JPH0854286A - Scanning type radiometer - Google Patents

Abstract

PURPOSE:To always obtain an excellent image without variation in an incident light quantity incident at a measuring angle when a rotary mirror is used and without influence of the lens effect of a measuring window by disposing the window of a spherical shape on an optical axis between an object to be measured and the mirror. CONSTITUTION:A measuring window 2 provided on an optical axis between an object 1 to be measured and a rotary mirror 3 is formed into a semicylindrical shape. Thus even if the measuring angle varys, the angle of the incident light always becomes constant, and the difference of the incident light quantity due to the measuring angle is eliminated. The window 2 is operated as a concave lens in the horizontal direction to radius gamma of curvature. However, when the reflecting surface of the mirror 3 is formed into a curved shape having a convex lens effect only on one direction and the radius of curvature and the disposition are so set as to cancel the lens effect of the window 2, the image formed position becomes equal to the state having no window 2 and no mirror 3. The distortion of the image due to the influence of the window 2 is automatically corrected. Accordingly, the increase of the scanning angle can be realized by a simple mechanism, and always clear image formation can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning radiometer used for measuring the brightness or temperature distribution in one direction such as a steel plate or a cement kiln.

[0002]

2. Description of the Related Art Conventionally, as a scanning radiometer used as a line scanner, there is known one having a mechanism for scanning a measuring field of a condensing optical system with a rotating polygon mirror such as a polygon mirror. However, this mechanical system has a problem that the amount of light in the peripheral portion of the effective scanning region becomes smaller than that in the center due to the shading phenomenon of the condensing optical system, and an electrical or optical correction means is required. Therefore, the apparatus becomes complicated and the effective scanning angle is limited.

Further, a rotating mirror for scanning the emitted light from the object to be measured is arranged in front of the condensing optical system, and a transparent plastic thin plate such as hard vinyl chloride is used for the measuring window to make the lens effect of the measuring window. A line scanner is commercially available that suppresses the difference and eliminates the difference in the amount of received light depending on the measurement angle. In this method, since the plastic thin plate used for the measurement window has low mechanical strength, it has a drawback that it is easily deformed or damaged. If the plastic window is made thick to compensate for this drawback, the lens effect of the measurement window cannot be ignored. Also,
In general, radiation thermometers use wavelengths in the infrared region, but since the transmittance of plastics in the infrared region is lower than that of infrared-transparent glass, energy loss is large, and in addition, the transmittance of specific wavelengths is high due to molecular bonds. Since it decreases, there is a problem that the measurement wavelength is restricted.

In Japanese Patent Application Laid-Open No. 2-306129, instead of using a rotating mirror, mechanical scanning of a mechanism in which an optical system and an optical path changing mirror are interlocked and tilted in order to scan an image pickup signal from an image pickup object. Radiometers have been proposed. However, this method has a drawback that the driving mechanism for linking the optical system and the optical path changing mirror is complicated.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art.
By arranging the measurement window with a special shape, it is possible to always obtain a good image without fluctuation of the incident light amount depending on the measurement angle when the rotating mirror is used and without being affected by the lens effect of the measurement window. It is an object to provide a scanning radiometer having a simple mechanism.

[0006]

In order to achieve the above object, a scanning radiometer according to the present invention includes a rotating mirror for scanning the emitted light from an object to be measured, and a light reflected by the rotating mirror. In the scanning radiation mechanism, which is composed of a condensing optical system, an optical sensor for converting the imaged light into an electric signal, and a signal processing circuit for processing the converted electric signal with data, rotation with an object to be measured is performed. A semi-cylindrical measurement window that transmits visible light or infrared rays is provided on the optical axis between the mirrors in a state where the curved inner surface faces the rotation mirror direction, and a rotation mirror having a curved reflection surface that faces the measurement window is provided. The structural feature is that it is installed at an angle of 45 ° with respect to the incident optical axis.

FIG. 1 is an explanatory view schematically showing a structural mechanism of a scanning radiometer according to the present invention. 1 is an object to be measured, 2 is a measurement window, 3 is a rotating mirror, and 4 is a converging optical system. 5 is an optical sensor, and 6 is a signal processing circuit. The light emitted from the measured object 1 passes through the measurement window 2 and is reflected by the rotating mirror 3 to enter the condensing optical system 4. The condensed light is imaged on the optical sensor 5, converted into an electric signal here, and then displayed by the signal processing circuit 6. According to the present invention, as shown in FIG. 2 (enlarged perspective view of the measurement window and the rotary mirror portion), the curved inner surface is on the optical axis between the object to be measured 1 and the rotary mirror 3 in the above-mentioned configuration mechanism. The measurement window 2 having a semi-cylindrical shape is provided in a state of facing the measurement window, and the rotating mirror 3 having a curved reflection surface is installed so as to face the measurement window 2 while being inclined at an angle of 45 ° with respect to the incident optical axis. The points have major components.

The measuring window 2 is formed in a thick semi-cylindrical shape from a material that transmits visible or infrared rays.
As the constituent material, for example, CaF ₂ , MgF ₂ , BaF
Fluoride glassy materials such as ₂ and transparent plastic materials such as hard vinyl chloride can be mentioned. However, the spectral transmittance of the transparent plastic plate is a phenomenon in which the transmittance locally decreases due to the absorption effect caused by the molecular bond,
The overall transmittance is also low. On the other hand, a fluoride-based vitreous material has an advantage in that it has a uniform transmission characteristic and a high transmittance, and a large received light energy can be obtained without being restricted by the measurement wavelength. For the purpose of the present invention, an optical glass or an optical crystal, particularly a material having a thickness of about 10 mm, which has a high mechanical strength and is formed into a semi-cylindrical shape by melt-forming CaF ₂ (refractive index 1.4) is preferably used. The rotating mirror 3 having a curved reflecting surface that is mounted in a state of facing the measurement window 2 has its rotation axis located at the center of the measurement window 2 and has an inclination angle of 45 ° with respect to the incident optical axis. It is installed and is always equipped to rotate at this tilt angle.

In this case, since the semi-cylindrical and thick measurement window 2 has a lens effect, the measurement visual field of the condensing optical system expands in only one direction to cause distortion, and depending on its radius of curvature r Since the entire system is a diverging system, it is necessary to make the curved reflecting surfaces of the rotating mirrors 3 facing each other have a radius of curvature r that cancels the lens effect. For this purpose, the radius of curvature r of each spherical surface in the semi-cylindrical measurement window 2 and the rotating mirror 3 having a curved reflecting surface is set to f _{1 as} the focal length when the measuring window is assumed to be a lens, and the focus of the rotating mirror is set. When the distance is f ₂ , it is set to satisfy the relationship of f ₁ = −f ₂ .

[0010]

According to the scanning radiometer of the present invention, by forming the measurement window in a semi-cylindrical shape, the angle of incident light is always constant even if the measurement angle changes, and the difference in the amount of incident light depending on the measurement angle. Disappears. Further, the measuring window acts as a concave lens only in the surface direction horizontal to the radius of curvature r, but the reflecting surface of the rotating mirror has a curved shape having a convex lens effect only in one direction, and its radius of curvature and arrangement are the lenses of the measuring window. If the setting is made so as to cancel the effect, the image forming position becomes equal to the state in which the measurement window and the rotating mirror are not provided, and the image distortion due to the influence of the measurement window is automatically corrected. Therefore, the scanning angle can be expanded by a simple mechanism, and a clear image can always be obtained.

[0011]

【Example】

Examples 1 to 2 In the scanning radiometer having the mechanism shown in FIG. 1, the thickness and the focal length (radius of curvature) of CaF ₂ (refractive index 1.4) formed on the optical axis of the measured object 1 were measured. A different semi-cylindrical measurement window 2 and a rotating mirror 3 having a curved reflecting surface were arranged in a state of facing each other as shown in FIG. The condensing optical system 4 is a Cassegrain optical system including a secondary mirror and a primary mirror. The image forming distance in this case is shown in Table 1. In addition, the image forming distance is determined by the condensing optical system 4.
The distance from the primary mirror to the optical sensor 5 for focusing.
As a standard, Table 1 also shows the image formation distances when a plane rotating mirror was used without setting a measurement window.

Example 3 A scanning radiometer having the same mechanism as in Example 1 except that the measurement window 2 was a semi-cylindrical shape made of a vinyl chloride thin plate having a thickness of 0.3 mm was manufactured. The imaging distance in this case is also shown in Table 1.

Comparative Example 1 A scanning radiometer having the same semi-cylindrical measurement window as in Example 1 and a rotating mirror as a plane mirror was prepared and the image forming position was measured. The results are also shown in Table 1.

Comparative Example 2 A scanning radiometer having the same semi-cylindrical measurement window as in Example 3 and having a rotating mirror as a plane mirror was prepared and the image forming position was measured. The results are also shown in Table 1.

[0015]

[Table 1]

From the results shown in Table 1, in the scanning radiometer of the embodiment, the image distortion due to the semi-cylindrical measurement window is automatically corrected,
The same imaging position as the standard is shown. Further, even when the measurement angle fluctuates, the angle of the incident light with respect to the measurement window is always constant, and there is no difference in the amount of incident light. But,
In Example 3, a problem that the film was easily deformed and the wavelength transmittance was low due to the use of a thin film of vinyl chloride in the measurement window was recognized. In Comparative Example 1 and Comparative Example 2, since the plane mirror was used as the rotating mirror, the lens effect of the semi-cylindrical measurement window was not canceled, and the image-forming position was largely displaced from the standard.

[0017]

As described above, according to the present invention, the allowable range of the measurement angle of the incident light quantity is expanded by combining the semi-cylindrical measurement window and the rotary mirror having the curved reflection surface for eliminating the lens effect. Moreover, it is possible to provide a scanning radiometer capable of always performing highly accurate measurement without image distortion. In addition, since it does not require a complicated mechanical structure and can be designed compactly, it is expected to have excellent practicability as a measuring device for measuring the brightness and temperature distribution of various objects at the manufacturing site.

[Brief description of drawings]

FIG. 1 is a structural explanatory view schematically showing a mechanism of a scanning radiometer according to the present invention.

FIG. 2 is an enlarged perspective view of a combined portion of a measurement window and a rotating mirror in FIG.

[Explanation of symbols]

 1 Object to be Measured 2 Measurement Window 3 Rotating Mirror 4 Condensing Optical System 5 Optical Sensor 6 Signal Processing Circuit

Claims (3)

[Claims] 1. A rotating mirror for scanning emitted light from an object to be measured, a condensing optical system for receiving light reflected by the rotating mirror, and light for converting the imaged light into an electric signal. In a scanning radiation mechanism consisting of a sensor and a signal processing circuit that processes the converted electrical signal, visible or infrared rays are emitted on the optical axis between the object to be measured and the rotating mirror with the curved inner surface facing the rotating mirror. A rotary mirror having a semi-cylindrical measurement window that is transparent and having a curved reflection surface facing the measurement window is provided at 45 ° with respect to the incident optical axis.
A scanning radiometer characterized by being installed at an angle of. 2. When the radius of curvature of a rotating mirror having a semi-cylindrical measuring window and a curved reflecting surface is f ₁ when the lens of the measuring window is assumed to be f ₁ , and the rotating mirror has a focal length of f _2. , scanning radiometer according to claim 1 wherein the set so as to satisfy the relation f ₁ = -f _2. 3. A scanning radiometer according to claim 1, wherein the semi-cylindrical measuring window is made of a thick material of optical glass or optical crystals.