25/09/11A cikin kowane tsarin aunawa - daga sadarwa mara waya zuwa daukar hoto na dijital - rabon sigina-zuwa-amo (SNR) shine babban ma'auni na inganci. Ko kuna nazarin hotunan na'urar hangen nesa, inganta rikodin makirufo, ko magance matsala ta hanyar haɗin waya, SNR yana gaya muku yawan bayanin da ke da fa'ida daga hayaniyar da ba a so.
Amma ƙididdige SNR daidai ba koyaushe ba ne mai sauƙi. Dangane da tsarin, ƙarin abubuwa kamar duhu halin yanzu, amo karanta, ko pixel binning na iya buƙatar la'akari. Wannan jagorar tana bibiyar ku ta hanyar ka'idar, ainihin ƙididdiga, kurakurai na gama gari, aikace-aikace, da kuma hanyoyi masu amfani don inganta SNR, tabbatar da cewa zaku iya amfani da shi daidai a cikin fa'idodi da yawa.
Menene rabon Sigina-zuwa-Amo (SNR)?
A ainihinsa, sigina-zuwa amo rabo yana auna alakar da ke tsakanin ƙarfin siginar da ake so da kuma hayaniyar bangon da ke rufe ta.
Sigina = bayani mai ma'ana (misali, murya a cikin kira, tauraro a cikin hoton na'urar hangen nesa).
● Hayaniya = bazuwar, canjin da ba'a so wanda ke karkata ko ɓoye siginar (misali, amo, ƙarar firikwensin, tsangwama na lantarki).
A lissafin, SNR an bayyana shi da:
Saboda waɗannan ma'auni na iya bambanta akan yawancin umarni na girma, SNR yawanci ana bayyana su a cikin decibels (dB):
● Babban SNR (misali, 40 dB): sigina ya mamaye, yana haifar da bayyananniyar bayanai masu inganci.
● Ƙananan SNR (misali, 5 dB): hayaniya ta mamaye siginar, yin fassarar wahala.
Yadda ake ƙididdige SNR
Ana iya yin lissafin rabon sigina-zuwa amo tare da madaidaicin matakan daban-daban dangane da abin da aka haɗa tushen amo. A cikin wannan sashe, za a gabatar da nau'i biyu: ɗaya wanda ke ba da lissafin duhu na halin yanzu da kuma wanda ke ɗauka cewa ana iya yin watsi da shi.
Lura: Ƙara ƙimar surutu masu zaman kansu yana buƙatar ƙara su cikin ma'auni. Kowane tushen amo yana da murabba'i, tara, kuma ana ɗaukar tushen murabba'in jimillar.
Rabo sigina-zuwa amo tare da duhu duhu
Mai zuwa shine lissafin da za a yi amfani da shi a cikin yanayi inda hayaniyar duhu ke da girma don buƙatar haɗawa:
Ga ma’anar sharuddan:
Sigina (e-): Wannan ita ce siginar sha'awa a cikin photoelectrons, tare da rage siginar halin yanzu mai duhu
Jimlar siginar (e-) za ta zama ƙidayar photoelectron a cikin pixel na sha'awa - ba kawai ƙimar pixel a cikin raka'a na matakan launin toka ba. Misali na biyu na sigina (e-), a kasan lissafin, shine hayaniyar photonshot.
Dark halin yanzu (DC):Ƙimar halin yanzu mai duhu don wannan pixel.
t: Lokacin fallasa cikin daƙiƙa
σr:Karanta amo a yanayin kamara.
Matsakaicin sigina-zuwa amo don duhu mai duhu
A cikin gajeren lokaci (< 1 seconds) lokutan bayyanarwa, da sanyaya, kyamarorin ayyuka masu girma, hayaniyar duhu mai duhu gabaɗaya za ta kasance ƙasa da amo, kuma ba a kula da ita cikin aminci.
Inda aka sake yin ma'anar kamar yadda aka bayyana a sama, ban da cewa siginar mai duhu ba ya buƙatar ƙididdige shi kuma a cire shi daga siginar kamar yadda yakamata yayi daidai da sifili.
Iyakokin waɗannan ƙididdiga da kalmomin da suka ɓace
Ma'anar kishiyar za ta ba da amsa daidai ga CCD daCMOS kyamarori. EMCCD da ingantattun na'urori suna gabatar da ƙarin hanyoyin amo, don haka ba za a iya amfani da waɗannan ma'auni ba. Don ƙarin cikakkiyar ma'aunin sigina-zuwa amo wanda ke lissafin waɗannan da sauran gudummawar.
Wani kalmar amo wanda (ko kuma ake amfani da shi) wanda aka haɗa a cikin ma'auni na SNR shine na rashin daidaituwar amsawar hoto (PRNU), kuma wani lokacin ana yiwa lakabin 'fixed pattern noise' (FPN). Wannan yana wakiltar rashin daidaituwa na riba da amsa sigina a fadin firikwensin, wanda zai iya zama rinjaye a manyan sigina idan ya isa, yana rage SNR.
Yayin da kyamarori na farko suna da isassun isassun PRNU don buƙatar haɗa shi, mafi yawan zamanikyamarori na kimiyyasuna da ƙarancin ƙarancin PRNU don ba da gudummawar ta da kyau ƙasa da na hayaniyar harbin hoto, musamman bayan an yi amfani da gyare-gyaren kan jirgi. Yanzu, saboda haka, yawanci ana watsi da shi a cikin lissafin SNR. Koyaya, PRNU har yanzu yana da mahimmanci ga wasu kyamarorin da aikace-aikace, kuma an haɗa su cikin ƙarin ci gaba na SNR equation don cikawa. Wannan yana nufin ma'auni da aka bayar suna da amfani ga yawancin tsarin CCD/CMOS amma bai kamata a kula da su kamar yadda ake aiwatar da su a duniya ba.
Nau'in Hayaniya a cikin Lissafin SNR
Ƙididdiga SNR ba kawai game da kwatanta sigina akan ƙimar amo ɗaya ba ce. A aikace, kafofin hayaniya masu zaman kansu da yawa suna ba da gudummawa, kuma fahimtar su yana da mahimmanci.
Hayaniyar harbi
● Asalin: zuwan ƙididdiga na photons ko electrons.
● Sikeli tare da murabba'in tushen siginar.
● Mafiyi a cikin iyakantaccen hoto (astronomy, fluorescence microscopy).
Hayaniyar thermal
Hakanan ana kiranta Johnson-Nyquist amo, wanda motsin lantarki ke samarwa a cikin resistors.
● Ƙara yawan zafin jiki da bandwidth.
● Mahimmanci a cikin kayan lantarki da sadarwa mara waya.
Duhun Hayaniyar Yanzu
Bambancin bazuwar a cikin duhu halin yanzu a cikin firikwensin.
● Mahimmanci a cikin dogon filaye ko na'urori masu dumi.
● Ragewa ta hanyar sanyaya firikwensin.
Karanta Surutu
● Hayaniyar amplifiers da canjin analog-zuwa dijital.
● Kafaffen kowane karantawa, yana da mahimmanci a cikin tsarin ƙananan sigina.
Ƙididdigar Hayaniyar
● An gabatar da shi ta hanyar ƙididdigewa (zagaye zuwa matakan da ba su dace ba).
● Mahimmanci a cikin ƙananan tsarin zurfin-bit (misali, 8-bit audio).
Hayaniyar Muhalli/tsari
● EMI, crosstalk, wutar lantarki ripple.
● Zai iya rinjaye idan garkuwa ko ƙasa ta yi rauni.
Fahimtar wanne daga cikin waɗannan ya fi rinjaye yana taimakawa wajen zaɓar madaidaicin dabara da hanyar ragewa.
Kuskuren gama gari a cikin ƙididdige SNR
Yana da sauƙi a gamu da hanyoyin 'gajerun hanyoyi' da yawa don kimanta rabon sigina-zuwa amo a cikin hoto. Waɗannan sun kasance ko dai ba su da rikitarwa fiye da ma'auni daban-daban, suna ba da damar samun sauƙi daga hoto da kansa maimakon buƙatar sanin sigogin kamara kamar amo, ko duka biyun. Abin takaici, yana yiwuwa kowane ɗayan waɗannan hanyoyin ba daidai ba ne, kuma zai haifar da ɓarna da sakamako mara amfani. An ba da shawarar sosai cewa ma'auni sabanin (ko sigar ci gaba yakamata a yi amfani da su a kowane yanayi.
Wasu daga cikin gajerun hanyoyin karya na yau da kullun sun haɗa da:
1, Kwatanta siginar tsanani vs baya tsanani, a cikin launin toka matakan. Wannan tsarin yana ƙoƙarin yin hukunci da hankalin kamara, ƙarfin sigina ko sigina zuwa rabon amo ta kwatanta ƙarfin kololuwa zuwa ƙarfin bango. Wannan dabarar tana da rauni sosai saboda tasirin sokewar kyamara na iya saita ƙarfin bango ba bisa ka'ida ba, riba na iya saita ƙarfin sigina ba da gangan ba, kuma ba a la'akari da gudummawar amo ko dai a sigina ko bango.
2. Rarraba kololuwar sigina ta daidaitaccen karkataccen yanki na bangon pixels. Ko, kwatanta ƙimar kololuwa da hayaniyar gani a bango wanda bayanin martabar layi ya bayyana. Tsammanin cewa an cire gyara daidai daga dabi'u kafin rarrabuwa, babban haɗari a cikin wannan hanya shine kasancewar hasken baya. Duk wani haske na bango yawanci zai mamaye amo a bangon pixels. Bugu da ari, amo a cikin siginar sha'awa, kamar karar harbi, ba a zahiri la'akari da shi kwata-kwata.
3. Ma'anar sigina a cikin pixels na sha'awa vs daidaitaccen karkatar da ƙimar pixel: Kwatanta ko lura da nawa siginar kololuwa ke canzawa a cikin maƙwabtan pixels ko firam ɗin da suka biyo baya ya fi kusa da zama daidai fiye da sauran hanyoyin gajeriyar hanya, amma ba shi yiwuwa a guje wa wasu tasirin karkatar da ƙima, kamar canji a cikin siginar da baya fitowa daga hayaniya. Hakanan wannan hanyar na iya zama mara kyau saboda ƙarancin ƙidayar pixel a cikin kwatancen. Hakanan ba dole ba ne a manta da raguwar ƙimar biya.
4, Lissafi SNR ba tare da juyawa zuwa tsanani raka'a na photoelectrons, ko ba tare da cire biya diyya: Kamar yadda photon harbi amo ne yawanci mafi girma amo tushen da kuma dogara a kan ilmi na kamara ta biya diyya da kuma samun ga ma'auni, shi ne ba zai yiwu a kauce wa lissafi da baya ga photoelectrons ga SNR lissafin.
5. Yin hukunci SNR da ido: Yayin da a wasu yanayi yin hukunci ko kwatanta SNR da ido na iya zama da amfani, akwai kuma ramukan da ba a zata ba. Yin hukunci a SNR a cikin firikwensin ƙima na iya zama da wahala fiye da ƙananan ƙima ko pixels na baya. Ƙarin illolin da hankali kuma na iya taka rawa: Misali, masu saka idanu na kwamfuta daban-daban na iya ba da hotuna tare da bambanci daban-daban. Bugu da ari, nuna hotuna a matakan zuƙowa daban-daban a cikin software na iya tasiri sosai ga bayyanar amo. Wannan yana da matsala musamman idan ƙoƙarin kwatanta kyamarori tare da girman pixel sarari abu daban-daban. A ƙarshe, kasancewar hasken baya na iya ɓata duk wani ƙoƙari na yin hukunci SNR a gani.
Abubuwan da aka bayar na SNR
SNR ma'auni ne na duniya tare da aikace-aikace masu fa'ida:
● Sauti & Rikodin Kiɗa: Yana ƙayyade tsabta, tsayayyen kewayon, da amincin rikodi.
Sadarwar Mara waya: SNR yana da alaƙa kai tsaye zuwa ƙimar kuskuren bit (BER) da kuma fitar da bayanai.
● Hoto na Kimiyya: A cikin ilmin taurari, gano taurarin da ba su da ƙarfi akan hasken sama yana buƙatar babban SNR.
● Kayan aikin likita: ECG, MRI, da CT scans sun dogara da babban SNR don bambanta sigina daga hayaniyar jiki.
● Kyamara & Hotuna: Kyamarar mabukaci da na'urori masu auna firikwensin CMOS na kimiyya duka suna amfani da SNR don nuna alamar aiki a cikin ƙaramin haske.
Inganta SNR
Tunda SNR irin wannan ma'auni ne mai mahimmanci, ƙoƙari mai mahimmanci yana tafiya don inganta shi. Dabarun sun haɗa da:
Hardware Hanyoyi
● Yi amfani da ingantattun na'urori masu auna firikwensin tare da ƙananan halin yanzu duhu.
● Aiwatar da garkuwa da ƙasa don rage EMI.
● Masu gano sanyi don murkushe amo mai zafi.
Hanyoyi na Software
● Aiwatar da matatun dijital don cire mitoci maras so.
● Yi amfani da matsakaita a cikin firam masu yawa.
● Yi amfani da algorithms rage amo a cikin hoto ko sarrafa sauti.
Pixel Binning da Tasirinsa akan SNR
Tasirin binning akan rabon sigina-zuwa amo ya dogara da fasahar kamara da halayyar firikwensin, saboda aikin hayaniyar kyamarori da ba a haɗa su ba na iya bambanta sosai.
Kyamarorin CCD na iya taƙaita cajin pixels na kusa da 'kan-chip'. Hayaniyar karantawa ana ɗaukar lokaci ɗaya ne kawai, kodayake siginar duhu na yanzu daga kowane pixel shima za'a taƙaita shi.
Yawancin kyamarori na CMOS suna yin kashe-kashen-chip binning, ma'ana ana auna dabi'u da farko (da karanta amo da aka gabatar), sannan a taƙaice su ta lambobi. Hayaniyar da ake karantawa don irin waɗannan taƙaitawar tana ƙaruwa ko da yake ninkawa ta tushen murabba'in adadin pixels da aka tara, watau ta hanyar 2 don binning 2x2.
Kamar yadda hayaniyar firikwensin na iya zama mai rikitarwa, don aikace-aikacen ƙididdigewa yana da kyau a auna kashewa, samun riba, da karanta hayaniyar kyamara a yanayin ɗaure, kuma a yi amfani da waɗannan dabi'u don ma'aunin sigina-zuwa amo.
Kammalawa
Matsakaicin siginar-zuwa-amo (SNR) yana ɗaya daga cikin mahimman ma'auni a kimiyya, injiniyanci, da fasaha. Daga bayyana fayyace a cikin kiran waya zuwa ba da damar gano taurari masu nisa, SNR tana ba da ingancin ma'auni da tsarin sadarwa. Jagoran SNR ba kawai game da haddar ƙididdiga ba ne - yana da game da fahimtar zato, iyakancewa, da cinikin-ba-da-kai na duniya. Daga wannan hangen nesa, injiniyoyi da masu bincike na iya yin ƙarin ma'auni masu dogaro da tsarin ƙira waɗanda ke fitar da fahimta mai ma'ana ko da a cikin yanayi mai hayaniya.
Kuna son ƙarin koyo? Dubi labarai masu alaƙa:
Tucsen Photonics Co., Ltd. Duk haƙƙin mallaka. Lokacin ambato, da fatan za a yarda da tushen:www.tucsen.com
