Distance measuring light source device and laser distance measuring equipment

Abstract

The present application discloses a ranging light source device and a laser ranging device. The ranging light source device includes a signal generator, a photoelectric oscillation loop, and an adder. The signal generator is used to generate an electrical signal, and the photoelectric oscillation loop is used to feed back the oscillation signal. The adder is connected to the signal generator and the photoelectric oscillation loop and is used to add the electrical signal and the oscillation signal to obtain a driving signal, so that the photoelectric oscillation loop can generate a dual-frequency laser signal based on the driving signal. The ranging light source device of the present application can generate a dual-frequency laser signal in the MHz to GHz level. When the ranging light source device is in operation, two frequency signals are emitted simultaneously. Distance is measured by the dual-frequency laser signal, and the device has the characteristics of high measurement accuracy, fast response speed, and strong anti-interference ability. The ranging light source device of the present application is low cost and small size.

Description

Technical Field

[0001] The present application relates to the field of laser ranging technology, and in particular to a ranging light source device and a laser ranging equipment. Background Art

[0002] Conventional laser ranging systems operate at relatively low modulation frequencies, typically ranging from a few kHz to several MHz. Using microwave energy storage elements (such as dielectric cavities) or acoustic energy storage elements (such as quartz oscillators) can increase the measurement frequency, but the parasitic parameters of these elements also limit the frequency band, and noise increases with increasing frequency.

[0003] To increase the measurement frequency and reduce the signal's phase noise, a long fiber resonator with a high quality factor can be used to improve signal quality. A typical solution is to use a traditional optical fiber optical element (OEO). OEOs using long fibers as energy storage elements often utilize MZM modulation. However, MZMs are bulky and expensive, hindering the design of low-cost, compact ranging light source generators. Summary of the Invention

[0004] In order to overcome the problems existing in the above-mentioned prior art, the main purpose of this application is to provide a low-cost and small-sized ranging light source device.

[0005] In order to achieve the above objectives, this application specifically adopts the following technical solutions:

[0006] The present application provides a distance measuring light source device, which includes:

[0007] A signal generator for generating an electrical signal;

[0008] Photoelectric oscillation loop, used to feed back oscillation signals;

[0009] An adder is connected to the signal generator and the photoelectric oscillation loop, and is used to obtain a driving signal after adding the electrical signal and the oscillation signal, so that the photoelectric oscillation loop can generate a dual-frequency laser signal based on the driving signal.

[0010] In some embodiments, the signal generator is used to generate a sinusoidal wave signal with a frequency of 1 MHz to 200 MHz.

[0011] In some embodiments, the photoelectric oscillation loop includes a laser diode, a photodetector, a bandpass filter, a transmission optical fiber, a first amplifier circuit and a second amplifier circuit. The anode of the laser diode is electrically connected to the adder, the backlight output surface of the laser diode is connected to the photodetector via the transmission optical fiber, and the photodetector is electrically connected to the adder via the first amplifier circuit, the bandpass filter and the second amplifier circuit in sequence.

[0012] In some embodiments, the first amplification circuit includes a first electrical amplifier electrically connected to a line between the photodetector and the bandpass filter.

[0013] In some embodiments, the voltage gain of the first electrical amplifier is 20 dB.

[0014] In some embodiments, the second amplification circuit includes a second electrical amplifier electrically connected to a line between the bandpass filter and the adder.

[0015] In some embodiments, the voltage gain of the second electrical amplifier is 20 dB.

[0016] In some embodiments, the center frequency tuning range of the bandpass filter is 1 GHz to 2 GHz.

[0017] Accordingly, the present application also provides a laser ranging device, which includes a light source receiving device and a ranging light source device as described in any of the above embodiments, wherein the ranging light source device is used to generate a dual-frequency laser signal, and the light source receiving device is used to receive the dual-frequency laser signal and determine the measured distance based on the dual-frequency laser signal.

[0018] The distance-measuring light source device of the present application includes a signal generator, a photoelectric oscillation loop, and an adder. The signal generator is used to generate an electrical signal, and the photoelectric oscillation loop is used to feed back the oscillation signal. The adder is connected to the signal generator and the photoelectric oscillation loop and is used to add the electrical signal and the oscillation signal to obtain a driving signal, so that the photoelectric oscillation loop can generate a dual-frequency laser signal based on the driving signal. Compared with the existing technology, the distance-measuring light source device of the present application can generate a dual-frequency laser signal in the MHz to GHz level. When the distance-measuring light source device is working, the two frequency signals are emitted simultaneously. Distance is measured by the dual-frequency laser signal, which has the characteristics of high measurement accuracy, fast response speed, and strong anti-interference ability. In addition, the distance-measuring light source device of the present application is low-cost and compact. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural diagram of the prior art ranging light source device.

[0020] Figure 2 This is a schematic diagram of the structure of the ranging light source device provided in an embodiment of the present application.

[0021] Figure 3 This is a diagram showing the relationship between the laser diode light power and operating current in the ranging light source device provided in an embodiment of the present application.

[0022] Figure ID:

[0023] 1. Signal generator; 2. Adder; 3. Laser diode; 4. Photodetector; 5. Transmission optical fiber; 6. First electrical amplifier; 7. Bandpass filter; 8. Second electrical amplifier; 1', Laser diode; 2' Modulator; 3' Transmission optical fiber; 4' Photodetector; 5' Electrical amplifier; 6' Bandpass filter. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solutions and advantages of this application more clearly understood, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0025] In the description of this application, unless otherwise expressly specified or limited, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance; unless otherwise specified or explained, the term "plurality" refers to two or more, and the term "multiple" refers to two or more; the terms "connected" and "fixed" should be understood in a broad sense. For example, "connected" can mean a fixed connection, a detachable connection, an integral connection, or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0026] Laser ranging generally involves two techniques: pulse and phase. The principle of laser pulse ranging is that laser light emitted by a light source is reflected by an object and received by the ranging system, which then calculates the round-trip time. Half the product of the speed of light and time is the distance between the ranging system and the object being measured. Laser phase ranging uses frequency to modulate the amplitude of the laser light and measures the phase delay caused by the round-trip propagation of the modulated light to calculate the distance. Both methods require a stable and reliable laser light source, and most commonly, single-frequency sources are used for ranging. Dual-frequency laser ranging has many advantages over single-frequency laser ranging. While single-frequency laser sources generate signals in a time-sharing manner, dual-frequency laser sources can simultaneously generate two ranging signals at different frequencies, increasing measurement speed. Using two laser beams of different frequencies effectively reduces errors in the calculation, resulting in higher measurement accuracy. Dual-frequency laser sources can eliminate multipath interference, minimizing environmental influences on measurement results and providing strong anti-interference capabilities. Furthermore, traditional laser ranging systems operate at relatively low modulation frequencies, typically ranging from a few kilohertz (kHz) to several megahertz (MHz). In order to increase the frequency of the measurement signal, a common method is to use an optoelectronic oscillator (English full name: Optoelectronic oscillator, abbreviated as: OEO).

[0027] OEO is a microwave photonic system that has excellent performance in generating microwave signals with higher frequencies and lower phase noise. It can usually generate microwave signals with frequencies ranging from tens of GHz (gigahertz) to hundreds of GHz and high quality factors, and can also output optical and electrical signals at the same time. Figure 1 shown Figure 1 This is a typical OEO structure, which includes a laser diode (full name in English: Laser diode, abbreviated as: LD) 1', a Mach-Zehnder Modulator (full name in English: Mach-Zehnder Modulator, MZM) 2', a transmission optical fiber 3', a photoelectric detector (full name in English: Photoelectric Detector, PD) 4', an electrical amplifier 5' and a bandpass filter 3'. The continuous optical signal emitted by the laser diode 1' is modulated by the feedback electrical signal at the MZM, and the modulated signal is transmitted into the PD through a long-distance transmission optical fiber. After the PD converts the optical signal into an electrical signal, it enters the amplification and frequency selection link composed of the electrical amplifier 5' and the bandpass filter 3'. Among them, the electrical amplifier 5' provides microwave signal gain, and the bandpass filter 3' performs frequency selection operations to suppress unnecessary clutter. Finally, the microwave signal is input into the MZM to modulate the continuous optical signal emitted by the light source, forming a closed positive feedback loop. Within the OEO loop, the selected signal circulates multiple times throughout the circuit, undergoing continuous photoelectric conversion, amplification, and feedback, ultimately establishing stable microwave oscillation and generating a single-frequency microwave signal with ultra-low phase noise. In other words, conventional OEOs establish stable microwave oscillation and can generate single-frequency microwave signals with ultra-low phase noise ranging from tens to hundreds of GHz.

[0028] The aforementioned OEO structure can generally easily generate microwave signals ranging from tens to hundreds of GHz, but stably generating oscillating signals exceeding several GHz using this design approach is somewhat challenging. This application utilizes simple components to build a system that generates dual-frequency microwave signals below 10 GHz, thereby resolving existing issues such as low signal quality factor, high noise, and high cost when operating at high bandwidth and high-speed frequency sweeps.

[0029] Reference Figure 2 As shown, Figure 2Schematic diagram of the structure of the ranging light source device provided in the embodiment of the present application. The embodiment of the present application discloses a ranging light source device, which includes a signal generator 1, an adder 2 and a photoelectric oscillation loop. The signal generator 1 is used to generate an electrical signal. In this example, the signal generator 1 is used to generate a sinusoidal wave signal with a frequency of 1 MHz to 200 MHz. The adder 2 is electrically connected to the signal generator 1, and the photoelectric oscillation loop is electrically connected to the adder 2. The photoelectric oscillation loop is used to feed back an oscillation signal. The adder 2 is used to add the electrical signal generated by the signal generator 1 and the oscillation signal fed back by the photoelectric oscillation loop to obtain a driving signal, so that the photoelectric oscillation loop can generate a dual-frequency laser signal based on the driving signal.

[0030] Specifically, the optoelectronic oscillator circuit includes a laser diode 3, a photodetector 4, a bandpass filter 7, a transmission fiber 5, a first amplifier circuit, and a second amplifier circuit. The first amplifier circuit includes a first electrical amplifier 6, and the second amplifier circuit includes a second electrical amplifier 8. The laser diode 3 is electrically connected to the adder 2 on one hand, and to the photodetector 4 via the transmission fiber 5 on the other hand. In this embodiment, the anode of the laser diode 3 is electrically connected to the adder 2, and the laser diode 3 has a forward light output surface and a backlight output surface. The backlight output surface of the laser diode 3 is connected to the photodetector 4 via the transmission fiber 5. The photodetector 4 is electrically connected to the bandpass filter 7 via the first electrical amplifier 6, and the bandpass filter 7 is electrically connected to the adder 2 via the second electrical amplifier 8.

[0031] In this embodiment, the voltage gain of the first electrical amplifier 6 is 20 dB (Decibel), the voltage gain of the second electrical amplifier 8 is 20 dB, and the center frequency tuning range of the bandpass filter 7 is 1 GHz to 2 GHz.

[0032] In this embodiment, the laser diode 3 has two light output surfaces, namely the forward light output surface (primary light output surface) and the backlight output surface (secondary light output surface). The light signal output by the forward light output surface of the laser diode 3 is used for ranging. The backlight output surface of the laser diode 3 is connected to the photodetector 4 through optical fiber coupling, so that the light signal output by the backlight output surface of the laser diode 3 can be transmitted to the photodetector 4 through the transmission optical fiber 5, thereby utilizing the backlight signal of the laser diode 3 to participate in the positive feedback of the loop.

[0033] During operation, the optical signal output from the backlight output surface of laser diode 3 enters the photodetector through a certain length of optical fiber. When the photosensitive surface of photodetector 4 is illuminated by the laser modulated signal, the pn junction is reverse biased, causing photogenerated carriers to drift under the action of the electric field, generating a photocurrent in the external circuit, thereby achieving the conversion of the optical signal into an electrical signal. The photodetector integrates a pre-transimpedance amplifier that converts the photocurrent signal into a voltage signal, achieving signal conversion and initial amplification. The resulting voltage signal is first amplified by a first electrical amplifier 6 with a voltage gain of 20dB. The amplified signal is then frequency-selected by a bandpass filter 7 with a center frequency tuning range of 1GHz-2GHz. The frequency-selected signal is then further amplified by a second electrical amplifier 8 with a voltage gain of 20dB.

[0034] Filters are essential components in optoelectronic oscillation loops. Without filters, the loop exhibits numerous oscillation modes, with a mode spacing approximately equal to nL / c, where n is the refractive index of light, L is the optical loop length, and c is the speed of light. These different modes share similar starting conditions and are in a state of mode competition. Ideally, a filter with a sufficiently narrow bandwidth can filter out only one mode, achieving high-Q oscillation within the loop while suppressing the other modes. The amplified signal, which serves as feedback, is combined with a 1MHz-200MHz signal generated by a signal generator through an adder to generate the drive signal for the LD, which then generates a dual-frequency laser signal, completing the feedback loop. The long optical fiber in the loop provides energy storage, the electrical amplifier provides gain, and the bandpass filter filters noise and selects the frequency. When the loop gain exceeds the loss and phase matching conditions are met, the selected mode with a specific frequency is continuously amplified within the ring cavity, ultimately forming a stable oscillation. The frequency of the oscillating signal is primarily determined by the ring cavity length of the feedback system and the center frequency of the bandpass filter. After the signal circulates multiple times within the link, a stable dual-frequency drive signal for the LD is obtained, further enabling a stable dual-frequency laser ranging signal. By using optical fibers of varying lengths, bandpass filters with varying tuning ranges, and signal generators generating signals of varying frequencies, dual-frequency ranging signals of varying frequencies can be obtained. Because long, low-loss, high-quality-factor optical fibers are present within the loop cavity, microwave signals with ultra-low phase noise can be generated, and the phase noise of the oscillating signal is independent of the signal frequency.

[0035] This embodiment injects another electrical signal of a different frequency into the loop, adds it to the oscillating electrical signal in the loop, and then feeds it back to the loop input end. This allows the loop to simultaneously generate two photoelectric signals of different frequencies. That is, a dual-frequency ranging signal is obtained without using an MZM, which significantly reduces system cost and size, and also facilitates the integration of the entire ranging system.

[0036] The optoelectronic oscillator loop in this embodiment replaces the bulky and expensive MZM with a compact and inexpensive active amplifier, facilitating system integration and reducing costs. Furthermore, this embodiment can generate dual-frequency laser signals in the MHz to GHz range. When the ranging light source device is operating, two frequency signals are emitted simultaneously, enabling distance measurement using the dual-frequency laser signals, offering high measurement accuracy, fast response, and strong anti-interference capabilities.

[0037] Since the luminous power of the laser diode changes almost linearly with the working current of the laser diode within a certain range after the driving current of the laser diode exceeds its threshold current, such as Figure 3 As shown, the purpose of intensity modulation can be achieved by applying a modulation signal to the active amplifier device and directly driving the laser diode through current. Specifically, the LDAM modulation formula is:

[0038]

[0039] Where, Eout(t) is the output photoelectric wave, Ein(t) is the input photoelectric wave, M is the modulation depth, and s(t) is the modulation signal.

[0040] According to the photoelectric oscillation resonance theory, the oscillation frequency fosc is inversely proportional to the delay time T of the photoelectric oscillation loop: So we have:

[0041] This embodiment does not use expensive MZM devices, but instead uses small and low-cost active amplifier devices to replace the large and expensive MZM, thereby reducing costs. The backlight signal of the laser diode is used to participate in the positive feedback loop, thereby generating a dual-frequency ranging signal with good signal quality.

[0042] Correspondingly, an embodiment of the present application also discloses a laser ranging device, which includes a light source receiving device and a ranging light source device described in any of the above embodiments, the ranging light source device is used to generate a dual-frequency laser signal, and the light source receiving device is used to receive the dual-frequency laser signal and determine the measured distance based on the dual-frequency laser signal.

[0043] The laser ranging device of this embodiment does not use expensive MZM devices, but instead adopts a small and low-cost active amplifier device to replace the large and expensive MZM, thereby reducing costs. The backlight signal of the laser diode is used to participate in the positive feedback loop, thereby generating a dual-frequency ranging signal with good signal quality.

[0044] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A distance measuring light source device, characterized in that: include: A signal generator for generating an electrical signal; Photoelectric oscillation loop, used to feed back oscillation signals; An adder is connected to the signal generator and the photoelectric oscillation loop, and is used to obtain a driving signal after adding the electrical signal and the oscillation signal, so that the photoelectric oscillation loop can generate a dual-frequency laser signal based on the driving signal.

2. The distance measuring light source device according to claim 1, wherein: The signal generator is used to generate a sine wave signal with a frequency of 1 MHz to 200 MHz.

3. The distance measuring light source device according to claim 1, wherein: The photoelectric oscillation loop includes a laser diode, a photodetector, a bandpass filter, a transmission optical fiber, a first amplifier circuit and a second amplifier circuit. The anode of the laser diode is electrically connected to the adder, the backlight output surface of the laser diode is connected to the photodetector via the transmission optical fiber, and the photodetector is electrically connected to the adder via the first amplifier circuit, the bandpass filter and the second amplifier circuit in sequence.

4. The distance measuring light source device according to claim 3, characterized in that: The first amplifying circuit includes a first electrical amplifier electrically connected to a line between the photodetector and the bandpass filter.

5. The distance measuring light source device according to claim 4, characterized in that: The voltage gain of the first electrical amplifier is 20 dB.

6. The distance measuring light source device according to claim 4, characterized in that: The second amplifying circuit includes a second electric amplifier electrically connected to a line between the bandpass filter and the adder.

7. The distance measuring light source device according to claim 6, characterized in that: The voltage gain of the second electrical amplifier is 20 dB.

8. The distance measuring light source device according to claim 3, characterized in that: The center frequency tuning range of the bandpass filter is 1 GHz to 2 GHz.

9. A laser ranging device, characterized in that: It comprises a light source receiving device and a ranging light source device as claimed in any one of claims 1 to 8, wherein the ranging light source device is used to generate a dual-frequency laser signal, and the light source receiving device is used to receive the dual-frequency laser signal and determine the measured distance based on the dual-frequency laser signal.

Images