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Computer and Human Vision Systems
Published in Sheila Anand, L. Priya, A Guide for Machine Vision in Quality Control, 2019
Six extraocular muscles control the movement of each eye: four rectus muscles and two oblique muscles. The medial, lateral, superior, and inferior rectus muscles move the eyeball horizontally and vertically. The superior and inferior obliques help in torsional movements like tilting the head to one side or looking up or down at an angle. The two oblique muscles of the eye are responsible for the rotation of the eye and assist the rectus muscles in their movements. The muscles of the eyes have also a role to play in the human vision system. The muscles perform a scanning function, called saccades, when looking at a large area and provide vital information to the brain. They also help in tracking moving objects in a visual field. The muscles of the eye also help in vergence, which is the simultaneous movement of both eyes to obtain or maintain a single binocular vision.
Smart Eye Tracking Sensors Based on Pixel-Level Image Processing Circuits
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Vergence moves the eyes in opposite directions, causing the intersection point of the lines of sight of the two eyes to move closer or further away. The purpose of vergence eye movements is to direct the fovea (area of the retina with the highest resolution) of both eyes at the same object. The vergence movements have the angular range of about 15°. Under natural conditions vergence movements are accompanied by saccades or pursuit movements.
Smart Eye-Tracking Sensors Based on Pixel-Level Image Processing Circuits
Published in Khosla Ajit, Kim Dongsoo, Iniewski Krzysztof, Optical Imaging Devices, 2017
Vergence moves the eyes in opposite directions, causing the intersection point of the lines of sight of the two eyes to move closer or farther away. The purpose of vergence eye movements is to direct the fovea (area of the retina with the highest resolution) of both eyes at the same object. The vergence movements have an angular range of about 15°. Under natural conditions vergence movements are accompanished by saccades or pursuit movements.
Liquid crystal technology for vergence-accommodation conflicts in augmented reality and virtual reality systems: a review
Published in Liquid Crystals Reviews, 2021
We first discuss VAC. Vergence refers to the rotation of the eyeballs to triangulate the object and is driven by retinal disparity. Accommodation refers to the change in the focal length of a crystalline lens of the eye to clearly see objects at different locations; it is driven by retinal blur. Vergence and accommodation are closely related based on life experiences, and their physiological response is coupled [10,11]. When human eyes intend to see a real object, as shown in Figure 3(a,b), the movement of both the eyes is triggered by the stereoscopic disparity, and the eyes start to rotate (vergence) toward the direction of the object of interest. Subsequently, the crystalline lenses of two eyes start to change their curvatures, which leads to a change in the focal length (i.e. accommodation) until the eyes clearly see the object of interest. In AR and VR optical systems, 2D images with disparity are generated for a binocular view to realize 3D experiences, as shown in Figure 3(c). Owing to the disparity of the virtual images, the eyeballs turn towards or away from each other. However, the projected 2D virtual images force the viewers to accommodate at the original depth which is the surface of projected 2D virtual image to maintain sharp images. As the accommodation state is not taken into account, there is a mismatch between vergence and accommodation, as shown in Figure 3(c). When the mismatch between vergence and accommodation is larger, the visual experience is hard to bear with visual discomfort and fatigue [11,12]. In monovision, when the virtual image does not coincide with a real object, it is so-called a registration problem (or focus rivalry), where the eyes have to accommodate constantly to clearly see the real object and the projected virtual image. The registration problem occurs only in AR optical systems, and the solutions proposed to address this problem can also be used to address the VAC problem. In summary, the optical elements in the current AR and VR systems provide fixed optical properties, resulting in a fixed image plane for 3D experiences with VAC. Tunability in optical systems may be conducive to realize VAC-free NEDs.