阅读说明：本技术 一种光电倍增管选通变增益系统 (Photomultiplier gating variable gain system ) 是由 周国清 赵大为 周祥 林锦纯 刘哲贤 徐超 伍宫北 于 2021-08-10 设计创作，主要内容包括：本发明公开了一种脉冲激光雷达的新型PMT选通变增益系统。包括多像素光子计数器、分压网络和AGC变增益单元、选通脉冲单元、直流高压网络、光电倍增管同步控制单元,多像素光子计数器将接收到的光信号转为电信号；分压网络将多像素光子计数器产生的电信号初步放大,一路进入AGC变增益单元,另一路进入选通脉冲单元；选通脉冲单元控制第一打拿极与光电阴极之间的电势在选通脉冲到达之前保持关闭,AGC变增益单元控制打拿极之间的电势差实现电路变增益放大；经直流高压网络到达光电倍增管同步控制单元控制PMT实现快速选通变增益的目的。本发明能够有效减小回波噪声造成的误差,扩展动态范围。(The invention discloses a novel PMT gating variable gain system of a pulse laser radar. The system comprises a multi-pixel photon counter, a voltage division network, an AGC variable gain unit, a gating pulse unit, a direct current high-voltage network and a photomultiplier synchronous control unit, wherein the multi-pixel photon counter converts a received optical signal into an electric signal; the voltage division network preliminarily amplifies the electric signals generated by the multi-pixel photon counter, one path of the electric signals enters the AGC variable gain unit, and the other path of the electric signals enters the gating pulse unit; the gating pulse unit controls the potential between the first dynode and the photoelectric cathode to be kept closed before the gating pulse arrives, and the AGC variable gain unit controls the potential difference between the dynodes to realize circuit variable gain amplification; the direct current high voltage network reaches the synchronous control unit of the photomultiplier to control the PMT to realize the purpose of fast gating and gain changing. The invention can effectively reduce the error caused by echo noise and expand the dynamic range.)

1. A novel PMT gating variable gain system of a pulse laser radar is characterized by comprising a multi-pixel photon counter (MPPC), a voltage division network, an AGC variable gain unit and a gating pulse unit;

a multi-pixel photon counter (MPPC) converts a signal received by a beam splitter of a laser emission system into an electric signal, and plays a main role in pre-collecting an optical signal before a photomultiplier receives the optical signal for gating gain change control; the voltage division network preliminarily amplifies the electric signal generated by the multi-pixel photon counter and divides the electric signal into two parts, one part enters the AGC gain-variable unit, and the other part enters the gating pulse unit; after the pulse signal is obtained, the gating pulse unit controls the electric potential between the first dynode and the photoelectric cathode to be kept closed before the gating pulse arrives, and the AGC variable gain unit controls the electric potential difference between the last-stage dynode and the penultimate dynode to realize the primary circuit variable gain amplification process; the signal reaches a photomultiplier synchronous control unit through a direct-current high-voltage network to control the photomultiplier to realize the function; the purpose of rapid gating gain change of the photomultiplier is achieved.

Technical Field

The invention relates to the field of laser measurement, in particular to a photomultiplier gating variable gain system, which is applied to the field of laser ranging.

Background

With the vigorous development of laser technology in various fields, the technology of laser ranging has already tended to be perfect and mature, wherein the pulse laser technology also tends to be mature gradually, and the application direction is also expanded. The pulse laser measurement adopts a laser as a light source, emitted laser reaches the surface of an object to be measured and is received by a distance meter after being reflected, the distance meter records the round trip time of the laser at the same time, and half of the product of the light speed and the round trip time is the distance between the distance meter and the object to be measured.

In order to detect different moments of laser echo pulses at different distances, a photomultiplier tube measurement method is generally adopted, and the photomultiplier tube distance measurement method aims to facilitate processing of laser signals received at different distances. When measuring the distance, the photomultiplier is controlled to receive the laser signal at the corresponding moment and convert the optical signal into an electrical signal, and the amplitude of the electrical signal reflects the distance of the measured object.

The current main photomultiplier tube measuring methods comprise a normally closed type measuring method and a normally open type measuring method; the normally open type photomultiplier measuring method has a simple structure, but is difficult to match the design requirements of different measuring distances; the normally closed photomultiplier measurement method needs to be controlled to be opened or closed through the outside, is usually applied to measurement in different depth ranges, but the selection of the opening time is difficult to meet the requirements of ns level or ps level, so that the control is difficult; the invention with application number 201510200729.8 discloses a research of a dual-channel time discrimination circuit, which has the defects that: it is difficult to accurately control the opening and closing of a normally closed photomultiplier, to provide selection of a gating pulse width (gate width) and a delay time, to adjust gain at different measurement distances is complicated, to saturate at a gating moment due to an excessive amplitude, and to improve and perfect the gated variable gain system.

Disclosure of Invention

The invention aims to provide a novel PMT gating variable gain system of a pulse laser radar, which can effectively avoid saturation of a photomultiplier tube caused by echo amplitude, can accurately judge gating time through a multi-pixel photon counter (MPPC), and improves the dynamic range of measurement, thereby further effectively improving the measurement precision of pulse laser ranging.

In order to realize the purpose of the invention, the following technical scheme is adopted for realizing the purpose: a novel PMT gating variable gain system of a pulse laser radar comprises a multi-pixel photon counter (MPPC), a voltage division network, an AGC variable gain unit, a gating pulse unit, a direct current high-voltage network and a photomultiplier synchronous control unit; in a multi-pixel photon counter (MPPC) and a voltage division network, a received laser signal is converted into an electric signal through the multi-pixel photon counter (MPPC), the electric signal enters the voltage division network, and the voltage division network is adjusted according to the received electric signal and transmits the electric signal to a next unit; after receiving the signal, the AGC variable gain unit generates a corresponding gain signal according to the signal intensity; the gating pulse unit receives the signal and then generates a gating signal, and the gain signal and the gating signal give corresponding control signals to the photomultiplier through the direct-current high-voltage network and the photomultiplier synchronous control unit.

The invention has the beneficial effects that: a novel PMT gating variable gain system of a pulse laser radar is adopted, a synchronous control unit of a photomultiplier comprises an external triggering photoelectric conversion technology, the gating technology is combined with the variable gain technology, and the two methods are combined to jointly acquire and determine the arrival time and the dynamic range of a laser echo, so that the dynamic range of laser ranging is improved, and gating main wave signals can be effectively controlled to be kept synchronous with the photomultiplier; on the other hand, the gating technology is combined with the variable gain technology, so that the problem that the normally closed photomultiplier is opened and closed at the gating moment is effectively solved, and the influence caused by the supersaturation problem caused by the change of the amplitude of the laser echo pulse is overcome; the invention is suitable for the detection of high-energy narrow pulse and large distance range, and can overcome the supersaturation caused by time gating and echo amplitude.

Drawings

Fig. 1 is a schematic block diagram of the present invention.

Fig. 2 is a circuit diagram of a strobe unit in the receiving system of the present invention.

Fig. 3 is a circuit diagram of an AGC variable gain unit in the receiving system of the present invention.

Fig. 4 is a waveform diagram illustrating the gating implementation principle of the receiving system of the present invention.

Detailed Description

Example (b):

the novel PMT gating variable gain system combined with the pulse laser radar in FIG. 1 comprises a multi-pixel photon counter (MPPC), a voltage division network, an AGC variable gain unit, a gating pulse unit, a direct current high voltage network and a photomultiplier synchronous control unit; in a multi-pixel photon counter (MPPC) and a voltage division network, a received laser signal is converted into an electric signal through the multi-pixel photon counter (MPPC), the electric signal enters the voltage division network, and the voltage division network adjusts and transmits the electric signal to an AGC variable gain unit and a gating pulse unit according to the received electric signal; and respectively setting inherent time delay for the AGC variable gain unit and the gating pulse unit according to the time delay of the optical pulse and the time delay of the electrical pulse. After receiving the signal, the AGC variable gain unit generates a corresponding gain signal according to the signal intensity; the gating pulse unit receives the signal and then generates a gating signal with ultrafast, high voltage and narrow pulse width, and the gain signal and the gating signal are used for synchronously controlling the signal for the photomultiplier through the direct-current high-voltage network and the photomultiplier synchronous control unit.

With reference to fig. 2, the strobe unit includes an avalanche transistor and a diode clipping circuit, the avalanche transistor generates the ultrafast step high voltage pulse, and the diode clipping circuit clips the ultrafast step high voltage pulse to output a strobe signal. Preferably, the strobe signal is a picosecond strobe signal. One output end of the voltage division network is connected with a first end of an avalanche transistor Q1, and a second end of the avalanche transistor Q1 is connected with a first end of a first diode VD 1; a second terminal of the avalanche transistor Q1 is connected with a second terminal of the second diode VD 2; the third end of the avalanche transistor Q1 is connected with the second end of the first voltage source E1, the third end of the avalanche transistor Q1 is connected with the first end of the second voltage source E2; a second terminal of the first diode VD1 is connected to a first terminal of a first voltage source E1; a first terminal of the second diode VD2 is connected to a second terminal of the second voltage source E2; a first end of the differentiator U1 is connected with the avalanche transistor Q1; the second end of the differentiator U1 is connected with the third end of the avalanche transistor;

with reference to fig. 3, the AGC variable gain unit includes a transimpedance amplifier circuit, an AGC circuit, a switch, and an output buffer circuit, the main amplifier circuit is divided into three stages of amplification to control signal gain, the AGC circuit generates a suitable switch control signal, and the AGC variable gain unit controls a potential difference between a last stage dynode and a penultimate dynode to realize a primary circuit variable gain amplification process. Preferably, the input dynamic range is increased.

With reference to fig. 3, the third terminal of the differentiator U1 is connected to the first terminal of the second operational amplifier U2; the second end of the second operational amplifier U2 is connected with the first end of the third operational amplifier U3; the second end of the third operational amplifier U3 is connected with the first end of the fourth operational amplifier U4; the second end of the fourth operational amplifier U4 is connected with the first end of the fifth operational amplifier U5; the second end of the fifth operational amplifier U5 is connected with the photomultiplier tube gating variable gain control circuit; a first end of the switch SWh1 is connected with a second end of the second operational amplifier U2; a second end of the switch SWh1 is connected with a second end of the 5 th operational amplifier U5; the third end of the switch SWh1 is connected with the first end of the AGC; a first end of the switch SWh2 is connected with a second end of the third operational amplifier U3; a second end of the switch SWh2 is connected with a second end of the 5 th operational amplifier U5; the third end of the switch SWh2 is connected with the second end of the AGC; a first end of the switch SWh3 is connected with a second end of the third operational amplifier U4; a second end of the switch SWh3 is connected with a second end of the 5 th operational amplifier U5; the third end of the switch SWh3 is connected with the second end of the AGC;

referring to fig. 4, a is a system off state, when the multi-pixel photon counter (MPPC) does not receive the laser signal, the photo-cathode potential is higher than the beat level potential. And a potential difference exists between the photocathode and the beating stage, and the system is in a closed state at the moment. And b is a system gating state, the multi-pixel photon counter receives a laser signal and transmits the signal to a voltage division network for primary processing, the voltage division network processes and divides the signal into two paths of electric pulse signals to trigger gating and gain variation, the electric pulse signals are loaded on a control circuit of the photomultiplier through a voltage generated by a direct-current high-voltage network, the potential of the photocathode is superposed with a pulse negative high voltage, and the photomultiplier is in a conducting state when the potential of the photocathode is lower than a beating level.

Referring to fig. 4, according to theoretical analysis and experimental verification, a schematic diagram of off and on state waveforms in a novel PMT gated variable gain system of a pulsed lidar is shown in fig. 4, where V1(t) is a photocathode potential waveform, and V2(t) is a beat-to-beat level potential. When the system is in the closed state, V1(t) < V2(t) shows that the photomultiplier tube is in the closed interval. V1(t) > V2(t) the photomultiplier is in the gating interval.

When the target laser signal is received, the oscilloscope detects whether the waveform of the target signal can be detected, and when the received signal generates a corresponding waveform in the gating interval, the system is considered to be effective.