JP7035736B2 - Concentration measuring device and concentration measuring method - Google Patents

Description

The present invention relates to a concentration measuring device and a concentration measuring method.

Conventionally, a collection tube is provided in front of the gas cell, and the gas component to be measured is adsorbed on the collection tube to collect it, and then the gas component is desorbed by heating with a heater to concentrate the gas component and enclose it in the gas cell. Then, a device has been proposed in which the enclosed gas is irradiated with interference light, the light emitted from the gas cell is detected by a detector, and the concentration of the gas is obtained based on the intensity of the detected light (Patent Document 1). ).

Japanese Unexamined Patent Publication No. 07-270316

In the concentration measuring device, when measuring a low-concentration gas, it is necessary to increase the distance (optical path length) through which light passes through the gas cell to increase the absorbance in order to increase the detection sensitivity. In the above-mentioned conventional device, a multiple reflection mirror is generated in the gas cell, and infrared light from a light source is reciprocated several times in the gas cell to lengthen the optical path length.

However, in the above-mentioned conventional device, when the gas has a high concentration, the infrared light is absorbed by the gas to be measured, so that the light cannot be detected by a light intensity detector such as an infrared sensor, or the absorbance for a change in concentration is increased. It may be difficult to guarantee the sensitivity. Further, the output signal of the light intensity detector may include transmitted light having a long optical path length and transmitted light having a short optical path length. Since the SN ratio of the signal showing the absorbance of the transmitted light having a short optical path length is lower than that of the transmitted light having a long optical path length, the gas concentration should be measured by the transmitted light having a long optical path length. In this device, it is not possible to separate transmitted light having a long optical path length from transmitted light having a short optical path length.

In view of the above, in order to accurately measure the gas concentration depending on whether the concentration of the gas enclosed in the gas cell is assumed to be high or low, the detector may be changed or the like. It is necessary to change the configuration of.

The present invention provides a concentration measuring device and a concentration measuring method for accurately measuring the gas concentration by absorption analysis using transmitted light having a long optical path length, excluding transmitted light having a short optical path length, without changing the device configuration. The purpose is to provide.

In order to achieve the above object, the concentration measuring device of the present invention according to claim 1 of the present application is arranged in a light source, an optical system forming a closed light path of light incident from the light source, and an optical path of the closed light path. A container in which gas is supplied to the inside and the light of the closed path passes through the inside and is emitted to the closed path, and the light from the light source is allowed to enter the closed path, and by the permission. A permitter that allows the light that has passed through the container to be emitted from the closed light path and a permitter that allows the light emitted from the closed light path to enter through the permitter are arranged according to the intensity of the incident light. The light intensity detector that outputs a signal and the light that can detect the permitted state, the light from the light source is incident on the closed path, and the light that has passed through the container a plurality of times through the closed path is the closed path. The permitting device is controlled so that the light that has passed through the container a plurality of times is given priority to the light intensity detector via the permitting device with respect to the light that has passed through the container once. The period from the time corresponding to the time when the state of permission is switched to the time corresponding to the time when the intensity of the signal output by the light intensity detector shows the maximum value and then the minimum value, which is the time zone to reach. A controller for calculating the concentration of gas in the container based on the signal output by the light intensity detector is provided.

The optical system forms a closed path for the light incident from the light source. Inside the optical path of the closed optical path, there is a container to which the gas to be measured is supplied, and the light incident from the light source passes through the inside of the container. The permitter permits the light that has passed through the container to be emitted from the closed path.

The controller controls the permitter to inject light into the light intensity detector so that the light that has passed through the container multiple times through the closed light path is emitted from the closed light path, and the permitter is in the permitted state. The concentration of gas in the container is calculated based on the signal output by the light intensity detector until the intensity of the signal output by the light intensity detector shows a minimum value.

As in the invention of claim 2, when the assumed concentration of the gas supplied to the container is low, the controller is allowed to enter the light path more than when the concentration is high. The permitter may be controlled so that the light passes through the inside of the container more often.

As in the invention of claim 3, the permitter has a moving member having a portion through which light can pass, a position where light of the closed optical path can pass through the portion, and a position where light can be emitted from the closed optical path. The controller comprises a mechanism for moving the moving member to a position where the light of the closed optical path is reflected at a predetermined portion other than the portion of the moving member and returns to the closed path, and the controller is supplied to the container. The mechanism may be controlled so that the number of times is adjusted according to the expected concentration of the gas.

As in the invention of claim 4, the moving member rotates about an axis to form a portion through which light can pass, and the rotating member is arranged at a position where light in the closed light path can pass through the portion. The mechanism controls the rotation of the rotating member, and the controller controls the rotation speed of the rotating member when the assumed concentration of the gas supplied to the container is low, as compared with the case where the concentration is high. The mechanism may be controlled so as to make it smaller.

Further, as in the invention of claim 5, a rotation angle detector for detecting the rotation angle of the rotating member is further provided, and the controller is authorized based on the rotation angle detected by the rotation angle detector. The state may be detected.

The permitter has a portion that can be changed into a passable state in which light can pass and a passable state in which light cannot pass, as in the invention of claim 6, and is changed to the passable state. The portion is selectively switched between the light passing state changing device arranged at a position where the light of the closed optical path can pass, and the portion of the light passing state changing device to be in the passable state or the non-passable state. The controller comprises a switch, and the controller is allowed to enter the light when the assumed concentration of the gas supplied to the container is low, rather than when the concentration is high. The switch may be controlled so that the number of times the light passes through the inside of the container increases.

The light passing state changing device is an electronic shutter as in the invention of claim 7, and the controller detects the permitted state based on the transmission of the control signal for opening the electronic shutter. May be good.

As in the invention of claim 8, at least the incident portion where the light of the closed optical path is incident and the exit portion which passes through the inside and is emitted to the closed optical path may be transparent in the container.

The concentration measuring method according to claim 9 is arranged in a light source, an optical system forming a closed light path of light incident from the light source, and an optical path of the closed light path, and gas is supplied to the inside and the closed light path is provided. The container in which the light of the optical path passes through the inside and exits to the closed path, and the light from the light source are allowed to enter the closed path, and the light passing through the container is allowed to enter the closed path by the permission. A permit device that allows light to be emitted from the light beam, a light intensity detector that is arranged so that light emitted from the closed light path is incident through the permit device, and outputs a signal according to the intensity of the incident light. The permitter is capable of detecting the state of permission so that light from the light source is incident on the closed path and light that has passed through the container a plurality of times through the closed path is emitted from the closed path. It is a time zone in which the light that has passed through the container a plurality of times reaches the light intensity detector preferentially through the permitter with respect to the light that has passed through the container once . The concentration of gas in the container is calculated based on the signal output by the light intensity detector from the time when the state is detected until the intensity of the signal output by the light intensity detector shows a maximum value and then a minimum value. It is equipped with a controller .

INDUSTRIAL APPLICABILITY According to the present invention, the gas concentration can be accurately measured by absorption analysis using transmitted light having a long optical path length, excluding transmitted light having a short optical path length, without changing the device configuration.

It is a schematic diagram which shows the structure of the concentration measuring apparatus of 1st Embodiment. (A) is a front view of the chopper type mirror 22, and (B) is a side view of the chopper type mirror 22. It is explanatory drawing which showed the state of the density measuring apparatus when the infrared ray from an infrared light source 12 is incident on a closed optical path. It is explanatory drawing which showed the position of the light passing part 34 of the chopper type mirror 22 when the infrared ray from an infrared light source 12 is incident on a closed optical path. It is explanatory drawing which showed how the incident infrared ray orbits a closed optical path many times. It is explanatory drawing which showed the position of the light reflection part 32 of the chopper type mirror 22 when the incident infrared ray orbits a closed optical path many times. It is explanatory drawing which showed the state that the infrared ray emitted from a closed light path reaches a light intensity detector 26. (A) is an explanatory diagram showing an example of an output signal 64 indicating the transmitted light intensity detected by the light intensity detector 26, and (B) is a signal (circular light signal) related to the circumferential light 60 included in the output signal 64. ) 66 and the signal (one-circle light signal) 68 related to the one-circle light 62 are explanatory views showing each. It is a schematic diagram which shows the structure of the concentration measuring apparatus of 2nd Embodiment. It is explanatory drawing which showed the state that the infrared ray from a light intensity detector 26 reaches a gas cell 20 through a chopper type mirror 22. It is explanatory drawing which showed how the infrared ray reciprocates between a chopper type mirror 22 and a reflecting mirror 44 many times through the inside of a gas cell 20. Infrared rays that reciprocate many times between the chopper type mirror 22 and the reflector 44 through the inside of the gas cell 20 pass through the light passing portion 34 of the chopper type mirror 22 and the beam splitter 42, and the light intensity is high. It is explanatory drawing which showed the state of reaching the detector 26. It is a schematic diagram which shows the structure of the concentration measuring apparatus of 3rd Embodiment. (A) is an explanatory diagram showing an example of an output signal 80 indicating the transmitted light intensity detected by the light intensity detector 26, and (B) is a signal (circular light signal) related to the circumferential light 74 included in the output signal 80. ) 82, The signal related to the reflected light 78 (reflected light signal) 84, and the signal related to the one-circle light 76 (one-circle light signal) 86, respectively. It is a schematic diagram which showed the structure of the concentration measuring apparatus of 4th Embodiment. It is explanatory drawing which showed the structure of the concentration measuring apparatus which concerns on 1st modification. It is explanatory drawing which showed the structure of the concentration measuring apparatus which concerns on 2nd modification.

Hereinafter, embodiments of the present invention will be described.

(First Embodiment)
FIG. 1 shows the configuration of the concentration measuring device according to the first embodiment. As shown in FIG. 1, the concentration measuring device of the first embodiment forms a closed light path so that an infrared light source 12 that emits infrared rays and light incident from the infrared light source 12 circulate. The reflector 14 to the third reflector 18 are provided. The concentration measuring device is arranged in the optical path of the closed optical path formed by the first reflecting mirror 14 to the third reflecting mirror 18, gas is supplied to the inside, and the light of the closed light path passes through the inside and is closed. It is provided with a gas cell 20 that emits light to an optical path. In the gas cell 20, at least the incident portion where the light of the closed optical path is incident and the exit portion which passes through the inside and is emitted to the closed optical path are transparent. The gas cell 20 may be entirely transparent.

The concentration measuring device includes a chopper type mirror 22 that allows infrared rays from the infrared light source 12 to enter the closed optical path and allows infrared rays that have passed through the gas cell 20 to be emitted from the closed optical path by the permission. ing. The chopper type mirror 22 is formed in a disk shape that rotates about an axis. The concentration measuring device includes a rotation speed adjusting mechanism 24 that controls the rotation speed (rotational speed) of the chopper type mirror 22 per unit time.

The concentration measuring device includes a light intensity detector 26 that detects the intensity of light emitted from the closed light path via the chopper type mirror 22.

The concentration measuring device includes an infrared light source 12, a rotation speed adjusting mechanism 24, and a controller 28 connected to a light intensity detector 26. The controller 28 is composed of a computer equipped with a CPU, ROM, RAM, a display, etc. (not shown). The ROM stores a concentration measurement processing program described later. The concentration measurement processing program is read from the ROM, expanded in the RAM, executed by the CPU, and the concentration measurement processing is executed.

The controller 28 is further connected to an infrared non-absorbing gas supply unit (not shown) that supplies infrared non-absorbing gas to the gas cell 20, and a measurement target gas supply unit (not shown) that supplies measurement target gas to the gas cell 20. Then, the controller 28 controls the infrared non-absorbing gas supply unit or the measurement target gas supply unit to supply the infrared non-absorbent gas or the measurement target gas to the gas cell 20.

The controller 28 is allowed to enter and adjusts the number of times the light incident on the closed optical path passes through the gas supplied to the gas cell 20 according to the assumed concentration of the gas supplied to the gas cell 20. Then, the rotation speed adjusting mechanism 24 is controlled so as to emit light from the closed optical path. The controller 28 calculates the gas concentration based on the light intensity detected by the light intensity detector 26.

Next, the configuration of the chopper type mirror 22 will be described. FIG. 2 shows the configuration of the chopper type mirror 22. FIG. 2A shows a front view of the chopper type mirror 22, and FIG. 2B shows a side view of the chopper type mirror 22.

As shown in FIG. 2, the chopper type mirror 22 is a rotating member that rotates about a rotating shaft 30. A light passing portion 34 through which light can pass at equal intervals is formed around the chopper type mirror 22. The chopper type mirror 22 is arranged at a position where the light of the closed light path can pass through the light passing portion 34. The portion of the chopper type mirror 22 other than the light passing portion 34 is formed in the light reflecting portion 32. The light passing portion 34 is defined between the incident start edge 34A and the incident end edge 34B in the light reflecting portion 32. The surface of the chopper type mirror 22 opposite to the surface provided with the light reflecting portion 32 is a light absorbing portion 36 that absorbs light without reflecting it. The light absorption unit 36 is subjected to surface treatment such as black matte coating as an example.

Next, referring to FIGS. 3 to 7, infrared rays from the infrared light source 12 are incident on the closed optical path, the incident infrared rays orbit the closed optical path many times, and then reach the light intensity detector 26. Explain how to do it.

FIG. 3 shows a state of the concentration measuring device when infrared rays from the infrared light source 12 are incident on the closed optical path. FIG. 4 shows the position of the light passing portion 34 of the chopper type mirror 22 when the infrared rays from the infrared light source 12 are incident on the closed optical path. FIG. 5 shows how the incident infrared rays orbit the closed optical path many times. FIG. 6 shows the position of the light reflecting portion 32 of the chopper type mirror 22 when the incident infrared rays orbit the closed optical path many times. FIG. 7 shows how the infrared rays emitted from the closed optical path reach the light intensity detector 26.

When the chopper type mirror 22 rotates and the light passing portion 34 is located in the closed optical path as shown in FIG. 4 and the infrared light source 12 emits infrared rays, the irradiated infrared rays are emitted as shown in FIG. Passes through the light passing portion 34 and heads for the first reflecting mirror 14. As shown in FIG. 5, the infrared rays directed to the first reflecting mirror 14 are incident on the gas cell 20 at the first reflecting mirror 14. Infrared rays directed from the first reflecting mirror 14 toward the gas cell 20 enter the inside of the gas cell 20 through the transparent incident portion of the gas cell 20, pass through the inside of the gas cell 20, and pass through the transparent exit portion of the gas cell 20. It emits to the closed light path through. The infrared rays emitted into the closed optical path through the transparent emitting portion of the gas cell 20 reach the second reflecting mirror 16, are reflected by the second reflecting mirror 16, reach the third reflecting mirror 18, and reach the third reflecting mirror 18. It is reflected by the reflector 18 and heads toward the chopper type mirror 22. As shown in FIG. 6, when the light reflecting unit 32 is located in the closed light path, the infrared rays reflected by the third reflecting mirror 18 and directed toward the chopper type mirror 22 are reflected by the light reflecting unit 32. It reaches the first reflector 14. As a result, a closed optical path is formed. In this state, the infrared rays orbit the closed optical path many times and pass through the inside of the gas cell 20 many times. If the measurement target gas that absorbs infrared rays is supplied to the gas cell 20, a part of the infrared rays is absorbed by the measurement target gas in the gas cell 20. Therefore, when the infrared rays orbit the closed optical path many times, the infrared rays that were not absorbed by the measurement target gas in one orbit will be absorbed by the measurement target gas.

After that, as shown in FIG. 7, when the light passing portion 34 is located in the closed optical path, the orbiting light 60, which is an infrared ray that orbits the closed light path many times and is not absorbed by the measurement target gas, becomes the light passing portion. It exits from 34 and reaches the light intensity detector 26. As a result, the light intensity detector 26 detects the light intensity of infrared rays and outputs a light intensity signal indicating the light intensity to the controller 28.

However, it is not only the ambient light 60 that is incident on the light intensity detector 26. The one-circle light 62 that enters the light intensity detector 26 after making only one round of the closed light path is included. In the first embodiment, the absorbance is calculated by excluding the light containing a large amount of one-circle light 62 from the light incident on the light intensity detector 26.

8 (A) is an explanatory diagram showing an example of an output signal 64 showing the transmitted light intensity detected by the light intensity detector 26, and FIG. 8 (B) shows the output signal 64 shown in FIG. 8 (A). It is explanatory drawing which showed the signal (circumferential light signal) 66 which concerns on the included circumferential light 60, and the signal (1 circuit light signal) 68 which concerns on 1 peripheral light 62, respectively.

As described above, the light incident on the light intensity detector 26 is a mixture of the orbital light 60 and the one-circumferential light 62, but in order for the orbiting light 60 to enter the light intensity detector 26, a chopper is placed in the closed optical path. It is necessary that the light passing portion 34 of the type mirror 22 is located and the chopper type mirror 22 is switched from the “reflection state” to the “incident state”. In such a case, the light emitted from the infrared light source 12 is incident on the closed optical path and becomes one round light 62. However, when the light passing portion 34 is located in the closed optical path, the circumferential light 60 reaches the light intensity detector 26, but the one round light 62 is irradiated from the infrared light source 12 and closed via the light passing portion 34. It is in a state of being incident on the optical path. Therefore, the circumferential light 60 is incident on the light intensity detector 26 earlier than the one-circle light 62.

Further, since the circumferential light 60 has passed through the gas cell 20 a plurality of times, the absorption by the measurement target gas becomes more remarkable than the one-circle light. In addition, the intensity differs due to the reflection by each reflecting mirror.

Considering the time difference between the orbiting light 60 and the one-circling light 62 reaching the light intensity detector 26, the intensity of the orbiting light 60 decreases as time elapses from the incident state, but the one-circling light 62 has. As long as the chopper type mirror 22 is in the incident state, the irradiation from the infrared light source 12 to the closed optical path is continued, so that the intensity of the one-circle light 62 increases or is constant even after the intensity of the circumferential light 60 is attenuated. To maintain.

From the above, the transmitted light intensity detected by the light intensity detector 26 mainly reaches a maximum value when the orbiting light 60 reaches the light intensity detector 26, then reaches a minimum value, and then the one-circle light 62 determines. It increases by reaching the light intensity detector 26.

As shown in FIG. 8A, the curve of the output signal 64 of the transmitted light intensity detected by the light intensity detector 26 shows a maximum value in an upwardly convex manner and then shows a minimum value A. .. Further, the curve of the output signal 64 shows a minimum value A and then turns to a monotonous increase.

The components of the output signal 64 are as shown in FIG. 8 (B). The output signal 64 of FIG. 8A includes a circumferential optical signal 66 and a 1-circumferential optical signal 68. Therefore, by adopting the output signal 64 from the time when the chopper type mirror 22 switches from the reflection state to the incident state to the time when the output signal 64 indicating the transmitted light intensity reaches the minimum value A, the light intensity detector 26 It is possible to calculate the absorbance by excluding the light containing a large amount of one round light 62 from the incident light. As a result, it becomes possible to calculate the absorbance by an output signal having a high SN ratio, and the concentration of the gas to be measured can be measured more accurately.

The time when the chopper type mirror 22 is switched from the reflection state to the incident state is a state in which the chopper type mirror 22 allows light to be emitted from the closed optical path. As shown in FIG. 8A, the permission state can be estimated from the monotonous increase of the output signal 64, but the surface of the chopper type mirror 22 facing the light intensity detector 26 is infrared. The light from the light source 12 may be reflected, and in such a case, it is difficult to accurately detect the state of the permission. In the first embodiment, as an example, the rotation speed adjusting mechanism 24 is provided with a rotation angle sensor (not shown) for detecting the rotation angle of a chopper type mirror such as a magnetic resistance (MR) sensor or a rotary encoder. The controller 28 calculates the rotation position of the chopper type mirror 22 from the rotation angle of the chopper type mirror 22 detected by the rotation angle sensor, and detects the permission state in which the chopper type mirror 22 starts emitting from the closed light path from the rotation position. do. The detection of the permitted state using the rotation angle sensor is also effective in the second to fourth embodiments described later.

In order to calculate the concentration of the target gas in the gas cell 20 from the output signal of the light intensity detector 26, the output signal 64 indicating the transmitted light intensity is the minimum value from the time when the chopper type mirror 22 switches from the reflected state to the incident state. It is based on the integrated value with respect to the time of the output signal 64 up to the time when it becomes A, but since it is a known calculation method, detailed description thereof will be omitted.

When the concentration of the measurement target gas in the gas cell 20 is high, the maximum value caused by the orbiting optical signal 66 shown in FIGS. 8A and 8B decreases, but as described above, the orbiting optical signal 66 Since the signal-to-noise ratio is high, the concentration of the gas to be measured can be measured more accurately even if the maximum value of the ambient light signal 66 detected by the light intensity detector 26 decreases.

Further, by controlling the rotation speed of the chopper type mirror 22 according to the concentration of the measurement target gas, the concentration of the measurement target gas can be accurately measured.

When the rotation speed of the chopper type mirror 22 becomes small, the time for forming the closed optical path becomes long, and the number of times that infrared rays pass through the gas cell 20 increases. On the contrary, when the rotation speed of the chopper type mirror 22 is increased, the time for forming the closed optical path is shortened, and the number of times that infrared rays pass through the gas cell 20 is reduced.

Further, when the assumed concentration of the gas supplied to the gas cell 20 is low, the number of infrared rays passing through the measurement target gas supplied to the gas cell 20 is increased as compared with the case where the concentration is high, so that the infrared rays are absorbed by the gas. Will be noticeably shown.

When the expected concentration of the gas supplied to the gas cell 20 is high, the number of infrared rays passing through the gas supplied to the gas cell 20 is reduced to prevent the infrared rays from being excessively absorbed by the gas. can.

Therefore, if the expected concentration of the gas supplied to the gas cell 20 is low, the rotation speed of the chopper type mirror 22 is reduced, and if the concentration of the measurement target gas supplied to the gas cell 20 is high, the rotation speed is reduced. By increasing the rotation speed of the chopper type mirror 22, the concentration of the gas to be measured can be measured accurately.

As described above, according to the first embodiment, the gas concentration can be accurately measured regardless of whether the concentration of the gas to be measured is high or low without changing the device configuration.

(Second embodiment)
Next, a second embodiment of the present invention will be described. Since the configuration of the second embodiment has the same parts as the configuration of the first embodiment (see FIG. 1), the same parts are designated by the same reference numerals and the description thereof will be omitted. Only the part will be explained.

FIG. 9 shows the configuration of the concentration measuring device according to the second embodiment. As shown in FIG. 9, in the concentration measuring device of the second embodiment, a beam splitter 42 is arranged between the infrared light source 12 and the chopper type mirror 22. The beam splitter 42 is configured by combining two triangular prisms so that the bottom surfaces are in contact with each other. The beam splitter 42 is not limited to being configured by combining two triangular prisms, and for example, a polarizing beam splitter may be adopted.

Further, in the second embodiment, instead of the first reflecting mirror 14 to the third reflecting mirror 18 of the first embodiment, one reflection is performed with the gas cell 20 sandwiched between the chopper type mirror 22. It is equipped with a mirror 44. When the light reflecting portion 32 of the chopper type mirror 22 is located directly below the gas cell 20, a closed optical path through which light reciprocates is formed.

FIG. 10 shows how the infrared rays from the light intensity detector 26 reach the gas cell 20 through the chopper type mirror 22. FIG. 11 shows how infrared rays reciprocate between the chopper type mirror 22 and the reflecting mirror 44 many times through the inside of the gas cell 20. In FIG. 12, infrared rays reciprocating between the chopper type mirror 22 and the reflecting mirror 44 many times through the inside of the gas cell 20 pass through the light passing portion 34 of the chopper type mirror 22 and the beam splitter 42. The state of reaching the light intensity detector 26 is shown.

As shown in FIG. 10, a part of infrared rays incident from one slope of the two triangular prisms of the beam splitter 42 passes through the bottom surface of one triangular prism and through the bottom surface of the other triangular prism, and the other. It is incident on the triangular prism. After that, it exits through the slope of the other triangular prism and reaches the chopper type mirror 22. When the light passing portion 34 of the chopper type mirror 22 is located in the closed optical path when reaching the chopper type mirror 22, the light emitted from the other triangular prism passes through the gas cell 20 and reaches the reflecting mirror 44 to be a reflecting mirror. Reflects at, passes through the gas cell 20, and reaches the chopper type mirror 22. As shown in FIG. 11, when the light reflecting portion 32 of the chopper type mirror 22 is located in the closed optical path when reaching the chopper type mirror 22, infrared rays are emitted from the gas cell 20 between the chopper type mirror 22 and the reflecting mirror 44. It goes back and forth many times through the inside of. Then, as shown in FIG. 12, a part of the infrared rays reciprocating between the chopper type mirror 22 and the reflecting mirror 44 many times through the inside of the gas cell 20 is the light passing portion 34 of the chopper type mirror 22. , Reflects on the bottom surface of the other triangular prism of the beam splitter 42 and reaches the light intensity detector 26 through the slope of the other triangular prism.

Also in the second embodiment, it is not only the ambient light 70 that is incident on the light intensity detector 26. The one-circle light 72 that enters the light intensity detector 26 after making only one round of the closed light path is included. In the second embodiment, the output signal from the time when the chopper type mirror 22 is switched from the reflection state to the incident state to the time when the output signal indicating the transmitted light intensity becomes the minimum value is adopted. By adopting such an output signal, the absorbance can be calculated using the output signal having a high SN ratio obtained by excluding the output signal of the light intensity detector 26 due to the light containing a large amount of one round light 72. ..

Therefore, also in the second embodiment, the gas concentration can be accurately measured without changing the apparatus configuration regardless of whether the assumed gas concentration is high or low. Further, also in the second embodiment, the concentration of the gas can be accurately measured even if the concentration of the measurement target gas supplied to the gas cell 20 changes.

Further, as in the first embodiment, in order to accurately measure the concentration of the gas to be measured, when the assumed concentration of the gas supplied to the gas cell 20 is low, the rotation speed of the chopper type mirror 22 is set. If it is made smaller and the concentration of the measurement target gas supplied to the gas cell 20 is assumed to be high, the rotation speed of the chopper type mirror 22 may be increased.

Further, in the second embodiment, instead of the first reflecting mirror 14 to the third reflecting mirror 18 of the first embodiment, one reflection is performed with the gas cell 20 sandwiched between the chopper type mirror 22. A mirror 44 is provided to form a closed light path. Therefore, in the second embodiment, the number of parts can be reduced as compared with the configuration of the first embodiment.

(Third embodiment)
Next, a third embodiment of the present invention will be described. Since the configuration of the third embodiment has the same parts as the configuration of the first embodiment (see FIG. 1), the same parts are designated by the same reference numerals and the description thereof is omitted. Only the part will be explained.

As shown in FIG. 13, in the third embodiment, the surface of the chopper type mirror 122, which was the light absorption unit 36 in the first embodiment, is a mirror surface similar to the light reflection unit 32. It differs from the first embodiment in that it is part 136. Therefore, the chopper type mirror 122 according to the third embodiment has mirror surfaces on both sides except for the light passing portion 34.

As a result, in addition to the circumferential light 74 and the one-circle light 76, the light reflected by the light reflecting unit 136 reaches the light intensity detector 26.

14 (A) is an explanatory diagram showing an example of an output signal 80 showing the transmitted light intensity detected by the light intensity detector 26, and FIG. 14 (B) shows the output signal 80 shown in FIG. 14 (A). An explanatory diagram showing a signal (circumferential light signal) 82 related to the included orbital light 74, a signal (reflected light signal) 84 related to the reflected light 78, and a signal (1 orbital light signal) 86 related to the 1-circumferential light 76, respectively. be.

In the third embodiment, when the light passing portion 34 is located in the closed optical path and the chopper type mirror 122 is switched from the reflected state to the incident state, the area of the light reflecting portion 136 is reduced, so that the reflected light is reflected. The intensity of 78 gradually decreases, and as shown in FIG. 4, when the optical axis portion is completely included in the light passing portion 34, the intensity of the reflected light 78 becomes 0.

In the third embodiment, as shown in FIG. 13, the light incident on the light intensity detector 26 is a mixture of the circumferential light 74 and the one-circle light 76 in addition to the reflected light 78. In order for the orbiting light 74 to enter the light intensity detector 26, it is necessary that the light passing portion 34 of the chopper type mirror 122 is located in the closed optical path. In such a case, the light emitted from the infrared light source 12 is emitted. , It is incident on the closed optical path and becomes one round light 76. However, when the light passing portion 34 is located in the closed optical path, the circumferential light 74 reaches the light intensity detector 26, but the one round light 76 is irradiated from the infrared light source 12 and closed via the light passing portion 34. It is in a state of being incident on the optical path. Therefore, the circumferential light 74 is incident on the light intensity detector 26 earlier than the one-circle light 76.

Since the orbiting light 74 has passed through the gas cell 20 a plurality of times, the absorption by the measurement target gas becomes more remarkable than that of the first orbiting light 76. In addition, the intensity differs due to the reflection by each reflecting mirror.

Considering the time difference between the orbiting light 74 and the one-circling light 76 reaching the light intensity detector 26, the intensity of the orbiting light 74 decreases as time elapses from the incident state, but the one-circle light 76 has. As long as the chopper type mirror 122 is in the incident state, the irradiation from the infrared light source 12 to the closed optical path is continued, so that the intensity of the one-circle light 76 increases or is constant even after the intensity of the circumferential light 74 is attenuated. To maintain.

Further, since the optical path length of the optical system of the concentration measuring device according to the third embodiment is finite, the intensity of the one-circle light 76 becomes the maximum after the intensity of the reflected light 78 becomes zero.

From the above, the transmitted light intensity detected by the light intensity detector 26 is the minimum value (the time when the intensities of the orbiting light 74 and the one-circling light 76 are the same, or the time when the intensity of the orbiting light 74 becomes 0). Minimum value) B.

As shown in FIG. 14A, the curve of the output signal 80 of the transmitted light intensity detected by the light intensity detector 26 gradually decreases when the chopper type mirror 122 switches from the reflection state to the incident state. , The minimum value B is shown. Further, the curve of the output signal 80 shows a minimum value B and then increases.

The output signal 80 component is as shown in FIG. 14 (B). The output signal 80 of FIG. 14A includes a circumferential optical signal 82, a reflected optical signal 84, and a single optical signal 86. Therefore, by adopting the output signal 80 from the time when the chopper type mirror 122 is switched from the reflection state to the incident state to the time when the output signal 80 indicating the transmitted light intensity becomes the minimum value B, the light intensity detector is used. It is possible to calculate the absorbance by excluding the light containing a large amount of the one-circle light 76 from the light incident on the 26. As a result, it becomes possible to calculate the absorbance by an output signal having a high SN ratio, and the concentration of the gas to be measured can be measured more accurately.

Further, as in the first embodiment, in order to accurately measure the concentration of the gas to be measured, when the assumed concentration of the gas supplied to the gas cell 20 is low, the rotation speed of the chopper type mirror 22 is set. If it is made smaller and the concentration of the measurement target gas supplied to the gas cell 20 is assumed to be high, the rotation speed of the chopper type mirror 22 may be increased.

(Fourth Embodiment)
Next, a fourth embodiment of the present invention will be described. Since the configuration of the fourth embodiment has the same parts as the configurations of the second embodiment and the third embodiment (see FIG. 13), the same parts are designated by the same reference numerals. The explanation is omitted, and only the different parts are explained.

FIG. 15 shows the configuration of the concentration measuring device according to the fourth embodiment. As shown in FIG. 15, the concentration measuring device of the fourth embodiment relates to the second embodiment in that it includes a chopper type mirror 122 having a light reflecting portion 136 similar to that of the third embodiment. Although it is different from the concentration measuring device, other configurations are the same as those of the concentration measuring device according to the second embodiment.

Even in the fourth embodiment, it is not only the ambient light 88 that is incident on the light intensity detector 26. The reflected light generated by the one-circle light 90 incident on the light intensity detector 26 after making only one round of the closed light path and the infrared light emitted from the infrared light source 12 reflected by the light reflecting portion 136 of the chopper type mirror 122. 92 and is included. In the fourth embodiment, the transmitted light intensity is shown from the light incident on the light intensity detector 26 from the time when the chopper type mirror 122 is switched from the reflected state to the incident state, as in the third embodiment. The output signal up to the time when the output signal becomes the minimum value is adopted. By adopting such an output signal, the absorbance can be calculated using the output signal having a high SN ratio obtained by excluding the output signal of the light intensity detector 26 due to the light containing a large amount of one round light 90. ..

Therefore, also in the fourth embodiment, the gas concentration can be accurately measured without changing the apparatus configuration regardless of whether the assumed gas concentration is high or low. Further, also in the fourth embodiment, the concentration of the gas can be accurately measured even if the concentration of the measurement target gas supplied to the gas cell 20 changes.

Further, as in the first embodiment, in order to accurately measure the concentration of the gas to be measured, when the assumed concentration of the gas supplied to the gas cell 20 is low, the rotation speed of the chopper type mirror 22 is set. If it is made smaller and the concentration of the measurement target gas supplied to the gas cell 20 is assumed to be high, the rotation speed of the chopper type mirror 22 may be increased.

Further, in the fourth embodiment, instead of the first reflecting mirror 14 to the third reflecting mirror 18 of the third embodiment, one reflection is provided with the gas cell 20 sandwiched against the chopper type mirror 22. A mirror 44 is provided to form a closed light path. Therefore, in the fourth embodiment, the number of parts can be reduced as compared with the configuration of the third embodiment.

(Modification example)
Next, a modified example will be described.

(First modification)
FIG. 16 shows the configuration of the concentration measuring device according to the first modification. As shown in FIG. 16, since the configuration of the first modification has the same parts as the configuration of the first embodiment (see FIG. 1), the same parts are designated by the same reference numerals. The explanation is omitted, and only the different parts are explained.

In the first modification, instead of the chopper type mirror 22, there is a portion that can be changed into a passable state in which light can pass and a passable state in which light cannot pass, and the state is changed to the passable state. The high-speed optical shutter 52 is arranged at a position where the light of the closed optical path can pass through the portion, and the high-speed optical shutter 52 can or cannot pass through the above portion depending on the pulse width of the signal from the controller 28. It is equipped with a pulse width adjusting mechanism 54 that selectively switches to a state.

The controller 28 can adjust the number of times infrared rays pass through the gas cell 20 depending on whether the concentration of the measurement target gas supplied to the gas cell 20 is assumed to be high or low. Specifically, when the expected concentration of the gas supplied to the gas cell 20 is low, the pulse width is adjusted so that the number of infrared rays passing through the gas supplied to the gas cell 20 is larger than when the concentration is high. The pulse width adjusting mechanism 54 may be controlled by the signal.

Even in the first modification, it is not only the ambient light 94 that is incident on the light intensity detector 26. The one-circle light 96 incident on the light intensity detector 26 after making only one round of the closed light path is included. In the first modification, the high-speed light shutter 52 shows the transmitted light intensity from the time when the closed state in which light does not pass is switched to the incident state in which light passes and the light is allowed to be emitted from the closed optical path. The output signal up to the time when the output signal reaches the minimum value is adopted. By adopting such an output signal, the absorbance can be calculated using the output signal having a high SN ratio obtained by excluding the output signal of the light intensity detector 26 due to the light containing a large amount of one round light 96. .. The time when the high-speed optical shutter 52 is switched to the incident state is calculated from the timing when the controller 28 controls the pulse width adjusting mechanism 54. For example, the time obtained by adding the time lag until the high-speed optical shutter 52 actually opens and becomes the incident state to the time when the control signal for switching the high-speed optical shutter 52 to the incident state is transmitted from the controller 28 to the pulse width adjusting mechanism 54. Is the time when the high-speed optical shutter 52 is switched to the incident state (permitted state).

Even in the first modification, the gas concentration can be accurately measured without changing the apparatus configuration regardless of whether the assumed gas concentration is high or low. Further, even in the first modification, even if the concentration of the measurement target gas supplied to the gas cell 20 changes, the gas concentration can be measured accurately.

(Second modification)
FIG. 17 shows the configuration of the concentration measuring device according to the second modification. As shown in FIG. 17, the configuration of the second modification is the same as the configuration of the second embodiment (see FIG. 9) and the first modification (see FIG. 16). The same reference numerals are given to the parts, the description thereof will be omitted, and only the different parts will be described. In the second modification, instead of the chopper type mirror 22, a high-speed optical shutter 52 and a pulse width adjusting mechanism 54 are provided.

The controller 28 can adjust the number of times infrared rays pass through the gas cell 20 depending on whether the concentration of the measurement target gas supplied to the gas cell 20 is assumed to be high or low. Specifically, when the expected concentration of the gas supplied to the gas cell 20 is low, the pulse width is adjusted so that the number of infrared rays passing through the gas supplied to the gas cell 20 is larger than when the concentration is high. The pulse width adjusting mechanism 54 may be controlled by the signal.

Even in the second modification, it is not only the ambient light 98 that is incident on the light intensity detector 26. The one-circle light 100 that enters the light intensity detector 26 after making only one round of the closed light path is included. In the second modification, the output signal from the time when the high-speed light shutter 52 switches from the closed state where the light does not pass to the incident state where the light passes to the time when the output signal indicating the transmitted light intensity becomes the minimum value. Is adopted. By adopting such an output signal, the absorbance can be calculated using the output signal having a high SN ratio obtained by excluding the output signal of the light intensity detector 26 due to the light containing a large amount of one round light 100. ..

Also in the second modification, as in the first modification, the high-speed optical shutter 52 is actually transmitted at the time when the control signal for switching the high-speed optical shutter 52 to the incident state is transmitted from the controller 28 to the pulse width adjusting mechanism 54. The time obtained by adding the time lag until the light enters the incident state is defined as the time when the high-speed optical shutter 52 switches to the incident state (permitted state).

Also in the second modification, the gas concentration can be accurately measured without changing the apparatus configuration regardless of whether the assumed gas concentration is high or low. Further, in the second modification, even if the concentration of the measurement target gas supplied to the gas cell 20 changes, the gas concentration can be measured accurately.

(Other variants)
Instead of the chopper type mirror 22 in the first embodiment and the second embodiment, a moving member having a hole or a notch may be made to enter or retract into the closed optical path.

Further, in the first modification and the second modification, instead of the high-speed optical shutter 52, a mechanically controlled shutter and a lens shutter (leaf) that releases a shutter by opening and closing a shutter blade installed in the lens to block light. Shutter) or the like may be adopted.
Further, the case where the concentration of the gas to be measured is measured by using the output signal in the section from the time when the state is switched to the incident state to the time when the output signal becomes the minimum value or the minimum value has been described as an example. The start time of the section is not limited, and may be shifted back and forth by a predetermined time as long as it corresponds to the time when the interval is switched to the incident state. Further, if the end time of the section corresponds to the time when the output signal becomes the minimum value or the minimum value, it may be shifted back and forth by a predetermined time.

12 Infrared light source 14 First reflector 16 Second reflector 18 Third reflector 20 Gas cell 22 Chopper type mirror 24 Rotation speed adjustment mechanism 26 Light intensity detector 28 Controller 30 Rotation axis 32 Light reflector 34 Light Passing part 34A Incident start edge 34B Incident end edge 36 Light absorption part 42 Beam splitter 44 Reflector 52 High-speed light shutter 54 Pulse width adjustment mechanism 60 Circumferential light 62 1-circumferential light 64 Output signal 66 Circumferential light signal 68 1-circumferential optical signal 70 orbits Light 72 1-round light 74 1-round light 76 1-round light 78 Reflected light 80 Output signal 82 Circular light signal 84 Reflected light signal 86 1-round light signal 88 1-round light 90 1-round light 92 Reflected light 94 Circumferential light 96 1-round light 98 orbit Light 100 1 Circumferential light 122 Chopper type mirror 136 Light reflector A Minimum value B Minimum value

Claims (9)

Light source and
An optical system that forms a closed path for light incident from a light source,
A container that is arranged in the optical path of the closed optical path, gas is supplied to the inside, and the light of the closed path passes through the inside and is emitted to the closed path.
A permitter that allows light from the light source to enter the closed path and allows light that has passed through the container to be emitted from the closed path by the permission.
A light intensity detector that is arranged so that the light emitted from the closed optical path is incident through the permit device and outputs a signal corresponding to the intensity of the incident light.
The permitter is capable of detecting the state of permission so that light from the light source is incident on the closed path and light that has passed through the container a plurality of times through the closed path is emitted from the closed path. It is a time zone in which the light that has passed through the container a plurality of times reaches the light intensity detector preferentially through the permitter with respect to the light that has passed through the container once . The signal output by the light intensity detector in the section from the time corresponding to the time when the state is switched to the time corresponding to the time when the intensity of the signal output by the light intensity detector shows the maximum value and then the minimum value. A controller that calculates the concentration of gas in the container based on
Concentration measuring device equipped with. When the assumed concentration of the gas supplied to the container is low, the controller is allowed to enter the controller more than when the concentration is high, and the light incident on the light path passes through the inside of the container. The concentration measuring device according to claim 1, wherein the permitter is controlled so that the number of times of the operation is increased. The permit is
A moving member with a part through which light can pass,
At a position where the light of the closed path can pass through the portion and exit from the closed path, and at a position where the light of the closed path is reflected by a predetermined portion other than the portion of the moving member and returns to the closed path. A mechanism for moving the moving member and
Equipped with
The concentration measuring device according to claim 2, wherein the controller controls the mechanism so that the number of times is adjusted according to the assumed concentration of the gas supplied to the container. The moving member is a rotating member that rotates about an axis to form a portion through which light can pass, and the portion is arranged at a position where light in the closed optical path can pass.
The mechanism controls the rotation of the rotating member.
The controller controls the mechanism so that when the assumed concentration of the gas supplied to the container is low, the rotational speed of the rotating member is lower than when the concentration is high.
The concentration measuring device according to claim 3. A rotation angle detector for detecting the rotation angle of the rotating member is further provided.
The concentration measuring device according to claim 4, wherein the controller detects the permitted state based on the rotation angle detected by the rotation angle detector. The permit is
A position that has a portion that can be changed into a passable state in which light can pass and a passable state in which light cannot pass, and a position in which light in the closed optical path can pass through the portion changed to the passable state. With the light passage state changer placed in
A switching device that selectively switches the portion of the light passing state changing device to the passing state or the non-passing state.
Equipped with
When the assumed concentration of the gas supplied to the container is low, the controller is allowed to enter the light more than when the concentration is high, and the light incident on the light path passes through the inside of the container. Control the switch so that the number of times of operation is increased.
The concentration measuring device according to claim 1. The light passage state changer is an electronic shutter.
The concentration measuring device according to claim 6, wherein the controller detects the permission state based on the transmission of the control signal for opening the electronic shutter. In the container, at least the incident portion where the light of the closed optical path is incident and the exit portion which passes through the inside and exits to the closed optical path are transparent.
The concentration measuring device according to any one of claims 1 to 7. Light source and
An optical system that forms a closed path for light incident from a light source,
A container that is arranged in the optical path of the closed optical path, gas is supplied to the inside, and the light of the closed path passes through the inside and is emitted to the closed path.
A permitter that allows light from the light source to enter the closed path and allows light that has passed through the container to be emitted from the closed path by the permission.
A light intensity detector that is arranged so that the light emitted from the closed optical path is incident through the permit device and outputs a signal corresponding to the intensity of the incident light.
The permitter is capable of detecting the state of permission so that light from the light source is incident on the closed path and light that has passed through the container a plurality of times through the closed path is emitted from the closed path. It is a time zone in which the light that has passed through the container a plurality of times reaches the light intensity detector preferentially through the permitter with respect to the light that has passed through the container once . The concentration of gas in the container is calculated based on the signal output by the light intensity detector from the time when the state is detected until the intensity of the signal output by the light intensity detector shows a maximum value and then a minimum value. Control and
A concentration measuring method in a concentration measuring device provided with.

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