Will IR Illuminator work with any CCD Camera?

Telephoto assemblies made of mirrors only such as Cassegrain designs have no color aberrations and work well with silicon CCDs over their full wavelength range for long focal lengths. Schmidt Cassegrain, Maksutov, and Ritchie Chretien designs have with weak corrector lenses little chromatic aberrations. Very fast (F/1.0) catadioptric designs exist with wide spectral range and flat fields are used for night vision devices. There are also fast zoom lenses (non mirror) specifically designed to have good correction from 400 to 950 nm for night surveillance cameras.

On top of all that, if the Bayer filter matrix uses organic dye filters (not multilayer interference filters), they are probably transparent to IR. That means that IR light passes through red, green, *and* blue filters, and looks like white light to the sensor. This desaturates all of the colours in the image. Blocking IR is necessary to avoid this.

If the camera did use interference filters (I don't know if any Bayer matrix filters are actually done this way), the IR would likely pass through only the red filter, and look like excess red light. This still messes up colour reproduction, because objects look redder to the camera than they do to the eye under IR-rich illumination.

Dave

On 30 Dec 2006 19:28:31 -0800, snipped-for-privacy@yahoo.com Gave us:

IR illumination night vision cameras allow you to see objects the illumination is cast on at night without being spotted yourself (UNLESS IR IS USED by the other side as well)

IR imagery cameras observe the natural emissions from any object and do not need or gain anything from IR illumination.

One is reflected IR light from surfaces which allow you to delineate them from the reflections. The other is a quantitative thermal image composed from the levels of IR all the objects in view emit on their own.

CCDs that are not specifically for IR must be worked on to get there. The baseline noise is higher so they typically like being chilled. They also utilize a germanium or other IR only transmissive window in them.

Regular cameras that claim to see in IR usually are pretty poor examples of it.

On Sat, 30 Dec 2006 22:49:36 -0500, "Robert L Bass" Gave us:

Snipped top posted CRAP.

Top posting TOFU Usenet idiot.

Also, Usenet line lengths should be limited BY THE POSTER at 74 characters or less.

Bone up on the forums you invade. It matters not what you may or may not know about a subject if you refuse to respect the conventions of the forum.

This ain't your e-mail, and I would care if you claimed to have been posting for years. You are still an utter dipshit if you can't learn and follow conventions.

f-u set for amusement.

lsmft

Yes there is fuckknuckle. Fix the line length like you were told, quit top posting, and hurry up and get on that respirator so you can't pollute Usenet anymore.

I just want to mention that these two different IR camera types work from very different IR wavelength ranges and use different sensors.

Cameras that work from IR illumination, with at most very few exceptions (I can't name any), work from infrared wavelengths generally in the IR-A range, which is .7 to 1.5 micrometers. For that matter, most of such work with illuminators is done with a narrower range, since silicon IR photodetectors don't do well with wavelengths longer than about 1.2 or so micrometers, and wavelengths a bit longer than .7 micrometer (up to .82 easily, maybe .9 or so) are visible enough for one to see the light source in the dark.

As for thermal IR - keep in mind that a 3000 K halogen lamp filament has peak close to 1 micrometer and at .4 micrometer (borderline violet-UV) output is down to about 7% of peak. At 300 nm output is close to or a little over 1% of peak. Keep in mind that this translates to 300 Kelvin radiation peaking close to 10 micrometers, 7% of peak at 4 micrometers, and 1% of peak at or hardly below 3 micrometers. I have a non-contact thermometer and IIRC it works from the 7-14 micrometer range according to its documentation.

Please know that "room temperature thermal IR" is generally absorbed by glass, water and most other transparent objects. A non-contact IR thermometer will not see through these objects but read the temperature of these objects.

Further digressing, many materials that absorb 10 micrometer ballpark IR, even if transparent in the visible, are transparent at microwave and radio frequencies. IIRC, Hertz managed some determination of an index of refraction of some material for radio waves from some kind of spark transmiter (presumably of frequency high enough to do this with) before Tesla and Marconi, before there was electronics. There are some materials with more limited rages of failing to be transparent to medium/long IR wavelengths. What comes to my mind now are some halides (such as potassium chloride - hygroscopic!) and (probably not all) non-metallic elements and non-metallic isotropes of elements in the 4 and 5 column of the periodic table (where 3-8 are the last 6 and 1,2 are the first 2), in periods/rows at least 4. Germanium and silicon come to my mind as being mentioned as transparent to "mid-IR"/"far-IR", and probably not transparent to all wavelengths in these ranges.

- Don Klipstein ( snipped-for-privacy@misty.com)

(I snip after that to edit for space)

So now it appears to me that someone that has drawn a lot of complaints, and often done so badly as used derogatory words employed mainly by people of age 9-15, and who has changed handles here a few times in the past decade, just got a new one.

In my experience, the biggest complainers of top posting tend to be those trying to establish themselves as not the very bottom of lower levels of the heap.

Do I need to mention past handles and some nicknames for one of them for what I think profiles well as authoring ?

I would advise getting another new handle, and not peck on others in ways done in lower levels of some pecking order. Peck on 2nd or 3rd from bottom - if you succeed, that gets you 3rd-4th from bottom. (And I say this at my risk of being pecked on by 5th-from-bottom and attempts from steps lower as opposed to avoiding some pecking order that the lowlifes all too often need to establish).

- Don Klipstein ( snipped-for-privacy@misty.com)

You are a real piece of work. I bet your eyes are crosseyed from all that cut and paste, huh?

To anyone reading this, dismiss this idiot's composition on cameras. If you want to know which camera to use post on ASA or cctvfourm.com.

Since the OP is clearly interested in CCTV surveillance cameras, it is highly unlikely that he needs information on thermal imaging cameras. I doubt he'll be helped further along the path to CCTV enlightenment by a lengthy dissertation on IR absorption and more than the typical home audio user needs a course in waveform propagation.

Someone else already noted that IR illuminators will work with any CCTV camera that doesn't have an IR filter.

unlikely that he needs information on thermal imaging

by a lengthy dissertation on IR absorption and more

that doesn't have an IR filter.

sdl