JPS5997077A - Time-voltage converter - Google Patents

Abstract

PURPOSE:To obtain voltage proportional to a time free from error even in a short time, by storing the voltage values of continuous wave forms when a start pulse and a stop pulse and inputted to calculate the difference of the voltage values. CONSTITUTION:An oscillator 1 oscillates continuous two phase wave forms V1, V2 shifted in phase and, when a start pulse PA is inputted, memory circuits 2, 3 respectively store the voltage values V1A, V2A of continuous wave forms V1, V2 at the start time. On the other hand, when a stop pulse PB is inputted, memory circuits 4, 5 similarily store the voltage values V1B, V2B of continuous wave forms at the stop time. In the next step, voltage values V1A-V1B and V2A-V2B are respectively calculated by subtractors 10, 11 to be imparted to a selection means 12. In this case, the selection means 12 selects the large output voltage among the outputs of the subtractors 10, 11 to output the same. By this method, voltage proportional to a time free from error can be obtained even in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a time-voltage converter for obtaining a voltage proportional to time.

This type of converter is used, for example, when exciting a measurement sample with pulsed light and detecting fluorescence emitted from the sample to measure the luminescence lifetime of the sample.

This is because when measuring the luminescence lifetime, the time from pulse excitation of the sample to the emission of fluorescent photons is important, but leaving the time as it is is inconvenient for later signal processing, and this is This is because it needs to be converted into a value.

Conventionally, this type of time-voltage converter basically utilizes the charging or discharging characteristics of a capacitor.

FIG. 1 shows an example of a conventional time-voltage converter. The operation of this converter is as follows: First, a start pulse PA is applied externally to set the flip-flop FF.
Switch S is closed to start charging capacitor C. Next, when the stop pulse PB is applied, the flip-flop FF is reset and the switch S is opened, and since it becomes a function of the time t, the start pulse is It is possible to obtain a voltage corresponding to the time from when the stop pulse is applied.

In the figure, M is a monomulti to ensure the operation of the sample and hold circuit.

By the way, in the case of this time-voltage converter, there is no problem if the handling time is long, but when the time is short on the nanosecond order, such as when measuring the luminescence lifetime of a sample, the capacitor C
As shown in FIG. 2, the charging voltage is distorted as the switch opens and closes, and the proportional relationship between time and voltage is impaired and cannot be ignored, resulting in an error.

In view of this, the present invention provides an extremely useful time-voltage converter that can output a voltage proportional to time without error even if the time is as short as nanosecond order.

Accordingly, the following is a time-voltage converter according to the present invention. The invention includes an oscillator that oscillates two-phase continuous waveforms that are out of phase;
A start memory circuit stores the voltage value of the continuous waveform generated by the oscillator when a start pulse is input, and a stop memory circuit stores the voltage value of the i-type reading waveform generated by the oscillator when a stop pulse is input. , a subtracter for calculating the difference between the voltage values stored in the start time storage circuit and the stop time storage circuit, and selection means for taking out the correct time-voltage conversion value as an output, and the selection means is configured to The gist of the present invention is that it is configured to select which of two continuous waveforms should be used to extract the difference in voltage value from among the device outputs.

The second invention also provides an oscillator that oscillates a two-phase continuous waveform whose phase is shifted, a start memory circuit that stores the voltage value of the continuous waveform generated by the oscillator when a start pulse is input, and a stop pulse. When input, there is a stop memory circuit that stores the voltage value of the continuous waveform generated by the oscillator, a subtracter that calculates the difference between the voltage values stored in the start memory circuit and the stop memory circuit, and the correct time voltage. The selection means selects the voltage value of which waveform of the two continuous waveforms generated by the oscillator should be stored in the start time storage circuit and the stop time storage circuit. The main points are that the system is configured to select the following.

The present invention will be described in detail below based on embodiments shown in the drawings. FIG. 3 shows an embodiment of the first aspect of the present invention, and in the figure, l is an oscillator that oscillates two phase continuous waveforms with different phases. Although the oscillation method of this oscillator does not matter, it is necessary to use one that can oscillate a waveform with good reproducibility.

In this embodiment, triangular waves V, , v2 as shown in FIG. 4 are used as continuous waveforms for each phase. However, any waveform can be used as long as the voltage value changes over time. Further, the phase difference between the continuous waveforms of each phase is set to V2 in this embodiment. However, even if the phase difference of the signals is not accurate, it does not matter if there is a slight deviation. The reason for using two continuous waveforms with a phase shift in this way is to cope with the situation since it is not known when the start pulse and stop pulse will be input. That is, to explain the reason in detail, the present invention uses a continuous waveform emitted from an oscillator instead of a conventional method that uses charging and discharging of a capacitor, and uses a continuous waveform when a start pulse and a stop pulse are input. It uses a method of storing voltage values and outputting the difference between the voltages. Therefore, in order for this voltage difference to be proportional to time, a start pulse and a stop pulse must be input when a continuous waveform (eg, a triangular wave) is changing one slope. However, since we do not know when the start and stop pulses will be input,
A single continuous waveform cannot be used. Therefore, by using two continuous waveforms with different phases, no matter when the start pulse and stop pulse are input, one continuous waveform is always one during the time from when the start pulse is input until when the stop pulse is input. The slope was made to appear to be changing.

Therefore, in this sense, it is most desirable that the two continuous waveforms have a significant phase difference as in the embodiment.

In this embodiment, the oscillator l generates the two continuous waveforms V
,, In addition to V2, a rectangular wave V of V2 period of the continuous waveform
3 is also oscillating. This rectangular wave v3 can be either continuous waveform V, V2 depending on when the start pulse is input.
This serves as a standard for selecting the voltage value of .

2 and 3 are sample and hold circuits, for example, as start memory circuits that store the voltage values V, A, and v2A of the continuous waveform Vl+V2 of each phase when the start pulse PA is input, and 4 and 5 are sample and hold circuits where the stop pulse PB is input. For example, a sample hold circuit 6 is used as a stop memory circuit that stores the voltage values V, B, V, , B of the continuous waveform of each phase when
．． 7. 8°9 indicates each memory circuit 2. 3. 4. 5(
7) Output voltage V, A.

A-D converter that converts V, B, V2A, V2B into digital quantities, to and tt are memory circuits at start 2゜3
This is a subtracter that calculates the difference between the voltage values stored in the stop storage circuits 4 and 5. One subtracter IO uses the voltage values V and A stored in the start time storage circuit 2 and the voltage value V stored in the stop time storage circuit 4 when vl is used among the two continuous waveforms. , B, and the other subtracter 11 calculates the difference between the voltage value v2A stored in the start memory circuit 3 and the voltage value V2B stored in the stop memory circuit 5 when V2 is used. 12 is a selection means for extracting a correct time-voltage conversion value as an output. Here, the time-voltage conversion value refers to a voltage value proportional to the time from when a start pulse is input until when a stop pulse is input. In this first invention, the selection means 12 is configured to select which of the two continuous waveforms VI+v2 should be used to extract the difference in voltage value from among the outputs of the subtracter 10.11. In the embodiment, a selector switch SW is used as the selection means 12, and the switch SW is switched by an AND circuit A to which a rectangular wave v3 generated by the oscillator 1 and a start pulse PA are added.

The AND circuit A has a rectangular wave v3 of 0 to -5π to -π.

2. When the start pulse PA is input between 2π and π..., the output of the subtracter 12 that calculates the voltage difference on the two phase side is taken, and on the other hand, the rectangular wave v3 is When the start pulse PA is input between 2π..., the switch SW is changed to take the output of the subtracter 11 that calculates the voltage difference on the 1-phase side.

By switching the switch SW at such timing, a correct time-voltage conversion value can always be taken out as an output. This is because we do not know when the stop pulse PB will be input, so it is better to use the time-voltage conversion value using the continuous waveform that takes as much time as possible from the input of the start pulse PA to the end of changing one slope. is considered to indicate a correct time-voltage conversion value, and the switching timing of the changeover switch SW is based on this idea.

To explain the reason for this with a specific example, for example, as shown in FIG. 4, the start pulse PA is input at time to,
Assume that the stop pulse PB is input at time t1. In this case, the continuous waveform v1 is t.

The peak is reached at the phase of the calendar up to 11, and the slope changes before and after that, so the difference in voltage value using this waveform V1 (VIA-VIB) is the voltage proportional to time (tt-to). Therefore, it does not indicate an accurate time-voltage conversion value. On the other hand, continuous waveform ■2 is t1 after to
Since it is a straight line and slopes up to
is proportional to. Therefore, if the switch SW is configured to take out the difference in voltage values (V, A-V, B) using the continuous waveform v1 at this time, it will not be possible to obtain an accurate time-voltage conversion value, but if l Since the time to when the start pulse FA is input is between 0 and 2, the switch SW is switched to extract the difference in voltage value (V2A-V2B) using the continuous waveform 2, so it is accurate. It is possible to obtain a time-voltage conversion value. And start pulse P
The time point at which A is input is not limited to between 0 and -, but between ~π, π
Even between ~-π..., the 2 inch SW switches to extract the voltage difference on the side of the continuous waveform V, v2, which takes a long time to change one slope after the start pulse is input. Therefore, the correct time-voltage conversion value can always be output no matter when the start pulse is input.

As is clear from the above explanation, the correct time-voltage conversion value is always the larger value of the output voltages of the two subtracters. It is also possible to use a comparator that compares the magnitude of . In that case, the AND circuit A and the rectangular wave 3 are unnecessary. In FIG. 3, 13 is a monomulti. The monomulti 13 functions to limit the time from when the start pulse PA is input until when the stop pulse PB is input based on the period of the continuous waveforms V, , v2.

Next, FIG. 5 shows another embodiment of the invention of %l. The embodiment shown in FIG. 3 converts the time taken until one stop pulse is input into a voltage value, and even if two or three stop pulses are subsequently input, the start pulse is from? It is not possible to perform voltage conversion processing on the time until the stop pulse of l. However, when measuring the luminescence lifetime of a sample, it is also possible to observe a plurality of fluorescent photons with one pulse excitation. In such a case, it is necessary to convert the voltage at each time period from input of a start pulse to input of a plurality of stop pulses. FIG. 5 shows a circuit constructed to deal with such a case. That is, in addition to the configuration shown in FIG. 3, this circuit has a plurality of stop memory circuits 4, 5 connected in parallel, and each stop memory circuit 4..., 5... is connected to a shift register or the like. The switching means L4 selectively operates each time a stop pulse is input.

In this embodiment as well, the selection means 12 is the switch S.
As in the previous embodiment, a comparator may be used instead of W.

FIG. 6 shows an embodiment of the second aspect of the present invention.

In the first invention, the selection means 12 for extracting the correct time type EE converted value as an output includes two subtracters 10.
However, in this second invention, the start time storage circuit 21 and the stop time storage circuit 22 store the two continuous waveforms V generated by the oscillator 1. The configuration is such that it is possible to select which waveform voltage value of V2 should be stored. In other words, in the first invention, the selection means 12 functions to select the correct one from the finally processed values, which are the outputs of the subtracter, whereas in the second invention, the selection means 12 selects the correct one from the finally processed values, which are the subtractor outputs, Continuous waveform V7
．． The function is to select a value that will yield a correct time-voltage conversion value before the process of storing the voltage value of v2. In this way, both inventions have the same main components, ie, an oscillator, a start memory circuit, a stop memory circuit, a subtracter, and a selection means, and also have the same effect of always obtaining a correct time-voltage conversion value.

In FIG. 6, the selection means 12 uses the changeover switch SW in the same way as in FIG.
This is performed by an AND circuit A to which A and A are added.

Therefore, the switching timing of the switch SW is 3rd and 4th.
The timing is the same as in the case explained in the figure. However, in this invention, the changeover switch SW selectively switches between the two continuous waveforms V, V2, and the continuous waveform selected by the switching is added to the start time storage circuit 21 and the stop time storage circuit 22. ing.

The start memory circuit 21 stores the voltage value V, A, or V2A of the continuous waveform selected by the switch SW when the start pulse PA is applied, and the stop memory circuit 22 stores the voltage value V, A, or V2A of the continuous waveform selected by the switch SW, and the stop memory circuit 22 stores the voltage value V, A, or V2A of the continuous waveform selected by the switch SW. Then, the voltage value V, B or 2B of the continuous waveform selected by the switch SW is stored. In this case, the switching of the changeover switch SW is performed at the time when the start pulse PA is input, so when the start time memory circuit 21 stores the voltage value of the continuous waveform at the moment when the start pulse is input, the changeover switch SW
Since the voltage in the transient part immediately after switching is stored, the voltage value may not be accurate. Therefore, in this embodiment, a delay circuit 23 is inserted so that the start memory circuit 21 stores the voltage value after a certain period of time has elapsed since the start pulse was input. Also, this delay circuit 2
3, the time until the stop pulse PB is input is shortened. Therefore, the stop memory circuit 22 also stores the voltage value after a certain period of time after the stop pulse PB is input. A delay circuit 24 having the same delay time as the delay circuit 23 is provided. The outputs of the two memory circuits 21 and 22 are converted into digital quantities by A-D converters 25 and 26, and the difference between the two voltage values is determined by a subtracter 27 and output. In this invention, 2
Since the selection means 12 selects in advance which voltage value of the two continuous waveforms V, , V, , should be stored, the subtracter 2
7 always gives the correct time-voltage conversion value, so
The subtracter output becomes the output to be extracted as data.

Although not shown, in this invention, if a large number of stop memory circuits 22 are connected in parallel and selectively switched by a shift register or the like, a multi-channel structure similar to that shown in FIG. 5 can be realized. It is possible to

Since the time-voltage converter according to the present invention is configured as described above, the continuous waveform V with good reproducibility is used as the oscillator 1.
As long as a device that oscillates V2 is used, it is possible to obtain a voltage proportional to time without error even if the time is as short as nanosecond order.

In addition, just by connecting a plurality of stop time memory circuits in parallel and operating them selectively as in the embodiment shown in FIG. 5, it is possible to convert different times into voltages. Therefore, there is also the effect that multi-channelization is easy. Also, since the signals handled are alternating current with continuous waveforms V, V2, there is no need to take measures against DC drift of the oscillator.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional time-voltage converter, Fig. 2 is a diagram explaining the drawbacks of the conventional circuit, and Fig. 3 is a time-voltage converter as an embodiment of the first invention of the present invention. circuit diagram,
FIG. 4 is a diagram explaining the operation of the circuit in FIG. 3, FIG. 5 is a diagram showing another embodiment of the first invention, and FIG. 6 is a diagram showing an embodiment of the second invention. be. 1... oscillator, 2. 3. 21...Start memory circuit, 4,5.22...Stop memory circuit, 10°11.27...Subtractor, 12...Selection means, V,
V2...Continuous waveform.

Claims (4)

[Claims] (1) An oscillator that oscillates a two-phase continuous waveform with a phase shift, a start memory circuit that stores the voltage value of the continuous waveform generated by the oscillator when a start pulse is input, and a start memory circuit that stores the voltage value of the continuous waveform generated by the oscillator when a stop pulse is input. , a stop memory circuit that stores the voltage value of the continuous waveform generated by the oscillator, a subtracter that calculates the difference between the voltage values stored in the start memory circuit and the stop memory circuit, and a correct time-voltage conversion value as an output. a selection means for extracting the voltage value, and the selection means is configured to select which of the two continuous waveforms should be used to extract the difference in voltage value from among the outputs of the subtracter. and time-voltage converter. (2) The time-voltage converter according to claim (1), wherein the phase shift is π/2. (3) The time-voltage converter according to claim 1 or 2, wherein the continuous waveform of each phase is a triangular wave. (4) An oscillator that oscillates a two-phase continuous waveform with a phase shift, a start memory circuit that stores the voltage value of the continuous waveform generated by the oscillator when a start pulse is input, and a start memory circuit that stores the voltage value of the continuous waveform generated by the oscillator when a stop pulse is input. , a stop memory circuit that stores the voltage value of the continuous waveform generated by the oscillator, a subtracter that calculates the difference between the voltage values stored in the start memory circuit and the stop memory circuit, and outputs the correct time-voltage conversion value. and a selection means for extracting the
A time-voltage converter, characterized in that the start time storage circuit and the stop time storage circuit are configured to select which of two continuous waveforms generated by an oscillator should store the voltage value of the waveform.