Visible Air-Spaced Achromatic Doublets, AR Coated: 350 - 700 nm

Minimal Focal Shift Over the Design Wavelength Range
Superior Performance When Compared to Cemented Doublets
1" Outer Diameter Aluminum Housing

ACA254-200-A

ACA254-030-A

Each mount includes an engraved arrow
indicating the direction of light propagation
required to collimate a point source.

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OVERVIEW

General Specifications
Coating Range^a	350 - 700 nm
Design Wavelengths	486.1, 587.6, 656.3 nm
Surface Quality	20-10 Scratch-Dig (to Prevent Scattering from High-Power Sources)
Clear Aperture	Ø20 mm
Irregularity per Surface	<λ/4 at 633 nm
Focal Length Tolerance	±1% at 587.6 nm
Reflectance	R_avg < 0.5% (350-700 nm)
Housing	Ø1" 6061-T6 Aluminum Barrel

The AR coating is designed for 350 - 700 nm, but the glass used to construct these doublets provides poor transmission in the UV. See the transmission plots below for more details.

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Air-Spaced Achromatic Doublet in an SM1L30C Slotted Lens Tube with Two SM1RR Retaining Rings

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Features

Air-Spaced Doublet Design Provides Superior Aberration Performance than Singlet Lenses
Ø20 mm Clear Aperture
1" Outer Diameter for Mounting Inside a Ø1" Lens Tube
AR Coating for the 350 - 700 nm Range

Thorlabs' Air-Spaced Achromatic Doublets are designed to provide superior spherical and chromatic aberration correction. Air-Spaced Doublets have two more degrees of freedom than cemented doublets because the interior lens surfaces do not need to have the same curvature. These extra variables allow the performance of these air-spaced doublets to exceed the performance of equivalent cemented doublets in some cases. For details, please see the Lens Comparison tab. The air-spaced design is also highly resistant to laser damage, since no cement is utilized in the fabrication process. Although these lenses have an AR coating for the 350 - 700 nm range deposited on both surfaces, the glass they are fabricated from displays limited or no transmission in the UV (<400 nm). Hence, please refer to the table below for exact specifications and transmission plots for each air-spaced doublet.

The doublets are pre-mounted in an aluminum barrel with tight tolerances on lens and barrel diameter to minimize the effects of lens decentering. Each mount includes an engraving with the part number, AR coating wavelength, focal length, and the direction of light propagation required to collimate a point source. The mount has a 1" outer diameter for mounting inside a Ø1" lens tube (as shown in the photo to the right).

Note: We do not recommend disassembly of these lenses, as this may affect performance.

Air-Spaced Doublets Selection Guide
UV (245 - 400 nm)	D (1.65 - 3 µm)
Visible (350 - 700 nm)	E (3 - 5 µm)
NIR (650 - 1050 nm)	E3 (7 - 12 µm)
Laser-Line (532 & 1064 nm)

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LENS COMPARISON

The table below contains links to pop-ups with plots containing a comparison of the theoretical performance of an air-spaced achromatic doublet and a cemented achromatic doublet with the same focal length. Comparisons are made for the transmitted wavefront error and spot radius. Raw data from each graph below can be downloaded by clicking here.

350 - 700 nm Lenses

Cemented Item #^a	Air-Spaced Item #^a	Wavefront Error Plots	Spot Diameter Plots
AC254-030-A	ACA254-030-A
AC254-050-A	ACA254-050-A
AC254-060-A	ACA254-060-A
AC254-075-A	ACA254-075-A
AC254-100-A	ACA254-100-A
AC254-150-A	ACA254-150-A
AC254-200-A	ACA254-200-A

For the f = 30 mm lenses, the wavefront error was calculated with a Ø7 mm aperture and the f=50 mm lenses with a Ø15 mm aperture. All other lenses are calculated over the clear aperture.

Plot Key
Cemented Doublets
Air-Spaced Doublets
Diffraction Limit
Airy Disk

Hide Air-Spaced Achromatic Doublets, 350 - 700 nm AR Coating

Air-Spaced Achromatic Doublets, 350 - 700 nm AR Coating

Item #	f (mm)	R₁ (mm)	R₂ (mm)	R₃ (mm)	R₄ (mm)	t_c1^a (mm)	t_c2^b (mm)	Air Gap^c (mm)	L (mm)	WD (mm)
ACA254-030-A	30	19.98	-27.32	-20.49	-40.68	7.76	5.00	1.23	15.2	21.3
ACA254-050-A	50	32.53	-32.53	-28.45	-78.02	6.82	3.23	1.25	13.3	41.4
ACA254-060-A	60	39.43	-39.43	-35.34	-97.49	6.83	3.16	1.16	13.3	51.5
ACA254-075-A	75	50.67	-50.67	-46.30	-122.59	4.68	4.63	1.10	13.1	67.5
ACA254-100-A	100	41.39	-41.39	-40.63	-361.30	5.39	4.94	1.02	14.1	88.8
ACA254-150-A	150	96.25	-46.58	-45.88	-312.80	4.00	4.00	1.02	12.5	141.3
ACA254-200-A	200	211.55	-34.81	-33.69	-199.82	4.00	4.00	1.05	12.7	191.5

a.Left Lens Center Thickness in the Reference Drawing b. Right Lens Center Thickness in the Reference Drawing c.Center Air Spacing Between the Lenses.

Item #	Left Lens Material^c	Right Lens Material^c	Image Space NA	Design RMS Wavefront Error
ACA254-030-A	N-SSK2	N-SF57	0.331	<3.5λ
ACA254-050-A	N-SSK2	N-SF57	0.198	<λ/5
ACA254-060-A	N-SSK2	N-SF57	0.166	<λ/5
ACA254-075-A	N-SSK2	N-SF57	0.133	<λ/8
ACA254-100-A	N-K5	N-KZFS8	0.101	<λ/10
ACA254-150-A	N-SSK2	N-KZFS8	0.060	<λ/20
ACA254-200-A	N-SSK2	N-KZFS5	0.045	<λ/20

The shaded region represents the specified coating range of the lenses.
The AR coating is designed for 350 - 700 nm, but the glass used to construct these doublets provides poor transmission in the UV (click the transmission plot links for more details on each item).
"Left" and "Right" refer to the orientations of the lenses in the Reference Drawing found by clicking on the info icon above.

Part Number	Description	Price	Availability
ACA254-030-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=30 mm	$576.15	3 Weeks
ACA254-050-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=50 mm	$576.15	Today
ACA254-060-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=60 mm	$576.15	Today
ACA254-075-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=75 mm	$576.15	Today
ACA254-100-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=100 mm	$576.15	Today
ACA254-150-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=150 mm	$576.15	Today
ACA254-200-A	Air-Spaced Achromatic Doublet, AR Coating: 350-700 nm, f=200 mm	$576.15	Today