Pseudorays tracing allows not only find high-order aberrations but also simplifies process of optical systems composition.
For example, this method made possible creation and certification of objectives consisting of only diffractive or diffractive and radial GRIN elements.
Now we represent them:
The third-order monochromatic aberration-free designs
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| Diffractive doublet |
Gradient - diffractive doublet |
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| Cemented GRIN Wood lens |
Objective consisting of three cemented gradient-index flat-parallel plates. |
The third- and fifth-order monochromatic aberration-free designs |
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| Objective consisting of four cemented gradient-index flat-parallel plates |
Cemented radial gradient-index triplet |
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| Diffractive-GRIN high-resolution objectives |
At these figures
DL - diffractive lens
SS - spherical surface
FS - flat surface
IM - ingomogenius media
Let’s consider a new hybrid objective consisting of a gradient-index optical
element having external flat refracting surfaces and made of two different inhomogeneous
materials, separated by a cemented spherical surface, on which flat surfaces
the micro-structures of diffractive lenses are put. The most surprising property of
this objective is that even calculation in the area of the third- and fifth-order
aberrations gives the efficient design for imaging with a Rayleigh resolution of 1 µm.
All calculations were carried out at a focal length F=24 mm., wavelength 0.4416
µm, and numerical aperture NA=0.27. The distribution of wave-front
aberration within of the exit pupil of this objective is represented
in Fig. 1 for edge of a field, i.e. for the field angle 19.5 degrees. The maximal value of
the wave-front aberration is 0.54 wavelenght. The intensity distribution in the diffraction point
image is shown in Fig.2 for the same field angle. Here Strehl intensity or Strehl ratio
is 0.87 and the relative energy concentrated within the Airy disk is 0.74.
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| Fig. 1. |
Fig. 2. |
