HUD; virtual image at infinity

In summary, the conversation discusses the use of a HUD display and the challenges in creating a virtual image at infinity. Set-up 1 involves using two plano-convex lenses and lasers to produce parallel beams, while Set-up 2 uses an OLED screen and a beam splitter. However, the OLED image is not at infinity and requires refocusing. The purpose of the plano-concave lens in the HUD schematic is to help correct for aberrations and produce a high-quality image.
  • #1
Smooth
6
3
Hi,

I am trying to create an HUD display - basically create a virtual image at infinity and look at it. I have two plano-convex lenses; the distance between them is the sum of their focal lengths; my object is therefore imaged at infinity. Here is the schematics that I'm pretty much trying to make:

HUD optics:
HUD.jpg
Virtual image at infinity (Galilean Telescope):
inage at infinity.gif

set-up 1.jpg

Set-up 1: (with lasers)
I have two plano-convex fresnel lenses with the focal lengths of ~120mm each; I position them with ~240mm between them (sum of two focal lengths). I have an object on the right; after the light from it passes through my lenses, the rays should be collimated. They are - the distances between the rays of the light source and between the points on the image on the right are about the same (5cm vs 5.5cm. As good as it gets though. Is it because the lenses are not perfectly vertical?).
set-up 2.jpg

Set-up 2, OLED screen, no lasers.
Now I get rid of the lasers, I put the OLED screen instead, put a beam splitter to the left of all the lenses, and an LCD screen behind the beam splitter.
This way when I look at the beam splitter I see both images - from OLED (went through optics) and from LCD. However, the image from OLED screen is not at infinity: I have to focus my eyes on the LCD, then refocus to the OLED.

Why does it happen - why isn’t the OLED image at infinity? I want the virtual image from OLED screen to be always crisp and clear - well, imaged at infinity.

Also, there is a plano-concave lens on the schematic that explains the HUD. What's its purpose? I don’t quite get it.

I would really appreciate some help here; many thanks in advance.
 

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  • HUD.jpg
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  • inage at infinity.gif
    inage at infinity.gif
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  • set-up 1.jpg
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  • set-up 2.jpg
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  • #2
Smooth said:
View attachment 214376
Set-up 1: (with lasers)
You put parallel beams in and get parallel beams out, so your setup doesn't change the image distance.
Smooth said:
View attachment 214377
Set-up 2, OLED screen, no lasers.

OLED screen is not at infinity:
Of course not. Your setup only outputs parallel beams, if you put parallel beams in.
 
  • #3
Smooth said:
Why does it happen - why isn’t the OLED image at infinity? I want the virtual image from OLED screen to be always crisp and clear - well, imaged at infinity.

Your setup does not produce an image at infinity. Try placing the LCD screen at the focal point of one of the lenses and then viewing this light via the beamsplitter.

Smooth said:
Also, there is a plano-concave lens on the schematic that explains the HUD. What's its purpose? I don’t quite get it.

That lens is just part of the overall lens assembly that correctly focuses the light. Simple plano-convex lenses cannot create a high-quality image due to aberrations introduced to the image as the light passes through. You need a number of different lenses of different shapes, focal lengths, and refractive indices.
 

Related to HUD; virtual image at infinity

What is a HUD?

A HUD, or Heads-Up Display, is a transparent display that presents information without requiring users to look away from their usual viewpoints. It is typically used in aircraft, cars, and other vehicles to display important information such as speed, altitude, and navigation directions.

What is a virtual image at infinity?

A virtual image at infinity is an image that appears to be located at an infinite distance from the observer. This is often used in HUDs to give the illusion of information being displayed in the distance, making it easier for the user to view and process the information without shifting their focus.

How does a HUD create a virtual image at infinity?

A HUD uses a special optical system to project the image onto a small, transparent screen or glass panel that is positioned in front of the user's line of sight. This screen acts as a combiner, reflecting the image from a display onto a mirror, which then reflects it into the user's eye, creating the illusion of a virtual image at infinity.

What are the benefits of using a HUD with a virtual image at infinity?

Using a HUD with a virtual image at infinity allows for important information to be displayed in the user's line of sight, without causing them to shift their focus away from their primary task. This can improve safety, efficiency, and convenience in various applications such as driving or flying.

Are there any limitations to using a HUD with a virtual image at infinity?

One limitation of using a HUD with a virtual image at infinity is that the image may not be as bright or clear as a physical display, especially in bright lighting conditions. Additionally, the size of the display may be limited, making it difficult to display large amounts of information. Careful design and calibration are necessary to ensure optimal viewing for the user.

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