Projector-based visual systems have been a mainstay of driving simulators since their inception. Even in the future, we at Cruden expect that many simulators will continue to use a multichannel projection system. With LED projectors now replacing the old-style, lamp-lit ones, both image quality and projector longevity are much better than they were a decade ago.
However, we’ve also been monitoring advances in direct-view LED panel technology for some time. In city centers and at sports venues, such screens are usually viewed from far away and often have distance between the pixels. But with recent advances for the pixel pitch (the closeness of the pixels to one another), the door has opened to their use in driving simulators, too.
In a driving simulator, a projection system is good for creating a large screen at a distance that is far enough away from the driver – typically 3-4m (10-13ft) – for them to feel like they are looking into the distance, which is important for the immersion of the simulator.
But projectors also have their challenges. One is that the light path to the screen must always be free of the envelope of positions created by the moving structure of the vehicle mock-up on the motion system. The need to avoid shadows on the screen can often lead to suboptimal projection layouts.
Instead of placing the projectors in the center, in line with the driver’s eyepoint, they are typically moved toward the ceiling. This shift upward means that the projectors are closer to the top of the screen than the bottom, leading to inconsistent pixel brightness and density, which compromise the uniformity of the image.
This brings us to the newer, high-end, direct-view LED panel solutions, the pixel pitch of which has reduced in recent years from a minimum of around 2.5mm to as little as 0.9-1.5mm. This matches the system resolution requirements for an immersive driving simulator visual system. Curved screens suitable for driving simulation can be built from planar LED segments. Cruden can provide the customer with a cylinder, U-form or any other screen shape or aspect ratio, simply by stacking the panels horizontally and vertically in the right combination.
The resulting LED panel image will have several advantages over that of a projector image. One is the absence of the need to blend adjacent images in order to create a single image from multiple projectors. Also, the geometric correction (warping) of the images is much more straightforward because with LED panels, the location of each pixel is known and can therefore be addressed directly from the image generator that renders the images. No pixels or render performance is spilled as all the rendered pixels will be used to show one synchronous image distributed over adjacent panels.
Removing the blend zones brings further advantages in low-light conditions. The possibility of showing true black with LED panels results in a huge contrast increase compared with images of a projection system with the same luminance. The additional contrast also helps us to create a better-defined image. It all adds up to greater immersion – the overriding goal of the simulator’s visual system.
With such promising fundamentals in place, we have been working with LED panel manufacturers and signal processing developers to fully harness the potential of this technology for driving simulators.
The low latency and 120fps frame rate requirements are aspects that we’ve been able to address. Both are essential for driving simulation, so developers have worked to ensure that this can be implemented. Carefully selecting the right LED panels, driver and signal processing to match our application also means that effects such as the smearing or ghosting that you sometimes see on a television can be eliminated.
The LED panels that are used in offboard simulator visual systems are currently not suited to use on board the simulators – screens mounted directly on the simulator motion system – as the panel structures are not designed for dynamic applications. Nor is the pixel pitch high enough yet for their use so close to the driver. Instead, Cruden is using OLED panels that can also be curved to wrap around the driver.
LED panels are setting a new standard for large, offboard visual systems. They won’t be for everyone, not least because such a solution can come at about three times the cost of a traditional projection system. But it’s for the enhanced technical capabilities that this option is now being requested by some of our customers – especially those who have extensive experience in simulation and projection systems.
Bastiaan Graafland is a product manager at Cruden, where he is often the interface between customers and Cruden specialists involved in the development of simulator products or projects. He has experience in industrial automation, robotics, mechanical engineering, manufacturing, computer graphics and simulation
