Optical: systems and elements – Image stabilization
Patent
1992-02-21
1993-08-17
Henry, Jon W.
Optical: systems and elements
Image stabilization
G02B 2764, G03B 500
Patent
active
052374505
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an inertial stabilizing system to be used preferably in connection with image stabilization for hand-held optical instruments. An ultralight oscillogyro functions as a reference element by which the angular position in inertial space is detected, and an electromechanical control system causes a gimbaled part of the optics to assume substantially the same angular position in space as that assumed by the rotational plane of the rotor of the oscillogyro. The oscillogyro is modified for a widened angular range, and the damping of the gyro is utilized for obtaining directly the possibility of target tracking.
PRIOR ART
Within the field of hand-held image stabilized binoculars and cameras a plurality of mutually different optical concepts have been presented. The great majority of these concepts have one feature in common, viz., that only one part of the optics within the instrument is maintained inertially stabilized, whereas the rest of the instrument is not stabilized. Relative angular movement of said inertially stabilized part of the optics and the instrument casing is made possible by a gimbaled bearing. This common principle of image stabilization is used in most instruments on the market intended for hand-held observation, and nowadays it can be considered as completely conventional.
Even if several solutions relating to the design of the gimbaled part have been proposed, the methods of inertially stabilizing said gimbaled part have exhibited remarkably few solutions working well. As a matter of fact, there is hardly any solution today which has not got at least some serious disadvantages.
One of these solutions of the stabilizing problem is the one proposed in U.S. Pat. No. 2,688,456. Unfortunately, this solution has great disadvantages among which sensitivity to bearing friction and play can be mentioned. Balancing of the gimbaled part must be carried out extremely accurately, still, good properties are never attained.
Therefore solutions have been presented where a gyro is mounted on the gimbaled part in order to enhance stability. Disadvantages here are a comparatively high power consumption for driving the rotor of the gyro, a long time before the gyro rotor reaches operative speed (15-60 seconds for some commercially available instruments) and a considerably increased weight, as in practice the gyro and the batteries have to be comparatively heavy. In order to make panning (target tracking) possible a precessing mechanism is necessary, which could cause a considerable loss of power when panning takes place.
In addition, there are problems associated with nutation oscillations when the gyro is rigidly secured to the gimbaled part. In order to solve these nutation problems a resilient and viscous coupling between the gyro and the gimbaled part can be used, which increases complexity, weight and volume. Examples of this technology is given in U.S. Pat. No. 3,564,931, where also the nutation problem is more closely elucidated.
A third possible principle to apply in order to obtain best stability is to refrain from connecting the gyro mechanically to the stabilized part, but to detect instead the position of the gyro by means of electronics so that signals are generated which are then used to urge, via small electromechanical actuators, the gimbaled part towards stability. The expected advantage of this solution is i.a. that it ought to be possible to design the gyro much smaller, resulting in reduced total weight and volume, but up to now it would seem that advancements have been modest in practice; in few if any of the hand-held image-stabilizing instruments on the market at present this principle is applied. The problem of reducing starting time, weight, power consumption and complexity does not seem to have been satisfactorily solved, for which reason the potential advantages appear not to have justified selection of this concept.
SUMMARY OF THE INVENTION
The present invention is a representative of this third category. An ultralight rotor in a
REFERENCES:
patent: 2688456 (1954-09-01), Jensen
patent: 3564931 (1971-02-01), Humphrey
patent: 3591250 (1971-07-01), Feinstein
patent: 3756686 (1973-09-01), Humphrey
patent: 4643539 (1987-02-01), Brignall
patent: 4662727 (1987-05-01), Griffin
patent: 4856882 (1989-08-01), Oshima et al.
R. Whalley et al., "The Oscillogyro", J. of Mechan. Eng. Sci., 1967, vol. 9, No. 1, pp. 55-61.
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