A spectral uniformity target simulation system of a certain output power and a design method thereof

Abstract

This invention relates to optical systems and their design methods, specifically to a spectrally uniform target simulation system and its design method with a specific output power. This system addresses the shortcomings of existing broadband simulated light sources, which focus on meeting standard requirements for irradiance ratios across different wavelengths while neglecting the influence of variations in light source radiance with different wavelengths. This results in an inability to simulate spatially spectrally uniform targets under complex environments. The spectrally uniform target simulation system and its design method with a specific output power include a light source module, a spectral homogenization module, an attenuation module, and a target simulation module. It can accurately simulate power within a specific output range under varying degrees of spatial environmental complexity and reduce analytical errors caused by differences in the spectral uniformity of the target.

Description

Technical Field

[0001] This invention relates to optical systems and their design methods, specifically to a spectral uniformity target simulation system with a specific output power and its design method. Background Technology

[0002] When spacecraft are in orbit, they face varying degrees of complexity in the space environment. To ensure their normal operation, accurate ground simulations of certain space scenarios are necessary. The key lies in understanding the background power requirements and the spectral characteristics of the target. When identifying targets and extracting crucial information, the spectral characteristics of the simulated light source need to be shaped and homogenized to prevent deviations in the simulation results due to spectral differences. Secondly, the radiation intensity is constant under certain special space backgrounds; therefore, the system output power needs to be designed during ground simulations, for example, to simulate the intensity of solar radiation outside the atmosphere or the signal strength at the receiver during satellite communication.

[0003] Traditional broadband simulation light sources are generally halogen lamps (such as xenon lamps) and LEDs, often used to match the target spectrum (such as the sun). The focus is on achieving the required irradiance ratio across different wavelengths, without considering the influence of wavelength variations on the light source's radiance. However, as the target environments to be simulated become increasingly complex, broadband, high-power laser sources are being used more widely. For broadband, high-power lasers, the output light is broadband, with each wavelength contributing differently to the output beam's spectrum, resulting in varying spectral transmittance for each wavelength. Furthermore, as the output laser power increases, its spectral characteristics change, affecting the final analysis results. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing broadband simulated light sources, which focus on meeting standard requirements for the irradiance ratio in different wavelength bands while ignoring the influence of light source radiance variations with different wavelengths, thus failing to achieve spatially uniform target simulation in complex environments. This invention provides a spectral uniform target simulation system with specific output power and its design method.

[0005] To address the shortcomings of the existing technology, the present invention provides the following technical solution:

[0006] A target simulation system with specific output power and uniform spectral strength is characterized by comprising a light source module, a spectral homogenization module, an attenuation module, and a target simulation module arranged sequentially along the optical path.

[0007] The spectral homogenization module includes a collimating lens, a spectral homogenization filter, and a focusing lens arranged sequentially along the optical path. The collimating lens is used to collimate the output beam of the light source module. The spectral homogenization filter is used to homogenize the spectral intensity differences of the output beam from the collimating lens. The focusing lens is used to converge the output beam from the spectral homogenization filter.

[0008] The attenuation module is used to attenuate the output beam of the spectral homogenization module in order to output a beam with a specific power.

[0009] The target simulation module is used to collimate the output beam of the attenuation module in order to output an optical target of the required size at infinity.

[0010] Furthermore, this invention also provides a design method for a spectral uniformity target simulation system with the aforementioned specific output power, characterized by the following steps:

[0011] Step 1: Select the operating wavelength λ and output power P of the light source module;

[0012] The operating band λ is greater than or equal to the spectral range [λ1, λ2] of the target to be simulated, and the output power P satisfies the following condition: the system output power Y after the output beam of the light source module passes through each subsequent module is greater than or equal to twice the maximum required power.

[0013] Step 2: Design the spectral homogenization filter and spectral homogenization module;

[0014] Step 2.1: Obtain the relationship between the spectral radiance of the light source module and the operating wavelength λ and output power P, L(λ, P);

[0015] Step 2.2: Calculate the ideal transmittance curve of the spectral homogenization filter in the spectral range [λ1, λ2];

[0016] Step 2.3: Obtain the coating tolerance curve based on the ideal transmittance curve from Step 2.2;

[0017] Step 2.4: Process the coating to obtain the spectral homogenization filter, evaluate the performance of the spectral homogenization filter, and record the processing error;

[0018] Step 3: Establish the spectral uniformity target simulation system without the attenuation module;

[0019] Step 4: Measure the system output power Y1 of the spectral uniform target simulation system established in Step 3, and perform curve fitting on the output power P of the light source module and the system output power Y1 to obtain Y1 = f(P);

[0020] Step 5: Add an attenuation module to the spectral uniformity target simulation system established in Step 3;

[0021] Step 6: Design the transmittance of each attenuation element in the attenuation module;

[0022] Step 7: Measure the system output power Y2 = f(P) × T of the spectral uniform target simulation system established in Step 5; where T is the transmittance of the attenuation module.

[0023] Step 8: Calculate the system spectral power ratio τ of the spectral uniformity target simulation system established in Step 5;

[0024] Step 9: By switching the attenuator of the attenuation module and controlling the output power P of the light source module, the spectral uniform target simulation system can realize the spectral uniformity of the infinitely far target within a specific continuous power range. The final system output power Y3 = f(P) × T × τ.

[0025] Further, step 2.2 specifically includes:

[0026] Step 2.2.1: Divide the range of output power P into discrete intervals to obtain a set of i output power points arranged from smallest to largest;

[0027] Step 2.2.2: Take the spectral radiance of the first output power point in the set within the spectral range [λ1, λ2] as the initial value, and calculate the corresponding initial transmittance curve;

[0028] Step 2.2.3: Substitute the spectral radiance of the remaining output power points in the set of Step 2.2.1 within the spectral range [λ1, λ2] into the initial transmittance curve of Step 2.2.2, calculate the spectral uniformity corresponding to each output power point, obtain the output power points that meet the preset spectral uniformity requirements, and determine the power applicability range corresponding to the initial transmittance curve of Step 2.2.2.

[0029] Step 2.2.4: Determine whether the power applicability range corresponding to the i initial transmittance curves has been obtained. If yes, proceed to step 2.2.5; otherwise, return to step 2.2.1, delete the first output power point in the set of step 2.2.1, take the second output power point as the first output power point, and then proceed to step 2.2.2.

[0030] Step 2.2.5: Select the initial transmittance curve corresponding to the largest power applicability range P1~P2 as the ideal transmittance curve of the spectral homogenization filter in the spectral range [λ1, λ2].

[0031] Furthermore, step 2.4 specifically includes:

[0032] Step 2.4.1: Design the film system using coating software and perform coating to obtain a spectral homogenization filter;

[0033] Step 2.4.2: Use a spectrophotometer to test the transmittance curve of the spectral homogenization filter. Quantify the coating error by comparing the actual transmittance of the spectral homogenization filter in the spectral range [λ1, λ2] with the average root mean square error of the maximum tolerance and minimum tolerance of the coating tolerance curve.

[0034] Step 2.4.3: Use a spectroradiometer to test the spectral homogenization effect of the spectral homogenization filter. Use the mean value of the spectral uniformity at different output power points in the spectral range [λ1, λ2] to represent the spectral uniformity of the system. Conduct an overall assessment and record the processing errors as follows:

[0035]

[0036] Where i represents the i-th output power point, j represents the j-th wavelength point within the spectral range [λ1, λ2], and T ij represents the transmittance of the spectral homogenization filter at the j-th wavelength point within the spectral range [λ1, λ2] under the condition of the i-th output power point, and n represents the number of output power points of the light source module selected within the range of P1 to P2 during the test.

[0037] Further, step 4 specifically involves: placing the off-axis parabolic mirror in front of the light output port of the spectral uniformity target simulation system without the attenuation module; using an optical power meter to test the system output power Y1 at the focal plane of the parabolic mirror; recording the power P3 received by the optical power meter and the output power P of the light source module; calibrating the reflectivity R of the parabolic mirror; and determining the system output power Y1 = P3 / R.

[0038] By performing curve fitting on the output power P of the light source module and the system output power Y1, we obtain Y1 = f(P).

[0039] Further, step 6 specifically involves: the attenuation module having N attenuation elements with transmittances of T1, T2, ..., T... N The transmittance of each attenuator satisfies the following formula:

[0040]

[0041] in, These represent the minimum and maximum system output power corresponding to the use of the first attenuator, respectively. These represent the minimum and maximum system output power corresponding to the use of the second attenuator, respectively. These represent the minimum and maximum system output power corresponding to the use of the Nth attenuator, respectively; α is the output power coefficient required by the target to be simulated; N is greater than 2.

[0042] Further, step 8 specifically involves: using a spectroradiometer to perform tests at the output port of the spectral uniformity target simulation system, and calculating the spectral energy percentage τ within the spectral range [λ1, λ2].

[0043]

[0044] Where n′ represents the number of points selected for the output power of the light source module within the spectral range [λ1, λ2].

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] (1) The present invention provides a target simulation system with specific output power and spectral uniformity, including a light source module, a spectral homogenization module, an attenuation module and a target simulation module. It can accurately simulate the power of a specific output range when faced with the influence of spatial environment backgrounds of different complexity, and can reduce the result analysis error caused by the difference in the spectral uniformity of the target.

[0047] (2) The design method of the spectral uniformity target simulation system with a specific output power of the present invention fully considers the variation of light source radiance with different wavelengths compared with the traditional design, and is more suitable for spectral uniformity target simulation with a high power output range. In addition, the design of the spectral homogenization filter of the present invention is carried out for each working wavelength point, and the actual manufacturability of the spectral homogenization filter is guaranteed by tolerance control design. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of an embodiment of a spectral uniformity target simulation system with a specific output power according to the present invention;

[0049] Figure 2 This is a flowchart illustrating an embodiment of a design method for a spectral uniformity target simulation system with a specific output power according to the present invention.

[0050] The reference numerals in the attached diagram are explained as follows: 1-Light source module; 2-Spectral homogenization module; 21-Collimating lens; 22-Spectral homogenization filter; 23-Focusing lens; 3-Attenuation module; 4-Target simulation module. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and exemplary embodiments.

[0052] Reference Figure 1 A target simulation system with specific output power and uniform spectral performance includes a light source module 1, a spectral homogenization module 2, an attenuation module 3, and a target simulation module 4 arranged sequentially.

[0053] The light source module 1 uses a laser, specifically a C-band high-power continuous output fiber laser with a maximum output power of 2.4W.

[0054] The spectral homogenization module 2 includes a collimating lens 21, a spectral homogenization filter 22, and a focusing lens 23 arranged sequentially along the optical path. The collimating lens 21 is used to collimate the output beam of the light source module 1, the spectral homogenization filter 22 is used to homogenize the spectral intensity difference of the output beam of the collimating lens 21, and the focusing lens 23 is used to converge the output beam of the spectral homogenization filter 22.

[0055] The attenuation module 3 employs an attenuation target wheel with four attenuators to attenuate the output beam of the spectral homogenization module 2, thereby outputting a beam with a specific power. In this embodiment, the transmittances of the four attenuators are 0.5, 0.25, 0.11, and 0.05, respectively. The transmittance of the attenuation module 3 is 1 when no attenuators are used.

[0056] The target simulation module 4 uses a collimating objective lens to collimate the output beam of the attenuation module 3 in order to output an optical target of the required size at infinity.

[0057] Reference Figure 2 A design method for a spectrally uniform target simulation system with a specific output power as described above includes the following steps:

[0058] Step 1: Select the operating wavelength λ and output power P of light source module 1;

[0059] The operating band λ is greater than or equal to the spectral range [λ1, λ2] of the target to be simulated, and the output power P satisfies the following: the system output power Y of the output beam of the light source module 1 after passing through each subsequent module is greater than or equal to twice the maximum required power;

[0060] In this embodiment, the spectral range of the target to be simulated is [λ1, λ2] [1540nm, 1560nm], the working band λ of the light source module 1 is [1530nm, 1570nm], and the output power P can reach 2.4W;

[0061] Step 2: Design the spectral homogenization filter 22 and the spectral homogenization module 2;

[0062] Step 2.1: Obtain the relationship L(λ, P) between the spectral radiance of light source module 1 and the working wavelength λ and output power P;

[0063] Step 2.2: Calculate the ideal transmittance curve of the spectral homogenization filter 22 in the spectral range [λ1, λ2];

[0064] Step 2.2.1: Divide the range of output power P into discrete intervals to obtain a set of i output power points arranged from smallest to largest;

[0065] Step 2.2.2: Take the spectral radiance of the first output power point in the set within the spectral range [λ1, λ2] as the initial value, and calculate the corresponding initial transmittance curve;

[0066] Step 2.2.3: Substitute the spectral radiance of the remaining output power points in the set of Step 2.2.1 within the spectral range [λ1, λ2] into the initial transmittance curve of Step 2.2.2, calculate the spectral uniformity corresponding to each output power point, obtain the output power points that meet the preset spectral uniformity requirements, and determine the power applicability range corresponding to the initial transmittance curve of Step 2.2.2.

[0067] Step 2.2.4: Determine whether the power applicability range corresponding to the i initial transmittance curves has been obtained. If yes, proceed to step 2.2.5; otherwise, return to step 2.2.1, delete the first output power point in the set of step 2.2.1, take the second output power point as the first output power point, and then proceed to step 2.2.2.

[0068] Step 2.2.5: Select the initial transmittance curve corresponding to the largest power applicability range P1~P2 as the ideal transmittance curve of the spectral homogenization filter 22 in the spectral range [λ1, λ2].

[0069] Step 2.3: Obtain the coating tolerance curve based on the ideal transmittance curve from Step 2.2;

[0070] Step 2.4: Process the coating to obtain the spectral homogenizing filter 22, evaluate the performance of the spectral homogenizing filter 22, and record the processing error;

[0071] Step 2.4.1: Design the film system using coating software and perform coating to obtain the spectral homogenization filter 22.

[0072] Step 2.4.2: Use a spectrophotometer to test the transmittance curve of the spectral homogenization filter 22. Quantify the coating error by comparing the actual transmittance of the spectral homogenization filter 22 in the spectral range [λ1, λ2] with the average root mean square error of the maximum tolerance and minimum tolerance of the coating tolerance curve.

[0073] Step 2.4.3: The spectral homogenization effect of the spectral homogenization filter 22 is tested using a spectroradiometer. The mean value of the spectral uniformity at different output power points in the spectral range [λ1, λ2] is used to represent the spectral uniformity of the system. Conduct an overall assessment and record the processing errors as follows:

[0074]

[0075] Where i represents the i-th output power point, j represents the j-th wavelength point within the spectral range [λ1, λ2], and T ij The transmittance of the spectral homogenization filter 22 at the j-th wavelength point within the spectral range [λ1, λ2] under the condition of the i-th output power point, and n represents the number of output power points of the light source module 1 selected within the range of P1 to P2 during the test;

[0076] Step 3: Establish the spectral uniformity target simulation system without attenuation module 3. The aperture of the spectral uniformity target simulation system is Φ200mm, F # It is 4;

[0077] Step 4: Measure the system output power Y1 of the spectral uniform target simulation system established in Step 3, and perform curve fitting on the output power P of the light source module 1 and the system output power Y1 to obtain Y1 = f(P);

[0078] Place the off-axis parabolic mirror in front of the light output port of the spectral uniformity target simulation system without attenuation module 3, ensuring that it does not block the light reflected to the detector during the test. Use an optical power meter to test the system output power Y1 at the focal plane of the parabolic mirror, and record the power P3 received by the optical power meter and the output power P of the light source module 1. The reflectivity R of the parabolic mirror is calibrated, and the system output power Y1 = P1 / R.

[0079] Curve fitting was performed on the output power x of light source module 1 and the system output power Y, yielding Y = f(x) = 7 × 10 - 6 P1 2 +0.0637P1-2.3543;

[0080] Step 5: Add attenuation module 3 to the spectral uniformity target simulation system established in step 3;

[0081] Step 6: Design the transmittance of each attenuation element in attenuation module 3;

[0082] Attenuation module 3 has four attenuation elements with transmittances of T1 = 0.5, T2 = 0.25, T3 = 0.11, and T4 = 0.05, respectively. When no attenuation elements are used, the transmittance of attenuation module 3 is T0 = 1. The transmittance of each attenuation element on the attenuation target wheel satisfies the following formula:

[0083]

[0084] in, These represent the minimum and maximum system output power corresponding to the use of the 4th attenuator, respectively; α is the output power coefficient required by the target to be simulated, and α is 10%.

[0085] Step 7: Measure the system output power Y2 = f(P) × T of the spectral uniform target simulation system established in Step 5; where T is the transmittance of attenuation module 3.

[0086] Step 8: Calculate the system spectral power ratio τ of the spectral uniformity target simulation system established in Step 5;

[0087] The spectral energy percentage τ within the spectral range [λ1, λ2] was calculated by using a spectroradiometer at the light output port of the spectral uniformity target simulation system.

[0088]

[0089] Where n′ represents the number of output power points of light source module 1 selected within the spectral range [λ1, λ2];

[0090] Step 9: By switching the attenuator of attenuation module 3 and controlling the output power P of light source module 1, the spectral uniform target simulation system can realize the spectral uniform infinite distance target simulation within a specific continuous power range. Finally, the system output power Y3 = f(P) × T × τ.

[0091] In this embodiment, there are five power output ranges: 2-5mW, 5-12mW, 12-25mW, 25-50mW, and 50-130mW, which correspond to five transmittances T0=1, T1=0.5, T2=0.25, T3=0.11, and T4=0.05, respectively.

Claims

1. A method of designing a spectral uniformity target simulation system of a specific output power, characterized in that, The system includes a light source module, a spectral homogenization module, an attenuation module, and a target simulation module arranged sequentially along the optical path; The spectral homogenization module includes a collimating lens, a spectral homogenization filter, and a focusing lens arranged sequentially along the optical path. The design method includes the following steps: Step 1, selecting the operating wavelength band of the light source module and output power ; The working waveband The spectral range of the target to be simulated The output power The system output power after the output light beam of the light source module passes through each subsequent module Greater than or equal to twice the maximum required power Step 2: Design the spectral homogenization filter and spectral homogenization module; Step 2.1, obtaining the relationship between the spectral radiance of the light source module and the working waveband and output power ;​ Step 2.2: Calculate the spectral homogenization filter in the spectral range [ The ideal transmittance curve; Step 2.2.1, Discretizing the range of output power to obtain a set of output power points arranged from small to large, which consists of N output power points. Step 2.2.2, Selecting the output power point with the maximum output power from the set of output power points. Step 2.2.3, Selecting the output power point with the minimum output power from the set of output power points. Step 2.2.2: The first output power point in the set is within the spectral range [ Using the spectral radiance within the range as the initial value, calculate the corresponding initial transmittance curve; Step 2.2.3: Sequentially assign the remaining output power points from the set in Step 2.2.1 to the spectral range [ Substitute the spectral radiance within the range into the initial transmittance curve in step 2.2.2, calculate the spectral uniformity corresponding to each output power point, obtain the output power points that meet the preset spectral uniformity requirements, and determine the power applicability range corresponding to the initial transmittance curve in step 2.2.

2. Step 2.2.4: Determine whether it has been obtained. If the power applicability range corresponding to the initial transmittance curve is within a certain range, then proceed to step 2.2.5; otherwise, return to step 2.2.1, delete the first output power point in the set of step 2.2.1, take the second output power point as the first output power point, and then proceed to step 2.2.

2. Step 2.2.5: Select the largest power applicability range The corresponding initial transmittance curve serves as the spectral homogenization filter in the spectral range [ The ideal transmittance curve; Step 2.3: Obtain the coating tolerance curve based on the ideal transmittance curve from Step 2.2; Step 2.4: Process the coating to obtain the spectral homogenization filter, evaluate the performance of the spectral homogenization filter, and record the processing error; Step 3: Establish the spectral uniformity target simulation system without the attenuation module; Step 4: Measure the system output power of the spectral uniformity target simulation system established in Step 3. and the output power of the light source module. System output power Perform curve fitting to obtain ; Step 5: Add an attenuation module to the spectral uniformity target simulation system established in Step 3; Step 6: Design the transmittance of each attenuation element in the attenuation module; Step 7: Measure the system output power of the spectral uniformity target simulation system established in Step 5. ;in, The transmittance of the attenuation module; Step 8: Calculate the system spectral power ratio of the spectrally uniform target simulation system established in Step 5. ; Step 9: Switch the attenuation filter of the attenuation module and control the output power of the light source module. This enables the spectrally uniform target simulation system to simulate targets at infinity with spectral uniformity over a specific continuous power range, ultimately resulting in a system output power of... .

2. The design method of a spectral uniformity target simulation system with specific output power according to claim 1, characterized in that, Step 2.4 specifically involves: Step 2.4.1: Design the film system using coating software and perform coating to obtain a spectral homogenization filter; Step 2.4.2: Use a spectrophotometer to test the transmittance curve of the spectral homogenization filter. The transmittance curve of the spectral homogenization filter is measured within the spectral range [...]. The mean value of the root mean square error of the actual transmittance and the maximum tolerance and minimum tolerance of the coating tolerance curve is used to quantify the coating error. Step 2.4.3: Test the spectral homogenization effect of the spectral homogenization filter using a spectroradiometer, using different output power points within the spectral range [ The mean value of the spectral uniformity represents the spectral uniformity of the system. Conduct an overall assessment and record the processing errors as follows: ； in Representing the One output power point, Represents the spectral range [ [Inner Section] Each wavelength point, Representing the Spectral range under each output power point condition [ [Inner Section] The transmittance of a spectral homogenizing filter at a given wavelength point. Representative test time The number of output power points of the selected light source module within the range.

3. The design method of a spectral uniformity target simulation system with specific output power according to claim 1, characterized in that, Step 4 specifically involves placing the off-axis parabolic mirror in front of the output port of the spectral uniformity target simulation system without an attenuation module, and using an optical power meter to test the system's output power at the focal plane of the parabolic mirror. Record the power received by the optical power meter With the output power of the light source module ; Reflectivity of parabolic mirror Perform calibration to determine the system output power. ; Output power of the light source module System output power Perform curve fitting to obtain .

4. The design method of a spectral uniformity target simulation system with a specific output power according to claim 1, characterized in that, Step 6 specifically involves: the attenuation module has a total of There are attenuation filters with transmittances of [number] and [number] respectively. , ... The transmittance of each attenuator satisfies the following formula: ； in, These represent the minimum and maximum system output power corresponding to the use of the first attenuator, respectively. These represent the minimum and maximum system output power corresponding to the use of the second attenuator, respectively. respectively using the first The minimum and maximum system output power corresponding to each attenuator; The required output power coefficient for the target to be simulated; Greater than 2.

5. The design method of a spectral uniformity target simulation system with a specific output power according to claim 1, characterized in that, Step 8 specifically involves: using a spectroradiometer to perform tests at the light outlet of the spectral uniformity target simulation system, and calculating the spectral range. Spectral energy percentage within : ； in Represents the spectral range [ The number of points selected for the output power of the internal light source module.

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