Patent US 5,743,349

A vehicle ignition interlock system including a non-invasive reader of a person's blood-alcohol concentration in combination with ignition interlock circuitry that prevents operation of a vehicle by an intoxicated person. The non-invasive blood-alcohol concentration reader, termed alcoh-meter, utilizes optical spectroscopic electromagnetic radiation technology to determine the alcohol levels in the blood. The alcoh-meter is preferably a dash mounted sensor for receiving a person's finger and absorbing incident light from a multiple wavelength light source and causing a light absorption reading to be generated based on the person's blood alcohol concentration in the finger tissue. After registering a reading, the results are compared electronically against a table of impaired/non-impaired levels of blood alcohol concentration. The impaired/non-impaired results are communicated to interlock circuitry that either enables, or disables start-up of the vehicle. If an impaired status is determined, the results are displayed instructing the operator to wait, or find a non-impaired operator.