TV pick-up systems Europe:Europe: –25 full-frames/sec –625 lines Pick-up systems:Pick-up...

TV pick-up systems

• Europe: Europe: – 25 full-frames/sec25 full-frames/sec– 625 lines625 lines

• Pick-up systems:Pick-up systems:– (Orthicon tube family(Orthicon tube family– Vidicon - Plumbicon)Vidicon - Plumbicon)– CCD : optoel. transformation, CCD : optoel. transformation,

integration, read-outintegration, read-out

Typical CCD Sensor

• 600 lines600 lines• 800 pixels / line800 pixels / line• 6,6 mm x 8,8 mm surface6,6 mm x 8,8 mm surface• 1, 2 and 3 CCD colour camera pick-1, 2 and 3 CCD colour camera pick-

up systemsup systems– mosaic filtersmosaic filters– V(V() + colour opponent) + colour opponent– RGB systemsRGB systems

TV camera with three CCDs

Transmission of the tree channels

Signals for TV transmisssion

• Signals produced by camera:Signals produced by camera:

E V s d

where

refl factorof object

radiantfluxof illu ant

s CCDresponsivity

T R G B

T T T

nm

nm

( ) ( ) ( ) ( )

( ): .

( ): min

( ):

: , ,

380

780

White balance

• For () = 1:

thus signals normalised • colour mixture curves:

1380

780

/ ( ) ( ) ( )V s dT T

nm

nm

eT() =

=VT ()T () s()

CCD camera responsivity

EBU primaries

Signal processing in a TV Camera

Electronic matrix

eRm () = 1,35 eR () - 0,25 eG () - 0,1 eB ()

eGm () = -,03 eR () +1,15 eG () - 0,12 eB ()

eBm () = -,04 eR () - 0,11 eG () + 1,15 eB ()

Matrixed colour matching functions

Colour rendering with and without matrixing

• Original Original chromaticity: chromaticity:

• x: without matrixx: without matrix• +: with matrix+: with matrix

Gamma correction

• Characteristics of a CRT tube:Characteristics of a CRT tube:

– F: normalised tristimulus valueF: normalised tristimulus value– E’: normalised input quantityE’: normalised input quantity– s: stray lights: stray light– h: offset h: offset – : approx. 2,2 , thus in camera: : approx. 2,2 , thus in camera: =,45=,45

F s h E h s 1 1 '

Gamma correction

Corrections in camera

• Gamma balance in camera:

• Nonlinear amplitude correction:– 80 % - 200 % input range corrected

to 80 % - 110 % output range

E E if E

E E if E

' , , ,

' ,

, 111 0111 0 025 1

4 0 0 025

0 455

Clamping & Knee in characteristics:

Method for getting highlights

Direct connenction between camera and

receiver• Camera:Camera:

– 3 receptors3 receptors– matrixingmatrixing– clampingclamping– gamma balancegamma balance

• Receiver:Receiver:– RGB signalsRGB signals

Luminance - chrominance

• Luminance: Luminance: – before gamma balancebefore gamma balance

• Chrominance signals:Chrominance signals:– no luminance information: no luminance information:

zero for achromatics:zero for achromatics:

L L R L G L BR G B

E L E L E L EL R R G G B B

E c E c E c E and c c cC r R g G b B r g b ; 0

Luminance - chrominance

• Luminance from Luminance from distorted distorted signal:signal:– based on NTSC primaries and not on based on NTSC primaries and not on

EBUEBU

– thus luminance signal depends on thus luminance signal depends on chromachroma

• Colour difference signals:Colour difference signals:

E E E EY R G B' , ' , ' , ' 0 299 0 587 0114

E E E E E ECR R Y CB B Y 0 713 0564, ' ' ; , ' '

EBU colour solid in Y -Chrominance Space

Chrominance signals of surface colours

Chrominance signals

• Luminance signal: 0<Luminance signal: 0<EEYY<700 mV<700 mV

• Chrominance signals:Chrominance signals:

-350 mV <...<+350 mV-350 mV <...<+350 mV• Inverse matrix in receiverInverse matrix in receiver

E E E

E E E E

E E E

R CR Y

G CR Y CB

B Y CB

' , , '

' , , ' ,

' , ' ,

1402 100

0 714 100 0 344

100 1772

Signals in TV transmission

Importance of component signals

• CCIR 601 standard: CCIR 601 standard: – 576 active lines576 active lines– 720 pixels per line720 pixels per line

» for 25 frames/s: 31,1 for 25 frames/s: 31,1 ..10106 6 pixel/spixel/s» with 8 bits/colour: 248,8.10with 8 bits/colour: 248,8.1066 bit/s bit/s

– Gamma pre-correction - L* similarityGamma pre-correction - L* similarity» helps to decrease number of quanta stepshelps to decrease number of quanta steps» smaller bandwidth in chrominance signalssmaller bandwidth in chrominance signals» differences visualy equidistantdifferences visualy equidistant

Comparing and brightness

The composit signal

• In PAL, SECAM, NTSC bandwidth = In PAL, SECAM, NTSC bandwidth = to black & white transmisssion signalto black & white transmisssion signal

• 1 step: Component signals: bandwidth of 1 step: Component signals: bandwidth of chrominance signals approx. 1/4 of chrominance signals approx. 1/4 of lum.signallum.signal

• 2 step: modulation of chrom.signal onto 2 step: modulation of chrom.signal onto colour carrier (PAL: 4,43 MHz),colour carrier (PAL: 4,43 MHz),chrominance + phase chrominance + phase

• 3 step: Modulated colour carrier added to 3 step: Modulated colour carrier added to Lum. signalLum. signal

Y

One line of a MAC signal

Multiplexed analog components

A possible TV system