25/09/04A cikin hoton dijital, yana da sauƙi a ɗauka cewa ƙuduri mafi girma ta atomatik yana nufin mafi kyawun hotuna. Masu kera kyamara galibi suna kasuwa tsarin bisa ƙidayar megapixel, yayin da masu yin ruwan tabarau ke haskaka ƙarfi da kaifi. Amma duk da haka, a aikace, ingancin hoto ya dogara ba kawai akan ƙayyadaddun ruwan tabarau ko firikwensin ɗaiɗaiku ba har ma da yadda aka daidaita su.
Wannan shine inda samfurin Nyquist ya shiga wasa. Asalin ƙa'ida daga sarrafa sigina, ma'aunin Nyquist yana saita tsarin ka'idar don ɗaukar cikakkun bayanai daidai. A cikin hoto, yana tabbatar da cewa ƙudurin gani ta hanyar ruwan tabarau da ƙudurin dijital na firikwensin kamara suna aiki tare cikin jituwa.
Wannan labarin yana buɗe samfurin Nyquist a cikin mahallin hoto, yana bayyana ma'auni tsakanin ƙudurin gani da kyamara, kuma yana ba da ƙa'idodi masu amfani don aikace-aikacen kama daga ɗaukar hoto zuwa hoton kimiyya.
Menene Samfurin Nyquist?
Hoto 1: Theorem Samfur na Nyquist
Sama:Ana auna siginar sinusoidal (cyan), ko samfurin, a wurare da yawa. Layin launin toka mai tsayi mai tsayi yana wakiltar ma'auni 1 a kowane zagaye na siginar sinusoidal, yana ɗaukar kololuwar sigina, gaba ɗaya yana ɓoye ainihin yanayin siginar. Jajayen lanƙwasa mai kyau yana ɗauka a ma'auni 1.1 a kowane samfurin, yana bayyana sinusoid amma yana ɓarna mitar sa. Wannan yana kama da tsarin Moiré.
Kasa:Sai kawai lokacin da aka ɗauki samfurori 2 a kowane zagaye (layi mai dige shuɗi) za a fara kama ainihin siginar.
Ka'idar Samfuran Nyquist ka'ida ce gama gari a tsakanin sarrafa sigina a cikin kayan lantarki, sarrafa sauti, hoto da sauran fagage. Ka'idar ta bayyana a sarari cewa don sake gina mitar da aka bayar a cikin sigina, dole ne a yi ma'auni aƙalla sau biyu, wanda aka nuna a cikin Hoto na 1. A cikin yanayin ƙudurinmu na gani, wannan yana nufin cewa girman pixel sararin abu ɗinmu dole ne ya kasance aƙalla rabin mafi ƙarancin dalla-dalla da muke ƙoƙarin kamawa, ko, a cikin yanayin na'urar microscope, rabin ƙudurin microscope.
Hoto 2: Samfuran Nyquist tare da pixels murabba'in: al'amuran daidaitawa
Yin amfani da kyamara tare da grid na pixels murabba'i, nau'in samfurin 2x na ka'idar Nyquist kawai zai ɗauki cikakkun bayanai waɗanda suka yi daidai da grid pixel. Idan ƙoƙarin warware tsarin a kusurwa zuwa grid pixel, ingantaccen girman pixel ya fi girma, har zuwa sau √2 girma a diagonal. Adadin samfurin dole ne ya zama sau 2√2 mitar sararin samaniya da ake so don ɗaukar bayanai a 45o zuwa grid pixel.
Dalilin wannan yana bayyana a fili ta hanyar la'akari da Hoto 2 ( rabi na sama). Ka yi tunanin an saita girman pixel zuwa ƙudurin gani, yana ba da kololuwar tushen maki biyu maƙwabta, ko kowane daki-daki da muke ƙoƙarin warwarewa, kowane pixel nasu. Ko da yake ana gano waɗannan daban daban, babu wata alama a cikin ma'aunin da aka samu da ke nuna cewa kololuwa ne daban-daban - kuma ma'anar mu na "warware" ba ta cika ba. Ana buƙatar pixel a tsakanin, yana ɗaukar tudun siginar. Ana samun wannan ta hanyar aƙalla ninka ƙimar samfurin sararin samaniya, watau rage girman girman abin sararin samaniya.
Resolution na gani da ƙudurin kyamara
Don fahimtar yadda samfurin Nyquist ke aiki a cikin hoto, muna buƙatar bambanta tsakanin nau'ikan ƙuduri biyu:
● Ƙimar gani: Ƙaddamar da ruwan tabarau, ƙudurin gani yana nufin ikonsa na sake fitar da cikakkun bayanai. Abubuwa kamar ingancin ruwan tabarau, buɗaɗɗen buɗaɗɗiya, da ɓarna sun saita wannan iyaka. Ana amfani da aikin canja wuri (MTF) don auna yadda ruwan tabarau ke watsa bambanci a mitoci daban-daban.
● Ƙimar kamara: Ƙaddamar da firikwensin, ƙudurin kyamara ya dogara da girman pixel, pixel pitch, da kuma girman firikwensin gaba ɗaya. Matsakaicin pixel na aCMOS kamarakai tsaye yana bayyana mitar ta Nyquist, wanda ke ƙayyade iyakar dalla-dalla da firikwensin zai iya ɗauka.
Lokacin da waɗannan biyu ba su daidaita ba, matsaloli suna tasowa. Ruwan tabarau wanda ya zarce ikon warwarewar firikwensin yana "ɓatacce", tunda firikwensin ba zai iya ɗaukar duk cikakkun bayanai ba. Akasin haka, babban firikwensin firikwensin haɗe tare da ƙananan ruwan tabarau yana haifar da hotuna waɗanda ba su inganta ba duk da ƙarin megapixels.
Yadda Ake Daidaita Ƙwararrun gani da Kamara
Daidaita na'urorin gani da na'urori masu auna firikwensin yana nufin dacewa da mitar Nyquist na firikwensin tare da mitar yankewar gani na ruwan tabarau.
● Ana ƙididdige mitar Nyquist na firikwensin kyamara azaman 1/ (2 × pixel pitch). Wannan yana bayyana mafi girman mitar sararin samaniya da firikwensin zai iya yin samfuri ba tare da laƙabi ba.
● Mitar yankewar gani ya dogara da halayen ruwan tabarau da diffraction.
Don kyakkyawan sakamako, mitar Nyquist na firikwensin ya kamata ya daidaita tare da ko dan kadan ya wuce ikon magance ruwan tabarau. A aikace, kyakkyawar ƙa'idar babban yatsan hannu ita ce tabbatar da ƙimar pixel ya kusan rabin girman girman fasalin da za a iya warwarewa na ruwan tabarau.
Misali, idan ruwan tabarau zai iya warware cikakkun bayanai har zuwa 4 micrometers, to, firikwensin mai girman pixel ~ 2 micrometers zai daidaita tsarin da kyau.
Daidaita Nyquist tare da ƙudurin Kyamara & Kalubalen Pixels Square
Kasuwancin kashewa tare da rage girman girman abu yana rage ƙarfin tattara haske. Don haka yana da mahimmanci don daidaita buƙatar ƙuduri da tattara haske. Bugu da ƙari, girman sararin abu mafi girma na pixel yana nuna isar da babban filin kallon abin da ake yin hoto. Don aikace-aikacen da ke da ɗan buƙatu mai kyau, ana faɗin ma'auni mafi kyawun 'dokar babban yatsan' kamar haka: Girman pixel sararin abu, lokacin da aka ninka shi da wani abu don lissafin Nyquist, yakamata ya zama daidai da ƙudurin gani. Ana kiran wannan adadin ƙudurin kyamara.
Daidaita na'urorin gani da na'urori masu auna firikwensin sau da yawa suna saukowa don tabbatar da cewa ingantaccen ƙudurin samfurin kamara ya dace da iyakar ƙudurin gani na ruwan tabarau. An ce wani tsari ya yi daidai da Nyquist lokacin:
Ƙaddamar kamara = Ƙimar gani
Inda aka bayar da ƙudurin kyamara ta:
Dalilin da za a yi la'akari da Nyquist wanda aka ba da shawarar shine 2.3, ba 2 ba. Dalilin wannan shine kamar haka.
pixels kamara (yawanci) murabba'i ne, kuma an shirya su akan grid 2-D. Girman pixel kamar yadda aka ayyana don amfani a kishiyar ma'auni yana wakiltar faɗin pixels tare da gatura na wannan grid. Idan fasalulluka da muke ƙoƙarin warwarewa sun yi ƙarya a kowane kusurwa sai dai cikakkiyar madaidaicin 90° dangane da wannan grid, ingantaccen girman pixel zai yi girma, har zuwa √2 ≈ 1.41 girman pixel a 45°. Ana nuna wannan a hoto na 2 (ƙasa na ƙasa).
Abubuwan da aka ba da shawarar bisa ga ma'aunin Nyquist a cikin duk hanyoyin da za su kasance 2√2 ≈ 2.82. Koyaya, saboda cinikin da aka ambata a baya tsakanin ƙuduri da tarin haske, ana ba da shawarar ƙimar daidaitawa na 2.3 azaman tsarin babban yatsan hannu.
Matsayin Samfurin Nyquist a Hoto
Samfurin Nyquist shine mai tsaron ƙofa na amincin hoto. Lokacin da ƙimar samfurin ya faɗi ƙasa da iyakar Nyquist:
● Ƙarƙashin ƙima → yana haifar da ƙayyadaddun bayanai: cikakkun bayanai na ƙarya, jakunkunan gefuna, ko tsarin moiré.
● Oversampling → yana ɗaukar ƙarin bayanai fiye da yadda na'urorin gani zasu iya bayarwa, wanda ke haifar da raguwar dawowa: manyan fayiloli da manyan buƙatun sarrafawa ba tare da haɓakawa ba.
Daidaitaccen samfurin yana tabbatar da cewa hotuna suna da kaifi da gaskiya ga gaskiya. Yana ba da ma'auni tsakanin shigarwar gani da kama dijital, guje wa ɓata ƙuduri a gefe ɗaya ko ɓarna kayan tarihi a ɗayan.
Aikace-aikace masu amfani
Samfuran Nyquist ba ka'ida ba ce kawai - tana da aikace-aikace masu mahimmanci a duk fannonin hoto:
● Microscope:Dole ne masu bincike su zaɓi na'urori masu auna firikwensin da ke samfur aƙalla sau biyu mafi ƙanƙantar dalla-dalla da za a iya warwarewa ta ainihin ruwan tabarau. Zabar damakyamarar microscopeyana da mahimmanci, saboda girman pixel dole ne ya daidaita tare da iyakance-iyakantaccen ƙuduri na makasudin microscope. Dakunan gwaje-gwaje na zamani sukan fi sosCMOS kyamarori, wanda ke ba da ma'auni na hankali, kewayo mai ƙarfi, da kyawawan tsarin pixel don babban aikin hoto na halitta.
● Hoto:Haɗa manyan na'urori masu auna firikwensin megapixel tare da ruwan tabarau waɗanda ba za su iya warware cikakkun cikakkun bayanai ba sau da yawa yana haifar da ƙarancin haɓakawa a cikin kaifin. ƙwararrun masu ɗaukar hoto suna daidaita ruwan tabarau da kyamarori don guje wa ɓata ƙuduri.
● Hoto:Haɗa manyan na'urori masu auna firikwensin megapixel tare da ruwan tabarau waɗanda ba za su iya warware cikakkun cikakkun bayanai ba sau da yawa yana haifar da ƙarancin haɓakawa a cikin kaifin. ƙwararrun masu ɗaukar hoto suna daidaita ruwan tabarau da kyamarori don guje wa ɓata ƙuduri.
● Injin hangen nesa &Kyamarar KimiyyaA cikin kula da inganci da binciken masana'antu, rasa ƙananan siffofi saboda ƙarancin ƙima na iya nufin ɓarna ɓarna ba a gano su ba. Ana iya amfani da wuce gona da iri da gangan don zuƙowa na dijital ko haɓaka aiki.
Lokacin Daidaita Nyquist: Ƙarfafawa da Ƙarfafawa
Samfuran Nyquist yana wakiltar ma'auni mai ma'ana, amma a aikace, tsarin hoto na iya yin sama da fadi da gangan ko rashin misali dangane da aikace-aikacen.
Menene Ƙarfafawa
A cikin yanayin aikace-aikacen da hankali ya fi mahimmanci fiye da warware mafi ƙanƙantar cikakkun bayanai, yin amfani da girman pixel sarari wanda ya fi girma da buƙatun Nyquist na iya haifar da fa'idodin tarin haske. Wannan shi ake kira undersampling.
Wannan yana ba da cikakkun bayanai, amma zai iya zama fa'ida idan:
Hankali yana da mahimmanci: pixels masu girma suna tattara ƙarin haske, haɓaka sigina-zuwa amo a cikin ƙaramin haske.
● Abubuwan saurin gudu: ƙananan pixels suna rage lokacin karantawa, yana ba da damar saye da sauri.
Ana buƙatar dacewar bayanai: ƙananan girman fayil sun fi dacewa a cikin tsarin iyakataccen bandwidth.
Misali: A cikin hoton calcium ko ƙarfin lantarki, yawanci ana ƙididdige sigina akan yankuna masu sha'awa, don haka ƙima yana inganta tarin haske ba tare da lalata sakamakon kimiyya ba.
Menene Oversampling
Sabanin haka, yawancin aikace-aikacen da warware kyawawan bayanai ke da mahimmanci, ko aikace-aikacen da ke amfani da hanyoyin bincike na bayan-saye don dawo da ƙarin bayani fiye da iyaka, suna buƙatar ƙananan pixels na hoto fiye da buƙatun Nyquist, wanda ake kira oversampling.
Duk da yake wannan baya haɓaka ƙudurin gani na gaskiya, yana iya ba da fa'idodi:
● Yana ba da damar zuƙowa na dijital tare da ƙarancin ƙarancin inganci.
● Haɓaka bayan aiwatarwa (misali, yanke hukunci, ƙin yarda, babban ƙuduri).
● Yana rage laƙabi da ake iya gani lokacin da aka saukar da hotuna daga baya.
Misali: A cikin maƙalli, babban kyamarar sCMOS mai ƙarfi na iya wuce misali tsarin salon salula ta yadda algorithms na lissafi su iya fitar da cikakkun bayanai sama da iyaka.
Rashin fahimta gama gari
1. Ƙarin megapixels koyaushe yana nufin hotuna masu kaifi.
Ba gaskiya bane. Kaifi ya dogara da ikon warwarewar ruwan tabarau da ko samfurin firikwensin ya yi daidai.
2. Duk wani ruwan tabarau mai kyau yana aiki da kyau tare da kowane firikwensin babban ƙuduri.
Rashin ƙarancin wasa tsakanin ƙudurin ruwan tabarau da ƙimar pixel zai iyakance aiki.
3. Samfur Nyquist yana dacewa ne kawai a cikin sarrafa sigina, ba hoto ba.
Akasin haka, hoton dijital shine ainihin tsarin samfur, kuma Nyquist yana da dacewa anan kamar a cikin sauti ko sadarwa.
Kammalawa
Samfuran Nyquist ya fi taƙaitaccen lissafi - ƙa'idar ce ke tabbatar da ƙudurin gani da dijital aiki tare. Ta hanyar daidaita ƙarfin warwarewar ruwan tabarau tare da ikon yin samfur na na'urori masu auna firikwensin, tsarin hoto yana samun cikakken haske ba tare da kayan tarihi ko ɓarna ba.
Ga masu sana'a a fannoni daban-daban kamar na'urar hangen nesa, ilmin taurari, daukar hoto, da hangen nesa na na'ura, fahimtar samfurin Nyquist shine mabuɗin ƙira ko zabar tsarin hoto wanda ke ba da ingantaccen sakamako. Ƙarshe, ingancin hoto ba ya zuwa daga tura takamaiman bayani zuwa matsananci amma daga samun daidaito.
FAQs
Me zai faru idan samfurin Nyquist bai gamsu ba a cikin kyamara?
Lokacin da ƙimar samfurin ta faɗi ƙasa da iyakar Nyquist, firikwensin ba zai iya wakiltar cikakkun bayanai daidai ba. Wannan yana haifar da aliasing, wanda ya bayyana azaman gefuna masu jakunkuna, ƙirar moiré, ko laushin karya waɗanda ba su wanzu a ainihin fage.
Ta yaya girman pixel ke shafar samfurin Nyquist?
Ƙananan pixels suna ƙara mitar Nyquist, ma'ana firikwensin zai iya warware cikakkun bayanai dalla-dalla. Amma idan ruwan tabarau ba zai iya isar da wannan matakin ƙuduri ba, ƙarin pixels suna ƙara ƙima kaɗan kuma suna iya ƙara ƙara.
Shin samfurin Nyquist ya bambanta don monochrome vs. launi na'urori masu auna firikwensin?
Ee. A cikin firikwensin monochrome, kowane samfurin pixel yana haskakawa kai tsaye, don haka ingantaccen mitar Nyquist yayi daidai da farar pixel. A cikin firikwensin launi tare da tacewa ta Bayer, kowane tashar launi ba a ƙididdige shi ba, don haka ingantaccen ƙuduri bayan ƙaddamarwa yana ɗan ƙasa kaɗan.
Tucsen Photonics Co., Ltd. Duk haƙƙin mallaka. Lokacin ambato, da fatan za a yarda da tushen:www.tucsen.com
