JPH07120321A - Spectrophotometer - Google Patents

Abstract

PURPOSE:To make it possible to correct measurement data by a proper base line function by providing a control means which drives a spectroscope by altering a wave length feeding interval of the spectroscope according to an arbitrary wavelength area or a wavelength of an entire wavelength area to be measured in a base line measurement to accomplish a quick base line measurement. CONSTITUTION:A CPU8 performs control of optical elements, control of a changeover switch 6 to acquire measurement data alternately from the measurement side and the side to be controlled, a computation of a base line function, a memorization of the results into a memory 7. When a switching wavelength of a high-order light cut filter 5 reaches a value 1nm before that preset, a wavelength feeding of a spectroscope 4 is switched over to 0.05nm interval of a measuring minimum wavelength interval to perform a driving so that the acquisition of measured values from the sample side and the side to be controlled and the memorization into the memory 7 are repeated until the switching wavelength of the filter 5 is exceeded by 1nm. When the switching wavelength of the filter 5 is exceeded by 1nm, the wavelength feeding interval of the spectroscope 4 is returned to 0.5nm. Thus, the switching wavelength of the filter 5, a margin before and after the switching wavelength of the light sources 1 and 2 and the wavelength of the spectroscope is switched at an interval of 0.05nm to perform a driving.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrophotometer capable of correcting measurement data with an appropriate baseline function, and more particularly to a wavelength feeding structure of a spectrometer during the baseline measurement.

[0002]

2. Description of the Related Art For example, in a conventional double-beam spectrophotometer, it is desirable that the light quantity ratio between the sample side and the control side is always constant irrespective of changes in wavelength when there is no sample.
In reality, the characteristics of the light source, the detector, and the optical elements such as the diffraction grating and the reflecting mirror in the device have wavelength dependence and are not constant. For this reason, when measuring by continuously changing the wavelength such as in spectrum measurement, measure the baseline of the entire measurement wavelength range without the sample before measurement, and measure the sample side and the control side for each wavelength. The light amount ratio is stored as a baseline function by using a CPU or a memory, and the measured data (photometric value) is corrected by the stored baseline function when measuring the sample. The correction formula is as follows.

Transmittance (or reflectance) T = (S / R) / (SB / RB) (1) where S: sample side photometric value R: control side photometric value SB: at baseline measurement Sample side photometric value RB: Control side photometric value at baseline measurement.

In the above equation, the correction of the dark current of the detector and the auto zero, that is, the correction of setting the specific photometric value level to the transmissivity = 1 are omitted because they are not related to the present invention.

[0005]

In the conventional spectrophotometer, the wavelengths for baseline correction must be discrete. When the wavelength transmission interval of the spectrometer during baseline measurement is wider than the measurement wavelength interval, the measured baseline data must be finely interpolated up to the measurement wavelength interval, but this method causes between baseline measurement wavelengths. There is a problem that a sharp change in the light amount ratio between the sample side and the control side, for example, a change in the light amount due to switching of the light source or switching of the high-order light cut filter cannot be corrected, resulting in a step or noise on the spectrum during sample measurement. .

On the other hand, if the wavelength sending interval of the spectroscope at the time of the baseline measurement is made the same as the measuring wavelength interval, the above problems will be eliminated, but in this case, the minimum wavelength interval that can be measured by the spectrophotometer. Therefore, the time required for baseline measurement becomes extremely long, which is not practical,
There is a problem.

In view of such problems, it is an object of the present invention to provide a spectrophotometer capable of speeding up the baseline measurement and correcting the measurement data with an appropriate baseline function. Is.

[0008]

In order to achieve the above object, in the spectrophotometer of the present invention, the wavelength sending interval of the spectroscope is changed at an arbitrary wavelength region of the entire measurement wavelength region or at the time of baseline measurement. It is equipped with a control means that can be driven.

The arbitrary wavelength region or wavelength of the entire measurement wavelength region for changing the wavelength sending interval of the spectroscope is expected to be before and after the wavelength for switching the light source, switching the high-order light cut filter, or anomaly of the diffraction grating. The wavelength corresponds to or around the wavelength.

The wavelength sending interval is changed by making the wavelength interval the same as the measurement minimum wavelength interval in a designated wavelength region or wavelength, and relatively wide (coarse) in other regions.
Driving is performed at wavelength intervals.

As described above, the CPU and the memory are used as the control means for changing and driving the wavelength sending interval of the spectroscope.

[0012]

[Function] The spectrophotometer configured as described above normally uses the baseline data (photometric value) of the sample side and the control side at a wavelength interval wider than the minimum measurement wavelength interval during baseline measurement.
Is acquired and the value of SB / RB is stored in the memory as a baseline function. When the wavelength at which the light source is switched or the high-order light cut filter is switched or the anomaly of the diffraction grating approaches the expected wavelength, the wavelength sending interval of the spectroscope is changed to a dense measurement minimum wavelength interval to drive. Similarly, the value of SB / RB is stored in the memory as a baseline function, and after passing these wavelengths or wavelength regions, the spectroscope is driven at the original relatively coarse wavelength interval to continue the baseline measurement.

At the time of measurement, the stored baseline function is used to correct the measurement data. Interpolation is performed for the range of baseline measurement at wide wavelength intervals, and for the range of baseline measurement at dense wavelength intervals. Uses the baseline function (data) as it is to correct the measurement data according to the above equation (1).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the spectrophotometer of the present invention will be described with reference to the drawings. In FIG. 1, each optical element such as a switching mirror 3 for switching the light sources 1 and 2, a spectroscope 4, a high-order light cut filter 5 and the like. Control of the device, control of the changeover switch 6 for alternately obtaining measurement data from the measurement side and the control side, calculation of the baseline function, storage in the memory 7, etc.
U8 does.

When a baseline measurement is started in a state where there is no sample in the sample-side cell holder 9 and the control-side cell holder 10 according to a command from the operator, a start wavelength (usually the shortest wavelength or the longest wavelength in the entire measurement wavelength region). .) To spectrometer 4
Is set, and the photometric values from the detectors 13 and 14 on the sample side and the control side are switched by the changeover switch 6 so that the amplifier 1
1 and the A / D converter 12 to take in the CPU 8, and the value of SB / RB is calculated and stored in the memory 7 as a baseline function.

Next, a wavelength sending mechanism (not shown) is driven to send the wavelength of the spectroscope 4 to 0.5 nm, and similarly, each photometric value on the sample side and the control side is acquired, and the SB / RB value is determined. The calculation and the storage in the memory 7 are performed, and this operation is sequentially repeated. Then, when the wavelength reaches 1 nm before the switching wavelength of the preset high-order light cut filter 5, the spectroscope 4
Is driven by switching to the 0.05 nm interval, which is the minimum wavelength interval for measurement. Similarly, each photometric value on the sample side and the control side is acquired, the SB / RB value is calculated, and the memory 7 stores the higher-order light. This is repeated until the switching wavelength of the cut filter 5 exceeds 1 nm.

When the switching wavelength of the filter 5 exceeds 1 nm, the wavelength sending interval of the spectroscope 4 is returned to the original wavelength interval of 0.5 nm. In this way, the wavelength feed of the spectroscope 4 is switched to the interval of 0.05 nm even before and after the switching wavelength of the next higher-order light cut filter 5 and the switching wavelength of the light sources 1 and 2, and even in the wavelength region where the anomaly of the diffraction grating is expected. After being driven, the same operation as described above is performed again, and when the end wavelength (the longest wavelength or the shortest wavelength of the entire measurement wavelength region) is reached, the baseline measurement ends.

When the spectrum measurement is started by the operator's command after the sample is installed, the spectroscope 4 is set to the start wavelength, and then the spectroscope 4 is wavelength-sent at a wavelength interval of 0.1 nm, for example. When the photometric values of the side and the control side are acquired, after the S / R value is calculated, the interpolated value is used in the wavelength range of the baseline measurement at the wavelength interval of 0.5 nm (1 The measured data corrected by the equation) and the measured data corrected by the equation (1) are obtained by using the baseline data as they are in the wavelength range of the baseline measurement at the wavelength interval of 0.05 nm. A set of these corrected measurement data is displayed on the display device 15 as spectrum data.

The present invention can be applied not only to spectrum measurement but also to the use of a plurality of different wavelengths, for example, the measurement of multiwavelength time change. Furthermore, the present invention is not limited to a double beam spectrophotometer but a single beam spectrophotometer However, the same can be applied. However, in this case, the equation (1) is R = RB
As follows.

Transmittance (or reflectance) T = S / SB

[0021]

Since the present invention is configured as described above, it is possible to obtain measurement data without steps or noise. Also, the time required to acquire the baseline data is short, and the capacity of the memory that stores the baseline data (function) may be small, so the memory can be retained by the battery even after the power supply of the spectrophotometer is turned off. It is possible.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a spectrophotometer of the present invention.

[Explanation of symbols]

 3 ... Light source switching mirror 4 ... Spectroscope 5 ... Higher-order light cut filter 6 ... Changeover switch 7 ... Memory 8 ... CPU

Claims (1)

[Claims] 1. A baseline in the entire measurement wavelength range is measured in the absence of a sample in advance, and this is stored as a baseline function, and the measured data is corrected by the baseline function stored when measuring the sample. In the spectrophotometer, the spectrophotometer is provided with a control means for changing and driving the wavelength sending interval of the spectroscope in an arbitrary wavelength region of the entire wavelength region or in the wavelength during the baseline measurement.