CN108614255A - A kind of reading circuit - Google Patents
A kind of reading circuit Download PDFInfo
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- CN108614255A CN108614255A CN201810682894.5A CN201810682894A CN108614255A CN 108614255 A CN108614255 A CN 108614255A CN 201810682894 A CN201810682894 A CN 201810682894A CN 108614255 A CN108614255 A CN 108614255A
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- reading circuit
- circuit
- pulse
- reading
- signal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
- G01S7/48—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S17/00
- G01S7/483—Details of pulse systems
- G01S7/486—Receivers
- G01S7/4861—Circuits for detection, sampling, integration or read-out
Abstract
The present invention provides a kind of reading circuits, it is characterized in that, the current signal that the reading circuit is used to would operate in the avalanche diode output of linear model is read out according to certain frame frequency, stopping criterion is provided for subsequent timing circuit, flight time and the echo luminous intensity that pulse is obtained with this, complete the function of laser acquisition.The reading circuit of the present invention at the time of obtaining timer stopping by the signal that APD is received, reduces moment driscrimination error and obtains more accurate range information to calculate more accurate flight time TOF as much as possible.
Description
Technical field
The present invention relates in laser three-dimensional imaging field of signal processing more particularly to a kind of reading circuit.
Background technology
Laser three-dimensional imaging is the typical case of laser radar.In general sense, Range Profile (angle-angle-distance) claims
For 3-D view.There are many kinds of optical 3-dimensional acquiring technologies, using it is more be pulse time-of-flight method.By to target surface
The pixel division of outline is sampled, and the angle-angle-range information for obtaining each pixel respectively carries out really its spatial position
Fixed, target shape outline can be described in the point cloud that all measurement pixels combine composition.
Pulse time-of-flight method (TOF, time offlight) is to obtain picture by measuring the single light pulse flight time
The distance of vegetarian refreshments.It reflects in target surface after light pulses, then echo optical signal is visited by photodetector
It surveys.If pulse to the flight time of system round trip is again t from system to target, the light velocity in transmission medium is c, can obtain mesh
Subject distance s is
By obtaining the corresponding flight time at object to be measured different location, you can reconstruct the three-dimensional shaped of object to be measured
Looks.Gate-control signal controls that laser is exomonental simultaneously, and timer starts timing, and APD is received after optical signal through oversampling circuit
Processing makes timer stop timing, to obtain the flight time of optical pulse.
If obtaining the intensity information of echo-signal, the material property of target just can be analyzed by absorbed light signal,
Angle-angle-distance-intensity can become four-dimensional imaging in this way.
APD focal plane array photodetectors are the core devices of laser radar, usually by APD array and corresponding reading
Go out circuit composition.Reading circuit needs have the characteristics that high speed, high s/n ratio, high bandwidth, and the electric current by handling APD outputs is believed
Number, at the time of obtaining timing stopping, obtaining the intensity of light pulse flight time TOF and the light pulse by target reflection.
The report in terms of calculating timer stopping criterion has following two schemes at present.Permanent threshold value differential method is also known as forward position
Moment differential method all chooses the same pulse amplitude values (or with pulse front edge for transmitting pulse and echo impulse
Amplitude) it is used as moment discrimination threshold, it is started or stopped when rising edge of a pulse reaches the threshold value and starts timing, when acquisition flight
Between.This method by factors such as target scattering characteristics and propagation in atmosphere due to being influenced, the laser pulse received and transmitting
Laser pulse can be very different in shape and amplitude, increase difficulty to the determination of timing stop timing, introduce drift
Error.In addition, input noise can also cause time jitter, error is caused to measurement.The timing of the program starts and stopping is logical
The charging complete of C3D is crossed to realize, that is, takes permanent threshold value discrimination method.And the time resolution of this method is very low.
Constant proportion discrimination method, for transmitting pulse and echo impulse, with the same specific percentage of respective peak pulse amplitude
The moment is started or stopped as timing at the time of correspondence than amplitude, obtains the flight time.Such as triggering ratio is taken as 50%, i.e., with arteries and veins
Rush to the start/stop time as time at the time of being raised to half height point.Constant fraction discriminator differential method is effectively eliminated since impulse amplitude becomes
Change caused error, but the influence that the factors such as noise and wave distortion can not be inhibited to bring.
Invention content
Based on the above issues, the present invention provides a kind of reading circuit, can be converted to the APD current signals exported and compare
Device voltage signal easy to identify.
To solve the above problems, the present invention provides a kind of reading circuits, which is characterized in that the reading circuit is used for will
The current signal for being operated in the avalanche diode output of linear model is read out according to certain frame frequency, is subsequent timing electricity
Road provides stopping criterion, and flight time and the echo luminous intensity of pulse are obtained with this, completes the function of laser acquisition.
The reading circuit of the present invention reduces as much as possible at the time of obtaining timer stopping by the signal that APD is received
Moment driscrimination error obtains more accurate range information to calculate more accurate flight time TOF.
Description of the drawings
Fig. 1 shows the reading circuit structure schematic diagram of the present invention；
Fig. 2 shows the reading circuit working timing figures of the present invention；
Fig. 3 shows the reading circuit schematic diagram of the single pixel of the present invention.
Specific implementation mode
With reference to the accompanying drawings and examples, the specific implementation mode of the present invention is described in further detail.Implement below
Example is not limited to the scope of the present invention for illustrating the present invention.
The reading circuit overall framework of this programme is that the function of linear APD focal plane reading circuit is by focus planar detector
In each pixel echo impulse flight time for measuring of APD and strength information be read out, complete " four-dimension " and be imaged.APD gusts
Each pixel in row corresponds to a reading circuit, which includes I/V conversions, integrator, filter and timer,
It will be discussed in detail in next trifle.The flight time of each pixel output and intensity information are sequential read out by link in tandem,
In data reading, it is multiplexed buffer register, using daisy chain structures, reading circuit series connection will when without timing
Timing result Serial output, as shown in Figure 1.
Fig. 2 illustrates the sequence diagram of linear APD focal plane reading circuit work, and when gate-control signal starts, laser is sent out
Timer starts timing while pulse, and after APD receives echo-signal, each pixel is obtained by the processing of reading circuit
Pulse time-of-flight TOF and intensity information.These data are transmitted to memory with speed quickly, then start next week
Phase.Therefore, the length of gate-control signal determines the measurement range of system.When array is larger, if serial transmission take it is longer, can be with
A plurality of daisy chain, such as four links are designed, 16 reading circuits of connecting in each of the links, so that it may to realize 64 battle array
Row timing exports.
Fig. 2 is the reading circuit of single pixel, and the major function of the circuit is to would operate in two pole of snowslide of linear model
The current signal of pipe output is read out according to certain frame frequency, is provided stopping criterion for subsequent timing circuit, is obtained with this
The flight time of pulse and echo luminous intensity, complete the function of laser acquisition.Overall plan block diagram is as shown in Figure 3.It realizes
The current pulse signal that avalanche diode exports is changed into comparator voltage pulse signal easy to identify by above-mentioned function first
(I/V conversions), I/V conversions are using resistance feedback across resistance amplifying circuit (RTIA, Resistive Trans-impedance
Amplifier), it need not be integrated, therefore have faster response speed, its transmission function is represented by：
Vout=-iapdR+Vref
Wherein, Vout is output voltage, and iapd is APD output currents, and R is resistance feedback across resistance amplifying circuit across resistance,
Vref is forward end input voltage of the resistance feedback across resistance amplifying circuit.
APD outputs are current pulse signal shown in Fig. 3, and the voltage pulse to form same shape is converted by I/V,
Into buffer (buffer).The effect of buffer is matching output impedance, increases driving capability.Voltage pulse passes through buffer
After be divided into two-way, the first via is integrating circuit, to buffer output voltage pulse signal integrate, obtained DC information
It indicates the intensity information that avalanche diode receives, the reflection characteristic of the information representation target surface, and then target can be analyzed
Material properties.
Second tunnel is moment discrimination circuit, and the peak detection used provides stopping criterion for subsequent timing circuit, is wrapped
Include filter and zero-crossing comparator.Flip-flop is removed after voltage pulse signal is filtered, becomes right above and below zero level
The AC signal of title, as shown in Figure 2.The zero crossing triggering zero-crossing comparator output signal overturning of the signal, makes timer stop
Only timing, the output of timer at this time becomes the laser pulse flight time, and then knows the distance of target.
This kind of method uses the criterion that filtered zero crossing stops as timing, which is echo-signal
Peak value.Pulse signal receives after being reflected by target to APD focal plane, has decaying and noise aliasing, and target material
Matter difference can cause the difference of reflection back echo luminous intensity, therefore can be wrong using permanent threshold value differential method or constant proportion differential method
Difference needs compensation circuit to be corrected.And signal is after amplification, decaying or noise aliasing, the position of peak value is kept not
Become, therefore this method is point-device.
The circuit another advantage is that can the intensity of flight time and echo light pulse be obtained simultaneously, and then obtain
The 3-D view of object to be measured, and the four-dimensional information comprising strength information.Two circuit paths share a set of I/V conversion circuits
And buffer, therefore signal will not lose in front end because of shunting, the luminous intensity that integrating circuit obtains is very accurate.Meanwhile
Another way signal is the criterion that the peak value of signal stops as timing, this moment discriminating side by generating zero crossing after filtering
Method is not based on permanent threshold value differential method, nor being based on constant proportion differential method, but emits pulse and echo impulse by measurement
Time difference between peak position is as the flight time.It is also more accurate to the judgement of flight time in this way, obtains higher
Range measurement accuracy.
Timing circuit uses pseudo-random counter, carries out Counter Design using nine primitive polynomials, 9 (bit) are posted
Storage carries out bigness scale to the time.It is carefully measured, 3 (bit) phase measurements, is realized using delay line type time-to-digit converter
Higher time precision.Clock, wherein level-one NAND gate are generated by 9 grades of oscillators, is controlled by start signals, is produced
The clock that the raw time calculates.Clock can be transmitted to entire reading circuit array by clock number.On single pixel, clock passes through
Tristate inverter operates pseudo-random counter.This tristate inverter can be placed in high-impedance state by Stop signals, to stop counting
Number, will be accurate on the single clock cycle arrival time.The clock can also drive 3 inverter chains, be used as delay line work(
Time precision can be increased.The output of 3 phase inverters is triggered by stop to be sampled, and 6 kinds of effective statuses can be obtained, for rising edge clock
Or failing edge transmission situation is mapped to corresponding delaying state.Since ring oscillator biases independently so that clock frequency is adjustable
Section, delay line boundary transmission delay can be to half of clock cycle.
Pseudo-random counter is 9 (bit) shift registers composition with feedback circuit, and input is generated by Q4 and Q9 exclusive or
Q0.It selects this structure and is and is for circuit small and exquisite.The combinational logic of XOR and MUX can introduce longer delay on feedback circuit,
The working frequency of meeting limit counter in this way.Therefore the pipeline design is used on feedback circuit.XOR increases by one are additional to post
Storage.XOR needs four inputs and its inverted logic, the assembly line of inverted logic to need two additional registers.Flowing water
Line counter needs Q2, Q3, Q7, the upper taps of Q8 on feedback path.After flight time measurement, data switching is realized by MUX, it will
Input of the output of adjacent pixels as shift register, has external clock to read the data of entire row of pixels.
The structure of timing circuit as shown in figure 3, entire circuit includes input signal data_in, select, clk, believe by output
Number data_out.It is described as follows from function connects：MUX has select signal gatings, and it is stream to input as Q0 and data_in, Q0
Waterline counter inputs, and data_in is the output of previous level production line.The output of MUX is connected to the input of register Q1, deposit
Device Q2 to register Q9, which is sequentially connected, constitutes assembly line counter.The output of register Q1 is also connected to register Q2_n, deposit
The output of device Q2_n, the output of register Q3, the output of register Q4 and the output of register Q8 are connected to four inputs of XOR
End, the output of XOR are connected to the input terminal of register Q0, generate the input of assembly line counter.All registers use same
Clock source clk.
Embodiment of above is merely to illustrate the present invention, and not limitation of the present invention, in relation to the common of technical field
Technical staff can also make a variety of changes and modification without departing from the spirit and scope of the present invention, therefore all
Equivalent technical solution also belongs to scope of the invention, and scope of patent protection of the invention should be defined by the claims.
Claims (4)
1. a kind of reading circuit, which is characterized in that it is characterized in that, the reading circuit is used to would operate in the snow of linear model
The current signal for collapsing diode output is read out according to certain frame frequency, and stopping criterion is provided for subsequent timing circuit, with
This obtains the flight time of pulse and echo luminous intensity, completes the function of laser acquisition.
2. reading circuit as described in claim 1, which is characterized in that the reading circuit includes I/V conversions, integrator, filter
Wave device and timer.
3. reading circuit as claimed in claim 2, which is characterized in that the reading circuit is for obtaining focus planar detector survey
The echo impulse intensity obtained is specially to obtain flight time and the intensity information of each pixel output.
4. reading circuit as claimed in claim 2, which is characterized in that the work schedule of the reading circuit is specifically, work as door
When control signal starts, timer starts timing while laser sends out pulse, after APD receives echo-signal, by reading
The processing of circuit obtains the pulse time-of-flight TOF and intensity information of each pixel.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810682894.5A CN108614255A (en) | 2018-06-28 | 2018-06-28 | A kind of reading circuit |
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| CN201810682894.5A CN108614255A (en) | 2018-06-28 | 2018-06-28 | A kind of reading circuit |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110109085A (en) * | 2019-04-15 | 2019-08-09 | 东南大学 | Low-power consumption wide-range array type photon timing reading circuit based on bimodulus switching |
| CN110308435A (en) * | 2019-08-05 | 2019-10-08 | 中国兵器工业集团第二一四研究所苏州研发中心 | A kind of time and intensity digital conversion circuit of Pixel-level |
| CN111273311A (en) * | 2020-01-03 | 2020-06-12 | 电子科技大学 | Laser three-dimensional focal plane array imaging system |
| WO2021016829A1 (en) * | 2019-07-30 | 2021-02-04 | Shenzhen Genorivision Technology Co., Ltd. | Image sensors for lidar systems |
| CN112903122A (en) * | 2021-01-21 | 2021-06-04 | 电子科技大学 | Laser three-dimensional focal plane reading circuit |
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| US20090014627A1 (en) * | 2004-02-02 | 2009-01-15 | Yukinobu Sugiyama | Photodetector device |
| CN104142504A (en) * | 2014-03-26 | 2014-11-12 | 常州大地测绘科技有限公司 | Pulse-based laser distance measuring instrument and distance measuring method thereof |
| JP2015108629A (en) * | 2014-12-26 | 2015-06-11 | トヨタ自動車株式会社 | Image acquisition device and method |
| CN105652259A (en) * | 2015-12-30 | 2016-06-08 | 天津大学 | Laser ranging reading sequential circuit and method based on Geiger mode APD array |
| CN107505608A (en) * | 2017-06-22 | 2017-12-22 | 西安电子科技大学 | Lidar array receiver front end reads integrated circuit |
| CN108139481A (en) * | 2015-09-29 | 2018-06-08 | 高通股份有限公司 | The LIDAR system measured with reflected signal strength |
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| US20090014627A1 (en) * | 2004-02-02 | 2009-01-15 | Yukinobu Sugiyama | Photodetector device |
| CN104142504A (en) * | 2014-03-26 | 2014-11-12 | 常州大地测绘科技有限公司 | Pulse-based laser distance measuring instrument and distance measuring method thereof |
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110109085A (en) * | 2019-04-15 | 2019-08-09 | 东南大学 | Low-power consumption wide-range array type photon timing reading circuit based on bimodulus switching |
| WO2021016829A1 (en) * | 2019-07-30 | 2021-02-04 | Shenzhen Genorivision Technology Co., Ltd. | Image sensors for lidar systems |
| CN110308435A (en) * | 2019-08-05 | 2019-10-08 | 中国兵器工业集团第二一四研究所苏州研发中心 | A kind of time and intensity digital conversion circuit of Pixel-level |
| CN110308435B (en) * | 2019-08-05 | 2024-02-20 | 中国兵器工业集团第二一四研究所苏州研发中心 | Pixel-level time and intensity digital conversion circuit |
| CN111273311A (en) * | 2020-01-03 | 2020-06-12 | 电子科技大学 | Laser three-dimensional focal plane array imaging system |
| CN112903122A (en) * | 2021-01-21 | 2021-06-04 | 电子科技大学 | Laser three-dimensional focal plane reading circuit |
| CN112903122B (en) * | 2021-01-21 | 2022-01-11 | 电子科技大学 | Laser three-dimensional focal plane reading circuit |
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Application publication date: 20181002 |