Computer graphics processing and selective visual display system – Display peripheral interface input device
Reexamination Certificate
1997-04-24
2001-12-18
Hjerpe, Richard (Department: 2674)
Computer graphics processing and selective visual display system
Display peripheral interface input device
C345S158000
Reexamination Certificate
active
06331848
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a projection display system comprising a projector for projecting a computer generated display on to a screen.
Slide and overhead projections have for many years been an effective technique for making information available to a wide audience, for example in a conference. The availability of high quality video projectors allows for direct visualisation of computer display contents such as text, graphics, images etc. instead of the production of photographic slides or overhead transparencies. This technique can also handle multimedia information more conveniently than traditional approaches and consequently it is likely to play an increasingly important role in future presentations at conferences and the like.
During the presentation of a paper at a conference two major types of interaction have been identified. The first may be called a referring interaction such as pointing at projected objects and the second a managing interaction, that is accessing new images or going back to previously shown images. Traditionally referring to objects on a screen is done with a pointer, the pointer may either be a stick or more elegantly a laser pointer. The latter allows the speaker to point at the image projected from almost any place in the room and gives maximum flexibility for the task of referencing. For the managing interaction a turntable on a slide projector may be controlled or with overhead transparencies the presenter has to manually remove and replace the transparencies on the projector.
When working with a projection display system which projects computer generated images directly the same types of interaction are required. The first can again be achieved with a stick or laser pointer while the second requires access to the computer. Clearly the presenter could turn away to a small computer monitor and use its mouse during a presentation. This, however, gives reduced flexibility for the presenter as he has to look away from the projected image and go to a particular location to use the computer, thus taking his attention away from the audience and interrupting the presentation.
SUMMARY OF THE INVENTION
It is an object of the invention to enable the provision of a projection display system in which the presenter can with greater flexibility perform both the referring function and the managing function.
The invention provides a projection display system comprising a projector for projecting a computer generated display on to a screen, a pointer producing a narrow beam of radiation of higher intensity than the projected image, a video camera located in a fixed position relative to the projector and arranged to view the screen, and means for analysing the video signal produced by the camera to determine the point on the screen illuminated by the pointer.
By these means the computer is provided with information which enables it to determine where the pointer is pointed at on the screen. Since the computer can detect that the pointer is pointed at a particular object on the screen both the presentational interaction and the managing interaction may be achieved without the presenter having to turn away from the audience. In this specification higher intensity means the intensity as perceived by the video camera after any filtering of the image, if provided, and not as seen by an observer.
The pointer may be a laser pointer, which is a convenient source of high intensity radiation having a narrow beam width so that a small area of the screeen may be indicated.
The managing interaction, that is the control of the images to be displayed, may be achieved in a number of different ways. It may be arranged, for example, that the computer is arranged to produced soft buttons on the screen and by pointing the laser beam at the position of the button on the screen and maintaining it there for a given period of time may cause the button to be operated. The computer then performs the appropriate operation in response to the simulated button pressing. Such operations may be for example to cause a preceding or succeeding image to be displayed or to enlarge a particular portion of the image currently being displayed. Further operations which may be carried out are for example to bring up a menu on the screen and to select items from that menu.
The computer may be arranged to display a cursor at the determined point on the screen.
By this means the computer provides a feedback signal to the presenter which reassures the presenter that the pointer is pointed at the desired point on the screen. This also allows the use of a laser or other radiation source which produces radiation in the non-visible region of the spectrum, for example in the infra red region, where the presenter cannot actually see the position on the screen that the radiation beam is striking but when the cursor appears then the presenter knows where the laser beam is positioned.
The pointer may have one or more button(s), one button may be used to switch the radiation beam on and off while further buttons may be provided to enable similar facilities to that of a conventional computer mouse.
A wireless link may be provided between the pointer and the computer. This link, which may be an infra red link, enables the function of the “mouse buttons” to be transmitted to the computer. Of course a wired link may be provided between the pointer and the computer, but a wireless link allows the presenter greater freedom by not requiring a physical connection between the pointer and the computer. Thus the presenter may move around more freely in the lecture theatre when presenting the lecture. The wireless link may take many forms. An infra link is convenient as infra red transmitters and receivers are readily available as used in conventional television remote control devices. Examples of alternatives are radio or ultrasonics which may have advantages in given situations, for example in terms of radiation pattern emitted or absorption of the signals by intervening objects.
The projection display system may include geometrical distortion correction means to correct distortion caused by the projector screen and video camera. There will be some distortion caused by the optics of the projector which means that the projected image will not be precisely the same as that which would have appeared on a computer monitor screen. In addition if the projection screen is not perfectly aligned there will be further distortion and the video camera will normally be viewing the screen from a different position from that of the projector. While the video camera and projector may be built into one unit so that the physical locations are fixed this does not overcome the problem of possible screen misalignment. Consequently, unless such geometrical distortion correction means is included, the setting up of the projection display system has to be very precise in order that the position of the laser spot on the screen corresponds with that the computer has generated. If such correspondence is not maintained then clearly, depending on the degree of misalignment the operation of the projection system may be completely erroneous. For example the operation of a soft button may, when there are several soft buttons in relatively close proximity, entail the detection by the computer of a different button from that which the presenter thinks the laser beam is pointing at.
The geometrical correction means may comprise means for generating a calibration pattern and feeding it to the projector, means for comparing the pattern produced by the video camera with the generated calibration pattern, means for generating a correction to bring the pattern produced by the video camera into conformity with the generated pattern, and means for applying the correction to subsequently displayed images.
The generated pattern may be for example a cross hatch pattern, that is a series of equally spaced vertical and horizontal lines. This is a pattern which is easy to generate and to compare. Clearly any other convenient calibration pattern could
Carlsen Ingwer
Grewer Ruediger
Moennich Karl-Juergan
Schmidt Joachim
Stove Andrew G.
Hjerpe Richard
Nguyen Francis
U.S. Philips Corporation
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