Abstract
The influence of incident angle and aberration of the microlens array on the optical efficiency in pico-projector is analyzed. By modifying the relevant parameters, a method to optimize the optical efficiency and uniformity of the illumination system is proposed. By changing the profile of the freeform double lens used for the concentrator of LED source, the incident angle can be reduced, thus the efficiency loss caused by large angle incident can be reduced. In addition, two spherical relay lenses instead of the Fourier lenses are used as integral component after the microlens array, which is not only low cost, but also more flexible in controlling aberrations. After system optimization, the illumination efficiency and uniformity of the pico-projector system can reach 60.51% and 86.2%, which verifies the feasibility and validity of the theoretical analysis.
Highlights
Pico-projector is becoming a very hot topic with numerous potential applications [1,2,3]
Digital micromirror devices (DMD), liquid crystal display (LCD), and liquid crystal on silicon (LCoS) microdisplay are always adopted as the display panel
As the radiant angle of light emitting diode (LED) is too large as 180°, a compact non-imaging optics is required to increase the illumination efficiency and uniformity
Summary
Pico-projector is becoming a very hot topic with numerous potential applications [1,2,3]. As the radiant angle of LED is too large as 180°, a compact non-imaging optics is required to increase the illumination efficiency and uniformity. A double-row microlens array with two spherical lens as relay lens and two aspherical lens as collecting unit are designed in the illumination system to achieve the compact structure and uniform illumination.
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