Tof distance measurement module
By setting an angle-selective filter in the TOF ranging module, the crosstalk problem between the measuring SPAD and the reference SPAD is solved, simplifying the design, reducing costs, and improving ranging accuracy and anti-interference capability.
Patent Information
- Application Number
- CN202423229376.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-26
- Publication Date
- 2026-01-06
- Estimated Expiration
- 2034-12-26
AI Technical Summary
In existing TOF ranging modules, crosstalk between the measuring SPAD and the reference SPAD increases the complexity of module design and chip cost, while stray light interference seriously affects ranging performance.
A first filter is set on the reference SPAD device to receive light at an angle greater than a preset incident angle, and a second filter is set on the measuring SPAD device to receive light at an angle less than a preset incident angle. By controlling the angle of light through the filters, each filter can receive light at a specific angle, simplifying the module design and reducing crosstalk.
It effectively solves the crosstalk problem of stray light inside the module to the measurement SPAD device, simplifies the module design, reduces chip cost, and improves measurement accuracy and anti-interference capability.
Smart Images
Figure CN223770402U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of optical sensors, and in particular to a TOF ranging module. Background Technology
[0002] A Time-of-Flight (TOF) camera is an active optical system that transmits laser pulses to a target object. A detector at the receiver identifies the target signal, and the depth information of the target is calculated based on the time of flight. The distance to the object is determined by the time of flight. Simultaneously, a set of reference SPADs is often required in a TOF module system to detect the light signal directly transmitted from the transmitter as a reference distance. Figure 1 As shown, the photons reflected by the transmitter A3 within the module can be directly detected by the reference SPADA4, but may also be received by the measurement SPADA5, causing crosstalk to SPADA5. Normally, the measurement SPADA5 should not receive the photons reflected from within the module, but should only receive the photons emitted by A3 outside the module and reflected back by the target object.
[0003] Existing technologies for resolving crosstalk typically involve setting up two separate chips for the measurement SPAD A5 and the reference SPAD A4, and then adding a baffle A6 and black adhesive between the measurement SPAD A5 and the reference SPAD A4 on the module to block them from interfering with each other. Figure 2 As shown, this method requires physically separating the measuring SPAD A5 and the reference SPAD A4, maintaining a certain distance, which increases the complexity of the module design and the cost of the chip. Furthermore, the closer the measuring SPAD A5 and the reference SPAD A4 are, the more severe the crosstalk phenomenon caused by stray light from the transmitting end A3 inside the module to the measuring SPAD A5 becomes, seriously interfering with the calculation of target depth information. Ultimately, this negatively impacts the module's ranging performance, such as detection range and accuracy. Therefore, this invention provides a TOF ranging module. Utility Model Content
[0004] In view of the shortcomings of the prior art, the purpose of this utility model is to provide a toF ranging module that, while simplifying the module design complexity and reducing chip costs, solves the crosstalk problem caused by stray light from the transmitter inside the module to the SPAD measurement device.
[0005] To solve the above technical problems, the present invention adopts the following technical solution:
[0006] A TOF ranging module includes a substrate and a package covering the substrate. A VCSEL laser, a reference SPAD device, and a measuring SPAD device are disposed on the substrate. The reference SPAD device is located between the VCSEL laser and the measuring SPAD device. A baffle for changing the direction of light emitted by the VCSEL laser is disposed above the interior of the package. The reference SPAD device is provided with a first filter for receiving light rays with an incident angle greater than a preset angle. The measuring SPAD device is provided with a second filter for blocking light rays with an incident angle greater than the preset angle and receiving light rays with an incident angle less than or equal to the preset angle.
[0007] In the TOF ranging module, the first filter and the second filter are filter films with angle-selective filtering formed by stacking multiple thin film structures; or, the first filter and the second filter are micro-nano structure thin films composed of nanoscale array structures; or, the first filter is a filter film with angle-selective filtering formed by stacking multiple thin film structures, and the second filter is a micro-nano structure thin film composed of nanoscale array structures; or, the first filter is a micro-nano structure thin film composed of nanoscale array structures, and the second filter is a filter film with angle-selective filtering formed by stacking multiple thin film structures.
[0008] In the tof ranging module, the incident angle of the received light from the first filter and the second filter is determined by the number of filter layers, the thickness of the filter layers, and the material of the filter layers.
[0009] In the TOF ranging module, the incident angle of the received light from the first and second filters is determined by the volume, spacing, and number of the micro / nano structure thin films. The micro / nano structure thin films can also contain nanoscale features, such as nanopillars, nanopores, or other periodic patterns. These structures can further modulate the behavior of light, thereby affecting the propagation path and intensity distribution of light.
[0010] In the TOF ranging module, the light rays with an angle greater than the preset incident angle are emitted by the VCSEL laser inside the package and reflected by the baffle, or the light rays with an angle greater than the preset incident angle are emitted by the VCSEL laser inside the package and reflected by the baffle or the ambient light outside the package.
[0011] In the tof ranging module, the reference SPAD device is located between the VCSEL laser and the measuring SPAD device, at a preset distance from the measuring SPAD device. The baffle is located between the reference SPAD device and the measuring SPAD device. Alternatively, the reference SPAD device is positioned near or close to the measuring SPAD device, and the baffle is located between the VCSEL laser and the reference SPAD device.
[0012] In the TOF ranging module, the preset incident angle is greater than or equal to the preset incident angle; the preset incident angle is 30-45°.
[0013] In the tof ranging module, a first lens is provided on the package at the VCSEL laser, and a second lens is provided at the measuring SPAD device.
[0014] Compared to existing technologies, the TOF ranging module provided by this utility model effectively solves the crosstalk problem caused by stray light from the transmitter inside the module to the measuring SPAD device by setting a first filter on the reference SPAD device for receiving light with an angle greater than a preset incident angle, and setting a second filter on the measuring SPAD device for receiving light with an angle less than a preset incident angle. The first and second filters ensure that the reference SPAD device and the measuring SPAD device each receive light at a specific angle, eliminating the need for a completely isolated baffle inside the module, simplifying the module design, solving the crosstalk problem, and thus improving the measurement accuracy. Attached Figure Description
[0015] Figure 1 This is a schematic diagram illustrating crosstalk in existing TOF ranging modules.
[0016] Figure 2 This is a schematic diagram of the structure of a TOF ranging module in the prior art.
[0017] Figure 3 This is a schematic diagram of an optional embodiment of the TOF ranging module provided by this utility model.
[0018] Figure 4 This is a schematic diagram of another optional embodiment of the TOF ranging module provided by this utility model.
[0019] Figure 5 This is a schematic diagram of another optional embodiment of the TOF ranging module provided by this utility model, which does not receive ambient light.
[0020] Figure 6 This is a schematic diagram of a first optional embodiment of the filter in the TOF ranging module provided by this utility model.
[0021] Figure 7 This is a schematic diagram of the filter covering the SPAD device in the TOF ranging module provided by this utility model.
[0022] Figure 8 This is a schematic diagram of a second optional embodiment of the filter in the TOF ranging module provided by this utility model.
[0023] Figure 9This is a schematic diagram illustrating the selective transmission characteristics of the filter in the TOF ranging module provided by this utility model.
[0024] Explanation of reference numerals in the attached figures
[0025] 1. Substrate; 2. Package; 21. Baffle; 3. VCSEL laser; 4. Reference SPAD device; 5. Measurement SPAD device; 6. First filter; 7. Second filter; 8. First lens; 9. Second lens Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.
[0027] The TOF ranging module provided by this utility model is mainly used in fields such as smartphones, autonomous vehicles, robot navigation, 3D scanning, and augmented reality. It calculates the distance to a target object by emitting light and measuring the time required for the light to reflect back. By referencing a first filter on the SPAD device and measuring a second filter on the SPAD device, it helps ensure that only light at specific angles is received, thereby reducing crosstalk caused by stray light inside the module to the measuring SPAD device and reducing ambient light interference to improve measurement accuracy.
[0028] Please see Figure 3 , Figure 4 and Figure 5 The toF ranging module provided by this utility model includes a substrate 1 and a package 2 covering the substrate 1. A VCSEL laser 3, a reference SPAD device 4 and a measuring SPAD device 5 are disposed on the substrate 1. The reference SPAD device 4 is located between the VCSEL laser 3 and the measuring SPAD device 5.
[0029] The package 2 has a baffle 21 located at the top inside for changing the direction of the light emitted by the VCSEL laser 3. The baffle 21 is mainly used to reflect the light emitted by the VCSEL laser 3. The reference SPAD device 4 has a first filter 6 for receiving light with an incident angle greater than or equal to a preset incident angle. The measuring SPAD device 5 has a second filter 7 for receiving light with an incident angle less than a preset incident angle. The preset incident angle is the absolute value of the angle between the light ray and the normal (i.e., the perpendicular line of the substrate 1).
[0030] This invention, through the first filter 6 and the second filter 7, enables the reference SPAD device 4 and the measuring SPAD device 5 to receive light only at a specific angle. This ensures that the light emitted by the VCSEL laser 3 reflected by the baffle 21 is only received by the reference SPAD device 4, and the measuring SPAD device 5 only receives the light emitted by the VCSEL laser 3 reflected by the target object, thereby improving measurement accuracy.
[0031] During the measurement process, for the SPAD device being measured, the light rays with an angle greater than the preset incident angle are emitted by the VCSEL laser 3 reflected by the baffle 21 inside the package 2. This is crosstalk light and is unwanted light.
[0032] During measurement, light is emitted by the VCSEL laser 3. A portion of the light is reflected by the baffle 21, changing the direction of the light path to adjust the emission angle and form a reference light. The reference light emitted by the VCSEL laser 3 is filtered by the first filter 6 (e.g., to remove light at other angles) to obtain light with an angle greater than or equal to a preset incident angle, ensuring that the reference SPAD device 4 can receive sufficient reference light. Simultaneously, the measuring SPAD device 5 receives the measuring light reflected back from the target object. In this embodiment, the second filter 7 blocks light with an angle greater than the preset incident angle while receiving light with an angle less than the preset incident angle, ensuring that the measuring SPAD device 5 can receive reflected light without interference, thereby guaranteeing measurement accuracy.
[0033] Specifically, the preset incident angle is greater than or equal to the preset incident angle; optionally, the preset incident angle is any value between 30-45°, such as 35° in practical applications.
[0034] Optionally, the first filter and / or the second filter may be a filter film with angle-selective filtering, which is composed of a multilayer thin film structure or a micro / nano structure thin film composed of a nanoscale array structure.
[0035] In a first optional embodiment, both the first filter 6 and the second filter 7 are angle-selective filtering filters composed of multiple thin film structures stacked together (e.g., Figure 6 and Figure 7 As shown, the angle-selective filter film can precisely control the range of light wavelengths that can pass through by stacking different material layers, such as light with wavelengths less than 30nm. Each filter layer can absorb or reflect light of a specific wavelength, thereby achieving selective transmission of light of a specific wavelength. Therefore, by adjusting the number, thickness and material of the filter layers, the incident angle of the received light can be finely adjusted.
[0036] In a second optional embodiment, both the first filter 6 and the second filter 7 are micro / nano structure thin films composed of nanoscale array structures (e.g., Figure 8 As shown, the micro / nanostructured thin film contains nanoscale features, such as nanopillars, nanopores, or other periodic patterns, which can further modulate the behavior of light, thereby affecting the propagation path and intensity distribution of light.
[0037] In a third optional embodiment, the first filter 6 is a filter film with angle-selective filtering composed of multiple thin film structures stacked together, and the second filter 7 is a micro-nano structure thin film composed of a nanoscale array structure, and its incident angle for receiving light can also be set.
[0038] In the fourth optional embodiment, the first filter 6 is a micro-nano structure thin film composed of a nanoscale array structure, and the second filter 7 is a filter film with angle selective filtering composed of multiple thin film structures stacked together, and its incident angle for receiving light can also be set.
[0039] The third and fourth optional embodiments can take advantage of the first and second optional embodiments described above to achieve more precise control of the light incident angle.
[0040] The four optional embodiments described above provide design flexibility, enabling TOF ranging modules to have better adaptability and performance in different environments and applications. For example, in scenarios requiring high resistance to ambient light interference, the properties of micro / nano structured thin films can be utilized to reduce the reception of non-target light; while in scenarios requiring precise control of the received wavelength, multi-layered filter layers can be used. Through this flexible design, TOF ranging modules can better meet the needs of specific applications.
[0041] The incident angle of the received light in the first filter 6 and the second filter 7 is determined by at least one of the following: the number of filter layers, the thickness of the filter layers, and the filter layer material. Specifically, increasing the number of filter layers increases the number of interactions of light as it passes through the filter layers, thereby changing the propagation path and angle of the light. Furthermore, by utilizing the different refractive indices and absorption coefficients of different filter layer materials, the propagation characteristics and reception angle of the light can be precisely controlled.
[0042] The combined effect of these factors allows the TOF ranging module to optimize the incident angle of the received light by adjusting the design of the filter, thereby improving ranging accuracy and anti-interference capability. Especially under complex lighting conditions, by precisely controlling the angle of the received light, interference from ambient light can be reduced, ensuring that the measuring SPAD device receives only the reflected light from the target object, thus improving measurement accuracy.
[0043] In this embodiment, for a multilayer medium filter, when light is incident at a certain angle θ, the following phase matching condition can produce constructive interference (i.e., high transmittance) or destructive interference (i.e., low transmittance): 2nLcos(θ)=mλ, where n is the refractive index of the medium layer, L is the physical thickness of a single medium layer, θ is the incident angle of light relative to the normal in the medium, λ is the wavelength of light in vacuum, and m is an integer representing the interference order.
[0044] To obtain angle-selective filters, a multilayer stacking method using alternating high and low refractive index materials is typically employed. Commonly used materials include SiO2 (low refractive index) and TiO2 (high refractive index). A common structure is quarter-wavelength stacking (λ / 4 layers), where the optical thickness of each layer is set to one-quarter of the desired wavelength. To achieve a narrower bandwidth, the number of layers can be increased or more periodic repeating units can be used. Theoretically, each additional pair of high and low refractive index layers can halve the bandwidth.
[0045] The key to angular selectivity lies in controlling the transmission characteristics at different angles. Larger incident angles lead to greater bandwidth variations and center wavelength shifts. To optimize angular selectivity, special material combinations, adjustments to layer thickness ratios, or the introduction of non-uniformly distributed multilayer structures may be employed.
[0046] like Figure 9 As shown, by alternately depositing multilayer thin films of different materials and thicknesses (such as...) Figure 9 Examples 1, 2, and 3 in the text utilize the interference effect of light to achieve angle-selective filtering, with a transmittance close to 100% in the working wavelength band and less than 0.1% in the non-working wavelength band. The waveform in Example 1 represents the transmittance performance of the second filter 7, and the waveform in Example 2 or 3 represents the transmittance performance of the first filter 6. The second filter 7 has a transmittance angle centered at 0 degrees, exhibiting a wide angle selectivity, and can also be composed of multiple thin films with smaller angle selectivity. The first filter 6 has a narrow transmittance angle centered at 35 or 45 degrees. Therefore, the reference SPAD device 4 can accept scattered or reflected light from within the module at approximately 35 or 45 degrees; while the measuring SPAD device 5 can only accept signal light reflected from external target objects at angles below 30 degrees, thus suppressing scattered light from within the module and large-angle ambient light from outside the module.
[0047] The incident angle of the received light by the first filter 6 and the second filter 7 is determined by the volume, spacing, and number of the micro / nano structure film. The micro / nano structure film may also contain nanoscale features, such as nanopillars, nanopores, or other periodic patterns. These structures can further modulate the behavior of light, thereby affecting the propagation path and intensity distribution of light.
[0048] In an optional embodiment, the reference SPAD device 4 is located between the VCSEL laser 3 and the measuring SPAD device 5, at a predetermined distance from the measuring SPAD device 5 (e.g., ...). Figure 3 As shown, the baffle 21 is located between the reference SPAD device 4 and the measurement SPAD device 5. The first filter 6 and the second filter 7 allow light from different angles to be received by their respective desired areas, thereby solving the problem of stray light from the VCSEL laser 3 within the module interfering with the optical path of the measurement SPAD device 5. This also simplifies the isolation design and process requirements of the transmitter and receiver modules, and eliminates the need for an additional narrowband filter component at the lens end, thus resolving the crosstalk problem caused by light reflection between the photodetector and the filter.
[0049] In another alternative embodiment, the reference SPAD device 4 is positioned adjacent to or close to the measuring SPAD device 5, and the baffle 21 is located between the VCSEL laser 3 and the reference SPAD device 4 (e.g., Figure 4 , Figure 5 (As shown). When the reference SPAD device 4 and the measuring SPAD device 5 are positioned adjacent to each other, the first filter 6 and the second filter 7 allow large-angle scattered light from inside the module to still be received by the reference area, without affecting the normal signal reception of the measuring SPAD device 5, effectively isolating crosstalk between the two functional areas. Furthermore, as... Figure 5 As shown, when ambient light at a large angle reaches the measuring SPAD device 5, unwanted ambient light (such as...) can still be effectively filtered out. Figure 5 Light rays marked with an "X" cannot be transmitted through the second filter 7, thereby improving the signal-to-noise ratio. Furthermore, since the reference SPAD device 4 and the measurement SPAD device 5 are positioned adjacent to each other, they can be integrated onto a single chip, thus reducing chip cost.
[0050] Both of these structures can ensure that light can effectively propagate from the VCSEL laser 3 to the measuring SPAD device 5, while minimizing losses and interference to meet the accuracy requirements of the measurement and ensure that the tof ranging module can work stably under different environmental conditions.
[0051] Please continue reading. Figures 3 to 5The package 2 has a first lens 8 located at the VCSEL laser 3 and a second lens 9 located at the measuring SPAD device 5. The first lens 8 can be used to collimate the light beam, making the light more parallel to reduce the divergence of light speed during propagation. It can also be used to adjust the diameter and intensity distribution of the light beam to meet the requirements of the subsequent optical path. The second lens 9 can focus the light signal arriving at the measuring SPAD device 5, improving the light signal collection efficiency. It is suitable for measuring weak light signals and can also help limit the field of view of the measuring SPAD device 5, receiving only light signals from specific directions or angles, thereby reducing the influence of ambient light on the measuring SPAD device 5.
[0052] In summary, the TOF ranging module provided by this utility model effectively solves the crosstalk problem caused by stray light from the transmitter inside the module to the measuring SPAD device by setting a first filter on the reference SPAD device for receiving light with an angle greater than a preset incident angle and a second filter on the measuring SPAD device for receiving light with an angle less than or equal to the preset incident angle. This ensures that both the reference SPAD device and the measuring SPAD device only receive light at specific angles, eliminating the need for completely isolated baffles within the module, simplifying the module design, resolving the crosstalk problem, and thus improving measurement accuracy.
[0053] It is understood that those skilled in the art can make equivalent substitutions or changes based on the technical solution and inventive concept of this utility model, and all such substitutions or changes should fall within the protection scope of the appended claims of this utility model.
Claims
1. A tof ranging module, characterized in that, The application relates to a substrate and a package covering the substrate, wherein a VCSEL laser, a reference SPAD device and a measurement SPAD device are arranged on the substrate, the reference SPAD device is located between the VCSEL laser and the measurement SPAD device, a baffle for changing the direction of light emitted by the VCSEL laser is arranged on the top of the package, a first light filter for receiving light with an angle greater than a preset incident angle is arranged on the reference SPAD device, and a second light filter for receiving light with an angle smaller than the preset incident angle is arranged on the measurement SPAD device.
2. The tof distance measurement module according to claim 1, wherein, The first light filter and the second light filter are angle-selective light filters formed by stacking a plurality of thin film structures; or the first light filter and the second light filter are micro-nano structure thin films formed by an array structure with nanometer scale; or the first light filter is an angle-selective light filter formed by stacking a plurality of thin film structures, and the second light filter is a micro-nano structure thin film formed by an array structure with nanometer scale; or the first light filter is a micro-nano structure thin film formed by an array structure with nanometer scale, and the second light filter is an angle-selective light filter formed by stacking a plurality of thin film structures.
3. The tof distance measurement module according to claim 2, wherein, The incident angle of the received light of the first light filter and the second light filter is determined by the number of light filters, the thickness of the light filters and the material of the light filters.
4. The tof distance measurement module according to claim 2, wherein, The incident angle of the received light of the first light filter and the second light filter is determined by the volume, the spacing and the number of the micro-nano structure thin film.
5. The tof distance measurement module according to claim 1, wherein, The light with an angle greater than the preset incident angle is light emitted by the VCSEL laser and reflected by the baffle in the package, and the light with an angle smaller than the preset incident angle is light emitted by the VCSEL laser and reflected by a target object outside the package.
6. The tof distance measuring module according to any one of claims 1 to 4, characterized in that The reference SPAD device is located between the VCSEL laser and the measurement SPAD device and is spaced apart from the measurement SPAD device by a preset distance, and the baffle is located between the reference SPAD device and the measurement SPAD device; or the reference SPAD device is arranged adjacent to or close to the measurement SPAD device, and the baffle is located between the VCSEL laser and the reference SPAD device.
7. The tof distance measuring module according to any one of claims 1 to 4, characterized in that The preset incident angle is any value in the range of 30-45 degrees. 8.The tof ranging module according to any one of claims 1 to 4, characterized in that, A first lens is arranged on the VCSEL laser on the package, and a second lens is arranged on the measurement SPAD device.