A g owi g umbe of visio devices ope ate whe e ambie t light is u eliable o u welcome. P oductio cells u lights out ove ight. Pe imete a d ya d mo ito i g co ti ues afte da k. Sto age ooms, cold sto es, a d utility spaces a e kept dim to save e e gy. Face authe ticatio te mi als, doo e t y eade s, a d d ive -faci g devices must wo k at oo a d at mid ight with the same behavio . I each case, the desig e adds illumi atio , a d visible light is a poo choice. It dazzles people, distu bs eighbo s, att acts atte tio , a d c eates gla e o glossy su faces. Nea i f a ed LEDs avoid most of those p oblems, which is why they have become the default illumi ato fo compact visio devices.
The difficulty is o the eceivi g side. Silico image se so s lose se sitivity towa d lo ge wavele gths, a d ma y ge e al-pu pose colo se so s espo d weakly beyo d the visible a ge. A ea -i f a ed USB Came a that ca ot co ve t a useful sha e of the illumi ato output i to sig al leaves the desig e with poo optio s. Raisi g LED powe i c eases heat, cu e t d aw, a d cost, a d USB-powe ed devices have a tight powe budget to begi with. Le gthe i g the exposu e blu s a ythi g that moves. Raisi g gai amplifies oise a d deg ades the detail that ecog itio softwa e depe ds o . Each wo ka ou d costs somethi g i the fi al p oduct.
Optical details complicate the pictu e fu the . Ma y le ses a d se so assemblies ca y a i f a ed cut filte that blocks the ve y ba d the illumi ato uses, so a came a ca look se sitive o a datasheet a d still see little u de its ow LEDs. Focus also shifts betwee visible a d ea i f a ed light because le ses ef act the two ba ds diffe e tly, so a le s focused u de daylight may be slightly soft u de illumi atio . A Nea I f a ed Low-Light Se so desc ibed o ly by its mi imum illumi atio figu e says othi g about these effects, a d a NIR Se sitivity USB HDR Came a tested o ly i visible light leaves the illumi ated case u tested.
Teams that fi d these issues late must cha ge the illumi ato , the le s, the filte , o the e closu e afte ha dwa e is built. Biomet ic a d secu ity p oducts add a fu the stake, si ce a device that fails at ight fails exactly whe it is eeded. I dust ial use s face a quiete ve sio of the same isk, because a came a that sees poo ly u de its ow lighti g p oduces bo de li e images that i c ease false ejects a d missed defects o the ight shift.
The Me li -662CRS add esses this with the So y STARVIS 2 IMX662. The IMX662 is a 2MP (1920 x 1080) colo olli g shutte se so with a 1/2.8 i ch optical fo mat a d 2.9 mic o pixels. Its back-illumi ated desig collects light efficie tly, a d it etai s mea i gful espo se i to the ea -i f a ed ba d. That NIR Qua tum Efficie cy Came a behavio mea s a la ge sha e of the photo s f om a 850 a omete o 940 a omete illumi ato becomes sig al. The p actical be efit is flexibility. A i teg ato ca lowe LED powe to save cu e t a d heat, sho te the exposu e to f eeze motio , hold gai dow to p otect detail, o take a mix of all th ee. This makes the module a NIR E ha ced Low-Light Came a i the se se that matte s to a illumi ated system, because it uses the light the system supplies. Vadzo does ot publish a si gle se sitivity figu e as a p omise, si ce esults depe d o the illumi ato , the le s, the dista ce, a d the ta get, a d it e cou ages teams to measu e with thei ow setup.
Wavele gth choice i volves a t ade-off that Vadzo helps i teg ato s weigh. Illumi atio ea 850 a omete s is ge e ally bette eceived by silico se so s, but it ca show a fai t ed glow to people looki g di ectly at the LEDs. Illumi atio ea 940 a omete s is i visible to the eye, which suits cove t o comfo t-se sitive devices, but se so s espo d mo e weakly the e, so mo e optical powe o lo ge exposu e is usually eeded. Vadzo evaluates the module u de illumi atio i both commo ba ds a d sha es what the i teg ato should expect, so the choice is made with data a d ot with habit. Some p oducts use both ba ds, fo example, a cove t 940 a omete a ay at the pe imete a d a 850 a omete a ay at a e t y eade , a d the same module ca se ve both.
HDR plays a suppo ti g ole. Nea i f a ed illumi ato s c eate hot spots, a d glossy su faces, eyeglasses, a d metal pa ts etu b ight eflectio s that ca swamp ea by detail. Whe the device also wo ks outdoo s o ea wi dows, su light adds mo e va iatio . The se so ‘s HDR mode combi es exposu es so that b ight eflectio s a d dim egio s ca sha e o e f ame. This keeps the NIR Se sitivity USB HDR Came a behavio useful i the messy lighti g that eal i stallatio s p ese t.
Optical choices emai with the i teg ato , a d Vadzo suppo ts them. Usi g the ea i f a ed ba d ge e ally equi es a optical path that does ot block it, eithe th ough a le s without a i f a ed cut filte o th ough a filte that passes the illumi ato ba d. Vadzo advises teams to choose the le s a d filte ea ly, to p efe le ses co ected fo ea -i f a ed focus, a d to co fi m focus u de illumi atio . The came a e ume ates as a UVC device ove USB 2.0, a d si ce USB 2.0 has limited ba dwidth, 1080p video t avels i a comp essed fo mat. The illumi ato is ot pa t of the came a. Its selectio , d ivi g, a d eye safety emai the i teg ato ‘s espo sibility, which matte s most i biomet ic devices whe e people look at the LEDs f om close a ge. Pulsed illumi atio ca also educe ave age powe a d heat, a d i teg ato s who pla to pulse thei LEDs should co fi m how the exposu e timi g of a olli g shutte se so i te acts with the pulse so that eve y ow eceives the same light.
