All-solid-state laser radar based on analog optical phased array

Abstract

The invention discloses an all-solid-state laser radar based on an analog optical phased array, which comprises a transmitting assembly and a receiving assembly, and is characterized in that the transmitting assembly comprises a transmitting chip and a scanning chip, and the receiving assembly comprises a receiving chip; wherein the scanning chip comprises a simulation optical phased array module, and the simulation optical phased array module comprises a coupler which is used for coupling a transmitting chip and guiding light emitted by the transmitting chip into the simulation optical phased array module; the optical splitter splits the guided light into a plurality of beams of parallel light, and the parallel light enters different optical waveguides for transmission; an optical waveguide that transmits light to the phase modulator; the phase modulator is used for adjusting the phase of the light to form light path deflection; and the transmitting antenna is connected with the phase modulator, and the light subjected to phase modulation in the phase modulator is emitted outwards through the transmitting antenna. According to the laser radar, the optical path is converted through the optical phased array, and the laser radar which is high in integration level, low in cost, high in stability and large in field angle is achieved based on the novel high-integration-level receiving chip.

Description

Technical Field

[0001] This application relates to the field of laser scanning, and more particularly to an all-solid-state lidar based on an analog optical phased array. Background Technology

[0002] Lidar (light detection and ranging) is a 3D ranging device that measures the distance to objects in a scene by utilizing the time of flight (ToF) of a light signal from emission, reflection, and reception. Lidar is primarily used in consumer electronics such as smartphones, tablets, and robotic vacuum cleaners, as well as in automation fields such as machine vision, autonomous driving, surveillance, and drones.

[0003] The core components of a lidar system can be divided into three parts: the light source emitting component, the light source receiving component, and the signal processing center. The lidar's light source emitting component emits 1D or 2D light pulses into the scene to cover a certain field of view. The receiving chip in the light source receiving component receives the pulse echoes reflected back from the target object. The signal processing center is responsible for recording the flight time of each received light signal and generating histograms and point cloud maps, thereby achieving 2D distance detection. Ideally, a lidar needs to cover 360 degrees of horizontal and vertical distance information; therefore, it is generally required that the lidar can emit and receive light over a wide angle.

[0004] Traditional mechanical LiDAR typically uses a vertically aligned array of light sources, driven by a motor system to rotate horizontally, achieving 360-degree two-dimensional scanning. However, mechanical LiDAR often requires multiple discrete components, leading to complex optical path debugging and assembly, low production efficiency, and high component costs, thus reducing its competitiveness. The high-frequency rotation of the motor and the complex mechanical structure also result in a mean time between failures (MTBF) of only 1000-3000 hours, falling short of the minimum requirement of 13000 hours. This aging issue of the motor system further reduces the reliability of mechanical LiDAR. Furthermore, when applied to autonomous driving in automobiles, mechanical LiDAR needs to be positioned at the highest point of the vehicle to avoid obstruction. However, placing mechanical LiDAR and reinforcing structures on the roof can affect the vehicle's center of gravity, impacting driving safety. The protruding LiDAR is also more susceptible to damage, and its placement on the roof significantly affects the vehicle's styling.

[0005] To overcome the problems of mechanical LiDAR, hybrid solid-state LiDAR has been proposed in recent years, employing methods such as rotating mirror scanning, prism scanning, or galvanometer scanning based on microelectromechanical systems (MEMS). The most representative of these is the MEMS-based galvanometer scanning scheme. A MEMS galvanometer is a miniature integrated system that utilizes microfabrication technology to mass-produce channels, holes, cantilever arms, films, cavities, and other micromechanical structures on a chip, and then integrates them with corresponding circuits using integrated circuit manufacturing technology. Light deflection on the miniature structure is achieved by controlling the rotation of the rotating arm. Compared to mechanical LiDAR, hybrid solid-state MEMS LiDAR significantly reduces cost and size. However, to achieve sufficient light deflection angle and accuracy, the weight of the mirror on the MEMS system has a significant impact on the galvanometer cantilever arm, thus affecting the system's reliability and severely limiting its application scenarios.

[0006] On the other hand, the rotating mirror scanning scheme is a high-speed polygon scanner, consisting of a motor and a polyhedron with multiple mirrors, also known as a multi-faceted laser motor. By rotating the motor, the multi-faceted mirrors can rotate at high speed, thus achieving beam scanning. It has wide applications in optical imaging, thin film inspection, materials processing, laser printing plate making, and printed circuit board inspection. The rotating mirror features a large scanning angle, high scanning frequency, and large effective optical aperture, meeting the performance requirements of lidar for a large field of view and high frame rate, and is therefore used in lidar. However, the rotating mirror is often quite large, making further miniaturization and cost reduction difficult.

[0007] In summary, both the rotating mirror solution and the MEMS solution have questionable reliability, stability, and integration due to the presence of internal micro-mechanical structures. Summary of the Invention

[0008] To address one of the technical problems existing in the prior art, this application provides an all-solid-state lidar based on a simulated optical phased array, which utilizes the simulated optical phased array to achieve a large field of view.

[0009] According to a first aspect of this application, an all-solid-state lidar based on an analog optical phased array includes a transmitting component and a receiving component. The transmitting component includes a transmitting chip and a scanning chip, and the receiving component includes a receiving chip. The scanning chip includes an analog optical phased array module, which includes: a coupler for coupling the transmitting chip and guiding light emitted by the transmitting chip into the analog optical phased array module; a beam splitter for splitting the guided light into multiple parallel beams that enter different optical waveguides for transmission; an optical waveguide for transmitting light to a phase modulator; a phase modulator for adjusting the phase of the light to form an optical path deflection; and a transmitting antenna connected to the phase modulator, through which the phase-modulated light is emitted outward.

[0010] According to the all-solid-state lidar based on an analog optical phased array provided in the first aspect of this application, the analog optical phased array module includes a calibration module, which is connected to the phase tuner.

[0011] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the emitting component includes an emitting driver and a scanning driver, the emitting driver being connected to the emitting chip and the scanning driver being connected to the scanning chip.

[0012] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the lidar further includes a control chip, which is connected to the transmit driver, the scan driver and the receive chip respectively.

[0013] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the receiving chip includes a SPAD chip or an APD chip.

[0014] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the transmitting chip includes an EEL chip or a VCSEL chip.

[0015] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the transmitting component is provided with two or more scanning chips.

[0016] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the transmitting antenna is configured as a 1D array or a 2D array.

[0017] According to the all-solid-state lidar based on an analog optical phased array provided in the first aspect of this application, the transmitting component includes an optical diffuser.

[0018] According to the all-solid-state lidar based on analog optical phased array provided in the first aspect of this application, the receiving component includes a lens group.

[0019] This application has the following beneficial effects:

[0020] This application discloses an all-solid-state lidar based on analog optical phased arrays. Through optical phased array technology, it utilizes electro-optic or thermo-optic phase modulation to change the refractive index of materials under the influence of electric fields or thermal energy, thereby changing the phase of light. It also uses methods such as light interference or polarization to transform the light path. Simultaneously, based on a novel highly integrated receiver chip, it realizes a lidar with high integration, low cost, high stability, and a large field of view.

[0021] Other features and advantages of this application will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the application. The objectives and other advantages of this application may be realized and obtained by means of the structures particularly pointed out in the description, claims and drawings. Attached Figure Description

[0022] To more clearly illustrate the technical solution of this application, the following description will be provided in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of this application and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings:

[0023] Figure 1 This is a block diagram of the all-solid-state lidar provided in this application;

[0024] Figure 2 This is a block diagram of the analog optical phased array provided in this application;

[0025] Figure 3 This is a structural diagram of the transmitting antenna using a 1D array arrangement;

[0026] Figure 4 This is a structural diagram of the transmitting antenna using a 2D array arrangement;

[0027] Figure 5 This is a schematic diagram of 1D scanning using a long strip of light.

[0028] Figure 6 This is a schematic diagram of 2D scanning using a single-point light spot;

[0029] Figure 7 This is a schematic diagram of 2D scanning using a long strip of light.

[0030] Explanation of icon numbers:

[0031] Transmitter 100, transmitter chip 110, scanning chip 120, coupler 121, beam splitter 122, optical waveguide 123, phase modulator 124, transmitting antenna 125, calibration module 126, transmit driver 130, scanning driver 140, receiver 200, receiver chip 210, control chip 300, single-point spot 410, long strip spot 420. Detailed Implementation

[0032] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0033] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0034] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0035] The following is in conjunction with the appendix Figure 1 To be continued Figure 7 The provided embodiments further illustrate the all-solid-state lidar based on analog optical phased array proposed in this application.

[0036] Please refer to Figure 1This application provides an all-solid-state lidar based on an analog optical phased array, including a transmitting component 100 and a receiving component 200. The light signal emitted by the transmitting component 100 is reflected back by an object and received by the receiving component 200, which calculates the time-of-flight (ToF) of the light signal to measure the distance to objects in the scene. The transmitting component 100 includes a transmitting chip 110 and a scanning chip 120, as well as a transmitting driver 130 for driving the transmitting chip 110 and a scanning driver 140 for driving the scanning chip 120. The transmitting driver 130 is connected to the transmitting chip 110, and the scanning driver 140 is connected to the scanning chip 120. The transmitting chip 110 can be a semiconductor laser chip, such as an edge-emitting laser (EEL) or a single-mode vertical-cavity surface-emitting laser (VCSEL). This application uses a single-mode VCSEL as an example to illustrate the system scheme, but it is not limited to this type of chip. The scanning chip 120 can be an optical device based on an integrated optical platform, such as a silicon photonic device based on a silicon / silicon nitride (Si / SiN) platform, or a photonic device based on a lithium niobate thin film (LNOI) platform. Since lithium niobate thin films have excellent electro-optic effects, they are highly efficient and reliable. This application uses an optical phased array (OPA) based on lithium niobate thin film as an example to illustrate the system scheme, but it is not limited to this type of chip. The emitter driver 130 and the scan driver 140 are configured to control the emitter chip 110 and the scan chip 120, respectively. The receiving component 200 includes a receiving chip 210. In some embodiments, the receiving chip 210 can be a chip developed based on an avalanche photodiode (APD); in other embodiments, the receiving chip 210 can also be a chip developed based on a single-photon avalanche diode (SPAD). The SPAD receiving chip uses 3D stacking technology of CMOS (Complementary Metal-Oxide Semiconductor) process and is equipped with an application-specific integrated circuit (ASIC) to form a highly customized integrated chip. This application uses a SPAD chip that uses near-infrared (NIR) band sensing as an example to illustrate the system scheme, but it is not limited to this type of chip. In addition, the lidar also includes a control chip 300, which is connected to the transmit driver 130, the scan driver 140 and the receiving chip 210 respectively. The function of the control chip 300 is to exchange status information between the transmit driver 130, the scan driver 140 and the receiving chip 210, so that the lidar operates in the correct state.Meanwhile, when the transmitting chip 110 emits a light signal, a synchronization signal is sent to the receiving chip 210, thereby achieving a more accurate ranging accuracy. This synchronization signal can be the signal of the transmitting component 100 itself, or it can be the synchronization signal generated by the photodetector reserved in the receiving chip 210.

[0037] like Figure 2 As shown, in some embodiments of this application, the scanning chip 120 includes an analog optical phased array module (analog OPA), which includes a coupler 121, a beam splitter 122, an optical waveguide 123, a phase modulator 124, and a transmitting antenna 125. The coupler 121 couples the transmitting chip 110 and guides the light emitted by the transmitting chip 110 into the analog optical phased array module. The beam splitter 122 splits the introduced light into multiple parallel beams, which are then transported through different optical waveguides 123. The optical waveguides 123 transport the light to the phase modulator 124. The phase modulator 124 adjusts the phase of the light, using light diffraction to form a light path deflection. The transmitting antenna 125 is connected to the phase modulator 124, and the phase-modulated light within the phase modulator 124 is emitted outward through the transmitting antenna 125. The analog optical phased array module can achieve scanning of any light spot within the field of view (FoV) by precisely controlling the voltage. The scanning accuracy depends on the control accuracy of the driving voltage provided by the scanning driver 140. Meanwhile, in some embodiments, the simulated optical phased array module also includes a calibration module 126, which is connected to the phase tuner 124. The calibration module 126 is used to enhance the accuracy of the phase tuner 124, so that the diffraction efficiency of light is maximized and light loss is reduced.

[0038] Furthermore, the emitting chip 110 employs either a side-emitting laser or a single-mode vertical-cavity surface-emitting laser, both of which facilitate miniaturization. However, both also face heat dissipation problems due to low electro-optical efficiency. Therefore, maintaining good heat dissipation while emitting high power is a critical issue. Taking ToF technology based on SPAD chips as an example, multiple emissions are required to improve the signal-to-noise ratio. Therefore, when the detection distance is long, the emission power needs to be high, and the number of emissions also increases significantly. Therefore, this application proposes an all-solid-state lidar based on an analog optical phased array. The signal light emitted by the emitting chip 110 is guided into the scanning chip 120 via optical fiber. Then, the coupler 121, beam splitter 122, and optical waveguide 123 at the coupling port complete the transmission of the corresponding optical channels, thereby forming effective optical manipulation. This can significantly reduce the number of light sources to 2-3 groups, thereby significantly reducing the use of the emitting chip 110, reducing heat generation, and incidentally reducing procurement costs. In addition, during scanning, different groups of light sources can be used alternately, and the duty cycle of the light source emission can be significantly reduced, thereby improving its heat dissipation capacity.

[0039] like Figure 3 and Figure 4 As shown, in some embodiments of this application, the transmitting antenna 125 can be configured as a one-dimensional array or a two-dimensional array. (Refer to...) Figure 3 The transmitting antenna 125 includes multiple transmitting elements arranged in a straight line, forming an N*1 one-dimensional array. Figure 3 The transmitting antenna 125 shown can perform both 1D and 2D scanning. (Refer to...) Figure 4 The transmitting antenna 125 also includes multiple transmitting elements, which are arranged in an N*M 2D array. Figure 4 The transmitting antenna 125 shown can achieve 2D scanning.

[0040] The following example illustrates the method of 1D scanning. For example... Figure 5 As shown, taking lateral scanning as an example, firstly, the light signal emitted by the transmitting component 100 forms a long strip of light spot 420 in the scanning area. Then, the control chip 300 controls the scanning drive 140 to output a drive current / voltage, and the scanning chip 120 deflects the light, thereby causing the long strip of light spot 420 to move along... Figure 5 Moving in the direction indicated by the arrow achieves horizontal scanning. Specifically, taking the field of view of an area array lidar as an example, it is generally FoV-H = 120°, FoV-V = 70°. Assuming the receiving resolution is RH = 0.2°, the emitted light spot can be a long strip of light spot 420 of 0.2° * 70°, covering a single pixel in the horizontal direction, or it can be a long strip of light spot of 1° * 70° covering 5 pixels in the horizontal direction, depending on the system configuration at the receiving chip. It should be noted that there are no restrictions on the number of light spots or the scanning direction (horizontal or vertical). Those skilled in the art can set two or more light spots according to the actual situation, or choose a vertical scanning method. In addition, the light spot emitted by the analog optical phased array module is generally a single-point light spot. Therefore, an optical diffuser is also provided in the transmitting component 100 to stretch the light spot in the vertical / horizontal direction, thereby obtaining the long strip of light spot 420. In some embodiments, the optical diffuser can be a cylindrical lens or a diffractive optical element (DOE).

[0041] Furthermore, since the analog optical phased array module uses electro-optic control, the deflection speed can reach the microsecond level, thus allowing for two-dimensional scanning. For example... Figure 6 As shown, in some embodiments, a single-point light spot 410 is used for two-dimensional scanning. First, the light signal emitted by the transmitting component 100 forms a single-point light spot 410 in the scanning area. Then, the control chip 300 controls the scanning drive 140 to output a drive current / voltage, and the scanning chip 120 deflects the light, thereby causing the single-point light spot 410 to move along... Figure 6The direction indicated by the arrow is first used for horizontal scanning, followed by vertical displacement. After displacement, another horizontal scan is performed, repeating this process multiple times until the entire scanning area is scanned, thus achieving 2D scanning. Using a single-point spot 410 for 2D scanning reduces the requirements for optical components because an optical diffuser is not needed, but it places higher demands on the system's frame rate and scanning speed. Furthermore, as... Figure 7 As shown, an optical diffuser can also be combined with 2D scanning to stretch a single-point light spot into a smaller, elongated light spot 420, such as... Figure 7 If FoV-V = 70°, then the vertical field of view RV covered by the long strip of light spot 420 can be 35° or 17.5°, etc. By using a sparse 2D array and a small-scale diffusion of the optical diffuser, the requirements for the optical diffusion device can be reduced while ensuring a large-scale FoV scan and a high-quality light spot. At the same time, the number of reciprocating scans can be reduced to ensure that the scanning speed meets the requirements.

[0042] It is easy to understand that in practical applications, the scanning path of the light spot is not necessarily as shown in the above figure. Under the condition of meeting the frame rate, the simulated optical phased array module can support arbitrary selection of scanning path according to the scene and system requirements, and also support pixel skipping scanning operation, which is not specifically illustrated in this application.

[0043] Furthermore, in some embodiments of this application, the lidar can support simultaneous scanning and reception using two or more light spots, which reduces the requirements for scanning speed. Meanwhile, because it is difficult to achieve a large field of view and low resolution with the scanning chip 120, and this can lead to a series of problems such as channel crosstalk and low sidelobe suppression ratio, thus affecting the signal-to-noise ratio, in order to solve these problems, in some embodiments of this application, two or more scanning chips 120 can be set within the transmitting component 100. By stitching together two or more scanning chips 120, it is easier to obtain a large field of view. Taking a 120° lateral field of view as an example, one scanning chip 120 covers a 60° field of view, and two chips can meet the product's requirements. Compared to a 120° field of view scanning chip 120, two 60° field-of-view scanning chips 120 significantly reduce the technical challenges in design and manufacturing.

[0044] Furthermore, in some embodiments of this application, a SPAD chip is used as the receiving chip 210. The SPAD chip employs a digital design, enabling simultaneous reception of multiple pixels. By selecting the corresponding pixel, the TDC (Time-to-digital Converter) module can record the timestamp of the corresponding pixel signal. Generally, SPAD chips typically use the Time-Correlated Single Photon Counting (TCSPC) or Coincidence Measurement principle to calculate the distance to an object using Time-of-Flight (ToF). Through multiple laser signal transmissions, the SPAD chip can detect the photon return time, thereby forming a histogram. To further improve the signal-to-noise ratio (SNR), common solutions include reducing ambient light levels, improving SPAD chip performance, and increasing transmission power and transmission frequency to ensure the SNR meets signal processing requirements. Based on this technical principle, the SPAD chip can control the corresponding pixels to read time-of-flight data according to different emission and scanning spot patterns, and use the histogram to form an effective point cloud map. SPAD chips can simultaneously receive multiple columns of pixels, whether adjacent or non-adjacent, thus receiving the light signals collected by these columns. The SPAD chip achieves this by controlling any one photosensitive pixel to match into its corresponding Time-Digital Converter (TDC). A TDC can be controlled by a data selector (Mux) to determine whether a signal from any pixel is connected to it. When connected, the signal serves as a stop signal, informing the chip that a flying photon was detected at that time. For example, when the transmitting component 100 emits a 0.4°*70° stripe of light, the receiving side can use two columns of pixels to ensure a one-to-one correspondence between transmission and reception, resulting in a 0.2° image resolution. Similarly, when the transmitting component 100 emits a 0.4°*70° stripe of light, the receiving side can use four columns of pixels to achieve the same one-to-one correspondence, resulting in an effective image resolution of 0.1°. This digital approach allows for flexible system configuration and measurement schemes. Under this architecture, the signal-to-noise ratio can be improved by emitting a small amount of power and counting multiple times. Furthermore, due to the high sensitivity of the SPAD chip, its requirements for the light source are lower compared to traditional APDs and PINs.

[0045] Furthermore, SPAD chips offer technological advantages. Generally, using a 40nm process as an example, a single SPAD chip can accommodate 8*180 TDCs, supporting up to 8 columns of pixels receiving signals simultaneously. Since SPAD chips employ a digital architecture, using a 22 / 28nm process can result in a smaller chip area, allowing for a greater number of TDCs within the same size. This is a key advantage of digital SPAD chips; following Moore's Law, upgrading the process node can improve chip performance and reduce costs.

[0046] Furthermore, in order to improve the accuracy of the receiving chip 210, a lens group is also provided in the receiving component 200. The lens group focuses the reflected light spot and allows the receiving chip 210 to receive it, which can improve the accuracy of the receiving chip 210.

[0047] It is understood that the above embodiments only illustrate preferred embodiments of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that, for those skilled in the art, without departing from the concept of this application, the above technical features can be freely combined, and several modifications and improvements can be made, all of which fall within the protection scope of this application. Therefore, all equivalent transformations and modifications made within the scope of the claims of this application should fall within the coverage of the claims of this application.

Claims

1. A fully solid-state lidar based on analog optical phased array, characterized in that, The laser radar comprises a transmitting assembly and a receiving assembly, the transmitting assembly comprises a transmitting chip and a scanning chip, and the receiving assembly comprises a receiving chip; The scanning chip comprises an analog optical phased array module, and the analog optical phased array module comprises: A coupler is arranged to couple the transmitting chip and guide light emitted by the transmitting chip into the analog optical phased array module; A beam splitter is arranged to split the guided light into multiple beams of parallel light to be respectively transmitted into different optical waveguides; An optical waveguide is arranged to transmit light to a phase adjuster; The phase adjuster is arranged to adjust the phase of the light to form light path deflection; A transmitting antenna is arranged to be connected to the phase adjuster, and the light whose phase has been adjusted in the phase adjuster is emitted outward through the transmitting antenna.

2. The analog optical phased array based all solid state lidar of claim 1, wherein, The analog optical phased array module comprises a calibration module connected to the phase adjuster.

3. The analog optical phased array based all solid state lidar of claim 1, wherein, The transmitting assembly comprises a transmitting drive connected to the transmitting chip and a scanning drive connected to the scanning chip.

4. The analog optical phased array based all solid state lidar of claim 3, wherein, The laser radar further comprises a control chip connected to the transmitting drive, the scanning drive and the receiving chip.

5. The analog optical phased array based all solid state lidar of claim 1, wherein, The receiving chip comprises an SPAD chip or an APD chip.

6. The analog optical phased array based all solid state lidar of claim 1, wherein, The transmitting chip comprises an EEL chip or a VCSEL chip.

7. The analog optical phased array based all solid state lidar of claim 1, wherein, Two or more scanning chips are arranged in the transmitting assembly.

8. The analog optical phased array based all solid state lidar of claim 1, wherein, The transmitting antenna is arranged in a 1D array or a 2D array.

9. The analog optical phased array based all solid state lidar of claim 8, wherein, The transmitting assembly comprises an optical diffuser.

10. The analog optical phased array based all solid state lidar of claim 1, wherein, The receiving assembly comprises a lens group.

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