JPH11183247A - Pyroelectric infrared sensor device - Google Patents

Abstract

(57) [Problem] To provide a small, low-cost, highly reliable pyroelectric infrared sensor device with high spatial resolution. SOLUTION: An optical modulator 2 for intermittently modulating incident infrared light is provided on a front surface of a pyroelectric infrared sensor 1 provided with a plurality of light receiving portions in a line shape, and an infrared lens 3 for condensing light on the front surface. Is provided. If a liquid crystal panel is used as the light modulator 2 in the light modulator 2, the light is modulated only by applying a voltage and a chopper mechanism is not required, so that a low-cost and highly reliable infrared sensor can be provided. It is preferable that the liquid crystal has a group that absorbs infrared rays, that the liquid crystal contains a dye that absorbs infrared rays, or that the liquid crystal is a polymer-dispersed liquid crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pyroelectric infrared sensor used for temperature distribution measurement, human body detection, non-contact thermal object detection, and the like.

[0002]

2. Description of the Related Art Conventionally, there are two methods for measuring a temperature distribution in a space using infrared rays. One is a method of obtaining a temperature distribution using a two-dimensional quantum solid-state imaging infrared sensor, and the other is a method of obtaining a spatial temperature distribution using a pyroelectric sensor. The latter method is disclosed in, for example, JP-A-64-88391 and JP-A-2-1837.
The temperature distribution is obtained by using a single pyroelectric sensor and mechanically operating the pyroelectric sensor in the vertical and horizontal directions.

[0003]

Among the above two methods, the quantum type solid-state imaging infrared sensor has a problem that although the resolution is high, the device needs to be cooled, so that the device becomes large and expensive. Exists.

On the other hand, those using a pyroelectric sensor have a problem that the sensor sensitivity is low and the spatial resolution and the temperature resolution are low. In addition, a pyroelectric sensor needs a chopping mechanism to detect infrared information as an AC signal, but if it does so, it requires a motor and a driving mechanism as a drive unit for moving the chopper, resulting in high costs. In addition, there is a problem that the size cannot be reduced or durability is required.

Accordingly, an object of the present invention is to provide a small-sized, low-cost, and high-sensitivity pyroelectric infrared sensor in consideration of the problem of such a sensor.

[0006]

In order to achieve the above object, a pyroelectric infrared sensor device of the present invention intermittently intermittently transmits a plurality of pyroelectric infrared sensors and infrared light incident on the pyroelectric infrared sensor. An optical modulator for modulating light is provided, and the optical modulator has a configuration having a liquid crystal panel as a means for modulating light. According to this configuration, the spatial resolution is improved by providing a plurality of pyroelectric elements, and further, by installing an optical modulator made of liquid crystal on the front surface of the pyroelectric element, a chopper and a driving device are unnecessary and a small size is achieved. Since there is no moving part such as a motor, a pyroelectric infrared sensor with low cost and high reliability can be provided.

In the above structure, it is preferable that the liquid crystal has a group that absorbs infrared rays, or that a dye that absorbs infrared rays is dissolved in the liquid crystal.

It is preferable to use a polymer-dispersed liquid crystal as the liquid crystal in terms of miniaturization and the like.

[0009]

(Embodiment 1) A pyroelectric infrared sensor device according to Embodiment 1 of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of a pyroelectric infrared sensor device according to the present embodiment. A pyroelectric infrared sensor 1 having a plurality of light receiving portions arranged in a line and a front surface of the pyroelectric infrared sensor 1 are shown. The optical modulator 2 intermittently modulates infrared light incident on the optical disk 1 and further includes an infrared lens 3 for condensing light on the front surface thereof.

Hereinafter, a specific configuration of the pyroelectric infrared sensor device and its operation will be described. For example, four electrode sections of the pyroelectric infrared sensor 1 are formed in one row. When the long axis direction is set in the horizontal direction, the field of view of each electrode is set to 4 in the horizontal direction in which the infrared lens 3 faces as shown in FIG.
The divided visual fields (a, b, c, d) are obtained, and the average radiation temperature of each visual field can be measured. That is, the infrared light condensed by the infrared lens 3 provided on the front surface of the infrared sensor 1 is intermittently modulated by the light modulator 2, and the pyroelectric infrared sensor 1 detects the temperature as a temperature change.

With this configuration, when a person passes through any one of the four visual fields, the radiation temperature of the person is high,
Since the average radiant temperature obtained from the field of view rises, it is possible to count the passage of a person by detecting this change. If the field of view is narrow, the number of electrodes may be small, but in the case of a wide entrance, if the number of sensors is small, the field of view per electrode will be widened and people will affect the temperature of the background (in this case, the floor) As a result, the change in the average radiant temperature is reduced and the detection rate is reduced. Therefore, it is necessary to design the number of electrodes and the lens in accordance with the visual field.

Next, the optical modulator will be described below.
As shown in FIG. 3, the optical modulator 2 has a configuration in which a transparent electrode 5 is formed on two glass substrates 4 so as to face each other, and a liquid crystal 6 is sealed between them. When a group that absorbs infrared rays, such as an alkyl group (CH bond) or an ether group (OC bond), is added to the liquid crystal 6 to be used, a voltage is applied to the electrode 5. By changing the orientation of the liquid crystal, the absorption of infrared rays can be changed. For example, if the liquid crystal is homogeneously oriented and the voltage rises when applied, the absorption of the collected infrared ray changes depending on the direction of the liquid crystal, so the transmittance of the infrared ray changes. When a voltage having a contrasting pulse waveform is applied to the electrode 5 to return to the original homogeneous state, a certain degree of modulation with respect to infrared rays can be obtained.
This modulation allows the infrared sensor 1 to detect a temperature difference.

A similar effect can be obtained by providing a polarizing plate outside the glass substrate 4. However, since the transmittance of infrared rays is 50% or less and the degree of modulation is low, a liquid crystal panel is used as in the present invention. Then, the transmittance of infrared rays can be increased.

If a dye that absorbs infrared light is dissolved in the liquid crystal 6 without introducing a group that absorbs infrared light into the liquid crystal 6, the direction of the dye changes with the movement of the liquid crystal (so-called guest-host effect). ) Infrared absorption can be changed. Furthermore, a certain wavelength (10.
If a dye or liquid crystal that selectively absorbs (micron) is used, a filter effect works and efficient measurement becomes possible.

As described above, if an optical modulator using a liquid crystal panel is used, infrared light can be chopped simply by applying a voltage having a contrasting pulse waveform to the electrode 5. If a chopper is used as in the past, a chopper drive unit is required, and major problems such as the reliability of the motor (deterioration due to the number of times of use), the cost of the drive unit, and noise during driving occur. By using the optical modulator 2 of a liquid crystal panel, a small, low-cost, and quiet infrared sensor that does not require a driving unit can be provided. Further, the chopping speed can be increased as compared with the conventional case using a chopper.

Embodiment 2 Hereinafter, a pyroelectric infrared sensor device according to Embodiment 2 of the present invention will be described with reference to the drawings.

FIG. 4 is a schematic diagram showing the configuration of a pyroelectric infrared sensor device according to the present embodiment. As shown in FIG. 4, the pyroelectric infrared sensors 1 are arranged, and a micro lens 7 is provided on the front surface of each sensor. Light modulator 2
Is installed. The light modulator 2 may be the same as that of the first embodiment, but in the present embodiment, a polymer-dispersed liquid crystal panel is used.

A polymer-dispersed liquid crystal is a liquid crystal having a dielectric anisotropy dispersed in a polymer and phase-separated into small spheres. When no voltage is applied, the liquid crystal in the small spheres is randomly dispersed. Although the light is scattered because the liquid crystal panel is directed to the liquid crystal panel, the scattering is suppressed when the voltage is applied to make the direction of electrolysis uniform, whereby the transmittance of infrared rays can be changed.

Also in the present embodiment, the response speed is increased by using a liquid crystal panel of a polymer dispersed liquid crystal, and the chopping speed of the conventional liquid crystal is increased from 10 Hz to 100 Hz. And high-speed measurement became possible. Further, according to the present embodiment, a mixture of liquid crystal and a UV-polymerizable resin containing a photopolymerization initiator is applied between two polyethylene films opposed to each other to form a conductive material, and the two are bonded together. The optical modulator 2 can be manufactured by a simple process of hardening by ultraviolet irradiation. Furthermore, since polyethylene has a high infrared transmittance, highly sensitive detection is possible according to this embodiment. In addition, silicon or quartz can be used as a substrate material. In addition, according to the present embodiment, a low-cost and flexible optical modulator can be formed, and the light modulator can be formed on the surface of an infrared sensor or the surface of a lens and can be integrated, so that usability can be improved.

A pyroelectric infrared sensor 1 arranged as shown in FIGS. 4 and 5, a microlens 7 was formed on each sensor, and a two-dimensional infrared sensor having a light modulator 2 added thereto was manufactured. The light modulator 2 can be formed on each microlens or can be formed on the front surface of the sensor. If an optical modulator is formed using a polyethylene film on the front surface of the sensor, the inside of the sensor cannot be seen from the outside, so that it can also serve as a cover. In addition, if an optical modulator is formed on a microlens, the pyroelectric infrared sensor, the microlens, and the optical modulator can be integrated as one microsensor at a time. Can respond flexibly.

A 16 × 16 sensor was actually manufactured as a microsensor and installed on the ceiling. This sensor divides the room into 256, and can measure the distribution of radiation temperature from the average distribution. In addition, since the high-response polymer-dispersed liquid crystal is used for the optical modulator, it can be detected in real time. As a result, from the indoor temperature distribution, information on the temperature of the air conditioner, such as the degree of adjustment and the occurrence of fire, can be obtained. You can also predict how many people are and where they are,
It can be used for security related purposes such as controlling air conditioning and lighting, and confirming safety when an abnormal situation occurs.

The present invention has been described with the embodiments. In the first embodiment, an optical modulator is provided on a pyroelectric infrared sensor, and a lens is provided thereon. In 2, the lens is provided on the pyroelectric infrared sensor and the optical modulator is provided thereon, but in the present invention, either configuration may be adopted.

[0024]

According to the present invention, the spatial resolution is improved by providing a plurality of pyroelectric elements, and the use of an optical modulator having a liquid crystal panel eliminates the need for a chopper and a driving device. Thus, a compact and highly reliable pyroelectric infrared sensor can be provided. In particular, by making the liquid crystal a polymer-dispersed type, it can be manufactured by a simple process and cost reduction can be achieved.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a field of view of an infrared sensor according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a light modulator of the infrared sensor according to the embodiment of the present invention.

FIG. 4 is a schematic diagram showing a configuration of an infrared sensor according to a second embodiment of the present invention.

FIG. 5 is a schematic diagram showing a configuration of an infrared sensor according to a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pyroelectric infrared sensor 2 Optical modulator 3 Infrared lens 4 Substrate 5 Electrode 6 Liquid crystal 7 Micro lens

Claims (3)

[Claims] 1. A liquid crystal panel comprising: a plurality of pyroelectric infrared sensors; and an optical modulator for intermittently modulating infrared light incident on the pyroelectric infrared sensor, wherein the optical modulator modulates light. A pyroelectric infrared sensor device comprising: 2. The pyroelectric infrared sensor device according to claim 1, wherein the liquid crystal has a group that absorbs infrared rays, or a dye that absorbs infrared rays is dissolved in the liquid crystal. 3. The pyroelectric infrared sensor device according to claim 1, wherein the liquid crystal is a polymer-dispersed liquid crystal.