Beam scanner for confocal microscopes

Details Beam scanner for confocal microscopes Beam scanner for confocal microscopes

1997-04-17

1999-12-14

Phan, James

Optical: systems and elements

Light control by opaque element or medium movable in or...

With rotating or pivoting element

359230, 359368, G02B 2602

Patent

active

060025093

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention involves a beam scanner for confocal microscopes with a rotary-drive disk as a base.
Beam scanners with disk-shaped, rotary-drive bases so-called disk scanners, have been used for several years in confocal microscopy. In the confocal microscopic imaging procedure only the structures of an object that are directly in the focal plane of the microscope objective are displayed. In a confocal optical arrangement the object is illuminated in the focal plane by a point light source. The light coming from the object is reflected by a beam splitter in the direction of a point light detector and detected. In this regard the point light source, point light detector, and the limited- diffraction light point on the object in the focal plane lie exactly in the optically conjugate points. Light that comes from outside the focal plane is not focussed sharply on the point light detector and hence is also not registered by the detector. For this reason there are no inputs from unfocussed parts of the object. Object parts that lie outside the focal plane are thus almost faded out. In practice very small pinhole apertures are used for the light source and point light detector. In order now to produce a three-dimensional image of an object, the light point must be guided relative to the object in an appropriate manner. One possibility for this is to use a multipoint scanner in the form of a Nipkow disk. This is a disk driven with an electric motor and having a grid of tiny apertures, so-called pinholes. A problem that occurs in practice in using the known disk scanner involves the light reflected back from the upper surface of the disk that falls on the eyepiece and irradiates or at least affects adversely the image of the object. Avoiding this kind of scattered light effects often requires substantial expenditure on apparatus. In addition, the use of a Nipkow disk as a beam scanner requires relatively expensive auxiliary optics because of the diffraction phenomena that occur at the pinhole apertures.


SUMMARY OF THE INVENTION

The invention has the objective of indicating a beam scanner for confocal microscopes of the kind initially mentioned having auxiliary optics that are relatively inexpensive in comparison to the auxiliary optics of Nipkow disks and that can be connected to a conventional microscope.
The beam scanner in accordance with the invention achieves the above objective through the characteristics describe in the present specification. According to it the beam scanner that was initially mentioned is designed in such a way that at least one main upper surface of the disk has a reflection raster in which the repetitive, reflecting pattern elements, i. e. either the zones corresponding to the mesh of the reflection raster or only the zones of the upper surface corresponding to the grid of the reflection raster reflect light.
In accordance with the invention it is recognized that the realization of a point light source or a point light detector is essential for the operation of a beam scanner.
The beam scanner in accordance with the invention can be used just like the known Nipkow disk as a point light source and point light detector.
In place of a raster-like arrangement of pinhole apertures in the base, a main upper surface of the beam scanner in accordance with the invention has a reflection raster. Normally a raster consists of a grid and the meshes formed by this grid. Below--just for the simplification of the explanations--it will always be assumed that only the meshes reflect light, although in principle only the areas corresponding to the grid also could reflect light.
Depending on the layout of the reflection raster, the individual meshes may lie closer to one another or farther apart, which has an effect on the signal to noise ratio, since through every mesh a small part of the light of the neighboring meshes from unfocussed object areas also is detected. The resolving power also depends on the design of the reflection raster, namely on the geometry of the individ

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