Optical: systems and elements – Compound lens system – Microscope
Patent
1991-05-31
1994-06-14
Arnold, Bruce Y.
Optical: systems and elements
Compound lens system
Microscope
359396, 359397, G02B 2126
Patent
active
053215451
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a stage for holding porous media (filters) or non-porous media, that are flexible or rigid, and that carry multiple samples which may be biological or otherwise, and also to a method of analyzing said samples using the above-mentioned stage. The stage is suitable for placing beneath an optical microscope and may constitute an over-stage, or else it may replace the conventional stage. The stage of the invention is particularly suitable for analyzing samples rapidly, in particular by making use of automatic image analysis by computer.
2. Description of the Prior Art
It is recalled that in microscopy the object rests on a glass slide and, in general, it is covered by a glass cover-slip. When analyzing bacteria on a filter, this additional medium is naturally present, given that the only possible technique presently known for ensuring that the filter is properly plane is to mount it between a slide and a cover-slip.
Conventionally, a microscope stage includes a fixing plane which is fixed to a focusing rack. The plane of the stage moves in the Y direction and the slide is held by a vice that is movable in the X direction. The slide is placed against the stage and a spring Jaw is pressed laterally against the slide. In practice, this system suffers from two defects:
1) the glass slide may be at a slight angle relative to the plane of the stage; and
2) the lateral stress exerted by the spring may curve the slide slightly.
At high magnification, and when performing X and Y displacement, it thus becomes essential to keep on readjusting the focus, to such an extent that a microscope operator generally works with one hand constantly active on the micrometer screw.
The ever increasing use of image-analyzing computers coupled to microscopes has led to X-Y stages being used that are driven by stepper motors. On the more sophisticated models, a special over-stage stresses the slide better.
Regardless of whether conventional analysis or automatic image analysis is being performed, the system includes a glass slide (with the commonest size being 75 mm.times.25 mm.times.1.2 mm) that will never be accurately plane given that the slide is very thin (1.2 mm) and very long (75 mm). In addition, slides are cheap consumable objects and they are not required to have very special optical properties.
It should be observed that the thinness of the slide is desirable for optical reasons. In conventional microscope applications, light arrives from below (transmitted light) via a condenser. To ensure that the illumination is intense and uniform, it is necessary to bring the condenser as close to the object as the objective lens.
This is not possible at very high magnification. An objective lens having a magnification of 100 times (giving a total magnification of 2000) is disposed at a distance of about 0.2 mm from the object (which leaves only just enough room for the cover-slip over the object).
Naturally, when using epifluorescence, there is no need for a condenser since the illumination arrives via the objective lens.
With filters, mounting a filter between a slide and a cover-slip is the only available technique for making the filter properly plane.
Filtration is being used more and more for analyzing particles contained in gases and liquids. These particles are varied in nature, being biological, mineral, metallic, etc. . . . One example is separating and counting bacteria in milk (using filters known under trade names "NUCLEOPORE", "MULLIPORE", etc.).
It should also be recalled that a liquid mounting medium is required, constituting either by oil, or by a viscous medium (Canada balsam) or else by a medium that sets over time.
The corresponding operations are relatively difficult and not very compatible with notions of high analysis throughput.
In addition, it is very difficult to obtain an accurately plane preparation. The filter cannot be pressed down accurately and the inevitable differences in the thickness of the above-mentioned mounting l
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"Work Holder and Alignment Device", Lanpdon et al., IBM Technical Disclosure Bulletin, vol. 5, No. 9, Feb. 1963, pp. 7-8.
Arnold Bruce Y.
Biocom S.A.
Nguyen Thong
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