This research proposes a method for estimating the minute motion of an object that is difficult to capture with a camera.
The proposed method uses the speckle pattern that occurs when the target is irradiated with laser light.
The speckle pattern is a pattern generated by mutual interference of coherent light with respect to the surface of an object.
It changes significantly depending on the movement in the depth direction with respect to the camera. Since the time change of this pattern is continuous and depends on the degree of surface movement, motion analysis by low-dimensional embedding is possible.
Speckle pattern
(a) is an example of the speckle pattern on the surface of an object when it is irradiated with coherent laser light.
The power of the incident light is uniform, but a speckled pattern is observed with the camera.
When the surface vibrates, the pattern changes randomly as shown in the three images on the right.
(b) shows how coherent light is reflected at multiple points on the rough surface of an object.
Since the reflected light from each point has different phases, mutual interference occurs and the speckle pattern changes significantly depending on the position of the camera, but it is reproduced when the relative positions are the same.
Displacement estimation due to speckle change
If the local patches around a pixel are considered as feature vectors of the pixel,
the distance between the feature vectors can be used as a measure of the difference in surface position.
In the proposed method, the next step is to analyze the small movements.
- Embedding the feature vectors of local patches around each pixel into a low-dimensional space.<
- Make the low-dimensional space coherent between neighboring pixels.
- Optimize the local planar parameters to fit the low-dimensional space.
Estimated plane parameters
Results of sound wave visualization by the proposed method
Visualization of vibration by sound
The following are the results of visualizing sound waves at various frequencies by the proposed method.
You can see how the sound propagates as a compressional wave.
Results of sound wave visualization by the proposed method
Publications
|
