How does phase retrieval work?

How does phase retrieval work?

Phase retrieval is a key component of coherent diffraction imaging (CDI). In CDI, the intensity of the diffraction pattern scattered from a target is measured. The phase of the diffraction pattern is then obtained using phase retrieval algorithms and an image of the target is constructed.

What is the phase retrieval problem?

Reconstructing the phase of a field from intensity measurements is a long-standing and ubiquitous challenge, known as the phase retrieval problem. Optical detection devices that rely on converting photons to electrons (electrical current), such as charge coupled devices, cannot measure the phase of a light wave.

What is phase reconstruction?

Abstract: Phase reconstruction, which estimates phase from a given amplitude spectrogram, is an active research field in acoustical signal processing with many applications including audio synthesis. The experimental results confirm that the proposed method outperformed the direct phase estimation by a DNN.

What is encoding and retrieval?

Encoding is defined as the initial learning of information; storage refers to maintaining information over time; retrieval is the ability to access information when you need it. Then you need to maintain the information over time.

What is the phase problem and how does one solve it?

In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography, where the phase problem has to be solved for the determination of a structure from diffraction data.

What is Griffin Lim?

The Griffin-Lim Algorithm (GLA) is a phase reconstruction method based on the redundancy of the short-time Fourier transform. It promotes the consistency of a spectrogram by iterating two projections, where a spectrogram is said to be consistent when its inter-bin dependency owing to the redundancy of STFT is retained.

What is the difference between encoding storage and retrieval?

Psychologists distinguish between three necessary stages in the learning and memory process: encoding, storage, and retrieval (Melton, 1963). Encoding is defined as the initial learning of information; storage refers to maintaining information over time; retrieval is the ability to access information when you need it.

What is a phase in XRD?

A phase is a crystalline solid with a regular 3-dimensional arrangement of the atoms. The measured diffraction peak positions and intensities are like a fingerprint of a particular crystalline phase.

What is phasing in crystallography?

The phase problem is notorious in x-ray crystallography. Each reflection on the diffraction pattern or structure factor corresponds to a wave consisting of an amplitude and a phase. The amplitude is easily calculated by taking the square root of the intensity, but the phase is lost during the data collection.

What is Mel spectrogram?

Mel spectrogram is a spectrogram that is converted to a Mel scale. A spectrogram is a visualization of the frequency spectrum of a signal, where the frequency spectrum of a signal is the frequency range that is contained by the signal.

What is the difference between FFT and STFT?

If you look closely, there is a difference in the time frame on 3D graphs between STFT and FFT. STFT has smaller time frames, consequently, the frequency spectrum moves smoother over time, therefore it is more accurate. Block size – defines the number of real data samples to be taken for the calculating FFT.

How is phase retrieval related to the phase problem?

Phase retrieval is the process of algorithmically finding solutions to the phase problem. Given a complex signal where x is an M -dimensional spatial coordinate and k is an M -dimensional spatial frequency coordinate. Phase retrieval consists of finding the phase that satisfies a set of constraints for a measured amplitude.

How are phase retrieval algorithms used in astronomy?

Phase retrieval algorithms can be used to reconstruct fine-resolution images of satellites and astronomical objects, despite the blurring effects of atmospheric turbulence. Telescopes having sparse apertures or are made up of an array of multiple smaller telescopes can give fine resolution images, while having large savings on size and weight.

Why do we need phase retrieval in telescopes?

Telescopes having sparse apertures or are made up of an array of multiple smaller telescopes can give fine resolution images, while having large savings on size and weight. Image restoration and phase retrieval (to align the sub-apertures) are needed to achieve good quality imagery.

How is phase retrieval used in diffraction imaging?

Phase retrieval is a key component of coherent diffraction imaging (CDI). In CDI, the intensity of the diffraction pattern scattered from a target is measured. The phase of the diffraction pattern is then obtained using phase retrieval algorithms and an image of the target is constructed.

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