Infrared spectrophotometer

Abstract

Provided is an infrared spectrophotometer that can safely perform a start-up operation while avoiding condensation inside a sealed housing. The infrared spectrophotometer includes: a sealed housing that houses an optical member, an infrared light source that irradiates infrared light inside the sealed housing, a dehumidifying agent that dehumidifies the inside of the sealed housing, a temperature and humidity sensor that detects the humidity inside the sealed housing, and a light source control device that controls the power supplied to the infrared light source. The light source control device starts up the infrared light source while limiting the power supplied to the infrared light source, judges whether there is a risk of condensation inside the sealed housing based on a detected value of the humidity detected in a state in which power is supplied to the infrared light source, and gradually increases the power supplied to the infrared light source while obtaining a balance between a rate of increase in the detected value of the humidity detected in the state in which power is supplied to the infrared light source and a rate of decrease in the humidity by the dehumidifying agent in a case in which there is a risk of condensation.

Description

[0001] This application claims priority to Japanese Patent Application No. 2022-025629, filed on February 22, 2022, which is incorporated herein by reference. Technical Field

[0002] This invention relates to a function that enables an infrared light source to start in a safe start mode to avoid condensation in an infrared spectrophotometer. Background Technology

[0003] Fourier transform infrared spectrophotometers (FTIR) use an interferometer to detect the interference waves of the measurement light in a non-dispersive manner. A computer then performs a Fourier transform on the interference waves to obtain the spectrum of the measurement light. By generating an interference wave of infrared light, each wavenumber component can be calculated from the intensity signal composed of all wavenumber components of the interference wave using a Fourier transform. Fourier transform spectrophotometry is suitable for high-speed measurements and has become the mainstream method in infrared spectrophotometers.

[0004] The interferometer used in this device is typically a Michelson interferometer, featuring a beam splitter (BS) and two mirrors (a fixed mirror and a movable mirror). The movable mirror allows for a variable optical path difference, with its position directly correlated to the optical path difference. The interferometer generates an interference wave based on infrared light from an infrared source, corresponding to the optical path difference. By detecting the intensity of this interference wave, an interferogram (interference curve) is obtained, with the optical path difference on the horizontal axis and the intensity signal on the vertical axis. A computer performs a Fourier transform on the interferogram data to calculate the spectrum.

[0005] In conventional FTIR, components made of potassium bromide (KBr) are widely used in optical parts such as beam splitters and window components due to the transmittance of infrared light. However, these optical components are hygroscopic and prone to condensation. Therefore, to prevent the optical components from being directly exposed to water vapor in the atmosphere and condensing, the optical components are housed together with a desiccant in a sealed housing (e.g., Patent Document 1) or the sealed housing is purged with nitrogen (Patent Document 2, etc.). Furthermore, a solution has been proposed that includes a protection device in which a humidity sensor is installed inside the sealed housing; if the detected humidity is higher than a reference value, the beam splitter cover is closed (Patent Document 3, etc.).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Utility Model Publication No. Hei 2-101239

[0009] Patent Document 2: Japanese Patent Application Publication No. 10-332574

[0010] Patent Document 3: Japanese Patent Application Publication No. 61-126436 Summary of the Invention

[0011] The problem the invention aims to solve

[0012] In recent years, the uses of FTIR have diversified, and there is a need to take FTIR to various measurement sites for measurement (portability).

[0013] Traditional FTIR systems are mostly stationary, meaning that even when the main power supply is cut off, it remains connected, allowing a constant current to flow to the infrared light source (always energized) to maintain temperature. This is because the temperature of the light source and the housing stabilizes quickly when the power is subsequently turned on. However, in the case of portable FTIR systems, the power supply is completely cut off for transport, creating a period where the infrared light source cannot be powered on. Therefore, the light source and housing cool during transport, posing a risk of condensation, particularly on the cooled optical components (BS), within the sealed housing when the infrared light source is subsequently turned on.

[0014] Generally, an infrared light source emits light by using the resistance heat of the current flowing through a metal conductor to heat a light-emitting element around the conductor, thus producing blackbody radiation. The infrared light source becomes a heat source due to this resistance heat, and naturally, the temperature of its outer periphery rises. If, for example, insulation materials near the infrared light source absorb moisture, water vapor is released along with the temperature rise. If this water vapor reaches a certain level near the optical element and condenses on the surface of the optical element, the surface of the optical element becomes contaminated (deliquescence occurs in deliquescent conditions). Especially when the optical element cools, the warm water vapor emitted from the light source cools, making condensation more likely.

[0015] Furthermore, if the interferometer is placed in a humid environment for an extended period during transport, even with a sealed structure, it cannot completely prevent atmospheric ingress, and unexpected water vapor may enter. In addition, water vapor may enter due to the following special circumstances.

[0016] • Opening of the interferometer chamber (sealed housing) due to component replacement, maintenance, etc.

[0017] • Long-term use or storage in high humidity environments

[0018] Transportation in environments with drastic temperature changes

[0019] • Operational errors, etc.

[0020] If excessive water vapor enters the sealed enclosure, it may adsorb onto the surfaces of the insulation material and metal partitions around the light source. This adsorbed water vapor may then be rapidly released back into the interferometer due to the heat generated by the light source, increasing the risk of condensation.

[0021] Even assuming that the infrared light source is activated after confirming the humidity inside the sealed casing (or after opening it in a low-humidity environment to release the internal water vapor), it is impossible to determine (or remove) the amount of adsorbed water.

[0022] As described above, when the power is turned on after the light source and device housing have cooled down, especially after water vapor has entered the sealed housing, the water vapor adsorbed on the inner surface of the housing is released due to the heat generated by the infrared light source, causing a sharp increase in humidity inside the housing and increasing the likelihood of condensation. In this situation, the dehumidification capacity of desiccant or nitrogen purging devices is insufficient, and the protection of the optical components inside the housing cannot be considered adequate.

[0023] It also has a process of slowly heating the FTIR before starting the infrared light source, but the waiting time until the measurement can be performed is longer.

[0024] This problem is not limited to FTIR; it also exists in spectrophotometers that use a heating element as a light source and avoid water vapor.

[0025] The purpose of this invention is to provide an infrared spectrophotometer that can safely perform the start-up action while avoiding condensation inside a sealed housing.

[0026] Solution for solving the problem

[0027] The inventors completed this invention by focusing on the following specific case: the water vapor generation source is located near the infrared light source (heat source), and the water vapor behavior occurs within a relatively short time within the sealed housing. That is, the infrared spectrophotometer according to this invention comprises:

[0028] A sealed housing that can be opened and closed, which contains optical components;

[0029] An infrared light source that irradiates infrared light into the interior of the sealed housing;

[0030] A dehumidification unit that dehumidifies the interior of the sealed housing;

[0031] A temperature and humidity sensor that detects the humidity inside the sealed housing; and

[0032] A control unit that controls the power supplied to the infrared light source.

[0033] The infrared spectrophotometer extracts infrared light using optical components within the sealed housing as the measuring light, and illuminates this infrared light onto a sample disposed outside the sealed housing. The spectrum is then obtained based on the detected light value from the sample.

[0034] The infrared spectrophotometer is characterized in that...

[0035] The control unit starts the infrared light source while limiting the power supplied to it.

[0036] The control unit determines whether there is a risk of condensation inside the sealed housing based on the humidity detection value detected while power is being supplied to the infrared light source.

[0037] In the event of the risk of condensation, the control unit gradually increases the power supplied to the infrared light source while achieving a balance between the rate of increase of the detected humidity value when power is supplied to the infrared light source and the rate of decrease of the humidity caused by the dehumidification unit.

[0038] Here, "humidity" refers to relative humidity, with the unit set as %RH, and "temperature" is set as ℃. Additionally, the "dehumidification unit" includes at least one of the following: a desiccant such as silica gel, a dehumidifier, and a purging device such as nitrogen gas.

[0039] For example, even if a humidity threshold (reference humidity) is determined based on dew point calculations, in the event of a sharp increase in humidity, the amount of water vapor may sometimes exceed the threshold before feedback to the light source control is initiated. Furthermore, even if the power supply is cut off after a sharp increase in humidity, the time required for heat dissipation until the temperature decreases will naturally follow, thus requiring a fixed amount of time to stop water vapor generation. In contrast, in the structure of this invention, when the infrared light source is activated, it is initially configured to activate while limiting the power supply to the infrared light source, thereby preventing a sharp increase in humidity.

[0040] Furthermore, according to the structure of the present invention, the infrared light source is started while the power supply to the infrared light source is limited, and the humidity detected during this period is used to predict whether the dew point (100% RH) has been reached inside the sealed housing. Moreover, if the dew point is likely to be reached, the infrared light source is controlled as follows: while achieving a balance between the rate of increase of the humidity detected while the infrared light source is powered and the rate of decrease of the humidity caused by the dehumidification unit, the power supplied to the infrared light source is gradually increased. In this infrared light source start-up control, since a balance is achieved between the rate of increase of humidity while the infrared light source is powered and the rate of decrease of the humidity caused by the dehumidification unit, even if a large amount of water vapor is adsorbed inside the housing, a rapid increase in humidity inside the housing can be avoided, thus preventing the risk of condensation inside the housing.

[0041] As a result, even if water vapor is adsorbed inside the interferometer due to unexpected operations (such as opening the interferometer, storing it in a non-powered state for a long time, or transporting it in cold regions), the device can be started safely while avoiding condensation.

[0042] Furthermore, the present invention is characterized in that the control unit acquires the rate of change of the detected humidity value when power is supplied to the infrared light source as an upward rate, and acquires the rate of change of the detected humidity value when power is stopped from being supplied to the infrared light source as a downward rate.

[0043] The control unit controls the power supplied to the infrared light source in a manner that maintains a balance between the rising speed and the falling speed, and controls the power supplied to the infrared light source in a manner that makes the detected humidity value close to a standard humidity set to be lower than 100%.

[0044] Regarding the dehumidification unit, the higher the humidity, the faster the dehumidification unit absorbs moisture. Therefore, as long as the humidity inside the sealed housing is kept as high as possible without condensation, water vapor can be captured more quickly. Thus, in the structure of this invention, by controlling the power supply to the infrared light source in a way that balances the rate of increase and decrease in humidity while simultaneously maintaining a humidity level close to the set standard, the total time required for moisture absorption can be shortened while avoiding a sharp rise in humidity, allowing the infrared light source to quickly reach the specified temperature.

[0045] Furthermore, the present invention is characterized in that the control unit estimates the total amount of water vapor adsorbed within the sealed housing based on the rate of change of the humidity detection value detected while power is supplied to the infrared light source and the temperature detection value within the sealed housing obtained by the temperature and humidity sensor.

[0046] The control unit estimates the dehumidification speed of the dehumidification unit based on the rate of change of the detected humidity value when power supply to the infrared light source is stopped.

[0047] The control unit will notify the user of the dehumidification time, which is calculated based on the total amount of water vapor and the dehumidification rate, as the waiting time.

[0048] Based on this structure, the control unit obtains the total amount of water vapor components within the sealed housing and the dehumidification rate, and calculates the required dehumidification time based on these values, thus informing the user of the approximate waiting time. Consequently, the user can efficiently begin the measurement operation. Attached Figure Description

[0049] Figure 1 This is a schematic diagram of the FTIR implementation method.

[0050] Figure 2 This is a flowchart illustrating the activation of an infrared light source according to one implementation method.

[0051] Figure 3 This is a schematic diagram illustrating the humidity change during startup of an infrared light source according to one embodiment.

[0052] Figure 4 This is a flowchart of the startup process of the infrared light source involved in the modified example. Detailed Implementation

[0053] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. The infrared spectrophotometer of the present invention is applicable to Fourier transform infrared spectrophotometers (FTIR) and infrared microscopes. Here, in particular, it is shown that it is suitable for applications such as… Figure 1 The FTIR 100 is illustrated below. The FTIR 100 includes: an infrared light source 10; an interferometer 12 for generating infrared interference waves; a sample holder 26 for holding the sample; an infrared detector 14 for detecting the intensity of the interference waves obtained by irradiating the sample with infrared interference waves; and a computer 16 for calculating the spectral information of the sample based on the detection signal from the infrared detector 14. The computer 16 may be a microcomputer built into the main body of the FTIR 100 or a separately installed computer, etc.

[0054] The housing (sealed housing) 60 of the interferometer 12 is configured to be openable and closable, and is kept sealed by a sealing material between the cover member and the housing body. The housing 60 houses the following optical devices: an infrared light source 10, a beam splitter 20 for splitting the infrared light from the infrared light source 10, and a fixed mirror 22 and a movable mirror 24 for reflecting the split beams, respectively, to combine two beams of different path lengths to generate an infrared interference wave. The movable mirror 24 is configured to move in both directions towards and away from the beam splitter 20.

[0055] Infrared interference waves exiting the ejection window 64 are irradiated onto the sample within the sample holder 26 positioned between the ejection window 64 and the infrared detector 14. The infrared detector 14 receives the infrared interference waves from the sample and outputs their intensity signal. The detection signal from the infrared detector 14 is input to the computer 16 via an amplifier 14a and an A / D converter 14b.

[0056] The optical components housed in the housing 60 include beam splitters 20 and window members 64, which are made of deliquescent materials and are most susceptible to condensation. Furthermore, even optical components that are not deliquescent can sometimes become contaminated due to condensation on their surfaces. Mirrors and lenses may also experience surface blurring due to condensation, which can sometimes affect measurements.

[0057] The housing 60 of the interferometer 12 houses a desiccant 80 for adsorbing and removing water vapor contained in the internal space, and a temperature and humidity sensor 82 for continuously detecting the temperature and humidity (relative humidity) inside the housing near the infrared light source 10. The desiccant 80 may be, for example, silica gel. The temperature and humidity sensor 82 may also be a combination of a temperature sensor and a humidity sensor. The temperature and humidity sensor 80 typically combines a thermometer (thermistor, etc.) and a hygrometer (capacitive or resistive type). The hygrometer is used to detect absolute humidity, i.e., the amount of water vapor per unit volume (g / m³). 3 The temperature and humidity sensor 80 reads the saturated water vapor content (g / m³) at the temperature detected by the thermometer from a meter or similar source. 3 The relative humidity (%RH) is calculated based on the ratio of the detected water vapor content to the saturated water vapor content.

[0058] The infrared light source 10 consists of a ceramic light-emitting element 86 that emits light through resistance heating caused by an applied current flowing in a metal wire, and a heat-insulating material 88 disposed around the light-emitting element 86. The heat-insulating material 88 (such as a ceramic fiber molded material) has a conical opening in the light-emitting direction of the light-emitting element 86. The infrared light source 10 is fixed to the housing 60 via a sealing material so that the conical opening aligns with an opening formed in the housing 60, thereby directly irradiating infrared light into the housing 60. The heat-insulating material 88 is provided to suppress temperature fluctuations of the light source, prevent the surface temperature from becoming too high, and avoid overheating nearby components.

[0059] The thermal insulation material 88 is generally porous and exhibits the following characteristics: it readily adsorbs atmospheric water vapor; furthermore, the water vapor adsorbed in the thermal insulation material 88 is released from the thermal insulation material 88 immediately upon heating. In this embodiment, since the conical opening of the thermal insulation material 88 is directly connected to the internal space of the housing 60, the thermal insulation material 88 may become a source of water vapor generation when the light source 10 is activated.

[0060] Not limited to the insulation material 88, the surface of the metal partition wall of the housing 60 and the surface of the metal part of the optical component housed therein can also easily adsorb water vapor components, and therefore may become a source of water vapor generation inside the housing 60.

[0061] The computer 16 includes: a control unit 40 that controls the various structures of the computer 16; an arithmetic unit 42 that calculates the spectral information of the sample based on the detection signal from the infrared detector 14 and performs the analysis of the spectrum; and a memory 44 that stores the data processing program executed by the arithmetic unit 42, the calculated spectral information, the analysis results, and background information. Additionally, a display device 46 and a user interface 48 are connected to the computer 16.

[0062] The power supply to the infrared light source 10 is handled by the light source control device 50. The light source control device 50, for example, is composed of a programmable logic device such as an FPGA, and receives instructions from the computer 16 to perform its operations. The light source control device 50 converts the AC power from the external AC power supply 52 into a specified DC power supply before supplying it to the infrared light source 10. The light source control device 50 can start the infrared light source 10 using two methods: a "normal mode" and a "safety start mode." In the safety start mode, the power supplied to the infrared light source is controlled to ensure that the detected humidity value does not exceed a reference humidity level. Alternatively, the safety start mode of the light source control device 50 can be either analog control of supplying a target value of power to the infrared light source 10, or duty cycle control of switching the power supply on / off according to the target value.

[0063] <How to activate the infrared light source>

[0064] based on Figure 2 The processing flowchart (processing flow S1 to S7) describes the start-up method of the infrared light source 10.

[0065] First, when it is necessary to confirm the safety of FTIR 100 while starting the infrared light source 10, that is, when there is concern about the rapid generation of water vapor accompanying the start-up of the infrared light source 10, the light source control device 50 slowly and gradually increases the power supplied to the infrared light source 10 from a low level (processing flow S1). In the control of the infrared light source 10 here, in order to minimize the fluctuation of the humidity detection value obtained by the temperature and humidity sensor 82, the fluctuation of the humidity detection value can be controlled by PID or controlled based on this value. In addition, regarding the adjustment parameters of the infrared light source 10, it is desirable to perform analog control of the supplied power value or duty cycle control of the on / off state.

[0066] In parallel with process S1, the humidity change over time obtained by the temperature and humidity sensor 82 is monitored, and the rate of increase of humidity within the housing 60 is detected (process S2). Then, the temporal correlation between the monitored humidity change over time and the control of the infrared light source 10 is obtained, thereby predicting whether the humidity has reached the dew point (100% RH) (process S3). This prediction can also be performed by comparing the monitored humidity change over time with the humidity change over time in several stored experimental data.

[0067] If, in process S3, it is determined that there is no risk of condensation, the control of the infrared light source 10 in process S1 is stopped, and the process is switched to supplying power at a fixed value so that the infrared light source 10 is used for temperature measurement (normal mode). With PID control applied to the variation in the humidity detection value, the power supply output can be fixed at 100%.

[0068] On the other hand, if the risk of condensation is determined in the processing step S3, the power supply to the infrared light source 10 is completely cut off at one point, and the rate of humidity decrease is monitored and detected as the rate of moisture absorption of the desiccant 80 (processing step S4).

[0069] Next, if in process S5 it is determined that the detected moisture absorption rate is low and the dehumidification effect is insufficient, all processes are stopped, and the user is notified in some way to urge the replacement of the dehumidifier. On the other hand, if in process S5 it is determined that the detected moisture absorption rate is above the specified level and the dehumidification effect is not a problem, process S6 is initiated.

[0070] In process S6, based on the relationship between the rate of increase in humidity (process S2) and the rate of decrease in humidity (process S4) used to determine the risk of condensation, a control value for the light source that balances these two factors is derived (i.e., the amount of water vapor released per unit time; in other words, the change in the power supply command value). Light source control is then restarted using this control value. By maintaining a balance between the rate of water vapor release and the rate of moisture absorption, at least a rapid release of water vapor can be avoided.

[0071] For example, after restarting the light source control, if water vapor is released further while the amount of water vapor adsorbed decreases, the humidity detection value will decrease accordingly, thus indicating a decrease in water vapor release. As a result, in order to restore the control value (water vapor release), a process is performed that increases the light source temperature, i.e., increases the power supply.

[0072] Furthermore, since the higher the humidity, the faster the desiccant absorbs moisture, it is necessary to maintain a high humidity (standard humidity) inside the housing 60 as much as possible within a range that does not produce condensation, thereby enabling faster capture of water vapor. Therefore, the infrared light source 10 is activated using an appropriate light source control value predicted by achieving a balance between the initial humidity rise and humidity fall, and the power supplied to the infrared light source 10 is adjusted to always be the target humidity (standard humidity) by monitoring humidity changes and applying feedback. As a result, it is possible to maintain a state of humidity (standard humidity) with a fixed humidity margin relative to 100% within the interferometer (processing flow S6). If it is possible to maintain a state of balance between the rate of water vapor release and the rate of moisture absorption, while maintaining a humidity value as close as possible to the standard humidity (the humidity obtained by subtracting the fixed margin from 100% humidity) as the allowable upper limit, the infrared light source 10 can be stabilized as quickly as possible while avoiding condensation.

[0073] As a simple method to implement the above-described processing flow S6, for example, PID control with enhanced derivative control can be used to control the infrared light source 10 with a fixed humidity as the target value (standard humidity) while suppressing humidity overshoot. By controlling the infrared light source 10 while feeding back the detected humidity value to the target value, the total amount of water vapor adsorbed by the infrared light source 10 gradually decreases, and the light source temperature gradually increases in order to obtain the same amount of water vapor released as before.

[0074] In the processing flow up to this point, if values ​​are obtained experimentally beforehand, the total amount of adsorbed moisture can be predicted with simple accuracy based on the initial rate of increase in humidity (processing flow S2) and the detected temperature value. Then, using the detected rate of decrease in humidity within the housing (processing flow S4), the time until the adsorbed moisture is absorbed by the desiccant (the waiting time until the device is usable) can be provided to the user as a predicted value. Furthermore, at least one of the rate of increase or decrease in humidity can be remeasured, the waiting time until the device is usable can be recalculated, and the latest waiting time can be provided to the user again.

[0075] Finally, if it can be determined that there is no possibility of releasing adsorbed water vapor that poses a risk of condensation based on a certain judgment value such as the temperature of the infrared light source 10 being fixed or above, then the control of the infrared light source 10 is stopped, and the output is switched to a fixed value to become the temperature for measurement. Additionally, the user is notified in some way that the device can be used (processing flow S7).

[0076] exist Figure 3 The diagram illustrates an example of humidity changes during startup of the infrared light source 10 according to this embodiment.

[0077] Furthermore, in the FTIR 100 of this embodiment, desiccant 80 is used as a dehumidification unit. However, desiccant 80 can be used instead of desiccant 80, or a dehumidifier or nitrogen purging device can be installed together with desiccant 80, and the same effect as this embodiment can be achieved. For example, if the dehumidification effect is insufficient (processing flow S5), all processing flows can be stopped (movable mirror control can also be stopped), and the user can be notified in some way of a message to urge the replacement of desiccant or to improve the dehumidification efficiency (by increasing the flow rate of the dehumidifier or gas purging).

[0078] Furthermore, in this embodiment, a temperature and humidity sensor 82 is used to monitor the temperature and humidity inside the housing 60. However, the significance of condensation countermeasures lies essentially in preventing saturated moisture from condensing into the cooled air after contacting the surface of the cooled optical element. Therefore, whether the temperature of the optical element is relatively low relative to the air becomes an important parameter. Thus, by adding a sensor to measure the temperature near the optical element where condensation is to be avoided, the required margin of humidity can be determined with higher accuracy.

[0079] exist Figure 4 The flowchart illustrating the activation of the infrared light source in the modified example is shown. This is different from the embodiment described in this version. Figure 2The processing flow is simplified. For example, in the startup of the infrared light source 10 in processing flow S11, instead of gradually increasing the power supply from a low level as in processing flow S1, a fixed power supply can be supplied to start the infrared light source 10 as in the normal process. Moreover, as in processing flow S21, it is not necessary to detect the rate of increase in humidity; it is sufficient to detect the degree of increase in humidity. The risk of condensation can also be determined by comparing it with past data stored in memory 44. Alternatively, as in processing flow S41, the infrared light source 10 can be controlled by determining a control quantity that balances the degree of increase in humidity with the degree of dehumidification pre-stored in memory 44.

[0080] Furthermore, the housing 60 of the FTIR 100 in this embodiment is a sealed structure, so water vapor will hardly penetrate from the outside under normal usage. The light source startup method of this embodiment has a longer startup time compared to the method of simply starting the infrared light source 10 with a fixed power supply (referred to as "normal mode"). Therefore, this light source startup method can be applied only when necessary to start the infrared light source 10. Therefore, a mode switching function can be provided in the computer 16 so that the computer 16 can determine that a special situation such as water vapor intrusion has occurred, and only when this situation exists will the light source startup method of this embodiment be set to "safe startup mode" for startup.

[0081] Examples of special cases where water vapor intrusion occurs, as described above.

[0082] (1) Initial startup when the power is completely disconnected

[0083] To maintain low humidity within the housing 60 and to quickly stabilize the light source during startup, the FTIR 100 is typically powered on continuously, even when not in use, to keep the infrared light source 10 heated at low temperatures (always powered). Therefore, complete power disconnection is mostly necessary during transportation, long-term storage, or power outages. Consequently, when the computer 16 detects a recovery from such a complete power outage, it automatically selects the "Safe Startup Mode" for startup.

[0084] (2) When accessing the interior of housing 60

[0085] The FTIR 100 can be modified by the user replacing optical components such as the beam splitter 20 to change the measurement wavenumber range. When the infrared light source 10 is activated and reaches a high temperature, even if some external gas containing moisture enters, adsorption will not occur, and the risk of condensation is low. However, in the aforementioned always-on state, there is a risk of adsorption due to unexpected operations such as opening the housing 60 to replace optical components, resulting in intruding water vapor. Therefore, in the following situation, the computer 16 automatically selects startup under the "safe startup mode": it uses a dedicated sensor to pre-identify the optical components that are about to enter the always-on state, and then uses the sensor again to identify the optical components when starting from the always-on state, thereby determining that the optical components have changed to other optical components.

[0086] (3) When maintenance is performed

[0087] Sometimes, the sealed housing 60 is opened to perform work when the engineer is maintaining the FTIR 100. Therefore, upon restarting after this maintenance, the "safe boot mode" is automatically selected for startup. For example, a hardware or software user interface 48 can be pre-built into the FTIR 100 that allows the engineer to specify the boot mode.

[0088] Alternatively, when the infrared light source 10 is started in normal mode instead of safe start mode, the light source control device 50 also uses a simple reference (whether the initial increase in humidity is greater than a reference level) included in this embodiment to determine whether there is any unforeseen risk. For example, even when the infrared light source 10 is started with a fixed power supply without controlling the power supply, humidity is monitored. If a risk of condensation is determined, the fixed power start is stopped at that point. Afterward, processes such as notifying the user of the condensation risk and automatically switching to safe start mode for restart can be performed.

[0089] In addition, if the humidity inside the casing 60 suddenly rises due to user error or other reasons, the computer 16 can also perform actions such as issuing a warning to the user.

[0090] Explanation of reference numerals in the attached figures

[0091] 10: Infrared light source; 12: Interferometer; 14: Infrared detector; 20: Beam splitter (beam splitting section); 22: Fixed mirror; 24: Movable mirror; 50: Light source control device (control unit); 60: Sealed housing; 82: Temperature and humidity sensor; 86: Light emitter; 88: Thermal insulation material; 100: Fourier transform infrared spectrophotometer (FTIR).

Claims

1. An infrared spectrophotometer, comprising: A sealed housing that can be opened and closed, which contains optical components; An infrared light source that irradiates infrared light into the interior of the sealed housing; A dehumidification unit that dehumidifies the interior of the sealed housing; A temperature and humidity sensor that detects the humidity inside the sealed housing; and A control unit that controls the power supplied to the infrared light source. The infrared spectrophotometer extracts infrared light using optical components within the sealed housing as the measuring light, and illuminates this infrared light onto a sample disposed outside the sealed housing. The spectrum is then obtained based on the detected light value from the sample. The infrared spectrophotometer is characterized in that... The control unit starts the infrared light source while limiting the power supplied to it. The control unit determines whether there is a risk of condensation inside the sealed housing based on the humidity detection value detected while power is being supplied to the infrared light source. In the event of the risk of condensation, the control unit gradually increases the power supplied to the infrared light source while achieving a balance between the rate of increase of the detected humidity value when power is supplied to the infrared light source and the rate of decrease of the humidity caused by the dehumidification unit.

2. The infrared spectrophotometer according to claim 1, characterized in that, The control unit acquires the rate of change of the detected humidity value when power is supplied to the infrared light source as the rate of increase, and acquires the rate of change of the detected humidity value when power is stopped from being supplied to the infrared light source as the rate of decrease. The control unit controls the power supplied to the infrared light source in a manner that maintains a balance between the rising speed and the falling speed, and controls the power supplied to the infrared light source in a manner that makes the detected humidity value close to a standard humidity set to be lower than 100%.

3. The infrared spectrophotometer according to claim 1 or 2, characterized in that, The control unit estimates the total amount of water vapor adsorbed within the sealed housing based on the rate of change of the humidity value detected while power is supplied to the infrared light source and the temperature value inside the sealed housing obtained by the temperature and humidity sensor. The control unit estimates the dehumidification speed of the dehumidification unit based on the rate of change of the detected humidity value when power supply to the infrared light source is stopped. The control unit will notify the user of the dehumidification time, which is calculated based on the total amount of water vapor and the dehumidification rate, as the waiting time.

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