| 摘要 |
<p>A device for measuring light scattered by an information support (12) comprising a light source (11) with which it is possible to expose a portion of the information support (12), a sensor (18) having a light-sensitive surface, with an output signal dependent upon the quantity of light falling on the light-sensitive surface, and an objective (16), disposed between the information support (12) and the sensor (18), the exposed portion of the information support (12) being smaller than the field of view of the sensor (18), the sensor (18) being disposed at a distance behind the objective (16) where the quantity of light on the light-sensitive surface of the sensor (18) remains constant to within 5% in the event of a variation of +/- 20% in the distance of the information support (12) from the objective (16) and the light-sensitive surface of the sensor (18) being disposed within the beam of light scattered by the information support (12) and emerging from the objective (16).</p> |
