Method for measuring a fluorescence lifetime of an excited state in a sample, characterized by the following steps: a. generating an excitation light pulse and illuminating a sample region with the excitation light pulse, b. generating a first digital data sequence, which represents the luminous power curve of the excitation light pulse over time, c. ascertaining a first switching time from the first digital data sequence, wherein i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, d. detecting the detection light emanating from the sample region as at least one photon event using a detector, e. generating a second digital data sequence, which represents the luminous power curve of the detection light over time, f. ascertaining a second switching time from the second digital data sequence, wherein i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the second data sequence is set as second switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as second switching time, g. calculating the time difference between the first and the second switching time and h. repeating steps a to g cyclically. a. generating an excitation light pulse and illuminating a sample region with the excitation light pulse, b. generating a first digital data sequence, which represents the luminous power curve of the excitation light pulse over time, c. ascertaining a first switching time from the first digital data sequence, wherein i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as first switching time, d. detecting the detection light emanating from the sample region as at least one photon event using a detector, e. generating a second digital data sequence, which represents the luminous power curve of the detection light over time, f. ascertaining a second switching time from the second digital data sequence, wherein i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the second data sequence is set as second switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as second switching time, i. the time at which there is a change from a lower standardized signal to an upper standardized signal or a change from an upper standardized signal to a lower standardized signal within the second data sequence is set as second switching time, or wherein ii. the time which is calculated from the time of a first change from a lower standardized signal to an upper standardized signal and from the time of a second change from an upper standardized signal to a lower standardized signal within the first data sequence is set as second switching time, g. calculating the time difference between the first and the second switching time and h. repeating steps a to g cyclically.