| 摘要 |
<p>A system enabling conversion of a conventional ringlight for differential illumination such as dark field or Rheinberg illumination is disclosed. The system comprises a ringlight having an annular light emitting portion and a hood that fits over the ringlight. The hood has an aperture and an annular reflective surface, disposed opposite the light emitting portion, that reflects the light from the ringlight through the aperture. An angle of the annular reflective surface is selected relative to a direction of light from the ringlight to form a cone of light exiting the aperture. To ensure good contrast, a light baffle in the form of a sleeve, inserted into the ringlight, may be incorporated to prevent stray light from the ringlight from directly exiting through the aperture. The differential illumination produced by the invention is applicable to machine vision applications, but also microscopy, gemology, and serology, for example.</p> |
