Best Form Lenses

These singlets are produced from 2 materials, i.e. fused silica or optical glass SF L57.
he optical design of these lenses is carried out in such a way that they are so called „best form lenses" for β' = 0 (M = 0, i.e. one infinite conjugate on the side of the stronger curvature and a focus in the focal plane on the side with less curvature). Such lenses have the best (least) spherical aberration which can be achieved with a (spherical) single element lens. Additionally our lenses are designed so that this correction is preserved over some amount of finite field.

Best form lenses produced from optical glass

The optical glass SF L57 (a dense flint glass produced by Schott) is particularly interesting for the visible and the infrared. It transmits very good up to about 2.7 µm. Furthermore it is virtually free of absorption bands as caused by OH-groups. With increasing absorption the transmission extends up to above 4.7 µm.
At short wavelengths transmission is limited at about 400 nm. It is only slightly yellow so that higher optical intensities can be applied above 500 nm.
Due to the high refractive index (1.83952 at 632.8 nm) these lenses have less spherical aberration than lenses from other glasses or even fused silica. With this high refractive index best form lenses are already convex-concave meniscus shaped (positive lenses; the negative ones are concave-convex). All lenses from SF L57 are designed so that they produce their nominal focal lengths at 632.8 nm.
The lenses are bevelled slightly and are delivered as standard items without AR coatings and without holders.

Positive focal length (SF L 57)

The center thicknesses are to be taken as guidance values only - the thicknesses may be varied up to about 1 mm from batch to batch.

Negative focal length (SF L 57)

Antireflection coatings

• The lenses can be AR coated for subranges of their transmission range or for single wavelengths. → on request
• A MgF₂ single layer on these lenses makes a good and comparatively broad banded AR coating: Rmin < 0.1% per surface at 633 nm and R < 1% between 550 nm and 800 nm. → on request

Available on special order

• Larger quantities → on request
• Other focal lengths → on request
• Other Diameters → on request
• Individual optical correction → on request
• Lenses made from other glasses or crystals → on request
• Have a look at our Holders for best form lenses

Best form lenses produced from fused silicia

The fused silica lenses are made from first grade synthetic fused silica to work in a wavelength range from about 180 nm to above 3.5 µm, however with OH-absorptions at about 1.4 (T=87%), 2.3 (T=76%), 2.8 (T=0%) und 3.8 µm (T=50%). The positive focal length lenses are asymmetric biconvex lenses (negative focal length lenses are asymmetric biconcave). The lenses from fused silica are designed to have their nominal focal lengths at 308 nm.
The lenses are bevelled slightly and are delivered as standard items without AR coatings and without holders.

Positive focal length (fused silicia)

The center thicknesses are to be taken as guidance values only - the thicknesses may be varied up to about 1 mm from batch to batch.

Negative Focal Length (fused silicia)

Antireflection coatings

• The lenses can be AR coated for subranges of their transmission range or for single wavelengths. → on request
• Please note that on fused silica MgF₂ single layers produce only a small AR effect due to the very low and similar refractive indices of fused silica and MgF₂: Rmin = 1,8% at 308 nm, per  surface.

Available on special order

• Larger quantities → on request
• Other focal lengths → on request
• Other Diameters → on request
• Individual optical corrections → on request
• Lenses made from other glasses or crystals → on request
• Have a look at our Holders for best form lenses