CN-119493356-B - Method for solving optical crosstalk in dual-wavelength digital holography

CN119493356BCN 119493356 BCN119493356 BCN 119493356BCN-119493356-B

Abstract

In order to solve the problem of optical crosstalk caused by low transmissivity of a common light splitting device in dual-wavelength digital holography, the invention provides a method for solving the problem of optical crosstalk in dual-wavelength digital holography, which mainly comprises the steps of adjusting the sizes of light spots with different wavelengths, adjusting the positions of reference light while adjusting the sizes and directions of carrier frequencies, and avoiding crosstalk areas. The invention can skillfully avoid the crosstalk area, is not limited by the transmissivity of the light splitting devices such as the polarization beam splitter prism, the dichroic mirror, the filter sheet and the like, and can effectively solve the problem of light wave crosstalk caused by the light splitting device with arbitrary transmissivity in the dual-wavelength digital hologram.

Inventors

XIE LINNA
ZHOU WEIQI
HE NAILONG
Su Zhongfang
ZHANG YUNING

Assignees

新型显示与视觉感知石城实验室

Dates

Publication Date: 20260512
Application Date: 20241121

Claims (5)

1. Before multiplexing the first wavelength laser and the second wavelength laser, adjust the spot size of the first wavelength laser and second wavelength laser respectively, make the spot radius of the first wavelength laser greater than the spot radius of the second wavelength laser; the first wavelength laser and the second wavelength laser after adjustment are coupled and transmitted, and the first and the second wavelength laser are respectively separated by a first beam splitter, the reference light comprises the first wavelength reference light and the second wavelength reference light, the object light comprises the first wavelength object light and the second wavelength object light, the second beam splitter is matched with the first plane reflector in the reference light path to respectively adjust the transmission directions of the first wavelength reference light and the second wavelength reference light, when the first wavelength reference light and the second wavelength reference light are transmitted to the second beam splitter at the same time, the transmission directions of the first wavelength reference light and the second wavelength reference light reflected by the second beam splitter are adjusted by the second beam splitter, so that a crosstalk-free area of the first wavelength reference light is received by an image sensor, and the crosstalk area is positioned outside a receiving area of the image sensor, and forms interference fringes with the first wavelength object light in a y direction, the second wavelength reference light is transmitted by the first plane reflector and then transmitted by the second plane reflector again, the second wavelength reference light is transmitted by the second plane reflector again, and the interference fringes are formed by the second wavelength reference light is adjusted by the second plane reflector, and the interference fringes are generated at the same time when the second wavelength reference light is transmitted by the second plane reflector, and the second wavelength reference light is transmitted by the second wavelength light in a certain direction, the x direction of the image sensor, the interference fringes is formed by the second interference fringes is generated at the second wavelength light, and the second interference fringes is generated at the second wavelength light, interference fringes of the first wavelength laser and the second wavelength laser are distributed orthogonally and have no crosstalk, and then object phase information under different wavelengths is extracted by utilizing Fourier transformation.
2. The method of claim 1, wherein the spot sizes of the first wavelength laser and the second wavelength laser are adjusted using a beam expander or other optical device capable of adjusting the spot size.
3. The method for solving the optical crosstalk in the dual-wavelength digital hologram according to claim 1, wherein the first beam splitter is a polarizing beam splitter prism or a non-polarizing beam splitter prism, and the second beam splitter is a filter, a dichroic mirror or a polarizing beam splitter prism.
4. A mach-zehnder interferometer, wherein the optical crosstalk problem in dual wavelength digital holography is solved by using the method of any of claims 1-3.
5. A michelson interferometer, characterized in that the problem of optical crosstalk in dual wavelength digital holography is solved by using the method of any of claims 1-3.

Description

Method for solving optical crosstalk in dual-wavelength digital holography Technical Field The invention relates to a method for solving optical crosstalk in dual-wavelength digital holography, which is mainly applied to dual-wavelength digital holography and other optical systems involving dual-wavelength multiplexing. Background The digital holographic technology is an effective means for realizing quantitative measurement of the phase of an object, has the advantages of full field, rapidness, high precision, non-contact and the like, and is widely applied to the fields of object surface morphology measurement, biological cell imaging and the like. The technology is characterized in that a measured object is used for modulating measuring light to form a substance light wave, the substance light wave is interfered with another reference light wave without sample modulation, and phase information is extracted from one or more interference patterns recorded by a digital image sensor through a phase extraction algorithm. In single-wavelength digital holography, when the optical path difference generated by the measuring light passing through the sample exceeds the wavelength of the measuring light, the phase distribution of the reconstructed object is folded between [ -pi, pi ], and the extracted wrapping phase needs to be unfolded by using a numerical unwrapping algorithm so as to obtain the real phase of the object. However, when the object to be measured has a high aspect ratio structure, the surface morphology contains steps and the surface roughness is high, a numerical unwrapping algorithm may bring about a large error, resulting in unwrapping failure. In order to solve the problem, researchers have proposed a dual-wavelength digital holographic technique, which uses two different wavelengths of light to respectively obtain the wrapping phases of the corresponding wavelengths, and the two phases are subtracted to obtain the phase diagram of the equivalent wavelength. Since the equivalent wavelength is larger than either wavelength that is introduced into the measurement, and the closer the two wavelengths are, the larger the equivalent wavelength. The measurement range of single wavelength digital holography technology can be extended from a few micrometers to millimeter levels. The dual-wavelength digital hologram introduces one more light wave than the single-wavelength digital hologram, so that most researchers adopt wavelength multiplexing technology on the basis of Michelson interferometer or Mach-Zehnder interferometer structure, and the interference patterns with different wavelengths can be recorded simultaneously by using a single image sensor, so that real-time dynamic measurement can be realized. Such wavelength multiplexing techniques typically use a light splitting device such as a polarizing prism, dichroic mirror, or filter in the reference optical path, along with a plane mirror, to adjust the magnitude and direction of the carrier frequency of the non-passing wavelength. However, since the transmittance of a light-splitting device such as a general polarization beam splitter prism, a dichroic mirror, or a filter is not high, some of the light that would otherwise be required to be transmitted is reflected, and the problem of optical crosstalk occurs. The existing method uses a high-transmittance light-splitting device to avoid the problem of optical crosstalk, but the high-transmittance light-splitting device has high manufacturing and processing technical difficulties and high cost. Therefore, there is a need for a light-wave crosstalk problem caused by a light-splitting device with arbitrary transmittance in dual-wavelength digital holography. The invention comprises the following steps: 1. Object of the invention In order to solve the problem of optical crosstalk caused by low transmissivity of a common light splitting device in dual-wavelength digital holography, the invention provides a method for solving the problem of optical crosstalk in dual-wavelength digital holography, which mainly comprises the steps of adjusting the sizes of light spots with different wavelengths, adjusting the positions of reference light while adjusting the sizes and directions of carrier frequencies, and avoiding crosstalk areas. 2. Technical proposal Two-wavelength digital holography technologies generally use two lasers to emit first-wavelength laser light and second-wavelength laser light respectively, before multiplexing the first-wavelength laser light and the second-wavelength laser light, a beam expander or other optical devices capable of adjusting the spot sizes of the first-wavelength laser light and the second-wavelength laser light are used to respectively adjust the spot sizes of the first-wavelength laser light and the second-wavelength laser light, the first beam expander is used to adjust the spot radius of the first-wavelength laser light to r 1, and the second beam expander is used to