In fluorescence, we usually talk about human detection of visible spectrum from violet to red wavelength. However, when we look from the perspective of intensity, what is the minimum fluorescence intensity that human can detect ?
Human eyes are very different in light detecting. There is definitely no scienfically valid threshold above which all humans can detect luminescence.
It is the same for smelling or hearing ...
Axel Klein , Thank you for the reply. So, luminescence detection (without the aid of UV irradiation) in general is subjective and there's no valid threshold.
I have heard that frog eyes can detect one photon.
Human eyes respond to ca. 6 photons.
(sorry, I have no source for that).
Just heard it while doing some time correlate single photon counting...
R
Dear Nadia,
Your questions seems to be unclear since you asking measurement limit but in an Arbitrary Unit (A.U.) or Procedure Defined Unit (P.D.U.). There will be no answer for that since AU is not a unit in SI or any unit standard. I suggest you to read again the definition of AU and fluorescence itself. I wondering what is the reason for you to ask this question.
The most sensitive receptors, the rods in the retina are sensitive to single photons. However, the electrical signal from a single photon is filtered out by the image processing in the optic nerve and brain. It was the belief that it takes a minimum of 7 photons to see an event, as suggested by Hecht and colleagues in the 1940s who established that dark-adapted human subjects are capable of reporting light signals as low as a few photons (∼5–7). Subsequently, Rebecca Holmes U Illinois) and Alipasha Vaziri from Rockefeller University ( Nature Communications volume 7, Article number: 12172 (2016) ) have provided experimental evidence in the past few years which suggests that single photons might be detectable by the human retina.
In the title of your question you mention AU? for me that means Arbitrary Units
But you are interested in absolute number(s)
Alan Knught
How is the sensitivity defined 1 photon perpendicularly arriving as the center of the eye?
the most accurate number is the number of photons as discussed by Rene and Alan, isn't it?
Then the next question
6 photons per what time period?
and apologies for missspelling the name of Alan Knight
Good question Harry - 6 photons where their temporal wave packets overlap sufficiently to give (to within the uncertainty principle) a superposition of waves with summed amplitude essentially equivalent to six photons (or wave packets). However, as suggested by the work of Vaziri, one photon may be enough.
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Physical Phenomena
- Luminescence
- Fluorescence