Justin G. Chen

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The estimation of material properties is important for scene understanding, with many applications in vision, robotics, and structural engineering. This paper connects fundamentals of vibration mechanics with computer vision techniques in order to infer material properties from small, often imperceptible motions in video. Objects tend to vibrate in a set of(More)
Video cameras offer the unique capability of collecting high density spatial data from a distant scene of interest. They could be employed as remote monitoring or inspection sensors because of their commonplace use, simplicity, and relatively low cost. The difficulty is in interpreting the video data into a usable format, such as displacement, that is(More)
Video cameras offer the unique capability of collecting high density spatial data from a distant scene of interest. They can be employed as remote monitoring or inspection sensors for structures because of their commonplace availability, simplicity, and potentially low cost. An issue is that video data is difficult to interpret into a format familiar to(More)
We present algorithms for extracting an image-space representation of object structure from video and using it to synthesize physically plausible animations of objects responding to new, previously unseen forces. Our representation of structure is derived from an image-space analysis of modal object deformation: projections of an object's resonant modes are(More)
Non-contact measurement of the response of vibrating structures may be achieved using several different methods including the use of video cameras that offer flexibility in use and advantage in terms of cost. Videos can provide valuable qualitative information to an informed person, but quantitative measurements obtained using computer vision techniques are(More)
Standoff methods of non-destructive testing (NDT) offer flexibility over traditional methods of inspection which typically require physical contact with the material being measured. The benefits are that difficult to access locations can be inspected and measurements of a large area can be made more quickly. Acoustic-laser vibrometry is a robust standoff(More)
The world is filled with important, but visually subtle signals. A person's pulse, the breathing of an infant, the sag and sway of a bridge---these all create visual patterns, which are too difficult to see with the naked eye. We present Eulerian Video Magnification, a computational technique for visualizing subtle color and motion variations in ordinary(More)
We investigated the fundamental limits to the performance of a laser vibrometer that is mounted on a moving ground vehicle. The noise floor of a moving laser vibrometer consists of speckle noise, shot noise, and platform vibrations. We showed that speckle noise can be reduced by increasing the laser spot size and that the noise floor is dominated by shot(More)
Acoustic-laser vibrometry, a non-contact method for nondestructive testing, was studied by altering operational and defect parameters to determine their effects on measured signatures and system performance. The method detects delamination and voids in fiber-reinforced polymer reinforced concrete by vibrating the material with an acoustic excitation and(More)
A hardware system has been developed to obtain data from multiple MEMS triaxial accelerometers for structural health monitoring research. The system can be easily configured for a single accelerometer or up to as many as 120 triaxial accelerometers with 24-bit data sampled up to a 2 kHz rate simultaneously. The system is modular where each module consists(More)