Optical sensor device and method of an optical sensor device

Abstract

The invention discloses an optical sensor device and a method of the optical sensor device. An optical sensor device includes a pixel array and a control circuit. The pixel array has pixel units arranged in N rows and M columns, each pixel unit comprising: a phototransistor for capturing and generating a first image signal in a first shutter exposure time period at a first time and capturing and generating a second image signal in a second shutter exposure time period at a second time, the first time and the second time being continuous; the first collective capacitor is coupled to the phototransistor and is used for storing the first image signal; the second collective capacitor is coupled with the phototransistor and is used for storing a second image signal; the control circuit performs motion detection according to the difference between the two image signals to judge whether motion occurs, so that whether motion occurs in the sensed image / frame can be accurately judged, and only lower power is consumed.

Description

Technical Field

[0001] The present application relates to an optical sensor device, and more particularly to an optical sensor device and a corresponding method. Background Art

[0002] Generally speaking, the performance of conventional optical sensor devices is easily degraded due to different shot noise levels under different lighting conditions. For example, conventional optical sensor devices may detect erroneous motion caused by higher shot noise. Conventional optical sensor devices cannot accurately detect motion. In addition, conventional optical sensors also consume higher power. Summary of the invention

[0003] Therefore, one of the objectives of the present application is to provide an optical sensor device and method to solve the above-mentioned problems.

[0004] According to an embodiment, an optical sensor device is disclosed. The optical sensor device includes a pixel array and a control circuit. The pixel array has a plurality of pixel units arranged in N rows and M columns, and a first pixel unit among the plurality of pixel units includes a phototransistor, a first set capacitor and a second set capacitor. The phototransistor is used to capture and generate a first image signal during a first shutter exposure time period of a first time, and to capture and generate a second image signal during a second shutter exposure time period of a second time, wherein the first time and the second time are continuous. The first set capacitor is coupled to the phototransistor for storing the first image signal. The second set capacitor is coupled to the phototransistor for storing the second image signal. The control circuit is coupled to the first pixel unit, wherein the first shutter exposure time period is different from the second shutter exposure time period, and the control circuit performs motion detection according to the difference between the first image signal captured during the first shutter exposure time period and the second image signal captured during the second shutter exposure time period to determine whether motion occurs.

[0005] According to an embodiment, a method of an optical sensor device is further disclosed. The method includes: providing the above-mentioned pixel array having a plurality of pixel units arranged in N rows and M columns; configuring the first shutter exposure time period to be different from the second shutter exposure time period; and performing motion detection to determine whether motion occurs based on the difference between the first image signal captured during the first shutter exposure time period and the second image signal captured during the second shutter exposure time period. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1It is a circuit diagram of a novel pixel unit such as a bipolar junction transistor (BJT) sensing pixel (or referred to as a BJT pixel unit) disposed in a pixel array according to an embodiment of the present application.

[0007] Figure 2 According to the embodiment of the present application Figure 1 Schematic diagram of an optical sensor device including multiple BJT sensing pixels.

[0008] Figure 3 is an example schematic diagram of the shutter exposure time period of time T1-T3 according to an embodiment of the present application.

[0009] Figure 4 FIG. 4 is a schematic diagram showing an example of the relationship between light intensity and a voltage level of a pixel output signal according to an embodiment of the present application.

[0010] Figure 5 It is a circuit diagram of two novel BJT sensing pixels arranged at different spatial positions in the same column of a pixel array according to an embodiment of the present application.

[0011] Figure 6 is a schematic diagram of an optical sensor device according to an embodiment of the present application.

[0012] Figure 7 According to the embodiment of the present application Figure 5 An example schematic diagram of control signals NSH1 and NSH2 and read control signals RD1 and RD2.

[0013] The reference numerals are described as follows:

[0014] 100, 500_1, 500_2BJT sensing pixel unit

[0015] 105 Shutter control circuit

[0016] 110 Readout control circuit

[0017] 200, 600 optical sensor device

[0018] 205, 605 pixel array

[0019] 210, 610 control circuit

[0020] 215 Counter

[0021] 606 Array Circuit

[0022] 607 column bias current source

[0023] 608 Column Comparison Circuit DETAILED DESCRIPTION

[0024] The purpose of the present application is to disclose a technical solution of an optical sensor device with BJT sensing pixels, which can accurately determine whether there is motion in the sensed image / frame and consumes only low power.

[0025] See also Figure 1 , Figure 1 1 is a circuit diagram of a novel pixel unit 100, such as a bipolar junction transistor (BJT) sensing pixel (or BJT pixel unit), disposed in a pixel array according to an embodiment of the present application. Figure 1 As shown, the BJT sensing pixel 100 includes a phototransistor (e.g., a photosensitive transistor BJT based on BJT), a shutter control circuit 105, a readout control circuit 110, a first integration capacitor INT, and a second integration capacitor INTD. The shutter control circuit 105 includes a plurality of MOS transistors, including, for example, NMOS (N-type channel MOS) transistors m1, m2, m4, and PMOS (P-type channel) transistors m3 and m5. The readout control circuit 110 includes a plurality of MOS transistors m6-m16 and two source follower transistors sf1 and sf2.

[0026] like Figure 1 As shown, for example, the transistor m1 has a first terminal (e.g., a drain terminal), a second terminal (e.g., a source terminal) and a control terminal (e.g., a gate terminal), wherein the first terminal of the transistor m1 is coupled to the control terminal of the transistor m2 (e.g., the gate terminal of the transistor m2) and the first terminal (e.g., the drain terminal) of the transistor m3, the second terminal of the transistor m1 is coupled to the ground level GNDA, and the control terminal of the transistor m1 is coupled to the base of the BJT type transistor BJT. The gate terminal of the transistor m2 is coupled to the transistor m1 The drain terminal of transistor m2 is coupled to the source terminal of transistor m4, the source terminal of transistor m5 and the source terminal of transistor m9, and the source terminal of transistor m2 is coupled to the emitter of BJT type transistor BJT. The gate terminal of transistor m3 is coupled to the control signal PBB, the source terminal of transistor m3 is coupled to the power supply voltage vdda, for example, 1.8 volts (but not limited to), and the drain terminal of transistor m3 is coupled to the gate terminal of transistor m2 and the drain terminal of transistor m1. The circuit structure and connection of other MOS transistors are as follows Figure 1 as shown in .

[0027] Specifically, the gate terminal of transistor m5 is coupled to the control signal NSH1, the source terminal of transistor m5 is coupled to the drain terminal of transistor m2, and the drain terminal of transistor m5 is coupled to the drain terminal of transistor m6 and the source terminal of transistor m7. The gate terminal of transistor m7 is coupled to the control signal NS1, the source terminal of transistor m7 is coupled to the drain terminal of transistor m6, and the drain terminal of transistor m7 is coupled to the first integrated capacitor INT and the gate terminal of the source follower transistor sf1. The first terminal of the first integrated capacitor INT is coupled to the drain terminal of transistor m7 and the gate terminal of the source follower transistor sf1, and the second terminal of the first integrated capacitor INT is coupled to the ground level GNDA. The drain terminal of the source follower transistor sf1 is coupled to the power supply voltage vdda, the source terminal of the source follower transistor sf1 is coupled to the drain terminal of transistor m8, and the gate terminal of the source follower transistor sf1 is coupled to the drain terminal of transistor m7 and the first integrated capacitor INT.

[0028] In addition, the gate terminal of transistor m9 is coupled to the control signal NSH2, the source terminal of transistor m9 is coupled to the drain terminal of transistor m2, the source terminal of transistor m4 and the source terminal of transistor m5, and the drain terminal of transistor m9 is coupled to the drain terminal of transistor m10 and the source terminal of transistor m11. The gate terminal of transistor m11 is coupled to the control signal NS2, the source terminal of transistor m11 is coupled to the drain terminal of transistor m9, and the drain terminal of transistor m11 is coupled to the gate terminal of the source follower transistor sf2 and the second integrated capacitor INTD. The first terminal of the second integrated capacitor INTD is coupled to the drain terminal of transistor m11 and the gate terminal of the source follower transistor sf2, and the second terminal of the second integrated capacitor INTD is coupled to the ground level GNDA. The drain terminal of the source follower transistor sf2 is coupled to the supply voltage vdda, the gate terminal of the source follower transistor sf2 is coupled to the drain terminal of transistor m11 and the first terminal of the second integrated capacitor INTD, and the source terminal of the source follower transistor sf2 is coupled to the drain terminal of transistor m12.

[0029] In this embodiment, the control signals PBB, NSH, NSH1 and NS1 can respectively control (turn on / off) transistors m3, m4, m5 and m7 to collect and capture light signals during the first shutter exposure period ST1 of time T1 and transfer the charge of the light signals from the BJT phototransistor to the first collection capacitor INT, so that the light signals collected / captured at time T1 can be stored in the first collection capacitor INT. The control signal RD is a read control signal, and the transistor m8 can be turned on under the action of the control signal RD, and cooperate with the first source follower transistor sf1 to generate and output the first output signal OUT corresponding to the light signal captured at time T1. Similarly, the control signals PBB, NSH, NSH2, NS2 can respectively control (turn on / off) transistors m3, m4, m9, m11 to collect and capture light signals during the second shutter exposure period ST2 of time T2, and transfer the charge of the light signals from the BJT phototransistor to the second collection capacitor INTD, so that the light signals collected / captured at time T2 can be stored in the second collection capacitor INTD. Then, the transistor m12 can be turned on by the control signal RD, and work together with the second source follower transistor sf2 to generate and output a second output signal OUTD corresponding to the light signal collected and captured at time T2. Similarly, the light signal can also be collected during the first shutter exposure period ST1 at time T3 after time T2, and the light signal can also be collected during the second shutter exposure period ST2 at time T4 after time T3. Figure 3 An example schematic diagram of a shutter exposure time period of time T1-T3 according to an embodiment of the present application is shown.

[0030] In addition, the control signal RST, ie, a reset control signal, is coupled to the gate terminals of the transistors m13 and m15 to control the transistors m13 and m15 to reset the operation of the readout control circuit 110, which will not be described in detail for the sake of brevity.

[0031] In this way, based on Figure 1The circuit structure of each BJT sensing pixel 100 can capture two optical signals at different times. At time T1, the control signals NSH1 and NS1 are at a low level, such as level "0", to select and turn on the corresponding PMOS transistors m5 and m7, and the control signals NSH2 and NS2 are at a high level, such as level "1", so that the PMOS transistors m9 and m11 will not be turned on (that is, they will not be selected). In this case, the captured first optical signal / data can be stored in the first collection capacitor INT through the turned-on PMOS transistors m5 and m7. Then, at time T2 (later than time T1), the control signals NSH2 and NS2 are at a low level, so the corresponding PMOS transistors m9 and m11 will be selected and turned on, while the control signals NSH1 and NS1 are at a high level, so the PMOS transistors m5 and m7 are not turned on (not selected). In this case, the captured second optical signal / data can be stored in the second collection capacitor INTD through the corresponding turned-on PMOS transistors m9 and m11. That is, the first integrated capacitance INT and the second integrated capacitance INTD respectively have two optical data / signals collected at different times.

[0032] Equivalently, when the control signal RD is at a high level, the transistors m8 and m12 are turned on respectively, and the two optical signals are read and transferred out as the first output signal OUT and the second output signal OUTD respectively. In fact, when the control signal RD is at a high level and the control signal NSH1 changes from a low level to a high level, the first optical signal is read out from the collective capacitor INT, and then when the control signal RD is at a high level and the control signal NSH2 switches from a low level to a high level, the second optical signal is read out from the collective capacitor INTD, as shown in FIG. Figure 3 shown.

[0033] See also Figure 2 , Figure 2 is a schematic diagram of an optical sensor device 200 including a plurality of BJT sensing pixels 100 according to an embodiment of the present application. Figure 2 In the embodiment, the optical sensor device 200 includes a pixel array 205 and a control circuit 210. The pixel array 205 includes a plurality of pixel units, for example, arranged in N rows and M columns. Figure 1 The BJT sensing pixels 100 in the embodiment of the present invention are configured to output two output signals OUT and OUTD thereof to the control circuit 210 at different times. The control circuit 210 is configured to respectively generate the above-mentioned control signals PBB, NSH, NSH1, NS1, NSH2, NS2, RST, and RD to each BJT sensing pixel 100, so as to obtain and receive the two output signals OUT and OUTD of each BJT sensing pixel 100.

[0034] In practice, the control circuit 210 includes a first current source CS1 , a second current source CS2 , a first switch unit SW1 , a second switch unit SW2 , a first buffer capacitor C1 , a second buffer capacitor C2 , a comparator COMP and a counter 215 .

[0035] exist Figure 2 In the embodiment, for a BJT sensing pixel 100, the output signal OUT of the first collective capacitor INT and the output signal OUTD of the second collective capacitor INTD are transmitted to the control circuit 210. The current sources CS1 and CS2 are used to provide reference current signals to the output signals OUT and OUTD respectively. The first switch unit SW1 and the second switch unit SW2 are controlled to be in a closed state. The output signals OUT and OUTD can be transmitted through the switch unit SW2 and the switch unit SW1 and then stored in the buffer capacitor C2 and the buffer capacitor C1, and the other plate of the capacitor C1-C2 is biased by the bias voltage Vref.

[0036] When the first switch unit SW1 and the second switch unit SW2 are turned on to a closed state (i.e., a conducting state), the control circuit 210 is used to receive the two output signals OUT and OUTD to check the difference thereof. Then, after the two output signals OUTD and OUT are stored by the two buffer capacitors C1 and C2, respectively, the first switch unit SW1 and the second switch unit SW2 are turned off to a non-conducting state.

[0037] When the first switch unit SW1 and the second switch unit SW2 are turned off to the off state (i.e., the non-conducting state), the bias voltage provided by the other plate of the buffer capacitor C2 is controlled by the control circuit 210 to be maintained at Vref, and the bias voltage provided by the other plate of the buffer capacitor C1 is controlled by the control circuit 210 to be quickly moved from Vref to Vref-Vth and Vref+Vth. For example (but not limited to), the bias voltage can be quickly moved from Vref to Vref-Vth, and then quickly moved from Vref-Vth to Vref+Vth. That is, the control circuit 210 controls the bias voltage provided by the other plate of the buffer capacitor C2 to move twice or switch twice to different reference voltage levels. It is worth noting that in the present embodiment (but not limited to), Vth is a threshold voltage used / configured by the comparator COMP (or by the control circuit 210) in a global setting, and the threshold voltage is applied to all BJT sensing pixels 100 included in the pixel array 205. However, this is not a limitation of the present application. For example, for different BJT sensing pixels 100 in the pixel array 205 , the value of the threshold voltage Vth may also be at different levels.

[0038] The comparator COMP compares the waveform of the output signal OUTD centered at the level Vref-Vth and the waveform of the output signal OUT centered at the level Vref to generate a first comparison result bit / signal, and then compares the waveform of the output signal OUTD centered at the level Vref+Vth and the level of the output signal OUT centered at the level Vref to generate a second comparison result bit / signal, thereby sequentially generating and outputting two comparison result bits / signals to the counter 215. Based on the first and second comparison result bits, the counter 215 can determine whether the second output signal OUTD collected at time T2 is darker or brighter than the first output signal OUT collected at time T1.

[0039] For example (but not limited to), if the second output signal OUTD collected at time T2 is darker than the first output signal OUT collected at time T1 due to a sufficient / significant pixel change, the first and second comparison result bits can indicate a result of "11", so the count value counted by the counter 215 (initial value equal to 0) will be accumulated and added by 1 to record a significant pixel difference.

[0040] If the second output signal OUTD collected at time T2 is brighter than the first output signal OUT collected at time T1 due to a sufficient / significant pixel change, the first and second comparison result bits may indicate "00", and the count value (initial value is zero) counted by the counter 215 will also be accumulated and added by one to record that a significant pixel difference has occurred. If the first and second comparison result bits indicate "01" and "10", the count value will not be increased and will not be accumulated.

[0041] For all BJT sensing pixels 100 in the pixel array 205, the counter 215 is used to use its count value to accumulate the number of BJT sensing pixels with significant pixel differences corresponding to the comparison result bit '11' or '00' in the entire pixel array 205. The control circuit 210 is used to compare the count value with a preset count threshold to determine whether motion occurs, so as to generate a motion signal, and the motion signal can be used to trigger to wake up the entire sensing system where the optical sensor device 200 is located. For example, when the accumulated count value is greater than the preset count threshold, the control circuit 210 (or the optical sensor device 200) can determine that motion occurs, and in other cases, the control circuit 210 can determine that no motion occurs.

[0042] Reference again Figure 3 ,exist Figure 3In the embodiment, at time T1, the control signal NSH1 changes to a low level to select and turn on the transistor m5. During the shutter exposure period ST1 of time T1, the control signal NS1 also turns on the transistor m7, and the control signal RD turns off the transistor m8, so that the charge is stored in the first collective capacitor INT. Then, in the second time period (i.e., the readout and comparison time interval) after the shutter exposure period ST1 of time T1, the control signal NSH1 changes to a high level to turn off the transistor m5, the control signal NSH2 remains at a high level to turn off the transistor m9, and the control signal RD turns on the transistor m8, so that the first collective capacitor INT transfers the stored charge as the first output signal OUT to the BJT sensing pixel 100, and the first output signal OUT is transmitted to the control circuit 210. During the readout and comparison time interval of time T1, the first output signal OUT is transmitted to the control circuit 210, and the control circuit 210 determines the charge stored in the first collective capacitor INT based on the first output signal OUT. Figure 2 The switching operation value of the bias voltage of the other plate of the buffer capacitor C1 is shown to compare the currently received first output signal OUT with the previously received / stored second output signal OUTD to determine whether a significant pixel difference occurs between the output signals OUT and OUTD. Once a significant pixel difference occurs, the count value counted by the counter 215 is increased by 1.

[0043] It should be noted that during the shutter exposure period ST1, all BJT sensing pixels 100 of the entire pixel array 205 are used to sense light (e.g., light reflected from a working surface), and then during the readout and comparison period at time T1, the control circuit 210 (or the optical sensor device 200) checks whether more or all BJT sensing pixels 100 in the entire pixel array 205 are associated with significant pixel differences to calculate and accumulate the specific count value at time T1, that is, count more or all BJT sensing pixels 100. If the accumulated specific count value at time T1 is greater than a preset count threshold, the control circuit 210 determines that motion has occurred at time T1.

[0044] Similarly, during the shutter exposure period ST2 of time T2, the control signal NSH2 becomes low to select and turn on the transistor m9. During the shutter exposure period ST2, the control signal NS2 also turns on the transistor m11, and the control signal RD turns off the transistor m12, so that the charge is stored in the second collective capacitor INTD. Then, in the second time period (i.e., the readout and comparison time interval) after the shutter exposure period ST2 of time T2, the control signal NSH2 becomes high to turn off the transistor m9, the control signal NSH1 remains high to turn off the transistor m5, and the control signal RD turns on the transistor m12, so that the second collective capacitor INTD transfers the stored charge as the second output signal OUTD to the BJT sensing pixel 100, and transmits the second output signal OUTD to the control circuit 210.

[0045] During the read and compare period of time T2, the second output signal OUTD is transmitted to the control circuit 210, and then the control circuit 210 controls the output signal OUTD based on the control circuit 210. Figure 2 The switching operation of the bias voltage of the other plate of the buffer capacitor C1 shown in the figure compares the currently received second output signal OUTD with the previously received first output signal OUT (i.e., the output signal collected during the above time period ST1) to determine whether a significant pixel difference occurs between the output signals OUT and OUTD. Once a significant pixel difference occurs, the count value counted by the counter 215 is increased by 1.

[0046] Similarly, during the shutter exposure period ST2 at time T2, all BJT sensing pixels 100 of the entire pixel array 205 are used to sense light (e.g., reflected from the working surface), and then during the readout and comparison period at time T2, the control circuit 210 (or the optical sensor device 200) checks whether more or all BJT sensing pixels 100 in the entire pixel array 205 are associated with significant pixel differences to calculate and accumulate the specific count value at time T2, that is, to count more or all BJT sensing pixels 100. If the accumulated specific count value at time T2 is greater than the preset count threshold, the control circuit 210 determines that motion has occurred at time T2.

[0047] For time T3, the above operations are similar or identical. During the shutter exposure period ST1 of time T3, all BJT sensing pixels 100 of the entire pixel array 205 are used to sense light (e.g., reflected from the working surface), and then during the readout and comparison period of time T3, the control circuit 210 (or the optical sensor device 200) checks whether there are more or all BJT sensing pixels 100 in the entire pixel array 205 at time T3 that are associated with significant pixel differences, so as to calculate and accumulate the specific count value at time T3, that is, to count more or all BJT sensing pixels 100. If the accumulated specific count value at time T3 is greater than the preset count threshold, the control circuit 210 determines that motion has occurred at time T3. Other operations are similar and will not be repeated.

[0048] In addition, equivalently, the phototransistor BJT of a BJT sensing pixel 100 is used to capture and generate an image signal (pixel image) during the shutter exposure period ST1, and then generate another image signal during the shutter exposure period ST2. Since time T2 follows time T1, the shutter exposure period ST2 is equivalently also following the shutter exposure period ST1. The two pixel images are stored by two integrated capacitors INT and INTD, respectively, as described above. In addition, the motion detection performed by the optical sensor device 200 (or the control circuit 210) is to determine whether motion occurs based on the difference between the two pixel images captured in different shutter exposure periods with the same / different time lengths. In addition, in one embodiment, the shutter exposure period used can be switched between different shutter exposure periods with different time lengths. The first shutter exposure period ST1 and the second shutter exposure period ST2 can be continuously alternated.

[0049] The disclosed optical sensor device 200 having multiple BJT sensing pixels 100 can be used to enhance / improve the sensitivity of motion detection operations and can be used to wake up the sensor system during rest or idle periods without running full digital operations. The optical sensor device 200 can improve the sensitivity of the sensor to detect image changes (i.e., motion).

[0050] In this embodiment, for example (but not limited to), when the pixel value corresponding to the second output signal OUTD collected and captured at time T2 is higher or lower than a threshold pixel value corresponding to the threshold voltage Vth, the control circuit 210 can determine that the pixel value of the BJT sensing pixel 100 is brighter or darker at time T2 than at time T1.

[0051] In one embodiment, the threshold voltage Vth is set high enough to avoid false motion caused by shot noise of the image.

[0052] In other embodiments, when the pixel unit 100 senses brighter light, the shot noise content in the output signal OUT / OUTD will also increase proportionally, and the control circuit 210 can dynamically adjust the threshold voltage Vth to increase the value of the threshold voltage Vth to be applied to the increased shot noise level and maintain the value of the threshold voltage Vth applied to the shot noise level currently maintained at the same level, so as to mitigate different noise levels accordingly.

[0053] For example (but not limited to), if the voltage level of the output signal of a brighter pixel unit (i.e., with a high pixel value) is 500mV, its peak-to-peak shot noise level may be ±10mV. In this case, the threshold voltage Vth can be used to be equal to or higher than the absolute value of ±10mV to avoid false motion. In practice, a sensed image may contain high / medium / low pixel values; for example, the voltage level of the output signal of a pixel unit with a lower pixel value may be 250mV, and its peak-to-peak shot noise level may be ±5mV. In this case, false motion can be avoided by simply setting the threshold voltage Vth to be equal to or higher than the absolute value of ±5mV. If the threshold voltage Vth of all pixel units is always high, the sensitivity of the motion detection operation will be reduced.

[0054] To solve this problem, in one embodiment, the control circuit 210 can dynamically adjust the threshold voltage Vth of different pixel units 100. That is, the optical sensor device 200 can use a high threshold voltage for a pixel unit with a high pixel value to mitigate a high shot noise level, provide a medium threshold voltage for a pixel unit with a medium pixel value to mitigate a medium shot noise level, and provide a low threshold voltage for a pixel unit with a low pixel value to mitigate a low shot noise level. Using a medium threshold voltage to mitigate a medium shot noise level and / or using a low threshold voltage to mitigate a low shot noise level can improve the signal sensitivity of the motion detection operation and accurately avoid false motion.

[0055] In some cases, it may be difficult to adaptively adjust the threshold voltage Vth of different pixel units 100 of the pixel array 205. In order to solve the above problems, the present application discloses an operation of dynamically adjusting the shutter exposure time period for multiple times continuously, thereby equivalently achieving the improvement of the sensitivity of the motion detection signal, and in an embodiment, it is not necessary to directly adjust the threshold voltage Vth of different pixel units of the pixel array 205. For example, in an embodiment, in order to improve the signal sensitivity of the motion detection operation, the control circuit 210 can dynamically adjust or change the shutter time period of different times such as T1, T2 and T3 to obtain / acquire different sensed images, and then compare the sensed images. The operation and function of changing the threshold voltage Vth can be replaced by the operation of dynamically adjusting or changing the shutter time period of different times such as T1, T2, and T3. The threshold voltage Vth can be set to zero, so there is no need to switch the bias voltage Vref to Vref-Vth and Vref+Vth, and the comparator COMP can directly compare the output signals OUTD and OUT to generate a comparison result bit / signal to the counter 215.

[0056] See also Figure 3 For a specific pixel unit 100 (or most or all of the pixel units), the control circuit 210 can control the exposure time periods corresponding to the continuous time of the continuous images / frames to have different time lengths. For example, the shutter exposure time period ST1 of the specific pixel unit 100 at the time T1 of the first image, that is, the time period when the control signal NSH1 is at a low level, can be equal to a longer exposure time period, such as 10us (but not limited to). The shutter exposure time period ST2 of the specific pixel unit 100 at the time T2 of the second image, that is, the time period when the control signal NSH2 is at a low level, can be equal to a shorter exposure time period, shorter than the exposure time period 10us, such as 9us. The shutter exposure time period ST1 of the specific pixel unit 100 at the time T3 of the third image, that is, the time period when the control signal NSH1 is at a low level again, can be equal to a longer exposure time period 10us. That is, the control circuit 210 (or the optical sensor device 200) can control the length value of its shutter exposure time period to continuously alternate between longer and shorter time periods.

[0057] If no motion occurs, the pixel value of the specific pixel unit 100 collected and captured during the shutter exposure time period ST2 should be darker than the pixel value of the specific pixel unit 100 collected and captured during the shutter exposure time period ST1, because the shutter exposure time period ST2 is shorter than the shutter exposure time period ST1. In this case, if no motion occurs between two consecutive shutter exposure operations / time periods, the value of the second output signal OUTD is lower or darker than the first output signal OUT, and the comparator COMP generates a comparison result bit "1" to the counter 215. If motion occurs, for example (but not limited to), the pixel value of the specific pixel unit 100 collected and captured during the shutter exposure time period ST2 may change significantly and become brighter than the pixel value of the specific pixel unit 100 collected and captured during the shutter exposure time period ST1. In this case, the output of the comparator COMP will switch to bit "0" to preliminarily indicate that a significant change has occurred in the pixel unit 100. By collecting the comparison result bits of most / all pixel units 100 in the pixel array 205 sequentially output from the comparator COMP, the counter 215 can count and accumulate the number of bits "0", and then compare the number of bits "0" with a specific threshold number to ultimately determine whether motion occurs in the image captured during the shorter shutter exposure period ST2. For example, if the number of bits "0" corresponding to the shorter shutter exposure period ST2 is greater than a specific threshold, the optical sensor device 200 (or the control circuit 210) can determine that motion occurs at a specific time (e.g., time T2).

[0058] In one embodiment, if motion is detected at time T2, the control circuit 210 may stop switching between the shutter exposure time periods ST1 and ST2, and may use one of ST1 and ST2 as the shutter exposure time period, and maintain the value of the shutter exposure time period. This is not a limitation of the present application.

[0059] In other embodiments, if no motion is detected at time T2, the control circuit 210 may continue to switch between the shutter exposure time periods ST1 and ST2 to perform motion detection operations. For example (but not limited to), assuming that if no motion occurs at time T2, the comparator COMP generates a comparison result bit '1' to the counter 215, and the control circuit 210 can control and switch the shutter exposure time period back to the longer shutter exposure time period ST1 at time T3. If no motion occurs at time T3, the pixel value of the specific pixel unit 100 collected at the longer shutter exposure time period ST1 at time T3 should be brighter or higher than the pixel value of the specific pixel unit 100 collected at the shorter shutter exposure time period ST2 at time T2, so the comparator COMP will generate and output a comparison result bit "0" to indicate that there is no motion at time T3. In this example, if motion occurs at time T3, the pixel value of the specific pixel unit 100 collected during the longer shutter exposure period ST1 at time T3 may change significantly and become darker than the pixel value of the specific pixel unit 100 collected and captured during the shorter shutter exposure period ST2 at time T2, for example (but not limited to). Therefore, in this case, the output of the comparator COMP will switch to bit "1" to preliminarily indicate that the pixel unit 100 has undergone a significant pixel change at time T3. Then, by collecting the comparison result bits of most / all pixel units 100 in the pixel array 205 sequentially output by the comparator COMP, the counter 215 can count and accumulate the number of bits "1", and then compare the number of bits "1" with a specific threshold number to finally determine whether motion occurs in the image captured during the longer shutter exposure period ST1. For example, if the number of bits "1" corresponding to the longer shutter exposure period ST1 is greater than a specific threshold, the optical sensor device 200 (or the control circuit 210) can determine that motion occurs at a specific time (e.g., time T3).

[0060] In one embodiment, the control circuit 210 determines that motion has occurred only when at least the number of bits '1' corresponding to the longer shutter exposure time period ST1 is detected to be greater than a specific threshold number and at least the number of bits "0" corresponding to the shorter shutter exposure time period ST2 is detected to be greater than a specific threshold number for multiple consecutive times.

[0061] In other embodiments, the control circuit 210 may individually and separately adjust and change the shutter exposure time periods of different pixel units 100 in the pixel array 205 according to different pixel output levels of the different pixel units 100 .

[0062] Figure 4 This is an example diagram of the relationship between light intensity and pixel output signal voltage level according to an embodiment of the present application. Figure 4 In FIG. 2 , line L1 represents the relationship between the light intensity and the pixel output signal voltage level when a longer shutter exposure time period ST1 is used, and line L2 represents the relationship between the light intensity and the pixel output signal voltage level when a shorter shutter exposure time period ST2 is used. For example (but not limited to), under low light intensity LI1, the pixel output voltage level collected during the longer shutter exposure time period ST1 may actually be 250mV plus a shot noise level of ±5mV. Under high light intensity LI2, the pixel output voltage level collected during the longer shutter exposure time period ST1 may be 500mV plus a shot noise level of ±10mV. In other words, the shot noise level increases proportionally with the light intensity. As described above, the control circuit 210 may adjust the threshold voltage Vth according to different light intensities to avoid detecting false motion caused by shot noise and maintain the signal sensitivity of motion detection.

[0063] In an embodiment, by switching between a longer shutter exposure period ST1 and a shorter shutter exposure period ST2 to provide an equivalent threshold voltage to avoid detecting false motion, the control circuit 210 (or the optical sensor device 200) may determine the pixel output voltage level corresponding to the low light intensity LI1 based on the pixel output voltage level of 250 mV plus the ±5 mV shot noise level and the pixel output voltage level corresponding to the high light intensity LI2 based on the ±10 mV shot noise level. Figure 4 As a result, the line L2 shown in FIG. 2 is obtained. For example, the optical sensor device 200 may fine-tune or adjust the actual time length of the shorter shutter exposure period ST2 so that the corresponding line L2 is located below the line L1 and is separated by a sufficient discrimination voltage range. For example, the control circuit 210 may configure the discrimination voltage range under high light intensity LI2 to be equal to twice the absolute value of the ±10mV shot noise level, that is, Figure 4 The control circuit 210 can set the discrimination voltage range under low light intensity LI2 to be equal to twice the absolute value of the ±5mV shot noise level, that is, Figure 4 10mV shown.

[0064] In this way, the optical sensor device 200 can find out and obtain the fine-tuned time length of the shorter exposure time period ST2, such as 9us (but not limited to). In fact, the control circuit 210 can directly control the shutter control circuits 105 of different BJT sensing pixels 100 to provide and use shutter exposure time periods of different lengths. For different BJT sensing pixels 100, compared with dynamically adjusting such as Figure 2For the operation of the threshold voltage Vth value shown, it is more convenient and flexible to adjust the exposure time period. In addition, compared with using a fixed threshold voltage Vth value for all BJT sensing pixels 100, adjusting the exposure time period of different BJT sensing pixels 100 can also improve performance.

[0065] In other embodiments, the comparison operation sequentially performed by the control circuit 210 on the BJT sensing pixels one by one can be replaced by a built-in comparison mechanism set in each BJT sensing pixel to further reduce power consumption and achieve the requirement of low-power motion detection.

[0066] See also Figure 5 and Figure 6 . Figure 5 is a circuit diagram of two BJT sensing pixels arranged at different spatial positions in the same column of a pixel array according to an embodiment of the present application. Figure 6 6 is a schematic diagram of an optical sensor device 600 according to an embodiment of the present application. The optical sensor device 600 includes a pixel array 605 and a control circuit 610 having a counter 215, wherein the pixel array 605 includes a Figure 5 The array circuit 606 includes a plurality of BJT sensing pixels arranged in N rows and M columns, M column bias current sources 607 arranged in 1 row and M columns, and M column built-in comparison circuits 608 arranged in 1 row and M columns. The integer N is, for example, equal to 2 (but not limited to), and the integer M is equal to 30 (but not limited to).

[0067] The pixel array 605 can simultaneously generate and output M comparison result signals OUT_1 to OUT_M (for example, M is 30) of each row to the control circuit 610. For example, the pixel array 605 has two rows, and the pixel array 605 can generate a set of comparison result signals OUT_1 to OUT_30 to the control circuit 610, and then generate another set of comparison result signals OUT_1 to OUT_30 to the control circuit 610. In other words, the control circuit 610 receives the comparison result signals OUT_1 to OUT_M (for example, M is 30 and N is 2) N times.

[0068] The control circuit 610 is coupled to the pixel array 605, and is used to generate N rows of read control signals (e.g., RD1 for the first row and RD2 for the second row) to the pixel array 605, so that the pixel array 605 outputs M comparison result signals on the first row in response to the control signal RD1 and outputs another M comparison result signals on the second row in response to the control signal RD2, and is used to control the counter 215 to receive the M comparison result signals of each row of the pixel array 605 and count the total number of specific bits "1" or "0" indicating significant pixel changes. In other words, the control circuit 610 in this example may not include a comparison operation.

[0069] Reference again Figure 5 . Figure 5 Two BJT sensing pixels 500_1 and 500_2 are shown located in the same column (e.g., the first column) of the pixel array 605, a column bias current source 607 disposed on the same column, and a built-in column comparison circuit 608 disposed on the same column. For example, the BJT sensing pixels 500_1 and 500_2 have the same circuit structure and components. For example, the BJT sensing pixel 500_1 (or 500_2) includes circuit components / structures similar to those included in the BJT sensing pixel 100, so for the sake of brevity, they are not described in detail. Figure 1 Compared with the embodiment of the present invention, the difference lies in that the drain terminal D3 of the source follower transistor sf1 of the BJT sensing pixel 500_1 on the first row and the first column of the pixel array 605 is coupled to the first input terminal of the column comparison circuit 608, the drain terminal D4 of the source follower transistor sf2 of the BJT sensing pixel 500_1 is coupled to the second input terminal of the column comparison circuit 608, the drain terminal D1 of the source follower transistor sf1 of the BJT sensing pixel 500_2 in the second row and the first column of the pixel array 605 is coupled to the first input terminal of the column comparison circuit 608, the drain terminal D2 of the source follower transistor sf2 of the BJT sensing pixel 500_2 is coupled to the second input terminal of the column comparison circuit 608, and the output signals OUT and OUTD of all the BJT sensing pixels 500_1 and 500_2 in the same column are coupled to the column bias current source 607, the other end of the column bias current source 607 is coupled to the ground level and is used to provide a bias current of, for example, 5uA to the output signals OUT and OUTD.

[0070] Each Figure 5 , Figure 6The built-in column comparison circuit 608 shown includes transistors m50, m51, m52 and m53. The first terminal (e.g., drain terminal) of the PMOS transistor m50 is coupled to the drain terminals (i.e., D3 and D1) of the first source follower transistor sf1 of all BJT sensing pixels 500_1 and 500_2 located in the same column, the second terminal (e.g., source terminal) of the PMOS transistor m50 is coupled to the power supply voltage vdda, such as 1.8 volts (but not limited to), and the control terminal (e.g., gate terminal) of the PMOS transistor m50 is coupled to its drain terminal. The first terminal (e.g., drain terminal) of the PMOS transistor m51 is coupled to the drain terminals (i.e., D4 and D2) of the second source follower transistor sf2 of all BJT sensing pixels 500_1 and 500_2 located in the same column, the second terminal (e.g., source terminal) of the PMOS transistor m51 is coupled to the power supply voltage vdda, and the control terminal (e.g., gate terminal) of the PMOS transistor m51 is coupled to the gate terminal of the PMOS transistor m50. The first terminals (e.g., drain terminals) of the M PMOS transistors m52 are coupled to the outputs of the M built-in comparison circuits 608, and a comparison result bit / signal (e.g., OUT_1) of one of the BJT sensing pixels 500_1 / 500_2 on the same column is generated and output at the first terminals (e.g., drain terminals), the second terminals (e.g., source terminals) of the PMOS transistors m52 are coupled to the power supply voltage vdda, and the control terminals (e.g., gate terminals) of the PMOS transistors m52 are coupled to the drain terminals of the PMOS transistors m51. The first terminals (e.g., drain terminals) of the PMOS transistors m53 are coupled to the outputs of one of the M built-in comparison circuits (or coupled to the drain terminals of the transistors m52), the second terminals (e.g., source terminals) of the PMOS transistors m53 are coupled to the ground level, and the control terminals (e.g., gate terminals) of the PMOS transistors m53 are coupled to a bias voltage nbias.

[0071] like Figure 5 As shown, for example (but not limited to), Figure 5 The two source follower transistors sf1 and sf2 in the BJT sensing pixel 500_1 (or 500_2) may form a differential pair of a comparator.

[0072] The drain terminals D3 and D4 of the two source follower transistors sf1 and sf2 are from Figure 5 The BJT sensing pixel 500_1 in the circuit is bypassed to construct a top portion of a comparison circuit. In addition, the drain terminals D1 and D2 of the two source follower transistors sf1 and sf2 can also be connected from Figure 5 The BJT sensing pixel 500_2 in the circuit is bypassed to construct a top portion of a comparison circuit.

[0073] The first output signal OUT and the second output signal OUTD are Figure 5The corresponding bias current (eg, 5uA) transmitted from the BJT sensing pixel 500_1 (or 500_2) and connected together outside the BJT sensing pixel 500_1 (or 500_2) and connected to the current source 607 in the same column form the bottom of the comparison circuit.

[0074] Therefore, when the control signal RD1 (i.e., the read control signal for reading the pixel data of the first row) becomes a high level "1", the BJT sensing pixel 500_1 on the first row and the first column is selected (because in this case, other read control signals such as RD2 are at a low level, so the transistors m8 and m12 of the BJT sensing pixel 500_1 are enabled and turned on by the control signal RD1, while the transistors m8 and m12 of the BJT sensing pixel 500_2 are not turned on by the control signal RD2).

[0075] Alternatively, when the control signal RD2 (i.e., the read control signal for reading the pixel data of the second row after the first row) becomes a high level "1", the BJT sensing pixel 500_2 on the second row and first column is selected (because in this case, other read control signals, such as RD1, are at a low level, the transistors m8 and m12 of the BJT sensing pixel 500_2 will be enabled and turned on by the control signal RD2, while the transistors m8 and m12 of the BJT sensing pixel 500_1 will not be turned on by the control signal RD1).

[0076] For the circuit structure and connection of the BJT sensing pixel 500_1 (or 500_2), if the voltage level of its first output signal OUT is higher than the voltage level of its second output signal OUTD, the comparison result bit represented by OUT_1 generated from the corresponding comparison circuit will be equal to "0".

[0077] Figure 7 According to the embodiment of the present application Figure 5 In the present embodiment, the first collective capacitor INT of the BJT sensing pixels 500_1 and 500_2 is used to store the light signal collected during the first shutter exposure period ST1 (e.g., a longer exposure period, such as 10us) of the time T1, and the second collective capacitor INTD of the BJT sensing pixels 500_1 and 500_2 is used to store the light signal collected during the second shutter exposure period ST2 (e.g., a shorter exposure period, such as 9us) of a time earlier than the time T1.

[0078] In the readout and comparison time period after the time period ST1 of the time T1, when the read control signal RD1 becomes high and the read control signal RD2 becomes low, the output signals OUT and OUTD of all BJT sensing pixels in the same row are read out and compared to generate and output comparison result bits / signals OUT_1 to OUT_30 to the control circuit 610, respectively. Figure 6 Subsequently, when the read control signal RD2 becomes high and the read control signal RD1 becomes low, the output signals OUT and OUTD of all BJT sensing pixels in the same row (e.g., the second row of the pixel array 605) are read out again and compared to generate and output comparison result bits / signals OUT_1 to OUT_30 to the control circuit 610, respectively. Figure 6 As shown. Therefore, in this case, the control circuit 610 can receive N×M comparison result bits, for example, 2×30 comparison result bits. Since the first output signal OUT corresponds to a longer shutter exposure period ST1 compared to the second output signal OUTD, if no motion occurs, the voltage level of the first output signal OUT will be higher than the voltage level of the second output signal OUTD, so ideally, the comparison result bit (for example, OUT_1) should be equal to "1". If motion occurs, the value of the comparison result bit will switch to "0". Therefore, the control circuit 610 can use the counter 215 to count the number of specific bits "0" used to indicate significant pixel changes, and then compare the total number of specific bits "0" at time T1 with the quantity threshold to determine whether motion occurs at time T1.

[0079] Similarly, at time T2, the second collective capacitors INTD of the BJT sensing pixels 500_1 and 500_2 are used to store the light signals collected during the second shutter exposure period ST2 of time T2. During the readout and comparison period after the period ST2 of time T2, when the read control signal RD1 becomes high and the read control signal RD2 becomes low, the output signals OUT and OUTD of all BJT sensing pixels in the same row (e.g., the first row of the pixel array 605) are read out and compared to generate and output comparison result bits / signals OUT_1-OUT_30 to the control circuit 610, respectively. Subsequently, when the read control signal RD2 becomes high and the read control signal RD1 becomes low, the output signals OUT and OUTD of all BJT sensing pixels in the same row (e.g., the second row of the pixel array 605) are read out and compared again to generate and output comparison result bits / signals OUT_1 to OUT_30 to the control circuit 610, respectively. Therefore, in this case, the control circuit 610 may also receive N×M comparison result bits, for example, 2×30 comparison result bits, at time T2. Since the second output signal OUTD corresponds to a shorter shutter exposure period ST2 than the first output signal OUT, if no motion occurs, the voltage level of the first output signal OUT will be higher than the voltage level of the second output signal OUTD, so ideally, the comparison result bit (e.g., OUT_1) should be equal to "1". If motion occurs, the value of the comparison result bit will switch to "0". Therefore, the control circuit 610 may use a counter 215 to count the number of specific bits "0" used to indicate significant pixel changes, and then compare the total number of specific bits "0" at time T1 with a quantity threshold to determine whether motion occurs at time T2. The operations and functions at time T3 or later are similar to the operations and functions of the circuits in the above-mentioned previous paragraphs.

[0080] In addition, it should be noted that the charge of the first collective capacitor INT will be overwritten by the light signal collected during the longer shutter exposure period ST1 at time T3, while the charge of the second collective capacitor INTD will be overwritten by the light signal collected during the shorter shutter exposure period ST2 at a later time T4 (not shown in the figure).

[0081] The advantages of the embodiments of the present application are: Figure 5 Matching Figure 6 In the embodiment of the circuit design / structure, in order to transmit / transfer each pixel signal to an external comparator or comparison circuit, each pixel element only needs to consume 5uA of current. Figure 1 Matching Figure 2In an embodiment of the circuit design / structure, each pixel unit may need to consume a current of 160uA. For example, the current provided by each current source CS1 and CS2 may be equal to 160uA, while the current provided by each column current source may only consume 5uA, which is significantly less than 160uA.

[0082] Furthermore, if Figure 7 As shown, since it is operated line by line, compared with Figure 2 For example (but not limited to), to achieve pixel transmission of all pixel units arranged in 30 rows and 30 columns, the optical sensor device 600 only needs to transmit pixel data 30 times to complete the reading of all pixel values ​​of an image / frame, instead of transmitting pixel data 900 times.

[0083] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical sensor device, comprising: A pixel array having a plurality of pixel units arranged in N rows and M columns; Features: A first pixel unit among the plurality of pixel units comprises: a phototransistor, configured to capture and generate a first image signal during a first shutter exposure period of time at a first time, and to capture and generate a second image signal during a second shutter exposure period of time at a second time, wherein the first time and the second time are continuous; a first collective capacitor, coupled to the phototransistor, for storing the first image signal; and a second collective capacitor, coupled to the phototransistor, for storing the second image signal; and a control circuit coupled to the first pixel unit; The first shutter exposure time period is different from the second shutter exposure time period, and the control circuit performs motion detection to determine whether motion occurs based on the difference between the first image signal captured during the first shutter exposure time period and the second image signal captured during the second shutter exposure time period.

2. The optical sensor device according to claim 1, characterized in that The phototransistor is a bipolar transistor, and the first pixel unit is a bipolar transistor sensing pixel.

3. The optical sensor device according to claim 1, wherein: The first shutter exposure time period and the second shutter exposure time period appear alternately and continuously.

4. The optical sensor device according to claim 1, wherein: The control circuit compares the first image signal with the second image signal to preliminarily determine whether motion occurs.

5. The optical sensor device according to claim 4, characterized in that When the first time is followed by the second time, the second shutter exposure time period is shorter than the first shutter exposure time period; when the second image signal is darker than the first image signal, the control circuit determines that no motion occurs during the second time, and when the second image signal is brighter than the first image signal, the control circuit determines that motion occurs.

6. The optical sensor device according to claim 4, characterized in that When the second time is followed by the first time, the second shutter exposure time period is shorter than the first shutter exposure time period; when the second image signal is brighter than the first image signal, the control circuit determines that no motion has occurred, and when the second image signal is darker than the first image signal, the control circuit determines that motion has occurred.

7. The optical sensor device according to claim 1, characterized in that The first pixel unit outputs the first image signal as a first output signal to the control circuit, and outputs the second image signal as a second output signal to the control circuit, and the control circuit includes: a first current source, coupled to the second output signal sent by the first pixel unit; a second current source, coupled to the first output signal sent by the first pixel unit; a first buffer capacitor, used for storing the second output signal; a second buffer capacitor, used for storing the first output signal; a first switch unit, disposed between the first buffer capacitor and the second output signal and selectively coupled between the first buffer capacitor and the second output signal; a second switch unit, disposed between the second buffer capacitor and the first output signal and selectively coupled between the second buffer capacitor and the first output signal; a comparator coupled to the first buffer capacitor and the second buffer capacitor, for comparing the first output signal with the second output signal biased by a plurality of different threshold voltages to generate a first comparison result bit and a second comparison result bit to a counter; and The counter is coupled to the comparator, and is used to increase the count value by one only when the first comparison result bit is the same as the second comparison result bit.

8. The optical sensor device according to claim 7, characterized in that The control circuit dynamically adjusts the plurality of different threshold voltages for a plurality of different pixel cells in response to a plurality of different light intensities, and compares the first image signal with the second image signal on a pixel cell by pixel cell basis.

9. The optical sensor device according to claim 1, wherein: The second shutter exposure time period is determined based on a first light intensity, a first shot noise level of the first light intensity, a second light intensity, and a second shot noise level of the second light intensity. When the second light intensity is higher than the first light intensity, the first shot noise level is lower than the second shot noise level.

10. The optical sensor device according to claim 1, wherein: The pixel array further comprises: M column bias current sources, each column bias current source is used to provide a bias current to a plurality of output signals sent by a plurality of pixel units on a corresponding column; M column comparison circuits are coupled to the multiple pixel units on the corresponding columns, and each column comparison circuit is used to compare the multiple output signals in response to a specific read control signal of a specific row sent from the control circuit to generate and output a corresponding comparison result bit to the control circuit.

11. The optical sensor device according to claim 10, characterized in that The control circuit includes a counter, which is used to count multiple comparison result bits of all pixel units in the pixel array to generate a number of specific bits used to indicate that a pixel has significantly changed, and then compare the number of the multiple comparison result bits with a number threshold to ultimately determine whether motion has occurred.

12. The optical sensor device according to claim 10, characterized in that The M column comparison circuits of the pixel array simultaneously generate M comparison result bits of a plurality of pixel units on the specific row in response to the specific read control signal of the specific row.

13. A method of an optical sensor device, comprising: Providing a pixel array having a plurality of pixel units arranged in N rows and M columns; Features: A first pixel unit among the plurality of pixel units comprises: a phototransistor, configured to capture and generate a first image signal during a first shutter exposure period of time at a first time, and to capture and generate a second image signal during a second shutter exposure period of time at a second time, wherein the first time and the second time are continuous; a first collective capacitor, coupled to the phototransistor, for storing the first image signal; and a second collective capacitor, coupled to the phototransistor, for storing the second image signal; and configuring the first shutter exposure time period to be different from the second shutter exposure time period; and Motion detection is performed to determine whether motion occurs based on a difference between the first image signal captured during the first shutter exposure period and the second image signal captured during the second shutter exposure period.

14. The method according to claim 13, characterized in that The first shutter exposure time period and the second shutter exposure time period appear alternately and continuously.

15. The method according to claim 13, characterized in that The method further comprises: The first image signal is compared with the second image signal to preliminarily determine whether motion occurs.

16. The method according to claim 15, characterized in that When the first time is followed by the second time, the second shutter exposure time period is shorter than the first shutter exposure time period, and the method includes: When the second image signal is darker than the first image signal, determining that no motion occurs at the second time; and When the second image signal is brighter than the first image signal, it is determined that motion has occurred.

17. The method according to claim 15, characterized in that When the second time is followed by the first time, the second shutter exposure time period is shorter than the first shutter exposure time period, and the method further comprises: When the second image signal is brighter than the first image signal, determining that no motion occurs; and When the second image signal is darker than the first image signal, it is determined that motion has occurred.

18. The method according to claim 13, characterized in that The first pixel unit outputs the first image signal as a first output signal and outputs the second image signal as a second output signal, and the method further includes: Providing a first current source, wherein the first current source is coupled to the second output signal sent by the first pixel unit; providing a second current source, wherein the second current source is coupled to the first output signal sent by the first pixel unit; providing a first buffer capacitor to store the second output signal; providing a second buffer capacitor to store the first output signal; Providing a first switch unit, wherein the first switch unit is disposed between the first buffer capacitor and the second output signal and selectively coupled between the first buffer capacitor and the second output signal; providing a second switch unit, wherein the second switch unit is disposed between the second buffer capacitor and the first output signal and selectively coupled between the second buffer capacitor and the first output signal; providing a comparator to compare the first output signal with the second output signal biased by a plurality of different threshold voltages to generate a first comparison result bit and a second comparison result bit into a counter; and The count value of the counter is increased by 1 only when the first comparison result bit is the same as the second comparison result bit.

19. The method according to claim 18, characterized in that The method further comprises: The plurality of different threshold voltages are dynamically adjusted for a plurality of different pixel cells in response to a plurality of different light intensities, and the first image signal is compared with the second image signal on a pixel cell basis.

20. The method of claim 13, wherein: The method further comprises: The second shutter exposure time period is determined based on a first light intensity, a first shot noise level of the first light intensity, a second light intensity, and a second shot noise level of the second light intensity; when the second light intensity is higher than the first light intensity, the first shot noise level is lower than the second shot noise level.

21. The method of claim 13, wherein: The pixel array further comprises: M column bias current sources, each column bias current source is used to provide a bias current to a plurality of output signals sent by a plurality of pixel units arranged on a corresponding column; and M column comparison circuits are coupled to the plurality of pixel units on the corresponding columns, and each column comparison circuit is used to compare the plurality of output signals in response to a specific read control signal of a specific row sent from the control circuit to generate and output a corresponding comparison result bit.

22. The method of claim 21, wherein the method further comprises: Providing a counter to count a plurality of comparison result bits of all pixel units in the pixel array to generate a number of specific bits indicating that a pixel has undergone a significant change; as well as The number of the plurality of specific bits is compared with a number threshold to determine whether motion occurs.

23. The method of claim 21, wherein: The M column comparison circuits of the pixel array simultaneously generate M comparison result bits of a plurality of pixel units of the specific row in response to the specific read control signal of the specific row.

Images