Top Gear, the Merc? with the IR headlights

[bryan35]

Now that is interesting.

I wonder what frequency IR they use, surely not 905nm.

I know that some headlights can jam laser guns already, but if any can surely these are the ones, especially if they use a chopper to dim them, at 33kHz perhaps!.

Get a speed reading off that.

Wonder how the law will sit with that one?

[parrot of doom]

I heard years ago that Volvo were experimenting with UV headlamps (low power), as many clothes are washed with bleach this shows up extremely well when a UV light is pointed at them.

Dunno if they're using it though.

[rsvmilly]

Cadillac tried this type of thing in the past.

[Pigeon]

parrot of doom said:

I heard years ago that Volvo were experimenting with UV headlamps (low power), as many clothes are washed with bleach this shows up extremely well when a UV light is pointed at them. Dunno if they're using it though.

Not bleach - it's called "optical brightener". The "whiter than white" claim about washing powder is not as nonsensical as it sounds, as clothes washed in this stuff do in fact give off more visible light than by straightforward reflection as this stuff converts solar UV into visible light. Pretty well all washing powders use this con.

"Xenon" headlights could potentially cause clothes to light up as the light source produces large amounts of UV, but most of it will be filtered out by the glass.

I didn't see the relevant Top Gear, and am somewhat puzzled as to why anyone would fit IR headlamps as not only is IR useless for this sort of thing but conventional headlamps give off a lot more IR than visible light anyway. What were they on about?

[smeggy]

Pigeon said:

I didn't see the relevant Top Gear, and am somewhat puzzled as to why anyone would fit IR headlamps as not only is IR useless for this sort of thing but conventional headlamps give off a lot more IR than visible light anyway. What were they on about?

A visual headlamp based lighting system augmented with an IR flood lamp is actually very good idea – for more than one reason!

Reason 1:

The visual dipped lights can be used as usual, to illuminate the immediate vicinity, as well as warning others of your presence.

A powerful IR flood lamp, coupled with a digital video imager and head-up-display, would be ideal as a main beam system – enabling vision over great distances without dazzling other road users, especially drivers of oncoming cars on un-separated carriageways.

It would be greatly preferable to have a pulsed LED array; controlled modulation will provide a means of illuminating passive objects, without your eyes being overwhelmed by steady state or synchronised IR sources. Short pulses will also result with reduced motion blur, just like ANPR.


In short: this would be a great safety aid




Reason 2

There’s absolutely no hope of anyone being able to prove intent of jamming Lidar, even when it quite obviously does just that


The big question is: does anyone have the balls to try this?

[cptsideways]

Anybody know any Merc dealers down my way to try it out?

>> Edited by cptsideways on Tuesday 5th July 14:50

[maxf]

Pigeon said:

I didn't see the relevant Top Gear, and am somewhat puzzled as to why anyone would fit IR headlamps as not only is IR useless for this sort of thing but conventional headlamps give off a lot more IR than visible light anyway. What were they on about?

It was going to be used in tandem with 'normal' headlamps and display an image on a screen to show badgers and other moving chicanes well in advance. They only briefly mentioned it but I think thats correct?

[scoule]

bryan35 said:

Now that is interesting. especially if they use a chopper to dim them, at 33kHz perhaps!.

33Khz? Any particular reason why anyone should "avoid" using that frequency?

[smeggy]

scoule said:

33Khz? Any particular reason why anyone should "avoid" using that frequency?

That's the typical carrier frequency for low data rate IR remote controllers. It doesn't apply in the case of Lidar which outputs a series of pulses at a much lower frequency (~150Hz IIRC).

[bryan35]

not entirely true, the carrier wavelength is 905nM, which is then modulated at 33kHz. This could then be refered to as the 'carrier' but is really a sub carrier, which is then modulated again at about 150Hz like you say.

Pretty sure Lidar uses the same as it makes the detection easier. It's much easier to make a high q factor 33kHz band pass filter than the same at 905nM.

[havoc]

Armed forces were using IR spotlights coupled with IR imaging back in the 50's as a way of fighting with tanks at night...only thing back then was the spots were the size of an average TV, and the imagers were £££.

Taken a while to come up with, but long overdue...HUD connected to either low-light vidcamera or to something ir-related is a VERY good safety idea for rural roads at night.

[smeggy]

bryan35 said:

not entirely true, the carrier wavelength is 905nM, which is then modulated at 33kHz. This could then be refered to as the 'carrier' but is really a sub carrier, which is then modulated again at about 150Hz like you say.

Hi Bryan.

Your comment is correct if applied to something like a bog-standard remote control, but it is not the case with lidar.

bryan35 said:

Pretty sure Lidar uses the same as it makes the detection easier. It's much easier to make a high q factor 33kHz band pass filter than the same at 905nM.

No-one will disagree that modulation will make carrier detection easier, but it is impossible for lidar to operate in this mode. I recently checked the patents of the LTI 2020; there is no mention of a carrier, only the pulse train.

The timing of the received edges are critical for the timing calculation because ‘C’ is so great; any resonant filtering will completely destroy the timing information. If you walk through the maths, the unit must have windows of 20 pico seconds (or ‘clocked in’ at 50GHz) to get a resolution of 1mph, hence use of an interpolation system.

It’ll all be over by the time a 33khz filter has even started moving.