CN105163048A - Dynamic vision sensor based on amplifier multiplexing - Google Patents

Abstract

The invention relates to the field of integrated circuits, and provides a sensor which uses a multiplexing structure to achieve two functions of continuously monitoring light current and quantitatively reading light intensity. The technical scheme adopted in the invention is: in a dynamic vision sensor based on amplifier multiplexing, a photodiode PD is connected with the source level of a logarithmic tube Mfb, and an amplifier A1 is added between the grid and the source electrode of the Mfb to constitute a negative feedback circuit for converting the light current detected by the photodiode into a voltage in a logarithmic manner; the grid of the logarithmic tube Mfb is further connected with a capacitor C1, and a switch SW3 is further added between the capacitor C1 and an amplifier A2; one end of a switch SW4 is connected with the input end of the amplifier A2, and the other end of the switch SW4 is connected with a reference voltage Vref; and a capacitor C2 and a reset switch SW2 are respectively connected with the amplifier A2 in parallel, and a capacitor C3 and a switch SW1 are connected to both ends of the amplifier A2 in parallel after being connected in series. The dynamic vision sensor based on amplifier multiplexing provided by the invention is mainly applied to the design and manufacture of integrated circuits.

Description

Based on the dynamic vision transducer that amplifier is multiplexing

Technical field

The present invention relates to integrated circuit fields, particularly relate to the dynamic vision transducer adopting amplifier multiplex mode to carry out light intensity quantification reading.Specifically, relate to based on the multiplexing dynamic vision transducer of amplifier.

Technical background

Dynamic vision transducer (DynamicVisionSensor, DVS) be a kind of New-type CMOS (ComplementaryMetalOxideSemiconductor, complementary metal oxide semiconductors (CMOS)) imageing sensor, the foundation structure of its pixel as shown in Figure 1, is made up of photodiode PD, logarithm pipe Mfb, amplifier A1, amplifier A2, electric capacity C1, electric capacity C2, switch RST, ON comparator, OFF comparator and logic module logic.Specific works mode is as follows:

Photodiode PD produces photoelectric current Iph because being subject to illumination, Iph is converted into corresponding photo signal voltage Vp by logarithm pipe Mfb.The effect of amplifier A1 is to form feedback loop, makes Vp can respond the change of Iph in time.The transforming relationship of Vp and Iph is

$V_p={\mathrm{\κ}}^{-1}.(V_S+U_T\·log(\frac{I_{ph}}{I_0}\left)\right)$

Wherein κ represents the sub-threshold slope factor of Mfb, and VS represents the source voltage of logarithm pipe Mfb, and UT represents thermal voltage, and I0 represents the constant reference current of photodiode PD.Electric capacity C1 and C2, amplifier A2 and switch RST form a switched capacitor amplifier.When switch RST disconnects, the changing value Δ Vdiff of amplifier out voltage Vdiff and the proportional change of changing value Δ Vp of amplifier in voltage Vp, namely have

${\mathrm{\ΔV}}_{diff}=-\left(\frac{C_1}{C_2}\right)\·{\mathrm{\ΔV}}_p$

Thus the situation of change of DVS energy Real-Time Monitoring Vp: if Δ Vdiff reaches set change threshold Vth, ON (being generally negative value), then ON comparator exports a pulse, is called and creates an ON event; If Δ Vdiff reaches set change threshold Vth, OFF (be generally on the occasion of), then OFF comparator exports a pulse, is called and creates an OFF event.When there being event to produce, logic module outgoing event control switch RST close, and removing event is gone forward side by side horizontal reset process.After reset completes, switch RST disconnects, and this periods of events completes, and DVS will start new round observation process.

As can be seen from the operation principle of above-mentioned DVS, traditional DVS only can realize monitoring the consecutive variations of photoelectric current thus the ON/OFF event pulse of its qualitative change of generation sign, and itself does not have the function being carried out by intensity signal quantizing to read.If require that DVS also can obtain intensity signal while the change of detection light intensity, then need in DVS dot structure, introduce extra quantification reading circuit.

Summary of the invention

For overcoming the deficiencies in the prior art, there is provided a kind of to adopt multiplexing structure to realize photoelectric current to monitor the transducer quantizing reading two kinds of functions with light intensity continuously, for this reason, the technical scheme that the present invention takes is, based on the dynamic vision transducer that amplifier is multiplexing, photodiode PD is connected with the source class of logarithm pipe Mfb, and between the grid level and source class of Mfb, add amplifier A1 formation negative feedback loop, is converted to voltage in logarithmic fashion for the photoelectric current detected by photodiode; The grid level of logarithm pipe Mfb is also connected with electric capacity C1, adds interrupteur SW 3 between electric capacity C1 and amplifier A2; Interrupteur SW 4 one end connects amplifier A2 input, and the other end then connects reference voltage Vref; Electric capacity C2 and reset switch SW2 is in parallel with amplifier A2 respectively, and electric capacity C3 is attempted by the two ends of amplifier A2 after connecting with interrupteur SW 1; The output of A2 is connected with OFF comparator with ON comparator respectively, and the output of ON comparator and OFF comparator all accesses in logic module Logic; Logic has five outputs, and the disconnection of control SW1 ~ SW5 is with closed respectively.

Each switch open and close sequential is that, in the incident detection stage, interrupteur SW 1, SW2, SW4 and SW5 are in off-state, and SW3 closes, and whether amplifier A2 is used for triggering being used for the time that judges after the amplification of light intensity variable signal; After event produces, SW3, SW4 and SW5 maintain the original state, SW1 and SW2 closes, and enters event resets process; After event resets process completes, SW2 disconnects, and the SW4 of SW3 disconnection simultaneously closes, and enters quantization stage, and the logarithm photoresponse voltage that now amplifier A2 is used for A1 feedback loop to obtain exports; Quantization stage continues some clock cycle, to ensure the foundation completely of amplifier output signal.At quantization stage end, SW5 closes, and reads the output signal of amplifier; After quantization stage terminates, SW4 and SW5 disconnects, SW2 and SW3 closes, thus enters into quantification reseting stage; At the end of quantizing to reset, SW1, SW2 disconnect, and complete the present event cycle, enter into the event detection process of next periods of events.

Compared with the prior art, technical characterstic of the present invention and effect:

1. adopt the transducer of amplifier multiplexing structure can not only Real-Time Monitoring change in optical signal, quantifications reading can also be carried out based on this structure to light signal.

2. transducer event detection process and quantize readout adopt be same photodiode input signal, avoid the deviation of signal that photoresponse nonuniformity is brought, eliminate the detection-quantization error of DVS pixel.

Accompanying drawing explanation

Fig. 1 tradition DVS dot structure figure.

Fig. 2 adopts multiplexing structure and the sequential chart carrying out the DVS pixel that light intensity quantification reads of amplifier.

Embodiment

The present invention passes through to increase port or the elements such as reference voltage, electric capacity and switch on traditional DVS architecture basics, and increase quantizes the course of work reading and quantize reset two amplifiers in a periods of events, make this DVS structure itself possess the ability of continuous intensity monitor and light intensity quantification output simultaneously.

Specifically describe as follows:

The dot structure that the present invention adopts and work schedule thereof are as shown in Figure 2.Pixel concrete structure is as follows: photodiode PD is connected with the source class of logarithm pipe Mfb, and between the grid level and source class of Mfb, add amplifier A1 formation negative feedback loop, is converted to voltage in logarithmic fashion for the photoelectric current detected by photodiode; Interrupteur SW 3 is added between electric capacity C1 and amplifier A2; Interrupteur SW 4 one end connects amplifier, and the other end then connects reference voltage Vref; C2 and reset switch SW2 is in parallel with amplifier A2 respectively, and electric capacity C3 is attempted by the two ends of amplifier A2 after connecting with interrupteur SW 1; The output of A2 is connected with OFF comparator with ON comparator respectively, and the output of two comparators all accesses in logic module Logic; Logic has five outputs, and the disconnection of control SW1 ~ SW5 is with closed respectively.

Represent when SW1 ~ SW5 is low level in sequential chart that this switch disconnects, for representing during high level that this switch closes.In the incident detection stage, interrupteur SW 1, SW2, SW4 and SW5 are in off-state, and SW3 closes, now consistent with event detection process in traditional DVS, and whether amplifier A2 is used for triggering being used for the time that judges after the amplification of light intensity variable signal.After event produces, SW3, SW4 and SW5 maintain the original state, SW1 and SW2 closes, and enters event resets process.After event resets process completes, SW2 disconnects, and the SW4 of SW3 disconnection simultaneously closes, and enters quantization stage, and the logarithm photoresponse voltage that now amplifier A2 is used for A1 feedback loop to obtain exports.Quantization stage continues some clock cycle, to ensure the foundation completely of amplifier output signal.At quantization stage end, SW5 closes, and reads the output signal of amplifier.After quantization stage terminates, SW4 and SW5 disconnects, SW2 and SW3 closes, thus enters into quantification reseting stage.At the end of quantizing to reset, SW1, SW2 disconnect, and complete the present event cycle, enter into the event detection process of next periods of events.

Because proposed method may have a lot of implementations, a more satisfactory scheme to be write here.

Be that example provides one embodiment of the present invention with 3.3V, 110nm manufacture craft.A designed clock cycle of imageing sensor is 20ns, and a periods of events is 160ns.Vref is 2.8V, C1 be 800fF, C2 be 50fF, C3 is 200fF, Vth, ON and Vth, and OFF is 40mV.

Claims (2)

1. one kind based on the multiplexing dynamic vision transducer of amplifier, it is characterized in that, electric diode PD is connected with the source class of logarithm pipe Mfb, and between the grid level and source class of Mfb, add amplifier A1 formation negative feedback loop, be converted to voltage in logarithmic fashion for the photoelectric current detected by photodiode; The grid level of logarithm pipe Mfb is also connected with electric capacity C1, adds interrupteur SW 3 between electric capacity C1 and amplifier A2; Interrupteur SW 4 one end connects amplifier A2 input, and the other end then connects reference voltage Vref; Electric capacity C2 and reset switch SW2 is in parallel with amplifier A2 respectively, and electric capacity C3 is attempted by the two ends of amplifier A2 after connecting with interrupteur SW 1; The output of A2 is connected with OFF comparator with ON comparator respectively, and the output of ON comparator and OFF comparator all accesses in logic module Logic; Logic has five outputs, and the disconnection of control SW1 ~ SW5 is with closed respectively.

2. as claimed in claim 1 based on the dynamic vision transducer that amplifier is multiplexing, it is characterized in that, each switch open and close sequential is, in the incident detection stage, interrupteur SW 1, SW2, SW4 and SW5 are in off-state, and SW3 closes, whether amplifier A2 is used for triggering being used for the time that judges after the amplification of light intensity variable signal; After event produces, SW3, SW4 and SW5 maintain the original state, SW1 and SW2 closes, and enters event resets process; After event resets process completes, SW2 disconnects, and the SW4 of SW3 disconnection simultaneously closes, and enters quantization stage, and the logarithm photoresponse voltage that now amplifier A2 is used for A1 feedback loop to obtain exports; Quantization stage continues some clock cycle, to ensure the foundation completely of amplifier output signal.At quantization stage end, SW5 closes, and reads the output signal of amplifier; After quantization stage terminates, SW4 and SW5 disconnects, SW2 and SW3 closes, thus enters into quantification reseting stage; At the end of quantizing to reset, SW1, SW2 disconnect, and complete the present event cycle, enter into the event detection process of next periods of events.