JPH0593650A - Infrared detector - Google Patents

Abstract

PURPOSE:To save power consumption of an infrared detector by driving the chopper only when it is necessary. CONSTITUTION:A reflecting photo sensor 14 is activated when a human body detection signal from a pyroelectric infrared detecting element 5 has not been outputted for a certain time. When the sensor 14 detects coincidence of a light receiving surface of the pyroelectric infrared detecting element 5 with a window of a chopper 3, rotation of the chopper 3 by a motor 4 is stopped by a motor control circuit 7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detecting device for detecting a human body or the like.

[0002]

2. Description of the Related Art For example, a pyroelectric infrared detecting element is
Even if there is an infrared radiation source such as a human body in the detection area, if it does not move or the infrared radiation intensity does not change,
The pyroelectric infrared detection element does not generate a detection signal.

For this reason, there is a chopper system in which a chopper is rotated in front of a pyroelectric infrared detecting element to interrupt infrared rays incident on the pyroelectric infrared detecting element to generate a detection signal from the infrared detecting element. Generally adopted. In this case, the chopper constantly rotates during use of the infrared detecting device regardless of the presence or absence of infrared rays from the signal source.

[0004]

The infrared detecting device in which the chopper is constantly rotated as described above consumes a large amount of electric power because the chopper is always rotated. For this reason,
When the battery is used as a power source, the battery has a short life.

An object of the present invention is to achieve power saving by driving the chopper only when necessary.

[0006]

According to the present invention, there is provided an infrared detecting device having a chopper having a window portion and a shielding portion on a front surface of an infrared detecting element, and a driving means for rotating the chopper. When the human body detection signal from the detection element is not output for a certain period of time, a control means for stopping the rotation of the chopper by the driving means at a position where the light receiving surface of the infrared detection element and the window portion of the chopper are aligned with each other. By providing it, the above-mentioned object is achieved.

Further, in an infrared detecting device having a chopper having a window portion and a shielding portion on the front surface of the infrared detecting element, and having a driving means for rotating the chopper,
The human body detection signal from the infrared detection element is put into operation from the time when it is no longer output, and the chopper position detection means for detecting the position where the light receiving surface of the infrared detection element and the window portion of the chopper coincide, and the infrared ray. When the human body detection signal from the detection element is not output for a certain period of time, and when the chopper position detection means detects a match between the light receiving surface of the infrared detection element and the window portion of the chopper, the driving means causes the chopper to move. The above object is achieved by providing a control means for stopping the rotation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to an embodiment shown in the drawings.

In FIG. 1, reference numeral 1 is a crystal oscillation circuit, which outputs a reference clock signal. Reference numeral 2 is a frequency dividing circuit, which divides the reference clock signal output from the crystal oscillation circuit 1 into a predetermined frequency signal. In this example, an 8 Hz signal is output. A chopper 3 has a window portion 3a and a shielding portion 3b as shown in FIG. 2, is provided on the front surface of a pyroelectric infrared detection element 5 described later, and is rotatable. Reference numeral 4 is a motor that constitutes a driving means, and rotates the chopper 3. Reference numeral 5 denotes an infrared detection element, which is a pyroelectric infrared element in this example, and outputs a detection signal when infrared rays are detected. An infrared detection circuit 6 receives a detection signal from the pyroelectric infrared detection element 5 and retriggerably generates a pulse having a constant time width. This pulse width is set to a time slightly longer than the cycle of the human body detection signal generated by the rotation of the chopper 3. Reference numeral 7 is a motor control circuit which constitutes a control means and comprises an inverter 8 and AND gates 9 and 10. Reference numeral 11 is a motor drive amplifier circuit, which comprises inverters 12 and 13. Reference numeral 14 is a reflection type photo sensor which constitutes a chopper position detecting means, and is a light emitting diode 1
5 and the light receiving element 16 and the light emitting diode 15
This is for detecting the positions of the window portion 3a and the shield portion 3b of the chopper 3 depending on whether or not the light receiving element 16 detects the light. Reference numeral 17 denotes a counter, which counts the number of passages through the window portion 3a of the chopper 3 when the detection signal from the pyroelectric infrared detection element 5 disappears. In this example, Q
Set 1 and Q2 to output "1". 18
Numerals 25 to 25 are gate circuits, 21 and 24 are inverters, and 23 is a buffer.

2 and 3 show the mechanical structure of this apparatus. In FIG. 2, the same reference numerals as in FIG. 1 indicate the same elements.

Reference numeral 26 denotes a rotor of the motor 4, which rotates in the direction of arrow A. A reduction gear 27 transmits the rotation of the rotor 26 to the chopper shaft 28. Chopper 3 on the chopper shaft 28
The chopper 3 rotates in the direction of arrow B in FIG. 2 by the rotation of the rotor 26. Behind this, a pyroelectric infrared detection element 5 is provided. A light receiving window 2 is provided on the front surface of the case 30 in front of the pyroelectric infrared detecting element 5.
9 is provided to transmit infrared rays from the front surface of the case 30. A reflection type photo sensor 1 is provided inside the front surface of the case 30.
4 is fixed, and its light emitting and receiving surfaces are choppers 3.
The window part 3 of the chopper 3 as shown in FIG.
It is provided so as to be located on the boundary line between the window portion 3a and the shielding portion 3b when the light receiving window 29 is located at the center of a. Reference numeral 31 is a circuit block containing the circuit configuration of FIG.

Next, the operation will be described.

In the initial state, it is assumed that the chopper 3 is stopped at the position where the light receiving surface of the pyroelectric infrared detecting element 5 and the window portion 3b of the chopper 3 coincide with each other, that is, in the state shown in FIG. Further, it is assumed that the outputs Q1 and Q2 of the counter in FIG. 1 are both "1", the output of the inverter 21 and the output of the gate circuit 25 are held at "0", and the photosensor 14 is in the immobile state. ..

In this state, when a human body moves into the human body detection area near the case light receiving window 29 and enters, a detection signal is generated from the pyroelectric infrared detection element 5, and the infrared detection circuit 6 outputs a signal with a constant time width. Since a pulse is generated, the OR gate 22
Output becomes "1". Therefore, the AND gates 9 and 10 in the motor control circuit 7 open, the AND gates 9 and 10 output the signals from the frequency dividing circuit 2 as signals of opposite phases, and the signals are amplified by the motor drive amplifier circuit 11 to be amplified by the motor 4 And the chopper 3 rotates. Therefore, while the human body is present in the human body detection area, the infrared detection circuit 6 is retriggered and its output is held at "1".

On the other hand, since the output of the inverter 24 is "0", the AND gate 25 is closed and the reflection type photo sensor 1
4 is held in the inoperative state, and the counter 17 is held in the reset state.

That is, when a human body is present in the human body detection area, the motor 4 is driven, but the reflection type photo sensor 14 and the counter 17 do not operate either. Therefore, power is saved by not operating the reflective photosensor 14 except when necessary.

Then, when the human body moves out of the human body detection area, the pyroelectric infrared detection element 5 stops outputting the detection signal and the output of the infrared detection circuit 6 becomes "0" after a certain period of time. Then, the output of the inverter 24 becomes "1", and A
Since the output of the ND gate 25 becomes "1", the reflective photosensor 14 starts its operation, and the reset of the counter 17 is also released. At this time, the output of the OR gate 22 is held at "1" by the output "1" of the inverter 21, and the chopper 3 continues to rotate. With this rotation, a pulse is generated from the reflection type photo sensor 14, and this produces a pulse in the counter 1.
The number of passages through the window of the chopper 3 is counted. In this example, the Q1 and Q2 outputs of the count 17 are set to "1" by passing through the window portion 6 times, so at the moment when the output pulse from the gate circuit 18 rises, that is, the window portion. The output of the AND gate 20 becomes "1" and the output of the inverter 21 becomes "0" at the moment when 3a passes and the shielding portion 3b is detected.
The gate 25 is closed, the reflection-type photo sensor 14 ends its operation, and the output of the OR gate 22 becomes "0", so that the motor 4 is also stopped.

At this time, the reflection type photo sensor 14 is shown in FIG.
Since it is attached at the position shown by, the window part 3 of the chopper 3
At the moment when a passes through and the shield 3b is detected, the motor 4
Is stopped, the chopper 3 is stopped at the position shown in FIG. 2, and this is the initial state.

As shown in FIG. 4, a case 30 may be provided with a chopper operation confirmation window so that whether or not the chopper 3 is rotating can be visually recognized. In this case, since the operation can be confirmed by the difference in contrast between the shielding portion and the window portion, the shielding portion of the chopper 3 may have a check pattern as shown in FIG. 5 or a striped pattern as shown in FIG.
By applying a color scheme, the rotation visibility of the chopper can be increased without adding a special element, and the human body detection state of the pyroelectric infrared detection element can be easily confirmed depending on whether the chopper is rotating. Like

[0020]

As described in detail above, according to the present invention,
Since the chopper can be driven only when necessary, power saving can be achieved.

Further, a chopper position detecting means is provided for stopping the window part of the chopper so that the window part of the chopper coincides with the infrared element of the pyroelectric type when no one is present. It is possible to detect and save power.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of an embodiment of the present invention.

FIG. 2 is a front view of an embodiment of the present invention.

FIG. 3 is a sectional view taken along the line CC of FIG.

FIG. 4 is a front view of another embodiment of the present invention.

FIG. 5 is a front view showing another example of the chopper.

FIG. 6 is a front view showing still another example of the chopper.

[Explanation of symbols]

 3 Chopper 4 Driving Means 5 Infrared Detecting Element 7 Control Means 14 Chopper Position Detecting Means

Claims (2)

[Claims] 1. An infrared detection device comprising a chopper having a window and a shield on the front surface of the infrared detection element, and a driving means for rotating the chopper, wherein a human body detection signal from the infrared detection element is transmitted. An infrared detecting device comprising a control means for stopping the rotation of the chopper at a position where the light receiving surface of the infrared detecting element and the window of the chopper are aligned when no output is made for a certain period of time. 2. An infrared detection device comprising a chopper having a window portion and a shield portion on the front surface of the infrared detection element, and a driving means for rotating the chopper, wherein a human body detection signal from the infrared detection element is transmitted. The operation state starts from the time when the output is stopped, the chopper position detecting means for detecting the position where the light receiving surface of the infrared detecting element and the window part of the chopper coincide, and the human body detection signal from the infrared detecting element is kept for a certain time. Control means for stopping the rotation of the chopper by the driving means when no output is made and the chopper position detecting means detects a coincidence between the light receiving surface of the infrared detecting element and the window portion of the chopper. Infrared detector.