STABILIZATION - Continued
All stabilization systems utilize a property called inertia in order to work.
The SB takes advantage of the augmented inertia of the gyroscope. The
erecting prism gimbal described above is mechanically linked to a second
small gimbal which carries the gyroscope. In the presence of vibration
inputs, which would ordinarily blur the image seen by the observer, the
gyroscope controls the motions of the prisms to remove this blur and stabilize
the image. Over the long term, the gyro and prism gimbals are returned to
their center position.
The results of this stabilization technique in removing unwanted image
motion are shown in the compensation curve of Figure 1. The curve plots
percentage compensation as a function of the input motion frequency. For
example, at two per revolution of the OH-58 helicopter, approximately 11
Hertz (Hz), the percentage compensation is 98 percent. This means that 98
percent of the input motion at 11 Hz is removed and only 2 percent remains.
If the input motion amplitude is 10 milliradians only 0.2 milliradians blur
will be left in the image observed through the device.