Slant Edge MTF Target

Overview
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Specifications
Design	Chrome-on-Glass
Substrate	Soda Lime Glass
Chrome Thickness	0.120 µm
Chrome Optical Density	OD ≥3 at 430 nm
Substrate Thickness	0.06" (1.5 mm)
Surface Flatness	<5 µm
Line Spacing Tolerance^a	±1 µm
Line Width Tolerance^a	±0.5 µm

This tolerance is valid for the mask used to create this target and may differ minimally for the targets themselves.

Click to Enlarge
An R2L2S2P Slant Edge MTF Target Mounted in an XYF1 Test Target Positioner

Features

Determine Modular Transfer Function (MTF) of an Imaging System
5° Slanted, L-Shaped Pattern (ISO 12233 Compatible)
20 Variable Ronchi Rulings, 10 lp/mm to 200 lp/mm

Thorlabs' Slant Edge MTF Target allows the user to determine the spatial frequency response of an imaging system via a slant edge pattern or Ronchi rulings. The slant edge pattern is L-shaped and tilted at 5° for compatibility with ISO 12233. The Ronchi rulings include twenty individual rulings, each 5 mm x 5 mm in dimension and ranging in resolution from 10 line pairs per millimeter (lp/mm) to 200 lp/mm in 10 lp/mm intervals. Made from a soda lime glass substrate with low-reflectivity, vacuum-sputtered chrome, the target also features a cross pattern at each of the four corners of the overall pattern for alignment. Each pattern is manufactured using photolithography, allowing for edge features to be resolved down to approximately 1 µm. The high edge sharpness provided by this method is essential when using the modulation transfer function (MTF), described below, to determine the performance of an imaging system.

Mounting
To mount this target, Thorlabs offers the XYF1(/M) Test Target Positioning Mount (see photo to the right). This mount is capable of translating the target over a 50 mm (1.97") x 30 mm (1.18") area and secures the target using nylon-tipped setscrews. The mount contains five 8-32 (M4) taps for six post-mountable orientations.

Modulation Transfer Function
The modulation transfer function (MTF) is used to determine the resolution and performance of an imaging system. Several kinds of targets exist to measure the MTF of a system, including sine wave targets, grill targets, and the slanted edge targets discussed here. For the slant edge method, a slant edge target, such as the one featured on this page, is imaged. The target consists of a distinct dark edge that is tilted at some angle, usually between one and five degrees. The edge should be produced using a method that will produce as distinct an edge as possible. In the case of the target sold here, photolithography is used.

To calculate the MTF, begin with the edge spread function (ESF), which is the intensity of the image as a function of spatial position as the the edge is approached and crossed over (see Zhang et al., Proc. SPIE 8293, 2012). Due to imperfections in the imaging system, the ESF will be sloped on the border of the slanted edge, as opposed to being a perfect step function. Next, take the derivative of the ESF to produce the line spread function (LSF). Finally, take the Fourier transform of the LSF and normalize it to produce the MTF. The MTF, which will range from zero to one, can be plotted versus frequency (typically measured in cycles/mm). Frequencies with a corresponding MTF value close to one will be reproduced at approximately their original resolution. As the frequency increases, the MTF will fall to zero and the frequency will become indiscernible. The frequency that corresponds to a MTF of 0.5 is typically used as a benchmark to compare different imaging systems.

Various packages are available commercially for the calculation of the MTF using Matlab or ImageJ. One such package for Matlab can be found here, while a package for ImageJ can be found here.

Targets Selection Guide
Resolution Test Targets	Distortion Test Targets	Slant Edge MTF Resolution Test Targets	Calibration Targets

Posted Comments:

Ralf Noijen (posted 2019-06-07 04:18:21.85)

Dear Thorlabs, I have two comments. My colleague had ordered the target which we received today. I inspected it under a microscope and found quite some damages, is that normal? Secondly I found a link to a mtf measurement application for imageJ which is not working. Can you please help. BR Ralf

YLohia (posted 2019-06-07 10:56:56.0)

Hello Ralf, thank you for contacting Thorlabs. We are sorry to hear about the damaged item. This is certainly not normal -- I am reaching out to you directly to look into what sort of defects your piece has. Please use this link for the ImageJ package: https://imagej.nih.gov/ij/plugins/se-mtf/index.html. It is a non-Thorlabs website and it is working for on our end.

dmiles (posted 2017-01-09 13:36:40.047)

The Slant Edge MTF Target looks very useful to us. It would help a lot if there were a scale image of it at normal incidence so we could design with the corner of the "L" at the focus of our system before we receive it. We are in a time crunch and our designer would be helped by that information.

tfrisch (posted 2017-01-10 09:37:29.0)

Hello, thank you for contacting Thorlabs. we do have a CAD drawing that may be useful for your application. It can be found by clicking the documents icon below. I will send you a link directly as well.

sebastien.avila (posted 2015-01-07 12:08:20.28)

Hello, I would like to know if the clear parts of the target R2L2S2P are transparent or opaque white? Is it meant to be backlighted? Should I use a diffuse source or a collimated source? Thank you very much. Sébastien AVILA R&D VISION- France

besembeson (posted 2015-01-19 01:12:36.0)

Response from Bweh at Thorlabs: The substrate is made from soda lime so transmission properties will be like that for soda lime in areas without the chrome. R2L2S2P is a positive target designed for front-lit applications. For MTF determination, you would typically image the slanted "L" so diffused or large diameter collimated source should be okay.

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Slant Edge MTF Target

Features