Optical evaluation method by means of laser pulses and corresponding apparatus
An optical evaluation method and an apparatus for performing said method are described. First laser pulses of a first type and second laser pulses of a second type that differs from the first type are sent onto a sample to be examined. The sample is hit with first incident light from the two laser pulses in at least one manner of simultaneously, within a very short time lag between the two laser pulses, and a time-correlated manner of the two laser pulses, thereby generating a first optical signal, and hit with second incident light from the two laser pulses, thereby generating a second optical signal. The generated first and second optical signals are detected with at least one detector; and an electronic difference between the first and second optical signals is generated.
1. An optical evaluation method, comprising:
using one of stimulated fluorescence, stimulated Raman gain and stimulated Raman loss for generating a first optical signal and a second optical signal;
directing first laser pulses of a first type and second laser pulses of a second type that differs from the first type onto a sample to be examined;
hitting the sample with first incident light from the two laser pulses in at least one manner of simultaneously, within a very short time lag between the two laser pulses, and a time-correlated manner of the two laser pulses, thereby generating a first optical signal;
hitting the sample with second incident light from the two laser pulses in at least one manner of non-simultaneously, not within a very short time lag between the two laser pulses, and a non-time-correlated manner of the two laser pulses, thereby generating a second optical signal;
detecting the generated first and second optical signals with at least one detector; and
generating an electronic difference between the first and second optical signals.
2. The optical evaluation method according to claim 1 , comprising:
generating the second laser pulses at a shorter repetition rate than the first laser pulses;
hitting the sample with the second laser pulses delayed by a predetermined delay time with respect to the first laser pulses;
feeding the second laser pulses to a detector; and
generating and evaluating the electronic difference between one of the second laser pulses and a subsequent second laser pulse.
3. The method according to claim 1 , comprising:
hitting the sample simultaneously with the first laser pulses and the second laser pulses; and
generating and evaluating the electronic difference between one of the adjacent successive first and second laser pulses.
4. The method according to claim 1 , comprising supplying the signals provided by the detector to an image processing unit.
5. The method according to claim 4 , comprising providing the image processing unit in connection with a laser scanning microscope.
6. The method according to claim 4 , comprising providing the image processing unit in connection with a confocal laser scanning microscope.
7. An apparatus for evaluating laser pulses in one of stimulated fluorescence, stimulated Raman gain and stimulated Raman loss for generating a first optical signal and a second optical signals, comprising:
a first laser that generates first laser pulses of a first type;
a second laser that generates second laser pulses of a second type that differs from the first type;
a light directing unit for directing the first laser pulses and the second laser pulses onto a sample to be examined, the light directing unit being configured to hit the sample with first incident light from the two laser pulses in at least one manner of simultaneously, within a very short time lag between the two laser pulses, and a time-correlated manner of the two laser pulses, thereby generating a first optical signal; and to hit the sample with second incident light from the two laser pulses in at least one manner of non-simultaneously, not within a very short time lag between the two laser pulses, and a non-time-correlated manner of the two laser pulses, thereby generating a second optical signal;
a first detector for detecting the generated first and second optical signals with at least one detector; and
an electronic signal processing unit generating an electronic difference between the first and second optical signals.
8. The apparatus according to claim 7 , wherein
the first and the second laser are configured to generate the second laser pulses at a shorter repetition rate than the first laser pulses and to hit the sample with the second laser pulse delayed by a predetermined delay time with respect to the first laser pulses;
a second light directing unit is provided feeding the second laser pulses to a second detector; and
the electronic signal processing unit is configured to generate and evaluate the electronic difference between one of the second laser pulses and a subsequent second laser pulse.
9. The apparatus according to claim 7 , wherein the first and the second laser are configured to generate the first laser pulses and the second laser pulses such that these hit the sample simultaneously, and the difference between successive pulses of one of the laser pulses is evaluated.
10. The apparatus according to claim 7 , comprising an image processing unit for processing the signals provided by the detector.
11. The apparatus according to claim 10 , comprising a laser scanning microscope.
12. The apparatus according to claim 11 , wherein the laser scanning microscope is a confocal laser scanning microscope.