Daily Image
26-09-2007
Alignment verification of MIRI's Spectrometer Main Optics
| Submitter: | Ad Oudenhuysen |
| Description: | The photo shows the red laser spots as imaged onto a screen by the MIRI Spectrometer Main Optics (SMO) of JWST. The screen is mounted at the position where the detector’s sensitive layer of the chip array will eventually be located. The scaling on the screen represents the target for the detector area. Although MIRI will work in IR light, the alignment is simulated in visible light, avoiding the necessity of the real detector. Also the measurement methods are much more feasible. The SMO box has two slit entrance locations for two wavelength bands. For verifying the alignment each channel is equipped with three laser input beams. Both slits (defined by two sets of three red spots) are imaged side by side onto one detector. To achieve this, the channels use 9 mirrors, including two mirrors mimicking the gratings. The magnification (M=1/5) of the optics fits the input slit (length 64 mm) nicely on each half of the detector (=12.8 mm). The grating substitution mirrors may project the spots in three spectral positions (top, middle and bottom of the screen). The photo shows the spots in the position that represents the spectrum at the shortest wavelength. To verify the alignment, in total 18 positions evenly distributed over the detector area are investigated. The total length of the optical path from slit to detector is 2030 mm. The calibrated grid positions on the screen and computer vision are used to determine the absolute position of the spots with a precision better than 40 microns. To pass the tests, the spots should be within an area of 225x125 microns around the nominal position. |
| Copyright: | Ad Oudenhuysen |
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