple sensors have received considerable attention. In particular, the image-based flame 3D reconstruction approaches using computerized tomography have been widely applied for the flame 3D reconstruction from a set of views by constructing the optimized linear combinations of the 3D scene and projected images. Previous techniques were easily computed but were weak against noise and blurring due to the underlying least square-based loss function. This paper presents a 3D density flame reconstruction method, captured from the sparse multi-view images, as a constrained optimization problem between the flame and its projected images. For effective estimation of the flame with a complicated structure in an arbitrary viewpoint, we extract the 3D candidate region of the flame and, then, estimate the density field using the compressive sensing. The objective function is a linear combination of the photo consistency cost and sparsity regularization terms, which avoids blurring in the reconstruction. The proposed approach is a powerful matrix factorization method with each voxel represented as a linear combination of a small number of basis vectors. The approach also effectively simplifies the reconstruction process and provides the whole 3D density field in one step. The experimental results verify that the proposed 3D density estimation performs favorably from the few flame images.

INVESTIGATION AND OPTIMIZATION OF A CLOSED CIRCUIT CRUSHING OF COPPERMOLYBDENUM ORE

To control the processes of ore treatment proposed adapted to the conditions of a closed cycle crushing-screening criterion "output productive class -2 + 10 mm", reflecting the effectiveness of all processes. The dependence of the outputs of the individual classes of ore and the proposed optimization criterion parameters of the grinding process shows their relationship with the energy intensity of the process. It is shown that the increase in the load on the screen causes a decrease in the screening efficiency and an increase in the mass fraction of class +2 mm in the circulating ore. Excessive increase in the width of the discharge gap of the crusher causes an increase in the output of the circulating product and an increase in energy consumption. Reducing the discharge gap of less than 7.5 mm leads to an increase in the output of the class - 2 mm. An improved system and algorithm for optical analysis of ore size was proposed and tested. The sensors for controlling the granulometric composition of ore are located above the conveyors for the transportation of over-and under-mortar products of the screening operation. The optical analysis mode provides for the sequential switching on / off of feeding conveyors and crushers, thereby ensuring the flow of the crushed product into the measurement zone from one crusher. The total duration of the analysis of ore from 6 crushers is 12 minutes, which does not affect the final performance of the device of crushing. The application of the developed algorithm can significantly improve the accuracy of the analysis of the size of crushed ore and reduce the power consumption during the processing of ore.

Averaging-free vector Brillouin optical time domain analyzer assisted by reference probe lightwave.

We propose and experimentally demonstrate a vector Brillouin optical time domain analyzer (BOTDA) system, which enables both distributed Brillouin gain spectrum (BGS) and Brillouin phase-shift spectrum (BPS) measurements without trace averaging. The proposed scheme generates and launches a reference light into the fiber under test (FUT), together with the Stokes probe light to indicate the phase noise and distortion in the probe. The commercial integrated coherent receiver at the detection end, using a local oscillator (LO) generated with single sideband (SSB) modulation, on the one hand, improves the signal-to-noise ratio (SNR) to avoid the need of trace averaging for the signal acquisition. On the other hand, by processing and analyzing the receiver outputs at specific intermediate frequencies (IF), the amplitude and phase signals carried by the Stokes probe and the reference light can be resolved at once. In this way, both Brillouin gain and Brillouin phase-shift signals can be obtained simultaneously. By scanning the the Stokes probe light frequency and recording the Brillouin response at each scanning frequency, both distributions of Brillouin gain spectrum and phase-shift spectrum have been acquired. The configuration is approved by experiments carried out over an 18.2 km FUT with the spatial resolution of 2 m.

Chaotic Brillouin optical correlation-domain analysis.

We propose and experimentally demonstrate a chaotic Brillouin optical correlation-domain analysis system for distributed fiber sensing. The utilization of a chaotic laser with a low coherence state ensures high spatial resolution. The experimental results demonstrate a 4cm spatial resolution over a 906m measurement range. The uncertainty in the measurement of the local Brillouin frequency shift is ±1.2 MHz. The analysis of the expected spatial resolution and signal-to-noise ratio is also given.

Intraocular light scatter in patients on topical intraocular pressure-lowering medication.

To quantify ocular light scattering in patients under treatment with intraocular pressure-lowering eye-drops. In this prospective, observational, cross-sectional case series study, 160 eyes of 160 patients with primary open angle glaucoma or primary ocular hypertension were consecutively recruited from our Glaucoma Department over 7 months. In total, 46 eyes of 46 healthy volunteers matched for age and sex served as the control group. The variables recorded in a single visit were as follows: drug and number of drops per day, treatment duration, OXFORD corneal staining grade, lower tear meniscus height as measured by spectral domain optical coherence tomography, ocular redness and non-invasive tear breakup time measured with the Oculus Keratograph 5M, ocular surface disease index questionnaire score and objective scatter index through a double-pass technique (Optical Analysis System II). Objective scatter index was higher in the patient group (3.1, interquartile range = 1.8-5.47) than in the control group (1.95; interquartile range = 0.7-5; p = 0.017). In a multiple linear regression model, non-invasive tear breakup time was identified as the most influential variable on light scatter (mean ratio = -1.015; p = 0.003; 95% confidence interval = -1.025 to -1.005). No correlation with objective scatter index was observed for number of daily eye-drops, preservative concentration or treatment duration. Participants on anti-glaucoma medication showed a significantly higher objective scatter index than control group individuals. In the treated patient group, a lower non-invasive tear breakup time was associated with a higher objective scatter index. This suggests that lubricating eye-drops to improve tear breakup time could also improve vision quality in these patients by diminishing light scattering.

Effect of CoFe2O4 nanoparticles on a carbonyl iron based magnetorheological suspension

Magnetic CoFe2O4 nanoparticles were successfully fabricated by a non-aqueous hydrothermal method and used as an additive in a micron-sized, carbonyl iron (CI) based-magnetorheological (MR) fluid to improve its dispersion stability and MR characteristics. The morphology and magnetic properties of CoFe2O4 were demonstrated by using X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. The results showed that CoFe2O4 was synthesized successfully with a nearly spherical morphology and excellent crystalline structure. The saturation magnetization (Ms) of the CoFe2O4 was also about 74.4 emu/g. The CI MR fluid was prepared by dispersing 50wt% of CI particles in silicone oil, and the CI/CoFe2O4 MR fluid was prepared by adding 0.1wt% of CoFe2O4 nanoparticles to the CI MR fluid. The MR characteristics of both MR fluids were tested via a rotational rheometer at various magnetic field strengths. The CI/CoFe2O4 MR fluid showed enhanced MR characteristics with higher yield stress, shear viscosity, and dynamic modulus than that of the CI MR fluid. Furthermore, the dispersion stability of both MR fluids were also investigated via a Turbiscan optical analyzer system, and these results showed that the sedimentation ratio after 24h had improved by about 21%.

A comparative study of visual quality between implantable collamer lens implantation and femtosecond LASIK for myopia

Background The incidence of myopia is gradually increasing, and how to choose a better corrective method of myopia for the best visual demand is very important. Objective This study was to compare visual quality of implantable collamer lens (ICL) implantation with femtosecond laser in situ keratomileusis (FS-LASIK) for moderate and high myopia using double-pass optical quality analysis system (OQAS). Methods A non-randomized controlled clinical trail was performed.Fifty-two eyes with -4.00 to -9.00 D of 26 consecutive patients were included in NO.1 Hospital of Xi'an from January 2015 to January 2016.Twenty-four eyes of 12 patients with the corneal thickness 0.05). All the patients were followed-up for 3 months after surgery.The preoperative best corrected distance visual acuity (BCDVA), spherical equivalent (SE), postoperative uncorrected distance visual acuity (UCDVA), BCDVA and SE were examined and compared between two groups.The parameters from OQAS were evaluated and intergrouply compared, including the objective scattering inders (OSI), modulation transfer function (MTF) cut off frequency, Strehl ratio and OQAS values under the contrast of 100%, 20% and 9%(OV100, OV20, OV9). Results The postoperative BCDVA was not significantly different from preoperative UCDVA in both ICL group and FS-LASIK group (-0.04±0.10 vs. 0.05±0.12; -0.07±0.12 vs.0.00±0.12) (t=3.128, 2.358, both at P>0.05). No statistically significant differnces were found in SE, UCDVA and BCDVA after operation between ICL group and FS-LASIK group (t=1.292, 0.900, -0.653, all at P>0.05). OQAS examination showed that MTF cut off, OSI, Strehl ratio, OV100 were not significantly different after operation between ICL group and FS-LASIK group (t=-2.032, -1.440, -0.224, all at P>0.05). The postoperative OV20 and OV9 were 0.82±0.14 and 0.80±0.21 in the ICL group, which were significantly higher than those in the FS-LASIK group(0.59±0.15 and 0.47±0.13)(t=4.105, 4.702, both at P<0.05). Conclusions Both ICL implantation and FS-LASIK provide good optical and visual quality for moderate to high myopic eyes, and ICL appears to have a better visual quality in comparison with FS-LASIK under the contrasts of 20% and 9%. Key words: Myopia/surgery; Refractive surgical procedure; Phakic intraocular lenses; Keratomileusis, laser in situ; Visual quality; Implantable collamer lens; Double-pass optical quality analysis system

Development of a 3D Gait Measurement Protocol for Amputees Walking on Treadmill

Walking motion is actually a complex activity since it involves many body parts, especially the lower limb. Due to the needs for gait analysis in many medical applications, Biomechanics Research Team at ITB has developed an affordable optical motion analyzer to measure motions of subject walking over ground. However, the needs for multicycles gait data is better met by measuring subjects walking on treadmill. This paper discusses the modification of the developed motion analyzer to accommodate data acquisition of subject walking on treadmill, including those of transfemoral amputees. Seven markers, two 95 fps cameras, a dual-channel Camera Link Acquisition NI PCIe-1430 frame grabber, and a workstation are employed in the optical motion analyzer system. The speed displayed on the treadmill is evaluated. Additional equipment such as the modified hydraulic engine crane and the body harness are introduced to ensure the safety of amputees and avoid the risk of falling down while walking on the treadmill. The modified motion analyzer system is then used to obtain gait parameters of normal (37 males and 31 females) and three amputee subjects. The gait parameters of normal subjects in the treadmill walking shows that there is a decrease in the stride length and range of motion, and increase in the cadence due to walking adaptation. There are also phase shifting and increase in the range of motion for amputee subjects compared to the normal subjects which imply that there is an extra work done by the residual limb in doing walking movement and the amputee subjects try to balance their walking on the treadmill.

Dynamic assessment of tear-film stability-associated objective vision in mild or moderate dry eyes based on Optical Quality Analysis System parameters

Background The progenesis and development of dry eye is closely associated with the stability of tear-film.Dry eyes often show the visual disturbance.Therefore, to evaluate the stability of tear-film based on visual quality and explore the relevant dynamic vision change in dry eyes is of important significance. Objective The aim of this study was to evaluate the dynamic changes of objective scattering index (OSI), modulation transfer function cut off (MTF cut off), objective visual acuity (OVA) with tear-film in the patients with mild or moderate dry eye disease using Optical Quality Analysis System. Methods A clinical diagnosis test was performed.Forty-two eyes of 42 consecutive patients with mild or moderate dry eyes were included in Tianjin Eye Hospital from December 2013 to May 2014 based on 'The Clinical Diagnosis and Treatment Recommendations for Dry Eye from Consensus of Expert Advice in 2013’, and 29 normal eyes of age-and gender-matched 29 healthy volunteers were simultaneously included as the healthy control group.The dynamic retinal images under non-blinking condition during 15 seconds were recorded by OQAS-Ⅱ system, and the OSI, MTF cut off and OVA values at 0, 5, 10 and 15 seconds were obtained, and the differences of OSI, MTF cut off and OVA between 0 second and 15 seconds were calculated (ΔOSI, ΔMTF cut off, ΔOVA) .The dynamic changes of ΔOSI, ΔMTF cut off and ΔOVA with time were evaluated.The sensitivity and specificity of ΔOSI, ΔMTF cut off and ΔOVA for the differential diagnosis of dry eyes were analyzed by receiver operating characteristic curve (ROC curve). Results The OSI values at 5, 10 and 15 seconds in the mild or moderate dry eye group were significantly higher than those at 0 second or those in the healthy control group (all at P<0.05), and the MTF cut off values and OVA values at 5, 10 and 15 seconds in the mild or moderate dry eye group were significantly lower than those at 0 second or those in the healthy control group (all at P<0.05). The ΔOSI, ΔMTF cut off and ΔOVA values were 1.03±1.53, (-8.37±9.64)c/d and -0.30±0.32 in the mild or moderate dry eye group, which were significantly higher than 0.06±0.16, (-0.37±5.27)c/d and -0.03±0.18 in the healthy control group (t=4.10, -5.19, -5.28, all at P<0.05). The area under ROC curve was 0.90, 0.79 and 0.78 in ΔOSI, ΔMTF cut off and ΔOVA, respectively.The sensitivity and specificity of ΔOSI was 78.6% and 93.1% respectively at the diagnostic cut off of 0.3. Conclusions The optical quality parameters related with tear-film stability are gradually reduced with extending of time in mild or moderate dry eyes, but they are stable in healthy eyes.The detecting outcomes by OQAS-Ⅱ system can reflect the dynamic status of tear-film, and this method is of important clinical value for the differential diagnosis and optical quality evaluation in dry eyes. Key words: Dry eye; Tear film; Optical quality; Scattering; Modulation transfer function cut off; Ophthalmic instrument

Mechanical characterization of a short fiber-reinforced polymer at room temperature: experimental setups evaluated by an optical measurement system

Composite materials are of great interest for industrial applications because of their outstanding properties. Each composite material has its own characteristics due to the large number of possible combinations of matrix and filler. As a result of their compounding, composites usually show a complex material behavior. This work is focused on the experimental testing of a short fiber-reinforced thermoplastic composite at room temperature. The characteristic behavior of this material class is often based on a superposition of typical material effects. The predicted characteristic material properties such as elasto-plasticity, damage and anisotropy of the investigated material are obtained from results of cyclic uniaxial tensile tests at constant strain rate. Concerning the manufacturing process as well as industrial applications, the experimental investigations are extended to multiaxial loading situations. Therefore, the composite material is examined with a setup close to a deep-drawing process, the Nakajima test (Nakazima et al. in Study on the formability of steel sheets. Yawate Technical Report No. 264, pp 8517–8530, 1968). The evaluation of the experimental investigations is provided by an optical analysis system using a digital image correlation software. Finally, based on the results of the uniaxial tensile tests, a one-dimensional macroscopic model is introduced and first results of the simulation are provided.

Optical measurements of paintings and the creation of an artwork database for authenticity.

Paintings have high cultural and commercial value, so that needs to be preserved. Many techniques have been attempted to analyze properties of paintings, including X-ray analysis and optical coherence tomography (OCT) methods, and enable conservation of paintings from forgeries. In this paper, we suggest a simple and accurate optical analysis system to protect them from counterfeit which is comprised of fiber optics reflectance spectroscopy (FORS) and line laser-based topographic analysis. The system is designed to fully cover the whole area of paintings regardless of its size for the accurate analysis. For additional assessments, a line laser-based high resolved OCT was utilized. Some forgeries were created by the experts from the three different styles of genuine paintings for the experiments. After measuring surface properties of paintings, we could observe the results from the genuine works and the forgeries have the distinctive characteristics. The forgeries could be distinguished maximally 76.5% with obtained RGB spectra by FORS and 100% by topographic analysis. Through the several executions, the reliability of the system was confirmed. We could verify that the measurement system is worthwhile for the conservation of the valuable paintings. To store the surface information of the paintings in micron scale, we created a numerical database. Consequently, we secured the databases of three different famous Korean paintings for accurate authenticity.

Porosity Formation in Al–Si Sand Mold Castings

The present study was performed on Al–Si–Cu 319 alloy castings obtained from cooling fin sand molds with variable fin size design. The amount of melt hydrogen, Sr, and Ti was also varied. In total 32 alloys were prepared to give 132 alloy/melt/solidification conditions. Porosity measurements were carried out on samples prepared from these castings using an optical microscope-image analysis system. It was found that at low solidification times, pore nucleation takes place predominantly in intergranular regions. The pore morphology is mostly elongated, the pores being observed to lie along the grain boundaries (due to the long freezing range of the alloy). The probability of pore nucleation taking place in interdendritic regions increases at higher solidification times, and the pore morphology tends to be more rounded, as well. Melt hydrogen levels of ~0.3 ml/100 g produce extremely large pores in the casting, even at high solidification rates. Thus, in order to produce sound castings, it is important that the melt be properly degassed in order to keep the hydrogen level at the minimum possible. Proper preheating of the sand mold is essential to ensure against the occurrence of reaction porosity along the casting surface.

Investigation and development of a high spectral resolution coherent optical spectrum analysis system.

Focusing on high resolution optical spectroscopy, a coherent optical spectrum analysis (COSA) system is investigated in this paper. Principle is built to demonstrate the operation of COSA and its signal processing in both time and frequency domain. According to COSA principle, resolution bandwidth (RBW) filters are found to have significant influence on power accuracy and spectral resolution of the optical spectrum analysis (OSA). Much effort is paid to design RBW filters, including center frequency, bandwidth and type of filters. Two RBW filters are optimized to reduce the power uncertainty of different spectral resolution and satisfy different signal under test. Then, simulations and experiments are conducted to verify COSA principle and results show that the power uncertainty is less than 0.5% and 1.2% for high and medium spectral resolution application, respectively. Finally, experiments on the OSA of actual spectra indicate that COSA system can achieve a 6 MHz spectral resolution and has an excellent capacity in analysis of fine spectrum structures.

Determination of Fracture Toughness by Single and Double Action Tensile Impact Fracture Tests

The characterization of the loading rate dependence of the fracture behavior of polymers is of prime theoretical and practical interest for supporting demanding engineering applications. To gain more insight into the high rate fracture behavior of polymers, fracture tests were performed under tensile loading conditions up to 12 m/s loading rate using a neat model polymer (PVC grey) in this study. A conventional single actuator test set-up for compact tension C(T) specimens was developed based on the previous experience of the authors and implemented on a new high rate servohydraulic testing machine. In addition, a novel double action test set-up was developed by applying two twin actuators and implemented in a rigid horizontal test frame. The conventional load and force measurement was extended by instrumented test specimens and by a high speed optical strain analysis system for both set-ups. Force based fracture toughness values using the peak load values, KIcPL and displacement based values using the critical crack opening displacement (CTOD) KICCTOD were determined up to a loading rate of 10 m/s. While the KIcPL values decreased up to a loading rate 103 MPam1/2s-1 an increase with a high data scatter was observed above them. Corresponding to the CTOD values the calculated KICCTOD values revealed a slight decrease and moderate data scatter up to the maximal loading rate.

Enhanced water resistance of extruded wood–polypropylene composites based on alternative wood sources

Polypropylene wood flour composites made from short-rotation coppice (SRC) and low valued beech wood (Fagus sylvatica) were investigated with respect to their suitability for use in the production of wood–polymer composites (WPC). An industrial wood source consisting of spruce wood flour (Picea abies) was used as reference material. All composites were compounded on a co-rotating twin screw extruder containing either 60 or 70 wt% wood flour. Consolidation was done by profile extrusion. Mechanical and physical properties of the composites were investigated. The wood sources were characterized concerning their particle length and shape by the use of a dynamic optical particle analysis system. X-ray microtomography (µ-CT) was used to study the dispersion of wood particles and the internal composite structure. However, all composites based on alternative wood sources showed an equivalent performance regarding mechanical properties compared to the composite reference. Composites containing beech wood flour showed notably reduced water absorption rates, whereas the composites based on SRC wood flour revealed significantly reduced moisture content compared to reference composites. A different particle length distribution was depicted between the industrial wood source and three other investigated wood sources. Moreover, all wood flour sources were characterized by a mean aspect ratio up to 3:1. The X-ray microtomography illustrated morphological differences between composites. Based on the X-ray images, an alignment along the melt flow and a decent encapsulation by polypropylene were shown.

Automated in vivo 3D high-definition optical coherence tomography skin analysis system.

The in vivo assessment and visualization of skin structures can be performed through the use of high resolution optical coherence tomography imaging, also known as HD-OCT. However, the manual assessment of such images can be exhaustive and time consuming. In this paper, we present an analysis system to automatically identify and quantify the skin characteristics such as the topography of the surface of the skin and thickness of the epidermis in HD-OCT images. Comparison of this system with manual clinical measurements demonstrated its potential for automatic objective skin analysis and diseases diagnosis. To our knowledge, this is the first report of an automated system to process and analyse HD-OCT skin images.

Evaluation of Local Deformation Values of Stamping in Comparison with Optical Forming Analysis System

There is a persisting trend in automotive industry to increase quality of parts along with productivity while decreasing the cost. All of those three goals are possible to achieve with help of the optical forming analysis system. However, optical forming analysis system is not always capable of calculating an exact result and there are cases when there is no such system available. Therefore there is a need for verification of results provided by the optical forming analysis system. Finding another method for cases where there is no such system available is also desirable. The dependence between grain size and strain is examined in this paper. The grain size was selected as an evaluating parameter due to its connection to the strain and because it is relatively easily measured. Measuring of the grain size was proved to be an alternative method to optical forming analyses in order to determine the strain of press formed parts.

Photometric correction for an optical CCD-based system based on the sparsity of an eight-neighborhood gray gradient.

In an optical measurement and analysis system based on a CCD, due to the existence of optical vignetting and natural vignetting, photometric distortion, in which the intensity falls off away from the image center, affects the subsequent processing and measuring precision severely. To deal with this problem, an easy and straightforward method used for photometric distortion correction is presented in this paper. This method introduces a simple polynomial fitting model of the photometric distortion function and employs a particle swarm optimization algorithm to get these model parameters by means of a minimizing eight-neighborhood gray gradient. Compared with conventional calibration methods, this method can obtain the profile information of photometric distortion from only a single common image captured by the optical CCD-based system, with no need for a uniform luminance area source used as a standard reference source and relevant optical and geometric parameters in advance. To illustrate the applicability of this method, numerical simulations and photometric distortions with different lens parameters are evaluated using this method in this paper. Moreover, the application example of temperature field correction for casting billets also demonstrates the effectiveness of this method. The experimental results show that the proposed method is able to achieve the maximum absolute error for vignetting estimation of 0.0765 and the relative error for vignetting estimation from different background images of 3.86%.