25/09/11Mune chero chiyero chekuyera - kubva kune isina waya kutaurirana kuenda kudhijitari mafoto - iyo chiratidzo-kune-ruzha reshiyo (SNR) ndiyo yakakosha bhenji yemhando. Kunyangwe iwe uri kuongorora mifananidzo yeteresikopu, kuvandudza maikorofoni kurekodha, kana kugadzirisa isina waya chinongedzo, SNR inokuudza kuti yakawanda sei ruzivo rwakakosha rwakasiyana neruzha rusingadiwe rwekumashure.
Asi kuverenga SNR nenzira kwayo hakusi nyore nguva dzose. Zvichienderana nehurongwa, zvimwe zvinhu zvakaita serima razvino, verenga ruzha, kana pixel binning zvingada kutariswa. Gwaro iri rinokufambisa kuburikidza nedzidziso, mafomula akakosha, zvikanganiso zvakajairika, maapplication, uye nzira dzinoshanda dzekuvandudza SNR, kuve nechokwadi chekuti unogona kuishandisa nenzira kwayo mumhando dzakasiyana siyana.
Chii chinonzi Signal-to-Noise Ratio (SNR)?
Papakati payo, chiratidzo-ku-ruzha reshiyo inoyera hukama pakati pesimba rechiratidzo chaunoda uye ruzha rwekumashure rwunoivharidzira.
● Chiratidzo = mashoko ane revo (somuenzaniso, izwi mukuridza runhare, nyeredzi iri pamufananidzo weteresikopu).
● Ruzha = kusarongeka, kushanduka kusingadiwi kunokanganisa kana kuvanza chiratidzo (semuenzaniso, static, ruzha rwe sensor, kupindira kwemagetsi).
Masvomhu, SNR inotsanangurwa se:
Nekuti aya mareshiyo anogona kusiyana pane akawanda maodha ehukuru, SNR inowanzo ratidzwa mumadecibel (dB):
● High SNR (semuenzaniso, 40 dB): chiratidzo chinotonga, chinokonzera ruzivo rwakajeka uye rwakavimbika.
● Low SNR (semuenzaniso, 5 dB): ruzha runokurira chiratidzo, zvichiita kuti kududzira kuome.
Maitiro ekuverenga SNR
Kuverengera kwechiratidzo-kune-ruzha reshiyo inogona kuitwa neakasiyana mazinga ehutsanana zvichienderana nekuti ndeapi masosi eruzha anosanganisirwa. Muchikamu chino, mafomu maviri achaunzwa: imwe inoverengera rima razvino uye imwe inofunga kuti inogona kuregeredzwa.
Ongorora: Kuwedzera yakazvimiririra ruzha kukosha kunoda kuwedzera iwo muquadrature. Imwe neimwe bviro yeruzha inopetwa, inopfupikiswa, uye sikweya midzi yehuwandu inotorwa.
Signal-to-noise reshiyo ine yakasviba current
Inotevera ndiyo equation yekushandisa mumamiriro ezvinhu apo ruzha rwemazuva ano rwakakura zvekuti zvinoda kubatanidzwa:
Heino tsanangudzo yematemu:
Chiratidzo (e-): Ichi ndicho chiratidzo chekufarira maphotoelectrons, nerima razvino chiratidzo chakabviswa
Iyo Yese siginecha (e-) ichave iyo photoelectron count mupixel yekufarira - chaizvo kwete kukosha kwepixel mumayuniti egrey mazinga. Chiitiko chechipiri cheChiratidzo (e-), pazasi peiyo equation, ruzha rwephotonshot.
Rima ikozvino (DC):Iko kwakasviba kukosha kweiyo pixel.
t: Nguva yekuratidzwa mumasekonzi
sr:Verenga ruzha mumodhi yekamera.
Signal-to-noise reshiyo yeinoregeredza yakasviba yazvino
Muzviitiko zvenguva pfupi (< 1 sekondi) nguva dzekuratidzwa, pamwe akatonhodzwa, makamera ekushanda-pamusoro, ruzha rwemazuva ano rwakasvibira runowanzo kuve pasi pekuverenga ruzha, uye kuregeredzwa zvakachengeteka.
Iko mazwi zvakare zvakare sekutsanangurwa pamusoro, kunze kwekuti chiratidzo cherima chazvino hachifanirwe kuverengerwa uye kubviswa kubva pachiratidzo sezvo chinofanirwa kuenzana zero.
Kuganhurirwa kwemafomula aya uye mazwi anoshaikwa
Mafomura akatarisana anongopa mhinduro dzechokwadi dzeCCD uyeCMOS kamera. EMCCD nemidziyo yakawedzera kuunza mamwe masosi eruzha, saka aya equation haagone kushandiswa. Kuti uwane imwe yakakwana yechiratidzo-kune-ruzha reshiyo equation iyo inomiririra izvi nezvimwe zvinopihwa.
Rimwe izwi reruzha iro (kana raimbove) rinowanzo kuverengerwa muSNR equations ndereiyo pikicha-mhinduro isiri-uniformity (PRNU), zvakare dzimwe nguva inodaidzwa kuti 'fixed pattern noise' (FPN). Izvi zvinomiririra kusaenzana kwekuwana uye kwekupindura kwechiratidzo mukati me sensor, iyo inogona kuve inotonga pamasaini akakwira kana yakakura zvakakwana, ichideredza SNR.
Nepo makamera ekutanga aive nePRNU yakakosha yekuda kuisirwa, yazvinomakamera esainzivane zvakaderera zvakaringana PRNU kuti iite mupiro wayo zvakanaka pazasi peiyo yephoton kupfura ruzha, kunyanya mushure mekugadziriswa kwebhodhi kwaiswa. Ikozvino, saka, inowanzoregeredzwa muSNR kuverenga. Nekudaro, PRNU ichiri yakakosha kune mamwe makamera uye maapplication, uye inosanganisirwa mune yakanyanya kumberi SNR equation yekuzara. Izvi zvinoreva kuti maequation akapihwa anoshanda kune mazhinji maCCD/CMOS masisitimu asi haafanire kubatwa seanoshanda pasi rese.
Mhando dzeRuzha muSNR Maverengero
Kuverengera SNR hakusi kungoita kuenzanisa siginecha inopesana nehumwe ruzha kukosha. Mukuita, akawanda akazvimiririra ruzha masosi anopa, uye kunzwisisa iwo kwakakosha.
Shot Noise
● Mabviro: nhamba yekusvika kwemafotoni kana maerekitironi.
● Zviyero zvine square root yechiratidzo.
● Inonyanya kukoshesa photon-limited imaging (astronomy, fluorescence microscopy).
Thermal Noise
● Inonziwo Johnson–Nyquist noise, inogadzirwa nemagetsi ekufamba muzvinodzivirira.
● Inowedzera tembiricha uye bandwidth.
● Zvakakosha mumagetsi uye kutaurirana kusina wireless.
Rima Current Noise
● Random variation mune yakasviba ikozvino mukati me sensors.
● Zvinonyanya kukosha mukuratidzwa kwenguva refu kana ma detectors anodziya.
● Yakaderedzwa nekutonhodza sensor.
Verenga Noise
● Ruzha kubva kune amplifiers uye analog-to-digital kutendeuka.
● Yakagadziriswa pakuverenga, saka yakakosha mune yakaderera-chiratidzo hurumende.
Quantization Noise
● Inounzwa nedigitization (kutenderera kune discrete mazinga).
● Yakakosha mune yakaderera-bit-yakadzika masisitimu (eg, 8-bit audio).
Environmental / System Noise
● EMI, crosstalk, simba rekupa ripple.
● Inogona kutonga kana kudzivirira/kuisa pasi kusina kunaka.
Kunzwisisa kuti ndeipi yeiyi inotungamira kunobatsira pakusarudza fomura chaiyo uye nzira yekudzikisa.
Kukanganisa kwakajairika pakuverenga SNR
Zviri nyore kuwana nzira dzakawanda dze "shortcut" yekufungidzira chiyero-kune-ruzha reshiyo mukufungidzira. Izvi zvinowanzoita kunge zvisinganyanyi kuomesesa pane equation yakatarisana, bvumidza nyore kutorwa kubva pamufananidzo pachayo pane kuda ruzivo rwemamera ekhamera senge ruzha rwekuverenga, kana zvese zviri zviviri. Zvinosuruvarisa, zvingangoita kuti imwe neimwe yeiyi nzira haina kururama, uye inozotungamirira kumigumisiro yakatsvedza uye isingabatsiri. Zvinokurudzirwa kuti maequations akatarisana (kana iyo yepamusoro vhezheni inofanira kushandiswa mune ese kesi.
Mamwe mapfupi enhema anowanzo sanganisira:
1, Kuenzanisa kusimba kwechiratidzo vs kusimba kwemashure, mumatanho egrey. Iyi nzira inoedza kutonga kunzwisiswa kwekamera, simba rechiratidzo kana chiratidzo kune ruzha reshiyo nekuenzanisa kusimba kwepamusoro kune kusimba kwemashure. Iyi nzira yakashata zvakanyanya sezvo pesvedzero yekamera yekubvisa inogona kuseta kusimba kwemashure, kuwana kunogona kuseta kusimba kwechiratidzo, uye hapana mupiro weruzha kungave muchiratidzo kana kumashure kunotariswa.
2, Kugovanisa mapikisi echiratidzo neyakajairwa kutsauka kwenzvimbo yemapikisi ekumashure. Kana, kuenzanisa mapeak values kune ruzha rwekuona kumashure kwakaratidzwa nemutsara profile. Tichifunga kuti iyo yekubvisa yakanyatso kubviswa kubva kuhunhu kusati kwapatsanurwa, njodzi inonyanya kukosha mune iyi nzira kuvepo kwechiedza chemashure. Chero mwenje wekumashure unozogara uchitonga ruzha mumapikseli ekumashure. Kupfuurirazve, ruzha rwuri muchiratidzo chekufarira, seruzha rwepfuti, haritariswe zvachose.
3, Zvinoreva siginecha mumapikisi ekufarira vs kutsauka kwakajairwa kwepixel kukosha: Kuenzanisa kana kucherechedza kuti ingani chiratidzo chepamusoro chinoshanduka pamapikiseli evavakidzani kana mafuremu anotevedzana ari pedyo nekuve akarurama pane dzimwe nzira dzekudimbudzira, asi hazvibviri kudzivirira zvimwe zvinokanganisa hunhu, sekuchinja kwechiratidzo chisingabvi paruzha. Iyi nzira inogona zvakare kuve isina kururama nekuda kwekuderera kwepixel kuverenga mukuenzanisa. Kubvisa kukosha kweoffset hakufanirwe kukanganikwa.
4, Kuverenga SNR pasina kuchinjika kusimba mayuniti emafotoelectrons, kana pasina kubvisa chinobvisa: Sezvo photon kupfura ruzha kunowanzoita ruzha rukuru uye rinotsamira paruzivo rwekugadziriswa kwekamera uye kuwana kuyerwa, hazvigoneke kudzivirira kuverenga kudzokera kumaphotoelectrons ekuverenga kweSNR.
5, Kutonga SNR neziso: Nepo mune mamwe mamiriro ekutonga kana kuenzanisa SNR neziso kunogona kubatsira, kune zvakare njodzi isingatarisirwe. Kutonga SNR muhukuru hwepixels kunogona kuoma kupfuura mumutengo wakaderera kana mapikisi ekumashure. Zvimwe zvinyengeri zvinogona kuitawo basa: Semuenzaniso, mamonitor akasiyana emakombuta anogona kupa mifananidzo ine musiyano wakasiyana. Kupfuurirazve, kuratidza mifananidzo pamatanho akasiyana e-zoom musoftware kunogona kukanganisa zvakanyanya kutaridzika kweruzha. Izvi zvinonyanya kunetsa kana uchiedza kuenzanisa makamera ane akasiyana chinhu nzvimbo pixel saizi. Pakupedzisira, kuvapo kwechiedza chekumashure kunogona kubvisa chero kuedza kutonga SNR nemaziso.
Zvishandiso zveSNR
SNR ndiyo metric yepasirese ine maapplication akasiyana-siyana:
● Kurekodha kweAudio & Mimhanzi: Inosarudza kujeka, dhizaini ine simba, uye kuvimbika kwezvakarekodhwa.
● Wireless Kukurukurirana: SNR inoenderana zvakananga nebit kukanganisa mitengo (BER) uye data throughput.
● Scientific Imaging: Mukuongorora nyeredzi, kuona nyeredzi dzisina simba dzichitarisana nekupenya kwedenga kunoda SNR yakakwirira.
● Mishonga Yezvokurapa: ECG, MRI, uye CT scans inovimba nepamusoro SNR kusiyanisa zviratidzo kubva kune ruzha rwemuviri.
● Makamera & Kutora Mapikicha: Makamera evatengi uye sainzi CMOS sensors zvese zvinoshandisa SNR kuenzanisa kuita muchiedza chakaderera.
Kuvandudza SNR
Sezvo SNR iri chiyero chakakosha, kuedza kwakakosha kunoenda mukuivandudza. Strategies inosanganisira:
Hardware Maitiro
● Shandisa masensa ari nani ane yakaderera rima ikozvino.
● Shandisa kudzivirira uye kuisa pasi kuderedza EMI.
● Ma detectors anotonhorera kudzvinyirira ruzha rwekupisa.
Software Approaches
● Isa mafirita edhijitari kubvisa ma frequency asingadiwi.
● Shandisa avhareji mumafuremu akawanda.
● Shandisa maalgorithms ekuderedza ruzha mukufungidzira kana kuti audio processing.
Pixel Binning uye Mhedzisiro Yayo paSNR
Mhedzisiro yekusunga pachiyero-kune-ruzha reshiyo zvinoenderana nekamera tekinoroji uye hunhu hwe sensor, sezvo ruzha rwekuita kwemakamera akasungwa uye asina kusungwa anogona kusiyana zvakanyanya.
Makamera eCCD anogona kuunganidza mapixels ari padyo 'kuchaja 'on-chip'. Ruzha rwekuverenga rwunongoitika kamwe chete, kunyangwe iyo yakasviba yazvino chiratidzo kubva kune yega pixel ichapfupikiswa.
Mazhinji makamera eCMOS anoita off-chip binning, zvichireva kuti hunhu hunotanga kuyerwa (uye kuverenga ruzha rwunounzwa), uye ndokupfupikiswa nedigital. Ruzha rwekuverenga rwemapfupiso akadaro runowedzera kunyangwe kuwanda nemudzi wenhamba yenhamba yemapikisi akapfupikiswa, kureva nechikamu che2 che2x2 binning.
Sezvo hunhu hweruzha hwemasensa hunogona kuomesesa, pahuwandu hwekushandisa zvinokurudzirwa kuyera kudzika, kuwana, uye kuverenga ruzha rwekamera mune yakavharwa modhi, uye shandisa izvi zvakakosha zvechiratidzo-ku-ruzha reshiyo equation.
Mhedziso
Chiratidzo-ku-ruzha chiyero (SNR) ndeimwe yeakakosha metrics musainzi, engineering, uye tekinoroji. Kubva pakutsanangura kujeka mukufona kusvika pakugonesa kuonekwa kwemapoka enyeredzi ari kure, SNR inosimbisa kunaka kwekuyera uye masisitimu ekutaurirana. Mastering SNR haisi yekungobata nemusoro mafomula - ndeye kunzwisisa fungidziro, zvipimo, uye chaiyo-yepasirese kutengeserana. Kubva pamaonero aya, mainjiniya nevaongorori vanogona kuita zviyero zvakavimbika uye masisitimu edhizaini anoburitsa nzwisiso ine musoro kunyangwe mumamiriro ane ruzha.
Unoda kudzidza zvakawanda? Tarisa uone zvinyorwa zvinoenderana:
Tucsen Photonics Co., Ltd. Kodzero dzese dzakachengetwa. Paunenge uchitaura, ndapota bvuma kwakabva:www.tucsen.com
