Ukuqonda Ukusampula Kwe-Nyquist: Ukulinganisa I-Optical kanye Nokulungiswa Kwekhamera |

Emfanekisweni wedijithali, kulula ukucabanga ukuthi ukulungiswa okuphezulu kusho ngokuzenzakalelayo izithombe ezingcono. Abakhiqizi bekhamera bavamise ukumaketha amasistimu asekelwe ekubalweni kwama-megapixel, kuyilapho abenzi bamalensi begqamisa amandla okuxazulula nokucija. Kodwa-ke, ekusebenzeni, ikhwalithi yesithombe ayincikile kuphela ekucacisweni kwe-lens noma inzwa ngayodwana kodwa futhi nokuthi ifaniswe kahle kangakanani.

Yilapho isampula ye-Nyquist iqala khona ukudlala. Ekuqaleni isimiso esivela ekucutshungulweni kwesignali, umbandela we-Nyquist ubeka uhlaka lwethiyori lokuthwebula imininingwane ngokunembile. Emfanekisweni, iqinisekisa ukuthi ukulungiswa kokubona okulethwa ilensi kanye nokulungiswa kwedijithali kwenzwa yekhamera kusebenza ndawonye ngokuvumelana.

Le ndatshana ivula amasampula e-Nyquist kumongo wokuthwebula izithombe, ichaza ibhalansi phakathi kokulungiswa kwe-optical nekhamera, futhi inikeza imihlahlandlela esebenzayo yezinhlelo zokusebenza ezisukela ekuthwebuleni izithombe kuye ekufanekisweni kwesayensi.

Iyini i-Nyquist Sampling?

Umfanekiso 1: I-Nyquist sampling theorem

Phezulu:Isignali ye-sinusoidal (cyan) iyalinganiswa, noma isampula, ezindaweni eziningi. Ulayini onedeshi empunga ompunga umele isilinganiso esingu-1 ngomjikelezo ngamunye wesignali ye-sinusoidal, ethwebula iziqongo zesignali kuphela, efihla ngokuphelele isimo sangempela sesiginali. Ijika elibomvu elinedeshi elicolisekile lithwebula ngezilinganiso ezingu-1.1 isampula ngayinye, liveza i-sinusoid kodwa ihlanekezela ukuvama kwayo. Lokhu kufana nephethini ye-Moiré.

Phansi:Kuphela uma kuthathwa amasampula angu-2 ngomjikelezo ngamunye (umugqa wamachashazi onsomi) lapho imvelo yangempela yesiginali iqala ukuthwebula.

I-Nyquist sampling theorem iyisimiso esivamile kukho konke ukucutshungulwa kwesignali ku-electronics, ukucubungula umsindo, ukuthwebula izithombe nezinye izinkambu. Ithiyori ikwenza kucace ukuthi ukuze kwakhiwe kabusha ifrikhwensi enikeziwe kusignali, izilinganiso kufanele zenziwe okungenani kabili kuleyo frikhwensi, eboniswe kuMfanekiso 1. Endabeni yokuxazulula kwethu ukubona, lokhu kusho ukuthi usayizi wephikseli yesikhala sento yethu kufanele okungenani ube uhhafu wemininingwane emincane kakhulu esizama ukuyithwebula, noma, esimweni se-microscope, uhhafu wokulungiswa kwesibonakhulu.

Umfanekiso 2: Isampula leNyquist elinamaphikseli ayisikwele: umumo ubalulekile

Isebenzisa ikhamera enegridi yamaphikseli ayisikwele, isici sesampula esingu-2x se-Nyquist theorem izothwebula kuphela imininingwane eqondaniswe kahle negridi ye-pixel. Uma uzama ukuxazulula izakhiwo nge-engeli yegridi ye-pixel, usayizi wephikseli osebenzayo mkhulu, ufika izikhathi ezingu-√2 ezinkulu kudiagonali. Ngakho-ke isilinganiso samasampula kufanele sibe izikhathi ezingu-2√2 kunemvamisa yendawo oyifunayo ukuze uthwebule imininingwane ku-45o kugridi yephikseli.

Isizathu salokhu senziwa sobala ngokucatshangelwa koMfanekiso 2 (ingxenye ephezulu). Cabanga ukuthi usayizi wephikseli usethelwe ekulungisweni kokubona, okunikeza iziqongo zemithombo yamaphoyinti amabili angomakhelwane, noma yimiphi imininingwane esizama ukuyixazulula, ngayinye ngamaphikseli ayo. Yize lezi zibe sezitholwa ngokwehlukana, akukho okukhombisayo ezilinganisweni eziwumphumela wokuthi zingamaqongo amabili ahlukene - futhi nakulokhu incazelo yethu "yokuxazulula" ayihlangabezwanga. Iphikseli phakathi iyadingeka, ithwebula umkhombe wesiginali. Lokhu kufinyelelwa ngokuphinda kabili isilinganiso sesampula sendawo, okungukuthi ngohhafu usayizi wephikseli yesikhala sento.

I-Optical Resolution vs. Ukulungiswa Kwekhamera

Ukuze siqonde ukuthi isampula ye-Nyquist isebenza kanjani ekucabangeni, sidinga ukuhlukanisa phakathi kwezinhlobo ezimbili zokuxazulula:

● I-Optical Resolution: Inqunywa ilensi, i-optical resolution ibhekisela ekhonweni layo lokukhiqiza kabusha imininingwane emihle. Izinto ezifana nekhwalithi yelensi, indawo yokuvula, kanye nokuphazamiseka misa lo mkhawulo. Umsebenzi wokudlulisa imodulation (MTF) uvamise ukusetshenziselwa ukukala ukuthi ilensi ikudlulisa kahle kangakanani ukugqama kumafrikhwensi ahlukene wendawo.

● Ukulungiswa Kwekhamera: Kunqunywa inzwa, ukulungiswa kwekhamera kuncike kusayizi wephikseli, ukuphakama kwephikseli, kanye nobukhulu benzwa bubonke. Ukuphakama kwephikseli kwe-aIkhamera ye-CMOSichaza ngokuqondile imvamisa yayo yeNyquist, enquma imininingwane ephezulu inzwa engayithatha.

Uma lezi ezimbili zingaqondani, kuba nezinkinga. I-lens edlula amandla okuxazulula wenzwa "imosheka" ngokuphumelelayo, ngoba inzwa ayikwazi ukuthatha yonke imininingwane. Ngokuphambene, inzwa yokulungiswa okuphezulu ebhangqwe nelensi yekhwalithi ephansi iphumela ezithombeni ezingathuthuki naphezu kwama-megapixel engeziwe.

Ungabhalansi kanjani i-Optical kanye nekhamera yokuxazulula

Ukulinganisa okubonwayo nezinzwa kusho ukufanisa imvamisa yenzwa yeNyquist nefrikhwensi yokusika yokubona yelensi.

● Imvamisa ye-Nyquist yenzwa yekhamera ibalwa njengo-1 / (2 × ukuphakama kwephikseli). Lokhu kuchaza imvamisa ephakeme kakhulu yendawo inzwa engayisampula ngaphandle kokuqamba igama.
● I-optical cutoff frequency incike ezicini zelensi kanye nokuphazamiseka.

Ukuze uthole imiphumela engcono kakhulu, imvamisa yenzwa yeNyquist kufanele ihambisane noma yeqe kancane ikhono lokuxazulula ilensi. Empeleni, umthetho omuhle wesithupha uwukuqinisekisa ukuthi ukuphakama kwephikseli cishe kuyingxenye yosayizi wesici esixazululekayo selensi.

Isibonelo, uma ilensi ingakwazi ukuxazulula imininingwane kuze kufike kuma-micrometer angu-4, inzwa enosayizi wamaphikseli angu-~2 micrometer izobhalansisa kahle isistimu.

Ukufanisa i-Nyquist Nokulungiswa Kwekhamera kanye Nenselele Yamaphikseli Ayisikwele

Ukuhwebelana ngosayizi wephikseli yesikhala sento enciphayo ukwehliswa kwekhono lokuqoqa ukukhanya. Ngakho-ke kubalulekile ukulinganisa isidingo sokuxazulula kanye nokuqoqwa kokukhanya. Ukwengeza, osayizi bephikseli yesikhala esikhulu sento bavame ukudlulisa inkambu enkulu yokubuka isihloko sesithombe. Kuzinhlelo zokusebenza ezinesidingo esithile sokulungiswa okuhle, 'umthetho wesithupha' ibhalansi ephezulu kuthiwa ishaywa kanje: Usayizi wephikseli yesikhala sento, uma uphindwa ngento ethile ukuze ubalekele i-Nyquist, kufanele ulingane nokulungiswa kokubonwayo. Leli nani libizwa ngokuthi ukulungiswa kwekhamera.

Ukulinganisa okubonwayo nezinzwa kuvame ukwehlela ekuqinisekiseni ukuthi ukulungiswa kwesampula okusebenzayo kwekhamera kufana nomkhawulo wokulungiswa kokubona kwelensi. Kuthiwa uhlelo "luzofanisa iNyquist" lapho:

Ukulungiswa kwekhamera = Ukulungiswa kokubona

Lapho ukulungiswa kwekhamera kunikezwa ngu:

Isici sokulandisa nge-Nyquist esivame ukutuswa ngu-2.3, hhayi u-2. Isizathu salokhu simi kanje.

Amaphikseli ekhamera (ngokujwayelekile) ayizikwele, futhi ahlelwa kugridi engu-2-D. Usayizi wephikseli njengoba uchazwe ukuze usetshenziswe esibalweni esiphambene umelela ububanzi bamaphikseli kuma-eksisi ale gridi. Uma izici esizama ukuzixazulula zingamanga kunoma iyiphi i-engeli ngaphandle kokuphindaphinda okuphelele okungu-90° ngokuhlobene nale gridi, usayizi wephikseli osebenzayo uzoba mkhulu, ufike ku-√2 ≈ 1.41 izikhathi zosayizi wephikseli ku-45°. Lokhu kuboniswa kuMfanekiso 2 (uhhafu ongezansi).

Isici esinconyiwe ngokuya ngombandela we-Nyquist kuzo zonke izimo sizoba ngu-2√2 ≈ 2.82. Kodwa-ke, ngenxa yokuhwebelana okukhulunywe ngakho ngaphambili phakathi kwesixazululo nokuqoqwa kokukhanya, inani le-compromise engu-2.3 liyanconywa njengomthetho wesithupha.

Iqhaza Le-Nyquist Sampling Emfanekisweni

Isampula ye-Nyquist ingumgcini-sango wokuthembeka kwesithombe. Lapho izinga lamasampula liwela ngaphansi komkhawulo weNyquist:

● Ukusampula okungaphansi → kubangela ukuqanjwa: imininingwane engamanga, imiphetho emangelengele, noma amaphethini e-moiré.

● Ukwenza isampula okweqile → kuthwebula idatha eningi kunaleyo engalethwa ama-optics, okuholela ekuncipheni kwembuyiselo: amafayela amakhulu kanye nezidingo zokucubungula eziphezulu ngaphandle kokuthuthukiswa okubonakalayo.

Ukusampula okulungile kuqinisekisa ukuthi izithombe zibukhali futhi ziyiqiniso eqinisweni. Inikeza ibhalansi phakathi kokufaka okubonakalayo nokuthwebula kwedijithali, ukugwema ukulungiswa okumoshiwe ngakolunye uhlangothi noma ama-artifact adukisayo kolunye.

Izicelo Ezisebenzayo

Ukusampula kwe-Nyquist akuyona nje ithiyori - kunezinhlelo zokusebenza ezibucayi kuzo zonke iziyalo zokucabanga:

● I-Microscopy:Abacwaningi kumele bakhethe izinzwa eziyisampula okungenani kabili kwemininingwane emincane exazululeka ngelensi yomgomo. Ukukhetha okulungileikhamera ye-microscopekubalulekile, njengoba usayizi wephikseli kufanele uhambisane nesinqumo esinqunyelwe se-diffraction yenhloso yesibonakhulu. Amalabhorethri anamuhla avame ukukhethaAmakhamera we-sCMOS, okunikeza ibhalansi yokuzwela, ububanzi obuguqukayo, nezakhiwo zamaphikseli amahle zokuthwebula okuseqophelweni eliphezulu kwe-biological.

● Isithombe:Ukumatanisa izinzwa ezine-megapixel ephezulu namalensi angakwazi ukuxazulula imininingwane emihle ngokulinganayo ngokuvamile kuholela ekuthuthukisweni okungenandaba kokucija. Abathwebuli bezithombe abangochwepheshe babhalansisa amalensi namakhamera ukuze bagweme ukuchithwa kwesinqumo.

● Umbono womshini &Amakhamera EsayensiEkulawuleni ikhwalithi nokuhlolwa kwezimboni, ukushoda kwezici ezincane ngenxa yesampula encane kungase kusho ukuthi izingxenye ezinesici azibonakali. Ukwenza isampula ngokweqile kungase kusetshenziswe ngamabomu ukusondeza kwedijithali noma ukucubungula okuthuthukisiwe.

Imataniswa nini i-Nyquist: I-Oversampling kanye ne-Undersampling

Isampula ye-Nyquist imele ibhalansi efanelekile, kodwa ekusebenzeni, amasistimu wokuthwebula izithombe angase enze amasampula amaningi ngamabomu noma enze isampula encane kuye ngohlelo lokusebenza.

Yini i-Undersampling

Esimeni sezinhlelo zokusebenza lapho ukuzwela kubaluleke kakhulu kunokuxazulula imininingwane emincane kakhulu, ukusebenzisa usayizi wephikseli yesikhala sento omkhulu kunezidingo ze-Nyquist kungaholela ezinhlelweni ezinkulu zokuqoqwa kokukhanya. Lokhu kubizwa nge-undersampling.

Lokhu kudela imininingwane emihle, kodwa kungaba usizo lapho:

● Ukuzwela kubalulekile: amaphikseli amakhulu aqoqa ukukhanya okwengeziwe, athuthukisa isilinganiso sesignali-kuya-nomsindo ezithombeni zokukhanya okuphansi.
● Isivinini sibalulekile: amaphikseli ambalwa anciphisa isikhathi sokufunda, okuvumela ukutholwa okusheshayo.
● Kudingeka ukusebenza kahle kwedatha: osayizi bamafayela amancane bayathandeka kumasistimu anomkhawulokudonsa.

Isibonelo: Esithombeni se-calcium noma se-voltage, amasignali avamise ukulinganiswa ezindaweni ezithakaselwayo, ngakho ukwenza amasampula aphansi kuthuthukisa ukuqoqwa kokukhanya ngaphandle kokuphazamisa umphumela wesayensi.

Yini i-Oversampling

Ngokuphambene, izinhlelo zokusebenza eziningi okubalulekile kuzo ukuxazulula imininingwane emihle, noma izinhlelo zokusebenza ezisebenzisa izindlela zokuhlaziya ngemva kokutholwa ukuze zibuyisele ulwazi olwengeziwe ngaphezu komkhawulo wokuhlukanisa, zidinga amaphikseli ezithombe amancane kunezimfuno zeNyquist, ezibizwa ngokuthi i-oversampling.

Nakuba lokhu kungakhulisi ukulungiswa kwe-optical kweqiniso, kunganikeza izinzuzo:

● Inika amandla ukusondeza kwedijithali ngokulahleka kwekhwalithi encane.
● Ithuthukisa ukucutshungulwa kwangemuva (isb., ukususa i-deconvolution, i-denoising, i-super-resolution).
● Yehlisa isibizo esibonakalayo uma izithombe zehliswa isampula ngokuhamba kwesikhathi.

Isibonelo: Kumakroskopu, ikhamera ye-sCMOS enokulungiswa okuphezulu ingase yeqe izakhiwo zeselula ukuze ama-algorithms okubalayo akwazi ukukhipha imininingwane emihle ngaphezu komkhawulo wokuphazamiseka.

Imibono Eyiphutha Evamile

1. Ama-megapixel amaningi ahlala esho izithombe ezicijile.
Akulona iqiniso. Ubukhali buncike kukho kokubili amandla okuxazulula ilensi nokuthi ingabe inzwa isampula ngendlela efanele yini.

2, Noma iyiphi ilensi enhle isebenza kahle nganoma iyiphi inzwa yokulungiswa okuphezulu.
Ukungafani kahle phakathi kokulungiswa kwelensi nokuphakama kwephikseli kuzokhawulela ukusebenza.

3, Ukusampula kwe-Nyquist kusebenza kuphela ekucubunguleni isignali, hhayi ukuthwebula izithombe.
Ngokuphambene, ukuthwebula kwedijithali kuyinqubo yokusampula, futhi iNyquist ibalulekile lapha njengokulalelwayo noma kwezokuxhumana.

Isiphetho

Ukusampula kwe-Nyquist kungaphezu kokufinyezwa kwezibalo - kuwumgomo oqinisekisa ukusebenza ngokubambisana kwe-optical and digital resolution. Ngokuqondanisa amandla okuxazulula amalensi namandla okusampula ezinzwa, amasistimu wokuthwebula afinyelela ukucaca okuphezulu ngaphandle kwama-artifact noma umthamo omoshiwe.

Kochwepheshe emikhakheni ehlukahlukene njenge-microscopy, isayensi yezinkanyezi, ukuthwebula izithombe, nokubona komshini, ukuqonda isampula ye-Nyquist kuyisihluthulelo sokuklama noma ukukhetha amasistimu wokuthwebula aletha imiphumela ethembekile. Ekugcineni, ikhwalithi yesithombe ayiveli ekuphusheleni ukucaciswa okukodwa kuya kweqisayo kodwa ekuzuzeni ibhalansi.

Imibuzo Evame Ukubuzwa

Kwenzekani uma isampula ye-Nyquist inganeliseki kukhamera?
Uma izinga lamasampula liwela ngaphansi komkhawulo we-Nyquist, inzwa ayikwazi ukumela imininingwane emihle ngendlela efanele. Lokhu kubangela i-aliasing, ebonakala njengemiphetho emagebhugebhu, amaphethini e-moiré, noma ukuthungwa okungamanga okungekho esigcawini sangempela.

Usayizi we-pixel ukuthinta kanjani ukusampula kwe-Nyquist?
Amaphikseli amancane akhuphula imvamisa ye-Nyquist, okusho ukuthi inzwa ingaxazulula imininingwane engconywana. Kodwa uma ilensi ingakwazi ukuletha lelo zinga lesinqumo, amaphikseli engeziwe engeza inani elincane futhi angase andise umsindo.

Ingabe isampula ye-Nyquist ihlukile kuzinzwa ze-monochrome vs. color?
Yebo. Kunzwa ye-monochrome, wonke amasampula ephikseli akhanya ngokuqondile, ngakho-ke ifrikhwensi ye-Nyquist esebenzayo ifana nokuphakama kwephikseli. Kunzwa yombala enesihlungi se-Bayer, isiteshi sombala ngasinye sinesampula encane, ngakho-ke ukulungiswa okusebenzayo ngemuva kokukhishwa kwedemosayikhi kuba ngaphansi kancane.

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