NOVELTY - A spectrally tunable detector comprises: (a) a tunable bandpass filter having a first at least partially reflective plate and a second at least partially reflective plate separated by a separation gap; and (b) a detector adjacent the tunable bandpass filter to receive wavelengths that are passed by the tunable bandpass filter and to provide an output signal in response to it.    USE - Optical filters useful in monitoring the spectral emission from power plants and engines to provide a level of combustion monitoring and control. They may also be used in biological particle identification systems to provide spectral resolution of the fluorescence needed for high levels of discrimination of biological materials.    ADVANTAGE - The tunable detector is wavelength tunable. It is sensitive to the entire spectral range of wavelengths that can be selected by the tunable bypass filter.    DETAILED DESCRIPTION - A spectrally tunable detector comprises:    (a) a tunable bandpass filter (12) having a first at least partially reflective plate (24) and a second at least partially reflective plate (26) separated by a separation gap (32); and    (b) a detector (14) positioned adjacent the tunable bandpass filter to receive wavelengths that are passed by the tunable bandpass filter and to provide an output signal in response to it.    The tunable bandpass filter is selectively tuned to a bandpass wavelength by moving the first plate and/or the second plate relative to one another to change the separation gap.    INDEPENDENT CLAIMS are also included for:    (a) a method for making a tunable bandpass filter, comprising providing a first substrate; providing a support layer adjacent the first substrate (18); providing an upper mirror adjacent the support layer; patterning the upper mirror; providing an upper electrode layer to provide upper electrode(s) (38); providing a second substrate (20); providing a lower mirror adjacent the second substrate; providing a lower electrode layer adjacent the second substrate; patterning the lower electrode layer to provide lower electrode(s) (40) that are in substantial registration with the upper electrode(s); providing posts that extend in an upward direction relative to the second substrate; providing a sacrificial layer over the upper mirror and the upper electrode(s), and/or over the lower mirror and the lower electrode(s); positioning the first substrate and the second substrate together so that the upper mirror and the upper electrode(s) are facing and are in a substantial registration with the lower mirror and the lower electrode(s), respectively, with the sacrificial layer in between; applying heat and pressure, and then cooling; removing the first substrate; patterning the support layer to expose at least part of the upper mirror while maintaining a mechanical connection between the upper mirror and the support layer; and removing the sacrificial layer; and    (b) an electrostatically actuated structure, comprising a substrate; lower electrode(s) secured relative to the substrate; upper electrodes suspended above the lower electrode(s); and upper electrode(s) positioned on a support layer having elongated legs that extend in at least two lateral directions away from the upper electrode(s), where each leg is secured to a supporting post that extends upward from the substrate.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-section of a tunable bandpass detector.    Tunable bandpass filter (12)    Detector (14)    First substrate (18)    Second substrate (20)    First at least partially reflective plate (24)    Second at least partially reflective plate (26)    Separation gap (32)    Upper electrode (38)    Lower electrode (40)