Digital device and biometric authentication method therein

A method of controlling a digital device, the method comprising:

• in response to a request to execute a first application on the digital device having a first security authentication level, controlling a camera unit to capture first vein image data at a first depth of a particular body part of a target and performing a first authentication process by comparing the captured first vein image data with prestored first vein image data;
• and
• in response to a request to execute a second application on the digital device having a second security authentication level more secure than the first security authentication level, controlling the camera unit to capture second vein image data at a second depth of the particular body part of the target and performing the first authentication process and a second authentication process by comparing the captured second vein image data with prestored second vein image data,
• wherein the second depth is deeper from a skin surface of the target than the first depth,
• wherein the camera unit comprises:
• a light emitting unit including a near infrared light source configured to emit near infrared light rays to the target, and a color light source configured to emit color light rays to the target;
• and
• a light receiving unit configured to detect both light rays reflected from the target,
• wherein the light receiving unit includes a focus lens, and
• wherein the method further comprises linearly moving, via the controller, the focus lens to and from the target in response to an autofocus signal of the controller, and
• wherein the light receiving unit further comprises:
• a filter unit configured to only transmit infrared light from the focused light reflected from the target;
• and
• a detecting unit configured to detect the infrared light filtered by the filter unit.