POWER-SAVING HEAD-MOUNTED LIQUID CRYSTAL DISPLAY

Abstract: An HMD for use in a virtual reality application has an LCD whose backlighting is provided by a light source external to the HMD, such as sun light. The HMD has an opening to allow light from the external source to be incident on the back of the LCD. This configuration saves a considerable amount of power during operational us of the HMD.

Description: Power-saving head-mounted liquid crystal display. FIELD OF THE INVENTION The invention relates to an information processing system comprising an information processing apparatus and a head-mounted display (HMD) with an integrated liquid crystal display (LCD) coupled to the apparatus for displaying the information as images. The invention also relates to an HMD and to a method of operating the HMD. BACKGROUND ART HMD's are well known user-interface devices, that currently receive special attention within the field of virtual reality. The graphics for a virtual world is created through software processed on a powerful computer. An HMD lets the user feel immersed in the virtual world made accessible through the images displayed in the HMD. For more background information, see, e.g., the web site of Virtuality at www.virtuality.com. Typical examples of HMD's now commercially available use one or more LCDs mounted in a frame that the user wears over his or her head. The frame of the HMD can be designed to block light from external sources to increase the sense of immersion. Also, blocking light from external sources enhances the visibility of the LCD images. The LCD has its own backlighting system known in the art. OBJECT OF THE INVENTION A drawback of the known HMD's is their power consumption. Typically, 90% of the power is consumed by the LCD's backlighting, the other 10% supplies the control circuitry of the LCD's matrix. It is an object of the invention to reduce power consumption of an HMD. SUMMARY OF THE INVENTION To this end, the invention provides a system as specified in the preamble wherein the HMD is provided with means to create the LCD's backlighting using light from the environment, i.e., from a source external to the HMD. For example, the frame of the HMD has openings positioned relative to the LCD so that light from an external source (e.g., the sun or artificial lighting from units at the ceiling) is incident on the back of the LCD. Alternatively, a passive optical system is mounted on or in the frame to provide a guide for ambient light toward the back of the LCD using, e.g., plastic lenses or optic fibers. The advantage of the invention is a considerable saving of power. The battery required to drive the LCD's matrix and serving as the power supply for the information processing apparatus has a longer life span than those in conventional HMD's. As a consequence, the information processing system can be made mobile as a whole, since power cords to a power outlet in the wall are not required anymore, and the system is environmentally more friendly than comparable systems. BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in further detail by way of example and with reference to the accompanying drawings, wherein: Fig.1 is a diagram of a system according to the invention; Fig.2 is a diagram of a first embodiment of an HMD of the invention; and Fig.3 is a diagram of a second embodiment of the invention. PREFERRED EMBODIMENTS Fig.l is a diagram of an information processing system 100 according to the invention. System 100 comprises an information processing apparatus 102 and an HMD 104. Apparatus 102 and HMD 104 are coupled through a cable 106. HMD 104 comprises an LCD 108 for display of images created on the basis of data supplied by apparatus 102. LCD 108 is controlled in a conventional manner. Apparatus 102 may include, e.g., a television receiver, a DVD-player or a CD-ROM. Fig.2 is a diagram of a first embodiment 200 of an HMD of the invention. HMD 200 comprises a frame 202, and an LCD 204 positioned in frame 202. LCD 204 displays graphics images under control of apparatus 102. Frame 202 has an opening 206 to allow ambient light to be incident on the back of LCD 204 for providing the backlighting. Opening 206 may be covered by a transparent cover (not shown) for protection of LCD 204. HMD 200 may comprise, in addition to components 202-206, an internal light source 208 to provide the LCD's backlighting when the ambient light has too low a level. Source 208 may be manually operated by the user, or may be automatically controlled through a sensing device 210 mounted in or on frame 202. Fig.3 is a diagram of a second embodiment 300 of an HMD according to the invention. HMD 300 comprises a frame 302 and an LCD 304. HMD 300 further comprises a portion 306 forming an input of a light guidance system 308 that may comprise one of more mirrors, lenses, prisms, or optical fibers. Light incident on portion 306 is guided to the back of LCD 304 by guidance system 308. Preferably, portion 306 can be made moveable in order to enable adjustment for the direction of the incident light from the external source.

Claims: CLAIMS 1. An information processing system comprising: - an information processing apparatus for processing information: - a head-mounted display (HMD) coupled to the apparatus and operative to display the information as an image under control of the processing apparatus; wherein the HMD comprises: - an LCD for display of the image; and - means to create the LCD's backlighting using light from a source external to the HMD. 2. The system of claim 1, wherein the HMD comprises a frame with an opening positioned relative to the LCD for having light from the external source incident on the back of the LCD. 3. The system of claim 1, wherein the HMD comprises a passive optical guide mounted on the frame for providing a guide for the light from the external source toward the back of the LCD. 4. The system of claim 1, wherein the HMD comprises an internal light source and a switch for turning on the internal light source. 5. The system of claim 4, wherein the HMD comprises a sensor for sensing a level of light from the external source and for operating the switch depending on the level sensed. 6. The system of claim 1 , wherein the apparatus comprises at least one of the following: a TV-receiver; a DVD-player; a CD-ROM player. 7. An HMD comprising: - an LCD for display of an image; and - means to create a LCD's backlighting using light from a source external to the HMD. 8. The HMD of claim 7, comprising a frame with an opening positioned relative to the LCD for having light from the external source incident on the back of the LCD. 9. The HMD of claim 7, comprising a passive optical guide mounted on the frame for providing a guide for the light from the external source toward the back of the LCD. 10. The HMD of claim 7, comprising an internal light source and a switch for turning on the internal light source.. 11. The HMD of claim 10, comprising a sensor for sensing a level of light from the external source and for operating the switch depending on the level sensed.. 12. A method of creating an image in an HMD with an LCD coupled to an information processing apparatus, the method comprising enabling light from a source external to the HMD to be incident on the back of the LCD.

Inventors: SISKENS WALDEMAR, SISKENS, WALDEMAR
Applicants: KONINKL PHILIPS ELECTRONICS NV, PHILIPS NORDEN AB, KONINKLIJKE PHILIPS ELECTRONICS N.V.
Application year: 1998
Main classification: G02F1
IPC codes: G02B27, G02F1