Vibration image acquisition and processing

1. A method of collecting and processing images of a device under test on a shaker table and generating a model of 3-dimensional movement of the device under test, comprising:

driving a shaker table with sinusoidal signal at a known exciting frequency, a device under test mounted to the shaker table obtaining a steady-state vibration characteristic corresponding to the excitation frequency;

imaging the device under test, while the shaker table is driving the device under test, as a series of still image frames taken by more than one camera at a regular sampling frequency that is less than the shaker excitation frequency, each image frame being stored together with a timestamp recording an image capture time for that frame;

reordering the stored series of still image frames from each camera, using the timestamps, into corresponding remapped series of images of each camera that represent a single vibration period beginning with an earliest captured image, where the reordering shifts each image frame, other than the earliest image frame, backwards in time by a specified multiple of vibration periods; and

creating a model, using the reordered series of images from more than one camera, of 3-dimensional movement of the device under test.

2. The method as in claim 1 , wherein an image capture rate of least one camera is not more than 200 Hz.

3. The method as in claim 1 , wherein at least one camera is a stereo camera.

4. The method as in claim 1 , wherein the timestamps are generated by an interface card timer associated with the camera at the close of the camera's shutter.

5. The method as in claim 1 , wherein the timestamps are generated by a system clock of a computer receiving and storing the image frames.

6. The method as in claim 1 , wherein the shaker table is driven at a series of stepped vibration frequencies, each frequency step lasting for a specified number of vibration cycles sufficient to capture a set of at least two dozen image frames.

7. The method as in claim 1 , further comprising calculating a resonant frequency of the device under test from the 3-dimensional movement modeled by the images.

8. The method as in claim 1 , further comprising calculating a mode shape of the device under test from the 3-dimensional movement modeled by the images.

9. The method as in claim 1 , wherein the shutters of all cameras are controlled and synchronized by one timer source.

10. The method as in claim 1 , wherein multiple shakers are employed to drive the device under test at the same time at same excitation frequency.

11. A shaker test apparatus, comprising:

a shaker table;

a vibration controller connected to the shaker table so as to drive the shaker table at a known frequency and period, wherein a device under test obtains a steady-state shake characteristic of that excitation frequency when mounted on the shaker table;

more than one camera directed toward the shaker table with any device under test mounted on that shaker table;

a trigger signal controller coupled to the camera so as to trigger the camera, while the shaker table is driving the device under test, to capture a series of still image frames at a regulated sampling frequency that is less than the shaking frequency;

a timer coupled to the camera(s) so as to record a timestamp of an image capture time for each image frame; and

a computer processing algorithm for reordering the stored series of still image frames, using the timestamps, into a remapped series of the images representing a single vibration period beginning with an earliest captured image, where the reordering shifts each image frame, other than the earliest image frame, backwards in time by a specified multiple of shake periods.