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Calcium Fluoride Positive Meniscus Lenses, AR Coated: 2 - 5 µm


  • AR Coating Optimized for the 2 - 5 µm Range
  • Choose from Ø1/2" or Ø1"

LE5801-E

(Ø1")

LE5243-E

(Ø1/2")

Related Items


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Common Specifications
Substrate Material Vacuum-Grade Calcium Fluoridea
AR Coating Range 2 - 5 μm
Reflectance over Coating Range (Avg.) <1.25%
Diameters Available 1/2" or 1"
Diameter Tolerance +0.00/-0.10
Thickness Tolerance ±0.1 mm
Focal Length Tolerance ±2%
Surface Quality 40-20 (Scratch-Dig)
Spherical Surface Powerb 3λ/2
Spherical Surface Irregularity
(Peak to Valley)
λ/2
Centration <3 arcmin
Clear Aperture >90% of Diameter
Design Wavelength 4 μm
  • Click Link for Detailed Specifications on the Substrate
  • 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.
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.

Features

  • Vacuum-Grade Calcium Fluoride Substrate
  • Ø1/2" and Ø1" Versions Available
  • Broadband AR Coating for the 2 - 5 μm Range
  • Focal Lengths from 20.0 mm to 1000.0 mm

Thorlabs' Ø1/2" and Ø1" Calcium Fluoride (CaF2) Positive Meniscus Lenses are available with a broadband AR coating optimized for the 2 µm to 5 μm spectral range deposited on both surfaces. This coating greatly reduces the surface reflectivity of the substrate, yielding high transmission and minimal absorption over the entire AR coating range. See the Graphs tab for detailed information.

CaF2 is commonly used for applications requiring high transmission in the infrared and ultraviolet spectral ranges. The material exhibits a low refractive index, varying from 1.35 to 1.51 within its usage range of 180 nm to 8.0 μm. Calcium fluoride is also fairly chemically inert and offers superior hardness compared to its barium fluoride, magnesium fluoride, and lithium fluoride cousins.

Optic Cleaning Tutorial

Positive meniscus (convex-concave) lenses, which are thicker in the middle than at the edges and cause light rays to converge, are designed to minimize third-order spherical aberration. When used to focus a collimated beam, the convex side of the lens should face the source to minimze spherical aberration. They are often used in conjunction with other lenses to decrease the focal length, and therefore increase the numerical aperture (NA), of an optical assembly. Since a positive meniscus lens has a greater radius of curvature on the concave side of the lens than on the convex side, real images can be formed.

Optical Coatings and Substrates
Lens Tutorial
Selection Guide
Other MIR Lenses

2 - 5 µm AR Coating Graphs

CaF2 -E Reflectance
Click to Enlarge

Click Here for an Excel File with Plot Data
Shown above is a graph of the measured percent reflectance of the enhanced AR coating as a function of wavelength. The average reflectance in the 2 - 5 μm range is <1.25%. The blue shading indicates the region for which the AR coating is optmized. Performance outside of the specified range is not guaranteed and varies from lot to lot. The excel file above provides the coating curve data over an extended wavelength range.
CaF2 Transmission 3 to 5 micron antireflective coating
Click to Enlarge

Click Here for an Excel File with Plot Data
Shown above is a graph of the measured percent transmission of the enhanced AR coating as a function of wavelength. The blue shading indicates the region for which the AR coating is optmized. Performance outside of the specified range is not guaranteed and varies from lot to lot. The excel file above provides the coating curve data over an extended wavelength range.
CaF2 Uncoated Transmission
Click to Enlarge

Click Here for an Excel File with Plot Data
Shown above is a graph of the measured transmission of an uncoated, 5 mm thick sample of CaF2.

Total Transmission of Optic (CaF2 Substrate, Uncoated)

The table below gives the approximate theoretical transmission of these uncoated optics for a few select wavelengths in the 0.18 - 8.0 μm range. To see an excel file that lists all measured transmission values for this wavelength range, please click here.

Wavelength (μm) Total Transmission
0.2 0.910
0.4 0.929
0.6 0.935
0.8 0.937
1.0 0.938
1.2 0.938
1.4 0.938
1.6 0.938
1.8 0.939
2.0 0.939
Wavelength
(μm)
Total Transmission
2.2 0.939
2.4 0.939
2.6 0.940
2.8 0.940
3.0 0.940
3.2 0.941
3.4 0.941
3.6 0.941
3.8 0.942
4.0 0.942
Wavelength
(μm)
Total Transmission
4.2 0.943
4.4 0.943
4.6 0.943
4.8 0.944
5.0 0.945
5.2 0.945
5.4 0.945
5.6 0.946
5.8 0.946
6.0 0.947
Wavelength
(μm)
Total Transmission
6.2 0.947
6.4 0.947
6.6 0.948
6.8 0.949
7.0 0.949
7.2 0.948
7.4 0.947
7.6 0.946
7.8 0.945
8.0 0.944

Using Positive Meniscus Lenses

  • Achieve Tighter Focusing by Combining a Meniscus Lens with Plano-Convex Lenses
  • Build Multi-Element Lens Systems to Achieve Higher NA without Significant Increases in Aberrations

Positive meniscus lenses are designed to minimize spherical aberration. They have one convex and one concave surface. When used in combination with another lens, a positive meniscus lens will shorten the focal length and increase the NA of the system. Figure 1c shows a meniscus lens being used to shorten the focal length of a 100 mm focal length plano-convex lens. In addition, the transverse and lateral aberrations are greatly reduced. The convex surface of both lenses should be facing away from the image.

Figure 1. These figures illustrate the performance gains that can be achieved by using multi-element imaging systems. The combination of a meniscus lens and a plano-convex lens yields a 21 µm focused spot versus a 240 µm spot from the single plano-convex lens.

Wavelength-Dependent Focal Length Shift

The paraxial focal length of a lens is wavelength dependent. The focal length listed below for a given lens corresponds to the value at the design wavelength (i.e., the focal length at 4 µm). Since CaF2 offers high transmission from 0.18 - 8.0 µm, users may wish to use these lenses at other popular wavelengths. Click on the icons below to view theoretically-calculated focal length shifts for wavelengths within the 0.18 - 8.0 µm range.

The blue shading indicates the region for which the AR coating is optimized. Please see the Graphs tab for more information.

Ø1/2" Positive Meniscus Lenses

Item # LE5838-E LE5243-E LE5234-E
Focal Length @ 4 µm 20.0 mm 50.0 mm 80.0 mm
Focal Length Shift
(Click for Details)
Raw Data
(Click to Download)
Data Data Data

Ø1" Positive Meniscus Lenses

Item # LE5183-E LE5801-E LE5802-E LE5803-E LE5382-E LE5414-E LE5990-E LE5656-E LE5714-E
Focal Length @ 4 µm 40.0 mm 50.0 mm 75.0 mm 100.0 mm 150.0 mm 200.0 mm 500.0 mm 750.0 mm 1000.0 mm
Focal Length Shift
(Click for Details)
Raw Data
(Click to Download)
Data Data Data Data Data Data Data Data Data
CXY1 in 30 mm Cage System
Click to Enlarge

CXY1 Translation Mount and
SM1 Lens Tube Mounted in a
30 mm Cage System
Threaded Mounting Adapter
Click to Enlarge

Ø1" Optic Mounted in a
ST1XY-S XY Translator

Click to Enlarge

LMR1 Fixed Mount with Ø1" Lens

Click to Enlarge

LM2XY Translating Mount with Ø2" Lens
Recommended Mounting Options for Thorlabs Lenses
Item # Mounts for Ø2 mm to Ø10 mm Optics
Imperial Metric
(Various) Fixed Lens Mounts for Small Optics, Ø5 mm to Ø10 mm
(Various) Small Optic Adapters for Use with Standard Fixed Lens Mounts, Ø2 mm to Ø10 mm
Item # Mounts for Ø1/2" (Ø12.7 mm) Optics
Imperial Metric
LMR05 LMR05/M Fixed Lens Mount for Ø1/2" Optics
LM05XY LM05XY/M Translating Lens Mount for Ø1/2" Optics
SCP05 16 mm Cage System, XY Translation Mount for Ø1/2" Optics
(Various) Ø1/2" Lens Tubes,
Optional SM05RRC Retaining Ring for High-Curvature Lenses (See Below)
Item # Mounts for Ø1" (Ø25.4 mm) Optics
Imperial Metric
LMR1 LMR1/M Fixed Lens Mount for Ø1" Optics
LM1XY LM1XY/M Translating Lens Mount for Ø1" Optics
ST1XY-S ST1XY-S/M Translating Lens Mount with Micrometer Drives (Other Drives Available)
CXY1 30 mm Cage System, XY Translation Mount for Ø1" Optics
(Various) Ø1" Lens Tubes,
Optional SM1RRC Retaining Ring for High-Curvature Lenses (See Below)
Item # Mounts for Ø2" (Ø50.8 mm) Optics
Imperial Metric
LMR2 LMR2/M Fixed Lens Mount for Ø2" Optics
LM2XY LM2XY/M Translating Lens Mount for Ø2" Optics
CXY2 60 mm Cage System, XY Translation Mount for Ø2" Optics
(Various) Ø2" Lens Tubes,
Optional SM2RRC Retaining Ring for High-Curvature Lenses (See Below)
Item # Adjustable Optic Mounts
Imperial Metric
LH1 LH1/M Adjustable Mount for Ø0.28" (Ø7.1 mm) to Ø1.80" (Ø45.7 mm) Optics
LH2 LH2/M Adjustable Mount for Ø0.77" (Ø19.6 mm) to Ø2.28" (Ø57.9 mm) Optics
VG100 VG100/M Adjustable Clamp for Ø0.5" (Ø13 mm) to Ø3.5" (Ø89 mm) Optics
SCL03 SCL03/M Self-Centering Mount for Ø0.15" (Ø3.8 mm) to Ø1.77" (Ø45.0 mm) Optics
SCL04 SCL04/M Self-Centering Mount for Ø0.15" (Ø3.8 mm) to Ø3.00" (Ø76.2 mm) Optics
LH160C LH160C/M Adjustable Mount for 60 mm Cage Systems,
Ø0.50" (Ø13 mm) to Ø2.00" (Ø50.8 mm) Optics
SCL60C SCL60C/M Self-Centering Mount for 60 mm Cage Systems,
Ø0.15" (Ø3.8 mm) to Ø1.77" (Ø45.0 mm) Optics

Mounting High-Curvature Optics

Thorlabs' retaining rings are used to secure unmounted optics within lens tubes or optic mounts. These rings are secured in position using a compatible spanner wrench. For flat or low-curvature optics, standard retaining rings manufactured from anodized aluminum are available from Ø5 mm to Ø4". For high-curvature optics, extra-thick retaining rings are available in Ø1/2", Ø1", and Ø2" sizes.

Extra-thick retaining rings offer several features that aid in mounting high-curvature optics such as aspheric lenses, short-focal-length plano-convex lenses, and condenser lenses. As shown in the animation to the right, the guide flange of the spanner wrench will collide with the surface of high-curvature lenses when using a standard retaining ring, potentially scratching the optic. This contact also creates a gap between the spanner wrench and retaining ring, preventing the ring from tightening correctly. Extra-thick retaining rings provide the necessary clearance for the spanner wrench to secure the lens without coming into contact with the optic surface.


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Ø1/2" CaF2 Positive Meniscus Lenses, AR Coated: 2 - 5 µm

Item # Diameter Focal
Length
Dioptera Radius of
Curvature 1
Radius of
Curvature 2
Center
Thickness
Edge
Thicknessb
Back Focal
Lengthc
Reference
Drawing
LE5838-E 1/2" (12.7 mm) 20.0 mm +50.0 7.5 mm 72.4 mm 4.7 mm 1.5 mm 16.3 mm Positive Meniscus Lens Drawing
LE5243-E 1/2" (12.7 mm) 50.0 mm +20.0 15.0 mm 52.8 mm 3.0 mm 2.0 mm 47.1 mm
LE5234-E 1/2" (12.7 mm) 80.0 mm +12.5 20.0 mm 49.1 mm 3.0 mm 2.4 mm 76.5 mm

Suggested Fixed Lens Mount: LMR05(/M)

  • Reciprocal of the Focal Length in Meters
  • Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
  • Measured at the Design Wavelength, 4 µm
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LE5838-E Support Documentation
LE5838-EØ1/2" CaF2 Positive Meniscus Lens, f = 20.0 mm, AR-Coated: 2 - 5 µm
$309.48
Today
LE5243-E Support Documentation
LE5243-EØ1/2" CaF2 Positive Meniscus Lens, f = 50.0 mm, AR-Coated: 2 - 5 µm
$309.48
Today
LE5234-E Support Documentation
LE5234-EØ1/2" CaF2 Positive Meniscus Lens, f = 80.0 mm, AR-Coated: 2 - 5 µm
$309.48
Today

Ø1" CaF2 Positive Meniscus Lenses, AR Coated: 2 - 5 µm

Item # Diameter Focal
Length
Dioptera Radius of
Curvature 1
Radius of
Curvature 2
Center
Thickness
Edge
Thicknessb
Back Focal
Lengthc
Reference
Drawing
LE5183-E 1" (25.4 mm) 40.0 mm +25.0 15.0 mm 146.9 mm 8.9 mm 2.4 mm 33.1 mm Positive Meniscus Lens Drawing
LE5801-E 1" (25.4 mm) 50.0 mm +20.0 15.5 mm 55.2 mm 7.1 mm 2.0 mm 43.3 mm
LE5802-E 1" (25.4 mm) 75.0 mm +13.3 15.5 mm 28.0 mm 5.6 mm 2.0 mm 67.2 mm
LE5803-E 1" (25.4 mm) 100.0 mm +10.0 20.0 mm 36.8 mm 4.0 mm 1.7 mm 94.1 mm
LE5382-E 1" (25.4 mm) 150.0 mm +6.7 35.0 mm 78.6 mm 4.0 mm 2.6 mm 145.0 mm
LE5414-E 1" (25.4 mm) 200.0 mm +5.0 40.0 mm 75.9 mm 4.0 mm 3.0 mm 194.2 mm
LE5990-E 1" (25.4 mm) 500.0 mm +2.0 125.0 mm 317.8 mm 4.0 mm 3.6 mm 495.4 mm
LE5656-E 1" (25.4 mm) 750.0 mm +1.3 150.0 mm 290.8 mm 4.0 mm 3.7 mm 744.2 mm
LE5714-E 1" (25.4 mm) 1000.0 mm +1.0 250.0 mm 638.5 mm 4.0 mm 3.8 mm 995.4 mm

Suggested Fixed Lens Mount: LMR1(/M)

  • Reciprocal of the Focal Length in Meters
  • Edge Thickness Given Before 0.2 mm at 45° Typical Chamfer
  • Measured at the Design Wavelength, 4 µm
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available
LE5183-E Support Documentation
LE5183-EØ1" CaF2 Positive Meniscus Lens, f = 40.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5801-E Support Documentation
LE5801-EØ1" CaF2 Positive Meniscus Lens, f = 50.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5802-E Support Documentation
LE5802-EØ1" CaF2 Positive Meniscus Lens, f = 75.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5803-E Support Documentation
LE5803-EØ1" CaF2 Positive Meniscus Lens, f = 100.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5382-E Support Documentation
LE5382-EØ1" CaF2 Positive Meniscus Lens, f = 150.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5414-E Support Documentation
LE5414-EØ1" CaF2 Positive Meniscus Lens, f = 200.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5990-E Support Documentation
LE5990-EØ1" CaF2 Positive Meniscus Lens, f = 500.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5656-E Support Documentation
LE5656-EØ1" CaF2 Positive Meniscus Lens, f = 750.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
LE5714-E Support Documentation
LE5714-EØ1" CaF2 Positive Meniscus Lens, f = 1000.0 mm, AR-Coated: 2 - 5 µm
$386.31
Today
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