JPS6318686B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a wavelength initial setting device for a spectrophotometer, and in particular, detects zero-order light obtained from a monochromator under predetermined conditions, and detects, for example, the maximum value of the zero-order light amount. The present invention relates to a wavelength initial setting device for a spectrophotometer that allows the initial setting of the wavelength when the power switch is turned on.

Chemical analysis has traditionally been used to determine the types and amounts of components contained in substances, but recently, most of the analysis has been carried out by instrumental analysis. This instrumental analysis can be roughly divided into optical analysis, electromagnetic analysis,
Examples include electrical analysis and separation analysis.

Incidentally, among the above-mentioned analyses, various types of analysis methods have been proposed for optical analysis, and a spectrophotometer is a device used for the spectroscopic analysis method of the above-mentioned optical analysis.

This spectrophotometer uses light emitted from a sample to irradiate a grating through an input slit, and an output slit arranged in a specific relationship by continuously and slowly rotating the angle of the grating. The diffracted light from the grating is detected by a photoelectric element or the like through the grating, and analysis is performed based on the signals from each slit and the photoelectric element arranged in a specific positional relationship.

Therefore, in the spectrophotometer, the initial position of the grating must be accurately set when the power switch is turned on or when analysis is started. That is, the initial setting of the wavelength needs to be done accurately and reliably.
Conventionally, regarding the initial wavelength setting of a spectrophotometer,
This was done using the method described below.

The first method uses the spectral emission line contained in the light source lamp (for example, the deuterium discharge tube 656.1 [nm]
A detection system installed after the output slit of the spectrometer detects the peak of the sample's absorption line (for example, the 360.8 [nm] line of a holmium glass filter) and performs the initial wavelength setting. It is.

The second method is to generate a signal using a position detection mechanism installed on the feed screw portion of the sine bar mechanism, and then rotate the stepping motor by a predetermined amount.

Therefore, since the first method requires a light source lamp or a sample having an emission line,
For example, it is not suitable for a spectrophotometer equipped only with a tungsten lamp. Further, the second method has the disadvantage that it is not suitable for a spectrophotometer in which a grating is driven using a cam mechanism.

An object of the present invention is to detect the zero-order light from the grating of a monochromator under predetermined conditions to initialize the wavelength, and is suitable for any of the conventional spectrophotometers having various configurations. The present invention provides a wavelength initial setting device for a spectrophotometer.

For this reason, the present invention includes a monochromator that diffracts light incident from an entrance slit using a grating and emits this diffracted light from an output slit;
In a spectrophotometer configured to include a grating driving means for continuously rotating the grating of the monochromator, zero-order light is detected when the grating is rotated in one direction. a comparator that outputs an output while the output from the zero-order light detection means exceeds a reference value; an addition/subtraction counter that counts the output from the comparator; The device comprises means for reversing the grating by half the value of the count of the addition/subtraction counter, and means for setting the wavelength when the grating is reversed by the half value.

EMBODIMENT OF THE INVENTION Hereinafter, one Example based on this invention is described based on drawing.

FIG. 1 shows a perspective view of a mechanical system for detecting zero-order light according to an embodiment of the present invention.
In this figure, reference numeral 1 indicates white light, and this white light 1 is supplied to a grating 4 through an input slit 3 of a monochromator 2, and the white light 1 is converted into monochromatic light 5 by the grating 4 and sent to an output slit. 6, it can be supplied to a photoelectric element, etc. (not shown). And monochromator 2 is
As shown, slits 3 and 6 and grating 4
It is composed of

Furthermore, as a means for detecting the 0th order light beam, we focus on the fact that the 0th order light 7 is always included in the light diffracted by the grating 4, and pass this 0th order light 7 through the slit 8. It is configured so that the detector 9 detects the detected value. The wavelength of the monochromatic light 5 when the zero-order light is incident on the slit 8 is preferably set to the longest wavelength in the measurement area or a wavelength longer than that.

Further, as means for driving the grating 4, the grating 4 is rotatably disposed on one mechanism of the cam mechanism 10, and the other mechanism of the cam mechanism 10 is fixed to the rotating shaft of the stepping motor 11. It is configured as follows. Incidentally, the grating 4 is configured to rotate in the direction of the arrow 12 or 13 shown in the figure. The control circuit 30 receives the signal from the detector 9 and outputs a control signal to the stepping motor 11 so that the intensity of the zero-order light detected by the detector 9 is maximized. FIG. 2 shows a block diagram of a control circuit 30 that controls the rotation direction, rotation time, etc. of the stepping motor 11. The control circuit 30 shown in this figure is configured as follows.

The detector 9 is, for example, a photoelectric conversion element such as a photodiode, and is connected together with the voltage reference device 14 between each input terminal of the comparator 15 and the ground. Reference numeral 16 denotes an addition/subtraction counter, and this addition/subtraction counter 16 is connected to the comparator 15 via a switch 17 that commands addition or subtraction based on the output signal of the comparator 15. A pulse signal from an oscillator 18 is supplied to the addition/subtraction counter 16, and this pulse signal is added or subtracted based on a command from a switch 17. That is, this addition/subtraction counter 16 uses the voltage reference device 14 for addition.
Counting starts when the value exceeds the value of the voltage reference device 14, the signal amount of the detector 9 reaches the maximum, and then decreases until the value of the voltage reference device 14 is reached again. It is designed to stop when it reaches 1/2 of the amount.

Further, an inversion circuit 19 and a stop circuit 20 are respectively disposed between the addition/subtraction counter 16 and the stepping motor 11, so that the stepping motor 11 can be rotated and stopped.

The operation of the spectrophotometer constructed as described above will be explained with reference to FIGS. 1 to 3.

FIG. 3 is a waveform diagram for explaining the operation of the device of the present invention, and the figure is a waveform diagram showing the relationship between the detection signal amount of the detector 9 and time, and the vertical axis represents the signal of the detector 9. The horizontal axis shows time. The figure is a waveform diagram showing the relationship between the count number of the addition/subtraction counter 16 and time, where the vertical axis shows the count number of the counter 16 and the horizontal axis shows time.

First, when a power switch (not shown) is turned on, the grating 4 starts rotating in the direction of arrow 12. After a while, the zero-order light 7 crosses the slit 8. At this time, the signal output from the detector 9 is an electrical signal that is symmetrical with respect to time _t1 , as shown in FIG. The comparator 15 operates at a point P where the signal amount of the detector 9 exceeds the reference value e of the voltage reference device 14. Then, the addition/subtraction counter 16 starts adding up the pulses of the oscillator 18. The addition/subtraction counter 16 continues to perform the addition until the signal amount of the detector 11 exceeds the peak and reaches a point Q where it crosses the level e again. During this addition period, the stepping motor 11 continues to rotate the grating 4 in the direction of arrow 12 in the figure.

When the signal amount of the detector 9 reaches point Q as shown in the figure, the comparator 15 operates again, and the addition/subtraction counter 16 is switched to the subtraction side, and at the same time, the inverting circuit 19 controls the stepping motor 1.
1 starts rotating in the opposite direction. That is, the grating 4 starts rotating in the direction of arrow 13 in the figure. Here, if the number of counts added by the addition/subtraction counter 16 from point P to point Q is N, then when the counter 16 goes from N to N/2 during subtraction, the stop circuit 20 operates and steps. Motor 11 stops. This position corresponds to midpoint R in FIG. That is, the grating 4 stops at approximately the Peter position of the zero-order light quantity.

In the embodiment of the present invention, a cam is used as the grating drive method, but the same applies to the sine bar method. Furthermore, it goes without saying that the operation of the control circuit configured according to the block diagram of FIG. 2 can be replaced by a computer program.

As described above, the present invention detects and processes zero-order rays under predetermined conditions, so there is no need for special equipment in conventional equipment such as a light source lamp having an emission line spectrum, and there is no need for any kind of grating. The present invention has the advantage that it can be applied even to drive mechanisms.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a mechanism for detecting zero-order light according to an embodiment of the present invention, FIG. 2 is a block diagram showing a motor control circuit according to an embodiment of the present invention, and FIG. The figure is a waveform diagram for explaining the operation of the device of the present invention. 2... Monochromator, 8... Slit, 9...
...Detector, 14...Voltage reference device, 15...Comparator, 16...Addition/subtraction counter.

Claims (1)

[Claims] 1. A monochromator that diffracts light incident from an input slit by a grating and emits this diffracted light from an output slit, and a grating drive means for continuously rotationally driving the grating of this monochromator. A spectrophotometer comprising a zero-order light detection means for detecting zero-order light when the grating is rotated in one direction, and an output from the zero-order light detection means exceeding a reference value. a comparator that outputs an output for a period of time; an addition/subtraction counter that counts the output from the comparator; a means for reversing the grating by half the count value of the addition/subtraction counter when the output from the comparator disappears; 1. A wavelength initial setting device for a spectrophotometer, comprising means for setting a wavelength when the wavelength is reversed.