| 摘要 |
A surface of a liquid, e.g. fuel, is measured, the surface (1) having an edge contacting a solid structure (5), e.g. tank wall, and an interior area not contacting the solid structure. The liquid surface and the structure are illuminated with a pattern (e.g. optical radiation pattern, such as from LED 8) so that an upper part of the pattern is projected onto the structure to form an upper pattern and a lower part of the pattern is projected onto the interior area of the surface of the liquid to form a lower pattern. An image of the upper pattern is acquired (e.g. by camera 2) and analysed to determine a height of the edge of the liquid surface, e.g. by detecting discontinuities. An image of the lower pattern is acquired and analysed to determine a characteristic of the interior area of the surface of the liquid, such as determining spatial frequency or floating contaminant. The liquid may be being carried by a vehicle, such as an aircraft. The determined height, optionally in conjunction with the determined characteristic, may be used to estimate a volume of the liquid. |
