Un array de cámaras de bajo costo con filtros apropiados permite obtener imágenes de gran utilidad para el monitoreo de la salud vegetal

Tenemos cuatro cámaras de tecnología CMOS mas el sensor termogŕafico

La cámara destinada a la luz visible es sensible en un rango total que va de los 400nm a los 950nm , pero está limitada mediante un filtro pasabajo aproximadamete en los 700nm que es el "red edge" más allá del cual empieza el infrarrojo cercano (NIR) ,

Los canales de luz visible entregan información separada para azul , verde y rojo

En la siguiente tabla se puede apreciar la sensibilidad relativa de cada canal de luz visible para cada longitud de onda. Estos valores son importantes en los cálculos que hacemos la detección por colorimetría.

Longitud de Onda nm rojo verde azul
400 15.6983958576 5.5268306226 56.7565026087
401 15.6983958576 5.5268306226 56.7565026087
402 15.6983958576 5.5268306226 57.2223744018
403 15.0778849797 5.4335218278 58.0412273158
404 14.4658045755 5.3507022713 59.4537348112
405 13.8663108302 5.2789059097 61.643218696
406 13.2613942399 5.2172255938 63.6830066682
407 12.6429040509 5.1614431001 65.0903736773
408 12.0433185426 5.115421375 65.9402109164
409 11.4944428957 5.0839440176 66.7868733437
410 11.0063935622 5.0762068636 67.6230987884
411 10.5667272903 5.095190781 68.3757296083
412 10.1619688104 5.1219342601 69.0188289327
413 9.7845106332 5.136744063 69.5096820685
414 9.4429050079 5.1288685654 69.9064470871
415 9.1256294173 5.1092927777 70.2918050176
416 8.8190354462 5.0889259135 70.7251448388
417 8.5164745726 5.0785250634 71.1415759121
418 8.2256108884 5.0749418059 71.5840937366
419 7.9460314418 5.0762628327 72.1188374318
420 7.676981388 5.0887070609 72.7893081127
421 7.4169633796 5.1184207556 73.5572714635
422 7.1667263616 5.1670828479 74.3747183432
423 6.929048121 5.2295506192 75.2182578822
424 6.706686692 5.3001233952 76.1060594224
425 6.4994497022 5.3742812402 76.9945846413
426 6.3018987762 5.4556993241 77.7928747612
427 6.1083234849 5.5432325639 78.5408777632
428 5.9178550587 5.6342897441 79.4172640241
429 5.7347013861 5.7248170927 80.6023701709
430 5.5632715082 5.8128162038 82.0482807892
431 5.407974466 5.9079095683 83.3101336881
432 5.2732193008 6.0204620484 84.4538723393
433 5.1670155499 6.1598172816 85.6561827637
434 5.0885212781 6.3215154133 86.8868323855
435 5.0202166157 6.4926787953 88.0907500721
436 4.9442795213 6.6603513499 89.2742177307
437 4.8565039408 6.8320425699 90.3504427101
438 4.7647662953 7.0098018906 91.313271987
439 4.6690668215 7.1718635874 92.1628816029
440 4.5693678053 7.2965272688 92.8788287942
441 4.4645230262 7.3744822319 93.4520466151
442 4.3555066911 7.4226595511 93.9151755631
443 4.2443917723 7.4612707077 94.3046733137
444 4.132594899 7.5079886025 94.6006834904
445 4.0158353638 7.5502874125 94.8036826536
446 3.8982703611 7.591477087 94.9663396578
447 3.7866370512 7.6429589742 95.1393684288
448 3.6868652894 7.7141453245 95.3110038991
449 3.5973222973 7.8005105984 95.4684562618
450 3.5141208655 7.8988949239 95.6179444342
451 3.4336332923 8.0072253287 95.7657437612
452 3.3525230216 8.1198714451 95.9138472533
453 3.2717595053 8.2337605872 96.0549573488
454 3.1954271499 8.3647053389 96.1807821582
455 3.1276719004 8.5294067777 96.2859087342
456 3.0689127452 8.7231332042 96.3763510199
457 3.0169250644 8.937049434 96.4488661704
458 2.9747558462 9.2002665616 96.4987899979
459 2.9455082435 9.5422672253 96.5234930311
460 2.9297294922 9.9753694902 96.5255802246
461 2.9259466099 10.4847332824 96.5052170573
462 2.9336413535 11.0562262122 96.4624035292
463 2.9525272191 11.6805000848 96.3899611012
464 2.9861708285 12.3793020021 96.289295697
465 3.0312595263 13.131584024 96.1774606704
466 3.0815743951 13.9066823039 96.0712559645
467 3.1314032336 14.7010614014 95.9594621814
468 3.1818157757 15.5202510941 95.8435499765
469 3.2358985044 16.3635980685 95.7447673171
470 3.2962426351 17.2262909584 95.6850578907
471 3.3658487067 18.1229332011 95.6807747606
472 3.4455158588 19.0708927719 95.7023252764
473 3.5299623595 20.0566903109 95.7108412053
474 3.6134875346 21.0533758956 95.6866957189
475 3.6964417777 22.0583407595 95.6984715898
476 3.7838850482 23.0002647915 95.6662842176
477 3.8649953353 23.8899924098 95.4818197513
478 3.9283712909 24.7183810854 95.0959956801
479 3.9696645526 25.3904012185 94.5847492974
480 3.9949150038 25.8630937563 93.806011499
481 4.0067279826 26.1922676359 92.6299270194
482 4.0075797906 26.4100257913 91.1537202218
483 3.9926654415 26.5471667913 89.5017992961
484 3.9645688876 26.5112570941 87.5430426027
485 3.9321002619 26.3451529261 85.3188735394
486 3.9026901738 26.2216130813 82.9697215598
487 3.86574171 26.3024591898 81.1143799205
488 3.8285905792 26.5113735672 79.4702852086
489 3.8062658312 26.8375235841 77.491062137
490 3.8131677244 27.3470861618 75.2852334926
491 3.8494545067 28.1236014169 73.2311234441
492 3.9012103341 29.1493400696 71.2887897905
493 3.9539243995 30.2683961802 68.9253651267
494 3.9995895443 31.4557038269 66.9043562592
495 4.0484314294 32.7161681254 65.107411742
496 4.0942748585 33.9741186419 63.2200034064
497 4.129346185 35.0439980169 61.4639802445
498 4.1535418132 36.0145814427 59.9232049372
499 4.1718343585 36.7128040067 58.6104923588
500 4.1746751823 36.9774839475 57.5386573833
501 4.152214222 36.87584279 56.7205421349
502 4.0865550247 36.573120871 56.2543099531
503 3.9897205438 36.2347966143 56.0853846538
504 3.8953965811 35.7979097384 56.0081429838
505 3.8355462727 35.1923869634 55.824529377
506 3.7844092704 34.6834014515 55.6175515803
507 3.7505366918 34.5266940938 55.3953254338
508 3.773315013 34.1169755788 55.0430957794
509 3.8894593898 33.9820070973 54.499194779
510 4.093094531 35.4731547636 53.8787745927
511 4.3660353326 38.4110302185 53.0111790936
512 4.6942892308 44.1080288228 51.6079250058
513 5.0745689417 49.3817447096 46.6101512736
514 5.5331462309 53.4827426972 41.6944663998
515 6.031772839 57.9150700203 39.7360238916
516 6.5238068867 64.0159176328 37.6550280927
517 6.9824909276 70.4127392804 35.2811099274
518 7.4348144706 75.1752648305 32.5954232046
519 7.8784289364 78.0665364212 30.4075542343
520 8.3086701369 80.8783329005 29.0960422667
521 8.7265456383 84.1649721602 27.9482882837
522 9.1343054628 86.4482329896 26.9399438576
523 9.5252806971 88.0618871753 26.0573712443
524 9.8928771628 89.0287099803 25.3290969482
525 10.2513014198 90.0322647191 24.7069725657
526 10.5940025843 90.9374948371 24.1060194179
527 10.8929955288 91.8362059661 23.5169873529
528 11.1215470379 92.7095188851 22.9664535828
529 11.2851030456 93.5594243194 22.4215623139
530 11.3918647815 94.4184161955 21.8482234409
531 11.4423504887 95.2609376342 21.2088370971
532 11.4343373101 96.063193981 20.6275203625
533 11.3552242297 96.8286430354 20.2461006982
534 11.2240169182 97.5574478462 20.0142031438
535 11.0655910446 98.2060978471 19.8143589467
536 10.8944986729 98.747478745 19.5691841779
537 10.6917400971 99.2141082109 19.3462484507
538 10.4702719159 99.5938815584 19.1069507117
539 10.2469370303 99.8687451987 18.7984101438
540 10.033334996 100.0317588815 18.3648751806
541 9.8213151219 100.0968609608 17.7930491332
542 9.6016319585 100.0623495164 17.1773954983
543 9.3652162515 99.9258648681 16.6225866773
544 9.0967235201 99.6921885633 16.1759689625
545 8.8047853142 99.3639267419 15.7865034713
546 8.5186698867 98.933940777 15.4179851263
547 8.2672443368 98.3957648056 15.0347393804
548 8.0492937022 97.773501063 14.6375918695
549 7.8541565893 97.049799308 14.2402463074
550 7.6815738766 96.1797158547 13.8442574235
551 7.5317503386 95.1601467846 13.450876154
552 7.408723128 93.9861659489 13.0579588595
553 7.3077817017 92.6066025166 12.6671787263
554 7.2216706561 91.0684592184 12.281645213
555 7.1465483503 89.3607823808 11.9007952041
556 7.0925555767 87.7724350105 11.5130884327
557 7.0483440146 86.2465223098 11.1364026786
558 6.9988846142 84.7938161869 10.7930223952
559 6.933730291 83.4194890408 10.5011446866
560 6.8603761483 82.2429197775 10.2528072032
561 6.7821300512 81.4159506781 10.0327109941
562 6.7015832153 80.7287792695 9.8258270094
563 6.5966303008 79.8990384713 9.6268700934
564 6.4629569424 78.7145017934 9.4441667421
565 6.3630066556 77.4298804385 9.2748371044
566 6.3600540104 76.4115552684 9.115775753
567 6.4563211718 75.5898555093 8.9675886841
568 6.6277080993 74.7865540807 8.8311226716
569 6.8880454278 73.8909291381 8.7043047432
570 7.2509456085 72.9722044281 8.5853080169
571 7.7187444811 72.0502000806 8.4781874059
572 8.2838047907 71.1419798946 8.3800655964
573 8.9393548624 70.237907285 8.2842054281
574 9.6511066062 69.3148771488 8.1842288023
575 10.4312932055 68.3793892371 8.0803848706
576 11.3463567843 67.4241229982 7.9770221185
577 12.2653601604 66.4350379767 7.8782864908
578 13.4898331939 65.4158629788 7.7871645909
579 15.054494788 64.3450487986 7.7011678846
580 17.3227804423 63.2145099274 7.6207580275
581 20.7843514327 62.0374992138 7.5469715058
582 25.6095393257 60.8374686772 7.4823262232
583 31.0646719978 59.5902394901 7.4275890359
584 36.546711588 58.2176234597 7.376279465
585 43.4057590955 56.7959975223 7.3216603503
586 48.5806479572 55.4013216027 7.2640954627
587 54.675835038 54.0924951108 7.2066839261
588 59.0591349071 52.9520167133 7.1432556097
589 64.3996186899 51.698115708 7.0676328484
590 67.7992809311 50.3438469545 6.979655367
591 70.3397619738 48.9658059048 6.8817733146
592 72.5858916615 47.5961359181 6.7739866913
593 74.3908854188 46.2447887012 6.6559160036
594 75.9175712263 44.9050915038 6.5229542624
595 77.2359002122 43.5785850982 6.3801230781
596 78.4552014748 42.0669505791 6.2357143403
597 79.5293456709 40.4747811501 6.0970323665
598 80.483436072 39.2063029325 5.9616010163
599 81.3103642661 38.1031671619 5.826452956
600 81.9887708954 36.8461627895 5.6895152131
601 82.4966920306 35.3507797774 5.5484482845
602 82.8161111393 33.822540176 5.402973227
603 82.9816942729 32.285815321 5.2570077509
604 83.0393776593 30.8097798569 5.114697801
605 83.0213301322 29.4185850531 4.9772262071
606 82.8812755296 28.0808742023 4.8420079166
607 82.6564282509 26.7893693361 4.7114830005
608 82.4028947408 25.531641926 4.5882426745
609 82.1601237834 24.3146903024 4.4726068599
610 81.8981445632 23.1747172642 4.3634265216
611 81.6090988952 22.10353915 4.261219659
612 81.2890481319 21.0977833309 4.1665124747
613 80.9325127166 20.1602494169 4.07983727
614 80.5406358363 19.2930618079 4.0005369303
615 80.1239383292 18.4821809771 3.9275749693
616 79.6930960032 17.7061230587 3.8598578137
617 79.2389203758 16.9667075139 3.7965858284
618 78.7609801643 16.2781668224 3.7394017928
619 78.2835289009 15.6527314634 3.6903786792
620 77.8308232794 15.0994571039 3.6514912862
621 77.4159888455 14.6119247282 3.6226718277
622 77.0199516213 14.179189373 3.6019228907
623 76.618009566 13.7903534742 3.5871715028
624 76.1921737354 13.4531956482 3.5782966215
625 75.7869148189 13.1652931129 3.5776454586
626 75.370544802 12.9055244908 3.5809532743
627 74.8863770426 12.6533742213 3.5835558807
628 74.2954061981 12.4087760507 3.5835993358
629 73.6412975853 12.1753214559 3.5835993358
630 72.8958812904 11.9513261467 3.5835993358
631 72.0107730908 11.7351058332 3.5835925173
632 70.9416253802 11.5249762251 3.5817378552
633 69.801432652 11.3192530324 3.5790872341
634 68.6207247769 11.116251965 3.5792683557
635 67.423657204 10.9137703986 3.5854585223
636 66.2127172132 10.7132744721 3.5915402014
637 65.1900117985 10.5255083356 3.6018326598
638 64.3542531999 10.3618733375 3.6261825163
639 63.7016366978 10.2336788774 3.6738138792
640 63.3526552488 10.1427030819 3.7439265858
641 63.365889832 10.0822488963 3.8304327272
642 63.6507917723 10.0454495995 3.9276316291
643 64.1015402684 10.0254384702 4.0335847587
644 64.6743770938 10.0153487874 4.1559372497
645 65.5059573941 10.00831383 4.2842951215
646 66.3640130191 9.9974784503 4.4062205396
647 66.9680486865 9.9780044691 4.5179374715
648 67.3143039724 9.9476816672 4.628189979
649 67.4848905048 9.9041779509 4.7274092543
650 67.4113672557 9.8439891586 4.8052304352
651 67.0221919949 9.749216669 4.8510892191
652 66.2421645018 9.623940049 4.8719786586
653 65.1924613139 9.4804675723 4.8855030732
654 64.0339561063 9.3311075127 4.9090680926
655 62.736203314 9.1881681437 4.9397821697
656 61.3454249877 9.0639577393 4.9730017487
657 60.0191398824 8.970784573 5.0139092608
658 59.1032046936 8.924514894 5.0667483585
659 58.4130402428 8.9410382868 5.1236138324
660 57.9701696046 9.0145171036 5.1906703667
661 57.8099873713 9.1376311607 5.2798375527
662 58.0330144203 9.3030602741 5.4040466258
663 58.5336964449 9.5034842602 5.5691230872
664 59.115883234 9.7315829349 5.7545879852
665 59.6141620379 9.980036111 5.93712038
666 60.2017143999 10.2375338206 6.1049174445
667 60.7933829511 10.4936884149 6.2762143625
668 61.1967615672 10.7425400982 6.4360091091
669 61.2503686431 10.9781290747 6.5661631757
670 61.0200966068 11.1944955488 6.6541498348
671 60.5638681207 11.3856797249 6.7090336949
672 59.9149159315 11.545721807 6.7428232636
673 58.9489418954 11.667354364 6.7674369585
674 57.8122105741 11.7428483581 6.7790982789
675 56.6887166846 11.8022556018 6.7749125105
676 55.5717623167 11.8828895987 6.7673174876
677 54.4916505868 12.0171157732 6.7682008272
678 53.4381291438 12.2009714984 6.7693477345
679 52.5919095246 12.4304630332 6.7727042641
680 52.0288985319 12.703959622 6.7907082502
681 51.6477375249 13.0198305095 6.8353601976
682 51.4120059661 13.3764449403 6.9075191872
683 51.2922848045 13.772172159 6.9979888919
684 51.3520961752 14.2053814101 7.097440936
685 51.5399298882 14.6408350987 7.1967084548
686 51.7552995938 15.0711875173 7.2954979132
687 51.9139298496 15.5700969177 7.4046003761
688 52.0657751935 16.2115446233 7.5354171916
689 52.2250749275 16.9598294042 7.6946080342
690 52.3878716837 17.7285977705 7.8756001706
691 52.578855344 18.4855930076 8.0788437206
692 52.8544621402 19.1985584011 8.3053751705
693 53.1239773006 19.8352372366 8.5948246508
694 53.2849699593 20.3633727996 8.9444481633
695 53.2958588263 20.7507083756 9.2548607984
696 53.2018049962 20.9945420619 9.4263489998
697 52.9528855656 21.1488069749 9.4520556683
698 52.4962055209 21.2191641791 9.3733660628
699 51.8225783874 21.2191641791 9.1902801834
700 51.8225783874 21.2191641791 9.1902801834

Crédito : KOEN HUFKENS - ov5647 spectral response

Las otras tres cámaras CMOS son monocromáticas , y si bien el rango de s sensibilidad completo tambien se extiende desde el azul a 400nm hasta cerca del 1000nm o sea 1 um, el filtro pasa-altos a 700nm y los filtros dielécticos pasabanda nos permiten separar bandas angostas que resultan relevantes, en particular:

RED para NDVI: 680nm +/- 10nm NIR para NDVI: 800nm +/- 10nm

Otros filtros pasabanda en la región visible pueden ser útiles para detectar los marcadores espectrales de la clorofila

Por último , el sensor de imágen térmico de baja resilución FLIR entrega informaciónen el rango de 8000nm a 14.000nm

Queda pendiente la evaluación e incorporación al dispositivo de los nuevos sensores de imágen de InGaAs para poder obtener imágenes en el rango de 900nm to 1700nm , que cubre algunas de las marcas espectrales de absorsión del agua líquida

RGB + NDVI RED + Edge RED+ NDVI NIR

Effective Sensor Range: 425 nm to 950 nm (Filters field changeable by users) Color Bands: Red: 570 nm – 700 nm, Green: 480 nm – 550 nm and Blue: 400 nm – 470 nm Narrow Bands (CWL): 680 nm (NDVI Red), 700 nm (Red Edge) and (each 20 nm wide) 800 nm (NDVI NIR)

Sensor térmico LWIR 8000nm - 14.000nm

Tetra Pi

http://www.khufkens.com/ov5647-spectral-response/

http://www.tetracam.com/PDFs/RGB%20+%203%20PRODUCT%20FLYER.pdf

Camera multiplexer http://www.ivmech.com/magaza/en/development-modules-c-4/ivport-raspberry-pi-camera-module-multiplexer-p-90

Filters https://www.thorlabs.com/navigation.cfm?guide_id=2210

[Monitoring Vegetation From Space](http://www.eumetrain.org/data/3/36/print.htm# page_3.3.0)

LWIR Lepton https://www.sparkfun.com/products/13233

SWIR http://www.new-imaging-technologies.com/media/doc/wdr_sensors_overview.pdf <http://www.sensorsinc.com/products/detail/micro-320csx-swir-camera >