An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in its entirety and for all purposes.
The present disclosure relates to a Time of Flight (TOF) optical sensing module.
Today's smart phones, tablet computers or other handheld devices are equipped with optical modules to achieve gesture detecting, three-dimensional (3D) imaging, proximity detecting or camera focusing and other functions. The TOF sensor emits near infrared light toward the scene to measure the distance from the object in the scene according to the TOF information of light. The advantages of the TOF sensor include the small depth information calculation loading, the strong anti-interference and the long measurement range, so it has gradually been favored.
The core components of the TOF sensor include: a light source, more particularly an infrared vertical chamber surface emitting laser (VCSEL); an optical sensor, more particularly a single photon avalanche diode (SPAD); and a time-to-digital converter (TDC). The SPAD is a photoelectric detection avalanche diode having the single photon detection ability of generating a current as long as a weak optical signal is received. The VCSEL in the TOF sensor emits infrared pulse light to the scene, the SPAD receives the infrared pulse light reflected back from a target object, and the TDC records a time interval (i.e., a TOF) between the time of emitting and receiving the light, and calculates the distance of the to-be-measured object according to the TOF. Therefore, the accurate determination of the time interval between the time of emitting and receiving the light is directly related to the accuracy of the distance. In other words, it is necessary to accurately determine the time at which the VCSEL emits the infrared pulse light and the time at which the SPAD receives the infrared pulse light reflected back from the target object.
However, when the traditional TOF optical sensing module is used, a portion of the infrared pulse light emitted from the VCSEL is directly received by the SPAD in the interior of the TOF optical sensing module, and a time instant at which the portion of the infrared pulse light is received by the SPAD is earlier than another time instant at which another portion of the infrared pulse light is received by the SPAD after being reflected back from the to-be-measured object. Therefore, the former one of the two time instants will be wrongly used to calculate the distance of the to-be-measured object, resulting in an inaccurate result.
The present disclosure provides a TOF optical sensing module to solve the problem that it is difficult for the traditional TOF optical sensing module to accurately determine the distance of a to-be-measured object.
The embodiments of the present disclosure provide a TOF optical sensing module, including a substrate, a cap, and a transceiving unit. The cap includes a body, and a transmitting window, a receiving window, a partition structure and at least one protruding structure all connected to the body. The body and the substrate together define a chamber, the body has a lower surface facing the substrate and the chamber, and the protruding structure protrudes from the lower surface toward the chamber. The transceiving unit is provided in the chamber, and the partition structure is provided between the lower surface and the substrate to divide the chamber into an emitting chamber and a receiving chamber respectively corresponding to the transmitting window and the receiving window, in conjunction with the transceiving unit. The transceiving unit is configured to emit detection light from the emitting chamber and receive sensing light in the receiving chamber through the receiving window. Each of the protruding structures is disposed in the emitting chamber to reflect and/or absorb the detection light traveling in the emitting chamber towards the receiving chamber.
In the TOF optical sensing module of the present disclosure, the protruding structure in the emitting chamber increases the inner surface area of the emitting chamber, thus increasing the reflection and absorption amount and/or reflection and absorption times of stray light, and attenuating energy of the stray light, so as to reduce or prevent the stray light from entering the receiving chamber through the partition structure or the gap between the partition structure and the substrate. Therefore, as compared with the prior art, the TOF optical sensing module of the present disclosure has a higher accuracy in measuring the distance of the target object.
In addition, the protruding structure in the emitting chamber can also reduce the detection light reaching the reference pixel, thus avoiding the problem that the energy of the detection light received by the reference pixel of the traditional TOF optical sensing module is too high and additional processing is required to reduce the energy received by the reference pixel.
The drawings illustrated here provide a further understanding of the embodiments of the present disclosure, constitute a part of the specification to illustrate the embodiments of the present disclosure, and serve to explain the principle of the present disclosure together with the description. Obviously, the drawings described below involve only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be derived from these drawings without any inventive efforts. In the drawings:
For a better understanding of the technical features of the present disclosure, a clear and complete description of the embodiments of the present disclosure will be set forth with reference to the drawings. Obviously, the described embodiments are only a part, rather than all, of the embodiments of the present disclosure. All other embodiments derived by persons skilled in the art from the embodiments of the present disclosure without making inventive efforts shall fall within the scope of the present disclosure.
The substrate 10 may include one or more insulating layers and electroconductive layers, such as a printed circuit board or a ceramic substrate.
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As an optional technical solution, the partition structure 24, in conjunction with the transceiving unit 30, divides the chamber 40 into the emitting chamber 41 and the receiving chamber 42 which are partially communicated with each other. In this solution, although there is a gap between the partition structure 24 and the transceiving unit 30, the protruding structure 25 can reduce or prevent the stray light from entering the receiving chamber 42 through the gap, thus improving the accuracy of measuring the distance of the object F.
As another optional technical solution, the partition structure 24, in conjunction with the transceiving unit 30, divides the chamber 40 into the emitting chamber 41 and the receiving chamber 42 which are completely uncommunicated with each other, so as to prevent the mutual interference between the receiving chamber 42 and the emitting chamber 41. In this solution, since there is no gap between the partition structure 24 and the transceiving unit 30, the stray light can be prevented from entering the receiving chamber 42 through the gap, while the protruding structure 25 can reduce or prevent the stray light from entering the receiving chamber 42 through the partition structure 24, thus further improving the accuracy of measuring the distance of the object F.
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In the embodiments, a single surface (e.g., a side surface or a bottom surface) of each of the protruding structures 25 may be a smooth surface or an uneven surface, and the latter has a larger surface area, which is more conducive to increasing the reflection and absorption amount and/or the reflection and absorption times of the stray light L3.
Optionally, at least one surface of the at least one protruding structure 25 is provided with a coating layer for absorbing the stray light L3, so as to reduce or prevent the stray light L3 from entering the receiving chamber 42. According to the light wave emitted by the light-emitting unit 31, a material that can easily absorb the light wave (e.g., infrared light) may 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 31 is infrared light, the coating layer may be an infrared light absorption coating layer, and the material of the coating layer may be an organic color material that can absorb the infrared light, such as an infrared light absorber.
Illustratively, at least one surface of each of the protruding structures 25 is provided with the coating layer, or all surfaces of each of the protruding structures 25 exposed in the emitting chamber 41 are provided with the coating layer to improve the absorption amount and/or the absorption times of the stray light L3.
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In the embodiments, optionally, the shape of the protruding structure 25 may be regular or irregular. Illustratively, the longitudinal section may be in the shape of a trapezoid (as illustrated in
In the embodiments, the gap g between various portions of the bottom surface of the protruding structure 25 and the transceiving unit 30 may be different. Optionally, the gap g between a lowest portion of the protruding structure 25 and the transceiving unit 30 is not more than 1 mm, i.e., a minimum gap g between the protruding structure 25 and the transceiving unit 30 is not more than 1 mm.
In the embodiments, optionally, a single surface (e.g., a side surface or a bottom surface) of the protruding structure 25 may be a smooth surface or an uneven surface, and the latter has a larger surface area, which is more conducive to increasing the reflection and absorption amount and/or the reflection and absorption times of the stray light L3.
In some embodiments, each of the protruding structures 25 is spaced apart from the partition structure 24, i.e., the protruding structure 25 is spaced apart from the partition structure 24 in the length direction L.
In other embodiments, at least one protruding structure 25 is in contact with the partition structure 24. When there are two or more protruding structures 25, the side surface of the protruding structure 25 closest to the partition structure 24 may be attached to the partition structure 24. When there is one protruding structure 25, the side surface of the protruding structure 25 facing the partition structure 24 may be attached to the partition structure 24, as illustrated in
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In some embodiments, at least part of the at least one protruding structure 25 is disposed between the reference pixel 33 and the transmitting window 22. For example, a part of the at least one protruding structure 25 is disposed between the reference pixel 33 and the transmitting window 22, and the other part of the at least one protruding structure 25 is disposed between the partition structure 24 and the reference pixel 33. Alternatively, all of the at least one protruding structure 25 is disposed between the reference pixel 33 and the transmitting window 22 (as illustrated in
In some other embodiments, all of the at least one protruding structure 25 may be disposed between the reference pixel 33 and the partition structure 24.
The ranging principle of the TOF optical sensing module will now be introduced with reference to the structure of the transceiving unit 30 in the embodiments.
The TOF optical sensing module measures the distance of the object based on a mathematical formula of 2 L=CΔt, where L denotes the distance from the optical sensing module to the target object F, C denotes the speed of light, and Δt denotes the traveling time of light (herein defined as the time difference between the emitting time and the receiving time), so it is necessary to determine an emitting time instant and a receiving time instant respectively. The receiving time instant may be determined according to the sensing electrical signal generated by the sensing pixel 32 upon receipt of the sensing light L2, and the emitting time instant may be determined according to the reference electrical signal generated by the reference pixel 33 upon receipt of the detecting light L1 in the emitting chamber 41. As mentioned above, the light-emitting unit 31 has a predetermined divergence angle, so the other portion of the detection light L1 emitted by the light-emitting unit 31 will be reflected in the emitting chamber 41. Since the traveling distance of the other portion of the detection light L1 reflected in the chamber 40 can be neglected when compared with the distance (2 L) of the target object F, the time instant at which the reference pixel 33 receives the other portion of the detection light L1 (i.e., the reference light L4) can be set as the emitting time instant.
In some other embodiments, a time instant at which the light-emitting unit 31 is controlled to emit light may be set as the emitting time instant, or the above time instant plus a predetermined delay time may be set as the emitting time instant.
In some embodiments, the light-emitting unit 31 is configured to emit the radiation (e.g., infrared (IR) light) with a specific frequency or frequency range. The light-emitting unit 31 may be a VCSEL or a Light-Emitting Diode (LED), such as an infrared LED. The light-emitting unit 31 may be attached to the upper surface of the substrate 10 through an adhesive material, and may be electrically connected to the substrate 10 through, for example, bonding wires or electroconductive bumps.
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A portion of the pixels is a photosensitive structure, such as a photodiode, an Avalanche Photo Diode (APD) and the like, which is the SPAD in this embodiment. The other portion of the pixels is a sensing circuit for processing an electrical signal coming from the photosensitive structure. The material of the pixel substrate 34 may include a semiconductor material, such as silicon, germanium, gallium nitride, silicon carbide, gallium arsenide, gallium phosphide, indium phosphide, indium arsenide, indium antimonide, silicon germanium alloy, gallium arsenide phosphide alloy, aluminum indium arsenic alloy, aluminum gallium arsenic alloy, gallium indium arsenic alloy, gallium indium phosphide alloy, gallium indium arsenic phosphide alloy or combinations thereof. The pixel substrate 34 may further include one or more electric elements (e.g., integrated circuits). The integrated circuit may be an analog or digital circuit, which may be realized as an active element, a passive element, an electroconductive layer, a dielectric layer and the like formed in a chip and achieve an electrical connection according to the electric design and the function of the chip. The pixel substrate 34 may be electrically connected to the substrate 10 through bonding wires or electroconductive bumps, and then electrically connected to an external device and the light-emitting unit 31, whereby the operations of the light-emitting unit 31, the sensing pixel 32 and the reference pixel 33 can be controlled by the chip, and a function of signal processing can be provided by the chip.
In some embodiments, the chamber 40 may be a solid body made of a light-transmission molding compound, and the body 21 may be made of an opaque material such as an opaque molding compound, metal and the like, and covers the chamber 40 made of the light-transmission molding compound with a portion of the light-transmission molding compound corresponding to the receiving window 23 and the transmitting window 22 being exposed.
In other embodiments, the chamber 40 may be filled with air with a pressure higher than or lower than one atmosphere. It can be understood that the cap 20 of this embodiment may be previously formed and adhered to the substrate 10. For example, the cap 20 may be directly and partially or entirely formed on the substrate 10 by way of injection molding. The receiving window 23 and the transmitting window 22 may be hollow openings penetrating the top wall 211 of the body 21, or may be optical devices with special optical functions such as optical filters of specific wavelengths, lenses or diffractive elements with the light defocusing or focusing function, and the like, or may be combinations of elements with multiple optical functions, such as the former two elements. For example, the transmitting window 22 is a scattering lens to increase an irradiation range of the detection light L1 for the target object F, and the receiving window 23 is a condensing lens to focus the sensing light L2 on the sensing pixel 32.
The disclosure has been described above with reference to the specific embodiments, but it should be clear to those skilled in the art that these descriptions are exemplary and not intended to limit the protection scope of the present disclosure. Variations and modifications can be made to the present disclosure by those skilled in the art in light of the spirit and principle of the present disclosure and should fall within the scope of the present disclosure.
Number | Date | Country | Kind |
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2022114037947 | Nov 2022 | CN | national |
Number | Date | Country | |
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63332280 | Apr 2022 | US |