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# finite conjugates cassegrain design

## finite conjugates cassegrain design

(OP)
I have to design a Cassegrain optical device for finite conjugates (obj height <0.125mm). The object minimum-maximum distances required from the primary mirror are: 13-16 cm.
Does anybody know the best radium-to-radium ratio and primary mirror radium-to-mirror spacing for best performance in terms of light collection, when a paraxial magnification of (-1) is required?
Any hints for interesting related sites?
I'm a novel Zemax-EE user.

### RE: finite conjugates cassegrain design

Magnification of -1? I would think that you would be better off to use a symmetrical system. Are you constrained to reflective optics?

CV

### RE: finite conjugates cassegrain design

(OP)
Yes, I'm constrained to reflective optics. What's the best design for this kinda system?
I outline that the obj-to-secondary mirror distance must be between 13 to 18 cm and that the obj height is no more than 0.125 mm. The image must be collected on an N.A.=0.22 optical fiber.

What do u suggest me to do?

### RE: finite conjugates cassegrain design

I don't know what your wavelength is, much other important information. I think your best system would be symmetric. In your case, imagine a "Z" shaped optical system. Your object and source are at the ends of the "Z", and there are two spherical mirrors at the bends in the "Z". The beam is collimated between the two mirrors. If you need more beam control, use a pair of off-axis parabolas. I don't know your object NA, but I assume it is not too large. You could probably use focal length F~= 100 mm and easily find off-the-shelf optics.

CV

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