Single-beam light field stability detection device and method

Abstract

The invention discloses a single-beam light field stability detection device and method, and relates to the technical field of laser. The device comprises a semiconductor laser, a He-Ne laser and a femtosecond laser, a reflecting mirror, a beam expanding mirror, an attenuation piece, a scattering medium, a bonding lens, a CCD camera and a computer used for image information extraction are arranged on emitting light paths of the semiconductor laser, the He-Ne laser and the femtosecond laser, and the semiconductor laser is placed in front of the reflecting mirror to serve as a light field to be measured; according to the invention, the scattering medium is adopted to carry out stable disturbance on the to-be-measured light beam, the optical structure is simplified, the measurement efficiency is improved, the stability change of the semiconductor laser field can be accurately reflected in real time through high-speed acquisition and long-time monitoring of the CCD camera, and the detection accuracy is improved through the detection device and method. The method has the advantages of simplicity and convenience in operation, low cost, wide application range and the like, and can be widely applied to the fields of semiconductor laser production, detection and scientific research and other types of light field stability detection occasions.

Description

Technical Field

[0001] The present invention relates to the field of laser technology, and in particular to a single-beam light field stability detection device and method. Background Art

[0002] Semiconductor lasers have important applications in laser imaging, quantum computing, and optical communications due to their high electro-optical conversion efficiency and compact structure. The stability of the laser output light intensity is crucial to the accuracy and reliability of these applications. In the fields of precision manufacturing and material processing, the stability of laser intensity is extremely critical to achieve precise cutting, welding, or surface treatment. Slight fluctuations in laser intensity may lead to inconsistencies in penetration depth, cutting width, or welding quality, thereby compromising the structural integrity and functional characteristics of the final product.

[0003] To meet this challenge, researchers have developed a variety of detectors to measure the stability of laser intensity. Common laser power meters in laboratories include thermal power meters and quantum power meters, which can monitor the power of continuous wave lasers or the average power of high repetition rate pulsed lasers in real time. Among these detectors, thermal detectors (such as thermopiles and thermoelectric sensors) have a wide spectral response, but the response speed is slow and the cost is high; quantum detectors (especially photodiodes) can measure fluctuations in low power levels due to their high quantum efficiency, so quantum detectors are suitable for use in scenarios that require extremely high precision measurement of intensity fluctuations. In addition, beam profile analysis technology has become an effective tool for evaluating laser intensity stability. This technology involves the use of advanced equipment (such as beam analyzers or charge-coupled devices) to capture the complex spatial distribution of laser intensity on the cross section of the beam. By analyzing these beam profiles, researchers can identify any deviations in intensity fluctuations, so that corrective measures can be taken quickly to ensure the quality of the laser process.

[0004] However, the limitation of detecting intensity alone is obvious, because intensity is only a quantitative measure of light energy, and it cannot obtain the full information of light fluctuations, which is why light field detection technologies (such as optical interferometry or holography) have emerged, which provide unprecedented capabilities to capture and analyze all the characteristics of light. Among these light field detection technologies, optical interferometry can obtain phase differences, revealing tiny changes in the light wavefront that cannot be observed by intensity detectors alone. However, interferometry relies on reference and detection beams, requiring precise alignment and stability of the optical path, which increases the complexity of the experimental setup;

[0005] Another commonly used light field detection technique is holography, which captures the entire wavefront of light, including amplitude and phase information, which also requires a complex experimental setup involving reference and object beams;

[0006] In view of the above problems, the inventors propose a single-beam light field stability detection device and method to overcome the deficiencies in the above technologies. Summary of the invention

[0007] In order to solve the above problems, the purpose of the present invention is to provide a single-beam light field stability detection device and method.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: a single-beam light field stability detection device, the detection device includes a semiconductor laser, a He-Ne laser and a femtosecond laser;

[0009] The emission light paths of the semiconductor laser, He-Ne laser and femtosecond laser are provided with reflectors, beam expanders, attenuation plates, scattering media, cemented lenses, CCD cameras and computers for image information extraction;

[0010] The semiconductor laser is placed in front of the reflector as the light field to be measured;

[0011] The beam expander is placed in front of the attenuation plate, the attenuation plate is placed behind the beam expander, the scattering medium is placed behind the attenuation plate, and the cemented lens is placed behind the scattering medium.

[0012] The scattering medium is any one of a solid material and a thin film material.

[0013] The solid material is any one of a polystyrene plate, a silicon dioxide plate and a titanium dioxide plate, and the film material is any one of a polystyrene film, a silicon dioxide film and a titanium dioxide film.

[0014] The light transmission aperture of the cemented lens is 5-10 cm, and the CCD camera is any one of a scientific research camera and an industrial camera.

[0015] The present invention also provides a method for detecting a single-beam light field stability device, comprising the following steps:

[0016] S1. Calculation of ballistic light and scattered light field intensity

[0017] After the light field to be measured passes through the scattering medium, the outgoing light can be divided into two parts: ballistic light and scattered light. The ballistic light is composed of ballistic photons with the shortest path, and the scattered light is composed of scattered photons with a much longer propagation distance. The ballistic light and scattered light can be expressed as: and

[0018] Where r is a position in three-dimensional space, t is the measurement time, and the total light field It can be expressed as:

[0019]

[0020] In addition, these two light fields can be expressed as complex numbers containing amplitude and phase information as follows:

[0021]

[0022] Among them, in formula (2) and formula (3), and are the amplitudes of the ballistic light wave field and the scattered light wave field, and are the phases of the ballistic light field and the scattered light field, ω is the angular frequency, and the intensity of the detected image It can be calculated by the square of the light field norm;

[0023]

[0024] In formula (4), the first and second terms are the intensities of the ballistic light and scattered light field, respectively, and the last term is the interference term, which determines the light and dark distribution of the speckle pattern. Therefore, the change of speckle intensity includes both amplitude fluctuation and phase fluctuation.

[0025] S2. Analysis of dynamic characteristics of laser field

[0026] By using a CCD camera to record the temporal disturbance of the light field after the laser field passes through the scattering medium as a video, and then converting this video into a sequence of 1800 frames using custom-written software on a computer, we first obtained time series images showing the evolution of the laser field through the scattering medium in time intervals not exceeding 100 seconds;

[0027] S3. Calculation of speckle pattern intensity and contrast

[0028] The intensity and contrast of the speckle pattern at different times are calculated. The intensity of the speckle pattern is defined as:

[0029]

[0030] In formula (5), I(i,j) represents the pixel intensity of the image;

[0031] The contrast (C) of the speckle pattern is defined as:

[0032]

[0033] In formula (6), σ represents the standard deviation of pixel intensity. represents the average intensity of the speckle pattern.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1. In the present invention, by using a scattering medium to stably disturb the light beam to be measured, the optical structure is simplified and the measurement efficiency is improved;

[0036] 2. In the present invention, the stability change of the semiconductor laser field can be reflected in real time and accurately through high-speed acquisition and long-term monitoring of the CCD camera;

[0037] 3. In the present invention, the detection device and method have the advantages of simple operation, low cost, wide application range, etc., and can be widely used in semiconductor laser production, detection, scientific research fields and other types of light field stability detection occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 This is a schematic diagram of the laser light field stability measurement of the present invention.

[0040] Figure 2 This is an image of the laser field of the present invention passing through a scattering medium.

[0041] Figure 3 Schematic diagram of speckle image analysis of the present invention.

[0042] In the figure: 1. Semiconductor laser; 2. Reflector; 3. Beam expander; 4. Attenuation plate; 5. Scattering medium; 6. Cemented lens; 7. CCD camera; 8. Computer. DETAILED DESCRIPTION

[0043] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0044] Example: Figure 1-3 As shown, the present invention provides a single-beam light field stability detection device, the detection device includes a semiconductor laser 1, a He-Ne laser and a femtosecond laser;

[0045] A reflector 2, a beam expander 3, an attenuation plate 4, a scattering medium 5, a cemented lens 6, a CCD camera 7 and a computer 8 for extracting image information are arranged on the emission optical paths of the semiconductor laser 1, the He-Ne laser and the femtosecond laser;

[0046] The semiconductor laser 1 is placed in front of the reflector 2 as the light field to be measured;

[0047] The beam expander 3 is placed in front of the attenuation plate 4, and the attenuation plate 4 is placed behind the beam expander 3. The beam expander 3 has a three-dimensional adjustment function and can better maintain the directional transmission characteristics of the incident light beam. The horizontal and vertical directions of the beam expander 3 require more precise adjustment to reduce the aberration of the light field to be measured. The scattering medium 5 is placed behind the attenuation plate 4. The attenuation plate 4 adjusts the intensity of the light field to be measured to avoid light intensity saturation of the CCD camera 7. The optical depth of the scattering medium 5 can be adjusted according to the actual intensity of the light field to be measured. The cemented lens 6 is placed behind the scattering medium 5.

[0048] The scattering medium 5 is any one of a solid material and a thin film material.

[0049] The solid material is any one of a polystyrene plate, a silicon dioxide plate and a titanium dioxide plate, and the film material is any one of a polystyrene film, a silicon dioxide film and a titanium dioxide film.

[0050] The light transmission aperture of the cemented lens 6 is 5-10 cm, and the CCD camera 7 is any one of a scientific research camera and an industrial camera.

[0051] The present invention also provides a method for detecting a single-beam light field stability device, comprising the following steps:

[0052] S1. Calculation of ballistic light and scattered light field intensity

[0053] After the light field to be measured passes through the scattering medium 5, the outgoing light can be divided into two parts: ballistic light and scattered light. The ballistic light is composed of ballistic photons with the shortest path, and the scattered light is composed of scattered photons with a much longer propagation distance. The ballistic light and the scattered light can be expressed as: and

[0054] Where r is a position in three-dimensional space, t is the measurement time, and the total light field It can be expressed as:

[0055]

[0056] In addition, these two light fields can be expressed as complex numbers containing amplitude and phase information as follows:

[0057]

[0058] Among them, in formula (2) and formula (3), and are the amplitudes of the ballistic light wave field and the scattered light wave field, and are the phases of the ballistic light field and the scattered light field, ω is the angular frequency, and the intensity of the detected image It can be calculated by the square of the light field norm;

[0059]

[0060] In formula (4), the first and second terms are the intensities of the ballistic light and scattered light fields, respectively, and the last term is the interference term, which determines the light and dark distribution of the speckle pattern. Therefore, the change of speckle intensity includes both amplitude fluctuations and phase fluctuations. Compared with the direct intensity detection method, the phase fluctuation amplifies the intensity fluctuation, which improves the sensitivity of laser field stability monitoring.

[0061] S2. Analysis of dynamic characteristics of laser field

[0062] The CCD camera 7 was used to record the disturbance of the light field over time after the laser field passed through the scattering medium 5 in the form of a video. Subsequently, this video was converted into a sequence of 1800 frames using custom-written software on a computer 8. We first obtained time series images showing the evolution of the laser field through the scattering medium 5 in time intervals not exceeding 100 seconds, e.g. Figure 2 As shown ( Figure 2 is the image of the laser field passing through the scattering medium, where Figure 2 (a) t = 0 s; Figure 2 (b) t = 20 s; Figure 2 (c) t = 40 s; Figure 2 (d) t = 60 s; Figure 2 (e) t = 80 s; Figure 2 (f) t = 100s), the speckle image is characterized by granular patterns, and these patterns are composed of randomly distributed bright and dark spots. Figure 2 (a) to Figure 2 (d) Grayscale images show the variation of the speckle pattern. The density of bright spots varies against a uniform gray background. This variation reveals the inherent intensity and phase instabilities of the laser field over time. Figure 2 (e) and Figure 2 (f) shows a similar speckle pattern, indicating an improvement in the intensity and phase stability of the output laser, an observation that highlights the dynamic nature of the laser field and the potential for extracting intensity and phase instabilities through image analysis;

[0063] S3. Calculation of speckle pattern intensity and contrast

[0064] In order to further quantitatively reveal the change of speckle pattern over time, the intensity and contrast of the speckle pattern at different times are calculated. The intensity of the speckle pattern is defined as:

[0065]

[0066] In formula (5), I(i,j) represents the pixel intensity of the image;

[0067] The contrast (C) of the speckle pattern is defined as:

[0068]

[0069] In formula (6), σ represents the standard deviation of pixel intensity. represents the average intensity of the speckle pattern, from Figure 3 It can be seen from (a) that Figure 3 For speckle image analysis, Figure 3 (a) shows the variation of speckle intensity and contrast over time. Figure 3 (b) To highlight the difference in speckle intensity and contrast), the intensity of the speckle pattern first increases and reaches a peak of 1 at 18 seconds. After that, the intensity decreases rapidly and drops to 0.42 at 150 seconds. Subsequently, the intensity of the speckle pattern remains at around 0.4 and fluctuates slightly after 150 seconds, but Figure 3 From the contrast of the speckle pattern shown in (a), the fluctuation of contrast is more obvious than that of intensity, which indicates that contrast can be used to accurately monitor the laser field through the amplification effect of speckle. In order to clearly show the instability of contrast and intensity, the difference in their fluctuation behavior from 220 seconds to 340 seconds is emphasized, as shown in Figure 2. Figure 3 As shown in (b), in addition, the standard deviations of contrast and intensity are calculated respectively. The standard deviations of contrast and intensity fluctuations are 0.0077 and 0.0028 respectively. The standard deviation of contrast fluctuation is about 3 times of the standard deviation of intensity.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A single beam light field stability detection device, characterized in that: The detection device comprises a semiconductor laser (1), a He-Ne laser and a femtosecond laser; A reflector (2), a beam expander (3), an attenuation plate (4), a scattering medium (5), a cemented lens (6), a CCD camera (7) and a computer (8) for extracting image information are provided on the emission light paths of the semiconductor laser (1), the He-Ne laser and the femtosecond laser; The semiconductor laser (1) is placed in front of the reflector (2) as the light field to be measured; The collimator (3) is placed in front of the attenuation plate (4), the attenuation plate (4) is placed behind the collimator (3), the scattering medium (5) is placed behind the attenuation plate (4), and the cemented lens (6) is placed behind the scattering medium (5).

2. A single-beam light field stability detection device as claimed in claim 1, characterized in that: The scattering medium (5) is any one of a solid material and a thin film material.

3. A single-beam light field stability detection device as claimed in claim 2, characterized in that: The solid material is any one of a polystyrene plate, a silicon dioxide plate and a titanium dioxide plate, and the film material is any one of a polystyrene film, a silicon dioxide film and a titanium dioxide film.

4. A single-beam light field stability detection device as claimed in claim 1, characterized in that: The light transmission aperture of the cemented lens (6) is 5 to 10 cm, and the CCD camera (7) is any one of a scientific research camera and an industrial camera.

5. A method for applying the single-beam light field stability detection device according to any one of claims 1 to 4, characterized in that: The steps include: S1. Calculation of ballistic light and scattered light field intensity After the light field to be measured passes through the scattering medium (5), the outgoing light can be divided into two parts: ballistic light and scattered light. The ballistic light is composed of ballistic photons with the shortest path, and the scattered light is composed of scattered photons with a much longer propagation distance. The ballistic light and scattered light can be expressed as: and Where r is a position in three-dimensional space, t is the measurement time, and the total light field It can be expressed as: In addition, these two light fields can be expressed as complex numbers containing amplitude and phase information as follows: Among them, in formula (2) and formula (3), and are the amplitudes of the ballistic light wave field and the scattered light wave field, and are the phases of the ballistic light field and the scattered light field, ω is the angular frequency, and the intensity of the detected image It can be calculated by the square of the light field norm; In formula (4), the first and second terms are the intensities of the ballistic light and scattered light field, respectively, and the last term is the interference term, which determines the light and dark distribution of the speckle pattern. Therefore, the change of speckle intensity includes both amplitude fluctuation and phase fluctuation. S2. Analysis of dynamic characteristics of laser field The temporal disturbance of the light field after the laser field passes through the scattering medium (5) is recorded as a video using a CCD camera (7). Subsequently, this video is converted into a sequence of 1800 frames using custom-written software on a computer (8). We first obtain time series images showing the evolution of the laser field through the scattering medium (5) in time intervals not exceeding 100 seconds; S3. Calculation of speckle pattern intensity and contrast The intensity and contrast of the speckle pattern at different times are calculated. The intensity of the speckle pattern is defined as: In formula (5), I(i,j) represents the pixel intensity of the image; The contrast (C) of the speckle pattern is defined as: In formula (6), σ represents the standard deviation of pixel intensity. represents the average intensity of the speckle pattern.

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