Memory and Display Flashcards
the memory allows us to store an image but also is responsible for giving us what
a grayscale
another name for memory
scan converter
analog vs digital (3 things)
A: continuous values (ramp), prone to drift, less reproducible
D: discrete numbers (stairs), stable, reproducible
analog scan converter is similar to a CRT except that the phosphor face is replaced with a ______ called a _____
wafer of silicon
dielectric matrix
analog scan converter: electrons are emitted by the filament, pass through the ______ plate and strike the silicon wafer leaving a _____ charge
deflection
negative
main advantage to analog scan converter vs disadvantage
allows for gray scale
vs
prone to drift and there was no long term memory
what do we use instead of an analog scan converter today
we use a digital scan converter
what can digital scan converters be connected to and what improved thing do they have
can be connected to many other systems or cameras and have superior resolution
DSC: consists of a matrix typically ________(number), which is divided into small rectangular square picture elements called _____
1024x768
pixels
each pixel contains a digital number to represent the ______ of the received echo
amplitude
a 1024x768 matrix has _____ pixels
786432
binary code
computers operate in a binary code, which is a language consisting of only 1s and 0s
how do you get several shades of grey using the binary code
You add additional matrices that are stacked on top of the other so that every pixel location can be represented by several 1s and 0s
all 256 shades of gray can be represented by ____ stacked matrices
8
more pixels = _____ resolution
increased
one binary digit
bit - 1 or 0
8 bits of data
byte - 10010101
bit vs byte
one binary digit vs 8 bits of data
word
combination of bits expressed as a unit
word length
number of bits in a word
bit depth
the word length at each address location
RAM
random access memory - fast, rewritable, cheap, erased when machine turned off
ROM
read only memory - permanent and used for system function (i.e, pre-sets)
the formula for calculating the shades of gray
2^n where n is the bit depth
the binary system relies on two digits - 1 or 0 which represents a circuit that is either ____ or ___
on
off
what is the decimal number
it is where you convert the binary numbers using the chart
128 64 32 16 8 4 2 1
Add up the numbers with a 1 in their space
ex. 1001=9
why is more pixels in a finite space better
the size of the pixels must decrease to fit the monitor better
we also impact the resolution by changing the _____
depth of field
axial res = (formula)
1/2 SPL
SPL = wavelength x ringdown
modern day units use a ____ monitor for display
LCD (liquid crystal display)
the _____ was the first to use a CRT and is used in __, __, and ___ mode. It can only display using a x and y axis and is not compatible with a _____ signal
oscilloscope
a
b
m
video
the television CRT _____ a video signal and is _____ of displaying a wide range of grays
accepts
capable
if equipped, the CRT is also able to display ____ which is useful for _____ applications
colour
Doppler
the CRT is a large ____ vacuum tube that contains a cathode or source of _____ (_____).
glass
electrons
negative
the electron beam of a CRT is aimed at ______ (______)
phosphor plate
positive
______ or _____ deflection plates are used to _____ the beam and the phosphor _____ will depend on the number of electrons that strike it
electrical
magnetic
steer
brightness
the number of electrons is dependent on the ___ of the ____ signal
amplitude
video
to obtain colour there are ____ electron guns that cause phosphor to light up either ____, ___, or _____
three
red
green
blue
to move the electron beam a specific method is used called the _____
Raster Format
Raster Format: the beam is moved from ____ to ___ and in addition interlacing is used to first write ____ lines and then the ____ lines
left
right
odd
even
a complete frame consists of ____ horizontal lines produced at ____ Hz (frame rate)
525
30
each frame has two field, the ____ and the ____, produced at ___ Hz (frame rate_
odd
even
60
raster format is done to help reduce the appearance of ____ to the observer
flicker
____ odd lines in 1/60s + _____ even lines in 1/60s = ____ lines every ____
263
262
525
1/30s
computer monitors are superior to CRTs in that they have more ____ and ____ and the pixels are _____. This means higher ____
scan lines
pixels
smaller
resolution
Where CRTs used ____ lines, monitors use ______ or higher
525
1024 x 768
computer monitor lines are written in a _____ manner with frame rates typically higher than ____
progressive
60Hz
