US 4,230,265 A · Adaptive threshold optical reader

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 optical path, means responsive to the adaptive threshold signal for storing the adaptive threshold signal, and means responsive to the stored adaptive threshold signal and the information signal for detecting the presence of optically encoded information in the information signal above a threshold level in accordance with the stored adaptive threshold signal.

Claims21

Dependent claims

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 output 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 optical path,
means responsive to the adaptive threshold signal for storing the adaptive threshold signal, and
means responsive to the stored adaptive threshold signal and the information signal for detecting the presence of optically encoded information in the information signal above a threshold level in accordance with the stored adaptive threshold signal.

2 more elements

An adaptive optical card reader for detecting information optically encoded on a card and with the card reader including a card guide to position the card within an optical path, including

a light source for producing light energy along the optical path,
a light detector for detecting the light energy along the optical path and for producing an output signal in accordance with the intensity of the detected light energy,
means responsive to the output signal from the light detector for producing an adaptive threshold signal when there is no card positioned in the card guide and with the adaptive threshold signal having a level representative of a desired minimum threshold level for the detection of the optically encoded information and with the threshold signal adaptive to changes in the optical properties of the detector and with the means responsive to the output signal from the light detector for producing an information signal when there is a card positioned in the card guide and with the information signal representative of the optically encoded information,
means responsive to the adaptive threshold signal for storing the threshold signal, and
means responsive to the information signal and the stored adaptive threshold signal for comparing the information signal and the stored adaptive threshold signal for providing a detection of optically encoded information in accordance with such comparison.

2 more elements

An adaptive threshold optical reader for detecting optically encoded information on a credit card, including

a card guide for receiving the credit card and positioning the credit card within an optical path,
a light emitting diode positioned on one side of the card guide for directing light energy along the optical path,
a photodiode positioned to the other side of the card guide for receiving light energy directed along the optical path and for producing an output current in accordance with the intensity of the received light energy,
an operational amplifier including a feedback resistance coupled to the photodiode and responsive to the output current for producing an output voltage in accordance with the output current and the value of the feedback resistance and with the feedback resistance having a first resistance value with no card in the card guide and a second resistance value with a card in the card guide,
the output voltage with the feedback resistance having the second resistance value representative of the optically encoded information on the credit card and with the output voltage with the feedback resistance having the first resistance value representative of a threshold level for the detection of the optically encoded information, and
means coupled to the operational amplifier and responsive to the output voltages with the feedback resistances having the first and second values for detecting the optically encoded information in accordance with the threshold level.

3 more elements

Dependencies are inferred from the claim text.

Adaptive threshold optical reader

Life of this patent

Adaptive threshold optical reader

Life of this patent

Abstract

Claims21