Automatic lock and automatic unlock method for computer system and computer system thereof

An automatic lock and automatic unlock computer system, comprising:

• a visible light image detector for detecting whether a user is in a predetermined range;
• an identifying module, for identifying an authority of the user;
• and
• a processing unit, coupled to the visible light image detector and the identifying module, for controlling the visible light image detector and the identifying module, and executing logic instructions for controlling the computer system to enter an unlock status or a lock status,
• wherein when the computer system is in the unlock status and the visible light image detector does not detect the user in the predetermined range, the processing unit records a duration;
• when the duration is greater than a predetermined time, the processing unit controls the computer system to enter the lock status;
• when the computer system is in the lock status and the visible light image detector detects the user in the predetermined range, the processing unit determines whether an authority of the user is an effective authority;
• and when the processing unit determines that the user has the effective authority, the processing unit controls the computer system to enter the unlock status,
• wherein the visible light image detector receives a detecting wave reflected from the user as a captured image, and the processing unit determines whether the user is in the predetermined range according to a skin color extent of the captured image.