SIGHT COMPRISING IR CAMERA AND HAVING A LARGE OBSERVATION AREA

Abstract: The invention relates to a sight comprising IR camera (K) and device (OA) for obtaining a large observation area. According to the invention, the device for obtaining a large observation area comprises an admission aperture which can be rotated vertically and sideways for receiving an incident image, a mirror arrangement (D, E, F) which can be rotated about a common axis (V) for derotation of the image incident through the admission aperture, and an output aperture which is related in fixed terms to the IR detector of the IR camera. By means of the invention it is not necessary, as it is in known constructions, to angle those parts of the IR camera which contain the IR detector.

Description: SIGHTCOMPRISING IR CAMERA AND HAVING A LARGEOBSERVATION AREA The present invention relates to a sight comprising IR camera and device for obtaining a large observation area. In order to increase the observation area for an IR camera, it is already known to angle those components of the IR camera which contain the IR detector. These are bulky components which have to be moved. Known designs are cumbersome and can be used within relatively restricted observation areas. The object of the present invention is to make available a compact construction of a sight with IR camera which at the same time permits use of a large observation area, for example of hemispherical shape. The object of the invention is achieved by means of a sight characterized in that the device for obtaining a large observation area comprises an admission aperture which can be rotated vertically and sideways for receiving an incident image, a mirror arrangement which can be rotated about a common axis for derotation of the image incident through the admission aperture, and an output aperture which is related in fixed terms to the IR detector of the IR camera. The invention uses an IR camera with fixed mounting of the IR detector, in combination with an admission aperture which can be rotated vertically and sideways. A mirror arrangement ensures that the image is rotated so that an observer always sees the image the right way round. It should be said here that arrangements for turning the image the right way round for an observer are already known. A prism arrangement can be used in this connection for turning the image. However, this entails completely different wavelength ranges from those which apply in the case of IR cameras. According to one advantageous embodiment of the invention, the mirror arrangement consists of three plane mirrors arranged to reflect an image incident on the mirror arrangement parallel to the axis of derotation, so that the image leaves the mirror arrangement in a continuation of the direction of incidence. The first mirror and third mirror are advantageously inclined relative to the axis of derotation and are arranged to meet at a common edge in front of which the second mirror is arranged. According to another advantageous embodiment of the invention, the arrangement for obtaining a large observation area comprises a first structure which can be rotated about a first axis, which structure comprises an admission aperture which consists of an objective with one or more lenses and a mirror inclined in relation to the admission aperture, a second structure which can be rotated about a second axis at right angles to the first axis and comprising an inclined mirror for directing the incident image towards the mirror arrangement, a third structure supporting the mirror arrangement and rotatable about the same second axis, and alβo a fourth structure which is fixed relative to the IR camera. By means of this arrangement with four structures, scanning of the desired area can be carried out in a simple and functionally reliable manner. The sight can advantageously comprise a channel for IR light and a channel for visible light. According to one advantageous embodiment of this kind, a prism arrangement, in combination with a mirror transparent to visible light, is arranged to combine the IR light and the visible light into a common channel. To divide the light up once again into IR light and visible light, a mirror which is transparent to IR light can be used. For receiving the visible light, the arrangement for obtaining a large observation area can advantageously comprise a fifth structure which can be rotated about the first axis, which structure comprises an admission aperture which consists of an objective with one or more lenses and a mirror which is inclined in relation to the admission aperture. The invention will be described in greater detail hereinbelow on the basis of illustrative embodiments and with reference to the attached drawings, in which: Figure 1 shows a partial cross-sectional side view of a first example of a sight with IR camera according to the invention. Figure 2 shows a partial cross-sectional top view of the sight according to Figure 1. Figure 3 shows a partial cross-sectional top view of a second example of a sight with IR camera according to the invention. Figure 4 shows a partial cross-sectional top view of the sight according to Figure 3. The sight shown in Figures 1 and 2 comprises an IR camera part K with an IR detector and a device OA for increasing the observation area. The device OA comprises a first structure Sl which can be rotated about an axis H. The structure Sl is mounted in a second structure S2 by means of a bearing Ll. The structure Sl supports an objective A which in the figure is represented by a single lens, but which in accordance with known principles can consist of a plurality of lenses. Inside the structure Sl there iβ a mirror B which is arranged at an angle of 45 degrees with respect to the viewing direction R. The structure S2 can be rotated about a second axis V essentially at right angles to the first axis H with the cooperation of a second bearing L2 mounted between the second structure S2 and a fourth structure S4 which is fixed in relation to the IR detector of the camera part. An angled mirror C is mounted in the structure S2. The mirror reflects an image incident in the longitudinal direction of the axis H through 90° in a direction corresponding to the longitudinal direction of the axis V. In the beam path of the image reflected by the mirror C there is a mirror arrangement consisting of three plane mirrors D, E and F. The mirror arrangement is fixed in a third structure S3. In the embodiment shown, the structure S3 is mounted, by means of a bearing L3, in the structure S2 so that it can rotate about the axis V. Alternatively, the structure S3 can be mounted so as to rotate in the structure S4. The three mirrors are thus arranged in relation to each other such that a beam incident on the first mirror, after reflection in the mirrors, .leaves the mirror arrangement in a continuation of the direction of the incident beam. In order to produce this beam path, the first mirror D and the third mirror F are arranged inclined in the beam path with a common edge G in front of the second mirror E. The rotation of the structures Sl, S2 and S3 can be obtained by means of drive motors of a suitable known design. The drive motors do not constitute a part of the invention and therefore have not been shown. By rotating the structure Sl about the axis H and the structure S2 about the axis V, any arbitrary viewing direction can be selected within a large observation area. Rotating the structure S3 ensures that the image is turned so that an observer sees the image the right way round. The sight shown in Figures 3 and 4 comprises, in addition to a channel for IR light, a further channel for visible light. The components which correspond to those described in the embodiment with reference to Figures 1 and 2 have been given the same reference labels and in principle function in the same way. In order to receive visible light, there is a fifth structure S5. Like the structure Sl, the structure S5 can be rotated about the axis H and is mounted in the second structure S2. The mounting is achieved by means of a fourth bearing L4. Like the structure Sl, the structure S5 is provided with an objective designated Al and a mirror designated Bl arranged at a 45 degree angle to the viewing direction R. During simultaneous use of the channels for visible light and IR light, the movement of the first structure Sl and of the fifth structure S5 is coordinated so that during the movement they monitor in parallel the same viewing direction. The structures Sl and S2 can advantageously be arranged to be driven independently of each other, which can be of value when only one channel is used. An image incident on the structure S5 is reflected, after it has passed through the objective Al, towards a prism arrangement P by the mirror Bl. The prism arrangement P combines the channel for visible light with the IR channel via the mirror C which is transparent to visible light. After passing the derotation arrangement D, E, F, : the channels are once again separated by means of a mirror M which transmits IR light and reflects visible light. The reflected visible light reaches an observer via an aperture N.

Claims: Patent Claims 1. Sight comprising IR camera and device for obtaining a large observation area, characterized in that the device for obtaining a large observation area compriseβ an admission aperture which can be rotated vertically and sideways for receiving an incident image, a mirror arrangement which can be rotated about a common axis for derotation of the image incident through the admission aperture, and an output aperture which is related in fixed terms to the IR detector of the IR camera. 2. Sight according to Patent Claim 1, characterized in that the mirror arrangement consists of three plane mirrors arranged to reflect an image incident on the mirror arrangement parallel to the axis of derotation, so that the image leaves the mirror arrangement in a continuation of the direction of incidence. 3. Sight according to Patent Claim 2, characterized in that the first mirror and third mirror are inclined relative to the axis of derotation and are arranged to meet at a common edge in front of which the second mirror is arranged. 4. Sight according to any of the preceding Patent claims, characterized in that the arrangement comprises a first structure which can be rotated about a first axis, which structure comprises an admission aperture which consists of an objective with one or more lenses and a mirror inclined in relation to the admission aperture, a second structure which can be rotated about a second axis at right angles to the first axis and comprising an inclined mirror for directing the incident image towards the mirror arrangement, a third structure supporting the mirror arrangement and rotatable about the same second axis, and also a fourth structure which is fixed relative to the IR camera. 5. Sight according to any of the preceding Patent claims, characterized in that the sight comprises a channel for IR light and a channel for visible light. 6. Sight according to Patent Claim 5, characterized in that a prism arrangement, in combination with a mirror transparent to visible light, is arranged to combine the IR light and the visible light into a common channel. 7. Sight according to Patent Claim 6, characterized in that a mirror transparent to IR light is arranged such that, after derotation of the combined light, it divides the light up once again into IR light and visible light. 8. Sight according to any of Patent Claims 5 - 7, characterized in that the arrangement for obtaining a large observation area comprises a fifth structure which can be rotated about the first axis, which structure comprises an admission aperture which consists of an objective with one or more lenses and a mirror which is inclined in relation to the admission aperture.

Inventors: BERGSTEDT DAN, BERGSTEDT, DAN
Applicants: BERGSTEDT DAN, CELSIUSTECH ELECTRONICS AB, BERGSTEDT, DAN
Application year: 1997
Main classification: G02B23
IPC codes: G02B23, G02B27