Spectroscopic detector

Abstract

To control the temperature of a light source with higher precision than conventional methods. [Solution] The spectroscopic detector includes a lamp house 6, a sample cell 12, an optical sensor 14, a heater 22, a cooling fan 30, a temperature sensor 32, and a control device 34. The heater 22 is in direct or indirect contact with the lamp house 6 that houses a light source 8, and heats the lamp house 6. The cooling fan 30 is for cooling the lamp house 6. The temperature sensor 32 is for detecting the temperature of the lamp house 6. The control device 34 is configured to control the operation of the light source 8, the heater 22, and the cooling fan 30. The control device 34 has a temperature control section 36 configured to maintain the temperature of the lamp house at a set temperature while the light source is on by controlling the output of at least the heater 22 based on a detection signal from the temperature sensor 32.

Description

[Technical Field]

[0001] The present invention relates to a detector, such as a spectrophotometer or a differential refractive index detector, that includes a spectroscope in an optical system that guides light from a light source to a sample cell and guides light from the sample cell to an optical sensor (hereinafter, such a detector will be referred to as a "spectroscopic detector"). [Background technology]

[0002] Spectroscopic detectors such as ultraviolet-visible spectrophotometers, spectrofluorometers, and differential refractive index detectors use lamps that emit light while generating heat, such as deuterium lamps or halogen lamps, as their light sources. In these detectors, the light source is housed in a light source housing component called a lamp house, and the optical system, including a spectroscope that guides light to a sample cell or optical sensor, is housed in a housing component separate from the lamp house (see Patent Document 1).

[0003] Light emitted from the light source is dispersed by a spectroscope and detected by an optical sensor. A sample cell is placed on the optical path of the light introduced into the optical system housing, and the light transmitted through the sample components flowing in the sample cell and the fluorescence emitted from the sample components are detected by the optical sensor to measure the absorbance and fluorescence intensity of the sample components, thereby allowing the sample components to be identified and quantified.

[0004] In recent years, detectors have become increasingly versatile, and they are required to be able to operate in a variety of environments. In particular, there are high demands for detectors that can withstand environmental temperatures, maintaining a stable baseline even when the environmental temperature changes by several degrees Celsius, and providing highly reproducible measurement results.

[0005] However, the light output of light sources such as deuterium lamps and halogen lamps is temperature dependent. For example, a 10°C change in the ambient temperature (lamp house temperature) of a deuterium lamp causes a change in light output of approximately 1%. This change is equivalent to approximately 4 mAU in absorbance. This means that a 1°C change in ambient temperature (lamp house temperature) causes a shift in the baseline of approximately 400 μAU.

[0006] Therefore, it has been proposed to control the temperature of the light source to a constant value so that the temperature of the light source does not fluctuate depending on the ambient temperature (see Patent Documents 2, 3, and 4). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-048176 [Patent Document 2] Japanese Patent Application Laid-Open No. 2000-074821 [Patent Document 3] Japanese Patent Application Laid-Open No. 2005-098765 [Patent Document 4] Japanese Patent Application Laid-Open No. 2011-002310 Summary of the Invention [Problem to be solved by the invention]

[0008] Since the lamp used as the light source emits light while generating heat, the device is provided with a cooling fan to release the heat generated by the light source. The technologies disclosed in Patent Documents 2 to 4 mentioned above all maintain the temperature of the light source at a constant temperature by adjusting the rotation speed of the cooling fan.

[0009] However, when controlling the temperature of a light source using a cooling fan, there is a problem with response time, which is that it takes time for the temperature of the light source to change after the rotation speed of the cooling fan changes, and therefore, if the environmental temperature changes suddenly, the temperature of the light source will fluctuate accordingly.

[0010] Furthermore, there is a limit to the range of temperature control of the light source with the rotation speed of the cooling fan, and the temperature of the light source cannot be effectively controlled, particularly in the low rotation speed range of the cooling fan.

[0011] The present invention has been made in view of the above problems, and has as its object to enable the temperature of a light source in a spectroscopic detector such as a spectrophotometer to be controlled with higher precision than conventionally possible. [Means for solving the problem]

[0012] The spectroscopic detector according to the present invention comprises a lamp house, a sample cell, an optical sensor, a heater, a cooling fan, a temperature sensor, and a control device. The lamp house accommodates a light source. The sample cell, through which a sample flows, is disposed on the optical path of light emitted by the light source and emitted from the lamp house. The optical sensor detects light from the sample cell. The light from the sample cell includes light transmitted through the sample cell, light reflected by the sample flowing through the sample cell, and fluorescence emitted from the sample flowing through the sample cell. The heater heats the lamp house by directly or indirectly contacting the lamp house. The heater being in indirect contact with the lamp house means that heat from the heater is transferred to the lamp house via a thermally conductive material. The cooling fan cools the lamp house. The temperature sensor detects the temperature of the lamp house. The control device is configured to control the operation of the light source, heater, and cooling fan. This control device has a temperature control unit configured to maintain the temperature of the lamp house at a predetermined temperature (hereinafter referred to as the set temperature) while the light source is on by controlling at least the output of the heater based on the detection signal of the temperature sensor.

[0013] In the spectroscopic detector according to the present invention, a heater and a cooling fan are used to control the temperature of the lamp house, i.e., the light source. In the field of temperature control of objects, the combined use of a heater and a cooling fan is not a special technique. However, when targeting the temperature control of a heat-generating element such as a light source, it is common to use a cooling fan to control the amount of heat dissipated from the light source, as in Patent Documents 2 to 4.

[0014] The inventors discovered that the conventional method of using only a cooling fan was unable to control the temperature of the light source with high precision due to issues such as response time. Therefore, they came up with the idea of using a heater to add heat to the lamp house that houses the light source, which is a heat-generating element, and controlling the temperature of the light source by controlling the amount of heat generated by the heater. It is not common to control the temperature of a heat-generating element such as a light source by adding heat with a heater.

[0015] When heat is applied to the lamp house by the heater, the lamp house temperature rise speed is improved. As a result, when the temperature of the lamp house is below a preset temperature, the heat generated by the light source and the heater quickly raise the lamp house temperature to the set temperature. This improves the responsiveness when raising the temperature of the lamp house.

[0016] Furthermore, by using a heater and a cooling fan together, the temperature of the lamp house can be stabilized at a higher temperature than before. The higher the temperature of the lamp house relative to the ambient temperature, the more efficient the heat dissipation from the lamp house. Therefore, by reducing or turning off the heater output when the lamp house temperature exceeds the set temperature, the lamp house temperature can be quickly reduced to the set temperature. This also improves the responsiveness when lowering the lamp house temperature.

[0017] The temperature control unit may be configured to control the output of the heater based on the output of the temperature sensor while maintaining a constant rotation speed of the cooling fan.

[0018] As mentioned above, the light emission intensity of a light source is temperature-dependent, and therefore the light emission intensity does not stabilize until the temperature of the light source stabilizes after the light source is turned on. Therefore, it is necessary to wait before starting measurement until the temperature of the light source stabilizes after the light source is turned on. Patent Document 2 proposes that, after the light source is turned on, the cooling fan is stopped or controlled to rotate at a lower speed than usual until the temperature of the lamp house reaches a predetermined temperature, thereby improving the temperature rise rate of the lamp house after the light source is turned on and allowing the temperature of the lamp house to reach a predetermined temperature in a short time. This shortens the time until the temperature of the light source stabilizes after the light source is turned on, allowing measurement to start sooner, thereby improving analysis efficiency.

[0019] In the spectroscopic detector according to the present invention, the lamp house is heated by a heater, so the temperature of the lamp house can be increased more quickly than in the past. Therefore, in the spectroscopic detector according to the present invention, it is preferable that the control device further includes a high-speed stabilization unit configured to heat the lamp house by the heater before or approximately simultaneously with the lighting of the light source, and to increase the temperature of the lamp house to a set temperature or a temperature close to the set temperature. This shortens the time it takes for the temperature of the lamp house to reach the set temperature after the light source is turned on, thereby further shortening the wait time until the temperature of the light source stabilizes, and improving analytical efficiency.

[0020] In the above case, it is preferable that the high-speed stabilization unit is configured to stop the cooling fan when the temperature of the lamp house is raised to a set temperature or a temperature close to the set temperature, thereby further improving the temperature rise speed of the lamp house and further shortening the time it takes for the temperature of the light source to reach the set temperature. [Effects of the Invention]

[0021] The spectroscopic detector according to the present invention is configured to maintain the temperature of the lamp house that houses the light source at a set temperature using a heater and a cooling fan, which improves the responsiveness of temperature control compared to conventional methods that use only a cooling fan, and enables temperature control of the light source with higher precision than conventional methods. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an embodiment of a spectrophotometer, which is an example of a spectroscopic detector. [Figure 2] 4 is a flowchart illustrating an example of the operation of temperature control of the lamp house in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] An embodiment of a spectrophotometer, which is an example of a spectroscopic detector of the present invention, will be described below with reference to the drawings.

[0024] As shown in Figure 1, the spectrophotometer 2 of this embodiment includes an optical system housing 4 and a lamp house 6. The lamp house 6 is made of a metal such as aluminum. A light source 8 is housed inside the lamp house 6. The optical system housing 4 houses a sample cell 12, an optical sensor 14, mirrors 16 and 18, and a diffraction grating 20.

[0025] In FIG. 1, the optical system housing portion 4 and the lamp house 6 are depicted as being independent of each other, but the optical system housing portion 4 and the lamp house 6 may be connected to each other to form an integrated housing.

[0026] The optical system housing portion 4 and the lamp house 6 have opposing surfaces, and windows are provided on these opposing surfaces to allow light from the light source 8 to pass through. The light source 8 is a deuterium lamp, a halogen lamp, or the like.

[0027] A sample cell installation section 10 is provided within the optical system housing section 4, and a sample cell 12 is placed in this sample cell installation section 10. A mirror 16 is arranged within the optical system housing section 4 to reflect light taken in through a window on the surface opposite the lamp house 6, and reflects light from the light source 8 and guides it to the sample cell 12. A mirror 18 is arranged on the optical path of the light that has passed through the sample cell 12, and a spectroscope 20 such as a diffraction grating is arranged on the optical path of the light reflected by the mirror 18. The light that enters the spectroscope 20 is split into individual wavelength ranges. An optical sensor 14 consisting of a photodiode array is arranged at a position to receive the light of each wavelength range split by the spectroscope 20.

[0028] Light emitted by light source 8 is reflected by mirror 16 and irradiated onto sample cell 12. Light transmitted through sample cell 12 is reflected by mirror 18 and directed to diffraction grating 20, and the intensity of light in each wavelength range dispersed by diffraction grating 20 is detected by optical sensor 14. By detecting the intensity of light in each wavelength range obtained by optical sensor 14, the absorption wavelength and absorbance of the sample components flowing through sample cell 12 are measured, and the sample components are identified and quantified.

[0029] The temperature of the lamp house 6 is controlled to a predetermined temperature by a heater 22 and a cooling fan 30. A temperature sensor 32 is attached to the lamp house 6, and the temperature of the lamp house 6 is detected by the temperature sensor 32. The temperature sensor 32 is realized by, for example, a thermocouple. The detection signal obtained by the temperature sensor 32 is input into a control device 34, which will be described later.

[0030] The heater 22 is, for example, a flat heater, and is adhered to the outer surface of the lamp house 6 by a thermally conductive adhesive. The heater 22 may also be a ribbon heater wound around the outer surface of the lamp house 6.

[0031] The cooling fan 30 is provided to blow cooling air onto the heat dissipation fins 28. The heat dissipation fins 28 are thermally connected via heat pipes 26 to a heat transfer member 24 attached to the outer surface of the lamp house 6 so as to be in close contact with the lamp house 6. The heat transfer member 24 is made of a metal material (e.g., copper) with good thermal conductivity. As a result, heat from the lamp house 6 is transferred to the heat transfer member 24, and the heat from the heat transfer member 24 is transferred to the heat dissipation fins 28 via the heat pipes 26. By blowing cooling air from the cooling fan 30 onto the heat dissipation fins 28, heat can be absorbed from the lamp house 6, thereby cooling the lamp house 6.

[0032] In this embodiment, the heat from the lamp house 6 is transported by the heat pipe 26 to a position away from the lamp house 6 and dissipated, but the present invention is not limited to this, and the cooling air from the cooling fan 30 may be blown directly onto the lamp house 6.

[0033] The operation of the heater 22 and the cooling fan 30 is controlled by a control device 34. The control device 34 is realized by, for example, a circuit board equipped with a processing element such as a microcomputer. The control device 34 includes a temperature control unit 36, a set temperature holding unit 38, and a high-speed stabilization unit 40. The temperature control unit 36 and the high-speed stabilization unit 40 are functions obtained by the processing element of the control device 34 executing a predetermined program. The set temperature holding unit 38 is a function realized by a partial area of a memory device provided in the control device 34.

[0034] The temperature control unit 36 is configured to control the output of at least the heater 22 based on the detection signal obtained by the temperature sensor 32 so that the temperature of the lamp house 6 while the light source 8 is turned on becomes a preset temperature (set temperature).

[0035] The rotation speed of the cooling fan 30 may be maintained constant. When the rotation speed of the cooling fan 30 is maintained constant, the temperature control unit 36 performs feedback control of the output of the heater 22 based on the detection signal obtained by the temperature sensor 32. In this case, the only object to be controlled is the output of the heater 22, and complicated control is not required.

[0036] On the other hand, the rotation speed of the cooling fan 30 may be changed as necessary. When the rotation speed of the cooling fan 30 is also controlled, the output of the heater 22 may be reduced and the rotation speed of the cooling fan 30 may be increased when the temperature of the lamp house 6 is higher than the set temperature, and conversely, the output of the heater 22 may be reduced and the rotation speed of the cooling fan 30 may be increased when the temperature of the lamp house 6 is lower than the set temperature.

[0037] Furthermore, in order to widen the temperature controllable range, the cooling fan 30 can be used as an auxiliary fan. Setting the rotation speed of the cooling fan 30 to a high level enables temperature control in a relatively low temperature range, while setting the rotation speed of the cooling fan 30 to a low level enables temperature control in a relatively high temperature range.

[0038] The temperature (set temperature) of the lamp house 6 to be maintained while the light source 8 is turned on is held in a set temperature holding unit 38. The set temperature may be one that can be changed arbitrarily by the user in accordance with the ambient temperature, etc., or may be a predetermined fixed value.

[0039] The spectrophotometer 2 of this embodiment is configured to heat the lamp house 6 with the heater 22, so that the set temperature of the lamp house 6 to be maintained while the light source 8 is on can be set to a temperature (for example, ambient temperature + 20°C) significantly higher than the ambient temperature (room temperature). Setting the set temperature to such a high temperature increases the temperature difference between the lamp house 6 temperature while the light source 8 is on and the ambient temperature, improving the efficiency of heat dissipation from the lamp house 6. This not only improves the rate at which the heater 22 heats up the lamp house 6, but also improves the rate at which the lamp house 6 cools down, improving the responsiveness of temperature control of the lamp house 6 and, ultimately, the light source 8.

[0040] In a conventional detector not equipped with the heater 22, the only factor that raises the temperature of the lamp house 6 is the heat generated by the light source 8, so it takes a considerable amount of time for the temperature of the lamp house 6 to reach such a high temperature, and it takes a long time for the temperature of the lamp house 6 to stabilize after the light source 8 is turned on. For this reason, it is not practical to set the set temperature to such a high temperature in a conventional detector.

[0041] The high-speed stabilization unit 40 is configured to heat the lamp house 6 with the heater 22 when the spectrophotometer 2 is started up, and quickly raise the temperature of the lamp house 6 to a set temperature or a temperature close to that set temperature. After the spectrophotometer 2 is started up, the faster the temperature of the lamp house 6 reaches the set temperature, the shorter the time it takes for the light emission amount of the light source 8 to stabilize, and the shorter the waiting time before measurement can begin. The timing at which the heater 22 starts heating the lamp house 6 may be before the light source 8 is turned on, or may be approximately simultaneously with the light source 8 being turned on. "Almost simultaneously" also includes the timing when a certain time (for example, within one minute) has elapsed after the light source 8 is turned on.

[0042] It should be noted that the high-speed stabilization section 40 is not an essential component.

[0043] An example of the temperature control operation of the lamp house 6 after the start-up of the spectrophotometer 2 of this embodiment will be described with reference to the flowchart of Fig. 2 along with Fig. 1. In this example, after the light source 8 is turned on, the cooling fan 30 is driven at a constant rotation speed, and the output of the heater 22 is feedback-controlled based on the detection signal of the temperature sensor 32.

[0044] When the spectrophotometer 2 (detector) is started up, the high-speed stabilization unit 40 turns on the heater 22 to quickly heat up the lamp house 6 (step S1). Then, the light source 8 is turned on (step S2). As described above, the heater 22 may be turned on before the light source 8 is turned on, or may be turned on approximately simultaneously with the light source 8 being turned on.

[0045] After the heater 22 starts heating the lamp house 6, the high-speed stabilization unit 40 reads the detection signal of the temperature sensor 32 at regular time intervals (step S3), and each time it reads the detection signal, it checks whether the temperature of the lamp house 6 has reached the set temperature (step S4). When the temperature of the lamp house 6 has reached the set temperature, the temperature control unit 36 starts feedback control of the heater 22.

[0046] The temperature control unit 36 turns on the cooling fan 30 and drives it at a constant rotation speed (step S5). Thereafter, the temperature control unit 36 reads the detection signal of the temperature sensor 32 at regular time intervals (step S6), and each time reads the detection signal, calculates the difference ΔT between the temperature of the lamp house 6 and the set temperature (step S7), and supplies power according to the difference ΔT to the heater 22 to control the output of the heater 22 (step S8).

[0047] In the above-described embodiment, a post-spectroscopic spectrophotometer has been described as the spectroscopic detector, but the spectroscopic detector of the present invention is not limited to this, and can be applied to any detector that includes a spectrometer in its optical system, such as a pre-spectroscopic spectrophotometer or a differential refractive index detector. [Explanation of symbols]

[0048] 2 Spectrophotometer 4 Optical system housing 6. Lamphouse 8 light source 10 Sample cell installation section 12 Sample cell 14 Optical Sensor 16,18 Mirror 20 spectrometer 22 Heater 24 Heat transfer material 26 Heat pipe 28 Heat dissipation fin 30 Cooling fan 32 Temperature Sensor 34 Control device 36 Temperature control unit 38 Set temperature holding part 40 High speed stable part

Claims

1. a light source that is a deuterium lamp or a halogen lamp; a lamp house that houses the light source therein; a sample cell arranged on an optical path of light emitted from the light source and exiting from the lamp house, the sample flowing therethrough; a light sensor for detecting light from the sample cell; a heater that is in direct or indirect contact with the lamp house and heats the lamp house; a cooling fan for cooling the lamp house; a temperature sensor attached to the lamp house to detect the temperature of the lamp house; a control device configured to control the operations of the light source, the heater, and the cooling fan, the control device having a temperature control unit configured to control the output of at least the heater based on a detection signal from the temperature sensor, thereby maintaining the temperature of the lamp house at a preset temperature while the light source is turned on; After the light source is turned on and the temperature of the lamp house reaches the predetermined temperature, the temperature control unit reads the detection signal of the temperature sensor at regular intervals, calculates the difference between the temperature of the lamp house read by the temperature sensor and the predetermined temperature, and supplies power to the heater according to the difference, thereby feedback-controlling the output of the heater so that the temperature of the lamp house reaches the predetermined temperature.

2. The spectroscopic detector according to claim 1 , wherein the temperature control unit is configured to control the output of the heater based on the output of the temperature sensor while maintaining a constant rotation speed of the cooling fan.

3. The spectroscopic detector according to claim 1 or 2, wherein the control device further has a high-speed stabilization unit configured to heat the lamp house using the heater before or approximately simultaneously with turning on the light source, and to raise the temperature of the lamp house to the predetermined temperature or a temperature close to it.

4. 4. The spectroscopic detector according to claim 3, wherein the high-speed stabilization unit is configured to stop the cooling fan when the temperature of the lamp house is increased to the preset temperature or a temperature in the vicinity thereof.

5. The spectroscopic detector according to claim 1 , wherein the preset temperature is higher than an ambient temperature.

6. 3. The spectroscopic detector according to claim 1, wherein the heater is bonded to the outer surface of the lamp house by a thermally conductive adhesive.

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