Biomedical subjects

Enbang Li

Publications and source records attributed to Enbang Li.

7 recordsLinked to original sources

PubMed2006

Discrete cosine transform-based shift estimation for fringe pattern profilometry using a generalized analysis model.

What is believed to be a new analysis algorithm to carry out profile measurement with low computational complexity and less noise sensitivity is presented. First, a discrete cosine transform (DCT)-based representation method is introduced to express the height distribution of a 3D surface. Then a novel shift estimation algorithm, called the DCT-based shift estimation (DCT-SE), is presented to reconstruct 3D object surfaces by using the proposed expression and the generalized analysis model. The advantage of DCT-SE is that without loss of measurement precision it provides lower computational complexity to implement 3D reconstruction from nonlinearly distorted fringe patterns and, at the same time, survives the random noise. Simulations and experiments show that the proposed DCT-SE is a fast, accurate, and efficient reconstruction algorithm for digital projection- based fringe pattern profilometry techniques.

Journal Article↗

PubMed2006

Continuous-wave, 15.2 W diode-end-pumped Nd:YAG laser operating at 946 nm.

A high-power continuous-wave (cw) Nd:YAG laser operating at 946 nm by utilizing a quasi-three-level transition is reported. The laser consists of a composite Nd:YAG rod end pumped by a fiber-coupled diode laser and a simple plane-concave cavity. At an incident pump power of 40.2 W, a maximum cw output of 15.2 W at 946 nm is obtained, achieving a slope efficiency of 45%. To the best of our knowledge, this is the highest output at 946 nm ever generated by diode-pumped Nd:YAG lasers. In addition, at an incident pump power of 15.2 W, a 1.25 W blue output at 473 nm is achieved with a simple compact three-element cavity and a type-I lithium triborate (LiB(3)O(5)) crystal as a frequency doubler.

Journal Article↗

PubMed2006

Three-dimensional profilometry based on shift estimation of projected fringe patterns.

This paper presents a new approach to fringe pattern profilometry. In this paper, a generalized model describing the relationship between the projected fringe pattern and the deformed fringe pattern is derived, in which the projected fringe pattern can be arbitrary rather than being limited to being sinusoidal, as are those for the conventional approaches. Based on this model, what is believed to be a new approach is proposed to reconstruct the three-dimensional object surface by estimating the shift between the projected and deformed fringe patterns. Additionally, theoretical analysis, computer simulation, and experimental results are presented, which show how the proposed approach can significantly improve the measurement accuracy, especially when the fringe patterns are distorted by unknown factors.

Journal Article↗

PubMed2006

Characterization of a fiber lens.

A practical method for characterizing microstructure fiber lenses in the near field is described. By detecting the optical power of the light reflected by a mirror and coupled back into the single-mode fiber, one can accurately determine the focal point and the working distance of a fiber lens. The approach is relatively simple and easy to implement. The accuracy in determining the focal point and working distance is better than 2%.

Journal Article↗

PubMed2005

Three-dimensional vision with dual acousto-optic deflection encoding.

We report a new method of sensing a three-dimensional (3D) object surface with an arbitrary geometric shape. In this approach, the first-order beams diffracted from two acousto-optic deflectors (AODs) interfere with each other to form a spatial carrier that is used to encode the depth information from the 3D object surface. A direct digital synthesizer is utilized to control two AODs to generate sequentially spatial carriers with different spatial frequencies so that a modified temporal phase-unwrapping technique can be applied for decoding the shape information of the test surface. Preliminary experimental results are presented to demonstrate the effectiveness of this method.

Algorithms↗

PubMed2005

Optical phase shifting with acousto-optic devices.

A novel optical phase-shifting method based on a well-known acousto-optic interaction is proposed. By using a pair of acousto-optic modulators (AOMs) and properly aligning them, we construct an optical phase shifter that can directly control the phase of a collimated beam. The proposed phase shifter is insensitive to the polarization of the incident beam when polarization-insensitive AOMs are used, and no calibration is necessary. The proposed approach is confirmed with experimental results.

Journal Article↗

PubMed2002

Influence of displacement and its first- and second-order derivative components on curvature fringe formations in speckle shearography.

The influence of displacement and its first- and second-order derivative components on curvature fringe formations in speckle shearography is discussed. The results show that (a) all the displacement components have no direct influence on curvature fringe formations; (b) only the first-order derivative component along the centerline of three apertures has an influence on curvature fringe formations, whereas all the other first-order components have no influence; and (c) all the second-order derivative components have no influence on curvature fringe formations. Results from theory and experiments are in good agreement.

Journal Article↗