Stabilized 3D optical sensing device

Abstract

An electro-optical module (EOM) included within a housing is provided. The EOM includes at least two camera modules and is configured to determine a depth of the target by using a block matching algorithm operable to match pixels originating from an image captured by one of the camera modules with pixels originating from an image captured by the other of the two camera modules. The EOM is characterized in that the EOM comprises: a first isolation material located between the EOM and its housing, the first isolation material being configured to prevent the generation of structural forces due to deformation of the EOM housing; a main processor substrate PCB, to which each of the camera modules is connected; and one or more flat cables connecting the EOM housing with the host processor substrate PCB, where the one or more flat cables are placed in an "s" shape within the EOM housing.

Description

Technical Field

[0001] This disclosure generally relates to optical devices, and more specifically to 3D optical sensing devices. Background Technology

[0002] Stereo 3D sensing / scanning optical modules typically rely on triangulation mechanisms to sense depth, where the result is obtained by processing the results from two nearly identical image sensors. The algorithm implemented by this mechanism utilizes block matching, that is, matching pixels from the left image with pixels from the right image.

[0003] In many 3D sensing optical modules, block matching algorithms operate in real-time, simultaneously matching several pixel lines from the left and right sensors to determine the depth of an object. Once calibrated, the module is expected to maintain its structural stability and not deform over time, with changes in temperature and other environmental factors, as mechanical variations can significantly impact the module's performance in accurately detecting distance (depth).

[0004] However, one of the main problems associated with operating such an optical module is the management of instabilities, such as those caused by thermal expansion in the integrated 3D sensing module. Thermal expansion, for example, due to heat generated by the module or heat generated outside the module, can cause mechanical deformation, which can result in slight movement of the optical elements (image sensor and / or lens) compared to the initial calibration settings.

[0005] 3D sensing systems can be sensitive even to microscopic movements in the XY plane, ranging from about 0.1 to 2 pixels in magnitude. These movements are translated into very small angular motions by lenses, since the typical size of a pixel is 1–3 μm. This means that the left and right sensors must maintain their relative positions in order to match pixels originating from the left and right sensors.

[0006] Thermal expansion is a natural phenomenon in which materials expand or contract with changes in temperature. Materials expand linearly with temperature according to their coefficient of thermal expansion.

[0007] To maintain structural stability, camera modules are typically housed in metal reinforcements. These reinforcements can help maintain the module's dimensional stability over time if they are heat-treated to relieve stress. Stress relief is crucial because metal reinforcements are exposed to very high stresses during CNC machining or injection molding. If this stress is not relieved, the material forming the metal reinforcement will deform slowly over time. This, in turn, can lead to structural stability issues. This is a "long-term" effect that can cause device performance to deteriorate over time, and its impact is often unpredictable.

[0008] In addition, other "short-term" effects occur during normal operation. Most of these short-term effects are caused by thermal expansion forces. These thermal expansion forces can be very high.

[0009] In 3D sensing applications, electrical components are typically placed on printed circuit boards (PCBs), and the depth processor, which also runs other algorithms, generates a lot of heat, which in turn causes thermal expansion of the PCB.

[0010] Figure 1 illustrates a prior art example of a 3D optical sensing device 100, which includes two optical sensors (110' and 110") as two camera modules and a housing 120.

[0011] Figure 2 shows a prior art example of a typical printed circuit board (PCB) 200 on which a processor is mounted, which is configured to be placed together with a camera module structure (aka “EOM” - electro-optical module) by connecting the PCB 200 to the EOM housing (not shown) via mechanical holes 210. As can be seen, the hot spots generated at PCB (220' and 220") due to the operation of the two camera modules cause PCB 200 to thermally expand in different (typically unpredictable) directions. Some possible such thermal expansion vectors are shown in the figure, such as 230. Since PCB 200 is fixed to the EOM housing as described above, the thermal expansion of PCB 200 will cause housing deformation due to the strong forces generated by the thermal expansion of PCB 200. This housing deformation may deform the EOM reinforcement, which expands at a different rate than the expansion rates of the PCB and housing, potentially leading to small angular structural differences between the left and right image sensors. The same applies to structured light 3D sensors, which rely on the accuracy of placement between the image sensor and the pattern projector. Mechanical holes 210 are used to pass screws that secure the PCB to the EOM housing. When these screws are tightened, they act as anchors, and the thermally expanding PCB pushes against these anchors in different directions. This, in turn, will cause deformation of the mechanical structure and thus degrade the performance of the electro-optical module. Summary of the Invention

[0012] This disclosure can be summarized by referring to the appended claims.

[0013] One object of this disclosure is to provide a 3D optical sensing device, characterized in that the optical sensor included in the 3D optical sensing device maintains its position relative to the device housing, thereby substantially preventing degradation of device performance.

[0014] Another object of the present invention is to provide a 3D optical sensing device, characterized in that each component included in the 3D optical sensing device expands at its own expansion rate without adversely affecting the performance of the 3D optical sensing device due to changes in the relative positions of the optical sensing devices.

[0015] Another object of the present invention is to provide a 3D optical sensing device that maintains its structural position over time and when operating at different temperatures, and thus maintains the performance of the 3D optical sensing device.

[0016] Another object of this disclosure is to provide an electro-optical module comprising two camera modules, wherein the positions of the two camera modules relative to each other are maintained.

[0017] Other objects of the invention will become apparent from the following description.

[0018] This invention relates to an electro-optic module (hereinafter referred to as "EOM"), which is a 3D sensing module requiring its optical elements to have accurate and fixed positions. Throughout the specification and claims, the term "EOM" is used to denote a module comprising at least two optical elements. One option includes using two or more camera modules (referred to herein as a compact camera module, "CCM"). Another option includes using at least one camera module and at least one projector, wherein the projector is referred to as a structured light 3D scanner. Furthermore, the EOM includes a metal reinforcement, optical components, and other components and a PCB that can be attached to the metal reinforcement.

[0019] According to a first embodiment of the present invention, an electro-optical module (“EOM”) is provided, the electro-optical module including a housing and including at least two camera modules, wherein the EOM is configured to determine the depth of a target by using a block matching algorithm operable to match pixels from an image captured by one of the at least two camera modules with pixels from an image captured by the other of the at least two camera modules, wherein the EOM is characterized in that the EOM includes a combination of the following:

[0020] - A first insulating material located between the EOM and its housing, wherein the first insulating material is configured to prevent structural forces from being generated due to deformation of the EOM housing, which could adversely affect the structural stability of one or both of the two camera modules;

[0021] - Main processor substrate PCB, each of the at least two camera modules (i.e., compact camera modules) is connected to the main processor substrate PCB;

[0022] - One or more flat cables connecting the EOM housing to the main processor substrate PCB, wherein the one or more flat cables are arranged in an "S" shape inside the EOM housing.

[0023] According to another embodiment of the present invention, the electro-optic module further includes:

[0024] - A metal reinforcement, to which the optical components are mounted; and

[0025] - A junction PCB is configured to attach to a metal reinforcement of the EOM and to connect to each of at least two camera modules mounted on the reinforcement. Optionally, the junction PCB may be configured to carry electrical components such as an inertial module (“IMU”), power supply, connectors, flash memory, etc.

[0026] In yet another embodiment, one or more flat cables are also configured to connect the EOM housing to the bonding PCB.

[0027] According to another embodiment of the invention, the EOM is further characterized in that stress is eliminated from the first insulating material before the first insulating material is incorporated into the EOM housing.

[0028] As another embodiment of the invention, the EOM also includes one or more heat sinks configured to remove heat dissipated from operating heat-generating components included within the EOM housing to a surface outside the EOM housing.

[0029] According to yet another embodiment, if the main processor substrate PCB or bonding PCB is connected to the rear side of the EOM, the connection is characterized by having a single connection point referred to herein as a "hard connection," which is configured to securely fasten the main processor substrate PCB or bonding PCB to a reinforcement (e.g., a screw) of the EOM; and the connection is characterized by having one or more soft connection points, each soft connection point adapted to ensure that the pressure applied to the main processor substrate PCB or bonding PCB does not exceed a predefined pressure, a lower pressure that will not adversely affect the EOM. The significance of this embodiment lies in its ability to extract heat dissipated from the substrate PCB assembly in a manner that overcomes the difference in expansion rate between the first insulating material located between the EOM structure and the housing (i.e., the metal reinforcement on which the camera module is mounted).

[0030] According to yet another embodiment of the invention, the bonding PCB is configured to be electrically connected to a connector located on the outer surface of the EOM housing via one or more flat cables arranged in an "S" shape. Attached Figure Description

[0031] To gain a more complete understanding of the present invention, reference is now made to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0032] Figure 1 shows a prior art example of a 3D optical sensing device;

[0033] Figure 2 shows a typical prior art PCB configured for a 3D optical sensing device;

[0034] Figure 3 A 3D electro-optic module illustrated according to an embodiment of the present invention is shown;

[0035] Figure 4 The rear side of the PCB is shown as an example;

[0036] Figure 5 Another example of an EOM (Entity Object Model) including both a camera module and a projector is shown; and

[0037] Figure 6 An example of a partially exploded view of a 3D sensing module (EOM) as illustrated in an embodiment of the present invention is shown. Detailed Implementation

[0038] In this disclosure, the term "comprising" is intended to have an open-ended meaning, so that when a first element is described as including a second element, the first element may also include one or more other elements that are not necessarily identified or described herein or stated in the claims.

[0039] In the following description, numerous specific details are set forth for purposes of explanation in order to provide a better understanding of the invention by way of example. However, it will be apparent, however, that the invention may be practiced without these specific details.

[0040] As discussed above, the present invention relates to a 3D sensing module (i.e., EOM) that requires its optical elements to have accurate and fixed positions relative to each other, i.e., relative positions that do not change over time.

[0041] To achieve this goal, the present invention provides a method for isolating the EOM from external mechanical forces that may be transmitted from the EOM housing inward toward the EOM assembly, such that the positions of the optical elements (e.g., two CCMs) relative to each other remain constant over time and with temperature changes.

[0042] Mechanical forces that may cause deformation of the EOM structure include:

[0043] 1. Thermal expansion of the EOM itself due to components installed at the EOM;

[0044] 2. Thermal expansion of different components anchored to the EOM at more than one point;

[0045] 3. This includes the thermal expansion of the EOM's outer casing;

[0046] 4. Mechanical deformation of the EOM casing due to the following:

[0047] a. When the EOM is installed where it needs to operate (target application, e.g., robot).

[0048] At that time, external mechanical forces are applied to the EOM shell.

[0049] b. Deformation of the EOM housing due to expansion of the PCB, which is firmly connected to the EOM housing.

[0050] c. Deformation caused by the flat cable used to connect the camera module to the main processor PCB.

[0051] Figure 3 A 3D electro-optic module 300 according to an embodiment of the present invention is shown. As depicted in the figure, the EOM 300 includes a PCB 310, an EOM reinforcement 320, and a second insulating material 330, which is a soft insulating material, such as molded silicon having a Shore hardness of 30.

[0052] Figure 4 The back of an illustrative bonding PCB 400 suitable for use with an EOM is shown. This view reveals a single connection point 410 for securely connecting the bonding PCB 400 to a reinforcement (not shown) of the EOM via a single screw. Furthermore, a flexible, loosely laid flat cable 420 connects the PCB 400 to the EOM housing. The flat cable 420 is positioned in an "S" shape when the 3D optical sensing device containing the EOM is assembled.

[0053] Preferably, when PCB bonding is achieved using EOM, an S-shaped flexible cable is used to connect the bonding PCB to the camera module, and another flexible cable is used to connect the bonding PCB to the main PCB.

[0054] If a bonding PCB is not used, the camera module is preferably connected directly to the main PCB using any suitable S-shaped flat flexible cable (FPC).

[0055] Figure 5This example shows a partial view of another example of the EOM 500. As can be seen from this example, the EOM includes a PCB 510, a projector 540, and three camera modules 520, 520', and 520" (two of which are IR camera modules for depth processing, and one is an RGB camera module) attached to the PCB 510 using S-shaped flexible flat cables 530, 530', and 530". The projector 540 is also attached to the PCB 510 using a flexible cable 550.

[0056] Figure 6 An example of a partially exploded view of a 3D sensing module (EOM) as illustrated in an embodiment of the present invention is shown.

[0057] The figure illustrates an electro-optical module (EOM) 600. This illustrated module has a housing (outer shell) 610, partially shown in the figure, and the module 600 also includes an optical bench (reinforcement) 620 on which two camera modules (i.e., left CCM 630 and right CCM 640) are mounted, each at a predefined precise location. The two camera modules 630 and 640 are each connected to a PCB (not shown in the figure).

[0058] As described above, the EOM housing 610 may be deformed due to the expansion of the bonding PCB, which is firmly attached to the EOM housing 610, and due to the external mechanical forces applied to the EOM housing after EOM installation and operation. To mitigate both types of deformation, a soft insulating material 65 is used.

[0059] In the specification and claims of this application, each of the verbs “comprising,” “including,” and “having,” and its conjugations, is used to indicate that one or more objects of the verb are not necessarily a complete list of components, parts, elements, or portions of one or more subjects of the verb.

[0060] The invention has been described through a detailed description of embodiments of the invention provided by way of example and not intended to limit the scope of the invention in any way. The described embodiments include various features, which are not necessarily required in all embodiments of the invention. Some embodiments of the invention utilize only some of the features or combinations of possible combinations of features. Those skilled in the art will appreciate variations of the described embodiments of the invention, as well as embodiments of the invention that include different combinations of the features recited in the described embodiments. The scope of the invention is limited only by the following claims.

Claims

1. An electro-optical module comprising at least two camera modules within a housing and comprising, The electro-optical module is configured to determine a depth of an object by using a block matching algorithm operable to match pixels originating from an image captured by one of the at least two camera modules with pixels originating from an image captured by another of the at least two camera modules, wherein the electro-optical module is characterized in that it comprises: a first isolation material located between the electro-optical module and a housing of the electro-optical module, wherein the first isolation material is configured to prevent structural forces from being generated due to deformation of the housing of the electro-optical module; a main processor PCB to which each of the at least two camera modules is connected; one or more flat cables connecting the housing of the electro-optical module to the main processor PCB, wherein the one or more flat cables are arranged in an "s" shape within the housing of the electro-optical module.

2. The electro-optical module of claim 1, further comprising: a metal reinforcement to which the optical assembly is mounted; and a junction PCB configured to be attached to the metal reinforcement and connected to each of the at least two camera modules mounted on the reinforcement. The one or more flat cables are further configured to connect the housing of the electro-optical module to the junction PCB.

3. The electro-optical module of claim 2, wherein, Stress is removed from the first isolation material prior to incorporating the first isolation material within the housing of the electro-optical module.

4. The electro-optical module of claim 1, further characterized by, 5. The electro-optical module of claim 1, further comprising one or more heat sinks configured to remove heat emitted from operational heat generating components included within the housing of the electro-optical module to a surface outside of the housing of the electro-optical module. In case the main processor PCB or the junction PCB is connected to a rear side of the electro-optical module, 6. The electro-optical module of claim 2, wherein, the connection is characterized by having a single connection point configured to firmly fix the main processor PCB or the junction PCB to a reinforcement of the electro-optical module, and the connection is characterized by having one or more soft connection points, each soft connection point adapted to ensure that a pressure applied on the main processor PCB or the junction PCB does not exceed a predetermined pressure, but a lower pressure which does not adversely affect the electro-optical module. The junction PCB is configured to be electrically connected to a connector located at an outer surface of the housing of the electro-optical module by the one or more flat cables arranged in an "s" shape.

7. The electro-optical module of claim 2, wherein, ​

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