JPS60207017A - Spectrophotometer - Google Patents

Abstract

PURPOSE:To make the relationship between the wavelength and time of a spectroscope linear, by providing a rest period for every driving of a diffraction grating at a specified angle, and changing the length of the rest period as the function of the angle of the diffraction grating. CONSTITUTION:Light from a light source L is inputted to a light detector P through a spectroscope 3 and a sample container S. The output signal is written into a computer 4 through a preamplifier A1 and an A/D converter AD. A pulse motor driving circuit 6 receives a command from the computer 4 and outputs driving pulses to the pulse motor M. A diffraction grating G is driven by the pulse motor M. At this time, a rest period is provided at every time the diffraction grating G is driven by a specified angle. The length of the rest period is changed as the function of the diffraction grating G. Thus the relationship between the wavelength and time of the spectroscope 3 is made linear.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a direct-axis drive type spectrophotometer in which a diffraction grating is rotated by gear transmission from a pulse motor without using a sine bar.

Conventional technology: In a direct-axis drive type spectrophotometer, the feeding speed is constant using a pulse motor.When the photometric signal is recorded using the formula t, the scale in the feeding direction of the chart is It does not correspond to the wavelength. Therefore, conventionally, to record photometric signals of a direct-axis drive spectrophotometer, the wavelength was calculated from the rotation angle of the diffraction grating, and the rotation amount of the horizontal-axis feed cipher motor of the digitally controlled recorder was controlled using the wavelength data. I had no choice but to record it in this way.

OBJECTIVE OF THE INVENTION The present invention attempts to record photometric signals from a direct-axis drive spectrophotometer linearly along the wavelength axis using an ordinary constant-speed drive recorder.

2. Structure The present invention is characterized in that the feed speed of the recording paper of the recorder is kept constant, a rest period is provided each time the diffraction grating is driven at a certain angle, and the length of this rest period is changed as a function of the angle of the diffraction grating. The purpose is to create a linear relationship between the wavelength of the spectrometer and time, and to perform measurements and records that are linear along the wavelength axis.

E. Embodiment FIG. 1 shows an example of a diffraction grating drive mechanism of a direct-axis drive type spectrometer l. G is a diffraction grating, which is rotated by an axis passing through the zero point. Reference numeral 1 indicates a sector gear integral with the diffraction grating G, and reference numeral 2 indicates a binion that meshes with the gear, and the binion is rotated by a pulse motor that is not visible in the figure.

FIG. 2 is a block diagram showing the configuration of a spectrophotometer according to an embodiment of the invention. L is a light source, 3 is the spectrometer shown in FIG. 1, and M is a pulse motor that drives a diffraction grating. be. S
is a sample container, P is a photodetector, and its output signal is stored in the RAM 5 as data of a preamplifier AI and an A/D conversion signal.

Reference numeral 6 denotes a pulse motor drive circuit which outputs drive pulses to the pulse smoke M upon receiving instructions from the computer 4.

In Figure 3, GO is the reference position of the diffraction grating, and N is the normal to the diffraction grating at that time. The diffraction grating is θ from this reference position.
When rotated by 1, the wavelength λ of the light that is incident on the diffraction grating at a tilt of α with respect to the normal N and is diffracted with a tilt of α with respect to N is λ −2d in the first-order diffracted light, where the grating constant is d. cos a day in θ ・・・・・・・・・
... is given by (1). If this relationship is plotted on a graph, it will look like Figure 4. This sets the wavelength scanning range of the spectrometer to λ-
1 to λ2, and the angular position of the diffraction grating for each wavelength is 01. Let it be θ2. The wavelength difference of the diffracted light when the diffraction grating is rotated by Δ at the angular position θ1 is 11, and the wavelength difference when the grating is rotated by the angle Δ at θ2 is 1.
Set it to 2. Let T be the time required for the diffraction grating to rotate by an angle Δ. Assuming that the wavelength scan is now started from λ2 to λ1, and the chart feed speed of the recorder is V, then at the start of the wavelength scan, the horizontal axis distance VT on the chart is the wavelength λ
Corresponds to 2. In other words, the wavelength scale is v T / z 2. However, at the position of the wavelength λ1, the wavelength difference with respect to the rotation of the angle Δ of the diffraction grating is lcm, so if the recorder's chart feed is at a speed of V, the wavelength scale at this position is v.
T/t will be reduced to 1.

In order to keep the chart feeding speed constant and also the width of the wavelength scale constant, at the λ2 position, the TX is rotated by the angle Δ.
It is necessary to take a time of (z 1 / t 2 ).

To avoid this, in the present invention, when the diffraction grating reaches the position of angle θ°, it is not rotated by Δ, and τ1 = T (
11/ l 2 ) -T is provided, and after this time, the angle Δ is rotated in the time T. As a result, the rotation of the angle Δ from 01 to θ1 takes 41+T, =T.
I decided to take the time of (/ 1//2). Using the same idea on the way from θ2 to 01, the pause period/f
and rotate the lattice by Δ with the same angular velocity. If the angle Δ is set small enough, the recording of photometric values will be completely smooth in practice. In this way, wavelength linear spectral recording is performed while keeping the rotational speed of the diffraction grating and the feeding speed of the chart constant.

The pause period τ is determined as follows. Differentiating the above equation (1) with respect to θ, dλ T(r=2 d cos α°008θ Therefore, the rotation angle Δθ of the diffraction grating for the unit wavelength difference Δλ is Δθ2Δλ/2 d cos α ・coe θ・
...It is given by (2). The goal is to make it take the same amount of time to rotate Δθ at any angular position of the grid. Assuming that the time required to rotate a unit of the diffraction grating is 1, the time required to rotate by Δθ at the maximum Δθ position within the wavelength scanning range, which is the position θ2 in Figure 4, is T.
2 T2=tΔθ=tΔλ/2dcoSα・cosθ2(3
) The time T required for the rotation of Δθ at any angular position is T = tJλ/ 2 d CO8cl e CO8θ To take the time T2 for the rotation of Δθ at any angular position, τ
If we set a pause period of・・・・・・・・・・・・
・・・・・・・・・(5) T2 in this equation (5) is replaced by the above (3
), the angular velocity of the diffraction grating is 1/t. Once l/t is determined, τ at each θ position is calculated according to equation (4). Further, the lattice rotation angle Δθ for a wavelength difference of 0·l nm at each θ position is calculated by equation (2). Therefore, wavelength scanning may be performed by pausing for τ every time the grating is rotated by 0.1 nm.

FIG. 5 is a flowchart of the operation when the above-mentioned operation is performed by the computer 4. After driving the pulse motor in one step, calculate the wavelength using equation (1) and set it to 0.1.
It is determined whether it has been driven by 0.1 nm (c), and when it has been driven by 0.1 nm, photometric data is taken in and output to the recorder via the D/A converter 7 (2). Next, calculate the pause time τ as described above (e), wait for the time τ, and get 0.
- Finish the wavelength scanning routine of lnm9t-.

In the above program, τ is calculated each time, but it may be calculated in advance for each wavelength and stored in the ROM, and then retrieved and used.

In reality, τ has almost the same value in the wavelength range, so
Divide the wavelength scanning range and determine τ for each division.・Effects Direct-axis drive spectrophotometers have the advantage of being simpler in structure and capable of high-speed driving than those using sine bars. On the other hand, the conventional conventional constant-speed feed recorder had the disadvantage of not being able to record wavelength linearly in real time, but the present invention overcomes this problem and has the advantages of simple structure and high speed. The practical value has greatly increased.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the spectrometer part of a direct-axis drive spectrophotometer, FIG. 2 is a block diagram of an embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between incident light and two diffracted lights in a diffraction grating. FIG. 4 is a graph of the relationship between the angular position of the diffraction grating and the wavelength of the diffracted light, and FIG. 5 is a flow chart of the operation in one embodiment of the present invention. G... Diffraction grating, L... Light source, 3... Spectrometer, M
...Pulse motor for driving the diffraction grating, S...Sample, P
...Original detector, 6...Pulse motor drive circuit. Agent Patent Attorney Kosuke Hiru

Claims (1)

[Claims] Equipped with a direct-axis drive type spectrometer, a pause period is provided each time the diffraction grating is rotated by a certain wavelength, and the sum of the drive period for a certain wavelength and the pause period in that rotation is the wavelength scanning. A spectrophotometer comprising a control circuit that controls the drive of a diffraction grating so that it is constant throughout the section.