View Full Version : 2 times colorwheel DLP problem

Jochem t Hoen
10-27-2004, 05:51 AM
Hi All,

I'm currently trying to get my infocus DLP projector to display images with a frame rate
of 120 Hz. I used refreshforce to force it to
a screen refreshrate of 120 Hz (800x600 px resolution) and wrote a simple full screen openGL application that displays red, green and blue squares on different locations on the screen. I filmed the result with a high speed video camera recording about a 1000 frames a second. I found that the projector somehow insists on displaying the same image twice, resulting in an actual frame rate of 60 Hz, skipping every 2nd frame

so I program (numbers are frame numbers):
1 swap 2 swap 3 swap 4 swap 5, and I get
1 1 3 3 5

would anyone know a way around this? I kind of hope that if it can draw the same scene twice, it
should be able to draw 2 separate scenes instead.



10-27-2004, 09:25 AM
Do you have more technical details about your videoprojector ?

1) is it a tri-DLP or single one+color wheel ? Use you uber camera to film a single white quad to tell...

2) 100% of projectors I have seen are displaying images at 60Hz, even if they do accept a fairly large range of refresh rates in input.

Jochem t Hoen
10-28-2004, 12:58 AM

I took the colorwheel out to be able to use the different colorlayers of an image as separate frames. That would work on a 1x speed colorwheel (resulting in a framerate of 180 Hz in grayscale) But my projector (infocus lp120) has a 2x speed colorwheel. It's going round twice for each frame in normal situations. So what I see is:

Red1-Green1-Blue1 Red1-Green1-Blue1
and then the next frame
Red2-Green2-Blue2 Red2-Green2-Blue2

is this the information you were after?