Sapphire and glass ball lenses
Description
Ball lenses have very low spherical aberration and so focus and collimate light very accurately; a sapphire ball has only 23% of the aberration of an equivalent BK7 planovex lens over the same aperture. They are available economically at very high precision and are simple to mount. Sapphire can be used from 200nm to 5.3μm and has exceptional hardness, strength and temperature resistance.
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Diameter |
±2.5μm (manufacturer's data) |
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Figure (sphericity) |
1λ (typical) (manufacturer's data) |
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Scratch-dig |
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Material data |
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 | Material | Focal length (mm) | Diameter (mm) | Back FL (mm) | Price per item (£ GBP) |
Stock available | Volume discount available |
Datasheets & customisation options |
Select amount |
|---|---|---|---|---|---|---|---|---|---|
| 07 VQ 10 | BK7 | 7.34 | 10 | 2.34 | £34.73 | ||||
| 003 VA 006 | Sapphire | 0.345 | 0.6 | 0.045 | £8.47 | ||||
| 006 VA 01 | Sapphire | 0.576 | 1 | 0.076 | £8.47 | ||||
| 009 VA 016 | Sapphire | 0.921 | 1.6 | 0.121 | £8.47 | ||||
| 014 VA 025 | Sapphire | 1.44 | 2.5 | 0.19 | £11.62 | ||||
| 023 VA 04 | Sapphire | 2.3 | 4 | 0.3 | £12.34 | ||||
| 035 VA 06 | Sapphire | 3.45 | 6 | 0.45 | £15.49 | ||||
| 06 VA 10 | Sapphire | 5.76 | 10 | 0.76 | TBA | Send us a stock query | |||
| 007 VQ 01 | BK7 | 0.734 | 1 | 0.234 | £12.34 | ||||
| 011 VQ 015 | BK7 | 1.1 | 1.5 | 0.35 | £12.34 | ||||
| 018 VQ 025 | BK7 | 1.83 | 2.5 | 0.58 | TBA | Send us a stock query | |||
| 03 VQ 04 | BK7 | 2.93 | 4 | 0.93 | TBA | Send us a stock query | |||
| 04 VQ 06 | BK7 | 4.4 | 6 | 1.4 | TBA | Send us a stock query | |||
For more information regarding stock availability icons, please see our shipping page.
