The fingerprint is a small area from which to take measurements, and the wear of daily life affects which ridge patterns show most prominently. Increasingly sophisticated mechanisms have been developed to capture the fingerprint image with sufficient detail and resolution. The technologies in use today are optical, silicon, and ultrasound. Optical technology is the oldest and most widely used. The finger is placed on a coated platen, usually built of hard plastic but proprietary to each company.
Latent prints are leftover prints from previous users.
This can cause image degradation, as severe latent prints can cause two sets of prints to be superimposed. Also, the coating and CCD arrays can wear with age, reducing accuracy. Optical is the most implemented technology by a significant margin. Identicator and its parent company Identix, two of the most prominent finger-scan companies, utilize optical technology, much of which is developed jointly with Motorola. As the Vendor page indicates, the majority of companies use optical technology, but the trend is toward silicon.