Light guide, line illumination apparatus, and image acquisition system

An image scanner comprising:

• a plurality of light sources provided along a first direction;
• a light guide including a transparent member in the shape of a bar along the first direction, the transparent member configured to transmit a light therein;
• a lens array receiving reflected light from a medium on an illumination area illuminated by a light exiting from the light guide, and forming a light image of the medium;
• and
• a linear sensor converting the light image of the medium into image data,
• wherein the light guide comprises:
• a scattering mark configured to scatter the light emitted by the light sources;
• a reflection surface, having a curved surface, configured to reflect the light emitted by the light sources inside the transparent member;
• and
• a light exit surface configured to enable the light reflected at the reflection surface to exit outside the transparent member therethrough, wherein:
• the shape of the reflection surface is determined so that the light scattered at the scattering mark is focused directly onto a predetermined position outside the transparent member;
• the shape of the curved surface of the reflection surface is determined by an optimizing calculation so that the light scattered at the scattering mark should illuminate the predetermined position outside the transparent member;
• and
• majority of contribution to the illumination is attributed to the reflected light.