Delay time measuring device

Abstract

To provide a delay time measuring device with which it is possible to more accurately measure a delay time.SOLUTION: A phase difference calculation unit 13 establishes a multiple N of light emission cycle needed for transition of timing from a state where the beginning of a video signal frame in which a light emission unit 10 is imaged by a video camera matches the beginning of on-transition of a light emission cycle to a state where the timing of the beginning of the frame matches the beginning of on-transition of the light emission cycle again. A light emission schedule determination unit 15 determines a light emission schedule of the light emission unit 10 in which the phase of the light emission cycle is shifted from 0 times to n times the unit time, for each N light emission cycle that is N times the light emission cycle. A light emission on / off control unit 16 turns the light emission unit 10 on and off according to the light emission schedule. A received light signal acquisition unit 21 acquires a received light signal generated by a light reception unit 20 that receives light from a display. A delay time measurement unit 22 measures a delay time on the basis of the difference in time between the time the light emission unit 10 is turned on and a rise time of the light signal.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a delay time measuring device. [Background technology]

[0002] In some cases, a video signal generated by a video camera is transmitted by a video transmitting device to a video receiving device at a remote location, and the video receiving device receives the video signal and displays it on a display. It is sometimes necessary to measure the delay time, which is the time between when the video camera generates the video signal and when the display displays the video signal (see Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-172539 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for a more accurate measurement of the delay time between when a video camera generates a video signal and when a display displays the video signal. An object of the present invention is to provide a delay time measuring device that can more accurately measure the delay time between when a video camera generates a video signal and when a display displays the video signal. [Means for solving the problem]

[0005] The present invention includes a phase difference calculation unit that calculates, based on an imaging frame rate when a video camera images a light emitting unit as a subject and an emission cycle for turning the light emitting unit on and off, where N is an integer of 2 or more, a multiple N of the emission cycle required to bring the timing of the beginning of a frame of a video signal generated by the video camera capturing the light emitting unit into alignment with the beginning of an on-state of the emission cycle again from a state in which the timing of the beginning of a frame of the video signal and the beginning of an on-state of the emission cycle are aligned; an emission schedule determination unit that determines an emission schedule for the light emitting unit, for every N emission cycles that are N times the emission cycle, where n is an integer of 2 or more, and sequentially increases a time by which the phase of the emission cycle is shifted by a predetermined time shorter than the time of one frame from 0 to n times the unit time; and a control unit that controls the light emitting unit to turn on and off according to the emission schedule. a light-emission on / off control unit that controls the light-emitting unit so that the video signal is transmitted to a video receiving device via a network, a light-receiving signal acquisition unit that acquires a light-receiving signal generated by a light-receiving unit that receives light emitted from the display when a video transmitting device transmits the video signal to a video receiving device via a network and the video receiving device displays the received video signal on a display; a delay time measurement unit that measures a delay time from when the video camera generates the video signal to when the display displays the video signal, based on the difference in time between the time when the light-emission on / off control unit turns on the light-emitting unit and the rise time of the light-receiving signal acquired by the light-receiving signal acquisition unit, or the difference in time between the time when the light-emission on / off control unit turns off the light-emitting unit and the fall time of the light-receiving signal acquired by the light-receiving signal acquisition unit; and a delay time determination unit that determines the minimum value of multiple delay times measured within the light-emission schedule by the delay time measurement unit as the delay time. [Effects of the Invention]

[0006] The delay time measuring device of the present invention can more accurately measure the delay time between when a video camera generates a video signal and when a display displays the video signal. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic block diagram showing a state in which a delay time measuring device according to a first embodiment is connected to a video transmission / reception system. [Figure 2] FIG. 2 is a block diagram showing the delay time measuring device according to the first embodiment. [Figure 3] FIG. 3 is a timing diagram showing the operation of the delay time measuring device according to the first embodiment. [Figure 4] FIG. 4 is a flowchart showing the operation of the delay time measurement device according to the first embodiment. [Figure 5] FIG. 5 is a block diagram showing a delay time measuring device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] The delay time measuring device according to each embodiment will be described below with reference to the accompanying drawings. First, a schematic configuration of a video transmission / reception system will be described using FIG. 1. In FIG. 1, a video camera 1 is connected to a video transmission device 2. The video transmission device 2 transmits a video signal generated by the video camera 1 capturing an image of a subject to a video reception device 4 via a network 3. The video reception device 4 receives the video signal. A display 5 is connected to the video reception device 4. The display 5 displays the video signal received by the video reception device 4.

[0009] The network 3 is, for example, an in-house LAN (Local Area Network). The location where the video camera 1 and the video transmitting device 2 are installed is usually separated by a predetermined distance from the location where the video receiving device 4 and the display 5 are installed. Here, in order to connect the delay time measuring device 100 according to the first embodiment to a video transmission and reception system, the location where the video camera 1 and the video transmitting device 2 are installed and the location where the video receiving device 4 and the display 5 are installed are set to be close to each other. In addition, the network 3 is constructed so that the two locations are virtually separated by the predetermined distance.

[0010] First Embodiment A light-emitting unit 10 and a light-receiving unit 20 are connected to the delay time measuring device 100. The light-emitting unit 10 can be configured, for example, by a light-emitting diode (LED), and the light-receiving unit 20 can be configured, for example, by a photodiode. The delay time measuring device 100 controls the light-emitting unit 10 to blink. A video camera 1 captures an image of the blinking light-emitting unit 10 and supplies the generated video signal to a video transmitting device 2. The video transmitting device 2 transmits the input video signal to a video receiving device 4 via a network 3.

[0011] The video receiving device 4 receives the video signal, and the display 5 displays the video signal received by the video receiving device 4. As a result, the image of the blinking light emitting unit 10 is displayed on the display 5. The light receiving unit 20 receives light emitted from the display 5 on which the image of the blinking light emitting unit 10 is displayed. The delay time measuring device 100 acquires the light receiving signal from the light receiving unit 20.

[0012] Here, the delay time for one emission of light from the light-emitting unit 10 is the difference between the time when the light-emitting unit 10 emits light and the time when the light-receiving unit 20 receives the light. However, the timing at which the light-emitting unit 10 emits light is not synchronized with the timing at which the video camera 1 captures the image. Therefore, depending on the timing of the light emission, a variation of up to one frame can occur in the delay time. The delay time measuring device 100 is required to measure the delay time excluding such variation due to the timing at which the light-emitting unit 10 emits light.

[0013] The specific configuration and operation of the delay time measurement device 100 will be described with reference to Fig. 2. As shown in Fig. 2, the delay time measurement device 100 includes a frame rate setting unit 11, a light emission cycle setting unit 12, a phase difference calculation unit 13, a phase shift amount setting unit 14, a light emission schedule determination unit 15, a light emission on / off control unit 16, a clock 17, a light reception signal acquisition unit 21, a delay time measurement unit 22, a memory 23, and a delay time determination unit 24.

[0014] The imaging frame rate set in the video camera 1 is set in the frame rate setting unit 11. The frame rate setting unit 11 can be configured with a non-volatile memory. The frame rate setting unit 11 may acquire and set the imaging frame rate from the video camera 1, or may set the imaging frame rate by user input. If the imaging frame rate is 60 frames / second, the time for one frame is approximately 16.6667 ms.

[0015] The light emission cycle setting unit 12 is set with a light emission cycle, which is the time for one cycle of turning the light emitting unit 10 on and off. The light emission cycle setting unit 12 can be configured with a non-volatile memory. The light emission cycle setting unit 12 sets the light emission cycle based on a user input. As an example, if the time for turning the light emitting unit 10 on is 0.06 seconds and the time for turning it off is 0.07 seconds, the light emission cycle is 0.13 seconds. The light emission cycle of the light emitting unit 10 is longer than the time for one frame, which is determined by the imaging frame rate.

[0016] The phase difference calculation unit 13 calculates the phase difference between the imaging frame rate set in the frame rate setting unit 11 and the light emission cycle set in the light emission cycle setting unit 12 as follows: The phase difference calculation unit 13 divides the light emission cycle by the time of one frame. In the above example, the result is 7.8, which is 0.13 seconds divided by (1 second / 60 frames). The integer part "7" in 7.8 indicates a multiple of 2π (=360 degrees), and the decimal part "0.8" indicates the phase difference. 0.8 means a phase difference of 288 degrees, or 72 degrees (360 degrees - 288 degrees). When the phase difference between the imaging frame rate and the light emission cycle is 288 degrees (or 72 degrees), multiplying the phase difference by 5 results in a multiple of 360 degrees.

[0017] Let's assume that the timing of the beginning of a frame of the video signal coincides with the timing of the beginning of the ON phase of a light emission cycle. In this case, the timing of the beginning of the ON phase of the fifth light emission cycle will again coincide with the timing of the beginning of the frame. Let N be the integer number representing a multiple of 360 degrees based on the phase difference calculated by dividing the light emission cycle by the time of one frame and taking the decimal point of the value. Multiple N is the multiple of the light emission cycle required to return from a state in which the timing of the beginning of the frame of the video signal coincides with the timing of the beginning of the ON phase of the light emission cycle to a state in which the timing of the beginning of the frame coincides with the timing of the beginning of the ON phase of the light emission cycle. In this case, phase difference calculation unit 13 outputs "5" as multiple N.

[0018] The phase shift amount setting unit 14 sets a phase shift amount for shifting the phase of the light emission cycle. The phase shift amount is a unit time for shifting the phase of the light emission cycle, and is a predetermined time shorter than the time of one frame. The phase shift amount is, for example, 1 ms. The phase shift amount setting unit 14 sets the phase shift amount according to a user input.

[0019] The light emission schedule determination unit 15 acquires the imaging frame rate set in the frame rate setting unit 11, the light emission cycle set in the light emission cycle setting unit 12, the phase shift amount set in the phase shift amount setting unit 14, and the multiple N calculated by the phase difference calculation unit 13. Based on the multiple N calculated by the phase difference calculation unit 13, the light emission schedule determination unit 15 determines a light emission schedule in which the phase shift amount for shifting the phase of the light emission cycle of the light emitter 10 is increased every five light emission cycles from 0 to n times the phase shift amount (1 ms). n is an integer, and may be determined as follows:

[0020] The light emission schedule determination unit 15 sets n to 16, which is the integer part of the value obtained by dividing the time for one frame, 16.6667 ms, based on the imaging frame rate, by the phase shift amount of 1 ms. The light emission schedule determination unit 15 determines a light emission schedule for a total of 17 light emission cycles, including 5 light emission cycles where the phase shift amount is set to 0, i.e., where the phase of the light emission cycle is not shifted, and 16 light emission cycles where the phase shift time is increased in order by multiplying the phase shift amount by 1 to 16.

[0021] One example is to set the light emission schedule to 17 light emission cycles. However, it is preferable to set one light emission schedule to (n+1) light emission cycles, which is the nth light emission cycle, which is the integer part of the value obtained by dividing the time of one frame by the phase shift amount, plus one light emission cycle with no phase shift. With such a light emission schedule, it is possible to measure the delay time at all possible relative time positional relationships between the start timing of the frame of the video signal and the start timing of the ON start of the light emission cycle.

[0022] 3, the thick solid lines indicate the light emission cycles of the light-emitting unit 10 according to the light emission schedule, and the thin solid lines indicate the frame cycles. The light emission schedule determination unit 15 does not shift the phase of the light emission cycles for the five light emission cycles from cycle P1 to cycle P5, but shifts the phase of the light emission cycles by 1 ms for the next five light emission cycles from cycle P6 to cycle P10 (not shown). Therefore, strictly speaking, cycle P5 is 0.13 seconds plus 1 ms.

[0023] For the next five light emission cycles, from cycle P11 to cycle P15 (not shown), the light emission schedule determination unit 15 shifts the phase of the light emission cycle by 1 ms relative to the five light emission cycles from cycle P6 to cycle P10. That is, the light emission schedule determination unit 15 shifts the phase of the light emission cycle by 2 ms compared to the five light emission cycles from cycle P1 to cycle P5. Similarly, for every five light emission cycles, the light emission schedule determination unit 15 shifts the phase of the light emission cycle by 3 ms to 16 ms compared to the five light emission cycles from cycle P1 to cycle P5. In this way, the light emission schedule determination unit 15 determines a light emission schedule that shifts the light emission cycle of the light emitter 10 by 1 ms to 16 ms every five light emission cycles.

[0024] The light emission schedule may include one set of five light emission cycles with no phase shift and n sets of five light emission cycles, and the order within the light emission schedule may be arbitrary. The phase shift time may be sequentially decreased instead of sequentially increased, and the length of the phase shift time may be random.

[0025] 3 shows a state in which the timing of the start of cycle P1 coincides with the timing of the start of a frame. When the phase of the light-emitting cycle is not shifted for the first five light-emitting cycles, the timing of the start of the light-emitting cycle does not necessarily coincide with the timing of the start of the frame. The reason for determining a light-emitting schedule in which the phase of the light-emitting cycle is shifted in order from 1 ms to 16 ms is to measure the delay time more accurately, regardless of whether the timing of the start of the light-emitting cycle coincides with the timing of the start of the frame when the phase of the light-emitting cycle is not shifted for the first five light-emitting cycles.

[0026] Returning to FIG. 2 , the light emission on / off control unit 16 controls the light emission unit 10 to turn the light emission unit 10 on and off in accordance with the light emission schedule determined by the light emission schedule determination unit 15. The light emission on / off control unit 16 acquires the times when the light emission unit 10 is turned on and off from the clock 17 and supplies these to the delay time measurement unit 22. The light reception signal acquisition unit 21 acquires the light reception signal from the light receiving unit 20, and acquires from the clock 17 the rise time when the light reception signal rises from a low level to a high level and the fall time when the light reception signal falls from a high level to a low level, and supplies these to the delay time measurement unit 22. In this way, the clock 17 is shared by both the light emission on / off control unit 16 and the light reception signal acquisition unit 21.

[0027] The delay time measurement unit 22 stores in the memory 23 the difference in time (ON side delay time) between the time when the light emitting unit 10 is turned on, which is supplied from the light emission ON / OFF control unit 16, and the rising time, which is supplied from the light reception signal acquisition unit 21. The delay time measurement unit 22 may store in the memory 23 the difference in time (OFF side delay time) between the time when the light emitting unit 10 is turned off, which is supplied from the light emission ON / OFF control unit 16, and the falling time, which is supplied from the light reception signal acquisition unit 21.

[0028] Delay time measurement unit 22 may store both the on-side delay time and the off-side delay time in memory 23, or may store only one of the on-side delay time and the off-side delay time in memory 23. The on-side delay time and the off-side delay time are delay times from when video camera 1 captures an image of light-emitting unit 10 and generates a video signal, when video transmitting device 2 transmits the video signal to video receiving device 4 via network 3, when video receiving device 4 receives the video signal, and when display 5 displays the video signal.

[0029] A plurality of delay times in the light emission schedule are stored in memory 23. Delay time determination unit 24 determines the minimum value of the plurality of delay times as the delay time from video camera 1 to display 5, and stores this in memory 23. Delay time determination unit 24 may also determine the average value of the plurality of delay times as the delay time, and store this in memory 23. Since determining the minimum value of the plurality of delay times as the delay time results in a more accurate delay time, it is preferable to determine the minimum value as the delay time.

[0030] In this way, the delay time measurement device 100 can measure the delay time from the video camera 1 to the display 5 multiple times to determine the delay time, and store the determined delay time in the memory 23. The delay time measurement device 100 can determine the delay time with an error of 1 ms or less.

[0031] The delay time stored in memory 23 may be displayed on a display unit (not shown) so that the user can check the delay time. The delay time stored in memory 23 may be read out from memory 23 and taken out to the outside of delay time measuring device 100.

[0032] The processing executed by the delay time measurement device 100 will be further described using the flowchart shown in Fig. 4. When processing by the delay time measurement device 100 starts, the phase difference calculation unit 13 and the light emission schedule determination unit 15 read the imaging frame rate in step S1, and read the light emission period in step S2. The order of steps S1 and S2 may be reversed, or they may be performed simultaneously. In step S3, the phase difference calculation unit 13 calculates the phase difference and outputs a multiple N of the light emission period.

[0033] In step S4, the light emission schedule determination unit 15 reads the phase shift amount. In step S5, the light emission schedule determination unit 15 determines the light emission schedule of the light emitter 10 based on the imaging frame rate, the light emission cycle, the multiple N of the light emission cycle, and the phase shift amount. In step S6, the light emission on / off control unit 16 controls the on / off of the light emitter 10 in accordance with the light emission schedule determined in step S5. In step S7, the light reception signal acquisition unit 21 acquires the light reception signal from the light receiver 20.

[0034] In step S8, the delay time measurement unit 22 measures the delay time. In step S9, the delay time measurement unit 22 determines whether all measurements in the light emission schedule have been completed. If all measurements in the light emission schedule have not been completed (NO), the processes of steps S6 to S9 are repeated. If all measurements in the light emission schedule have been completed (YES), the delay time determination unit 24 determines the delay time in step S10 and ends the process.

[0035] The delay time measurement device 100 shown in Fig. 2 may be configured as a microcomputer. In Fig. 2, the phase difference calculation unit 13, the light emission schedule determination unit 15, the light emission on / off control unit 16, the clock 17, the delay time measurement unit 22, and the delay time determination unit 24 may be configured as a central processing unit of a microcomputer. In Fig. 2, the frame rate setting unit 11, the light emission cycle setting unit 12, the phase shift amount setting unit 14, and the memory 23 may be configured as a memory of the microcomputer.

[0036] Second Embodiment As shown in Fig. 1, the delay time measurement device 100 according to the first embodiment can be used when the location where the video camera 1 and the video transmission device 2 are installed is close to the location where the video reception device 4 and the display 5 are installed. The delay time measurement device 200 according to the second embodiment shown in Fig. 5 can be used even when the location where the video camera 1 and the video transmission device 2 are installed is far from the location where the video reception device 4 and the display 5 are installed. In Fig. 5, the same parts as those in Fig. 2 are designated by the same reference numerals, and their description may be omitted.

[0037] The delay time measurement device 200 includes an emission control device 101 and a light receiving and measuring device 102. The emission control device 101 and the light receiving and measuring device 102 are connected via a network 3. The emission control device 101 includes a frame rate setting unit 11, an emission cycle setting unit 12, a phase difference calculation unit 13, a phase shift amount setting unit 14, an emission schedule determination unit 15, an emission on / off control unit 16, a clock 17, a memory 18, and a transmission unit 19. The light receiving and measuring device 102 includes a received light signal acquisition unit 21, a delay time measurement unit 22, a memory 23, a delay time determination unit 24, a clock 27, and a reception unit 29. The clock 17 is a first clock, and the clock 27 is a second clock.

[0038] Clock 17 and clock 27 are clocks that keep the same time with sufficient accuracy based on time information transmitted from a satellite for a Global Navigation Satellite System (GNSS). Typically, the satellite for the GNSS is a Global Positioning System (GPS) satellite. If network 3 is a LAN, PTP (Precision Time Protocol) or the like may be used.

[0039] The light emission on / off control unit 16 acquires the times when the light emitting unit 10 was turned on and off from the clock 17 and stores them in the memory 18. The memory 18 may be a temporary memory. The transmission unit 19 transmits the on-time and off-time stored in the memory 18 to the light receiving / measuring device 102 via the network 3.

[0040] The receiving unit 29 receives the turn-on time and turn-off time transmitted from the light-emission control device 101 and stores them in the memory 23. The delay time measuring unit 22 stores, as a delay time, an on-side delay time (or an off-side delay time) which is the difference between the turn-on time (or turn-off time) stored in the memory 23 and the rise time (or fall time) supplied from the light-receiving signal acquiring unit 21. The delay time determining unit 24 determines the minimum value of the plurality of delay times or the average value of the plurality of delay times as the delay time and stores it in the memory 23.

[0041] In this way, the delay time measuring device 200 can determine the delay time from the video camera 1 to the display 5 and store the determined delay time in the memory 23, even if the location where the video camera 1 and the video transmitting device 2 are installed is far from the location where the video receiving device 4 and the display 5 are installed.

[0042] The present invention is not limited to the first or second embodiment described above, and various modifications are possible without departing from the gist of the present invention. [Explanation of symbols]

[0043] 1 video camera 2. Video transmission device 3 Network 4. Video receiving device 5. Display 11 Frame rate setting section 12 Light emission cycle setting section 13 Phase difference calculation section 14 Phase shift amount setting section 15 Light emission schedule determination section 16 Light emission on / off control section 17,27 Clock 18,23 memory 19 Transmitter 21 Light receiving signal acquisition unit 22 Delay time measurement unit 24 Delay time determination unit 29 Receiving unit 100,200 Delay time measuring device 101 Light-emitting control device 102 Light receiving and measuring device

Claims

1. a phase difference calculation unit that calculates, based on an imaging frame rate when the video camera images the light emitting unit as a subject and an emission cycle for turning the light emitting unit on and off, the emission cycle having a time longer than the time of one frame determined by the imaging frame rate, where N is an integer of 2 or more, a multiple N of the emission cycle required to again bring the timing of the frame head of the video signal generated by the video camera imaging the light emitting unit into agreement with the timing of the on head of the emission cycle, from a state in which the timing of the frame head of the video signal and the timing of the on head of the emission cycle are in agreement with each other; a light emission schedule determination unit that determines a light emission schedule for the light emitter, for every N light emission cycles that is N times the light emission cycle, where n is an integer of 2 or more, and that sequentially increases a time by which the phase of the light emission cycle is shifted from 0 times to n times a unit time, using a predetermined time that is shorter than a time of one frame as a unit time; a light emission on / off control unit that controls the light emitting unit to turn on and off according to the light emission schedule; a light-receiving signal acquiring unit that acquires a light-receiving signal generated by a light-receiving unit that receives light emitted from a display when the video transmitting device transmits the video signal to a video receiving device via a network and the video receiving device displays the received video signal on a display; a delay time measurement unit that measures a delay time from when the video camera generates the video signal to when the display displays the video signal, based on the difference in time between the time when the light emission on / off control unit turns on the light emission unit and the rise time of the light reception signal acquired by the light reception signal acquisition unit, or the difference in time between the time when the light emission on / off control unit turns off the light emission unit and the fall time of the light reception signal acquired by the light reception signal acquisition unit; a delay time determination unit that determines a minimum value of a plurality of delay times measured by the delay time measurement unit within the light emission schedule as the delay time; A delay time measuring device comprising:

2. 2. The delay time measuring device according to claim 1, further comprising a clock shared by the light emission on / off control unit and the light reception signal acquisition unit, which measures the time when the light emission on / off control unit turns the light emission unit on or off and measures the rise time or fall time of the light reception signal acquired by the light reception signal acquisition unit.

3. a first clock that measures the time when the light emission on / off control unit turns on or off the light emitting unit; a second clock that measures the rising time or falling time of the light reception signal acquired by the light reception signal acquisition unit; Furthermore, the phase difference calculation unit, the light emission schedule determination unit, the light emission on / off control unit, and the first clock are provided in a light emission control device, the light receiving signal acquiring unit, the delay time measuring unit, the delay time determining unit, and the second clock are provided in a light receiving and measuring device; The light-emitting control device and the light-receiving / measuring device are connected via the network. The delay time measuring device according to claim 1 .

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