Optical Methods for Data Processing in Heat and Fluid Flow

20

Flame Visualization Enhancement by Image Processing

W B Ng, K Y Cheung, and Y Zhang

Abstract

This Chapter presents flame image visualization enhancement using image capturing and processing techniques. Test cases of the enhancement of flame visualization have been demonstrated. It has also been shown that the images could be pre-processed by the manipulation of the shutter speeds (or gating times) of a camera, in order to obtain the desired aspects of flame dynamics such as the time and spatial scales.

20.1 Introduction

In the last few decades, laser technology has developed progressively which enables laser-based optical diagnostic technique to play a dominant role in combustion research. Direct photography and its potential, on the other hand, has been overlooked even though it has been applied to flame studies ever since the first camera was invented. This is due to the fact that the flame light emission is integrated along the line of sight, which leads to ambiguity in spatial resolution. As a result, quantitative analysis is difficult. In addition, the sensitivity of a film is often too low to capture the flame dynamics and the images are either blurred or too dim to be of any use. The situation has changed recently since we are in the middle of a revolution of imaging techniques, sparked by the rapid progress not only in advanced image sensing technology but also in digital image processing power. Conventional film cameras are being replaced by high-end digital cameras. ...