Patent ID: 7529636

Claim:
A method of marking an item in free space with a marking system comprising: detecting an identifying feature of the item while the item is in a field of view of a marking system, which is in a free space environment; commencing a marking process using a laser source of the marking system; while commencing the marking process, monitoring at least a portion of the field of view for an unacceptable change; and terminating the marking processing within a safety period of time when an unacceptable change is detected in the portion of the field of view being monitored, wherein the unacceptable change comprises at least one of an appearance of an item within the field of view, a removal of an item from the field of view, a change of position of an item within the field of view, a presence of an unexpected heat bloom in the field of view, a presence of a predefined level of smoke in the field of view, a presence of fire in the field of view; wherein said item comprises a product code, wherein said marking process is configured to mark the product code as a proof of a completed sale.