| dc.description.abstract | The depth of field (DOF) in traditional optical systems is difficult to be extended without considering the reduction of the optical power or increase of the system complexity. In recent years, with the rise of diffraction theory, many researchers developed wavefront coding (WFC) technique and employed various forms of phase elements to extend the DOF by placing it in the aperture stop or exit pupil of an incoherent optical system. However, the WFC technique encounters some issues. For example, the phase element placed in the aperture stop is not physically possible for various systems since it will cause the phase element to collide with the mechanical structure or adjacent lenses. In addition, if the exit pupil with the phase element is not located in the region of the back focal length, the wavefront cannot be modulated correctly. Therefore, this thesis takes the cubic phase plate (CPP) as an example by adjusting its position, cubic coefficient, and refractive index to accomplish the application of flexibility; The CPP can be flexibly changed in its placement position while maintaining the same coding strength to get the correct coding result. First, taking a reflecting telescope as an example. Once the position of the CPP is changed, the diameter of the CPP is reduced by nearly three times, and the cubic coefficient of the polynomial surface is increased by two orders of magnitude. Therefore, the difficulty of manufacturing is eased when the precision is reduced. Second, for the example of the microscope, this thesis employs the CPP on the surface of the optical components and eliminates the CPP in the aperture stop, which solves the problem of collisions with optical components and mechanical structure in some cases, thus the assembly difficulty can be reduced. Therefore, the microscope with flexibility can also improve the efficiency of microscopy applications without loss of illumination level. However, when the CPP is employed in these optical systems, its performance is quite limited due to the severe effects of the off-axis field of view and aberrations. Therefore, this thesis proposes a method to separate the CPP and assign it on different surfaces of lenses by taking the Double-Gauss system as an example. Different distribution factors are applied to adjust the coding strength of different surfaces of lenses with cubic coefficients so that the phase function is nearly independent of the field of view. Therefore, under the condition that the position of the CPP, refractive index and cubic coefficient can be adjusted, this thesis presents the feasibility of the flexibility of the CPP to extend the DOF. Finally, without the restriction that the CPP must be placed in the aperture stop, this thesis also presents the application of a WFC see-through display to extend the DOF of the projected image by applying the cubic coefficient in the concave mirror. This research uses the inverted WFC process, the technique eliminates the requirement that the human eyes focus between the object and projected image, meanwhile, the safety can be improved. | en_US |