Multispectral imaging with frequency-modulated reticles

Frequency modulated (FM) reticles can be used to create imaging systems that operate simultaneously from the ultraviolet to the far-infrared regions of the optical spectrum. The reticle modulates different spatial locations at different temporal frequencies, and these locations are optically condensed onto a single detector. Modulation takes place prior to splitting into spectral bands, resulting in excellent pixel-to-pixel registration of the different spectral images. Sensitivity is better than the spinning filter wheel technique sometimes used to achieve good registration. Modulation also allows multiplexing many pixels onto fewer detectors by utilizing the bandwidth of the detectors more effectively. Thus, a single detector may perform as a linear array and a linear array may perform as a staring array.