I recently rented a car which had an HUD for your speed, as well as the current speed limit.
When looking at it, it seemed to float above the front of the hood. I took [a picture](https://imgur.com/8rC0Ijv) of it which came out pretty well.
I am wondering how they get it to float, instead of looking like it’s sitting on the windsheild, and whether they can control where it appears to float. For example, could something be changed that would make it feel like it was closer, perhaps in the middle of the hood instead of at the front of it? How about if they wanted to make it seem like it was three car lengths in front of the car?
If it is possible to change where it appears to float, what do they have to change about it to have that effect?
EDIT silly fingers added an apostrophe to the “its” in the title, and I can’t change it.
In: Technology
There is a small projector embedded in the dash of the vehicle. It basically just projects the image onto the windshield.
It uses several mirrors to magnify the image, and (probably more importantly) adjust the image to take the angle of the windshield into account.
Usually they can have their height adjusted a bit, and they may have a “focus” adjustment, but to be able to make it appear closer or farther away, I think it would need a completely different set of mirrors.
The image you see on the HUD is a reflection of an image that is passed through special culminating lenses and mirrors inside the HUD. The optics in the HUD are designed to focus the image at infinity so when you read the information on the display your eye does not have to focus on the windshield, then focus on the objects outside of the car.
Hoave you ever been to an eye test in a small room? The poster with the letters on it should be 20 feet (6 metres) away (hence 20:20 vision), but this is obviously hard to achieve in a small room. Instead what they sometimes do is put the poster (reversed) on the wall behind you, and they you look at a mirror in front of you. That way you are seeing the mirror (say) 2.5m in front of you, plus the distance from the poster to the mirror of 3.5m = 6m
The HUD in the car is doing a similar thing; taking an object which is near (in this case the LCD screen that is displaying the speed and is embedded somewhere in the dash) and using lenses (plus the windscreen acting as a mirror) to make it appear further away. Think of the arrangement of lenses (called a collimator) as like looking through a camera’s zoom lens in reverse. If a camera lens or telescope makes far objects look close then the reverse makes close objects look far.
My Ioniq5 has this feature. It’s a throwback to the “pepper’s ghost” effect from the theatre.
Adjusting it can move it up or down (so you don’t get blocked by the steering wheel if you’re shorter I assume and it doesn’t sit in the middle of your eyeline otherwise) but it always appears to focus at the same distance on my car, somewhere just above the end of the bonnet.
It’s a great feature in my opinion.
That is really cool. What kind of car did you rent?
A very bright LCD screen is reflected on the windshield. It only looks far away due to its distance from the reflective surface. Look at your dash from the other side of the windshield and you’ll see the screen.
You can imitate this effect by placing your phone on your dashboard, and you’ll faintly see your phone screen on the windshield.
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