IEEE Consumer Electronics Magazine - September/October 2019 - 64

Special Section on Human Centric AR&VR Display and Human Interface Technologies for Automobile

Figure 3. Visualization of AR-HUD fundamentals for
augmentation by a projected virtual object. The virtual object
should be placed at an adequate distance by the AR-HUD
requiring a dedicated FOV. The colors of the lines correspond to
those in the inset.

and motion parallax reduce the noticeable
difference between monoscopic and 3-D HUDs.
Therefore, monoscopic HUDs with a projection
distance of 5-10 m show a comparable depth
perception to 3-D-HUDs.5
With these assumptions, we can calculate the
vertical FOVV values from aV according to
Figure 4 (top) and the above data:
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FOVV for look-down from aV min À aV max ¼
15 À 1 % 15 (calculated with the tangent
function using h ¼ 1.3 m and d as being 5 m
and 80 m)
1 to 2 have to be added for eye box adjustment, image warping, etc.
Framing cars in boxes and annotated (added)
information require a look-up angle aVlu. Distant objects such as traffic signs on highways
require a look-up angle of at least 5 . This
results in a total FOVV of about 20 for highway use cases.

Figure 4. Visualization of geometrical conditions for AR-HUDs:
Vertical (top) and horizontal (bottom) FOV and real object
distance d. For details, see text.

AR augmentation of close objects like shops
and traffic signs require at first approach
20 for look-up angle aVlu (Figure 2, right).
This angle depends strongly on the minimum distance (both horizontal and vertical)
at which the AR image should overlay the
real object.

The vertical FOVV for augmented content
should therefore be at least 20 for highways
(no signs, Figure 1, top right). For traffic signs
and urban areas 40 is regarded as the minimum FOVV (both 20 for the look-up and lookdown angle). This is about one order of magnitude larger than present HUDs.
Corresponding considerations have to be
made for the horizontal FOVH for different use
scenarios:
-

Lane guidance on highway aH ¼ 10 , see
Figure 4, bottom.
Passing a car on highway: aH % 20 (see
Figure 1, top right, Figure 4, bottom).
Urban wayfinding (e.g., highlighting lane):
aH % 40 (see Figure 2, left).
Annotated information and warnings (e.g.,
pedestrians) in cities: aH % 60 (see Figure 2,
right).

A horizontal FOVH ¼ 40 is proposed as a
reasonable compromise in terms of AR performance, volume and cost.
Summarizing, a field of view of 20 (h) Â 20
(v) is regarded as the lower end for visualization
of AR effects in highway scenarios. Annotating
traffic signs, city traffic, wayfinding and, for
instance, warnings by marking, e.g., pedestrians
raise the FOV towards 60 (h) Â 40 (v) with a
projection distance of $ 2 m for operational and
10 m for AR data.

System Challenges and Solutions for AR-HUDs
As pointed out above, AR-HUDs require FOVs
in the range of 20 -60 for the horizontal and
20 -40 for the vertical angle. This is hardly
achievable with today's technologies of HUDs.
The following topics have to be addressed:
-

Optical system design for large FOV at a reasonable volume.

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IEEE Consumer Electronics Magazine - September/October 2019

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