Distance measuring apparatus having automatic gain control
First Claim
1. A distance measuring apparatus comprising a light emitting device for emitting infrared light blinking at a constant frequency toward an object, a light receiving device for receiving infrared light reflected from the object, the light receiving device being adapted to generated two output signals which correspond respectively to positive and negative amounts of deviation of a position of light received therein with respect to a center thereof, a pair of amplifiers for amplifying the output signals of the light receiving device, respectively, means for picking up signal components, each having a frequency corresponding of the blink frequency of the infrared light, from the output signals of the amplifiers, respectively, means for determining a distance to the object of the basis of the signal components picked up by the picking up means, and means or controlling a gain of each of the amplifiers, the controlling means including:
- a pair of resistor circuits each having a changeable resistance for determining the gain of corresponding one of the amplifiers;
a comparator which compares in magnitude one of the signal components with a reference voltage and generates control signal having modes which change with the difference in magnitude between one of the signal components and the reference voltage; and
means or changing the resistance of each of the resistor circuits in accordance with the modes of the control signals of the comparator.
1 Assignment
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Accused Products
Abstract
A distance measuring apparatus comprises a light emitting device for emitting infrared light blinking at a constant frequency toward an object, and a light receiving device for receiving infrared light reflected from the object. The light receiving device can generate two output signals which correspond respectively to positive and negative amounts of deviation of a position of light received therein with respect to a center thereof. The output signals are amplified by amplifiers, respectively. A signal component having a frequency corresponding to the blink frequency of the infrared light is picked up by a picking-up circuit from each of the output signals of the amplifiers. A distance determining device is provided to determine a distance to the object on the basis of the signal components. A gain control circuit for controlling gains of the amplifiers includes a pair of resistor circuits each having a changeable resistance for determining the gain of the corresponding amplifier. A comparator compares in magnitude one of the signal components with a reference voltage and generates a control signal having modes which change with the difference in magnitude between the signal component and the reference voltage. A resistance changing circuit is operative to change the resistance of each of the resistor circuits in accordance with the modes of the control signals.
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Citations
8 Claims
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1. A distance measuring apparatus comprising a light emitting device for emitting infrared light blinking at a constant frequency toward an object, a light receiving device for receiving infrared light reflected from the object, the light receiving device being adapted to generated two output signals which correspond respectively to positive and negative amounts of deviation of a position of light received therein with respect to a center thereof, a pair of amplifiers for amplifying the output signals of the light receiving device, respectively, means for picking up signal components, each having a frequency corresponding of the blink frequency of the infrared light, from the output signals of the amplifiers, respectively, means for determining a distance to the object of the basis of the signal components picked up by the picking up means, and means or controlling a gain of each of the amplifiers, the controlling means including:
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a pair of resistor circuits each having a changeable resistance for determining the gain of corresponding one of the amplifiers; a comparator which compares in magnitude one of the signal components with a reference voltage and generates control signal having modes which change with the difference in magnitude between one of the signal components and the reference voltage; and means or changing the resistance of each of the resistor circuits in accordance with the modes of the control signals of the comparator. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification