Chapter 6: Maintenance and Adjustments
SPD-M20A Service Manual
41
6.3 Optical Axis Adjustment
6.3.1 Process when Performing Wavelength Calibration
The SPD-M20A has 1.2 nm/8 nm wide slits to adjust the optical path. When wavelength calibration is
performed, the reference point of PDA element is determined using the 656 nm light using the 1.2 nm
slit and span adjustment (wavelength assignment for each PDA element) is performed using the
360 nm light. Then, the position of the reference point of the 1.2 nm/8 nm slits is finely adjusted using
the 656 nm light with using the 8 nm slit. The wavelength calibration data is created as described
below.
(1) Using the 1.2 nm slit, 656 nm light from the D2 lamp is stored as the wavelength standard
position when the 1.2 nm slit is used.
(2) The 360 nm light is checked at the Ho filter using the 1.2 nm slit and span adjustment is
performed for the wavelength standard position. (656 nm and 360 nm are designed to be 330
elements away from each other.)
(3) Using the 8 nm slit, the 656 nm light from the D2 lamp is stored as the wavelength standard
position when the 8 nm slit is used. The difference from the 1.2 nm slit standard position
recorded in step (1) is checked. Span adjustment value is adjusted using the data created in step
(2). When the 8 nm slit is used, span adjustment value is adjusted by horizontally shifting the
data by the difference from the standard position.
Process of wavelength calibration
656 nm (D2 lamp) when
the 8 nm slit is used
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