Human Visual System (HVS)

The Human Visual System (HVS) has two primary components:
• Eye.
• Brian.
* The structure that we know the most about is the image receiving sensors (the human eye).
the brain can be thought as being an information processing unit analogous to the computer in our computer imaging system. These two are connected by the optic nerve, which is really a bundle of nerves that contains the path ways for visual information to travel from the receiving sensor (the eye) to the processor (the brain).
Computer Imaging Systems(Digital Image Processing System)
Computer imaging systems are comprised of two primary components
types, hardware and software. The hardware components can be divided into image acquiring sub system (computer, scanner, and camera) and display devices (monitor, printer).The software allows us to manipulate the image and perform any desired processing on the image data.
A simple image model:
• To be suitable for computer processing, an image f(x,y) must be digitalized both spatially and in amplitude.
• Digitization of the spatial coordinates (x,y) is called image sampling.
• Amplitude digitization is called gray-level quantization.

Digitization
The process of transforming a standard video signal into digital image
.This transformation is necessary because the standard video signal in analog (continuous) form and the computer requires a digitized or sampled version of that continuous signal. The analog video signal is turned into a digital image by sampling the continuous signal at affixed rate. In the figure below we see one line of a video signal being sampled (digitized) by instantaneously measuring the voltage of the signal at fixed intervals in time.
The value of the voltage at each instant is converted into a number
that is stored, corresponding to the brightness of the image at that point.
Note that the image brightness of the image at that point depends on both the intrinsic properties of the object and the lighting conditions in the scene.