JPH0427495B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a polarimeter that measures the optical rotation of a sample as a function of the wavelength or frequency of light.

BACKGROUND ART Conventionally, a polarimeter has been used to identify a sample substance by focusing on the optical rotation of a substance and measuring the optical rotation of a sample as a function of the wavelength or frequency of light. As shown in Figure 1, this polarimeter includes a light source (sodium lamp) 1, a polarizer 3 that converts the light that enters from the light source 1 through an interference filter 2 into linearly polarized light, and A measurement cell 5 as a sample storage means that receives light via a polarization modulator 4, an analyzer 6 that receives the light that has passed through the measurement cell 5, and a pulse motor 7 for rotating the analyzer 6. It has a photoelectric means, for example, a photomultiplier tube 8, which emits an electric signal according to the intensity of the light transmitted through the analyzer 6, and a drive means A, which drives the pulse motor 7 according to the output signal of the photomultiplier tube 8. It will be done.

The polarizer 3 and the analyzer 6 are arranged so that the angle θ between their respective polarization planes is π/2, and when no sample is stored in the measurement cell 5, the light source The light emitted from the analyzer 6 passes through the polarizer 3 and is converted into linearly polarized light, but if the intensity of that light is I ₀ , even if the light enters the analyzer 6, it will not pass through the analyzer 6.
The intensity I of the light emitted from is L=I ₀ cos ² (π/2)=0. However, when a sample is stored in the measurement cell 5, the plane of polarization of the light that has passed through the polarizer 3 is rotated by a predetermined angle α according to the optical rotation of the sample by passing through the sample stored in the measurement cell 5. do. Therefore, the angle θ between the polarization plane of the light after passing through the sample and the polarization plane of the analyzer 6 is π/2±α, and the intensity I of the light emitted from the analyzer 6 is I=I ₀ cos ² ( π/2±α). That is, the analyzer 6 emits light with an intensity corresponding to the optical rotation of the sample stored in the measurement cell 5, and a signal corresponding to the intensity of the light is output from the photomultiplier tube 8, and the output A signal is input to drive means A.

The driving means A includes a preamplifier 9 and a main amplifier 10 that amplify the output signal of the photomultiplier tube 8. This preamplifier 9 and main amplifier 1
The signal amplified at 0 is synchronously rectified in a synchronous rectifier 11 and output as a signal having a positive or negative potential depending on the optical rotation direction of the sample transmitted light. The signal output from the synchronous rectifier 11 is input to the VF converter 14 via the number detection circuit 12, and a pulse signal of a frequency corresponding to the potential of the input signal is output from the VF converter 14 to the motor drive circuit 13. Since the driving means A is configured as described above, the photomultiplier tube 8
The pulse motor 7 is driven by a pulse signal with a frequency corresponding to the intensity of light incident on the analyzer 6, which rotates the analyzer 6 and changes the angle θ between the polarization plane of the analyzer 6 and the polarization plane of the sample transmitted light. When it reaches the position where π/2, the intensity I of the light entering the photomultiplier tube 8 from the analyzer 6 becomes 0, and the rotation of the analyzer 6 stops.

On the other hand, the pulse signal output from the VF converter 14 to the motor drive circuit 13 is simultaneously output to the up-down counter 15, so that the pulse signal is outputted to the up-down counter 15 and the numeric display circuit 16. Then, the optical rotation of the sample corresponding to the rotation angle of the analyzer 6 is displayed on the display 17.

However, in the above-described conventional polarimeter, when the frequency of the pulse signal emitted from the VF converter 14 is increased in order to increase the measurement speed, pulses by the pulse motor 7 are missed, and the rotation of the pulse motor 7 is interrupted. It becomes difficult to completely correspond to the input pulse signal, and the accuracy particularly at the end of rotation of the pulse motor 7 deteriorates. Therefore, if a certain level of accuracy is to be achieved, the measurement speed must be set to a low level without deteriorating the accuracy, and the actual demand for faster measurement cannot be met. Furthermore, the measurement accuracy was not necessarily satisfactory, and there was still room for improvement.

The present invention has been made in view of the above-mentioned conventional circumstances, and an object of the present invention is to provide a polarimeter that can measure optical rotation at high speed and with high precision.

That is, the polarimeter of the present invention includes a light source, a polarizer that converts light received from the light source into linearly polarized light, a sample storage means for receiving light emitted from the polarizer, and a sample stored in the sample storage means. an analyzer that receives the light that has passed through the analyzer, a pulse motor that rotates the analyzer, a photoelectric means that emits an electrical signal in accordance with the intensity of the light that has passed through the analyzer, and an output signal of the photoelectric means. and a driving means for driving the pulse motor accordingly, the driving means comprising a pulse generating means for generating a high speed pulse and a low speed pulse respectively corresponding to the output signal of the photoelectric means, and a pulse generating means for generating the pulse. switching means for switching the pulses input from the means to the pulse motor according to the magnitude of the output signal of the photoelectric means with respect to a reference potential; The present invention is characterized in that when a high-speed pulse is input and the output signal of the photoelectric means is smaller than a reference potential, a low-speed pulse is input to the pulse motor.

An embodiment of the present invention will be described below with reference to FIG. Note that the same parts as in the conventional polarimeter shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 2, in the polarimeter of the present invention, the driving means A that drives the pulse motor 7 that rotates the analyzer 6 is provided with high-speed pulses and low-speed pulses corresponding to the output signals of the photomultiplier tube 8, respectively. A switching means C is provided for switching the pulse input from the pulse generating means B to the pulse motor 7 in accordance with the magnitude of the output signal of the photomultiplier tube 8 with respect to a reference potential.

The switching means C includes a level monitor 18 to which the output signal of the synchronous rectifier 11 is input, and a switch 20 to which the output signal of the level monitor 18 is input.
It becomes more. Further, the pulse generating means B includes a VF converter 14 to which the output signal of the synchronous rectifier 11 is input, and a pulse attenuator 19 to which the output signal of the VF converter 14 is input.

A signal synchronously rectified by the synchronous rectifier 11 is input to the level monitor 18, the input signal is compared with a preset reference potential, and the result is output from the level monitor 18 to the switch 20. In addition, the pulse attenuator 19
The pulse signal output from the VF converter 14 is input, and from this pulse attenuator 19, the VF
Pulse signal (high-speed pulse) obtained by slightly thinning out the pulse signal from converter 14 and slowing it down to some extent
and a pulse signal (low-speed pulse) obtained by increasing the degree of thinning of the pulse signal from the VF converter 14 to make it even slower (low-speed pulse), and both pulse signals are input to the switch 20. In this switch 20, either the high-speed pulse or the low-speed pulse inputted from the pulse attenuator 19 is selected based on the output signal from the level monitor 18, and the up-down counter 15
is output to. That is, when the potential of the signal input from the synchronous rectifier 11 to the level monitor 18 is higher than the reference potential, a high-speed pulse is output to the up-down counter 15 via the switch 20, and the potential of the signal input to the level monitor 18 is When the potential becomes lower than the reference potential, the switch 20 is switched and a low-speed pulse is output to the up-down counter 15.

Therefore, when measuring the optical rotation of a sample using the polarimeter of the above embodiment, the angle θ between the polarization plane of the sample and the polarization plane of the analyzer 6 is large, and When the intensity I of the emitted light is large,
Corresponding to the strength, a signal having a higher potential than the reference potential is input to the VF converter 14 and the level monitor 18. The VF converter 14 outputs a pulse signal with a speed corresponding to the large potential to the pulse attenuator 19, and the pulse attenuator 19 thins out the pulse signal and outputs a high-speed pulse whose speed has been reduced to a certain degree and a pulse from the VF converter 14. A low-speed pulse obtained by making the signal even slower is output to the switch 20. Further, the level monitor 18 outputs the result of comparing the reference potential and the input signal potential to the switch 20, and based on the result, a high-speed pulse is output to the switch 20.
The signal is outputted to the motor drive circuit 13 and up/down counter 15 via. Thereby,
The pulse motor 7 rotates at high speed in response to the high frequency of the high speed pulse, and the analyzer 6 is rotated at high speed by the pulse motor 7. Next, as the analyzer 6 rotates, the angle θ between the polarization plane of the sample and the polarization plane of the analyzer 6 becomes smaller, and the intensity I of the light entering the photomultiplier tube 8 decreases. Corresponding to its strength, a signal with a smaller potential than the reference potential is generated.
It is input to the VF converter 14 and level monitor 18. Then, the VF converter 14 outputs a pulse signal with a speed corresponding to the small potential to the pulse attenuator 19.
From 9 onwards, the pulse signal is thinned out, and a high-speed pulse whose speed has been slowed down to a certain degree and a low-speed pulse whose speed has been further slowed down are outputted to the switch 20. Also,
The level monitor 18 outputs the result of comparing the reference potential and the input signal potential to the switch 20, and based on the result, a low-speed pulse is sent to the motor drive circuit 13 via the switch 20.
and is output to the up-down counter 15.
Therefore, the pulse motor 7 is driven at a low speed corresponding to the low frequency of the low-speed pulse, and the analyzer 6 is rotated at a low speed. As the angle θ between the polarization plane of the sample and the polarization plane of the analyzer 6 approaches π/2, the frequency of the pulse signal input to the pulse motor 7 gradually decreases, and the rotation speed of the analyzer 6 also decreases. The speed gradually decreases, and when θ=π/2, the intensity I of the light entering the photomultiplier tube 8 becomes zero, the pulse motor 7 gradually stops, and the rotation of the analyzer 6 also stops.

In the above process, the motor drive circuit 13
The pulse signal input to the up-down counter 15 is simultaneously input to the up-down counter 15, and therefore, the optical rotation of the sample is displayed on the display 17 via the numerical display circuit 16 based on the input signal.

In addition, in the above embodiment, the synchronous rectifier 11 and
A time constant circuit 21 may be provided between the VF converter 14 and the VF converter 14. By doing so, the potential change of the signal input to the VF converter 14 is alleviated, and the frequency of the pulse signal output from the VF converter 14 to the pulse attenuator 19 is prevented from changing rapidly. The frequency change of the pulse signal input from the attenuator 19 to the motor drive circuit 13 via the switch 20 can be made continuous. Therefore, there is no possibility that a high-frequency pulse signal is suddenly input to the pulse motor 7 and the pulse signal is not read by the pulse motor 7 at the start of driving, and slow starts and slow stops of the pulse motor 7 can be realized. I can do it.

Further, in the above embodiment, the pulse generating means includes the VF converter 14 and the pulse attenuator 19.
Therefore, from this pulse attenuator 19,
A pulse signal (high-speed pulse) obtained by slightly thinning out the pulse signal input from the VF converter 14 and slowing it down to a certain extent, and a pulse signal (low-speed pulse) obtained by increasing the degree of thinning of the pulse signal input from the VF converter 14 and making the speed even slower. is output. However, the pulse generating means of the present invention is not limited thereto, and can generate pulses whose speed is proportional to the potential of the output signal of the photoelectric means, and which have different degrees of proportionality, such as relatively faster pulses. , it suffices to emit slower pulses. Therefore, for example, in the above embodiment, the VF converter 1
The pulse generating means may be constructed so that a high-speed pulse obtained by further increasing the speed of the pulse signal output from VF converter 14 and a low-speed pulse obtained by thinning out the pulse signal output from VF converter 14 and lowering the speed thereof are output. .

As described above, according to the polarimeter of the present invention, the driving means for driving the pulse motor includes a pulse generating means that generates high-speed pulses and low-speed pulses corresponding to the output signals of the photoelectric means, respectively, and By providing a switching means for switching the pulse input from the means to the pulse motor according to the magnitude of the output signal of the photoelectric means with respect to the reference potential, it is possible not only to increase the measurement speed without causing a decrease in measurement accuracy. The measurement accuracy itself can also be made extremely good.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a conventional polarimeter, and FIG. 2 is a block diagram showing the configuration of the polarimeter of the present invention. 1... Light source, 2... Interference filter, 3... Polarizer,
5...Measurement cell, 6...Analyzer, 7...Pulse motor,
8...Photomultiplier tube, 11...Synchronous rectifier, 14...
VF converter, 18...Level monitor, 19...
Pulse attenuator, 20... switch, 21... time constant circuit.

Claims (1)

[Scope of Claims] 1. A light source, a polarizer that converts the light received from the light source into linearly polarized light, a sample storage means that receives the light emitted from the polarizer, and a light source that transmits the sample stored in the sample storage means. a pulse motor for rotating the analyzer; a photoelectric means for emitting an electrical signal in accordance with the intensity of the light transmitted through the analyzer; and a pulse motor for rotating the analyzer; and a driving means for driving the pulse motor, wherein the driving means includes pulse generating means for generating high-speed pulses and low-speed pulses corresponding to the output signals of the photoelectric means, respectively, and pulse generating means from the pulse generating means. switching means for switching the pulses input to the pulse motor according to the magnitude of the output signal of the photoelectric means with respect to a reference potential; and when the output signal of the photoelectric means is greater than the reference potential, high-speed pulses are applied to the pulse motor. A polarimeter characterized in that a low-speed pulse is input to the pulse motor when the output signal of the photoelectric means is smaller than a reference potential.