Electronic – Removing ripples from PWM controlled LED in camera vision application

cameraledpwmripple

I have made a camera vision setup with highpower LED's which are controlled with a simple NE555 timer and a mosfet. The LED system is lighting up an area where a camera is looking, but unfortunately i am experiencing ripples/stripes on the video stream due to the nature of the PWM dimmer. Is there a way to reduce these stripes or even eliminate them?

The camera: http://charmedlabs.com/default/?page_id=211

NE555 circuit:

enter image description here

Best Answer

If you used an inductor (with maybe a capacitor) filter in line with the LEDs you would get much lower ripple voltage on the LEDs. At the moment it sounds like the LEDs are being modulated directly by the PWM frequency and this will generate "beats" with the video frame and line rate. This produces ripples in the same way as aliasing can occur when sampling a frequency that is too high. You could also try increasing the PWM frequency or maybe locking it to the video signal somehow.

Here's a circuit that does this: -

enter image description here

By the way the circuit link doesn't work for me.