Curved band-pass filter

#Illumination systems and other devices may utilize a lamp as a source of light. In some applications, the light is filtered to attenuate undesirable wavelengths of light such as infrared light and ultraviolet light. The filtering of such light may be inefficient or may lessen the intensity or brightness of the desired wavelengths of light emitted by the lamp.

#FIG. 1 is a schematic illustration of one example of a projection system including one example of a lamp according to one example embodiment.

#FIG. 2 is a front elevational view of the lamp of FIG. 1 taken a long line 2-2 according to an example embodiment.

#FIG. 3 is a fragmentary sectional view of the lamp of FIG. 2 taken along line 3-3 according to an example embodiment.

#FIG. 1 schematically illustrates one example embodiment of a projection system 10. As will be described hereafter, projection system 10 employs a lamp that effectively filters undesirable wavelengths of light using a curved filter. Projection system 10 generally includes screen 12 and projector 14. Screen 12 constitutes a structure configured to reflect light projected upon it by projector 14. In one embodiment, screen 12 may be passive in that screen 12 has a predetermined reflectivity. In other embodiments, screen 12 may be active having one or more portions that may have selectively adjustable reflectivities.

#Projector 14 constitutes a device configured to project light upon screen 12. Projector 14 generally includes arc lamp 20, condenser 22, optical modulator 24 and projection lens 26. Arc lamp 20 serves as a light source for projection system 10. Lamp 20 provides visible light for system 10 in an efficient manner while efficiently filtering and absorbing other selected wavelengths of light such as infrared light and ultraviolet light. Lamp 20 generally includes burner 30, reflector 32 and filter 34. Burner 30 comprises that portion of lamp 20 configured to generate light including visible light. Burner 30 generally includes a pair of electrodes 38, 40 separated by an arc gap 42 and a rare gas under pressure at least within the arc gap 42. Application of appropriate voltages to electrodes 40 and 42 creates an electrical arc across arc gap 42 and through the gas, resulting in the generation of light.

#According to one embodiment, burner 30 comprises a short arc lamp. In one embodiment, arc gap 42 is filled with pressurized xenon gas. This pressurized gas is sealed by filter 34 within reflector 32. In other embodiments, burner 30 may have other configurations. For example, in lieu of xenon gas, burner 30 may alternatively include a Mercury gas. In yet other embodiments, burner 30 may comprise a metal-halide burner.