JPH0772702B2 - Infrared imaging system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared image system for measuring infrared rays and acquiring radiation temperature information, and in particular, enables automatic correction of emissivity and influence of reflected light when acquiring an infrared image. Infrared imaging system.

[0002]

2. Description of the Related Art As is well known, an infrared image system acquires image data showing a planar distribution of infrared radiation intensity emitted from an object to be measured by two-dimensionally changing a visual field direction of an optical system. Since the image contains temperature information, it is widely used for applications different from visible images on a television, for example, abnormality diagnosis of plants and the like, outer wall diagnosis of buildings, and the like.

Specifically, in diagnosing the separation of tiles and mortar from the exterior wall of a building, when the tiles and mortar of a building exterior wall finishing material that has deteriorated over time are separated and a gap (separation part) is generated between the tile and the mortar, heat transfer is performed. Since the coefficient of thermal transmission is smaller than that in the sound part, the outer wall is uniformly cooled or heated to cause a temperature (surface temperature) difference between the peeled part and the sound part. It is measured by the system.

By using the infrared imaging system as described above, a scaffold or the like is not required as compared with a conventional diagnosis method such as a percussion method, a wide range can be remotely measured in a short time, and an objective diagnosis result can be obtained. There are features such as being.

[0005]

By the way, in the example of the diagnosis of the building exterior wall tile / mortar separation described above, direct solar radiation is generally used for heating the wall. Reflection of light and rays from surrounding hot sources,
Furthermore, since there is reflection of light rays from the atmosphere, the temperature distribution obtained in the infrared image contains a reflection component that is irrelevant to temperature. (B) The emissivity of the measurement target is not uniform due to dirt, etc. It has been pointed out that the absorption of direct solar radiation is not uniform and the heating of the surface to be measured is uneven.

These problems are caused by the fact that the outer wall of the building, which is the object to be measured, is not a black body, that is, the reflectance ρ is 0 or more because the emissivity ε is 1 or less. (A) and (b) can be corrected in principle if the amount of direct light, the rays from the surrounding high temperature radiation source) and the amount of rays from the atmosphere and the emissivity of individual objects in the infrared imaging area are known. It is possible. In fact, there is known an infrared image system capable of correcting the emissivity of an infrared image when the emissivity of an object to be measured has already been set.

However, in practice, there are many problems as will be described later, and the conventionally known emissivity correction system lacks versatility and cannot be said to be in practical use.
In the current state of the art, the correction relating to (b) is based on experience to eliminate image parts that are difficult to judge as good or bad. This is a problem encountered not only in building exterior wall diagnosis but also in many applications of infrared imaging systems, and is an urgent issue for improving diagnosis accuracy.

Next, a correction method relating to (a) and (b) will be briefly described with reference to FIG. In FIG. 2, the object itself emits radiation W _S according to its temperature, but external light W ₀ such as direct sunlight and rays of a high temperature radiator and radiation W _a from the atmosphere are incident on the surface of the object. To do. These are largely reflected but partially absorbed by the object. Here, the absorptance and the emissivity are equal, and the sum of the reflectance and the emissivity is 1.
That is, ρ = 1−ε. Most of the wavelength components of the external light W ₀ are visible light (0.45 to 0.75 μm) and near infrared light (0.75 to
2.5 μm), and some mid-infrared region (2.5 ~
25 μm). On the other hand, the wavelength component of the radiation W _a from the atmosphere is in the mid-infrared region (2.5 to 25 μm). Therefore, in FIG. 2, the reflectance in the visible region and the near-infrared region is ρ _V , the emissivity is ε _V , the reflectance in the mid-infrared region is ρ _i , and the emissivity is ε _V.
Shown as _i .

That is, in FIG. 2, the radiation W _S of the object is
10μ in the mid infrared range (2.5 to 25μm) at room temperature
Although it has a peak near m, it is represented by the product of the radiation amount W _b assuming that the object is a black body and the emissivity ε _i determined by the surface properties of the object. External light W ₀ is ρ _V · W _0V = (1-ε _V ) W _0V
And ρ _i · W _0i = (1-ε _i ) W _0i are reflected, and (1
−ρ _V ) W _0V = ε _V · W _0V and (1-ρ _i ) W _0i = ε _i · W _0i
Is absorbed. Also, the radiation W _a from the atmosphere is ρ
_{The component of i} · W _a = (1-ε _i ) W _a is reflected, and (1-
The component of ρ _i ) W _a = ε _i · W _a is absorbed.

Now, to the optical system of the infrared image system, the radiation W _S emitted by the object itself, the reflected light of the external light W ₀ such as the direct rays of the sun and the rays of the high temperature radiator, and the radiation W from the atmosphere.
_Although the reflected light of a is incident, the amount of radiation directly related to the desired temperature information is the product W _S , and the reflected light of the extraneous light W _{0 and} the reflected light of W _a from the atmosphere must be excluded. I have to. In addition, the product W _{S is} also the radiation amount W _b, which is originally assumed to be a black body.
Since this must be measured, this also needs to be corrected. On the other hand, the infrared sensor of the infrared image system electrically converts mid-infrared rays. Therefore, the output voltage E _i of the infrared sensor is expressed by Equation 1 with the conversion coefficient K _i.
Therefore, the radiation amount W _b is given by Equation 2 from this.

[0011]

E _i = K _i {ε _i · W _b + ρ _i (W _0i + W _a )} = K _i {ε _i · W _b + (1-ε _i ) (W _0i + W _a )}

[0012]

## EQU00002 ## W _b = {E _i −K _i (1-ε _i ) (W _0i + W _a )} / K _i · ε _i

The true value of the radiant temperature is calculated from the mathematical expression 2. The emissivity ε _i of each object constituting the object to be measured is unique, and the data is not sufficiently accumulated. It is practically impossible to give emissivity data to individual objects in the infrared image forming area for correction.
Further, it is actually extremely difficult to grasp the amount of extraneous light W ₀ such as direct sunlight and the amount of radiation W _a from the atmosphere. Therefore,
As described above, conventionally, there is no choice but to make corrections based on experience, and improvement is desired.

The present invention has been made in order to meet such a demand, and an object thereof is to provide an infrared image system having an automatic correction function of the emissivity and the influence of reflected light.

[0015]

In order to achieve the above object, the infrared image system of the present invention has the following configuration. That is, the infrared image system according to the first aspect of the present invention includes the first electric conversion unit and the second electric conversion unit that receive the light rays acquired from the measurement target object and electrically convert the infrared rays and the visible and near-infrared rays.
An electric conversion unit; an individual electric power conversion unit that receives the output of the second electric conversion unit and that is set in the infrared image forming region and has a known reflectance for visible and near infrared rays. A reflectance signal section for outputting a reflectance signal proportional to the reflectance of an object; an emissivity signal section for receiving an output of the reflectance signal section and outputting an emissivity signal corresponding to the reflectance signal; An image processing unit that superimposes each output of the reflectance signal unit and the emissivity signal unit on the infrared image signal output from the conversion unit to correct the emissivity of the radiant temperature of the object to be measured and the influence of reflected light; It is characterized by having.

The infrared image system of the second invention includes a first electric conversion unit and a second electric conversion unit which receive the light beam acquired from the object to be measured and electrically convert the infrared light and the visible and near-infrared light beams, respectively. Provided with a setter capable of arbitrarily setting the reflectance, and being proportional to the reflectance of each object in the infrared image forming area with reference to the reflectance set by the setter upon receiving the output of the second electric conversion unit A reflectance signal section that outputs a reflectance signal; an emissivity signal section that receives an output of the reflectance signal section and outputs an emissivity signal corresponding to the reflectance signal; an infrared ray that is an output of the first electrical conversion section And an image processing unit for superimposing the outputs of the reflectance signal unit and the emissivity signal unit on the image signal to correct the emissivity of the radiant temperature of the object to be measured and the influence of reflected light. To do.

[0017]

Next, the operation of the infrared image system of the present invention configured as described above will be described. As described above, it is practically impossible to correct the emissivity of the infrared image by giving the emissivity data of each object at the time of forming the infrared image data. If the emissivity information of each individual object can be obtained, it can be used to form a corrected infrared image.

In general, the emissivity varies depending on the wavelength of the object (especially the surface property), the temperature, and the radiation angle, but in the case of a solid, it is often determined by the surface property, and there is no significant difference depending on the wavelength, so-called gray radiator. Is. Therefore, in many solids, if the emissivity in the adjacent wavelength region is known, it is possible to roughly estimate the emissivity in the detection wavelength region.

That is, the radiation from a room temperature object has a peak at a wavelength of about 10 μm, and there is no radiation power to be measured in the wavelength range of 1 to 2 μm, but when the object is illuminated by the sun or an illumination lamp, 1 in addition to visible light
Since the near-infrared light of ˜2 μm is also included, this near-infrared light can be used as the “close wavelength range”. This is because the reflectance ρ and the emissivity ε are related to ρ = 1−ε.

The original infrared image is formed on the basis of the light rays in the mid-infrared region, and an infrared sensor is used for the electrical conversion thereof, but silicon is used for the electrical conversion between the visible light region and the near infrared region. A CCD sensor made of an element or the like can be used, and a signal including reflectance information proportional to the reflectance of the object as described above can be acquired.

From the above description, it can be understood that the reflectance of each object can be measured, but generally in the abnormality diagnosis, the relative brightness difference in the acquired infrared image is used, so that This point must be taken into consideration when correcting the infrared image.

Therefore, in the present invention, the incident light rays include infrared rays and visible and near-infrared rays, so that they are electrically converted to form respective image signals. An object whose reflectance is known is set in the formation region, and in the second invention, a setter capable of arbitrarily setting the reflectance is provided in the reflectance signal section, and the reflectance signal section is the second electrical conversion unit. The image from the object to be measured is obtained by storing the reference reflectance obtained based on the image signal from the object whose reflectance is known in response to the output of the section. Forming a reflectance signal proportional to the reflectance of the individual object in the infrared image forming area from the signal, the emissivity signal unit forms an emissivity signal corresponding to the reflectance signal,
The image processing unit superimposes the reflectance signal and the emissivity signal on the infrared image signal, corrects the emissivity of the radiant temperature of the object to be measured, corrects the influence of reflected light, and outputs infrared image data.

Thus, since the correction problem relating to the reflectance and the emissivity, which has been excluded from the use of the infrared image system, can be processed in real time, the accuracy of the diagnosis and the like can be improved, and the infrared image system can be improved. Wider range of uses can be expected.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an infrared imaging system according to an embodiment of the present invention. In FIG. 1, a condenser system 1 and a semitransparent mirror (mirror having wavelength selectivity) 2 are shown as an incident optical system in the present embodiment, but the light beam condensed by the condenser system 1 is a semitransparent mirror. 2 is divided into an infrared radiation a and a near-infrared radiation b consisting of a visible region and a near-infrared region, and the infrared radiation a is given to the infrared signal section 3 and Radiation b of the system is the near infrared signal part 3
Given to. Note that the infrared radiation a is W _S and ρ _i · W _0i
And ρ _i · W _a , the near infrared radiation b is ρ _V · W
It is _0V (Fig. 2).

As described above, the infrared signal section 3 electrically converts the radiation a in the mid-infrared region by the infrared sensor, and at the same time performs processing such as amplification and shaping to form the image signal E _i, which the image processing section 7 receives. Output. This image signal E _i is expressed by the equation 1
It is shown by.

The near-infrared signal section 4 electrically converts the radiation b in the visible region and the near-infrared region by a CCD sensor and amplifies / amplifies it.
Although the image signal E _V is formed by processing such as shaping and is output to the reflectance signal section 5, in the present embodiment, an object whose reflectance is known in the infrared image forming region, for example, a standard diffuse reflector (ρ _VS =
1) is installed or a white wall (ρ _VS ≈1) is set, the image signal E _V includes an image signal of which reflectance is known. The light source is sunlight.

The reflectance signal section 5 forms the reflectance signal E (ρ) by utilizing the fact that the visible and near infrared image signals are signals proportional to the reflectance. That is, the image signal E _V includes an image signal from an object whose reflectance is known, but the reflectance signal E (ρ _VS ) formed from the image signal is the input signal between the input and output of the near infrared signal unit 4. Conversion coefficient of K _V , reflectance signal section 5
When the transform coefficient between input and output of the K _r, radiation b is [rho _VS ·
Since it is W _0V , it can be expressed as Equation 3.

[0028]

[Equation 3] E (ρ _VS ) = K _V · K _r · ρ _VS · W _{0 V}

Further, the reflectance signal E (ρ) formed from the image signal from the measuring object in the infrared image forming area is ρ _V , where the reflectance of one object in the infrared image forming area is ρ _V It can be expressed by Equation 4.

[0030]

[Equation 4] E (ρ) = K _V · K _r · ρ _V · W _0V

Therefore, from the equations 3 and 4, the reflectance signal E
(Ρ) is given by Equation 5, but if ρ _VS = 1 then Equation 6 is obtained.

[0032]

[Equation 5] E (ρ) = (ρ _V / ρ _VS ) E (ρ _S ).

[0033]

[Equation 6] E (ρ) = ρ _V · E (ρ _S ).

In short, the reflectance signal unit 5 extracts and stores the signal E (ρ _VS ) from the reflectance conversion processing of the image signal E _V pixel by pixel, and uses this as a reference reflectance signal for the other pixels. The reflectance ρ _V is obtained as the signal E (ρ). The reflectance signal E proportional to the reflectance ρ _V
(Ρ) is given to the image processing unit 7 and the emissivity signal unit 6.

In the emissivity signal section 6, the emissivity signal E (ε) is converted from the input reflectance signal E (ρ) according to the equation (7) and output to the image processing section 7.

[0036]

[Equation 7] E (ε) = 1−E (ρ)

The image processing unit 7 superimposes the reflectance signal E (ρ) and the emissivity signal E (ε) on the infrared image signal E _i , and outputs infrared image data W _{out in} which the emissivity and the direct sunlight of the sun are corrected. To do.
That is, from the assumption of a gray radiator, the reflectances in the visible light region and the infrared region are equal, and ρ _i = (1−ε _i ) = ρ _V. Therefore, the conversion coefficient K _i between the input and output of the infrared signal section 3, the conversion coefficient K _V between the input and output of the near infrared signal section 4 and the conversion coefficient K _r between the input and output of the reflectance signal section 5 are If each is designed so that K _i = K _V · K _r , then K _i
(1-ε _i ) (W _0i + W _a ) is equivalent to the reflectance signal E (ρ). Similarly, K _i · ε _i in the equation 2 is equivalent to the emissivity signal E (ε).

Therefore, the above equation 2 becomes the following equation 8 after all,
From the reflectance signal E (ρ) and the emissivity signal E (ε), the radiation amount W _b of the object in each part can be obtained.

[0039]

(8) W _b = {E _i −E (ρ)} / E (ε)

This radiation amount W _b can be converted into radiation temperature by comparing with the black body radiation, and this conversion can be performed by calibration using a black body furnace.

In the above description, the standard diffuse reflection plate is installed in the measurement environment, or there is a white wall in the vicinity. However, if they cannot be obtained, the reflectivity signal section 5 is provided with a setter. The reflectance signal corresponding to the reference reflectance signal E (ρ _VS ) can be appropriately variably set. By doing so, it is possible to perform emissivity correction and removal of the influence of reflected light while confirming the magnitude of the influence of reflection on the object of each part on the monitor screen.

Further, the above description is for the case where the outdoor direct sunlight is used for the measurement, but the indoor measurement can be similarly performed by using the indoor illumination. At this time, it goes without saying that there is a high-temperature radiation source including radiation in the visible / near-infrared region around the object to be measured, and even if it is affected by the radiation, the measurement can be performed without any trouble.

When a color image is used instead of the near-infrared image, the reference reflectance is obtained by using the R signal of the R, G, and B primary color signals.

In the embodiment described above, the infrared system and the near infrared system are separated by the semi-transparent mirror 2 in order to avoid the difficulty or complexity of adjusting the optical axis. Since the sensor is available, the semi-transparent mirror 2 can be omitted by disposing the micro CCD sensor near the optical axis of the infrared sensor.

[0045]

As described above, according to the infrared image system of the present invention, attention is paid to the fact that visible light rays and near infrared rays among incident light rays include reflectance information of an object. Since correction problems related to reflectance and emissivity, which have been excluded from use, can be processed in real time, accuracy of diagnosis and the like can be improved, and there is an effect that a wider range of use of the infrared image system can be expected.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of an infrared image system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a state of radiation and reflection on an object surface.

[Explanation of symbols]

 1 Condensing system 2 Semi-transparent mirror 3 Infrared signal part 4 Near infrared signal part 5 Reflectance signal part 6 Emissivity signal part 7 Image processing part

Claims (2)

[Claims] 1. A first electric conversion unit and a second electric conversion unit for electrically converting infrared rays and visible and near-infrared rays by receiving a light ray acquired from a measurement object; and an output of the second electric conversion unit. In response to this, the reflectance signal proportional to the reflectance of each object in the infrared image forming area is output based on the object whose reflectance for visible and near infrared rays set in the infrared image forming area is known. A reflectance signal section for receiving the output of the reflectance signal section and outputting an emissivity signal corresponding to the reflectance signal; and a reflectance for the infrared image signal output from the first electrical conversion section. An infrared image system comprising: an image processing unit that superimposes outputs of a signal unit and an emissivity signal unit to correct emissivity of radiant temperature of an object to be measured and effect of reflected light; . 2. A first electric conversion part and a second electric conversion part which receive a light beam acquired from a measurement target object and electrically convert infrared rays and visible and near-infrared rays, respectively; the reflectance can be arbitrarily set. A reflectance that includes a setting device and outputs a reflectance signal that is proportional to the reflectance of each object in the infrared image forming area on the basis of the reflectance set by the setting device when receiving the output of the second electrical conversion unit. A signal section; an emissivity signal section for receiving an output of the reflectance signal section and outputting an emissivity signal corresponding to the reflectance signal; and a reflectance signal section for the infrared image signal output from the first electrical conversion section, and An infrared image system comprising: an image processing unit that superimposes each output of the emissivity signal unit to correct the emissivity of the radiation temperature of the object to be measured and the effect of reflected light.