Optical: systems and elements – Projection screen – Curved
Reexamination Certificate
2000-06-13
2004-05-11
Adams, Russell (Department: 2851)
Optical: systems and elements
Projection screen
Curved
C359S443000, C359S449000, C348S121000, C353S013000, C353S079000, C353S094000, C353S098000, C353S099000, C434S040000, C434S043000, C434S044000
Reexamination Certificate
active
06735015
ABSTRACT:
This invention relates to display apparatus for the presentation of computer graphics or video images.
Display apparatus for aircraft flight simulators is well known. This display apparatus provides a technological base line from which similar display apparatus for more cost sensitive applications such as ground vehicle driving simulators could be built. The ground vehicle driving simulators may be, for example, car and truck simulators. However, the cost of commercial flight simulator display apparatus has in the past been prohibitive for all but the most specialised top range ground vehicle driving simulators. Contradicting this aspect however, is that the requirements for simulation of environments and situations for vehicles can be more demanding than for flight simulators.
Ground vehicle driving simulators fall into two simple categories, namely those used for training and those used for research. Ground vehicle driving simulators used for training are designed to impart some new skill to the driver. Examples could be for base vehicle operation, conversion between vehicle types, emergency services such as police pursuit, and post-injury rehabilitation. Ground vehicle driving simulators used for research may use the driver as part of an experiment or study. The experiment or study could be in vehicle design such for example as vehicle performance and aesthetics. The study could be a human factor study, for example studying the effects of drugs or ageing on drivers. The experiment could even be with regard to road planning, for example with regard to sign and signal design and placement, and road markings.
Generally, justification of manufacturing costs is quite different between training and research. For training, the balance of justification on cost effectiveness alone is very difficult, because today all training is performed successfully in real vehicles, and the cost of a simulator of sufficient fidelity would normally far exceed the cost of the vehicle it simulates. An exception is where the end user is not the general public but rather a specialist user such for example as police, fire or other emergency services, military vehicle users, and users of specialist equipment such as cranes and earth movers. In such cases, the vehicle can be expensive, training may be unacceptable in the real vehicle, and simulation is normally valued for the reason that the simulation can take place in varying environmental conditions such for example as in varying weather conditions and in dangerous situations.
Known display apparatus for ground vehicle driving simulators endeavours to provide a visual display which is known as an out-of-the-window display. There is always a quest for as large a field of view as possible, with as high a resolution as possible for the lowest possible manufacturing cost. With regard to resolution, there seems to be a wide range of opinion as to what is acceptable. One important factor is the visibility of a simulated sign, which with a display resolution of 6 arc-min/olp, would not be legible until it is much closer than the real sign would be. However to specify, for example 3 arc-min/olp everywhere would be cost prohibitive. One pragmatic solution taken has been to artificially magnify the size of signs, such that the signs are legible at the appropriate distances. This tends to give the sign an unnatural appearance. Progressively reducing the sign size to the correct value as it comes into range may help, but this can present a dynamic artifact that detracts from realism. Target projectors as used in some flight simulators could be used to display signs by overlaying or cutting into the main scene. However, the cost of such a solution is likely to be prohibitive and, unless the dynamic correlation is perfect, the signs would give the sensation of floating in the simulated world. Currently known out-of-the-window display solutions have been such that manufacturers of training simulators have built what they could afford, rather than what they would like to build. In doing so, important trade-offs have been related to the ability to complete the training objectives with the display selected. Car and truck simulators have been built with a wide range of different types of out-of-the-window display apparatus. For training usage, they have been mainly confined to four basic types, namely direct-view monitors, front-projected real-image, rear-projected real-image, and rear-projected tilted mirror collimators. Head mounted displays have recently also been used, although mainly in research application environments. These different types of display apparatus will now be considered.
Direct View Monitors
Direct-view monitors are such that graphic monitors are fitted directly on to the simulator cab, around the driver. Whilst this provides the most cost effective and compact type of display apparatus, the extremely short accommodation (or viewing) distance and large gaps between viewable channels do not really result in a high fidelity display. Such direct-view monitors have value where these aspects do not impact on the training requirement, and the relative restrictive cab environment fidelity can be tolerated. This is however not usually the case. Cab fidelity is usually required together with acceptable accommodation, and as continuous a visual field as possible.
Front-projected Real-Image Display Apparatus
Front-projected real-image display apparatus may provide a wrap around display by placing a curved screen around the simulator cab, and front projecting on to the curved screen using cathode ray tube projectors. The cathode ray tube projectors form their images from what is essentially a continuous scanning process, which gives the technology the distinguishing characteristic of “infinite addressability”. What this amounts to in practice is that, through the introduction of terms in the electronic scanning sub-system of the projector, the projected image formed can be distorted in a continuous fashion. This ability is particularly useful when projecting on to curved screen surfaces and it has been a key factor in cathode ray tube projection remaining dominant in simulation display apparatus for more than twenty years. In such systems, the projectors must be placed within the screen volume, effectively sharing space with the rest of the simulator. Experience has found that this can be particularly difficult where the cab to be simulated is large and/or where there is a small room size. Various solutions can be made to work and so the benefits of front-projected cathode ray tube systems can be given as continuous image presentation, mature projection technology giving low risk and off-the-shelf availability, high performance digital electronic blending, and good dynamic image presentation. However, drawbacks include the fact that designs tend to be cab-specific and thus require a one-time design for each new simulator. Often the required field-of-view must be compromised, and the cab may require modification to eliminate shadowing.
Front-Projected Liquid Crystal Display Systems
General comparisons between liquid crystal display and cathode ray tube technologies have previously been made in the field of display apparatus for flight simulation. Liquid crystal display technologies are regarded as being particularly attractive, primarily due to the promise of reduced system maintenance, versatile lens options, and small physical size and weight for a given light output. Until recently, liquid crystal display front-projected display apparatus was not deemed to be acceptable to realise simulation displays of adequate performance. Recently however, improved performance of the projectors, along with new technologies of digital distortion correction and optical blending, have come together to offer a new capability option. This has only previously been recognized for flight simulation application, but it does apply equally to ground vehicle application.
Generally, the cathode ray tube front-projected layout can be replicated using liquid crystal display projectors.
Adams Russell
Cruz Magda
Iandiorio & Teska
SEOS Limited
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