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Homo Sapiens (“Us”): Strengths and Weaknesses
Published in Michael Hehenberger, Zhi Xia, Huanming Yang, Our Animal Connection, 2020
Michael Hehenberger, Zhi Xia, Huanming Yang
Light energy enters the eye through the cornea, through the pupil and then through the lens. The ciliary muscle controls the lens shape, to make sure it will be changed for near focus (accommodation). When light photons are hitting the retina’s photoreceptor cones, they are converted into electrical signals that are then transmitted to the brain via the optic nerve. There are about 100 million sensory cells in the retina of a human healthy eye.
Lighting
Published in Sue Reed, Dino Pisaniello, Geza Benke, Kerrie Burton, Principles of Occupational Health & Hygiene, 2020
Accommodation is the process by which the refractive power of the eye is modified for viewing nearby objects by a thickening of the lens. The lens is an elastic capsule that is normally flat, but when acted upon by the ring-shaped ciliary muscles that encircle the lens, it assumes a more spherical shape; this process is known as accommodation. The ciliary muscles relax when the eye is focused on distant objects. This is why people working with computer screens or other items in the near visual field are advised to take regular breaks and relax their eyes by, for example, gazing out the window.
Homo Sapiens (“Us”): Strengths and Weaknesses
Published in Michael Hehenberger, Zhi Xia, Our Animal Connection, 2019
Light energy enters the eye through the cornea, through the pupil and then through the lens. The ciliary muscle controls the lens shape, to make sure it will be changed for near focus (accommodation). When light photons are hitting the retina’s photoreceptor cones, they are converted into electrical signals that are then transmitted to the brain via the optic nerve. There are about 100 million sensory cells in the retina of a human healthy eye.
Visual acuity response when using the 3D head-up display in the presence of an accommodation-convergence conflict
Published in Journal of Information Display, 2020
All stereoscopic 3D displays are affected by the AC conflict. The accommodation is the ability of the eye lens to change its focal length and to focus on different objects at different depths to draw a sharp image on the retina [7–12]. On the other hand, convergence is the rotation of both eyeballs in the inward direction to converge on an object (fixed depth) and to produce a brain-fused single image [13,14]. Under the natural viewing conditions, the accommodation and convergence are coupled and change together synchronously when the viewer looks at different objects at different depths, as shown in Figure 1(a). In the stereoscopic 3D displays, the AC relation is disturbed when the images are displayed on the screen at a fixed distance, but the amount of convergence varies with the level of disparity, as seen in Figure 1(b). The mismatch or conflict forces the eyes to focus on the screen distance but to converge at a different distance, resulting in the reduced sharpness of the perceived image and in visual discomfort. The amount of discomfort can increase further when head-mounted displays are involved [9]. The amount of AC conflict is calculated as the difference in the accommodation and convergence distances in dioptres, which can be expressed as: where DS is the screen distance (displayed image distance) and DC is the convergence distance (perceived depth distance) from the viewer. The amount of conflict is negative when the perceived image is in front of the screen, and positive when the perceived image is inside the screen, as shown in Figure 1(b).
The effects of seat width, load factor, and passenger demographics on airline passenger accommodation
Published in Ergonomics, 2019
Elizabeth L. Miller, Samuel M. Lapp, Matthew B. Parkinson
As load factor increases, there are fewer open seats to extend the effective width of a passenger’s seat. This results in decreased accommodation levels. As seat width decreases, the effect of load factor becomes more pronounced. For the average economy seat, accommodation ranges from 77% (at load factor =1) to 100% (load factor =0.6).
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.