As the module that is most easily perceived by users as the intelligent human-computer interaction module of automotive intelligent cockpit, AR-HUD has ushered in rapid development. Driven by consumer demand and technology upgrade, the AR-HUD field of view Angle is getting larger and larger, the display is becoming clearer and clearer, and the functions are becoming richer and richer, but there are also many small AR-HUD or semi-AR-HUD with castration performance, such as small imaging, fuzzy imaging, poor combination of virtual and real, etc. In addition, stray light has a "veto". Because it directly affects the user's visual experience.
A HUD has a large stray light problem
▎ Stray light,
optical "noise" that is difficult to eliminate
In AR-HUD, stray light refers to the light from
the outside world and the AR-HUD itself, which is imitated in the AR-HUD
display area through a non-imaging path, and is the unexpected light in the
system and also the optical "noise". The driver can tolerate tire
noise, wind noise, and even play music to reduce the impact of noise, but
generally will not tolerate line of sight occlusion and stray light
interference. This is because auditory stimuli and visual stimuli compared to
visual stimuli, visual processing speed and response speed is faster, but also
more sensitive.
When the vehicle is driving, it will face complex
situations, the external light is changeable, and the stray light generated by
the AR-HUD itself is not as controllable as the laboratory conditions, even if
the system is designed to have good imaging quality, unexpected stray light
will still affect the imaging quality. Safety is no small matter, in high-speed
driving and other dangerous car driving situations, the harm of stray light
will be infinitely amplified, even if the smaller stray light can not be
ignored. Therefore, stray light has a veto effect on the AR-HUD optical system,
and in the design of AR-HUD, stray light is a problem that needs to be paid
attention to.
Remote AR-HUD stray light elimination effect
How to eliminate
stray light? This tests both the technical strength of the AR-HUD supplier and
its project experience, both of which are indispensable.
▎ Different kinds of
stray light elimination methods
Stray light generated outside the AR-HUD system
includes: stray light on the edge of the mirror, glare on the outside of the
dust shield, stray light on the edge of the decorative cover on the car, etc.
Stray light generated in the AR-HUD system includes: stray light repeatedly
reflected between the LCD screen and the mirror, LCD reflection, mirror edge
reflection, dust plate inside stray light, sunlight backflow stray light,
structural reflection, etc.
Schematic diagram of glare on the outside of the
dustproof plate
Method of eliminating stray light
outside system
The edge of the mirror and the outer side of the
dust shield are close to the AR-HUD light outlet. External light is reflected
through the burrs at the edge of the mirror and the dust shield, forming stray
light such as glare or ghost on the windshield.
The edge stray light of the mirror can be treated
by edge shielding. Stray light on the outside of the dustproof plate can be
avoided by adjusting the arc shape of the dustproof plate, so that the stray
light that can be reflected into the eye box is located under the IP, that is,
the IP directly blocks the outside light that can enter the eye box, so as to
eliminate it.
Stray light caused by repeated reflections between the
LCD screen and the mirror
Method of eliminating stray light in
system
Because the LCD itself is also a luminous body,
the light emitted by the LCD may not reach the human eye through the normal
path, then there will be a series of stray light in the system.
The stray light
reflected repeatedly between the LCD screen and the mirror and the stray light
of sunlight backflow can be eliminated by adjusting the Angle of the LCD
design. For stray light inside the dust plate, the relative position and Angle
of the mirror can be adjusted to eliminate it.
In optical design, stray light is difficult to
form a fixed theoretical analysis of the content, ray tracing results analysis,
system design improvement have no unified solution, only through continuous
analysis, summary of project experience, to seek more and better ways to
eliminate stray light.
Based on this, Jiang Cheng set up an optical
design team a long time ago to explore the elimination of stray light under the
premise of not increasing the volume, not improving the complexity of the
system, and not affecting the quality of imaging, accumulated rich experience
in optical design, and successfully mass production landing, and won customer
praise. In the future, Jiangcheng will give full play to the advantages of
technology development and project experience accumulation, continue to lead the
development of intelligent display technology for mobile travel, so that
intelligent display can enable safe travel and enrich the mobile third space.
