25/09/11Mumakina aliwonse oyezera - kuyambira kulumikizana opanda zingwe mpaka kujambula kwa digito - chiŵerengero cha signal-to-noise (SNR) ndi chizindikiro chofunika kwambiri cha khalidwe. Kaya mukusanthula zithunzi za telescope, kukonza zojambulira maikolofoni, kapena kuthana ndi ulalo wopanda zingwe, SNR imakuuzani zambiri zothandiza zomwe zimasiyana ndi phokoso losafunikira lakumbuyo.
Koma kuwerengera SNR molondola sikumakhala kosavuta nthawi zonse. Kutengera ndi dongosolo, zinthu zina monga mdima wakuda, phokoso lowerengera, kapena binning ya pixel zingafunike kuganiziridwa. Bukuli limakupatsani malingaliro, njira zazikuluzikulu, zolakwika zomwe wamba, kugwiritsa ntchito, ndi njira zothandiza zosinthira SNR, kuwonetsetsa kuti mutha kuyigwiritsa ntchito molondola pazinthu zosiyanasiyana.
Kodi Signal-to-Noise Ratio (SNR) ndi chiyani?
Pakatikati pake, chiŵerengero cha chizindikiro-ku-phokoso chimayesa mgwirizano pakati pa mphamvu ya chizindikiro chomwe chimafunidwa ndi phokoso lakumbuyo lomwe limabisa.
● Chidziwitso = chidziwitso chatanthauzo (monga mawu akuyitana, nyenyezi yomwe ili pachithunzi cha telescope).
● Phokoso = kusinthasintha kwachisawawa, kosafunikira komwe kumasokoneza kapena kubisa chizindikiro (monga static, phokoso la sensa, kusokoneza magetsi).
Mwamasamu, SNR imatanthauzidwa kuti:
Chifukwa ziwerengerozi zimatha kusiyanasiyana pamadongosolo ambiri a ukulu, SNR nthawi zambiri imawonetsedwa mu ma decibel (dB):
● High SNR (mwachitsanzo, 40 dB): chizindikiro chimalamulira, zomwe zimapangitsa kuti mudziwe bwino komanso odalirika.
● Kutsika kwa SNR (mwachitsanzo, 5 dB): Phokoso limagonjetsa chizindikiro, zomwe zimapangitsa kutanthauzira kukhala kovuta.
Momwe mungawerengere SNR
Kuwerengera kwa chiŵerengero cha chizindikiro-ku-phokoso kungathe kuchitidwa ndi magawo osiyanasiyana olondola malinga ndi zomwe magwero a phokoso akuphatikizidwa. M'chigawo chino, mitundu iwiri idzafotokozedwa: imodzi yomwe imawerengera mdima wakuda ndi yomwe ikuganiza kuti ikhoza kunyalanyazidwa.
Zindikirani: Kuwonjezera phokoso lodziyimira pawokha kumafuna kuwawonjezera mu quadrature. Chilichonse chaphokoso chimakhala ndi masikweya, kufupikitsidwa, ndipo chiwongolero cha chiwonkhetso chimatengedwa.
Chiyerekezo cha Signal-to-noise chokhala ndi mphamvu yakuda
Zotsatirazi ndizomwe zimagwiritsidwa ntchito pakakhala phokoso lakuda ndi lalikulu mokwanira kuti liphatikizidwe:
Nayi tanthauzo la mawu:
Chizindikiro (e-): Ichi ndi chizindikiro cha chidwi ndi ma photoelectrons, ndi chizindikiro chamdima chomwe chachotsedwa
Chidziwitso chonse (e-) chidzakhala chiwerengero cha photoelectron mu pixel ya chidwi - osati mtengo wa pixel mu magawo a imvi. Chitsanzo chachiwiri cha Signal (e-), pansi pa equation, ndi phokoso la photonshot.
Mdima wakuda (DC):Mtengo wakuda wa pixel umenewo.
t: Nthawi yowonetsera mumasekondi
sr:Werengani phokoso pamawonekedwe a kamera.
Chiyerekezo cha Signal-to-noise cha mdima wakuda wosasamala
Pafupipafupi (<1 sekondi imodzi) nthawi zowonekera, kuphatikiza zoziziritsa, makamera ochita bwino kwambiri, phokoso lakuda lakuda nthawi zambiri limakhala phokoso lochepera lowerengedwa, ndikunyalanyazidwa bwino.
Kumene mawu alinso monga tafotokozera pamwambapa, kupatula kuti chizindikiro chakuda chakuda sichiyenera kuwerengedwa ndikuchotsedwa pa siginecha chifukwa chiyenera kufanana ndi ziro.
Zochepa za mafomuwa ndi mawu osowa
Njira zotsutsana ndi izi zidzangopereka mayankho olondola kwa CCD ndiMakamera a CMOS. EMCCD ndi zida zokulirapo zimabweretsa magwero owonjezera a phokoso, kotero ma equation awa sangathe kugwiritsidwa ntchito. Kuti mupeze chiŵerengero chokwanira cha ma signal-to-noise omwe amawerengera izi ndi zina.
Liwu lina laphokoso lomwe (kapena lomwe kale linali) lomwe limaphatikizidwanso mu SNR equations ndi lija la photo-response non-uniformity (PRNU), lomwenso nthawi zina limatchedwa 'fixed pattern noise' (FPN). Izi zikuyimira kusagwirizana kwa kupindula ndi kuyankha kwa ma siginecha kudutsa sensa, yomwe imatha kukhala yayikulu pazikwangwani zazikulu ngati zazikulu zokwanira, kuchepetsa SNR.
Ngakhale makamera oyambirira anali ndi PRNU yokwanira yofunikira kuti ikhalepo, yamakonomakamera asayansiali ndi PRNU yotsika mokwanira kuti apereke chithandizo chake pansi pa phokoso la photon, makamaka pambuyo pa kukonza pa bolodi. Chifukwa chake, nthawi zambiri imasiyidwa pakuwerengera kwa SNR. Komabe, PRNU ndiyofunikirabe pamakamera ndi mapulogalamu ena, ndipo ikuphatikizidwa mu equation yapamwamba kwambiri ya SNR kuti ikwaniritse. Izi zikutanthauza kuti ma equation omwe aperekedwa ndi othandiza pamakina ambiri a CCD/CMOS koma sayenera kuwonedwa ngati akuyenera kugwiritsidwa ntchito konsekonse.
Mitundu ya Phokoso mu Mawerengedwe a SNR
Kuwerengera SNR sikungoyerekeza kuyerekeza siginecha ndi mtengo umodzi waphokoso. M'malo mwake, magwero angapo odziyimira pawokha amathandizira, ndipo kuwamvetsetsa ndikofunikira.
Kuwombera Phokoso
● Chiyambi: chiwerengero cha kufika kwa ma photon kapena ma electron.
● Masikelo okhala ndi sikweya mizu ya chizindikiro.
● Kaŵirikaŵiri amajambula zithunzi za photon (astronomy, fluorescence microscopy).
Kutentha Phokoso
● Amatchedwanso kuti Johnson–Nyquist phokoso, lopangidwa ndi ma elekitironi akuyenda mu zopinga.
● Kuwonjezeka ndi kutentha ndi bandwidth.
● Zofunika pamagetsi ndi mauthenga opanda zingwe.
Phokoso Lakuda Kwambiri
● Kusintha kwachisawawa mumdima wakuda mkati mwa masensa.
● Chofunikira kwambiri pakuwonekera kwa nthawi yayitali kapena zodziwira kutentha.
● Kuchepetsedwa ndi kuziziritsa sensa.
Werengani Phokoso
● Phokoso lochokera ku amplifiers ndi kutembenuka kwa analogi kupita ku digito.
● Kukhazikika pakuwerengera, kofunikira kwambiri pamadongosolo otsika.
Quantization Noise
● Kudziwitsidwa ndi digito (kuzungulira kumagulu osiyanasiyana).
● Zofunikira pamakina ozama pang'ono (monga ma audio a 8-bit).
Phokoso Lachilengedwe/Kachitidwe
● EMI, crosstalk, magetsi akuchulukirachulukira.
● Ikhoza kulamulira ngati kutchinga/kutsetsereka sikuli bwino.
Kumvetsetsa kuti ndi iti mwa izi yomwe ili yayikulu kumathandizira posankha njira yoyenera komanso njira yochepetsera.
Zolakwitsa zofala pakuwerengera SNR
Ndikosavuta kukumana ndi njira zambiri za 'chidule' kuti muyerekeze chiŵerengero cha siginecha ndi phokoso pazithunzi. Izi zimakonda kukhala zocheperako poyerekeza ndi ma equations omwe amatsutsana nawo, amalola kuti atengeke mosavuta pa chithunzi chokhacho m'malo mofuna chidziwitso cha magawo a kamera monga phokoso lowerengera, kapena zonse ziwiri. Tsoka ilo, zikutheka kuti imodzi mwa njirazi ndi yolakwika, ndipo izi zidzabweretsa zotsatira zopotoka komanso zosathandiza. Zimalangizidwa kwambiri kuti ma equations otsutsana (kapena mtundu wapamwamba uyenera kugwiritsidwa ntchito nthawi zonse.
Zina mwa njira zazifupi zabodza ndizo:
1, Kuyerekeza kulimba kwa siginecha vs kulimba kwam'mbuyo, mumilingo yotuwa. Njirayi imayesa kuweruza kukhudzika kwa kamera, mphamvu ya ma siginecha kapena chiŵerengero cha chiŵerengero cha phokoso poyerekezera kuchulukira kwambiri ndi kulimba kwakumbuyo. Njirayi ndi yolakwika kwambiri chifukwa mphamvu ya kamera yochotsamo imatha kuyika kumbuyo kukulirakulira, kupindula kumatha kuyika mphamvu yazizindikiro, ndipo palibe phokoso lililonse pazizindikiro kapena kumbuyo komwe kumaganiziridwa.
2, Kugawa nsonga za siginecha ndi kupatuka kokhazikika kwa malo a pixel yakumbuyo. Kapena, kuyerekeza nsonga zapamwamba ndi phokoso lowoneka chakumbuyo lomwe limawululidwa ndi mbiri ya mzere. Pongoganiza kuti kuchotserako kumachotsedwa molondola pazikhalidwe musanayambe kugawanika, choopsa kwambiri panjirayi ndi kukhalapo kwa kuwala kwambuyo. Kuwala kulikonse kwakumbuyo kumalamulira phokoso la ma pixel akumbuyo. Komanso, phokoso la chizindikiro cha chidwi, monga phokoso lowombera, silimaganiziridwa nkomwe.
3, Chidziwitso chodziwika mu ma pixel achidwi vs kupotoza koyenera kwa ma pixel: Kuyerekeza kapena kuwona kuchuluka kwa chizindikiro chapamwamba kumasinthira ma pixel oyandikana nawo kapena mafelemu otsatizana ali pafupi kukhala olondola kuposa njira zina zachidule, koma sizingatheke kupewa zisonkhezero zina zosokoneza, monga kusintha kwa siginecha komwe sikumachokera kuphokoso. Njirayi ingakhalenso yolakwika chifukwa cha chiwerengero chochepa cha pixel poyerekezera. Kuchotsa kwa mtengo wamtengo wapatali sikuyeneranso kuyiwalika.
4, Kuwerengera SNR popanda kutembenukira ku mayunitsi amphamvu a ma photoelectrons, kapena osachotsa chotsitsa: Monga phokoso la photon nthawi zambiri limakhala gwero lalikulu kwambiri laphokoso ndipo zimadalira kudziwa momwe kamera yasinthira ndikupeza muyeso, sizingatheke kupeŵa kuwerengera kubwerera ku ma photoelectrons powerengera SNR.
5, Kuweruza SNR ndi diso: Ngakhale nthawi zina kuweruza kapena kuyerekeza SNR ndi diso kungakhale kothandiza, palinso misampha yosayembekezereka. Kuweruza SNR mu pixel zamtengo wapatali kungakhale kovuta kuposa mtengo wotsika kapena ma pixel akumbuyo. Zotsatira zowoneka bwino zimathanso kuchitapo kanthu: Mwachitsanzo, zowunikira zamakompyuta zosiyanasiyana zimatha kupanga zithunzi zosiyana kwambiri. Kupitilira apo, kuwonetsa zithunzi pamawonekedwe osiyanasiyana mu pulogalamu kumatha kukhudza kwambiri mawonekedwe a phokoso. Izi zimakhala zovuta kwambiri ngati mukuyesera kufananiza makamera okhala ndi ma pixel osiyanasiyana a danga. Pomaliza, kukhalapo kwa kuwala chakumbuyo kumatha kulepheretsa kuyesa kulikonse kuweruza SNR mowoneka.
Mapulogalamu a SNR
SNR ndi metric wapadziko lonse lapansi wokhala ndi ntchito zosiyanasiyana:
● Kujambulira Nyimbo ndi Nyimbo: Zimatsimikizira kumveka bwino, kusinthasintha, ndi kukhulupirika kwa zojambulira.
● Kulankhulana Opanda Mawaya: SNR imagwirizana mwachindunji ndi mitengo ya zolakwika pang'ono (BER) ndi kutulutsa kwa data.
● Kujambula kwa Sayansi: Pa zakuthambo, kudziwa nyenyezi zosaoneka bwino poyang'ana kuwala kwa mlengalenga kumafuna SNR yokwera kwambiri.
● Zida Zachipatala: ECG, MRI, ndi CT scans zimadalira SNR yapamwamba kuti isiyanitse zizindikiro ndi phokoso la thupi.
● Makamera & Kujambula: Makamera ogula ndi masensa a sayansi a CMOS onse amagwiritsa ntchito SNR kuti awonetsere momwe amagwirira ntchito pakuwala kochepa.
Kupititsa patsogolo SNR
Popeza SNR ndi gawo lofunikira kwambiri, kuyesetsa kwakukulu kumapita kuwongolera. Njira zikuphatikizapo:
Njira za Hardware
● Gwiritsani ntchito masensa abwino okhala ndi mdima wocheperako.
● Gwiritsani ntchito kutchinga ndi kuyika pansi kuti muchepetse EMI.
● Zodziwira zoziziritsa kukhosi zotsekereza phokoso la kutentha.
Mapulogalamu a Mapulogalamu
● Ikani zosefera za digito kuti muchotse ma frequency osafunika.
● Gwiritsani ntchito mafelemu angapo.
● Gwiritsani ntchito njira zochepetsera phokoso pojambula kapena kukonza mawu.
Pixel Binning ndi Zotsatira Zake pa SNR
Zotsatira za binning pa chiŵerengero cha signal-to-phokoso zimatengera luso la kamera ndi khalidwe la sensa, monga momwe phokoso la makamera omangidwa ndi osakanizidwa amatha kusiyana kwambiri.
Makamera a CCD amatha kuwerengera ma pixel oyandikana ndi 'on-chip'. Phokoso lowerengera limangochitika nthawi imodzi, ngakhale chizindikiro chakuda chapa pixel iliyonse chidzafotokozedwanso mwachidule.
Makamera ambiri a CMOS amachita zinthu zopanda chip binning, kutanthauza kuti mikhalidwe imayesedwa koyamba (ndikuwerenga phokoso), kenako kufotokozedwa mwachidule. Phokoso lowerengedwa la zophatikiza zotere limawonjezeka ngakhale kuchulukitsidwa ndi muzu wa sikweya wa kuchuluka kwa ma pixel ofotokozedwa mwachidule, mwachitsanzo ndi gawo la 2 pa 2x2 binning.
Popeza khalidwe laphokoso la masensa likhoza kukhala lovuta, chifukwa cha kuchuluka kwa ntchito ndi bwino kuyeza kuchepetsa, kupindula, ndi kuwerenga phokoso la kamera mumayendedwe otsekedwa, ndikugwiritsa ntchito mfundozi pa chiwerengero cha signal-to-noise ratio.
Mapeto
Chiyerekezo cha signal-to-noise (SNR) ndi chimodzi mwazinthu zofunika kwambiri pa sayansi, uinjiniya, ndi ukadaulo. Kuchokera pakutanthauzira momveka bwino pamayimbidwe amafoni mpaka kupangitsa kuzindikira kwa milalang'amba yakutali, SNR imathandizira mtundu wa zoyezera ndi njira zoyankhulirana. Kudziwa SNR sikungokhudza kuloweza mafomula - kumakhudza kumvetsetsa zongoganiza, zolepheretsa, komanso kusinthanitsa kwenikweni. Kuchokera pamalingaliro awa, mainjiniya ndi ochita kafukufuku amatha kupanga miyeso yodalirika kwambiri ndi machitidwe opangira omwe amatulutsa zidziwitso zomveka ngakhale pamakhala phokoso.
Mukufuna kudziwa zambiri? Yang'anani zolemba zogwirizana:
Tucsen Photonics Co., Ltd. Ufulu wonse ndi wotetezedwa. Potchulapo, chonde vomerezani gwero:www.tucsen.com
