Ir illuminators...

[Don Y]

I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

 

[Lasse Langwadt Christensen]

mandag den 11. september 2023 kl. 23.50.46 UTC+2 skrev Don Y:

I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

if you are trying to save power you\'ll need a switching regulator so it is
trivial to control the output level and controlling the level instead of
number won\'t change the light pattern

 

[Don Y]

On 9/11/2023 3:11 PM, Lasse Langwadt Christensen wrote:

mandag den 11. september 2023 kl. 23.50.46 UTC+2 skrev Don Y:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

if you are trying to save power you\'ll need a switching regulator so it is
trivial to control the output level and controlling the level instead of
number won\'t change the light pattern

There are a lot of emitters (in many designs) so I suspect putting every
other or third, fourth, etc. in a different string -- still spread out
around the lens -- won\'t appreciably change the light pattern for the
sorts of scenes where lower illumination is acceptable.

I may opt to excite the illuminator with a higher potential
to get more compliance (some of the cameras I\'ve torn down
have as few as three emitters in a string -- with a dozen
or more strings! This seems like a lot is being lost in the
ballast)

I think I may have to hack together a prototype that
lets me control individual emitters so I can see what the
effect on illumination will be. That might make the driver
choice more obvious...

(the units I\'ve examined drive all of the emitters simultaneously,
regardless of how wired; so, PCB layout is the driving factor,
not \"dispersal of light\")

 

[Martin Brown]

On 11/09/2023 22:50, Don Y wrote:

I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

Decide what signal to noise in the video image is acceptable for your
application and use only that much artificial light.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

If you get down to 1 or 2 LEDs then that is a whole stop difference in
exposure, but once you go up to 2 or more LEDs you can get exposure
right to the nearest half stop which is good enough for all practical
purposes (even back in the days of conventional film).

You effectively want a sequence of LEDs lit up along the lines of:

2 3 4 6 8 11 16 22 32

just like the old f stops on a classical camera.

Beware that if they are too far off axis the lighting profile might
change as you switch more distant ones on and off.

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

Using the least amount of illumination you can get away with.

--
Martin Brown

 

[Don Y]

On 9/12/2023 12:28 AM, Martin Brown wrote:

On 11/09/2023 22:50, Don Y wrote:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

Decide what signal to noise in the video image is acceptable for your
application and use only that much artificial light.

I\'m trying to come up with *one* camera that I can \"adjust\"
to suit different scenes.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

If you get down to 1 or 2 LEDs then that is a whole stop difference in
exposure, but once you go up to 2 or more LEDs you can get exposure right to
the nearest half stop which is good enough for all practical purposes (even
back in the days of conventional film).

You effectively want a sequence of LEDs lit up along the lines of:

2 3 4 6 8 11 16 22 32

just like the old f stops on a classical camera.

The cameras I\'ve found (so far) tend to have a lot of emitters
(the one I toredown tonight had ~40). I can afford to move the
emitters *out* of the camera (and disable any that are internal)
but still need the Ir filter, inside, to be operable.

Beware that if they are too far off axis the lighting profile might change as
you switch more distant ones on and off.

Yes but most seem to be arranged in concentric rings.
I suspect the large numbers are intended just to boost range.

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

Using the least amount of illumination you can get away with.

The question is whether that can be obtained by running a bunch
of emitters at a low current *or* a fewer number at a higher
current.

(I\'ve already taken care of the case of using the camera
at an effective lower frame rate for scenes that aren\'t
changing -- much. But, there\'s only so much I can do
in software to juggle the power budget...)

 

[Dan Purgert]

On 2023-09-12, Don Y wrote:

On 9/12/2023 12:28 AM, Martin Brown wrote:
[...]
Beware that if they are too far off axis the lighting profile might
change as you switch more distant ones on and off.

Yes but most seem to be arranged in concentric rings.
I suspect the large numbers are intended just to boost range.

The multitude of LEDs in the ring(s) are to ensure the scene is
illuminated clearly. That is, they\'re less to increase range, and more
to combat things like multiple shadows or other visual artifacts
without resorting to a diffuser.

--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

 

[Martin Brown]

On 12/09/2023 09:32, Don Y wrote:

On 9/12/2023 12:28 AM, Martin Brown wrote:
On 11/09/2023 22:50, Don Y wrote:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

Decide what signal to noise in the video image is acceptable for your
application and use only that much artificial light.

I\'m trying to come up with *one* camera that I can \"adjust\"
to suit different scenes.

Even so your lowest power budget will still be when you have just enough
illumination to do the task at hand (and no more than that).

You effectively want a sequence of LEDs lit up along the lines of:

2 3 4 6 8 11 16 22 32

just like the old f stops on a classical camera.

The cameras I\'ve found (so far) tend to have a lot of emitters
(the one I toredown tonight had ~40).  I can afford to move the
emitters *out* of the camera (and disable any that are internal)
but still need the Ir filter, inside, to be operable.

Beware that if they are too far off axis the lighting profile might
change as you switch more distant ones on and off.

Yes but most seem to be arranged in concentric rings.
I suspect the large numbers are intended just to boost range.

Probably to act much like a ring flash in close up and macro work to
avoid there being any distinct shadows in the field of illumination.
That may not always be what you want - off axis illumination casts
better sharp shadows that highlight targets in the field of view.

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

Using the least amount of illumination you can get away with.

The question is whether that can be obtained by running a bunch
of emitters at a low current *or* a fewer number at a higher
current.

I suspect it will be very similar until you start pushing the power LEDs
quite hard. Conversion efficiency only falls off gradually with
increasing current until you get fairly close to Imax.

I\'d expect several emitters at lower current to be very slightly more
efficient but I doubt it is by enough to make more than 1% saving.

(I\'ve already taken care of the case of using the camera
at an effective lower frame rate for scenes that aren\'t
changing -- much.  But, there\'s only so much I can do
in software to juggle the power budget...)

You might want to take a look at QCUIAG who are the (amateur astronomy)
masters at tweaking standard webcams for ultra low light use.

http://www.qcuiag.org.uk

Although they mostly want longer exposures and low noise sensors and are
very price sensitive. Beginners destroy two or three when learning...


--
Martin Brown

 

[Don Y]

On 9/12/2023 2:29 AM, Dan Purgert wrote:

On 2023-09-12, Don Y wrote:
On 9/12/2023 12:28 AM, Martin Brown wrote:
[...]
Beware that if they are too far off axis the lighting profile might
change as you switch more distant ones on and off.

Yes but most seem to be arranged in concentric rings.
I suspect the large numbers are intended just to boost range.

The multitude of LEDs in the ring(s) are to ensure the scene is
illuminated clearly. That is, they\'re less to increase range, and more
to combat things like multiple shadows or other visual artifacts
without resorting to a diffuser.

That;s not what I\'m seeing. If I use, for example, every other
group of three emitters in the outer ring, coupled with the
alternate groups of three emitters in the inner ring, I get
uniform illumination -- but not as much distance if I turn
ALL of them on, simultaneously.

So, when the objective is near enough, I can easily drop
half of the power used in those \"extra\" emitters and
keep the same NEAR scene fidelity as if all were on.

 

[Don Y]

On 9/12/2023 7:46 AM, Martin Brown wrote:

On 12/09/2023 09:32, Don Y wrote:
On 9/12/2023 12:28 AM, Martin Brown wrote:
On 11/09/2023 22:50, Don Y wrote:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

Decide what signal to noise in the video image is acceptable for your
application and use only that much artificial light.

I\'m trying to come up with *one* camera that I can \"adjust\"
to suit different scenes.

Even so your lowest power budget will still be when you have just enough
illumination to do the task at hand (and no more than that).

Yes, but will it matter if I drive 4 emitters at the compass points
to 100% vs. 16 emitters (evenly filling in the gaps) at 25%? Or,
by extension, if I drive ALL of the emitters at a set of N different
power levels, will this give the same results as driving N subsets
at on/off levels?

You effectively want a sequence of LEDs lit up along the lines of:

2 3 4 6 8 11 16 22 32

just like the old f stops on a classical camera.

The cameras I\'ve found (so far) tend to have a lot of emitters
(the one I toredown tonight had ~40).  I can afford to move the
emitters *out* of the camera (and disable any that are internal)
but still need the Ir filter, inside, to be operable.

Beware that if they are too far off axis the lighting profile might change
as you switch more distant ones on and off.

Yes but most seem to be arranged in concentric rings.
I suspect the large numbers are intended just to boost range.

Probably to act much like a ring flash in close up and macro work to avoid
there being any distinct shadows in the field of illumination. That may not
always be what you want - off axis illumination casts better sharp shadows that
highlight targets in the field of view.

I\'ve found \"Ir Illuminators\" (i.e., no camera). They are just large
arrays of emitters arranged in whichever configuration they will
fit in the enclosure. No attention to geometry. So, \"more is
better\" seems to be the operative premis.

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

Using the least amount of illumination you can get away with.

The question is whether that can be obtained by running a bunch
of emitters at a low current *or* a fewer number at a higher
current.

I suspect it will be very similar until you start pushing the power LEDs quite
hard. Conversion efficiency only falls off gradually with increasing current
until you get fairly close to Imax.

What about at the *low* end? Are they as (luminous) efficient
at 10% drive as at 90%? Or 50%?

The OS (which manages resources in any system) has to be able
to manage the power budget of the different tasks in the
system. It would be nice if this was a simple calculation
(it\'s already NP-complete -- NP-Hard?)

I\'d expect several emitters at lower current to be very slightly more efficient
but I doubt it is by enough to make more than 1% saving.

But, does that extend to the LOWEST end of the range?
I.e., is there a point where I am driving 40 emitters
at a level that *exceeds* the requirements that could
be met with just 20? I.e., I\'m just heating extra die
and not getting anything useful from them?

(I\'ve already taken care of the case of using the camera
at an effective lower frame rate for scenes that aren\'t
changing -- much.  But, there\'s only so much I can do
in software to juggle the power budget...)

You might want to take a look at QCUIAG who are the (amateur astronomy) masters
at tweaking standard webcams for ultra low light use.

http://www.qcuiag.org.uk

Although they mostly want longer exposures and low noise sensors and are very
price sensitive. Beginners destroy two or three when learning...

I\'m not as concerned over how to achieve low light (as in
many cases I will be pushing a lot of light from the emitters
but not as much as is *available*). My focus is entirely on power
(and the efficiency consequences that come with that).

But, I\'ll have a look. There might be some assertions that
i can rely on to guide my efforts (I\'d hate to throw together
a design only to discover it\'s only operated at extremes)

 

[Martin Brown]

On 12/09/2023 18:44, Don Y wrote:

On 9/12/2023 7:46 AM, Martin Brown wrote:

I suspect it will be very similar until you start pushing the power
LEDs quite hard. Conversion efficiency only falls off gradually with
increasing current until you get fairly close to Imax.

What about at the *low* end?  Are they as (luminous) efficient
at 10% drive as at 90%?  Or 50%?

They seem to be linear right down to the point where you can barely see
them which for a high efficiency modern LED is somewhere around 1-10uA
once your eyes are dark adapted. I\'d be surprised if IR LEDs were any
different (I found a datasheet for a suitable one).

It only becomes non-linear and lower efficiency at >Imax/4. eg

https://www.mouser.co.uk/datasheet/2/917/downloaddatafile-2853791.pdf

See the graph of luminous flux vs I_f log log graphs can hide a
multitude of sins but that one is die straight for I_f < 1A.

I\'d expect several emitters at lower current to be very slightly more
efficient but I doubt it is by enough to make more than 1% saving.

But, does that extend to the LOWEST end of the range?
I.e., is there a point where I am driving 40 emitters
at a level that *exceeds* the requirements that could
be met with just 20?  I.e., I\'m just heating extra die
and not getting anything useful from them?

In general I think they are so close to linear output unless over driven
quite hard that it is linear to all intents and purposes all the way
down to zero intensity.


--
Martin Brown

 

[Lasse Langwadt Christensen]

tirsdag den 12. september 2023 kl. 08.50.14 UTC+2 skrev Don Y:

On 9/11/2023 3:11 PM, Lasse Langwadt Christensen wrote:
mandag den 11. september 2023 kl. 23.50.46 UTC+2 skrev Don Y:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

if you are trying to save power you\'ll need a switching regulator so it is
trivial to control the output level and controlling the level instead of
number won\'t change the light pattern
There are a lot of emitters (in many designs) so I suspect putting every
other or third, fourth, etc. in a different string -- still spread out
around the lens -- won\'t appreciably change the light pattern for the
sorts of scenes where lower illumination is acceptable.

I may opt to excite the illuminator with a higher potential
to get more compliance (some of the cameras I\'ve torn down
have as few as three emitters in a string -- with a dozen
or more strings! This seems like a lot is being lost in the
ballast)

I think I may have to hack together a prototype that
lets me control individual emitters so I can see what the
effect on illumination will be. That might make the driver
choice more obvious...

(the units I\'ve examined drive all of the emitters simultaneously,
regardless of how wired; so, PCB layout is the driving factor,
not \"dispersal of light\")

I\'m sure you will find a way to make something simple extremely complicated

 

[Don Y]

On 9/12/2023 2:09 PM, Lasse Langwadt Christensen wrote:

tirsdag den 12. september 2023 kl. 08.50.14 UTC+2 skrev Don Y:
On 9/11/2023 3:11 PM, Lasse Langwadt Christensen wrote:
mandag den 11. september 2023 kl. 23.50.46 UTC+2 skrev Don Y:
I have lots of cameras in my current design (solve problem once, apply
many times!).

Most instances require Ir illuminators (I am trying to standardize on
a single device \"used appropriately\" instead of different devices
for the different applications).

I\'d like to save power on the illuminators.

One approach is to drive the entire \"illuminator\" with different
current levels to get varying intensity output.

Another approach is to drive varying *numbers* of emitters
(at fixed drive levels).

[In each case, closing the loop with video feedback to ensure
I\'m not over-illuminating the scene]

Suggestions as to which will give me most *effective* control
vs. power dissipated?

if you are trying to save power you\'ll need a switching regulator so it is
trivial to control the output level and controlling the level instead of
number won\'t change the light pattern
There are a lot of emitters (in many designs) so I suspect putting every
other or third, fourth, etc. in a different string -- still spread out
around the lens -- won\'t appreciably change the light pattern for the
sorts of scenes where lower illumination is acceptable.

I may opt to excite the illuminator with a higher potential
to get more compliance (some of the cameras I\'ve torn down
have as few as three emitters in a string -- with a dozen
or more strings! This seems like a lot is being lost in the
ballast)

I think I may have to hack together a prototype that
lets me control individual emitters so I can see what the
effect on illumination will be. That might make the driver
choice more obvious...

(the units I\'ve examined drive all of the emitters simultaneously,
regardless of how wired; so, PCB layout is the driving factor,
not \"dispersal of light\")

I\'m sure you will find a way to make something simple extremely complicated

If you want bog-standard performance, then you SETTLE for
what you get OTS.

 

[Don Y]

On 9/12/2023 1:40 PM, Martin Brown wrote:

On 12/09/2023 18:44, Don Y wrote:
On 9/12/2023 7:46 AM, Martin Brown wrote:

I suspect it will be very similar until you start pushing the power LEDs
quite hard. Conversion efficiency only falls off gradually with increasing
current until you get fairly close to Imax.

What about at the *low* end?  Are they as (luminous) efficient
at 10% drive as at 90%?  Or 50%?

They seem to be linear right down to the point where you can barely see them
which for a high efficiency modern LED is somewhere around 1-10uA once your
eyes are dark adapted. I\'d be surprised if IR LEDs were any different (I found
a datasheet for a suitable one).

It only becomes non-linear and lower efficiency at >Imax/4. eg

https://www.mouser.co.uk/datasheet/2/917/downloaddatafile-2853791.pdf

See the graph of luminous flux vs I_f log log graphs can hide a multitude of
sins but that one is die straight for I_f < 1A.

I\'d expect several emitters at lower current to be very slightly more
efficient but I doubt it is by enough to make more than 1% saving.

But, does that extend to the LOWEST end of the range?
I.e., is there a point where I am driving 40 emitters
at a level that *exceeds* the requirements that could
be met with just 20?  I.e., I\'m just heating extra die
and not getting anything useful from them?

In general I think they are so close to linear output unless over driven quite
hard that it is linear to all intents and purposes all the way down to zero
intensity.

OK. Then I can scale nominal performance just by controlling the
drive to the illuminator.

And, if I want to overdrive it at a reduced duty cycle, I\'ll
have to consider thermal effects (I suspect most illuminators
just run at DC).

Thanks!

 

[Liz Tuddenham]

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

--
~ Liz Tuddenham ~
(Remove the \".invalid\"s and add \".co.uk\" to reply)
www.poppyrecords.co.uk

 

[John Larkin]

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

 

[Joe Gwinn]

On Wed, 13 Sep 2023 07:51:50 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

X-Ray vision?

 

[Phil Hobbs]

Joe Gwinn <joegwinn@comcast.net> wrote:

On Wed, 13 Sep 2023 07:51:50 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

X-Ray vision?

It’s only bad if it’s unmodulated CW.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

 

[Liz Tuddenham]

John Larkin <jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

Why did the reversing cameras in my van come with I.R. illuminators
built-in?

I had to dismantle the cameras and disconnect the L.E.D.s before they
would work properly in dim light. Now the 21-watt reversing lamp gives
more than enough light for the cameras to work properly, even in fog or
heavy rain.


--
~ Liz Tuddenham ~
(Remove the \".invalid\"s and add \".co.uk\" to reply)
www.poppyrecords.co.uk

 

[John Larkin]

On Wed, 13 Sep 2023 15:35:37 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

Joe Gwinn <joegwinn@comcast.net> wrote:
On Wed, 13 Sep 2023 07:51:50 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

X-Ray vision?


It’s only bad if it’s unmodulated CW.

Cheers

Phil Hobbs

I suppose the illuminator could be nanosecond pulsed and the imager
fast-gated. Get some time-of-flight data too. Maybe some advanced
civilization could do that.

But more likely, movies do that to make evil robots look more evil.
Good robots don\'t have eyes that glow.

 

[Joe Gwinn]

On Wed, 13 Sep 2023 09:02:37 -0700, John Larkin
<jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 15:35:37 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

Joe Gwinn <joegwinn@comcast.net> wrote:
On Wed, 13 Sep 2023 07:51:50 -0700, John Larkin
jjlarkin@highlandtechnology.com> wrote:

On Wed, 13 Sep 2023 13:57:07 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:

Don Y <blockedofcourse@foo.invalid> wrote:

[...] I can afford to move the
emitters *out* of the camera (and disable any that are internal)

In my experience that is by far the best thing to do.

Having the emitters inside the camera housing causes reflection off the
window which reduces the contrast of the scene. If the window \'fogs\',
even slightly, the scene will almost \'white-out\'. If the camera is
outdoors and there is the slightest mist, the light will be reflected by
the droplets straight back into the camera lens making it unusable.

The illumination needs to come from the sides or above or below --
anywhere except directly in line with the camera. Slight shadows will
also give a 3D effect which helps with recognising people and objects.

Why do evil robots in movies have eyes that glow? That\'s bad optics.

X-Ray vision?


It’s only bad if it’s unmodulated CW.

Cheers

Phil Hobbs

I suppose the illuminator could be nanosecond pulsed and the imager
fast-gated. Get some time-of-flight data too. Maybe some advanced
civilization could do that.

Well, if they use a crypto key generator to determine when to emit a
flash, they\'ll have security too.

But more likely, movies do that to make evil robots look more evil.
Good robots don\'t have eyes that glow.

They wouldn\'t do that, it would be false advertising ....