JPH0572037A - Spectrophotometer - Google Patents

Abstract

PURPOSE:To improve a wavelength scanning speed and to make it possible to perform excellent measurement even if the detected signal is steeply changing by obtaining the correcting amount of an applied voltage on a detector with a function, which can obtain the optimum correcting amount in response to the lareger signal amount of either of a reference luminous flux signal or a sample luminous flux signal. CONSTITUTION:The monochromatic light which has undergone spectroscopy with a monochrometer is split into reference side luminous flux, sample-side luminous flux and a state wherein light is shielded with a photointerruptor 26, which is attached to a splitting mirror 11. The split parts are incident on a detector 19 through a different paths, respectively. The light incident on the detector 19 undergoes photoelectric conversion and further undergoes current-voltage conversion with a preamplifier 20. The signal undergoes A/D conversion 21 and inputted into a computer 22. In the computer 22, the larger signal of either of the reference-side luminous flux signal or the sample-side luminous flux signal is compared with a specified value, and a correcting amount is obtained. The correcting amount undergoes A/D conversion 23, and the result is inputted into a high-voltage generator 24 of the detector 19. The applied voltage is controlled based on the output value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer, and more particularly, to controlling a voltage applied to a detector.

[0002]

2. Description of the Related Art A conventional correction amount calculation of an applied voltage of a detector is a method which is performed only by a difference between a larger signal of a standard side light beam signal and a sample side light beam signal and a constant voltage.

[0003]

There is a demand for speeding up the measurement by the spectrophotometer, and along with this, it is necessary to improve the wavelength scanning speed.

The prior art lacks the following considerations.

1. The wavelength scanning speed is very fast, and
The correction method should not take into consideration that the detection signal changes abruptly.

2. Operational amplifier (op-amp) for photoelectric conversion
Also, the correction method should not consider the limitation of the dynamic range of the analog-digital converter.

As described above, in both cases 1 and 2, there is a problem that a measurement result different from an actual measurement result is produced.

An object of the present invention is to solve the above problems.

[0009]

To calculate the correction amount of the applied voltage to the detector, the standard light beam signal and the sample light beam signal are read, and the optimum signal is read according to the larger signal. This is done by using a function that can obtain the correction amount.

[0010]

[Function] The standard side light beam signal and the sample side light beam signal are read respectively. Next, the magnitude of each signal is compared. Then, the prescribed value D0 is subtracted from the larger one. Further, the optimum correction amount is obtained according to the magnitude of the signal by changing the arithmetic expression for obtaining the correction amount depending on the magnitude of the subtracted value and the specified value K0.

The present invention is not limited to this function, and is effective even if the correction amount is calculated by a different function.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A spectrophotometer has a spectroscope for dispersing light from a light source to extract monochromatic light, and the monochromatic light from the spectroscope is split into two light beams by a splitting mirror. One is guided to the standard photometric path and the other is guided to the sample side optical path. The light passes through each optical path, enters the detector, and is photoelectrically converted there. Further, the diverging mirror has a portion that blocks light, and the detector output at this time becomes a zero signal Z, and an electric signal R corresponding to the amount of light passing through the standard side optical path and an electric signal S corresponding to the amount of light passing through the sample side optical path. The ratio (S-Z / R-Z) is the measurement result.

Each photoelectric conversion signal is converted from analog to digital, taken into a computer, and the above calculation is performed to obtain a measurement result.

Further, the applied voltage of the detector is controlled by calculating a correction amount such that the larger one of the S and R signals is always constant.

The conventional correction amount calculation is a method which is performed only by the difference between a signal having a large S or R signal and a constant voltage.

This method has no problem when the wavelength scanning spread is slow and when the amount of change in energy is small.

In recent years, there has been a demand for speeding up measurement by a spectrophotometer, and a technique that can cope with this has been required.

In the above-mentioned conventional description, since only the difference between R or S and a constant value is detected and corrected, consideration is insufficient in the following points.

1. The wavelength scanning speed is very fast, and
The correction method should not take into consideration that the detection signal changes abruptly.

2. It should not be a correction method that does not consider the limitation due to the dynamic range of the operational amplifier for photoelectric conversion and the analog / digital converter.

In any of the above cases 1 and 2, there is a problem that a measurement result different from the actual measurement result is produced.

An object of the present invention is to provide a spectrophotometer which can cope with a high wavelength scanning speed by using a new correction amount calculation method.

According to the present invention, there is provided a spectrophotometer capable of correction with an optimum applied voltage correction amount for a detector corresponding to a high wavelength scanning speed.

FIG. 1 is a system diagram of an optical system showing an embodiment of the present invention.

The light source switching mirror 1 automatically switches the light from the light source in accordance with the measurement wavelength and guides it to the monochromator 2. Visible region is WI lamp 3, UV region is D2 lamp 4
To use. The light from the lamp passes through the filter 5 and is guided by the mirror 6 to the monochromator. The dispersive element 9, the entrance slit 7 and the exit slit 8 constitute a monochromator. The monochromatic light separated by the monochromator passes through the mirror 10 and strikes the dispersion mirror 11. The branching mirror splits the light into a standard light beam and a sample light beam. The standard luminous flux is incident on the detector 19 through the mirrors 12, 13 and 14. In addition, the sample side luminous flux is
The light enters the detector through the mirrors 15, 16, 17, and 18.

The wavelength scanning is performed by changing the rotation angle of the branch element. FIG. 2 is a system diagram of a signal processing system showing an embodiment of the present invention.

The photoelectric conversion signal of the light incident on the detector is converted into current and voltage by the preamplifier 20. Next, this voltage signal is digitally converted by the A / D converter 21 and read by the computer 22.

The computer calculates the following equation and displays the measurement result.

[0029]

[Equation 1]

The standard side light beam signal or the sample side light beam signal, whichever is larger, is compared with the specified value to calculate the correction amount and output the correction value to the D / A converter 23. To do. This output is input to the high voltage generator 24 of the detector, and the applied voltage is controlled based on this output value.

The standard-side light beam signal, the sample-side light beam signal, and the zero signal are used for the photointerrupter 2 attached to the branch mirror.
It is separated by 6 and is recognized as each output.

The control of the mechanical system such as the wavelength scanning is performed by the computer via the digital I / F 25.

FIG. 3 shows an example of detector output voltage and A / D conversion.

The output voltage of the detector is the output voltage of the preamplifier. The split mirror separates the zero signal, the standard-side signal, and the sample-side signal, and the respective parts of the respective signals are A / D converted.

The applied voltage of the detector is the standard side signal,
Sample side signal or sample signal, whichever is larger, in this example,
The correction amount is calculated and controlled so that the standard signal has a constant value of about 8V.

FIG. 4 shows a flow chart for calculating the correction amount.

The standard side light flux signal R and the sample side flux signal S are read respectively. Next, the magnitude of each signal is compared. Then, when the standard-side light flux signal R is large, it is calculated from R, and when the sample-side light flux signal S is small, it is calculated from S to a specified value D.
Subtract 0.

Further, when the subtracted value is equal to or less than the specified value K0, the correction value DE is obtained by the arithmetic expression shown in the equation (2).

[0039]

[Equation 2]

When this value is equal to or greater than the specified value K0, the correction value DE is obtained by the calculation formula shown in the equation (3).

[0041]

[Equation 3]

FIG. 5 shows this as a graph of the input signal and the correction amount.

In the above description, only the function of the correction amount shown in FIG. 5 has been described, but the present invention is not limited to this function, and it is effective even if the correction amount is calculated by a different function. Is. For example, a quadratic function or a non-linear function can be applied.

[0044]

【The invention's effect】

1. Good measurement results can be obtained even when the wavelength scanning speed is very high and the detection signal changes abruptly.

2. It is possible to eliminate the limitation due to the dynamic range of the operational amplifier for photoelectric conversion and the analog / digital converter.

[Brief description of drawings]

FIG. 1 is a system diagram of an optical system.

FIG. 2 is a system diagram of a signal processing system.

FIG. 3 is a detector output voltage and A / D conversion diagram.

FIG. 4 is a flowchart of a calculation formula of a correction amount.

FIG. 5 is a diagram showing a function graph of a correction amount.

[Explanation of symbols]

1 ... Light source switching mirror, 2 ... Monochromator, 3 ... WI lamp, 4 ... D2 lamp, 5 ... Filter, 6 ... Mirror, 7
... incident slit, 8 ... exit slit, 9 ... dispersion element, 1
0 ... Mirror, 11 ... Branching mirror, 12 ... Mirror, 13 ... Mirror, 14 ... Mirror, 15 ... Mirror, 16 ... Mirror, 17
... mirror, 18 ... mirror, 19 ... detector, 20 ... preamplifier, 21 ... A / D converter, 22 ... computer, 23
... D / A converter, 24 ... High voltage generator, 25 ... Digital I / F, 26 ... Photointerrupter.

Claims (2)

[Claims] 1. A spectroscope which has a light source and a dispersion means for wavelength-dispersing light from the light source, emits monochromatic light, a detector which detects monochromatic light emitted from this spectroscope, and this detector. A spectrophotometer comprising means for changing the voltage of the high-voltage generator according to 1., according to the output signal of the detector. 2. A means according to claim 1, wherein an output signal of each of the sample-side signal and the standard-side signal of the detector is read so as to be constant, and a correction amount is calculated by a prescribed function. And a spectrophotometer.