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Mounted N-BK7 Bi-Concave Lenses, Uncoated


LD1464-ML

(Ø1")

LD1357-ML

(Ø1/2")

  • Negative Focal Length
  • Zemax Files Available
  • Ø1/2" or  Ø1" Optics in SM-Threaded Mounts

These Lenses are Also Available in the LSB04 Kit

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N-BK7 Bi-Concave Lenses
Lens Shape Bi-Concave
Material N-BK7a
Wavelength Rangeb 350 nm - 2.0 μm
Design Wavelength 633 nm
Index of Refraction
(at Design Wavelength)
1.515
Surface Quality 40-20 Scratch-Dig
Spherical Surf ace Powerc
(Concave Side)
3λ/2
Surface Irregularity
(Peak to Valley)
λ/4
Diameter Tolerance +0.0/-0.1 mm
Thickness Tolerance ±0.1 mm
Centration ≤3 arcmin
Clear Aperture Ø1/2" Lenses: >Ø11.0 mm
Ø1" Lenses: >Ø22.86 mm
Focal Length Tolerance ±1%
  • Click Link for Detailed Specifications on the Substrate
  • Custom Coatings are also available. Please contact our technical support staff for a quote.
  • Much like surface flatness for flat optics, spherical surface power is a measure of the deviation between the surface of the curved optic and a calibrated reference gauge, typically for a 633 nm source, unless otherwise stated. This specification is also commonly referred to as surface fit.
  • Limited by the antireflection coating.
Zemax Files
Click on the red Document icon next to the item numbers below to access the Zemax file download. Our entire Zemax Catalog is also available.
Optic Cleaning Tutorial

Features

  • Material: N-BK7 
  • Uncoated N-BK7 Wavelength Range: 350 nm - 2.0 μm 
  • Focal Lengths from -50.0 mm to -100.0 mm Available
  • Mounted in SM-Compatible Lens Cells
  • Spherical Surface Irregularity: λ/4

Thorlabs offers Bi-Concave lenses fabricated from an N-BK7 substrate. N-BK7 is one of the most common types of optical glass used for high quality optical components. It is typically chosen whenever the additional benefits of UV fused silica (i.e., good transmission further into the UV and a lower coefficient of thermal expansion) are not necessary. Since the Abbe Number of N-SF11 (25.76) is lower than that for N-BK7 (64.17), lenses fabricated from N-SF11 will exhibit higher dispersion than those fabricated from N-BK7.

These Ø1/2" and Ø1" lenses are mounted in SM05- (0.535"-40) and SM1- (1.035"-40) compatible mounts, respectively, for compatibility with our line of SM-threaded lens tubes

Although uncoated lenses are highlighted on this page, these N-BK7 bi-concave lenses are also available with one of three antireflective coatings (-A, -B, or -C), which reduce the amount of light reflected from each surface of the lens over the specified wavelength range. Links to each of these pages can be found in the table below. Please see the Graphs tab for detailed coating curve information. These lenses are also available unmounted.

Bi-concave lenses have a negative focal length and are best used to diverge a converging beam. Similar to a plano-concave lens, a bi-concave lens can diverge a collimated beam to a virtual focus like in a Galilean-type beam expander.

Lens kits with bi-concave lenses made from N-BK7 are available.

N-BK7 and N-SF11 Bi-Concave Lens Selection Guide
Unmounted Lenses Mounted Lenses
Uncoated Uncoated
A Coating (350 - 700 nm) A Coating (350 - 700 nm)
B Coating (650 - 1050 nm) B Coating (650 - 1050 nm)
C Coating (1050 - 1700 nm) C Coating (1050 - 1700 nm)
Optical Coatings Guide
Lens Tutorial
Quick Links to Other Spherical Singlets
Plano-Convex Bi-Convex Best Form Plano-Concave Bi-Concave Positive Meniscus Negative Meniscus
N-BK7 TransmittanceClick to Enlarge
Click Here for Raw Data
Above is the transmission curve for N-BK7, a RoHS-compliant form of BK7. Total Transmission is shown for a 10 mm thick, uncoated sample and includes surface reflections.

The lenses sold on this page are also available with broadband antireflective coatings, the reflectance traces of which are shown in the graph below.

These high-performance multilayer AR coatings have an average reflectance of less than 0.5% (per surface) across the specified wavelength ranges and provide good performance for angles of incidence (AOI) between 0° and 30° (0.5 NA). The plot shown below indicates the performance of the standard coatings in this family as a function of wavelength. Broadband coatings have a typical absorption of 0.25%, which is not shown in the reflectance plots.

Thorlabs' Standard Broadband Antireflection Coatings


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Ø1/2" Mounted N-BK7 Bi-Concave Lenses, Uncoated

Item #Optic DiameterFocal LengthaDiopterbRadius of CurvatureCenter
Thickness
Edge ThicknesscBack Focal Lengtha,d,eWorking Distance 1aWorking Distance 2aHousingReference
Drawing
LD1357-ML 1/2" -50.0 mm -20.0 -52.1 mm 3.5 mm 4.3 mm -51.4 mm -42.3 mm -44.4 mm SM05-Threaded
Mount
Bi-Concave Lens Drawing
  • The focal length tolerance is ±1%. The back focal length and working distance values here are referenced to the design focal length.
  • Reciprocal of the Focal Length in Meters
  • Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
  • Measured at the Design Wavelength, 633 nm
  • Specified for Unmounted Lens
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LD1357-ML Support Documentation
LD1357-MLCustomer Inspired! Ø1/2" N-BK7 Bi-Concave Lens, SM05-Mounted, f =-50 mm, Uncoated
$40.86
Today

Ø1" Mounted N-BK7 Bi-Concave Lenses, Uncoated

Item #Optic DiameterFocal LengthaDiopterbRadius of CurvatureCenter
Thickness
Edge ThicknesscBack Focal Lengtha,d,eWorking Distance 1aWorking Distance 2aHousingReference
Drawing
LD1464-ML 1" -50.0 mm -20.0 -52.0 mm 3.0 mm 6.1 mm -51.8 mm -40.9 mm -42.6 mm SM1-Threaded
Mount
Bi-Concave Lens Drawing
LD1170-ML 1" -75.0 mm -13.3 -77.9 mm 3.5 mm 5.6 mm -77.1 mm -66.2 mm -67.7 mm
LD1613-ML 1" -100.0 mm -10.0 -103.7 mm 4.0 mm 5.6 mm -102.1 mm -91.2 mm -92.7 mm
  • The focal length tolerance is ±1%. The back focal length and working distance values here are referenced to the design focal length.
  • Reciprocal of the Focal Length in Meters
  • Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
  • Measured at the Design Wavelength, 633 nm
  • Specified for Unmounted Lens
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LD1464-ML Support Documentation
LD1464-MLCustomer Inspired! Ø1" N-BK7 Bi-Concave Lens, SM1-Mounted, f =-50 mm, Uncoated
$40.86
Today
LD1170-ML Support Documentation
LD1170-MLCustomer Inspired! Ø1" N-BK7 Bi-Concave Lens, SM1-Mounted, f =-75 mm, Uncoated
$38.42
Today
LD1613-ML Support Documentation
LD1613-MLCustomer Inspired! Ø1" N-BK7 Bi-Concave Lens, SM1-Mounted, f =-100 mm, Uncoated
$38.15
Today
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