human_hair

Project Description

In this work, we compare the performance of previously proposed ultra-miniature diffraction gratings with ideal lenses and zone plates of similar structural characteristics. The analysis aims at understanding the differences of designs utilizing non-focusing gratings and the potential benefits of their use in computational imaging systems.

Publications

"Performance Comparison of Ultra-Miniature Diffraction Gratings with Lenses and Zone Plates"
L. Spinoulas, O. Cossairt, A. K. Katsaggelos, P. Gill and D. G. Stork
Imaging and Applied Optics 2015, OSA Technical Digest (online) (Optical Society of America, 2015), paper CM3E.1.
[PDF]

Images

Simulation1

Sensor Measurement Simulation


Assuming far field imaging, each point in the scene produces a plane wave which passes through the diffraction grating and propagates onto the sensor using Fresnel diffraction.

Simulation2

Sensor Measurement Simulation


The image is formed by calculating the propagation from all points in the scene as well as considering shot and read noise on the sensor.

Simulation3

Sensor Measurement Simulation


The propagation process can be modeled as a matrix vector product where the matrix stores the diffraction grating responses for all possible points of incoming radiation in the scene.

phase_antisymmetry

Phase-Antisymmetric Gratings


Description of the main geometric characteristics of phase-antisymmetric gratings.

Spiral_phase_antisymmetry

Spiral Phase-Antisymmetric Gratings


Description of the main characteristics of spiral phase-antisymmetric gratings. They produce a wide point spread function instead of focusing the incoming radiation.

Studied_optical_elements

Studied Optical Elements


Phase delay and structural characteristics for each one of the studied optical elements. All three elements were optimized for a wavelength of λ = 500 nm keeping the same aperture size, focal length and refraction index of the propagating medium. A phase delay of π is imposed by the gratings while the lens provides a continuous range of phase delays based on its curvature. Note that, phase delay color coding is to be understood as modulo π for the lens.

Light_attenuation

Light Attenuation - Reconstruction


During propagation we consider light attenuation. Reconstruction is performed using baseline Tikhonov regularization.

Results_mona_low

Performance Comparison


Visual performance comparison for the reconstruction of the Mona Lisa image under low noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_mona_high

Performance Comparison


Visual performance comparison for the reconstruction of the Mona Lisa image under high noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_mona_psnr

Performance Comparison


Peak signal to noise ratio (PSNR) performance comparison for the reconstruction of the Mona Lisa image under varying levels of noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_qr_low

Performance Comparison


Visual performance comparison for the reconstruction of a QR code image under low noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_qr_high

Performance Comparison


Visual performance comparison for the reconstruction of a QR code image under high noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_qr_psnr

Performance Comparison


Peak signal to noise ratio (PSNR) performance comparison for the reconstruction of a QR code image under varying levels of noise and different wavelengths. Reconstruction was performed using the response of each optical element for each one of the different wavelengths (400, 500 and 600 nm).

Results_mona_wave_low

Performance Comparison


Visual performance comparison for the reconstruction of the Mona Lisa image under low noise and different wavelengths. Reconstruction was performed using the response of each optical element for a wavelength of 500 nm.

Results_mona_wave_psnr

Performance Comparison


Peak signal to noise ratio (PSNR) performance comparison for the reconstruction of the Mona Lisa image under varying levels of noise and different wavelengths. Reconstruction was performed using the response of each optical element for a wavelength of 500 nm.

Results_qr_wave

Performance Comparison


Visual performance comparison for the reconstruction of a QR code image under high noise and different wavelengths. Reconstruction was performed using the response of each optical element for a wavelength of 500 nm. Note that the reconstructed QR code using the spiral gratings is detectable by a conventional QR code reader.

Results_qr_wave_psnr

Performance Comparison


Peak signal to noise ratio (PSNR) performance comparison for the reconstruction of a QR code image under varying levels of noise and different wavelengths. Reconstruction was performed using the response of each optical element for a wavelength of 500 nm.

Acknowledgements

This project was funded in part corporate sponsorship from RAMBUS Inc.