Thermal Imaging Lenses

Lenses for Thermal Imaging Cameras
Focus Infrared Light without Introducing Spherical Aberration
Horizontal Field of View (FOV) Options from 18° to 56°

TIL4

4.0 mm Focal Length

TIL8

7.7 mm Focal Length

TIL15

15 mm Focal Length

TIL20

20 mm Focal Length

TIL24

24 mm Focal Length

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Overview
Refractive Index
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Common Specifications
Lens Substrate	Black Diamond-6^a
AR Coating Range	8 - 12 µm
Reflectance over Coating Range (Avg.)^b	<0.75% at 0° AOI
AR Coating Reflectance (Click Icon for Plot)
Transmission (Click Icon for Plot)
Substrate Properties
Refractive Index	2.7867 at 8 µm^c
Coefficient of Thermal Expansion	22.5 x 10^-6 / °C
Thermooptic Coefficient (Δn / ΔT)	30.5 x 10^-6 / °C

Click link for detailed specifications on the substrate.
Per Surface.
See the Refractive Index tab for the wavelength-dependent refractive index.

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.

Webpage Features
	Clicking this info icon below will open a window that contains specifications, a reference drawing, and horizontal field of views for various detector sizes.

Features

Focus Infrared Light without Introducing Spherical Aberration
8 - 12 µm AR Coating for Long-Wave Infrared (LWIR) Applications
Black Diamond Substrate Provides Stable Operation up to 110 °C
Horizontal Field of View (FOV) Options from 18° to 56°
Focal Lengths of 4.0 to 24 mm Available
Mounted in Threaded, Engraved Black Anodized Aluminum Housings
Internally Sealed to IP67 Standard

Thorlabs offers Thermal Imaging Lenses that are ideal for focusing long-wave infrared (LWIR) sources onto detectors or image sensors. The lenses, manufactured by LightPath Technologies, are mounted in threaded, black anodized aluminum housings engraved with the focal length and f/# (see the table below for details). Designed using Black Diamond-6 glass, their aspheric geometry allows them to focus light without introducing spherical aberration. The TIL4 and TIL8 lenses feature singlet designs, while the TIL15, TIL20, and TIL24 are doublets.

Black Diamond
Black Diamond-6 (BD-6), a chalcogenide made of an amorphous mixture of arsenic (40%) and selenium (60%), has several advantages over germanium, which is traditionally used to fabricate IR optics. BD-6's thermally stable refractive index (see the Refractive Index tab) and low coefficient of thermal expansion (22.5 x 10^-6 / °C) result in a smaller change in focal length as a function of temperature than for germanium. Additionally, germanium suffers from transmission loss as temperature increases, while BD-6 aspheric lenses can be used in environments up to 110 °C. This material performs particularly well over the 2 - 12 µm spectral range (click here for the transmission of an uncoated 1 mm thick sample).

Item #	EFL^a	WD^b	HFOV^c	VFOV^c	Ideal Detector Format^d	Surface Quality	Aperture	Height	f/#^e	Design	Thread
TIL4	4.0 mm	5.33 mm	56°	42°	320 x 240 / 12 µm	80-60 Scratch-Dig	Ø3.33 mm	6.50 mm	1.2	Singlet	M10 x 0.5 - 6g
TIL8	7.7 mm	10.06 mm	41°	31°	320 x 240 / 17 µm	100-60 Scratch-Dig	Ø5.80 mm	11.50 mm	1.3	Singlet	M19 x 0.5 - 6g
TIL15	15 mm	10.07 mm	25°	18°	640 x 480 / 10 µm	80-50 Scratch-Dig	Ø12.46 mm	17.00 mm	1.2	Doublet	M19 x 0.5 - 6g
TIL20	20 mm	7.96 mm	18°	14°	640 x 480 / 10 µm	80-50 Scratch-Dig	Ø16.60 mm	21.42 mm	1.2	Doublet	M19 x 0.5 - 6g
TIL24	24 mm	10.00 mm	26°	19°	640 x 480 / 17 µm	100-60 Scratch-Dig	Ø19.90 mm	26.50 mm	1.2	Doublet	M25 x 0.5 - 6g

EFL is magnification-based.
Assumes 0.76 mm Si Window, Nominal Focus at Infinity
Given for Ideal Detector Format
Given in Resolution (H x V) / Pixel Size
Obtained by dividing the effective focal length of the lens by its aperture.

EFL = Effective Focal Length
WD = Working Distance

HFOV = Horizontal Field of View
VFOV = Vertical Field of View

$Refractive Index of Black Diamond-2$
Click to Enlarge

Herzberger Coefficient	Value
A	2.787
B	1.194 x 10^-1
C	1.760 x 10^-2
D	-1.161 x 10^-4
E	-3.870 x 10^-8
F	-6.037 x 10^-11

The refractive index, n, of Black Diamond-6 (BD-6) as a function of wavelength, shown above, was calculated using the Herzberger Equation, an infrared-specific analog of the Sellmeier Equation. The Herzberger coefficients for BD-6 are given in the table to the right.

Herzberger Equation (for λ in µm)

Posted Comments:

user (posted 2023-01-25 17:22:55.35)

You might want to link to a MSDS sheet for these items or the substrate data. Amorphous 40% arsenic and 60% selenium is arsenic selenide glass (As_2Se_3). Arsenic selenide probably has the highest potential toxicity of any substrate you sell. It is a 4 on the health part of the MSDS diamond. While nominally inert, if exposed to acids it will release hydrogen selenide, a very toxic gas. It is fairly brittle and leaves many small pieces when it breaks. Ingestion or inhalation of dust can be lethal. Takes a few grams.

ksosnowski (posted 2023-01-26 11:57:58.0)

Thanks for reaching out to Thorlabs. These materials can be quite harmful if handled improperly. We do provide the MSDS for each of these thermal imaging lenses which you can access under the red document icon next to each product listing.

user (posted 2022-03-18 09:58:27.483)

Hi These lenses have threads of 0.5mm pitch. Do you have any adapters for your mounts?

jdelia (posted 2022-03-18 03:56:05.0)

Thank you for contacting Thorlabs. While we do not currently offer adapters for the M25 x 0.5 threads of the TIL24, or our M19 x 0.5 threaded lenses. I can certainly pass along your feedback to our internal suggestion forum. We do have the S1TM10 adapter to adapt the M10 x 0.5 threads of the TIL4 to our SM1 components. I have also contacted you directly to discuss your application.

Thermal Imaging Lenses

Features

Lightpath Thermal Imaging Lenses