| 摘要 |
An illuminator (1) has a printed circuit board (5) supporting a ring of ligh t emitting diodes (LEDs) (6). An annular Fresnel lens (7) and the board (5) are both mounted in a housing (2) having a central through-hole (3) for a camera field of vie w. The lens (7) mixes light from the LEDs (6) in the tangential direction and it al so controls spread in the radial direction so there is uniform illumination over a targe t plane (4). Any individual point on the target plane (4) receives illumination from over 25% of the light sources (6). The illuminator is thus particularly effective, compact, and suitable for a wide range of industrial applications. Choice of lens and of the spatial arrangement allows versatility. The illuminator design is easily scaleable b y changing the size and spacing between the light sources.
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