Optical: systems and elements – Deflection using a moving element
Reexamination Certificate
1999-08-24
2001-01-09
Phan, James (Department: 2872)
Optical: systems and elements
Deflection using a moving element
C359S201100, C359S202100, C359S206100, C359S393000, C356S317000
Reexamination Certificate
active
06172785
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-emitting device for emitting excitation light having a wavelength which is suitable for exciting secondary light on or in the sample, a scanning unit for scanning at least one subarea of the sample with said excitation light, and a detection unit for the secondary light emitted in response to excitation of the sample, said detection unit comprising a detection optics and a detector device.
BACKGROUND ART
Light scanning devices of the above-mentioned type are used e.g. for a spatially resolved fluorescence examination of a sample. For this purpose, the scanning light is produced in the form of a single beam by means of the light-emitting device, which is a laser in most cases, said scanning light being then directed onto the sample. By means of the scanning unit, e.g. in the form of tilting mirrors with two orthogonal tilting axes or axes of rotation in the optical path of the light beam, the beam can be rastered over the sample. The scanning light excites on the surface of the sample or in the sample the generation of secondary light, e.g. in the form of fluorescent light. This secondary light is collected via an imaging optics and detected on a detection unit. Since the scanning unit irradiates, in a precisely definable manner, a respective specific spot on the sample in dependence upon the position of the tilting mirrors relative to one another and relative to the sample, a locally dependent statement with regard to the respective property of the sample can be made by means of the detection unit detecting the intensity of the secondary light.
Since the spatial resolution is already obtained by the scanning unit, the detector device according to the prior art is a simple spot detector without spatial resolution which only detects the presence or the absence of secondary light emission independently of the point of its generation on the sample. However, after the irradiation of a specific scanning point on the sample, the irradiation of the next scanning point on the sample must be delayed until the electric signal produced by the secondary light in the photodetector has been recognized and read out and until the photodetector has been re-initialized for the next measurement. Even if a fast read-out electronics is used, this waiting time represents an undesirable delay in a fluorescence examination of a comparatively large sample to be scanned.
The scanning time for measuring the whole sample depends on various additional parameters, such as the size of the angular field on the sample, the scanning increment, the spot size of the scanning beam on the sample, the integration time of the detection unit, the scanning or mirror velocity of the scanning unit as well as the desired signal-to-noise ratio. When samples with dimensions in the centimeter range are scanned with a high spatial resolution by a scanning beam focussed to a few micrometers, the scanning times of conventional scanning devices are in the range of minutes to hours. Such long scanning times are, however, a great problem for the operation of scanning devices of this kind.
SUMMARY OF THE INVENTION
It is therefore the object of the present invention to provide an improved light scanning device which can be used for scanning a sample and for detecting secondary radiation excited by the scanning light and by means of which a faster and more efficient scanning of a large sample with high spatial resolution can be accomplished.
According to the present invention, this object is achieved by a light scanning device of the type cited at the start, which is characterized in that the detector device comprises a large number of detection elements arranged in an array with predetermined position coordinates, said detection elements being arranged in an imaging plane of the detection optics and converting light detected in a spatially resolved manner into electric signals.
In the case of the solution according to the present invention, a subarea of the sample, which depends on the magnification of the detection optics and which is scanned by the scanning light, (or the whole sample area) is imaged by means of the detection optics onto the planar detector device provided with a fieldlike array of detection elements. On the basis of the capability of detecting the secondary light in a spatially resolved manner, unequivocal imaging is guaranteed and it is guaranteed that the respective detector elements can unequivocally be associated with the corresponding area on the sample onto which the scanning light is focussed. Hence, it is possible to scan the sample subarea, which has been imaged on the detector device, without any waiting times between the individual rastering positions and to read out the whole detector device with all detection elements in common after the end of the scanning operation. This has the effect that much faster scanning is achieved than in cases in which a spot detector is used. A further advantage of the solution according to the present invention is to be seen in the fact that the accuracy of the spatial resolution on the sample is guaranteed by the resolution of the detector and is no longer influenced by tolerances which may perhaps occur in the tilting mirrors during scanning. Due to the sequential scanning of the sample with the excitation light, in the case of which the location illuminated with comparatively intensive radiation is always only one location on the sample having the size of the scanning beam, a much higher local fluorescent signal is achieved than in cases where a full-area illumination of the sample is carried out. It follows that the provision of a dual spatial resolution by the scanning unit as well as by the detector device leads, on the one hand, to an increase of the fluorescent signal of the respective scanning spot and, on the other hand, still to a drastic reduction of the scanning time required for a sample having a comparatively large surface, said dual spatial resolution being not known in the prior art.
A further advantage of the device according to the present invention is to be seen in the fact that imaging errors of the detection optics can be determined e.g. with the aid of a testing method, which is carried out once and which is executed e.g. with the aid of a test grating, such as a Ronchi grating, and that these imaging errors can subsequently be used for image correction. This permits the use of simple lenses for the detection optics, which are corrected to a comparatively low degree and which are therefore less expensive.
According to a preferred further development of the present invention, the detection optics is a varifocal optics with variable magnification in the case of which a variable sample area is imaged onto the constant detector area. It is thus possible to adjust the resolution in a comparatively simple manner while varying the scanning area accordingly. If a reducing image scale is used, a survey of a larger area can be obtained without any necessity of changing the scanning carried out by the scanning unit. If, however, a enlarged image is used, details can be made visible on the sample area again without any change of the scanning conditions produced by the scanning unit.
In the above-mentioned further development, it will be particularly advantageous to provide a sample holder which is adapted to be displaced in at least one direction relative to the optical axis of the scanning light. When details of the sample are examined, different areas of the sample can be moved into the object plane of the detection optics by means of this arrangement.
According to an additional advantageous further development of the present invention, the detection optics comprises a first lens and a second lens which are arranged in spaced relationship with each other. Additional optical elements for processing or influencing the secondary light can be provided between the two spaced-apa
Bodenseewerk Perkin-Elmer GmbH
Perman & Green LLP
Phan James
LandOfFree
Light-scanning device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Light-scanning device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Light-scanning device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2478915