25/09/11Kuyo nayiphi na inkqubo yokulinganisa - ukusuka kunxibelelwano olungenazingcingo ukuya kwifoto yedijithali - i-signal-to-noise ratio (SNR) luphawu olusisiseko lomgangatho. Nokuba uhlalutya imifanekiso yeteleskopu, uphucula ushicilelo lwemakrofoni, okanye ulungisa ingxaki kwikhonkco elingenazingcingo, i-SNR ikuxelela ukuba lungakanani ulwazi oluluncedo oluphuma kwingxolo engasemva engafunwayo.
Kodwa ukubala i-SNR ngokuchanekileyo akusoloko kuthe ngqo. Kuxhomekeka kwisixokelelwano, imiba eyongezelelweyo efana nobumnyama bangoku, ingxolo yokufunda, okanye i-pixel binning inokufuna ukuqwalaselwa. Esi sikhokelo sikuhamba ngethiyori, iifomula eziphambili, iimpazamo eziqhelekileyo, izicelo, kunye neendlela ezisebenzayo zokuphucula i-SNR, ukuqinisekisa ukuba unokuyisebenzisa ngokuchanekileyo kuluhlu olubanzi lweemeko.
Yintoni iSignal-to-Noise Ratio (SNR)?
Embindini wayo, umlinganiselo wesignali ukuya kwingxolo ulinganisa ubudlelwane phakathi kwamandla omqondiso ofunekayo kunye nengxolo engasemva eyifihlayo.
● Umqondiso = ulwazi olunentsingiselo (umzekelo, ilizwi xa ufowuna, inkwenkwezi ekumfanekiso weteleskopu).
● Ingxolo = ukuguquguquka okungafunekiyo, okungafunekiyo okuphazamisa okanye ukufihla umqondiso (umz., ingxolo, ingxolo yesivamvo, ukuphazamiseka kombane).
Ngokwezibalo, i-SNR ichazwa ngolu hlobo:
Ngenxa yokuba olu lungelelwaniso lunokwahluka kwii-odolo ezininzi zobukhulu, i-SNR ihlala ibonakaliswa ngeedecibels (dB):
● I-SNR ephezulu (umz., i-40 dB): isignali ilawula, ibangele ulwazi olucacileyo noluthembekileyo.
● I-SNR ephantsi (umzekelo, i-5 dB): ingxolo yongamela umqondiso, yenza ukutolika kube nzima.
Uyibala njani i-SNR
Ukubalwa komlinganiselo wesignali ukuya kwingxolo kunokwenziwa ngamanqanaba ahlukeneyo okuchaneka ngokuxhomekeke kwimithombo yengxolo ebandakanyiweyo. Kweli candelo, iifom ezimbini ziya kuqaliswa: enye i-akhawunti yangoku emnyama kwaye enye ithatha ukuba inokungahoywa.
Qaphela: Ukongeza amaxabiso ingxolo azimeleyo kufuna wongezwe kwiquadrature. Umthombo ngamnye wengxolo uphindwe kabini, ushwankathelwa, kwaye ingcambu yetotali ithathwa.
Umlinganiselo wesignali ukuya kwingxolo kunye nobumnyama bangoku
Oku kulandelayo yinxaki yokusetyenziswa kwiimeko apho ingxolo yangoku emnyama inkulu ngokwaneleyo ukuba ifune ukubandakanywa:
Nantsi ingcaciso yamagama:
Umqondiso (e-): Lo ngumqondiso womdla kwiifotoelectrons, kunye nomqondiso wangoku omnyama othathiweyo
Isiginali iyonke (e-) iya kuba yi-photoelectron count kwi-pixel yomdla - ngokungqongqo hayi ixabiso lepixel kwiiyunithi zamanqanaba angwevu. Umzekelo wesibini weSignali (e-), ezantsi kwe-equation, ingxolo ye-photonshot.
Umsinga omnyama (DC):Ixabiso langoku elimnyama lalo pixel.
t: Ixesha lokuvezwa kwimizuzwana
sr:Funda ingxolo kwimowudi yekhamera.
Umlinganiselo wesignali ukuya kwingxolo yobumnyama obungahoywanga
Kwiimeko ezimfutshane (< 1 isekhondi) amaxesha okuvezwa, kunye neekhamera ezipholileyo, ezisebenza kakhulu, ingxolo yangoku emnyama iya kuba ngaphantsi kwengxolo efundwayo, kwaye ingahoywa ngokukhuselekileyo.
Apho imigaqo iphinda ichazwe ngasentla, ngaphandle kokuba umqondiso wangoku omnyama akufuneki ubalwe kwaye uthatyathwe kumqondiso njengoko kufuneka ulingane no-zero.
Unyino lwezi fomula kunye nemigaqo engekhoyo
Iifomula ezichaseneyo ziya kunika iimpendulo ezichanekileyo kuphela kwiCCD kunyeIikhamera zeCMOS. I-EMCCD kunye nezixhobo ezongeziweyo zazisa imithombo yengxolo eyongezelelweyo, ngoko ke ezi zibalo azinakusetyenziswa. Ukufumana ulungelelwaniso olupheleleyo lwesignali ukuya kwingxolo olubalela ezi kunye namanye amagalelo.
Elinye igama lengxolo eli (okanye liqhele ukuba) elidla ngokuqukwa kwii-equations ze-SNR lelo le-photo-response non-uniformity (PRNU), nayo ngamanye amaxesha ibhalwe 'ipatheni yengxolo elungisiweyo' (FPN). Oku kubonisa ukungalingani kwenzuzo kunye nempendulo yesignali kuyo yonke inzwa, enokuthi ibe yinto elawulayo kwimiqondiso ephezulu ukuba inkulu ngokwaneleyo, ukunciphisa i-SNR.
Ngelixa iikhamera zangaphambili zine-PRNU ebalulekileyo ngokwaneleyo ukuba ifune ukubandakanywa kwayo, uninzi lwangokuiikhamera zenzululwazibabe nePRNU ephantsi ngokwaneleyo ukwenza igalelo layo ngaphantsi kwengxolo yefotoni, ngakumbi emva kokuba izilungiso ezisebhodini zifakiwe. Ngoku, ke, ihlala ingahoywa kwizibalo ze-SNR. Nangona kunjalo, i-PRNU isabalulekile kwezinye iikhamera kunye nezicelo, kwaye ibandakanyiwe kwi-equation ye-SNR engaphezulu yokugqibezela. Oku kuthetha ukuba ii-equations ezinikeziweyo ziluncedo kwiinkqubo ezininzi zeCCD/CMOS kodwa akufuneki zithathwe njengezisebenza jikelele.
Iindidi zengxolo kwiizibalo ze-SNR
Ukubala i-SNR ayikokuthelekisa nje umqondiso ngokuchasene nexabiso elinye lengxolo. Ngokwesiqhelo, imithombo yengxolo emininzi ezimeleyo inegalelo, kwaye ukuyiqonda kubalulekile.
I-Shot Ingxolo
● Imvelaphi: ukufika kwezibalo zeefotoni okanye ii-electron.
● Izikali ezinengcambu yomqondiso.
● Eyona ibalaseleyo kwifoton-limited imaging (astronomy, fluorescence microscopy).
Ingxolo yoThermal
● Ikwabizwa ngokuba yiJohnson–Nyquist ingxolo, eveliswa yintshukumo ye-electron kwizixhasi.
● Ukunyuka ngobushushu kunye ne-bandwidth.
● Kubalulekile kunxibelelwano lwe-elektroniki kunye nonxibelelwano olungenazingcingo.
Ingxolo yangoku emnyama
● Ukwahluka okungaqhelekanga kumbane omnyama ngaphakathi kwabenzi boluvo.
● Okubaluleke ngakumbi kwiindawo zokutyhileka ezide okanye izixhobo ezibonisa ubushushu.
● Uncitshiswe ngokupholisa inzwa.
Funda Ingxolo
● Ingxolo evela kwi-amplifiers kunye ne-analog-to-digital conversion.
● Ilungisiwe ngokufundwayo, ibaluleke kakhulu kwiinkqubo ezinophawu oluphantsi.
Quantization Ingxolo
● Ukwaziswa ngedijithali (ukusondeza kumanqanaba ahlukeneyo).
● Kubalulekile kwiisistim ezinobunzulu obuphantsi (umzekelo, i-8-bit audio).
Ingxolo yokusingqongileyo/yeNkqubo
● I-EMI, i-crosstalk, i-ripple supply power.
● Inokongamela ukuba ukukhusela/ukubekwa phantsi akukuhle.
Ukuqonda ukuba yeyiphi kwezi eyona iphambili kunceda ekukhetheni ifomula eyiyo kunye nendlela yokunciphisa.
Iimpazamo eziqhelekileyo ekubaleni i-SNR
Kulula ukufumana iindlela ezininzi 'ezimfutshane' ukuqikelela umlinganiselo wesignali ukuya kwingxolo kumfanekiso. Ezi zithande ukuntsokotha kancinane kuneequations ezichaseneyo, zivumela ukutsalwa lula kumfanekiso ngokwawo kunokuba zifune ulwazi lweeparamitha zekhamera njengengxolo yokufunda, okanye zombini. Ngelishwa, kunokwenzeka ukuba nganye yezi ndlela ayichanekanga, kwaye iya kukhokelela kwiziphumo ezigwenxa nezingeloncedo. Kucetyiswa ngamandla ukuba ii-equations ezichaseneyo (okanye i-advanced version isetyenziswe kuzo zonke iimeko.
Ezinye zezona ndlela zimfutshane zobuxoki ziquka:
1, Ukuthelekisa ukuqina komqondiso ngokuchasene nokuqina okungasemva, kumanqanaba angwevu. Le ndlela izama ukugweba ubuntununtunu bekhamera, amandla omqondiso okanye umlinganiselo wesignali kumlinganiselo wengxolo ngokuthelekisa ubunzulu bencopho kumandla angasemva. Le ndlela ineziphene ezinzulu njengoko impembelelo yekhamera yekhamera inokuseta ngokungathandabuzekiyo ubunzulu obungasemva, inzuzo inokuseta ubunzulu bomqondiso ngaphandle kwesizathu, kwaye akukho mnikelo wengxolo nokuba kuphawu okanye ngasemva kuthathelwa ingqalelo.
2, Ukwahlula iincopho zesignali ngokutenxa okusemgangathweni kwendawo yeepikseli ezingasemva. Okanye, ukuthelekisa amaxabiso encopho kwingxolo ebonakalayo ngasemva evezwe yiprofayile yomgca. Ukucinga ukuba i-offset ikhutshwe ngokuchanekileyo kumaxabiso phambi kokwahlula, eyona ngozi ibaluleke kakhulu kule ndlela kubukho bokukhanya okungasemva. Nakuphi na ukukhanya okungasemva kuya kulawula ingxolo kwiipikseli ezingasemva. Ngaphaya koko, ingxolo kumqondiso womdla, njengengxolo yokudubula, ayiqwalaselwa kwaphela.
3, Umqondiso wentsingiselo kwiipikseli zomdla vs ukutenxa okusemgangathweni kwamaxabiso epikseli: Ukuthelekisa okanye ukujonga ukuba ingakanani na isignali eyincopho eguqukayo kuzo zonke iipikseli ezingabamelwane okanye izakhelo ezilandelelanayo zisondele ekuchanekeni kunezinye iindlela ezimfutshane, kodwa akunakwenzeka ukuba ziphephe ezinye iimpembelelo ezigqwethekileyo amaxabiso, njengotshintsho kuphawu olungaveli kwingxolo. Le ndlela isenokungachanekanga ngenxa yokubala kwepixel ephantsi xa kuthelekiswa. Ukuthabatha ixabiso lokulinganisa kufuneka kwakhona lingalibaleki.
4, Ukubala i-SNR ngaphandle kokuguqula ubunzulu beeyunithi zeefotoelectrons, okanye ngaphandle kokususa i-offset: Njengoko ingxolo yefoton idla ngokuba ngowona mthombo wengxolo mkhulu kwaye ixhomekeke kulwazi lokususwa kwekhamera kunye nokufumana umlinganiselo, akwenzeki ukubaleka ukubala ubuyela kwii-photoelectrons ukubala kwe-SNR.
5, Ukugweba i-SNR ngeso: Ngelixa kwezinye iimeko ukugweba okanye ukuthelekisa i-SNR ngeso kunokuba luncedo, kukho nemigibe engalindelekanga. Ukujonga i-SNR kwixabiso eliphezulu leepixels kunokuba nzima kunexabiso eliphantsi okanye ipixels yangasemva. Iziphumo ezifihlakeleyo ngakumbi zinokudlala indima: Umzekelo, iimonitha zekhompyuter ezahlukeneyo zinokunika imifanekiso ehluke kakhulu. Ngaphaya koko, ukubonisa imifanekiso kumanqanaba ahlukeneyo okusondeza kwisoftware kunokuchaphazela kakhulu inkangeleko yembonakalo yengxolo. Oku kuyingxaki ngakumbi xa uzama ukuthelekisa iikhamera ezinobungakanani bepikseli yendawo eyahlukileyo. Okokugqibela, ubukho bokukhanya okungasemva bunokuphelisa nayiphi na inzame yokugweba i-SNR ngokubonakalayo.
Usetyenziso lwe-SNR
I-SNR yimetriki yehlabathi jikelele enezicelo ezinoluhlu olubanzi:
● Ukurekhodwa kweAudio kunye noMculo: Imisela ukucaca, uluhlu oluguquguqukayo, kunye nokuthembeka kweerekhodi.
● Unxibelelwano olungenazingcingo: I-SNR inxulumene ngokuthe ngqo namazinga empazamo yebit (BER) kunye nokuhanjiswa kwedatha.
● Umfanekiso weNzululwazi: Kwi-astronomy, ukufumanisa iinkwenkwezi ezibuthathaka ngokuchasene nokukhanya kwesibhakabhaka kufuna i-SNR ephezulu.
● Izixhobo zonyango: I-ECG, i-MRI, kunye ne-CT scans zithembele kwi-SNR ephezulu ukuhlula imiqondiso kwingxolo ye-physiological.
● Iikhamera kunye nokuFota: Iikhamera zabathengi kunye nezinzwa ze-CMOS zenzululwazi zombini zisebenzisa i-SNR ukulinganisa ukusebenza ekukhanyeni okuphantsi.
Ukuphucula i-SNR
Kuba i-SNR ilinyathelo elibaluleke kangaka, umzamo omkhulu uya ekuwuphuculeni. Ubuchule bubandakanya:
Iindlela ze-Hardware
● Sebenzisa izixhobo zoluvo ezingcono ezinobumnyama obusezantsi.
● Faka isicelo sokukhusela kunye nesiseko sokunciphisa i-EMI.
● Ii-detectors ezipholileyo zokucinezela ingxolo ye-thermal.
Iinkqubo zeSoftware
● Faka izihluzi zedijithali ukususa iifrikhwensi ezingafunwayo.
● Sebenzisa i-avareji kwiifreyimu ezininzi.
● Sebenzisa i-algorithms yokunciphisa ingxolo kwi-imaging okanye kwi-audio processing.
I-Pixel Binning kunye nempembelelo yayo kwi-SNR
Umphumo wokubamba i-binning kwi-signal-to-noise ratio ixhomekeke kwitekhnoloji yekhamera kunye nokuziphatha kwenzwa, njengoko ukusebenza kwengxolo yeekhamera eziboshwe kunye nezingafakwanga zingahluka kakhulu.
Iikhamera zeCCD zingenza isishwankathelo seepixels ezikufuphi' zihlawulise 'kwi-chip'. Ingxolo yokufunda yenziwa ngexesha elinye, nangona isiginali yangoku emnyama kwipixel nganye nayo iya kushwankathelwa.
Uninzi lweekhamera ze-CMOS zenza i-off-chip binning, ixabiso elithetha ukuba liyalinganiswa kuqala (kwaye kufundwa ingxolo yaziswa), emva koko ishwankathelwe ngokwedijithali. Ingxolo efundwayo yolu shwankathelo iyenyuka nangona ukuphindaphinda ngengcambu yenani leepixels ezishwankathelweyo, okt ngomlinganiselo we-2 ku-2x2 binning.
Njengoko ukuziphatha kwengxolo yeenzwa kunokuba nzima, kwizicelo zobungakanani kuyacetyiswa ukuba ulinganise i-offset, ukuzuza, kwaye ufunde ingxolo yekhamera kwimowudi ye-binned, kwaye usebenzise ezi xabiso kwi-signal-to-noise ratio equation.
Ukuqukumbela
Umlinganiselo we-signal-to-noise ratio (SNR) yenye yezona metrics zibalulekileyo kwisayensi, ubunjineli kunye neteknoloji. Ukusuka ekuchazeni ukucaca kwiifowuni ukuya ekuvumeleni ukubonwa kweminyele ekude, i-SNR ixhasa umgangatho wokulinganisa kunye neenkqubo zonxibelelwano. I-Mastering SNR ayikokuba nje unkqaye iifomyula - imalunga nokuqonda iingcinga, imida, kunye norhwebo lwehlabathi lokwenyani. Ngokwale mbono, iinjineli kunye nabaphandi banokwenza imilinganiselo ethembeke ngakumbi kunye neenkqubo zokuyila ezikhupha ukuqonda okunentsingiselo nakwiimeko ezinengxolo.
Uyafuna ukufunda ngakumbi? Jonga amanqaku anxulumeneyo:
Tucsen Photonics Co., Ltd. Onke amalungelo agciniwe. Xa ucaphula, nceda wazise umthombo:www.tucsen.com
