JPS61147120A - Double beam spectrophotometer - Google Patents

Abstract

PURPOSE:To reduce the cost of a device, and to remove restrictions of an optical system and reduce an error by rotating or moving a half-mirror which has a small hole. CONSTITUTION:Luminous flux from a light source 2 or 4 is made into homogene ous light through the diffraction grating 16 of a spectroscope part 10 and the light is incident on a beam splitter 24 through reflecting mirrors 18, 20, and 22. The splitter 24 is composed of the half-mirror formed by boring numbers of small holes in a mirror or by forming a film with numbers on small holes on a base material which is transparent to ultravoilet visible light, and the splitter is rotated by a motor 26. Namely, an image of the small holes moves on a sample and detectors 42 and 44, so substantially no image of the small holes is formed. The incident light is split by the splitter 24 continuously into sample light 28 and reference light 30, which are incident on the detectors 42 and 44 through the sample cell 38 and reference cell 40 in a sample chamber 36 and detected respectively, so that a measuring circuit calculates the transmissivity or absorbance of the sample.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a spectrophotometer used in a wide range of fields such as qualitative and quantitative analysis of samples, and in particular uses a beam splitter to separate the light beam from the sample light and the contrast light. This invention relates to a double-beam spectrophotometer that continuously separates sample light and reference light or continuously mixes sample light and reference light using a beam combiner.

(Prior Art) Conventionally, a half mirror using a semi-transparent film has been used as a beam splitter or beam combiner in a double-beam spectrophotometer. Although 30% of the incident light is reflected and 30% is transmitted, the remaining 40% is absorbed, resulting in poor light utilization efficiency.In addition, it is difficult to control the thickness of the chromel film. There are also drawbacks to the above.

Therefore, in recent years, half mirrors have been created by making a large number of small holes in a mirror, and half mirrors are made by forming a film such as an aluminum vapor-deposited film with many small holes on a base material that is transparent to m-constant wavelengths. came into use. This half mirror has the advantages of good light utilization efficiency and easy manufacture.

(Problems to be Solved by the Invention) However, the following problems occur in this half mirror due to the small holes.

In a spectrophotometer that uses this half mirror as a beam splitter behind the monochromator to separate the incident light beam into sample light and reference light, (1) depending on the optical system and accessories, the small hole in this half mirror may An image may be formed, and if a sample is placed at this image formation point, an error will occur in the transmittance.

Particularly when the sample is small, a large error occurs due to the image of this small hole.

(2) If the sample concentration is not uniform, an error will occur if the image of the small hole of this half mirror is formed at the sample position.

Further, in a spectrophotometer of the above type and this half mirror installed in front of a monochromator as a beam combiner to mix sample light and control light.

(3) When the image of the small hole of this half mirror is formed on the detector, an error occurs due to the non-uniformity of the sensitivity of the detector depending on the location.

(4) If dirt adheres to the small hole of this half mirror,
An error occurs.

(5) As the sample becomes smaller, the size of the small hole in the half mirror cannot be ignored, and errors still occur.

The present invention is a method of double beam spectrophotometry that uses a half mirror, in which a mirror has many small holes or a film with many small holes is formed on a base material that is transparent to the measurement wavelength, as a beam splitter or beam combiner. The purpose of this invention is to solve the above-mentioned problems caused by small holes.

(Means for Solving the Problems) The double beam spectrophotometer of the present invention is configured such that a half mirror having a small hole is rotated or moved.

(Function) Even under conditions where rotating or moving the half mirror creates an image of the small hole of the half mirror on the sample or detector,
This is equivalent to the fact that no image of the small hole is substantially formed due to the movement of the small hole image on the sample or the detector. Also,
Even if the small hole is large enough to not be ignored relative to the sample size, the effect of the small hole size is reduced by moving the small hole. Similarly, even if dirt adheres to a small hole, the effect of the dirt will be reduced by moving the small hole.

(Example) Fig. 1 shows an example in which the present invention is applied to a spectrophotometric ultraviolet/visible spectrophotometer. 2 is a deuterium lamp, 4 is a tungsten lamp, 6 is a reflecting mirror, and 8 is a condensing mirror. The reflecting mirror 6 is displaced so that the light flux from the deuterium lamp 2 or the light flux from the tungsten lamp 4 is incident on the condenser mirror 8.

Reference numeral 10 denotes a spectroscope section, which includes reflecting mirrors 12 and 14 and a diffraction grating 16, and spectrally spectra the light incident from the condensing mirror 8. 18,2
0.22 is a reflecting mirror that makes the monochromatic light from the spectrometer section 10 enter the beam splitter 24.

The beam splitter 24 consists of a half mirror with a large number of small holes in the mirror or a half mirror with a film having many small holes formed on a base material transparent to ultraviolet and visible light, and is rotated by a motor 26. ing. As the film formed on the latter transparent base material, for example, an aluminum vapor-deposited film can be used.

A sample chamber 36 includes a sample cell 38 and a control cell 40. 42 and 44 are respectively sample cells 38. This is a detector that detects the light beam transmitted through the control cell 40, and for example, a photomultiplier tube is used.

In this embodiment, the light beam from the light source 2 or 4 is transmitted to the spectrometer section 10.
The light is converted into monochromatic light by the diffraction grating 16.

The light enters the beam splitter 24 through the reflecting mirrors 18, 20, and 22. The beam splitter 24 continuously outputs the sample light 2.
8 and a reference light 30, each of which is separated into a sample cell 38.8 of a sample chamber 36. Through the control cell 40 to the detector 42.44
After the sample is detected, the transmittance or absorbance of the sample is calculated by a measurement circuit (as shown).

(Embodiment 2) FIG. 2 shows an embodiment in which the present invention is applied to a specific photometric infrared spectrometer. Reference numeral 50 denotes a light source, and a Grover, Nernst Blower, Nichrome wire, etc. are used. 52.54 and 56.58 respectively convert the light flux from the light source 50 into the sample light 60.
and a reflecting mirror that separates the control light 62. A sample chamber 63 includes a sample 64 and a sample case 66, into which sample light 60 and control light 62 are incident, respectively.

68 is a chopper that chops the sample light 60 transmitted through the sample 64 at a frequency f1; 69 is a motor for driving the chopper 68; 70 is a reference light 62 transmitted through the sample case 66 at a frequency f different from the frequency f+ of the chopper 68.
2 is a chopper for chopping; 71 is a driving motor for the chopper 70; Reference numerals 72 and 74 are reflecting mirrors that make the chopped sample light and contrast light enter the beam combiner 76, respectively.

The beam combiner 76 is the beam splitter 24 in FIG.
Similarly, the motor 78 is made of a half mirror with a large number of small holes in the mirror, or a half mirror with a film such as an aluminum vapor-deposited film having a large number of small holes formed on a base material transparent to infrared rays. It is rotated by Beam combiner 76 is rotated faster than chopper 68,70.

The light flux mixed by the beam combiner 76 passes through one reflecting mirror 80
．． The light passes through 82 and enters a spectrometer section equipped with a diffraction grating 90 and reflecting mirrors 86° and 88. 84 is an entrance slit of the spectrometer section, and 92 is an exit slit.

99 is a detector, for example, a thermocouple is used.

94, 96, and 98 are reflecting mirrors that guide the light flux from the spectroscope section to the detector 99.

In this embodiment, the light beam from the light source 50 is separated into a sample light 60 and a reference light 62, which are respectively a sample 64 and a sample case 6.
6, the chopper 68°70 increases the frequency f+
, f2. The combined light beams are continuously mixed by a rotating beam combiner 76, separated by a diffraction grating 90, and then detected by a detector 99.

The output signal of the detector 99 is amplified by a preamplifier 100 in a normal measurement circuit, and then passed through a bandpass filter 102,
104, the frequencies f+ and f2 are amplified by main amplifiers 106 and 108, respectively, and the A/D converter 1
After being converted into a digital signal at 10,112, (:PU
At 114, transmittance or absorbance is calculated.

In the above embodiments, a half mirror having small holes serving as a beam splitter or a beam combiner is rotated, but the half mirror may be moved by vibrating vertically or horizontally.

(Effects of the Invention) According to the present invention, by using a half mirror having small holes, it is possible to reduce the cost of the device compared to using a half mirror using a semipermeable membrane. Then, by rotating or moving the half mirror having the small hole, the image of the small hole is substantially no longer formed on the sample or the detector, and the limitations of the optical system are eliminated. Furthermore, errors caused by smaller samples and errors caused by dust adhering to the half mirror are also reduced.

[Brief explanation of the drawing]

1 and 2 are schematic plan views showing embodiments of the present invention, respectively. 24... Beam splitter using a half mirror with small holes, 26... Motor,
28,60...Sample light, 30,62...
. . . Control light, 76 . . . Beam combiner using a half mirror with small holes, 78 . . . Motor.

Claims (1)

[Claims] (1) A half mirror with many small holes made in the mirror or a film with many small holes formed on a base material that is transparent to the measurement wavelength is used as a beam splitter to contrast the light flux with the sample light. A double-beam spectrophotometer that continuously separates the sample light and the reference light or uses it as a beam combiner to continuously mix the sample light and the control light, characterized in that the half mirror is rotated or moved. Total.