Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-12-17
2001-04-03
Schuberg, Darren (Department: 2872)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S209100, C356S317000
Reexamination Certificate
active
06211989
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a light scanning device for exciting and detecting secondary light, especially fluorescent light, on a sample, comprising a light emission device for emitting exciting light with a wavelength suitable for exciting secondary light on or in said sample, a focussing optics for focussing the exciting light on said sample, a sample holding device for releasably holding the sample, a detection unit comprising a detection optics for the secondary light emitted by the sample in response to excitation and a detector device for converting the secondary light into electric signals.
BACKGROUND ART
Such light scanning devices are used e.g. for examinations in the field of molecular biology or genetic technology. For these examinations, a large number of materials to be examined are applied to a carrier in a fieldlike configuration, whereupon said materials are temporarily brought into contact with a fluorescent tracer. The materials to be examined having an affinity for the tracer will bind said tracer to themselves and can therefore be excited so as to emit fluorescent light. It follows that, due to the excitability of the fluorescence, the property of the examined material to bind to itself the tracer becomes visible, whereby it is possible to draw conclusions with regard to the nature of the sample material.
When examinations in the field of molecular biology or genetic technology are carried out, large fields of such materials marked with fluorescent substances are sequentially scanned with exciting light. In hitherto known devices, the carrier holding the sample materials has been scanned by means of two tilting mirrors provided in the optical path of the exciting light, the two axes of rotation of said tilting mirrors extending at right angles to one another. When the scanning light beam impinges on a location where a marked and, consequently, fluorescent sample material is present secondary light will be emitted, which is detected by a detection unit comprising a detection optics and a detector device, and converted into electric signals.
In such devices the rotation of the tilting mirrors for the purpose of scanning is, however, subject to tolerances, and due to the long beam path this results in major inaccuracies in the local resolution of the scanning. In the case of a “pre-objective-scanning” arrangement of the focussing optics (i.e. between the scanning unit and the sample), it is additionally necessary that said focussing optics has a large diameter so that an image of the light ray bundle deflected from the optical axis by the scanning mirrors can be formed in the plane of the sample. When such large-diameter lenses are used, a correction for large angular fields and a good field flatness is, however, very complicated and entails therefore higher costs.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a light scanning device of the type mentioned at the beginning, by means of which an improved local resolution can be achieved on the basis of a simplified structural design.
According to the present invention, this object is achieved by a light scanning device of the type mentioned at the beginning, which is characterized in that the sample holding device is adapted to be rotated for rotating the sample relative to the exciting light in such a way that different subareas of said sample can be excited by means of the exciting light so as to emit secondary light.
According to the present invention, this object is additionally achieved by a light scanning device of the type mentioned at the beginning, which is characterized in that the focussing optics is rotatably supported so as to conduct the exciting light along a circular arc on the sample.
According to these two solutions, the hitherto known scanning system making use of tilting mirrors is replaced by a mechanical rotation of either the sample or the scanning light beam, a circular arc on the surface of the sample being scanned in both cases. An increase of inaccuracies and tolerances, respectively, which occurs according to the galvanometer principle when the tilting mirrors are rotated in the hitherto known scanning devices and which results in comparatively large inaccuracies of the position coordinates of the scanning beam on the sample, is excluded in the device according to the present invention, since the beam axis is not tilted relative to the sample surface. Devices according to the present invention can therefore achieve high local resolutions of up to 2 &mgr;m, e.g. in cases where a suitable laser diode is used as a light emission device. In addition, the focussing optics used for focussing the exciting light onto a subarea of the sample can consist of a comparatively economy-priced lens having a small diameter and a small corrected field area. The device according to the present invention permits therefore a substantial reduction of costs due to the fact that a simple and inexpensive focussing optics is used and that the complicated holding and control means for the tilting mirrors can be dispensed with.
According to an advantageous further development of the present invention, the focussing optics is adapted to be radially displaced relative to the axis of rotation of the sample holding device or the sample holder is adapted to be displaced in the radial direction relative to the optical axis of the focussing optics. A two dimensional local resolution by means of a simple mechanical movement of the focussing optics and of the sample holder, respectively, is achieved in this way, without changing the angle of the beam axis relative to the surface of the sample. It follows that, according to this advantageous further development, the very good local resolution is achieved also in the second dimension. The above-mentioned economy-priced lens having a small diameter and requiring little expenditure with regard to, field correction can also be used in this embodiment.
According to another advantageous further development, two or more respectively associated pairs of the focussing optics and of the detection unit are provided. This permits a substantial reduction of the scanning time, especially in cases where large samples and a high resolution are used. When two focussing optics and detection unit pairs are used, the scanning time of the sample surface will be halved. The optical paths of the two focussing optics and detection unit pairs should preferably extend at a distance from one another which corresponds to half the radius of the total area scanned. In particular, it will be advantageous when said focussing optics and detection unit pairs are mechanically coupled. In this case, adjusting elements for radially displacing the focussing optics can be dispensed with due to the mechanical coupling, and this will, in turn, reduce the costs of the light scanning device according to the present invention, and, in addition, a more precise positioning will be guaranteed due to the rigid mechanical connection.
When a plurality of detectors is used simultaneously, it will be advantageous to provide pinhole diaphragms in a respective imaging plane of a detection optics in front of the detector device in question. This will prevent crosstalk between the individual detectors and an acceptance of stray light from the surroundings of the exciting light spot.
Finally, a plurality of light sources with different emission light wavelengths and/or colour filters of different transmission wavelengths can be provided in front of the individual detector devices in the light scanning device according to the present invention, whereby the flexibility and the versatility of the system will be increased.
Further advantageous embodiments are disclosed in the sub-claims.
REFERENCES:
patent: 4626684 (1986-12-01), Landa
patent: 5022757 (1991-06-01), Modell
patent: 504 432 (1992-09-01), None
patent: 753 779 (1997-01-01), None
patent: 96/09548 (1996-03-01), None
Klemm Henry
Steinwand Michael
Wulf Jurgen
Bodenseewerk Perkin-Elmer GmbH
Perman & Green LLP
Schuberg Darren
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