Optics: measuring and testing – Range or remote distance finding – External basis type
Reexamination Certificate
2000-06-23
2003-10-21
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Range or remote distance finding
External basis type
C033S277000, CD10S070000
Reexamination Certificate
active
06636296
ABSTRACT:
FIELD OF INVENTION
This invention relates to range finders, specifically to a range finder that relies on the reduction in the size of an object's image as distance increases, as viewed through an opening in the range finder, to determine the object's distance from the user where the object's width, length, height or other visible linear dimension is known or can be estimated.
PRIOR ART
There has been a long-standing need for “range finders,” ie., devices that allow the user to gauge his or her distance from an object without physically measuring the distance. Although various devices have been utilized for this purpose, two categories of range finder are relevant here: (1) “image-based” range finders that use the decrease in size of an object's image as distance increases to determine what that distance is; and (2) devices that can bounce a signal or beam off a target object, such as sonar, radar and laser range finders. The instant invention is an image-based range finder that improves upon the prior image-based art and, in addition, in some instances, complements or substitutes for signal reflection range finders.
Range Finders Based on Image Size—General
It has long been known that the perceived size of an object's image decreases with distance. This phenomenon has been the basis for simple range finding devices, which have used, for instance, a ruler to measure the size of the object's image. If the user knew both one linear dimension of the object and, via the ruler, the size of the image of that dimension, he could determine his distance from the object by using the well-established formula d=xy/z, where d is the object-to-eye distance, x is the known dimension of the object, y is the eye-to-device distance and z is the size of the image as measured by the ruler. Of course, if d is known, z can like wise be predicted (z=xy/d). As further discussed below, devices based on this concept have mainly taken three forms: reference line devices, stadia-line devices and window-based devices.
Image-Based Range Finders—Reference Line
Most common in this category of range finders are devices that employ a reference line comprising a system of measurement. Essentially a ruler drawn across the reticle of a scope, this device permits a comparison between the image size and previously determined distance information. Thus, in periscopes on submarines, distance to a surface ship has been roughly calculated based on the measurement provided by an engraved reference line on the reticle and compared to separately compiled information on the dimensions of various ships. This device provided a numeric measurement of the apparent size of the measured object which would then be compared to previously determined distance information calculated through the distance formula discussed above. Generally, this involved an additional step separate from the device itself These devices can determine distances from differently sized objects, but they pose difficulties in object alignment (i.e. having to superimpose a thin line over the image while simultaneously measuring the image size), and they require the user to access separately compiled information.
Image-Based Range Finders—Stadia-Line
Stadia-line range finders are a conceptually and practically distinct category utilizing similar distance determination principles. In these devices, a series of lines with accompanying numerals denoting distance are expressed on the reticle of a telescope or viewfinder. Each line is a different length and corresponds to the size of an image of an object of known dimension at a particular distance. The placement of lines and their lengths are also determined by the formula z=xy/d. Consequently, the plurality of lines, when centered on the reticle, have generally formed a curvilinear shape. In operation, the user superimposes the appropriate line over the object image in order to determine distance. This approach allows for the user to view the object image and access distance information at the same time, but it is less flexible than reference line devices because the stadia lines can only determine distance to one dimension of one item. Like reference line devices, this device partially obscures the target object.
Window-Based Range Finders
A conceptually and practically distinct category utilizing similar distance determination principles is the “window-based” range finder. Such devices enclose the object image at a particular position on an opening and correlate the image size to previously determined distance markings imprinted adjacent to the opening. The advantages of this art over reference-line devices are that the opening makes target alignment much easier, and the distance information imprinted on the device itself allows for a quicker determination of distance in that this information does not need to be separately accessed. It is superior to stadia-line art in that the object image is more easily framed and the user's view of the object is not obscured. However, as discussed below, window-based range finders have had several serious limitations, and their use has been limited.
Image-Based Range Finders—Miscellaneous
Other range finders in this general area are a range finder having a notch sized to accommodate the image of one object at one distance (Williams, U.S. Pat. No. 3,977,086); a range finder that interposes one or more two-dimensional outlines of the entire object image (e.g., a full representation of a deer) in a viewer or scope (Gregory, U.S. Pat. No. 4,787, 739); a range finder that discloses a vertically expressed reference line with unevenly spaced calibration lines (Murdoch U.S. Pat. No. 4,263,719); and a range finder that causes a reference line in a viewer to vary in length, making it easier to measure image size. (Landon, U.S. Pat. No. 3,999,853).
Signal Reflection Range Finders
An additional category of distance determination art is found in devices that can bounce a signal or beam off a target object back to a receptor (e.g., radar, sonar and laser devices). These signal reflection range finders, while not directly related to the instant invention, offer an alternative prior art category of distance determination devices.
LIMITATIONS OF THE PRIOR ART
Limitations of Prior Art—Image-Based Range Finders
Image-based range finders have to date been quite limited in their effective uses.
To our knowledge, image-based range finders have thus far not been used to determine short-range distances (ie., less than 60 feet). This is not surprising because making a useful device is more complicated for short-range distance determination. Even though the standard formula d=xy/z, which is applicable to distance determination and has been used in the prior art, can generally predict the size of the image at a short distance, it is often not the sole determinant. At short ranges, additional factors which do not exist (or are practically irrelevant) at longer ranges become more important. Thus, depending on the circumstances, the device may have to account for the height of the user, changes in the distance at which the device is held, and differences in the way the eye views objects at very short range. Although such adjustments are not always necessary, they would likely have presented significant difficulties. A device that has the flexibility to adjust for such factors where necessary and to provide for distance determination at relatively short distances would be a substantial improvement over the prior art, which is tied to the standard formula.
In addition, we understand that image-based range finders have thus far not been used to estimate distances to relatively small objects (i.e., objects with a linear dimension of less than 1.5 feet), such as a golf hole on the golf green. Useful applications for such a device would have been thought limited given that (1) absent a magnifying element, only short ranges can be determined, and (2) the less distance involved, the more likely the need for precision. (A margin of error of 25 yards m
Faulkner Robert L.
Faulkner Robert P.
Erbe Richard S.
Faulkner Robert L.
Rosenberger Richard A.
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