| 摘要 |
An ultrasonic distance measuring device for use, for instance, in the building trades, conventionally measures distance by projecting a sonic beam towards the target and detecting the reflection from the target. Also provided is an associated co-axial laser pointer which provides a visual indication of where the sonic beam is pointed. This laser pointer provides a laser beam which illuminates the target. However, the laser beam is not a typical laser beam, but instead is diffracted so that it covers an area at the target approximately the same size and shape as the area covered by the sonic beam. This provides a clear indication to the user that the sonic beam is not a single point beam but instead is possibly reflecting from any one of a number of points on the target. This provides a better indication to the user than does the single point beam of what possible locations are being measured on the target The laser beam pattern is, for instance, a circular area, a pattern of lines or rings, or a set of dots including a bright central dot.
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