Introduction to DLP Optics DLP Optics Scott Dewald
Ways to use the DMD • Object plane – project an image of the DMD surface onto another surface (or a virtual image, e.g. HUD) • Place at a system stop or Fourier plane– spatial filtering or light modulation (including spatial filtering or light modulation (including holographic data storage) • Place in a diffracted beam – wavelength selection/spectroscopy www. DL i nnovations .com
How the Light Is Steered Light • +/- 12º tilt angle Dump on mirrors permits 48º “ “ “ “ Flat” 4 nonoverlapping State cones of light at 24º Projection Projection “ Off” “ “ “ f/2.4 f/2.4 Lens On State State 0º Energy (-12º) “ “ “ “ On” F Light D -24º Source F/# = F/D = 2.4 State (+12º) for 11.5 º beam www. DL i nnovations .com
What Does Telecentric Mean? Pupil at Infinity Pupil • • Telecentric: Projection and/or Telecentric: Projection and/or Illumination pupils at infinity • Each pixel “sees” rays from the • Non-Telecentric: Projection pupil same f/# and direction near entrance of projection lens • Better uniformity in on and off • Generally requires offset states illumination • Can be more compact • Larger projection lens • Requires TIR prism www. DL i nnovations .com
TIR Prism • TIR Prism discriminates between incoming and outgoing rays based on angle • All rays less than critical angle (approx. 41.2 degrees in BK7) will (approx. 41.2 degrees in BK7) will pass; rest will reflect • Air gap is made small (approx. 10 um) to reduce astigmatism in projected image www. DL i nnovations .com
Lamp and Integrator www. DL i nnovations .com
Illumination Relay Optics Projection Lens Integrator Integrator TIR TIR Prism Aperture Stop DMD To obtain maximum uniformity of illumination at the DMD, the relay optics should be telecentric in both object and image space, with no vignetting. www. DL i nnovations .com
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