High-index planoconcave laser lenses
Description
Lenses in high-index glass (n = 1.785) have only 55% of the spherical aberration of equivalent BK7 lenses, and can be very efficiently AR coated with a single-layer coating. Beam expanders etc. can therefore be made with near diffraction-limited performance and very high transmittance and suitable for high powers, having no cemented interfaces.
These AR-coated negative lenses complement the positive lenses in the PX range, with which they may be combined to form Galilean beam-expanders (TE range). The high index reduces spherical aberration and allows use of an efficient and economical single-layer AR coating.
|
Diameter |
+0, -0.1mm |
|
Focal length |
±0.2mm (≤10mm) |
|
Figure (sphericity) |
λ/4 (typical) |
|
Scratch-dig |
|
|
Centeration |
0.05mm |
|
Material |
|
|
AR coating |
see curve below |
Spherical aberration calculation
To calculate the spherical aberration of a system and evaluate its effect proceed as follows.
1. Calculate element contributions
For each lens element work out the wavefront aberration A:
A = ky4/f3
where y is the semi-aperture, or maximum ray height at the element (from an on-axis object); f is the element focal length, and the coefficient k depends on material, shape and conjugates and is given in the relevant section of this catalogue.
2. Sum contributions
Simply add the contributions algebraically to give the total wavefront aberration ΣA (deviation from the best-fit sphere).
3. Evaluate effect
If ΣA is less than λ/4 the system is diffraction limited and aberration can usually be neglected. For larger aberration, the geometrical spot diameter D is given by:
D = 8 ΣAv/y
where y is as above, for the last element, and v is the distance from this element to the image.
For further detail request our Technical Note ‘Spherical aberration’.
| Item code | Focal length (mm) | Diameter (mm) | Back FL (mm) | Centre thickness (mm) | Edge thickness (mm) | Radius (mm) | Price per item (£ GBP) |
Stock available | Volume discount available |
Datasheets & customisation options |
Select amount |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 16 NX 10 | 16 | 10 | 16.8 | 1.5 | 2.5 | 12.6 | £37.87 | ||||
| 10 NX 06 | 10 | 6.3 | 10.8 | 1.5 | 2.2 | 7.85 | £40.05 | ||||
| 06 NX 04 | 6.3 | 4 | 6.9 | 1 | 1.4 | 4.95 | £40.05 | ||||
| 04 NX 025 | 4 | 2.5 | 4.4 | 0.75 | 1 | 3.14 | £49.43 | ||||
| 25 NX 16 | 25 | 16 | 25.8 | 1.5 | 3.2 | 19.6 | TBA | Send us a stock query | |||
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