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Figure&44! Showing$ the$ separate$ processing$ of$ the$ dual$ pixel$ data$ from$ the$ image$ sensor$ —$ for$
video$and$for$Auto$Focus$—$at$the$entry$sta ge $of$the$D igic$8$ processor$
Figure!44!illu s tra te s !the!m a n n er!in!wh ic h !the!se ts !of!dua l!pixel!o ut p u ts!from! t he !CMOS!image !sensor!are!
sent!to!the!DIGIC!8!processing!microcircuit!that!was!developed!by!Canon.!!W ithin!this!processor,!these!
streams! are! separately! fed! to! the ! primary ! RGB! video! proce ssing ! system! (where! the! two! photodiode !
signals!are!summ ed)!an d! to!a! data!processing! system! that!analyzes!the!phase!difference!between!the!
two!and!makes!all!of!the!decision-making!and!data!processing!associated!with!the!Auto!Focus!system.!!!
While! all!of! the! millions!o f! photosites!are! delivering!the! “dual! pixel”! data,! the! op eratio na l! aspects! of!
Auto!Focus!dictate!that!only!a!select!number!of!these!are!activated!at!any!given!time.!!This!is!because!
the!cam era !operator!(or!for!the!camera,!when!AF!me tho d s!like!Face!Detect!+!Tracking!are!active)!will!
make!the!decision!on!which!particular! subject! within!the!overall!picture!frame!is!chosen!for!sharpest!
focus.!!Consequently,!a!cursor!typ e !system!mu st!be!implem e n te d!to!facilitate!this!choice.!!!Experiences!
gained!in!the!early!generations!of!Dual!Pixel!CMOS!AF!system s !p ro d u ce d !th e !fo llo w in g : !
1.!!!Broad!request!to!provide!spatial!movement!of!the!sampling!area!—!so!that!different!subjects!
within!a!given!scene!can!be!selected!for!sharpest!focus!
!!!!!!!!!!!!!!!2.!!Ranging!performance!improvement!is!needed!in!low!scene!illum ination!situations!
!!!!!!!!3.!!Im p ro v ement!in!accu ra c y!o f!t h e !sy ste m!as!ISO!settin g !in cr e as e d!
!4.!Auto!focus!should!ideally!be!a!realtime!action!(or!as!close!as!possible!to!realtime)!so!speed!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
of!calculations!should!be!increased!
!!!!!!!!5.!!Im p ro v ement!in!the!c a lcu la tin g !a lgo r ith m!to!elevate!re lia b ility!
A!more!dense!samp ling!lattice!of! photosites!for!the!cursor!was!developed!to!increase!sensing!sensitivity!
and!accuracy!over!a!wider!range!of!scene!illumination!and!camera!ISO!settings.!!The!cursor!size!can!be!
adjusted!to!accommodate!the!specific!AF!needs!of!a!given!scene!and!situation.!!!
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