Sensors and Digital Imaging pt. 2 Flashcards
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how does it work?
cesium iodide scintillator converts x-rays into visible light
photosensitive pixels convert scintillators light into electrical signals. on-chip circuitry turns electrical signals into digital output
digital data is sent to a computer
digitization
CCD, CMOS types
x ray photons cause ionization of pixel silicone; ejected electrons’ are trapped in the pixel similar to the charge in a battery
simplified sensor concept
each pixel is like a tiny battery with its charge equal to the number of electrons trapped inside. the computer records the charge in each pixel and converts it into a gray value
— shades of gray
256
255- light
0- dark
To be able to manipulate the image, the
computer will turn the voltage signal to
numbers and then to shades of gray
All images consist of ‘pixels’ (picture
elements), including (3)
human vision,
insect vision and photographs
Each pixel is characterized by
its (2)
location and intensity.
Digital computer technology allows for enhancement through the
manipulation of the
binary bits of each individual pixel !
011000100011100101001000011110101…
Sensor thickness “sweet spot” is
4-
6mm i.e.
— source preferred i,e, not
limited to proprietary software
Open
Cost – is related to (2)
buying price +
warranty
Size – most come in sizes equivalent
to
dental film
Shape – (3)
square, rounded or cut (See
product examples)
types of sensors (2)
CMOS vs CCD
Resolution
Pixel size -
~ 15 μM (10-6 M)
~ 15 microns (10-6 M)
~ 15 10-3 mm
