JP6921592B2 - Sensor output processing device and sensor output processing method - Google Patents

Description

The present invention relates to a sensor output processing device and a sensor output processing method.

Conventionally, there is known an infrared measuring device that adjusts the drift of an infrared detector by changing the integration time of the infrared detector according to the temperature (for example, Patent Document 1).
[Patent Document]
[Patent Document 1] International Publication No. 2009/089897

In the sensor output processing device that processes the output of the sensor, it is desirable to reduce the current consumption.

In the first aspect of the present invention, the sensor output processing device that processes the output of the sensor has a high sensor impedance by acquiring information on the sensor impedance and the integrating unit that integrates the signal from the sensor. Provided is a sensor output processing device including an integration time control unit that controls the integration time per unit time by the integration unit.

In the second aspect of the present invention, it is a sensor output processing method for processing the output of the sensor.
A sensor including a step of integrating a signal from a sensor and a step of acquiring information on the impedance of the sensor and controlling so that the higher the impedance of the sensor, the shorter the integration time per unit time in the step of integrating. Provides an output processing method.

The outline of the above invention does not list all the necessary features of the present invention. Sub-combinations of these feature groups can also be inventions.

An outline of the infrared detection device 10 according to the first embodiment of the present invention is shown. An example of the configuration of the infrared detection device 10 in the first embodiment is shown. An example of the configuration of the processing device 100 in the first embodiment is shown. An example of the configuration of the integrating unit 110 and the sample holding unit 120 is shown. An example of the output signal waveform of the integrating unit 110 is shown. An example of controlling the integration time based on impedance is shown. Another example of controlling the integration time based on impedance is shown. The relationship between integration time, noise, and current consumption is shown. The relationship between the impedance of the infrared sensor 20 and the infrared sensor output conversion noise is shown. An example of the relationship between the impedance, noise, and current consumption of the infrared sensor 20 in the processing device 100 of the first embodiment is shown. An example of the configuration of the infrared detection device 11 in the comparative example is shown. The relationship between the impedance, noise, and current consumption of the infrared sensor 20 in the processing device 200 of the comparative example is shown. An example of the infrared detection device 10 in the modified example is shown. The relationship between the temperature at the location of the infrared sensor 20, the impedance of the infrared sensor 20, and noise is shown. An example of the configuration of the impedance measuring unit 390 in the modified example is shown. An example of the relationship between the temperature, noise, and current consumption of the infrared sensor 20 in the processing device 100 of the modified example is shown. An example of the relationship between the temperature, noise, and current consumption of the infrared sensor 20 in the processing device 200 of the comparative example is shown. An example of the processing content by the infrared detection apparatus 10 of the first embodiment of the present invention is shown. An example of the configuration of the infrared detection device 10 according to the second embodiment of the present invention is shown. An example of the processing content by the infrared detection apparatus 10 of the second embodiment of the present invention is shown.

Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the inventions that fall within the scope of the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

FIG. 1 shows an outline of the infrared detection device 10 according to the first embodiment of the present invention. The present invention can also be applied to a sensor processing device for a sensor other than an infrared sensor. In particular, it is applied to a sensor output processing device for a sensor connected to a transimpedance amplifier regardless of the type of sensor. In a sensor connected to a transimpedance amplifier, the higher the impedance of the sensor, the smaller the noise. In the following description, a case where the present invention is applied to the infrared detection device 10 will be described as an example.

The infrared detection device 10 detects infrared rays. The infrared detection device 10 may be a motion sensor for detecting infrared rays emitted from the human body and determining whether or not the human body is present in the detection region. The infrared detection device 10 includes an infrared sensor 20 and a processing device 100. The infrared sensor 20 is a sensor that detects infrared rays. The infrared sensor 20 is an example of a type of sensor in which noise fluctuates depending on the impedance of the sensor. The processing device 100 is a sensor output processing device that processes the output of the sensor. In this example, the processing device 100 processes the output of the infrared sensor 20. The processing device 100 may be an integrated circuit formed on one semiconductor chip.

The infrared sensor 20 and the processing device 100 may be incorporated in one package. The infrared detection device 10 of this example adopts the form of a surface mount type package, and has a plurality of external terminals 12a to 12f. However, the configuration of the infrared detection device 10 is not limited to this case. The infrared sensor 20 and the processing device 100 may be built in different packages.

FIG. 2 shows an example of the configuration of the infrared detection device 10. The infrared sensor 20 includes a sensor element 22. The sensor element 22 may be a photodiode or a phototransistor. In this example, the sensor element 22 is a photodiode. The sensor element 22 may be formed of a compound semiconductor such as InSb. The infrared sensor 20 generates a signal according to the intensity of infrared rays. Specifically, the sensor element 22 generates a photocurrent I according to the intensity of infrared rays. The equivalent circuit of the sensor element 22 may be represented as a circuit in which a constant current source and a resistor are connected in parallel. The infrared sensor 20 may be configured to carry an electric current due to the difference between the temperature of the background and the temperature of the object.

The processing device 100 of this example includes an integration unit 110, a sample hold unit 120, an ADC unit 130, a logical operation unit 140, an integration time control unit 160, a threshold value control unit 170, and an impedance measurement unit 190. Further, the processing device 100 may include a comparison unit 180. However, the processing device 100 does not include the comparison unit 180, and as shown in FIG. 2, the comparison unit 180 may be provided outside the processing device 100. Further, the processing device 100 itself may include an infrared sensor 20.

The integrating unit 110 may have a current-voltage conversion circuit that converts the photocurrent I into a voltage. The integrating unit 110 integrates the signal from the sensor. In this example, the integrating unit 110 integrates the photocurrent I, which is a signal output from the infrared sensor 20. The integration unit 110 may repeat the integration and the reset of the integrated value a plurality of times within the data update period. The sample hold unit 120 sample-holds the integration signal obtained by the integration unit 110. However, the sample hold unit 120 is not an essential component and may be omitted.

The ADC unit 130 is an analog-to-digital converter that converts an analog signal into a digital signal. The ADC unit 130 may convert the integrated signal sample-held by the sample-hold unit 120 into a digital signal. When the sample hold unit 120 is omitted, the ADC unit 130 converts the integrated signal obtained by the integrating unit 110 into analog-digital conversion.

The ADC unit 130 may be an incremental delta-sigma type AD converter. The delta-sigma AD converter samples an analog signal at a frequency higher than the original sampling frequency. The delta-sigma AD converter takes a difference between the sampled signal and the signal obtained by converting the output signal of the AD converter into a digital analog signal, integrates the differences, and compares them with a comparator. The output signal of the AD converter is processed by a digital filter.

However, the ADC unit 130 is not limited to the incremental ΔΣ type AD converter. The ADC unit 130 may be a SAR type (sequential comparison type) AD converter including a sequential comparison register (Successive Approximation Register). Alternatively, the ADC unit 130 may be a flash type AD converter. The logical operation unit 140 may be a signal processing logic circuit. For example, the logical operation unit 140 includes the above digital filter. The logical operation unit 140 may have a function of calculating the average of the integrated values by using the data obtained by digitizing the integrated values acquired a plurality of times.

The impedance measuring unit 190 measures information about the impedance of the sensor. The impedance measuring unit 190 of this example measures information about the impedance of the infrared sensor 20. The impedance measuring unit 190 may be configured to measure the impedance itself, or may be configured to measure another physical quantity as information on the impedance. Measuring information about impedance includes measuring electrical resistance or measuring information about electrical resistance.

In this example, the processing device 100 has a built-in impedance measuring unit 190. However, the impedance measuring unit 190 may be provided outside the processing device 100. In this case, the processing device 100 acquires information on the impedance of the infrared sensor 20 from the external impedance measuring unit 190.

The integration time control unit 160 acquires information on the impedance of the infrared sensor 20. The integration time control unit 160 controls the integration time in the integration unit 110 based on the acquired information on the impedance. The integration time may be the operating time during which the integration unit 110 is executing the integration process. The integration time control unit 160 may acquire information regarding the impedance of the infrared sensor 20 from the impedance measurement unit 190.

The integration time control unit 160 controls so that the higher the impedance of the infrared sensor, the shorter the integration time per unit time by the integration unit 110. In this example, the higher the impedance of the infrared sensor element 22 in the infrared sensor 20, the shorter the integration time per unit time by the integration unit 110 is controlled. When the integrating unit 110 repeatedly integrates the signal and resets the integrated value a plurality of times per unit time, the integration time per unit time may mean the total time of the intervals of the plurality of integrations. The integration time control unit 160 may be realized by a control logic circuit, a microcomputer, or the like.

The comparison unit 180 compares the target signal with the threshold value. The target signal is a signal obtained from the output from the integrating unit 110. In this example, the target signal is a digital signal obtained by converting the integrated signal output from the integrating unit 110 through the sample hold unit 120 and the ADC unit 130. Further, when the integrating unit 110 repeatedly integrates the signal according to the intensity of infrared rays and resets the integrated value a plurality of times within a predetermined data update period, the target signal is a plurality of integrated signals. May be the average of the digitized signals. However, the target signal is not limited to these cases. The target signal may be a signal obtained from the integration signal that is the output of the integration unit 110. The comparison unit 180 may determine that the human body exists in the detection region when the target signal is equal to or greater than the threshold value.

The threshold control unit 170 generates a voltage serving as a threshold value and inputs it to the comparison unit 180. The threshold control unit 170 may be a circuit that inputs a constant voltage to the input terminal of the comparison unit 180. The threshold value control unit 170 may have a function of correcting the threshold value. The threshold value may be a human sensation threshold value for determining whether or not a human body exists in the detection region.

FIG. 3 shows an example of the configuration of the processing device 100 according to the first embodiment. In this example, the impedance measuring unit 190 includes a constant current source 192, a first changeover switch 195, a second changeover switch 196, and an ADC unit 130. The constant current source 192 passes a constant current through the infrared sensor 20. The first changeover switch 195 electrically connects one end 193 and the other end 194 of the infrared sensor 20 to the ADC unit 130 in a state where a constant current is flowing through the infrared sensor 20.

The ADC unit 130 functions as a voltage measuring unit that measures the voltage across the infrared sensor 20 as information regarding the impedance of the infrared sensor 20 in a state where a constant current is flowing through the infrared sensor 20. The second changeover switch 196 electrically disconnects the ADC unit 130 when the ADC unit 130 measures the voltage across the infrared sensor 20. The ADC unit 130 measures the voltage across the infrared sensor 20 in a state where the infrared sensor 20 is electrically disconnected from the measurement path including the integrating unit 110. As a result, the voltage across the infrared sensor 20 can be accurately measured without being affected by the input impedance of the measurement path including the integrating unit 110.

The processing device 100 of this example also uses the ADC unit 130 for analog-to-digital conversion of the integration signal output from the integration unit 110 or the signal obtained by sample-holding the integration signal as the voltage measurement unit. Therefore, the processing device 100 can save space and cost as compared with the case where the processing device 100 has a separate voltage measuring unit. However, unlike this example, the processing device 100 may have a separate voltage measuring unit.

FIG. 4 shows an example of the configuration of the integrating unit 110 and the sample holding unit 120. The integrating unit 110 of this example includes an operational amplifier 112, a capacitor 113, a capacitor 114, and an input terminal 115. A capacitor 113 and a capacitor 114 may be electrically connected between the input end and the output end of the operational amplifier 112. Both ends of the sensor element 22 of the infrared sensor 20 may be electrically connected to the input end of the operational amplifier 112. Further resistors may be connected to both ends of the sensor element 22 and the input end of the operational amplifier 112. The operational amplifier 112 and the capacitors 113 and 114 of this example function as a transimpedance amplifier.

A switch for resetting the integral may be provided between the input end and the output end of the operational amplifier 112 in parallel with the capacitor 113 (or the capacitor 114). The switch for resetting the integration is closed when the command of the integration time control unit 160 is received, and the integration value is reset. Specifically, the reset switch discharges the electric charge accumulated in the capacitors 113 and 114.

The sample hold unit 120 of this example includes an operational amplifier 122, capacitors 123 and 124, a first switch 125, a grounding capacitor 126, and a second switch 127. A capacitor 123 and a capacitor 124 may be electrically connected between the input end and the output end of the operational amplifier 122. In this example, the first switch 125 and the second switch 127 are connected in series to the input end of the operational amplifier 122. The connection point between the first switch 125 and the second switch 127 may be grounded via the grounding capacitor 126.

During the sampling operation, the first switch 125 is closed and the capacitors 123 and 124 are charged. During the hold operation, the first switch 125 is in the open state. As a result, the charged voltage is maintained regardless of the fluctuation of the integrated signal of the integrating unit 110. The ADC unit 130 may convert the integrated signal sample-held by the sample-hold unit 120 into a digital signal. The configuration of the integrating unit 110 and the sample holding unit 120 described above is an example, and other configurations may be adopted.

FIG. 5 shows an example of the output voltage waveform of the integrating unit 110. The vertical axis represents voltage V and the horizontal axis represents time. The voltage corresponds to the integrated value. As shown in FIG. 5, the processing device 100 of this example executes the chopper operation. However, the processing device 100 is not limited to the one that executes the chopper operation. The integration unit 110 is controlled by a command from the integration time control unit 160, and repeats integration in the integration interval and resetting of the integration value a plurality of times.

In the integration interval, the integration signal 31 changes as a linear function of time. Then, the voltage is reset by the reset operation. The voltage value 32 at the apex of the integration signal 31 may be sample-held by the sample-hold unit 120. The sample hold unit 120 and the ADC unit 130 may operate at a time when the integration signal 31 which is the output of the integration unit 110 is near the apex.

The sensor output processing device 100 of this example configured as described above controls the integration time in the integration unit 110 based on the acquired information on the impedance of the infrared sensor 20. FIG. 6 shows an example of controlling the integration time based on impedance. When the integrating unit 110 is executing the integrating operation, the ADC unit 130 may be stopped (powered off). On the other hand, when the ADC unit 130 AD-converts the integration signal 31, the integration unit 110 is being reset.

In the example shown in FIG. 6, the data update period is 100 msec. The time for each integration operation and AD conversion operation may be set to a time of 1 msec or less. In this example, during the data update period, the integrating unit 110 repeats the integration and the resetting of the integrated value a predetermined number of times. The integration time control unit 160 controls so that the higher the impedance of the infrared sensor 20, the smaller the number of times the integration and the reset of the integrated value are repeated per data update period. Since the integration interval for each time is the same, as the number of repetitions decreases, the integration time, which is the sum of the intervals for a plurality of integrations per unit time (for example, the data update period), becomes shorter.

In the example shown in FIG. 6, the case where the impedance of the infrared sensor 20 is the first impedance and the case where the impedance is the second impedance higher than the first impedance is shown. When the impedance of the infrared sensor 20 is the first impedance, the number of repetitions of integration and resetting of the integrated value is N times. The second impedance may be twice or more, preferably three times or more, the first impedance. The integration time control unit 160 reduces the number of repetitions as the impedance of the infrared sensor 20 increases. As a result, as the impedance of the infrared sensor 20 increases, the time during which the integrating unit 110 pauses can be lengthened. Therefore, the integration time control unit 160 can reduce the current consumption in the integration unit 110.

In FIG. 6, the rest time is collectively displayed in the final period of the data update period. However, the control by the integration time control unit 160 is not limited to this case, and a pause time may be provided each time the integration and the reset of the integrated value are repeated.

FIG. 7 shows another example of impedance-based integration time control. In this example, the integration time control unit 160 controls so that the higher the impedance of the infrared sensor 20, the shorter the time of the integration section per integration. The number of times the integration and the reset of the integration value are repeated per data update period does not change. However, since the time of the integration interval is shortened, the voltage value 32 at the apex of the integration signal 31 becomes smaller. Therefore, it is necessary to reduce the threshold value used in the comparison unit 180 in conjunction with the shortening of the integration interval time. The relationship between the time of the integration interval and the threshold value may be stored in advance in the storage unit as a lookup table or a conversion formula. The threshold value control unit 170 may determine the threshold value by referring to a look-up table or the like so that the threshold value becomes smaller in conjunction with the shortening of the integration interval time. Alternatively, instead of determining the threshold value so that the threshold value becomes smaller in conjunction with the shortening of the integration interval time, the logical operation unit 140 in the logical operation unit 140 interlocks with the shortening of the integration interval time so that the final output gain becomes constant. The signal may be amplified.

The control shown in FIG. 7 can also shorten the integration time, which is the sum of the intervals of a plurality of integrations per unit time (for example, a data update period) as the impedance increases. When the integration time is shortened, the time during which the integration unit 110 pauses can be lengthened. Therefore, the current consumption in the integrating unit 110 can be reduced.

FIG. 8 shows the relationship between integration time, noise, and current consumption. The horizontal axis of FIG. 8 indicates the integration time, which is the sum of the intervals of a plurality of integrations per unit time. The noise in this example is frequency-independent noise. The noise may be thermal noise (thermal noise) or the like. Noise is inversely proportional to the positive square root of the integration time. The current consumption is proportional to the integration time. As the integration time increases, the noise decreases while the current consumption increases. As the integration time becomes shorter, the noise increases while the current consumption decreases. Therefore, there is a trade-off between current consumption and noise.

When the output signal of the infrared sensor 20 is buried in noise, the infrared detection device 10 cannot detect the human body in the detection region. That is, when the signal-to-noise ratio (S / N ratio: signal (S) / noise (N)) becomes small, the infrared detection device 10 cannot detect the human body in the detection region. Therefore, the processing device 100 needs to suppress the noise to a level that can be distinguished from the output of the infrared sensor 20. Specifically, the processing device 100 of this example lengthens the integration time to reduce noise.

FIG. 9 shows the relationship between the impedance of the infrared sensor 20 and the infrared sensor output conversion noise. Infrared sensor output referred noise is roughly classified sensor impedance noise N _R caused by the infrared sensor _20, the amplifier noise N _AMP of the current-voltage conversion circuit integrator 110 _has, and other noise. However, other noise can be ignored. Sensor impedance noise N _R is given by the following equation. k is the Boltzmann constant, T is the absolute temperature, and R is the impedance of the infrared sensor 20. The impedance of the infrared sensor 20 may be the resistance of the infrared sensor 20.

The amplifier noise N _AMP is given by the following equation. N _{A is} the input voltage referred noise of the amplifier of the current-voltage conversion circuit.

Therefore, the infrared sensor output conversion noise N of the infrared detection device 10 is given by the following equation.

As shown in the above equation, the noise N becomes smaller as the impedance of the infrared sensor 20 is higher. When the impedance of the infrared sensor 20 is high, the noise becomes small, so that the minimum number of integrations required to satisfy the noise specification Nspec can be small.

If the allowable noise specification is Nspec and the noise N when the predetermined integration interval (integration time) is executed once is N1, the flicker noise depends on the frequency of the flicker noise depending on the case where the flicker noise can be ignored or the chopper operation or the like. If the property can be ignored, the minimum number of integrations required to satisfy the noise specification Nspec is given by the following equation. The noise specification Nspec may be determined so that the noise is smaller than the signal when the human body is detected in the detection region. The noise N1 corresponds to the above-mentioned noise N. Therefore, the higher the impedance of the infrared sensor 20, the smaller the noise N1.

As described above, as the impedance of the infrared sensor 20 increases, the noise N1 decreases, so that the noise specifications can be satisfied even if the integration time is reduced. In Equation 4, as the noise N1 becomes smaller, the minimum number of integrations required to satisfy the noise specification Nspec, that is, the number of repetitions of the integration and the reset of the integrated value per data update period can be reduced. Therefore, the integration time control unit 160 controls so that the higher the impedance of the infrared sensor 20, the shorter the integration time, which is the sum of the intervals of a plurality of integrations per unit time (for example, the data update period) by the integration unit 110. .. As described with reference to FIG. 8, as the integration time becomes shorter, the current consumption of the integration unit 110 can be reduced.

FIG. 10 shows an example of the relationship between the impedance, noise, and current consumption of the infrared sensor 20 in the processing device 100 of the first embodiment. In maintaining a constant integration time regardless of the impedance of the infrared sensor 20, as shown from Equation 1 to Equation 3, due to the characteristics of the sensor impedance noise N _R, an amplifier noise N _AMP of the current-voltage conversion circuit Then, as the impedance of the infrared sensor 20 increases, the noise decreases. However, in this example, the integration time is shortened as the impedance of the infrared sensor 20 increases. When the integration time is shortened, the noise becomes high as shown in FIG.

Therefore, according to the processing apparatus 100 of the present embodiment, the reduction of noise due to the characteristics of the amplifier noise N _AMP sensor impedance noise N _R and the current-voltage conversion circuit, an increase in noise due to the shorter integration time By canceling out, the change in noise when the impedance of the infrared sensor 20 changes is maintained within a certain range. FIG. 10 schematically shows that the noise is constant even if the impedance of the infrared sensor 20 changes. However, in reality, the noise may increase or decrease within a certain range. On the other hand, since the integration time control unit 160 controls so that the integration time becomes shorter as the impedance of the infrared sensor 20 increases, the current consumption in the integration unit 110 decreases.

FIG. 11 shows an example of the configuration of the infrared detection device 11 in the comparative example. The infrared detection device 11 includes an infrared sensor 20 and a processing device 200. The processing device 200 is a sensor output processing device that processes the output of the infrared sensor 20. The processing device 200 may include an integration unit 210, a sample hold unit 220, an ADC unit 230, a logical operation unit 240, an integration time control unit 260, and a threshold control unit 270. In the processing device 200, the integration time of the integration unit 210 does not change according to the impedance of the infrared sensor 20. Except for this point, the processing device 200 of the comparative example is the same as the processing device 100 of the first embodiment described above. Therefore, the repetitive description will be omitted.

FIG. 12 shows an example of the relationship between the impedance, noise, and current consumption of the infrared sensor 20 in the processing device 200 of the comparative example. As shown in the left column of FIG. 12, the noise decreases as the impedance of the infrared sensor 20 increases. It includes a sensor impedance noise N _R as described in Figure 9, due to the characteristics of the amplifier noise N _AMP of the current-voltage conversion circuit. In the comparative example, the integration time control unit 260 does not change the integration time according to the impedance of the infrared sensor 20. In the processing apparatus 200 of the comparative example, the reduction of noise due to the characteristics of the amplifier noise N _AMP sensor impedance noise N _R and the current-voltage conversion circuit, does not offset the increase in noise due to the shorter integration time.

In the processing device 200 of the comparative example, for example, the noise N when the impedance of the infrared sensor 20 is XkΩ, which is the lowest value under the actual usage conditions based on the temperature characteristics of the infrared sensor and the manufacturing variation, is used. The number of integrations is determined so that the noise N satisfies the noise specification Nspec. Therefore, the current consumption is not reduced even if the impedance is lowered.

Unlike the processing device 200 of the comparative example, the processing device 100 of the first embodiment of the present invention sets the integration time for integrating the signal corresponding to the intensity of infrared rays detected by the infrared sensor 20 according to the impedance of the infrared sensor 20. Fluctuate. Therefore, as in the processing device 200 of the comparative example, the integration time is determined based on the noise at XkΩ, which is the lowest value under the conditions of actual use, and the integration time is not changed according to the impedance. In comparison, as the impedance of the infrared sensor 20 increases, the effect of reducing the current consumption can be obtained.

As will be described later, the impedance of the infrared sensor 20 increases as the temperature of the infrared sensor 20 decreases. Therefore, as the temperature of the infrared sensor 20 decreases, the impedance of the infrared sensor 20 increases, so that the current consumption is reduced. Further, even when the impedance of the infrared sensor 20 differs due to the variation in the manufacturing of the infrared sensor 20, the integration time is controlled to fluctuate for each product, and the current consumption is reduced.

Processing apparatus 100 of the first embodiment of the present invention, a reduction in noise due to the characteristics of the amplifier noise N _AMP sensor impedance noise N _R and the current-voltage conversion circuit, an increase in noise due to the shorter integration time By canceling out, the change in noise can be maintained within a certain range, so that the frequency of false positives is not increased.

FIG. 13 shows an example of the infrared detection device 10 in the modified example. The impedance measuring unit 390 of this example may include a temperature measuring unit that measures the temperature at the location of the infrared sensor 20 as information on impedance. Since the other configurations are the same as the configurations shown in FIG. 2, the repetitive description will be omitted.

FIG. 14 shows the relationship between the temperature at the location of the infrared sensor 20, the impedance of the infrared sensor 20, and noise. The left column of FIG. 14 shows that the impedance of the infrared sensor 20 increases as the temperature at the location of the infrared sensor 20 decreases. As described with reference to FIG. 9, as the impedance of the infrared sensor 20 increases, the noise decreases. Therefore, as shown in the right column of FIG. 14, the noise decreases as the temperature at the location of the infrared sensor 20 decreases.

The impedance of the infrared sensor 20 and the temperature at the location of the infrared sensor 20 have a one-to-one correspondence as shown in the left column of FIG. Therefore, the impedance measuring unit 390 of this example measures the temperature at the location of the infrared sensor 20 as information on impedance. The impedance measuring unit 390, which also functions as a temperature measuring unit, is, for example, a resistance temperature detector, a thermistor, a thermocouple, or an IC temperature sensor. Resistance temperature detectors and thermistors measure resistance values that change with temperature. Thermocouples measure thermoelectromotive forces that change with temperature. The temperature measuring unit may be arranged adjacent to the sensor element 22. The impedance measuring unit 390 of this example measures the resistance value of the semiconductor element that changes in relation to the temperature.

FIG. 15 shows an example of the configuration of the impedance measuring unit 390 in the modified example. The impedance measuring unit 390 measures the temperature of the place where the infrared sensor 20 is installed. In this example, the temperature of the place where the infrared sensor 20 is installed is measured by measuring the resistance value of the transistor element (semiconductor element). The impedance measuring unit 390 includes a constant current source 392 and a transistor element 394 as a temperature measuring unit. In this example, the emitter electrode 395 of the transistor element 394 may be grounded. The base electrode 396 and the collector electrode 397 of the transistor element 394 are electrically connected. A constant current source is connected to the collector electrode 397.

The voltage between the collector electrode 397 (the same potential of the base electrode 396) and the emitter electrode 395 changes with temperature. The temperature can be calculated by AD-converting the voltage between the collector electrode 397 (the same potential of the base electrode 396) and the emitter electrode 395. The impedance measuring unit 390 may be provided adjacent to the sensor element 22.

FIG. 16 shows an example of the relationship between the temperature, noise, and current consumption of the infrared sensor 20 in the processing device 100 of the modified example. According to the processing apparatus 100 of the present embodiment, due to the characteristics of the amplifier noise N _AMP sensor impedance noise N _R and the current-voltage conversion circuit, a decrease of the noise generated in accordance with the temperature becomes lower, the temperature is lowered At that time (that is, when the impedance of the infrared sensor 20 becomes high), the increase in noise due to the control to shorten the integration time is offset. As a result, the change in noise due to the change in the impedance of the infrared sensor 20 in response to the change in the temperature at the location of the infrared sensor 20 is maintained within a certain range.

In FIG. 16, the noise is schematically shown to be constant even if the temperature of the location of the infrared sensor 20 changes, but in reality, the noise may increase or decrease within a certain range. On the other hand, the integration time control unit 160 controls so that the integration time is shortened when the temperature at the location of the infrared sensor 20 becomes low and the impedance of the infrared sensor 20 becomes high. Therefore, the current consumption in the integrating unit 110 when the temperature becomes low is reduced.

FIG. 17 shows an example of the relationship between the temperature, noise, and current consumption of the infrared sensor 20 in the processing device 200 of the comparative example. As shown in the left column of FIG. 17, the noise decreases as the temperature of the infrared sensor 20 decreases. This is as described in FIG. In the comparative example, the integration time control unit 260 does not change the integration time even if the impedance of the infrared sensor 20 changes according to the temperature of the location of the infrared sensor 20. In Comparative Examples of the processing apparatus 200, due to the temperature of the location of the infrared sensor 20 becomes lower, the reduction of noise due to the characteristics of the amplifier noise N _AMP sensor impedance noise N _R and the current-voltage conversion circuit, the integration time Does not offset the increase in noise caused by shortening.

In the processing device 200 of the comparative example, for example, using the noise N when the location of the infrared sensor 20 is a specific temperature, the number of integrations is determined so that the noise N satisfies the noise specification Nspec. Therefore, the current consumption is not reduced even if the temperature is lowered and the impedance is raised.

Unlike the processing device 200 of the comparative example, the processing device 100 of the modified example of the present invention sets the integration time for integrating the signal corresponding to the intensity of infrared rays detected by the infrared sensor 20 to the infrared sensor related to the impedance of the infrared sensor 20. It fluctuates according to the temperature of 20 places. Therefore, the temperature at the location of the infrared sensor 20 is lower than that of the processing device 200 of the comparative example, in which the integration time is determined based on the noise at a constant temperature and the integration time is not changed according to the temperature. As it becomes, the effect of reducing the current consumption can be obtained. In particular, the current consumption is reduced in the temperature region where the infrared detection device 10 is frequently used.

FIG. 18 shows an example of processing contents by the infrared detection device 10 according to the first embodiment of the present invention. FIG. 18 describes a sensor output processing method for processing the sensor output. The infrared sensor 20 detects infrared rays. A photocurrent I is generated according to the intensity of infrared rays (step S101). The infrared sensor 20 may be configured to carry an electric current due to the difference between the temperature of the background and the temperature of the object.

The integration time control unit 160 acquires an initial value of the number of repetitions in the integration unit 110 (step S102). The number of repetitions is the number of repetitions of integration and reset of the integrated value during the data update period. The initial value of the number of repetitions may be stored in advance in a storage unit such as a memory. Further, the integration time control unit 160 may determine the initial value of the number of repetitions based on the information about the impedance of the infrared sensor 20.

The integrating unit 110 integrates the photocurrent I, which is a signal output from the infrared sensor 20 (step S103). Step S103 corresponds to an integration step of integrating the signal from the infrared sensor 20. The integrator 110 converts the input photocurrent I into a voltage and outputs the integrator signal 31. The sample hold unit 120 samples the voltage value 32 at the apex of the integration signal 31 (step S104). The ADC unit 130 may convert the integrated signal 31 sample-held by the sample-hold unit 120 into a digital signal (step S105). However, the process of step S104 may be omitted.

The integration unit 110 repeats the integration and the reset of the integrated value during the data update period over the number of repetitions determined by the integration time control unit 160. Specifically, if the number of times the integration and the reset of the integrated value are executed has not reached the number of repetitions (step S106: NO), the process returns to step S103. When the integrating unit 110 executes the integration and the reset of the integrated value over the number of repetitions (step S106: YES), the logical operation unit 140 may calculate the average of the integrated values executed over the number of repetitions (step S107). The processing device 100 of this example uses the calculated average as the target signal. However, the target signal is not limited to the calculated average. The target signal may be a signal obtained from the integration signal 31 which is the output of the integration unit 110.

The comparison unit 180 compares the target signal with the threshold value. When the target signal is equal to or greater than the threshold value (step S108: YES), the comparison unit 180 may determine that the human body exists in the detection region (step S109). If the target signal is less than the threshold value (step S108: NO), it is not determined that the human body exists in the detection region.

The impedance measuring unit 190 measures information about the impedance of the infrared sensor 20 (step S110). The integration time control unit 160 determines a new number of times the integration and the reset of the integration value are repeated by the integration unit 110 within the next data update period based on the information about the impedance measured by the impedance measurement unit 190 ( Step S111). The integration time control unit 160 reduces the number of repetitions as the impedance of the infrared sensor 20 increases. As the number of repetitions decreases, the integration time, which is the sum of a plurality of integration intervals per unit time (for example, a data update period), becomes shorter. The process of step S111 corresponds to a step of acquiring information about the temperature at the location of the infrared sensor 20 and controlling so that the higher the impedance, the shorter the integration time per unit time in the integration step (step S104).

The impedance measurement step (step S110) and the repetition number determination step (step S111) may be executed before the step of repeating the integration and the resetting of the integrated value (steps S103 to S105).

The process returns to step S103, and the next data update period begins. The processing apparatus 100 executes the processing of step S103 or less by using the number of repetitions determined by the integration time control unit 160 based on the information about the impedance. In step S103, the integration time by the integration unit 110 becomes shorter as the impedance of the infrared sensor 20 increases. Therefore, according to this example, the higher the impedance of the infrared sensor 20, the shorter the integration time in the integration stage. Therefore, the current consumption can be reduced.

FIG. 19 shows an example of the configuration of the infrared detection device 10 according to the second embodiment of the present invention. The infrared detection device 10 of this example includes an impedance measuring unit 190 and a temperature measuring unit 150.

The temperature measuring unit 150 measures the temperature at the location of the infrared sensor 20. The temperature measuring unit 150 is, for example, a resistance temperature detector, a thermistor, a thermocouple, or an IC temperature sensor. The temperature measuring unit 150 may measure a physical quantity as information related to temperature. Resistance temperature detectors and thermistors measure resistance values that change with temperature. Thermocouples measure thermoelectromotive forces that change with temperature. The temperature measuring unit 150 may be arranged adjacent to the sensor element 22.

In this example, the processing device 300 has a built-in temperature measuring unit 150. However, the temperature measuring unit 150 may be provided outside the processing device 300. In this case, the processing device 300 acquires information about the temperature at the location of the infrared sensor 20 from the external temperature measuring unit 150. The integration time control unit 160 of this example acquires both information on the impedance of the infrared sensor 20 and information on the temperature at the location of the infrared sensor 20. The integration time control unit 160 controls the integration time in the integration unit 110 based on both acquired information.

The integration time control unit 160 may acquire information about the temperature from the temperature measurement unit 150. The integration time control unit 160 controls so that the higher the impedance of the infrared sensor 20, the shorter the integration time per unit time by the integration unit 110, and the lower the temperature at the location of the infrared sensor 20, the lower the unit time by the integration unit 110. The integration unit 110 is controlled so as to shorten the integration time per unit.

The threshold control unit 170 of this example acquires information about the temperature at the location of the infrared sensor 20 and controls the threshold value input to the comparison unit 180 based on the acquired information. The threshold value may be a human sensation threshold value for determining whether or not a human body exists in the detection region. The threshold control unit 170 may acquire information about the temperature from the temperature measurement unit 150. The threshold value control unit 170 may control the threshold value to be higher as the temperature at the location of the infrared sensor 20 is lower. The threshold voltage controlled according to the temperature is input to the input end of the comparison unit 180. The threshold control unit 170 may be realized by a control logic circuit, a microcomputer, or the like.

When the output signal of the infrared sensor 20 is buried in noise, the infrared detection device 10 cannot detect the human body in the detection region. That is, when the signal-to-noise ratio (S / N ratio: signal (S) / noise (N)) becomes small, the infrared detection device 10 cannot detect the human body in the detection region. Therefore, it is necessary to suppress the noise to a level that can be distinguished from the output of the infrared sensor 20. Specifically, the processing device 300 of this example lengthens the integration time to reduce noise. When the output signal of the infrared sensor 20 becomes large, the condition of a desired signal-to-noise ratio is satisfied without necessarily increasing the integration time.

As the output signal of the infrared sensor 20 becomes larger, the permissible noise specifications (noise specifications) can be increased. Assuming that the allowable noise specification is Nspec and the noise when the predetermined integration interval (integration time) is executed once is N1, the minimum number of integrations num required to satisfy the noise specification Nspec is described above. As shown, it is given by Equation 4.

In the infrared sensor 20, the larger the temperature difference between the temperature of the infrared sensor 20 itself and the temperature of the object to be detected, the larger the output signal. When the object is a homeothermic animal such as the human body, the temperature of the object is less dependent on the temperature of the place than other objects. On the other hand, the temperature of the infrared sensor 20 is the same as the temperature of the place of the infrared sensor 20. Therefore, the output signal (S) from the infrared sensor 20 becomes smaller as the air temperature rises and approaches the temperature of the human body. The assumed operating temperature (recommended temperature) of the infrared sensor 20 when used as a motion sensor may be 0 ° C. or higher and 35 ° C. or lower.

As the temperature at the location of the infrared sensor 20 decreases, the output signal (S) of the infrared sensor 20 increases, so that the permissible noise specification Nspec can be increased. The temperature and the noise specification Nspec may have a proportional relationship. In the above equation 4, as the noise specification Nspec increases, the minimum number of integrations required to satisfy the noise specification Nspec, that is, the number of repetitions of the integration and the reset of the integrated value per data update period should be reduced. Can be done. Therefore, the integration time control unit 160 shortens the integration time, which is the sum of the intervals of a plurality of integrations per unit time (for example, the data update period) by the integration unit 110, as the temperature at the location of the infrared sensor 20 becomes lower. Control. As described with reference to FIG. 8, as the integration time becomes shorter, the current consumption of the integration unit 110 can be reduced.

According to this example, the current consumption is reduced by considering not only the change in noise N1 caused by the change in the impedance of the infrared sensor 20 but also the change in the signal S caused by the change in the temperature at the location of the infrared sensor 20. Is planned. The impedance measuring unit may have a configuration of an impedance measuring unit 190 that measures the voltage between both ends of the infrared sensor 20 as information on impedance, and measures the temperature at the location of the infrared sensor 20 as information on impedance. The impedance measuring unit 390 may be configured. Since the impedance measuring unit 390 measures the temperature at the location of the infrared sensor 20, it may also have the function of the temperature measuring unit 150. The measurement result of the temperature at the location of the infrared sensor 20 is used for the evaluation of the noise N1 and the evaluation of the noise specification Nspec, and enhances the effect of reducing the current consumption.

FIG. 20 shows an example of processing contents by the infrared detection device 10 according to the second embodiment of the present invention. FIG. 20 describes a sensor output processing method for processing the output of a sensor that detects infrared rays. Step S201 and step S202 are the same as steps S101 and S102 in the infrared detection device 10 of the first embodiment shown in FIG. Therefore, the repeated description will be omitted.

The threshold control unit 170 acquires the initial value of the threshold value input to the comparison unit 180 (step S203). The initial value of the threshold value may be stored in advance in a storage unit such as a memory. Further, the threshold value control unit 170 may determine the initial value of the threshold value based on the temperature information of the location of the infrared sensor 20. The order of steps S202 and S203 is not limited to this case. The processes of step S202 and step S203 may be executed in parallel. The process from step S204 to step S211 is the same as the process from step S103 to step S110 described in FIG.

The impedance measuring unit 190 measures information about the impedance of the infrared sensor 20 (step S211). The temperature measuring unit 150 measures information about the temperature at the location of the infrared sensor 20 (step S212). The processing order of steps S211 and S212 is not limited to this case. The process of step S211 and the process of step S212 may be executed in parallel.

The integration time control unit 160 integrates by the integration unit 110 within the next data update period based on the information about the impedance measured by the impedance measurement unit 190 and the information about the temperature measured by the temperature measurement unit 150. A new number of times of repeating the reset of the integral value is determined (step S213). The integration time control unit 160 may reduce the number of repetitions as the temperature at the location of the infrared sensor 20 is lower. Further, the integration time control unit 160 may reduce the number of repetitions as the impedance of the infrared sensor 20 increases. As the number of repetitions decreases, the integration time, which is the sum of a plurality of integration intervals per unit time (for example, a data update period), becomes shorter.

In the process of step S213, information on the impedance of the infrared sensor 20 and information on the temperature of the infrared sensor 20 are acquired, and the higher the impedance of the infrared sensor 20, the shorter the integration time per unit time by the integrating unit 110. In addition to controlling the infrared rays, the lower the temperature of the place, the shorter the integration time per unit time by the integration unit 110.

The threshold control unit 170 determines a new threshold value to be used by the comparison unit within the next data update period based on the information about the temperature measured by the temperature measurement unit 150 (step S214). The impedance measurement step (step S211), the temperature measurement step (step S212), the repetition number determination step (step S213), and the threshold value determination step (step S214) are steps in which integration and resetting of the integrated value are repeated (step). It may be executed before step S204) from S204, or may be executed in parallel.

The process returns to step S204, and the next data update period begins. The processing device 300 executes the processing of step S204 or less by using the number of repetitions and the threshold value determined by the integration time control unit 160 and the threshold value control unit 170. In step S204, the integration time by the integrating unit 110 decreases as the impedance of the infrared sensor 20 increases, and decreases as the temperature at the location of the infrared sensor 20 decreases. The threshold value that the comparison unit 180 compares with the target signal in step S209 becomes higher as the temperature at the location of the infrared sensor 20 is lower.

Therefore, according to this example, the higher the impedance of the infrared sensor 20, the shorter the integration time in the integration stage, and the lower the temperature at the location of the infrared sensor 20, the shorter the integration time in the integration stage. Therefore, the current consumption can be reduced. When the temperature of the place of the infrared sensor 20 becomes low, even if the noise becomes large, the output signal (S) of the infrared sensor 20 also becomes large. Therefore, the S / N ratio should be maintained within a predetermined range. Can be done.

In the above description, the case where the threshold value control unit 170 controls the threshold value input to the comparison unit 180 has been described, but the processing device 300 is not limited to this case. Depending on the relationship between noise and the threshold value, it may not be necessary to control the temperature of the threshold value by the threshold value control unit 170. In this case, the threshold control unit 170 is omitted.

The processing device 100 is also used for sensors other than the infrared sensor. In particular, it is suitably used for a sensor connected to a transimpedance amplifier. The processing device 100 acquires information on the integration unit 110 that integrates the signal from the sensor and the impedance of the sensor, and controls so that the higher the impedance of the sensor, the shorter the integration time per unit time by the integration unit 110. As long as the integration time control unit 160 is provided, the configuration is not limited to the above-mentioned configuration, and various circuit configurations can be added or omitted. Further, as long as the integrating unit 110 integrates the signal from the sensor, the circuit configuration is not limited.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various changes or improvements can be made to the above embodiments. It is clear from the description of the claims that such modified or improved forms may also be included in the technical scope of the present invention.

The order of execution of each process such as operation, procedure, step, and step in the device, system, program, and method shown in the claims, specification, and drawings is particularly "before" and "prior to". It should be noted that it can be realized in any order unless the output of the previous process is used in the subsequent process. Even if the scope of claims, the specification, and the operation flow in the drawings are explained using "first", "next", etc. for convenience, it means that it is essential to carry out in this order. It's not a thing.

10 ... Infrared detector, 11 ... Infrared detector, 12 ... External terminal, 20 ... Infrared sensor, 22 ... Sensor element, 31 ... Integrated signal, 32 ... Voltage value, 100 ... Processing device, 110 ... Integrator, 112 ... Op amp, 113 ... Capacitor, 114 ... Capacitor, 115 ... Input terminal, 120 ... Sample hold, 122 ... Op amp, 123 ... Capacitor, 124 ... Capacitor, 125・ ・ 1st switch, 126 ・ ・ Capacitor for grounding 127 ・ ・ 2nd switch, 130 ・ ・ ADC unit, 140 ・ ・ Logic calculation unit, 150 ・ ・ Temperature measurement unit, 160 ・ ・ Integration time control unit, 170 ・ ・・ Threshold control unit, 180 ・ ・ Comparison unit, 190 ・ ・ Impacitor measurement unit, 192 ・ ・ Constant current source, 193 ・ ・ One end, 194 ・ ・ Other end 195 ・ ・ Switch, 196 ・ ・ Switch, 200 ・ ・ Processing Device, 210 ... integration unit, 220 ... sample hold unit, 230 ... ADC unit, 240 ... logic calculation unit, 260 ... integration time control unit, 270 ... threshold control unit, 300 ... processing device, 390・ ・ Impacitor measurement unit, 392 ・ ・ Constant current source, 394 ・ ・ Transistor element, 395 ・ ・ Emitter electrode, 396 ・ ・ Base electrode, 397 ・ ・ Collector electrode

Claims (9)

It is a sensor output processing device that processes the output of the sensor.
An integrator that integrates the signal from the sensor,
An integration time control unit that acquires information on the impedance of the sensor and controls that the higher the impedance of the sensor, the shorter the integration time per unit time by the integration unit.
A sensor output processing device comprising. The sensor output processing device according to claim 1, further comprising an impedance measuring unit for measuring the information regarding the impedance. The impedance measuring unit
The sensor output processing device according to claim 2, further comprising a voltage measuring unit that measures a voltage between both ends of the sensor as the information regarding the impedance in a state where a constant current flows through the sensor. The impedance measuring unit
The sensor output processing apparatus according to claim 2, further comprising a temperature measuring unit that measures the temperature at the location of the sensor as the information regarding the impedance. Within a predetermined data update period
The integrating unit repeatedly integrates the signal and resets the value of the integration over a plurality of times.
The impedance measuring unit measures the information about the impedance and
The second aspect of the present invention, wherein the integration time control unit determines a new number of times the integration and the reset of the value of the integration are repeated by the integration unit within the next data update period based on the information regarding the impedance. Sensor output processing device. The integration time control unit acquires both the information about the impedance and the information about the temperature at the location of the sensor.
The higher the impedance of the sensor, the shorter the integration time per unit time by the integration unit, and the lower the temperature at the location, the shorter the integration time per unit time by the integration unit. do,
The sensor output processing device according to any one of claims 1 to 5. A comparison unit that compares the target signal obtained from the output signal from the integration unit with the threshold value, and
The sensor output processing device according to claim 6, further comprising a threshold control unit that controls the threshold value to be raised as the temperature at the location is lower. The sensor output processing device according to any one of claims 1 to 7, further comprising the sensor. It is a sensor output processing method that processes the output of the sensor.
The stage of integrating the signal from the sensor and
A step of acquiring information on the impedance of the sensor and controlling so that the higher the impedance of the sensor, the shorter the integration time per unit time in the integration step.
A sensor output processing method comprising.

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