Wednesday, October 23, 2013

Car HUD Version 2.0

To clarify: I'm not entirely convinced this design is better than version 1, so for our purposes, "version 2" merely means it was built after version 1.

Major differences that I experimented with:

  • I took out the lens completely.  Although I do love the concept of collimation, I wanted to see what it would look like if the display wasn't focused at all.
  • The glass combiner is a simple two-way mirror instead of a fancy teleprompter mirror.  This cuts down on the cost considerably, at the expense of having a darker tint on the glass.
  • The combiner is low in the driver's field of vision, so it is less distracting:
  • The Arduino is wrapped in black paper, for aesthetics.
  • The glass is mounted to a holder made out of wood with super tape, which eliminates the distracting suction cups:
The wood holder

I have had this design in my car for about a month now, and these are some of my conclusions:

  • Having a lens definitely makes the display safer.  Not only does it cut down on transition time when you glance at the display, you can actually see the road better in your peripheral vision.  If I just kept staring straight at the display while driving, I would be able to see the road significantly clearer if the display was collimated.
  • The fact that the display is so low in the driver's field of vision almost negates the effect of a heads-up display.  A HUD is supposed to overlay information so that it seems part of the real world.  This display is in the same line of sight as the top of my hood, which I do not normally look at when driving.  I think a better placement of glass would be slightly higher so that it overlays the road instead of the hood.
  • The display is much closer to the windshield, which creates an unwanted second reflection off the windshield.  In the future I can fix this by blocking that path of light with cloth or paper.


Questions or comments? Email me at!


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  2. I wonder how well using one of the cheap LED projectors would work for a HUD. The low light output might be a consideration, but if using it at a close distance to your "display" it may not be all that important.

  3. Simple solution is you need the mirror in a head up display. This does what the combiner does. It is concave, and curved at the same time. This mirror is what aligns the light to remove the ghost image off the windshield. It seems like it accounts for the curve of the windshield
    If you would like to focus at a distance then this reflective stuff you have going on, you will need a second mirror.
    If you set the leds aimed across your dash towards the passenger side, then put a mirror at a 45 degree angle facing the front drivers side corner of the car (about 4 -6 inches away from the led display, with the curved concave mirror in front of you eye sight, as well as the 45 degree mirror. you should be able to get this projected up on the windshield with some minor headache aligning all of it. once this happens you will see if you move the leds closer or further away from the mirror, the distance changes. you focal point. You will also notice you have created deep space with 2 mirrors.
    If you do get this to work, put it in a box. You want to build a box inside the box for the led driver and the 45 degree mirror. Obviously you would need open areas for the led lights to shine, but you also want to block out sunlight and anything else. Also red does not reflect as well as blue/green.

    best of luck, I will check back in at some point.
    Guy who mods HUD's

    1. Also, you may want to play with a prism. You can buy a toy one for 7 bucks or whatever. It will mirror and object, or led's so you dont have to do fancy wiring. Just remember every time you leds hit a mirror, they get mirrors of vice versa. So if you do a 1 mirror hud like the cadillac night visions had, the image has to be regular, and upside down. If you have a dual mirror hud design, it has to be upside down and mirrored like you are playing with now.

  4. do you think the bmw 6 series projector would be hackable?

  5. Having test driven the Audi B9 platform, I'll never go back to a cheap non-collimated HUD. I'm young(ish) so I don't have eye focusing issues, but people should try a collimated display before making an opinion. My dad has presbyopia so a collimated display helps a LOT. He would never need to look down at the dash for speed or nav data. A non-collimated display wouldn't help either because his intermediate vision is slightly out of focus.