a 3d full windshield head up display. - small projector

Responsible person-Up Displays (HUD)
It has been on the plane for decades.
Originally designed for military applications, as a means of targeting, they are now used to improve situational awareness due to the ability to superimpose information based on the external environment.
So HUD is the first application we now call augmented reality. AR).
To reduce the re-eye
In order to shorten the focus time and reduce the occurrence of parallel problems, we calibrated the image so that the symbol can be perceived far away.
But the head projection unit that can produce a bright straightener is very large, and the associated complex optical engines are very expensive.
Only on very small eyes can you see the same school image
Resulting in poor user experience.
This paper presents a new system using analog aiming, holographic optics and spectral interference filters.
These breakthrough technologies are applied to the flat-screen display, which meets the needs of complex refraction optical systems and provides a theoretical infinite perspective.
Excellent user experience.
Background head-
The Up display has retained the same primary architecture for the past few decades: Source, projector, and combiner.
The projector creates an intermediate image from the object source, which is assembled to infinity and superimposed on the outside world through a synthesizer.
First, HUDs uses CRT and partial reflection plane combiners, and then holographic bending combiners.
More people introduced the LCD display with the backlight of The CCFL lamp, followed by the LED backlight, combined with the dielectric coating combiner.
The latest generation of diffraction optics and ultra-thin combination devices based on pupil expansion are introduced.
In these generations, the function of each element is the same.
The avionics flat-screen display is far enough to be considered infinite.
In this case, symbols such as speed vector, horizontal position, synthetic vision, enhanced vision are very similar to the real world, when the pilot moves hishead to the eye frame, no parallax problems provide augmented reality.
In addition, the combiner located near the pilot's eyes provides a broad view, usually more than 30 [degrees]
At level and 20 [degrees]in vertical.
These features improve the user experience and increase the situational awareness of pilots at key stages of flight such as proximity, landing and taxiing.
Corresponding to this, the shortcomings of the current avionics HUDs are the large projector space envelope, limited head clearance and limited eye movement box.
To solve these problems, it is envisaged to use the surface of the windshield.
Windscreen projection has been exploring the automotive market for years
The Up display is mainly used to display information while keeping the eyes on the road.
This includes speed, navigation direction, warnings, and information related to the condition of the car.
This information is not in line with the landscape, resulting in parallax errors between the symbols displayed a few meters away and the real world in the background.
Automotive Field of View (FOV)
Limited by the size of the hud box, this limitation comes from the large mirror needed to reflect the image on the full windshield, as shown in figure 4, and augmented reality applications require a very large field of view.
However, this key parameter has a great impact on the size of the HUD box, mainly due to the level (X)and vertical (Y)
Mirror size, as shown in figure 5.
With this optical structure, HUD with a view of 14 [degrees]x6[degrees]
A mirror size of 325mm x 175mm is required.
Application of aviation electronics, 35 [degrees]
Level and 25 [degrees]
Vertical is a common value.
The HUD box architecture then requires mirrors larger than 500mm, which are not compatible with the cockpitinstallation installation restrictions, so different optical architectures are often used for avionics applications, resulting in limited eye masks.
A full windshield head
Using direct projection for up-display on the atransparent screen is an alternative and breakthrough to the current hud architecture. Papers [4]and [5]
At present, this kind of flat-screen display and this kind of HUDsimulator.
Due to the use of a small projector, the direct windshield projection on the windshield reduces the installation limit and is able to remove the attachment. Paper [6]
A system using a small UV laser projector and windshield with a layer of transparent fluorescent material on the windshield is introduced.
With this concept, a large HUD system can be replaced by a basic video projector with a small footprint and a transparent screen embedded in the windshield.
However, it raises several questions, especially the mismatch between the real world and the images presented at short distances, providing a poor user experience for augmented reality applications (Fig. 6).
All in all, direct projection on a transparent screen can be a good solution for the eyes
It solves most of the space envelope problems.
But lack of AIM and wisdom-
Conflict of accommodation is the key performance [7].
An efficient augmented reality (AR)
In the real world, the system should be virtual.
For ar hud, Horizon, velocity vector, synthetic or enhanced vision should be shown in line with the real world without adjusting the effort and convergence issues.
This has historically been achieved through the complexity of the projector's interior and bulkycolli optics.
However, the same color light will have an elimination effect, and the image is visible only in a small eyebox.
By projecting directly on the transparent screen, the image is formed at a limited distance on the screen.
Without using aim, it is impossible to superimpose the real world.
For transparent display, we recommend using stereo vision to simulate aiming (figure 7).
Display to the left using a stereo projector-
Right eye image
The eye image on the transparent screen is actually a windshield with an optical layer.
When the distance of the two images on the screen matches,
Virtual objects can be seen in an infinite distance.
At the same time, since the 3D glasses only allow one image to be seen per eye, the dual vision problem is solved.
This system provides unlimited viewing directions without any restrictions, such as small eye frames and unique viewing points of traditional HUD.
3D transparent screen for HUD user wearing a pair of 3D glasses and camera
Based on head tracking to compensate parallax errors caused by head movement (figure8).
The 3D principle of windshield projection using the 3D system of the polarized goggles will cut off at least 50% of the external brightness due to the polarization of the light.
The active shutter 3D system to achieve an external brightness transmission of more than 50% requires a complex synchronous mechanism between the projection source and the time eye template, so it becomes tricky and cumbersome in the head.
Look at the most appropriate settings-
The wavelength multiplexing method through the system seems to be [8].
By using a pass-through filter for each color and for each eye, a 60% transmission rate can be achieved (
More if using a narrow-band source)
Only the light passive parts on the head are used.
For avionics head-up display, the image shown is green as required by the current avionics standard [9].
The principle proposed and applied to our proposed application only eliminates a small portion of the bandwidth of the visible spectrum of gogglenotches, typically green less than 30 nm at 520 nm and 540 nm, resulting in excellent mirror transmission of more than 75%.
Since the two gaps are applied to the left and right, respectively, the entire spectrum can be seen in both eyes except for the non-otch wavelength, and only one eye can see.
In fact, in order to avoid the possibility of crosstalk between the two images (
Part or all on the left
Image of the eye that can be seen in the right eye)
, It can easily design two gaps with small overlap.
Adjusting this overlap to about nm will help reduce hazards associated with some green laser lighting.
In order to achieve spectral multiplexing, two filtered projectors can be used, but such a system is large and incompatible.
Distance projection required in the cockpit of an aircraft or car.
Using a short-shot projector in time mode is a solution but needs to double the image rate.
In this case, a specific active spectral modulator is required to be able to tune the two bandwidths accurately and efficiently, as described in the document [10]
The remaining problem with this new system is that aim is generated by stereo vision, head motion detection and browsing the legacy HUD using 3D glasses simulation, but there is no risk of losing the image because of a small eye mask.
When the left and right images are displayed on the windshield, adjust the deviation from the viewing distance, and the adjustment is still carried out on the glass, while the adjustment deviation is infinite.
It generated a stay
The famous convergence conflict in 3d projection11][12].
In our system, when the pilot looks out, it will naturally converge at infinity.
Solve the accommodation problem-
Vergence problem, the pilot must see the landscape and symbols without any accommodation.
Since the distance of these two objects is different, in order to avoid a mismatch of accommodation, they should be within the visual depth range.
The results show that if a specific rule is applied and the loss of vision is small, the adjustment problem of [can be dealt]13].
This number is the result of an experiment designed to measure the relative vision of a normal person when reading a symbol at a virtual infinite distance on the screen.
We can see that normal vision can be obtained when the subject is far enough from the screen.
At a distance of more than 1.
6 m, there is no difficulty in reading symbols.
When the distance to the screen is small, the sensitivity is reduced to 50 cm when the distance is about 2/10.
The windshield HUD is problematic in this concept, with images of the left and right eyes projected onto a screen located at a limited distance in front of the pilot or driver.
To avoid the installation of additional optical components in the cockpit (
With mechanical interface, positioning and safety mechanism)
, The preferred solution is to use the windshield as a projection screen.
The following features must then be displayed on the windshield screen: * it must allow viewing-
Through the observation of the external scene, without affecting the visual effect, the transfer factor as high as possible
Image seen by the pilot.
* When the projector lights up, each point of the screen must transmit the energy received by the projector at a solid angle compatible with the desired eye movement box (EMB)
Size, aluminum that meets HUD contrast requirements.
In fact, in order to ensure the ease of the symbols displayed by HUD . . , the brightness level of the HUD image must reach at least 30% of the background brightness transmitted through the windshield.
Holographic windshield display is close to a solution by studying the spectral size of the light to improve the tradeoff between the transmission and reflection properties required for the windshield screen.
Usually, the external scene is illuminated by the sun in a wide spectral range, where the pilot's physiological features are limited to visible areas.
We can then take advantage of HUD's narrow bandwidth light source by adjusting the screen's reflection efficiency to this specific narrow bandwidth.
As shown in Figure 12, only a small portion of the spectrum is removed in the transmission, providing high definition
Pass by light.
On the other hand, when the HUD lighting spectrum corresponds to this reflection peak (
Position and width)
Most of the energy from the projector will then be reflected on the pilot with limited transmission loss.
One of the remaining issues is the "reflection-" needed to implement-
The "diffuse" function of the screen.
This can be achieved by using custom holographic optics (HOE)
LighTrans for Web mining development [14](see figure 13).
At each point on the screen, specific optical functions enable the incoming light to propagate at the desired solid angle at a given wavelength.
This function is recorded as a volume phase hologram on sensitive media.
At playback, the function will be activated for any light that respects the local Prague conditions between the wavelength and the angle.
Away from Prague conditions, the feature is inactive and the screen works as a passive transmission component.
In terms of the manufacturing process, it takes two steps to make HOE on a flat substrate.
The first step of the previous page, the-side reliefdiffractive structure produces the main electronsBeam.
This structure is a miniature Engineering Association.
When lighting from the specified projector position, the grating can ensure a uniform filling of the eye movement box.
In the second step, by recording the interference between the event coherent beam and its reflection on the master on the photosensitive polymer layer, the main function is reproduced as volume holographic.
Typically, for high diffraction efficiency components, the spectral bandwidth of HOE is proportional to the exponential modulation in the volume phase holographic.
Today, with the advent of photopolymers, the spectral bandwidth varies between 8 and 10 nanometers.
For optical polymers with a thickness of about 20micro]
M, it can be easily embedded inside the windshield or laminated on the PET board.
For this 3D HUD concept, the windshield screen consists of two hoes, one for the right eye image and one for the left eye image.
However, these two wavelengths can also be recorded on the same HOE with two different laser sources (Figure 14).
For curved windshields, the curvature is usually such that the photosensitive polymer can be laminated on a curved surface (
Development surface).
In this case, this curvature will be taken into account in the design of the main diffraction structure to ensure the correct "reflection-
The "diffusion" function in the final assembly.
Discussion the use of a stereo mirror to simulate aiming can be achieved through high transmission spectrum glasses on the windshield and astronomical screens of holographic optics.
With the spectrum goggles, see you.
Through the 75% nm light transmission rate, unwanted light from the 532 nm laser pointer can be blocked.
Using HOE, the reflection efficiency is over 85% while maintaining the visual effect
Over 90% by transmission.
This value is superior to the poor efficiency of today's car HUD: The image brightness reflects less than 20% to the driver, using the reflection loss on the uncoated clear glass or plastic parts at a high angle (
Cf Fresnel formula).
Color is ideal for automotive applications, and today
End HUDs is full color.
On this device, the windshield reflects a color image (used as a half-mirror).
To improve efficiency and transparency, we used two HOEs on two green wavelengths.
It is possible to display a color image, and two hoes are required for each color component (
Red, green, blue)
One for each eye
The adjustable pass band filter will be more complex with three bands (
One of the primary colors)
, Filter used as 3D projection [4]
There is a high limit on the spectral position and bandwidth of each band, but it is still possible to replace the bulky rotating wheel.
This solution requires a wide spectrum color source.
Today, the compatible LED source is only green for a single chip component.
For blue and red, using two bins for each color is a viable solution.
The main advantages of the proposed concept of projecting HUDimage onto a transparent screen come from the way the geometric features of the whole system are handled.
From the observer's point of view of observer, the geometric etendue of HUDimage can be summarized as a product of a solid angle related to the accessible field of view (FOV)
The lateral dimensions of the eye movement Box (EMB).
The natural trend/requirement of the customer is to increase the FOV and EMB, resulting in great pressure, whether for the avionics of forautomotive or for optical systems that are always larger in size, and only one (complex)
The optical system is used to transmit images from the target source to the pilot.
The law of optics requires that from the beginning to the end of the optical system, etendue remains the same: if we try to use a small object source, etenduservserv will enforce an opposite that cannot be very large.
The concept proposed can break this limit: We have two separate optical systems here.
The first optical system projects the image onto the screen.
According to the standard projection system (ie cinema)
, The small object source can be used with a short focal length lens and generate a large image.
The screen itself plays the role of a second optical system: each point on the screen redirects the energy received from the projector at a solid angle corresponding to the EMB.
Finally, the concept is able to obtain a huge etendue in the pilot's space, while using a relatively small etendue in the object space.
It may look like magic, but that's not the case and it works!
Even if we managed to solve the etendue problem, there is still a problem with energy savings: the power required for the pilot's eyes to get the same brightness comes only from the projector.
The key problem with this concept is how to deal with the energy generated by the projector.
Summary/conclusion a new HUD architecture is proposed using the windshield as a random screen using holographic optics.
This new concept breaks the size limit of today's HUD box and provides a prominent view and eye mask as large as the full windshield, which is a very ideal performance that can improve future enhancementsREFERENCES (1. )
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A full windshield head
Use the up display of analog aiming ", showing the week record San Francisco 2016 (Mai2016)(14. )
LighTrans, custom holographic screen HUDApplications ", contact details of Coni display expert Thales SAS Philip. coni@fr. thalesgroup.
This work is carried out within the framework of several studies funded by DGAC (
Direction of civil aviation --
Air France)
The author thanks Tim Pike for his careful review of themanuscript.
Definition/abbreviation of AR-
Augmented reality ARHUD -
Augmented reality HUD 3D-Three-
Dim AOI
Angle of AR-
Augmented reality CCFL-
CRT of cold cathode fluorescent lamp-Cathode-Ray Tube EMB -
Eye movement box FOV-
Hoe vision-
Holographic optical element HUD-
LCD head Display-
LCD RGB-
Red Green Blue UV-Ultraviolet (Radiation)
Appendix Philip Corey, Jean Luc Baden, and Xavier seltier Thales Avionics4271/2017-01-