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A method for verifying off-axis and defocus values

A technology of aberration correction and correction method, which is applied in the field of digital holography to achieve the effect of eliminating non-paraxial aberration

Inactive Publication Date: 2008-04-09
NORTHWESTERN POLYTECHNICAL UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0006] So far, there is no systematic and complete method to eliminate the defocus aberration and non-paraxial aberration in lensless Fourier transform holography, so as to directly obtain the ideal aberration-free hologram numerical reconstruction result

Method used

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  • A method for verifying off-axis and defocus values
  • A method for verifying off-axis and defocus values
  • A method for verifying off-axis and defocus values

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Embodiment 1

[0042] Embodiment 1: please refer to Fig. 2, the numerical correction method of described a kind of non-paraxial and defocus aberration comprises steps as follows: 1. measure the object to the hologram, that is, the distance from the object to the CCD, and determine it initially is the recording distance d of the hologram, d=37.5cm; 2. Perform non-paraxial aberration correction on the lensless Fourier transform digital hologram; 3. Perform defocused image on the hologram after non-paraxial aberration correction 4. Directly perform the inverse fast Fourier transform operation on the hologram after the defocus aberration correction. After the operation is completed, the numerical reconstruction image of the hologram is obtained; 5. Judging the numerical focal plane for the numerical reconstruction image, determine The optimal correction distance d' of the hologram; 6. determine the optimal reproduction distance d" of the hologram, d"=d+Δd=1 / (d+n'×Δ), in this embodiment d "=0.3746...

Embodiment 2

[0047] Embodiment 2: As far as the current technological development is concerned, the size of the area array CCD used to record digital holograms is generally not large. Usually, the recorded lensless Fourier transform hologram has almost no non-paraxial aberration, and can be Non-paraxial aberrations in lensless Fourier transform digital holography are ignored.

[0048] Please refer to Figure 7, the numerical correction method of the defocus aberration includes the following steps: 1. Measure the distance from the object to the hologram, that is, the distance from the object to the CCD, and preliminarily determine it as the recording distance d of the hologram; 2. Perform defocus aberration correction on the lensless Fourier transform digital hologram; 3. Directly perform inverse fast Fourier transform operation on the hologram after defocus aberration correction, and obtain the numerical reproduction of the hologram after the operation is completed 4. Judging the numerical ...

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Abstract

The invention discloses a non-paraxial and defocusing aberration numerical correction method. Firstly, a hologram recording distance is defined as d. The non-paraxial aberration correction and the defocusing aberration correction are carried out for a non-lens Fourier transformable digital hologram . The corrected hologram is carried out with IFFT to obtain a numerical reconstruction image. A numerical focusing plane is judged to define an optimal correction distance d' and an optimal reconstruction distance d '. The d'is taken as d and is substituted into a non-paraxial aberration correction factor, and the hologram is again carried out with the non-paraxial aberration correction. The d' is substituted into a correction distance D of the defocusing aberration correction factor, and the hologram is again carried out with the non-paraxial aberration correction. The corrected hologram is carried out the IFFT and then the ideal hologram numerical reconstructed image without aberration is obtained.

Description

technical field [0001] The invention relates to the technical field of digital holography, in particular to a numerical correction method for defocus aberration and non-paraxial aberration in lensless Fourier transform digital holography. Background technique [0002] Digital holography technology uses solid-state imaging devices CCD (Charge Coupled Device, Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor, Metal Oxide Semiconductor) to replace traditional silver salt dry plates to record holograms, and simulate digital holograms through computer numerical simulation The diffraction reproduction process, using the fast Fourier transform algorithm and spectral filtering processing to obtain the amplitude and phase information of the object optical wave field, realizes the reconstruction of the three-dimensional object optical wave field, avoids the traditional wet chemical processing process, and has the advantages of fast and real-time . Combining this...

Claims

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Application Information

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IPC IPC(8): G03H1/08G03H1/16G02B27/00
Inventor 赵建林邸江磊姜宏振闫晓博孙伟伟杨德兴
Owner NORTHWESTERN POLYTECHNICAL UNIV
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