GB2090989A - Cameras and attachments therefore - Google Patents

Abstract

An attachment 1 for connection to a camera body 9 includes an inlet and an outlet 2 and 3 respectively, and deflecting means 4 in the form of a prism to deflect light entering inlet 2 through a substantial angle towards and through outlet 3. The outlet 3 includes a flange and collar arrangement 7 adapted to engage the lens mount means 8 of the camera body 9. The inlet means may include lens mount means 6 to which may be attached a conventional image- forming lens system 5, or alternatively the inlet means itself may include an image-forming lens system integral therewith. A stabilized mirror 10 may be used to deflect light from the scene to be viewed into the lens system 5. <IMAGE>

Description

SPECIFICATION Cameras and attachments there This invention relates to cameras and attachments therefor which allow the output optical axis of the principal image-forming lens system to be reflected through an angle prior to entering the camera body. This invention also relates to cameras and attachments which furthermore allow stabilization of the image received by the camera body.

According to one aspect of this invention, there is provided an attachment for connection to a camera body which includes mounting means for receiving an image-forming lens system and image-sensing means, the attachment comprising inlet and outlet means for light, the inlet means including mounting means for enabling a lens system to engage the inlet means in optical communication therewith, the outlet means including connection means for enabling the attachment to engage the lens mount means of the camera body with said outlet means in optical communication with said image-sensing means, and deflecting means adapted to deflect light which passes through said inlet through a substantial angle (preferably at least 490) towards and through said outlet means.

It will be understood that the outlet means of the attachment is of a similar configuration to the outlet of a conventional lens; this may be of screw-threaded form, bayonet fitting or any other configuration conventionally employed.

The reflecting means preferably comprises an odd number of reflecting surfaces, so as to produce an inverted and reversed image in the camera body.

Alternatively, the inlet means of the attachment itself may include a lens system. As above, the lens system preferably produces an inverted and reversed image in the camera body.

In order to offset the optical axis of the viewed scene and that input to the camera, a further deflecting element may be interposed between the scene viewed and the image-forming lens system, the further deflecting surface being adapted to deflect light from the scene viewed into the image-forming lens system. Naturally, if the angles of deflection of the further deflecting surface and the deflecting means are equal, a periscope effect may be achieved which may be of particular benefit when a camera to which such an attachment is fitted is used ta photograph scenes in a crowd or in a situation where the cameraman wishes to remain obscured from the viewed scene.

Furthermore, in order to effect stabilization of the image against inadvertent movement received by the camera body, e.g. by hand tremor or when the camera is used in a vehicle by buffeting, the further deflecting element may be in the form of a mirror or prism mounted in gimbals and controlled by a gyroscope or inertial mass or other means to reflect light from the viewed scene into the imageforming lens, the optical axis of the incoming light being steady relative to inertial space. Such as stabilizing arrangement is described in our published U.K. Application No. 2,036,998A and reference is directed to that Application.

The attachment may include further lens means adapted to compensate for any change in length of the optical path between the image-forming lens system and the image-sensing means arising by virtue of the use of the attachment. The further lens means may be in the form of an extender lens or a relay lens.

If a relay lens is used, this may either effect simple transfer of the image, or it may produce an image in the camera which is an enlargement or reduction of the image normally produced by the image-forming lens employed.

In one embodiment, the light transmitted through the image-forming lens system is reflected by a series of first, second and third reflecting surfaces, which series includes two adjacent surfaces mutually perpendicular with their intersection (or projected intersection) parallel to the plane containing the axes incident upon and reflecting from the further reflection surface. In this case, the reflecting surfaces may be mirrors, or they may be the walls of a prism or a roofpenta-prism. Where three or more reflecting surfaces are used, the attachment should include a relay lens assembly.

In one possible preferred embodiment, the attachment includes second inlet means adapted to be engaged by the outlet of a secondary imageforming lens system, said secondary inlet means being adapted so that light passing through said secondary image-forming lens system is transmitted into the camera body.

The secondary image-forming lens preferably forms an inverted and reversed image of the object in the camera body.

It will be appreciated that the attachment of this invention may also be used with equipment, other than cameras, which include image-forming lens systems, for example the attachment may be used in conjunction with telescopes, laser rangefinders, target markers, optical communicators etc. The attachment may also be used with equipment operating on optical principles but adapted to receive infra-red radiation.

By way of example only, five specific embodiments of apparatus constructed in accordance with this invention will now be described in detail, reference being made to the accompanying drawings, in which Figure 1 is a diagrammatic side view of a camera to which a first embodiment of attachment is mounted; Figure 2 is a diagrammatic side view of a camera to which a second embodiment of attachment is mounted; Figurees 3a and 3b are diagrammatic side and partial end views respectively of a camera to which a third embodiment of attachment is mounted; Figure 4 is a cross-section of a camera to which a fourth embodiment of attachment is attached, and Figures 5a and 5b are diagrammatic side and partial end views respectively of a camera to which a fifth embodiment of this invention is attached.

Referring initially to Figure 1, the attachment shown comprises a casing 1 having inlet and outlet means 2 and 3 respectively, and a reflecting surface 4 arranged to reflect light transmitted via an image-forming lens system 5 through 900 into the camera body.

The inlet means 2 includes lens mount means in the form of a flange 6 adapted to engage the collar of the mount mechanism of the image-forming lens system 5. The outlet means 3 includes a flange and collar arrangement 7 adapted to engage the lens mount means 8 of a camera 9. A further reflecting surface 10 reflects light from the scene view through 900 into the image-forming lens system 5. The arrangement is such that the image formed in the camera will be inverted and reversed, as is the case in a normal camera.

In order to provide a reduced field of view and, at the same time, transfer the image plane of the lens system 5 further along the optical axis, to be in the plane of the image-sensing means in the camera 9, the attachment may include an auxilliary lens, comprising lens assemblies 11 and 12, which has a negative power and which is positioned between the lens system 5 and the position at which its focal plane would normally occur.

The auxilliary lens may be of a form commonly known as an "extender lens" and available for use with a variety of camera lenses to provide an extension of the focal length of the camera lens when attached at its rear end. The combination of camera lens and extender forms a lens known as a telephoto lens, comprising essentially a front part of positive power and a rear part of negative power but, in combination, having positive power.

This arrangement has three advantages; firstly, the reduced field of view (or range of fields of view if the lens is a zoom lens) is compatible with the need to stabilize the image (which becomes increasingly important as the field of view decreases); secondly, the reduced field of view is compatible with the use of the offset viewpoint (which is useful when behind crowds or in hazardous circumstances, the object being at a substantial distance); and thirdly, the reduced field of view is compatible with the use of the fixed or stabilizing mirror which would have to be inconveniently large to accept the wide field of view of the camera lens used normally.

The lens assembly 11 and an optical assembly 12 may comprise several elements of glass or other transparent materials having refractive indeces, relative dispersions and surface curvatures so arranged to control and minimise aberrations in the image. If a prism is used to provide the reflecting surface 4, the lens system 5 will be corrected to work through this prism. In the case of some cameras, a beam-splitting prism 14 is used in front of the image planes so that, for use with such cameras, the adaptor must be corrected to allow for the prism in the camera, as well as for the allowance made for it in the camera lens design.

The reflecting surface 10 may be fixed, or controlled so as to reflect a stabilized image, by means of a gyroscope, or an inertial mass, as described in our co-pending published Application No. 2,036,998A.

Referring to Figure 2, certain parts are similar to those shown in Figure 1; such parts are given like reference numerals and will not be described in detail again. In this embodiment of attachment, three reflecting surfaces are defined by a roofpenta-prism 20. The roof surfaces are shown as the second and third surfaces but may alternatively be the first and second.

A field lens 21 is positioned near the primary image plane of the image-forming lens system 5.

A relay lens system 22 is provided adjacent the outlet means 3 of the attachment to orientate the image correctly and to move its position into the plane of the image-sensing means in the camera 9. The relay lens system 22 may be arranged to produce either a magnified image or a reduced image, or mereiy an image of the same size in the camera.

Referring to Figures 3a and 3b, like parts of those of Figures 1 or 2 are given like reference numerals and will not be described in detail again.

In this arrangement, the casing 1 contains two mirrors 32 and 33, mutually at right angles and a third mirror 34 reflecting the optical axis through relay lens assembly 22 to form an image in the camera 9. A field lens 23 is positioned near the primary focal plane of the camera lens and the whole lens system may be designed to work with a beamsplitting prism 14 where is incorporated in the camera. A protective transparent cover 35 is provided to protect the elements within the casing when it is removed from the image-forming lens system 5.

Referring to Figure 4, there is shown a form of attachment which includes an image-forming lens system comprising lens assemblies 5, 40 and 41 and a reflecting surface 4 all in one housing. Parts similar to those shown in the preceding Figures are given like reference numerals and will not be described in detail again. This form of attachment comprises casing elements 1, 1 a and 1 b. Casing element 1 houses a reflecting surface 4 in the form of a prism arranged to reflect light entering the elements through 900, and lens assemblies 40 and 41 are positioned either side of the prism.

Casing element 1 a houses the image forming lens assembly 5 which may be a part of a lens of fixed focal length providing a fixed field of view or may be a part of a zoom lens having movable elements controlled locally or remotely which provide a range of focal lengths and corresponding fields of view. The lens may also include movable elements which provide adjustable focus on objects at various distances and may also include an adjustable diaphragm to allow for varying scene luminance. These adjustments may be controlled either locally or remotely.

Casing element 1 b houses a further reflecting surface 10 which is normally aligned in a plane parallel to that including the primary reflecting surface 4, so that the axis of light from the scene viewed incident upon the further reflecting surface 10 is parallel to and spaced from that reflected from the reflecting surface 4. The further reflecting 1 0 surface can be either fixed or stabilized as previously described. The casing element 1 b also includes an inlet window 42 to prevent atmospheric contamination of the further reflecting surface 10 and the image-forming lens system 5.

The casing element 1, 1 a and 1 h may be either securely attached to each-other as an integral housing, or they may be removably attached to each-other.

In those cases where a unit, such as the adaptor unit or the mirror unit, may be temporarily removed from its neighbour, a plain window or windows may be included to seal the interior from the effects of atmospheric contamination.

Referring to Figures 5a and 5b, the embodiment of attachment shown is a modification of the embodiment shown in Figures 3a and 3b and like parts are given like reference numerals. This form of attachment includes a coupling for a secondary lens 5'. The attachment has secondary inlet means 2' including a flange 6' adapted to engage the collar of the mount mechanism of lens 5'.In this attachment, there is provided a secondary reflecting surface 50 which is movable to the position shown in Figures 5a and Sb to reflect light entering the attachment through secondary inlet 2' on to reflecting surface 32 whence it is reflected into the camera body by means of reflecting surfaces 33 and 34, so that the camera can be adjusted to view a scene through either of two lenses 5, 5', by appropriate positioning of reflecting surface 50. The mirror may be mounted for sliding or pivotting movement. Means (not shown) are provided to prevent light from the lens not in use from entering the camera body. The secondary lens may conveniently be of shorter focal length. This form of attachment allows a user to select a wider field of view without dismantling the camera.

In all the forms described, the reflecting surfaces may be either mirrors or the surfaces of prisms. One or more of the lens elements may be adjustable axially in order to provide initial focus adjustment to locate the image plane precisely at the camera sensor plane. It is preferable that the surfaces of the optical elements (exept reflecting surfaces) be coated in order to reduce reflectance by known means. If mirrors are used, they should be first - surface mirrors coated with a highly reflecting layer such as aluminium. Where rays may be incident internally upon prism reflecting surfaces at angles less than the "critical angle of reflection", those surfaces should be coated with a highly reflective coating such as silver and protected from tarnishing.

Where the invention is in the form of an adaptor for use with normal camera lenses and cameras, couplings should be provided to allow the adaptor to be rigidly attached to the camera, and to allow the camera lens to be rigidly attached to the adaptor, the optical path and lenses in the adaptor being such that the image produced by the combination of camera lens and adaptor is accurately located both longitudinally and laterally at the camera sensor.

The lenses of the adaptor should be designed to be compatible with the relative apertures of the camera lenses with which it may be used. Where the controls provided on the camera lens and on the stabilizing mirror are removed to an inconvenient position for operation by the use of the invention, these controls may be extended by mechanical or electrical or other means to convenient positions for the camera operator.

Slots or turrets may be provided in the adaptor for the insertion of filters, when required. It should be noted that where the adaptor provides a magnified image, the effective relative aperture of the camera lens is reduced. The effective transmission of the combination will, in all cases, be reduced due to absorption and reflection losses in the adaptor and mirror units. The adaptor coupling to the camera may be arranged so that the camera lens axis may be rotated about the camera axis and preferably provided with an indexing mechanism to allow it to be locked in the four positions-upward, downward, to the right and to the left. Extra supporting means may be provided for the adaptor, camera lens or mirror unit, extending from the camera or in the form of a handle or body brace.

Claims (14)

1. An attachment for connection to a camera body which includes mounting means for receiving an image-forming lens system and image-sensing means, the attachment comprising inlet and outlet means for light, the inlet means including mounting means for enabling a lens system to engage the inlet means in optical communication therewith, the outlet means including connection means for enabling the attachment to engage the mounting means of the camera body with said outlet means optical communication with said image sensing means, and deflecting means adapted to deflect light which passes through said inlet through a substantial angle towards and through said outlet means.

2. An attachment according to Claim 1, wherein said deflecting means deflects light which passes through said inlet through an angle of at least 490

3. An attachment according to Claim 1 or Claim 2, wherein said deflecting means comprises an odd number of reflecting surfaces.

4. An attachment according to Claim 3, wherein said deflecting means comprises a single reflecting surface.

5. An attachment as claimed in any of Claims 1 to 4, wherein said inlet means includes the image forming lens system.

6. An attachment as claimed in Claim 5, wherein a further deflecting element is arranged to deflect light from the scene to be viewed through a substantial angle into the image-forming lens system.

7. An attachment as claimed in Claim 6, wherein the deflecting means and the further deflecting element are arranged so that the optical axis of light falling on the further deflecting means is substantially parallel to, but spaced from, that of the light falling on the image-sensing means of the camera body.

8. An attachment as claimed in Claim 6 or Claim 7, wherein the further deflecting element is controlled by stabilizing means, so that the image sensed by the image-sensing means remains substantially steady.

9. An attachment as claimed in any of the preceding Claims, wherein the primary image formed by the image-forming lens system is transferred by a relay lens system on to the imagesensing means.

10. An attachment as claimed in Claim 9, wherein the relay lens system provides an image in the camera body which is a magnification of the primary image.

1 An attachment as claimed in any of the preceding Claims, wherein the deflecting means include a series of first, second and third reflecting surfaces, in which series two adjacent surfaces are mutually perpendicular.

12. An attachment as claimed in Claim 11, wherein said first, second and third reflecting surfaces constitute walls of a prism.

13. An attachment according to any of the preceding Claims, which further includes a second inlet means including mounting means for enabling a second lens system to engage the second inlet means in optical communication therewith, there being reflecting means movable into the path of the second inlet means both to cause light entering the second inlet to pass to the outlet of said attachment and to prevent light from the first inlet means reaching the outlet.

14. An attachment according to any of the preceding Claims, wherein the attachment includes an extender lens system.

1 5. An attachment substantially as hereinbefore described with reference to, and as illustrated in, any of the accompanying drawings.