Abstract: A method for indicating the value of a time varying measurement signal which may contain interference that would lead to a systematic error in the value indication, the method including: providing a representation of the measurement signal; providing a representation of a threshold value with respect to which the representation of the measurement signal has a given polarity when interference is present in the measurement signal; identifying each time period during which the measurement signal representation has the given polarity relative to the threshold value representation; and producing an indication of the value which the measurement signal has outside of each identified time period.

Abstract: Method and apparatus for determining the velocity of an object in a given direction without contacting the object, by: directing coherent radiation to the object in a direction substantially perpendicular to the given direction to cause radiation to be scattered from the object to produce a speckle pattern exhibiting a speckle spectrum, the speckle pattern at a location spaced from the object having a time dependency which is a function of movement of the object, detecting the speckle pattern intensity at the location spaced from the object, producing a first signal representative of the detected speckle intensity, and producing, from the first signal, a time-dependent intensity signal having a value which is weighted as a function of the frequency of the first signal.