Applied Research on Pixel Ray Method: Common Technology Platform of Light Field Camera, Confocal Microscope, Wavefront Sensor
Date Issued
2014
Date
2014
Author(s)
Chang, Hao-Jung
Abstract
Pixel ray is a method that can be used to describe the light propagation behavior. Analyzing pixel ray information thus can lead to the development of various metrology systems. Some of the system developed based on pixel ray approach are the main foci of this thesis.
Shack-Hartmann wavefront sensor is an instrument capable of retrieving pixel ray information. This thesis started by improving Shack-Hartmann wavefront sensor through circumventing the limitation imposed by the microlens array. More specifically, as the diameter of the microlens is around several hundred micrometers, the resolution achievable in traditional Shack-Hartmann wavefront sensor is also in the range of several hundred micrometers. More specifically, the resolution is limited by the size of the microlens. Following our prior research on sub-wavelength annular aperture (SAA), which possesses properties such as long depth of focus and sub-wavelength focusing capability, an improved wavefront sensor was developed. This design can improve the spatial resolution of wavefront sensor and also improve the precision of the pixel ray measurement.
Two instrument based on pixel ray method were developed throughout the course of this research. First, sub-wavelength annular aperture was used to replace the microlens array in order to improve the performance of Shack-Hartmann wavefront sensor. This improved system was then used to measure and reconstruct the wavefront of a 650 nm wavelength diode laser. Comparing the measured wavefront with that of the theoretical value confirms that pixel ray method can be adopted to perform wavefront measurement. In addition, the improvement obtained by replacing the microlens array with SAA was also demonstrated.
Secondly, the concept of pixel ray was implemented to pursue enhanced microscope system. In traditional microscope, depth of field decreases when higher magnification ratio objective is used. Thus, only few micrometer thickness of object can be observed under microscope clearly. For object with thickness large than this range, image will blur and object profile cannot be clearly reconstructed. This thesis applied the microlens array based light field camera technology to capture pixel ray information. The results confirmed that the microscope depth of field of system can be increased. The images obtained in different focusing plan can then be used to reconstruct the object’s full 3D profile
In summary, the successful implementation of the pixel ray based approaches in this thesis can facilitate the development of various metrology instrument. In addition, since the 3D profile of arbitrary objects can be digitized quickly by using the methods developed in this thesis, data input that hindered the development of 3D printing can potentially be circumvented.
Subjects
像素射線法
Shack-Hartmann
波前感測器
顯微鏡
光場
光場相機
外型重建
Type
thesis
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