Spectral optical system with chips

We present a spectral sensor device with a very compact planar technology arrangement. It uses a high precision dispersive pattern prepared on a glass chip. The chip is mounted at a small distance (typically about 100 µm) in front of a CCD or CMOS image sensor. The 2-dimensional monochrome diffraction image depends strongly on the wavelength and the superposition of diffraction images encodes a whole spectrum. It is read out for example by 13 x 13 pixels of the CCD. Instead of an entrance slit a pinhole is used in a similar short distance in front of the dispersive pattern (DOE). A parallelization of the spectral sensor – e.g. for implementing a snapshot spectral imager – is easily reached due to the planar technology. A compact optical set up without intermediate imaging stages is realized. Different technologies of the dispersive pattern are discussed. Results of a set-up with a spectral resolution better than 50 nm and a spectral region of the VIS up to the NIR are presented. The system is compared with compact spectral sensors. The principle in relation to apertures and other dimensions is discussed as well as limits and applications are given.