An off-axis parabolic mirror converts plane waves into spherical ones and vice versa with high accuracy. This aspherical mirror is indispensable for spectrometers and astronomical optical instruments which require high resolution.
When a spherical mirror is used under off-axis conditions, spherical and coma aberrations occur, which cause the degradation of resolution of a spectrometer. Off-axis parabolic mirrors theoretically eliminates these aberrations and ensures high resolution even in a short focal length compact spectrometer.
The off-axis parabolic surface used in Shimadzu off-axis parabolic mirrors is, when expressed mathematically, a part of a rotary symmetric parabolic surface represented by Y = X2/4F (where, F: focal length, Y is the rotary symmetric axis and X is the displacement on the axis.)
- Shimadzu off-axis parabolic mirrors are replicated by master mirrors that pass through rigorous inspections such as zone, Foucault, and interference tests.
- At the rear side of each mirror, a notch is grooved to indicate the mounting direction (points to the rotary symmetric axis).
- Non-Use of Specific Chemical Substances*1
Product List(Table of Code Number)
|Code Number*1||On-axis focal length f(mm)||Off-axis focal length f'(mm)||Off-axis angle
|Dimensions W×H(mm)||Effective area FA(mm)||Central thickness T(mm)|
|Classification||Replica parabolic mirror*1|
|Blank Material||Soda glass|
|Dimensional Tolerance(W,H)||0/-0.2 mm|
|Central Thickness Tolerance(T)||±0.2 mm|
|On-axis Focal Length Tolerance(f)||±0.5%|
|Surface Accuracy||Within λ /2*2|
|Effective area(FA)||Ref table|
|Scratches & Digs||80-50(as per MIL-O-13830A)|
|Thermal and Humidity Conditions for Storage||0°C to 50°C,50% RH max.(no conensation)
*When temperature is from 0°C to 40°C,humidity should be 80% RH max.
- Astronomical optical instruments
- Spectrum analyzers
- Beam Expander and Beam Collimator
Examples of application in spectrometers
- Off-axis parabolic mirrors with the following optional coating are available upon request
- Al + MgF2 (for vacuum ultraviolet)
- Au (for vacuum ultraviolet)
- Au (for infrared)
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