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Key Points Medical Video: - Know the principle of how a CRT works - Know the hazards of working with CRT circuitry - Know the differences between the sweep lines and frequencies for NTSC and PAL - Know how an image is formed by the fields and frame of the NTSC format - Know the standard color temperature for medical video displays - Understand the three most commonly used analog video formats: composite, S-video, and component; and why one is better than another - Recognize three digital signal connectors: SDI, HDMI, & DVI
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Medical Video 1rev 2016-02-04this is now slide 1 do not print it to pdf
things to do (check off when complete):
add revision date to cover pageremove trianglescreate list for pages to print in the handout
2-3,7-13,16-18,24-26,29-33,36-40,43,45-46,48-52,54,58,60-64,71-73,78add captions for photo slidesincorporate notes taken during presentationadd Key Points page 3
(cover page is an animation!)slide 29; corrected additive (light) color vs subtractive (ink, pigment) colorI should add a slide about perception of color, rods & cones, wiki: photoreceptor cells, Guy Deutscher’s
Through the Language Glass, etc. But not today.
useful characters: ° degrees Ω ohms μ micro checkbox ☑ ☐ slash-zero Ø CO2 O2 SpO2 N2O ® ™ trademarks
à 224 E0á 225 E1â 226 E2ã 227 E3ä 228 E4å 229 E5æ 230 E6ç 231 E7Ð 208 D0è 232 E8é 233 E9ê 234 EAë 235 EBì 236 ECí 237 EDî 238 EEï 239 EFÑ 209 D1Ò 210 D2Ó 211 D3Ô 212 D4Õ 213 D5Ö 214 D6Ø 216 D8ß 223 DFÞ 222 DEÙ 217 D9Ú 218 DAÛ 219 DBÜ 220 DCÝ 221 DDÞ 222 DEß 223 DF
Medical Video 1Essential Components
© D. J. McMahon 150512 rev cewood 2016-02-04
Key PointsMedical Video:
- Know the principle of how a CRT works- Know the hazards of working with CRT circuitry- Know the differences between the sweep lines and frequencies for NTSC and PAL - Know how an image is formed by the fields and frame of the NTSC format- Know the standard color temperature for medical video displays- Understand the three most commonly used analog video formats: composite, S-video, and component; and why one is better than another- Recognize three digital signal connectors: SDI, HDMI, & DVI
Early Television –1923 - First patent on a TV camera tube
1927 - First long distance TV transmission, New York to Wash D.C.
1928 - First TV station licensed by the FCC
1930 - First TV commercial ad
1936 - 200 TV sets in use world-wide
1939 - TV demonstrated at NY World’s Fair
1941 - FCC approves the standard for black & white TV
1948 - Cable TV introduced in Pennsylvania
1950 - FCC approves the first standard for color TV
Analog Video Format -
Basic Cathode Ray Tube (CRT)
Creating the raster on a CRT -
Horizontal and vertical synchronization signals:tell the trace when to blank and restart.
NTSC Video Scan:(National Television Standards Committee)
Upper left to lower right,1st field: 262½ lines in 1/60th second2nd field: 262½ lines interlaced with first fieldTotal = 525 lines in 1/30th second = 1 frame
Horizontal sweep frequency: 525 lines x 30 lines/sec = 15,750 Hz
Black & white video “step” test pattern on a CRT :
Black & white video “step” pattern as seen on an o-scope :
Video Formats in use Worldwide:NTSC: National Television Standards Committee
> 525 lines, 60 Hz, color subcarrier at 3.58MHz
PAL: Phase-Alternating Line
> 625 lines, 50 Hz, color subcarrier at 4.43 MHz
SECAM: Systeme Electronique Couleur Avec Memoire
(Electronic Color System with Memory)
> 625 lines, 50 Hz, colors sent in sequence with a time delay
There are about twelve variants of all three of these standards,
differing in lines per frame, sweep frequency, and color formatting.
Analog Television Standards of the World Green = NTSC Yellow = PAL Orange = SECAM
Beware the NTSC/PAL switch !
Generic 6.0 MHz television channel:
78.5 MHz
77.25 MHz
82.0795 MHz
83.0 MHz
For Television Channel 5:
Detail of the picture carrier with color:
More information than you wanted:
R, G, B, and sync signal(s) apart
Detail of the Color Burst:
More information than you wanted:
Hue: specific wavelength of a colorSaturation: amount of additional wavelengths in a colorBrightness: amplitude of the wavelengths in a color
Any color is defined in three parameters:
+
-+
-
“Color Temperature” :The color temperature of a light source is determined by comparison to a ‘black-body radiator’. The temperature at which the black-body radiator matches the color of the light source is that source's “color temperature”.
Any light source has a specific color temperature:room lights, car headlights, video displays, etc.
How do we ‘quantify’ color?
Black Body: a theoretical object that absorbs all incident light energy, at any frequency or angle of incidence.
A black body emits light based only on its temperature in ° Kelvin.(Kelvin = centigrade +273)
More information than you wanted:
The ideal color temperature for video displays is usually set at 6500°K, but most displays can be adjusted to other values.
CIE Standard “Color Space” Chart, 1931
6500° K
Hue
:
Saturation:
R-G-B is used in video - Colors are additive
( C-M-Y-K is used in ink & pigment - Colors are subtractive)
Primary Colors in Displays:
Video & Light Dye, Ink & Pigment
K
R + G + B = white
If red is missing, image is light blue (cyan).
If green is missing, image is purple (magenta).
If blue is missing, image is yellow (yellow).
Troubleshooting Video R-G-B:
Y = luminance (brightness signal)
C = chrominance (color signal)
R = red
G = green
B = blue
Pb = difference between Y and Blue
Pr = difference between Y and Red
Decoding the color signals:
Analog Video Signal Formats:
1) Composite (good): Luminance Y, Chrominance C, and synchronization (“sync”), all superimposed on one signal. “Sync” are the horizontal and vertical sweep signals.
Yellow connector is the composite video signal.Red and white connectors are the R and L audio signals.
Analog Video Signal Formats:
2) Y/C (“S-Video”) (better) - Luminance (Y) and Chrominance (C) separated - 4-wire cable: 2 for each component (separate grounds)
Pin Name Function 1 GND
Ground for Y
2 GND Ground for C
3 Y Luminance
4 C Chrominance
LuminanceChrominance
Female connector
(male connector)
Use caution with DIN-type S-video connectors:
Composite: Y/C (S-video):
Why S-video is better:
In S-video, Luminance and chrominance are separated, and don’t interfere with each other.
Analog Video Signal Formats:
3) Component (R-G-B) (best) - Red, Green, Blue, and sync signals are separate. - may be 3, 4, or 5 shielded wires: 3 wires: R, G, B (with syncs on the Green signal (“SOG”)) 4 wires: R, G, B, and horizontal sync (white wire) 5 wires: R, G, B, and horizontal and vertical syncs
VGA is an implementation of Analog Component (R-G-B) (best) 5 (signal) wires: R, G, B, and horizontal and vertical syncs
Pin 1 RED Red videoPin 2 GREEN Green videoPin 3 BLUE Blue videoPin 4 ID2/RES formerly Monitor ID bit 2,
reserved since E-DDCPin 5 GND Ground (HSync)Pin 6 RED_RTN Red returnPin 7 GREEN_RTN Green returnPin 8 BLUE_RTN Blue returnPin 9 KEY/PWR formerly key, now +5V DCPin 10 GND Ground (VSync, DDC)Pin 11 ID0/RES formerly Monitor ID bit 0,
reserved since E-DDCPin 12 ID1/SDA formerly Monitor ID bit 1,
I²C data since DDC2Pin 13 HSync Horizontal syncPin 14 VSync Vertical syncPin 15 ID3/SCL formerly Monitor ID bit 3,
I²C clock since DDC
Analog Video Signal Formats:4) YPBPR (“Yipper”) (even bester )
- Y, PB, and PR signals are separate as in R-G-B - Uses less bandwidth, and image is crisper - Can handle higher resolutions than other analogs
YPBPR is converted from the RGB video signal by splitting it into three components:
Y carries the luminance (brightness) and synchronization (sync) information: Y = 0.2126 R + 0.7152 G + 0.0722 B (With color, Y still represents intensity but it is a composite of R. G, and B.)
PB carries the difference between blue and luma (B − Y).
PR carries the difference between red and luma (R − Y).
More information than you wanted:
Generic analog TV or monitor with CRT display:
Three analog inputs into one monitor:
Digital Video Format -
Digital color:
worth looking at: https://en.wikipedia.org/wiki/Lists_of_colors
Any color can be assigned a triplet of R-G-B digital values:
(0, 0, 0) is black (255, 255, 255) is white (255, 0, 0) is red (0, 255, 0) is green (0, 0, 255) is blue (255, 255, 0) is yellow (0, 255, 255) is cyan(255, 0, 255) is magenta
(this defines 224 or ~ 16 million colors)
Various colors and their digital value assignments:
Digital displays consist of picture elements, or “pixels”.
Digital displays light-up all the screen pixels in one frame at a time.
Each pixel has one color.
The color depth is typically 24 bits per pixel. (More bits = better color.)
The frame rate is the number of frames displayed per second.
The bit rate is the total number of bits being moved per second.
Example:
If a display has 640 x 480 pixels, there are 307,200 pixels.
If there are 24 bits per color, we have 307,200 x 24 = 7,372,800 bits (7.37 Mbits)
If there are 25 frames per second, we have 7.37 x 25 = 184.25 Mbits/sec
If we have a 10-minute (600 sec) video presentation, the video size is 184.25 x 600 = 110,550 Mbits or 13,819 MBytes or 13.819 GBytes
How is digital video displayed ?
Resolution - the amount of information per unit area
DVB-T: Digital Video Broadcasting, TerrestrialATSC: Advanced Television Systems CommitteeISDB-T: Integrated Service Digital Broadcast, TerrestrialDMB-T/H: Digital Multimedia Broadcast - Terrestrial/Handheld
The Brave New Digital World:Four different digital television standards
1) Serial Digital Interface (SDI) – - 270 MBits/Second digital stream - Single conductor, but must be low-loss coaxial cable - Uses a BNC connector
Digital Video Signal Formats:
2) High Definition Media Interface (HDMI) – - multiple scan rates - multi-conductor, 10.2 Gbits / Second - common in consumer video, but not often used in medical
Digital Video Signal Formats:3) Digital Visual Interface (DVI) – - RGB data, clock, channel formatting, & audio - 3.96 Gbits/s
Pin 1 TMDS data 2−Digital red− (link 1)Pin 2 TMDS data 2+Digital red+ (link 1)Pin 3 TMDS data 2/4 shieldPin 4 TMDS data 4−Digital green− (link 2)Pin 5 TMDS data 4+Digital green+ (link 2)Pin 6 DDC clockPin 7 DDC dataPin 8 Analog vertical syncPin 9 TMDS data 1−Digital green− (link 1)Pin 10 TMDS data 1+Digital green+ (link 1)Pin 11 TMDS data 1/3 shieldPin 12 TMDS data 3-Digital blue− (link 2)Pin 13 TMDS data 3+Digital blue+ (link 2)Pin 14 +5 VPower for monitor when in standby
Pin 15 GroundReturn for pin 14 and analog syncPin 16 Hot plug detectPin 17 TMDS data 0−Digital blue−(link 1) & dig syncPin 18 TMDS data 0+Digital blue+(link 1) & dig syncPin 19 TMDS data 0/5 shieldPin 20 TMDS data 5−Digital red− (link 2)Pin 21 TMDS data 5+Digital red+ (link 2)Pin 22 TMDS clock shieldPin 23 TMDS clock+Digital clock+ (links 1 and 2)Pin 24 TMDS clock−Digital clock− (links 1 and 2)C1 Analog red C2 Analog green C3 Analog blueC4 Analog horizontal syncC5 Analog groundReturn for R, G, and B signals
Female DVI-I socket from the front:
Displays -
Displays in Medical Applications:
- Cathode Ray Tube (CRT)past gold standard, but going extinct
- Electroluminescent (EL)light-emitting, high current draw
- Liquid Crystal Display (LCD) impractical unless back-lit, but efficient
- Plasma Displays better angle of view, run hot
Interlaced Scan vs Progressive Scan -
Interlaced: Each frame is ‘painted’ in two fields which use odd and even-numbered lines
then..
Progressive: Entire frame is ‘painted’ in one sequence of lines, top left to bottom right. (There are no ‘fields’.)
First Field Second Field
Two fields = one Frame
Resolution: 720p vs 1080p
Most medical video is in 1080p
Electroluminescent (EL) display –
Plasma display –
Liquid Crystal Technology (LCD) display:
CCFLs: Cold Cathode Fluorescent Tubes for back-lighting LCD displays
CCFLs require a high voltage (60 – 90 Vac),produced by an inverter
CCFL inverter board in a medical monitor
Video Test Patterns
Society of Motion Picture & Television Engineers (SMPTE)Early standard test pattern
SMPTE Standard Test Pattern RP 219:2002
SMPTE Gamma test pattern.
Gamma (γ) is a correction made to the luminance level to adjust for human vision.
SMPTE resolution test pattern
Safety Issues with Monitors & CRTs:> System Power Supply - may be non-isolated
> High Voltage Power Supply - develops very high voltages which
can reside for hours after power is off
> The CRT - tough, but can crack or implode
Safe Practices:> Use an isolation transformer on the device
> Discharge large capacitors
- use a high wattage resistor,100 ohms/volt of capacitor value
- ( do NOT use a screwdriver ! )
> Stay away from the CRT anode wire, the HV supply, and
the PC board on the neck of the CRT
Humble beginnings:
