Gradient-Index (GRIN) Lenses for Imaging

Overview
Specs
Lens Handling & Care
Feedback

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500 µm Field of View

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200 µm Field of View

Neuronal activity in an awake mouse. Both laser-scanned multiphoton images used the G2P10 GRIN lens implanted 3 mm deep and a 20X, 0.5 NA Nikon Objective Lens. Images courtesy of Dr. Mackenzie Mathis, Rowland Institute, Harvard University.

Features

Use as Implantable Lens Elements for In Vivo Imaging Applications
Ideal for Widefield, Confocal, or Multiphoton Microscopy
Ø1.0 mm Uncoated Lenses
Ø0.5 mm or Ø1.0 mm AR-Coated Lenses for 500 - 1000 nm, or 515 - 670 nm and 900 - 1100 nm

Thorlabs' gradient-index (GRIN) lenses are available for imaging applications in which the region of interest is inaccessible with a microscope objective. These GRIN lens can be implanted deeply into a target specimen with minimal invasiveness and load. We offer Ø1.0 mm uncoated lenses that are ideal for widefield and laser-scanned confocal imaging. These lenses have high transmission over a wide wavelength range. We also have available Ø0.5 mm or Ø1.0 mm broadband AR-coated lenses that are ideal for multiphoton imaging. The Ø1.0 mm lens is AR-coated for 500 - 1000 nm, while the Ø0.5 mm lens is AR-coated for 515 - 670 nm and 900 - 1100 nm. For more specifications on each lens, please see the Specs tab.

Unlike a traditional lens, a GRIN lens affects the optical path by varying the index of refraction within the lens itself. In contrast to a spherical or aspheric lens, all optical path lengths (refractive index multiplied by distance) are the same in a GRIN lens due to the radially varying refractive index. For information on how to calculate the refractive index as a function of radius, please see the Specs tab.

Item #	G1P10	G1P11	G2P10	G2P11
Design Wavelength	550 nm
AR Coating Range (Both Ends)	N/A		500 - 700 nm, R_avg < 0.5% 700 - 1000 nm, R_avg < 1.5%	515 - 670 nm and 900 - 1040 nm, R_avg < 1% 950 - 1100 nm, R_avg < 2.5%
Working Distance^a	0.20 mm on Sample Side (Water Immersion) and on Objective Side (Dry)		0.25 mm on Sample Side (Water Immersion) 0.19 mm on Objective Side (Dry)	0.20 mm on Sample Side (Water Immersion) and on Objective Side (Dry)
Viewing Angle (Max)	70°			50°
Refractive Index (n₁) @ 550 nm	1.666			1.333
Gradient Constant (√A) @ 550 nm	0.724 mm^-1		0.782 mm^-1	1.291 mm^-1
Pitch^b (P) @ 550 nm	0.433	0.933	0.423	0.387
Face Angle	0°
Numerical Aperture (NA) in Water	0.50			0.486
Magnification^c	-0.92	+0.98	-1	+0.96
Length (Z)	3.758 mm ± 0.500 mm	8.091 mm ± 1.100 mm	3.400 mm ± 0.085 mm	1.883 mm ± 0.620 mm
Diameter (D)	1.0 mm +0/-0.03 mm		1.0 mm +0/-0.05 mm	0.5 mm +0/-0.03 mm
Field Curvature^d	100 µm			50 µm
Polarization Preservation	Not Specified
Protective Coating	SiO₂ (Silica)		N/A
Operating Temperature	<350 °C		<200 °C	<350 °C

The working distance is the distance between the edge of the lens and the focus.
The pitch of the lens is the fraction of a full sinusoidal period that the ray traverses in the lens (i.e., a lens with a pitch of 0.25 has a length equal to 1/4 of a sine wave, which would collimate a point source located at the surface of the lens).
Positive magnification indicates the image is upright. Negative magnification indicates the image is inverted.
The field curvature is the difference in image positions at the lens center and at 80% of the lens radius. See the figure at the top right for details.

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An example setup when imaging with an arbitrary GRIN lens. Note the light ray trajectory will change depending on the GRIN lens specifications.

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Transmission for G1P10 and G1P11 Uncoated GRIN Lenses

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AR Coating Reflectance for the G2P10 Lens. The blue shaded region denotes the specified wavelength range for optimum performance.

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AR Coating Reflectance for the G2P11 Lens. The blue shaded region denotes the specified wavelength range for optimum performance.

Index as a Function of Radius
The index as a function of radius, as shown in the diagram to the lower left, may be calculated with the equation:

where n₁ is the index of refraction on the optical axis, √A is the gradient constant, and r is the radial position (ranging from -D/2 to +D/2, where D is the diameter). The refractive index decreases quadratically as the radial position from the center increases. The steepness of the parabolic drop depends on the gradient constant.

Relating Pitch and Lens Length
The pitch and length of a GRIN lens may be related using the following equation:
Relating Pitch and Lenght
where P is the pitch of the lens, Z is the length of the lens, and √A is the gradient constant. The pitch of the lens is the fraction of a full sinusoidal period that the ray traverses in the lens; see the diagram below (center).

$GRIN Lens Refractive Index Variation$
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Refractive Index Profile of a GRIN Lens

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GRIN Lenses with Different Pitches. As the length of the lens increases, the pitch increases.

Handling

A GRIN lens should be handled with stainless steel tweezers, preferably those with a tapered end like our TZ3 optic tweezers, and picked up by firmly grasping the side of the cylinder rather than the flat ends.

Cleaning

Use methyl alcohol as a cleaning solvent when necessary. Acetone may also be used without harm to a GRIN lens, but should be pure enough to not leave a residue on the lens surface.

Storage

For extended periods of time, a GRIN lens should be stored in a "dry box" environment. This entails the use of a desiccant or heat source to prevent humidity from leaching the lens material. For short-term storage (less than a month), the plastic box and foam packing in which the lens is shipped will provide adequate storage, provided the lens is placed securely in the built-in slot to avoid chipping or scratching from other lenses.

Posted Comments:

tgeorges (posted 2018-10-11 09:55:44.97)

Would it be possible to have a coating for 450nm wavelength?

YLohia (posted 2018-10-11 09:39:39.0)

Hello, thank you for contacting Thorlabs. I will reach out to you directly to discuss the possibility of offering a custom version of this.

kyrollosyanny (posted 2018-08-26 22:16:17.03)

This lens will be a lot more useful if it was infinity corrected. Many people in the field of neuroscience use headmonted microscopes (miniscope.org), having a 1.8 or 2mm diameter infinity corrected GRIN is very useful in that regard and it is an area with huge demand

YLohia (posted 2018-08-28 11:32:23.0)

Hello, thank you for your feedback. I have posted this new product idea on our internal engineering forum for further consideration.

mlippert (posted 2018-07-14 11:56:13.65)

I can only reinforce dennis' opinion. This is exactly what the field needs! People are looking for lenses to image mouse hippocampus, cortex with attached 1 mm microprisms as well as various deep brain structures (in our case mouse VTA), so various lengths and thicknesses would be ideal (thickness 1mm and 2 mm for short lenses, 0.5 mm and 0.3 mm for long (ca. 5-7mm lenses)), focal distance in tissue desn't need to exceed 150 um. A company with "opix" in its name has cornered everybody not using their system by supposedly blocking the release of the Grintech lenses to non-customers (at least its hard to get them). There is widespread discontent in the community regarding these business practices which many consider unethical. Gofoton is apparently looking at making equivalent lenses, but regardless of manufacturer, it would be amazing to have an independent manufacturer of imaging lenses for the purpose. If you have any candidate lenses, we would always be willing to test them in our lab with one of our systems.

YLohia (posted 2018-07-19 09:50:21.0)

Hello, thank you for your valuable feedback. I have posted this idea on our internal engineering forum for further consideration.

dennis.kaetzel (posted 2017-09-17 21:27:24.387)

Dear Thorlabs, it would be fantastic, if you could offer a range of imaging GRIN lenses that are for chronic implantation (uncoated) and permissive to blue exctitation light as required for MOST applications of those lenses for imaging in life rodents (single-photon, implanted miniscopes). There is only one supplier (GRINtech) of GRIN lenses with a 4th order index of refraction profile, i.e. of high quality ... and that supplier does not sell those lenses for imaging application due to a contract with Inscopics. At the same time, the demand for this technology is surging dramatically as dozens, if not hundreds of labs are starting to use the Miniscope Technology. What would be required are lenses with 0.25 pitch (for the cope) and uncoated lenses with 0.4 pitch and 0.5mm Working Distance and a diameter of 1mm and 0.5 or 0.6mm. You can contact me for more info.

tfrisch (posted 2017-10-05 12:01:31.0)

Hello, thank you for contacting Thorlabs. GRIN lenses for single photon and water immersion are a part of an open discussion we have internally. I will reach out to you with more details on what you'd be looking for in the future.

GRIN Lenses, Uncoated

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Transmission for G1P10 and G1P11 Uncoated GRIN Lenses

Ideal for Widefield and Laser-Scanned Confocal Imaging
G1P10: Ø1.0 mm and 3.758 mm Long
G1P11: Ø1.0 mm and 8.091 mm Long
Working Distance:
- 0.20 mm on Sample Side (Water Immersion)
- 0.20 mm on Objective Side (Dry)
0.50 Numerical Aperture in Water

These uncoated GRIN lenses feature a 0.20 mm working distance on both the sample and the objective side. Each lens is 1.0 mm in diameter and ideal to be used in widefield and laser-scanned confocal imaging. The G1P10 lens is 3.758 mm long, while the G1P11 lens is 8.091 mm long. Each lens provides a large collection angle due to a numerical aperture of 0.50 in water. See the Specs tab for more details on optical properties.

GRIN Lens, AR Coating: 500 - 1000 nm

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AR Coating Reflectance for the G2P10 Lens. The blue shaded region denotes the specified wavelength range for optimum performance.

Ideal for Widefield, Confocal, and Multiphoton Imaging
Ø1 mm and 3.400 mm Long
Working Distance:
- 0.25 mm on Sample Side (Water Immersion)
- 0.19 mm on Objective Side (Dry)
0.50 Numerical Aperture in Water

This GRIN lens features a 0.25 mm working distance on the sample side and a 0.19 mm working distance on the objective side. It has a broadband AR coating optimized for 500 - 1000 nm. Suitable for excitation wavelengths from 800 to 1000 nm, the AR coating extends down to 500 nm to reduce losses for the corresponding emission wavelengths. This range is useful for Ca²⁺imaging. The lens supports widefield imaging techniques to locate the target region of interest (ROI), as well as confocal and multiphoton laser scanning of the sample. At 1.0 mm in diameter and 3.400 mm in length, the GRIN lens provides a large collection angle due to a numerical aperture of 0.50 in water. See the Specs tab for more details on optical properties.

GRIN Lens, AR Coating: 515 - 670 nm and 900 - 1100 nm

Zoom

Click to Enlarge
Click Here for Raw Data
AR Coating Reflectance for the G2P11 Lens. The blue shaded region denotes the specified wavelength range for optimum performance.

Ideal for Multiphoton Imaging
Ø0.5 mm and 1.833 mm Long
Working Distance:
- 0.20 mm on Sample Side (Water Immersion)
- 0.20 mm on Objective Side (Dry)
0.486 Numerical Aperture in Water

This GRIN lens features a 0.20 mm working distance on both the sample and the objective side. It is designed to minimize losses for excitation wavelengths from 900 - 1100 nm and emission wavelengths from 515 - 670 nm, which is useful for eGFP and eYFP. At 0.5 mm in diameter and 1.883 mm in length, this GRIN lens provides a large collection angle due to a numerical aperture of 0.486 in water. See the Specs tab for more details on optical properties.

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Gradient-Index (GRIN) Lenses for Imaging

Features

Handling

Cleaning

Storage

GRIN Lenses, Uncoated

GRIN Lens, AR Coating: 500 - 1000 nm

GRIN Lens, AR Coating: 515 - 670 nm and 900 - 1100 nm