1. Using a Classroom Projector to Study the Properties of Light Drs. Michael Ottinger and Brian Bucklein Missouri Western State University St Joseph, MO 64507 Missouri Association of Physics Teachers Meeting November 6, 2010

2. Outline Creating a Three-Color Image (RGB) How LCD and LCoS Projectors create color images Obtaining and Using Spectral Glasses Demonstration of the Separation and Mixing of Colors Demonstration of the Polarization of Light

3. Three Color Image System Object RGB Filters Red Image Blue Image Green Image Low Pass High Pass

4. Three Color Image System Red Image Blue Image Green Image Superimpose Images Red Lamp Blue Lamp Green Lamp

5. Methods for Reproducing RBG Digital Light Processing (DLP) Liquid Crystal Display (LCD) Liquid Crystal on Silicon (LCoS)

6. Digital Light Processing (DLP)

7. Liquid Crystal Display (LCD)

10. LCD Projector 1.Light Source (Bulb) 2.Polarizer Lens 3.Beam Splitter 1.Low Pass Mirror (red passes/ blue and green reflected) 2.High Pass Mirror (blue passes / green reflected)) 4.3 LCD’s (one per color) 5.Dichroic Combiner Cube

11. Dichroic Combiner Cube

12. Liquid Crystal over Silicon

13. An LCoS Projector

14. LCoS Projector UHP Mercury Lamp Note: Green is Polarized Perpendicular to Red and Blue

15. Using the Projector to Study Colors Diffraction Grating Glasses Available through many companies for about $0.25 to $0.45 each 500 lines/mm, linear diffraction grating

16. Breaking down the Colors The following slides were made by using the “Shapes” drop down in PowerPoint to make two thin rectangular lines. The top line was set to white and, using the color setting the bottom line was set to different color combinations.

18. White

19. Red

20. Green

21. Blue

22. Yellow = Red + Green

23. Magenta = Red + Blue

24. Cyan = Green + Blue

25. White = Red + Blue + Green

27. Polarization LCD and LCoS Projectors use Polarized Light – Typically the Red and Blue have the same polarization – Green is polarized perpendicularly to the Red and Green

29. Conclusions Classroom projectors create images from three color regions of polarized light (RGB) Using the projector and inexpensive spectral glasses you can demonstrate color mixing. Polarization of light can be demonstrated from the different polarizations of the light

31. Pictures were taken by placing the spectral glasses on the front of a digital camera