elex test 1

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Author:
hehe_girl
ID:
62347
Filename:
elex test 1
Updated:
2011-03-09 01:39:40
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video light
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  1. 4 basic parts of an oscilloscope
    • display system
    • vertical system
    • horizontal system
    • trigger system
  2. Common controls for CRT scope
    • beam finder
    • focus
    • intensity
    • scale illumination
    • trace rotation
  3. graticule of a scope
    • i cm intervals
    • 8 vertical x 10 horizontal
    • 1/5 minor divisions
  4. vertical system
    • controls amplitude & appearance
    • adjusts vertical position
    • input coupling (AC/DC)
    • vertical sensitivity
    • volts/div
    • Ch.2 Inversion
    • Chop and Alt modes
  5. horizontal system
    • time aspect
    • horizontal position
    • sweep rate
    • sec/div
    • horizontal magnification
    • delayed sweep
  6. trigger system
    • trigger level and slope
    • holdoff
    • auto/normal trigger
  7. eye vs. camera
    • band pass filter: 430 - 750 THz
    • lens/focus ~ lens
    • aperture ~ pupil/iris
    • film(CCD) ~ retina
  8. retina
    • rods - light sensor
    • cones - colour sensor
    • central part most sensitive
  9. angle of resolution
    ability to distinguish b/w adjacent points of about 1/40th of 1 degree
  10. flicker & persistence of vision
    • distinct flicker - 5 Hz
    • noticeable flicker - 25 Hz
    • imperceptible flicker - 30 Hz
  11. angle of view
    clear perception of objects, 15o
  12. aspect ratio
    • ratio b/w H and V dimensions
    • NTSC (National Television System Committee) - 4:3
    • HDTV - 16:9
  13. characteristics for a realistic representation of display
    • shades of light and dark
    • scene motion reproduced as picture motion
    • natural colour
    • 3D displacement required
  14. hue
    brain's response to one or more wavelengths of light being sensed
  15. brightness
    intensity of the light being observed
  16. saturation
    purity of the colour being observed
  17. TV adjustment of hue, saturation, brightness
    • hue: tint control
    • saturation: colour control
    • brightness: contrast & brightness controls
  18. 3 primary colours
    • red
    • green
    • blue
  19. Yellow is produced from:
    saturated red + green
  20. magenta is produced from:
    saturated red + blue
  21. cyan is produced from:
    saturated green + blue
  22. white is produced from:
    saturated red + green + blue
  23. black is produced from:
    0% red + green + blue
  24. grey is produced from:
    50% red + green + blue
  25. luminance level formula
    Y = 0.299R + 0.587G + 0.144B
  26. Colours seen when objects are small:
    • cyan
    • orange
  27. From RGB+B/W to Y+C signal transmission, the bandwidth requirement changed from ___ to ____:
    17 MHz to 8 MHz
  28. Function of Balanced Modulators:
    mix the R-Y and B-Y signals with a 3.58 MHz local oscillator to incerase the colour signal frequency so noise generated will be too high frequency to be noticed by the eye
  29. Sidebands
    • by-product of increasing the frequency, humps below and above the carrier signal frequency on the frequency spectrum
    • generally suppressed otherwise would "beat" with the sound carrier to produce visible interference at 920 kHz
  30. chrominance signal
    phasor produced by the R-Y and B-Y colour signals, transmitted with the luminance level (Y)
  31. characteristic of the NTSC video signal
    • luminance level (Y) + chrominance signal (C) transmitted
    • 3.58 MHz phase shifted
  32. Angular displacement & amplitude of the phasor in the NTSC system correspond to:
    • angular displacement: hue
    • magnitude: degree of saturation
  33. In the phasor diagram of I/Q signals, what do I, -I, Q, -Q represent?
    • I = orange
    • -I = cyan
    • Q = magenta
    • -Q = green
  34. shadow mask
    made of steel, placed b/w electron guns & phosphor coated inner surface of picture tube to make a higher accelerating voltage (20-30 kV)
  35. timing reference signals are
    • w/in the horizontal blanking interval
    • EAV (end of active video)
    • SAC
    • current line number
    • 18-bit frame check sequence
  36. why does HDTV need data compression
    signal is encoded as MPEG-2 in the studio
  37. computer video requires four parts:
    • monitor
    • memory
    • graphics adapter
    • application program
  38. multi-synch capability
    can be used with a number of standards operating at different picture (vertical) frequencies
  39. resolution is determined by:
    • # pixels/line
    • # lines/frame
    • speed the display technology can turn on/off the phosphor or LCD/plasma device
    • scanning & retrace time of a line
  40. scan lines calculated by
    • H freq
    • --------
    • V freq
  41. number of pixels per line is determined by
    • dot freq
    • ---------
    • H. freq
  42. dot pitch
    distance between adjacent pixels, in mm
  43. DPI
    dots per square inch, for printers
  44. graphics adapter / CRT controller
    provide timing signals and refresh actions to constantly update the visual display device
  45. To ensure graphics adapter has access always to RAM:
    • only allow CPU access during retrace
    • use fast RAM
    • use dual-port RAM
    • CRT controller higher priority of access than CPU
  46. VGA
    • video graphics adapter
    • IC system developed by IBM
    • display up to 256 colours on screen at a time
    • analog system
  47. VGA interface to monitor via:
    • new: 15 pin D connector
    • old: 9 pin D connector
  48. DVI
    • digital visual interface
    • allows digital monitors to be used with PCs
  49. debug
    • make use of machine code mnemonics or
    • use direct numerical coding in hex or
    • enter assembly language code
  50. normal text mode organized as ____ columns & ____ rows
    80 columns 25 rows
  51. cosine correction
    • correction when the light strikes the sensor at an angle
    • reading = treading if the light strikes the sensor at a perpendicular angle x cosine of the angle of incidence
  52. Describe the light distribution of incandescent and fluorescent lightbulbs
    • incandescent - brighter at sides than at base or the other end
    • fluorescent - uniform radiation along the tube and no radiation from the ends
  53. means of categorizing artificial sources
    • correlated colour temperature (CCT)
    • colour rendering index (CRI)
    • source efficacy
    • lamp lumen depreciation
    • rated average life
  54. correlated colour temperature
    • chromaticity of the source
    • <3000K - appear orange-white, "feels" warm
    • >4000K - appears blue-white, "feels" cold
    • >5000K - daylight
  55. colour rendering index
    degree of resultant colour-shift objects undergo when illuminated by the light source as compared with the colour of those same objects when illuminated by a reference source of comparable colour temperature
  56. source efficacy
    ratio of lumen/watt (light output per electrical power unit input)
  57. lamp lumen depreciation
    • reduced light production due to aging
    • caused by deterioration of phosphor, filament, cathode, or electrode
  58. average rated life
    statistically determined estimate of average or median operational life
  59. shapes for incandescent lamps
    • A - arbitrary
    • G - globular
    • ER - eliptical reflector
    • PS - pear shaped
  60. fluorescent lamps
    • uses ballast to provide proper starting voltage and operating current
    • base conducts electricity to the cathode (filament) to heat it up
    • filament produces electron cloud & its heat vapourizes the Hg vapour inside the bulb
    • Hg energized to a higher state, release photon when drops back to shell
    • photons collide with phosphor on inside of bulb
    • light emitted
  61. advtanges of electronic ballasts (newer) over magnetic ballasts (older)
    • better control of gas discharge process
    • greater efficiency
    • longer life
    • operate at 25-60kHz (compared to powerline freq)
  62. run-length encoding
    • form of data compression
    • same data value occurs in many consecutive data elements are stored as a single data value and count
  63. relative encoding
    transmitting the difference between each value and its predecessor, in place of the value itself
  64. quantizing error
    error b/w the actual signal & the binary result
  65. DICOM
    • Digital Imaging and Communications in Medicine
    • 1024 levels (10 bits)
  66. TIFF
    • Tagged Image File Format
    • very large files, mostly uncompressed
    • can produce compressed lossless files with LZW algorithm
  67. GIF
    • Graphical Interchange Format
    • 256 colours
    • run-length encoding
  68. BMP
    • Bit Map Picture
    • invented by Microsoft
  69. JPEG
    • Joint Photographic Experts Group
    • stores images in a 24 bit format
    • allows variable degrees of compression
  70. Huffman Coding
    employs data structures of a binary tree to create smaller codes for common characters
  71. luminous intensity
    • symbol: I
    • unit: candela (cd)
    • light intensity from a source in specific direction
  72. luminous flux
    • symbol:
    • unit: lumen (lm)
    • intensity of light from a source
  73. illuminance
    • symbol: E
    • unit: lux (lx, lumen per square meter)
    • density of luminous flux on a surface
    • luminous flux/area
  74. luminous exitance
    • symbol: M
    • unit: lumen per square meter (lm/m2)
    • flux density leaving a surface
  75. luminance
    • symbol: L
    • unit: candela per square meter (cd/m2)
    • nrg reflected in a particular direction or passed through translucent material
    • luminous intensity/(Acosa)
  76. quantity of light
    • symbol: Q
    • unit: lumen-second (lm.s)
    • luminous nrg emitted or received during a period of time from a source whose luminous flux output varies with time
  77. 4 ways of measuring light:
    • photoemissive: release of electrons from photosensitive surface when light hits that surface
    • photoconductive (junction): alteration of semiconductor material by radiation so its conductance is increased; fast response but low sensitivity
    • photoconductive (bulk): higher sensitivity than junction, slower response
    • photoelectric: radiation alters semiconductor material and generates a small voltage; Si - 0.5V, Ge - 0.1V

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