WO1998027867A1

WO1998027867A1 - Electromagnetic radiation imaging device with controlled diaphragm means

Info

Publication number: WO1998027867A1
Application number: PCT/NL1997/000713
Authority: WO
Inventors: Sven Ploem
Original assignee: Sven Ploem
Priority date: 1996-12-20
Filing date: 1997-12-19
Publication date: 1998-07-02
Also published as: EP0954242A1; JP2001506899A; NL1004862C2

Abstract

Image recording means for receiving electromagnetic radiation, comprising diaphragm means (2) for at least partially screening the electromagnetic radiation, processing means (9), diaphragm-control means (11), which are connected to processing means (9) in order to receive a control signal therefrom and are connected to the diaphragm means (2) for controlling the diaphragm means in response to the control signal. The image recording means being also provided with a contouring device (14'; 27; 28), which is connected to the processing means (9), in order to manually input at least one contour (16), and the processing means (9) being designed to execute a predetermined function depending on the at least one contour (16), for example controlling the diaphragm means or metering radiation intensity in specific areas of an image.

Description

ELECTROMAGNETIC RADIATION IMAGING DEVICE WITH CONTROLLED DIAPHRAGM MEANS

The present invention relates to image recording means for receiving electromagnetic radiation, comprising diaphragm means for at least partially screening the electromagnetic radiation, processing means, diaphragm-control means, which are connected to processing means in order to receive a control signal therefrom and are connected to the diaphragm means for controlling the diaphragm means in response to the control signal. Image recording means of this kind are known, for example, from European patent application 0,496,438.

Binoculars, telescopes, microscopes, in photography, film and X- ray pictures make use of electromagnetic radiation for recording images. These images can be used, for example, for diagnosing and treating illnesses. Electromagnetic radiation covers a broad spectrum. Large parts of that spectrum can be used for recording images. For recording purposes, it will always be necessary to select the correct imager and the correct material for the diaphragm for each selected frequency band. In photography, cinematography and video, electromagnetic radiation is deflected so that it can reach an imager in the correct manner. The quantity of radiation is determined by means of a diaphragm which at least partially screens the radiation received. In cameras and film equipment, the diaphram is generally more or less round. The radiation is then screened symmetrically in a concentric manner from the outer edge towards the centre of the image.

Examples of imagers for recording moving images are: video- recording (vacuum) tubes, CCD imagers and visible-light image intensifiers, as used in night vision goggles or night sights. The intensity of the electromagnetic radiation is frequently measured prior to recording. Such metering generally takes place in the vicinity of an imager. The imager is generally a chemical emulsion, which is sensitive to this radiation, on a substrate, for example a roll of film. Sometimes there are a plurality of metering units which are situated at fixed positions with respect to the image. With a plurality of metering units, it is possible to meter the amount of light picked up by the entire image; this is known as an integral metering. It is also possible to carry out local metering, which is known as spot metering. If a plurality of metering units are used, it is possible to select different combinations of selected metering units. In other words, it is possible to select a measurement field. It is thus possible to meter the radiation intensity at various locations in the image. This results in "spots" which are at a fixed position with respect to the image. If desired, the measurement information from these spots can be averaged.

As is known, X-rays form part of the electromagnetic spectrum. X- rays are generated in an X-ray tube. During use, the X-rays pass outwards through a window in the tube, so that a beam with a defined direction is generated.

In medical X-ray equipment, just as in photography, the dimensions of the beam of rays are limited by a diaphragm. The diaphragm is made of a material which to a large extent blocks the X- rays. In practice, an object is situated downstream of the diaphragm. In medical applications, the object is a patient. Downstream of the patient is situated an imager which is sensitive to the X-rays. With some imagers, it is possible to capture an image, so that a static photograph is produced. However, other imagers are able to capture a number of images per unit time, so that a moving image is produced. Consideration may be given here to, for example, X-ray image intensifiers.

Just as in photography, the intensity of the X-rays can be measured by metering units in the vicinity of the imager. Moreover, just as in photography, the position of the metering units is fixed with respect to the image. Here too, it is possible to speak about an integral metering or a spot metering. Here too, the "spots" are in a fixed position with respect to the image. The diaphragms employed in existing X-ray equipment and photography have one common feature: they limit the beam of radiation symmetrically. Most diaphragms used in X-ray equipment do this with the aid of four strips of lead, which are able to limit the beam of radiation from the outside. As has been mentioned, the diaphragms used in photography generally do this concentrically from the outside of the beam. Moreover, the measurement sensors are usually in a fixed position and measure a predetermined part of the image.

These existing situations are associated with various disadvantages .

When using binoculars and sights, which are optionally provided with image intensifiers (for example in night sights), bright light sources in the image are not only troublesome but also potentially hazardous. For example, if a night sight is being used to enter a harbour, continuous illumination from the light provided by a lighthouse may be inconvenient or blinding. In situations where the armed forces are in combat, it may be necessary to aim a weapon using a sight, optionally provided with optics, and optionally provided with light intensification. If, in doing so, it is necessary to look at the sun, because the enemy is approaching from that direction, it is possible to be blinded. The diaphragms used in practice make it difficult to selectively mask such interfering elements , for example the sun or a local excess of X-radiation passing through. Since the diaphragms used in practice can only provide a symmetrical masking effect, parts of the beam which have nothing to do with the abovementioned interfering element will also be blocked, if the beam of radiation allowed through is made smaller. If the said interfering element is situated on the outside of the image, this is not unduly problematical. However, if the interfering element is situated in the centre of the image, it is then impossible to mask this out without destroying virtually the entire image.

Moreover, current intensity measurements do not allow measurements to be taken wherever the user wishes. It is not possible to define the size of the measurement field freely.

Particularly in the case of X-ray equipment, symmetrical diaphragms have major drawbacks for the patient. That part of the patient which is to be exposed to X-radiation is frequently in itself not symmetrical, so that it is also necessary to expose undesired parts of the patient to the X-radiation.

Moreover, poor intensity measurements when taking X-rays mean that parts of the image cannot be evaluated accurately, so that diseases may remain unnoticed.

German Laid-Open Specification DE-A-3621 868 describes a diaphragm with diaphragm control for an X-ray machine, as is explained in more detail below with reference to Figure 3- The diaphragm comprises various parallel lamellae, which can be moved parallel to one another. The lamellae are disposed in two groups opposite one another. Each lamella can be moved parallel to and independently of the other lamellae. Since it is possible in this way to diaphram a beam of X-radiation asymmetrically, this known diaphragm can in principle be used to overcome the problems associated with the known symmetrical diaphragm. Each of the lamellae is controlled using its own control device. Each of the control devices is coupled to an evaluation circuit, which, from a video signal of the object, derives a control signal for each of the control devices. On the basis of the video signal, the evaluation circuit itself calculates the positions into which the various lamellae have to be moved in order to obtain the desired screening of the beam of X-radiation. By way of example, the situation is shown in which the evaluation device itself, on the basis of a weak beam of X-radiation, automatically detects the shape of a knee joint and, on the basis of this, generates a control signal, after which the control devices control the various lamellae in such a manner that only the knee joint is exposed by the beam of X-radiation. The drawback of this known device is that the evaluation circuit has to make use of discontinuities which are present in the video signal and indicate where the limits of an object which is to be exposed by the beam of X-radiation are situated. Discontinuities of this kind are caused not only by the object which is in fact to be exposed but also by interference and by other objects in the human body. In practice, this known diaphragm arrangement has still not achieved common acceptance. The object of the invention, then, is to provide image recording means which enable the above problems to be avoided.

The invention therefore provides image recording means as defined in the preamble, characterized in that the image recording means are also provided with a contouring device, which is connected to the processing means, in order to manually input at least one contour, and in that the processing means are designed to execute a predetermined function depending on the at least one contour.

According to the invention, the image recording means thus comprise a contouring device for manually inputting a contour. A user is thus able to indicate him/herself the area in an image which is reproduced on the reproduction means and is the only area which should not be screened by the diaphragm means. This has considerable advantages, since it has been found that people seldom make errors when indicating a contour of this kind. Also, a person will immediately recognize which parts of an image are not important to the recording.

In some embodiments, the image recording means are also provided with converter means, which are connected to the processing means, for receiving electromagnetic radiation and converting it into a video signal, which video signal is fed to the processing means, and a screen, which is connected to the processing means during operation, for reproducing an image corresponding to the video signal. The image recording means may relate both to an X-ray machine and to binoculars, a microscope, camera, film equipment, video equipment, infrared viewfinders, observation means, sights and other optical instruments.

If the image recording means relate to an X-ray machine, they furthermore comprise a source of X-radiation for generating X- radiation, which forms the electromagnetic radiation, the converter means comprising, inter alia, an image intensifier.

The image recording means according to the invention may furthermore comprise means for a user to input instructions. Using these means, the user can make clear to the processing means what has to be done with the image situated inside the contour which is input manually. As indicated above, the activity to be executed by the processing means may, for example, relate to the control of the diaphragm means in such a manner that the diaphragm means screen the entire image apart from that section which is inside the input contour. However, as an alternative the processing means may be designed, to measure the radiation intensity inside the contour, as a function of the instructions input by the user.

The diaphragm means may comprise the groups of lamellae which are known from the abovementioned German Laid-Open Specification 3 21 868.

However, in an alternative embodiment the diaphragm means comprise various passages, which are transparent to the electromagnetic radiation, as well as means which are non-transparent to the electromagnetic radiation, the diaphragm-control means comprising introduction means for introducing the non-transparent means into the passages over a distance which is determined by the control signal. In this alternative embodiment of the diaphragm means, they may also comprise means which are transparent to the electromagnetic radiation, and the introduction means are designed for successively introducing both the non-transparent means and the transparent means into the passages as a function of the control signal.

In this latter embodiment, there is the advantage that the transparent and non-transparent means can be introduced alternately, in a specific desired sequence, into the passages in accordance with the contour(s) input via the contouring device. As a result, it is possible to screen the beam of radiation not only starting from the outside but also to screen it in desired areas at any required locations in the image.

The non-transparent means may, for example, comprise mercury, which is permeable neither to visible light nor to X-radiation. If the device in question is an X-ray machine, the transparent means may, for example, comprise alcohol, which is permeable to X-radiation.

On the other hand, the non-transparent means may comprise segments which are connected by a flexible strip and are made, for example, of lead. The reproduction means may be provided with all known means for inputting contours by hand. Examples of such means are a touch screen, on which the user can draw the at least one contour using a finger or a pen, a screen with cursor-control means for controlling a cursor, by means of which the user can draw the at least one contour, an infrared X-Y screen, a touch pad, a glide pad and an X-Y tablet.

The present invention also relates to a combination of diaphragm means and diaphragm-control means, characterized in that the diaphragm means comprise various passages, which are transparent to the electromagnetic radiation, as well as means which are non-transparent to the electromagnetic radiation, the diaphragm-control means comprising introduction means for introducing the non-transparent means into the passages over a distance which is determined by a control signal.

As has already been noted above, diaphragm means of this kind can be used to screen any desired areas in, for example, an X-ray image, a possibility which is not available in any of the known diaphragm means.

Here too, the non-transparent means may comprise, for example, lead segments or mercury, while the transparent means may comprise alcohol .

The present invention will be explained in more detail below with reference to a number of figures. The figures serve only to illustrate the invention and not to limit the scope of protection thereof.

In the figures:

Figure 1 shows an X-ray machine;

Figure 2 shows a diaphragm which is currently used in an X-ray machine;

Figure 3 shows a diaphragm as is known from German Laid-Open Specification DE-A-3621 868;

Figure 4 shows a diagrammatic illustration of a diaphragm which can be used in the arrangement in accordance with Figure 1; Figure 5 shows a possible cross-section through a number of small passages situated next to one another and forming part of the diaphragm in accordance with Figure 4;

Figure 6 shows a diagrammatic illustration of the screening of an image which can be achieved using the diaphragm in accordance with Figure 4, and

Figure 7 shows a camera, video equipment or film equipment or the like in accordance with the present invention;

Figures 8a, 8b and 8c show an alternative diaphragm.

Figure 1 shows an arrangement for forming X-ray images . The arrangement comprises a source 1 of X-radiation, which is able to generate a beam 5 of X-rays. The beam 5 of X-rays is directed at an image intensifier 6. In this arrangement, a space in which an object 13 can be placed is situated between the image intensifier 6 and the source 1 of X-rays. In the medical field, the object 13 is generally part of the human body. An input screen and an output screen 1 , which is coupled to a video recording machine 8, are situated in the image intensifier. Together, the image intensifier 6, the screen 7 and the video recording machine 8 form converter means for converting the beam 5 of X-rays that is received into an electrical video signal, which is fed to a suitable processor 9-

Instead of a video recording machine, it is possible to employ a camera, film machine or the like. Sometimes, it is possible for various items of equipment of this kind to be present, in which case a mirror can be used to select which machine is actually used.

The video recording machine may, for example, be a vacuum tube or a CCD-element.

The processor 9 is connected to a diaphragm control 11. The diaphragm control 11 is in turn connected to a diaphragm 2, which is situated in the propagation path of the beam of X-rays, specifically between the position where the object 13 can be placed and the source 1 of X-rays. The aim of the diaphram 2 is to limit the extent of the beam 5 of X-rays in such a manner that the object 13 is not exposed to an unnecessary amount of X-radiation.

Furthermore, the arrangement in accordance with Figure 1 comprises a means 12 for controlling the source of X-rays, which control means is connected both to the source 1 of X-rays and to the processor 9» The means 12 for controlling the source of X-rays controls the intensity of the source 1 of X-rays and communicates with the processor 9-

The processor 9 is furthermore connected to reproduction means 10 for reproducing an image which corresponds to that part of the object 13 which is exposed to the beam 5 of X-rays. The reproduction means 10 comprise a screen 15 and a keyboard 14. If desired, a mouse 14' may be used.

With suitable means, for example a cursor controlled by the mouse 14', a contour 16 can be reproduced on the screen 15 of the reproduction means 10. As an alternative, a separate touch screen 28 or the like can be used with the screen 15. On a touch screen 28 of this kind, the contour 16 can be drawn, for example using a finger or a drawing pen. This contour 16 is transmitted during use to the processor 9_t which uses the contour to define one or more areas in the image received which have to be screened using the diaphragm 2 or in which an intensity measurement is to be carried out.

As illustrated in Figure 1 , the contour 16 can be reproduced on the screen 15 of the reproduction means 10, on which screen the object to be reproduced can also be seen during use. The contour 16 can then be drawn along the edges of the object, as will be explained below with reference to Figure 6.

The contour 16 can be input using a touch screen 28 which is attached to a monitor, or, for example, an LCD/TFT screen can be used.

It is also conceivable to employ a separate contouring device 27 without reproducing the image of the object, for example a touch pad, glide pad, X-Y tablet or a separate infrared screen. This separate contouring device 27 is connected to the processor 9 for the purpose of inputting a desired contour. Figure 2 shows the situation where the diaphragm 2 comprises four strips of lead. The four strips of lead consist of two parallel strips of lead 3 and 4 and two further parallel strips of lead 18 and 1 . The strips of lead 3. 4 are perpendicular to the strips of lead 18, 19- With the aid of the diaphragm control 11, the strips of lead 3. 4 can be moved to and fro in one direction, symmetrically with respect to the centre of the image. The strips of lead 18, 19 can likewise be moved to and fro, as indicated in Figure 2. The strips of lead 18, 19 also move symmetrically with respect to the centre of the image. The direction of movement of the strips of lead 3. 4 is perpendicular to the direction of movement of the strips of lead 18, 19- A diaphragm comprising four strips of lead, as shown in Figure 2, is generally used in medical X-ray equipment.

In Figure 2, reference numeral 17 indicates that part of the object 13 which is to be exposed to the beam 5 of X-rays. It will immediately be clear from Figure 2 that the strips of lead 3. 4, 18 and 19 are moved towards the centre of that part 17 of the object which is to be examined in such a manner that the part 17 to be examined just avoids being screened from the beam 5 of radiation, and will remain completely visible. At the same time, Figure 2 clearly shows that owing to the shape of the strips of lead 3. 4, 18 and 19 a very considerable part, for example 10% , of the tissue around the part 17 to be examined will still be exposed to the beam 5 of X-rays, because it is not possible to screen this area using the strips of lead 3. 4, 18 and 19- This results in needless exposure to X- radiation.

Figure 3 shows another known diaphragm which is provided with two groups of parallel lamellae 20. As has been stated, a diaphragm of this kind is known, for example, from German Laid-Open Specification DE-A-3621 868. The lamellae 20 can be moved to and fro independently of one another in the direction indicated. This results in the possibility of better separation of that part 17 of the object which is to be examined from the surrounding tissue, so that a considerably smaller fraction of the surrounding tissue will be exposed to the beam 5 of X-rays. The direction of movement indicated is parallel to the longitudinal direction of the lamellae 20. In the arrangement in accordance with the abovementioned Laid-Open Specification 3 21 868, the lamellae 20 can be rotated as a whole about a predetermined pivot point. The direction of movement indicated then rotates together with the longitudinal direction of the lamellae 20.

The situation may from time to time arise where a part 17. which is to be examined, of the object 13 is more or less circular and where an area inside the image, which area is surrounded by the part 17 to be examined, does not have to be exposed to the beam 5 of X-rays.

A situation of this kind is shown in Figure 6, in which the part 17 to be examined is indicated diagrammatically on reproduction means 10.

The situation illustrated in Figure 6 may relate, for example, to part of a human intestine 17. in which case the tissue around the intestine 17 does not have to be exposed to beam 5 of X-rays. Those parts of the tissue which are not to be exposed in this situation are indicated as the grey area which is delimited by contour 16. It will be clear that the contour 16 outlined in the centre of Figure 6 surrounds an area which cannot be screened using the strips of lead of the diaphragm in accordance with Figure 2. Using the diaphragm in accordance with Figure 3. it is possible, after the lamellae 20 thereof have been rotated through 0° , to screen a large part of the grey area shown in Figure 6. However, further improvement is desired. Figures 4 and 5 show a diaphragm which makes this possible.

Figure 4 diagrammatically shows a diaphragm which is composed of various parallel passages 21. The passages are made, for example, of glass. However, other transparent materials, such as perspex, are also suitable. The selection of material for the passages 21 depends on the spectrum of the electromagnetic radiation which is to be allowed through. The passages themselves must be transparent to the selected spectrum of the electromagnetic radiation.

At least one diagrammatically depicted pump 22 is associated with each passage 21. As an alternative, it is possible to provide for one single pump to be used, the outlet of which can be connected alternately to a desired passage 21.

Figure 4 again illustrates the situation in which the diaphragm has to allow through only a specific area of the beam of electromagnetic radiation. That area corresponds, for example, to part of a circle, for example corresponding to part of a human intestine 17, which is likewise illustrated diagrammatically in Figure 4.

Each passage 21 is now filled alternatively, using the pump 22, with a substance which is either transparent to the electromagnetic radiation used or is non-transparent to this radiation. Figure 4 illustrates the situation in which the passages 21 are alternately filled with mercury 20 and alcohol 26. A diaphragm of this kind can be used in an X-ray machine, since mercury is non-transparent to X- radiation, while alcohol is transparent to X-radiation. With the aid of the pumps 22 , the passages 21 can be filled with mercury and alcohol in such a manner that those parts in which there is alcohol 26 correspond precisely to the shape of the intestine 17- Those parts of the tissue which are outside the intestine 17 can be screened approximately using the mercury parts 20.

Instead of using one pump per channel, it is possible to use two, one for mercury and one for alcohol.

After use, the pumps 22 can be used to flush each of the passages 21 clean. The mercury 20 can then easily be separated from the alcohol 26, after which both the mercury 20 and the alcohol 26 can be reused. The advantage of mercury and alcohol is that they are both liquid but nevertheless do not merge into one another. Nevertheless, the invention is not limited to these two substances. It is conceivable to use other liquids or powders which are not necessarily reused after use .

It will be clear to a person skilled in the art that the pumps 22 in the embodiment shown in Figure 4 are the control means 11 from Figure 1. The pumps 22 are therefore controlled by the processor (cf. Figure 1) . It will be clear that it is not easy in the situation illustrated in Figures 4 and 6 to calculate the contours 16 automatically. The invention therefore envisages the possibility of providing means with which the contours 16 can be input manually. Before actually recording, for example, an X-ray image, the source 1 of X-rays for this purpose transmits a weak beam of X-rays through the object 13 • This is used to generate an image on the reproduction means 10. An operator can see this image and manually indicates the contours 16, such as for example those illustrated in Figure 6. As pointed out above, this can be carried out, for example, with the aid of a touch screen, by means of which a user can indicate the contours 16 with the aid of a finger. However, as an alternative the contours 16 can also be indicated with the aid of a cursor on a screen, which cursor can be moved, for example, using a mouse 14'. Further alternative contouring devices have already been specified above.

It is also possible, during an X-ray examination, to store one or more images in an image memory which is intended for this purpose. These images can be called up from the image memory and redisplayed on the reproduction means. The operator can then use the contouring device to input the at least one contour at his/her leisure. The X-ray photograph can then be taken; to do this, a higher dose of X-radiation is given per unit time than is necessary for the examination. It is clear that this one contour may relate both to the diaphragm means and to the location of the desired intensity measurement.

It is also possible to view the contour indicated by the operator by means of a so-called light viewfinder. With the aid of visible light, the light viewfinder indicates where on the patient the beam of X-rays will subsequently be situated. Since the beam from the light viewfinder is masked in the same way as the beam of X-rays, the operator can see whether the diaphragm is masking the correct areas on the patient. Naturally, this feature can only be used for anatomical features which can be seen externally using ordinary light.

After a user has indicated contours 16 in this way, he/she will use suitable means, for example the keyboard 14, to send the contours 16 to the processor 9> The way in which this is carried out forms part of the prior art and does not need further explanation.

It is important, however, that it be made clear to the processor 9 on which side of the contours 16 the diaphragm 2 is to screen the radiation. This can be carried out, for example, with the aid of the keyboard 14.

After the contours 16 have been input and a user has made clear on which sides of the contours 16 screening is to take place, the processor 9 sends a control signal which is calculated from these contours to the diaphragm control 11. The diaphragm control 11 then controls the diaphgram 2 in such a manner that the desired areas are screened.

It is also possible to use contouring device 27. the contour 16 not being reproduced on the screen of the reproduction means 10. The unreproduced contour is then simply fed to the processor 9. which on the basis of this contour calculates the control signal for the diaphragm control 11. On the basis of the control signal, the diaphragm control 11 controls the diaphragm 2, so that an area of the image corresponding to the contour is screened. The user can see this on the screen of the reproduction means 10. In other words , the user controls the diaphragm directly via the processor 9 without showing the contour. With the aid of the diaphgram shown in Figure 4, it is possible to screen any desired locations on the image. However, the invention is not limited to the use of the diaphragm shown in Figure 4. The diaphragm in accordance with Figure 3 can also be used with contours 16 input manually. As a further alternative, the diaphragm 2 may comprise an LCD screen, the individual cells of which are driven by the diaphragm control 11 (which if desired may form part of the processor 9) so as to allow through or block electromagnetic radiation. Since it is possible in an LCD screen, as is known per se to the person skilled in the art, to control arbitrary areas to allow through or block radiation, an LCD screen of this kind forms a very flexible diaphragm. In the diaphragm in accordance with Figure 4, it is necessary to avoid the possibility of X-radiation (or other electromagnetic radiation) passing between adjacent mercury columns 20. To do this, the side walls between adjacent passages 21 may be of slightly inclined design, as shown in Figure 5> Electromagnetic radiation, for example X-radiation, which is incident perpendicular to the surface of the diaphgram 2 is then completely blocked by the non- transparent material 20. Figure 7 shows the use of the invention in a diagrammatically depicted camera or film equipment 25. The film equipment may, for example, be a video camera. The same reference numerals refer to the same component as in Figure 1.

The reference numeral 23 indicates one or more lenses. The reference numeral 24 refers to converter means for converting visible or infrared light into an electrical video signal, which is fed to the processor 9« The ultimate recording means, such as a photographic film or video film, are not shown in more detail in Figure 1 . One of the differences between the arrangement in accordance with Figure 1 and that in accordance with Figure 7 is that the object 13 of importance is situated between the diaphragm 2 and the converter means 6, 7. 8 in the arrangement in accordance with Figure 1. By contrast, in the case of photographic or film pictures, the object of importance is situated outside the apparatus 25.

In the case of photographic and film pictures, the invention can advantageously be used if there are undesirable light sources, such as the sun or a brightly shining lamp, inside the field of view. Most film and photographic equipment has an automatic exposure meter, which is adversely affected by light-emitting sources of this nature. It is then impossible to take a good picture of the desired part of the field of view. It is therefore also advantageous for photographic and film equipment if part of the field of view can be screened asymmetrically. This is possible in principle using a diaphragm as illustrated in Figures 3 and 4. On the other hand, it is also possible to use an LCD screen as the diaphragm. An LCD screen of this kind can be placed outside the lens 23, where there is usually already a holder for, for example, a UV filter, and this holder can advantageously be used for attaching an LCD screen of this kind. Here too, the contours 16 can be applied with the aid of, for example, a touch pad arranged at a suitable location on the camera, or a cursor with a mouse, or a screen with a suitable drawing pen, as is known to a person skilled in the art. Both in the arrangement in accordance with Figure 1 and in the arrangement in accordance with Figure 7. the contour 16 input manually by the user can also be used for another purpose. In addition to the processor 9 using the contour 16 to actuate the diaphragm control 11, the processor 9 can also use the contour 16 to determine one or more measurement areas in the image picked up. The processor 9 then determines the intensity of the electromagnetic radiation received inside these measurement areas. On the basis of these measurements, the opening time of a shutter (not shown) of a camera can be determined, for example. It is thus possible, with the aid of light metering inside one or more picture segments indicated by contours 16, to take photographs of those areas inside the field of view which are most important to the user.

Figures 8a to 8c show an alternative embodiment of a diaphragm according to the invention. Figure 8c shows a top view of the diaphragm, while Figures 8a and 8b show cross-sections on the lines Vllla-VIIIa and Vlllb-VIIIb, respectively.

In the same way as the diaphragm in accordance with Figure 4, the diaphragm in accordance with Figures 8a - 8c comprises small passages 30. In the passages 30 there are situated segments 31 which are non- transparent to the electromagnetic radiation and, if this radiation is X-radiation, are made, for example, of lead. Inside each passage 30, segments 31 are connected to one another via a flexible strip 32, which can be transported through the passage by drive means 3 , for example a motor.

The diaphragm preferably comprises two layers one above the other. The passages 30 in the two layers are preferably perpendicular to one another. Figure 8a shows that the passages 30 in the top layer form an angle of 90° at the outside edge. This makes it possible to arrange the diaphragm, as it were, around part of the image recording means, for example an X-ray machine. This saves space. Obviously, such angles of 0 can also be used for the passages 30 in the bottom layer (not shown) . Figure 8a shows that a group of segments 31 is situated on the left and right in the top passage 30. Both groups can be moved independently of one another inside the passage 30, as if they were two curtains which can be moved towards and away from one another. For this purpose, both groups are attached to their own flexible strips and have their own drive means 34.

Figure 8c shows a situation in which the segments are arranged in the bottom layer and top layer of passages in such a way that they screen virtually the whole of the electromagnetic radiation except for where the object 17 is situated.

Claims

1. Image recording means for receiving electromagnetic radiation, comprising diaphragm means (2) for at least partially screening the electromagnetic radiation, processing means (9), diaphragm-control means (11), which are connected to processing means (9) in order to receive a control signal therefrom and are connected to the diaphragm means (2) for controlling the diaphragm means in response to the control signal, characterized in that the image recording means are also provided with a contouring device (14'; 27; 28), which is connected to the processing means (9) , in order to manually input at least one contour (16) , and in that the processing means (9) are designed to execute a predetermined function depending on the at least one contour (16) .

2. Image recording means according to Claim 1, characterized in that they are also provided with converter means (6, 8; 24). which are connected to the processing means (9) . for receiving electromagnetic radiation and converting it into a video signal, which video signal is fed to the processing means (9) during operation, and a screen (10), which is connected to the processing means, for reproducing an image corresponding to the video signal.

3* Image recording means according to Claim 1 or 2, characterized in that the electromagnetic radiation is selected from the spectrum which comprises visible light, ultraviolet light and infrared radiation, and in that the image recording means comprise, for example, a sight or optical instrument.

4. Image recording means according to Claim 3, characterized in that the diaphragm means (2) comprise an LCD screen.

5. Image recording means according to Claim 2, characterized in that they furthermore comprise an X-ray source (1) for generating X- radiation, and in that the converter means comprise an image intensifier (6) .

6. Image recording means according to one of the preceding claims, characterized in that the image recording means are also provided with input means (14), which are connected to the processing means (9). for a user to input instructions, and in that the processing means (9) are designed for calculating the control signal, as a function of the instructions input by the user, on the basis of the at least one contour (16) . which separates areas of the electromagnetic radiation which are to be screened using the diaphragm means end areas which are not to be screened.

7- Image recording means according to one of the preceding claims, characterized in that the image recording means are also provided with input means (14), which are connected to the processing means (9), for a user to input instructions, and in that the processing means (9) are designed for metering, as a function of the instructions input by the user, radiation intensity in en area of the electromagnetic radiation which is defined by the at least one contour (16).

8. Image recording means according to one of Claims 1 to 3 or 5 to 7. characterized in that the diaphragm means comprise various lamellae (20) . which can be displaced adjacently to one another and are non- transparent to the electromagnetic radiation.

9- Image recording means according to one of Claims 1 to 3 ^or 5 ^to 7, characterized in that the diaphragm means comprise various passages (21; 30). which are transparent to the electromagnetic radiation, as well as means (20; 31) which are non-transparent to the electromagnetic radiation, the diaphragm-control means (11) comprising introduction means (22; 34) for introducing the non-transparent means (20; 3D into the passages (21; 30) over a distance which is determined by the control signal.

10. Image recording means according to Claim 9, characterized in that the diaphragm means also comprise means (26) which are transparent to the electromagnetic radiation, and in that the introduction means (22) are designed for successively introducing both the non-transparent means (20) and the transparent means (26) into the passages (21) as a function of the control signal.

11. Image recording means according to Claim 9 or 10, characterized in that the non-transparent means (20) comprise mercury.

12. Image recording means according to Claim 10 or 11, characterized in that the transparent means (26) comprise alcohol.

13- Image recording means according to Claim 9. characterized in that the non-transparent means comprise segments (31) which are connected by a flexible strip (32) and are made, for example, of lead.

14. Image recording means according to one of the preceding claims, characterized in that the contouring device is selected from the following group of equipment: a touch screen (28), on which the user can draw the at least one contour (16) using a finger or a pen, a screen (15) with cursor-control means (14') for controlling a cursor. by means of which the user can draw the at least one contour (16), an infrared X-Y screen, a touch pad, a glide pad and an X-Y tablet.

15. Combination of diaphragm means (2) and diaphragm-control means (11). characterized in that the diaphragm means comprise various passages (21; 30), which are transparent to the electromagnetic radiation, as well as means (20; 31) which are non-transparent to the electromagnetic radiation, the diaphragm-control means (11) comprising introduction means (22: 34) for introducing the non-transparent means (20; 31) into the passages (21; 30) over a distance which is determined by a control signal.

16. Combination according to Claim 15, characterized in that the diaphragm means also comprise means (26) which are transparent to the electromagnetic radiation, and in that the introduction means (22) are designed for successively introducing both the non-transparent means (20) and the transparent means (26) into the passages (21) as a function of the control signal.

17. Combination according to Claim 15 or 16, characterized in that the non-transparent means (20) comprise mercury.

18. Combination according to Claim 16 or 17, characterized in that the transparent means (26) comprise alcohol.

19. Combination according to Claim 15, characterized in that the non- transparent means comprise segments (31) which are connected by a flexible strip (32) and are made, for example, of lead.