ABSTRACT
In the traditional optics, there is a contradiction between depth of field and High
resolution. An optical system couldn’t achieve the effect of large depth of field and high
resolution, but now many applications are in pursuit of an optical imaging system with
high resolution and large depth of field, for example in the large-aperture optical remote
sensors, three-dimensional microscopic imaging, optical storage, and television camera
and many other practical applications, Therefore the optical system both can satisfy the
imaging quality requirements and has great depth of field range is become hot issue in
the research of application of optical field.
According to conventional optical system, usually by narrowing the system relative
aperture to increase the depth of field, But it will affect system MTF and resolution,
reduce the detector ability of sensor, and finally reduce the image quality. This paper
introduces a new method can keep the values of MTF changed little in larger range,
wavefront coding technique is modulate the incoming non-coherent light waves through
inserting a three-phase plate into the traditional imaging system, make the MTF
insensitive to the defocus, thus receive the middle image with small differences in large
range, finally using digital image processing techniques to restore the middle image to
get a clear picture. This technical creatively combine the optical design and digital
image processing technology in together, solved the incompatible contradiction between
resolution and large depth of field, so wavefront coding technology has an extensive
prospect of application in many research fields.
The wavefront coding technique is studied in detail from theory and experiment in
this paper. In Chapter 2, reference the study of the stationary phase method and the
ambiguity function, deduced a cubic wavefront coding system invariant to defocus, and
taking a cubic wavefront coding system as example, the basic principle of the
prolongation of the DOF utilizing the wavefront coding technology is explained from
two points of view, one geometry optics, the other Fourier optics, And analyzes the no
coherent optical imaging system’s PSF and optical transfer function relation, deduce the
influence defocus to pupil function.
In Chapter 3, analysis the characteristics of wavefront coding system in
theoretically, deeply study the effect of defocus and the modulation coefficient of Phase