22.04.22Dark Signal Non-Uniformity (DSNU) yog ib qho kev ntsuas ntawm theem ntawm lub sij hawm ywj pheej variation nyob rau hauv keeb kwm yav dhau ntawm lub koob yees duab duab. Nws muab cov lej ntxhib qhia txog qhov zoo ntawm cov duab tom qab ntawd, hais txog cov qauv lossis cov qauv uas muaj peev xwm qee zaum tuaj.
Hauv kev pom lub teeb qis, lub koob yees duab tom qab zoo tuaj yeem dhau los ua qhov tseem ceeb. Thaum tsis muaj photons tshwm sim ntawm lub koob yees duab, cov duab tau txais yuav feem ntau tsis pom pixel qhov tseem ceeb ntawm 0 qib grey (ADU). Ib qho 'offset' tus nqi feem ntau yog tam sim no, xws li 100 qib grey, uas lub koob yees duab yuav tso tawm thaum tsis muaj lub teeb, ntxiv lossis rho tawm cov suab nrov ntawm qhov ntsuas. Txawm li cas los xij, tsis muaj kev ntsuas ceev thiab kho, tej zaum yuav muaj qee qhov kev hloov pauv ntawm pixel mus rau pixel hauv tus nqi them offset. Qhov kev hloov pauv no hu ua 'Fixed Pattern Noise'. DNSU sawv cev rau qhov twg ntawm cov suab nrov nrov no. Nws sawv cev rau tus qauv sib txawv ntawm pixel offset qhov tseem ceeb, ntsuas hauv electrons.
Rau ntau lub koob yees duab qis qis, DSNU feem ntau yog qis dua ib ncig ntawm 0.5e-. Qhov no txhais tau hais tias rau nruab nrab- lossis siab-teeb daim ntawv thov nrog ntau pua lossis ntau txhiab tus photons ntes ib pixel, qhov kev ua suab nrov no yog qhov tsis txaus ntseeg kiag li. Tseeb tiag, rau cov ntawv thov uas tsis tshua muaj teeb pom kev zoo ib yam nkaus, muab DSNU qis dua lub koob yees duab cov suab nrov (feem ntau 1-3e-), cov suab nrov ntawm cov qauv no tsis zoo li ua lub luag haujlwm hauv cov duab zoo.
Txawm li cas los xij, DSNU tsis yog tus sawv cev zoo tshaj plaws ntawm cov suab nrov ruaj khov, vim nws tsis tuaj yeem ntes ob yam tseem ceeb. Ua ntej, CMOS cov koob yees duab tuaj yeem nthuav tawm cov qauv tsim hauv qhov kev hloov pauv no, feem ntau nyob rau hauv daim ntawv ntawm kab ntawm pixels txawv ntawm ib leeg hauv lawv cov nqi offset. Qhov 'Fixed Pattern Kem Noise' lub suab nrov no pom tau rau peb lub qhov muag ntau dua li cov suab nrov tsis muaj teeb meem, tab sis qhov sib txawv no tsis yog sawv cev los ntawm tus nqi DSNU. Cov kab kos duab no tuaj yeem tshwm sim hauv keeb kwm yav dhau ntawm cov duab teeb pom kev tsawg, xws li thaum lub ncov pom cov teeb liab tsawg dua 100 daim duab-electrons. Saib daim duab 'kev tsis ncaj ncees', cov duab uas lub koob yees duab tsim tsis muaj teeb pom kev zoo, yuav tso cai rau koj los xyuas seb qhov muaj suab nrov ntawm cov qauv tsim.
Qhov thib ob, qee qhov xwm txheej, kev hloov pauv hauv kev sib txawv tuaj yeem yog lub sijhawm nyob ntawm, sib txawv ntawm ib tus ncej mus rau lwm qhov. Raws li DSNU qhia tsuas yog lub sijhawm hloov pauv hloov pauv, cov no tsis suav nrog. Saib ib ntu ntawm cov duab tsis ncaj ncees yuav tso cai rau koj txheeb xyuas qhov muaj lub sijhawm nyob ntawm cov qauv tsim suab nrov.
Raws li tau sau tseg, DSNU thiab keeb kwm kev hloov pauv hloov pauv yuav tsis yog qhov tseem ceeb rau kev siv nruab nrab mus rau lub teeb pom kev zoo nrog ntau txhiab photons ib pixel, vim tias cov teeb liab no yuav muaj zog dua li qhov hloov pauv.
