IR distance question

[mike_va 0]

This website is a good read, but I have a question that perhaps someone with more experience than me can help with.

 

http://www.cctv-information.co.uk/i/Why_LED_lighting_is_the_best_technology_to_use_with_CCTV

 

I'm just curious why IR would have as an advantage longer distances? Or is this just certain types that have a different beam spread?

 

Also it seems looking at sensor sensitivity vs wavelength sensors typically have less sensitivity at 850nm compared to the visible range.

[Soundy 1]

Camera sensors' sensitivity does fall off as you get farther from the visible spectum, just as it does with human sight... just not as quickly. So yes, you will lose sensitivity the further into the IR range you go.

 

It's generally true of any form of energy that lower frequencies/longer wavelengths will travel farther (depending somewhat on the transmission medium). That's why VLF is used for long-distance (especially underwater) radio communications, and why low sounds carry farther than higher-pitched sounds.

 

In this case, however, we don't know how they're calculating "longer distances"... are they using IR at the same measured output as white light? Are they focusing it more? Are they using the same camera with the same configuration, or are they comparing a basic B&W camera with no IR cut filter for the IR measurements, vs. a color camera WITH the IR cut filter for the white-light measurements? Take that cut filter off and you'll see more out of the color camera as well (although the color will be off).

 

It's a pretty vague statement - I mean, they bounce visible-light lasers off the freakin' moon.

 

Personally, I'm a fan of white-light, *motion activated* illuminators/flood lights as a deterrent. "Light pollution" is thereby limited to when there's actually movement... a bright light snapping on while he's prowling around will often startle a prowler enough to simply scare him off... and think about it, if you're creeping around in the dark and a bright light comes on, what's the first thing you're going to do? Probably look for the source of the light in case it's someone you need to run away from. Have a camera located near that light source, and bingo: nice, clear, well-lit, full-color facial shot.

[mike_va 0]

Thanks Matt. Have to agree about the visible light. I leave a flood on out back, have not added motion yet. As it was a general statement, I was assuming all things being equal from a light standpoint which is what seemed confusing. I'll try to look into the wavelength aspect.

 

There are some spots that I wanted to play with IR, due to the light pollution aspect and also people might get annoyed. Down the street one of the neighbors had a motion light backing to a walking path. Personally I appreciated this, but I think one of the teenagers most likely did not and ripped it off the house. If I remember the conversation right he was going to add some cameras...

 

Kid is lucky he didn't get caught or..., guy's neighbor is in the Secret Service and there are a lot of other TS types in the neighborhood.

[mike_va 0]

Have not found much yet but ran across a similar statement in Axis "Lighting for Network Video"

[rory 0]

I dont know why, but white LEDs suck compared to Infrared LEDs.

The light "looks" like its there somewhat to the human eye, and its bright and painful to our eyes, but the cameras just dont like it as much, even in BW mode. The main reasons to use visible light would be you can use ANY camera color OR bw cheap OR expensive and its added security. Normally get a better image also, but not with White LEDs. I used the Fusion 50 and 100 from Raymax and used Extreme's Infrared for years prior, both at the same location. My cheap dusk to dawn NON LED puts out a ton of light though, draws more current.

[rory 0]

as for 850 vs 950 nm .. a stronger filter means less light gets through.

[Stanislav 0]

Three years ago I made several calculations and practical experiments with IR LED Illuminators and cameras with different image sensors. In power efficiency for B/W CCD sensors( taking into account IR spectrum and CCD spectral sensitivity) 920nm IR LED worse than even incandescent lamp in 4-5 times.

For example, taking into account about 50% light loss in spotlight's armature, 25Watt 920nm IR Illuminator and 10 Watt spotlight with the same angle of radiation with incandescent lamp produce approximately the same images from B/W CCD camera.

850nm IR LED worse than incandescent lamp in 2-3 times.

White LED is better than incandescent lamp for B/W sensors in 1.5-3 times, for Color sensors in 3-5 times.

http://www.cctvcad.com/videocad_help/prim18_irmes.htm

[IRCCTV 0]

Well IR distance totally depends on the Camera, Lens, and the illumination source, and the resolution.

 

Active IR can range from 800nm up to 1550nm for illumination.

 

Active Ir you can get ranges from 5m up to 10km but I prefer to only use active Ir up to 3km becasue afer that you lose the ability to identify targets in which case thermal imaging should be used.

 

The company I work for deigns Active IR and passive thermal systems for extreme long range imaging for boarder protection, perimeter defense, and Aeriel surveillance.

 

demo videos: http://www.ascendentgroup.com/zlid.htm

 

Advantages Over Thermal Imaging

Active IR imaging has significant advantages over thermal imaging by producing images with up to 500% higher resolution. Active IR also has the ability to go through optically pure substances such as windshields. Since thermal relies on heat waves it works great for long range detection but does not have the ability to capture details making virtually useless for identification unlike optical systems.

 

 

Unparalleled Active IR Imaging

Unlike Unlike traditional IR

night vision cameras that use standard CCD, lens and LED’s that operate autonomously, Ascendent’s Active IR cameras have integrated AMC (Automatic Processor Control) and EPC (Electronic Photocell Control), MICF and a host of other technologies, to ensure the Optics, image sensor, lens, MICF and Super bright IR LED’s work in tandem to eliminate hot-spots, washout, and under exposure usually associated with IR cameras for flawless active IR performance up to 200m (650ft) Ascendent’s IR are optimally spaced and use different sized and angled LED’s to provide evenly distributed IR to offer both long rage and wide angle illumination the (MICF) mechanical IR cut filter blocks parasitic light before it reaches the sensor father enhancing the image clarity. Ascendent’s IR cameras are designed to offer absolute performance and use the highest quality components and unique manufacturing processes to increase performance and reliability, such as dual PC board design and hand welding of all the IR LED’s (Vista and Apex Series). All these components are integrated into Rugged IP 66-68 Nema 4X enclosures constructed of extruded aluminum and thick high impact optically pure polycarbonate to withstand the most brutal assaults and extreme climates for 24/7 surveillance in mission critical applications.

 

 

Zoom Laser IR Diode (ZLID)

Ascendent's ZLID laser illuminators combine laser diode technology with precision engineered optics and sophisticated electronics to provide extreme long range Active IR illumination greatly exceeding both performance and Distance over traditional IR LED illumination in application that require over

200m (650ft) of illumination. Ascendents ZLID (Zoom Laser IR Diodes) Technology (IR Laser) synchronizes IR intensity and area illumination with motorized zoom lens for outstanding active IR performance, eliminating over exposure, washout, and hot-spots for unparalleled performance at distances up to3.5km (11,500ft) in complete darkness.

 

The Sigma Series PTZ delivers long range day/night surveillance. Its powerful 20-3000mm or 5000mm motorized zoom lens can detect intruders at distances of up to 35km. The high-output, continuous-wave laser provides recognition for up to 8km and identification up to 3km. Ascendents Sigma series provides unparalleled video surveillance and situation assessment for perimeter protection and border defense.

 

Thermal imaging

Unlike optical systems, which like the human eye requires light, thermal imaging uses infrared electromagnetic radiation 900-14,000 nm wavelengths (heat) to produce images. All objects that are above -213C emit infrared radiation, the amount of radiation emitted is proportional to the temperature of the objects and thermal imaging detects these minute temperature variations and thus accurately reproduces the scene. Since all objects emit infrared radiation a thermal imager is able to "see" the environment regardless of lighting conditions.

 

Ascendnt offer thermal imagers with up to 1280 HD resolution with lens up to 1000mm (up to 2000mm by the end of 2013) for up to 50km of detection.

 

Best Regards

Tim

 

e: tim@ascendentgroup.com

Skype: tim.ascendent

http://www.ascendentgroup.com