GB2299873A

GB2299873A - Steerable image display device

Info

Publication number: GB2299873A
Application number: GB9601326A
Authority: GB
Inventors: David Scanlan
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-01-23
Filing date: 1996-01-23
Publication date: 1996-10-16
Also published as: GB9601326D0

Abstract

In a display system in which images, created by an image generator 3, are directed towards a head mounted display systems through two adjustable reflectors 1 and 2, the adjustable reflectors pivot about a central base which, in the case of reflector 1, is rigidly connected to the head mounted display system and, in the case of reflector 2 is fixed at a set point. Each adjustable reflector is controlled in two dimensions by linear actuators so as to direct the image to the correct point on the head mounted display system. Errors in the image display may be measured by using light source to direct a beam of light onto head mounted reflective strip, which is then reflected back to two sensors. The difference in signal between the two sensors provides a control signal to the actuators.

Description

STEERABLE IMAGE DISPLAY DEVICE This invention relates to an image display device in which an image may be steered in a number of directions.

In the high quality visual simulation and virtual reality markets current head mounted display systems suffer from a variety of problems. The image is normally created in a device known as an image generator and then fed to the head mounted display system via a bundle of fibreoptic cables. The connection of the bundle to the head mounted display can restrict head movement and cause a deterioration in image quality. A means of steering the image directly from the image generator to the head mounted display system alleviates these problems.

According to the present invention there is a head mounted adjustable reflector to steer the image towards the head mounted display, and an adjustable off-head reflector to steer the image from the image generator towards the head mounted reflector.

A specific embodiment of the invention will now be described by way of example with reference to the accompanying drawing in which : Figure 1 shows a typical path of the image through the steering device to the head mounted display system; Figure 2 illustrates the mounting and actuation system for the reflectors so that they may be controlled to steer the image in the required direction; Figure 3 shows the means by which light, reflected from the head mounted display system, may be passed to the system for measuring positional errors in the displayed image in order to generate control signals for the actuators.

Referring to the drawing the steerable image display device comprises a head mounted reflector 1 and an off-head reflector 2. The image generator 3 points a beam of collimated light containing the image towards reflector 2. Reflector 2 is controlled by means of actuators 7 and 9 to steer the collimated light beam towards reflector 1. In like manner reflector 1 is controlled by 2 actuators to steer the collimated light beam towards head mounted reflector 4 (which does not require dynamic adjustment). Reflector 4 steers the light beam towards the display system 5 which presents the image to the eyes 6 as shown in Fig 1. This arrangement allows the image to be delivered to the eyes even when a wide range of head movement takes place.

Within given limits reflector 2 is required to maintain a central position with respect to the image. To achieve this a central support 8 is fixed at the base and connected to the centre of the reflector through a yoked bearing arrangement 10 as shown in Fig 2. This allows the reflector to move in two dimensions. The same arrangement applies to reflector 1 except that the base of the central support is rigidly connected to the head mounted display system. The actuators 7 and 9 are linear solenoids and are mounted at right angles to each other relative to the central support 8. The actuator bodies are connected to the base through a bearing arrangement 11 which allows the actuators to tilt towards the central support. The actuators are also attached to the reflectors through yoked bearing arrangements 10.In this way movement of the solenoids will allow control of each reflector to maintain the required path of the image.

Fig 3 shows an outline of the system necessary to measure errors in image position in one dimension. A reflective strip 12 is mounted radially from the periphery of the collimated light beam between reflector 1 and reflector 4. A narrow beam of light is produced from light source 13 mounted at the periphery of the beam from the image generator 3 and directed towards the reflective strip through reflectors 1 and 2. If the image is moved to the right (by a head movement to the left) then light sensor 14 will receive more light returned from the reflective strip than light sensor 15. The signals from these sensors are fed to a differential amplifier 16 so that the output is a signed value related to positional error in one dimension.

Four light source/sensor units and head mounted reflective strips mounted at ninety degree positions around the periphery of the collimated light beam provide sufficient system integrity to measure image errors in two dimensions. Error signals in one dimension are amplified to provide a control signal to one actuator controlling reflector 1 and another actuator controlling reflector 2. Error signals in the other dimension are amplified to provide control signals for the other two actuators.

Claims

1 An image steering system, using two steerable reflectors, to present images from an image generator to a head mounted visual display system.

2 An image steering system as claimed in Claim 1, wherein errors in image position on the head mounted display system may be measured, in two dimensions, by reflecting back light signals from the head mounted display to light sensors at the image generator.

3 An image steering system as claimed in Claim 1 or Claim 2, wherein a signal related to a one dimensional error in image position may be used to control actuators, connected to steerable reflectors, so as to minimise the error in that dimension.

4 An image steering system substantially as described herein with reference to Figures 1-3 of the accompanying drawing.

4 An image steering system as claimed in Claim 3, wherein multiple signals related to error in image position may be used to control actuators, connected to steerable reflectors, so as to minimise errors in two dimensions.

5 An image steering system as claimed in Claim 1 or Claim 3, wherein a steerable reflector is attached to a central base through a bearing system which allows the reflector to pivot in two dimensions about its centre.

6 An image steering system as claimed in Claim 4 or Claim 5, wherein two linear actuators are attached to a steerable reflector to control movement of the reflector in two dimensions about a central point.

7 An image steering system as claimed in Claim 5 or Claim 6, wherein the supporting central base of one steerable connector is maintained at a fixed position and the supporting central base of the other steerable connector is rigidly attached to the head mounted display system at any suitable location.

8 An image steering system substantially as described herein with reference to Figures 1-3 of the accompanying drawing.

Amendments to the claims have been filed as follows 1 An image steering system, using two dynamically adjustable reflectors, to present images from an image generator towards a continuously moving target. The target is a display screen which moves in 3 dimensions in accordance with normal movements of a simulation system such as a motion platform or a head mounted display system.

2 An image steering system as claimed in Claim 1, wherein two dynamically adjustable reflectors are centrally mounted on bearing systems which allow the reflectors to pivot in 2 dimensions about each centre. Two linear actuators are attached to each reflector in order to control movement of the reflectors in 2 dimensions about each central point. The supporting central base of one reflector is maintained at a fixed position relative to the image generator and the supporting central base of the other reflector is rigidly attached to a fixed position relative to the display screen.

3 An image steering system as claimed in C!aims 1 and 2 wherein the errors in image position are measured in only 2 dimensions even though the display screen is moving in 3 dimensions. The 2 dimensional errors are used to control the linear actuators so as to minimise the positional error of the image on the display screen even when rapid movements of the display screen take place.