Light Transmission Measurements: What Else Can You Find?

[btb4198]

If you measure the light transmission over time of the human thumb you can get the heart rate.

Is there another thing you can get by using light transmission ? like the Heart rate?
can you find bacteria in water using light transmission ?is light transmission measurement even the right word ?

 

[berkeman]

• Pulse Oximetry
• Smoke Alarm

 

[btb4198]

• Pulse Oximetry
• Smoke Alarm

Smoke Alarm use light transmission measurement ?

 

[berkeman]

Smoke Alarm use light transmission measurement ?

Google is your friend. Try a search on:

How Do Photoelectric Smoke Detectors Work?​

 

[sophiecentaur]

Summary:: usages for light measurement

Is there another thing you can get by using light transmission ?

The most common accurate way to find out what elements are present in astronomical objects is to use Absorption Spectroscopy. For instance, the spectrum of light from a star, passing through the atmosphere of a planet or through a Nebula will have dark bands in it, corresponding to the elements in the gas it has gone through. Helium was discovered in the atmosphere of the Sun by this method, long before its presence was identified on Earth. (Helios is Greek for Sun)
We can't go and visit distant objects so their effect on light can be the only information we have about them.

Your question looks like a homework assignment to me. Use the keywords in all the above answer to search for more information.

 

[btb4198]

The most common accurate way to find out what elements are present in astronomical objects is to use Absorption Spectroscopy. For instance, the spectrum of light from a star, passing through the atmosphere of a planet or through a Nebula will have dark bands in it, corresponding to the elements in the gas it has gone through. Helium was discovered in the atmosphere of the Sun by this method, long before its presence was identified on Earth. (Helios is Greek for Sun)
We can't go and visit distant objects so their effect on light can be the only information we have about them.

Your question looks like a homework assignment to me. Use the keywords in all the above answer to search for more information.

I promise you, I have been out of school since 2010. lol No, over the pass two years, I have develop software that can interpret light intensity from different cameras and I just wanted to see what all I can do with this software.

 

[DaveE]

find bacteria in water using light transmission ?

Like with a microscope? Yes, although you do have to do the right sample preparation.

I'm not sure it's exactly what you had in mind, but try searching for "spectroscopy" or "flow cytometry"

I would argue that measuring light that has been transmitted through things, reflected off of things, or created by things is the most common and powerful scientific tool in use. The applications are far to numerous to elaborate. Everyone uses it for everything.

 

[btb4198]

Like with a microscope? Yes, although you do have to do the right sample preparation.

I'm not sure it's exactly what you had in mind, but try searching for "spectroscopy" or "flow cytometry"

I would argue that measuring light that has been transmitted through things, reflected off of things, or created by things is the most common and powerful scientific tool in use. The applications are far to numerous to elaborate. Everyone uses it for everything.

Wow, I did not know that. I am new to the optic field. This software was the 1st time I had coded anything with a video camera before. DaveE, did you happen to see my other post? https://www.physicsforums.com/threads/pulse-oximetry-equations.1004269/

 

[btb4198]

Like with a microscope? Yes, although you do have to do the right sample preparation.

I'm not sure it's exactly what you had in mind, but try searching for "spectroscopy" or "flow cytometry"

I would argue that measuring light that has been transmitted through things, reflected off of things, or created by things is the most common and powerful scientific tool in use. The applications are far to numerous to elaborate. Everyone uses it for everything.

Dave can you find knots in a person's back with this ?

 

[DaveE]

Dave can you find knots in a person's back with this ?

What? Muscle spasms? I think there are less expensive ways, like a physical therapist.

Although I would guess you could look at IR radiation to find the heat generated by muscular contraction, if you had to. There have been experiments with using thermography to locate solid cancers, which also make localized heat (from increased blood flow mostly).

 

[btb4198]

What? Muscle spasms? I think there are less expensive ways, like a physical therapist.

Why would that be expensive ? Most people have an iPhone. I would just use that

 

[DaveE]

Why would that be expensive ? Most people have an iPhone. I would just use that

Go for it.

 

[btb4198]

Go for it.

so it can be done ? What is the science? Like for the heart rate monitor , Your heart pumps oxygen into your blood, causing your blood cells to become redder and blocking out more light that you can measure. How would finding Knots or muscle spasms work ?

 

[DaveE]

so it can be done ? What is the science? Like for the heart rate monitor , Your heart pumps oxygen into your blood, causing your blood cells to become redder and blocking out more light that you can measure. How would finding Knots or muscle spasms work ?

Probably not with a cell phone camera. Those cameras are designed to only see the same colors we can see, so that your vacation photos won't be ruined by UV or IR light. For thermography, you want IR light. Read about "thermography" or "black body radiation" to learn more about measuring heat by looking at the IR light it creates. This is like when a stove top glows "red hot" for example. What you are looking for is hotter parts of the skin due to increased heat generated by the muscles that are working. I'm pretty sure it can be done if you spend enough money and hire good engineers, spending tens or hundreds of thousands of dollars. I not at all sure you can do it. But, it is a good thing to learn more about in any case. You don't have much to lose by trying.

Instead of a cell phone try getting a cheap web cam. Most of these have a filter in front of the sensor that blocks IR light. Take it apart and experiment to see if you can find it and remove it. It may be as subtle as a plastic film or coating on a lens. Then you will have a cheap IR camera, sort of like the night vision cameras the military uses.

 

[btb4198]

Probably not with a cell phone camera. Those cameras are designed to only see the same colors we can see, so that your vacation photos won't be ruined by UV or IR light. For thermography, you want IR light. Read about "thermography" or "black body radiation" to learn more about measuring heat by looking at the IR light it creates. This is like when a stove top glows "red hot" for example. What you are looking for is hotter parts of the skin due to increased heat generated by the muscles that are working. I'm pretty sure it can be done if you spend enough money and hire good engineers, spending tens or hundreds of thousands of dollars. I not at all sure you can do it. But, it is a good thing to learn more about in any case. You don't have much to lose by trying.

Instead of a cell phone try getting a cheap web cam. Most of these have a filter in front of the sensor that blocks IR light. Take it apart and experiment to see if you can find it and remove it. It may be as subtle as a plastic film or coating on a lens. Then you will have a cheap IR camera, sort of like the night vision cameras the military uses.

DaveE, I have a IR cam from flir that works with my software. However, it only reads IR like from a laser or from a lighter. I have tested this. How could I use it in my case ? lol lighting the human body with fire or a laser is a bad idea ...

 

[sophiecentaur]

I promise you, I have been out of school since 2010.

Sorry. I have a suspicious mind. You are 'just interested in the World' and that's good.

If you are interested I spectroscopy, you can use a cheap prism from eBay (a 60 degree one) and produce a spectrum of the light from a slit or point. Your camera will give you a set of light level values across the band of colours. The spectrum of sunlight, various filament lamps, CFLs and LEDs will all look different. I am sure your software will allow you to dig out the values from your images. Getting a spectrum and photographing it is not too hard if you use a narrow slit and let the coloured bands fall on a white card. Take your images with the other lights off and you will get better results.
Note: the thinner the slit, the more spectral detail can be seen but the light level drops, of course.