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GRIN lenses technology

The Refractive Index Distributions (RID) in GRIN lens preforms are made by multi-stage optimized ion-exchange diffusion between silicate mineral glasses and salt melts.

The proprietary interferometric techniques are used to optimize the diffusion procedure and to determine GRIN lens characteristics.

Fig.1

Fig.2

In the LAG lenses - Low Aperture GRIN the nature of the changing of refractive index in glass via ion-exchange lies mainly in molecular volume increase. That is why in relatively high index mother glass the longitudal chromatic F-C difference of ray-trajectory pitch is very low (0.25%) and negative P_F>P_d>P_C (Fig.1).

Special annealing treatment is used to eliminate the residual post-diffusion birefringence.

LAG lenses are specially treated to create the dark anti-flick surface coating (Fig.2). The elimination of the out-of-aperture rays by this 20-mkm coating makes the image contrast significantly enhanced. The LAG resolution is not worse than 200 lines per mm in 90% zone.

Fig.3

In the HAG - High Aperture GRIN - imaging lenses and GTC - GRIN Tele Com - fiber collimating lenses the nature of the changing of refractive index via ion-exchange lies in polarizability difference of changing ions.

Due to great dispersion difference between mother glass and ion-exchanged-glass the longitudal chromatic F-C difference of ray-trajectory pitch is comparatively high ( 3.5%) and positive P_F>P_d>P_C.

Special achromatic length is used for HAG endoscope objective lenses (Fig.3) The resolution is not worse than 500 lines per mm in 90% diameter zone.