Baffle blade type ToF optical sensing module

Abstract

The invention provides a baffle blade type ToF optical sensing module, which belongs to the technical field of optical sensing and comprises a substrate, a cap and a transceiving unit. The cap includes a transmitting window, a receiving window, and at least one protruding vane. A cavity is formed between a body of the cap and the substrate, the body is provided with a lower surface facing the substrate and the cavity, the protruding blade protrudes towards the interior of the cavity from the lower surface, and the baffle is arranged on the substrate and located between the light-emitting unit and the pixel substrate. The transmitting-receiving unit is located in the cavity, the protruding blade is located between the lower surface and the substrate, and the protruding blade is matched with the transmitting-receiving unit to divide the cavity into a transmitting cavity and a receiving cavity corresponding to the transmitting window and the receiving window respectively. The transceiving unit is used for emitting measuring light in the emitting cavity and receiving sensing light in the receiving cavity through the receiving window. The protruding blade and the baffle are located in the emission cavity and reflect or absorb the measuring light. Compared with the prior art, the baffle blade type ToF optical sensing module is higher in packaging reliability and more accurate in distance measurement.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical sensing, and in particular relates to a baffle blade type ToF optical sensing module. Background Art

[0002] Today's smartphones, tablets or other handheld devices are equipped with optical modules to achieve functions such as gesture detection, 3D imaging or proximity detection or camera focus. When operating, the ToF sensor emits near-infrared light into the scene and uses the flight time information of the light to measure the distance of objects in the scene. The advantages of ToF sensors are small depth information calculation, strong anti-interference, and long measurement range, so they have gradually become popular.

[0003] The core components of a ToF sensor include: a light source, especially an infrared vertical cavity surface emitting laser (VCSEL); a light sensor, especially a single photon avalanche diode (SPAD); and a time to digital converter (TDC). SPAD is a photodetection avalanche diode with single-photon detection capability, which can generate current as long as there is a weak light signal. The VCSEL in the ToF sensor emits infrared pulses to the scene, the SPAD receives the infrared pulses reflected from the target object, and the TDC records the time interval between the emitted light and the received light (i.e., the flight time), and uses the flight time to calculate the distance of the object to be measured. Therefore, the accurate determination of the time interval between the emitted light and the received light is directly related to the accuracy of the distance. In other words, it is necessary to accurately determine the time when the VCSEL emits the infrared pulse light and the time when the SPAD receives the infrared pulse light reflected from the target object.

[0004] In order to solve the problem that part of the infrared pulse light emitted by the VCSEL is directly received in advance by the SPAD inside the ToF optical sensing module, resulting in inaccurate results, the traditional ToF optical sensing module directly adds a partition structure on the chip, which will cause stress deformation of the chip and errors in the signal receiving area, thereby reducing the product's service life. Summary of the invention

[0005] The object of the present invention is to provide a baffle blade type ToF optical sensing module, characterized in that it comprises a substrate, a cap covered on the upper surface of the substrate, a baffle disposed on the upper surface of the substrate and a transceiver unit, wherein a cavity is formed between the substrate and the cap;

[0006] The inner bottom surface of the cap is provided with a protruding blade extending toward the substrate, the cavity is divided into an emitting cavity and a receiving cavity by the protruding blade, and the measuring light in the emitting cavity is reflected or absorbed by the protruding blade, and an emitting window and a receiving window are respectively provided at the cap and the emitting cavity and the receiving cavity;

[0007] The transceiver unit includes a light-emitting unit and a sensing pixel. The light-emitting unit is arranged in the emitting cavity and is located directly below the emitting window, and is used to emit measurement light. The sensing pixel is arranged in the receiving cavity and is located directly below the receiving window, and is used to receive the measurement light reflected by the target object.

[0008] The baffle prevents external light from affecting the sensing pixels and cooperates with the protruding blades to guide the propagation of the sensing light. It is arranged inside the emission cavity and between the light-emitting unit and the protruding blades to reflect or absorb the measuring light in the emission cavity.

[0009] Furthermore, a pixel substrate is provided on the upper surface of the substrate, and the pixel substrate is located in the receiving cavity and extends into the interior of the emitting cavity;

[0010] The transceiver unit also includes a reference pixel. The sensing pixel and the reference pixel are both arranged on the upper surface of the pixel substrate. The reference pixel is located below the protruding blade and is used to receive the measuring light reflected by the baffle and the protruding blade.

[0011] Furthermore, a gap is left between the protruding blades and the pixel substrate.

[0012] Furthermore, the number of the protruding blades is at least one. When the number of the protruding blades is multiple, the multiple protruding blades are arranged at intervals in the length direction of the cavity, and the closer the protruding blades are to the receiving window, the higher their height, and the greater the angle between the inclined surface and the height surface.

[0013] Furthermore, the protruding blade and the baffle are set to have their initial positions set with the edges close to the receiving window and the transmitting window as the starting points, respectively. Then:

[0014] and / or, the angle between the inclined surface of each protruding blade and the height surface and the angle between the inclined surface of the baffle and the bottom surface are at least 15°;

[0015] And / or, the distance between two adjacent protruding blades is at least 0.3 mm;

[0016] And / or, the height between the protruding blade and the baffle is at least 0.2 mm.

[0017] Further, at least one surface of at least one protruding blade is coated with a coating layer for absorbing the measurement light.

[0018] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0019] 1. The present invention increases the inner surface area of ​​the emitting cavity by protruding blades in the emitting cavity, thereby increasing the amount of reflection and absorption of stray light and / or the number of reflections and absorptions, so that the energy of the stray light passing through the protruding blades is attenuated below the sensitivity threshold of the sensing pixel. The design of the inclined blades can guide the propagation of stray light, while reducing the stray light in the receiving cavity and increasing the probability of the reference pixel receiving the reference light.

[0020] 2. The baffle on the substrate can block external stray light, reduce or prevent stray light from penetrating the protruding blades or the gap between the protruding blades and the substrate and entering the receiving cavity. Some stray light can also be used to improve the accuracy of signal measurement.

[0021] 3. Compared with the prior art, the baffle blade type ToF optical sensing module provided by the present invention reduces the stress deformation of internal parts caused by the packaging design, improves the service life of the product, and has higher accuracy in measuring the distance to the target object.

[0022] 4. The present invention can also change the stray light reaching the reference pixel by adjusting the slope angles of the protruding blades and baffles in the emission cavity, thereby avoiding the problem that the light energy received by the reference pixel of the traditional ToF optical sensing module is too high and requires additional processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a baffle blade type ToF optical sensing module having two protruding structures according to the present invention.

[0024] Figure 2 It is a schematic cross-sectional structure diagram of a baffle blade type ToF optical sensing module with two protruding structures according to the present invention.

[0025] Figure 3 Schematic diagram of light path analysis of a baffle blade type ToF optical sensing module with two protruding structures according to the present invention.

[0026] Figure 4 This is a structural schematic diagram of a baffle blade type ToF optical sensing module of the present invention having only one protruding structure.

[0027] Figure 5 It is a schematic cross-sectional structure diagram of a baffle blade type ToF optical sensing module having only one protruding structure according to the present invention.

[0028] Figure 6 This is a schematic diagram of the optical path analysis of a baffle blade type ToF optical sensing module of the present invention which has only one protruding structure.

[0029] Among them, 10. substrate;

[0030] 20. Cap; 21. Body; 211. Top wall; 212. Lower surface; 22. Transmitting window; 23. Receiving window; 24. Protruding blades;

[0031] 30. Baffle;

[0032] 41. Light-emitting unit; 42. Sensing pixel; 43. Reference pixel; 44. Pixel substrate;

[0033] 51. Transmitting cavity; 52. Receiving cavity;

[0034] L1, measuring light; L2, sensing light; L3, stray light; L4, reference light; F, target; L, length direction;

[0035] W, width direction; H, height direction; α, blade angle; β, blade height; γ, blade spacing; δ, blade initial position; a, baffle angle; b, baffle height; c, baffle initial position. DETAILED DESCRIPTION

[0036] A baffle blade type ToF optical sensing module of the present invention will be described in more detail below in conjunction with a schematic diagram, in which a preferred embodiment of the present invention is shown. It should be understood that those skilled in the art can modify the present invention described herein and still achieve the beneficial effects of the present invention. Therefore, the following description should be understood as being widely known to those skilled in the art and not as a limitation to the present invention.

[0037] like Figure 1-3 As shown, a baffle blade type ToF optical sensing module according to an embodiment of the present disclosure includes a substrate 10, a cap 20, a baffle 30 and a transceiver unit.

[0038] The substrate 10 may include one or more insulating layers and conductive layers, such as a printed circuit board or a ceramic substrate.

[0039] The cap 20 includes a light-proof body 21, an emission window 22, a receiving window 23, and at least one protruding blade 24 connected to the body 21. The body 21 and the substrate 10 together define a cavity. Exemplarily, the body 21 is generally in an inverted U-shaped structure and covers the substrate 10 to form the cavity. The body 21 has a top wall 211, and the top wall 211 has a lower surface 212 facing the substrate 10 and the cavity. It can be understood that the lower surface 212 is located in the cavity and is opposite to the substrate 10. The protruding blade 24 protrudes from the lower surface 212 toward the cavity, or in other words, the protruding blade 24 protrudes from the lower surface 212 toward the substrate 10.

[0040] The baffle 30 is a triangular structure with its inclined surface facing the emission window. The baffle 30 is placed between the pixel substrate and the light-emitting unit and is located in the emission cavity 51 .

[0041] The transceiver unit is located in the cavity and is disposed on the substrate 10. The protruding blades 24 are located between the lower surface 212 and the substrate 10 to cooperate with the transceiver unit to separate the cavity into a transmitting cavity 51 and a receiving cavity 52 corresponding to the transmitting window 22 and the receiving window 23, respectively. All the protruding blades 24 are located in the transmitting cavity 51. Optionally, the protruding blades 24 and the body 21 are an integrated structure or a split structure.

[0042] The transceiver unit is used to transmit the measuring light L1 in the emitting cavity 51. Since the emitted measuring light L1 has a certain divergence angle, a part of the measuring light L1 passes through the emitting window 22 and irradiates a target F located above the cap 20, and after being reflected by the target F, passes through the receiving window 23 as the sensing light L2 and is received by the transceiver unit in the receiving cavity 52. ​​The other part of the measuring light L1 (hereinafter referred to as the part of the measuring light L1 as stray light L3) cannot pass through the emitting window 22, but is reflected in the emitting cavity 51. In this embodiment, the protruding blades 24 and the baffle 30 are arranged in the emitting cavity 51 to enhance the reflection and / or absorption of the stray light L3 by the emitting cavity 51, thereby reducing or preventing the stray light L3 from entering the receiving cavity 52. Specifically, the protruding blades 24 and the baffle 30 increase the inner surface area of ​​the emitting cavity 51, thereby increasing the amount of reflection and absorption of the stray light L3 and / or the number of reflections and absorptions, attenuating the energy of the stray light L3, and accurately transmitting the reference light L4 to the reference pixel 43. The baffle 30 also prevents the possibility of external stray light passing through the gap between the protruding blades 24 and the substrate 10 and entering the receiving cavity 52. ​​Therefore, compared with the traditional ToF optical sensing module, this embodiment reduces the stress deformation of the internal parts caused by the packaging design, improves the product life, and has a higher accuracy in measuring the distance of the target object.

[0043] like Figure 2 As shown, the cavity defines a length direction L, a width direction W, and a height direction H that are perpendicular to each other, and the cavity is divided into a transmitting cavity 51 and a receiving cavity 52 in the length direction L by the protruding blade 24 close to the edge of the receiving window. In the length direction L, the protruding structure 24 is distributed within the length range of the transmitting window 22. In the width direction W, each protruding blade 24 extends in the entire width area or a part of the width area of ​​the cavity. In the former case, the size of the protruding blade 24 in the width direction W is equal to the width of the cavity. In the height direction H, there is a gap between each protruding blade 24 and the substrate 10, and it does not contact the upper surface of the transceiver unit.

[0044] like Figure 4-6As shown, the cap 20 includes at least two protruding blades 24 arranged at intervals in the length direction L to further increase the inner surface area of ​​the cavity, especially the inner surface area of ​​the emitting cavity 51, increase the reflection and absorption amount and / or the number of reflections and absorptions of the stray light L3, thereby further improving the measurement accuracy of the distance to the target object F.

[0045] like Figure 3 and 6 As shown, optionally, each protruding blade 24 sets the initial blade position δ with the right edge of the receiving window 23 as the starting point, and the blade angle α (the angle between the inclined surface of the protruding blade 24 and the height surface) is in the vertical direction, at least 15°. If the angle is too small, the stray light cannot be concentrated, and if it is too large, the stray light cannot enter the specified position. The baffle 30 sets the initial baffle position c with the left edge of the emission window 22 as the starting point, and the baffle angle a (the angle between the inclined surface of the baffle 30 and the bottom surface) is in the horizontal direction, at least 15°. If the angle is too small, the stray light from the outside cannot be blocked, and if it is too large, it will prevent the reference pixel from receiving the stray light.

[0046] like Figure 3 As shown, optionally, the blade spacing γ between two adjacent protruding blades 24 in the length direction L is not less than 0.3 mm. The blade spacing γ provides a transmission space for the stray light L3. If the blade spacing γ is too small, it is not conducive to the transmission of the stray light L3, resulting in a reduction in the number of times the stray light L3 is reflected. If the blade spacing γ is too large, the propagation of the stray light cannot be guided. Therefore, in actual design, the appropriate blade angle α and blade spacing γ can be reasonably selected within the above numerical range according to the specific size of the emitting cavity 51. Optionally, the blade spacing γ of two adjacent protruding blades 24 can be the same or different.

[0047] like Figure 3 and 6 As shown, optionally, the blade height β of each protruding blade 24 and the baffle height b of the baffle 30 are not less than 0.2 mm, wherein the blade height β of the protruding blade 24 does not contact the horizontal height of the upper surface of the transceiver unit, and the higher the height, the better the shielding effect of stray light. Optionally, the heights of the protruding blades 24 can be the same or different.

[0048] like Figure 2 and 4As shown, the number and shape of each protruding blade 24 can be the same or different. The number of protruding blades 24 should be maintained at least one or more, within the size range allowed by the cap 20. For a single protruding blade 24, its shape can be regular or irregular. For example, the shape of its longitudinal section can be any one of a circle, a rectangle, a triangle, an inverted trapezoid, a regular trapezoid, a parallelogram, a rectangle on the top and a semicircle or ellipse on the bottom, a wave shape, and a stepped shape. Each protruding blade 24 can extend in a vertical direction or in an inclined direction inclined relative to the vertical direction. In the latter case, the inclination direction and inclination angle of each protruding blade 4 can be the same or different.

[0049] In this embodiment, a single surface (such as a side surface or bottom surface) of each protruding blade 24 can be a smooth surface or an uneven surface. The latter has a larger surface area, which is more conducive to increasing the reflection and absorption amount and / or the number of reflections and absorption times of the stray light L3.

[0050] Optionally, at least one surface of the baffle 30 and at least one protruding blade 24 is provided with a coating layer for absorbing stray light L3 to reduce or prevent the stray light L3 from entering the receiving cavity 52. ​​According to the light wave emitted by the light emitting unit 41, a material that easily absorbs the light wave (e.g., infrared light) can be selected as the material of the coating layer to increase the absorption rate of the light wave. When the light wave emitted by the light emitting unit 41 is infrared light, the coating layer can be an infrared light absorbing coating, and the material of the coating layer can be an organic color material that can absorb infrared light, such as an infrared light absorber.

[0051] The transceiver unit includes a light emitting unit 41 , a sensing pixel 42 , a reference pixel 43 and a pixel substrate 44 .

[0052] The pixel substrate 44 is disposed on the upper surface of the substrate 10 , with most of it being located in the receiving cavity 52 and a small portion extending into the emitting cavity 51 .

[0053] like Figure 3 As shown, the reference pixel 43 is disposed in the emission cavity 51 and below the protruding blade 24 for receiving the reference light L4.

[0054] The sensing pixel 42 is disposed in the receiving cavity 52 and below the receiving window 23 for receiving the sensing light L2 .

[0055] like Figure 3As shown, the light emitting unit 41 is disposed in the emission cavity 51 and is located below the emission window 22. The light emitting unit 41 is used to emit the measuring light L1. A portion of the measuring light L1 is irradiated onto a target F located above the cap 20 through the emission window 22, and is reflected by the target F and then received by the sensing pixel 42 through the receiving window 23 as the sensing light L2. Another portion of the measuring light L1 (i.e., the stray light L3) is reflected and / or absorbed by the protruding blades 24 in the emission cavity 51, and at least a portion of it is received by the reference pixel 43 as the reference light L4. It can be understood that the reference light L4 received by the reference pixel 33 is significantly less than the stray light L3, which helps to reduce the measuring light L1 reaching the reference pixel 33, thereby avoiding the problem that the measuring light energy received by the reference pixel of the conventional ToF optical sensing module is too high and requires additional processing to reduce the received light energy.

[0056] Now, in combination with the structure of the transceiver unit in this embodiment, the ranging principle of the ToF optical sensing module is introduced.

[0057] The mathematical formula based on the distance measurement of the ToF optical sensing module is 2L=CΔt, where L is the distance from the optical sensing module to the target object F, C is the speed of light, and Δt is the flight time of light (defined here as the time from emission to reception), so it is necessary to determine the emission time point and the reception time point respectively. The reception time point is determined based on the sensing electrical signal generated by the sensing pixel 42 after receiving the sensing light L2, while the emission time point can be determined based on the reference electrical signal generated by the reference pixel 43 after receiving the measurement light L1 in the emission cavity 51. As mentioned above, the light-emitting unit 41 has a certain divergence angle, so another part of the measurement light L1 emitted by the light-emitting unit 41 will be reflected in the emission cavity 51. Since the travel distance of this part of the measurement light L1 reflected in the cavity can be ignored compared to the detection distance (2L) of the target object F, the time point when the reference pixel 43 receives this part of the measurement light L1 (i.e., the reference light L4) can be used as the emission time point.

[0058] In other embodiments, the time point when the light-emitting unit 41 is controlled to emit light may be used as the emission time point, or the time point when the light-emitting unit 41 is controlled to emit light plus a predetermined delay time may be used as the emission time point.

[0059] In some embodiments, the light-emitting unit 41 is configured to emit radiation at a specific frequency or frequency range, such as emitting infrared (IR) rays. The light-emitting unit 41 may be a VCSEL or a light-emitting diode (LED), such as an infrared LED. The light-emitting unit 41 may be fixed to the upper surface of the substrate 10 by an adhesive material, and may be electrically connected to the substrate 10 by, for example, wire bonding or conductive bumps.

[0060] In some embodiments, Figure 1 , Figure 2 , Figure 3 As shown, the transceiver unit and the baffle 30 can be fixed on the substrate 10, and the cavity is divided into a transmitting cavity 51 and a receiving cavity 52 by the protruding blade 24 as a boundary. There is a gap between the bottom end of the protruding blade 24 and the upper surface of the pixel substrate 44. The sensing pixel 42 and the reference pixel 43 are formed in the pixel substrate 44.

[0061] A part of the above-mentioned pixel is a photosensitive structure, such as a photodiode, an avalanche photodiode (APD), etc. In this embodiment, it is a SPAD, and the other part of the pixel is a sensing circuit for processing the electrical signal from the photosensitive structure. The material of the pixel substrate 44 may include a semiconductor material, such as silicon, germanium, tin nitride, silicon carbide, arsenic, phosphide, indium phosphide, indium arsenide, indium antimonide, silicon germanium alloy, arsenic phosphorus alloy, arsenic aluminum alloy, arsenic aluminum alloy, arsenic indium alloy, arsenic phosphorus alloy, arsenic phosphorus alloy or a combination of the above materials. The pixel substrate 44 may also include one or more electrical components (such as integrated circuits). The integrated circuit may be an analog or digital circuit, and the analog or digital circuit may be implemented as an active component, a passive component, a conductive layer and a dielectric layer formed in the chip and electrically connected according to the electrical design and function of the chip. The pixel substrate 44 can be electrically connected to the substrate 10 through bonding wires or conductive bumps, and further electrically connected to the outside and the light-emitting unit 41, so that the chip can control the operation of the light-emitting unit 41, the sensing pixel 42 and the reference pixel 43, and provide signal processing functions.

[0062] In some embodiments, the cavity can be a solid body made of a transparent mold, and the main body 21 is made of an opaque material, such as an opaque mold or metal, etc., and covers the cavity of the transparent mold, leaving only the portion of the transparent mold corresponding to the receiving window 23 and the emitting window 22 exposed.

[0063] In other embodiments, the cavity may be air (may contain pressures higher or lower than one atmosphere). It is understood that in this embodiment, the cap 20 may be prefabricated and pasted on the substrate 10, for example, partially or entirely formed directly on the substrate 10 by injection molding. The receiving window 23 and the emitting window 22 may be hollow openings penetrating the top wall 211 of the body 21, or optical devices with special optical functions, such as optical filters of specific wavelengths, or lenses or diffraction elements with functions such as astigmatism or focusing, or a combination of multiple optical functions, such as the first two. For example, the emitting window 22 is a lens for astigmatism to increase the irradiation range of the measuring light L1 to the target F; the receiving window 23 is a lens for focusing to focus the sensing light L2 on the sensing pixel 42.

[0064] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A baffle blade type ToF optical sensing module, characterized in that: It comprises a substrate, a cap disposed on the upper surface of the substrate, a baffle disposed on the upper surface of the substrate, and a transceiver unit, wherein a cavity is formed between the substrate and the cap; The inner bottom surface of the cap is provided with a protruding blade extending toward the substrate, the cavity is divided into an emitting cavity and a receiving cavity by the protruding blade, and the measuring light in the emitting cavity is reflected or absorbed by the protruding blade, and an emitting window and a receiving window are respectively provided at the cap and the emitting cavity and the receiving cavity; The transceiver unit includes a light emitting unit and a sensing pixel, wherein the light emitting unit is disposed in the emitting cavity and is located directly below the emitting window, and is used to emit the measuring light, and the sensing pixel is disposed in the receiving cavity and is located directly below the receiving window, and is used to receive the measuring light reflected by the target object; The baffle is arranged inside the emission cavity and between the light emitting unit and the protruding blades, and is used for reflecting or absorbing the measuring light in the emission cavity.

2. The baffle blade type ToF optical sensing module according to claim 1, characterized in that: A pixel substrate is also provided on the upper surface of the substrate, and the pixel substrate is located in the receiving cavity and extends into the interior of the emitting cavity; The transceiver unit further includes a reference pixel. The sensing pixel and the reference pixel are both arranged on the upper surface of the pixel substrate. The reference pixel is located below the protruding blade and is used to receive the measurement light reflected by the baffle and the protruding blade.

3. The baffle blade type ToF optical sensing module according to claim 2, characterized in that: A gap is left between the bottom end of the protruding blade and the pixel substrate.

4. The baffle blade type ToF optical sensing module according to claim 2, characterized in that: The number of the protruding blades is at least one. When the number of the protruding blades is multiple, the multiple protruding blades are arranged at intervals in the length direction of the cavity, and the closer the protruding blades are to the receiving window, the higher their height is, and the larger the angle between the inclined surface and the height surface is.

5. The baffle blade type ToF optical sensing module according to claim 4, characterized in that: The protruding blades and the baffle are set to have initial positions with the edges of the receiving window and the emitting window as starting points, respectively. Then, the angle between the inclined surface and the height surface of each protruding blade and the angle between the inclined surface and the bottom surface of the baffle are at least 15°, the distance between two adjacent protruding blades is at least 0.3 mm, and the height between the protruding blades and the baffle is at least 0.2 mm.

6. The baffle blade type ToF optical sensing module according to claim 4, characterized in that: At least one surface of at least one protruding blade is coated with a coating layer for absorbing measurement light.

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