Abstract: An adaptive threshold optical reader for detecting optically encoded information when positioned within an optical path, including a light source for producing light energy along the optical path, a light detector responsive to the light energy along the optical path and for producing an ouput signal in accordance with the light energy detected by the light detector, means responsive to the output signal from the light detector and with the means having at least two states and with the means in a first state producing an adaptive threshold signal when there is no optically encoded information positioned within the optical path and with the adaptive threshold signal representative of the output signal from the light detector with a threshold level of optically encoded information and adaptive to optical changes and with the means in a second state for producing an information signal representative of the output signal from the light detector when there is optically encoded information positioned within the opt