WO1992014982A1

WO1992014982A1 - Alignment device

Info

Publication number: WO1992014982A1
Application number: PCT/SE1991/000105
Authority: WO
Inventors: Göte PÅLSGÅRD; Lars-Olov ÖSTLIN
Original assignee: Paalsgaard Goete; Oestlin Lars O
Priority date: 1989-09-07
Filing date: 1991-02-14
Publication date: 1992-09-03
Also published as: SE8902940L; SE8902940D0; SE466517B

Abstract

A device for alignment controlled by the gaze direction of a person of an object (1) with respect to a thing (3) comprises means (9, 10, 13-16) for determining the gaze direction of a person, an evaluating unit (17) adapted to treat information received from said means about the gaze direction of the person and emit control signals, and a unit (18) for receiving the control signals from the evaluating unit so as to by an adjusting member (19) adjust the direction of the object in dependence on the gaze direction of the person. This device comprises furthermore a camera (2) adapted to by means of a displaying arrangement (4, 6-10) show a picture including said thing (3) to the person. The camera (2) is fixed to or constitutes the object. The evaluating unit (17) is adapted to send control signals to the direction adjusting unit (18) adapted to cause the latter to adjust the object and by that the camera so that the gaze of the person strikes said thing in a certain position on said picture.

Description

Alignment device

FIELD OF THE INVENTION AND PRIOR ART

The present invention relates to a device for alignment controlled by the gaze direction of a person of an object with respect a thing, which comprises means for determining the gaze direction of a person, an evaluating unit adapted to treat information received from said means about the gaze direction of the person and emit control signals, and a unit for receiving the control signals from the eva¬ luating unit so as to by an adjusting member adjust the direction of the object in dependence on the gaze direction of the person.

Such a device is already known by for example US patent publication 3 462 604 which describes a device for ad¬ justing the direction of a weapon or a machine in de¬ pendence on the gaze direction of a person. The person is in this device looking directly on the thing towards which the weapon shall be adjusted and a picture sensor senses the picture of the eye of the person so as to determine in which direction the person looks and on the basis thereof control the weapon. A disadvantage of this device is that said thing towards which a person intends to direct a weapon may be located in the periphery of the field of sight of the person and watching that thing may be un¬ comfortable. Another disadvantage is that the person may not himself by simple means control that the weapon is really directed in the direction he is looking in.

BRIEF DESCRIPTION OF THE INVENTION

The object of the present invention is to provide a device of the kind mentioned in the introduction, which is freed from the disadvantages of the device discussed above.

This object is according to the invention obtained by providing a device of said kind with a camera arranged to by means of a displaying arrangement show a picture in¬ cluding said thing to the person, that said means are adapted to determine the direction of the gaze of said person, when this is directed towards said thing on this picture, that the camera is fixed to or constitutes the object, and that the evaluating unit is adapted to send control signals to the direction adjusting unit adapted to cause the latter to adjust the object and by that the camera so that the gaze of the person strikes said thing in a certain position on said picture.

Thanks to the fact that a camera is adapted to by means of a displaying arrangement show a picture including said thing to the person and the camera is fixed to or constitu¬ tes the object to be aligned with respect to said thing, the person may look at said thing in a desired part of the field of sight corresponding to comfortable looking, and the person may easily check that the object has a certain alignment with respect to said thing, since the position of said thing on the picture viewed at directly corresponds to the alignment of the object with respect to said thing. An advantage characteristic of the invention is defined in subclaim 3, namely that the evaluating unit is arranged to in dependence on the gaze direction of a person influence the direction adjusting unit to adjust the object and by that the camera so that the thing viewed at by the person arrives in the middle of the camera picture. This makes it very comfortable for the person to achieve the alignment adjustment of the object aimed at.

The present invention also concerns a device for distance measuring, which has as object to simplify the measuring of a distance to a thing with respect to prior art devices for this purpose.

This object is according to the invention obtained by a device comprising two cameras located at a mutual distance along a base line and so as to be directed with their camera axes substantially in the same plane, and a picture filter unit adapted to receive picture signals from the respective cameras and filter them, so as to send picture lines with certain serial numbers coming from one camera and picture lines with the rest of the serial numbers coming from the other camera to a displaying arrangement also being a part of the device, that the displaying arrangement is arranged to show a picture created by the picture lines sent from the picture filter unit, that at least one of the cameras is pivotally arranged, that the direction of the camera axes relative to each other is arranged to be adjusted so that a thing to which a distance is to be measured occures continuously in the middle of a picture shown by the displaying arrangement, and that means are arranged to after this adjustment measure the angle of each of the camera axes relative to the base line so as to permit to calculate the distance between the thing and a chosen point along said base line by means of infomation about these two angles and the distance between the cameras along the base line.

Thanks to the characteric of the picture filter unit to send on only certain picture lines from the respective camera to the displaying arrangement, it is possible to create one single picture from the two camera pictures and in a very exactly way direct the two cameras towards the thing in question. When a continuous picture of said thing has been obtained in the middle of the picture of the displaying arrangement, the distance between said thing and a point on said base line, for example one of the cameras, may be calculated by putting the two angles and a distance between the cameras into trigonometric formulas.

In order to further increase the accuracy of the distance measuring device according to the invention the cameras may be provided with a zoom function, so that first of all a coarse adjustment may be made with a comparatively large picture angle and after that a fine adjutment may be carried out with a smaller picture angle, i. e. with the thing magnified on the picture of the displaying arrange¬ ment.

Further advantages and preferred characteristics of the inventions will appear from the following description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a description of preferred embodiments of the inventions cited as examples. In the drawings: Fig. 1 is a simplified block diagram illustrating the function of an embodiment of the alignment device according to the invention,

Fig. 2 is a perspective view illustrating a second embodi¬ ment of the alignment device according to the invention,

Fig. 3 is a simplified block diagram illustrating a first embodiment of the distance measuring device according to the invention, and

Fig. 4 is a schematic view illustrating a particular application of the distance measuring device according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION

The principal of function of a preferred embodiment of the alignment device according to the invention is illustrated in a simplified way in Fig. 1. The device is adapted to align an object 1 with respect to a thing 3 viewed at through a camera 2. The camera 2 is fixed to the object 1 and accordingly movable together therewith. The camera 2 is arranged to send picture signals to a displaying arrange¬ ment, which comprises a camera picture producing unit 4, a cable 6 with optical fibres carrying a picture from the unit 4 to a carrier 5, the end of said cable being arranged with the cross section surface in a fixed position on the carrier and so directed that light from the cable 6 strikes a first lens arranged on the carrier 5, which is adapted to carry the light from the unit 4 on to a first plane mirror 8, which is so arranged that it reflects the light last mentioned towards a second lens 9. The light from the unit 4 will strike a second plane mirror 10 and behind this plane mirror produce a virtual picture 12 perceptable to an eye 11 of a person, said picture corresponding to the picture produced by the camera 2 through the camera picture producing unit 4.

The carrier 5 is intended to be arranged in a fixed posi¬ tion with respect to and in front of an eye of a person. The carrier may be constituted by conventional glasses, spectacle frames being specially designed and the like.

The device comprises also means for determining the gaze direction of the eye 11 of the person. These means comprise a second plane mirror 10, which is so arranged that the light emitted by the eye 11 of the person strikes said mirror and is reflected towards the second lens 9, which is arranged to bring said light together, so that it strikes a third lens 13 being considerably smaller, which is arranged to influence the light emitted by the eye to strike upon a comparatively small third plane mirror 14 located therebe- hind, which is so directed that it guides said light towards a cross section surface of a second cable 15 with optical fibres. Thus, the light striking said cross section surface corresponds to a picture of the eye 11. Light information arriving to the cable 15 is passed on by this and transmitted to a light sensitive element 16, for example a photo-diod. The piece of light information are here converted to a picture corresponding to the direction of the eye, which is made possible by the fact that dif¬ ferent parts of the eye emit light of different intensity, e.g. the light intensity emitted from the pupil surface unit is considerably lower than the one emitted from the white part of the eye. Information about the direction of the eye is sent on from the light sensitive element 16 to an evaluating unit 17 schematically indicated, which is adapted to treat said information and send control signals to a unit 18 for adjusting the direction of the object 1 through an adjusting member 19. A black plate 20 is at¬ tached to the carrier 5 in a suitable position with respect to the optical system, which consists of the parts 9, 10, 13-15, in order to avoid that environmental light is falling onto the third plane mirror 14 and reflected by the cable 15, with incorrect information about the position of the eye 11 as a consequence.

The picture 12 shown to the eye 11 of the person is devided by the evaluating unit 17 into an imagined system of Cartesian coordinates with the origin of coordinates in the middle of the picture. It is the intention that the person with his eye 11 shall view at the thing 3 shown on the virtual picture 12. The evaulating unit is adapted to, from the piece of picture information coming from the light sensitive element 16, derive a signal corresponding to the X-coordinate of the striking point of the gaze on the picture shown and a signal corresponding to the Y-coordi- nate thereof and convert these coordinate signals to signals for adjusting the direction of the object 1, so that said thing 3 is moved to the origin of coordinates of the imagined system of coordinates. Thus, an alignment of the camera 2 towards said thing 3 takes place and thanks to the fixation of the camera to the object 1 also of the latter with respect to said thing 3. The object 1 may be directed parallelly to the camera 2, so that also the object 1 with one extremity thereof points towards said thing 3, but it would also be conceivable that a different relative alignment of the object 1 and the thing 3 takes place.

The evaluating unit may be adapted to send control signals to the direction adjusting unit 18 not until it during a predetermined period of time has received substantially unchanged information about the gaze direction of the person from the light sensitive element 16. This delay may be advantageous so as to avoid disturbances of the direc¬ tion adjustment of the object 1 induced by short twinklings or side glances of the eye of the person.

A preferred embodiment of the device according to the invention is shown in Fig. 2. The object to be aligned or directed and the camera are in this embodiment combined in a TV-camera 1. The carrier 5 is arranged on a spectical frame in front of one eye of the person and has the compo¬ nents with the reference numerals 4-10 and 13-17 shown in Fig. 1. The evaluating unit arranged on the carrier is adapted to send control signals to the direction adjusting unit 18, which in its turn is adapted to cause adjusting of the direction of the TV-camera 1. The person in question may accordingly look at a desired thing on the picture shown by the TV-camera 1 through the displaying arrangement and by his gaze control the TV-camera to be aligned with said thing, i.e. bring it into the middle of the picture. This may be a very comfortable way to control a TV-camera.

It would of course also be possible to control quite different objects by means of the device according to the invention, and microscopes, astronomical instruments and different types of weapons are some examples of such possible objects.

It would of course also be possible to in the alignment device according to the invention replace the means shown in Fig. 1 for determining the gaze direction of the eye of a person by any other means with the same ability, for instance a camera directed towards the eye of the person. However, it is very advantageous to use a carrier fixed with respect to the eye of the person of the type shown in Figs. 1 and 2, since otherwise problems arise concerning the position of the eye of the person with respect to the means for determining the gaze direction.

The schematical construction and the way to operate of a distance measuring device according to the present inven¬ tion is illustrated by means of Fig. 3.

The device comprises two cameras 1, 2, which are pivotally arranged about one optical centre each, said optical centres being located at a fixed mutual distance along a base line. The cameras may be pivotally arranged also in the vertical direction besides in the horisontal direction, but it is the intention that the camera axis of one of the cameras is continuously directed in the same plane as the camera axis of the other camera. The cameras 1, 2 are adapted to send picture signals to a picture filter unit 3 schematically indicated, which is arranged to filter these signals so as to only send picture lines having odd serial numbers and coming from one of the cameras and picture lines having even serial numbers and coming from the other camera to a displaying arrangement. The displaying arrange¬ ment is adapted to show a picture created by the picture lines sent by the picture filter unit, as in the case in Fig. 3, since the two cameras 1 and 2 are directed towards the stick A, in which also B is a stick, looks like the picture indicated in the Figures at the reference numeral 4. When the two cameras are directed towards one and the same thing, here the stick A, this thing may accordingly occur continuously in the middle of the picture. The reference numeral 4 represents here the displaying arrange¬ ment as well as the picture shown thereby. Pieces of information about the appearance of the picture are led or are by hand entered into an evaluating unit 5, which is arranged to treat these pieces of information and send control signals elaborated on the basis thereof to adjusting members not shown for adjusting the direction of the cameras. The perfect direction adjustment of the cameras has already been obtained in Fig. 3, if it is desirable to direct them towards the stick A in order to measure a distance thereto. However, should the distance to the stick B be measured, the evaluating unit 5 would send control signals to said adjusting members for pivoting the camera 1 to the left and the camera 2 to the right until the strokes B¹ on the picture 4 form a continuous picture of the stick B in the middle of the picture. When the eva¬ luating unit or the operator is satisfied with the ap¬ pearance of the picture 4, a unit 7 for calculating the distance between the thing in question (in Fig. 3 the stick A) and any point along the base line between the cameras is activated through a starting unit 6. Each camera is con¬ nected to an angle measuring member for measuring the angle made by the camera axis of the respective camera with said base line and continuously sending information thereabout to the calculating unit 7. These angles are in Fig. 3 indicated by α and β.

Trigonometrical formulas well known are adapted for the calculation of the distance mentioned above. Assume that for example the distance C between the stick A and the optical centre of the camera 1 shall be calculated. The calculating unit 7 is then using the following formula.

S = 1 sin α sin γ

in which 1 is the distance between the two optical centres and γ = 180° - α - β.

The cameras 1, 2 may advantageously be provided with a zoom function, so that first of all a coarse adjustment may be done with a comparatively large picture angle of the cameras and the evaluating unit sends signals to the cameras after obtaining a continious picture of the thing in question in the middle of the picture so as to reduce the picture angle, i.e. magnifying said thing, for fine adjustment of the camera angles before the calculating unit 7 is activated. This further increases the reliability of the distance measuring device already delivering very accurate results.

A special application of the distance measuring device according to the invention is schematically illustrated in

Fig. 4. One of the cameras 1 is fixed on a gun-carriage 8 of a gun. The gun-carriage is rotatable about a vertical axis, but preferably also about a horisontal axis, so as to adjust the direction of the camera 1. The camera 2 is rotatably arranged about an optical centre in at least the horisontal direction, but preferably also in the vertical direction. The relative distance between the centres of rotation of the two cameras is preferably fixed, but it could also be varied in the case there are means for determining the distance existing therebetween in each moment. Picture signals are led from the two cameras to a picture filter unit 9. This unit is adapted to filter the picture signals and send signals corresponding to requested picture lines from a respective camera on to a displaying arrangement. This displaying arrangement is of the type described in Fig. 1 and arranged on a carrier 10 located in front of an eye of a person. Means for determining the gaze direction of the person of the kind shown in Fig. 1 are also arranged on the carrier 10. Thus these means include an optical system with mirror and lenses. Accordingly, a virtual picture is shown to the person, said picture being created by the views of the cameras 1 and 2. The person directs his gaze towards a presumtive target on said picture and after determining the gaze direction of the person information thereabout is sent to an evaluating unit 11, which is arranged to, from these pieces of information, elaborate control signals and send them to direction adjusting units 12 of the gun-carriage 8 and the second camera 2, respectively, (not shown).

The picture filter unit 9 may be adapted to, during a first period of time, attend to that the displaying arrangement only show the picture from a first camera to the person and a direction adjustment of this camera towards said thing takes place through information about the gaze direction of the person and the evaluating unit, whereupon, during a second period of time, the picture filter unit 9 only sends pictures from the second camera to the displaying arrange¬ ment, whereupon a direction adjustment of the second camera takes place through the gaze direction of the person and the evaluating unit. The picture filter unit could after that send picture lines coming from one of the cameras and having odd serial numbers and picture lines coming from the other camera and having even serial numbers to the display¬ ing arrangement, so as to display the continuous thing in the middle point of the picture. In the case that the thing is movable, it is important that means are arranged to, after adjustment of said thing in the middle of the picture, make the direction adjusting units and by that the direction of the cameras to slaves of the position of the target so as to keep the target picture in the middle of the picture shown independent of the movement of the target. The picture filter unit does in this case send information on directly to the evaluating unit, which elaborates and sends control signals to the direction adjusting units for continuously correcting deviations from the picture centre of the respective camera of said thing occuring. This slavery may be started automatically or by the person, when he is satisfied with the direction adjust¬ ment of the two cameras.

By the fixed arrangement of the first camera 1 on the gun-carriage 8 of the canon the gun-carriage 8 will on directing the camera 1 towards said thing automatically also be directed thereagainst. Angle measuring members are arranged on each camera to send information about the angle between the camera axis of the camera in question and the base line connecting the centres of rotation of the two cameras to a calculating unit 13. The calculating unit 13 functions in the way described in connection with the calculating unit 7 in Fig. 3. Thus, the calculating unit 13 may calculate a distance between the camera 1, i.e. the gun-carriage 8 and the thing 14, in this case an aeroplane. The calculating unit 13 is adapted to send this piece of distance information to a unit 15 for controlling the elevation adjustment of the tube 16 of the canon in dependence thereon. The angle measuring unit and a computor unit may also be incorporated into the unit 15. The calcu¬ lating unit 13 may also be adapted to, from information about the movement of the camera 1 and the distance change between the camera 1 and said thing 14, calculate the velocity of said thing and send these signals to the unit 15, so that a direction adjustment of the tube 16 may take place while taking the movability of the target into consideration. The tube may also be laterally movable, so that an aming ahead may be achieved on lateral movement of the target.

Of course no unit for making slaves will be needed should the target be fixed, but the person may look at the camera pictures for direction adjustment of one camera at the time, so that a continuous picture of said thing is created in the middle of the virtual picture. It would then also be possible to omit the gaze direction control and instead arrange a control of the kind shown in Fig. 3.

The invention is of course not limited to the distance measuring devices described above, but several modification possibilities thereof would be apparent to a man skilled in the art without diverting from the basic idea of the invention.

The displaying arrangement in the device according to Fig. 3 could for instance be arranged to show the picture of said thing on a viewing screen with a cursor controllable by a so called joy-stick, wherein the actuation of said joy-stick then would be intended to generate and send control signals to the adjustment members for adjusting the relative direction of the camera axis.

The fields of use could be very different, but as some possible ones distance determinations in the country, for instance for military or land-surveying purposes, and navigation on the see, especially in harbour light-houses, may be mentioned.

The picture filter unit could of course be arranged to select picture lines coming from a camera and having arbitary serial numbers and picture lines coming from the other camera and having the rest of the serial numbers for the displaying arrangement.

The word the rest here means the picture lines lying between the picture lines selected from the first camera in the region of the picture in which the thing in question is located, so that said thing may be reproduced continuously on the picture. Thus, it is also within the scope of the invention to remove picture lines with certain serial numbers from both camera pictures, in the case that these lines lie clearly outside the picture region of interest for the directing of the cameras. This should be considered when interpreting the expression "the rest of the serial numbers" in the appended independent claim.

In the embodiment shown in Fig. 3, it would also be pos¬ sible to omit the calculating unit and the distance calcu¬ lation after reading the camera axis angles could take place "by hand" for instance by using a pocket calculator.

Claims

1. A device for alignment controlled by the gaze direction of a person of an object with respect to a thing, which comprises means (9, 10, 13-16) for determining the gaze di¬ rection of a person, an evaluating unit (17) adapted to treat information received from said means about the gaze direction of the person and emit control signals, and a unit (18) for receiving the control signals from the evaluating unit (17) so as to by an adjusting member (19) adjust the direction of the object (1) in dependence on the gaze direction of the person, c h a r a c t e r i z e d in that it furthermore comprises a camera (2) adapted to by means of a displaying arrange¬ ment (4, 6-10) show a picture (12) including said thing (3) to the person, that said means are adapted to determine the direction of the gaze of said person, when this is directed towards said thing on this picture, that the camera (2) is fixed to or constitutes the object, and that the evaluating unit (17) is adapted to send control signals to the direc¬ tion adjusting unit (18) adapted to cause the latter to adjust the object (1) and by that the camera (2) so that the gaze of the person strikes said thing in a certain position on said picture.

2. A device according to claim 1, c h a r a c t e r i z e d in that said means are adapted to deliver a signal corresponding to the x-coordinate of the strike point of the gaze on the picture shown and a signal corresponding to the y-coordinate of the same of a system of Cartesian coordinates drawn up with the centre of the picture as origin of coordinates to the evaluating unit (17), and that the evaluating unit is arranged to transform these coordinate signals to signals for adjusting the direction of the object (1) so that the object is moved to a desired point in the system of coordinates of the picture.

3. A device according to claim 2, c h a r a c t e r i z e d in that the evaluating unit (17) is adapted to, in dependence on the deviation of the picture point with respect to the origin of coordinates, send control signals to the direction adjusting unit (18) for adjusting the object (1) so that the gaze of the person strikes said thing in the origin of coordinates of the system of coordinates of the picture and by that the camera (2) and the object (1) are directed towards said thing (3).

4. A device according to any of the claims 1-3, c h a r a c t e r i z e d in that the displaying arrange¬ ment (4, 6-10) is adapted to show the camera picture in a position fixed with respect to the head of the person, and that said means comprise members (9, 10, 13-15) arranged in a fixed position with respect to the head of the person for absorbing a picture of an eye (11) of the person.

5. A device according to claim 4, c h a r a c t e r i z e d in that said members comprise an optical system arranged closely in front of one of the eyes (11) of said person, comprising mirrors (10, 14) and/or lenses (9, 13) and arranged to throw a picture of the eye of the person directly upon a light sensitive element (16), or the optical system comprises also or only a light recei¬ ving and transmitting conduit (15) arranged closest to the light sensitive element (16) in the path of the light from the eye.

6. A device according to any of the preceding claims, c h a r a c t e r i z e d in that said object (1) is a TV-camera adapted to be controlled by that the person is looking at the thing he wishes to film.

7. A device according to any of the preceding claims, c h a r a c t e r i z e d in that the evaluating unit (17) is adapted to send control signals to the direction adjus¬ ting unit (18) not until it during a predetermined period of time has received unchanged information about the gaze direction of the person from said means.

8. A device for measuring distances, c h a r a c t e r i z e d in that it comprises two cameras (1, 2) located at a mutual distance along a base line and so as to be directed with their camera axes substantially in the same plane, and a picture filter unit (3) adapted to receive picture signals from the respective cameras and filter them, so as to send picture lines with certain serial numbers coming from one camera and picture lines with the rest of the serial numbers coming from the other camera to a displaying arrangement (4) also being a part of the device, that the displaying arrangement is arranged to show a picture created by the picture lines sent from the picture filter unit, that at least one of the cameras is pivotally arranged, that the direction of the camera axes relative to each other is arranged to be adjusted so that a thing (A) to which the distance is to be measured occures continuously in the middle of the picture shown by the displaying arrangement, and that means are arranged to after this adjustment measure the angle of each of the camera axes relative to the base line so as to permit to calculate the distance between the thing (A) and a chosen point along said base line by means of infomation about these two angles and the distance between the cameras along the base line.

9. A device according to claim 8, c h a r a c t e r i z e d in that said picture filter unit (3) is arranged to send picture lines having odd serial numbers coming from one camera and picture lines having even serial numbers coming from the other camera to said displaying unit (4).

10. A device according to claim 8 or 9, c h a r a c t e r i z e d in that said cameras are pi¬ votally arranged about an optical centre each, and that the device comprises a control unit for controlling adjusting members of the cameras and by that adjusting the direction thereof in dependence on the appearance of the picture of said thing of the displaying arrangement.

11. A device according to claim 10, c h a r a c t e r i z e d in that the displaying arrange¬ ment is adapted to display the picture of said thing on a viewing screen with a cursor controlled by means of a so called joy stick, and that actuating of said joy stick is adapted to generate and send control signals to said adjusting members for adjusting the direction of the camera axes relative to each other.

12. A device according to any of the claims 8-11, c h a r a c t e r i z e d in that said angle measuring means are connected to a calculating unit (7) adapted to calculate the distance requested after receiving said angle information.

13. A device according to any of the claims 8-10 and 12, c h a r a c t e r i z e d in that the displaying arrange¬ ment is arranged to show said picture to a person, that the device comprises means for determining the gaze direction of the person, when this is directed on portions of said thing on this picture, and an evaluating unit (11) adapted to receive and treat information about the gaze direction of the person from said gaze direction means and send control signals elaborated on the basis of information about the gaze direction of the person to a unit (12) adapted to adjust the direction of the cameras (1, 2) by adjusting members so that the person sees a continuous picture of said thing in the middle of said picture.

14. A device according to claim 13, c h a r a c t e r i z e d in that it comprises means for controlling the picture filter unit to during a first period of time only send picture lines with said serial numbers coming from a first of the cameras to the display¬ ing arrangement, said person being expected to direct his gaze towards these portions of said thing on the picture shown during said first period, that the evaluating unit (5, 11) is adapted to control the direction adjusting unit in dependence on the gaze direction of the person so as to adjust the direction of this first camera so that said portions of said thing arrive to the middle region of said picture, that said control means are arranged to during a second period of time following the first one control the picture filter unit to also send picture lines having said serial numbers coming from the second camera to the dis¬ playing arrangement, said person being expected to direct his gaze towards the portions of said thing remote with respect to the middle region of the picture, and that the evaluating unit (5, 11) is arranged to during said second period of time control the direction adjusting unit in dependence on the gaze direction of the person to adjust the direction of the second camera so that said thing appears continuously in the middle of the picture shown by the displaying arrangement.

15. A device according to claim 13 or 14, c h a r a c t e r i z e d in that a first (1) of the cameras is secured to an object (8) to be aligned with respect to said thing (14), so that said object (8) and the first camera (1) are arranged to be jointly aligned by means of the gaze direction of the person.

16. A device according to claim 15, c h a r a c t e r i z e d in that the object (8) comprises a rotatable part of a weapon, said thing being a target, that said calculating unit (13) is arranged to send infor¬ mation calculated about the distance between the first camera (1) and the target (14) to a firing unit (15) for adjusting the tube (16) of the weapon in dependence on the distance to the target and the position thereof with respect to the weapon.

17. A device according to claim 16, c h a r a c t e r i z e d in that the evaluating unit (11) is arranged to, after obtaining a continuous picture of the target in the middle of the picture shown to the person, make the alignment of the direction adjusting unit (12) and by that the cameras to slaves of the position of the target so as to keep the picture of the target in the middle of the picture shown independently of the movement of the target, that means are arranged to detect the velocity of the first camera on the direction adjustment thereof and send information thereabout to the calculating unit (13), which is also arranged to calculate the velocity of the target, and that the firing unit (15) is arranged to receive information also about the velocity of the target for adjusting the tube (16) of the weapon while taking also the velocity of the target under consideration when the target (14) is moving.

18. A device according to any of the claims 13-17, c h a r a c t e r i z e d in that the displaying arrange¬ ment is arranged to show the camera picture in a position fixed with respect to the head of the person, and that said means for determining the gaze direction of the person comprise members arranged in a fixed position with respect to the head of the person for absorbing a picture of an eye of the person.

19. A device according to claim 18, c h a r a c t e r i z e d in that said members comprise an optical system arranged closely in front of one of the eyes of said person and comprising mirrors and/or lenses ar¬ ranged to throw a picture of the eye of the person directly upon a light sensitive element, or the optical system also or only comprises a light receiving and transmitting conduit arranged closest to the light sensitive element in the path of the light from the eye.

20. A device according to any of the claims 8-19, c h a r a c t e r i z e d in that the cameras (1, 2) have a zoom-function, and that the evaluating unit (5, 11) is arranged to, after receiving information about the obten- sion of a continuous picture of said thing in the middle of the picture shown, control the cameras to reduce the picture angle, i. e. magnify said thing on the picture for fine adjustment of the camera angles before said distance calculation takes place.