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Microlens Array in Sequential Mode

  • 1 September 2021
  • 3 replies
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Hi,

I’m trying to model lens array imaging using mixed mode (array defined in NSC).

My question is, how valid is the Image Analysis for such a setup? The on-axis field component appears to shape a proper image, but from the layout rays I have a hard time imaging how an actual image is formed (see below picture). When using the off-axis field to make the Image Simulation, the picture appears to have multiple overlays (4).

 

Second question (perhaps the reason behind my misunderstanding), is how can Microlens Arrays be used to form images. I would think that placing the object and image plane 2f before and after the array would give a 1:1 imaging of the object (f being the single lens focal length). Additionally, I’m guessing some kind of post-processing of the image is necessary to actually make the image resolvable? 

Simulation file is attached.

Best regards,
Ahmed

 

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Best answer by David 1 September 2021, 18:55

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Userlevel 6
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Hi Ahmed,

Microlens arrays do not perform the kind of imaging you are trying to achieve. They are used in a way that each lenslet forms its own image. The common applications are to 1) increase the collection efficiency of pixelated detectors by providing each pixel with a lenslet aligned so as to couple light into it; 2) perform source homogenization by overlapping sections of a source.

Here is an illustration made by modifying your file:

 

Userlevel 5
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Hi Ahmed,

You may find more information and sample files about the two common applications of microlens arrays that David mentioned here:

For 1) to increase the collection of pixelated detectors, please see the Lenslet Array sample file in the \Documents\Zemax\Samples\Physical Optics folder. This example also shows how to describe lenslet arrays in fully sequential mode using the us_array User Defined Surface DLL. 

For 2) homogenization, please see this knowledgebase article about how to model microlens arrays in non-sequential mode:
Fly’s eye arrays for uniform illumination in digital projector optics – Knowledgebase (zemax.com)

Best,
Csilla

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Thank you both for the answers.

I guess for imaging applications it has to be something like a GRIN lens array (see for instance SELFOC lens arrays).

I know there is Gradient surface types in sequential mode, can those somehow be made as a periodic array? Refractive index information appears to be lost when converting these into NSC mode where it would have been possible to make them into arrays.

 

Best,
Ahmed

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