Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2001-07-11
2004-02-03
Pyo, Kevin (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S227180
Reexamination Certificate
active
06686583
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This invention claims priority of a German patent application DE 100 33 269.2 which is incorporated by reference herein.
FIELD OF THE INVENTION
The present invention concerns an apparatus for coupling light of a laser light source into an optical assemblage
BACKGROUND OF THE INVENTION
Apparatuses of the generic type are used in practice to couple light into a wide variety of optical assemblages. In particular when laser light of several wavelengths is to be coupled into an optical assemblage, an optically active component is used to couple it in, since with the optically active component light of one wavelength can in each case be selected and coupled into the optical assemblage. In particularly advantageous fashion in this context, the power of the coupled-in light of a specific wavelength can also be adjusted and modified by means of the optically active component. An optical assemblage could be, for example, a confocal scanning microscope or an apparatus for projecting laser light onto a screen. In the case of the latter assemblage it is possible by means of a suitable scanning apparatus to project a color image or a color image sequence, with the possibility of a different color value being present at each projected image point. An optically active component makes possible a rapid modification of the power of the light of the different wavelengths, so that by using an optically active component to couple laser light into a projection apparatus it is possible to display images at video speed. In the case of confocal fluorescent scanning microscopy as well, excitation of several fluorescent dyes with laser light of different wavelengths, in a manner modified line by line and/or pixel by pixel, is useful for many applications and is utilized in practice.
Many laser light sources in some cases exhibit, however, large fluctuations in light output and in the wavelength of the emitted light. The emission wavelength of diode lasers, for example, depends on the operating temperature of the laser diode: the emitted wavelength of the diode laser changes by approx. 2 to 3 nm per degree K. This is moreover associated with a change in the emitted power of the diode laser, which in itself is not tolerable for many applications. When the wavelength of the emitted light changes, however, there is usually also a change in the power of the light coupled into the optical assemblage, since generally the optically active component acts only on light of a specific wavelength or within a sharply delimited wavelength region. But if the wavelength or wavelength region of the laser light source changes, the power of the light coupled in by the optically active component also, disadvantageously, changes.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to describe an apparatus for coupling light of at least one wavelength of a laser light source into an optical assemblage, in which changes in the power and/or wavelength of the laser light source have no effect on the power of the light coupled into the optical assemblage.
The apparatus of the generic type according to the present invention achieves the aforesaid object, wherein the apparatus comprising: a laser light source generating at least one wavelength, an optically active component for selecting the wavelength and for setting the power of the coupled-in light, and a control system for influencing the coupled-in light with regard to minimize fluctuations in the light output of the coupled-in light.
It is an other object of the present invention to provide a confocal scanning microscope, in which changes in the power and/or wavelength of the laser light source have no effect on the power of the light coupled into the microscope.
The above object is accomplished by a confocal scanning microscope comprising: a laser light source defining at least one wavelength, an apparatus for coupling light of the laser light source into the confocal scanning microscope, an optically active component being arranged in the apparatus for coupling light of the laser light source into the confocal scanning microscope, wherein the optically active component serves to select the wavelength and to set the power of the light to be coupled-in, and a control system for influencing the component in order to minimize fluctuations in the light output of the light to be coupled-in.
What has been recognized according to the present invention is firstly that the optically active component can be used not only to couple the laser light into the optical assemblage, but moreover also as the adjusting element of a control system. It is thereby advantageously possible—assuming a suitable control loop—for the coupled-in light to be influenced in such a way that fluctuations of the laser light source affect the power of the coupled-in light only within an acceptable range, or not at all.
In particularly advantageous fashion, only the optically active component is used as an adjusting element by the control system. No attempt is therefore being made to regulate the laser light source itself; rather the control system makes use of an adjusting element that often is provided in any case for coupling light into an optical assemblage. Accordingly, and advantageously, it is not necessary to provide additional, expensive optical elements (in some cases also affected by aberrations) which are capable of achieving the object mentioned initially.
Several control strategies that can meet the differing requirements of an optical assemblage will be described below.
The control system could be designed in such a way that it serves to minimize fluctuations in the light output of the coupled-in light. In this context, particular consideration can be given to short-term fluctuations of the laser light source, which are correspondingly minimized by the control system. If the fluctuations of the laser light source are the result of thermal changes, they are generally fluctuations on a scale of seconds, which must also be minimized by the control system.
It would also be possible to define a time-related power profile of the light that is to be coupled in, said profile to be achieved by the control system. Here again, provision is made for minimizing fluctuations in the power of the light being coupled in. The time-related power profile could be, for example, a periodic amplitude modulation or a continuously rising and/or falling change in the power of the light being coupled in. Examples of an amplitude modulation of this kind are square-wave, sawtooth, or sinusoidal power profiles.
The control system could also be designed in such a way that it serves to maximize the light output of the coupled-in light. This is necessary in particular when the available power of the laser light source differs only slightly from the light output needed in the optical assemblage.
For many applications, the control system will attempt to couple a substantially constant light output into the optical assemblage. The coupling in of light of any fraction of the maximum light output is also conceivable.
In a concrete embodiment, the control system is configured in such a way that a modification and/or setting made by a user is taken into account, i.e. the control system is aware of the modified setting. If the control system is not aware of the modifications and/or settings made by a user, then for example after an increase in the output power of the laser directly at the laser controller, the control system would, however, annul that change so as to continue maintaining a constant light output for the coupled-in light, by the fact that the control system couples into the optical assemblage the originally defined constant light output. It is therefore important to ensure that the modifications and/or settings made by a user are taken into account by the control system as new setpoints, and are controlled accordingly. In addition to modifications and/or settings of the emission power of the laser light source, the ratio between coupled-in and non-coupled-in
Leica Mircrosystems Heidelberg GmbH
Pyo Kevin
Sohn Seung C.
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