Matched filters require explicit knowledge of the target. This limits the usefulness of the filters where the target is unspecified or dynamically changing. This research presents... Read more.
Key concepts for phase-to-coordinate conversion in fringe projection systems
The operation of fringe projection system with the camera and projector arranged arbitrarily is modeled using four key concepts. This approach will support the development of new advanced arrangements and... Read more.
Flexible camera-projector calibration using superposed color checkerboards
Calibration of structured-light systems for 3D imaging is difficult because the camera and projector must be calibrated together. This paper reports a camera-projector calibration method useful for arbitrary system arrangements. Read more.
How do phase-shifting algorithms work?
Interference is an important phenomenon that plays a key role to understand the properties of light. However, novice students have difficulties with optical interference experiments because fringe-pattern processing algorithms are not a topic of the optics course. Read more.
Homography estimation by two PClines Hough transforms and a square-radial checkerboard pattern
Homographies are important matrices useful for camera calibration and other applications. We show that a homography can be obtained using only three particular points of the reference plane. Read more.
Real-time haze removal in monocular images using locally adaptive processing
Images with low visibility diminish the performance of computer vision systems. The visibility restoration problem becomes challenging when only monocular images are available, and a real-time image processing is required. Read more.
Operator-based homogeneous coordinates: application in camera document scanning
Homogeneous coordinates are an essential tool for vision-based applications. However, this topic and some others of projective geometry are poorly studied in the computer vision approach. Read more.
Estimation of amplitude and standard deviation of noisy sinusoidal signals
The amplitude of a sinusoidal signal can be estimated if the phase is properly modeled or known. Otherwise, the estimation is biased because of the noise. We show that the amplitude and standard deviation of a noisy sinusoid can be estimated without knowledge of the phase. Read more.
Single-shot camera position estimation by crossed grating imaging
Many applications in image processing and optical metrology depend critically on the position of a camera to a reference plane. Moreover, in real-time applications such as visual control of robots and augmented reality guiding, the position of the camera is required in real-time. Read more.
Nonparaxial geometrical Ronchi test for spherical mirrors: an inverse ray-tracing approach
Usually, ronchigrams are generated by the direct ray-tracing method. However, the resulting image is parametrized by the coordinates in the plane of the mirror. This parameterization produces irregularly sampled images (scattered pixels). Read more.
Fringe-patterns encode only one phase distribution; when more than one phase distribution is encoded, the result is an intensity pattern. Read more.
Camera calibration by multiplexed phase encoding of coordinate information
A camera calibration method based on the principle of phase encoding and coordinate transformation is proposed. First, we use the coordinate reference frame encoded in a crossed grating. Read more.
Phase-based measurement systems have applications in physics, engineering, medicine, biometry, and many others. Thus, algorithms for phase demodulation become a staple requirement of considerable importance. Read more.
Usually, phase-shifting algorithms assume that the phase shift is a linear function of time and space. Unfortunately, this requirement is not always satisfied in practice. Read more.
Phase-unwrapping algorithm by a rounding-least-squares approach
Phase-unwrapping is an essential procedure of fringe analysis routines. In this paper, an efficient phase-unwrapping algorithm, which operates over the gradient of the phase jumps by a robust and noniterative scheme, is proposed. Read more.
Phase-shifting interferometry based on the lateral displacement of the light source
Lateral displacements of the laser source induce phase shifts in the Twyman-Green Interferometer. Thus, phase-shifting is performed without expensive and complicated phase shifters. Read more.
We analyze the effects of the zero-order spectrum associated to the background light in the Fourier fringe analysis method. Then, the benefits of the fringe pattern normalization is examined. Read more.
Generalized phase-shifting interferometry by parameter estimation with the least squares method
We report a phase-shifting algorithm that recovers the wrapped phase from two or more fringe patterns with arbitrary and unknown phase shifts. For this, a new fringe-pattern normalization method is developed. Read more.