Biometric data card and authentication method

A biometric data card (100) includes an image sensor (130) for capturing an image of a biometric feature (500) of a user of the biometric data card (100) and producing first image data (170) representing the image. The biometric data card (100) compares the first image data (170) to second image data stored within the biometric data card (100) to authenticate the user. The biometric data card (100) is usable with a terminal (400) including a slot (450) for receiving the biometric data card (100). The terminal (400) can further include an optical element (540) optically coupled to direct the image onto the image sensor (130) of the biometric data card (100).