22/04/29The Photo-response Non-uniformity (PRNU) ndi chithunzi cha kufanana kwa kuyankhidwa kwa kamera pa kuwala, kofunikira muzinthu zina zowunikira kwambiri.
Kuwala kukazindikirika ndi kamera, kuchuluka kwa ma electron omwe amajambulidwa ndi pixel iliyonse panthawi yowonekera amayesedwa, ndipo amadziwitsidwa ku kompyuta ngati digital greyscale value (ADU). Kusinthaku kuchokera ku ma elekitironi kupita ku ma ADU kumatsata chiŵerengero cha ADU pa electron chomwe chimatchedwa phindu la kutembenuka, kuphatikizapo mtengo wokhazikika (nthawi zambiri 100 ADU). Izi zimatsimikiziridwa ndi chosinthira cha Analogue-to-digital ndi Amplifier chomwe chimagwiritsidwa ntchito kutembenuza. Makamera a CMOS amapeza liwiro lodabwitsa komanso mawonekedwe aphokoso pang'ono pogwira ntchito limodzi, ndi chosinthira chimodzi kapena zingapo za analogi-to-digital pagawo lililonse la kamera, ndi amplifier imodzi pa pixel. Izi zimabweretsa mwayi wosintha pang'ono pakupeza ndikusintha kuchokera ku pixel kupita ku pixel.
Kusiyanasiyana kwa mtengo wamtunduwu kungayambitse phokoso lokhazikika pamawu otsika, oimiridwa ndiDSNU. PRNU imayimira kusiyana kulikonse pakupeza, chiŵerengero cha ma elekitironi odziwika ndi ADU yowonetsedwa. Imayimira kupatuka kokhazikika kwa phindu la ma pixel. Popeza kuti kusiyana kwamphamvu kumatengera kukula kwa ma siginecha, kumaimiridwa ngati peresenti.
Zodziwika bwino za PRNU ndi <1%. Pazithunzi zonse zotsika ndi zapakatikati, zokhala ndi zizindikiro za 1000e- kapena zochepa, kusiyana kumeneku kudzakhala kochepa poyerekeza ndi phokoso lowerengedwa ndi magwero ena a phokoso.
Komanso pojambula kuwala kwapamwamba, kusiyanako sikungakhale kofunikira poyerekeza ndi magwero ena a phokoso pa chithunzi, monga phokoso la photon. Koma muzojambula zowala kwambiri zomwe zimafuna kulondola kwapamwamba kwambiri, makamaka zomwe zimagwiritsa ntchito mafelemu-average kapena frame-summing, PRNU yotsika ikhoza kukhala yopindulitsa.
