Shared optic assembly for combined dot and flood illumination modules

Abstract

SOLUTION: A shared optic assembly for combined flood and dot illumination modules is disclosed. The shared optic assembly includes a first high-powered VCSEL element for providing a flood beam and a second high-powered VCSEL element for providing a dot beam, where both the first and second VCSEL elements share the same optics and are incorporated onto the same module for space saving.EFFECT: Because the flood and dot modules share the same optics, significant cost and space savings are realized.SELECTED DRAWING: None

Description

Background Art

[0001] Flood illuminators are incorporated into various products such as, for example, mobile devices and other applications, and provide 3D sensing functions, 3D mapping in robotics, face detection, and the like. For example, referring to FIG. 1, an optical assembly 100 incorporated within, for example, a mobile device that includes a flood illuminator uses a vertical-cavity surface-emitting laser (VCSEL) 102 to provide a flood beam 104 to an optical system 106, thereby generating a uniform illumination field of infrared (IR) light from an output 108 to an object or a person of interest (not shown). FIG. 2 shows an example of a flood beam generated using a known optical assembly as shown in FIG. 1.

[0002] Dot projectors may also be used in combination with flood illuminators. The dot projector uses a second VCSEL 103 to generate a dot beam 105 to an optical system 107, and then generates a number of IR light dots from an output 108 to create a three-dimensional map of an illuminated object of interest for area and depth determination. An infrared camera (not shown) captures an image of the depth signature from the modulated IR flood light and also, if used, from the dot pattern reflected from the illuminated object of interest. Next, the processing of the captured data can be used for a desired purpose such as, for example, face recognition. One drawback associated with conventional flood illuminators is that their range is limited to about 1.5 m. This relatively short range significantly limits the types of applications for which this technology can be used.

[0003] The subject matter of the present disclosure is aimed at overcoming one or more of the above problems or at least reducing their impact.

Summary of the Invention

[0004] A shared optical assembly combining flood and dot illumination modules is disclosed. The shared optical assembly includes a first high-power VCSEL element for providing a flood beam and a second high-power VCSEL element for providing a dot beam, with both the first and second VCSEL elements sharing the same optical system. The dot beam is generated using the same level of optical output as the flood beam, but the dot beam is condensed into a dot. As a result, the returned signal is high enough to detect over longer distances than would be achieved with the flood beam alone. The trade-off is that the resolution of the received information is lower because only information about where the dot is located is reflected back to the infrared camera. The entire system uses the same infrared camera for both the dot and flood functions, but achieves high-resolution short-range detection using the flood beam and lower-resolution long-range detection using the dot beam. With the use of the present invention, the effective range is increased from approximately 1.5 m to approximately 6 m. Furthermore, significant cost and space savings are achieved because the flood and dot modules share the same optical system.

[0005] The above summary is not intended to summarize any or all of the potential embodiments of this disclosure. [Brief explanation of the drawing]

[0006] [Figure 1] This shows an optical assembly with separate dot and flood illumination modules, as is known in the art. [Figure 2] This shows a flood beam generated using a standard randomization diffuser, as is known in the art. [Figure 3] This exhibits a shared optical assembly combining dot and flood illumination modules with a shared optical system, according to an exemplary embodiment of the present invention. [Figure 4A] The following shows a dot projector pattern generated according to an exemplary embodiment of the present invention. [Figure 4B] The image shows a flood beam generated according to an exemplary embodiment of the present invention. [Figure 5] This illustrates the expected space savings based on the working distance according to an exemplary embodiment of the present invention. [Figure 6] The configuration of a shared optical system according to an exemplary embodiment of the present invention is shown. [Figure 7] This shows a dot VCSEL layout according to an exemplary embodiment of the present invention. [Figure 8] This shows a flood VCSEL layout according to an exemplary embodiment of the present invention. [Figure 9] The X-axis and Y-axis difference distribution between an individual flood VCSEL emitter (Figure 8) and the nearest diffuser lenslet center (Figure 6) is shown according to an exemplary embodiment of the present invention. [Figure 10] The dot field generated using an exemplary embodiment of the present invention is shown. [Figure 11] The flood field generated using an exemplary embodiment of the present invention is shown. [Modes for carrying out the invention]

[0007] Referring to Figure 3, the high-power VCSEL illuminator assembly 300 includes a combination of a dot illumination module and a flood illumination module. The combined module includes a first VCSEL element 303 configured to provide a flood beam 305 and a second VCSEL element 302 configured to provide a dot beam 304. The two VCSEL elements 302, 303 are mounted on a substrate 301, and the assembly 300 includes a shared optical system 306 positioned adjacent to the substrate 301. The assembly 300 is intended to be used as a component of an overall system, such as a facial recognition unit in a mobile device.

[0008] The dot-beam VCSEL element 302 is mounted on the substrate 301 in a defined configuration at a defined distance (called the working distance ("WD")) relative to the shared optical system 306. The flood-beam VCSEL element 303 is also mounted on the substrate 301 in a defined configuration at a defined distance relative to the shared optical system 306, where the defined distance is offset from the working distance. The dot beam and flood beam are imaged by the shared optical system 306 to produce an output 307.

[0009] As will be described in more detail below in relation to exemplary embodiments, the shared optical system 306 includes a periodic diffuser optical element that generates both a dot field and a flood illumination field by using the emission of two separate VCSELs 303, 302 that are relatively close to each other. The combined beams result in high-resolution short-range detection using the flood beam and low-resolution long-range detection using the dot beam. The dot beam concentrates the VCSEL emission into a small spot of increased intensity, thus extending the overall system range. Resolution is somewhat reduced over a wider range because only the dot beam reflects back from the object to the detector. The effective range of the overall system is extended from about 1.5 m when using only the flood beam to about 6 m when using the dot beam.

[0010] In one application of the present invention, the IR sensor can extract depth information from a flood beam and then switch to extract depth information from a dot beam, combining the depth information from both modes. The dot mode can be used, for example, when scanning room dimensions to visualize furniture. The flood mode can be used, for example, when mapping faces or close-ups of objects. Furthermore, since the dot VCSEL and flood VCSEL share a common optical system, both can be incorporated into the same module, resulting in significant size savings compared to modules where the optical system is not shared.

[0011] Continuing to refer to Figure 3 in general, the dot-field VCSEL 302 is configured to operate at a predetermined working distance from the shared optical system 306 and has a defined pitch between emitters such that the diffraction effect in the shared optical system 306 generates a dot field. The distance between the flood-field VCSEL 303 and the shared optical system 306 is offset from this working distance to avoid such diffraction effects. For example, the required offset distance can be generated by using a thicker VCSEL substrate 303 or additional height from the mounting substrate 301 compared to the dot-field VCSEL 302. The offset distance avoids having a high-contrast diffraction effect, which is desirable for a dot imager but undesirable for a flood imager.

[0012] Continuing to refer to Figure 3 in general, due to the diffraction effect from the self-imagement of the periodic diffuser array from a small light source, individual emitters are re-imaged within the envelope of the diffuser's output profile. The emitters are pitched appropriately so that all single-emitter array images are aligned with each other. This phenomenon is theoretically similar to the Lau effect, but with an array of lasers instead of an illuminated first grating. See, for example, Sudol, R. (1981), Lau Effect: An Interference Phenomenon in Partially Coherent Light [Thesis], The University of Rochester, Rochester, New York. This theory states that high-contrast images are obtained at distance Z=np 2 This provides that it can be achieved with / 2λ, where n is a positive integer, p is the pitch of the diffuser array, and λ is the wavelength of light.

[0013] Because this high-contrast phenomenon occurs only at specific distances, the contrast can be reduced by an offset or misfocus between the VCSEL laser array and the periodic diffuser array. The diffraction effect is almost eliminated if the second VCSEL emitter (i.e., flood VCSEL303) layout is designed so that the X and Y difference between the laser and the nearest diffuser freeform lenslet optical center is distributed somewhat evenly across the entire region of the single diffuser freeform lenslet surface.

[0014] This can be done with a simple configuration. For example, a 35um pitch square diffuser array can have high contrast at a distance of 2606um for n=4 and λ=940nm. A VCSEL operating at 2400um in a 20x20 emitter layout with a square pitch of 35*(1+1 / 20) can provide a very uniform X and Y difference distribution. A uniform X and Y difference distribution can be achieved in various ways, including rectangular, square, or hexagonal arrays of VCSELs with various pitches and specific rotation angles, or specially designed pseudo-random VCSEL arrays. The 940nm wavelength is used in this example for both dot and flood VCSEL emitters because it is a wavelength commonly used for 3D sensing applications, but it should be noted that the present invention is not limited to a specific emitter wavelength or specific application. For example, a VCSEL emitter with a wavelength of 850nm, another commonly used VCSEL wavelength, can be used. Longer or shorter wavelengths can also be used. Furthermore, the wavelengths of the dot and flood VCSEL emitters do not need to be the same. For example, the wavelength of a dot emitter could be 940 nm, while the wavelength of a flood emitter could be 850 nm, or vice versa. Using two different wavelengths for the emitters requires a wider filter on the receiver side than if both arrays were emitting the same wavelength. Alternatively, if the emitter wavelengths are different, a filter with multiple passbands can be used on the receiver side.

[0015] FIG. 4A shows an image of the projection pattern of the dot VCSEL 302 that is properly aligned with the shared optical system 306 and at the appropriate working distance.

[0016] FIG. 4B shows an image of the projection pattern of the flood VCSEL 303 that is misaligned with the shared optical system 306, has a 150 um offset, or is out of focus.

[0017] Referring now to FIG. 5, some examples of the size reduction of the VCSEL illuminator assembly achievable with the present invention are shown. On the left side of FIG. 5 is a prior art VCSEL illuminator assembly 100, and on the right side is a VCSEL illuminator assembly 300 (described in FIG. 3) according to an exemplary embodiment of the present invention. In the illustrated example, referring to the table (center row), for a working distance of 2.3 mm, the beam width of the shared optical system of assembly 300 is 2.7 mm, while the beam width of assembly 100 with individual optical systems is 3.9 mm. Thus, in this example, there is a size reduction of approximately 24% achieved as a result of the present invention.

[0018] For a smaller working distance of 1.7 mm, the beam width of the shared optical system of assembly 300 is 2.4 mm, while the beam width of assembly 100 with individual optical systems is 3.2 mm. In this example, there is a size reduction of approximately 19% achieved as a result of the present invention. Finally, for a larger working distance of 2.8 mm, the beam width of the shared optical system of assembly 300 is 3 mm, while the beam width of assembly 100 with individual optical systems is 4.6 mm. In this example, there is a size reduction of approximately 28% achieved as a result of the present invention. Thus, as the working distance increases, the percentage of size reduction increases.

[0019] Referring now to FIG. 6, the diffuser of the shared optical system 306 (FIG. 3) includes a periodic array of the same freeform surface that shapes the incident light into a desired illumination or diffusion profile. In this exemplary embodiment, the periodic diffuser has a square layout 601 with X and Y pitches of 33 microns. Each microlens 602 is the same and is designed to spread the incident light into a specific illumination field. In this example, the working distance (WD), i.e., the distance between the dot field VCSEL 302 and the shared optical system 306, is 2.32 mm (i.e., np 2 / 2λ = 4 * 33 2 / (2 * 0.94) = 2.32 mm).

[0020] Referring now to FIG. 7, an array of dot VCSELs 302 (FIG. 3) according to an exemplary embodiment of the present invention is shown. The array of dot VCSELs 302 is a periodic array with a square layout having X and Y pitches of 33 microns (532 emitters / 8um oxide aperture). In particular, the array of dot VCSELs 302 needs to be aligned with the diffuser optics in some way.

[0021] The pitch of the array of dot VCSELs 302 needs to be an integer multiple or fraction (i.e., 3, 2, 1, 1 / 2, 1 / 3) of the optical pitch. It has been found that 1x functions well. Alternatively, much larger optical system pitches and fractional VCSEL pitches can be used, but this results in an increase in the number of dots within the dot field and a decrease in the peak intensity of each dot. As the optical system pitch and the fraction increase, the working distance may become too long. It should also be noted that a smaller optical system pitch can also be used together with twice the VCSEL pitch, but manufacturing problems of the optical system may occur in this arrangement.

[0022] Turning to Figure 8, a flood VCSEL303 (Figure 3) array according to an exemplary embodiment of the present invention is shown. The flood VCSEL303 array is a periodic array in a hexagonal layout with a pitch of 40 microns (327 emitters / 10 μm oxide aperture) rotated by 24.5 degrees. In particular, for the flood VCSEL303, any layout that results in a relatively well-spread distribution of the VCSEL emitter difference relative to the center of the nearest lenslet 602 (Figure 6) yields suitable performance. In this exemplary embodiment, the flood VCSEL303 is mounted on a 300 μm thick CuW spacer to provide the required focus shift. In this case, 1.738 mm (i.e., 3*33 2 The working distance of / (2*0.94)) is at a different high-contrast distance, so it was found that about half of the distances corresponding to n=3 and n=4, which are about 2mm apart, function well.

[0023] Referring here to Figure 9, as explained in relation to Figure 8, the distribution of X and Y differences between individual flood VCSEL 303 emitters and the centers of the nearest diffuser lenslet 602 is shown. Each point in the scatter plot represents the X and Y delta between a single VCSEL emitter and the center of the nearest diffuser lenslet. In the examples shown in Figures 6 and 8, the size of the lenslet 602 is 33 μm, so the delta range is + / - 16.5 μm for both sizes. Essentially, the VCSEL emitters are scattered around and therefore will not coincide with the periodicity of the diffuser lenslet. This arrangement helps to eliminate any residual diffraction effects.

[0024] Referring here to Figures 10 and 11, the dot field and flood field are shown, respectively, as generated with the configurations described in relation to Figures 6-9. Using the principles and specific arrangements described herein, a range of approximately 1.5 m was achieved in the flood field of Figure 11, and a range of approximately 6 m was achieved in the dot field of Figure 10.

[0025] The foregoing description of preferred and other embodiments is not intended to limit or restrict the scope or applicability of the concept of the invention as devised by the applicant. It will be understood that, by the merits of this disclosure, the features described above in any embodiment or aspect of the disclosed subject matter may be used alone or in combination with any other described features in any other embodiment or aspect of the disclosed subject matter.

[0026] In exchange for disclosing the concepts of the present invention as contained herein, the applicant requests all patent rights granted by the appended claims. Accordingly, the appended claims are intended to include all modifications and changes that fall within the scope of the following claims or their equivalents.

Claims

1. a first VCSEL array for generating a dot beam; a second VCSEL array adjacent to the first VCSEL array for generating a flood beam; a diffuser optical system shared by the first and second VCSEL arrays for receiving light emission from the first and second VCSEL arrays; A VCSEL illuminator assembly comprising:

2. The VCSEL illuminator assembly according to claim 1, wherein the first VCSEL array is disposed at a first distance from the shared diffuser optical system, and the second VCSEL array is disposed at a second distance from the shared diffuser optical system, the second distance being different from the first distance.

3. The VCSEL illuminator assembly according to claim 2, wherein the first distance is about 2.3 mm and the second distance is about 2 mm.

4. The VCSEL illuminator assembly according to claim 3, wherein the substrate under the second VCSEL array is 300 um thicker than the substrate under the first VCSEL array.

5. The VCSEL illuminator assembly according to claim 4, wherein the second VCSEL array is attached to a CuW spacer having a thickness of 300 um.

6. The VCSEL illuminator assembly according to claim 1, wherein the pitch of the first VCSEL array is an integer multiple of the pitch of the shared diffuser optical system.

7. The VCSEL illuminator assembly according to claim 6, wherein the pitch of the first VCSEL array is 1 times the pitch of the shared diffuser optical system, or the pitch of the first VCSEL array is 2 times the pitch of the shared diffuser optical system, or the pitch of the first VCSEL array is 3 times the pitch of the shared diffuser optical system.

8. The VCSEL illuminator assembly according to claim 1, wherein the pitch of the first VCSEL array is a fraction of an integer of the pitch of the shared diffuser optical system.

9. The VCSEL illuminator assembly according to claim 7, wherein the pitch of the first VCSEL array is 1 / 2 of the pitch of the shared diffuser optical system, or the pitch of the first VCSEL array is 1 / 3 of the pitch of the shared diffuser optical system.

10. The VCSEL illuminator assembly according to claim 8, wherein X and Y deltas exist between each emitter of the second VCSEL array and the center of the closest lenslet of the shared diffuser optical system.

11. The VCSEL illuminator assembly according to claim 10, wherein both of the X and Y deltas are at most + / −16.5 microns.

12. The VCSEL illuminator assembly according to claim 1, wherein the light emissions from the first and second VCSEL arrays have the same wavelength, and the light emissions from the first and second VCSEL arrays have a wavelength of 940 nm, or the light emissions from the first and second VCSEL arrays have a wavelength of 850 nm.

13. The VCSEL illuminator assembly according to claim 1, wherein the wavelength of the light emission from the first VCSEL array is different from the wavelength of the light emission from the second VCSEL array.

14. A first VCSEL array for generating a first light emission, a second VCSEL array adjacent to the first VCSEL array for generating a second light emission, a diffuser optical system shared by the first and second VCSEL arrays for receiving the first and second light emissions, comprising the first VCSEL array is configured such that a diffraction effect occurs in the shared diffuser optical system, and the second VCSEL array is configured such that no diffraction effect occurs in the shared diffuser optical system. VCSEL illuminator assembly.

15. The VCSEL illuminator assembly according to claim 14, wherein the wavelengths of the first and second light emissions are the same, and the wavelengths of the first and second light emissions are 940 nm, or the wavelengths of the first and second light emissions are 850 nm.

16. The VCSEL illuminator assembly according to claim 14, wherein the wavelength of the first light emission is different from the wavelength of the second light emission.

17. The VCSEL illuminator assembly according to claim 14, wherein the first VCSEL array is disposed at a first distance from the shared diffuser optical system, and the second VCSEL array is disposed at a second distance from the shared diffuser optical system, which is different from the first distance.

18. The VCSEL illuminator assembly according to claim 17, wherein the first distance is about 2.3 mm and the second distance is about 2 mm.

19. The VCSEL illuminator assembly according to claim 14, wherein the pitch of the first VCSEL array is an integral multiple of the pitch of the shared diffuser optical system. **Claim 20** The VCSEL illuminator assembly according to claim 19, wherein the pitch of the first VCSEL array is 1 times the pitch of the shared diffuser optical system.

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