Optical waveguides – With optical coupler – Input/output coupler
Reexamination Certificate
1998-10-15
2001-04-24
Font, Frank G. (Department: 2877)
Optical waveguides
With optical coupler
Input/output coupler
C606S003000, C606S015000, C359S368000
Reexamination Certificate
active
06222961
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority of German patent applications DE-A-196 14 929.0 and DE-A-196 33 185.4.
1. Field of the Invention
Point light source for a laser scanning microscope and process for coupling at least two lasers of different wavelength into a laser scanning microscope
The invention relates to a point light source for a laser scanning microscope, it being possible to couple at least two lasers of different wavelengths into the microscope. The invention further relates to a process for coupling at least two lasers of different wavelength into a laser scanning microscope.
2. Background of the Invention
Light sources of the type under discussion here are required in laser scanning microscopes, in particular in the case of confocal microscopy. In this case, what principally matters is, within the context of a multicolor application, to couple laser light of different wavelength into the microscope. This has to take place with quite particular consideration being given to the adjustability of the laser and with consideration being given to the stability of the adjustment.
From practice, two different arrangements are known for multicolor application in laser scanning microscopes. Within the context of a first alternative, a laser (ArKr) having a plurality of simultaneous wavelengths is used. In this case, it is inherent in the system that in that instance all laser lines—per se—are adjusted to one another. In this case, the selection of the wavelengths as well as the setting of the power is accomplished by an AOTF (Acousto Optical Tunable Filter). Consequently, each laser line may be set, independently of the others, in its power continuously even down to very low powers. The coupling in takes place in each instance through a single mode fiber. The advantage of the above possibility of coupling in resides in a compact scanner, in absolute adjustability as well as in decoupling of the vibration caused by the laser cooling.
SUMMARY OF THE INVENTION
The advantages described hereinabove do however also involve quite considerable disadvantages. An ArKr laser covers—as has already been mentioned above—a plurality of laser lines simultaneously. As these are generated in a resonator, this always brings about an instability of the individual lines, particularly as, in the laser, only the total power is kept constant by a regulating system. Depending upon the setting of the total power, the noise occurring in this case may amount to up to 10 percent “peak to peak” and thus reduces the image quality with respect to the signal
oise ratio. In contrast to this, single-line lasers achieve noise of only just 1 percent.
Furthermore, in the event of failure of the—singular —laser the system is entirely incapable of functioning. The available laser lines are in all cases dependent upon the laser-active gas and the mixing thereof. As this alters over the service life of the laser, an impairment of all laser lines takes place in the course of time. Finally, only the laser lines of the gas mixture employed are available, so that in this case there is always a restriction-on selection.
In the case of a system which is further known from practice, in all instances a plurality of lasers are coupled directly into a laser scanning microscope. In the event of a laser fault, only one laser line fails. In correspondence with the function of these lasers, the other laser lines remain available. By reason of the single line operation, the laser power exhibits high stability. Single-line lasers have a longer service life than lasers having a plurality of wavelengths. For each laser line, the laser power may be optimally coordinated with the experimental conditions without further auxiliary measures.
It is also the case that the abovementioned coupling of a plurality of lasers into a laser scanning microscope exhibits considerable disadvantages, since, specifically, the laser beams from the different lasers have to be focused or adjusted onto one and the same point in precisely the same direction. In this case, there are four degrees of freedom per laser. If the focusing or adjustment does not take place to a sufficient extent, the images recorded using the different laser lines are not in register. However, the analysis of images which are in register is precisely the purpose of a multiple excitation of the type under discussion here.
A further disadvantage of the use of a plurality of different lasers is to be seen in that conventional beam combining arrangements and adjustment systems have to be readjusted frequently. This procedure is extremely complicated, since in the conventional arrangements the various degrees of freedom of the adjustments are not sufficiently decoupled from one another.
Thus, an alteration of angle always also leads to an alteration of position. Consequently, the adjustment target is attained only after many adjustment cycles, so that the adjustment can scarcely be carried out by the user himself. A particular service provided by the manufacturer of the equipment is accordingly absolutely necessary. Finally, a plurality of lasers together are always more costly than a single laser having a plurality of wavelengths.
Now, the object of the invention is to specify a point light source for a laser scanning microscope, which light source makes use of the advantages of the two abovementioned systems—multiline laser and a plurality of single-line lasers—and at least to a very great extent eliminates the disadvantages thereof. Furthermore, the intention is to specify a process for using such a point light source.
The point light source according to the invention achieves the above object by, a point light source for a laser scanning microscope which comprises at least two laser light sources which couple into a beam combiner and an optical fiber leading indirectly or directly from the beam combiner to the microscope.
According to the invention, it has been recognized in this case that the use of at least two independent laser light sources and thus of at least two different lasers involves the advantages which have been discussed hereinabove. The associated disadvantages may—likewise according to the invention—be eliminated in that, even before coupling into the laser scanning microscope, a beam combination takes place, so that from there onward mutually adjusted laser beams or laser lines having a plurality of wavelengths—in the sense of a multiline laser—are available, which is so in the case of a laser having a plurality of simultaneously occurring wavelengths.
After the beam combination, the combined laser lines are guided simultaneously via an optical fiber to the microscope and are coupled in there—as in the case of a laser having a plurality of simultaneously occurring wavelengths. Consequently, from the beam combination into the fiber onward, all laser lines are automatically adjusted to one another. Accordingly, an adjustment or setting takes place exclusively in the beam combiner, which may be realized in the form of a compact component. A particular adjustment to the coupling in of the laser scanning microscope is not necessary in any circumstances.
In a particularly advantageous manner and to minimize the expenditure on design or apparatus, in particular also for the optimal use of the available space, one of the lasers couples directly into the beam combiner. In other words, this laser is directly allocated to the beam combiner. At least one further laser is coupled into the beam combiner via an optical fiber; in this case, a single mode fiber may be involved. Besides the laser coupling directly into the beam combiner, specifically and in a quite particularly advantageous manner two or three further lasers may in each instance couple into the beam combiner via a separate optical fiber. In this case, laser lines having different wavelengths may be coupled in, so that the result is a multicolor application.
The beam combiner may comprise a conventional component known from the prior art or an appropriate arrangement. Thus, the beam
Engelhardt Johann
Ulrich Heinrich
Foley & Lardner
Font Frank G.
Lauchman Layla G.
Leica Microsystems Heidelberg GmbH
LandOfFree
Point light source for a laser scanning microscope and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Point light source for a laser scanning microscope and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Point light source for a laser scanning microscope and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2520282