Phase-adjustable zero-eliminating interference system

Abstract

The invention discloses a phase-adjustable zero-elimination interference system, which relates to the field of photoelectric measurement and comprises a first telescope, a second telescope, a first collimating lens, a second collimating lens, a phase adjusting device, a plurality of plane mirrors, a spectroscope, a convex lens, a detector and a control device. Incident light passes through the first telescope and the second telescope respectively and is converted into parallel light beams through the first collimating lens and the second collimating lens. Wherein one light beam is subjected to phase adjustment through a phase adjustment device, and then the two light beams are continuously transmitted through a plurality of plane mirrors. At the spectroscope, the two beams of light are subjected to coherent superposition to generate an interference pattern. And the pattern is focused on the plane of the detector through the convex lens to form interference imaging for analysis. The detector receives an image and transmits the image to the control device, and the control device processes and analyzes the image and controls the phase adjusting device to adjust the phase difference of the two paths of light so as to realize the movement of interference fringes.

Description

Technical Field

[0001] The invention relates to the field of photoelectric measurement, and in particular to a phase-adjustable nulling interference system. Background Art

[0002] Nulling interference is an interferometric measurement technique that is mainly used for high-precision observations in astronomy. This technique is particularly suitable for observing faint objects around extremely bright stars, such as exoplanets. By eliminating the interference of starlight, nulling interference can more clearly detect planets orbiting stars.

[0003] Based on the principle of light interference, when two coherent light beams meet, their combined light intensity depends on the phase difference Δφ. The combined light intensity can be expressed as:

[0004] ,

[0005] Where I1 and I2 are the light intensities of the two beams. When Δφ = π, cos(Δφ) = -1, so the light intensity reaches its minimum value:

[0006] ,

[0007] However, for the light from the planets, since their angular position is slightly deviated from that of the stars, the conditions for destructive interference cannot be fully met. Therefore, the planetary light will not be completely eliminated at the interference center, and there will still be a certain light intensity, which makes it possible to extract the planetary light in a high-contrast environment.

[0008] The core of zero interference technology lies in effectively eliminating errors and dealing with noise interference. The main challenges currently faced include wavefront error, atmospheric turbulence, detector noise, mechanical vibration and thermal deformation. To meet these challenges, adaptive optical systems, high-order deformable mirrors and advanced wavefront sensors are used to significantly improve wavefront errors; lucky imaging technology and post-processing algorithms are used to alleviate the impact of atmospheric turbulence; low-noise devices are developed and ultra-low temperature refrigeration technology is applied to reduce detector noise; mechanical vibrations are suppressed through precise vibration isolation systems and structural optimization design; and active thermal management systems are implemented and low-expansion materials are used to control thermal deformation. In addition, advanced coronometer technology enhances the ability to suppress stray light, and in terms of data processing, differential imaging technology and machine learning algorithms have greatly improved the ability to extract weak signals. However, despite significant progress, error elimination and noise suppression still face many challenges.

[0009] Traditional nulling interferometry systems usually only produce a phase of π, which results in a limited number of dark fringes in the image. The information obtained from the dark fringes is relatively small, and they are easily affected by noise, resulting in low detection accuracy. Therefore, it is necessary to increase the number of dark fringes to obtain more valid data. Summary of the invention

[0010] The technical problem to be solved by the present invention is: the phase-adjustable nulling interference system described in the present invention moves the dark fringes to different positions by adjusting the phase to move the interference fringes, so as to obtain planetary signals at different positions, thereby increasing the data abundance in the phase dimension and improving the system's resolution and detection accuracy for targets.

[0011] The technical solution adopted by the present invention to solve its technical problem is: a phase-adjustable zero-interference system, including a telescope, a collimating lens, a plane mirror, a spectroscope, a phase adjustment device, a convex lens, a detector and a control device. The system uses two telescopes to receive incident light signals, and the incident light is collected and focused by the telescope to form a preliminary optical path signal. These light signals are then collimated by collimating lenses and converted into two parallel light beams. One of the light beams passes through a phase adjustment device to accurately change the phase of the light beam to control the phase difference between the two light beams when interfering. The adjustment of the phase difference can be achieved by changing the optical path difference, satisfying the following relationship:

[0012] ,

[0013] Wherein, Δφ is the phase difference between the two beams of light, λ is the wavelength of light, and ΔL is the optical path difference. By precisely controlling the optical path difference ΔL, the phase difference Δφ can be precisely controlled.

[0014] After phase adjustment, the two light beams are reflected by a series of plane mirrors so that the light beams propagate along the designed path and overlap precisely in space. At the spectroscope, the two beams of light are coherently superimposed to produce an interference effect. The interfering light beams are focused onto the plane of the detector through a convex lens. After receiving the interference pattern, the detector converts the optical signal into an electrical signal and transmits it to the control device. The control device performs data processing and analysis on the received interference image. First, the interference pattern is preprocessed by denoising and smoothing, and then the sine fitting method is used to analyze the distribution of the interference fringes and determine the center position of the light and dark fringes. The data of the center position of the dark fringes is recorded, and further analysis is performed based on information such as phase difference and fringing position to provide a basis for subsequent fringing movement. The intensity distribution of the interference fringes can be expressed as:

[0015] ,

[0016] Among them, I(x) is the light intensity at position x, I0 is the average light intensity, V is the contrast of the stripes, Λ is the stripe period, φ0 is the initial phase, α is the attenuation coefficient, and x0 is the stripe envelope center. By fitting the experimental data, the position of the center of each dark stripe can be accurately extracted, that is, the position where the light intensity reaches the minimum value. After obtaining the light intensity at the center of the dark stripe, that is, the planetary signal, the control device analyzes the position, contrast and other information of the stripes. According to the current phase difference and stripe position, combined with the system parameters and the characteristics of the target, the direction and distance that the stripes need to move are determined.

[0017] In order to obtain a complete planetary image, the system needs to fit and reconstruct the light intensity distribution of the planet. The reconstruction process uses a fitting method, assuming that the light intensity distribution of the planet can be represented by a Gaussian distribution:

[0018] ,

[0019] Where I0 is the peak light intensity of the planet, (x0, y0) is the center position of the planet, and σ is the standard deviation of the light spot. p (n), x(n), y(n)) can be fitted to solve for the parameters I0, x0, y0 and σ, thereby determining the position and characteristics of the planet.

[0020] Since a single measurement can only obtain limited spatial information, the control device adjusts the phase adjustment device to change the phase difference Δφ between the two light beams, thereby achieving the movement of the interference fringes. After each phase adjustment, the position of the dark fringes in the interference pattern will change, and the new dark fringes center position corresponds to the position where the new star light is suppressed. By adjusting the phase difference multiple times, the control device extracts pixel information at each new dark fringes center position, accumulates multiple measurement data, and obtains the planetary light intensity value and corresponding position coordinates under different phase conditions.

[0021] In order to achieve the movement of the stripes, the control device adjusts the phase adjustment device to change the optical path difference ΔL, thereby adjusting the phase difference Δφ. After each phase adjustment, the position of the stripes after the movement is recaptured, and the new dark stripe center position data is extracted. By adjusting the phase difference and moving the stripes multiple times, the stripe position data obtained under different phase conditions are accumulated to form rich measurement data. The movement amount Δx of the stripes and the change in the phase difference satisfy the following relationship:

[0022]

[0023] Where f is the focal length of the nulling interferometer system, and d is the distance between the first telescope and the second telescope. By precisely controlling Δφ, the interference fringes can be moved as expected. The moved fringes are captured by the detector again, and the control device re-extracts the position data of the center of the dark fringes. By adjusting the phase difference, moving the fringes, and extracting data multiple times, the fringes position data under different phase conditions are obtained, increasing the abundance of the measurement data.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] The present invention can move dark stripes to different positions, obtain planetary signals at different positions, increase the data abundance of the phase dimension, and improve the system's resolution and detection accuracy for targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A schematic diagram of a phase-adjustable nulling interference system;

[0027] Figure 2 Observation results of star-planet system;

[0028] Figure 3 Observation results: X-direction cross-sectional view;

[0029] Figure 4 Planet position fitting results.

[0030] In the figure, the reference numerals are: a first telescope 1, a second telescope 2, a first collimating lens 3, a second collimating lens 4, a phase adjustment device 5, a first plane mirror 6, a second plane mirror 7, a third plane mirror 8, a fourth plane mirror 9, a fifth plane mirror 10, a beam splitter 11, a convex lens 12, a detector 13, and a control device 14. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above-mentioned purpose, the present invention adopts the following technical scheme.

[0032] like Figure 1As shown, the present invention provides a phase-adjustable nulling interference system, comprising a first telescope 1 and a second telescope 2, a first collimating lens 3 and a second collimating lens 4, a phase adjustment device 5, first to fifth plane mirrors 6-10, a spectroscope 11, a convex lens 12, a detector 13 and a control device 14. The incident light passes through the first and second telescopes 1 and 2 respectively, and is converted into a parallel light beam through the first and second collimating lenses 3 and 4. One of the light beams is phase-adjusted by the phase adjustment device 5, and then the two light beams continue to be transmitted through a plurality of plane mirrors 6-10. At the spectroscope 11, the two light beams are coherently superimposed to generate an interference pattern. The pattern is focused on the plane of the detector 13 through the convex lens 12 to form an interference image that can be analyzed. The detector 13 receives the image and transmits it to the control device 14, which processes and analyzes the image and controls the phase adjustment device 5 to adjust the phase difference between the two light beams to achieve the movement of the interference fringes.

[0033] The control device 14 obtains the image collected by the detector 13, analyzes the interference pattern using the sine fitting method, and determines the center position of the dark stripes, that is, the position with the lowest light intensity. The data of the center position of the dark stripes is recorded, and further analysis is performed based on information such as the phase difference and the stripe position to provide a basis for subsequent stripe movement. Combined with parameters such as the current position, the direction and distance that the stripes need to move are determined, and then the phase adjustment device 5 is controlled to adjust the phase difference of the two light beams to achieve the movement of the interference stripes.

[0034] The control device 14 adjusts the phase adjustment device 5 to change the optical path difference to adjust the phase difference, so that the interference fringes move in a predetermined direction and distance. After each phase adjustment, the position of the moved fringes is recaptured, and the new dark fringes center position data is extracted. By adjusting the phase difference and moving the fringes multiple times, the fringes position data obtained under different phase conditions are accumulated to form rich measurement data. These accumulated data are further used to fit the Gaussian distribution model, fit and reconstruct the light intensity distribution of the planet, and thus obtain complete planetary image information.

[0035] One of the light beams passes through the phase adjustment device 5 to accurately change the phase of the light beam to control the phase difference between the two light beams when interfering. The adjustment of the phase difference can be achieved by changing the optical path difference to satisfy the following relationship:

[0036] ,

[0037] Wherein, Δφ is the phase difference between the two beams of light, λ is the wavelength of light, and ΔL is the optical path difference. By precisely controlling the optical path difference ΔL, the phase difference Δφ can be precisely controlled.

[0038] After phase adjustment, the two light beams are reflected by a series of plane mirrors 6-10, so that the light beams propagate along the designed path and overlap precisely in space. At the spectroscope 11, the two beams of light are coherently superimposed to produce an interference effect. The interfered light beams are focused onto the plane of the detector 13 by the convex lens 12. After receiving the interference pattern, the detector 13 converts the optical signal into an electrical signal and transmits it to the control device 14. The control device 14 performs data processing and analysis on the received interference image. First, the interference pattern is preprocessed by denoising and smoothing, and then the sine fitting method is used to analyze the distribution of the interference fringes and determine the center position of the light and dark fringes. The data of the center position of the dark fringes is recorded, and further analysis is performed based on information such as phase difference and fringing position to provide a basis for subsequent fringing movement. The intensity distribution of the interference fringes can be expressed as:

[0039] ,

[0040] Among them, I(x) is the light intensity at position x, I0 is the average light intensity, V is the visibility (contrast) of the stripes, Λ is the stripe period, φ0 is the initial phase, α is the attenuation coefficient, and x0 is the stripe envelope center. By fitting the experimental data, the position of the center of the dark stripe, that is, the position where the light intensity reaches the minimum value, can be accurately extracted. After obtaining the light intensity at the center of the dark stripe, that is, the planetary signal, the control device 14 analyzes the position, contrast and other information of the stripe. According to the current phase difference and stripe position, combined with the system parameters and the characteristics of the target, the direction and distance that the stripe needs to move are determined.

[0041] In order to obtain a complete planetary image, the system needs to fit and reconstruct the light intensity distribution of the planet. The reconstruction process uses a fitting method, assuming that the light intensity distribution of the planet can be represented by a Gaussian distribution:

[0042] ,

[0043] Where I0 is the peak light intensity of the planet, (x0, y0) is the center position of the planet, and σ is the standard deviation of the light spot. p (n), x(n), y(n)) can be fitted to solve for the parameters I0, x0, y0 and σ, thereby determining the position and characteristics of the planet.

[0044] Since a single measurement can only obtain limited spatial information, the control device 14 adjusts the phase adjustment device to change the phase difference Δφ of the two light beams, thereby realizing the movement of the interference fringes. After each phase adjustment, the position of the dark fringes in the interference pattern will change, and the new dark fringes center position corresponds to the position where the new star light is suppressed. By adjusting the phase difference multiple times, the control device extracts pixel information at each new dark fringes center position, accumulates multiple measurement data, and obtains the planetary light intensity value and corresponding position coordinates under different phase conditions.

[0045] In order to achieve the movement of the stripes, the control device 14 adjusts the phase adjustment device 5 to change the optical path difference ΔL, thereby adjusting the phase difference Δφ. After each phase adjustment, the position of the stripes after the movement is recaptured, and the new dark stripe center position data is extracted. By adjusting the phase difference and moving the stripes multiple times, the stripe position data obtained under different phase conditions are accumulated to form rich measurement data. The movement amount Δx of the stripes and the change in the phase difference satisfy the following relationship:

[0046]

[0047] Wherein, f is the focal length of the nulling interference system, and d is the distance between the first telescope and the second telescope. By precisely controlling Δφ, the interference fringes can be moved as expected. The moved fringes are captured again by the detector 13, and the control device 14 re-extracts the position data of the center of the dark fringes. By adjusting the phase difference, moving the fringes, and extracting the data multiple times, the fringes position data under different phase conditions are obtained, thereby increasing the abundance of the measurement data.

[0048] This embodiment constructs a zero-interference system consisting of a first telescope 1 and a second telescope 2 with an aperture of 20 mm and a focal length of 2 meters, and the baseline length is set to 0.1 meters. In order to verify the performance of the system, a typical star-planet system is simulated as the observation target, with the primary star light source located in the center of the picture and the planetary light source located 0.4 arc seconds to the left of the primary star. The intensity of the planetary light source is set to one tenth of the primary star light source, that is, I planet = 0.1I star . The observation data was acquired by a simulated high-resolution detector with a pixel size of 1.1×1.1 microns. Based on the system parameters, it was calculated that the theoretical position of the planet should be 3.64 pixels to the left of the image center. At the same time, a DC bias term was added to the signal to simulate the background response of detector 13, and noise was introduced to simulate the noise effect in the real observation environment. The noise level was set to a signal-to-noise ratio (SNR) of 5 to reflect the real observation conditions. 10,000 images were read continuously and superimposed to simulate long exposure to improve the signal-to-noise ratio. Subsequently, the superimposed images were normalized to obtain the relative brightness distribution. Figure 2The simulated observation result image is shown, and the horizontal and vertical coordinates represent the pixel positions in the X and Y directions respectively.

[0049] In order to further analyze the intensity distribution of the light spot, one-dimensional brightness data was extracted from the middle row of the image, namely Figure 3 The data obtained represent the relative brightness distribution in the X direction, such as Figure 3 The scatter plot is shown in (b).

[0050] For the extracted one-dimensional data, a Gaussian function is used for fitting to determine the center position of the light spot and related parameters. The mathematical expression of the Gaussian function is:

[0051] ,

[0052] This formula is used to intercept one-dimensional data in preparation for the subsequent fringe fitting, where A represents the peak amplitude, x0 represents the center position, and σ represents the standard deviation of the spot. Through the fitting results, the center position x0 and standard deviation σ of the spot are obtained. Based on this, the data within the range of 3σ to the left and right of the spot center are intercepted to reduce the influence of background noise and improve the purity of the signal.

[0053] In order to more precisely describe the characteristics of the interference fringes within the intercepted 3σ range, a sine function containing eight harmonics is used for fitting. This model can accurately capture the periodic changes of the interference fringes, and its mathematical form is:

[0054] ,

[0055] Among them, I(x) is the light intensity at position x, I0 is the average light intensity, V is the visibility (contrast) of the fringe, Λ is the fringe period, φ0 is the initial phase, α is the attenuation coefficient, and x0 is the fringe envelope center. By fitting the data, an accurate model of the interference fringe is obtained. Subsequently, the position of the dark fringe in the interference fringe is extracted using the local minimum detection algorithm. These local minima correspond to the positions where the main starlight is weakened by interference, that is, the planetary signal.

[0056] To further determine the position of the planet, the extracted planet signal is fitted with a Gaussian function. The light intensity distribution of the planet can be expressed by a Gaussian distribution:

[0057] ,

[0058] Where I0 is the peak light intensity of the planet, (x0, y0) is the center position of the planet, and σ is the standard deviation of the spot. The fitting results are as follows: Figure 4As shown in (a), the center position x0 of the Gaussian function is the pixel position of the planet in the X direction. According to the fitting parameters, it is calculated that the planet is located 3.14 pixels to the left of the image center, with a relative error of 13.7%.

[0059] In order to improve the accuracy and robustness of the measurement, this embodiment introduces a phase modulation method. By changing the phase difference of the interference system, 50 equally spaced phase values ​​are taken in the range of 0 to 2π. For each phase difference, the above data acquisition and processing process is repeated to obtain local minimum data under different phase conditions. The mathematical expression of phase modulation is:

[0060]

[0061] Where N = 50 is the total number of phase samples. By accumulating local minimum data at different phases, the statistical characteristics of the signal are enhanced and the influence of noise interference is reduced.

[0062] The local minimum data under all phase conditions are summarized and fitted again using the Gaussian function. Figure 4 As shown in (b), the fitting curve shows the comprehensive estimate of the planet's position. Finally, the planet center position is calculated to be 3.65 pixels to the left of the image center. The relative error of the phase modulation method is 0.2%, which greatly improves the positioning accuracy compared with the single measurement result.

[0063] It should be understood that the above-described embodiments are only used to illustrate the method and application of the present invention, and other improvements and modifications based on the concept of the present invention are still within the protection scope of the present invention. Therefore, the protection scope of the present invention is not limited to the above-described specific embodiments, but covers all equivalent solutions and technologies based on the concept of the present invention.

Claims

1. A phase-adjustable nulling interference system, characterized in that: The invention comprises a first telescope and a second telescope, a first collimating lens and a second collimating lens, a phase adjustment device, a plurality of plane mirrors, a beam splitter, a convex lens, a detector and a control device; the incident light passes through the first and second telescopes respectively, and is converted into parallel light beams through the first and second collimating lenses, one of which is phase-adjusted through the phase adjustment device, and then the two light beams are continuously transmitted through the plurality of plane mirrors, at the beam splitter, the two light beams are coherently superimposed to generate an interference pattern, the pattern is focused on the detector plane through the convex lens to form an interference image for analysis, the detector receives the image and transmits it to the control device, the control device processes and analyzes the image and controls the phase adjustment device to adjust the phase difference between the two light beams, so as to realize the movement of the interference fringes.

2. The phase-adjustable nulling interference system according to claim 1, characterized in that: The control device obtains the image collected by the detector and uses the sine fitting method to analyze the interference pattern. The fringe intensity distribution of the interference pattern is expressed as: Where I(x) is the light intensity at position x, I0 is the average light intensity, V is the contrast of the fringe, Λ is the fringe period, φ0 is the initial phase, α is the attenuation coefficient, and x0 is the fringe envelope center; the center position of each dark fringe is determined by fitting, that is, the position with the lowest light intensity, and the center light intensity and position of the dark fringe are recorded (I p (n), x(n), y(n)), and further analyze the phase difference and fringe position information to provide a basis for subsequent fringe movement. Combined with the current position parameters, the direction and distance of fringe movement are determined, and then the phase adjustment device is controlled to adjust the phase difference of the two light beams to achieve the movement of interference fringes.

3. The phase-adjustable nulling interference system according to claim 2, characterized in that: The system fits and reconstructs the light intensity distribution of the planet. The reconstruction process uses the fitting method, assuming that the light intensity distribution of the planet is represented by a Gaussian distribution: Among them, I0 is the peak light intensity of the planet, (x0, y0) is the center position of the planet, σ is the standard deviation of the spot, and (I p (n), x(n), y(n)) are fitted to solve the parameters I0, x0, y0 and σ, thereby determining the position and characteristics of the planet.

4. The phase-adjustable nulling interference system according to claim 3, characterized in that: The control device adjusts the phase adjustment device to change the optical path difference ΔL to adjust the phase difference Δφ, so that the interference fringes move in a predetermined direction and distance. The movement amount Δx of the fringes and the change of the phase difference Δφ satisfy the following relationship: Wherein, f is the focal length of the nulling interferometer system, and d is the distance between the first telescope and the second telescope.

5. The phase-adjustable nulling interference system according to claim 4, characterized in that: After each phase adjustment, the position of the moved stripes is recaptured and the new dark stripe center position data is extracted. By adjusting the phase difference and moving the stripes multiple times, the stripe position data obtained under different phase conditions are accumulated to form rich measurement data. These accumulated data are used to fit the Gaussian distribution model, fit and reconstruct the planet's light intensity distribution, and thus obtain complete planetary image information.

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