The basic idea of total internal reflection to image fingerprints, as discussed in Ref. 1 of our Applied Optics paper, has been known for a long time. According to Gregory, this idea dates back to his earlier patents. We would like to point out, however, that our holographic technique of correcting the 1/# factor is novel and gives high-contrast and low-distortion fingerprint images. The technique is easy to implement without the need for elaborate correcting optics. Also, it is in no way related to Gregory's earlier study.
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