Jianle Ren

Display and detail enhancement for high-dynamic-range infrared images

Dynamic range reduction and detail enhancement are two important issues for effectively displaying high-dynamic-range images acquired by thermal camera systems. They must be performed in such a way that the high dynamic range image signal output from sensors is compressed in a pleasing manner for display on lower dynamic range monitors without reducing the perceptibility of small details. In this paper, a new method of display and detail enhancement for high dynamic range infrared images is presented. This method effectively maps the raw acquired infrared image to 8-bit domain based on the same architecture of bilateral filter and dynamic range partitioning approach. It includes three main steps: First, a bilateral filter is applied to separate the input image into the base component and detail component. Second, refine the base and detail layer using an adaptive Gaussian filter to avoid unwanted artifacts. Then the base layer is projected to the display range and the detail layer is enhanced using an adaptive gain control approach. Finally, the two parts are recombined and quantized to 8-bit domain. The strength of the proposed method lies in its ability to avoid unwanted artifacts and adaptability in different scenarios. Its great performance is validated by the experimental results tested with two real infrared imagers.

SNR Improvement in Three-Step Phase Shifting Profilometry

Three-step phase-shifting is an extensively employed method for 3D shape measurement, especially for high speed 3-D image acquisition. However, since only three fringe images are used, the measurement result is susceptible to sensor and environment noise. In this paper, we propose a third harmonic injection technique for three-step phase shifting profilometry to reduce the error caused by the uncertainty noise. By adding a measure of third harmonic to the sinusoidal waveform, the amplitude of the sinusoidal fundamental component can be increased by 15.5-percent, which resulting in the reduction of the phase error caused by noise. Theoretical analysis, simulation, and experiment are presented to verify the effectiveness of the proposed technique.

Scene-Based Nonuniformity Correction with Multiframe Registration

A scene-based nonuniformity correction method for infrared focal plane arrays based on multiframe registration has been undertaken in this paper. It is based on the estimation of global translation between several adjacent frames, and the resulting mean square error function is optimized using a least mean square (LMS) algorithm. The proposed method make use of the relation of adjacent frames sufficiently, and it provides enhanced results when applied to infrared image sequences with simulated nonuniformity and infrared imagery with real nonuniformity. The experimental results have shown that it can estimate the nonunifomity parameters accurately of each detector with fast convergence speed and almost no ghosting artifacts.