Array projector design for projection on arbitrarily curved surfaces

Abstract

The micro-optical array projector is a new and innovative possibility to project patterns onto arbitrary shaped surfaces1 . In contrast to single-aperture systems the illuminance of the projected image is raised by only increasing the lateral extent of the projector while keeping the length constant. Thanks to the setup - analogous to a fly’s eye condenser – we obtain a very compact design with homogenization of illumination. The images to be projected are presented as arbitrarily curved CAD-objects. Because of its complexity, the first attempt was a chief-ray backtrace implemented into a CAD-program, with the individual projectorlets modelled as pinhole cameras. With this principle one can trace the slides for several applications like the projection on perpendicular, as well as tilted and curved surfaces. Since aberrations cannot be considered with the simple CAD backtrace described above, we used the commercially available raytracer Zemax®, controlled by a macro, working in conjunction with a CADprogram for improved slide mask generation. Despite both methods, depending on the complexity of the optical system, are generating the fundamental mask data, the paper will show that there is a tradeoff between calculation time and accuracy. Based on this evaluation we will discuss further development as well as the possibility of improvement concerning the calculation methods. The different methods were investigated to determine their advantages and disadvantages. This provides the basis for the scope of application. Further we will demonstrate simulations as well as results obtained with built demonstrators

Grayscale projection design method based on micro lens array

“…Using MLA instead of a traditional projection lens in a projection system can greatly reduce the size of the system. MLA-based projection system achieves the same output flux as a single aperture projection system but with a much smaller thickness [1][2][3][4] . In 2010, Sieler proposed a design method for a projection system based on MLA and demonstrated a system capable of projecting static images [5] .…”

Multi-aperture pattern projection using arbitrary shaped microlenslets

“…1 mm) of the lenslets, the individual channels have a large depth-of-focus (DOF), thus allowing sharp projections on tilted and curved surfaces. To compensate distortion and keystone effects arising from such projection geometries, the slide structures are pre-distorted, leading to a corrected projected image [2]. Optionally a layer of aperture arrays is also used below the projection lenslets to shut-off dead spaces between the lenslets or to control the f/# of the projection lenslets.…”

“…Illuminance measurement of a single chevron projected perpendicular to the measurement screen showing the various scan lines along which illuminance cross sections are created (top left). Scans along the center of the chevron[1] and along the flank of the chevron[2]…”