Formation of Digital Images

efer to Fig. 7.17 and Fig. 7.20. The output from a camera (either CMOS

or CCD) is a continuous stream of images (video). In the case of a color

Visual Sensory System of Robots 417

camera, however, the direct output from an imaging sensor consists of three

streams of images: red component color images, blue component color im-ages and green component color images.

If a camera's output has an analogue signal, the camera is called an ana-logue video camera. Output from an analogue video camera will be a con-tinuous one-dimensional signal, representing a stream of two-dimensional

analogue images. This analogue signal is also called an analogue video.

Digital cameras have been on the market since the late 1990s. Output

from a digital camera can be a stream of two-dimensional digital images,

called a digital video. If a digital camera outputs digital video, then it is

called a digital video camera.

As shown in Fig. 7.21, the computing hardware in a robot's visual sen-

sory system is digital. Thus, if a camera outputs analogue video, it is

necessary to convert this into a stream of digital images. Since analogue

video cameras are still popular, a robot's visual sensory system needs an

image digitizer which converts analogue video into the corresponding digital

video. (See Fig. 7.21).