Film scanner with dust and scratch correction by use of dark-field illumination

A method of detecting surface artifacts on a transmissive image medium, the method comprising the following steps:

• (a) providing illumination through the medium, at a point, along a first optical path;
• (b) measuring light intensity that passes through the point along the first optical path;
• (c) measuring light intensity along a second optical path that passes through the point on the medium, the second optical path being different than the first optical path, so that the measured light intensity results from light along the first optical path being redirected onto the second optical path at the point on the medium;
• (d) computing a difference between the measurement of step (b) and the measurement of step (c);
• (e) comparing the result of step (d) to a predetermined threshold;
• and
• (f) identifying the point on the medium as a surface artifact on the medium as a result of the comparison of step (c).

An image scanner comprising:

• a photosensor, the photosensor adapted to receive light along a first light path through a point;
• a light source, the light source adapted to provide light along a second light path through the point, the second light path not directed onto the photosensor;
• and
• wherein when some of the light from the light source is redirected at the point onto the first light path and onto the photosensor, an artifact is identified at the point.

An image scanner comprising:

• a photosensor, the photosensor adapted to receive light through a point along a first light path;
• a first source of light adapted to provide light through the point and along the first light path onto the photosensor;
• a second source of light adapted to provide light through the point and along a second light path, the second light path not directed onto the photosensor;
• and
• wherein when some of the light from the second source of light is redirected at the point onto the first light path and onto the photosensor, an artifact is identified at the point.

An image scanner comprising:

• a first photosensor, the first photosensor adapted to receive light through a first point along a first light path;
• a second photosensor, the second photosensor adapted to receive light through a second point along a second light path;
• a light source, the light source adapted to provide light through the first point along the first light path and adapted to provide light through the second point that is not along the second light path;
• and
• wherein when some of the light from the light source is redirected at the second point onto the second light path and onto the second photosensor, an artifact is identified at the second point.