Polychromators
Polychromator is a darkness field correlation spectrometer system, electronically programmable and based on an optical micro system made of a programmable grating. This device was implemented as part of the collaboration between Honeywell, the MIT and Sandia National Lab. Instead of being a means of displaying images, the polychromator is a new sensor system able to distinguish between many gaseous species from a distance by using a combination of optical systems and MOEMS[1]. This device also allows a sufficient sensitiveness and selectivity to detect very weak quantities of gas for imagery applications for biology and security.
Polychromators don't need reference cells unlike numerous conventional techniques of gas analysis. For this, the reference spectrum for each measure is get thanks to the modulation of the polychromator grating. The latest devices consist in thousands of mechanical beam components on a silicon plate. Beams and actuators are made according standard techniques of thin films development. Each grating component is 10µm wide and 1cm long and is developed to move vertically upwards or downwards as in the picture below:
The light coming from the environment (for instance the light from a suspect gaseous cloud) is led to the sensor after being collected by an optical relay like a telescope or a binocular scope. Then the grating is planned to bring together the incident spectrum to a reference spectrum. That's the way we know if the gaseous cloud contains the substance that the grating needs to go work. Of course, the main feature of the device is its capacity to be reset. So the polychromator replaces a whole row of gas cylinders containing reference chemical products which should have been used to implement a correlation spectrometry technique.