Jaime Meneses

Phase-unwrapping algorithm for images with high noise content based on a local histogram

We present a robust algorithm of phase unwrapping that was designed for use on phase images with high noise content. We proceed with the algorithm by first identifying regions with continuous phase values placed between fringe boundaries in an image and then phase shifting the regions with respect to one another by multiples of 2pi to unwrap the phase. Image pixels are segmented between interfringe and fringe boundary areas by use of a local histogram of a wrapped phase. The algorithm has been used successfully to unwrap phase images generated in a three-dimensional shape measurement for noninvasive quantification of human skin structure in dermatology, cosmetology, and plastic surgery.

Real time determination of the optical thickness and topography of tissues by chromatic confocal microscopy

In this work, a miniaturized probe of chromatic confocal microscopy to measure the optical thickness and topography of tissues is presented. The experimental model is based on the principle of focus multiplexing by wavelength encoding due to a phase Fresnel lens. The device is composed of a point polychromatic illumination system, a wavelength–height codification system of confocal microscopy and a spectral detection system. The illumination system has a broad and continuum spectrum and it is constituted by the combination of a high energy pulsed laser and an air–silica microstructured optical fibre. The first two systems form a wavelength segment on the device output. The coding of the optical thickness and the topography is based on the detection of the most intense spectral components coming from the interphases of the organic membranes. The measurement sensitivity is related to the width of the spectral response, which depends on the resolving power of the dispersive element and the detection system. The experimental results and a brief discussion of the resolution criterion and the perspectives of the work are provided.

Extended depth of field using shapelet-based image analysis.

One way to extend depth of field of any optical system is to take several images with different focus positions and combine them into a single composite image, which contains all regions fully focused. The challenge then becomes to select from each image the pixels that are in focus. We describe a new focus measure based on the shapelet decomposition. Results using simulated images with high noise content show that the shapelet-based focus measure is the most performance that traditional neighborhood-based focus approaches. Similarly shapelet focus measure provides significant improvement compared to traditional methods when objects have nontextured or homogeneous regions.

Object recognition using three-dimensional correlation of range images

Optical object recognition has been approached mainly from two points of view. The first one is based on the extraction and matching of local features of the object, such as contours or perspectives,1 and the other is based on the correlation of the object in global form2,3.

3D localization of a labeled target by means of a stereo vision configuration with subvoxel resolution

We present a method for the visual measurement of the 3D position and orientation of a moving target. Three dimensional sensing is based on stereo vision while high resolution results from a pseudo-periodic pattern (PPP) fixed onto the target. The PPP is suited for optimizing image processing that is based on phase computations. We describe experimental setup, image processing and system calibration. Resolutions reported are in the micrometer range for target position (x,y,z) and of 5:3x10(-4) rad: for target orientation (θx,θy,θz). These performances have to be appreciated with respect to the vision system used. The latter makes that every image pixel corresponds to an actual distance of 0:3x0:3 mm2 on the target while the PPP is made of elementary dots of 1 mm with a period of 2 mm. Target tilts as large as π=4 are allowed with respect to the Z axis of the system.

Axial resolution of a chromatic dispersion confocal microscopy

An analysis of the axial resolution of a chromatic dispersion confocal microscopy is presented. The system is based on the principle of focus multiplexing by wavelength encoding due to a phase Fresnel lens. The axial resolution is related with the measure of the FWHM value of every spectral response.

A hand-held 3D laser scanning with global positioning system of subvoxel precision

In this paper we propose a hand-held 3D laser scanner composed of an optical head device to extract 3D local surface information and a stereo vision system with subvoxel precision to measure the position and orientation of the 3D optical head. The optical head is manually scanned over the surface object by the operator. The orientation and position of the 3D optical head is determined by a phase-sensitive method using a 2D regular intensity pattern. This phase reference pattern is rigidly fixed to the optical head and allows their 3D location with subvoxel precision in the observation field of the stereo vision system. The 3D resolution achieved by the stereo vision system is about 33 microns at 1.8 m with an observation field of 60cm x 60cm.

Chromatic confocal method for determination of the refractive index and thickness

The chromatic confocal method to measure the refractive index and thickness of membranes is developed. The method is based on the longitudinal chromatic aberration produced by a diffractive element. The identification of the maximal spectral components coming from the membranes are used for measuring its thickness or its refractive index.

Measurement of the Topography, Refractive Index and Thickness in Tissues by mean of a Chromatic Confocal Method

The chromatic confocal methods are attractive for various applications, such as imaging of biological samples and semiconductor materials. In this paper a chromatic confocal method to measure the topography, the refractive index and optical thickness of tissues is develop. The experimental model is based on the longitudinal chromatic aberration produced by a diffractive element. The setup is composed by a point polychromatic illumination system, a wavelength‐height codification system of confocal microscopy and a spectral detection system. The illumination system has a broad and continuum spectrum and it is constituted by the combination of a high energy pulsed laser and an air‐silica microstructured optical fibre. The first two systems form a wavelengths segment on the device output. The coding of the topography and the thickness is based in the spectral analysis of the reflected spectral components coming from the surface of the sample and the interphase of the organic membranes respectively. It mean th...

A Structure-from-Motion Pipeline for Topographic Reconstructions Using Unmanned Aerial Vehicles and Open Source Software

In recent years, the generation of accurate topographic reconstructions has found applications ranging from geomorphic sciences to remote sensing and urban planning, among others. The production of high resolution, high-quality digital elevation models (DEMs) requires a significant investment in personnel time, hardware, and software. Photogrammetry offers clear advantages over other methods of collecting geomatic information. Airborne cameras can cover large areas more quickly than ground survey techniques, and the generated Photogrammetry-based DEMs often have higher resolution than models produced with other remote sensing methods such as LIDAR (Laser Imaging Detection and Ranging) or RADAR (radar detection and ranging).