抬头显示器（Head-Up-Display， HUD），最早出现在战斗机上，用于降低飞行员低头看仪表盘信息的频率，使其更好的将注意力集中在驾驶操作上。通过HUD将重要信息显示在驾驶员前方的透明玻璃区域。由于飞行器/机动车等移动工具具有高速移动特性，飞行员/驾驶员从低头至抬头的短时间内，会出现视线方向切换，而飞行员/驾驶员已经从原来场景移动出几百米（飞行器）或几十米（机车）的距离，会导致飞行员/驾驶员在短时间内失去时间判断和空间位置把控能力，形成巨大的安全隐患和财产损失。
近年来，HUD技术逐渐引入到汽车领域，用于保障司机驾驶的安全性和稳定性，使驾驶者不用低头观察仪表盘、导航等信息，进而将更多精力放在观察路面信息上，避免视线频繁切换引发的视觉疲劳。HUD从最初某系高端车型开始搭载尝试，至今已有二十年，目前已经从高端车型延伸到中端车型。HUD已经成为汽车辅助驾驶（Advanced Driving Assistance System， ADAS）和自动驾驶的重要组成设备。
Head-Up-Display (HUD) enables a driver to view information with his head positioned “up” and looking forward, instead of angled down looking at lower instruments. By adding the Augmented Reality technology, targets, like people and cars, can be marked to alarm to the drivers to avoid the potential accidents.
随着车载传感器的大量使用和人工智能识别技术的迅速推广，将所识别到的路面信息通过HUD技术进行实时显示，实现物理空间和信息空间的增强现实（Augmented Reality，AR）融合显示，将导航信息、前车碰撞警告、行人动作危险预判等内容直接准确的显示在驾驶员视野前方，形成具有智能驾驶辅助信息的抬头显示器（AR HUD）。
然而，传统的二维抬头显示器（2D HUD），在进行AR标定时，需要维持观察者、HUD、真实物体与光轴重合，即三点一线的空间绝对位置，才能保证真实物体与标定信息重合（如图1左1）。当观察者头部位置移动，出现偏离光轴的情况，标定信息就会偏移，进而造成错误的信息引导（如图1左2）。因此，传统的2D HUD不适宜用作AR HUD。
Traditional 2D AR HUD projects information messages at a certain distance away from the driver. It asks a driver to observe the projection along the optical axis at a certain point. When the driver moves his head, a miss-matching projection occurs between the projected data and the target in the real world.
本项目的三维抬头显示器（3D HUD）为“真三维”显示技术，不采用左右眼视差的“伪三维”显示方式。本项目的3D HUD将结合观察物体的（如图1右、行人或汽车）不同距离，在相对应的不同深度空间显示标定信息，即使在驾驶员头部移动的情况下，依然能够显示准确的的标定信息。
In this 3D AR HUD technology, a 3D virtual display can be projected in front of the driver. AR messages will be dynamically projected according to the 3D locations of the targets. In our 3D HUD, a virtual display is projected into a three-dimensional world, so there will be no mismatch when the driver moves.
Figure 1. (Left) When a user observes in a good position that follows the specified optical axis, the projected data and the target will be well matched. However, when the observing axis have any movement, in position (b), there will be a mismatch projection between the display and the real world.. (Right) In this 3D HUD technology, a 3D virtual display can be projected. AR markers will be dynamically projected according to the 3D locations of the targets. Because the message is projected into a three dimensional world, there will no mismatch even when the drivers moves.
对比在不同观察位置使用相机采集的照片，可以发现，当相机在光轴位置时2D和3D HUD的标定（红色2D、绿色3D）信息能够和人重合。当相机从光轴移开，并与光轴成一定角度拍摄时，能够观察到2D标定与人出现偏移，而3D标定依然与人重合。
The following demos were recorded by two cameras, which were placed at different places. When the camera was placed along the optical axis, 2D and 3D markers were all perfectly matched. When the camera was placed at an angle to the optical axis, a mismatch was found in 2D HUD, but 3D HUD was still well matched.
此项技术是东京大学石川渡辺研究室同柯尼卡美能达公司的共同研究。
This work was conducted by a collaborate research project between Ishikawa Watanabe Laboratory and Konica Minolta Inc..
Figure 2-1. A photo of 2D HUD projection. All the 2D HUD markers were projected at a certain distance.
Figure 2-2. A photo of 3D HUD projection. 3D HUD markers were projected at different distance. This photo were token when it focused at close.
Figure 2-3. A photo of 3D HUD projection. 3D HUD markers were projected at different distance. This photo were token when it focused at far.
Video/视频
Reference/参考
- Konica Minolta Release. [Link]. (2017.02) (In English/柯尼卡美能达 英文)
- Konica Minolta Release. [Link]. (2017.01) (In Japanese/柯尼卡美能达 日文)
- The Nihon Keizai Shimbun. [Link].(2017.01) (In Japanese/日本经济新闻 日文)
Access/联系
wanglihui@gdisit.com
Lihui Wang/王立辉，For more/更多
Dynamic Image Perception 