Light detection system and method for controlling light detection system

Abstract

The present invention improves detection accuracy in a system for detecting an address event.　This light detection system comprises a light detection device and a light emission control unit. In the light detection system, a prescribed number of pixels are arranged in the light detection device, the pixels detecting, as an address event and in synchronism with a prescribed vertical synchronization signal, that the absolute value of the amount of change in the luminance of incident light including reflected light for irradiation light from a light-emitting unit has exceeded a prescribed threshold value. The light emission control unit controls the luminance of the irradiation light in synchronism with an external synchronization signal synchronized with the vertical synchronization signal.

Description

Optical detection system and method for controlling an optical detection system

[0001] The present technology relates to a light detection system, and more particularly to a light detection system that detects that a change in luminance has exceeded a threshold, and a method for controlling the light detection system.

[0002] Sensors that detect changes in luminance that exceed a threshold as address events have been used in various fields, such as transportation and entertainment. Such sensors are called event-based vision sensors (EVSs) or dynamic vision sensors (DVSs). For example, an eye-tracking system has been proposed in which multiple light sources irradiate the pupil with a certain light pattern as glint, and an event camera equipped with an EVS detects address events as glint (see, for example, Patent Document 1).

[0003] Special Publication No. 2020-536309

[0004] The above-mentioned conventional technology attempts to track the gaze direction by detecting glint. However, in the above-mentioned system, the event camera may not be able to detect glint when the eyeball is not moving, resulting in a problem of reduced glint detection accuracy.

[0005] This technology was developed in light of these circumstances, and aims to improve the detection accuracy in systems that detect address events.

[0006] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is a light detection system and a control method thereof, including a light detection device having an array of a predetermined number of pixels that detects, as an address event, in synchronization with a predetermined vertical synchronization signal, that an absolute value of a change in luminance of incident light, including reflected light, relative to irradiated light from a light-emitting unit, exceeds a predetermined threshold, and a light-emission control unit that controls the luminance of the irradiated light in synchronization with an external synchronization signal that is synchronized with the vertical synchronization signal, thereby improving the accuracy of glint detection.

[0007] In this first aspect, the threshold value may include an upper threshold value and a lower threshold value, and the address event may include an ON event indicating that the amount of change has exceeded the upper threshold value and an OFF event indicating that the amount of change has fallen below the lower threshold value, thereby providing the effect of detecting an ON event and an OFF event.

[0008] In this first aspect, a predetermined detection period may be set each time a period of the vertical synchronization signal elapses, and the pixel may detect the on-event or the off-event within the detection period, thereby providing an effect that the on-event or the off-event is detected within the detection period.

[0009] In addition, in this first aspect, an on-event detection period and an off-event detection period may be set each time a period of the vertical synchronization signal elapses, and the pixel may detect the on-event within the on-event detection period and the off-event within the off-event detection period, thereby providing an effect of detecting the on-event and the off-event in a time-division manner.

[0010] In addition, in this first aspect, the light-emission control unit may control the state of the light-emitting unit to one of on and off within a predetermined pulse period, and control the state of the light-emitting unit to the other of on and off outside the pulse period, thereby achieving the effect of flashing the light-emitting unit.

[0011] In addition, in this first aspect, the pulse period may include the on-event detection period, the light-emission control unit may turn on the light-emitting unit during the pulse period and turn off the light-emitting unit outside the pulse period, and the light detection device may detect, as a second event, that both the on-event and the off-event have been detected within the cycle. This brings about an effect of further improving the accuracy of glint detection.

[0012] In addition, in this first aspect, the on-event detection period may include a first on-event detection period and a second on-event detection period, the off-event detection period may include a first off-event detection period and a second off-event detection period, the first on-event detection period and the first off-event detection period and the second on-event detection period and the second off-event detection period may be set alternately every time a period of the vertical synchronization signal elapses, and the pulse period may include one of the first on-event detection period and the first off-event detection period. This brings about an effect of improving the accuracy of glint detection in the case of a time division method.

[0013] In addition, in this first aspect, the pulse period may include only the first off-event detection period of the first on-event detection period and the first off-event detection period, and the light-emission control unit may turn off the light-emitting unit during the pulse period and turn on the light-emitting unit outside the pulse period. This brings about an effect of improving glint detection accuracy in the case of a time-division method.

[0014] In addition, in this first aspect, the pulse period may include only the first on-event detection period of the first on-event detection period and the first off-event detection period, and the light-emission control unit may turn on the light-emitting unit during the pulse period and turn off the light-emitting unit outside the pulse period, thereby achieving an effect of reducing power consumption.

[0015] In addition, in this first aspect, the light-emitting unit may include first and second light-emitting diodes, the light-emission control unit may transmit different pulse signals to the first and second light-emitting diodes, and the photodetector may separately detect an address event corresponding to the first light-emitting diode and an address event corresponding to the second light-emitting diode, thereby providing an effect of removing noise.

[0016] In addition, in this first aspect, the light-emission control unit may blink the light-emitting unit within a predetermined modulation period and continuously light the light-emitting unit outside the modulation period, thereby achieving the effect of blinking or continuously lighting the light-emitting unit.

[0017] In addition, in this first aspect, the light detection device may further include a signal processing circuit that processes data indicating the detection result of the address event and causes the light detection device and the light emission control unit to operate in synchronization with each other, thereby achieving the effect of causing the light detection device and the light emission control unit to operate in synchronization with each other.

[0018] In addition, in this first aspect, the light detection device may operate the light emission control unit in synchronization with the light detection device, thereby providing an effect that the light detection device and the light emission control unit operate in synchronization with each other.

[0019] In addition, in this first aspect, the light emission control unit may operate the light detection device in synchronization with the light emission control unit, thereby providing an effect that the light detection device and the light emission control unit operate in synchronization with each other.

[0020] According to a second aspect of the present technology, there is provided a light detection system including: a light detection device having an array of multiple pixels that detects, as an address event, an occurrence when an absolute value of a change in luminance of incident light exceeds a predetermined threshold; and a light emission control unit that alternately controls the luminance of the irradiated light to a predetermined value within a pulse period that has a length between a delay time from a predetermined timing until the pixels are initialized and a delay time from the timing until the absolute value of the change exceeds the threshold, and controls the luminance of the irradiated light to a value different from the predetermined value outside the pulse period. This provides an advantage of improving the accuracy of glint detection when using an arbiter method.

[0021] 1 is a block diagram showing an example configuration of a light detection system according to a first embodiment of the present technology. FIG. 2 is a block diagram showing an example configuration of an EVS camera according to the first embodiment of the present technology. FIG. 3 is a block diagram showing an example configuration of a pixel according to the first embodiment of the present technology. FIG. 4 is a circuit diagram showing an example configuration of a logarithmic response unit, a buffer, a differential detector, and a comparator according to the first embodiment of the present technology. FIG. 5 is a timing chart showing an example operation of the light detection system according to the first embodiment of the present technology. FIG. 6 is a timing chart showing an example operation of the light detection system when the waveform of a pulse signal according to the first embodiment of the present technology is inverted. FIG. 7 is a timing chart showing an example waveform of a pulse signal according to the first embodiment of the present technology. FIG. 8 is a timing chart showing an example operation of a light detection system in a comparative example. FIG. 9 is a block diagram showing an example configuration of a light detection system according to a first modified example of the first embodiment of the present technology. FIG. 10 is a block diagram showing an example configuration of a light detection system according to a second modified example of the first embodiment of the present technology. FIG. 11 is a circuit diagram showing an example configuration of a logarithmic response unit, a buffer, a differential detector, and a comparator according to the second embodiment of the present technology. FIG. 12 is a timing chart showing an example operation of the light detection system according to the second embodiment of the present technology. 10 is a timing chart showing an example of operation of a light detection system in a modified example of the second embodiment of the present technology. 11 is a timing chart showing an example of operation of a light detection system in a third embodiment of the present technology. 12 is a circuit diagram showing an example of a configuration of a signal processing unit in an EVS camera in the third embodiment of the present technology. 13 is a diagram showing an example of EVS data when a pseudo eyeball in a comparative example is stationary and when it is moving. 14 is a diagram showing an example of EVS data when a pseudo eyeball in the second embodiment of the present technology is stationary and when it is moving. 15 is a diagram showing an example of EVS data when a pseudo eyeball in the third embodiment of the present technology is stationary and when it is moving. 16 is a diagram showing an example of EVS data when a pseudo eyeball in the third embodiment of the present technology is stationary and when it is moving. 17 is a diagram showing an example of EVS data with different glint patterns when a pseudo eyeball in the third embodiment of the present technology is stationary and when it is moving. 18 is a block diagram showing an example of a configuration of a light detection system in a fourth embodiment of the present technology.10 is a timing chart showing an example of operation of a light detection system according to a fourth embodiment of the present technology. FIG. 11 is a block diagram showing an example configuration of a light detection system according to a fifth embodiment of the present technology. FIG. 12 is a block diagram showing another example of a light detection system according to the fifth embodiment of the present technology. FIG. 13 is a block diagram showing another example of a light detection system according to the fifth embodiment of the present technology. FIG. 14 is a block diagram showing another example of a light detection system according to the fifth embodiment of the present technology. FIG. 15 is a block diagram showing another example of a light detection system according to the sixth embodiment of the present technology. FIG. 16 is a block diagram showing another example of a light detection system according to the sixth embodiment of the present technology. FIG. 17 is a block diagram showing another example of a light detection system according to the sixth embodiment of the present technology. FIG. 18 is a block diagram showing another example of a light detection system according to the sixth embodiment of the present technology. FIG. 19 is a block diagram showing another example of a light detection system according to the sixth embodiment of the present technology.

[0022] Hereinafter, modes for implementing the present technology (hereinafter referred to as embodiments) will be described. The description will be made in the following order. 1. First embodiment (an example in which the brightness of irradiated light is controlled in synchronization with a synchronization signal) 2. Second embodiment (an example in which the brightness of irradiated light is controlled in synchronization with a synchronization signal and an address event is detected in a time-division manner) 3. Third embodiment (an example in which the brightness of irradiated light is controlled in synchronization with a synchronization signal and a Bose event is detected) 4. Fourth embodiment (an example in which the brightness of irradiated light is controlled in synchronization with a synchronization signal and identification information is associated with a detection signal) 5. Fifth embodiment (an example in which a camera synchronizes a driver that controls the brightness of irradiated light in synchronization with a synchronization signal) 6. Sixth embodiment (an example in which a driver controls the brightness of irradiated light in synchronization with a synchronization signal and synchronizes a camera) 7. Seventh embodiment (an example in which the brightness of irradiated light is controlled in synchronization with a synchronization signal and an arbiter system is used) 8. Application to a moving body

[0023] 1 is a block diagram showing an example of a configuration of a light detection system 100 according to a first embodiment of the present technology. The light detection system 100 is a system used for eye tracking or the like, and includes a signal processing circuit 110, an LED (Light-Emitting Diode) driver 120, a light emitting unit 130, and an EVS camera 200.

[0024] The signal processing circuit 110 performs predetermined signal processing on the EVS data from the EVS camera 200. For example, the EVS data includes a glint detection result, and the signal processing circuit 110 performs processing to detect the gaze direction, the open / closed state of the pupil, and the like based on the detection result. An integrated circuit such as an FPGA (Field-Programmable Gate Array) is used as the signal processing circuit 110.

[0025] Furthermore, the signal processing circuit 110 transmits an external synchronization signal ESYNC to the LED driver 120 via a signal line 118, and transmits a vertical synchronization signal VSYNC to the EVS camera 200 via a signal line 119. The external synchronization signal ESYNC is a signal synchronized with the vertical synchronization signal VSYNC, and these synchronization signals allow the signal processing circuit 110, as a master device, to operate the LED driver 120 and the EVS camera 200 in synchronization.

[0026] The light-emitting unit 130 emits a certain pattern of light onto the human eye or other target. IR (Infra-Red) light or the like is used as the light. A predetermined number of LEDs (not shown) are arranged within the light-emitting unit 130. The light pattern emitted by these LEDs corresponds to the aforementioned "glint."

[0027] The LED driver 120 controls the brightness of the light (such as IR light) emitted from the light-emitting unit 130 in synchronization with the external synchronization signal ESYNC. The LED driver 120 generates a pulse signal PLS synchronized with the external synchronization signal ESYNC and supplies it to the light-emitting unit 130 via a signal line 129. This pulse signal PLS is used in common by all LEDs in the light-emitting unit 130. For example, each LED is turned on when the pulse signal PLS is at a high level and turned off when the pulse signal PLS is at a low level. As will be described later, the LED driver 120 can also turn on the LEDs at a lower illuminance than during a high-level period without turning them off during a low-level period. The LED driver 120 is also an example of a light-emitting control unit as defined in the claims.

[0028] The EVS camera 200 detects address events. The EVS camera 200 has an array of pixels. These pixels receive incident light, including reflected light from the light emitted from the light-emitting unit 130 and other ambient light. The EVS camera 200 may also use a visible light cut filter or a filter that cuts out light other than that emitted by the light-emitting unit 130. Each pixel detects, in synchronization with the vertical synchronization signal VSYNC, an address event when the absolute value of the change in luminance of the incident light exceeds a threshold. Address events include an ON event, which indicates that the change in luminance has exceeded an upper threshold, and an OFF event, which indicates that the change in luminance has fallen below a lower threshold. ON events and OFF events are also referred to as positive and negative events.

[0029] The EVS camera 200 detects glints based on the detection results of address events, and generates EVS data by arranging the glint detection results for each pixel. The EVS data is supplied to the signal processing circuit 110 via a signal line 209.

[0030] The EVS camera 200 is an example of a light detection device described in the claims.

[0031] 2 is a block diagram showing an example of the configuration of an EVS camera 200 according to the first embodiment of the present technology. The EVS camera 200 includes a drive unit 210, a signal processing unit 220, a pixel array unit 230, a signal generation unit 240, a readout area selection unit 250, and a timing control unit 260. A predetermined number of pixels 300 are arranged in a two-dimensional lattice in the pixel array unit 230.

[0032] The EVS camera 200 further includes an optical system, a communication circuit, a memory for storing EVS data, and the like, but these are omitted from the figure.

[0033] The driver 210 drives each pixel 300 to output a detection signal indicating the detection result of an address event to the signal processor 220. The detection signal includes, for example, one bit indicating the detection result of an on-event and one bit indicating the detection result of an off-event. The driver 210 scans the rows in sequence and causes each pixel in that row to output a detection signal. This method of scanning the rows in sequence is called a scanning method.

[0034] The readout region selection section 250 selects, as a readout region, at least a part of the pixel array section 230. Only the pixels 300 in the selected readout region output detection signals.

[0035] The signal generation unit 240 generates address information and polarity information (e.g., (X, Y, P)) for a pixel in which an address event is detected and outputs the information to the signal processing unit 220. The signal generation unit 240 can output not only address information and timestamp information, but also frame-format information (e.g., (0, 0, 1, 0, ...)) indicating the presence or absence of an address event for each frame. The signal generation unit 240 also outputs information for the entire pixel array unit 230 or for all pixels within a selected range. If no address event has occurred, the signal generation unit 240 also outputs a signal to that effect. For example, two bits are assigned to each pixel, with "00" indicating no event, "01" indicating an ON event, "10" indicating an OFF event, and "11" indicating a Bose event (described below). The signal generation unit 240 also assigns one timestamp to the entire frame.

[0036] The signal processing unit 220 performs various signal processing on the detection signal for each pixel. For example, the signal processing unit 220 performs processing to detect glint for each pixel and supplies EVS data indicating the detection results to the signal processing circuit 110.

[0037] It should be noted that part or all of the processing performed by the signal processing unit 220 in the EVS camera 200 can be performed by an external signal processing circuit 110 instead of the signal processing unit 220 .

[0038] The timing control section 260 controls the operation timing of each of the drive section 210, the signal processing section 220, the signal generating section 240, and the readout area selecting section 250 in synchronization with the vertical synchronization signal VSYNC.

[0039] 3 is a block diagram showing an example of a configuration of a pixel 300 according to the first embodiment of the present technology. The pixel 300 includes a photoelectric conversion element 310, a logarithmic response unit 320, a buffer 330, a difference detector 340, a comparator 350, and an output circuit 360.

[0040] The photoelectric conversion element 310 generates a photocurrent by photoelectric conversion of incident light. The logarithmic response unit 320 converts the photocurrent into a logarithmic voltage and supplies it to the difference detector 340 via the buffer 330.

[0041] The difference detector 340 detects the difference between the logarithmic voltage and the signal during auto-zero and outputs the result to the comparator 350. The comparator 350 compares the difference with an upper threshold and a lower threshold. The comparator 350 supplies the output circuit 360 with a detection signal VCO+ indicating the result of the comparison with the upper threshold and a detection signal VCO- indicating the result of the comparison with the lower threshold.

[0042] The output circuit 360 holds the detection signals VCO+ and VCO- and outputs them to the signal processing unit 220 and the signal generating unit 240 under the control of the driving unit 210 and the readout area selecting unit 250. When an on-event or an off-event is detected, the output circuit 360 initializes the difference detector 340 using a control signal AZ.

[0043] FIG. 4 is a circuit diagram showing an example configuration of the logarithmic response unit 320, the buffer 330, the difference detector 340, and the comparator 350 according to the first embodiment of the present technology.

[0044] The logarithmic response unit 320 includes nMOS (n-channel Metal Oxide Semiconductor) transistors 321, 322, 323, and 324, and a current source transistor 325. The current source transistor 325 is, for example, a pMOS (p-channel MOS) transistor.

[0045] The nMOS transistors 321 and 322 are inserted in series between the power supply voltage and the photoelectric conversion element 310. The current source transistor 325 and the nMOS transistors 323 and 324 are connected in series between the power supply voltage and a reference voltage (such as a ground voltage).

[0046] The gate of nMOS transistor 322 is connected to the connection node of nMOS transistors 323 and 324, and the gate of nMOS transistor 324 is connected to the connection node of nMOS transistor 322 and photoelectric conversion element 310. The gate of nMOS transistor 321 is connected to the connection node of current source transistor 325 and nMOS transistor 323, and the gate of nMOS transistor 323 is connected to the connection node of nMOS transistors 321 and 322. The connection node of current source transistor 325 and nMOS transistor 323 is connected to buffer 330. A predetermined bias voltage V ｂｌｏｇ is applied.

[0047] With the above-described circuit configuration, the photocurrent generated in the photoelectric conversion element 310 is converted into a logarithmic voltage VLOG.

[0048] It is also possible to eliminate either the loop circuit formed by nMOS transistors 321 and 323 or the loop circuit formed by nMOS transistors 322 and 324, thereby reducing the loop circuit to one stage. Also, the loop circuit can be formed into three or more stages.

[0049] The buffer 330 includes nMOS transistors 331 and 332. These transistors are connected in series between a power supply voltage and a reference voltage (such as a ground voltage), with the nMOS transistor 331 on the power supply side. A logarithmic voltage VLOG is input to the gate of the nMOS transistor 331, and a predetermined bias voltage V ｂｓｆ The connection node of the nMOS transistors 331 and 332 is connected to the difference detector 340.

[0050] With the above-described circuit configuration, the buffer 330 supplies the voltage VSF corresponding to the logarithmic voltage VLOG to the difference detector 340 .

[0051] The difference detector 340 includes capacitors 341 and 343 , nMOS transistors 342 and 345 , and a pMOS transistor 344 .

[0052] The pMOS transistor 344 and the nMOS transistor 345 are connected in series between the power supply voltage and the reference voltage. They function as an inverter that inverts the input signal, with the gate of the pMOS transistor 344 as the input terminal and the connection node between the pMOS transistor 344 and the nMOS transistor 345 as the output terminal. The output terminal of this inverter is connected to the comparator 350. A predetermined bias voltage V ｂｄｉｆｆ is applied.

[0053] One end of the capacitor 341 is connected to the output terminal of the buffer 330, and the other end is connected to the input terminal of the inverter (i.e., the gate of the pMOS transistor 344). The capacitor 343 is connected in parallel with the inverter. The nMOS transistor 342 opens and closes the path connecting both ends of the capacitor 343 in accordance with a control signal AZ from the output circuit 360.

[0054] With the above circuit configuration, the difference V from the voltage VSF corresponding to the logarithmic voltage is ｄｉｆｆ is generated.

[0055] The comparator 350 includes pMOS transistors 351 and 353 and nMOS transistors 352 and 354 .

[0056] The pMOS transistor 351 and the nMOS transistor 352 are connected in series between the power supply voltage and the reference voltage. The pMOS transistor 353 and the nMOS transistor 354 are also connected in series between the power supply voltage and the reference voltage. The gates of the pMOS transistors 351 and 353 are connected to the output terminal of the difference detector 340. A bias voltage Vth+ indicating the upper threshold is applied to the gate of the nMOS transistor 352, and a bias voltage Vth− indicating the lower threshold is applied to the gate of the nMOS transistor 354.

[0057] The connection node between pMOS transistor 351 and nMOS transistor 352 is connected to output circuit 360, and the voltage at this connection node is output as detection signal VCO+ indicating the presence or absence of an on-event. The connection node between pMOS transistor 353 and nMOS transistor 354 is also connected to output circuit 360, and the voltage at this connection node is output as detection signal VCO- indicating the presence or absence of an off-event.

[0058] With the above circuit configuration, the difference V ｄｉｆｆ exceeds the upper threshold, the comparator 350 outputs a high-level detection signal VCO+, and the difference V ｄｉｆｆ falls below the lower limit threshold, a low level detection signal VCO- is output.

[0059] [Example of Operation of the Light Detection System] Fig. 5 is a timing chart showing an example of operation of the light detection system 100 according to the first embodiment of the present technology. It is assumed that the eyeball is in a stationary state. The same applies to the subsequent timing charts. The signal processing circuit 110 supplies the vertical synchronization signal VSYNC, which rises at timings T1, T3, T5, T7, etc., to the EVS camera 200.

[0060] The EVS camera 200 detects address events in synchronization with the vertical synchronization signal VSYNC. For example, during the detection period from timing T10 to T11 immediately after timing T1, all pixels detect an ON event or an OFF event and retain the detection results. Thereafter, an address event is detected every time a period of the vertical synchronization signal VSYNC elapses.

[0061] If an address event is detected within the conditional reset period from timing T11 to T2, the output circuit 360 in the pixel uses the control signal AZ to initialize the difference detector 340. On the other hand, if no address event is detected, the difference detector 340 is not initialized.

[0062] Then, during the readout period from timing T2 to T21, the driving section 210 scans the rows in order and outputs detection signals.

[0063] Furthermore, the signal processing circuit 110 supplies the LED driver 120 with an external synchronization signal ESYNC that rises at timings T0, T4, and the like.

[0064] The LED driver 120 outputs the pulse signal PLS to the V ＯＦＦ The LED is turned off by turning off the LED. This off-pulse period includes a period for detecting an address event. The pulse width of the off-pulse period is adjusted to a value such that an address event occurs only in pixels that receive glint.

[0065] Then, the LED driver 120 outputs the pulse signal PLS to V during the period from timing T2 to timing T4 at the start of the next off-pulse period. ＯＦＦ Set it higher to light up the LED.

[0066] In the figure, VLOG1 indicates the logarithmic voltage of a pixel that receives reflected light (in other words, glint) from a fixed pattern of light emitted from an LED, and VLOG2 indicates the logarithmic voltage of a pixel that does not receive the glint.

[0067] After timing T1, the LED is turned off, so the logarithmic voltage VLOG1 decreases, and after timing T2, the LED is turned on, so the logarithmic voltage VLOG1 increases. On the other hand, the level of the logarithmic voltage VLOG2 changes little.

[0068] When the amount of change in the logarithmic voltage VLOG1 falls below the lower limit threshold, an OFF event is detected in the pixel that received the glint within the detection period immediately after timing T1.

[0069] Furthermore, after timing T2, when the amount of change in the logarithmic voltage VLOG1 exceeds the upper threshold, an ON event is detected in the pixel that received the glint within the detection period immediately after timing T3. In the figure, circles indicate the detection timing of an ON event or an OFF event.

[0070] As shown in the figure, the frequency of the external synchronization signal ESYNC is set to half that of the vertical synchronization signal VSYNC, so the LED driver 120 repeatedly turns off the LED for an off-pulse period, and then turns on the LED for nearly two periods of the vertical synchronization signal VSYNC after the off-pulse period has elapsed.

[0071] Here, more current flows through the photoelectric conversion element 310 in a pixel that receives glint than through a pixel that does not receive glint. Therefore, more current also flows through the logarithmic response unit 320 in the subsequent stage, widening the bandwidth and increasing the response speed of the logarithmic voltage VLOG1 to changes in current. In the control shown in the figure, the off-pulse period during which the LED is turned off is shorter than the period during which the LED is turned on, so only the differential value of the output of the logarithmic response unit 320, which has a faster response speed, crosses the threshold. Therefore, only the pixel that received the glint responds during the off-pulse period, generating an off-event. Then, because the LED is not turned off during the next detection period, the logarithmic voltage VLOG1 returns to its original value, generating an on-event in the pixel that received the glint.

[0072] On the other hand, in pixels that do not receive glint, the response speed of the logarithmic voltage VLOG2 due to LED modulation is slow, so an address event due to LED modulation is not detected. In other words, a global event (described below) does not occur. However, when the eyeball moves, pixels at the edge of the pupil generate address events as usual. The downstream signal processing unit 220 detects the coordinates of the pixel where the address event occurred as the coordinates of the glint.

[0073] 6, the waveform of the pulse signal PLS can also be inverted. In this case, the LED driver 120 repeatedly controls the LEDs to be turned on for an on-pulse period, such as from timing T0 to T2, and then to be turned off for nearly two periods of the vertical synchronization signal VSYNC after the on-pulse period has elapsed.

[0074] According to the control shown in the figure, the on-pulse period during which the LED is on is shorter than the period during which it is off, thereby reducing power consumption. In addition, since the logarithmic response unit 320 operates in a narrow band, this is advantageous when performing eye tracking using only glint.

[0075] As illustrated in FIGS. 5 and 6 , the LED driver 120 controls the state of the light-emitting unit 130 to either on or off within a predetermined pulse period, and controls the state of the light-emitting unit 130 to the other of on or off outside the pulse period.

[0076] As shown in FIG. 7, the LED driver 120 can also control the brightness of the LEDs in a lit state in synchronization with the vertical synchronization signal VSYNC.

[0077] For example, the LED driver 120 sets the level of the pulse signal PLS to V during a pulse period such as from timing T0 to T2. ＯＦＦ Higher V ＯＮ＿Ｈ and outside that period, the level of the pulse signal PLS is controlled to V ＯＦＦ and V ＯＮ＿Ｈ Between ＯＮ＿Ｌ Controlled to V ＯＮ＿Ｌ is set to a value equal to or greater than the level required for pupil detection. This control increases the brightness of the LED during the pulse period and decreases the brightness of the LED outside of the pulse period. By lowering the illuminance to the level required for pupil detection without turning off the LED, the logarithmic response unit 320 can be operated over a wider bandwidth.

[0078] The LED driver 120 sets the level of the pulse signal PLS to V during the pulse period. ＯＮ＿Ｌ and outside that period, ＯＮ＿Ｈ It can also be controlled to

[0079] Here, a comparative example is assumed in which the LED in the light-emitting unit 130 continues to light up at a constant brightness.

[0080] 8 is a timing chart showing an example of the operation of the light detection system in the comparative example. ＯＦＦ A pulse signal PLS having a higher constant level causes the LED to emit DC (Direct Current) light.

[0081] This comparative example has the following problems: First, the logarithmic voltage VLOG1 hardly changes even in pixels that receive glint, and the pixels cannot detect address events.

[0082] The second reason is that because the size of the glint itself is small, the size of the glint edge is also small, and the number of events corresponding to the glint edge is also smaller than that of the pupil, making it difficult to detect the glint.

[0083] The third problem is that the occurrence of address events due to glint is so small that the detection results are lost when noise processing is performed.

[0084] Fourth, when detecting an address event or integrating or storing frames, it is necessary to distinguish between an address event caused by a glint and an address event caused by a pupil, which makes the processing difficult.

[0085] Fifth, when the eyeball is stationary, no address event occurs at the pixel receiving the glint, making eye tracking impossible.

[0086] The sixth reason is that the LED driver 120 drives the LED to emit light using DC, which consumes more power than when the LED is flashed.

[0087] Seventh, eye tracking could be performed by alternating the illumination of a pair of LEDs to avoid global events, which are address events that occur across the entire eye regardless of edges such as glint. However, this would double the number of LEDs and increase costs. For example, typical eye tracking uses both pupil detection using pupil edge detection and glint detection using glint edge detection to detect gaze. In such a system, if two adjacent LEDs are alternately turned on and off, only the corresponding glint will generate a local event. However, if the entire eye is viewed, the illuminance does not change and no global event will be generated.

[0088] The eighth point is that when a pair of LEDs are alternately illuminated, the number of address events due to glint increases, and therefore complex measures such as masking are required to prevent this from affecting the calculation accuracy of the algorithm for detecting the pupil.

[0089] 5 to 7, the LED driver 120 controls the brightness of the LEDs in synchronization with the external synchronization signal ESYNC, which is synchronized with the vertical synchronization signal VSYNC, and therefore the logarithmic voltage VLOG1 changes in the pixels that receive the glint. This allows the EVS camera 200 to detect the glint even if the eyeball does not move, thereby improving the accuracy of glint detection.

[0090] Furthermore, since the LED driver 120 blinks the LED, power consumption is reduced compared to the comparative example.

[0091] Furthermore, although the irradiated light is modulated, the logarithmic voltage band of the pixels that do not receive the glint is narrow, resulting in a slow response speed. As a result, when the LED is turned on and off at high speed, the output of the logarithmic response unit 320 of that pixel cannot keep up, and no address event due to modulation occurs. As a result, no global event occurs.

[0092] Therefore, all of the first to eighth problems can be solved.

[0093] As described above, according to the first embodiment of the present technology, the LED driver 120 controls the brightness of the LED in synchronization with the external synchronization signal ESYNC, which is synchronized with the vertical synchronization signal VSYNC, thereby improving the accuracy of glint detection.

[0094] [First Modification] In the first embodiment described above, the signal processing circuit 110 generates the external synchronization signal ESYNC and supplies it to the LED driver 120. However, this is not limiting. The light detection system 100 in this first modification of the first embodiment differs from the first embodiment in that the EVS camera 200 generates the external synchronization signal ESYNC and supplies it to the LED driver 120.

[0095] 9 is a block diagram showing a configuration example of a light detection system 100 according to a first modification of the first embodiment of the present technology. In this first modification of the first embodiment, the signal processing circuit 110 does not generate an external synchronization signal ESYNC. Instead, the EVS camera 200 generates the external synchronization signal ESYNC in synchronization with the vertical synchronization signal VSYNC and supplies the external synchronization signal ESYNC to the LED driver 120. For example, the timing control unit 260 in FIG. 2 generates the external synchronization signal ESYNC.

[0096] Thus, according to the first modified example of the first embodiment of the present technology, the EVS camera 200 generates the external synchronization signal ESYNC in synchronization with the vertical synchronization signal VSYNC, so the signal processing circuit 110 does not need to generate the external synchronization signal ESYNC.

[0097] [Second Modification] In the first embodiment described above, the signal processing circuit 110 generates the vertical synchronization signal VSYNC and supplies it to the EVS camera 200, but this configuration is not limiting. The light detection system 100 in this second modification of the first embodiment differs from the first embodiment in that the LED driver 120 generates the vertical synchronization signal VSYNC and supplies it to the EVS camera 200.

[0098] 10 is a block diagram showing an example configuration of a light detection system 100 according to a second modification of the first embodiment of the present technology. In this second modification of the first embodiment, the signal processing circuit 110 does not generate a vertical synchronization signal VSYNC. Instead, the LED driver 120 generates the vertical synchronization signal VSYNC in synchronization with the external synchronization signal ESYNC and supplies the signal to the EVS camera 200.

[0099] As described above, according to the second modified example of the first embodiment of the present technology, the LED driver 120 generates the vertical synchronization signal VSYNC in synchronization with the external synchronization signal ESYNC, so that the signal processing circuit 110 does not need to generate the vertical synchronization signal VSYNC.

[0100] 2. Second Embodiment In the first embodiment described above, EVS camera 200 detects either an ON event or an OFF event within a detection period, but it can also detect these events sequentially in a time-division manner. EVS camera 200 in this second embodiment differs from the first embodiment in that it detects ON events and OFF events sequentially in a time-division manner.

[0101] 11 is a circuit diagram showing an example configuration of a logarithmic response unit 320, a buffer 330, a difference detector 340, and a comparator 350 according to the second embodiment of the present technology. The difference detector 340 according to the second embodiment differs from the first embodiment in that it does not include a capacitor 343 and further includes a selector 346. Furthermore, the comparator 350 does not include a pMOS transistor 353 or an nMOS transistor 354, and a predetermined bias voltage Vth is applied to the gate of the nMOS transistor 352.

[0102] The selector 346 selects one of the bias voltages VAZ, Vth+, and Vth− in accordance with the control signal SW from the driver 210, and supplies the selected voltage to the gate of the nMOS transistor 345. The bias voltage VAZ is a voltage selected during the conditional reset period. During this conditional reset period, a predetermined reference value is held in the capacitor 341.

[0103] The bias voltage Vth+ indicates an upper threshold, and the bias voltage Vth- indicates a lower threshold. The driver 210 sets the detection periods for the ON and OFF events each time a period of the vertical synchronization signal VSYNC elapses.

[0104] During the on-event detection period, the driver 210 controls the selector 346 to select the bias voltage Vth+, which causes the difference detector 340 to determine whether the difference exceeds the upper threshold, and the comparator 350 to output the on-event detection signal VCO+.

[0105] During the off-event detection period, the driver 210 controls the selector 346 to select the bias voltage Vth−, which causes the difference detector 340 to determine whether the difference is below the lower threshold, and the comparator 350 to output the off-event detection signal VCO−.

[0106] The method of detecting ON events and OFF events in sequence in a time-division manner using the circuit configuration illustrated in the figure will be referred to as the "time-division method" hereinafter.

[0107] 12 is a timing chart showing an example of the operation of the photodetection system 100 according to the second embodiment of the present technology. An on-event detection period is set from timing T10 to T11 immediately after timing T1 of the rising edge of the vertical synchronization signal VSYNC, and during this period, the pixel detects an on-event. A conditional reset period is set from timing T11 to T2, and when an on-event is detected, the difference detector 340 is initialized during this period. Rows are scanned in sequence between timings T2 and T20.

[0108] An off-event detection period is set from timing T20 to T21, during which the pixel detects an off-event. A conditional reset period is set from timing T21 to T3, and when an off-event is detected, the difference detector 340 is initialized during this period. After timing T3, the rows are scanned in order.

[0109] The LED driver 120 turns off the LEDs using the pulse signal PLS during an off-pulse period from timing T2 to T3. This off-pulse period includes only the off-event detection period of the on-event detection period and the off-event detection period immediately after timing T1. Because the logarithmic voltage VLOG1 decreases during the off-pulse period, the pixel corresponding to the glint detects an off-event during the off-event detection period.

[0110] The LED driver 120 then uses the pulse signal PLS to light up the LEDs during the period from timing T3 to T6. This period includes an on-event detection period and an off-event detection period immediately after timing T4, and an on-event detection period immediately after timing T5. Because the logarithmic voltage VLOG1 rises, the pixel corresponding to the glint detects an on-event during the on-event detection period immediately after timing T4.

[0111] After timing T5, the control from timing T1 to just before timing T5 is repeatedly executed.

[0112] The on-event detection period and the off-event detection period immediately after timing T1 are examples of the first on-event detection period and the first off-event detection period set forth in the claims. The on-event detection period and the off-event detection period immediately after timing T4 are examples of the second on-event detection period and the second off-event detection period set forth in the claims.

[0113] As shown in the figure, the LED driver 120 turns off the LED during an off-pulse period that includes only an off-event detection period, and turns on the LED outside of that pulse period. This control causes pixels that receive glint to alternately detect on-events and off-events. On the other hand, pixels that do not receive glint do not generate address events due to the LED being turned on or off. However, if the eyeball moves, address events will occur at edges such as the pupil edge, as usual. The downstream signal processor 220 detects the coordinates of pixels where on-events and off-events alternately occur as the coordinates of the glint.

[0114] In the figure, the rising edge of the pulse signal PLS is set to coincide with timing T2, but it may occur before timing T2. Even in this case, timings T10 to T11 are the on-event detection period, and the LED is turned off when the pulse signal PLS falls, so no on-event occurs. Also, while the falling edge of the pulse signal PLS is set to coincide with timing T3, it may occur after timing T3, as long as the logarithmic voltage VLOG1 exceeds the upper threshold by the on-event detection period immediately after timing T4.

[0115] 13 is a diagram illustrating an example of EVS data according to the second embodiment of the present technology, where a shows an example of EVS data when the pseudo eyeball is stationary, and b shows an example of EVS data when the pseudo eyeball is moving.

[0116] The LED in the light-emitting unit 130 emits a certain pattern of irradiation light (such as IR light) onto the artificial eyeball, and the reflected light is received as glint by the EVS camera 200. When the irradiation light is irradiated onto the artificial eyeball, the points that become the reflected light (glint) become brighter than other areas. Therefore, when the artificial eyeball is photographed with the EVS camera 200, the amount of light at the pixels that receive the glint is greater than that at the pixels that do not receive the glint.

[0117] As the amount of light increases, more current flows through the photoelectric conversion element 310 in the pixel that receives the glint, and more current flows through the logarithmic response unit 320 in the subsequent stage. The greater the current, the wider the bandwidth of the logarithmic response unit 320 and the faster the response speed. For this reason, the response speed of a pixel that receives glint is faster than that of a pixel that does not receive glint.

[0118] For example, as shown in FIG. 1A, a glint consisting of four points is used. These four pixels have a fast response speed, and ON events and OFF events are detected alternately. On the other hand, pixels that do not receive the glint have a slow response speed, and therefore hardly any address events are detected. Therefore, no global events occur, and the EVS camera 200 can detect only the glint with high accuracy, and the light detection system 100 can perform eye tracking using the detection results.

[0119] Furthermore, as shown in the example of b in the figure, even when the pseudo eyeball is moving, no global event occurs, and ON and OFF events are alternately detected at four points corresponding to the glint. Events also occur at the edges of the pupil as in the past, and can be detected at the pixels at those edges. This allows the EVS camera 200 to detect glint with high accuracy based on the address event detection signal. Because address events are generated by pixels corresponding to the glint itself, rather than pixels corresponding to the edge of the glint, the event density is high, allowing the signal processing circuit 110 to perform eye tracking without frame integration.

[0120] Furthermore, because the event density is higher in pixels corresponding to glint than in pixels corresponding to the pupil edge, it is easier to distinguish between the pupil edge and events. Although there is a concern about interference between the glint and the event density being higher in pixels corresponding to the pupil edge than in pixels corresponding to the glint, the interference is less than when using a pair of LEDs that emit IR light.

[0121] The first and second modifications of the first embodiment can be applied to the second embodiment.

[0122] As described above, according to the second embodiment of the present technology, the LED driver 120 turns off the LED within the off-pulse period that includes the off-event detection period, and therefore the light detection system 100 can detect glint with high accuracy when using the time-division method.

[0123] [Modification] In the second embodiment described above, the LED driver 120 turns off the LEDs during the off-pulse period, but it is preferable to further reduce power consumption. The LED driver 120 in this modification of the second embodiment differs from the second embodiment in that the waveform of the pulse signal PLS is inverted.

[0124] 14 is a timing chart showing an example of the operation of the light detection system 100 in a modified example of the second embodiment of the present technology. In this modified example of the second embodiment, the LED driver 120 repeatedly controls the LED to be turned on for an on-pulse period, such as from timing T2 to T3, and then to be turned off for nearly two periods of the vertical synchronization signal VSYNC after the on-pulse period has elapsed. Also, immediately after the rising edge of the vertical synchronization signal, such as timing T1, an off-event detection period is set first, and then an on-event detection period is set. The on-pulse period includes only the on-event detection period among these detection periods.

[0125] According to the control shown in the figure, the on-pulse period during which the LED is lit is shorter than the period during which the LED is turned off, so that power consumption can be reduced compared to the second embodiment.

[0126] In the figure, the rising edge of the pulse signal PLS is set to coincide with timing T2, but it may occur before timing T2. Even in this case, timings T10 to T11 are the OFF event detection period, and the LED is turned on by the rising edge of the pulse signal PLS, so no OFF event occurs. Also, while the falling edge of the pulse signal PLS is set to coincide with timing T3, it may occur after timing T3, as long as the logarithmic voltage VLOG1 falls below the lower limit threshold by the time of the OFF event detection period immediately after timing T4.

[0127] The first and second modifications of the first embodiment can be applied to the modification of the second embodiment.

[0128] As described above, according to the modification of the second embodiment of the present technology, the LED driver 120 turns on the LED during the on-pulse period including the on-event detection period, thereby reducing power consumption.

[0129] 3. Third Embodiment In the second embodiment described above, each pixel alternately detects on-events and off-events, but it is preferable to further improve the accuracy of glint detection. The photodetection system 100 in this third embodiment differs from the second embodiment in that it detects, as a glint event, the detection of both an on-event and an off-event within the period of the vertical synchronization signal VSYNC.

[0130] 15 is a timing chart showing an example of the operation of the light detection system 100 according to the third embodiment of the present technology. In the third embodiment, the LED driver 120 blinks the LED every time a period of the vertical synchronization signal VSYNC elapses.

[0131] For example, immediately after timing T1 of the rising edge of the vertical synchronization signal VSYNC, an on-event detection period and an off-event detection period are set in that order. Of these detection periods, the LED driver 120 turns off the LEDs during a period from timing T2 to T4, which includes only the off-event detection period.

[0132] Then, immediately after timing T5, the next rising edge of the vertical synchronization signal VSYNC, an on-event detection period and an off-event detection period are set in sequence. Of these detection periods, the LED driver 120 turns on the LEDs during an on-pulse period from timing T4 to T6, which includes only the on-event detection period. From timing T6 onwards, the same control is repeatedly executed.

[0133] A pixel receiving glint detects an OFF event because the logarithmic voltage VLOG1 drops during the period when the LED is off. The pixel also detects an ON event because the logarithmic voltage VLOG1 rises during the ON pulse period when the LED is on. In this way, a pixel receiving glint detects both an ON event and an OFF event within the period of the vertical synchronization signal VSYNC. On the other hand, a pixel not receiving glint barely detects an address event because the logarithmic voltage VLOG2 changes little.

[0134] Furthermore, in the control illustrated in the figure, the LED lighting period is shorter than in the second embodiment, so power consumption can be reduced.

[0135] 16 is a circuit diagram showing an example configuration of a signal processing unit 220 in an EVS camera 200 according to the third embodiment of the present technology. The signal processing unit 220 includes a switching control unit 221, a selector 222, a flip-flop 223, an inverter 224, an AND (logical product) gate 225, and a post-processing unit 226. Of these, the selector 222, the flip-flop 223, the inverter 224, and the AND gate 225 are each arranged for each column of the pixel array unit 230, but for convenience of description, only one column is shown in the same figure.

[0136] The switching control unit 221 controls the selector 222 in synchronization with the vertical synchronization signal VSYNC to switch the output destination. The selector 222 sequentially receives the detection signals VCO+ and VCO- from the pixels 300 in the corresponding column. During the period in which the detection signal VCO+ is input, the switching control unit 221 controls the selector 222 to output the signal to the flip-flop 223. Furthermore, during the period in which the detection signal VCO- is input, the switching control unit 221 controls the selector 222 to output the signal to the inverter 224.

[0137] The flip-flop 223 holds the detection signal VCO+ in synchronization with the vertical synchronization signal VSYNC and outputs the signal to the AND gate 225. The inverter 224 inverts the detection signal VCO- and outputs the result to the AND gate 225. The AND gate 225 outputs the logical product of the detection signal VCO+ and the inverted signal of the detection signal VCO- as a detection signal VCOb to the subsequent processing unit 226.

[0138] Here, the detection of an ON event or an OFF event within the period of the vertical synchronization signal VSYNC is referred to as a “Bose event.” The detection signal VCOb goes high when a Bose event is detected, and goes low when no Bose event is detected.

[0139] The post-processing unit 226 detects the coordinates of the pixel where the bose event occurred as the coordinates of the glint, and generates EVS data indicating the glint detection result. The EVS data is transmitted to the signal processing circuit 110 outside the EVS camera 200.

[0140] The signal processing unit 220 is not limited to the configuration shown in the figure as an example, as long as it can detect a Bose event.

[0141] Furthermore, although the Bose events are detected by the signal processing unit 220 in the EVS camera 200, the Bose events can alternatively be detected by the signal processing circuit 110 external to the EVS camera 200.

[0142] 17 is a diagram showing an example of EVS data when the pseudo eyeball in the comparative example is stationary and when it is moving. In the figure, a and b show EVS data when the pseudo eyeball in the comparative example in which the LED emits DC light is stationary, and c and d show EVS data when the pseudo eyeball in the comparative example is moving. For example, assume that a glint consisting of four points is used. In a and c of the figure, gray indicates an on-event, and black indicates an off-event.

[0143] As shown in FIG. 1A, in the comparative example, when the pseudo eyeball is stationary, no on-events or off-events occur in the pixels at the edge of the pupil, making it impossible to detect the pupil. Furthermore, no on-events or off-events occur in the pixels that receive glint or in the edge pixels, making it impossible to detect glint. Furthermore, as shown in FIG. 1B, in the comparative example, no bose event occurs when the pseudo eyeball is stationary. Furthermore, because the LED is driven by DC current, no global event occurs.

[0144] As shown in Fig. 1C, in the comparative example, when the pseudo eyeball moves, on-events and off-events occur at the pixels at the edge of the pupil. This makes it possible to detect the pupil. Address events also occur at the pixels at the edge of the glint, but the number of events is small and the density is low. This makes it possible to detect glint, but frame integration and storage are required to improve detection accuracy. As shown in Fig. 1D, in the comparative example, no bose events occur even when the pseudo eyeball moves. Furthermore, because the LED is driven by DC current, no global events occur.

[0145] 18 is a diagram showing an example of EVS data when the pseudo eyeball in the second embodiment of the present technology is stationary and when it is moving. In the figure, a and b show EVS data when the pseudo eyeball in the second embodiment is stationary, and c and d show EVS data when the pseudo eyeball in the second embodiment is moving. For example, assume that a glint consisting of four points is used. In a and c of the figure, gray indicates an on-event, and black indicates an off-event.

[0146] As shown in the example of "a" in the figure, in the second embodiment, when the eyeball is stationary, no on-events or off-events occur in the pixels at the edge of the pupil, making it impossible to detect the pupil, as in the comparative example. Furthermore, since on-events or off-events occur in almost all pixels where glint is detected, the number of events is large and the density is high. Therefore, highly accurate glint detection is possible without integrating or storing frames. Furthermore, as shown in the example of "b" in the figure, in the second embodiment, no bose events occur when the pseudo eyeball is stationary. Furthermore, although the LED is turned on and off, no global events occur because a pulse signal PLS synchronized with the vertical synchronization signal VSYNC is used.

[0147] As illustrated in FIG. 1C, in the second embodiment, when the pseudo eyeball moves, on-events and off-events occur at the pixels at the edge of the pupil. Therefore, pupil detection is possible, similar to the comparative example. Furthermore, since on-events or off-events occur at almost all pixels where glint is detected, the number of events is large and the density is high. Therefore, highly accurate glint detection is possible without integrating or storing frames. Furthermore, as illustrated in FIG. 1D, in the second embodiment, no bose events occur even when the pseudo eyeball moves. Furthermore, although the LED is turned on and off, no global events occur because a pulse signal PLS synchronized with the vertical synchronization signal VSYNC is used.

[0148] 19 is a diagram showing an example of EVS data when the pseudo eyeball is stationary and when it is moving in the third embodiment of the present technology. In the figure, a and b show EVS data when the eyeball is stationary in the third embodiment, and c and d show EVS data when the eyeball is moving in the third embodiment. For example, assume that a glint consisting of four points is used. In a and c of the figure, gray indicates an on-event, and black indicates an off-event. In b and d of the figure, black indicates a bose event.

[0149] As shown in the example of "a" in the figure, in the third embodiment, when the eyeball is stationary, no on-events or off-events occur at the pixels at the edge of the pupil, making pupil detection impossible, as in the comparative example and the second embodiment. On the other hand, as shown in the example of "b" in the figure, bose events occur at almost all pixels where glint is detected, resulting in a large number of events and a high density. This allows for highly accurate glint detection without integrating or storing frames. Furthermore, although the LED is turned on and off, no global events occur because a pulse signal PLS synchronized with the vertical synchronization signal VSYNC is used.

[0150] As illustrated in FIG. 1C, in the third embodiment, when the eyeball moves, on-events and off-events occur at pixels at the edge of the pupil. Therefore, pupil detection is possible in the same way as in the comparative example and the second embodiment. Furthermore, while on-events and off-events also occur at pixels at the edge of the glint, these can be easily masked and deleted using the coordinates of the bose events, improving pupil detection accuracy. Furthermore, as illustrated in FIG. 1D, when the eyeball moves, bose events occur at almost all pixels where glint is detected, resulting in a large number of events and a high density. Therefore, highly accurate glint detection is possible without integrating or storing frames. Furthermore, because glint appears as a bose event, it does not interfere with the pupil edge, which appears as an on-event or off-event, improving pupil detection accuracy. Furthermore, although the LED is turned on and off, a global event does not occur because a pulse signal PLS synchronized with the vertical synchronization signal VSYNC is used.

[0151] 20 is a diagram showing an example of EVS data with different glint patterns when the pseudo eyeball is stationary and when it is moving according to the third embodiment of the present technology. In the figure, a and b are examples of EVS data when the pseudo eyeball is stationary according to the third embodiment, and c and d are examples of EVS data when the pseudo eyeball is moving according to the third embodiment. For example, assume that a glint consisting of eight points is used. In a and c of the figure, gray indicates an on-event, and black indicates an off-event. In b and d of the figure, black indicates a bose event.

[0152] Similar results are obtained when the number of glint points is eight, as shown in the example of Figure 20. The light detection system can detect glints without any problems even in high illumination conditions.

[0153] The first and second modifications of the first embodiment can be applied to the third embodiment.

[0154] As described above, according to the third embodiment of the present technology, the EVS camera 200 detects bose events, and therefore the accuracy of glint detection can be further improved.

[0155] 4. Fourth Embodiment In the first embodiment described above, the LED driver 120 transmits the same pulse signal PLS to the multiple LEDs in the light-emitting unit 130. However, with this configuration, it is difficult to distinguish between the reflected light of each LED. The LED driver 120 in this fourth embodiment differs from the first embodiment in that it transmits pulse signals with different waveforms to each LED.

[0156] 21 is a block diagram showing a configuration example of a light detection system 100 according to a fourth embodiment of the present technology. In this fourth embodiment, a plurality of LEDs, such as LEDs 131 and 132, are arranged in a light-emitting unit 130. An LED driver 120 generates and transmits pulse signals having different waveforms for each LED. For example, a pulse signal PLS is transmitted to the LED 131. １ is transmitted, and the LED 132 displays a pulse signal PLS ２ is sent.

[0157] 22 is a timing chart illustrating an example of an operation of the light detection system according to the fourth embodiment of the present technology. It is assumed that N (N is an integer) LEDs are arranged, and a pulse signal transmitted to the nth (n is an integer from 1 to N) LED is transmitted by PLS. ｎ Let's say.

[0158] The light emission patterns of the N LEDs are different. A modulation period and a DC light emission period are set for each LED, but the timings at which they start and end are different. In the figure, the white parts indicate DC light emission periods, and the gray parts indicate modulation periods. For example, when the pulse signal PLS １ A modulation period is set from timing T1 to T3, and a DC light emission period is set from timing T3 to T5. ２ A modulation period is set from timing T1 to T4, and a DC light emission period is set from timing T4 to T6. ＮIn the example, a DC light emission period is set from timing T1 to T2, and a modulation period is set from timing T2 to T7.

[0159] The LED driver 120 modulates the pulse signal in synchronization with the vertical synchronization signal VSYNC during the modulation period, and keeps the pulse signal at a high level continuously during the DC light emission period.

[0160] The EVS camera 200 detects an address event for each LED individually based on the light emission pattern of each LED. For example, during the period from timing T1 to T2, the Nth LED emits DC light, while the first and second LEDs blink. Therefore, the EVS camera 200 can determine that the pixel in which an address event is detected during that period has received reflected light corresponding to the first and second LEDs.

[0161] Pulse signal PLS １ and PLS ２ Since the modulation periods of the pulse signals PLS and PLS overlap, they must be distinguished. １ In the odd-numbered frames, a pulse period (on-pulse period or on-pulse period) is set, and the pulse signal PLS ２ In the odd-numbered frame, a pulse period is set in the even-numbered frame. When an off-pulse period is set, the EVS camera can determine that a pixel in which an off-event is detected in an odd-numbered frame has received reflected light corresponding to the first LED. Also, a pixel in which an off-event is detected in an even-numbered frame is determined to have received reflected light corresponding to the second LED. The EVS camera 200 generates EVS data that associates LED identification information with detection signals and transmits the data to the signal processing circuit 110.

[0162] As described above, the LED driver 120 transmits pulse signals with different waveforms to each LED, which allows the EVS camera 200 to associate the LED identification information with the detection signal, thereby eliminating specific noise.

[0163] For example, let the glint be four points, and let the identification information of the four LEDs be L1 to L4. The EVS camera 200 determines whether the arrangement pattern of the address events corresponding to each of L1 to L4 matches the pattern of the glint emitted by the light-emitting unit 130. This makes it possible to remove noise other than the glint. Note that this processing can also be performed by the signal processing circuit 110 instead of the EVS camera 200.

[0164] Furthermore, by setting the modulation period and the DC light emission period, the light detection system 100 can normally perform eye tracking by DC emitting light from the LEDs, and can realize control to temporarily emphasize only the glint. Note that this control can also be realized when the same pulse signal is sent to all the LEDs.

[0165] Furthermore, by setting the modulation period and the DC light emission period, the optical detection system 100 can change the tracking method according to the movement of the eye. For example, when the pupil is stationary (or moving slowly), the modulation period is set, and when the pupil is moving (or moving quickly), the DC light emission period is set. Note that this control can be realized even when the same pulse signal is sent to all LEDs.

[0166] It should be noted that the first and second modifications of the first embodiment, the second embodiment, the modification of the second embodiment, and the third embodiment can each be applied to the fourth embodiment.

[0167] Thus, according to the fourth embodiment of the present technology, the LED driver 120 transmits a pulse signal with a different waveform for each LED, and therefore the EVS camera 200 can detect an address event for each LED in association with its identification information.

[0168] 5. Fifth Embodiment In the above-described first embodiment, the signal processing circuit 110 acts as a master to synchronize the LED driver 120 and the EVS camera 200, but the master can also be something other than the signal processing circuit 110. The light detection system 100 in this fifth embodiment differs from the first embodiment in that the EVS camera 200 acts as a master to synchronize the LED driver 120 with itself.

[0169] 23 is a block diagram showing a configuration example of a light detection system 100 according to a fifth embodiment of the present technology. In this fifth embodiment, the EVS camera 200 serves as a master in place of the signal processing circuit 110 and synchronizes the LED driver 120 with itself. For example, a timing control unit 260 in the EVS camera 200 generates an external synchronization signal ESYNC in synchronization with the vertical synchronization signal VSYNC and supplies it to the LED driver 120. This eliminates the need for the signal processing circuit 110 to generate the vertical synchronization signal VSYNC and the external synchronization signal ESYNC.

[0170] 24, the EVS camera 200 can also generate a clock signal CLK in synchronization with the vertical synchronization signal VSYNC and supply it to the signal processing circuit 110. The signal processing circuit 110 processes the EVS data in synchronization with the clock signal CLK.

[0171] 25 , the EVS camera 200 can further generate a clock signal CLK in synchronization with the vertical synchronization signal VSYNC and supply it to the signal processing circuit 110. The signal processing circuit 110 can also generate an external synchronization signal ESYNC in synchronization with the clock signal CLK and supply it to the LED driver 120.

[0172] 26, the LED driver 120 can further generate a clock signal CLK in synchronization with the external synchronization signal ESYNC and supply it to the signal processing circuit 110. The signal processing circuit 110 can also process the EVS data in synchronization with the clock signal CLK.

[0173] Moreover, the second embodiment, the modified example of the second embodiment, the third embodiment, and the fourth embodiment can be applied to the fifth embodiment.

[0174] Thus, according to the fifth embodiment of the present technology, the EVS camera 200 becomes the master and synchronizes the LED driver 120 with itself, so the signal processing circuit 110 does not need to generate the vertical synchronization signal VSYNC and the external synchronization signal ESYNC.

[0175] 6. Sixth Embodiment In the first embodiment described above, the signal processing circuit 110 acts as a master to synchronize the LED driver 120 and the EVS camera 200, but the master can be something other than the signal processing circuit 110. The light detection system 100 in this fifth embodiment differs from the first embodiment in that the LED driver 120 acts as a master to synchronize the EVS camera 200 with itself.

[0176] 27 is a block diagram showing a configuration example of a light detection system 100 according to a sixth embodiment of the present technology. In this sixth embodiment, the LED driver 120 serves as a master in place of the signal processing circuit 110 and synchronizes the EVS camera 200 with the LED driver 120. For example, the LED driver 120 generates a vertical synchronization signal VSYNC and supplies it to the EVS camera 200. This eliminates the need for the signal processing circuit 110 to generate the vertical synchronization signal VSYNC and the external synchronization signal ESYNC.

[0177] 28, the LED driver 120 can further generate a clock signal CLK and supply it to the signal processing circuit 110. The signal processing circuit 110 processes the EVS data in synchronization with the clock signal CLK.

[0178] 29 , the LED driver 120 can also generate a clock signal CLK and supply it to the signal processing circuit 110. The signal processing circuit 110 can also generate a vertical synchronization signal VSYNC in synchronization with the clock signal CLK and supply it to the EVS camera 200.

[0179] 30, the EVS camera 200 can also generate a clock signal CLK in synchronization with the vertical synchronization signal VSYNC and supply it to the signal processing circuit 110. The signal processing circuit 110 can also process the EVS data in synchronization with the clock signal CLK.

[0180] Moreover, the second embodiment, the modified example of the second embodiment, the third embodiment, and the fourth embodiment can be applied to the sixth embodiment.

[0181] Thus, according to the sixth embodiment of the present technology, the LED driver 120 becomes the master and synchronizes the EVS camera 200 with itself, so the signal processing circuit 110 does not need to generate the vertical synchronization signal VSYNC and the external synchronization signal ESYNC.

[0182] 7. Seventh Embodiment In the first embodiment described above, the EVS camera 200 outputs detection signals using a scanning method, but an arbiter method can be used instead of the scanning method. The arbiter method is a method in which an arbiter arbitrates requests from pixels. The light detection system 100 in this seventh embodiment differs from the first embodiment in that the EVS camera 200 uses the arbiter method.

[0183] 31 is a block diagram showing a configuration example of an EVS camera 200 according to a seventh embodiment of the present technology. The EVS camera 200 according to the seventh embodiment differs from the first embodiment in that it does not include a readout area selection unit 250 or a timing control unit 260, but further includes an arbiter 270. In this case, the signal generation unit 240 may generate address information, polarity information, and timestamp information (e.g., (X, Y, P, T)) of a pixel in which an address event is detected, and output the information to the signal processing unit 220.

[0184] Furthermore, the driving unit 210 simultaneously drives all of the pixels 300. When an address event is detected, each of the pixels 300 transmits a request to the arbiter 270. The arbiter 270 arbitrates the requests of the pixels 300 and returns a response based on the arbitration result. Upon receiving the response, the pixel 300 supplies a detection signal to the signal processing unit 220 and the driving unit 210. The driving unit 210 initializes the pixel 300 that transmitted the detection signal.

[0185] FIG. 32 is a timing chart showing an example of the operation of the light detection system 100 according to the seventh embodiment of the present technology.

[0186] In the seventh embodiment, the LED driver 120 turns off the LEDs using the pulse signal PLS during an off-pulse period, such as from timing T1 to T2. The LED driver 120 then turns on the LEDs during the period up to timing T3, when the next off-pulse period begins. Thereafter, similar control is repeatedly executed in synchronization with the external synchronization signal ESYNC.

[0187] When the arbiter method is used, the pulse width of the off-pulse period is set to a value that satisfies the following formula: t Ｉｇ +t ｄｒ <pulse width < t ＩＯ In the above equation, t Ｉｇ is the time from when the LED is turned off until the change in luminance of the pixel receiving the glint falls below the lower threshold. ｄｒ is the time from when the change in luminance of the pixel falls below the lower threshold to when the pixel is initialized. ＩＯ is the time it takes for the change in luminance of the pixel that does not receive glint to fall below the lower threshold. These times are adjusted to appropriate values ​​in advance by calibration, evaluation, etc. depending on the environment, such as the characteristics of the EVS camera and the eye.

[0188] In other words, the time from when the LED is turned off until the pixel receiving the glint is initialized (t Ｉｇ +t ｄｒ ) and the time from the timing of turning off until the amount of change in luminance of other pixels (that do not receive glint) falls below the lower limit threshold (t ＩＯ) is set to the pulse width.

[0189] The above pulse width allows the pixel corresponding to the glint to detect an OFF event during the OFF pulse period and an ON event after the OFF pulse period has elapsed. In the figure, the black part indicates the OFF event detection period, and the white part indicates the ON event detection period.

[0190] The waveform of the pulse signal PLS can also be inverted. In this case, the pulse width is set to a value between the time from when the LED is turned on until the pixels that receive the glint are initialized and the time from when the LED is turned on until the amount of change in luminance of the other pixels (that do not receive the glint) exceeds the upper threshold.

[0191] Furthermore, the LED driver 120 turns off the LED during the off-pulse period, but can also lower the brightness of the LED compared to outside of that period without completely turning it off. When the waveform of the pulse signal PLS is inverted, the brightness of the LED during the on-pulse period can be made higher than outside of that period.

[0192] It should be noted that the first and second modifications of the first embodiment, the third embodiment, the fourth embodiment, and the fifth embodiment can each be applied to the seventh embodiment.

[0193] As described above, according to the seventh embodiment of the present technology, the pulse width is set to a value between the time from the timing of turning off the lights until the pixels that receive the glint are initialized and the time until the amount of change in luminance of the other pixels (that do not receive the glint) falls below the lower limit threshold, thereby enabling the light detection system 100 to detect glint when using the arbiter method.

[0194] 8. Application Examples to Mobile Bodies The technology according to the present disclosure (the present technology) can be applied to various products. For example, the technology according to the present disclosure may be realized as a device mounted on any type of mobile body, such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, personal mobility, an airplane, a drone, a ship, or a robot.

[0195] FIG. 33 is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a mobile object control system to which the technology according to the present disclosure can be applied.

[0196] The vehicle control system 12000 includes a plurality of electronic control units connected via a communication network 12001. In the example shown in Fig. 33, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside-vehicle information detection unit 12030, an inside-vehicle information detection unit 12040, and an integrated control unit 12050. Also shown as functional components of the integrated control unit 12050 are a microcomputer 12051, an audio / video output unit 12052, and an in-vehicle network I / F (interface) 12053.

[0197] The drivetrain control unit 12010 controls the operation of devices related to the drivetrain of the vehicle in accordance with various programs. For example, the drivetrain control unit 12010 functions as a control device for a drive force generating device for generating a drive force of the vehicle, such as an internal combustion engine or a drive motor, a drive force transmission mechanism for transmitting the drive force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating a braking force of the vehicle.

[0198] The body system control unit 12020 controls the operation of various devices equipped in the vehicle body according to various programs. For example, the body system control unit 12020 functions as a control device for a keyless entry system, a smart key system, a power window device, or various lamps such as headlamps, backup lamps, brake lamps, turn signals, and fog lamps. In this case, radio waves transmitted from a portable device that serves as a key or signals from various switches can be input to the body system control unit 12020. The body system control unit 12020 receives these radio waves or signals and controls the vehicle's door lock device, power window device, lamps, etc.

[0199] The outside-vehicle information detection unit 12030 detects information outside the vehicle equipped with the vehicle control system 12000. For example, an imaging unit 12031 is connected to the outside-vehicle information detection unit 12030. The outside-vehicle information detection unit 12030 causes the imaging unit 12031 to capture images outside the vehicle and receives the captured images. The outside-vehicle information detection unit 12030 may perform object detection processing or distance detection processing for people, cars, obstacles, signs, characters on the road surface, etc. based on the received images.

[0200] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of light received. The imaging unit 12031 can output the electrical signal as an image or as distance measurement information. The light received by the imaging unit 12031 may be visible light or invisible light such as infrared light.

[0201] The in-vehicle information detection unit 12040 detects information inside the vehicle. For example, a driver state detection unit 12041 that detects the state of the driver is connected to the in-vehicle information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that captures an image of the driver, and the in-vehicle information detection unit 12040 may calculate the degree of fatigue or concentration of the driver based on the detection information input from the driver state detection unit 12041, or may determine whether the driver is dozing off.

[0202] The microcomputer 12051 can calculate control target values ​​for the driving force generating device, steering mechanism, or braking device based on the information inside and outside the vehicle acquired by the outside-vehicle information detection unit 12030 or the inside-vehicle information detection unit 12040, and output control commands to the drive system control unit 12010. For example, the microcomputer 12051 can perform cooperative control aimed at realizing the functions of an ADAS (Advanced Driver Assistance System), including vehicle collision avoidance or impact mitigation, following driving based on the distance between vehicles, maintaining vehicle speed, vehicle collision warning, vehicle lane departure warning, etc.

[0203] In addition, the microcomputer 12051 can perform cooperative control for the purpose of autonomous driving, which allows the vehicle to travel autonomously without relying on driver operation, by controlling the driving force generating device, steering mechanism, braking device, etc. based on information about the surroundings of the vehicle obtained by the outside vehicle information detection unit 12030 or the inside vehicle information detection unit 12040.

[0204] Furthermore, the microcomputer 12051 can output a control command to the body system control unit 12020 based on the information outside the vehicle acquired by the outside information detection unit 12030. For example, the microcomputer 12051 can control the headlamps according to the position of a preceding vehicle or an oncoming vehicle detected by the outside information detection unit 12030, and perform cooperative control aimed at preventing glare, such as switching from high beams to low beams.

[0205] The audio / video output unit 12052 transmits at least one of audio and video output signals to an output device capable of visually or audibly notifying information to vehicle occupants or the outside of the vehicle. In the example of Fig. 33, the output devices are exemplified by an audio speaker 12061, a display unit 12062, and an instrument panel 12063. The display unit 12062 may include, for example, at least one of an on-board display and a head-up display.

[0206] FIG. 34 is a diagram showing an example of the installation position of the imaging unit 12031.

[0207] In FIG. 34, the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0208] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided, for example, at positions such as the front nose, side mirrors, rear bumper, back door, and the top of the windshield inside the vehicle cabin of the vehicle 12100. The imaging unit 12101 provided on the front nose and the imaging unit 12105 provided on the top of the windshield inside the vehicle cabin mainly acquire images of the front of the vehicle 12100. The imaging units 12102 and 12103 provided on the side mirrors mainly acquire images of the sides of the vehicle 12100. The imaging unit 12104 provided on the rear bumper or back door mainly acquires images of the rear of the vehicle 12100. The imaging unit 12105 provided on the top of the windshield inside the vehicle cabin is mainly used to detect preceding vehicles, pedestrians, obstacles, traffic lights, traffic signs, lanes, etc.

[0209] 34 shows an example of the imaging ranges of the imaging units 12101 to 12104. Imaging range 12111 indicates the imaging range of the imaging unit 12101 provided on the front nose, imaging ranges 12112 and 12113 indicate the imaging ranges of the imaging units 12102 and 12103 provided on the side mirrors, respectively, and imaging range 12114 indicates the imaging range of the imaging unit 12104 provided on the rear bumper or back door. For example, by overlaying the image data captured by the imaging units 12101 to 12104, an overhead image of the vehicle 12100 viewed from above can be obtained.

[0210] At least one of the image capturing units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of the image capturing units 12101 to 12104 may be a stereo camera made up of multiple image capturing elements, or may be an image capturing element having pixels for phase difference detection.

[0211] For example, based on the distance information obtained from the imaging units 12101 to 12104, the microcomputer 12051 can calculate the distance to each three-dimensional object within the imaging ranges 12111 to 12114 and the change in this distance over time (relative speed with respect to the vehicle 12100), thereby extracting as a preceding vehicle, in particular, the three-dimensional object that is the closest three-dimensional object on the path of the vehicle 12100 and traveling in approximately the same direction as the vehicle 12100 at a predetermined speed (e.g., 0 km / h or higher). Furthermore, the microcomputer 12051 can set a vehicle-to-vehicle distance to be maintained in advance in front of the preceding vehicle, and perform automatic braking control (including follow-up stop control), automatic acceleration control (including follow-up start control), etc. In this way, cooperative control can be performed for the purpose of autonomous driving, which runs autonomously without relying on driver operation.

[0212] For example, the microcomputer 12051 classifies and extracts three-dimensional object data regarding three-dimensional objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other three-dimensional objects based on distance information obtained from the imaging units 12101 to 12104, and can use the data for automatic obstacle avoidance. For example, the microcomputer 12051 distinguishes obstacles around the vehicle 12100 into obstacles that are visible to the driver of the vehicle 12100 and obstacles that are difficult to see. The microcomputer 12051 then determines a collision risk that indicates the risk of collision with each obstacle, and when the collision risk is equal to or greater than a set value and a collision is possible, the microcomputer 12051 can provide driving assistance for collision avoidance by outputting an alarm to the driver via the audio speaker 12061 or the display unit 12062, or by performing forced deceleration or avoidance steering via the drive system control unit 12010.

[0213] At least one of the image capturing units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 can recognize a pedestrian by determining whether a pedestrian is present in the images captured by the image capturing units 12101 to 12104. Such pedestrian recognition is performed, for example, by extracting feature points from the images captured by the image capturing units 12101 to 12104 as infrared cameras and performing pattern matching on a series of feature points that indicate the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian is present in the images captured by the image capturing units 12101 to 12104 and recognizes the pedestrian, the audio / image output unit 12052 controls the display unit 12062 to superimpose a rectangular outline on the recognized pedestrian for emphasis. The audio / image output unit 12052 may also control the display unit 12062 to display an icon or the like indicating the pedestrian at a desired position.

[0214] An example of a vehicle control system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to, for example, the in-vehicle information detection unit 12040 among the above-described configurations. Specifically, the optical detection system 100 of FIG. 1 can be applied to the in-vehicle information detection unit 12040. By applying the technology according to the present disclosure to the in-vehicle information detection unit 12040, eye tracking can be performed to detect when the driver is looking away, thereby improving the safety of the system.

[0215] Note that the above-described embodiment shows an example for realizing the present technology, and the matters in the embodiment and the matters specifying the invention in the claims correspond to each other. Similarly, the matters specifying the invention in the claims and the matters in the embodiment of the present technology having the same name correspond to each other. However, the present technology is not limited to the embodiment, and can be realized by applying various modifications to the embodiment within the scope of the gist thereof.

[0216] The effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

[0217] The present technology may also be configured as follows: (1) A photodetection system comprising: a photodetector device in which a predetermined number of pixels are arranged, the photodetector device detecting, as an address event, in synchronization with a predetermined vertical synchronization signal, that an absolute value of a change in luminance of incident light, including reflected light, relative to irradiated light from a light-emitting unit, exceeds a predetermined threshold; and a light-emission control unit controlling the luminance of the irradiated light in synchronization with an external synchronization signal synchronized with the vertical synchronization signal. (2) The thresholds include an upper threshold and a lower threshold, and the address events include an ON event indicating that the change has exceeded the upper threshold and an OFF event indicating that the change has fallen below the lower threshold. (3) The photodetection system according to (2), in which a predetermined detection period is set each time a period of the vertical synchronization signal elapses, and the pixels detect the ON event or the OFF event within the detection period. (4) The optical detection system according to (2) or (3), wherein an on-event detection period and an off-event detection period are set each time a period of the vertical synchronization signal elapses, and the pixel detects the on-event within the on-event detection period and the off-event within the off-event detection period. (5) The optical detection system according to (4), wherein the light-emission control unit controls the state of the light-emitting unit to be either on or off within a predetermined pulse period, and controls the state of the light-emitting unit to be the other of on or off outside the pulse period. (6) The optical detection system according to (5), wherein the pulse period includes the on-event detection period, and the light-emission control unit turns on the light-emitting unit within the pulse period and turns off the light-emitting unit outside the pulse period, and the optical detection device detects the detection of both the on-event and the off-event within the period as a double event.(7) The optical detection system according to (5), wherein the on event detection period includes a first on event detection period and a second on event detection period, the off event detection period includes a first off event detection period and a second off event detection period, the first on event detection period and the first off event detection period and the second on event detection period and the second off event detection period are set alternately every time a period of the vertical synchronization signal elapses, and the pulse period includes one of the first on event detection period and the first off event detection period. (8) The optical detection system according to (7), wherein the pulse period includes only the first off event detection period of the first on event detection period and the first off event detection period, and the light emission control unit turns off the light emitting unit within the pulse period and turns on the light emitting unit outside the pulse period. (9) The optical detection system according to (7), wherein the pulse period includes only the first on-event detection period of the first on-event detection period and the first off-event detection period, and the light-emission control unit turns on the light-emitting unit within the pulse period and turns off the light-emitting unit outside the pulse period. (10) The optical detection system according to any of (1) to (9), wherein the light-emitting unit includes first and second light-emitting diodes, and the light-emission control unit transmits different pulse signals to the first and second light-emitting diodes, respectively, and the optical detection device separately detects an address event corresponding to the first light-emitting diode and an address event corresponding to the second light-emitting diode. (11) The optical detection system according to any of (1) to (10), wherein the light-emission control unit blinks the light-emitting unit within a predetermined modulation period and continuously lights up the light-emitting unit outside the modulation period. (12) The optical detection system according to any one of (1) to (11), further comprising a signal processing circuit that processes data indicating the detection result of the address event and causes the optical detection device and the light emission control unit to operate in synchronization with each other. (13) The optical detection system according to any one of (1) to (11), wherein the optical detection device causes the light emission control unit to operate in synchronization with the optical detection device.(14) The light-emission control unit operates the light-detecting device in synchronization with the light-emission control unit. (15) A light-detecting system comprising: a light-detecting device having an array of multiple pixels that detects, as an address event, that an absolute value of a change in luminance of incident light has exceeded a predetermined threshold; and a light-emission control unit that alternately controls the luminance of the irradiated light to a predetermined value within a pulse period having a length between a delay time from a predetermined timing until the pixels are initialized and a delay time from the timing until the absolute value of the change has exceeded the threshold, and controls the luminance of the irradiated light to a value different from the predetermined value outside the pulse period. (16) A control method for a light-detecting system comprising: a light-detection procedure in which each of a predetermined number of pixels in the light-detecting device detects, as an address event, that an absolute value of a change in luminance of incident light, including reflected light from the irradiated light from a light-emitting unit, has exceeded a predetermined threshold, in synchronization with a predetermined vertical synchronization signal; and a light-emission control procedure in which the light-emission control unit controls the luminance of the irradiated light in synchronization with an external synchronization signal that is synchronized with the vertical synchronization signal.

[0218] 100 Light detection system 110 Signal processing circuit 120 LED driver 130 Light emitting unit 131, 132 LED 200 EVS camera 210 Driving unit 220 Signal processing unit 221 Switching control unit 222, 346 Selector 223 Flip-flop 224 Inverter 225 AND gate 226 Post-processing unit 230 Pixel array unit 240 Signal generating unit 250 Readout area selecting unit 260 Timing control unit 270 Arbiter 300 Pixel 310 Photoelectric conversion element 320 Logarithmic response unit 321 to 324, 331, 332, 342, 345, 352, 354 nMOS transistor 325 Current source transistor 330 Buffer 340 Difference detector 341, 343 Capacitor 344, 351, 353 pMOS transistor 350 comparator 360 output circuit 12040 in-vehicle information detection unit

Claims

1. A light detection system comprising: a light detection device having an array of a predetermined number of pixels that detects, as an address event, in synchronization with a predetermined vertical synchronization signal, when the absolute value of the change in luminance of incident light, including reflected light, relative to irradiated light from a light emitting unit exceeds a predetermined threshold; and a light emission control unit that controls the luminance of the irradiated light in synchronization with an external synchronization signal that is synchronized with the vertical synchronization signal.

2. The optical detection system of claim 1, wherein the thresholds include an upper threshold and a lower threshold, and the address events include an on-event indicating that the amount of change has exceeded the upper threshold and an off-event indicating that the amount of change has fallen below the lower threshold.

3. The optical detection system according to claim 2, wherein a predetermined detection period is set each time a period of the vertical synchronization signal elapses, and the pixel detects the on-event or the off-event within the detection period.

4. The optical detection system according to claim 2, wherein an on-event detection period and an off-event detection period are set each time a period of the vertical synchronization signal elapses, and the pixel detects the on-event within the on-event detection period and detects the off-event within the off-event detection period.

5. The optical detection system according to claim 4, wherein the light emission control unit controls the state of the light emitting unit to either on or off within a predetermined pulse period, and controls the state of the light emitting unit to the other of on or off outside the pulse period.

6. The optical detection system of claim 5, wherein the pulse period includes the on-event detection period, the light emission control unit turns on the light emitting unit within the pulse period and turns off the light emitting unit outside the pulse period, and the optical detection device detects, as a both event, that both the on-event and the off-event have been detected within the cycle.

7. The optical detection system of claim 5, wherein the on event detection period includes a first on event detection period and a second on event detection period, the off event detection period includes a first off event detection period and a second off event detection period, the first on event detection period and the first off event detection period, and the second on event detection period and the second off event detection period are set alternately every time a period of the vertical synchronization signal elapses, and the pulse period includes one of the first on event detection period and the first off event detection period.

8. The optical detection system according to claim 7, wherein the pulse period includes only the first off event detection period of the first on event detection period and the first off event detection period, and the light emission control unit turns off the light emitting unit within the pulse period and turns on the light emitting unit outside the pulse period.

9. The optical detection system according to claim 7, wherein the pulse period includes only the first on-event detection period out of the first on-event detection period and the first off-event detection period, and the light emission control unit turns on the light-emitting unit within the pulse period and turns off the light-emitting unit outside the pulse period.

10. The optical detection system of claim 1, wherein the light-emitting unit includes first and second light-emitting diodes, the light-emitting control unit transmits different pulse signals to each of the first and second light-emitting diodes, and the optical detection device detects an address event corresponding to the first light-emitting diode and an address event corresponding to the second light-emitting diode separately.

11. The light detection system according to claim 1, wherein the light emission control unit blinks the light emitting unit within a predetermined modulation period and continuously lights the light emitting unit outside the modulation period.

12. The light detection system according to claim 1, further comprising a signal processing circuit for processing data indicating the detection result of the address event and for operating the light detection device and the light emission control unit in synchronization with each other.

13. The light detection system according to claim 1, wherein the light detection device operates the light emission control unit in synchronization with the light detection device.

14. The light detection system according to claim 1, wherein the light emission control unit operates the light detection device in synchronization with the light emission control unit.

15. A photodetection system comprising: a photodetection device having an array of multiple pixels that detects, as an address event, when the absolute value of the amount of change in luminance of incident light exceeds a predetermined threshold; and a light emission control unit that alternately controls the luminance of the irradiated light to a predetermined value within a pulse period that is between the delay time from a predetermined timing until the pixels are initialized and the delay time from said timing until the absolute value of the amount of change exceeds said threshold, and controls the luminance of the irradiated light to a value different from the predetermined value outside said pulse period.

16. A method for controlling a light detection system comprising: a light detection procedure in which each of a predetermined number of pixels in a light detection device detects, as an address event, in synchronization with a predetermined vertical synchronization signal that the absolute value of the amount of change in luminance of incident light, including reflected light, relative to irradiated light from a light emitting unit has exceeded a predetermined threshold; and a light emission control procedure in which a light emission control unit controls the luminance of the irradiated light in synchronization with an external synchronization signal synchronized with the vertical synchronization signal.

Images