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 ;)
Ir illuminators
Started by ●September 11, 2023
Reply by ●September 12, 20232023-09-12
Reply by ●September 12, 20232023-09-12
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.
Reply by ●September 12, 20232023-09-12
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!
Reply by ●September 13, 20232023-09-13
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
Reply by ●September 13, 20232023-09-13
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.
Reply by ●September 13, 20232023-09-13
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?
Reply by ●September 13, 20232023-09-13
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
Reply by ●September 13, 20232023-09-13
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
Reply by ●September 13, 20232023-09-13
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 HobbsI 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.
Reply by ●September 13, 20232023-09-13
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 ....
