An optical scanner device includes at least one image capture device and a transmitter of at least one aimer beam. The scanner device determines ranging to a subject using the at least one aimer beam projected to reflect off of a surface of the subject, and detects a position of the aimer-beam reflection within an image frame captured by the image-capture device, the position being a primary indicator of a distance to the subject from the optical scanner device. A secondary indicator of the distance to the subject within the image frame in combination with the first indicator is used to help detect the aimer beam reflection against noise and detect an occurrence of an optical misalignment with possible self-correction of calibration after such misalignment.