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Method and apparatus for retrieving a phase of a wavefield

A wave field and phase technology, applied in optics, instruments, discharge tubes, etc., can solve problems such as intolerance to radiation, and achieve the effect of increasing effectiveness and increasing sample damage

Inactive Publication Date: 2012-08-01
UNIV OF SHEFFIELD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Some samples cannot withstand radiation for the required length of time
[0013] Data acquisition time can be reduced somewhat by using brighter and costly radiation sources, but it will cause even increased sample damage

Method used

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  • Method and apparatus for retrieving a phase of a wavefield
  • Method and apparatus for retrieving a phase of a wavefield
  • Method and apparatus for retrieving a phase of a wavefield

Examples

Experimental program
Comparison scheme
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example 1

[0171] Presents results obtained from wavefield measurements with softer edges and stronger phase variations.

[0172] Conventional CDI methods have difficulty in addressing this situation.

[0173] Use of wave field Figure 7 The images shown in (a) and (b) are generated. Will Figure 7 The intensity value of the image pixel of (a) is multiplied by the intensity value of the corresponding pixel of the Airy disk in order to define the magnitude of the wavefield. Combined with AiryBlade to provide a soft border to the image. Amplitude scaled to the range [0,1].

[0174] The corresponding value of the wavefield phase is scaled to the [0,2π] range using the phase Figure 7 (b) image to define. overlap in Figure 7 (b) The dotted circle on the image indicates the application of Figure 7 The corresponding position of the first zero-valued contour of the Airy disc in (a).

[0175] The setup parameters used for the algorithm are: λ=635 nm; d 1 =9.7 mm; d 2 =47.7 mm,...

example 2

[0207] The beam from the 635 nm laser diode is collimated and converged by a lens with a focal length of 50 mm to provide as Figure 5 The irradiation probe is shown. Place the WTD at a distance of approximately 18.45 mm behind the crossing point of the beam. WTDs are formed from silica glass etched into varying thicknesses in order to impart the desired phase retardation.

[0208] The WTD is formed to have 1100 x 1100 pixels, according to Figure 6 The examples shown are each square in shape and 16 μm wide. Each pixel is provided with a pinhole, whereby the pixel array provides a phase map. The pinholes have a hole size of 6 μm to minimize artifacts due to transition edges between pixels.

[0209] It will be appreciated that pinholes are not required, and arrangements that do not include pinholes are also useful.

[0210] A CCD camera with square pixels of 7.4 μm on each side was placed 70 mm downstream of the WTD in order to record the diffraction pattern.

[0211] Mic...

example 3

[0222] It is well known that phase recovery for one-dimensional (1D) signals is much more difficult than for higher-dimensional cases (2D or 3D), since the phase problem itself becomes more likely to be underdetermined. Restoring the phase of a one-dimensional signal has many applications, such as shape determination of ultrashort pulses and in geodesy, among others. This example proves that the method according to the embodiment of the present invention can also be applied to 1D signals through numerical experiments.

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Abstract

A method of retrieving a phase of a wavefield comprising the steps of: providing an estimate of the wavefield [phi]0 at an initial plane; and propagating the wavefield to and fro between an entrance plane being a plane having an area to which the wavefield is confined and a detector plane via a wavefield transform device, wherein at the entrance plane a support constraint is applied and at the detector plane a magnitude constraint is applied, the wavefield transform device being arranged to apply a wavefield transform function to the wavefield, wherein the wavefield transform function is characterized by a finite deviation from a lens function.

Description

technical field [0001] The invention relates to a method and a corresponding device for recovering the phase of a wave field. In some embodiments, a method of composing an image of an object based on intensity measurements of a diffraction pattern formed by radiation scattered from the object is provided. Background technique [0002] It is recognized that an image of an object can be constructed from measurements of the phase and intensity of the wavefield scattered by the object. However, image detectors typically cannot measure the phase of the wavefield, but only provide a measure of the intensity. The so-called 'phase problem', the problem of determining the phase of a wave field, has been the subject of greater attention. [0003] Solutions to the phase problem typically involve iterative wavefield calculations based on intensity measurements of diffraction patterns. [0004] Sayre proposed the possibility of recovering the phase of the wavefield diffracted from a f...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G02B27/44G03H1/00H01J25/00
CPCG02B26/0833G02B27/0075G02B27/44G03H1/00H01J25/00
Inventor 张福才
Owner UNIV OF SHEFFIELD
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