GB2149141A

GB2149141A - Day and night sighting apparatus

Info

Publication number: GB2149141A
Application number: GB08427000A
Authority: GB
Inventors: Roderich Ruger
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1983-10-27
Filing date: 1984-10-25
Publication date: 1985-06-05
Also published as: GB8426120D0; FR2554247A1; DE3338928A1; FR2554247B1; GB2149141B; GB8427000D0; DE3338928C2

Abstract

Day and night sighting apparatus 1 comprising a day sighting apparatus, consisting of a periscope 2 and a aiming head 4, as well as with a thermal-imager 10, a cathode-ray tube 13 for reproducing the thermal image converted into visible frequencies. The necessary axis harmonisation of the day sighting apparatus and the thermal imager of known like apparatus is abolished in that in the apparatus 1 a reticle 16 is generated electronically and is displayed on screen 14 of the cathode-ray tube 13. Thus, the reticle 16 can be used not only in an eyepiece 3, but also by a coupled-up automatic target detection or tracking apparatus. <IMAGE>

Description

SPECIFICATION Day and night sighting apparatus This invention relates to day and night sighting apparatus comprising a day sighting device, a thermal-imager, a cathode-ray tube or the like for producing a thermal image converted into visible frequencies, and a reticle which is mirrored into the ray path.

In the case of such day/night sighting apparatus, the thermal image picked up by the thermal-imager is converted into an image with visible frequencies, for example with the aid of a cathode-ray tube or an arrangement consisting of light emitting diodes (LED), and then mirrored by way of deflection mirrors, prisms and so forth into the ray or beam path of the day sighting apparatus in register or coincidental with the image thereof. This coincident mirroring-in requires that the optical axes of the day sighting apparatus and the thermal imager are aligned parallel to one another. This is achieved in known apparatus with so-called collimators, which for the adjustment of the two axes are superimposed onto one of the devices thereof or else are incorporated fixedly into the day/night sighting apparatus.Compared with the apparatus in which the so-called axis harmonisation is achieved only with additional means such as collimators, in the case of the apparatus disclosed Federal Republic of Germany patent publication P 32 32 092.2-51 provision is made for undertaking the axis harmonisation with the aid of a visible heat spot, for example a coloured heated thermistor, which is run into the centre of the screen of the cathoderay tube. The heat spot is mirrored, by way of a beam splitter, into the ray or beam path of the day sighting apparatus, in which respect serving as reference for the image centre is an optical/mechanical reticle, arranged in the periscope of the day sighting apparatus on a graduated plate.In this respect, by observation by way of an eyepiece the heat spot can be brought into coincidence with the reticle with the aid of an electrical adjustment of the cathode-ray tube. As a result of this arrangement, the axis harmonisation is already considerably facilitated.

The reticle, intended for this, on the graduated plate is, however, not usable by automatic target detection and tracking apparatus which is connected to the day/night sighting apparatus. Upon operation of these apparatus which are coupled together, an extremely accurate axis harmonisation to an accuracy of < 0.1 mrad is necessary, which can be observed with previously known apparatus only with great difficulty in rough conditions of use, for example in conjunction with tanks or with helicopters.

The problem underlying the invention to avoid the above-described disadvantages of known day and night sighting apparatus of the kind mentioned at the beginning hereof.

In accordance with the present invention this problem is solved in that the reticle is generated electronically and is displayed on the screen of the cathode-ray tube.

The reticle produced electronically in this way can be perceived through the eyepiece of the day sighting apparatus by the human eye and can also be jointly used by coupled automatic systems both for the thermal-imager and for the day sight. Because thus the electronically produced reticle can be perceived in all parts of the day/night sighting apparatus and also in coupled target detection and tracking apparatus, no problems of axis harmonisation arise so that the optical and/or electrical checking of the axes which is necessary in the case of the known apparatus is abolished.In accordance with modifications of the preferred apparatus of the invention, the reticle can be produced in the thermal-imager and transferred onto the screen of the cathode-ray tube or alternatively the reticle can be produced directly in the cathode-ray tube, in which respect it is keyed in by two electronic lines standing perpendicularly to one another. Of course, this can be undertaken subsequently even in the incorporated state of the day/ night vision apparatus.

The invention will be described further, by way of example, with reference to the accompanying drawing in which: Figure 1 is a schematic section through a preferred embodiment of the day and night sighting apparatus of the present invention; and Figure 2 is a plan view of a screen of a cathode-ray tube of the preferred embodiment of Fig. 1 with the representation of a reticle thereon.

The preferred embodiment of the day/night sighting apparatus 1 illustrated in Fig. 1 comprise a day sighting device consisting of a periscope 2 with an eyepiece 3 and an aiming head 4 housing a tiltable aiming mirror 5.

Provided on the front side of the aiming head 4 is a window 6 through which light is incident, is deflected at the aiming mirror 5 and is finally conducted through an optical system 7 (not illustrated in detail) and a deflection mirror 8 into the eyepiece 3. Although a day sighting apparatus in the form of a periscope has been described, other conventional kinds of sighting apparatus can be used. For example, in the periscope additionally a goniometer 2a can be present. From the ray path of the periscope 2 a proportion of the light is mirrored out for the goniometer 2a.

Arranged between aiming head 4 and the housing of the periscope 2 is a block 9 for a thermal-imager 10. In the block 9, a frequency-selective beam splitter 11 is situated at an angle of 45 towards the vertical axis of the periscope in the ray path for the periscope 2. This beam splitter 11 allows the visible light for the periscope 2 through, but reflects thermal radiation for the thermal-image device 10 and guides the thermal radiation onto an input optical system 1 2 of the thermal-imager 10.

Situated on that side of the beam splitter 11 which lies opposite to the thermal-imager 10 is a cathode-ray tube 13, screen 14 of which is turned to face the beam splitter 11.

On the screen 1 4 of the cathode-ray tube 1 3 there appears the thermal image which is picked up by the thermai-imager 10. This is mirrored by way of the beam splitter 11 into the periscope 2 and can be observed at the eyepiece 3.

In the known 'per se' thermal-imager 10, the infra-red light incident through the input optical system 1 2 is conducted by way of scanning mirrors and a collecting optical system (not shown) onto a detector 15, the output signals of which detector 1 5, after amplification, are fed to the signal input of the cathode-ray tube 1 3. By reason of the input signals, the thermal image is shown on the screen 14. In a similar way, signals can be fed into the detector 1 5 which signals produce on the screen 14 of the cathode-ray tube 13, as illustrated in Fig. 2, horizontal and vertical lines to generate a reticle 1 6.

It is equally possible to generate the signals for generating the lines for the reticle 1 6 directly in the cathode-ray tube 1 3 and to display them on the screen 14. The thus electronically produced reticle 1 6 can be both observed directly through the eyepiece 3 and jointly used also by automatic systems, coupled with the day/night sighting apparatus 1, both for the thermal-imager 10 and for the day sighting apparatus.

Claims

1. Day and night sighting apparatus comprising a day sighting apparatus, a thermalimager, a cathode-ray tube or the like for reproducing a thermal image converted into visible frequencies, and a reticle which is mirrored into the ray path, characterised in that the reticle is generated electronically and is represented on the screen of the cathoderay tube.

2. Day and night sighting apparatus as claimed in Claim 1, characterised in that the reticle is generated in the thermal-imager and is transferred onto the screen of the cathoderay tube.

3. Day and night sighting apparatus as claimed in claim 1, characterised in that the reticle is generated directly in the cathode-ray tube.

4. Day and night sighting apparatus as claimed in claims 1 to 3, characterised in that the reticle is generated by a keying in of two electronic lines standing perpendicularly to one another.

5. Day and night sighting apparatus as claimed in claims 1 to 4, characterised in that the reticle is usable by a coupled-up automatic target detection or tracking apparatus.

6. Day and night sighting apparatus substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.