Patent attributes
The invention employs a linear variable interference filter, which can be manually moved back and forth along its long axis in front of a slit parallel to its short axis. Thus, the filter pass-band varies linearly from 4,000 angstroms to 10,000 angstroms with a pass-band half-width no greater than 65 angstroms. Therefore, this combination of filter and slit can be placed in front of a charge coupled device (CCD) or other electro-optical imaging device and real time images can be taken as the filter is slid back and forth. Magnifying optics, beam-splitters and scale illuminators can be used to make the scale visible within the field of view of the camera imager. Or, as a simpler embodiment, the graduated image scale could in the form of a hologram of a graduated image scale taken at distance consistent with the desired depth of focus of the camera/imager.
