Stripe illuminator based on LED array and parabolic mirror for active triangulation sensors used on mobile robots

Abstract

This article proposes a new, efficient and cost effective stripe illuminator for active optical triangulation sensors. The long distance stripe-shaped collimation of the light radiated by a linear LED array is achieved by means of a cylindrical parabolic mirror with a focus line coinciding with the internal reflectors of the LEDs. A computer based design process using a model of the LED is presented to find the optimal parabolic shape, radiating aperture and mounting tolerances. A very simple and inexpensive mechanical construction of the light source was realized. Test measurements showed that the light source produces a light stripe with an average incidence between 0.6-5.5 mW/cm 2 depend- ing on the range, which enables the detection of objects even with very low reflectivity. The width of the light stripe is 6 -10 cm in the 0- 2m range, which allowed a resolution of 5-15 cm using it in a special stripe lighting sensor setup. Test results on an autonomous mobile robot are briefly presented. The eye safety of the source is also discussed. © 2000 Society of Photo-Optical Instrumentation Engineers. (S0091-3286(00)02810-5)