JPH02221828A - Optical system for thermographic device - Google Patents

Abstract

PURPOSE:To obtain an infrared image and a visible image having the same axis and the same visual field without parallax by condensing light by a Cassegrain lens consisting of a concave mirror and a convex mirror and then separating visible light from infrared rays. CONSTITUTION:After condensing the light by the Cassegrain lens consisting of the concave mirror 3 and the convex mirror 4, the visible light is separated from the infrared rays. A relay lens 12 is a lens for visible light and forms the image of an object 1 on an image-formation plane 13. By arranging a TV image pickup element consisting of CCD on the image-formation plane 13, the visible image is observed on a CRT. At such a time, the range of the visual field of the visible image can be allowed to coincide with the range of the visual field of the infrared image by adjusting the focal distance of the lens 12 and the angle of a mirror 11. Since the visible light beam and the infrared rays are divided from one optical axis 15, the infrared image and the visible image are obtained on the same axis and in the same visual field. By allowing a scanning means 7 to overscan or rotating a chopper having a proper shape, the infrared rays from a reference black body 14 is made incident on a detector.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermography apparatus, and more particularly to an optical system of a thermography apparatus that can obtain an infrared image and a visible image without variation.

[Prior Art] A device that measures the temperature distribution of a subject by detecting infrared rays emitted from the subject is widely known as a thermography device. What is shown in FIG. 3 is an example of the configuration of an optical system of a conventional thermography apparatus. vertical scanning means 23;
Vertical or horizontal scanning means 24 are provided. Also, 25
2 indicates a relay lens, and 26 indicates an infrared detection element.

In the configuration shown in FIG. 3, the image spot of the infrared detection element 26 is formed on the subject 20 by the relay lens 25 and the objective lens 21, and the scanning means 2
2 horizontally and vertically. Although not shown, the infrared image signal of the object 20 obtained from the infrared detection element 28 as the image spot scans the object 20 is transmitted to the CRT display device via a signal processing device such as an absolute temperature correction circuit and an image amplifier. The infrared image is displayed [
Problems to be Solved by the Invention] However, in the optical system shown in FIG. 3, a lens made of a material that does not transmit visible light, such as germanium (Ge), is used as the first objective lens 21.
The following problems arise.

In other words, although thermography devices generally display infrared images of objects in black and white or pseudo-color, the shape of the object cannot always be clearly recognized from the infrared images alone. Therefore, it is often not possible to accurately determine which parts are at what temperature.

Therefore, in the one shown in FIG. 3, the objective lens 21
A visible image was obtained by converting the optical system into a unit and replacing it with a visible optical system unit as shown in FIG. 4, for example. That is,
In FIG. 4, 30 is a subject, 31 is an objective lens for visible light, 33 and 34 are fixed reflecting mirrors, and 36 is an eyepiece lens. made of material.

Therefore, the operator can use the objective lens unit 2 shown in FIG.
1 with the visible optical system unit shown in FIG.
The shape of the subject can be recognized by looking at the image displayed on the screen.

In addition, in the above explanation, when displaying a visible image on a CRT, it is easier to make a comparison by displaying the visible image on the same screen side by side with an infrared image read from an image file. .

In this way, it is possible to compare the infrared image and the visible image, but since the units are replaced, the fields of view do not match, and it is not always easy to correspond between the infrared image and the visible image. A problem arises.

The present invention solves the above-mentioned problems, and aims to provide an optical system for a thermography apparatus that can obtain an infrared image and a visible image on the same axis and in the same field of view.

[Means for Solving the Problems] In order to achieve the above object, the optical system of the thermography apparatus of the present invention includes a reflective optical system in which a concave mirror and a convex mirror are combined, a first lens, a scanning means, An optical system for a thermography apparatus, wherein a light flux diaphragm, a second lens, and an infrared detector are arranged in this order, and the reflective optical system and the scanning means are in a conjugate relationship with respect to the first lens. wherein the reflective optical system and the first
It is characterized in that an optical member that reflects visible light can be fixed or inserted between the lens and the lens.

[Operations and Effects of the Invention] As is clear from the above explanation, according to the present invention, light is collected by a Cassegrain lens consisting of a concave mirror and a convex mirror, and then visible light and infrared rays are separated. In other words, it is possible to obtain an infrared image and a visible image with the same axis and field of view, so by comparing the two or displaying them side by side or superimposed, it is possible to determine the temperature of which part of the object. It is possible to make a clear judgment as to whether there is such a thing.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 shows one of the optical systems of the thermography apparatus according to the present invention.
1 is a diagram showing the configuration of an embodiment, in which 1 is a subject, 2 is a Cassegrain lens, 3 is a concave mirror, 4 is a convex mirror, 5 is an infrared lens, 6 is an intermediate imaging plane, 7 is a scanning means, 8 1 is a light flux diaphragm, 9 is a relay lens, 10 is an infrared detection element, 11 is a mirror, 12 is a relay lens, 13 is an image forming surface, 14 is a reference black body, and 15 is an optical axis.

In FIG. 1, a Cassegrain lens 2 is a reflective optical system in which a concave mirror 3 and a convex mirror 4 are combined, and since it uses mirrors, it can reflect and condense not only infrared rays but also visible light. The infrared lens 5 is made of, for example, Ge, and transmits only infrared rays. The scanning means 7 two-dimensionally scans the image spot of the infrared detecting element 10 on the intermediate imaging plane 6, and may be performed by one scanning means as shown in the figure, or horizontally as shown in FIG. The scanning and vertical scanning may be performed by separate scanning means. The light flux diaphragm 8 limits the light flux incident on the infrared detection element 10, and has a structure in which, for example, as shown in FIG. 2, a light shielding part 18 is disposed at the center of the through hole 17. This light shielding part 18 has an aperture provided at the center of the Cassegrain lens 2, and therefore the center of the light beam does not have information about the subject 1, so information about the unnecessary part is not detected. It is designed for this purpose.

Now, if we ignore the mirror 11, in the optical system shown in Figure 1, the infrared image of the subject 1 will be reflected by the Cassegrain lens 2.
The light is focused by the infrared lens 5 and imaged onto the intermediate image forming plane 8, while the image of the infrared detecting element 10 is projected as a small spot onto the intermediate image forming plane θ by the relay lens 9. It is done like this. Here, infrared lens 5
The convex mirror 4 of the Cassegrain lens 2 is used as an entrance pupil, and the scanning means 7 is used as an exit pupil.

In other words, this means that the convex mirror 4 of the Cassegrain lens 2 and the scanning means 7 are in a conjugate relationship with respect to the infrared lens 5.

Because of this configuration, the scanning means 7 can be placed horizontally,
If the beam is deflected vertically, the image spot of the infrared detection element 10 will two-dimensionally scan the intermediate image plane θ, but the deflected beam will not protrude from the convex mirror. That is, when the infrared light beam is traced backward from the infrared detection element 10, the light amount is limited by the light flux diaphragm 8 and then reflected and deflected by the scanning means 7, regardless of the deflection angle of the scanning means 7. The light is incident on the convex mirror 4 of the Cassegrain lens 2.

In addition, when there are two scanning mirrors as shown in FIG. 3, the position having the above-mentioned conjugate relationship is preferably located at one of the two scanning mirrors or in the middle thereof.

Regarding the Cassegrain lens side, it may be better for the Cassegrain lens as a whole if the position of the conjugate relation is slightly shifted from the position of the convex mirror.

In FIG. 1, a mirror 11 reflects visible light and reflects the optical axis by a predetermined angle. When a mirror is used, it can be inserted as necessary, and it also transmits infrared rays. If a dichroic mirror that reflects visible light is used, it may be fixed in the state shown in FIG. The relay lens 12 is a lens for visible light, and forms an image of the subject 1 on an imaging plane 13. COD on the imaging plane 13
By arranging a T V illil elementary image consisting of the following, a visible image can be observed on a CRT, and of course it is also possible to visually observe it through an eyepiece (not shown). At this time, by adjusting the focal length of the relay lens 12 and the angle of the mirror 11, the visual field range of the visible image can be matched with the visual field range of the infrared image.

In this way, since visible light and infrared rays are separated from one optical axis, an infrared image and a visible image can be obtained on the same axis and in the same field of view.

Further, in FIG. 1, the reference black body 14 serves as a reference for temperature indication, and for example, by overscanning the scanning means 7 or rotating a chive plate having an appropriate shape, the reference black body 14 is set at a desired period. Infrared rays from the body 14 can be incident on the infrared detector, thereby making it possible to correct the absolute temperature of the subject. Please note that this matter is well known.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible. For example, the surface of the Cassegrain lens 2 is usually spherical, but it can also be aspherical to reduce aberrations. Furthermore, although the infrared detector has been described as using one element, it may also have an array structure of multiple elements. Furthermore, the Cassegrain lens 2 may be made replaceable so that lenses with various focal lengths can be used.

[Brief explanation of the drawing]

FIG. 1 shows one of the optical systems of the thermography apparatus according to the present invention.
2 is a diagram showing an example of the configuration of a light flux diaphragm, FIG. 3 is a diagram showing an example of an optical system of a conventional thermography apparatus, and FIG. 4 is a diagram showing an example of an optical system for obtaining a visible image. It is a figure showing an example of composition of a replacement unit. 1...Subject, 2...Cassegrain lens, 3...
・Concave mirror, 4... Convex mirror, 5... Infrared lens, 6.
... Intermediate imaging plane, 7... Scanning means, 8... Luminous diaphragm, 9... Relay lens, 10... Infrared detection element,
11...Mirror 12...Relay lens, 13...
Image plane, 14... Reference black body, 16... Optical axis. Figure 3 Applicant JEOL Ltd.

Claims (1)

[Claims] (1) A reflective optical system in which a concave mirror and a convex mirror are combined, a first lens, a scanning means, a light flux diaphragm, a second lens, and an infrared detector are arranged in this order, and the reflective optical system In an optical system of a thermography apparatus, the optical system and the scanning means are configured to have a conjugate relationship with respect to the first lens, and an optical axis of visible light can be reflected between the reflective optical system and the first lens. 1. An optical system for a thermography apparatus, characterized in that an optical member is fixed or insertable.