Patent Description:
Time-of-flight (TOF) imaging techniques are used in many depth mapping systems (also referred to as 3D mapping or 3D imaging). In so-called "direct" TOF techniques, a light source, such as a pulsed laser, directs pulses of optical radiation toward the scene that is to be mapped, and a high-speed detector senses the time of arrival of the optical radiation reflected back from the scene. The depth value at each pixel in the depth map is derived from the difference between the emission time of the outgoing pulse of optical radiation and the arrival time of the optical radiation reflected from the corresponding point in the scene, which is referred to as the "time of flight" of the optical pulses.

<CIT> describes micro-machined microlens assemblies. <CIT> describes a distance-measuring unit for measuring a detection field based on a time-of-flight signal. <CIT> describes a dynamic micro-positioner and aligner.

For some desired applications, in order to meet desired performance and resolution metrics, it is desired to scan the optical light source across the scene, and to properly receive the optical radiation reflected back from the scene during that scan. As an example, the light source and high-speed detector may be scanned with respect to optical lenses through which the outgoing pulses of optical radiation and incoming optical radiation reflected back from the scene.

However, current scanning techniques may consume an undesired amount of area. In addition, the thickness of optical modules used with such techniques is greater than desired. Given that depth mapping systems are typically incorporated into compact electronic devices, the excess area consumption and excess thickness is particularly undesirable. As such, development into compact TOF systems utilizing a scanning solution to depth map a scene is necessary, and it is desirable for such compact TOF systems to maintain the robustness of existing systems.

An optical module includes: a substrate; an optical detector carried by the substrate; a laser emitter carried by the substrate; a support structure carried by the substrate; and an optical layer. The optical layer includes: a fixed portion carried by the support structure; a movable portion affixed between opposite sides of the fixed portion by a spring structure; a lens system carried by the movable portion, the lens system including an objective lens portion and a beam shaping lens portion, the objective lens portion being positioned such that it overlies the optical detector, the beam shaping lens portion being positioned such that it overlies the laser emitter; and a MEMS actuator for in-plane movement of the movable portion with respect to the fixed portion.

The MEMS actuator may include a comb drive. The comb drive may be formed by: a first comb structure extending from the fixed portion to interdigitate with a second comb structure extending from the movable portion; and actuation circuitry configured to apply voltages to the first and second comb structures to cause the movable portion of the optical layer to oscillate back and forth between opposite sides of the fixed portion such that at a first travel limit the movable portion of the optical layer is closer to the a first side of the fixed portion than to a second side of the fixed portion, and such that at a second travel limit the movable portion of the optical layer is closer to the second side of the fixed portion than to the first side of the fixed portion.

The MEMS actuator may be formed by: a first comb structure extending from a first side of the fixed portion to interdigitate with a second comb structure extending from an adjacent side of the movable portion; a third comb structure extending from a second side of the fixed portion to interdigitate with a fourth comb structure extending from an adjacent side of the movable portion; and actuation circuitry configured to apply voltages to the first, second, third, and fourth comb structures to cause the movable portion of the optical layer to oscillate back and forth between opposite sides of the fixed portion such that at a first travel limit the movable portion of the optical layer is closer to a first side of the fixed portion than to a second side of the fixed portion, and such that at a second travel limit the movable portion of the optical layer is closer to the second side of the fixed portion than to the first side of the fixed portion.

The optical detector may be a two dimensional array of single photon avalanche diodes arranged to match an expected diffraction pattern displayed by light incident thereon.

The laser emitter may be a one dimensional array of vertical cavity surface emitting lasers (VCSELs).

The spring structure may be a MEMS spring structure.

The fixed portion, movable portion, and spring structure may be integrally formed as a monolithic unit.

An encapsulating layer may be carried by the fixed portion and overlying the lens system.

The lens system may include a metasurface optic.

The lens system may include an objective lens and a beam shaping lens spaced apart from the objective lens.

The lens system may be carried by a top surface of the movable portion, and a back surface of the movable portion may be thinned opposite portions of the movable portion where the objective lens portion and beam shaping lens portion reside.

The movable portion may include a shuttle carrying the lens system, with the spring structure comprising first, second, third, and fourth flexures respective extending from different corners of the shuttle to anchor at different corners of the fixed portion.

The first, second, third, and fourth flexures may be S-shaped.

The shuttle may include a first shuttle portion carrying the objective lens portion, a second shuttle portion carrying the beam shaping lens portion, and a connector portion extending between the first and second shuttle portions, with a width of the connector portion being less than a width of the first and second shuttle portions.

The shuttle may have first and second openings defined therein in which the objective lens portion and the beam shaping lens portion are carried.

The shuttle may be formed by first and second spaced apart shuttle portions.

The lens system may include a glass substrate carried by the moving portion, with the objective lens portion and the beam shaping lens portion being carried by the glass substrate.

An additional glass substrate may be carried by the support structure, the additional glass substrate carrying the optical layer.

Also disclosed herein is an optical module, including: a substrate; an optical detector carried by the substrate; a laser emitter carried by the substrate; a support structure carried by the substrate; and an optical layer. The optical layer may include: a fixed portion carried by the support structure; a movable portion affixed between opposite sides of the fixed portion by a spring structure; a lens system carried by the movable portion; wherein the movable portion has at least one opening defined therein across which the lens system extends, with at least one supporting portion extending across the at least one opening to support the lens system; and a MEMS actuator for in-plane movement of the movable portion with respect to the fixed portion.

The at least one supporting portion may extend parallel to an axis of movement of the movable portion.

The at least one supporting portion may include a plurality of supporting portions.

The plurality of supporting portions may include at least some supporting portions extending parallel to an axis of movement of the movable portion.

The plurality of supporting portions may include at least some other supporting portions extending perpendicular to an axis of the movement of the movable portion.

The plurality of supporting portions may include at least some supporting portions extending antiparallel to an axis of movement of the movable portion.

The plurality of supporting portions may include at least some supporting portions extending elliptically about a central point of the lens system.

The first portion, the movable portion, the at least one supporting portion, and the spring structure may be integrally formed as a monolithic unit.

The following disclosure enables a person skilled in the art to make and use the subject matter disclosed herein. The general principles described herein may be applied to embodiments and applications other than those detailed above without departing from the spirit and scope of this disclosure. This disclosure is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed or suggested herein.

Now described with reference to <FIG> is a MEMS based optical module <NUM> for use in a TOF system. The optical module <NUM> includes a substrate <NUM>, such as silicon or an organic material, on which a high speed optical detector integrated circuit (IC) <NUM> and a laser emitter array integrated circuit (IC) <NUM> are mounted. As an example, the MEMS based optical module <NUM> may be realized using an assembly process in which the high speed optical detector IC <NUM> and laser emitter array IC <NUM> are mounted by die attach to the substrate <NUM>, utilizing back-end processing techniques.

The high speed optical detector IC <NUM> may be comprised of a two-dimensional array of single photon avalanche diodes (SPADs), and the laser emitter array IC <NUM> may be comprised of an array (one dimensional or two dimensional) of vertical cavity surface emitting lasers (VCSELs). Support structures 12a and 12b are carried by the substrate <NUM> on opposite sides of the optical detector IC <NUM> and laser emitter array IC <NUM>, and may also be formed from silicon, metal, or plastics. The support structures 12a and 12b may be opposite sides of a frame shaped support structure <NUM>, as shown in <FIG>.

An optic layer <NUM> is carried by the support structures 12a and 12b. The optic layer <NUM> is comprised of fixed portions 15a and 15b carried by the respective support structures 12a and 12b. The fixed portions 15a and 15b may be formed from silicon. The fixed portions 15a and 15b may be opposite sides of a frame shaped fixed portion <NUM>, as shown in <FIG>.

Between the fixed portions 15a and 15b is a moving portion <NUM>, which may also be formed by silicon or by an optically transparent material. Although not shown in <FIG>, as will be explained below, MEMS flexures extend from the moving portion <NUM> to anchor points on the fixed portions 15a and 15b, and when the moving portion <NUM> is actuated, serve to permit movement of the moving portion <NUM> in the positive and negative x-direction (away from one fixed portion 15a and toward the other fixed portion 15b, then away from the fixed portion 15b and back toward the fixed portion 15a, and so on). Lenses 17a and 17b are carried by the moving portion <NUM>, with lens 17a being positioned on the moving portion <NUM> so that it overlies the optical detector IC <NUM>, and lens 17b being positioned on the moving portion <NUM> so that it overlies the laser emitter array IC <NUM>. Note that lens 17a is sized such that, regardless of the position of the moving portion <NUM> as it moves, light <NUM> incident on the lens 17a is bent by the lens 17a such that it impinges upon the optical detector IC <NUM>, and such that light <NUM> emitted by the laser emitter IC array IC <NUM> is bent by the lens 17b such that it is directed at a desired angle toward the scene (for example, in the z-direction).

Lens 17a is an objective lens and focuses the light reflected from the scene to the optical detector IC <NUM>, and may be a multi-level diffractive optic or a metasurface. The light reflected from the scene has a pattern of parallel lines, due to the pattern of the lasers of the laser emitter array IC <NUM>, explained below. The incident light reflected from the scene at which it was directed by the laser emitter array IC <NUM> and lens 17b may be seen in <FIG>, where it can observed that the incident light <NUM> has been focused into the pattern of parallel lines on the optical detector IC <NUM> shown in <FIG>. Note that in some cases, the SPADs of the optical detector IC <NUM> may be pre-arranged into this pattern at the time of the formation of the optical detector IC <NUM>.

Lens 17b is a beam shaping optic and is shaped and formed so as to collimate the laser light <NUM> emitted by the VCSELs of the laser emitter array IC <NUM> along a direction parallel to the MEMS scan direction, and to expand the circular beam of each laser shown in <FIG> along a direction perpendicular to this direction. As a result, as shown in <FIG>, a light pattern comprised of a set of parallel lines is obtained. This pattern is scanned along the MEMS scanning direction by the movement of the moving portion <NUM>. The lens 17b may also be a multi-level diffractive optic or a metasurface. Note that the laser emitter array IC <NUM> may be a one dimensional array or line of VCSELs.

A top view of one potential arrangement for the optic layer <NUM> may be seen in <FIG>. The moving portion <NUM> includes a shuttle <NUM>, with the lenses 17a and 17b affixed within openings in the shuttle <NUM>. Flexures 22a-22d formed using MEMS technology extend in a squared off S-pattern from the corners of the shuttle <NUM> to anchor points 23a-23d that are affixed to the fixed portions 15a and 15b, with anchor point 23a and 23d being affixed to fixed portion 15a, and anchor points 23b and 23c being affixed to fixed portion 15b. Note that the flexures 22a-22d are actually integrally formed with the shuttle <NUM> and fixed portions 15a and 15b as a monolithic unit, and therefore extend from the shuttle <NUM> to the fixed portions 15a and 15b instead of being affixed to the shuttle <NUM> and fixed portions 15a and 15b.

Conductive combs 25a and 25b extend from the sides of the shuttle <NUM>, and are interdigitated with conductive combs 26a and 26b that extend from comb drive actuators 24a and 24b that are respectively affixed to the fixed portions 15a and 15b. The combs 25a and 25b are integrally formed with the shuttle <NUM> and flexures 22a-22d as a monolithic unit, and therefore they are short circuited together and set at a constant reference voltage (e.g., ground) by biasing the fixed portions 15a and 15b at which they are connected. The electrical routing is realized through the flexures 22a-22d themselves. The comb drive actuators 24a and 24b are circuits configured to apply a voltage (a DC bias with a superimposed AC drive waveform) to the combs 26a and 26b so that a comb drive is formed, and the shuttle <NUM> is moved back and forth in the x-direction via electrostatic actuation to thereby scan the laser pulses emitted by the laser emitter array IC <NUM> across the scene to permit detection of reflections therefrom by the optical detector IC <NUM> to collecting depth information about the scene. Note that since the lenses 17a and 17b are on the same shuttle <NUM>, both the light emitted by the laser emitter array IC <NUM> and the light collected at the optical detector <NUM> is scanned synchronously, so that the optical detector <NUM> views the portion of the scene illuminated by the laser emitter array IC <NUM> at any given movement and in such a way that less background light than reflected laser light is collected, since the optical detector <NUM> is viewing but a portion of the scene at a given time.

In the above examples, the thickness tsi of the substrate <NUM> may be on the order of <NUM> to <NUM>. The thickness of the layers <NUM> and <NUM> may be on the order of <NUM>. , In addition, the length Lx of the lenses 17a and 17b may be <NUM>, and the width Ly of the lenses 17a and 17b may be <NUM>.

A variant of the optical layer <NUM>' is seen in <FIG>. Here, the shuttle is divided into a first shuttle portion 20a carrying the lens 17a, and a second shuttle portion 20b carrying the lens 17b, with a connector portion <NUM> extending between the first shuttle portion 20a and second shuttle portion 20b. Note that the connector portion <NUM> is narrower in the z-direction than the first shuttle portion 20a and second shuttle portion 20b, and is integrally formed with the first and second shuttle portions as a monolithic unit. Note here that in addition to the flexures 22a-22d extending from the outside corners of the first shuttle portion 20a and seconds shuttle portion 25b, flexures 29a and 31a extend from the inside corners of the first shuttle portion 20a, while flexures 29b and 31b extend from the inside corners of the second shuttle portion 20b. Each flexure 22a-22d, 29a-29b, and 31a-31b is U-shaped, and extends toward respective anchor points 23a-23d, 30a-30b, and 32a-32b. Flexures 22a, 22d, 29a, 31a are integrally formed with shuttle portion 20a as a monolithic unit, and flexures 22b, 22c, 29b, 31b are integrally formed with shuttle portion 20b as a monolithic unit. Operation of the optical layer <NUM>' is the same as the optical layer <NUM> described above.

Another variant of the optical layer <NUM>" is seen in <FIG>. Here, it can be observed that, as compared to the optical layer <NUM>' of <FIG>, there is no connector portion <NUM>, and that shuttle portions 20a' and 20b' are separate unconnected components. Keeping in mind that the fixed portion <NUM> may be shaped as a frame (<FIG>), the anchor points 30a and 30b, and 32a and 32b are connected to and supported by the fixed portion <NUM>. Note here that while the lenses 17a and 17b are scanned synchronously, this is not accomplished passively by being carried by the same shuttle, but is instead accomplished by the driving of the comb drive being such that the first shuttle portion 20a' and second shuttle portion 20b' move synchronously.

In a situation where it would be desired for the shuttle <NUM> to be opaque, as shown in <FIG>, the moving portion may be separated into two disconnected and spaced apart moving portions 16a and 16b by completely removing portions of the fixed portion from the side thereof opposite the lenses <NUM> (here, the lenses 17a and 17b are formed as one metalens with a diffractive portion 17a and a collimating portion 17b), such as by using silicon deep reactive ion etching. As an alternative, windows may be formed within the moving portion <NUM>, and the lenses 17a and 17b are held within those windows.

As an alternative as shown in <FIG>, a thin layer (e.g., <NUM>-<NUM> microns thick) of the moving portion <NUM> may be left adjacent the diffractive portion 17a and collimating portion 17b if the moving portion <NUM> is formed from silicon.

As another alternative shown in <FIG>, moving portion <NUM> is separated into two spaced apart moving portions 16a and 16b, with a glass substrate <NUM> extending on top of and between the moving portions 16a and 16b, and the lens <NUM> being carried by the glass substrate <NUM>.

In any arrangement described herein, the moving portion <NUM> may have first and second openings defined therein for carrying the lenses 17a and 17b.

Note that any of the variants of the optical layer described above may be encapsulated by a glass layer <NUM> carried by support blocks 43a and 43b which are in turn carried by the spaced apart fixed portions 15a and 15b, as shown in <FIG>. A top view of this embodiment may be found in <FIG>, where it can be observed that the support structures 12a and 12b may be opposite sides of a frame shaped support structure <NUM>, the fixed portions 15a and 15b may be opposite sides of a frame shaped fixed portion <NUM>, and the support blocks 43a and 43b may be opposite sides of a frame shaped support block <NUM>.

A variant of the design of <FIG> is shown in <FIG>, where in the illustrated optical module <NUM>, the fixed portions 15a and 15b are carried by support portions 51a and 51b (that also may be opposite sides of a frame shaped support portion), and that electrical routing <NUM> may extend through the support portion 51a between the fixed portion 15a and a terminal carrying block <NUM>, with a metal pad <NUM> for wire bonding being carried by the terminal carrying block <NUM> and electrically coupled to the electrical routing <NUM>.

A further embodiment of the optical module <NUM>' is shown in <FIG>, where, instead of the glass substrate <NUM> encapsulating the lens <NUM>, optical detector <NUM>, and laser emitter array <NUM> against the substrate <NUM>, the support portions 51a and 51b are carried by a second glass substrate <NUM>, which is in turn carried by the support structures 12a and 12b extending from the substrate <NUM>. Therefore, in this embodiment, the lens <NUM>, fixed portions 15a and 15b, and moving portions 16a and 16b are encapsulated by glass on both sides, providing enhanced environmental protection. This embodiment also allows for low pressure operation, increasing efficiency. Also note here that this structure may be used in applications unrelated to depth sensing, such as picoprojection. In such a case, the optical detector <NUM> is removed, and the size of the other components adjusted accordingly.

Returning now to the general design of <FIG>, a variant is shown in <FIG>. Here, the lens 17a is still contained within the optic layer <NUM>, but is attached to and carried by the fixed portion 15a. Therefore, here, the lens 17a is not moved, while the lens 17b is still moved as described above.

As a further alternative shown in <FIG>, rather than a lens 17a being within the optic layer 19a, the fixed portion 15a is frame shaped and separated from the fixed portion 15b, and contains a standard imaging lens 17c. Therefore, here, the lens 17c is now moved, while the lens 17b is still moved as described above. Here, a bonding pad <NUM> is carried by the fixed portion 15a, and used for applying a drive signal to the MEMS actuator.

In the above examples, the moving portion <NUM> is moved by a comb drive, but it should be understood that any MEMS actuation technique may be used. For example, thermal, magnetic, and piezoelectric actuation may be used to move the moving portion <NUM> with respect to the fixed portion <NUM>.

In the example optical modules described above, notice that in some instances, the metalens <NUM> (forming the lenses 17a and 17b, and best shown for this description in <FIG>, <FIG>, and <FIG>) is suspended between the disconnected and spaced apart moving portions 16a and 16b. Therefore, since the metalens <NUM> is thin, having a thickness on the order of <NUM> to <NUM>, it could break during manufacturing or operation. As such, it may be desirable to correct this fragility of the metalens <NUM> without reducing its optical transparency or with a minimal reduction in its optical transparency.

Certain ways of accomplishing this have been described above. For example, in the embodiment of <FIG>, a thin layer (e.g., <NUM>-<NUM> microns thick) of the moving portion <NUM> is left adjacent the metalens <NUM>, with the moving portion <NUM> being formed from silicon in this instance. This thin layer is left to provide support to the metalens <NUM>. As another example, in the embodiment of <FIG>, the metalens <NUM> is carried by a glass substrate <NUM>, with the glass substrate <NUM> being suspended between the disconnected and spaced apart moving portions 16a and 16b. The glass substrate <NUM> may be thicker than the metalens <NUM> and may have a greatest resistance to fracture and cracking than the metalens <NUM>, and therefore provides support for the metalens <NUM>.

Other approaches to providing support to the metalens <NUM> may be desirable, depending upon application and manufacturing constraints. A first such example of an optical module <NUM>" in which the metalens <NUM> is provided with support is now described with reference to <FIG>. This optical module <NUM>" illustratively has the same structure as that of <FIG>, with the addition of reinforcing elements 99a-99c between the spaced apart moving portions 16a and 16b and supporting the metalens <NUM> at its bottom surface (the bottom surface facing the substrate <NUM>). The reinforcing elements 99a-99c are spaced such that the reinforcing element 99a closest to the moving portion 16a is spaced apart from the moving portion 16a by a gap Wgap, the reinforcing element 99a is spaced apart from the reinforcing element 99b by Wgap, the reinforcing element 99b is spaced apart from the reinforcing element 99c by Wgap, and the reinforcing element 99c is spaced apart from the moving portion 16b by Wgap. The width of the reinforcing elements 99a-99c in the y-direction is Wreinf.

The width Wreinf of the reinforcing elements 99a-99c is substantially smaller than the width Wgap, for example, Wreinf ≤ <NUM>×Wgap, so as to allow suitable transmissivity of incoming and outgoing light through the metalens <NUM>. The transmissibility of light through the metalens <NUM> can be calculated as Wgap/(Wgap + Wreinf). Example values may be Wgap = <NUM>, Wreinf = <NUM>, such that a sample transmissibility of light through the metalens <NUM> with the use of the reinforcing elements 99a-99c is still <NUM>%, while providing the metalens <NUM> with substantial protection against fracture and cracking.

A top view of the optical layer <NUM>‴ within the optical module <NUM>" may be seen in <FIG>, where it can be observed that the reinforcing elements 99a-99c extend across the x-axis from a first end of the shuttle <NUM> to a second end of the shuttle <NUM>, keeping in mind that the shuttle <NUM> is part of the moving portion <NUM>. Since the x-axis is the axis of movement, in this example, the reinforcing elements 99a-99c extend parallel to the axis of movement of the moving portion <NUM>.

Although three reinforcing elements 99a-99c have been illustrated and described in this example, keep in mind that any suitable number of reinforcing elements may be used so as to achieve the desired protection with a given minimum acceptable transmissibility of light through the metalens <NUM>.

The reinforcing elements 99a-99c may be constructed from the same material as the moving portion <NUM>. Indeed, the reinforcing elements 99a-99c may be parts of the moving portion <NUM> that are purposely not removed during formation, and therefore may be integrally formed with the moving portion <NUM> as a monolithic unit.

The reinforcing elements 99a-99c may, in addition to being different in number than shown, be different in shape than shown. For example, in the optical layer 19ʺʺ shown in <FIG>, there are three such reinforcing elements 99a-99c as described above that extend across the x-axis from a first end of the shuttle <NUM> to a second end of the shuttle <NUM>, and there also are two reinforcing elements 98a and 98b extending across the y-axis from a first side of the shuttle <NUM> to a second side of the shuttle <NUM>.

As another example, in the optical layer <NUM>‴ʺ shown in <FIG>, there is one reinforcing element 99a extending across the x-axis from the first end of the shuttle <NUM> to the second end of the shuttle, two reinforcing elements 98a and 98b extending across the y-axis from a first side of the shuttle <NUM> to a second side of the shuttle <NUM>, a first circular reinforcing element 97a having its origin point at the center of the metalens <NUM>, a second circular reinforcing element 97b also having its origin point at the center of the metalens <NUM> and being concentric to the first circular reinforcing element 97a, and a third circular reinforcing element 97c also having its origin point at the center of the metalens <NUM> and being concentric to the second circular reinforcing element 97b. As illustrated, the first circular reinforcing element 97a has a larger radius than the second reinforcing element 97b, but not so great that the first circular reinforcing element 97b crosses the reinforcing elements 98a and 98b. As also illustrated, the second circular reinforcing element 97b has a larger radius than the third circular reinforcing element 97c. Reinforcing elements 95a and 95b extend diagonally across the metalens <NUM> in a criss-cross fashion such that they cross from corner to corner thereof, crossing the center of the metalens <NUM> along the way.

It should be appreciated that the illustrated arrangements for the reinforcing elements are simply examples. Indeed, appreciate that any suitable arrangement and number of reinforcing elements may be utilized, and may be formed by selectively removing portions of the moving portion <NUM> during formation to form the desired number and arrangement of reinforcing elements.

Claim 1:
An optical module (<NUM>, <NUM>', <NUM>", <NUM>‴, 10ʺʺ, <NUM>, <NUM>', <NUM>), comprising:
a substrate (<NUM>);
an optical detector (<NUM>) carried by the substrate;
a laser emitter (<NUM>) carried by the substrate;
a support structure (<NUM>) carried by the substrate;
an optical layer (<NUM>, <NUM>', <NUM>", <NUM>‴, 19ʺʺ, <NUM>‴ʺ) comprising:
a fixed portion (<NUM>) carried by the support structure;
a movable portion (<NUM>) affixed between opposite sides of the fixed portion by a spring structure (<NUM>, <NUM>, <NUM>, <NUM>);
a lens system (<NUM>) carried by the movable portion; and
a MEMS actuator (<NUM>, <NUM>) for in-plane movement of the movable portion with respect to the fixed portion;
wherein the lens system (<NUM>) includes an objective lens portion (17a) and a beam shaping lens portion (17b), the objective lens portion being positioned such that it overlies the optical detector (<NUM>), the beam shaping lens portion being positioned such that it overlies the laser emitter (<NUM>).