JPH02179427A - Spectrophotometer with function of switching light source - Google Patents

Abstract

PURPOSE:To realize a correct spectrum by measuring a spectrum by wavelength scanning, by calculating a spectral value by a method of moving averages, and by calculating a display wavelength on the basis of an actual wavelength and a range of a moving average wavelength. CONSTITUTION:Wavelength feeding of a spectroscope 2 is conducted by a stepping motor. CPU 16 for control supplies the spectroscope 2 with a pulse for driving the stepping motor and a light source switching signal and supplies counters 22 and 24 with the pulse for driving the stepping motor to be counted. Next, a spectral signal outputted from a spectrophotometer is converted into a digital signal by an A/D converter 18 and stored in a memory device 20. In addition, the CPU 16 reads the spectral signal out of the device 20, executes moving average computation and outputs an average value as a measured value of a spectrum to a display device 12. Moreover, the CPU 16 outputs a count value of the counter 24 to the device 12 as a display wavelength corresponding to the measured value of the spectrum calculated by the moving average computation.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a spectrophotometer, and particularly to a spectrophotometer that uses a switched light source to measure a spectrum over a wide wavelength range.

Examples of such spectrophotometers include visible and ultraviolet spectrophotometers that measure continuous spectra from the visible to the ultraviolet range, using a tungsten lamp for visible range measurements and a deuterium lamp for ultraviolet measurements. There is a plan.

(Prior art) Photometric values for the actual wavelength determined by the rotation angle of the diffraction grating of a spectrometer vary due to noise caused by instability of the optical system and electric circuit, so the photometric value at a certain moment is used as the photometric value for the actual wavelength. When I get it and display it, it's very noisy all
l becomes a constant value. Therefore, generally, a time averaging method is often used, which takes the average value of data over a certain period of time. Also,
Since it is meaningless to obtain data for wavelength resolution below a certain wavelength range, which is related to the spectral bandwidth that depends on the slit width of the spectrophotometer, in the case of spectral scanning, the moving average value of a certain wavelength range is calculated. A moving average method is used in which the measured value is taken at a certain wavelength within that wavelength range. Furthermore, there are also devices that use both the time average method and the moving average method.

In the moving average method, the wavelength range for averaging processing is assumed to be Δλ. Treating the actual wavelength of the spectrometer as the displayed wavelength simplifies handling, but the wavelength of the photometric value and the displayed wavelength are always Δλ/
It will be off by 2.

On the other hand, if the display wavelength is set to a wavelength delayed by Δλ/2 from the actual wavelength, the above-mentioned deviation will be eliminated, but near the scan starting point wavelength,
Data near the end point wavelength will not be output correctly. Therefore, the scanning start point wavelength for the moving average calculation for the starting point wavelength of the specified spectrum display range and the scanning end point wavelength for the moving average calculation for the display end point wavelength are calculated, and these calculated wavelength ranges are scanned. The present inventors have already proposed a spectrophotometer that is capable of accurately calculating measured values even near the scanning start point wavelength and the scanning end point wavelength.

(Problem to be solved by the invention) In our spectrophotometer cited above.

It is not assumed that the light source is switched within the wavelength scanning range. If the above spectrophotometer using the moving average method were to switch the light source at the wavelength point as in the conventional method,
A step difference occurs in the spectrum at the switching wavelength point, which in some cases cannot be ignored.

The present invention provides a spectrophotometer with a light source switching function.
The purpose is to obtain measurement values with less noise using the moving average method.

(Means for Solving the Problems) In the spectrophotometer of the present invention, scanning is performed from a starting point λS on the long wavelength side to an ending point λe on the short wavelength side, and the light source switching wavelength λC is within the scanning range, and the moving average If the wavelength range is Δλ, scanning starts from λS+Δλ/2 at the actual wavelength, and λC
-Δλ/2, and at the same time the light source is switched, the spectroscope is returned to λC+Δλ/2 at the actual wavelength, scanning is started again from there, and scanning is continued until λe−Δλ/2, ending the side chamber.

The present invention will be explained with reference to FIG.

2 is a spectrometer with a light source switching function. 4 is a light source switching means for switching the light source at a wavelength determined by the light source switching wavelength λC and the moving average wavelength range Δλ; 6 is a scanning starting point wavelength for calculating the moving average for the starting point wavelength of the spectrum display range designated for each light source; The spectrometer driving means calculates an end point wavelength for a moving average calculation for the display end point wavelength of a specified spectrum display range for each light source, and scans these calculated wavelength ranges for each light source. 8 is a calculation means for measuring a spectrum by wavelength scanning and calculating a spectrum value using a moving average method; 10 is a display wavelength calculation means for calculating a display wavelength based on the actual wavelength λ and the moving average wavelength range Δλ; 12 is a display means for displaying the calculated spectrum value for the calculated display wavelength. In addition, 18 is A that converts the photometric value into a digital signal.
/D converter 20 is a memory device that stores photometric data.

(Operation) The present invention will be explained in detail with reference to FIGS. 1, 2, and 3.

As shown in FIG. 2, wavelength scanning is performed from the long wavelength side to the short wavelength side. The wavelength scanning range for the display wavelength is from the starting point λS on the long wavelength side to the ending point λe on the short wavelength side, and the light source is switched at the wavelength λC. Assume that scanning from wavelength λS to wavelength λC is performed using, for example, a tungsten lamp, and scanning from wavelength λC to wavelength λe is performed using, for example, a deuterium lamp.

λS, λC9λe, and Δλ are read (step SL
).

The spectrometer driving means 6 uses λs + Δλ/2 as the scanning starting point wavelength.
is calculated, and the spectrometer 2 is set to the actual wavelength (step S2). The wavelength shift of the spectrometer 2 is started from the starting point wavelength (step S3). As the wavelength body moves, the photometric value becomes A.
The signal is converted into a digital signal by the /D converter 18 and stored in the memory device 20.

When the actual wavelength becomes λS - Δλ/2 (step S4), the calculating means 8 calculates a moving average of the photometric values for the wavelength range Δλ up to that wavelength (step S5). This moving average may be a simple average, A weighted average may also be used. The display wavelength for the calculated photometric value at that time is calculated from the actual wavelength λ and the moving average wavelength range Δλ by the display wavelength calculation means 10, and becomes λ+Δλ/2 (step S
6).

Along with wavelength driving, moving average calculation of photometric values and calculation of display wavelength are performed sequentially, and when wavelength scanning is performed up to λC - Δλ/2 at the actual wavelength (step S7), the value of λC becomes λ
The value of λe is assigned to λC (step S
9, 5IO), the light source is switched by the light source switching means 4 (step 5ll).

With the switching of the light source, the spectrometer driving means 6 returns the spectrometer 2 to the actual wavelength λS+Δλ/2, and the drive is restarted from that wavelength (steps S2 and S3), so that the actual wavelength becomes λS-Δλ/2. 2 (step S4), moving average calculation is started and the display wavelength is calculated (step S4).
5,86).

When wavelength scanning is performed to λe-Δλ/2 (steps S7 and S8), the measurement ends.

The calculated photometric value and the calculated display wavelength are displayed on the display device 12.
will be displayed.

(Example) FIG. 4 represents one embodiment.

Wavelength feeding of the spectrometer 2 is performed by, for example, a stepping motor. 16 is a control CPU, which supplies stepping motor drive pulses and light source switching signals to the spectrometer 2, and outputs the stepping motor drive pulses to a counter (C1
)22. It is supplied to the counter (C2) 24 and counted.

A spectral signal output from the spectrophotometer is converted into a digital signal by an A/D converter 18 and stored in a memory device 20. CPU16 also. The spectrum signal is read from the memory device 20, a moving average calculation is performed, and the average value is outputted as a spectrum measurement value to a display device 12 such as a recorder. The C-PU 16 also outputs the count value of the counter C2 to the display device r1112 as a display wavelength corresponding to the spectrum measurement value calculated by the moving average calculation.

The CPU 16 realizes the functions of the light source switching means 4° spectrometer driving means 6 and calculation means 8 in FIG.

26 inputs λS, λC9λe, and Δλ.

This is the keyboard for operating the spectrophotometer.

Specifically, the moving average calculation is performed as follows, for example.

Spectral measurements are performed at wavelength intervals of δλ. δλ
corresponds to the wavelength feed amount for one pulse of the stepping motor. Since the spectrum measurements are performed intermittently in this way, the spectrum measurements are numbered 1, 2, etc. from the beginning. The spectrum number for each number measurement is stored in the address of the same number in the memory device 20. Suppose now that the measurement has progressed to number m+n. The moving average is inherited (takes 2n+1 spectrum numbers and averages them. In this case, the CPtJ 16 reads data from addresses m-n to m+n from the memory device 20,
Add and divide by 2n+1.

The value thus obtained is the spectrum measurement value for the wavelength λ corresponding to the m-th measurement number.

In actual calculation, from m-n-1 to m using the moving average in the previous stage.
Since the sum of the spectrum signals up to +n-1 has been determined, it is sufficient to subtract the m-n-1 data and add the m+n data. The starting point of the displayed spectrum is the n+1st measurement number, and when the moving average for this point is obtained, the spectrometer has advanced to the 2n+1st measurement position. That is, the contents of counters c1 and C2 need to differ by n. The counter c2 initially has a count value of -n, and in actual operation, the counters C1 and C2 count stepping motor drive pulses in the same way.

The moving average method is not only a simple average method in which each wavelength within the moving average wavelength range is averaged, but also a weighted average method in which each sampling point is weighted. In the case of the weighted average method, when performing asymmetric weighting, a wavelength other than the center of the wavelength width related to the calculation may be used as the wavelength corresponding to the average value.

In addition, not only are the counters C1 and C2 in FIG. You may also do so.

(Effects of the Invention) In the present invention, at the start and end of scanning, the wavelengths necessary for the moving average process are extra scanned, and when the light b (1χ is switched, the wavelengths necessary for the moving average process are extra scanned, The light source is switched, and after switching, scanning is restarted from the wavelength returned by the wavelength necessary for moving average processing, so that within the entire specified wavelength scanning area, the wavelength corresponding to the light value and the display wavelength are can be matched, and
It is possible to obtain a correct spectrum I/L without a step in the vicinity of the light source switching wavelength.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the present invention, FIG. 2 is a diagram showing an example of the operation of the present invention, FIG. 3 is a flowchart 1 diagram showing an example of the operation, and FIG. 4 is a block diagram showing one embodiment. It is a diagram. 2...Spectroscope, 4...Light source switching means, 6...Spectrometer driving means, 8...Calculating means, 10...Display wavelength calculation Means, 12...Display means. Patent applicant: Shimadzu Corporation

Claims (1)

[Claims] (1) A spectrometer with a light source switching function, a light source switching means that switches the light source at a wavelength determined by the light source switching wavelength and the moving average wavelength range, and a moving average calculation for the starting wavelength of the spectrum display range specified for each light source. Spectrometer driving means that calculates a scanning start point wavelength for a scanning start point wavelength for a display end point wavelength of a specified spectral display range for each light source, and an end point wavelength for a moving average calculation for a display end point wavelength of a specified spectral display range for each light source, and scans these calculated wavelength ranges for each light source. , a calculation means for measuring a spectrum by wavelength scanning and calculating a spectrum value using a moving average method, a display wavelength calculation means for calculating a display wavelength based on the actual wavelength and the moving average wavelength range, and a calculation means for calculating a display wavelength based on the actual wavelength and the moving average wavelength range. A spectrophotometer comprising display means for displaying a spectral value calculated for a displayed wavelength.