Gaussian spot spatial intensity peak automatic addressing method and device

Abstract

The present invention provides a method and device for automatically addressing the peak value of the spatial intensity of a Gaussian spot. A small-aperture aperture is installed in front of the photodetector to subdivide the measured light beam. The X-Z two-dimensional motion platform is driven by a stepper motor, and the stepper motor is controlled by a motion control card. The aperture is placed close to the center of the spot, and the starting point, direction and step length of the stepper motor are set; after each step, the photodetector measures the light intensity signal, records the position coordinates and the corresponding photodetector signal, and makes a Gaussian fitting curve for the obtained signal intensity and coordinate data to obtain the coordinate x corresponding to the peak intensity of the Gaussian spot in this direction. max ;Fixed x-coordinate max , collect data in the z direction, and fit the obtained data to obtain the peak coordinate z in this direction max ; Move the photodetector to (x max , z max ) is the peak position of the Gaussian light spot. The present invention can efficiently and accurately obtain the peak position coordinates of the Gaussian light spot.

Description

Technical Field

[0001] The invention relates to the field of surface thermal lens measurement, and in particular to a method and device for automatically addressing a Gaussian spot spatial intensity peak value. Background Art

[0002] Surface thermal lens technology is a thermal wave detection method, which is widely used in weak absorption measurement of optical films and in vivo defect detection. It uses Gaussian-shaped detection light that is larger than the pump spot for measurement. It has good stability and is easy to adjust, so it is widely favored by people.

[0003] The principle of surface thermal lens technology is that the intensity-modulated pump laser converges and incidents on the surface of the thin film sample. The thin film absorbs heat and diffuses it to the substrate, causing the temperature of the thin film system to rise. The temperature rise causes thermal expansion to form a "surface heat bag", which is also called "photothermal deformation". The existence of the heat bag further modulates the intensity distribution change of the detection beam, that is, the photothermal signal. In actual measurement, the detection laser needs to coincide with the pump laser, and the spot of the detection laser on the thin film sample must be equivalent to or larger than the spot of the pump laser. In order to maximize the signal and improve the measurement limit, the pump laser needs to be focused by the lens and irradiated on the surface of the thin film sample. Therefore, the pump laser spot size is usually small; similarly, in order to increase the signal, the peak position of the detection laser and the pump laser should coincide as much as possible, so that the heat bag is in the center area of ​​the detection spot; accordingly, the photodetector needs to find the peak position of the detection laser to ensure the accuracy of the measurement.

[0004] Among the current testing methods, some need to collect the intensity information of the entire light spot, and then find the position of the center of the light spot through post-data processing. Although the accuracy is high, the efficiency is low. Some find the peak position of the Gaussian light spot by manually adjusting the detector position. This method is complicated to operate and inefficient, and cannot guarantee the measurement accuracy. At the same time, due to the differences between different operators, human errors are introduced, and even the same operator has poor repeatability of measurement results due to different states. Based on the above problems, it is particularly important to find a method and device that can automatically adjust the position of the photoelectric detector and efficiently and accurately obtain the coordinates of the peak position of the Gaussian light spot.

[0005] At present, no description or report of similar technology to the present invention has been found, and similar information at home and abroad has not been collected yet. Summary of the invention

[0006] To solve the above problems, the present invention proposes a method and device for automatically addressing the spatial intensity peak of a Gaussian spot, which can efficiently and accurately obtain the coordinates of the peak position of the Gaussian spot and accurately position the photoelectric detector to the peak position of the Gaussian spot.

[0007] According to one aspect of the present invention, a method for automatically addressing a Gaussian spot spatial intensity peak is provided, comprising:

[0008] The XZ two-dimensional motion platform, the motion control card and the computer are sequentially arranged on the reflection detection optical path of the pump light and the detection light passing through the sample to be tested; the aperture is installed at the front end of the photodetector; and the photodetector is installed on the XZ two-dimensional motion platform;

[0009] The diameter of the detection spot is known to be D. The position of the photodetector is roughly adjusted according to the position of the spot so that the center of the spot is roughly located at the center of the aperture at the front end of the photodetector. At this time, the position coordinates of the photodetector are marked as (x0, z0);

[0010] The z-axis position is fixed, and the computer sets the motion control card to move from (x0-D / 2) to (x0+D / 2) along the x-axis with a step length of D / 20. The photoelectric detector outputs a light intensity signal for each step length, and the computer records the signal intensity and the corresponding coordinate information.

[0011] The computer fits the recorded signal intensity and the corresponding coordinate information into a Gaussian curve, and calculates the x-axis coordinate x corresponding to the peak value of the Gaussian curve. max Set to the motion control card, the motion control card controls the photoelectric detector to move along the x-axis to (x max , z0);

[0012] The x-axis position is fixed and the computer sets the motion control card to move from (z o -D / 2) moves to (z0+D / 2) with a step length of D / 20, and each time it moves a step length, the photodetector outputs a light intensity signal, and the computer records the signal intensity and the corresponding coordinate information;

[0013] The computer fits the recorded signal intensity and the corresponding coordinate information into a Gaussian curve, and calculates the z-axis coordinate z corresponding to the peak value of the Gaussian curve. max Set to the motion control card, the motion control card controls the photoelectric detector to move along the z-axis to (x max , z max );(x max , z max ) is the coordinate of the peak position of the Gaussian spot spatial intensity;

[0014] According to the spot size and actual accuracy requirements, the step size is changed and the above process is repeated and iterated multiple times to complete the automatic addressing of the Gaussian spot spatial intensity peak.

[0015] According to another aspect of the present invention, there is provided a Gaussian spot spatial intensity peak automatic addressing device for implementing the above-mentioned Gaussian spot spatial intensity peak automatic addressing method, comprising: a pump optical path device, a detection optical path device, an XZ two-dimensional motion platform, a photodetector, an aperture, a first stepper motor, a second stepper motor, a motion control card and a computer; wherein:

[0016] The pump light output by the pump light path device vertically illuminates the sample to be tested;

[0017] The detection light output by the detection light path device illuminates the sample to be tested at a nearly vertical angle;

[0018] The XZ two-dimensional motion platform, motion control card and computer are sequentially arranged on the reflection detection light path passing through the sample to be tested;

[0019] The aperture is installed at the front end of the photoelectric detector;

[0020] The photoelectric detector is mounted on the XZ two-dimensional motion platform;

[0021] The first stepper motor and the second stepper motor are drivingly connected to the XZ two-dimensional motion platform and are control-connected to the motion control card;

[0022] The input end of the motion control card and the output end of the photoelectric detector are respectively connected to a computer.

[0023] Optionally, the first stepper motor and the second stepper motor drive the XZ two-dimensional motion platform to automatically move in two directions of the X axis and the Z axis with a set step length.

[0024] Optionally, the aperture is used to filter the reflected detection light.

[0025] Due to the adoption of the above technical solution, the present invention has at least one of the following beneficial effects compared with the prior art:

[0026] The method and device for automatically addressing the peak value of the spatial intensity of a Gaussian light spot provided by the present invention can realize the calculation of the coordinates of the peak value of the spatial intensity of a Gaussian light spot and automatically adjust the detector to the peak position.

[0027] The method and device for automatically addressing the spatial intensity peak value of a Gaussian spot provided by the present invention have a simple device structure and are improved on the basis of an existing surface thermal lens technology measurement device. The corresponding functions can be realized by adding a stepper motor and a motion control card.

[0028] The method and device for automatically addressing the spatial intensity peak of a Gaussian spot provided by the present invention have low initial adjustment requirements, and the addressing operation can be iterated and repeated multiple times. The addressing efficiency and accuracy are balanced according to actual needs, and the measurement of the peak coordinates of the Gaussian spot is finally achieved, and the detector is automatically positioned to the peak coordinates.

[0029] The Gaussian spot spatial intensity peak automatic addressing method and device provided by the present invention can automatically adjust the position of the photoelectric detector to efficiently and accurately obtain the Gaussian spot peak position coordinates and move the photoelectric detector to the peak position. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0031] Figure 1 The figure is a flowchart of the automatic addressing method for the spatial intensity peak value of a Gaussian spot in one embodiment of the present invention.

[0032] Figure 2 Schematic diagram of the structure of a Gaussian spot spatial intensity peak automatic addressing device in one embodiment of the present invention.

[0033] Figure 3 It is a schematic diagram of the principle of automatic addressing of the spatial intensity peak of a Gaussian spot in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0034] The following is a detailed description of the embodiments of the present invention: This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

[0035] Figure 1 A flowchart of a method for automatically addressing a Gaussian spot spatial intensity peak value provided by an embodiment of the present invention.

[0036] like Figure 1 As shown, the Gaussian spot spatial intensity peak automatic addressing method provided in this embodiment may include the following steps:

[0037] S000, the XZ two-dimensional motion platform 4, the motion control card 9 and the computer 10 are sequentially arranged on the reflection detection optical path of the pump light and the detection light passing through the sample to be tested 3; the aperture 7 is installed at the front end of the photodetector 8; the photodetector 8 is installed on the XZ two-dimensional motion platform 4;

[0038] S100, the diameter of the detection light spot is known to be D, and the position of the photodetector 8 is roughly adjusted according to the position of the light spot, so that the center of the light spot is roughly located at the center of the small aperture 7 in front of the photodetector. At this time, the position coordinates of the photodetector 8 are marked as (x0, z0);

[0039] S200, the z-direction position is fixed, and the computer 10 sets the motion control card 9 to move from (x0-D / 2) to (x0+D / 2) in the x-direction with a step length of D / 20, and each time it moves a step length, the photoelectric detector 8 outputs a light intensity signal, and the computer 10 records the signal intensity and the corresponding coordinate information;

[0040] S300, the computer 10 fits the recorded signal strength and the corresponding coordinate information to a Gaussian curve, and calculates the x coordinate x corresponding to the peak of the Gaussian curve. max Set to the motion control card 9, the motion control card 9 controls the photoelectric detector 8 to move along the x-axis direction to (x max , z0);

[0041] S400, the x-direction position is fixed, and the computer 10 sets the motion control card 9 to move from (z0-D / 2) to (z0+D / 2) in the z direction with a step length of D / 20, and each time it moves a step length, the photodetector 8 outputs a light intensity signal, and the computer 10 records the signal intensity and the corresponding coordinate information;

[0042] S500, the computer 10 fits the recorded signal strength and the corresponding coordinate information to a Gaussian curve, and calculates the z coordinate z corresponding to the peak of the Gaussian curve. max Set to the motion control card 9, the motion control card 9 controls the photoelectric detector 8 to move along the z-axis direction to (x max , z max ). (x max , z max ) is the coordinate of the peak position of the Gaussian spot spatial intensity;

[0043] S600, (x max , z max ) as (x0, z0), change the step size multiple times, and repeat the above steps to improve the addressing accuracy of the Gaussian spot spatial intensity peak. In a specific application example, the step size can be changed to D / 30.

[0044] Figure 2 The schematic diagram of the structure of the Gaussian spot spatial intensity peak automatic addressing device provided by one embodiment of the present invention is used to implement the Gaussian spot spatial intensity peak automatic addressing method provided by the above embodiment of the present invention.

[0045] like Figure 2As shown, the Gaussian spot spatial intensity peak automatic addressing device provided in this embodiment includes a pump optical path device 1, a detection optical path device 2, an XZ two-dimensional motion platform 4, a photodetector 8, a small-aperture aperture 7 arranged at the front end of the photodetector, a first stepper motor 5 and a second stepper motor 6 for driving the XZ two-dimensional motion platform, a motion control card 9 and a computer 10.

[0046] The pump light output by the pump light path device 1 irradiates the sample 3 to be tested vertically, and the detection light output by the detection light path device 2 irradiates the sample 3 to be tested at a nearly vertical angle. On the reflection detection light path passing through the sample 3 to be tested, an XZ two-dimensional motion platform 4, a motion control card 9 and a computer 10 are sequentially arranged. A photodetector 8 equipped with a small-aperture aperture 7 is installed on the XZ two-dimensional motion platform 4. The XZ two-dimensional motion platform 4 is driven by a first stepper motor 5 and a second stepper motor 6, and the first stepper motor 5 and the second stepper motor 6 are controlled by a motion control card 9, and the input end of the motion control card 9 and the output end of the photodetector 8 are respectively connected to the computer 10.

[0047] In a preferred embodiment, the first stepper motor 5 and the second stepper motor 6 drive the XZ two-dimensional motion platform 4 to automatically move in the X-axis and Z-axis directions with a set step length, and then drive the photoelectric detector 8 to automatically move in the X-axis and Z-axis directions with a set step length.

[0048] The method and device provided by the above embodiments of the present invention work as follows:

[0049] Gaussian spot is the most common form of spatial distribution of beam intensity. Gaussian spot is usually distributed in a circle with circular symmetry. The light intensity at the center is the largest. As the distance from the center increases, the light intensity decreases according to the Gaussian function. Based on the above characteristics, the two coordinates of the peak position of the Gaussian spot can be separated into variables and processed separately.

[0050] Therefore, when measuring, it is only necessary to roughly adjust the position of the detector to pass through part of the light spot without accurately passing through the center of the light spot. The light intensity on the test axis still satisfies the Gaussian or quasi-Gaussian distribution, and the center coordinates corresponding to this direction can be obtained through Gaussian fitting. After fixing the detector at this coordinate, scanning the intensity distribution in another direction can pass through the center of the light spot relatively accurately.

[0051] In the method and device provided by the above embodiment of the present invention, a small-aperture diaphragm needs to be installed in front of the photodetector to subdivide the measured light beam (since the upper and lower bottom surfaces of the sample may reflect light, there may be more than one light beam reflected by the detection light, so a small-aperture diaphragm is used to subdivide the required reflected light beam), and the XZ two-dimensional motion platform is driven by a stepper motor, and the stepper motor is controlled by a motion control card. First, roughly adjust the position of the detector so that the diaphragm is close to the center of the light spot, and then set the starting point, direction and step length of the stepper motor; during the movement, the photodetector measures the light intensity signal once after each step, and the computer records the position coordinates and the corresponding photodetector signal; after the photodetector completes the data collection in the x direction, a Gaussian fitting curve is made for the above-mentioned signal intensity and coordinate data to obtain the coordinate x corresponding to the peak intensity of the Gaussian light spot in this direction. max ; Then fix the x direction coordinate x max , collect data in the z direction, and fit the obtained data to obtain the peak coordinate z in this direction max ; Finally, move the photodetector to (x max , z max ) is the peak position of the Gaussian spot.

[0052] Experiments have shown that the method and device provided by the above embodiment of the present invention are simple and easy to implement, and can realize automatic adjustment of the position of the photodetector and set the moving step size according to the actual spot size and measurement requirements. By repeating the above addressing process many times, the peak position coordinates of the Gaussian spot can be obtained efficiently and accurately.

[0053] All matters not covered in the above embodiments of the present invention are well known in the art.

[0054] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for automatically finding the peak value of the spatial intensity of a Gaussian spot, characterized in that: include: The XZ two-dimensional motion platform (4), the motion control card (9) and the computer (10) are sequentially arranged on the reflection detection light path of the pump light and the detection light passing through the sample to be tested (3); the aperture (7) is installed at the front end of the photodetector (8); and the photodetector (8) is installed on the XZ two-dimensional motion platform (4); It is known that the diameter of the detection light spot is D. The position of the photodetector (8) is roughly adjusted according to the position of the light spot so that the center of the light spot is approximately located at the center of the aperture (7) at the front end of the photodetector (8). At this time, the position coordinates of the photodetector (8) are marked as (x0, z0); The position in the z-axis direction is fixed and unchanged, and the motion control card (9) is set by the computer (10) to move from (x0-D / 2) to (x0+D / 2) in the x-axis direction with a step length of D / 20, and each time a step length is moved, the photoelectric detector (8) outputs a light intensity signal, and the computer (10) records the signal intensity and the corresponding coordinate information; The computer (10) fits the recorded signal strength and the corresponding coordinate information to form a Gaussian curve, and calculates the x-axis coordinate x corresponding to the peak value of the Gaussian curve. max The motion control card (9) controls the photoelectric detector (8) to move along the x-axis to (x max , z0); The x-axis position is fixed and unchanged, and the motion control card (9) is set by the computer (10) to move from (z0-D / 2) to (z0+D / 2) along the z-axis direction with a step length of D / 20, and each time a step length is moved, the photoelectric detector (8) outputs a light intensity signal, and the computer (10) records the signal intensity and the corresponding coordinate information; The computer (10) fits the recorded signal intensity and the corresponding coordinate information into a Gaussian curve, and calculates the z-axis coordinate z corresponding to the peak value of the Gaussian curve. max The motion control card (9) controls the photoelectric detector (8) to move along the z-axis to (x max , z max );(x max , z max ) is the coordinate of the peak position of the Gaussian spot spatial intensity; According to the spot size and actual accuracy requirements, the step size is changed and the above process is repeated and iterated multiple times to complete the automatic addressing of the Gaussian spot spatial intensity peak.

2. A Gaussian spot spatial intensity peak automatic addressing device for implementing the Gaussian spot spatial intensity peak automatic addressing method according to claim 1, characterized in that: include: A pump optical path device (1), a detection optical path device (2), an XZ two-dimensional motion platform (4), a photoelectric detector (8), an aperture (7), a first stepper motor (5), a second stepper motor (6), a motion control card (9) and a computer (10); wherein: The pump light output by the pump light path device (1) vertically irradiates the sample to be tested (3); The detection light output by the detection light path device (2) irradiates the sample to be tested (3) at a nearly vertical angle; The XZ two-dimensional motion platform (4), motion control card (9) and computer (10) are sequentially arranged on a reflection detection light path passing through the sample to be tested (3); The aperture (7) is installed at the front end of the photoelectric detector (8); The photoelectric detector (8) is mounted on the XZ two-dimensional motion platform (4); The first stepper motor (5) and the second stepper motor (6) are drivingly connected to the XZ two-dimensional motion platform (4), and are control-connected to the motion control card (9); The input end of the motion control card (9) and the output end of the photoelectric detector (8) are respectively connected to the computer (10).

3. The Gaussian spot spatial intensity peak automatic addressing device according to claim 2, characterized in that: The first stepper motor (5) and the second stepper motor (6) drive the XZ two-dimensional motion platform (4) to automatically move in the X-axis and Z-axis directions at a set step length.

4. The Gaussian spot spatial intensity peak automatic addressing device according to claim 2, characterized in that: The aperture (7) is used to filter the reflected detection light.

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