As for editing the prescription, I’d like it edit it in the spreadsheet mode rather than per surface.

]]>I have looked at MTF before and was not quite sure how to compute it for arbitrary lens systems. It would need further study on my part.

I am unclear what you mean by editing the prescription. RayLab already lets you edit all the lens surface parameters. ]]>

… What you say is indeed quite logical.

.

MichaelG. ]]>

In theory (i.e. mistakes on my part not withstanding) RayLab is taking a similar approach to units as Zemax. That is you can use whatever units you want as the Lens Units so long as you remain consistent.

As with Zemax, Lens units are the primary unit of measure for the lens system. Lens units apply to radii, thicknesses, apertures,

and other quantities, and may be millimeters, centimeters, inches, meters, etc.

Being consistent means that Lens Power has units of 1/Lens Units. So if all your dimensions are in mm, then power is in 1/mm.

The only thing which has a prescribed unit is wavelength which is in nm.

]]>A quick question:

What ‘unit of measure’ does RayLab use for Lens Power ?

… I am confused.

I have just ‘created’ the Thorlabs plano-convex lens LA1131-633

https://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=5383

This has a nominal focal length of 50mm and a nominal power of +20 Diopter … RayLab shows a focal length of 49.9mm [which is fine], but expresses the Lens Power as .020

Obviously, I can multiply RayLab’s number by 1000

… but I am keen to understand why it is expresed that way.

Thanks and Best Wishes

MichaelG.

Thanks for the prompt reply.

… I have sent you an eMail.

MichaelG.

]]>It has been a while since I looked at that model and I am hard pressed to say why Magnification is -51.3 instead of -40.

RayLab is reporting the Paraxial Magnification calculation, and I do know that Zemax also calculates -51.2 as the Paraxial Magnification for this model.

It may be that there is some aspect of the 40x objective specification from the patent which I am missing. For example, I just noticed that the patent mentions the presence of the 0.17mm cover slide, which is not included in the model.

Another possibility is that there is a difference between how magnification is defined for a microscope objective and the way paraxial magnification is defined. For one thing the paraxial magnification depends of the distance of the object from the lens. If I increase the distance between the object and first lens surface to 1.556mm we get -40x for paraxial magnification value. I am not exactly sure how Microscope objective magnification is defined. If you do, let me know.

]]>Note that you have to manually cancel subscription in iTunes. ]]>

My main ‘optical’ interest is photo-microscopy & photo-macrography, so I was pleased to see the Zeiss 40x Objective featured as a sample. … I have to wonder, though: Why does Ray Lab compute its Magnification as -51.3 ?

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