The present invention relates to a new and novel optical system providing optical magnification.
From a historical perspective, conventional telescopes and binoculars are some of the earliest demonstrated forms of optical magnifiers. In general, these tend to be afocal magnifiers as they are viewed directly from the human eye. Binoculars include two telescope systems, one for each eye. In order to present an erect magnified image, binoculars employ telescope design forms such as the prior art Galilean telescope depicted in
The earliest telescopes and binoculars from the 17th century employ the Galilean form as shown in
The vast majority of binoculars manufactured and sold today employ an erecting telescope as depicted in
Observers of an event, in particular sports fans, concert-goers and opera-goers, often use binoculars to observe the event from a distance. Binoculars are typically operated with one or both hands. This is sometimes problematic, for example, during a sporting event, since a sports fan cannot simultaneously watch the game through binoculars and perform other activities that require the use of hands.
While various hands-free binoculars have been proposed, they are often expensive and not optimally designed in form and function for the requirements of the sports fan, concert-goer or opera-goer in mind. For example, U.S. Pat. No. 2,422,661 issued Jun. 24, 1947 to C. A. Ellis, describes a binocular magnifying lens holder. U.S. Pat. No. 2,437,642 issued Mar. 9, 1948 to F. C. P. Henroteau, describes spectacles for vision correction. U.S. Pat. No. 3,741,634 issued Jun. 26, 1973 to Stoltze, describes binocular spectacles.
Further, U.S. Pat. No. 4,429,959 issued Feb. 7, 1094 to Walters, describes a spectacle mounted hinged monocular or binocular vision aid. U.S. Pat. No. 5,485,305 issued Jan. 16, 1996 to Johnson, describes a lightweight binocular telescope. U.S. Pat. No. 6,002,517 issued Dec. 14, 1999 to Elkind, describes flat, hands-free, convertible Keplerian binoculars.
Some of the most sophisticated head-worn binoculars available today are the head-worn binocular vision aids for people with eye problems such as macular degeneration. They are still relatively bulky (which affects their wider acceptance for broader applications), and their weight is significant as well. The Eschenbach Model 1634 is an example of this type of binocular magnifier, with a magnification of 3×, a field of view of 9.5 degrees, and a weight of 70 grams. These binoculars are typically mounted in a pair of custom spectacle frames. Generally, the nearest optical surface to the eye for a pair of spectacles or head-mounted optics is approximately 15 mm in front of the eye. The telescopes then extend a further 20-25 mm from the eye in the case of the Eschenbach 1634 model as an example. This significant weight at a distance from the eye tends to exert a torque on the head and leads to neck strain when used for extended viewing periods.
In order to reduce the weight of the head-worn binoculars, one of the approaches employed has been to use all plastic optics (rather than glass lenses as normal), and some models have used a Fresnel lens for the objective. This does serve to reduce the overall weight, but still has the same basic form as in
Another challenge for headworn magnifiers or binoculars is that the size of the human head varies from one person to the next. The distance between the left eye and the right eye, or interpupillary distance (IPD), varies from individual to individual as well. In order to accommodate this variation in IPD, binoculars generally incorporate an adjustment mechanism allowing the spacing between the left eye telescope and the right eye telescope to vary. The binocular user can then adjust the binocular IPD spacing for maximum comfort. As an example, the IPD of the Eschenbach Model 1634 can be adjusted between a minimum of 54 mm and a maximum of 74 mm. These adjustments are well understood and accommodated, but it does require additional mechanical complexity and cost.
The limitations of the prior art are that the constraints of a standard Galilean telescope mean that the system is by nature heavy and bulky as discussed. If one prioritizes size, weight and field of view as the primary design goals, it is possible to conceive of a very lightweight and compact optical system that employs multiple apertures to create a composite overlayed image of a scene over a wide field of view. An example is to use multiple miniature Gililean telescopes in specific orientation to each other to create a composite image that is indistinguishable to the viewer or detector from an image created by a regular single aperture telescope system.
The applications for such a system are many, including, but not limited to, a wide angle attachment for camera systems, afocal magnifier for rifle scopes and night vision systems, telescope and binocular systems, and others as will be obvious to those skilled in the art.
There is very little prior art to be found in this area of multiple aperture magnifiers, telescopes or binoculars of this nature. Wirth, et al., U.S. Pat. No. 5,270,859, discusses configurations of micro-optic multiplets (MOM) which include a limited 2-dimensional array of Galilean telescopes, the disclosure of which is incorporated by reference.
It is therefore an object of the present invention to provide an improved optical system for providing optical magnification—in particular utilizing a multi-aperture approach. Further and more specifically it is an object of the present invention to provide a head-worn binocular that is extremely lightweight and has a center of mass close to the face (reducing torque on the head and resulting neck fatigue), has a wide field of view, and provides a large eyebox (zone within which eye pupil can move without significant vignetting) eliminating the need for any IPD adjustment mechanism.
An optical system for the magnification of an object presented to an image receiver, said optical system comprises a frame configured to position at least one optical element between said object and said image receiver said optical element comprising a plurality of Galilean telescopes supported on a substrate, each Galilean telescope comprising a positive lens and negative lens, said positive lens being further distanced from said image receiver than said negative lens when said optical element is positioned between said object and image receiver, each of said Galilean telescopes having an axis substantially parallel to the axes of other Galilean telescopes in said optical system such that light passing through each of said plurality of Galilean telescopes is substantially collimated. The plurality of Galilean telescopes can be positioned anywhere in 3-dimensional space as long as placement does not occlude adjacent elements. Ideally, each negative lens is positioned on said substrate to be on a spherical radius whose center of curvature is substantially at the image receiver.
The basic building block of this invention is a miniaturized Galilean telescope. One of the most important properties of a Galilean telescope is that the emerging light which travels to the eye (or is focused onto a detector or imaging system) is collimated or very nearly collimated. This property allows one to construct a composite imaging system that employs a plurality of these miniaturized Galilean telescopes, with the telescopes arranged arbitrarily in 3-dimensional space. The critical thing required in order to ensure that the composite image (made up of the superposition of the images emerging from each of the miniaturized Galilean telescopes) appears to be a single seamless image, and the image quality is not significantly affected, is that the axes of each of the miniaturized Galilean telescopes must be substantially parallel. This design approach allows a much more general and versatile system than disclosed by the prior art. The plurality of miniaturized Galilean telescopes can be positioned anywhere in 3-dimensional space, with the practical constraint that the placement should not occlude adjacent elements.
An example of the utility and versatility of this approach is demonstrated in
The lenses can be made from normal optically transparent materials such as glass and plastic. For headworn applications, molding the array out of plastic will have advantages over glass with regard to weight minimization. On the other hand, for applications requiring a more durable system capable of withstanding harsh environments (e.g. military applications), glass will have advantages. Furthermore, glass has many more available types with different properties compared with the limited set of plastic materials available. Use of higher index glasses and better color matching will allow better correction of aberrations and better viewing performance. Applications involving wavelength ranges other than the visible can be accommodated by judiciously selecting materials that are optically transparent in the appropriate wavelength range.
One of the practical tradeoffs of the present invention is that while it has advantages in weight, head torque, field of view, and eyebox when compared with a standard Galilean telescope, it suffers from reduced brightness. This is due to the fact that the present invention does not have the same pupil magnification in object space as a standard Galilean telescope. The system shown in
The focus of the system can be adjusted by changing the spacing between the array of front positive lenses and the array of rear negative lenses. A mechanical adjustment mechanism can be introduced in order to change this spacing and adjust focus for each eye. In order to minimize cost, one implementation of the present invention will involve setting the spacing to a fixed distance and having no adjustment mechanism. With a fixed distance between the arrays, in order to maximize the depth of field, it is best to set the focus of the system not at infinity (in object space) but rather at a closer distance such as 50 to 75 feet. By doing this, the system maintains good focus between infinity and approximately 10-15 feet. The fact that the apertures of the lenslets are small also tends to give excellent depth of field.
Turning now to the miniaturized Galilean telescopes that are replicated to make the present composite optical system. Perhaps the simplest and lowest cost approach is to utilize all spherical surfaces. The Galilean telescope 60 shown in
The above example represents a substantially afocal system with the following properties:
The on-axis performance is limited by spherical aberration and off-axis performance is limited by lateral color. In order to more easily analyze this afocal system, the scale of these diagrams (and all subsequent spot diagrams and ray fans) has been chosen to correspond to micro-radians. For example, the on-axis spot radius is 1113 micro-radians, which corresponds to approximately 4 minutes of arc.
In order to improve the performance of the system, aspherical surfaces can be employed. Examples of aspherical elements that can be introduced include conic surfaces, or perhaps polynomial aspheric surfaces (odd or even). In particular, the limiting on-axis spherical aberration apparent in the all-spherical design, is significantly reduced by the introduction of simple conic surfaces to the design.
It was observed that the on-axis performance has improved significantly over the telescope of
Further performance improvement can be achieved by the use of binary or diffractive surfaces. As the residual aberration limiting overall system performance is lateral color, diffractive surfaces can prove helpful in reducing this and thus improving system performance.
The positive and negative lenses are ideally arranged on a curved surface as disclosed and illustrated in
Another configuration that may be useful is shown in
Another configuration is shown in
In general, the number of miniaturized Galilean telescopes (or lenslet facets) should be sufficient to provide the desired field of view.
The present invention when configured into headworn binoculars may find application at sporting events, concerts, plays and with opera-goers as an example. The frames can be molded or painted in team colors and adorned with team logos or identification at prominent locations such as the temples or bridge. Also, team colors or national colors or other insignia or colors or trademarks could be painted or otherwise applied to the lens blank in the section surrounding the magnifier in order to make that section opaque, as described in the configuration above. This has the benefit of providing additional promotional real estate as well as shielding the eye or detector from unwanted stray light and allowing the pupil to open to its maximum extent in low light conditions.
A further embodiment of the invention involves a configuration which incorporates diopter and aberration correction, as would normally be found in prescription spectacles or contact lenses. This would allow the extension of utility to those who would otherwise need vision correction optics.
Another method of accommodating those people who need vision correction or visual aids is to integrate left eye and right eye multiple aperture telescopes (as previously described) with a clip-on mechanism that will allow them to be attached to normal prescription spectacles.
Cross-talk is a phenomenon for undesirable stray light to reach the eye or detector. As shown in
Further variations of this invention can be more readily appreciated by considering
System performance can be further refined by optimizing the telescopes at the center of the system separately from the telescopes at the edge of the field. The image as observed by the image receiver 141 is made up of the superposition of all of the images formed by each individual Galilean telescope. The center of the field of view, as observed by the image receiver, tends to be transmitted through the telescopes at the center of the system. The higher field angles (which correspond to the edge of the apparent field of view), as observed by the image receiver, tend to be transmitted by the telescopes at the edge of the system. Consequently, optimizing the telescopes separately and differently can provide improved performance. It is of critical importance to maintain constant magnification and to match distortion from individual telescope to telescope when optimizing in order to maintain an apparently seamless image when all the individual images are superimposed.
Turning first to
This application relies on provisional application Ser. No. 60/988,917 filed on Nov. 19, 2007.
Number | Date | Country | |
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60988917 | Nov 2007 | US |