Patent ID: 8107812

Claim:
An optical entry sensor system, comprising: an optical transmitter for transmitting a source beam of light along a source beam of light path; a mirror, which reflects the source beam of light transmitted from said optical transmitter, resulting in a reflected beam of light that travels along a reflected beam of light path; an optical receiver situated adjacent to the optical transmitter, the optical receiver for receiving the reflected beam of light from the mirror; a movable attenuation filter that is positioned in the path of the reflected beam of light but not substantially in the path of the source beam of light, wherein said movable attenuation filter is rotatable to produce different amounts of attenuation to the reflected beam of light before the reflected beam of light reaches the optical receiver; and wherein said attenuation filter is rotated until the optical entry sensor system does not function properly, such that a measurement of a specific rotation angle of said attenuation filter, which is proportional to an attenuation value, represents a measure related to a dynamic range of said optical entry sensor system.