Adaptive optics system

1. A method comprising:

performing fluorescence fluctuation microscopy analysis by laser beam excitation of an observable volume of a sample using an optical system comprising a phase modulation device and a photon detector;

receiving, by a processing device, a first plurality of photon count values indicating a number of photons detected by the optical system during a plurality of first time periods;

calculating, by the processing device based on said first plurality of photon count values, a first count rate per molecule indicating the average number of photons detected per molecule of the observation volume;

generating, by the processing device based on the first count rate per molecule, a control signal; and

reducing optical aberrations by configuring the phase modulation device of said optical system using the control signal.

2. The method of claim 1 , wherein said control signal is generated based on said first count rate per molecule and on at least one or more reference values.

3. The method of claim 2 , wherein:

said first plurality of photon count values indicate the number of photons detected while said phase modulation device is in a first configuration; and

said one or more reference values comprise a second count rate per molecule based on a second plurality of photon count values indicating the number of photons detected during second time periods while said phase modulation device was in a second configuration different to said first configuration, and a third count rate per molecule based on a third plurality of photon count values indicating the number of photons detected during third time periods while said phase modulation device was in a third configuration different to said first and second configurations.

4. The method of claim 1 , wherein generating said control signal comprises calculating said control signal to maximize the count rate per molecule.

5. The method of claim 3 , wherein said first and second configurations are different degrees of at least one of the following optical effects:

astigmatisms;

comas;

trefoils;

primary spherical aberrations; and

secondary spherical aberrations.

6. The method of claim 1 , wherein generating said first count rate per molecule comprises determining the average number of molecules in said observation volume based on said first count values.

7. The method of claim 6 , wherein said first count rate per molecule (CRM) is calculated based on the following equation:

CRM=(< n>/δt )/< N>

where <N> is the average number of molecules in the observation volume, δt is the duration of each of said first time periods and <n> is the average of said first count values during said first time periods.

8. The method of claim 7 , wherein the reciprocal (1/<N>) of the number of molecules in the observation volume is determined based on the following equation:

1

〈

N

〉

=

〈

δ

⁢

⁢

n

i

⁢

δ

⁢

⁢

n

i

+

1

〉

〈

n

〉

2

where <n> is the average of the first count values, δni is equal to ni−<n>, ni being the ith count value, and δni+1 is equal to ni+1−<n>, ni+1 being the (i+1)th count value.

9. The method of claim 7 , wherein the reciprocal (1/<N>) of the number of molecules in the observation volume is determined based on the following equation:

1

〈

N

〉

=

〈

n

i

⁢

n

i

+

1

〉

〈

n

〉

2

-

1

where <n> is the average of the first count values, ni and ni+1 are the ith and (i+1)th count values.

10. The method of claim 7 , wherein the reciprocal (1/<N>) of the number of molecules in the observation volume is determined based on a temporal autocorrelation function.

11. The method of claim 1 , further comprising performing fluorescence microscopy analysis of said sample while said phase modulation device is configured by said control signal to at least partially correct optical aberrations.

12. A fluorescence fluctuations microscopy analysis system, comprising:

an adaptive optics system configured to perform fluorescence fluctuation microscopy analysis by laser beam excitation of an observable volume of a sample comprising:

a phase modulation device;

a photon detector; and

a computer storage device storing a computer program, which when executed by a processing device, causes the processing device to:

receive a first plurality of photon count values indicating a number of photons detected by the photon detector during a plurality of first time periods;

calculate based on said first plurality of photon count values, a first count rate per molecule indicating the average number of photons detected per molecule of the observation volume; and

generate a control signal based on the first count rate per molecule to maximize the count rate per molecule and to configure the phase modulation device to reduce optical aberrations.

13. A fluorescence fluctuation microscopy analysis system comprising:

an adaptive optics system comprising:

a phase modulation device configured to reduce optical aberrations;

a processing device configured to:

receive photon count values for a plurality of time periods indicating a number of photons detected by the optical system as a result of laser beam excitation of an observation volume of a sample during fluorescence fluctuation microscopy analysis;

calculate, based on said photon count values, a count rate per molecule, indicating the average number of photons detected per molecule of the observation volume; and

generate, based on the determined count rate per molecule, a control signal for controlling the phase modulation device of said optical system; and

a photon detector.

14. The fluorescence microscopy analysis system of claim 13 , wherein said phase modulation device is a deformable mirror.