| 摘要 |
<p>A focussing element (50) is incorporated in an infrared detector, the focussing element (50) being in the form of a series of grooves (54) which form one or more diffractive optical elements. The diffractive optical elements may have spatial filtering properties and may also be arranged to correct chromatic aberrations. Alternatively, the focussing element may comprise a holographic optical element.</p> |
