Objectives with both high resolution and large field of view, e.g. lithography lenses, are extremely expensive and difficult to manufacture, which makes them impractical for microscopic applications.
In order to solve these problems, using DOEs as array illuminators has already been proposed to scan large-area samples with comparable resolution to objectives with the same NA.
However, for such DOEs, the imaging systems must be placed on the opposite sides. Thus they are not suitable for measuring 3D surfaces of opaque samples and only semi-transparent samples like biological tissues can be measured.
In order to avoid this limitation, we propose new kinds of DOEs which utilize superposition of different field distributions to allow more flexible functionality.
The DOEs has higher zero-order diffraction and becomes more transparent to enable the illumination and imaging to be on the same side. Moreover, they can also designed to act like high-NA objectives to directly image the spots onto the sensor.
The DOEs are produced by lithography and they are tested in experiments. The experimental results show good agreement with the simulation, which proves that the proposed DOEs have the potential for application in 3D surface measurement. Furthermore, they provide the possibilities to improve the field of view and reduce the cost of current high-NA objectives.