Добавил:
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз: Предмет: Файл:
Jack H.Integration and automation of manufacturing systems.2001.pdf
Скачиваний:
86
Добавлен:
23.08.2013
Размер:
3.84 Mб
Скачать

page 486

17.5 FRAME GRABBER

• A simple frame grabber is pictured below,

video

 

 

 

pixel

 

 

digital

 

 

 

intensities

 

 

values

signal

signal

 

 

 

 

 

 

fast A/D

 

 

RAM

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

splitter

 

 

 

 

 

 

Computer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

line start

 

 

 

 

 

 

bus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

address

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

picture start

 

generator

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

• These items can be purchased for reasonable prices, and will become standard computer

components in the near future.

17.6 IMAGE PREPROCESSING

Images are basically a set of pixels that are often less than a perfect image representation. By preprocessing, some unwanted variations/noise can be reduced, and desired features enhanced.

Some sources of image variation/noise,

-electronic noise - this can be reduced by designing for a higher Signal to Noise Ratio (SNR).

-lighting variations cause inconsistent lighting across an image.

-equipment defects - these cause artifacts that are always present, such as stripes, or pixels stuck off or on.