GB2404993A

GB2404993A - Magnifying adapter for camera lenses

Info

Publication number: GB2404993A
Application number: GB0318885A
Authority: GB
Inventors: Kenneth Neil Midwinter
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-08-12
Filing date: 2003-08-12
Publication date: 2005-02-16
Also published as: GB0318885D0

Abstract

An adapter (101) is described for coupling to a camera lens (1) and an eyepiece lens (18) to produce a viewing device that enables a user to view a magnified distant image. The adapter (101) is arranged to produce an image at the eyepiece lens (18) suitable for viewing with the human eye and therefore enables a user to employ the camera lens (1) to which the adapter (101) is coupled as a telescope.

Description

Improvements in and Relating to Adapters for Camera Lenses

Field of the Invention

The present invention relates to adapters for camera lenses, to kits comprising camera lenses and adapters for camera lenses, to kits comprising cameras and adapters for camera lenses, to methods for manufacturing adapters for camera lenses, and to methods for assembling viewing devices including adapters for camera lenses.

Background to the Invention

High quality optical imaging systems are widely available in the form of camera lenses. Camera lenses are designed to provide high quality, well resolved images.

Furthermore, camera lenses are designed to produce a uniformly focused image across a field of view, and can have additional functionality such as zoom. However, the use of camera lenses is restricted to providing an image within a camera at a light sensitive element such as film or a CCD. Adding further lens elements directly to a camera lens is ineffective in producing a readily observable telescopic image for viewing by the human eye, and does not allow a user to conveniently adapt various camera lenses to produce telescopic images.

It is an aim of preferred embodiments of the present invention to enable a camera lens to be easily converted to telescope use. Further aims and advantages of the present invention will become apparent from the

description below.

Summary of the Invention

In a first aspect, the present invention provides an adapter for a camera lens, the adapter comprising first engagement means and second engagement means, wherein the first engagement means is arranged to couple the adapter to a camera lens, the second engagement means is arranged to couple the adapter to an eyepiece lens, and wherein when coupled to a camera lens and an eyepiece lens the lo adapter is arranged to produce an image at the eyepiece lens suitable for viewing by the human eye.

Suitably, the adapter is arranged to in use couple to a camera lens and an eyepiece lens and thereby provide a telescope.

Suitably, the adapter further comprises an eyepiece lens.

Suitably, the eyepiece lens comprises any one of a Huygens eyepiece lens, a Kellner eyepiece lens, and a Plossl eyepiece lens, an Erfle eyepiece lens, a Rameden eyepiece lens, an achromatic Ramsden eyepiece lens, a Tolles eyepiece lens, a monocentric eyepiece lens, a Nagler eyepiece lens and an orthoscopic eyepiece lens.

Suitably, the adapter may further comprise an input enhancer. Suitably, the input enhancer comprises the first optical element in the adapter. Suitably, the input enhancer comprises a lens. Suitably, the input enhancer comprises a Barlow lens.

Suitably, the adapter further comprises an image inverter.

Suitably, the image inverter comprises at least one prism.

Suitably, the image inverter comprises a 45-degree prism.

Suitably, the image inverter may comprise at least one mirror. Suitably, the image inverter may comprise at least one lens.

Suitably, the adapter defines an input optical axis at the first engagement means and an output optical axis at the eyepiece. Suitably, the output optical axis is arranged at an angle to the input optical axis. Suitably the output optical axis is arranged at an angle of 45 to 90 degrees to the input optical axis.

In a second aspect, the present invention provides a kit comprising a camera lens and an adapter for a camera lens, wherein the adapter is in accordance with the first aspect of the invention.

In the third aspect the present invention provides a kit comprising a camera and an adapter for a camera lens, wherein the adapter is in accordance with the first aspect of the invention.

In a fourth aspect, the present invention provides a method of manufacturing an adapter for a camera lens comprising steps of: (a) providing first engagement means arranged to couple the adapter to a camera lens; and (b) providing a second engagement means arranged to couple the adapter to an eyepiece lens, wherein when coupled to a camera lens and an eyepiece lens the adapter is arranged to produce an image at the eyepiece lens suitable for viewing by the human eye.

In the fifth aspect, the present invention provides a method of assembling a viewing device, the method comprising the steps of: (a) providing an adapter for a camera lens, the adapter comprising first engagement means and second engagement means; (b) providing a camera lens; (c) providing an eyepiece lens; and (d) coupling the adapter to the camera lens by the first engagement means and coupling the adapter to the eyepiece lens by the second engagement means, wherein following step (d) the lo viewing device produces an image at the eyepiece suitable for viewing by the human eye.

Brief introduction to the Drawings

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figure 1 shows a side sectional view of a first embodiment of the present invention arranged in use with a camera lens and an eyepiece lens to produce a viewing device; Figure 2 shows a side sectional view of a second embodiment of the present invention; Figure 3 shows a side sectional view of a third embodiment of the present invention; Figure 4 shows a side sectional view of the adapter of Figure 3 coupled to a Plossl eyepiece lens; Figure 5 shows a side sectional view of the adapter of Figure 3 coupled to a Huygens eyepiece lens; Figure 6 shows a side sectional view of the adapter of Figure 3 coupled to a Kellner eyepiece lens; Figure 7 shows a side sectional view of the adapter of Figure 1, with Barlow lens, but excluding eyepiece; and lo Figure 8 shows a side sectional view of a fourth embodiment of the present invention.

Detailed Description of Preferred Embodiments

Figure 1 shows a side sectional view of an adapter 101 according to a first embodiment of the invention. The adapter 101 is arranged in use with a camera lens 1.

In use, the adapter 101 is coupled to the camera lens 1 and an eyepiece lens 18 to produce a viewing device that enables a user to view a magnified distant image with the camera lens 1. By enabling the user to employ the camera lens 1 as a telescope, the user does not need to have separate camera lenses and telescopes to suit particular needs. For example, a user who wishes to observe and/or photograph wildlife, sporting events or other potentially distant scenes can carry the relevant camera lens equipment, and the adapter 101, allowing a user- friendly and optically accurate telescope to be produced.

As has been previously mentioned, camera lenses are designed to provide high quality, well-resolved images

that are uniformly focused across a field of view.

Therefore, their optical systems are well suited to telescope use. However, the output of a camera lens is intended to be received on film, a CCD or another man-made optical receiver, and is therefore not suited to telescope use in itself. In use, light incident on the camera lens 1 is operated on by the camera lens 1, and passes to the adapter 101 and the eyepiece lens 18, which presents a suitable image for convenient viewing by a user. The focusing, zoom or other variable characteristics of the camera lens 1 can be used to alter the image observable at the output of the adapter 101. The adapter 101 can be used in combination with photographic camera lenses, e.g. detachable lenses used with single lens reflex (SLR) cameras, or with video or digital camera lenses.

Referring again to Figure 1, the adapter 101 comprises a first engagement means 12, a second engagement means 16, an input enhancer 20, and an image inverter 22. The adapter 101 defines an input optical axis at the first engagement means 12 and an output optical axis at the eyepiece lens 18.

The input optical axis is collinear with the optical axis of the camera lens 1. The output optical axis is arranged at 45 degrees to the input optical axis.

The camera lens 1 comprises a standard arrangement of optical elements, including a skylight filter 2, lenses 3, a focus ring 4, a tripod mount 5, and a diaphragm 6.

The first engagement means 12 comprises a camera lens fitting, and is arranged to be coupleable to the camera lens 1.

Camera lens fittings are normally used to couple camera lenses to camera bodies, and allow lenses of different manufacturers to be coupled to a range of cameras.

The input enhancer 20 comprises the first optical element in the adapter, that is, the input enhancer 20 is the first element that light entering the adapter 101 is incident upon. In the embodiment of Figure 1 the input enhancer 20 is a diverging lens in the form of a Barlow lens. A Barlow lens is a doublet diverging lens, which lo can be used in the adapter 101 to provide an increase in magnification, enhance eye relief of the image presented at the output of the adapter 101, and also provide an improvement in close focus performance. The Barlow lens is arranged inside the focal plane of the camera lens 1, and acts as a focal length multiplier or tale-extender, with typical multiplication ratios of around 1.75 to 5, with a ratio of 2 a common example. Furthermore, the Barlow lens reduces any inward curvature of the focal surface produced by the camera lens 1, and this reduces the effect of any astigmatism or off-axis alignment at the eyepiece lens 18. The Barlow lens offers an improvement in sharpness across the output field of view, as the lens ensures more light from the central region of the light path is coupled into the output image. Light from the central region is typically subject to less spherical and chromatic aberration, meaning the output image is less affected by these effects.

Furthermore, by using an input enhancer 20 to improve the quality of the image produced at the eyepiece lens 18, a lower quality eyepiece lens 18 can be used to produce a desired image quality.

The camera lens 1 produces an inverted image at its output. It is not desirable for an inverted image to be presented at the output of the adapter 101, as this would reduce the usability of the adapter 101 in combination with the camera lens 1. To correct the inversion produced by the camera lens 1, the adapter 101 comprises an erector in the form of an image inverter 22.

In the embodiment of Figure 1 the image inverter 22 lo comprises a 45degree prism. The prism provides a cost effective way to produce an erect image, however, the image inverter may comprise one or more mirror, or other prisms. As well as providing an erect image, the image inverter 22 provides the change in angle between the input optical axis and the output optical axis. By providing this change in angle, the adapter 101 allows the user to observe telescopic images in a convenient and comfortable position without having to hold or raise the arrangement of camera lens 1 and adapter 101 to eye level. The desired range of angles is between 45 and 90 degrees.

The eyepiece lens 18 comprises an optical output at which a user can conveniently view a telescopic image. In the embodiment of Figure 1, the second engagement means 16 is adapted to receive an output enhancer in the form of the eyepiece lens 18. The eyepiece lens 18 comprises a Plossl eyepiece lens, however other eyepiece lens 18 can be used as will be discussed below in relation to other embodiments of the invention. The eyepiece lens 18 is coupled to the adapter 101 by the second engagement means 16.

The second engagement means 16 comprises a tube in which the eyepiece lens 18 locates, and further comprises a retaining screw which passes through the wall of the tube to hold the eyepiece lens 18 in place by friction against the tube and the retaining screw.

In alternative embodiments, the second engagement means 16 may comprise a threaded end of a tube or a thread machined directly into the body of the adapter 101. The thread of lo the adapter 101 is adapted to co-operate with a corresponding thread portion of the eyepiece lens 18.

This configuration allows the easy attachment/removal of different eyepiece lenses 18 to/from the adapter 101 without the need for additional tools. By reducing the length of the tube, a compact and ergonomic design can also be produced.

It is important that the eyepiece lens 18 is positioned correctly to ensure that the adapter can produce a suitable output image across the full focal range of a camera lens to which the adapter may be attached.

The Plossl eyepiece lens consists of two closely spaced achromatic doublets. It is relatively easy to manufacture and offers good optical performance when used with camera lenses over a range of optical powers. It also offers good performance for relatively faster camera lenses, such as faster than f/5.

Figure 2 shows a second embodiment of the invention. The adapter 102 of Figure 2 is similar to that of Figure 1, however it does not comprise the input enhancer 20.

In this embodiment the second engagement means 16 comprises only a tube, in which an eyepiece lens can be coupled by way of a push fit.

The image inverter 22 comprises a 45-degree prism which is covered by a plastic casing 23. The plastic casing 23 protects the image inverter 22 from damage and from contamination by dust or other dirt. The plastic casing 23 comprises a first screw thread 13 which can comprise lo the first engagement means 12.

The first screw thread 13 may alternatively receive a camera lens ring adapter to form the first engagement means 12. The plastic casing 23 comprises a second screw thread 15 to receive the second engagement means 16.

Figure 3 shows a third embodiment of the invention. The adapter 103 of Figure 3 is similar to that of Figure 2, however the first engagement means 12 comprises a plastic adapting ring 19 to attach to a camera lens, held in place on the adapter 103 by engagement with a metal screw threaded retaining ring 21. The metal screw threaded retaining ring 21 engages with the first screw thread 13 and comprises a flange to clamp the plastic adapting ring 19 to the plastic casing 23 of the adapter 103. The adapter 103 further comprises second engagement means 16, as discussed above in relation to the first embodiment of the invention 101.

The eyepiece lens 18 may comprise any one of a Huygens eyepiece lens, a Kellner eyepiece lens, and a Plossl eyepiece lens, however other suitable optical eyepieces may be used.

Figure 4 shows the adapter of Figure 3 with Plossl eyepiece lens 18 coupled thereto by the second engagement means 16.

Figure 5 shows the adapter of Figure 3 with a Huygens eyepiece lens 18 coupled thereto by the second engagement means 16. A Huygens eyepiece is relatively inexpensive, but does not offer high quality optical performance.

lo Figure 6 shows the adapter of Figure 3 with a Kellner eyepiece lens 18 coupled thereto by the second engagement means 16. A Kellner eyepiece offers good eye relief, and works effectively with longer focal length camera lenses.

However, some chromatic aberration will occur. The Kellner eyepiece offers a good balance between performance and cost.

Figure 7 shows the adapter 101 of Figure 1, however no eyepiece lens is coupled thereto. The adapter can be used with any desired eyepiece lens 18 to allow a choice of both overall optical performance and telescopic magnification.

Figure 8 shows a fourth embodiment of the invention. The adapter 104 of Figure 8 is an eyepiece lens 18. The adapter 104 comprises a first engagement means 12, a second engagement means 16, an input enhancer 20, a first screw thread 13, a second screw thread 15 and a plastic adapting ring 19. In the adapter 104 the input optical axis is collinear with the output optical axis. In this arrangement the eyepiece lens 18 may include an image inverter 180 such that when the adapter 104 is coupled to a camera lens and the eyepiece lens 18 an erect image is produced at the output of the eyepiece lens 18. The image inverter 180 may comprise a lens or series of lenses.

As well as the eyepiece lenses described herein, other known lenses or other optical elements such as filters may be used as output enhancers, depending on the optical quality required. For example, any one of an Erfle eyepiece lens, a Ramsden eyepiece lens, an achromatic Ramsden eyepiece lens, a Tolles eyepiece lens, a lo monocentric eyepiece lens, a Nagler eyepiece lens, an orthoscopic eyepiece lens or other designs may be used.

Furthermore, by varying the lenses used as input enhancer and eyepiece, a range of magnifications can be achieved with the adapter. Alternatively, the adapter can be supplied with a predetermined eyepiece lens coupled thereto. The eyepiece lens 18 can be formed integrally with a part of the adapter comprising the second engagement means.

The adapter described enables a user to make use of a camera lens or range of camera lenses to produce a telescopic image. A user avoids having to possess both camera and telescope lenses if they wish to photograph and conveniently view distant scenes.

Attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be lo replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features

disclosed in this specification (including any

accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

Claims: 1. An adapter for a camera lens, the adapter comprising first

engagement means and second engagement means, wherein the first engagement means is arranged to couple the adapter to a camera lens, the second engagement means is arranged to couple the adapter to an eyepiece lens, and wherein when coupled to a camera lens and an eyepiece lens the adapter is arranged to produce an image at the lo eyepiece lens suitable for viewing by the human eye.
2. The adapter of claim 1, arranged to in use couple to a camera lens and an eyepiece lens and thereby provide a telescope.
3. The adapter of claim 1 or 2, further comprising an eyepiece lens.
4. The adapter of claim 3, wherein the eyepiece lens comprises any one of a Huygens eyepiece lens, a Kellner eyepiece lens, and a Plossl eyepiece lens, an Erfle eyepiece lens, a Rameden eyepiece lens, an achromatic Ramsden eyepiece lens, a Tolles eyepiece lens, a monocentric eyepiece lens, a Nagler eyepiece lens and an orthoscopic eyepiece lens.
5. The adapter of any preceding claim further comprising an input enhancer.
6. The adapter of claim 5, wherein the input enhancer comprises the first optical element in the adapter.
7. The adapter of claim 5 or 6, wherein the input enhancer comprises a lens.
8. The adapter of any one of claims 5 to7, wherein the input enhancer comprises a Barlow lens.
9. The adapter of any preceding claim further comprising an image inverter.

lo
10. The adapter of claim 9, wherein the image inverter comprises at least one prism.
11. The adapter of claim 10, wherein the image inverter comprises a 45degree prism.
12. The adapter of claim 9, wherein the image inverter may comprise at least one mirror.
13. The adapter of claim 9, wherein the image inverter comprises at least one lens.
14. The adapter of any preceding claim, where the adapter defines an input optical axis at the first engagement means and an output optical axis at the eyepiece.
15. The adapter of claim 14, wherein the output optical axis is arranged at an angle to the input optical axis.
16. The adapter of claim 15, wherein the output optical axis is arranged at an angle of 45 to 90 degrees to the input optical axis.
17. A kit comprising a camera lens and an adapter for a camera lens, wherein the adapter is in accordance with any one of claims 1 to 16.
18. A kit comprising a camera and an adapter for a camera lens, wherein the adapter is in accordance with any one of claims 1 to 16.
19. A method of manufacturing an adapter for a camera lens lo comprising steps of: (a) providing first engagement means arranged to couple the adapter to a camera lens; and (b) providing a second engagement means arranged to couple the adapter to an eyepiece lens, wherein when coupled to a camera lens and an eyepiece lens the adapter is arranged to produce an image at the eyepiece lens suitable for viewing by the human eye.
20. The method of claim 19, wherein the adapter is in accordance with any one of claims 1 to 16.
21. A method of assembling a viewing device, the method comprising the steps of: (a) providing an adapter for a camera lens, the adapter comprising first engagement means and second engagement means; (b) providing a camera lens; (c) providing an eyepiece lens; and (d) coupling the adapter to the camera lens by the first engagement means and coupling the adapter to the eyepiece lens by the second engagement means, wherein following step (d) the viewing device produces an image at the eyepiece suitable for viewing by the human eye.
22. The method of claim 21, wherein the adapter is in accordance with any one of claims 1 to 16.
23. An adapter substantially as herein described, with particular reference to Figures 1 to 8.
24. A viewing device substantially as herein described, with particular reference to Figure 1.