Addressable structured light system using metasurface optics and individually addressable VCSEL array

• Chenyang Wu, Xuanlun Huang, Yipeng Ji, Tingyu Cheng, Jiaxing Wang, Nan Chi, Shaohua Yu, and Connie Chang-Hasnain
• received 01/08/2024; accepted 03/26/2024; posted 03/29/2024; Doc. ID 516942
• Abstract: Structured-light (SL) based 3D sensors have been widely used in many fields. Speckle SL is the most widely deployed among all SL sensors due to its light weight, compact size, fast video rate and low cost. The transmitter (known as the dot projector) consists of a randomly patterned vertical-cavity surface-emitting lasers (VCSEL) array multiplicated by a Diffractive Optical Element (DOE) with a fixed repeated pattern. The receiver is a CMOS image sensor placed at a fixed distance from the dot projector. The randomness of speckles is used to identify the two-dimensional x-y coordinates of a given pair of speckles. The depth information associated with this x-y coordinate is derived from the deformed speckle images deviated from the pair’s known separation based on triangulation principle. Based on matching deformed speckle images reflected from the detected target with a known speckle reference image, the 3D image is obtained. Given that the separation of any two speckles is only one known and fixed number (albeit random), there are no other known scales to calibrate or average. Hence, typical SL sensors require extensive in-factory calibrations, and the depth resolution is limited to 1mm at ~60 cm distance. In this paper, we propose a novel dot projector and a new addressable SL (ASL) 3D sensor by using a regularly spaced, individually addressable VCSEL array, multiplicated by a metasurface-DOE (MDOE) into a random pattern of the array. The randomness of the MDOE enables the determination of the x-y coordinates of the VCSEL array. Dynamically turning on or off the VCSELs in the array provides multiple known distances between neighboring speckles, which is used as a “built-in caliper” to achieve higher accuracy of the depth. Serving as a precise "vernier caliper", the addressable VCSEL array enables fine control over speckle positions and high detection precision. We experimentally demonstrated the proposed method can result in sub-hundred microns level precision. This new concept opens new possibilities for applications such as 3D computation, facial recognition and wearable devices.