A multifunctional tunable laser system based on VCSEL

Abstract

The invention discloses a multifunctional tunable laser system based on VCSEL, comprising: an emitting module comprising a vertical cavity surface emitting laser; a lens module comprising a first lens module and a second lens module; the second lens module comprising a micro-optical adjustable optical power distributor; a receiving module for collecting and applying a light beam output by the micro-optical adjustable optical power distributor; a control module for controlling the micro-optical adjustable optical power distributor to change the optical power of each output end of the micro-optical adjustable optical power distributor; the micro-optical adjustable optical power distributor comprises a half-wave plate and a rotating mechanism for controlling the rotation of the half-wave plate; the control module comprises a control unit and an external monitoring module; the external monitoring module is used for acquiring external data related to optical power distribution and sending the external data to the control unit; the control unit sends a control signal to the rotating mechanism; the rotating mechanism is used for adjusting the angle between the optical axis of the half-wave plate and the vibration direction of the input light.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser radar, and in particular relates to a multifunctional tunable laser system based on VCSEL. Background Art

[0002] Laser systems are currently mainly used for distance measurement, image scanning, pollution detection, information processing, and three-dimensional surface mapping. As an important electro-optical system, it is currently being developed in the fields of drones and automatic car driving. The laser system mainly includes the laser transmitting module, lens module, receiving module, signal processing module, etc. In terms of working principle, the laser system emits a light beam through the laser stimulated emission, and the light beam passes through the lens system to hit the target object, and then reflects and feeds back to the receiving module. The propagation distance between the receiving end, the transmitting end and the target object is measured, and the energy strength of the light reflected from the surface of the target object, the amplitude, phase, frequency, and speed of the emitted light are analyzed, so as to analyze the precise information of the target object.

[0003] The transmitting module includes a laser transmitter. Semiconductor lasers use semiconductor materials as gain media, and have the characteristics of high-efficiency photoelectric conversion, low cost, and reliable use. According to the laser projection classification, the semiconductor laser emission part is mainly divided into two types, edge-emitting lasers (EEL) and surface-emitting lasers. Compared with edge-emitting lasers, vertical cavity surface lasers (VCSELs) have the advantages of simple structure, stable wavelength, small size, no cavity threshold damage, higher beam quality, high coupling efficiency, and can be made into one-dimensional or two-dimensional arrays, easy to adapt to coupling with optical fibers, can be changed at any time according to different needs, single longitudinal mode, inexpensive, and low power consumption. With the development of time, the current vertical cavity surface laser (VCSEL) can also participate in tuning.

[0004] Compared with traditional semiconductor lasers (LD), the vertical cavity surface laser (VCSEL) has a small divergence angle of the output beam and a circular output spot, which simplifies the coupling link. Its high reliability and wide operating temperature range can better meet the needs of modern industrial lasers. In addition, its electro-optical conversion efficiency is much higher than that of all similar lasers. The required driving voltage and current requirements are low, and single-channel and parallel optical transmission and optical interconnection can be performed. The advantages of high output power, high energy utilization, simple packaging, low cost, and long life have made it recognized and praised by a large number of people. The only drawback is that the effective detection distance of the vertical cavity surface laser (VCSEL) is relatively small, and multi-level optical amplification is required to meet daily use needs.

[0005] In laser systems, how to improve the signal-to-noise ratio of the system beam, filter out stray light, and how to design the structure of the laser system to meet daily production and life are the key points we need to explore. Summary of the invention

[0006] Purpose of the invention: In order to solve the problem that the existing laser system based on vertical cavity surface laser cannot meet the daily use, the present invention proposes a multifunctional tunable laser system based on VCSEL, which can improve the signal-to-noise ratio of the output signal while excluding the interference of background clutter signals such as fluorescence signals, natural scattered light signals, and light signals oscillating inside the structure as much as possible.

[0007] Technical solution: A multifunctional tunable laser system based on VCSEL, comprising: a transmitting module, a lens module, a receiving module and a control module; the transmitting module is used to transmit laser light, which includes a vertical cavity surface emitting laser; the lens module includes a first lens module for emitting laser light to a target object and a second lens module for receiving a reflected light beam from the target object; the second lens module includes a micro-optical adjustable optical power distributor; the receiving module is used to collect and apply the light beam output by the micro-optical adjustable optical power distributor; the control module is used to control the micro-optical adjustable optical power distributor to change the optical power of each output end of the micro-optical adjustable optical power distributor; wherein the micro-optical adjustable optical power distributor includes a half-wave plate and a rotating mechanism for controlling the rotation of the half-wave plate; wherein the control module includes a control unit and an external monitoring module; the external monitoring module is used to obtain external data related to optical power distribution and send the external data to the control unit; the control unit is used to compare the external data with a preset condition and send a control signal to the rotating mechanism according to the comparison result; the rotating mechanism is used to adjust the angle between the optical axis of the half-wave plate and the vibration direction of the input light according to the control signal to achieve optical power distribution.

[0008] Furthermore, the first lens module includes a beam expander, a collimating lens, a reflector and a first resonant cavity in sequence according to the optical path.

[0009] Furthermore, the second lens module includes a second resonant cavity, a Fourier transform lens, a narrowband filter and a micro-optical adjustable optical power distributor in sequence according to the optical path.

[0010] Furthermore, the vertical cavity surface emitting laser is a bottom-emitting vertical cavity surface emitting laser.

[0011] Furthermore, the external monitoring module is a speed monitoring module, which is used to obtain the driving speed of the vehicle; when the driving speed of the vehicle exceeds a preset condition, the control unit sends a control signal to the rotating mechanism so that different vehicle speeds correspond to different optical power distributions.

[0012] Furthermore, the receiving module includes a distance measuring module and an image scanning module; the distance measuring module is connected to one output end of the micro-optical adjustable optical power distributor; and the image scanning module is connected to another output end of the micro-optical adjustable optical power distributor.

[0013] Furthermore, the angle between the optical axis of the half-wave plate and the vibration direction of the input light is set to θ, the incident light intensity is I0, and the light intensity received by the ranging module is recorded as I1=I0*cos 2 θ, the light intensity received by the image scanning module is recorded as I2 = I0*sin 2 θ;

[0014] When the speed monitoring module obtains the vehicle speed v 车 =0, θ=45°;

[0015] When the speed monitoring module obtains the vehicle speed v 车 Satisfy 0km / h<v 车 When ≤40km / h, the rotating mechanism controls the half-wave plate to rotate to increase θ, satisfying θ=45+0.375v 车 , until θ = 60° and then stop;

[0016] When the speed monitoring module obtains the vehicle speed v 车 Meet 40km / h<v 车 When ≤120km / h, the rotating mechanism controls the half-wave plate to rotate to reduce θ, satisfying θ=75-0.375v 车 , until θ = 30° and then stop;

[0017] When the speed monitoring module obtains the vehicle speed v 车 When the speed exceeds 120 km / h, the rotating mechanism controls the half-wave plate to rotate so that θ=0°.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0019] (1) The present invention adopts a narrow-band filter to control the light beam to only receive light transmission within a certain range, while also reducing the influence of other external background clutter signals on the information transmitted by the system, thereby improving the signal-to-noise ratio of the system, ensuring the accuracy of the detection results, and improving the stability of the structural operation;

[0020] (2) The present invention utilizes components such as a resonant cavity and a Fourier transform lens to ensure the stability and high power of the light beam output, and adjusts the power distribution through a micro-optical adjustable optical power divider, which in a sense flexibly realizes the focused selection of system functions. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the basic schematic diagram of the laser system and the target object (obstacle) during the vehicle's autonomous driving;

[0022] Figure 2 is a distribution diagram of design elements of the present invention;

[0023] Figure 3 It is a simplified internal diagram of a micro-optical adjustable optical power divider;

[0024] Figure 4 This is the optical power allocation trigger condition of Example 1. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is now further described in conjunction with the accompanying drawings.

[0026] A multifunctional tunable laser system based on VCSEL of the present invention comprises: a transmitting module 1, a lens module, a receiving module 11 and a digital control circuit 9.

[0027] The transmitting module 1 of the present invention mainly includes a vertical cavity surface emitting laser (VCSEL), which can be designed into a one-dimensional or two-dimensional array to meet a specific use background. The vertical cavity surface emitting laser (VCSEL) of the present invention is a bottom-emitting vertical cavity surface emitting laser (a semiconductor laser that emits laser light perpendicular to the substrate surface), and its main structure consists of an active layer, a distributed Bragg reflector (DBR) and a substrate. The Bragg reflector (DBR) has a high reflectivity, and the laser system is stimulated to radiate when powered. The blocking of the active layer limits the loss of carriers. By adjusting the length of the resonant cavity inside the laser, the laser is oscillated to form an emitted laser under the continuous reflection of the Bragg reflector. Compared with traditional lasers, the bottom-emitting vertical cavity surface emitting laser has better beam quality, does not need to use a complex and expensive beam shaping system, and is easy to be integrated in two dimensions in actual production. Compared with other members in the semiconductor laser, the vertical cavity surface emitting laser (VCSEL) can obtain a larger relaxation oscillation frequency, so that high-frequency modulation can be performed, and the luminous efficiency is also much higher than other LD lasers. Moreover, VCSEL does not require high driving voltage and current, and can be realized even if it is very small. In the case of single-mode fiber output, the reduction of the cavity makes its spontaneous radiation factor several orders of magnitude higher than that of ordinary lasers, greatly improving its overall physical properties. Compared with the high-priced traditional LD ​​laser, its manufacturing process is similar to that of LED, so it is inexpensive and suitable for large-scale low-cost manufacturing. In the field of parallel optical transmission and parallel optical interconnection, it currently also has broad development prospects, with more outstanding heat dissipation performance, a wide operating temperature range, and a long life.

[0028] The vertical cavity surface laser (VCSEL) of the present invention is based on GaAs material and is commonly used in the near-infrared band. The present invention selects an 850nm vertical cavity surface laser (VCSEL) as the emission source, which has the advantages of strong anti-interference ability, convenient high-density integration, tunability, and less loss of beam energy by superimposing low frequency on high frequency and emitting it in the form of radio frequency signal. Compared with visible light, it has stronger penetration and can cope with road conditions scanning in severe weather such as heavy fog, rain, sandstorm, etc. At the same time, it can realize its application in the field of laser radar in smart car driving within a large temperature range.

[0029] See also Figure 2 The lens module of the present invention mainly includes a beam expander 2, a collimating lens 3, a reflector 4, a resonant cavity 5, a Fourier transform lens 7, a narrowband filter 8 and a micro-optical adjustable optical power divider 10; the positions of the optical components are further explained in conjunction with the optical path. The transmitting module emits a high-frequency and stable radio frequency light signal with uniform light beam distribution and uniform light spot energy. The light signal propagates in the lens group part of the structure until it hits the target object and then reflects. The reflector of the present invention uses two pieces, which are placed up and down to make the incident light parallel to the outgoing light. The resonant cavity 5 of the present invention includes a first resonant cavity and a second resonant cavity.

[0030] Under external power supply, the vertical cavity surface laser (VCSEL) emits stimulated radiation inside, and under the oscillation tuning of the p and n pole Bragg reflectors, a high-frequency and stable output laser is obtained;

[0031] The outgoing laser is expanded by the beam expander 2, so that the divergence range of the outgoing laser is increased;

[0032] The output light beam of the beam expander passes through the collimating lens 3, which can make the light beam emit stably in one direction.

[0033] The output light beam of the collimating lens 3 is incident on the first resonant cavity after two reflections. The first resonant cavity is used to achieve optical path coupling and increase the optical power so that the light beam can propagate farther without a large energy loss, that is, the incident light beam is strengthened.

[0034] The output light beam of the first resonant cavity hits the receiving target object. The narrow-band filter here is used to reduce the influence of natural light on the structural parameters and improve the actual signal-to-noise ratio.

[0035] After the light beam output by the narrowband filter hits the receiving target, the light beam returns to the second resonant cavity, where it is strengthened to reduce the optical power loss. The wavelength of the light beam reflected by the target is consistent with the wavelength of the laser emitted by the stimulated radiation of the transmitting module.

[0036] The light beam outputted by the second resonant cavity is incident on the Fourier transform lens 7. The Fourier transform lens 7 is installed to gather the reflected light beam, ensure the concentration of the light beam energy, and reduce the dispersion of signal energy.

[0037] The output light beam of the Fourier transform lens 7 passes through the narrowband filter 8 to obtain a relatively pure light beam, which is then incident on the micro-optical adjustable optical power distributor 10. The narrowband filter 8 here is to selectively reduce the interference of solar scattered light, fluorescent signals, etc. on the effective light signal, better filter the clutter signal, and improve the accuracy of the feedback data.

[0038] When the light beam passes through the micro-optical adjustable optical power distributor 10, the digital control circuit 9 sends a digital control electrical signal to the micro-optical adjustable optical power distributor 10 to control the distribution of optical power on each optical path.

[0039] The light beam output by the micro-optical adjustable optical power divider 10 is collected by the receiving module 11. According to the distribution of optical power, the light beam output by the micro-optical adjustable optical power divider can realize multiple functions. For example, the light beam can be converted into an electrical signal through an external detection circuit to participate in the operation of the self-driving car. In order to reduce the transmission loss of the light beam in each component, an optical power amplifier can be added at the output end of the lens module, that is, the output end of the micro-optical adjustable optical power divider.

[0040] like Figure 3 As shown, the micro-optical adjustable optical power distributor 10 of the present invention mainly includes a single-fiber collimator 101 at the input end, a half-wave plate 102, a birefringent crystal 103, a roof prism 104, a dual-fiber collimator 105 at the output end, and a rotating mechanism (in Figure 3 The light beam enters from the single fiber collimator 101 at the input end, adjusts the polarization state of the input end through the half-wave plate 102, and is finally output after split coupling.

[0041] The receiving module 11 of the present invention is used to collect the light beam output by the lens module for subsequent circuit operation, such as converting the optical signal into an electrical signal to participate in the operation of the autonomous driving vehicle. The participation here includes but is not limited to participating in ranging or participating in image scanning.

[0042] The digital control circuit 9 of the present invention comprises a control unit and an external monitoring module; the external monitoring module and the rotating mechanism are both connected to the control unit.

[0043] The external monitoring module is used to obtain external data related to optical power distribution. The control unit receives the external data obtained by the external monitoring module, compares the external data with the preset conditions, and according to the comparison result, the control unit sends an electrical signal to the rotating mechanism to make the rotating mechanism rotate the half-wave plate, adjust the angle between the optical axis of the half-wave plate and the vibration direction of the input light, thereby adjusting the optical power distribution of the micro-optical adjustable optical power distributor 10. The present invention can also control the optical power distribution of the micro-optical adjustable optical power distributor without using the digital control circuit 9, and can directly use manual modulation.

[0044] Embodiment 1:

[0045] Figure 1 The schematic diagram of applying the laser system of the present invention to the automatic driving of a vehicle is shown. The transmitting module of the laser system transmits the laser, and the laser is reflected after encountering the target object (obstacle). The reflected light beam will be collected by the receiving module of the laser system for the next step of analysis and processing. In this embodiment, the light signal collected by the receiving module of the laser system will be used for ranging and image scanning. The external monitoring module of this embodiment is a speed monitoring module, which is used to obtain the driving speed of the vehicle. When its speed exceeds the preset speed threshold condition, the control unit sends an electrical signal to the rotating mechanism to ensure that the signals for ranging and image scanning are reasonably allocated under different vehicle speed conditions.

[0046] In this embodiment, the output ports of the micro-optical adjustable optical power divider are set to two, the angle between the optical axis of the half-wave plate and the vibration direction of the input light is set to θ, the incident light intensity is I0, and the light intensities of the two ports at the output end are respectively the ranging port I1 = I0*cos 2 θ, image scanning port I2 = I0*sin 2 θ, the default initial distribution ratio is 50:50 when the vehicle is stationary, and the angle of θ is 45°.

[0047] like Figure 4 As shown, when the vehicle is at low speed (0km / h<v 车 ≤40km / h), a higher proportion of light signals are used for image scanning, and the angle θ is set to change with the speed v 车 The boost gradually increases, and both satisfy θ=45+0.375v 车 , until the angle reaches 60°, the vehicle is continuously scanned at close range with high precision, and a small part is used for distance measurement; when the vehicle maintains high speed (40km / h<v 车 ≤120km / h), the setting angle θ changes with the speed v 车 The boost gradually decreases, and both satisfy θ=75-0.375v 车, until the angle is 30°, most of the light signal is used for ranging to ensure the distance and accuracy of ranging, and a small part is used for far-field low-precision image scanning; when the vehicle speed v 车 When the speed exceeds 120 km / h, θ changes suddenly and becomes 0° directly. All light signals are used for distance measurement to achieve distance control and timely avoid obstacles ahead.

Claims

1. A multifunctional tunable laser system based on VCSEL, characterized in that: include: Transmitting module, lens module, receiving module and control module; The transmitting module is used to transmit laser light, and includes a vertical cavity surface emitting laser; The lens module comprises a first lens module for emitting laser light toward a target object and a second lens module for receiving a light beam reflected by the target object; the second lens module comprises a micro-optical adjustable light power distributor; The receiving module is used to collect and apply the light beam output by the micro-optical adjustable optical power distributor; The control module is used to control the micro-optical adjustable optical power distributor to change the optical power of each output end of the micro-optical adjustable optical power distributor; Wherein, the micro-optical adjustable optical power distributor comprises a half-wave plate and a rotating mechanism for controlling the rotation of the half-wave plate; Wherein, the control module includes a control unit and an external monitoring module; The external monitoring module is used to obtain external data related to optical power distribution and send the external data to the control unit; The control unit is used to compare the external data with the preset conditions and send a control signal to the rotating mechanism according to the comparison result; The rotating mechanism is used to adjust the angle between the optical axis of the half-wave plate and the vibration direction of the input light according to the control signal to achieve optical power distribution; The second lens module includes a second resonant cavity, a Fourier transform lens, a narrowband filter and a micro-optical adjustable optical power distributor in sequence according to the optical path.

2. A multifunctional tunable laser system based on VCSEL according to claim 1, characterized in that: The first lens module includes a beam expander, a collimating lens, a reflector and a first resonant cavity in sequence according to the optical path.

3. The multifunctional tunable laser system based on VCSEL according to claim 1, characterized in that: The vertical cavity surface emitting laser is a bottom-emitting vertical cavity surface emitting laser.

4. The multifunctional tunable laser system based on VCSEL according to claim 1, characterized in that: The external monitoring module is a speed monitoring module, and the speed monitoring module is used to obtain the driving speed of the vehicle; When the vehicle's running speed exceeds a preset condition, the control unit sends a control signal to the rotating mechanism so that different vehicle speeds correspond to different optical power distributions.

5. The multifunctional tunable laser system based on VCSEL according to claim 4, characterized in that: The receiving module includes a distance measuring module and an image scanning module; The distance measurement module is connected to an output end of a micro-optical adjustable optical power distributor; The image scanning module is connected to another output end of the micro-optical adjustable light power distributor.

6. The multifunctional tunable laser system based on VCSEL according to claim 5, characterized in that: Set the angle between the half-wave plate optical axis and the input light vibration direction to θ, the incident light intensity to I0, and the light intensity received by the ranging module to I1 = I0*cos 2 θ, the light intensity received by the image scanning module is recorded as I2 = I0*sin 2 θ; When the speed monitoring module obtains the vehicle speed v 车 =0, θ=45°; When the speed monitoring module obtains the vehicle speed v 车 Satisfy 0km / h<v 车 When ≤40km / h, the rotating mechanism controls the half-wave plate to rotate to increase θ, satisfying θ=45+0.375v 车 , until θ = 60° and then stop; When the speed monitoring module obtains the vehicle speed v 车 Meet 40km / h<v 车 When ≤120km / h, the rotating mechanism controls the half-wave plate to rotate to reduce θ, satisfying θ=75-0.375v 车 , until θ = 30° and then stop; When the speed monitoring module obtains the vehicle speed v 车 When the speed exceeds 120 km / h, the rotating mechanism controls the half-wave plate to rotate so that θ=0°.

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