Illumination – Light fiber – rod – or pipe – With optical fiber bundle
Reexamination Certificate
2001-06-15
2004-09-28
O'Shea, Sandra (Department: 2875)
Illumination
Light fiber, rod, or pipe
With optical fiber bundle
C362S553000, C385S116000
Reexamination Certificate
active
06796699
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This invention claims priority of the German patent applications 100 30 013.8 and 101 15 488.7 which are incorporated by reference herein.
FIELD OF THE INVENTION
The invention relates to a method for illuminating an object.
The invention also relates to an instrument for illuminating an object.
BACKGROUND OF THE INVENTION
Laid-open patent specification DE 198 53 669 A1 discloses an ultrashort-pulse source with controllable multiple-wavelength output, which is used especially in a multiphoton microscope. The system has an ultrashort-pulse laser for producing ultrashort optical pulses of a fixed wavelength and at least one wavelength conversion channel.
U.S. Pat. No. 6,097,870 discloses an arrangement for generating a broadband spectrum in the visible and infrared spectral range. The arrangement is based on a microstructured fibre, into which the light from a pump laser is injected. The pump light is broadened in the microstructured fibre by non-linear effects. So-called photonic band gap material or “photonic crystal fibres”, “holey fibres” or “microstructured fibres” are also employed as microstructured fibres. Configurations as a so-called “hollow fibre” are also known.
Another arrangement for generating a broadband spectrum is disclosed in the publication by Birks et al.: “Supercontinuum generation in tapered fibres”, Opt. Lett. Vol. 25, p.1415 (2000). A conventional optical fibre having a fibre core, which has a taper at least along a subsection, is used in the arrangement. Optical fibres of this type are known as so-called “tapered fibres”.
An optical amplifier, whose gain can be adjusted as a function of the wavelength, is known from the PCT application with the publication number WO 00/04613. The said publication also discloses a fibre light source based on this principle.
Arc lamps are known as broadband light sources, and are employed in many areas. One example is the U.S. Pat. No. 3,720,822 “XENON PHOTOGRAPHY LIGHT”, which discloses a xenon arc lamp for illumination in photography.
Especially in microscopy, endoscopy, flow cytometry, chromatography and lithography, universal illuminating devices with high luminance are important for the illumination of objects. In scanning microscopy, a sample is scanned with a light beam. To that end, lasers are often used as the light source. For example, an arrangement having a single laser which emits several laser lines is known from EP 0 495 930: “Konfokales Mikroskopsystem für Mehrfarbenfluoreszenz” [confocal microscope system for multicolour fluorescence]. Mixed gas lasers, especially ArKr lasers, are mainly used for this at present. Examples of samples which are studied include biological tissue or sections prepared with fluorescent dyes. In the field of material study, illumination light reflected from the sample is often detected. Solid-state lasers and dye lasers, as well as fibre lasers and optical parametric oscillators (OPOs), upstream of which a pump laser is arranged, are also frequently used.
Microspot arrays or so-called microplates are used in genetic, medical and biodiagnosis for studying large numbers of specifically labelled spots, which are preferably applied in a grid. A microplate reader which can be adjusted both in excitation wavelength and in detection wavelength is disclosed in the European Patient Application EP 0 841 557 A2.
The illumination methods and illuminating instruments known from the prior art have several disadvantages. The known broadband illuminating instruments mostly have a low luminance compared with laser-based illuminating devices, whereas the latter provide the user only with discrete wavelength lines whose spectral position and width can be adjusted only to a small extent, if at all. Owing to this limitation of the working spectrum, the known illuminating devices are not flexibly usable. Laser-based illuminating devices and illuminating methods also have the disadvantage that, owing to the high coherence of the laser light, disruptive interference phenomena, such as e.g. diffraction rings and Newton's rings, occur. To reduce these interference effects, additional optical elements are often used, which reduce the light power by intrinsic absorption and by scattering.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for illuminating an object which is universally usable and flexible, furthermore provides a broad wavelength spectrum together with a high luminance, and also minimizes interference phenomena.
The object is achieved by a method for illuminating an object comprising the following steps:
generating a light beam with a laser,
injecting a light beam into a microstructured optical element which spectrally broadens the light of the light beam,
shaping the spectrally broadened light beam to form an illumination light beam, and
directing the illumination light beam onto the object.
It is another object of the invention to specify an instrument for illuminating an object, which is universally usable and flexible, furthermore provides a broad wavelength spectrum together with a high luminance, and also minimizes interference phenomena.
The object is achieved by an Illuminating instrument comprising: a laser that emits a light beam, a microstructured optical element that spectrally broadens the light from the laser and an optical means for shaping the spectrally broadened light into an illumination light beam.
It is another object of the invention to specify a device for a microscopic inspection of an object, which is universally usable and flexible, furthermore provides a broad wavelength spectrum together with a high luminance, and also minimizes interference phenomena.
The object is achieved by a device comprising: a laser that emits a light beam, a microstructured optical element that spectrally broadens the light from the laser and an optical means for shaping the spectrally broadened light into an illumination light beam.
The invention has the advantage that it is universally usable, easy to handle and flexible, and furthermore provides illumination with light from a wide wavelength range. The light also has very low coherence, so that disruptive interference phenomena are avoided.
By using microstructured fibres, as described in the previously mentioned U.S. Pat. 6,097,870 or in the publication by Birks et al., a broad continuous wavelength spectrum is accessible. Arrangements of the disclosed type, however, are difficult to handle, inflexible and susceptible to interference, especially because of the complexity of the individual optical components and their relative adjustment.
A configuration variant in which a lens, which shapes the spectrally broadened light into a beam, is arranged downstream of the microstructured optical element, is especially advantageous. This lens is preferably located inside a casing which houses the entire instrument, immediately in front of or in a light exit opening. The lens is preferably a variable lens with which various divergent, collimated or convergent beam shapes can be produced.
All common laser types may be used as the laser. In a preferred configuration, the laser is a short-pulse laser, for example a mode-locked solid-state laser, which emits light pulses with a pulse width of from 100 fs to 10 ps. The wavelength of the laser is preferably matched to the “zero dispersion wavelength” of the fibre, or vice versa. Apparently, the zero dispersion wavelength can be “shifted” over a certain wavelength range, and this needs to be taken into account when pulling the fibre.
An embodiment of the illuminating device which contains an instrument for varying the power of the spectrally broadened light is especially preferred. In this case, it is more particularly advantageous to configure the illuminating device in such a way that the power of the spectrally broadened light can be varied or can be fully stopped-out with respect to at least one selectable wavelength or at least one selectable wavelength range.
An instrument for varying the power of the spectrally bro
Birk Holger
Engelhardt Johann
Moellmann Kyra
Storz Rafael
Foley & Lardner
Leica Microsystems Heidelberg GmbH
Negron Ismael
O'Shea Sandra
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