# Infrared cameras for detecting people inside cars

## Main Question or Discussion Point

For an experiment we are doing, we need to be able to accurately detect people inside a car moving at high speed. Any suggestions for an IR/other camera that can help us effectively do it? The car has a hot engine, so I am concerned an IR camera may or may not work. Any thoughts.

Cost not a big concern though would like it to be <$2K if possible. ## Answers and Replies Related General Engineering News on Phys.org Mech_Engineer Science Advisor Gold Member A long wave infrared camera wouldn't work because glass is opaque that far into the infrared spectrum... My guess would be a camera system in the near-infrared spectrum (night vision rather than thermal) that can recognize a head shape. Last edited: berkeman Mentor For an experiment we are doing, we need to be able to accurately detect people inside a car moving at high speed. Any suggestions for an IR/other camera that can help us effectively do it? The car has a hot engine, so I am concerned an IR camera may or may not work. Any thoughts. Cost not a big concern though would like it to be <$2K if possible.
Too funny -- I started laughing until I realized that you want to detect how many people there are in the moving car. I was thinking, "of course there are people in moving cars!" :rofl:

What angles do you have available? Just from the sides, or can you put a camera facing the oncoming cars on an overcrossing support?

Welcome to the PF, BTW.

berkeman
Mentor
BTW, what is the application? Something like catching carpool cheaters or something?

this may be useful
attachment-TUBITAK– MRC, International Laboratory for High Technologies
(ILHT), 41470 Gebze–Kocaeli, Turkey
Web: http://www.mam.gov.tr/eng/institutes/me/me-uytl.htm [Broken]

http://www.camero-tech.com/xaver800.shtml [Broken]

#### Attachments

• 1.3 MB Views: 495
Last edited by a moderator:
Too funny -- I started laughing until I realized that you want to detect how many people there are in the moving car. I was thinking, "of course there are people in moving cars!" :rofl:

What angles do you have available? Just from the sides, or can you put a camera facing the oncoming cars on an overcrossing support?

Welcome to the PF, BTW.
Hahaha, you are right. I should have been more careful with my words :-)

Yes, it is for a carpool violation application. Yes, we can put camera facing the cars on overcrossing support. Thanks for any ideas.

this may be useful
attachment-TUBITAK– MRC, International Laboratory for High Technologies
(ILHT), 41470 Gebze–Kocaeli, Turkey
Web: http://www.mam.gov.tr/eng/institutes/me/me-uytl.htm [Broken]

http://www.camero-tech.com/xaver800.shtml [Broken]
Thanks for the input. Any idea if this would work on high speed vehicles? The pdf was great but unfortunately I am unable to open the website - "page not found".

Last edited by a moderator:
I saw a video a while back about removing the IR filter from a DSLR and replacing it with a different filter will make the camera take IR photographs, but I am not to sure on this claim.

berkeman
Mentor
I saw a video a while back about removing the IR filter from a DSLR and replacing it with a different filter will make the camera take IR photographs, but I am not to sure on this claim.
It's common for digital cameras and camcorders to be able to image the near infrared. Just look at your TV IR remote control in your cell phone camera or other digital camera..

The IR filter that you mention was likely to block near IR from the imaging CCD array of the DSLR. Removing it (or replacint it with an IR transparent filter) would let it image in the near IR.

Mech_Engineer
Gold Member
I saw a video a while back about removing the IR filter from a DSLR and replacing it with a different filter will make the camera take IR photographs, but I am not to sure on this claim.
There is a niche of digital photographers that like to take infrared photos. From the factory, the camera comes with a filter that filters NIR and transmits visible. The photographers remove the filter and replace it with one that transmits NIR, and blocks visible so they can take a pure NIR picture.

http://en.wikipedia.org/wiki/Infrared_photography

Digital SLR's have actually created a boom in this hobby, especially ones that have a live view option because you can see in real-time what the infrared picture will look like helping with focusing and exposure.

berkeman
Mentor
Cool info, ME. I didn't know that.

Removing the IR cutoff filter from a camera will allow you to detect light out to abut 1 um wavelength. This is due to the bandgap of silicon so you can't do much to change it.

For 1 um to 1.7 um or up to about 2.5 um InGaAs detector based cameras are commonly used. In this range water absorption makes people appear dark skinned so people look the same regardless of their skin color in the visible. You won't see a thermal response unless something is very hot, I don't know off hand but I would guess over 300 C, certainly not heat from a person.

For 3-5um or 8-12 um (mid or long wave infrared) the lowest cost would be a microbolometer based camera. You would need to see if the thermal response time was adequate for your speeds. If not, there are compound semiconductor materials (InSb, HgCdTe, etc.) in that range which can be used in high speed detectors.

Removing the IR cutoff filter from a camera will allow you to detect light out to abut 1 um wavelength. This is due to the bandgap of silicon so you can't do much to change it.

For 1 um to 1.7 um or up to about 2.5 um InGaAs detector based cameras are commonly used. In this range water absorption makes people appear dark skinned so people look the same regardless of their skin color in the visible. You won't see a thermal response unless something is very hot, I don't know off hand but I would guess over 300 C, certainly not heat from a person.

For 3-5um or 8-12 um (mid or long wave infrared) the lowest cost would be a microbolometer based camera. You would need to see if the thermal response time was adequate for your speeds. If not, there are compound semiconductor materials (InSb, HgCdTe, etc.) in that range which can be used in high speed detectors.
Thanks davidrit. It certainly looks like I need someone who understands physics of light to get involved. I am an electrical engineer, so I can see some angles of what you talk about, but I sure need to get some help to build this camera.

mgb_phys
Homework Helper
It might be practical if you can point the camera through the windscreen.
A lot depends on the environment - for a good signal you need a biog temperature difference between the person and background. So would work great in Canada in winter, or in the US where everyone has the AC on near-freezing, wouldn't work if the ambient temperature is near 37C

Uncooled systems (microbolometers/ ferro-electric) can generally do about 100mK NETD at video frame rates - affordable ones are cheap-webcam resolution so you would need one camera/lane and would only get a couple of blobs as images of the passengers

Of course this wouldn't work for a person in the backseat unless you had multiple cameras - even then with something like an SUV it would be hard to spot other occupants (this is why Police are very nervous, and trigger happy, when stopping large SUVs with blacked out rear windows)

Mech_Engineer
Gold Member
Removing the IR cutoff filter from a camera will allow you to detect light out to abut 1 um wavelength. This is due to the bandgap of silicon so you can't do much to change it.

For 1 um to 1.7 um or up to about 2.5 um InGaAs detector based cameras are commonly used. In this range water absorption makes people appear dark skinned so people look the same regardless of their skin color in the visible. You won't see a thermal response unless something is very hot, I don't know off hand but I would guess over 300 C, certainly not heat from a person.
You can make most digital sensors sensitive to near IR (800-900nm) but this wouldn't give you thermal data, so you would probably need an infrared illuminator and some software to detect a head shape.

For 3-5um or 8-12 um (mid or long wave infrared) the lowest cost would be a microbolometer based camera. You would need to see if the thermal response time was adequate for your speeds. If not, there are compound semiconductor materials (InSb, HgCdTe, etc.) in that range which can be used in high speed detectors.
All of this is moot, because mid and long wave IR (3-14um) doesn't pass through glass!!! Indeed, most automotive glass is made to reflect these thermal infrared regions to help insulate the vehicle. You would only get a thermal signature of the windshield (or perhaps a reflection since it will likely act like a mirror), not the people behind it. A thermal camera is useless for trying to see inside a car.

All of this is moot, because mid and long wave IR (3-14um) doesn't pass through glass!!! Indeed, most automotive glass is made to reflect these thermal infrared regions to help insulate the vehicle. You would only get a thermal signature of the windshield (or perhaps a reflection since it will likely act like a mirror), not the people behind it. A thermal camera is useless for trying to see inside a car.
Mech Engineer, no need to shout. I didn't disagree with you I merely offered a 30 second breakdown of the infrared into a few commonly used spectra to help increase the OP's understanding of detecting infrared. Judging from the OP's response he understood that even if you didn't.

Having read with interest the posts, is the project impractical?

Mech_Engineer
Gold Member
The project is difficult but not impossible. It's doubtful you'll be able to detect 100% of people in vehicles, but you can probably see if there are ones in the front seats using a night vision camera in the near-infrared spectrum.

The project is difficult but not impossible. It's doubtful you'll be able to detect 100% of people in vehicles, but you can probably see if there are ones in the front seats using a night vision camera in the near-infrared spectrum.
Unfortunately that is not good news I guess. We would be OK with being pessimistic by accounting for people when they are not actually in the car and hence missing out on some potential carpool violators. But missing out people in back seats would be pretty bad, since that would open up problems that commuters would complain that they actually had a person sleeping in the back seat etc, but were still tagged.

I wonder if there are more expensive non IR options...

I have watched this post and have a single observation.
This gets dangerously close to violating personal rights, and subverting criminal law
If I get a ticket, based upon false or true data, I still do not get to go to court and
"face my accuser" as is required by law
there is no accuser
Its my opinion that if you want to monitor a persons activity, you are assuming all persons are guilty just by monitoring them
stop light cameras, auto speed detectors are in this catagory.

if its such a problem, hire A PERSON (which would provide a job) and have them do the work, not a mindless automated machine
sorry, end of rant

dr

mgb_phys
Homework Helper
if its such a problem, hire A PERSON (which would provide a job) and have them do the work, not a mindless automated machine
Not just a person, a whole team.
3-4 highway dept people to flag down each car,
a police officer to request the warrant
a judge to sign the warrant
a lawyer for each side
a legal junior to go to starbucks
another legal junior for the other lawyer to get their starbucks (confilict of interest)
coffee guy for the highway people (union rules)

The demand for hi-vis vests alone would mean a return to full employment.
Of course the fines wouldhave to go upto \$1M to cover this.

Mech_Engineer
Gold Member
Unfortunately that is not good news I guess. We would be OK with being pessimistic by accounting for people when they are not actually in the car and hence missing out on some potential carpool violators. But missing out people in back seats would be pretty bad, since that would open up problems that commuters would complain that they actually had a person sleeping in the back seat etc, but were still tagged.

I wonder if there are more expensive non IR options...
If you had a set of cameras on the side wall, and a camera in front looking through the windshield, you will probably be able to see people in the back seat as well. I'm not sure how window tint would affect the camera though.

You're right that it will be tough to prove beyond a shadow of a doubt that there was only one person in the car.

I have watched this post and have a single observation.
This gets dangerously close to violating personal rights, and subverting criminal law
If I get a ticket, based upon false or true data, I still do not get to go to court and
"face my accuser" as is required by law
there is no accuser
Its my opinion that if you want to monitor a persons activity, you are assuming all persons are guilty just by monitoring them
stop light cameras, auto speed detectors are in this catagory.
I don't think it's just danegerously close, many perceive them to be "big brother" incarnated. It has been shown that red light cameras and speed cameras don't help make the roads safer either. Red light cameras reduce red light running, but increase rear-endings because people are desperate to stop. Speed cameras are fixed, and people just slow down before and speed up after passing one.

In the HOV lane case, cars could just move out of the lane before and re-merge after a camera system. Additionally, in California for example certain vehicle are allowed to drive in the carpool lane with only one occupant. Hybrids and electric vehicles for example, which means the camera system would need to be able to recognize certain kinds of vehicles.

You have to decide before you start, it there really a problem, and would this solve it? Are there really so many people using the HOV lane illegally that an automated detection system is needed? Couldn't there just be police officers checking from time to time?

if its such a problem, hire A PERSON (which would provide a job) and have them do the work, not a mindless automated machine
sorry, end of rant

dr
I think a person is much less likely to be able to discern if there are multiple people in a vehicle than a multi-angle camera. Especailly at night.

I think a person is much less likely to be able to discern if there are multiple people in a vehicle than a multi-angle camera. Especailly at night.
I agree, but the person fulfills the requirement as "accuser"

dr

Mech_Engineer
Gold Member
I agree, but the person fulfills the requirement as "accuser"

dr
Having an in-person "accuser" is a non-issue. Most red light cameras for example list the accuser as either the city or an assigned police officer which reviews the video and/or pictures. Just because there is no in-person witness to the event does not mean recorded video or pictures cannot be used as evidence of a crime taking place. Just like red-light cameras or speeding cameras, the evidence collected by the camera would probably have to be reviewed by an official before fines are sent out.

yes thats true, but the reason they can get away with it is because the camera infractions are local ordinance violations (civil court like a dirty yard)
then no matter who was driving the car, the owner of the car is guilty
no fighting it, but its not a moving violation, either

ok,
I have hijacked the thread, and this is not the time or place for me to rant about "civil liberties, big bro (and their holding company)

(nice discusssion though, thanks)

dr