JPH08178750A - Infrared array sensor - Google Patents

Abstract

PURPOSE: To obtain an infrared array sensor for detecting the heat source information accurately regardless of the ambient temperature of the sensor. CONSTITUTION: The infrared array sensor comprises an infrared detecting section 1 where elements for detecting the infrared rays from a heat source are arranged in array, a chopper mechanism 2 for interrupting the infrared rays impinging on the infrared detecting section 1 periodically, an analog circuit 8 for subjecting a detection signal from the infrared detection element to impedance conversion and amplifying the converted signal, and a section 4 for extracting an output signal from the analog circuit 8 having a level exceeding a threshold value and deciding that a heat source is detected, wherein a threshold varying means 9 is provided at the deciding section. A thermistor 5 detects the inner temperature of the sensor and the threshold varying means 9 regulates the threshold level linearly to decrease as the inner temperature of sensor increases but to increase as the inner temperature of sensor decreases. An infrared signal is then extracted selectively from a human body, for example, and the heat source information thereof is detected and investigated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared array sensor for detecting the position of an infrared heat source such as a human body and the moving direction of the heat source position.

[0002]

2. Description of the Related Art Radiant light (infrared rays) from an infrared heat source such as a human body is detected by an infrared sensor. The detection of the heat source by the infrared sensor is a passive method such as detecting the radiant energy of the radiant light naturally emitted from the heat source without irradiating the human body to be measured with any light. It is widely applied because it has no adverse effect on the human body and can detect a heat source at night without lighting.

FIG. 7 is a block diagram showing the configuration of a pyroelectric infrared array sensor which is a type of infrared sensor. As shown in the figure, the infrared array sensor
The infrared detection unit 1, the analog circuit 8, and the determination unit 4 are included in the infrared detection unit 1.
A chopper mechanism 2 that intermittently blocks infrared rays that enter the infrared detector 1 is provided.

As shown in FIG. 6, for example, the infrared detecting section 1 is formed by arranging infrared detecting elements 3 for detecting infrared rays from a heat source in an array. Each infrared detection element 3 corresponds to each area 11 of the target area 6 to be detected by the heat source in a 1: 1 relationship. Further, an infrared lens 18 (not shown in FIG. 7) is provided between the target area 6 and the infrared detector 1, and, for example, infrared rays from the area 11 of A ′ of the target area 6 are detected. Is collected by the infrared lens 18 and detected by the infrared detecting element 3 (3A) of the infrared detecting section 1. Similarly, the infrared ray from the area 11B is detected by the infrared detecting element 3B. Infrared rays from the area 11C are detected by the infrared detecting element 3C.

As shown in FIG. 7, the chopper mechanism 2
For example, by periodically rotating as shown by an arrow C in the figure, the radiant energy of infrared rays incident on the infrared detecting section 1 is periodically cut off. By doing so, The radiant energy incident on the infrared detector 1 is forcibly modulated. And thereby, the infrared detector 1
A signal obtained by converting the radiant intensity of the radiant energy into a relative value of current is generated in each infrared detection element 3 and is applied to the analog circuit 8 as an infrared detection signal.

Since the magnitude (level) of the detection signal detected by each infrared detection element 3 is proportional to the temperature of the heat source, as shown in FIG. When the human body 7 and the window 13 are present, normally,
The detection signal from the human body 7 whose temperature is higher than that of the window 13 is the window 13
The signal level becomes higher than the detection signal from.

The analog circuit 8 is a circuit for impedance-converting and amplifying the detection signal of the infrared detecting element. The current applied from each infrared detecting element 3 of the infrared detecting section 1 is impedance-converted and amplified, For example, it is converted into a voltage in the range of 0 to 5 V and this voltage signal is applied to the determination unit 4.

The determination unit 4 extracts the signal of the level exceeding the threshold value from the signals applied from the analog circuit 8 to detect and determine the heat source information. The magnitude of the voltage signal applied from the analog circuit 8 to the determination unit 4 is proportional to the temperature of the heat source in order to correspond to the detection signal level of each infrared detection element 3, and, for example, as shown in FIG. The signal from the human body 7 which is a heat source having a high temperature (the signal from the infrared detection signal 3B) is higher in signal level than the signal from the window 13 which is a heat source having a low temperature (the signal from the infrared detection signal 3C). Grows larger. Therefore, the determination unit 4 sets, for example, a signal level due to radiation around 30 ° C. as a threshold value, and extracts only a voltage signal that exceeds the threshold value to cut most of the background of the window and the like, and the target region 6 The position of the human body inside is detected and judged as the heat source information.

In this way, the determination unit 4 extracts the signal of the level exceeding the threshold value from the voltage signal applied from the analog circuit 8 to detect and determine the heat source information,
For example, as described above, when the human body 7 as a heat source and the window 13 are present in the target area 6, as shown in FIG.
The position and size of the human body 7 can be selectively detected as heat source information.

[0010]

By the way, recently, such an infrared array sensor is installed in an air conditioner or the like, and the temperature of the air conditioner is adjusted based on the heat source information detected by the infrared array sensor.

However, especially when the infrared array sensor is attached to an air conditioner or the like, the temperature inside the infrared array sensor often rises due to the heat generated by the circuit on the air conditioner body side, and then the radiation from the chopper mechanism 2 occurs. The energy rises and the difference from the radiant energy from the heat source in the target area 6 is reduced, and as a result, the detection signal level from the infrared detection element 3 of the infrared detection unit 1 is lowered overall, and As shown in (a), the analog circuit 8 to the determination unit 4
The level of the voltage signal applied to all of them becomes lower than the threshold value set in the determination unit 4, and the human body 7 exists in the infrared detection target region 6 as shown in FIGS. However, there is a problem that the human body 7 cannot be detected as shown in FIG.

On the contrary, when the temperature around the infrared array sensor is low, the detection signal level of the infrared detecting element 3 of the infrared detecting section 1 rises as a whole, as shown in FIG. 9 (b). In addition, since the level of the voltage signal applied from the analog circuit 8 to the determination unit 4 rises and the signal level of the window 13 also exceeds the threshold value, the background of the window 13 and the human body 7 cannot be distinguished. As shown in (b) of FIG. 10, there is a problem that the window 13 and the human body 7 are detected together as heat source information.

As described above, since it is not possible to obtain accurate heat source information from the infrared array sensor when the ambient temperature of the infrared array sensor is high or low, the infrared array sensor is conventionally used, for example. It has been difficult for the air conditioner and the like to be accurately controlled based on the heat source information detected by the sensor.

The present invention has been made to solve the above-mentioned conventional problems, and an object thereof is to accurately detect heat source information in a detection target region when the ambient temperature is high or low. It is to provide an infrared array sensor that can be used.

[0015]

In order to achieve the above object, the present invention is constructed as follows. That is, the first aspect of the present invention intermittently interrupts the infrared detecting section formed by arranging the infrared detecting elements for detecting the infrared rays from the heat source in an array, and the infrared entering the infrared detecting section. A chopper mechanism, an analog circuit that impedance-converts and amplifies the detection signal of each infrared detection element, and a signal of a level exceeding a threshold value among signals applied from the analog circuit is extracted to detect and determine heat source information. An infrared array sensor having a determination unit, wherein a temperature detection unit for detecting the temperature inside the sensor is provided, and the determination unit has the above-mentioned value as the detection temperature increases in accordance with the detection temperature of the temperature detection unit. It is characterized in that threshold value changing means is provided which lowers the threshold value and adjusts the threshold value to be higher as the detected temperature becomes lower.

The second aspect of the present invention is an infrared detecting section comprising infrared detecting elements arranged in an array for detecting infrared rays from a heat source, and the infrared rays incident on the infrared detecting section are intermittent. To a heat source information by extracting a signal of a level exceeding a threshold value from the signals applied from the analog circuit An infrared array sensor having a determination unit for detecting and determining, the temperature detection unit for detecting the temperature inside the sensor is provided, and the determination unit has a high detection temperature according to the detection temperature of the temperature detection unit. Level changing means for adjusting the signal level applied from the analog circuit to a higher level and adjusting the signal level applied from the analog circuit to a lower level as the detected temperature decreases. It is configured as characterized in that there.

[0017]

In the present invention having the above-mentioned structure, the temperature detecting section detects the temperature inside the sensor, and the detected temperature is added to the judging section.

Generally, when the temperature inside the sensor becomes high,
The signal level detected by the infrared detection element and applied from the analog circuit to the judgment section decreases, and conversely, when the temperature inside the sensor becomes low, it is detected by the infrared detection element and added from the analog circuit to the judgment section. Although the signal level rises, in the first aspect of the invention, according to the temperature detected by the temperature detector, the threshold is lowered as the detected temperature becomes higher, and the threshold is raised as the detected temperature becomes lower. By the threshold varying means of the determination unit, only the signal level of the heat source desired to be detected as the heat source information exceeds the threshold value, and the signal level is selectively extracted and detected as the heat source information.

According to the second aspect of the present invention, according to the temperature detected by the temperature detector, the signal level applied from the analog circuit is increased as the detected temperature becomes higher and the analog circuit becomes lower as the detected temperature becomes lower. By adjusting the level of the signal added by the control unit by the level changing means of the determination unit, only the level of the signal desired to be extracted as the heat source information exceeds the threshold value as in the first aspect of the invention. Are selectively extracted as heat source information.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the present embodiment, the same reference numerals will be given to the same names as those in the conventional example, and the duplicated description will be omitted.
FIG. 1 is a block diagram showing a main configuration of an infrared array sensor according to a first embodiment of the present invention. Similar to the conventional example, the present example is also a pyroelectric infrared array sensor, and the characteristic of the present example different from the conventional example is that the thermistor 5 is provided as a temperature detecting unit for detecting the temperature inside the sensor. The determination unit 4 is provided with a threshold variable unit 9 that adjusts the threshold value as the detected temperature becomes higher and the threshold value as the detected temperature becomes lower, according to the detected temperature of the thermistor 5. It is that you are.

The variable adjustment of the threshold value by the threshold value changing means 9 is performed as follows.
Based on the temperature detected by the thermistor 5, the operation is performed according to the following equation (1). By doing so, the threshold variable means 9 linearly changes the threshold according to the temperature detected by the thermistor 5. Let

V _th = β-α · V _t (1)

Note that V _th in equation (1) is a threshold for signal processing,
V _t is the signal level of the thermistor 5, and α and β are arbitrary constants.

This embodiment is constructed as described above,
In the present embodiment as well, as in the conventional example, the detection signal of each infrared detection element 3 of the infrared detection unit 1 is impedance-converted and amplified by the analog circuit 8 and added to the determination unit 4. Simultaneously with the operation, the temperature inside the sensor is detected by the thermistor 5 and added to the analog circuit 8, and the analog circuit 8 performs impedance conversion of this temperature detection signal. Then, the converted voltage signal is applied to the determination unit 4, and the threshold varying means 9 of the determination unit 4 linearly lowers the threshold value as the temperature detected by the thermistor 5 increases according to the equation (1). Is also done,
An operation of linearly increasing the threshold value as the detected temperature decreases is performed.

Specifically, as shown in FIG. 2 (a),
When the temperature inside the infrared array sensor rises due to an increase in the ambient temperature or the like, the signal level applied from the analog circuit 8 to the determination unit 4 is lowered overall. In accordance with the equation (1), the threshold is variably adjusted to a low value, for example, the value of B in the figure, according to the temperature detected by the thermistor 5.
Then, as is clear from the figure, only the signal from the human body 7 exceeds the threshold value and is extracted, and only the infrared ray from the human body 7 is detected and judged as the heat source information, as shown in FIG. Such a detection result can be obtained.

For comparison with the conventional example, FIG. 2A shows the threshold value preset in the determination unit 4 of the conventional infrared array sensor by the value of A in the figure. As shown in the figure, when the threshold value is A, both the signal from the human body 7 and the signal from the background (such as the window 13) are lower than the threshold value A, and the determination unit 4 performs the detection determination of the heat source information. It turns out that you can't.

On the other hand, contrary to the above, when the ambient temperature of the infrared array sensor is low and the temperature inside the sensor is low,
As shown in (b) of FIG. 2, the detection signal level of infrared rays rises as a whole, but in such a case, the threshold value changing means 9 sets the threshold value to the detection temperature of the thermistor 5 according to the equation (1). Accordingly, the value of C is adjusted higher. Then, only the signal from the human body 7 exceeds the threshold, and the human body 7
Only signals from are extracted, and the detection result as shown in FIG. 5 is obtained in the same manner as above.

FIG. 2B also shows the threshold value set in the conventional infrared array sensor by the value A in the figure. When the threshold value is A, the signal from the human body 7 and the background are shown. Both the signal from (window 13 etc.) exceeds the threshold A and the human body 7
It cannot be distinguished from the background, and therefore, when the threshold value is A, both the human body 7 and the background are erroneously detected and determined as heat source information.

Since the variable adjustment of the threshold value by the threshold value changing means 9 of this embodiment is performed linearly, for example, when the inside of the sensor detected by the thermistor 5 gradually rises, The threshold value is gradually changed as shown in FIG. 2C according to the detected temperature. That is, even if the level of the infrared detection signal gradually changes according to the temperature change inside the sensor, the threshold value is variably adjusted finely in response to the change, whereby the determination unit 4
The detection determination operation of the heat source information by is flexibly performed according to the temperature change inside the sensor.

According to this embodiment, according to the above operation, according to the temperature inside the sensor detected by the thermistor 5,
The threshold varying means 9 linearly lowers the threshold as the temperature detected by the thermistor 5 increases, and linearly variably adjusts the threshold higher as the detected temperature lowers. Since it is possible to obtain only the signal from the human body and obtain only the signal from the human body as the heat source information, it is possible to obtain accurate heat source information regardless of whether the ambient temperature of the infrared array sensor is low or high. If this infrared array sensor is installed in an air conditioner or the like, it is possible to prompt the air conditioner control operation to be performed accurately based on the heat source information of the infrared array sensor.

FIG. 3 is a block diagram showing the configuration of the essential parts of the second embodiment of the infrared array sensor according to the present invention. This embodiment is different from the first embodiment in that the judging section 4 is provided with a level changing means 10 instead of the threshold changing means 9. The level varying means 10 raises the signal level of the infrared detection signal applied from the analog circuit 8 as the detected temperature rises and the analog circuit as the detected temperature falls, depending on the detected temperature of the thermistor 5. The signal level of the infrared detection signal added from 8 is variably adjusted low.

The signal level is variably adjusted by the level varying means 10 based on the temperature detected by the thermistor 5 in accordance with the following equation (2). The signal level from the detection element 3 is always kept at a constant level around the threshold value.

V _h ′ = V _h + γ · (V _t −V _t0 ) ... (2)

Note that V _{h in} the equation (2) is the level changing means 10
Is the signal level before level adjustment, and V _h ′ is the signal level after level adjustment. Further, V _t is a signal level of the thermistor 5, V _t0 is a signal level of the thermistor 5 when the sensor internal temperature is 25 ° C., and γ is an arbitrary constant.

The present embodiment is configured as described above,
For example, as shown in FIG. 4A, when the temperature inside the sensor is high and the temperature detected by the thermistor 5 is high,
Since the level of the infrared detection signal is generally low, the signal level of the infrared detection signal is generally increased according to the detection temperature of the thermistor 5, so that only the infrared detection signal from the human body exceeds the threshold value. Conversely, when the temperature inside the sensor is low and the detection signal detected by the thermistor 5 is low, the level of the infrared detection signal is generally high.
(B), the level of the infrared detection signal applied from the analog circuit 8 to the determination unit 4 is entirely lowered so that only the infrared detection signal from the human body 7 exceeds the threshold value. To do.

Then, like the first embodiment,
Only the infrared detection signal from the human body 7 is extracted by the determination unit 4, only the infrared light from the human body 7 is detected and determined as the heat source information, and the detection result as shown in FIG. 5 is obtained.

Further, the variable adjustment of the signal level is linearly performed by the level varying means 10, and therefore the detection judgment of the heat source information according to the present embodiment is flexibly performed as in the first embodiment. The same effect as that of the above embodiment is obtained.

The present invention is not limited to the above-mentioned embodiment, and various embodiments can be adopted. For example, in the above embodiment, the variable adjustment of the threshold value by the threshold value changing means 9 is
Although it was performed according to the above equation (1), the method of variably adjusting the threshold value by the threshold value varying means 9 is not particularly limited,
It is set appropriately.

Further, in the second embodiment, the signal level is variably adjusted by the level varying means 10 according to the equation (2), but the method of variably adjusting the signal level by the level varying means 10 is as follows. There is no particular limitation, and it is set appropriately.

Further, in the above-described embodiment, the judging section 4 is configured to have either one of the threshold value changing means 9 and the level changing means 10, but the judging section 4 has the threshold value changing means 9 and the level changing means 9. A configuration having both the variable means 10 may be used.

Further, in the above embodiments, the human body 7 is used.
An example of detecting and determining infrared rays radiated from the heat source information has been described, but the heat source information to be detected and determined by the determination unit 4 is set variously.

Further, in the above embodiment, the chopper mechanism 2
Is designed to block infrared rays at regular intervals by rotating at a constant speed, thereby blocking infrared rays incident on the infrared detecting section 1. However, the chopper mechanism 2 moves up and down at a constant speed, for example. By doing so, the infrared rays incident on the infrared detecting section 1 may be blocked, and the configuration of the chopper mechanism 2 is appropriately set.

Further, the number of the infrared detecting elements 3 arranged in the infrared detecting section 1 is not particularly limited and may be set appropriately, and the infrared detecting elements 3 are the same as those in the above embodiment. The adjacent infrared detection elements 3 do not necessarily contact each other and are arranged in a two-dimensional array. For example, the adjacent infrared detection elements 3 may be arranged with a space therebetween. Alternatively, the infrared detection elements 3 may be arranged in a one-dimensional array.

Further, although the infrared array sensor is a pyroelectric infrared sensor in the above embodiment, the infrared array sensor may be another infrared sensor such as a thermopile or a bolometer.

[0045]

According to the first aspect of the invention, according to the temperature detected inside the sensor detected by the temperature detecting section, the threshold varying means increases the detected temperature and the reference of signal extraction by the judging section is increased. In order to lower the threshold value that becomes, and variably adjust the threshold value higher as the detected temperature becomes lower,
When the temperature inside the sensor rises and the signal level for infrared detection is decreasing, the threshold value is also lowered, and it becomes possible to detect the signal of the level exceeding the threshold value and detect the heat source information, and vice versa. In addition, when the temperature inside the sensor becomes low and the signal level of infrared detection becomes high overall, the threshold value is also raised and only the signal to be extracted as heat source information (for example, infrared signal from the human body) is selectively extracted. However, the heat source information can be detected and judged.

Further, according to the second aspect of the present invention, as the detection temperature inside the sensor detected by the temperature detection unit increases, the signal level of infrared detection added from the analog circuit to the determination unit is increased to detect the detection temperature. As the signal level decreases, the temperature inside the sensor rises in order to adjust the signal level to a low level, and even if the infrared detection signal level is low overall, the sensor internal temperature is low and the infrared detection signal level increases. Even if it becomes higher overall, by correcting and adjusting these levels to a constant signal level around the threshold value, similarly to the first invention, only the signal to be extracted as heat source information is selectively extracted, and The heat source information can be obtained.

Therefore, according to the present invention, when the temperature around the place where the infrared array sensor is installed is high or low and the temperature inside the sensor rises or falls, accurate heat source information is obtained. It is possible to effectively solve the problem of the conventional infrared array sensor that it is not possible to obtain, and to always accurately detect the heat source information without making a misjudgment due to the temperature change around the infrared array sensor. It is possible to obtain an excellent infrared array sensor capable of

[Brief description of drawings]

FIG. 1 is a main part configuration diagram showing a first embodiment of an infrared array sensor according to the present invention.

FIG. 2 is a graph showing the relationship between the infrared detection signal detected by the infrared array sensor of the first embodiment and the threshold value adjusted by the threshold value changing means.

FIG. 3 is a main part configuration diagram showing a second embodiment of an infrared array sensor according to the present invention.

FIG. 4 is a graph showing signal levels of an infrared detection signal detected by the infrared array sensor of the second embodiment before and after adjustment by a level varying means.

FIG. 5 is an explanatory diagram showing an example of an infrared detection target area 6 and correct heat source information of a human body 7 detected by an infrared array sensor.

FIG. 6 is an explanatory diagram showing an arrangement state of infrared detection elements 3 in an infrared detection section of the infrared array sensor and a target area 6 to be detected by the infrared array sensor.

FIG. 7 is an explanatory diagram showing an example of a conventional infrared array sensor.

FIG. 8 is a graph showing a relationship between an example of an infrared detection signal from a conventional infrared array sensor and a threshold value.

FIG. 9 is a graph showing a relationship between an infrared detection signal and a threshold by a conventional infrared array sensor when the ambient temperature of the sensor is high and when the ambient temperature is low.

FIG. 10 is an explanatory diagram showing heat source information detected by a conventional infrared array sensor when the ambient temperature of the sensor is high and low.

[Explanation of symbols]

 1 infrared detecting section 2 chopper mechanism 3 infrared detecting element 4 judging section 5 thermistor 8 analog circuit 9 threshold changing means 10 level changing means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location G01J 1/04 C 5/02 Q G01V 8/20 8/12

Claims (2)

[Claims] 1. An infrared detecting section comprising infrared detecting elements arranged in an array for detecting infrared rays from a heat source, and a chopper mechanism for intermittently blocking infrared rays incident on the infrared detecting section. An analog circuit that impedance-converts and amplifies the detection signal of each infrared detection element, and a determination unit that extracts a signal of a level exceeding a threshold value among signals applied from the analog circuit and detects and determines heat source information In addition, the infrared array sensor is provided with a temperature detecting section for detecting the temperature inside the sensor, and the judging section lowers the threshold value as the detected temperature increases in accordance with the detected temperature of the temperature detecting section. An infrared array sensor, further comprising threshold changing means for variably adjusting the threshold as the detected temperature becomes lower. 2. An infrared detecting section having infrared detecting elements arranged in an array for detecting infrared rays from a heat source, and a chopper mechanism for intermittently cutting off infrared rays entering the infrared detecting section. An analog circuit that impedance-converts and amplifies the detection signal of each infrared detection element, and a determination unit that extracts a signal of a level exceeding a threshold value among signals applied from the analog circuit and detects and determines heat source information In addition, the infrared array sensor is provided with a temperature detecting section for detecting the temperature inside the sensor, and the judging section adds from the analog circuit as the detected temperature rises according to the detected temperature of the temperature detecting section. And a level varying means for variably adjusting the signal level applied from the analog circuit to a lower level as the detected temperature becomes lower. Infrared array sensor.