| 摘要 |
A transmitter unit is described for an open path gas detector. The unit comprises:
an enclosure (14) having a window (16); and
a coherent radiation transmitter (10), e.g. a tuneable laser diode transmitter, located within the enclosure and configured to direct a beam of radiation through the window.
The window is slanted with respect to the axis of the beam emitted by the transmitter such that no radiation from the transmitter that is directly incident on the window is reflected by the window directly onto the transmitter. Thereby interference fringes within the emitted radiation are reduced. Alternatively, the window may be replaced by a lens followed by an aperture such that the beam emitted by the transmitter is focused onto the aperture, thereby forming a beam of radiation passing out of the enclosure.
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