Methods and apparatus for retroreflective surface inspection and distortion measurement

A method for creating retroreflective images of a target comprising the steps of:

• providing a group of retroreflecting elements;
• illuminating the target with light from a light source by directing the light to the target in such a manner that the light incident on the target forms a light field larger than the group of retroreflecting elements and which then irradiates the group of retroreflecting elements;
• moving the group of retroreflecting elements through at least a portion of the light field so as to retroreflect the light incident on the group of retroreflecting elements and reilluminate the target at a multiplicity of sequential locations;
• and
• imaging the light which reilluminates the target to form the retroreflective image.

A method for creating retroreflective images of a target comprising the steps of:

• providing a single retroreflective element;
• illuminating the target with light from a light source by directing the light to the target in such a manner that the light incident on the target forms a light field larger than the single retroreflective element and which irradiates the single retroreflective element;
• moving the single retroreflective element through at least a portion of the light field so as to retroreflect the light incident on the single retroreflective element and reilluminate the target at a multiplicity of sequential locations;
• and
• imaging the light which reilluminates the target to form the retroreflective image.

A method for creating retroreflective images of a target comprising the steps of:

• providing a single retroreflective element which returns light incident thereon over a range of angles;
• illuminating the target with divergent light from a light source by directing the divergent light from the light source to the target in such a manner that the divergent light forms a light field;
• positioning the retroreflective element in a position such that the divergent light of the light field impinges on the retroreflective element and is then returned over the range of angles to the illuminated target;
• and
• imaging the returned light from the illuminated target to form the retroreflective image.