A nanosecond pulse integral type measuring device

Abstract

This invention proposes a nanosecond-level pulse integration measurement device, capable of determining the arrival time of the first pulse, integrating and holding a single optical pulse signal before A / D acquisition, thus reducing the speed requirements of the A / D circuit. It includes a PIN photodiode, a photocurrent integrator, an A / D acquisition circuit, and an FPGA controller; the photocurrent integrator, A / D acquisition circuit, and FPGA controller are connected sequentially; the PIN photodiode generates a photocurrent signal representing optical power when laser signals of different widths and frequencies illuminate it; the photocurrent integrator integrates and holds the photocurrent; the A / D acquisition circuit acquires a voltage signal representing the laser pulse intensity; and the FPGA controller determines the first pulse signal, the pulse arrival time, and controls the charging and discharging of the photocurrent integrator.

Description

Technical Field

[0001] This invention relates to the field of laser signal detection technology, and in particular to a nanosecond-level pulse integration measurement device. Background Technology

[0002] Semi-active laser detection is the earliest, most mature, and most widely used guidance technology in laser guidance applications. It uses an independent laser illuminator to illuminate the target object and then receives and utilizes the diffusely reflected echo signal to achieve target localization and tracking. The width of the received laser echo pulse signal is from a few nanoseconds to hundreds of nanoseconds, and it needs to be converted into a signal that can be recognized and used by a processor to determine the position of the target object and the distance between the tracker and the target object. The conversion of the laser signal into an electrical signal and the accurate acquisition of the electrical signal are key factors affecting the accuracy of laser-guided detection.

[0003] Nanosecond-level laser pulses typically have pulse widths ranging from a few nanoseconds to hundreds of nanoseconds, and repetition frequencies generally ranging from a few Hz to a few kHz. Conventional measurement methods include direct A / D sampling and long-time integration. However, direct A / D sampling requires a very high-speed sampling chip, and its measurement accuracy is limited by the chip. Long-time integration measures the average energy over a period of time and cannot measure individual nanosecond-level pulses. Summary of the Invention

[0004] This invention proposes a nanosecond-level pulse integration measurement device that can determine the arrival time of the first pulse, integrate and hold a single optical pulse signal, and then perform A / D acquisition, thereby reducing the speed requirements of the A / D circuit.

[0005] The present invention is achieved through the following technical solution.

[0006] A nanosecond-level pulse integration measurement device includes a PIN photodiode, a photocurrent integrator, an A / D acquisition circuit, and an FPGA controller. The photocurrent integrator, A / D acquisition circuit, and FPGA controller are connected sequentially. The PIN photodiode generates a photocurrent signal representing optical power when laser signals of different widths and frequencies are irradiated onto it. The photocurrent integrator is used for integrating and holding the photocurrent. The A / D acquisition circuit is used to acquire a voltage signal representing the laser pulse intensity. The FPGA controller is used for determining the first pulse signal, determining the pulse arrival time, and controlling the charging and discharging of the photocurrent integrator.

[0007] The beneficial effects of this invention are:

[0008] 1. Unlike conventional measurement methods, including direct A / D sampling and long-term integration, this invention can determine the arrival time of the first pulse, integrate and hold a single optical pulse signal, and then perform A / D acquisition, which reduces the speed requirements of the A / D circuit and overcomes the shortcomings of conventional methods.

[0009] 2. This invention uses an integrating circuit for signal acquisition, which can determine the arrival time of the first pulse and integrate and hold a single optical pulse signal;

[0010] 3. This invention employs an integral measurement method, which can filter out the influence of background light on the accuracy of laser pulse signal acquisition;

[0011] 4. This invention uses a 16-bit A / D chip. If 1 LSB of attenuation is allowed, the maximum allowable hold time is 38 ms, which greatly reduces the requirements for the A / D acquisition chip and helps to reduce production costs.

[0012] 5. The nanosecond-level pulse integration measurement device of the present invention can achieve high guidance and detection accuracy. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the nanosecond-level pulse integration measurement device of the present invention;

[0014] Figure 2 This is a schematic diagram showing the charging and discharging timing of the integrating circuit of the present invention. Detailed Implementation

[0015] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. It should be understood that the embodiments shown and described in the drawings are merely exemplary and are intended to illustrate the principles and spirit of the present invention, and are not intended to limit the scope of the present invention.

[0016] like Figure 1 As shown in the figure, a nanosecond-level pulse integration measurement device according to this specific embodiment includes a PIN photodiode, a photocurrent integrator, an A / D acquisition circuit, and an FPGA controller; the photocurrent integrator, the A / D acquisition circuit, and the FPGA controller are connected in sequence.

[0017] The PIN photodiode is used to generate a photocurrent signal representing optical power when laser signals of different widths and frequencies are irradiated onto the PIN photodiode.

[0018] The working principle of the PIN photodiode in this embodiment is based on the semiconductor photovoltaic effect. When a reverse bias voltage is applied to the PIN photodiode, a depletion region is generated inside it. When light with energy greater than the semiconductor bandgap is incident on the device surface, electron-hole pairs are generated, and a photocurrent is formed under the action of an external electric field. Specifically, it includes highly doped P-regions, N-regions and intrinsic I-regions of the semiconductor.

[0019] The photocurrent integrator is used for integrating and holding the photocurrent. In this embodiment, the photocurrent integrator N1 is used as the integration and holding element. The specific model is the IVC102 current integrator from TI. The IVC102 integrates three integrating capacitors. S1 is an integrating switch. When S1 is closed, the photocurrent begins to be integrated on the capacitor. S2 is a reset switch. When S2 is closed, the charge on the capacitor is discharged.

[0020] like Figure 2 As shown, in this embodiment, the integration and holding of the photocurrent are performed in the following manner:

[0021] Let the integrating capacitor of the integrator be CINT, and the instantaneous photocurrent generated on the photodiode by the laser pulse be i. S (t), the photocurrent generated by the background light is i B (t), the integration window width is T. i Then, after integration, the output voltage of the integrator is:

[0022]

[0023] Since the background light is a slowly changing signal, it is assumed to be stable within the integration window, i.e.: i B (t)=I B ,but

[0024]

[0025] Within the linear measurement range of the photodiode i S (t)=R e P(t), where R e Let P(t) be the responsivity of the photodiode and P(t) be the incident light power.

[0026]

[0027] Among them, V B This represents the output voltage generated after integrating the background light, and is generally measured before receiving the laser signal. This integration measurement method can filter out the influence of background light on the accuracy of laser pulse signal acquisition.

[0028] The A / D acquisition chip acquires the voltage signal representing the intensity of the laser pulse; in this embodiment, the A / D acquisition chip is 16-bit with a reference voltage of 2.5V.

[0029] The FPGA is used for first pulse signal determination, pulse arrival time determination, and charge / discharge control of the photocurrent integrator; the specific control rules are as follows:

[0030] If the acquired signal is greater than the threshold, the arrival time of the first pulse is determined. Based on the arrival time of the first pulse and the periodic characteristics of the laser pulse, the arrival time of the next laser pulse is predicted. Before the arrival of the next laser pulse, the integrator circuit is reset. After the reset is completed, the integrator switch is closed to integrate the next laser pulse.

[0031] Those skilled in the art will recognize that the embodiments described herein are intended to help the reader understand the principles of the invention, and should be understood that the scope of protection of the invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical teachings disclosed in this invention without departing from the spirit of the invention, and these modifications and combinations are still within the scope of protection of this invention.

Claims

1. A nanosecond-level pulse integrating measurement device, characterized in that, It includes a PIN photodiode, a photocurrent integrator, an A / D acquisition circuit, and an FPGA controller; the photocurrent integrator, A / D acquisition circuit, and FPGA controller are connected sequentially; the PIN photodiode is used to generate a photocurrent signal representing optical power when laser signals of different widths and frequencies are irradiated onto the PIN photodiode; the photocurrent integrator is used for integrating and holding the photocurrent; specifically, it adopts the following method: Let the integrating capacitor of the integrator be CINT, and the instantaneous photocurrent generated by the laser pulse on the photodiode be... The photocurrent generated by the background light is The width of the integration window is Then, after integration, the output voltage of the integrator is: Since the background light is a slowly changing signal, it is assumed to be stable within the integration window, i.e.: ,but Within the linear measurement range of photodiodes ,in, The responsivity of the photodiode. For the incident light power, then in, This represents the output voltage generated after integrating the background light, which is generally measured in advance before receiving the laser signal; The A / D acquisition circuit is used to acquire the voltage signal representing the intensity of the laser pulse; the FPGA controller is used for the first pulse signal judgment, pulse arrival time judgment, and the charging and discharging control of the photocurrent integrator.

2. The nanosecond-level pulse integrating measurement device as described in claim 1, characterized in that, The PIN photodiode operates using the semiconductor photovoltaic effect. When a reverse bias voltage is applied to the PIN photodiode, a depletion region is generated inside it. When light with energy greater than the semiconductor bandgap is incident on the device surface, electron-hole pairs are generated, forming a photocurrent under the action of an external electric field.

3. A nanosecond-level pulse integrating measurement device as described in claim 1 or 2, characterized in that, The PIN photodiode includes highly doped P-regions, N-regions, and intrinsic semiconductor I-regions.

4. A nanosecond-level pulse integrating measurement device as described in claim 1 or 2, characterized in that, The photocurrent integrator uses the IVC102 current integrator from TI. The IVC102 integrates three integrating capacitors. S1 is an integrating switch. When S1 is closed, the photocurrent is integrated on the capacitor. S2 is a reset switch. When S2 is closed, the charge on the capacitor is discharged.

5. A nanosecond-level pulse integrating measurement device as described in claim 1 or 2, characterized in that, The A / D acquisition circuit is 16-bit with a reference voltage of 2.5V.

6. A nanosecond-level pulse integrating measurement device as described in claim 1 or 2, characterized in that, The FPGA control rules are as follows: If the acquired signal is greater than the threshold, the arrival time of the first pulse is determined. Based on the arrival time of the first pulse and the periodic characteristics of the laser pulse, the arrival time of the next laser pulse is predicted. Before the arrival of the next laser pulse, the integrator circuit is reset. After the reset is completed, the integrator switch is closed to integrate the next laser pulse.

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