Radial shearing interferometer based on bifocal photon sieve

Abstract

A radial shearing interferometer based on a bifocal photonic sieve includes two identical bifocal photonic sieves, an image detector, and a computer. The focal points of the two bifocal photonic sieves correspond to each other, generating two 4f systems. This causes the incident wavefront to be measured to be split into two beams of different sizes, which undergo shearing interference on the image detector. The computer can extract the shearing phase difference from the interferogram received from the image detector, thus obtaining the phase information carried in the beam. This invention features a simple structure, low requirements for the experimental environment, and strong anti-interference capability, and can be applied to many fields such as wavefront detection, interferometric imaging, and adaptive optics.

Description

Technical Field

[0001] This invention relates to optical detection, and in particular to a radial shearing interferometer based on a bifocal photonic sieve. Background Technology

[0002] The basic principle of shearing interferometry is to replicate the wavefront to be measured by beam splitting, and then interfere with the replicated wavefront by causing it to be laterally or radially misaligned or rotated with itself, resulting in overlapping beams. The radial shearing interferometer, proposed by Brown in 1959, has been widely used in wavefront detection, optical component quality inspection, adaptive optics, and many other fields due to its advantages such as not requiring a standard reference wave, ease of designing a common optical path, and strong system stability. While there are many different structures for radial shearing interferometers, they all require multiple optical components to achieve shearing interference, making the optical path complex, demanding on the experimental environment, and difficult to apply to different optical systems. Summary of the Invention

[0003] This invention proposes a radial shearing interferometer based on a bifocal photonic sieve. By aligning the focal points of two bifocal photonic sieves to form two 4f systems, the incident plane wave is split into two beams of different magnitudes, which then undergo shearing interference on an image detector. The shearing phase difference is then extracted from the interferogram received by the image detector, thereby obtaining the phase information carried in the beam.

[0004] The technical solution of this invention is:

[0005] A radial shearing interferometer based on a bifocal photonic sieve is characterized by comprising a first bifocal photonic sieve, a second bifocal photonic sieve, an image detector, and a computer; the first bifocal photonic sieve, the second bifocal photonic sieve, and the image detector are arranged sequentially along the input direction of the wavefront to be measured. The output terminal of the image detector is connected to the input terminal of the computer. The first and second bifocal photonic sieves are identical, with their two focal lengths being f1 and f2, respectively. After the laser beam to be measured is incident on the first bifocal photonic sieve, diffraction occurs, forming two converging beams. The Airy disk of the first converging light wave is located at f1 after the first bifocal photon sieve and f2 in front of the second bifocal photon sieve. The Airy disk of the second converging light wave is located at f2 after the first bifocal photon sieve and f1 in front of the second bifocal photon sieve. The two bifocal photon sieves form two 4f systems, so that the two spherical light waves are converted into two plane waves of different sizes after exiting the second bifocal photon sieve. The two plane light waves undergo shearing interference on the image detector to form an interference image, which is input into the computer.

[0006] The two photon sieves are amplitude-type diffraction elements that can be applied to short-wavelength fields such as X-rays.

[0007] The image detector is a CCD, CMOS, or other array-type detector.

[0008] Compared with the prior art, the beneficial effects of the present invention are:

[0009] 1. Unlike traditional radial shearing interferometers, the purpose of using two bifocal photon sieves to form a 4f system is to generate radial shearing interference between plane waves, reducing the difficulty of interferogram processing and improving phase extraction accuracy. This invention eliminates the need for a telescope system to magnify and reduce the beam, thus greatly simplifying the experimental optical path and improving system stability.

[0010] 2. The interference pattern obtained by this invention is an interference image of two plane light waves, which reduces the difficulty of interference image processing while improving the accuracy of phase extraction. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the radial shearing interferometer based on the bifocal photon sieve of the present invention;

[0012] Figure 2 It is the generated peak function image;

[0013] Figure 3 It is a shearing interferogram;

[0014] Figure 4 It is the result of wavefront phase reconstruction;

[0015] Figure 5 This is a comparison of the reconstructed wavefront phase and the generated peak function. The solid line represents the curve of a row extracted from the initial peak function, and the dashed line is the curve of the corresponding row in the reconstructed graph. Detailed Implementation

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the scope of protection of the present invention.

[0017] Example 1

[0018] Please refer to Figure 1 , Figure 1This is a schematic diagram of the structure of Embodiment 1 of the radial shearing interferometer based on a bifocal photonic sieve of the present invention. As shown in the figure, the radial shearing interferometer based on a bifocal photonic sieve of the present invention is characterized by including a first bifocal photonic sieve 1, a second bifocal photonic sieve 2, an image detector 3, and a computer 4; the first bifocal photonic sieve 1, the second bifocal photonic sieve 2, and the image detector 3 are arranged sequentially along the input direction of the wavefront to be measured O. The output terminal of the image detector 3 is connected to the input terminal of the computer 4. The first bifocal photonic sieve 1 and the second bifocal photonic sieve 2 are identical, and their two focal lengths are f1 and f2, respectively; the laser beam to be measured O enters... After being emitted into the first bifocal photon sieve 1, the light undergoes diffraction, forming two converging spherical waves. The Airy disk of the first converging wave is located at f1 after the first bifocal photon sieve 1, and simultaneously at f2 in front of the second bifocal photon sieve 2. The Airy disk of the second converging wave is located at f2 after the first bifocal photon sieve 1, and simultaneously at f1 in front of the second bifocal photon sieve 2. The two bifocal photon sieves form two 4f systems, causing the two spherical waves to transform into two plane waves of different magnitudes after exiting the second bifocal photon sieve 2. The two plane waves undergo shearing interference on the image detector 3, forming an interference image. This interference image is input into the computer 4. The computer 4 is used to store and process the interference image.

[0019] The image detector 3 is a CCD, which generates images such as... Figure 2 The image shown is a peak function graph as a simulated wavefront of a random phase.

[0020] A laser beam passes through a simulated phase-type object and is incident on a radial shearing interferometer based on a bifocal photon sieve. The shearing interferogram is received on a CCD, as shown in the image. Figure 3 As shown, input the aforementioned computer 4.

[0021] The computer 4 uses phase extraction technology to extract the sheared phase difference from the interferogram, and then uses an iterative method or a mode method to restore the original phase from the sheared phase difference, thus completing the reconstruction of the wavefront under test. The simulation results are as follows: Figure 4 As shown, Figure 5 This is a comparison of the reconstructed wavefront phase and the generated peak function. The solid line represents the curve of a row extracted from the initial peak function, and the dashed line is the curve of the corresponding row in the reconstructed graph.

[0022] Experiments show that the present invention has a simple structure, low requirements for the experimental environment, and strong anti-interference ability. It can be applied to many fields such as wavefront detection, interferometric imaging, and adaptive optics.

[0023] The contents not described in this invention are common knowledge to those skilled in the art.

[0024] The specific implementation examples described above further illustrate the purpose, technical solution, and beneficial effects of the present invention in detail. It should be understood that the above descriptions are merely specific implementation examples of the present invention and are not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A radial shearing interferometer based on a bifocal photon sieve, characterized in that, The system includes a first bifocal photonic sieve (1), a second bifocal photonic sieve (2), an image detector (3), and a computer (4). Along the input direction of the wavefront (0) to be measured, the components are, in sequence, the first bifocal photonic sieve (1), the second bifocal photonic sieve (2), and the image detector (3). The output of the image detector (3) is connected to the input of the computer (4). The first bifocal photonic sieve (1) and the second bifocal photonic sieve (2) are identical, with focal lengths f1 and f2 respectively. After the laser beam to be measured is incident on the first bifocal photonic sieve (1), diffraction occurs, forming two converging spherical beams. The Airy disk of the first converging light wave is located at f1 after the first bifocal photonic sieve (1) and at f2 in front of the second bifocal photonic sieve (2). The Airy disk of the second converging light wave is located at f2 after the first bifocal photonic sieve (1) and at f1 in front of the second bifocal photonic sieve (2). The two bifocal photonic sieves form two 4f systems, so that the two spherical light waves are converted into two plane waves of different sizes after exiting the second bifocal photonic sieve (2). The two plane light waves undergo shearing interference on the image detector (3) to form an interference image, which is input into the computer (4).

2. The radial shearing interferometer based on a bifocal photon sieve according to claim 1, characterized in that, The first bifocal photon sieve (1) and the second bifocal photon sieve (2) are amplitude-type diffraction elements that can be applied to the X-ray shortwave field.

3. The radial shearing interferometer based on a bifocal photon sieve according to claim 1 or 2, characterized in that, The image detector (3) is a CCD, CMOS or other array-type detector.

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