中南大学医学图像处理英文课件 chapter 2 fundamentals.pptVIP

Chapter2 Digital Image Fundamentals Those who wish to succeed must ask the right preliminary questions. – Aristotle The purpose of this chapter is to introduce several concepts related to digital images and some of the notion used throughout the book. Elements of visuals perception Light and electromagnetic spectrum Image sensing and acquisition Image sampling and quantization Some basic relationship between pixels 2.1 Elements of visual perception 2.2 Light and electromagnetic spectrum 2.3 Image sensing and acquisition 2.4 Image sampling and quantization 2.5 some basic relationships between pixels Any problems?  School of Info-Physics and Geomatics Engineering, CSU * * 2.1.1 Structures of the human eye Several nouns: Cornea, sclera, choroid, ciliary body, lens, retina, fovea, vitreous humor, blind spot. Demands: understanding the mean, feature of structure, function and usefulness of every element. Two types of light receptors over the surface of the retina: Cones: the number in every eye is between 6 to 7 million. They are primarily in the fovea and highly sensitive to color. Each one is connected to its own nerve end and human can resolve details with them. Cone vision is called photopic or bright-light vision. Rods: about 75 to 150 million. The area of distribution of rod is larger and several rods are linked to a single nerve end. Rods serve to give a general, overall picture of the field of view. They are not involved in color vision and are sensitive to low levels of illumination. Rod vision is called scotopic or dim-light vision. 2.1.2 Image formation in the eye 2.1.3 Brightness adaptation and discrimination A knowledge: subjective brightness (intensity as perceived by the human visual system) is a logarithmic function of the light intensity incident on the eye. Several interesting phenomena: 1) Brightness adaptation 2) Weber ratio: evaluate the ability of the eye to discriminate between changes in light intensity at any specific ada