Avalanche diode based detection device

Abstract

A detection device includes a light source, an avalanche diode, a first counter, a second counter, and a processor. The light source emits light during a first period and turns off during a second period, a third period, and a fourth period. The avalanche diode detects photons relative to the first period, the second period, the third period, and the fourth period to activate an avalanche event. The first counter counts up the avalanche event during the first period and counts down the avalanche event during the third period to generate a first count value. The second counter counts up the avalanche event during the second period and counts down the avalanche event during the fourth period to generate a second count value. The processor calculates the flight time according to the first count value and the second count value.

Description

[0001] This application is a divisional application of the Chinese invention patent application with application number 201910206860.3, application date March 19, 2019, and name “Object detection device based on avalanche diode”. Technical Field

[0002] The present invention relates to an optical object detection device, and more particularly to an object detection device for calculating the flight time according to the count value of an avalanche event of an avalanche diode. Background Art

[0003] Currently, most optical distance measuring devices use imaging technology based on CCD image sensors or CMOS image sensors. The method of calculating the distance of an object by estimating the time difference between the light beam emitted by a light source and the light beam being detected by the sensor after being reflected by the object is called time of flight technology.

[0004] Single photon detection is another option when dealing with low-light environments and high-frequency optical signals.

[0005] For example, a single photon avalanche diode (SPAD) can be used as a reflected light detector. When a photon is received by the SPAD, an avalanche current is activated to reflect the detection of a photon. The pulse caused by the avalanche current can be regarded as an event.

[0006] However, the operating environment of the ranging device is usually a situation where the light source signal and the ambient light exist at the same time. In addition to the avalanche event with respect to the light source signal, the SPAD will also have an avalanche event with respect to the ambient light to form noise, resulting in reduced detection accuracy.

[0007] Furthermore, when the intensity of the ambient light varies, it will also affect the detection results.

[0008] In view of this, an object detection device based on an avalanche diode that can eliminate the influence of ambient light is needed. Summary of the invention

[0009] The invention provides an object detection device using an avalanche diode and a time-of-flight technology.

[0010] The present invention also provides an object detection device, which can calculate the object distance and eliminate environmental noise only by counting the number of occurrences of avalanche current.

[0011] The present invention provides a detection device, comprising a light source, an avalanche diode, a first counter, a second counter and a processor. The light source is used to emit light toward an object during a first period, and to be extinguished during a second period, a third period and a fourth period. The avalanche diode is used to expose relative to the first period, the second period, the third period and the fourth period to generate an electric pulse. The first counter is used to count up the electric pulses during the first period and then count down the electric pulses during the third period to generate a first count value. The second counter is used to count up the electric pulses during the second period and then count down the electric pulses during the fourth period to generate a second count value. The processor is used to control the emission and extinguishing of the light source, and to control the counting direction of the first counter and the second counter.

[0012] The present invention also provides a detection device, comprising a light source, a sensing array, a plurality of first counters, a plurality of second counters and a processor. The light source is used to emit light toward an object during a first period, and to be extinguished during a second period, a third period and a fourth period. The sensing array comprises a plurality of avalanche diodes arranged in an array. The plurality of avalanche diodes are exposed relative to the first period, the second period, the third period and the fourth period to generate electrical pulses. Each first counter corresponds to one of the plurality of avalanche diodes, and is used to count up the electrical pulses generated by the corresponding avalanche diode during the first period and then count down the electrical pulses generated by the corresponding avalanche diode during the third period to generate a first count value. Each second counter corresponds to one of the plurality of avalanche diodes, and is used to count up the electrical pulses generated by the corresponding avalanche diode during the second period and then count down the electrical pulses generated by the corresponding avalanche diode during the fourth period to generate a second count value. The processor is used to control the emission and extinguishing of the light source, and to control the counting direction of the plurality of first counters and the plurality of second counters.

[0013] In the object detection device of the embodiment of the present invention, the event count of the avalanche current is regarded as energy accumulation, and the count ratio representing the phase shift is directly calculated according to the event count. The count ratio can be further converted into flight time using the modulation frequency.

[0014] In the object detection device of the embodiment of the present invention, the energy of the ambient light is also represented by event counts. The influence of the ambient light can be eliminated by subtracting the event counts activated only by the ambient light from the event counts activated by both the light source signal and the ambient light.

[0015] In order to make the above and other purposes, features and advantages of the present invention more obvious, the following will be described in detail with reference to the accompanying drawings. In addition, in the description of the present invention, the same components are represented by the same symbols, which are hereby described together. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a block diagram of an object detection device according to an embodiment of the present invention;

[0017] Figure 2 is a schematic diagram of the operation of the object detection device according to the first embodiment of the present invention;

[0018] Figure 3 is a schematic diagram of the operation of an object detection device according to a second embodiment of the present invention;

[0019] Figure 4 is a schematic diagram of the operation of an object detection device according to a third embodiment of the present invention;

[0020] Figure 5 is a schematic diagram of the operation of an object detection device according to a fourth embodiment of the present invention;

[0021] Figure 6 is a schematic diagram of a filter transfer function of an object detection device according to a fourth embodiment of the present invention;

[0022] Figure 7 Schematic diagram of switch control connected to a counter in an object detection device according to a fourth embodiment of the present invention.

[0023] Description of Reference Numerals

[0024] 100 Object Detection Device

[0025] 11 Light Source

[0026] 13 Sampling switch

[0027] 15 First counter

[0028] 17 Second counter

[0029] 19 Processor

[0030] O Object

[0031] AD Avalanche Diode DETAILED DESCRIPTION

[0032] Please refer to Figure 1, which is a block diagram of an object detection device 100 according to an embodiment of the present invention. The object detection device 100 is used to calculate the light transmission time according to the accumulated counts of avalanche events by two counters during the exposure period of the light detection element. Since the speed of light is known, the object detection device 100 can calculate the distance between the object O and the object detection device 100 (more specifically, its light detection element) according to the transmission time.

[0033] like Figure 1 As shown, the object detection device 100 includes a light source 11 , a light detection element (eg, an avalanche diode AD), a sampling switch 13 , a first counter 15 , a second counter 17 and a processor 19 .

[0034] Please refer to Figure 2 As shown, an implementation of the object detection device 100 according to the first embodiment of the present invention is described next.

[0035] The light source 11 is a laser diode (LD), such as a vertical cavity surface emitting laser (VCSEL). The light source 11 emits light with a recognizable spectrum (such as red light and / or infrared light) toward the object O; wherein the object O is any object within the detectable distance range of the object detection device 100, as long as it can reflect the light emitted by the light source 11, without any specific limitation. For example, Figure 2 The display light source 11 emits light in the first period T1 of the exposure period and turns off in the second period T2, and operates repeatedly in this manner. For example, the exposure period = T1 + T2.

[0036] Figure 2 After the display light source 11 starts to emit light, the emitted light is reflected from the object O back to the avalanche diode AD after a time interval Tf. The avalanche diode AD is, for example, a single photon avalanche diode (SPAD). It can be understood that each time the SPAD receives or detects a photon, an avalanche current (or avalanche event) is activated to generate an electrical pulse, such as a current pulse. The object detection device 100 of the present invention calculates the time of flight (TOF) by using the number of occurrences of this avalanche event within a predetermined time (such as the first period T1 and the second period T2), and further obtains the distance of the object O based on it. It can be understood that the length of Tf is determined according to the distance of the object, and t1 and t2 are also affected.

[0037] The sampling switch 13 is, for example, a switch component or a multiplexer (MUX), and is used to conduct the avalanche diode AD and the first counter 15 during the first period T1, so that the first counter 15 can sample the avalanche diode AD (herein referred to as the first channel). The sampling switch 13 is also used to conduct the avalanche diode AD and the second counter 17 during the second period T2, so that the second counter 17 can sample the avalanche diode AD (herein referred to as the second channel).

[0038] The sampling in the present invention is to count avalanche events. For example, in period t1, the avalanche diode AD receives the light energy of the light source signal and the ambient light at the same time, so the first counter 15 can count to a higher count value, which includes the avalanche current pulse caused by the light source signal and the ambient light; and in period Tf, the avalanche diode AD only receives the light energy of the ambient light, so the first counter 15 counts to a lower count value, which only includes the avalanche current pulse caused by the ambient light. Figure 2 The events of the second channel are also shown. The periods of dense events indicate the presence of both the light source signal and ambient light, while the periods of sparse events indicate the presence of only ambient light.

[0039] The first counter 15 and the second counter 17 may be asynchronous counters, such as ripple counters.

[0040] The number of avalanche events within a predetermined time (e.g., first period T1) of the first channel can theoretically be expressed by equation (1):

[0041] CN1=t1×FF×PDP×(P LD / E ph )+t p ×FF×PDP×(P AMB / E ph ) (1),

[0042] The number of avalanche events within a predetermined time (e.g., second period T2) of the second channel can theoretically be expressed by equation (2):

[0043] CN2=t2×FF×PDP×(P LD / E ph )+t p ×FF×PDP×(P AMB / E ph ) (2)

[0044] Among them, FF is the fill factor of the avalanche diode AD, PDP is the photon detection probability, P LD is the detected light source signal energy, P AMB is the detected ambient light energy, E ph is the photon energy. In the present invention, the flight time is defined as equation (3)

[0045] TOF1=(1 / 2f mod )×(CN2 / (CN1+CN2)) (3)

[0046] Among them, f mod It is the modulation frequency of the light source 11, the first channel sampling frequency or the second channel sampling frequency. In fact, CM1 and CN2 are detected by the first counter 15 and the second counter 17 respectively.

[0047] Since the speed of light is known, the processor 19 can calculate the distance or depth between the object O and the object detection device 100 according to the time of flight TOF1 (which is related to Tf).

[0048] It can be clearly seen from equations (1) to (3) that due to the presence of ambient light energy P AMB , the time of flight TOF1 is affected by the ambient light. At the same time, since the PDP of each avalanche diode AD is different, in a sensing array including multiple avalanche diodes, there will be a situation where the detection energy between pixels is uneven, resulting in distance ambiguity.

[0049] In order to reduce the influence of ambient light, the light and dark exposure difference method can be used. Figure 3 FIG. 1 is a schematic diagram of the operation of the object detection device according to the second embodiment of the present invention, which is also applicable to Figure 1 An object detection device 100 is provided.

[0050] Figure 3 In the embodiment of the present invention, the first exposure period includes a plurality of bright exposures, and the operation mode of each bright exposure is different from that of Figure 2 The exposure period (T1+T2) is the same, so Figure 3 The event timing diagram is omitted. Therefore, during the first exposure period, the first counter 15 accumulates N Figure 2 The first count value Q1 of the avalanche event of the first channel during the exposure period ON , for example, Q1 ON =N×CN1 (refer to equation 1). Similarly, the second counter 17 accumulates N Figure 2 The second count value Q2 of avalanche events in the second channel during the exposure period ON , for example, Q2 ON =N×CN2 (refer to equation 2). The processor 19 reads the first count value Q1 during the first reading period. ON and the second count value Q2 ON And stored in the memory (not shown) of the object detection device 100 .

[0051] Next, in the second exposure period, except that the light source 11 is not turned on, the operations of the sampling switch 13, the first counter 15 and the second counter 17 are the same as those in the first exposure period. Since the light source 11 is not turned on in the second exposure period, each exposure period is referred to as a dark exposure. Similarly, after N dark exposures, the first counter 15 accumulates the third count value Q1 of the avalanche event of the first channel in the N dark exposure periods. OFF , and the second counter 17 accumulates the fourth count value Q2 of the avalanche event of the second channel during the N dark exposure periods OFF .

[0052] In this embodiment, the N value is based on the first count value Q1 ON , the second count value Q2 ON , the third count value Q1 OFF and the fourth count value Q2 OFF The expected value of Q1 and the detectable distance of the object detection device 100 are preset. OFF Used to eliminate the first count value Q1 ON The fourth count value Q2 is affected by ambient light. OFF Used to eliminate the second count value Q2 ON The influence of ambient light.

[0053] Similarly, according to equation (3), the flight time of the second embodiment can be defined as equation (4):

[0054] TOF2=(1 / 2f mod )×(Q2 ON -Q2 OFF ) / ((Q1 ON -Q1 OFF )+(Q2 ON -Q2 OFF )) (4)

[0055] Similarly, the processor 19 can calculate the distance or depth between the object O and the detection device 100 according to the time of flight TOF2.

[0056] Figure 3 Although the noise caused by the ambient light is eliminated by the differential operation of the bright and dark exposures (see Equation 4), since N bright exposure times elapse during the first exposure period and N dark exposure times elapse during the second exposure period, when the intensity of the ambient light changes over time, the noise elimination effect will be reduced.

[0057] Please refer to Figure 4 FIG. 1 is a schematic diagram of the operation of the object detection device according to the third embodiment of the present invention. Figure 1 The object detection device 100 is implemented. Figure 4 and Figure 3 The difference is that Figure 4 The periods of medium-bright and medium-dark exposure are arranged adjacent to each other to further reduce the influence of the ambient light changes over time.

[0058] like Figure 4 As shown, the light source 11 is used to emit light toward the object O during the first period T1, and is extinguished during the second period T2, the third period T3 and the fourth period T4. In this embodiment, an exposure period is formed between the first period T1, the second period T2, the third period T3 and the fourth period T4. For example, the exposure period = T1 + T2 + T3 + T4 and T1 to T4 are preferably equal. Since the first sampling channel detects the energy of the light source signal during the first period T1 and the second sampling channel detects the energy of the light source signal during the second period T2, the first period T1 and the second period T2 are called bright exposure. For example, the bright exposure period = T1 + T2. On the other hand, since the first sampling channel does not detect the energy of the light source signal during the third period T3 and the second sampling channel does not detect the energy of the light source signal during the fourth period T4, the third period T3 and the fourth period T4 are called dark exposure. For example, the dark exposure period = T3 + T4.

[0059] The avalanche diode AD is exposed to the first period T1 , the second period T2 , the third period T3 , and the fourth period T4 to generate an electrical pulse when receiving photons.

[0060] The sampling switch 13 conducts the avalanche diode AD and the first counter 15 during the first period T1 and the third period T3, so that the first counter 15 counts the electrical pulses generated by the avalanche diode AD during the first period T1 and the third period T3 to generate a first count value. In this embodiment, the first counter 15 is used to count up the electrical pulses during the first period T1 (for example, the count is increased by 1 when a pulse is read) and then count down the electrical pulses during the third period T3 (for example, the count is decreased by 1 when a pulse is read) to generate a first count value. In other words, the first counter 15 may include an up counter and a down counter or use a counter that can count up and down, and there is no specific limitation, as long as the counting direction can be changed when receiving the control signal value from the processor 19. In this embodiment, the final count value of the first counter 15 is not reset after the first period T1 ends, and the down count starts from the final count value of the first period T1 when entering the third period T3. The down count in the third period T3 can be regarded as eliminating the electrical pulses activated by the ambient light from the electrical pulses counted in the first period T1 , so as to serve as a method of eliminating the influence of the ambient light.

[0061] Similarly, the sampling switch 13 turns on the avalanche diode AD and the second counter 17 during the second period T2 and the fourth period T4, so that the second counter 17 counts the electrical pulses generated by the avalanche diode AD during the second period T2 and the fourth period T4 to generate a second count value. In this embodiment, the second counter 17 is used to count up the electrical pulses during the second period T2 (for example, the count is increased by 1 when a pulse is read) and then count down the electrical pulses during the fourth period T4 (for example, the count is decreased by 1 when a pulse is read) to generate a second count value. The second counter 17 can select the same counter as the first counter 15. Similarly, after the end of the second period T2, the final count value of the second counter 17 is not reset, and when entering the fourth period T4, the count starts from the final count value of the second period T2. The count down of the fourth period T4 can be regarded as eliminating the electrical pulses activated by ambient light from the electrical pulses counted in the second period T2, as a method of eliminating the influence of ambient light.

[0062] In this embodiment, the first count value obtained after the third period T3 and the second count value obtained after the fourth period T4 indicate that the influence of the ambient light has been eliminated, and there is no need to perform a difference or subtraction operation.

[0063] The processor 19 is used to process the first count value and the second count value to calculate the flight time or distance between the object O and the object detection device 100. For example, the processor 19 calculates the flight time based on the first count value and the second count value based on the same concept of equation (3). Similarly, based on the same concept of equation (1), the first count value in a predetermined time (e.g., one exposure period) can be expressed by equation (5):

[0064] CN1=(t1×FF×PDP×P LD / E ph +tp×FF×PDP×P AMB / E ph )-(tp×FF×PDP×P AMB / E ph ) (5)

[0065] Similarly, according to the same concept of equation (2), the second count value in a predetermined time (for example, an exposure period) can be expressed by equation (6):

[0066] CN2=(t2×FF×PDP×P LD / E ph +tp×FF×PDP×P AMB / E ph )-(tp×FF×PDP×P AMB / E ph ) (6)

[0067] The flight time can be calculated based on equation (3).

[0068] As mentioned above, since both equations (5) and (6) contain probability value PDP, the processor 19 preferably Figure 4 The first count value CN1 and the second count value CN2 of multiple exposure periods are accumulated during the accumulation exposure period; wherein the number of the multiple exposure periods is determined by the expected values ​​of the first count value and the second count value and the detectable distance of the object detection device 100. Finally, after reading out the N-fold first count value CN1 and the N-fold second count value CN2 during the reading period, the flight time is calculated according to equation (3).

[0069] As mentioned above, after the flight time is obtained, the processor 19 can also calculate the distance or depth of the object O according to the obtained flight time.

[0070] The above embodiment is described by taking a single avalanche diode AD as an example. In other embodiments, the object detection device 100 includes a sensing array of a plurality of avalanche diodes AD arranged in an array, which are exposed relative to the first period T1, the second period T2, the third period T3, and the fourth period T4, so that each avalanche diode AD generates an electrical pulse.

[0071] At this time, the object detection device 100 includes a plurality of first counters 15. Each first counter 15 corresponds to one of the plurality of avalanche diodes AD. Each first counter 15 counts up the electrical pulses generated by the corresponding avalanche diode AD during the first period T1, and then counts down the electrical pulses generated by the corresponding avalanche diode AD during the third period T3 to generate a first count value, such as CN1. The object detection device 100 also includes a plurality of second counters 17. Each second counter 17 corresponds to one of the plurality of avalanche diodes AD. Each second counter 17 counts up the electrical pulses generated by the corresponding avalanche diode AD during the second period T2, and then counts down the electrical pulses generated by the corresponding avalanche diode AD during the fourth period T4 to generate a second count value, such as CN2.

[0072] In this embodiment, the operation of each avalanche diode AD is as described above and shown in FIG. Figure 4 Therefore, I will not elaborate on it here.

[0073] The processor 19 calculates the flight time associated with each avalanche diode AD according to the first count value CN1 and the second count value CN2 associated with each avalanche diode AD, so a plurality of flight times can be obtained.

[0074] The processor 19 further calculates a depth map (or a 3D image of the object) of the object O according to the multiple flight times of the multiple avalanche diodes AD.

[0075] In this embodiment, each avalanche diode AD is configured with a corresponding sampling switch 13. Each sampling switch 13 conducts the avalanche diode AD and the corresponding first counter 15 during the first period T1 and the third period T3, so that the first counter 15 counts the electrical pulses generated by the avalanche diode AD. Each sampling switch 13 also conducts the avalanche diode AD and the corresponding second counter 17 during the second period T2 and the fourth period T4, so that the second counter 17 counts the electrical pulses generated by the avalanche diode AD.

[0076] When the ambient light has an AC frequency (such as the frequency of the power system), the count value of the counter can also be used to achieve a filter-like effect to reduce the impact of the AC frequency.

[0077] Please refer to Figure 5 FIG. 4 is a schematic diagram of the operation of the object detection device according to the fourth embodiment of the present invention, which can also be Figure 1 The object detection device 100 is implemented by the object detection device 100. As mentioned above, the object detection device 100 includes a light source 11 that is turned on or off, for example, controlled by the processor 19. The avalanche diode AD is used to perform bright exposure when the light source 11 is turned on and to perform dark exposure when the light source 11 is turned off to generate electrical pulses. In the present invention, the bright exposure period does not mean that the light source 11 is always on, but that it is on for part of the time, and the light source 11 is not on at all during the dark exposure period.

[0078] As mentioned above, the first counter 15 and the second counter 17 can be ripple counters. A conventional ripple counter includes a plurality of serially connected D flip-flops as a multi-stage counting unit, such as Figure 7 The number of stages depends on the count value. The electric pulse generated by the avalanche diode AD during the bright exposure period is input to the first stage of the multi-stage counting unit, and the electric pulse generated by the avalanche diode AD during the dark exposure period is switched (for example, by a switching element or a multiplexer) to be input to other counting units after the first stage of the multi-stage counting unit, that is, the first stage counting unit is bypassed. In addition, the sampling switch 13, such as Figure 1 As shown, the avalanche diode AD is also connected to one of the first counter 15 and the second counter 17, so that the first counter 15 or the second counter 17 can count the electrical pulses generated by the avalanche diode AD.

[0079] Figure 6 A diagram showing the transfer function of a second-order filter. Figure 5As shown, if you want to achieve Figure 6 When the transfer function is used, each exposure period includes a bright exposure period (such as T1+T2) and two dark exposure periods (such as T3+T4 and T5+T6). It can be understood that different transfer functions correspond to different operations, and are not limited to Figure 5 As shown, the exposure period only needs to include one bright exposure period and a plurality of dark exposure periods. The transfer function can be determined according to the AC frequency of the ambient light to be eliminated.

[0080] Figure 5 During the bright exposure period T1, the electric pulse is input to the first-stage counting unit of the first counter 15 to count up the avalanche events of the first channel. After the bright exposure ends, the count value of the first counter 15 is not reset. During the first dark exposure period T3, the electric pulse is input to the second-stage counting unit of the first counter 15 to count down the avalanche events of the first channel, which starts from the count value at the end of the bright exposure period T1. After the first dark exposure ends, the count value of the first counter 15 is still not reset. During the second dark exposure period T5, the electric pulse is again input to the first-stage counting unit of the first counter 15 to count up the avalanche events of the first channel, which starts from the count value at the end of the first dark exposure period T3.

[0081] Similarly, during the bright exposure period T2, the electric pulse is input to the first-stage counting unit of the second counter 17 to count up the avalanche events of the second channel. After the bright exposure ends, the count value of the second counter 17 is not reset. During the first dark exposure period T4, the electric pulse is input to the second-stage counting unit of the second counter 17 to count down the avalanche events of the second channel, which starts from the count value at the end of the bright exposure period T2. After the first dark exposure ends, the count value of the second counter 17 is still not reset. During the second dark exposure period T6, the electric pulse is again input to the first-stage counting unit of the second counter 17 to count up the avalanche events of the second channel, which starts from the count value at the end of the first dark exposure period T4.

[0082] After an exposure period, the first counter 15 generates a first count value and the second counter 17 generates a second count value. The processor 19 calculates the flight time Tf according to the first count value and the second count value based on the same concept of the above equations (3) and (4), and further calculates the distance of the object O.

[0083] In this embodiment, the up-count or down-count is represented by the positive and negative signs of the calculation coefficient of the transfer function, for example, a positive sign indicates up-count and a negative sign indicates down-count, and vice versa. The number of stages into which the electric pulse is input into the multi-stage counting unit is determined by the value of the calculation coefficient of the transfer function, for example, a value of 1 is input into the first stage, a value of 2 is input into the second stage, a value of 4 is input into the third stage, and so on.

[0084] Similarly, in order to make the first count value and the second count value reach the expected value, the processor 19 does not reset (e.g., return to zero) the first count value and the second count value at the end of each exposure period, and continues to accumulate the first count value and the second count value of multiple exposure periods until the accumulated exposure period ends. Alternatively, the processor 19 may store the first count value and the second count value in the memory at the end of each exposure period and then reset (return to zero), and accumulate the count value of each exposure period of the predetermined number of times to the stored value in the memory. As mentioned above, the accumulated exposure period values ​​are determined according to the expected value and the detectable distance of the object detection device 100.

[0085] In summary, although the single photon avalanche diode can detect extremely weak light and high frequency signals, the influence of ambient light still needs to be removed to improve the detection accuracy and reduce the distance ambiguity between pixels. Therefore, the present invention also provides a detection device that directly calculates the flight time based on the count of avalanche events of the avalanche diode ( Figure 1 ) and its operation method ( Figure 2-5 ), which can eliminate the noise of ring light by calculating the cumulative counts of bright and dark exposures.

[0086] Although the present invention has been disclosed through the above examples, they are not intended to limit the present invention. Any person skilled in the art with ordinary knowledge in the art to which the present invention belongs can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A detection device, comprising: a light source configured to emit light toward the object during a first period and to be turned off during a second period, a third period, and a fourth period; an avalanche diode, the avalanche diode being used for exposing relative to the first period, the second period, the third period and the fourth period to generate an electric pulse; a first counter, the first counter being used for counting up the electrical pulses in the first period and then counting down the electrical pulses in the third period to generate a first count value; a second counter, the second counter being used for counting up the electrical pulses in the second period and then counting down the electrical pulses in the fourth period to generate a second count value; and A processor is used to control the lighting and extinguishing of the light source, and control the counting direction of the first counter and the second counter. 2 . The detection device according to claim 1 , wherein the first counter and the second counter are asynchronous counters.

3. The detection device according to claim 1 further comprises a sampling switch, the sampling switch is used to The avalanche diode and the first counter are turned on during the first period and the third period, so that the first counter counts the electrical pulses generated by the avalanche diode, and The avalanche diode and the second counter are turned on during the second period and the fourth period, so that the second counter counts the electrical pulse generated by the avalanche diode. 4 . The detection device according to claim 1 , wherein the first period, the second period, the third period and the fourth period form an exposure period, and the processor is further used to accumulate the first count value and the second count value of multiple exposure periods. 5 . The detection device according to claim 4 , wherein the number of the plurality of exposure periods is determined by expected values ​​of the first count value and the second count value and a detectable distance. The detection device according to claim 1 , wherein the processor further calculates the distance of the object based on the flight time. The detection device according to claim 1 , wherein the avalanche diode is a single photon avalanche diode.

8. A detection device, comprising: a light source configured to emit light toward the object during a first period and to be turned off during a second period, a third period, and a fourth period; A sensing array, the sensing array comprising a plurality of avalanche diodes arranged in an array, the plurality of avalanche diodes being exposed relative to the first period, the second period, the third period, and the fourth period to generate electrical pulses; A plurality of first counters, each of which corresponds to one of the plurality of avalanche diodes, for counting up the electrical pulses generated by the corresponding avalanche diode during the first period and then counting down the electrical pulses generated by the corresponding avalanche diode during the third period to generate a first count value; A plurality of second counters, each second counter corresponding to one of the plurality of avalanche diodes, for counting up the electrical pulses generated by the corresponding avalanche diode during the second period and then counting down the electrical pulses generated by the corresponding avalanche diode during the fourth period to generate a second count value; as well as A processor is used to control the lighting and extinguishing of the light source, and control the counting directions of the plurality of first counters and the plurality of second counters. 9 . The detection device according to claim 8 , wherein the plurality of first counters and the plurality of second counters are wave-link counters.

10. The detection device according to claim 8, further comprising a plurality of sampling switches, each sampling switch being arranged relative to an avalanche diode and used for During the first period and the third period, the avalanche diode and the corresponding first counter are turned on so that the first counter counts the electrical pulses generated by the avalanche diode, and The avalanche diode and the corresponding second counter are turned on during the second period and the fourth period so that the second counter counts the electrical pulse generated by the avalanche diode. 11 . The detection device according to claim 8 , wherein the first period, the second period, the third period, and the fourth period form one exposure period, and the processor further accumulates the first count value and the second count value of a plurality of exposure periods. 12 . The detection device according to claim 11 , wherein the number of the plurality of exposure periods is determined by expected values ​​of the first count value and the second count value and a detectable distance. 13 . The detection device according to claim 8 , wherein the processor further calculates a depth map of the object based on the flight times of the plurality of avalanche diodes. The detection device according to claim 8 , wherein the avalanche diode is a single photon avalanche diode.

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