Underwater depth camera

Abstract

An underwater depth camera comprises a transmitting module, a receiving module, a driving IC (integrated circuit) and a shell, and is characterized in that the transmitting module is used for transmitting polarized structured light; the receiving module comprises a receiving lens used for collecting reflected light; the narrow-band polarization filter is located on a light path of the receiving lens and is used for enabling light of a specific wave band to pass through; the SPAD sensor is used for receiving the light passing through the narrow-band polarization filter; the driving IC can open and close the transmitting module and the receiving module at the same time; and the shell is hermetically packaged, and a light-transmitting window is reserved on the light path of the transmitting module and the receiving module. According to the utility model, the precision of underwater modeling and obstacle avoidance and the adaptability to different application scenes are effectively improved.

Description

Technical Field

[0001] This utility model relates to the field of depth camera technology, specifically to an underwater depth camera. Background Technology

[0002] Ultrasonic sensors are commonly used in underwater unmanned equipment such as pool cleaning robots and submersibles for environmental perception and obstacle avoidance. While widely used, ultrasonic sensors also have some limitations, including:

[0003] Environmental factors: The measurement accuracy of ultrasonic sensors may be affected by factors such as temperature and ambient noise.

[0004] The influence of soft materials: Soft materials such as fabrics, aquatic plants, jellyfish and other small objects in the water only slightly refract sound waves and cannot form obvious reflections, making it difficult for the receiver to detect the target.

[0005] Measurement accuracy: The measurement accuracy of ultrasonic sensors is usually at the centimeter level, which may not be accurate enough for applications that require higher precision.

[0006] Large beam angle: Ultrasonic sensors have a large beam angle and poor directionality, which may lead to instability in ranging.

[0007] The above background information is provided only to assist in understanding the inventive concept and technical solution of this utility model. It does not necessarily belong to the prior art of this utility model application. In the absence of clear evidence that the above information was disclosed on the filing date of this utility model application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Utility Model Content

[0008] To address this, this invention proposes an underwater depth camera that uses blue structured light as its light source. It boasts advantages such as high environmental adaptability, the ability to measure flexible objects, high measurement accuracy, and stable underwater penetration distance. When applied to underwater unmanned equipment such as pool cleaning robots and submersibles, it can effectively improve the accuracy of underwater modeling and obstacle avoidance, as well as its adaptability to different application scenarios.

[0009] This utility model provides an underwater depth camera, characterized in that it includes: a transmitting module, a receiving module, a driver IC, and a housing, wherein,

[0010] The transmitting module is used to emit polarized structured light;

[0011] The receiving module includes:

[0012] A receiving lens is used to collect reflected light;

[0013] A narrow-band polarizing filter is located in the optical path of the receiving lens to allow light of a specific wavelength to pass through;

[0014] SPAD sensor for receiving light passing through the narrowband polarizing filter;

[0015] The driver IC can simultaneously turn the transmitting module and the receiving module on and off;

[0016] The outer casing is hermetically sealed and has light-transmitting windows in the optical paths of the transmitting module and the receiving module.

[0017] Optionally, the underwater depth camera is characterized by further comprising: a processor, configured to calculate a depth map using parallax based on the signal received by the SPAD sensor.

[0018] Optionally, the underwater depth camera is characterized in that the light-transmitting window in front of the transmitting module and the light-transmitting window in front of the receiving module are separated.

[0019] Optionally, the underwater depth camera is characterized in that the narrow-band polarizing filter has a metal grid on the side near the receiving lens, which can filter light and allow light of a specific polarization direction to pass through.

[0020] Optionally, the underwater depth camera is characterized in that the narrow-band polarizing filter is coated with a multilayer dielectric film on the side near the SPAD sensor, allowing light of a specific wavelength to pass through while blocking light of other wavelengths.

[0021] Optionally, the underwater depth camera is characterized in that the transmitting module includes a laser, a collimating lens, a microlens array, and a projection lens;

[0022] The laser is a blue-green light band laser diode;

[0023] The collimating lens is located in the output optical path of the laser;

[0024] The microlens array is located between the collimating lens and the projection lens, and is used to form speckle;

[0025] The object plane of the projection lens is conjugate with the focal plane of the microlens array, projecting the speckle pattern from the focal plane to form a speckle pattern.

[0026] Optionally, the underwater depth camera is characterized by further comprising: a prism located between the collimating lens and the microlens array, the inclined surface of which is coated with a metal film or a highly reflective dielectric film for changing the direction of the light path.

[0027] Optionally, the underwater depth camera is characterized in that one side of the microlens array is a plane, and the other side contains randomly arranged microlenses with an average spacing smaller than the diameter and overlapping microlens boundaries.

[0028] Optionally, the underwater depth camera is characterized in that the collimating lens includes a first freeform surface lens and a second freeform surface lens;

[0029] The first freeform lens is used to shape the beam emitted by the laser into a rectangular spot;

[0030] The second freeform lens is used to adjust the beam direction to parallel light.

[0031] Optionally, the underwater depth camera is characterized in that the outer shell adopts a honeycomb-shaped internal support structure.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] Currently, the measurement accuracy of traditional ultrasonic sensors in the industry is easily affected by environmental factors such as temperature and noise. The underwater depth camera proposed in this invention has better environmental adaptability.

[0034] Traditional ultrasonic sensors currently used in the industry have difficulty detecting soft materials. The underwater depth camera proposed in this invention, by employing optical reflection, is able to detect soft materials.

[0035] Currently, traditional ultrasonic sensors in the industry can only achieve measurement accuracy at the centimeter level. The underwater depth camera proposed in this invention can achieve detection accuracy at the millimeter level.

[0036] Traditional ultrasonic sensors in the industry currently suffer from large beam angles and poor directionality, which may lead to unstable ranging. The underwater depth camera proposed in this invention can achieve a specific beam angle through lens design, meeting both long-distance detection needs and short-range wide-angle detection needs. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort. Other features, objects, and advantages of this utility model will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0038] Figure 1This is a schematic diagram of the structure of an underwater depth camera according to an embodiment of the present invention;

[0039] Figure 2 This is a schematic diagram of the structure of a transmitting module in an embodiment of the present utility model;

[0040] Figure 3 This is a schematic diagram of the structure of a laser in an embodiment of the present invention;

[0041] Figure 4 This is a schematic diagram of the structure of a collimating lens in an embodiment of the present invention;

[0042] Figure 5 This is a schematic diagram of the structure of a prism in an embodiment of the present utility model;

[0043] Figure 6 This is a cross-sectional schematic diagram of a microlens array according to an embodiment of the present invention;

[0044] Figure 7 This is a schematic diagram of the surface of a microlens array according to an embodiment of the present invention;

[0045] Figure 8 This is a schematic diagram of the optical path of a microlens array in an embodiment of this utility model;

[0046] Figure 9 This is a schematic diagram of the optical path of another microlens array in an embodiment of this utility model;

[0047] Figure 10 This is a schematic diagram of the structure of a transmitting module in an embodiment of the present utility model;

[0048] Figure 11 This is a schematic diagram of the structure of a gradient filter in an embodiment of the present invention;

[0049] Figure 12 This is a schematic diagram of a speckle brightness gradient in an embodiment of the present invention;

[0050] Figure 13 This is a schematic diagram of the structure of a receiving module in an embodiment of the present utility model;

[0051] Figure 14 This is a schematic diagram of a TE wire grid polarization in an embodiment of the present invention;

[0052] Figure 15 This is a schematic diagram of the structure of a narrowband polarizing filter according to an embodiment of the present invention;

[0053] Figure 16 This is a schematic diagram of a 430-470nm bandpass filter in an embodiment of the present invention.

[0054] 1- Launch module;

[0055] 2-Receiver module;

[0056] 3-Driver IC;

[0057] 4-Circuit board;

[0058] 5-Module housing;

[0059] 11-Laser;

[0060] 12-Collimating lens;

[0061] 13-Prism;

[0062] 14-Microlens array;

[0063] 15-Projection lens;

[0064] 16-Gradual attenuation filter;

[0065] 21-Receiving lens;

[0066] 22- Narrow-band polarizing filter;

[0067] 23-SPAD sensor;

[0068] 24-Polarization plane;

[0069] 25 - Coated surface; Detailed Implementation

[0070] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0071] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this utility model are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the utility model described herein can be implemented, for example, in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0072] This utility model provides an underwater depth camera, which aims to solve the problems existing in the prior art.

[0073] The technical solutions of this utility model and this application solve the above-mentioned technical problems in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this utility model will now be described with reference to the accompanying drawings.

[0074] Figure 1 This is a schematic diagram of the structure of an underwater depth camera according to an embodiment of this utility model. Figure 1 As shown, an underwater depth camera in this embodiment of the present invention includes components such as a transmitting module 1, a receiving module 2, a driving IC 3, and a module housing 5.

[0075] The transmitting module emits polarized structured light to detect the distance, shape, and motion of underwater targets.

[0076] The receiving module captures the laser echo reflected from the target, converts it into an electrical signal, and generates an image.

[0077] The driver IC coordinates system timing, signal processing, and communication to ensure high-precision synchronization and low-power operation.

[0078] The outer casing is sealed with dual redundant O-rings (Viton material), and helium mass spectrometry leak detection ensures a leak rate of <1×10⁻⁸ Pa·m. 3 / s. Employs a honeycomb internal support structure. Uses thermal grease and copper heat pipes to conduct heat to the external heatsink fins. The module housing features wet-plug electrical connectors, supporting rapid underwater deployment.

[0079] Collaborative Workflow

[0080] Trigger: The driver IC sends a trigger signal to the transmitting module, and the laser pulse is emitted after collimation.

[0081] Detection: The receiving module synchronously starts the TDC, receives the reflected signal, generates a speckle image, and uses parallax to calculate the depth map.

[0082] Processing: The driver IC fuses multi-pulse data, generates a 3D point cloud, and uploads it through the communication interface.

[0083] The transmitting module, driving module, and driving IC can be directly packaged on a single circuit board via common substrate mounting, or they can be independently mounted. The housing is external to the above components, hermetically sealed, and has light-transmitting windows above the transmitting and receiving modules.

[0084] In some embodiments, the system further includes a processor configured to calculate a depth map using parallax based on signals received by the SPAD sensor. Compared to parallax calculations on water, underwater calculations suffer from the influence of light refraction on structured light; therefore, the intrinsic and extrinsic parameters obtained from surface calibration cannot be directly used for underwater depth calculations. Underwater parallax calculations require recalibration underwater.

[0085] In some embodiments, the light-transmitting window in front of the transmitting module and the light-transmitting window in front of the receiving module are separated. The light-transmitting window in front of the transmitting module and the light-transmitting window in front of the receiving module can be a single window or two independent windows. When they are two independent windows, light cannot propagate between them. When they are a single window, a separator needs to be provided internally to prevent light from propagating between the two parts. This embodiment can prevent light from the front end of the transmitting module from interfering with the receiving module, thereby affecting image quality.

[0086] Figure 2 This is a schematic diagram of the structure of a transmitting module according to an embodiment of this utility model. Figure 2 As shown, the transmitting module includes a laser 11, a collimating lens 12, a microlens array 14, and a projection lens 15.

[0087] Laser 11 is a blue-green wavelength laser diode, as this wavelength experiences minimal attenuation in water and has strong penetrating power. Laser 11 emits high-energy, narrow-pulse laser pulses as a detection signal source. For example... Figure 3 As shown, the laser is a side-emitting semiconductor laser with a wavelength range of 430–470 nm. The emitted light is TE-mode polarized light with a polarization degree DOP > 95%.

[0088] Pulse energy: 1-10mJ (adjustable to adapt to different detection depths).

[0089] Repetition frequency: 1kHz-100kHz (high frequency is used for close-range high-speed scanning, low frequency is used for long-range scanning).

[0090] Pulse width: 1-10ns (shorter pulse width improves distance resolution, longer pulse width increases energy penetration into murky waters).

[0091] Sealed nitrogen-filled chamber (moisture-proof). Thermoelectric cooler (TEC) temperature control maintains wavelength stability (temperature drift <0.1nm / ℃).

[0092] Collimating lens 12 adjusts the laser beam into parallel light, reducing the divergence angle (e.g., <1 mrad). Collimating lens 12 converts the diverging beam output from the laser into parallel light, reducing energy loss and increasing the detection range. Collimating lens 12 is an aspherical lens (or a reflective collimating lens), eliminating spherical aberration and achieving high-precision collimation. Figure 4As shown, the collimating lens includes a first freeform surface lens and a second freeform surface lens; the first freeform surface lens is used to shape the elliptical beam emitted by the laser into a rectangular light spot, the aspect ratio of which is the same as that of the SPAD sensor at the receiving end; the second freeform surface lens is used to adjust the beam direction to parallel light.

[0093] The microlens array 14 spatially shapes the aligned laser beam, enabling multi-beam emission, increasing the intensity of a single laser point, and thus extending the detection range. The shape of the microlens array 14 is the same as that of the laser. Figure 6 As shown, one side of the microlens array is a plane, and the other side contains randomly arranged microlenses. Figure 7 As shown, the average spacing between the microlenses is smaller than the diameter, and the boundaries of the microlenses overlap. In applications, light can be incident from a plane and focused onto the surface of the microlens (e.g., ...). Figure 8 As shown), it can also be incident from the surface of the microlens and focused on the planar side (e.g. Figure 9 (As shown).

[0094] like Figure 10 As shown, the object plane of the projection lens 15 is conjugate to the focal plane of the microlens array, enabling the projection and magnification of the light spot on the focal plane to the desired FOV. Underwater moving parts are supported by a dynamic O-ring (fluororubber) combined with a magnetohydrodynamic rotary seal.

[0095] The light emitted by the laser is collimated by a collimating lens and then projected onto a microlens array, forming a speckle pattern on the focal plane. The light is then projected out through a projection lens and a graduated attenuator.

[0096] In some embodiments, the transmitting module further includes a prism 13. The prism 13 deflects the laser path by rotating or fixing the angle, achieving non-mechanical scanning (such as a rotating prism) or fixed field-of-view expansion (such as a beam splitter prism). Figure 5 As shown, the angle between the inclined plane and the right-angled plane of the prism is 45°, and the inclined plane is coated with a metal film or a highly reflective dielectric film. It can reflect light in the range of 430–470 nm.

[0097] In some embodiments, such as Figure 11 As shown, the transmitting or receiving module also includes a graded attenuator 16. When the graded attenuator 16 is located on the outermost side of the optical path of the transmitting module, it can cause a gradual change in the brightness of the projected speckle. When the graded attenuator 16 is located on the outermost side of the optical path of the receiving module, it can cause a gradual change in the brightness of the received speckle. In applications such as pool cleaning robots that operate close to the pool wall, this can prevent overexposure at close range. Figure 12 An example of a speckle pattern with gradual brightness variation is shown. From Figure 12As can be seen, the brightness of the speckle pattern changes significantly, which can prevent overexposure. It should be noted that the gradient speed of the graduated attenuator 16 should be adapted to the working environment of the underwater depth camera. For example, when the distance between the robot housing the underwater depth camera and the wall is relatively large, the gradient speed of the graduated attenuator 16 can be relatively slow; when the distance between the robot housing the underwater depth camera and the wall is relatively small, the gradient speed of the graduated attenuator 16 can be relatively fast.

[0098] Figure 13 This is a schematic diagram of the structure of a receiving module according to an embodiment of this utility model. Figure 13 As shown, a receiving module in an embodiment of this utility model includes:

[0099] The receiving lens 21 is used to collect reflected light.

[0100] Specifically, the receiving lens efficiently collects the laser echo reflected from the target and focuses it onto the detector surface to maximize signal acquisition capability.

[0101] A narrowband polarizing filter 22 is located in the optical path of the receiving lens and is used to allow light of a specific wavelength to pass through.

[0102] Specifically, the narrowband polarization filter selects the laser wavelength and suppresses ambient light interference, improving the signal-to-noise ratio. The linear polarization direction of the narrowband polarization filter matches the polarization state of the emitted laser (extinction ratio > 1000:1). Since the polarization direction of the light scattered by suspended particles in water is random, the narrowband polarization filter only transmits signals with the same polarization direction as the emitted light, thus suppressing backscattering. The substrate material of the narrowband polarization filter 22 is glass.

[0103] SPAD sensor 23 is used to receive light passing through the narrowband polarizing filter.

[0104] Specifically, the SPAD (Single-Photon Avalanche Diode) sensor detects echo signals with single-photon-level sensitivity, enabling detection in extremely weak light. This sensor can be used to gain light propagation time or to acquire light spot images, thereby gaining two different types of depth values: structured light depth and Time-of-Flight (TOF) depth, allowing for a more comprehensive analysis of the target object.

[0105] The FOV of the receiving lens is the same as that of the transmitting lens. After passing through the receiving lens, the light passes through a narrow-band polarizing filter and forms an image on the surface of the SPAD sensor.

[0106] Figure 14 This is a schematic diagram of a TE wire grid polarization. Wire grid polarization only allows light rays with a specific polarization state to pass through.

[0107] Figure 15 This is a schematic diagram of the structure of a narrowband polarizing filter according to an embodiment of this utility model. Figure 15 In the image, the left side is the polarization surface 24, equipped with a metal grid, which allows TE-polarized light to pass through while reflecting light in other directions. The right side is the coating surface 25, coated with multiple layers of dielectric film, which allows light in the 430-470nm range to pass through while reflecting other light. Its filtering effect is as follows: Figure 16 As shown.

[0108] The various embodiments described in this specification are presented in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. The above description of the disclosed embodiments enables those skilled in the art to implement or use this invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this invention. Therefore, this invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0109] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the substantive content of this utility model.

Claims

1. An underwater depth camera, characterized in that, include: Transmitter module, receiver module, driver IC, and housing, among which, The transmitting module is used to emit polarized structured light; The receiving module includes: A receiving lens is used to collect reflected light; A narrow-band polarizing filter is located in the optical path of the receiving lens to allow light of a specific wavelength to pass through; SPAD sensor for receiving light passing through the narrowband polarizing filter; The driver IC can simultaneously turn the transmitting module and the receiving module on and off; The outer casing is hermetically sealed and has light-transmitting windows in the optical paths of the transmitting module and the receiving module.

2. The underwater depth camera according to claim 1, characterized in that, Also includes: A processor is used to calculate a depth map using parallax based on the signals received by the SPAD sensor.

3. The underwater depth camera according to claim 1, characterized in that, The light-transmitting window in front of the transmitting module and the light-transmitting window in front of the receiving module are separated.

4. The underwater depth camera according to claim 1, characterized in that, The narrow-band polarizing filter has a metal grid on the side near the receiving lens, which can filter light and allow light of a specific polarization direction to pass through.

5. The underwater depth camera according to claim 1, characterized in that, The narrowband polarizing filter is coated with a multilayer dielectric film on the side near the SPAD sensor, allowing light of a specific wavelength to pass through while blocking light of other wavelengths.

6. The underwater depth camera according to claim 1, characterized in that, The transmitting module includes a laser, a collimating lens, a microlens array, and a projection lens; The laser is a blue-green light band laser diode; The collimating lens is located in the output optical path of the laser; The microlens array is located between the collimating lens and the projection lens, and is used to form speckle; The object plane of the projection lens is conjugate with the focal plane of the microlens array, projecting the speckle pattern from the focal plane to form a speckle pattern.

7. An underwater depth camera according to claim 5, characterized in that, Also includes: A prism, located between the collimating lens and the microlens array, has a metal film or a highly reflective dielectric film coated on its inclined surface, used to change the direction of the light path.

8. The underwater depth camera according to claim 5, characterized in that, One side of the microlens array is a plane, and the other side contains randomly arranged microlenses with an average spacing smaller than the diameter and overlapping microlens boundaries.

9. An underwater depth camera according to claim 5, characterized in that, The collimating lens includes a first freeform surface lens and a second freeform surface lens; The first freeform lens is used to shape the beam emitted by the laser into a rectangular spot; The second freeform lens is used to adjust the beam direction to parallel light.

10. An underwater depth camera according to claim 1, characterized in that, The outer shell adopts a honeycomb-shaped internal support structure.

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