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 vertical sync signal analysis unit 12 detects a first time at which the imaging element of a video camera 1 terminates exposure to light for generating a video signal of a prescribed line in a video signal frame. A light emission control unit 13 causes a light-emitting unit 10 to emit light at a second time immediately preceding the first time. A light emission time storage unit 14 stores the second time as a light emission time at which the light-emitting unit 10 emits light. A received light signal acquisition unit 21 acquires, from a light reception unit 20, a received light signal representing light of the prescribed line emanated from a display 5 that is received. A received light signal analysis unit 22 determines a third time at which a prescribed proportion or more of light of the prescribed line is asserted high. A received light time storage unit 23 stores the third time as a light reception time of the light reception unit 20. A delay time determination unit 31 determines that the difference in time between the light emission time and the light reception time is a delay time till when the video signal generated by the video camera 1 is displayed by the display 5.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 vertical synchronization signal analysis unit that analyzes a vertical synchronization signal of a video signal generated by a video camera and detects a first time when an image pickup element included in the video camera finishes exposure for generating a video signal of a predetermined line in a frame of the video signal; a light emission control unit that controls a light emission unit captured by the video camera to emit light at a second time immediately before the first time; a light emission time storage unit that stores the second time as the light emission time when the light emission unit emits light; and a video signal transmission unit that transmits the video signal to a video receiving device via a network and, when the video receiving device receives the video signal and displays it on a display, outputs a light from the display. a light-receiving signal analysis unit that analyzes the light-receiving signal to determine a third time when the light of the predetermined line rises to a predetermined rate or more; a light-receiving time memory unit that stores the third time as the light-receiving time when the light-receiving unit receives the light of the predetermined line; and a delay time determination unit that determines the difference between the light-emission time stored in the light-emission time memory unit and the light-receiving time stored in the light-receiving time memory unit as the delay time from when the video camera generates the video signal to when the display displays the video signal.

[0006] The present invention includes a vertical synchronization signal analysis unit that analyzes a vertical synchronization signal of a video signal generated by a video camera and detects a first time when an image pickup element included in the video camera ends exposure for generating a video signal of a predetermined line in a frame of the video signal; a light emission control unit that controls a light emission unit captured by the video camera to emit light before the image pickup element starts exposure for generating a video signal of the predetermined line; a reference time storage unit that stores the first time as a reference time; and a video signal receiving unit that transmits the video signal to a video receiving device via a network and displays the video signal received by the video receiving device on a display. Provided is a delay time measuring device comprising: a light receiving signal acquiring unit that acquires a light receiving signal generated by a light receiving unit that receives light of the specified line emitted from a play; a light receiving signal analyzing unit that analyzes the light receiving signal to determine a second time when the light of the specified line rises to a specified rate or more; a light receiving time memory unit that stores the second time as the light receiving time when the light receiving unit receives light of the specified line; and a delay time determining unit that determines the difference between the reference time stored in the reference time memory unit and the light receiving time stored in the light receiving time memory unit as the delay time from when the video camera generates the video signal to when the display displays the video signal. [Effects of the Invention]

[0007] 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]

[0008] [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 diagram showing the video signal of each frame that is generated by a video camera through exposure by a rolling shutter type image sensor and displayed on a display. [Figure 4] FIG. 4 is a diagram showing the times at which the light emitting unit emits light in the delay time measuring device according to the first embodiment. [Figure 5] FIG. 5 is a waveform diagram showing an example of a waveform displayed on an oscilloscope in the delay time measurement device according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing the times at which the light emitting units emit light and conceptually illustrating the amplification of video signals in the delay time measurement device according to the first embodiment. [Figure 7] FIG. 7 is a diagram conceptually illustrating the time at which the light emitting unit emits light when a global shutter type image sensor is used in the delay time measurement device according to the first embodiment, and amplifying the video signal. [Figure 8] FIG. 8 is a block diagram showing a modification of the delay time measuring device according to the first embodiment. [Figure 9] FIG. 9 is a schematic block diagram showing a state in which a delay time measuring device according to the second embodiment is connected to a video transmission and reception system. [Figure 10] FIG. 10 is a block diagram showing a delay time measuring device according to the second embodiment. [Figure 11] FIG. 11 is a diagram showing the times at which the light emitting unit emits light in the delay time measuring device according to the second embodiment. [Figure 12] FIG. 12 is a block diagram showing a modification of the delay time measuring device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, delay time measuring devices according to each embodiment will be described with reference to the accompanying drawings.

[0010] First Embodiment First, a schematic configuration of a video transmission / reception system including a delay time measurement device 100 according to the first embodiment will be described with reference to Fig. 1. In Fig. 1, a video camera 1 is connected to the delay time measurement device 100. The delay time measurement device 100 also functions as a video transmission device that 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.

[0011] The network 3 is, for example, an in-house LAN (Local Area Network). The location where the video camera 1 and delay time measuring device 100 are installed is usually a predetermined distance away from the location where the video receiving device 4 and display 5 are installed. In this example, the location where the video camera 1 and delay time measuring device 100 are installed and the location where the video receiving device 4 and display 5 are installed are considered 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.

[0012] An oscilloscope 6, a light-emitting unit 10, and a light-receiving unit 20 are connected to the delay time measuring device 100. Connecting the oscilloscope 6 to the delay time measuring device 100 is not essential. The light-emitting unit 10 can be configured, for example, as a light-emitting diode (LED), and the light-receiving unit 20 can be configured, for example, as a photodiode. The delay time measuring device 100 controls the light-emitting unit 10 to turn on at a predetermined timing, which will be described later. The video camera 1 captures an image of the light-emitting unit 10 switching from an off state to an on state, and supplies the generated video signal to the delay time measuring device 100. The delay time measuring device 100 transmits the input video signal to the video receiving device 4 via the network 3.

[0013] 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 display 5 displays an image of the light emitting unit 10 switching from an off state to an on state. The light receiving unit 20 receives light emitted from the display 5 displaying the image of the lit light emitting unit 10. The delay time measuring device 100 acquires the light reception signal from the light receiving unit 20. The oscilloscope 6 is supplied with an on / off control signal that turns on or off the light emission of the light emitting unit 10, and the light reception signal from the light receiving unit 20.

[0014] The specific configuration and operation of the delay time measurement device 100 will be described using Fig. 2. As shown in Fig. 2, the delay time measurement device 100 includes a video signal input / output unit 11, a vertical synchronization signal analysis unit 12, a light emission control unit 13, a light emission time memory unit 14, a clock 15, a light reception signal acquisition unit 21, a light reception signal analysis unit 22, a light reception time memory unit 23, a delay time determination unit 31, a delay time memory unit 32, a display unit 33, and an oscilloscope output unit 61. The video signal input / output unit 11 preferably includes an amplifier 111 built therein.

[0015] Assuming that video camera 1 is equipped with a rolling-shutter CMOS (Complementary Metal Oxide Semiconductor) sensor as an imaging element, video camera 1 generates a video signal for each frame as shown in Figure 3, and display 5 displays the video signal for each frame. Assume that video camera 1 generates a full HD video signal with 1920 pixels horizontally and 1080 lines vertically. As shown in Figure 3, the CMOS sensor sequentially exposes each line from exposure E1 for the first line to exposure E1080 for the 1080th line. 1H indicates one horizontal period. Corresponding to exposure E1 for the first line to exposure E1080 for the 1080th line, video signals VL1 for the first line to VL1080 for the 1080th line are generated.

[0016] Video camera 1 generates one frame of video signal V1V from video signal VL1 of the first line to video signal VL1080 of the 1080th line. One frame of video signal V1V is supplied to display 5 with a predetermined delay time, and display 5 displays one frame of video signal V5V. Video camera 1 and display 5 repeat the above operations. If the imaging frame rate is 60 frames / second, the time for one frame, indicated by V in Figure 3, is approximately 16.6667 ms.

[0017] In Figure 3, exposure E1 for the first line is taken as an example. If the time from the start of exposure E1 for the first line until the first line of video signal VL1 is displayed on display 5 is taken as the delay time between when video camera 1 generates a video signal and when display 5 displays the video signal, the delay time includes the exposure time required to generate one line of video signal, and therefore cannot be considered a correct delay time. It is desirable to measure a delay time that does not include the exposure time required from when video camera 1 generates a video signal and when display 5 displays the video signal. As shown in Figure 3, delay time measurement device 100 desirably measures delay time Td from when video camera 1 starts generating video signal VL1 for the first line to when display 5 finishes displaying video signal VL1 for the first line.

[0018] The delay time measurement device 100 is not limited to measuring the delay time Td based on the video signal VL1 of the first line, but may measure the delay time Td based on the video signal of a predetermined line. However, it is preferable that the delay time measurement device 100 measures the delay time Td based on the video signal VL1 of the first line. Hereinafter, the predetermined line will be referred to as the first line.

[0019] The operation of the delay time measurement device 100 shown in Fig. 2 will be described with reference to Fig. 4. The vertical synchronization signal analysis unit 12 analyzes the vertical synchronization signal of the video signal generated by the video camera 1. The vertical synchronization signal analysis unit 12 detects the time t0 (first time) at which the image pickup element (CMOS sensor) included in the video camera 1 ends exposure for generating the video signal VL1 for the first line in the frame of the video signal.

[0020] Video camera 1 captures an image of light-emitting unit 10 so that the entire light-emitting unit 10 is displayed within the frame. There is no light other than the light emitted by light-emitting unit 10, and the area around light-emitting unit 10 is dark when light-emitting unit 10 is not emitting light. Assume that light-emitting control unit 13 controls light-emitting unit 10 to emit light at time t1 before starting exposure E1 for the first line. At this time, video camera 1 generates one frame of video signal V1V through all exposures from exposure E1 for the first line to exposure E1080 for the 1080th line, so video signal V1V has a high brightness as shown in frame Ft1.

[0021] Suppose that light-emission control unit 13 controls light-emitting unit 10 to emit light at time t2 during exposure E1 of the first line. At this time, the upper lines cannot capture light from the partial exposure of each line, so the video signal V1V becomes darker in the upper lines as shown in frame Ft2. Suppose that light-emission control unit 13 controls light-emitting unit 10 to emit light at time t3 (second time), which is just before time t0 when exposure E1 of the first line ends. At this time, the upper lines cannot capture light from the partial exposure of each line compared to when light-emitting unit 10 emitted light at time t2, so the video signal V1V becomes even darker in the upper lines as shown in frame Ft3.

[0022] Thus, while illuminating the light-emitting unit 10 at time t3 dims the video signal V1V, the light-emitting control unit 13 controls the light-emitting unit 10, captured by the video camera 1, to emit light at time t3, just before time t0, when the exposure E1 for the first line ends, based on the time measured by the clock 15. Although time t3 differs from time t0, when the exposure E1 for the first line ends, by positioning time t3 close to time t0, time t3 can be considered equivalent to time t0. The time from time t3 to time t0 may be set to, for example, one-tenth of the scanning time for one line. For example, in the case of a full HD video signal with an imaging frame rate of 60 frames per second, the time is calculated as 868 ns, calculated by 1 / (60 × 1920 × 10).

[0023] The light emission time memory unit 14 stores time t3 as the light emission time at which the light emitting unit 10 emits light. The video signal input / output unit 11 transmits the video signal of each frame, including the video signal V1V, to the video receiving device 4 via the network 3. The light receiving unit 20 is disposed at a position corresponding to the first line of the frame. When the video receiving device 4 displays the received video signal V1V on the display 5, the light receiving unit 20 receives the light of the first line emitted from the display 5. The light receiving signal acquisition unit 21 acquires the light receiving signal generated by the light receiving unit 20. The light receiving signal analysis unit 22 analyzes the light receiving signal to determine the time (third time) at which the light of the first line rises to a predetermined rate or more. The predetermined rate is, for example, 90%.

[0024] The light reception time memory unit 23 stores the third time as the light reception time at which the light receiving unit 20 receives the light of the video signal VL1 for the first line, based on the time measured by the clock 15. The delay time determination unit 31 determines the difference between the light emission time (time t3) stored in the light emission time memory unit 14 and the light reception time (third time) stored in the light reception time memory unit 23 as the delay time from when the video camera 1 generates the video signal to when the display 5 displays the video signal.

[0025] The delay time memory unit 32 stores the delay time determined by the delay time determination unit 31. The display unit 33 displays the delay time stored in the delay time memory unit 32. The oscilloscope output unit 61 outputs the on / off control signal for the light emitting unit 10 by the light emission control unit 13 and the light reception signal from the light receiving unit 20 acquired by the light reception signal acquisition unit 21 to the oscilloscope 6. This allows the oscilloscope 6 to display waveform diagrams of the on / off control signal and the light reception signal as shown in FIG. 5. The delay time measurement device 100 may have the function of the oscilloscope 6.

[0026] As described above, the luminance of frames Ft2 and Ft3 is lower than the luminance of frame Ft1. If the light receiving unit 20 cannot generate a light reception signal from frame Ft3 and the light reception signal acquiring unit 21 cannot acquire the light reception signal, as shown in FIG. 6, the amplifier 111 may amplify frame Ft3 to generate frame Ft3'. The amplifier 111 multiplies the luminance of frame Ft3 by a gain G3 that makes the luminance of frame Ft3 the same as that of frame Ft1, thereby generating frame Ft3'. The light emission control unit 13 does not control the light emitting unit 10 to emit light at time t2. However, if frame Ft2 is used, the amplifier 111 may multiply the luminance of frame Ft2 by a gain G2 that makes the luminance of frame Ft2 the same as that of frame Ft1, thereby generating frame Ft2'.

[0027] Video camera 1 may be equipped with a global shutter CMOS sensor as an image sensor instead of a rolling shutter CMOS sensor, or may be equipped with a global shutter CCD sensor (Charge Coupled Device). Fig. 7 shows the relationship between exposures E1 to E1080 and video signals V1V and V5V when video camera 1 is equipped with a global shutter image sensor. When video camera 1 is equipped with a global shutter image sensor, light emission control unit 13 controls light emission unit 10 to emit light at time t3, which is immediately before time t0 when exposure of each line ends.

[0028] Even when the video camera 1 is equipped with a global shutter type image sensor, it is preferable to amplify the frame Ft3 by the amplifier 111 to generate the frame Ft3'. The amplifier 111 multiplies the luminance of the frame Ft3 by a gain G3 that makes the luminance of the frame Ft3 the same as that of the frame Ft1 to generate the frame Ft3'. If the frame Ft2 is used, the amplifier 111 may multiply the luminance of the frame Ft2 by a gain G2 that makes the luminance of the frame Ft2 the same as that of the frame Ft1 to generate the frame Ft2'. Note that the gains G2 and G3 in FIG. 7 are different from the gains G2 and G3 in FIG. 6.

[0029] As shown in FIG. 1, the delay time measurement device 100 can be used if the location where the video camera 1 is installed is close to the location where the video receiving device 4 and display 5 are installed. If the location where the video camera 1 is installed is far from the location where the video receiving device 4 and display 5 are installed, as shown in FIG. 8, a delay time measurement device 100' separated into a light-emitting control and measurement device 101 and a light-receiving device 102 can be used instead of the delay time measurement device 100. The delay time measurement device 100' is a modified version of the delay time measurement device 100. In FIG. 8, the same parts as those in FIG. 2 are designated by the same reference numerals, and their description may be omitted.

[0030] 8, the light emission control and measurement device 101 includes a video signal input / output unit 11, a vertical synchronization signal analysis unit 12, a light emission control unit 13, a light emission time memory unit 14, a clock 15, a network interface (hereinafter referred to as I / F) 17, a light reception time memory unit 23, a delay time determination unit 31, a delay time memory unit 32, a display unit 33, and an oscilloscope output unit 61. The light receiving device 102 includes a light reception signal acquisition unit 21, a light reception signal analysis unit 22, a clock 25, a memory 26, and a network interface (hereinafter referred to as I / F) 27. The light emission control and measurement device 101 and the light receiving device 102 are connected via a network 3.

[0031] Clock 15 is a first clock, and clock 25 is a second clock. Clock 15 and clock 25 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.

[0032] In FIG. 8, I / F 17 transmits the video signal output from video signal input / output unit 11 to video receiving device 4 via network 3. Memory 26 temporarily stores a third time based on the time measured by clock 25. I / F 27 transmits the third time and the light-receiving signal from light-receiving unit 20 acquired by light-receiving signal acquisition unit 21 to light-emission control and measurement device 101 via network 3. Light-receiving time memory unit 23 stores the third time received by I / F 17 as the light-receiving time. Oscilloscope output unit 61 outputs the on / off control signal supplied from light-emission control unit 13 and the light-receiving signal received by I / F 17 from light-receiving unit 20 to oscilloscope 6.

[0033] The delay time measuring device 100' can determine the delay time from the video camera 1 to the display 5 and display the determined delay time on the display unit 33 even if the location where the video camera 1 is installed is far from the location where the video receiving device 4 and the display 5 are installed.

[0034] As described above, delay time measurement device 100 (including delay time measurement device 100') can more accurately measure the delay time between when video camera 1 generates a video signal and when display 5 displays the video signal.

[0035] Second Embodiment The second embodiment is configured to achieve higher brightness and a better S / N ratio than the first embodiment. A schematic configuration of a video transmission / reception system including a delay time measurement device 200 according to the second embodiment will be described with reference to FIG. 9. In FIG. 9, the same components as those in FIG. 1 are designated by the same reference numerals, and their description may be omitted. In FIG. 9, a video camera 1 is connected to the delay time measurement device 200. The delay time measurement device 200 also functions as a video transmission device that 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 delay time measurement device 200 supplies an on / off control signal to a light-emitting unit 10 and supplies a pulse generated at a reference time (described later) to an oscilloscope 6.

[0036] 10 and 11, the specific configuration and operation of the delay time measurement device 200 will be described. As shown in Fig. 10, the delay time measurement device 200 includes a video signal input / output unit 11, a vertical synchronization signal analysis unit 12, a light emission control unit 13, a clock 15, a light reception signal acquisition unit 21, a light reception signal analysis unit 22, a light reception time storage unit 23, a delay time determination unit 31, a delay time storage unit 32, a display unit 33, a reference time storage unit 44, and an oscilloscope output unit 61.

[0037] As shown in FIG. 11 , the vertical synchronization signal analyzer 12 detects time t0 (first time) at which the image sensor included in the video camera 1 ends exposure for generating a video signal VL1 for the first line in a frame of the video signal. The light-emission controller 13 controls the light-emission unit 10 to emit light at time t1, before the start of exposure E1 for the first line. The light-emission controller 13 may also control the light-emission unit 10 to emit light immediately after generating a video signal VL1080 for the 1080th line based on exposure E1080 for the 1080th line of the previous frame. The reference time memory 44 stores the first time as the reference time. When the light-emission unit 10 emits light from time t1, the video signal V1V becomes highly luminous, as shown in frame Ft1. Therefore, the video signal V1V has a sufficiently high luminance and therefore a favorable S / N ratio. Furthermore, amplification by the amplifier 111 is not required.

[0038] When the video receiving device 4 displays the received video signal V1V on the display 5, the light receiving unit 20 receives the first line of light emitted from the display 5. The light receiving signal acquiring unit 21 acquires the light receiving signal generated by the light receiving unit 20. The light receiving signal analyzing unit 22 analyzes the light receiving signal to determine the time (second time) when the light of the first line rises to a predetermined rate or more. The light receiving time memory unit 23 stores the second time as the light receiving time when the light receiving unit 20 receives the light of the first line of the video signal VL1, based on the time measured by the clock 15.

[0039] The delay time determination unit 31 determines the difference between the reference time (time t0) stored in the light emission time memory unit 14 and the light reception time (second time) stored in the light reception time memory unit 23 as the delay time from when the video camera 1 generates a video signal to when the display 5 displays the video signal. The oscilloscope output unit 61 supplies the pulse generated at the reference time and the light reception signal from the light reception unit 20 to the oscilloscope 6. Although not shown in the figure, the oscilloscope 6 can display a waveform diagram of the pulse generated at the reference time and the light reception signal.

[0040] 8, when the location where the video camera 1 is installed is far from the location where the video receiving device 4 and the display 5 are installed, it is possible to use a delay time measuring device 200' shown in FIG. 12, which is divided into a light emission control / measuring device 201 and a light receiving device 202, instead of the delay time measuring device 200. The delay time measuring device 200' is a modified example of the delay time measuring device 200. In FIG. 12, the same parts as those in FIG. 8 are assigned the same reference numerals, and their description may be omitted.

[0041] 12, the light emission control and measurement device 201 includes a video signal input / output unit 11, a vertical synchronization signal analysis unit 12, a light emission control unit 13, a clock 15, an I / F 17, a light reception time memory unit 23, a delay time determination unit 31, a delay time memory unit 32, a display unit 33, a reference time memory unit 44, and an oscilloscope output unit 61. The light receiving device 202 includes a light reception signal acquisition unit 21, a light reception signal analysis unit 22, a clock 25, a memory 26, and an I / F 27. The light emission control and measurement device 201 and the light receiving device 202 are connected via a network 3.

[0042] As described above, delay time measurement device 200 (including delay time measurement device 200') can more accurately measure the delay time between when video camera 1 generates a video signal and when display 5 displays the video signal.

[0043] 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]

[0044] 1 video camera 3 Network 4. Video receiving device 5. Display 11 Video signal input / output section 12 Vertical sync signal analysis section 13 Light emission control unit 14 Light emission time memory section 15,25 watch 17,27 Network Interface 21 Light receiving signal acquisition unit 22 Received light signal analysis section 23 Light reception time storage section 26 memory 31 Delay time determination unit 32 Delay time memory unit 33 Display section 44 Reference time storage section 100,100',200,200' Delay time measuring device 101,201 Light emission control and measurement equipment 102,202 Light receiving device

Claims

1. a vertical synchronization signal analysis unit that analyzes a vertical synchronization signal of a video signal generated by a video camera and detects a first time when an image pickup element included in the video camera ends exposure for generating a video signal of a predetermined line in a frame of the video signal; a light emission control unit that controls a light emission unit to emit light at a second time immediately before the first time; a light emission time storage unit that stores the second time as a light emission time at which the light emitting unit emits light; a light-receiving signal acquiring unit that transmits the video signal to a video receiving device via a network, and acquires a light-receiving signal generated by a light-receiving unit that receives the predetermined line of light emitted from the display when the video signal received by the video receiving device is displayed on the display; a light receiving signal analysis unit that analyzes the light receiving signal and determines a third time when the light of the predetermined line rises to a predetermined rate or more; a light-receiving time storage unit that stores the third time as a light-receiving time at which the light-receiving unit receives the predetermined line of light; a delay time determination unit that determines a difference between the light emission time stored in the light emission time storage unit and the light reception time stored in the light reception time storage unit as a delay time from when the video camera generates the video signal to when the display displays the video signal; A delay time measuring device comprising:

2. 2. The delay time measuring device according to claim 1, further comprising an amplifier for amplifying the video signal to be transmitted to the video receiving device.

3. a vertical synchronization signal analysis unit that analyzes a vertical synchronization signal of a video signal generated by a video camera and detects a first time when an image pickup element included in the video camera ends exposure for generating a video signal of a predetermined line in a frame of the video signal; a light emission control unit that controls a light emission unit to emit light before the image pickup element starts exposure for generating the predetermined line of video signals; a reference time storage unit that stores the first time as a reference time; a light-receiving signal acquiring unit that transmits the video signal to a video receiving device via a network, and acquires a light-receiving signal generated by a light-receiving unit that receives the predetermined line of light emitted from the display when the video signal received by the video receiving device is displayed on the display; a light receiving signal analysis unit that analyzes the light receiving signal and determines a second time when the light of the predetermined line rises to a predetermined rate or more; a light-receiving time storage unit that stores the second time as a light-receiving time at which the light-receiving unit receives the predetermined line of light; a delay time determination unit that determines a difference between the reference time stored in the reference time storage unit and the light-receiving time stored in the light-receiving time storage unit as a delay time from when the video camera generates the video signal to when the display displays the video signal; and A delay time measuring device comprising:

4. a first clock that measures the first and second times; a second clock that measures the third time; Furthermore, the vertical synchronization signal analysis unit, the light emission control unit, the light emission time storage unit, the light reception time storage unit, the delay time determination unit, and the first clock are provided in a light emission control and measurement device; the light receiving signal acquiring unit, the light receiving signal analyzing unit, and the second clock are provided in a light receiving device, The light emission control and measurement device and the light receiving device are connected via the network.

3. The delay time measuring device according to claim 1 or 2.

5. a first clock that measures the first time; a second clock that measures the second time; Furthermore, the vertical synchronization signal analysis unit, the light emission control unit, the reference time storage unit, the light reception time storage unit, the delay time determination unit, and the first clock are provided in a light emission control and measurement device, the light receiving signal acquiring unit, the light receiving signal analyzing unit, and the second clock are provided in a light receiving device, The light emission control and measurement device and the light receiving device are connected via the network. The delay time measuring device according to claim 3 .

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