Detection of transcribed seal impressions using 3-D pressure traces

Seals have been frequently used to certify that individuals or organizations have authorized or approved a document that bears these impressions. Much attention has been focused on the detection of forged seal impressions to expose and prevent seal-related frauds. This paper describes an image-processing technique that detects seal impressions transferred from a genuine document to a target document using transcription media. The proposed method utilizes a three-dimensional (3-D) scanner to generate a pressure trace map of the suspect seal impression. After utilizing a noise-reduction algorithm to improve image quality, the pressure map is aligned with a 2-D image of the same seal impression. The pressure ratio, determined by comparing the pressure map and inked impression of a suspect seal, can be used to determine whether the seal is genuine or was transferred to the target document. The results show that the proposed technique successfully identified transcribed seal impressions with an error rate of <1%.