JPH042930A - Thermography apparatus - Google Patents

Abstract

PURPOSE:To enlarge an effective screen by providing an aperture of a luminous flux stop only at one side of an optical axis thereby to eliminate generation of narcissus. CONSTITUTION:A camera part 1 consists of a scanning mirror 3, a condenser lens 4, an extinction filter 5, a wavelength limiting filter 6, a luminous flux stop 7, a relay lens (image forming lens) 8 and an infrared detecting element 9 sequentially in a direction of incidence of infrared rays from a surface 2 of an object to be measured. An image of the element 9 is formed by the lens 8 along a direction reverse to the direction of incidence, which is formed again by the lens 4 with a focus met on the object surface 2. A closeup magnifying lens 10 is provided in front of the mirror 3. When the lens 4 is focused on an infinitely far point, the light from the element 9 which is converted to a parallel luminous flux by the lens 4 is condensed at the object surface 2 by the lens 10. Accordingly, the temperature distribution of the minute object can be monitored. If the circular luminous flux stop 7 is blocked at the lower half thereof around the optical axis, the reflecting light of the incident light is blocked at the lower side of the stop 7, so that the light from the element 9 at the low temperature is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in a thermography device that measures the temperature distribution of an object by detecting its infrared radiation intensity distribution. The present invention relates to a thermography device that eliminates narcissus, which is a phenomenon in which infrared rays are reflected on the surface of an object and the temperature distribution of the object is incorrectly detected due to the reflected light.

[Conventional technology]

When an object has an emissivity of 1, it corresponds to a black body and has a reflectance of zero, but there are general objects whose emissivity is close to zero and have a large reflectance. When measuring the temperature distribution of an object with low emissivity and high reflectance using a thermography device, the temperature distribution of surrounding objects is reflected by the object and detected as if it were radiated from the object, making the temperature distribution accurate. Therefore, as shown in Figure 6, a reflection source object with a uniform temperature distribution, such as a cardboard paper coated with black body paint, is usually prepared, and the image from this reflection source object is the image of the measurement object. The light is reflected from the surface and enters the thermography apparatus, and the reflected light from surrounding objects with non-uniform temperature distribution is prevented from entering, thereby eliminating the influence of non-uniformity in the temperature distribution of the environment. In addition, when measuring the temperature distribution of an object with an emissivity of ε smaller than 1, as shown in Figure 7, the infrared rays emitted from the object and the infrared rays emitted from the environment and reflected by the object are added together, and thermography is performed. Without emissivity correction for the radiation incident on the device, the apparent temperature is measured as follows:

R(T')-E R(T)+(1-E)R(Ta)where, T is the temperature of the measuring object, Ta is the temperature of the environmental reflection source,
To is the apparent temperature to be measured, and R(T) is the effective amount of infrared radiation in the wavelength range detected by the thermography apparatus out of the amount of infrared radiation emitted from a black body at temperature T.

However, when a close-up magnifying lens is attached as the objective lens of a thermography device and the temperature distribution of a minute object placed directly in front of the objective lens is to be measured, the method shown in Figure 6 cannot be adopted, and the thermography device itself, especially Radiation from an infrared detection element such as HgCdTe, 1nsb (usually cooled with liquid nitrogen to improve sensitivity) cooled to a low temperature hits the surface of the object, and it appears as if it were radiation from the object. By being detected again by an infrared detector, narcissus, a phenomenon in which a region of low temperature appears in the center of the normal visual field, appears. In particular, when measuring the temperature distribution on the surface of an IC as a micro object, the IC surface has a metal evaporated wiring pattern such as aluminum, which has a low emissivity and a high reflectance, so narcissus appears in the thermal image of the IC surface. , the temperature indication T' at the center of the screen becomes low, which is extremely inconvenient.

Conventionally, it was thought that the appearance of the above-mentioned narcissus was unavoidable, especially when measuring temperature distribution with close magnification.

[Problem to be solved by the invention]

The present invention was made in view of this situation, and
In particular, it is an object of the present invention to provide a thermography apparatus in which the appearance of the above-mentioned narcissus is reduced.

[Means to solve the problem]

To achieve the above object, the thermography apparatus of the present invention includes a scanning device that optically scans a measurement object surface, an imaging optical system that images the scanned object surface on an infrared detection element, and an infrared ray from the scanning device. In a thermography apparatus having a beam diaphragm placed in the optical path leading to the detection element and limiting the opening angle of the beam incident on the infrared detection element to a constant, the aperture of the beam diaphragm is arranged only on one side with respect to the optical axis. It is characterized by the fact that

At that time, it is possible to adjust the light intensity to change the measurement temperature range using a neutral density filter inserted in the optical path, especially when measuring a high-temperature minute object by magnifying it. Measurements can be made without reducing resolution.

Another thermography apparatus of the present invention includes an imaging optical system that optically forms an image of the surface of the measurement object, an infrared one-dimensional or two-dimensional detection element disposed on the imaging surface of the imaging optical system, and , in a thermography apparatus having a beam diaphragm disposed in an optical path from a measurement object to an infrared detection element to limit the aperture angle of a beam incident on the infrared detection element to a constant, the aperture of the beam diaphragm is set to one side with respect to the optical axis. It is characterized by being placed only on the side of the

[Effect]

In the present invention, by arranging the aperture of the beam diaphragm only on one side with respect to the optical axis, the light from the infrared detection element cooled to a low temperature is reflected by the measurement object and returns to the infrared detection element itself. The temperature of the infrared detection element is measured as if it were the temperature of an object.The light that causes Narcissus can be blocked, especially on one side from the center of the image in the viewing range, so when you look at the entire screen, the area where Narcissus appears is in the center. You can push him to the periphery and increase the number of effective screens without Narcissus.

〔Example〕

FIG. 1 shows the optical path of a camera section 1 of a thermography apparatus. The camera section 1 includes a scanning mirror 3, a condenser lens 4, a neutral density filter 5, a wavelength limiting filter 6, a light flux diaphragm 7, and a relay lens ( The image of the infrared detecting element 9 is formed by the relay lens 3 at one end, and then re-imaged by the condensing lens 4. The focus can be set on 2. Focusing on the object 2 is performed by adjusting the condenser lens 4 back and forth.

As mentioned above, the infrared detection element 9 is heated with liquid nitrogen (77°K) or an electronic cooler (-70°C) to improve sensitivity.
) cooled by tlgcdTe, InSb
HgCdTe (77°K) has wavelength sensitivity in the 8-13μm band, and InSb (77°K) and fl
gcdTe (-70°C) is used in the atmospheric window wavelength range of 3-5 μm band. The light flux diaphragm 7 adjusts the aperture angle of the light flux (
This is an aperture that limits the brightness of the optical system, and its presence keeps the brightness of the optical system constant.
Also by screen scanning), a detector output of a constant magnitude can be obtained for an object 2 whose temperature is constant. Conventionally, as shown on the right side of the figure, a light flux diaphragm 7 having a circular aperture centered on the optical axis is used. Note that the neutral density filter 5 and the wavelength limiting filter 6 are essential for increasing the reliability of the temperature measuring instrument, and the neutral density filter 5 is inserted when measuring a high temperature object (the present invention). (This is not provided in the conventional model.) Using the camera unit 1, the condenser lens 4 is adjusted back and forth to focus on the object to be measured, and the surface of the object to be measured is scanned by the scanning mirror 3 to obtain an infrared radiation image. The light is taken in and photoelectrically converted by the infrared detection element 9, and the temperature distribution is measured from the intensity distribution.

By the way, as shown in FIG. 2, when a close-up magnifying lens 10 is attached in front of the scanning mirror 3 and the condensing lens 4 is focused at infinity, the infrared rays are emitted from the infrared detection element 9 and collimated by the condensing lens 4. The converted light is focused on the object plane 2 by the proximity magnifying lens 10. Therefore, the temperature distribution of the minute object on the object plane 2 can be observed in an enlarged manner.

In the figure, H and H' represent the main surfaces of the proximity magnifying lens 10, and the "entrance pupil" is the image of the scanning mirror 3 (exit pupil) taken by the proximity magnifying lens 10. passes through this "entrance pupil".

Now, referring to FIG. 3, when the close-up magnifying lens 10 is attached in front of the scanning mirror 3, the infrared detection element 9
The traveling direction of the light reflected by the object surface 2, which is emitted from the object plane 2 and converted into a parallel beam by the condensing lens 4, will be considered. Figure (a) shows the optical path when the scanning mirror 3 is looking at the center of the field of view, and all the light incident on the object plane 2 is light emitted from the low-temperature infrared detection element 9. According to the symbols in the figure, incident light 11 is reflected and becomes reflected light 12, and incident light 21
becomes reflected light 22, incident light 31 is reflected as reflected light 31, conversely, incident light 12 is reflected and becomes reflected light 11, incident light 22 becomes reflected light 21, and the optical axis as shown in FIG. If you use a circular light flux diaphragm centered at It will be shown. Therefore, in the present invention, as shown on the right side of Fig. 2 and on the right side of Fig. 3, either half of the circular light flux diaphragm centered on the optical axis (lower half in Fig. 3) is shielded from light. shall be taken as a thing. In this way, in FIG. 3(a), reflected light 12 resulting from the reflection of the incident light 11 is blocked below the light flux diaphragm 7, and reflected light 22 resulting from the reflection of the incident light 21 is similarly blocked. , the light from the low-temperature infrared detection element 9 itself is not detected. Conversely, the incident light 12 and the incident light 22 reach the infrared detection element 9 without being blocked, but their reflection source is the light flux diaphragm 7.
Since the temperature is the temperature inside the camera unit 1 (normal temperature), Narcissus does not appear in the center of the field of view. next,
The state shown in FIG. 3(b) is the optical path when the scanning mirror 3 is looking at the upper end of the field of view, and the incident light 4]) becomes reflected light 42 and reaches the room temperature region, and the incident light 51 becomes reflected light 52, which reaches the infrared detection element 9 itself when the light flux diaphragm 7 has a circular aperture. Further, the light 61 that enters through the lower side of the optical axis becomes reflected light 62 and reaches the infrared detection element 9 itself. Therefore, when the light flux diaphragm 7 has a circular aperture, approximately half of the luminous flux (rays within the aperture of rays 51 and 52) returns to the infrared detection element 9, so the degree of Narcissus is approximately half that at the center of the field of view. Become. On the contrary,
When the lower half of the light flux diaphragm 7 is made light-shielding as shown in the figure, the incident light 41 and the incident light 51 either reach the room temperature range or are blocked by the light flux diaphragm 7, so that the light from the infrared detection element 9 is There is no going back to yourself. Therefore, narcissus does not occur in the upper part of the visual field. Next, the state of FIG. 3(C) shows the optical path when the scanning mirror 3 is looking at the lower end of the field of view, and the incident light 71 becomes reflected light 72 and reaches the infrared detection element 9, and the incident light The light 81 becomes reflected light 82 and similarly reaches the infrared detection element 9, and the light 91 that enters through the lower side of the optical axis becomes reflected light 92 and reaches the room temperature region. Therefore, when the light flux diaphragm 7 has a circular aperture, approximately half of the luminous flux (rays within the aperture of rays 81 and 82) returns to the infrared detection element 9, so the degree of Narcissus is approximately half that at the center of the field of view. Become. On the other hand, if the lower half of the light flux diaphragm 7 is made to have per-minute light properties as shown in the figure, the light that becomes the reflected light 72 from the incident light 71 is blocked by the light flux diaphragm 7, but the infrared detection element Since the incident light 81 coming from 9 returns to itself as reflected light 82, a relatively wide luminous flux between the light rays 81 and 82 generates Narcissus.

In the above explanation, the light beam has been explained only within the plane of the paper of FIG. 3 (up-down direction reflection), but reflection in the left-right direction perpendicular to the paper must also be considered.

Taking this into consideration, the shape of Narcissus in the field of view becomes as shown in FIG. That is, FIG. 4(a) is
This is a conventional example using a circular aperture 7, and Narcissus exists as a circular shape that gradually weakens from the center of the screen to the periphery, but if a semicircular aperture 7 that covers the lower side of the circular aperture is used, As shown in b), a narcissus with the shape shown in the figure appears at the bottom of the visual field. In addition, the temperature distribution in the vertical section and horizontal section on the center line of the screen is schematically shown in the figure, and represents the distribution of the strength of Narcissus. Comparing (a) and (b) in FIG. 4, it can be seen that in the case of (b), there is no Narcissus at all in the upper half of the screen. This point is the most important point in the present invention. The following method can be used to further reduce the area of Narcissus in FIG. 4(b) and move it from the center of the screen to the periphery.

First, as shown in FIG. 5(a), the light shielding range of the light flux diaphragm 7 is increased by more than half of the circular aperture.

If this is done, as shown in FIG. 3(b), Narcissus' position will be pushed to the lower part of the screen, and the effective screen will increase. Furthermore, the close-up magnifying lens 10 shown in FIG. 2 can be mounted eccentrically with respect to the optical axis to move Narcissus away from the center of the screen. Furthermore, one method is to limit the scanning range to an area where Narcissus does not appear, as shown by a black frame in FIG. 5(b). A thermal image free of narcissus can be obtained by using the above-mentioned methods (1) to (2) singly or in combination.

By the way, when measuring a high-temperature object, the amount of infrared light emitted from the object is large, so it is necessary to reduce the amount of infrared light. In the configuration shown in Fig. 2, the brighter the light flux, that is, the larger the numerical aperture of the optical system, the higher the theoretical resolution that can be achieved using wave optics, so reducing the light flux will worsen the resolution. Connect.

Therefore, for the purpose of removing Narcissus, the luminous aperture 7
It is unavoidable to make half of the light shielding property, but when measuring temperature in a high-temperature range as described above, it is not a good idea to further narrow down the light flux diaphragm 7 for the purpose of light attenuation. Conventionally, since the neutral density filter 5 is expensive, high-temperature ranges were supported by narrowing down the light flux diaphragm 7. However, for the reasons mentioned above, in the present invention, the incident light flux is attenuated by the neutral density filter 5. (Figure 2).

The present invention has been described assuming that when the close-up magnifying lens 10 is attached to the thermography apparatus as shown in FIG. Not only when the magnifying lens 10 can be accessed, but also the state shown in Figure 1 (measuring objects at a distance longer than normal)
It should be clear that it is effective in getting rid of Narcissus even in the case of

In the above explanation, the optical scanning of the camera section was explained as object world scanning in which the image spot by the imaging optical system of the detection element scans on the object plane. The present invention is also applicable to so-called image field scanning optical scanning in which the image spot is scanned over the formed two-dimensional image. Furthermore, it goes without saying that not only a single element but also a multi-element device in which a plurality of elements are arranged in a one-dimensional direction may be used as the red evening one-ray detection element 9.

Furthermore, FIG. 8 shows another embodiment. In this example,
The measurement object 2 is imaged by an imaging optical system 11, and an infrared multi-element detection element 12 is disposed at the position of this imaging plane.

The infrared multi-element detection element 12 is, for example, an infrared CCD detection element (CCD) arranged two-dimensionally as shown in FIG.
=Charge (:upled[]evice
: charge transfer device), which can create a thermal image by sequentially extracting signals from each device. recently,
A device with 512×512 elements has been announced. H, H"
is the main surface of the imaging optical system 11, and the light flux diaphragm 7 is placed at the exit side main plane H° for the sake of simplicity.

If the light flux diaphragm 7 is made semicircular as shown on the right side of FIG. 8, Narcissus can be blocked in half of the screen for the same reason as explained in FIG. 3. Further, by using the above-mentioned items (1) to (2) alone or in combination, the area of Narcissus can be reduced and moved from the center of the screen to the periphery. However, in this embodiment, the scanning range (3) refers to the electrical scanning range for extracting the output signal from the infrared multi-element detection element 12.

By arranging the infrared multi-element detection element 12 at a position eccentric to the optical axis, Narcissus can also be driven from the center of the screen to the periphery. Note that the infrared multi-element detection element 12 is not necessarily limited to a two-dimensional arrangement; for example, a one-dimensional arrangement, such as a line sensor, may be used when simply measuring heat distribution in a one-dimensional direction.

〔Effect of the invention〕

In the thermography apparatus according to the present invention, by arranging the aperture of the light flux diaphragm only on one side with respect to the optical axis, the light from the infrared detecting element cooled to a low temperature is reflected by the measurement object, and the infrared detecting element itself is reflected. Returning to , the temperature of the infrared detection element is measured as if it were the temperature of an object.The light that causes narcissism can be blocked, especially on one side from the center of the image, so if you look at the entire screen, you can see the area where narcissism appears. It can be moved from the center to the periphery, increasing the number of effective screens.

By using the above-mentioned methods (1) to (2) singly or in combination, a thermal image free of narcissus can be obtained.

In addition, if the light amount is adjusted to change the temperature measurement range using a neutral density filter inserted in the optical path,
In particular, when magnifying and measuring a high-temperature minute object, the measurement can be performed without reducing the resolution of the magnifying optical system by adjusting the light amount.

[Brief explanation of the drawing]

Figure 1 is an optical path diagram of the camera section of the thermography device, Figure 2
The figure is an optical path diagram when a close-up magnifying lens is attached to the camera section in Figure 1, Figure 3 is a diagram for explaining the presence or absence of Narcissus occurrence based on the present invention, and Figure 4 is a diagram of Narcissus in the field of view. Figure 5 is a diagram showing the shape of the modified light flux diaphragm and the shape and position of Narcissus in that case. Figure 6 explains the conventional method of removing the effects of uneven temperature distribution in the environment. Figure 7 is a diagram for explaining that the infrared rays incident on the thermography device is the sum of the infrared rays emitted from the object and the infrared rays reflected by the object, and Figure 8 is another diagram of the present invention. FIG. 9, which is an optical path diagram of the camera section of the thermography apparatus according to the embodiment, is a plan view of an infrared CCD as an example of an infrared one-dimensional or two-dimensional detection element. Camera section of tothermography device, 2. Object surface of measurement object, 3. Scanning mirror, 4. Condensing lens, 5.
Neutral density filter, 6...Wavelength limiting filter 7, light flux diaphragm, 8...Relay lens, 9.Infrared detector, 0...Proximity magnifying lens, 1...Imaging optical system, 12. ...Infrared multi-element detection element applicant JEOL Ltd.

Claims (2)

[Claims] (1) A scanning device that optically scans the measurement object surface, an imaging optical system that images the scanned object surface onto an infrared detection element consisting of a single, one-dimensional, or two-dimensionally arranged multiple elements, and a scanning device. In a thermography device having a beam diaphragm disposed in an optical path from the device to an infrared detection element to limit the aperture angle of a beam incident on the infrared detection element to a constant, the aperture of the beam diaphragm is placed on one side with respect to the optical axis. A thermography device characterized in that it is placed only in. (2) an imaging optical system that optically forms an image of the measurement object surface;
An infrared one-dimensional or two-dimensional detection element arranged on the imaging plane of the imaging optical system, and an infrared detection element arranged in the optical path from the measurement object to the infrared detection element to keep the opening angle of the light flux incident on the infrared detection element constant. What is claimed is: 1. A thermography apparatus having a limiting beam diaphragm, characterized in that the aperture of the beam diaphragm is disposed only on one side with respect to an optical axis.