This invention relates to visual display apparatus.

The invention has particular application in periscope systems for submarines.

At present, submarines are commonly provided with an optical periscope relaying to the operator information about the surface of the sea and the horizon.

However, a conventional periscope only has a limited angle of view and thus to obtain a complete view around the submarine an operator must rotate the periscope through one complete rotation. This may take some time and put the submarine at considerable risk as the periscope is visible above the surface of the sea during the operation and may be spotted by an enemy craft. Further, it is difficult for the operator to interpret such information, particularly if several ships or obstacles are spread around the boat. The control of submarines therefore reqires very skilled operators.

The control would be easier if the operator is presented with information about the surroundings of the submarine, ^' in

a manner resembling as closely as possible the field of view which the operator is used to in normal life.

It is an object of the present invention to obviate or mitigate this disadvantage.

According to the present invention there is provided visual display apparatus having viewing means for simultaneously viewing around a point in all directions means being provided for displaying the view obtained by the viewing means on a substantially cylindrical viewing screen.

Thus the operator is presented with information about the environment, acquired and displayed over the full 360° horizon. As such, the viewing of the environment will be interpreted by the observer, as if brought within the world presented to him.

Whether the image is a "true" real projection in visible light obtained from the viewing of the environment or a simulated/fictitious projection of forms, shapes and colours, generated by processors, the resulted projection presented to the operator will be perceived as a realistic relation of the environment.

The viewing means may detect visible light, infra-red radiation^ ultra violet radiation, active or passive sound scanning, radio waves or some other form of radiation.

In the case of visible light being detected by the viewing eans^ the viewing means may have a reflective conical viewing surface which may be provided by a mirror and a viewing camera for receiving the images reflected by the viewing mirror.

The display means may be in the form of a cathode ray screen or laser projector which project images on to a reflective conical projecting surface which may be provided by a mirror.

Preferably, recording means is provided for recording the view obtained by the apparatus such that a view may be displayed on the screen some time after the view was obtained.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:-

Fig. 1 is a diagrammatic sectional side view of viewing means of visual display apparatus in accordance with the present invention; Fig. 2 is a diagrammatic sectional side view of display means of visual display apparatus in accordance with the present invention;

Fig. 3 is a detail view of a lens system of viewing means of the apparatus of the invention;

Fig. 4 is a block diagram of the visual display apparatus of the invention; and Fig. 5 is a perspective overall view of the system of the invention.

Referring to Figs. 1 and 2 of the drawings, visual display apparatus for use in a submarine comprises viewing means 1, in the form of a video camera 2 and a conical viewing mirror

3, and display means 4 in the form of a projector 5 and a conical projecting mirror 6, for displaying the information

obtained by the viewing means on a substantially cylindrical viewing screen 7.

The viewing means 1 is located within the upper portion of a periscope 8. The video camera 2 is mounted above the conical viewing mirror 3 which is contained in a portion of the periscope having a transparent cylindrical wall 9.

The mirror 3 reflects images from all sides of the periscope 8 and these images are detected by the camera 2. To alter the field of view obtained by the viewing means 1 the camera 2, or the lens of the camera; may be moved upwards or downwards relative to the mirror 3.

The information obtained by the camera 2 is passed to the display means 4 within the submarine. In this particular embodiment the projector 5 is a cathode ray screen which projects the images from the camera 3 on to the conical projecting mirror 6 which is positioned directly below the projector 5. The images are then reflected outwards and downwards on to the screen 7. To avoid distortion the screen 7 is varied slightly from a true cylindrical shape.

An operator 10 may sit within the screen 7 and thus obtain a complete view around the submarine.

The images obtained by the camera 2 may be recorded and displayed on the screen 7 after the periscope 8 has been withdrawn below the surface. This is particularly useful where it is desired to have the periscope above the surface for only a short period in order to avoid detection by surface vessels. The images obtained can then be displayed on the screen 7 for as long a period as is desired.

In a similar fashion it is possible to project

simultaneously the images obtained from two separate viewings.

If the time interval between the viewings is known the speed of vessels under surveillance may be calculated.

Computer generated information may be projected over images on the screen 7 to display navigational or firing data to assist the operator 10.

A transmitter is provided in the submarine to transmit information obtained by the viewing means 4 to other locations. This is particularly useful in dangerous locations where the submarine may be remotely controlled and the images obtained can be safely viewed from, for example, another vessel which is located in safer waters.

With reference to Fig.3 of the drawings, the viewing means may comprise a reflective parabolic surface 20 which acquires information over a 360° angle and passes the light signals through appropriate lenses 21; 22 and 23 onto a television camera or other signal gathering means 24.

In general terms, the overall system is illustrated in block diagram form in Fig. 4.

The system comprises a retractable non-penetrating mast 30 which houses the signal receiving optics 31, information from which is passed to a processing unit 32 through an image sensor 33. The processing unit 32 configures the received signal to make it suitable for transmission through a link system 34 via a hull penetrator 40. The power supply 41 for the units 32 and 33 is provided within the hull.

The received signal is passed through a signal processing

unit 51 to a cylindrical display 50 through appropriate image processing units 52 and data storage units 53. Ancillary data 54 maybe provided and the signal maybe controlled through a micro-processor 55 having an input console 56.

In other embodiments of the invention the display means may be in the form of a plurality of cathode ray screens on which back images are projected. Equally, a purpose made solid state screen could be used.

A cylindrical screen as just described can be relatively small, and can provide a display system suitable for use aboard submarines where space for equipment and personnel is very limited. Where space is not limited, one can use a similar larger display for one or more viewers.

Overlaid grids and data for navigation can be generated by computer, in the manner of a "head up" display. Other overlaid information may comprise acoustic images, and computer-generated drawings of a target.

Modifications and improvements may be made without departing from the scope of the invention.

In further embodiments; the viewing means may; for example, utilise acoustic information receivers and thus may obtain an underwater sonic interpretation below the surface of the sea.