Creating digital images Flashcards
In the correct order, the three fundamental steps in the process to digitise analogue music are:
scanning, sampling, quantisation
If during the scanning stage, large pixel size is used, which statement is incorrect?
The image will not have the desired location
The image will looked pixelated
Resolution will exceed what is necessary and it will have wasted unnecessary electronic resources
The image will be continuous in space
The image will be continuous in space
The purpose of the quantisation stage in the digitising process is to:
assign discrete values for each intensity measurement
An image that is digital is said to be: continuous in value, continuous in space continuous in space, discrete in value discrete in space, continuous in value discrete in value, discrete in space
discrete in value, discrete in space
Which statement best describes the term sampling as it relates the creating digital images?
Where the measured light intensity is distributed into discrete steps within the allowable dynamic range.
Where the light intensity from each designated pixel area is measured.
Where you take the field of the image and divide it up into a matrix of small cells.
Where the ADC takes the continuous intensity values and rounds them or down.
Where the light intensity from each designated pixel area is measured.
A digital radiographic image consists of a matrix of numerical values relating to the intensity of x-rays. With Digital radiography the matrix consists of:
dexels
Which would not be a consequence of over sampling or quantising, i.e. creating a radiograph with more than the necessary diagnostic quality?
Low resolution so image looks pixelated.
Slow transmission speeds.
Large file sizes.
High computer processing power requirements.
Low resolution so image looks pixelated
The range of numerical values of brightness that can be captured by a digital radiography system is limited by the:
The sampling pitch
Which statement is INCORRECT about a Radiographic image? It is a reverse image It is a polychromatic image It is a monochromic image Is black and white
It is a polychromatic image
A pixel in an photograph is displayed as [(IR IB I?) (x,y)]. What would the ? Represent?
Green
Why is meant by the term fill factor with regard to digital radiography?
The term fill factor refers to the ratio between the light sensitive area to the entire area of each detector element
How is fill factor calculated
Fill Factor = Sensitive area/Overall Area
Explain the ‘read out process’ of the individual dexels (detector elements) in the TFT array after an exposure.
Caesium Iodide absorbs x-ray photons and releases light photons, these light photons are then absorbed in the photodiodes and the charge stored in the charge storage capacitor at each pixel location. The latent image is then read out sequentially to a bank of charge sensitive amplifier (TFT switches). The resulting voltage signal is then digitised and transferred to the system computer where the DR image is built up.
