JPS6017071B2 - heating metal detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heated S metal detector that detects the presence or absence of a metal body by using the radiation emitted from the metal body heated to a high temperature.

In the past, there was one of this kind of hishi taka as shown in Figure 1.

In the figure, 1 is the object to be detected (heated metal), 2 is the scale light emitted from the object to be detected, 3 is the detection field of view, 4 is the condenser lens that collects the forehead emitted light 2, 5 is the rotary slit plate for the chopper, and 6 is the 7 is an AC amplifier, 8 is a DC converter, 9 is a comparison amplifier, and lo is an output relay. Next, the operation will be explained.

When the fly emitted light 2 emitted from the detected object 1 moving in the direction of the arrow 11 enters the detection field of view 3, the neck emitted light 2 is condensed by the condensing lens 4, and is photoelectrically converted via the rotary slit plate 5 for the chopper. The light enters the light receiving surface of the device 6.

The optical fin converter 6 generates an electrical signal proportional to the energy intensity of the input light. Therefore, theoretically, when the detected object 1 enters the detection field of view, in other words, at the moment when the cervical radiation 2 crosses the detection field of view 3, the photoelectric converter 6 emits an electrical signal proportional to the light intensity. Output. This signal changes as the detected object 1 moves, and shows a continuous output distribution as shown in FIG. Therefore, after being sufficiently amplified by the AC amplifier 7, it is converted to a DC signal and compared with the DC reference level 22 by the comparator amplifier 9. When the tail end of 1 leaves the set reference position, a trigger action occurs at the trigger point 21, generating an electrical 1.0 signal. This signal turns output relay 10 ON and OFF.
By performing F, it is possible to detect the presence or absence of a metal object. However, in reality, when the temperature of the detected object 1 passing through the detection field of view 3 ranges over a wide range, the following drawbacks occur.

As shown in FIG. 3a, the detection field 3 is
1 passes through, the output voltage of the photoelectric converter 6 is shown in Fig. 3c.
It is indicated by the reference numeral 26.

Further, as shown in FIG. 3M, the output voltage when a high-temperature metal body lh passes is indicated by reference numeral 25 in FIG. 3C. The output of the vertical key in FIG. 3c is expressed on a logarithmic scale.
The output voltage of the photoelectric converter 6 due to the reflected light emitted by an object is proportional to the temperature of the object, for example, to the fourth power (if the saturation state is not considered) (the relationship between temperature and output voltage is more complicated). , the fourth power shown here only shows the approximate relationship), low temperature metal body 1 1 and high temperature metal body l
The output voltage ratio with h may be a large value exceeding 10". Generally, the reflectance of a reflector existing within the range in which the detected object 1 moves is approximately 10%, and the third As shown in FIG.
%, it may be almost the same or larger than the direct Korean radiation from the cold metal body 11. Therefore, in the apparatus shown in FIG. 1, it is not possible to distinguish whether the Korean radiation is directly from the low-temperature metal body 11 or whether the Korean radiation from the high-temperature metal body is diffusely reflected by another object. Thus, the detection operation is performed even though the high-temperature metal body lh does not enter the detection field of view 3. This invention was made to eliminate the drawbacks of conventional detectors as described above.
By using an infrared bandpass filter that transmits only light of a specific wavelength, it is possible to reduce the difference in radiant energy caused by temperature differences, so that the tip or tail of the object to be detected is within the detection field of view. It is an object of the present invention to provide a heated metal detector that can be used to determine when a preset reference position within the heating area has actually been reached. Embodiments of the present invention will be described below based on the drawings. FIG. 4 is a block diagram showing one embodiment of a heated metal detector according to the present invention. In the figure, numerals 1 to 5 and 7 to 11 are the same as the respective parts of the subordinate detector described in FIG. Reference numeral 12 is an infrared bandpass filter that transmits only the solar radiation of a selected specific wavelength, and reference numeral 6' is a photoelectric converter that senses the radiation of the wavelength range that has passed through the filter 12.

As described above, after the same operation as the conventional counterfeiting is performed by the items 1 to 5 in FIG. The light enters the light-receiving surface of the photoelectric converter 6' through the photoelectric converter 12.

Figure 5a is a distribution diagram showing the energy distribution of Frank's black body crane radiation under temperature parameters.If we pay attention to Figure 5a, we can see that the energy distribution of the fin radiation from an ideal black body As the temperature increases, the area it occupies becomes wider, and the amount of reflected energy also increases.

In addition, the maximum sensitivity wavelength (the wavelength exhibiting the maximum spectral radiance)
is shifted toward shorter wavelengths. In the case of the conventional device shown in FIG. 1, if, for example, a Mr. P photoconductive cell is selected as the photoelectric converter 6, its sensitivity wavelength range is approximately 0.8 microns to 2.5 microns.
It is micron.

Figure 5b shows this wavelength range as input ab, and the output ratio from the photoelectric converter 6 at a maximum temperature of 1000 qo and a minimum temperature of 400°C is 110 as shown in Figure 5c, if the saturation state is not considered. :1. As mentioned above, the reflectance of the reflector that exists within the range in which the object to be detected generally moves is:
It is said to be approximately 10%, and the above output voltage ratio is 110:1.
In this case, it became difficult to distinguish between the diffused reflection from other objects (reflectors) due to the light emitted from the low temperature (lowest temperature) metal object, or the diffused reflection from other objects (reflectors) due to the forehead shot from the high temperature (highest temperature) metal object, which caused malfunctions. . In this invention, whereas the conventional photoelectric converter 6 collects light in the entire sensitivity range ^ab of the photoelectric converter 6, the infrared bandpass filter 12 collects only light in a narrow band on the long wavelength side. It is targeted. That aspect is the fifth
In Fig. b, the energy ratio at the highest and lowest temperatures, that is, the output voltage ratio of the photoelectric converter, is greatly reduced. For example, if the center wavelength ^c of the infrared bandpass filter 12 is 4.3 microns, the output voltage ratio from the photoelectric converter 6' is 9: as shown in FIG. 5c.
1, making it possible to prevent errors from occurring even if there is a reflector with a reflectance of about 0 to 10%. That is, as the center wavelength of the infrared bandpass filter 12 is selected toward the longer wavelength side, the output voltage ratio from the photoelectric converter tends to decrease, as shown in FIG. 5c.

From the above, if the infrared bandpass filter and photoelectric converter are selected according to the site environment (reflectance of the reflector), error factors can be eliminated. Practically, when considering the sensitivity range of a photoelectric converter, the center wavelength of an infrared bandpass filter is between 4.3 microns and 30 microns.
With ^d, the error factor caused by the reflector can be eliminated from a reflectance of zero to about 50%.

After sufficiently reducing the difference in radiation energy caused by the difference in temperature using the infrared bandpass filter, that is, the output voltage ratio of the photoelectric converter,
With the section 0, the same operation as in the conventional one described above is performed.

In the above embodiment, an infrared bandpass filter is used, but a photoelectric converter that is sensitive only to a certain narrow range of infrared wavelengths may also be used.

As described above, according to the present invention, by using the infrared band-pass filter 12, only light of a specific wavelength on the longer wavelength side of the infrared light 2 is used. The difference in beam energy, i.e. the output voltage ratio from the photoelectric converter 6', can be reduced to a large extent, with error factors such as reflectance within a limited range due to beam radiation from a hot metal body. It is possible to eliminate deviations in the operating point caused by diffused reflection from the reflector, resulting in a significant improvement in accuracy.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing a conventional heated metal detector, Figure 2 is a block diagram showing a conventional heated metal detector.
3 and 3 are explanatory diagrams for explaining the operation of the conventional heated metal detector, FIG. 4 is a block diagram showing an embodiment of the heated metal detector according to the present invention, and FIG. 5 is a block diagram showing an embodiment of the heated metal detector according to the present invention. FIG. 3 is an explanatory diagram for explaining the operation of the heated metal detector. In the figure, 1 is the object to be detected, 2 is the neck radiation from the object to be detected, 3 is the detection field of view, 4 is the condenser lens, 5 is the rotary slit plate for the chopper, 6' is the photoelectric converter, and 7 is the AC amplifier. , 8
is a DC converter, 9 is a comparison amplifier, 10' is an output relay,
12 is an infrared bandpass filter. Hakama - Figure 4 Hakama Figure 2 Figure 3 Hakama Figure 5

Claims (1)

[Claims] 1. A lens for condensing a radiant from a moving heated metal body, and a narrow band whose center wavelength is within a limited range on the long wavelength side of the light condensed by this lens. an infrared bandpass filter that transmits only the light of A heated metal detector comprising a converter and a comparison amplifier that compares and amplifies the DC signal with a constant DC reference level. 2. A lens that focuses radiation light from a moving heated metal body, and is sensitive only to a narrow band of light that has a center wavelength within a limited range on the long wavelength side of the light focused by this lens. A photoelectric converter that converts the electrical signal into an electrical signal, an AC amplifier that amplifies the electrical signal, a DC converter that converts this amplified electrical signal into a DC signal, and an amplification device that compares this DC signal with a fixed DC reference level. A heated metal detector characterized in that it is equipped with a comparison amplifier.