GB2277603A

GB2277603A - Viewing system having aspheric lens element

Info

Publication number: GB2277603A
Application number: GB9308743A
Authority: GB
Inventors: Justin Miles Thomas
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-28
Filing date: 1993-04-28
Publication date: 1994-11-02
Also published as: GB9308743D0

Abstract

A lens has a first face and a second face each being disposed on a respective side of a median plane. The lens comprises a plurality of elemental prism sections, the prismatic angles of the elemental sections progressively changing along the length of the lens whereby rays of light incident on the first face 2 refracted through the lens are in parallelism or substantial parallelism one with the other, irrespective of the angles of incidence of the rays, on the second face 1. The shape of the lens is such as to afford a wide angular scope of view to the system up to approximately 180 degrees. The lens is so formed to ensure that incident rays undergo essentially minimum deviation through the prismatic elemental sections. The lens may be used in a periscope, endoscope, telescope, camera on vehicle headlight. <IMAGE>

Description

IMPROVEMENTS IN OR RELATING TO VIEWING SYSTEMS This invention concerns improvements in or relating to viewing systems and installations incorporating such systems.

In particular, although not exclusively, the present invention has reference to such a system suitable for static or mobile applications in security, observation, medical, vehicular and analytical installations.

Conventionally, it is known that viewing systems rely on lenses to focus or direct an image to a viewing position, receiver or direct to the naked eye in order to provide a vision of a required subject or area. Often it is desirable to afford as comprehensive as possible a view of the prevailing ambient conditions and so a method of manoeuvring the system is incorporated in order to provide a panoramic view, but clearly the degree to which such can be achieved is impaired by the angular viewing scope of the system and the necessity to redirect the view to cover a particular area.

Similarly, endeavours have been made to improve vision given by said system for example by providing a 'fisheye' lens in an attempt to give a wider viewing spectrum. However, the image is inevitably distorted which naturally militates against the alleged advantage of providing vision of greater breadth.

It is an object of the present invention to provide a viewing system having the capacity of facilitating inspection of a vista and for capturing a wider field of view than is possible with conventional or known systems.

It is further an object of the invention to provide vehicles and static installations incorporating such systems.

According to the first aspect of the invention, a viewing system including a light transmitting member having a first face and a second face each face being disposed on a respective side of a median plane, the member comprising a plurality of elemental prismatic sections, the prismatic angles of the elemental sections progressively changing along the length of the member whereby rays of refracted light incident on the first face are in parallelism or substantial parallelism one with the other irrespective of the angles of incidence of the rays on the second face.

Advantageously, the member is so formed to ensure that the incident rays undergo essentially minimum deviation through the prismatic elemental sections.

Conveniently, the shape of the first face of the member is generated by a locus of points calculated by the following formulae wherein the 'y' axis is aligned along the median plane and the 'x' axis extends orthogonally thereto: xn = sin [(An + dn)/2]. fn/cos(An/2) +xn-i yn = cos [(An+dn)/2]. fn/cos(An/2) + yn-1 wherein A = the prismatic angle d = deviation = = the correction factor = (Yn-1-yn-2) 2nd side/ (Yn-1~Yn 2) 1st side n = the number of the element Similarly, the second face of the member is generated by a locus of points calculated by the following formulae wherein the 'y' axis is aligned along the median plane and the 'x' axis extends orthogonally thereto:: Xn = [sin{(An-dn)/2}].[fn+sin{(dn-dn-1)/2}.Wn-1]/cos(An/2)+xn yn = [cos{(An-dn)/2}].[fn+sin{(dn-dn-1)/2}.Wn-1]/cos(An/2)+yn wherein A = the prismatic angle d = deviation = = the correction factor= (yn-1-yn-2) 2nd side/ (Yn-1~Yn 2) 1st side Wn = width of member = tan(A/2).(2.fn+Wn1.sin[(dndn1)12]) +Wn-1.cos[(dn-dn-1)/2] n = the number of the element WO = 2(i x) at the narrowest part of the member In practice the member is substantially concavo-convex form.

The first and second faces progressively diverge from one another with the increasing prismatic angle of the elemental sections, Wn giving the varying width of the member. The first face may be angularly disposed in relation to the median plane and may be concave or convex. The ends of the member may be planar or of any convenient shape.

The length of the member is chosen to give the broadest spectrum of image capture, and a particular and unique advantage of the present invention resides in the angular scope which the configuration of the member affords. The angular scope extends from 0 on a line perpendicular to the median plane to approximately 1800 thereto.

The depth of the member may be chosen dependent upon the individual requirements.

According to a second aspect of the invention, a periscope viewing system including a member according to the first aspect wherein the light transmitting member may be located at the desired viewing position of the system. The periscope is preferably provided with a means for positively directing or collimating the rays from the first face of the member to the viewing position of the observer.

The periscope may be motorised or manually powered or static.

According to the third aspect of the invention, a direct viewing system according to the first aspect of the invention whereby the light transmitting member is preferably located in the direct line of view of the viewer so as to provide the wide angular scope of view as directly as is conveniently possible.

Alternatively, the light transmitting member may be located in a suitable position in a body. The member may be held in a housing and the housing may be integral with the mounting or mounted thereon. It may be mounted in an appropriate manner without the need for housing.

According to the fourth aspect of the invention, a viewing system according to the first aspect of the invention for example, for medical purposes though not exclusively includes in combination a light source and a light transmitting member whereby the light source may preferably be combined so that light rays from the source of illumination are refracted through the light transmitting member on to a surface in order that the light is then reflected back through the light transmitting member to provide a view of the subject.

Alternatively the light source may be combined in any convenient manner such that the reflected light is adequately refracted back through the light transmitting member.

According to the fifth aspect of the invention a security system including a viewing system according to the first aspect of the invention wherein the member is mounted in such a way as to afford the viewer a large angular scope in order that images refracted through he light transmitting member may be conveniently analysed for security purposes.

According to the sixth aspect of the invention a safety device including a light transmitting member according to the first aspect of the invention wherein the member is mounted, for instance, though not exclusively, in or on the frame of an aircraft or other vehicular body such that images refracted through the member provide the viewer with information relating to the aircraft, vehicular body or ambient conditions.

By way of example, with reference to Figures 1 and 2 of the drawings, a light transmitting member as described hereinbefore.

In this example the values of the x, y for both faces have been calculated over a full range of prismatic angles from -82" to +820.

As will be more clearly seen from Figure 2, the angles of incidence of rays on face 2 are illustrated to vary from -10" to +10 . The rays are refracted by the member undergoing minimum of deviation in relation to face 1.

The principal advantage of the present invention is that the viewer is provided with an angular scope of vision up to 1800 giving a more comprehensive and preferably undistorted picture of the ambient conditions than is possible with conventional lenses or known devices, and thus the process of analysis is considerably enhanced.

The present invention described mav be manufactured usina

glass, perspexl,diacon and it is to be understood that other materials or media may be used.

Claims

1. A viewing system including a light transmitting member having a first face and a second face each face being disposed on a respective side of a median plane, the member comprising a plurality of elemental prismatic sections, the prismatic angles of the elemental sections progressively changing along the length of the member whereby rays of light incident on the first face refracted through the member are in parallelism or substantial parallelism one with the other irrespective of the angles of incidence of the rays on the second face.

2. A viewing system incorporating a light transmitting member as itemised in claim 1 so formed to ensure that the incident rays undergo essentially minimum deviation through the prismatic elemental sections.

3. A viewing system incorporating a light transmitting member according to claims 1 and 2 in which the shape of the first face of the member is generated by a locus of points calculated by the following formulae wherein the 'y' axis is aligned along the median plane and the 'x' axis extends orthogonally thereto: Xn = sin [(An + dn)/2]- fn/cos(An/2) +Xn-1 yn = cos [(An+dn)/2]. fn/cos(An/2) + Yn-1 wherein A = the prismatic angle d = deviation = = the correction factor = (yn1 yn-2) 2nd side/ (Yn-1 -Y,,2) 1 sot side n = the number of the element

4.A viewing system including a light transmitting member according to claims 1, 2 and 3 in which the second face of the member is generated by a locus of points calculated by the following formulae wherein the 'y' axis is aligned along the median plane and the 'x' axis extends orthogonally thereto: xn = [sin((An-dn)/2)].[fn+Sin((dn-dn1 )/2).Wn1 ]/cos(An/2)+xn yn = [cos{(An-dn)/2}].[fn+sin{(dn-dn-1)/2}.Wn-1 ]1cos(A/2)+y wherein A = the prismatic angle d = deviation = = the correction factor = (yn-1-yn-2) 2nd side/ (yn-1-yn-2) 1st side Wn = width of member = tan(A/2).{2.fn+Wn-1.Sin[(dn-dn1)/2]} +Wn-1.cos[(dn-dn-1)/2] n = the number of the element Wo = 2(i x) at the narrowest part of the member

5.A viewing system including a light transmitting member according to claims 1, 2, 3 and 4 in which the first face of the member is angularly orientated relative to the median plane.

6. A viewing system including a light transmitting member according to claims 1, 2, 3, 4 and 5 described with reference to the accompanying drawings numbered Fig 1 and fig 2.

7. A viewing system incorporating a light transmitting member according to claims 1 to 6 in which the two faces may be flat, concave, convex or concavo-convex.

8. A viewing system incorporating a light transmitting member according to claims 1 to 7 in which the system is a periscope.

9. A viewing system incorporating a light transmitting member according to claims 1 to 7 in which the system is a medical observation instrument for example, though not exclusively, an endoscope which includes in combination a light source.

10. A viewing system including a light transmitting member according to claims 1 to 7 in which the system is a security system which includes for example though not exclusively in combination a video camera.

11. A vehicle incorporating a viewing system including a light transmitting member according to claims 1 to 7 in which the member is disposed in or on the frame of a vehicle body.

12. A vehicle incorporating a viewing system including a light transmitting member according to claim 11 in which the vehicle is an aircraft.

13. A vehicle incorporating a light transmitting member according to claim 8.

14. A viewing system incorporating a light transmitting member according to claims 1 to 7 where the system is a telescope.

15. A vehicle including a viewing system incorporating a light transmitting member according to claim 8, 11 and 13 where the vehicle is a submarine.

16. A viewing system incorporating a light transmitting member according to claims 1 to 7 where the system is a camera.

17. A viewing system according to any one of the preceding claims in which the light transmitting member is orientable.

18. A viewing system according to any one of the preceding claims where the housing is streamlined.

19. A viewing system incorporating in combination a light source and a light transmitting member according to claims 1 to 7.

20. A vehicle incorporating a viewing system according to claim 19.

21. A vehicle incorporating a viewing system according to claim 20 where the system is a headlight.