T.O.C.-----Search
..
.
.
.
.
.
.
.
.
.
.
 1_ NTSC: Introduction
 2_ Scanning, Timing/Sync, Sync Recovery,  Numbers
 3_ Gain & Offset, D.C. Restoration, Gamma Correction
 4_ Resolution, Bandwidth, Spectrum
 5_ Color Physics: Eye, CIE
 6_ Color Encoding: Color Bars, Camera, 
RGB, YIQ, Color  Subcarrier
 7_ Color Decoding:
 8_ Digital TV/Graphics: ADC-DAC, Frame Buffers, Timebase Correction, VGA
 9_ VCR: Spectrum, Circuits
10_ Circuits & Practices: D.C. Restore, Proc Amps, DAs
 
Loop Thru
Loop Thru is a method of driving several monitors from a single Video Source. All but the last monitor are said to be "Bridging" the Video.
Video Amplifier
Note it is a Non-inverting emitter coupled arrangement, with high frequency peaking.

Video Amplifiers NEVER invert the Video signal.

 Low Noise Video Interconnection
Noise immunity is enhanced by preserving the electrical isolation of the coaxial cable's shield; as well as proper terminations of each end. 

Note that input & output "ground returns" are connected; Isolation from chassis, bulkheads, and shields are preserved.

 
Genlock
Genlock is where several video sources are synchronized with each other, e.g., either a master sync generator or a camera or a VTR/VCR.

However it cannot be used synchronize a VTR/VCR to an external source; a TimeBase Corrector (TBC) is used for that purpose.

 
Example of Genlock
 
Auto Blacklevel
As scenes change, i.e., background lighting, etc., some image detail can be lost if the maximum white & black peaks are allowed to exceed certain limits (White: 100 ire; Black: 10 ire). The Auto Black Level System is designed to prevent this loss.
 
TimeBase Corrector (TBC)
The TimeBase Corrector is similar to Genlock, but able to "genlock" an unsynchronizable source like a Video Tape Recorder (VTR) by the use of a Frame Store (frame buffer).
 
Barstow-Christopher Function
Effect of Noise at various frequencies verses perceived picture disturbance.

Low frequency noise cause the greatest Disturbance; some high frequency noise can actually enhance image edge resolution.

 
Gamma Correction
Gamma correction is made necessary due to the Exponential Voltage- to -Light transfer function of the Display CRT.
 

 
Numerical Relationships
 
Sequential Scan Color Camera
Sequential Color Cameras have the Advantages of needing only one BW sensor; inexpensive optics; high resolution; no registration errors (as with 3 sensor cameras). 

Disadvantage: motion aliasing.



The "Apollo" and "Space Shuttle" used this type of technology.
 
 williamson-labs.com
TOC
 TOC
TOC TOC TOC TOC TOC TOC TOC TOC TOC
Television-For-EEs
Television Technology for Engineers, Technicians & Hobbyists
Television encompasses more subject areas than any other single technology. You learn switching power supplies, perception, wireless communications, ergonomics, physics: --the list is endless...
-INFO-
-ORDER: DOWNLOAD
Implementation
(Overview)
One could use a small brushless DC motor (e.g., floppy/HD spindle motor). 

The color wheel uses three RGB filters; there is a single notch (index) cut in the edge of the wheel where a photo interrupter is used to sync the Phase Locked Loop (PLL) to the Vert Sync/3.

For control of frame alignment, you can insert a oneshot between the photo interrupter (or the sync pulse) and the phase detector (MC 4044) to give you control over when the CCD exposes for a particular field. 

Remember after vertical sync, CCDs allow exposure time, and then dump the image for readout; this can happen in 1/50,000 of a second to ~15 msec, depending on the brightness of the scene. Just when this process begins isn't clear; but, after the "dump" the CCD throws away any successive exposure until the next frame. So when adjusting the delay--from the oneshot--do it in low light --longest exposure. 

Suggestions are Solicited, P l e a s e !

© 1999  2012  Comments or Questions about this site Contact