GB2346755A

GB2346755A - Aperture setting for infrared microscope using virtual aperture superimposed on sample image

Info

Publication number: GB2346755A
Application number: GB9929066A
Authority: GB
Inventors: Yasushi Nakata
Original assignee: Shimadzu Corp
Current assignee: Shimadzu Corp
Priority date: 1998-12-10
Filing date: 1999-12-08
Publication date: 2000-08-16
Also published as: JP2000180726A; DE19959184A1; GB9929066D0; JP3322227B2

Abstract

An image of a virtual aperture (51, Figure 3A) is superimposed on an image of a microscope sample (50, Figure 3A) on the screen 8 of a display. Looking at the screen, an operator gives commands to a virtual aperture generator 12 to set the image 51 of the virtual aperture at a desired position, dimensions and orientation with respect to the image of the sample 50, using mouse or other input device. When the setting operation is finished, information representing the position of the image of the virtual aperture 51 with respect to the image of the sample 50 is obtained from the virtual aperture generator 12 and the sample stage driver 18, or from the display controller 15. The information is converted to corresponding values of the actual sample stage 41 and the aperture 36, and control values for bringing the the actual aperture 36 to the target position of the virtual aperture 51 and the image 50 of the sample on the screen set by the operator.

Description

2346755 INFR,kRED MICROSCOPE The present invention relates to an infrared

microscope in which infrared light is cast to a sample, and the infrared light transmitted through the sample or reflected from the sample is observed to probe into the sample.

BACKGROUND OF THE D4VETsMON

In an infrared microscope, the spectrum (which is a plot of the intensity against wavelength) of the reflected or transmitted infrared light is obtained, and the spectrum is analyzed to probe into the sample. When a sample is observed with an infrared microscope, the size of the observation field is generally as small as 100 micrometers to 1 mm, and it is often the case that a smaller area within the observation field is further observed or a small inclusion found in the observation field is then specifically observed. For performing an observation of such a further smaller area (we call it "spotted area"), a field restrictor (which is composed of one or more movable plates, for example) having an aperture is usually provided in an infrared microscope. Only the transmitted/reflected infrared light from the spotted area of the sample is allowed to pass through the aperture and can reach the infrared processing part of the microscope. This provides more precise analysis of the spectrum because noise caused by infrared lights other than from the spotted area is eliminated.

Figs. 4A and 4B illustrate a portion of a conventional infrared microscope around the field restrictor, where Fig. 4A is a side view and Fig. 4B is the plan view. In Fig. 4A, the field restrictor 30 is shown by the cross-sectional view. The sample stage 41 is movable two- dimensionally in the X-Y plane owing to a stage driving mechanism (not shown). The sample stage 41 is further movable in the Z direction by the stage driving mechanism. An objective lens unit 42 is positioned right above the sample stage 41, and the field restrictor 30 is positioned right above the ob ective lens unit 42 having the center axis 43 in common with the objective lens unit 42. As shown in Fig. 4B, the field restrictor 30 includes four aperture plates 32-35 and a plate holder 31. The plate holder

I 31 is held in the main body and is rotatable around the central axis 43. The four aperture plates 32-35 are held in the plate holder 3 1, where a pair of opposing aperture plates 32, ')4 are movable in the X direction and the other pair of opposing aperture plates 33, ')5 are 1.

movable in the Y direction. An aperture driving mechanism is provided (not shown in the drawing g) in the infrared microscope, and the aperture driving mechanism usually moves two opposing aperture plates [3)2, 34] or [3)3, 35] within each pair synchronously by the same amount but in the opposite direction, and rotates the plate holder 31 with the two pairs of aperture plates 32-35 within a certain preset angle around the central axis 43.

The stage driving mechanism and the aperture driving mechanism are operated manually using screws or electrically using motors.

When a sample 44 is observed, the sample 44 is placed on the sample stage 41, brought to right under the objective lens unit 42, and the visible light lamp 45 is turned on to cast visible light onto the sample 44. When the vertical position of the sample stage 41 is properly adjusted, a magnified image of the sample 44 is produced on the imaging plane behind the objective lens unit 42. The imaging plane lies on the contact plane of the lower aperture plates (32 and 34 in Fig. 4A) and the upper aperture plates (33 in Fig. 4A).

Looking at the image passing through, and restricted by, the aperture 36 formed by the four aperture plates 32-35, the observer moves the sample stage 41 in the X-Y plane, change the widths of the aperture plate pairs 32-35 and rotates the plate holder 31 to bring a desired observation spot of the sample 44 into the aperture 36. When the spotting operation is finished, the visible light lamp 45 is turned off and the infrared light lamp 46 is turned on to perform an infrared spectrum analysis of the sample 44.

In the above field restrictor of the infrared microscope, the aperture 36 is formed by four aperture plates 32-35 and the aperture adjusting operation is as follows.

(1) The sample stage 41 is moved in the X-Y plane to determine the position (X,Y) of the aperture 36 with respect to the sample 44.

(2) The distance dl between the first pair of aperture plates 32, 34 and the distance d2 between the second pair of aperture plates 33, 35 are adjusted to determine the two widths of the aperture 36.

2 (3) The plate holder 31 is rotated with respect to the main body of the infrared microscope to determine the orientation of the aperture 36 with respect to the sample 44.

The order of the above three operations may be changed. Anyway the observer performs the operations looking at the image of the sample 44 restricted by the aperture 36.

As explained above, the observer needs to perform two-stage operations: one for adjusting the position of the sample stage 41 and the other for adjusting the position of the aperture '16 including the widths and the orientation. Such operations require a lot of care and are usually time consuming.

It is designed, as described above, that the center of the aperture 36 is the same as the central axis 43 of the aperture holder 31, but there is actually a displacement between the two centers due to manufactural (or dimensional) inaccuracy of constituting parts and assembling inaccuracy of the parts. When, in such a situation, the plate holder 31 is rotated, the center of the image restricted by the aperture 36 moves and, in the extreme case, the desired observation spot goes out of the restricted observation field. In this case, the sample stage 41 must be operated again to bring it back within the restricted observation field, and sometimes the aperture adjusting operation and the sample stage adjusting operation need to be repeated several times to bring the desired observation spot properly within the restricted area.

An object of the present invention is therefore to provide an improved infrared microscope in which the spotting operation is facilitated and the accuracy of the spottinia is high.

SUMMARY OF THE DNETMON

An infrared microscope according to the present invention includes:

a sample stage on which a sample is mounted; a sample stage driver for moving the sample stage laterally; a field restrictor having an aperture for restricting light from the sample; an aperture driver for setting dimensions and an orientation of the aperture with respect to the sample stage; 3 a camera for taking an image of the sample on the sample stage; a virtual aperture generator for generating an image of a virtual aperture whose position, dimensions and orientation can be changed by externally given commands; a display controller for showing the image of the sample and the image of the virtual aperture superimposed on the image of the sample on a screen; and a controller for controlling the sample stage driver and the aperture driver based on the relative position of the image of the sample and the image of the virtual aperture.

When an operator uses the above infrared microscope, the operator looks at the screen and gives commands to the virtual aperture generator to set the image of the virtual aperture at a desired position, dimensions and orientation with respect to the image of the sample. Input devices such as a keyboard or mouse may be used in giving such commands. When the setting operation is finished, the controller obtains information representing the position of the image of the virtual aperture with respect to the image of the sample from the virtual aperture generator and the sample stage driver, or from the display controller. The information is converted to corresponding values of the actual sample stage and the actual aperture, and control values are made from the converted values. The control values are used to bring the sample stage and the field restrictor from the current position to the target position corresponding to the position of the virtual aperture and the image of the sample on the screen set by the operator. The controller sends signals representing the control values to the sample stage driver and the aperture driver, whereby the actual aperture and the sample are brought to the position desired and set by the operator on the screen.

Since the relative position of the sample and the aperture is virtually shown on the screen, the operator can set the aperture at a desired position with respect to the sample before effecting the actual relationship of the aperture and the sample. Thus it is very easy to set the aperture as desired and even a novice can operate the microscope in a short time with a high efficiency.

Since, in a conventional infrared microscope, as described above, the two opposing sides of a rectangular aperture always move together, it is sometimes difficult to 4 set a desired point of the sample at the center or desired place of the aperture. In the infrared microscope described hereinbelow, on the other hand, each side of the virtual aperture can be independently and arbitrarily moved while looking at the virtual aperture and the sample on the screen. Thus it is also easy for the operator to bring a desired point of the sample at the center or at any position of the aperture.

Further aspects and features of the invention are exemplified by the attached claims. BRIEF DESCRIPTION OF THE DRAWINGS

Fi". 1 is a construction diagram of an infrared microscope system embodying the present invention.

Fig. 2 is a system diagram of the parts relating to setting and positioning of the aperture and the sample.

Fig. 3A is a diagram illustrating the images on the display screen.

Fig. 3B is a diagram corresponding to Fig. 3A illustrating the actual positions of the aperture and the sample.

Fig. 4A is a side view of a sample stage and field restrictor of a conventional infrared microscope.

Fig. 4B is a plan view of the field restrictor of Fig. 4A.

DETAELED DESCRIPTION OF A PREFERRED EMBODMIENT

An infrared microscope system embodying the present invention is described using Figs. 1-3B. As shown in Fig. 1, the infrared microscope system 1 mainly corsists of an analyzing section 2 and a control section 3. The analyzing section 2 includes: two lamps for respectively casting visible light and infrared light onto a sample; a sample stage on which a sample to be observed is mounted; a stage moving mechanism for moving the sample stage horizontally in the X-Y plane and vertically in the Z direction; an objective lens unit for converging light reflected by the sample to produce a magnified image on an imaging plane placed within the field restrictor subsequently mentioned; a field restrictor for forming a rectangular aperture composed of slidable aperture plates and a rotatable plate holder; an aperture setting mechanism for moving the aperture plates and the plate holder; a CCD camera for converting the image produced on the imaging plane into electric signals; and an infrared analyzer for receiving infrared light coming ftom the sample and generating signals responsive to the infrared light. In Fig. 1, only the sample C 17 stage 41, sample 44 and the restrictor 30 are numbered.

The control section 3 is realized by a personal computer including, a processing section 4 (consisting of a CPU, memory and other peripheral devices), a display 5, and input devices such as a mouse 6 and a keyboard 7. Other input devices such as a tablet may be equipped. The electrical signals generated by and sent out from the camera of the analyzing section 2 are converted in the processing section 4 into an image signal, and the image signal is sent to the display 5, whereby the magnified image 9 of the sample 44 restricted by the aperture is shown on the screen 8 of the display 5.

Fig. 2 illustrates the parts relating to aperture setting. T'he light from the sample 44 passes through and is restricted by the aperture 36 of the field restrictor 30, and is reflected by a mirror 25 to enter the CCD camera 24. The mirror 25 is movable and can be displaced from the light path. The CCD camera 24 produces electrical signals of the (7 given image, and the signals are sent through an image signal interface 16 to a display controller 15 of the processing section 4. The image signal interface 16 is equipped with an A/D converter.

The aperture setting mechanism is composed of first (x-) and second (y-) motors 20, 21 for moving the two pairs of the aperture plates 32, 34/33, 35 and a third motor 19 for rotating the plate holder 31. The three motors 19-21 are controlled by control signals sent from an aperture controller 17. The stage moving mechanism is composed of two motors 22 and 23 for X and Y directions respectively, and the two motors 22, 23 are controlled by control signals sent from a stage controller 18. The stage 41 is also moved in Z direction by a third motor, which is not shown in Fig. 2. For the motors 19-23, stepping motors are used which move through an angle corresponding to the number of pulses sent from the controllers 17, 18.

The processing section 4 includes, besides the above-described display controller 15, an input interface 11, a virtual aperture generator 12 and a position controller 13 which includes a coordinate converter 14. Input devices 10 such as a mouse 6 and a keyboard 7 6 are connected to the input interface 11.

The aperture setting operation is then described. First the aperture 36 is fully opened, the visible light lamp 45 is turned on, and the mirror 25 is brought into the light path. In this situation, light reflected from a rather broad area of the sample surface enters the CCD camera 24. The signal of the image taken by the CCD camera 24 is sent via the interface 16 to the display controller 15 and the image is shown on the screen 8 of the display 5. By operating the input device 10, the operator moves the sample stage 41 to brinc, a desired observation spot within the screen 8 of the display 5. This is a rough positioning.

The virtual aperture generator 12 generates image signal for showing an image of a rectangular virtual aperture 51 superimposed on the image of the sample surface on the screen 8 of the display 5. Fig. 3A shows an example of such superimposed images of the sample 50 and the virtual aperture 51 on the screen 8. Looking at the screen 8, the operator can place the virtual aperture 51 at any position of the screen 8 and can change it to any shape (rectangular, though) and size by operating the input device 10. Image generation and such operations to the virtual aperture 51 on the screen 8 can be easily realized by using various well-known graphic program tools (line-drawing, enlarging/shrinking, shift, rotation, etc.).

The rectangular virtual aperture 51 on the screen 8 is determined by the following parameters.

(1) Ile coordinates (Cx,Cy) of the center point (Q in Fig. 3A) of the virtual aperture 51. The origin (0,0) of the x-y coordinate system is set at the center (P in Fig. 3A) of the screen 8, and the unit is a pixel.

(2) The lengths of the two sides [Ax,Ay] of the rectangular virtual aperture 51 in pixels.

(3) The inclination (or angle) E9 of the virtual aperture 51 from the xaxis.

The shape and size of the virtual aperture 51 can be arbitrarily changed, while the property as a rectangular is maintained. When, for example, a side 51a of the virtual aperture 51 is translated in parallel to another place 51b as shown by the dotted line in Fig.

7 3A, the length Ax of the other side changes and the coordinates (Cx,Cy) of the center point Q also changes.

When the operator finishes bringing the virtual aperture 51 to a desired place and C determining its shape and size, he/she gives a command through the input interface 11 to the position controller 13 instructing that the aperture setting operation has finished.

IP Responsive to the command, the coordinate converter 14 performs calculations to convert the above parameters of the virtual aperture 51 in the x-y and e coordinate system of the screen 8 to parameters representing the position of the actual aperture 36 and the sample stage in its proper X-Y and 0 coordinate system. It is supposed here that the x direction and y direction of the x-y coordinate system respectively correspond to the X direction and Y direction of the X-Y coordinate system of the actual aperture and sample stage, and the dimensional ratio of the two coordinate systems is R. The ratio R may differ from machine to machine but does not change in a machine. Tbus it is possible to determine the value of R beforehand in a machine.

1] If the position of the sample stage 41 is (Sx,Sy) in the X-Y coordinate system when the operator finishes setting the virtual aperture 51, aperture setting parameters Ax', Ay', 0 'and sample stage position parameters Sx', Sy' are calculated as follows.

Ax'= R X Ax Ay'= R X Ay 61 = 0 Sx'= Sx + RX Cx Sy'=Sy+RxCy The relative position of the sample 44 and the aperture 36 in the X-Y and e coordinate system is as shown in Fig. 3B. The parameters in the X-Y and 0 coordinate system are used as the target values for moving the sample stage 41 and for setting the distances (or aperture widths) and rotative position of the aperture plates 32-35 in the plate holder 31, and the position controller 13 including the coordinate converter 14 sends the target values of Ax% Ay' and 6' to the aperture controller 17 and the values of Sx' and Sy' 8 to the sample stage controller 18.

The aperture controller 17 and the sample stage controller 18 respectively include data storages for storing reference tables comparing coordinate values in the X-Y and 0 coordinate system and the numbers of pulses corresponding to the coordinate values for driving the pulse motors 19-23 to brina the aperture 36 and the sample stage 41 to the position corresponding to the coordinate values. When above parameters are given, the aperture controller 17 and the sample controller 18 refer the reference tables in the data storages, determine the numbers of pulses and send pulses of the numbers to the motors 19-23. Accordingly the aperture plates 32-35 slide, the plate holder 31 rotates and the sample stage 41 moves. The field restrictor 30 and the sample stage 41 thus move in cooperation to bring the actual sample 44 and the aperture 36 exactly as shown by the sample image 50 and the virtual aperture 51 on the screen 8.

When setting and positioning of the sample stage 41 and the aperture 36 is finished, the image of the sample 44 taken by the CCD camera 24 is restricted by the aperture 36. By allowing the image of the sample 44 restricted by the aperture 36 to be shown on the screen 8 of the display 5, the operator can confirm whether the aperture 36 is correctly set on the desired spot of the sample 44.

After the position of the sample 44 and the aperture 36 is determined as described above, the visible light lamp 45 is turned off, the infrared light lamp (not shown) is turned on, and the mirror 25 is removed from the light path. The infrared light reflected by the sample 44 is restricted by the aperture 36, and the restricted infrared light is introduced to the infrared analyzer (not shown), whereby the spectrum of the infrared light is produced and the sample is analyzed based on the spectrum.

Modifications to the above embodiment is easy by those skilled in the art according to the present invention. For example, the CCD camera 24 may be placed at a position where, instead of receiving light restricted by the aperture 36 as described above, it receives the unrestricted light reflected by the sample 44 directly. In this case, though, it is impossible to confirm the actual image of the view of the sample restricted by the aperture 36 on the screen 8. Another alternative example of the embodiment is as follows 9 For setting the aperture 36 infrared light and infrared light camera may be used instead of C using visible light and a CCD camera 24. In this case, the infrared image of the sample taken by the infrared light camera is easily converted to a visible image of the sample with its original properties including the color or shape on the screen 8 by well-known signal ptocessing methods or image processing methods.

I

Claims

CLAIMS:

1. An infrared microscope comprising:

a sample stage on which a sample is mounted; a sample stage driver for moving the sample stage laterally; a field restrictor having an aperture for restricting light from the sample; an aperture driver for setting dimensions and an orientation of the aperture with respect to the sample stage; a camera for takinc, an image of the sample on the sample stage; 0 C, a virtual aperture generator for generating an image of a virtual aperture whose position, dimensions and orientation can be changed by externally given commands; a display controller for showing the image of the sample and the image of the virtual aperture superimposed on the image of the sample on a screen; and a controller for controlling the sample stage driver and the aperture driver based on a relative position of the image of the sample and the image of the virtual aperture.

2. An infrared microscope according to claim 1 wherein the controller fully opens the aperture while the virtual aperture is being set, and drives the field restrictor to form the aperture as being set when the virtual aperture is finished being set.

3. An infrared microscope according to claim I or 2 wherein the aperture and tlie virtual aperture are rectangular, and each side of the virtual aperture is independently movable in setting the virtual aperture.

4. An infrared microscope according to claim 1, 2 or 3 wherein the camera is placed at a position to receive light from the sample without being restricted by the aperture.

5. An infrared microscope according to any preceding claim wherein visible light is provided for setting the virtual aperture.

11 6. An infrared microscope according to any one of claims I to 4 wherein the camera is an infrared camera and infrared light is provided for setting the virtual aperture.

7. An infrared microscope substantially as hereinbefore described with reference to Figures I to 3) of the accompanying drawings.

8. A method of operating an infrared microscope, comprising: generating an image of a virtual aperture whose position, dimensions and orientation can be changed; showing on a screen an image of a sample and the image of the virtual aperture superimposed thereon; and controlling a sample stage driver and an aperture driver based on the relative positions of the image of the sample and the image of the virtual aperture on the screen.

9. A method according to claim 8, wherein visible light is used in setting the virtual aperture.

10. A method according to claim 8, wherein infrared light is used in setting the virtual aperture.

11. A method substantially as hereinbefore described with reference to Figures I to 3 of the accompanying drawings.

12 I