Spectroscopic device

A spectroscopic device includes a lamp house accommodating a light source inside, a spectrometer configured to disperse light from the lamp house, a temperature measurement means for measuring a temperature of the spectrometer, a heating means for heating the spectrometer, a storage means and a control unit. The storage means stores the detection temperature of the temperature measurement means at a time when an optical axis is stable in the spectrometer in a state where the light source is illuminated. The control unit is configured to control operation of the heating means, and to cause the heating means to operate, when the light source is illuminated from a light-off state, until a detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means.

TECHNICAL FIELD

The present invention relates to a spectroscopic device including a lamp house accommodating a light source inside, and a spectrometer for dispersing light from the lamp house.

BACKGROUND ART

FIG. 5is a diagram schematically showing a configuration of a conventional spectroscopic device. Here, as an example of the spectroscopic device, a PDA (photodiode array) absorbance detector, for a liquid chromatograph, including a multiple wavelength detection function will be described.

As shown inFIG. 5, the spectroscopic device includes a lamp house1, and a spectrometer3.

A light source5is provided inside the lamp house1. Light emitted from the light source5is radiated on the spectrometer3via an aperture plate (not shown).

The spectrometer3is provided with, in the order of passing of light, an aperture plate (not shown), a focusing mirror7, a flow cell9, a focusing mirror11, a slit13, a concave diffraction grating15, and a photodiode array17.

The lamp house1and the spectrometer3are arranged with a spacer19having an opening for light transmission therebetween.

Also, a fan21for cooling the lamp house1is provided to the spectroscopic device.

The lamp house1and the fan21are provided to suppress a change in the amount of light emission of the light source5due to a change in the ambient temperature of the device. Generally, the amount of light emission of the light source5changes according to a change in the temperature of the light source5. When the amount of light of the light source5changes, the output value of the photodiode array17changes, and thus, high sensitivity measurement is possibly prevented. Accordingly, to prevent the output value of the photodiode array17from changing due to a change in the ambient temperature of the device, the light source5is accommodated in the lamp house1whose heat capacity is high to a certain degree and the lamp house1is cooled by the fan21with certain air volume so as to radiate heat, and the temperature of the light source5is thus not easily changed even if the ambient temperature of the device changes.

The spectroscopic device shown inFIG. 5is a device for measuring an absorption spectrum of an analysis sample flowing into the flow cell9, by emitting light radiated by the light source5on the flow cell9and causing the light which has passed through the flow cell9to be dispersed on the photodiode array17by the diffraction grating15.

According to this spectroscopic device, when the light source5is illuminated from a light-off state, the spectrometer3is thermally expanded due to the heat generated by the light source5, and the optical axis changes inside the spectrometer3. Because of this influence, stabilization of the baseline of a chromatogram after the lighting of the light source5takes time.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

With conventional technology, increase in the temperature of the lamp house1is accelerated by temporarily stopping the fan21for cooling the lamp house immediately after the light source5has been illuminated, and increase in the temperature of the spectrometer3is accelerated through the increase in the temperature of the lamp house1, to thereby reduce the stabilization time of the baseline of a chromatogram (for example, see Patent Document 1).

However, even if the time from the lighting of the light source until the temperature of the lamp house1is increased to a predetermined temperature is reduced, stabilization of the temperature distribution in the spectrometer3takes time, and it takes certain time for the optical axis to become stable in the spectrometer3and for the baseline of the chromatogram to become stable.

Such a problem is present not only with respect to the PDA absorbance detector for a liquid chromatograph, but also with respect to spectroscopic devices including a lamp house and a spectrometer, such as an absorption spectrophotometer, a spectrofluorometer, a UV detector for a liquid chromatograph, and a fluorescence detector. That is, a light source device including a lamp house and a spectrometer has a problem that it takes certain time for an optical axis to become stable in the spectrometer after the lighting of the light source.

The present invention has its object to reduce, for a spectroscopic device including a lamp house accommodating a light source inside, and a spectrometer for dispersing light from the lamp house, the time from the lighting of the light source until stabilization of an optical axis in the spectrometer.

Solutions to the Problems

A spectroscopic device according to the present invention is a spectroscopic device including a lamp house accommodating a light source inside, and a spectrometer configured to disperse light from the lamp house, and includes temperature measurement means for measuring a temperature of the spectrometer, heating means for heating the spectrometer, storage means for storing a detection temperature of the temperature measurement means at a time an optical axis is stable in the spectrometer in a state where the light source is illuminated, and a control unit configured to control an operation of the heating means, where the control unit causes the heating means to operate, when the light source is illuminated from a light-off state, until a detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means.

With the spectroscopic device of the present invention, when the light source is illuminated from the light-off state, the spectrometer is heated by the heat from the lamp house, and it is also heated by the heating means until the detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means.

The spectroscopic device of the present invention may further include a fan configured to cool the lamp house, where the control unit may keep the fan stopped when the light source is illuminated from the light-off state, and cause the fan to operate at a predetermined number of revolutions after the detection temperature of the temperature measurement means has reached the detection temperature stored in the storage means. Accordingly, increase in the temperature of the lamp house is accelerated compared to a case where the fan is operated from immediately after the lighting of the light source. Incidentally, with the spectroscopic device of the present invention, the fan may be operated at the predetermined number of revolutions or at a smaller number of revolutions than the predetermined number of revolutions until the detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means.

Furthermore, the spectroscopic device of the present invention may include a plurality of sets of the temperature measurement means and the heating means for performing temperature measurement and heating of the spectrometer at different positions, where the storage means may store, for each temperature measurement means, the detection temperature of the temperature measurement means at a time the optical axis is stable in the spectrometer, and where the control unit may cause the plurality of heating means to operate based on the detection temperatures of the corresponding temperature measurement means. The temperature distribution of the spectrometer at a time the optical axis is stable in the spectrometer is thereby achieved faster compared to a case where there is one set of temperature measurement means and heating means, and the time from the lighting of the light source to the stabilization of the optical axis in the spectrometer is further reduced.

Furthermore, according to the spectroscopic device of the present invention, the storage means may store, instead of the detection temperature, a time after the light source is illuminated from the light-off state until the detection temperature of the temperature measurement means reaches the detection temperature at a time the optical axis is stable in the spectrometer according to an operation of the heating means, and the control unit may cause the heating means to operate, based on the time stored in the storage means. Also, in the case where the operation of the heating means is controlled based on the time stored in the storage means, as in the case where the operation of the heating means is controlled based on the detection temperature of the temperature measurement means, the spectrometer is appropriately heated, and the time from the start of lighting of the light source to stabilization of the optical axis in the spectrometer is reduced.

Effects of the Invention

A spectroscopic device of the present invention is a spectroscopic device including a lamp house accommodating a light source inside, and a spectrometer configured to disperse light from the lamp house, the spectroscopic device including temperature measurement means for measuring a temperature of the spectrometer, heating means for heating the spectrometer, storage means for storing a detection temperature of the temperature measurement means at a time an optical axis is stable in the spectrometer in a state where the light source is illuminated, and a control unit configured to control an operation of the heating means. Also, the control unit causes the heating means to operate, when the light source is illuminated from a light-off state, until a detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means. Accordingly, when the light source is illuminated from the light-off state, the spectrometer is heated by the heat from the lamp house, and it is also heated by the heating means until the detection temperature of the temperature measurement means reaches the detection temperature stored in the storage means. Thus, compared to a case of no heating by the heating means, the temperature distribution of the spectrometer at a time the optical axis is stable in the spectrometer is achieved faster, and the time from the lighting of the light source to the stabilization of the optical axis in the spectrometer is reduced.

EMBODIMENTS OF THE INVENTION

FIG. 1is a diagram schematically showing a configuration of an embodiment. Here, as an example of a spectroscopic device, a PDA absorbance detector, for a liquid chromatograph, including a multiple wavelength detection function will be described.

As shown inFIG. 1, the spectroscopic device includes a lamp house1and a spectrometer3.

A light source5is provided inside the lamp house1. A housing forming the lamp house1is formed of, for example, aluminum. As the light source5, a discharge lamp such as a deuterium lamp, a tungsten lamp or the like is used. Light emitted from the light source5is radiated on the spectrometer3via an aperture plate (not shown) and a spacer19.

The spectrometer3is provided with, in the order of passing of light, an aperture plate (not shown), a focusing mirror7, a flow cell9, a focusing mirror11, a slit13, a concave diffraction grating15, and a photodiode array17. A housing forming the spectrometer3is formed of, for example, aluminum. Light from the lamp house1is collected on the flow cell9by the focusing mirror7. Light which has passed through the flow cell9is collected at the slit13by the focusing mirror11. Light which has passed through the slit13is dispersed by the diffraction grating15. The photodiode array17detects light intensity for light of a plurality of wavelengths from the diffraction grating15.

The lamp house1and the spectrometer3are arranged with the spacer19having an opening for light transmission therebetween. The spacer19is formed of, for example, stainless steel.

Also, a fan21for cooling the lamp house1is provided to the spectroscopic device.

A thermistor23and a heater25are provided on an outer surface of the housing of the spectrometer3. The thermistor23configures temperature measurement means for measuring the temperature of the spectrometer3. The heater25configures heating means for heating the spectrometer3.

Storage means27is provided for storing the detection temperature of the thermistor23at the time the optical axis in the spectrometer3is stable in a state where the light source5is illuminated.

A control unit29is provided for controlling the operation of the heater25. The control unit29also controls the operation of the fan21.

An operation of the embodiment will be described.

When the light source5is illuminated from a light-off state, the control unit29causes the heater25to operate, and heats the spectrometer3. The control unit29causes the heater25to operate until the detection temperature of the thermistor23reaches the detection temperature stored in the storage means27. The spectrometer3is thus heated by the heat from the lamp house1, and also by the heater25.

At this time, the control unit29keeps the fan21in a stopped state. Accordingly, increase in the temperature of the lamp house1is accelerated compared to a case where the lamp house1is cooled by the operation of the fan21immediately after the lighting of the light source5.

When the detection temperature of the thermistor23reaches the detection temperature stored in the storage means27, the control unit29stops the operation of the heater25, and stops heating of the spectrometer3by the heater25. Also, at the same time, the control unit29causes the fan21to operate at a predetermined number of revolutions to stabilize the temperature of the lamp house1.

FIG. 2is a diagram showing a change in a baseline of a chromatogram after lighting of the light source, according to the embodiment shown inFIG. 1.FIG. 3is a diagram showing a change in a baseline of a chromatogram after lighting of a light source, according to conventional technology shown inFIG. 5. InFIGS. 2 and 3, the vertical axes indicate the absorbance (arbitrary unit (mAU)), and the horizontal axes indicate time (minute). Absorbance at wavelengths of, for example, 250 nm (nanometer) and 4 nm is detected in the chromatograms inFIGS. 2 and 3. In the embodiment, the detection temperature of the thermistor23reaches the detection temperature stored in the storage means27in about 10 minutes (heating time) from the start of lighting of the light source5. With conventional technology, the fan21is stopped for 10 minutes (heating time) from the start of lighting of the light source5.

For example, it is assumed that the baseline is stabilized when the range of change of the baseline of the chromatogram is 0.5 mAU/h or less. As shown inFIG. 3, according to conventional technology, it takes about 75 minutes for the baseline to be stabilized from the start of lighting of the light source5(stabilization time). In contrast, as shown inFIG. 2, according to the embodiment, it takes about 15 minutes for the baseline to be stabilized from the start of lighting of the light source5(stabilization time). As described, the embodiment shown inFIG. 1is capable of reducing, compared to conventional technology, the time from the start of lighting of the light source5to stabilization of the baseline, that is, the time from the start of lighting of the light source5to stabilization of the optical axis in the spectrometer3.

FIG. 4is a diagram schematically showing a configuration of another embodiment. Parts inFIG. 4that serve the same functions as those inFIG. 1are denoted with the same reference signs, and description thereof will be omitted.

Compared to the embodiment inFIG. 1, the present embodiment further includes a thermistor31, and a heater33. The set of thermistor31and heater33is for performing temperature measurement and heating of a spectrometer3at a position different from the set of the thermistor23and heater25.

Storage means27stores, for each of the thermistors23and31, the detection temperature of the thermistor23or31at the time the optical axis is stable in the spectrometer3.

A control unit29causes the heaters25and33to operate when a light source5is illuminated from a light-off state. Also, the control unit29keeps a fan21in a stopped state.

The control unit29stops the heater25when the detection temperature of the thermistor23reaches the corresponding detection temperature stored in the storage means27. Also, the control unit29stops the heater33when the detection temperature of the thermistor31reaches the corresponding detection temperature stored in the storage means27. Furthermore, the control unit29causes the fan21to operate at a predetermined number of revolutions so that the temperature of a lamp house1is stabilized, when the detection temperature of one or both of the thermistors23and31reach the corresponding detection temperature stored in the storage means27.

According to this operation, the temperature distribution of the spectrometer3at the time the optical axis is stable in the spectrometer3is achieved faster compared to a case where there is one set of thermistor and heater, and the time from the lighting of the light source5to the stabilization of the optical axis in the spectrometer3is further reduced.

Two sets of thermistors and heaters are provided in the embodiment inFIG. 4, but the spectroscopic device of the present invention may include three or more sets of thermistors and heaters.

Moreover, the arrangement of the thermistor23and the heater25shown inFIGS. 1 and 4, and the arrangement of the thermistor31and the heater33shown inFIG. 4are only examples, and the arrangement positions of the sets of thermistors and heaters are arbitrary.

The embodiments described above are examples of the present invention, and various modifications are possible within the scope of the present invention.

In the embodiments described above, the operation of the fan21is controlled based on the detection temperature of the thermistor23or31. However, the present invention is not limited to be such. For example, temperature measurement means for a lamp house for measuring the temperature of the lamp house1may be further provided, and the fan21may be made to operate at a predetermined number of revolutions when the temperature of the lamp house1reaches a predetermined temperature, as disclosed in Patent Document 1. The operation of the fan21is controlled by, for example, the control unit29. This prevents the lamp house1to be heated more than necessary. Also, the time until the lamp house1is stabilized at a predetermined temperature is reduced.

Also, the storage means27may store, instead of the detection temperature of the thermistor23or31, the time after the light source5is illuminated from the light-off state until the detection temperature of the thermistor23or31reaches the detection temperature at the time the optical axis is stable in the spectrometer3according to the operation of the heater25or33. In this case, the control unit29causes the heater25or33to operate from the start of lighting of the light source5based on the time stored in the storage means27. Also in this case, the spectrometer3is appropriately heated, as in the case where the heater25or33is operated based on the detection temperature of the thermistor23or31, and the time from the start of lighting of the light source5to stabilization of the optical axis in the spectrometer3can be reduced.

Furthermore, the thermistors23and31, and the heaters25and33are arranged on the outer surface of the housing of the spectrometer3, but the arrangement positions of the thermistors23and31, and the heaters25and33may be on the inside of the housing of the spectrometer3.

Moreover, in the embodiments described above, the thermistors23and31are used as the temperature measurement means, and the heaters25and33are used as the heating means. However, the present invention is not limited to such. The temperature measurement means may be configured in any way as long as it is capable of measuring the temperature of the spectrometer3at a predetermined position. The heater may be configured in any way as long as it is capable of heating the spectrometer3at a predetermined position.

Moreover, the configuration of the lamp house1and the configuration of the spectrometer3described in the embodiments above are only examples. For example, the lamp house of the spectroscopic device of the present invention may include a focusing lens, as disclosed in Patent Document 1.

Further, according to the embodiments described above, the present invention is applied to a PDA absorbance detector for a liquid chromatograph, but the spectroscopic device to which the present invention is applied is not limited to such. The present invention is applicable to a spectroscopic device including a lamp house accommodating a light source inside, and a spectrometer for dispersing light from the lamp house. For example, the present invention may be applied to an absorption spectrophotometer, a spectrofluorometer, a UV detector for a liquid chromatograph, a fluorescence detector, and the like.

DESCRIPTION OF REFERENCE SIGNS

1: Lamp house

5: Light source

27: Storage means

29: Control unit