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1

Binocular summation evaluated by early and late visual evoked potentials

Czaińska M., Przekoracka-Krawczyk A., Naskręcki R., van der Lubbe R.

Optica Applicata

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2018

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Vol. 48, nr 1

137--148

EN

The visual evoked potential technique makes it possible to explore the visual system with a high temporal resolution, thereby providing information about different phases of binocular integration. The aim of the study was to characterize the amplitude, latency and scalp distribution of pattern-reversal gratings visual evoked potentials related to binocular viewing. 12 adult participants without any pathology of the visual system were examined by electroencephalography (EEG), with three viewing conditions: the dominant eye, non-dominant eye, and both eyes. They were tested with reversed checkerboard patterns presented with a frequency of 1.02 Hz. The amplitudes of visual evoked potentials were calculated to detect the effect of binocular integration. The strongest binocular summation was observed on the N75 component. P100 component was also affected by binocular viewing, mainly above parieto-occipital cortex. In the later time window binocular summation was reflected in changes in amplitude of N145 component over the right parieto-occipital region. The obtained results suggest that binocular summation is not limited to occipital cortex as its influence was also observed above parieto-occipital regions. Changes in amplitude of N75 component looks to be a good predictor of binocular summation.

2

A super depth of field height measurement based on local disparity

Cui L., Liu Y., Yu M., Jiang G., Fan S., Wang Y.

Optica Applicata

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2015

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Vol. 45, nr 2

205--214

EN

A super depth of field height measurement method is proposed to measure the object height with the optical stereoscopic microscope. The quasi-Euclidean epipolar rectification algorithm is utilized on the original stereoimage to obtain rectified stereoimages and calibrate two camera parameters. Then, feature points are obtained by the SURF (speed up robust feature) algorithm and their corresponding disparities are calculated. The disparity-depth of field curve is fitted by combining the step height values of a stepper motor. Moreover, through local disparity value got from feature points on the object, the relative shift height is calculated through regression analysis. Finally, according to binocular vision geometry, the thickness of the object can be calculated. Experimental results show that the measurement error in Z direction is from 1.51% to 7.71%, which indicates that the proposed method is able to measure the height of a microobject beyond depth of field within a tolerant error.

3

Fixation disparity curve in dyslexic adults

Brenk-Krakowska A., Szady M., Naskrecki R.

Optica Applicata

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2012

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Vol. 42, nr 4

805--820

EN

Dyslexia is a worldwide disorder in children and adults. The visual characteristics of dyslexics has been studied with variable results. One area of interest is fixation disparity (FD). This is a measure of alignment of the oculomotor system during binocular fusion. A graphical plot of the FD as it changes as a function of induced prisms before the eyes results in a forced vergence fixation disparity curve (FDC). The associated phoria is defined as the prism needed to return the FD to the ortho position. We performed FD evaluations and compared FDC characteristics with a group of 50 subjects: 25 dyslexic adults and 25 typically reading adults. The comparisons suggest that exo FD and the absolute amount of associated phoria tend to be higher in dyslexic adults. Moreover, they experience more instability of FD compared to the controls. They also have more limited convergence range and total vergence range. Both instability in motor responses and reduced vergence ranges indicate that binocular instability is likely to occur in dyslexic adults.

4

Stereovision system with active vergence and gaze control mechanism

Szewczyk P.

Pomiary Automatyka Kontrola

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2011

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R. 57, nr 11

1344-1347

EN

The paper describes a prototypical stereovision system with active vergence and gaze control mechanism. The model and mechanical construction enable the accurate positioning of cameras. Increase in the measurement resolution of the binocular vergence angle in the selected range of depth is specified. The vergence control mechanism uses a kinematic chain with 3-DOF joints. In order to obtain a linear characteristic of the measurement system, there was performed the optimisation process of the kinematic chain parameters.

PL

W artykule przedstawiony jest opis prototypowego układu stereo-wizyjnego z aktywnym systemem zmiany kąta widzenia oraz zbieżności osi optycznych kamer. Zmiana kąta zbieżności osi optycznych kamer wraz z obrotem głowicy umożliwia koncentrację systemu na pewnym, dowolnie wybranym obiekcie w rzeczywistej przestrzeni trójwymiarowej. Prowadzi do nałożenia pól widzenia obu kamer i niewielkich wartości dysparycji bliskich zeru dla wybranego, śledzonego obiektu umożliwiając szybką segmentację obrazu. Zaprezentowano model oraz konstrukcję mechaniczną umożliwiającą dokładne pozycjonowanie kamer, a także zwiększenie rozdzielczości pomiarowej kąta zbieżności w wybranym przedziale mierzonej głębi. W mechanizmie kontroli zbieżności osi optycznych kamer zastosowano łańcuch kinematyczny wykorzystujący złącza o trzech stopniach swobody, a następnie dokonano optymalizacji parametrów tego łańcucha tak, aby zapewnić możliwie linową charakterystykę przetwarzania układu pomiarowego.

5

Examination and optical correction of the vision system following the procedure of cataract removal

Debinska E, Styszynski A, Naskrecki R

Optica Applicata

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2006

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Vol. 36, nr 4

s. 601--607

EN

The main goal of this thesis was a comprehensive assessment of the condition of the vision system following cataract surgery and implantation of posterior chamber artificial lens and assessment of the postoperative astigmatism, considering the dynamics of reduction of the postoperative astigmatism in the early postoperative period (3 months after the surgery). Also, the assessment of binocular vision of the operated patients was carried out. The results obtained were related to the currently used procedure methods, i.e., phacoemulsification and extracapsular cataract removal. The thesis is realized in cooperation with the Ophthalmic Department of the Province Hospital in Poznañ (Szpital Wojewódzki w Poznaniu), Poland.