Delay time measurement system

Abstract

To provide means for synchronizing timing of a video sending side and a video receiving side without any cable connection when video delay measurement is performed between remote places.SOLUTION: A delay time measurement system executes the steps of synchronizing a timing holding unit with a signal of a reference timing generator, moving the timing holding unit to the vicinity of a measurement target object while maintaining the operation of the timing holding unit with a battery, measuring a delay time using an output signal from the timing holding unit, moving the timing holding unit to the vicinity of the reference timing generator while maintaining the operation of the timing holding unit with a battery, and comparing the timing holding unit with the reference timing generator to measure a time error. The timing holding unit includes a high frequency stability oscillator, a frequency dividing circuit, a waveform shaping circuit, a clear pulse generating circuit, a switch for switching application of a clear pulse, a comparison circuit that outputs a time difference between frequency dividing circuit output and reference timing input, and a circuit that displays a measurement result of the output pulse width of the comparison circuit.SELECTED DRAWING: Figure 6

Description

[Technical field]

[0001] This invention relates to a delay time measurement system that accurately measures the time required to perform a series of operations in a measurement target that captures, transmits, and displays images, etc., between remote locations using a satellite positioning system such as GPS (Global Positioning System). Measurement targets are not limited to images, but also include audio and haptics. [Background technology]

[0002] There are many examples of methods for measuring video delay time, including inserting a time stamp, capturing and displaying a clock, and measuring round trip time using ICMP (Internet Control Message Protocol), which is one of the protocols for IP (Internet Protocol) networks.

[0003] In the method using the time stamp, the video sending side sends information with an accurate time stamp together with the video signal, transmits it through the system under test, and then analyzes it on the receiving side. For example, the details are described in Patent Document 1. However, this method cannot measure the delay time that occurs inside the video camera or display included in the system under test, and can only measure the delay time of a part of the system. Also, in addition to the original video signal, it is necessary to insert a signal with a time stamp on the video sending side and extract it on the receiving side, which makes the measurement system complicated.

[0004] A method of capturing and displaying an image of a clock is described in, for example, Patent Document 2, in which an image of the clock is captured by a video camera of 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. Although this system can measure the delay time including the video camera and the display, it has an issue with its poor accuracy because it cannot accurately capture changes in the clock display.

[0005] Measurements using ICMP, one of the protocols for IP networks, i.e., the so-called ping command, are widely used, and there is no need to refer to any literature to measure delay times. However, this is only for round-trip delay times, and measurements are limited to those transmitted over IP networks. In addition, it cannot measure delay times including those of video cameras and displays.

[0006] Another method is shown in Non-Patent Document 1. In this method, a light source blinking by the measuring device is captured and transmitted by the video camera of the system under test, the blinking image shown on the display is converted to an electrical signal by an optical sensor, and the delay time is measured from the response.

[0007] The configuration diagram is shown in FIG. 1. In FIG. 1, 1 is a light source, for example, a light emitting diode (LED), and 2 is an optical sensor, for example, a photodiode (PD). 3 is a reference signal generator, which outputs a predetermined rectangular wave under the control of a controller 7. 4 is a light source driving unit, which generates a signal to drive the light source 1 from the signal of the reference signal generator 3. 5 is a trigger signal generator, which inputs the signal of the reference signal generator 3 and generates a signal to be applied to a waveform measurement unit 6. The timing of signal changes of the light source driving unit 4 and the trigger generation 5 are the same. The waveform measurement unit 6 measures the waveforms of the signals of the optical sensors 2 to 5 and the signal from the trigger generation 5. The waveforms acquired by the waveform measurement unit 6 are sent to the controller 7, which analyzes them and calculates the delay time. The controller 7 is, for example, a personal computer, and displays the delay time calculation results on its display unit. 10 is a system to be measured, which includes a video camera 11, a video transmission system 12, and a display 13.

[0008] This operation is shown in the time chart of Figure 2. When the light source drive signal, i.e., the trigger signal, is at low level, the light source 1 is turned off, and when it is at high level, the light source is turned on. The output of a video camera 11 of the system under test 10 which captures an image of the light source is displayed on a display 13 via a video transmission system 12. The delay time of this operation is a delay in the light intensity signal output from the optical sensor 2 as shown in Figure 2, and the delay time can be measured by analyzing it in the controller 7, for example, the time when the light source 1 goes from off to on is shown as T1, and the time when it goes from on to off is shown as T2.

[0009] The configuration in Figure 1 does not use timestamps, so the video signal under test is left untouched, and all delays from the video camera to the display can be measured. Furthermore, delay times can be calculated simply using the two values ​​of the light source being on and off. Unlike the ICMP protocol, it is not limited to transmissions using IP networks, and can evaluate one-way delays in any video transmission system.

[0010] The delay time measurement system in Fig. 1 is based on the premise that the video camera 11 and display 13 of the system under test 10 are close to each other and can be connected appropriately via a cable to send measurement signals. However, when 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 use GPS to achieve time synchronization as shown in Fig. 3. It should be noted that it is also possible to use the Global Navigation Satellite System (GNSS), which includes not only GPS but also other satellite positioning systems, and GPS as described in this specification is a general term for satellite positioning systems.

[0011] In Fig. 3, GPS receiver 1 (21) and GPS receiver 2 (31) are installed at the respective points. In general, when receiving signals in a location with good radio wave conditions, the time accuracy of the GPS receiver has a performance that is within an error of about ±10 nanoseconds with respect to the absolute time. On the other hand, the frame rate of a general video signal of the system to be measured is, for example, 60 Hz, and it is desirable that this period is smaller than 16.7 milliseconds. The signal from the GPS receiver has sufficient accuracy. Based on the signal from the GPS, a predetermined square wave is generated from reference signal generator 1 (22) and reference signal generator 2 (32) under the control of controller 1 (23) and controller 2 (24). The output of reference signal generator 1 (22) drives light source 2 via light source driver 4. On the other hand, 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 in time by the GPS function, and are signals that can be considered to be the same as if they were generated by a single reference signal generator. When configured in this manner, the same operation as that shown in the timing chart of FIG. 2 can be realized, making it possible to measure delay times between remote locations.

[0012] However, another problem is that in the configuration of Figure 3, controller 1 (23) and controller 2 (33) need to communicate with each other and control the entire measurement system so that there is no discrepancy in their operations. This communication can be realized, for example, using the Internet, but it is cumbersome. In addition, it is necessary to have reference signal generator 1 (22) and reference signal generator 2 (32), and the control of these is also cumbersome.

[0013] Furthermore, when measuring delay times in remote locations, the configuration shown in Figure 3 is used, and when measuring delay times in close distances, the configuration shown in Figure 1 is used, but control software suitable for each is required. This requires both hardware switching and software switching depending on the difference in distance, which is cumbersome. It would be desirable to be able to measure delay times even when synchronized with GPS by using the same software used for short-distance measurements without modification, without creating software compatible with GPS.

[0014] In order 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 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 from each other, 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 receiver is 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 for controlling 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 through communication, but is performed solely by signals from the first GPS receiver installed at the first location; The controller software uses the same software that operates without signals from the first and second GPS receivers, and establishes a delay time measurement system that measures a predetermined time difference.

[0015] In this way, the first GPS receiver and the second GPS receiver are configured to look like one reference signal generator, so that it is easy to switch between the configuration using GPS when measuring delay times between remote locations and the configuration of FIG. 1 when measuring delay times in close ranges without GPS. Furthermore, there is no need to switch software. The same software for measuring close ranges can be used without modification when using GPS to measure delay times. Furthermore, instructions for measurement from the controller are not sent to remote locations, that is, no communication for measurement is performed from point 2 where the controller is installed to point 1 where the controller is not installed, so a simple system can be realized. [Prior art documents] [Patent documents]

[0016] [Patent Document 1] Patent No. 3892844 [Patent Document 2] Patent No. 5553409 [Non-patent literature]

[0017] [Non-Patent Document 1] Taro Ogawa, Hiroyuki Matsuura, “Zero-delay optical video transmission technology and its applications,” Large Display & Digital Signage Review 2020, pp.12-22, Japan Social Systems Laboratory, 2020. Summary of the Invention [Problem to be solved by the invention]

[0018] However, to effectively use GPS signals, it is desirable to perform reception in a place where the entire sky can be seen, such as the rooftop of a building or an open space with no buildings nearby. On the other hand, the location where the measurement target for delay time measurement is located is often a place where GPS radio waves cannot reach, such as inside a reinforced concrete building. It would be ideal if we could deal with this by extending the electrical cables for signal connection, but situations where this is difficult easily arise.

[0019] Depending on the distance between the video camera and the display to be measured, if GPS is not used as a reference, there is a method of sharing a reference timing signal between the vicinity of the video camera 11 to be measured and the vicinity of the display 13 by means of laying a long cable, etc. 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 to be measured and the vicinity of the display 13. [Means for solving the problem]

[0020] The main premise is as follows: the device drives an actuator installed at a first point by turning it on and off with an electric drive signal, senses and transmits the signal with a system under test, converts the physical quantity output from a second point of the system under test into an electric signal with a sensor, and measures the time difference between the change in the electric drive signal and the electric signal from the sensor.

[0021] Further, the following is a prerequisite: Regarding 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 a timing keeper to a signal from a reference timing generator; moving the timing holding unit to a position close to an object to be measured while maintaining operation by a battery; measuring a time difference using the output signal of the timing holding unit; moving the timing holding unit to a position close to the reference timing generator while maintaining the timing holding unit powered by a battery; A delay time measurement procedure is executed which sequentially executes a step of comparing the output signal of the timing holding unit with that of the reference timing generator and measuring the time error of the timing holding unit.

[0022] The timing holding section is configured as follows. A high frequency stability oscillator; a frequency divider circuit for dividing 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 an output of a timing holding unit; a clear pulse generating circuit for generating 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 timing input; The comparator circuit has at least one of a circuit that counts and displays the output pulse width of the comparator circuit by clock pulses, and a circuit that displays when a preset threshold value is exceeded.

[0023] The problems described in this specification can be solved by using a delay time measuring system characterized by having the above-mentioned timing holding unit. Effect of the Invention

[0024] A place where the GPS signal can be received and time information can be calculated is preferably a place where the whole sky can be seen, such as the rooftop of a building or an open space with no buildings nearby. The GPS receiver can be operated in any place where it can operate without any problems. The output timing of the GPS receiver is transmitted to the timing keeper and is kept there. The timing keeper moves to the vicinity of the measurement target for which the delay time is to be measured while being operated by a battery. Even if the measurement target is installed in a place where GPS radio waves cannot reach, such as inside a reinforced concrete building, the timing is kept by the timing keeper, so that the delay time of the measurement target can be measured correctly. Furthermore, after the measurement of the delay time is completed, the timing keeper can be connected to the GPS receiver while being operated by a battery again to check the timing error, so the accuracy of the delay time measurement can be confirmed.

[0025] When the GPS signal is not used, the reference signal can be shared between two points by copying the first timing keeper to a free-running second timing keeper and moving the first and second timing keeper to the two points, respectively. There is no need to take measures such as laying a long cable. [Brief description of the drawings]

[0026] [Figure 1] 1 is a diagram illustrating a conventional example of a delay time measurement system that does not use GPS. [Diagram 2] 2 is a timing chart showing the operation of FIG. 1; [Diagram 3] 1 is a diagram illustrating a conventional delay time measurement system using GPS. [Figure 4] 1 is a diagram showing the concept of a first embodiment of the present invention. [Diagram 5] FIG. 5 is an explanatory diagram of a case where the timing holding unit in FIG. 4 is used. [Figure 6] FIG. 2 is a diagram showing details of an embodiment of the present invention. [Figure 7] 7 is a first timing chart showing the operation of FIG. 6. [Figure 8]7 is a second timing chart showing the operation of FIG. 6. [Figure 9] FIG. 2 is a second diagram showing details of the embodiment of the present invention. [Figure 10] FIG. 13 is a diagram showing the concept of a second embodiment of the present invention. [Figure 11] 11 is an explanatory diagram when the timing holding unit in FIG. 10 is used. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0027] 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 period of 1 second, called 1PPS (1 Pulse Per Second), whose change timing matches the absolute time with an error of, for example, within ±10 nanoseconds. This 1PPS signal is often output as standard from parts and devices sold commercially as normal GPS receivers. However, the outputs of GPS receiver 1 (21) and GPS receiver 2 (31) are configured to output signals with a specified duty ratio, for example a 50% duty cycle. If the parts used do not have this, the above can be achieved by adding appropriate circuits.

[0028] A timing hold unit 1 (29) is prepared, which is a device that copies the output signal of the GPS receiver 1 (21). The internal details will be described later, but the timing hold unit 1 (29) is configured to apply a signal from the GPS receiver 1 (21) and to continue to generate a 1PPS signal as an output even if the input signal is cut off by being specified to hold the signal. The same is true for the timing hold unit 2 (39), which applies a signal from the GPS receiver 2 (31) and to continue to generate a 1PPS signal as an output even if the input signal is cut off by being specified to hold the signal.

[0029] FIG. 5 is an explanatory diagram of the first embodiment, showing the procedure for measurement. First, connect the timing hold unit 1 (29) and timing hold unit 2 (39) to the GPS receiver 1 (21) and GPS receiver 2 (31), and perform a synchronous operation by specifying to apply and hold a 1PPS signal. Next, disconnect the timing hold unit 1 (29) and timing hold unit 2 (39) from the GPS receiver 1 (21) and GPS receiver 2 (31), and physically move the timing hold unit 1 (29) and timing hold unit 2 (39) to the vicinity of the object to be measured. The timing hold unit 1 (29) and timing hold unit 2 (39) are configured to operate on batteries, so they can be easily moved. The timing hold unit 1 (29) is connected to the light source drive unit 5, and the timing hold unit 2 (39) is connected to the trigger generation unit 5.

[0030] At the point where the video camera 11 of the system under test 10 is installed, the output of the timing hold unit 1 (29) is connected to the light source drive unit 4, so that the light source 1 repeatedly turns on and off with a duty ratio of 50% in a 1-second period accurately synchronized with the absolute time.

[0031] At the point where the display 13 of the system under test 10 is installed, the output of the timing holding unit 2 (39) is connected to the trigger generator 35, so that a trigger signal with a duty ratio of 50% is output from the trigger generator 5 at a 1 second period related to the blinking of the light source.

[0032] The waveform measurement unit 5 receives signals from the optical sensor 2 and the trigger generator 5, sends the data to the controller, analyzes the waveform, and measures the delay time. Even though they are remote, they operate as if the signals were coming from a single reference signal generator.

[0033] The delay time can now be measured, but after the series of measurements is complete, it is desirable to verify that the timing hold unit is continuing to operate correctly. To do this, a function is provided to reconnect to the GPS receiver and measure the timing error.

[0034] 5, after measuring the delay time, timing hold unit 1 (29) and timing hold unit 2 (39) are disconnected from the light source drive unit 4 and trigger generator 5. Timing hold unit 1 (29) and timing hold unit 2 (39) are then physically moved near GPS receiver 1 (21) and GPS receiver 2 (31), respectively, and connected to them.

[0035] Timing Holder 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 Holder 1 (29). This makes it possible to verify the timing fluctuation after delay measurement. The same applies to Timing Holder 2 (39).

[0036] If GPS reception is not possible at least 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 is 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.

[0037] The configuration and operation of timing hold unit 1 (29) and timing hold unit 2 (39) will be described in detail with reference to FIG.

[0038] The high stability crystal oscillator 101 is an oscillator with an accurate output frequency and little fluctuation over a long period of time, such as an oven controlled crystal oscillator OCXO (Oven Controlled Crystal Oscillator) or a temperature compensated crystal oscillator TCXO (Temperature Compensated Crystal Oscillator). The explanation will be given assuming that the output frequency is, for example, 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 the timing pulse from the GPS receiver or the like, so an appropriate clear pulse is applied to the 7-digit decimal counter 102.

[0039] A timing chart is shown in Figure 7. The timing input from a GPS receiver or the like has a 1 second period. This falling edge is detected by clear pulse generation 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 at the clock input.

[0040] Here, if the operator manually turns the switch 104 to the hold side, the output of the clear pulse generating circuit 1 is no longer applied to the 7-digit decimal counter 102. The maximum value of the 7-digit decimal counter is 9,999,999 (1E7-1), and then it returns to 0 and counts up repeatedly. This is a free-running state in which no external synchronization is applied. In this state, the counter is driven by a battery or the like and moved to the vicinity of the object under test to measure the delay time. Since the frequency of the high-stability crystal oscillator 101 is extremely stable, the amount of deviation is extremely small. For example, when the frequency error of the high-stability crystal oscillator 101 is +1E-8, the timing error after one hour, i.e., 3600 seconds, is 1E-8×3600=0.00003600 seconds=0.036 milliseconds, which is an example of the numerical value of the deviation in the free-running state. When measuring the delay time of video transmission, the time for one frame is about 16.7 milliseconds for a 60 Hz video, so 0.036 milliseconds is a sufficient accuracy.

[0041] In this way, a 1 Hz signal is obtained as the output of the 7-digit decimal counter. This is then shaped into a level suitable for use in the delay measurement system, and output as pulse output 1 via pulse shaping circuit 1 (105). This allows the generation of the pulses required for delay measurement, i.e., outputs from timing hold units 29 and 39.

[0042] Next, 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 will be explained using the configuration diagram in Fig. 6 and the timing chart in Fig. 8. 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 is kept on hold to continue the free-run state.

[0043] 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 level when the levels of the two input signals do not match, and low level when they match. An appropriate clock is introduced to measure this pulse width. In this embodiment, a 10 KHz signal, which is the output of the third digit from the top of the 7-digit decimal counter, is used.

[0044] The AND circuit 112 takes the logical product of the output of the exclusive OR 111 and the 10KHz signal, and applies this to a two-digit decimal counter 114. The two-digit decimal counter 114 applies a clear pulse generated by a clear pulse generating circuit 2 (103) at each rising edge of the output of the exclusive OR 111, and performs a counting operation of counting up from zero. This content is displayed as a numerical value on a display circuit 115. In FIG. 6, the display circuit 115 is configured with a two-digit seven-segment display, with the lower digits being in units of 0.1 milliseconds and the upper digits being in units of 1 millisecond. As a premise, since the amount of frequency deviation is not large, the counting time is short, and the time during which the result output is visible is long. Although the example of a two-digit decimal display has been described, the number of digits is not limited to two.

[0045] Also, it is not necessary to display the timing difference numerically. You can set a threshold in advance and have an LED light turn on to indicate an error if the threshold is exceeded.

[0046] With the above operation, the timing error is displayed in units of 0.1 milliseconds 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 rising and falling errors of the timing input are the same.

[0047] In the above operation, the absolute value of the error is displayed, but it is not possible to determine whether the timing input or the 1 Hz output of the 7-digit decimal counter 102 is ahead or behind. It is desirable to have a phase lead / lag discrimination circuit. Therefore, both signals are applied to the 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 trigger). When the 7-digit decimal counter 102 is ahead of the timing input, the Q output of the D-type flip-flop 116 is at a high level as shown in FIG. 8. At this time, the Qbar output of the D-type flip-flop 116 is at a low level. Although not shown, when the 7-digit decimal counter 102 is behind the timing input, the Q output of the D-type flip-flop 116 is at a low level and the Qbar output is at a high level.

[0048] Using these signals, it was possible to determine which was leading or lagging. To indicate this, when the Q output of the D-type flip-flop 116 is in a state where the timing holder is leading, an ADVANCE display is displayed, for example, by lighting an LED lamp to that effect. Similarly, when the Qbar output of the D-type flip-flop 116 is in a state where the timing holder is lagging, an LED lamp is lit to indicate the LAG state.

[0049] 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 may be detected and an LED may be lit to indicate an error.

[0050] 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 is slightly off from 10 MHz, the timing of the timing keeper will shift in a certain direction over time after switch 104 is connected to the hold side. With the above operation, this shift can be confirmed after measuring the delay time.

[0051] Regarding the timing hold unit, a modified configuration from that of FIG. 6 is described in FIG. 9. When measuring the delay time, the output of the timing hold unit is connected to the light source drive unit 4 or the trigger generator 5. When the input levels of each are different, it is cumbersome to provide a dedicated unit, so a pulse shaping circuit 1 (105) and a pulse shaping circuit 2 (106) are provided, and for example, the pulse shaping circuit 1 (105) has an output level suitable for connection to the light source drive unit 4, and the pulse shaping circuit 2 (106) has an output level suitable for connection to the trigger generator 5.

[0052] An explanation of the power supply circuit is added to the bottom left of Figure 9. Although omitted from the explanation so far, fluctuations in the power supply voltage are undesirable as they cause frequency fluctuations when free-running for long periods of time, so a circuit that stabilizes the power supply voltage, such as a DC-DC converter 123, is inserted. Also, it is essential that the timing hold unit is 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 in combination. Therefore, both a power supply input for the battery and a power supply input for the AC adapter are provided and connected via Schottky diodes 121 and 122, which have a small forward voltage drop. EXAMPLES

[0053] Up to this point, the operation has been described on the assumption that timing synchronization is performed by installing GPS receivers at remote locations. As a second embodiment, another way of using the timing hold unit will be described with reference to Figs.

[0054] In Fig. 10 showing 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 Fig. 11, first timing hold unit 1 (29) is set to a free-run state, which is used 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 cut. This ensures that the output of timing hold unit 1 (29) and the output of timing hold unit 2 (39) have the same timing.

[0055] Next, the timing hold unit 1 (29) and the timing hold unit 2 (39) are moved close to the object to be measured and connected to the light source drive unit 5 or the trigger generator 5 for delay time measurement to measure the delay time.

[0056] In the first embodiment, which uses the 1PPS signal from the GPS receiver as a 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%.

[0057] 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 drive unit 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.

[0058] The explanation so far has been about measuring 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, the video camera of the system under test is replaced by a microphone, and the display is replaced by a speaker. The microphone receives the sound on the measurement system side. In this case too, the present invention can be applied in the same way, where the audio is converted into an electrical signal, which is then detected and converted into an electrical signal of audio intensity.

[0059] Haptics can also be measured. Haptics is a technology that obtains skin sensation feedback by applying force, vibration, movement, etc. to the user. In other words, the system to be measured has a sensor that senses vibration instead of a video camera, and an actuator that generates vibration instead of a display, and the measuring side has an actuator that generates vibration instead of a light source and a sensor that senses vibration instead of a light sensor, and the intensity of the vibration is used to measure the delay. [Explanation of symbols]

[0060] 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 --- 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

1. An apparatus for driving an actuator installed at a first point by turning it on and off with a driving electric signal, sensing and transmitting the signal in a measured system, converting a physical quantity output from a second point of the measured system into an electric signal by a sensor, and measuring a time difference between a change in the driving electric signal and the electric signal from the sensor, comprising: A timing holding unit that determines at least one of a timing of a change in the driving electrical signal and a timing of a change in the electrical signal from the sensor, synchronizing a timing keeper to a signal from a reference timing generator; moving the timing holding unit to the vicinity of an object to be measured while maintaining operation by a battery; measuring a time difference using the output signal of the timing holding unit; moving the timing holding unit to a position close to the reference timing generator while maintaining the timing holding unit powered by 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, A high frequency stability oscillator; a frequency divider circuit for dividing 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 an output of a timing holding unit; a clear pulse generating circuit for generating 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 timing input; At least one of a circuit for counting and displaying the output pulse width of the comparator circuit by a clock pulse, and a circuit for displaying when the output pulse width exceeds a preset threshold value; This is a delay time measurement system that features

2. The delay time measuring system according to claim 1, further comprising an advance / delay discrimination circuit for discriminating between an advance or delay of the change in the input timing signal and an advance or delay of the change in the output of the frequency divider circuit.

3. The delay time measurement system according to claim 1, characterized in that the reference timing generator is a receiver that outputs a time signal from a satellite positioning system.

4. 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.

5. The delay time measuring system according to claim 1, characterized in that the system under test comprises a video camera, a video transmission unit, and a display, the actuator is a light source, and the sensor is an optical sensor.

6. The delay time measuring system according to claim 1, characterized in that the system under test comprises a first microphone, an audio signal transmission section, and a first speaker, the actuator is a second speaker, and the sensor is a second microphone.

7. The delay time measurement system according to claim 1, characterized in that the system under test comprises a first vibration sensor, a vibration signal transmission section, and a first vibration actuator, the actuator being a second vibration actuator, and the sensor being a second vibration sensor.

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