Optical sensor and method of suppressing interference light therefor
First Claim
1. A method of suppressing noise in an optical sensor having a light transmitter and a light receiver, said method comprising the steps of:
- transmitting light from said light transmitter towards said light receiver according to a specified pattern, said pattern including pulses in packages, said packages being separated from each other by a specified interval, the pulses within each of said packages following one another with a specified carrier frequency;
receiving a light signal by said light receiver;
converting said received light signal into an electrical signal; and
directly thereafter passing said electrical signal through a bandpass filter adapted to selectively pass signals with said carrier frequency.
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Accused Products
Abstract
An optical sensor includes a light transmitter for transmitting pulsed light signals and a light receiver for receiving them. In order to suppress the effects of interfering noise light, the light signals are transmitted according to a specified pattern including pulses in packages separated from each other by a specified interval, the pulses within each of the packages following one another with a specified carrier frequency. Groups each including two or more such pulse packages may be employed. The light receiver converts a received light signal into an electrical signal and directly thereafter passes the electrical signal through a bandpass filter with a pass band including this carrier frequency. The light receiver may normalize received electrical pulses by suppressing those which are too low or narrow and uniformizing the width of those not suppressed, expand the pulses with the uniformized widths to improve accuracy of evaluation, integrate the expanded pulses and examine whether the integrated signal exceeds a specified threshold value.
15 Citations
16 Claims
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1. A method of suppressing noise in an optical sensor having a light transmitter and a light receiver, said method comprising the steps of:
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transmitting light from said light transmitter towards said light receiver according to a specified pattern, said pattern including pulses in packages, said packages being separated from each other by a specified interval, the pulses within each of said packages following one another with a specified carrier frequency;
receiving a light signal by said light receiver;
converting said received light signal into an electrical signal; and
directly thereafter passing said electrical signal through a bandpass filter adapted to selectively pass signals with said carrier frequency. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. An optical sensor comprising:
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a light transmitter for transmitting pulsed light signals, said light transmitter having a modulator circuit for modulating said pulsed light signals with a carrier frequency; and
a light receiver for receiving said pulsed light signals from said light transmitter, said light receiver having a photoelectric converting element for converting a received light signal into an electrical signal and a bandpass circuit disposed immediately downstream to said photoelectric converting element, said bandpass circuit having a bandpass range including said carrier frequency. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification