A Novel and Systematic Signal Extraction Method for High-Temperature Object Detection via Structured Light Vision

Structured light vision fails to detect the high-temperature objects up to 1700 °C because the projected light patterns are drowned by the strong self-emitted radiation of the high-temperature objects. For this problem, signal enhancement and extraction of the projected laser light patterns are carried out in this article. Signal enhancement consists of two steps. The first step involves physical enhancement of the laser light signal by spectrum selective of the laser light source and filtering of the radiation by the optical filter. Theoretical analysis finds that, the working wavelength of the laser light source should be short, and the pass-bandwidth and the transmittance in the stopband of the optical filter should be small. The second step involves modulation of the projected light patterns. A novel modulation method is derived mathematically with optimal solutions. Based on the modulation method, strong radiations of the high-temperature objects are transformed into radiation noise with zero mean while half of the intensities of the structured light patterns are preserved. Interfered with the radiation noise, signal distribution of the structured light patterns is uncoupled from that of the radiation noise to extract the structured light patterns with desired confidence. The signal enhancement and extraction methods are applied and validated for slag level measurement in the converter in the steelmaking industry.