Event-type image sensor and control method

Abstract

The present invention relates to an event-type image sensor and control method, which is applied to an event camera, and the method includes: obtaining a real-time voltage in response to an incident light signal; using the difference voltage between the real-time voltage and a preset reference voltage as an input voltage, performing frequency separation on the input voltage and a noise voltage, and then filtering the noise voltage according to the separated frequency to obtain an output voltage; comparing the output voltage with a preset voltage range; and outputting an event signal according to the comparison result. In an embodiment of the present invention, the input voltage and the noise voltage are frequency separated, and the noise voltage is filtered according to the separated frequency to obtain an output voltage with the noise voltage removed; since the output voltage is the voltage after the noise voltage is removed, when the event signal is output according to the comparison result, the output event signal is more accurate.

Description

Technical Field

[0001] The present invention belongs to the technical field of computer vision, and in particular relates to an event-type image sensor and a control method. Background Art

[0002] Traditional cameras, whether CMOS sensors, CCD sensors, or RGBD cameras, capture images at a constant frequency. In this way, even if the frame rate can reach 1KHz, there is still a delay of 1ms. Therefore, traditional cameras have certain delay problems. With the development of the times, an event camera (Event-based Vision, EVS) has emerged. The event camera is a dynamic visual sensor that senses changes in incident light and generates events based on the changes in light, outputs event signals, and has the advantages of fast frame rate and low power.

[0003] However, due to process deviations in the integrated circuit production process of existing event cameras, there are some noise, offset and other factors between the sub-circuits, which may lead to event signal output errors. Summary of the invention

[0004] The present invention provides an event-type image sensor and a control method, which are used to solve the technical problem of inaccurate event signal output in the prior art.

[0005] On the one hand, the present invention provides an event-type image sensor, which is applied to an event camera. The event-type image sensor comprises: an input unit, a chopping unit, a comparison unit and a readout unit, wherein the input unit, the chopping unit, the comparison unit and the readout unit are connected in sequence; wherein:

[0006] The input unit is used to obtain a real-time voltage in response to an incident light signal;

[0007] The chopping unit is used to take the difference voltage between the real-time voltage and the preset reference voltage as the input voltage, perform frequency separation on the input voltage and the noise voltage, and then filter the noise voltage according to the separated frequency to obtain the output voltage;

[0008] The comparison unit is used to compare the output voltage with a preset voltage range;

[0009] The readout unit is used to output an event signal according to the comparison result.

[0010] In a second aspect, the present invention provides an event-type image sensor control method, which is applied to an event camera, and the method comprises:

[0011] acquiring a real-time voltage in response to an incident light signal;

[0012] The difference voltage between the real-time voltage and the preset reference voltage is used as the input voltage, the input voltage and the noise voltage are frequency separated, and then the noise voltage is filtered according to the separated frequency to obtain the output voltage;

[0013] comparing the output voltage with a preset voltage range;

[0014] An event signal is output according to the comparison result.

[0015] It can be seen from the above-mentioned embodiments of the present invention that the embodiments of the present invention obtain an output voltage with the noise voltage removed by frequency separation of the input voltage and the noise voltage, and then filtering the noise voltage according to the separated frequency; since the output voltage is the voltage after the noise voltage is removed, when the event signal is output according to the comparison result, the output event signal is more accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying creative labor.

[0017] Figure 1 Schematic diagram of the process of the event-type image sensor control method in the embodiment of the present application;

[0018] Figure 2 is a circuit structure diagram of an event-type image sensor in an embodiment of the present application;

[0019] Figure 3 : is a circuit structure diagram of a chopper unit in an embodiment of the present application;

[0020] Figure 4 Schematic diagram of the relationship between the signal frequency / chopping frequency, input voltage and noise voltage in the embodiment of the present application;

[0021] Figure 5 This is a schematic diagram of the relationship between the signal frequency / chopping frequency and the intermediate voltage signal in the embodiment of the present application;

[0022] Figure 6 Schematic diagram of the relationship between the signal frequency / chopping frequency, the demodulation voltage and the noise voltage in the embodiment of the present application;

[0023] Figure 7 Schematic diagram of the relationship between the signal frequency / chopping frequency, the output voltage and the noise voltage in the embodiment of the present application;

[0024] Figure 8A schematic diagram showing the relationship between input voltage and time in an embodiment of the present application;

[0025] Fig. 9 A schematic diagram showing the relationship between modulation voltage and time in an embodiment of the present application;

[0026] Fig.10 This is a schematic diagram of the relationship between the demodulation voltage and time in the embodiment of the present application;

[0027] Fig.11 Schematic diagram of the relationship between output voltage and time in the embodiment of the present application. DETAILED DESCRIPTION

[0028] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0029] In the description of the embodiments of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0030] In the embodiments of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0031] See also Figure 1 , shows an event-type image sensor control method according to an embodiment of the present invention, which is applied to an event camera, and the method includes:

[0032] Step S100: acquiring a real-time voltage in response to an incident light signal.

[0033] In an exemplary embodiment, the step S100 specifically includes:

[0034] A photocurrent is generated in response to the incident light signal; and the photocurrent is converted into a real-time voltage.

[0035] In this embodiment, the event camera is an event-type image sensor, which includes a pixel array composed of multiple pixels, each pixel in the pixel array includes a corresponding pixel sensor, and the pixel sensor can collect incident light signals. The incident light signal is collected by the pixels in the image sensor, and each pixel performs corresponding collection. The collected incident light signal is photoelectrically converted by a photoelectric conversion element to obtain a corresponding current value, and the current value is converted from current to voltage by a current-voltage conversion element to obtain a corresponding real-time voltage, and the light signal is converted into a voltage signal for data calculation. The photoelectric conversion element can be a photodiode, a phototransistor, a clamped photodiode or any other similar component for photoelectric conversion. The implementation circuit of the current-to-voltage element is relatively common, and can be implemented by a voltage divider method, a Hall sensor method, an integration circuit method, etc., which will not be described in detail here.

[0036] Step S120: taking the difference voltage between the real-time voltage and the preset reference voltage as the input voltage, performing frequency separation on the input voltage and the corresponding noise voltage, filtering the noise voltage according to the separated frequency, and obtaining the output voltage.

[0037] In this embodiment, the input voltage is modulated by the first chopper according to a preset modulation signal, and the noise voltage is not modulated. The modulated input voltage and the noise voltage are amplified together to obtain an intermediate voltage signal. Finally, the modulation voltage in the intermediate voltage signal is demodulated by a corresponding demodulation signal, so that the modulation voltage and the noise voltage in the intermediate voltage signal are frequency-separated, the noise voltage is a high-frequency signal, and the demodulated modulation voltage is a low-frequency signal; the noise voltage is then low-pass filtered according to the separated frequency to obtain the output voltage.

[0038] In this embodiment, the step S120 specifically includes:

[0039] The difference voltage between the real-time voltage and the preset reference voltage is used as the input voltage. After the input voltage is modulated, it is frequency-amplified simultaneously with the noise voltage to obtain an intermediate voltage signal; the modulated voltage in the intermediate voltage signal is demodulated and low-pass filtered, and the output voltage is obtained after the noise voltage is filtered.

[0040] In this embodiment, as a preferred implementation, step S120 specifically includes:

[0041] The difference voltage between the real-time voltage and the preset reference voltage is modulated as the input voltage; the modulated input voltage and the noise voltage are frequency-amplified simultaneously to obtain an intermediate voltage signal; the modulated voltage in the intermediate voltage signal is demodulated; the demodulated intermediate voltage signal is low-pass filtered, and the output voltage is obtained after filtering the noise voltage.

[0042] In this embodiment, the input voltage is accompanied by a noise voltage, and the first chopper can modulate the input voltage according to a preset modulation signal and output the modulated input voltage. Then, the modulated input voltage and the noise voltage are frequency-amplified by an amplifier to obtain an intermediate voltage signal, and the noise voltage is amplified to a high-frequency voltage. Then, the modulation voltage in the intermediate voltage signal is demodulated by a second chopper, that is, the modulation voltage is demodulated to a low-frequency signal. Finally, the demodulated modulation voltage and the noise voltage are low-pass filtered together after passing through a low-pass filter to filter out the noise voltage and obtain the output voltage.

[0043] Step S140: compare the output voltage with a preset voltage range.

[0044] In this embodiment, a relatively accurate event signal is output by comparing the voltage value of the output voltage after the noise voltage is removed with a preset voltage range.

[0045] Step S160: output an event signal according to the comparison result.

[0046] In this embodiment, the output voltage is compared with the preset voltage range. When the output voltage is greater than the preset voltage range, an UP event occurs in the incident light signal collected by the pixel, that is, the incident light intensity collected by the pixel becomes stronger, and an UP event signal is generated; when the output voltage is less than the preset voltage range, a DN event occurs in the incident light signal collected by the pixel, that is, the incident light intensity collected by the pixel becomes weaker, and a DN event signal is generated. Assuming that the preset voltage range is (-0.1V, 0.1V), when the output voltage is 0.2V, the comparison result is (1, 0), indicating that 0.2V is greater than 0.1V, and an UP event signal is output; when the output voltage is -0.2V, the comparison result is (0, 1), indicating that -0.2V is less than -0.1V, and a DN event signal is output; when the output voltage is 0.05V, the comparison result is (0, 0), indicating that no event is generated, no event signal is output, and the real-time voltage continues to be collected. Of course, in practical applications, it is not ruled out that the system may make mistakes and output (1, 1). This event signal is usually a noise signal, but in this embodiment, the noise voltage is removed to reduce the system error rate. Since the output voltage eliminates the offset voltage, when the output voltage is compared with the preset voltage range, the comparison result is more accurate, which improves the accuracy of the output event signal.

[0047] In this embodiment, the event-type image sensor control method further includes updating the preset reference voltage stored in the capacitor, and if the real-time voltage collected at the current moment and the preset reference voltage are processed according to steps S120 to S160 to output an event signal, the real-time voltage at the current moment is stored in the capacitor as the updated preset reference voltage. If the real-time voltage collected within the preset collection time period does not output an event signal after being processed according to steps S120 to S160, the switch is closed and then opened to reset the preset reference voltage in the capacitor; and then steps S100 to S160 are re-executed according to the updated preset reference voltage to output the event signal.

[0048] In this embodiment, the demodulated modulation voltage is filtered by a low-pass filter to filter out the noise voltage, effectively removing the high-frequency noise. The input voltage is frequency-separated from the noise voltage after modulation and demodulation by the first chopper and the second chopper, and the noise voltage is amplified into a high-frequency signal during amplification, which is filtered out after low-pass filtering, and the offset voltage is also eliminated during the modulation and demodulation process.

[0049] In this embodiment, the input voltage is the difference voltage between the real-time voltage and the preset reference voltage. The input voltage is accompanied by a noise voltage during the transmission process. When the input voltage is modulated, the noise voltage is not modulated. The noise voltage is input into the amplifier together with the modulated input voltage. The modulated input voltage and the noise voltage are amplified into high-frequency signals to obtain an intermediate voltage signal. The intermediate voltage signal is demodulated. Since the noise voltage is not modulated, only the modulated voltage in the intermediate voltage signal is demodulated. Finally, the demodulated modulated signal and the amplified noise voltage are both low-pass filtered to obtain the output voltage. At this time, the noise voltage is a high-frequency signal and can be filtered out by a low-pass filter, thereby filtering out the offset voltage and high-frequency noise.

[0050] It can be seen from the above-mentioned embodiments of the present invention that the embodiments of the present invention frequency modulate the input voltage to separate the frequency of the input voltage from the noise voltage so as to remove the offset voltage; then after amplifying the modulated input voltage and the noise voltage, the noise voltage is converted into a high-frequency signal, which can be filtered out through filtering; then the intermediate voltage signal is demodulated to demodulate the modulated voltage in the intermediate voltage signal into a low-frequency signal, and the frequency is separated from the noise voltage amplified into a high-frequency signal, and finally the noise voltage amplified into a high-frequency signal is filtered out through a filter; since the output voltage is the voltage after the noise voltage is removed, when the event signal is output according to the comparison result, the output event signal is more accurate.

[0051] Please refer again Figure 2, shows an event-type image sensor 20 according to an embodiment of the present invention, which is applied to an event camera. The event-type image sensor 20 includes: an input unit 21, a chopping unit 22, a comparison unit 24, and a readout unit 25. The input unit 21, the chopping unit 22, the comparison unit 24, and the readout unit 25 are connected in sequence. The specific description is as follows:

[0052] The input unit 21 is used to obtain a real-time voltage in response to an incident light signal.

[0053] In an exemplary embodiment, the input unit 21 includes a conversion element 210, a switch 211 and a capacitor 212, the switch 211 is connected between a first output terminal of the conversion element 210 and a first input terminal of the differential unit 23, a connection terminal between the switch 211 and the first input terminal of the differential unit 23 is connected to a non-grounded terminal of the capacitor 212, and a second output terminal of the conversion element 210 is connected to a second input terminal of the differential unit 23;

[0054] The conversion element 210 is used to convert the incident light signal into a real-time voltage;

[0055] The capacitor 212 is used to update the preset reference voltage when the switch 211 is switched from a closed state to an open state.

[0056] In an exemplary embodiment, the conversion element 210 includes a photoelectric conversion element and a current-voltage conversion element, the output end of the photoelectric conversion element is connected to the input end of the current-voltage conversion element, the first output end of the current-voltage conversion element is connected to the switch 211, and the second output end of the current-voltage conversion element is connected to the second input end of the differential unit 23;

[0057] The photoelectric conversion element is used to generate a photocurrent in response to the incident light signal;

[0058] The current-voltage conversion element is used to convert the photocurrent into the real-time voltage.

[0059] The chopping unit 22 is used to take the difference voltage between the real-time voltage and the preset reference voltage as the input voltage, perform frequency separation on the input voltage and the corresponding noise voltage, and obtain the output voltage after filtering the noise voltage according to the separated frequency.

[0060] In an exemplary embodiment, the chopping unit 22 includes a first chopping unit and a second chopping unit, wherein the first chopping unit is connected between the input unit 21 and the second chopping unit;

[0061] The first chopping unit is used to take the difference voltage between the real-time voltage and the preset reference voltage as the input voltage, modulate the input voltage, and perform frequency amplification together with the noise voltage to obtain the intermediate voltage signal;

[0062] The second chopping unit is used for demodulating the modulation voltage in the intermediate voltage signal and performing low-pass filtering, and filtering the noise voltage to obtain an output voltage.

[0063] In an exemplary embodiment, see Figure 3 The first chopper unit includes a first chopper 221 and an amplifier 222, the input end of the first chopper 221 is connected to the output end of the input unit 21, the output end of the first chopper 221 is connected to the input end of the amplifier 222, and the output end of the amplifier 222 is connected to the input end of the second chopper unit;

[0064] The first chopper 221 is used to modulate the difference voltage between the real-time voltage and the preset reference voltage as the input voltage;

[0065] The amplifier 222 is used to simultaneously amplify the frequency of the modulated input voltage and the noise voltage to obtain an intermediate voltage signal.

[0066] In an exemplary embodiment, the second chopper unit includes a second chopper 223 and a low-pass filter 224, the input end of the second chopper 223 is connected to the output end of the amplifier 222, the output end of the second chopper 223 is connected to the input end of the low-pass filter 224, and the output end of the low-pass filter 224 is connected to the comparison unit 24;

[0067] The second chopper 223 is used to demodulate the modulation voltage in the intermediate voltage signal;

[0068] The low-pass filter 2231 is used to perform low-pass filtering on the demodulated intermediate voltage signal, and obtain an output voltage after filtering the noise voltage.

[0069] The comparison unit 24 is used for comparing the output voltage with a preset voltage range.

[0070] In this embodiment, the comparison unit 24 may be a processor or a controller, and the output voltage is compared with a preset voltage range through the processor.

[0071] The readout unit 25 is used to output an event signal according to the comparison result.

[0072] In this embodiment, when the output voltage is greater than the preset voltage range, an UP event occurs in the incident light signal collected by the pixel, that is, the incident light intensity collected by the pixel becomes stronger, and an UP event signal is generated; when the output voltage is less than the preset voltage range, a DN event occurs in the incident light signal collected by the pixel, that is, the incident light intensity collected by the pixel becomes weaker, and a DN event signal is generated. Since the output voltage eliminates the noise voltage, when the output voltage is compared with the preset voltage range, the comparison result is more accurate, thereby improving the accuracy of the output event signal.

[0073] In an exemplary embodiment, the event-type image sensor further includes: a controller, which may also be a processor in the comparison unit. The controller sends a control signal to the input unit 21, the chopping unit 22, the comparison unit 24, and the readout unit 25, so that the input unit 21, the chopping unit 22, the comparison unit 24, and the readout unit 25 perform corresponding operations according to the control signal.

[0074] In this embodiment, the input voltage is accompanied by a low-frequency noise voltage during the transmission process. The input voltage is modulated when it is input into the first chopper, and the noise voltage is not modulated. The noise voltage and the modulated input voltage are input into the amplifier together, and the noise voltage and the modulated input voltage are amplified into a high-frequency signal, that is, an intermediate voltage signal. The intermediate voltage signal is demodulated by the second chopper, and the modulated voltage of the intermediate voltage signal is demodulated, while the amplified noise voltage does not need to be demodulated, and the modulated voltage is demodulated into a low-frequency signal, thereby separating the frequency of the modulated voltage from the frequency of the amplified noise voltage; finally, the output voltage is obtained through low-pass filtering, and the noise voltage before filtering is a high-frequency signal, which can be filtered out by a low-pass filter, thereby filtering out high-frequency noise.

[0075] In an exemplary embodiment, the event-type image sensor further includes: a differential unit 23, an input end of the differential unit 23 is connected to an output end of the input unit 21, and an output end of the differential unit 23 is connected to an input end of the chopping unit 22;

[0076] The differential unit 23 is used to obtain the difference voltage by subtracting the real-time voltage from a preset reference voltage.

[0077] In an exemplary embodiment, applied to an event camera, the event-type image sensor includes: an input unit 21, a differential unit 23, a chopping unit 22, a comparison unit 24, and a readout unit 25, wherein the input unit 21, the differential unit 23, the chopping unit 22, the comparison unit 24, and the readout unit 25 are connected in sequence; wherein,

[0078] The input unit 21 is used to obtain a real-time voltage in response to an incident light signal;

[0079] The differential unit 23 is used to obtain the difference voltage by subtracting the real-time voltage from a preset reference voltage;

[0080] The chopping unit 22 is used to use the difference voltage as an input voltage, perform frequency separation on the input voltage and the corresponding noise voltage, and obtain an output voltage after filtering the noise voltage according to the separated frequency;

[0081] The comparison unit 24 is used to compare the output voltage with a preset voltage range;

[0082] The readout unit 25 is used to output an event signal according to the comparison result.

[0083] In this embodiment, the voltage value of the output voltage is within the preset voltage range, indicating that no event signal is output and it is necessary to continue to collect the real-time voltage. When a valid event signal is output, the current real-time voltage is stored in the capacitor as a preset reference voltage. At this time, the switch is in the off state and the operations of steps S100 to S160 are re-executed.

[0084] In this embodiment, if the real-time voltage collected within the preset collection time period does not output an event signal after being processed according to steps S120 to S160, the switch is closed and then opened to reset the preset reference voltage in the capacitor; and then steps S100 to S160 are re-executed according to the updated preset reference voltage to output the event signal.

[0085] Please refer again Figure 2 , shows a circuit diagram of an event-type image sensor 30 according to an embodiment of the present invention. The circuit diagram includes: a differential unit 23, a conversion element 210, a switch 211, a capacitor 212, a chopping unit 22, a comparison unit 24, and a readout unit 25.

[0086] The input end of the differential unit 23 is connected to the output end of the conversion element 210, and the output end of the differential unit 23 is connected to the input end of the chopping unit 22; the conversion element 210 is used to convert the current corresponding to the incident light signal to obtain the real-time voltage corresponding to the incident light signal; the differential unit 23 is used to subtract the real-time voltage from the preset reference voltage to obtain the difference voltage.

[0087] See also Figure 3 , the chopper unit 22 includes a first chopper 221, a second chopper 223, an amplifier 222 and a low-pass filter 224. 1 The incident light signal is sampled at all times, and the voltage corresponding to the incident light signal is V 1 , turn off switch 211, voltage V 1 The capacitor 212 is recorded as the preset reference voltage V 1(That is, the voltage at node A is V 1 ); 2 The real-time voltage corresponding to the incident light signal collected at each moment is V 2 (That is, the voltage at node B is V 2 ), that is, the input voltage is V 2 -V 1 .

[0088] The second output terminal B of the conversion element 210 is connected to the second input terminal of the differential unit 23, the output terminal of the differential unit 23 is connected to the input terminal of the first chopper 221, the first output terminal of the conversion element 210 is connected to one end of the switch 211, the other end of the switch 211 is connected to one end of the capacitor 212 and the first input terminal of the differential unit 23, and the other end of the capacitor 212 is grounded. The output terminal of the first chopper 221 is connected to the amplifier 222, the output terminal of the amplifier 222 is connected to the input terminal of the second chopper 223, the output terminal of the second chopper 223 is connected to the low-pass filter 224, and the output terminal of the low-pass filter 224 is connected to a processor or a controller (not shown in the figure).

[0089] In this embodiment, the first chopper 221 modulates the difference voltage outputted by the differential unit 23 as an input voltage to separate the frequency of the input voltage from the noise voltage.

[0090] The amplifier 222 amplifies the modulated input voltage and the noise voltage together to obtain an intermediate voltage signal. The intermediate voltage signal is then demodulated by the second chopper 223 according to a preset demodulation signal. The low-pass filter 224 performs low-pass filtering on the demodulated modulation signal and the amplified noise voltage to remove the noise voltage and obtain an output voltage. The modulation and demodulation processing of the first chopper 221 and the second chopper 223 is used to remove the offset voltage.

[0091] In this embodiment, the principle of the chopping unit 22 is described exemplarily, as follows:

[0092] Assume that the current signal voltage (V signal ) and the noise voltage (V noise ) are respectively related to the signal frequency (f) / chopping frequency (f chop ) Figure 4 As shown, the chopping frequency (f chop ) is the operating frequency of the chopper, the signal frequency (f) is the signal voltage (V signal ) frequency, it can be understood that the current signal voltage is the real-time voltage. The input voltage is modulated by the first chopper 221, while the noise is not modulated and only passes through the amplifier 222. The modulated input voltage and the noise voltage are amplified by the amplifier 222, and the signal voltage (V signal ) and the noise voltage (Vnoise ) Figure 5 As shown, it can be understood that the signal voltage is the intermediate voltage signal and the chopping frequency is the operating frequency of the first chopper. Then the signal voltage (V signal )Noise Voltage(V noise ) pass through the second chopper 223, the signal voltage (V signal ) and the noise voltage (V noise ) Figure 6 As shown, it can be understood that the signal voltage is the modulated signal after demodulation. Finally, the signal voltage (V signal ) and the noise voltage (V signal ) passes through a low-pass filter, and its noise voltage (V noise ) Since it is a high frequency signal, it can be filtered out by the low pass filter 224, and the output voltage V out ,like Figure 7 As shown, it can be understood that the input voltage is the demodulation voltage and the chopping frequency is the operating frequency of the second chopper. Thus, the modulation and demodulation of the voltage by the chopping unit 22 are realized, so that the signal voltage (V signal ) and the noise voltage (V noise ) frequency to filter out the offset voltage and high-frequency noise in the signal voltage.

[0093] The time (t) and input voltage (V in ) relationship, when the input voltage (V in ) passes through the first chopper, and its input voltage (V in ) after modulation, time (t) and input voltage (V in )like Figure 8 As shown, the input voltage at this time is the modulated input voltage. Then the input voltage (V in ) passes through the amplifier, and its input voltage (V in ) is amplified, time (t) and input voltage (V in ),like Fig. 9 As shown, the input voltage is the modulation voltage. Then the input voltage (V in ) passes through the second chopper, and its input voltage (V in ) after demodulation, time (t) and input voltage (V in )like Fig.10 As shown, the input voltage is the demodulated modulation signal, that is, the demodulated voltage. The final input voltage (V in ) passes through a low-pass filter, time (t) and input voltage (V in )like Fig.11 As shown, the output is Fig.11 The output voltage V out .

[0094] In the existing offset removal scheme, in the traditional event camera, the voltage margin expression after the amplifier input equivalent offset correction is as follows:

[0095]

[0096] Among them, V offset-residue It represents the voltage margin after correction, and A represents the amplification factor.

[0097] This solution requires a high-gain amplifier to reduce the impact of random offset voltage, but it is very difficult to integrate a high-gain amplifier in each pixel of the image sensor. In addition, the high-gain amplifier will lead to high power consumption and low sampling rate. In this application, the steps of eliminating the inherent random offset storage are simplified by utilizing the modulation and demodulation principle of the chopper unit. Specifically, the input voltage and the accompanying noise voltage are frequency-separated by the chopper unit, and the noise voltage is filtered according to the separated frequency to obtain the output voltage, that is, there is no need to use a high-gain amplifier, and large-scale high-quality, high-resolution, low-power, and high-frame-rate event-type pixels are integrated.

[0098] The above is a description of the event-type image sensor and control method provided by the present invention. For those skilled in the art, according to the ideas of the embodiments of the present invention, there may be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An event-type image sensor, characterized in that: Applied to an event camera, the event-type image sensor comprises: an input unit, a chopping unit, a comparison unit and a readout unit, wherein the input unit, the chopping unit, the comparison unit and the readout unit are connected in sequence, the chopping unit comprises a first chopping unit and a second chopping unit, and the first chopping unit is connected between the input unit and the second chopping unit; wherein, The input unit is used to obtain a real-time voltage in response to an incident light signal; The first chopping unit is used to take the difference voltage between the real-time voltage and the preset reference voltage as the input voltage, modulate the input voltage, and perform frequency amplification together with the noise voltage to obtain an intermediate voltage signal; The second chopping unit is used to demodulate the modulation voltage in the intermediate voltage signal and perform low-pass filtering, and obtain an output voltage after filtering the noise voltage; The comparison unit is used to compare the output voltage with a preset voltage range; The readout unit is used to output an event signal according to the comparison result.

2. The event-type image sensor according to claim 1, characterized in that: The first chopper unit includes a first chopper and an amplifier, the input end of the first chopper is connected to the output end of the input unit, the output end of the first chopper is connected to the input end of the amplifier, and the output end of the amplifier is connected to the input end of the second chopper unit; The first chopper is used to modulate the difference voltage between the real-time voltage and the preset reference voltage as the input voltage; The amplifier is used to simultaneously frequency-amplify the modulated input voltage and the noise voltage to obtain the intermediate voltage signal.

3. The event-type image sensor according to claim 2, characterized in that: The second chopper unit comprises a second chopper and a low-pass filter, the input end of the second chopper is connected to the output end of the amplifier, the output end of the second chopper is connected to the input end of the low-pass filter, and the output end of the low-pass filter is connected to the comparison unit; The second chopper is used for demodulating the modulation voltage in the intermediate voltage signal; The low-pass filter is used to perform low-pass filtering on the demodulated intermediate voltage signal, and obtain an output voltage after filtering the noise voltage.

4. The event-type image sensor according to claim 1, characterized in that: Also includes: A differential unit, wherein an input end of the differential unit is connected to an output end of the input unit, and an output end of the differential unit is connected to an input end of the chopping unit; The differential unit is used to obtain the difference voltage by subtracting the real-time voltage from a preset reference voltage.

5. The event-type image sensor according to claim 4, characterized in that: The input unit includes a conversion element, a switch and a capacitor, the switch is connected between a first output end of the conversion element and a first input end of the differential unit, a connection end between the switch and the first input end of the differential unit is connected to a non-grounded end of the capacitor, and a second output end of the conversion element is connected to a second input end of the differential unit; The conversion element is used to convert the incident light signal into the real-time voltage; The capacitor is used to update the preset reference voltage when the switch is switched from a closed state to an open state.

6. The event-type image sensor according to claim 5, characterized in that: The conversion element includes a photoelectric conversion element and a current-voltage conversion element, the output end of the photoelectric conversion element is connected to the input end of the current-voltage conversion element, the first output end of the current-voltage conversion element is connected to the switch, and the second output end of the current-voltage conversion element is connected to the second input end of the differential unit; The photoelectric conversion element is used to generate a photocurrent in response to the incident light signal; The current-voltage conversion element is used to convert the photocurrent into the real-time voltage.

7. A method for controlling an event-type image sensor, characterized in that: Applied to an event camera, the method comprises: acquiring a real-time voltage in response to an incident light signal; The difference voltage between the real-time voltage and the preset reference voltage is used as the input voltage, the input voltage and the noise voltage are frequency separated, and then the noise voltage is filtered according to the separated frequency to obtain the output voltage; comparing the output voltage with a preset voltage range; Output an event signal according to the comparison result; Among them, the difference voltage between the real-time voltage and the preset reference voltage is used as the input voltage, the input voltage and the noise voltage are frequency separated, and then the noise voltage is filtered according to the separated frequency to obtain the output voltage, including: the difference voltage between the real-time voltage and the preset reference voltage is used as the input voltage, after modulating the input voltage, the frequency is amplified simultaneously with the noise voltage to obtain an intermediate voltage signal; the modulation voltage in the intermediate voltage signal is demodulated and low-pass filtered, and the noise voltage is filtered to obtain the output voltage.

8. The event-type image sensor control method according to claim 7, characterized in that: The step of obtaining a real-time voltage in response to an incident light signal comprises: generating a photocurrent in response to the incident light signal; The photocurrent is converted into the real-time voltage.

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