Interactive input systems that allow users to inject input (e.g., digital ink, mouse events, etc.) into an application program using an active pointer (e.g., a pointer that emits light, sound or other signal), a passive pointer (e.g., a finger, cylinder or other object) or other suitable input device such as for example, a mouse or trackball, are well known. These interactive input systems include but are not limited to: touch systems comprising touch panels employing analog resistive or machine vision technology to register pointer input such as those disclosed in U.S. Pat. Nos. 5,448,263; 6,141,000; 6,337,681; 6,747,636; 6,803,906; 7,232,986; 7,236,162; and 7,274,356 and 7,532,206, all assigned to SMART Technologies ULC of Calgary, Alberta, Canada, assignee of the subject application, the entire contents of which are incorporated herein by reference; touch systems comprising touch panels employing electromagnetic, capacitive, acoustic or other technologies to register pointer input; tablet and laptop personal computers (PCs); personal digital assistants (PDAs) and other handheld devices; and other similar devices.
In some interactive input systems, conventional projection units are employed to project a computer-generated image onto a display or interactive surface. For example, U.S. Pat. No. 6,540,366 to Keenan, et al., assigned to SMART Technologies ULC, discloses an overhead projection system comprising an overhead projector support assembly extending generally horizontally from a generally vertical support surface. A touch-sensitive display screen having a display surface is mounted on the support surface beneath the projector support assembly. A projector is mounted on the projector support assembly adjacent its distal end and is aimed to project images onto the display surface of the touch-sensitive display screen. The touch-sensitive display screen outputs control signals in response to contacts made thereon. The control signals are then conveyed to a personal computer, which uses the control signals to update the application program being executed and to update the image projected onto the touch-sensitive display surface by the projector, if appropriate.
Unfortunately, interactive input systems that employ conventional projection units to project images onto display or interactive surfaces suffer from a number of problems including for example long startup time, limited bulb life and high power drain when the bulb is on. These projection units also provide little if any feedback to users concerning their state of operation (e.g., on standby, shutting down or warming up).
In order to improve the performance of projection units, various techniques have been considered. For example, U.S. Pat. No. 6,109,752 to Itoh, et al. discloses a lighting device that has two lamp units suitable for use in a projector-type display apparatus to realize bright illumination. The two lamp units and their integrator optical system enable an illumination area to be illuminated uniformly and evenly. The lamp units are arranged in parallel and in a direction perpendicular to a longitudinal direction of the illumination area.
U.S. Pat. No. 7,244,032 to Inamoto discloses a liquid crystal projector for full-color image projection. The projector includes three liquid crystal display (LCD) panels, each associated with a respective primary color. An ultra high pressure mercury lamp illuminates the LCD panels through three illuminating light paths associated with the primary colors. An auxiliary or laser illuminating device is also included. Light from the laser illuminating device is reflected by a mirror and introduced into the red color light path to compensate for shortage in light intensity in red color.
U.S. Pat. No. 6,467,911 to Ueyama, et al. discloses a projector having a liquid crystal display panel for displaying an image, a lamp for illuminating the liquid crystal display panel and a projection optical system for projecting light. The lamp is held by a member whose position is variable to allow fitting of different types of lamps and to allow the lamp to be moved to an optimum light-emission center position. The supply voltage of the lamp can be varied and controlled based on the input data related to the light-emission amount at different stages of the life of the lamp. An auxiliary lamp is provided so that the lamp that is lit can be switched to the auxiliary lamp as required.
U.S. Patent Application Publication No. 2009/0154153 to Lin discloses a light emitting diode (LED) projector lamp including a lamp holder, an LED light source, a light-mixing lens and a cover lens along an optical axis. The LED light source has LED chips arranged inside the lamp holder around the optical axis for emitting different wavelengths of light. The light-mixing lens has a structural surface with parallel lines of protrusions facing the cover lens such that emitted light rays of the LED chips that pass through the structural surface are scattered and then pass through the cover lens. As a result, the emitted different wavelengths of light from the LED light source are well mixed before going through the cover lens to the outside of the LED projector lamp, improving light uniformity and brightness in the projection zone.
While projection units have been designed to improve performance, further improvements are desired. It is therefore an object of the present invention at least to provide a novel projection unit and method for controlling the same.