Graduation Year
2024
Date of Submission
4-2024
Document Type
Campus Only Senior Thesis
Degree Name
Bachelor of Arts
Department
Physics
Reader 1
Janet Sheung
Reader 2
Scot Gould
Rights Information
© 2024 James Papas
Abstract
Light has wave-like properties. I use these wave-like properties of light to explore the field of Fourier Optics. The Fourier Transform, which is integral in this field, decomposes the spatial domain of an image to its spatial frequency distribution. Through the work of Kirchhoff and Fraunhofer, who established their light diffraction equations, it is demonstrated that a lens naturally performs a Fourier Transform. As light passes through a lens, the diffraction pattern that occurs at the focal point of the lens is the Fourier image. This represents the spatial frequency distribution of the light used to pass through the lens. Leveraging these fundamental concepts, we can manipulate the Fourier image and block out certain frequencies from the original image.
In this thesis, I use these techniques to perform optical filtering of images. Directional filtering, which blocks frequencies in specific directions within the Fourier Plane, is used to manipulate an image. One example of this is transforming a lattice to only horizontal lines. Low pass filters, which block out high frequencies, soften an image. High-pass filters, which block out low frequencies from the original image, enhance the edges of the final image.
Lastly, I applied the principles of Fourier Optics to microscopy by constructing a dark field microscope. In this setup, an annular stop is positioned before the condenser lens to block out certain light rays. This allows only light that strikes the specimen (a diatom) to scatter and pass through the objective lens. The remaining light misses the objective lens and fails to reach the camera. This technique creates a clear image of the specimen while the background stays dark.
Recommended Citation
Papas, James, "Fourier Optics and Dark Field Microscopy" (2024). CMC Senior Theses. 3575.
https://scholarship.claremont.edu/cmc_theses/3575
This thesis is restricted to the Claremont Colleges current faculty, students, and staff.
