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Light Emitting Diodes
      LED color schemes for white
            whites
      CRI
      common multicolor combinations
            colors
            colors with white
            whites
            Additional colors to RGB
      food illumination whites
      plant growth LEDs
      vision wavelengths, meltopic photoreceptors

COLORS
      common LED wavelengths
            phosphor-converted ("PC")
            Standards for machine vision:
            RGB
            colors
                  sample vendor
            microscopy fluorescence excitation
            optogenetics
            fiber optics LED/laser wavelengths
      longer-wave IR LEDs
      ultraviolet LEDs
            UVC (280-100nm)
            UVA (400-315nm)
                  applications by Rahn
      Laser diode wavelengths
            laser diode mounts
            laser module diameters

DEVICES/MATERIALS
      common SMD LED sizes
      phosphors
            phosphor compositions
            IR upconversion phosphors
            xray phosphors
      static electricity ESD damage
      materials

SMART LEDS
      Neopixel/WS2812b alternatives
            Singlewire (asynchronous)
                  WS2812
                  APA106
                  SK6812
                  PD9823
            Two-wire (separate CLK)
                  APA102
                  SK9822

MEDICAL
      SAD therapy
      oximeters

SENSORS, IMAGING
      spectral sensors
      night vision
            common IR illuminators
                  LEDs:
            photocathodes
      thermal imagers
            people sensing
            singlepoint
      ROIC - Readout integrated circuit

Light Emitting Diodes 



 LED color schemes for white





 whites



6500K - cool white
5500K - cool white
4000K - neutral white
3000K - "gallery white"
2200K - warm white

running phosphor too hot shifts LED towards blue; remote phosphor (not in direct contact in LED, typically coating on the enclosure) is immune





 CRI



Color Rendering Index
usually used test strips TCS01..TCS08
extended variant uses TCS09, deep red below 600nm - important for skin tones, etc
even lamps with good CRI often have poor "R9" rendering [ref]
sample profiles: https://www.waveformlighting.com/tech/cri-ra-test-color-samples-tcs/

USA: CRI usually refers to CRI(R1..R8) - aka "general CRI" or CRI(Ra)
EU/Asia: usually CRI(R1..R14) - aka extended CRI, CRI(e), or CRI(Re)






 common multicolor combinations





 colors





 colors with white





 whites





Additional colors to RGB



lime makes cool colors more vibrant
near-UV (deep blue?) makes most fabrics more saturated in color
RGBA gives warrm tones and enhances red colors (brick facade)




 food illumination whites



special white hues for illumination of different kinds of merchandise, engineered spectral characteristics
https://cz.mouser.com/new/lumileds/lumileds-luxeon-freshfocus-led/
https://cz.mouser.com/pdfdocs/lumileds-freshfocus-brochure.pdf



 plant growth LEDs



https://cz.mouser.com/new/Luminus-Devices/luminus-hortilum-cob-leds/
280nm         reduces photosynthesis quantum yield, UVR8 photoreceptor pathway, used to increase THC in cannabis
315..400nm    promotes pigmentation, thickens leaves, maybe harms insects
440..470nm    chlorophyll peaks 439,469nm; most efficiently absorbed, promotes vegetative growth
510nm         quantum absorption in green spectrum(?), little in yellow
610nm         no chlorophyll effect, absorbed by phycocyanin - initiates photoperiodism (onset of flowering)
640..660nm    chlorophyll peaks 642,667nm; speeds up germination, flower/bud onset; 660nm most vital for flowering
690nm         unclear, some benefit maybe?
720..740nm    Emerson Enhancement Effect - red+far red together increase photosynthesis rate
1000..1400nm  no known activity, just heat




 vision wavelengths, meltopic photoreceptors



[ref]



 COLORS





 common LED wavelengths





 phosphor-converted ("PC")





 Standards for machine vision:





RGB



LED strip: 624,518,471
RGB LEDs:  624,525,470
           625,528,470
           627,538,476

most common:
blues:  470nm,   some 465,480,485, rare 458,453
greens: 525-535, some 518,525,528,530,538,540
reds:   624-627, some 605,620,630,




 colors



https://www.ledtuning.nl/en/about-colors



 sample vendor





 microscopy fluorescence excitation



https://www.coolled.com/product-detail/led-wavelengths/
365
380
400
425
440
470
490
500
525
535 - wide peak
550 - wide peak
565 - wide peak
585 - wide peak
595
615
635
660
700
740
770




 optogenetics



https://www.prizmatix.com/Optogenetics/Prizmatix-in-vivo-Optogenetics-Toolbox.htm



 fiber optics LED/laser wavelengths



 -OH group vibration attenuates at 1380nm (also less at 950 and 720nm)

 850nm -  770..920  - 3.5-2.5dB/km loss, common for short 100..500m distances with multimode fibers
1310nm - 1270..1370 - lowest dispersion (zero group velocity dispersion), single and multimode fibers, 0.35-0.5dB/km loss, cheap simple intensity-modulated systems for shorter distances
1550nm - 1500..1610 - fiber optics, lowest attenuation, singlemode fibers, 0.2dB/km loss, eye-safe
                      Er-doped amplifiers peak at 1530,1550nm

SFP transceivers: http://www.fiber-optic-solutions.com/single-mode-sfp-vs-multimode-sfp.html
singlemode cable - usually yellow
multimode cable - usually orange

VCSEL laser - multimode, cheap
edge-emitting laser - Fabry-Perot, singlemode, more expensive design


Yb3+-doped silica laser: pump at 840 and 975nm
1020nm for pumping praseodymium fiber amplifiers
1140nm for pumping thulium-doped fluoride fiber upconversion lasers

common telco laser/LED wavelengths
850nm
1300nm
1310nm
1550nm




 longer-wave IR LEDs



1020nm, 1060nm, 1300nm,1450nm,1550nm,1650nm
SWIR illuminators

808nm (NVG)
1064nm (SWIR)
1550nm (SWIR, eye-safe)

free-space optics communications:
http://www.fsona.com/product.php?sec=compdiff
808nm systems are low-power (safety), have low fog-penetration margin




 ultraviolet LEDs



most commonly used for fluorescence, disinfection, UV curing
the shorter wavelength the higher the price per watt
in ultraviolet polymerization, shorter wavelengths are usually better absorbed by the photoinitiator (better surface cure, worse depth cure)
shorter wavelengths are also better for disinfection/sterilization and for photocatalysis




 UVC (280-100nm)



sterilization, fluorescence analysis



 UVA (400-315nm)



UV curing, fluorescence analysis



 applications by Rahn





 Laser diode wavelengths



    375nm       Thorlabs
!   404/405nm   purple/violet/UVA; watt-class powers available; some laser pointers; GaN; some use frequency-doubled 808nm laser diode
!   445/450nm   royal blue; common in cheap high-power cutting/engraving lasers; some laser pointers; InGaN
    465/470nm   blue (Nichia)
    473nm       DPSS, doubled 946nm of Nd:YVO4
    488nm       mint-blue (Sharp); some laser pointers
    505nm       mint-green
    515/520nm   green; atypical green laser pointers, more expensive than 532nm doubled; Nichia, OSRAM
!   532nm       green (DPSS, Nd:YAG doubled); common laser pointers, poor low-temperature performance
    561nm
    577nm       yellow; medical lasers for vascular skin conditions
    589nm       yellow; some laser pointers; doubled 1178nm diode
    593.5nm     orange; some laser pointers; DPSS, summed 1064nm and 1342nm of Nd:YVO4
!   633/635nm   red; appears brighter per mW than 650nm
!   637/638/639nm red; similar to 630nm, higher powers
    640/642nm   red
!   650nm       red (plentiful)
    658nm       red
    660nm       red
    671nm       deeper red, uncommon, DPSS (higher beam quality)
    685nm       red
    690nm       deep red
    705nm
    730nm
    755nm       IR; medical
    761nm
    770nm
    780nm       IR
    785nm       IR; higher powers, common
    795nm
!   808nm       IR (plentiful); common as night vision illuminators, medical, high-power modules for pumping Nd:YAG crystals; GaAlAs
    816nm/820nm
    828/830nm   IR; common-ish, high power
    850/852nm   IR; telco laser; black SFP modules, multimode; 770..920nm band, 3.5-2.5dB/km loss, common for short 100..500m distances with multimode fibers
    880/895nm   IR; uncommon
    904/905nm   IR; lidars, cheap, output power limited by eye safety, 100m range; common as pulsed high-power
    915nm
    935nm
    940nm       IR; higher power
    960nm       IR; higher power, uncommon
    976nm       IR; single-frequency (longitudal-mode) available
    980nm       IR; higher power; medical, spider veins, good fat tissue absorption
   1060nm
   1064nm       IR; matches Nd:YAG laser; higher power
   1083nm
!  1310nm       IR; telco laser; blue SFP modules; 1270..1370nm band, lowest dispersion (zero group velocity dispersion), single and multimode fibers, 0.35-0.5dB/km loss, cheap simple intensity-modulated systems for shorter distances; high power available
   1425nm
   1436nm
   1450/56/80nm
   1490nm       IR; telco laser; purple SFP modules
!  1550nm       IR; automotive lidars, eye-safe so high powers allowed; telco lasers; yellow SFP modules; fiber optics, lowest attenuation, singlemode fibers, 0.2dB/km loss; high power available
   1575nm
   1625nm       IR
   1650nm       IR
   1940nm
   1950nm       IR; surgery diode lasers, seems to be an ideal wavelength for laser microvascular anastomoses
   2000nm
   3850nm       MWIR, Fabry-Perot Quantum Cascade
   4040nm       MWIR, Fabry-Perot Quantum Cascade
   4050/4055nm  MWIR, Fabry-Perot Quantum Cascade
   4060/4065nm  MWIR, Fabry-Perot Quantum Cascade
   4..5um       MWIR, Distributed Feedback Quantum Cascade
   5..6um       MWIR, Distributed Feedback Quantum Cascade
   6..7um       MWIR, Distributed Feedback Quantum Cascade
   7..8um       MWIR, Distributed Feedback Quantum Cascade
   8..8.1um     MWIR, Distributed Feedback Quantum Cascade
   8..9um       MWIR, Distributed Feedback Quantum Cascade
   8450nm       MWIR, Fabry-Perot Quantum Cascade
   9..10um      MWIR, Distributed Feedback Quantum Cascade
   9150nm       MWIR, Fabry-Perot Quantum Cascade
   9550nm       MWIR, Fabry-Perot Quantum Cascade
   10..11um     MWIR, Distributed Feedback Quantum Cascade

1350nm wavelength has lowest solar background noise, investigated for lidar use [ref]




 laser diode mounts



   TO-5, "9mm"     thick base press fit; 9.0mm diameter base, 6.7mm dia can, "big laser diode", "bigger small transistor"; variety of lenses; common also for photosensors/photodiodes
   TO-18, "5.6mm"  thick base press-fit; 5.6mm diameter base, 3.5mm dia can, "small laser diode", very common for low powers; "small transistor"; common also for photosensors/photodiodes
   TO-38           3.8mm diameter base, flattened on both sides to 3.2mm; 2.5mm dia can
   TO-46           4.6mm diameter can (MISNOMER?!? TO-46 is a variant of TO-18!); variety of lenses
   TO-56           can; 5.6mm diameter base, 3.5mm dia can
   TO-72           TO-18 with 4 leads
   C-mount
   F-mount      flat, two screws to base

   variants:
   TO-3:  flange mount on heatsink, two screw holes TO-3
          TO-41: solder pads with holes instead of pins; TO-41 = TO-204-AB
          TO-204: JEDEC family designation; eg. TO-3 = TO-204-AA

   TO-5:  8.9mm diameter, 6.3mm high cap TO-5
          TO-39,9,16,42: differ in lead lengths; TO-39 = TO-205-AD
          TO-12,33: 4-lead; TO-12 = TO-205-AB, TO-33 = TO-205-AC
          TO-75: 6-lead
          TO-76,77: 8-lead
          TO-78,79,80,99: 8-lead, 4.45/3.81/2.41mm high cap; TO-78/99 similar to TO-205-AF
          TO-74: 10-lead
          TO-96,97,100: 10-lead, flatter cap
          TO-73: 12-lead
          TO-101: 12-lead, flatter cap
          TO-205: overarching family, JEDEC, eg. TO-5 = TO-205-AA

   TO-8:  12.3mm diameter cap, 7.62mm high cap; common for optical sensors; TO-8
          TO-233: JEDEC family designation; eg. TO-8 = TO-233-AA

   TO-18: 4.7mm diameter cap, 4.83mm cap; common for optical sensors; TO-18
          TO-46,52: differ in can height, 3.3mm/1.9mm; TO-46 = TO-206-AB
          TO-71: 8-lead
          TO-72: 4-lead; TO-72 = TO-206-AF
          TO-206: JEDEC family designation; eg. TO-18 = TO-206-AA

   TO-66: flange mount on heatsink, two screw holes, 1.9mm base plate, smaller TO-3 TO-66
          TO-123: 1.02mm base plate; TO-123 = TO-213-AB
          TO-124: 2.6mm base plate; TO-124 = TO-213-AC
          TO-213: JEDEC family designation; eg. TO-66 = TO-213-AA




 laser module diameters



    4mm   cheapest "pointer" modules
    9mm   less common
   12mm   common chrome-plated cylindrical modules; typ. 40mm long; typ. M9x0.5 lens
    





 DEVICES/MATERIALS





 common SMD LED sizes





 phosphors





 phosphor compositions



https://www.yujiintl.com/phosphor.html
YAG:Ce         - most common for white LEDs, good chem-thermal stability, degrades at higher temp; excitation at 455nm, emission at 550nm
LuAg:?         - emits at 510..540nm, comparable to YAG, green, use with nitride red
nitride red    - emits at 600..660nm, excit. with 400..460nm, for white LEDs and plant growth lamps; violet LED, phosphate blue, beta-SiAlON gives full-spectrum high-CRI white
oxynitride red - emits at 500..650nm (max 615nm), excit. 455nm
nitride green  - emits at 525..545nm, narrowband; blue LED+SiAlON green for LCD backlights
KSF yellow     - emits at 631nm, narrow peaks, excit. 455nm
infrared       - emits at 710..730nm (max 712nm), excit. 455nm, blue 460nm + red 660nm + IR for best plant growth
Sr[Li2Al2O2N2]:Eu2+ - red, SiAlON, 
(Ba,Sr)3N2:Eu  - amber, for pc-amber LEDs; 595nm, ext.quantum efficiency 30-40%
Sr(LiAl3N4):Eu2+ - red, narrowband, Lumileds
yellow-green   - in white LEDs
red            - in white LEDs, narrowband or wideband (less efficient)

silicate phosphors - lower lifetime, very bright, for cellphones

LED phosphors for sale: https://phosphortech.com/products/led-phosphors/
  $215..$450/100g, yellows
  $450/100g, greens
  $1120/100g, reds




 IR upconversion phosphors



phosphors: https://maxmax.com/phosphorsdyesandinks/infrared-phosphors-dyes-and-inks/infrared-up-conversion-powder
used with 940..980nm laser
IRUCG    948..983nm -> 552nm   - most efficient
IRUCG-EX 948..983nm,1510nm,1550nm,1600nm -> 552nm
IRCUR    980nm -> 660nm
IRUCY    948..983nm -> 575nm
IRUCB    980nm -> 445nm
IRSPG    700..1500nm -> 490nm - needs charging with visible light

antistokes phosphors hard to manufacture, low-availability, used in security applications




 xray phosphors



Gd2O2S:Tb - green, 7.5g/cm3, 8..80 kVp (540..550nm, tiny peak at 490nm)
Y2O2S:Tb  - blue-white, 5g/cm3, 30..100 kVp (blue-white, 540..550nm peak, more peaks in 400..500nm)
both $44/10g

UV phosphors:
UVSWR    270nm -> 610nm, 10nm particles
UVSWG    250..270nm -> 525nm
UVSWB    293nm -> 480nm, 5nm particles
UVLWR    360nm -> 628nm
UVLWG    380nm -> 518nm
UVLWB    365nm -> 450nm
all $44/5g
UVInkLWRSWG-1   254nm -> green, 365nm -> red





 static electricity ESD damage



LEDs sensitive to ESD
diagnosed by forward voltage at very low current (e.g. for 260nm UV LED fail is Vfwd below 4.0V at 500 µA)




 materials





 SMART LEDS





 Neopixel/WS2812b alternatives





 Singlewire (asynchronous)



input DI (data in), output DO (data out); relies on precision bit timing



WS2812



       -----              -----              -----            --flat
   DO |/    | GND    GND |/    | DO       R |/    | +5V     /    |---- |--   DO
   DI | ( ) | +5V        | ( ) |          G |     | SET    |     |---- |---- GND
 3.3V |     | nc      DI |     | +5V      B |     | DI     |     |--   |---  +5V
       -----              -----         GND |     | DO      \    |--   |--   DI
      WS2812             WS2812B             -----            ---
                                            WS2811          round
SET: 800kHz(nc), 400kHz(+5V)




APA106





SK6812





PD9823



virtually identical to WS2812 [ref]






 Two-wire (separate CLK)



input CI/DI (clock/data input), output CO/DO (clock/data output)



APA102



APA102 (presumably also 104, 106) - 32bit (111+global bright(5bit)+RGB)



SK9822



      -----
  DI |/    | +5V
  CI | ( ) | DO
 GND |     | CO
      -----

similar to APA102 [ref]



 MEDICAL





 SAD therapy



10,000 lx, 5000K temperature, half-hour
min. 2,500 lx
lx-to-watt calculator: https://www.rapidtables.com/calc/light/lux-to-watt-calculator.html

1 lux=1 lumen/m2
1 cd/m2 = 1 lux = 1 nit

1 cd/m2 = 8 lux on light pavement, 14 lx on average, 18 lx on dark pavement
https://books.google.cz/books?id=ppBgBqWIdCgC&pg=PA20&lpg=PA20&dq=cd/m2+lux&source=bl&ots=3ynXa9_yqp&sig=ACfU3U3BOtnI-1nHaFfv-Wg_wa6AtQQV-w&hl=en&sa=X&ved=2ahUKEwj_uMGhgqDmAhWcQ0EAHWBcAE84ChDoATAFegQIChAB#v=onepage&q=cd%2Fm2%20lux&f=false ;
In Belgium, the most commonly encountered road pavements were bituminous asphalts (R3, with Qo from 0.07 to 0.10 cd/m2/lux) and porous asphalts (R2, with 0.05 to 0.08 cd/m2/lux)
road brightness at least 1-2 cd/m2
https://spie.org/samples/TT63.pdf

diffuse reflectance: cd/m2/lux

LED: 2500lx on 1 m2 =  28W  (90lm/W)
lightbulb           = 166W  (15lm/W)
halogen             = 125W  (20lm/W)
metalhalide         =  29W  (87lm/W)
highpres sodium     =  21W (117lm/W)

LCD panels: usual brightness???





 oximeters



dual-wavelength sensing, difference for absorption between oxy and deoxyhaemoglobin
660/880nm
660/905nm     less common
660/940nm

7 or more wavelengths is becoming more standard - measure haemoglobin, oxygen content, carboxyhaemoglobin, methaemoglobin

660nm - oxyHb absorbs MUCH less than deoxy
800nm - both equal
800+nm - deoxyHb absorbs slightly more than oxyHb, diff rough equal from about 850-900nm

carboxyHg causes false high reads of SpO2
graph for O2Hb, HHb, COHb, MetHb: https://ars.els-cdn.com/content/image/1-s2.0-S095461111300053X-gr2.jpg

AS7263 NIR: 610, 680, 730, 760, 810, 860nm, each 20nm wide






 SENSORS, IMAGING



section to be moved to own notes




 spectral sensors



AS726x: 6 wavelengths, on-chip filter
AS7262 vis: 450, 500, 550, 570, 600, 650nm, each 40nm wide (half-width)
AS7263 NIR: 610, 680, 730, 760, 810, 860nm, each 20nm wide
AS7341: 11-chan (clear, flicker, NIR, 6x ADC, input mux) 210czk(Mouser)
     F1: 410+-10nm/29nm halfw
     F2: 440+-10nm/33nm
     F3: 470+-10nm/36nm
     F4: 510+-10nm/40nm
     F5: 550+-10nm/42nm
     F6: 573+-10nm/44nm
     F7: 620+-10nm/53nm
     F8: 670+-10nm/60nm

AS72651: 410,435,460,485,510,535
AS72652: 560,585,645,705,900,940
AS72653: 610,680,730,760,810,860
AS7331: 240-280,280-320,320-410





 night vision





common IR illuminators



808nm
915nm
(also 940nm)

808nm (NVG)
1064nm (SWIR)
1550nm (SWIR, eye-safe)




LEDs:



(805nm)
850nm
940nm

https://www.pulsar-nv.com/glo/support/night-vision-technologies/77
common illuminator powers:
30..100mW for LED
10..50mW for lasers





photocathodes



https://www.azooptics.com/Article.aspx?ArticleID=1058
(minimizing parasitic sources of NIR light to avoid nightvis saturation in cockpits)
gen.III - from 500nm (present) or 600nm (old, 1990's) to just over 900nm


night sky - strong NIR light at 920..1000nm, up from 640nm, tapering down to way beyond 1100nm
luxmeters work between 380..780nm, need also bands 780..810nm (average, high-sensitivity of CCD/CMOS sensors) and 910..940nm (high-value of night sky, lower sensitivity)
GaAs photocathode 680..840nm, tapers to 900nm, next to zero at 920nm
CCD/CMOS sensitive most at 640nm, tapers slow to quite over 920nm

915/940nm lamps/lasers invisible on photocathode nightvis amp tubes

passive mode - advantage on image amplifiers; gen2+ tubes outside of cities need additional illumination





 thermal imagers



FLiR Lepton - 160x120 (earlier 80x60)
MLX90621 - 16x4, 120/25deg FOV, -20..+300 +-1c/3% °C, I2C, 3.3v, operating temp -40..+85c, 0.5..64 Hz
MLX90640 - 32x24, 55x37 or 110x75deg FoV (fixed), -40..+300 +-1.5 °C, I2C, 3.3v, operating temp -40..+85c, 0.5..64 Hz
MLX90641 - 16x12, 110x75deg FOV (fixed), -40..+300 +-1.5 °C, I2C, 3.3v, operating temp -40..+125c
AMG8833  - 8x8, 60deg FOV, 0..80 +-2.5 °C, I2C, 3.3v




 people sensing



AK9753   - presence sensor, 80' FOV, 4-quadrant photoelectric NDIR, I2C, 1.7..3.3v, dig.filt. 0.2..9.7 Hz




 singlepoint



MLX90614 - infrared thermometer, 5 or 35deg FOV, -70..+380c, body temp range accuracy +-0.2c, 0.5..64 Hz






 ROIC - Readout integrated circuit



Readout integrated circuit

FLiR offers ROIC chips, bias for low-bandgap p-on-n sensors, some for n-on-p
sensors InSb, InGaAs, MCT(== HgCdTe), QWIP, SLS(n-on-p?)

modes:
integrate-while-read
integrate-then-read
nondestructive read (only ISC0402)
https://www.flir.com/globalassets/imported-assets/document/flir-isc9803-specifications.pdf
https://www.flir.com/globalassets/imported-assets/document/flir-large-format-roic-brochure.pdf

electron wells (integration caps): 11.2 or 3.2 millions electrons (350 or 100 femtofarads?)
1 farad == 6.25e18 electrons

xray ROIC
https://www.flir.com/globalassets/imported-assets/document/17-0740-oem-cor-xray-datasheet-update_final_v1_web.pdf
with Se, CsI, Si, amorphous Si, GaAs, CdZnTe sensors











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