Investigation of rectangular apertures and their application on speckle imaging

Background

An aperture in the form of four squares arranged symmetrically along the cartesian coordinates with equal distances from the center investigated. Three models are suggested in the computation of the Point Spread Function PSF using the FFT technique. In the 1st model, circular annulus is placed in the center, while in the 2nd model a square annulus is shown, and in the 3rd model, two symmetric squares in the models 1, 2 are replaced by two symmetric rectangles while the center remains of square annulus. In all the models, central obstruction is made seeking to improve the PSF.

Results

An analytical formula for the PSF for the aperture described in the 1st model is obtained. In addition, the autocorrelation corresponding to these apertures are computed and compared with the known autocorrelation corresponding to the whole square aperture. An application on speckle imaging is given using these apertures combined with the diffuser. All images for the design of the apertures and the speckle images are made using the MATLAB code.

Conclusions

The resolution computed from the FWHM showed an improvement for the suggested square apertures as compared with the uniform square aperture where the total width is kept constant. In addition, the strength of the legs in the PSF for the suggested apertures is much higher than that corresponding the uniform aperture which makes it useful for imaging of extended objects.

Investigation of a new modulated aperture using speckle techniques

Background

A design of equally spaced eight-circles placed at equal distances from the origin is suggested. Three models corresponding to the eight-circle design considering conic, linear, and quadratic distributions are investigated. This arrangement is considered for the sake of improving both microscope resolution and image contrast as compared with the pure annular aperture. This design is different compared with other recent work on aperture modulation.

Results and discussions

The point spread function (PSF) is computed in all the models using the fast Fourier transform (FFT) algorithm that computes the discrete Fourier transform (DFT) corresponding to the models and compared with the corresponding PSF in the case of uniform circular aperture. In addition, the autocorrelation images for the apertures are shown differently. It is shown smooth pattern for the circular arrangement as compared with the deformation and shrinking appeared in the central peak in case of conic model. Finally, the speckle images corresponding to the considered apertures are investigated. Reconstructed apertures are obtained from the speckle images using the FFT algorithm.

Conclusions

The PSF is computed for the described models, and the autocorrelation corresponding to the apertures showed difference. The reconstructed apertures from the speckle images can be improved using filtering techniques. It is noted that MATLAB codes are constructed in the computations of all images and plots.

A hyper-resolving polynomial aperture and its application in microscopy

Background

A hyper-resolving aperture composed of a polynomial distribution is suggested. The point spread function (PSF) is computed and compared with that corresponding to linear, quadratic, and circular apertures. In addition, the influence of the number of zones on the PSF is discussed. An application on confocal scanning laser microscope using Siemen’s star pattern as an object considering the polynomial apertures is given.

Results

We have made polynomial apertures using MATLAB code, and we tested the resolution from the computation of the cut-off spatial frequency obtained from the computation of the point spread function.

Conclusions

We get compromised resolution and contrast for the polynomial apertures as compared with uniform circular apertures.

Reconstruction of images in non-scanned confocal microscope (NSCM) using speckle imaging

Background

The common formation of images in CSLM assumes mechanically scanned object placed in the common short focus of the objective lenses of the microscope, while in the arrangement under study, the scanning of the object is realized by placing a diffuser behind the collimating lens. A model is suggested in the formation of images in Confocal Scanning Laser Microscope (CSLM) using non-scanned object. Since the illumination and detection are coherent, the obtained image is constructed from the simple product of the Resultant Point Spread Function (RPSF) modulated by the diffuser spread over the object transparency. Hence, the product of the object and the image of the diffuser replace the mechanical scanning of the object.

Results

Reconstructed images using this novel arrangement of CNSM are presented using mammographic X-ray image.

Conclusions

Convolution of the RPSF and the object is realized by the spreading of the diffuser image over the object. A coherent detector captures the whole image affected by a noisy diffused function. It is noted that image processing is necessary to improve noisy images making use of filtration techniques.

Fabrication of a novel low-cost superoleophilic nonanyl chitosan-poly (butyl acrylate) grafted copolymer for the adsorptive removal of crude oil spills

A novel superoleophilic-hydrophobic nonanyl chitosan-poly (butyl acrylate) grafted copolymer was fabricated as a low-cost oil-adsorbent. Chitosan (CS) was coupled with a hydrophobic nonanal (N) to form nonanyl chitosan (NCS) schiff base, and followed by grafting with butyl acrylate monomers (ButA). The grafted copolymer was characterized by FTIR, TGA and SEM tools. The grafting percent was augmented and reached 88.5% with increasing ButA concentration up to 156 mM. Moreover, measurements of contact angle proved the superoleophilic character of NCS-g-poly (ButA) copolymer with an oil-contact angle 31°. Factors affecting the removal process such as contact time, oil type, oil dose, adsorbent dose, temperature and agitation speed were optimized. An increment in the oil removal (%) was observed with increasing the oil viscosity in the order of gasoil < mobil-1 oil < light crude oil < heavy crude oil. Besides, the adsorption process followed the pseudo-second order model and the equilibrium data were sufficiently fitted with the Langmuir model with a maximum adsorption capacity 108.79 g/g at 25 °C. Thermodynamic parameters computed from Van't Hoff plot confirmed the process to be exothermic, favorable and spontaneous. The results nominate the superoleophilic adsorbent as a potential oil- adsorbent for petroleum oil spills removal.

Endothelial dysfunction marker YKL-40 is elevated in male patients with idiopathic infertility

Metabolic syndrome represents a collection of cardiovascular risk factors, including overweight, hypertension, dyslipidemia and impaired glucose metabolism, with insulin resistance. In recent years, the potential relationship between metabolic syndrome and male factor infertility has been studied. As endothelial dysfunction is the hallmark of metabolic syndrome, the aim of this work was to assess serum levels of YKL-40 as a marker of endothelial dysfunction in male patients with idiopathic infertility. The study revealed that YKL-40 levels were elevated in patients than controls denoting that endothelial dysfunction might play a role in the pathogenesis of idiopathic infertility and that YKL-40 as a marker of endothelial dysfunction could be a useful marker of idiopathic infertility.

Applying tactile sensing with piezoelectric materials for minimally invasive surgery and magnetic-resonance-guided interventions

Medical technologies have undergone significant development to overcome the problems inherent in minimally invasive surgery such as inhibited manual dexterity, reduced visual information, and lack of direct touch feedback to make it easier for surgeons to operate. A minimally invasive tool incorporating haptic feedback is being developed to increase the effectiveness of diagnostic procedures by providing force feedback. Magnetic resonance imaging guidance is possible to allow tool localization; however, this engenders the requirement of magnetic resonance compatibility on the device. This paper describes the work done towards developing a sensing device using piezoelectric sensor elements to locate subsurface inclusions in soft substrates, with its magnetic resonance compatibility tested in a 1.5 T scanner. Results show that the position of a hard inclusion can be determined.

Preoperative screening of contact lens wearers before refractive surgery

PURPOSE

To evaluate corneal stability, measured by computerized videokeratography (CVK) after discontinuation of contact lens wear in preoperative refractive surgery candidates.

SETTING

Baylor College of Medicine, Cullen Eye Institute, Houston, Texas, USA.

METHODS

Topographic differences were analyzed in 136 noncontact lens wearers (NCLW) and 76 contact lens wearers (CLW) (18 rigid gas-permeable contact lenses [RGPCL], 58 soft contact lenses [SCL]) using EyeSys CVK after discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks.

RESULTS

There were no differences in CVK patterns between the NCLW and the CLW groups. There were no statistically significant differences between the 2 groups in topographic symmetry, asphericity, corneal uniformity index, predicted corneal acuity, and irregular astigmatism. The dioptric range for the axial and the profile difference maps in the CLW group was slightly lower than in the NCLW group.

CONCLUSIONS

For patients whose manifest refraction and CVK maps were within 0.5 diopters of earlier values, discontinuation of SCL wear for 2 weeks and RGPCL wear for 5 weeks was adequate for the cornea to return to its baseline topographic state.

Corneal topography classification in myopic eyes based on axial, instantaneous, refractive, and profile difference maps

PURPOSE

To refine and develop systems for classifying the topography of myopic corneas using axial, instantaneous, refractive, and profile difference maps.

SETTING

Baylor College of Medicine, Cullen Eye Institute Houston, Texas, USA.

METHODS

Using the EyeSys Corneal Analysis System, computerized videokeratographs of 153 corneas of 78 myopic patients were retrospectively analyzed. Patterns were defined with respect to the mid-dioptric green color. Relationships among pattern types, refractive power, corneal power, corneal uniformity index (CU index), and predicted corneal visual acuity (PC acuity) were calculated.

RESULTS

Six types of patterns for axial, instantaneous, and refractive maps and 3 types of patterns for the profile difference map were defined. For a given cornea, there was a weak correlation among the patterns in the axial, instantaneous, and profile difference maps. The circular with central irregularity pattern in auto-scale refractive maps and the irregular pattern in profile difference maps and axial maps were correlated with lower CU index and PC acuity values. Clinical classification of instantaneous maps did not contribute substantially to the information provided by axial maps.

CONCLUSION

Patterns of computerized videokeratographs varied according to the type of topographic map. The classification systems used provide a baseline for analyzing the response of the cornea to various interventions.