Generation of a high-resolution 3D-printed freeform collimator for VCSEL-based 3D-depth sensing

Abstract

This Letter discusses the generation of 3D-printed micro-optics to obtain the desired beam profile from a multimode vertical-cavity surface-emitting laser (VCSEL) with a significantly reduced divergence angle via the usage of high-resolution two-photon polymerization. Due to the low cost and compact packaging, the VCSEL array is a novel light source for structured-light projection. Particularly for long-distance 3D sensing applications, a greatly reduced divergence angle ensures that a good signal with a sufficiently large number of photons can be recorded, and the projected illumination spots do not overlap. Therefore, exact laser beam characterization and appropriate physical modeling are required in accurate production of an optimal collimator lens. Furthermore, elliptical beam profiles with different orientations can solve the correspondence problem and improve the post-processing speed and robustness in structured light. To generate this special type of beam profile and verify the optical design process, this Letter describes thoroughly the optical prototyping process starting from the beam characterization, the optical design to the production of the two-photon polymerized optics, and its validation. The test of the beam profile and divergence confirm a good match of the produced optics with the physical optical simulation in Zemax. The collimator transforms the input laser beam divergence angle of 324 mrad to an output angle of 20 mrad only.

Direct 3D-printing of microlens on single mode polarization-stable VCSEL chip for miniaturized optical spectroscopy

“…Considering the precision required for the fabrication of micro-optical elements, this technique offers appropriate characteristics 19 – 21 and was successfully applied to fabricate a complete miniature visible spectrometer, 22 as well as for the precise fabrication of micro-optical elements on single-mode optical fibers 23 or LED devices 24 . It was also recently exploited to couple VCSEL arrays to multimode fibers for data transmission experiments 25 and to fabricate an external collimator for VCSEL used in 3D sensing systems 26 . However, direct fabrication on a VCSEL chip to be used for miniaturized optical spectroscopy has not been yet reported.…”

“…24 It was also recently exploited to couple VCSEL arrays to multimode fibers for data transmission experiments 25 and to fabricate an external collimator for VCSEL used in 3D sensing systems. 26 However, direct fabrication on a VCSEL chip to be used for miniaturized optical spectroscopy has not been yet reported.…”

3D Direct Laser Writing of Highly Absorptive Photoresist for Miniature Optical Apertures

“…The use of 3D direct laser writing as a fast and highly accurate fabrication process for nano‐ and micro‐optical devices is widely used in different scientific fields such as biology, [ 1–3 ] microfluidics, [ 4–8 ] imaging, [ 9,10 ] optical communication, [ 11–13 ] beam shaping, [ 14–17 ] sensing, [ 18–25 ] trapping, [ 26,27 ] or endoscopy. [ 28–31 ] Furthermore, the complexity of 3D‐printed optics increased drastically over the years by utilizing new optical designs with multi‐lens objectives, [ 32–35 ] diffractive surfaces, [ 36 ] novel photoresists with different dispersion and their combination, [ 37,38 ] or even moving parts.…”

Surface grating loaded VCSEL with single mode power of over 80 mW

“…As technology matures, VCSEL applications diversified including laser mice, printers, medical imaging and so on [6,7,8,9,10,11]. In recent years, VCSEL technology for 3D sensing has been attracting more and more interests [12,13,14,15,16]. For 3D sensing applications such as LiDAR, a high-power light source has been developed.…”