JPS6058809B2 - Double beam spectrophotometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double-beam spectrophotometer, and in particular, it has a processing unit, a storage device, and a control device, and the response is , relates to improvements in a double-beam spectrophotometer in which the slit width and wavelength scanning speed are controlled.

Figure 1 shows a portion of the spectrum obtained with a conventional double beam spectrophotometer. In the figure, the horizontal axis shows the wavelength, and the vertical axis shows the photometric value, and the wavelength scan is performed from the long wavelength side to the short wavelength side, as shown by arrow A. In the figure, spectrum 1 shown by a solid line and spectrum 2 shown by a broken line were measured from the same sample, but spectrum 1 and spectrum 2 have different measurement conditions such as response, slit width, and scanning speed. Spectrum 2 shows a case where the response, slit width, and scanning speed, which are important parameters on the device when performing spectrum recording with a double beam spectrophotometer, are inappropriate. That is, peak 4 of spectrum 2 appears later than the corresponding peak 3 of spectrum 1 in the scanning direction A, and the peak value itself is also lower. This is because the response when spectrum 2 is measured is too slow to follow such a steep peak. Moreover, the shoulder peak 5 of spectrum 1 does not appear in spectrum 2, but simply becomes shoulder peak 6. One reason for this is that the response is slow, but it is also due to the fact that the slit width of the device is so wide that the shoulder peak 5 cannot be broken. Furthermore, if the slit width is too wide, not only the top of the peak will be blunted, but also the half width B of the peak will appear larger as shown in C. Conversely, regardless of the spectrum waveform, if you make the response very fast and record the spectrum with the slit width at its minimum, the peak signal will be buried in the noise, making it difficult to distinguish between the peak and the noise. Furthermore, if the scanning speed is slowed down to eliminate the spectrum tracking delay, there is a problem that the measurement time becomes extremely long. Therefore, the response, slit width, and scanning speed must be set to optimal conditions depending on the spectrum of the sample to be measured. Conventionally, in order to accurately observe the spectrum of an unknown sample with a double-beam spectrophotometer, a preliminary scan was performed in advance using a standard response, slit width, and scanning speed, and the recorded results were checked while the operator's experience and I had no choice but to rely on a trial-and-error method of correcting these based on my intuition and re-measuring. However, with this method, a skilled operator is required to measure the spectrum of a sample that is not at the peak of the measurement conditions, and for samples that change over time, it is difficult to find the optimal measurement conditions. It has the disadvantage that it deteriorates in quality, making accurate measurement impossible. Generally, the shape of the spectrum that appears during scanning exhibits various aspects such as steep peaks, gentle peaks, and portions that do not change much. In this way, the spectrum that changes miscellaneously,
If scanning was done with the same response, slit width, and scanning speed from the beginning to the end as in the past, the spectrum would be faithfully reproduced in some parts, but in some places the spectrum shape would be extremely distorted. Therefore, it has been difficult to efficiently reproduce a distortion-free spectrum over the entire spectral range. The present invention was made to eliminate the above-mentioned conventional drawbacks, and an object of the present invention is to provide a double-beam spectrophotometer that can obtain a spectrum with little distortion over the entire scanning range.

The present invention includes an arithmetic processing device, a storage device, and a control device,
In a double-beam spectrophotometer in which the response, slit width, and wavelength scanning speed are controlled via a control device operated by an output signal of an arithmetic processing device, the wavelength λ is used during wavelength scanning to measure a spectrum.

The photometric value at and the wavelength λ of the previous sampling point. The above object is achieved by controlling the response, slit width, and wavelength scanning speed according to the difference from the photometric value at -1. The present invention was made by experimentally confirming that the distortion of the spectral curve mainly depends on the response of the device, the slit width, and the scanning speed.

Embodiments of the present invention will be described in detail below with reference to the drawings. explain.

As shown in FIG. 2, this embodiment includes a central processing unit (hereinafter abbreviated as CPU) 20, a read-only memory (hereinafter abbreviated as ROM) 21, a random access memory (hereinafter abbreviated as RAM) 22, and a controller. an input/output device 23, a detector 24, an analog-to-digital converter (hereinafter abbreviated as A-D conversion!) 25, a slit 26, and a slit 26.
a slit control motor 27 that controls the opening degree of the slit control motor 27, a slit control output device 28, a wavelength feed motor 29 that performs wavelength scanning, a wavelength control input/output device 30 that controls the wavelength feed motor 29, and a response It consists of a response control input/output device 31 and a bus line 32 for controlling the response control. Control of this device is executed by the CPU 2O, which operates according to a program written in advance in the ROM 2l, and necessary data is calculated and controlled while being stored in the RAM 22. The signal from the detector 24 is converted into a digital value by the A-D converter 25, and is taken into the CPU 2O via the bus line 32. The slit 26 is a CPU
It is opened and closed by a slit control motor 27 driven by a slit control input/output device 28 which operates in response to a command from 2O. The wavelength is scanned by a wavelength feed motor 29 controlled by the wavelength control input/output device 30, and the wavelength position,
The scanning speed is controlled by the CP through the wavelength control input/output device 30.
Controlled by U2O. When the response is switched by hardware by driving a relay etc. by the response control input/output device 31, a program to smooth the input data by software is written in the ROM 2l and constants are changed. However, in either case, the response value itself is
It is under the management control of O. In a double-beam spectrophotometer with such a control system, wavelength scanning is performed to
A case in which a spectral curve 40 as shown in the figure is drawn will be described below.

Now the wavelength λ. Let the photometric value at the wavelength λ1-1 of the previous sampling point be Sn-1. Then, this difference 1ΔSl=1Sn-Sn-11 is small in the flat portion before the peak rising point 41, but becomes a large value after passing the peak rising point 41 and reaching the peak ending point 42. In other words, the difference 1ΔS1 indicates the shape of the peak, and it is shown that the difference ΔS is at the peak when the power is emitted (1). Therefore, in order to correctly reproduce this peak without distortion, it is necessary to have a fast response that can respond sufficiently to the scanning speed and a high resolution that can resolve even sharp peaks using a narrow slit width.
Therefore, this device calculates the difference 1ΔSl at each sampling point every time, and! While ΔSl is small, scanning is performed at the standard scanning speed, response speed, and slit width.
When the power becomes weak, the CPU2O issues a control signal to slow down the scanning speed and speed up the response.
By narrowing the slit width, even sharp peaks can be reproduced accurately without distortion. Furthermore, when the peak is passed and the difference 1ΔSl becomes small, the original standard measurement conditions are returned, so a spectrum with less noise can be efficiently measured in a short time. According to this embodiment, there is no need for preliminary scanning required for spectrum measurement of unknown samples, and there is no need for setting measurement conditions that depend on the operator's experience and feeling. A desired spectrum can be obtained in a single scan, and even samples that change over time can be measured quickly and efficiently. Also, since the measurement conditions are changed depending on the peak condition,
Since a distortion-free spectrum can be reproduced over the entire spectrum and the scanning speed is slowed down only for the peak portion, the overall scanning time can be relatively short. In addition, in the above example, the slit, scanning speed, and response were all changed according to the spectral shape.
Change one or two of these depending on the peak,
Even if the other parts are fixed, the object of the present invention can be achieved.

For example, a spectrum with less distortion can be obtained even when the scanning speed is fixed and the slit and response are varied depending on the peak. In this case, since the scanning speed is fixed, a complicated circuit for changing the scanning speed is not required, and the cost of the apparatus can be reduced. It is also effective in cases where it is a problem if the slit width varies depending on the wavelength, ie, when it is desired to perform full wavelength scanning with a constant bandpass. In the above embodiment, the difference in photometric values at the time of sampling the spectral shape is 1t5. S
1, when the difference 1ΔSl becomes large, a control signal is issued to slow down the scanning speed, quicken the response, and narrow the slit width.In general, these three It is also possible to control the parameters as a function of lΔSl.

Furthermore, as an application example of the present invention, in addition to the scanning speed key, response key, and slit key, an automatic spectrum scanning key is provided, and when this key is pressed, the scanning speed, response, and slit are automatically adjusted according to the spectrum shape. Spectral recording may be performed in a controlled manner.

With such a spectrophotometer, even an operator who is ignorant of the relationship between the device parameters, such as scanning speed, response, and slit, and the obtained spectrum curve can easily and accurately obtain a spectrum. As explained above, according to the double-beam spectrophotometer according to the present invention, the response of the device, the slit width, and the scanning speed are automatically controlled according to the shape of the spectrum. It has an excellent effect of being able to efficiently obtain a spectrum.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of a spectrum obtained by a conventional double-beam spectrophotometer, FIG. 2 is a block diagram showing a control system of the double-beam spectrophotometer according to the present invention, and FIG. is double beam spectroscopy according to the present invention. FIG. 3 is a spectral diagram illustrating the operation of the control system of the photometer. 20...Central processing unit, 21...Read only memory, 22...Random access memory l
823... Control input/output device, 24... Detector, 25... Analog-digital converter, 26...
...Slit, 27...Slit control motor, 2
8... Input/output device for slit control, 29... Wavelength feed motor, 30... Input/output device for wavelength control,
31...Response control input/output device, 32...
...7 bus lines.

Claims (1)

[Claims] 1 A double beam spectrophotometer is equipped with an arithmetic processing unit, a storage device, and a control device, and the response, slit width, and wavelength scanning speed are controlled via the control device that is operated by the output signal of the arithmetic processing device. During wavelength scanning for measurement, the response, slit width, and wavelength scanning speed are controlled according to the difference between the photometric value at wavelength λn and the photometric value at wavelength λ_n_-_1 of the previous sampling point. Features: Double beam spectrophotometer.