JP7825281B2 - Delay Time Measurement System - Google Patents

Description

This invention relates to a delay time measurement system that accurately measures the time required for a series of operations to be performed between remote locations by a device under test that captures, transmits, and displays video and other data using a satellite positioning system such as the Global Positioning System (GPS). Measurement targets are not limited to video, but also include audio and haptics.

There are many ways to measure video delay time, including inserting a timestamp, capturing and displaying a clock, and measuring round-trip time using ICMP (Internet Control Message Protocol), one of the protocols for IP (Internet Protocol) networks.

In the method using timestamps, the video sending side sends information with an accurate time stamp along with the video signal, which is then transmitted through the system under test and analyzed on the receiving side. For example, details of this method are described in Patent Document 1. However, this method cannot measure the delay time that occurs inside the video cameras and displays included in the system under test, and can only measure the delay time of part of the system. Furthermore, in addition to the original video signal, a signal with a timestamp must be inserted on the video sending side and extracted on the receiving side, making the measurement system complicated.

A method for capturing and displaying a clock is described, for example, in Patent Document 2, in which an image of the clock is captured using a video camera in the system under test, and the image displayed on the display of the system under test after transmission is compared with the image of the clock at that time to calculate the delay time. While this system is capable of measuring delay times including the video camera and display, it has the drawback of being inaccurate because it cannot accurately capture changes in the clock display.

Measurements using ICMP, one of the IP network protocols, i.e., the so-called ping command, are widely used, and there is no need to cite any literature on this subject. However, this only targets round-trip delay time, and is limited to measurements transmitted over IP networks. Furthermore, it cannot measure delays including those from video cameras and displays.

Another method is shown in Non-Patent Document 1. In this method, a light source blinks using a measuring device, and the image is captured and transmitted using a video camera in the system under test. The blinking image displayed on the display is then converted into an electrical signal using an optical sensor, and the delay time is measured from the response.

Figure 1 shows the configuration. In Figure 1, 1 is a light source, such as a light-emitting diode (LED), and 2 is an optical sensor, such as a photodiode (PD). 3 is a reference signal generator that outputs a predetermined rectangular wave under the control of controller 7. 4 is a light source driver that generates a signal to drive light source 1 from the signal from reference signal generator 3. 5 is a trigger signal generator that inputs the signal from reference signal generator 3 and generates a signal to be applied to waveform measurement unit 6. The timing of signal changes from light source driver 4 and trigger generator 5 is identical. Waveform measurement unit 6 measures the waveforms of the signals from optical sensors 2 and 5 and the signal from trigger generator 5. The waveform acquired by waveform measurement unit 6 is sent to controller 7, where it is analyzed and the delay time is calculated. Controller 7 is, for example, a personal computer, and the delay time calculation result is displayed on its display. 10 is the system under test, which includes a video camera 11, a video transmission system 12, and a display 13.

This operation is shown in the timing chart of Figure 2. When the light source drive signal, i.e., the trigger signal, is low level, light source 1 is turned off, and when it is high level, the light source is turned on. The output of video camera 11 of system under test 10, which captures an image of the light source, is displayed on display 13 via video transmission system 12. The delay time of this operation is a delay in the light intensity signal output from optical sensor 2, as shown in Figure 2, and the delay time can be measured by analyzing it in controller 7, such as the time indicated by T1 when light source 1 goes from off to on, and the time indicated by T2 when it goes from on to off.

The configuration in Figure 1 does not use timestamps, so the video signal under test is left untouched, and it can measure all delays from the video camera to the display. Furthermore, it uses two values, the on/off state of the light source, so it can simply calculate delay time. Unlike the ICMP protocol, it is not limited to transmissions using IP networks, and can evaluate one-way delays in any video transmission system.

The delay time measurement system in Figure 1 assumes that the video camera 11 and display 13 of the system under test 10 are located close to each other, at a distance that allows the measurement signals to be connected appropriately via cable. However, if the video camera 11 and display 13 of the system under test 10 are installed in remote locations and it is desired to measure the delay time between them, it is common to achieve time synchronization using GPS, as shown in Figure 3. Note that it is also possible to use GNSS (Global Navigation Satellite System), which includes not only GPS but also other satellite positioning systems; GPS as used in this specification is a general term for satellite positioning systems.

In Figure 3, GPS receiver 1 (21) and GPS receiver 2 (31) are installed at different locations. When receiving signals in locations with good signal reception, the GPS receiver's time accuracy typically achieves an error of approximately ±10 nanoseconds relative to absolute time. Meanwhile, the system being measured typically has a video signal frame rate of, for example, 60 Hz, and this period should desirably be shorter than 16.7 milliseconds. The signal from the GPS receiver has sufficient accuracy. Based on this signal from GPS, controller 1 (23) and controller 2 (24) control reference signal generator 1 (22) and reference signal generator 2 (32) to generate a specific rectangular wave. The output of reference signal generator 1 (22) drives light source 2 via light source driver 4. Meanwhile, the output of reference signal generator 2 (32) is applied to waveform measurement unit 6 via trigger generator 5. The outputs of reference signal generator 1 (22) and reference signal generator 2 (32) are precisely synchronized by the GPS function, and are considered identical signals generated by a single reference signal generator. When configured in this way, the same operation as the timing chart shown in Figure 2 can be achieved, making it possible to measure delay times between remote locations.

However, another issue is that in the configuration shown in Figure 3, Controller 1 (23) and Controller 2 (33) must communicate with each other and control the entire measurement system to ensure consistent operation. While this communication can be achieved using the Internet, for example, it is cumbersome. Furthermore, it is necessary to have Reference Signal Generator 1 (22) and Reference Signal Generator 2 (32), respectively, and the control of these is also cumbersome.

Furthermore, if you want to measure delay time in a remote location, you would use the configuration shown in Figure 3, and if you want to measure delay time over a short distance, you would use the configuration shown in Figure 1, but each requires controller control software suitable for that purpose. This requires both hardware and software switching depending on the distance, which is cumbersome. It would be desirable to be able to measure delay time even when synchronized with GPS by using the same software used for short-distance measurements without modification, without creating GPS-compatible software.

To solve the above problem, the device is configured as follows: a light source installed at a first location is turned on and off by a light source drive signal, and in the system under test, the image of the light source is converted into a video signal by a video camera and transmitted, and then an image of the light source displayed on a display of the system under test is converted into an electrical signal by an optical sensor at a second location, and a time difference between the change in the light source drive signal and the electrical signal from the optical sensor is measured;
When the first point and the second point are located far apart, a first GPS receiver is installed at the first point and a second GPS receiver is installed at the second point, and the signals from the first GPS receiver and the second GPS receiver are used as the time reference at each point; when the first point and the second point are located close to each other, no GPS receivers are used, and the signal from a single reference signal generator connected by electrical wiring is used as the time reference;
Even when the first and second GPS receivers are used, a controller that controls the entire system is installed only at the second location, and control of time synchronization at the first location is not performed by instructions from the controller via communication, but is performed solely by signals from the first GPS receiver installed at the first location;
The controller software uses the same software as that which operates without signals from the first and second GPS receivers, and establishes a delay time measurement system that measures a predetermined time difference.

This configuration allows the first GPS receiver and the second GPS receiver to appear as if they were a single reference signal generator, making it easy to switch between a configuration using GPS for measuring delay times between distant locations and the configuration shown in Figure 1 for measuring delay times over short distances without GPS. Furthermore, there is no need to switch software. The same software used for short-distance measurements can be used without modification when using GPS to measure delay times. Furthermore, since the controller does not issue instructions for measurement to a remote location, i.e., no communication for measurement is performed from point 2 where the controller is installed to point 1 where the controller is not installed, a simple system can be realized.

Patent No. 3892844 Patent No. 5553409

Taro Ogawa and Hiroyuki Matsuura, "Zero-Delay Optical Video Transmission Technology and Its Applications," Large Display & Digital Signage Overview 2020, pp. 12-22, Japan Social Systems Laboratory, 2020.

However, to effectively use GPS signals, it is desirable to perform reception in a location where the entire sky can be seen, such as the rooftop of a building or an open space with no nearby buildings. However, the location where the measurement target for delay time measurement is located is often a location where GPS signals cannot reach, such as inside a reinforced concrete building. While it would be ideal to address this issue by extending the electrical cables used for signal connection, situations can easily arise where this is difficult.

Depending on the distance between the video camera and the display under test, if GPS is not used as the reference, one method is to lay a long cable or the like to share a reference timing signal between the vicinity of the video camera 11 under test and the vicinity of the display 13. However, laying a cable is generally not easy, so a method is desired that allows some kind of reference signal timing to be shared between the vicinity of the video camera 11 under test and the vicinity of the display 13 under test.

The main premise is as follows: the device drives an actuator installed at a first location on and off with a driving electrical signal, senses and transmits this with the system under test, converts the physical quantity output from a second location of the system under test into an electrical signal with a sensor, and measures the time difference between the change in the driving electrical signal and the electrical signal from the sensor.

Further, the following is a prerequisite: With respect to a timing holding unit that determines at least one of the timing of the change in the drive electrical signal and the timing of the change in the electrical signal from the sensor,
synchronizing the timing keeper to a reference timing signal from a reference timing generator;
a step of moving the timing holding unit to the vicinity of the object to be measured while maintaining operation by a battery;
measuring a time difference using the output signal of the timing holder;
moving the timing holding unit to a position near the reference timing generator while maintaining its operation on a battery;
A delay time measurement procedure is executed in which the output signal of the timing holder is compared with that of the reference timing generator, and the time error of the timing holder is measured.

The timing holding section is configured as follows.
High- stability crystal oscillator and
a frequency divider circuit that divides the frequency of the output of the high stability crystal oscillator;
a waveform shaping circuit that outputs the output of the frequency divider circuit as the output of a timing holding unit;
a clear pulse generating circuit that generates a clear signal from an input timing signal;
a switch for switching whether or not the clear signal is applied to the frequency divider circuit;
a comparison circuit that outputs a pulse corresponding to the time difference between the output of the frequency divider circuit and the reference timing signal ;
The comparator has at least one of a circuit that counts and displays the output pulse width of the comparator using clock pulses, and a circuit that displays when the output pulse width exceeds a preset threshold value.

The problems described in this specification can be solved by using a delay time measurement system characterized by having the above-mentioned timing holding unit.

The location where GPS signals can be received and time information can be calculated is preferably a location with a view of the entire sky, such as the rooftop of a building or an open space with no nearby buildings. However, this is not limited to these locations, and the GPS receiver can be operated in any location where it operates without any interference. The output timing of the GPS receiver is transmitted to a timing keeper, which then keeps it there. The timing keeper runs on battery power and moves to the vicinity of the measurement target where the delay time is to be measured. Even if the measurement target is located inside a reinforced concrete building, where GPS signals cannot reach, the timing is maintained by the timing keeper, allowing the measurement of the target's delay time to be performed accurately. Furthermore, after the delay time measurement is complete, the timing keeper can be connected to the GPS receiver again while running on battery power, allowing the timing error to be checked, thereby confirming the accuracy of the delay time measurement.

When GPS signals are not used, a reference signal can be shared between two locations by copying the first timing keeper to a free-running second timing keeper and moving the first and second timing keeper to each of the two locations, eliminating the need to lay long cables.

1 is a diagram illustrating a conventional example of a delay time measurement system that does not use GPS. 2 is a timing chart showing the operation of FIG. 1; 1 is a diagram illustrating a conventional delay time measurement system using GPS. 1 is a diagram illustrating the concept of a first embodiment of the present invention. FIG. 5 is an explanatory diagram of when the timing holding unit in FIG. 4 is used. FIG. 2 is a diagram showing details of an embodiment of the present invention. 7 is a first timing chart showing the operation of FIG. 6. 7 is a second timing chart showing the operation of FIG. 6. FIG. 2 is a second diagram showing details of an embodiment of the present invention. FIG. 10 is a diagram illustrating the concept of a second embodiment of the present invention. FIG. 11 is an explanatory diagram when the timing holding unit in FIG. 10 is used.

The first embodiment is shown in Figure 4. Here, the output signals of GPS receiver 1 (21) and GPS receiver 2 (31) are signals with an accurate 1-second period known as 1PPS (1 Pulse Per Second), and the timing of their changes matches the absolute time with an error of, for example, ±10 nanoseconds. This 1PPS signal is often output as standard from commercially available components and devices used as ordinary GPS receivers. However, the outputs of GPS receiver 1 (21) and GPS receiver 2 (31) are configured to output signals with a specified duty cycle, for example, a 50% duty cycle. If the components used do not have this, the above can be achieved by adding appropriate circuitry.

A timing hold unit 1 (29) is provided, which is a device that copies the output signal of GPS receiver 1 (21). Details of its internal structure will be described later, but timing hold unit 1 (29) is configured to apply the signal from GPS receiver 1 (21) and, by being designated to hold it, continue to generate a 1PPS signal as an output even if the input signal is cut off. The same is true for timing hold unit 2 (39), which applies the signal from GPS receiver 2 (31) and, by being designated to hold it, continues to generate a 1PPS signal as an output even if the input signal is cut off.

Figure 5 is an explanatory diagram of the first embodiment, showing the measurement procedure. First, connect timing hold unit 1 (29) and timing hold unit 2 (39) to GPS receiver 1 (21) and GPS receiver 2 (31), and specify that a 1PPS signal be applied and held to perform synchronization. Next, disconnect timing hold unit 1 (29) and timing hold unit 2 (39) from GPS receiver 1 (21) and GPS receiver 2 (31), and physically move timing hold unit 1 (29) and timing hold unit 2 (39) near the object under test. Timing hold unit 1 (29) and timing hold unit 2 (39) are configured to operate on batteries, making them easy to move. Timing hold unit 1 (29) is connected to light source drive unit 5, and timing hold unit 2 (39) is connected to trigger generator 5.

At the point where the video camera 11 of the system under test 10 is installed, the output of the timing holding unit 1 (29) is connected to the light source driving unit 4, so that the light source 1 repeatedly turns on and off with a duty cycle of 50% at a one-second interval precisely synchronized with absolute time.

At the point where the display 13 of the system under test 10 is installed, the output of timing holding unit 2 (39) is connected to trigger generator 35, so that a trigger signal with a 50% duty cycle is output from trigger generator 5 at a 1-second period related to the blinking of the light source.

The waveform measurement unit 5 receives signals from the optical sensor 2 and trigger generator 5, sends the data to the controller, analyzes the waveform, and measures the delay time. Despite being in a remote location, it operates as if the signal were coming from a single reference signal generator.

This completes the delay time measurement, but it is desirable to verify that the timing hold unit continues to operate correctly after the series of measurements is complete. To do this, connect it to the GPS receiver again and provide a function to measure the timing error.

The procedure is as follows: after measuring the delay time in Figure 5, Timing Hold Unit 1 (29) and Timing Hold Unit 2 (39) are disconnected from the Light Source Driver 4 and Trigger Generator 5. Timing Hold Unit 1 (29) and Timing Hold Unit 2 (39) are then physically moved and connected near GPS Receiver 1 (21) and GPS Receiver 2 (31), respectively.

Timing Hold Unit 1 (29) has the function of measuring and displaying the difference between the 1PPS signal from GPS Receiver 1 (21) and the internal timing of Timing Hold Unit 1 (29). This allows for verification of timing fluctuations after delay measurement. The same applies to Timing Hold Unit 2 (39).

Note that if GPS reception is not possible at either the location where the video camera 11 of the system under test 10 is installed or the location where the display 13 is installed, the timing holding unit will be used at that location as described above. In other words, if GPS reception is possible at that location without any problems, there is no need to use the timing holding unit.

The configuration and operation of timing hold unit 1 (29) and timing hold unit 2 (39) are described in detail below using Figure 6.

The high-stability crystal oscillator 101 is an oscillator with an accurate output frequency and little fluctuation over long periods of time, such as an oven-controlled crystal oscillator (OCXO) or a temperature-compensated crystal oscillator (TCXO). For the purposes of explanation, the output frequency is assumed to be 10 MHz. This is applied to the clock input of the 7-digit decimal counter 102. The output of the 7-digit decimal counter 102 then becomes 1 Hz, which is 10 MHz divided by 10,000,000. This alone is not synchronized with timing pulses from a GPS receiver or the like, so an appropriate clear pulse is applied to the 7-digit decimal counter 102.

Figure 7 shows a timing chart. The timing input from a GPS receiver or similar device has a 1-second period. This falling edge is detected by clear pulse generator circuit 1 (103) and a pulse is generated. When switch 104 in Figure 6 is connected to the synchronous side, this is applied to the clear input of the 7-digit decimal counter, and its state becomes 0. When the clear pulse is released, it counts up with the arrival of a 10 MHz pulse from the clock input.

If an operator manually flips switch 104 to the hold position, the output of clear pulse generator 1 is no longer applied to 7-digit decimal counter 102. The 7-digit decimal counter reaches a maximum value of 9,999,999 (1E7-1), then returns to 0 and counts up again. This is a free-running state without external synchronization. In this state, the counter is powered by a battery or other power source and moved near the device under test to measure the delay time. Because the frequency of high-stability crystal oscillator 101 is extremely stable, the amount of deviation is extremely small. For example, if the frequency error of high-stability crystal oscillator 101 is +1E-8, the timing error after one hour, i.e., 3600 seconds, is 1E-8 x 3600 = 0.00003600 = 0.036 milliseconds. When measuring video transmission delay, the frame time for 60 Hz video is approximately 16.7 milliseconds, so 0.036 milliseconds is sufficient accuracy.

In this way, a 1 Hz signal is obtained, which is the output of the 7-digit decimal counter. This is then shaped to a level suitable for use in the delay measurement system, and output as pulse output 1 via pulse shaping circuit 1 (105). This generates the pulses required for delay measurement, i.e., outputs from timing hold units 29 and 39.

Next, we will use the configuration diagram in Figure 6 and the timing chart in Figure 8 to explain the operation for verifying whether timing hold unit 1 (29) and timing hold unit 2 (39) continue to operate correctly after delay time measurement is completed. By reconnecting timing hold units 29 and 39 to GPS receivers 21 and 31, a 1PPS signal is applied to the timing input of the waveform hold unit. At this time, switch 104 remains in the hold state, allowing the free-run state to continue.

By comparing the timing input with the 1 Hz output of the 7-digit decimal counter 102, the timing discrepancy can be extracted. Specifically, the above two signals are applied to an exclusive OR (XOR) 111. The output of the exclusive OR 111 is high if the levels of the two input signals do not match, and low if they match. An appropriate clock is introduced to measure this pulse width. In this example, a 10 kHz signal, which is the output of the third digit from the top of the 7-digit decimal counter, is used.

The AND circuit 112 takes the logical product of the output of the exclusive OR 111 and the 10 kHz signal, and applies this to the two-digit decimal counter 114. The two-digit decimal counter 114 applies a clear pulse generated by the clear pulse generating circuit 2 (103) every time the output of the exclusive OR 111 rises, and counts up from zero. This content is displayed as a numerical value on the display circuit 115. In Figure 6, the display circuit 115 is configured with a two-digit 7-segment display, with the lower digits in 0.1 millisecond units and the upper digits in 1 millisecond units. Assuming that the frequency deviation is not large, the counting time is short and the resulting output is visible for a long time. Note that although the example of a two-digit decimal display was explained, the number of digits is not limited to two.

Also, it is not necessary to display the timing discrepancy numerically. One way is to set a threshold in advance and have an LED light up to indicate an error if that value is exceeded.

The above operation displays the timing error value in 0.1 millisecond increments for the rising and falling edges of the timing input. Since the duty ratio of both the timing input and the 7-digit decimal counter 102 is 50%, the error value for the rising and falling edges of the timing input will be the same.

Note that while the absolute value of the error is displayed in the operation described above, it is impossible to determine whether the timing input or the 1 Hz output of the 7-digit decimal counter 102 is leading or lagging. A phase lead/lag discrimination circuit is desirable. Therefore, both signals are applied to a D-type flip-flop 116. The 1 Hz output of the 7-digit decimal counter 102 is applied to the D input of the D-type flip-flop 116, and the timing input is applied to the clock input (rising edge trigger). When the 7-digit decimal counter 102 leads the timing input, the Q output of the D-type flip-flop 116 goes high, as shown in Figure 8. At this time, the Qbar output of the D-type flip-flop 116 goes low. Although not shown, when the 7-digit decimal counter 102 lags the timing input, the Q output of the D-type flip-flop 116 goes low, and the Qbar output goes high.

Using these signals, it was possible to determine which was ahead or behind. To display this, when the timing holder is ahead of the Q output of the D-type flip-flop 116, an ADVANCE display is displayed, for example, by lighting an LED lamp to that effect. Similarly, when the timing holder is behind the Qbar output of the D-type flip-flop 116, an LED lamp is lit to indicate a LAG state.

Note that if the timing error is large, the two-digit decimal counter may overflow and the correct number may not be displayed. For example, the counter overflow can be detected and an LED may light up as an error indication.

The timing error assumed here is due to a frequency error in the high-stability crystal oscillator 101. The frequency is adjusted in advance, but if the frequency deviates slightly from 10 MHz, the timing of the timing keeper will deviate in a certain direction over time after switch 104 is connected to the hold side. Using the above operation, this deviation can be confirmed after measuring the delay time.

Regarding the timing hold unit, Figure 9 shows a modified configuration from Figure 6. When measuring delay time, the output of the timing hold unit is connected to the light source driver 4 or the trigger generator 5. If the input levels of each are different, it would be cumbersome to provide dedicated units, so pulse shaping circuit 1 (105) and pulse shaping circuit 2 (106) are provided. For example, pulse shaping circuit 1 (105) has an output level suitable for connection to the light source driver 4, and pulse shaping circuit 2 (106) has an output level suitable for connection to the trigger generator 5.

An explanation of the power supply circuit has been added to the bottom left of Figure 9. Although omitted from the explanation so far, fluctuations in the power supply voltage are undesirable because they can cause frequency fluctuations when the device is coasting for long periods of time, so a circuit to stabilize the power supply voltage, such as DC-DC converter 123, is inserted. Furthermore, the timing controller must be battery-powered when moving, so if an AC power source is available, it is desirable to have a configuration that allows the use of an AC adapter as well. Therefore, both a power input for the battery and a power input for the AC adapter are provided, and these are connected via Schottky diodes 121 and 122, which have a small forward voltage drop.

So far, the operation has been described assuming that GPS receivers are installed in different remote locations and timing synchronization is performed. As a second example, another way of using the timing hold unit will be described using Figures 10 and 11.

In Figure 10, which shows the second embodiment, only Timing Hold Unit 1 (29) and Timing Hold Unit 2 (39) are used without a GPS receiver. As also shown in Figure 11, Timing Hold Unit 1 (29) is first placed in a free-running state, which serves as the timing reference. Next, the output of Timing Hold Unit 1 (29) is applied to the timing input of Timing Hold Unit 2 (39) to synchronize them. Once synchronized, the connection between Timing Hold Unit 1 (29) and Timing Hold Unit 2 (39) is disconnected. This ensures that the output of Timing Hold Unit 1 (29) and the output of Timing Hold Unit 2 (39) have the same timing.

Next, timing hold unit 1 (29) and timing hold unit 2 (39) are moved near the object to be measured, and connected to the light source driver 5 or trigger generator 5 for delay time measurement, and the delay time is measured.

In the first embodiment, which uses the 1PPS signal from the GPS receiver as the reference, the repetition period is limited to 1 second, but in the second embodiment, it is not limited to that. All that is required is that the repetition periods of timing hold unit 1 (29) and timing hold unit 2 (39) are the same, and that the duty ratio of their outputs is 50%.

To verify the timing deviation after the measurement is completed, Timing Hold Unit 1 (29) and Timing Hold Unit 2 (39) are disconnected from the Light Source Driver 4 and Trigger Generator 5. The two Timing Hold Units are again physically moved, and the output of Timing Hold Unit 1 (29) is applied to the timing input of Timing Hold Unit 2 (39). The timing difference can be measured and displayed by Timing Hold Unit 2 (39). This makes it possible to verify the timing fluctuation after the delay measurement.

So far, we have been explaining how to measure video delay. The object of measurement is not limited to video; it can also be audio, for example. In this case, what is turned on and off is the sound from the speaker instead of the light source, a microphone instead of a video camera in the system being measured, and a speaker instead of a display. The microphone receives the sound on the measurement system side. In this case, too, the present invention can be applied in the same way, converting the audio into an electrical signal, detecting it, and converting it into an electrical signal of audio intensity.

Haptics can also be measured. Haptics is a technology that obtains tactile feedback by applying force, vibration, movement, etc. to the user. In other words, the system under test has a vibration-sensing sensor instead of a video camera, and a vibration-generating actuator instead of a display. On the measurement side, an actuator that generates vibrations is installed instead of a light source, and a vibration-sensing sensor is installed instead of an optical sensor, and the intensity of the vibrations is used to measure delay.

The symbols in FIGS. 1 to 11 are as follows:
1 --- Light source
2 --- Optical sensor
3 --- Reference signal generator
4 --- Light source driver
5 --- Trigger occurs
6 --- Waveform measurement section
7 --- Controller
10 --- System under test
11 --- Video camera
12 --- Video transmission system
13 --- Display
21 --- GPS receiver 1
22 --- Reference signal generator 1
23 --- Controller 1
29 --- Timing Holder 1
31 --- GPS receiver 2
32 --- Reference signal generator 2
33 --- Controller 2
39 --- Timing Holder 2

101 --- High-stability crystal oscillator
102 --- 7-digit decimal counter
103 --- Clear pulse generator circuit 1
104 --- Switch
105 --- Pulse shaping circuit 1
106 --- Pulse shaping circuit 2
111 --- Exclusive OR (XOR)
112 --- Logical product circuit (AND)
113 --- Clear pulse generator circuit 2
114 --- 2-digit decimal counter
115 --- Display section
116 --- D-type flip-flop
121 --- Schottky barrier diode
122 --- Schottky barrier diode
123 --- DC-DC conversion

Claims (7)

An apparatus for driving an actuator installed at a first point on/off with a driving electric signal, sensing and transmitting the signal in a system under test, and then converting a physical quantity output from a second point of the system under test into an electric signal by a sensor, and measuring the time difference between the change in the driving electric signal and the change in the electric signal from the sensor, comprising:
a timing holding unit that determines at least one of the timing of the change in the driving electrical signal and the timing of the change in the electrical signal from the sensor;
synchronizing the timing keeper to a reference timing signal from a reference timing generator;
a step of moving the timing holding unit to the vicinity of the object to be measured while maintaining operation by a battery;
measuring a time difference using the output signal of the timing holder;
moving the timing holding unit to a position near the reference timing generator while maintaining its operation on a battery;
a step of comparing an output signal of the timing holding unit with an output signal of the reference timing generator to measure a time error of the timing holding unit,
High-stability crystal oscillator and
a frequency divider circuit that divides the frequency of the output of the high stability crystal oscillator;
a waveform shaping circuit that outputs the output of the frequency divider circuit as the output of a timing holding unit;
a clear pulse generating circuit that generates a clear signal from an input timing signal;
a switch for switching whether or not the clear signal is applied to the frequency divider circuit;
a comparison circuit that outputs a pulse corresponding to the time difference between the output of the frequency divider circuit and the reference timing signal ;
At least one of a circuit that counts and displays the output pulse width of the comparator circuit using clock pulses, and a circuit that displays when the output pulse width exceeds a preset threshold value;
This is a delay time measurement system that features The delay time measurement system according to claim 1, further comprising an advance/delay discrimination circuit that discriminates between an advance or delay in the change in the input timing signal and an advance/delay in the change in the output of the frequency divider circuit.
The delay time measurement system according to claim 1, wherein the reference timing generator is a receiver that outputs a time signal from a satellite positioning system.
The delay time measurement system according to claim 1, wherein the reference timing generator is a second timing holder that free-runs without being synchronized with another reference timing generator.
The delay time measurement system according to claim 1, wherein the system under test comprises a video camera that performs the sensing function of the system under test, a video transmission unit that performs the transmission function in the system under test, and a display that outputs the physical quantity of the system under test, the actuator being a light source, and the sensor being an optical sensor.
The delay time measurement system according to claim 1, wherein the system under test comprises a first microphone that performs the sensing of the system under test, an audio signal transmission unit that performs the transmission in the system under test, and a first speaker that outputs the physical quantity of the system under test , and wherein the actuator is a second speaker and the sensor is a second microphone.
The delay time measurement system according to claim 1, characterized in that the system under test comprises a first vibration sensor that performs the sensing of the system under test, a vibration signal transmission unit that performs the transmission in the system under test, and a first vibration actuator that outputs the physical quantity of the system under test , the actuator being a second vibration actuator, and the sensor being a second vibration sensor.