Patent Application
20050250085
The inventions described below relate the field of astronomy, specifically to an electronic device capable of locating and identifying celestial objects.
Norton, Viewing And Display Apparatus, U.S. Pat. No. 5,311,203 (May 10, 1994) describes a viewing device for identifying features of interest which appear in the field of view of the device. Though Norton was described in the context of a hand-held star-gazing device, and purported to provide information about asterisms (constellations or groups of stars) in the field of view, the device does not work unless held with certain components held perfectly vertical during use. Any twisting or rotation of the device about the viewing axis necessarily causes errors, and introduces ambiguity that cannot be resolved. Thus, it is not possible to implement the Norton system, as proposed by Norton, in a hand-held device. Norton consists of a box-like housing with a viewing channel therethrough, an LCD display and image overlay system for superimposing an image on the field of view, optics for manipulating the superimposed image to make it appear at infinity, a single axis eccentrically weighted inclinometer to measure inclination of the device and three magnetic sensors to determine the bearing of the device, a database with information regarding the constellations which might be viewed with the device, and a microprocessor. The viewing channel establishes a field of view for the user, through which the user can see constellations. The microprocessor is programmed to interpret sensor input and search the database for constellations in the field of view, and transmit a reference display data to the display.
The Norton system suffers from crippling defects. An operational device depends on perfect vertical alignment of the inclinometer. Without perfect vertical alignment of the inclinometer the device cannot unambiguously determine its orientation. The slightest deviation from vertical introduces ambiguity, such that the device can determine only that the viewing channel is aligned somewhere on a wide arc of the sky. If the device is not held perfectly vertically, that is, if it is twisted or rotated about the viewing axis, projection errors are introduced into the output from the inclinometer, so that the device has inadequate information regarding its inclination. In the case that the twist induced error is small enough that the device can determine its viewing axis with enough precision to generate a reference display that corresponds to constellations in the field of view, the device has no way to determine that it is twisted, and thus cannot rotate the reference display to align with the constellation.
The Norton system has a further limitation in regards to the viewing system employed. The Norton system discloses an approach utilizing a predetermined field of view using a beam combiner, mirrors and a lens so that the superimposed image is positioned at infinity and of the correct scale to align properly with the background of stars and celestial objects. There is an inherent problem with this approach, it does not allow for any deviation in the distance that the operator is holding the device between their eye and the device. For example, users with glasses will see a dramatically different field of view than users without. This is a problem with no disclosed or obvious solution proposed by Norton. As the Norton system requires a predetermined field of view, this means that the distance between the users eye and the device must be fixed. Any deviation will change the field of view and the superimposed image will not be of the proper scale to align with the background stars and celestial objects.
The devices and methods described below provide critical enablement and improvements for the Norton device. One improvement provides for gimballing of the inclinometer of Norton, to eliminate a source of large error inherent in normal use of the device. Another improvement provides for gimballing of an inclinometer or gravitational sensor, and a hunting gravitational sensor, to provide accurate direction sensing. Another improvement provides for use of accelerometer based sensor disposed parallel to the viewing axis of the device to minimize rotation error. Other improvements provide rotation sensing and for rotation and scaling of superimposed images to account for user rotation of the device and user-created variation in the field of view presented by the device to the eye.
As described by Norton, the direction-sensing mechanism 7 includes an potentiometer-type inclinometer for sensing the inclination of the line of sight of the instrument to the horizontal and three orthogonal magnetic sensors for sensing the orientation of the instrument with respect to the local magnetic field of the earth. This potentiometer-type inclinometer includes a potentiometer having an eccentrically weighted shaft for varying the potentiometer resistance. The shaft tends to seek a resting position with the eccentric weight on the bottom. The potentiometer is mounted with the shaft axis of rotation perpendicular to the instrument and lying in the horizontal plane. As the inclination of the instrument is changed, i.e., as the line of sight is raised or lowered, the shaft rotates under the pull of the eccentric weight and causes the resistance to vary and the voltage across the wiper of the potentiometer to vary commensurately. Thus, the voltage output of the potentiometer is proportional to, and provides a measure of, the inclination of the line of sight to the horizontal.
However, if the device is rotated even slightly about the viewing axis, the output of the potentiometer will not vary corresponding unambiguously to the inclination of the viewing axis.
Our own patents, Lemp, Celestial Object Location Device, U.S. Pat. No. 6,366,212 (Apr. 2, 2002) and U.S. Pat. No. 6,570,506 (May 27, 2003) and our pending patent application Lemp, U.S. Publication 20030218546 (Nov. 27, 2003) (the entirety of which is hereby incorporated by reference) provides solutions to this problem. Lemp shows a device for viewing celestial objects from a location at a time and date ascertained by the device, comprising a viewing means to observe along a viewing axis defined by an azimuth angle and a nadir angle or altitude; a processor, a 3-axis magnetic sensor adapted to provide the processor with azimuth data representing the azimuth angle, a 3-axis gravitational sensor adapted to provide the processor with nadir data representing the nadir angle; location means for providing location data representing the location of the viewing device to the processor; time means for providing time and date data representing the time and date to the processor; and a database adapted to be accessed by the processor and provide data such that the processor determines celestial coordinates of right ascension and declination corresponding to the viewing axis based on the azimuth data, the nadir data, the location data, and the time and date data. The device can be used to direct a user to a celestial object (its resolution is very high, so that it can direct the user to individual stars and planets, as well as constellations and asterisms) and it can be used to identify an object to which the user has pointed the device.
Additional solutions may be employed to limit, if not totally eliminate, the errors inherent in the Norton device. One solution is illustrated in
The device may be implemented also with a single-axis magnetic sensor in a gimbaled housing which rotates under control of a motor, with an encoder, potentiometer or other sensing means for sensing the angle between the sensor and the viewing axis, wherein the magnetic sensor output and direction of the sensor position relative to the housing are sampled by the microprocessor. The direction in which the magnetic sensor reading indicates maximum (or minimum, depending on the sensor electronics) will correspond to the local direction of magnetic north, and the angle corresponding to this point correlates to the azimuth angle. If in combination with this, a single-axis gravitational sensor is placed in a perpendicularly mounted gimbaled housing, and rotated as described earlier, then the altitude angle can be recovered. If a third sensor is used to read the angle that the gimbaled gravitational sensor rests relative to the housing, than the information required to determine altitude, azimuth and rotation are all present.
Regarding the database structure proposed by Norton, the system can be greatly improved with the use of a two dimensional data set rather than a three dimensional data set. The preferred two-dimensional data set correlate Right Ascension and Declination with celestial objects and reference data regarding the celestial objects. This is only possible after a translation of the terrestrial coordinates to celestial coordinates which require time/date and location information. However, after this translation is done, there are several benefits. First the size of the database would be smaller, thus reducing memory requirements and cost. Also, because the searching algorithm would need to perform the search on reduced set of criteria, the searches may be accomplished more quickly, and require a lower processing power CPU, thereby reducing the cost further.
With the improvements disclosed above, a Norton-type device can be enabled to provide reference data which corresponds to viewed constellations. If, however, it is desired to superimpose reference data including constellation outlines over a constellation in the field of view, Norton must be further improved because it cannot sense rotation of the device about the viewing axis, and thus cannot determine the appropriate orientation of the constellation outline. If it is intended to present text data, the text data will appear at an angle as well. With the addition of gravitational sensors sensing gravity on a plurality of axes (two or three axes) as disclosed in Lemp, the rotation of the device about the viewing axis can be unambiguously determined. Also, a potentiometer, encoder, or other angle sensing means may be operably connected between the inclinometer and the gimbal mount 30 or gimbal shaft 25 shown in
With further improvements, the dependence of the Norton device on a fixed distance between the user's eye and the ocular lens of the device may be eliminated. Norton provides a device with a predetermined field of view. However, the field of view presented to the eye by any scope changes drastically as the scope is moved away from the eye by mere millimeters. Thus, users wearing eyeglasses (or for other reasons, preferring to hold the device far away from the eye) will experience a different field of view compared to users without eyeglasses. Accordingly, the superimposed image may not be properly scaled to correspond to a constellation viewed by the user, as shown in
The scaling effect illustrated in
The various aspects of the inventions may be implemented with various types of sensors. The magnetic field sensors may include induction sensors, fluxgate sensors, magneto resistors, Hall effect sensors, magneto-optical sensors, resonance magnetometers, SQUIDS (superconducting quantum interference devices) and others. Thus, while the preferred embodiments of the devices and methods have been described in reference to the environment in which they were developed, they are merely illustrative of the principles of the inventions. Other embodiments and configurations may be devised without departing from the spirit of the inventions and the scope of the appended claims.
