CN114827467A - Event type image sensor and control method - Google Patents
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Abstract
The invention relates to an event type image sensor and a control method thereof, which are applied to an event camera and comprise the following steps: acquiring a real-time voltage in response to an incident optical signal; taking the difference voltage of 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 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. According to the embodiment of the invention, the input voltage and the noise voltage are subjected to frequency separation, and then the noise voltage is filtered according to the separated frequency to obtain the output voltage without the noise voltage; because 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
The invention belongs to the technical field of computer vision, and particularly relates to an event type image sensor and a control method.
Background
Conventional cameras, whether CMOS sensors, CCD sensors, or RGBD cameras, capture images at a constant frequency. Thus, even if the frame rate can reach 1KHz, that has a 1ms delay. There is a certain delay problem with the conventional camera. With the development of the times, an Event-based Vision (EVS) has appeared, which is a dynamic Vision sensor that senses a change of incident light, generates an Event based on the change of light, outputs an Event signal, and has advantages of a fast frame rate, low power, and the like.
However, in the conventional event camera, due to process variations in the integrated circuit production process, some factors such as noise and misalignment exist between sub-circuits, which may cause an event signal output error.
Disclosure of Invention
The invention provides an event type image sensor and a control method thereof, which are used for solving the technical problem of inaccurate event signal output in the prior art.
In one aspect, the present invention provides an event type image sensor applied to an event camera, the event type image sensor including: the device 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 sequentially connected; wherein the content of the first and second substances,
the input unit is used for responding to an incident light signal to obtain a real-time voltage;
the chopper unit is used for taking the difference voltage of 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 filtering the noise voltage according to the separated frequency to obtain an output voltage;
the comparison unit is used for comparing the output voltage with a preset voltage range;
the reading unit is used for outputting an event signal according to the comparison result.
In a second aspect, the present invention provides a method for controlling an event-type image sensor, applied to an event camera, the method comprising:
acquiring a real-time voltage in response to an incident optical signal;
taking the difference voltage of 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 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.
As can be seen from the foregoing embodiments of the present invention, in the embodiments of the present invention, the input voltage and the noise voltage are frequency-separated, and then the noise voltage is filtered according to the separated frequency, so as to obtain the output voltage from which the noise voltage is removed; because the output voltage is the voltage after removing the noise voltage, when the incident signal is output according to the comparison result, the output incident signal is more accurate.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without inventive exercise.
FIG. 1 is a flowchart illustrating a method for controlling an event-based image sensor according to an embodiment of the present disclosure;
fig. 2 is a circuit configuration diagram of an event type image sensor according to an embodiment of the present application;
FIG. 3 is a circuit configuration diagram of a chopper unit in an embodiment of the present application;
FIG. 4 is a diagram illustrating the relationship between signal frequency/chopping frequency, input voltage and noise voltage in the embodiment of the present application;
FIG. 5 is a schematic diagram of the relationship between signal frequency/chopping frequency and intermediate voltage signal in the embodiment of the present application;
FIG. 6 is a diagram illustrating the relationship between signal frequency/chopping frequency, demodulation voltage and noise voltage in the embodiment of the present application;
FIG. 7 is a diagram illustrating the relationship between signal frequency/chopping frequency, output voltage and noise voltage in the embodiment of the present application;
FIG. 8 is a diagram illustrating the relationship between input voltage and time according to an embodiment of the present application;
FIG. 9 is a diagram illustrating modulation voltage versus time according to an embodiment of the present application;
FIG. 10 is a diagram illustrating demodulation voltage versus time according to an embodiment of the present application;
fig. 11 is a schematic diagram of the relationship between the output voltage and the time in the embodiment of the present application.
Detailed Description
In order to make the objects, features and advantages of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
In the description of the embodiments of the present invention, it should be understood that the terms "first", "second", and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the embodiments of the present invention, "a plurality" means two or more unless specifically limited otherwise.
In the embodiments of the present invention, unless otherwise explicitly specified or limited, the terms "mounted," "connected," "fixed," and the like are to be construed broadly, e.g., as being fixedly connected, detachably connected, or integrated; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. Specific meanings of the above terms in the embodiments of the present invention can be understood by those of ordinary skill in the art according to specific situations.
Referring to fig. 1, a method for controlling an event type image sensor according to an embodiment of the present invention is shown, and applied to an event camera, the method includes:
step S100, acquiring real-time voltage in response to an incident light signal.
In an exemplary embodiment, the step S100 specifically includes:
generating a photocurrent in response to the incident optical signal; converting the photocurrent to a real-time voltage.
In this embodiment, the event camera is an event-type image sensor, the event-type image sensor includes a pixel array composed of a plurality of pixels, each pixel in the pixel array includes a corresponding pixel sensor, and the pixel sensor can collect an incident light signal. The method comprises the steps of collecting incident light signals through pixels in an image sensor, correspondingly collecting each pixel, carrying out photoelectric conversion on the collected incident light signals through a photoelectric conversion element to obtain corresponding current values, carrying out current-voltage conversion on the current values through a current-voltage conversion element to obtain corresponding real-time voltages, and converting the light signals into voltage signals to facilitate data calculation. The photoelectric conversion element may be a photodiode, a phototransistor, a clamp photodiode, or any other similar element that performs photoelectric conversion. The current-to-voltage element is usually implemented by a voltage divider method, a hall sensor method, an integrator method, and the like, and details thereof are not repeated herein.
Step S120, taking the difference voltage of the real-time voltage and a preset reference voltage as an input voltage, performing frequency separation on the input voltage and a corresponding noise voltage, and filtering the noise voltage according to the separated frequency to obtain an output voltage.
In the embodiment, the input voltage is modulated according to a preset modulation signal through a first chopper, the noise voltage is not modulated, the modulated input voltage and the noise voltage are amplified together to obtain an intermediate voltage signal, and finally the modulation voltage in the intermediate voltage signal is demodulated through a corresponding demodulation signal, so that the modulation voltage in the intermediate voltage signal is subjected to frequency separation from the noise voltage, the noise voltage is a high-frequency signal, and the demodulated modulation voltage is a low-frequency signal; and low-pass filtering the noise voltage according to the separated frequency to obtain an output voltage.
In this embodiment, the step S120 specifically includes:
taking the difference voltage of the real-time voltage and a preset reference voltage as an input voltage, modulating the input voltage, and simultaneously performing frequency amplification on the modulated input voltage and the noise voltage to obtain an intermediate voltage signal; and demodulating the modulation voltage in the intermediate voltage signal, performing low-pass filtering, and filtering the noise voltage to obtain an output voltage.
In this embodiment, as a preferred implementation manner, the step S120 specifically includes:
modulating the difference voltage of the real-time voltage and a preset reference voltage as an input voltage; performing frequency amplification on the modulated input voltage and the modulated noise voltage at the same time to obtain an intermediate voltage signal; demodulation of the modulated voltage in the intermediate voltage signal; and low-pass filtering the demodulated intermediate voltage signal, and filtering the noise voltage to obtain an output voltage.
In this embodiment, the input voltage is accompanied by a noise voltage, and the first chopper may modulate the input voltage according to a preset modulation signal and output the modulated input voltage. And then the modulated input voltage and the noise voltage are subjected to frequency amplification simultaneously through an amplifier to obtain an intermediate voltage signal, and the noise voltage is amplified into a high-frequency voltage at the moment. The modulated voltage in the intermediate voltage signal is then demodulated by a second chopper, i.e. the modulated voltage is demodulated to a low frequency signal. And finally, after passing through a low-pass filter, carrying out low-pass filtering on the demodulated modulation voltage and the noise voltage together, and filtering the noise voltage to obtain an output voltage.
Step S140, comparing the output voltage with a preset voltage range.
In this embodiment, the voltage value of the output voltage with the noise voltage removed is compared with the preset voltage range, so as to output a more accurate event signal.
And step S160, outputting an event signal according to the comparison result.
In this embodiment, the output voltage is compared with a preset voltage range, and when the output voltage is greater than the preset voltage range, an UP event occurs to an incident light signal collected by a pixel, that is, the intensity of the incident light collected by the pixel becomes stronger, and an UP event signal is generated; when the output voltage is smaller than the preset voltage range, a DN event occurs to the incident light signal collected by the pixel, namely the incident light intensity collected by the pixel is weakened, 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), which means that 0.2V is greater than 0.1V, then an UP event signal is output; when the output voltage is-0.2V, the comparison result is (0, 1), which indicates that-0.2V is less than-0.1V, and then a DN event signal is output; when the output voltage is 0.05V, the comparison result is (0, 0), which indicates that no event is generated, no event signal is output, and the real-time voltage is continuously collected. Of course, in practical application, it is not excluded that the system may have errors, and the output (1, 1) is a noise signal, but the noise voltage is removed in this embodiment, so that the system error rate is reduced. Because the offset voltage is eliminated by the output voltage, when the output voltage is compared with a preset voltage range, the comparison result is more accurate, and the accuracy of the output event signal is improved.
In this embodiment, the event-based image sensor control method further includes updating a preset reference voltage stored in the capacitor, and if the real-time voltage collected at the current time and the preset reference voltage are processed according to steps S120 to S160, outputting an event signal, and storing the real-time voltage at the current time as the updated preset reference voltage in the capacitor. If the real-time voltage acquired in the preset acquisition time period does not output an event signal after being processed according to the steps S120 to S160, performing the operation of switching on and switching off the switch, and resetting the preset reference voltage in the capacitor; and re-executing steps S100 to S160 according to the updated preset reference voltage to output the event signal.
In this embodiment, after the demodulated modulation voltage is filtered by the low-pass filter, the noise voltage is filtered, and the high-frequency noise is effectively removed. The input voltage is subjected to frequency separation with the noise voltage after modulation and demodulation of the first chopper and the second chopper, the noise voltage is amplified into a high-frequency signal during amplification, filtering is performed after low-pass filtering, and offset voltage is also eliminated in modulation and demodulation processing.
In this embodiment, the input voltage is a difference voltage between the real-time voltage and the preset reference voltage, the input voltage is accompanied by a noise voltage in the transmission process, when the input voltage is modulated, the noise voltage is not modulated, the noise voltage and the modulated input voltage are input into the amplifier together, and the modulated input voltage and the noise voltage are amplified to be a high-frequency signal to obtain an intermediate voltage signal. The intermediate voltage signal is demodulated, the noise voltage is not modulated, only the modulation voltage in the intermediate voltage signal is demodulated, the finally demodulated modulation signal and the amplified noise voltage are subjected to low-pass filtering to obtain an output voltage, and the noise voltage at the moment is a high-frequency signal and can be filtered through a low-pass filter, so that the offset voltage and the high-frequency noise can be filtered.
As can be seen from the above embodiments of the present invention, the embodiments of the present invention separate the input voltage from the frequency of the noise voltage by performing frequency modulation on the input voltage, so as to remove the offset voltage; amplifying the modulated input voltage and the noise voltage, converting the noise voltage into a high-frequency signal, and filtering the high-frequency signal by filtering; then, demodulating the intermediate voltage signal, demodulating the modulation voltage in the intermediate voltage signal into a low-frequency signal, performing frequency separation on the low-frequency signal and the noise voltage amplified into a high-frequency signal, and finally filtering the noise voltage amplified into the high-frequency signal through a filter; because 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.
Referring to fig. 2 again, an event image sensor 20 according to an embodiment of the present invention is shown, which is applied to an event camera, and the event image sensor 20 includes: the device comprises an input unit 21, a chopping unit 22, a comparison unit 24 and a readout unit 25, wherein 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:
the input unit 21 is used for acquiring a real-time voltage in response to an incident light signal.
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 of the switch 211 and the first input terminal of the differential unit 23 is connected to a non-ground 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;
the conversion element 210 is used for converting an incident light signal into a real-time voltage;
the capacitor 212 is used for updating the preset reference voltage when the switch 211 is switched from a closed state to an open state.
In an exemplary embodiment, the conversion element 210 includes a photoelectric conversion element and a current-voltage conversion element, an output terminal of the photoelectric conversion element is connected with an input terminal of the current-voltage conversion element, a first output terminal of the current-voltage conversion element is connected with the switch 211, and a second output terminal of the current-voltage conversion element is connected with a second input terminal of the difference unit 23;
the photoelectric conversion element is used for generating a photocurrent in response to the incident light signal;
the current-voltage conversion element is used for converting the photocurrent into the real-time voltage.
The chopper unit 22 is configured to use a difference voltage between the real-time voltage and a preset reference voltage as an input voltage, perform frequency separation on the input voltage and a corresponding noise voltage, and filter the noise voltage according to the separated frequency to obtain an output voltage.
In an exemplary embodiment, the chopping unit 22 includes a first chopping unit and a second chopping unit, the first chopping unit being connected between the input unit 21 and the second chopping unit;
the first chopper unit is used for taking a difference voltage of the real-time voltage and a preset reference voltage as an input voltage, modulating the input voltage, and then performing frequency amplification on the modulated input voltage and the noise voltage to obtain an intermediate voltage signal;
the second chopper unit is used for demodulating the modulation voltage in the intermediate voltage signal, performing low-pass filtering, and filtering the noise voltage to obtain an output voltage.
In an exemplary embodiment, referring to fig. 3, the first chopping unit includes a first chopper 221 and an amplifier 222, an input terminal of the first chopper 221 is connected with an output terminal of the input unit 21, an output terminal of the first chopper 221 is connected with an input terminal of the amplifier 222, and an output terminal of the amplifier 222 is connected with an input terminal of the second chopping unit;
the first chopper 221 is configured to modulate a difference voltage between the real-time voltage and a preset reference voltage as an input voltage;
the amplifier 222 is configured to perform frequency amplification on the modulated input voltage and the modulated noise voltage at the same time to obtain an intermediate voltage signal.
In an exemplary embodiment, the second chopping unit comprises a second chopper 223 and a low-pass filter 224, an input terminal of the second chopper 223 is connected to the output terminal of the amplifier 222, an output terminal of the second chopper 223 is connected to the input terminal of the low-pass filter 224, and an output terminal of the low-pass filter 224 is connected to the comparing unit 24;
the second chopper 223 is used for demodulating the modulated voltage in the intermediate voltage signal;
the low-pass filter 2231 is configured to perform low-pass filtering on the demodulated intermediate voltage signal, and filter the noise voltage to obtain an output voltage.
The comparing unit 24 is configured to compare the output voltage with a preset voltage range.
In this embodiment, the comparing unit 24 may be a processor or a controller, and compares the output voltage with a preset voltage range through the processor.
The readout unit 25 is configured to output an event signal according to the comparison result.
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 intensity of the incident light collected by the pixel becomes stronger, and an UP event signal is generated; when the output voltage is smaller than the preset voltage range, a DN event occurs to the incident light signal collected by the pixel, namely the incident light intensity collected by the pixel is weakened, and a DN event signal is generated. Because the output voltage eliminates the noise voltage, when the output voltage is compared with the preset voltage range, the comparison result is more accurate, and the accuracy of the output event signal is improved.
In an exemplary embodiment, the event-type image sensor further includes: the controller, the controller can also be a processor in the comparison unit. The controller sends control signals to the input unit 21, the chopper unit 22, the comparison unit 24 and the readout unit 25, so that the input unit 21, the chopper unit 22, the comparison unit 24 and the readout unit 25 respectively perform corresponding operations according to the control signals.
In the present embodiment, the input voltage is accompanied by a low-frequency noise voltage during transmission, the input voltage is input to the first chopper to be modulated, the noise voltage is not modulated, the noise voltage and the modulated input voltage are input to the amplifier, 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 through a second chopper, the modulation voltage of the intermediate voltage signal is demodulated, the amplified noise voltage does not need to be demodulated, the modulation voltage is demodulated into a low-frequency signal, and therefore the frequency of the modulation voltage is separated from the frequency of the amplified noise voltage; and finally, obtaining output voltage through low-pass filtering, wherein the noise voltage before filtering can be filtered through a low-pass filter because the noise voltage is a high-frequency signal, so that high-frequency noise can be filtered.
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 with an output end of the input unit 21, and an output end of the differential unit 23 is connected with an input end of the chopper unit 22;
the difference unit 23 is configured to perform a difference between the real-time voltage and a preset reference voltage to obtain the difference voltage.
In an exemplary embodiment, applied to an event camera, the event type image sensor includes: the circuit comprises an input unit 21, a difference unit 23, a chopper unit 22, a comparison unit 24 and a readout unit 25, wherein the input unit 21, the difference unit 23, the chopper unit 22, the comparison unit 24 and the readout unit 25 are connected in sequence; wherein the content of the first and second substances,
the input unit 21 is used for responding to an incident light signal to obtain a real-time voltage;
the difference unit 23 is configured to perform a difference between the real-time voltage and a preset reference voltage to obtain a difference voltage;
the chopper unit 22 is configured to perform frequency separation on the input voltage and a corresponding noise voltage by using the difference voltage as an input voltage, and filter the noise voltage according to a separated frequency to obtain an output voltage;
the comparison unit 24 is configured to compare the output voltage with a preset voltage range;
the readout unit 25 is configured to output an event signal according to the comparison result.
In this embodiment, the voltage value of the output voltage is within the preset voltage range, which indicates that no event signal is output, and the real-time voltage needs to be collected again, when an effective event signal is output, the current real-time voltage is stored in the capacitor as the preset reference voltage, and at this time, the switch is in the off state, and the operations of step S100 to step S160 are executed again.
In this embodiment, if the real-time voltage acquired within the preset acquisition time period does not output an event signal after being processed according to steps S120 to S160, the operation of switching on and switching off the switch is performed to reset the preset reference voltage in the capacitor; and re-executing the step S100 to the step S160 to output the event signal according to the updated preset reference voltage.
Referring to fig. 2 again, a circuit diagram of an event type image sensor 30 according to an embodiment of the invention is shown. The circuit diagram includes: a difference unit 23, a conversion element 210, a switch 211, a capacitor 212, a chopper unit 22, a comparison unit 24, and a readout unit 25.
The input end of the differential unit 23 is connected with the output end of the conversion element 210, and the output end of the differential unit 23 is connected with the input end of the chopper unit 22; the conversion element 210 is configured to convert a current corresponding to an incident light signal to obtain a real-time voltage corresponding to the incident light signal; the difference unit 23 is configured to difference the real-time voltage and a preset reference voltage to obtain a difference voltage.
Referring to fig. 3, the chopper unit 22 includes a first chopper 221, a second chopper 223, an amplifier 222, and a low pass filter 224. At t 1 Sampling incident light signals at a moment, wherein the voltage corresponding to the incident light signals is V 1 The switch 211 is turned off and the voltage V is set 1 Stored in the capacitor 212 as a predetermined reference voltage V 1 (i.e., the voltage at node A is V 1 ) (ii) a At t 2 The real-time voltage corresponding to the incident light signal collected at any moment is V 2 (i.e., the voltage at node B is V 2 ) I.e. input voltage is V 2 -V 1 。
The second output end B of the conversion element 210 is connected to the second input end of the differential unit 23, the output end of the differential unit 23 is connected to the input end of the first chopper 221, the first output end 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 end of the differential unit 23, and the other end of the capacitor 212 is grounded. The output end of the first chopper 221 is connected with the amplifier 222, the output end of the amplifier 222 is connected with the input end of the second chopper 223, the output end of the second chopper 223 is connected with the low-pass filter 224, and the output end of the low-pass filter 224 is connected with a processor or a controller (not shown in the figure).
In the present embodiment, the first chopper 221 modulates the difference voltage of the output of the difference unit 23 as an input voltage to separate the input voltage from the frequency of the noise voltage.
The amplifier 222 amplifies the modulated input voltage together with the noise voltage to obtain an intermediate voltage signal. The intermediate voltage signal is 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, so as to obtain an output voltage. The modulation and demodulation processes of the first chopper 221 and the second chopper 223 are used to remove the offset voltage.
In the present embodiment, the principle of the chopper unit 22 is exemplarily described as follows:
assume the present signal voltage (V) signal ) And noise voltage (V) noise ) Respectively with signal frequency (f)/chopping frequency (f) chop ) As shown in FIG. 4, the chopping frequency (f) chop ) For the operating frequency of the chopper, the signal frequency (f) is the signal voltage (V) signal ) It can be understood that the present signal voltage is a real-time voltage. The input voltage is modulated by the first chopper 221 without the noise being modulated and is passed through the amplifier 222, the modulated input voltage is amplified by the amplifier 222 together with the noise voltage, and the signal voltage (V) is obtained signal ) And noise voltage (V) noise ) As shown in fig. 5, it can be understood that the signal voltage is an 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 ) Together through the second chopper 223, the signal voltage (V) signal ) And noise voltage (V) noise ) As shown in fig. 6, it can be understood that the signal voltage is a demodulated modulated signal. Final signal voltage (V) signal ) And noise voltage (V) signal ) Passing through a low-pass filter, the noise voltage (V) of which noise ) Since it is a high frequency signal, it can be filtered by the low pass filter 224 to output the voltage V out As shown in fig. 7, it can be understood that the input voltage is a demodulated voltage, and the chopping frequency is the operating frequency of the second chopper. This realizes modulation and demodulation of the voltage by the chopper unit 22, thereby enabling alternate change of the signal voltage (V) signal ) Sum noise voltage (V) noise ) To filter out offset voltages and high frequency noise in the signal voltage.
Exemplary description of time (t) and input voltage (V) in ) When the input voltage (V) is in ) Through a first chopper, the input voltage (V) of which in ) After modulation, time (t) and input voltage (V) in ) As shown in fig. 8, the input voltage at this time is a modulated input voltage. Then inputting the voltage (V) in ) Via an amplifier, the input voltage (V) of which in ) Amplified, time (t) and input voltage (V) in ) As shown in fig. 9, the input voltage is a modulation voltage. Then input the voltage (V) in ) Through a second chopper, the input voltage (V) of which in ) After demodulation, time (t) and input voltage (V) in ) As shown in fig. 10, the input voltage is a demodulated signal, i.e., a demodulated voltage. Final input voltage (V) in ) Passing through a low pass filter, the time (t) and the input voltage (V) in ) As shown in fig. 11, thereby outputting an output voltage V as shown in fig. 11 out 。
In the existing offset removal scheme, since in the conventional event camera, the equivalent offset corrected voltage headroom expression is input through the amplifier as follows:
wherein, V offset-residue The corrected voltage margin is shown, and a represents the magnification.
This solution would require high gain amplifiers to reduce the effect of random offset voltage, which is very difficult to be implemented in each pixel of the image sensor, and in addition, high gain amplifiers would result in high power consumption and low sampling rate. In the application, the step of eliminating the intrinsic random offset memory is simplified by using a modulation and demodulation principle of a chopping unit, specifically, an input voltage and an accompanying noise voltage are subjected to frequency separation by the chopping unit, and the noise voltage is filtered according to the separated frequency to obtain an output voltage, namely, a high-gain amplifier is not required to be used, and the integration of large-scale high-quality, high-resolution, low-power consumption and high-frame-rate event type pixels is realized.
In view of the above description of the event-based image sensor and the control method provided by the present invention, those skilled in the art will recognize that changes may be made in the embodiments and applications of the invention.
Claims (10)
1. An event type image sensor applied to an event camera, the event type image sensor comprising: the device 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 sequentially connected; wherein the content of the first and second substances,
the input unit is used for responding to an incident light signal to obtain a real-time voltage;
the chopper unit is used for taking the difference voltage of 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 filtering the noise voltage according to the separated frequency to obtain an output voltage;
the comparison unit is used for comparing the output voltage with a preset voltage range;
the reading unit is used for outputting an event signal according to the comparison result.
2. The event-type image sensor according to claim 1, wherein the chopper unit includes a first chopper unit, a second chopper unit, the first chopper unit being connected between the input unit and the second chopper unit;
the first chopper unit is used for taking a difference voltage of the real-time voltage and a preset reference voltage as an input voltage, modulating the input voltage, and then performing frequency amplification on the modulated input voltage and the noise voltage to obtain an intermediate voltage signal;
the second chopper unit is used for demodulating the modulation voltage in the intermediate voltage signal, performing low-pass filtering, and filtering the noise voltage to obtain an output voltage.
3. The event-type image sensor according to claim 2, wherein the first chopping unit includes a first chopper and an amplifier, an input terminal of the first chopper is connected to an output terminal of the input unit, an output terminal of the first chopper is connected to an input terminal of the amplifier, and an output terminal of the amplifier is connected to an input terminal of the second chopping unit;
the first chopper is used for modulating the difference voltage of the real-time voltage and a preset reference voltage as an input voltage;
the amplifier is used for simultaneously carrying out frequency amplification on the modulated input voltage and the modulated noise voltage to obtain the intermediate voltage signal.
4. The event-type image sensor according to claim 3, wherein the second chopper unit comprises a second chopper and a low-pass filter, an input end of the second chopper is connected with an output end of the amplifier, an output end of the second chopper is connected with an input end of the low-pass filter, and an output end of the low-pass filter is connected with the comparison unit;
the second chopper is used for demodulating the modulation voltage in the intermediate voltage signal;
the low-pass filter is used for performing low-pass filtering on the demodulated intermediate voltage signal and filtering the noise voltage to obtain an output voltage.
5. The event type image sensor according to claim 1, further comprising: the input end of the differential unit is connected with the output end of the input unit, and the output end of the differential unit is connected with the input end of the chopping unit;
the difference unit is used for making a difference between the real-time voltage and a preset reference voltage to obtain the difference voltage.
6. The event-type image sensor according to claim 5, wherein the input unit includes a conversion element, a switch, and a capacitor, the switch is connected between a first output terminal of the conversion element and a first input terminal of the differential unit, a connection terminal of the switch and the first input terminal of the differential unit is connected to a non-ground terminal of the capacitor, and a second output terminal of the conversion element is connected to a second input terminal of the differential unit;
the conversion element is used for converting an incident light signal into the real-time voltage;
the capacitor is used for updating the preset reference voltage when the switch is switched from a closed state to an open state.
7. The event-type image sensor according to claim 6, wherein the conversion element includes a photoelectric conversion element and a current-voltage conversion element, an output terminal of the photoelectric conversion element is connected to an input terminal of the current-voltage conversion element, a first output terminal of the current-voltage conversion element is connected to the switch, and a second output terminal of the current-voltage conversion element is connected to a second input terminal of the differential unit;
the photoelectric conversion element is used for generating a photocurrent in response to the incident light signal;
the current-voltage conversion element is used for converting the photocurrent into the real-time voltage.
8. An event type image sensor control method applied to an event camera, the method comprising:
acquiring a real-time voltage in response to an incident optical signal;
taking the difference voltage of 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 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.
9. The event-type image sensor control method according to claim 8, wherein the step of obtaining an output voltage by using a difference voltage between the real-time voltage and a preset reference voltage as an input voltage, frequency-separating the input voltage from a noise voltage, and then filtering the noise voltage according to the separated frequency comprises:
taking the difference voltage of the real-time voltage and a preset reference voltage as an input voltage, modulating the input voltage, and simultaneously performing frequency amplification on the modulated input voltage and the noise voltage to obtain an intermediate voltage signal;
and demodulating the modulation voltage in the intermediate voltage signal, performing low-pass filtering, and filtering the noise voltage to obtain an output voltage.
10. The event-type image sensor control method according to claim 8, wherein the acquiring a real-time voltage in response to an incident light signal includes:
generating a photocurrent in response to the incident optical signal;
converting the photocurrent to the real-time voltage.
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