Standards of highway conservation and maintenance are
improved gradually following the improvement of requirements of road service.
Before obvious damage such as obvious cracking (block，transverse, longitudinal ) and
rutting emerge, inconspicuous distress (micro-cracks, polishing, pockmarked) is
generated previously. These inconspicuous distresses may provide basis and
criteria for pavement preventive maintenance. Currently most of preventive
conservation measures are determined by experienced experts in maintenance and
repair of road after site visits. Thus method is difficult in operation, and
has a certain amount of instability as it is based on experience and personal
knowledge. In this paper, camera and laser were used for automated high-speed
acquisition images. Methods to preprocess pavement image are compared. The
pretreatment method suitable for analyze micro-cracks picture is elected, an effective
way to remove shadow is also proposed.