InFocus sues 3M over US Patent No. 6,424,097

InFocus Corporation announced on August 31, 2004 that it filed a patent infringement lawsuit against 3M Company on August 27, 2004 in the United States District Court in Oregon. The infringment lawsuit alleges that certain 3M products fall within the scope of claims of US Patent No. 6,424,097, directed to a safety interlock device on front projector technology.


InFocus is seeking an injunction to prevent 3M from continuing to use InFocus patented technology, as well as seeking to obtain monetary damages resulting from patent infringement by products 3M has sold and continues to sell to its customers.

The first claim of the '097 patent reads as follows:

1. A safety interlock apparatus for an electrical device that includes a power supply and an electrical load, comprising:

a frame;

a DC power supply, a ballast power supply including a ballast control circuit and a ballast power circuit, and a lamp module configured for insertion into or removal from the frame, the ballast control circuit producing control signals for delivery to the ballast power circuit to control its operation and the lamp module configured for installation of a lamp;

a first electrical connection between the DC power supply and the ballast power supply, the first electrical connection including a relatively low voltage electrical connection supplying a relatively low voltage for control of the ballast power supply;

a second electrical connection between the lamp and the ballast power supply;

a switch positioned in operative association with the ballast power supply to provide an interruptible low voltage electrical connection that controls production of the control signals or their delivery to the ballast power circuit, the switch including a switch lever and having a first state in which the relatively low voltage electrical connection enables production and delivery of the control signals to and thereby enables power output from the ballast power circuit, and a second state in which the relatively low voltage electrical connection does not enable production and delivery of the control signals to and thereby disables power output from the ballast power circuit; and

a panel fixable to the frame and positioned to provide access to and sufficient clearance for the lamp module to facilitate its removal from the frame for lamp access, the panel having an actuator that is operable to actuate the switch from the first state to the second state when the panel is moved to open the frame, thereby disabling power output from the ballast power circuit to the lamp, and to contact the switch lever to actuate the switch from the second state to the first state when the panel is fixed to the frame.

To date, the '097 patent has been cited by no other U.S. patent.

InFocus has a number of other patents related to imaging. An ultimate application is to digital electronic cinema. Of current interest are multimedia systems driven by a personal computer.

For example, US 6,767,100 reads:

Projection systems have been used for many years to project motion pictures and still photographs onto screens for viewing. More recently, presentations using multimedia projection systems have become popular for conducting sales demonstrations, business meetings, and classroom instruction.

In a common operating mode, multimedia projection systems receive analog video signals from a personal computer ("PC"). The video signals may represent still, partial-, or full-motion display images of a type rendered by the PC. The analog video signals are typically converted in the projection system into digital video signals, and the signals are electronically conditioned and processed to control an image-forming device, such as a liquid crystal display ("LCD") or a digital micromirror display device ("MDD").

A popular type of multimedia projection system employs a broad spectrum light source and optical path components upstream and downstream of the image-forming device to project the image onto a display screen. An example of a MDD-based multimedia projector is the model LP420 manufactured by in Focus Systems, Inc., of Wilsonville, Oreg., the assignee of this application.

Significant effort has been invested into developing projectors producing bright, high-quality, color images that are also compact so that they can be portable. However, it is desirable to further decrease the size and weight of such projectors. Furthermore, conventional projectors, which use high pressure mercury arc lamps, have lamp lifetimes of roughly 2000 hours. It is desirable to use a light source with lifetime in excess of 10,000 hours so that the user need not worry about failure of the projector or the cost and effort of lamp replacement.

An alternative optical architecture is, therefore, desired that substantially decreases the size and weight of the projection system as compared with conventional projection systems and significantly enhances light source lifetime.



Also, US 6,719,429 mentions:

Brightness-reducing overfill of light valves, such as MDDs is a common problem that prior workers have toiled to solve. For example, U.S. Pat. No. 5,159,485 for SYSTEM AND METHOD FOR UNIFORMITY OF ILLUMINATION FOR TUNGSTEN LIGHT describes employing a tungsten lamp and an anamorphic optical system to illuminate an elongated, linear MDD array used for line-scanning a photo-sensitive drum in a printer. (Conventional anamorphic optical systems employ a lens or lenses having different focal lengths or magnification factors in perpendicular planes to the optical axis.) The anamorphic optical system receives a substantially rectangular light bundle from the tungsten lamp and squashes the light bundle in one axis so that the resulting squashed light bundle illuminates the elongated, linear MDD without substantial overfill. Unfortunately, employing a tungsten lamp without an integrator tunnel results in insufficient illumination uniformity and brightness for use in a multimedia projector.