JPH1137842A - Infrared spectrophotometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the wavelength deviation of a monochromatic light caused by temperature increase of an interference filter. SOLUTION: At nonmeasuring time, a control unit 20 closes a shutter 12 provided in front of a monochrometer 13 in proximity, and intercepts incident light. Besides, a motor 18 is driven at this time so as to rotate a disklike holder 131 intermittently. The shutter 12 is struck by infrared rays and heated, and the temperature of air in its vicinity is locally increased, too. However, an interference filter 132 closest to the shutter 12 changes in order with the rotatin of the holder 131. Accordingly, it becomes possible to prevent the temperature of a specified interference filter from increasing and to prevent its wavelength deviation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared spectrophotometer for measuring an absorbance or the like by irradiating a sample with infrared light and detecting transmitted light or reflected light.

[0002]

2. Description of the Related Art FIG. 3 is a schematic diagram showing an example of an optical system of a conventional infrared spectrophotometer. Light emitted from the light source 10 by a halogen lamp or the like includes various wavelengths centered on near-infrared light, and monochromatic light having a predetermined wavelength is extracted by the monochromator 13 as measurement light. The measurement light is applied to the sample cell 16 filled with the sample solution, and when the light passes through the inside of the sample cell 16, light having a wavelength specific to the sample is absorbed. The transmitted light is detected by the photodetector 17, and the absorbance or transmittance is calculated based on the detection signal.

The monochromator 13 has a disc-shaped holder 1.
A plurality of interference filters 132 having different transmission wavelengths are attached to 31. The holder 131 is rotatable about its axis, and its rotation operation is controlled so that the plurality of interference filters 132 are sequentially irradiated with light and monochromatic light of different wavelengths is extracted. Thereby, the absorbance or transmittance at the same number of wavelength points as the number of interference filters 132 can be measured.

Generally, the passing wavelength of the interference filter 132 has a temperature dependency, and a change in the ambient temperature causes a shift in the wavelength of the monochromatic light to be extracted. Therefore, the monochromator 13 is housed in a case 14 whose temperature can be adjusted. For example, the case 14 is maintained at about 50 ° C. However, since the incident light to the monochromator 13 includes near-infrared light, if the light is continuously irradiated on the interference filter, the temperature of that portion rises to 70 to 80 ° C.

In this case, it is practically difficult to prevent the interference filter 132 from being irradiated with light by turning on and off the light source 10. The reason is that it takes a relatively long time for the halogen lamp to light up to reach a stable state after it is turned on. Is required.

Therefore, in the apparatus shown in FIG. 3, a shutter 12 capable of blocking incident light is provided very close to the front side of the monochromator 13 so that the shutter 12 is not used for measurement (for example, during standby).
The incident light is blocked by a shutter 12 and the interference filter 1
Light is prevented from reaching 32. Needless to say, the shutter 12 can also be used when measuring the dark current by blocking the light incident on the photodetector 17.

[0007]

However, in the above-mentioned conventional spectrophotometer, although the light irradiated to the monochromator 13 is shielded during non-measurement, the metal shielding plate of the shutter 12 is heated by infrared light. The ambient temperature is significantly higher locally due to heat dissipation from the shield. Then, the interference filter in the immediate vicinity of the shutter 12 is also warmed, and its temperature becomes 2-3 ° C. higher than the other interference filters. As a result, the transmission wavelength of the interference filter shifts, which hinders accurate spectroscopic measurement.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an infrared spectrophotometer capable of preventing deterioration of measurement accuracy due to a rise in temperature of an interference filter. Is to do.

[0009]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, is directed to an infrared spectrophotometer for irradiating a sample with infrared light emitted from a light source and measuring transmitted light or reflected light. A) filter holding means which is provided with a plurality of switchable interference filters for converting light emitted from a light source into monochromatic light, b) light shielding means for shielding light incident on the interference filter during non-measurement, c) the light shielding And a driving means for moving the filter holding means such that an interference filter closest to the light shielding means is replaced when the means is blocking incident light.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In an infrared spectrophotometer according to the present invention, for example, the filter holding means has a configuration in which a plurality of interference filters are arranged on the outer periphery of a disk member, and rotates the disk member in the circumferential direction. Thus, the interference filter can be switched. The light blocking means blocks the optical path during non-measurement, and prevents the interference filter from being irradiated with light.
On the other hand, the drive means rotates the disc member of the filter holding means continuously or intermittently when the light blocking means blocks the optical path. In other words, in the same manner as when the interference filter is switched to select the wavelength of the monochromatic light at the time of measurement, the position where light is to be incident, that is, the interference filter that comes closest to the light shielding means is sequentially switched. The temperature of the light-shielding portion of the light-shielding means rises due to the irradiation of infrared light, and the surrounding temperature rises. Therefore, the interference filter adjacent to the light shielding unit is also heated. However, since the interference filters are sequentially replaced, the temperature of the specific interference filter does not particularly rise, and the interference filter heated when approaching the light-shielding means cools down to the original temperature when separated from the light-shielding means. Return.

[0011]

According to the infrared spectrophotometer of the present invention, it is possible to prevent the temperature of the interference filter from rising during non-measurement time. A measurement can be made.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the infrared spectrophotometer according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a main part of the infrared spectrophotometer according to the present embodiment. The basic configuration of this infrared spectrophotometer is the same as that of a conventional spectrophotometer. That is,
An openable and closable shutter 12 is provided near an optical path on the near side of the monochromator 13, and the shutter 12 is driven to be opened and closed by a shutter drive unit 19. The disc-shaped holder 131 of the monochromator 13 is provided with the attached motor 1.
8 rotates about the axis. The control unit 20 is mainly configured by a CPU, and controls the operation of the motor 18 and the shutter driving unit 19 in response to an instruction from the operation unit 21 as described later. Although not shown, as in FIG. 3, the entire shutter 12 and the monochromator 13 are housed in a case capable of controlling the temperature.

The spectrophotometer of this embodiment operates as follows at the time of spectroscopic measurement. In other words, when a measurement instruction is given by the operation unit 21, the control unit 20 sends a shutter release signal to the shutter drive unit 19 as shown in FIG. Thereby, the light emitted from the light source 10 and collimated by the lens 11 reaches the monochromator 13. Further, as shown in FIG. 2B, the control unit 20 sets the holder 131 so that light enters the plurality of interference filters 132 provided in the monochromator 13 for a predetermined time (for example, 0.5 seconds). The motor 18 is controlled to rotate intermittently. Thereby, the monochromatic light having the passing wavelength of each interference filter 132 reaches the lens 15 sequentially, is collected, and is irradiated on the sample cell 16. Then, the light transmitted through the sample cell 16 enters the photodetector 17. A detection signal is extracted from the photodetector 17 in synchronization with the measurement timing during a period in which the rotation of the holder 131 of the monochromator 13 is stopped (that is, a period other than the switching operation of the interference filter 132). Therefore, the transmission wavelength λ1 of the interference filter 132,
A detection signal corresponding to λ2,... is obtained.
For example, an absorbance spectrum can be created. When the holder 131 makes one rotation and the light passing through all the interference filters 132 is obtained, the controller 20 sends a shutter closing signal to the shutter driver 19 as shown in FIG.

Next, the operation at the time of non-measurement will be described. Since the shutter 12 is closed when the measurement is completed as described above, the light is blocked by the shielding plate of the shutter 12 and does not reach the monochromator 13. When the measurement is completed, the control unit 20 closes the shutter 12 and controls the motor 18 so as to perform an intermittent rotation operation in which the stop time is set longer than at the time of the previous measurement. For example, as shown in FIG. 2B, the motor 18 is intermittently rotated once every 10 seconds such that the interference filter 132 coming to the light irradiation position is replaced with a neighboring one on the circumference. Thereby, after a certain interference filter is positioned close to the shielding plate of the shutter 12 for about 10 seconds and then stopped, the next adjacent interference filter comes close to the shielding plate.

Since the light is continuously applied to the shielding plate of the shutter 12, the temperature thereof is considerably increased, and the air in the vicinity thereof is locally high. Then, due to heat conduction from the heated air or radiant heat from the shield plate itself, the interference filter located close to the shield plate is also heated in about 10 seconds. However, the time is short, and when it is separated from the shielding plate, it is cooled by the air maintained at a substantially uniform temperature in the case, so that the temperature returns to the temperature before the heating. For this reason, the temperature of the monochromator 13 as a whole is substantially maintained at the ambient temperature in the case. Thereby, the wavelength of the monochromatic light passing through the interference filter 132 during measurement can be made highly accurate.

In the above description, the holder 1 is not used when no measurement is performed.
31 is rotated intermittently, but this is simply performed by changing the time width of the intermittent drive because each interference filter is intermittently driven so as to sequentially come to the position of the incident light at the time of measurement. It is because it can respond to. Therefore,
Naturally, the same effect can be obtained even if the holder 131 is continuously rotated during non-measurement.

Further, the above-described embodiment is merely an example, and it is apparent that variations and modifications can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of an infrared spectrophotometer of the present invention.

FIG. 2 is a waveform chart for explaining a control operation of a shutter and a motor in the embodiment of FIG.

FIG. 3 is a schematic configuration diagram of an optical system of a conventional infrared spectrophotometer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Light source 12 ... Shutter 13 ... Monochromator 131 ... Holder 132 ... Interference filter 16 ... Sample cell 17 ... Photodetector 18 ... Motor 19 ... Shutter drive part 20 ... Control part 21 ... Operation part

Claims (1)

[Claims] 1. A sample is irradiated with infrared light emitted from a light source,
In an infrared spectrophotometer that measures transmitted light or reflected light, a) a filter holding unit that is provided with a plurality of switchable interference filters that convert light emitted from a light source into monochromatic light, and b) the interference filter when not measuring. C) a driving means for moving the filter holding means such that the interference filter closest to the light shielding means is replaced when the light shielding means is blocking the incident light. An infrared spectrophotometer, comprising: