Dielectric Fresnel lens in Near-field

Hello every one
I want to collimate the beam of the microstrip antenna array with flat (Fresnel) dielectric lens.
By the way, I want the whole antenna structure to be as compact as possible
And it is very important for me to achieve this goal.
I was thinking to make individual lenses for each element of array and by the mean of Fresnel Technique, curve it on a thick individual substrate and attach it directly on the antenna substrate board.
But there are several problems, for example:

1)It seems that the lens must be quite far from antenna (~40xlambda) in order to operate properly.

2)If we assume that above idea is practical, I don?t know how the individual lenses will affect the overall pattern of the array.

Is there any way to create a lens that could operate in near-field zone?

Is there any alternative way for creating collimated beam without lens (for example by changing the way that the elements of array are excited)?