Patent ID: 6867921

Claim:
A method of making a focus-position compensator for a microlens array having a substrate, the method comprising the steps of: determining the spatial variation of focus distance of the microlens array; choosing a number of tiles, a spatial distribution of tiles, and a tile focus-position correction Δ i of the i-th tile, such that the focus variation of the microlens array is reduced to within a desired limit; selecting a tile thickness t i of the i-th tile and a tile refractive index n i , so as to obtain the chosen tile focus-position correction Δ i , choosing a reference thickness t ref , the reference thickness being greater than or equal to the maximum tile thickness; determining a spacer-block thickness si corresponding to the i-th tile such that s i =t ref −t i ; constructing tiles, the i-th tile having thickness t i ; constructing spacer blocks for all s i >0, the i-th spacer block having thickness s i ; micromachining a tile tray, the tile tray having a receptacle for receiving each tile, the i-th receptacle being positioned to receive the i-th tile; for s i >0, placing the i-th spacer block in the i-th receptacle; placing the i-th tile in the i-th receptacle, wherein for s i >0, i-th tile is disposed on top of the i-th spacer block; placing an intervening structure on top of the tiles; bonding the tiles to the intervening structure; removing the tile tray and the spacer blocks.