BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the functional principle of an inventive distance sensor;
FIG. 2 shows the functional principle of an inventive distance sensor having a screening electrode;
FIG. 3 shows a distance sensor plugged onto an objective in a fashion corresponding to the invention;
FIG. 4 shows an oblique view of a distance sensor similar to that in accordance with FIG. 3;
FIG. 5 shows an inventive distance sensor for screwing into an objective revolver of a microscope;
FIG. 6 shows the distance sensor in accordance with FIG. 5 and in the screwed-in state;
FIG. 7 shows an inventive arrangement having three sensors, which are connected to the objective via a disc as spacer;
FIG. 8 shows an inventive arrangement having in each case three sensors per objective, the sensors being interconnected via a disc, and the discs being fastened on the objective revolver via a further holding device;
FIGS. 9
a-9c show an inventive arrangement having a sensor fastened via a holding device;
FIG. 10 shows the sensor in accordance with FIG. 4, on which an electronic unit for carrying out the measurement and for transmitting the measured values via a wireless connection is additionally fitted; and
FIG. 11 shows an electronic circuit for operating an inventive arrangement.
DETAILED DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a section through a distance sensor, and is intended to illustrate the functional principle of such a sensor. The distance sensor 1 includes an outer electrode 2 and an inner electrode 3, between which an electric stray field is formed. Individual field lines 4 of this stray field are illustrated in FIG. 1 schematically. An object 5 is located at a distance d from the sensor 1. Irrespective of whether the object 5 includes a conductor or a nonconductor, the object 5 will influence the capacitance of the sensor as a function of the distance d. This change in the capacitance can be detected by a suitable measuring and evaluation circuit and be assigned to the distance d.
FIG. 2 likewise shows the functional principle of an inventive distance sensor which, however, has a screening electrode 6 in addition to the components of the distance sensor from FIG. 1. A stray field whose field lines 4 are indicated in FIG. 2 is likewise formed between the electrodes 2 and 3 when a voltage is applied to the sensor. However, by contrast with the field lines from FIG. 1, the field extends in the outer region of the sensor, whereas essentially no field lines are formed in the interior.
FIG. 3 shows the application of this functional principle to an inventive distance sensor which can be advantageously plugged onto an objective of a microscope. FIG. 3 shows a section through such a sensor, the sectional plane containing the optical axis 9 of the objective 8. The distance sensor 7 again has an outer electrode 2, which is configured as the lateral surface of a cylinder in this refinement of the sensor. The inner electrode 3 is essentially modeled on the shape of the objective 8, and touches the objective 8 in a form-fitting fashion, even if, for reasons of clarity, a small gap is shown between the objective 8 and outer electrode 3 in the drawing. In addition, the inner electrode 3 has a disc-shaped region 10, which is arranged substantially parallel to the object 5, i.e., the sample being examined or the microscope slide supporting the sample. In the region of the mid-point of the disc-shaped region 10, the objective 8 passes through the inner electrode 3 such that the objective lens 11 is not covered by the distance sensor 7. This ensures that it is possible to conduct microscopy, which includes parallel measurement of the distance.
An electric field, which likewise has components in the form of a stray field is formed between the electrodes 2 and 3. The field lines 4 of the stray field form between the electrode 2 and the disc-shaped region 10 of the electrode 3. If the object 5 now enters the measuring range of the sensor 7, that is to say if the electric field reaches the object 5 with an adequate field strength, a change in capacitance is set up as a function of the distance d of the objective from the object 5. If the object 5 includes a nonconductor, it will be an increase in the capacitance that is to be recorded as a consequence of the dielectric constant of the object 5, increased by comparison with the surroundings.
FIG. 4 shows such a distance sensor in a perspective illustration without the objective. However, both the outer electrode 2 and the inner electrode 3 are modeled on the shape of an objective 8 in the embodiment illustrated here. Consequently, the inner electrode 3 does not have a disc-shaped region 10. Nevertheless, the inner electrode 3 forms an opening 12, which provides the objective lens with free access to the light coming from the sample. Via a connecting cable 13, electrical energy is supplied to the sensor 7 and an evaluation of the capacitance of the sensor 7 is carried out.
FIG. 5 illustrates a further refinement of an inventive distance sensor 7″. Similarly to the distance sensor in accordance with FIG. 4, the distance sensor 7″ has an outer and an inner electrode, which are modeled on the shape of an objective. However, the sensor 7″ additionally has a threaded end 14 with which the sensor 7″ can be screwed into an objective revolver of a microscope.
FIG. 6 shows the distance sensor 7″ of FIG. 5 in a screwed-in state while it is directed towards an object 5 for the purpose of measuring the distance. In addition to the distance sensor 7″, two objectives 8 are screwed into the objective revolver 15. If the distance between the sensor 7″ and the object 5 is determined, the objective revolver 15 can be rotated in such a way that one of the objectives 8 is directed towards the object 5, and the object 5 can be viewed. This sensor, which can be screwed into the objective revolver, is suitable for an autofocus system but is, however, less suited for directly monitoring the microscopy operation in order to protect against destruction of the sample. It would be possible here only to determine once the distance between the sample 5 and the sensor 7″, and then subsequently to track the changes in distance between the sample 5 and one of the objectives 8, and to calculate the actual distance therefrom. Nevertheless, it is thereby possible to determine comparatively accurate distance information, which is suitable for warning the operator of the microscope against too slight a distance.
A further refinement of the arrangement is illustrated in FIG. 7. A holding device 16 is fastened on an objective 8, which is provided with a thread 14 to be screwed into an objective revolver, and has an objective lens 11. The holding device 16 is configured as a disc and supports 3 distance sensors 7′″. The disc is ideally arranged such that the optical axis of the objective 8 is at right angles to the holding device 16. If the distance sensors 7′″ are of identical configuration, it is possible in this way to determine the orientation of the sample 5 and of the object 8 relative to one another in addition to the distance of the objective 8 from the sample 5.
FIG. 8 shows such an arrangement in an installed state. The arrangement in accordance with FIG. 7 is present in a double embodiment and is screwed into an objective revolver 15. One of the holders 17 in the objective revolver remains empty in this case for illustrative purposes. However, this could likewise be fitted and have a sensor system like the other objectives. Both holding devices 16 illustrated are connected to a central unit 18 which is, in turn, connected to the objective revolver 15 via a fastening element 19. This central unit can fulfill a number of tasks. Firstly, it can serve the purpose purely of fixing or holding the holding devices with reference to the objective revolver 15. In this case, a holding device can also be fastened exclusively on the central unit and not on an objective. Secondly, it is possible to arrange in the central unit 18 an electronic circuit which carries out a measurement of the capacitance of the sensors 7′″ and conditions the measured values for further evaluation and/or transmission. However, it would also already be possible here to undertake the evaluation of the measured values. The fastening element 19 could in this case serve not only to fasten the central unit 18, but also have lines which are used to transmit energy and data.
A further refinement of an inventive arrangement is illustrated in FIG. 9. An objective 8 having a thread 14 for screwing into an objective revolver, and an objective lens 11 is connected to a sensor 7′″ via a holding device 16. Arranged around the objective 8 is a collar 20 on which, in turn, there is fastened a part of the holding device 16 with the aid of which the sensor 7′″ is held at a distance from the objective lens 11. In a fashion similar to the case of the exemplary embodiments described above, it is also possible here for the holding device 16 or the collar 20 to be plugged onto the objective 8, bonded or welded thereto, secured with bayonet locks or the like, screwed onto the objective, crimped, or connected in any other way known from practice.
The arrangement illustrated in FIG. 9a can be operated in various ways. If the sensor 7′″ is aligned parallel to the optical axis 9 of the objective 8, it is possible to measure and observe a slightly offset region of a sample located in front of the arrangement. If as illustrated in FIGS. 9b and 9c, the sensor 7′″ is angled in relation to the optical axis 9 of the objective 8, the arrangement can be configured to be able to swivel into a measuring position and an observing position. FIG. 9b shows the arrangement in an observing position. The sample 5 can be subjected to microscopy in this way. If the arrangement is tilted into a measuring position, a distance measurement can be carried out at substantially the same position of the sample 5. A reliable distance measurement can be carried out in this way even in the case of samples of very irregular height.
FIG. 10 shows a distance sensor 7′ in accordance with FIG. 4, on which an electronic unit 21 is additionally fastened. The electronic unit 21 includes an electronic circuit which can carry out a measurement of the capacitance and suitably condition the measured values. It is possible here, in turn, already to carry out first evaluations of the measured values such as, for example, a comparison with a reference value, linearizations or the like. At the same time, the electronic unit 21 can condition the measured values or the evaluated measured values for transmission to a further unit, and transmit them to this unit using a method with or without cables.
FIG. 11 illustrates a circuit which is suitable for operating the inventive arrangement and for carrying out the inventive method. A distance sensor 7 is directed towards a sample 5, it thereby being possible to determine the distance between the sensor 7 and the sample 5. In order to vary the distance, the sample is connected along the z-direction to a suitable drive unit 22. In general, this drive unit 22 will be the adjustment drive for the microscope stage, which supports the sample 5 or the microscope slide supporting the sample. Alternatively, or in addition, the sensor can be moved in, or against the z-direction. This can be performed, for example by moving the objective revolver with the aid of drive unit 23, as a result of which the objective screwed into the objective revolver and supporting the sensor is also moved.
The sensor 7 is connected to a sensor electronic system 24 which is, in turn, connected to a receiving unit 26 via a transmission link 25. The three components (24, 25, 26) can be configured in various ways. Thus, the sensor electronic system 24 can carry out a measurement of the capacitance of the sensor 7, prepare the measured values for wireless transmission, and transmit them to the receiving unit 26 via a radio transmission link 25. Alternatively, the sensor electronic system 24 could be eliminated, and the transmission link 25 could be formed by a coaxial cable. The receiving unit 26 would in this case be a unit which simultaneously carries out the supply of energy to the sensor 7 and measures the capacitance of the sensor 7. Further configurations of such connections are efficiently known from practice and obvious to a person skilled in the art.
The receiving unit 26 is connected to an evaluation circuit 27. The evaluation circuit 27 assigns the determined capacitance value to a distance value between the sensor and sample. This is generally performed via assignment rules known from practice. These assignment rules can be implemented in the form of tables, something which can be implemented with particular ease, especially for an evaluation circuit in the form of a digital computer. Capacitance values between stored values could be suitably interpolated. Alternatively, the assignment between capacitance values and distance value could be suitably calculated by the evaluation circuit. The evaluation circuit could additionally carry out a digital or analog linearization and eliminate nonlinear measuring effects.
The evaluation circuit 27 additionally generates control signals, which can be used to address a control unit 28. This control unit 28 drives the drive unit 22 and/or the drive unit 23 in a suitable way to vary the distance between the sensor 7 and sample 5.
In addition, the evaluation circuit 27 can be connected to an external control unit 29. This control unit 29 can be used, for example, in order to input into the evaluation circuit 27 knowledge relating to the sample 5. However, this control unit 29 can also serve the purpose of visualizing the determined distance values to the user, or of outputting warning notices to the user. The control unit 29 can be implemented in various ways. For example, reference may be made to the use of a personal computer, a PDA (Personal Digital Assistant), a SmartPhone or special hardware.
It may be stressed very particularly in conclusion that the exemplary embodiments previously selected purely arbitrarily serve merely for explaining the inventive teaching but do not confine the latter to the exemplary embodiments.
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
Patent Application
20080068028
