This invention, relates to a microscope slide position recorder and is applicable to microscopes of the kind having a compound stage on which a microscope slide may be mounted and can be moved relative to the optical axis of an objective lens of the microscope, in two directions independently, both directions being normal to the optical axis.

It is often desired to record the location of a point of interest of an object or sample being examined by a microscope- This is so that the point of interest may be relocated at a subsequent time, perhaps by another observer and perhaps using a different microscope. One application is the examination of cervical smears, in which the sample is examined under the microscope so that any suspected cancer cells can be identified: at present it is common for a first observer to mark a point of interest on the slide with a dab of ink, so that a second observer can subsequently locate the point of interest under his or her microscope for further or confirmatory examination. Alternati ely, the first observer must read off the position of the microscope slide from its two vernier scales and make a written note of the co-ordinates concerned. However, these processes are time-consuming both in the position recording and in the position re¬ location, and are prone to errors.

In accordance with, this invention, there is provided a microscope slide position recorder, comprising transducers producing electrical signals representing the position of a slide on the microscope stage relative to its optical axis, and a computer processing unit receiving said signals and operable to record and store in memory data representing the position of the slide at selected instants

of time.

Preferably the computer processing unit responds to actuation of a predetermined key by the operator to record and store in memory data representing the position of the slide at that instant of time. Preferably a visual display unit is provided, which displays the co-ordinates of any slide positions which have been recorded. Preferably the system enables the operator to record information against each recorded slide position, for example the date, reference numbers, description, magnification used, or comments.

When any of the recorded positions on the slide are to be relocated, perhaps by a different observer and perhaps on a different microscope, the position co¬ ordinates can be recalled from memory and displayed on the visual display unit, together with any information also recorded against each set of co-ordinates. Each recorded position can then be relocated by appropriate adjustment of the slide on the microscope. Preferably in order to aid this the visual display unit gives a continual display of the actual position of the slide. It will be appreciated that if the slide is being re-examined on a different microscope, that microscope will be provided with a similar slide position recorder apparatus and the memory disc or tape etc on which the data has been recorded will be transferred to the computer processing unit of this other apparatus.

Preferably for use in relocating a recorded slide position, the visual display unit gives a two-dimensional display of the slide with the position of the microscope optical axis marked on it and also any recorded position which has been selected for relocation. The visual display unit therefore provides a visual reference for achieving co¬ incidence of the slide position to be relocated with the microscope optical axis. Preferably the apparatus emits

audible tones to assist in aligning the slide position to be relocated with the optical axis of the microscope. For example, one distinct tone is emitted when the microscope optical axis is aligned with one co-ordinate axis of the slide position to be relocated, and another distinct tone is emitted when the microscope optical axis is aligned with the other co-ordinates axis of the slide position to be relocated.

The apparatus in accordance with this invention enables observers to locate and record and subsequently relocate points of interest on the slide both quickly and accurately. Furthermore, relevant information or data can be recorded against each recorded point of interest, for recall and display subsequently. Also, the data recorded in memory can be pointed out if required.

An embodiment of this invention will now be described by way of example only and with reference to the accompanying drawings, in which:

FIGURE 1 is a plan view in diagrammatic form of a microscope compound stage, fitted with a microscope slide position recorder in accordance with this invention;

FIGURE 2 is a view in the direction of the arrow II in Figure 1;

FIGURE 3 is a schematic block diagram of the microscope slide position recorder; and

FIGURE 4 is a representation of a typical display given on the screen of the visual display unit of the recorder apparatus.

Referring to Figures 1 and 2 of the accompanying drawings, an optical microscope includes a first stage member 10, fixed relative to the optical axis of an objective lens (not shown) of the microscope, with the optical axis of the microscope normal to the upper surface 11 of the stage member 10.

A second stage member 12 is held on the first

stage member 10 by a slideway which enables the second stage member 12 to move on the first stage member 10 in the direction of the arrow A only. Similarly, a third stage member 13 is held on the second stage member 12 by a slideway which enables the third stage member 13 to move on the second stage member 12 in the direction of the arrow B only, at right angles to the direction of the arrow A. The relative movements of the stage members is effectd by manually operable mechanisms (not shown) , e.g. rotary control knobs geared to displacement devices of the stage members.

A microscope slide which is to be observed is located on the third stage member 13, with the position to be recorded located over an aperture 14 through the stage members.

An L-shaped flat metal body 15 is fastened by screws 16 to the upper face of the second stage member 12, with the limbs of the L adjacent two edges thereof.

Two linear resistive potentiometers 17, 13 are fastened by L— section brackets 19, 20 along the limbs of the body 15. Each potentiom ter 17, 18 includes an internal resistance track along which respective sliders 21, 22 are movable. The slider 21 is mounted on the third stage member 13 and the slider 22 is mounted on a block 25 screwed to the underside of the first stage member 10. The potentiometers 17, 18 have connecting wires 23, 24 connected to a computer processor unit. The resistive impedances across the wires 23, 24 vary linearly with the distances of the respective sliders 21, 22 along the tracks of the potentiometers 17, 18. Thus, electrical voltage signals appearing across the wires 24 will be proportional to the movememnt of the microscope slide relative to the optical axis in the direction of arrow A only. Similarly, electrical voltage signals appearing across the wires 23 will be proportional to the movement of the microscope

slide relative to the optical axis in the direction of arrow B only.

The body 15 is easily removed and can be fitted to another, similar microscope. The positions of the potentiometers 17, 18 on body 15 are adjustable, if necessary.

If preferred, the potentiometers 17, 18 may be inductive or capacitive instead of resistive and the impedances may be arranged to vary non-linearly with slider movement.

Referring to Figure 3, the stage member 10 is shown together with the potentiometers 17, 13 and their sliders 21, 22. The microscope slide 26 is placed against an L-shape register 27 on the stage member 13 (not shown in Figure 3) and the optical axis of the microscope is indicated at 14a. The signals from the potentiometers are fed to an analogue to digital converter 28 which provides digital signals representing the co-ordinates of that position of the slide which is co-incident with the microscope optical axis at that instant, to the computer processing unit 29. The d.c. supply 34 for the potetiometers and the supply for the unit 29 are derived from the mains 35 by a regulator 33. A visual display unit 30 is connected to the processing unit 29, as also are a disc drive unit 31 and a printer 32.

In use of the apparatus, the microscope slide once prepared with its specimen is placed on the microscope stage against the register 27. The microscope stage is then displaced manually until a point of interest on the slide is spotted by the user. If the position of this point of interest is to be recorded, the user simply presses a predetermined key on a keyboard of the processing unit: the digital data at that instant received from the analogue-to-digital converter (and representing the co¬ ordinates of the point of interest) is recorded and stored

in memory, being the disc in ^" the drive unit 31. In addition, the user may record against each recorded point of interest any desired data, for example the date, reference numbers, description, magnification used, or comments. The apparatus may be used for recording the co¬ ordinates of several hundred points of interest and related data on the same disc.

The apparatus also serves for relocating points of interest which have been recorded to the memory disc. The slide is placed on the microscope stage against the register 27. The co-ordinates of each point of interest are recalled f om the memory in turn by the user actuating a predetermined key on the keyboard: for each point of interest, its co-ordinates appear on the visual display at 40 (Figure 4) and its related data appears at 42. The visual display unit gives a representation of the slide at 37 with indications at 38 and 39 of the position of the target or point of interest and of the optical axis of the microscope. The co-ordinates of the microscope optical axis, relative to a reference point on the slide, are displayed at 41. The microscope stage is now displaced by the user in the normal way, the co-ordinates of the present position being updated at 41. The user now wants to displace or adjust the position of the microscope stage until the point of interest (the co-ordiates of which remain displayed at 40) co-incides with the microscope optical axis. In order to assist this relocation process, the computer unit 29 is arranged to emit a first distinctive audible tone when the optical axis 39 and the target point of interest 38 are aligned on the same X-axis, and to emit a second distinctive audible tone when the optical axis 39 and the target point of interest 38 are aligned on the same Y-axis. Thus the user may simply displace the stage along one of the two axes until the respective audible tone is heard, then displace the stage

along the other axis until the other audible tone is also heard, at which instant the point of interest 38 will be aligned on the optical axis of the microscope, or in particular the cross 39 indicating the position of the microscope optical axis is entirely within the circle 38 indicating the position of the target point of interest. Once the user has finished studying this point of interest, he may call up the next point of interest from the memory by pressing the appropriate key on the keyboard, and repeat the process.

Instead of the position of the microscope stage being adjusted manually, electric drive motors may be provided for this purpose. The drive motors may then automatically adjust the stage position to the target position each time a point of interest is recalled from the memory. This may be done by the computer processing unit generating electrical signals in proportion to the difference between the actual position of the slide relative to the optical axis of the microscope, and the recorded information regarding a particular point of interest. However, even for a manual stage adjustment, the drive motor may be used and controlled from e.g. a joystick rather than from individual control knobs which adjust the stage along its respective axes.

In a modification of the apparatus which has been described, a transducer may be coupled to the objective lens carrier of the microscope so that information as to the position of the point of interest along the optical axis (the Z axis) can be recorded together with the X and Y co-ordinate information, and similarly used for relocation as described above.