CN115900968B - Infrared event-radiation dual-mode imaging system for remote small target detection - Google Patents
Infrared event-radiation dual-mode imaging system for remote small target detection Download PDFInfo
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Abstract
The invention discloses an infrared event-radiation dual-mode imaging system for remote small target detection. The detection of the full-scene infrared radiation variation is realized through a logarithmic conversion circuit and a differential comparison circuit; and (3) controlling sampling enabling of all pixel circuits of the radiation intensity mode by using a global signal, starting synchronous integral sampling by the pixel circuits of the radiation intensity mode after the sampling enabling is effective, and then converting the analog signal of the radiation intensity into a digital signal, buffering the digital signal in an on-chip FIFO and temporarily not outputting the digital signal. The output of the infrared radiation intensity modal signal is controlled by the event signal, namely the event signal is required to be subjected to motion extraction of a target area after the event mode is extracted, an infrared radiation intensity modal pixel unit circuit corresponding to the target area is further calculated, then the output of the infrared mode target area pixel intensity is controlled, and finally 'dynamic event full scene output and infrared radiation intensity area output' are realized, so that the imaging effect of low redundancy, low power consumption and high dynamic is achieved.
Description
Technical Field
The invention belongs to the technical field of infrared imaging detection, and particularly relates to an infrared event-radiation dual-mode imaging system for long-distance small target detection.
Background
The infrared imaging detection technology has important strategic value and is widely applied to the fields of monitoring and reconnaissance, medical imaging, post-disaster searching and the like. The changes of targets, environments and mission tasks have prompted the continuous development and evolution of the systems, theory and methods of infrared imaging detection. Along with the development of an informatization network, the existing infrared frame imaging camera faces the problems of large data volume, large power consumption of the camera, small dynamic range and the like, severely restricts the target detection capability of an infrared imaging system, and needs to develop a novel infrared imaging detection system with low redundancy, low power consumption and high dynamic performance so as to efficiently process dynamic and static information in a scene.
The infrared frame imaging camera integrates the infrared radiation intensity of the scene within a specific exposure time, synchronously outputs the infrared radiation intensity of all pixel positions of the scene, and then recognizes and extracts the target according to the radiation intensity. However, in most application scenes such as surveillance reconnaissance, only moving targets in the scenes are required to be identified and extracted, target signals are weak, the traditional frame imaging mode has the problems of high data redundancy and insufficient dynamic range, and because each pixel circuit is in a working state at all times, the power consumption of a platform is also challenged greatly. Since the 40 s of the last century, researchers developed many visible light cameras based on neuromorphic, which realize the perception of the variation of illumination intensity by means of hardware circuits and output asynchronously in the form of event pulses. Based on the theoretical research foundation of a visible light event camera, christoph Posch et al combined a micro-bolometer infrared thermal element with a dynamic sensing pixel circuit of DVS and an event signal AER reading frame in 2008-2010, explored the technical feasibility of a 64×64 array long-wave infrared dynamic vision sensor, however, a binarized infrared dynamic event only can indicate the position information of a moving target in a scene and cannot provide support for subsequent target type identification.
In summary, the infrared camera based on the traditional frame imaging has a long detection distance, reflects the infrared radiation intensity of the target, and can reversely derive the spatial target type according to the radiation characteristic, but the imaging data has large redundancy, high power consumption and small dynamic range; due to the asynchronous imaging characteristics of the infrared event camera, the change of radiation intensity in a scene is reflected, the imaging data volume is small, the power consumption is low, the dynamic range is large, but the infrared event camera lacks of target infrared radiation intensity information, and cannot provide powerful support for subsequent target anti-diffraction recognition.
Disclosure of Invention
Aiming at the defects and improvement demands of the prior art, the invention provides an infrared event-radiation dual-mode imaging system for remote small target detection, which organically fuses an infrared dynamic event mode and an infrared radiation intensity mode for the first time, designs the infrared dynamic event-radiation dual-mode imaging system based on feedback, and realizes the full-scene dynamic sensing of the infrared event and the static sensing of an infrared radiation intensity area.
To achieve the above object, in a first aspect, the present invention provides an infrared event-radiation dual-mode imaging system for remote small object detection, including:
the photoelectric conversion module is used for receiving the infrared radiation intensity signal of the monitored scene and converting the infrared radiation intensity signal into a continuous current signal;
the infrared event mode sampling module is used for receiving the continuous current signal and converting the continuous current signal into a voltage signal of a logarithmic domain through a logarithmic conversion circuit; sensing the variation of the voltage signal through a differential comparison circuit; when the variation exceeds a threshold value, packaging the current pixel position, the variation polarity of the voltage signal and the time stamp into an infrared event for asynchronous output;
the moving target event stream extraction module is used for stripping a target moving event stream from the mixed infrared event stream by modeling different characteristics of an induced motion field of a target motion field and an induced motion field of a background so as to acquire edge position information of a moving target;
the infrared radiation intensity modal sampling module is used for receiving the continuous current signals and synchronously integrating the continuous current signals to obtain analog voltage signals of the infrared radiation intensity signals; converting the analog voltage signal into a digital signal, and caching the digital signal in an on-chip FIFO;
and the logic sampling control module is used for calculating the pixel position of the whole region of the moving target corresponding to the infrared radiation intensity mode according to the edge position information of the moving target so as to control the infrared radiation intensity mode sampling module to output an infrared radiation intensity signal of the whole region of the moving target.
Further, the infrared event triggering process of the infrared event mode sampling module is represented by the following mathematical model:
lnR(x k ,y k ,t i )-lnR(x k ,y k ,t i-1 )＝pθ
wherein R (x) k ,y k ,t i ) At t i At time [ x ] k ,y k ]Radiation intensity at the pixel location; p represents the direction of change of the radiation intensity, i.e. becoming larger or smaller; θ represents the trigger threshold of the infrared event;
triggering one-time pulse signal output when the radiation intensity change value at the same position exceeds theta, recording corresponding time stamp by a reading circuit, and packaging the corresponding triggered pixel position, change polarity and time stamp into [ x ] k ,y k ,p,t]In the form of an output of an infrared event modality.
Further, the logarithmic conversion circuit comprises an NMOS tube M working in a subthreshold state log And a photoelectric tube PD, wherein an NMOS tube M log The resistive load as PD connects PD negative terminal and power supply, the grid applies constant bias voltage V b Source voltage V o As reflected photocurrent I ph A varying log domain voltage signal; and satisfy the following
Wherein, kappa n Is M log Back gate coefficient of (U) T Is thermal voltage, I 0,log Is M log Is a characteristic current of (a).
Further, the differential comparison circuit includes a differential amplification circuit and two voltage comparators comp1 and comp2;
the source voltage at the current moment is taken as input V in The reverse input end of the differential amplifying circuit is connected, and the source voltage at the last moment is used as the reference voltage V ref The same-direction input end of the differential amplifying circuit is connected;
the output end of the differential amplifying circuit is connected with the reverse input ends of the voltage comparators comp1 and comp2; the reference voltages of voltage comparators comp1 and comp2 are V respectively refl And V refh The same-direction input ends of the voltage comparators comp1 and comp2 are respectively connected, and the following conditions are satisfied:
V refh -V ref ＝V ref -V refl 。
further, the infrared radiation intensity mode and the infrared event mode in the single pixel share the same photoelectric conversion module so as to ensure that the infrared radiation intensity mode and the infrared event mode are aligned in space.
Further, the logic sampling control module is further configured to compress a time discrete object motion event within a certain time range into an event frame, and then perform closed curve fitting on object motion event information within a single frame to obtain a contour of a motion object; based on the outline of the moving object, the whole area of the moving object in the infrared event mode is obtained through an outline approximation method, so that the pixel position of the whole area of the moving object corresponding to the infrared radiation intensity mode is calculated.
In a second aspect, the present invention provides an infrared event-radiation dual-mode imaging method for remote small target detection, comprising the steps of:
receiving an infrared radiation intensity signal of a monitoring scene and converting the infrared radiation intensity signal into a continuous current signal;
receiving the continuous current signal and converting the continuous current signal into a voltage signal of a logarithmic domain through a logarithmic conversion circuit; sensing the variation of the voltage signal through a differential comparison circuit; when the variation exceeds a threshold value, packaging the current pixel position, the variation polarity of the voltage signal and the time stamp into an infrared event for asynchronous output;
stripping the target motion event stream from the mixed infrared event stream by modeling different characteristics of the target motion field and the induced motion field of the background, thereby obtaining edge position information of the moving target;
receiving the continuous current signal and synchronously integrating to obtain an analog voltage signal of an infrared radiation intensity signal; converting the analog voltage signal into a digital signal, and caching the digital signal in an on-chip FIFO;
and calculating the pixel position of the whole region of the moving object corresponding to the infrared radiation intensity mode according to the edge position information of the moving object so as to control and output an infrared radiation intensity signal of the whole region of the moving object.
In general, through the above technical solutions conceived by the present invention, the following beneficial effects can be obtained:
(1) The infrared event-radiation dual-mode imaging system provided by the invention outputs two modes of infrared event and infrared radiation intensity simultaneously, and the two modes only output data when a motion target appears, wherein the infrared event is asynchronously output in a binary pulse form, and the data volume is extremely low; the infrared radiation intensity mode only outputs a moving target area in the scene, and the target area has extremely low data volume compared with the full-image data because the far-distance small target scene is oriented to the scene.
(2) Compared with long-time uninterrupted sampling output of an infrared frame camera, the infrared event-radiation dual-mode imaging system provided by the invention only outputs data when a target area exists, and the infrared radiation intensity mode only samples the target area when a moving target exists in the infrared event-radiation dual-mode imaging system, so that the power consumption of the system provided by the invention is lower compared with that of the frame camera imaging.
(3) When the imaging 'wide dynamic' is designed in the infrared event mode sampling circuit, the current signal reflecting the radiation intensity signal is converted into the voltage signal in the logarithmic domain by adopting the logarithmic conversion circuit, and compared with the traditional frame camera integral imaging, the dynamic range is larger, so that the advantages are obvious when the remote detection of a small target is carried out.
Drawings
FIG. 1 is a flow chart of infrared event-radiation dual-mode imaging for remote small target detection provided by the invention.
Fig. 2 is a schematic diagram of a logarithmic conversion circuit according to the present invention.
FIG. 3 shows a source voltage V provided by the present invention o And photocurrent I ph A graph of the relationship between the two.
Fig. 4 is a schematic diagram of a differential comparison circuit provided by the present invention.
Fig. 5 is an input-output graph of the differential comparison circuit provided by the invention.
Fig. 6 is a diagram of infrared event-radiation dual-mode pixel sampling logic provided by the present invention.
Fig. 7 is a schematic diagram of an infrared event mode pixel sampling analog circuit provided by the invention.
Fig. 8 is a schematic diagram of a comparator analog circuit principle and an output waveform according to the present invention.
Fig. 9 is a schematic diagram of a comparator threshold generation analog circuit provided by the present invention.
Fig. 10 is a schematic diagram of an infrared radiation intensity modal pixel sampling analog circuit provided by the invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.
In the present invention, the terms "first," "second," and the like in the description and in the drawings, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.
Referring to fig. 1, in combination with fig. 2 to 10, the invention provides an infrared event-radiation dual-mode imaging system for remote small target detection, which comprises a photoelectric conversion module, an infrared event mode sampling module, a moving target event stream extraction module, an infrared radiation intensity mode sampling module and a logic sampling control module. The modules are described in detail below.
And the photoelectric conversion module is used for receiving the infrared radiation intensity signal of the monitored scene and converting the infrared radiation intensity signal into a continuous current signal.
There are generally two photoelectric conversion modes. The first is based on charge conversion, and due to the built-in electric field generated near the PN junction contact surface, the photo-generated electrons move to the N+ region to accumulate, and then are converted into voltage signals in a junction capacitance mode. The voltage signal after photoelectric conversion can only represent the average value of the radiation intensity in the integral time period, and the pixel integral time is longer under the condition of weak light to ensure the signal to noise ratio, so that the image tailing condition is easy to generate. The second mode is based on current conversion, under the illumination of infrared radiation, the photo-generated electrons do directional motion in the tube, continuous photo-generated current is formed in the time domain, and the magnitude of the photo-current is always in direct proportion to the intensity of the infrared radiation, so that the invention prefers a photoelectric conversion scheme based on the current mode in order to improve the dynamic detection energy of a detection system.
The infrared event mode sampling module is used for receiving the continuous current signal and converting the continuous current signal into a voltage signal of a logarithmic domain through a logarithmic conversion circuit; sensing the variation of the voltage signal through a differential comparison circuit; and when the variation exceeds a threshold value, packaging the current pixel position, the variation polarity of the voltage signal and the time stamp into an infrared event for asynchronous output.
In this embodiment, a photocurrent signal proportional to the intensity of infrared radiation is applied to an infrared event mode sampling circuit, and is converted into a voltage signal in a logarithmic domain by a logarithmic conversion circuit, and then the change of the voltage signal is sensed by a differential comparison circuit, and the infrared dynamic event information of a scene is asynchronously output in the form of pulses, and the triggering process can be represented by using the following mathematical model:
lnR(x k ,y k ,t i )-lnR(x k ,y k ,t i-1 )＝pθ
wherein R (x) k ,y k ,t i ) At t i At time [ x ] k ,y k ]Radiation intensity at the pixel location; p represents the direction of change of the radiation intensity, i.e. becoming larger or smaller; θ represents the triggering threshold for an infrared event.
Triggering one-time pulse signal output when the radiation intensity change value at the same position exceeds theta, recording corresponding time stamp by a reading circuit, and packaging the corresponding triggered pixel position, change polarity and time stamp into [ x ] k ,y k ,p,t]In the form of an output of an infrared event modality.
As shown in FIG. 2, the logarithmic conversion circuit includes a circuit operating at a subthresholdMOS tube M with value state log Is composed of photoelectric tube PD, in which logarithmic tube M log The resistive load as PD connects PD negative terminal and power supply, the grid applies constant bias voltage V b Source voltage V o As reflected photocurrent I ph A varying log domain voltage signal. Source voltage V o And photocurrent I ph The graph of the relationship between these is shown in fig. 3.
Due to photocurrent I ph Far less than M log So M in this configuration log Always operating in the subthreshold regime.
Let M be log Is an N-type MOSFET and is applicable to a simple subthreshold model, then:
wherein I is 0,log Is M log Characteristic current, κ of (2) n Back gate coefficient of N-type MOSFET, V G,log And V S,log Respectively M log Gate, source voltage, U T Is a thermal voltage. Further, the above formula is rewritable as I ph Expression for argument:
as shown in fig. 4, the differential comparison circuit includes a differential amplification circuit and two voltage comparators comp1 and comp2, wherein the differential amplification circuit is composed of an operational amplifier A1, two integrating capacitors C1 and C2, and a reset switch S.
The source voltage, which is the logarithmic domain voltage signal reflecting the photocurrent, is used as the input V in The same-direction input end of the differential circuit is connected, and the source voltage number at the last moment is used as the reference voltage V ref And the reverse input end of the differential amplifying circuit is connected. Voltage comparators comp1 and comp2 have reference voltages V respectively refl And V refh Representing the forward threshold and the reverse threshold of event triggering respectively, and there are:
V refh -V ref ＝V ref -V refl
the specific working process is that the initial time t 1 When the switch S is closed, the voltage V is output diff With floating node voltage V float Are all equal to the reference voltage V ref At this time, the comparator's comp1 output voltage is low and the comp2 output is high, which is in a reset state. S is disconnected, the differential comparison circuit enters a working state and is connected with an input signal V in Change occurs at t 2 The moment is based on the principle of conservation of charge:
(V in (t 1 )-V float (t 1 ))*C 1 +(V diff (t 1 )-V float (t 1 ))*C 2 ＝
(V in (t 2 )-V float (t 2 ))*C 1 +(V diff (t 2 )-V float (t 2 ))*C 2
amplifier A1 is coupled to floating node voltage V float Clamping action of (c) such that V float (t 1 )＝V float (t 2 )＝V ref The above formula can thus be simplified as:
at DeltaV diff reach-DeltaV ev At this time, the output terminal voltage V of the comparator comp1 on From level jump to high level, comp2 output voltage nV off Hold high, which is referred to as generating an ON event; at DeltaV diff Reaching DeltaV ev When nV off Jump from high to low and V on The low level is maintained and an OFF event is generated. After the event is generated and read out, the logic module generates an effective RESET signal, so that the switch S is closed, the differential comparison circuit enters a composite state, and the signal input and output waveforms of the differential comparison circuit are shown in fig. 5.
And the moving object event stream extraction module is used for stripping the object moving event stream from the mixed infrared event stream by modeling different characteristics of the induced motion field of the object motion field and the induced motion field of the background so as to acquire the edge position information of the moving object.
In this embodiment, the event stream caused by the background induced motion is stripped from the event stream caused by the target motion by motion clustering.
The infrared radiation intensity modal sampling module is used for receiving the continuous current signals and synchronously integrating the continuous current signals to obtain analog voltage signals of the infrared radiation intensity signals; and converting the analog voltage signal into a digital signal, and buffering the digital signal in the on-chip FIFO.
In order to ensure the spatial alignment of the infrared radiation mode and the infrared event mode, the infrared radiation mode and the infrared event mode in a single pixel share the same photoelectric conversion module, the infrared radiation mode samples through an integrator after receiving a photocurrent signal reflecting the infrared radiation intensity, then converts a voltage signal reflecting the radiation intensity into a digital signal through an analog-to-digital conversion circuit, and the digital signal is buffered in an on-chip FIFO (first in first out) to reduce the data volume of an imaging system, and the output of the infrared radiation mode signal of each pixel is controlled by a logic circuit.
And the logic sampling control module is used for calculating the pixel position of the whole region of the moving target corresponding to the infrared radiation intensity mode according to the edge position information of the moving target so as to control the infrared radiation intensity mode sampling module to output an infrared radiation intensity signal of the whole region of the moving target.
Further, according to the edge position information of the moving object, the pixel position of the whole area of the moving object corresponding to the infrared radiation intensity mode is calculated, specifically:
compressing a time discrete target motion event within a certain time range into an event frame, and performing closed curve fitting on target motion event information in a single frame to obtain a contour of a motion target; based on the outline of the moving object, the whole area of the moving object in the infrared event mode is obtained through an outline approximation method, so that the pixel position of the whole area of the moving object corresponding to the infrared radiation intensity mode is calculated. Since the infrared radiation intensity mode is spatially synchronized with the infrared event mode, the entire area of the moving object of the event mode can be equivalent to the entire area of the moving object of the infrared radiation intensity mode.
In the logic sampling control module, the sampling and reading of the infrared radiation intensity are controlled by the processed event signals, specifically:
the infrared radiation-event dual-mode imaging essence can be regarded as different characterization forms of the infrared radiation intensity of a scene, namely, the infrared radiation mode perceives the absolute value of the infrared radiation intensity of the scene in unit integration time, the dynamic event mode perceives the variation quantity of the infrared radiation intensity of the scene, but the variation quantity cannot be directly reflected on the existing material and can only be realized through subsequent circuit design, so that the pixel materials of the infrared-dynamic and static dual modes in the system can be regarded as the same, namely, the same PD tube can be theoretically adopted.
Based on the above analysis, the present invention designs a dual mode pixel sampling logic as shown in FIG. 6 to accomplish the temporal and spatial alignment of the IR radiation events. Specifically, the pixel is mainly divided into two parts, namely an emission intensity sampling (APS) part and a dynamic event sampling (DVS) part, and the two parts share one PD photodiode, namely each pixel is respectively provided with an emission intensity sampling circuit and a dynamic event sampling circuit corresponding to the two parts.
Specifically, when the intensity of infrared radiation changes, the photoelectric conversion circuit converts the radiation intensity signal into a current signal, and the current signal is then converted into two branches which are used as the input of the APS and DVS sampling circuits. The APS mainly comprises an integrator, wherein the integrator is interacted with a peripheral reading circuit through three signal lines, namely a sampling clock line, a reading control signal line and an intensity output signal line. The sampling clock line is provided by the reading circuit, so that the APS samples the infrared radiation intensity of the scene according to the corresponding frequency moment, but does not output the intensity after sampling. And then the FPGA finishes the conversion from the target position to the specific pixel coordinate and feeds back the target position to the readout circuit, and the readout circuit directly controls the on-off state of the APS in the single pixel circuit through the readout control signal line, so that the sampled infrared radiation intensity value in the pixel circuit is output to the readout circuit for processing through the intensity output signal line, and the synchronism of the event and the radiation intensity is ensured to a certain extent. The minimum error is controlled within one sampling period of the infrared radiation intensity.
More specifically, as shown in fig. 7, the infrared event mode pixel sampling circuit specifically includes five parts: logarithmic amplifier, source follower, switched capacitor amplifier, comparator and logic unit.
The logarithmic amplifier is controlled by a MOS tube M working in a subthreshold region 1 Converting the photocurrent into a photovoltage in a logarithmic manner, wherein the output voltage and the input photocurrent satisfy the following formula:
wherein n is a subthreshold slope factor of the MOS tube, which is determined by the manufacturing process and is generally 1-2; k is Boltzmann constant, about 1.38X10 -23 J/K; t is absolute temperature, q is the charge of the electron, about 1.6X10 -19 C，V 0 Is a fixed voltage value.
The source follower is divided into two paths, M SF1 And M is as follows B1 For the absolute value output path, M SF2 And M is as follows B2 The path is output for the event pulse. Each path comprises a common drain source follower M SF1/2 And a bias tube M B1/2 。
The switched capacitor amplifier further amplifies the output voltage of the source follower with a gain of:
comprising an amplifying tube M DP0 Two switching tubes M GR 、M R And a bias tube M DN0 . In addition to amplification, the switched capacitor amplifier also functions to reset the level.
The comparator is used for converting the voltage variation into the event pulse. As shown in figure 8 of the drawings,when the photocurrent increases, V DIFF The voltage at the terminal drops, when the voltage is lower than the lower threshold, the output of the comparator is inverted to generate an ON event, after which V DIFF Returning to a reset level under control of a reset signal; when the photocurrent decreases, V DIFF The terminal voltage rises and when the voltage is above the upper threshold, the comparator output toggles, generating an OFF event, and the VDIFF output voltage returns to the reset level, also under control of the reset signal.
The logic unit circuit performs preliminary processing on the digital signal inside the pixel. Comprises two transmission gates, an OR gate, a NOR gate and an AND gate. The transmission gate is controlled by the column selection signal to transmit the event output to the column bus, and the nor gate combines the outputs of the two comparators into an event flag signal and forms a column application signal AX with the preceding stage event flag phase. When the external column reset signal is generated, the event flag signal is detected to be identical with the external column reset signal or the internal reset signal of the pixel is generated.
The comparison threshold generating circuit is used for providing comparison threshold voltages of comparators in all pixel units, and the sensitivity switching of 10% -40% and every 10% can be realized through the switching of external control signals.
As shown in fig. 9, the comparison threshold generation circuit is mainly composed of two parts of a reset level generation circuit and a sensitivity switching circuit. The reset level parameter circuit comprises a PMOS tube load M connected with a diode dp1 (state after analog switched capacitor amplifier reset), a bias tube M dn1 . The sensitivity switching circuit comprises an operational amplifier, an amplifying tube M THP Two sets of resistor arrays R1, R2 and one resistor R0. The final output is output to the inside of the pixel unit through the unity gain amplifier. Wherein vh=v DIFF +V TH ，VL＝V DIFF -V TH 。V TH A corresponding voltage value is determined for sensitivity control.
The digital control signal TH <1:2> controls the resistance values of the resistor arrays R1 and R2, so that the VTH is changed, and the sensitivity is switched.
As shown in fig. 10, reflects infraredThe photocurrent signal of the radiation intensity is simultaneously applied to an infrared radiation intensity sampling circuit, wherein the infrared radiation intensity sampling circuit comprises three MOS tubes and an integrating capacitor. M is M 0 The tube realizes the periodic reset of the integrating capacitance node, M 1 The tube is a source follower tube, which connects node V aps Voltage is transmitted to bus, M 2 The tube is a switch tube and controls the gating output of the inverted signal bus of the pixel unit.
In summary, the invention uses the logarithmic conversion circuit of the infrared event mode to increase the imaging dynamic range, and uses the differential comparison circuit to convert the change of the infrared radiation intensity into the binary pulse signal and asynchronously output, thereby obviously reducing the data volume. However, the infrared dynamic event lacks the absolute value of radiation intensity and cannot carry out a subsequent target recognition task, so that in order to acquire the infrared radiation intensity and not obviously increase the data quantity and the power consumption of the infrared dynamic event-radiation dual-mode imaging system, the invention firstly provides an infrared dynamic event-radiation dual-mode imaging system, namely after the infrared event mode outputs event information, an event stream caused by background induced motion and an event stream caused by target motion are stripped through motion clustering, the position of a target motion area in a scene is acquired, then an infrared radiation intensity sampling pixel circuit of a corresponding area is calculated through an FPGA, and the sampling output of the infrared radiation intensity is only carried out in the target area.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. An infrared event-radiation dual-mode imaging system for remote small target detection, comprising:
the photoelectric conversion module is used for receiving the infrared radiation intensity signal of the monitored scene and converting the infrared radiation intensity signal into a continuous current signal;
the infrared event mode sampling module is used for receiving the continuous current signal and converting the continuous current signal into a voltage signal of a logarithmic domain through a logarithmic conversion circuit; sensing the variation of the voltage signal through a differential comparison circuit; when the variation exceeds a threshold value, packaging the current pixel position, the variation polarity of the voltage signal and the time stamp into an infrared event for asynchronous output;
the moving target event stream extraction module is used for stripping a target moving event stream from the mixed infrared event stream by modeling different characteristics of an induced motion field of a target motion field and an induced motion field of a background so as to acquire edge position information of a moving target;
the infrared radiation intensity modal sampling module is used for receiving the continuous current signals and synchronously integrating the continuous current signals to obtain analog voltage signals of the infrared radiation intensity signals; converting the analog voltage signal into a digital signal, and caching the digital signal in an on-chip FIFO;
and the logic sampling control module is used for calculating the pixel position of the whole region of the moving target corresponding to the infrared radiation intensity mode according to the edge position information of the moving target so as to control the infrared radiation intensity mode sampling module to output an infrared radiation intensity signal of the whole region of the moving target.
2. The infrared event-radiation dual-mode imaging system for remote small object detection of claim 1, wherein the infrared event triggering process of the infrared event modality sampling module is represented by the following mathematical model:
lnR(x k ,y k ,t i )-lnR(x k ,y k ,t i-1 )＝pθ
wherein R (x) k ,y k ,t i ) At t i At time [ x ] k ,y k ]Radiation intensity at the pixel location; p represents the direction of change of the radiation intensity, i.e. becoming larger or smaller; θ represents the trigger threshold of the infrared event;
triggering one-time pulse signal output when the radiation intensity change value at the same position exceeds theta, recording corresponding time stamp by a reading circuit, and packaging the corresponding triggered pixel position, change polarity and time stamp into [ x ] k ,y k ,p,t]In the form of an output of an infrared event modality.
3. The infrared event-radiation dual-mode imaging system for remote small object detection as recited in claim 1, wherein said logarithmic conversion circuit comprises an NMOS tube M operating in a subthreshold state log And a photoelectric tube PD, wherein an NMOS tube M log The resistive load as PD connects PD negative terminal and power supply, the grid applies constant bias voltage V b Source voltage V o As reflected photocurrent I ph A varying log domain voltage signal; and satisfy the following
Wherein, kappa n Is M log Back gate coefficient of (U) T Is thermal voltage, I 0,log Is M log Is a characteristic current of (a).
4. The infrared event-radiation dual-mode imaging system for remote small object detection according to claim 3, wherein said differential comparing circuit comprises a differential amplifying circuit and two voltage comparators comp1 and comp2;
the source voltage at the current moment is taken as input V in The reverse input end of the differential amplifying circuit is connected, and the source voltage at the last moment is used as the reference voltage V ref The same-direction input end of the differential amplifying circuit is connected;
the output end of the differential amplifying circuit is connected with the reverse input ends of the voltage comparators comp1 and comp2; the reference voltages of voltage comparators comp1 and comp2 are V respectively refl And V refh The same-direction input ends of the voltage comparators comp1 and comp2 are respectively connected, and the following conditions are satisfied:
V refh -V ref ＝V ref -V refl 。
5. the infrared event-radiation dual-mode imaging system for long-distance small target detection of claim 1, wherein the infrared radiation intensity mode and the infrared event mode in a single pixel share the same photoelectric conversion module to ensure that the infrared radiation intensity mode and the infrared event mode are spatially aligned.
6. The infrared event-radiation dual-mode imaging system for remote small target detection according to claim 1, wherein the logic sampling control module is further configured to compress a time-discrete target motion event within a certain time range into an event frame, and then perform closed curve fitting on target motion event information within a single frame to obtain a contour of a moving target; based on the outline of the moving object, the whole area of the moving object in the infrared event mode is obtained through an outline approximation method, so that the pixel position of the whole area of the moving object corresponding to the infrared radiation intensity mode is calculated.
7. An infrared event-radiation dual-mode imaging method for remote small target detection is characterized by comprising the following steps:
receiving an infrared radiation intensity signal of a monitoring scene and converting the infrared radiation intensity signal into a continuous current signal;
receiving the continuous current signal and converting the continuous current signal into a voltage signal of a logarithmic domain through a logarithmic conversion circuit; sensing the variation of the voltage signal through a differential comparison circuit; when the variation exceeds a threshold value, packaging the current pixel position, the variation polarity of the voltage signal and the time stamp into an infrared event for asynchronous output;
stripping the target motion event stream from the mixed infrared event stream by modeling different characteristics of the target motion field and the induced motion field of the background, thereby obtaining edge position information of the moving target;
receiving the continuous current signal and synchronously integrating to obtain an analog voltage signal of an infrared radiation intensity signal; converting the analog voltage signal into a digital signal, and caching the digital signal in an on-chip FIFO;
and calculating the pixel position of the whole region of the moving object corresponding to the infrared radiation intensity mode according to the edge position information of the moving object so as to control and output an infrared radiation intensity signal of the whole region of the moving object.
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