JPS61149888A - Time counting instrument - Google Patents

Abstract

PURPOSE:To eliminate the need for correction when the 2nd signal is not generated by setting a specific reference time from the point of time when the 1st signal is generated, and counting the time from the point of time of the generation of the 2nd signal to the end of the reference time and calculating the time between both signals. CONSTITUTION:A device which counts the time from the generation of the 1st signal A to the generation of the 2nd signal B is provided with a timer 2 in which the specific time longer than an estimated time is set. The timer 2 is started simultaneously with the generation of the 1st signal A and a counter 11 counts clock pulses generated from the generation of the 2nd signal B to the end of the reference time of the timer 2. The counted time is subtracted from the reference time to calculate the time between both signals A and B. Consequently, the counter 11 does not operate unless the 2nd signal B is generated, so an error in measurement is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a time counting device that measures the time from one point to another based on the number of clock pulses.

(Prior Art) As a system using a device that measures the time from a certain point to another point (hereinafter referred to as event time), for example, the light is There is a distance measuring system that measures the event time until the light is reflected by a target object and is received, and calculates the distance to the target object from this event time.

Conventional event time measurement in distance measuring systems is performed using the following method. That is, counting of clock pulses is started at the time of light projection, and the counting of the clock pulses is stopped when the reflected light of the projected light from the target object is received, and this operation is repeated every time light is projected. Then calculate the average number of clock pulses per event time by calculating the "accumulated clock pulse spread value ÷ the number of projections", and calculate the number of clock pulses per event time from this average value. Seeking distance.

According to this conventional event time calculation method, the counting of clock pulses starts from the moment the light is projected, so if the reflected light from the target object is not received for some reason, the relevant light is not received. It is necessary to subtract the number of clock pulses counted and added for each event time from the integrated value, and the calculation process is extremely complicated.

(Object of the Invention) The present invention was made to solve the above-mentioned conventional problems, and an object of the present invention is to obtain a time counting device that does not require the subtraction process of the number of clock pulses.

(Summary of the Invention) For the above purpose, the present invention provides a reference time setting means for setting a fixed length of time (longer than the assumed maximum value of the event time) as a reference time, starting from the start point of the event time;
a counter that counts the number of clock pulses inputted from the end of the event time to the end of the reference time; and a time calculation means that calculates the event time from the counted value of the counter based on the reference time. A time counting device is constructed by the following.

(Embodiments of the invention) All drawings are for explaining embodiments of the present invention.
The figure is a block diagram, and Figure 2 is a time chart showing the operation.
FIG. 3 is a flowchart showing the calculation process.

In FIG. 1, 1 is a clock oscillator, 2 is a reference time setting timer (hereinafter referred to as an event timer), and 3 is a light projection interval cycle setting timer (hereinafter referred to as a timer).

), 4 is a light emitting element drive unit (hereinafter referred to as a driver),
5 is a light emitting element, 6 is a light receiving element, and 7 is a light receiving unit (hereinafter referred to as
It's called a receiver. ), 8 is set reset 7, differential 0
21 circuit (hereinafter referred to as flip-frog), 9 is an AND gate, and 10 is an event count counter (hereinafter referred to as
It's called a hit counter. ), 11 is a clock pulse number integration counter (hereinafter referred to as a counter), 12 is a time calculation processing unit (hereinafter referred to as a processor), and A-1 is a second
The waveform observation points of the time chart shown in the figure are shown.

First, the functions of each block will be explained.

The clock oscillator 1 generates a clock pulse with a constant period t, and the period t of this clock pulse determines the resolution of measurement time.

The event timer 2 constitutes a reference time setting means, and the flip 70
7''8 acts to make the signal from the receiver 7 ready for reception.
1 is the reference time for event time calculation.

The timer 3 sets the light emitting period based on the clock pulse. For example, it is a 17n frequency divider (n is a natural number of n≧2), and it outputs one pulse every time it counts n clock pulses. Output.

The driver 4 supplies light emitting power to the light emitting element 3, and causes the trap light emitting element 5 to emit light for a set time period every time a pulse is output from the timer 3.

The light emitting element 5 is, for example, a semiconductor radar light emitting element (laser diode), and is used for time measurement (final 6 to Irp
+ I: I 7 small p yen t〃 Nyoyou II 't /n J-shi ζ n) low sea 7) Rato. The period of light projection matches the period of pulses output by the timer 3.

The light receiving element 6 is, for example, a semiconductor light receiving element (photodiode), and receives the projected light from the light emitting element 5 reflected by the target object, that is, the reflected light.

The receiver 7 detects the reflected light received by the light receiving element 6 and outputs an electric signal (/4' pulse signal).

When the output of event type f-2 becomes high level (hereinafter referred to as ■ level), the 7-bit differential flop 8 enters a state of waiting for a signal from the receiver 7, and when it receives a signal from the receiver 7, it is set and outputs it. Raise Q to H level, and lower than event timer 2's output color level C to L level. ), it is reset and the level of its output Q is lowered to L level.

And dart 9 has an output Q of flip 70 and 768 that is H.
While at level, the clock pulses output from the clock oscillator 1 are passed through the counter 11.

The hit counter 10 is the output Q of one flip 7°70 knob 8
The number of occurrences of the event time is counted by counting the number of times that the event time rises to H level, and the counter 1 is counted until the number of occurrences of the event time reaches the set number.
Outputs an enable signal that sets 1 to the counting operation state.

The counter 11 counts the clock pulses that have passed through the AND gate 9, and cumulatively counts the number of clock pulses for the set number of occurrences of an open can in which the enable signal from the hit counter 10 is present, that is, an event time.

The processor 12 constitutes a time calculation means, and receives event time occurrence number information from the hit counter 10, reference time information from the event timer 2, and the counter 11.
The event time is calculated based on the count information from.

Next, the operation will be explained.

The clock oscillator 1 always oscillates clock pulses with a constant period t. This clock pulse from the clock oscillator 1 is input to the timer 3, and is divided into a constant period nt.
Each time this pulse signal is input to the driver 4, a drive pulse current is supplied from the driver 4 to the light emitting element 5, and the light emitting element 5 projects light toward the target.

The pulse signal output from the timer 3 is also input to the event timer 2, and the event timer 2 receives the pulse signal from the timer 3 for a certain period of time (reference time) TI from the time when the light emitting element 5 emits light. During the
The 7 rig 70 tube 8 is reset by outputting an H level signal.

As a result, the 717 lag flop 8 enters the waiting state for the set signal (output signal of the receiver 7).

The reference time T1 is set to be longer than the expected maximum measurement time and equal to or shorter than the light projection period (the period of the output of the timer 3 and the base pulse signal).

The light projected from the light emitting element 5 is reflected by the target object and enters the light receiving element 6. The time from when the light is projected until the reflected light is incident corresponds to the event time,
In this embodiment, the event time is the round trip propagation time of the light to the target.

When reflected light is incident on the light receiving element 6, the receiver 7 checks the incident level of the reflected light, and when the receiver 7 detects that the level is above a certain level L, the flip frog 80 is activated.
A pulse signal is sent to the set terminal S to flip the flip 70.
The level of output Q of Tsug 8 is raised from L level to H level. This opens the AND gate 9 and the clock pulse from the clock oscillator 1 is input to the input terminal IN of the counter 11.

On the other hand, the hit counter 10 increments at the rising edge of the level of the output Q of the flip-flop 8, and outputs an enable signal to the counter 11 to enable the counter 11 to perform counting operations. The clock pulses generated are counted by the counter 11.

When the reference time T1 has elapsed since light was projected from the light emitting element 5, the output of the event timer 2 is inverted to L level, and the flip-flop 8 is thereby reset.
The level of the output Q is inverted to L level. This closes the gate 9 and stops inputting the clock signal from the clock oscillator 1 to the counter 11. That is,
A clock pulse is inputted to the counter 11 for a time corresponding to the difference between the reference time T1 and the event time T2, and the number of clock pulses is counted.

The above operation is one cycle of measurement, and this measurement cycle is repeated a set number of times. That is, the hit counter 10 increments every time the level of the output Q of the flip-flop 8 rises to count the number of occurrences of the event time, and the enable signal is activated until the count value reaches the set value from 1. Since the counter 11 is maintained in a counting operable state by continuously outputting , the counter 11 integrates the number of clock pulses inputted in each measurement cycle for the set number of times set by the hit counter 10.

Based on the above operations, the processor 12 calculates the time (event time) T2 from the time of light emission to the time of light reception, for example, according to the processing flow shown in FIG. This calculation process will be explained below.

The memory (not shown) of the processor 12 stores in advance the reference time T1 and the number of measurement cycles required for one measurement process (setting value of the number of event times to be accumulated set in the hit counter 10, hereinafter referred to as the number of events). This is called a set value.

) SA is stored.

When the arithmetic processing by the processor 12 is started, the processor 12 first reads out the event count setting value SA from its memory, reads the current count value S of the hit counter 10, compares the two, and determines whether the two match. Decide whether or not. This judgment control is repeated until the hit counter count value S matches the event count setting value SA.

When the hit counter count value S matches the event count setting value SA, the processor 12 outputs the cumulative count value S of the counter 11 at that time! 1 is read and the average number of clock pulses KA per counting cycle is calculated by KA=SB/SA.

Next, the processor 12 reads the reference time T1 set in the event timer 2 from its memory, and calculates the event time T2 from the average clock pulse number KA and the period t of the clock pulses by T2-Tl-KA-t. do. That is, the above "KA-t" is from the end of the event time to the end of the reference time TI.

The time to the point sb is subtracted from the reference time T1 to calculate the event time, that is, the time from the time the light is projected to the time the reflected light is received from the target object. can.

When the calculation of the event time T2 is completed as described above, the processor 12 clears the count values of the hit counter 10 and the counter 11, and prepares for the next measurement operation.

In the above operation, if the event count setting value SA and the reference time T1 are variable depending on the measurement conditions (
However, these remain unchanged as long as the measurement control is performed only once.

), these values sA and Tl may be received from the event timer 2 and the hit counter 10 each time.

Further, in a system that measures the length of an event time every time the event time occurs, the event count setting value SA is not required.

Next, the operation when the light emitted from the light emitting element 5 cannot be received by the light receiving element 6 or when the light receiving signal level does not reach the specified value t will be described.

At this time, the receiver 7 does not send out the pulse signal that occurs when receiving light, so the free lag flop 8 is not set.
The level of the output Q remains at the L level and does not change. Therefore, since the hit counter 10 does not increment and the AND/DART 9 remains closed, the counter 11 also does not increment its integrated count value in the measurement cycle. That is,
For sections where light is emitted but the reflected light from the target cannot be confirmed, it is one black and one hundred tons of Kupalus! Since no white body is generated during i-motion, and this section is not included in the measurement cycle, there is no need for the processor 12 to correct the count value due to the inability to receive light.

The embodiment described above is an example in which the present invention is implemented to measure the time between light emission and reception in an optical pressure measurement system. This can be implemented in any system in which the time is calculated based on the counting of clock pulses.

(Effects of the Invention) As described above in detail, according to the present invention, the counting of clock pulses is started by the second signal (light reception signal) that occurs later. The present invention has extremely remarkable advantages, such as eliminating the need to correct the count value of the counter by subtracting the count value, which was conventionally required when reception is not possible, simplifying the signal processing, and simplifying the signal processing already performed. It is effective.

[Brief explanation of drawings]

The drawings are for detailed explanation of the present invention, and the first drawing is for explaining the invention in detail.
FIG. 2 is a block diagram, FIG. 2 is a time chart explaining the operation, and FIG. 3 is a flow chart explaining control in the processor. (Main symbols) 1...Clock oscillator 2...Reference time setting timer (event timer) 5
...Light emitting element 6...Light receiving element 8...Set reset flip flag circuit
) 11... Clock pulse number integration counter (counter) 12... Time calculation processing unit (processor) Figure 2 Section 3 ○HiD

Claims (1)

[Claims] In a time counting device that measures the time from the occurrence of a first signal to the occurrence of a second signal by counting clock pulses, the time of occurrence of the first signal is the starting point,
a reference time setting means for setting a constant length of time longer than the time to be measured as a reference time; and a counter for counting the number of clock pulses input from the generation of the second signal until the end of the reference time. and a time calculation means configured to calculate the time between the first signal and the second signal from the count value of the counter based on the reference time.