WO2007016718A1

WO2007016718A1 - Wide-angle, deep-field, close-focusing optical system

Info

Publication number: WO2007016718A1
Application number: PCT/AU2005/001675
Authority: WO
Inventors: James Albert Frazier
Original assignee: Global Bionic Optics Pty Ltd
Priority date: 2005-08-11
Filing date: 2005-11-03
Publication date: 2007-02-15
Also published as: ZA200802178B; CN101194197B; CN101194197A; CN101208626A

Abstract

Wide-angle, deep-field, close-focusing optical systems (100, 200. 300. 400) are disclosed. According to one aspect, the optical system (100) comprises a negative lens unit (110) and a relay lens (160). The negative lens unit (100) accepts radiation from an object in space. The relay lens (160) is coupled to the negative lens unit (110). The negative lens unit (110) and the relay lens (160) are aligned on an optical axis in that order. The negative lens units (110) forms a first image on the relay lens (160) to form a final image at a final image plane at a distance from the relay lens (160).

Description

WIDE-ANGLE, DEEP-FIELD, CLOSE-FOCUSING OPTICAL SYSTEM

TECHNICAL FIELD The present invention relates generally to an optical system for still or motion picture cameras including digital cameras, video cameras, or the like.

BACKGROUND

U.S. Patent No. 5,727,236 that issued to Frazier on 10 March 1998 describes an optical system that has the features of a wide angle lens, a deep field lens and a close focusing lens. The optical system aims to achieve a deep focus image, i.e. to make it possible to film macro subjects in focus in the foreground, while holding infinity also in focus.

The system of U.S. Patent No. 5, 727,236 comprises an objective lens, a field lens and a relay lens aligned sequentially on an optical axis and arranged in a lens cylinder or barrel. The objective lens forms an intermediate image at or near the field lens, either in front or in back of the field lens. The objective lens may be fixed at infinity focus and have a wide open aperture for forming the intermediate image of a larger size than is otherwise normal for an objective lens of that focal length. The field lens and relay lenses transmit that same image to a smaller final image at a film plane. The relay lens is a macro lens and may have an iris and focusing mechanism, so that the objective and field lenses are not required to be used for aperture control and focusing. A Pechan prism, a roof prism, and a mirror for inverting and reversing (reverting) the intermediate image are provided in the barrel between the field and relay lenses. The Pechan prism, the roof prism, and the mirror ensure that the final image at the film plane has the normal orientation of the final image (instead of being inverted and reversed). Such an optical system requires a substantial amount of light to provide good depth of field. Also, the optical system has a substantial number of optical surfaces (i.e., air to optical media surfaces). Every time a light ray has to travel from air to glass to air again, there is some degradation of the image. There may be as many as 50 air-to-glass surfaces in such an optical system. Further the Pechan prism or its optical equivalent and the roof prism are bulky and heavy making the optical system larger and heavier than otherwise would be the case.

A need therefore exists for an improved wide-angle, deep-field optical system.

SUMMARY

In accordance with an aspect of the invention, there is provided a wide-angle, deep- field, close-focusing optical system, comprising a negative lens unit for accepting radiation from an object in space, and a relay lens coupled to the negative lens unit. The negative lens unit and the relay lens are aligned on an optical axis in that order. The negative lens unit forms a first image on the relay lens to form a final image at a final image plane at a distance from the relay lens.

The final image plane may be a film plane. The film plane may comprise film in a camera or a charge-coupled device ("CCD") of a digital or video camera.

The optical system may further comprise focusing and aperture controls located within the relay lens.

The optical system does not require image orientation correction optics located between the negative lens unit and the relay lens for inverting and reverting the first real image to the final image.

The optical system may further comprise a lens barrel coupled between the negative lens unit and the relay lens.

The optical system may further comprise optical axis deviation optics located between the negative lens unit and the relay lens for causing deviation of the optical axis. The optical axis deviation optics may comprise a dispersion prism or its optical equivalent. The dispersion prism may be a 60-degree dispersion prism. The relay lens may be a macro lens. The macro relay lens may comprise a zoom lens or zoom lens components.

The optical system may further comprise an Aspheron or Aspheron-type lens coupled to the negative lens unit.

The negative lens unit may comprise a negative lens, or a negative lens cluster.

The negative lens unit may comprise a movable zoom lens component.

The negative lens cluster may comprise positive and negative lens elements, but the combination of lens elements remains negative in function. The negative lens cluster may comprise a plano-concave lens, a concave-concave lens, and a doublet lens. The optical system may further comprise a barrel housing in which the plano-concave lens, the concave-concave lens, and the doublet lens are housed.

The optical axis deviation optics may be rotatably provided on the optical axis. The optical system may further comprise a rotatable lens barrel coupled to the optical axis deviation optics and the relay lens.

The optical system may be a probe-type deep focus lens for video and/or cine cameras, the deep focus lens comprising a lens barrel coupled between the negative lens unit and the relay lens.

The optical system may be an attachment-type deep focus lens for digital and/or still cameras.

In accordance with another aspect of the invention, there is provided a camera, comprising a housing, an image capturing mechanism disposed within the housing, and an optical system in accordance with any of the foregoing aspects coupled to the housing.

The optical system may be coupled to the housing so that an optical axis of the optical system is perpendicular to a film plane of the image capturing mechanism.

The camera may be a still camera, a motion picture camera, a video camera, and/or a digital camera.

The image capturing mechanism may comprise analog film or a charge coupled device (CCD).

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention are described hereinafter with reference to the drawings, in which:

Fig. 1 is a side elevation view of a wide-angle, deep-field, close-focusing optical system in accordance with an embodiment of the invention, including a partial cross- sectional view a negative lens unit;

Fig. 2 is a side elevation view of a wide-angle, deep-field, close-focusing optical system in accordance with another embodiment of the invention, including a partial cross-sectional view a negative lens unit;

Fig. 3 is a side elevation view of a wide-angle, deep-field, close-focusing optical system in accordance with a further embodiment of the invention, including a partial cross-sectional view a negative lens unit; and

Fig. 4 is a side elevation view of a wide-angle, deep-field, close-focusing optical system in accordance with still a further embodiment of the invention. DETAILED DESCRIPTION

Wide-angle, deep-field, close-focusing optical systems are disclosed hereinafter. In the following description, numerous specific details, including particular film formats, lens materials, and the like are set forth. However, from this disclosure, it will be apparent to those skilled in the art that modifications and/or substitutions may be made without departing from the scope and spirit of the invention. In other circumstances, specific details may be omitted so as not to obscure the invention.

Where reference is made in any one or more of the accompanying drawings to features, which have similar reference numerals, those features have for the purposes of this description the same function(s) or operation(s), unless the contrary intention appears. Like features are given like reference numerals in the drawings (e.g. negative lens clusters 110 and 210 in Figs. 1 and 2) for the sake of brevity.

In the context of this specification, the word "comprising" has an open-ended, nonexclusive meaning: "including principally, but not necessarily solely", but neither "consisting essentially or" nor "consisting only of. Variations of the word "comprising", such as "comprise" and "comprises", have corresponding meanings.

Fig. 1 illustrates a wide-angle, deep- field, close-focusing optical system 100 in accordance with an embodiment of the invention. The optical system 100 comprises a negative lens unit 110, an optional lens cylinder 150 (which may be of any one of various lengths), and a relay lens 160, which are configured in that sequence. The relay lens 160 may be a macro lens. The optical system 100 may be mounted on the front face of a camera (not shown). The camera may be a still or motion picture camera, a video camera, a digital camera, or the like. Behind the (macro) relay lens 160, a film plane 170 of the camera is positioned at a distance, so that the final image of the optical system is focused on the film plane 170. The film plane 170 symbolically represents the image plane for film in a camera or the charge coupled device ("CCD") of a digital or video camera. The lens barrel 150 and the relay lens 160 are depicted as block elements only, since numerous components of these types may be employed without departing from the scope and spirit of the invention. For example, any of a number of standard macro lenses may be used. Further the components of the system 100 may be tailored to suit the macro lens used. Such components are well known to those skilled in the art. Further, the lens barrel 150 is depicted using a broken line in its central region to indicate that the barrel 150 may have any of a number of different lengths, again, without departing from the scope and spirit of the invention. Longer lenses may be preferred. Standard lengths of the lens barrel may include 1 foot (1'), 18 inches, and 2 feet (2'), for example. The length used is determined by factors including the diameter of the negative lens unit's aperture, the power of the (macro) relay lens, and the film or video format used (e.g., a smaller format leads to a longer lens). In an embodiment of the invention, an extremely long optical system can be built. Such a system may comprise a two-foot (2') long tube between a negative lens cluster or lens (acting as an objective lens) and the macro relay lens.

The negative lens unit 110 functions as an objective lens. Negative lenses 110 of various powers can be used, so there can be a choice of angle of acceptance. The negative lens unit 110 may be implemented in a variety of ways, provided that the unit remains negative in function. Further, the unit 110 may comprise both positive and negative lens elements, provided the combination remains negative in overall function. In the embodiment shown in Fig. 1, the negative lens unit 110 comprises a negative lens cluster. The negative lens cluster may comprise (from left to right in Fig. 1) a plano-concave lens 114, a concave-concave lens 116, and a doublet lens 118. The doublet lens 118 may comprise a concave-concave lens bonded with a plano- convex lens. In this embodiment, the negative lens unit 110 further comprises a barrel housing 112, which the lenses 114, 116, and 118 are housed in. Both lenses 114 and 116 are seated in annular grooves formed in the internal surface of the barrel housing 112 for a complementary fit.

The optical system 100 comprises the negative lens unit 110 as an objective lens and the relay (macro) lens 160 only. The system 100 does not require a field lens. The system 160 also does not require a Pechan prism or its equivalent, a roof prism, or a mirror. The embodiment of the invention utilizes a negative lens cluster or lens, rather than a positive lens. This is contrast to existing systems that use a positive lens, which produces an image that is upside down and requires the use of a mirror and prisms to correct the orientation of the image. Alternatively, this may be done using a series of evenly spaced, positive field or relay lenses. Further, the use of a positive lens in existing systems requires the use of a field lens to magnify the image of the (positive) objective lens.

The use of the negative lens unit 110 as the objective lens simplifies the optical system 100, since the image focused on by the (macro) relay lens 160 is already the correct way up. Because of the size of a negative lens image, a field lens is not required to enlarge the image. The size requirements of the objective negative lens unit 110 are governed more by the power of the macro relay lens 160 and the required working distance, the aperture size of the negative lens unit, the power of the macro relay lens, and the film or video format used. If a one-to-one 100 mm macro relay lens gives a working distance of one foot (1 '), a one-to-one 200 mm macro relay lens gives a working distance of two feet (2'). For example, a 55 or 60 mm macro relay lens can provide good deep focus, hi such an embodiment, the negative lens unit 110 is close to the macro relay lens 160. This can be a distinct advantage in embodiments for still photography application, for example, since the negative lens unit 110 (i.e. acting as an objective lens) can be a simple screw on attachment, hi other embodiments of the invention, the macro relay lens 160 may comprise a zoom lens or zoom lens components.

hi the embodiments of the invention, there are substantially fewer air-to-glass-to-air surfaces and therefore little or virtually nil image degradation. For example, in an embodiment of the invention, there may only be two or three such air-to-glass-to-air surfaces. Negative lenses are less wide angle if a positive element is used in tandem. The negative lens unit 110 may comprise a movable zoom component used in zoom lenses and works very satisfactorily as an objective lens. Negative lens clusters 110 combine positive and negative lens elements, but remain negative in function.

Fig. 2 illustrates a wide-angle, deep-field, close-focusing optical system 200 in accordance with another embodiment of the invention. The optical system 200 comprises a negative lens unit 210, an optional lens cylinder 250, and a macro relay lens 260, again configured in that sequence. The optical system 200 may be mounted on the front face of a camera (not shown), of the types noted hereinbefore. The negative lens unit 210 may be implemented in a variety of ways, provided that the unit remains negative in function. The unit 210 may comprise both positive and negative lens elements, provided the combination remains negative in overall function, hi the embodiment shown in Fig. 2, the negative lens unit 210 comprises a negative lens cluster. The negative lens cluster may again comprise a plano-concave lens 214, a concave-concave lens 216, and a doublet lens 218. The doublet lens 218 may comprise a concave-concave lens bonded with a plano-convex lens. These components are housed in a barrel housing 212. Behind the macro relay lens 260, a film plane 270 of the camera is positioned at a distance, so that the final image of the optical system is focused on the film plane 270. The system 200 shown in Fig. 2 is a simple "probe" type deep focus lens that may be used for video and cine cameras, including 35 mm, 16 mm, and various video formats.

The negative lens cluster 210 may be configured the same as that shown in Fig. 1 and may be of the type used in a zoom lens to zoom an image. An optional Aspheron or Aspheron-type attachment 280 may be used as well. The optional Aspheron or Aspheron-type attachment 280 can correct linear distortion and can increase the wide angle. The Aspheron-type negative lenses 280 keep the image linear without gross distortion, as well as increasing the angle of acceptance. Again, the long lens barrel 250 and the macro relay lens 260 are depicted as block elements only, hi this embodiment of the invention, a long optical system is provided. The macro relay lens 260 may be a 55, 60, 105 or 200 mm lens. The macro relay lens module may comprise a focus control mechanism 262 and an aperture control mechanism 264. In other embodiments of the invention, the macro relay lens 260 may comprise a zoom lens or zoom lens components. Optionally, the system 200 may have a supplementary lens 266 coupled between the barrel 250 and the macro relay lens 260. The supplementary lens 266 permits a shorter lens barrel to be used. The supplementary lens 266 can be useful because it cause the macro lens to lose less light than might otherwise be the case.

Fig. 3 illustrates a wide-angle, deep-field, close- focusing optical system 300 in accordance with still another embodiment of the invention. The optical system 300 comprises a negative lens unit 310 and a macro relay lens 360 configured in that sequence. The negative lens unit 310 may be implemented in a variety of ways, provided that the unit remains negative in function. The unit 310 may comprise both positive and negative lens elements, provided the combination remains negative in overall function, hi the embodiment shown in Fig. 3, the negative lens unit 310 comprises a negative lens cluster. The negative lens cluster may comprise a planoconcave lens 314, a concave-concave lens 316, and a doublet lens 318. The doublet lens 318 may comprise a concave-concave lens bonded with a plano-convex lens. These components are housed in a barrel housing 312. The optical system 300 may be mounted on the front face of a camera (not shown), of the types noted hereinbefore, e.g. a still camera. Behind the macro relay lens 360, a film plane 370 of the camera is positioned at a distance, so that the final image of the optical system is focused on the film plane 370. The system 300 shown in Fig. 3 may be implemented as an attachment-type deep focus lens for digital and still cameras (e.g. 35 mm).

The negative lens cluster 310 may be configured the same as that shown in Fig. 1 and may be of the type used in a zoom lens to zoom an image. The negative lens unit 310 is directly coupled to the macro relay lens (e.g. 55 mm or 60 mm) using a mated, screw-in assembly. In this embodiment, the negative lens unit 310 has a male screw- in member and the macro relay lens 360 has a corresponding female screw-in receptacle connected to the focus control 362. The focus control 362 and aperture control 364 are as provided in the macro relay lens. In other embodiments of the invention, the macro relay lens 360 may comprise a zoom lens or zoom lens components.

Fig. 4 illustrates a wide-angle, deep-field, close-focusing optical system 400 in accordance with a further embodiment of the invention. The optical system 400 comprises a negative lens unit 410, a dispersion prism 480, a lens barrel 450, and a macro relay lens 460 configured in that sequence. The negative lens unit 410 may be implemented in a variety of ways, provided that the unit remains negative in function. The unit 410 may comprise both positive and negative lens elements, provided the combination remains negative in overall function. In this embodiment, as shown in Fig. 4, the negative lens unit 410 comprises a single negative lens. Alternatively, the negative lens unit may comprise a negative lens cluster as shown in any of Figs. 1 to 3. In this embodiment, a 60-degree dispersion prism may be practiced. Further, the lens barrel 450 is rotatably coupled to the macro relay lens 460, behind which is disposed the film plane 470. The macro relay lens 460 comprises aperture and focus control mechanisms (not depicted separately as in Figs. 2 and 3). In other embodiments of the invention, the macro relay lens 460 may comprise a zoom lens or zoom lens components. As shown in Fig. 4, the negative lens unit 410 is connected to an inclined surface of the prism 480, so that the unit 410 is aligned off-axis relative to the central longitudinal axis of the lens barrel 450. This deviation aspect allows the lens barrel 450 to be rotated to give the correct camera geometry in certain difficult positions, e.g. from a floor position. Thus, for example, the camera can be sat on the ground to capture images at difficult angles. This allows easy access to difficult perspectives. Rotation of the lens barrel enhances this aspect, permitting easy overhead and underslung shots, for example.

The embodiments of the invention involved less degradation of an image due to fewer components and hence less air-to-glass-to-air degradation. Also the negative lens cluster as objective lens inverts the resulting image to the correct orientation, which permits the embodiments of the invention to do away with mirrors and prisms required by existing systems. In the embodiments of the inventions, different lens lengths can be used, making the lens suitable for different cameras and film formats.

Only a small number of embodiments of the invention have been described.

However, in view of this disclosure, it will be apparent to one skilled in the art that modifications and/or substitutions can be made without departing from the scope and spirit of the invention.

Claims

CLAUvIS I claim:

1. A wide-angle, deep-field, close-focusing optical system, comprising: a negative lens unit for accepting radiation from an object in space; and a relay lens coupled to said negative lens unit, said negative lens unit and said relay lens being aligned on an optical axis in that order, said negative lens unit forming a first image on said relay lens to form a final image at a final image plane at a distance from said relay lens.

2. The optical system according to claim 1, wherein said final image plane is a film plane.

3. The optical system according to claim 2, wherein said film plane comprises film in a camera or a charge-coupled device ("CCD") of a digital or video camera.

4. The optical system according to claim 1, further comprising focusing and aperture controls located within said relay lens.

5. The optical system according to claim 1, wherein said optical system does not require image orientation correction optics located between said negative lens unit and said relay lens for inverting and reverting the first real image to the final image.

6. The optical system according to claim 1, further comprising a lens barrel coupled between said negative lens unit and said relay lens.

7. The optical system according to claim I₅ further comprising optical axis deviation optics located between said negative lens unit and said relay lens for causing deviation of the optical axis.

8. The optical system according to claim 7, wherein said optical axis deviation optics comprises a dispersion prism or its optical equivalent.

9. The optical system according to claim 8, wherein said dispersion prism is a 60-degree dispersion prism.

10. The optical system according to claim 1, wherein said relay lens is a macro lens.

11. The optical system according to claim 10, wherein said macro relay lens comprises a zoom lens or zoom lens components.

12. The optical system according to claim 1, further comprising an Aspheron or Aspheron-type lens coupled to said negative lens unit.

13. The optical system according to claim 1, wherein said negative lens unit comprises a negative lens.

14. The optical system according to claim 1, wherein said negative lens unit comprises a negative lens cluster.

15. The optical system according to claim 14, wherein said negative lens cluster comprises a movable zoom lens component.

16. The optical system according to claim 14, wherein said negative lens cluster comprises positive and negative lens elements, but the combination of lens elements remains negative in function.

17. The optical system according to claim 14, wherein said negative lens cluster comprises a plano-concave lens, a concave-concave lens, and a doublet lens.

18. The optical system according to claim 17, further comprising a barrel housing in which said plano-concave lens, said concave-concave lens, and said doublet lens are housed.

19. The optical system according to claim 7, wherein said optical axis deviation optics are rotatably provided on the optical axis.

20. The optical system according to claim 19, further comprising a rotatable lens barrel coupled to said optical axis deviation optics and said relay lens.

21. The optical system according to claim 1, wherein said optical system is a probe-type deep focus lens for video and/or cine cameras comprising a lens barrel coupled between said negative lens unit and said relay lens.

22. The optical system according to claim 1, wherein said optical system is an attachment- type deep focus lens for digital and/or still cameras.

23. A camera, comprising: a housing; an image capturing mechanism disposed within said housing; and a wide-angle, deep field optical system in accordance with any one of claims 1 to 22 coupled to said housing.

24. The camera according to claim 23, wherein said optical system is coupled to said housing so that an optical axis of said optical system is perpendicular to a film plane of said image capturing mechanism.

25. The camera according to claim 23, wherein said camera is selected from the group consisting of a still camera, a motion picture camera, a video camera and a digital camera.

26. The camera according to claim 23, wherein said image capturing mechanism comprises analog film.

27. The camera according to claim 23, wherein said image capturing mechanism comprises a charge coupled device (CCD).

28. A wide-angle, deep-field, close-focusing optical system substantially as hereinbefore disclosed with reference to any one or more of Figs. 1 to 4 of the accompanying drawings.

29. A camera, comprising a housing, an image capturing mechanism disposed within said housing, and a wide-angle, deep-field, close-focusing optical system substantially as hereinbefore disclosed with reference to any one or more of Figs. 1 to 4 of the accompanying drawings.