Hands down the best description of the interferometer I've come across. Thank you for the great presentation and discussion on sources with multiple wavelengths!
Would you believe that I have been repairing FTIR's for 15 years and this is the first time I have had a truly clear idea of exactly HOW it used the interferogram? Thank you
This is a great video video with very clear explanations. I could not find any text about FTIR online that described all of the fundamental aspects together in the same place. Thank you!
what a wonderful lecture. i think it can make understand even a child. i'm so jealous of your student, because my professor doesn't care about student's understanding.
Hello, Thank you for the great video.. I have a question, at 8:20 when you slide backward the moving mirror then how did the coming back (left) signal cancelled down from the moving mirror? Shouldn't it be cancelled at the other end of the splitter?
I have made the slides for this presentation available as a PDF document at the website that supports this channel: KeynoteChemistry.com. Go to keynotechemistry.com/presentations#Post3 to get the slides and follow along. Thank you everyone for all your comments.
This is an excellent run down of interferometry in FTIR, thank you so much. Your diagram at 29:10 perfectly captures what I want to express in an essay on FTIR. May I use a screenshot of it, and if so, how should I reference you?
I often give training to customers on the use of my companies Multigas FTIR (MKS 2030) and I like to show them this video as you do so much better at explaining this in an understandable and entertaining fashion than I am capable of doing. The problem is, sometimes I don't have internet available when giving these classes and frankly I am concerned that at some point the video may become unavailable in the future. Is there any chance I can get a copy of this video if I promise to include credit to you and links to your youtube channel?
I want to make a simple test setup of FTIR on a optical bench for the range of 2-14um for gas. We have all the mounts in our lab. I found all the items (i.e. beamsplitter, mirrors, windows for sample chamber, 16bit ADC) except the sensor. Please tell me the Model of a sensor which can be used (tried) on this setup.
Ok dumb question; When the moving mirror is at a distance where there is maximum destructive interference, so no light is directed at the detector, where does the beam go to? Is everything reflected back to the source then?
The power does not go away. When we have perfect destructive interference we have a situation where 1+(-1)=0 and when we have constructive interference we have 1+(+1)=2. In one case we have the minimum signal and in the other the maximum. The two beams are still moving to the detector but if the cancel each other out we will observe no power.
Great videos! They're really helpful but I have a question. Does this work any differently if the light source isn't coherent? In your example, all the waves are have a maximum at the same point but is that different from the light you get from a lamp?
The final signal is a total power signal. No matter what phase the individual photons are start in they will meet again at the second beam splitter an recombine with a power that depends on the different distance they travelled. I am no physicist but I believe that, since every possible phase is represented in the light source, the problems due to different phases will all cancel out for the total power signal at the photomultiplier. For more precise distance measurements you would need a coherent laser (and a laser is used to measure the distance the mirror moves, that is why you see a red laser beam in an FTIR instrument). For measuring the wavelengths contained in the signal the phase shouldn't matter.
the best lecture I have seen so far on the subject. I really appreciate it.
Way better than what I actually pay for!
I didn't understand how a spectrum was created from this for the longest time. this is such a satisfying relief to finally understand. Thank You!
Thanks for this great explanation. American professors are the best in making complicated things very simple.
Excellent explanation. Combined with the Fourier transform description, lectures clarified how the FTIR works. Thank you.
Hands down the best description of the interferometer I've come across. Thank you for the great presentation and discussion on sources with multiple wavelengths!
This is the best tutorial in FTIR, very useful in electronic engineering and physics
One of the best lectures on FTIR! Way better than textbooks. Thanks a lot!
Would you believe that I have been repairing FTIR's for 15 years and this is the first time I have had a truly clear idea of exactly HOW it used the interferogram? Thank you
oh sir, can you give me some repairing documents of FTIR, i'm frrom Viet Nam, so many thanks you so much
This is a great video video with very clear explanations. I could not find any text about FTIR online that described all of the fundamental aspects together in the same place. Thank you!
I really liked the way it was presented. Jokes, info, and well paced.
what a wonderful lecture. i think it can make understand even a child. i'm so jealous of your student, because my professor doesn't care about student's understanding.
31:30 bam, they confirmed it years later:) spacetime moved.! What a time to be alive, we even knew the direction and pointed our telescopes there:)
Thank's Man, that was a very very good one, compared with the res of the content in the internet. You make the science earth turning!!!
So cool, This Video is the one of so clear lectures in TH-cam
Very clear explanation of the theories behind FTIR. Thank you :)
Thanks a lot!, I was looking for a clear and precise explanation like this
The fact that this was made before the first GWs were "seen" with interferometers OMG
Excellent explanation. Much appreciated.
THE BEST explaination ,thankyou
Very nice. Thank you!
Very Helpful Presentation. Thanks sir!
marvelous !
This video is excellent, thank you!
Hey, I want you to know that that was an amazing lecture. Thank you!!
really good lecture！
Hello, Thank you for the great video.. I have a question, at 8:20 when you slide backward the moving mirror then how did the coming back (left) signal cancelled down from the moving mirror? Shouldn't it be cancelled at the other end of the splitter?
excellent
Very good, thank you very much
I have made the slides for this presentation available as a PDF document at the website that supports this channel: KeynoteChemistry.com. Go to keynotechemistry.com/presentations#Post3 to get the slides and follow along. Thank you everyone for all your comments.
classic video
This is an excellent run down of interferometry in FTIR, thank you so much. Your diagram at 29:10 perfectly captures what I want to express in an essay on FTIR. May I use a screenshot of it, and if so, how should I reference you?
I often give training to customers on the use of my companies Multigas FTIR (MKS 2030) and I like to show them this video as you do so much better at explaining this in an understandable and entertaining fashion than I am capable of doing. The problem is, sometimes I don't have internet available when giving these classes and frankly I am concerned that at some point the video may become unavailable in the future. Is there any chance I can get a copy of this video if I promise to include credit to you and links to your youtube channel?
I want to make a simple test setup of FTIR on a optical bench for the range of 2-14um for gas. We have all the mounts in our lab. I found all the items (i.e. beamsplitter, mirrors, windows for sample chamber, 16bit ADC) except the sensor.
Please tell me the Model of a sensor which can be used (tried) on this setup.
Ok dumb question; When the moving mirror is at a distance where there is maximum destructive interference, so no light is directed at the detector, where does the beam go to? Is everything reflected back to the source then?
The power does not go away. When we have perfect destructive interference we have a situation where 1+(-1)=0 and when we have constructive interference we have 1+(+1)=2. In one case we have the minimum signal and in the other the maximum. The two beams are still moving to the detector but if the cancel each other out we will observe no power.
Great videos! They're really helpful but I have a question.
Does this work any differently if the light source isn't coherent? In your example, all the waves are have a maximum at the same point but is that different from the light you get from a lamp?
The final signal is a total power signal. No matter what phase the individual photons are start in they will meet again at the second beam splitter an recombine with a power that depends on the different distance they travelled. I am no physicist but I believe that, since every possible phase is represented in the light source, the problems due to different phases will all cancel out for the total power signal at the photomultiplier. For more precise distance measurements you would need a coherent laser (and a laser is used to measure the distance the mirror moves, that is why you see a red laser beam in an FTIR instrument). For measuring the wavelengths contained in the signal the phase shouldn't matter.
you are a god
What happens when you add different weight to the components instead of keeping all at unity.
PS they found the gravity waves
For chemists it is enough, I feel