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Physiological metrics of mental workload: A review of recent progress
Published in Diane L. Damos, Multiple-task performance, 2020
The pupil, which can vary in size from 0.2 mm to 0.8 mm, is controlled by a set of antagonistic muscles in the iris. One muscle group, the dilator pupillae, is innervated by fibers from the SNS. Stimulation of this muscle causes a retraction of the iris, thereby increasing the size of the pupil. The second muscle group, the sphincter pupillae, is innervated by fibers from the PNS. Stimulation of this muscle expands the iris, thereby decreasing the size of the pupil. While the relationship between the branch of the ANS (i.e., the SNS and PNS) and the muscles controlling the pupil is clear, the relative contribution of the SNS and the PNS to changes in the size of the pupil can vary. For example, pupil dilation can be accomplished by either an increase in SNS activity or a decrease in PNS activity.
Introduction to Digital Image Processing
Published in Vipin Tyagi, Understanding Digital Image Processing, 2018
Various parts of the human eye are identified:Primary Lens: Cornea and aqueous humour, used to focus incoming light signal.Iris: The iris dynamically controls the amount of light entering the eye, so that the eye can function in various lighting conditions, from dim light to very bright light. The portion of the lens not covered by the iris is called the pupil.Zonula: This is a muscle that controls the shape and positioning (forward and backward) of the eye’s lens. Retina: provides a photo-sensitive screen at the back of the eye; it converts the light hitting the retina into nerve signals.Fovea: A small central region of the retina that contains a large number of photo-sensitive cells and provides very good resolution.Optic nerve: These nerves carry the signals generated by the retina to the brain.
Digital Picture Compression and Coding Structure
Published in H.R. Wu, K.R. Rao, Digital Video Image Quality and Perceptual Coding, 2017
Jae Jeong Hwang, Hong Ren Wu, K.R. Rao
A critical design goal for a digital video/image coding system is that the video/images produced by the system should be acceptable and pleasant to the viewer, i.e., human eye is the final observer. In order to achieve this goal it is necessary to take into account the response of the human visual system (HVS). The HVS is the system by which a human observer views, interprets and responds to visual stimuli. The simplified human eye cross section is shown in Figure 1.19. The image is focused on the retina surface by the lens that changes shape under muscular control to perform proper focusing of near and distant objects. The iris controls the aperture of the lens and hence the amount of light entering the eye. The retina consists of an array of cones (photoreceptors sensitive to color at high light levels) and rods (photoreceptors sensitive to luminance at low light levels). The more sensitive cones are concentrated in a central region (the fovea) which means that high-resolution color vision is only achieved over a small area at the center of the field of view. Nerves connecting to the retina leave the eyeball through the optic nerve. The human brain processes and interprets visual information, based partly on the received information (the image detected by the retina) and partly on prior learned responses (such as known object shapes).
Effective Monitoring for Early Detection of Hypoxia in Fighter Pilots
Published in The International Journal of Aerospace Psychology, 2023
Kosuke Kumagai, Satoshi Maruyama, Takahiro Imamura, Tetsuya Iwamoto, Yoshiki Kanamaru, Masaki Mine, Kunio Takada, Kojiro Wada
Pupil diameter (PD) is controlled by the autonomic nerves, so is a sensitive indicator of the physical condition. Change in PD may provide a direct measure of brain function (Wilson et al., 2008). Activation of the iris sphincter muscle innervated by the parasympathetic nerves causes pupillary constriction (miosis), whereas activation of the iris dilator muscle innervated by the sympathetic nerves causes pupillary dilation (mydriasis). On the other hand, heart rate (HR) is also controlled by the autonomic nerves, and is another sensitive indicator of the physical condition. Rapid exposure to hypoxia will lead to enlarged PD, increased blood pressure (BP) and HR, and decreased SpO2 (Oliveira et al., 2017). However, the relationships between SpO2, BP, HR, and PD during hypoxia have not been clarified.
Capturing Luminous Flux Entering Human Eyes with a Camera, Part 1: Fundamentals
Published in LEUKOS, 2022
Siqi He, Hankun Li, Yonghong Yan, Hongyi Cai
The pupil dilates or constricts as controlled by the iris to allow more light to enter human eyes under dim ambient light conditions but prevent too much light exposure of eyes in bright light conditions. The effective pupil size in reaction to the ambient light level is determined by the corneal flux density in a non-linear relationship (Atchison et al. 2011), as shown in Fig. 6a. Corneal flux density reflects the light level at the corneal position () coming from the entire visible environment without cosine correction, which can be calculated using Equation (1), as the summation of the product of the luminance (Li) across the entire visual field and its solid angle () subtense to the eye’ nodal point. In the field measurement, a binocular luminance HDR map of the observer’s luminous environment can be used to retrieve the luminance and solid angle subtense of every pixel (as target point), to calculate the corneal flux density () value accordingly.
A New Design of Iris Recognition Using Hough Transform with K-Means Clustering and Enhanced Faster R-CNN
Published in Cybernetics and Systems, 2022
Gorla Babu, Abdul Khayum Pinjari
Iris recognition is a biometric identification and verification technique, which authenticates a human through an image of a person’s eye that is used for more accurate analysis because of the high entropic iris patterns (Liu et al. 2020). Iris is a circular membrane, which is located among the lens and the cornea of the human eye, which aims for controlling the amount of light crossing with the pupil by relaxing and contracting the dilator muscles and the pupillary sphincter (Labati et al. 2020). Due to the unique and invariant features of the human iris texture of each person, it is robust for using it in identification systems (Shuai et al. 2020). The major factors for developing an iris recognition model are the durability of the iris structure in the human’s lifetime, the unique pattern of the iris, and the user-friendly image attained by devices with a broad range of improved abilities that promotes biometric identification among the public (Proença and Neves 2018). Pattern recognition and computer vision sectors are the major efficient fields, which prevent diverse issues in multiple aspects. In recent years, with the progressions in technology particularly in biometrics, features have been promoted to get protection around the world (Trokielewicz, Czajka, and Maciejewicz 2020; Lin, Liu, and Chen 2009).