Object detection device
First Claim
1. An object detection device for detecting an object in a target space, said object detection device comprising:
- a pyroelectric element configured to output a current signal in response to a change in an amount of infrared light received from the target space;
an I/V conversion circuit including an operational amplifier connected to said pyroelectric element, a capacitive element connected to said operational amplifier to serve as a feedback circuit, and a discharging circuit for discharging said capacitive element, said I/V conversion circuit being configured to convert the current signal to a voltage signal and output the voltage signal;
an A/D conversion circuit configured to convert the voltage signal to a first digital signal and output the first digital signal;
a digital filter configured to extract a detection component having a frequency included in a frequency band associated with the object, from a waveform represented by the first digital signal, by subjecting the first digital signal to an arithmetic processing, and create a second digital signal representing a waveform of the detection component, and output the second digital signal;
a judgment circuit configured to judge, based on the second digital signal, whether or not the object exists in the target space; and
a control unit configured to control said discharging circuit in such a manner to eliminate a low-frequency component having a frequency not greater than a predetermined frequency from the voltage signal, the predetermined frequency being not greater than a lower limit of the frequency band,wherein said control unit is configured to control said discharging circuit based on a reset period corresponding to the predetermined frequency to discharge the electric charges stored in said capacitive element.
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Accused Products
Abstract
The object detection device includes: a pyroelectric element configured to output a current signal in response to a change in an amount of infrared light; an I/V conversion circuit including an operational amplifier, a capacitive element serving as a feedback circuit, and a discharging circuit, and configured to convert the current signal to a voltage signal; an A/D conversion circuit configured to convert the voltage signal to a first digital signal; a digital filter configured to extract a detection component having a frequency included in a frequency band associated with an object from a waveform represented by the first digital signal by subjecting the first digital signal to an arithmetic processing, and create a second digital signal representing a waveform of the detection component; a judgment circuit configured to detect the target based on the second digital signal; and a control unit configured to control the discharging circuit based on a period corresponding to a predetermined frequency not greater than a lower limit of the frequency band to discharge electric charges stored in the capacitive element.
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Citations
18 Claims
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1. An object detection device for detecting an object in a target space, said object detection device comprising:
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a pyroelectric element configured to output a current signal in response to a change in an amount of infrared light received from the target space; an I/V conversion circuit including an operational amplifier connected to said pyroelectric element, a capacitive element connected to said operational amplifier to serve as a feedback circuit, and a discharging circuit for discharging said capacitive element, said I/V conversion circuit being configured to convert the current signal to a voltage signal and output the voltage signal; an A/D conversion circuit configured to convert the voltage signal to a first digital signal and output the first digital signal; a digital filter configured to extract a detection component having a frequency included in a frequency band associated with the object, from a waveform represented by the first digital signal, by subjecting the first digital signal to an arithmetic processing, and create a second digital signal representing a waveform of the detection component, and output the second digital signal; a judgment circuit configured to judge, based on the second digital signal, whether or not the object exists in the target space; and a control unit configured to control said discharging circuit in such a manner to eliminate a low-frequency component having a frequency not greater than a predetermined frequency from the voltage signal, the predetermined frequency being not greater than a lower limit of the frequency band, wherein said control unit is configured to control said discharging circuit based on a reset period corresponding to the predetermined frequency to discharge the electric charges stored in said capacitive element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification