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TV pick-up systems

TV pick-up systems. Europe: 25 full-frames/sec 625 lines Pick-up systems: (Orthicon tube family Vidicon - Plumbicon) CCD : optoel. transformation, integration, read-out. Typical CCD Sensor. 600 lines 800 pixels / line 6,6 mm x 8,8 mm surface

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TV pick-up systems

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  1. TV pick-up systems • Europe: • 25 full-frames/sec • 625 lines • Pick-up systems: • (Orthicon tube family • Vidicon - Plumbicon) • CCD : optoel. transformation, integration, read-out

  2. Typical CCD Sensor • 600 lines • 800 pixels / line • 6,6 mm x 8,8 mm surface • 1, 2 and 3 CCD colour camera pick-up systems • mosaic filters • V() + colour opponent • RGB systems

  3. TV camera with three CCDs

  4. Transmission of the tree channels

  5. Signals for TV transmisssion • Signals produced by camera:

  6. White balance • For  () = 1: thus signals normalised • colour mixture curves:

  7. CCD camera responsivity

  8. EBU primaries

  9. Signal processing in a TV Camera

  10. Electronic matrix

  11. Matrixed colour matching functions

  12. Colour rendering with and without matrixing • Original chromaticity: • x: without matrix • +: with matrix

  13. Gamma correction • Characteristics of a CRT tube: • F: normalised tristimulus value • E’: normalised input quantity • s: stray light • h: offset • : approx. 2,2 , thus in camera: =,45

  14. Gamma correction

  15. Corrections in camera • Gamma balance in camera: • Nonlinear amplitude correction: • 80 % - 200 % input range corrected to 80 % - 110 % output range

  16. Clamping & Knee in characteristics: Method for getting highlights

  17. Camera: 3 receptors matrixing clamping gamma balance Receiver: RGB signals Direct connenction between camera and receiver

  18. Luminance - chrominance • Luminance: • before gamma balance • Chrominance signals: • no luminance information: zero for achromatics:

  19. Luminance - chrominance • Luminance from  distorted signal: • based on NTSC primaries and not on EBU • thus luminance signal depends on chroma • Colour difference signals:

  20. EBU colour solid in Y -Chrominance Space

  21. Chrominance signals of surface colours

  22. Chrominance signals • Luminance signal: 0<EY<700 mV • Chrominance signals: -350 mV <...<+350 mV • Inverse matrix in receiver

  23. Signals in TV transmission

  24. Importance of component signals • CCIR 601 standard: • 576 active lines • 720 pixels per line • for 25 frames/s: 31,1 .106 pixel/s • with 8 bits/colour: 248,8.106 bit/s • Gamma pre-correction - L* similarity • helps to decrease number of quanta steps • smaller bandwidth in chrominance signals • differences visualy equidistant

  25. Comparing  and brightness

  26. The composit signal • In PAL, SECAM, NTSC bandwidth = to black & white transmisssion signal • 1 step: Component signals: bandwidth of chrominance signals approx. 1/4 of lum.signal • 2 step: modulation of chrom.signal onto colour carrier (PAL: 4,43 MHz),chrominance + phase • 3 step: Modulated colour carrier added to Lum. signal

  27. Y

  28. One line of a MAC signal Multiplexed analog components

  29. A possible TV system

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