Continuous low-latency 3D measurements using efficient freeform GOBO pattern projection and close-to-sensor image rectification

C. Munkelt; H. Speck; C. Bösel; C. Junger; S. Töpfer; G. Notni

doi:10.1117/12.2558466

21 April 2020 Continuous low-latency 3D measurements using efficient freeform GOBO pattern projection and close-to-sensor image rectification

C. Munkelt, H. Speck, C. Bösel, C. Junger, S. Töpfer, G. Notni

Author Affiliations +

Proceedings Volume 11397, Dimensional Optical Metrology and Inspection for Practical Applications IX; 1139705 (2020) https://doi.org/10.1117/12.2558466
Event: SPIE Defense + Commercial Sensing, 2020, Online Only

Abstract

Optical 3D measurement using active pattern projection is well known for its high precision and high 3D point density. Recently, increasing the reconstruction frame rate and the number of active sensors in a simultaneous and continuous operation regime used for sensor networks has become more important. Traditionally, light modulators such as LCoS, DMD, or GOBO (GOes Before Optics) have been used, which generate the projected pattern by blocking the light at dark areas of the pattern. In order to further increase the measurement speed and/or the number of time-sequential continuously active sensors, brighter light sources must be chosen to achieve sufficient short exposure times. Alternatively, as we show in this paper, a more efficient pattern modulator can be used. By applying an optical freeform element to generate an aperiodic sinusoidal fringe pattern, up to 100 % of the available light can be utilized. In our prototype, we show how to employ a freeform element moved in a linear bearing to create a compact low-cost, high-speed projection unit. Furthermore, to reduce the computational burden in processing numerous simultaneous image streams, we have implemented the rectification step of the 3D reconstruction pipeline into the field programmable gate array (FPGA) sensor module. Both approaches enable us to use structured light sensors for continuous high-speed 3D measurement tasks for industrial quality control. The presented prototype utilizes a single irritation-free near-infrared (NIR) LED to illuminate and reconstruct within a measurement field of approximately 300 mm × 300 mm at a measurement distance of 500 mm.

Citation Download Citation

C. Munkelt, H. Speck, C. Bösel, C. Junger, S. Töpfer, and G. Notni "Continuous low-latency 3D measurements using efficient freeform GOBO pattern projection and close-to-sensor image rectification", Proc. SPIE 11397, Dimensional Optical Metrology and Inspection for Practical Applications IX, 1139705 (21 April 2020); https://doi.org/10.1117/12.2558466

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KEYWORDS

Sensors

3D metrology

Light sources

Near infrared

Field programmable gate arrays

Cameras

3D image processing

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