We propose a lens design ray tracing engine that is derivative-aware, using automatic differentiation. This derivative-aware property enables the engine to infer gradients of current design parameters, i.e., how design parameters affect a given error metric (e.g., spot RMS or irradiance values), by back-propagating the derivatives through a computational graph via differentiable ray tracing. Our engine not only enables designers to employ gradient descent and variants for design optimization, but also provides a numerically compatible way to perform back-propagation on both the optical design and the post-processing algorithm (e.g., a neural network), making hardware-software end-to-end designs possible. Examples are demonstrated by freeform designs and joint optics-network optimization for extended-depth-of-field applications.
Recently, a method for synthesizing a hologram of three dimensional (3D) objects from captured light field array is demonstrated. The 3D objects can be captured under incoherent light illumination using a micro lens array and their orthographic projection view images are generated from the captured elemental images. The synthesized orthographic projection view images are then multiplied by the corresponding phase functions and combined to form a digital hologram. For the first time, we analysis the performance of synthesized hologram under photon counting (low light imaging) conditions. The feasibility of this technique is experimentally verified by recording the orthographic projection images using a micro lens array and the reconstructed photon counted hologram is presented with varying photoncounting measurements.
Fourier ptychography microscopy (FPM) provides gigapixel imaging with both a high image resolution and a wide field-of-view (FOV). However, it is time consuming during the image capture process. In this paper, we perform an analysis on the FPM imaging process. With numerical and experimental comparison, we find that the reconstructed high resolution images with half number of the total captured images is less degenerated compare to that using all the captured images, especially in the case that the object is amplitude or phase-only.
KEYWORDS: Holograms, Wavefronts, 3D image reconstruction, Digital holography, Holography, Charge-coupled devices, Image processing, Interferometry, Near field optics, Wave propagation
We propose a digital hologram generation method from diffracted intensity images based on the transport of intensity
equation. In this paper we do experiment to verify the proposed method with coherent illumination with simple
experiment setup using the intensity images capture process. The experiment results show that our proposed method has
advantages compared to both the conventional holography with interferometry and the hologram generation based on
multiple intensity images.
A novel method to capture a Fourier holography of the three-dimensional objects under regular incoherent illumination is
proposed. Multiple images of the three-dimensional objects are captured by a camera while moving the focal plane along
the optic axis over the whole object space. Captured multiple defocused images are processed considering the point
spread function of the camera and the Fourier holography is finally synthesized. The principle is explained and verified
experimentally.
The resolution of the reconstructed object from the Fourier hologram that is generated from multiple view images is
analyzed in this paper. We found that the maximum view angle and the wavelength limit the maximum frequency of the
reconstructed object. The relationship between the bandwidth of the object and the lens pitch of the lens array affects the
aliasing of the reconstruction. All these four parameters determine the resolution of the reconstruction from the Fourier
hologram. Based on these analyses, we propose a lens array shift method to enhance the resolution of the reconstructed
object from the Fourier hologram. By shifting the lens array, multiple sets of element images are obtained, and high
spatial density element image is combined from the multiple sets of element images. The resolution enhanced
reconstruction of the object can be obtained from the Fourier hologram of the combined element images. The principles
are verified by experiment.
We propose a method for generating holograms of real existing 3D objects without coherent optical system. Multiple
orthographic view images of the 3D objects are captured under incoherent illumination and Fourier or Fresnel hologram
is synthesized using captured view images. A lens array is used to capture multiple orthographic view images efficiently.
We also present a method enhancing the phase-only Fourier hologram. By applying the constraints to the orthographic
view images and the generated hologram iteratively, the enhanced phase hologram is obtained.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.