JPH0712728A - Method and device measuring burning condition - Google Patents

Abstract

PURPOSE:To provide a measuring method and a measuring device which can minimize the affection of heat radiation from a wall of a furnace or a burner flame so as to precisely detect a furning condition of a material in the furnace. CONSTITUTION:An image inside of a furnace 20 is picked up through a bandpass filter 10 which can selectively pass therethrough electromagnetic waves in a wavelength range of excited light radiated from a specific product produced from a raw material 30. Further, an actural burning condition of the material 30 in the furnace 20 is measured from thus obtained image. Accordingly, optical stray light and distorted signals which have been conventionally caused by burner flame 23 having a high brightness can be removed, and the affection by heat radiation from the burner flame 23 and a wall of the furnace 22 can be reduced so as to precisely measures a burning condition of the raw material 30. Further, the position of a burning range or the degree of the range can be known.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for measuring the firing state of raw materials in a firing furnace such as a rotary kiln,
In particular, the present invention relates to a baking state measuring method and a measuring apparatus for measuring a baking state based on an image obtained by photographing the inside of a baking furnace.

[0002]

2. Description of the Related Art Conventionally, for example, in the case of coke or the like, in order to remove water, volatile components and the like to improve the quality, the coke as a raw material is fired in a firing furnace such as a rotary kiln. A rotary kiln may also be used to obtain sulfuric acid or the like by firing sulfide ore. This rotary kiln has a long length (for example, 50-
While injecting the burner flame from the low side into the firing furnace of about 100 m), the raw material is put into the furnace from the high side and the firing is completed until the raw material reaches the low side. ing.

At this time, in order to burn the raw material in the optimum temperature region in the furnace and keep its position, the firing state in the furnace is observed, and the amount of fuel gas and the amount of combustion air supplied to the furnace are observed. Etc. are adjusted appropriately. As a method for observing the inside of the furnace, the position of the combustion region of the raw material is detected by photographing the inside of the furnace with an image pickup device such as a television camera or a CCD camera and performing image analysis for binarizing the obtained image. The method is known (Japanese Patent Laid-Open No. 63-230787).

[0004]

However, as described in JP-A-63-230787 mentioned above, if the inside of the furnace is simply photographed by the video camera, the image processing is performed to perform the binarization. It was made clear by the present inventors that a sufficiently high-quality image cannot be obtained. As a cause, if the camera captures electromagnetic waves in a wide wavelength range (for example, the entire range of visible light or the range from ultraviolet to infrared), the brightness of the burner flame becomes extremely large, so stray light in the optical system. For example, the burner flame may bleed around the burner flame to obscure the combustion region of the raw material, or the brightness of the combustion region may be modulated.

Further, the intensity of light (line spectrum) emitted by the combustion of the raw material is larger than the intensity of thermal radiation (continuous spectrum) from the furnace wall or burner flame in a wavelength band of the light, but it is wide. In the wavelength range, the integrated value of the intensity of the heat radiation becomes much larger, and it becomes extremely difficult to distinguish between the combustion region and other places. Therefore, it is extremely difficult to clearly detect the position of the combustion region, because even if the image processing is performed, only information having many disturbing elements, that is, inaccurate information can be obtained.

The present invention has been made in order to solve the above problems, and its purpose is to minimize the influence of heat radiation from the furnace wall and burner flame and to calcine the raw material in the furnace. It is an object of the present invention to provide a measuring method and a measuring device for a firing state, which makes it possible to accurately know the state and combustion region.

[0007]

In order to achieve the above object, the inventors of the present invention, for example, in the case of coke, CH, CO ₂ and CO (in the case of sulfide ore in the case of combustion of volatile components contained therein). SO ₂ ) generation reaction occurs, but since the reaction is in an energetically excited state, it was considered that peculiar excitation light was emitted from these products.
Then, when the spectral characteristics of the electromagnetic wave radiated in the furnace were measured, as shown in FIG. 8, the light (line (a) in FIG. 8) and the light emitted from the burning region (reaction region) of the raw material and In the spectral characteristics of the light emitted from the vicinity ((b) line in FIG. 8), it was found that there is a peak associated with the excitation of CH ions in the wavelength band near 435 nm. On the other hand, in the spectral characteristics of heat radiation from the burner flame ((c) line in Fig. 8) and heat radiation from the furnace wall ((d) line in Fig. 8), there is a peak near 435 nm, but its magnitude Was found to be relatively small compared to the overall intensity. That is, it was confirmed from the combustion region in the furnace that excitation light of a specific wavelength was radiated from a specific product generated from the raw material during firing. Therefore, it is considered that the reaction state in the furnace can be known by measuring the excitation light.

The present invention was made on the basis of the above findings, and when measuring the firing state of the raw material being fired in the firing furnace by an image obtained by photographing the inside of the firing furnace, the raw material being fired is measured. It is proposed that the electromagnetic waves in the wavelength band of the excitation light emitted from the specific product substance that is generated are photographed through a bandpass filter that can selectively pass through.
Further, the brightness of the image obtained by the above photographing may be corrected. In addition, the first image described above,
Arithmetic processing is performed using the second image obtained by photographing the inside of the firing furnace through a filter capable of selectively transmitting electromagnetic waves in the wavelength band other than the wavelength band of the excitation light emitted from the specific product. You may do it. Furthermore, the correspondence relationship between each location in the image and each location in the firing furnace is determined in advance, and the actual raw material flow path in the firing furnace is determined in advance to correspond to the raw material flow path. In the firing furnace by continuously obtaining the luminance along the virtual reference line on the image, specifying the burning region on the image based on the luminance, and comparing the burning region on the image with the corresponding relationship. The position of the actual combustion region may be specified.

Further, the present invention is an apparatus used in the above-mentioned measuring method, wherein the first imaging means capable of photographing the inside of the firing furnace and the excitation light emitted from a specific product generated from the raw material during firing. And a bandpass filter capable of selectively transmitting electromagnetic waves in the wavelength band of, and the first imaging means is connected to the firing furnace through the bandpass filter. To propose. Further, it is assumed that the present apparatus is provided with a video signal correcting means for correcting the brightness of the image obtained by the above photographing. Furthermore, in the present apparatus, the second imaging means is connected to the firing furnace via a filter capable of selectively transmitting electromagnetic waves in a wavelength band other than the wavelength band of the excitation light emitted from the specific product. The first image obtained by the first image pickup means is changed to a desired image by using the second image obtained by the second image pickup means. It is assumed that the image processing means for conversion is provided. Further, the combustion region on the image is specified based on the brightness continuously measured along the virtual reference line on the image corresponding to the actual flow path of the raw material in the firing furnace, and the combustion on the image is determined. It is assumed that the image processing means is provided for identifying the position of the actual combustion region in the firing furnace by comparing the regions with the corresponding relationship between each location in the image and each location in the firing furnace. The term "firing furnace" as used herein refers to a type of furnace, such as a rotary kiln, in which raw materials are baked while moving in the furnace.

[0010]

According to the above-mentioned means, since the inside of the furnace is photographed through the bandpass filter capable of selectively transmitting the electromagnetic wave in the wavelength band of the excitation light emitted from the specific substance generated by the combustion reaction of the raw material, this band is taken. The pass filter largely blocks the transmission of burner flame and heat radiation from the furnace wall (see Fig. 2), so the brightness of the burner flame is suppressed to a low level, stray light of the optical system and signal distortion are eliminated, and the image is It becomes clearer and the burning area is captured brighter than elsewhere. Therefore, it is also possible to measure the firing state, the position of the combustion region, its size (area), and the like.

Further, the brightness of the image obtained by photographing is corrected, and the burning region of the raw material, the burned raw material that has passed through the burning region, the burner flame, and the furnace wall of the burning furnace closer to the burner flame than the burning region, By increasing the mutual contrast of each luminance in the area on the image corresponding to each part of
The image obtained by shooting becomes an image suitable for image processing.

Further, the first image capturing the wavelength band of the excitation light emitted from the above-mentioned specific product is calculated using the second image capturing the wavelength band excluding the wavelength band of the excitation light. Even if the intensity of the heat radiation from the burner flame or the furnace wall in the transmission band of the bandpass filter becomes equal to or higher than the intensity of the light emitted by the combustion reaction of the raw material, for example, the first If the information of the second image is subtracted from the information of the image, the effect of heat radiation is removed to obtain an image in which the burning region is emphasized. Further, even if the intensity of heat radiation is weaker than the light due to the combustion reaction, the effect of heat radiation is removed by reducing the information of the second image, and a clearer image can be obtained. Then, from the second image, it is possible to know the distribution of the intensity of thermal radiation in each part in the furnace, and it is also possible to accurately grasp the temperature in the furnace.

Furthermore, by previously obtaining the correspondence between the image and the actual position in the firing furnace, the firing state in the firing furnace can be grasped by looking at the displayed image. If the brightness is continuously calculated along the virtual reference line on the image corresponding to the path of the actual raw material flow, the brightness is higher in the combustion area than in the front side and the back side, so the brightness corresponds to the combustion area. The area on the image to be displayed can be specified.

[0014]

EXAMPLE As an example to which the present invention is applied, a case of monitoring the inside of a rotary kiln for producing electrode coke will be described as an example. (First Embodiment) FIG. 1 schematically shows an example of a rotary kiln to which a measuring device according to the present invention is attached. As shown in the figure, the measuring apparatus 1 includes a bandpass filter 10 capable of selectively transmitting excitation light emitted from a specific product produced by firing of a raw material, and a rotary camera including a television camera and a CCD camera. The first image pickup means 11 for photographing the inside of the firing furnace 20 of the kiln 2, the video signal correction means 12 for correcting the brightness of the obtained image, and the luminance on the obtained image are measured to measure the inside of the furnace 20. An image processing means 13 for specifying an area on the image corresponding to the combustion area A;
And a display device 14 for displaying an image. And
The measuring apparatus 1 is attached to the observation window 21 of the baking furnace 20 via an imaging lens (not shown).

FIG. 2 shows the wavelength characteristic of the bandpass filter 10. As shown in the figure, the bandpass filter 10 has ± several nm to several tens of nm centered at 435 nm.
It has a transmission band D of about nm (for example, ± 5 to 20 nm). Electromagnetic waves such as light having a wavelength in a shaded region (absorption band) E in FIG. 2 and heat radiation cannot pass through the filter 10. Therefore, the raw material 30 (see FIG. 1),
That is, since the peak (435 nm) due to the excitation light (CH line in FIG. 2) of CH ions generated by the combustion reaction of the volatile components in the raw coke is located within the transmission band D, almost the entire bandpass is generated. The light is transmitted through the filter 10 and captured by the image pickup means 11.

On the other hand, since the thermal radiation of the furnace wall 22 and the burner flame 23 (see FIG. 1) (the (f) line in FIG. 2) is a continuous spectrum, the portion in the transmission band D shown by the broken line in FIG. Only the thermal radiation passes through the bandpass filter 10 and the imaging means 1
Although it reaches 1, the thermal radiation of the other portion indicated by the alternate long and short dash line in the absorption band E is blocked by the bandpass filter 10 and is not photographed. That is, the furnace wall 22 and the burner flame 2
Since most of the heat radiation of No. 3 is shielded by the bandpass filter 10, its influence is reduced, stray light of the optical system and signal distortion are eliminated, and a clear image is obtained, and the combustion area A is It is captured brighter than the place. In this embodiment, a thin film interference filter is used as the bandpass filter 10.

The video signal correction means 12 is provided in a computer and converts the video signal output from the image pickup means 11 into, for example, an 8-bit digital signal and corrects it so as to be suitable for image processing. Is. That is, the image obtained by photographing with the image pickup means 11 has a low contrast as it is and is not suitable for image processing. Therefore, the video signal correction means 12 corrects the contrast and brightness of the obtained image.

An example of the contents of the correction process will be described. FIG. 3 schematically shows the inside of the firing furnace 20 photographed by the image pickup means 11, but the bandpass filter 10
For example, an image that has been shot via
When sampled at (point), the difference in brightness between the darkest part and the brightest part is only about 100 points, and the difference in brightness between the combustion region A and its surroundings (the inner part 20a of the furnace, the calcined raw material 31, etc.) is ± 30
It becomes about a point. Therefore, the contrast is increased so that the brightness difference in the required range, that is, the periphery of the combustion area A becomes 256 points. In this way, the brightness of each of the inner part 20a of the furnace, the combustion region A, the calcined raw material 31, the furnace wall 22a near the calcined raw material 31, and the burner flame 23 is, for example, 10, 100, 160, 250, and 256
Therefore, the difference in brightness between the combustion area A and its surroundings becomes large, which makes it suitable for image processing.

The image processing means 13 is provided in the computer and specifies the position of the combustion area A in the furnace 20 by associating each area on the image with the actual position in the baking furnace 20. Is. That is, the unprocessed image is
It is only divided into several regions based on the digital signal output from the video signal correction means 12, and in which of these regions, for example, the combustion region A, the calcined raw material 31, or the vicinity of the calcined raw material is located. This is because it is not known whether the furnace wall 22a or the like corresponds.

An example of the processing content will be described. First, the correspondence range of the photographing range of the image pickup means 11, that is, the portion in the image captured by the image pickup means 11 in the actual firing furnace 20, is obtained in advance. in addition,
Although the display range of the image is schematically shown in FIG. 4, as shown in the drawing, the actual flow of the raw material in the firing furnace 20, that is, the raw material was introduced from the inlet 24 of the firing furnace 20 in advance. An imaginary raw material flow reference line ((Toch) line in FIG. 4) corresponding to the raw material flow in the image is determined based on the path from the raw material 30 being baked to the outlet 25.

Then, with respect to the image composed of the corrected video signal sent from the video signal correcting means 12, for example, along the raw material flow reference line (torch), the front side (image pickup means 1
The brightness is continuously measured from the side close to 1) toward the inner part 20a of the furnace. The typical measurement result is schematically shown in FIG. 5, but as shown in the figure, after the brightness gradually decreases toward the back side, the high brightness state continues, The brightness decreases again. This is because in the combustion area A, the brightness is higher than that on the front side or the back side.

Therefore, in this graph, the range (region F in FIG. 5) from the time when the luminance, which was in the downward trend, starts to change to the upward trend, to the time when it again changes to the downward trend, corresponds to the combustion region A. Then, on the image, a region including a portion corresponding to the region F on the raw material flow reference line (torch) is defined as a combustion region A. Based on the identified combustion region A, regions corresponding to the burned raw material 31, the furnace wall 22a near the burned raw material, the burner flame 23, and the like are identified. Then, a signal for displaying an image composed of the specified areas is output to the display device 14. In addition, in FIG.
The concentric lines are equidistant lines marked on the furnace wall 22,
It is shown that the distance from the front side of the firing furnace 20 is, for example, 10 m, 20 m, 30 m, 40 m, and 50 m in order from the outer side (the same applies to FIG. 3). Further, the reference numeral 26 is a mark (reference mark) 26 provided at a position 25 m from the front side of the firing furnace 20. If necessary, the image 26 and the actual firing furnace 20 may be used as a reference. Calibrate the correspondence between the positions of and.

By the way, in the obtained image, the burner flame 23 may cover the combustion area A. In this case, the image processing means 13 determines whether the burner flame 23 is covered. If it is determined that the burner flame 23 is covered, the image is rejected, and the combustion region A is measured by the image that is determined not to be covered by the other burner flames 23. In addition, the judgment standard is, for example, that the burner flame 2 near the expected combustion region A is
Whether or not there is a region corresponding to the luminance of 3 (256 in the case of the above 8-bit sampling).
If present, it is considered covered by the burner flame 23.

The processing contents of the video signal correction means 12 and the image processing means 13 are the same as the band pass filter 10.
If the area corresponding to the combustion area A can be specified in the image obtained by the image pickup means 11 via the camera and the position of the combustion area A in the actual firing furnace 20 can be specified, It goes without saying that the processing content is not limited. Moreover, it goes without saying that the design of the measuring apparatus 1 may be changed in various ways.

(Second Embodiment) FIG. 6 shows another example of the optical system of the measuring apparatus according to the present invention. The same members and the same points as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted. As shown in the figure, in this second embodiment, the observation window 21 of the firing furnace 20 is used.
A spectroscopic means such as a dichroic mirror 16 is provided between the image forming lens 15 attached to the image forming lens 15 (see FIG. 1) and the band pass filter 10 described above, and an optical path (re, null) from the image forming lens 15 to the dichroic mirror 16 is provided. , Wo)
Is transmitted through the mirror 16 to the bandpass filter 10 and the first image pickup means 11 in the first optical path (R, W)
And a second optical path (le, work) which is reflected by the mirror 16 and reaches the filter 17 and the second image pickup means 18. Then, the image obtained by the first image pickup means 11 is subjected to arithmetic processing using the image obtained by the second image pickup means 18.

The filter 17 prevents the excitation light having a peak at 435 nm from entering the at least second image pickup means 18, and at least the absorption band E other than the transmission band D of the bandpass filter 10 (see FIG. 2)). This gives the second image
The image is one in which the influence of the combustion of the raw material 30 is removed.

Therefore, for example, if the content of the arithmetic processing is to subtract the information of the second image from the information of the first image to obtain the difference, the portion of the first image other than the combustion region A is The influence can be almost eliminated. That is,
The combustion region A can be extracted, and an image in which the combustion region A is made clearer can be obtained. Such calculation processing is performed in the image processing means 13. The second image pickup means 18 is a camera having the same structure as the image pickup means 11.

Here, in order to detect the black body radiation from the furnace wall or the like, the transmission band of the filter 17 is preferably provided in a wavelength band extending from visible light to the near infrared region, and more preferably. The wavelength band is preferably 600 to 1000 nm, more preferably 650 nm. If the filter 17 having such a transmission band is used, the difference in luminance between the black body radiating portion and the excited reaction portion (combustion area A) increases, and it becomes easier to extract the excited reaction portion.

Instead of branching the optical path by using the dichroic mirror 16 or the like, as shown in FIG. 7, two image pickup means 11 and 18 whose optical axes are parallel to each other may be arranged close to each other. In this case, the portion to be monitored, that is, the position of the combustion region A is near the optical axis, and the image pickup means 1
If the distance between 1 and 18 is several tens of times or more, the same effect as in the second embodiment can be obtained.

In addition to the processing content of subtracting the information of the second image from the information of the first image to obtain the difference in the arithmetic processing, the following processing content can be considered, for example. That is, in each portion (pixel) corresponding to each other between the first image (intensity is P ₁ ) and the second image (intensity is P ₂ ) the intensity represented by the equation (1) Ratio,
The relative intensity difference represented by the equation (2) is obtained, and the image is reconstructed based on the value. By doing so, since the intensity ratio and the relative intensity difference depend on the property of the emitted light regardless of the brightness of the obtained image, not only the combustion region A can be easily distinguished, but also It is also possible to measure the temperature distribution in the firing furnace 20. _{P 1 / P 2 ...... (1} ) (P 2 -P 1) / P 2 = 1-P 1 / P 2 ...... (2)

Further, instead of obtaining the intensity ratio and the like as described above, different colors may be assigned to the first image and the second image, and the two images may be combined and displayed. By doing so, the combustion region A can be discriminated by the difference in color, which is extremely effective when the firing state is monitored by looking at the image displayed on the color display device 14. For example, if the first image is blue and the second image is red, the combustion area A is displayed in blue and the other areas are displayed in purple or red, so that the determination of the combustion area A is obvious. .

In the above first and second embodiments, the case where the present invention is applied to the firing of coke has been described. However, the present invention is applied when firing a material other than coke such as sulfide ore. Of course, it is applicable. For example, in the case of calcination of sulfide ore, SO ₂
Occurs as a specific product. Therefore, the inside of the firing furnace 20 may be photographed using a bandpass filter capable of transmitting light in the wavelength band (570 to 580 nm) of excitation light based on the SO ₂ .

[0033]

According to the firing state measuring method and measuring apparatus of the present invention, since the specific excitation light based on the combustion reaction of the raw material is selectively transmitted by the bandpass filter, the inside of the furnace is photographed. The stray light of the optical system and signal distortion, which were conventionally caused by the burner flame with high brightness, can be removed, and the influence of heat radiation from the burner flame and the furnace wall is reduced, and the firing state can be accurately grasped. can do. In addition, the position of the combustion region and its size (area) can be known.

Further, the brightness of the image obtained by photographing is corrected to increase the mutual contrast of each luminance in the area on the image corresponding to each portion in the furnace.
An image that is not suitable for image processing as captured can be converted into an image that is suitable for image processing, and image processing can be performed. Therefore, a clearer image can be obtained by image processing.

Further, arithmetic processing is performed on the first image obtained by capturing the specific excitation light and the second image obtained by removing the excitation light, and, for example, the information of the first image is changed to the information of the second image. Is reduced to obtain an image in which the influence of thermal radiation is removed and the burning region is emphasized. And from the second image,
It is possible to know the distribution of the intensity of heat radiation in each part of the furnace, and it is possible to accurately grasp the temperature inside the furnace.

Furthermore, the correspondence between the image and the actual position in the firing furnace is obtained in advance, and the luminance is continuously obtained along the virtual reference line on the image corresponding to the path of the actual raw material flow. As a result, the region on the image corresponding to the combustion region can be specified, so that the actual combustion region in the firing furnace can be known and the firing state can be grasped only by looking at the displayed image.

From the above effects, it becomes easy to measure and monitor the position and range of the combustion region of the raw material and the firing state in the firing furnace, which has been difficult to measure in the past, and it is possible to optimize the operating state of the firing furnace. The quality of coke obtained by firing can be stabilized and improved.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a rotary kiln to which a measuring device according to the present invention is attached.

FIG. 2 is a characteristic diagram showing wavelength characteristics of a bandpass filter in the measuring apparatus.

FIG. 3 is a schematic view showing a state inside the firing furnace, which is photographed by an image pickup means in the measuring apparatus.

FIG. 4 is a schematic diagram showing a display range of an image.

FIG. 5 is a characteristic diagram schematically showing typical results obtained by continuously measuring the brightness of the obtained image along the raw material flow reference line.

FIG. 6 shows another example of the optical system of the measuring apparatus according to the present invention.

FIG. 7 shows still another example of the optical system of the measuring apparatus according to the present invention.

FIG. 8 is a characteristic diagram showing measured values of spectral characteristics of electromagnetic waves radiated in a firing furnace.

[Explanation of symbols]

A combustion region torch raw material flow reference line (virtual reference line on corresponding image of material flow path) 1 measuring device 2 rotary kiln 10 band pass filter 11 first imaging means 12 video signal correction means 13 image processing means 17 Filter 18 Second Imaging Means 20 Baking Furnace 22a Furnace Wall Near Burned Raw Material (Burning Furnace Wall Near Burner Flame to Combustion Region) 23 Burner Flame 31 Burned Raw Material

Claims (8)

[Claims] 1. Excitation emitted from a specific product generated from the raw material during firing in measuring the firing state of the raw material being fired in the firing furnace by an image obtained by photographing the inside of the firing furnace. A method for measuring a fired state, which comprises photographing through a bandpass filter capable of selectively transmitting electromagnetic waves in a wavelength band of light. 2. At least each part of the combustion region of the raw material, the calcined raw material that has passed through the combustion region, the burner flame blown into the firing furnace, and the furnace wall of the firing furnace that is closer to the burner flame than the combustion region. 2. The method for measuring a baked state according to claim 1, wherein the brightness of the image obtained by the photographing is corrected so that the mutual contrast of the respective luminances in the corresponding regions on the image is increased. 3. The first image obtained by photographing through the bandpass filter is capable of selectively transmitting electromagnetic waves in a wavelength band excluding the wavelength band of excitation light emitted from the specific product. The method for measuring a firing state according to claim 1 or 2, wherein the second image obtained by photographing the inside of the firing furnace through a filter is subjected to arithmetic processing. 4. The route of the raw material flow is obtained by previously determining the correspondence relationship between each location in the image and each location in the firing furnace, and also determining the actual route of the raw material flow in the firing furnace. The brightness is continuously obtained along the virtual reference line on the image corresponding to, the burning region on the image is specified based on the brightness, and the burning region on the image is compared with the above-mentioned correspondence to obtain a firing furnace. The method for measuring a firing state according to claim 3, wherein the position of the actual combustion region in the inside is specified. 5. An apparatus used in the above measuring method, comprising: a first imaging means capable of photographing the inside of a firing furnace; and a wavelength band of excitation light emitted from a specific product produced from a raw material during firing. A bandpass filter capable of selectively transmitting electromagnetic waves, wherein the first imaging means is arranged to be connected to the firing furnace through the bandpass filter. measuring device. 6. At least each part of the combustion region of the raw material, the calcined raw material that has passed through the combustion region, the burner flame blown into the firing furnace, and the furnace wall of the firing furnace that is closer to the burner flame than the combustion region. 6. The baking state measuring device according to claim 5, further comprising a video signal correcting means for correcting the brightness of the image obtained by the photographing so that the mutual contrast of the luminance is increased. 7. The second imaging means is connected to the firing furnace via a filter capable of selectively transmitting electromagnetic waves in a wavelength band excluding the wavelength band of excitation light emitted from the specific product. In addition, the first image obtained by the first image pickup means is converted into a desired image by using the second image obtained by the second image pickup means. 7. The apparatus for measuring the firing state according to claim 5, further comprising an image processing means. 8. The combustion region on the image is specified based on the luminance continuously measured along a virtual reference line on the image corresponding to the actual flow path of the raw material in the firing furnace, and the image is identified. By providing the image processing means for identifying the position of the actual combustion region in the firing furnace by comparing the above combustion region with the corresponding relationship between each location in the image and each location in the firing furnace. The apparatus for measuring the firing condition according to claim 7.